International Journal of Modern Physics: Conference Series

A 0.79C-1.5Si-1.98Mn-0.98Cr-0.24Mo-1.06Al-1.58Co (wt%) steel was isothermally heat treated at 200°C for 10 days to produce a nano-structured bainitic steel. The microstructure consisted of nanobainitic ferrite laths with a high dislocation density and retained austenite films having extensive twins. The crystallographic analysis using TEM and EBSD revealed that the bainitic ferrite laths are close to the Nishiyama-Wassermann orientation relationship with their parent austenite. There was only one type of packet identified in a given transformed austenite grain. Each packet consisted of two different blocks having variants with the same habit plane, but different crystallographic orientations. Atom Probe Tomography (APT) revealed that the carbon content of nanobainitic ferrite laths was much higher than expected from the para-equilibrium level. This was explained due to the long heat treatment time, which led to the formation of fine Fe-C clusters on areas with high dislocation densities in bainitic ferrite laths.

Fe-10Ni-7Mn (wt %) martensitic steel is a member of ultrahigh strength steels. This alloy is ductile in the solution annealed condition and shows good age hardenability but it suffers from severe embrittlement after aging. Discontinuous coarsening of grain boundary precipitates was found as the main source of embrittlement. In this paper the effect of cold rolling on the mechanical properties and phase stability of Fe-10Ni-7Mn steel was investigated. Cold rolling for 20%, 60%, and 90% were carried out on a solution annealed material with subsequent aging at 753 K. X- ray diffraction results and transmission electron microscopy (TEM) micrographs showed the presence of austenite in severely cold rolled samples. This austenite is likely formed as a result of deformation, and it seems to originate from a reverse transformation from bcc-martensite to hcp-martensite to austenite, stimulated by increasing the amount of deformation. This transformation improves the mechanical properties in this steel while in as annealed and aged condition it has premature fracture and zero ductility.

In this paper, nano-crystalline Cu powder with a mean crystallite size of 45 nm and commercial micron-size Cu powder were either hot pressed or cold pressed and sintered conventionally to fabricate bulk samples. Hardness, density, crystallite size and microstructure of the samples after consolidation were examined. The results show that the hardness of the hot pressed nano-crystalline Cu is in the range of 0.75-1.2 GPa which is higher than that of commercial Cu. The density of the bulk nano-crystalline sample showed that the rising sintering temperature increases the density up to 97% of the theoretical value. The mean crystallite size of the hot pressed sample was 64 nm, which still was in the nano scale. The scanning electron microscopy (SEM) images revealed that the hot pressed samples contain less porosities compared to the conventionally consolidated samples.

Nano-sized nickel hydroxide powder has been synthesized by complexation-precipitation method through various decomposition routes in order to investigate its effect on textural and structural characteristics of the nickel hydroxide products. The products were then characterized by various analytical techniques such as XRD, SEM, ICP and FTIR. The results showed that the product with different size, shape and structure could be obtained by using different routes for decomposition of the complex.

This paper addresses the Adhesion of mica surface employing Atomic Force Microscope (AFM) as a surface force apparatus. AFM is commonly used for atomic and nano-scale surface measurements. Based on the relations between cantilever responses and tip–sample interaction, methods for quantitative evaluation of a sample's mechanical parameters are described and issues concerning the use of AFM are discussed. The measurement of the Force-Distance curve was performed implementing Atomic Force Spectroscopy (AFS). During these measurements, the static deflection of the cantilever is monitored as a function of piezoelectric element displacement. The recorded plot is then used to quantitatively measure the mechanical properties like adhesion and elastic modulus. Forces were measured by multiplying the distance by force constant of the cantilever thorough Hook's law. It was necessary to calibrate the force constant of the cantilever to perform a precise force measurement. Force-Distance curves were obtained in three different points on the surface of mica and Distant Dependant Measurement (DDM) was conducted 10 times per each point by 1.5s interval. Adhesion force was then calculated in every single curve and the final data was the mean of thirty different curves.

The morphology, composition and the electrochemical behavior of the anodic nanoporous layer, prepared by the galvanostatic anodisation of titanium, followed by galvanostatic deposition of noble metal particles have been investigated. The morphology and surface characteristics of result electrodes were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The results indicated that noble metal particles were homogeneously deposited on the surface of TiO₂ nanotubes. The nanotubular TiO₂ layers consist of individual tubes of about 40-80 nm diameters. The electrocatalytic behavior of result electrodes for electro-oxidation of organic compounds (glucose, dopamine, ascorbic acid and hydrazine) was studied by cyclic voltammetry. The results showed that the result electrodes possess catalytic activity toward the oxidation organic compounds.

In this study, the effect of Mn on α to γ transformation in the nanostructured high nitrogen Fe-18Cr-xMn stainless steel produced by mechanical alloying (MA) was investigated. MA was performed under nitrogen atmosphere using a high-energy planetary ball mill. X- ray diffraction (XRD) patterns of produced samples showed that α to γ transformation starts after 20 hours of milling and propagates by increasing the milling time. Completion of this phase transformation occurred in the Fe-18Cr-8Mn sample after 100 hours of milling. But, in the Fe-18Cr-7Mn sample, some α phase remained even after 150 hours of milling. Also, nitrogen analysis revealed that nitrogen solubility in the milled powders increased significantly by increasing the milling time, and ultimately reached 1wt%. This is believed to be due to the increase of the lattice defects and development of nanostructure through MA. Variations in grain size and internal lattice strain versus milling time in both cases showed that the critical ferrite grain size for austenite nucleation was lower than 10nm. Moreover, a lower transformation rate was found in samples containing lower Mn content.

Aluminum nanoparticles were synthesized by pulsed laser ablation of Al targets in ethanol for 5-15 minutes using the 1064 and 533 nm wavelengths of a Nd:YAG laser with energies of 280-320 mJ per pulse. It has been found that higher wavelength leads to significantly higher ablation efficiency, and finer spherical nanoparticles are also synthesized. Besides, it was obvious that higher ablation time resulted in higher ablated mass, while lower ablation rate was observed. Finer nanoparticles, moreover, are synthesized in higher ablation times.

In this paper aluminum nano-powder was produced by evaporation and condensation in a low pressure argon gas atmosphere. The process was modified according to the argon pressure to decrease the aluminum nano-particle size. Therefore, the argon gas pressure was changed from 0.1 to 1 mbar by change of injection flow rate, while other parameters were maintained constant. To evaluate the morphology of produced nano-powders at each argon pressure, the nano-powders were analyzed by Brunauer- Emmett- Teller (BET) method and transmission electron microscopy (TEM). It was found that the final particle diameter decreased with argon pressure. This decrease of particle size reaches a minimum of 85 nm, which corresponds to the pressure of 1 mbar. This powder had a specific surface area of 26.22 m²g^-1.

In present study ZnO nanorods were synthesized in an aqueous solution using a domestic microwave oven for irradiation. The nanorods have been grown on substrates immersed in an aqueous solution which contains zinc nitrate and hexamethylenetetramine as precursors. Eventually, effect of some parameters such as precursor's concentration and heating time on growth mechanism was characterized. The product phase was detected using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) exhibited the resultant structure is uniform and single crystalline. Finally Uv-Vis spectroscopy was used to measure the nanorod's band gap.

The present study reports a novel chemical route to synthesize different sizes of conducting polypyrrol (ppy) nanoparticles by hydrogen-bonding directionality in the presence of a crown ether, ionic liquid ([octmim]Br, octhyl-methyl imidazulim bromide) and ammonium persulfate in HCl solution. The morphology of the nanoparticle of PPy was confirmed by SEM images. The effects of reaction conditions on the morphology of the resultant ppy nanostructures were studied. The conductivity of the product varied with the mass ratio of aniline monomer to crown ether and IL. The chemical and electronic structures of the ppy nanoparticle were also studied by FT-IR and UV–Vis spectrometry, respectively.

Barium carbonate nano-particles have been synthesized by a simple PVA-assisted precipitation method using hydrated barium chloride and sodium carbonate as the starting materials. Crystal structure and morphology of the products were evaluated by XRD and SEM techniques, respectively. XRD results indicated that under the identical experimental conditions, single phase BaCO₃ was produced. SEM results showed that in the presence of PVA as guide reagent in the solution, nano-rods with regular (facet) surfaces were obtained. The results also showed that the concentration of PVA in the solution, reaction time and temperature have obvious influence on the agglomeration nature and mean particle size of the products. At high concentration of PVA less agglomerated nano size particles of BaCO₃ were synthesized. Increasing the synthesis time and temperature resulted in increasing the average diameter of BaCO₃ nano-rods. The performance of produced barium carbonate in the processing of barium hexaferrite ceramic magnet via conventional route has been approved.

Boron carbide is one of the advanced ceramic materials which is used in a wide range of applications. However, this material needs a high sintering temperature (~2200°C). Using nano-size powders for producing ceramic parts results in lowering sintering temperature and also enhances toughness and hardness of the material. One of the methods for producing ceramic nano powders is attrition milling. However, as the milling balls and wall are made of steel, some impurities specially iron will be introduced to the powder during milling. Chemical analysis of the milled powder shows that more than 33wt% of the powder consists of iron. These uncontrolled impurities affect the mechanical and physical properties of sintered ceramic parts that are made of such a powder. Therefore, these impurities must be removed from the powder. Hydro metallurgical beneficiation technique with two different solvents has been used for purification of the powder. The result of chemical analysis after purification showed that the weight percentage of iron in powder dropped to 9% and 0.8% (depending on the solvents). Moreover, the sintering behavior of hot-pressed boron carbide powder with different percentages of iron as sintering aid has been studied. The results showed excellent densification and hardness of the sintered parts.

The hardness, toughness and sum of cracks measurement of fine-grained WC-Co hard metals were studied. Thirty commercial and experimental hard metal grades with different additives such as boron carbide (B₄C), vanadium carbide (VC), chromium carbide (Cr₃C₂) and silicon carbide (SiC) were prepared in a commercial sinter HIP furnace. Physical, mechanical and microstructure properties were investigated to build up a representative hardness/sum of cracks measurement band. This band was then used to estimate the most effective sintering temperature and the amount of each additives. Afterwards, influence of grain growth inhibitors in optimum condition were compared. The results showed that the grades, doped with B₄C and VC as growth inhibitor exhibits more hardness than other comparable doped alloys. However, Cr₃C₂ is favorable in toughness improvement.

Ultra fine metallic powders have an increasing application in magnetic materials, catalysts and chemical and metallic industries. In this research, magnesium-thermic reduction in gas phase was used to synthesize an ultra-fine nickel-iron intermetallic compound. Synthesis of nickel-iron submicron powder by metal chlorides and magnesium vapors was studied. Evaporation rate of the chlorides and magnesium in the range of 800 to 920 degrees Celsius was measured in order to control the composition of the resulting compound. The simultaneous reduction of the chlorides was done in a tubular furnace under argon atmosphere at 920 degrees Celsius. Chemical analysis of the resulting compound and the X ray diffraction analysis identified the formation of Ni₃Fe compound. The particle size of the compound was measured 60 to 230 nano-meters by scanning electron microscopy. In addition, the particles were spherical and homogeneous. The product may be used for production of magnetic and catalytic applications.

In this study, mechanical alloying was used to produce MoSi₂ powder directly from molybdenum trioxide. Mixture of MoO₃, Si and Al powders were exposed to high mechanical activation in a planetary ball mill. The ball to powder mass ratio was constant at 33:1 and the rotation speed (cup speed) was 290 rpm during the milling operations. Phase compositions and structural evolutions during milling were investigated by X-ray diffraction analysis. The morphology of the mechanically alloyed powders was evaluated with scanning electron microscope (SEM). From XRD results, it was observed that within 3 hours of milling, MoO₃ was completely reduced and a MoSi₂-Al₂O₃ composite powder was produced. Further milling resulted in transformation of β- MoSi₂ phase to α- MoSi₂. Mean crystallite sizes in product phases in the sample milled for 30 hours calculated by Scherer method using XRD patterns were found to be less than 100 nm.

Optical analysis (UV-vis spectroscopy) of solution of ZnS nanoparticles prepared at room temperature by a chemical capping method using methacrylic acid (MAA) capping agent at concentration of 0.05, 0.2, 0.5 and 1.17 molar is investigated. The spectroscopy results indicate increasing of band gap of ZnS through increasing concentration of the methacrylic acid as capping agent in the solution. According to the relation of Effective Mass Approximation, it is concluded that the size of nanoparticles decreased with the increasing concentration of the capping agent in the tested solutions. The size of the particles is found to be in 1.77-2.05 nm range.

In this study, the effect of ammonia solution addition as a pH adjusting component on the thermal behavior, phase composition, morphology, and magnetic properties of reduced Co- B nano-particles fabricated by chemical reduction route have been studied using DSC, XRD, SEM, and VSM techniques, respectively. Chemical composition of the samples was measured by ICP.

The ICP results showed that basic pH of reagent solution, derived from utilizing ammonia solution, caused the boron content to decrease. XRD results indicated an amorphous structure for both samples synthesized with and without ammonia solution. Analysis of the DSC results showed that crystallization behavior has dramatically altered, owing to utilize ammonia solution. While the sample synthesized without ammonia solution showed three distinctive exothermic peaks at 216,470, and 540°C, the sample synthesized in the presence of ammonia solution exhibited only two exothermic peaks at 235 and 470°C and one endothermic peak at 370°C. SEM images reveal that the samples have a net- like morphology and the net is formed by many interconnected spherical fine particles with sizes less than 100 nm. Saturation magnetization of the sample synthesized in the presence of ammonia solution has improved significantly, probably due to the less amount of boron.

Cobalt-Molybdenum alloy nanopowder has magnetic properties and is used as catalyst for production of carbon nanotubes. Properties of this nanopowder depend on, for example, its size, morphology and internal residual stress. Synthesis of nanopowder of Molybdenum-Cobalt alloy by co-precipitation in an aqueous media using NH₄OH as precipitating agent followed by calcination and reduction was investigated. The synthesis was started by dissolving salts of Cobalt and Molybdenum in water. A suspension of alumina or silica powders was used as a bed for precipitation. The effect of bed materials on size and morphology of the precipitate was investigated. The particles observed with scanning electron microscope possess a spherical shape and a needle shape for the samples participated on alumina and silica beds, respectively. XRD analysis of the calcined precipitate showed the formation of mixed oxide of CoMoO₄ as well as single oxides of Co₃O₄ and MoO₃. Particle size of the precipitate observed with transmission electron microscope was about 100 nm. Finally, the powders were reduced by hydrogen gas in a tubular furnace to prepare metallic nanopowder with composition of Co₃Mo.

A nanostructure modified silica with good fluorescence properties was prepared by grafting Al³⁺ ions on the surface of nanoporous silica and then binding of 8-hydroxyquinoline (8-HQ) to the grafted Al³⁺ ions. The prepared material, denoted as NS-AlQ₂, was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), nitrogen adsorption–desorption measurements, FT-IR and fluorescence spectra. This compound shows emission spectra approximately in the emission range of AlQ₃ complex. This procedure provides a simple method for grafting fluorescent molecules in the channels of nanoporous silica materials.

Magnetite nano-particles have been synthesized by reverse co-precipitation method using iron salts in alkaline medium in the presence of diethylene glycol (DEG). Effect of DEG on the nano-particle characteristics was investigated by XRD, FE-SEM, FTIR and VSM techniques. From XRD results it was concluded that in the presence of DEG the composition of magnetite did not change, however the mean crystallite size reduced from 10 to 5 nm. SEM micrograph showed that DEG decreased the size of spherical magnetite nano-particles from 50 to 20 nm. Fourier transform infrared spectra (FTIR) indicated that the DEG molecules chemisorbed on the magnetite nano-particles. Under the given experimental conditions, the rate of crystallization and growth reduced, which is probably due to the capping of DEG to the magnetite nano-particles. The agglomeration was also decreased which is attributed to the coating of magnetite nano-particles by DEG which prevents the formation of hydrogen bonding between magnetite and water molecules.

We report the propane dehydrogenation behavior of catalysts prepared using wet impregnation method that immobilize Pt nano cluster on the alumina surface. The immobilization of the metal particles and their nano size dimensions were demonstrated by transmission electron microscopy. Selectivity to propylene for these catalysts is comparable to those obtained over industrial Pt catalysts, yet the resistance to deactivation by carbon poisoning is much greater for our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts on γ-alumina than of catalysts supported onθ-alumina.

Salt-matrix annealing of mechanically alloyed Co-ferrite nanopowder was used to modify its particle size and morphology. Efficiency improvement due to suppression of sintering and growth resulted in reduction of average particle size from ~100nm for salt-less to ~40nm for salt-full annealing procedure. Nanosized single-phase cobalt-ferrite particles were observed after 2h annealing at 750°C in the samples milled for 20 hours both with and without NaCl. NaCl:CoFe₂O₄ ratio of 10:1 resulted in cabbage-like clusters containing particles smaller than ~50 nm.

One-dimensional tin oxide nanostructures were synthesized by carbothermal reduction process. Results showed that using Au as catalyst on Si wafer and shorter distance from source materials lead to higher nucleation and growth rate. It was understood that SnO₂ to carbon mixing ratio of 1:4 is appropriate. SnO₂ nanostructures were grown by VLS mechanism.

Ba_0.7Sr_0.3TiO₃ was prepared via simple sol-gel method by using titanium tetrabutoxide, barium and strontium carbonates, citric acid and ethylene glycol as starting materials. Simultaneous Thermal Analysis (STA) was used to examine thermal behavior of xerogel. The crystallite size of BST was about 21nm calculated by X-Ray diffraction (XRD) and confirmed by transition electron microscopy (TEM). Using these nanocrystalline powders, BST pellets were prepared and sintered in various temperatures. The grain size effect on electrical properties was studied and found that as the grain size decreased, the dielectric constant decreased too.

In this study, Mg doped hydroxyapatite [(Ca, Mg)₁₀(PO₄)₆(OH)₂] and β-tricalcium phosphate nanoparticles were synthesized via sol gel method. Triethyl phosphite, calcium nitrate tetrahydrate and magnesium nitrate hexahydrate were used as P, Ca and Mg precursors. The ratio of (Ca+Mg)/P and the amount of magnesium (x) were kept constant at 1.67 and ranging x = 0 up to 3 in molecular formula of Ca_10-xMg_x (PO₄)₆(OH)₂, respectively. Phase composition and chemical structure were performed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Phase percentages, crystallite size, degree of crystallinity and lattice parameters were investigated. The presence of magnesium led to form the Mg doped tricalcium phosphate (β-TCMP) and Mg doped hydroxyapatite (Mg-HA). Based on the results of this study, lattice parameters, degree of crystallinity and crystallite size decreased with magnesium content. In addition, with increasing magnesium content, the amount of CaO phase decreased whereas the amount of MgO phase increased significantly. Obtained results can be used for new biomaterials design.

In this investigation, TiB₂ nanocrystalline powder was synthesized by mechanical alloying of the elemental mixture of Ti and B powders in argon atmosphere. In order to study the structural evolution of the powder during ball milling, X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used. Adiabatic temperature calculations were performed for characterization of TiB₂ powder. Also, the effects of heat treatment on the structural evolution and thermal stability of mechanically alloyed powders were investigated. It was found from the XRD patterns that TiB₂ was formed via combustion mechanism. By increasing milling time, the grain size decreased while the lattice strain increased. SEM micrographs showed that TiB₂ particles were spherical. The grain size and lattice strain reached 24 nm and 1.8% respectively, after 60 hours ball milling.

In this study, the effect of Zn doping on photoluminescence, Chromaticity and structural properties of Y₂O₃:Eu compound were studied. For this purpose, various Y₂O₃:Eu samples containing different Zn²⁺ concentration and distribution were prepared by combustion method. The resultant samples were characterized by X-ray diffractometry (XRD), Photoluminescence spectroscopy (PL) and scanning electron microscopy (SEM). The XRD patterns of samples were also examined by Rietveld refinement method and results showed that the samples had nano-sized crystallites. It has been also shown that doping of Zn²⁺ ion in structure of Y₂O₃:Eu compound can effectively enhance the PL intensity and chromaticity of Y₂O₃:Eu compound, while doping of Zn at surface of Y₂O₃:Eu powder reduces PL intensity, crystallinity and chromaticity of this compound.

Titanium diboride (TiB₂) has attracted great interests for its excellent mechanical properties, chemical resistance and good thermal and electrical conductivities. So it is widely applied as cutting tool composites, wear resistant parts, metal melting crucibles and electrode materials. This paper presents synthesis of nano titanium diboride powders via sol-gel method using a mixture of TTIP and B₄C as precursors. In the hydrolysis step, B₄C to TTIP molar ratio varied from 1.3 to 2.5. Solution samples stirred well and after aging and drying process, they were heat treated in an argon atmosphere. X-ray diffraction (XRD) patterns and Scanning electron microscopy (SEM) analysis showed that the percentage of synthesized TiB₂ increased gradually as the molar ratio of B₄C to TTIP reached to 2.3, afterward increasing the B₄C to TTIP molar ratio caused decreasing of titanium diboride percentage.

Ultra fine WO₃ nanoparticles were synthesized by nanocasting route, using mesoporous SiO₂ as a template. BET measurements showed a specific surface area of 700m²/gr for synthesized SiO₂ while after impregnation and template removal, this area was reduced to 43m²/gr for WO₃ nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5nm possessing a monoclinic structure which is the favorite crystal structure for gas sensing applications. Alternative electric field was applied to align synthesized WO₃ nanoparticles between electrodes. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO₂ at 250°C.

Nanostructured hybrid silica/epoxy films containing boehmite nanoparticles were investigated in the present work as pretreatments for AA2024 alloy. To produce the nanocomposite sol-gel films, boehmite nanoparticles prepared from hydrolysis/condensation of aluminum isopropoxide (AlI) were doped into another hybrid organosiloxane sol. The produced oxide nanoparticles have the capability to act as nanoreservoirs of corrosion inhibitors, releasing them controllably to protect the metallic substrate from corrosion. For this purpose the corrosion inhibitor, cerium nitrate, was introduced into the sol-gel system via loading the nanoparticles. The morphology and the structure of the hybrid sol-gel films were studied by Scanning Electron Microscopy (SEM). The corrosion protection properties of the films were investigated by Potentiodynamic Scanning (PDS) and Electrochemical Impedance Spectroscopy (EIS). The results show that the presence of boehmite nanoparticles highly improved the corrosion protection performance of the silica/epoxy coatings. Moreover, they can act as nanoreservoirs of corrosion inhibitors and provide prolonged release of cerium ions, offering a self-healing property to the film.

The synthesis and properties of high luminescent thio-stabilized nanocrystals (NCs) in aqueous media was discussed in this paper. The sharp peaks of photoluminescence (PL) and full width at half-maximum (fwhm), were observed in the range of 50 to 70nm. The PH was 9 and the molar ratio of Cd to thiol (1:2.4) was constant during the experiment. The stabilized NCs through thioglycolic acid (TGA) show great luminosity in which the spectral of PL emission is variable with controlling the size of NCs. The size ranges of thioglycerol(TG) stabilized NCs and the spectral range of PL emission are more limited than TGA in the same condition. The concentration of thio-ligands and heating time are two factors that that will discuss in this paper to control the size of NCs.

The particles of TiO₂ core/ SnO₂ shell nanocomposite were prepared by hydrolysis of SnCl₄.5H₂O in the presence of titania nanoparticle after drying and calcinations treatments. TiO₂ particle were produced from titanium isopropoxide sol by hydrothermal processing. X-ray diffraction (XRD), Fourier transformed infrared (FTIR), and transmission electron microscopy (TEM) were used to characterize the TiO₂/ SnO₂ core shell nanocomposites. The obtained results from XRD show that the SnO₂ nanoparticles coated on TiO₂ yields diffraction peaks correspond to the crystalline SnO₂ phase. Also, TEM results show that the nanocomposite particles have a spherical morphology and a narrow size distribution. The thickness of SnO₂ shell on the surface of TiO₂ particles were about 8 nm. Moreover, the results obtained from EDX analysis show that the core-shell structured nanocomposites have crystalline structure.

Biodegradable polymers and bioactive ceramics are being combined in a variety of composite materials for tissue engineering scaffolds. Porous nano-biphasic calcium phosphate/gelatin structure was prepared by freeze-drying method. Pre-pores were created by using naphthalene with different particle sizes. Stabilization of gelatin network matrix carried out by EDC (N-(3-dimethyl aminopropyl)-N′-ethyl carbodiimide hydrochloride) with cross-linking method. Three different amount of gelatin (2, 6 and 10 mg/ml) solution were used to study the effect of gelatin amount on properties of the scaffold. Microstructural properties of scaffolds were characterized by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical composition of scaffold. Also the morphology and bending strength were investigated.

A mixture of silicon carbide nano-particles and nano-whiskers has been synthesized through solid state reduction of silica by graphite employing high energy planetary ball milling for 25 h and subsequent heat treatment at 1300-1700°C in dynamic argon atmosphere. Effects of process conditions on the thermal behavior, phase composition and morphology of the samples were investigated using DTA/TGA, XRD and SEM, technique, respectively.

DTA/TGA analysis shows that silicon carbide starts to form at ~ 1250°C. Analysis of the XRD patterns indicates that the phase composition of the sample heat treated at 1300°C for 2 h mainly consists of SiO₂ together with small amount of β-SiC. Nano-crystalline silicon carbide phase with a mean crystallite size of 38 nm was found to be dominate phase on heat treatment temperature at ~ 1500°C. Substantial SiO₂ was still remained in the above sample. SEM studies reveal that the sample heat treated at 1500°C for 2 h contains nano-particles and nano-whisker of β-SiC with a mean diameter of almost ~ 85 nm. The results obtained were also showed that the characteristics of the synthesized SiC particles strongly depend on the mechanical activation and heat treatment conditions.

Nickel oxide (NiO) nano-particles were produced via a rapid microwave-assisted method. Ni(OH)₂ precursor was obtained by slow drop-wise addition of 0.1M sodium hydroxide to 0.1M nickel nitrate. The mixture was vigorously stirred until the pH reached 7.2. The mixture was then irradiated with microwave to deposit Ni(OH)₂ at an intensified precipitation rate. Drying of the precipitate at 320°C resulted in formation of NiO nano-powder. Mean dimension of this powder was ~30nm according to the images analyzed by transmission electron microscope (TEM) and scanning electron microscope (SEM). X-ray diffraction (XRD) patterns revealed well-crystallized/high-purity nanostructures of the synthesized powder. Microwave utilization increased homogeneity and decreased the mean particle size of the produced NiO powder.

Titanium dioxide (titania) is a cheap, nontoxic and highly efficient photocatalyst being extensively applied for the degradation of organic pollutants, air purification, water splitting, reduction of nitrogen to ammonia, and optical devices due to its optical behaviors. The third-order nonlinear optical properties of TiO₂/PS nano-composite were studied by means of single beam transmission technique, using a continuous-wave (CW) He-Ne laser beam with a wavelength of 632.8 nm with three different incident intensities. The magnitude and sign of the third-order nonlinear refractive index (n₂) and nonlinear absorption (β) of TiO₂/PS nano-composite were determined by use of both the closed-aperture and opened-aperture z-scan techniques. Z-scan technique, developed by Sheik-Bahae et al., has been used widely in material characterization. A single-beam (also called z-scan method) for measuring the sign and magnitude of nonlinear refraction that has simplicity and very high sensitivity has been reported recently. Optical limiting property of TiO₂/PS nano-composite is studied.

The positive sign obtained for nonlinear refractive index indicated that there is a self-focusing effect in the sample. The nonlinear refractive index was in order of 10^-8 (cm²/W) and the nonlinear absorption coefficient was obtained in order of 10^-2 (cm/W) with negative sign. The values of nonlinear refractive index and nonlinear absorption coefficient are enhanced by decreasing the intensity.

Nano-crystalline titanium diboride (TiB₂) was prepared by self-propagating high-temperature synthesis through putting a hot filament on top of the compact mixture of TiO₂, H₃BO₃ and Mg with a stoichiometric ratio. Effects of the addition of various chloride salts e.g. NaClO₄ and NH₄Cl as process control agents on phase evolution and chemical analysis and the morphology of the products were investigated by XRD and SEM techniques, respectively. Analysis of the X-ray diffraction patterns confirmed the formation of TiB₂ together with some intermediate phases such as Mg₃B₂O₆ and Mg₂TiO₄ in as synthesized powder. MgO phase was detected as a major phase in the XRD patterns. Nano-crystalline TiB₂ became the major phase in some of the leached samples by HCl. The results also showed that the powder particle characteristics were influenced by the addition of the chloride salts.

Spark discharge is a technique for producing nanoparticles from conductive materials. We had previously used this method to produce Au-Pd bimetallic nanoparticles with a mean diameter of around 6 nm. In this study we changed the operating parameters (e.g. spark energy and frequency, carrier gas type and flow rate) and analyzed the generated particles for their structures and compositions. X ray diffraction (XRD) patterns showed evidence of the formation of alloy phase in all the samples. Compositional analysis by Inductively Coupled Plasma (ICP) revealed that the average mixing ratio was influenced by the polarity, the spark frequency and the gap distance between anode and cathode.

Processing through the application of severe plastic deformation (SPD) provides a very attractive tool for the production of bulk ultrafine-grained materials. These materials typically have grain sizes in the submicrometer or nanometer ranges and they exhibit high strength at ambient temperature and, if the ultrafine grains are reasonably stable at elevated temperatures, they have a potential for use in superplastic forming operations. Several procedures are now available for applying SPD to metal samples but the most promising are Equal-Channel Angular Pressing (ECAP) and High-Pressure Torsion (HPT). This paper examines the basic principles of ECAP and HPT and describes some of the properties that may be achieved using these processing techniques.

Different amounts of Al-5Ti-1B master alloy (TiBAl) were added to the AZ31 magnesium alloy (Mg-3Al-1Zn-0.2Mn) as grain refiner and the resulting microstructure and grain size distributions were studied after extrusion and equal channel angular pressing (ECAP). Results showed that the addition of 0.6% TiBAl had the strongest grain refinement effect, reducing the grain sizes by 54.5 and 48.5% in the extruded and ECAPed conditions, respectively. The observed grain refinement was partly due to the presence of the thermally-stable micron- and submicron-sized particles in the melt which act as nucleation sites during solidification. During the high-temperature extrusion and ECAP processes, dynamic recrystallization (DRX) and grain growth are likely to occur. However, the mentioned particles will help in reducing the grain size by the particle stimulated nucleation (PSN) mechanism. Furthermore, the pinning effect of these particles can oppose grain growth by reducing the grain boundary migration. These two phenomena together with the partitioning of the grains imposed by the severe plastic deformation in the ECAP process have all contributed to the achieved ultrafine-grained structure in the AZ31 alloy.

A new noble severe plastic deformation method, called accumulative back extrusion (ABE), was developed to assist generating ultra fine grain materials. In the present work the ABE process was successfully applied on AZ31 magnesium alloy up to three passes without any danger of cracks. The results showed that a large shear deformation may introduce through step one, where extensive shear banding and twinning are present in the microstructure. As the second step proceeds via constrained compressive deformation, more deformation inhomogenieties, which may act as preferred nucleation sites for new grains, were introduced in the microstructure. By increasing the number of passes to 3, more homogeneous microstructure with no significant smaller grain size was formed. The strain induced twinning and strain localization, which were led to occurrence of dynamic recrystallization (DRX), were found to be the main reasons of grain refinement during ABE process.

The present research is concerned with the aluminum layer of a loosely packed tri-layer copper-aluminum-copper composite deformed by ECAE process. Electron back scattered diffraction (EBSD), transmission electron microscope, and X-ray technique were employed to investigate the detailed changes occurring in the microtexture, microstructure (cell size and misorientation), and dislocation density evolution during consecutive passes of ECAE process performed on the composite based on route Bc. According to tensile test results, the yield stress of the aluminum layer was increased significantly after application of ECAE throughout the four repeated passes and then slightly decreased. An ultrafine grain size within the range of 500-600 nm was obtained in the Al layer by increasing the thickness of copper layers. It was observed that the reduction of grain size in the aluminum layer is nearly 57% more than that of an ECAE-ed single layer aluminum billet. Also, the grain refinement of the aluminum layer is accelerated throughout 8 passes. This observation was attributed to the higher rate of dislocation interaction, cell formation and texture development during the ECAE of the composite compared to those of the single billet.

In preset work, the bake hardening behavior of 6056 aluminum alloy with nanostructured layer, produced by surface severe plastic deformation (SSPD), was compared with that of AA6056 with conventional coarse grain structure. Wire brushing process was employed in order to produce surface layers with nanograins. After formation of nanostructured surface layer, the structure was characterized using X-ray Diffraction (XRD) and scanning electron microscopy (SEM) techniques. According to the microhardness measurements, the depth of nanostructured layer, with the grains of 50-110 nm, was about 40-50 μm on each side of specimens. The bake hardenability of the produced nanostructured AA6056 was then studied. The results indicate an increase of about 40% in the bake hardening of nanograin AA6056 comparing to the bake hardening of coarse-grain AA6956. The maximum microhardness of nanograin layer was about 250 HV, whereas it was 65 HV for coarse-grain AA6056.

A novel SPD process for manufacturing high strength tubes and cylinders titled as accumulative spin-bonding (ASB) is proposed. This process is applied to a commercially pure aluminum up to four cycles and its effects on the microstructure and mechanical properties are examined by optical microscopy, TEM, microhardness and tension tests. The results show that ultra-fine grains are developed during the process leading to a nanostructure with average grain size in order of 150 nm. Mechanical properties indicate that while the hardness of outer layers is more than inner ones, the hardness and its homogeneity is increased by increasing the ASB cycles. As a result of grain refinement and the scheme of hardness development, the yield and tensile strength of material are increased significantly up to the values of 194 and 235 MPa, respectively.

High Si bainitic steel has received much interest because of combined ultra high strength, good ductility along with high wear resistance. In this study, the microstructural evolution of dual phase bainitic ferrite-austenite steel after heavy compression was investigated. Compression tests were conducted at temperature of 298K on the rectangular billets at the strain rate of 0.001s_-1. The samples were deformed to 40% and 70% of their original thickness. The EBSD results show formation of nano grains with high angle grain boundaries through 70% compression, which confirms grain refinement. Additionally, 40% deformation resulted in enhancement of the dislocation density and formation of subgrains at ferrite unites. Also, it was found during 70% compression of the steel, the austenite transforms to the martensite, which is in agreement with thermodynamic calculations.

Recently, severe plastic deformation processes have been the essence of metal forming researches to produce ultrafine-grained materials. Twist Extrusion is one of the most unprecedented methods developed in recent years, but has some deficiencies. The main one is the microstructure and mechanical heterogeneity, occurring after twist extrusion. Performing rolling as a conventional forming technique was suggested as a solution in this paper. It not only decreased the grain size, but also reduced the mechanical heterogeneity, and improved the grain size distribution. Employing the twist extrusion process on pure copper samples was carried out using a twisted die with 60° die angle, and the samples were processed through rolling subsequently. The results demonstrated that employing the rolling process enhanced grain size homogeneity and bulk strength.

In the present investigation, novel Ti/SiC surface nano-composite layer was successfully fabricated by dispersing nano-sized SiC particles into commercially pure titanium plates employing friction stir processing technique. The process parameters such as tool rotation and advancing speeds were adjusted to produce defect-free surface composite layer, however, uniform distribution of the nano-size SiC particles in a matrix of titanium was achieved after the second pass. The micro hardness value of the Ti/SiC nano-composite surface layer was found to be ~534 HV; this is 3.3 times higher than that of the commercially pure titanium substrate. No reaction was detected between SiC powders and the titanium matrix after friction stir processing.

Friction stir processing (FSP) is an effective tool to produce a surface composite layer with enhanced mechanical properties and modified microstructure of as-cast and sheet metals. In the present work, the mechanical and microstructural properties of as-cast AZ91 magnesium alloy were enhanced by FSP and an AZ91/SiC surface nanocomposite layer has been produced using 30 nm SiC particles. Effect of the FSP pass number on the microstructure, grain size, microhardness, and powder distributing pattern of the surface developed has been investigated. The developed surface nanocomposite layer presents a higher hardness, an ultra fine grain size and a better homogeneity. Results show that, increasing the number of FSP passes enhances distribution of nano-sized SiC particles in the AZ91 matrix, decreases the grain size, and increases the hardness significantly. Also, changing of the tool rotating direction results much uniform distribution of the SiC particles, finer grains, and a little higher hardness.

Nano/Submicron crystalline grains of about 250 nm were obtained in a metastable austenitic stainless steel AISI304L by an advanced thermomechanical process consisting of heavy conventional cold rolling and annealing. Effects of cold thickness reduction and temperature and time of the reversion treatment on microstructure and mechanical properties of the steel were investigated. The nano-structured austenitic steel exhibited not only high strength (above 1 GPa) but also good elongation (above 50%).

Theoretical and experimental Investigations of shock wave consolidation processes of Ti-Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al. The normal and tangential stresses in the cylindrical steel tube (containers of Ti-Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (≤ 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al. Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

During the last years lots of efforts have been done to industrialize equal channel angular pressing (ECAP) technique. Both Continuous Confined Strip Shearing (C2S2) and ECAP-Conform methods are rather recent techniques, making a continuous process from ECAP method. In present study both mentioned processes were simulated with ABAQUS Finite Element software for commercially pure aluminum. During C2S2 process the sample gradually experienced equivalent plastic strain (PEEQ) of 0.13 at initial stages of bending, while during ECAP-Conform the sample underwent rather sudden magnitude of strain of about 0.52 at primary stages, and it remained constant during the rest of the process. The final magnitude of the PEEQ differed significantly between two processes, as it was 0.86 and 1.36 in C2S2 and ECAP-Conform, respectively. Therefore, in the same processing condition employing the ECAP-Conform method led to a finer microstructure in comparison with C2S2 technique.

Molecular Dynamics (MD) simulation was used to figure out the fracture behaviors of nanocrystalline materials (NCM). The simulation was based on more than 13 thousand atoms considered for two systems with sharp and blunt crack tip in NCM. Their atomic level resolution provides novel insights into the fracture behavior of NCM. The results show semi brittle manner for both sharp and blunt tips. Dislocation nucleation and pile up at grain boundary (GB), lead to forming voids at GB. Merging mechanism of voids ahead of crack tip causes crack growth.

The effect of temperature on the noncontact atomic force microscopy (NC-AFM) surface imaging is investigated with the aid of molecular dynamics (MD) analysis based on the Sutton-Chen (SC) interatomic potential. Particular attention is devoted to the tip and sample flexibility at different temperatures. When a gold coated probe is brought close to the Au (001) surface at high temperatures, the tip and surface atoms are pulled together and their distance becomes smaller. The tip and sample atoms displacement varies in the different environment temperatures and this leads to the different interaction forces. Along this line, to study the effect of temperature on the resulting images, we have employed the well-known NC-AFM model and carried out realistic non-equilibrium MD 3D simulations of atomic scale imaging at different close approach positions to the surface.

The powder of the micro Al and variant volume fractions of nano Al₂O₃ were milled by a high energy planetary ball-mill. By milling, a homogenous distribution of nano Al₂O₃ particles in the metal matrix were developed. Then the milled powder was cold compressed and sintered at 545°C for one hr. The mold and the sintered sample hold in a furnace until the temperature reached 545°C. Then the hot 27mm diameter sample was extruded to 6mm diameter. From the extruded specimens, tensile, hardness and microstructure of the prepared specimens were determined. By these tests the effect of milling time, the percent of nano-particles and the microstructure were evaluated. The hardness and tensile behaviors of aluminum matrix composites reinforced with nano Al₂O₃ particulate have been found to increase remarkably with the volume fraction of the reinforcement.

In this research, effect of milling time on solid state reduction of MoO₃ with carbon has been investigated. It was found that mechanical activation of a mixture of MoO₃ and carbon at ambient temperature by high energy ball milling was not able to reduce MoO₃ to metallic molybdenum. MoO₃ was converted to MoO₂ at the first stage of reduction and peaks of the latter phase in X-ray diffraction patterns were detected when the milling time exceeded from 50 hours. The main effect of increased milling time at this stage was decreasing of MoO₃ peak intensities and significant peak broadening due to decrease in size of crystallites. After prolonged milling, MoO₃ was fully reduced to nano-crystalline MoO₂ and its mean crystallite size was calculated using Williamson–Hall technique and found to be 17.5 nm.

Thermodynamic investigations also confirm the possibility of reduction of MoO₃ to MoO₂ during the milling operation at room temperature. But, further reduction to metallic molybdenum requires thermal activation at higher temperature near 1100 K.

XRD and SEM techniques were employed to evaluate the powder particles characteristics.

In the present work, high energy ball milling of binary (Mg₂Ni) and ternary powder mixtures (Mg_1.75Nb_0.25Ni and Mg₂Ni_0.75Nb_0.25, i.e., substitution of Nb for Mg and Ni, respectively) was carried out. The effects of milling process parameters on the microstructure of binary and ternary milled products were studied. Also, electrochemical properties of the nano-structured electrodes made from the milled products were measured. It was found that Nb substitution for Mg (Mg_1.75Nb_0.25Ni) has beneficial effect on the formation kinetic of Mg₂Ni-based nano-crystallites. Electrode made from the 20h milled product using initial composition of Mg_1.75Nb_0.25Ni exhibited a high discharge capacity of ~600mAhg-1 and relatively longer discharge life. Such electrode showed a microstructure consisting of an amorphous core surrounded by nano-crystallites.

In the present study nanostructured Cu(Mo) compound with 15 weight percent Mo was produced by mechanical alloying using a planetary ball mill. The milling operation was carried out in hardened chromium steel vial and balls under argon atmosphere with a constant ball to powder ratio of 10:1. The structural evolution and characterization of powder particles after different milling times were studied by X-Ray Diffraction, SEM observation and Microhardness measurements. The results showed the displacement of broadened Cu peaks to lower angles, because of dissolving Mo in Cu. The final product was a nanocomposite contains nanocrystalline Cu(Mo) supersaturated solid solution matrix and dispersion of nanometric Mo reinforcements. The microhardness of formed nanocomposite increased to 350HV because of grain refinement, formation of solid solution and dispersion hardening.

Nano-sized intermetallic powders have received great attention owing to their property advantages over conventional micro-sized counterparts. In the present study nano-sized MoSi₂ powder has been produced successfully from commercially available MoSi₂ (3 μm) by a mechanical milling process carried out for a period of 100 hours. The effects of milling time on size and morphology of the powders were studied by SEM and TEM and image analyzing system. The results indicate that the as-received micrometric powder with a wide size distribution of irregular shaped morphology changes to a narrow size distribution of nearly equiaxed particles with the progress of attrition milling up to 100 h, reaching an average particle size of 71 nm. Structural evolution of milled samples was characterized by XRD to determine the crystallite size and lattice microstrain using Williamson-Hall method. According to the results, the crystallite size of the powders decreases continuously down to 23 nm with increasing milling time up to 100 h and this size refinement is more rapid at the early stages of the milling process. On the other hand, the lattice strain increases considerably with milling up to 65 h and further milling causes no significant changes of lattice strain.

BaTiO₃-based solid solutions involve high piezoelectric and ferroelectric properties. One of the most favorable systems of this material is Ba(Zr_xTi_1-x)O₃. While nano structured ceramics of which have a great potential for using them in capacitors, actuators, transducers and dielectrics to reach high K values. In this study, nano crystalline Ba(Zr_xTi_1-x)O₃(x=0.1-0.8) which is called BZT composite has been prepared by mechanical alloying. The parameters affecting the process and properties were evaluated. The starting powders that are used here were nano sized high pure ZrO₂; submicron sized high pure TiO₂ and BaCO₃. The prepared powder was calcined, compacted and sintered at different temperatures and in various times. The structural changes and phase developments during mechanical alloying were studied by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) and Transition Electron Microscopy (TEM). The results showed that by using mechanical alloying method, high dense nano crystalline BZT ceramics were obtained successfully at very low sintering temperature. The dielectric constant of BZT was much great, because of using nano materials in this method at the temperatures of 1250-1400°C. The effect of high energy milling in micro structural development of nano crystalline BZT has been discussed as well as dielectric properties.

Aluminum carbide (Al₄C₃) seems to be an ideal reinforcement for producing aluminum matrix composites. Al₄C₃ has high hardness and shear strength as well as a high melting point. The dispersion of Al₄C₃ particles in the matrix produces a pinning effect that reduces aluminum grain growth, which improves the mechanical properties. In this study, aluminum powders were mixed with 4.5 wt.% graphite and mechanically alloyed using a high-energy ball mill in order to produce Al-Al₄C₃ nanocomposite. The structural evaluation of powder particles after different milling times was studied by X-ray diffractometry, scanning electron microscopy and microhardness measurements. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson–Hall formula. XRD results suggested that the grain size of aluminum decreased to nanometer range (30 nm) during ball milling. No Al₄C₃ formed during the mechanical alloying process. Milled powders were then annealed at 300-600 °C for 1 h under argon atmosphere. Annealing at temperatures higher than 300 °C led to formation of Al₄C₃ phase which increased as annealing temperature increased. Aluminum grain size remained in nanometer range after annealing process. The microhardness of powder particles increased after annealing. Both effects are due to the formation of nanosized Al₄C₃ particles.

In this study, mechanical alloying (MA) of Fe-50Al, Fe-49.5Al-1B, and Fe-47.5Al-5B (at.%) alloy powders and mechanical properties of sintered products of the as-milled powders were investigated. X-ray diffraction (XRD) results showed the addition of B caused more crystallite refinement compared to the B-free powders. To consider the sintering and ordering behaviors of the parts produced from cold compaction of the powders milled for 80 h, sintering was conducted at various temperatures. It was found that the sintering temperature has no meaningful effect on the long-range order parameter. The transformation of the disordered solid solution developed by MA to ordered Fe-Al- (B) intermetallics was a consequence of sintering. Also, the nano-scale structure of the samples was retained even after sintering. The microhardness of pore-free zones of the nanostructured specimens decreased by increasing the sintering temperature. Moreover, the sintering temperature has no effect on the compressive yield stress. However, the fracture strain increased by increasing the sintering temperature. The samples containing 1 at.% B showed more strain to fracture compared with the B-free and 5 at.% B samples.

In this paper, the influence of toluene as the process control agent (PCA) and pre-milling on the extension of solid solubility of 7 wt.% Cr in Cu by mechanical alloying in a high energy ball mill was investigated. The structural evolution and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The solid solution formation at different conditions was analyzed by copper lattice parameter change during the milling process. It was found that both the presence of PCA and pre-milling of Cr powder lead to faster dissolution of Cr. The mean crystallite size was also calculated and showed to be about 10 nm after 80 hours of milling.

Nanocomposite fiber materials, particularly those constructed with uniform reinforcements, have been sought for a long time in materials science. The hoped-for enhancement of the properties of polymer–nanofiber composites have remained elusive, owing in part to the difficulties in performing mechanical measurements. Harnessing the strength of atomic force spectroscopy therefore offers a new handle for the measurement of mechanical properties such as elastic modulus. The paper, here, addresses distance dependent measurements (DDM) performed on the multi-walled carbon nanofiber (CNF) reinforced composite fibers. To quantitatively measure the elastic modulus of nanocomposite materials, measurements were carried out on different points on the surface of the sample and Force-Distance curves were then plotted. The obtained results fairly agree to previously measured values. The great improvement in elastic modulus was achieved without sacrificing the mechanical strength and stiffness of the polymer, and with minimal weight penalty.

In spite of attractive bioactivity of bioactive ceramics i.e. hydroxyapatite and bioactive glasses, their poor mechanical properties have restricted their clinical applications. To overcome these limitations, an alternative approach suggested is preparation a composite including these bioactive ceramics with others. It is expected that a ceramic reinforcement with reduced grain size below 100 nm promotes theirs. The aim of this work was fabrication and characterization of hydroxyapatite-forsterite-bioglass composite nanopowder. Novel hydroxyapatite-forsterite-bioglass composite nanopowder was synthesized by incorporation of the forsterite and bioactive glass in hydroxyapatite matrix via a sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fourier transform infrared (FTIR) spectroscopy techniques were utilized in order to evaluate the phase composition, agglomerates size distribution, morphology and particle size and functional groups of synthesized. The effects of sintering temperature and time were also investigated. Results showed that the appropriate temperature for calcination was 600°C and the particle size of composite nanopowder was about 60-70nm. The decomposition of hydroxyapatite was increased with the increase of the sintering temperature and sintering time. Obtained results indicate that prepared composite nanopowder could be a good candidate for medical applications.

Barium hexaferrite (BaFe₁₂O₁₉) is a hard magnetic ceramic with superior magnetic properties and in powder form has potential for application in high density recording media. In this research a mechano-chemical approach was applied in order to achieve a nano-structured magnetic composite. Graphite was used to reduce barium hexaferrite in mechanical milling medium under argon atmosphere. Milling was carried out with a ball to powder mass ratio of 35 and rotation speed of 300 rpm. Effects of milling time on phase composition and morphology of the samples were evaluated by XRD and SEM techniques, respectively.

XRD results revealed that after 20 hours of milling, nano-composite of BaFe₁₂O₁₉/Fe₃O₄/Fe₂O₃ was obtained. By extending the milling time to 40 hours, FeO was detected as the dominant crystalline phase with crystallite size of 22 nm. Composite of Fe/FeO/Fe₃O₄ was synthesized by controlled heat treatment of the 40 hours milled sample. SEM results revealed that particle size in the aforementioned heat treated composite sample reached to about 89 nm and the morphology of the samples changed slightly.

In this paper, carbon nanotube (CNT)- polyaniline (PANI) nanocomposites were developed from in situ polymerization of aniline. The CNT can be prepared by either acid treatment of CNTs suspension by grafting functional groups to CNTs surface. In this study, CNT and acid treatment CNT was used for preparation of nanocomposite. The PANI-CNT nanocomposite was characterized by FTIR, SEM. CNT can be prepared by either acid treatment of CNTs suspension to make them ionized or by grafting functional groups to CNTs surface. In addition, the electrochemical measurements such as cyclic voltametric (CV) curves showed that the conductivity of the obtained nanocomposite increased. Therefore, the supercapacitors behavior of polyaniline improves with adding CNT especially with acid treatment CNT.

In this research, the melt blending technique was used to prepare various polypropylene (PP) based nanocomposites containing 1,3,5,7 wt% montmorillonite (MMT). A commercial organoclay (denoted K-10) served as the filler for PP matrix and the polypropylene grafted maleic anhydride (PP-g-MA) was used as compatibalizer. The morphology of the nanocomposites was studied by X-ray diffraction (XRD), results of which showed that the nanocomposites are best described as intercalated-exfoliated systems. PP/MMT nanocomposites showed good thermal stability in the TGA analysis. Introducion of ~ 3% MMT in the nanocomposites increased the onset temperature of the degradation by 27.5 °C compared to that of pure PP. Test results showed that PP/clay nanocomposites had an enhanced tensile strength, hardness and decreased wear rates.

In order to translate the superior properties of carbon nanofibers (CNFs) to macro-scale structures, an electrospinning route capable of placing CNFs into a continuous nano-scale composite fibril is introduced. In this work, composite fibers were produced by electrospinning solution of polyacrylonitrile (PAN) with carbon nanofibers dispersed in dimethylformamide (DMF), which is an effective solvent for carbon nanofibers. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) demonstrated rough and globular surfaces on the CNF containing fibers. Raman spectra confirmed the presence of CNFs in the polymer fibers prepared employing the electrospinning method. Raman observation served as the direct evidence of successful filling of PAN fibers with CNFs and complemented the results obtained by SEM and AFM studies.

In this study Al₂O₃-SiC nanocomposites have been fabricated by mixing of alumina and silicon carbide nano powders, followed by hot pressing at 1700°C. The mechanical properties and fracture mode of Al₂O₃-SiC nanocomposites containing different volume fractions (5, 10 and 15%) of nano scale SiC particles were investigated and compared with those of alumina. Al₂O₃-SiC powders were prepared by planetary milling in isopropanol. Fracture mode of specimens was investigated by means of scanning electron microscopy. Nanocomposites were tougher than alumina when they were hot pressed at the same temperature, and the values of nanocomposite's flexural strength and hardness were higher than those of alumina. Flexural strength, hardness and fracture toughness of the nanocomposites increase by increasing the volume percent of SiC up to 10% and then decrease slightly. The Scanning electron microscopy observations showed that fracture mode changes from intergranular for alumina to transgranular for nanocomposites. Finally X-ray diffraction analysis couldn't detect any chemical reactions between Al₂O₃ and SiC particles.

In the water-in-oil (W/O) microemulsions based on anionic (AOT) surfactants, the ω value (molar ratio of water to surfactant), precursor, and surfactant could remarkably affect the synthesis of CuO-ZrO₂ nanocomposite and the morphologies of the sol-gel products simultaneously. In this study, CuO-ZrO₂ nanoparticles are synthesized using microreactors made of surfactant/water/n-hexane microemulsions and discusses the effect of different microemulsion variables on the particle size and particle size distribution by water-to-surfactant molar ratio. The obtained powders are characterized by DTA, XRD, SEM, EDS, and TEM and their physical properties are compared. For AOT surfactant the particle size increased with increasing the water to surfactant molar ratio. The particles size of CuO-ZrO₂ nanocomposite in sample with anionic surfactant with molar ratio of 6 that calcined at 600°C is between 15-20 nm.

Small amount of MgO in the range of ppm and distribution of SiC particles in Al₂O₃-10vol%SiC nanocomposite has an obvious effect on improving of density and mechanical properties such as hardness of sintered nanocomposite. Improving of these properties continues to 1000 ppm of MgO, but decreases above this amount. Transgranularly fractured alumina grains were observed on the fracture surface of this kind of nanocomposites. The effects of such a small amount of MgO on the sintering and microstructural development of Al₂O₃-10vol%SiC nanocomposite may be explained using the arguments which have been documented for the beneficial effects of a small amount of MgO in alumina ceramics. In Al₂O₃-10vol%SiC nanocomposite, Al₂O₃ particles were coated by nano scale SiC particles which inhibited the abnormal grain growth of Al₂O₃.

Two kinds of tungsten-copper composites with the composition of 85%W-15%Cu were synthesized using mechanochemically produced nano size and conventional micro size powders. The densification, mechanical and electrical properties of these composites was examined. It was found that the samples sintered from nanopowders had more densities and better physical and mechanical properties than those produced from micro sized powders. The micro W-Cu powder mixtures were pressed to 60 percent of its theoretical density but the nano composite powders were difficult to press due to its high friction energy and only reached to 30 percent of its theoretical density. The highest densities were obtained from nano composite mixtures at 1200°C.

In this investigation, TiN/TiB₂/TiAl nano-composite powder was produced by mechanical alloying technique and subsequent heat treatment. A powder mixture of Ti, BN, and Al with a molar ratio of 4:2:1 was milled for up to 70 h. Microstructures were studied and characterized using X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. The results indicated that TiN and TiB₂-based phases were formed in an amorphous Ti (Al) matrix after 30 h of ball milling. With progression of the milling, the amorphous Ti (Al) solid solution is partially crystallized and the particle size reduced significantly. Subsequent annealing of the milled product at 600 °C for 0.5 h resulted in the transformation of the unstable amorphous Ti (Al) to TiAl crystal structure and formation of TiN/TiB₂/TiAl nano-composite powder.

Gas atomized Al (6061) powder particles were used to synthesize nano-structured Al based composite powders reinforced with 2 and 5wt.% of nano and micro sized boron carbide particles by mechanical alloying. These composite powders as well as the un-reinforced Al powders were compacted by cold uniaxial pressing. In order to investigate the effect of consolidation procedures on the properties of the resultant Al-B₄C composites, a number of the samples were subjected to sintering at 620 °C for 2h while the others were hot extruded at 520 °C with the extrusion ratio of 8:1. The effect of percentage and size of B₄C on the density, hardness and mechanical properties (such as yield strength, compression strength) of the composites were evaluated and compared with those of the un-reinforced alloy. The fractured surfaces of the samples were studied by scanning electron microscopy (SEM). The results of the present study revealed a higher hardness for the extruded samples as compared with their sintered counterparts attributable to their increased density and decreased matrix grain size. It was also shown that addition of 2 and 5wt.% of B₄C nano-particles increased yield strength of the extruded samples by 3 and 4 times respectively as compared with the un-reinforced aluminum.

In this study, titanium diboride (TiB₂) with silicon carbaid (SiC) nano particles as a sintering aid was isostatic-pressed, then sintered at a temperature of 1800°C. The amount of SiC had a significant influence on the sinterability and mechanical properties of TiB₂. When a small amount (10 wt%) of SiC was added, SiC reacted with titania (TiO₂) that was present on the surface of TiB₂ powder to form titanium carbaid (TiC) and amorphous silica (SiO₂). Elimination of TiO₂ suppressed the grain growth effectively, which led to an improvement in the densification of TiB₂. Vickers hardness was enhanced remarkably through these improvements in the sinterability and microstructure. On the other hand, when a large amount (≥10 wt%) of SiC was added, the density and hardness were not improved much, presumably because of the extensive formation of SiC phase at the grain boundaries.

The objective of the present investigation was to evaluate the microstructural and mechanical properties of Al/nano MgO composite prepared via powder metallurgy method. Pure atomized aluminum powder with an average particle size of 1μm and MgO particulate with an average particle size between 60 to 80 nm were used. Composites containing 1.5, 2.5 and 5 percent of volume fraction of MgO were prepared by powder metallurgy method. The specimens were pressed by Cold Isostatic Press machine (CIP), subsequently were sintered at 575, 600 and 625°C. After sintering and preparing the samples, mechanical properties were measured. The results of microstructure, compression and hardness tests indicated that addition of MgO particulates to aluminum matrix composites improves the mechanical properties.

Ni-Co/SiC nano-composites were prepared by electrodeposition in modified watts bath. The average size of SiC particles was 50 nm. In this study the effect of nano-particle incorporation, Co²⁺ and saccharin concentration in electroplating bath on morphology and mechanical properties of Ni-Co/SiC nano-composites were investigated. The electrodeposits were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Vickers micro-hardness and tensile tests. The results indicate that an increase in Co²⁺ and saccharin concentration in electrolyte lead to a decrease in size of SiC agglomerates and grain size refining of matrix and improvement in mechanical properties. The hardness, tensile and yield strengths of the nano-composite material with nano-structure matrixes were higher than those for microcrystalline ones.

In this study, TiO₂/PAN-based fibers were prepared by electrospinning a composite solution containing both the desirable contents of TiO₂ and a 10 wt. % PAN polymer solution dissolved in N, N-dimethylformamide. The TiO₂ loaded electrospun PAN nanofibers were then carbonized at 1000 °C in N₂ atmosphere furnace after stabilization at 230 °C in air. Then CNF/TiO₂ nanofibers were oxidized at 450 °C in air. The morphology and structure of the TiO₂-embeded carbon nanofibers were investigated by SEM and Raman spectroscopy. Specific surface area was determined using BET equation from N₂ adsorption analysis. Photocatalytic tests were conducted in a UV illuminated set-up specialized for the filters using ethanol vapor. The results have shown that ethanol vapor was efficiently degraded on TiO₂/CNF composite nanofiber mat under UV illumination. The aim of this study was to further investigate the feasibility of TiO₂/ACF for practical indoor air purification.

One of the most important objectives in the field of biomaterials science and engineering is development of new materials as bone substitutes. Silica (SiO₂) has an important role in the biomineralization and biological responses. The aim of this research was to prepare and characterize hydroxyapatite-silica (HA-SiO₂) composite nanopowder with different content of silica. Hydroxyapatite-silica composite nanopowders with 20 and 40 wt% silica were prepared using a sol–gel method at 600°C with phosphoric pentoxide and calcium nitrate tetrahydrate as a source of hydroxyapatite; also, tetraethylorthosilicate and methyltriethoxisilane as a source of silica. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for characterization and evaluation of the products. The results indicated the presence of nanocrystalline hydroxyapatite phase beside amorphous silica phase in prepared composite nanopowders. Moreover, by increasing the content of silica in composite nanopowders, the crystallinity will be decreased,and the ability of the product as a bone substitute material might be controlled by changing the content of the ingredients and subsequently its structure.

In this study effect of adding various process control agents (PCAs) to powder mixtures of Al and TiO₂ which are mechanically activated so as to form TiAl-Al₂O₃ nano-composite have been investigated. Phase constitutions and morphology of the milled powders were evaluated by XRD and SEM techniques, respectively. The mean crystallite sizes of the milled powders were calculated by Cauchy-Gaussian method. Thermal behavior of the milled powders was also studied by DTA to investigate formation of the final phases. The results showed that the mean crystallite size of the milled powders in the presence of PCAs was smaller than that of the sample milled without PCA addition. DTA traces showed that addition of PCAs retards the reduction of TiO₂ by Al. In samples milled in presence of PCA, the reductive reaction generally took place after melting of Al particles whereas the sample milled without PCA addition showed an opposite behavior. Also, in comparison with the sample milled with no PCA addition, in other samples the reductive reaction took place at relatively lower temperatures.

A reciprocating extrusion process was used to produce graphite and alumina reinforced pure aluminium composite. The graphite particles (0~5vol%), alumina particles (10 vol%) and pure aluminium particles (balanced) were dehydrated separately at 70°C in vacuum for 3 hours, and then mixed together. A round billet with 50 mm in diameter was prepared by hot pressing at 350°C with the mixed particles and then extruded to a fully-consolidated goblet-like sample at 480°C and 430MPa by reciprocating extrusion. The results showed that all reinforced particles were refined and uniformly distributed in the matrix by reciprocation extrusion severe plastic deformation. The presence of graphite particles caused the reduction in the friction coefficient and wear rate of the Gr/Al₂O₃/Al composite. Compared with the composite prepared only by alumina particles (10 vol%) and pure aluminium particles, the friction coefficient and wear rate of the Gr/Al₂O₃/Al composite, which contains 5vol% graphite and 10vol% alumina particles, decreased 45.3% and 33.5%, respectively, and thereafter it displays an excellent combination of low friction coefficient (0.37) and wear rate (2.2×10^-7mm³/(N.m)), and appears to be more promising.

In this research, the simultaneous growth of Al₃Ni₂ and Al₃Ni on nanocrystalline nickel was investigated. Nanocrystalline nickel samples with mean grain size of about 25 nm were prepared by direct current electroplating. The samples were aluminized for different durations by pack cementation method at 500, 550 and 600 °C. The aluminide phases were identified by SEM, EDS and XRD. In contrast to reported results suggesting the formation single layer of Al₃Ni₂ phase on coarse grained nickel, it was observed that long time aluminizing of nanocrystalline nickel resulted in the formation and simultaneous growth of two distinct layers of Al₃Ni₂ and Al₃Ni phases. The growth of both phases followed the parabolic growth kinetics, but the growth rate constant of Al₃Ni₂ was much greater than Al₃Ni layer. Also, the simultaneous growth of Al₃Ni₂ and Al₃Ni was modeled. Based on this model, the activation energy of the coating growth (total Al₃Ni₂ and Al₃Ni layers) was determined as about of 178 kJ/mol.

TiO₂ thin film was deposited by a DC reactive magnetron sputtering on ZnO/soda-lime glass substrate and single crystal SiO₂ below 200 °C. ZnO layer was used as a buffer layer. Deposition was performed at Ar + O₂ gas mixture with a pressure of 1.0 Pa and oxygen with a constant pressure of 0.2 Pa. The TiO₂ / ZnO thicknesses were approximately 1000 nm and 80 nm, respectively. As-deposited films were annealed at 400 °C. The structure and morphology of deposited layers were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The transmittance of the films was measured using ultraviolet–visible light (UV–vis) spectrophotometer. Photocatalytic activities of the samples were evaluated by the degradation of 2-propanol. The microstructure of annealed films was anatase, having improved photocatalytic activity. The surface grain size of TiO₂ thin film after annealing was found about 25-35 nm and crystal size was approximately 8 nm. By using ZnO thin film as buffer layer, the photocatalytic property of TiO₂ films was improved.

High solar absorber coatings of Ni-P on aluminum substrate have been fabricated by electroless technique as an alternative to complex PVD coatings. For this purpose, the Ni-P coating was deposited on commercially pure aluminum and then blacking process was carried out. Upon heat treatment, the amorphous structure of the coatings transformed to a nanocrystalline structure which is accompanied by variation in properties. The phase structure of the coatings was studied by X-ray diffraction; the crystallite size measured by using Sherrer method indicated an average crystallite size of about 15 nm with an increase in hardness. Morphological studies of coatings were performed by scanning electron microscopy. The coatings generally had a sound, crack-free surface with a thickness value of around 10μm. The optical properties of the coatings were determined by means of spectrophotometer. The black electroless nickel possessed higher absorption in the range of visible light, with a coefficient in the order of 0.98. The results of this study indicate that the coating process described herein is suitable as solar absorber coating.

Nanoscale multilayers of Cr-Ni coatings were deposited on low carbon steel by pulse electroplating and agitation modulation in chromium (III)-nickel (II) bath. The coatings were characterized by using SEM, EDS, XRD and microhardness techniques. For hardness measurement, the total thickness of the coatings was fixed at 5 μm and the thickness of the monolayers in the coatings varied from 20 to 100 nm. Single chromium and single nickel coatings with similar thickness of 5 μm were also produced by using DC electroplating. Microhardness testing was carried out on the surface of the coatings by using a range of loads from 25 to 1000 gf. A composite hardness model was used to estimate and compare the hardness of the single and multilayer coatings. It was shown that multilayer deposition significantly increases the hardness of the coating and the hardness increases further as the thickness of the nano- monolayers is reduced.

Electron Beam-Physical Vapor Deposition (EB-PVD) is being used in coating component for many applications such as electronic industry for producing nanostructures and ICs coatings. In this work, nanostructured copper was deposited on glass using EB-PVD technique. Surface and elemental characteristics of EB-PVD coatings investigated and evidenced corrosion resistance of nanostructured coatings produced by this technique are higher than Cu sheet in chloride media.

Effects of sodium citrate dosage and current density on composition and phase structure of nanocrystalline CoFe thin films were systematically studied. Energy dispersive spectroscopy (EDS) showed when sodium citrate dosage in the bath was less than 10 g/L, with increasing citrate in the bath, iron content in the deposited films remarkably decreased. However, sodium citrate dosage more than 20 g/L had no effect on composition of the deposited films. In low current densities, cobalt content decreases and iron content increases, as the current density increases. The current density of 15 ma/cm² could be considered as alloy limiting current density. The XRD analyses showed that only BCC and/or FCC formed in the deposited films and average grain size, estimated by Scherrer formula, were below 55 nm. The results indicated that phase formation in the electrodeposition of CoFe deviated from equilibrium conditions and was controlled by kinetic conditions. The lattice constants for BCC and FCC phases in CoFe films were close to those of BCC iron and FCC cobalt, respectively.

Multi-walled carbon nanotubes films formed randomly aligned laterally by electrophoresis. Multi-walled carbon nanotubes with lengths of about 10 μ was shortened and functionalized by a mixture of sulfuric and nitric acid. The functional groups on carbon nanotubes were elaborated by FT-IR. Chemically shortened MWCNTs disperse in organic and aqueous solvent and deposited on electrode vertically-aligned by applying a constant DC electric field. The alignment of MWCNTs was observed by scanning electron microscopy. It also the effect of various substrates on alignment of multi-walled carbon nanotubes was investigated.

The microstructures of nanocrystalline CoFeNi thin films in direct current electrodeposition, under various processing conditions, have comparatively been investigated. Morphological studies by SEM showed that CoFeNi films plated from the sodium citrate-added baths were more uniform and denser than those deposited from the conventional citrate-free baths. Energy dispersive spectroscopy (EDS) showed the anomalous behaviors in electrodeposition of CoFeNi films from both citrate-added and citrate-free baths. It was also noticed that addition of 10g/L sodium citrate in the bath strongly decreases the iron content and increases nickel contents of the deposit. Addition of citrate up to 50g/L in the bath has reverse effect on the film composition. Further addition of sodium citrate appears to have no or little effect on the film composition. Addition of sodium citrate to the bath has no significant affect on the cobalt content of the deposit. XRD analyses showed that all CoFeNi films were nanocrystalline and their average grain sizes, estimated by Scherrer formula, were below 80nm. It was also noticed that FCC and BCC phases could be co-deposited in electroplated CoFeNi films by controlling the bath composition and/or the plating conditions.

Conventional and nanostructured zirconia coatings were deposited on In-738 Ni super alloy by atmospheric plasma spray technique. The hot corrosion resistance of the coatings was measured at 1050°C using an atmospheric electrical furnace and a fused mixture of vanadium pent oxide and sodium sulfate respectively. According to the experimental results nanostructured coatings showed a better hot corrosion resistance than conventional ones. The improved hot corrosion resistance could be explained by the change of structure to a dense and more packed structure in the nanocoating. The evaluation of mechanical properties by nano indentation method showed the hardness (H) and elastic modulus (E) of the YSZ coating increased substantially after hot corrosion.

Titanium carbide (TiC) is a widely used hard coating to improve the wear resistance and lifetime of tools because of its outstanding properties such as high melting point, high hardness, corrosion resistance and abrasion resistance. These properties were drastically improved by using nanotechnology. So in this project, TiC_x was applied on hot-working die steel (H11) by Plasma CVD (PACVD). The effect of operating temperatures on TiC_x structure properties have been studies by typical and advanced analyses methods such as SEM, XRD, FTIR and Raman. The best properties of TiC_x nanoparticle, such as nanostructure, mechanical properties and chemical properties, were obtained at 480 °C.

Electrodeposition of nano-structured Cr-WC had been carried out from a trivalent chromium bath using a square shaped pulse current. The average size of WC particles was 70 nm. The effect of sodium saccharin and sodium dodecyl sulfate (SDS) additives as well as pulse electroplating parameters such as current density, duty cycle and frequency on the amount of incorporated WC particles and morphology of the coatings was investigated. The structure and morphology of the coatings were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. In addition, the hardness and tribological behavior of the coatings were investigated by microhardness and pin on disk methods, respectively. The results showed that although the addition of saccharin and SDS decreased the amount of WC particles in the coating, but reduced the size of WC agglomerates which, in turn, increased the wear resistance of the coatings. Also, the optimum wear resistance was achieved at the current density of 8 A/dm², duty cycle of 50% and frequency of 10 Hz.

In this research Sr-hexaferrite powder was synthesized by a sol–gel auto-combustion route using two different fuels (glycine and citric acid) and two different basic agents (ammonia and trimethylamine). N-decyltrimethylammonium bromide (C₁₃H₃₀BrN) was also employed as a cationic surfactant. The results showed the finest crystallite size and the lowest calcination temperature have been obtained as 27.2 nm and 800 °C respectively, in the presence of citric acid, trimethylamine and surfactant.

In this research the influence of dynamic CH₄ heat treatment on Sr-hexaferrite has been investigated. With the gas heat treatment, the phase composition, particles size and the morphology of Sr-hexaferrite change significantly. Due to this, the hard magnetic nature of the material changes from hard to soft.

The strontium hexaferrite powder was prepared by conventional route with calcination of the mixture of strontium carbonate and hematite at 1100°C for 1 hour. Then the resultant Sr-hexaferrite was isothermally heat treated in methane dynamic atmosphere at various temperatures and gas flows for different times. The rate of heating and cooling were 10°C/min. The optimum conditions were obtained at 950°C and 15CC/min flow for 0.5 hour.

The effects of gas heat treatment on the phase composition and the particles size and morphology were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibration Sample Magnetometery (VSM) techniques.

The results show the decomposition of Sr-hexaferrite and reduction of the resultant hematite mainly to iron. The crystallite size of the resultant iron was also measured below 50nm.

BaM thin films have been synthesized by dispersing the dried gel nano powders prepared by Sol-Gel method. The solution was made by dissolving iron nitrate Fe(NO₃).9H₂O, barium nitrate Ba(NO₃)₂ and citric acid in deyonized water and methanol. This sol was slowly evaporated until a dried gel was formed. This dried gel was then added to ethylene glycol. The final solution was vigorously shaken and mixed in ultrasonic cleaner for 30 min to disperse particles sufficiently. Then the prepared solution spin coated on Si(110) substrate. The obtained thin films were dried at 120 °C and then calcined at 900 °C for 1 h. The films were characterized using X-ray diffraction (XRD) and vibrating sample magnetometer (VSM).

In this research SrFe₁₂O₁₉ nanocrystalline synthesized by sol-gel auto-combustion method and subsequent annealing at 1000°C for 1h subjected to mechanochemical treatment in a high-energy ball mill and then re-annealing. A planetary ball mill (Fritsch Pulveristte 6) was used to mill the strontium hexaferrite powder at 300 rpm in air for 10, 20 and 40 hours. The process was studied by X-ray diffraction technique and scanning electron microscopy. The X-ray study showed that SrFe₁₂O₁₉ phase was decomposed by milling. Strontium hexaferrite and α-Fe₂O₃ were obtained with 10 hours milling. There were α-Fe₂O₃ and strontium hexaferrite in XRD patterns of 20 hours milled sample. With increasing of the milling time to 40 hours, strontium hexaferrite was decomposed completely. The annealing of the 20 and 40 h milled powders at 900°C for 1h led to the formation of single phase strontium hexaferrite with smaller crystallite size compare to that of the hexaferrite powder before milling and subsequent annealing.

Higher environmental standards have made the removal of toxic metals such as hexavalent chromium from wastewater; an important problem for environmental protection. Iron oxide is a particularly interesting adsorbent to be considered for this application.

In this study, a new method combining adsorption and magnetic separation was developed to remove Cr(VI) from wastewater. The nanocrystalline magnetite as adsorbent was produced via thermo- mechanical reduction of hematite. Various parameters which affect the adsorption of Cr(VI) such as time, pH, temperature and initial concentration were investigated using thermo-gravimeters (TG), X-Ray diffraction (XRD), scanning electron microscopy (SEM) and atomic adsorption spectroscopy (AAS) techniques. The maximum adsorption was occurred at pH 2. The adsorption data were fitted well to Langmuir isotherm model. The adsorption of Cr(VI) increased significantly with increasing of temperature and time.

The Active Screen Plasma Nitriding (ASPN) treatment of Fe_73.5Si_13.5B₉Nb₃Cu₁ alloy was investigated for 3 h at 480 °C and 560 °C in various N₂-H₂ gas mixtures at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum at the same time and temperatures. The samples were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Microhardness measurements and Vibrating Sample Magnetometer (VSM). It was observed that the ASPN treatment leads to finer grain size and higher crystalline volume fraction and modifies the structural features of Fe(Si) phase. The Fe(Si) lattice parameter for the nitrided samples was higher than that for the annealed samples due to the diffusion of nitrogen into the Fe(Si) phase and the formation of Si-N precipitates. In ASPN treatment, the lowest magnitude of coercivity and the maximum saturated magnetization were obtained at 480 °C and 560 °C, respectively, in75% H₂-25% N₂ gas mixture. ASPN treatment increased the microhardness of the samples.

The effects of grain size reduction on the corrosion inhibition of sodium nitrite were investigated using polarization curves and electrochemical impedance spectroscopy (EIS). Nanocrystalline iron (~ 45 nm) was produced by pulse electrodeposition using citric acid bath. The grain size of a nanocrystalline surface was analyzed by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM). The most intensive first-order peak (211) of the XRD patterns was taken for detailed analysis using a Gaussian fitting curve. The tests were carried out in 25 mg/lNaCl + 57 mg/lNa₂SO₄ with different concentration of sodium nitrite aqueous solutions.

The results revealed that due to the adsorption process which leads to the formation of a protective layer with a greater charge transfer resistance the inhibition effect and corrosion protection of sodium nitrite inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to nanocrystalline. The standard free energy of adsorption (ΔG_ads) revealed a strong interaction between inhibitor and nanocrystalline surface. This was attributed to the increased number of the active sites caused by nanocrystalline surface.

The ceramic lead zirconate titanate (PZT) films near the morphotropic phase boundary are successfully integrated into MEMS devices, especially for applications in microsensors and actuators. The ferro/piezo electric properties of PZT thick films are widely dependent on its surface quality and crystallographic orientation growth. This paper indicates the influences of platinum bottom electrode on the surface and crystallographic properties of PZT. Ti (10nm) and Pt (100nm) thin films have been deposited on silicon substrate by thermal evaporation and electron beam respectively without vacuum breaking. After annealing treatment, the Pt film exhibited (111) preferred orientation. Finally one micron thick PZT (54/46) film was deposited by a RF magnetron sputtering at room temperature in pure Argon followed by a conventional post annealing treatment on silicon substrate. The XRD measurements have shown the provskite structure of PZT films with (100) preferred orientation at annealing temperatures above 600°C and (111) preferred orientation above 650°c. The SEM results demonstrate that whatever the annealing temperature is increased, recrystallization grains and black holes on Pt surface occurs and cause morphological change of PZT surface. The AFM test shows the strong RMS roughness of platinum surface after annealing temperature at 650°C.

The process of electroless plating Ni-P and Ni-P/nano-SiO₂ on API-5L X65 carbon steels was improved. The Ni-P/nano-SiO₂ composite coatings were prepared from the bathes containing different concentrations of nano-SiO₂ particles. The coatings surface and morphologies were observed via scanning electron microscopy (SEM). The chemical compositions were analyzed by EDAX. The corrosion behaviors were evaluated by electrochemical impedance spectroscopy tests. The experimental results indicated that SiO₂ nano-particles co-deposited but some agglomeration occurred. Micro-hardness of electroless Ni-P-SiO₂ composite coatings increased due to the existence of nano-particles. Corrosion tests showed that both electroless Ni-P and Ni-P/nano-SiO₂ composite coatings demonstrated significant improvement of corrosion resistance of substrate in salty atmosphere and latter coating type appeared to offer a better corrosion protection.

SiC and SiO₂ nano-particles were co-deposited with electroless NiP coating onto API-5L-X65 steel substrates with 7g/L load of nano-particles in the bath at pH 4.6 ± 0.2 and temperature of 90 ± 2°C. The hardness and corrosion resistance of the composite coatings were measured using micro-hardness, polarization and electrochemical impedance spectroscopy techniques, respectively. Moreover, the structure of the composite coatings was investigated by means of X-ray diffraction (XRD) technique, while their morphologies and elemental compositions were analyzed using a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). Results showed that co-deposited nano-particles caused an increase in the hardness of the composite coatings. Corrosion tests showed that addition of nano-SiO₂ particles improved corrosion resistance of electroless Ni-P coatings in salty atmosphere but addition of nano-SiC particles decreased, due to the agglomeration of SiC nano-particles together with an increase in the porosity of the composite coatings.

Carbon and low alloy steels are the most commonly used construction materials for oil and gas pipelines. In order to improve their performance, various types of coatings are frequently applied on them. Electroless nickel composite coatings containing nano-particles are widely used on steel substrates. In this paper, CO₂ corrosion of X70 carbon steel coated with Ni-P and Ni-P-nanoSiO₂ in 3%Wt NaC1 electrolyte, saturated with CO₂ at 85°C and pH 6.5 in 1bar CO₂ pressure for 72 h, was investigated and the results were compared against each other. SEM and XRD techniques were used for investigating the corrosion products morphology and composition, respectively. In addition, the corrosion process was studied using EIS technique. The experimental results showed that the formation of FeCO₃ protective film on coated samples was limited. Moreover, the addition of SiO₂ nano-particles to Ni-P coating improved corrosion resistance of the substrate, which also showed the ability of nano-particle addition to the Ni-P coating in decreasing the corrosion rate.

Electroless composite coatings have been vastly used in various industries during last decades due to their good properties, such as corrosion and wear resistance, hardness and uniform thickness. In this paper, co-deposition of TiO₂ nano-particles with Nickel-Phosphorus electroless coatings on API-5L-X65 steel substrates was investigated. Surface morphology and composition of coatings were studied via SEM and EDX, respectively. XRD analyses showed that these coatings had amorphous structure with TiO₂ crystalline particles. TiO₂ nano-particles increased microhardness of coatings. Corrosion resistance of these coatings was tested using linear polarization in 0.5M sulfuric acid electrolyte. Results showed that NiP-TiO₂ electroless composite coatings increased corrosion resistance of substrates.

Melt spun ribbons of Co₆₄Fe₄Ni₂B₁₉Si₈Cr₃ alloy have been prepared and the nanocrystallization process was carried out by the heat treatment of the as spun ribbons above the crystallization temperature. Structural studies of the samples have been performed by transmission electron microscopy and X-ray diffraction. Magnetic properties of the samples and magnetoimpedance measurements were investigated and it was revealed that magnetic properties and magnetoimpedance of the samples deteriorate by the formation of nanocrystalline phases.