International Journal of Modern Physics B

Mechanical performance parameters such as the fatigue strength, tensile strength, ductility and Young's modulus of newly developed Ti-29Nb-13Ta-4.6Zr, referred to as TNTZ, can be improved considerably by microstructural control via thermomechanical processing. Thermomechanical processing including severe cold wire drawing can generate functionalities such as super elasticity in TNTZ. The abovementioned improvement in the mechanical performance and functionality of TNTZ is associated with its nanosize structure. The cytotoxicity of TNTZ is very low and equivalent to that of pure titanium. It is expected that TNTZ will be used as a structural biomaterial.

A bulky Cu-Zn alloy was multi-directionally forged (MDFed) at 77 K and 300 K up to a cumulative strain of 6.0 at maximum. With increasing strain, the evolved substructure changed gradually to uniform ultra fine grains. The tendency of the microstructural evolution and its mechanism depended strongly on the MDF temperature. Mechanical twins accelerated the finer grain fragmentation by subdivision of the grains and by intersection of the twins themselves due to MDF. Twinning appeared more frequently and uniformly at 77 K than at 300 K. The average grain size obtained at a cumulative strain of 6.0 was about 17 nm at 77 K and 26 nm at 300 K. The evolution of the microstructure accompanied by mechanical twinning is precisely investigated.

A novel approach was used to produce an ultrafine grain structure in low carbon steels with a wide range of hardenability. This included warm deformation of supercooled austenite followed by reheating in the austenite region and cooling (RHA). The ultrafine ferrite structure was independent of steel composition. However, the mechanism of ferrite refinement changed with the steel quench hardenability. In a relatively low hardenable steel, the ultrafine structure was produced through dynamic strain induced transformation, whereas the ferrite refinement was formed by static transformation in steels with high quench hardenability. The use of a model Ni-30Fe austenitic alloy revealed that the deformation temperature has a strong effect on the nature of the intragranular defects. There was a transition temperature below which the cell dislocation structure changed to laminar microbands. It appears that the extreme refinement of ferrite is due to the formation of extensive high angle intragranular defects at these low deformation temperature that then act as sites for static transformation.

Maraging steels are a group of martensitic steels possessing ultra high strength along with good fracture toughness. Conventional 18 wt.% Ni maraging steels are very costly in part because of expensive alloying elements such as Ni and Co. Replacement of Ni by cheaper elements like Mn has been studied by many researchers. Fe–Ni–Mn ternary alloys show good age hardenability formation of nanometer sized intermetallic precipitates such as f.c.t. θ-NiMn during aging. These alloys are ductile in the solution annealed condition but suffer from severe embrittlement after aging by intergranular fracture along prior austenite grain boundaries (PAGBs). 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 of Fe-10Ni-7Mn steel was investigated. Cold rolling for 20%, 40%, 60%, 80% and 90% were carried out on a solution annealed material with subsequent aging at 753 K. Improvements in the tensile properties of the as-deformed and aged alloys were found. Substantial improvement is found at thickness reductions larger than 60%, where severe plastic deformation and ultrafine grain formation are realized.

Creep and superplasticity of the fine-grained Sn-1wt.% Bi alloy, processed by conventional rolling (CNR), cryorolling (CRR) and equal channel angular pressing (ECAP) routes, were investigated by indentation testing at room temperature (T > 0.6T_m). Based on the steady-state power law creep relationship, the stress exponents of 4.1, 2.8 and 2.5 were obtained for the CNR, CRR and ECAP routes, respectively. The corresponding strain rate sensitivity (SRS) indices of 0.24, 0.36 and 0.40, corresponding respectively to the grain sizes of 2.8, 2.1 and 1.2 μm, indicate that the materials processed by ECAP and CRR exhibit superplastic deformation behavior for which, grain boundary sliding is the possible creep mechanism.

This work conducted to investigate the effects of accumulative roll bonding (ARB) method on achieving the ultra-fine grain microstructure in AZ31 alloy. Accordingly, a number of ARB routes at 400°C, applying thickness reductions per pass of 35%, 55%, and 85% were performed. The results indicate that both the final grain size and the degree of bonding have been dictated by the thickness reduction per pass. The larger pass reductions promote a higher degree of bonding. Increasing the total strain stimulates the formation of a more homogeneous ultra fine grain microstructure.

An ultrafine grained (UFG) aluminum sheet was produced using severe plastic deformation (SPD) by a process known as accumulative roll bonding (ARB). Electron Back Scattered Diffraction (EBSD) method and Transmission Electron Microscopy (TEM) were utilized for characterization of the subgrain and grain structures of the processed sheets. The results indicate that different mechanisms at different levels of strain lead to the gradual evolution of ultrafine or nanocrystalline grains. Grain fragmentation as well as the development of subgrains are the major mechanisms at the early stages of ARB. Strain induced transformation of low angle to high angle grain boundaries and formation of a thin lamellar structure occur at the medium level of strain. Finally, the progressive fragmentation of these thin lamellar structures into more equi-axed grains is the dominant mechanism at relatively high strains which results in grain size reduction to submicron scale.

Ultra-fine grained 1100 Al alloy was successfully produced by accumulative roll bonding (ARB) process. TEM investigation and SAD patterns showed that, after eight cycles of ARB, sheets were found to contain ultra-fine grains with high angle grain boundaries. The mechanical properties of the ARB processed (ARBed) 1100 aluminum alloy increased with increasing the number of ARB cycles. The elongation dropped abruptly at the first cycles. Wear properties were investigated using a pin on disk wear machine at ambient environment. Contrary to an expectation, the wear resistance of the ARBed Al alloy was less than the non-processed Al alloy. Morphologies of worn surfaces were studied by scanning electron microscope (SEM).

Nowadays, Severe Plastic Deformation (SPD) methods are at the focus of material researchers and among these methods, Twist Extrusion (TE) is one of promising ones to pave the way of commercialization. In this Investigation the magnitude of strain distribution along 4 selected paths of sample after 3 passes of Twist Extrusion were investigated by computer simulation and its influence on aluminum 1100 microstructure by experimental tests. ABAQUS 6.5 software based on FEM was applied for the former and 70 mm length samples with cross-section of 18*28 mm were exploited for the latter. According to the simulation results, corner, middle of small side, middle of long side and center of the cross-section are placed from maximum to minimum magnitude of strain respectively. Theses achievements were verified with metallographic images in aspect of metal flow and grain size as well.

This work aims to investigate whether accumulative roll bonding (ARB) is an effective grain refinement technique for ultra-low-carbon steel strips containing 0.004% C. For this purpose, a number of ARB processes were performed at 500 °C, with 50% reduction in area of each rolling pass. It was found that both the ultimate grain size achieved, as well as the degree of bonding, depend on number of rolling pass and reduction of area as a whole. The mean grain size was obtained using AFM was about 130nm. The mechanical properties after rolling and cooling were obtained. Also, the fracture surfaces were studied by Scanning Electron Microscopy (SEM). It was concluded that metal's tensile strengths increased by 334% while the ductility dropped from a prerolled value of 50.5% to 2.6%. Effect of wire brushing on samples observed too. It increased on the wire brushed sheet for 7 HV. The rolling process was stopped when cracking of the edges became pronounced.

Recently friction stir processing (FSP) has emerged as an effective tool for enhancing metal properties through microstructure modification. FSP is a solid-state process where the material within the processed zone undergoes intense plastic deformation resulting in dynamically recrystallized grain structure. This research demonstrates the use of FSP for creating ultrafine grained materials through severe plastic deformation. FSP was applied to extruded 6082-T4 aluminum alloy to produce ultrafine grained microstructure with grain sized from 0.5 to 3μm. The hardness of the FS processed 6082 aluminum alloy increased significantly with decreased tool rotation speed.

Friction stir processing (FSP) is a novel technique to produce ultrafine grained materials. Most of the researches conducted on FSP focus on aluminum alloys. Despite the potential weight reduction that can be achieved by using magnesium alloys, a few researches have been reported on FSP of magnesium alloys. In this work, the possibility of using FSP with and without SiC particles to modify the microstructure and hardness of commercial AZ31 is examined. SiC particles were uniformly dispersed into an AZ31 matrix by FSP. The mean grain size of the stir zone with the SiC particles was obviously smaller than the same zone without the SiC particles. SiC reinforced magnesium matrix composites created by FSP with cooling rapidly the plate that exhibit ultrafine grain size approximately 1μm and nearly doubled the hardness of the base material.

The understanding of nanoscale interactions of nuclear materials will help to mastering the complex behavior of actinides and of fission products, and the interfacial behavior of fuel-cladding under extreme conditions. Ultrafine grained and nanostructured engineering materials are also suggested as protective armors on the plasma-facing first wall of D-T fusion power plants. We review the constitution and preparation by arc-melting and ball milling of ultrafine grained materials for the advanced nuclear reactor fuels UC, UC-W, UN, UN-Mo, and UN-W. We report also the preparation of the first wall armour materials nano-W, nano W-Y alloys, nano-graphite, and nano-B₄C by high energy ball milling and their characterization by metallography, XRD, DSC and HRTEM.

Nanocrystalline NiAl powder was prepared by mechanical alloying. The prepared powder was cold compacted and sintered at different temperatures and times. The crystallite size of green and sintered compacts was estimated from X-Ray Diffraction peak profile analysis. Thereafter, the Generalized Parabolic Grain Growth model and Master Sintering Curve concept based on Combined Stage Sintering model were employed to investigate the grain growth and densification behavior of nanocrystalline NiAl powder during sintering, respectively. The results of modeling were in a very good agreement to that of experiment. Finally, by comparing the modeling results the sintering parameters were optimized.

Mechanical alloying by high energy ball milling is a promising method for the production of bulk metallic glasses, amorphous alloys and nanostructured materials. Amorphous alloys reinforced by nanocrystals represent a big step in the optimization of new ultra high strength materials. Nano-scale W-Y solid solutions were synthesized by high energy ball milling. Only 1 at. % oxygen can stabilize the bulk metallic glassy state of Zr₅₄Cu₁₉Ni₈Al₈Si₅Ti₅O₁ to higher T_x and to large supercooled liquid range ΔT_xg.

The TiAl3/Al2O3 metal-ceramic composite was synthesized using high energy ball milling, powder compaction and thermal treatment. Micron sized powders of titanium oxide (TiO2) and aluminum were subjected to high energy ball milling under an argon protected atmosphere. Milling of this powder mixture although reduced crystallites sizes to a nano scale, did not result in a reaction between the reactants. Further compaction of the milled powder and annealing, paved the way to a reduction reaction and led to the formation of an ultrafine grained composite structure. The reaction appeared to proceed through two-steps. Titanium oxide was first reduced to TiO and later on, TiO was reduced to Ti. The resulting Ti was alloyed with extra Al to produce TiAl3 intermetallic in which alumina particles were dispersed. Also, mechanical activation was found to reduce the reaction temperature between Al and TiO2. The morphology and phase composition of the milling products were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.

In the present work the effect of milling time (2-16h), milling speed (320 and 420rpm), as-received aluminum particle size (21 and 71 μm), B₄C size (90, 700 and 1200nm) and its content (5% and 10%) on the characteristics of Al-B₄C powder particles during milling was investigated by scanning electron microscopy (SEM) and laser particle size (LPS) analyzer. X-ray diffraction was used to investigate the crystal size and internal strains within the processed aluminum particles at different conditions. It was concluded that powder particles size increased after 4h milling but further milling (up to 16h) resulted in decreased powder particles size. By increasing milling speed from 320rpm to 420rpm, finer aluminum powder particle sizes were obtained in any specific milling time. XRD results confirmed that nanocrystalline structures with the size of 80nm for aluminum powder particles can be achieved in different milling conditions. SEM micrographs and EDX maps of Al-B₄C mixtures confirmed that milling at optimum conditions breaks the reinforcement particle clusters and a homogenous distribution of B₄C nanoparticles in Al-B₄C powder mixture can be achieved after milling.

High energy ball milling was performed on a mixture of titanium and aluminum elemental powders with a composition of Ti-48(at.%)Al. Stearic acid was added to this powder mixture as a process control agent (PCA) to study its effect on the microstructure evolution and crystallite size of the milled powder after various milling times. Phase compositions and morphology of the milled powders were evaluated using X-ray diffraction and scanning electron microscopy. Crystallite sizes of milled powders were determined by Cauchy-Gaussian approach using XRD profiles. It was shown that addition of 1wt.% of stearic acid not only minimizes the adhesion of milling product to the vial and balls, but also reduces its crystallite sizes. It has also a marked effect on the morphology of the final product.

The effects of mechanical alloying on the microstructure of binary and ternary powder mixtures with stoichiometric compositions of Mg₂Ni and Mg₂Ni_0.75Nb_0.25 were studied, respectively. Also, the electrode properties of the milled products were investigated in 6M KOH solution. X-ray diffraction and scanning electron microscopy of the milled products showed the formation of Mg₂Ni-based nanocrystallites after 15 and 10h of milling using the initial binary and ternary mixtures, respectively. It was found that partial substitution of Nb for Ni has beneficial effect on the formation kinetic of nanocrystalline Mg₂Ni. Longer milling times resulted in the formation of an amorphous phase. A relatively high discharge capacity of 350mAhg^-1 was measured for the electrode made up of the ternary milled product after 20h. Also, the ternary milled product showed longer discharge life. This ternary electrode showed a microstructure consisting of Mg₂Ni nanocrystallites and an amorphous phase. Nb substitution for Ni was found to be beneficial to electrode properties of the milled products.

Nano-sized mullite was synthesized by mechano-chemical, sol-gel/milling, process. Aluminum nitrate and tetraethyl ortho silicate were used as precursors to prepare the single phase gel. The prepared gel was subjected to intense mechanical activation using a planetary ball mill prior to annealing. DTA/TGA results showed that mullitization temperature significantly decreases due to mechanical activation as mullite starts to form at 1094°C in unmilled sample whereas intermediate milling for 20 hours decreases this temperature to 988°C. Also, mullite formation occurs at 1021 and 1003°C for samples milled for 5 and 10 hours, respectively. SEM results showed that the morphology of the products was altered by the intermediate mechanical activation. Calculation of the mullite crystallite sizes indicated that they were indeed in nano scale and this result was confirmed by TEM investigations which shows the mean crystallite size of 70 nm.

Titanium dioxide nanoparticles have great potential for use in photocatalytic applications, cosmetics, white pigments and so on. In this paper, the effect of milling time on particle size, morphology and phase composition of TiO₂ nanoparticles, prepared by mechanochemical method, was investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). TiO₂ nanoparticles were prepared by the use of high energy ball milling of titanyl sulphate (TiOSO₄) and NaCl powders as the starting mixture in different milling durations. The milled powder was annealed at 700°C for 30 min. The NaCl powder, used as the diluent phase, was removed by washing the annealed powder with distilled water. It was found that with increasing milling time, decrease in the size of equiaxed spherical particles and increase in temperature of anatase to rutile transformation (A → R) can be observed.

Nanocrystalline Cu particles were prepared by mechanochemical reduction of cuprite (CU₂O) with graphite in a high-energy ball mill. In order to gain an understanding into the possible mechanisms, the kinetic of the process was investigated using Johnson-Mehl-Avrami (JMA) model. It can be seen that theoretical calculation agrees well with experimental data. It was found that the most important effect of mechanical activation is the formation of the lattice defects and grain boundaries in addition to activated fresh surface areas during milling, which promote the reduction process. The Cu nanopowder was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM results showed the nano-structure nature of the product processed under the synthesis conditions; the crystallite size was measured almost 30 nm in the 30 h milled powders.

NiTi intermetallic with nanocrystalline structure was produced by mechanical alloying of the elemental powders and the effect of subsequent heat treatment was investigated. The products were characterized using X-ray diffraction and microhardness measurements. The results showed that after 60 h of mechanical alloying, disordered B2-NiTi phase can be obtained as a metastable phase at room temperature with grain size of 25 nm, lattice strain and high microhardness of 1.2% and 922 HV, respectively.

After heat treatment, disordered structure transformed to ordered NiTi and a small amount of NiTi2 and Ni3Ti phases. The long range order parameters of nanocrystalline NiTi were obtained to be 0.63 and 0.94 after annealing for 30 and 60 mins respectively. After 30 mins of heat treatment, 81.5% of Ni (or Ti) atoms were on the right sites and after 60 mins it increased to 97%. Grain growth and decrease of microhardness and lattice strain were also observed after heat treatment. After 60 mins of heat treatment the grain size, lattice strain and microhardness of NiTi were 95, 0.09 and 624 HV respectively.

A new category of hard nanocomposite coatings with adjustable improved hardness or enhanced toughness consisting of nanocrystalline (nc-) titanium nitride grains embedded in an amorphous (a-) metallic intergranular nickel phase i.e. nc-TiN/a-Ni type has been produced and investigated. Coatings were deposited at 573K on different substrates using a reactive dual ion beam sputtering (RDIBS) technique. A composite Ti-Ni target was sputtered with 1.2 keV Ar⁺ ions and the growing films were bombarded with a mixture of 50 eV Ar⁺+N²⁺+N⁺ ions. XRD, nanoindentation, high load indentation and pin-on-disk tests were used to characterize structural and mechanical properties. By adjusting Ni content enhanced hardness or toughness is obtained with an important improvement in wear resistance corresponding to the coatings exhibiting the highest toughness than highest hardness.

In this study, titanium dioxide nano powders were electrophoretically deposited on the stainless steel in Isopropanol and Triethanolamine as a solvent and dispersant, respectively. The effects of deposition parameters including deposition voltage (5 to 20 V) and deposition time (5 to 60 s) on the microstructure and surface topography were examined by scanning electron microscope (SEM) and scanning probe microscope (SPM), respectively. In addition, the effects of these deposition parameters on packing density were investigated. This research revealed that substrate surface is fully covered with increasing deposition voltage and deposition time. Therefore packing density of deposited films is strongly dependent on the deposition parameters and reached its highest value at 20 V and 60 s. In addition, results show that surface roughness is increased by increasing the deposition voltage and deposition time.

Electrolytic Plasma nitrocarburizing was carried out on the hard chromium coating deposited in SM45C mild carbon steel substrate by electroplating in two different times and voltages. The electroplated samples were connected cathodically to a high-current pulsed power supply and biased with a negative voltage of 400 V. The treatment times were 5 and 60 minutes. A 5-μm thick layer was formed on the surface of Cr coating with microhardness of about 950- 1200 HV0.1. The microstructure of the treated layers depends strongly on the treatment time length. The corrosion properties of the treated layers depend on microstructure and can be improved, especially if a thin and dense complex layer is produced at the surface.

This paper reports our recent studies on nanocrystalline layer of copper produced using pulse plating method. The grain size of the copper layer was about 60 nm. Electrochemical and physical Properties of the nanocrystalline surface were investigated using Potentiostatic scanning and Impedance measurements. Microcrystalline copper deposits were also produced by direct current electrodeposition processes and compared with pulse plated ones. Effects of deposition parameters, such as the peak Density, frequency, current-on time and current-off time of the pulse current (PC), on the grain size were investigated for the purpose of process optimization. It was demonstrated that the nanocrystalline film was markedly superior to regularly grained film made by direct current (DC) plating; the nanocrystalline deposit shows higher electrochemical stability and lower electrical resistance.

The Co-Ni alloy nanowires were electrodeposited into porous anodic aluminum oxide (AAO) templates. At the first, highly ordered AAO templates were synthesized by two-step anodizing of aluminum to increase pore ordering. Arrays of nanowires with diameter about 30 nm and length about 5000 nm were electrodeposited by alternating current. The composition and structure property of nanowires were investigated by EDX, SEM and TEM techniques. It was found that nanowire composition was related to ions concentration in solution and it was shown that at the optimum potential range of electrodeposition (17-19 V), a change at the potential was shown no strong effect on chemical composition of nanowires. It was observed that nano pores were filled continuously and so nanowires were dense with uniform composition in nanowire length.

Zn-Fe alloy electroplated coatings have attracted industrial interest because of their significantly higher corrosion resistance in comparison to pure zinc deposits. In this study pulse currents was applied for electrodeposition of Zn-Fe alloys, using alkaline bath. SEM studies confirmed that pulse electrodeposits are quite dense and smooth. It was also shown that increasing of peak current density (PCD) and duty cycle in pulse electrodeposition coarsen the structure and increase irregularity of the surface. Increasing of the frequency, on the other hand, results in the formation of finer structure.

Composite coatings constitute a new class of materials which are mostly used for mechanical and tribological applications. The corrosion resistance of these composite coatings, however, has not been systematically studied and compared. In this study, electroless Ni–P composite coatings are formed on St37 steel through the addition of nano-scale SiC particles to the plating bath. This work aimed to investigate the corrosion characteristics of electroless nickel composite coatings using electrochemical measurements which include polarization and electrochemical impedance spectroscopy tests. The morphology and structure of the composite coatings were studied by scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The results showed that both electroless nickel and electroless nickel composite coatings demonstrated significant improvement of corrosion resistance in salty atmosphere.

Nano-composite Ni-Al₂O₃ coatings due to their good wear and corrosion resistance have been widely used in different industries. The agglomeration of nano-particle ceramics in the electrolyte is a serious problem in electrodeposition process that leads to the presence of agglomerated particles in the coating and influences its properties. Using a suitable surfactant can be helpful to control the agglomeration of ceramic particles. In this research nano-composite Ni-Al₂O₃ coating has been deposited from an alumina containing Watts bath using a square pulse current and Sodium Dodecyl-Sulphate (SDS) as surfactant. It was observed that SDS addition has an important effect on the reduction of particles agglomeration and increases the incorporation of finer particles into the coating. Addition of saccharin to the electrolyte, decreases the grain size and the alumina content in the coating, and also, leads to lower agglomeration and better distribution of ceramic particles. Moreover, the synergistic addition of SDS and saccharin, decreases the grain size, increases the hardness and wear resistance, but has no effect on the crystallographic texture of the coating.

The cobalt-nickel/copper multilayer films were prepared by electrodeposition process in sulfate solution using a three electrode cell. Cyclic voltammetry and double chronoampermetry techniques were utilized to characterize the multilayer system and to obtain the nucleation and growth mechanism. The cyclic voltammograms determined the reduction potential range of the three components and also clearly emphasized that electrodeposition of cobalt-nickel alloy was controlled by a kinetic process, while copper ions were reduced with diffusion-controlled mechanism. These results were confirmed with those which were extracted from the chronoampermetry curves. In addition, the current transients revealed that nucleation mechanism was a typical three-dimensional nucleation process. The Atomic Force Microscope images (AFM) of these multilayers also confirmed the three-dimensional nucleation mechanism. The compositional analysis of these multilayers was carried out by Atomic Absorption Spectroscopy (AAS) and X-ray Photoelectron Spectroscopy (XPS) methods. The bulk and surface compositional analysis both revealed that the amount of Copper component within the cobalt-nickel layers is less than 3%.

Nanocrystalline pure metals with grain size below 10nm are very difficult to prepare. Alloying enables the production of such a fine grains, even down to an amorphous state. In this work, Ni-Mo nanocrystalline coatings were electrodeposited from a citrate-ammonia base solution using a direct current (DC) technique. The grain sizes were estimated from X-ray line broadening. Mo content of the coatings was determined by energy dispersive X-ray analysis (EDS). The results showed that the grain size decreased when the Mo content of alloy was increased through reducing the bath pH. The microhardness measurements showed an increase in hardness with decreasing the pH, a maximum hardness of 820 Vickers was obtained for the coating deposited at pH9 with a 17 wt% Mo. Although, at pH values lower than 9, alloys with higher than 17wt% Mo were obtained, a softening effect was observed despite the decrease in grain size which is the result of transition from a nanocrystalline to amorphous structure.

The aim of this study is to investigate the effect of atomic structure of polycrystalline materials on cell-substrate interactions. Samples are prepared from rods and sheets of Ti-6Al-4V substrates with predominately two distinct crystallographic orientations as well as nano-structured and annealed titanium fabricated through high-pressure torsion and heat treatment processes. The degree of preosteoblast attachment and rate of growth, which are regulated through the activity and interaction of proteins present in the extracellular matrix, are notably increased on the nano-structured titanium and substrate having predominant orientation. The improved cell activity is attributed to the nano-structured feature of these substrates consisting of ultra-fine crystals (< 50 nm) and specific atomic order of substrate which provide higher degree of surface wettability. These findings demonstrate the advantages of nano-structured titanium over the conventional and coated titanium implants, as both mechanical properties and cellular response are improved. Furthermore, crystal orientation of the substrates can influence cell responses and, therefore, substrate engineering can be used to improve and control cell-substrate interactions.

Recent investigations suggest that forsterite ceramics possess good biocompatibility and mechanical properties and might be suitable for potential application like bone implant material. In this study, nanocrystalline forsterite (Mg₂SiO₄) powder was prepared by mechanochemical method and subsequent heat treatment and the effect of fluorine ion as catalyst was studied. Mechanochemical process and heat treatment were done on the MgCO₃, SiO₂ and (NH₄)₂SiF₆ powders. The synthesized powders were characterized by X-ray diffraction (XRD), thermogravimetric (TG) analyses and scanning electron microscopy (SEM). The synthesized nano-powder had particle size smaller than 100 nm. The crystallite size of powders after 5 hours mechanical activation was 18 nm. Mechanical activation in the presence of fluorine ion affects the mechanism of forsterite formation and increase the rate of decomposition of MgO and fabrication of forsterite.

Hydroxyapatite and other calcium phosphates are the most important mineral parts of human bone. HA is applied on 304 stainless steel using cathodic electrodeposition in an electrolyte consisting of Ca(NO₃)₂ and NH₄H₂PO₄. The effect of electrodeposition parameters such as voltage, temperature and current density on the morphology and adhesion of the deposits were examined. Needle-like structure with nano width was obtained at 80°C and 2V while higher operating voltage resulted in flake type and coarse needle-like deposits. In fact, the lower voltage can change the electronation and diffusion of acting species. The adhesion of the coating, examined by tape test, improved by this method. TEM and SEM images showed the needle-like structure with nanometric width which is very similar to structure of natural bone. Corrosion resistance of the deposits was checked using polarization method and confirmed better performance of the nano HA coating.

Recently fluoridated hydroxyapatite (FHA) has been developed since it possesses lower solubility than pure hydroxyapatite (HA), while maintaining the comparable bioactivity and biocompatibility in dental and orthopedic application. The aim of this work was to synthesize and characterize the FHA nanopowder via mechanochemical activation method. Mechanochemical reaction was performed in the planetary ball mill at 300 rpm rotation speed by using 8 balls with 2 cm diameter. XRD technique was used to evaluate phase and composition and determine the grain size of prepared FHA nanopowder. FTIR spectroscopy was utilized to identify the functional groups and to compare obtained powder with bone apatite. The results showed that the synthesis of FHA after 6 hr ball milling at 300 rpm was completed. Fluorhydroxyapatite grain size was almost 37nm after 6 hr of milling.

A new chemical adsorbent for fluoride, phosphate and chromium removals for use in a high magnetic filtration process was produced by applying a novel nanomagnetite aggregation process through the generating procedure of an iron oxide hydroxide. The experimental work to produce the new adsorbent can be divided into two sequential steps: (1) the formation of nanomagnetite particles by means of a chemical precipitation and (2) embedding the nanomagnetite particles, in a solute state, into an iron oxyhydroxide crystal aggregates, before crystallization, to form the new adsorbent. The experimental results obtained from VSM, zeta potential, adsorption trials and SEM pictures obviously reveal a great alteration in the main properties of the new adsorbent comparing to the base iron component material. The new adsorbent not only has a much higher ions adsorption capacity but also can effectively comes to work with a magnetically assisted water treating system due to its enhanced magnetic susceptibility.

Nano size particles of barium hexaferrite were produced by conventional mixed oxide ceramic method from BaCO₃ and αFe₂O₃ as starting materials with a Fe/Ba molar ratio of 11. The mixture of precursors was intensively milled by high energy ball mill and the The influence of various process control agents (PCA) on the process has been investigated. Analysis of the XRD patterns indicates that PCA can strongly alter the morphology and phase composition of ball milled powder particles. In all milled samples, BaCO₃ completely decomposed and slight displacement of reflections of hematite phase due to the dissolving of various ions like Ba or C in its lattice is observed. Nano size particles exhibiting angular shape together with some amorphous structure were observed in the sample processed in the presence of NaCl. Barium hexaferrite magnetic phase was partially formed in sample milled in the presence of stearic acid.

Nano crystalline barium hexaferrite, BaFe₁₂O₁₉, were synthesized from mixture of barium acetate and iron oxide by conventional mixed oxide ceramic method. The mixture of precursors together with a 3wt% salt-catalyst (ammonium and sodium chlorides) was intensively milled by high energy ball mill for 10 hr. The influence of addition of catalyst on the synthesis process has been studied by XRD, SEM, DTA/TG and TEM techniques. Analysis of the XRD patterns indicates that salt-catalysts can strongly alter the morphology and phase composition of ball milled powder particles. Sample with 3wt% NH₄Cl after milling for 10 hr and annealing at 900°C for 1 hr exhibited single phase barium hexaferrite with mean crystallite size of 20 nm.

In this research, the effect of milling time and annealing temperature on a heat activated synthesis of barium hexaferrite from mechanically activated mixture of hematite and barium acetate was investigated. The properties of samples were examined by XRD, DTA/TGA, SEM and VSM methods. The initial mixture with Fe/Ba molar ratio of 11 was milled for 24–48 h and then annealed at 800–1100°C. The XRD results showed the reflections of hematite as a major phase and barium hydroxide as a minor phase during mechanical milling in all three samples. It was observed that the specimen milled for 48 h exhibits the smallest mean crystallite size of 25 nm for hematite, as major phase. XRD results showed that annealing at 1100°C produces more pure barium hexaferrite phase comparing to lower temperatures. So, it was concluded that single phase BaFe₁₂O₁₉ can be achieved by milling for 48 h and then annealing at 1100°C. The sample processed at these conditions exhibited nano-crystalline barium hexaferrite powders with a mean crystallite size of 46 nm, mean particle size of about 200 nm and high coercivity of 334.2 kA/m.

In this research the influence of dynamic carbon monoxide heat treatment on Sr-hexaferrite has been investigated. Sr-hexaferrite is a hard magnetic material which under gaseous heat treatment, its phase composition and particles size and morphology change significantly. Due to these changings, the magnetic nature of the material changes from hard to soft. Strontium hexaferrite was prepared by conventional route with calcination of Sr-carbonat and hematite at 1100°C for 1 hour. Then Sr-hexaferrite was isothermally heat treated in carbon monoxide dynamic atmosphere at various temperatures and gas flows for different times. The rate of heating and cooling were 10°C/min. The optimum conditions was obtained at 850°C and 20cc/min flow for 0.5 hour. The effect of gaseous heat treatment on phase composition and particles size and morphology characterized by XRD and SEM. The results show the decomposition of Sr-hexaferrite and reduction of the resultant hematite mainly to iron. The crystallite size of the resultant powder was also measured below 50nm.

In this study, the effects of the molarity of the precipitating agent on the synthesis of nanostructured NiFe₂O₄ powders by coprecipitation, followed by calcination were investigated and its optimum amount was also determined. Ni-ferrite powder was synthesized for the first time by dissolving Fe and Ni chlorides and ammonium ferrous sulfate in deionized water with different molar proportions. While stirring, the precipitating agent of NaOH was added to the solution with different molarities and after 1 hour of aging, the resultant precipitate was washed with deionized water and acetone.

It was concluded that single phase nickel ferrite nanocrystalline powders can be prepared by use of 2.2M NaOH, with crystallite size of 30-50 nm.

Nano-crystalline particles of barium ferrite have been prepared by co-precipitation route using aqueous and non-aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11. Water and a mixture of diethylene glycol and water with volume ratio of 3:2 were used as solvents in the process. Co-precipitated powders were annealed at various temperatures for 1 h. Phase composition of the samples was evaluated by XRD while their morphology was studied by TEM and SEM techniques. The XRD results showed that the single phase barium ferrite obtained at 750°C when diethylene glycol/water mixture was used as a solvent. This temperature increased to 900°C when the starting materials dissolved in water. Nano-size particles of barium ferrite with mean particle size of almost 50 and 80 nm were observed in the SEM micrographs of the samples synthesized in diethylene glycol/water solution after annealing at 750°C and 800°C for 1 h, respectively. The corresponding mean crystallite size measured by TEM for sample annealed at 800°C was 40 nm.

In this research a sol-gel auto-combustion route has been proposed to synthesize nickel-zinc ferrite nanocrystalline powder, using metal nitrates, citric acid as fuel and ammonia as pH adjusting agent. The influence of pH value of the solution on phase evolution, crystallite size and morphology of as-burnt powders were investigated by XRD, SEM and TEM techniques. The results revealed that with pH=7 the single phase nickel-zinc ferrite nanocrystalline powders with crystallite size of about 27nm were formed directly after auto combustion process.

Strontium hexaferrite is a hard magnetic material and has been extensively used as a permanent magnet. In this work a novel sol-gel auto-combustion method was used to synthesize ultra fine strontium hexaferrite. The investigations show that the model of combustion changes with the change of basic agent. The XRD results show that using ammonia or trimethylamine does not change the composition of the combustion product and it also shows that the surfactant burns completely during the combustion process. The average crystallite size of hexaferrite powders was also measured by X-ray line broadening technique employing Scherrer formula. The results show that changing the basic agent makes the particle size of the final product much smaller. Basic agent also affects the formation temperature of the single phase strontium hexaferrite.

Nano-particle materials with large optical nonlinearities are in great need for the development of nonlinear optical technology and are being studied intensively in recent years. ZnO nanoparticles have been synthesized by precipitation from zinc acetate in a series of n-alkanols from ethanol to 1-hexanol as a function of temperature. The formation and microstructure of ZnO particles were monitored by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectrum and z-scan technique. We studied the optical limiting effect of ZnO nano-particles. Using a CW He-Ne laser at 632.8 nm. The UV-Visible spectrum of this material shows a 373.5 nm peak. Using the UV-Visible, the band gap of this nano-particle is obtained about 3.31 eV. Also the XRD spectroscopy indicates that the structure is wurtzite hexagonal. Average particle size obtained from SEM analysis about 43nm. Furthermore the nonlinear refractive index, n₂, and nonlinear absorption coefficient, β, were measured using close and open aperture z-scan respectively, at peak laser irradiation of 1.743 kW/cm². Then the nonlinear refraction index of this nano-particle was measured in order of 10^-7 (cm²/W) with negative sign and the nonlinear absorption coefficient was obtained in order of 10^-3 (cm/W).

Study of the quality of carbon black dispersion by using UV-Visible Spectroscopy was carried out. Carbon materials have a main absorption around 200 nm (UV region) due to π→π* excitation. Based on UV absorption of carbon black and the parameter affects the absorption, UV Visible spectroscopy was used to study CB dispersion. Result showed that Triton X-100 was proper kinds of dispersant which resulted in higher UV absorption compared to other used dispersants. Also proper weight ratio of Triton X-100 to initial carbon solid was calculated of 50 wt% which no significant change was observed for sample containing higher amount of dispersant. Finally AFM images and PSA results asserted the results obtained from UV-Visible Spectroscopy.

Titanium diboride (TiB₂) is one of the candidate materials for high temperature structural applications and also for control rod elements in high temperature nuclear reactors. In this paper the nano-sized titanium diboride powders were synthesized through a borothermic reduction by using TTIP and B₄C as titanium and boron sources. Three different concentration of TTIP solutions were prepared: 0.033, 0.050 and 0.10 M. After heat treating of products between 900 to 1200°C, the scanning electron microscopy (SEM) images and X-ray diffraction patterns of powder indicated that by using the 0.10 M TTIP, the only product was TiB₂; otherwise the product was TiB₂-B₄C composite.

Nanostructured MgO powders have been synthesized using chemical methods. Ammonium oxalate and Magnesium sulphate were used as the precursor materials. The weight ratios of the raw materials (ammonium oxalate/Magnesium sulphate) were 0.9, 1, 1.1, 1.2, 1.3, and 1.4. As a result of chemical reaction (between them), Magnesium oxalate was synthesized. Produced samples were analyzed by XRD and SEM. The results show that the best ratio (for ammonium oxalate/Magnesium sulphate) is 1.4. Produced Magnesium oxalate powder was heated at 450 and 550°C. The final product was MgO nanopowder. XRD studies indicate that the highest ratio of MgO was observed in the specimen heated at 450°C.

We synthesized TiO₂ nanoparticles by pulsed laser ablation of titanium target immersed in an aqueous solution of surfactant sodium dodecyl sulfate (SDS) or deionized water. The surfactant concentration dependence on size of TiO₂ nanoparticles was investigated. The maximum amount of nanoparticles (with mean size of 40 nm in diameter) was obtained in an aqueous solution of 0.001 M SDS. We have also studied the effect of laser wavelength on growth of TiO₂ nanoparticles. UV/visible spectroscopy and Scanning Electron Microscopy observations were employed for characterization of optical properties and particle sizes respectively. As TiO₂ is a famous photocatalyst, we have also done photocatalytic test by Methyl Orange under UV irradiation for prepared samples.

Nano sized copper oxide-zirconia particles were prepared by using a sol-gel technique. The phase change with the calcinations temperature was also investigated for the sample containing 30 wt% copper. It was found that the calcinations temperature strongly influenced the interaction between the active species and support and hence the structure and catalytic performance. Low calcinations temperature yielded poorly crystallized catalysts and favored the formation of a Cu(OH)₂ and Zr(OH)₄ like structure. The results show that cubic ZrO₂ and copper oxide were present below calcinations at 400°C, and cubic ZrO₂ with some amount of monoclinic ZrO₂ and tetragonal ZrO₂, as well as copper oxide, formed after calcinations at 500°C. However, below heating at 500°C, amorphous compounds were obtained; suggesting that 500°C could be a phase transition point. The incorporation of copper in the ZrO₂ lattice resulted in a loss of order in the ZrO₂ structure when calcined at 500°C, with a further increase in the calcinations temperature leading to the phase change. In this work, the latest results on nano crystalline CuO-ZrO₂ as the catalyst for hydrogen synthesis from methanol is reported. The effect of calcinations temperature on the nanoparticle structure of catalyst is focused.

Titanium dioxide nanoparticles were prepared by precipitation of aqueous TiCl₄ solution with ammonium hydroxide as precipitation agent. Freshly prepared Titania gel is allowed to crystallize under refluxing and stirring condition for 6 h over 90°C and oven dried over night in temperature above 100 C. X-ray diffraction studies on oven dried powder indicate formation of anatase phase TiO₂ with average crystalline size of 4.5 nm. Powders with variable amount of anatase and rutile phase were prepared by calcination of pure anatase in the temperature range 400-1000 c for 4 h. the XRD patterns show that phase transition from anatase to rutile occur in calcination above 600°C. The morphology and microstructure characteristics were obtained by XRD, TEM. and TGA.

Ceramic materials based on zirconium titanate prepared by sol-gel method are used extensively in microwave, telecommunications and catalysis. In order to investigate the effects of concentration of TTIP, a series of ZrO₂–TiO₂ mixed oxides was prepared by a modified sol–gel method and varying mole fraction of TTIP from 0.002, to 0.1. The samples were characterized by XRD, TG/DTA, and SEM. The XRD pattern of 370°C calcined samples showed the formation of TiO₂ phase. The optimum concentration of TTIP in the zirconia-titania mixed oxide in the precipitation solution was 0.032 for obtaining complete coating. Each oxide was calcined between 250 and 620°C. The results showed that concentration of TTIP have a pronounced effect on particle size of the calcined zirconium titanate (ZT) powders. The results showed that the surface area of the composite powder increased proper to monolithic ZrO2 powder.

The present paper attempts as how the pigments comprising of nano-sized hematite particles deposited on mica surfaces in optimum conditions offer an excellent pearlescent properties. To record the influencing parameters on the synthesis process, response surface methodology (RSM) technique was used where temperature of reaction, synthesis time and concentration of urea were selected as variable parameters. Taking into account colorimetric parameters, the whole process was then analyzed by "Design Expert" software that finally gave following optimum factors: reaction temperature=82.02°C, synthesis time=11.98 h, urea concentration=37.5 g/l. Once the above optimum parameters selected, seemingly, the spherical hematite particles of about 60 nm in diameter are deposited uniformly on mica surfaces.

In this study, hematite (Fe₂O₃) and aluminum (Al) powder mixtures were mechanically alloyed in a high-energy shaker ball mill to synthesize the iron-alumina (Fe-Al₂O₃) nanocomposite powder. The structural changes and phase developments occurring during mechanochemical process were studied by X-ray diffractometery (XRD) and scanning electron microscopy (SEM). The results showed that mechanochemical reaction of Fe₂O₃ and Al completed after 3 hours of milling time in a nanocrystalline Fe and Al₂O₃ embedded form and further milling produced a Fe-Al₂O₃ nanocomposite powder. Kinetics consideration according to the calculated adiabatic temperature demonstrated the sudden displacement reaction during mechanical alloying that accord well with XRD results. Also, particle size decrease as well as crystallite size with increasing the milling time.

Gelcasting process as a promising method for fabrication of reliable ceramics has been utilized to develop alumina-zirconia nanocomposites from nanosized powders. Sedimentation and viscosity measurement were performed to find the accurate dispersing condition for production of alumina-zirconia nanocomposite slurry with high solid loading and low viscosity. The gelcasting was accomplished by in situ polymerization of an acrylamide base monomer. The effects of solid loading, viscosity and deairing were also studied. Finally, crack and flaw free samples with relative densities of 99%, were achieved from the optimal slurry with 35vol. % solid loading, by performing sintering at 1600°C for 2 hours. SEM micrographs showed dense microstructure with fine and homogenous dispersion of zirconia phase in the alumina matrix.

In this investigation, the mechanical and thermal properties of the montmorillonite-epoxy nanocomposites were studied. The epoxy compounds were prepared by in situ polymerization and the intercalation dispersion were obtained as evidenced using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results reveal remarkable stiffening effect and slight toughening effect of the MMT in the epoxy resin and an insight about the crack tip and notch tip toughening mechanism. According to the DMA, the glass transition temperature increases as increasing the MMT content.

Relatively low strength and fracture toughness of ceramics have restricted their applications. Various solutions have been studied to overcome the abovementioned drawbacks. One of the most sophisticated and promising solution is production of multilayer ceramic composites. High hardness, heat and wear resistance, low electrical and thermal conductivity, and resistance to chemical attacks are the most important characteristics of Al₂O₃. Therefore, it is a common candidate for various industrial applications. Multilayer alumina-zirconia composites were made using two methods of isostatic and hydraulic compaction of dry ceramic powders. The green articles were conventionally sintered at 1420, 1550 and 1650°C for 3h. The microstructure and density of composites were investigated. The results show that the pressing method and sintering temperature have a relatively moderate effect on the microstructure and density of the sintered samples.

We explain the mechanism of defect screening in GaInN/GaN quantum wells, which are used as active layers in white and blue light emitting diodes (LEDs). Despite the fact that these devices have now been commercially available for some time, the reason for the high luminescence efficiency had not been really understood. The high defect densities in these devices commonly would not allow the use as an optical emitter. We present the mechanism turning an actually poor-quality material into a powerful optical emitter.

Surface conditions of aluminum can influence the final arrangement of nano-pores in fabrication of ordered nanoporous anodic alumina membranes (AAMs). This study is mainly focused on the different applied voltages of aluminum electropolishing by keeping all the other parameters constant. After heat treatment (stress relieving and annealing at 500°C) of pure aluminum sheets, the samples were electropolished at different voltages (10-60V) to obtain desirable surface smoothness, while the temperature of the container was kept constant. The current-time curves were recorded during electropolishing process. The surface roughness obtained in each applied voltage was examined using optical microscope and atomic force microscope (AFM). The process was followed by two-step anodization in order to reach ordered nano-pores. Finally, the influence of surface roughness on regularity of nano-pores was observed using scanning electron microscope (SEM). The SEM images were analyzed to investigate the morphology and the degree of self ordering of pores of the samples by using a new designed analytical method aiming MATLAB and fast Fourier transform (FFT) technique. It was concluded that the electropolishing voltage and the resulted surface roughness and also formed defects can competitively affect the arrangement of membrane's nano-pores. A desired smoothness obtained from electropolishing voltage of 30V. Also 40V provided the best order with respect to the other voltages.

Calcined Na-ZSM-5 zeolite was directly reacted with the chloroauric acid solution in different concentrations and pH for gold loading process. The synthesized Au/ZSM-5 catalyst was then characterized using XRD, BET, SEM, TEM and EDS techniques. In order to evaluate its catalytic activity, effect of temperature on CO conversion was investigated.

ZnO nanorods and bamboo-like structures were fabricated by carbothermal evaporation in Ar gas and air atmosphere on Au-coated silicon wafers. Deposition in air atmosphere led to the fabrication of nanostructured ZnO. Investigation of substrate distance from the source material revealed that thinner nanorods are grown at shorter distances.

Densification behavior of sub micron tungsten carbide composites based on boron doped Fe₆₀Al₄₀ and Ni₃Al binders were investigated. Soft cobalt binder phase in WC hard metals was replaced by harder and tougher Fe₆₀Al₄₀ and Ni₃Al intermetallics with boron level up to 0.1wt%. Intermetallic binders were prepared in ultrafine form under controlled atmosphere using ring grinding, blended with sub micron WC powder and then uniaxilly hot pressed under 20 MPa pressure in argon atmosphere for 4 minutes duration at temperatures of 1450 °C, 1500 °C and 1550 °C. It was found that the density of composites increased significantly and WC grain size increased slightly with increase in sintering temperature. The composites exhibited highest density (about 99.5 %TD) and minimal grain growth in WC at sintering temperature of 1500 °C. The presence of boron was found to facilitate densification during liquid phase sintering and boron also resulted in achieving uniform microstructure with continuous binder phase, nearly full density and high faceted features in the structure.

In the present study, alloy powder batches of Al-20Si (wt. %) were generated by SAMD technique using NaCl as the solid media. The method consists of introducing and mixing a specified amount of NaCl particles (mean diameter 254 μm) in aluminum melt at the temperature of 710°C. Melt disintegration occurs in 5 min by kinetic energy transfer from a rotating impeller (1400 rpm) to the metal via the solid atomizing medium (NaCl particles). The resulting mixture of aluminum droplets and NaCl particles are subsequently quenched in water to dissolve NaCl and solidify Al droplets to produce powder particles. In order to investigate the effect of phosphorus modification on the size and morphology of the primary Si particles, the SAMD technique was also performed to produce Al-20Si-0.015P powder particles. The resultant powders were screened through 6 different sized sieves ranging from 38 to 500 μm and different powder fractions were cold mounted, polished and studied by optical microscopy.

It was concluded that for both un-modified and modified alloys, there was a decrease in the size of primary Si particles corresponding to a decrease in the powder particle size. However, the same sized phosphorus modified powders exhibited considerably finer primary Si particles in which the average size of these ultrafine Si particles was about 1.1 μm for the smallest sieved particles.