Modern Physics Letters B

In this paper, corrosion behavior of an AISI 304 stainless steel modified by niobium or niobium nitride (denoted as niobized 304 SS and Nb-N 304 SS, respectively) is investigated in simulated solid polymer fuel cell (SPFC) operating conditions. Potentiodynamic polarizations show that the corrosion potentials of surface modified 304 SS shift to positive direction while the corrosion current densities decrease greatly comparing with the bare 304 SS in simulated anodic SPFC environments. The order of corrosive resistance in corrosive potential, corrosive current density and pitting potential is: Nb-N 304 SS > niobized 304 SS > bare 304 SS. In the methanol-fueled SPFC operating conditions, the results show that the corrosion resistance of bare and niobized 304 SS increases with the methanol concentration increasing in the test solutions.

This experiment chooses A356 aluminum matrix composites containing 55% SiC particle reinforcing phase as the parent metal and Al–Si–Cu–Zn–Ni alloy metal as the filler metal. The brazing process is carried out in vacuum brazing furnace at the temperature of 550°C and 560°C for 3 min, respectively. The interfacial microstructures and fracture surfaces are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy spectrum analysis (EDS). The result shows that adequacy of element diffusion are superior when brazing at 560°C, because of higher activity and liquidity. Dislocations and twins are observed at the interface between filler and composite due to the different expansion coefficient of the aluminum alloy matrix and SiC particles. The fracture analysis shows that the brittle fracture mainly located at interface of filler and composites.

Halloysite nanotube, which has been used in the polymer, has been spotlighted as a useful functional materials in the improvement of mechanical properties. In the current study, we established the optimal nanoparticle dispersion and analyzed the mechanical characteristics and the behavior of composites reinforced by HNTs have been synthesized by dispersing HNTs to the unsaturated polyester resin (UPR) and their mechanical characteristics, especially the tensile strength, interlaminar shear strength have been analyzed. Additionally, the reinforcement effect and its variation according to the amount of HNTs was also studied.

Composites are vulnerable to the impact damage by the collision as to the thickness direction, because composites are being manufactured by laminating the fiber. The understanding about the retained strength after the impact damage of the material is essential in order to secure the reliability of the structure design using the composites. In this paper, we have tried to evaluate the motion of the material according to the kinetic energy and potential energy and the retained strength after impact damage by testing the free fall test of the basalt fiber reinforced composite in the limelight as the environment friendly characteristic.

Diamond-like carbon (DLC) coating is becoming a promising protective coating layers due to its superior properties. In this study, instead of protective coating, DLC film was applied as the only component for micropattern then etched with lithography and lift-off process selectively. Furthermore, DLC film has been fabricated on aluminum roll mold. Then UV curing resin was applied to form the pattern on the polyethylene terephthalate (PET) film. The dimension and formation of the DLC micropattern on roll mold were analyzed. Moreover, the Raman spectroscopic of nitrogen-doped DLC film was analyzed.

The influence of root radius of notch applied fracture load on piezoelectric ceramics under various conditions of electric fields was studied using the three-point bending test. And the linear finite element analysis associated with energy density of crack as a feasible parameter of fracture was performed with piezoelectricity. It was found that the fracture load is decreased according to reduction of the curvature radius of notch but the finite element analysis showed reverse result, the fracture load in case of the crack is increased. The energy density of crack as the governing fracture parameter was finally introduced and discussed.

Aluminum diffusion coatings were applied to the Inconel 617 by a pack cementation. The effect of coatings on the thermal stability and wear resistance of the Inconel alloy after heat-treatment under an air and a helium atmosphere at 1000°C, 48 h has been studied. The aluminide-coated Inconel specimens are prepared at 850°C and 1000°C for 1 h. An aluminiding layer indexed as Al_xNi_1-x (x = 0.4–0.6) was formed near the surface region and it played a role as a barrier layer against the surface diffusion of Cr. The thin Cr₂O₃ film formed in situ on the alloy surface is protective inhibiting further oxidation at moderate temperatures. As the temperature increases further, the thermal stability of the Inconel alloy is limited by the instability of the Cr₂O₃ scale. The aluminide-coated Inconel 617 samples showed the better performances, the enhanced thermal stability and improved wear resistance, most likely due to the barrier layer formation with the reduced amount of Cr₂O₃ scale formation.

This paper introduces a procedure to predict failure strain for an arctic class marine structural steel, EH36. Based on previous results,^1-4 this paper explains formulation procedure for a failure strain curve of the EH36 in medium-low and high average stress triaxiality zones by performing tensile tests for round and flat specimens with various notches. Verification of the validity of the failure strain envelope using user-defined subroutine imbedded in commercial finite element code Abaqus/Explicit is also described. The failure strain envelope provides relatively accurate simulation results by comparing tensile test results of asymmetric notch structures with fracture simulations using the user-defined subroutine.

We present an application of high-aspect-ratio (high-AR) silicon structures (black silicon) with high water repellency and good wettability by oils and solvents. The fabrication of black silicon consists of a deep reactive-ion etching process for extremely-high-AR silicon structures and surface treatment with C₄F₈ gas. Such high-AR structures were found to be highly resistant against wetting by water, but they also have good wetting characteristics with respect to certain liquids such as ethanol, hexane and mineral oil. To determine the relationship between the AR of nanostructures and wetting selectivity, four different black silicon samples with different pattern heights were used. The static contact angles of various liquid were measured for the analysis of wetting properties of the four black silicon samples. To explore feasible applications, ethanol–water separation was performed as a miniaturized experimental simulation of environmental remediation.

Magnesium alloys are known to be hard-forming materials at room temperature owing to their material structure. This study analyzes the optimal temperature conditions of warm-forming and the forming process by using a high-pressure laminating test and FM analysis, respectively. The effect of temperatures on the fatigue limit was examined from the collected specimens by analyzing the material properties after the fatigue test. The material formed at a temperature of 230°C shows occasional defects, but the best forming quality was obtained at 270°C. The optimal temperature for the forming process was found to be 250°C considering the material quality and thermal efficiency. The overall fatigue life of specimens decreases with an increase in the processing temperature. The fatigue limit of AZ31 formed at 250°C was approximately 100 MPa after 10⁶ cycles.

Rapid prototyping (RP) technologies have been extensively applied to build products in recent decades. The area-forming rapid prototyping is an emerging RP technology with the advantages of a simple procedure with a short processing time. With the expansion in fields of application, the strictness on product quality has also increased. The dimensional accuracy of a product is one of the most critical quality characteristics. In order to improve the dimensional accuracy of a product from an area-forming RP system, this study optimizes the seven factors via the Taguchi method, and the result is verified with an extra sample.

At the viewpoint of energy saving and the increasing needs of seaside leisure activities in Korea, floating architecture is recently to be focused on, but it is in the early stage of technological development. Considering the features of floating structures that can float and move on sea and/or river, this study proposes Single-U type Sea Water Heat Exchanger (SWHEx) and Spring type SWHEx that installed into or outside the submerged concrete structure of pontoon, respectively. As the results from CFD and mock-up tests, it is found out that the mean temperature difference is 3°C between the inlet and outlet temperatures of working fluid which flows inside the Single-U type SWHEx and 1.5°C for Spring type SWHEx. Also it is clear that the heat exchange performance of Single-U type SWHEx is better than Spring type.

Vision-based recognition of the object as a general interface gives us high cost and complicated problem. This research suggests human tracking system by Arduino, and Laser-CdS cell system track wire that pass laser line. In this paper, we review existing literature on application systems of recognition which involves many interdisciplinary studies. We conclude that our method can only reduce cost, but is easy way to trace people's location with the use of wire. Furthermore, we apply several recognition systems including CdS-based mobile robot that is applied IV stand used at the hospital effectively.

This paper describes the mathematical modeling and control algorithms of an unmanned underwater vehicle (UUV) named Minekiller. This UUV has two longitudinal thrusters, one vertical thruster, and an internal mass moving system, which can control the pitch rate. The UUV is equipped with a movable mass for pitch control. It is different from other common UUVs, in that it can maintain a static pitch angle. The UUV's 6-DOF (Degrees of Freedom) dynamics model is derived from the hydrodynamic forces and moments acting on it. We applied these hydrodynamic coefficients to dynamic modeling for numerical simulations by MATLAB/SIMULINK^©. To compare the performance in various cases, we used a PID controller for depth and heading control. Also, the navigation controller can analyze the way-point tracking performance. These simulation results show the performance of the control algorithms and maneuvering performance of the underwater vehicle.

To improve the corrosion resistance of an electro-galvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at 250–330°C. The zinc–magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at 270–290°C showed better corrosion resistance than others. In X-ray diffraction analysis, ZnMg₂ was detected throughout the temperature range, whereas Mg₂Zn₁₁ and FeZn₁₃ were detected only in the film annealed at 310°C. The depth composition profile showed that the compositions of Mg at 270–290°C are evenly and deeply distributed in the film surface layer. These results demonstrate that 270–290°C is a proper temperature range to produce a layer of MgZn₂ intermetallic compound to act as a homogenous passive layer.

Presently in shipbuilding, transportation and aerospace industries, the potential to apply welding using laser and laser-arc hybrid heat sources is widely under research. This study has the purpose of comparing the weldability depending on the arc mode by varying the welding modes of arc heat sources in applying laser-arc hybrid welding to aluminum alloy and of implementing efficient hybrid welding while controlling heat input. In the experimental study, we found that hybrid welding using CMT mode produced deeper penetration and sounder bead surface than those characteristics produced during only laser welding, with less heat input compared to that required in pulsed arc mode.

Continuous silicon carbide fiber-reinforced silicon carbide (SiC_f/SiC) composites are promising structure candidates for future fusion power systems such as gas coolant fast channels, extreme high temperature reactor and fusion reactors, because of their intrinsic properties such as excellent mechanical properties, high thermal conductivity, good thermal-shock resistance as well as excellent physical and chemical stability in various environments under elevated temperature conditions. In this study, bonding of tungsten and SiC_f/SiC was produced by hot-press method. Microstructure analyses were performed using SEM and TEM.

Graphite is one of the effective lubricant additives due to its excellent high-temperature endurance and self-lubricating properties. In this study, wear behavior of graphite used as sealing materials to cut off hot gas is evaluated at room and elevated temperature. Wear occurs on graphite seal due to the friction of driving shaft and graphite. Thus, a reciprocating wear test to evaluate the wear generated for the graphite by means of the relative motion between a shaft material and a graphite seal was carried out. The friction coefficient and specific wear rate for the changes of applied load and sliding speed were compared under different temperature conditions considering the actual operating environment. Through SEM observation of the worn surface, the lubricating film was observed and compared with test conditions.

Thermal spray coating method has been known to be an attractive technique due to its relatively high coating speed. However, a high corrosion resistance of the coating film deposited by thermal spray method should be improved to prolong its lifetime. In this study, four types of coated films (DFT: 400 μm), that is, pure zinc, pure aluminum and two Al – Zn alloy (Al:Zn = 85:15 and Al:Zn = 95:5) films were coated onto a carbon steel (SS401) with arc spraying, and the corrosion behaviors of these samples were investigated using the electrochemical method. The pure aluminum sample had the best corrosion resistance in seawater solution and alloy (Al:Zn = 85:15) film, so called galvalume followed the pure aluminum sample, moreover, the alloy (Al:Zn = 95:5) sample exhibited the worst corrosion resistance.

In this paper, we propose a localization simulator based on the random walk/waypoint mobility model and a hybrid-type location–compensation algorithm using the Mean kShift/Kalman filter (MSKF) to enhance the precision of the estimated location value of mobile modules. From an analysis of our experimental results, the proposed algorithm using the MSKF can better compensate for the error rates, the average error rate per estimated distance moved by the mobile node (Err_ Rate_DV) and the error rate per estimated trace value of the mobile node (Err_Rate_TV) than the Mean shift or Kalman filter up to a maximum of 29% in a random mobility environment for the three scenarios.

This experiment has examined the corrosion and tribological properties of basalt fiber reinforced composite materials. There were slight changes of weight after the occurring of corrosion based on time and H₂SO₄ concentration, but in general, the weight increased. It is assumed that this happens due to the basalt fiber precipitate. Prior to the corrosion, friction-wear behavior showed irregular patterns compared to metallic materials, and when it was compared with the behavior after the corrosion, the coefficient of friction was 2 to 3 times greater. The coefficient of friction of all test specimen ranged from 0.1 to 0.2. Such a result has proven that the basalt fiber, similar to the resin rubber, shows regular patterns regardless of time and H₂SO₄ concentration because of the space made between resins and reinforced materials.

Inductively coupled plasma etching of ultrananocrystalline diamond (UNCD) films was performed in O₂/CF₄ and O₂/SF₆ discharges. Higher etch rates were produced for the O₂/SF₆ discharges and the films etched in the 10O₂/5CF₄ discharges retained smooth surface morphology similar to the unetched control sample. Al mask showed a good etch selectivity to the UNCD for both plasma chemistries and highly anisotropic pattern transfer with a vertical sidewall profile was achieved.

In this paper, a new variable-focus LED light device is developed for underwater communication. Usually used as an underwater lighting fixture, the LED light device in this study is utilized as an underwater communication device (UCD) by controlling the distance between light source and lens when communication is needed. A transmission and a receiving part of LED light for communication using photoelectric sensor and Fresnel lens are also developed. The communication system was tested in fresh water and sea water to verify its communication performance; results of which are presented in this study.

The growth of ternary semiconductor thin films of cadmium indium selenide nanofibers has been carried out from aqueous solution of cadmium sulphate, indium trichloride, and selenium dioxide by electrochemical route. These thin films have been further optimized using photoelectrochemical cell (PEC). Optimized thin film has been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Cellulose nanofibers have been showing much greater potential to enhance the mechanical and physical properties of polymer-based composite materials. The purpose of this study is to extract the cellulose nanofibers from waste bio-resources; such as waste newspaper and paper sludge. The cellulosic raw materials were treated chemically and physically in order to extract individualized cellulose nanofiber. The combination of acid hydrolysis and following mechanical treatment resulted in the extraction of cellulose nanofibers having diameter of about 40 nm. In order to examine the reinforcing effect of the extracted cellulose nanofibers, fully biodegradable green nanocomposites were fabricated by composing polyvinyl alcohol (PVA) resin with the extracted cellulose nanofibers, and then the tensile tests were conducted. The results showed that the enhancement in mechanical properties was successfully obtained in the cellulose nanofiber/PVA green nanocomposites.

The samples of La_1-xCa_xCoO₃ (x = 0, 0.05, 0.10, 0.15) were synthesized by solid state reaction method for studying thermoelectric properties. The properties of electrical conductivity and Seebeck coefficient were measured in the temperature ranging from room temperature to 573 K. The results of electrical conductivity was increasing Ca substitution. The highest value of electrical conductivity is 1574 S/cm. It is concluded that Ca²⁺ doping in LaCoO₃ has the effect to inhibit Seebeck coefficient from decreasing.

Transparent conductive oxide is a thin film to be used in numerous applications throughout the industry in general. Transparent electrode materials used in these industries are in need of light transmittance with excellent high and low electrical characteristics, substances showing the most excellent physical properties while satisfying all the characteristics such as indium tin oxide film. However, reserves of indium are very small, there is an environmental pollution problem. So the study of zinc oxide (ZnO) is actively carried out in an alternative material. This study analyzed the characteristics by using a direct current (DC) magnetron sputtering system. The electric and optical properties of these films were studied by Hall measurement and optical spectroscopy, respectively. When the Al target input current is 2 mA and 4 mA, it demonstrates about 80% transmittance in the range of the visible spectrum. Also, when Al target input current was 6 mA, sheet resistance was the smallest on PET substrate. The minimum resistivity is 3.96×10^-3 ohm/sq.

The fatigue-induced damage and crack growth behavior were studied on the ultrafine grained copper processed by equal channel angular pressing (ECAP). At high stresses, fatigue cracks were initiated at the shear bands (SBs) formed along the shear plane of the final ECAP. At low stresses, the grain coarsening occurred due to dynamic recrystallization. The slip bands were then formed inside these grains and subsequently served as an initiation sites for cracks. The direction of crack growth, either 45° or perpendicular to the loading axis, varied depending on the stress. The formation and growth mechanisms of fatigue crack are discussed based on the micrographic observation of surface damage.

Green oxynitride phosphors Ba₃Si₆O₁₂N₂ were prepared with metallic ratio of Si/Ba = 3. It was found that the nonstoichiometric mixture at Si/Ba = 3 formed the Ba₃Si₆O₁₂N₂-type phase easier than the stoichiometric one at Si/Ba = 2 after it was fired at 1200°C for 5 h under a diluted hydrogen flow (5%H₂–95%N₂). The excess Si source led to a formation of SiO₂ glass, which can act as a flux in case of formation of Ba₃Si₆O₁₂N₂.

This paper reports the effect of hydrogen (H₂) plasma treatment on field emission property of double walled carbon nanotubes (DWCNTs) synthesized by using chemical vapor deposition method. The hydrogen plasma treatment was carried out for various duration. The DWCNTs films were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that the field emission properties of DWCNTs were influenced with increasing plasma treatment duration. The Raman spectra of samples clearly show structural defects after hydrogen plasma treatment. It is observed that the change in the field emission characteristics of DWCNTs is attributed to the structural defects due to the H₂ plasma and depends on the plasma treatment duration.

Borate has been used for various industrial products and excessive dose of boron is harmful to humans. We investigated the removal of borate by direct coprecipitation with Mg/Al layered double hydroxide. In this study, the maximum removal of boron was 90% when Mg 30 mmol and Al 15 mmol at pH = 10 were used for 498 mg/l as B. The boron adsorption isotherms could be fitted to Langmuir model. The calculated constant W_s, saturation limit of boron adsorption, is 25 ± 2 mg/g and it is larger than that of ion exchange reaction (W_s = 15±1 mg/g).

Copper phthalocyanine (CuPc) is synthesized chemically and used for making CuPc thin films using spin coating technique. Films were prepared from trifluroacetic acid (TFA) and chlorobenzene mixed solution on the glass substrate. Spin coated films of unsubstituted CuPc films were heat annealed at 150°C for 2 h duration and were used to study NO₂ gas sensing characteristics. α-phase of CuPc is noted by UV-visible absorption spectra. IR spectra of undoped CuPc films and doped CuPc films with NO₂ revealed that, doping of nitrogen dioxide modifies and deletes some of the bands. The effect of NO₂ at various concentrations from 50 ppm to 500 ppm in atmospheric air at room temperature on the electrical conductivity of CuPc films was studied. Sensitivity, response time and repeatability of the CuPc sensor were discussed in this paper.

Drying shrinkage of concrete is one of the typical problems related to reduce durability and defilation of concrete structures. Lime stone, expansive additive and low-heat Portland cement are used to reduce drying shrinkage in Japan. Drying shrinkage is commonly evaluated by methods of measurement for length change of mortar and concrete. In these methods, there is detected strain due to drying shrinkage of free body, although visible cracking does not occur. In this study, the ring test was employed to detect strain and age cracking of concrete. The acoustic emission (AE) method was adopted to detect micro cracking due to shrinkage. It was recognized that in concrete using lime stone, expansive additive and low-heat Portland cement are effective to decrease drying shrinkage and visible cracking. Micro cracking due to shrinkage of this concrete was detected and evaluated by the AE method.

Metal nanoparticles have the ability to localize and strongly enhance the incident electromagnetic field due to the surface plasmon polariton. The coupling between AuNPs and ZnO thin films affects their emission properties. In this study, we prepared the ZnO/Al₂O₃/AuNPs multilayer films, and investigated the effect of spacer layer on enhancement and quenching of photoluminescence by surface plasmon. The emission intensities of the thin films vary when Al₂O₃ space layer with different thickness was embedded in the ZnO/Au films, consistent with theoretical predictions. The photoluminescence modulation is also made via controlling the polarization of the excitation source. The photoluminescence anisotropy of these systems shows that enhanced photoluminescence can be achieved through coupling of the emission from ZnO with the surface plasmon resonance of AuNPs.

Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates by a facile electrochemical route employing cyclic voltammetry (CV) mode. The morphology of the PPy thin films was observed to be influenced by the monomer concentration. Furthermore, FTIR revealed formation of electrically conducting state of PPy. Field emission investigations of the PPy nanostructures were carried out at base pressure of 1×10^-8mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm² were observed to be 0.6, 1.0 and 1.2 V/μm for the PPy films characterized with rod-like, cauliflower and granular morphology, respectively. In case of PPy nanorods maximum current density of 1.2 mA/cm² has been drawn at electric field of 1 V/μm. The low turn on field, extraction of very high emission current density at relatively lower applied field and good emission stability propose the PPy nanorods as a promising material for field emission based devices.

In this paper, a synthesis of conducting polyaniline nanowires electrode junction (CPNEJ) has been reported. Conducting polyaniline nanowires electrode junction on Si/SiO₂ substrate (having 3 μm gap between two gold microelectrodes) is prepared. Polyaniline nanowires with diameter (ca. 140 nm to 160 nm) were synthesized by one step electrochemical polymerization using galvanostatic (constant current) technique to bridge this gap. The surface morphology of CPNEJ was studied by scanning electron microscope (SEM). The synthesized CPNEJ is an excellent platform for biosensor applications.

The tungsten fiber reinforced titanium composite (W/Ti) was produced by the spot welding method. The internal stress alteration of the W/Ti composite was measured by the neutron diffractometer, DN1, which had been installed at beam port #6 in National Nuclear Energy Agency Indonesia. The two-dimensional detector and cryostat system were mounted on the DN1 diffractometer, and the residual stress alterations were measured by the in situ neutron stress measurement technique under the cooling cycles from 300 K to 10 K. Residual stresses in tungsten fiber were investigated at several temperatures. In the longitudinal fiber direction, the thermal residual stresses of tungsten fiber became a large compressive state and represented the maximum value is about -950 MPa. The calculated results of the simple elastic model agreed with the experimental results of the in situ thermal stress measurement qualitatively. It is assumed that the stresses in the fiber longitudinal direction are the dominant stresses in the W/Ti composite.

In this paper, leaching behavior of metallic species from steel samples in peracetic acid was investigated. We compared the leaching efficiency between peracetic acid and acetic acid to estimate the role of peroxo functional group for the leaching. As a result, peracetic acid enhanced the leaching ability of metallic species from the high speed steel and the alloy steel samples. MoO₃, Mo, MO₂C, W, WO₃, VC and MnO₂ were effectively leached by peracetic acid, while the stainless steel had a high resistance against corrosion by peracetic acid.

Cellulose nanofibers have been used to reinforce polymers, delivering composites with strength that in some cases can be superior to that of engineering plastics. The extraction of nanofibers from plant fibers can be achieved through specialized equipment that demands high energy input, despite delivering extremely low yields. The high extraction cost confines the use of cellulose nanofibers to the laboratory and not for industrial applications. This study aims to extract nanofibers from grass by using a kitchen blender. Earlier studies have demonstrated that paper sheets made of blender-extracted nanofibers (after 5 min to 10 min of blending) have strengths on par with paper sheets made from commercially available cellulose nanofibers. By optimizing the design of the blender bottle, nanofibrillation can be achieved in shorter treatment times, reducing the energy consumption (in the present case, to half) and the overall extraction cost. The raw materials used can be extended to the residue straw of agricultural crops, as an alternative to the usual pulp fibers obtained from wood.

Amperometric glucose sensors with a diameter of less than 10 μm were fabricated by the immobilization of glucose oxidase (GOx) on carbon fiber electrodes. Carbon fiber electrodes with platinum thin film were also prepared using electroplating and sputtering. The combination of electrodeposition and electropolymerization was employed for the immobilization of GOx. Although the introduction of Pt film satisfactorily improved the oxidation current of the electrode to hydrogen peroxide, sensitivities of obtained GOx-immobilized electrodes to glucose were not significant. Formation of electroplated-platinum thin film on carbon fiber was effective to reduce the influence of electroactive compounds existing in biological fluid such as ascorbic and uric acids.

An electron beam surface alloying was applied to a medium carbon steel disk using hBN, W and WC powders in order to examine the effect of these powder materials on the microstructure and hardness. The study reveals that, the surface hardness was improved by the electron beam irradiation with all powders and no surface cracks were observed due to the martensitic transformation and the surface alloying. However the influence of powder materials on the hardness was little. Thus, it was found the surface modification by the electron beam irradiation with various powders is effective way to improve the surface hardness as well as the prevention of surface cracking.

This paper describes the influence of surface roughness of steel plate on self-assembly behavior of silica particles based on SEM observations and the wettability of the suspension. The 304 stainless steel plate having two different surface roughness and spherical silica powder were used for the investigation. The silica layer was obtained by dipping the steel plate into the suspension and drawing it under various drawing speed. As a result, silica particle layers were formed on the plate surface when the stainless steel had a rough surface. In contrast, it was difficult to obtain the silica layers for the smooth surface.

Present communication reports the LPG and NH₃ sensing properties of Co₃O₄ films prepared on throughly cleaned stainless steel (SS) and copper (CU) substrates by using DC electrochemical deposition method followed by air annealing at 350°C/2 h. The resultant films are characterized by using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The LPG and NH₃ gas sensing properties of these films are measured at room temperature (RT) by using static gas sensing system at different concentrations of test gas ranging from ~ 25 ppm to 350 ppm. The XRD and Raman spectroscopy studies clearly indicated the formation of pure cubic spinel Co₃O₄ in all films. The LPG and NH₃ gas sensing properties of films showed (i) the increase in sensitivity factor (S.F.) with gas concentrations and (ii) more sensibility to LPG as compared to NH₃ gas. In case of NH₃ gas (conc. ~ 150 ppm) and LPG gas (conc. ~ 60 ppm) sensing, the maximum S.F. = 270 and 258 are found for the films deposited on CU substrates, respectively. For all films, the response time (3–5 min.) is found to be much higher than the recovery time (30–50 sec). For all films, the response and recovery time are found to be higher for LPG as compared to NH₃ gas. Further, repeatability–reproducibility in gas sensing properties is clearly noted by analysis of data for number of cycles recorded for all films from different set of depositions.

Synthesis of vertically well-aligned ZnO nanorods on Au coated silicon substrate by a facile electrochemical route has been carried out. The transformation of as-deposited ZnO nanorods into nanotubes was achieved via simple, single step, chemical etching process using KOH as etchant. The influence of various parameters of the etching, such as concentration of the etchant, bath temperature and duration on morphological features of the ZnO nanotubes has been investigated. It is observed that formation of ZnO nanotubes with smooth inner and outer surfaces is achieved when the etching was performed at 65°C for 1 h duration, and at higher bath temperatures and longer durations, over etching of nanorods takes place. Field emission investigations of the ZnO nanorods and nanotubes were carried out at base pressure of 1 × 10^-8 mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm² were observed to be 7.2 V/μm and 8.4 V/μm, corresponding to ZnO nanorods and nanotubes emitter respectively, and emission current density of ~ 352.5 μA/cm² has been drawn from the ZnO nanotubes emitter at an applied field of 13.77 V/μm. The ZnO nanotubes emitter exhibits excellent emission current stability at the preset value of 1 μA over duration of 3 h, indicating its potential as electron source for practical applications.

In the present investigation, a glucose sensor based on conducting polyaniline nanowire electrode junction (CPNEJ) has been reported. The CPNEJ platform was modified by glucose oxidase by cross-linking in the presence of glutaraldehyde. The signal transduction mechanism of the sensor is based on the change in micro electrode junction conductance as a result of glucose oxidation induced change in the polymer redox state. Small size of CPNEJ sensor causes to regenerate enzyme naturally without need of redox mediators, as a result it consumes minimum amount of oxygen and also gives very fast response. This sensor exhibited good linear response range from 1 mM to 20 mM of glucose concentration with excellent sensitivity of 12 μA/mM.

In the present investigation, a chemiresistive sensor based on conducting polythiophene-modified single-walled carbon nanotubes (SWNTs) for NO₂ detection has been reported. The SWNTs were aligned across 3 μm gap between two gold microelectrodes on Si/SiO₂ substrate. Alignment of SWNTs was carried out by using AC dielectrophoretic technique and it was confirmed by current–voltage (I–V) measurement. Aligned SWNTs were modified by conducting polythiophene using charge controlled potentiostatic deposition and it was confirmed by field-effect transistor (FET) and electrochemical measurements. Polythiophene-modified SWNT devices were used for the NO₂ detection in chemiresistive modality. This sensor exhibited very good linear response range from 10 ppb to 10 ppm.

Present study reports the biochemical synthesis of silver nanoparticles (Ag-NPs) from aqueous medium by using the extract of medicinal mushroom Ganoderma, as a reducing and stabilizing agents. The Ag-NPs are prepared at room temperature by the reduction of Ag⁺ to Ag in aqueous solution of AgNO₃. The resultant particles are characterized by using UV-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) measurement techniques. The formation of Ag-NPs is confirmed by recording the UV-visible absorption spectra for surface plasmon resonance (SPR) where peak around 427 nm. The prominent changes observed in FTIR spectra supported the reduction of Ag⁺ to Ag. The morphological features of Ag-NPs are evaluated from HRTEM. The spherical Ag-NPs are observed in transmission electron microscopy (TEM) studies. The particle size distribution is found to be nearly uniform with average particle size of 2 nm. The Ag-NPs aged for 15, 30, 60 and 120 days showed no profound effect on the position of SPR peak in UV-visible studies, indicating the protecting/capping ability of medicinal mushroom Ganoderma in the synthesis of Ag-NPs.

Diamond-coated cutting tools are used primarily for machining non-ferrous materials such as aluminum–silicon alloys, copper alloys, fiber-reinforced polymers, green ceramics and graphite. Because the tool life of cemented carbide cutting tool is greatly improved by diamond coating, and typically more than 10 times of the tool life is obtained. However, research of boron-doped diamond (BDD) coating tool has not been fully researched yet. In this study, we have succeeded to make boron-doped microcrystalline and nanocrystalline diamond-coated Co-cemented tungsten carbide (WC–Co) inserts. Microcrystalline BDD thin film is deposited on WC–Co insert by using microwave plasma enhanced chemical vapor deposition (MPECVD) method. Scanning electron microscope (SEM) and Raman spectroscopy are used to characterize the as-deposited diamond films.^1,2

An optimum repair welding for the piston crown which is one of the engine parts exposed to the combustion chamber is considered to be very important to prolong the engine lifetime from an economical point of view. In this study, two types of filler metals such as 1.25Cr–0.5Mo, 0.5Mo were welded with SMAW method and the other two types of filler metals such as Inconel 625 and 718 were welded with GTAW method, respectively, and the used base metals were the cast and forged steels of the piston crown material. The weld metal zones welded with Inconel 625 and 718 filler metals exhibited higher corrosion resistance compared to 1.25Cr–0.5Mo and 0.5Mo filler metals. In particular, the weld metal zone welded with Inconel 718 and 0.5Mo, filler metals indicated the best and worst corrosion resistance, respectively. Consequently, it is suggested that the corrosion resistance of the weld metal zone surely depends on the chemical components of each filler metal and welding method irrespective of the types of piston crown material.

Various educational Arduino modules with its simplicity have been developed since Arduino's release into the market. In this study, the helium gas airship was employed to make an Arduino module by applying Arduino Mini, Bluetooth and Android applications.