bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Photoluminescent Silicon Nanowires Based on Multicrystalline Silicon Wafers
Authors: Sun Xian Zhong , Feng Jia You
Published: June 2010

Single crystal silicon (sc-Si) wafers are widely used as the precursors to prepare silicon nanowires (SiNWs) by employing a silver-assisted chemical etching process. In this work, we obtained SiNWs arrays using multicrystalline silicon (mc-Si) wafers. Firstly, silver nanoparticles were deposited on the textured solar-grade mc-Si wafer by a galvanic displacement process; secondly, the SiNWs arrays were formed by a silver-assisted chemical etching process conducted in a HF-H2O2 aqueous solution. The etching process indicated that the growth of SiNWs is independent on the orientation of the Si wafer. TEM images showed that the SiNWs have rough and nanoporous structures on the top side along axial directions. The photoluminescence (PL) spectrum of SiNWs showed a broad visible emission centred around 700 nm, which is attributed to the emission properties of silicon nanocrystallites in SiNWs. This work may contribute to the development of SiNWs in application including optoelectronic devices, solar energy conversion devices, chemical sensors, and lithium secondary batteries, etc.
Formation of Deformation Twins and Related Shear Bands in Copper Single Crystals Pressed by ECAP
Authors: Ikeda Takumi , Miyamoto Hiroyuki , Uenoya Toshiyuki , Hashimoto Satoshi , Vinogradov Alexei
Published: June 2010

The pure copper single crystals with specific crystallographic orientated were subjected to ECAP for one pass at room temperature. Two types of shear bands were observed. Type 1 shear bands were constructed with clusters of distorting micro shear bands and matrix. Micro shear band and matrix were delineated by large-angle grain boundaries, and these two orientations are in a twinning relationship. Parallel sets of deformation twins were observed in the matrix. Type 2 shear bands had no crystallographic feature, and shear band and matrix were considered as low-angle grain boundaries. Deformation twin was not observed both in matrix and the shear bands.
Deformation Characteristics in AlphaType Brass Worked by Torsion
Authors: Shinsen Masahiro , Furui Mitsuaki , Ikeno Susumu , Nagae Takekazu
Published: June 2010

In present work, bar samples of pure copper and Cu-Zn alpha single phase alloys setting 20mm in diameter and 150mm in length processed by torsion in the rotation speed to 1rpm every 60° twist angles. Then, deformed samples were researched microstructure and their characteristics. Microstructures of non-deformation samples were isometric, however, deformed samples streaky. Elements of bar drawn 10×10mm mesh were developed parallelogram. It was trend angle of between stretchable direction in microstructures and torsion axis increased more torsion angles. It was coincident with between the angle and deformed direction of microstructures. Shear strain was calculated by twist angle by theoretical formula. Their value corresponded rough with measurement from mesh variation. Pure copper and Cu-Zn alpha phase alloys were similar deformation microstructure, but fracture twist angle in copper was more than Cu-Zn alloys, and it was trend fracture angle had decreased as concentration of Zn increased. This trend was difference of fracture elongation obtained in tensile test.
In Situ Observation of Microstructure Evolution in Low Carbon Bainite Steels Isothermally Held Below A1 Temperature
Authors: Zhang Rui , Yang Shan Wu , Sun Chao , He Xin Lai
Published: June 2010

The dominant microstructures in low carbon bainite steels such as bainitic ferrite are non-equilibrium phases, which will tend to evolve into equilibrium phases when the steels are subjected to thermal disturbance. In-situ observation by optical and scanning electron microscopy was carried out in this investigation to track the evolution when the steels were isothermally held below A1 temperature. It is found that the primary polygonal ferrite grows slowly during isothermal holding, while bainitic ferrite changes rapidly into polygonal ferrite. Self-tempered bainitic ferrite would recover further and recrystallize. The lower the concentration product of carbon and niobium, the faster is the evolution.
Numerical Simulation for Effects of Friction on Deformation Behaviors in a 3-Dimensional Hot Upsetting Process
Authors: Lin Yong Cheng , Ding Yan Bao
Published: June 2010

The friction between the die and workpiece plays an important role in determining the quality of the finished products during the hot deformation. Based on the experimental results, a rigid-viscoplastic finite element model was made to study the effects of friction conditions on the strain distribution and microstructural evolution in high strength low alloy steel during hot upsetting process. Also, the effects of friction conditions on the forging loadings and shape geometry of the deformed specimen were also investigated. The results show that: (1) the deformation of specimen is inhomogeneous, and the degree of deformation inhomogeneity decreases with the increase of friction coefficient; (2) the dynamic recrystallization volume fraction decreases with the increase of friction coefficient; (3) the distribution of the average grain size is inhomogeneous in the deformed specimen, and the average grain size increase as the friction coefficient is increased; (5) the effects of friction conditions on the peak forging loading and shape geometry of the deformed specimen are significant.
Effect of Prior Cold-Working on Strength and Electrical Conductivity of Cu-Ti Dilute Alloy Aged in a Hydrogen Atmosphere
Authors: Semboshi Satoshi , Numakura Hiroshi , Gao Wei Lin , Suda Hisashi , Sugawara Akira
Published: June 2010

Aging solution-treated Cu-Ti alloys in a hydrogen atmosphere significantly improved their electrical conductivity without degradation of the mechanical strength, compared to conventionally aged alloys. In this study, the influence of prior deformation on the mechanical and electrical properties of Cu-4.2 at.% Ti alloys aged in a hydrogen atmosphere was examined. The Vickers hardness of the solution-treated specimen increased from 127 kgf/mm2 to 265 kgf/mm2 by aging at 673 K for 180 h in a hydrogen atmosphere of 0.8 MPa, while that of the deformed specimen achieved a maximum of approximately 280 kgf/mm2 by aging for 100 h in the same atmosphere. Prior deformation resulted in a more rapid increase in conductivity during aging than that without deformation. The conductivity at the peak-hardness of the deformed specimen was 22% IACS (International Annealed Copper Standard), which exceeded that for the solution-treated specimen. Thus, prior deformation assisted in a significant improvement of the mechanical and electrical properties during aging in a hydrogen atmosphere.
Development of High Strength and High Conductivity Cu-Ag-Zr Alloy
Authors: Cho Hoon
Published: June 2010

The development trend for diagnostics is reducing the diameter of coaxial signal cables that comprise the probe cable. The thinner super-fine coaxial cable which is offering superior electronic and mechanical properties, such as 75% IACS (International Annealed Copper Standard, electrical conductivity) and 700 ~ 800 MPa in tensile strength has to be developed. Three binary systems, Cu-Ag, Cu-Zr and Ag-Zr were thermodynamically optimized in the present study. Integration of optimized binary phase diagram can give useful information to predict the possible phases for the ternary Cu-Ag-Zr during manufacturing process. The large Cu5Zr particles were found at grain boundaries of as-cast alloys, which results from the strong affinity between Cu and Zr as well as no solubility of Zr in the Cu matrix. This coarse Cu5Zr phase was not dissolved fully during homogenization resides within the microstructure. Therefore, this phase induces decreasing in tensile strength after ageing.
Optimization of the Cooling Process of a Heavy Hydraulic Turbine Runner Band Casting in Heat Treatment
Authors: Kang Jin Wu , Wang Tian Jiao , Yu Hai Liang , Huang Tian You , Liu Bai Cheng
Published: June 2010

Hydraulic turbine band castings are susceptible to deformation in heat treatment process if their cooling is not well controlled. The coupled analysis of forced air flow and heat transfer in normalizing process of a heavy turbine band runner casting with outer diameter of 8000 mm was carried out by using ANSYS software. The band undergoes significant deformation because of uneven cooling resulted by uneven air flow around it during normalizing. The forced air flow pattern is a key factor which influences the cooling uniformity and efficiency. It is optimized by adjusting the cooling fans’ orientation relative to the casting to form cyclone around it. Consequently, cooling uniformity is improved to avoid deformation.
Heterogeneous Nucleation and Grain Formation on Spherical and Flat Substrates
Authors: Qian Ma
Published: June 2010

Turnbull’s transformation nucleus model initiated the concept of a growth barrier for a spherical-cap crystal nucleus growing on a small flat substrate. The recently developed free growth model provided a clear physical picture of the growth barrier concept with experimental and modelling support. Fletcher’s spherical substrate model enhanced the understanding of the geometrical effect of a substrate on nucleation. A recent novel analysis of Fletcher’s model furnished new insights into the similarities and differences between nucleation on spherical and flat substrates. It is necessary to distinguish between the undercooling required for nucleation and that for overcoming the growth barrier; the greater one determines the early stages of grain formation.
Microstructural Observation on Materials of the Japanese Sword under Fold-Forging Process
Authors: Takami Go , Ohba Takuya , Morito Shigekazu , Das Ananda Kumar
Published: June 2010

The Japanese sword is produced from a special kind of steel called tamahagane, using a forge-fold operation repeated several times. The purpose of this study is to clarify the development of microstructures with successive forge-fold operations using tamahagane. Specimens under several stages of sword making have been investigated with optical microscopy, scanning electron microscopy and electron probe micro analysis methods. Microstructures have been found to be a combination of ferrite and pearlite with a lot of nonmetallic inclusions. The ferrite bands become finer and among other inclusions Fe2SiO4 takes a spherical shape with increasing recurrence of forge-fold operations.
Microstructure Evolution and Compression Properties of a Directionally Solidified Ni-24.8%Nb Hypereutectic Alloy
Authors: Li Shuang Ming , Jiang Bing Lun , Fu Heng Zhi
Published: June 2010

At normal solidification conditions, in-situ composites of a Ni-24.8%Nb hypereutectic alloy can be produced at growth velocities below 5μm/s, with a thermal gradient of 180K/cm, and this low productivity remarkably restricts the application of this kind of in-situ composites. In this paper, we proposed an approach that employs an abrupt growth velocity to make the in-situ composites grow stably out of the coupled zone. In-situ composites of the Ni-24.8%Nb hypereutectic alloy were obtained at a growth velocity of 100μm/s and the productivity was greatly improved. This value is in the same order magnitude imposed on the single-crystal superalloys. The compression strengths were investigated on different microstructures involving the coupled eutectics and non-coupled eutectics. The results showed that the crack distribution and extension were mainly localized in primary Ni3Nb dendrites in the non-coupled eutectics, and that in-situ composites with the entirely coupled eutectics have improved mechanical properties and different deformation behaviors.
Strength and Conductivity of Deformed Cu-Fe Composites after Solidified with a Horizontal Magnetic Field
Authors: Zuo Xiao Wei , Wang En Gang , Qu Lei , Jia Peng , Zhang Lin , He Ji Cheng
Published: June 2010

In this paper, the Cu-Fe alloys are fabricated by solidifying with and without a 1.0 Tesla horizontal magnetic field and they are drawn to composite wires under different drawing ratios, then their further strength and conductivity are investigated. The results show that, when the drawing ratio is lower, the strength of the Cu-Fe composites pre-solidified with a horizontal magnetic field is lower, which is caused by the coarser solidification microstructures induced by the injected magnetic field. However, the increase ratio in the strength of the Cu-Fe composites, which is plotted as a function of the Fe content and the drawing ratio, is higher in the case of the imposed magnetic field. It indicates that it is more efficient applying the magnetic field to fabricate Cu-Fe composites with high Fe contents and larger drawing ratio. A quantitative relationship is fitted to predict the influence of the Fe content on the strength of the Cu-Fe composites wires. On the other hand, the conductivity of the Cu-Fe composite wires is decreased with increasing Fe content. The injected magnetic field has no effect on the conductivity.
The Correlation between the Liquid Structure and the Solidification Microstructure of Sn-Cu Lead-Free Solders
Authors: Pan Xue Min , Zhao Ning , Ding Rui Fang , Wei Guang Lin , Wang Lai
Published: June 2010

The liquid structure of two lead-free solder molten alloys, Sn-0.5Cu and Sn-1.8Cu (wt.%), have been investigated using X-ray diffraction method. The main peak for liquid structure of Sn-0.5Cu is similar to that of pure Sn. A pre-peak has been found in the low Q part on the structure factor S(Q) of Sn-1.8Cu tested under 320°C and the pre-peak decreases its intensity with increasing temperature, but it disappeared finally when the testing temperature reached 350°C. The microstructure of the solder matrix as well as interfacial reaction between liquid solders and Cu substrate was also studied. The structural unit size corresponding to the pre-peak almost equals to magnitude of crystal planar distance of Cu6Sn5 phase. The appearance of a pre-peak may be due to existence of clusters with Cu6Sn5-phase-like structure in the melt. Quantity and size of clusters increases with decreasing temperature but their structural unit size remains constant. Cu6Sn5 phases develop from incorporating and growing of the clusters during solidification, thus result in the correlation between liquid structure and solid microstructure.
Effect of Polygonal Rotor Process on Solidification Structure of Lead-Free Bismuth Bronze
Authors: Kose Takahisa , Uetani Yasuhiro , Nakajima Katsuyuki , Matsuda Kenji , Ikeno Susumu
Published: June 2010

Semi-solid slurry with fine solid granules for rheocasting was made from lead-free bismuth bronze by passing the low-superheat melt through an opening between a rotating regular octagonal rotor and a circumscribed chill block. We mainly investigated the effect of rotational speed on the structure of a solidified small ingot. The ingot structures changed from the dendrite of rotor-free condition to the rosette at the rotational speed of 50rpm and to the granular with a mean grain size of about 50m at higher than100 rpm. If the slurry made at 100rpm was rheocast to a disk shape by the use of a high pressure casting machine, the disk had almost uniform granular structures from the center to the edge regions.
Monte Carlo Simulation of Thermophysical Properties for Al-Ce Liquid Alloys
Authors: Yao Wen Jing , Wang Nan
Published: June 2010

The Monte Carlo method with EAM potential is applied to simulate the liquid Al-Ce binary alloy system and the thermophysical properties including surface tension (), viscosity () and diffusion coefficient (D) of liquid Al-8at%Ce alloy are determined. The simulated  values decrease with temperature. Based on the relationship between ,  and D, the various viscosity and diffusion coefficient of liquid Al-Ce alloys under different temperatures were determined. The comparison of the simulated results with some experimental measurements is performed and discussed, indicating that the simulation method and EAM parameters in simulation are acceptable. The dependence of viscosity and diffusion coefficient of liquid Al-Ce alloys on temperature is established to be helpful in further investigation of amorphrization ability of Al-Ce alloys.
Improving the Microstructures and Mechanical Properties of Hypereutectic Al-Si Alloys by Spray Forming Technique
Authors: Cui Hua , Hou L.G. , Cai Yuan Hua , Zhang Ji Shan
Published: June 2010

The hypereutectic Al-Si alloys with different Cr additions have been prepared by spray forming and cast processes. With adding Cr into Al-25Si-5Fe-3Cu (wt.%, denoted as 3C) alloy, the long needle-like δ-Al4FeSi2 phases in the cast 3C alloy were almost substituted by skeletal α-Al(Fe,Cr)Si phase, which was refined into granular α-Al(Fe,Cr)Si phase (≤ 3-5 μm) in Cr-added deposits. By using hot extrusion almost full densification of the deposits can be made, but induces coarsening of Fe-bearing phases in as-deposited 3C and C10 (adding 1.0 wt.% Cr into 3C alloy) alloys. The size of the granular α-Al(Fe,Cr)Si phase is still less than 5 μm after hot extrusion of the as-deposited C20 alloy, while some plate-like β-Al5(Fe,Cr)Si phases (~20 μm) disappeared. The thermal stability, mechanical properties were also evaluated.
Colored Metallography Study of Bainite Steel Used for High Speed Railway Crossing
Authors: Zhang Fu Cheng , Han Bo , Lv Bo , Wang Tian Sheng
Published: June 2010

Using the technique of colored metallography, the phase compositions of two medium-/low-carbon low-alloy carbide-free bainite steel used for railway crossings are obtained. The etching of the samples was carried out using the Lepera reagent and a mixed reagent of hyposulphite and picric acid respectively. The proportion of the bainite phase was calculated using an image processing system with an optical microscope and the residual austenite content was measured using XRD method. The martensite phase content can then be determined. It is found that the reagents can effectively and quantifiably analyze the phase composition of bainite steel and produce approximately the same results.
Observation of Hot Tear Formation by Acceleration Sensor
Authors: Esaka Hisao , Naitoh Yoshiaki , Uotani Daisuke , Shinozuka Kei
Published: June 2010

Hot tear is the one of the biggest problems of cast products. There have been many researches in order to understand the formation mechanism of hot tear. However, it is still uncertain when a hot tear initiates and how it propagates. Thus, the preliminary research has been carried out to observe the vibration of permanent mold which correspond to the initiation or propagation of hot tear. Al-2.0 wt% Cu alloy was used for test alloy. The signals of acceleration sensor were recorded at an interval of 5 ms. After casting, the vibration, which lasted scores of milliseconds, was observed intermittently. This may indicate that hot tear initiates or propagates intermittently and the strain due to contraction of solidification or cooling is relaxed by hot tear.
The Effect of Cu on the Microstructure and the Elevated Temperature Properties of Ferritic Heat Resistant Cast Iron
Authors: Choe Kyeong Hwan , Lee Sang Mok , Kim Myung Ho , Lee Kyong Whoan
Published: June 2010

The effects of copper addition on the microstructure and the elevated temperature properties of ferritic heat resistant cast iron were investigated. The as-cast pearlite formed due to the addition of Cu was fully eliminated by full annealing. As the content of Cu increased, the grain size of ferrite decreased. The grain refinement due to the addition of Cu enhanced the mechanical properties at room temperature, however, those at elevated temperature deteriorated. The addition of Cu diminished the volume change during α→γ transformation. The starting point of α→γ transformation increased with Cu contents under 1.15wt% Cu but this tendency was reversed above this point. This trend can be found also in the case of lattice parameter of ferrite matrix. It is inferred from Fe-Cu phase diagram that the addition of Cu enlarged the coexistence zone of α and γ, so it diminished the volume change during α→γ transformation.
The Effect of Constricting the Melt Flow on Mechanical Properties of High Pressure Die Castings
Authors: Gunasegaram Dayalan R. , O'Donnell Robert G. , Givord Michel , Finnin Barrie R.
Published: June 2010

The addition of a constriction in the melt flow path of high pressure die castings is discussed in terms of its influence on modifications to mechanical properties. It is shown through experimentation that the ultimate tensile strength and elongation to fracture of as-cast tensile specimens increased when the melt flowed through a constricted path. It is proposed that defect-forming inclusions were disintegrated more efficiently in the constricted runner through increased strain rates and turbulent dissipation rates. Increased turbulence is also presumed to be the cause for the greater dispersion of defects. The suggestions are supported with calculations aided by computational fluid dynamics simulations.
Relationship between Particle Size and Martensitic Transformation in an Fe-30at%Ni Alloy
Authors: Nam J.M. , Terai Tomoyuki , Mino Masashi , Aikawa Y. , Kakeshita Tomoyuki
Published: June 2010

We have investigated the effect of particle size on martensitic transformation by using single crystalline specimens of an Fe-30at%Ni alloy by scanning electron microscope (SEM) observation, X-ray diffraction(XRD), magnetic susceptibility and magnetization measurements. As a result, we have found that an athermal martensitic transformation changes to an isothermal martensitic transformation with decreasing particle size. Considering the result of the TTT diagram, we have estimated the driving force for the martensitic transformation and the cluster size for nucleation of the isothermal martensitic transformation based on the model previously proposed.
Development of a Magnesium Alloy Rotor with a Pin-Point Gate Mold
Authors: Lee Young Cheol , Jo Hyung Ho , Park In Deok
Published: June 2010

The rotor is a key determinant of the performance of a compressor and many attempts have been made to improve the efficiency of compressors by optimising rotor design. Rotors are usually made of several layers of steel sheets with thin cavities through the steel sheets, and aluminium alloys are used to fill the cavities by high pressure die casting process, and so bind the steel sheets together. Because of their high fluidity and good damping ability, magnesium alloys can be a good alternative for a high efficiency rotor. In this study, magnesium alloys were used for manufacturing rotors by high pressure die casting process using pin-point gate mold. By adopting a pin-point gate system, additional machining was eliminated and casting defects were reduced due to good castability of magnesium alloys.
Application of Continuous Displacement Cluster Variation Method to Study Phase Equilibria
Authors: Mohri Tetsuo
Published: June 2010

Cluster Variation Method (CVM) has been widely recognized as one of the most reliable theoretical tools to study phase equilibria in metallic alloy systems. The conventional CVM, however, does not allow atomic local displacements and, therefore, calculated results often encounter various inconveniences such as the overestimation of transition temperatures. Continuous Displacement Cluster Variation Method (CDCVM) was proposed to circumvent such deficiencies of the conventional CVM. Preliminary studies on an order-disorder phase diagram based on CDCVM indicate that the transition temperature is shifted downward reproducing experimental tendencies. In the present study, lattice thermal vibration effects are also incorporated through Morse potential. It is concluded that the local lattice distortion effects are quite effective to reduce the transition temperature.
Spheroidization Behavior of Cementite in a High Carbon Steel
Authors: Ha Tae Kwon , Lee Chang Hoon , Kim Ki Soo
Published: June 2010

The effect of initial microstructure, cold reduction ratio, and annealing temperature on the spherodization rate of SK85 high carbon steel sheet was investigated. High carbon steel sheet fabricated by POSCO was soaked at 800oC for 2 hr in a box furnace and then treated at 570oC for 5 min in a salt bath furnace followed by water quenching to obtain a fine pearlite structure. Cold rolling was conducted on the sheets of fine pearlite by reduction ratios of 20, 30, and 40 % and heat treatment for spheroidization was carried out at 600 and 720oC for the various time intervals from 0.1 to 32 hrs. Area fraction of spheroidized cementite was measured with an image analyzer as a function of cold reduction ratios and duration times.
The Identification of Phase by Overlapping of First Derivative of Dilatation in Low Carbon Steels Multi-Phase Presenting
Authors: Park B.J. , Choi Jong Min , Lee S.H. , Lee Kwan Soo , Lee Kyung Jong
Published: June 2010

The phase transformation in steels has been widely measured by dilatometer using the lever rule. However, the concept of lever rule is no longer applied in case of multi-phase present. Furthermore, it is quite difficult to differentiate a low temperature phase from the others due to the small fraction change (10-3 - 10-4 fraction of original length) and the plastic deformation during transformation. The overlapping of first derivatives of LVDT of several continuous cooling dilatations could be better way to identify and to analyze low temperature phases. In addition, the length change is simulated by considering the lattice parameter changes due to the temperature, composition and phase as well as decomposition kinetics of austenite in order to verify the method suggested. By comparing the simulated length change with the measured, the first derivative of dilatation interfered could be separated for each phase. As a result, the start, finish and peak temperature and the amount of each phase are determined. The method is also confirmed by OM and SEM.
A New Algorithm of Phase Field Approach to Polycrystalline Dendritic Solidification in Two and Three Dimensions
Authors: Wang M.Y. , Jing Tao
Published: June 2010

A new algorithm of phase field model is developed to simulate polycrystalline dendritic solidification growth in undercooled melts. The algorithm adopts a single phase field order parameter model incorporated with the anisotropy of solid-liquid interfacial energy and mobility. The model validation is performed by comparing the simulations with the theory analytical results and experimental information for both single and multi-grain dendritic growth, which demonstrates the quantitative capabilities of the proposed algorithm.
Physical Model of Aluminium Refining Process in the Batch and Continuous Reactors
Authors: Saternus Mariola , Botor Jan
Published: June 2010

Both primary and secondary aluminium need to be refined. The most popular methods of aluminium refining is barbotage. This method is based on the introduction of refining gas bubbles into liquid metal. It can be done in batch or continuous reactors. The refining gas can be introduced to the metal by lances, ceramic porous plugs or rotary impellers. The gas bubbles generated in this way are then mixed with the liquid metal and the level of mixing depends on the processing parameters such as the flow rate of refining gas or the impeller speed. Five patterns of the refining gas dispersion in the liquid metal are known: no dispersion, minimal dispersion, intimate dispersion, uniform dispersion and over-dispersion. Physical modelling is the best way to visualize these kinds of dispersion. It also helps to choose the adequate processing parameters. However, it is also important to keep the dynamic and geometrical similarities to the refining process. In the paper the physical modelling of the aluminium refining process is presented. Two reactors: URO-200 batch reactor with a rotary impeller and URC-7000 continuous reactor with ceramic porous plugs were taken into consideration.
Analysis of {10-12} Twin Structure by Molecular Dynamics Method
Authors: Nakamura Kounosuke , Kitahara Hiromoto , Ando Shinji
Published: June 2010

{10 2} twin is common in pure hcp metals. In this study, initiation and development of {10 2} twin in hcp metal was simulated by molecular dynamics (MD) method. Two types of model crystals were stretched along the y-axis by applying displacement of 0.005a (a is lattice constant of the basal plane) every 1000 MD steps and relaxed atoms by molecular dynamics method. The Y-boundary of the model was applied fixed boundary condition and the X and the Z-boundary were free boundary condition. The Lennard-Jones type interatomic potential was employed in this simulation. In the single crystal, {10 1} pyramidal slip initiated at the crack tip and the pyramidal slip was stopped at Y-boundary atoms. After that, a {10 2} twin was initiated at a front of the slip. With increasing external strain, the twin grew with increasing external strain. In the bi-crystal, {10 0} prismatic slip occurred at the crack tip in Crystal 1 and a-dislocation of the slip stopped at a grain boundary between the Crystal 1 and 2. With increasing applied strain, {10 2} twin was initiated in the Crystal 2 at the grain boundary. From the simulation results, the ‘shuffling’ process of twin deformation was estimated.
Residual Stresses in Cold Spray Process Using Finite Element Analysis
Authors: Phan Thanh Duoc , Masood Syed H. , Jahedi Mahnaz Z. , Zahiri Saden H.
Published: June 2010

In cold spray process, the simulation of coating deposition and the arising residual stress analysis are critical for an optimisation of process conditions. However, there are not many published literatures on the role of residual stresses in a cold sprayed coating. In addition, the multi-particles deposition behavior is also not well known, especially when coating of pure titanium powder is considered. This paper considers the development of an explicit finite element model of a cold spray process with defined initial and boundary environment. The explicit finite element model is then used to determine the optimum operating parameters to deposit titanium particles. It is also used to predict the residual stress developed in the coating by examining a fluid/structure interaction. The measured velocity and temperature from Computational Fluid Dynamics model are then use as initial input parameters to the explicit dynamic simulation. The predicted results reveal that Finite Element Method can be used to study the development of residual stress in a cold-sprayed coating as well as to find the optimum operating conditions to deposit coating of titanium particles before doing a real time fabrication.
Effect of Grain Boundary Serration on the Tensile Properties of the Super 304H Heat Resistant Austenitic Stainless Steel
Authors: Hong Sung Min , Min Dong Joon , Fleury Eric
Published: June 2010

Grain boundary serrations were produced in heat-resistant austenitic stainless steel containing Cu by applying after solution heat-treatment a holding time in the range 700-800oC between 30 minutes to 3 hours. These special treatments provide an enhancement of the tensile ductility of about 40 and 113%at room temperature and 750oC, respectively, while no significant change in the yield stress and tensile strength could be observed.
Constrains of Super-Current Flow in YBCO Coated Conductors
Authors: Pysarenko Serhiy , Pan Alexey V. , Dou Shi Xue
Published: June 2010

High temperature superconducting YBa2Cu3O7 films have been prepared by pulsed laser deposition on top of single crystal substrates and metallic templates. Films have been investigated in order to determine the influence of microstructural peculiarities on the critical current density. It has been found that there is an inherent mechanism limiting the superconductive current flow in YBa2Cu3O7 film deposited on metallic template. This mechanism is associated with YBa2Cu3O7 film architecture, fabrication procedure and following low temperature usage.
Synthesis and Its Characteristic of Silicon Nitride Film Deposited by ECR-PECVD at Low Temperature
Authors: Wu Ai Min , Yue Hong Yun , Zhang X.Y. , Qin Fu Wen , Li T.J. , Jiang Xin
Published: June 2010

The silicon nitride films have been deposited by Electron Cyclotron Resonance-plasma enhanced chemical vapor deposition (ECR-PECVD) method at low temperature, and the pure nitrogen is introduced into the ECR chamber as the plasma gas, the silane(Ar diluted, Ar:SiH4=19:1) is used as precursor gas. The optimum deposition parameters of SiN films for photovoltaic application as an efficient antireflection coating(ARC) have been investigated. The actual composition of the films will be varied with the deposition conditions, such as gas flow rate ratio(N2/SiH4), substrate temperature, and microwave power. The effect of deposition parameters on the optical performance of SiN films was determined by Ellipsometry. The Si-N and N-H stretching characteristic peaks of SiN films have been observed by FTIR spectroscopy. Results shown that uniform silicon nitride films with low hydrogen content can be deposited at high deposition rate(10.7nm/min), and the refractive index increased with the increasing of substrate temperature and microwave power. The film shows good optical properties (refractive index is 2.0 or so) and satisfied surface quality (average roughness is 1.45nm) when the deposition parameter is 350oC and microwave power is 650W.
Effect of Nitridation on GaN Film Grown on Glass Substrate by ECR-PEMOCVD Method
Authors: Qin Fu Wen , Wu Ai Min , Liu Feng Chun , Liu Bao Dan , Jiang Xin
Published: June 2010

Nitridation of Corning 7101 glass substrate and the following GaN deposition were carried out in a self-developed electron cyclotron resonance plasma enhanced metalorganic chemical vapor deposition (ECR-PEMOCVD) system equipped with in-situ reflection high-energy electron diffraction (RHEED) monitoring. RHEED pattern and X-Ray diffraction (XRD) spectrum showed that the nitridation can effectively improve the C-axis orientation of as-prepared GaN film. Atomic force microscope (AFM) analysis indicated that the average grain size increased significantly with 5 min of nitriding, but degraded as nitriding time increased. The optimum nitriding time was achieved as 5 min. The effect of nitridation on the GaN film deposition and its formation mechanism were discussed.
Research on Influence of Ion-Assisted Deposition to the Optical and Mechanical Properties of SiO2 Film
Authors: Wang Duo Shu , Luo Chong Tai , Chen Tao , Xiong Yu Qing , Wang Ji Zhou
Published: June 2010

In the paper, ion-assisted e-beam evaporation (IAEE) method was used to deposit SiO2 film on CBA(CaO-Al2O3-BaO) glass substrate, and the influence of processing parameters on the performance of the thin films was studied. The result shows that the ion energy, substrate temperature and evaporating rate are key factors that affect the abrasion resistance and transmission of the SiO2 film. Heat treatment was used to eliminate the absorption of H2O in spectrum range of 2.7~3.5μm. SiO2 film with good abrasion resistance and high transmission in spectrum range 3.0~5.0μm was deposited successfully on the special glass substrate.
Tensile Deformation Behavior of Tempered Martensitic Steels Produced in CGL Lines
Authors: Song Tae Jin , Kwak Jai Hyun , De Cooman Bruno C.
Published: June 2010

Thermal cycles of conventional galvanizing and galvannealing processes were applied to low carbon martensitic steels to examine the mechanical property of martensitic steels after their processing in conventional Continuous Galvanizing Lines (CGL). During the thermal cycle simulation, tempering phenomena occurred resulting in changes of microstructure and mechanical properties. In this study, the tensile deformation behavior of martensitic steels was studied in detail in order to understand the tempering phenomena occurring during their processing. It was found that, after tempering, the strain hardening ability decreased drastically and that the plastic flow became localized. An experimental analysis of this phenomenon will be presented based on TEM microstructural observation and Internal Friction measurements.
The Effects of Substrate Temperature on the Composition and IR Transmission Properties of Germanium Carbon Films Deposited by Reactive RF Magnetron Sputtering
Authors: Li Yang Ping , Liu Zheng Tang , Yan Feng , Liu Wen Ting
Published: June 2010

Germanium carbon films were prepared on ZnS substrates by reactive RF magnetron sput- tering of a Ge target in Ar and CH4 mixtures for IR antireflective and protective purposes. IR transmit- ttance spectra of the specimens were measured, with which H content in the films was investigated. The C and Ge contents and the atomic binding state were studied by X-ray photoelectron spectroscopy. The results show that H involved in the films combine mainly with C at low substrate temperatures. IR absorption peaks caused by the C-H bonds decrease with increasing temperature, indicating the drop of the C-H bonds content in the film. At relatively low temperature the film is high in C content and low in refractive index; at high temperature the film is low in C content and high in refractive index. Both C-Ge and C-C bonds exist in the film and O impurity combines mainly with Ge.
Technological Parameters and Electrical Properties of Ti/TiN Multilayer Films Prepared by Magnetron Sputtering
Authors: Hu Min , Liu Ying , Lai Zhen Quan
Published: June 2010

A series of Ti/TiN multilayer films was deposited on Si substrates by DC reactive magnetron sputtering process. The influence of sputtering current density and substrate temperature on cycle membrane structure and its electrical properties was investigated in this study. The results show that: when the current density is 0.4A, the sheet resistance and electrical resistivity of the film are of the minimum value. The sheet resistance and electrical resistivity of the film decrease with an increase of substrate temperature. Therefore, sputtering current density should be controlled between 0.3-0.4A, while the substrate temperature should be above 400°C. For a given modulation period and modulation ratio, with the change of number of cycles the films can present a unique set of colours, and its electrical resistivity decreases with an increase in the number of cycles. When the number of cycles is greater than 4, the sheet resistance is significantly reduced, and when the number is greater than 15, the prepared films come off. To keep the number of cycles at five and change the modulation period, it is shown that a minimum electrical resistivity exists.
Triangular Dislocation Loop Model for Surface Displacement in Indented Thin Films
Authors: Muraishi Shinji , Chinen Hiromitsu , Takaya Masaaki , Hara Kousuke
Published: June 2010

The surface displacement of the indented layered composite has been observed by AFM and TEM, and the elastic recovery due to the indentation residual stress is compared with the prediction of the triangular dislocation model. At the shoulders of the indentation, the upheaval of Al-4wt%Cu film is smoothly connected, whereas that of Al2Cu film is localized as the intensive sheared displacement. The magnitude of the elastic recovery in film/substrate composite is larger than the predicted value, which might be attributed to the repulsive interaction between the glide dislocations and the hard Si substrate.
Effect of Ultra-Thin Pt Layer on the Preferred Orientation of AlN Films
Authors: Harumoto Takashi , Muraishi Shinji , Shi Ji , Nakamura Yoshio
Published: June 2010

Preferred orientation of AlN film has been changed from random to c-axis textured by inserting the ultra-thin Pt/AlN underlayer. The ultra-thin Pt underlayer also exhibits the same effect on the preferred orientation control of AlN film. According to intensity distributions of diffracted X-ray collected as the function of 2θ and ψ on these films, it is clearly shown that c-axis of AlN is altered from titled to the surface normal. AlN film and AlN films with underlayers demonstrate tensile stress, and it can be reduced by inserting underlayers. The effects of underlayers on the development of the preferred orientation and the reduction of stresses are similar to that of decreasing sputtering gas pressure.
Surface Treatment of 316L Stainless Steel by High Current Pulsed Electron Beam
Authors: Hao Sheng Zhi , Xu Yang , Li Min Cai , Dong Chuang
Published: June 2010

High current pulsed electron beam has been developing as a useful tool for surface modification of materials. This paper presents our research on the surface treatment of 316L stainless steel with an equipment of working parameters as electron energy 20-30keV, pulse duration 1.5µs and energy density ~6J/cm2. The surface microstructure was characterized with metallography, X-ray diffractometry and electron backscatter diffraction (EBSD) techniques. It was found that the modified samples showed significant improvement on corrosion resistance when using increased pulse number and higher energy density. This result is discussed in relation to the coupled temperature-stress fields formed after the absorption of electron beam energy.
Effect of Pre-Deforming on Plasma Nitriding Response of 304 Stainless Steel
Authors: Nishimoto Akio , Akamatsu Katsuya
Published: June 2010

The effect of a modified layer caused by pre-deforming on the low temperature plasma nitriding of AISI 304 austenitic stainless steel was investigated. The aim of using the deformed layer is to produce a thicker nitrided layer and to decrease the nitriding temperature due to the much faster diffusion of nitrogen. The pre-deformed sample was prepared by the rolling in 0, 1, 2, 3, and 4% ratios. Plasma nitriding was carried out at 673 and 723 K for 18 ks under 600 Pa pressures in presence of N2/H2 in 50:50 ratio. The microhardness, thickness and phase composition of nitrided layers formed on the surface of pre-deformed and non-deformed samples were investigated using Vickers microhardness tester, optical microscope and X-ray diffraction techniques, respectively. After nitriding, maximum hardness ~1150 HV was achieved on the pre-deformed sample. XRD pattern showed that most dominant phase of the nitrided layer consisted of the expanded austenite (S phase). In addition, the pre-deforming by rolling had a significant influence on the hardness and thickness of the S phase. That is, the hardness and thickness of the S phase were increased by applying the pre-deformation.
The Addition of Silica Nanoparticles with Different Sizes for a Silica Film on Stainless Steel without Crack Formation
Authors: Kim Hoh Yeong , Kim Gyun Tak , Lee Heung Yeol , Hwang Tae Jin
Published: June 2010

Inorganic protective silica film was tried on the surface of stainless steel using a sol-gel chemical route where tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) were used. In the coating solution silica nanoparticles with different sizes were mixed. Then the film was deposited on the stainless steel substrate. It was intended that by mixing the small and the large particles at the same time a sufficient consolidation of the film was possible because of the high surface activity of the small nanoparticles and a modest silica film would be obtained with a low temperature heat treatment at as low as 200 °C. The prepared film showed enhanced adhesion when compared with a silica film without nanoparticle additions. The films also showed improved protect-ability against corrosion. Scanning electron microscopy (SEM), scratch test, potentiodynamic polarization scan and electrochemical impedance analysis were also used to characterize the films.
PEM Fuel Cell Separator with Thermally Nitrided Low Carbon Steel
Authors: Nam Dae Geun , Choi Chang Yong , Jang Jae Ho , Park Young Do , Kang Nam Hyun
Published: June 2010

The separator is one of the most important parts in PEM fuel cells. Stainless steels are widely used as separator for its good mechanical properties and mass production. However, for a good chemical compatibility, stainless steels need to have high chromium content or surface treatment, which makes separator high cost. Low cost of separator is important for commercial use. In this study, conventional low carbon steel is used as base metal of separator. Low carbon steel is low at cost, but has poor chemical properties for separator. For a good corrosion resistance, low carbon steel needs to be surface treated. To make a uniform surface treated layer on low carbon steel, chromium is conventionally electroplated on the steel and thermally nitrided. Surface treated low carbon steel is investigated using microstructure and element analysis tools. Interfacial contact resistance and polarization test is applied for the properties of fuel cell separator. The results show that chromium nitrided layer uniformly formed on low carbon steel. And the surface treated steel showed a good corrosion resistance as a separator.
Deposition of Superconducting Thin Films of Magnesium Di-Boride on Various Substrates by Electroless Plating Process
Authors: Putatunda Susil K. , Vijayaragavan Khurpa S. , Lawes Gavin
Published: June 2010

Superconducting thin films of magnesium diboride (MgB2) has been synthesized on various substrates such as gold, silver, copper and silicon using a novel electroless plating technique. The microstructures and the superconducting properties of these films have been characterized using X-ray diffraction, scanning electron microscopy and temperature dependent magnetometry. X-ray diffraction measurements confirm that the films are crystalline magnesium diboride with some impurity phases. Clear evidence for a superconducting transition in the magnetization measurements was observed.
Raman Scattering Studies in Oxygen-Vacancy Induced Ferromagnetism of Co-Doped ZnO Films
Authors: Chen Shi Jian , Suzuki Kiyonori
Published: June 2010

Zn1-xCoxO thin films ( ) have been grown on Si (100) substrates by pulsed laser deposition. The as-prepared films showed paramagnetic characteristics at room temperature, while the films after annealing in a H2 atmosphere exhibited clear ferromagnetic behaviors. Raman scattering has been used to study the influence of the post-deposition H2 annealing on the structural properties and consequently on the magnetic properties of Co-doped ZnO films. It is found that the post-deposition annealing increases defect oxygen vacancies in the host lattice and induces an additional Raman vibration mode. The ferromagnetism of Zn1-xCoxO is believed to be strongly related to the oxygen deficiency in ZnO.
In Situ TiB2 Particles Reinforced Copper Matrix Composite Coating on Mould Steel by Laser Cladding
Authors: Liu Xue , Yang Sen
Published: June 2010

To extend the mould cycle duration and to reduce cost, a TiB2 particulate reinforced Cu based composite coating was produced on hot-working die steel substrate using laser cladding. The experimental results showed that TiB2 particles embedded in copper based alloy were in-situ synthesized during laser processing. An excellent bonding between the coating and the substrate was obtained. The microstructure of the coating was mainly composed of -Cu dendrites and dispersed TiB2 particles. The maximum microhardness of the coating was about 800HV0.2. The wear resistance of the coating was evaluated under room temperature dry-sliding wear test condition. Due to the presence of a large amount of TiB2 particles, the composite coating exhibited excellent wear resistance compared with that of substrate.