bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology-Controlled Syntheses, Growth Mechanisms, and Optical Properties of ZnO Nanocombs/Nanotetrapods
Authors: Zhuo R.F. , Xu X. Y. , Feng H. T. , Yan D. , Li H. J. , Cheng S. , Yan Peng Xun
Published: March 2010

Both ZnO nanocomb and nanotetrapod structures have been synthesized via a simple chemical vapor deposition process in a horizontal tube furnace. The morphology of the products is affected by the distance between the source material and the deposition substrate. The formation of nanocombs has been attributed to the self-catalysis effect of polar surface. The octahedral multiple-twin model is responsible for the formation of tetrapods and tripod-like arms at the end of nanowires. The evolutive process of them has been given out in detail and the results provided valuable models in understanding crystal growth mechanisms in nanometer building-blocks and to further grow net nanostructures. And their photoluminescence properties also have been discussed.
Optical Characteristics of Tungsten Oxide Thin Films Prepared by Sputtering Technique
Authors: Aly S.A.
Published: March 2010

The optical properties of tungsten oxide (WO3) films prepared by DC sputtering on unheated glass substrates with different film thicknesses have been studied. The structural characteristics of the samples were investigated using X-ray diffraction. The optical properties of the prepared films were studied by transmittance and reflectance measurements, and the integrated transmittance (TUV, TVIS, and TNIR) and absorption (AUV, AVIS, and ANIR) in UV, VIS and NIR regions. The integrated UV absorption and transmittance are varied with the film thicknesses, also, no remarkable change in VIS and NIR regions was observed. The dependence of refractive index as well as extinction coefficient on wavelength was also reported. The energy gap was calculated and is located around 3.25 eV.
Fracture Energy and Fracture Behavior of Short-Fiber-Reinforced SMC Composites
Authors: Suzuki H. , Sekine Hideki
Published: March 2010

A probabilistic fracture model is introduced to clarify the influence of the fiber bundle-matrix interfacial condition on the fracture energy and fracture behavior of short-fiber-reinforced SMC composites. In this paper, we focus on the study of the influences of two parameters of the interfacial condition, i.e., the debond stress and the constant which governs the frictional forces acting on the debonding interfaces between fiber bundles and matrix in a debonding process, and then the influences of these parameters on the fracture energy and load-displacement curve are elucidated.
Tensile Strength Deterioration of Short-Glass-Fiber Reinforced Thermoplastics by Addition of a Slight Amount of Inorganic Agent
Authors: Sekine Hideki , Yamada K.
Published: March 2010

This paper concerns a micromechanical study of the tensile strength deterioration of short-glass-fiber reinforced thermoplastics by addition of a slight amount of inorganic agent. Tensile tests were conducted using short E-glass fiber reinforced polyamide 6 with a slight amount of the inorganic addition agents TiO2, ZnO and ZnS. It is found by the tensile tests that the tensile strength decreases with increasing the hardness of the inorganic addition agents, and scarcely depends on the amount of the inorganic addition agents. After measuring the pull-out length of glass fibers on the fracture surfaces of test specimens, the variation of the scale parameter of Weibull moduli is estimated from the cumulative probability of pull-out length. Finally, the tensile strength deterioration is numerically predicted using the data. The predicted values of tensile strength are consistent with the experimental ones.
Simulation of Microstructure Evolution Coupled with Fabrication Pressure for Two-Phase Ceramic Tool Materials
Authors: Huang Chuan Zhen , Fang Bin , Xu Chong Hai , Sun Sheng , Liu Han Lian
Published: March 2010

A computer simulation coupled with fabrication pressure for the sintering process of two-phase ceramic tool materials has been developed using a two-dimensional hexagon lattice model mapped from the realistic microstructure. The mean grain size of simulated microstructures by Monte Carlo Potts model integrated with pressure increases with an increase in fabrication pressure, which is consistent with the experiment results. Monte Carlo Potts model coupled with fabrication pressure is suitable for simulating the microstructure evolution at the different fabrication pressure during the fabrication of ceramic tool materials.
Study on the Cutting Force Modeling and Forecast Analysis in Machining Nickel Base Superalloy
Authors: Wang Xin Yong , Pang Si Qin , Yu Qi Xun
Published: March 2010

Nickel-based superalloy is one kind of typical hard-processing materials, its cutting force is more complicated than other materials. Studies have shown that Response Surface Methodology model is more suitable than classical linear regression model, especially regression coefficients are more significantly. And the analysis of the linear effects , secondary effects and interactions effects can be more effective ,so as to achieve a good effect of cutting force prediction, to provide a reliable basis for a reasonable choice of processing parameters.
Development of Fe-VC Cermet from Powder by In Situ Reaction Synthesis
Authors: Sun Zhi Ping , Shen Bao Luo
Published: March 2010

The present work studies the development of a 40Fe-60VC (vol-%) cermet by powder metallurgy techniques. The base powder was obtained by mechanical high energy milling to reduce both particle and reinforcement size in order to improve powder microstructure. The modified powder was compacted by uniaxial and cold isostatic pressing. The compacts were sintered in vacuum at different temperatures and times, and characterised by several techniques, including the determination of density and hardness, study by XRD to determine the constituents after sintering, and a complete microstructural analysis by SEM and TEM. The present study reveals that a Fe-VC cermet with favorable microstructure and performance can be obtained by in-situ reaction synthesis.
Wavelet Neural Network – Based Research on Online Wearing Prediction of TI6AL4V Cutter in High Speed Milling
Authors: Zhu Hong Yu , Chen Wei Jin , Li Ying
Published: March 2010

TI6AL4V is a kind of hard-machining material, which has bad thermal conductivity, good chemical reactivity, little elastic modulus, great friction coefficient, severe work hardening, short cutter life, low machining efficiency and poor machining surface quality. To improve the machining efficiency, reduce machining cost and improve products quality, the cutting tool wear is the key factor affecting machining quality, machining efficiency and production safety. In this paper, a test system which takes TI6AL4V as the research object, and the dynamic milling force during the high speed milling as the detection signal is built for online tools wear prediction. The method of wavelet packet transform and neural network are presented to diagnose and predict the situation of tools wear. The practical example shows that this system has good practicability and could identify the tools wear states exactly through verification tests.
The Influence of Milling Parameters on Surface Residual Stresses during Milling AF1410 Ultrahigh Strength Steel
Authors: Song Ge , Li Jian Feng , Sun Jie , Jiang Feng , Mu Tao , Yuan Rong Hua
Published: March 2010

AF1410 steel is a kind of high alloy ultrahigh strength steel with perfect hardness, strength and fracture toughness after secondary hardening heat treatment. The distribution of residual stresses affects the fatigue life and stress corrosion resistance of the components in service. Little investigation about the residual stresses on AF1410 steel had been studied previously. The distribution of surface residual stresses on the components should be controlled by the machining process. In this study, two AF1410 workpieces machined by the orthogonal end-milling experiment of AF1410 were performed. The axial depth of cut, cutting speed, feed rate per tooth and radial depth of cut were involved in to the experimental factors. The residual stresses were measured by X-ray diffraction method. The influence of milling factors on distribution of surface residual stresses was studied with range analysis method. The influence sequence of the factors on surface residual stresses were obtained and the optimum value of cutting parameters were selected.
Experimental Investigation of the Effect of Ozone in Green Cutting
Authors: Han Rong Di , Wang Hui , Tang Yan Li , Wang Yang
Published: March 2010

In recent years, environmental concerns call for the reduced of cutting fluids in metal machining. The green cutting techniques are to be studied to achieve this objective. In this paper, application of ozone gas in metal cutting was investigated, compared with oxygen gas, cutting fluids and dry cutting. The effects of ozone on cutting force, cutting temperature and chip deformation have been examined in turning of C45 steel with carbide tool YT14. The results of experiments indicated that the cutting force and cutting temperature application of ozone were reduced about 7 percent and 10 percent respectively compared with dry cutting, both of them were less than oxygen gas and cutting fluids condition. The chip deformation coefficient was also less than oxygen, wet and dry cutting conditions. The research results showed that ozone had positive effects in metal machining and it was probable to be a clean and eco-friendly coolant and lubricant under specific conditions.
Finite Element Simulation of Drilling Based on Third Wave Systems AdvantEdge
Authors: Han Rong Di , Wu Jian
Published: March 2010

Drilling is one of the most complex machining processes. The 3D coupled thermo-mechanical model was developed based on Third Wave Systems AdvantEdge to study the drilling process. The workpiece was set as elastic-plastic model, which considering strains hardening, heat generation of friction in tool-chip interface and shearing deformation. Adaptive meshing technology was used, the mesh of work region refined. Contrast tests were conducted to study the chip, drilling forces and drilling temperature in drilling 45 steel and TI6AL4V. Results indicated that the results of simulation were according to experimental results; the torque of drilling TI6AL4V was less than that of drilling 45 steel, but the drilling temperature was higher than that of drilling 45 steel. Thus, finite element simulation is also an important tool to study the drilling process.
A Study on the Abrasive Waterjet Milling Mechanisms of Ceramic Materials
Authors: Feng Yan Xia , Huang Chuan Zhen , Wang Jun , Zhu H.T.
Published: March 2010

In this paper, the micro-topography of the milled surface and chips are investigated, and the milling mechanisms of ceramics are analyzed. The results show that there are many deep and flat craters due to material fractures on the milled surface of Al2O3 ceramics and evidence of plastic flow is also observed around the craters. The milled surface of Si3N4 ceramics is smooth and even, and the trace of plastic flow can be observed. The abrasives after milling are very different from those before milling, which reflects the strong impact between abrasives and materials during the milling process. It is shown that the dominant milling mechanisms of ceramics are crack and exfoliating due to brittle fracture and plastic distortion according to the form of the chips.
Research on Product Platform Innovation and Evolution Based on Lifecycle
Authors: Hou Liang , Wang Hao Lun , Liu Yu Yi
Published: March 2010

To enhance the ability of product platform innovation and upgrading under Mass Customization (MC) environment, the concept of Product Platform Life Cycle (PPLC) was put forward. The innovation and evolving process and the characters of PPLC were analyzed. The Stability of the platform and its disturbance factors were discussed. A model which describes the process of product platform innovation and evolution was proposed. Then disturbance factors affecting product platform stability and platform innovation process were discussed.
Optimization of Product Assembly Relations Based on Connection Reliability
Authors: Jiang Zhao Liang , Xuanyuan Si Si , Li Zhao Qian , Meng Xiang Xu
Published: March 2010

Enhancing the reliability of product becomes one of the most important ways to perfect its quality. Based on the traditional reliability definition, the definition of assembly connection reliability is presented to describe the connection ability of two assembled parts firstly. Then, the design method based on assembly connection reliability is proposed and a new step-by-step mathematical model for assigning assembly reliability to the parts and sub-systems is established. Based on the model, design scheme oriented assembly reliability is optimized.
Finite Element Simulation for Pre-Stress Hard Cutting Process of 42CrMo Steel
Authors: Ye Bang Yan , Liu Jian Ping , Wu C.L. , Liu X.L. , Peng R.T. , Zhao X.Z.
Published: March 2010

This paper puts forward a new method of pre-stress hard cutting which integrates pre-stress and hard cutting technology. A thermo-mechanical coupling model of Finite Element Analysis (FEA) for pre-stress hard cutting on material 42CrMo steel is established. In this model, chip-work separating is made by applying shear fracture failure criterion, element deletion and adaptive mesh technique based on arbitrary Lagrangian Eulerian (ALE) method. The key technology for FEA, such as intrinsic equation of workpiece material, chip separating criterion and friction model of tool-chip interface and thermal conduction equation are researched respectively. Then FE simulation of chip forming and cutting force in pre-stress hard cutting is made and relationship between pre-stress and residual stress on machined surface under various cutting conditions is got. Simulation result is compared with that of experiment and found they are good in accordance.
A Novel 5-DOF NC Serial-Parallel Machine Tool and its Position Analysis
Authors: San Hong Jun , Zhong Shi Sheng , Wang Zhi Xing
Published: March 2010

In this paper, a novel 5 degrees-of-freedom (DOF) numerical control (NC) serial-parallel machine tool is proposed. It can provide 3 translational DOF and 2 rotational DOF. The proposed mechine tool is composed of a 2-TPR/2-TPS special 4-DOF parallel mechanism in series with a rotatable component. The structure of this machine tool is simple. The machine tool can process the workpieces which have complex surfaces.The structural characteristics of this machine tool is introduced. The position inverse solution of this machine tool is deduced by analytical method and the position forward solution of this machine tool is achieved by numerical method.
A Two-Stage Method for Cell Formation Based on Machine Utility
Authors: Cao Le , Li Shu Ge , Liu Fei
Published: March 2010

Cell formation is one of the key issues in cellular manufacturing research. A two-stage cell formation method is proposed. With this approach, parts are first clustered into different groups based on similarity factor; then, machines are assigned to these part groups according to the principle of maximum machine utility. Examples show that the proposed method is feasible in grouping parts and machines into cells so that machine utilization and manufacturing systems efficiency are improved.
Rapid Parameter Optimization of High Speed Milling Aluminum Alloy Thin-Walled Workpiece
Authors: Xu Feng , Zhu Jian Jun , Zang Xiao Jun , Wu Xin
Published: March 2010

At present, the lack of the optimal cutting parameters of high speed milling is the obstacle to its widely application. In this paper, the simplified and rapid optimization method is proposed on high speed milling alloy thin-walled workpiece. The normal selection method of cutting tools and cutting conditions is put forward as the precondition of parameter optimization. The acquirement method of optimal parameters is presented. The maximal critical axial depths of cut at the different cutting conditions are achieved according to chatter stability theory. The materials removal rate is selected as the optimal objective. The optimal parameters are filtrated up and validated according to the constraint conditions including machining tool, cutting tools, surface quality and precision of the parts.
Electrode Wear Compensation for Micro-EDM Deep Hole Drilling
Authors: Wang Yuan Gang , Wu Meng Hua , Zhao Fu Ling , Wang Jin
Published: March 2010

Lateral and edge wear of electrodes in micro-EDM affects workpiece shape accuracy. A method that change materials property of lateral side of electrode was put forward, based on discharge performance difference of different materials, and it was demonstrated with experiments. Results show that the method proposed is more effective and improves the precision of deep holes, compared with traditional sampling methods. The technology can provide reference to practicality of micro-EDM for 3D structure cavity and deep holes.
Optimization of Tap Parameters for Internal Thread Cold Extrusion of High Strength Steel Based on Genetic Algorithm
Authors: Miao Hong , Zuo Dun Wen , Wang Hong Jun , Wang Hong Feng
Published: March 2010

The ideal of genetic algorithm was introduced in optimizing tap parameters for internal thread cold extrusion of high strength steel. The use of genetic algorithm was analyzed in the optimization design of the extrusion tap. Based on optimal result, the extrusion tap was machined to reduce the extrusion force effectively. It was completely feasible to using genetic algorithm to optimize tap parameters for internal thread cold extrusion of high strength steel. Results from this study provide important basis for practical application of internal thread cold extrusion of high strength steel.
Experimental Study on Residual Stresses of Al2O3 Coating by Laser Re-Melting
Authors: Kong De Jun , Luo Kai Yu , Miao Hong
Published: March 2010

The surface of Al2O3 coating sprayed on 40Cr substrate was re-melted with high power continuous CO2 laser, and its micro-hardness and residual stresses were measured, respectively. The strengthening mechanism of Al2O3 coating by laser re-melting was analyzed and discussed. The experimental results shown that the surface of Al2O3 coating by laser re-melting is neat and smooth, and its compositions are even, its structures are compact, and Al2O3 coating is evenly distributed in its surface with grain forms, and its micro-hardness increases about 200%; Residual stress of Al2O3 coating by laser re-melting is changed into compressive stress from tensile stress, which is benefit to improving bonding strength of coating-substrate interface.
Modeling and Analyzing the Temperature Field of the Swing Substrate in Miniature EACVD System
Authors: Wang Hong Xiang , Zuo Dun Wen , Lu Wen Zhuang , Xu Feng
Published: March 2010

The magnitude and the uniformity of the substrate temperature are the most important factors that affect the quality and the growth rate of diamond films deeply. In this paper, the model of the swing substrate temperature field is established according to the heat transfer theory in Miniature EACVD System, the effects of the hot-filament parameters and the substrate swing parameters on the magnitude and uniformity of the substrate temperature were discussed. The calculated results show that the hot-filament parameters have great influence on the magnitude of the substrate temperature , the results also show that the hot-filament number , the substrate swing angle and the distance between the hot-filament and the substrate affect the uniformity of the substrate temperature field deeply. All the results provide a basis for optimizing the parameters of deposition in Miniature EACVD System.
Effect of Surface Finish of Braced Pillars on Stress Distribution of Vacuum Plate Glass
Authors: Zhang Rui Hong
Published: March 2010

The braced pillars were machined by grinding and spark machining. 3-D topography and surface roughness of two kinds of braced pillars were measured. The effect of two kinds of braced pillars on stress distribution of vacuum plate glass was analyzed by electrometric method, and was in comparison. The stress distribution of their important sides was obtained such as sealing side, supporting side and braced pillar. The experimental result showed that maximal stress of braced pillar for vacuum glass occurred in the end side of each braced pillar. Controlling high precision of the brace height and good flatness of the glass sheet considerably improve vacuum plate glass quality, such as its strength, its dependability and service life.
Three Hierarchical Optimization Design for Power Distributional Planet Gear Drive Based on Matlab
Authors: Zhu Zeng Bao , Zhu Ru Peng , Bao He Yun
Published: March 2010

According to the theory of planet gear drive and the actual design requirements of ship reducer, the mathematical model of optimization for power distributional planet gear drive is set up, the optimization design variables, the optimization objective function and the restraint conditions are definited. On the base of the establishment of three hierarchical optimization method, to take advantage of its powerful optimization toolbox in Matlab, combine the basic algorithm of optimization design, optimize respectively power distributional planet gear drive from three single-objective optimization for the lightest weight, the smallest center distance, most efficient and from one multi-objective optimization of the lightest weight and smallest center distance. The optimal results showed that ship reducer weight could be further reduced.
Experimental Investigation on Dry Point Grinding Process Based on Green Manufacturing
Authors: Xiu Shi Chao , Geng Zhi Jie , Cai Guang Qi
Published: March 2010

Due to point contact cause, the point grinding process have the lower grinding power and heat to measure and the better cooling conditions. For green manufacturing, the point grinding process has the significance to reduce the consumption of grinding fluid and improve the ground surface integrity and the process greenness. This study analyzes the geometric configuration of the contact area between the wheel and the workpiece in point grinding process, establishes the geometric and mathematic models of the contact area, and investigates the relations between the grinding parameters. The dry point grinding experiments are performed on the ground surface integrity. These investigations show that the dry grinding can be achieved in point grinding process under less depth of cut and the higher grinding speed for the high machining greenness demand.
The Clamping System Based on Giant Magnetostrictive Material and Displacement Amplifier with Area Effect
Authors: Wang Ming , Zhong Kang Min , Zuo Dun Wen , Wang Min
Published: March 2010

The green fixture is the research focus, but the current research is centralized on the fixture driven by the air. It will lead to a noise polution and a small clamping force. Using the green electromagnetic conversion technology, a new clamping system to clamp the workpiece is provided, which is composed of the giant magnetostrictive material as working medium and the displacement amplifier with the area effect. This device can realize the flexible configuration of clamping at multi-place, for multi-workpiece and in multi-direction. Furthermore, this clamping system using the A/D converter and the sensor technology of pressure and displacement to collect the relative data, the collected data can to be putted in the computer and be processed，so it is easy to control the clamp force and clamping displacement intelligently.
Gas-Liquid Combined Multiple Cut for WEDM
Authors: Wang Tong , Lu Yu Mei , Qiu Feng , Xu Xiao Cun
Published: March 2010

This study investigates the dry WEDM in multiple cut. To improve surface quality with high-speed WEDM (HS-WEDM), a new procedure as Gas-liquid Combined Multiple Cut (roughing is processed in dielectric liquid, and semi-finishing is in liquid or gas, while the finishing is in gas) is presented. Effects of pulse duration, peak current, offset, worktable feed and wire length on roughness and removal rate for dry semi-finishing were studied were studied with L16(45) design, and significant order inflluncing roughness and removal rate were found. Experiment results show that multiple cut with dry WEDM in semi-finishing and finishing can improve surface roughness significantly.
Ant Colony Algorithm and its Applications to Optimization of PID Parameters
Authors: Song Sheng Li , Zhou Jian Zhao , Wang Hai Tao , Feng Hu Sheng , He Ren
Published: March 2010

In this paper, an improved ACA (IACA) is used for tuning PID parameters. Firstly, the mathematical representation of conventional digital PID controller is deduced. Then genetic algorithms (GAs) and ACA are described. Thirdly, a PID controller based on IACA is designed. Computer simulation is performed for the proposed IACA-based PID controller finally. The results show that the proposed method could search the optimization PID parameters efficiently. The tryout of the designed controller in a paver walk system driven by valve-controlled motor runs well up to present.
Area Effect of Bath Mode Micro Electro-Discharge Machining
Authors: Ming Ping Mei , Zhu Di , Hu Yang Yang , Zeng Yong Bin
Published: March 2010

This paper investigated the impact of area effect in the batch mode micro-EDM on shape accuracy and surface morphology of the machined microstructures, as well as electrode wear, using both the positive-type and the negative-type electrode arrays fabricated by the UV-LIGA process. Experimental results showed that ,with the increase of electrode-pair scale from Φ1mm, Φ2mm, Φ4mm to Φ8mm, the shape accuracy of the machined stainless steel microstructures increased, but the eroded microcavities of the machined area reduced in both the positive-type and the negative-type micro-EDM using the same electrical pulse parameters. It was also found that, with the same pulse energy and electrode-pair area, the electrode wear reduced as the electrode-couple area increased, and the wear ratio in the positive-type micro-EDM was larger than that in the negative-type micro-EDM.
Effects of Relative Position of Balls and Tool on the Formation of Axial Micro Grooves Inside Circular Micro Heat Pipe during Spinning
Authors: Pan Min Qiang , Zeng De Huai , Liu Xiao Qing , Tang Yong
Published: March 2010

Based on the principle of spinning process of micro grooves inside the circular micro heat pipe, the effects of relative position of balls and tool on the formation of micro grooves were investigated in this work. Experimental results showed that the relative position of balls and tool and ball equivalent diameter generally determined the pattern of grooves, including groove width and depth. Micro grooves could be produced when suitable value of D was chosen and the rake face of tool was near to the center of balls. In the experiment, the largest aspect ratio of micro grooves were achieved with the conditions of D= 5.56mm, d=-3.293mm and v=5.08mm/s. And the structural parameters were w=135μm, h=154μm and k=1.141.
Research on Product Platform Innovation and Evolution Based on Lifecycle
Authors: Hou Liang , Wang Hao Lun , Liu Yu Yi
Published: March 2010

Based on the principle of spinning process of micro grooves inside the circular micro heat pipe, the effects of relative position of balls and tool on the formation of micro grooves were investigated in this work. Experimental results showed that the relative position of balls and tool and ball equivalent diameter generally determined the pattern of grooves, including groove width and depth. Micro grooves could be produced when suitable value of D was chosen and the rake face of tool was near to the center of balls. In the experiment, the largest aspect ratio of micro grooves were achieved with the conditions of D= 5.56mm, d=-3.293mm and v=5.08mm/s. And the structural parameters were w=135μm, h=154μm and k=1.141.
Tool Wear in Diamond Cutting Sinusoidal Microstructured Surfaces
Authors: Zhang Hai Jun , Zhou Ming
Published: March 2010

Tool wear in diamond cutting sinusoidal mircostructured surfaces may be quite different from that in conventional diamond turning as the sharp point tip tool is used and the depth of cut changes cyclically along the profile of the cutting surfaces. In present paper, the diamond tool geometry requirements for cutting sinusoidal microstructured surfaces were analyzed. A series of controlled cutting tests of LY12 were executed on a 2-aixs bench type ultra-precision turning machine which equipped a fast tool servo (FTS). Tool wear patterns were investigated with varied feed speed in diamond cutting sinusoidal microstructured surfaces. The scanning electron microscope (SEM) examination results of tool wear showed that the visible wear was occurred after a short cutting distance. The gradual wear around tool tip and along cutting edges was predominant wear pattern with a low feed speed. The catastrophic fracture wear at tool tip was happened with a high feed speed and the wear of sharp point tip of tool was more serious than that of cutting edges of tool.
Mechanical Strength Evaluation of a CuAlBe Shape Memory Alloy under Different Thermal Conditions
Authors: De Oliveira Danniel Ferreira , de Lima Severino Jackson Guedes , Brito Ieverton Caiandre Andrade , Gomes Rodinei Medeiros , Melo Tadeu Antônio de Avezedo
Published: March 2010

CuAl shape memory alloys containing 0.6wt% and 0.65wt% was casted by induction melting at room temperature without protective atmosphere and their mechanical strength evaluated as a function of the temperature. It was observed that the melting at room temperature does not promote any difficulty to control de beryllium content. The ultimate stress to rupture drop significantly with decreasing the test temperature is such way that the alloys became brittle irrespective to beryllium content.
Iron Distribution in Geopolymer with Ferromagnetic Rich Precursor
Authors: Gomes Kelly Cristiane , Lima Gabriel S.T. , Torres Sandro Marden , de Barros Silvio Romero , Vasconcelos Igor Frota , Barbosa Normando Perazzo
Published: March 2010

Geompolymers and their engineering applications have attracted significant attention of the scientific community. This is due to properties such as good thermal stability and high resistance to aggressive environments. Most studies on this subject are based on traditional precursor materials such as calcined kaolinite clay (metakaolinite) and fly ash. The iron content is significant, reaching around 10% in metakaolinite, for instance. The role of iron in geopolymers still lacks systematic investigation. This can be attributed to the limitations presenting nuclear magnetic resonance (NMR) spectroscopy, which is a widely used technique to study geopolymers structure. Ferromagnetic elements such as iron, which is often present in some precursors, affect the magnetic response of the material, compromising the proper analysis of its structure by NMR results. Iron content in some industrial residues may be several times higher as it is often found in metakaolinite. This work presents x-ray diffraction, infrared and Mössbauer spectroscopy studies on the distribution of iron species in iron oxide/hydroxide-rich precursor, which was used to synthesized geopolymers.
Influence of Thermomechanical Processing on the Martensitic Transformation Temperatures of NiTi SMA Wire
Authors: Kabayama Leonardo Kyo , Rigo Odair Doná , Otubo Jorge
Published: March 2010

Most of the applications of NiTi SMA are as a wire form. In this sense it is important to know the effects of thermo-mechanical processing such as reduction per pass and intermediate annealing on the wire drawing process. For this work they were produced wire by cold drawing using 15 % area reduction per pass with and without intermediate annealing. The starting ingot was produced by VIM process. The influence of thermo-mechanical processing will be related to the martensitic transformation temperatures.
Formation of Si Nanocrystals in Thin SiO2 Films for Memory Device Applications
Authors: Curiel Mario , Petrov Ivan , Nedev Nicola , Nesheva Diana , Sardela Mauro R. , Murata Yuya , Valdez Benjamin , Manolov Emil , Bineva Irina
Published: March 2010

X-ray Diffraction and Reflectivity, Transmission Electron Microscopy and Atomic Force Microscopy were applied to study the effect of thermal annealing on the properties of thin SiOx films (~ 15 nm) prepared by thermal evaporation of SiO in vacuum. It has been shown that furnace annealing at 1000 oC causes phase separation and formation of uniformly distributed Si nanocrystals into a SiO2 matrix. Clockwise hysteresis has been observed in the C-V curves measured and explained by assuming charging and discharging of the NCs with carriers, which tunnel from the Si substrate.
Synthesis of Plasticizer-Based Ferrofluid and its Use in the Preparation of Magnetic PVC Nanocomposite
Authors: Servín-Hernández E. , Rodríguez-Fernández Oliverio S. , García-Cerda L.A.
Published: March 2010

A magnetic polyvinylchloride (PVC) nanocomposite was prepared by static casting using a plasticizer-based ferrofluid. Two sets of nanocomposites were prepared: one under the influence of magnetic field and the other without magnetic field. The effects of ferrofluid content and the magnetic field on the magnetic and mechanical properties of the nanocomposite were studied in detail. Magnetite (Fe3O4) nanoparticles used for the ferrofluid preparation were prepared by the chemical co-precipitation method. Dioctyl phtalate (DOP)-based ferrofluid was prepared by the peptization technique. X-ray diffraction (XRD) was used to characterize the superparamagnetic behavior of the nanocomposite. A Universal tensometer was used to evaluate their mechanical properties. The results showed that the magnetization value of the nanocomposites increased as a function of ferrofluid concentration with all the samples showing superparamagnetic behavior. The mechanical studies showed that the tensile strength and elongation at break of the magnetic PVC nanocomposite were increased by the addition of ferrofluid and the applied magnetic field.
Preparation and Properties of CoFe2O4 Synthesized by the Modified Citrate-Gel Method
Authors: Múzquiz-Ramos E.M. , Cortés-Hernández Dora A. , Herrera-Romero O.A. , Escobedo-Bocardo José C.
Published: March 2010

In this work, the synthesis of CoFe2O4 via sol-gel auto-combustion method, using iron nitrate, cobalt nitrate and citric acid, with subsequent heat treatment in air was studied. The effects of the molar ratio of the metal nitrates to citric acid and the heat treatment temperatures on the magnetic properties have been investigated. The X-ray diffraction patterns showed peaks consistent with cubic spinel-type structure. The average crystallite sizes were determined from the (311) peak of the diffraction pattern using Scherrer equation. Particle sizes in the range of 18-44 nm were obtained. The crystallite size increases with annealing temperature. Magnetic properties, such as saturation magnetization (Ms), remanent magnetization (Mr) and coercivity field (Hc) were measured at room temperature using a vibrating sample magnetometer. Saturation magnetization was found to increase with particle size, whereas coercivity was found to reduce exponentially as the particle size was increased, apart from the Hc of the sample treated at 300 °C. The present work shows that magnetic properties vary over a wide range by changing the synthesis conditions.
Alumina-Copper Composites with High Fracture Toughness and Low Electrical Resistance
Authors: Rocha-Rangel Enrique , Miranda-Hernández José G.
Published: March 2010

Through an intense mixing process of Al2O3 powder with different copper contents, Al2O3-Cu composites were fabricated by sintered at 1300°C during 1h, where the likely liquid sintering mechanism, lead to obtain composites with relative densities greater than 95%. Scanning electron microscopy was used to observe the resulting microstructures, which indicated that these composites were mostly formed by a fine and homogeneous Al2O3-ceramic matrix with immerse nano-metallic copper particles. The behavior of both fracture toughness and electrical resistance of the composites is directly dependent with the copper content in the matrix. As the copper contents increased, the composites exhibited high values of fracture toughness, whereas, their electrical resistance is reduced considerably.
Study of Hafnium (IV) Oxide Nanoparticles Synthesized by Polymerized Complex and Polymer Precursor Derived Sol-Gel Methods
Authors: Ramos-González Rodolfo , García-Cerda L.A. , Alshareef Husam N. , Gnade B.E. , Quevedo-López M.A.
Published: March 2010

This work reports the preparation and characterization of hafnium (IV) oxide (HfO2) nanoparticles grown by derived sol-gel routes that involves the formation of an organic polymeric network. A comparison between polymerized complex (PC) and polymer precursor (PP) methods is presented. For the PC method, citric acid (CA) and ethylene glycol (EG) are used as the chelating and polymerizable reagents, respectively. In the case of PP method, poly(acrylic acid) (PAA) is used as the chelating reagent. In both cases, different precursor gels were prepared and the hafnium (IV) chloride (HfCl4) molar ratio was varied from 0.1 to 1.0 for the PC method and from 0.05 to 0.5 for the PP method. In order to obtain the nanoparticles, the precursors were heat treated at 500 and 800 °C. The thermal characterization of the precursor gels was carried out by thermogravimetric analysis (TGA) and the structural and morphological characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns of the samples obtained by both methods shows the formation of HfO2 at 500 °C with monoclinic crystalline phase. The PC method exhibited also the cubic phase. Finally, the HfO2 nanoparticles size (4 to 11 nm) was determined by TEM and XRD patterns.
TEM Characterization on the Nanocomposite Al 7075 and Silver Nanoparticles Synthesized by Powder Metallurgy
Authors: Flores-Campos Ruben , Deaquino-Lara Rogelio , Herrera-Ramírez J. Martin , Ponce Arturo , Estrada-Guel Ivanovich , Miki-Yoshida Mario , Martínez-Sánchez Roberto
Published: March 2010

Aluminum-based nanocomposites have been produced by mechanical milling, introducing silver nanoparticles within the matrix of a 7075 aluminum alloy using a high energy ball mill. The milled products were compacted by uniaxial load and pressure-less sintered under argon atmosphere, and finally hot extruded. Silver nanoparticles are well dispersed into the matrix of the powder particles as well as in the matrix of the extruded material. Transmission electron microscopy (TEM) analyses are used to corroborate and understand the hypothesis that second-phase particles finely and homogeneously dispersed in the matrix give greater strength to the material. In addition to the strengthening effect, the nanoparticles act like a process control agent (PCA) since the crystallite size of the nanocomposite is smaller at higher contents of nanoparticles.
Electron Diffraction Study of Pentagonal Cross-Sections Nanowires
Authors: Reyes-Gasga J. , Montejano-Carrizales J.M. , José-Yacamán Miguel
Published: March 2010

The selected area electron diffraction patterns and structure of pentagonal cross-section nanowires reported for silver are commented and interpreted in is work. We show that they are closely related to a decahedron-base structure.
Influence of Thermal Annealing on the Properties of Sputtered Si Rich Silicon Oxide Films
Authors: Manolov Emil , Curiel Mario , Nedev Nicola , Nesheva Diana , Terrazas Juan , Valdez Benjamin , Machorro Roberto , Soares Julio , Sardela Mauro R.
Published: March 2010

Thin SiOx films deposited by reactive r.f. magnetron sputtering of Si at partial pressure ratios R between oxygen and argon in the range 15%-0.03% are studied. X-ray photoelectron spectroscopy and Variable angle spectroscopic ellipsometry prove enrichment with Si of the layers deposited at R < 0.5 %. Ellipsometric data give information about the refractive index and extinction coefficient of the films. Atomic Force Microscopy results show that for all samples high temperature annealing at 1000oC leads to a decrease of the surface roughness.
Investigation of Pulsed Laser Annealing of CdS Layers Designed for Thin-Layer Solar Cells
Authors: Shindov Peter , Kakanakov Roumen , Bedikyan Lidiya , Kaneva Svetlana , Anastasova Teodora
Published: March 2010

The effect of the pulsed – laser annealing on the parameters of CdS thin layers in the medium of oxygen was studied. The CdS thin layers were deposited by spray pyrolysis at different technological conditions. The changes of the layers’ characteristics were studied by SEM, XRD and XPS and electrical measurements were carried out. The results showed that a change in the morphology and the phase composition of the surface occurred; a by-surface layer consisted of CdО with high conductivity was formed in consequence of oxidation of CdS. The parameters of the CdS thin layers were retained in- depth after pulsed laser annealing. These results are discussed in the context of transparent layers in solar cells.
Nanomechanics of Coatings for Electronic and Optical Applications
Authors: Bull S.J.
Published: March 2010

In most coating applications damage resistance is controlled by the mechanical properties of the coating, interface and substrate. For electronic and optical applications the design of coating-substrate systems has been predominantly controlled by their functional properties but more recently the mechanical response of the system has been used to enhance functional properties, as in the case of strained silicon/SiGe microelectronic devices where tensile strain has been used to enhance mobility and increase device speed. As coatings become more complex, with multilayer and graded architectures now in widespread use, it is very important to obtain the mechanical properties (such as hardness, elastic modulus, fracture toughness, etc.) of individual coating layers for use in design calculations and have failure-related design criteria which are valid for such multilayer systems. Nanoindentation testing is often the only viable approach to assess the damage mechanisms and properties of very thin coatings (<m) since it can operate at the required scale and provides fingerprint of the indentation response of the coating/substrate system. If coating properties are to be assessed, the key point is to ensure any measured value is free from the influence of the deforma-tion of the substrate or lower coating layers. Finite element analysis of indentation load displace-ment curves can be used to extract materials properties for design; as coating thicknesses decrease it is observed that the yield strength required to fit the curves increases and scale-dependent materials properties are essential for design. Since plasticity is less likely, non-linear elasticity is increasingly important as the size of a nanostructure is reduced. Similarly the assessment of fracture response of very thin coatings requires modeling of the indentation stress field and how it is modified by plas-ticity during the indentation cycle. An FE approach using a cohesive zone model has been used to assess the locus of failure and demonstrates the complexity of adhesive failure around indentations for multilayer coatings. Finally the mechanical design of a metallization stress sensor based on na-noindentation-derived materials properties, non-linear elastic and plastic behavior and the treatment of geometrical non-linearities (stress stiffening) is discussed.
Wetting Ability of Ag Based Molten Alloys on Graphite Substrate
Authors: Weltsch Zoltán , Lovas Antal , Takács János , Cziráki Ágnes , Tichy Géza , Tóth Attila Lajos , Illés L.
Published: March 2010

The wetting angle (Θ) of molten Ag (Zn, Cu, Ga) drops on graphite substrate is investigated. A texture formation was found in the substrate/drop interphase region after solidification. The enrichment (segregation) of Ag atoms in the interface layer was observed in the Ag-Cu alloy, and unexpected mixing between graphite substrate and the Ag-Ga melt was also detected in the solidified structure.
Synthesis of “Main – Chain” Type Polyimide Matrix with a Chemically Bound Azo Group
Authors: Georgiev Anton , Strijkova Velichka , Dimov Dean , Spassova Erinche , Assa Jacob , Danev Gencho
Published: March 2010

A method for obtaining thin vacuum deposited azopolyimide layers is established. On the basis of the thermogravimetric and differential thermal analyses, the chemical reaction in the solid state between the initial precursors - 4,4’-diaminoazobenzene and pyromellitic dianhydride is discussed. Also, the preparation parameters allowing for a condensation of films of desired composition are determined. Fourier Transform Infrared Spectroscopy analyses confirm that the azo group is chemically bound in a thin polyimide layer matrix. This is a solution to the task of preparing a “Main – Chain” type polyimide matrix with a chemically bound azo- group.
Characterization of Oblique Deposited Nanostructured SiOx Films by Ellipsometric and IR Spectroscopies
Authors: Szekeres A. , Vlaikova E. , Lohner T. , Tóth Attila Lajos , Lisovskyy I.P. , Zlobin S.O. , Shepeliavyi P.E.
Published: March 2010

Studies of oblique deposited nanostructured SiOx films by ellipsometric and IR spectroscopies are presented, as additional information is obtained by scanning electron microscopy (SEM). The films were deposited onto Si substrates under a 75° incidence vapor by vacuum evaporation of SiO and were annealed in Ar at 950oC. The thickness and composition of the films were estimated from the ellipsometric data analysis applying the Bruggeman effective approximation theory. Three-layer optical model described satisfactory the annealed film structure and verified the formation of nanocrystalline Si clusters. SEM micrographs showed that evaporated films consisted of silicon oxide pillars separated by air space and tilted at an angle of ~57o to Si substrate surface. The thin silica pillars were most probably free from Si-SiO2 interface leading to absence of strong absorption on LO vibrations in the IR spectrum. The estimated porosity factor was ~62 %. By annealing, the film oxidized to SiO2 but it remained columnar with a porosity factor of ~47 %.
Nanosized Silicon Carbide Obtained from Rice Husks
Authors: Radev Dimitar D. , Uzunov Ivan
Published: March 2010

Two ways to obtain nanosized silicon carbide (SiC) powders from the products of thermal decomposition of rice hulls and posterior thermal and chemical treatment of SiO2-C precursors are shown in the present paper. The reagents and products were analyzed using BET, DTA, IR, XRD and SEM/TEM. Precursors obtained from rice husks containing pure SiO2 and a controlled SiO2-C ratio were used for the synthesis of SiC. The synthesis of SiC proceeded for 30-45 min in a graphite heater furnace under protective Ar atmosphere at relatively low temperatures (1450oC-1550oC). Nanosized dimensions of reagents obtained from rice husks and their high activity allow obtaining SiC in relatively milder thermal regimes. TEM and XRD analysis revealed synthesis of nanostructured mainly β-SiC with a mean crystallite size of 40-100 nm. Due to their purity and nano-scale properties, the products obtained are appropriate for production of bulk SiC or design of SiC–based ultra high-temperature materials using the methods of powder metallurgy.