bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the Preparation and Properties of Epoxy/PEI/Nano-Attapulgite Nanocomposites
Authors: Fan Chang Xiu , Duan Jing Kuan , Li Ya , Shao Shuang Xi , Han Pei De
Published: March 2013

Polyether imides (PEI) and nanoattapulgite particles organically synthesized by the active silane containing epoxide groups (OAT) were used to modify the epoxy resin (ER). The effect of the concentration of OAT on the morphology, thermal and mechanical properties of ER/PEI/OAT nanocomposites was explored in the present work. The microscopic structure of nanocomposites was investigated by Scanning electric microscopy (SEM). The results showed that a homogeneous nanoattapulgite organically-modified by silane in the polymeric matrix was obtained. SEM images showed that the morphology transformation increased with the increase of OAT content, which would lead the improvement of the impact strengths of nanocomposites. The results of mechanical and thermal measurements indicated that the introduction of PEI and OAT into the epoxy resulted in the great improvement of the impact strength and storage module. With the OAT concentration increasing, the glass translation temperature (Tg) value of nanocomposites was gradually increased. Additionally, the results of thermo-gravimetric analysis (TGA) revealed that thermal stability of nanocomposites was apparently improved in comparison to the epoxy resin systems.
Influence of Annealing on Magnetic Performance for 1K107 Amorphous-Nanocrystalline Soft Magnetic Alloy
Authors: Lv Wei
Published: March 2013

The morphology, microstructure and magnetic properties in 1K107 alloy annealed by nitrogen and transversal magnetic (N2) are studied. The results show that coercivity (Hc), remanence ratio (Br/Bs), core loss (Pc), and effective permeability (μe) are efficiently optimized by transversal magnetic annealing (N2) according to the methods of digital electric bridge, rectifier bridge, X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM), etc.
Synthesis of Carbon Nanospheres with Small Diameterby Microwave Pyrolysis of Methane Directly
Authors: Fu Dong Ju , Zeng Xie Rong , Zhang Wei Li , Chen Jian Jun , Li Dong Shuang , Tan Man Lin
Published: March 2013

Carbon nanospheres of uniform diameter around 40 nm have been achieved in the absence of catalyst by microwave pyrolysis chemical vapor deposition. The products have been characterized by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The results show that the nanospheres with high purity, which are solid by their cross-sections, consisting of concentric incompletely closed graphitic layers. Their thermal stability in dynamic air atmosphere is also discussed.
Advances in Numerical and Experimental Study of Dielectrophoretic Assembly of Carbon Nanotubes
Authors: Zhen Shao Hua , An Li Bao , Liu Yan Yan
Published: March 2013

Study of the effect of dielectrophoresis (DEP) parameters is important in high-precision DEP assembly of carbon nanotubes (CNTs). The DEP parameters usually considered in the literature include the magnitude and frequency of the applied voltage, the assembly time, the concentration of the CNT suspension, and the geometry of the electrodes. This paper reviews the current progresses on both numerical and experimental study of the CNT assembly by DEP, especially the influence of the DEP parameters on the assembly process and results. The review shows that the magnitude of the applied voltage affects the DEP force and the number of deposited CNTs. The assembly time and CNT concentration influence the density of deposited CNTs. Different electrode geometries have an effect on the distribution of the electric field. The electrode spacing changes the field strength and the direction of the field gradient. The related discussion is presented as well.
Surfactant-Induced Nanofibrous Architecture of Silk Fibroin Hydrogels
Authors: Deng Chun Min , Zhong Tian Yi , Zuo Bao Qi
Published: March 2013

Hydrogels had been prepared by blending four types of surfactants such as alkyl betaine (zwitterion surfactant), tween 60 (non-ionic surfactant), sodium fatty alcohol ether sulfate (anionic surfactant) and silicone quaternary ammonium salt (cationic surfactant) with bombyx mori silk fibroin (SF) solution. Surfactant molecules would interact with SF molecules, resulting in lower critical micelle concentration (CMC). Gelation time measurements showed surfactants had significantly accelerated the hydrogelation process of SF solution, which could be controlled by the type or blend ratio of surfactants. Fourier transform infrared (FTIR) indicated that the addition of surfactants affected the molecular secondary of SF. The results from X-ray diffraction indicated that surfactants and SF were only blended but phase separation with two kinds of crystalline structure. SEM images showed that the surfactants had significantly changed the morphology of hydrogels according to certain rules, especially non-ionic and cationic surfactants could induce silk fibroin solutions into porous and nanofibrous hydrogels. These results indicated that a novel and potential method not only can be used to accelerate hydrogelation process of SF solution but also can be used to alter the structural and morphological of SF hydrogels. Furthermore, the porous and nanofibrous hydrogels of SF induced by surfactants provided a novel strategy to mimic the nanofibrous structure of collagen in extracellular matrix (ECM).
Effects of Annealing on the Crystallization and Morphology of Electrospun Poly(L-lactic acid) Fibers
Authors: Su Feng , Yu Hao , Zhu Shu Qi , Chen Wen Juan , Huang Fang , Zhu Mei Fang
Published: March 2013

Biodegradable polymeric nanofibers produced by electrospinning have been used as scaffolds for tissue engineering. As one kind of biodegradable material, electrospun polylatic acid fibers have an important application on biomedical materials. For better application of this kind of material, the properties of annealed electrspun poly (L-lactic acid) (PLLA) was studied in this investigation. The material properties of as-spun and annealed nanofibers were studied using differential scanning calorimeter (DSC), X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Thermal and XRD analysis revealed that PLLA as-spun fiber exhibited amorphous phase and began to crystalline when annealing temperature was above its glass transition temperature. SEM measurements of annealed fibers showed that fusion among fibers occurred when annealing temperature was too high.
Fabrication and Characterization of CuInS2 Sensitized TiO2 Electrodes Based on Improved SILAR Process
Authors: Mei Feng Jiao , Wan Qing Cui , Ping An , Liao Hua , Xu Xue Qing , Shi Ji Fu , Xu Gang
Published: March 2013

CuInS2quantum dots have been deposited onto mesoporous TiO2films on TCO glass substrate via successive ionic layer absorption and reaction process (SILAR) by using three different routes and post-deposition annealing in sulfur ambiance. The influence of the deposition sequence of the In-S and Cu-S on the microstructure of CuInS2sensitized TiO2electrodes and the photovoltaic performance of the solar cells have been investigated. The microstructure of CuInS2sensitized TiO2electrodes has been investigated by using X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The optical absorption property of the electrodes has been detected by using UV-Vis spectroscopy, and the photovoltaic performance of CuInS2quantum dots sensitized solar cells has been determined by cyclic voltammetry measurement. It has been found that when the Cu-S was deposited prior to In-S, the chalcopyrite phase CuInS2could not be observed due to the sublimation of InxS during the annealing under low pressure. A small amount of CuInS2has been detected when In-S and Cu-S was deposited alternately onto the TiO2films. However, chalcopyrite phase CuInS2can be obtained when In-S was deposited prior to Cu-S, and a relative high efficiency of ca. 0.92% (Voc= 0.35V, Jsc= 8.49 mA·cm-2, FF = 0.31) has been achieved via SILAR without KCN treatment and rapid thermal annealing.
Preparation of Graphene Nanosheet/Alumina Composites
Authors: Liu Xia , Fan Yu Chi , Feng Qian , Wang Lian Jun , Jiang Wan
Published: March 2013

Graphene nanosheet (GNS)/ Al2O3 composite powder with homogeneously distributed GNSs has been fabricated from wet ball milled expanded graphite and Al2O3, and then followed by the rotary evaporator at relatively low temperature to dry the mixture and the residual solvent was removed in atmosphere-vacuum pipe-type furnace accessing mixed gases of Argon and Hydrogen at 600 for 6h. During the process, homogeneously dispersed and mixed GNS/ Al2O3 composite powders with quite few damage of GNSs structure and properties have been obtained. The microstructures and grain sizes of GNS/ Al2O3 composite powders have been investigated. The results showed that the addition of GNSs had diminished the size of Al2O3 particles and also the as-prepared GNSs/ Al2O3 composite powders can be dispersed and mixed more homogeneously remarkably with the presence of GNSs.
Mechanical Evaluation of the Porous Ceramics Prepared by Filtration with a Framework Structure of the Polycrystalline Fibers
Authors: Dong Xue , Liu Jia Chen , Hou Zhen Guang , Wang Min , Tian Geng
Published: March 2013

Porous ceramics with a framework structure of the polycrystalline mullite fibers, in which the silica sol were impregnated into the intertwined points, were synthesized by the infiltration method. The sample has a porosity of 90 %, and the compression strength was significantly improved compared with the matrix without any addictives. The elastic behavior was investigated by changing the loading speeds. It is found that the elastic behavior of the porous ceramics was different from the traditional ceramics. The compression set is about 15% and the rebound resilience is 85 % at room temperature. The composite can keep good performance of compression-rebound.
In Vitro Antibacterial Properties of Vancomycin-Loaded Nano-Hydroxyapatite/Collagen/Calcium Sulfate Hemihydrates (VCM/nHAC/CSH) Bone Substitute
Authors: Lian Xiao Jie , Wang Xu Mei , Cui Fu Zhai
Published: March 2013

In the present study, a new antibacterial bone graft substitute has been developed for repairing bone defects and inhibiting related infections at the same time. Calcium sulphate hemihydrate (CSH) was introduced into nanohydroxyapatite/collagen (nHAC) to prepare a self-settingin situbone repair materials. The nHAC/CSH was used as a carrier of vancomycin (VCM) for anti-infection and the treatment of osteomyelitis. The VCM/nHAC/CSH composite was a porous scaffold with porosity of 38.8% and the compressive mechanical strength was about 4.8 MPa. The final setting time was about 15~20 min. The inhibition ratio of VCM/nHAC/CSH was more than 99.8% and the distinct inhibition zone of 18 mm was formed in Staphylococcus aureus bacterium incubation dish with VCM/nHAC/CSH disc in the center of agar matrix for 16 hours of incubation. After incubating 17 days at 37in vitro, the concentration of vancomycin in elution fluild was around 12 μg/mL. Therefore, the VCM/nHAC/CSH bone substitute presents ideal self-setting antibacterial, cytocompatibility, sustained release properties and has great potential applications for the treatment of bone defect-related infection in orthopedic surgeries.
Study on the Preparation of Silver Nanoparticles Coated with Diamond-Like Carbon Film and their Properties
Authors: Ma Nan Yu , Zeng Dan , Huang Yu Jie , Di Jun Wei , Li Mu Sen
Published: March 2013

Ag nanoparticles (NPs) have prominent local surface plasma resonance effect (LSPR), and Ag NPs exhibit sharpest and strongest bands among all metals. Diamond-like carbon (DLC) film have good biological compatibility and also have high transmissibility in the visible and near-infrared region. A new LSPR interface between Ag NPs and ultra-thin DLC film was formed by Plasma Enhanced Chemical Vapor Deposition. The morphologies and properties of the Ag NPs coated with DLC film were studied with SEM and AFM. The results indicated that the thickness of DLC film increased with the deposition time. LSPR peak became sharper after depositing for 1 or 2 min. DLC film was prior to nucleate on the surface of Ag NPs, and it has high content of sp2 bonds near the interface. The sensitivity of new LSPR interface deposited for 20s was about the half of the sensitivity of bare Ag NPs and the sensitivity significantly decreased with deposition time. This result is helpful to understand the behavior of the new LSPR interface and to improve its sensitivity.
Influence of Spinel on the Fracture Energy of Refractory Castable
Authors: Qin Hong Bin , Li Hong Xia , Wang Jian Dong , Liu Guo Qi , Feng Hai Xia
Published: March 2013

The specific fracture energy of alumina-spinel refractory castables was studied by the wedge-splitting method in this paper. The influence of synthetic spinel on the specific fracture energy of aluminamagnesia refractory castables was investigated. In-situ formation spinel was replaced by sintering spinel as the synthetic spinel. The experimental results indicated that the specific fracture energy and the compressive flesural mechanical properties had the same changing trend with the increase of the synthetic spinel, but the thermal shock resistance of the materials showed the opposite trend. However, the thermal shock resistance was closely associated with the specific fracture energy according to one theory raised by Hasselman.
Orthogonal Preparation and Microscopic Analysis of Porous Ceramic Foamed by Aerogen
Authors: Chen Yun Xia , Zhu Hua Qing
Published: March 2013

Porous ceramics foamed by aerogens with pores of specific characteristics in shape and size can be widely applied in many fields such as biological engineering, enzyme engineering, environmental engineering, etc. However, the Preparation is prone to structure defects such as inequality of pore size and distribution, crack, contraction deformation, etc. Four-level orthogonal tests based on three improving factors such as water content and carboxymethyl cellulose (CMC) and stirring time (ST) were carried out to improve the method of preparing porous ceramic body foamed by aerogens at ordinary temperature. It is concluded that water content is the key improving factor followed by stirring time and CMC content, and the optimized formula could be A3B3C1 or A3B4C2. Microscopic analysis indicates that there are about 107 pores within 100μm2 with diameter below 10μm and about 117 pores within 10000μm2 with diameter range from 20μm to 100μm in the sample.
Effect of Nb Addition on the Glass-Forming Ability, Soft-Magnetic Properties and Mechanical Properties of CoFeNiBSiNb Bulk Glassy Alloys
Authors: Dong Ya Qiang , Man Qi Kui , Shen Bao Long
Published: March 2013

The effect of Nb addition on the glass-forming ability (GFA), soft-magnetic properties and mechanical properties of [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx(x=36) alloy system were investigated. The results showed that by adjusting the content of Nb, the thermal stability of the supercooled liquid and the GFA increased effectively. With increasing the amount of Nb, the supercooled liquid region (ΔTx) increased from 45 to 65 K and the reduced glass transition temperature (Trg=Tg/Tl) was located in the range of 0.5840.644. As a result, the [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx bulk glassy alloys (BGAs) with diameters up to 5.0 mm were produced by copper mold casting. In addition to the high GFA, the Co-based glassy alloys exhibited excellent soft-magnetic properties, i.e., saturation magnetization of 0.530.81 T, low coercive force of 0.511.75 A/m, and high effective permeability of (1.522.53)×104 at 1 kHz under a field of 1 A/m. Besides, the Co-based BGAs also exhibited super high fracture strength of 42704490 MPa and vickers hardness of 11271182.
Numerical Simulation and Process Optimization of Investment Casting of the Blades for High Nb Containing TiAl Alloy
Authors: Yang Liang , Chai Li Hua , Zhang Lai Qi , Lin Jun Pin
Published: March 2013

Low pressure turbine blades (LPT) made by investment casting from intermetallic titanium aluminide alloys for aero-engine applications have about 50% weight saving compared with that from nickel-based counterparts. Investment casting process of the low pressure turbine blades for high Nb containing TiAl alloy was simulated by Procast. The height of the blade is about 125mm and the thinnest part of it is about 6mm. Compositions of the cast and mould are Ti-45.5Al-8Nb (at %) and Zircon sand, respectively. The simulation result showed that there were porosities appearing in the centre of blades, which may be due to the formation of isolated liquid. In this work, the simulation, analysis and comparison of different casting ways were carried out. The result showed that compared with top and bottom casting, blades made by side casting have less porosity defects. And then the casting temperature, casting velocity, mould preheating temperature and interface heat transfer coefficient were optimized based on orthogonal design. The result also indicated that the influence of process parameters to porosity defects of blades can be ranked from strong to weak as follow: casting temperature>shell mould preheating temperature>casting velocity>interface heat transfer coefficient. When the casting temperature was 1700, the mould preheating temperature was 500, the casting velocity was 0.5 m·s-1, and the interface heat transfer coefficient was 500 W·m-2·K-1, the volume of porosity defects was the smallest.
Effect of Al on Microstructures and Properties of Ti-45Al-8.5Nb-0.2B-0.2W Alloy
Authors: Xu Xiang Jun , Lin Jun Pin , Han Dong Dong
Published: March 2013

In the present paper, the necessity of strictly controlling Al content is demonstrated for Ti-45Al-8.5Nb-0.2B-0.2W alloy by analyzing solidification microstructure, compressive properties at room temperature and α phase transformation point of alloys containing 43-47at.%Al. The results show that the alloy has an optimal combination of mechanical properties and microstructure. Increasing Al content leads to increase in lamellar colony size and decrease in B2 phase for the solidification microstructure. Yield strength decreases linearly with Al content, but total strain increases linearly with Al content. The phase transformation temperature of β + αα rises more than 20 °C when Al increases to 46at. %, and drops about 20 °C when Al decreases to 44at %. Therefore, Al deviation should be as small as possible in producing technical alloy to ensure the stability in terms of properties, microstructure and processing route.
Analysis of Factors Influencing CPU Heat Dissipation of Porous Magnesium
Authors: Wang Lu Cai , Wang Yan Li , Wang Chao Xing
Published: March 2013

Orthogonal experiments were used to investigate the porous magnesium CPU heat dissipation under the forced convection condition. Three factors were involved in the experiment, i.e. different porosity level (50%, 60%, and 70%), different pore size (0.8-1.6mm, 1.6-2.2mm, 2.2-3.2mm) and different thickness (20mm, 35mm, 50mm) of open-cell porous magnesium. The materials used in the present study were prepared by upper-pressure infiltration method. Experimental results indicated that cooling effect factors of porous magnesium are relevant with the pore structure while the most important one is pore size, followed by porosity. Under the experimental conditions with the pore size of 2.2~3.2mm, porosity of close to 70%, and thickness of 35mm, the maximum heat dissipation benefit was obtained. Compared with the commercial radiator, the fluid flow and heat transfer on the surface of radiators integral fins are better than the others when the CPU is fully busy. Average reduced temperatures of porous magnesium CPU by using upper-pressure infiltration method are 4.4 - 8 lower compared with the commercial ones.
Effects of Coating on Surface Recrystallization of DD6 Single Crystal Blades
Authors: Jia Yu Liang , Zhao Yun Song , Luo Yu Shi , Yang Shuai , Xu Jian Wei , Tang Ding Zhong
Published: March 2013

The fully heat-treated DD6 single crystal turbine blades were treated in three ways: (1) surface grinding, without coating; (2) firstly surface grinding, then surface coated with HY3(NiCrAlY) anti-oxidation coating; (3) after surface grinding, coated surface with the bond layer of NiCrAlY and top layer of YSZ(Y2O3 stabilize ZrO2) for the double-layer thermal barrier coatings. All these three experimental blades were treated with vacuum heat-treatment at 1120°C for 4h. The effects of coating on surface recrystallization of single-crystal blades have been investigated. The results indicate that: just with surface polishing blade generated a 6~9μm thick cellular recrystallization zone on the surface. The γ' presented coarse morphology and distributed discretely within cellular, and the γ' growth direction was perpendicular to the cellular interface; blade surface coated with anti-oxidation coating after polishing formed a 3~6μm thick cellular recrystallization zone in the matrix interface. But the grain boundary was fuzzy and recrystallization morphology was incomplete; the matrix interface morphology of blade coated with thermal barrier coatings after polishing changed insignificantly, but some local cellular recrystallization was found. The results indicate that the coating changes the cellular recrystallization morphology of the original matrix of the blade, which can effectively reduce the occurrence degree of recrystallization.
Interaction between Two Ni-Base Alloys and Ceramic Moulds
Authors: Yao Jian Sheng , Tang Ding Zhong , Liu Xiao Guang , Xiao Cheng Bo , Li Xin , Cao Chun Xiao
Published: March 2013

The interfacial reactions between ceramic moulds and DZ417G and DZ125 superalloys were investigated. The microstructure and composition of the interface region were observed by optical microscope, X-ray diffraction and scanning electron microscope with energy dispersive spectroscopy. The results showed that (Al1-xCrx)2O3 solid solution phase with pink color was formed from the dissolution of Cr2O3 and Al2O3 and vapour phase, which was transferred to the reaction surfaces. The reaction layer thicknesses of DZ417G and DZ125 alloys were about in the range of 40-50μm. The interface reaction product between DZ417G alloy and ceramic mould was TiO2 and the product between DZ125 alloy and ceramic mould was HfO2.
Research on Effects of Uneven Macrostructure to Mechanical Properties in TC21 Forging
Authors: Li Jun , Zhu Zhi Shou , Wang Xin Nan , Fei Yue , Shang Guo Qiang , Zhu Li Wei
Published: March 2013

The microstructure, tensile properties, fracture toughness, fatigue crack growth rate and fatigue limit of different macrostructure regions in TC21 open-die forging were investigated. The results show that the microstructure is also uneven corresponding to non-uniform macrostructure. The ultimate tensile strength (UTS) and yield strength (YS) of coarse-grained zone are that UTS1070MPa, YS960MPa, which can meet the requirement of technical standard, whereas the strength of fine-grained zone drops more than 100MPa. The fracture toughness of this forging is that KIC90MPa·m1/2, being equivalent to the normal one. But when K=11MPa·m1/2, the fatigue crack growth rate is that da/dN=2.488758×10-5mm/cycle, higher than the normal TC21 open-die forging for an order of magnitude. The fatigue limit of fine-grained zone drops about 40MPa compared with coarse-grained zone. Uneven macrostructure and microstructure lead to a decline of tensile and fatigue property in TC21 forging.
Influence of Extrusion Temperature on Microstructures and Properties of Cu-17Ni-3Al-X Alloy
Authors: Yan Wei , Weng Yuan Hui , Luo Zong Qiang , Zhang Wei Wen
Published: March 2013

The microstructures and mechanical properties of the Cu-17Ni-3Al-X alloy extruded at different temperatures were investigated by hardness and tensile tests, optical microscope and scanning electronic microscope. The experimental results showed that dynamic re-crystallization occured during the hot extrusion at 1000 . The grain size of the extruded alloy was significantly refined and the mechanical properties increased remarkably compared to the as-cast alloy. The alloy extruded at 1075 exhibited good mechanical properties with tensile strength of 994 MPa, Brinell hardness of 296 and elongation of 8.0%, which are 30%, 9% and 285% higher than that of the as-cast alloy.
Numerical Simulation Analysis of Aluminium Alloy Wheels Casting Defects and Casting Process Optimization
Authors: Yang Lv Ming , Zhao Li Li , Zhang Qing Qing , Zhou Tie Tao
Published: March 2013

In the low pressure casting process of A356 aluminum alloy wheel hub, casting defects including shrinkage cavity, shrinkage porosity, impurity and pore usually occur inside the casting. These defects affect the mechanical properties of the casting. To solve this problem, we conducted a study based on a cooperation project with a well-known domestic automobile wheel manufacturer. In the present study, uniaxial tensile test of aluminum alloy casting containing defects was simulated and analysed, and the effect of types and number of defects on mechanical properties was studied by finite element analysis software. Statistical analysis of the data was provided by the manufacturer. It has been found that the degassing technology is effective by the quantitative analysis method. Based on the analyses of experimental data and the numerical simulation it is deduced that the tensile strength of casting increases with the increase of the defects due to the presence of impurity. This was confirmed in this research project, it has been observed that the defect rate of the casting sample is reduced from 5%-6% to less than 1%.
Experimental and Numerical Study on Dieless Bending of 2-Piece Parallel Flow Microchannel Heat Exchanger
Authors: Wang Zhuo , Zhang Zhi Wei , Li Da Yong , Peng Ying Hong
Published: March 2013

Parallel flow microchannel heat exchangers have been increasingly applied in HVAC (Heating, Ventilation and Air Conditioning) field due to their characteristics, such as high efficient heat transfer performance, compact form and low cost. Production rationalization of the heat exchanger is required for realization of a competitive, light-weight and easy-to-assemble product. The heat exchanger is usually bent to L-shape so as to decrease the volume of air conditioner. To correspond with design changes for multi-generation use and to achieve good forming quality, a dieless forming technique is developed to offer flexible manufacturing. Using this method, heat exchangers can be formed with variable bending radius conveniently, which can reduce the mold cost and obtain high productivity. Meanwhile, product defects such as fin damage can also be reduced because there is no physical contact against tools in the bending portion. In the present study, the forming principle of dieless bending process is first stated by theoretical analysis. Then to verify the proposed forming mechanism, a NC dieless bending machine is manufactured to implement the bending experiment. Finally, based on the verified FE model, the bending process for the 2-piece heat exchanger has been improved. As a result, the dieless bending process has been successfully developed and can be applied to produce square-shape heat exchanger with variable bending radius.
Effects of In/Ce to Sn-3.5Ag Lead-Free Solder on Microstructures and Properties
Authors: Chen En Jia , Zhao Xiu Chen , Liu Ying , Li Dong Mei , Cheng Jing Wei , Li Hong
Published: March 2013

The Sn-3.5Ag based lead-free electronic solder doped with element In /Ce were prepared respectively using a smelting method with protection by molten salt (SMPMS). The effects of In addition and Ce addition on microstructure, melting point and wettability of Sn-3.5Ag solder were investigated comparatively. And the effects of addition on the intermetallic compound (IMC) layer formed at solder/Cu substrate interface and the shear strength of solder joint were also studied. The results showed that appropriate In or Ce addition can refine Ag3Sn grains and improve the shear strength of solder joint. Element In can significantly reduce the melting point, narrow the melting range of the solder alloy and improve wettability on Cu substrate. When the content of In was 3%, the spreading area was the largest and the wettability was the best. The addition of Ce can efficiently reduce the thickness of the IMC layer grown at the solder/Cu substrate interface and improve the shear strength of solder joint. When the content of Ce was 0.5%, the solder joint had the minimum average IMC thickness and the maximum shear strength.
The Influence of Inhomogeneous Deformation on the Microstructures and Properties of Thick-Plate 7150 Alloy
Authors: Zhao Feng , Cao Ling Yong , Lang Yu Jing , Cui Hua , Zhuang Lin Zhong , Zhang Ji Shan
Published: March 2013

The diversities and relations of microstructures and properties between the center and surface layer in thick-plate 7150 alloy were investigated by means of OM, TEM, SEM and tensile tests. The results indicated that the average width of elongated grains with fewer substructures in the center of hot-rolling thick plate is about 2 times larger than that in the surface layer. The coarser second phases are massed up at the grain boundaries of the center layer while those are crushed into smaller particles in the surface layer. By aging, the strengthening precipitates in the center are mainly GP zone and η' phase, while in the surface layer η' and η phases play the main roles. Consequently, the strength is about 80Mpa (15%) higher in the center than in the surface, with lower elongations (26% lower).
Microstructure Evolution in Undercooled Ni-Si Melt
Authors: Fan Kai , Liu Feng , Fu Bao Quan , Luo Wen Zhong , Zhou Yao He
Published: March 2013

Upon non-equilibrium solidification, the intrinsic parameters, such as moving velocity, temperature, solute partition coefficient, and liquid and solid concentrations at the interface, deviate from their equilibrium characteristics, and the morphology of the as-solidified structure and the grain size are influenced by the non-equilibrium liqulid/solid transformation, which further influences the subquent solidstate transformation. Adopting molten glass purification technology combined with cycle superheating method, the microstructure evolution of Ni-11at.%Si alloy in different undercooling was investigated. It was found that, with the increase of the initial undercooling, grain refinement occurred in microstructures of undercooled Ni-11at.%Si alloy. Meanwhile, the NL model was used to discuss the two different dendrite morphologies. According to Karmas model for dendrite fragmentation, the grain refinement of undercooled Ni-11at.%Si alloy was in good agreement with the experimental data, and the grain size was reduced with the increasing ΔT. The energy-dispersive spectroscopy (EDS) measurement was applied to analyze the solid solubility of Si atom in α-Ni matrix. It was found that the solid solubility of Si atom in α-Ni matrix increased with undercooling. At the undercooling of T>220K , a complete solute trapping occurred.
Softening Mechanism in Heat Affected Zone of 2519 High Strength Al-Cu Alloy
Authors: Yang Cheng Gang , Zhen Qiang , Huang Zhi Jiang , Xu Wei Ping
Published: March 2013

With the thermal simulated technique, the softening mechanism in heat affected zone (HAZ) of 2519 Al-Cu Alloy is studied. The results show that over aging of the precipitates leads θ' to the softening of HAZ. With the thermal cycling peak temperature increasing, the dimension of precipitates become coarse and the amount is reduced, therefore the strength and the hardness decreased. When the peak temperature is 476, the strength and the hardness are the lowest. With the peak temperature keeps on increasing, small part precipitates continue to grow. Most of fine needle-like θ' phases dissolve and separate out renewably, which is the reason that the strength and hardness are gradually enhanced.
Effect of Composite Master Alloy on Mechanical Properties and Electrochemical Corrosion of ZL101 Alloy
Authors: Xu Hong , Zhang Xin , Ren Ji Ping , Peng Min , Yang Shi , Zhang Yu Long , Kong Kong Ying
Published: March 2013

The mechanical properties and corrosion performances of the ZL101 alloy modified by the composite master alloy were investigated. The results showed that the master alloy had not only obvious effect of grain refinement, but also a significant role in refining dendrite grain of ZL101 alloy. The grain size decreased dramatically from 150μm to 62μm when the addition of composite master alloy is up to 0.5%(mass fraction) and the temperature is 720 for 30 minutes,. Its tensile strength and elongation increased by 27% and 42% respectively. The grain refinement of ZL101 alloy decreased its corrosion performance. The morphology of Si changed into globular from needle modified by NaF, instead of AlTiB.
Analysis of Density and Mechanical Properties of Iron Powder with Upper Relaxation Assist through High Velocity Compaction
Authors: Khan Dil Faraz , Yin Hai Qing , Matiullah Matiullah , Asadullah Asadullah , Qu Xuan Hui
Published: March 2013

For producing higher density PM parts a new method, High-Velocity Compaction process with additional upper relaxation assist (URA) device is presented in the paper. Using zinc stearate as a die wall lubricant, iron powder was pressed with and without upper relaxation assist device of mass 0.14 Kg focusing to investigate the density and mechanical properties. To explain a compaction process in loading stage a conservation of momentum principle has been introduced during collision of hammer, upper piston and upper relaxation assist device in die compaction. To observe the morphological characteristics and mechanical properties, a scanning electron microscopy (SEM) and computer controlled universal testing machine were used. The experimental results showed that the samples compacted with URA device had an improved green density and mechanical properties compared to the samples compacted in the absence of URA device.
Theoretical Calculation of Electronic Structure and Mechanical Properties of Quenched Carbon Structural Steel
Authors: Sun Yue Jun , Li Si Nan , Shi Hai Fang , Gao Zhi Yu , Yang Shao Bin
Published: March 2013

To investigate the fatigue property of carbon structural steel in theory, the microstructure and properties of quenched martensite must be studied in detail. In this paper, the electronic structure and mechanical properties of carbon structural steel in quenched state were calculated by the empirical electron theory of solids and molecules (EET). The relationship between electronic structure parameters and mechanical properties of martensite was investigated. The mechanical properties of quenched carbon structural steel were calculated theoretically, and the result of theoretical calculation is consistent with the experiment result.
Computational Modeling of Sand Cementation by Bio-Mineral CaCO3
Authors: Li Li , Qian Chun Xiang , Zhao Yong Hao , Zhu Yun Tian
Published: March 2013

An innovative sand cementation method of bio-mineral carbonate formation in sand spacing through urea hydrolysis inspired by microbial urease was introduced in the present investigation. A sand column prepared for experimental data and a set of engineering equations for 1-D numerical modeling data of the sand cementation process were adopted. Important characteristic of CaCO3 weight vertically along the sand column and the urea concentration variation under the effect of microbial urease was investigated based on the experiment and the modeling. Future study was suggested to focus on the models parameters modification in order to construct an applicable model for industrial up-scaling application in sand or soil strengthening.
Research on Characteristics of Heat Treatment of Squeeze Cast Al-Cu-Mg Alloy
Authors: Gan Yao Qiang , Lu Lei , Zhang Da Tong , Zhang Wei Wen , Li Yuan Yuan
Published: March 2013

A high strength Al-Cu-Mg alloy was prepared by squeeze casting. The effects of squeeze casting and heat treatment on the microstructures and mechanical properties of the alloy were studied. It was found that squeeze casting refined the microstructure and reduced the micro-segregation markedly, and also accelerated the diffusion process of solute atoms during solution heat treatment. Tensile strength and elongation of squeeze casting alloy were much higher than those of gravity casting alloy under both the as-cast and heat-treated conditions. In addition, the Al-Cu-Mg alloy prepared by squeeze casting showed good natural aging response, and the naturally-aged alloy possessed a slightly lower tensile strength but better elongation compared to full artificial aging. After solution heat treatment at 495 for 9h and further natural aging for 48h or artificial aging at 190 for 6h, the tensile strength of squeeze casting alloy reached to 472MPa and 475MPa, respectively, and the elongation was 18.9% and 12.7% accordingly. Based on the experimental results, the mechanism of microstructural evolution of squeeze casting Al-Cu-Mg alloy during heat treatment was discussed, and the effect of squeeze casting on the kinetics of solute diffusion and aging precipitation was studied.
Optical Properties of Heterodiamond BC3 from First-Principles
Authors: Li Lei , Li Wen Xue , Han Dong , Xin She Wei , Yang Yi , Zhou Wei , Lu Ya Feng
Published: March 2013

First principles calculation for optical properties of a tetragonal BC3 (t-BC3) are performed through the pseudopotential density functional method. The exchange correlation potential is treated by the Perdew-Burke-Eruzerhof form of generalized gradient approximation. The basic optical constants including the real and imaginary parts of the dielectric function, the optical absorption coefficient, the reflectivity and the energy loss function were calculate in detail by this method. The results indicate that the t-BC3 is an optical anisotropic crystal and its electron-deficiency characteristic can cause some features in low energy region.
Numrical Simulation on Electric Field of Galvanic Corrosion for U-Nb Alloy and 45-Steel
Authors: Dong Ping , Pu Zhen , Shuai Mao Bin
Published: March 2013

Based on the galvanic corrosion experiment for U-Nb alloy and 45-steel in the 3.5 mass percent NaCl solutions, the galvanic corrosion electric field has been calculated by finite element method. The electric potential and the current density evolution during galvanic corrosion have been obtained. The results show that the electric potential drop between cathode and anode had obvious difference. The electric potential drop in the U-Nb alloy cathode is higher than that in the 45-steel anode, which makes the electric field in the U-Nb alloy higher than that in the 45-steel. A rather high current density exists at the ends and corners of the specimen. The permittivity of the corrosion medium only has a little effect on the corrosion electric potential, but has obvious effects on the corrosion current density. The electrode size has obvious effects on the corrosion electric potential and current density.
Interfacial Behavior of Micro-Cellular Structural Al90Mn9Ce1/TiO2 Composite Prepared by Spark Plasma Sintering
Authors: Deng Na , Wang Ming Gang , Zhao Zhan Kui
Published: March 2013

With micron Al90Mn9Ce1 alloy powder clad by TiO2 nanopowder, a dense closed micro-cellular ceramics structure was fabricated. The alloy composite was filled inside by spark plasma sintering at temperature 793 K, and with the composite density of 98.2%. Micro-temperature area of Al90Mn9Ce1/ TiO2 matrix was simulated through ANSYS, and the macro lower temperature sintering mechanism was analyzed. The microstructure of the interface was investigated via scanning electron microscope, and the composition distribution of the interface was investigated via energy dispersive spectrometry. The formation and evolution of the interfaces were analyzed from plastic deformation, the interface creep, interfacial diffusion and other aspects. It was found that the application of DC pulse current has important effect on interfacial behavior and the performance of composite.
Preparation of 8YSZ and Double-Ceramic-Layer La2Zr2O7/8YSZ Thermal Barrier Coatings on GH4169 Superalloy Substrates and their Static High Temperature Oxidation Behaviour
Authors: Wang Liang , Wang You , Sun Xiao Guang
Published: March 2013

Thermal barrier coatings (TBCs) are very important ceramic coating materials due to their excellent performance at high temperature. Double-ceramic-layer (DCL) La2Zr2O7 (LZ)/8YSZ TBCs, nanostructured single-ceramic-layer (SCL) 8YSZ and conventional SCL 8YSZ TBCs with the same thickness were fabricated by atmospheric plasma spraying in the present work. The static high temperature oxidation behaviour of the three as-sprayed coatings at 1000 and 1200 was investigated systematically. The results indicated that the LZ/8YSZ has higher oxidation resistance than that of SCL 8YSZ. The addition of LZ ceramic layer can increase the insulation temperature, impede the oxygen transferring to the bond coat and decrease the formation rate of the thermally grown oxide (TGO). The formation of the oxidized isolated islands in the bond-coat has decreased the effective thickness of the TGO at the bond coat/ceramic layer interface due to the depletion of the metallic elements in the bond-coat.
Impact on Solidification Dendrite Growth by Interfacial Atomic Motion Time with Phase Field Method
Authors: Zhao Yu Hong , Liu Wei Jin , Hou Hua , Zhao Yu Hui
Published: March 2013

The Phase Field model of solidification processes was carried out coupled with temperature field model. The influence of interface atomic time on dendrite growth morphology in undercooled melt was simulated with pure nickel. The experimental results show that when the interface atomic motion time parameter is minor, the liquid-solid interfaces were unstable, disturbance can be amplified easily so the complicated side branches will grow, and the disturbance speed up the dendrite growth. With the increase of , the liquid-solid interfaces become more stable and finally the smooth dendrite morphology can be obtained.
Shear Strength Evaluation of Laminated Binderless Bamboo Composites
Authors: Takagi Hitoshi , Matsukawa Hirohito , Nakagaito Antonio Norio
Published: March 2013

In this paper, the interlaminar shear strength properties of laminated binderless bamboo composites is described. The binderless bamboo composites were prepared by hot-pressing of steam-exploded Moso bamboo stripes. In order to explore the effect of node section on the mechanical properties of the laminated binderless bamboo composites, the node section was flattened by shaving the nodes off. The result of our experiment clearly shows that the shear strength of the laminated binderless bamboo composites increased by flattening of the node section.
Crack Healing Behavior of SiC Whisker Reinforced Si3N4 Composite
Authors: Hu Jun Feng , Zhu Shi Jie , Wang Wen Xue , Nakahara Yukiko
Published: March 2013

SiC whisker reinforced Si3N4 composite was used for studying crack healing behavior. Surface crack and straight-through crack were introduced on the tensile surface of specimens by Vickers hardness indenter and single edge pre-crack beam method. The cracked specimens were heat-treated at 1000 , 1100 , 1200 and 1300 for 1 hour in air. Bending strength was measured at room temperature by three point bending tests system. It was investigated that the best heat treatment temperature of Si3N4/SiC whisker composite is 1200 -1300 . The relationship between bending strength and logarithm of crack area was near linear and parabola in original and heat-treated specimens, respectively. Crack healing behavior was analyzed by oxidation filling model according to oxidation kinetics.
Analysis of Bonging Temperature and Interfacial Characterization of 3Y-TZP and SUS304 by Diffusion Bonding
Authors: Zhao Ming , Ju Dong Ying
Published: March 2013

This paper studies mainly the diffusion bonding of 3Y-TZP/SUS304 by using the chemical bonding method. In the bonding interface of 3Y-TZP and SUS304, the Ti-Cu powder/sheet was used as bonding materials. In bonding process, multi-alloy with Fe-Ti and Fe-Cu have been confirmed by Electron Probe Micro-Analyzer (EPMA) determination. Through the microstructure observed by AFM and SEM, bonding boundaries of 3Y-TZP/SUS304 by Ti-Cu powder/sheet had good formation. The distribution of the residual stress on near interface was measured by XRD method. By using of these results, the mechanism of the ceramic and stainless steel was discussed.
Microstructure Evolution of AZ31 Magnesium Alloy in Rolling Zone
Authors: Hu Xiao Dong , Yu Qun , Sun Ke Ming , Zhao Hong Yang , Ju Dong Ying , Zhu Ming
Published: March 2013

In order to study the details of deformation and microstructures evolution during rolling and annealing process, magnesium alloy AZ31 blank, cast by unidirectional solidification and then sliced, has been rolled at high temperature with one pass deduction of 50% in a 2-high mill. During the rolling process, the mill was stopped, and the rolled sheet was rapidly cooled by the cold rolls. Samples with full length of rolling bite zone were cut form the semi-rolled sheet. Because twinning deformation can be reserved even the sample was polished and etched. The continuous changes of microstructure, from entrance to exit of roll bite, both rolled and annealed samples, were evaluated by Optical Microscope (OM), Scanning Electron Microscope (SEM). The results revealed that grain refinement mechanism was twinning intersection which segmented large grains into small pieces. The average grain size is 7µm after one pass 50% reduction hot rolling and 350°C, 15min annealing.
Purification of Silicon Using the Liquid Phase Migration Technique under Temperature Gradient
Authors: Matsunaga Kunitoshi , Yoshikawa Takeshi , Morita Kazuki
Published: March 2013

A new conceptual technique for solar grade silicon (SOG-Si) purification was proposed in the present work. Most impurity elements in metallurgical grade silicon (MG-Si) exist in the grain boundary phases and their contents inside of silicon grains are extremely small, which is resulted from significant segregation during the solidification. Thus, the excellent purification was expected by selective ejection of grain boundary phases from silicon matrix. Such phases can be melted above the eutectic temperature of the system to form impurity-enriched liquid phase. In order to achieve the selective ejection of the liquid phase, its migration in the silicon matrix was investigated by conducting the heat treatment of silicon under the temperature gradient in this paper.
Estimation for Fatigue Behavior of Notched Plate with Mean Stress Effect
Authors: Ogata Chihiro , Shojima Kenji , Yanase Keiji
Published: March 2013

In this paper, McEvily’s fatigue crack growth equation is modified and newly combined with the modified Goodman equation to estimate the fatigue strength with arbitrary mean stress, σm. Firstly, based on McEvily’s equation, the threshold stresses for fatigue crack initiation and propagation with stress ratio R = –1 or σm = 0 are predicted with reasonable accuracy. Then, a simple calculation is presented to predict the fatigue strength with arbitrary mean stress. The adequacy of present method is examined based on the comparison with the available experimental data in the literature.