bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Antibacterial Effect of Silver-Carrying Nano-Hydroxyapatite Powder
Authors: Huang Jin Xia , Wang Jian Rong , Liu Jing He , Liu Bin , Wang Jin Qing , Chen Yun Fa , Lu Jin Jun
Published: March 2010

Hydroxyapatite (HA) has attracted many attentions because it has a similar structure to that of human bones and favorable biocompatibility. However, the antibacterial effect of HA must be improved. In this paper, HA nanoparticles were prepared by a simple method. Then, Ag-carrying HA powder (Ag-HA) was prepared by an ion-solution reaction and its antibacterial property was investigated. The results showed that Ag-HA powder had excellent ability in inhibiting the growth of two species of bacteria, namely E. coli and S. aureus. Ag ion was believed to play a key role in killing bacteria.
Nonlinear Elastic Deformation of MAX Phases
Authors: Zhou Ai Guo , Barsoum M.W.
Published: March 2010

MAX phases, include Ti3SiC2, Ti2AlC etc, are machinable ternary carbides or nitrides with excellent properties. These materials, however, have obvious nonlinear elastic deformation due to nano- layered crystal structure. The stress-strain curves of cyclically load-unload test have obvious hysteretic loops. Because of this mechanical hysteresis, the strain of MAX phases at one time is not determined only by the stress applied to the sample at this time. Here the influence of grain size, chemical composition and porosity on the nonlinear elastic strain was introduced. Because of two properties of this hysteresis: wiping out and congruency, the classic hysteretic mathematic model (Preisach-Mayergoyz model, P-M model) can be applied to calculate the strain of MAX phases after any complex deformation history.
Finite Element Analysis on Temperature-Stress of Permeable Refractory Ceramic under Working Process in Ladle
Authors: Gu Hua Zhi , Huang Ao , Wang Hou Zhi
Published: March 2010

According to the practical physical dimension and processing parameters of ladle with bottom gas blowing in a factory, a geometrical model was established and mesh structure was completed, Eulerian multiphase model and porous media model were adopted for the two-phase flow in ladle, which was coupled, the effect of temperature field and thermal stress in course of working process of permeable- gas refractory ceramic was studied by finite element approach. The correlations between processing, structure, and high-temperature mechanical properties were discussed, and the material and structure of permeable-gas ceramic were designed to optimum. The results show that: The steady gas flow rate can avoid wearing of permeable-gas refractory ceramic from cataclysm of temperature-stress; After the material and structure of permeable-gas refractory ceramic are optimized, the effect on ceramic wearing of temperature-stress in condition of oxygen washing is weakened. It is an important guiding for prepara- tion of permeable-gas refractory ceramic with long life, which will make for highly active refining ladle.
Convective Heat Transfer Steady Thermal Stress in a ZrO2/FGM/Ti-6Al-4V Composite ECBF Plate with Temperature-Dependent Material Properties
Authors: Xu Yang Jian , Du Hai Yang , Tu Dai Hui
Published: March 2010

A NFE model is constructed to analyze the convective heat transfer steady thermal stress in a ZrO2/FGM/Ti-6Al-4V composite ECBF plate with temperature-dependent material properties. From numerical calculation, when , T0=300K, Ta=550K and Tb=1800K, the stress distributions in the plate were obtained. The results are as follows. With the increase of the FGM gradient layer thickness, the stress distribution in the composite plate is more reasonable. With the increase of M, the thermal stress change increases obviously in metal and ceramic layers, and the stress on the ceramic surface reduces. With the increase of porosity, the change of stress at the bonding interfaces increases, and the tensile stress on the surface of ceramics reaches the maximum. Compared with , when , the stress on the metal surface reduces by 25.1%, and the maximum compressive stress on the surface of ceramics increases about 1.2GPa. Compared with the nongraded two-layered ceramic/metal composite plate, the thermal stress of ZrO2/FGM/Ti-6Al -4V composite ECBF plate is very gentle. When we consider the temperature dependency of the material properties, the thermal stress in graded three-layered composite plate becomes small obviously. The results provide the foundations of theoretical calculation for the design and application of the composite plate.
Synthesis, Microstructure and Mechanical Properties of ZrB2 Ceramic Prepared by Mechanical Alloying and Spark Plasma Sintering
Authors: Hu Chun Feng , Sakka Yoshio , Uchikoshi Tetsuo , Suzuki Tohru , Jang Byung Koog , Grasso Salvatore , Suarez Gustavo
Published: March 2010

Dense bulk ZrB2 ceramic was synthesized by mechanical alloying (MA) and followed spark plasma sintering (SPS) using zirconium and boron as initial materials. It was found that MA process was effective to fragment the coarse metal zirconium particles from 45 m to less than 1 m within 20 hours. In comparison with the commercial ZrB2 powder, the as-obtained zirconium and boron mixture powders showed higher sinterability. When the sintering was carried out at 1800oC, the relative density of synthesized ZrB2 samples using mixture powder was above 95%, higher than that of ZrB2 sample prepared using commercial powder (73%). Vickers hardness of those ZrB2 samples was at the same level of 15 GPa. However, the fracture toughness of ZrB2 samples seemed to depend on the heating rate of the SPS process. Corresponding to the heating rates of 10, 50, and 100oC/min, the fracture toughness of as-prepared ZrB2 samples were 3.83, 3.19, and 2.74 MPa•m1/2, respectively.
Microstructure and Mechanical Properties of Hot Pressed ZrC-SiC-ZrB2 Composites
Authors: Ma Bao Xia , Han Wen Bo , Zhang Xing Hong
Published: March 2010

Ternary ZrC-SiC-ZrB2 ceramic composites were prepared by hot pressing at 1900 °C for 60 min under a pressure of 30 MPa in argon. The influence of ZrB2 content on the microstructure and mechanical properties of ZrC-SiC-ZrB2 composites was investigated. Examination of SEM showed that the microstructure of the composites consisted of the equiaxed ZrB2, ZrC and SiC grains, and there was a slight tendency of reduction for grain size in ZrC with increasing ZrB2 content. The hardness increased considerably from 23.3 GPa for the ZS material to 26.4 GPa for the ZS20B material. Flexural strength was a strong function of ZrB2 content, increasing from 407 MPa without ZrB2 addition to 627 MPa when the ZrB2 content was 20vol.%. However, the addition of ZrB2 has little influence on the fracture toughness, ranging between 5.5 and 5.7 MPam1/2.
Electronic Structures and Chemical Bonding of the Layered Tungsten Borides: An Ab Initio Calculation
Authors: Xu Xue Wen , Li Yang Xian , Zhou Wei Bing , Zhu Jiao Qun , Mei Bing Chu
Published: March 2010

We have investigated the electronic structures and chemical bonding of four tungsten borides, including two WB2 compounds with different crystal structures, α-W2B5 and ε-WB2.5, by ab initio calculations based on density function theory (DFT). The calculated density of state (DOS) shows that all compounds are metallic. The DOS at Fermi level is mainly contributed from 5d states of W atoms. The strong covalent bonds of boron atoms make these compounds stable. Due to a lack of electrons in boron sublattices, weak ionic bonds are generated. The charge density distributions indicate the solid B layers or B polyhedrons are interleaved by the W layers.
Pressureless Sintering of ZrB2-SiC Ceramics Incorporating Sol-Gel Synthesized Ultra-Fine Ceramic Powders
Authors: Zhang Hui , Yan Yong Jie , Huang Zheng Ren , Liu Xue Jian , Jiang Dong Liang
Published: March 2010

Ultra-high temperature ceramic composites of ZrB2-SiC were densified by pressureless sintering. Ultra-fine ZrB2-SiC composite powders synthesized by sol-gel method were mixed with commercial ZrB2 and SiC powders. The sintered body of hybrid powders (combined commercial and synthesized composite powders) showed excellent properties not only in the relative density but also the flexure strength. Dry-pressed compacts using 4wt% Mo as a sintering aid were sintered to nearly full density at 2200°C/2h. The average strength was ~560MPa and the maximum was ~632MPa. SEM and TEM showed that SiC particles were distributed homogenously in the ZrB2 matrix and the average particle size was ~5μm. From HRTEM observations, the grain boundaries were apparently free of glassy phases and no intermediate phases existed.
Estimating Energy Dissipation of Ceramics via H-E Ratio
Authors: Bao Yi Wang , Wan De Tian , Qiu Yan
Published: March 2010

Mechanical properties of ceramics are important for its engineering application. It would be significant and efficient if some properties could be estimated without tests. Energy dissipation capacity of ceramics is estimated in this work via two common parameters, hardness and elastic modulus, which could be obtained from basic data of commercial ceramics or simple tests. The ratio of hardness to reduced modulus H/Er is found to be related to recovery resistance and energy dissipation capacity of the materials, and the related equations were induced. The reduced modulus can be expressed by conventional elastic modulus E. Thus, the capacity of energy dissipation and elastic recovery can be estimated simply from the H/E ratio. The calculated results indicate that the value of H/E ratio is in reverse proportion to the energy dissipation. Several ceramics with different H/E ratio are analyzed and their energy dissipation capacities are estimated.
Low-Temperature Firing and Microwave Dielectric Properties of Zn3Nb2O8 Ceramics with CuO-V2O5-Bi2O3
Authors: Lin Xu Ping , Ma Jing Tao , Zhang Bao Qing , Zhou Ji
Published: March 2010

The influence of CuO-V2O5-Bi2O3 addition on the sintering behavior, phase composition, microstructure and microwave dielectric properties of Zn3Nb2O8 ceramics were investigated. The co- doping of CuO, V2O5 and Bi2O3 can significantly lower the sintering temperature of Zn3Nb2O8 ceramics from 1150°C to 900°C. The Zn3Nb2O8-0.5wt% CuO-0.5wt% V2O5-2.0wt% Bi2O3 ceramic sintered at 900°C showed a relative density of 97.1%, a dielectric constant (εr) of 18.2, and a quality factor (Q×f) of 36781 GHz. The dielectric properties in this system exhibited a significant dependence on the relative density, content of additives and sintering temperature. The relative density and dielectric constant (εr) of Zn3Nb2O8 ceramics increased with increasing CuO-V2O5-Bi2O3 additions. And also the relative density and dielectric constant of Zn3Nb2O8 ceramics increased by the augment of the sintering temperature.
Microstructure and Leakage Current Characteristics of ZrTiO4 Thin Films by Sol-Gel Method
Authors: Hsu Cheng Hsing , Lin Shih Yao , Tung Hsin Han
Published: March 2010

This paper describes microstructure and leakage current characteristics of ZrTiO4 thin films on ITO/Glass substrate were deposited by sol-gel method with a fix per-heating temperature of 250oC for 30min at various annealing temperatures from 600oC to 800oC for 1 hr. The annealed films were characterized using X-ray diffraction. The surface morphologies of annealed film were examined by atomic force microscopy. The dependence of the microstructure and leakage current characteristics on annealing temperature was also investigated.
Magnetic Properties of Manganese-Titanium Substituted Barium Ferrite Ba(TiMn)xFe12-2xO19(x=0.0, 0.5, 1.0, 1.5, 2.0) Prepared by the Molten Salt Method
Authors: Li Hai Feng , Gong Rong Zhou , Luo Hao , Zhou Jun , Fan Li Ren , Wang Xian
Published: March 2010

M-type hexaferrites Ba(TiMn)xFe12-2xO19 (x=0 to 2) powders were synthesized by molten salt method. X-ray diffraction, scanning electron microscope and vibrating sample magnetometer were used to analyze the structures and electromagnetic properties. The results showed that, the magnetoplumbite structures for all samples were formed. Magnetic hysteresis loop measurements of the Ba(TiMn)xFe12-2xO19, exhibitted that the saturation magnetization (Ms), the remanent magnetization (Mr) and the coercitivity (Hc) of compounds depended strongly on the chemical composition of materials. The maxium values of Ms (52.68emu/g) and Mr (32.89emu/g) of the compounds were found at x=0.5; however, the values of Hc and the areas of magnetic hysteresis loop of compounds decreased with increasing the value of x. The Ba(TiMn)1.5Fe9O19/paraffin wax composites containing 40vol% of doped barium ferrite exhibitted good absorption performances in the frequency range of 2–14 GHz.
The Influence of Annealing Temperature on the Characteristics of 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 Thin Films
Authors: Diao Chien Chen , Wu Chia Ching , Yang Cheng Fu , Chan Chao Chin
Published: March 2010

In this study, 0.95 (Na0.5Bi0.5)TiO3-0.05 BaTiO3 + 1 wt% Bi2O3 (NBT-BT3) composition sintered at 1200oC for 2h is used as target to deposit the NBT-BT3 thin films. The excess 1wt% Bi2O3 is used to compensate the vaporization of Bi2O3 during the deposition process. Ferroelectric NBT-BT3 thin films are deposited on SiO2/Si and Pt/Ti/SiO2/Si substrates using RF magnetron sputter method using the ceramic target fabricated by ourselves. After depositing under the optimal parameters, the thin films are then heated by a conventional thermal annealing (CFA) process conducted in air at temperatures ranging from 600- 800oC for 60min. The morphologies of NBT- BT3 thin films are observed using SEM the crystalline structures of NBT-BT3 thin films are investigated using XRD patterns. The large memory window and stable leakage current density examination reveals that NBT-BT3 thin films annealed on 600oC are better than other thin films under different CTA temperatures. Finally, the top view and cross-sectional images of SEM, memory windows, leakage currents and polarization characteristics of NBT-BT3 thin films are also well developed.
The Electrical and Physical Properties of (Ba0.7Sr0.3)(Ti0.9Zr0.1)O3 Thin Films under Conventional Annealing Process
Authors: Chen Kai Huang , Yang Cheng Fu , Diao Chien Chen
Published: March 2010

In this study, conventional furnace annealing (CFA) is used as the post-treated process, the effects of annealing temperatures on the crystallization and microstructure of (Ba0.7Sr0.3)(Ti0.9 Zr0.1)O3 (BSTZ) thin films will be developed, and the further influences on the electrical properties of BSTZ thin films are also investigated. A previous study made in our laboratory had shown that the dielectric constant and leakage current density of BSTZ thin film with 640 nm thickness are 192 and 10-6 A/cm2 under the frequency of 100 KHz, respectively. However, the maximum dielectric constant and minimum leakage current density of BSTZ thin films under CFA process are 420 (annealed at 800oC) and 10-8 A/cm2 (700oC), respectively. Besides, the X-ray diffraction (XRD) patterns and the SEM morphology show that crystalline features and grain size of BSTZ thin films increase with the increase of CFA-treated temperatures. These experiment results suggest that a strong correlation exhibits that the physical properties will influence the dielectric properties and nucleation features of BSTZ thin films.
Mechanical and Tribological Properties of 3D Carbon Fiber Reinforced SiC Composites Prepared by Liquid Silicon Infiltration
Authors: Zhou Hai Jun , Dong Shao Ming , Zhang Xiang Yu , Yang Jin Shan , Lu Bo
Published: March 2010

C/SiC composites were prepared by liquid silicon infiltration process, and their microstructure, mechanical and tribological properties were studied in this paper. The results showed that the composites demonstrated non-catastrophic fracture behavior with long fibers pulled out and about 115 MPa flexural strength. The stability of coefficient of friction (COF) was improved and wear rate demonstrated a linear variation with the increasing of rotation speeds. However, wear rate exhibited a higher value (~3.6 μg/m) under a higher load (~150 N), even though the COF curves for C/SiC composites showed no significant changes.
The Influence of Annealing Treatment on Physics and Electrical Characteristics of Ba(Zr0.1Ti0.9)O3 Ferroelectric Films on ITO/Glass Substrate
Authors: Tzou Wen Cheng , Cheng Chien Min , Chen Kai Huang , Yang Hung Chi , Shen Guan Hung , Yang Cheng Fu
Published: March 2010

Perovskite Ba(Zr0.1Ti0.9)O3 (BZ1T9) ferroelectric thin films well deposited on ITO/glass substrates for applications in system-on-panel (SOP) devices are produced and investigated. The sputtering parameters of as-deposited BZ1T9 thin films were rf power of 160 W, chamber pressure of 10 mTorr, substrate temperature of 550oC, and an oxygen concentration of 40%. From the SEM cross- sectional observation, the deposition rate were about 2.5 nm/min. Additionally, the maximum dielectric constant and leakage current density of annealed BZT films under the rapid temperature annealing would be increased, as the temperature increased to 6500C. Further, the maximum remnant polarization and coercive field of BZT films were found and calculated from the p-E curves.
Bi4Ti3O12 and Bi3.25La0.75Ti3O12 Thin Films Prepared by RF Magnetron Sputtering
Authors: Yang Jian Ping , Li Xing Ao , Zuo An You , Yuan Zuo Bin , Weng Zhu Lin
Published: March 2010

Bi4Ti3O12 (BTO) and Bi3.25La0.75Ti3O12 (BLT) ferroelectric thin films were deposited on Pt/Si substrates by RF magnetron sputtering with Bi4Ti3O12 (BTO) and Bi3.25La0.75Ti3O12 (BLT) targets with 50-mm diameter and 5-mm thickness. The microstructure and ferroelectric properties of thin films were investigated. The grain growth behavior and ferroelectric properties such as remanent polarization were different in these two kinds of film, the effects of La doping in the BLT thin film were very obvious.
Hydrothermal Synthesis of Nano-Structured Barium Titanate from Metatitanic Acid
Authors: Chu Jing , Jiang Dan Yu , Zhang Na , Zhang Min , Li Qiang
Published: March 2010

Nano-structured Barium Titanate (BaTiO3) was prepared by a hydrothermal method with the reaction between metatitanic acid and an alkaline solution of Ba(OH)2•8H2O. The morphology of as-obtained powders of BaTiO3 was determined by Scanning Electron Microscope, which revealed that well-dispersed nanoparticles were successfully synthesized. The phase composition was analyzed by X-ray diffraction, which shows that cubic phase of Barium Titanate was prepared. The optimal reaction conditions were discussed in detail.
Synthesis of BaTiO3 Nanorods at Room Temperature and Normal Pressure
Authors: Sun Tie Yu , Wang Xiao Hui , Zhang Xiao Quan , Li Long Tu
Published: March 2010

In this paper, a method to synthesis barium titanate nanorods at room temperature and normal pressure by soft chemical is devoloped. Oleic acid is one important raw material in this method which will help to form reaction containers. The nanorods crystallized in the process. Samples were investigate by XRD, TEM and SAD and so on.
Effect of Gel-Calcination on Piezoelectric Property in (1-x)BiScO3-xPbTiO3  Ferroelectrics
Authors: Wang Han , Wang Xiao Hui , Zhang Shao Peng , Li Long Tu , Huang Zhao Hui
Published: March 2010

In this paper, the effect of gel-calcination on piezoelectric property in (1-x) BiScO3-xPbTiO3 with the composition of x=0.635 is investigated. According to previous work, the heating rate of 200°C/h and holding for 210min having been taken as the basic processing condition. The BSPT powders were obtained from the same sol solution but calcined at different temperatures, and then the powders were used to prepare BSPT ceramics. The result shows that for the bulk ceramics with higher relative density ( higher than 95%), with the increasing calcining temperature of the gel (from 420°C to 500°C), the piezoelectric coefficient d33 of ceramic specimens first increases to maximum of 636pC/N at 450°C, then shows a fluctuation. In this work how the powder activity and the grain size affect (which was leaded by powder particle size) piezoelectric properties of BSPT ceramics are discussed.
Effects of Co2O3 on the Piezoelectric Properties of Na0.5Bi0.5TiO3 Lead-Free Piezoelectric Ceramics
Authors: Jiang Xiang Ping , Feng Zi Yi , Lin Mei , Chen Chao , Shu Kai Zheng
Published: March 2010

Lead-free piezoelectric ceramics Na0.5Bi0.5TiO3+xmol%Co3+ (NBT-xC) were synthesized by conventional solid-state process. Effects of Co3+ addition on the phase structure, dielectric and piezo- electric properties of NBT-xC were investigated. The X-ray diffraction suggested that all specimens were rhombohedral perovskite structure. After a small addition of Co2O3, a dense microstructure with increased grains was developed. The doping with Co3+ enhanced mechanical quality factor Qm significantly, whereas piezoelectric constant d33 and electromechanical coupling factor kp decreased slightly with increasing amount of Co3+. For the ceramics with x=3, the electric properties become optimum, which are as follows: d33=~70pC/N, kp=~13%, Qm=~934, tanδ=~0.02 (1kHz), respectively. These results indicate that the Co3+ ion was considered to replace Ti4+ ion and present “hard doping” effect.
Effect of Specific Surface Area on Growth and Porosity of Oxide Superconducting Ceramic YBCO Single Domain
Authors: Zhang C.P. , Chaud Xavier , Cao Hai Tao , Beaugnon E. , Zhou Lian
Published: March 2010

The effect of specific surface area on the growth and the porosity of oxide ceramic superconductor YBCO single domain are investigated. The enhancement of growth depth depends on the large specific surface area σ. When the specific surface area σ is more than the critical value 200mm2/g, the YBCO single domain is full-growth in the sample of size Ф20mm×18mm. It reveals that a large specific surface area providing an effective tunnel of oxygen diffusion for the crystal growth. On the other hand, this tunnel makes oxygen gas emitting out resulting in porosity diameter decreased. The mean porosity diameter is observed as 5μm in hole sample smaller than 80μm in plain sample. The porosity distribution is calculated as 1/(100μm)2 in plain sample and 8/(10μm)2 in hole sample.
Synthesis of Magnetic Nano-Composite by Partial Reduction of Barium Hexaferrite via High-Energy Ball Milling
Authors: Molaei M.J. , Ataie Abolghasem , Raygan Sh.
Published: March 2010

In this work, nano-composite of barium hexaferrite/magnetite was produced by partial reduction of barium hexaferrite with graphite via ball milling. Phase composition, morphology and magnetic properties of the samples were evaluated by XRD, SEM and VSM, respectively. XRD results revealed that after 15 hours milling, a nano-composite of BaFe12O19/Fe3O4 formed which mean crystallite size of BaFe12O19 was 17 nm. After milling for 20 and 40 hours, the peaks of BaFe12O19 were weakened and Fe3O4 was detected as a dominant phase. The coercivity decreased from 703 to 153 Oe when the milling time increased from 15 to 20 hours.
Glass Binder in Thick Film Metallization Paste for AlN
Authors: Wang Li Li , Wang Yu , Yang De An
Published: March 2010

In this paper, the sol-gel process was used to synthesize a glass binder in thick-film paste for aluminum nitride (AlN) metallization. Some major factors that influenced the sol-gel process including PH value, quantity of water were discussed in detail. The xerogel was analyzed by means of TG-DSC in order to determine its optimum heat treatment process. Meanwhile, the sintering behavior of silver/glass composite thick film had been studied by varying the glass content. The results show that a glass powder of a low melting point and chemically compatible with AlN substrate can be obtained by sol-gel method when the composition (wt %) is CaO (40), B2O3 (15), SiO2 (35), BaO (10). During sintering, the glass becomes liquid and largely affects the microstructure development and square resistance of the thick film. When the glass content is optimum (10wt %), the film adhesion strength achieves maximum and the square resistance has a relatively low value.
Microstructure and Performance of the Hot-Pressed Silicon Nitride Ceramics with Lu2O3 Additives
Authors: Tong Jian Feng , Cheng Da Ming , Li Bao Wei , Ling Huang Hao , Ling Wang
Published: March 2010

The influence of Lu2O3 on phase transformation and seeds morphology was investigated. The result showed that the β-Si3N4 seeds with up to 95% β phase content could be obtained with 2wt% Lu2O3 as the additive content under 1750°C for two hours. The microstructure and mechanical properties of hot-pressed Si3N4 ceramics, using 9wt.% of Lu2O3• additives were investigated by the means of MTS measurements and Vickers indentation crack size measurements, as well as XRD and SEM. It was known that the high fracture toughness of Si3N4 ceramics was attributed to the rodlike morphology of β-Si3N4 grains. And the reinforcement effect and mechanism of β-Si3N4 seed were studied. It was found that the grain size and its distribution influence the property and microstructure of Si3N4 ceramics, namely, the relative narrow distribution of grain diameter in some extent and relative wide range of bimodal distribution of grain aspect ratio could improve the property of Si3N4 ceramics. The improvement in the fracture toughness with the amount of additive was mainly attributed to elongated grain growth during the sintering process.The high temperature properties of self-reinforced Si3N4 with different additives were studied. By this method, self-reinforced Si3N4 ceramics with an increment of 10~20 percent of fracture toughness was successfully fabricated.
Origin of Leakage Currents in ZnO Based Varistor Ceramics with Al(NO3)3 Dopant
Authors: Hu Jun , Long Wang Chen , He Jin Liang , Liu Jun , Luo Feng Chao
Published: March 2010

The additive of Al(NO3)3 has been doped into ZnO varistors in order to reduce their residual voltages. However, the leakage currents of samples always increase at the same time. Generally, it is recognized that some of doped Al3+ ions enter the ZnO grains and reduce their resistivity, which results in lower residual voltages of varistor samples. On the other hand, the remnant Al3+ ions appear in the grain boundaries and also reduce their resistivity, which results in larger leakage currents. In this paper, the electrical properties of ZnO varistor samples with various amounts of Al(NO3)3 dopant were measured. The experimental data are compared with the numerical simulation results, which reveals that the increased leakage currents of ZnO varistors with Al(NO3)3 dopant are not only due to the decreased resistivity of grain boundaries, but also the increased donor density of ZnO grains.
ZnO-Pr6O11-Co3O4-TiO2-Based Ceramic Varistor Materials
Authors: Feng Hai , Peng Zhi Jian , Wang Cheng Biao , Fu Zhi Qiang , Miao He Zhuo
Published: March 2010

The preparation and characterization of ZnO-Pr6O11-Co3O4-TiO2 (ZPCT) based varistor materials with different doping levels of TiO2 and Pr6O11 were investigated. The results reveal that: (1) TiO2 is an important additive, acting as an inhibitor of ZnO grain growth. The doping of appropriate amount of TiO2 can significantly improve the nonlinear properties and decreases the leakage current of the varistors, achieving a relatively high nonlinear exponent and low leakage current with 1.0 mol% TiO2 doped. (2) The oxide of Pr6O11 microstructurally plays the role of inhibition in grain growth. The doping of appropriate amount of Pr6O11 can improve the nonlinear property, and decrease the leakage currents of the varistors, acquiring the optimum results with 1.5 mol% Pr6O11 doped.
Rapid Synthesis of Bi Substituted Ca3Co4O9 by a Polyacrylamide Gel Method and its High-Temperature Thermoelectric Power Factor
Authors: Song Ying , Sun Qiu , Zhao Li Rong , Wang Fu Ping
Published: March 2010

A series of polycrystalline (Ca1-xBix)3Co4O9 ( x = 0.0 ~ 0.075 ) powders were synthesized rapidly by a polyacrylamide gel method. The dense ceramics were fabricated using the spark plasma sintering ( SPS ) technique. Effects of Bi substitution on high temperature thermoelectric properties of Ca3Co4O9 were evaluated. Both the electrical conductivity and Seebeck coefficient increased with increasing Bi content up to x = 0.05, thus leading to an enhanced thermoelectric power factor. The Bi substituted sample with x = 0.05 obtained in this study has the highest thermoelectric power factor in the measured temperature range. It reaches 4.810-4 Wm-1K-2 at 700 °C, which is 26 % higher than that of Ca3Co4O9 without Bi substitution, and is by up to 15 % larger as compared to the Bi substituted sample synthesized by the solid state reaction method and the SPS technique due to the high chemical homogeneous powder prepared by the polyacrylamide gel method.
Preparation and Thermoelectric Properties of LaCoO3 Ceramics
Authors: Fu Li , Li Jing Feng
Published: March 2010

LaCoO3 ceramics were prepared by conventional solid state reaction and normal sintering at the temperatures ranging from 1373 to 1523 K. The sintered densities increased with increasing sintering temperature and exceeded 90 % of the theoretical values when sintered above 1473 K. The thermoelectric properties of the samples sintered at different temperatures were investigated from 323 to 673 K. The LaCoO3 samples showed a negative Seebeck coefficient, whose absolute values decreased dramatically with increasing temperature in the range of 323 to 460 K, then changed to a positive value and lightly decreased above 460 K. The electrical conductivity increased with increasing temperature, indicating a semiconducting behavior. The Seebeck coefficients showed little difference between the samples sintered at different temperatures, but the power factor of the sample sintered at a higher temperature was larger because of the higher electrical conductivity.
Effect of Mn2O3 Addition on the Electric and Physical Properties of Lead-Free 0.98(Na0.5Bi0.5)TiO3-0.02 Ba(Sn0.08Ti0.92)O3 Piezoelectric Ceramics
Authors: Wang Chun Huy
Published: March 2010

In this paper, the effect of Mn2O3 additions on the electrical and physical properties of 0.98(Na0.5Bi0.5)TiO3 -0.02Ba(Sn0.08Ti0.92)O3 was investigated. X-ray diffraction analysis revealed that, during sintering, all of the Ba(Sn,Ti)O3 diffuse into the lattice of (Na0.5Bi0.5)TiO3 to form a solid solution, in which a hexagonal phase with a perovskite structure was found. The 0.98(Na0.5Bi0.5)TiO3 -0.02Ba(Sn0.08Ti0.92)O3 [0.98NBT-0.02BST] ceramics with the addition of 0~4.0 wt% Mn2O3 have been prepared following the conventional mixed oxide process. For 0.98NBT-0.02BST ceramics by doping 1.0 wt% Mn2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.12 and 0.52, respectively, at the sintering of 1100 oC for 3 h. The 0.98NBT-0.02BST ceramic with 1 wt% Mn2O3 addition exhibit a more homogeneous and grain size of ~3.5 μm. With suitable Mn2O3 doping, a dense microstructure and good piezoelectric properties were obtained.
Improvement Luminance of Flexible Organic Light-Emitting Diode (FOLED) by Alignment Thickness Rate
Authors: Chou Dei Wei , Chen Kan Lin , Huang Chien Jung , Chen Wen Ray , Meen Teen Hang , Shih Wen Chieh
Published: March 2010

In this investigation, the effect of the thickness in the flexible organic light-emitting diode (FOLED) is studied. The larger luminance and luminance efficiency, 1160 cd/m2 and 2.71 lm/W, can be obtained at NPB thickness of 45 nm with the Alq3 thickness of 35 nm. The luminance dramatically rises when the Alq3 thickness is 45 nm at bias voltage of 19 V. The highest luminance is up to 2190 cd/m2. The extreme characteristic of FOLED may be useful to an organic electrically pumped laser.
Microstructure and Mechanical Property of Three-Dimensional Needled C/SiC Composites Prepared by Precursor Pyrolysis
Authors: Han Cui Lin , Zhao Dong Lin , Zhang Lei , Shen Zeng Min
Published: March 2010

Three-dimensional needled carbon/silicon carbide (C/SiC) composites with pyrolytic carbon interfacial layer were fabricated by precursor pyrolysis. The microstructure and mechanical property of the three-dimensional needled C/SiC composites were investigated. A thin pyrolysis carbon layer (0.2m) was firstly deposited on the surface of carbon fiber as the interfacial layer with C3H6 at 850 °C and 0.1 MPa by chemical vapor infiltration. Polycarbosilane and divinylbenzene were selected as a precursor to silicon carbide ceramics and a cross-linking reagent for PCS, respectively. The density of the composites was 1.94 g cm-3. The flexural strength of the three-dimensional needled C/SiC composites was 135 MPa. The three-dimensional needled C/SiC composites with pyrolytic carbon interfacial layer exhibit good mechanical properties and a typical failure behavior involving fibers pull-out and brittle fracture of sub-bundle.
Fabrication of Self-Healing Ceramic Coatings Against Oxidation for Carbon/Carbon Composites Using Polysilazane and B4C Filler
Authors: Tian Chun Ying , Liu Hong Li
Published: March 2010

The self-healing ceramic coating against oxidation for carbon/carbon composites was fabricated via preceramic polymer pyrolysis process using polysilazane as preceramic and B4C powder as filler. By means of SEM and XRD, the phase composition and the microstructure of coatings were characterized, and preliminarily study on its anti-oxidation ability and thermal shock resistance was conducted. The results showed that the parameters including content of B4C, coating thickness, number of times of coating/pyrolysis play an important role on anti-oxidation ability of coatings. The optimal anti-oxidation ability was obtained when the content of B4C reached 50wt%, the number of times of coating/pyrolysis reached three and 1200°C was chosen as pyrolysis temperature. The thermal shock resistance test was conducted 50 times and the weight loss rate was 7.14% at 1000°C, which proved that the thermal shock resistance was excellent.
Tribological Behaviors of W-Doped DLC Films
Authors: Fu Zhi Qiang , Wang Cheng Biao , Du Xiu Jun , Peng Zhi Jian , Yu Xiang , Lin Song Sheng , Dai Ming Jiang
Published: March 2010

W-doped DLC films were synthesized from CH4 and W by ion beam deposition and magnetron sputtering, and the influence of W target current on the surface morphology and the mechanical properties of W-doped DLC films deposited were studied. The W-doped DLC films in the study have a smooth dense surface with several particles of about 2micron. The hardness, the modulus, and the film-substrate adhesion of the films are increased with the rise of W target current and the critical load of the scratch test for all the W-doped DLC films is above 70N. The friction coefficient of W-doped DLC films is increased with the increase of W target current while the lowest wear rate is obtained when W target current is 1A.
In Situ-Fabrication of TiCN Ceramic Coating on Titanium Alloy by Laser Cladding Technology
Authors: Yang Yu Ling , Yan Wei , Zhang Duo , Song Gen Zong , Zheng Yi Ran
Published: March 2010

The insitu-fabrication of TiCN ceramic coating by laser cladding-laser nitriding technique (LC-LN) was investigated. Pulsed YAG laser with the power of 500W was used as radiation source. Highly pure N2 was selected as the nitriding element; Titanium powder whose size is 20 m and the pure carbon powder were utilized as the coating materials. The influence of technology parameters such as pulse width, pulse frequency and scanning speed etc. on the insitu-formation of TiCN ceramic coating was studied. XRD results show that the main phases of the coating are TiC0.3N0.7 (or TiC0.2N0.8),TiN and TiN0.3. It was revealed that the appropriate process parameters for insitu-fabrication are the pulse frequency 15 Hz, pulse width 3.0ms, the scanning speed in the range of 9cm/min to 12cm/min, the pressure of N2 0.4MPa. The result of OM showed a metallurgical bonding without crack and bubble between the coating and the substrate was obtained. The microstructure of cladded coating is characterized by fine dentrites. The average microhardness in the coating is more than 1300HV which is about 4 times of that in the substrate.
Influence of Electrophoretic Deposition Voltage on the Phase, Microstructure and Property of a Nano-SiC Coating
Authors: Wang Bo , Huang Jian Feng , Liu Miao , Cao Li Yun , Zeng Xie Rong
Published: March 2010

In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a nano-SiC (SiCn) coating for SiC pre-coated C/C was prepared by a hydrothermal electrophoretic deposition process. The phase compositions, surface and cross-section microstructures of the SiCn coatings deposited at different voltages were investigated. XRD and SEM analyses show that SiCn outer layer without penetrative holes and cracks can be achieved at the deposition voltage range from 120 V to 210 V. The thickness and density of the SiCn coatings improve with the increase of deposition voltage. The multi-layer coatings deposited at 210 V can effectively protect C/C composites from oxidation in air at 1773 K for 202 h with a weight loss of 0.79%.
Fabrication of Superhydrophobic Surfaces of Titanium Dioxide and Nickel through Electrochemical Deposition on Stainless Steel Substrate
Authors: Hu Ya Wei , Liu Shan , Huang Si Ya , Pan Wei
Published: March 2010

Binary microstructures at both micro- and nano-scale are constructed by the electrochemical depositing Ni and TiO2 on the stainless steel surface. Superhydrophobicity is achieved with a water contact angle greater than 150° after modifying the textured surface with fluoroalkylsilane (FAS-17, CF3(CF2)7CH2CH2Si(OCH3)3). The morphology of the Ni-TiO2 compound coating is studied by scanning electron microscopy.
Preparation of Electroless Ni-Mo Coated TiC Powder
Authors: Peng Wu , Zheng Yong , Yuan Quan , Yu Hai Zhou , Wang Shao Gang
Published: March 2010

Ni-Mo coated TiC powders were prepared by electroless plating technique assisted by ultrasonic wave with hydrazine as reducing agent. The surface microstructure of the Ni-Mo coated TiC powders was characterized with scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). The results showed that the as-plated powders, which were of nearly spheric shape, were the composite of TiC and Ni-Mo alloy. The Ni and Mo elements were uniformly distributed around the TiC powders with some plating leakage. In addition, the Ni-Mo plated thin layers on the surface of TiC powders were amorphous or microcrystalline in a supersaturated state. Diffraction peaks corresponding to Ni and Mo weren’t found, and the Ti (NO3)4 and an unknown phase were formed as the load decreased from 15 g/L to 5 g/L.
Superoleophobic and Superhydrophobic Surfaces from Microtextured ZnO-Based Surfaces on Si Substrate
Authors: Liu Chang Song , Zhang Qiang , Li Tao , Li Zhi Wen
Published: March 2010

Theoretical calculations suggest that creating superoleophobic surfaces would require a surface energy lower than that of any known materials. In the present work, we demonstrate micronanostructured ZnO-based surfaces displaying apparent contact angles (CA) greater than 150, even with hexadecane (surface tension l = 27.5 mN/m). The specific ZnO microtextures were fabricated by a chemical solution method, and fluoroalkylsilane (FAS) was then used to tune the surface wettability. The combination of ZnO microtextures and FAS modification resulted in a superoleophobicity with CA for hexadecane was 154.6 (161.9 for diethylene glycol (l = 45.2 mN/m). This apparent superoleophobic behavior was induced on intrinsically oleophilic materials mainly by topography (i.e. the specific ZnO microtextures), which form a composite surface of air and solid with oil drop sitting partially on air. Such special wetting state is a metastable Cassie state. The results are expected to promote the study on self-cleaning applications, especially in the condition with oil contaminations.
Synthesis and Characterterization of Flower-Like NiO Nano-Architectures by Homogeneous Precipitation
Authors: Luo Ling Hong , Wu Ye Fan , Wei Fei , Shi Ji Jun , Cheng Liang
Published: March 2010

Flower-like NiO powders with nano-architectures, self-assembled nano-sheets, were synthesized using Ni (NO3)2•4H2O and urea in mix solvents of ethanol and water by homogeneous precipitation. XRD patterns showed that the NiO powders were of hexagonal structure. FESEM and TEM confirmed that the average diameter of the flower-like NiO was 10μm, and the ultra-thin nano-sheets had micro-porous structure, with the thickness less than 100nm and the size of 2μm×3μm. Specific surface area (BET) was around 130.92m2/g.
Evaluation of Hardness, Local Strength and Contact Fatigue of Brittle Ceramic Coatings at High Temperatures by Hertz Indentation
Authors: Wan De Tian , Bao Yi Wang , Liu Xiao Gen , Li Kun Ming
Published: March 2010

In this work, Hertz indentation method was proposed to investigate the hardness, local strength and cyclic contact fatigue of brittle ceramic coating at high temperatures. The testing fixture for high temperature tests is designed, which is made of SiC. A Si3N4 ball with a diameter of 5 mm is used as the indenter and the CVD SiC/SiC composite is used as testing samples. The applied loads are ranged from 300 N to 700 N and the temperatures are among of room temperature to 1100 oC. The critical load and indent size are used to calculate the Brinell hardness and local strength of CVD SiC coating at room temperature and high temperatures. The contact damage under different loading number and period are analyzed. The mechanisms for the improved local strength and contact fatigue lifetime are discussed.
Mechanical Characterizations of Saxidomus purpuratus Shells
Authors: Yang W. , Jiang Y. , Zhang G.P. , Chao Y.S. , Li Xiao Wu
Published: March 2010

A sort of biological shells (Saxidomus purpuratus), which belongs to Bivalve, was selected as the target material, and hardness and dynamic three point bending fatigue tests were conducted to examine its mechanical properties. Microhardness measurements showed that the inner layer is the hardest. The indentation on the specimen with a lower bending strength was damaged more seriously by the same load. Three point bending fatigue tests demonstrated that this kind of the shells with a special structure comprising mineral and organic matrix can experience the repeated loads instead of immediate breaking. The fatigue results on a single shell investigated here indicated that the fatigue strength is usually less than the static bending strength. Most of the fatigue lives of the specimens are less than 2105 cycles. In addition, fatigue fracture surfaces are observed by scanning electron microscopy.
Defects Analysis of Large Size Silicon Nitride Balls Sintered by Gas Pressure Sintering
Authors: Sun Feng , Zhang Wei Ru , Tian Ting Yan , Teng Xiang Hong , Ru Min Chao , Ding Yan
Published: March 2010

The sections of Φ55mm silicon nitride balls, sintered by gas pressure sintering were analyzed. The results show that temperature gradient during of the sintering process from the surface to the core of large size silicon nitride balls occurred because of the lower thermal conductivity of Si3N4. With the diameter increasing, the temperature gradient was more visible. The impurity of raw materials, such as free Si, free C and other metal oxides, like the SiO2 could produce gas, such as SiO, CO and so on, during the sintering process through the thermodynamic analysis. The producing gas exhausted more difficultly with the diameter of silicon nitride balls increasing. These factors were the most important to the defects of large size silicon nitride balls during the sintering process and made cracks and crescent on the surface of balls.
In-Situ Templating Synthesis of Thermally Stable Hydroxyapatite with Ordered Nanostructures
Authors: Guo Hai Feng , Ye Feng , He Xiu Lan , Zhang Hai Jiao
Published: March 2010

Alkyl phosphates, the products from the reaction between phosphorous pentoxide and various alcohols, were used as the in-situ templates of nanostructure as well as phosphorus source of HAP. The obtained precursor samples had ordered nanostructures:lamellar structure for dodecyl and n-octyl phospahes templated samples, cubic for n-pentyl and hexagonal for ethyl phosphates templated samples. The calcined ethyl phosphate templated sample was pure HAP with a specific surface area of 42m2/g, and sustained with an orderly hexagonal nanostructure at 400°C. But the calcination at 400°C caused the collapse of other alkyl phosphates templated nanostructures.
Ceramic Coatings of Magnesium Alloy for Biomaterial Applications
Authors: Zhang Pu Liang , Liu Bin , Zhang Dong , Tao Yong Wei , Yang Sheng Rong , Wang Jin Qing
Published: March 2010

Ceramic coatings were produced on magnesium (Mg) alloy of AZ91D for biomaterial applications by micro-arc oxidation (MAO) and electrodeposition methods. The morphology, microstructure, phase composition and corrosion properties of the prepared coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and potentiodynamic polarization tester, etc. The results indicated that a porous oxide layer was grown on the Mg alloy sheets after MAO process and the compositions of oxides were mainly Mg2SiO4 and MgO. After further electrodeposition and alkaline treatment, a flake-like structure diverging from centre to periphery was grown on the MAO coating and the coating was mainly made up of hydroxyapatite (HA). Moreover, the corrosion resistance of the Mg alloy after being treated with MAO and electrodeposition technique increases obviously, which was evaluated in stimulated body fluid (SBF).
Characteristic of Al-Doped ZnO Nanorods by a Hydrothermal Process
Authors: Tsai Jenn Kai , Wei Ju Yu , Chen Yi Chi , Jheng You Cheng , Meen Teen Hang
Published: March 2010

In this study, well-aligned single-crystalline zinc oxide (ZnO) nanorods arrays were synthesized on Si substrate by simple hydrothermal process in dilute aqueous solution which consisting of zinc nitrate tetrahydrate (Zn(NO3)2•4H2O) and hexamethyltetramine (C6H12N4, HMT) at 90 °C, in the autoclave. ZnO thin film was pre-deposited on Si substrate by the sputter deposition to serve as the seed layer. Aluminum nitrite (Al(NO3)3) also has been mixed into reaction solution. Al doped ZnO nanorod arrays were fabricated successfully. ZnO nanorods were characterized by high resolution X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, and photoluminescence measurement.
Preparation and Characterization of Fe/SiC Ceramic-Metal Composites
Authors: Liu Zhong Sheng , Shao Gang , Chen De Liang , Zhang Rui
Published: March 2010

SiC is a perfect reinforced material, characteristic of high hardness, high wear- and corrosion-resistant property, and low cost. SiC-reinforced iron-matrix composites show high wear resistance, high hardness, high inflexibility and high strength, with wide applications as superior wear-resistant and high temperature materials. This paper reported a heterogeneous precipitation method to coat SiC with copper particles. The vacuum hot-pressing method was used to sinter the Fe/SiC composites with Cu-coated SiC powders. The techniques of XRD and SEM were used to characterize the compositions and microstructures of the samples. The Archimedes method was used to test the density. The results showed that SiC and Cu were homogeneously mixed in the composite powders obtained by the heterogeneous deposition method, and that the composites with 5wt% of SiC (Cu) obtained at 950°C have a high relative density of 96%, a high hardness of 4121 MPa and a high bending strength of 646 MPa. The enhanced properties of Fe/SiC composites could result from the improved interfacial consistency by using Cu-coated SiC powders, which could inhibit some adverse interfacial reactions.