bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructure and Mechanical Property of Zirconia Nanocomposites
Authors: Li Wen Xu , Yu De Zhen , Wang Fu Ping
Published: March 2010

ZrO2 nanocomposites were prepared and studied by microstructure observation and mechanical property detection. First, yttria stabilized zirconia (3Y-TZP) nanopowders were synthesized by sol-gel method. TEM photograph showed that the addition of yttria restrained the growth of the grain, but caused the agglomeration of the nanopowder. XRD analysis showed that the amount of yttria influenced the phase character of the materials, and the monoclinic zirconia changed gradually into tetragonal and cubic phase with increasing yttria content. Second, the micro-size 3Y-TZP materials was mixed with the former prepared nano-size particles and pressed by cold isostatic pressing, and then sintered at 1300 °C to prepare ZrO2 ceramic nanocomposites. The results of microstructure analysis showed that the amount of nano-size powder affected the fracture mode of nanocomposites, thus changed the fracture toughness. The mechanical testing results indicated that both the flexural strength and the hardness decreased with increasing nano-size powder, whereas fracture toughness increased and decreased subsequently. ZrO2 ceramic nanocomposites with 20% nano-size powder would be a promising kind of dental restoration material due to its low hardness, high fracture toughness and moderate flexural strength.
Comparative Study of Biomorphic Silicon/Silicon Carbide Ceramic from Birch and Compressed Birch
Authors: Yan Zi Li , Liu Jie , Zhang Jian Chun , Ma Tian , Li Zheng Cao
Published: March 2010

Wood compression process was innovatively introduced as a pre-treatment method to birch into the fabrication of biomorphic silicon/silicon carbide (Si/SiC) ceramic with high density. Firstly, birch blocks were compressed to the density in the range of 0.85-1.00g/cm3. Secondly, both birch blocks and compressed birch blocks were carbonized at 1200°C to get carbon templates. Lastly, carbon templates were infiltrated with liquid silicon to obtain biomorphic Si/SiC ceramics. The effect of compression process on the density and microstructure of both carbon template and ceramic was investigated. The results show that the maxium density of biomorphic Si/SiC ceramic from compressed birch is 3.01g/cm3, whereas the density of the ceramic from birch is only 2.80-2.89g/cm3. So the compression process was an effective method to increase the density of biomorphic Si/SiC ceramic.
In Vivo Study of Carbon Artificial Femoral Head
Authors: Chen Lan , Yuan Xiao Bing , Sun Hong Wei , Chen Ming Zhao , Zhao De Ben , Yu Dan , Bao Yi Wang
Published: March 2010

Hip hemiarthroplasty is a popular method for curing hip joint diseases. Comparing with the total hip replacement (THR), hip hemiarthroplasty has some advantages, such as simpler operation, lower cost and less injury. However, inevitable acetabular cartilage wear, which leads to ultimately conversion to THR, has been reported by many authors. That limits its applications. To solve this problem, more suitable biomaterial should be chosen to make the femoral head. In this research, a kind of carbon femoral head, which was made of graphite coated with low temperature isotropic pyrolytic carbon, was studied in vivo. Nineteen New Zealand adult white rabbits were divided into 3 groups. Every rabbit was taken the replacement operation and time-dependently killed after certain periods. X-ray photographs of the hip joint, macroscopic apperarance and histological morphometry of the neocartilage around the prosthesis, were examined. The results proved that the coating material of the femoral head was biocompatible and the neocartilage tissue around the prothetic head might protect the acetabulum from wear. However, because of the complicated physiological environment, further research is needed.
Develop an Implantable CPW-Fed Antenna on the MgTa1.5Nb0.5O6 Ceramic Substrate
Authors: Yang Hung Chi , Chien Tsung Fu , Cheng Chien Min , Chen Kai Huang
Published: March 2010

An implantable antenna for the applications of biomedical telemetry has been widely studied in the modern medical science. The purpose of this study is to design and fabricate an implantable antenna which exhibits enhanced bandwidth (25%) and miniaturization for the use of implantation. In this letter, the microwave dielectric ceramic (MgTa1.5Nb0.5O6) substrate which possesses high dielectric constant (εr = 28) and high quality factor is used as the substrate of the implantable antenna, a CPW-fed monopole dual spiral structure is adopted as the antenna pattern and fabricated by the print-screening technique. The effects of shape, length, size, and thicknesses of the proposed antenna would be evaluated and investigated in this letter. In addition, the center frequency is required to conform to the band (402 ~ 405 MHz) provided by Medical Implant Communication Services (MICS). From the experimental results of the proposed antenna immersed in phantom fluid, the optimum antenna exhibits a miniaturized volume of 288 mm3, bandwidth of 134 MHz (33%), return loss 16.32 db at 404 MHz, the SAR of 142 W/Kg, and gain of 16 db, respectively.
Effects of SiO2 and Fe2O3 on Morphological of Mullite
Authors: Huang Cun Shu , Liu Jia Chen , Guo An Ran , Yang Lu , Song Di
Published: March 2010

Effects of SiO2 and Fe2O3 on morphological of mullite were investigated for a special use related to mullite containing SiO2 and Fe2O3. It was concluded that, when Al2O3/SiO2 ratio near the theoretical component of mullite, the composites cannot been sintered at 1600°C. The normal morphology of mullite presents granule form with Fe2O3 addition, while takes a long column shape with the condition of excessive. SiO2 presenting. Fe2O3 can promote sintering of mullite, as well as growing in needle-like morphology.
Application of Vertically Oriented TiO2 Nanotube Arrays on Dye Sensitized Solar Cells
Authors: Meen Teen Hang , Shih Wun Yue , Water Walter , Tsai Jenn Kai , Liu Yu Sung , Ho Chi Ting , Huang Chien Jung
Published: March 2010

In this research, vertically oriented TiO2 nanotube was fabricated on ITO glass by electrochemistry method, and investigated by the measurements of X-ray diffractometer (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV/VIS) spectrometer. X-ray diffraction patterns show that the best sintering temperature of TiO2 nanotube is 500°C, at which TiO2 anatase phase forms best. SEM images reveal that the diameter and height of TiO2 nanotube are 70 nm and 230 nm, respectively. Transmittance curves reveal that the transmittance of annealed TiO2 nanotube is about 80%~90%, and is obviously higher than non-annealed TiO2 nanotube. The absorption band of annealed TiO2 nanotube is at 330~370 nm. The results of current-voltage (I-V) characteristics analysis reveal that dye-sensitized solar cell with TiO2 nanotube electrode has better I-V characteristics and efficiency than TiO2 film electrode. This result may be due to the annealed TiO2 nanotube applied on the electrode of dye-sensitized solar cell can increase the contact area between TiO2 and dye, resulting in the enhancement of I-V characteristics and efficiency for dye-sensitized solar cell.
Influence of Deposition Parameters on the Characteristics of AZOY Transparent Conducting Oxide Thin Film
Authors: Diao Chien Chen , Chan Chao Chin , Wu Chia Ching , Yang Cheng Fu
Published: March 2010

“GfE Coating Materials Company” had developed a novel AZOY transparent conducting oxide (TCO) material that used ZnO as raw material and contained a small amount of Y2O3 and Al2O3. In this study, the AZOY material developed by GfE company is used as the based TCO material and we will develop the influences of substrate temperatures on the characteristics of AZOY TCO films by RF sputtering method, under optimal O2/argon ratio and depositing pressure. After deposition, the sheet resistance of AZOY films is measured with a four point probe, and surface morphology and cross-sections are studied using a field emission scanning electron microscope (FESEM). And finally, the UV-Vis spectrophotometer is used to find the transmittance of AZOY TCO films.
Preparation and Properties of Translucent Y-α-Sialon Ceramics by Two-Steps Hot Pressing
Authors: Shan Ying Chun , Xu Jiu Jun , Guan Chun Long , Li Jiang Tao
Published: March 2010

Yttrium-doped α-sialon ceramics with different compositions were prepared by two-steps hot pressing (first heating to 1750 °C holding for 60 min, then continue heating to 1900 °C holding for 60 min) at 25 MPa in nitrogen, their design compositions were Y0.4Si9.8Al2.2O1.0N15 (Y1210, m=1.2 and n=1.0), Y0.4Si9.7Al2.3O1.1N14.9 (Y1211, m=1.2 and n=1.1) and Y0.4Si9.6Al2.4O1.2N14.8 (Y1212, m=1.2 and n=1.2) respectively, and the effects of n value on phase composition, microstructure and optical property were approached. It is found that only α-sialon is detected in Y1210, however, there exist β-sialon besides of major phase α-sialon in Y1211 and Y1212. The density of sintered sample decreases with the increase of n value, higher n value contributes to elongated grain growth, and both the size and content of elongated grain increase with the increase of n value. The samples all show light transmission in the near infrared and infrared region, and their maximal optical transmittances decrease with the increase of n value. All those indicate that lower n value contribute to higher density, single α-sialon phase, smaller size and lower content of elongated grain, which is better for the preparation of higher optical transmittance Y-α-sialon.
Effects of the Starting Powders on Microstructure and Properties of Porous Silica Ceramics
Authors: Zhou Li Zhong , Wang Chang An , Huang Yong
Published: March 2010

Porous silica ceramics with above 70% porosity were fabricated by gelcasting process using tert-butyl alcohol (TBA) as solvent. Two types of starting powders, α-silica and fused silica, were chosen to fabricate porous silica ceramics. According to XRD analysis, only single α-cristobalite phase can be identified in the sintered samples. SEM observation showed that highly porous skeleton formed by the bonding of molten ceramic particles in porous silica ceramics. Comparing to the samples using α-silica as starting materials, a compressive strength of 6.30MPa was achieved at a porosity of 70.7% when using fused silica as starting materials. A relatively high specific surface area higher than 10m2/g was obtained for both samples, which should be suitable for catalysis applications as catalyst supports.
Preparation of Porous Mullite Ceramics Using Al as Foaming Agent
Authors: Yin Jia Zhi , Liu Jia Chen , Guo An Ran , Song Di , Wang Wen Jun
Published: March 2010

Effects of Al in different added condition on pores shape and mullite configuration were investigated. Three sorts of hole were got by using Al as foaming agent in mullite composites. It was concluded that isolated holes could be formed by Al changing to Al2Ol3 with acidity condition in green state, open holes could be formed by Al changing to Al2O3 directly in sintering process, and mixed hole of isolated and open ones could be formed by Al changing to Al(OH)3 with alkalescence condition in green state followed changing to Al2O3 in sintering process. These holes could supply a position for growth of mullite as well.
Preparation and Properties of Porous Diamond Preforms
Authors: Dong Ying Hu , He Xin Bo , Ud-Din Rafi , Guo Cai Yu , Huang Yu Ting , Qu Xuan Hui
Published: March 2010

A binder comprising of 60% PW (paraffin wax), 10% HDPE (high-density polyethylene), 12% PS (polystyrene), 13% PPR (random-polypropylene), and 5% SA (stearic acid) has been selected and successfully employed to fabricate the diamond preforms possessing high strength and well shape retention capability. Various effects of processing methods on the properties of the diamond preforms have been investigated. The results indicate that the binder consisting of PW-HDPE-PS-PPR-SA possesses excellent comprehensive rheological properties and is more appropriate as the organic vehicle for fabricating porous diamond preform. It has been evaluated that the mixing of 140m size diamond particles with 20m size diamond particles in the weight proportion of 3:1 provides the best particle size distribution for preparation of diamond preforms. It is also observed that impregnation of preform with 1.7wt (SiO2)% water glass and subsequently heat-treated in vacuum at 800°C for 40min yields in high strength (with the strength of 7.1 MPa) diamond preform for infiltration. The strengthened preforms have been observed to possess an excellent shape maintaining capability. It is concluded that the diamond-copper composites fabricated by utilizing this high strength preform through hot-press infiltration method have high relative density of 96.4% and thermal conductivity of 300W.m-1.K-1.
Effects of Infrared Scattering Powders on the Thermal Properties of Porous SiO2 Insulation Material
Authors: Shi Xing , Zhang Shi Chao , Chen Yu Feng , Li Mao Qiang , Ouyang Shi Xi , Peng Xiao Ying
Published: March 2010

Porous SiO2 insulation material was made by wet process. Fibrous xonotlite crystal and glass fiber were used as reinforced fibers, and graphite, zirconia and titania powders were added as infrared scattering materials into the porous SiO2 insulation material. The density of the SiO2 insulation material was about 0.3g/cm3. The porosity was about 85%, and the pore size was mainly ranged from 20 to 60 nm in diameter. Heat transfer due to solid conduction and gas convection was reduced greatly because of the existence of larger amount of nano pores. Thermal radiation was partly blocked by the infrared scattering powders. Thermal conductivity of the porous SiO2 insulation material added with graphite powder as infrared scattering powder can reach as low as 0.04W/m.K at 700°C. The type and amount of added infrared scattering powders had important influence on the thermal performances of insulation materials.
Comprehensive Evaluation of Machinabilities of Dental Ceramics
Authors: Zhang Cheng , Lu Ji , Huang Hui
Published: March 2010

Machinability of ceramics is a comprehensive behavior resulting from the interactions of several factors. In this paper, the fuzzy comprehensive evaluation system was applied to establish a model for machinabilities of several dental ceramics, including zirconia, empress feldspar, empress toughening leucite and lithium disilicate glass. The hardness (HV), fracture toughness (KIC) and elastic modulus (E) of ceramic samples were used in evaluation model with different weighted indexes. The ceramics could be thus divided into 4 groups of “easiest”, “easy”, “difficult” and “most difficult”, based on evaluated results. Lithium disilicate glass belongs to “easiest”, empress feldspar and empress toughening leucite are at the “easy” level, and zirconia is “difficult” to be machined compared with other counterparts. The evaluations by established model are well supported by the practical machining experiments while these dental ceramics being undergone cutting. This implies that the derived evaluation model is an easy and simple way to estimate machinability of dental ceramics.
Mechanical Behaviors of Foam Nickel Ceramic
Authors: Zhao Rong Guo , Chen Chao Zhong , Luo Xi Yan
Published: March 2010

The uniaxial tensions for foam nickel ceramic specimens with different relative densities are carried out on a CSS-44020 Universal Electronic Test Machine at ambient temperature, and the uniaxial tensile tests at various strain rates and temperatures are performed as well. The effects of relative density, strain rate and temperature on the elastic modulus are investigated. It is found that the elastic modulus of the foam nickel ceramic material increases with the density and stain rate, while decreases with the temperature. Simultaneously, the effects of relative density, strain rate and temperature on the yield strength of the foam nickel ceramic material are studied. It is shown that the yield stress increases with relative density and strain rate, but is reversed with increasing temperature. The comparison between the calculated result and experimental data demonstrates that the theoretical model can well predict the mechanical behavior of foam nickel ceramic material.
Effect of Hexagonal BN on the Microstructure and Mechanical Properties of Pressureless Sintered Porous Si3N4 Ceramics
Authors: Li Yong Feng , Liu Ping , Wang Xiang Dong , Jin Hai Yun , Qiao Guan Jun
Published: March 2010

Porous silicon nitride ceramics with various amounts (25, 35, and 45 vol %) of hexagonal boron nitride (h-BN) were fabricated at 1800°C for 2h by the pressureless sintering process. With FESEM and TEM, the effects of h-BN on the microstructure and mechanical properties of Si3N4 ceramics were investigated. Results of the microstructure and mechanical properties of Si3N4/BN composites showed that the growth of the elongated β-Si3N4 were hindered by h-BN additive, which resulted in the decrease of fracture toughness of Si3N4/BN ceramics with increasing h-BN content. The morphologies of the fracture surfaces by FESEM revealed the fracture mode for Si3N4/BN composites to be intergranular. However, phase analysis by XRD indicated that the effect of h-BN on the α- to β- Si3N4 phase transformation of Si3N4/BN composites was negligible.
Dielectric Properties of Porous Si3N4 Ceramics Prepared by In Situ Cordierite Bonding
Authors: Xia Yong Feng , Zeng Yu Ping , Jiang Dong Liang
Published: March 2010

In situ bonding porous silicon nitride (Si3N4) ceramics were fabricated in air using a conventional ceramic process using Si3N4, Al2O3 and MgO as the starting materials. The effects of additives content, sintering temperature and holding time on phase composition, microstructure, dielectric properties and porosity were studied. The porous Si3N4 ceramics were composed of α- Si3N4, SiO2 (cristobalite) and cordierite. Porous Si3N4 ceramics with porosities of 34.12~50.22%, dielectric constant of 2.95~4.45 and dielectric loss of ~0.0025 were obtained.
A Facile Template-Free Synthesis of Praseodymium-Doped Ceria Nanorods
Authors: Ren Yao Yu , Deng Chang Sheng , Ai De Sheng , Ma Jing Tao , Zan Qing Feng , Kong Jiang Rong , Xu Jing Ming
Published: March 2010

Pr-doped ceria solid solutions have attracted much attention as promising mixed electronic-ionic conductor and oxygen storage materials. However, little effort has been made to synthesize Pr-doped ceria with one-dimensional nanostructure. In this paper, Pr-doped ceria nanorods were prepared via a facile hydrothermal method using Pr(NO3)3, Ce(NO3)3 and NaOH as raw materials. X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED) indicated that the as-prepared Pr-doped ceria nanorods had a cubic fluorite structure, with the length around 200 ~ 400 nm and the diameters around 10 ~ 18 nm. The effect of alkaline concentration has been systematically studied and the results indicated that higher alkaline concentration was favorable for the formation of nanorods.
Zircontes/Sulfates Composites: Perfect Combination of High- and Low-Temperature Protonic Conductors
Authors: Peng Zhen Zhen , Guo Rui Song , Yin Zi Guang , Li Juan
Published: March 2010

Two typical classes of proton conductors, zirconates and solid acids (such as CsHSO4) or related sulfates, are intensively investigated recently. Based on the different proton-conducting mechanisms of zirconates and sulfates, we designed and fabricated Y2O3-doped barium zirconate/sulfates composites, aiming to make full use of the benefits, and eliminate the drawbacks of the two individual materials. The electrical conduction of the composite was studied by electrical and electrochemical methods. Microstructure of the composites was examined by SEM. Electromotive force (EMF) measurements were conducted under fuel cell conditions. The results indicated that small amount of sulfates was introduced at the grain boundaries of BaZr0.9Y0.1O2.95. The electrical conductivity of the composites was greatly improved and the total ionic transport numbers of the composites are more than 0.9 at 750 °C.
Synthesis and Impedance Spectroscopy of Ga-Doped La9.33(SiO4)6O2 Apatite Oxide Ion Conductor
Authors: Huang Zhao Xiang , Li Bu Yin , Liu Jia
Published: March 2010

Apatite materials are interesting alternative solid oxide fuel cell (SOFC) electrolytes because of their open structure including tunnels for the diffusion of oxide ions and their good chemical stability. However, the conductivity was still relative low when it was used as SOFC in the intermediate operating temperature range. So the apatite-type lanthanum silicates/germanates and doping were widely researched for enhancing conductivity recently. This study reports the influence of Ga doping on conductivity of the apatite phase La9.33(SiO4)6O2 according to the formula La9.33+x/3(SiO4)6-x(GaO4)xO2 where 0  x  2. Samples were prepared by a sol-gel process. The conductivities of all compositions have been obtained by impedance spectroscopy analysis. The conductivity enhancement observed for moderate x values and illustrates further influenced by the tetrahedral cation sublattice and the La vacancies in optimizing the conductivity.
Preparation and Electrochemical Performance of Hydrogen Electrode and Electrolyte for SOEC by Tape Casting and Lamination
Authors: Ma Jing Tao , Ge Ben , Lin Xu Ping , Deng Chang Sheng
Published: March 2010

The solid oxide electrolysis cell (SOEC) has been receiving increasing research and attention worldwide due to its potential usage for large-scale production of hydrogen. Tape casting and lamination technique were successfully used to fabricate the NiO-YSZ hydrogen electrode substrate cermets of planar solid oxide electrolysis cell. In this paper the green tape with thickness of 350μm was prepared by tape casting and then the lamination was used to obtain the required thickness for the NiO-YSZ hydrogen electrode-supported electrolyte cermets. The rheological properties of the suspensions with NiO-YSZ and YSZ were studied, respectively. The optimal temperature and pressure of the lamination were determined, and four direction of lamination mode was used according to tape casting direction to obtain symmetrical and even hydrogen electrode-supported electrolyte after co-sintering. Pore-formers were used to increase the porosity of the hydrogen electrode. The green tape was analyzed by TG-DSC analysis, the microstructure was observed by scanning electron microscope. The electrochemical performance of unit cell was measured at 850°C.
Ni/SDC Materials for Solid Oxide Fuel Cell Anode Applications by the Glycine-Nitrate Method
Authors: Yang Cui , Cheng Ji Gui , He Hai Gen , Gao Jian Feng
Published: March 2010

NiO/Ce0.8Sm0.2O1.9 (NiO/SDC, 65wt.% NiO) composite powders were synthesized by a glycine-nitrate process (GNP) to fabricate Ni/SDC anode-supported solid oxide fuel cell (SOFC). The results show that the composite powders are composed of single cubic phases of NiO and SDC and have a particle size in nanometer range. NiO/SDC ceramics were prepared from the NiO/SDC powders and were converted into Ni/SDC cermets by reduction in H2, which were employed as anode materials for SOFC with SDC electrolyte. It is shown that Ni/SDC cermets from the NiO/SDC composite powders by the GNP have porous and homogeneous microstructures and show good electrical conductivity. A single SOFC based on Ni/SDC anode with about 50µm SDC electrolyte film and about 80µm La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode was constructed. Open circuit voltage (OCV) of the cell is about 0.8V and maximum power density is 361.42 and 394.78 mWcm-2 at 750 and 800°C, respectively.
Fabrication of YSZ Film by Aqueous Tape Casting Using PVA-B1070 Cobinder for IT-SOFC
Authors: Luo Ling Hong , Lang Ying , Huang Zu Zhi , Cheng Liang , Shi Ji Jun
Published: March 2010

Aqueous tape casting was developed to fabricate YSZ films using a cobinder. The processing parameters such as pH value, dispersant content, and binder type and content on the quality of YSZ films were investigated and optimized. The results show that at pH = ~ 9.6, the YSZ suspensions with 0.8wt% of the dispersant PAA have a good stability. The degree of pseudo-plastic and viscosity of slurry using different binders increased with the increasing of PVA content, in contrast, the degree of pseudo-plastic and viscosity decreased with the increasing of B1070 content. The density and drying shrinkage of YSZ green tape are tightly related to the different binders. The sintered density of YSZ film increased as the density of green tape increased. The green tape using PVA (30wt %) +B1070 (70wt %) cobinders was sintered at 1400 °C for 2 hours. The films of YSZ with 98.5% of theoretical density have been obtained.
Resonance Properties of a Functionally Gradient Piezoelectric Actuator Based on PNN-PZ-PT Ceramics
Authors: Chen Hai Yan , Meng Zhong Yan
Published: March 2010

A functionally gradient piezoelectric actuator based on PbNi1/3Nb2/3O3-PbZrO3-PbTiO3 (PNN-PZ-PT) system was prepared. The cantilevered actuator consists of a high piezoelectric & low dielectric layer, a low piezoelectric & high dielectric layer and a thin middle diffusion layer. Frequency dependences of impedance were measured from 100Hz to 3MHz. The resonance modes were characterized. A number of low frequency modes were observed and identified as bending resonance. The dimension dependence of resonance frequency of bending resonance was investigated. The results of the measurement were compared with calculated values. There is a good agreement between the determined resonance frequencies and calculated values.
Effect of Ball Milling on Microstructure and Flexural Strength of Ti(C,N)-Ni Cermets
Authors: Wang Xiao Yan , Li Jian , Wu Rui Fen , Pan Wei
Published: March 2010

Ti(C,N) cermets were prepared by SPS method. The effects of nickel salt coating as well as ball milling times on the microstructure and mechanical properties of the cermets were investigated. SEM images shows that the nickel was coated homogeneously on the surface of Ti(C,N) powders by mixing Ni salt and Ti(C,N) powder. The grains of Ti(C,N)-based cermets became finer with increasing ball milling time. The flexural strength increased when the balling milling was below 48h, and then decreased with increasing of ball milling time, which was due to the decrease of the flake structure in cermets.
Single Walled Carbon Nanotubes (SWCNTs) Assembled Site-Selectively on Flexible Substrate
Authors: Xing Li , Xiang Jun Hui , Zhang Fu Shi , Liang Xiao Hong , Song Bo , Yang Jing Kui
Published: March 2010

Site-selectively array of single walled carbon nanotubes (SWCNTs) is one of the key points for the fabrication and application of nanodevices. This research is focused on developing a technology to assemble site-selective high density SWCNTs on flexible substrate. Patterned SWCNTs were assembled on flexible poly (ethylene terephthalate) (PET) substrate via inducing directed charge (DC) field. In this process, the modification of hydrophilic or hydrophobic substrate surface is accomplished by selective ultraviolet (UV) irradiation, and which is very important to the self-assemble behavior and accurately site-selective location of SWCNTs. This method, a composition of “Top-Down” approach and “Bottom-Up” approach, is expected to give a way for the fabrication of nanodeivces and nanosystems.
Preparation of Si3N4-Al2O3 Functional Gradient Joining Material Using Transient β-Sialon Interlayer
Authors: Wang Lin Jiang , Xie Xiang Li , Zhang Ye , Chen Ying Guang
Published: March 2010

The joining of high temperature structural ceramics to other materials is an important process commercially and technologically. Due to the existence of physical and economic limitations for the manufacture of large parts, joining is essential. Functional gradient materials (FGMs) are designed to exhibit a desirable gradient in a property, due ether to a gradient in composition, or microstructure, or both. In this paper, Si3N4-Al2O3 functional gradient joining material was prepared by hot press sintering of multilayered FGMs with 20 layers of thickness 400um each using β-Sialon as transient interlayer. The structure and properties of the materials were analyzed by the means of scan electron microscopy(SEM), X-ray diffraction(XRD) and micro-sclerometer. The components of the materials have gradient distribution and successional. The microhardness is gradient changing with the change of micro-structure. The interface between layers is tightly coupling and has no stress convergence. The test of thermal shock and fatigue cracks of FGM between 1300 °C and 900 °C show good properties of thermal stress relaxing and resistance for high temperature.
Fabrication of MoSi2 Nanocrystal by Mechanical Alloying Large Particle-Sized Starting Powders
Authors: Luo Jun Ting
Published: March 2010

The MoSi2 nanocrystal was prepared by mechanical alloying (MA) large particle-sized starting powders, in which the milling time is much longer than usual MA time. It was found that the Mo-Si powder mixture mixed at stoichiometry proportion forms α-MoSi2 and β-MoSi2 in the MDR mode rather than pure α-MoSi2 in the SHS mode. The grain size of MoSi2, calculated using Scherrer′s formula, is 18nm when milled for 96h, and decreases to 12nm when further milling to 144 h. This is because that the milling balls provide enough energy to refine most of the rough crystal grain. The average grain size increased to 15nm when milled for 192 h, which indicates that further expand time could not refine the crystal grain while cause the growth of a part of the crystal grain. The particle size of MoSi2 is about 0.5μm when milled for 96 h and the agglomerating phenomenon is severe. The particle size of MoSi2 decreases to 0.4μm and releases the agglomerating phenomenon with the milling time for 144 h.
Working Principle and Design of a Cylindrical Standing Wave Ultrasonic Motor Using Cantilever Type Bending Transducer
Authors: Liu Ying Xiang , Liu Jun Kao , Chen Wei Shan , Shi Sheng Jun
Published: March 2010

A cylindrical standing wave ultrasonic motor using cantilever type bending transducer is proposed in this paper. There are four cantilevers outside the cylinder, and four PZT ceramics are set on each end surface of cantilevers. The bending mode of cylinder is excited by the bending vibration of transducers. Thus, a linear simple harmonic motion is achieved at the particle on the tooth. The working principle of proposed motor is analyzed. The cylinder and transducer are designed with FEM. The bending vibration modals of transducer and cylinder are degenerated. The transient analysis is developed to gain the vibration characteristics of stator, and the results indicate the proposed motor has potential good output characteristics. The results of this paper verify the theoretical feasibility and provide instructions for the development of proposed motor.
Actuating Mechanism and Design of a Double Driving Feet Linear Ultrasonic Motor Using Longitudinal Vibration Transducer
Authors: Chen Wei Shan , Liu Ying Xiang , Liu Jun Kao , Shi Sheng Jun
Published: March 2010

A double driving feet linear ultrasonic motor using longitudinal vibration transducer is proposed in this paper. The stator of proposed motor contains a horizontal transducer and two vertical transducers. The horizontal transducer includes two exponential shape horns located at the leading ends, and each vertical transducer contains one exponential shape horn. The horns intersected at the tip ends where located the driving feet. The horizontal and vertical vibrations of driving feet are generated by the longitudinal vibrations of horizontal and vertical transducers, respectively. Longitudinal vibrations are superimposed in the stator and generated elliptical motions at the driving feet. The two vibration modals of stator are gained with FEM, and the resonant frequencies of two vibration modals are degenerated by adjusting the structural parameters. Transient analysis of piezoelectric coupling states the good and strong elliptical motions of driving feet, and verifies the theoretical feasibility of proposed motor.
Preparation of Xonotlite Whiskers from Carbide Slag
Authors: Liu Fei , Zeng Ling Ke , Cao Jian Xin , Lin Qian , Li Jing
Published: March 2010

Carbide slag was used as raw materials for the first time to prepare xonontlite whiskers via a hydrothermal route without special instruments and synthesis conditions. And the effect of pH value of emulsion of carbide slag and hydrothermal conditions on removal rate of impurities, morphology and crystallinity of synthesized xonotlite whiskers were explored using ICP, SEM and XRD techniques. The results indicated that the carbide slag after purification could be used to prepare xonotlite whiskers, and different pH values of emulsion of carbide slag had great impact on the removal rate of impurities and morphology of xonotlite whiskers. Xonotlite whiskers with 20-40 μm in length and 100-500 nm in diameter were hydrothermally synthesized at 230 °C for 15 h with using silicic acid as kiesel material.
Preparation of Zinc Oxide Whisker on Carbon Fibers
Authors: Zhang Hu , Wang Ling , Tong Jian Feng , Yi Xiao Su
Published: March 2010

A process is adopted to grow whiskers on carbon fibers. The whisker growth is carried out in a two-step process. Plasma spraying, electroplating and magnetron sputtering are used to pretreat the surface of carbon fibers and then ZnO whiskers are grown by hydrothermal method. By comparing three different methods of surface pretreatment, it is concluded that magnetron sputtering is most available and has no damage to the carbon fibers. Combining preparation method of the ZnO whiskers, a new process is developed to surface modified of carbon fibers which is expected apply to carbon fiber composites.
Luminescent Properties of Eu3+-Doped HfO2 Powders Prepared by Combustion
Authors: Meng Jing , Jiang Dan Yu , Li Qiang
Published: March 2010

Scintillators are ideal candidates used in detectors for X-ray ,γ-ray and high energy ray , and have been widely applied in nuclear medicine , high energy physics ,geologic survey , security inspection and material flaw detection. The high density of HfO2 is an attractive compound for host lattice activated by rare earth for applications as scintillating materials. This paper reported the synthesis of Eu3+ doped HfO2 nanopowders by chemical self-combustion method at low temperature. Analytical grade Eu(NO3)3 and high pure HfOCl2 were used as raw materials. The requisite amount of urea and glycine as the mixed fuel were added to the mixed solution. A little EDTA was used as a complexant. The mixed solution was dried at 200°C, and fired at 450°C. The powders synthesized by self-combustion were then calcined at 800°C to profit the crystal growth and improve the luminescent properties. XRD, TEM were employed to analyze the phase composition and the characteristics of as-obtained powders. The TEM images display typical nano-structured morphology of Eu3+ doped HfO2. Analysis of XRD indicates that Eu3+ doped HfO2 nanopowders are cubic phase. The excitation and emission spectra were analyzed by the fluorescence photometer. There are two peaks in emission spectra .One is at 595nm, and another is at 614nm. The luminescent properties also reveal the structure of cubic phase.
Preparation of Porous Mullite Ceramics by Fly Ash/Al Compositions
Authors: Jia Qi Hui , Liu Jia Chen , Guo Ji Ping , Du Xiong Wei , Wang Zhong Jie , Wang Wen Jun
Published: March 2010

Porous mullite was prepared from a reactive mixture of Al metal powder and the fly ash produced by power plant. The sintering ceramics was characterized for the pore structure and phase identification studies. It was found that the sintered specimen expands at first (1300-1400°C) and then shrinks which was correspondence to the changing of open porosity. The expansion was attributed to the fact that the alumina produced from the oxidation reaction of Al powder made the volume larger than the starting mixtures. At 1550°C, it was inferred that the alkaline element in the fly ash made the mullite decomposed then destroyed the mullite structure. The SEM photographs suggested us that the pore diameter of the sintered ceramics might be adjusted by adding Al powder with different grain sizes. Moreover, because of the rod-like mullite produced in the pores, Mg metal addition could develop the further modification of the pore structure with similar porosity (47% at 1400°C/4h) compared with that (53%) with 0wt % Mg metal powders.
Preparation of Ni – MgO– La2O3 Catalyst on Alumina Support for Catalytic Tar Cracking Process
Authors: Thassanaprichayanont Sildara , Atong Duangduen , Sricharoenchaikul Viboon
Published: March 2010

This study reported the synthesis of Ni -based catalysts on Al2O3 support carried out by two different methods including co-impregnation and sequential impregnation. Different nitrate solutions of nickel, lanthanum, and magnesium were used for support impregnation. The calination process was carried out at 650 °C and 850 °C for 2 h under air. The XRD patterns of the catalyst samples presented main phases of Al2O3 and other diffraction lines corresponding to metal and oxide promoters; Ni, MgO and/or NiO, (Ni,Mg)Al2O4, La2O3 and La(AlO3). Prepared catalysts appeared in irregular shaped agglomerates of small particles of less than 1 micron. Surface area of co-impregnated catalysts increased with increasing calcination temperature while ones from sequential impregnation decreased except for those last impregnated with nickel salts. The La2O3-MgO-Ni/Al2O3 sequential impregnated catalyst had the highest surface area of 8.0-8.5 m2/g.
Properties of AlN Powder Synthesized by Self-Propagating High Temperature Synthesis Process
Authors: Pee Jae Hwan , Park Jong Chul , Hwang Kwang Taek , Kim Soo Ryong , Cho Woo Seok
Published: March 2010

The synthesis of AlN via self-propagating high-temperature synthesis (SHS) was attempted, using various ratio of Al powder mixed with AlN powder as diluents. Al and AlN powder mixtures with various weight ratios were ignited a nitrogen atmosphere with various amounts of carbon as additives. High crystalline AlN by SHS were successfully synthesized. The microstructure development during the reaction and the influence of these additives were determined by SEM and XRD analysis. A mechanism for the formation of high purity AlN with a very low content of residual oxygen (<0.8wt %) was proposed.
Redesign and Optimization for Ceramic Injection Mould of ZrO2 Fiber Ferrule
Authors: Liu F. , Lin Bin , Zhang Mei Min , Li L.J.
Published: March 2010

The output for ZrO2 fiber ferrule can be improved by ceramic injection moulding technology efficiently. In order to increase the ratio of ceramic powder which can improve mechanics quality and dimensional precision of ZrO2 ferrule, the gating system for ferrule mould is redesigned in this paper. After analytic calculation and simulation analysis, U-shape is adopted as the optimal cross-section shape in the cold flow channel injection mould for higher efficiency and filling effects. Moreover, three common cooling systems for ceramic injection mould are analysed and the results show that the cooling system with the pipe layout of double ring can be considered to be optimal to improve cooling efficiency, uniform temperature and heat balance effect of fiber ferrule mould.
Preparation and Characterization of Monodisperse Ceria Microspheres
Authors: Wang Qi , Yin Bo , Wang Zhen , Shen Gen Li , Chen Yun Fa
Published: March 2010

In present work, ceria microspheres were synthesized by template hydrothermal method. Crystalline form of the as-synthesized ceria microspheres was defined by X-ray powder diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Dispersibility of ceria microspheres was comprehensively characterized using scanning electron microscope (SEM) observation and laser particle size analyzer. Furthermore, the ultraviolet light absorption performances of ceria microspheres with several different sizes were compared by ultraviolet visible spectrophotometer. The results showed that ceria microspheres presented excellent UV absorbent property and the size influence was remarkable.
Preparation of Complicated SiC Green Bodies via Aqueous Slip Casting
Authors: Li Yuan , Gao Ji Qiang , Yang Jian Feng
Published: March 2010

Two domestic silicon carbide powders with different particle size distribution and one petroleum coke powder were blended in proportion and then dispersed in aqueous medium. Green bodies were solidified from these suspensions via conventional slip casting. The effects of pH, solid loading, and the amount of dispersant on the formability and packing ability were evaluated. The results showed that the pH within 9.5-10.5, solid loading of 42vol%, aging time more than 24h, and 0.3wt% of dispersant were optimal. Complicated green bodies with height of 300mm and thickness of 3.5mm were obtained. The corresponding suspension viscosity was 1200mPa∙s and the relative packing density was 64.8%. The density is 3.01g∙cm-3 and the flexural strength is 305±15 MPa after reaction sintering. These results may be attributed to accurately using of dispersant and in-depth study of processing parameter.
The Microstructure and Tribological Properties of Carbon Fibre Reinforced Carbon/SiC Dual Matrix Composites
Authors: Peng Xiao , Zhuan Li , Xiang Xiong
Published: March 2010

Carbon fibre reinforced carbon and silicon carbide dual matrix composites (C/C-SiC) are new type of high performance brake materials, and possess a series of outstanding advantages. In the present study, the C/C-SiC brake composites were fabricated by the combination of chemical vapor infiltration with liquid silicon infiltration. The fabric preforms were prepared by three dimension needling method. Results show the SiC form inside the short-cut fabric, around the needing fibre and among the fibre bundles in the non-woven web of the C/C-SiC composites. The average static friction coefficient of the C/C-SiC materials was 0.61. The average dynamic friction coefficient were between 0.41 and 0.54 with the increase of brake speed, and the wear rates are not sensitive to the brake speed and maintained about 0.02 cm3•MJ-1 all along.
Synthesis and Properties of Al4SiC4 by Carbothermal Reduction
Authors: Zhao Jian Li , Wang Chang An , Yamaguchi Akira , Sun Jia Lin , Zhang Xin Sheng
Published: March 2010

Al4SiC4 is probably used as non-oxide raw material for high-temperature ceramics. Al4SiC4 was synthesized by using starting materials of metal-carbon, metal-oxide- carbon or carbides. In this paper, Al4SiC4 has been synthesized by using oxides (Al2O3 and SiO2) and carbon as starting materials through carbothermal reduction process. The oxidation properties in air and O2 atmosphere by TG method and the stability of the synthesized Al4SiC4 heated in moisture were investigated. Pure Al4SiC4 phase was synthesized when heating the mixture powder of Al2O3, SiO2 and C (C : Al2O3 : SiO2 = 8 : 2 : 0.8, in molar ratio) at 1700°C for 8h in flowing Ar atmosphere. The synthesized Al4SiC4 powder consists of platelet shape grains with size of 68μm length, 35μm width and 1μm thickness. Al4SiC4 obviously oxidized from 800°C when heated in flowing air or O2 atmosphere. When keeping Al4SiC4 powder in moisture, it was not observed to be reacted with water by XRD and SEM analysis.
Diversity, Threats and Conservation of Herpetofauna in and around the Eastern Sinharaja
Authors: Surasinghe Thinlina D , Jayaratne Ravindra L
Published: March 2010

The Eastern Sinharaja is a moist montane tropical forest that falls within the Rakwana mountain range and is 30km2 in area. Eastern Sinharaja is the home for many threatened endemic herpetofauna where seven species of anuran amphibians three agamids, one species of gecko are known to be spot endemics where all of them are considered to be critically endangered. The eastern Sinharaja is confronting different degrees of threats due to human disturbances including deforestation and habitat destruction due to cardamom and tea cultivation, the land degradation as a result of Illegal gem mining, extraction of forest resources, illicit timber felling, collection of non-woody products, wild cardamom, medicinal plants and firewood, setting fire to the forest and grasslands and the excessive usage of pesticides in plantations. The relative abundances of the above mentioned endemic herpetofauna is significantly low. Therefore it is assumed that the population size of these species is extremely low. Having a small land area, where the primary forest vegetation is rapidly declining, the herpetofaual populations are facing an imminent threat. Therefore, immediate conservation actions are recommended. Specific attention must be paid over restoration of regarded areas with native fast growing forest species and establishment of habitat corridors to bridge the neighboring forest patches to yield space and resources to sustain the minimum viable populations. Establishment of a buffer is imperative to mediate the human impacts. The landowners must be encouraged to adopt agro-forestry practices instead of monocultures like tea/cardamom plantation, allowing establishment of small populations of herpatofauna in those agroforestry plots adjoining the reserve. DOI: 10.4038/suslj.v6i1.1685 Sabaragamuwa University Journal, vol 6, no. 1, pp 3-12
Commercialization of Agriculture and Role of Agricultural Extension
Authors: Mahaliyanaarachchi Rohana P , Bandara RMAS
Published: March 2010

Today commercialization of agriculture is an inevitable reality throughout the whole world.  There are a number of factors affecting the commercialization process in agriculture. Some of them could be named as rapid growth of economies in the both developing and developed countries, introducing of new technologies, market expansion, market liberalization, urbanization, rapid increase of demand for food, decreasing of farming population, liberalized and open economic policies, bilateral and multilateral economic agreements, developed infrastructure facilities in farming areas and government agricultural policies. However, commercialization in agriculture is not a new phenomenon and it is not a surprise to the farming community. Since the nineteen fifties, farmers in most of the countries have moved towards commercial agriculture. Their major objective was surplus production aiming market prospects. Agricultural extension plays a major role in agricultural production.  Role of agricultural extension in a commercialized agricultural system is different from such service in subsistence farming system. In the commercialized agriculture the extension service will mainly concentrate on the resourceful big farmers, with favorable environmental conditions and higher socio-economic status. Under the commercialized agriculture the number of farmers is to be reduced and the size of the farm land should be increased. This is a generally accepted concept in commercial agriculture. Do we have to accept this concept under each and every situation? We think the answer is "no". By using improved technologies farmers can move towards commercial agriculture without considering the size of land. Under protected agriculture, farmers follow concepts of the commercial agriculture. Commercial livestock farming does not rely on the farm size except diary farming. However, the role of agricultural extension in the commercialized agricultural system is mainly dependent on the type and way of commercialization in a given society. We have to expect that agricultural extension services are supposed to fulfill many aims, from reducing rural poverty and improved livelihoods for rural households to increasing the overall production and contributing to foreign exchange earnings from exports. But the level and percentage of this contribution may vary from one situation to another. DOI: 10.4038/suslj.v6i1.1686 Sabaragamuwa University Journal, vol 6, no. 1, pp 13-22