bluuebunny/crossref_metadata_2025 huggingface dataset:
Arsenic Contamination and its Speciation in the Water System around the Abandoned Dongil Au-Ag Mine in Korea
Authors: Yi Ji Min , Lee Jin Soo , Chon Hyo Taek
Published: March 2009

This study was made to investigate the extent and degree of As contamination in waters and sediments influenced by previous mining activity in the abandoned Dongil Au-Ag mine. Arsenic species was also identified in surface waters and groundwater. The chemical form of As in sediments was examined using sequential extraction analysis. The major contamination source of As in the mine area is suggested to be tailings with elevated levels of 8,718 As mg/kg. This was associated with the release of high level of As into the water system in the study area. The pH values of water samples ranged from 7.7 to 10.1, which was neutral to strong alkaline due to
buffering effect by high concentration of Ca and Mg dissolved from carbonate mineral and weathering of concrete. Stream waters contained high level of As within the range of 40.5 to 150.4 ㎍/L and most waters exceeded the permissible level (50 ㎍/L) of As for stream water in Korea. The concentration ratios of As(Ⅲ) to As (total), however, extended in the range of 5.8 to 75% and increased at low pH condition in stream waters. Arsenic concentration in sediments digested by
aqua regia (HNO3+HCl) ranged from 162 to 2,077 mg/kg. The highest concentration of As may be due to the direct inflow of tailings. The relatively high percentage (17.1~35.3%) of As coprecipitated with amorphous Fe oxyhydroxides indicates that more severe contamination of As can occur by re-extracting due to changes of chemical environment such as reducing condition.
Pcdd/Fs Concentrations in Blood of Male Chemists Working for Dioxin Analysis
Authors: Jeon Sang Eun , Lee Sang Won , Choi Kyung Sik , You Jae Cheon , Moon Dong Ho , Lee Chang Jae , Hwang Yong Youl , Hwang Tae Woong , Joo Chang Han
Published: March 2009

The level of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans
(PCDD/Fs) concentration in blood of 4 chemists conducting dioxin analysis at a laboratory was estimated. The level of PCDDF/s concentration ranged from 4.48 pg I-TEQ/g-fat to 8.17 pg ITEQ/ g-fat (mean level : 6.19 pg I-TEQ/g-fat, median level : 6.07 pg I-TEQ/g-fat, standard deviation in this study : 1.51 pg I-TEQ/g-fat). The level of PCDD/Fs in bloods of the chemists in this study is not higher compared with other studies in Korea. The portion of PCDFs to the total PCDD/F I-TEQ concentration in this study was found to be over 80%. This is not the case in other
countries where the portion of PCDDs to the total TEQ in blood was generally much higher than that of PCDFs. In Korea, the portion of PCDFs to the total PCDD/F I TEQ concentration in food was higher than that of PCDDs. In other countries, the portion of PCDFs was relatively lower. It is considered that the portion of PCDFs in blood has interrelation with that of PCDFs in food in both Korea and other countries.
Energy Minimization Model for Pattern Extraction of the Movement Behavior of Animals
Authors: Kang Jin Sook , Cha Eui Young , Chon Tae Soo
Published: March 2009

Recently, patterning and analyzing complex data of behaviors of animals in response to external stimuli such as toxic chemicals has become focus of attentions. In this paper, an energy minimization model to extract the features of response behavior of chironomids under toxic treatment is proposed, which is applied on the image of velocity vectors. The model is based on the improved active contour model and the variation of the energy values produced by the evolving active contour. We attempt to implement an adaptive computational method to characterize the changes in response behaviors of chironomids after treatment with an insecticide, diazinon. Active contour is formed around each collection of velocities to gradually evolve to find the optimal boundaries of velocity collections through processes of energy minimization. The energy minimization model effectively reveals characteristic patterns of behavior for the treatment versus no treatment, and identifies changes in behavioral states as the time progressed.
Radiological Impact of the PARR-1 Operation on the Environment
Authors: Bakhtyar S. , Raza S.S. , Tayyab M. , Pervez S. , Salahuddin A.
Published: March 2009

This paper presents a study related to the assessment of the radiological impact on the environment due to the operation of the Pakistan Research Reactor-1 (PARR-1) at the Pakistan Institute of Nuclear Sciences and Technology (PINSTECH), Islamabad. The parameters studied include the radioactivity releases in a gaseous form and also those originating from the liquid and solid wastes produced due to the operation of this research facility. The analysis is based on the environmental monitoring data for the last 10 years (1992-2002) and the conclusions have been
drawn for the impact of the PARR-1 operation on the occupational workers as well as the general public living in the vicinity of the reactor site. Further, on the basis of this data, yearly average doses and the cumulative doses for the expected life of PARR-1, due to different radiation sources have been estimated. The analysis indicated that the maximum yearly doses at ground level for the occupational workers as well as for the public are a fraction of the International Atomic Energy
Agency’s (IAEA) defined limiting values. It is, therefore, concluded that the impact of the PARR-1 normal operation on the environment is negligible and it can be regarded as “ safe to the public as well as the occupational workers”.
Stress Corrosion Cracking of Alloy 600 in a High-Temperature Water Containing Sulfate and Thiosulfate
Authors: Lee Eun Hee , Kim Kyung Mo , Kim Uh Chul
Published: March 2009

The stress corrosion cracking (SCC) susceptibility of Alloy 600 MA has been studied in deaerated 0.01 M sodium sulfate (Na2SO4) and sodium thiosulfate (Na2S2O3) solutions at 340°C. Pre-strained reverse U-bend (RUB) specimens are tested using a static-autoclave system. The specimens show an intergranular SCC and a higher resistance to SCC in a Na2S2O3 solution than in
a Na2SO4 solution. The results of the deposits and surface analyses by using XRD and SEM/EDS confirm the existence of the sulfides. The SCC of Alloy 600 MA is associated with the reduced sulfur species and protective oxide film properties formed on the alloy surface in the Na2SO4 and Na2S2O3 solutions.
R&D Strategy of the Korean Electric Industry Using a Technology Roadmap(Trm) Approach
Authors: Lee Young Eal
Published: March 2009

The proper allocation of the limited R&D resources under the restructuring of the electric industry is a primary motivator for this electricity technology roadmap (eTRM) initiative. Because the major interests of CEOs could be the short term profit of their company under the competitive electric industry, it would wrong of them to cut back on the long term R&D budgets which make it impossible to develop all the technologies. Therefore, we should select and support only the favorable and competitive technologies to meet the future market needs using the TRM approach with the concept of "Selection and Concentration." This study aims at defining the key technologies basis from the forecasts of what is possible or likely to happen in the future and planning the course of action for the technology development in the electricity field in Korea. The selected technologies could be the candidates for the
mid and long term R&D program supported concentrically by the Electricity Industry Infrastructure Fund.
Tritium Application: Self-Luminous Glass Tube (SLGT)
Authors: Kim Kyeong Sook , Lee Sook Kyung , Chung Eun Su , Kim Kwang Sin , Kim Wi Soo , Nam Gi Jung
Published: March 2009

To manufacture SLGTs (Self-Luminous Glass Tubes), 4 core technologies are needed: coating technology, tritium injection technology, laser sealing/cutting technology and tritium handling technology. The inside of the glass tubes is coated with greenish ZnS phosphor particles with sizes varying from 4~5 [µm], and Cu, and Al as an activator and a co-dopant, respectively. We also found that it would be possible to produce a phosphor coated glass tube for the SLGT using the well established cold cathode fluorescent lamp (CCFL) bulb manufacturing technology. The conceptual design of the main process loop (PL) is almost done. A delicate technique will be needed for the sealing/cutting of the glass tubes. Instead of the existing torch technology, a new technology using a pulse-type laser is under investigation. The design basis of the tritium handling facilities is to minimize the operator's exposure to tritium uptake and the emission of tritium to the environment. To fulfill the requirements, major tritium handling components are located in the
secondary containment such as the glove boxes (GBs) and/or the fume hoods. The tritium recovery system (TRS) is connected to a GB and PL to minimize the release of tritium as well as to remove the moisture and oxygen in the GB.
Amorphous Manganese Dioxide as a Material for an Electrochemical Pseudocapacitor
Authors: Wen Sun , Yeo In Hyeong , Park Jong Man , Mho Sun Il
Published: March 2009

The charge storage process of amorphous hydrated manganese dioxide (MnO2) as a pseudo-capacitor involves a fast redox reaction at the electrode surface. In order to understand the charge storage mechanism of MnO2 as a pseudo-capacitor in an aqueous KCl solution, we monitored the change of the capacitance by varying the pH of the solution, the cation of the electrolyte, the concentration of the KCl electrolyte, and the solvent. The charge storage mechanism of a metal oxide electrode such as MnO2 is concluded to involve a fast redox reaction through both
the potassium ion exchange, MnO2 + δK+ + δe- ⇔ MnO2-δ(OK)δ and the proton exchange, MnO2 + δH+ + δe- ⇔ MnO2-δ(OH)δ dependent upon the availability of the cations in the electrolyte.
Controlled Release of Vancomycin from Poly(Dl-Lactide-Co-Glycolide) Disc: Inhibition of Mrsa(Methicillin Resistant Staphylococcus Aureus) Growth in Vitro
Authors: Lim Jeong Ok , Lee Won Kiel , Park Il Soo , Hwang Jin Seok , Suh Jeong Min , Baek Woon Yi , Lee Sang Heun
Published: March 2009

A different range of vancomycin was incorporated into a poly dl-lactide-co-glycolide) [PLGA] disc matrix using the hot compression method. The disc was placed in phosphate buffered saline (PBS) and incubated at 37oC. The PBS was changed periodically, and the removed solution was analyzed using high performance liquid chromatography. The sensitivity of the antibiotic-polymer
matrix was evaluated using cultured-human-ear methicillin-resistant staphylococcus aureus (MRSA). The MRSA growth was inhibited proportionally to the incorporated vancomycin concentration in the disc matrix. A disc incorporating 400 µg of antibiotics inhibited the growth of MRSA 10 times longer than the disc containing 30 µg as a control. It was found that the biodegradable polymer matrix
enabled the control-release of an antibiotic, and the release profile was observed as zero order.
Measurement of Outgassing in a Vacuum Environment
Authors: Shin Yong Hyeon , Hong Seung Soo , Lim In Tae , Kim J.H. , Seong Dae Jin , Chung Kwang Hwa , Moon G.W. , Choi Sung Woo
Published: March 2009

Outgassing, the evolution of gas from the material in a vacuum, is not only a source of micro contamination in a semiconductor or the flat display panel production process, but it also a limitation factor in the ultra clean process of nano-technology. The outgassing from the materials of satellites and spacecrafts must be controlled for increased safety and function because space is also a vacuum environment. Several methods are used in outgassing measurement in general, but there is no one method suitable for obtaining all outgassing data. The most suitable method for a particular application must be chosen by the experimenter or user. Three types of outgassing measurement systems were fabricated and characterized, ‘Throughput method,’ ‘Rate of Rise method’ and ‘Mass Loss Measurement method’. The outgassing rates of many kinds of materials were measured and characterized using these systems.
Development of RF System Performance Evaluation Test Set for KOMPSAT-2
Authors: Kim Tae Youn , Lim Seong Bin , Chun Yong Sik , Choi Seok Weon
Published: March 2009

The satellite RF system is an essential part of the control and management of a satellite from the ground station and provides a communication link during the entire satellite mission life. The RF system should be fully evaluated for reliability and stability on the ground, as defined by the requirements of the satellite mission. The evaluation of an RF system can be verified by measuring the RF link parameter and then comparing and analyzing the result with the RF system requirements. Since the system test for satellites requires advanced technology and has a high cost with limited time, however, it is difficult to access technically for many parts. This paper describes the design and verification of the RFTS (Radio Frequency Test Set) and the RTS (RFTS Test Software), which AITC developed in KARI to evaluate a satellite RF system. The developed test system was used to perform an RF functional test on an ETB (Engineering Test Bed), and the RFTS’s full functions were debugged to provide a reliable function for the KOMPSAT-2 Satellite Test. The RFTS showed a high degree of reliability, conformity and repeatability for each test case at any time. It is now being applied to the RF system evaluation test of KOMPSAT-2 FM during KOMPSAT-2’s integration and environment test phases. Hereinafter, this system can be applied to the next generation of satellites as well as to the RF payload system as a unique KOMPSAT series RF test system.
Shear Flow Analysis of Nanosize Particle Flow Behavior Using Kinetic Theory
Authors: Kim Hae Ryung , Seu Jaihyun , Arastoopour Hamid
Published: March 2009

Nanosize particle flow is significantly affected by inter-particle force. Due to the
inter-particle force, the most significant characteristic of nanosize particle flow may become the formation of agglomerates or clusters which considerably affects the flow patterns. The formation of agglomerates or clusters results in a reduction in the number and an increase in the size of particles, both of which directly affect the frequency of inter-particle collisions and, in turn, the particle phase properties such as viscosity and pressure, as well as gas/particle drag force in gas/particle flow
systems. In this present work, we focus our attention on the verification of nanosize particle flow behavior due to the formation of agglomerates or clusters under different fluctuation of flow and inelasticity of particle collision. By extending the application of the cohesive model using kinetic theory to nanosize particle flow system, we performed the homogeneous simple shear flow analysis using various fluctuation energy and restitution coefficient. The predicted flow properties, such as
particle diameter growth, agreed well with the expected trends.
Signal Characteristics of Biophoton Emission from Human Hands
Authors: Jung Hyun Hee , Yang Joon Mo , Woo Won Myung , Yi Seung Ho , Yang J.S. , Soh Kwang Sup
Published: March 2009

The signal characteristics of the biophotons from human hands were studied using
correlation and δ-value analyses. Three healthy individuals without any history of disease participated in the measurements, six times every Friday for 52 weeks, while staying in a room with dim lighting to eliminate any delayed luminescence caused by the sun or room lights. Two head-on type photomultiplier tubes inside a dark room were used to simultaneously measure the biophoton emissions from the palm and dorsum of the left and right hand with a 100ms gate time. In view of the signal process, a cross-correlation of the long-term data, i.e. the weekly measurements, revealed a strong correlation between the signals from the left and right hand, yet only a very weak correlation between the palm and dorsum. The non-classical light property of the biophotons, that has a quantum coherence nature, was compared with that of the dark counts of the PMTs using a δ- value analysis. The average δ-value for the biophotons was 0.08±0.07. As such, it was found that the palm emissions were very coherent, while the dorsum emissions showed an occasional lack of coherence.
Sonochemical Synthesis and Photocurrent of HgTe NANOPARTICLES
Authors: Kim Hyun Suk , Cho Kyoungah , Song Hyun Woo , Kim Jin Hyoung , Lee Jun Woo , Lee Jong Soo , Min Byungdon , Kim Sung Hyun , Kim Sang Sig
Published: March 2009

We report the sonochemical synthesis of mercury telluride (HgTe) nanoparticles and the photocurrents of these nanoparticles and their organic hybrid system. The HgTe nanoparticles were about 5 nm in size and their lattice structure was cubic. Poly(N-vinylcarbazole)(PVK) was added to the HgTe nanoparticles for the formation of an inorganic(HgTe)-organic(PVK) hybrid system. The room-temperature photocurrents of the HgTe nanoparticles and the HgTe-PVK hybrid system were compared in this study. The photocurrent was significantly enhanced for the HgTe-PVK hybrid system.
Surface Modification of Al2O3 Fine Powders and Application in Epoxy Resin
Authors: Du Shi Guo , Yan Jun , Zhang Tong Lai , Cui Hai Ping , Liu J.Z.
Published: March 2009

In this paper the surfaces of Al2O3 fine powders with average size of 500nm were modified by heterogeneous azeotropic distillation process. IR spectrums of the powders show that the distillation can effectively dehydrate hydrous Al2O3 powders, and succeed in substituting the hydrate water with butanol molecular. The dispersion of Al2O3 powders in epoxy resin is improved remarkably, which is observed by means of SEM. Experimental results show that abrasion property of
the resin filled with modified Al2O3 powders is improved.
Modification of Al2O3 Microfiltration Membrane by Nano-ZnO Coating
Authors: Zhou Jianer , Wu Jian Qing , Wang Yong Qing , Jiang Wei Hui , Ma Guang Hua , Cao Rui Bei
Published: March 2009

In this paper, the α-Al2O3 microfiltration membrane modified by nano-ZnO coating was obtained using zinc nitrate and urea as raw materials via homogeneous precipitation method. The effects of reaction temperature and coating times on the modification of the membrane were emphatically studied. The test results show that the flux of modified membrane is raised by 43% when the nano-ZnO particles (5 ~ 10 nm) are smoothly and densely coated on the surface of the membrane. The mechanism of the modification was studied by means of TEM, FTIR, XPS, Zeta electric potential analyzer, etc.
Fabrication of Nano-Micron Al2O3-ZrO2 Ceramic Eutectic Composites from the Melts by the SHS Metallurgical Process
Authors: Zhao Zhong Min , Zhang Long , Bai Hong Bai , Zheng Jian , Wang Jian Jiang , Fu Y.
Published: March 2009

New nano-submicron textured Al2O3-ZrO2 ceramic eutectic composites were obtained from high-temperature melts produced by the SHS metallurgical process with intro-granular and 1-3 composite structures. Nano-micron textured ceramic composites were naturally self-assembled in one quick step by the SHS metallurgical process, in-situ synthesis and symbotic eutectic transformation
under high degree of undercooling. The experimental results indicated that the Al2O3-ZrO2 ceramic eutectic composites with ZrO2 fibers at the nano-submicron scale are only suitable for the ceramic composite with hypoeutectic composition under the conditions of the experiment.
Machinability Evaluation of Ce-ZrO2/CePO4 Ceramics with Digraph Method
Authors: Yu Ai Bing , Zhong L.J. , Tian Xin Li , Zou F.
Published: March 2009

A new method is proposed for machinability evaluation of machinable ceramic materials. The relation of machinability attributes is modeled as a digraph, and machinability attribute matrix is defined. Machinability indexes are calculated with permanent function of the matrix, and machinabilities of machinable ceramics are ranked. Five composites consisting of CePO4 and zirconia were fabricated, measured and drilled with tungsten-cobalt carbide bits. Mechanical property
parameters of Ce-ZrO2/CePO4 composites, including Vickers hardness, fracture toughness and Elastic modulus, are selected as machinability attributes. The experimental results of material removal rates are consistent with the ranking of machinability index values of Ce-ZrO2/CePO4 ceramics. The machinabilities of Ce-ZrO2/CePO4 ceramics improve with the increase of CePO4 proportions. Machinability of machinable ceramics can be evaluated with digraph method.
Synthesis and Properties of Al2O3 Nanocomposite Ceramics Toughened by Nano Metallic Particles
Authors: Gu Sidi , Zeng Zhao Qiang
Published: March 2009

Al2O3/Ni composite ceramics toughened by metallic particles was fabricated by the
vacuum reduction of Al2O3 and nickel nitrate (Ni(NO3)2•6H2O) mixed powders at 800-1000° for 2-4h and hot pressed at 1400° ~ 1500°C for 1-2h. Three-point bending strength and facture toughness of the composite were studied. With the increase of Ni content, its flexural strength and facture toughness increases significantly. Microstuctural investigations of the composite revealed that fine
nickel particles dispersed homogeneously at the matrix grain boundaries, forming the intergranular nanocomposite.
Wear Resistant of Al2O3/Heat-Resistant Steel at High Temperature
Authors: Bao Chong Gao , Xing Jian Dong , Gao Yi Min , Wang En Ze
Published: March 2009

The high temperature abrasive wear resistant of the composites with different Al2O3
volume fractions, particle coating and size were investigated and the failure action of composites under different conditions at high temperature was analyzed. The results showed that the high temperature abrasive wear resistant of composite with Ni coating and wide size and 39% volume fraction of particle is the best among all composites examined.
Fabrication of Silica Colloidal Crystal Multilayer with Controlled Thicknesses by Vertical Deposition
Authors: Li Qun Yan , Gao Wei Min , Chen Yun Fa , Dong Peng , Wu Zhen Jiang
Published: March 2009

The silica colloidal crystal multilayers were deposited from ethanol suspensions with
different particle concentrations by vertical deposition method. The microstructures and thicknesses of silica colloidal multilayers were characterized by scanning electron micrography. The thicknesses of colloidal crystal multilayers increased with the particle concentration increasing within a certain range of particles concentrations. When the particle concentration exceeded 2.48wt%, the thicknesses of colloidal crystal multilayers didn’t increased with the concentration increasing. Colloidal crystal multilayers with few defects could be deposited from the suspensions with the particle concentration 2.48wt%. The optical properties of the silica colloidal multilayers were investigated by a UV-Vis scanning spectrophotometer in normal incidence. They corresponded well to the microstructure obtained by SEM images.
Synthesis of MgO Nanowires Combined with C Nanotubes
Authors: Gong Yan Li , Li Jian Bao , Yang Xiao Zhan , Chi Bo
Published: March 2009

MgO nanowires combined with C nanotubes have been prepared through method of
high-temperature catalytic reaction. The nanostructures consist of nanowires that have right-angled zigzag manner to elongate in three dimensions. Structural characterization and elemental composition analysis identified that the nanowires were made of MgO nanowires combined with C nanotubes. A growth mechanism based on the vapor-liquid-solid (VLS) process is proposed for the formation of the
combined nanostructures. With the aid of XRD, SEM, HRTEM and EDS, the morphology, structure and growth mechanism were investigated.
Negative Thermal Expansion up to 1000°C of ZrTiO4-Al2TiO5 Ceramics for High-Temperature Applications
Authors: Kim Ik Jin , Kim Hyung Chul , Han In Sub , Aneziris Christos G.
Published: March 2009

High temperature structural ceramics based on Al2TiO5-ZrTiO4 (ZAT) having excellent thermal-shock-resistance were synthesized by a reaction sintering. The ZAT ceramics sintered at 1600oC had a negative thermal expansions up to 1000oC and a much lower thermal expansion coefficient (0.3 ~ 1.3 x 10-6 /K) than that of polycrystalline Al2TiO5 (1.5 x 10-6 /K). These low thermal expansion are
apparently due to a combination of microcracking caused by the large thermal expansion anisotropy of the crystal axes of the Al2TiO5 phase. The microstructural degradation of the composites after various thermal treatment for high temperature applications were analyzed by scanning electron microscopy, X-ray diffraction, ultrasonic and dilatometer.
Fabrication and Properties of the Tape-Cast Si3N4 with Rod-Like Si3N4 Seed Addition
Authors: Zeng Yu Ping , Kondo Naoki , Hirao Kiyoshi , Ohji Tatsuki , Kanzaki Shuzo
Published: March 2009

Silicon nitride ceramics with and without β-Si3N4 seed addition were prepared via tape casting nonaqueous ceramic slurries, laminating the green ceramic tapes, and gas pressure sintering the green bodies in nitrogen atmosphere. Lu2O3 and SiO2 were used as sintering additives. The results showed that the rod-like β-Si3N4 seed was helpful to enhance β-Si3N4 grain growth unidirectionally. The elongated grains grown from seeds were preferentially oriented parallel to the casting direction,
resulting in anisotropic microstructure. When a stress was applied with along the grain alignment, the bending strength of the tape-cast Si3N4 with 3 wt% β-Si3N4 seed addition measured at 1500oC was 738 MPa, which was almost the same as the room temperature bending strength 739 MPa, and the fracture energy can be improved from 301 J/m2 at room temperature to 781 J/m2 at 1500oC. The large
fracture energy and bending strength at 1500oC were attributable primarily to the unidirectional alignment fibrous grains and a high melting point grain boundary phase.
Preparation of β-SiAlON Powder at Low Temperature
Authors: Chen Qian Lin , Wu Jian Qing , He Xian Ping , Cao Jian Xin
Published: March 2009

In this article, the β–Sialon with average diameter size less than 20µm is prepared and researched by use of aluminum, silicon, and corundum at 1300°C holding temperature for 8h under nitrogen atmosphere. The preparation temperature of β–Sialon powder was optimized according to the results from the experiments that different aluminum and silicon reacted with pure nitrogen at different temperature. The reaction at the preparation of β–Sialon powder was discussed by
thermodynamic calculation. The reaction mechanism was investigated by x–ray diffraction (XRD) and scanning electron microscope (SEM) was discussed in detail.
Effect of Microstructure on Sliding Wear of Ca α-SiAlON Ceramics
Authors: Xie Zong Han , Hoffman Mark , Moon Robert  J. , Munroe P. R. , Cheng Yi Bing
Published: March 2009

The wear behaviour of Ca a-sialon ceramics of two distinct microstructures, fine equiaxed grains (EQ) and large elongated grains (EL), with the same chemical composition was investigated as a function of apparent contact pressure and sliding speed, using ball-on-disc type tribometers at room temperature and at 600°C. For room temperature tests, the EL microstructure exhibited a lower wear rate
than EQ in the severe wear regime due to a greater resistance to large crack-induced material removal. As the apparent contact pressure decreased, mild wear appeared for both microstructures. The mechanism that dominated the material removal in EQ was grain pullout. In contrast, the controlling mechanism for
EL was transgranular fracture. Therefore, EL had a lower wear rate than EQ in the mild wear regime. For wear tests at 600°C, crack-induced severe wear occurs in both EQ and EL samples for all contact pressures. EL had a slightly lower wear rate than EQ. Wear particles were generated on the wear track, but no tribofilm was observed and no oxidation products were detected. Wear models revealed that the grain aspect ratio plays a more important role than grain diameter in influencing the crack propagation during severe wear and grain pull-out during mild wear.
Preparation and Dielectric Properties of SiC-AlN Solid Solutions
Authors: Zhang Xiang Yu , Tan Shou Hong , Xu Wei-Wei , Dong Shao Ming , Huang Zheng Ren , Dong Ye , Wu Pei-Heng , Jiang Dong Liang
Published: March 2009

The microstructure and microwave dielectric properties of inhomogeneous SiC-AlN solid solutions, hot pressed under a pressure of 40 MPa, have been investigated. Microstructure analysis detected the existence of BN in the resulted samples, which may be a reason that homogeneous solid solution was not formed for the samples with AlN content higher than 20%. The dc resistivity of the solid solutions at room temperature varies from 8 × 103 Ω m to 1 × 109 Ω m. Ion jump and dipole
relaxation losses are the main mechanism of dielectric losses.
Sintering and Properties of CaO-Al2O3-B2O3-SiO2 System Glass Ceramics
Authors: Wang Shao Hong , Zhou He Ping , Chen Ke Xin , Ning Xiao Shan
Published: March 2009

Preparation technology and sintering characteristics of the CaO-Al2O3-B2O3-SiO2 system glass ceramics were investigated. Results showed that the glass ceramics of this system could be sintered at 850oC; the material has fine sintering properties, outstanding dielectric properties including low dielectric constant (about 4.85, 1GHz) and low dielectric loss (about 0.1%, 1GHz). XRD analysis indicated that the crystalline phases in the sintered body are mainly Al5(BO3)O6, a trace amount of SiO2 and CaSiO3.
Unlubricated Sliding Wear of TiN Particle Reinforced Si3N4 Matrix Composites Against AISI-52100 Steel Ball
Authors: Liu Chien Cheng , Huang Jow Lay
Published: March 2009

The effects of TiN addition to Si3N4 on its mechanical and wear properties were
investigated. The size and content of TiN particles were found having effects on the strength and toughness of Si3N4-based composites. The friction and wear behavior of Si3N4 based composites against AISI-52100 steel were investigated in the ball -on- disc mode in a non-lubrication reciprocation motion. It has been found that under the conditions used all the ceramic components exhibited rather low friction and wear coefficients. For monolithic silicon nitride materials, high friction coefficients between 0.6 and 0.7 and wear coefficients between 1.63 × 10-8 and 1.389 × 10-6
mm3/N.m were measured. The contact load was varied from 100 to 300 N. By adding titanium nitride, the friction coefficients was reduced to a value between 0.4 and 0.5 and wear coefficients between 1.09×10-8 and 0.32×10-6 mm3/N.m at room temperature.
Oxidation Behaviors of MgAlON/Si3N4 Composite at High Temperature
Authors: Zhang Hou Xing , Huang Y. , Hong Yan Ruo , Sun Jia Lin , Zhou N.S.
Published: March 2009

The isothermal oxidation behaviors of MgAlON/Si3N4 composite which was synthesized by pressureless nitridation reaction sintering have been investigated in flowing air at 1100°C, 1200°C and 1300°C respectively. The results show that the composite represents excellent self-healing property of oxidation at 1300°C, which might be attributed to the formation of protective silicate film with reasonable viscosity, good spreading power and very low oxygen diffusion coefficient, and to the formation of compact surface resulted from the expansion effect of forming mullite from SiO2 and Al2O3. However, the self-healing property of it is relatively poor at 1100°C and 1200°C as compared to 1300°C.
Dielectric Characteristics of BZT Nano-Powder Based Ceramics
Authors: Chen Lei , Wang Xiao Hui , Li Long Tu , Gui Zhi Lun
Published: March 2009

Titanate ferroelectric materials play more and more important roles in electronic industry due to their particular performances, so the synthesis of ultra-fine ferroelectric powder with high purity is the key issue to improve the performance of electronic components. In this paper, Ba(Ti0.85Zr0.15)O3 nano-powder with perovskite structure and homogeneous granularity was prepared by oxalate precipitation method, the particle size of the powder calcined at 800oC is about 50 nm. The sintering ability of the powder is excellent so that the compact ceramics can be obtained at sintering temperature of 1200°C, which is much lower than that of the powder prepared by the conventional solid method. With the powder prepared by oxalate precipitation method, we developed an ultrafine-grained dielectric material showing Y5V characteristics with the room temperature dielectric constant over 14,000, which can be used in base metal electrodes multilayer chip capacitors.
Sintering of Vitrified Bond CBN Grinding Tool
Authors: Li Zhi Hong , Zhang Yong Hong , Zhu Y.M. , Yang Zheng Fang
Published: March 2009

Cubic boron nitride(CBN) is a superhard materials with many advantages and many uses. Vitrified bond CBN grinding tool is a promising abrasive tool of high performance used for high speed, high efficiency, high precision grinding with lower grinding cost and less environment pollution. Sintering of vitrified bond CBN grinding tool was investigated in this paper. The results showed that practical sintering temperature of this tool was much lower than the initial oxidation temperature of CBN particle measured by comprehensive thermal analysis. The upper limit of sintering temperature should be determined by taking account of the thermal analyzing results, heating process of CBN and its change in strength and structure. Within the sintering temperature range of the vitrified bond, relatively higher sintering temperature was beneficial to the strength of bond bridge and the holding strength between bond and CBN abrasive particles. CBN tool sintered at relatively lower temperature tended to fracture through the bond bridge, while the one sintered at higher temperature tended to fracture along the boundary between CBN abrasive grain and vitrified bond.
Tribological Behaviour of Combined Coatings Deposited on Aluminium
Authors: Akin U. , Mindivan Harun , Samur R. , Kayali E.S. , Çimenoğlu H.
Published: March 2009

In this paper the tribological performance of oxide (Cr2O3, ZrO2CaO and Al203) and combined coatings applied on a commercially pure aluminum sheet were presented. Combined coatings were produced by applying Polytetrafluoroethylene (PTFE) film on the oxide coatings. Among the oxide coatings Cr2O3 exhibited the highest and Al2O3 exhibited the lowest wear resistance, in accordance with
their hardness. Combined coatings exhibited superior wear resistance than oxide coatings even at heavy wear testing conditions.
The Mechanism of the Formation of MoSi2 by Self-Propagating High-Temperature Synthesis
Authors: Gao Jian Ying , Jiang Wan , Wang Gang
Published: March 2009

A combustion front quenching (CFQ) technique was used to investigate the mechanism of selfpropagating high-temperature synthesis (SHS) of MoSi2 from Mo and Si powders. Based on the experimental results, a combination of reactive diffusion and dissolution-precipitation mechanism of the formation of MoSi2 was proposed, and a model corresponding to this mechanism was drawn.
Study on Physicochemical Properties of the Carbonated Hydroxyapatite Bone Cement
Authors: Dong Li Min , Wang Chen , Tian Jie Mo , Pan Jian , Zan Qing Feng
Published: March 2009

Carbonated hydroxyapatite (CHA) bone cement is capable of self-setting and has the component similar to the mineral phase of natural bone. But it is compact in structure and short of cavity, which limits new bone growing into CHA bone cement. In this paper, the foaming method was adopted to prepare the porous CHA. The setting time, compressive strength, porosity and pore size of the CHA were examined. The phase composition of the CHA was tested with XRD and FT-IR. The
microstructure of the CHA was observed with SEM. The results show that setting time of 7~19 minutes, compressive strength of 26~32MPa, pore size of 100~200µm, porosity of 50~60%.
Preparation and Evaluation of Macroporous Sol-Gel Bioglass with High Mechanical Strength
Authors: Li Na , Wang Chao , Zhu Su Min , Li Qin , Wang Ruo Ding
Published: March 2009

Bioactive glasses are known to have the ability to regenerate bone, but their use has been restricted mainly to powder, granules, or small monoliths. This work reports on the development of bioactive glasses with macroporosity of controlled size and volume through sol-gel and pore forming technologies. The macroporous structure (greater than 100µm) can provide the potential for tissue
ingrowth. Simultaneously the samples exhibit mesoporous (2-50nm) texture and high specific surface which can enhance bioactivity and release of ionic products. The most important advantage is that these samples show satisfactory mechanical strength. This method should be a useful approach for preparation scaffolds with applications to repair and reconstruct damaged tissue.
Microstructure and Bio-Mineralization Behavior of the Sol-Gel Derived Bioactive Materials
Authors: Chen Xiao Feng , Wang Ying Jun , Zhao Na Ru , Ye Jian Dong , Zheng Yu Dong , Ning Cheng Yun , Wu Gang
Published: March 2009

The biomaterials in system CaO-P2O5-SiO2 were synthesized via sol-gel method. The biomaterials can be applied to bone reparation and bone tissue engineering scaffolds The nano-pore structure, degradability, bioactivity and bio-mineralization characteristic of the biomaterials were investigated in details using XRD, SEM/EDX, FTIR, BET and DSC/TG techniques. It was indicated that the sol-gel derived biomaterials have a higher bioactivity than that of the melt derived bioactive glasses or glass-ceramics. It just takes 4-8 hours for HCA to form on the surface of the sol-gel samples in SBF solution at 37°C. The spherical HCA crystal clusters formed on the surface of the sol-gel derived samples immersed in SBF for 8 hours have a low crystallinity. Owing to their interconnected nano-sized pores, the sol-gel samples possess much higher surface areas and the hydrous porous SiO2 gel layer containing a great amount of ºSi-OH groups can be rapidly formed on the biomterials’ surface through a quick ion exchange between H3O+ in the solution and Ca2+ in the surface of the materials. ºSi-OH groups can play a very important role in inducing formation of HCA. They make the material surfaces electronegative,
which resulted in a double electrode layer formed between the samples surface and SBF solution. The double electrode layer is in favor of formation of HCA on the surface of the materials.
Improving Subcritical Crack Growth Resistance for Alumina Glass Dental Composite
Authors: Zhu Q. , de With G.
Published: March 2009

Abstract. The improvement of subcritical crack growth (SCG) resistance for alumina glass dental composites was explored in this study. The addition of nitrogen to the glass phases in the composite was found to increase the SCG resistance, where the SCG exponent n increases from 22 for the oxide glass composites to 30 for the composites containing 0.5 mol% nitrogen in the glass phases. The improvement was tentatively attributed to the nitrogen addition, which makes the glass network stronger through forming the non-flexible Si-N bonds and thus inhibits the hydrolysis reactions under the SCG conditions. Analyses demonstrated that the increase of the n value from 22 to 30 offers the potential to greatly extend the lifetime and improve the long-term reliability for the alumina glass dental composites.
Fabrication and Ferroelectric Properties of Ba-Doped Strontium Bismuth Titanate Ceramics
Authors: Xie Dan , Pan Wei , Dang Zhi Min , Ren Tian Ling
Published: March 2009

In the paper, the microstructure and properties of Sr1-xBaxBi4Ti4O15 (SBBT) ceramics with different Ba contents were investigated. SBBT ceramics were fabricated by means of the method combining Sol-Gel process and ordinary firing. The morphology will change when Ba2+ is doped in SrBi4Ti4O15 (SBTi), which will lead to the change of structure and ferroelectric properties. The microstructure of SBTi and BaBi4Ti4O15 (BBTi) ceramics were characterized by scan electron microscopy (SEM). With the increase of Ba2+ doping contents, the sintering temperature of SBBT ceramics decreases, 1120°C for SBTi and 1060°C for BBTi. BBTi ceramics contain more and larger plate-like grains than that in SBTi, the
diameter of the grains in BBTi is about 8~10 µm, the thickness is about 2.5 µm. With the increase of Ba2+ doping contents, remanent polarization (Pr) and coercive electric-field (Ec) increase first and then decrease. At the molar ratio of Sr:Ba=0.5:0.5, SBBT ceramics exhibited the highest Pr and Ec.
Study on Corrosion Mechanism of CAS Glass-Ceramic to Refractories by EPMA
Authors: Li Hong , Cheng Jin Shu , Long Xin Jiang
Published: March 2009

CaO-Al2O3-SiO2 (CAS) glass-ceramic is a novel material developed in recent years. It has a number of excellent properties, such as shining appearance, high strength, and good erosion resistance. So its practical prospect is wide. Many glass and ceramic scientists have studied this glass-ceramic, but there have been no publication made regarding corrosion mechanism. In order to choose the most suitable refractory materials for melting furnace for this glass-ceramic system, the corrosion and erosion mechanism must be investigated. The results can then be used to design the furnace and predict the life of the melting furnace. Also such investigation will reveal the extent of contamination of the final glass-ceramic product. According to the experiment that the glass liquid corrodes refractory materials in static condition, various effective material test method were used, especially Electron Probe Microanalysis (EPMA). Using EPMA, the chemical species, morphology, size and distribution of refractory materials corroded can be observed, so we know the microstructure of refractory materials prior to and after being corroded as well as the features of changing. In this paper, the authors present the features of refractory materials microstructure prior to and after being corroded by means of analyzing these pictures, which is very useful to provide the reliable theory to establish the mechanism that CAS glass-ceramic liquid corrodes the refractory materials.
Slurry Erosive Wear Characteristics of Engineering Ceramics for Hydraulic Machinery
Authors: Liu Juan , Qi Long Hao , Xu Hong Yuan , Miao He Zhuo
Published: March 2009

Engineering ceramics have a high application potential for wear-protection of different equipment used for electric power generating, mining and mineral industries. The ZTA (zirconia toughened alumina) and alumina (92%, 95%) have been prepared. Effects of varying the impact velocity and volume content of erodent particle and erosive time are investigated. Scanning electron
microscopic examination of the eroded ceramic surfaces provides insights into the erosive wear mechanisms. The material removal processes include chipping out of lateral cracks caused by impact of the erodent particles, grain boundary cracking and grain pull out, as well as plastic deformation caused by the repeated sliding and impact of the particles.
Oxidation Process of FeNi42Cr6 Alloy Array Materials
Authors: Geng Zhi Ting , Zhang Rong , Ma Ju Sheng
Published: March 2009

In this paper, the oxidation process of the VFD array material in wet hydrogen at high temperature was studied. By the aid of SEM, EDAX, and XRD, the effect of temperature, duration, volume and dew point of hydrogen flow during oxidation on weight gain, percentage of the oxide phase, constitution and morphology of oxide scale were investigated, and a suitable oxide technology was obtained, it was as follows: 950°C, 40 ~ 60 min, D.P. 35°C, 8 l/min.
Properties of Cracking Resistance of Cemfiber Reinforced Concrete
Authors: Xing Feng , Leng Fa Guang , Li Wei Wen
Published: March 2009

Polypropylene fiber is a new measure to prevent plastic cracks of concrete. Effects of the parameters, such as dosage and types of fibers, on the plastic cracks were studied systematically. The properties of cracking resistance of mortar, ordinary concrete and high performance concrete were investigated by using samples of two types in shape. The results show that: (1) polypropylene fibers may increase the
cracking resistance of concrete further; (2) as smaller quantity of cement and higher quantity of aggregate as possible should be used to prevent concrete form cracking; (3) the main reason why polypropylene fibers increase cracking resistance of concrete is that they increase strain capacity of concrete at early age,
decrease shrinkage strain, improve plastic tensile strength and decrease tensile stress of the capillary.
Investigation on Stress Fields in Lined-Ceramics of the Composite Pipes Fabricated by SHS Metallurgical Process
Authors: Lu Xiao Bo , Liu J.Z. , Wen Jin Hua , Han Bao Hong , Yan Jun , Cui Hai Ping
Published: March 2009

Based on the SEM observation on cracks in lined ceramics of the composite pipes, the stress fields in lined ceramics were analyzed. The results indicated that there are the compressive field and heat stress field in lined ceramics, resulting in the existence of radial cracks and net cracks; besides being influenced by wall thickness of ceramic layer, the strength of compressive stress field is also dependent on bonding strength between metal and ceramics, and the strength of heat stress field is dependent on temperature gradient in lined ceramics during cooling of the ceramics.
Sphering Mechanism for the Green Ceramic Balls Ground with the Two-Wheels Grinding Technique
Authors: Ren Cheng Zu , Gao Da Xiao , Zhang Lian Hong , Jin Xin Min
Published: March 2009

The machining of ceramic balls is one of the main difficulties of the manufacture process of ceramic ball bearings. This paper introduces a new grinding technique for green ceramic balls, the twowheels grinding technique. The sphering mechanism for the green ceramic balls ground with the technique was analyzed in theory, and the influencing factors were studied by experiment. The experimental research presents that the spherical deviation of the ground green ceramic balls can be improved to 0.02mm.
A Novel Approach for Metal Surface Modification
Authors: Cao Zhi Jun , Liu Jia Chen , Liu Li Bin , Ye Hao , Wei Yan Qiu
Published: March 2009

A new approach was developed for surface modification of metallic surface. By treating nano-zirconia particles and metal surface in different charge state, nano-zirconia particles can be dispersedly inlaid in metal surface owing to electrostatic and nanometer effects. By using this method, metal components of complex shapes, especially those having inside surfaces, might be easily improved, i.e., enhanced surface hardness and wear rate.
Nonlinear Dynamic Analysis and Nonlinear Structure of Self-Propagating High-Temperature Synthesis Process
Authors: Zou Zheng Guang , Yu Shi Jin
Published: March 2009

The Self-propagating High-temperature Synthesis(SHS) process is a nonlinear one far from thermodynamic equilibrium, many nonlinear structures present in the process. After SHS processes of Ti-C-Fe and Ni-Si systems have been studied by the numbers, the effects of initial parameter conditions on nonlinear structure have been gained. On the base of establishing the model of combustion reaction dynamic characteristics, backward finite-difference approximation equations and central finite-difference approximation equations were applied to numerically calculate and
simulate the characteristics of combustion wave and its’ change rules in the SHS process. All the experimental results are consistent with the simulative results.
Some Aspects of Research on Layered Ceramic Composites in China
Authors: Cao Wen Bin , Ge Chang Chun
Published: March 2009

Layered structure can greatly improve the toughness of the ceramics. Manufacture techniques, including matrixes and interlayer materials choosing and matching, structure and interface design, parameter deciding, processing of layered materials making were introduced in this paper.