bluuebunny/crossref_metadata_2025 huggingface dataset:
Thick Film Metallization of AlN by Reactive Binders
Authors: Shuai Ren Zhong , Zheng Hong Lei , Yang De An
Published: April 2010

The thick-film metallization of AlN has received considerable attention because of its potential applications in electronic packaging. Here we reported on the thick film metallization of AlN by reactive binders. The metallization paste of Ag was prepared with organic vehicle of castor oil, ethyl cellulose and beta-terpineol and reactive binders of TiB2 and Co3O4. The control of the paste viscosity was discussed by changing the dispersant content. Meanwhile effects of the components and sintering process on the thick film properties were investigated. The properties of metallization film were analyzed with XRD, SEM and electrical test. The adhesion strength and the electrical resistance of the film were 12.7MPa and 5.3mΩ/□ respectively when the paste composition of Ag, TiB2, Co3O4 and the organic vehicle was 72.8%, 1.5%, 0.7% and 25% and the film was sintered in air at 850°C for 15 minutes.
Fabrication of SiC/Ti3SiC2/TiC Ceramic Composites by Pressureless Sintering of 3TiC/2.2Si/0.2Al
Authors: Liang Bao Yan , Han Xin , Zou Qin , Wang Ming Zhi
Published: April 2010

SiC/Ti3SiC2/TiC composites were fabricated by means of pressureless sintering using the 3TiC/2.2Si/0.2Al as raw materials. At the temperatures from 1000°C to 1200 °C, the main phase of the composite synthesized was Ti3SiC2. At the same time, there was a small amount of TiC and SiC existing. The composite had loose microstructure. At the temperature of 1300 °C, the TiC and Ti3SiC2 were the primary phases. And the SiC was the second phase. The SEM images showed that there were two kinds of microstructures in the composite. One was the Ti3SiC2 and the TiC platelets on its surface, another one was the TiC and the SiC equixed grains in its interior.
Influences of Donor Additives on Properties of TiO2-Based Varistor
Authors: Zou Ming , Wang Yuan , Chen Yan Yan , Zhang Yun
Published: April 2010

In this paper, the TiO2-based varistor ceramics added different donor additives were prepared and their propreties had been compared. The effects of added methods and added amounts of V2O5 (Nb2O5, or Ta2O5) on the microstructure, dielectric and varistor properties of TiO2 double functional ceramics were investigated. The ceramic phase and the microstructure of the disks were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The frequency dependences of the samples capacitance (C), the dielectric loss (tanδ) were determined on LCR meter, and the varistor voltage V1mA was measured by using FC-2G meter. It is found that the proper amount of V2O5, Nb2O5 or Ta2O5 additves can promote the growth of the crystal and the formation of the grain boundary layer at a different extent. Meanwhile, the proper addition amount can increases the nonlinear exponent and the dielectric constant, but decreases the breakdown voltage. It can also improve the sintering properties of the samples.
Preparation of Sr2CeO4 Nano-Crystallites with a Sonochemical Process
Authors: Cao Li Yun , Huang Jian Feng , Wu Jian Peng , He Hai Yan
Published: April 2010

Sr2CeO4 nanocrystallites were prepared by a sonochemical process with a later heat treatment using CeO2 and SrCO3 as source materials. The influence of processing factors on the phase composition and morphology of the crystallites were investigated. Results show that nano-Sr2CeO4 monophase could be prepared at the calcining temperature up to 800oC for 2h. Particle size of Sr2CeO4 crystallites decrease with the increase of ultrasonic irradiation power. Around 20-30nm Sr2CeO4 crystallites can be obtained at 800oC when ultrasonic irradiation power reaches 300W.
A Fracture Dynamics Model for Fiber Reinforced Ceramics
Authors: Lü Nian Chun , Cheng Yun Hong , Wang Yun Tao
Published: April 2010

After fiber reinforced ceramics occur a crack, their fibrous position form bridging fibers, moreover a crack usually extends in the modality of similarity. In order to analyze facilely problems of fiber reinforced ceramics, bridging fiber segment is substituted for loads. A dynamic model of crack propagation is built and its fracture dynamics problems are researched by the approaches of self-similar functions. When a crack propagates at high speed its fiber continues to break. By application of the theory of complex functions, the problems dealt with can be easily translated into Remann-Hilbert problem. Using the built dynamic model and the ways of self-similar functions, analytical study of the displacements, stresses, dynamic stress intensity factor and bridging fibrous fracture velocity α under the action of a running constant force P and an running increasing load Pt, respectively, can be attained, and it is also utilized to obtain the concrete solution of the model by means of superposition theorem.
Influence of Preparation Parameter on the Grain Size of LaB6 Powder Synthesized by SHS with Reduction Process
Authors: Jiang Ni , Wang Wei Min , Fu Zheng Yi , Wang Hao , Wang Yu Cheng , Zhang Jin Yong
Published: April 2010

Self-propagating high-temperature synthesis with reduction process was used to fabricate LaB6 ceramic powder from La2O3-B2O3-Mg system. The combustion reaction carried out in inert atmosphere (Ar) and the combustion temperature was about 1600°C. The products were washed with dilute hydrochloric acid and distilled water, respectively, to remove LaBO3, Mg3B2O6, MgO and other impurities. The influence of compact pressure and addition of SHS diluent on the grain size was studied. The result indicates that as the compact pressure increased, the mean size of powder decreased gradually. The addition of diluents reduced the synthesis temperature, and as the amount of diluent increased, the grain size of LaB6 powder was found to reduce continuously. Microstructure analyses show that the mean grain size of LaB6 powder prepared by SHS with reduction process is less than 500 nm, which is finer compared with the grain size prepared by traditional process.
Microstructure and Wear Resistance of TiC/Ni3Al Composites Made by Pressureless Melt Infiltration Processing
Authors: He Bo Lin , Yu Ying Xia , Miao Yan Ping
Published: April 2010

Porous TiC-Ni3Al performs were fabricated by using Ni, Al, Ti and graphite powder with self-propagating high-temperature combustion synthesis (SHS) method. Then, the porous perform were infiltrated with melt Ni3Al via the conventional pressureless infiltration process to prepare TiC/Ni3Al composites. Effects of the infiltration temperature and time on the microstructure, hardness and wear resistance of the composites were studied. XRD, SEM and EDS were used to analyze the phase identification and the solubility of Ni3Al and TiC in each other. The results show that pressureless melt infiltration is an effective method to fabricate dense TiC/Ni3Al composites. The infiltration time can greatly decrease when the infiltration temperature suitably increases. No obvious effect of the infiltration temperature and time on the hardness and the wear resistance of the composites were found. Ni3Al and TiC were well bonded, and they are the only two phases in the composites after infiltration. The wear resistance of TiC/Ni3Al composites including 70% and 80% TiC were promoted 3.25 and 4.33 times compared with pure Ni3Al, respectively.
Influences of SiO2 on Densification and Properties of Large Bulk Al2O3/ZrO2 (4Y) Eutectics
Authors: Yang Quan , Zhao Zhong Min , Zhang Long , Pan Chuan Zeng , Qu Zhen Sheng , Wang Min Quan
Published: April 2010

Based on preparing large bulk Al2O3/ZrO2 (4Y) eutectics, SiO2 additive is used for controlling the microstructures, densification and mechanical properties. XRD pattern showed SiO2 additive in the ceramics was in the form of glass phase. SEM images showed that the microstructure morphologies transformed from the cellular eutectics to the rod-shaped colonies with increasing content of SiO2 additive. With increasing content of SiO2 additive, the relative density of the ceramics increased whereas the hardness of the ceramics decreased. As the content of SiO2 additive reached 4%, fracture toughness of the ceramics had the maximum value due to the coupled toughening mechanisms of crack-pinning, crack- bridging and crack-deflection by rod-shaped colonies. As content of SiO2 additive reached 6%, the highest flexural strength of the ceramics was achieved due to high fracture toughness and small-size critical defect.
Synthesis of Calcium Metaphosphates Fine Powders by Chemical Precipitation Methods
Authors: Zhang Yin , Kong De Shuang , Tao Ya Qiu , Zhu Jian Ping , Yao Neng Jian
Published: April 2010

Calcium metaphosphate (CMP) fine powders were produced by a chemical precipitation method. In order to produce the powders, CMP was prepared by the mixing of two precursors, such as calcium oxide (CaO) and phosphate acid (H3PO4). Sparingly soluble chemicals, the Ca/P ratio of the mixture was set to be 0.50 to produce stoichiometric CMP, were chemical agitated in phosphate acid solution. At least 3 hours of pre-hydrolysis of phosphorus precursor were required to obtain CMP phase. The CMP powders were dried in a drying oven at 60°C for 72 hours and then heat-treated at various temperatures at a ramp of 1°C /min in air for various hours. The obtained powder was analyzed using XRD, XRF, FT-IR, SEM, TG-DTA, Zeta Potential Meter, Specific Surface Area, and Particle Size Analyzer. The results showed that obtained CMP powders have a significantly powder characteristics.
Degradation Characteristic of Strontium-Containing Calcium Phosphate Cement In Vivo
Authors: Zhao Xin Yi , Li Feng , Li Shi Bao
Published: April 2010

The objective of this study is to compare the degradation of three strontium-containing calcium phosphate cement (Sr-CPC) and one calcium phosphate cement without strontium (CPC) in vivo. Three Sr-CPCs, containing 1%, 5%, 10% strontium respectively, and a CPC without strontium were tested in this study. The specimens in rod-shape (2 mm  6 mm) were prepared, and were implanted in the erector spine muscle of 15 New Zealand rabbits. After 4, 8 and 12 weeks, 5 rabbits were sacrificed respectively and the specimens were taken out, cleaned, dryed and weighed. The weight losses of the specimens were calculated and the data were analyzed by ANOVA. The results showed that the CPC containing 5%, 10% strontium showed obviously higher degradation rates at the three observation periods than that containing 1% strontium and that without strontium (P<0.05). Addition of 1% strontium into CPC did not increase degradation rate (P>0.05), and the CPC containing 5% and 10% strontium showed no difference in degradation rate at the three observation periods (P>0.05).
Preparation and Properties on Silk Fibers Reinforced Hydroxyapatite/Chitosan Composites
Authors: Wang Jing , Sun Q.Z. , Gao Jing , Liu D.M. , Meng Xiang Cai , Li Mu Qin
Published: April 2010

Silk fibers were introduced into hydroxyapatite(HA)/chitosan(CS) matrix to prepare scaffold materials of bone tissue engineering with the adequate initial strength and improved cellular affinity using combination of in situ synthesis and freeze-drying technique. Chemical component was investigated using X rays diffraction (XRD) and Fourier transform infrared spectrum (FTIR). Structure and morphology of the composites were observed by scanning electron microscope (SEM). Porosity was tested by liquid substitution method. The mechanical properties of the composites were also measured. The simulated body fluid (SBF) and the cell culture experiments were conducted to assess biological properties of the composites. Results show that the composites with a pore size of 100~250μm have a porosity of 75%~90%and the maximum compressive strength of 5.7 MPa. The compressive strength of the composite is greatly improved in comparison with that of HA/CS matrix (4.6 MPa). In the SBF tests, a layer of randomly oriented apatite crystals form on the scaffold surface after sample immersion in SBF. The cell culture experiments show that the osteoblast cells are attached and proliferated on the surface of the composite, which suggests good bioactivity and cellular compatibility of the composite material. It is concluded that the composites have a promising prospect as bone tissue engineering materials.
Effect of Artificial Saliva with Fluoride Ions on the Color of Ti-Porcelain
Authors: Wu Hai Tao , Shang Hai Yan , Guo Li Tong , Yang Jian Feng , Guo Tian Wen
Published: April 2010

In the acidic oral environments containing fluoride ions, hydrofluoric acid (HF) would form and affect the color of Titanium porcelain crown, but there is a lack of information on how color is affected by this oral fluid. The purpose of this study was to investigate the effects of various artificial saliva simulating oral environments in the presence of fluoride ions with different pH value on the color of self-made dental opaque, body porcelain, belonging to the Na2O-K2O–MgO–CaO–Al2O3–SiO2 glass system. Disc-shaped specimens, 5 mm diameter and a 2-mm thickness, were made by firing. Specimens were immersed in artificial saliva in the presence of fluoride ions with different pH value for 7, 14, 21 days, and then the color of the specimens was compared with the color of the initial specimen. The interactions were present in L*a*b* values between pH value and the day of immersion. The changes in L*a*b* color data as the day of immersion and pH value increased were revealed, which can resulted in perceptual color changes in L*a*b* color parameters.
Influence of Composition on the Characterization and Crystallization of Calcium-Magnesium-Silicate Glass-Ceramics
Authors: Liu Hao , Wang Xi Tang , Zhang Bao Guo , Wang Zhou Fu
Published: April 2010

The effects of replacement of MgO by CaO, on the characterization and crystallization behavior of glas-ceramics in the CaO-MgO-SiO2 system were investigated by DTA, XRD and FTIR techniques and by density measurements. The results show that the glass transition temperature (Tg) and crystallization temperature (Tc) increase and glassy structural network becomes denser with increasing the CaO/MgO weight ratio. After certain heat-treatment procedure, the major crystal phases change from calcium magnesium silicate (diopside) to calcium silicate (parawollastonite) at the replace of MgO by CaO. Studying of density measurement shows that, the density of glass samples increase by increasing CaO content on the expense of MgO.
Preparation of Porous Hydroxyapatite-Zirconia Composite Scaffolds by Combination of Gel-Casting and Polymer Sponge Methods
Authors: Wang Li Li , Wang Xiu Feng , Jiang Hong Tao , Yu Cheng Long
Published: April 2010

Hydroxyapatite (HA) doped with 3%yttria-stabilized 20wt% zirconia (ZrO2) ceramic were developed in order to produce a porous composite biomaterial by integrating the gel-casting technique with polymer sponge method with improved mechanical strength and controllable porous structure. The pore morphology, size, and distribution of the scaffolds were characterized using an electron microscope. The scaffolds prepared have an open, uniform and interconnected porous structure with a pore size of 300~500m. The porosity of the open pores in the scaffold can be controlled by changing HA-ZrO2 composite concentration and it is between 87%~35%. A compressive strength of 12MPa for HA-ZrO2 porous scaffolds with HA-ZrO2 concentration of 55wt% was achieved, which is comparable to that of cortical bone.
Effect of SiC on Microstructures and Properties of Clay Foam Ceramics
Authors: Bai Jian Guang , Liu Guang Liang , Yang Jian Feng
Published: April 2010

A foam ceramic was prepared using clay, SiC, Fe2O3, feldspar and other raw materials as main starting material in a furnace at 1140~1170oC for 15~25min. Effects of silicon carbide’s content and powder size on the bulk density, moisture absorption rate and compressive strength were studied, and the fracture surface morphology was observed and analyzed using Scanning Electron Microscope (SEM) and X-ray diffraction analysis (XRD). The results show that SiC powder reacted with Fe2O3, Fe3O4, CO2, iron, SiO2 and form foam. The sintering behavior and properties of the foam ceramics are influenced by the content and particle size of SiC, when the content of SiC is as high as 8%, and the mass ratio of grain size is 1:1, the foam ceramics with the rate of moisture absorption is 0.05%, the bulk density is 0.32g/cm3, and compressive strength is than 2.2MPa.
Preparation of Double-Perovskites Sr2Fe1-xScxMoO6-δ Powders for the Cathode of SOEC by Sol-Gel Citrate Method
Authors: Ge Ben , Ma Jing Tao , Ai De Sheng , Lin Xu Ping , Deng Chang Sheng
Published: April 2010

Double-perovskite Sr2Fe1-xScxMoO6- (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4) powders have been synthesized by sol-gel citrate method. Initial powders were calcined in different temperature and atmosphere (air, H2(4vol%)/Ar), then analyzed by using the methods of X-ray, scanning electron microscopy (SEM), as well as thermal analysis. It is found that the formation of perovskite structure is related to the content of Sc, pH value, calcination temperature and sintering atmosphere. Especially, a pure perovskite structure almost completely formed after three hours sintering in atmosphere of H2(4vol%)/Ar. Although the formation of perovskite structure also happened in the air atmosphere, at the same time the SrMoO4 structure formed undesirably as a result of oxidization of Mo.
Properties of Composite Ceramic Coatings on Ti-6Al-4V Alloy by Surface Nanocrystallization/Micro-Arc Oxidation
Authors: Hao Guo Dong , Guo Yong Liang , Liu Gang , Zhang Xin Mei
Published: April 2010

Nanostructured surface layer was produced on Ti-6Al-4V alloy by surface mechanical attrition treatment (SMAT) technique, and the composite ceramic coatings of surface nanocrystallization/ micro-arc oxidation (SNC/MAO) were prepared on the nanocrystallized surface of Ti-6Al-4V alloy by pulsed single-polar micro-arc oxidation in NaAlO2 solution. XRD, SEM and TEM techniques were used to investigate the phase and surface morphology of ceramic coatings and the influences on the surface state of the alloys. Meantime, the mechanical properties of Ti alloys were measured by tensile test. The results show that after the SMAT treatment for a short period of time, the surface layer was refined into ultrafine grains. The influences of the SMAT technique on the surface morphology of the ceramic coatings were also studied. The ceramic coatings are mainly composed of Al2TiO5, more compact and less porous than those untreated. The mechanical properties of Ti-6Al-4V alloy by SMAT technique are improved, compared with those untreated by SMAT technique.
Orthogonal Experiment of Glass-Alumina Functionally Gradient Materials Produced with Rapid Prototyping
Authors: Jiang Hong Tao , Wang Xiu Feng , He Bao Cheng , Yu Cheng Long
Published: April 2010

A novel rapid prototyping technology for glass-alumina functionally gradient materials (G-A FGMs) based on the quick solidification of wax was proposed. The feature of the technology came from its layer-by-layer fabrication of the wax-glass/alumina composite layer. With the help of orthogonal experiment method, the influence of different parameters (sintering temperature, component ratio (the glass and the alumina), and number of layers) on the flexural strength of FGMs was discussed. Optimum conditions obtained from the above experiments were applied to prepare the G-A FGM with three layers. The G-A FGM was analyzed in detail, by observing it under an environmental scanning electron microscope (ESEM) coupled with an X-ray energy dispersive spectrometer (X-EDS). The results of orthogonal experiment show that number of layers is the principal parameter to the flexural strength of FGMs, component ratio is the secondary factor, and sintering temperature may be not an important factor. The special microstructure appears in the cross section of the G-A FGM, observed by ESEM. It is from the X-EDS graph concluded that alumina and glass probably react to form the special microstructure with part removal of wax.
Influence of the Reinforcement’s Number on the Mechanical Properties of the Reinforced Concrete Beam
Authors: Li Wei Hong , Yang Xue
Published: April 2010

Basing on the experimental data collected, the mechanical model of reinforced concrete beams’ gradual failure has been set up, to test differ reinforced components with loads and study the process of split. At last the influence of reinforcement’s number on components’ intensity and failure process are analyzed by using MFPA2D (Material Failure Process Analysis) software, started with the analysis of formula cracks after experiments. The results showed that the number of reinforcement is not the more the better. When ultra-reinforced beam appears, its mechanical capacity enhances but the bars won’t do their best, furthermore, it is uneconomical. Accordingly, less-reinforced beam should also be avoided for safe. Everything possible should be made to avoid ultra-reinforced beam and less-reinforced beam in engineering. By all means, this conclusion has practical significance during our practice.
Synthesis of Ti3SiC2 Machinable Ceramics by High-Energy Milling and Hot-Pressing
Authors: Liu Bo Bo , Wang Fen , Zhu Jian Feng , Li Ya Ling
Published: April 2010

The ternary layered machinable Ti3SiC2 ceramics were synthesized at 1300°C by high-energy milling and hot pressing sintering using Ti,Si and C powder as starting material. The reaction mechanism was examined by XRD, SEM and thermodynamic analysis. The results show that Ti-Si-C powders were transformed to Ti, Si and little TiSi, SiC,Ti5Si3 intermetallics by milled for 18 hours. In this process, the little Ti and C transformed to TiSi phase in early stage, and then the most of residual elements reacted to form SiC and Ti5Si3 intermetallics. Finally, Ti, Si, SiC, Ti5Si3 intermetallics and TiSi reacted to yield Ti3SiC2 by hot pressing sintering. And the sintering temperatures had a significant impact on the yielded content of Ti3SiC2 phase. Besides. The Ti3SiC2 would decompose if the temperature was high enough.
Nitrogen-Doped Nano-TiO2 Ceramic Film: Fabrication and Application to Photocatalysis
Authors: Jiang Yan Li , Yao Zhong Ping , Yang Li Juan , Liu Yan , Jiang Zhao Hua , Liu Hui Ling
Published: April 2010

Owing to the defects of the fixed TiO2 photocatalysts, the research employed the approach of anodic oxidation to produce high efficiend N-TiO2/Ti ceramic film oxidized on the surface of titanium, in order to make the absorbable spectrum of light catalyst spread to the visible region and constrain the high recombination rate of electron-hole pairs during photoreaction. The surface appearance and the distribution of elements have been checked with scanning electron microscopy and EPMA. The microcrystal structure of the films has been checked with XRD. The results showed that the main components of nitrogen-doped catalyzer were rutile and anatase, meanwhile, the nitrogen element distributing on the film was fairly uniform. Films of N-TiO2 photocatalysis reduction K2CrO4 revealed that with the amount of N-contained increased, the rate of reduction K2CrO4 decreased under ultraviolet light while that increased under visible light. It was found that the highest reduction rate of K2CrO4 was achieved through an optimal (NH4)2S2O8 dosage of 0.4g/L in ceramic film prepared processes.
Synthesis of MgAlON-Bonded MgO Refractory
Authors: Cheng Zhu , Sun Jia Lin , Li Fu Shen , Chen Zhao You , Wan Long Gang
Published: April 2010

Fused magnesite, α–Al2O3 micropowder and aluminum powder were used as starting materials to form MgAlON and MgAlON-bonded MgO materials in nitrogen atmosphere. Influence of technical conditions, such as composition, on formation of MgAlON was studied. Influence of vapouring of MgO in low PO2 atmosphere at high temperature on sintering of MgAlON-bonded MgO material was also discussed, showing that vapouring of MgO makes the material porous and damages its sintering.
Preparation of Integrated Ceramic Armor for Body Bulletproof by Semi-Aqueous Gel-Casting
Authors: Liang Yan Yuan , Chen Da Ming , Tong Jian Feng , Huang Xian Cong
Published: April 2010

Arc-shaped integrated alumina ceramic armor for body bulletproof with the size of 300 × 250 × 6 mm, R400mm were prepared by semi-aqueous gel-casting. The excellent characters and advantages of the semi-aqueous gel-casting were analyzed; ballistic experiments were carried out to test the protection coefficient of 92%, 96%and 99 alumina ceramics. The experimental results showed that the 92% alumina ceramic and the 99% alumina ceramic had favorable performance while the 96% alumina ceramic had the worst one. But the 92% alumina ceramic had the highest protection coefficient which is 9.96.
Effect of Phase Separation Structure on the Crystallization Property of Blast Furnace Slag
Authors: Li Yu , Zong Yan Bing , Cang Da Qiang
Published: April 2010

Performance of slag glass ceramic largely depends on the phase separation structure formed in heat treatment. In the paper, the crystallization properties and its relation with phase separation structure of blast furnace slag (BFS) are researched. Three water-quenched samples and an air-quenched sample were respectively prepared. After conducting temper experiments and analyzing XRD and DTA results, the following conclusions have been acquired. Two crystallization regions exist in BFS system. In parent glass with phase separation structure, Ca3Mg(SiO4)2 and Ca2MgSi2O7 would form at lower temperature but Ca2Al2Si2O7 would appear at higher temperature than that in parent glass with homogenous structure. The former contributes to the existence of lower polymerized [SiO4] units and more Ca2+ or Mg2+ in Ca-rich phase of phase separation glass, while the later is due to the diffusing hindrance of [AlO4] in diffusing path and interface resistance in phase separation structure.
Preparation and Properties of a New Ti3C2-Cu(Al) Cermet Series
Authors: Huang Zhen Ying , Zhai Hong Xiang , Li Meng Qi , Wang Wen Juan
Published: April 2010

Several Ti3C2-Cu(Al) cermets were prepared by pressureless sintering or by in-situ hot-extruding a mixture of Ti3AlC2 and Cu powders, their microstructure and properties were investigated. The Al of Ti3AlC2 was dissolved and diffused into liquid Cu, forming Ti3C2-Cu(Al) cermet. Due to strong combination between Ti3C2 and Cu(Al), and special network microstructure formed by Cu(Al) phase surrounding sub-micro-sheet layered Ti3C2 phase, the cermets have quite high fracture strength and electric conductivity. Properties of cermets fabricated by in-situ hot-extruding were further increased.
Simulation of Temperature Distribution during Ceramic Sintering Based on BP Neural Network Technology
Authors: Liu Li Ping , Lin Bin , Chen Shi Huan , Zhang Xiao Feng
Published: April 2010

It is difficult to calculate with finite element method or actually measure the temperature distribution of the ceramic sintering at irregular sintering curve. Trained by the temperature distribution data of ceramic sintering analyzed with ANSYS under linear sintering curves including different slopes, the neural network can be used to simulate that under irregular sintering curve at certain precision, so the temperature evolution of the ceramic hot geometry centroidal point (HGCP) can be fast obtained by the result simulated with the trained neural network. This research sets up series-parallel BP neural network model with MATLAB. The ceramic sintering date analyzed with ANSYS under linear sintering curves with ten different slopes is used as training sample of the neural network which is tested by the sample under non-linear sintering curve. The result indicates that the BP neural network is feasible for simulating temperature distribution of the ceramic sintering.
Microstructure and Properties of Graphite Embedded SiC Composite by Coating Method
Authors: Yu Liang , Zhao Jing , Yue Xin Yan , Li Jing Yang , Ru Hong Qiang
Published: April 2010

Gp/SiC composite was prepared with electrode graphite particle and SiC powders as the raw materials, using coating process and hot-pressing sintering technology. The microstructure and phase constitution was measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron energy spectrum (EDS). It was found that the graphite cores are embedded in the SiC matrix as the islands. The apparent porosity increased, density decreased, with graphite particle content increasing, the bending strength decreased, however, fracture toughness increased with the graphite particle content increasing. Increasing hot-pressing sintering temperature imparted Gp/SiC composite characteristic behaviors of better mechanical strength. The apparent porosity, bulk density, bending strength, fracture toughness were 4.0%, 2.58 g•cm-3, 50 MPa, 6.3 MPa•m1/2, respectively, with the size 200 μm graphite core at 2050 °C, while the volume rate of SiC and graphite was 6:4.
Densifying Ti3AlC2/Cu Composites Using a Cold-Extruding and Temper Means
Authors: Zhang Hong Bing , Zhai Hong Xiang , Zhou Yang , Huang Zhen Ying
Published: April 2010

A cold-extruding and temper means was developed in order to densify the Ti3AlC2 toughened Cu matrix composites with a lower content of Ti3AlC2 ceramic. The Ti3AlC2/Cu samples, with 10%, 15% and 20% of Ti3AlC2 in volume ratio, ware prepared by pressless sintering a mixture of copper and Ti3AlC2 powders, after which were formed by the cold isostatic compaction. The sintered samples ware extruded at room temperature, and then tempered at 950oC. Such treatment was performed twice for obtaining a more remarkable densifying effect. Changes in microstructures were observed by SEM after every extrusion and temper. The results show that particle size of Ti3AlC2 was reduced more than 50% after secondary extrusion and temper, and the particles distribution became more uniform in compared with the untreated samples. As a result of the microstructural change, the densities of the Ti3AlC2/Cu samples were increased about 5 %, and defects such as pores and microcracks were almost entirely slaked.
Microstructure of Nanoceramic during Sintering and Preparation
Authors: Ren Ju Ping , Zhang Ke , Tang Yu Lan
Published: April 2010

The microstructure evolution during sintering and preparation of nanoceramic materials is studied by molecular dynamics (MD) simulation. A 3D model for nanoceramic crystal body including mainly crystal planes of (100) and (110) is developed. This model is used to simulate the hot pressing of nanoceramic, especially for SiC, by rapid heating-up and cooling-down under certain pressure. In this model, the Tersoff potential function is used to simulate the interatomic force between atoms. The microstructure during melting process and crystallizing process are investigated by analyzing energy evolution, pair correlation function and the graph of instantaneous place of the atoms. The results show that the microstructure is amorphous after melting, and crystal planes of (100) and (110) are different in density, melting point and microstructure, showing anisotropy.
Activated Carbons Prepared from Natural and Synthetic Raw Materials with Potential Applications in Gas Separations
Authors: Cansado Isabel P.P. , Mourão Paulo A.M. , Ribeiro Carrott Manuela M.L. , Carrott Peter J.M.
Published: April 2010

A carbon molecular sieve for the purification of a gas mixtures containing O2, N2 and CO2, CH4 was produced from a waste granulated PET by means of a single carbonisation step at 973 K. Activated carbon materials presenting good adsorption capacity and some selectivity for O2/N2 and CO2/CH4 were prepared from granulated PET and cork oak with pore mouth narrowing using CVD from benzene. The diffusion coefficients of O2, N2, CO2 and CH4 in these materials were calculated and are comparable to published values determined on Takeda 3A and on a carbon molecular sieve prepared from PET textile fibres by means of carbonisation and subsequent CVD with benzene. However, the selectivities were not quite as good as those given by Takeda 3A. However, taking into account that this is a first attempt at producing CMS from PET, the results are encouraging, and it is to be expected that further development of the experimental procedure will result in new materials with improved performance.
Study of Thermal Conductivity of Materials Made of Sludges Water Depuration of the Brewing Industry
Authors: Martínez-García Carmen , Palomino Cotes Teresa , Corpas-Iglesias Francisco  A. , Martínez Cartas Lourdes , Pérez Cruz Nicolás
Published: April 2010

Industrial wastes contribute significantly to environmental pollution following the directives of European environmental policies, we must look for alternatives for minimization, treatment and / or recovery of wastes [1]. Several studies have found that basic materials such as polymers, cements and ceramics are better suited to inerting and neutralization of the waste by encapsulation in your matrix [2]. They are also increasingly used more insulating bricks. One way to increase this capacity is introduce additives organics into the matrix [3]. This is the case presented below, where they have used sludge from water purification of the brewing industry for the manufacture of ceramics.
Preliminary Study of the Influence of Machining Conditions in the Response to Corrosion of UNS-A92024 Alloy
Authors: Bienvenido Rafael , Díaz Vázquez J.E. , Botana Francisco Javier , Cano M.J. , Marcos Bárcena Mariano
Published: April 2010

In the aeronautical industrial sector, the control of the manufacturing process allows to fit the results to the conditions of design of pieces. This manufacturing process conditions the functional behaviour of pieces. In this work are presented the preliminary results of a study conducing to obtain the influence of machining parameters in the response to corrosion of aerospace aluminium alloys in seawater. This results show a high influence of feed, and a minor influence of cutting speed.
Identification, Analysis and Evolution of the Mechanisms of Wear for Secondary Adhesion for Dry Turning Processes of Al-Cu Alloys
Authors: Batista Moisés , Salguero J. , Gómez Alvaro , Carrilero M.S. , Álvarez Miguel , Marcos Bárcena Mariano
Published: April 2010

In this work, Stereoscopic Optical Microscopy (SOM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) have been applied for analyzing the evolution of tool wear during the dry turning process of aerospace Al-Cu alloys. The results derived from this analysis have revealed that secondary adhesion is the main tool wear mechanism that takes place in such process. So, in the first instants of the machining process, a Built-Up Layer (BUL) is developed onto the tool rake face by thermomechanical causes, promoting the conditions for developing a Built-Up Edge (BUE) which grows to a critical size. Starting from it, BUE is extruded giving rise to secondary BUL-BUE effects. When these are removed, tool particles are dragged out provoking the tool wear.
Sustainable Manufacturing in Aerospace Industry – Analysis of the Viability of Intermediate Stages Elimination in Sheet Processing
Authors: Salguero Jorge , Batista Moisés , Sánchez-Carrilero Manuel , Álvarez Miguel , Marcos Bárcena Mariano
Published: April 2010

Manufacturing performance improvement must take into account energetic, environmental and economic considerations. Thus, when intermediate manufacturing processes are avoided, that performance is improved from the cited viewpoints. In the aeronautical industry, pre-shaped elements of UNS A92024 alloy based structural elements are machined in T3 temper state previously to be thermally treated to reach an O state in order to facilitate its posterior plastic forming process. In this work, a comparative study on the dry turning of UNS A92024 alloy in both states has been achieved in order to analyze the possibilities of eliminating the thermal treatment process, so improving the three above commented considerations. This study has been carried out on the basis of the analysis of surface finish and cutting tool wear.
A TEM Microstuctural Study of the Factors Affecting the Compositional Modulation in GaInAsSb/GaSb Films
Authors: Konidaris S. , Welser E. , Dimroth F. , Polychroniadis Efstathios K.
Published: April 2010

Quaternary semiconductor alloys based on GaSb are suitable for thermo-photo voltaic cell applications as they have low and adjustable band-gap. However, they exhibit phase separation which destroys band-gap uniformity. In this work, GalnAsSb thin films grown on GaSb vicinal substrates were studied by Transmission Electron Microscopy, in order to determine the influence of the growth parameters on phase separation. It was found that the coatings exhibit two types of compositional modulation, one parallel and the other forming an angle with the substrate plane.
Characterization and Biocompatibility Properties of Silver Nanoparticles Produced Using Short Chain Polyethylene Glycol
Authors: Jokar Maryam , Rahman Russly Abdul , Ibrahim Nor Azowa , Abdullah Luqman Chuah , Ping Tan Chin
Published: April 2010

Silver nanoparticles are of interest due to their unique physicochemical and antimicrobial properties. The nanoparticles were produced by chemical reduction using short chain polyethylene glycol (PEG) as reducing agent, solvent and stabilizer in absence of other chemicals. Silver nanoparticles were separated from colloidal dispersion by ultra centrifuge at 14000 rpm. The reduction of silver ion (Ag+) to silver nanoparticles (Agº) was monitored by pH measurement and UV-visible spectroscopy of colloidal dispersion at fixed intervals. Silver nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and diphenyl-picrylhydrazyl (DPPH) radical scavenging method. Antimicrobial activity of silver nanoparticles was investigated against Escherichia coli, Staphylococcus aureus and Vibrio parahaemolyticus by agar plate test. Results indicated 51.5% conversion efficiency of silver ions to silver nanoparticles. Colloidal dispersion containing 4.12 mg/ml silver nanoparticles showed uniform size of 5.5 ± 1.1 nm with a typical visible spectra band at 447 nm. Silver nanoparticles showed significant (p < 0.05) antimicrobial efficiency and with concentration of 100 ppm resulted in 46.22%, 66.51% and 69.06% inhibition against S. aureus, E. coli and V. parahaemolyticus, respectively. The nanoparticles were also found to reduce DPPH free radical up to 88.9%. Results of this study proved that the silver nanoparticles produced by polyethylene glycol possess antimicrobial and antioxidant activity.
Scale-Invariant Drain Current in Nano-FETs
Authors: Wulf Ulrich , Richter Hans
Published: April 2010

Starting from a three-dimensional transport model in the Landauer-Buttiker formalism we derive a scale-invariant expression for the drain current in a nano-transistor. Apart from dimensionless external parameters representing temperature, gate-, and drain voltage the normalized drain current depends on two dimensionless transistor parameters which are the characteristic length l and -width w of the electron channel. The latter quantities are the physical length and -width of the channel in units of the scaling length = ~(2mF )1=2. Here F is the Fermi energy in the source contact and m is the eective mass in the electron channel. In the limit of wide transistors and low temperatures we evaluate the scale-invariant IDVD characteristics as a function of the characteristic length. In the strong barrier regime, i. e. for l & 20 long-channel behavior is found. At weaker barriers source-drain tunneling leads to increasingly signicant deviations from the long-channel behavior. We compare with experimental results.
Fabrication of Copper Nanowires by Electrodeposition Using Anodic Alumina and Polymer Templates
Authors: Virk Hardev Singh , Kishore Kamal , Balouria Vishal
Published: April 2010

Copper is one of the most important metals in modern electronic technology. Keeping in view its role in nanoelectronics, we have fabricated copper nanowires of diameters 100 and 200nm using Anodic Alumina and polymer membranes as templates. Electrodeposition technique based on the principle of electroplating was adopted for copper nanowire fabrication in an electrochemical cell designed in our laboratory. SEM micrographs are used to calculate the aspect ratio of nanowires. The morphology of nanowires shows some interesting features.
Work–home interference: Examining socio-demographic predictors in the South African context
Authors: De Klerk Marissa , Mostert Karina
Published: April 2010

Orientation: The focus of this study was to investigate the relationship between socio-demographic characteristics and the work–home interaction in different occupational groups in South Africa.Research purpose: The main research aim of the study was to investigate the socio-demographic predictors of negative and positive work–home interaction of South African employees.Motivation for the study: Little information is known about the prevalence of work–home interaction within groups. This study is aimed at enabling the researcher and organisations to identify those groups that are at risk of negative interference and which are prone to positive interaction, to allow for the development of appropriate strategies and intervention programmes.Research design, approach and method: A cross-sectional survey design was used in the study. A sample (N = 2040) was taken from four South African industries (i.e. the police service, the earthmoving equipment industry, mining and nursing). A socio-demographic questionnaire and the Survey Work–Home Interaction-Nijmegen (SWING) were used.Main findings: The results indicated that robust predictors included occupation, gender and language for negative work–home interference; occupation, age and language for positive work–home interference; occupation and language for negative home–work interference; and occupation, age, education and language for positive home–work interference.Practical/managerial implications: The implications of the study are that negative and positive work–home interaction is uniquely associated with socio-demographic characteristics. Work–life balance initiatives should, therefore, be carefully tailored to address the needs of each socio-demographic group.Contribution/value-add: The findings of the study suggest answers to the management of the work–home interaction among various socio-demographic groups in organisations.
Measurements of primary productivity and nitrogenase activity of coral reef algae in a chamber incorporating oscillatory flow
Authors: Carpenter Robert C. , Hackney John M. , Adey Walter H.
Published: April 2010

Diffusive limitation of C and nutrient uptake can be an important factor regulating metabolic processes in aquatic plants. Relationships between the flow regime and both primary productivity and nitrogenase activity (ethylene production) of coral reef algal components were studied via a productivity chamber that simulates oscillatory flow. Net primary productivity of algal turfs was increased significantly by flow speeds (steady flow equivalent) up to 16 cm s−1. The mode of water flow also was important; primary productivity of algal turfs increased by 21% under an oscillatory flow regime as compared to vortex flow created by stirring. Acanthophora spicifera exhibited increased primary productivity at flow speeds up to 10 cm s−1, while primary productivity of another rhodophyte, Coelothrix irregularis, increased up to 4 cm s−1. Rates of nitrogenase activity exhibited by algal turfs also were affected significantly by flow speed. These data indicate that diffusive limitation is important to varying degrees in reef algal turfs and macroalgae and suggest that primary productivity and rates of nitrogenase activity depend on ambient flow speeds and boundary‐layer dynamics.
Differential growth rates of three cladoceran species in response to mono‐ and mixed‐algal cultures
Authors: Lundstedt Lisa , Brett Michael T.
Published: April 2010

Population growth rates for Daphnia longispina, Bosmina longispina, and Chydorus sphaericus were determined in monocultures or mixtures of algae typical of the spring bloom (Stephanodiscus, Rhodomonas, and Chlamydomonas) and summer (Scenedesmus, Chlorella, and Microcystis). Algae from the spring bloom resulted in optimal population growth, whereas the green algae and cyanobacteria were of poorer quality. Daphnia showed the highest growth rates in all resources tested. Chydorus attained similar positive growth rates in most of the resources. In contrast, Bosmina achieved positive growth only in Stephanodiscus and Rhodomonas. For Bosmina, a combination of Stephanodiscus and Rhodomonas resulted in a positive synergisic effect on growth. The quality of resources depends greatly on the grazer of interest and cannot be generalized from results with Daphnia alone.
Trophic interactions between copepods and microplankton: A question about the role of diatoms
Authors: Kleppel G. S. , Holliday D. V. , Pieper R. E.
Published: April 2010

Relationships among microplankton composition, copepod diet, and egg production are examined with data from gut content analysis of copepods from California coastal waters and from the Irish Sea, feeding and egg production experiments on Acartia tonsa off southern California, and egg production measurements on copepods from a subtropical estuary (Port Everglades, Florida), temperate shelf waters (southern California, Irish Sea), and the open ocean (Gulf Stream). The copepod species studied appeared to feed preferentially on dinoflagellates and microzooplankton relative to diatoms. Patterns of variability in egg production conform, generally, to changes in dinoflagellate and microzooplankton biomass, but seem to be independent of changes in diatom biomass.
Estimation of phosphorus exchange between littoral and pelagic zones during nighttime convective circulation
Authors: James William F. , Barko John W.
Published: April 2010

A fluorescent dye was used in Eau Galle Reservoir, Wisconsin, to examine nighttime convective circulation patterns and exchanges of P between the littoral and pelagic zones during 25–26 July and 12–13 September 1988. Cooler littoral bottom water moved into the pelagic zone at night as an interflow at 2.5 m in July and at 4.0 m in September. Warmer pelagic water moved into the littoral zone as a surface flow during both periods. The littoral zone exhibited high total P concentrations above the sediment in July, but much lower concentrations in September. Estimated net areal total P flux to the pelagic zone was 1.8 mg m−2 d−1 in July but only 0.2 mg m−2 d−1 in September. Net areal total P flux in July accounted for 22% of the summer average, lakewide internal total P load to the reservoir.
Physiological characteristics and food‐web dynamics of Synechococcus in Lakes Huron and Michigan
Authors: Fahnenstiel Gary L. , Carrick Hunter J. , Iturriaga Rodolfo
Published: April 2010

Single Synechococcus cells accounted for an average of 10% (range 1–26%) of surface mixed‐layer primary production in Lakes Huron and Michigan in 1986–1988. Maximal photosynthetic rates (Pmax) were relatively low (range = 1.9–6.0 fg C cell−1 h−1) and no significant photoinhibition was found at irradiances as high as 3.0 Einst m−2 h−1. Synechococcus growth rates estimated by four techniques (ampicillin, 14C uptake, dilution, and small inocula) ranged from 0.1 to 0.9 d−1 with a mean of 0.37. Although substantial variability was noted among techniques on any one date, on average all estimates were in reasonable agreement with the exception of the dilution estimates which were significantly lower (P < 0.01). Three techniques for estimating grazing loss rates (ampicillin, dilution, and 14C‐labeling of Synechococcus) provided similar estimates ranging from 0.1 to 0.7 d−1. On specific dates, grazing loss rates were 33–120% of growth rates, suggesting that grazing was the major loss for Synechococcus populations in these lakes. Most of the grazing loss (68%) was attributable to small (4–10 µm), heterotrophic flagellates and ciliates. Crustaceans and rotifers accounted for only a small percentage of total grazing loss (5–21%) even when Daphnia accounted for 40% of crustacean biomass.