NIE Shuhong, LIU Xiaolong, XIONG Shoumei, LIU Baicheng. Characterization of Surface Films Formed on Molten Magnesium with Air and SF6 as Protective Gases[J]. Journal of Materials Engineering, 2005, 0(6): 3-6,26.
The characterization of surface films of magnesium melt protected by air and SF6 gases was studied. As the exposure time increases, the atom fraction of fluorine in surface films increases, while the atom fraction of oxygen almost keeps unchanged. Therefore, the reaction between magnesium and protective gases should mainly happen between magnesium and fluorine after the initial film is formed. The SEM observations of the cross section of the surface films show that there are some discontinuous small semicircular white spots which contain about 74% atom fraction in some near surface zone; and there are some white cingula with different thickness in the other near surface zone with distinct uneven fluorine content. The crystal size in surface films increases with the increase of the exposure time under protective atmosphere. Many cracks appear on the surface films of the solidified magnesium, these cracks may result from the shrinkage of surface film with crystal growing up and the shrinkage of bulk magnesium when the temperature lowers down.
PAN Chongchao, LI Dianguo, LING Gang, YIN FaJie, MA TianJun. Model for Flow Stress of Fe-15Cr-25Ni Superalloy Under Hot Compression[J]. Journal of Materials Engineering, 2005, 0(6): 7-10,30.
The flow stress of Fe-15Cr-25Ni superalloy was investigated in the temperature range from 950℃ to 1200℃ and at strain rate range from 0.005s-1 to 1.0s-1 on Gletble-1500 test machine. The experimental results show that dynamic recrystallization occur in evidence during hot compression of Fe-15Cr-25Ni superalloy in the experiment condition. The flow stress of Fe-15Cr-25Ni superalloy can be represented by a Zener-Hollom parameter in the hyperbolic logarithm type equation. The regressed peak stress expression is σp=2.3139ln ε+9.580495×105·Τ-1-538.12. The hot deformation activation energy of Fe-15Cr-25Ni superalloy during hot compression is 373.71kJ/mol.
TANG Gengping, CHENG Haifeng, ZHAO Jianfeng, CHU Zengyong, ZHOU Yongjiang. Surface Modification on Cenospheres and Its Wave Absorbing Properties[J]. Journal of Materials Engineering, 2005, 0(6): 11-12,35.
The magnetic film plating on the surface of cenospheres was studied by chemical vapor deposition method. The results of SEM and EDAX analysis indicated that iron could be plated on the surface of cenospheres comparatively homogenous. Absorbing materials made of modified cenospheres were prepared and tested. The modified cenospheres exhibited excellent wave absorbing properties at the testing frequency range from 8GHz to 18GHz,the reflectivity was below -10dB at the frequency range from 17.2GHz to 18GHz and the lowest reflectivity was -11.27dB at 18GHz.
YUAN Jie, XIAO Gang, CAO Maosheng. Programmed Realization for Multi-layered Thin Radar Absorbing Materials Using Genetic Algorithms[J]. Journal of Materials Engineering, 2005, 0(6): 13-16,40.
The method and programmed realization for multi-layered RAMs system, based on optimization design towards integration CAD system, were studied in the article. The system was based on both an optimization engine on genetic algorithms, and reflection index was calculated by means of transmission-line or tracking calculation. The electromagnetic parameter database was realized by server software-MYSQL based on open source software. Therefore, under the open source software system, the intelligent system of calculating design and performance prediction towards multi-layered RAMs was created successfully. The optimization calculating of multi-generation towards multi-layered RAMs was carried out, and the ideal design results were gained. Finally, the evaluation both result and intelligent system were also given.
HE Qian, LIU Lin, ZOU Guangrong, LI Shuangming, LI Houbu, FU Hengzhi. Investigation of Microstructure of Nd-Fe-B Peritectic Alloys Under Directional Solidification[J]. Journal of Materials Engineering, 2005, 0(6): 17-19,44.
The solidification microstructure of NdxFe100-1.5xB0.5x(x=10.8%,11.76%,13.5%) alloys are researched at the withdraw velocity ranging from 5μm/s to 500μm/s under directional solidification. The results indicate that the final microstructure of three compositions alloys is all primary α-Fe phase, Nd2Fe14B phase and Nd-rich phase. With increase of withdraw velocity, primary dendrite arm spacing of primary α-Fe phase decreases, the volume fraction of primary α-Fe phase decreases and then increases,Nd2Fe14B phase increases and then decreases.
SONG Guixiang, LIU Junhai, HUANG Jihua, ZHANG Jiangang. Influence of Composition Parameters on In situ Reactive Synthesis of TiC/Cr18Ni8 Steel Bonded Carbides[J]. Journal of Materials Engineering, 2005, 0(6): 20-23,49.
TiC/stainless steel-bonded-carbides was in situ synthesized by vacuum sintering the compacts of mixed ferrotitanium, ferrochromium, iron and carbon powders, etc. The microstructure of the steel bonded carbides was analyzed by scanning electron microscope(SEM), X-ray diffraction(XRD) and EDS.The results show that TiC particles are fine and the particle sizes are mostly less than 1μm.With the increasing of drafted amount of the hard phase TiC, the porosity of steel bonded carbides and the size of TiC particles increased,but the density and hardness of steel bonded carbides decreased. The steel-bonded-carbides which drafted C/Ti atomic ratio is 0.9 has higher density and hardness, better refinement and much uniform of TiC particles than those that drafted C/Ti atomic ratio 1.0.
Wuyunqiqige, LIAO Zilong. Study on Properties of 3233 Resin[J]. Journal of Materials Engineering, 2005, 0(6): 24-26.
Apparent activation energy and kinetic order of 3233 moderate temperature curing epoxy resin system were determined by DSC tests.The results showed that curing reaction activation energy was 85.05 kJ/mol and reaction order was 0.971. According to DSC analysis and viscosity-temperature curve,the optimal curing procedure was determined,and it was curing at 125℃ for 90min.
WANG Zhengping, CHEN Xingjuan, LI Chensha. Preparation of Mesoporous TiO2 and the Photocatalytic Activity of Degradating Rhodamine[J]. Journal of Materials Engineering, 2005, 0(6): 27-30.
Using cetyl trimethyl ammoniunm bromide as templating agent, the mesoporous TiO2 with special performance was synthesized by a tartaric acid sol-gel method. The UV irradiation was used in this process. The TiO2 was analyzed and characterized by XRD, adsorption-desorption, UV-VIS spectra, DRS, surface photovoltage spectroscopy (SPS). Using ultraviolet lamp as light source, the photocatalytic activity of photo-assisted mesoporous TiO2 katalyst was studied by photodegradation of Rhodamine B.
MENG Bo, TAN Xiaoyao, YANG Naitao, ZHANG Baoyan. Synthesis and Characterization of SrCe0.95Y0.05O3-δ Nano Powders by the Low Temperature Combustion[J]. Journal of Materials Engineering, 2005, 0(6): 31-35.
Nanosized SrCe0.95Y0.05O3-δ powders with homogeneous composition were synthesized via the low temperature combustion process based on the Pechini method. A polymeric precursor sol was formed by using of nitric acid and ethylene glycol as chelating agents of metal ions. The perovskite-type SrCe0.95Y0.05O3-δ powders, smaller than 25nm in size and uniform in shape, were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. Sample characterization was performed by means of thermal analysis (TA), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope(TEM). The powder, when pressed and sintered in air at 1300℃ for 10h, attained the sintered density ≈96% of its theoretical density.
YANG Wei, CAO Chuantang, CAO Chuanbao. Synthesis of LiFePO4 by Liquid-state Co-precipitation Method and Its Performance[J]. Journal of Materials Engineering, 2005, 0(6): 36-40.
The cathode materials of LiFePO4 were synthesized under liquid-state co-precipitation method. The crystalline structures,morphology of particles,spectroscopic character were investigated by X-ray diffraction, scanning electron microscopy and FTIR. Morphology of particles and electrochemical performance were also compared with that synthesized by solid-state reaction. The results showed that LiFePO4 were simple pure olive-type phase, and exhibit a 3.4V discharge voltage plateau.LiFePO4 as prepared possessed excellent electrochemical performance, whose first specific capacities were 142.3mAh/g at0.2mA/cm2,127mAh/g at 0.4 mA/cm2, after 20 times cycling, the specific capacities were 129.7mAh/g,105.5mAh/g respectively.
GU Lixin, JIN Jianjun, LIU Furong. Effect of Heat Treatment on Microstructure and Hardness of 9Cr13Ni6Co5Be Steel[J]. Journal of Materials Engineering, 2005, 0(6): 41-44.
The effect of heat treatment on microstructure and hardness of 9Cr13Ni6Co5Be steel was studied.The results showed that the highest hardness was gained on quenching at 1020℃. The hardness has unconspicuous change after tempering under 350℃. Tempering at about 470℃ the formation of finely dispersed Be2Fe phase which coherent with the matrix was responsible to the peak of hardness of steel.
ZHANG Wei, FAN Zhikang, XU Guohui, WEN Jiuba. Effect of Diffusion on Cyclic Oxidation and Spalling Resistance of Aluminized Steel[J]. Journal of Materials Engineering, 2005, 0(6): 45-49.
The cyclic oxidation, spalling resistance and mechanisms of hot dip aluminizing steel were studied by different diffusion treatment. The results show that, with the diffusion temperament rising and time prolonging, the voids of the diffusion layer continuously increase and a wavy voids zone forms between subsurface layer and transition layer due to the aggregation of voids. The wavy void zone aggregates further into a lineal crack parallel to surface and the internal oxidation occurs in it during high temperament oxidation. Therefore, the cyclic oxidation resistance of hot dip aluminizing steel is controlled both by the internal oxidation and external oxidation of diffusion layer and the formation of voids seriously influences cyclic spalling resistance. The optimum technical parameter is diffusion at 900℃ for 2 hours.
ZHANG Ming, XU Yahong, XING Jun, AN Xuefeng, YI Xiaosu. Study on Rheological Behavior of 3266 Epoxy for Resin Transfer Molding[J]. Journal of Materials Engineering, 2005, 0(6): 50-53,58.
The rheological behavior of epoxy resin for resin transfer molding(RTM) was studied with DSC analysis and viscosity experiments. A rheological model based on the dual-Arrhenius equation was established and used to simulate the rheological behavior of the resin. The model prediction determined from the dual-Arrhenius equation was in good agreement with experimental data. The processing window of the resin system can be well determined based on the developed model. The rheological model is important for processing simulation and quality control of RTM processing for high performance composites.
Many kinds of one-dimensional nanomaterials have been prepared by the oxide-assisted growth mechanism,which was proposed during the preparation of silicon nanowires. The oxide-assisted growth mechanism and preparation methods of silicon nanowires according to the oxide-assisted growth mechanism are introduced. The effects on different gases, pressures, and starting materials for synthesizing silicon nanowires using oxide-assisted method is reviewed in detail, and the development direction of studying silicon nanowires is also discussed.
HAN Yuanyuan, ZHANG Yumin, HAN Jiecai, ZHANG Jianhan, YAO Wang, ZHOU Yufeng. Development of the Silicon Carbide Mirror and System in the World[J]. Journal of Materials Engineering, 2005, 0(6): 59-63.
Physical properties of several kinds of general mirror materials are compared. Many characters of the most promising SiC mirror material are listed. The development of the SiC mirror manufacture, optical surfacing and SiC system are introduced. The prospect of SiC mirror and system is also suggested briefly.
