Effects of La~(3 ) doping on MnZn ferrite nanoscale particles synthesized by hydrothermal method

1　INTRODUCTIONMnZnferritesarewidelyusedinelectronicappli cationsbecauseoftheirhigh permeabilityandlowmagneticlossesathighfrequencies[1,2 ] .Theproper tiesofferritesdependlargelyontheirmicrostructure ,sothenano techniqueisintroducedtocontroltheirultramicrostructure ,insteadofthetraditionalceramicway .Additionally ,aprecisesmallamountofcationicsubstitutionisusedusually .ThemagneticlossofMnZn ferritesdopedwithCaO SiO2 athighfrequencyisdiminishedforincreasesofresistivitylayersatgrainbound…     

中低温固体氧化物燃料电池合金连接体保护涂层研究进展

Fe-Cr铁素体合金是中低温固体氧化物燃料电池理想的连接体材料,但其在高温下缺乏良好的抗氧化性能,且会引起阴极"Cr中毒"现象,影响了电池的高效安全运行,目前解决上述问题的主要方法是对合金连接体进行表面改性,在连接体表面开发导电性保护涂层。介绍了中低温固体氧化物燃料电池Fe-Cr合金连接体表面涂层材料的主要作用和具体要求,着重阐述了目前连接体涂层材料的主要类型及其研究进展,并指出了目前该领域研究中存在的问题及今后的发展方向。     

非晶晶化法制备高性能ZTM微纳米复相陶瓷

采用非晶晶化法制备了Si-Al-Zr-O系氧化锆增韧莫来石(ZTM)微纳米复相陶瓷.分析了不同热处理温度和氧化锆含量对材料微观结构及其力学性能的影响.锆含量为15%(质量分数)的样品在1150℃热处理后能得到较好的力学性能,断裂韧性和抗弯强度分别达到了5.13 MPa·m1/2,520 MPa.比用传统方法制各的ZTM陶瓷性能提高约40%.     

Mechanical properties and structure of zirconia-mullite ceramics prepared by in-situ controlled crystallization of Si-A1-Zr-O amorphous bulk

Zirconia-mullite nano-composite ceramics were fabricated by in-situ controlled crystallization of Si-A1-Zr-O amorphous bulk, which were first treated at 900-1 000℃ for nucleation, then treated at higher temperature for crystallization to obtain ultra-fine zirconia-mullite composite ceramics. The effects of treating temperature and ZrO2 addition on mechanical properties and microstructure were analyzed. A unique structure in which there are a lot of near equiaxed t-ZrO2 grains and fine yield-cracks has been developed in the samples with 15% zirconia addition treated at 1 150℃. This specific microstructure is much more effective in toughening ceramics matrix and results in the best mechanical properties. The flexural strength and fracture toughness are 520 MPa and 5.13 MPa·m^1/2, respectively. Either higher zirconia addition or higher crystallization temperature will produce large size rod-like ZrO2 and mullite grains, which are of negative effect on mechanical properties of this new composite ceramics.     

加入WTO湖南高教面临的挑战和对策

通过分析加入ＷＴＯ后对我国高等教育可能的冲击和湖南高等教育与其他省区的差距，提出了地处内陆、高等教育不发达的湖南，如何利用加入ＷＴＯ后的机遇，在高等教育领域缩小与国际先进水平、国内先进水平的差距的对策。     

高锆Si-Al-Zr-O系非晶晶化过程

采用差示扫描量热分析(DSC)、X射线衍射(XRD)分析、红外光谱(IR)分析和扫描电镜(SEM)观察等方法,对Si-Al-Zr-O系非晶晶化过程、晶核剂对晶化过程的影响进行了研究.结果表明:Si-Al-Zr-O系非晶在935～970℃和1 100～1 200℃分别发生了四方氧化锆和莫来石的析出反应;TiO2和ZrO2作为晶核剂引入对四方氧化锆和莫来石的析出有一定影响;TiO2含量的增加可使四方氧化锆晶相的析出能力显著提高,而ZrO2含量的增加可提高莫来石晶相的析出能力.根据晶化过程的研究结果制定了合理的晶化热处理工艺,并获得晶粒大小均匀、结构致密的微米晶、纳米晶、莫来石/SiO2-t-ZrO2复相陶瓷.     

Chemistry principles for thermoplastic polymer binder formula selection for powder injection molding

The polymer binder selection is one of the very important aspects for the powder injection molding.However, even nowadays the binder selection is still mainly performed by try and error method, Six commercial or intensive studied binder formulas were analyzed according to state diagram and chemical characteristics of ingredients in each binder formula. In addition, the interactions between the binder components and additives were also taken into account. Based on the analysis, the optimum binder formula was selected and some selection criterions were put forward for the binder and additives.     

预变形对含Sc铝锂合金拉伸性能和显微组织的影响

研究了Ａｌ－１．４２Ｌｉ－２．４１Ｃｕ－０．９３Ｍｇ－０．０７３Ｚｒ－０．１７Ｓｃ（ｗｔ％）合金在１６０℃和预变形（１７％）＋１６０℃不同时效时间下的室温拉伸性能。利用透射电（ＴＥＭ）观察了合金的显微组织。结果表明：该合金具有较好的室温室性能，合金主要强化相为δ＇（Ａｌ３Ｌｉ）和δ＇／β复合相。由于合金中同时加入Ｓｃ，Ｚｒ，尤其是添加了０．１７ｗｔ％Ｓｃ导致大量的复合相出现（复合相粒径为２４～３２     

Al—TiO2自蔓延高温合成反应机理

以激冷法制得的高纯、超细金属铝粉和化学纯试剂TiO_2为原料,通过对燃烧过程的观察分析和结构、成分、化学状态分析,研究了Al-TiO_2自蔓延高温合成(SHS)反应的机理。结果表明,反应分三阶段:反应前期、反应期、产物反应期。反应前期主要反应是液态铝表面氧化膜分解。反应期则发生Al与TiO_2的界面反应,并诱发TiO_2颗粒链式劈裂效应,使反应速度成倍增长,最后反应放出足够的热量将TiO_2熔化,使反应以燃烧的形式进行,合成Ti、Al_2O_3。最后是合成产物进一步反应形成微量TiO、TiO_2。     

New development of Einstein′s viscose law for powder suspension systems

Through the analysis of the present situation of the rheology of suspension disperse systems, the classical Einstein′s viscosity law was developed into the generalized Einstein′s viscosity law which can be further developed into universalized form, called the universalized Einstein′s viscosity law by introducing modification function f(φ). Some rational forms of the function f(φ) were discussed according to functional approximation method, and were consequently developed into a few suspension disperse system rheological equations suitable for high particle concentration. These equations all keep good consistence with the models acquired in experiments or other mathematical physics analysis.