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采用固相反应制备了Mg1-xCux TiO3(0.00≤x≤0.20)微波介电陶瓷,研究CuO烧结助剂对MgTiO3陶瓷的微观结构和微波介电性能的影响。实验结果表明,CuO中的Cu2+离子会进入到MgTiO3晶格中并取代Mg2+,形成Mg1-xCux TiO3固溶体。由于液相效应,适量的CuO可以促进MgTiO3陶瓷的致密化烧结,降低其烧结温度。Cu2+离子的A位取代会改变样品的TiO6八面体扭曲度。随着Cu2+离子含量的增加,会使MgTiO3陶瓷的结构稳定性降低。随着CuO含量的增加,晶粒的不均匀生长和液相的出现导致样品的品质因数(Qf)下降。同时,Mg1-xCux TiO3陶瓷的相对密度、结构... 相似文献
85.
Cerium doped gadolinium gallium aluminum garnet (GGAG:Ce) ceramic precursors have been synthesized with an ultrasonic chemical co-precipitation method (UCC) and for comparison with a traditional chemical co-precipitation method (TCC). The effect of ultra-sonication on the morphology of powders and the transmittance of GGAG:Ce ceramics are studied. The results indicate that the UCC method can effectively improve the homogenization and sinterability of GGAG:Ce powders, which contribute to obtain high transparent GGAG ceramic with the highest transmittance of 81%. 相似文献
86.
采用固相合成法制备了(WO4)2(NBW)陶瓷,研究了NBW陶瓷的相结构、形貌、烧结特性和微波介电性能。NBW陶瓷在625~800℃烧结1~4 h能够致密化。X射线衍射表明在625~800℃烧结2 h的NBW陶瓷均为四方晶系白钨矿结构的单相陶瓷。随着烧结温度的提高,NBW陶瓷的介电常数、品质因数(Qf值)先增加后降低,谐振频率温度系数逐渐降低。经650℃烧结2 h获得的NBW陶瓷的介电常数为14.36,Qf值为16 503 GHz,谐振频率温度系数为-1.055×10-5℃-1。NBW陶瓷与银共烧反应生成Ag2W2O7相,而与Au、Al共烧具备化学兼容性。 相似文献
87.
In a capillary discharge experiment for the neon-like argon lasing, we have proposed an experimental scheme to verify that the multi-spike of X-ray diode (XRD) signal is a multi-pulse laser or is a reflection of the laser pulse in the XRD.The ceramic capillary has an inner diameter of 3mm and a length of 200mm.At the gas pressure of 28Pa and discharge current of 27kA, stable lasing has been realized.The experimental results prove that the multi-spike of XRD signal is a reflection of the electromagnetic signal produced by the laser pulse in the XRD.The improved electrocircuit scheme of the XRD to minimize the reflection phenomena is also found. 相似文献
88.
Ceramic hollow microspheres (CHMSs) were prepared to use as supports for the removal of heavy metal ions from industrial waste-water. A water extraction sol–gel technique was used to prepare porous CHMS by extracting water from an emulsion of LUDOX (silica colloid; SiO2, Aldrich Co.) and 2-ethyl-1-hexanol. Experiments were conducted to control pore size, wall thickness, and separation yield by examining the ratio of precursors (LUDOX and 2-ethyl-1-hexanol), catalyst (NH4OH), sintering temperature, surfactant (SPAN 80), extractant (n-butanol), stirring speed, and concentration of precursor (LUDOX). The results revealed that the optimum conditions were 20 ml of a 10 wt% solution of LUDOX, 10 ml of NH4OH, a sintering temperature of 500°C, 0.4 ml of SPAN 80, 200 ml of n-butanol, and a stirring speed of 730 rpm/100 ml of 2-ethyl-1-hexanol. CHMSs were impregnated in Cyanex 272 and examined for their ability to remove heavy metal ions from a solution. Based on an experiment involving the removal of metal ions using CHMSs that were prepared under optimum conditions, Zn ion was removed at a level of 0.354 mmol/g at pH 4, which was about twice the adsorption capacity of CHMSs prepared by Wilcox (Mater. Res. Soc. Symp. Proc.346, 201 (1994)). 相似文献
89.
Marc Bourdon Hervé Pajot 《Proceedings of the American Mathematical Society》1999,127(8):2315-2324
In this paper we shall show that the boundary of the hyperbolic building considered by M. Bourdon admits Poincaré type inequalities. Then by using Heinonen-Koskela's work, we shall prove Loewner capacity estimates for some families of curves of and the fact that every quasiconformal homeomorphism is quasisymmetric. Therefore by these results, the answer to questions 19 and 20 of Heinonen and Semmes (Thirty-three YES or NO questions about mappings, measures and metrics, Conform Geom. Dyn. 1 (1997), 1-12) is NO.
90.
Let ( G) be a flag-transitive c.c*-geometry whose point-stabilizer is not an affine group. We list all known examples and show that, if (, G) is a minimal unknown example, then G is an almost simple group and the commutator subgroup G is a simple group of Lie type. 相似文献