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排序方式: 共有7665条查询结果,搜索用时 15 毫秒
61.
机械活化-湿化学合成LiMn2O4的组成、结构与表征 总被引:4,自引:2,他引:4
以MnO2和LiOH·H2O为原料,采用机械活化与湿化学集成的方法,在水溶液中直接合成了结晶态的尖晶石锂锰氧化物.当锂含量介于3.78%~4.35%之间时,所得锂锰氧化物为纳米级球形粉末,以尖晶石结构为主,含极少量的Mn3O4杂相;在300~800℃温度范围内热处理后,Mn3O4杂相消失,尖晶石结构更趋完善.所合成的含锂5.80%的高锂样品则以LiMnO2层状结构为主,含少量Mn3O4杂相,其SEM形貌为片状;在300~700℃下热处理8 h后,层状LiMnO2转变成尖晶石LiMn2O4,Mn3O4杂相峰明显减弱并随热处理温度的升高而消失;当温度升高至700~800℃时,开始出现缺锂的Li1-xMn2O4相.结果表明:该法制备锂锰氧化物可实现锂、锰、氧在原子级水平的均匀混合,所得产物的热稳定性能良好,其化学计量组成与结构易于调整和控制. 相似文献
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63.
Desilication from illite by thermochemical activation 总被引:1,自引:0,他引:1
Illite occurs widely in bauxite ores and results in low alumina grade of the ores. Differential thermal analysis (DTA), thermal gravimetric analysis (TGA) and X-ray diffraction analysis (XRD) show the OH groups split off from the structural framework of illite between 500 ℃ and 700 ℃. With the increase in temperature up to about 1 100 ℃, the layer structure of illite breaks up and Si in the layers is transformed into the amorphous state. Meanwhile, mullite comes out at 1 100 ℃. Quartz occurring in illite keeps unchanged in structure in the range of 500 -1 200 ℃. A desilication process from illite by thermochemical activation followed by alkali leaching is therefore developed on the basis of the behavior that amorphous silica is alkali soluble. The investigation finds that the optimum parameters for desilication are activation temperature of 1 100 - 1 150 ℃, activation time of 90 - 120 min, leaching temperature of 95 - 110 ℃, leaching time of 90 - 120 min and concentration of caustic soda (Na2Ok) 120 - 150 g/L. An overall desilication about 45% is attained under these conditions. XRD analysis confirms that the active amorphous SiO2 has been dissolved in the alkali solution and removed from the samples, while quartz and mullite have not. The investigation also shows that the formation of mullite during activation and formation of sodium hydroalu minosilicates (Na96 Al96 Si96 O384 and 0.95Na2 O · Al2 O3 · 3.25SiO2 · 4.79 H2 O) during leaching lead to the relatively low desilication of illite. 相似文献
64.
晶化机制与激活能的晶化速率参比法确定 总被引:1,自引:0,他引:1
本文根据修正的Kissinger公式提出一种确定非晶材料晶化机制与激活能的最大晶化速率参比法。以Ar_(70)Cu_(30)非晶合金为例,研究了晶化机制与激活能及其与压力的关系。 相似文献
65.
T. Yang B.H. LiDepartment of Materials Physics University of Science Technology Beijing Beijing ChinaK. Kang T. SuzukiInformation Storage Materials Laboratory Toyota Technological Institute Nagoya - Japan 《金属学报(英文版)》2003,16(4):261-265
(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25m3, showing the promising of being the recording medium for future high density perpendicular recording. 相似文献
66.
LI Ximing CHEN Jiayong Institute of Chemical Metallurgy Academia Sinica Beijing ChinaR.KAMMEL Institut Für Metallurgie Technische Universitt Berlin Germany Research Assistant Institute of Chemical Metallurgy Academia Sinica Beijing China 《金属学报(英文版)》1992,5(9):153-157
The influence of mechanical activation on the leaching behaviour of scheelite was studied bymeans of fine grinding in an attritor and subsequently HCl leaching in presence of PO_4~(3-).Results showed that after fine grinding in the attritor,the reaction rate of scheelitewith HCl-Na_3PO_4 solution was remarkably increased,the extraction of W increased fromabout 8 to 99%.The IR spectra and X-ray diffraction analysis indicated that in addition toan enlargement of surface area the fine grinding action had made also changes of fine struc-ture and reactivity of solid surface,hence the leaching process of scheelite can be carried outunder mild leaching conditions. 相似文献
67.
68.
Ti40阻燃钛合金的高温蠕变行为 总被引:7,自引:0,他引:7
计算了Ti40合金在不同应力、不同温度下的稳态蠕变速率、应力指数及在460℃-540℃范围内蠕变激活能Q=94.0kJ/mol,并以此基础上研究了其蠕变强化机制。实验结果表明:该合金在此温度范围内的蠕变受位错和扩散双重机制控制,晶界移动对蠕变也有一定的贡献。在目前实验条件下,Ti40合金在620℃蠕变性能较差。 相似文献
69.
The deformation mechanisms in a wide temperature rnage from room temperature to 1200K were investigated by thermal activation approach.Using observed instantaneous stress response to the strain rate jump (Δσtr),the activation volume Vs,then the activation enthalpy ΔH,activation free enthalpy ΔG and activation entropy ΔS were calculated.The apparent activation energy of high temperature deformation is estimated to be 3.66eV,which is larger than the self-diffusion coefficient of binary TiAl(3.01eV).The dislocations at 1173K are generally curved or bowed,even helical-shaped dislocations.The climb of ordinary dislocations as well as twinning has grealty contributed to the plastic deformation.The CRSS at 1173K is estimated to be 180MPa.The higher resisting stress at both room temperature and elevated temperature might relate to the high Nb content of the alloy. 相似文献
70.