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111.
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
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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
114.
锻模型腔的电解加工技术 总被引:1,自引:0,他引:1
通过电解加工与其它常用加工方法的比较,以及电解加工应用的实例,论证了电解加工是提高锤模型腔加工水平的重要工艺手段。 相似文献
115.
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
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The relative reactivities of the lower alkanes in hydrogenolysis on a Pt/Al2O3 catalyst depend on the H2 pressure used, as do those of a Ru/Al2O3 catalyst, pretreated in various ways, for propane hydrogenolysis. Apparent activation energies also vary with H2 pressure. No single rate measurement adequately represents catalytic activity, which is properly defined as the rateconstant for the slow step. 相似文献
119.
A programmed temperature technique has been developed for the measurement of the self-diffusion coefficients of additives in polymers. This has been applied to the diffusion of three dialkylphthalate plasticizers in poly(vinyl chloride). Values of the self-diffusion coefficients and the calculated activation energies obtained in this way have been compared with values previously obtained from measurements at constant temperature. It has been shown that the programmed temperature technique gives a very rapid method for the estimation of the activation energy of self-diffusion. 相似文献
120.
Alkyl radicals produced in the indirect reduction of alkyl halides or alkyldimethylsulfonium salts by electrochemically generated aromatic radical anions couple fast with the latter and alkylated or dialkylated dihydro compounds are formed. Rate constants measured for the coupling reaction between on one hand methyl, primary, secondary and tertiary alkyl radicals as well as benzyl and cumyl radicals and on the other hand a wide spectrum of electrochemically generated aromatic radical anions are found to be about 1×109 M−1 s−1. Previous measurements of coupling rate constants for primary alkyl radicals have been re-evaluated since they were affected by the presence of an SN2 reaction occurring between the alkyl halides used as radical precursors and the aromatic radical anions. New experiments are also included using alkyldimethylsulfonium salts as precursors in order to prevent such SN2 artefacts. It is concluded that sterical hindrance does not play a significant role for the radical-radical anion coupling reactions. In general the rate constants for the coupling reactions are all close to 109 M−1 s−1. 相似文献