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The influence of temperature, pH, acid type, and surface area on the kinetics of the acid dissolution of natural and synthetic
willemites and natural hemimorphites has been investigated. Specific rate constants, based upon areas determined by krypton
adsorption measurements, were estimated from the experimental data obtained. For both willemite and hemimorphite, the rates
of dissolution in different acids are shown to be related to the relative strengths of zinc-acid anion complexes. The reactivity
of willemite toward acids increases with increasing replacement of zinc by manganese. Mixed chemical/diffusion control is
responsible for the observed rates of willemite dissolution under the conditions studied (HNO3, HCl, HClO4, H3PO4, H2SO4, pH 0.31 to 3.00,T 21 to 94 °C). Estimates of the relative contributions of chemical and diffusional resistances to the overall rate have been
made for the dissolution of manganese-free willemite in sulfuric acid solutions. The experimentally measured rates have been
demonstrated to be in reasonable agreement with predicted overall dissolution rates. Proposals are made regarding the nature
of the diffusion and chemical steps involved in the dissolution process. Hemimorphite was found to be considerably more reactive
than willemite and its dissolution is primarily diffusion controlled under the conditions studied (T 20 to 76 °C, pH 2 to 3.5).
Formerly a Postgraduate Research Student, Department of Metallurgy and Materials Science, Royal School of Mines, Imperial
College, London 相似文献
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(ZrO2)0.96(Y2O3)0.03(Al2O3)0.01陶瓷的制备及性能研究 总被引:1,自引:0,他引:1
采用化学共沉淀法制备(ZrO2)0.96(Y2O3)0.03(Al2O3)0.01的粉末, 在不同的升温速率、不同的烧结时间和不同的烧结温度等烧结工艺下制备出(ZrO2)0.96(Y2O3)0.03(Al2O3)0.01三相体系复合陶瓷. 经研究发现, 在升温速率和降温速率均为5 ℃·min^-1 的烧结制度下, 1550 ℃烧结时, 可以得到抗弯强度达998 MPa, 抗热震次数达33次, 相对密度达96%和电性能较好的烧结体. 相似文献
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