机械活化闪锌矿的量热研究

用Calvet型微量热计对不同条件下机械活化闪锌矿进行了量热实验, 并对量热前后的活化闪锌矿进行透射电镜（TEM）、 X射线衍射（XRD）及激光粒度测试。 结果表明： 闪锌矿经机械活化后, 在量热过程中存在能量释放; 随着活化时间的增加, 能量释放依次增加;在不同气氛下, 机械活化闪锌矿能量释放基本一致。 量热前后其晶体结构不变, 但能量释放后颗粒变粗, 细粒子明显减少, 表面积减小, 初步认为该能量释放是由于温度升高导致细粒子团聚,表面积减少而引起的。     

机械活化黄铁矿的热分解动力学

用Friedman法研究了未活化黄铁矿和机械活化不同时间的黄铁矿 (机械活化 2 0min和 40min的黄铁矿分别记为黄铁矿 1和黄铁矿 2 )在升温速率分别为 2 .5 ,5 ,7.5和 15K/min下的热分解动力学。结果表明 ,未活化黄铁矿及机械活化黄铁矿 1和黄铁矿 2的表观活化能 (E)、反应级数 (n)和指前因子 (A)分别为 :2 6 8.6 12kJ/mol,0 .42 ,1.0 94× 10 15min-1;2 43.72 5kJ/mol,0 .6 2 ,2 .0 0 8× 10 13 min -1和 177.2 88kJ/mol,0 .6 5 ,5 .92 4× 10 15min-1。对黄铁矿的X射线衍射谱进行线形分析 ,求取机械活化黄铁矿 1和黄铁矿 2的晶格畸变率 (ε)和晶块尺寸(D)。发现黄铁矿的热分解活化能降低与活化后黄铁矿的晶格畸变率增大及晶块尺寸降低有关     

机械活化对闪锌矿物化性质及焙烧动力学的影响

研究机械活化对闪锌矿的物化性质以及焙烧宏观动力学的影响,采用X射线衍射仪、扫描电镜、激光粒度分析仪、比表面积测试仪、热重分析,分析活化前后闪锌矿的晶体结构、表观形貌、粒度和比表面积的变化规律。使用MDTA分析法研究未活化与机械活化闪锌矿在空气气氛下的氧化焙烧宏观动力学。结果表明：机械活化使闪锌矿的物化性质发生明显改变。在焙烧过程中,经过机械活化的闪锌矿氧化速率远大于未活化闪锌矿的。机械活化可显著提高闪锌矿的反应活性。经机械活化30、120 min后,闪锌矿在焙烧过程中的表观活化能由未活化时的239.78 kJ/mol分别降至171.25和57.17 kJ/mol。并计算出其相应的非等温氧化动力学方程。     

机械活化对异极矿碱法浸出及物理性能的影响

为了提高异极矿在碱性溶液中的浸出效率, 采用QM-1SP行星球磨机对云南南坪异极矿进行机械活化强化浸出研究.通过浸出动力学实验、扫描电镜分析(SEM)、粒度分析、热重-差热分析、X射线衍射分析探讨机械活化对异极矿晶体结构和浸出行为影响的规律.结果表明:机械活化使异极矿细化分散、矿晶格显著畸变并在表面形成非晶态层,矿物颗粒处于高能亚稳态;机械活化可有效阻止不溶性浸出产物在矿物颗粒表面的积累,消除直接浸出的停滞期,使浸出速率加快,相同浸时间内锌浸出率显著提高;碱法直接浸出异极矿浸出率达到80.5%需6 h,球磨15 min后异极矿达到相同浸出率仅需3 h;磨-浸结合(Mechano-chemical)具有更佳的浸出效果.     

机械活化和氧化-还原处理对攀西钛铁矿精矿盐酸浸出的影响(英文)

研究机械活化和氧化-还原处理对攀西钛铁矿精矿盐酸浸出过程的影响。结果表明:机械活化和氧化-还原处理均可明显提高钛铁矿精矿中铁、钙和镁的浸出;氧化-还原处理的钛铁矿经盐酸浸出后得到的人造金红石,其钙镁含量过高,不能满足沸腾氯化法的要求;经机械活化处理的氧化-还原钛铁矿,能进一步降低盐酸浸出渣的钙镁含量,所得到的人造金红石含TiO290.50%、全铁1.37%、钙镁总量1.00%,完全满足沸腾氯化法的生产要求。最佳的氧化还原处理条件为:在900℃氧气气氛中氧化15min,在750℃氢气气氛中还原30min。     

机械活化黄铁矿的活性与失效性

通过比较由活化和未活化黄铁矿在相同种类、相同浓度的电解质溶液中构成原电池的最大电势差,确定了活化矿的失效性和最佳活化时间。实验结果表明,经机械活化10min后的黄铁矿具有更高的能量和活性,随着电解质浓度增加活化矿呈现更大的反应活性,且机械活化后 矿物活性随搁置时间增加迅速下降,10天后则完全丧失活性。     

用镍机械研磨的ZrCrNi合金及其活化行为

韩国汉阳大学冶金工程系 Ｃ． Ｂ． Ｊｕｎｇ、Ｊ．Ｈ．Ｋｉｍ和Ｋ．Ｓ．Ｌｃｅ最近共同发表文章指出,人们已经广泛地研究 ＡＢ、ＡＢ_２和 ＡＢ_５型储氢合金;在这些类型的合金中,ＡＢ２型的Ｌａｖｅｓ相合金是一种对于氢能用途来说很有前途的材料,原因是不仅其储氢能力比较高,而且循环寿命也比较长． 值得注意的是,这些韩国人是采用纯净的镍粉进行机械研磨的方法改善了ＺｒＣｒＮｉ合金的电解活性和活化行为．研究结果显示,机械合金化（ＭＡ）或者机械研磨（ＭＭ）是生产具有控制显微组织的金属粉末复合材料的有效途径,其基本过程…     

铸造生产用高岭土和膨润土的机械活化

本文说明了机械活化对高岭土和膨润土性质的影响。通过实验得出结论：对于各种晶体化学结构的黏土,在行星式球磨机中进行机械活化,经历不同的研磨时间后可达到最大限度的粒度分散和活化,〈1μm的微米含量增加5%～10%,黏土悬浮液的胶度增加15%～20%,吸水率降低1.2～1.5倍,从而使型砂强度提高1.5～2倍,保证节约天然黏土20%～30%,减少铸件废品5%～10%;通过实验确认了在合理规程内的机械活化效率。     

黄铜矿机械活化的研究进展

黄铜矿是自然界分布最广的含铜矿物。采用湿法处理黄铜矿经济环保,较低的浸出速率限制了其应用。机械活化预处理是促进黄铜矿浸出的重要手段,该工艺在国内外受到广泛关注。本文对机械活化的原理、机械活化对黄铜矿物理化学性质和浸出的影响以及机械活化在黄铜矿生产中的应用进行了系统综述。通过机械活化可以降低黄铜矿粒度、增大比表面积、降低晶格尺寸、提高微应变和非晶化程度等,进而提高反应活性、降低反应温度、大幅度提高浸出率和浸出速度。对于黄铜矿的机械活化湿法提取技术、降低能耗和规模化应用依然是有待改进的关键。     

白钨精矿的机械活化碱分解

测定了氢氧化钠与白钨反应的平衡常数，初步查明了有关动力学规律性，从理论到实践完善了氢氧化钠分解白钨精矿的新工艺。在１６０℃下，碱用量为理论量的２．２０￣２．４０倍时，保温１ｈ左右，白钨精矿分解率达９８．３３％￣９９．３９％。     

Quantum-mechanical study of effect of lattice defects on surface properties and copper activation of sphalerite surface

The electronic properties of sphalerite (110) surface bearing Fe, Mn and Cd impurities were calculated using density-functional theory, and the effects of impurities on the copper activation of sphalerite were investigated. Calculated results indicate that both Fe and Mn impurities narrow the band gap of sphalerite surface and lead to the Fermi level shifting to conduction band. Impurity levels composed of Fe 3d and Mn 3d orbital appearing in band gap are beneficial to electrons transfer from the valence band to the conduction band and promote the surface conductivity and the electrochemical activity. The results show that Fe and Mn impurities cannot be replaced by Cu atom, which reduces the exchange sites (Zn) for Cu atom, hence Fe- and Mn-bearing sphalerites are hard to be activated by copper. Cd impurity has little effect on electronic structure of sphalerite surface; however, Cd atom is easily replaced by Cu atom, and this is the reason why the Cd-bearing sphalerite can be easily floated.     

High-Temperature Oxidation Behavior of Chromium: Effect of Different Batches

The isothermal and cyclic-oxidation behavior of three different batches of commercial chromium (purity >99.9%) at 900 and 1000°C has been investigated by means of conventional thermogravimetry and thin-layer activation. Two batches with a similar microstructure and one, with a five times larger average grain size, were used. Isothermal-oxidation experiments were performed in synthetic air for 150 hr. Cyclic-oxidation experiments were executed in static laboratory air with each cycle corresponding to a period of 1 hr at test temperature and 12 min at ambient temperature up to a maximum of 3000 cycles. Results showed significant differences between the oxidation behavior of chromium derived from the three different batches. This was found under isothermal as well as under cyclic-oxidation conditions, especially at 1000°C. The mass-loss rates during cyclic oxidation for the different batches differed up to more than 30 times at 1000°C. In addition, the complementary nature of the different specimen-evaluation techniques, i.e., conventional thermogravimetry and thin-layer activation in cyclic oxidation is shown.     

机械合金化ODS钴基合金粉末的放电等离子烧结

采用机械合金化（MA）和放电等离子烧结（SPS）技术制备了Y2O3弥散强化Co基合金,研究了高能球磨过程中粉末形貌和微观结构的变化规律以及机械合金化粉末的放电等离子烧结行为。结果表明：在球磨的初始阶段（≤8h）,粉末粒度和晶粒尺寸显著减小,晶格畸变增大;球磨8h以后,粉末粒度、晶粒尺寸和晶格畸变的变化渐缓;但进一步延长球磨时间,使Y2O3弥散粒子的分布更加均匀。采用放电等离子烧结技术,在1100℃,10min条件下便可制备出相对密度〉99％的合金试样,所得合金平均晶粒小于5μm,经过均匀化热处理后,合金的室温抗压强度和压缩延伸率分别达到1982MPa和27％,优于铸造钻基合金。     

全球钛原料现状与市场展望

发展正交结构的高压相β-TiO2可通过高能球磨锐钛矿TiO2而得到。高能机械球磨减小了颗粒尺寸,球磨40h后,发现样品存在2nm～4nm的类点状颗粒和10nm～35nm的类花瓣状颗粒。高能球磨改变了锐钛矿TiO2晶粒的晶格常数,该晶格畸变现象可能与晶界区行为相关。红外吸收峰随球磨而先“蓝移”后“红移”,该“蓝移”与“红移”与晶格常数a的变化紧密相关。另外发现随着球磨时间增长,TiO2的光催化效果变差。     

Oxidation and embrittlement of Ti-6Al-2Sn-4Zr-2Mo alloy

Ti-6Al-2Sn-4Zr-2Mo titanium alloy is a candidate material for multiwall thermal protection system concepts for advanced space transportation system vehicles. The total oxidation kinetics for this alloy, exposed to laboratory air in the 593–760°C range, were monitored by thermogravimetric analysis. The oxide thickness was measured by microscopy and the substrate contamination was estimated from microhardness measurements. Tensile elongation was determined for selected foil specimens after exposure to simulated space shuttle reentry conditions. The variation of total weight gain with time was found to have two distinct parabolic stages separated by a transient region. This transient was due to a process which involved an increase in the parabolic growth rate constant for the oxide and a simultaneous increase in oxygen solubility at the oxide metal interface. The time dependent increase in oxygen solubility at the interface was from about 7 at. % in stage 1 to about 18 at. % in stage 2. The diffusion coefficient for oxygen in the alloy was determined as a function of temperature using the difference between the total weight gain in stage 1 and the corresponding weight gain due to oxide growth. A model for the total oxidation kinetics, accounting for the two individual components namely oxide growth and solid solution formation, is proposed. The activation energy for the diffusion of oxygen in the alpha-solid solution is shown to be roughly equal to the activation energy for the degradation of tensile elongation for the alloy in the foil gage condition.     

Theoretical study of heterogeneous reaction kinetics: A comparison between microcalorimetric and thermogravimetric curves

In the kinetic theories of Bodenstein or Semenov the expression for the rate of a chemical reaction with several elementary stages can be expressed by different physical parameters. If two experimental methods are used, one method of necessity being microcalorimetry to measure the thermal flux produced by the reaction, it is possible to distinguish a pure kinetics case from a mixed one. The two-method technique has been verified by a study of the oxidation of niobium.     

Dynamics in simultaneous electro-generative leaching for sphalerite-MnO2

The principle for the electro-generative leaching was applied to simultaneous leaching of sphalerite-MnO2. A galvanic system for the bio-electro-generative leaching was set up. The effects of grain size and temperature on rate of zinc extraction fi＇om sphalerite under the conditions of presence and absence ofAcidithiobacillusferrooxidans （A.ferrooxidans） were studied, respectively. The results show that with bacteria, the maximum extraction of zinc fi＇om the ores with grain size of 16.6 μm can reach 32.01% after leaching for 12 h, while to obtain the same extraction ratio in the traditional bio-leaching route （i.e. not electro-generative one）10 d is needed to ore granules with same size. The unreacted shrinking core model was used for describing the reaction-relative and diffusion-relative phenomena presented in the process of the electro-generative leaching with and without bacteria, which is considered to be diffusion controlled. The activation energies of the anodic reaction for leaching system in the presence and absence of bacteria are 11.97 and 14.39 kj/mol, respectively, indicating that leaching rate can be decreased by A. ferrooxidans. SEM was used to study the effect ofA. ferrooxidans on the ores in the simultaneous electro-generative leaching, which indicates that the produced sulfur on the surface of the sulfides can be oxidized by A. ferrooxidans after bio-electro-generative leaching for 24 h, and the transferred charge due to the bacterial oxidation is up to 17.86%, which is an important part of the output electric quantity.