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。     

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     

Effect of processing history of pyrite on its leaching kinetics

1　INTRODUCTIONThereliableknowledgeaboutleachingkineticofmineralsisofgreatimportancefordevelopinghy drometallurgical processes .Butmanyatime ,re searchersobtainedscatteredresultsforthesamepro cess .Forexample ,theapparentactivationenergyforthedigestionofpyritebyoxygeninsulfateacidsolu tionrangeswidelyfrom 39to 84kJ/mol[13] .Usual ly ,thedifferenceisascribedtothevarietyinmineralresource ,chemicalcompositionand ,accuracyofex perimentalmethods.Howeveronlythisisstillunsat isfactoryforexplain…     

机械活化黄铜矿的团聚−集聚及浸出性能

研究机械活化对黄铜矿粒度参数、显微组织和浸出性能的影响,并探讨活化过程中团聚和集聚的发生和转变.结果表明,研磨8h前黄铜矿的团聚与显微组织变化互不影响;然而,研磨8h后晶粒尺寸的降低达到极限,显微组织变化停滞,使得团聚被集聚取代.浸出实验结果表明,机械活化能显著提高黄铜矿的浸出性能,而集聚对浸出的阻碍作用远强于团聚.经...     

未活化与机械活化闪锌矿的氧化行为

用TG分析法研究了未活化与机械活化闪锌矿在氧气氛下的氧化行为，结果表明，在400—873K之间，机械活化闪锌矿的剩余质量随着球磨时间的增加而增加，未活化闪锌矿则表现为热质量损失。用粒度分析、X射线衍射分析和重量分析法分别对机械活化闪锌矿的结构进行了表征。发现随着球磨时间的增加，机械活化闪锌矿球磨一定时间后，其比表面积基本保持不变，而晶格畸变率增大，晶块尺寸降低，且机械活化闪锌矿中的单质硫磺含量极低，可忽略不计。机械活化和未活化闪锌矿在TG曲线上的表现主要与晶格畸变率增大和晶块尺寸降低有关。     

Spark plasma sintering on mechanically activated W-Cu powders

Mechanically activated W-Cu powders were sintered by a spark plasma sintering system (SPS) in order to develop a new process and improve the properties of the alloy. Properties such as density and hardness were measured. The microstructures of the sintered W-Cu alloy samples were observed by SEM (scanning electron microscope). The results show that spark plasma sintering can obviously lower the sintering temperature and increase the density of the alloy. This process can also improve the hardness of the alloy. SPS is an effective method to obtain W-Cu powders with high density and superior physical properties.     

动力锂离子电池电极结构对其极化特性影响的仿真研究

基于COMSOL数值仿真平台构建锂离子动力电池电化学-热耦合模型,深入研究了正极材料厚度,正、负极材料颗粒半径与电池内部极化间的作用规律,并在此基础上,归纳阐明了动力锂离子电池放电电压平台衰退、放电周期骤减与电池内部极化间的内在关联。结果表明:正、负极活化极化随正极厚度的增加变化差异较大,正极活化极化在18～31 m V之间波动,而负极可达到260 m V;放电末期负极固相浓差极化急剧增加,最大值达到425 mV。正极颗粒半径对极化的影响较小;负极颗粒半径减小为原来的一半,即0.5R_n时放电中期的负极活化过电势约为55 mV,较1R_n降低45%左右。负极活化极化的增加将导致电池放电电压平台下降,负极活化极化和固相浓差极化在放电末期急剧增加,是电压提前达到放电截止电压的最主要原因。     

非等温条件下机械活化Ag2O-石墨混合物Arrhenius参数的测定

采用DSC和TGA及模型拟合Malek法和无模型改进Vyazovkin等转化率法研究机械化学还原Ag2O和石墨混合物的非等温动力学。为了测定动力学参数,选取研磨活化2 h和4 h的及未球磨的Ag2O-石墨混合物为样品。基于Vyazovkin法计算得到的活化能最大值和最小值之间的差比平均活化能小20%-30%（（99.38±2.36）k J/mol）,Ag2O机械活化2 h的热分解是一个多步过程,机械活化4 h的热分解是一个单步过程（平均活化能为（93.68±2.26）k J/mol）。动力学模型表明,未球磨的Ag2O-石墨混合物的热分解过程比其他的复杂。Ag2O-石墨混合物的自动催化趋势比其他的低。     

Microstructures of mechanically activated Ti-46at.%Al powders and spark plasma sintered ultrafine TiAl alloy

Powder of Ti-46at.%Al was synthesized through mechanical activation (MA) for different milling times, and the 16 h MAed powder was sintered by using a spark plasma sintering (SPS) process at different sintering temperatures. The XRD profiles showed that the MAed Ti-46at%Al powder for 12,16, and 20 h contained initial α-Ti and Al phases, and that the SPSed TiAl alloys contained the gamma TiAl and α2-Ti3Al phases. The TEM showed two different types of regions in the 16 h MAed Ti-46at.%Al powder. One type consisted of only Al with a grain size about 80 nm, and the other type a mixture of Al and Ti with a grain size of 30 nm. According to the optical micrographs of MA-SPSed samples, the alloys sintered at higher temperatures showed a coarser microstructure. In the case of the 1473 K sintering, typical duplex structures ((α2 γ) lamella and γ phases) with interlamellar spacings of 50-400 nm and the grain size either less man 100 nm, or 1000 nm were observed.     

Microstructures of mechanically activated Ti-46at.% Al powders and spark plasma sintered ultrafine TiAl alloy

Powder of Ti-46at.%Al was synthesized through mechanical activation (MA) for different milling times, and the 16 h MAed powder was sintered by using a spark plasma sintering (SPS) process at different sintering temperatures. The XRD profiles showed that the MAed Ti-46at%Al powder for 12,16, and 20 h contained initial α-Ti and Al phases, and that the SPSed TiAl alloys contained the gamma TiAl and α2-Ti3Al phases. The TEM showed two different types of regions in the 16 h MAed Ti-46at.%Al powder. One type consisted of only Al with a grain size about 80 nm, and the other type a mixture of Al and Ti with a grain size of 30 nm. According to the optical micrographs of MA-SPSed samples, the alloys sintered at higher temperatures showed a coarser microstructure. In the case of the 1473 K sintering, typical duplex structures ((α2 + γ) lamella and γ phases) with interlamellar spacings of 50-400 nm and the grain size either less man 100 nm, or 1000 nm were observed.     

Molten salt synthesis of tungsten carbide powder using a mechanically activated powder

A novel method for synthesizing ceramic powders in molten salt was introduced in this paper. Unlike traditional mechanochemical process, the novel method is based on mechanical alloying followed by chemical reaction in liquid phase (molten salt). The reaction temperature to synthesize tungsten carbide in molten salt was 1000 °C. Results in this paper showed that W₂C and WC powder could be successfully synthesized by the method. Under raised reaction conditions, there was a transformation from W₂C to WC. The mechanism of the reaction in molten salt was discussed finally.     

Synthesis of nanocrystalline molybdenum by hydrogen reduction of mechanically activated MoO3

Nanocrystalline molybdenum with a mean crystallite size of 50 nm was synthesized by mechanical activation of MoO₃ powder and its subsequent hydrogen reduction. MoO₃ powder was severely activated in a high energy planetary ball mill under a pure argon atmosphere. Temperature-programmed reduction (TPR) by hydrogen was used to investigate hydrogen reduction behavior of the powder samples activated for 5 and 20 h. It was found that by increasing the activation time, the peak temperature for the reduction was shifted slightly to lower temperatures and the peak for the reduction of MoO₃ to MoO₂ was completely separated from the one for the reduction of MoO₂ to molybdenum. In order to evaluate the effect of mechanical activation on the reduction behavior of MoO₃, the initial micron-sized powder and the sample activated for 20 h were reduced at similar conditions. It was found that the activated sample with finer particles was reduced faster than the un-milled sample. Hydrogen reduction of the non-activated MoO₃ produced a very fine grained molybdenum powder but the crystallite size changes of the sample activated for 20 h was negligible during reduction.     

Pulsed current activated combustion synthesis and consolidation of ultrafine NbSi2 from mechanically activated powders

Dense ultrafine NbSi₂ was synthesized using the pulsed current activated combustion synthesis (PCACS) method within 2 min and in one step from mechanically activated powders of Nb and 2Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense NbSi₂ with a relative density of up to 98 % was produced under simultaneous application of a 60 MPa pressure and a pulsed current. The average grain size and mechanical properties (hardness and fracture toughness) of the compound were investigated.     

Steady polarization process modelling of noble metal-electrolyte cermet composite electrode

Cermet composites containing mixture of noble metal phase and electrolyte phase are the state-of-the-art electrode materials used for electrochemical sensor and solid oxide fuel cell（SOFC）. A steady polarization model was developed. The model was based on electronic and ionic transfer process together with the electrochemical reaction regardless of mass transport in the electrode. The modelling results can help to understand the electrochemistry of cermet composite electrode.     

Influence of mechanical activation on leaching kinetics of arsenopyrite

The influence of mechanical activation on the leaching kinetics of arsenopyrite was studied using a planetary centrifugal mill. It shows that mechanical activation can enhance the leaching process of arsenopyrite in a nitric-sulfate acidic solution. The leaching ratio within 20 min leaching time can increase from 2 % to 80 %～ 100 % ; 10 and 20 minties‘ activation can depress the apparent activation energy of leaching reaction from 54.5 kJ/mol to 39.0 kJ/mol and 34.0 kJ/mol, respectively. This means that the leaching reaction becomes little dependent on tempeerature, and arsenopyrite can change from refractory to flexible one; mechanical activation also increases the interplanar distance between crystal faces. The displacement of atoms from its equilibrium position indicates the increase in inner energy.     

The effect of additives on the corrosion resistance of Zn electrode in alkaline battery system

Zn electrodes are widely used as an anode material in alkaline battery systems in highly concentrated KOH electrolyte. However, it is well known that their life cycle is significantly shortened due to dendrite growth caused by high dissolution and rapid electrochemical reaction. In this study, additives such as Ca(OH)_￡σ, citrate, tartrate, and gluconate were added to 40% KOH electrolyte solution at 25 and 5 wt.% Pb₃O₄ was mixed with the Zn electrode. The effects of both Pb₃O₄ and the additives on the electrochemical behavior of the Zn electrode were investigated through corrosion potential measurements, potentiodynamic polarization curves, cyclic voltammetry, and SEM photographs. The addition of Pb₃O₄ had a considerable effect on decreasing the corrosion rate of the Zn electrode, and the corrosion potential of the Zn electrode with Pb₃O₄ addition shifted to a more positive potential than that of a pure Zn electrode. However, upon addition of other additives, the corrosion potential was slightly shifted to the negative direction again. The addition of 4 kinds of additives appeared to play an important role in improving the corrosion resistance. Moreover, among the four additives, tartrate displayed a relatively good effect in terms of increasing the corrosion resistance as well as improving the discharging characteristics among.     

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。     

Electro-enhanced adsorption of As(V) by activated carbon in three-dimensional electrode reactor

This study focused on As(V) removal by electrosorption in a self-made three-dimensional electrode reactor, in which granular activated carbon (GAC) was used as the particle electrode. Under the optimal conditions, the removal efficiency of As(V) was 84%, and its residual concentration in solution was 0.08 mg/L. From kinetic investigation, the rate determining steps of the entire process may involve more than two processes: membrane diffusion, material diffusion and physical/chemical adsorption processes. During the desorption process, As(V) can be desorbed from GAC, and the GAC was able to electro-adsorb As(V) again after desorption, which means that the electrode has good cycling performance.     

机械活化对铟铁酸锌溶解动力学及物化性质的影响

以人工合成的高纯度铟铁酸锌为研究对象,采用搅拌球磨对其进行机械活化。以锌的浸出率为评价指标,研究不同活化试样在硫酸溶液中的浸出特性和溶解动力学,并利用X射线衍射仪、扫描电镜、激光粒度分析仪和比表面积分析仪分别考察机械活化对铟铁酸锌晶体结构、颗粒形貌、粒度和比表面积的影响。结果表明:机械活化使铟铁酸锌的物化性质发生明显改变,并由此提高了铟铁酸锌的反应活性。经机械活化30和60 min后,铟铁酸锌与硫酸反应的表观活化能由未活化时的76.4 kJ/mol分别降至58.6和51.8 kJ/mol,表观反应级数也由原来的0.79分别降至0.62和0.59。未活化铟铁酸锌的酸溶过程受化学反应控制,活化后则为混合控制。     

机械活化-湿化学合成LiMn2O4的组成、结构与表征

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.