制备超细镍粉的研究进展

介绍了制备超细镍粉的主要方法,并对这些方法的制备过程、优缺点以及目前用这些方法制备的超细镍粉的情况进行了介绍.最后指出了存在的问题和未来的发展方向.     

前驱体对多元醇还原制备超细镍粉的影响

采用Ni(NO3)2.6H2O、NaOH、乙二醇(EG)和聚乙烯吡咯烷酮(PVP)为原料,用多元醇法制备超细镍粉,研究前驱体对产物粒径和形貌的影响。结果表明,前驱体制备过程中,pH值应控制在11左右,前驱体含水率对反应速度以及制备的超细镍粉的粒径和形貌均有影响,前驱体含水率为63.5%时,制备的镍粉呈球形且分散性好,平均粒径为0.24μm。     

超声波喷雾液相还原法制备超细镍粉

以联氨为还原剂通过控制液相还原反应条件, 从硫酸镍溶液中制备出超细镍粉, 讨论了该方法的反应机理, 分析了超声波喷雾加料方式、反应温度、Ni²⁺浓度、溶液pH 值、还原剂用量、表面活性剂等因素对镍粉的形貌、尺寸、转化率的影响。结果表明超声波喷雾液相还原法制备超细镍粉反应速度快, 产品纯度高, 粒子呈类球形。     

配位沉淀-直接还原法制备球形超细镍粉

以碳酸氢铵为沉淀剂、氯化镍为原料、氨为配位剂, 用配位沉淀法制备球形镍粉前驱体沉淀, 再于氢还原气氛中直接还原前驱体制备球形超细镍粉。系统地研究了前驱体制备过程中反应物浓度、pH值、添加剂、温度和直接还原过程中反应温度、还原气氛对镍粉形貌及粒度的影响。实验结果表明: 在Ni²⁺浓度为0.8 mol/L, pH值为7.5, 反应温度为室温, 添加剂PVP添加量为1%的条件下可制备出类球形、形状较规则、分散性好的镍粉前驱体; 将球形的、分散性好的前驱体粉末在350～400 ℃的N₂和H₂混合气氛中进行还原即可得到分散性好、纯度高的超细金属镍粉。     

激光粒度仪湿法测定不同形貌超细镍粉平均粒度的研究

超细镍粉诸多物化性质随粉末形貌、粒径等参量的变化发生显著改变,因此针对超细镍粉的粒度的准确测定至关重要。确定激光粒度仪测定超细镍粉平均粒度的最佳测试条件,选用湿法测定方法,以多孔状、片状和球状超细镍粉对研究对象,研究了分散剂种类、超声时间、分散剂质量分数、遮光度及采样轮数等参数对超细镍粉平均粒径测定结果的影响。结果表明,在实验选用的6种分散剂FMES、L64、CAB、PECPM、CTAC和G-18中,添加FMES分散剂测得的超细镍粉D₅₀值最小,而添加G-18分散剂测得的超细镍粉D₅₀值最大,表明FMES分散剂改善了3种形貌的超细镍粉在水中的团聚,使粒度测量的准确性更高。当超声时间为8 min时,孔状超细镍粉测得的D₅₀=4.403 μm,片状超细镍粉测得的D₅₀=1.345 μm,球状超细镍粉测得的D₅₀=1.289 μm。随着超声时间持续延长,3种形貌的超细镍粉测得的D₅₀值逐渐趋于平稳,其中片状和球状形貌超细镍粉测得的D₅₀值与电镜测试结果较为相符,而孔状超细镍粉D₅₀值与电镜测试结果差别明显,表明激光粒度仪湿法测定不适用于孔状形貌的镍粉。采样轮数与粒度测试值具有强线性相关性,超声时间为8 min时,相邻两轮的测试结果更相近,从而确定了适宜的超声时间为8 min。综上所述,确定了片状和球状超细镍粉平均粒度的最佳测试条件为：超声时间8 min、分散剂FMES质量分数1.5%、遮光度10%—20%。在最佳测试条件下重复测试6次,片状和球状超细镍粉的平均粒度数据具有较高的准确性和重现性。     

纳米金属镍粉/超细陶瓷涂层材料的研究

在超细陶瓷涂料中分别添加了不同含量的纳米金属镍粉,用扫描电镜观察了纳米金属/超细陶瓷涂料中纳米颗粒的尺寸和微观形貌以及在涂层中的分布情况;通过摩擦实验评价了涂层的耐磨损性能。结果表明:合理控制各工艺过程,用流涂法获得了纳米镍粉/超细高温无机陶瓷涂层,涂层中的纳米颗粒趋于靠近涂层/基体界面处分布;在900℃保温过程中,涂层中纳米颗粒没有明显长大;添加纳米金属镍粉可以明显提高涂层的耐磨损性能,随纳米镍粉含量的增加,涂层的耐磨损性能提高。     

电极用超细铜粉的制备及其研究进展

对电极用超细铜粉的制备方法进行了介绍和评述。指出球形超细铜粉有助于制备优质电极, 超细铜粉通过表面改性可以显著提高抗氧化性。     

超细氧化镁粉体的制备新方法及应用

总结分析了超细氧化粉体的传统制备方法,对制备超细氧化镁的几种制备新方法--直接沉淀法、氢氧化钙法、高分子保护法和白云石制备超细氧化镁方法等作了介绍,并且将其应用于阻燃剂、中和剂、吸附剂、催化剂,抗菌材料等领域.由于超细氧化镁独特的物理性能,决定其具有非常重要的应用价值和广阔的应用前景.     

超细镍粉制备的前驱物真空热分解研究

采用TG、XRD等手段对草酸镍热分解过程进行研究,确定了草酸镍的热分解步骤;研究了真空热分解温度、升温速度、草酸镍形貌对镍粉的影响;采用充入氩气对镍粉进行钝化处理,制得氧含量小于0.64%,573 K前氧化率小于2%,粒度小于lμm的超细镍粉.     

超细合金粉末材料的研究进展

超细粉末材料因其具有独特的结构和性质而受到人们的关注。主要介绍了超细合金粉末的制备方法特点、表征及应用情况。     

Dynamic microbial populations in heap leaching of zinc sulphide ore

Polymerase chain reaction (PCR) technology was used to monitor the microbial population within two 6-m-high sulphide ore heaps where zinc was bioleached. Genomic DNA was isolated from microorganisms attached to the ore particles. The microbial population varied in diversity at different heap heights and at different stages of the leaching cycle. Nine bioleaching microorganisms were identified, including iron oxidizers, sulphur oxidizers, whether mesophiles, or moderate thermophiles. No bioleaching extreme thermophiles were detected. Moderate thermophiles were present at average heap temperatures of 40 °C or higher. No moderate thermophiles were present in the top 2 m of the heaps. Mesophiles were present throughout the lifetime of the heaps and at all heap depths. Cultures of Acidithiobacilluscaldus and Sulfobacillusthermosulfidooxidans originally introduced to inoculate the heaps did not proliferate but were instead displaced by other species; no benefits were obtained from heap inoculation. The most predominant species were Acidithiobacillus thiooxidans and Acidithiobacillus albertensis. Leptospirillum sp. was not predominant in the heaps, in contrast to the dominant role this organism plays in tank bioleaching operations.     

Iron solubilization during anaerobic growth of acidophilic microorganisms with a polymetallic sulfide ore

Acidithiobacillus ferrooxidans at 30 °C and Sulfobacillus thermosulfidooxidans at 47 °C were selected from a preliminary screening of various acidophiles for their ferric iron reduction capacities during anaerobic, autotrophic growth on sulfur. The selected cultures were used with a polymetallic sulfide ore under anoxic conditions to demonstrate enhanced solubilization of iron during leaching in shaken flasks and enhanced removal of iron from laboratory ore-leaching columns, compared to leaching with continuous aeration. Ore-associated, ferric iron-rich precipitates, which were formed under previously oxidizing conditions, were a potential influence on extraction of target metals and percolation through ore columns and were available as the source of ferric iron for anaerobic sulfur oxidation. Over twice as much iron was removed by moderate thermophiles when anoxic phases were introduced during the leaching. Enhanced removal of iron and some improvement in extraction of base metals from ore fragments were also demonstrated with a selected “Sulfolobus”-like strain during growth and leaching with alternating periods of aeration and anoxic conditions at 70 °C.     

大采高综采采场关键层运动型式及对工作面矿压的影响

掌握大采高综采采场关键层结构形态及运动型式是分析工作面矿压显现规律的基础。采用理论分析方法,得出了大采高综采采场关键层存在2种结构形态和6种运动型式,并给出了各结构形态和运动型式的形成条件,2种结构形态为垮落带关键层"悬臂梁"结构形态和断裂带关键层稳定"铰接"结构形态,6种运动型式为"悬臂梁"直接垮落式、"悬臂梁"双向回转垮落式、"悬臂梁"二次回转垮落式、"悬臂梁-铰接"结构交替式、"砌体梁"结构运动型式和"短砌体梁"结构运动型式。采用UDEC数值模拟方法验证了各形成条件下的关键层的运动型式,揭示了6种关键层运动型式对采场矿压的影响规律,最后得到了现场实测数据的验证。     

高水压下基岩冻结壁设计方法

首先提出了高水压基岩冻结在冻结壁和井壁设计方面存在的问题;其次回顾了冻结法凿井中冻结壁厚度设计理论的发展,客观地揭示了井筒井壁内外分层的力学原因,以及基岩冻结壁设计方面所需考虑的基本问题;第三,探讨了包神公式设计冻结壁的载荷性质,及与冻结壁外缘载荷的关系,剖析了冻结壁与井筒的几何尺寸、刚度等因素对冻结壁外缘载荷的影响;第四,深入研究了采用拉麦和包神公式进行冻结壁弹性设计的力学条件;第五,定量分析了井筒冻结壁弹性设计的深度范围;最后探讨了冻结基岩许用强度、剪切模量之比等参数对设计冻结壁厚度的影响。     

新疆准东煤田PM2.5、PM10时空变异性及其与气象因素的关系

准东地区大规模的露天煤矿开采及工业活动和交通活动使得区域大气颗粒物浓度增加,大气环境恶化,通过分析PM_2.5和PM₁₀质量浓度及数量和即时的风速、温度、相对湿度数据,探讨PM_2.5和PM₁₀污染特征,确定其时空差异特征及与气象因子的关系,了解我国大规模工矿产区的大气污染特征,可以为区域大气环境治理提供依据。结果表明：1.)研究区PM_2.5、SPM₁₀是非均匀化分布,浓度均值低于国家标准限值2)可吸入颗粒物浓度与颗粒数间相关性高,PM_2.5浓度与颗粒数的相关系数为0.99,PM₁₀的为0.77;PM_2.5与PM₁₀浓度间的相关性高达0.84。3.)各样点夏秋两季可吸入颗粒物浓度水平较为接近,冬季颗粒物浓度明显高于其它两季4)IDW插值结果显示颗粒物污染浓度的高值区夏季主要分布在研究区的西部,东南部存在小范围高值区;秋季主要集中在西北部;冬季主要聚集在五彩湾煤电煤化工产业带及研究区东部。5)研究区PM_2.5、PM₁₀的浓度与温度和相对湿度相关性显著,受相对湿度影响更大。与温度呈显著负相关性;与相对湿度呈显著正相关;与风速呈非显著性负相关,相关系数不大。     

Influence of NaOH solution on the synthesis of fly ash geopolymer

A study was conducted on leaching of fly ash mixed with NaOH solution and on mixing procedure for preparing geopolymer. Leaching of SiO₂ and Al₂O₃ was investigated by mixing fly ash with NaOH solution for different time intervals and leachates were analyzed in terms of silica and alumina contents. To make geopolymer paste, separate mixing and normal mixing were used. For separate mixing, NaOH solution was mixed with fly ash for the first 10 min; subsequently sodium silicate solution was added into the mixture. For normal mixing, fly ash, sodium hydroxide and sodium silicate solution were incorporated and mixed at the same time. Geopolymers were cured at 65 °C for 48 h. Microstructure of paste and compressive strength of mortar were investigated. Results revealed that solubility of fly ash depended on concentration of NaOH and duration of mixing with NaOH. For mixing procedure, separate mixing gave slightly better strength mortar than normal mixing. High strength geopolymer mortar up to 70.0 MPa was obtained when the mixture was formulated with 10 M NaOH and sodium silicate to NaOH ratio of 1.0, and the separate mixing sequence was used.     

Explanation for peat-forming environments of coal seam 2 and 9−2 based on the maceral composition and aromatic compounds in the Xingtai coalfield, China

Maceral composition and aromatic compounds were determined on column samples to study the peat-forming environments of Permian coal seam 2 and Carboniferous coal seam 9⁻² from the Xingtai coalfield, China. The macerals were dominated by inertinite in seam 2 and by vitrinite in seam 9⁻². Three maceral groups were selected as indicators of peat-forming environments. Two triangle diagrams were drawn based on the indicators to explicate the peat-forming environments of permian seam 2 and Carboniferous seam 9⁻². The results indicate that the peat of carboniferous seam 9⁻² formed dominantly in wet swamps, whereas the peat of Permian seam 2 formed dominantly in dry swamps and open moor environments. Supported by the National Natural Science Foundation of China(40773040) and the National Basic Research Program of China (2003CB214607)     

钾长石焙烧渣的酸化溶液中钾钠的回收利用

以钾长石焙烧渣为原料,通过酸化、水浸、沉铝、净化等工艺得到钾钠的混合酸液,再采用分步结晶法制备硫酸钾、硫酸钠产品。本实验考察了硫酸钾、硫酸钠制备过程中搅拌强度和结晶时间对其结晶率的影响,得到优化工艺条件。并采用化学成分分析、XRD、SEM对产品进行表征。结果表明：在反应温度40°C,搅拌强度400 r/min,结晶时间4 h的条件下,硫酸钾的结晶率可达88.17%。在反应温度10°C,搅拌强度400 r/min,结晶时间8 h的条件下,硫酸钠的结晶率可达90.13%。得到的产品粉体晶型良好,颗粒均匀,符合国家标准。     

Evaluation of equilibrium, kinetic and thermodynamic parameters for biosorption of nickel(II) ions onto bacteria strain, Rhodococcus opacus

The present study explores the ability of Rhodococcus opacus bacteria strain for the removal of nickel(II) under different experimental conditions. The effects of relevant parameters such as solution pH, biomass loading, ionic strength, and temperature on nickel(II) biosorption capacity were evaluated. Although the tests were carried out using synthetic solutions, the results are representative of typical waste effluents from chemical, dyestuffs, battery manufacture, porcelain enameling, metallurgical industries and electroplating circuits. The sorption data followed the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, and Sips isotherms. The maximum sorption capacity was found to be 7.63 mg g⁻¹ at pH 5. Thermodynamic parameters have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The dynamics of the sorption process were studied and the values of rate constants for different kinetic models were calculated. The activation energy of biosorption (E_a) was determined as 12.56 kJ mol⁻¹ using the Arrhenius equation.     

Enrichment and characterisation of thermophilic acidophiles for the bioleaching of mineral sulphides

Thermophilic acidophilic Archaea were enriched from samples collected from geothermally active sites in Papua New Guinea. Pure cultures (JP2 and JP3) were obtained from mixed culture enrichments and were characterised and tested for their bioleaching ability. All cultures possessed Sulfolobus-like morphology, and the presence of distinctive cyclized tetraether lipids. The two pure cultures were identified by their 16S rRNA gene sequences as being most closely related to Sulfolobus solfataricus. Each isolate was able to oxidise both Fe²⁺ and sulphur, and grow on both pyrite and chalcopyrite under autotrophic conditions. Leaching experiments showed that the isolates were capable of rapidly leaching a chalcopyrite concentrate (up to 91% Cu release in 108 h). Optimal temperatures for growth and chalcopyrite leaching were determined for each strain. Chalcopyrite dissolution rates for JP2 at different temperatures were determined using a previously described kinetic model. An Arrhenius plot to investigate the relationship between dissolution rate and temperature, showed that for JP2, an increase in temperature from 70 to 83 °C resulted in a 6.6-fold rate increase. Studies with both mixed and pure cultures showed that these cultures were capable of rapidly leaching a chalcopyrite concentrate at very high temperatures (up to 90 °C), but also were capable of bioleaching at 50 °C. These thermophilic acidophiles possess the ability to bioleach over a wide range of temperatures. They are potentially well suited to industrial leaching applications where considerable temperature fluctuations limit the growth of other non-thermophilic bioleaching microorganisms.