液相还原两步法中前驱体对铜粉密实性的影响研究

通过液相还原两步法制备氧化亚铜颗粒进而制备铜粉,分别以立方体、球形、八面体氧化亚铜颗粒为前驱体,考察了前驱体对铜粉密实性的影响。利用XRD、SEM、激光粒度分析仪、氮吸附比表面仪对样品进行了表征。研究结果表明:以立方体氧化亚铜为前驱体制备的球形铜粉更密实,即振实密度大、比表面积小、粒径分布窄,适合制备导电铜浆。     

以碳酸氢铵为沉淀剂制备纳米氧化锌粉体

以硫酸锌、碳酸氢铵为主要原料，采用直接沉淀法制备出纳米氧化锌粉体。对前驱体进行DSC-TG分析，对煅烧样品进行x射线衍射（XRD）分析，利用谢乐公式计算晶粒度。结果显示，前驱体在300℃时基本分解完毕；550℃煅烧可制备出结晶良好、35-45nm的氧化锌粉体；提高沉淀反应的温度能降低纳米ZnO粉体的粒度。     

PDP用高亮度(Y,Gd)BO_3:Tb~(3+)绿色荧光粉的合成

采用共沉淀法制备了稀土氧化物前体,再将其和H3BO3及BaB4O7混合后,用高温固相合成法制备出了2.0-3.0μm粒径的(Y,Gd)BO3:Tb3+绿色荧光粉。研究发现,荧光粉的粒度随前驱体粒度与助熔剂引入量的增加而增大,助熔剂的引入量超过0.18%会使荧光粉的亮度猝灭;随着灼烧温度的增高,荧光粉的亮度会变大。综合PDP用荧光粉的使用特性,BaB4O7的引入量在0.10%,灼烧温度为1100℃时,采用共沉淀法前驱体可得到亮度104,粒度2.5um,晶型完美的(Y,Gd)BO3:Tb3+绿色荧光粉。     

微乳液法制备超细Co-Cr-Fe-Ni钴黑陶瓷颜料

利用AEO7(脂肪醇聚氧乙烯(7)醚)/环己烷/正丁醇体系,以微乳液法制备超细钴黑陶瓷颜料。绘制了不同温度下AEO7/环己烷/正丁醇/水的拟三元相图;运用马尔文粒度分布仪测定了不同前驱离子浓度制备的钴黑颜料粒径;通过XRD和FT-IR测定了钴黑颜料物相及结构,采用UV-Vis和色差仪对钴黑颜料呈色进行分析。结果表明,该微乳液体系制备的钴黑颜料颗粒度随着前驱离子浓度降低而减小,粒度分布窄且均匀;钴黑颜料是系列尖晶石型物质;随着煅烧温度升高,钴黑颜料呈现较纯正黑色,偏红现象降低。     

沉淀-共沸蒸馏法合成超细钴蓝颜料的研究

利用沉淀-共沸蒸馏法合成超细钴蓝颜料,并采用扫描电镜(SEM)、X射线衍射(XRD)、荧光反射仪现代分析测试技术对样品性能进行表征.结果表明,用正丁醇共沸蒸馏能有效防止干燥过程中颗粒间的团聚.经1000℃煅烧2h后的钴蓝粉体材料具有良好的分散性、结晶度高、外形规则.其蓝光波段反射率为67 %,红光波段反射率为13 %,达到彩色显象管用钴蓝颜料的要求.为实现性能优异、超细钴蓝的国产化提供了借鉴意义.     

矿化剂氟化锂对镨锆黄陶瓷色料的影响

谱锆黄陶瓷色料由于呈色稳定,价格较低廉已成为高温陶瓷色料市场的宠儿,但传统固相法所制备的谱锆黄陶瓷色料煅烧温度高(1 600℃),导致颜料粒径过大影响呈色性能,因此,降低合成温度减小粒径已成为这一方向的研究的热点.本文利用八水合氧氯化锆、正硅酸乙酯、稀土氧化镨为主要原料,采用溶剂热法制备镨锆黄粉体颜料前驱体,加入不同含量的矿化剂氟化锂(LiF)以降低合成温度,对其在1 100℃煅烧,保温50 min获得镨锆黄陶瓷粉体颜料.采用色度分析仪、粒度分析仪、紫外可见光光谱分析仪、扫描电镜和X射线衍射分析技术对样品结构和性能进行表征.实验结果表明:当矿化剂LiF含量为0.35%时,样品中的ZrSiO_4结晶度较高,颗粒尺寸分布较小且较均匀,样品在400~480 nm蓝紫光有非常强的吸收,呈现较纯正的黄色色调,其色度值为L~*=84.92,a~*=4.70,b~*=68.00.该谱锆黄陶瓷色料可望应用于陶瓷喷墨打印技术领域.     

并加共沉淀水热法制备锰锌铁氧体粉末工艺

采用不同的共沉淀方式制备前驱体 ,在 180℃、6h水热条件下制备锰锌铁氧体粉末。将得到的样品进行XRD分析和粒度分析 ,发现采用并加共沉淀水热法制备得到的样品其粒度最小 ,且颗粒一致性很好。差热分析结果表明 ,这种粉体开始发生烧结的温度显著降低。     

前驱体反应温度对CeO2粉体抛光性能的影响

以CeCl3为铈源,Na2CO3为沉淀剂,采用沉淀法在不同反应温度下制备CeO2前驱体,焙烧前驱体制备CeO2粉体,研究前驱体反应温度对产物组成、结构、形貌及抛光性能的影响。结果表明,当反应温度低于或高于50℃时,前驱体分别以Ce2(CO3)3·8H2O或CeCO3OH为主;反应温度对由2种前驱体制备的CeO2粉体的抛光性能影响较大,当前驱体反应温度为45~50℃时,制备的CeO2粉体粒度均匀,抛光性能最优。     

LiFePO4的前驱体制备与性能

以Fe2(SO4)3、H3PO4和NH3·H2O为原料,采用控制结晶法制备了多孔的前驱体FePO4·xH2O.通过研究pH值和合成时间对前驱体的物相结构、成分、表面形貌、粒度、比表面积和振实密度的影响,发现在pH=2.1的条件下反应8h制备的前驱体性能最佳.将前驱体、Li2CO3及葡萄糖均匀混合,用碳热还原法合成了LiFePO4/C,结果表明,以pH=2.1时制备的前驱体为原料合成的LiFePO4/C在0.1C时的首次放电比容量为156mAh/g,其振实密度高达1.20g/cm3.     

CoxR1-xAl2O4(R=Zn,Mg)钴蓝颜料反射性能的研究

采用化学共沉淀法成功地制备出适用于彩电显象管内荧光体着色的ＣｏｘＲ１－ｘＡＩ２Ｏ４）Ｒ＝Ｚｎ,Ｍｇ,ｘ＝０．８～１．０）钴蓝颜料,４５０ｎｍ波长处反射率最大提高１８．２％,６００ｎｍ处反射率最大了和低５％,通过对该颜料反射率的影响因素,如掺杂离子类型、掺杂浓度和Ｃｏ＾２＋浓度的探讨,结论如下,Ｚｎ＾２、Ｍｇ＾２＋改变钴蓝颜料反射性能的作用机理为晶格畸变引起Ｃｏ＾２＋３ｄ轨道是 级分裂程度的变化,对     

纳米钴蓝共沉淀法制备技术

以硝酸钴、硝酸铝为原料,NaOH或尿素为沉淀剂,采用共沉淀法制备纳米钴蓝。考察了Co/Al摩尔比、沉淀剂种类和煅烧温度等因素对纳米钻蓝呈色性能影响,采用包括可见光分度计等多种方法表征了纳米钴蓝的结构及形貌特征及纳米钴蓝色度值。研究结果表明:(1)煅烧温度为1000℃时,当Co/Al摩尔比从1∶3升至1∶1,钴蓝颜色从蓝色依次向蓝绿色、暗绿色转变,同时,以NaOH为沉淀剂制备的钴蓝其亮度比以尿素为沉淀剂制备的钴蓝高;(2)以NaOH为沉淀剂,Co/Al摩尔比为1∶3时,当煅烧温度为900℃,钴蓝呈蓝绿色,当煅烧温度为1000-1100℃,钴蓝呈蓝色;(3)钴蓝不同制备工艺会改变钴d电子层状态,导致钴蓝呈现不同颜色,最终优化工艺制备的纳米钴蓝粒径为45-65nm,呈尖晶石型晶体结构,色度值为CIE(35.86,-12.63,-34.83)。     

介孔铝酸钴的溶胶-凝胶法合成与表征

采用嵌段聚合物P123为表面活性剂,以氯化铝和氯化钴为无机先驱物,采用溶胶-凝胶法合成介孔铝酸钴纳米粒子。X射线衍射(XRD)表明样品具有单一的尖晶石型结构,利用氮气吸附-脱附比表面测定仪测得不同焙烧温度样品的比表面积,发现700℃焙烧的样品比表面积最大,其比表面积为59.3m2/g,孔径为10.8nm。紫外可见光谱仪测示表明纳米铝酸钴样品为明亮的蓝色,在545nm、585nm和625nm处有三重吸收峰。     

Enhancement of catalytic activity of Raney nickel by cobalt addition

The effects of cobalt as a promoter of the catalytic activity of Raney nickel for various manufacturing esses have been studied. The variation of particle size distribution, specific surface area and residual aluminium content can also affect the catalytic properties of Raney nickel. The characteristics of the catalyst are considerably influenced by the relative nickel and aluminium contents. When the catalysts are prepared from 60 wt.% nickel and 40 wt.% aluminium, the electrode performance shows the highest current density of 450 mA/cm². With the addition of cobalt, the particle size is diminished from 13.92 to 11.70 μm and the decrease of the particle size contributes to a slight enlargement of the specific surface area. The mass activity of a hydrogen electrode manufactured with cobalt Raney nickel in alkaline solution is increased from 3.74 to 4.03 A/g when 120 mg/cm² of catalyst are loaded in the electrode.     

Morphology and crystal-chemical characteristics of cobalt and nickel nanopowders prepared by thermochemical and electrolytic methods

The phase composition and morphology of cobalt and nickel powders and nickel foam have been studied by X-ray diffraction and scanning electron microscopy. The cobalt and nickel powders prepared through solution electrolysis are shown to have a dendritic microstructure. The particle morphology of the nanostructured cobalt and nickel powders and nanostructured nickel foam can be described by a three-level (according to the particle size) model.     

Preparation of cobalt nanoparticles by hydrogen reduction of cobalt chloride in the gas phase

Cobalt nanoparticles were produced by the hydrogen reduction of cobalt chloride vapor in a multistage tubular aerosol flow reactor. Reaction zone temperature, preheating temperature, mole fractions of CoCl₂ and H₂, and residence time were considered as key process variables for the control of particle size and size distribution. Ranging from 50 to 78 nm in average diameter, cobalt nanoparticles with narrow size distributions were synthesized throughout our experiments. All of the considered process variables affected the particle size and size distribution in the synthesis of cobalt nanoparticles. As the reaction zone temperature and the CoCl₂ mole fraction increased, the average particle diameter increased. But the average particle diameter decreased as the residence time of reactants increased.     

草酸钴循环氧化还原法制备粗颗粒CoO

以草酸钴为原料,通过草酸钴在空气中热分解为CoO,然后将此CoO在高纯、露点低于-40℃的氢气中进行还原,CoO还原的钴粉在空气中被氧化为CoO,如此反复进行。利用扫描电子显微镜和激光粒度分析仪对试样进行形貌和粒度表征。结果表明:经过循环两次还原和两次氧化,可以制备出粒径分布在9～21μm之间颗粒的体积分数为77.10%的粗颗粒CoO粉。     

Bayesian Inference Approach to Particle Size Distribution Estimation in Ferrofluids

We present an effective direct extraction method for particle size distribution based on Bayesian inference theory with a free-form model. We give an example of the application to the particle size distribution analysis in ferrofluid consisting of cobalt particles in toluene. The method gives a unique solution to the distribution without assuming the shape of the distribution of the particle size     

超细钴粉的制备及国内外的研究现状

超细钴粉一般是指平均粒度小于2μm的钴粉.主要综述了超细钴粉的制备方法,分析了Umicore公司(上海百洛达公司)、OMG公司、Eurotungstene公司、南京寒锐公司和金昌长庆公司等国内外公司生产的超细钴粉产品的性能和应用特点,并展望了超细钴粉的发展.     

Cobalt rich phase formation in metastable Cu–Co alloys by means of melt spinning

Abstract

Metastable CO_xCU_100?x alloys with extended cobalt solubility (5≤x≤20), which can not be obtained by equilibrium methods, were prepared by melt spinning. The separation of the cobalt rich phase upon heating was monitored by X-ray diffraction and calorimetric measurements. The volume fraction of cobalt rich particles can not be determined using X-ray diffraction if the cobalt rich particle size is below a critical value. The separation of the cobalt rich phase seems to be a three step process including nucleation, growth, and coarsening. The non-isothermal kinetics of nucleation and growth of the cobalt rich phase were analysed in terms of a modified Kissinger model. The heat release during phase separation is closely related to the amount of cobalt dissolved in the copper matrix.

MST/3258