形貌控制合成纤维状氧化亚镍粉末新型前驱体

以可溶性镍盐和草酸或草酸铵为原料, 利用氨为配位剂, 通过配位沉淀法制备了纤维状氧化亚镍粉新型前驱体, 并采用XRD、红外光谱(IR)和扫描电镜(SEM) 研究了前驱体粉末的物相、成分与形貌, 系统考察配位沉淀条件包括溶液pH值、反应温度、反应物浓度和表面活性剂对前驱体粉末形貌、粒度和成分的影响。结果表明: Ni(Ⅱ)-C₂O4^2--NH₃-NH₄⁺-H₂O反应体系中, 在溶液pH值为8.2～8.8, 温度为60～70 ℃, Ni²⁺浓度为0.5～0.8 mol/L, 表面活性剂聚乙烯吡咯烷酮(PVP)用量为0.1%～0.5%条件下得到的新型前驱体为草酸镍氨复盐, 其形貌为纤维状; 氨与镍离子配合并生成草酸镍氨复盐是纤维状形貌形成的内在机制。通过在空气中热分解该种前驱体即可得到比表面积为5.944 m²/g、轴径比大于50的纤维状氧化亚镍粉末。     

纤维状氧化亚钴前驱体制备热力学分析

根据同时平衡原理和质量平衡原理,从理论上推导出了常温常压下Co(Ⅱ)-C2O42--NH3-NH4+-H2O体系中金属钴离子和草酸盐在水溶液中的热力学平衡数学模型,计算并绘制出体系的lg[Me2+]T～pH图,热力学分析表明,当pH<5.5时,游离的钴离子是溶液当中的主导离子,pH>5.5时,大部分钴离子主要以钴氨配合离子的形式存在,沉淀反应为钴氨配合离子与草酸根离子之间的反应。在此基础上,利用氨为配位剂,通过配位沉淀法制备了纤维状复杂前驱体,并采用X射线衍射、红外光谱和扫描电镜研究了前驱体粉末的物相、成分与形貌。结果表明:纤维状前驱体为含氨草酸钴复盐,氨与钴离子配合并生成含氨草酸钴复盐是纤维状形貌形成的内在机制。通过控制热分解温度和热分解气氛,最终得到了纤维状CoO粉末。     

形貌控制合成介孔纤维状钴酸镍粉末

以可溶性氯化镍、氯化钴和草酸为原料, 利用氨为配位剂, 通过配位共沉淀-热分解法制备了多孔纤维状钴酸镍(NiCo₂O₄)粉末。采用XRD、SEM、TEM、IR以及BET对前驱体和NiCo₂O₄粉末的物相、成分与形貌进行了表征, 系统考察了配位共沉淀条件对前驱体粉末形貌、粒度和成分的影响。采用DTA/TG研究了钴酸镍前驱体粉末的热分解历程。结果表明：Ni²⁺-Co²⁺-NH₃-NH₄⁺-C₂O₄^2--H₂O反应体系中, 在溶液pH=8.0、温度50 ℃、金属离子浓度0.5 mol/L的条件下可得到纤维状钴酸镍前驱体粉末; 氨与镍钴离子配合生成含氨草酸镍钴复盐是纤维状形貌形成的机理。在空气气氛中300 ℃热分解该前驱体粉末即可得到比表面积97 m²/g、平均孔径11 nm、轴径比30~50的纤维状多孔NiCo₂O₄粉末。     

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。     

纤维状纳米级镍粉制备的前驱体热分解

通过1R、TGA／DTA、XRD、SEM等分析手段，研究纤维状镍粉前驱体粉末的热分解过程，对分解产物的组成及形貌进行表征。结果表明，前驱体的形貌是影响热分解产物镍粉形貌的决定性因素。低温区分解得到的粉末较粗且大部分粒子形状不规则，480℃以上分解得到的粉末团聚程度非常高。400℃下分解30min得到的镍粉纤维状明显且分散性较好，随着分解时间的延长，金属粉末粒子之间团聚加重。最佳工艺条件下制得的镍粉呈毛线般纤维状，其构成粒子粒径小于50nm。     

共沉淀法合成镍锰酸锂正极材料前驱体

通过共沉淀法合成了类球形镍锰酸锂正极材料前驱体, 研究了反应温度、溶液pH值、溶剂组成和表面活性剂十六烷基三甲基溴化铵(CTAB)添加量对前驱体镍锰碳酸盐形貌、粒径及物相组成的影响。结果表明, 适宜的合成条件为:pH=9.0, 反应温度80 ℃, 乙醇与水体积比1∶3, 表面活性剂CTAB添加量为1.5倍临界胶束浓度(CMC)。在该条件下制备的前驱体镍锰碳酸盐具有层片状堆垛的类球形结构; 煅烧后得到的镍锰酸锂材料为无序型的尖晶石结构, 属于Fd-3m空间群, 结晶度高, 粒径约150 nm。对镍锰酸锂进行电化学性能测试, 结果显示, LiNi_0.5Mn_1.5O₄在0.5C下的最大放电比容量为124.8 mAh/g, 20次循环后容量保持率为62.3%, 在大倍率下放电后再次回到0.5C, 放电比容量为73.8 mAh/g。     

固体草酸加料对草酸镍粒度与形貌的影响

采用固体草酸加料方式沉淀可溶性镍盐,可得到类球形颗粒,并显著减少沉淀母液废水的排放量,有利于缓解湿法生产镍系列粉末过程造成的环境负荷。实验证实采用一次性加料、施加超声波、缩短陈化时间、降低温度、选择硝酸镍、添加分散剂均可有利于促使沉淀颗粒粒度细化和提高分散性,而溶液pH对颗粒形貌具有显著影响。从pH为11的中强碱性溶液中开始添加固体草酸,随着pH值的逐步下降,存在沉淀颗粒的"溶解-再结晶"过程,使得晶粒形貌从结实颗粒转化成为由大量细小长方体晶粒聚集而成的大颗粒。在碱性条件下沉淀颗粒的主要成分是含铵草酸镍复盐,而在酸性条件下沉淀的主要成分是草酸镍,均可在400℃完全分解。     

超细草酸镍沉淀过程中颗粒大小及形貌控制

在以硫酸镍盐为原料、草酸铵为沉淀剂制备超细草酸镍粉末的过程中，对影响草酸镍颗粒大小及形貌的主要因素进行了研究．结果表明：加料方式及草酸铵溶液的初始pH对草酸镍形貌和大小的影响很大，而镍盐及分散剂的种类只对颗粒大小有一定的影响．当草酸铵溶液初始pH为4、硫酸镍浓度为0．5mol／L及在1L NiSO4溶液中分别添加分散剂PVP和PEG6．2g时，以草酸铵溶液向硫酸镍溶液中加入的方式，可制得呈类球形的、均匀分散的、粒径0．3～0．5μm的草酸镍粉末．     

纳米氧化钇粉体前驱体固相法合成及其悬浮液分散稳定性

以YCl3.6H2O和Na2C2O4为反应物,固相法制备氧化钇纳米粉体前驱体,用差热-热重法分析前驱体的分解过程,用X射线衍射和透射电镜对产物的组成、粒度和形貌进行表征。结果表明,产物为粒度分布均匀、纯度高、立方晶系的氧化钇,其一次颗粒尺寸在15nm左右。体系ζ电位和吸光度的测定表明,介质pH和表面活性剂类型和浓度对氧化钇粉体的悬浮稳定性有显著的影响。在阴/非离子表面活性剂复配物的水溶液中,pH在10左右,氧化钇粉体悬浮液稳定性最好。     

碳酸氢铵沉淀法制备二氧化铈超细粉体

采用碳酸氢铵作为沉淀剂制二氧化铈超细粉体。X射线衍射结果表明，焙烧温度在300－900℃时，所得二氧化铈纳米晶为立方晶系，其平均粒径随焙烧温度的升高而增大，热失重结果表明，样品的失重率取决于焙烧温度，反应物浓度为0．25－0．3mol/L，沉淀剂浓度为0．2－0．4mol/L,pH值为7－8，沉淀温度为60－80℃，焙烧温度为600℃，可制得平均晶粒度小于20nm。分散性好的二氧化铈超细粉体。     

Current situation and future trend of China rare earth luminescent material industry

<正>Rare earth luminescent material is one of the most important application sectors of rare earths.China enjoys the exceptional advantage to develop rare earth luminescent material for its abundant rare earth resources.After several decades'endeavor,China's rare earth luminescent material industry,headed by rare earth phosphor for lamp and LED and high efficient rare earth energy-saving light source,has been gradually developed into a scale industry.China has become a major production base of rare earth phosphor for lamps and rare earth     

China rare earth market review

正June 1~10,2014Rare earth market remained weak.Quoted price of rare earth products was similar to that in May.There was no sign of recovery in downstream market.The market of NdFeB magnetic materials and phosphor was depressed.Catalyst,polishing powder and ceramic industries remained inactive.Demand from downstream industry was soft.Consumers purchased on their needs.Suppliers had strong intention to sell.Prices of rare earth products     

Annual Report analysis of Chinese rare earth-related listed companies in 2013

<正>Chinese rare earth-related listed companies have published their 2013 annual reports.It can be understood from their reports that production and operation activities of Chinese rare earth-related companies were still heavily affected by macro economy and industrial policies.They basically followed the steps of national economy.In 2013,world economy recovered slowly but the economy     

Market opportunities and challenges for rare earth polishing powder

正1.Status of rare earth polishing powder Rare earth polishing powder with high content of cerium oxide began to replace iron oxide for glass polishing and became one of the key materials in glass polishing process since 1940.Compared with traditional iron oxide,rare earth polishing powder has many advantages,such as fast polishing rate,high polishing quality and long service life.It can achieve good surface quality and improve operation conditions.For example,in lens polishing,the polishing work that cerium     

Baotou Research Institute of Rare Earths developed a new RE alloy preparation technology

正Pyrometallurgy Laboratory of Baotou Research Institute of Rare Earths had independently developed a new preparation technology of rare earth alloy for NdFeB.The alloy can remarkably enhance the coercivity of NdFeB magnet but also evidently reduce the production cost of the magnet.The new master alloy was prepared in the kA pilot-scale electrolytic cell by the independent technology.The rare earth master alloy can be used as the raw material for NdFeB.Compared     

Market and recycling of NiMH battery

<正>Market status and future trend of NiMH battery1.Global market of small NiMH battery Global market size of small NiMH batteries declined year on year since 2011.The trend will continue to 2018,at the rate of 5%to 10%annually.Demand for small NiMH batteries will be stable gradually.Many electrical apparatuses are powered by the built-in lithium battery today,which is the main reason for the shrunk market of small NiMH batteries.But,for some products,small NiMH     

China rare earth market review

正September 1-10,2014 Affected by the National Day holiday,rare earth transaction was stagnant and the market showed a weak steady state.As there was no good news for downstream market,some products with flat demand would likely rally slightly for some time to     

2014 second batch of rare earth quota released

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矿用防爆轴流对旋主要通风机叶片ANSYS模态分析及应用

高效节能矿用防爆对旋主要通风机的叶片是主要通风机运行的关键部件,叶片在运行时不断受到气流的作用力,从而使叶片产生振动,当叶片振动的频率与叶片的固有频率接近时,容易产生共振从而导致叶片的断裂。一旦叶片断裂时,对主要通风机的安全运行产生致命的影响,从而导致矿山、化工等企业发生重大事故,将会产生不可估量的损失。基于有限元分析软件ANSYS,对高效节能矿用防爆轴流对旋主要通风机叶片进行模态分析及产生对应的六阶模态频率,对主要通风机叶片的运行频率、固有频率及产生的共振问题进行了原理分析,并且解决了叶片频率共振的问题,从而为主要通风机叶片结构设计提供理论依据,并对主要通风机叶片的安全运行提供保障。     

2013 NdFeB export analysis

<正>China totally exported nearly 24,000 tonsof NdFeB products during 201 3,including 18,825 tons of permanent magnet,valued USD 1.34 billion at an average price of 71.4 USD/kg;3,277 tons of NdFeB magnetic powder,valued USD 1 01 million at an average price of 30.9 USD/kg;1,334 tons of strip casting ribbon,with total export value of USD 74million at an average price of 55.3 USD/kg;and 586