高活性Mn_2O_3制备尖晶石LiMn_2O_4及其性能研究

尖晶石LiMn_2O_4是当前最具研究价值的锂离子电池正极材料之一。采用碳酸锰热解法制备高活性Mn_2O_3粉末作为尖晶石LiMn_2O_4的前驱体,探究锰锂比对高温固相法合成尖晶石LiMn_2O_4的影响。利用热重分析(TG-DSC)及热力学分析确定碳酸锰热解制备前驱体高活性Mn_2O_3的最佳热解条件:热解温度为600℃时,制备出结晶性能良好、无杂质、分散均匀的Mn_2O_3粉末。通过X射线衍射(XRD)、扫描电镜(SEM)和电化学测试对尖晶石LiMn_2O_4的结构、形貌和电化学性能进行表征。结果表明,随着锂锰比增加,产物的结构、形貌和电化学性能均有所改善和提高。锂源的添加量决定了尖晶石LiMn_2O_4结构、形貌,当Mn∶Li=2. 0∶1. 2时,尖晶石LiMn_2O_4样品的结晶形态完善,表面光滑,颗粒均匀,且无杂质;在0. 5C下,其首次充电比容量达到117. 6 mAh·g~(-1),放电比容量为114. 8 mAh·g~(-1)。循环100周后容量保持率达到91. 8%。在高倍率放电下,仍保持较高的放电比容量和较好的循环性能。     

Mn1.5-0.5xCo1.5-0.5xCuxO4尖晶石粉体及涂层的制备与性能

采用溶胶-凝胶法制备Mn1.5-0.5xCo1.5-0.5xCuxO4(x=0、0.1、0.2、0.3和0.4,摩尔分数)尖晶石粉体,并将该粉体涂覆在SUS 430合金表面,经高温烧结后制成涂层。研究Cu含量对尖晶石的晶体结构、热膨胀行为和高温电导率的影响,测试Mn1.35Co1.35Cu0.3O4涂层的抗氧化性能。结果表明:随Cu含量增加,Mn1.5-0.5xCo1.5-0.5xCuxO4尖晶石的物相组成由立方-四方复合相逐渐转变为纯立方相。当x=0时,物相为立方-四方复合相;x≥0.2时,物相转变为纯立方相。尖晶石的热膨胀系数(CTE)随Cu含量增加而增大,原本出现在500℃左右CTE降低的现象被抑制。在30~800℃范围内,Mn1.35Co1.35Cu0.3O4尖晶石涂层的CTE与SUS 430不锈钢相匹配(分别为12.45×10-6和12×10-6~12.4×10-6 K-1)。此外,该尖晶石的高温电导率随Cu含量增加而升高,800℃以下电导率均大于1.3 S/cm,符合连接体材料电导率的要求。涂覆Mn1.35Co1.35Cu0.3O4尖晶石涂层后,SUS 430合金在800℃的氧化速率下降87.5%。因此,涂覆Mn1.35Co1.35Cu0.3O4尖晶石涂层的SUS 430合金可以用作固体氧化物燃料电池(SOFC)连接体。     

硫酸锰溶液碱化沉淀—焙烧法制备Mn_3O_4

针对传统Mn3O4生产过程中存在工艺控制复杂和污染物排放量大的问题,结合传统液相法和焙烧法的优点,提出了先用NaOH滴加含有分散剂十二烷基硫酸钠(SDS)的硫酸锰溶液制备四氧化三锰前驱体,再焙烧前驱体制备Mn3O4,用SEM、XRD对产物进行表征。试验结果表明:在SDS投加量1.5g/L、反应温度60℃、反应时间30min和搅拌转速300r/min条件下,可得到粒径约100nm、大小分布均匀的纳米级前驱体颗粒,其主要由Mn(OH)2、MnOOH和Mn3O4组成;前驱体焙烧制备Mn3O4最佳温度为1 000℃,此时可得到呈四方尖晶石结构、粒径约500nm、颗粒大小均匀的Mn3O4产品。     

四氧化三锰的研制

Mn_3O_4是用于电子工业的重要原料之一。本文介绍了以MnCO_3和电解二氧化锰(EMD)为原料,用焙烧法制取Mn_3O_4,并测定了所制得的Mn_3O_4的杂质含量,团粒和晶粒直径、表观密度、比表面积、x射线衍射、红外光谱及磁化率等理化性能。     

高电压镍锰酸锂LiNi_(0.5)Mn_(1.5)O_4制备实验研究

以镍锰二元前驱体和电池级碳酸锂为原料,采用高温固相法合成高电压正极材料LiNi_(0.5)Mn_(1.5)O_4。分别从烧结温度、配锂量和烧结方式的角度研究了合成工艺对材料物化性能与电化学性能的影响。实验结果表明,碳酸锂和镍锰二元前驱体的配比为0.50,经过500℃低温预烧,然后850℃高温烧结的二次烧结下合成的LiNi_(0.5)Mn_(1.5)O_4,0.5 C放电容量133.02 m A·h/g,1.0C放电容量130.67 m A·h/g,结晶度较高,其综合性能最佳。     

Mn-Co尖晶石涂层对铁素体不锈钢的高温防护

本文针对铁素体不锈钢的高温氧化特性,简要介绍了目前国内外常用不锈钢防护涂层材料、Mn-Co尖晶石氧化物涂层的特性、制备方法以及研究现状;并针对热喷涂技术在Mn-Co尖晶石涂层的应用进行了探讨。在此基础上,通过优化等离子喷涂工艺,在T441不锈钢基体上沉积了致密Mn_(1.5)Co_(1.5)O_4保护涂层,并对该体系的抗长时(1000h)高温氧化性能进行了研究。结果表明:通过等离子喷涂及后续还原/氧化处理技术制备的Mn_(1.5)Co_(1.5)O_4涂层对T441不锈钢基体起到了有效的保护作用,显著提高了T441的抗长时氧化性能。     

基于La掺杂固相法合成LiNi_(0.5)Mn_(1.5-x)La_xO_4及其性能研究

采用高温固相法制备尖晶石5V正极材料LiNi_(0.5)Mn_(1.5-x)La_xO_4(x=0,0.005,0.01,0.02)。通过XRD,SEM及电化学手段等探讨La~(3+)不同掺杂量对LiNi_(0.5)Mn_(1.5)O_4材料结构和电化学性能的影响。XRD测试结果表明,通过La~(3+)部分取代晶格中Mn~(3+)后使得LiNi_(0.5)Mn_(1.5)O_4材料晶胞体积增大,增加了Li~+迁移速率,进而提高了材料电子电导率,该结论得到了电化学性能测试验证,LiNi_(0.5)Mn_(1.495)La_(0.005)O_4表现出最优秀的循环和倍率性能,经过1C倍率循环275周后,容量保持率为93.8%;20C放电比容量保持率高达65.6%。     

富锂锰基正极材料Li1.2-xNaxNi0.13Co0.13Mn0.54O2的制备及电化学性能

采用共沉淀法制备碳酸盐前驱体,通过高温固相反应制备Na~+掺杂的富锂锰基正极材料Li_(1.2-x)Na_xNi_(0.13)Co_(0.13)Mn_(0.54)O_2(x=0,0.01,0.02,0.04,0.08).X射线衍射(XRD)和扫描电镜(SEM)分析表明,x≤0.04时为层状富锂锰基材料的α-NaFeO_2六方相结构,Na掺杂量过大时颗粒表面出现团聚絮状物并发现第二相—P2型层状氧化物.电化学测试发现适量的Na掺杂可提高材料的比容量、倍率和循环性能;掺杂量为0.02时电化学性能最佳:在2.0～4.6 V充放电, Li_(1.18)Na_(0.02)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2在0.1 C放电比容量为273.4 mAh/g,首次库伦效率为93.1%, 1 C循环100次后容量超过200 mAh/g,保持率为84.3%.离子半径较大的Na~+占据Li位,起到柱撑作用,稳定了结构,增大了层间距,利于Li~+扩散;此外,材料表面形成的P2型层状氧化物能够减缓层状结构向尖晶石结构的转变,从而提高了电化学性能.     

Li~+掺杂LiNi_(0.5)Mn_(1.5)O_4的制备与性能

用固相反应法合成了Li~+掺杂的LiNi_(0.5)Mn_(1.5)O_4,并用XRD、SEM和恒电流充放电技术研究Li+掺杂对材料结构、形貌和充放电性能的影响。结果表明Li+掺杂和未掺杂LiNi_(0.5)Mn_(1.5)O_4均具有Fd3m尖晶石结构,掺杂的Li~+以固溶体形式存在,掺杂少量的Li+能显著提高材料循环性能,但放电比容量稍有降低,其中Li_(1.05)Ni_(0.45)Mn_(1.5)O_4的放电比容量为136.1 m A·h/g,循环30次后基本不变,具有很好的循环稳定性。     

回转窑不同温度场钒渣物相演变规律探讨

通过对实验室模拟现场回转窑的6组不同温度点下焙烧渣样品进行钒尖晶石形貌变化、物相含量变化、钒元素的赋存规律及不同温度点下物相转变机理的研究。钒尖晶石形貌变化结果表明,整个焙烧过程中钒尖晶石形貌变化经历了致密光滑块状-氧化铁的镶边结构-钒尖晶石完全直接为隐晶质物质-小颗粒物质重新组合并且长大5个过程;矿物自动解理分析仪(MLA)物相含量分析数据显示焙烧过程中石灰石、铁橄榄石、钒尖晶石和白云石在逐渐减少,普通辉石相是逐渐增加,而氧化铁固溶体、部分氧化钒尖晶石、钒酸钙固溶体和铁板钛矿固溶体的变化趋势是先增加后减少;钒元素的赋存形式规律为绝大多数钒元素赋存于氧化物中,占到总量的85%左右,其次赋存于硅酸盐中,占到钒总含量的14%左右,还有极少部分分布于碳酸盐等矿物中;整个焙烧过程物相变化机理主要分为铁元素向外扩散-氧元素向内扩散-氧化物的化合过程-化合物雏形晶体的长大4个反应过程。     

熔炼次数对M17返回料合金成分、组织和性能的影响

实验结果表明,M17铸造高温合金(%:0.16C、8.79Cr、5.79A1、4.93Ti、3.29Mo、15.20Co、0.78V、0.015B、0.073Zr、0.002S、0.001P、0.001 1O、0.001 0N)经25 kg真空感应炉返回重熔后,Si含量随重熔次数的增加而略有增加,合金中主要元素和其它杂质元素S、P、H的含量变化不大,而氧、氮略有增加;合金中初生碳化物由新合金中的草书体逐渐向返回合金块状转变,初生碳化物的遗传性堵塞合金凝固时的补缩通道,使返回料合金的疏松倾向增大,高温塑性下降较大。     

China's Major Non-ferrous Metals Imports & Exports

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Zinc Production by Province in 2014

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80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.