Effects of zirconium silicate and chromite addition on the microstructure and bulk density of magnesia–magnesium aluminate spinel-based refractory materials

Six synthesized magnesium aluminate spinel-based refractory compositions used in steel and cement applications, were prepared using a two stage sintering process at 1760 °C, starting with approximately 1:1 wt% ratio of pure magnesia and alumina with additions of zirconium silicate (0.5, 1.0 and 2.0 wt%) and chromite (2.0, 3.0 and 5.0 wt%). These compositions were investigated for effects on densification, chemical and mineralogical phases formed.     

添加剂对尖晶石型锰酸锂性质表征的影响

以LiOH·H_20和MnO_2为原料,分别掺入H_2BO_3、Al_2O_3、SiO_2和P_2O_5等添加剂,用固相分段法制备尖晶石型锰酸锂。结果表明,SiO_2和P_2O_5可以有效地改善LiMn_2O_4的电化学性能,H_3BO_3对锰酸锂的电化学性能影响不大,而Al_2O_3破坏了LiMn_2O_4的电化学性能。面扫描结果显示,Si或P元素各自都均匀地分散于LiMn_2O_4的物相中。从元素电负性和原子半径的角度分析了B、Si、P和Al元素对尖晶石型LiMn_2O_4结构和性能的影响。     

添加尖晶石对氧化锌压敏电阻性能的影响

通过添加尖晶石（Ｚｎ７Ｓｂ２Ｏ（１２））改性研制出电位梯度为１００Ｖ／ｍｍ左右，压敏电压在８２～１５０Ｖ，通流容量可达１６００Ａ／ｃｍ２，漏电流＜２μＡ系列压敏电阻器，从而满足了国内电话交换机行业对８２Ｖ、１００Ｖ、１２０Ｖ、１５０Ｖ压敏电阻器的电性能要求。从工艺的角度解释了尖晶石对氧化锌瓷晶粒的作用原理，并分析了尖晶石的微观结构及粒度对瓷片电性能的影响。     

纳米晶镁铝尖晶石透明微晶玻璃的晶化行为研究

利用DTA、XRD和TEM研究了制备工艺对微晶玻璃晶化行为的影响，并制备出具有纳米镁铝尖晶石为晶相的微晶玻璃。     

锌空气电池空气电极催化材料的研究

采用将Li2CO3,电解二氧化锰(EMD)和Co(NO3)2·6H2O混合进行高温固熔反应的合成方法,制备了1种尖晶石型金属氧化物催化材料LiMn2-xCoxO4。通过电化学测试(极化曲线、放电曲线)、X射线衍射分析(XRD)以及扫描电镜(SEM)等方法对电极的微观结构和性能进行了研究。实验结果表明,以LiMn1.95Co0.05O4为催化材料的气体扩散电极具有最好的综合电化学性能。其0.9V极化电位时的最大电流密度可达210mA/cm2AA型(5号)样品电池以100mA电流恒流放电,容量可高达4439mAh。     

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.     

工艺参数对微区沉淀法制备纳米MgAl2O4粉体的影响

采用高分子网络微区沉淀法制备纳米镁铝尖晶石（MgAl2O4）粉体，并采用TGA／DTA、XRD和TEM等分析测试技术对前驱体的热分解和所制得粉体的物相组成、形貌及颗粒尺寸进行表征，结果表明所制得的MgAl2O4粉体颗粒粒径小，结晶良好，成分单一且粒径大小均匀。而实验过程中工艺参数的改变会对生成粉体的粒径和形貌产生一定的影响，进而即研究了各种工艺参数的改变对该方法制备纳米MgAl2O4粉体的影响。     

In situ synchrotron X-ray studies on copper-nickel 5 V Mn oxide spinel cathodes for Li-ion batteries

Partial substitution of Mn in lithium manganese oxide spinel materials by Cu and Ni greatly affects the electrochemistry and the cycle life characteristics of the cathode. Substitution with either metal or a combination of both metals in the spinel lattice structure reduces the 3.9-4.2 V potential plateaus associated with the conversion of Mn³⁺ to Mn⁴⁺. Higher potential plateau associated with oxidation of the substituted transition elements is also observed. These substituents also significantly alter the onset of Jahn-Teller distortions in the 3 V potential plateau. Synchrotron based in situ X-ray absorption (XAS) was used to determine the exact nature of the oxidation state changes in order to explain the overall observed capacities at different potential plateaus. The studies on LiCu_0.5Mn_1.5O₄ show single phase behavior in the 4-5 V potential region with a good cycle life. Lower cycle life characteristic observed in cycling LiNi_0.5Mn_1.5O₄ and LiNi_0.25Cu_0.25Mn_1.5O₄ versus Li metal are ascribed to coexistence of several phases in this potential region. However, LiCu_0.5Mn_1.5O₄ shows onset of Jahn-Teller distortions in the 3 V potential plateau, in contrast to LiNi_0.5Mn_1.5O₄ and LiNi_0.25Cu_0.25Mn_1.5O₄ cathode materials.     

Synthesis and electrochemical characterization of a new Se-doped spinel material for lithium secondary batteries

A new Se-doped spinel material, LiAl_0.18Se_0.02Mn_1.8O₄ powder with a phase-pure polycrystalline was synthesized by a sol–gel method. The material in the 3 V region (2.4 3.5 V) and both the 3 and 4 V region (2.4 4.4 V) initially deliver a discharge capacity of 81 and 178 mA h g^–1 which increase with cycling to reach 110 and 204 after 50 cycles, respectively. The material shows excellent cycleability in the 4 V region (3.0 4.4 V) with almost no capacity loss. The structural integrity of the Se-doped spinel was characterized by charge–discharge cycling tests and X-;ray diffraction.     

TiO2加入量对富铝尖晶石烧结性能的影响

以α-Al2O3、分析纯的MgO及分析纯的TiO2为原料,研究了在1400℃、1500℃、1600℃保温3 h下,TiO2加入量(分别为0、1%、2%、4%)对Al2O3与MgO物质的量比为21的富铝尖晶石烧结性能的影响,并利用XRD进行物相组成分析,利用SEM和EDAX进行显微结构分析.结果表明由于TiO2与MgAl2O4的固溶作用,加入TiO2可显著改善富铝尖晶石的烧结性能;随着TiO2加入量的增加,试样的体积密度增加,显气孔率降低,特别是在1600℃烧结后的试样尤为显著.