溶胶—凝胶—酯化法制备LiMn2O4超细粉及其电化学性质的研究

溶胶－凝胶－酯化方法是通过金属离子与多元有机酯的均一的螯合物。在较低的温度（〈２５０℃）下形成尖晶石型ＬｉＭＮ２Ｏ４正极材料。雇轩的ＬｉＭｎ２Ｏ４具有很好的电化学活性。Ｌｉ＝ＬｉＭｎ２Ｏ４二次电池首次充放电容量超过１３０ｍＡｈ／ｇ,循环１０次以后容量仍然保持在１２０ｍＡｈ／ｇ的较高水平。     

柠檬酸溶胶-凝胶法制备纳米Y_2O_3:Eu~(3+)粉体

以Eu2O3,Y2O3为原料通过柠檬酸溶胶-凝胶法合成了Y2O3:Eu3+纳米粉,研究了pH值、柠檬酸用量(n[H3Cit]:n[Y3++Eu3+])及煅烧温度对粉体制备过程的影响。利用TG-DTA、XRD、SEM等测试手段对粉体的形成过程进行了分析。结果表明:Y2O3:Eu3+纳米粉体的一次粒径为25nm左右,二次粒径为250nm左右。纳米Y2O3:Eu3+粉体制备最佳实验条件为pH=5,n[H3Cit]:n[Y3++Eu3+]为2:1,煅烧温度为600℃。     

Synthesis of nanocrystalline NiO/doped CeO2 compound powders through combustion of citrate/nitrate gel

The ultrafine NiO/doped CeO₂ (Ce_0.8Gd_0.2O_1.9) compound powders were synthesized through the combustion of a citrate/nitrate gel. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that this method is effective to prepare uniform NiO/Ce_0.8Gd_0.2O_1.9 double phase compound powders. Moreover, the appropriate molar ratio of citric acid to rare earth metal ions (MRCM) in the precursors has a strong influence on forming a cross-linked framework, moderate oxygen element in gel and employing steady combustion. When the molar ratio of citric acid to metal ions is equal to 1.5, the compound powders with fine and homogeneous particles of about 13–18 nm were obtained.     

Spinel LiMn2O4 nanorods as lithium ion battery cathodes

Spinel LiMn2O4 is a low-cost, environmentally friendly, and highly abundant material for Li-ion battery cathodes. Here, we report the hydrothermal synthesis of single-crystalline beta-MnO2 nanorods and their chemical conversion into free-standing single-crystalline LiMn2O4 nanorods using a simple solid-state reaction. The LiMn2O4 nanorods have an average diameter of 130 nm and length of 1.2 microm. Galvanostatic battery testing showed that LiMn2O4 nanorods have a high charge storage capacity at high power rates compared with commercially available powders. More than 85% of the initial charge storage capacity was maintained for over 100 cycles. The structural transformation studies showed that the Li ions intercalated into the cubic phase of the LiMn2O4 with a small change of lattice parameter, followed by the coexistence of two nearly identical cubic phases in the potential range of 3.5 to 4.3 V.     

Acrylamide assisted polymeric citrate route for the synthesis of nanocrystalline ZrO2 powder

Nanocrystalline ZrO₂ powders have been prepared using acrylamide assisted polymeric citrate combustion (autoignition) route. Process parameters (i.e., total metal ions to citric acid ratio) were varied for the formation of polymeric resin in order to obtain the final product with desired properties (organic free, smaller crystallite size, etc.). The effect of three different citric acid amounts in the formation of nanocrystalline ZrO₂ powder was investigated using FTIR, XRD, TG/DTA and SEM-EDS, respectively, to identify the structural coordination, phase, thermal behavior and microstructure of the polymeric intermediates as well as the final ZrO₂ powders. Organic free ZrO₂ powder with two different phases of metastable t-ZrO₂ and m-ZrO₂ were prepared by calcining the polymeric intermediates at 600 °C. The lowest crystallite was found to be 18 and 16 nm, respectively, for the t-ZrO₂ and m-ZrO₂ phases prepared with total metal ions to citric acid ratio of 1:3.     

溶胶-凝胶法合成锂离子筛前驱体LiMn2O4的研究

用溶胶 凝胶法、以柠檬酸和乙二醇作为聚合反应的单体合成了正尖晶石结构LiMn2 O4的前驱体 ,研究了反应物摩尔比、pH值及焙烧温度对材料性能的影响 ,并通过XRD、IR和SEM等方法研究了柠檬酸螯合法合成正尖晶石结构LiMn2 O4 的溶胶 凝胶过程 ,探讨了反应机理。研究表明白 ,在Li/Mn摩尔比为 0 6、pH值为 3 0及焙烧温度为 6 0 0℃时 ,合成的正尖晶石结构LiMn2 O4 的前驱体具有较好的晶粒结构 ,其一次粒子直径大多在 1 0 0nm以内。     

硫酸盐还原法制备La_2O_2S∶Yb,Er及其上转换发光性能

采用硫酸盐还原法制备了Yb、Er双掺的La2O2S粉体,考察了柠檬酸用量、前驱体煅烧温度、碳还原温度、Er3+离子浓度和Yb3+离子浓度对粉体的影响。分别采用X-射线衍射分析(XRD)、扫描电子显微镜(SEM)、比表面积分析(BET)、紫外可见光分光光度计(UVPC)和荧光光谱分析(PL)对粉体的相组成、形貌、颗粒尺寸、反射率和上转换发光性能进行表征。研究结果表明,800℃时可以得到纯相的La2(SO4)3;碳还原温度为900℃以上可以得到纯相的结晶较好的La2O2S;样品的粒径大约为100～200nm,颗粒存在一定的团聚;柠檬酸与硝酸盐的最佳摩尔比为1.5∶1;Er3+离子掺杂浓度为2mol%、Yb3+离子掺杂浓度为12mol%时粉体的上转换发光强度最强。     

Polymeric precursor synthesis of Ba2Ti9O20

Ba₂Ti₉O₂₀ was synthesized by Pechini method using citric acid as a chelating agent and ethylene glycol as an esterification agent. The effects, of the pH of the starting solutions and the molar ratio of citric acid to total metal cations concentration on the formation of Ba₂Ti₉O₂₀, were investigated. Increasing the pH of the starting solutions enhances the formation of Ba₂Ti₉O₂₀, but the increase of the molar ratio of citric acid to total metal cations concentration retards the formation of Ba₂Ti₉O₂₀ due to increased diffusion distances. Single-phase Ba₂Ti₉O₂₀ was obtained at 1200 °C for 4 h when the molar ratio of citric acid to total metal cations concentration was unity, regardless of the pH of the starting solutions. Increasing the molar ratio of citric acid to total metal cations concentration up to 2, single-phase Ba₂Ti₉O₂ was synthesized at 1200 °C for 6 h for the precursors with pH 3.5 and 6, but not for the precursors with pH 2.0. DTA, TG, XRD, FT–IR spectroscopy and Raman spectroscopy were used to characterize the precursors and the derived oxide powders. Details of the synthesis and characterizations of the resultant products were given.     

Low temperature preparation of nanocrystalline Sr0.5Ba0.5Nb2O6 powders using an aqueous organic gel route

Nano-sized Sr_0.5Ba_0.5Nb₂O₆ (SBN50) ceramic powders have been synthesized by an aqueous organic gel route. Homogeneous Sr-Ba-Nb precursor gels are prepared with Ba-EDTA, Sr-EDTA, and Nb-citrate complex as source of Sr, Ba, and Nb, respectively. Citric acid and ethylenediaminetetraacetic acid (EDTA) were used as the chelating agents. The structural variation of the SBN powder with annealing temperature was studied by TG-DTA, FT-IR and XRD. The precursor gel on calcination at 800 °C for 2 h produces a pure tungsten bronze SBN phase and the corresponding average particle size is 30-50 nm. The influences of the pH and the molar ratio of citric acid:Nb cation on the formation of homogeneous Sr-Ba-Nb precursor gels were also studied. The results show that a homogeneous Sr-Ba-Nb precursor gel with no precipitate is formed at pH 8 and the optimum molar ratio of citric acid and the metal cations is 3:1.     

Synthesis of Ba6-3xNd8+2xTi18O54 ceramic powders via citric acid precursor

Ba_6-3xNd_8+2xTi₁₈O₅₄ ceramic powders have been synthesized by the Pechini method. The precursors and derived oxide powders were characterized by DTA, TG, XRD and TEM. The effect of the molar ratio of citric acid to total metal cation concentration on the crystallization behavior of Ba_6-3xNd_8+2xTi₁₈O₅₄ was investigated. Single-phase and well crystallized Ba_6-3xNd_8+2xTi₁₈O₅₄ powders were obtained from pulverized resin at 900 °C for 3 h, without the formation of any intermediate phase, when the correct molar ratio of citric acid to total metal cations concentration is used.     

溶液燃烧法合成Co3O4纳米粉体及热处理研究

分别以氨基乙酸、柠檬酸、葡萄糖为燃料,Co(NO_3)_2·6H_2O为氧化剂,采用溶液燃烧法合成Co_3O_4粉体,并对氨基乙酸为燃料合成的Co_3O_4粉体在500℃、600℃和700℃热处理,研究其结构、微观形貌和磁学性能。研究表明各燃料配制的前驱体溶液在300℃均可发生燃烧反应合成Co_3O_4粉体,以氨基乙酸为燃料时,合成粉体的颗粒较大,中间有气孔,分散性好,残留少量的氨基乙酸。n(氨基乙酸)∶n(硝酸钴)=1.11∶1时合成的Co_3O_4粉体600℃热处理后得到了高纯度、分散性好、平均径向尺寸80nm的Co_3O_4纳米粉体。以氨基乙酸为燃料合成的Co_3O_4产物在600℃和700℃热处理后,其矫顽力和剩磁值都比500℃热处理后的要小。     

溶胶凝胶法制备尖晶石型LiMn2O4的研究现状及展望

综述了用溶胶凝胶法制备锂离子电池正极活性材料尖晶石型LiMn2O4的方法及其发展方向。溶胶凝胶法制备材料具有贩优越性,研究工作取得了很大进展,但还不够系统深入,工业化尚有较大困难,认为这一领域的研究方向为：溶胶凝胶过程的基础性研究;尖晶石型LiMn2O4正析材料的掺杂改性、低温合成、纳米化和薄膜化;优化工艺过程,降低制备成本,实现工业化。     

Influences of Sintering Process of Sprayed Precursors on the Structure and Electrochemical Properties of LiMn2O4 Cathode Material

Well-defined spinel LiMn2O4 powders were synthesized via sintering a precursor, which was prepared by spraydrying method. The effects of sintering process on the structure and electrochemical properties of LiMn2O4 were discussed. It was found that a single sintering could not synthesize a pure LiMn2O4 compound, while two-step sintering procedure consisting of decomposing sprayed precursors at 350℃ and further sintering at an elevated temperature leads to the formation of a single-phased LiMn2O4 with homogeneous particle size distribution. As compared to that sintered in air, the two-step sintered LiMn2O4 in oxygen shows tighter structure and more uniform particle size, as well as better electrochemical properties. It delivers an initial discharge capacity of 131 mAh·g^-1 （1/10C）, and still has excellent cycling stability at higher rate （1/5C）.     

Synthesis and characterization of nano crystalline BaFe12O19 powders by low temperature combustion

Nano crystalline BaFe₁₂O₁₉ powders have been prepared at a relatively low calcination temperature by a gel combustion technique using citric acid as a fuel/reductant and nitrates as oxidants. The effects of processing parameters, such as Ba/Fe ratio, citric acid/nitrates ratio, reaction temperature on the powder characteristics and magnetic properties of the resultant barium ferrites were investigated. By controlling the molar ratio of citric acid to metal nitrates, nano crystalline BaFe₁₂O₁₉ powders with different particle sizes have been obtained. Phase attributes, microstructures and magnetic properties of the powders were characterized using X-ray diffraction analysis, X-ray line-broadening technique, Fourier transform infrared spectroscopy measurements, transmission electron microscopy and vibrating sample magnetometer. The maximum saturation magnetization value and intrinsic coercivity value for the obtained barium hexaferrites are 59.36 emu/g and 5540 Oe.     

固相配位化学反应法合成LiMn2O4的研究

采用固相配位反应法合成了锂离子电池阴极材料LiMn     

锂离子电池正极材料LiMn_2O_4制备新工艺

采用球磨湿混和旋转合成相结合的新工艺来制备锂离子电池正极材料ＬｉＭｎ２Ｏ４,并对制备的材料进行了粒度、化学成分以及电化学性能测试．制备的ＬｉＭｎ２Ｏ４为正尖晶石结构,而且物质纯净．同一批次制备的材料化学成分均匀,粉末粒度分布范围窄,中粒径为１０．６７μｍ,首次充电容量为１２４ｍＡｈ／ｇ,放电容量为１１５ｍＡｈ／ｇ．循环次数达３０次时,放电容量还大于１００ｍＡｈ／ｇ,循环稳定性良好．球磨湿混工艺能将原料混合均匀,并能有效地使原料粒度细化而且粒度均匀．旋转合成工艺能使反应物和反应产物的温度均匀、粒度均匀、晶型结构与成分均匀．球磨湿混和旋转合成相结合的固相合成新工艺能制备出电化学性能性能良好的ＬｉＭｎ２Ｏ４     

尖晶石锰酸锂的组成对其结构和性能的影响

以电解二氧化锰和碳酸锂为原料用高温固相法合成了尖晶石锰酸锂,在锂与锰的原子比从0.95:2到1.1:2范围内,其结构为单一尖晶石相,晶格常数和比容量随着锂锰比的增加呈现出先增大后降低的变化规律.在锂锰比为1.0:2和1.02:2附近,晶格常数和比容量分别达到最大.这种变化规律与锂离子在晶格中的位置有关.在锂锰比从1.0:2到1.1:2的范围内,随着锂锰比的增加,尖晶石锰酸锂嵌脱锂反应过程的动力学极化逐渐降低,大电流性能逐渐提高.以尖晶石锰酸锂为正极,MCMB为负极组装了423048型电池,锂锰比从1.0:2到1.1:2,电池循环稳定性随锰酸锂的锂锰比的增大而提高.     

微波均相合成YAG纳米粉体及其可烧结性研究

采用微波辐照尿素法均相合成技术制备了具有良好分散性的纳米级单相YAG粉体,分析了YAG前驱体的化学组成及其物相变化过程,并对YAG粉体的粒度和形貌进行了表征,结果表明在尿素与钇铝离子的摩尔比为15:1的低尿素用量条件下,合成的无定形前驱物经900℃煅烧直接结晶生成YAG单相粉体,在反应体系中添加适量(NH₄)₂SO₄可使YAG粉体的粒度分布和可烧结性明显改善,添加8%的(NH₄)₂SO₄得到的YAG粉体具有良好的可烧结性,在1500℃烧结即可实现致密化.     

Effect of preparation methods and optical band gap of ZnO nanomaterials on photodegradation studies

Improving of photo-oxidative efficiency of ZnO has become of importance to meet the requirements of environmental protection. In this research, ZnO nanomaterials prepared by three different methods (thermal decomposition, precipitation and sol-gel-combustion using metal nitrate and different fuels (urea, oxalic acid and citric acid)). Various molar ratios of citric acid to salt used as variable parameter (0.50, 0.75, 1.00, 1.25, and 1.50). These nanomaterials were characterized by studying their structural, morphological, surface and optical properties. The photocatalytic activity was evaluated by photocatalytic degradation of Remazol Red RB-133 (RR) under UV-light irradiation. The obtained results showed that the photocatalytic efficiency was affected by preparation method, type and ratio of fuel to salt. The optimum is a gel precursor containing zinc nitrate and citric acid prepared in the molar ratio of 1. The highly active nanomaterial was applied for photocatalytic degradation of mixtures of two dyes – (RR) and Methylene Blue (MB).     

前驱体溶液配比及pH值对凝胶-燃烧合成纳米MgO颗粒的影响

以硝酸镁、柠檬酸及氨水为原料,用凝胶-燃烧合成法制备了MgO纳米颗粒.系统研究了前驱体溶液中硝酸镁与柠檬酸的配比及其pH值对凝胶的形成、凝胶的形态、凝胶的燃烧过程以及最终合成产物特性的影响,并在优选的工艺条件下,获得了平均尺寸约为10nm且粒径分布窄的MgO颗粒.