改进溶剂热法制备锂离子电池负极材料用多级孔Co3O4微球

将溶剂热法与高温煅烧法相结合制备多级孔Co3O4微球,采用XRD、SEM、TEM和电化学测试等技术研究该多级孔Co3O4微球的结构和性能.结果表明:当煅烧温度为700℃时,所合成的Co3O4(Co3O4-700)是由丰富的纳米颗粒(50～200 nm)和大量孔洞(～100 nm)构成的微米级微球(1～2μm);该Co3...     

化学共沉淀法制取NiFe2O4

探讨了用化学共沉淀法制备NiFe2O4陶瓷材料的工艺过程，研究了影响材料性质的各种因素，并对材料的结构成分进行了X射线衍射、差热和热重分析。结果表明：采用氢氧化钠调节混合液的pH值、在1300℃锻烧4h的工艺，可以制备出合格的NiFe2O4陶瓷粉末。     

Shape-controlled synthesis of nanocubic Co3O4 by hydrothermal oxidation method

The nanocubic Co3O4 was synthesized by hydrothermal oxidation method. The effects of cobalt salt, precipitating agent, surfactant, solvent, pH value of the suspension and the amount of oxidant H2O2 on the morphology and structure of Co3O4 were investigated. The Co3O4 powders were characterized by transmission electron microscope and X-my diffraction. The results show that the morphology of Co3O4 is closely dependant on the anion in cobalt salts, but it is not so sensitive to the precipitating agents and solvents. The amount of H2O2 is the key factor to obtain Co3O4 with spinel crystal structure. The optimum synthetic conditions of uniform shape-controlled Co3O4 nanocubes are as follows： Co（CH3COO）2·4H2O as cobalt salt, KOH as precipitating agent, polyethylene glycol with relative molecular mass of about 20 000 as surfactant, water-n-butanol as solvent system, pH value of 8-9, the molar ratio of H2O2 to Co^2＋ above 2.5：1.0, hydrothermal temperature of 160 ℃ and hydrothermal holding time of 10 h. The tap density and apparent density of nanocubic Co3O4 obtained with the average particle size of 20 nm are 1.01 g/cm^3 and 0.70 g/cm^3, respectively.     

Nanoparticles α-Al2O3 prepared by combustion synthesis method

Nanometer α-Al2O3 powders were synthesized by the method of low-temperature combustion synthesis (LCS) with aluminum nitrate nonahydrate and urea as raw materials. The prepared powders were studied by XRD,TG-DTA, FT-IR and TEM. It is found that the average size of particles is 60 -80 nm. The optimal synthetic conditions are obtained, i. e. , the suitable fuel is urea; the molar ratio of oxidizer to fuel is 1: 2 and the igniting temperature is 700 ℃. The results show that the size of particles is governed by synthesizing temperature, the fuel and the molar ratio of oxidizer to fuel. TEM image of the particles collected shows that the crystal habits of particles have a spheric structure and particles are polycrystal.     

Hydrogen gas sensing of Co3O4-Decorated WO3 nanowires

Co₃O₄ nanoparticle-decorated WO₃ nanowires were synthesized by the thermal oxidation of powders followed by a solvothermal process for Co₃O₄ decoration. The Co₃O₄ nanoparticle-decorated WO₃ nanowire sensor exhibited a stronger and faster electrical response to H₂ gas at 300 °C than the pristine WO₃ nanowire counterpart. The former showed faster response and recovery than the latter. The pristine and Co₃O₄-decorated WO₃ nanowire sensors showed the strongest response to H₂ gas at 225 and 200 °C, respectively. The Co₃O₄-decorated WO₃ nanowire sensor showed selectivity for H₂ gas over other reducing gases. The enhanced sensing performance of the Co₃O₄-decorated WO₃ nanowire sensor was explained by a combination of mechanisms: modulation of the depletion layer width forming at the Co₃O₄-WO₃ interface, modulation of the potential barrier height forming at the interface, high catalytic activity of Co₃O₄ for the oxidation of H₂, active adsorption of oxygen by the Co₃O₄ nanoparticle surface, and creation of more active adsorption sites by Co₃O₄ nanoparticles.     

前驱体对四氧化三钴形貌的影响与表征

以Co(CH3COO)2.4H2O为钴源,聚乙二醇(PEG)20 000为表面活性剂,在水-正丁醇溶剂体系中,分别以氢氧化钾、碳酸铵和草酸为沉淀剂,采用沉淀法制备氢氧化钴、碱式碳酸钴和草酸钴前驱体。氢氧化钴前驱体于160℃通过水热氧化法,可制得立方体状四氧化三钴(Co3O4);碱式碳酸钴和草酸钴前驱体采用水热-热分解法分别于450℃和400℃煅烧3 h可制得球链状和棒状Co3O4。用热重分析、红外光谱、X射线衍射和透射电镜对所制得前驱体和产物Co3O4的形貌和结构进行表征,并对所制备的不同形貌Co3O4进行电化学性能测试。研究结果表明:产物Co3O4的形貌与其前驱体和制备方法有关,当采用氢氧化钴前驱体可制备平均晶粒度约为15 nm的立方体状Co3O4;当采用碱式碳酸钴和草酸钴前驱体可分别制得直径约为40 nm、长约为100 nm的球链状Co3O4和直径约为0.1μm、长度可达1μm的棒状Co3O4。通过对不同形貌的Co3O4进行循环充放电测试,可知纳米级Co3O4的电化学性能优于微米级Co3O4的;立方体状Co3O4的电化学性能优于其他形貌Co3O4的电化学性能,其循环10次后的充电比容量为406 mA.h/...     

水热法法合成Bi4Ti3O12纳米晶

以Bi(NO3)3·5H2O和Ti(OCrH9)4为原料,KOH作为矿化剂,在200℃温度下水热反应24 h获得了纯相Bi4Ti3O12粉体.利用XRD对合成粉体的物相进行了表征,利用TEM和SEM观察了合成粉体颗粒的微观形貌.结果显示,所合成的粉体为片状或带状的单晶Bi4Ti3O12颗粒,片状颗粒的平面与(001)面平行.分析了片状结构Bi4Ti3O12形成的机制.     

Aluminum matrix composites reinforced by in situ Al2O3 and Al3Zr particles fabricated via magnetochemistry reaction

Aluminum matrix composites reinforced by in situ Al₂O₃ and Al₃Zr particles are fabricated from A356-Zr(CO₃)₂ system via magnetochemistry reaction, and the morphologies, sizes and distributions of the in situ particles as well as the microstructures, mechanical mechanisms of the composites are investigated by XRD, SEM, TEM and in situ tensile tests. The results indicate that with the pulsed magnetic field assistance, the morphologies of the in situ particles are mainly with ball-shape, the sizes are in nanometer scale and the distributions in the matrix are uniform. The interfaces between the in situ particles and the aluminum matrix are net and no interfacial outgrowth is observed. These are due to the strong vibration induced by the applied magnetic field in the aluminum melt, which in turn, accelerates the melt reactions. The effects of the magnetic field on the above contributions are discussed in detail.     

锂离子电池纳米Co3O4-PTFE复合负极材料的循环性能

采用在加温的水溶液中电沉积然后烧结方法制备锂离子电池的纳米Co3O4-PTFE复合负极材料.XRD分析表明,电沉积的物质在245℃真空热处理后转变为Co3O4-PTFE.SEM观察可以发现,Co3O4-PTFE中的Co3O4呈现蜂窝结构,其厚度为30～50nm;PTFE则形成交联的柱状体吸附在片状Co3O4两侧,其直径为50～100nm.这种纳米Co3O4-PTFE复合沉积层具有结构稳定、抗粉化的特点.充放电实验结果表明,Co3O4掺杂PTFE可明显提高负极材料的可逆比容量和循环性能,其首次放锂比容量为920.1mAh·g-1,20次循环后放锂比容量为685.6mAh·g-1;而没有掺杂PTFE的试样对应的数据分别为865.1mAh·g-1和180.4mAh·g-1.     

K+掺杂改性的Ca3Co4O9基氧化物热电性能

用溶胶-凝胶法和放电等离子烧结(SPS)制备了层片状结构的(Ca1-xKx)3Co4O4陶瓷,烧结块体相对密度可达97%～99%.XRD(X-ray Diffraction)和SEM(Scanning Electronic Microscope)分析结果表明当K的掺杂量x＜0.08时为单一的Ca3Co4O9相,SPS烧结可以使样品带有一定的织构取向.在室温至700℃的范围内测量了不同K掺杂量时样品电导率和Seeback系数,测试结果表明,当K的掺入量小于0.06时,随着掺入量的增加,可以显著提高样品的电导率(400℃～700℃)和Seebeck系数.其中,700℃时(K0.06Ca0.94)3Co4O9样品的功率因子P=4.43×10-4W·m.-1K-2,与Ca3Co4O9(P=3.51×10-4W.m.-1K-2)相比提高了26.2%,表明K掺杂是改善Ca3Co4O9高温热电性能的有效途径之一.     

溶胶-凝胶法制备La2O3纳米粉体

以普通La2O3,硝酸,聚乙二醇为原料,利用溶胶-凝胶法制备了纳米La2O3粉体,利用TG-DTA,XRD,TEM等各种测试方法对干凝胶300℃灼烧所得前驱体粉末的分解过程及最终形成的纳米氧化镧粉体进行了分析和表征,并研究了浓度、搅拌和分散剂聚乙二醇(PEG)添加量等因素的改变对La2O3粉体的粒径、形态的影响.实验结果表明,在适当工艺参数下,可以制得平均粒径小于50 nm的La2O3粉体.     

Nanocrystalline LiMn2O4 thin film cathode material prepared by polymer spray pyrolysis method for Li-ion battery

Nanocrystalline cubic spinel lithium manganese oxide thin film was prepared by a polymer spray pyrolysis method using lithium acetate and manganese acetate precursor solution and polyethylene glycol-4000 as a polymeric binder. The substrate temperature was selected from the thermogravimetric analysis by finding the complete crystallization temperature of LiMn₂O₄ precursor sample. The deposited LiMn₂O₄ thin films were annealed at 450, 500 and 600 °C for 30 min. The thin film annealed at 600 °C was found to be the sufficient temperature to form high phase pure nanocrystalline LiMn₂O₄ thin film. The formation of cubic spinel thin film was confirmed by X-ray diffraction study. Scanning electron microscopy and atomic force microscopy analysis revealed that the thin film annealed at 600 °C was found to be nanocrystalline in nature and the surface of the films were uniform without any crack. The electrochemical charge/discharge studies of the prepared LiMn₂O₄ film was found to be better compared to the conventional spray pyrolysed thin film material.     

均分散球形Y2O3：Eu^3＋纳米晶的制备

采用凝胶网格共沉淀法，以明胶为反应基质制备了单分散球形纳米Y2O3：Eu^3 荧光粉，考察了制备条件对产物粒径的影响。利用X射线衍射(XRD)、透射电子显微镜(TEM)和荧光光谱等手段对样品进行了表征。结果表明：该法制得产物为球形，一次晶粒粒径在13nm～25am之间，且粒度分布均匀，与微米晶相比，该纳米晶的激发光谱发生明显红移。     

化学共沉淀法制取NiFe_2O_4

探讨了用化学共沉淀法制备NiFe2O4陶瓷材料的工艺过程,研究了影响材料性质的各种因素,并对材料的结构成分进行了X射线衍射、差热和热重分析。结果表明:采用氢氧化钠调节混合液的pH值、在1300℃煅烧4h的工艺,可以制备出合格的NiFe2O4陶瓷粉末。     

Au/Co_3O_4的制备、表征及加氢催化性能研究

采用化学浸渍法制备出Au/Co_3O_4纳米复合材料,用透射电子显微镜(TEM)、X射线能谱(EDS)和X射线粉末衍射(XRD)等对其结构和组成进行了表征,并考察了其在对硝基苯酚加氢反应中的催化性能。表征结果表明,Au纳米粒子很好地分散在Co_3O_4载体上。催化性能测试表明,Au/Co_3O_4纳米复合材料对于对硝基苯酚加氢反应表现出优异的催化活性,TOF值为5.01 min~(-1);此外,催化剂经过5次循环仍然保持优异的催化性能。     

由草酸钴热分解制备Co3O4及其物性表征

根据草酸钴的热重/差热分析曲线,利用热分解法,在不同条件下由草酸钴制备了各种Co3O4微粉,并对其进行了X射线衍射分析和扫描电镜表征.结果表明:在低温下制得了具有标准Co3O4晶形结构的树枝状Co3O4;在高温下,尤其是采用两段升温制得了具有标准活性Co3O4晶形结构的球形Co3O4,其中位粒径为1.35μm,松装密度为0.83 g/cm3,并由此获得了由草酸钴热分解制备活性球型Co3O4的分解条件.     

LiNi1/3Co1/3Mn1/3O2和LiNi3/8Co1/4Mn3/8O2纳米纤维的合成与电化学性能

以溶胶前驱体为纺丝液,通过静电纺丝法合成锂离子电池正极材料LiNi1/3Co1/3Mn1/3O2和LiNi3/8Co1/4Mn3/8O2纳米纤维.采用原子力显微镜(AFM)、X射线衍射(XRD)、充放电实验对纳米纤维的形貌、结构和电化学性能进行研究.结果表明,纳米纤维的直径在150～200 nm之间,且具有典型的α-NaFeO2层状结构.LiNi1/3Co1/3Mn1/3O2和LiNi3/8Co1/4Mn3/8O2纳米纤维的首次放电容量均超过170 mAh·g-1,50次循环后容量保持率在90%以上.     

电沉积-烧结法制备掺杂碳的Co3 O4锂离子电池负极材料

采用电沉积-烧结法制备了掺杂C的Co3O4锂离子电池负极材料。XRD分析结果表明,电沉积物质是Co（OH）2,经245℃的真空烧结后转变为Co3O4。能谱分析表明,镀液中添加甲醛后,获得的镀层中含有Co SEM观察发现加入甲醛后镀层表面形成的孔间距加大、空隙增多、孔壁变薄。在Li／Co3O4电池充放电过程中,加入甲醛不但使电极的稳定性得到明显改善,而且比容量的值也有所提高。电极性能试验表明加入甲醛后电池的循环寿命得到明显改善。     

从废旧锂离子电池中回收制备超细Co3O4

用湿化学法从废旧锂离子电池中回收并制备出了Co3O4粉体.研究了过程参数对粉体性能的影响,测定了Co3O4粉体的比表面积和红外光谱,观察了粉体的微观形貌.结果表明,制备的粉体比表面积大,其值都在100m2/g左右,颗粒粒径分布在10nm～20nm之间,颗粒形貌呈球形结构,其红外特征峰与市售Co3O4的特征峰相比发生了一定的红移.