CaTiO3∶Zn溶胶-凝胶法制备、结构及介电性能

采用溶胶-凝胶法制备了CaTiO3∶Zn纳米粒子,透射电镜图显示平均粒径为25 nm。Zn的掺杂位置对于陶瓷相组成和烧结特性有很大影响。Ca1-xZnxTiO3和CaTiO3+zZnO样品的Zn以Zn2TiO4相形式存在;而CaZnyTi1-yO3-δ(y=0.01)样品中的Zn进入Ti位形成固溶体,无明显的降温效果,当Zn量增至0.05和0.1时,出现ZnO相。ZnO和Zn2TiO4第二相的存在均能明显促进陶瓷烧结。CaTiO3∶Zn超细粉体可在较低温度下致密烧结(≤1 250℃)。1 250℃烧结的CaZnyTi1-yO3-δ(y=0.01)陶瓷具有较好的介电性能:介电常数ε=157,品质因数Q×f=6 819 GHz,谐振频率温度系数τf=7.51×10-4℃-1。     

溶胶凝胶法制备Nd2O3改性钛酸钡陶瓷的研究

The technological condition for the preparation of BaTiO₃ ceramics doped with Nd₂O₃ by Sol-Gel was deter-mined through orthogonal experiment. When n_Ba(Ac)2∶n_Ti(OC4H9)4∶n_Nd2O3∶n_{CH3(CH2)2CH2OH}∶n_H2O=1.00∶1.00∶0.003∶7.30∶37.04, pH=3.5,T=25℃,the light-yellow-transparent-stable solution and thorough transparent gel was generat-ed, the transforming time of solution to gel was 25h. The crystal structure and particle size of BaTiO₃ ceramics doped with Nd₂O₃ were studied by SEM and X-ray respectively, the type of the crystal was tetragonal, the particle size was about 24.7nm. The dielectric constant (ε) and dielectric loss (tanδ) of BaTiO₃ ceramics doped with Nd₂O₃ were determined between 10⁴～10⁶Hz, and the results showed that the dielectric constant was increased obviously, the dielectric loss was decreased clear and the resistivity (ρ_V) was also decreased noticeably.     

溶胶-凝胶法制备纳米WO3气致变色材料

本文主要阐述了纳米WO₃气致变色材料的溶胶-凝胶制备方法、气致变色机理及其应用的研究新进展,重点评述了溶胶-凝胶法中各种制备条件诸如掺杂、模板剂、溶剂、热处理温度等对这种材料的结构和性能的影响,最后展望了纳米WO₃气致变色材料的研究和应用前景。我们认为,在未来的溶胶-凝胶法制备纳米WO₃气致变色材料领域,如何进行最优化的掺杂设计和选择高效模板剂、如何降低气体检测温度、以及气致变色机理等将是该项研究的重点。     

Li3V2(PO4)3的溶胶-凝胶法合成及其性能研究

以LiOH·H₂O、NH₄VO₃、H₃PO₄和柠檬酸等为原料采用溶胶-凝胶法合成了锂离子二次电池正极材料磷酸钒锂(Li₃V₂(PO₄)₃)。考察了煅烧温度和配位剂种类等条件对产物组成及电化学性能的影响。研究了优化条件下制得样品的循环伏安、充放电性能和循环性能。0.1 C条件下,样品首次放电比容量达129.81 mAh·g^-1，经过100次循环后容量几乎没有衰减，仍保持在128 mAh·g^-1。X射线衍射研究表明合成单一Li₃V₂(PO₄)₃晶体所需温度比固相法低；并考察了循环20次后材料充电到各个单相的晶体结构，通过X射线衍射和最小二乘法计算给出了其晶胞参数变化过程，证实了循环嵌Li过程中晶体结构能够得到重现。     

Li3V2(PO4)3的溶胶-凝胶合成及其性能研究

以LiOH·H₂O(LiF、Li₂CO₃、LiCH₃COO·2H₂O)、NH₄VO₃、H₃PO₄和柠檬酸为原料,采用Sol-gel法合成锂离子电池正极材料Li₃V₂(PO₄)₃。优化了锂源、溶胶的pH值、预烧条件、煅烧温度等合成条件,并采用XRD、SEM、恒电流充放电及循环伏安试验等方法,研究了所合成的Li₃V₂(PO₄)₃的结构形貌和电化学性能。结果表明,以LiOH·H₂O为锂源,溶胶的pH值等于3,于氩气氢气(体积比9∶1)混合气中300 ℃预烧 4 h,并在氩气氢气(体积比9∶1)混合气中600 ℃煅烧8 h合成的Li₃V₂(PO₄)₃正极材料为标准的单斜结构,具有较高的放电比容量和较好的循环稳定性,0.1C和1C倍率下首次放电比容量分别为130 mAh·g^-1和129 mAh·g^-1;1C倍率下循环40次后,容量仍为127 mAh·g^-1,容量保持率为98.4%;随后又进行10C倍率放电,10次循环后容量为105 mAh·g^-1,容量保有率达98.1%。循环伏安测试表明,该正极材料具有较好的电化学可逆性。     

纳米SnO2的非水溶剂溶胶-凝胶法制备与表征

Nanometer SnO₂ powders were successfully prepared by non-hydrolytic sol-gel approach combined with heat treatments using tin tetrachloride as starting material and ethylene glycol as solvent. The reaction mechanism of the sol-gel process is proposed. Results indicate that the -OHCH₂CH₂OH- prevent Cl^- ion from accessing to tin Sn⁴⁺ due to steric effect, and hence increaseing the stability of the sol solution. Ethylene glycol functions not only as a complextion agent to form a polymer network but also as a “spacer” to modulate the distance between metal ions, preventing metal oxide particles from aggregation during desiccation of the sol. The effects of heat treatments on the evolution of structure and morphology of nanosized SnO₂ powders were studied. The powders with narrow size distribution around 15～20 nm could be obtained at 500 ℃ for 4 h.     

溶胶-凝胶法制备Li3V2(PO4)3及其性能研究

0引言具有类NASICON结构的Li3V2(PO4)3是继过渡金属氧化物LMO后的一种新型的锂离子二次电池正极材料。与目前市场上应用最为广泛的正极材料LiCoO2相比,Li3V2(PO4)3具有超常的稳定性,即使在脱出的Li 与过渡金属原子的物质的量之比大于1的时候仍然具有超乎寻常的稳定性,而通常情况下1mol LiCoO2在脱出0.5mol Li 就会变得不稳定。并且Co是一种战略物资,全球储量十分有限;Co也是一种有毒金属,对于环境污染较为严重。LiNiO2因其合成较为困难而使应用受限,尖晶石LiMn2O4虽然属于环境友好型化合物,但其理论比容量仅为148mAh·g-1,且…     

单相Ba2Ti9O20柠檬酸凝胶法制备、表征及介电性能

采用柠檬酸凝胶法两步热处理工艺制备了单相Ba₂Ti₉O₂₀。干凝胶在750 ℃热处理得到了物相为BaTi₅O₁₁和Ba₄Ti₁₃O₃₀、尺寸为30～50 nm的前驱体粉体。纳米前驱体具有高表面活性，促使单相Ba₂Ti₉O₂₀在1 200 ℃热处理温度下形成。两步热处理所得的粉体比一步热处理所得的粉体具有更好的烧结和介电特性，两步热处理所得的粉体，在1 250 ℃烧结4 h，可获得理论密度为97%的Ba₂Ti₉O₂₀微波介质陶瓷，其介电性能：ε_r=38.5，Qf=19 320 GHz，τ_f=8.7×10^-6 ℃^-1。     

Li4Ti5O12溶胶-凝胶法合成及其机理研究

The precursors of Li₄Ti₅O₁₂ were prepared from tetrabutyl titanate and lithium acetate by sol-gel process. The Li₄Ti₅O₁₂ samples were synthesized by calcining the gel precursors at 400～900 ℃ in air for 6～20 h. Its reaction mechanism was investigated by infrared spectroscopy(IR), thermogravimetry(TG) and X-ray diffraction(XRD). The effects of sinter-temperature, calcination-time and thermal-treatment for the products were discussed. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM). The results showed that the single-phase products were obtained by calcining the gel precursors at 800 ℃ in air for 20 h, the sinter-temperature was lower than that of solid-state method, the particles were narrowly distributed, well crystallized with a size range from 0.3μm to 0.5 μm.     

WO3纳米管的模板法制备及表征

0引言 WO3纳米材料具有光致变色、电致变色、气致变色等特性,可用于光学信息和储存显示器、pH值探测器、气敏传感器、灵敏窗口等[1,2];并且在太阳能的储存与利用、光电转换、光催化降解大气和水中的污染物等方面有着广阔的应用前景[3,4],成为近几年重点研究的半导体材料之一.以前纳米WO3的制备主要集中在薄膜上,其薄膜的制备工艺已经相当成熟,主要包括蒸发法、溅射法、CVD法、喷涂法、阳极氧化法、溶胶-凝胶法等[3].     

Synthesis and red luminescence of Pr-doped CaTiO3 nanophosphor from polymer precursor

Uniform and sphere-like nanoparticles of crystalline Pr³⁺-doped CaTiO₃ have been prepared from complex polymer precursor at 600°C, in which, metal atoms are previously dispersed by citric acid in ethylene glycol solvent. The decomposition process of the precursor, crystallization, and particle sizes of CaTiO₃ have been investigated by using thermal analysis, powder X-ray diffraction and transmission electron microscopy. Diffuse reflectance spectra, photoluminescence and decay curve indicate that a strong red emission located at the nearly NTCS “ideal red” site is deduced from the energy transfer from the band gap absorption to doping Pr³⁺ ions. The thermoluminescence curves exhibit that a potential long phosphorescent material based on Pr³⁺-doped CaTiO₃ will be explored in future.     

Spectroscopic properties of Nd ions in nano-perovskite CaTiO3

In this work, we present for the first time the spectroscopic properties of perovskite nanocrystals CaTiO₃: Nd³⁺, measured at room and liquid nitrogen temperature. Samples were prepared by the sol–gel method and annealed at 700 and 1000 °C. The concentration of Nd³⁺ ranged from 0.5% to 5%. Average nanocrystallite size primarily depends on the annealed temperature and is about 25 and 50 nm for 700 and 1000 °C, respectively. The absorption, emission and excitation spectra (monitored at 1078 nm) as well as the decay time profile of the emission from the ⁴F_3/2 energy level of Nd³⁺ are obtained. The increasing amount of Nd³⁺ ions decreases the lifetime of the ⁴F_3/2 level and that changes from 146 μs for 0.5% to 50 μs for 5% of Nd³⁺ concentration. The strongest emission was observed at two regions: 1050–1120 nm and 865–930 nm and was assigned to the ⁴F_3/2→⁴I_11/2 and ⁴F_3/2→⁴I_9/2 transitions, respectively. The spectroscopic quality parameter of neodymium in the CaTiO₃ lattice has been calculated from the emission spectra. The influence of luminescent properties depending on the annealing temperature and concentration of neodymium ions is discussed.     

LiV3O8的合成及其电化学性能研究

The layered trivanadate, LiV₃O₈, was prepared by sol-gel method with LiOH, V₂O₅ and H₂O₂ as initial reagents. The materials at different heat treatment conditions were characterized by XRD and TG-DTA. Their electrochemical behaviors were studied by galvanostatic charge-discharge and cyclic voltammetry. The results show that LiV₃O₈ prepared by sintering at 300 ℃ for 16 h has higher capacity, and its initial discharge capacity is 333.1 mAh·g^-1, and maintains a discharge capacity of 302.8 mAh·g^-1 after 10 cycles at 0.2 C and the voltage range of 1.8～4.0 V.     

多层多孔Co3O4纳米粒子组装体的合成、表征和电化学性能研究

利用十二烷基磺酸钠(SDS)作为表面活性剂,合成了形貌化的CoC₂O₄配合物前驱物,然后在500 ℃下热分解形貌化的前驱物,得到了多层多孔Co₃O₄纳米粒子组装体。采用FESEM、TEM、HRTEM、XRD、N₂吸附脱附和Raman散射等手段对产物进行了分析和表征。低角XRD,TEM和N₂吸附脱附测试表明所得组装体具有多孔结构。常规XRD、HRTEM和Raman结果证明组装体中Co₃O₄纳米粒子建筑块结晶较好。与体相Co₃O₄晶体相比,Co₃O₄纳米粒子组装体的5个拉曼活性峰发生了明显的红移。将Co₃O₄纳米粒子组装体作为锂离子电池的正极材料进行了电化学性能测试,结果表明该组装体电极的首次放电容量为1 115 mAh·g^-1,远高于目前文献报道的Co₃O₄纳米管、纳米粒子和纳米棒电极。但是,该组装体电极的循环性能不好,有待进一步提高。     

碳包覆Li3V2(PO4)3:溶胶-凝胶法合成及性能

利用V₂O₅、LiOH·H₂O、H₂O₂、NH₄H₂PO₄与柠檬酸为原料,通过溶胶-凝胶法合成了碳包覆的Li₃V₂(PO₄)₃复合正极材料。采用XPS、XRD、SEM、TEM、拉曼光谱和电化学方法对材料的性能进行了研究。还研究了其结构与焙烧温度、样品电导率和电化学性能的关系。研究表明复合材料具有空间群为P2₁/n的单斜结构,表面包覆粗糙多孔的碳层。在800 ℃下制备的碳包覆样品的电子导电率高达9.81×10^-5 S·cm^-1,约为高温固相氢气还原法制备的未包覆碳Li₃V₂(PO₄)₃的10000倍。测试结果表明碳包覆Li₃V₂(PO₄)₃的电化学性能远优于未包覆碳的样品。在3.0～4.3 V电压范围内,以0.1C和2C倍率充放电时,碳包覆的Li₃V₂(PO₄)₃具有高比容量(分别为128和109 mAh·g^-1)和优异的循环性能。     

柠檬酸溶胶凝胶法制备LiCoO2电极材料及其表征

LiCoO₂ precursors of the cathode material for lithium-ion batteries were prepared from lithium hydroxide， basic cobalt carbonate and citric acid by a sol-gel method. The LiCoO₂ samples were obtained by sintering the gel pre-cursors at different temperatures and for different times. The thermal decomposition behavior of the gel precursors was examined by means of thermo-gravimetric analysis and differential thermal analysis using a PCT-IA thermal analyzer system. Their structures and morphologies were characterized by powder XRD and SEM techniques. It was found that using citric acid realized that the formation of LiCoO₂ crystal can be clearly differentiated to the nucle-ation and growth processes of the crystals; furthermore， the crystal size can be controlled. Electrochemical tests using the LAND BT1-10 test system showed the electrochemical performance of the material is affected by its in-tegrity and stability.     

纳米CaMgSi2O6粉体的低温合成与微波介电性能

以硝酸锂、偏钒酸铵、硝酸钙、硝酸镁、正硅酸乙酯为原料，采用溶胶-凝胶法低温合成纳米CaMgSi₂O₆微波介质陶瓷粉体，研究了不同粒径粉体的烧结行为与微波介电性能。结果表明，通过在钙镁硅溶胶中引入锂钒烧结助剂可大大降低陶瓷粉体的晶相合成温度，干凝胶在750 ℃煅烧后可获得主晶相为CaMgSi₂O₆、分散性良好、粒径为78～98 nm的陶瓷粉体，可满足微型片式元器件用超薄陶瓷介质层的制备要求;该粉体在890 ℃烧结后获得致密结构的陶瓷，具有良好的微波介电性能:介电常数为7.68，品质因数为24 542 GHz，频率温度系数为-57.25×10^-6 ℃^-1。