溶液冻干法制备纳米粉体之特点分析

总结了溶液冻千法制备纳米粉体的工艺过程和特点。与其他制粉方法相比,溶液冻干法的特点是：所制备的粉体毛硬团聚,粉体粒径小且均匀,粒度大小在一定程度上受冻结速率影响,化学组成准确,多为非晶体颗粒;与其他物料的冻干过程相比,制备纳米粉体的含水量比例大,已经干燥的物质对干燥传质的阻力小,产品的热敏性小。     

Synthesis of dispersed PrBaCo0.9Cu0.1O5+δ cathode nanopowders with layered perovskite structure for intermediate temperature solid oxide fuel cells

PrBaCo_1.9Cu_0.1O_5+δ (PBCCO) nanopowders were synthesized by an EDTA-citrate complexing process using water and ethanol as solvents, and their structures and electrochemical properties were characterized. PBCCO precursor gels were highly oxidized at 450 °C, using either water (PBCCO-W) or ethanol (PBCCO-E) as the solvent. PBCCO powders calcined at 450 °C had a second phase, while those calcined at 850 °C for 4 h were obtained as single phase PBCCO with a layered perovskite structure in the P4mm space group. PBCCO-E primary particles were approximately 5–10 nm in size and were well-dispersed compared with those of the PBCCO-W powder. We hypothesized that the enhanced dispersibility of the PBCCO-E powder was caused by a decrease in bridging hydrogen bonds on the chelate surface, which prevents chelate agglomeration in sol state. It causes the larger specific surface area of PBCCO-E powders and thus a lower polarization resistance (R_p) than that of PBCCO-W powders at the measured temperature. The R_p value of PBCCO-E powder was 0.041 Ω cm² at 750 °C, which is about 1.5 times lower than that of PBCCO-W at the same temperature.     

均匀沉淀-水热法制备稳定Y-Ce-ZrO2纳米粉体

以尿素为沉淀剂,采用均匀沉淀-水热法成功地制备了2mol%Y2O3-5.5mol?O2稳定的纳米四方相ZrO2.研究了溶液的浓度、水浴时间、水热时间对ZrO2粉体的晶型和形貌的影响.结果表明在一定工艺条件下可制备平均粒径在10-20nm,粒度分布窄,分散性好的纳米稳定Y2O3-CeO2-ZrO2粉体.     

复合沉淀法制备(Y,Gd)2O3:Eu纳米粉体及其发光性能

报道了一种采用氨水和碳酸氢铵的混合溶液作为复合沉淀剂来制备(Y，Gd)203：Eu发光粉体的新工艺，采用热分析(TG-DTA)、红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等手段对粉体制备过程中的物理化学变化进行了研究．通过X射线激发的发射光谱研究了Eu掺杂浓度和煅烧温度对(Y，Gd)2O3：Eu粉体发光性能的影响．结果表明采用复合沉淀法制备工艺，经过850℃烧2h，可以得到晶粒尺寸为50nm左右，且基本无团聚的(Y，Gd)2O3：Eu粉体，比表面积为23m^2／g，其X射线激发的发光强度较草酸盐沉淀法所得到的相同组分的粉体大大增强．     

制备条件对纳米TiO2晶型及其晶相含量影响的研究

分别用TiCl4，Ti(SO4)2和Ti(OC4H9)4为原料制备纳米二氧化钛粉体。用XRD和TEM对纳米二氧化钛粉体的晶型及晶粒形貌进行了分析。研究了在同一条件下制备的3种纳米二氧化钛粉体对光催化降解亚甲基蓝溶液的影响；结果表明：在相同的制备条件下，用TiCl4为原料制备的纳米二氧化钛晶型较易控制，容易得到含有一定金红石相、催化活性较高的混合晶型的纳米二氧化钛；因此，其降解效果优于其他两种。同时研究了外界条件(如分散剂、干燥方式、温度及烧结温度等)对纳米二氧化钛晶相及其含量变化的影响。实验结果为：用异丙醇做分散剂时，当分散剂与水的体积比为3时，选用冷冻干燥法可得到均分散的粒度可控的球形纳米二氧化钛晶粒。     

纳米镍粉的粒度分析

纳米材料的性质强烈依赖于其颗粒和晶粒的大小，测量纳米颗粒或晶粒尺寸无论从粉体制备还是从应用上都具有重要的意义。本文针对纳米镍粉进行了一系列粒度分析研究，包括SEM、TEM、激光粒度分析法、比表面分析法、X射线衍射法和X射线小角度散射法(SAXS)。不同的研究手段得到的纳米镍粉的粒径不尽相同。比较各种研究手段得到的结果可以知道其准确程度，并且针对不同的分析要求可选择不同的方法。     

超声波技术应用现状

阐述了超声波的特性和基本原理,探讨了目前超声波在废水处理、医疗、防除结垢、纳米材料制备等方面的应用现状,指出超声波技术将会在纳米粉体材料的研制方面发挥巨大的作用。     

A new sol-gel process for preparing Ba(Mg_(1/3)Nb_(2/3))O_3 nanopowders

Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN) nanopowders. At first, Nb2O5 reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after cooling was dispersed and washed several times in distilled water to remove the Na ions. The as-prepared colloidal Nb2O5-nH2O was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃for 1 h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.     

Effect of Surface Modification on Behaviors of Cerium Oxide Nanopowders

Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders.A surfactant-sodium dodecyl sulfate（C12H25SO4Na）was used to modify the surface of CeO2 powder particles.The unmodified and modified CeO2 powders were characterized by using a powder comprehensive characteristic tester,laser particle size analyzer,specific surface area tester,X-ray diffraction tester,and a scanning electron microscope.The testing and analysis results showed that C12H25SO4Na surface modification might increase the flowability and dispersity,and decrease the specific surface area and agglomeration of CeO2 powders.The mechanism of the surface modification of CeO2 powder particles was also discussed.     

纳米氧化铈颗粒的粒度分析研究

针对自制的纳米CeO2进行了一系列粒度分析研究,包括XRD、SEM、TEM、动态光散射法、比表面分析法、X射线衍射法和X射线小角度散射法(SAXS).不同的研究手段得到的纳米CeO2的粒径不尽相同,并阐述了各种研究手段的优缺点及适用范围.