炭吸附共沉淀纳米铁酸钐的制备及其可见光催化性能EI北大核心CSCD

采用炭吸附共沉淀法制备铁酸钐(SmFeO 3)纳米粉体。利用热重分析仪(TG-DTA)、X射线衍射仪(XRD)、紫外-可见分光光度计(UV-Vis)和透射电镜(TEM)等分析方法对样品进行表征。以甲基橙(MO)为目标污染物,镝灯为可见光源,研究SmFeO 3纳米粉体的光催化性能。结果表明:炭吸附共沉淀法合成的SmFeO 3粉体粒径小,分布均匀,团聚较少;SmFeO 3的吸收波长发生红移,且SmFeO 3在紫外光、可见光区域的吸收强度增强。炭吸附共沉淀法制得的SmFeO 3粉体在60 min内降解率达到82%,是沉淀法所得SmFeO 3粉体降解率的2.6倍,光催化效果明显增强。     

化学共沉淀法制备NiCuZn铁氧体微粉及其磁性能

采用预烧氧化法(化学共沉淀法制备的前驱体在高温下预烧)制备了NiCuZn铁氧体微粉。结果表明,预烧氧化法制备的NiCuZn铁氧体微粉平均晶粒尺寸约为44.1nm。随着预烧温度升高,样品D50增大。当预烧温度为850℃时,平均颗粒尺寸为2μm左右,比饱和磁化强度为62A.m2/kg,起始磁导率约为90,损耗也较小,截止频率为59MHz。     

碳铵共沉淀法合成LaAlO3粉体材料的研究

用碳铵共沉淀法制备LaAlO3粉体前驱体，1200℃下烧结，可得到性能稳定的LaAlO3粉体。经X射线衍射分析产物为单相，属具有钙钛矿结构的三角晶系，其XRD图谱与JCPDS卡84-0848完全一致。采用库尔特LS-230粒度分析仪对共沉淀法和高温固相法合成的两种粉末样品进行粒度分析，发现共沉淀法合成的样品粒度细且分布均匀。分析了上述两种方法合成的粉末样品的SEM照片，发现共沉淀法不仅能降低合成温度，而且可使生成产物结晶均匀，对细化粉体晶粒也有较大作用。     

Sol-gel/co-precipitation method for the preparation and characterization of zirconia-tungsten composite powders

Sol-gel and co-precipitation are interesting processes in view to prepare ceramic-metal composite powder. Using metal salts as starting compounds it is possible in a first step to synthetise a mixed precipitate and in a second reduction step, in a H₂/Ar atmosphere, to obtain such a composite powder. Stabilized zirconia-tungsten composite powder have been prepared by this way without mixing and milling steps. Each step of the synthesis has been characterized. Stability of the mixed precipitate suspension and surface area of the dried powder are largely influenced by the tungsten salts content. The temperature of formation of zirconia changes from 510 °C without tungsten precursor up to 695 °C for a 60% tungsten molar ratio composition. Composite zirconia-tungsten powders, in a large range of composition, are obtained at 1100 °C with morphologies depending on humidity and thermal treatment conditions.     

化学共沉淀法制备纳米ITO粉体及结构表征

以InCl3·5H2O和SnCl4·5H2O为原料,在掺杂浓度In2O3与SnO2的质量比为9∶1的条件下,采用化学共沉淀法合成了纳米ITO粉体。利用TEM、XRD、IR、粒度分布仪等实验手段对粉体的形貌、物相、粒度进行了表征,讨论了煅烧温度对粉体物相和粒度的影响。研究结果表明:当煅烧温度>300℃时,可以获得立方In2O3结构的球形纳米ITO粉体。     

Effect of dispersant on preparation of barium-strontium titanate powders through oxalate co-precipitation method

The quantitative precipitation of barium-strontium titanyl oxalate: (Ba_0.6Sr_0.4TiO(C₂O₄)₂·4H₂O, BSTO) precursor powders were successfully prepared through oxalate co-precipitation method. The pyrolysis of BSTO at 800 °C/4 h produced the barium-strontium titanate (Ba_0.6Sr_0.4TiO₃, BST) powders. Two kinds of dispersants namely ammonium salt of poly mathacrylic acid (PMAA-NH₄) and polyethylene glycol (PEG) were added respectively during the co-precipitation procedure. The powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), etc. Experimental results show that the addition of the dispersants reduced the productive rate of BST powders. The BSTO and BST powders obtained by aforementioned technique without dispersants were homogeneous with quasi-orbicular morphology. The particles grew into spindle shape with the effect of PEG. The morphology homogeneity was broke with small grains as well as large agglomerated particles concurrent when PMAA-NH₄ was added. The mechanism of the effect of the two dispersants was investigated in detail.     

共沉淀法制备Nd:YAG纳米粉体与机理探讨

以碳酸氢铵为沉淀剂采用共沉淀法和添加分散剂的方式．获得具有高烧结活性的碳酸盐前驱体,这种前驱体在较低的温度下烧结即可转变成相。同时借助DTA-TG、IR、XRD和TEM等测试手段对前驱体和YAG粉体进行表征。结果表明：在分散剂存在的情况下,此800℃左右煅烧2h前驱物直接转变为纯的YAG相,而无其它的杂质相,所得的YAG粉体的颗粒尺寸约20nm．是单分散的形貌近似球形的。此外不同温度下粉体的荧光性质表明,随着烧结温度的提高发光强度有所增加。     

纳米3Y-TZP陶瓷粉体形貌的分形分析

为了应用分形理论确定纳米3Y－TZP粉体制备方法的优劣，采用共沸蒸馏法和醇水溶液加热法制备了纳米3Y－TZP粉体，利用TEM观察确定了粉体粒径尺寸和团聚体形貌，并运用分形理论分析了分形维数和粉体烧结性能的关系。结果表明：纳米粉体在颗粒尺寸相同的情况下，粉体分形维数越低，团聚体半径越小，烧结性能越好；对粉体TEM图像进行分形维数计算并与粉体红外光谱分析和烧结结果进行了比较，确定醇水溶液加热法制备纳米3Y－TZP粉体效果较好。     

共沉淀法制备HA/β-TCP双相生物陶瓷粉末新工艺研究

在加热条件下，通过调节Ca(NO3)2-(NH4)2HPO4-NH3H2O-H2O体系的pH值．制得了不同HA和β-TCP比例的纯双相粉末．并对其反应历程进行了初步研究。新工艺和常规方法比较，大大缩短了陈化时间，反应重复性好。     

Synthesis and characterization of magnetite nanoparticles via the chemical co-precipitation method

Magnetite nanoparticles were synthesized via the chemical co-precipitation method using ammonium hydroxide as the precipitating agent. The size of the magnetite nanoparticles was carefully controlled by varying the reaction temperature and through the surface modification. Herein, the hexanoic acid and oleic acid were introduced as the coating agents during the initial crystallization phase of the magnetite. Their structure and morphology were characterized by the Fourier transform infrared spectroscopy (FTIR), the X-ray diffraction (XRD) and the field-emission scanning electron microscopy (FE-SEM). Moreover, the electrical and magnetic properties were studied by using a conductivity meter and a vibrating sample magnetometer (VSM), respectively. Both of the bare magnetite and the coated magnetite were of the cubic spinel structure and the spherical-shaped morphology. The reaction temperature and the surface modification critically affected the particle size, the electrical conductivity, and the magnetic properties of these particles. The particle size of the magnetite was increased through the surface modification and reaction temperature. In this study, the particle size of the magnetite nanoparticles was successfully controlled to be in the range of 10–40 nm, suitable for various biomedical applications. The electrical conductivity of the smallest particle size was 1.3 × 10^?3 S/cm, within the semi-conductive materials range, which was higher than that of the largest particle by about 5 times. All of the magnetite nanoparticles showed the superparamagnetic behavior with high saturation magnetization. Furthermore, the highest magnetization was 58.72 emu/g obtained from the hexanoic acid coated magnetite nanoparticles.     

配位均匀共沉淀法制备Ag/ZnO纳米复合材料的研究

采用配位均匀共沉淀法成功制备出了粒径20～50nm的Ag/ZnO纳米复合材料,用TG-DTA、XRD、IR及TEM等技术对前驱物及不同温度下焙烧前驱物所得的产品进行了表征分析.结果表明,当前驱物的焙烧温度为300℃时,粒子呈球形,粒径小,且其粒径随前驱物焙烧温度的升高而增大.对Ag/ZnO晶粒生长动力学的研究发现,在较低温度范围内,晶粒生长速度较快,其晶粒生长动力学指数为1.32.     

Molten salts synthesis and electrical properties of Sr- and/or Mg-doped perovskite-type LaAlO3 powders

Lanthanum-based LaBO₃ oxides adopting the very stable perovskite structure are currently considered attractive materials for a growing number of applications in the field of solid-state ionics. In particular, LaAlO₃-based perovskites are promising electrolyte materials for solid oxide fuel cells because they show almost pure oxygen ion conductivity at low oxygen partial pressures and high temperatures as well as excellent thermal and chemical stability under the standard operating conditions. This article describes a low-temperature synthesis of pure and acceptor-doped perovskite-type LaAlO₃ nanopowders via a facile and environmental-friendly molten salts method. Using hydrated metal nitrates and sodium hydroxide as raw materials, the proposed methodology consists of two steps: a mechanically induced metathesis reaction and short firing above NaNO₃'s melting point. The purpose of the first is twofold: i.e., to generate in situ the NaNO₃ flux and to obtain a suitable precursor for the synthesis of the target materials in molten nitrates. Accordingly, pure and Mg- and/or Sr-doped LaAlO₃ powders were obtained directly without using any purification step at temperatures ≤500 °C. When preparing the Mg-containing samples, NaNO₂ was also added to the reaction mixture to increase melt reactivity. The formation of the target series in the molten salt is thought to proceed through a “dissolution–precipitation” mechanism with LaAlO₃ particles precipitating during cooling from a solution oversaturated with reactants. Electrical properties of the as-prepared materials were measured as a function of temperature and frequency by means of impedance spectroscopy and found comparable to those shown by similar materials prepared using more complicated routes.     

Formation of high-density scintillation ceramic from LuAG:Ce + Lu2O3 powders obtained by co-precipitation method

The results of formation of the high density effective scintillation ceramics consisting of two compounds of the cubic symmetry, LuAG:Ce and Lu₂O₃ (LuAG:Ce + Lu₂O₃), are described. Powders of a novel material LuAG:Ce + Lu₂O₃ were synthesized by co-precipitation method. The introduction of Lu₂O₃ into LuAG:Ce was shown to increase the density of the ceramics obtained and modify its scintillation properties.     

LaAlO3顶层结构对LaAlO3-BaTiO3铁电超晶格薄膜性能的影响

X射线衍射技术分析发现,通过生长一层较厚的LaAlO3顶层结构,可以把LaAlO3-BaTiO3超晶格中界面处的应变有效地控制在薄膜中,从而增加超晶格薄膜的平均面外晶格常数c.电学性能测试证明LaAlO3顶层结构的存在极大地改善了超晶格薄膜的电学性能,使其剩余极化强度增加了40多倍.     

A novel approach for the synthesis of nanocrystalline zinc oxide powders by room temperature co-precipitation method

A single step co-precipitation route has been employed for the first time in the preparation of ZnO nanoparticles using ammonium hydroxide and zinc nitrate tetrahydrate. The X-ray diffraction analysis revealed that the synthesized powder has the hexagonal (wurtzite) structure. The as-prepared ZnO powder was well crystalline, without any calcination. This is a promising result compared to those mentioned in the literature, in which crystallization of ZnO nanoparticles was detected at > 300 °C. The average crystallite size of the as-prepared ZnO nanopowder is 20-40 nm. The nanocrystalline ZnO could be sintered to ~ 95% of the theoretical density at 1300 °C in 4 h.     

Synthesis of SrLaAlO4 fine ceramic powders by co-precipitation process

SrLaAlO₄ fine ceramic powders were synthesized by a co-precipitation process from the raw materials of La(NO₃)₃·6H₂O (99 %), Al(NO₃)₃·9H₂O (98–102 %) and SrCl₂·6H₂O (99 %). Effects of the precipitating pH value and thermal treatment temperature upon the phase constitution and microstructures of the product powders were determined together with the reaction mechanisms. The precipitating pH value indicated a key role dominating the reaction process. For the situation of precipitating pH = 7, SrLaAlO₄ phase began to form around 900 °C and became the major phase above 1,000 °C where small amount of secondary phases of La₂O₃, LaSrAl₃O₇, La₁₀Al₄O₂₁ were detected. With increasing the precipitating pH value to 8 and 9, SrLaAlO₄ major phase were obtained at 900 °C together with small amount of secondary phases of La₂O₃, LaSrAl₃O₇ and La(OH)₃, and the amount of secondary phases decreased with increasing thermal treatment temperature. The grain morphology of the product powders was also determined by the precipitating pH value and the thermal treatment temperature. SrLaAlO₄ fine ceramic powders with homogenous morphology and less secondary phases were obtained by heating the precursors with precipitating pH = 9 at 900 and 1,000 °C in air for 10 h. Densification of SrLaAlO₄ ceramics derived from the present powders could be achieved at 1,450 °C, and the optimal microwave dielectric properties were obtained as: ε _r  = 19.5, Qf = 56,500 GHz, τ _f  = ?32.8 ppm/°C.     

Capacitive characteristics of Ni–Co oxide nano-composite via coordination homogeneous co-precipitation method

A series of Ni–Co oxide nano-composites were prepared by thermal decomposition of the precursors obtained via coordination homogeneous co-precipitation method. Thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), and transition electron microscopy (TEM) tests were applied to investigate the thermal behavior, crystalline. and morphology of the Ni–Co oxide composites. The electrochemical properties of Ni–Co oxide electrodes were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance measurements. Results showed that the calcination temperature had great effect on morphology and specific capacitance of product. The effect of the molar ratios of Ni²⁺/Co²⁺ in the reaction system on the electrochemical properties of Ni–Co oxide electrodes was also discussed.