热分解法制备希土氧化物超微粉末

引言超微粉未已被视为九十年代的新材料,它的许多奇特的性质和令人惊异的应用不仅引起人们的重视,并开展了许多研究。但目前对希土金属及其化合物的超微粉未的研究则报道甚少。尽管如此,希土超微粉未已经在磁性材料、超导材料、传感器、超高温耐热合金等方面获得应用,并取得了明显的效果。超微粉末的合成方法其多,但均不成熟、寻求合成希土超微粉末的方法则是一个重要的课题。我们在研究醇盐法制备氢氧化钕、氧化钕超微粉末的同时,采用热分解法制备了一系列希土氧化物超微粉末,观察了它们粒径变化的规律,得到一些新的结果。     

激光气相法研制硅系超微粉

激光气相法是制备超微粉末的新方法之一,目前还存在超微粉末粒径太小难于收集,原料SiH_4价格较昂贵等困难。我们以SiH_4为主要原料,成功地合成出超微Si、Si_3N_4、SiC粉末,研究了反应条件对超微粉性能的影响,探索了用廉价原料代替SiH_4的可能性,并且在超微粉的收集方面做了若干探索,取得了一些有意义的结果。     

共沉淀法制备铝酸镧超微粉末的研究

用尿素-氨水在热水溶液中调pH共沉淀制备铝酸镧超微粉末。研究了氨水浓度、尿素浓度和尿素-氨水滴加速度对超微粉末颗粒的影响和焙烧温度对超微粉末颗粒微观变化的作用。在选定的条件下,制备成粒径为0.1～0.7μm、比表面93～112m~2/g的铝酸镧超微粉末。     

纳米器件制备的新方法--微接触印刷术

微接触印刷术是一内米器件制备的新方法,能在金、银、硅片、陶瓷等基材表面印刷出纳人米－微米量级的精细结构,印制导电离子微电路,以及制作结三维结构微制品。该方法精确重复,工艺简单,对实验室条件要求也不高分子高,在微电子学、超微机械加工等超微器件制备中有很好的应用前景。     

聚合物前驱体3D打印制备高性能陶瓷

3D打印制备陶瓷可以实现结构-材料设计一体化,为复杂形状陶瓷材料快速成型提供了新途径。但是传统的3D打印制备陶瓷是以陶瓷粉末或陶瓷颗粒为打印材料,存在陶瓷构件尺寸精度差、表面光洁度低和力学性能不佳等问题。近年来,以聚合物前驱体为打印材料,通过3D打印成型、高温裂解等工艺制备高性能陶瓷技术的出现为改善这些不足提供了新方法,成为3D打印陶瓷领域的研究热点。本文概述了聚合物前驱体3D打印制备高性能陶瓷的研究进展,重点阐述了本体聚合物前驱体、聚合物前驱体/光敏化合物、聚合物前驱体/巯基化合物、光敏基团改性聚合物前驱体、增强体/聚合物前驱体五种典型材料体系的研究现状,并对其今后的发展方向进行了展望。     

沉淀转化法制备不同形状的氢氧化镍及氧化镍超微粉末的研究

本工作采用沉淀转化法制备了不同形状的氢氧化镍及氧化镍超微粉末，详细的研究了转化温度、沉淀转化剂及阻聚剂的浓度等实验参数对超微粉末组成和结构的影响。     

溶胶-凝胶法制备Y_3Al_5O_(12)超微粉末

使用溶胶-凝胶法制备了平均粒径为20～150nm的Y_3Al_5O_(12)超微粉末。从凝胶至超微粉末的过程中,发生了较大的失重现象。纯相晶态的Y_3Al_5O_(12)超微粉末的最低生成温度为900℃。粉末平均粒径随着灼烧时间的增加而逐渐增大,随着灼烧温度的增加而显著增大。     

CaCO3超细粉末的低温水热合成与表征

超细碳酸钙有颗粒尺寸小、比表面积大和表面活性高等优良特性,在橡胶、塑料、纸张、涂料、日用化学品等领域有广泛的应用。因此,研究CaCO3超细粉末的制备方法,开发CaCO3超细微粉的用途,具有十分重要的意义。目前其制备方法主要是碳化法,本文利用水热法制备单一相超细CaCO3粉末,通过不同的反应前驱物在120℃和150℃下进行水热反应直接合成出超细CaCO3粉末,并对产品的结构和形貌进行了表征。     

硅基聚合物前驱体转化陶瓷微观结构研究进展

聚合物前驱体转化法使得陶瓷材料的制备实现了可分子设计和可聚合物工艺加工,在陶瓷基复合材料、陶瓷纤维、功能涂层、特种胶粘剂等方面具有重要应用价值.不同于传统粉末烧结工艺,该方法涉及有机聚合物至无机陶瓷的转化过程,因此,聚合物前驱体的分子结构以及陶瓷化工艺对所制备陶瓷材料的微观结构和功能特性具有直接影响.本文综述了基于聚合...     

α-Fe纳米粉末制备及其表征

αFe粉末是一种性能优良的磁性记录材料,它在电子工业、化学工业和国防高科技研究领域中具有特殊的多方面的应用价值。特别是纳米级αFe粉末具有超强的磁特性技术指标,是高密度磁记录介质、高效催化剂和微波吸收剂的理想原料[1～3]。目前,国内外已有多种方法制备αFe微粉?..     

Preparation of PZT Film and Powder by Sol-Gel Technique Using Ti- and Zr-Alkoxides and a Novel Pb-Precursor; Pb(NO3)2 1.5EO3

PZT (PbZr0.53Ti0.47O3) films and powders have been prepared by a precursor mixture containing Pb(NO3)1.5EO3 (EO3=triethylene glycol) and Zr- and Ti-methoxy ethanolates. The gel films have been deposited on Si/Ti/Pt substrates and on glass substrates from which they can easily be removed. The PZT films on the Si/Ti/Pt substrates were prepared with thicknesses up to 200 nm per layer after heating to 700°C. The phase development on heat-treatment of loose gel films to yield PZT was investigated by Powder-XRD, FT-IR, SEM-EDS, TEM-EDS, thermo-mass spectroscopy and DSC and the PZT was found to form in the region 550–700°C. PZT powders of 50–5000 nm sizes were prepared by hydrolysis under basic conditions and washing with water followed by heat-treatment to 650°C.     

Solvothermal synthesis of nanosized particles of vanadium oxide

The interaction of vanadyl acetate, vanadium(V) oxide, and vanadium(V) isopropylate with capronic acid has afforded a series of nanosized vanadium oxide powders. The products structure has been studied by X-ray diffraction analysis. Both amorphous and crystalline powders of vanadium oxide can be prepared depending on the starting compound, temperature, and the synthesis duration, the V₂O₃ (karelianite) structure being in all the cases the most thermodynamically stable. Photocatalytic properties of the prepared powders have been studied.     

掺杂改性纳米TiO2降解挥发性污染物及产物研究

本文系统研究了水热法制备的铁掺杂纳米TiO₂和氮掺杂纳米TiO₂在可见光照射下对挥发性有机物(volatile organic compounds,VOCs)的降解能力和降解产物.铁掺杂纳米TiO₂和氮掺杂TiO₂对光的吸收边分别红移到540 nm和580 nm;在可见光下具有良好的催化活性,24 h内对挥发性有机物的降解率达20%—50%,降解后的最终产物可能主要为CO₂.     

Synthesis of (K,Na)NbO3 particles by traditional hydrothermal method and high-temperature mixing method under hydrothermal�Csolvothermal conditions

Pure (K,Na)NbO₃ (KNN) powders have been successfully prepared by using traditional hydrothermal method and high-temperature mixing method (HTMM) under solvothermal and hydrothermal conditions. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to show the change of phase, morphology, and size of the as-prepared particles with the alkalinity of the starting solution. Compared with the traditional hydrothermal method, smaller particles with higher phase purity are prepared using HTMM under hydrothermal conditions. It is found that the alkalinity has significant effects on the crystal size. The KNN grain size first increases and then decreases with increasing alkalinity. Typical samples solvothermally synthesized in a mixed solvent with isopropanol/deionized water ratio of 50/50 by volume were made of well-crystallized single-crystalline nanoparticles with size of about 500 nm.     

Magnetic properties of lanthanum orthoferrite fine powders prepared by different chemical routes

Fine powders of lanthanum iron oxide, LaFeO₃, have been prepared by solid state reaction as well as sol-gel synthesis and nebulized spray pyrolysis. Structures, morphologies and magnetic susceptibility measurements of these powders have been examined. The powders prepared by all the three low-temperature routes contain nearly spherical particles with an average diameter of 40 nm. These samples show a lower Neel temperature than the powder prepared by solid state reaction besides showing much lower magnetic susceptibility at low temperatures. Dedicated to Professor C N R Rao on his 70th birthday     

Synthesis of polylactide/clay nanocomposites by in situ intercalative polymerization in supercritical carbon dioxide

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted onto the clay surface, leading to an exfoliated morphology. Nanocomposites with high clay contents (30-50 wt.%), called masterbatches, have also been successfully prepared and were recovered as fine powders thanks to the unique properties of the supercritical fluid. Dilution of these masterbatches into commercial l-polylactide by melt blending has led to essentially exfoliated nanocomposites containing 3 wt.% of clay. The mechanical properties of these materials have been assessed by flexion and impact tests. Significant improvements of stiffness and toughness have been observed for the PLA/clay nanocomposites compared to the pure matrix, together with improved impact resistance.     

Bi12 TiO20纳米粉体的制备及其光吸收特性研究

Nano-cystal Bi12 TiO20 powders have been prepared by the chemical solution decomposition（ CSD）method using bismuth nitrate and titanium butoxide as the starting precusors. The powders were characterized by the thermogravimetry and differential thermal analysis（TG-DTA）,X-ray diffractometry（XRD）and transmission electron microscopy（TEM）. The formation mechanism of Bi12TiO20 naocrystal has been analyzed. The UV-Vis diffuse reflectance spectra of the prepared Bi12TiO20 powders were measured to determine their optical absorption characteristic. The results showed that pure nano-crystal Bi12TiO20 powders could be easily prepared from stoichiometric precursor solutions at the annealing temperature 1550℃. A broad optical absorption band between 560-385 nm （about 2. 2-3. 22 eV）was observed for the prepared nano-crystal Bi12TiO20 powders.     

Role of reaction atmosphere in preparation of potassium tantalate through sol–gel method

Potassium tantalate (KT) thin films and powders of both K₂Ta₂O₆ (KT pyrochlore) and KTaO₃ (KT perovskite) structures were prepared by means of chemical solution deposition method using Si(111) with ZnO and MgO buffer layers as a substrate. The influence of reaction atmosphere on reaction pathway and phase composition for both KT powders, and KT thin films has been studied mainly by means of powder diffraction and infrared spectroscopy. When an oxygen flow instead of static air atmosphere has been used the process of pyrolysis in oxygen runs over much narrower temperature interval (200–300 °C), relatively to air atmosphere (200–600 °C) and almost no (in case of powders), or no (in case of thin films) pyrochlore intermediate phase has been detected in comparison with treatment in air, where the pyrochlore phase is stable at temperatures 500–600 °C (powders). KT perovskite phase starts to crystallize at temperatures 50° and 150 °C lower compared to air atmosphere in case of powders and thin films, respectively. Microstructure formed by near-columnar grains and small grains of equiaxed shape was observed in films treated in oxygen and air atmosphere, respectively.     

Direct solid sample analysis of SiC-powders by DC glow discharge and DC-ARC emission spectroscopy

Glow discharge atomic emission spectroscopy (GD-OES) and the classical spectrographic method with a dc arc source (DC-ARC OES) have been applied to the direct analysis of SiC powders. The homogeneity of pellets prepared from mixtures of SiC with copper powder and used for the GD experiments was investigated in detail. Various methods have been tested for the analytical calibration. These have been applied to the direct solid sample analysis of technical SiC powders. The experimental data were evaluated by chemometrical procedures. The results of the two methods have been compared.     

Synthesis of various morphological Ca0.75Er0.25MnO3 powders by hydrothermal method and their electrical properties

Research on Chemical Intermediates - The Ca0.75Er0.25MnO3 powders with better conductive properties and various morphologies have been prepared by using hydrothermal method with different...