水热条件下钛酸钡粉体晶粒形成机理

以圩采用加直流电场水热法制备的ＢａＴｉＯ３粉体体系，测定了反应过程中外直流电场电流和反应反溶液中残 ＯＨＪ一。水热反应初期，电流随着反应温度的升高而增大，反应继续进行，电流达到极大值，然后急剧减小。反应温度越高，反应时间越长，反应后溶液里残留的ＯＨ量越少。结合粉体物相和晶粒形貌的表征，对水热条件下ＢａＴｉＯ３晶粒的形成机量进行了探讨。在反应初期，随着温度的升高驱物逐渐溶解，体系中导电离子数不断增多     

水热法制备BaTiO3粉体

以Ｂａ（ＯＨ）２·８Ｈ２Ｏ和ＴｉＯ２为前驱物,在水热条件下制得了单一物相的ＢａＴｉＯ３粉体中产生裂纹等发现产物的物相与反应温度和前驱物的Ｂａ,Ｔｉ摩尔比有关,由负离子配位多面体生长基元模型分析了ＢａＴｉＯ３粉体的形成机理,指出了形成ＢａＴｉＯ３粉体的生长基元为Ｂａ（ＯＨ）１２＾１０－和Ｔｉ（ＯＨ）６＾２－,由此比较合理地解释了粉体的物相以及Ｂａ,Ｔｉ摩尔比对ＢａＴｉＯ３粉体形成的影响。     

醇盐水解法合成高纯超细BaTiO3粉体

近年来，高纯超细ＢａＴｉＯ３粉体的制备技术发展十分迅速，它们在ＢａＴｉＯ３电子陶瓷的应用研究中起着日益重要的作用。尽管ＢａＴｉＯ３粉体的合成方法很多，但醇盐水解法有其不可解辨的优点。本文就醇盐水解法合成ＢａＴｉＯ３粉体的制备技术及其发展作了综合评述。     

液相原料制备PTC粉体及其性能研究

本文介绍了一种通过液相原料形式引入以草酸盐共沉淀来制备ＰＴＣ粉体的新方法。即ＢａＴｉＯ３、Ａｌ２Ｏ３、ＳｉＯ２、ＭｎＯ２、Ｙ２Ｏ３等均采用液相原料引入，然后用草酸进行共沉淀，通过灼烧制得ＰＴＣ粉体。用这种粉体制得的ＰＴＣ陶瓷，其晶粒均匀性和电性能都优于传统固相法制得的ＰＴＣ陶瓷。     

pH值对Ti（O^nBu）4—Ba（OAc）2水解法合成BaTiO3粉体性能的影响

以乙酸和氢氧化钾为辅助原料，通过Ｔｉ（Ｏ＾ｎＢｕ）４－Ｂａ（ＯＡｃ）２水解法合成ＢａＴｉＯ３粉体。借助ＳＥＭ、ＴＥＭ、ＸＲＤ和ＥＰＭＡ等分析手段，研究了ＰＨ值对ＢａＴｉＯ３粉体性能的影响。论述了合成ＢａＴｉＯ３的反应机理，同时探讨了ＰＨ值对其反应机理的影响。     

pH值对Ti（O~nBu）_4－Ba（OAc）_2水解法合成BaTiO_3粉体

以乙酸和氢氧化钾为辅助原料，通过Ｔｉ（Ｏ￣ｎＢｕ）＿４－Ｂａ（ＯＡｃ）＿２水解法合成ＢａＴｉＯ＿３粉体。借助ＳＥＭ、ＴＥＭ、ＸＲＤ和ＥＰＭＡ等分析手段，研究了ｐＨ值对ＢａＴｉＯ＿３粉体性能的影响。论述了合成ＢａＴｉＯ＿３的反应机理，同时探讨了ｐＨ值对其反应机理的影响。     

正丁醇钛—乙酸钡水解法合成BaTiO3粉体的研究

本文着重研究了Ｔｉ（Ｏ＾ｎＢａ）４－Ｂａ（ＤＡｃ）２水解法合成高纯超细ＢａＴｉＯ３粉体的制备工艺。借助ＴＧＤＴＡ，ＸＲＤ，ＴＥＭ，ＳＥＭ，ＳＡＸＳ和ＩＣＰ－ＡＥＳ等分析手段，研究了ＰＨ值，Ｂａ／Ｔｉ比和（Ｂａ／Ｔｉ）比，反应温度，浸泡处理等对ＢａＴｉＯ２粉体性能的影响，采用本工艺方法合成的ＢａＴｉＯ３粉体，纯度达９９．８０ｗｔ％，比表面积为６８ｍ＾２／ｇ，一次粒子平均粒径４６．７ｎｍ，二次粒子粒径     

超细BaTiO3粉体成瓷技术研究

基于液相化学共沉淀法合成超细ＢａＴｉＯ３粉末，研究了制备ＰＴＣ ＢａＴｉＯ３陶瓷的成瓷技术。利用ＸＲＤ和ＳＥＭ分析手段，对制备的ＢａＴｉＯ３陶瓷的结构进行了表征。对于影响ＢａＴｉＯ３陶瓷的主要性能，如致密化、ＰＴＣ效应和半导化性能的工艺参数进行了较为详细的研究和讨论。     

BaTiO3超细粉的研究

通过对ＢａＴｉＯ３超细粉制备过程的探索，研究了影响化学配比及粒度的因素，提出反应过程中的ＰＨ值是影响Ｂａ：Ｔｉ比的关键因素，反应条件，分散剂，陈化剂及煅烧温度对粒度具有决定性作用，本研究提供了一条ＢａＴｉＯ３超细粉制备的新途径。     

超细BaTiO3粉的液相合成技术研究

把快速混合技术运用于草酸盐沉淀法，制备了超细ＢａＴｉＯ３颗粒。运用ＸＲＤ，ＴＥＭ等测试手段，研究了制备超细ＢａＴｉＯ３粉末前驱体的液相合成工艺条件，过程规律及相应的表面处理技术。     

Coprecipitation and Hydrothermal Synthesis of Ultrafine 5.5 mol% CeO2-2 mol% YO1.5ZrO2 Powders

Ultrafine 5.5 mol% CeO₂—2 mol% YO_1.5ZrO₂ powders with controllable crystallite size were synthesized by two kinds of coprecipitation methods and subsequent crystallization treatment. The amorphous gel produced by ammonia coprecipitation and hydrothermal treatment at 200°C for 3.5 h results in an ultrafine powder with a surface area of 206 m²/g and a crystallite size of 4.8 nm. The powder produced by urea hydrolysis and calcination exhibits a purely tetragonal phase. In addition, the powders crystallized by hydrothermal treatment exhibit high packing density and can be sintered at lower temperature (,1400°C) with nearly 100% tetragonal phase achieved.     

Hydrothermal synthesis of ZrO2–Y2O3 solid solutions at low temperature

Ultrafine powders of ZrO₂–Y₂O₃ solid solutions have been synthesized by hydrothermal treatment at 110°C. Zirconia gel, crystalline Y₂O₃ and various mineralizing solutions have been utilized as precursors for the hydrothermal synthesis. Yttria-stabilized zirconia (YSZ) with different Y₂O₃ content and characterized by different crystallite sizes have been produced by changing the hydrothermal treatment temperature, and the nature and concentration of the mineralizer solution. The role of mineralizer solutions on the crystallization-stabilization of zirconia gel at low temperature of hydrothermal treatment is discussed.     

水热合成制备超细氢氧化镁阻燃剂

采用低温水热、高温水热、氢氧化钠环境水热、引入晶种水热等不同水热工艺制备出超细氢氧化镁粉体。分别对制备出的粉体进行了XRD、TEM、BET等表征,并将所得粉体添加到软质PVC中,进行了阻燃及力学性能测试。结果表明,在上述水热方法中,氢氧化钠环境水热与引入晶种水热法制得的氢氧化镁超细粉体比表面积低、极性小、分散性好,改性后添加于软质PVC中得到良好的应用效果,且引入晶种水热法易于工业化生产。     

Effects of hydrothermal temperature and time on the photocatalytic activity and microstructures of bimodal mesoporous TiO2 powders

Bimodal nanocrystalline mesoporous TiO₂ powders with high photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate (TiO(C₄H₉)₄, TBOT) as precursor. The as-prepared TiO₂ powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption–desorption measurements. The photocatalytic activity of the as-prepared TiO₂ powders was evaluated by the photocatalytic degradation of acetone (CH₃COCH₃) under UV-light irradiation at room temperature in air. The effects of hydrothermal temperature and time on the microstructures and photocatalytic activity of the TiO₂ powders were investigated and discussed. It was found that hydrothermal treatment enhanced the phase transformation of the TiO₂ powders from amorphous to anatase and crystallization of anatase. All TiO₂ powders after hydrothermal treatment showed bimodal pore-size distributions in the mesoporous region: one was intra-aggregated pores with maximum pore diameters of ca. 4–8 nm and the other with inter-aggregated pores with maximum pore diameters of ca. 45–50 nm. With increasing hydrothermal temperature and time, the average crystallite size and average pore size increased, in contrast, the Brunauer-Emmett-Teller (BET) specific surface areas, pore volumes and porosity steadily decreased. An optimal hydrothermal condition (180 °C for 10 h) was determined. The photocatalytic activity of the prepared TiO₂ powders under optimal hydrothermal conditions was more than three times higher than that of Degussa P25.     

The influence of starting materials on the structure of ultrafine carbon powders

The primary ultrafine carbon powders were prepared by sol–gel supercritical fluid drying method using different starting materials. After heat-treatment at 1100 and 2600°C, respectively, the ultrafine carbon powders were obtained. The properties of primary ultrafine carbon powders and their annealed products were characterized by TEM, XRD, Raman spectra and nitrogen adsorption. The results reveal that starting materials have influence on the structure of ultrafine carbon powders.     

Polyacrylamide gel synthesis and sintering of Mg2SiO4:Eunanopowder

A Mg₂SiO₄:Eu³⁺ nanopowder was synthesized by a polyacrylamide gel method. In this route, the gelation of the solution is achieved by the formation of a polymer network which provides a structural framework for the growth of particles. The densification of the powders was also studied. An amorphous nanopowder was synthesized and crystallized to Mg₂SiO₄ after heat-treatment via a solid-state reaction at a relatively low temperature of about 700 °C. The powders prepared by the polyacrylamide gel method showed better sinterability than the powders synthesized by the conventional sol–gel method. The relative density of the sample was 97% at 1500 °C.     

Green synthesis of calcium silicate bioceramic powders

Calcium silicates have proven to be potential candidates for biomedical applications because of their osteogenic properties. Sol–gel methods are typically used for the preparation of calcium silicate powders. However, in the sol–gel route, an acid or base and ethanol are used to catalyze the precursors. From the perspective of green chemistry, it is better to avoid the use of organic solvents. The objective of this study was to prepare calcium silicate powders using a green synthesis route (hydrothermal method) without organic solvents. The powders were also prepared via the sol–gel process using tetraethoxysilane (TEOS) and calcium nitrate as the raw materials for the purpose of comparison. The powders were sintered at temperatures ranging from 600 to 1000 °C after the application of both methods. To understand the feasibility of using the resulting materials in medical applications for bone repair, the powders were mixed with water to form cements. The results indicated that the powder composition was not significantly affected by the different techniques but was dependent on the Ca:Si ratio of the precursors and on the sintering temperature. The different techniques produced no differences in powder morphology. In addition, the setting times of the powder-derived cements were found to be independent of the sintering temperature and synthesis technique, but it was affected by the Ca:Si ratio of the precursors. The mechanical strength of the cements was similar. These encouraging results suggest that the hydrothermal method is a potentially beneficial alternative to the sol–gel route for the production of calcium silicate powders.     

水热法制备高比表面积介孔TiO2粉体及其光催化性能研究

实验以β环糊精(β-CD)为造孔剂,采用水热法制备了高比表面积介孔TiO2纳米粉体.利用BET、XRD、N2 ad-sorption-sorption等方法对样品进行了测试.考察了水热温度、水热时间、焙烧温度、造孔剂添加量等因素对材料的比表面积及其光催化性能的影响.实验结果表明:当体系的水热温度180℃、水热时间8h、...     

Hydrothermal Synthesis of Spherical Perovskite Oxide Powders Using Spherical Gel Powders

Spherical perovskite oxide powders, composed of fine particulates, were prepared by using spherical gel powders under hydrothermal conditions. Spherical PbTiO₃, BaTiO₃, and SrTiO₃ powders were synthesized from spherical TiO₂ gel powders, and spherical PbZrO₃ powder from spherical ZrO₂ gel powder. Spherical Pb(Zr_0.5, Ti_0.5)O₃ and Ba(Zr_0.5,Ti_0.5)O₃ powders were prepared from spherical ZrTiO₄ gel powders. Lead acetate trihydrate, barium hydroxide octahydrate, and strontium hydroxide octahydrate were used as the sources of A-site ions in each perovskite oxide (ABO₃). The spherical TiO₂ and ZrO₂ gel powders were prepared by thermal hydrolysis of titanium tetrachloride and zirconium oxychloride, respectively, and spherical ZrTiO₄ gel powder by thermal hydrolysis of a mixture of them in alcohol-water mixed solvent. During the hydrothermal treatment, the spherical gel powders retained their spherical shape to produce spherical perovskite oxide powders, composed of nanometer-sized particulates.     

钛酸钡粉体的微波水热合成

结合水热法和微波加热的优点,采用微波水热在低温条件下合成了钙钛矿结构的钛酸钡纳米粉体,并与水热法合成产物进行了适当的比较。通过X射线衍射(XRD)、红外光谱(IR)和SEM电镜,分析了BaTiO_3纳米粉体的结构和组成,并初步探讨了微波水热合成钛酸钡的机理。结果表明,与传统水热法比较,微波水热合成BaTiO_3纳米粉的温度更低,而且微波加热可明显提高反应速度。