室温研磨固相反应法制备γ-Fe2O3纳米粉体及其气敏性能研究

本文首次以硝酸铁Fe(NO₃)₃·9H₂O、氢氧化钠NaOH和聚乙二醇(PEG-200)为反应物，采用室温研磨固相反应法合成了γ-Fe₂O₃纳米粉体，并用红外光谱(FTIR)、X射线粉末衍射(XRD)、透射电镜(TEM)和气敏元件测试系统对产物的结构、表观形貌及气敏性能进行表征。结果表明，FeOOH在300~500 ℃热处理1 h均为γ-Fe₂O₃晶相，粒径为4~10 nm；600 ℃热处理1 h后转化为α-Fe₂O₃晶相。300 ℃焙烧后获得的γ-Fe₂O₃纳米粉体制成的气敏元件对乙醇有较高的灵敏度和较好的选择性。另外，以FeCl₃为铁源时仅能得到纯α-Fe₂O₃纳米粉体，表明不同的铁源和PEG碳链的长短对产物的形成具有至关重要的影响。     

聚合氯化铝中Al13形态的分离纯化方法及特性

采用柱层析法、沉淀置换法和乙醇-丙酮混合溶剂法对聚合氯化铝(PAC)中的Al₁₃形态进行了分离提纯, 采用Al-Ferron逐时络合比色法, ²⁷Al NMR, TEM, SEM, 电位测定法, 粒度测定法等多种现代分析仪器和方法对不同分离提纯方法得到的Al₁₃形态进行了分析表征和比较, 并初步比较研究了Al₁₃形态的水处理效果. 实验结果表明, 不同分离纯化方法得到的 Al₁₃形态具有不同的结构形貌、粒度分布、电性和水处理效果. 乙醇-丙酮混合溶剂法得到的Al₁₃形态具有良好的纯度和水处理效果. 该研究初步证实了Al₁₃是PAC中的最佳絮凝形态.     

聚合氯化铝中Al13形态的分离纯化方法及特性

采用柱层析法、沉淀置换法和乙醇-丙酮混合溶剂法对聚合氯化铝(PAC)中的Al₁₃形态进行了分离提纯, 采用Al-Ferron逐时络合比色法, ²⁷Al NMR, TEM, SEM, 电位测定法, 粒度测定法等多种现代分析仪器和方法对不同分离提纯方法得到的Al₁₃形态进行了分析表征和比较, 并初步比较研究了Al₁₃形态的水处理效果. 实验结果表明, 不同分离纯化方法得到的 Al₁₃形态具有不同的结构形貌、粒度分布、电性和水处理效果. 乙醇-丙酮混合溶剂法得到的Al₁₃形态具有良好的纯度和水处理效果. 该研究初步证实了Al₁₃是PAC中的最佳絮凝形态.     

Dawson结构(NH4)6P2Mo18O62·12H2O纳米粉体的室温固相合成及形成机理

以H₆P₂Mo₁₈O₆₂·23H₂O和(NH₄)₂C₂O₄·H₂O为原料，首次采用室温固相反应合成出(NH₄)₆P₂Mo₁₈O₆₂·12H₂O纳米粉体，并运用元素分析、FTIR、XRD、TEM、TG-DTA和BET等技术对其组成、结构和性能进行了表征。发现(NH₄)₆P₂Mo₁₈O₆₂·12H₂O纳米粉体平均粒径为40 nm，保留着杂多阴离子的Dawson结构，具有Dawson结构的特征衍射峰，比表面积为143.9 m²·g^-1，在445 ℃以下杂多阴离子有良好的热稳定性。在该固相反应中，研磨和放热反应热能可加速反应物分子的扩散速率和生成物分子的成核速率，使产物粒径减小；反应物含有结晶水和生成物H₂C₂O₄·2H₂O对形成小粒径的(NH₄)₆P₂Mo₁₈O₆₂·12H₂O纳米粉体起关键作用。     

纳米Re2O7的萃取法制备及光催化特性研究

本工作从N235-正庚烷萃取体系中，以饱和萃取法制得前体物和纳米粉体Re₂O₇，平均粒径30 nm。以此纳米粉为光催化剂，研究了光降解甲基橙染料的最佳条件，并在相同条件下，与非纳米Re₂O₇及工业常用的纳米TiO₂进行比较，光降解甲基橙能力大小为：纳米Re₂O₇ > 锐钛矿型纳米TiO₂ > 非纳米Re₂O₇。     

具有不同形貌和择优取向的MxWO3·xH2O粉晶的制备与表征

采用沉淀结合渗析的方法，以钨酸钠、钨酸铵为原料，制备了不同形貌、具有择优取向的M_xWO₃·xH₂O(M=Na⁺，NH₄⁺，x<1)粉晶，利用SEM、XRD、TG、IR、XPS等手段对粉体进行表征，考察了不同渗析时间和焙烧温度对粉晶形貌、晶化程度及结构转变的影响。结果表明，长时间渗析后粉体的晶化程度明显提高，并沿(010)晶面方向择优生长，形貌由不规则形变为梭形和蝴蝶形。经空气气氛400 ℃焙烧后，Na_xWO₃·xH₂O和(NH₄)_xWO₃·xH₂O粉晶均转变为沿(200)晶面方向择优生长的立方青铜相，且形貌也发生改变。     

(ZrO2)0.86(Sm2O3)0.14纳米粉体的水热法合成及其烧结体的电性能

以湿化学法制得Zr(OH)₄和Sm(OH)₃的共沉淀为前驱体, 在碱性介质中用水热法合成了(ZrO₂)_0.86(Sm₂O₃)_0.14及(ZrO₂)_0.88(Sm₂O₃)_0.12纳米粉体. 将纳米粉体在较低温度(1450 ℃)下烧结制得了致密的固体电解质陶瓷样品, 比通常高温固相反应法采用的烧结温度(＞1600 ℃)降低了150 ℃以上. XRD测定结果表明, (ZrO₂)_0.86(Sm₂O₃)_0.14纳米粉体及其烧结体均为立方相, 但(ZrO₂)_0.88(Sm₂O₃)_0.12纳米粉体为立方相, 它的烧结体为立方相和单斜相的混合相. 用交流阻抗谱法、氧浓差电池法及氧泵(氧的电化学透过)法研究了(ZrO₂)_0.86(Sm₂O₃)_0.14陶瓷样品在600～1000 ℃下的离子导电特性. 结果表明, 该陶瓷样品在600～1000 ℃下氧离子迁移数为1, 氧离子电导率的最大值为3.2×10^－2 S•cm^－1, 是一个优良的氧离子导体; 它的氧泵性能明显地优于YSZ.     

WS2/CuGa2O4复合材料的制备及其气敏性

采用共沉淀法制备了CuGa₂O₄纳米材料,并利用水热法制备了一系列WS₂/CuGa₂O₄复合材料。结合X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等对制备的材料进行了物相组成、表面形貌以及元素价态的分析。研究了WS₂的复合量对 CuGa₂O₄材料检测乙醇气体敏感性能的影响。实验结果表明,当 WS₂与 CuGa₂O₄质量比为 1%时,该复合材料制备的传感器在室温下对 100 μL·L^-1乙醇气体表现出 345.3 的灵敏度,响应时间和恢复时间分别为 184 和 69 s,且最低检测限为 0.1μL·L^-1。     

溶剂热法合成Fe-CeO2与N-Fe-CeO2纳米粉体及其光催化性能

采用溶剂热法合成了不同Fe掺杂含量的Fe-CeO₂纳米粉体及不同氮源掺杂的N-10% Fe-CeO₂（n_Fe/（n_Fe+n_Ce）=10%）纳米粉体。利用TEM、XRD、XPS、Raman和UV-Vis等技术对其微观结构与形貌进行了表征,并通过降解亚甲基蓝溶液对其光催化性能进行了研究。结果表明,Fe掺杂可以提高CeO₂的光催化性能,以10% Fe-CeO₂催化效率最高,对亚甲基蓝的降解率从纯CeO₂的67%提高到95%。而N的掺杂可调节10% Fe-CeO₂催化性能。以浓氨水为氮源的N-10% Fe-CeO₂（NH₃·H₂O-N-10% Fe-CeO₂）的降解率可进一步提高到97%,并且具有较好的稳定性,经5次循环使用,对亚甲基蓝的光催化降解率仍高达89%。CeO₂催化活性的提高主要由于掺杂Fe和N改变了CeO₂的晶体结构与能带结构,促进了光生电子与空穴的产生与催化反应。     

球磨-溶剂热诱导法合成WS2纳米棒及其摩擦性能

采用行星式高能球磨机，将WS₂与S粉末混合球磨，得到纳米片状结构的前驱体，然后添加分散剂聚乙二醇(PEG)用溶剂热诱导的方法使纳米片状前驱体发生结构转变，制备了棒状结构的WS₂纳米材料。用XRD、SEM、TEM等方法对WS₂纳米棒进行了形貌和结构表征，并对其作为润滑油添加剂的摩擦性能进行了初步的研究。     

溶剂热法制备立方状ITO粉体及其电性能

以乙二醇、乙醇为溶剂通过溶剂热法制备出立方状ITO纳米粉体,研究了反应时间、NaOH浓度对ITO纳米粉体形貌的影响,并讨论了溶剂体积比、NaOH浓度对ITO粉体导电性的影响及机理。结果表明：采用乙二醇与乙醇做溶剂,V_EG：V_EtOH=4：1时,制备出分散性良好的立方状ITO纳米粉体,平均粒径为10.7 nm,且其XRD衍射峰强度比I₄₀₀/I₂₂₂最高为0.380;乙二醇与乙醇做溶剂,V_EG：V_EtOH=4：1,且NaOH浓度为0.275 mol·L^-1时,粉体电导率最高为46.75 mS·cm^-1。     

溶剂热法制备立方状ITO粉体及其电性能

以乙二醇、乙醇为溶剂通过溶剂热法制备出立方状ITO纳米粉体,研究了反应时间、NaOH浓度对ITO纳米粉体形貌的影响,并讨论了溶剂体积比、NaOH浓度对ITO粉体导电性的影响及机理。结果表明:采用乙二醇与乙醇做溶剂,V_(EG)∶V_(EtOH)=4∶1时,制备出分散性良好的立方状ITO纳米粉体,平均粒径为10.7 nm,且其XRD衍射峰强度比I_(400)/I_(222)最高为0.380;乙二醇与乙醇做溶剂,V_(EG)∶V_(EtOH)=4∶1,且NaOH浓度为0.275 mol·L~(-1)时,粉体电导率最高为46.75 mS·cm~(-1)。     

反应溶剂对Bi2S3粉体形貌的影响

利用溶剂热法在不同反应溶剂中制备了不同尺寸的Bi2S3纳米管和纳米棒.利用XRD、SEM、TEM、选区电子衍射(SAED)和高分辨透射电镜(HRTEM)对其结构和形貌进行了表征.结果表明,所制备的产物是结晶良好的正交相Bi2S3,反应溶剂的表面张力、粘度大小和反应溶剂中的比例影响纳米粉体的形貌和尺寸.紫外-可见光吸收光谱测量表明,由于尺寸效应所有粉体的吸收谱相对于正交相的Bi2S3块体都出现蓝移.     

Preparation of nanocrystalline CuAlO<Subscript>2</Subscript> through sol–gel route

Nanocrystalline powders of CuAlO₂ were synthesized through sol–gel method using nitrate-citrate route and also through solid state reaction method. We used a new set of precursor materials for the synthesis of CuAlO₂ through sol–gel route which were not reported in the past. A little lowering of the synthesis temperature (1,000 °C) was observed in case of sol–gel process compared to the solid state reaction method (1,100 °C) and also at shorter time duration. The particle size of the synthesized powders was determined through small angle X-ray scattering. It has been observed that the particle size prepared by nitrate-citrate technique is less than the particle size prepared by the solid-state reaction method. Chemical states of the atomic species were determined by X-ray photoelectron spectroscopy. The formation of phase pure CuAlO₂ were also confirmed by Fourier transformed infrared spectroscopy. A number of solvents were also used for finding the best possible combinations for obtaining phase pure CuAlO₂ at 1,000 °C and it was observed that only the combination of nitrate salts, citric acid and ethanol resulted phase pure CuAlO₂.     

Synthesis of Spherical Titanium Dioxide Particles by Homogeneous Precipitation in Acetone Solution

Titania powders were synthesized by thermal hydrolysis of titanium tetrachloride in a mixed solvent was studied. The dielectric constant was tuned by regulating the acetone/water volume ratio (R/H ratio) and temperature of the solvent. Hydroxypropyl cellulose (HPC) was used as a steric dispersant. The synthesis were carried out at R/H ratios of 0–4, temperatures of 70–90°C, TiCl₄ concentrations of 0.05–0.2 M, HPC concentrations of 0–5 × 10^–3 g/cm³, and synthesis times of 15–60 min. The TiO₂ particles obtained at an R/H ratio of 0, i.e., pure water system, were fine and agglomerated. In contrast, the TiO₂ particles prepared at an R/H ratio of 3 were uniform and spherical. The TiO₂ particle size increased with increasing TiCl₄ concentration. The synthesis temperature did not influence the particle size, but greatly influenced the morphologyof the TiO₂. Adding HPC to the solution yielded more uniform and spherical particles. In addition, the synthesis time should be longer than 30 min to obtain the most uniform and spherical particles. The dielectric constant of the acetone-water mixed solvent at 28 gave the most uniform and spherical TiO₂ particles. The powders prepared at the condition of 0.1 M TiCl₄, R/H ratio of 3, HPC concentration of 0.001 g/cm³, temperature of 70°C, and synthesis time of 1 h exhibited the most uniform and spherical morphology. The as-synthesized powder was anatase and retained the phase below 400°C. It transformed to the rutile phase after calcination at 700°C.     

Low-temperature synthesis of K2NbO3F powders by an alternative approach of solid-state reaction

K₂NbO₃F powders were directly synthesized by an alternative solid-state method at low temperature. Stoichiometric ammonium niobium oxalate, K₂C₂O₄ and KF were mixed with small amounts of water and then dried at room temperature. X-ray diffraction results show that layered perovskite K₂NbO₃F powders can be obtained by calcining the mixture in temperature range from 550 to 700 °C for 3 h. The elemental composition, powder morphology and particle size of calcination products were analyzed by scanning electron microscope-energy dispersive spectroscopy (SEM/EDS). The SEM images suggest that the particles of the powders obtained at 550 °C are irregular platelets with a diameter of 0.5-1 μm and a thickness of 100-200 nm. The platelets are 3-5 μm in diameter and 1-2 μm in thickness when the calcination temperature reaches 700 °C. K₂NbO₃F decomposes to K₅(NbO₃)₄F and KF when the temperature reaches 800 °C.     

Solvothermal synthesis and photoluminescence properties of BiPO4 nano-cocoons and nanorods with different phases

Hexagonal phase BiPO₄ nano-cocoons and monoclinic phase BiPO₄ nanorods have been synthesized in the mixed solvents of glycerol and distilled water with the volume ratio of 2:1 at 200 °C. The solvothermal evolution process from hexagonal phase BiPO₄ nano-cocoons to monoclinic phase BiPO₄ nanorods was observed by varying the reaction time from 1 to 3 h. In the hydrothermal condition at 160 °C, the similar phase transformation from hexagonal phase BiPO₄ to monoclinic phase BiPO₄ was also observed, accompanying with a morphology transformation from nanorods to octahedron-like microcrystals. It was found that the volume ratio of glycerol to water in the solvothermal condition had a great impact on the shapes of products, while it had no influence on the formation of different phases. The fluorescence spectra of hexagonal phase BiPO₄ nano-cocoons and monoclinic phase BiPO₄ nanorods were also studied.     

Mixed solvents: a key in solvothermal synthesis of KTaO3

Perovskite and pyrochlore KTaO₃ were selectively synthesized in mixed solvents (water-ethanol and water-hexane systems) by solvothermal reaction with KOH, whose concentration was one order of magnitude lower than that in traditional methods. The samples were characterized by X-ray diffraction and transmission electron microscopy. Results show that the ratio of inert solvents (ethanol or hexane) to active solvent (water) played a significant role in the manipulation of the crystalline behavior of KTaO₃ to the form pyrochlore or perovskite nanocrystals. The possible mechanisms of the reactions are also discussed.     

Solvothermal Preparation and Effects of Mixed Solvent on the Properties of Copper Indium Diselenide Nanoalloys

We have developed a simple solvothermal method by using solvent mixtures of ethylenediamine with ethanol and deionized water to produce the CuInSe₂ nanoalloys. The phase structure, morphology, elemental composition and optical band gap (E_g) of synthesized the CuInSe₂ nanoalloys were characterized by Raman spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS) and zeta potential particle sizer measurements. The factors affecting product purity in the mixed solvent are also discussed. The results showed that CuInSe₂ nanoalloys with a chalcopyrite tetragonal structure were produced by adjusting the ratio of ethylenediamine to ethanol (1:2.33 by volume) and their corresponding energy band gap was found to be 1.27 eV. In addition, we prepared and coated the CuInSe₂ ink on the Mo substrate by the doctor blade method to produce a compact thin film. The crystallinity and the morphology of these polycrystalline CuInSe₂ films were characterized.     

TiO<Subscript>2</Subscript>-based nanopowders obtained from different Ti-alkoxides

Pure TiO₂ and S-doped TiO₂ sol–gel nanopowders were prepared by controlled hydrolysis-condensation of titanium alkoxides. The influence of different Ti-alkoxides (tetraethyl-, tetraisopropyl- and tetrabutyl-orthotitanate) used in obtaining TiO₂ porous materials in similar conditions (water/alkoxide ratio, solvent/alkoxide ratio, pH and temperature of reaction) has been investigated. The relationship between the synthesis conditions and the properties of titania nanosized powders, such as thermal stability, phase composition, crystallinity, morphology and size of particles, BET surface area and the influence of dopant was investigated. The nature of the alkyl group strongly influences the main characteristics of the obtained oxide powders, fact which is pointed out by thermal analysis, X-ray diffraction, TEM and BET surface area measurements.