纳米Ni-Mo复合氧化物催化剂加氢脱氧性能研究

用溶胶-凝胶法制备了非负载Ni-Mo复合氧化物催化剂,用X-射线能谱、N_2吸附-脱附、SEM等手段对催化剂进行了表征。以苯酚和乙酸为探针分子考察了在制备过程中添加硝酸铝和乙醇对催化加氢脱氧性能的影响。由结果可知:溶胶-凝胶法可制备纳米结构的Ni-Mo复合氧化物催化剂,颗粒尺寸达70 nm;溶胶凝胶溶液中不添加硝酸铝可提高催化剂中活性组分Mo和Ni的利用率;溶剂中乙醇的体积分数为50%所制备的催化剂具有较高加氢脱氧活性,在0.3 MPa,270℃,液时空速2 h~(-1)的条件下,催化剂催化苯酚加氢脱氧的脱氧率达到98.4%。     

一种铝溶胶的快速制备方法

在铝溶胶制备时加入表面活性剂A,异丙醇铝(AIP)在85℃时迅速水解,抽滤,得到白色勃姆石沉淀,加入适量硝酸,胶解,即可得贮存期至少6个月的透明铝溶胶,其中水解和胶解过程分别只要0.5 h;讨论了水与醇盐摩尔比、硝酸的浓度和用量对体系pH值和铝溶胶粒径大小的影响。结果表明,水与醇盐摩尔比越高,制得的铝溶胶的粒径越小;加等量硝酸时,酸浓度对铝溶胶的粒径无影响(除了浓硝酸外),且随着硝酸加入量的增加,铝溶胶粒径减小,pH值及粘度逐渐降低,贮存稳定期变长。     

溶胶-凝胶法制备钛酸铝薄膜的工艺研究

采用溶胶-凝胶法,以钛酸四丁酯(Ti(OC4H9)4)和硝酸铝(Al(NO3)3.9H2O)为前驱体,乙醇为溶剂,利用硝酸铝中所含的结晶水进行水解反应,制备了适于镀膜的钛酸铝溶胶。利用旋转粘度计、光学显微镜和SEM研究了水解抑制剂种类及用量、pH值、前驱体浓度、陈化时间等因素对镀膜效果的影响。在此基础上,采用浸渍-提拉法经过三次镀膜在碳化硅基片上成功制备出均匀、致密的钛酸铝薄膜。     

铝、铝硅溶胶及其粉末的合成

以硝酸铝为铝源、硅溶胶为硅源、柠檬酸为稳定剂,采用溶胶凝胶法制备出了稳定的铝溶胶及铝硅溶胶,分析了硝酸铝与柠檬酸的摩尔比(N/C比)、反应温度、保温时间对铝溶胶形成的影响,确定N/C比3:1、100℃及保温1h是铝溶胶较优的工艺参数。XRD分析表明,经1200℃煅烧2h后,铝凝胶粉转变成了α-Al2O3晶相,铝硅凝胶粉末经1200℃煅烧2h后,样品主要为正交莫来石结构,SEM显示所得粉末为无规则形态。     

利用溶胶-凝胶法制备钛酸铝微粉

本以钛酸丁酯和硝酸铝为原料．无水乙醇为溶剂．冰醋酸为螯合剂．利用溶胶-凝胶法制备钛酸铝微粉：采用差热分析(DTA)．X-射线衍射分析(XRD)，扫描电子显微镜(SEM)考察了溶液的pH值、煅烧温度、分散剂等T艺参数对钛酸铝微粉的合成率和微粒粒径的影响。通过调节[Al^3 ]：[Ti^4 ]、(C4H9O)；Ti：CH3COOH、CH3CH2OH：(C4H9O)4Ti的比例和溶液pH值，可得到透明稳定的溶胶．煅烧后获得合成率高并且粒径为0.3～0.4μm的钛酸铝微粉。     

Sol-Gel法制备莫来石粉末的研究

本文研究了以正硅酸乙酯（TEOS）和硝酸铝为原料，用溶胶-凝胶法制备莫来石粉末的过程。探讨了温度和pH值对Al2O3-SiO2凝胶时间的影响；用IR和XRD研究了凝胶在热处理过程中的晶相变化。研究结果表明：温度升高，凝胶时间缩短；pH=3时，溶胶的聚集速度减慢，胶凝时间较长；莫来石相是经铝硅尖晶石转化而成．铝硅尖晶石在1000℃开始转化为莫来石，至1250℃全部转化；制备的莫来石粉末晶粒尺寸为100-200nm。     

酸碱条件下莫来石形成机理研究

以正硅酸乙酯(C8H20O4Si),硝酸铝(Al(NO3)3·9H2O)为主要原料,氨水调节pH值,通过溶胶凝胶法制备出酸碱条件下纯相莫来石粉体.通过热分析得知粉体在升温过程中吸热、放热和晶相转换过程;通过XRD研究了凝胶在热处理过程中的结晶变化;通过红外吸收光谱测定了粉体中Si-O-Al键的存在和变化;通过环境扫描电子显微镜测定研究了莫来石粉末的表面特性.最终得出凝胶转变至莫来石的相变过程:酸碱条件下莫来石的生成过程都经历了由无定形铝和无定形硅转变为硅铝尖晶石再到莫来石的过程;在碱性条件下,莫来石开始转变温度低于酸性;同时生成的莫来石中,碱性条件比酸性条件粒度小.     

溶胶-凝胶法ZrO_2/聚苯酯复合材料的性能研究

纳米二氧化锆有着广泛而重要的应用。基于新的方法和发展使得国内外二氧化锆各种各样的制备方法和新的应用随处可见。笔者采用ZrOCl_2·8H_2O,使用溶胶-凝胶法制备了锆溶胶。通过溶胶-凝胶法,在室温条件下,缓慢将氨水与氧氯化锆溶液滴加至缓冲溶液中,制得前驱体沉淀,经抽滤洗涤后用硝酸重新分散滤饼,于75℃水浴加热5~12h,制得澄清透明状纳米级锆质溶胶。系统分析了不同浓度的前躯体溶液、pH值以及缓冲溶液等因素对制备的锆溶胶粒径、稳定性的影响。结果表明,溶胶中粒子呈伞状、柱状,且分散均匀。溶胶粒子大小为12~15nm。在pH值为0.8~1.4条件下,溶胶能长期稳定存在。再和聚苯酯反应,发现聚苯酯的耐热性明显提高。     

溶胶-凝胶法制备ZrO_2/聚苯酯复合材料的性能研究

纳米尺寸的二氧化锆有着广泛而重要的应用。基于新的方法和发展使得国内外二氧化锆各种各样的制备方法和最近的应用随处可见。本文采用ZrOCl_2·8H_2O,使用溶胶-凝胶法制备锆溶胶。通过溶胶-凝胶法,在室温条件下,缓慢将氨水与氧氯化锆溶液滴加至缓冲溶液中,制得前驱体沉淀,经抽滤洗涤后用硝酸重新分散滤饼,于75益水浴加热5~12 h,制得澄清透明状纳米级锆质溶胶。系统分析了不同浓度的前躯体溶液、pH值以及缓冲溶液等因素对制备的锆溶胶粒径、稳定性的影响。结果表明,溶胶中粒子呈伞状、柱状,且分散均匀。溶胶粒子大小为12~15 nm。在pH值为0.8~1.4条件下,溶胶能长期稳定存在。再和聚苯酯反应,发现聚苯酯的耐热性明显提高。     

溶胶-凝胶法制备Li-β-Al203纳米粉体

以硝酸锂、硝酸铝和碳酸氢铵为原料,采用溶胶-凝胶法制备了Li-β-Al2O3纳米粉体.研究了pH值、热处理温度和锂铝物质的量比[n(Li)/n(Al)]对制备Li-β-Al2O3纳米粉体的影响.用X射线衍射仪(XRD)、场发射扫描电镜(FE-SEM)和自动电位粒度仪对制备的粉体进行了表征.结果表明,当n(Li)/n(Al) =1∶ 5(为化学计量比时),pH值在3.6左右时,可得到稳定透明的凝胶,经1000℃热处理后,产物为纯相的Li-β-Al2O3,FE-SEM结果表明粉体的粒度在100nm以内.     

Effect of peptiser species on crystallisation of alumina gel produced by sol–gel process

The present work reports a study on the effect that a peptiser species has on the crystallisation of alumina gel produced by a sol–gel process to help develop a method for producing α-Al₂O₃ at low temperature. The white precipitate of aluminium hydroxide, which was prepared with a homogeneous precipitation method using aluminium nitrate and urea in an aqueous solution, was peptised using various peptisers at room temperature to form a transparent alumina sol. The alumina gel obtained from the alumina sol, which was produced using formic acid as the peptiser, was most dominantly crystallised into α-Al₂O₃ by annealing at 900°C. The optimal [peptiser]/[Al³⁺] (P/A) molar ratio for the crystallisation into α-Al₂O₃ was 0.2. The alumina gel began to crystallise into α-Al₂O₃ with annealing at as low as 500°C when formic acid and a P/A ratio of 0.2 were used.     

Dispersion of Alumina and Silicon Carbide Powders in Alumina Sol

Dispersion of Al₂O₃ and SiC particles in an alumina sol has been investigated through determination of particle-size distribution, zeta potential, and agglomerate morphology. The particle size of Al₂O₃ and SiC (as determined by the particle-size analyzer) is strongly affected by the presence of alumina sol in the solution. The average agglomerate size is decreased by at least 50%. The zeta potential of Al₂O₃ in 1 M alumina sol increases slightly, whereas that of SiC reverses its sign over a wide range of pH values. It is proposed that these effects are caused by AlO₄Al₁₂(OH)₂₄(H₂O)⁷⁺₁₂ sol clusters (1-2 nm in size) that are absorbed on the surface of the large (1-5 µm) ceramic particles. The electrostatic and steric effects of the cluster absorption help to control the dispersion and stabilize the suspension of ceramic particles in the alumina sol during wet processing. It is expected that the alumina-sol clusters can be used as an efficient, clean dispersant for single-phase and composite ceramic powders.     

Dependence of zinc aluminate microscopic structure on its synthesis

Alumina doped with zinc oxide was synthesized by sol–gel method in alcohol solution. Hybrid oxides of aluminum and zinc were prepared from various aluminum precursors (aluminum sec-butoxide, aluminum nitrate, and aluminum isopropoxide) and zinc acetate solution with ethylacetoacetate and nitric acid as a chelating agent and catalyst, respectively. Types and molar ratio of the precursor to the chelating agent and acidic catalyst were found to remarkably affect the formation of transparent sol of aluminium–zinc sol composite. With relatively low temperature of 50 °C, the suitable molar ratio of aluminum sec-butoxide to ethylacetoacetate to nitric acid for preparing the homogeneous sol was 1:0.40:0.86. Furthermore, the calcination at elevated temperature higher than 400 °C would be essential for preparing ZnAl₂O₄ with the face centered cubic microstructure. The primary crystalline size of the synthesized zinc aluminate nanostructure was approximately 20 nm with lattice spacing of 0.55 nm.     

硅溶胶、铝溶胶在陶瓷原位胶态成形中的应用

陶瓷原位胶态成形方法是制备近净尺寸复杂陶瓷部件最具应用前景的方法，硅溶胶、铝溶胶也越来越多的应用于其中。本文主要介绍了硅、铝溶胶的分散胶凝原理以及在胶态成形中的应用。     

基于响应面法的硅溶胶注浆材料配比优化研究

硅溶胶注浆材料具有可注性好、凝胶时间可控、环保无毒、耐久性高等优点,但常规的硅溶胶固砂体抗压强度偏低,其推广应用受到了一定限制。本文通过单因素实验分别研究了胶凝剂种类、胶凝剂浓度、硅溶胶与胶凝剂质量比、注浆材料pH值对硅溶胶固砂体抗压强度的影响,同时通过响应面法研究了胶凝剂浓度、硅溶胶与胶凝剂质量比、注浆材料pH值交互作用对抗压强度的影响。试验结果表明:单因素对抗压强度影响的显著程度依次为胶凝剂浓度、注浆材料pH值、硅溶胶与胶凝剂质量比;双因素交互作用对抗压强度影响的显著程度依次为胶凝剂浓度和注浆材料pH值、胶凝剂浓度和硅溶胶与胶凝剂质量比、硅溶胶与胶凝剂质量比和注浆材料pH值。采用响应面法获得的硅溶胶固砂体抗压强度最优配比为胶凝剂质量浓度为7%,硅溶胶与胶凝剂质量比为7 ∶1,注浆材料pH值为7。响应面法的预测值和实测值误差较小,表明响应面法可用于硅溶胶注浆材料的配比优化。     

添加剂对酸性硅溶胶及料浆胶凝与流变行为的影响

以酸性硅溶胶及其结合料浆为研究对象,通过对比胶凝时间、黏度、触变环面积、剪切应力等流变参数,研究了聚丙烯酰胺、氢氧化镁、柠檬酸三铵等对酸性硅溶胶及结合料浆流变行为、凝聚过程的作用规律。结果表明:氢氧化镁电离出Mg²⁺促进了酸性硅溶胶的缩合反应,对酸性硅溶胶胶凝过程的影响较为显著;氢氧化镁添加量的增加,增大了胶凝速度,酸性硅溶胶的稳定性下降。聚丙烯酰胺作为阴离子表面活性剂,通过空间位阻效应,缔合溶胶中的氢键,在溶胶中形成三维网络结构,同时聚丙烯酰胺水解吸附在溶胶胶团颗粒表面,加快了SiO₂粒子的絮凝,提高了酸性硅溶胶及其结合料浆的黏度。控制柠檬酸三铵的含量低于10 mg/mL,有助于降低硅溶胶结合料浆的黏度,提高体系的稳定性。     

Packaging of Sol–Gel-Made Porous Nanostructured Titania Particles by Spray Drying

Porous titania granules (1–20 μm) were made by spray drying titania solutions with and without peptization. An unpeptized titania slurry was prepared by hydrolyzing titanium tetraisopropoxide, while a peptized sol was prepared by adding nitric acid to the slurry. The characteristics of the granules depended on the feed solution properties. In particular, granules from the unpeptized slurry showed a bimodal pore size distribution (PSD), with a rough surface attributed to hard aggregates; granules from the peptized sol showed a monomodal PSD, with a smooth surface of well-packed nanoparticles. The effect of dopants (alumina and zirconia) also was investigated. Doping slowed the crystallite growth of the titania granules, as well as the anatase-to-rutile phase transformation. All of the peptized granules exhibited a monomodal PSD of intraparticle pores, from 2 to 15 nm. However, the PSD of the pure titania granules collapsed at 600°C, mainly by phase transformation.     

Regenerated cellulose aerogel: Morphology control and the application as the template for functional cellulose nanoparticles

This article focuses on controlling the morphology of regenerated cellulose aerogel (RCA) and its application as a template for the preparation of functional cellulose nanoparticles (FCNPs). RCA is prepared by lyophilizing cellulose hydrogel which is fabricated through a sol–gel method in sodium hydroxide (NaOH)/urea aqueous solution. The morphology of RCA is adjusted by varying the gelation temperature and time. With the gelation temperature and time increasing, lamellar RCA transforms into strings of cellulose nanoparticles. Subsequently, RCA with the morphology of "strings of nanoparticles" is modified through the bulk condensation of l -lactic acid and RCA. Eventually, the prepared functionalized RCA (FRCA) is dispersed in an organic solvent to obtain purified FCNPs. The results demonstrate that single FCNP can be obtained by dispersing FRCA in dimethyl sulfoxide. Moreover, the prepared FCNPs have uniform size, good thermal-stability, and increasing hydrophobicity, which are ideal candidates for polymer composites in terms of fillers.     

Temperature induced gelation of non–aqueous alumina suspension using oleic acid as dispersant

A novel temperature induced gelation method for alumina suspension using oleic acid as dispersant is reported. Non–aqueous suspension with high solid loading and low viscosity is prepared using normal octane as solvent. Influence of oleic acid on the dispersion of suspension was investigated. There was a well disperse alumina suspension with 1.3 wt% oleic acid. Influence of gelation temperature on the coagulation process and properties of green body was investigated. The sufficiently high viscosity to coagulate the suspension was achieved at −20 °C. The gelation temperature was controlled between the melting point of dispersant and solvent. The gelation mechanism is proposed that alumina suspension is destabilized by dispersant separating out from the solvent and removing from the alumina particles surface. The alumina green body with wet compressive strength of 1.07 MPa can be demolded without deformation by treating 53 vol% alumina suspension at −20 °C for 12 h. After being sintered at 1550 °C for 3 h, dense alumina ceramics with relative density of 98.62% and flexural strength of 371±25 MPa have been obtained by this method.