无机盐溶胶-凝胶工艺合成ZrO2纳米粉体及其表征

以ZrO(NO3)2·2H2O为原料,采用溶胶-凝胶工艺,在乙醇-水混合体系中合成ZrO2超微颗粒.考察溶液浓度、醇-水比例、反应温度对溶胶-凝胶过程和粉体性能的影响.研究发现,通过适当配置工艺参数,可以获得粒度分布均匀的ZrO2超微粉体.与现有方法相比,该方法原料廉价、工艺简单,有利于材料的规模生产此外该工艺合成的纯组分ZrO2干凝胶表现出特殊的晶化行为,结晶时首先析出四方相,而且600℃热处理粉体的XRD谱线仍然主要显示四方ZrO2的特征.初步分析其原因在于组成ZrO2颗粒的纳米晶粒之间形成硬团聚结构,限制了ZrO2 t→m相变的体积膨胀,从而阻止了t→m相变的发生.     

BaTiO3超细粉体的溶胶-沉淀法制备及其表征

采用溶胶-沉淀工艺制备BaTiO3纳米粉体,探讨了沉淀剂NaOH溶液浓度对制备BaTiO3粉体相组成的影响,提出了溶胶-沉淀法合成纯相BaTiO3的反应机理,并对沉淀水洗后的湿凝胶进行表面改性.探讨了添加表面活性剂及有机溶剂脱水过程对粉体团聚程度的有效控制.     

溶胶-凝胶法制备纳米氧化镁

以六水硝酸镁为前驱体，采用柠檬酸溶胶-凝胶法合成不同粒径（10～100nm）和结晶度的纳米氧化镁粉末。研究了柠檬酸的作用机理，不同的工艺条件（水、无水乙醇、柠檬酸的加入量）对溶胶-凝胶稳定性的影响以及焙烧温度对粉末晶体粒径、结晶度的影响。结果表明：未引入柠檬酸时，凝胶的稳定性较差，氧化镁产物粒径较大且团聚严重。     

溶胶-凝胶自蔓燃合成二氧化钛光催化剂的研究进展

对溶胶-凝胶自蔓燃合成(SAS)的机理、影响因素以及在TiO2制备方面的研究现状进行了综述.认为利用溶胶-凝胶自蔓燃工艺制备高纯纳米TiO2粉具有广阔的应用前景,并可为钛铁矿深加工生产钛白粉提供技术支持.     

薄膜制备技术中溶胶-凝胶工艺研究

综述了溶胶-凝胶工艺在薄膜制备技术中的现状和技术动态、溶胶-凝胶工艺的成膜理论和成膜工艺对薄膜工业发展的促进,并简要提出了溶胶-凝胶薄膜工艺影响薄膜厚度的因素和存在的主要技术问题.     

直接甲醇燃料电池溶胶-凝胶流动相的制备与表征

对直接甲醇燃料电池溶胶-凝胶流动相的制备工艺进行了分析,采用溶胶-凝胶法以正硅酸甲酯为前驱体制备出了溶胶-凝胶流动相.分别以溶胶-凝胶流动相和液体流动相为燃料对比研究了直接甲醇燃料电池的放电性能,测定了溶胶-凝胶流动相在Nation117膜中的甲醇渗透率,研究了溶胶-凝胶流动相的质子电导率.实验结果表明,使用溶胶-凝胶...     

新的Y_2Cu_8复合物合成

<正> 加拿大温莎大学化学系助理教授,王淑宁(译音)发现了一种新的钇-铜复合物,导致一些超导材料更易合成。新的Y_2Cu_8化合物是第一例双金属钇-铜合金材料,以化学工艺制造高温超导材料使科技界发生了很大的兴趣。她从溶胶-凝胶工艺提供了良好的控制条件,可以制出各种组份的化合物,进一步的研究工作是如何深入了解中间的溶胶-凝胶工艺。     

溶胶凝胶法合成玻璃和玻璃陶瓷

玻璃、玻璃陶瓷或陶瓷科学和工艺是近年来发展变化最迅速,在研究和应用方面最有希望得到显著改善的领域之一。在这一领域中,溶胶凝胶工艺享受较高的地位。本文在阐述溶胶凝胶工艺合成玻璃、玻璃陶瓷化学原理的基础上,与传统法比较,对溶胶凝胶工艺的特点进行了讨论;对用溶胶凝胶工艺合成玻璃、玻璃陶瓷在今后值得深入探索的问题进行了着重阐述;最后对溶胶凝胶产品的未来应用作了讨论和展望。     

溶胶-凝胶技木制备新型微晶玻璃

溶胶-凝胶法是一种在低温下即可得到化合物的新方法.简述了溶胶-凝胶法的基本原理,总结了溶胶-凝胶技术的基础研究和工艺过程;着重介绍了溶胶-凝胶技术在制备微晶玻璃等方面的应用现状;并指出了溶胶-凝胶技术的不足及未来发展前景.     

胶凝剂对Sol-Gel法合成PZT95／5粉体的影响

在以无机盐为主要反应前驱物、水为主要溶剂的溶胶一凝胶法制备PzT95/5粉体中,胶凝剂具有重要的作用.研究表明:胶凝剂主要起到调节溶液pH值的作用.可影响溶胶和凝胶的形成,并影响凝胶的微观结构和PZT粉体的性能;当选用氨水为凝胶剂时,控制pH值在3.5～4.0时对溶胶-凝胶的形成有利,且在700℃/2.5h煅烧后能合成单一钙钛矿相PZT95/5粉体,粉体粒度细且均匀.     

过程系统综合集成优化法的研究进展

综述了目前国内外过程系统综合集成优化的主要方法：直观推断法、最优化法、夹点分析法和过程系统火用经济调优法．并分析了各自的优缺点,指出利用各种方法的优点,发展数学规划、人工智能方法、夹点分析和火用经济学集成的方法、开发节源型过程耦合技术、进行过程系统综合和环境保护的协同优化研究,将是过程系统综合集成优化法研究的重要课题。     

A two-step synthesis of NiZn–W hexaferrites

We have investigated the formation of single-phase NiZn–W hexaferrites using two different approaches to the synthesis: a direct synthesis from an initial reagent mixture and a two-step synthesis from intermediates. As calculated, the probability of forming single-phase powders with a direct synthesis was lower than for the two-step synthesis. Powders were synthesized with both approaches via coprecipitation followed by a calcination at 1200–1300 °C. The synthesis was monitored with X-ray powder diffraction, thermogravimetric and thermomagnetic analyses. Single-phase NiZn–W hexaferrite powders were only obtained with the two-step synthesis. The electromagnetic properties of the NiZn–W powders and ceramics were measured.     

SYNTHESIS OF MONODISPERSED IRON OXIDE PARTICLES BY A LARGE-SCALE MICROWAVE REACTOR

Well-defined mondispersed iron oxide particles can be synthesized in conventional hydrolysis approaches, but the synthesis generally takes two to seven days. Microwave hydrothermal approaches offer the possibility of significantly reducing synthesis time. This work demonstrates the feasibility of microwave synthesis in large scale. The batch size was 5 L, and the holding time was two hours. The crystallinity of the powders and the morphology and the monodispersity of the synthesized particles were comparable to those produced from conventional approaches. The particle size was in the nanosize range. The results indicated that for synthesis of monodispersed Fe₂O₃ nanopowders, it is possible to achieve the production rate of a 2.1 m³ conventional reactor with a 5 L microwave accelerated reactor.     

化学-酶法合成普瑞巴林的研究进展

综述了近年来将酶催化拆分与传统的有机合成相结合制备普瑞巴林的研究新进展,重点介绍酶在普瑞巴林手性中间体制备中的应用,并对生物催化应用于普瑞巴林合成的意义及存在的问题进行了分析.     

SYNTHESIS OF MONODISPERSED IRON OXIDE PARTICLES BY A LARGE-SCALE MICROWAVE REACTOR

Well-defined mondispersed iron oxide particles can be synthesized in conventional hydrolysis approaches, but the synthesis generally takes two to seven days. Microwave hydrothermal approaches offer the possibility of significantly reducing synthesis time. This work demonstrates the feasibility of microwave synthesis in large scale. The batch size was 5 L, and the holding time was two hours. The crystallinity of the powders and the morphology and the monodispersity of the synthesized particles were comparable to those produced from conventional approaches. The particle size was in the nanosize range. The results indicated that for synthesis of monodispersed Fe₂O₃ nanopowders, it is possible to achieve the production rate of a 2.1 m³ conventional reactor with a 5 L microwave accelerated reactor.     

Approaches to the Preparation of Enantiomerically Pure (2R,2′R)‐(+)‐threo‐Methylphenidate Hydrochloride

Various approaches to the preparation of enantiomerically pure (2R,2′R)‐(+)‐threo‐methylphenidate hydrochloride ( 1 ) are reviewed. These approaches include synthesis using enantiomerically pure precursors obtained by resolution, classical and enzyme‐based resolution approaches, enantioselective synthesis approaches, and approaches based on enantioselective synthesis of (2S,2′R)‐erythro‐methylphenidate followed by epimerization at the 2‐position. 1 Introduction 2 Methods for the Enhancement of Enantiomeric Purity of 1 3 Approaches Using Enantiomerically Pure Precursors Obtained by Resolution 4 Classical Resolution Approaches 4.1 Resolution of Amide and Acid Derivatives 4.2 Resolution of (±)‐threo‐Methylphenidate 5 Enzyme‐Based Resolution Approaches 6 Enantioselective Synthesis Approaches 7 Approaches Based on Enantioselective Synthesis of (2S,2′R)‐erythro‐Methylphenidate and Epimerization 8 Conclusions     

反应器网络综合优化方法的研究进展

反应器网络综合优化方法在选择反应器类型和反应工艺条件时,比传统的方法表现出了很大的优势。综述了各类反应器网络综合优化方法的基本原理和研究进展,并分析了它们的优缺点。这些方法有基于过程特征的方法,包括可得区法和导数分析法;超结构优化法;目标类方法,包括目标法、构造目标法和构造MINLP法;以及经验推断法和分布参数法等。最后分析了这方面研究的发展趋势。     

纳米CeO2的制备方法研究现状

介绍了固相法、液相法及气相法制备纳米CeO_2材料的工艺过程及原理,分析了纳米CeO_2制备方法的研究现状,并提出了当前纳米CeO_2制备研究中的难点和工业化生产的解决途径。     

Mathematical programming tools for chemical engineering process design synthesis

The objective of this paper is to review different optimization techniques used in chemical process synthesis. The paper first defines the process synthesis problem as a mixed-integer programming problem and then discusses the three approaches which have been used to solve it. In the discrete approach, where the operating conditions of unit operations are fixed, combined heuristic and algorithmic procedures are promising tools. In the continuous approach, the synthesis problem is a nonlinear programming problem, where the design and structural variables are optimized simultaneously. Since efficient large-scale nonlinear programming codes are now available, this approach will be a great success. A recent alternative consists in merging the two previous approaches to implement large-scale mixed-integer nonlinear programming codes. This method will have wide applications in complex chemical process synthesis.     

二氧化碳加氢合成甲醇铜基催化剂研究进展

二氧化碳加氢合成甲醇研究的催化剂体系有多种,包括铜基催化剂、贵金属为主要活性组分的负载型催化剂以及其他类型催化剂。其中,对铜基催化剂的研究较多,其催化性能也较好。目前选用的铜基催化剂以Cu—Zn系催化剂为主,综述了包括CuO—ZnO—Al2O3、CuO—ZnO—ZrO2、CuO—ZnO—SiO2等典型的催化剂。