介孔分子筛材料的发展及其研究进展

介绍了介孔分子筛的类型、特性及发展,包括硅基和非硅基介孔分子筛,各种含过渡金属原子和负载有金属及其络合物的介孔分子筛。论述了合成介孔分子筛所用的各类模板剂,如阳离子,阴离子,非离子,双子表面活性剂和混合模板剂以及对合成的介孔分子筛的结构的影响。综述了介孔分子筛的合成方法及研究进展,包括水热合成法、微波和超声合成方法,以及在非水介质中合成介孔分子筛的方法。     

新型催化材料——介孔氧化铝分子筛的合成、表征以及应用前景

与传统的γ-Al2O3相比,介孔氧化铝分子筛具有较大的比表面积和较窄的孔径分布,作为工业催化剂或催化剂载体,具有更为广阔的应用前景.本文重点介绍了介孔氧化铝分子筛的不同合成方法、结构表征方法和催化性能,分析了模板剂类型、凝胶pH值、洗涤方法、焙烧方式等制备条件对其结构的影响.并对其催化应用进行了评述和展望.     

水蒸气诱导自组装制备介-微孔ZSM-5分子筛的研究

软模板剂方法可以合成介-微孔分子筛,但有些模板剂与硅铝酸盐之间弱的化学结合力导致晶化过程模板剂与合成体系的相分离,结果形成了无定型的介孔材料和微孔分子筛的混合物。采用新的技术路线:通过使用四丙基氢氧化铵(TPAOH)作模板剂,以三嵌段共聚物P123原位植入介孔结构,采用水蒸气诱导干凝胶自组装晶化的方法制备介-微孔ZSM-5分子筛。优点是:大大减少了模板剂的使用量,省去了产品与母液分离的繁琐步骤,无大量废液产生,对环境友好。采用X射线衍射 (XRD)、傅立叶变换红外光谱(FT-IR)、N₂吸附-脱附比表面分析(BET)、扫描电镜(SEM)、高倍透射电镜(TEM)系列表征方法对介-微孔ZSM-5分子筛进行表征,可知样品具有典型的ZSM-5分子筛的骨架结构和明显地介孔孔道。在800 ℃,100%水蒸气条件下经15 h水热老化后,分子筛的比表面积保留率73.44%,孔容保留率74.35%,表明分子筛的水热稳定性良好。     

有序介孔材料的合成及应用

自从1992年Mobil公司的研究人员选用烷基季铵盐阳离子表面活性剂作为模板剂,首次合成了介孔氧化硅分子筛M41S系列以来,中孔SiO2纳米粒子(MSNs)始终吸引研究人员,因为介孔材料具有大比表面积、高孔道规整度和孔径分布范围集中等优点,而且具有优良的结构可设计性。结合国内外研究成果,主要介绍了介孔SiO2材料的不同合成方法,如溶胶-凝胶法、微波辅助技术、化学蚀刻技术和模板法等,并简单介绍了其应用,对其未来的发展前景进行了展望。     

哈密钾长石合成介孔分子筛及其结构表征

以新疆哈密钾长石为硅源前躯体,十六烷基三甲基溴化铵为模板剂分别通过高温煅烧与水热法合成了介孔分子筛。采用XRD,SEM,FT-IR,Raman,BET等测试方法表征了两种方法合成的介孔分子筛的微观结构和吸附性能。上述研究结果表明:水热合成法比高温煅烧法合成的介孔分子筛具有较好的微观结构与性能。当其晶化时间为96h,pH为10.5时,合成的介孔分子筛的吸附性能最好。     

ZSM-5分子筛介孔的构筑

在微孔结构的ZSM-5沸石分子筛中构筑介孔,可以有效地解决ZSM-5分子筛在催化反应过程中的扩散传质和催化剂失活问题.重点阐述了在初始的合成体系中加入炭黑、介孔碳、表面活性剂等作为模板剂来构筑含介孔结构的ZSM-5和利用碱液或酸液对已合成的微孔的ZSM-5进行后处理来构筑介孔,并对含有介孔结构的ZSM-5的性质和相关的应用做了评价和展望.     

新型两亲性嵌段共聚物导向合成有序大孔径介孔材料的研究进展

自从1992年首次报道介孔氧化硅分子筛M41S系列以来, 人们采用各种商业化表面活性剂为模板, 合成了多种骨架组成、丰富的有序介观结构、不同孔径尺寸的介孔材料, 并将其应用在能源、环境、催化等诸多领域。然而, 由于常规商业化模板剂的分子量大小有限, 合成的介孔材料具有较小的孔径(< 8.0 nm), 从而极大地限制了其面对大尺寸客体分子的相关应用。此外, 利用常规模板剂难以合成出具有晶化墙壁的介孔金属氧化物材料。近年来, 大分子量两亲性嵌段共聚物相继被报道用来合成新型介孔材料, 本文将综述基于这种嵌段共聚物为模板剂合成各种具有大孔径和晶化墙壁介孔材料的研究进展。     

含稳定骨架铁的Fe-MCM-41介孔分子筛的合成与表征

以离子液体1-十六烷基-3-甲基溴代咪唑([C₁₆mim]⁺Br^-)为模板剂合成了含铁介孔分子筛Fe-MCM-41,并对其结构和形态进行了表征. 研究结果表明, 用该方法合成的Fe-MCM-41不仅具有比较大的比表面积, 规则的介孔孔道结构等特征, 而且形成了双孔道结构. UV-Vis和EPR 顺磁共振的表征结果表明, 采用离子液体[C₁₆mim]⁺Br^-为模板剂所合成的Fe-MCM-41介孔分子筛, 铁物种能稳定地存在于介孔分子筛骨架中.     

微波加热在有序介孔材料研究中的进展

利用微波进行化学合成是近年发展起来的一种简单、快捷、高效的合成方法.综述了微波在有序介孔材料合成、模板剂脱除和在介孔材料负载活性组分中的应用,介绍了一些典型的有序介孔材料的微波合成新进展,指出了该方法在有序介孔材料合成中的优势及发展前景.     

聚乙二醇模板剂制备介孔材料的研究进展

聚乙二醇作为模板剂被广泛用于介孔材料的制备。介绍了使用单一聚乙二醇模板剂合成硅基、非硅基、复合类介孔材料的研究工作,探讨了聚乙二醇与表面活性剂、非表面活性剂类物质作复合模板剂制备介孔材料的方法。综述了聚乙二醇单一模板剂及复合模板剂制备介孔材料的机理。     

Theory and synthesis of advanced thermal-protective composite materials

We present the results of synthesis of an advanced performance thermal protective material based on silicon-organic materials. This material compares favourably with the existing traditional thermal-protective materials based on phenolic resins. The characteristics of the material developed closely resemble the characteristics of thermal-protective glass-plastics in airodynamic gas flow, although its density is more than three times lower. Covering technology for the material developed makes use of the method of pneumatic spraying, which is essentially simpler and more inexpensive than the manufacturing technology for glass-plastics. The mathematical design method developed especially for this material is presented.     

Mg2Si基热电材料研究现状及进展

介绍了热电材料的基本原理与应用情况,总结了现阶段提高Mg2Si基热电材料热电性能的途径：包括对Mg2Si材料进行多种元素的掺杂;制备低维数材料、纳米材料与超晶格结构材料。评述了Mg2Si基热电材料在掺杂改性和制备方面的研究进展。分别阐述了掺杂Ge、Sn、Pb、Te、Sb、Bi、Ag等几种元素对Mg2Si热电性能的影响。对溶体生长法、固相烧结法、机械合金化、放电等离子烧结法与电场激活压力辅助合成法的优缺点进行了评价,通过对比最后指出了场激活压力辅助合成法是新的合成Mg2Si节能和高效的新的制备方法。     

磁性离子液体的制备与应用研究进展

磁性离子液体是一种新型的功能化离子液体材料,具有优良的热稳定性、优异的电化学性能、良好的溶解性能以及可回收性等特性,使其在萃取分离、反应催化和复合材料等领域具有较好的应用前景。对目前合成的磁性离子液体做了概述并根据构效关系对主要的磁性离子液体进行了分类。综述了磁性离子液体的主要制备方法,主要有一步合成法、二步合成法和辅助合成法。介绍了磁性离子液体在萃取分离、反应催化及碳纳米管复合材料领域应用研究进展。最后根据磁性离子液体在合成和应用中的不足做了展望。     

Application of Ni:SiO2 nanocomposite to control the carbon deposition on the carbon dioxide reforming of methane

Stable Ni nanoparticles embedded in a mesoporous silica material were used as catalysts for the conversion of methane into synthesis gas. This catalyst has the singular properties of controlling the carbon deposition and deactivation of active sites. A comparative study of our nanocomposites with conventional catalysts showed that impregnation material presented a preferential encapsulation and growth of carbon nanotubes on the metal surface. The impregnated catalyst showed a higher tendency for carbon nanotube and whiskers formation.     

Mechanochemical synthesis of titanium carbide using carbons of various origins

The data presented in this paper show that the limiting factors in the mechanochemical synthesis of titanium carbide from mixtures of titanium and a carbon-containing raw material are the structure of the carbon and the degree of aromaticity of the starting material. Our results demonstrate the possibility of producing mechanochemical titanium carbide using mixtures of carbon black and graphite.     

Lead-Free,Luminescent Perovskite Nanocrystals Obtained through Ambient Condition Synthesis

Heterovalently substituting toxic lead is an increasingly popular design strategy to obtain environmentally sustainable variants of the exciting material class of halide perovskites. Perovskite nanocrystals (NCs) obtained through solution-based methods exhibit exceedingly high optical quality. Unfortunately, most of these synthesis routes still require reaction under inert gas and at very high temperatures. Herein a novel synthesis routine for lead-free double perovskite (LFDP) NCs is presented. An approach based upon the hot injection and ligand-assisted reprecipitation (LARP) methods to achieve a low-temperature and ambient atmosphere-based synthesis for manganese-doped Cs₂NaBiCl₆ NCs is presented. Mn incorporation is critical for the otherwise non-emissive material, with a 9:1 Bi:Mn precursor ratio maximizing the bright orange photoluminescence (PL) and quantum yield (QY). Higher synthesis temperatures slightly increase the material's performance, yet NCs synthesized at room temperature are still emissive, highlighting the versatility of the synthetic approach. While the material's indirect bandgap limits its appeal for optoelectronics, this feature could benefit photocatalysis due to longer carrier lifetimes. Moreover, the developed synthesis is facile and can rapidly be adapted to other more viable material compositions and up-scaled to realize applications directly.     

Low-temperature synthesis of zeolite from perlite waste — Part I: review of methods and phase compositions of resulting products

In this paper a review of the recent studies on the synthesis of zeolites from expanded perlite under hydrothermal conditions is presented. Attention is paid to possible outcomes of synthesis from low cost glass material, such as perlite. The study also investigates the phase composition of zeolitic materials obtained by modification of by-product derived from an expanded perlite production process. The synthesis was made using the hydrothermal method with sodium hydroxide under autogenous pressure at a temperature below 100 °C for 1 to 72 h. It was possible to obtain a zeolitic material at a temperature as low as 60 °C using 4.0 M NaOH. The X-ray diffraction pattern showed the biggest peak intensity of zeolite X with 4.0 M NaOH at the temperature of 70 °C. During synthesis at higher temperature zeolite Na-P₁ (with 3.0 M NaOH at 90 °C) and hydroxysodalite (with 5.0 M NaOH at 90 °C) were obtained.     

锂离子电池磷酸铁锂正极材料的制备及改性研究进展

橄榄石型磷酸铁锂(LiFePO4)由于安全性能好、循环寿命长、原材料来源广泛、无环境污染等优点被公认为是最具发展潜力的锂离子动力与储能电池正极材料。综述了近年来磷酸铁锂正极材料在制备和改性方面的最新进展。在此基础上,提出了磷酸铁锂正极材料未来的主要研究和发展方向。     

Review of the anatase to rutile phase transformation

Titanium dioxide, TiO₂, is an important photocatalytic material that exists as two main polymorphs, anatase and rutile. The presence of either or both of these phases impacts on the photocatalytic performance of the material. The present work reviews the anatase to rutile phase transformation. The synthesis and properties of anatase and rutile are examined, followed by a discussion of the thermodynamics of the phase transformation and the factors affecting its observation. A comprehensive analysis of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this review, yielding a plot of the cationic radius versus the valence characterised by a distinct boundary between inhibitors and promoters of the phase transformation. Further, the likely effects of dopant elements, including those for which experimental data are unavailable, on the phase transformation are deduced and presented on the basis of this analysis.     

Dendritic Silica Particles with Center‐Radial Pore Channels: Promising Platforms for Catalysis and Biomedical Applications

Dendritic silica micro‐/nanoparticles with center‐radial pore structures, a kind of newly created porous material, have attracted considerable attention owing to their unique open three‐dimensional dendritic superstructures with large pore channels and highly accessible internal surface areas compared with conventional mesoporous silica nanoparticles (MSNs). They are very promising platforms for a variety of applications in catalysis and nanomedicine. In this review, their unique structural characteristics and properties are first analyzed, then novel and interesting synthesis methods associated with the possible formation mechanisms are summarized to provide material scientists some inspiration for the preparation of this kind of dendritic particles. Subsequently, a few examples of interesting applications are presented, mainly in catalysis, biomedicine, and other important fields such as for sacrificial templates and functional coatings. The review is concluded with an outlook on the prospects and challenges in terms of their controlled synthesis and potential applications.