海藻酸钠基炭气凝胶的研究进展

海藻酸钠基炭气凝胶是以天然海洋生物质资源海藻酸钠为原料,通过凝胶、干燥和高温炭化制得,其生产原料来源广泛、制备工艺简单,并且十分符合绿色环保的理念,因此受到了国内外科研工作者的广泛关注。本文介绍了海藻酸钠基炭气凝胶的制备工艺,总结了其在超级电容器、锂离子电池、电催化和吸附领域的研究进展,并对该材料的进一步研究进行了展望。     

硼酸催化炭气凝胶的制备

以苯酚、间甲酚和糠醛为原料,正丙醇作为溶剂,硼酸作为催化剂,通过溶胶-凝胶反应、超临界正己烷干燥以及高温炭化得到了炭气凝胶,并利用扫描电镜、N2吸附、傅立叶变换红外光谱和热重分析等表征手段对所制备的有机气凝胶及其炭气凝胶进行了表征,考察总反应物浓度对有机气凝胶及其炭气凝胶结构的影响.实验结果表明:所制备的炭气凝胶主要是...     

炭气凝胶复合材料及其衍生物的研究现状及应用进展

炭气凝胶复合材料是一种新型多孔炭材料,它不仅具有气凝胶材料的多孔、轻质、高比表面积和低密度等特性,同时具有炭材料的耐热、导电和耐腐蚀等优点,是近年材料研究领域中的热点。同时,以炭气凝胶材料为基体的衍生物及其复合材料赋予了炭气凝胶新的功能与用途。概述了炭气凝胶复合材料及其衍生物在应用方面的研究进展,综合分析了炭气凝胶复合材料的研究现状,并对未来发展方向与前景进行了展望。     

多元酸催化炭气凝胶的常压制备及表征

在多元有机酸催化和表面活性剂的作用下,间苯二酚和甲醛反应生成有机凝胶,经过常压干燥、高温炭化得到炭气凝胶。用扫描电镜(SEM)、X射线衍射(XRD)和亚甲基蓝吸附测试表征所制备的样品。结果表明,所制备的炭气凝胶属于非晶态物质,呈现均匀的球状结构,且微球内富含连通的电荷转移的孔道,其比表面积达到740m2/g。循环伏安扫描测试表明,所制备的炭气凝胶具有良好的电化学性能,有望成为超级电容器的电极材料。     

新型炭气凝胶的制备及电化学性能研究

以间苯三酚、间苯二酚和甲醛为原料,碳酸钠为催化剂,经溶胶-凝胶、溶剂置换、常压干燥制得有机气凝胶,然后高温炭化得到炭气凝胶。采用正交实验法考察了间苯三酚与间苯二酚的摩尔比、催化剂用量、原料质量分数和反应温度对炭气凝胶结构的影响。采用低温液氮吸附法、XRD等手段对炭气凝胶的微观结构进行表征和分析,采用循环伏安、恒流充放电等检测技术评价了其电化学性能。结果表明,炭气凝胶最佳合成条件为间苯三酚与间苯二酚摩尔比1∶4,催化剂用量800(n(P+R)/nC=800),原料质量分数35%。在最佳条件下,炭气凝胶平均比表面积为609.11 m~2/g,平均孔径为5.42 nm;XRD分析表明:炭气凝胶主要以非晶炭形式存在;在6 mol/L KOH溶液中,炭气凝胶的比电容为229.17 F/g,并且具有良好的电容特性和可逆性。     

溶胶-凝胶法制备金属-炭凝胶材料的研究进展

溶胶-凝胶法制备炭材料是近年来材料研究中的热点之一。该方法通过在成胶过程中直接加入金属前驱体的缩聚-干燥-炭化过程来制备炭凝胶及金属-炭凝胶。本文评述了金属-炭材料制备、应用的研究进展,阐述了炭凝胶及金属-炭凝胶的合成机理,介绍了多种金属-炭凝胶的制备和应用情况,并对其未来的发展方向进行了展望。     

合成条件对常压干燥炭气凝胶电导率的影响

以间苯二酚/甲醛为反应物,采用常压干燥工艺制备了高电导率的炭气凝胶,并用XRD和四探针电导率测试仪对其进行了表征。结果表明：炭气凝胶具有典型的非晶态结构,且其结构中存在特殊的半石墨相微晶;凝胶陈化时间、催化剂种类和溶胶pH值对炭气凝胶电导率影响不大;炭气凝胶的电导率随催化剂摩尔比、溶质固含量、炭化终温和升温速率的增大而升高。以Na2CO3为催化剂,催化剂摩尔比为500、溶质固含量为60%,5℃/min升温至1050℃炭化制备的炭气凝胶电导率高达98.0S/cm。     

超临界流体干燥法制备炭气凝胶

以间苯二酚和甲醛为原料, Ca(OH)2为催化剂,经溶胶—凝胶过程得水凝胶 ;以超临界 CO2干燥水凝胶,得到网络间充满气体的固态材料气凝胶,再经高温热解得炭气凝胶。 TEM表征结果显示：气凝胶和炭气凝胶均具有规则的纳米网络结构,网络节点粒径约 10 nm,典型网络孔径小于 50 nm。     

常压干燥法制备炭气凝胶微球的储电性能研究

采用间苯二酚和甲醛为原料,通过乳液-悬浮聚合经常压干燥和炭化,成功制备了炭气凝胶微球,并以所制备的炭气凝胶微球为超级电容器的电极,采用循环伏安法与恒流充放电法测定了该超级电容器的电化学性能。结果表明,常压干燥法所制炭气凝胶微球作电极的超级电容器的比电容最高可达197 F/g,循环伏安曲线有氧化还原反应峰存在。炭气凝胶微球的微孔表面积和中孔孔径对超级电容器的比电容影响最大。     

添加剂PVB对炭气凝胶制备工艺及结构的影响

采用溶胶—凝胶法,以间苯二酚(R)、甲醛(F)为原料、无水碳酸钠(C)作催化剂、聚乙烯醇缩丁醛(PVB)为添加剂、无水乙醇作溶剂,通过常温常压干燥和高温炭化制备炭气凝胶。考察了中间产物有机凝胶的热解行为和催化剂浓度及PVB用量对炭气凝胶孔隙结构的影响。结果表明:PVB的加入不仅加强了有机凝胶的网络结构,使其更利于常温常压干燥,而且能够较好地调控炭气凝胶的孔径分布;在一定的PVB加入量范围内,随着PVB加入量的增加,炭气凝胶的比表面积增加,孔径分布也更加集中;催化剂浓度对炭气凝胶的比表面积及孔径分布有较大的影响,当R/C=300,PVB/R=1/10时比表面积达到最大值(386m~2/g)。     

植物纤维素基碳气凝胶的制备及应用研究进展

植物纤维素基碳气凝胶具有低密度、可生物降解、优异的吸附性能和电化学性能稳定等特点。本文围绕其原料来源、制备工艺及其在环境治理和能量储存与转化方面的应用,分析了植物纤维素基碳气凝胶的性能及研究进展。详细叙述了以棉花、木材、竹纤维等为原料的植物纤维素基碳气凝胶的制备方法,如：溶胶-凝胶法、水热炭化法、直接炭化法等。分析了制备过程中干燥方法、溶剂的选择及置换、复合改性等影响因素,并介绍了碳气凝胶在空气净化、油水分离、有毒化合物、重金属离子的去除等环境治理及能量转化与储存方面的。     

生物质基碳气凝胶的研究进展

碳气凝胶是一种新型的纳米多孔碳材料,具有孔隙率高、比表面积大、导电性能优良、耐高温等优点,在催化剂载体、电容器及吸附材料等领域具有广阔的应用前景。与传统的碳气凝胶相比,生物质基碳气凝胶具有前驱体环保可再生的优势,可为生物质高值化、功能化利用提供新思路。本文在简单介绍生物质基碳气凝胶制备过程（包括溶胶-凝胶化、干燥、炭化）的基础上,重点介绍了3类来自不同生物质前驱体（植物纤维素、细菌纤维素和具有三维多孔结构的植物本身）碳气凝胶的制备方法,并对碳气凝胶及其复合材料在催化剂载体、吸附材料、超级电容器、锂离子电池方面的应用进行了综述,最后对生物质基碳气凝胶的研究方向和发展前景进行总结和展望。     

Preparation of carbon aerogel by ambient pressure drying and its application in lithium/sulfur battery

Formaldehyde, resorcinol, and sodium acetate were used to synthesize the carbon aerogels by ambient pressure drying. The effect of the ratio of resorcinol and sodium acetate for carbon aerogels was researched by scanning electron microscope and Brunauer-Emmett-Teller characterizations. Then the carbon aerogels were applied in synthesizing sulfur/carbon aerogel composites through a melting method, the specific capacity and cycle performance of lithium/sulfur batteries that adopted the prepared composites as cathodes were measured by galvanostatic discharge?Ccharge. X-ray diffraction, conductivity measurement, cyclic voltammetry, and electrochemical impedance spectra tests were also carried out to help explain the electrochemical performance. Finally, the carbon aerogel with the best properties was chosen for the comparative study of replacement of water by acetone as solvent in the preparation of carbon aerogels. According to our study, the carbon aerogel prepared by ambient pressure drying with high electrical conductivity, controllable pore structure, and high specific surface area was proposed to be used for lithium/sulfur batteries, and the key factors to the performance of carbon aerogel/sulfur composites were discussed.     

Organic and carbon aerogels from the NaOH‐catalyzed polycondensation of resorcinol–furfural and supercritical drying in ethanol

Organic aerogels and related carbon aerogels were prepared from the NaOH‐catalyzed polycondensation of resorcinol–furfural (RF) and supercritical drying in ethanol. The effect of the preparation conditions, including the RF concentration, molar ratio of resorcinol (R) to NaOH, and molar ratio of R to furfural, on the gelation time and bulk density was studied. The chemical structure of the organic aerogel was revealed by IR spectroscopy. The pyrolysis process of the organic aerogel was investigated by thermogravimetric analysis. According to characterizations of transmission electron microscopy and nitrogen adsorption, the organic and carbon aerogels we obtained had a three‐dimensional network that consisted of around 30‐nm particles, which defined numerous mesopores of less than 30 nm. As a result, the aerogels had high Brunauer–Emmett–Teller surface areas (698–753 m²/g) and large mesopore volumes (1.09–1.64 cm³/g). X‐ray diffraction characterization indicated that the carbon aerogel was more crystalline than activated carbon but less activated than graphite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1429–1435, 2005     

二氧化硅气凝胶常压干燥工艺的研究进展

二氧化硅气凝胶因具有低密度、高比表面积、稳定的物理化学性质等特性在吸附分离、隔热保温等领域表现出巨大的应用潜力。但长耗时、高成本的制备工艺限制了它的发展,尤其是湿凝胶向气凝胶转变的干燥工艺。本文介绍了二氧化硅气凝胶在常压干燥的过程中面临的主要难点及解决方法,虽然常压干燥方法工艺简单、过程安全、对设备要求低且可连续制备,成为近年来的研究热点,但也存在制备周期长、体积收缩大、需要消耗大量有机溶剂和改性剂等不足。文中从凝胶基体增强与优化、降低毛细管力与减少不可逆收缩两种角度,介绍了二氧化硅气凝胶常压干燥的改进方法及其发展现状,分析归纳了不同改进方法的优缺点,总结了二氧化硅气凝胶常压干燥目前面临的技术挑战。并且,立足于目前二氧化硅气凝胶基体增强和表面改性技术发展的趋势,对今后二氧化硅气凝胶常压干燥过程中结构可控、成本降低以及产品多功能化的发展路线进行了展望。     

Fabrication and Physical Properties of Organic and Carbon Aerogel Derived from Phenol and Furfural

Phenol can be used as a cheap raw material to prepare organic and carbon aerogels based upon the gelation and supercritical drying in ethanol. In addition, organic and carbon aerogels could also be obtained by directly drying phenol-furfural alco-gels at ambient pressure under proper preparation conditions. The effect of the preparation conditions, such as the phenol-furfural (PF) concentration, the mass ratio of HCl to phenol (HCl/P), the mole ratio of phenol to furfural (P/F) and the gelation temperature, on the gelation ability and the bulk density was studied. The aerogels obtained have a three-dimensional network that consists of approximately 20 nm particles, which define numerous mesopores with diameter less than 50 nm. Organic aerogels obtained have high BET surface areas of 267–503 m/g and large mesopore volumes of 0.657–2.734 cm/g. Carbonization generates numerous micropores of ca. 0.45 nm in diameters but impairs to some extent the mesopore structure. As a result, carbon aerogels have high BET surface areas of 507–561 m/g, large micropore volumes of 0.106–0.168 cm/g and small mesopore volumes of 0.505–0.710 cm/g relative to their organic aerogel precursors. XRD characterization indicates that carbon aerogels are more crystalline than activated carbon but less than graphite.     

Improved electro-assisted removal of phosphates and nitrates using mesoporous carbon aerogels with controlled porosity

Three-activated carbon aerogels were synthesized by CO₂ activation of the materials prepared by the polycondensation of resorcinol and formaldehyde mixtures followed by supercritical drying. The obtained carbon aerogels were characterized and used as electrode materials for the electrosorption of sodium phosphate and nitrate. X-ray diffraction and Raman spectroscopy showed the dependence of the structural ordering of the aerogels with the resorcinol/catalyst ratio and the extent of activation. The electrosorption capacitance evaluated by cyclic voltammetry revealed large values for the activated samples containing a large contribution of mesopores, regardless the electrolyte salt. Due to an adequate combination of chemical and porous features, the desalting capacity of the activated carbon aerogel electrodes exceeded that of the as-prepared materials. The evaluation of the kinetic properties by chronocoulometric relaxation and impedance spectroscopy showed a decrease of time constant and resistances for highly mesoporous activated samples. A high deionization capacity and fast electrode discharge was detected for the deionization of sodium nitrate on the highly mesoporous activated aerogel. Data also showed the efficient electrosorption of ionic species on consecutive charge/discharge cycles, confirming the stability of the aerogel electrodes at the high applied potentials.     

On Porosity of Carbon Aerogels from Sol-Gel Polymerization of Phenolic Novolak and Furfural

Carbon aerogels were prepared by sol-gel polymerization of phenolic novolak and furfural followed by supercritical drying and pyrolysis. The porosity and morphologies of carbon aerogels were characterized by nitrogen adsorption, apparent density, He- pycnometer method, and transmission electronic microscopy (TEM). Effect of ratios of phenolic novolak to furfural (Ra) and total concentration of reactants (C) in sol-gel step on porosity and morphologies of carbon aerogels was investigated. The carbon aerogels synthesized are rich in meso- and macropores. The Ra determines the cross-linking density of polymers, thereby the compatibility of the polymers, and ultimately the shrinkage of gels in the drying and pyrolysis. The network sizes and the porosity of organic and carbon aerogels are mainly determined by Ra. The C has no effect on volume shrinkage of gels in drying and pyrolysis and has only dilute effect in determining bulk density of organic and carbon aerogels, and ultimately the porosity of carbon aerogels. Conversion of mesopores to micro- and macropores is observed, which is related to combination of C and Ra, and determines the partition of micro-, meso- and macropores.     

气凝胶复合材料的研究进展

气凝胶材料是一种质轻、低密的多孔材料,对其研究较多。它具有良好的发展前景和巨大的科研价值。通过介绍高分子气凝胶、碳气凝胶等复合材料的制备方法,阐述了结构与性能的关系,并对气凝胶材料未来的发展作了展望。