炭气凝胶的制备

通过对ＲＦ有机气凝胶进行炭化,成功地制备了具有纳米网络结构的炭气凝胶。系统考察了炭化条件及溶胶－凝胶过程条件对炭气凝胶性质的影响,并对所得的炭气凝胶进行了ＴＥＭ表征。     

一锅法制备酚醛基炭气凝胶

炭气凝胶因其优异的隔热性能和耐高温性能，成为热保护系统中的最具潜力的高温隔热材料之一。然而，由于现有炭气凝胶制备工艺复杂、周期过长等因素，限制了其工业化制备及其应用。论文采用一锅法制备酚醛气凝胶、经炭化制得炭气凝胶，与传统法制备的炭气凝胶进行了对比，表征了炭气凝胶的孔结构、微观形貌，考察了固含量对炭气凝胶密度、收缩率的影响及热导率随密度及温度的变化。结果表明，随着固含量的增加，密度逐渐增大，而收缩率基本维持在22%左右，不随固含量的变化而变化，固含量从16%增加到46%时，炭气凝胶的密度从0.15 g/cm³增加到0.58 g/cm³,其中，密度为0.15 g/cm³的炭气凝胶室温下热导率低至0.074 W/(m·K),随着温度升高热导率逐渐增大，1 800℃高温下热导率为0.620 W/(m·K)。一锅法有望成为一种快速、批量、低成本制备炭气凝胶的新技术路径。     

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。     

金属铅沉积下的超电容器用炭气凝胶的制备和表征

制备了铅沉积下的超电容器用炭气凝胶。使用场发射扫描电子显微镜,循环伏安法对其形貌和电化学性能进行了表征,结果显示所制备的炭气凝胶具有微米级的球状结构和理想的电容行为。通过铅沉积,炭气凝胶的比电容得到了显著提高,是超级电容器的理想电极材料。     

金属铅沉积下的超电容器用炭气凝胶的制备和表征

制备了铅沉积下的超电容器用炭气凝胶。使用场发射扫描电子显微镜，循环伏安法对其形貌和电化学性能进行了表征，结果显示所制备的炭气凝胶具有微米级的球状结构和理想的电容行为。通过铅沉积，炭气凝胶的比电容得到了显著提高，是超级电容器的理想电极材料。     

酚醛基炭气凝胶的研究进展

炭气凝胶是一种多孔纳米炭材料,具有低密度、高孔隙率、高比表面积、优异的导电性和良好的成型性能等优点,是炭材料研究的热点和重要方向。本文旨在通过阐明酚醛基炭气凝胶的制备原料和制备工艺的发展过程,从而突出未来酚醛基炭气凝胶的发展方向。基于此,本文首先重点介绍了酚醛基炭气凝胶的制备方法,主要包括溶胶-凝胶化、干燥以及炭化过程三个最主要的步骤;进而详述了以三种不同的前体,即间苯二酚、苯酚、生物质单宁/木质素分别制备酚醛基炭气凝胶的方法及其优缺点;接下来对酚醛基炭气凝胶作为吸附材料（气体吸附/液体吸附）的吸附量以及在电化学储能以及其他领域的应用进行了综述;最后对酚醛基炭气凝胶未来的研究方向和发展前景进行了总结和展望。文章指出,传统的以间苯二酚为原料辅以超临界干燥的方法制备的酚醛基炭气凝胶,原料成本较高,反应条件苛刻,实际生产应用受限;以苯酚取代间苯二酚,亦或是采用冷冻干燥等方法改进其制备工艺,可以大幅度降低原料和生产成本;但未来的发展方向和重点将是绿色、可再生的生物质原料（单宁、木质素、腰果酚等）及复合气凝胶材料的研发。因此,酚醛基炭气凝胶在未来的发展还需要进一步改进其制备工艺和方法,拓宽其原料来源,从而提高性能,扩大应用领域。     

间甲酚甲醛气凝胶炭化工艺的研究

以间甲酚为原料,经溶胶－凝胶合成,酸洗老化,超临界干燥得到有机气凝胶、进一步炭化得炭气凝胶。采用正交试验方法重点考虑了炭化工艺条件对炭气凝胶结构和性能的影响。     

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。     

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。     

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)。     

Nanoporous phloroglucinol-formaldehyde carbon aerogels for electrochemical use

Phloroglucinol-Formaldehyde (PF) organic aerogels were prepared from alcoholic sol-gel polycondensation of phloroglucinol with formaldehyde using KOH as base catalyst and followed by supercritical drying with carbon dioxide. Subsequent pyrolysis of PF organic aerogel under He flow produced carbon aerogels. Textural properties of PF organic and carbon aerogels were obtained by nitrogen adsorption-desorption, and their specific capacitances were measured by cyclic voltammetry. The resultant PF carbon aerogels were mostly mesoporous material with high surface area. The nanoporous structure and electrochemical behavior of PF carbon aerogels could be controlled by the molar ratio of phloroglucinol to catalyst (P/C) and carbonization conditions. PF carbon aerogels exhibited the highest surface area in excess of 1,200 m²/g and specific capacitance up to 250 F/g in comparison to other carbons.     

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.     

Organic and carbon aerogels derived from poly(vinyl chloride)

Organic aerogels were derived from dimethylformamide solution of poly(vinyl chloride) (PVC) via dehydrochlorination using a strong base, 1,8-diazabicyclo[5,4,0]undec-7-ene, and supercritical drying using carbon dioxide. From these organic aerogels, carbon aerogels were yielded via stabilization and carbonization. Changes in the porous structure of the aerogels during the preparation process and influences of the preparation conditions on the porous structure were investigated. The framework of the aerogels composed the walls of the meso- and macropores. The volume and the size of these pores were reduced during stabilization and carbonization due to the shrinkage of the framework caused by the release of decomposition gases and densification of the material. Simultaneously, the release of decomposition gases produced additional micropores. The extent of dehydrochlorination, the concentration of PVC in the starting solution and the molecular weight of PVC were the factors with which the porous structure of the aerogels could be controlled over a wide range. In addition, the stabilization conditions notably influenced the carbonization behavior of the organic aerogels and the porous structure of the carbon aerogels. The optimum stabilization conditions that minimized the loss of mass and maximized the pore volume of the carbon aerogels were determined.     

Drying processes for preparation of titania aerogel using supercritical carbon dioxide

Supercritical carbon dioxide drying was performed for the preparation of titania aerogels from sol–gel routes. The conditions of supercritical carbon dioxide drying were 313–323 K and 7.8–15.5 MPa. The solvents in titania wet gels obtained from the sol–gel routes were replaced by acetone. The titania aerogels obtained from supercritical carbon dioxide drying form needle-like structures. In supercritical carbon dioxide drying, the extraction rates of acetone from the wet gels were measured by using an on-line Fourier transform infrared spectroscope. It was found that the titania aerogels with lower cohesion were induced from the formations of homogenous phase for carbon dioxide + acetone system and the lower extraction rates of acetone. Furthermore, titania films were prepared by the depositions of the titania aerogels on ITO-coated PET substrates. The needle-like aerogels with lower cohesion derive the titania film with high surface area.     

二氧化碳活化法制备高比表面积碳气凝胶

以间苯二酚-甲醛为原料,常压干燥条件下制备传统的碳气凝胶,通过活化工艺成功地将其比表面积提高了3倍以上. 用比表面积测试及孔径分布、扫描电镜(SEM)等手段对其微观结构进行了表征并优化了工艺参数.     

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.     

Starch-derived carbon aerogels with high-performance for sorption of cationic dyes

Environmentally green carbon aerogels have been prepared as adsorbents for dye-containing wastewater. The aerogels were prepared by carbonization of starch aerogels synthesized from soluble starch through a sol-gel process followed by drying at ambient pressure. The Brunauer-Emmett-Teller (BET) surface areas and pore size distribution were measured by N₂ adsorption/desorption, and the surface zeta-potential and microstructure of carbon aerogels were characterized using a scanning electron microscope (SEM) and zeta-potential analyzer. SEM images indicate that the carbon aerogels consist of flakes with side length of 60-120 μm and thickness of 3-4 μm. The flakes are irregular in shape and composed of spherical carbon nanoparticles of 10-30 nm. The carbon aerogels have both microporous and mesoporous structures and exhibit high specific surface areas, the highest value is 1571 m²/g. The mean diameter of the micropores is 0.89 nm and that of the mesopores is 2-10 nm. At pH = 10, the carbon aerogels have a zeta-potential of −40 mV and exhibit high adsorption capacities for cationic dyes, such as crystal violet (CV), methyl violet (MV) and methylene blue (MB), from aqueous solution. The largest adsorption capacities for CV, MV and MB are 1515, 1423 and 1181 mg/g, respectively.     

Facile fabrication of ultra-low density,high-surface-area,broadband antireflective carbon aerogels as ultra-black materials

Carbon aerogels with various densities, even as low as 20 mg/cm³, were fabricated by pyrolysis of organic aerogels formed by aqueous condensation of resorcinol and formaldehyde. It was found that carbon aerogels with the density below 70 mg/cm³ exhibited the total reflectance values of typically less than 0.24 % across wavelengths in the range of 400–2000 nm. The change of antireflective properties between the lowest-density carbon aerogel monolith and its powder coating was discussed. Furthermore, we studied the effect of the density on the structure and antireflective property of carbon aerogels. As a result, the low-density carbon aerogels showed broadband low-reflectivity and high absorption to incident light.     

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。