混甲酚甲醛炭气凝胶的制备及表征

以混甲酚和甲醛为原料,经溶胶－凝胶民、酸洗老化、超临界干燥得有机气凝胶,密度０．１５０７ｇ／ｃｍ＾３,进一步炭化得炭气凝胶。采用正交试验方法重点考察了炭化工艺条件对炭气凝胶结构和性能的影响,并用ＴＥＭ、ＴＧ、低及附等手段进行了表征。结果表明,炭化工艺条件影响因素顺序为：升温速率〉炭化终温〉维温时间,最佳炭化条件下炭气凝胶密度为０２６０ｇ／ｃｍ＾３,幽静面积人１０２２ｍ＾２／ｇ,平均戏５．６ｍｍ。Ｔ     

有机气凝胶及炭气凝胶对茶碱的吸附动力学研究

制备出一系列不同结构的炭气凝胶和有机气凝胶。通过吸附实验,研究了其吸附茶碱的动力学行为。实验表明,炭气凝胶比有机气凝胶吸附速率快,吸附平衡时间短。炭气凝胶与文献报道的酚醛树脂对茶碱的吸附量相当,但吸附速率较快。茶碱在气凝胶上的吸附量随时间的变化规律遵从Langmuir方程,也符合假二级动力学吸附方程。     

纳米银负载的炭气凝胶制备及抗菌性能研究

以常压干燥法制备的酚醛有机气凝胶为原料,通过在硝酸银溶液中浸渍使银吸附或沉积在有机气凝胶上,在常压条件下干燥并炭化制得纳米银负载的炭气凝胶。利用扫描电镜(SEM)、透射电镜(TEM)、X-射线衍射(XRD),比表面积及孔径分析等方法研究了浸渍前后凝胶密度和结构的变化,以及制备条件对银负载炭气凝胶的载银量和凝胶结构的影响;研究了载银炭气凝胶对大肠埃氏杆菌(ATCC25922)和金黄色葡萄球菌(ATCC25923)的抗菌效果。结果表明,这类银负载炭气凝胶对大肠杆菌和金黄色葡萄球菌均有很强的杀灭能力,预期炭气凝胶在作为催化剂或吸附杀菌材料方面有良好的应用前景。     

常压干燥制备酚醛树脂基炭气凝胶研究进展

以间苯二酚-甲醛为代表的酚醛树脂基炭气凝胶是一种轻质、多孔、非晶态的纳米炭材料,在催化、吸附、电化学和隔热等领域中有广阔的应用前景。但是复杂且高成本的超临界干燥工艺极大地限制了炭气凝胶的工业化制备及其应用,因此常压干燥工艺成为目前研究最为广泛的炭气凝胶制备技术之一。本文综述了酚醛树脂基炭气凝胶常压干燥制备过程的四种结构调控方法:调控溶胶-凝胶反应参数、添加模板法、纤维增强法和添加剂法,并对不同结构调控方法所制材料的结构特性及其制备过程优缺点进行了总结。最后对其发展前景进行了展望。     

基于普通酚醛树脂有机气凝胶的高效制备与研究

基于普通线性酚醛树脂体系,采用溶胶-凝胶(sol-gel)法制备了酚醛树脂有机气凝胶.通过调节交联剂——六亚甲基四胺(HMTA)的浓度对酚醛树脂有机气凝胶的微观孔结构进行优化,减小溶剂在干燥过程中的毛细作用力,采用常压干燥的手段即可得到较小收缩率、较强骨架强度的有机气凝胶.详细研究了交联剂(HMTA)用量对有机气凝胶内部微观孔结构/形貌、表观密度、热稳定性、力学性能等方面的影响.孔结构与微观形态研究结果表明,随着HMTA浓度的减小,有机气凝胶平均孔径减小,比表面积增加,在较低交联剂浓度下,平均孔径达到100 nm,并且孔径分布均匀,内部聚合物有机骨架完好.纳米尺度的孔径和均匀的孔径分布能够显著提高有机气凝胶的骨架稳定性,与微米尺度孔径的气凝胶材料相比,压缩模量和压缩强度均有显著的提高.HMTA浓度的提高使酚醛树脂气凝胶体系中引入大量不稳定的N—CH2基团,造成气凝胶材料的热稳定性下降.     

溶胶--凝胶法制备间甲酚甲醛炭气凝胶

以间甲酚为原料 ,与甲醛在NaOH催化作用下经溶胶—凝胶过程制备出新型块状纳米材料炭气凝胶 ,考察了原料配比对凝胶时间和气凝胶特性的影响 ,用TG、FT -IR、TEM和低温N2 吸附等手段表征了气凝胶的微结构。     

碳气凝胶的孔结构及其对电化学超级电容器性能的影响

通过改变碳气凝胶的溶胶-凝胶制备条件和炭化活化工艺,实现了对碳气凝胶纳米孔洞结构的控制.采用扫描电子显微镜(SEM)和氮气等温气体吸附法对碳气凝胶和KOH活化碳气凝胶的形貌和孔结构进行了表征和分析,并且使用循环伏安法(CV),恒流充放电,电化学阻抗谱(EIS)等检测技术评价了电化学性能.结果表明:发达的三维纳米网络结构与合理的孔径分布是影响碳气凝胶电化学超级电容器性能的关键因素.经适度活化后的碳气凝胶材料含有丰富的介孔,比表面积可达1480m2·g-1.在6mo·lL-1的KOH溶液中,在100mV·s-1的扫描速率下其比电容量高达216F·g-1.通过拟合发现,碳气凝胶类材料的大孔和介孔拥有更高的单位面积比电容量.     

有机-无机复合气凝胶研究进展

气凝胶具有低密度、低热导率、高比表面积及高孔隙率等优异性能,在隔热、传感、催化、吸附、储能等领域显示出良好的应用前景。但气凝胶的多孔网络结构也造成了其强度低和韧性差等问题,严重制约了气凝胶的实际应用,有机-无机复合是一种增强气凝胶力学性能的有效方法。而且,采用有机-无机复合方法制备气凝胶还可以赋予气凝胶阻燃等其他新颖的性能。本文综述了有机-无机复合气凝胶的新研究进展,分析其原理、合成方法及相关性能,指出了有机无机复合气凝胶的优势和存在问题并展望了未来的发展方向。     

以纤维素/AmimCl溶液制备纤维素气凝胶

利用离子液体AmimCl溶解结合超临界CO2干燥的方法制备了纤维素气凝胶材料.研究了不同初始浓度的纤维素溶液及其在不同凝固浴中制备的纤维素凝胶的流变行为,进一步考察了纤维素溶液浓度和凝固浴种类对纤维素气凝胶材料结构的影响.结果表明,随着初始纤维素溶液浓度的增大,气凝胶的孔结构逐渐致密,比表面积随之减小;凝固浴的组成对纤维素气凝胶的结构也有较大影响.采用适当的制备条件,可以制备出高比表面积的纤维素气凝胶材料.对纤维素气凝胶的热性能进行了表征,结果表明所得到的气凝胶材料具有较好的热稳定性和较高的炭残余含量.     

氯化锌活化对炭气凝胶微球的结构与电化学性能的影响

对炭气凝胶微球在高温下进行氯化锌活化改性,并用于制作超级电容器的电极。采用扫描电镜、N2物理吸附-脱附等对炭气凝胶微球的形貌结构进行表征,采用循环伏安、恒流充放电等测定了材料的电化学性能。结果表明,氯化锌活化有效地改善了炭气凝胶微球的孔结构,通过增加炭气凝胶微球的微孔面积和体积,提高了材料的比表面积和孔隙率。经过氯化锌活化,炭气凝胶微球的电化学性能也随之得到提高,电阻明显减小,比电容提高了2倍以上。     

THE FABRICATION OF CARBON AEROGELS BY GELATION IN ISOPROPANOL WITH BASIC CATALYST

1.INTRODUCTIONIn1987,Pekalapatentedthefirstorganicaerogel,i.e.resorcinol-formaldehydeorganicaerogel,undercarbondioxidesupercriticalcondition[1],whichcanbepyrolyzedinaninertatmospheretoformcarbonaerogelduetoahighlycrosslinkingstructure[2].Duetotheiruniquemicrostructureconsistingofporesandparticleswithnanometersize,carbonaerogelsareexpectedtobeusedasthermalandphonicinsulators,electricdoublelayercapacitors,chromatographicpackings,adsorbents,andcatalystsupports[3,4].Uptonowhowever,carbonaerog…     

THE FABRICATION OF CARBON AEROGELS BY GELATION IN ISOPROPANOL WITH BASIC CATALYST

A new method for the fabrication of carbon aerogels is reported in this paper. Resorcinol and furfural were gelated in isopropanol with basic catalysts and then dried directly under isopropanol supercritical condition, followed by carbonization under nitrogen atmosphere. The bulk densities of carbon aerogels obtained are in the range of 0. 21g/cm3～0. 27g/cm3 and the sizes of the interconnected carbon nano-particles are in the range of 20nm～30nm. All of the aerogel samples exhibit high BET surface areas in the range of 730m2/g～900m2/g. The bulk density, micro-porevolume, meso-pore volume and meso-pore diameter can be controlled by gelation conditions such as R/I ratio and R/C ratio.     

Porous structure of polybenzoxazine-based organic aerogel prepared by sol–gel process and their carbon aerogels

New organic aerogels were successfully prepared from a new class of phenolic resins called polybenzoxazines synthesized via conventional thermal curing reaction of a benzoxazine monomer using xylene as a solvent. Without the need for using supercritical conditions to remove the solvent during the process, the carbon aerogels were obtained with a much shortened time. From two different concentrations of benzoxazine solution, 20 and 40 wt%, the resulting polybenzoxazine aerogels, having densities of 260 and 590 kg/m³, respectively, were obtained after the curing process. The subsequent carbon aerogels were prepared by the carbonization of polybenzoxazine aerogels. The corresponding carbon aerogels exhibited a microporous structure with pore diameters less than 2 nm, the densities of 300 and 830 kg/m³, and surface area of 384 and 391 m²/g, respectively. The texture of the carbon aerogels was denser than that of their organic aerogel precursor, as evidenced by scanning electron microscopy. The transformation of the polybenzoxazine aerogel to the carbon aerogel was clearly observed using fourier transform infrared spectroscopy.     

High surface area, mesoporous, glassy alumina with a controllable pore size by nanocasting from carbon aerogels

A strategy to synthesize amorphous, mesoporous alumina by nanocasting has been developed, involving carbon aerogel as a hard template and aluminum nitrate solution as an alumina precursor. The alumina generated exhibits small, transparent granules with a 3-6 mm diameter and has inherited the three-dimensional network structure of the carbon template. The mesopore surface area of the alumina can be as high as 365 m2 g(-1), and the pore volume reaches 1.55 cm3 g(-1) after calcination at 600 degrees C in air for 8 h. The pore parameters can be varied within a certain range by variation of the carbon aerogel template and the loading amount of the alumina precursor. At high loadings, the obtained glassy alumina clearly has a bimodal pore size distribution in the mesopore range.     

Polymerization under Hypersaline Conditions: A Robust Route to Phenolic Polymer‐Derived Carbon Aerogels

Polymer‐derived carbon aerogels can be obtained by direct polymerization of monomers under hypersaline conditions using inorganic salts. This allows for significantly increased mechanical robustness and avoiding special drying processes. This concept was realized by conducting the polymerization of phenol–formaldehyde (PF) in the presence of ZnCl₂ salt. Afterwards, the simultaneous carbonization and foaming process conveniently converts the PF monolith into a foam‐like carbon aerogel. ZnCl₂ plays a key role, serving as dehydration agent, foaming agent, and porogen. The carbon aerogels thus obtained are of very low density (25 mg cm^?3), high specific surface area (1340 m² g^?1), and have a large micro‐ and mesopore volume (0.75 cm³ g^?1). The carbon aerogels show very promising potential in the separation/extraction of organic pollutants and for energy storage.     

多壁碳纳米管的制备及改性处理

用自制的镍 硅二元气凝胶作催化剂,合成了多壁碳纳米管.甲烷在680℃催化裂解120min,再升温至800℃继续裂解20min,得到多壁碳纳米管.TEM、HRTEM和Raman光谱分析表明,所得多壁碳纳米管与高定向石墨具有相似的层状结构,其管径分布均匀,约15～30nm左右,长径比大,管端封闭,并含有金属催化剂粒子;采用不同方法改性处理,发现经过稀硝酸浸泡和空气氧化处理后,能去除碳管中金属催化剂,同时碳纳米管管长变短,端帽开口,能有效利用内表面,比表面积增大.     

碳气凝胶活化对于电极嵌锂性能的影响

碳气凝胶由于其对于可充电锂离子电池的高能嵌锂特性, 近年来受关注程度逐渐增加. 碳气凝胶以间苯二酚-甲醛在碳酸钠催化下, 通过溶胶-凝胶工艺、常压干燥技术、碳化、活化后制得. 经CO₂气体活化后的碳气凝胶结合了无定型和纳米多孔结构的优点, 在材料原有基础上丰富了多孔结构, 增加了嵌锂点位. 其中, 微孔提供了高比表面积和孔体积以容纳锂及其化合物; 介孔则提供了锂离子大量传输的通道, 从而使得电极具有更高的离子电导率. 这些微结构的优化使材料获得了更高的嵌锂比容量. 此外, 活化碳气凝胶显示了2032 m²·g^-1的比表面积. X射线衍射(XRD)和扫描电子显微镜(SEM)的测试结果分别表明了其无定型特质以及纳米颗粒的网络状骨架. 该材料在首次和第50次恒流充放电(50 mA·g^-1)循环的嵌锂容量分别为3870和352 mAh·g^-1, 对应的可逆容量分别为658 和333 mAh·g^-1. 表明了CO₂活化对于改善碳气凝胶嵌锂性能的可行性, 且对于其它多孔电极材料的制备及特性优化提供了一种途径.