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...     

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。     

炭气凝胶及其有机气凝胶前驱体的研究进展

介绍了炭气凝胶及其有机气凝胶前驱体的发展概况，着重总结了制备工艺条件(如催化剂及其浓度、反应物总浓度、反应物配比、溶剂、反应温度及时间、超临界干燥工艺条件和炭化工艺条件等)对有机气凝胶及其相应炭气凝胶中孔网络结构的影响，综述了中孔网络结构改性研究的进展．     

载银油茶果壳抗菌剂的制备和性能

考察银离子浓度、pH、温度、时间等制备条件对油茶果壳载银抗菌剂性能的影响,并考察了材料对大肠杆菌、金黄色葡萄球菌的抑制效果。结果表明:油茶果壳载银抗菌剂的最佳制备条件为吸附时间6 h,搅拌温度35℃,pH=4,银离子浓度是0.2 mol/L,制备的油茶果壳载银抗菌剂对大肠杆菌、金黄色葡萄球菌具有优异的抗菌性能。     

通过柠檬酸改性提高载银活性炭的抗菌性能

通过负载柠檬酸对活性炭进行改性,用N2吸附法测定活性炭的比表面积,用AAS、SEM、XRD测试技术分析了银在活性炭上的吸附和分布,并研究了载银活性炭的抗菌性能。结果表明,负载柠檬酸使活性炭的比表面积下降约24%,但载银后活性炭的比表面积增大。柠檬酸改性为[Ag(NH3)2] 的还原吸附提供更多的活性点,使银的吸附速率加快,吸附量提高约25%,表面的银颗粒变得非常密集,粒径减小,且颗粒均匀,因此抗菌性能显著增强,其中对金黄色葡萄球菌的杀灭效果明显优于对大肠杆菌的,同时对于高分散Ag/C催化剂的制备及银的回收也具有重要的价值。     

常压干燥法制备气凝胶的研究进展

气凝胶是一类轻质、低密度的三维纳米多孔固态材料,因其独特的高孔隙率、高比表面积和低导热系数等特性,使其在吸附、催化、保温隔热和隔音等诸多领域具有广泛的用途,目前其相关研究在材料科学领域受到了广泛的关注。气凝胶的制备主要包括溶胶-凝胶过程和湿凝胶干燥两个步骤,湿凝胶的干燥是制备气凝胶过程中至关重要而又较为困难的一步。传统的气凝胶通过超临界干燥制备,工艺复杂、成本高,而且由于干燥过程在高温高压条件下进行,有一定的危险性并且不适宜大规模生产,因此如何通过常压干燥获得高比表面积、高孔隙率、低密度的性能优异的气凝胶是其研究的重要方向之一。本文简要介绍了湿凝胶的制备以及凝胶干燥理论,详细介绍了近年来常压干燥方法气凝胶制备的研究进展,并对其未来发展前景做出了展望。     

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.     

通过柠檬酸改性提高载银活性炭的抗菌性能

通过负载柠檬酸对活性炭进行改性,用N2吸附法测定活性炭的比表面积,用AAS、SEM、XRD测试技术分析了银在活性炭上的吸附和分布,并研究了载银活性炭的抗菌性能。结果表明,负载柠檬酸使活性炭的比表面积下降约24％,但载银后活性炭的比表面积增大。柠檬酸改性为[Ag（NH3）2]^＋的还原吸附提供更多的活性点,使银的吸附速率加快,吸附量提高约25％,表面的银颗粒变得非常密集,粒径减小,且颗粒均匀,因此抗菌性能显著增强．其中对金黄色葡萄球菌的杀灭效果明显优于对大肠杆菌的,同时对于高分散Ag／C催化剂的制备及银的回收也具有重要的价值。     

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     

块状石英纤维/Al_2O_3气凝胶复合材料的非超临界干燥法制备及表征

采用溶胶-凝胶法和常压干燥法以N,N′-二甲基甲酰胺(DMF)作为干燥控制化学添加剂制备了低密度石英纤维增强Al2O3气凝胶复合材料.通过氮气吸附-脱附实验比较研究了石英纤维对氧化铝气凝胶孔结构参数的影响;采用X射线衍射技术表征了在升温过程中石英纤维/Al2O3气凝胶复合材料的相结构变化;利用扫描电子显微镜和透射电子显微镜观察了Al2O3气凝胶基体及其石英纤维复合材料的微观形貌;初步探讨了DMF对Al2O3气凝胶形貌和密度的影响.研究结果表明石英纤维/Al2O3气凝胶复合材料成块性好,纤维与气凝胶基体结合紧密,石英纤维提高了Al2O3相转变温度,适量的DMF有利于形成均匀凝胶网络结构,减小干燥收缩压力.     

Inter- and intra-primary-particle structure of monolithic carbon aerogels obtained with varying solvents

Different carbon aerogels were obtained by carbonization of organic aerogels prepared from the polymerization of resorcinol and formaldehyde using potassium carbonate as catalyst. Various solvents were added to the initial mixture to study their effects on the inter- and intra-primary-particle structure of the carbon aerogels. To carry out this study, various techniques were used, including high-resolution transmission and scanning electron microscopy, mercury porosimetry, mechanical tests, N2 and CO2 adsorption at -196 and 0 degrees C, respectively, and immersion calorimetry into benzene. Variation of the solvent used produced changes in the gelation time of the organic aerogels, which gave rise to variations in the inter- and intra-primary-particle structure of the carbon aerogels obtained. The monolith density of the carbon aerogels ranged from 0.37 to 0.87 g/cm3. Samples with a density higher than 0.61 g/cm3 had micropores and mesopores but no macropores. Macro- and mesoporosity had a monomodal pore size distribution. The elastic modulus showed a scaling relationship with density. In all samples studied, which had a mean micropore width of 0.62-1.06 nm, the surface area obtained by enthalpy of immersion into benzene yielded a realistic value of their total surface area.     

碳气凝胶的结构重整及其电化学行为

将碳气凝胶(CAs)在金属钠熔体中于800°C加热3h,制得结构重整的碳气凝胶(RCAs),并研究了它们的电化学行为.采用X射线粉末衍射(XRD)、激光散射拉曼(Raman)光谱、气体的吸附与脱附(BET法)、透射电子显微镜(TEM)以及电化学阻抗谱(EIS)等手段,对CAs和RCAs样品分别进行了表征.结果表明:无定形态的碳单质微粒在金属钠作用下发生结构重排;所得RCAs的比表面积比CAs的大约增加48%;RCAs中孔径在2和4nm尺寸处,呈现比较集中的分布,孔径小于10nm以下的孔体积占其总孔容的30%,是CAs的3倍.CAs和RCAs样品的电化学测试结果表明:RCAs内部接触电阻约为CAs的45%,并保持了明显的电容特性.     

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.     

A versatile strategy to fabricate hydrogel-silver nanocomposites and investigation of their antimicrobial activity

In this study, hydrogel-silver nanocomposites have been synthesized by a unique methodology, which involves formation of silver nanoparticles within swollen poly (acrylamide-co-acrylic acid) hydrogels. The formation of silver nanoparticles was confirmed by transmission electron microscopy (TEM) and surface plasmon resonance (SPR) which was obtained at 406 nm. The TEM of hydrogel-silver nanocomposites showed almost uniform distribution of nanoparticles throughout the gel networks. Most of the particles, as revealed from the particle-size distribution curve, were 24-30 nm in size. The X-ray diffraction pattern also confirmed the face centered cubic (fcc) structure of silver nanoparticles. The nanocomposites demonstrated excellent antibacterial effects on Escherichia coli (E. coli). The antibacterial activity depended on size of the nanocomposites, amount of silver nanoparticles, and amount of monomer acid present within the hydrogel-silver nanocomposites. It was also found that immersion of plain hydrogel in 20 mg/30 ml AgNO(3) solution yielded nanocomparticle-hydrogel composites with optimum bactericidal activity.     

Large-Scale Synthesis of MOF-Derived Superporous Carbon Aerogels with Extraordinary Adsorption Capacity for Organic Solvents

Carbon aerogels (CAs) with 3D interconnected networks hold promise for application in areas such as pollutant treatment, energy storage, and electrocatalysis. In spite of this, it remains challenging to synthesize high-performance CAs on a large scale in a simple and sustainable manner. We report an eco-friendly method for the scalable synthesis of ultralight and superporous CAs by using cheap and widely available agarose (AG) biomass as the carbon precursor. Zeolitic imidazolate framework-8 (ZIF-8) with high porosity is introduced into the AG aerogels to increase the specific surface area and enable heteroatom doping. After pyrolysis under inert atmosphere, the ZIF-8/AG-derived nitrogen-doped CAs show a highly interconnected porous mazelike structure with a low density of 24 mg cm⁻³, a high specific surface area of 516 m² g⁻¹, and a large pore volume of 0.58 cm⁻³ g⁻¹. The resulting CAs exhibit significant potential for application in the adsorption of organic pollutants.     

Large‐Scale Synthesis of MOF‐Derived Superporous Carbon Aerogels with Extraordinary Adsorption Capacity for Organic Solvents

Carbon aerogels (CAs) with 3D interconnected networks hold promise for application in areas such as pollutant treatment, energy storage, and electrocatalysis. In spite of this, it remains challenging to synthesize high‐performance CAs on a large scale in a simple and sustainable manner. We report an eco‐friendly method for the scalable synthesis of ultralight and superporous CAs by using cheap and widely available agarose (AG) biomass as the carbon precursor. Zeolitic imidazolate framework‐8 (ZIF‐8) with high porosity is introduced into the AG aerogels to increase the specific surface area and enable heteroatom doping. After pyrolysis under inert atmosphere, the ZIF‐8/AG‐derived nitrogen‐doped CAs show a highly interconnected porous mazelike structure with a low density of 24 mg cm^?3, a high specific surface area of 516 m² g^?1, and a large pore volume of 0.58 cm^?3 g^?1. The resulting CAs exhibit significant potential for application in the adsorption of organic pollutants.     

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.     

Embedded silver ions-containing liposomes in polyelectrolyte multilayers: cargos films for antibacterial agents

A new antibacterial coating made of poly(L-lysine)/hyaluronic acid (PLL/HA) multilayer films and liposome aggregates loaded with silver ions was designed. Liposomes filled with an AgNO 3 solution were first aggregated by the addition of PLL in solution. The obtained micrometer-sized aggregates were then deposited on a PLL/HA multilayer film, playing the role of a spacer with the support. Finally, HA/PLL/HA capping layers were deposited on top of the architecture to form a composite AgNO 3 coating. Release of encapsulated AgNO 3 from this composite coating was followed and triggered upon temperature increase over the transition temperature of vesicles, found to be equal to 34 degrees C. After determination of the minimal inhibitory concentration (MIC) of AgNO 3 in solution, the antibacterial activity of the AgNO 3 coating was investigated against Escherichia coli. A 4-log reduction in the number of viable E. coli cells was observed after contact for 120 min with a 120 ng/cm (2) AgNO 3 coating. In comparison, no bactericidal activity was found for PLL/HA films previously dipped in an AgNO 3 solution and for PLL/HA films with liposome aggregates containing no AgNO 3 solution. The strong bactericidal effect could be linked to the diffusion of silver ions out of the AgNO 3 coating, leading to an important bactericidal concentration close to the membrane of the bacteria. A simple method to prepare antibacterial coatings loaded with a high and controlled amount of AgNO 3 is therefore proposed. This procedure is far superior to that soaking AgNO 3 or Ag nanoparticles into a coating. In principle, other small bactericidal chemicals like antibiotics could be encapsulated by this method. This study opens a new route to modify surfaces with small solutes that are not permeating phospholipid membranes below the phase transition temperature.     

Low-Density Forsterite (Mg2SiO4) Powders Prepared from Modified Alkoxides

2MgO-SiO₂ low-density powders have been prepared from alkoxide precursors modified with acetic anhydride. The resultant solutions did not gel, but formed precipitates. These consisted of an organic magnesium compound and amorphous silica. Tapping densities comparable with those of forsterite aerogels were obtained, with the density increasing as the precursor solution concentration increased. Crystalline forsterite formed around 790°C. Higher initial solution concentrations led to greater amounts of MgO in the powders after heating to 1000°C. Transmission electron microscopy showed primary particles between 20 and 30 nm which formed loose fractal agglomerates. By altering the preparation conditions, powders with morphologies more like aerogels than xerogels could be produced.     

碳气凝胶的制备研究

气凝胶是由纳米量级超细粒子或高聚物分子聚结构成的多孔性轻质固态材料 ,它在声学、光学、电学、动力学和低温热学等方面具有独特性质 ,因此受到多方面研究者的重视 [1～ 4 ] .碳气凝胶最先是由 Pekala等 [5] 在 80年代末研制成功的 ,其突出特点是网络连续 ,电导率高 ,孔洞微小且相互贯通 ,比表面大 ,密度变化范围大 ,是制造高性能电容器和电池的新一代理想材料[6 ,7] .这种材料的低温电导率随温度连续单调变化 ,在一定温区范围内 ( <1 0 0 K)其电阻温度敏感度远大于传统的掺碳玻璃、锗以及其它金属电阻温度计材料 ,可望成为一种理想的低…