基于疏水型二氧化硅气凝胶制备无氟自清洁超疏水棉织物

以甲基三甲氧基硅烷(MTMS)为硅源,水为溶剂,在表面活性剂十六烷基三甲基溴化铵(CTAB)作用下,通过溶胶-凝胶反应,并采用环境压力干燥法(APD)制备了超疏水二氧化硅气凝胶.将二氧化硅气凝胶粉和聚二甲基硅氧烷(PDMS)通过喷涂法整理到棉织物上,分别采用扫描电镜、红外光谱仪、接触角测量仪对整理棉织物的结构、形貌和疏...     

可用于包装的纤维素基电磁屏蔽材料研究进展

目的 为推动可用于包装的纤维素基电磁干扰(Electromagnetic Interference,EMI)屏蔽材料更深入的研究,综述一些具有包装材料潜质和EMI屏蔽功能的纤维素基薄膜、织物和气凝胶的最新研究进展。方法 主要介绍纤维素基薄膜、织物和气凝胶等3类EMI屏蔽材料的制备方法、EMI屏蔽性能、多功能性和在包装上应用的潜力。结果 当下纤维素基EMI屏蔽材料表现出令人满意的EMI屏蔽效能(EMI Shielding Effectiveness, EMI SE)和力学性能,有望作为包装材料。同时一些材料还显示出抗菌、隔热、抗冲击等特性,使得这些材料能在复杂的场景下应用。结论 通过合理的设计,纤维素基EMI屏蔽材料可拥有优异的EMI屏蔽性能、出色的力学性能和良好的耐用性。归因于上述优势和绿色可降解的特性,这类材料有望在未来取代传统的EMI屏蔽包装材料,然而这些材料通常需要精细的制备工艺,材料的量产和实际应用依然是亟待解决的问题。     

二氧化硅气凝胶制备条件的选择

二氧化硅气凝胶是典型的纳米多孔轻质材料,由于具有独特的性能并在许多领域存在潜在的应用价值而受到广泛关注。本文从气凝胶制备过程中的硅源的选择、溶剂的选择、制备工艺的选择、催化剂等方面进行了研究,有利于确定常压干燥制备二氧化硅气凝胶的生产条件。     

Mn2O3/carbon aerogel microbead composites synthesized by in situ coating method for supercapacitors

A series of Mn₂O₃/carbon aerogel microbead (Mn₂O₃/CAMB) composites for supercapacitor electrodes have been synthesized by in situ encapsulation method. The structure and morphology of Mn₂O₃/CAMB are characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrum and scanning electron microscopy (SEM). Electrochemical performances of the synthesized composites are evaluated by cyclic voltammetry and galvanostatic charge/discharge measurement. All the composites with different Mn₂O₃ contents show higher specific capacitance than pure CAMB due to the pseudo-capacitance of the Mn₂O₃ particles dispersed on the surface of CAMB. The highest specific capacitance is up to 368.01 F g⁻¹ when 10 wt% Mn₂O₃ is coated on the surface of CAMB. Besides, 10%-Mn₂O₃/CAMB supercapacitor exhibits excellent cyclic stability, the specific capacitance still retains 90% of initial capacitance over 5000 cycles.     

Solar photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) using TiO2/SiO2 aerogel composite photocatalysts

Silica aerogels and TiO₂/silica aerogel composite photocatalysts were synthesized by sol–gel technique at ambient pressure using orthosilioate and tetra-n-butyl titanate as precursors, respectively. The prepared composite photocatalysts were characterized by XRD, TEM, BET surface area, FT-IR and UV–vis absorption spectra. The results showed that the TiO₂/silica aerogel composite photocatalysts possess high surface area. The addition of silica aerogels inhibited the grain growth and phase transformation of anatase to rutile during calcination. The TiO₂/silica aerogel composite sample calcined at 500 °C with an optimal silica aerogel content of 7 wt.% afforded the highest photocatalytic activity. The photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) was investigated by using this novel TiO₂/silica aerogel composite photocatalyst under solar light irradiation. The effects of irradiation time, pH, catalyst concentration, temperature and initial DNBP concentration were examined as operational parameters. The optimal operational parameters were found as follows: pH as solution pH 4.82, 8 g L⁻¹ catalyst concentration, 20 °C, and 240 min irradiation time. The kinetics of DNBP degradation by TiO₂/silica aerogel composite fit well a pseudo-first-order kinetic model. The repeatability of photocatalytic activity was also tested. This study showed the feasible and potential use of TiO₂/silica aerogel composite photocatalysts in degradation of toxic organic contaminants.     

Alcogel and aerogel of nitrocellulose formed in nitrocellulose/acetone/ethanol ternary system

Nitrocellulose (NC) alcogels were formed in NC/acetone/ethanol ternary system and NC aerogels were prepared from NC alcogels after drying under supercritical CO₂ (scCO2). NC alcogel with lower modulus was formed in the ternary system with a higher ethanol ratio. The densities and porosities of NC aerogels were related directly to the initial ethanol content. The NC aerogels clearly retained the crystalline structure of NC powder. NC aerogels that were formed in the system with higher ethanol content had larger pore size distribution range, larger average pore diameter, and larger mesopore and macropore volume. The thermal decomposition of NC aerogel was more accelerated and more acute compared with NC powders.     

Fluorinated γ-alumina aerogels and xerogels: characterisation and catalytic behaviour

The porosity of -alumina-based materials is an important parameter affecting the extent of fluorination (aerogels > commercial -Al₂O₃ > xerogels) and, consequently, also the textural, acidic and catalytic properties of the final fluorinated materials. Only the highly fiuorinated aluminas having strong Lewis acidic sites catalyse the isomerisation of CHF₂CHF₂ to CF₃CH₂F.     

干燥方法对木薯淀粉基碳气凝胶制备和吸附性能的影响

为研究干燥方法对淀粉基碳气凝胶的结构及吸附能力的影响,以木薯淀粉为碳源,采用常压干燥和冷冻干燥制备气凝胶,再将其高温碳化制备相应的碳气凝胶。利用红外光谱仪、X射线衍射仪、扫描电镜和全自动物理/化学吸附仪对所制备的淀粉基气凝胶和碳气凝胶进行表征,并考察了淀粉基碳气凝胶对阳离子染料的吸附能力。研究结果表明,2种干燥方法制备的淀粉基气凝胶化学结构与晶体结构基本相同,但采用冷冻干燥制备的淀粉基气凝胶（SA-FD）成孔数量更多,所对应的淀粉基碳气凝胶（SCA-FD）具有更大的比较面积（887.4 m2/g）、孔容积（0.444 cm3/g）和更强的阳离子染料吸附能力,与常压干燥法相比更具优势。     

硝化棉气凝胶的微结构及热分解特性

为研究硝化棉(NC)气凝胶的微结构及其与热性能的关系,用溶胶-凝胶法以及超临界干燥法制备了硝化棉气凝胶。用扫描电子显微镜(SEM)、X射线衍射(XRD)、热重-红外联用(TG-FTIR)表征了其微观结构、结晶性及热性能。结果表明:NC气凝胶的微观结构为纳米颗粒堆积成的纳米多孔结构。其结晶遭到破坏,呈非晶无序特征。与NC相比,NC气凝胶的DTG峰温及DSC放热峰温度分别提前7℃和11℃,分解热由1429.87 J·g-1提高至1689.21 J·g-1。