环氧氯丙烷引发的氧化钽气凝胶表征(英文)

介绍了一种以环氧氯丙烷为凝胶促进剂,乙醇为溶剂的块状氧化钽气凝胶的合成工艺及气凝胶样品表征。氧化钽气凝胶的微观显微结构分别由场发射扫描电子显微镜(FESEM),高分辨透射电镜(HRTEM)给出,其孔结构及其分布由等温N2吸附实验给出。结果表明,气凝胶的骨架主要由粒径约1.5nm的初级颗粒构成,等温吸附结构表明,气凝胶主要是由微孔和中孔构成的BET比表面积为835m2/g气凝胶样品。     

稻壳灰制备掺杂TiO2硅气凝胶研究

以稻壳为硅源制备SiO2气凝胶，在溶胶凝胶过程中加入TiO2纳米粉末，可制得掺杂TiO2硅气凝胶。通过SEM、BET吸附．脱附测试等手段，与同种方法制得的纯SiO2气凝胶在结构和物性特征方面等进行了比较。结果显示，掺杂TiO2气凝胶的平均颗粒直径为50nm左右，而纯SiO2气凝胶的粒径约为20nm，且孔洞直径明显减小、孔径分布更为均匀；此外，TiO2纳米粉末的加入可以使气凝胶的弹性模量提高约23％，并且通过TiO2对气凝胶溶胶-凝胶过程的影响研究了其影响机理。     

Bi_(3.15)Nd_(0.85)Ti_3O_(12)纳米管阵列的制备与微结构表征

采用溶胶凝胶法,在孔径为200 nm的阳极氧化铝模板中制备了Bi_3.15Nd_0.85Ti_3O_(12)纳米管阵列.通过XRD、SEM、TEM、HRTEM、SAED和Raman光谱测试手段对纳米管阵列的物相、微结构和声子振动特性进行了表征.研究表明,所合成BNdT纳米管为钙钛矿相多晶结构,纳米管外径约为200 nm,管壁厚约10 nm,管径和长度与所用AAO模板尺寸一致.Raman光谱分析表明,Nd离子取代了类钙钛矿层中A位的Bi离子.     

SiO_2气凝胶的凝胶化过程理论研究（英文）

将理论研究的凝胶点pH值、颗粒尺寸、较高的孔隙率等参数与实验参数直接对应,对于凝聚结构的研究来说是一件有巨大挑战性的课题。但是分形模拟可以用一个幂律指数来处理粒子尺度的分布和气凝胶凝胶时的自相似性质。在凝胶过程中,胶体颗粒在高分子溶液骨架中的凝聚具有分形的特性。所以,研究SiO_2气凝胶的胶粒生长过程和内部结构的分形特性对于研究高分子骨架的形成过程具有很重要的意义。本文采用有限扩散集团凝聚模型(DLCA)模拟气凝胶的凝聚过程。所得结果也得到了讨论。     

RuO260%-TiO240%纳米材料的制备与表征

Ru Ti氧化物是电化学工业中常用的阳极材料之一 ,通常是采用热分解法制备。我们采用溶胶凝胶工艺制备纳米级RuO2 60 % TiO2 4 0 %氧化物材料 ,并对其组织结构特点进行分析。研究表明采用溶胶凝胶工艺获得了金红石型Ru Ti氧化物烧结体 ,未出现金属钌和锐钛矿等副反应产物。所制备的氧化物纳米晶在 4 80℃烧结后 ,其尺寸为 3～ 6nm ;在 60 0℃烧结后 ,尺寸约为 10～2 0nm ;80 0℃烧结后 ,晶粒尺寸约为 30～ 60nm ,大颗粒呈典型的柱状形态     

小角X光散射法测定疏水二氧化硅气凝胶疏水层厚度

采用小角X光散射(SAXS)研究了疏水SiO2气凝胶X光散射特性.运用Porod方法、Shull-Roess平均粒径法研究了气凝胶疏水层厚度.计算结果表明气凝胶疏水层厚度在0.2～0.3mm之间,说明气凝胶的疏水层仅仅是由一层改性剂分子所组成,其凝胶骨架颗粒表面被疏水的甲基基团所覆盖.     

Sn(OBun)4溶胶-凝胶法制备SnO2气凝胶

以锡酸正丁酯(Sn(OBun)4)为前驱体,利用溶胶-凝胶工艺和CO2超临界干燥技术制备了透明和半透明的单块SnO2气凝胶.这些二氧化锡气凝胶密度小,孔隙分布宽,比表面积高.SEM分析表明,这种气凝胶由尺寸不一的如棉花团一样的团块堆积而成,团块之间为大尺寸孔隙(＞50 nm),棉花团块内还具有细小的微孔(＜2 nm)和介孔(＜50 nm).TEM分析表明,在不同的放大倍数下,二氧化锡气凝胶具有相似的结构.     

聚甲基硅倍半氧烷气凝胶的制备及相分离控制研究

以甲基三甲氧基硅烷(methyltrimethoxysilane, MTMS)为先驱体、二甲基亚砜(dimethylsulfoxide, DMSO)为溶剂,采用溶胶—凝胶法和超临界干燥技术制备了聚甲基硅倍半氧烷(polymethylsilsesquioxane, PMSQ)气凝胶。通过改变碱性催化剂氨水和DMSO的相对含量用量,获得了PMSQ凝胶时间的变化规律。PMSQ气凝胶具有典型的纳米多孔结构。凝胶时间随氨水用量的增加而缩短,随DMSO用量的增加而延长。DMSO含量越多,溶胶粘度变化越缓慢;氨水含量越多,粘度变化越快。不可水解基团–CH₃的存在将引起短链或环状Si–O–Si结构,造成颗粒团聚,产生沉淀,引起相分离。控制凝胶时间与相分离时间的关系,可获得均匀凝胶。     

不同晶粒尺寸的(La0.47Gd0.2)Sr0.33MnO3纳米颗粒磁性能

采用非晶态多核配合的方法制备了(La0.47Gd0.2)Sr0.33MnO3纳米颗粒,用XRD、HRTEM和MPMS等手段对纳米颗粒的微观结构和磁性能进行研究。XRD和SAD分析表明,所有的样品都具有单相钙钛矿结构;TEM分析表明, 经过600,800和1000 ℃烧结10 h后的样品颗粒尺寸分别为40~50 nm,90~100 nm和140~150 nm。样品的磁学性能结果表明：(La0.47Gd0.2)Sr0.33MnO3纳米颗粒的居里温度TC (298 K)基本上不随颗粒尺寸的变化而变化,而相对磁制冷能力取决于颗粒尺寸;颗粒尺寸为90~100 nm的(La0.47Gd0.2)Sr0.33MnO3纳米颗粒的相对磁制冷能力最大,可以作为室温下使用的磁制冷工质侯选材料。     

铂纳米颗粒形貌控制研究进展

铂作为催化剂在光化学催化、燃料电池和工业生产等方面有重要的应用,通过控制纳米颗粒的尺寸和形貌可以降低铂用量的同时提高其催化性能。本文对晶体成核与生长的相关理论和利用无机分子或有机分子控制合成特定形貌铂纳米颗粒的研究进行了总结。     

Controllable fabrication of carbon aerogels

Nano-pore carbon aerogels were prepared by the sol-gel polymerization of resorcinol (1,3-dihydroxybenzene)(C6H4(OH)2) with formaldehyde (HCHO) in a slightly basic aqueous solution, followed by super-critical drying under liquid carbon dioxide as super-critical media and carbonization at 700 ℃ under N2 gas atmosphere. The key of the work is to fabricate carbon aerogels with controllable nano-pore structure, which means extremely high surface area and sharp pore size distribution. Aiming to investigate the effects of preparation conditions on the gelation process, the bulk density, and the physical and chemical structure of the resultant carbon aerogels, the molar ratio of R/C (resorcinol to catalyst) and the amount of distilled water were varied, consequently two different sets of samples, with series of R/C ratio and RF/W (Resorcinol-Formaldehyde to water, or the content of reactant) ratio, were prepared. The result of N2 adsorption/desorption experiment at 77 K shows that the pore sizes decreasing from 11.4 down tO2.2 nm with the increasing of the molar ratio of R/C from 100 to 400, and/or, the pore sizes decreasing from 3.8 down to 1.6 nm with the increasing of reactant content from 0.4 to 0.6.     

Carbon aerogels for electric double-layer capacitors

In this study, carbon aerogels were derived via the pyrolysis of resorcinol-formaldehyde (RF) aerogels, which were cost-effectively manufactured from RF wet gels by an ambient drying technique instead of conventional supercritical drying. By varying the R/C ratio (molar ratio of resorcinol to catalyst), mesoporous carbon aerogels with high specific surface area were prepared successfully and further investigated as electrode materials for electric double-layer capacitors (EDLCs). The textural properties of carbon aerogels obtained were characterized by nitrogen adsorption/desorption analysis and SEM. The electrochemical performances of carbon aerogels were investigated by impedance spectroscopy, galvanostatic charge/discharge and cyclic voltammetry methods. The results show that BET surface area and specific capacitance increase with R/C ratio, the maximum values of 727 m2·g-1 and 132 F·g-1 are achieved at R/C ratio will of 300. Increasing R/C ratio increase the average pore size of carbon aerogel electrode, which has improved the rate capability. Furthermore, EDLC with carbon aerogel electrodes has an excellent stability at large discharge current and long cycle life.     

Effect of dehydration on porous structure of monolithic aerogels based on fibrous aluminum oxyhydroxide

Aluminum oxide monolithic aerogels (PMAOs) with specific surfaces of up to 400 m²/g and densities of up to 0.004 g/cm³ were obtained by the direct oxidation of metallic aluminum by water vapors. Studies of the obtained aerogels using the methods of scanning and transmission electron microscopy showed that a freshly prepared aerogel represents the amorphous structure from alumina fibrous with a diameter of about 5 nm. Parameters of a porous aerogel structure were determined from the isotherms of adsorption of nitrogen vapors at 77 K. It is shown that the specific surface area decreases by 50% upon the dehydration of aerogel by temperature pretreatment at 900°C until the phase transition temperature is reached. At the same time, heat treatment at temperatures above 1200°C results in a phase transition at which significant contraction of structure occurs and the specific surface area decreases to 20 m²/g. The number of primary adsorption centers was obtained from comparative plots of water vapor adsorption. It was found that preliminary dehydration only slightly affects the number of primary centers of water adsorption.     

Preparation and characterization of CuO-CoO-MnO/SiO2 nanocomposite aerogels as catalyst carriers

CuO-CoO-MnO/SiO₂ nanocomposite aerogels were prepared by using tetraethyl orthosilicate (TEOS) as Si source, and aqueous solution of Cu, Co and Mn acetates as the precursors via sol-gel process and ethanol supercritical drying technique. The gelatination mechanism was investigated by nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The microstructure and composition of the CuO-CoO-MnO/SiO₂ nanocomposite aerogels were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron dispersive spectroscopy (EDS) and XPS. The specific surface area, pore size and pore size distribution of the nanocomposite aerogels were determined by the Brunauer-Emmett-Teller (BET) method. The products were analyzed by gas chromatography (GC). The results show that the CuO-CoO-MnO/SiO₂ nanocomposite aerogels are porous, with a particle size distribution of 10–150 nm, a pore size distribution of 2–16 nm, an average pore size of 7.68 nm, and a specific surface area of 664.4–695.8 m²/g. The molar fraction of transition metals in the nanocomposite aerogels is 0.71%-13.77%. This kind of structure is favorable not only to increase the loading of catalysts, but also to make full use of the effect of transition metal oxides as cocatalysts; CuO-CoO-MnO/SiO₂ nanocomposite aerogels can be used as a novel catalyst carrier in the safer and environment-friendly synthesis of diphenyl carbonate and other fields of catalysis.     

Equilibrium adsorption of stilbenoids at metal oxides

The isotherms of adsorption of trans-hydroxystilbenes (stilbenoids) and hydroxybenzenes (phenols) from n-hexane-ethyl acetate (1: 1) at nanodispersed aerogels of aluminum and titanium oxides were measured under static conditions. The adsorption isotherms can be approximated well by the Freundlich equation for the model of localized adsorption at energetically heterogeneous solids. It was found that the adsorption value of both stilbenoids and phenols is improved with an increase in the number of OH groups in their molecules, being sensitive to the chemistry of the adsorbent surface. trans-Hydroxystilbenes adsorb at TiO₂ better than do the corresponding phenols. The opposite pattern was observed for Al₂ O₃. The adsorption of trans-hydroxystilbenes at TiO₂ is irreversible and accompanied by the formation of colored surface compounds.     

碳纳米管掺杂SiO2气凝胶隔热材料的制备与性能表征

以正硅酸乙酯（TEOS）和碳纳米管（CNTs）为原料，采用溶胶-凝胶法和常压干燥法制备不同碳纳米管（CNTs）含量的SiO2气凝胶隔热材料。采用DET、SEM、XRD等测试方法考察了添加CNTs对SiO2气凝胶比表面积、孔结构特征和密度的影响。结果表明：添加CNTs不仅能够增强SiO2气凝胶的强度，而且能够在很大程度上提高气凝胶的比表面积，使孔结构分布更加均匀。     

醇醚基双咪唑啉缓蚀剂的性能及机理研究

目的模拟CO_2强采工艺,研究醇醚基双咪唑啉缓蚀剂DIM-OE的缓蚀性能及机理,解决CO_2对整个注采及地面集输系统的低碳钢设备的腐蚀问题。方法采用傅里叶红外光谱仪对醇醚基双咪唑啉进行了分子结构表征,采用动态挂片法评价了DIM-OE在不同CO_2分压、不同温度、不同质量浓度下对N80的缓蚀性能,采用动电位极化曲线研究了DIM-OE的电化学机理,采用扫描电镜和EDS分析了N80腐蚀后的表面形貌和元素含量。结果随CO_2分压的增加,N80的腐蚀速率显著增大。N80的腐蚀速率随腐蚀介质温度的升高先是增大,后又明显下降。随着DIM-OE质量浓度的增加,腐蚀速率逐渐减小,缓蚀率逐渐增大,最终均趋于稳定,腐蚀速率最小为0.063 mm/a,缓蚀率均达到90%以上。DIM-OE为抑制阳极为主的混合型缓蚀剂,其分子在N80表面的吸附为单分子层吸附,是物理吸附和化学吸附的共同作用。未加DIM-OE的N80表面腐蚀产物中的C、O元素质量分数较高,Fe元素的质量分数较低,腐蚀严重;加有200mg/LDIM-OE的N80表面腐蚀产物中的C、O元素质量分数较低,Fe元素的质量分数较高,腐蚀较轻。结论在CO_2强采工艺条件下,DIM-OE缓蚀剂分子在N80表面可形成稳定的吸附层,有效地抑制CO_2对N80钢片的腐蚀,具有较好的缓蚀作用。     

N杂化石墨烯气凝胶制备反应过程研究

以含有氨基的试剂还原氧化石墨烯分散液可以制备含N的石墨烯气凝胶,这种气凝胶应用十分广泛。本文以对苯二胺为还原剂和功能化试剂制备了N杂化石墨烯气凝胶,研究了其制备反应过程。由于羰基的强吸电子效应,对苯二胺上的氨基首先与羧基上的羟基发生反应。之后氨基与醚键发生反应,这一反应不仅向氧化石墨烯上引入了吡咯N,而且改变了其层间距。反应过程很好地解释了N杂化石墨烯气凝胶制备过程中的组成和结构变化,加深了对其制备反应过程的理解,有助于其组成和结构的优化。同时这些发现也有助于理解其它氨基试剂还原制备石墨烯气凝胶的反应过程。     

铂铱合金与316L不锈钢微激光点焊气孔形成机理

采用第一性原理方法研究了H2分子在Li2NH (110) 晶面的表面吸附。通过研究Li2NH (110)/H2体系的吸附位置、吸附能和电子结构,发现H2分子吸附在Li长桥位时会发生解离,并在Li2NH (110) 面形成NH2基,其吸附能为1.178 eV,属于强化学吸附,吸附最稳定。此时,NH2基中的H原子与Li2NH表面的相互作用主要源于H 1s轨道与Li2NH表层N原子的2s,2p轨道重叠杂化的贡献,且N–H键为共价键;另一个H原子与Li2NH表面的相互作用主要是与Li之间的离子键作用;H2分子的解离能垒为1.31 eV,表明在一定热激活条件下H2分子在Li2NH (110)表面发生解离吸附。N顶位吸附时,优化结束后形成NH3,但该吸附方式不稳定,可见Li2NH (110)面与H2反应不易直接生成NH3。