Cu/SiO2纳米复合气凝胶的制备与表征

采用含铜硅酸乙酯(CuTEOS)进行溶胶-凝胶反应来制备高Cu含量的Cu/SiO2纳米复合气凝胶,复合气凝胶中的Cu含量可在小于66%(质量分数)的范围内调节.研究了水量、催化剂浓度、溶剂量及含铜硅酸乙酯的组成对溶胶-凝胶过程的影响.本研究中Cu/SiO2纳米复合气凝胶中粒子粒径大部分小于25nm,其孔径小于50nm,比表面积在400～650m2/g范围内.     

SiO2/TiO2复合气凝胶的孔道结构研究

为了在常压干燥下制备高比表面积且具有多级孔道结构的SiO2/TiO2复合气凝胶,以正硅酸乙酯、钛酸丁酯为原料,利用低聚体聚合将分相平行引入到溶胶凝胶过程中,获得SiO2/TiO2醇凝胶,并通过溶剂替换技术实现气凝胶的常压干燥制备.不同硅钛比气凝胶的内部结构研究表明:合成的气凝胶是由纳米SiO2和TiO2颗粒分散复合而成的介孔块体,其中Ti—O—Ti、Si—O—Si和Ti—O—Si键相互交织.气凝胶的结构变化是分相与溶胶凝胶过程相互竞争的结果.Si含量能显著改善气凝胶的结构,当n(Ti)∶n(Si)为3∶1时,比表面积高达712.2 m2/g,平均孔径为3.36 nm;当n(Ti)∶n(Si)为1.5∶1时,复合气凝胶具有明显双连续孔道,比表面积高,同时孔状结构清晰.     

SiO2气凝胶/壳聚糖复合药物载体材料的制备和表征

采用常压干燥法制备了SiO2气凝胶,所得气凝胶为介孔结构,比表面积618.8m2/g,孔径分布5～20nm.以SiO2气凝胶为原料,通过静电吸附法制备了SiO2气凝胶/壳聚糖复合药物载体材料,采用扫描电镜(SEM)、红外光谱(FTIR)等对复合材料的结构形貌进行了分析,研究了复合材料对硫酸庆大霉素药物的担载和释放性能.结果表明,所得SiO2气凝胶/壳聚糖复合材料为多孔网络结构,其中,由450℃处理的SiO2气凝胶制得的气凝胶/壳聚糖复合材料对硫酸庆大霉素具有较好的药物担载和缓释性能.     

掺杂六钛酸钾晶须SiO_2气凝胶复合材料的研究

以正硅酸四乙酯(TEOS)为硅源,在溶胶-凝胶过程中添加六钛酸钾晶须制备SiO2复合凝胶,通过表面改性和超临界CO2干燥技术获得了大块无裂纹的SiO2气凝胶复合材料。由分析可知,SiO2溶胶的凝胶时间与溶胶体系酸碱性有密切关系,而掺杂不同含量的六钛酸钾晶须对凝胶时间无显著影响;用红外光谱(FT-IR)、BET技术等进一步对其表征,结果表明,制备的样品密度范围为0.20g/cm3~0.29g/cm3,经过疏水改性后,气凝胶表面存在大量憎水基团。BET检测显示,SiO2气凝胶复合材料比表面积达到700m2/g以上,平均孔径为18nm左右,是一种轻质纳米多孔材料。     

聚酰亚胺/SiO_2纳米复合抗原子氧气凝胶的合成与性能

以3,3′,4,4′-联苯四酸二酐(sBPDA)和2,2′-二甲基-4,4′-二氨基联苯胺(DMBZ)为聚合单体,八(氨基苯基)聚倍半硅氧烷(OAPS)为交联剂,SiO2纳米粒子为填料,采用超临界二氧化碳干燥工艺制备了一系列聚酰亚胺(PI)/SiO2纳米复合气凝胶(CPIA-SiO2-0~CPIA-SiO2-7)。研究表明:SiO2纳米粒子的引入对PI气凝胶的耐热性能未产生显著的影响。然而,随着SiO2纳米粒子含量的增加,PI气凝胶的孔隙率从89.6%逐渐降低至79.4%,BET表面积也随之从425.5m2/g降低至380.2m2/g,纳米泡孔孔径分布呈现出变宽的趋势。SiO2的引入显著提高了PI气凝胶的抗原子氧侵蚀能力,含量为7%(质量分数,下同)的PI/SiO2复合气凝胶CPIA-SiO2-7的原子氧侵蚀率(2.6%)仅为不含SiO2气凝胶CPIA-SiO2-0的原子氧侵蚀率(12.3%)的1/5左右。     

CoO/MgO气凝胶催化剂合成单壁纳米碳管

以Co(NO)3·6H2O和Mg(NO)3·6H2O为催化剂前驱体,采用溶胶凝胶和超临界干燥法制备了CoO/MgO气凝胶。用XRD、EDS和TEM对气凝胶的组成和微观结构进行了表征,并通过BET法计算其比表面积和孔体积分别为243 9m2/g和0 7245cm3/g。利用CoO/MgO气凝胶作为催化剂合成单壁纳米碳管,采用TEM、HRTEM、Raman对产物形貌和结构进行了表征,结果表明:产物主要是由高质量单壁纳米碳管组成。     

SiO2-TiO2复合气凝胶制备研究

采用同步溶胶凝胶方法,制备了TiO2分布均匀的SiO2-TiO2复合气凝胶.研究了SiO2溶胶预反应时间、不同催化剂和螯合剂对复合溶胶凝胶过程的影响,并用BET、SEM和XRD等测试方法对其结构进行了表征;复合SiO2-TiO2气凝胶具有典型的气凝胶特征,其比表面积为483.35m2/g,密度在0.1～0.12g/cm3范围内.     

超级电容器MnO2/CRF复合电极材料的制备及性能的研究

以间苯二酚(R)和甲醛(F)为原料,碳酸钠(C)为催化剂,制备碳气凝胶(CRF),并以KMnO4和Mn(CH3COO)2·4H2O为原料,采用了化学沉淀法制备MnO2/CRF复合材料.用N2吸附、X射线衍射(XRD)和扫描电镜(SEM)对所制备的MnO2、CRF和MnO2/CRF复合材料进行了表征,结果表明碳气凝胶具有珍珠串式的无序多孔网络结构,所制备的MnO2为纳米级颗粒,复合材料为纳米级粉体.并对不同配比的MnO2/CRF复合材料的电化学性能进行了研究.循环伏安、恒流充放电实验表明了所制备的MnO2/CRF复合电极材料具有良好的可逆性和充放电性能.当MnO2含量为60%时,MnO2与碳气凝胶复合制成的新型电极材料具有226.3F/g的比电容,比碳气凝胶电极的比电容提高了1倍.此外,对复合电极的循环寿命进行了研究,表明复合电极具有良好的循环充放电性能.     

纳米孔隔热材料——SiO_2气凝胶的表面改性及其表征

采用溶胶-凝胶法制备SiO2气凝胶,以三甲基氯硅烷/环己烷、二甲基二氯硅烷/环己烷体系为化学表面修饰剂,通过衍生法制备了疏水性SiO2气凝胶.利用气质联用对表面改性过程中发生的反应进行了剖析;并利用扫描电镜、红外光谱、比表面测定等测试方法对2种改性方法所获得的SiO2气凝胶的结构、形貌及性能组成进行了比较.研究表明,2种改性方法均可获得连续网络结构、多孔纳米材料.所得SiO2气凝胶的比袁面积分别为652m2/g和656m2/g,主要孔径尺寸为2～10nm.样品表面连有疏水基团,呈现明显的疏水性.     

SiO2气凝胶增强增韧方法研究进展

SiO2气凝胶的轻质纳米多孔网络结构使其在热学、声学、光学及电学等领域具有广阔的应用前景,但强度低和韧性差的缺点很大程度上限制了其应用发展.分析了SiO2气凝胶的主要力学性能指标和提高其强度的两种途径(控制制备工艺参数与材料复合法),讨论了这两种增强途径的最新研究进展.通过控制制备工艺参数获得结构均匀的SiO2气凝胶,并采用材料复合技术进一步提高SiO2气凝胶的强韧性能,可望获得结构稳定并具有良好强韧性的SiO2气凝胶材料.     

SiO2/M纳米复合材料的结构及催化性能

采用溶胶-凝胶法和超临界干燥法制备了SiO2/M(Cu,Co)纳米复合材料,对其结构、形貌进行了TEM和比表面分析,并研究了SiO2/M纳米复合材料的催化性能.结果表明,制得的SiO2/M纳米复合材料保留了SiO2气凝胶的纳米网络和高比表面积,金属组份Cu与Co均匀地分散在纳米级SiO2气凝胶骨架中,对CO的氧化反应以及CO-NO反应均表现出高的催化活性.     

疏水SiO_2气凝胶的常压制备及应用进展

阐述了常压制备疏水SiO2气凝胶的关键技术,综述了表面后处理法、原位法等常压制备疏水SiO2气凝胶的工艺措施,介绍了疏水SiO2气凝胶在电磁学、光学、原子核物理等领域的应用现状,指出疏水处理可明显提高SiO2气凝胶的性能(低介电常数、高激光损伤阈值和耐环境能力等),从而拓宽了SiO2气凝胶的应用范围,最后展望了疏水SiO2气凝胶的发展和应用前景。     

In situ generation of well-dispersed ZnO quantum dots on electrospun silica nanotubes with high photocatalytic activity

The ZnO quantum dots-SiO(2) nanotubes (ZQDs-SNTs) nanocomposite was successfully fabricated by direct heat treatment of the electrospun zinc acetate/tetraethyl orthosilicate (TEOS)/polymer nanotubes (NTs). The results indicated that the ZnO quantum dots (ZQDs) with diameter about 3-5 nm were highly dispersed on the SiO(2) nanotubes (SNTs). And, there might be Zn-O-Si bonds between ZQDs and SiO(2) matrix, which formed interface states in the ZQDs-SNTs nanocomposite. The photocatalytic studies revealed that the ZQDs-SNTs nanocomposite exhibited high photocatalytic activity to degrade Rhodamine B (RB) under ultraviolet (UV) light irradiation, which might be ascribed to two reasons. The first one was the high dispersity of ZQDs; another one was the high separation efficiency of photogenerated electron-hole pairs due to the trap effect for photogenerated electrons of the interface states between ZQDs and SiO(2). During the photocatalytic reaction, the ZQDs-SNTs nanocomposite also exhibited high chemical stability in a wide range of pH values, which might be ascribed to the protective action of SiO(2) and the presence of Zn-O-Si bonds between ZQDs and SiO(2). Furthermore, the ZQDs-SNTs nanocomposites could be easily recycled because of their one-dimensional nanostructure property.     

工业水玻璃制备疏水性SiO2气凝胶

以工业水玻璃为硅源,稀H2SO4为催化剂,三甲基氯硅烷(TMCS)为表面改性剂,无水乙醇和正己烷为溶剂,在常温常压下通过"两步法"成功地制备出轻质疏水性SiO2气凝胶。通过BET、FTIR、接触角测试以及SEM、EDS和TG等手段证实,所得SiO2气凝胶的比表面积为512.44~737.19m2/g,平均孔径为15.19~19.09nm,且凝胶表面-OH基团已被-OSiCH3取代,接触角高达137°,呈现出明显的疏水性和良好的热稳定性。     

Poly(vinyl alcohol)/silica nanocomposites: morphology and thermal degradation kinetics

The morphology of self-assembled poly(vinyl alcohol)/silica (PVA/SiO2) nanocomposites is investigated with atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the SiO2 nanoparticles are homogenously distributed throughout the PVA matrix in a form of spherical nano-cluster. The average size of the SiO2 clusters is below 50 nm at the low contents (SiO2 < or =5 5 wt%), while particle aggregations are clearly observed and their average size markedly increases to 110 nm when 10 wt% SiO2 is loaded. The thermogravimetric analysis (TGA) shows that the nanocomposite significantly outperforms the pure PVA in the thermal resistance. By using a multi-heating-rate method, the thermal degradation kinetics of the nanocomposite with a SiO2 content of 5 wt% is compared to the PVA host. The reaction activation energy (E) of the nanocomposite, similar to the pure PVA, is divided into two main stages corresponding to two degradation steps. However, at a given degradation temperature, the nanocomposite presents much lower reaction velocity constants (k), while its E is 20 kJ/mol higher than that of the PVA host.     

热处理温度对TiO2/SiO2复合气凝胶光催化性能的影响

采用溶胶–凝胶法在常压下经不同温度热处理制备了TiO2/SiO2复合气凝胶光催化剂,利用XRD、TGA和BET等手段对其微观结构进行表征,以甲基橙溶液光催化降解实验评价其光催化性能,研究了热处理温度对TiO2/SiO2复合气凝胶的微观结构及光催化性能影响规律.结果表明:随着热处理温度升高,TiO2/SiO2复合气凝胶中锐钛矿结晶度升高,晶粒尺寸增大,比表面积减小,使TiO2/SiO2复合气凝胶对甲基橙溶液的光催化降解活性呈现先升后降的变化趋势.当热处理温度为700℃左右,紫外光照20 min TiO2/SiO2复合气凝胶对甲基橙溶液的降解率达到95.4%.     

Interfacial Engineering of Hierarchical Transition Metal Oxide Heterostructures for Highly Sensitive Sensing of Hydrogen Peroxide

Hydrogen peroxide (H₂O₂) is a major messenger molecule in cellular signal transduction. Direct detection of H₂O₂ in complex environments provides the capability to illuminate its various biological functions. With this in mind, a novel electrochemical approach is here proposed by integrating a series of CoO nanostructures on CuO backbone at electrode interfaces. High‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction, and X‐ray photoelectron spectroscopy demonstrate successful formation of core–shell CuO–CoO hetero‐nanostructures. Theoretical calculations further confirm energy‐favorable adsorption of H₂O₂ on surface sites of CuO–CoO heterostructures. Contributing to the efficient electron transfer path and enhanced capture of H₂O₂ in the unique leaf‐like CuO–CoO hierarchical 3D interface, an optimal biosensor‐based CuO–CoO‐2.5 h electrode exhibits an ultrahigh sensitivity (6349 µA m m ^?1 cm^?2), excellent selectivity, and a wide detection range for H₂O₂, and is capable of monitoring endogenous H₂O₂ derived from human lung carcinoma cells A549. The synergistic effects for enhanced H₂O₂ adsorption in integrated CuO–CoO nanostructures and performance of the sensor suggest a potential for exploring pathological and physiological roles of reactive oxygen species like H₂O₂ in biological systems.     

Synthesis and magnetic properties of FePt nanoparticles with hard nonmagnetic shells

Chemically synthesized FePt nanoparticles were coated with nonmagnetic SiO2 and MnO shells by sol-gel and polyol processes. TEM images show that the FePt/SiO2 nanoparticles exhibit a thick spherical shell. The size and morphology of the MnO shell can be controlled by changing the reaction temperature, the molar ratio of surfactants/Mn(acac)2, and/or the concentration of precursor. The morphology of the MnO shell can be either spherical-like or cubic-like, depending on whether the molar ratio of surfactants/Mn(acac)2 is less than or larger than 2. From XRD measurements, the spherical core/shell nanoparticles exhibit 3D random crystallographic orientation, while the cubic core/shell nanoparticles prefer (200) texture. The magnetic moment of FePt particles can be enhanced by coating with SiO2 and MnO shells. Furthermore, the agglomeration of FePt particles upon the thermal annealing can be significantly inhibited with SiO2 and MnO shells.