疏水改性对SiO2气凝胶薄膜性能与结构的影响

以正硅酸乙酯(TEOS)为前驱体,采用溶胶-凝胶法制备SiO2气凝胶薄膜,并以不同体积分数的六甲基二硅胺烷(HMDZ)对SiO2气凝胶薄膜进行了疏水改性研究,采用椭偏仪、FITR、接触角测试仪、SEM和光谱仪等对薄膜的疏水性、微观结构及透光性进行了表征,研究了HMDZ疏水改性对SiO2气凝胶薄膜性能与结构的影响。结果表明,疏水改性后,SiO2胶粒表面的大部分亲水性-OH被疏水基团-CH3所取代,其与水的接触角达159°,疏水性好;SiO2气凝胶薄膜在可见光范围内透光率接近90%,透光性高;其孔隙率为78.8%,密度为0.464g/cm3,骨架颗粒尺寸小于40nm,具有纳米多孔网络结构特性。     

疏水SiO2气凝胶的制备及表征

以聚二乙氧基硅氧烷(PDEOS)为原料,通过六甲基二硅氮烷(HMDZ)改性剂对制备的凝胶进行表面改性,并常压干燥得到疏水的SiO2气凝胶.研究了改性剂用量对气凝胶疏水性和结构的影响.疏水气凝胶与水的接触角达120°,常压干燥制备的气凝胶具有典型的气凝胶结构特征,气凝胶颗粒尺寸＜100nm,密度和比表面积分别在140～255kg/m3和480～605m2/g范围内.     

SiO2气凝胶的疏水性改性研究

采用三甲基氯硅烷（TMCS）对硅溶胶制备的湿SiO2气凝胶进行表面疏水改性处理,研究了TMCS与孔洞中水的摩尔比对气凝胶的疏水改性作用与性能,用红外光谱法检测了疏水性改性的SiO2气凝胶,发现气凝胶表面的-OH被-OR基团取代,以此构建SiO2气凝胶的疏水性改性机理及模型,试验结果表明,TMCS与孔洞中水的摩尔比控制在0．35左右时可获得不开裂、完好的、具有憎水性特征的二氧化硅气凝胶。     

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。     

基于仿生机理的超疏水有机无机复合膜的制备

采用溶胶-凝胶法制备了粒径分布窄、单分散性好的SiO2颗粒,并用低表面能硅烷偶联剂对其进行改性.改性后的SiO2粒子与聚偏氟乙烯(PVDF)按一定的质量比共混,利用相转化法制备了有机无机复合微孔膜.分析了偶联剂种类及SiO2粒径对微孔膜疏水性的影响,探讨了微孔膜表面能对其疏水性能的影响,并对复合膜的微观形貌进行了表征.研究结果表明:硅烷偶联剂可以有效阻止SiO2溶胶的凝胶作用,降低SiO2的表面能,而表面能对膜的疏水性有显著的影响;制备的复合微孔膜具有良好的有机-无机双微观阶层结构,疏水角达到了151°.     

实验条件对SiO2-MTES-CTAB纳米疏水薄膜的影响

以正硅酸乙酯(TEOS)为硅源,采用溶胶-凝胶技术,通过两步酸法控制实验条件引入有机硅烷甲基三乙氧基硅烷(MTES)和表面活性剂十六烷基三甲基溴化氨(CTAB),制备了疏水型SiO2前驱体溶胶.以旋涂法成膜出SiO2-MTES-CTAB纳米疏水薄膜,研究了正硅酸乙酯与甲基三乙氧基硅烷不同的混合比以及不同的热处理温度等对纳米疏水薄膜的影响,并且分析了纳米疏水薄膜的表面形态.研究表明,利用有机基团甲基三乙氧基硅烷改性SiO2溶胶和薄膜的热处理温度对制备的SiO2基纳米疏水薄膜的性能以及表面形态都具有非常重要的影响.     

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.     

Al2O3-SiO2纳米复合薄膜的制备及性能研究

以正硅酸乙酯、异丙醇铝为先驱体,甲基三乙氧基硅烷为有机硅烷,采用溶胶-凝胶旋涂方法在普通玻璃和硅片表面镀制纳米复合薄膜.通过FT-IR、VIS透射光谱的分析及薄膜表面接触角的测量,研究了Al2 O3与SiO2配比和热处理温度对复合薄膜的化学结构、透光率及疏水性的影响.结果表明该薄膜具有疏水、致密、透明等性能;Al2 O3的加入未降低复合薄膜的可见光透光率,其中经400℃热处理后不同配比复合薄膜在可见光区的透光率均大于85%,且不影响复合薄膜的疏水性.     

大块SiO_2气凝胶的制备及疏水性能的研究

以廉价工业水玻璃为原料,乙二醇为干燥控制化学添加剂,三甲基氯硅烷为表面改性剂,醋酸为催化剂,通过溶胶凝胶法和常压干燥技术制备出SiO2气凝胶。采用XRD、SEM和FT-IR等方法研究了醋酸浓度对SiO2气凝胶结构的影响,以及表面改性对其疏水性能的影响。结果表明:SiO2气凝胶为典型的无定型非晶态,呈现疏松多孔三维网络纳米结构。采用浓度为1.2mol/L的醋酸进行催化时,得到大块不开裂SiO2气凝胶,其表观密度为0.22g/cm3,孔隙率高达90%。当用三甲基氯硅烷对气凝胶表面进行疏水处理后,凝胶骨架表面接上了硅甲基,表现出较好的疏水性。     

SiO2气凝胶表面特性对其吸附性能的影响

以多聚硅E-40为硅源,采用溶胶-凝胶方法,通过常压干燥、表面修饰、450℃热处理等工艺制备了具有不同表面特性的SiO2气凝胶.用扫描电镜SEM,13C,29Si NMR谱以及孔径分布仪对其结构进行了表征,并对其吸附特性进行了研究.结果表明:在不同制备条件下,SiO2气凝胶的表面亲、疏水特性差异非常大,比表面积、孔体积、孔径以及对有机物吸附量的变化也很大.SiO2气凝胶具有纳米多孔结构,较好的疏水、亲水特性可调性,很强的吸附能力,具有广阔的应用前景.     

纳米多孔SiO2薄膜疏水性的研究进展

超低介电常数纳米多孔SiO2薄膜在未来超大规模集成电路(ULSI)中有着广阔的应用前景,但其疏水性能的好坏是决定其能否在ULSI中应用的重要因素之一.介绍了国内外有关纳米多孔SiO2薄膜疏水性的原理、工艺以及表征方法.     

聚乙二醇对纳米多孔二氧化硅薄膜性能的影响

以聚乙二醇(PEG)为添加剂,正硅酸乙酯(TEOS)为先驱体,采用溶胶-凝胶法、结合 旋转涂胶和超临界干燥等工艺在硅片上制备了纳米多孔SiO₂薄膜.利用FTIR、TG-DTA、 AFM和椭偏仪研究了该SiO₂薄膜的性能.与未加.PEG的SiO₂薄膜相比,加入PEG得到 的SiO₂薄膜表面粗糙度增大,但孔隙率较高,介电常数可降至2.0以下.PEG参与并修饰了 TEOS的溶胶-凝胶过程.加入PEG制备的SiO₂薄膜因含有Si-OH基团而呈亲水性,该薄 膜经三甲基氯硅烷(TMCS)修饰后为疏水性.     

A scratch-resistant and hydrophobic broadband antireflective coating by sol-gel method

A double-layer broadband antireflective (AR) and scratch-resistant coating with hydrophobic surface is fabricated via sol-gel process using acid and base catalyzed silica as precursor solutions. The coating is composed of a dense and a porous silica films of which the refractive indices are high and low respectively, realizing a step-index gradient structure with glass as the substrate. The AR property of the coating is optimized to maximize the amplification yield of the laser disk amplifiers used in high power laser system. The average transmittance of BK7 glass coated in this way increased to more than 99.5% over the range of 500 to 850 nm. After NH₃-heat treatment at 200 °C, the scratch-resistance of the coating is improved in a large degree. Trimethylchlorosilane is employed to modify the coating surface to improve the optical stability by resisting moisture. These treatments can ensure that this broadband AR coating is durable for its real application.     

Electrical sensing properties of silica aerogel thin films to humidity

Mesoporous silica aerogel thin films have been fabricated by dip coating of sol-gel derived silica colloid on gold electrode-patterned alumina substrates followed by supercritical drying. They were evaluated as the sensor elements at relative humidity 20-90% and temperature 15-35 °C under an electrical field of frequency 1-100 kHz. Film thickness and pore structure were two main parameters that determined the sensor performance. The film with a greater thickness showed a stronger dielectric characteristic when moisture abounded, and presented a smaller hysteresis loop and a higher recovery rate, due to the large size of pore throats. As the film thickness decreased, at low humidity the surface conductivity enhanced and the response rate increased. The silica aerogel based humidity sensor can be modeled as an equivalent electrical circuit composed of a resistor and a capacitor in parallel, and is driven by ionic conduction with charged proton carriers.     

Synthesis and characterization of silica aerogel films for inter-metal dielectrics via ambient drying

Low-dielectric silica aerogel films could be synthesized via solvent exchange-ambient drying of wet gel films that were obtained by spin-coating the isopropanol based silica sol on a p-Si (100) wafer. Using isopropanol as a drying solvent, the thickness and the dielectric constant of silica films significantly changed from 1100 nm to 350 nm and from 2.1 to 3.6, respectively, with the drying pressure of [8 MPa (270 °C)→2.6 MPa (200 °C)]. However, when isopropanol in pores was exchanged with n-heptane followed by ambient drying technique, the aerogel films had 1350 nm thickness, 80% porosity, and 2.0 dielectric constant, regardless of the drying pressure. The degree of planarization and the gap filling capability on 0.7 μm tungsten patterning wafer were excellent. It was proven that the ambient-dried aerogel films have a possibility of an application to IMD (inter-metal dielectrics) materials in the next generation of semiconductor devices beyond the giga level.     

疏水型纳米SiO2增透薄膜的制备与性能研究

采用溶胶-凝胶技术,以正硅酸乙酯(TEOS)为有机醇盐前驱体,无水乙醇(EtOH)为溶剂,在碱催化体系中通过选择合适的原料的比例,制得碱性的增透膜,然后对所得的薄膜进行表面修饰,制得既有增透性质又有疏水性的增透膜,克服了增透膜防潮性能差的缺点.采用椭偏仪、傅立叶型红外分光光度计、UV-VIS-NIR分光光度计和接触角测试仪对膜的折射率、厚度、红外特性、透过光谱、接触角进行表征.     

常压干燥制备SiO2气凝胶的研究

以水玻璃为硅源,采用常压干燥制备了SiO2气凝胶。研究了老化时间、老化剂种类、干燥溶剂种类以及表面改性对SiO2气凝胶结构和性能的影响。结果表明:制得的SiO2气凝胶具有良好的疏水性,密度为0.082g/cm3,孔隙率为96.26%,比表面积达到585.4m2/g。采用扫描电镜(SEM)、傅里叶变换红外分析(FT-IR)、热重分析(TG)、差热分析(DTA)等对疏水型气凝胶的结构和性能进行了研究。     

High strain recovery with improved mechanical properties of gelatin–silica aerogel composites post-binding treatment

Silica aerogels are very light and highly porous materials that are intriguingly and complexly networked with large internal surface area, high hydrophobicity with extremely low density and thermal conductivity. These features make them ideal choice for applications as thermal and acoustics insulators or as optical, electrical, and energy storing devices. However, their exploitation for structural applications is primarily inhibited by their brittleness. The brittleness of the silica aerogels makes their processing and handling difficult. Volumetric shrinkage occurs, which becomes more apparent at elevated temperatures. While there are hybrid silica aerogels doped with materials such as polymer, ceramics, metals in the market, the improvements in the mechanical properties are compromised with tremendous increase in density and reduction in the insulation performance. Post-synthesis binding treatment of silica aerogels composites are not extensively explored due to the chemically inert trimethylsilyl (TMS) terminal groups on the surface of the hydrophobic silica aerogels. This paper discusses a unique fabrication method of developing a ductile silica aerogel composite solid via post-synthesis binding treatment. Gelatin–silica aerogel (GSA) and GSA–sodium dodecyl sulfate (SDS) composite blocks were produced by mixing hydrophobic aerogel granulates in a gelatin–SDS foamed solution by frothing method. The entire fabrication process and grounds for using a controlled % of gelatin as the main binder and SDS as an additive are explained. The compression testing of the blocks is presented. The associated strain recovery—an unusual phenomenon with brittle silica aerogels, observed upon unloading is highlighted and studied. The microstructure and surface characterization of these composites was examined via FESEM/EDX and XPS/ESCA, respectively. The dependency of process variables involved were analyzed through analysis of variance (ANOVA) model. Empirical models that relate the composition of gelatin, aerogel, and SDS to achieve the optimal strain recovery with the associated compressive modulus and strength and density are established. The transition from brittleness to ductility is measured in terms of compressive stress versus strain behavior for various mass fractions of gelatin and SDS. The test data presented indicate analogous behavior of these to creep-like behavior of a material typically identified as the primary, secondary, and tertiary stages. The rationale and mechanisms behind such creep-like three stages are explained using schematic diagrams.