聚合物/疏水性SiO2超疏水复合涂层的制备及表征

使用低密度聚乙烯、聚甲基丙烯酸甲酯和疏水性SiO2为原料,通过简单的共混涂膜方法在玻璃基底上制得了具有超疏水性能的聚乙烯/疏水性SiO2和聚甲基丙烯酸甲酯/疏水性SiO2复合涂层;用接触角测量仪、扫描电子显微镜、X-射线光电子能谱仪等分析手段对涂层的润湿性能、微观结构以及表面化学成分等进行了表征。结果表明,所制备的两种聚合物/疏水性SiO2复合涂层的静态水接触角都超过150°,滚动角低至3.0°。聚合物和疏水性SiO2共混涂膜后形成了类似于荷叶的微纳米二元结构,是其表面具有优异超疏水性能的主要原因。     

水热法制备碱式硫酸镁晶须的过程机制

以MgSO₄和NaOH为原料,采用常温合成-水热反应方式制备出直径0.5-1.0μm、长30-50μm的碱式硫酸镁(5Mg(OH)₂·MgSO₄·3H₂O)晶须。电导率实验表明:添加氢氧化镁可显著提高硫酸镁水热溶液的电导率,由此初步推测晶须的水热合成属溶解-结晶机制:氢氧化镁首先溶解,然后溶液中Mg²⁺、SO₄^2-和OH^-发生反应生成碱式硫酸镁晶须。晶须的水热合成过程受晶体生长控制,宏观动力学方程为:-dc/dt=0.438(c-0.417)4     

碱式硫酸镁晶须/橡胶复合材料的制备

将超声分散后的硅烷偶联剂3-氨丙基三乙氧基硅烷改性碱式硫酸镁晶须（KH550-MgOS_W）分散液加入天然胶乳（NR）中,对其进行补强,制得绿色环保高性能的KH550-MgOS_W/NR复合材料。系统研究了KH550-MgOS_W/NR复合材料的力学性能、阻燃性能及热稳定性能。结果表明,用KH550改性后的MgOS_W与橡胶基体具有很好的相容性。KH550-MgOS_W/NR复合材料的力学性能、阻燃性能及热稳定性能均比纯胶有所提高。当KH550-MgOS_W与NR质量比为4%时,KH550-MgOS_W/NR复合材料的各项性能均达到最佳,300%定伸应力、拉伸强度、撕裂强度、断裂伸长率、交联密度比纯胶胶膜分别提高了25.0%、36.8%、37.3%、11.4%、44.2%,垂直燃烧等级由FV-1提高到了FV-0级,比纯胶的起始热降解温度（T₀）、最大热降解温度（T_p）和终止热降解温度（T_f）分别提高了6.2℃、5.2℃和4.1℃。     

碱式硫酸镁晶须的制备表征及应用研究

首先以制盐母液和氨水为原料制备出氢氧化镁滤饼,再以硫酸镁和自制的氢氧化镁为原料,通过水热合成法制备出碱式硫酸镁晶须。实验确定了制备碱式硫酸镁晶须的适宜条件∶n(Mg(OH)2)∶n(MgSO4)=1:4,反应时间为4h,反应温度为190℃,硫酸镁溶液的浓度为0.3mol/L。对碱式硫酸镁晶须进行组成分析、SEM、XRD及TG-DTG分析,制备的晶须为扇状,直径为1～2μm,长度为200～300μm.长径比为150～250。合成的碱式硫酸镁晶须组成为MgSO4.5Mg(OH)2.2H2O。在聚丙烯中加入碱式硫酸镁晶须后,有明显的阻燃性能。     

常压制备低孔径高比表面积疏水SiO2气凝胶

以正硅酸乙酯为先驱体,丙三醇为干燥控制化学添加剂(DCCA),通过酸碱两步溶胶-凝胶法制备了二氧化硅气凝胶,同时利用六甲基二硅氮烷(HMDZ)和正己烷的混合液对湿凝胶进行表面疏水改性。测试分析了所制备气凝胶的密度、疏水性、比表面积和形貌。结果表明,经过表面改性的SiO2气凝胶具有良好疏水性,与水的接触角约为139.4°,比表面积为952m2/g,平均孔径为5～10nm,孔隙率达94.2%,且其密度仅为0.127g/cm3。     

羟基硅油改性SiO2制备复合粒子及超疏水涂层的制备与性能

利用羟基硅油的独特性质改性纳米SiO₂制备了一种具有纳米结构的弹性微米级复合SiO₂粒子,并用其与107硅橡胶复合制备出了超疏水涂层。探究了粒子用量对疏水性的影响。使用扫描电镜、接触角测量仪、傅里叶变换红外光谱仪和热失重分析仪对改性后的粒子和超疏水涂层进行表征。结果表明：羟基硅油改性后的粒子与硅橡胶涂料相容性极好,由于粒子表面的硅氧烷分子链能与硅橡胶分子链缠结,且拥有多级粗糙结构的粒子能与固化后的硅橡胶树脂产生机械咬合,因此超疏水涂层拥有良好的机械性能。在40%含量时综合性能最好,疏水角为154.6°,能在500g负载下(约5.4kPa压强),在1000目砂纸上磨损6m仍具有良好的超疏水性。     

环氧树脂/SiO2纳米颗粒复合超疏水表面的制备

利用环氧树脂和纳米SiO₂混合溶液在玻璃基材进行表面成膜,对得到的微米级粗糙结构进行氟硅烷修饰,制备得到具有超疏水性复合膜层。采用扫描电镜、接触角测量仪、高速摄影系统和紫外-可见光谱分析仪进行形貌表征、润湿性表征和膜层透光率测量。结果表明,环氧树脂与纳米颗粒构建的粗糙结构对超疏水表面的构建起到重要作用,该膜层呈现低黏附、低滚动角性能;复合膜层的接触角随SiO₂含量的提高逐渐增大至趋于稳定;复合膜层透光率随SiO₂含量的提高呈现下降趋势,制备膜层的透光率均在75%以上。     

纳米CaCO3/TiO2复合粒子制备超疏水膜

采用溶胶-凝胶法,用γ-(2,3-环氧丙氧基)丙基三甲基氧硅烷和油酸修饰纳米CaCO3/TiO2复合粒子,制备具有类似荷叶表面形貌的超疏水涂层。结合扫描电镜、红外光谱、热重和示差扫描量热仪对复合粒子进行表征。结果表明,纳米TiO2粒子物理复合在纳米CaCO3表面,复合粒子经修饰后引入了疏水性的甲基,形成纳米复合双重粗糙结构,使所制备的涂层表现出优良的超疏水性能,其中接触角为162.1°,滚动角7°。     

纳米SiO2@超支化PDMS复合超疏水涂层的制备与性能调控

超疏水涂层在实际应用中受化学腐蚀、刮擦磨损等外界环境的影响,易造成涂层老化、开裂甚至脱落,造成涂层失效。因此,针对这一问题,设计出具备耐候性的自修复超疏水表面：以超支化聚二甲基硅氧烷为柔性基底和低表面能物质,引入纳米二氧化硅构筑表面粗糙结构,制备超疏水涂层。当SiO₂粒径为50 nm、固含量为30wt%时,得到了接触角为154.87°的超疏水涂层。经过5次胶带剥离试验,涂层表现出良好的机械稳定性。经历10次温差循环试验和24 h紫外光照射后,涂层表面接触角仍大于150°,表明涂层具有良好的耐候性。涂层经过80℃、2 h的热处理可修复划痕,表明该涂层具有一定的自修复功能。同时,Tafel及Nyquist测试结果表明,对基底进行超疏水处理可显著提高防腐性能,并且该涂层具有明显的自清洁效果。综上所述,本文所制备的纳米SiO₂@超支化聚二甲基硅氧烷(PDMS)复合超疏水涂层具有自修复功能,为自修复超疏水涂层的开发提供了新的研究策略。     

Hierarchical electrospun SiO2 nanofibers containing SiO2 nanoparticles with controllable surface-roughness and/or porosity

Herein we report that hierarchical electrospun SiO₂ nanofibers incorporated with SiO₂ nanoparticles with fiber diameters being ∼ 500 nm and particle sizes being tens of nanometers were developed through the combination of sol-gel process and electrospinning technique followed by high-temperature pyrolysis; and their morphologies and BET surface areas were examined. The study revealed that the pre-gelation of tetraethyl orthosilicate (TEOS) in spin dopes was important to achieve the morphological consistence of the electrospun precursor nanofibers and the resulting final SiO₂ nanofibers; additionally, SiO₂ nanoparticles appeared to be enriched on the fiber surface, while the surface-roughness and/or porosity of the nanofibers could be controlled through adjusting the incorporation amount of SiO₂ nanoparticles. The developed hierarchical electrospun SiO₂ nanofibers are expected to have important applications in composites (particularly dental composites) as well as catalyst support and adsorption.     

SBR-SiO2超疏水涂层的制备与性能

利用羟基硅油(HSO)对白炭黑(SiO2)进行疏水改性,并用过氧化二异丙苯(DCP)对丁苯橡胶(SBR)胶浆进行适度交联,通过粒子填充法制备了超疏水SBR-SiO2涂层。研究了HSO、SiO2和DCP用量及交联条件对涂层成膜性能和润湿性能的影响,探讨了涂层热氧老化和紫外光老化过程中超疏水性能的变化。结果表明,当m(HSO)∶m(SiO2)=1∶1、HSO-SiO2用量为3.5g、DCP用量为0.25g、交联温度为155℃、交联时间为20min时,涂层成膜性能好,接触角为157.0°,且热氧老化和紫外光老化后仍保持较好的超疏水性。扫描电镜照片表明涂层具有微纳米多尺度粗糙结构。     

Fabrication of antibacterial monodispersed Ag-SiO2 core-shell nanoparticles with high concentration

Monodispersed Ag-SiO₂ core-shell nanoparticles with a high concentration of 400 mg/L were successfully fabricated by using tetraethoxysilane as silica precursor and reducing silver nitrate with ascorbic acid in the presence of cetyltrimethylammonium bromide as stabilizing agent. The nanoparticles had a spherical silver core in a size range from 14-26 nm in diameter and an amorphous silica shell of 15-28 nm thickness, respectively. The antibacterial effects of Ag-SiO₂ core-shell particles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were tested by the usual twofold serial dilution method for minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The results indicated that the core-shell nanoparticles owned excellent antibacterial effects.     

Fabrication of thermochromic composite using monodispersed VO2 coated SiO2 nanoparticles prepared by modified chemical solution deposition

Monodispersed thermochromic VO₂ particles were fabricated by VO₂ coating onto monodispersed SiO₂ nanoparticles with the modified chemical solution deposition technique using vanadium isopropoxide solution and monodispersed SiO₂ particle suspension solution. The average size of the resultant VO₂–SiO₂ particle was 57 nm and the coating thickness of the VO₂ layer was 6 nm. A thermochromic composite was fabricated using the VO₂–SiO₂ particles and a poly lactose acid polymer as a transparent matrix, and the transmittance of the composite at a high temperature was 10% less than that at a low temperature.     

Nanomechanical characterization of cement-based pastes enriched with SiO2 nanoparticles

Microstructural and nanomechanical surface properties of cement based pastes were experimentally investigated. Samples were prepared from CEMI42.5 cement, with water to cement ratio equal to 0.5 and enriched with SiO₂ nanoparticles (d = 14 nm), with low concentration ranging from 0% up to 0.5% (by weight of binder). X-rays diffraction (XRD) patterns revealed a linear increase of crystal size of calcium hydrate (CH) products with the addition of nanoparticles, while scanning electron microscopy (SEM) images showed a denser microstructure with more defined grains for the higher SiO₂ nanoparticles concentration. Atomic force microscopy (AFM) studies of samples after the grinding/polishing process indicated a strong dependence of surface roughness with the CH crystallite mean size and the materials mechanical properties. Finally, statistical analysis of nanoindentation mapping data revealed a decrease of elastic modulus with the increase of nanoparticles concentration.     

Ion irradiation induced amorphization of SnO2 nanoparticles embedded in SiO2

SnO₂ nanoparticles (NPs) of average diameter of ∼10.5 nm, synthesized in SiO₂ using Sn⁻ ions implantation combined with thermal annealing, were irradiated with 1.5 MeV Au²⁺ ions at room temperature. The NP structure was studied as a function of ion fluence by transmission electron microscopy and micro-Raman spectroscopy. Prior to ion irradiation, SnO₂ NPs have been found to exhibit the rutile crystal structure. Upon irradiation, amorphization in the nanocrystals has been seen to increase with increase in ion fluence. In particular, at a fluence of 1 × 10¹⁴ ions cm⁻² we argue for the presence of an amorphous SnO₂ phase. Beyond this fluence, the NPs have been found to dissolve in the matrix. The observed results are explained in the frame work of ion irradiation induced defects production in the NPs as well as in the NP/matrix interface.     

Natural and persistent superhydrophilicity of SiO2/TiO2 and TiO2/SiO2 bi-layer films

Sol-gel SiO₂/TiO₂ and TiO₂/SiO₂ bi-layer films have been deposited from a polymeric SiO₂ solution and either a polymeric TiO₂ mother solution (MS) or a derived TiO₂ crystalline suspension (CS). The chemical and structural properties of MS and CS bi-layer films heat-treated at 500 °C have been investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscospy. Water contact angle measurements show that MS SiO₂/TiO₂ and CS TiO₂/SiO₂ bi-layer films exhibit a natural superhydrophilicity, but cannot maintain a zero contact angle for a long time over film aging. In contrast, CS SiO₂/TiO₂ bi-layer films exhibit a natural, persistent, and regenerable superhydrophilicity without the need of UV light. Superhydrophilic properties of bi-layer films are discussed with respect to the nature of the TiO₂ single-layer component and arrangement of the bi-layer structure, i.e. TiO₂ underlayer or overlayer.     

Viscoelastic properties of silicone rubber with admixture of SiO2 nanoparticles

Measurements have been carried out to investigate the change of dynamic viscoelastic properties of silicone rubber with the admixture of small amount SiO₂ nanoparticles. A novel measurement method for the dynamic viscoelastic properties including the modulus of elasticity, the loss factor and the Poisson's ratio is employed. It was found that an admixture of rather small amount of SiO2 nanoparticles can substantially affect the viscoelastic properties of the silicone rubber. It is observed that the modulus of elasticity is increased, while the loss factor and the Poisson's ratio are reduced.     

SiO2 and Al2O3/SiO2 coatings for increasing emissivity of Cu(In, Ga)Se2 thin-film solar cells for space applications

In this study, optical coatings were investigated as substitutes for the coverglass on flexible thin-film space solar cells. The inherent low emissivity of copper-indium-gallium-diselenide (CIGS) thin-film solar cells was increased using optical coatings for thermal balance in space. Evaporated silicon dioxide (SiO₂) and an additional aluminum oxide (Al₂O₃) coating on the CIGS solar cell increased the emissivity from 0.18 to 0.77. Higher emissivity was realized with the Al₂O₃/SiO₂ double-layer coating than with the SiO₂ single-layer coating. The straightforward double-layer coating gives the CIGS solar cells appropriate radiative properties for keeping the cell within a permissible temperature range in space.