硅溶胶的表面改性及应用研究进展

首先简要概述了硅溶胶的结构、性质及应用,同时指出了传统的硅溶胶结构及性能上存在的不足而导致对其应用所造成的限制。重点阐述了国内外改性硅溶胶的方法和改性机理。最后展望了改性硅溶胶的应用前景。     

硅溶胶-苯丙无机/有机复合乳胶建筑涂料的研制

采用正硅酸乙酯(TEOS)为主要原料通过溶胶聚合法制备硅溶胶,制得的硅溶胶与苯丙乳液冷拼复配得到复合基料,将该基料结合优质的颜、填料和助剂经研磨分散制得硅溶胶-苯丙复合建筑涂料。通过正交试验分别确定了制备硅溶胶、硅溶胶-苯丙复合乳液和硅溶胶-苯丙复合建筑涂料的最优方案。对硅溶胶-苯丙复合建筑涂料综合性能检测,耐洗刷次数高达11296次、涂膜吸水率为3.21%、附着力达1级,表明该涂料具有优异的耐磨性、耐水性和附着性,适合建筑涂料的应用要求。     

磋溶胶-苯丙无机/有机复合乳胶建筑涂料的研制

采用正硅酸乙酯(TEOS)为主要原料通过溶胶聚合法制备硅溶胶,制得的硅溶胶与苯丙乳液冷拼复配得到复合基料,将该基料结合优质的颜、填料和助剂经研磨分散制得硅溶胶-苯丙复合建筑涂料.通过正交试验分别确定了制备硅溶胶、硅溶胶-苯丙复合乳液和硅溶胶-苯丙复合建筑涂料的最优方案.对硅溶胶-苯丙复合建筑涂料综合性能检测,耐洗刷次数高达11296次、涂膜吸水率为3.21%、附着力达1级,表明该涂料具有优异的耐磨性、耐水性和附着性,适合建筑涂料的应用要求.     

基于NMR的低渗岩体硅溶胶吸渗注浆试验研究

为研究纳米硅溶胶对含泥质低渗岩体的吸渗注浆机制,采用2种低渗人造岩芯开展了硅溶胶的无压自吸渗试验,并基于低场核磁共振(NMR)系统测试了低渗岩芯吸浆过程中微观渗流特征,从微观尺度揭示了吸渗过程中孔隙填充及封闭规律。结合岩芯孔径分布和硅溶胶凝胶生长规律分析了硅溶胶对低渗岩体的可注性,并讨论了硅溶胶的吸渗注浆机制和工程应用前景。结果表明：硅溶胶对低渗岩芯吸渗能力突出,亲和力为去离子水的92.2%。硅溶胶的吸渗曲线呈指数三阶段分布特征,其中0.1 mD岩芯吸渗过程主要受微孔控制,20 mD样品吸渗先后受中孔和微孔控制。岩体纳微孔隙特征和硅溶胶凝胶生长对硅溶胶吸渗注浆可注性影响显著,且可注性与毛细管力共同影响吸渗结果。硅溶胶吸渗注浆能够满足低渗岩体纳微尺度孔隙–裂缝封闭的工程需求。     

SiO2溶胶对硅酸盐水泥性能的影响研究

初步研究了2种不同的硅溶胶对硅酸盐水泥浆体流动性、凝结时间、安定性以及对水泥硬化浆体的抗折强度和抗压强度的影响,并利用XRD分析了其对水泥性能的影响机理.结果表明,2种硅溶胶均具有良好的水泥适应性,能明显地改善硅酸盐水泥的力学性能,JN-40硅溶胶和SP-40硅溶胶的最佳掺量分别为1.5％和1.0％,硅溶胶的掺入能有效地减少水泥硬化浆体中氢氧化钙的含量,促进水泥的水化反应.     

分析硅溶胶及含硅溶胶无机建筑涂料的性能

对硅溶胶以及含硅溶胶无机建筑涂料的性能进行了分析和测试,将其与碱金属硅酸盐类无机涂料的性能差异进行了比对,结果表明,硅溶胶无机建筑涂料有着良好的使用性能。     

高硅溶胶含量复合乳液的研究

制备了高硅溶胶含量的硅溶胶/丙烯酸酯复合乳液,通过粒径大小及其分布和Zeta电位等的测试,研究了引发体系、硅溶胶含量对复合乳液体系的影响。结果表明,对于复合乳液聚合,氧化还原引发体系对乳液稳定性的影响远远优于热引发体系;当硅溶胶含量达到45%～50%时,体系的稳定性、黏度等最佳,粒径最小,粒径分布最窄,Zeta电位最大。     

水泥表面硬化剂的制备

以正硅酸乙酯(TEOS)、甲基三甲氧基硅烷(MTMS)、硅溶胶为主要原料制备了水泥表面硬化剂,研究TEOS/MTMS比例、硅溶胶用量、硅溶胶粒径等因素对涂层硬度、附着力的影响,研究了反应程度、体系的pH值等对储存稳定性的影响.结果表明,TEOS/MTMS比例对涂层硬度有显著影响,涂层硬度随着TEOS用量的增加而增大,但TEOS/MTMS比例过大会造成涂层脆性增大；随着MTMS用量增加,涂层的附着力增大,但涂层硬度会显著降低；加入适量的硅溶胶可提高涂层的硬度,但硅溶胶的用量不能过大,且硅溶胶的粒径越小,涂层硬度越高.     

硅溶胶-苯丙乳液复合涂料的稳定性研究

针对硅溶胶-苯丙乳液复合涂料贮存稳定性问题,采用ξ电位、流变行为测定及原子吸收光谱分析等手段,研究了影响该涂料稳定性的因素和硅溶胶凝聚物的组成,提出了改进措施。     

硅溶胶对建筑石膏性能的影响

对添加了硅溶胶的建筑石膏进行研究,测定了这种胶凝材料的物理—力学性能。结果表明,硅溶胶可作为石膏材料的增强剂。     

Silica sol for rock grouting: Laboratory testing of strength,fracture behaviour and hydraulic conductivity

A recently introduced non-cementitious grout silica sol is a refined product of colloidal silica, where the particle sizes have been reduced to between 5 and 100 nm. Laboratory tests were performed to determine the behaviour of silica sol as a permeation grout in hard rock. The tests have involved methods such as fall-cone, unconfined compression, triaxial, and oedometer tests. Samples were tested at different time intervals and in different storage environments. Results showed that the initial strength of silica sol, a few kPa, increases over time. Silica sol has a ductile behaviour during the first few days and then becomes elastic–plastic. Its hydraulic conductivity ranges from 10^?10 to 10^?11 m/s. When immersed in water, silica sol hardens and a thin layer of weaker strength is formed at the surface. However, this layer only extends a couple of millimetres into the sample; beyond that the silica sol is not affected, rendering breakdown by erosion a negligible risk. The conclusions are: (1) the strength obtained in silica sol after hardening is sufficient to withstand most grouting conditions; (2) when sufficiently confined, silica sol is able to withstand loading and unloading cycles; (3) a pH environment of around 11 does not appreciably change the strength of the silica sol; (4) silica sol is a material with low risk of failure under blasting vibrations; and (5) due to its low hydraulic conductivity, silica sol can be compared to low permeable clays.     

Mechanical tests on a new non-cementitious grout, silica sol: A laboratory study of the material characteristics

This introductory study on mechanical properties aims to characterize silica sol and to improve knowledge of the suitability of silica sol as grout. Silica sol is a non-cementitious grout that consists of spherical particles of amorphous silica, with a diameter of 5–100 nm. For a testing period of six months, specimens of silica sol were kept at 8 °C with three relative humidities: 75%, 95% and 100%. During the test period measurements of the drying shrinkage, compressive strength, modulus of elasticity (Young’s modulus), shear strength and flexural strength were made. The results show that the strength of silica sol continues to increase for a long time and during the test period of six months the strength kept increasing. The increase of strength depends on the humidity to which silica sol is exposed but the humidity also affects the drying shrinkage. A lower humidity results in a faster increase in strength but also a larger shrinkage.     

SiO2微粒增强水泥基复合材料的研究

讨论了硅溶胶、纳米SiO2和SiO2微粉对水泥基材料的改性效果和增强规律。测试结果显示，硅溶胶对水泥基体有明显的增强效果，其抗压强度增加规律与抗折强度增加规律有较好的一致性。通过扫描电镜分析，比较了微观结构的差异，并提出了关于它们增强机理的假设。     

建筑用竹制脚踏板的防火阻燃

以自制硅溶胶和铝溶胶为阻燃体系,研究阻燃浸注处理压力、处理时间、阻燃成分含量及样品不同处理方式等对建筑用竹制脚踏板防火阻燃性能的影响。试验结果表明:硅溶胶比铝溶胶更易渗入到竹片内部;在真空条件下以硅溶胶对竹片进行阻燃浸注处理时,浸注时间越长、阻燃体系中阻燃组分含量越高,所得样品的载药率和氧指数越高;样品的不同阻燃处理方式对其载药率和氧指数有较大影响。     

硅溶胶改性环氧树脂E-44的合成及其涂料制备

采用硅溶胶与环氧树脂E-44直接开环反应的合成方法改进环氧树脂的性能.通过红外光谱对改性环氧树脂结构分析表明,有机硅成功引入到了环氧树脂上.探讨了反应条件、催化剂用量及反应物配比对改性环氧树脂的影响,并以改性环氧树脂为基料,制备了富锌防腐涂料.试验结果表明,当m(硅溶胶):m(环氧树脂E-44)=5∶3,催化剂用量2.5%,反应温度65℃,反应时间2h时,所得环氧树脂性能最佳,同时由该涂料制备的涂层具有较好的物理性能、耐热性和耐腐蚀性能.     

Sealing narrow fractures with a Newtonian fluid: Model prediction for grouting verified by field study

The increased demand for efficiency when sealing tunnels by grouting has led to a need to seal narrow fractures. The more conductive fractures are sealed by cement-based grouts, however, the limitations in penetrability make these grouts less useful for low permeable rock. Silica sol is an inorganic grouting material with high potential to penetrate narrow fractures. Its two components, silica sol and a salt solution, are both considered harmless. The salt solution (CaCl₂) is the accelerator. The field study investigates whether the penetration of a Newtonian fluid (silica sol) can be predicted and verified using numerical models, based on grout properties and hydraulic tests. The field study was conducted, in 2004, on a pillar located at 0/670 m at Äspö Hard Rock Laboratory (Äspö HRL).One, well characterised and grouted fracture was selected to be grouted with silica sol and analysed. To check the conditions of the fracture hydraulic tests were used, namely, constant head tests with single packer and they were directly followed by pressure logging in the recovery phase. The transmissivity, T, was estimated from the recovery phase of single-hole injection tests using Jacob’s method. Further, the hydraulic aperture was estimated using the well-known cubic law. For the design of the grouting parameters, gel time, injection pressure, and injection time were determined from a one-dimensional model with the penetration length set to 2.2 m. The grout was mixed with optical brightener to make the grout easier to see in the six cores drilled. The grouted borehole was over-cored, and specimens from the grouted fracture were analysed by microscope. Hydraulic tests were made after grouting to estimate the sealing efficiency of the rock mass. The penetration was also estimated in a two-dimensional model to verify length for selected grouting times.Visual observation and the hydraulic properties of two boreholes show that the penetration length is at least 1.0 m. For the numerical model in 2D, a good agreement is found. The final penetration is underestimated by the model underestimates. The hydraulic tests show that at least two boreholes were sealed with silica sol within the predicted penetration radius. The sealing efficiency was approximately 70%.