折射率可调气凝胶薄膜的制备及其光学特性研究

Nanostructured silica aerogel films have many unusual properties such as quite low density, dielectric constant, thermal conductivity, sound propagation velocity, adjustable refractive index and high laser damage threshold because of their high porosity and large surface area. And therefore they can be used in a variety of commercial purposes such as optical, microelectronic, high power laser system, and thermal applications for anti-glare and anti-reflective coatings, and thermal insulation and other applications..Conventional aerogel film preparation uses a supercritical drying process, but it is expensive and hazardous, and therefore this process hinders commercial applications of the aerogels materials. Here we have employed a novel route by the surface modification, ambient drying, together with the two-step catalysis to prepare pristine and doped silica aerogel films at the ambient pressure. With TEOS, E-40, Ti(OC4H9) 4, ZrOCl2o8H2O as the starting materials, nano-porous structure of the aerogel films can be successfully controlled based on sol-gel process together with a predrying surface modification step known as silylation and exchange of the solvent with low surface tension; and refractive index of the films can be continuously adjusted from 1.18 to 2.20 using base and acid two-step catalysis with controlling TEOS ratio and doping TiO2. The films were characterized with FE-SEM, AFM, TEM, XPS, FTIR, SiNMR, CNMR, spectrophotometer, an ellipsometer, and the abrasion test, respectively. Based on the thin film optical design, the broadband antireflective coatings have been prepared with a large area about 110×80m2, and the average reflectance in the visible and solar region is lower than 0.84% and 1.5%, respectively. The one-layer scratch-resistant anti-reflective aerogel SiO2 films have very high transmittance rearching about 99.6% at 355nm wavelength with a laser damage threshold more than 45.9J/cm2. And reflectance of the multilayer coating mirror compose of aerogel SiO2 and nanostructured ZrO2 films is higher than 99% at 1064nm with a laser damage threshold of 30.0J/cm2. .A scratch-resistant improvement and strengthening of the structure of sol-gel derived pristine and doped silica aerogel films by a base/acid two-step catalysis and the mixed gas annealing were investigated. The experimental results have shown that the two-step catalysis obviously improves the scratch-resistance and adhesion of the films, and that the mixed gas treatment further strengthens the silica network. The increase in strength is attributed to more Si-O-Si bond cross-linkages between silica particles formed by the two-step catalysis and the mixed gas treatment.. Finaly, research contents in this project have been widened. A variety of interesting materials such as electrochromic, gasothromic, carbon aerogels, light thermal insulation materials, flexible thermal insulation foils and transparent thermal insulation nano-composite films have been carried out based on the process and principles from the project. Also, the pristine and doped SiO2 aerogel films have been successfully applied to color-shift nano-composite materials, surfaces of infrared detectors, targets with ultralow density for ICF and others.

通过溶胶----凝胶过程，结合表面修饰和水及氨混和蒸汽中热处理、紫外光辐照，在常规条件下制备纳米多孔结构可控、机械强度高、折射率连续可调气凝胶薄膜；通过光与纳米多孔材料相互作用及膜层强化机理研究，在优化材料设计与表面改性增强基础上形成成本低、设备简单、适合工业生产的新型气凝胶薄膜，在减反射、提高光电耦合效率方面有广泛应用前景。