Abstract Functionally gradient silica aerogels have been applied in many areas with their gradient porosity, refractive indices and acoustical impedance. For the purpose of accurately controlling the process of gradient formation, a new approach called slope-rotation method was proposed. Such a method could benignly fabricate gradient density sol by sloping, rotating and mixing the two different density sols in one-step. Gradient density aerogel was obtained after ethanol supercritical drying. The microstructure and density distribution of aerogels were characterized by nitrogen adsorption, scanning electron microscopy, and X-ray phase contrast. The transmittance and refractive index were tested by UV–visible absorption spectrum and a self-built device. The results indicated that the transmittance and refractive index had been gradient changed with the gradient density. This approach was an effective method for the preparation of gradient density silica aerogels and could be suitable for producing gradient density porous materials derived from a sol-gel process.

中文翻译：

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斜率旋转法制备具有梯度透射率和折射率的功能性二氧化硅气凝胶

摘要 功能梯度二氧化硅气凝胶以其梯度孔隙率、折射率和声阻抗等特性在许多领域得到应用。为了准确控制梯度形成的过程，提出了一种新的方法，称为斜率旋转法。这种方法可以通过一步倾斜、旋转和混合两种不同密度的溶胶来良性地制造梯度密度溶胶。乙醇超临界干燥后得到梯度密度气凝胶。气凝胶的微观结构和密度分布通过氮吸附、扫描电子显微镜和 X 射线相衬进行表征。通过紫外-可见吸收光谱和自建装置测试透光率和折射率。结果表明，随着梯度密度的增加，透射率和折射率发生了梯度变化。该方法是制备梯度密度二氧化硅气凝胶的有效方法，适用于制备由溶胶-凝胶工艺衍生的梯度密度多孔材料。