常压干燥条件下乙醇对SiO_(2)气凝胶密度的影响

Effect of ethanol on density of silica aerogels by ambient pressure drying method

SiO_(2)气凝胶是一种经典的三维网状多孔纳米材料,具有低密度、高孔隙率、高比表面积、低热导率、低光学折射率和低声速等特点,在许多领域都具有巨大的应用潜力。以四乙氧基硅烷(TEOS)为硅源,采用常压干燥的方法,通过改变乙醇、氨水的物质的量之比实现对二氧化硅气凝胶的密度的研究。当TEOS、乙醇、水(0.01 mol/L草酸催化剂∶0.5 mol/L氨水催化剂)的物质的量之比分别在1∶4~10∶(1.0~3.5∶0.2~2.2)范围之间时,通过酸碱两步催化法制备得到的气凝胶密度为70~120 kg/m^(3)。当乙醇与氨水催化剂物质的量之比为10∶1.8时,气凝胶密度能达到76 kg/m^(3),且其导热系数也能低至0.0150 W/(m·K),降低气凝胶成本的同时所得低密度、低导热系数气凝胶也能够实现当前绿色建筑对五步节能的要求。

Silica aerogels are nanostructured porous solids with an open pore structure,high surface area,high porosity,low bulk density,and low thermal/electrical conductivity,which have drawn great interest in both science and technology.Using tetraethoxysilane(TEOS)as precursors,the molar ratio variables of EtOH and NH_(4)OH were discussed in the effect of silica aerogels density by ambient pressure drying method.When the molar ratio of EtOH/TEOS was varied from 4 to 10,the 0.01 mol/L oxalic acid(A)/TEOS was varied from 1.0 to 3.5 and 0.5 mol/L NH_(4)OH(B)/TEOS was varied from 0.2 to 2.2,silica aerogels density was 70-120 kg/m^(3).Optically transparent silica aerogels with low density(76 kg/m^(3))as well as lowthermalconductivity(0.0150 W/(m·K))were successfully prepared using TEOS∶EtOH∶H_(2)O(A)∶H_(2)O(B)molar ratio at 1∶10∶3.5∶1.8 respectively by ambient pressure drying method.Silica aerogels with low density and low thermal conductivity were achieved for lower cost and five-step energy saving requirements of green building.