内疏外亲SiO_2气凝胶的制备及表征

Preparation and characterization of surface hydrophilic and internal hydrophobic silica aerogels

以正硅酸乙酯(TEOS)为硅源,无水乙醇为溶剂,硝酸为催化剂,氨水为凝胶剂,经溶胶-凝胶过程制备块状湿凝胶。再以三甲基氯硅烷(TMCS)为疏水改性剂,3-氨丙基三羟基硅烷为亲水改性剂对制备的湿凝胶进行改性处理,最后经超临界CO2干燥得到块体SiO2气凝胶。考察了亲水改性剂加入量分别为0、0.15、0.75、1.5、2.70 mL时对块体SiO2气凝胶亲水性的影响,并通过扫描电子显微镜(SEM)、接触角、吸水率、红外光谱(FT-IR)等对气凝胶进行表征。结果表明:所得气凝胶块体具有纳米多孔结构,内部疏水(最大接触角可达123°),表面亲水,试样亲水性随亲水剂用量的增加而增大;同一试样亲水性存在一定的梯度变化,亲水性由内到外逐渐增强。

Wet silica gel monoliths were prepared by sol-gel process using tetraethoxysilane （TEOS）as sil-ica source,absolute ethyl alcohol as solvent,nitrating acid as catalyzer,and ammonia as gelata.Then the wet gels were modified by trimethyl methylchlorosilane（TMCS）and 3-ammonia three hydroxyl propyl si-lane as hydrophobic modifier and hydrophilic modifier,respectively.After CO2 supercritical drying,silica aerogels were obtained.The impacts on hydrophilicity of silica aerogels with hydrophilic modifier dosages of 0,0.15,0.75,1.05 and 2.70 mL were investigated,respectively.Silica aerogels were characterized by scanning electron microscope （SEM）,contact angle,water absorption rate,and infrared spectroscopy （FT-IR）.The results show that：the prepared silica aerogels have nano-porous structures;the inner aerogel is hydrophobic （the maximum contact angle can reach 123°）and the surface is hydrophilic,the hydrophilicity of silica aerogels increases with the dosage of hydrophilic modifier increasing.There is a certain gradient change of hydrophilicity in the same specimen and the hydrophilicity increases from inner to outer.