纳米SiO_2包覆改性薄片铝粉颜料及其耐酸性研究

以正硅酸乙酯为前驱体,氨水为催化剂,采用溶胶-凝胶法在薄片铝粉颜料表面包覆了一层薄而致密的纳米SiO_2层,考察了反应工艺参数对包覆层形貌及耐酸性的影响.通过调节反应温度和时间、铝硅比、水硅比、催化剂用量等工艺条件,可以控制正硅酸乙酯的水解速率、活性硅酸在铝粉粒子表面的吸附速率及缩合速率之间的相对大小,从而控制SiO_2以膜沉积的方式对铝粉进行包覆,得到均匀致密的包覆膜.实验得到较优的条件为:同时滴加正硅酸乙酯和氨水水溶液,控制铝硅比为5.5,水硅比为30,氨水用量3 mL,在40 ℃下反应6 h,铝粉粒子表面的SiO_2包覆层均匀致密,包覆型铝粉在pH＝1的酸溶液中能稳定存在30 d而不产生H_2.

Aluminum Pigments Encapsulated with Nano-SiO_2 Coatings and Their Acid-resistance

Aluminum pigments were encapsulated with a thin but dense film of nano-SiO_2 particles in sol-gel method, using tetraethoxysilane as the precursor and ammonia as the catalyst. The influences of reaction factors on the film's pattern and the acid proof behavior were studied. The relative rates of tetraethoxysilane hydrolyzation, silicic acid absorption and condensation polymerization on aluminum pigments could be controlled by adjusting the reaction parameters, such as the reaction temperature, time and the ratio of reactants. And the homogeneous and dense SiO2 layer could be deposited thoroughly around the surface of the aluminum pigments. It was found that, when dropping tetraethoxysilanc and ammonia simultaneously into the pigments solution and controlling the mole ratio of aluminum to tetrathoxysilane at 5.5, the ratio of water to tetraethoxysilane at 30, the dosage of catalyst with 3 mL, the reaction temperature at 40 ℃ and time of 6h respectively, the encapsulated aluminum pigments obtained could be immersed in the acid media of pH=1 for 30 d without H_2 giving-off.