Three common silane coupling agents KH550

KH560 and KH570 were used as modifiers to modify the nano-silica respectively. The nano-SiO2/epoxy composite materials were prepared from the three modified nano-silicas. The characterizations of the infrared test of the modified nanoparticles and the dynamic light scattering of the particle size have been tested. The characterizations of the impact strength at normal temperature and coefficient of thermal expansion at low temperature of the prepared composite material have been tested. The results showed that the average particle sizes of SiO2 modified with the three coupling agents are in the range of (200±50)nm.The distribution coefficient (PDI) of the modified SiO2 particles in ethanol is within the range of 0.30±0.05. The effect of different coupling agent modifications on the impact strength of composite materials is small

the difference is not more than 7.37%

but it has the great influence on the CTE of the composite materials. When the concentration of SiO2 is 9%

and under –183℃

KH560 has the best effect on improving CTE of SiO2 / epoxy composite system among the three coupling agents

while under the same conditions

the CTE of the SiO2 / epoxy composite system modified by KH550 and KH570 are higher about 1.19% and 23.7% respectively.