Research On Surface Modification Of Diamond For Thermal Conductive Fillers

The composite materials prepared by the combination of diamond and polysiloxane are useful with high thermal conductivity and good fluidity and processability.However,the surface of diamonds is practically inert to most chemical agents,and the interface wettability is also relatively poor,and it is difficult to combine well with the polysiloxane matrix.Therefore,it is necessary to modify the surface of diamonds first.and then combine them with polysiloxane,thereby improving the overall thermal conductivity of the composite material.This thesis took diamond thermal conductive filler as the main research object,by various surface modification methods to study the influencing factors of the change of their surface groups,and to study the thermal conductivity changing discipline of the thermal conductive composite material formed by them and polysiloxane.The main research work of this thesis is as follows:（1）The diamonds were treated with silane coupling agent KH-550The changing discipline of the functional groups on diamond surface under different process conditions was studied,and the thermal conductivity changes of corresponding composite materials were studied under the best process conditions.The research shows that the content of silane coupling agent is 80%and the reaction time is 4h,which can achieve sufficient grafting of silane coupling agent.（2）The diamonds were treated with strongly acid liquid-phase oxidation system composed of H₂SO₄,HNO₃ and KMn O₄.The changing discipline of the functional groups on the diamond surface under different process conditions was studied,and the thermal conductivity changes of corresponding composite materials were studied under the best process conditions.The results show that the strongly acid liquid-phase oxidation system can oxidize the hydroxyl groups on the diamond surface to carbonyl or aldehyde groups.（3）The diamonds were treated by gaseous ozone direct oxidation.The changing discipline of the functional groups on the diamond surface under different process conditions was studied,and the thermal conductivity changes of corresponding composite materials were studied under the best process conditions.The research shows that when the ozone concentration is 115（±5）mg/L and the reaction time is 15min,the surface hydroxyl density is the largest,the filling ratio of the diamond which filled into polysiloxane can be 75%,and the thermal conductivity of the system can be 8.02 W/m K.