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In order to find out the best range of diamond powder content for heat conductive adhesive, the influence of diamond powder content on the heat conductive adhesive was studied. The surface of diamond powder with different particle sizes was modified by silane coupling agent. In order to increase the specific surface area of diamond powder, a new type of inorganic thermal conductive adhesive was prepared by using 60 μm, 20 μm and 10 μm diamond powder as filler and water glass as matrix at the mass ratio of 6∶2∶1. The results show that the adhesive property of thermal conductive adhesive increases at first and then decreases, and that the adhesive property is best when the content of diamond is 60% and the tensile shear strength is 1.98 MPA. Besides, the thermal conductivity of the adhesive increases first and then decreases. The best thermal conductivity is 6.32 W/(m · K) when the content of diamond is 50%. Therefore, when the mass fraction of diamond is 50% ~ 60%, the adhesive and thermal conductivity of thermal conductive adhesive is the best.

In order to improve the thermal stability of PCD during practical application, the mixed solution of sulfuric acid and hydrogen peroxide was selected to remove cobalt from PCD. The effect of decobaltization on microstructure and mechanical property of PCD as well as its mechanism were studied. According to the SEM results, several deep corrosion pits were observed on the surface of PCD after the 48 h decobaltization process under room temperature, indicating that the cobalt phase was almost removed. Besides, the depths of decobaltization on the upper and lower surfaces were 176 μm and 162 μm, respectively. Based on the EDS results, the remaining mass fraction of cobalt in the decobaltized layer was determined to be 0.93%, while that in the non-decobaltized layer was 7.64%. This suggested that 87.83% of cobalt was dissolved and removed in the mixed solution of sulfuric acid and hydrogen peroxide. The residual stress of PCD samples was also measured. The residual stress before and after decobaltization was 483.91 MPa and 330.35 MPa, respectively. The reduction of 31.73% indicated that decobaltization could effectively reduce the residual thermal stress in PCD.