Investigation On The Technology And Properties On The Metallization Of Man-made Diamond Surface

The metallization of diamond surface was prepared by means of electroless precoatand electroplate thickening. The testing method contains SEM, XRD, EDS, diamondsingle particle compressive strength tester, impact toughness test apparatus and so on, theeffects of the bath composition, technological conditions and the weight rate on themorphology, phase analysis, compressive strength and impact toughness value areinvestigated.Through the study of metallization on man-made diamond surface, meaningfulresults were found out as follows:(1) Each component of electroless plating solution has a certain effect on thedeposition velocity of Ni. The results show that the deposition velocity increased withincreasing of the concentration of NiCl2when the concentration was under25g/L, butwhen it was greater than25g/L, the deposition velocity decreased with increasing of theconcentration of NiCl2; the deposition velocity increased with increasing of theconcentration of NaH2PO2when the concentration was under24g/L, but when it wasgreater than24g/L, the deposition velocity decreased with increasing of theconcentration of NaH2PO2; the deposition velocity increased with increasing of theconcentration of C4H4Na2O4when the concentration was under18g/L, but when it wasgreater than18g/L, the deposition velocity decreased with increasing of theconcentration of C4H4Na2O4.(2)Technological conditions of electroless plating have a great effect on depositionvelocity of Ni. The results show that the reaction cannot proceed normally when thetemperature under70℃, the deposition velocity increased with increasing of thetemperature when the temperature was at70~80℃, but when it was greater than80℃, the deposition velocity decreased with increasing of the temperature, withthe continuous extension of time reaction, the solution appeared unstable and black, Niplating appeared on the wall and bottom of bath; the deposition velocity increased withincreasing of the stirring rate when the stirring rate was under200r/min, but when it wasgreater than200r/min, the deposition velocity decreased with increasing of thestirring rate.(3) Compared with the man-made diamond grain, the average compressive strengthof single nickel plated diamond grain is not obviously changed under the condition of thethin coating; the variance of the compressive strength with different content of Ni wasquite different, and it decreased with increasing of Ni.(4) The surface roughness of diamond is increased with the increase of weight rate,and the compressive strength of diamond is increased with the increase of weight rate.(5)The400℃heating has no effect on the surface morphologies ofdiamond.Compared with the sample before heat treatment, the phenomenon of blue shiftis discovered on the diamond and nickel under the condition of heating it to400℃andkeeping it for30min. The average compressive strength is greatly improved and it isincreased with the increase of weight rate, even it is a little increased after heat treatment.(6) NaCl is the main factor in influencing the electrical conductivity of platingsolution, and NiSO4has no effect on the electrical conductivity of plating solution. Theimpact toughness value of diamond increased with increasing of the concentration ofNaCl when the concentration was at5-30g/L, but when it was greater than30g/L, theimpact toughness value of diamond decreased with increasing of the concentration ofNaCl, the impact toughness value of diamond increased with increasing of theconcentration of NiSO4when the concentration was at100-250g/L. The concentration ofNaCl and NiSO4has no effect on the compressive strength tester of diamond.