Preparation And Properties Of TiB₂ Composite Powder By Electroless Plating

The titanium diboride metal ceramic composite powder was prepared by electroless plating.The hydrogen evolution behavior was investigated during preparing the titanium diboride composite powder.We also showed the effects of the composition,loading,reaction temperature,pH value of the solution,and the plating amount.The surface morphology,composition of the coating and specific surface area of the composite powder were studied using SEM,EDS,XRD and BET.The results show that the amount of hydrogen evolution is proportional to the plating amount during preparation of composite powder.In the sodium citrate system,the order of the effects of the above mention facts on the volume of hydrogen evolution and plating amount is sodium hypophosphite> temperature> nickel sulfate> pH> sodium citrate.In the lactic acid system,the order is sodium hypophosphite> lactic acid> temperature> pH> nickel sulfate.In sodium pyrophosphate system,the order is sodium hypophosphite> nickel sulfate> sodium pyrophosphate> temperature> pH.The technological conditions in sodium citrate system are the concentration of nickel sulfate 20-30g/L,the concentration of sodium hypophosphite 25-35g/L,the concentration of sodium citrate 25-35g/L,the pH 5.0-6.0,the plating temperature 85-90 ?.The better technological conditions in the lactic acid system: the nickel sulfate concentration is 20-30g/L,the sodium hypophosphite concentration is 25-35g/L,the lactic acid concentration is30-40mL/L,the pH is 4.0-5.0,the plating temperature is 90-95 ?.The technological conditions in sodium pyrophosphate system are the concentration of nickel sulfate 25-35g/L,the concentration of sodium hypophosphite 25-35g/L,the concentration of sodium pyrophosphate 25-35g/L,the pH 9.0-10.0,the plating temperature 65-75?.After plating,the powder whose coating is Ni-P shows a cellular structure.The addition of dispersant improves the agglomeration of the powder,and is helpful to the uniform plating on the surface of the powder.The specific surface area of composite powder decreases after electroless plating in sodium citrate and lactic acid systems;On the contrary,the specific surface area increases in sodium pyrophosphate system.