Of Tih <sub> 2 </ Sub> Powder Surface Of Electroless Nickel Plating Process

TiH₂ is widely used as the best foaming agent of synthesizing foaming aluminum by fused mass froth method. It affects the production process of foam aluminum very much.The key point of synthesizing foaming aluminum by fused mass froth method is to make the TiH₂ releasing gas release slowly.At present, coated TiH₂ is widely used to delay the rate of releasing gas of TiH₂.The methods are generally classified into two kinds, physical and chemical methods. In the research: TiH₂ is coated by Ni in different situation.The microstructure and phases of coated TiH₂ is determind by SEM and XRD ; The performance of releasing hydrogen gas of coated TiH₂ is anlysised by DSC and TG.The results indicate: (1) The mechanical fragmentated TiH₂ has large specific surface and high activity. The activity of TiH₂ reduced after surface pretreatment.It is not conducive to sensitization and activation.It is Nickel better when use the two-step surface pretreatment. (2)The role of the factors which affect the rate of nickel descending order is: nickel plating reaction temperature>hydrazine hydrate concentration>reaction pH value>Nickel sulfate concentration>reaction time. (3)The optimal reaction conditions of Electroless plating in thisstudy was:nickel sulfate concentration of 75g/L,hydrazine hydrate mass concentration of 17.5g/L,nickel reaction temperature of 85℃,nickel reaction PH value of 9.5,and nickel reaction time of 15min. By controlling the reaction conditions can be produced different Ni content Ni/TiH₂ composite powder. (4)The beginning hydrogen release temperature of TiH₂ is improved when TiH₂ is coated by Ni layer.The mass fraction of Ni/TiH₂ with 49.5% Ni beginning hydrogen release temperature reached 450℃.At the same time, the existence of Ni layer, reduced the average rate of the release of hydrogen TiH₂ . The average hydrogen release rate of original TiH₂ at 450-700℃is 11.11ml/min, while the average hydrogen releas rate of Ni/TiH₂ composite powders with 49.5% Ni at 450-700℃is 6.45ml/min. (5)The TiH₂ electroless nickel plating rate kinetic equation was:Experimental verified that TiH₂ electroless nickel plating rate wasconsistent with this reaction kinetic equation.