占位剂K2SO4对NiCu合金多孔膜孔结构的影响

以Ni元素粉末为原料,K₂SO₄粉末为占位剂,将Ni-K₂SO₄混合粉末加入聚乙烯缩丁醛(PVB)乙醇溶液中制成浆料,刮涂在Cu箔上,利用Kirkendall效应,经真空烧结制备多孔NiCu合金膜。研究K₂SO₄含量对NiCu合金多孔膜收缩率、透气度、孔径、宏观和微观形貌的影响。结果表明:随Ni-K₂SO₄混合粉末中的w(K₂SO₄)增加,多孔膜的透气度先增大后减小。当w(K₂SO₄)<40%时,随w(K₂SO₄)增加,膜层的烧结收缩率减小,透气度增大,最大达到2361 m3/(m2·h·kPa),最大孔径在45μm左右变化不大;w(K₂SO₄)大于40%时,多孔膜的透气度下降,孔径明显减小;当w(K₂SO₄)>60%,膜层透气度低于测试仪器下限。适量的K₂SO₄通过在涂覆层中的占位作用阻碍Ni颗粒烧结致密化,提高多孔膜的透气度,但过量的K₂SO₄会在烧结过程中阻断Cu原子向Ni粉层扩散,使Cu箔上难以形成通孔,透气度大幅降低。

Effect of K2SO4space-holder on pore structure of NiCu alloy porous membrane

The Ni-K₂SO₄mixed powder,in which Ni element powder is the raw material,and K₂SO₄powder is the space-holder,is added into the polyvinyl butyral(PVB)ethanol solution to make a slurry,which is coated on the Cu foil.NiCu alloy porous membrane was prepared basing on Kirkendall effect by vacuum sintering.The influence of K₂SO₄contenton on area shrinkage,permeability,pore size,macro and micro morphologies of porous membrane and the influence of K₂SO₄on the pore structure of porous membranes at different temperatures were investigated.The effect mechanism of K₂SO₄on pore structure of the porous alloy membrane during sintering process was also studied.The results show that with the increase of w(K₂SO₄)in Ni-K₂SO₄mixed powder,the permeability of porous membrane first increases and then decreases.When the mass fraction of K₂SO₄is lower than 40%,with the increase of K₂SO₄content,the shrinkage rate of the film decreases and the permeability increases.The maximum permeability is 2361 m3/(m2·h·kPa).The maximum pore diameter of the sample with little change is about 45μm.When the w(K₂SO₄)is more than 40%,the permeability and pore diameter of the porous film both decrease obviously.When the w(K₂SO₄)is more than 60%,the permeability of the film layer is lower than that of the lower limit of the test instrument.Proper amount of K₂SO₄can improve the permeability of porous alloy membrane through hindering sintering densification based on the space occupying effect in the Ni coating,but excessive amount of K₂SO₄will block the diffusion of Cu atoms to Ni powder layer,which makes it difficult to form through-pores on the Cu foil,resulting in a significant decrease in permeability.