Research On Plating Technology Of Palladium Film On Porous Stainless Steel Substrate

Membrane separation technology is one of the main technologies for separating and purifying hydrogen,helium and other impurities in a fusion-fission reactor.Among them,palladium and its alloy membrane are the main separation membrane materials used currently because of their high hydrogen selectivity and permeation rate,as well as relatively chemical inertness.The porous material/Pd membrane is becoming a research hotspot for its significant benefit of reducing the thickness of the palladium membrane and improving hydrogen permeability.There are mainly two types of matrix materials of the existing porous material/Pd membrane,namely porous ceramic material and porous metal material,respectively.In this paper,the Pd membrane was prepared on the substrate of the porous stainless steel which was selected as the support material.In order to obtain the dense Pd membrane,electroless plating,electroplating,and combined plating are compared.Moreover,the processing parameters are optimized based on the electroless plating solution concentration,electroless plating time,electroplating current density,electroplating time,and pre-treatment of porous stainless steel substrate.The density and purity of the membrane were characterized by SEM and XRD.The porous stainless steel/Pd membrane with excellent membrane quality was subjected to thermal shock resistance and hydrogen permeation test.The results are shown as follows:(1)Pure electroless plating or electroplating fail to produce a dense palladium membrane on the surface of porous stainless steel,whereas combined plating succeeds.And it is recommend that the dense palladium membrane can be obtained after electroless deposition for 60 min in 0.1 g/L PdCl2-HCL solution,followed by electroplated for 60 min in palladium ion concentration of 17 g/L palladium ammonia solution.(2)The results of the structure and performance of the porous stainless steel/Pd membrane prepared by the electroless-plating combination method shows that the surface morphology of the metal palladium membrane is dense without holes,and the crystal grains were tightly bound together.The size of grains is related to the region,the grain in the center of the matrix is in the form of small particles,the grains in the edge region of the matrix are in the form of slender needles,the size of the same region is uniform,and the thickness of the membrane is about 10-20 μm.The composition of the membrane layer is pure,without impurities,complete nucleation,good crystallization,and the grain structure is fcc type.There are five different growth orientations,of which(111)is its preferred orientation.(3)Within the experiment temperature of 573.15 K-723.15 K,porous stainless steel/Pd membrane shows stable properties and excellent membrane-based bonding.And no obvious change in surface morphology is observed.It can withstand 50 times the test of high-temperature thermal shock test,without intermetallic diffusion between membrane layers.(4)Hydrogen permeability of porous stainless steel/Pd membrane is 3.42×10-8 mol-m-1·s-1·Pa-0.5 at 723.15 K and 13 KPa,while deuterium permeability is 2.08×10-8 mol·m-1·s-1·Pa-0 5.Under the same conditions,the hydrogen permeability is about 1.67 times that the deuterium permeability.The gas separation coefficient is approximately 80 for D2/Ar mixture with a ratio of 1:1,and the D2 concentration of product gas is 98.8%.