The Nickel Porous Material, And Nickel Microfiltration Membranes Developed

The study of preparing microfiltration nickel membrane has been carried out in this thesis, which includes two successive parts: preparing sintered porous nickel plates by powder metallurgy and coating them a thin layer of porous nickel film by electrolytic deposition.The factors that can affect the property of the sintered porous plates have been studied carefully. The results of this research show that the characters of the sintered porous plates such as tensile strength, linear shrinkage, maximal pore diameter, permeability, the rang of pore diameter can be controlled by using suitable nickel powder, which will be pressed in a mould under proper pressure to form briquette which then be sintered at favorable conditions. It was found that the fibrous powder is difficult to be compressed into a whole plate, which is almost unpermeable, whereas the spherical nickel powder is easy to be shaped into plates which have excellent permeability and high tensile strength. It is very clear that the fibrous powder is not suitable to be used as the material of a filter even though it has high porosity, as is the spherical nickel powder. When the spherical nickel powder is used as the raw material of a sintered porous plate, the affecting parameters such as the pressure under which the nickel powder is compressed, the sintering temperature of the briquette, the holding time of sintering, are investigated carefully. Taking the results of these experiments and the overall property of the product such as the tensile strength, permeability, and the maximal pore diameter into accounted, the optimal parameters were thus determined: the compressing pressure is 150MPa; the highest sintering temperature 700℃; the holding time of sintering 1 hour. The sintered plates produced at these conditions have fine pore size, the maximal one is less than 1 μ m; close pore size distribution, 99 % pore size is within 0.4⁰.8μm; and the permeability of N₂ is 1.03 1.18×10^-3m/Pa· h. Subsequently these plates were used as membrane supporters and coated a porous layer by electrolytic deposition to study whether or not a porous membrane with finer pore size and desirablepermeability can be achieved.It is a interesting test to fabricate porous membrane by electrolytic deposition as it's usually a common method to produce pore-free metals. In this thesis main factors that affect the membrane filtration property were investigated carefully. The results of the experiments show that the value of pH of the electroplating solution, electrode distance, Ni2+ density of the electroplating solution, the organic additive, the holding time of electroplating and current density have significant impact on the filtration property of the membrane, and the temperature of the electroplating solution also has some affect. With the perpendicularity experiments we know the influence sequence of this seven parameters on electroplating, and thus determined the optimal parameters for electroplating: pH is 4.5—5, electrode distance 60mm, the concentration of Ni 20g/l, the concentration of additive 0.15g/l, the current density 300A/m2, the time of electroplating 20mim, the temperature of the solution 40 °C ? With these parameters, we can make products which have pore size less than 0.32 u m, and permeability about 3X10"5m/ Pa ? h.After making substantial work of experiment and testing, we know that it is a simple way to make porous nickel filter by powder metallurgy, which has excellent characteristics such as fine pore size, high permeability and tensile strength, low deviation of these properties. With the development of powder metallurgy, the properties of the products will surely be improved. We also know that it is feasible to make porous membrane by electroplating. Due to difficulty in controlling the morphology, what's more the forming and growing speed of electrolytic nucleus is remain unknown, It is hard to improve the permeability of the products.