Research On Direct Preparation Of Porous Foam Nickle By Jet Electrodeposition

Based on the all-pervading complicated technology and high cost on preparing the porous foam metal, jet electrodeposition, a new method to prepare porous foam metal directly was put forward. Its principle were listed as follows. Deposited Layers generated loose and porous vesicular tissue on the condition of high current density. What's more, the hydrogen evolution reaction produced a lot of bubbles and porous deposition layers were easily formed owing to that metal could only depose among those bubbles'clearance. Compared to other methods, vesicular tissue formed by jet electrodeposition growed totally all by itself at original place, without any auxiliary materials added. Meanwhile, the process is rather simplied and the cost is low relatively. This process can be carried out at normal temperature and atmospheric pressure, having no high requirement of external environment and equipments. This research is meaningful to enrich processes for preparing porous foam metals. The major works were as follows:1. The principles about jet electrodeposition and preparation of porous metals were investigated. The shape and growth process of porous dendritic structure in jet electrodeposition were simulated by the Diffusion-Limited Aggregation(DLA) model. Then, experiments were carried out to verify the simulation products by jet electrodeposition equipments. The results show that the DLA model was rather usable to explain the growth of dendritic structure. Migration of particles, releasing number of particles, joint probability in the DLA model were corresponding to voltage, deposition time, and electrolyte temperature during jet electrodeposition inherently. The deposition layer in simulation had obvious dendritic structures. Some particles which were moving toward cathode along main migration direction were captured by cathode polar plate and deposited together, forming the dendritic structure. At last, morphology of metal deposited layer was generated with foam point's growth and extension.2. The devices of the direct fabrication of porous metals were designed and developed all by ourselves, including computer control system, nozzle lifting mechanism, the mechanical body, electrolyte injection and circulatory system, equipment to constant temperature and circulation of electrolyte, anode cavity and nozzle. A group of foam nickel metal samples with simple shape and a certain thickness were prepared. Microstructure, porosity and relative density of foam nickel metal were investigated. The results show as follows. One, current density in Jet electrodeposition can be very high. It can be 100 times of conventional one or even higher. Two, dendritic structure tended to grow under a higher current density and foam nickel has a typical dendritic structure. Three, hydrogen evolution reaction occured easily under a high current density, releasing a lot of bubble. It was only in the vacuity among the bubbles that metal ions could be reduced to be porous deposition layers. Four, experimental parameters in jet electrodeposition had a apparent effect on relative density and porosity of nickel foam. With current density, concentration of Ni2+, jet speed and distance of electrolyte increasing, the porosity of nickel foam became lower. Generally speaking, the porosity of nickel foam samples range from 50~70%, relative density 0.3~0.5 and aperture was confined within 0.3mm.3. Relational mechanical properties, electrical properties and heat transfer properties were studied. The results show that: hardness of foam metal is much lower than entitative metal. There were also much difference among the nickel foams. Static compressive properties of nickel foam had three stages: linear elastic deformation, plateau region and compacted section. The higher porosity was , the smaller plateau stress was. And, foam metal's resistivity was much higher than entitative metal. Opening nickel foam prepared by jet electrodeposition had excellent heat dissipation performance, capable to be used in electronic industry as heat radiation elements. Give its basic nature, nickel foam is potential to be applied in battery or catalyst carrier , et al.