Preparation Of Surface Nanocrystalline Ni-P Material

Surface treatment technology is not only a decorative technology of products, but also a manufacturing technology of products, improvement technology of products function and manufacturing technology of the latest nano materials.The progresses of using three kinds of surface engineering technology of electroless plating, heat treatment and plasma bombardment to produce surface nanocrystalline Ni-P material are researched in this paper.The effect of the main composition of complex agent on phosphorus of electroless Ni-P alloy is reasearched. Using three kinds of complex agents - citric acid, DL-lactic acid and acetic acid obtains the electroless Ni-P coatings of high, medium and low phosphorus content. As the pK value of complex agent increases, the P content in the coating varies from 3.82wt% to 6.40% and 11.69%. The structures and surface morphology of electroless Ni-P alloy coatings have been studied by means of X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). As the P content increases in the coating, the structure transits into amorphous gradually. It also shows that the global particles become large with the incrase of P content in the Ni-P coating.After treatment at 300℃, the coatigs of Ni-6.40%P and Ni-11.69%P translate into Ni nanocrystalline in which the grain size is about 20~40nm. At 400℃, the coatings translate into Ni3P. The crystallization behaviors of the two kinds of coatings have been characterized by differential scanning calorimetry (DSC). The apparent activation energy of Ni-6.40%P coaing is 212.46~264.23KJ/mol, and that of Ni-11.69%P coaing is 224.29-284.32KJ/mol. During isothermal crystallization process, the Avrami exponent of two kinds of Ni-P coatings has three values, which indicats the crystallization progress has three different stages. The crystallization mechanism of each stage is different.Furthermore, the crystallization progresses of the coatigs of Ni-6.40%P and Ni-11.69%P with Ar plasma bombardment are researched. The tow kinds of coatings translate into Ni nanocrystalline in which the grain size is about 20—40nm. The degrees of crystallization in two kinds of coatings increase obviously with the increase of the substrate bias voltage, but the grain sizes reduce slightly.At last, CNFs are prepared by catalytic pyrolysis of coal gas over Ni-P catalysts. The experiments are carried out to investigate the effects of prolysis time, P content in catalyst and grain sizes of catalysts. The results indicate that the diameters of CNFs are strongly affectedby the size and morphology of Ni-P catalysts. The synthesized CNFs have a diameter distribution about 100~200nm. The longer the raction time, the higher graphitization degree of the synthesized CNFs .