Preparation And Properties Of Chemically Deposited Nickel Base Alloy/Fe₃O₄ Composites

In this paper,nickel base alloy/Fe₃O₄ composite was prepared by electroless plating method,and the effects of bath composition and deposition time on deposition rate,coating composition and apparent morphology of Ni-N alloys were studied.The phase,composition and surface morphology of the samples were characterized by X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscope?SEM?,transmission electron microscope?TEM?and optical microscope.The electromagnetic parameters of the sample were measured by the vector network analyzer?VNA?and the wave absorbing performance was simulated.The main research contents of this paper are as follows:?1?The Ni-N alloy was electroless plated on the surface of copper substrate under alkaline condition with hydrazine hydrate as reducing agent sodium citrate as complexing agent,and the reaction process and coating growth mechanism were discussed.It was found that continuous and complete Ni-N alloy films were deposited on the surface of red copper substrate by electroless plating technique.Electroless nickel plating can be carried out in the bath at about 70?,which greatly reduces the evaporation rate of the bath compared with the traditional formula?reaction temperature is usually around 90??,improves the stability of the bath,and makes the reaction easier to control.The coating grows in the form of island bond.The coating with larger thickness can be obtained by extending the reaction time appropriately.However,the coating obtained by this method is rough and the surface fluctuates greatly,which can be improved by adding brightener in the plating solution or annealing in reducing atmosphere.?2?The two-step hydrothermal method was used to prepare rod-shaped FeOOH with different particle sizes as the reaction precursor under different pH conditions,explore the relationship between the morphology of the reduced products and the morphology of the precursor under different reaction temperatures and reaction times,and study its wave absorption performance.The results show that Fe₃O₄ obtained by this method has good crystallinity,high purity,narrow particle size distribution,low preparation temperature and high magnetic particle properties.Moreover,under the same reaction environment,the products with high reaction temperature have smaller particle size.The good crystallinity of the precursor leads to the more complete morphology of the product.Reduced products are more likely to retain the original form of the precursor at lower temperatures.FeOOH synthesized in 2.0mL/L HCl acidic environment was used as the precursor,and the Fe₃O₄ prepared by reaction of hydrazine hydrate as reducing agent at 120?for 24 hours was uniform in size.Its maximum electromagnetic wave reflection loss is more than-60dB,When the matching thickness is 2.5mm.The absorption rate is more than 90%and the frequency band width is more than 3GHz of this sample.It has excellent absorbing performance.?3?NaH₂PO₂ was used as the reducing agent to prepare the plating solution.The Ni-P-Fe₃O₄ composite powder with high phosphorus content of about 10%,good dispersion and good conductivity was prepared.The research shows that the optimal reaction temperature is 80?and the pH value is 8-9.After 30min of reaction,Ni-P-Fe₃O₄ dispersed particles were obtained,which coating was an amorphous Ni-P alloy.The composite powder has many advantages,such as weak magnetism,low resistivity and high conductivity.When the thickness is 3.5mm,the maximum reflection loss is-12.5dB.The absorption rate of electromagnetic wave reaches 90%,and the absorption effect is obvious in the low-frequency region.Figure[35]table[6]reference[96]...