Preparation Of Rice Husk Ceramic Particles And Its Effect On Tribological Properties Of Aluminum Matrix Composites

In this paper,rice husk ceramic particles were prepared via high temperature carbonization process using the rice husk and phenolic resin as the raw materials.Ni coated rice husk ceramics?Ni-RHC?particles were prepared by a common electroless plating method.The optimum technological parameters of homogeneous chemical electroless plating were investigated via a series of experiments.Then,Ni-RHC particles and aluminum matrix composites were prepared,and their tribological behaviors were also investigated using a controllable environmental tribometer.The effect of Ni-RHC contents on the tribological properties of the composites was also investigated.Effect of different process parameters on the plating effect was investigated via single and orthogonal tests.The results show that the influencing order of the factors for the chemical electroless nickel plating is: the concentration of sodium hypophosphite > temperature > pH > time.The optimum parameters?Temperature,time,pH and concentration of sodium hypophosphite?are 60 ?,180 min,pH=11,180 g/L,respectively.The structure,morphology and compositions of RHC were analyzed by the scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FT-IR?and X-ray diffraction?XRD?.The results show that the surface of RHC particles has-OH,-CH₃,-CH₂-,-C₆H₅ and other functional groups.X-ray diffraction pattern showed RHC particles contained a lot of amorphous carbon and a small amount of graphite microcrystals.The nickel peaks of Ni-RHC with help of the XRD proved the Ni particles successfully coated on the surface of RHC particles.SEM/EDS results can also prove that the result,besides Ni-RHC particles mainly contain 5 kinds of elements which were carbon,silicon,phosphorus,nickel and oxygen elements,respectively.RHC and Ni-RHC were used to preparing friction material such as RHA and Ni-RHA by a cold pressing technology.Besides that the influences of load and speed on the friction properties of two materials were also investigated.The results show that Ni-RHA wear volume is nearly 100 times lower than that of RHA under the same friction conditions.Under the condition of high load and speed,Ni-RHA anti-friction performance is better than RHA.It is found that the RHA has a layer of black attachments on the surface of the steel ball,and the main compositions are C and O.Raman analysed the surface carbon of RHA has a certain degree of graphitization.As for Ni-RHA materials,the coating of Ni particles was exfoliated from the surface of RHC to froming the protecting film which resulted in strengthening the anti-wear property of materials.RHC/Al and Ni-RHC/Al composites were prepared by a cold sintering process.The influence of the addition amount on the friction properties of the composites was mainly studied.The results show that the wear volume is the smallest one than the others when the Ni-RHC added amount is 15 wt%.Besides,the hardness of Ni-RHC/Al composites is higher than that of RHC/Al.The addition of 5 wt% MoS₂ obviously improved the anti-wear property of the composites.The mechanism of anti-friction is attributed to anti-friction and anti-wear roles of molybdenum disulfide.Pure substrate material cause severe plastic deformation and adhesive wear during the friction process.The composites including the RHC particles can obvious enhance the carrying capacity and anti-wear property which was ascribed the increase of hardness of materials but the exfoliation of RHC particles results in the appearance of the abrasive wear during the friction process.As for adding Ni-RHC particles,friction effect firstly makes the metal nickel particles surface exfoliation which can effectively protect the friction interface.