Preparation And Performances Of Denitrified Secondary Aluminum Dross-Epoxy Resin Gradient Composites

Denitrified secondary aluminum dross(DSAD)is a solid powder obtained from secondary aluminum dross after water washing,desalting and denitrifying.Its main phase composition is Al₂O₃,Al(OH)₃,Mg Al₂O₄.The rich content of aluminum indicates its great potential as an aluminum source for the production of high value-added products such as aluminate cement,high aluminum refractory,aluminum-containing catalyst or catalytic carrier.Based on the good wettability between the DSAD and the mixture of epoxy resin(EP)and anhydride curing agent,the DSAD was used as the enhanced particle of brittle EP to make the DSAD-EP composite to improve the mechanical properties of EP.The main work of this paper will include the following three aspects.(1)Phase and chemical analysis show that the DSAD is mainly composed of Al₂O₃ and Mg Al₂O₄.The wettability test of the mixture of DSAD and epoxy resin mixture shows that the composite with excellent interface bonding between matrix phase and enhanced particles can be obtained,which may be related to the hydrogen bonding between epoxy group in epoxy prepolymer and-OH on the surface of DSAD.The epoxy resin mixture with high DSAD filling was settled in the direction of gravity by standing.After curing,it was made into composite material with certain performance gradient in the direction of gravity.The segmented characterization in the gradient direction shows that the density,tensile properties and hardness of the samples show similar changes in the gravity direction.The maximum average density(1.42 g/cm³)was found in the range of 0?2 mm along the gradient direction.2?4 mm region showed the highest tensile strength(75.7 MPa),elongation at break(10.2%),fracture toughness(3.75 MPa)and higher Young's modulus(2.31 GPa).The high filled area has low tensile properties due to trans-particle fracture,and the low filled area can be toughened by shear yield,crack deflection,particle pull-out and microcrack,so as to improve the brittleness of epoxy matrix.The hardness test results show that the composite area with high DSAD filling shows higher hardness.Dynamic thermal analysis shows that high filling content(>20 wt.%)can effectively improve the storage modulus of sample.(2)The friction and wear test on the high filled surface of the composite show that the filling of DSAD can effectively improve the tribological properties of the composite,which is manifested in the improvement of wear resistance and friction stability.By comparing the test results of different samples,it can be found that increasing the filling amount of DSAD and increasing the sedimentation coefficient of DSAD can effectively enhance the improvement of tribological properties of epoxy matrix caused by DSAD filling.The addition of DSAD can enhance the tribological properties of epoxy matrix by transforming the fatigue wear and adhesive wear of pure epoxy resin into abrasive wear of composite.The application of centrifugal method can deposit a dense layer of DSAD particles on the friction surface of the sample to improve the wear resistance of the matrix.Compared with the former,the strengthening effect is more significant by increasing the sedimentation coefficient of DSAD.(3)The DSAD dispersion model with random orientation is established by using the Voronoi element method,and the thermal conductivity of the composite material is predicted by the thermo-mechanical coupling calculation using the finite element software Solid Works2018 to obtain the temperature field and force field data.The results of numerical simulation show that the interfacial pores have more influence on the thermal conductivity than the residual pores in the matrix.The simulation of thermal stress and strain shows that dsad-ep composite with high filling ratio has lower thermal stress and strain.