Study On Acid-base Etching And Electrochemical Behavior Of Zr₃Al₃C₅

MAX phase has excellent properties of ceramics and metals,and has excellent electrical and thermal conductivity.The MAX phase can be represented by M_n+1+1 AX_n,where M is a transition metal element,A is a main group element,and X is a nitrogen or carbon element,n=1,2 or 3.Since the force of the M-A bond is much smaller than that of the M-X,the atomic layer A can be detached by etching,and the remaining M and X combine to form a two-dimensional structure.Therefore,some etching agents can be selected to etch the Al atomic layer,in order to prepare layered structure Zr₃C₂.This paper uses HF,HCl+KF,KOH+KF to etch Zr₃Al₃C₅ to prepare two-dimensional Zr₃C₂.In this experiment,Zr₃Al₃C₅ was synthesized by the raw material ZrH₂:Al:C:Si=3:3.2:5:0.2 in the vacuum high-temperature tube furnace under the protection of Ar.It was sintered with Si and without Si,and the synthesized products were all obvious.The tight layered structure,and the sample with no Si synthesis incorporated into the compact layer,resulted in disordered crystal formation and a large number of pores also appeared on the surface.When the sintering temperature is 1500°C,the layered structure significantly increases,and the stripe structure also appears a little.It is concluded that when the sintering aid Si is added,the temperature is 1500°C,and the ZrH₂:Al:C:Si molar ratio is 3:3.2:5:0.2,the synthesized Zr₃Al₃C₅contains the least impurities.Secondly,in the etching of Zr₃Al₃C₅ process,the effect of etching temperature and etching concentration on the etching effect respectively.HF etching showed that at the concentration of 10%HF-40%HF,with the increasing of temperature and concentration between layer and layer spacing increasing,the particle size is smaller,the effect of etching is also getting better and better.HCl+KF showed the best effect in etching,etching at 80°C and 7.2 mol/L,Zr₃Al₃C₅ in Al is completely out of the formation of K₂AlF₅ and etching,Zr₃C₂,accompanied by H₂,a two-dimensional layered structure material etching.KOH+KF showed the best etching,at 90°C and 1mol/L time Zr₃Al₃C₅,Al inhibition effect,etching,the formation of K₃AlO₃ and AlF₃·3H₂O.Finally,in the polarization process of Zr₃Al₃C₅ with HCl+KF and KOH+KF,the effects of HCl and KOH concentration,temperature and the presence or absence of KF on the electrode reaction were studied.With the increase of HCl and KOH concentration and temperature and the addition of KF,the whole The polarization curve moves to the left,and the reaction is easier to proceed.The current density increases with the increase of the potential.To sum up,Zr₃Al₃C₅ with Si sintering and 1500°C works best.In the process of etching Zr₃Al₃C₅,the etching effect is best when the 40%HF and etching temperature are 60°C,80°C and HCl 7.2 mol/L,90°C and 1 mol/L KOH.