Study On Repassivation Behavior And Catalytic Degradation Performance Of Al-based Amorphous Alloys

Al-based glassy alloys with aluminum content over 80 at.%,especially Al-TM(Fe,Co and Ni:1-15 at.%)-RE(Y,Gd and Ce:3-20 at.%)alloys exhibit excellent electrochemical properties.In recent years,amorphous formation ability,corrosion resistance and catalytic degradation performance of Al-based amorphous alloys have become the hot topics in the amorphous area.The corrosion and degradation mechanism were thoroughly studied by changing the alloy compositions and adopting the heat treatment,hope to obtain more excellent alloy compositions and further promote their applications in amorphous coating and sewage treatment.In this paper,the influence of element addition on the precipitation tendency of intermetallic compounds and repassivation behavior of Al-Fe-Y amorphous alloys were studied.In addition,amorphous alloys show the excellent catalytic degradation performance due to their particular atomic structure.Therefore,we also researched the degradation mechanism of Al-Co-Y and Al-Ni-Y alloy ribbons and analyzed the effect of crystallization methods and the precipitation of crystallization phases on the degradation.The effect of Au addition on the precipitation tendency of AlY and AlFe phases in the Al88Fe5Y7 alloy was analyzed by the calculation of atomic packing efficiency(?)and thermodynamic compound parameters(F).Moreover,the corrosion behavior of Al88-xFe5Y7Aux(x=0,0.5 and 1)amorphous alloys was investigated by the electrochemical workstation.When Au content x=0,the atomic packing efficiency of AlY cluster is lower than that of AlFe clusters so that AlY phases have the larger precipitation tendency.At the same time,the electrochemical research shows that it has the larger ?E(=Ep-Eprot,Ep and Eprot are piting and protective potentials)and the higher steepness ks(=dE/dlog(I))in Tafel curve than after adding Au.This indicates that pitting corrosion occurs easily and many pitting tunnels are created in the pit interiors so that the repassivation becomes more difficult;whereas in case of x=0.5 and 1,the AlFe phases precipitate more easily due to their higher packing efficiency,which is the start point to trigger the destabilization.The ?E and ks of the alloys are lower obviously.This shows that the corrosion resistance of alloys has been improved,they can repassivate quickly after pitting and have excellent passivation film repair capability.The catalytic degradation performance of Al95-xTMxY5(x=7 and 10)(TM=Ni and Co)amorphous ribbons was investigated by UV-Vis spectrophotometer.In addition,the degradation of alloy ribbons after annealing was also compared.We found that Al85TM10Y5 alloy ribbons degraded faster than Al88TM7Y5 alloy ribbons.This indicates that AlTM clusters play an important role in the degradation of dye molecules.Crystallization methods of amorphous alloys also have an extremely important effect on degradation.The degradation rate of Al85Co10Y5 alloy ribbons is the fastest in all samples.This is due to their unique eutectic crystallization method,there are more Al9Co2 pre-existing crystal nucleuses in the amorphous matrix,cobalt atoms are prone to electron transfer during degradation to accelerate reaction.The amorphous ribbons of Al88Co7Y5,Al88Ni7Y5 and Al85Ni10Y5 are all primary crystallization which is not conducive to the degradation of dye molecules.The degradation rates of the crystallized Al88Co7Y5 and AI85Co10Y5 alloy ribbons slow down.Amorphous alloys have more excellent degradation properties compared to the crystallized alloy ribbons.This is mainly due to their special disordered atomic structure and non-equilibrium metastable feature,the specific surface energy is higher so that the dye molecules can be rapidly adsorbed.At the same time,micro-batteries which can accelerate degradation reaction are easily formed between the Co-rich and Y-rich clusters.The crystallized alloy ribbons which have the poor adsorption capacity degrade slowly in the early stage,the later degradation is mainly through the selective dissolution of A1 and Y elements to form the Co-rich nanoporous structure which accelerates the degradation of dye molecules.