Isothermal crystallization kinetics of Cu_(40)Ti_(60)amorphous alloy has been studied using differential scanning calorimetry(DSC).Both as-quenched and pre-annealed ribbons were inves- tigated.For crystallization of a...Isothermal crystallization kinetics of Cu_(40)Ti_(60)amorphous alloy has been studied using differential scanning calorimetry(DSC).Both as-quenched and pre-annealed ribbons were inves- tigated.For crystallization of as-quenched amor- phous ribbon in Ar,it was found that the kinetics follows Johnson-Mehl-Avrami equation with mean Avrami exponent n=2.58,which indicates that crystallization of amorphous Cu_(40)Ti_(60)is a three-dimensional diffusion controlled growth pro- cess with constant nucleation rate,i.e.,primary crystallization process.The primary phase is the tetragonal CuTi_2.The as-quenched amorphous ribbons were also crystallized in air,the results re- veal that oxidation has no significant influence on crystallization kinetics of amorphous Cu_(40)Ti_(60). The results of crystallization of pre-annealed rib- bons show a decreasing tendency of Avrami expo- nent with increasing pre-anneal time.The local activation energy and local Avrami exponent dur- ing crystallization process of as-quenched amor- phous alloy were also examined.展开更多
The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ...The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ion bombardment.There are great distinctions in compositions and chemical states between the surface layer and the bulk.The main constituents Ni,P and Fe are lower in the sur- face layer,and they are mostly in oxidized states, whereas C,O and N are enriched in the surface lay- er.The thickness of surface oxide layer is approximately 20 nm,this layer was assumed to be of great significance to various properties of amor- phous alloy Ni_(64)P_(20)Fe_(16),expecially to the chemical and catalytic properties.Experiments proved that transitional element Fe cannot improve oxidation resistance of the amorphous Ni-P system.展开更多
文摘Isothermal crystallization kinetics of Cu_(40)Ti_(60)amorphous alloy has been studied using differential scanning calorimetry(DSC).Both as-quenched and pre-annealed ribbons were inves- tigated.For crystallization of as-quenched amor- phous ribbon in Ar,it was found that the kinetics follows Johnson-Mehl-Avrami equation with mean Avrami exponent n=2.58,which indicates that crystallization of amorphous Cu_(40)Ti_(60)is a three-dimensional diffusion controlled growth pro- cess with constant nucleation rate,i.e.,primary crystallization process.The primary phase is the tetragonal CuTi_2.The as-quenched amorphous ribbons were also crystallized in air,the results re- veal that oxidation has no significant influence on crystallization kinetics of amorphous Cu_(40)Ti_(60). The results of crystallization of pre-annealed rib- bons show a decreasing tendency of Avrami expo- nent with increasing pre-anneal time.The local activation energy and local Avrami exponent dur- ing crystallization process of as-quenched amor- phous alloy were also examined.
文摘The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ion bombardment.There are great distinctions in compositions and chemical states between the surface layer and the bulk.The main constituents Ni,P and Fe are lower in the sur- face layer,and they are mostly in oxidized states, whereas C,O and N are enriched in the surface lay- er.The thickness of surface oxide layer is approximately 20 nm,this layer was assumed to be of great significance to various properties of amor- phous alloy Ni_(64)P_(20)Fe_(16),expecially to the chemical and catalytic properties.Experiments proved that transitional element Fe cannot improve oxidation resistance of the amorphous Ni-P system.
