Study On The Structural Properties Of FeCu Nanoparticles

Nano alloy has been developed rapidly in the past 30 years because of its high efficiency catalytic performance.FeCu nano alloy has been widely used in the purification of water quality and medical treatment due to its high efficiency decontamination ability.Abundant theoretical and experimental studies on FeCu nanoparticles had emerged.Based on these experimental and theoretical studies,this thesis mainly studies the following issues from the perspective of structure:In the third chapter,according to the calculation of NEB method,the diffusion of Cu adatom on the Fe-RHO₁₁₀₅substrate and Fe adatom on the Cu-Wulff₁₂₈₉substrate were studied respectively.It was found that the single Cu adatom diffused between the two{111}facets on Fe-RHO₁₁₀₅substrate via the Hopping mechanism and did not exchange with the Fe atom of the substrate.At Cu-Wulff₁₂₈₉substrate,when activate the interfacet diffusion of Fe adatom on the surface,the energy of the system decreases obviously after chosen the Exchange mechanism.However,the large energy barriers need to be overcome when chosen the Exchange mechanism.The results show that the core-shell structure of Fe_coreCu_shellshould be the general structure of Fe based FeCu nanoparticles,while the metastable core-shell structure of Fe_shellCu_coreshould be the general structure of Cu based FeCu nanoparticles formed at low temperature.In the fourth chapter,by controlling the temperature and substrate type,the deposition simulation of Cu?or Fe?on the Fe-RHO₁₁₀₅(or Cu-Wulff₁₂₈₉)substrate were carried out at different temperatures.It was shown that when Cu atoms grown on the Fe substrate,the Cu atoms were uniformly concentrated on the surface of the substrate and did not exchange with the substrate Fe atoms.Finally,the perfect core-shell structure of Fe_coreCu_shellwas formed;When Fe atoms grown on the Cu substrate,some of them were exchanged with the surface atoms of the substrate,but due to the strong interaction between Fe and Fe atoms and it couldn't provide the energy needed for excessive exchanged at low temperature,it led to the Fe atoms formed a local accumulation on the surface of the substrate,and finally formed a metastable Fe_shellCu_corecore-shell structure with the accumulation to a certain extent.The results are consistent with the results of Chapter 3,which are mutual evidences.Moreover,it was further indicated that the metastable Fe_shellCu_corecore-shell nanoparticles can be obtained by controlling the substrate type and temperature of the growth.Finally,in Chapter 5,the MC calculation based on the Metropolis algorithm further displayed that the perfect core-shell structure of Fe_coreCu_shellshould be the stable structure of Fe based FeCu nanoparticles at room temperature.The results of the previous chapters 3 and 4 could be proved,that was,if Fe was used as the substrate,the perfect Fe_coreCu_shellnanoparticles will be formed.However,the Fe atoms tends to exchange with the atoms inside the substrate to obtain the nanoparticles with lower energy in Cu based FeCu nanoparticles.Finally,formed another core-shell structure,that was,the core component was phase separated Fe and Cu,and the shell was Cu.So,under the condition of high temperature with enough energy,Cu based FeCu nanoparticles usually form a stable core-shell structure with Cu shell,and the core component is phase separated Fe and Cu.