Amorphization was achieved by a non.equilibrium process of ion mixing of multilayered films iii an inuniscible Fe-Cu system with a large positive heat of formation(+19kJ/mol).The free energy diagrtiin of the Fe-Cu sys...Amorphization was achieved by a non.equilibrium process of ion mixing of multilayered films iii an inuniscible Fe-Cu system with a large positive heat of formation(+19kJ/mol).The free energy diagrtiin of the Fe-Cu system was constructed.In calculation,the inter facial free energy,ferromugnctic effect and the structure ch arac-tenstics were considered.The calculated Fe-Cu free energy diagram can explain the ainorphization behavior in this imniiscible system.展开更多
Fe_(75)Cu_(25) nano-multilayers were prepared by alternative deposition of pure Fe and Cu metals and then annealed in situ in transmission electron microscopy to investigate the structural phase transformation.A new p...Fe_(75)Cu_(25) nano-multilayers were prepared by alternative deposition of pure Fe and Cu metals and then annealed in situ in transmission electron microscopy to investigate the structural phase transformation.A new phase was formed in the Fe-Cu multilayers by interdiffusion at 820℃ for about I0min and was identified to be of fcc structure with a lattice parameter of 0.854±0.005nm.展开更多
A fractal aggregation process in the ion irradiated films was recognized.The process was intrinsic of interaction of ions with solids and sincerely modelled by the cluster diffusion-limited-aggregation model.The energ...A fractal aggregation process in the ion irradiated films was recognized.The process was intrinsic of interaction of ions with solids and sincerely modelled by the cluster diffusion-limited-aggregation model.The energetic ions not only drive the atoms and clusters in the area of collision cascade in motion which may be modelled as random walks,but also create vacancies and voids which contribute to the aggregation process.The process was also of percolation characteristic with a fractal dimension 1.82 at the critical point.展开更多
Percolation structures of precipitated new phases were observed in Au-Ti and Ni-A1 amorphous films upon ion irradiation.The experimental evidences showed that the observed structures were formed in the surface layer,c...Percolation structures of precipitated new phases were observed in Au-Ti and Ni-A1 amorphous films upon ion irradiation.The experimental evidences showed that the observed structures were formed in the surface layer,ca 20nm thick.It was revealed that the formation of percolation clusters was sensitive to alloy composition as well as irradiation dose.展开更多
The enhancement of adhesion between deposited metal layers(Ti and Cu)and the oxide substrates at RT and 300°c respectively was studied by argon ion irradiation to various doses.The experimental results showed tha...The enhancement of adhesion between deposited metal layers(Ti and Cu)and the oxide substrates at RT and 300°c respectively was studied by argon ion irradiation to various doses.The experimental results showed that the adhesive strength increased after a threshold dose irradiation and reached as aturation value at higher doses in all metal/oxide pairs.RBS spectra showed that chemical reaction had taken place in Ti/oxide case,while in Cu/oxide case,both RBS and XPS analysis showed that no evidence of such reaction had been induced.展开更多
Dendrites were observed for the first time in the Ni-Mo thin films irradiated by ion beam.Various patterns are presented and a typical one features no specific orientation.The formation of dendrites induced by ion bea...Dendrites were observed for the first time in the Ni-Mo thin films irradiated by ion beam.Various patterns are presented and a typical one features no specific orientation.The formation of dendrites induced by ion beam is attributed to the critical phenomenon during amorphous to crystalline phase transformation.展开更多
Metastable Ag80Cr20 alloy was produced by ion mixng of Ag-Cr multilayers at liquid nitrogen temperature.The immiscibility in Ag-Cr system was accounted for in terms of the characteristics of the electronic structures ...Metastable Ag80Cr20 alloy was produced by ion mixng of Ag-Cr multilayers at liquid nitrogen temperature.The immiscibility in Ag-Cr system was accounted for in terms of the characteristics of the electronic structures of the constituent metals,and the ion beam induced alloy formation was explained by considering ion mixing as a process favoring the co-resonance process required for forming the new energy band of the metastable Ag-Cr alloy.展开更多
By taking into account the valence electron number and periodic number of constituting metals, a new method is first proposed to calculate the structural enthalpy in the Miedema's model and the modified Miedema...By taking into account the valence electron number and periodic number of constituting metals, a new method is first proposed to calculate the structural enthalpy in the Miedema's model and the modified Miedema's model is then used to predict the formation of metastable phases in Ni-Ti system. To testify the relevance of the present prediction, the multilayered films of Ni1-xTix (x=27.3, 30.5, 42.4, 83.1, 89) are prepared and irradiated by 200 keV xenon ions. Experiment results reveal that uniform amorphous phases are obtained in the Ni72.7Ti27.3, Ni69.5Ti30.5, and Ni57.6Ti42.4 films by increasing the irradiation dose. While for the Ni16.9Ti83.1 and Ni11Ti89 films, an hcp Ti-based solid solution phase and a bcc Ti-rich solid solution phase coexist upon irradiation dose higher than 6×1014 Xe+/cm2. The predictions of relative stabilities of metastable phases in Ni-Ti system by the modified Miedema's model match well with IBM experiments, thus justifying the modification proposed in the present study.展开更多
The self-consistent electronic structure calculations were carried out with the accurate frozen-core full-potential projector augmented-wave method on 13 Ni-Pt intermetallic compounds of simple crystalline structures,...The self-consistent electronic structure calculations were carried out with the accurate frozen-core full-potential projector augmented-wave method on 13 Ni-Pt intermetallic compounds of simple crystalline structures,i.e. A15,D019,D03 and L12 Ni3Pt and NiPt3,and α-NiAs,B1,B2,L2a,and L10 NiPt. The calculations reveal that the L12 Ni3Pt,L10 NiPt and L12 NiPt3 are energetically more stable than their respective competitive structures,indicating that the three structures may be formed in some appropriate conditions. The obtained results match well with the experimental observation or other theory predictions. It is found that there is hybridization between Ni 3d and Pt 5d states,which may significantly affect the structural stability and magnetism of metastable Ni-Pt intermetallic compounds.展开更多
In the ion beam mixing experiments,eight Fe-Hf-Nb multilayered films,with overall compositions of Fe67Hf22Nb11,Fe67Hf11Nb22,Fe54Hf38Nb8,Fe54Hf30Nb16,Fe54Hf11Nb35,Fe25Hf67Nb8,Fe25Hf50Nb25 and Fe25Hf11Nb64,were irradiat...In the ion beam mixing experiments,eight Fe-Hf-Nb multilayered films,with overall compositions of Fe67Hf22Nb11,Fe67Hf11Nb22,Fe54Hf38Nb8,Fe54Hf30Nb16,Fe54Hf11Nb35,Fe25Hf67Nb8,Fe25Hf50Nb25 and Fe25Hf11Nb64,were irradiated by 200 keV xenon ions to doses ranging from 3×1014 Xe+/cm2 to 7×1015 Xe+/cm2.The results showed that unique amorphous phases were obtained at designed alloy compositions,falling in the favored glass-forming region deduced from three binary metal sub-systems.Interestingly,at some alloy compositions,the crystal-amorphous-crystal transformations were observed back and forth while varying the irradiation doses.In addition,at the alloy composition of Fe25Hf67Nb8,a metastable FCC phase was formed through an HCP-FCC structural phase transformation and it had a large lattice constant identified to be a=4.51 .Besides,the formation mechanism of non-equilibrium alloy phases was also discussed in terms of thermodynamics of solids and atomic collision theory.展开更多
基金Supported by the National Natural Science Foundation of China。
文摘Amorphization was achieved by a non.equilibrium process of ion mixing of multilayered films iii an inuniscible Fe-Cu system with a large positive heat of formation(+19kJ/mol).The free energy diagrtiin of the Fe-Cu system was constructed.In calculation,the inter facial free energy,ferromugnctic effect and the structure ch arac-tenstics were considered.The calculated Fe-Cu free energy diagram can explain the ainorphization behavior in this imniiscible system.
基金Supported in part by the National Natural Science Foundation of China。
文摘Fe_(75)Cu_(25) nano-multilayers were prepared by alternative deposition of pure Fe and Cu metals and then annealed in situ in transmission electron microscopy to investigate the structural phase transformation.A new phase was formed in the Fe-Cu multilayers by interdiffusion at 820℃ for about I0min and was identified to be of fcc structure with a lattice parameter of 0.854±0.005nm.
文摘A fractal aggregation process in the ion irradiated films was recognized.The process was intrinsic of interaction of ions with solids and sincerely modelled by the cluster diffusion-limited-aggregation model.The energetic ions not only drive the atoms and clusters in the area of collision cascade in motion which may be modelled as random walks,but also create vacancies and voids which contribute to the aggregation process.The process was also of percolation characteristic with a fractal dimension 1.82 at the critical point.
基金Project supported in part by the National Science Foundation of China.
文摘Percolation structures of precipitated new phases were observed in Au-Ti and Ni-A1 amorphous films upon ion irradiation.The experimental evidences showed that the observed structures were formed in the surface layer,ca 20nm thick.It was revealed that the formation of percolation clusters was sensitive to alloy composition as well as irradiation dose.
基金Project supported by the National Science Foundation of China.
文摘The enhancement of adhesion between deposited metal layers(Ti and Cu)and the oxide substrates at RT and 300°c respectively was studied by argon ion irradiation to various doses.The experimental results showed that the adhesive strength increased after a threshold dose irradiation and reached as aturation value at higher doses in all metal/oxide pairs.RBS spectra showed that chemical reaction had taken place in Ti/oxide case,while in Cu/oxide case,both RBS and XPS analysis showed that no evidence of such reaction had been induced.
基金the Science Fund of the Chinese Academy of Sciences.
文摘Dendrites were observed for the first time in the Ni-Mo thin films irradiated by ion beam.Various patterns are presented and a typical one features no specific orientation.The formation of dendrites induced by ion beam is attributed to the critical phenomenon during amorphous to crystalline phase transformation.
文摘Metastable Ag80Cr20 alloy was produced by ion mixng of Ag-Cr multilayers at liquid nitrogen temperature.The immiscibility in Ag-Cr system was accounted for in terms of the characteristics of the electronic structures of the constituent metals,and the ion beam induced alloy formation was explained by considering ion mixing as a process favoring the co-resonance process required for forming the new energy band of the metastable Ag-Cr alloy.
基金support from the National Natural Science Foundation of China (Grant Nos. 50871058 and 50971072)the Ministry of Science and Technology of China (Grant No. 20011CB606301)+1 种基金the Ministry of Education of China (Grant No. 200800030054)the Administration of Tsinghua University
文摘By taking into account the valence electron number and periodic number of constituting metals, a new method is first proposed to calculate the structural enthalpy in the Miedema's model and the modified Miedema's model is then used to predict the formation of metastable phases in Ni-Ti system. To testify the relevance of the present prediction, the multilayered films of Ni1-xTix (x=27.3, 30.5, 42.4, 83.1, 89) are prepared and irradiated by 200 keV xenon ions. Experiment results reveal that uniform amorphous phases are obtained in the Ni72.7Ti27.3, Ni69.5Ti30.5, and Ni57.6Ti42.4 films by increasing the irradiation dose. While for the Ni16.9Ti83.1 and Ni11Ti89 films, an hcp Ti-based solid solution phase and a bcc Ti-rich solid solution phase coexist upon irradiation dose higher than 6×1014 Xe+/cm2. The predictions of relative stabilities of metastable phases in Ni-Ti system by the modified Miedema's model match well with IBM experiments, thus justifying the modification proposed in the present study.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 50531040, 50871058)the Ministry of Science and Technology of China (Grant No. 2006CB605201)the Administration of Tsinghua University
文摘The self-consistent electronic structure calculations were carried out with the accurate frozen-core full-potential projector augmented-wave method on 13 Ni-Pt intermetallic compounds of simple crystalline structures,i.e. A15,D019,D03 and L12 Ni3Pt and NiPt3,and α-NiAs,B1,B2,L2a,and L10 NiPt. The calculations reveal that the L12 Ni3Pt,L10 NiPt and L12 NiPt3 are energetically more stable than their respective competitive structures,indicating that the three structures may be formed in some appropriate conditions. The obtained results match well with the experimental observation or other theory predictions. It is found that there is hybridization between Ni 3d and Pt 5d states,which may significantly affect the structural stability and magnetism of metastable Ni-Pt intermetallic compounds.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50871058 and 50971072)the Ministry of Science and Technology of China (Grant No. 2011CB606301)+1 种基金the Ministry of Education of China (Grant No. 200800030054)the Administration of Tsinghua University
文摘In the ion beam mixing experiments,eight Fe-Hf-Nb multilayered films,with overall compositions of Fe67Hf22Nb11,Fe67Hf11Nb22,Fe54Hf38Nb8,Fe54Hf30Nb16,Fe54Hf11Nb35,Fe25Hf67Nb8,Fe25Hf50Nb25 and Fe25Hf11Nb64,were irradiated by 200 keV xenon ions to doses ranging from 3×1014 Xe+/cm2 to 7×1015 Xe+/cm2.The results showed that unique amorphous phases were obtained at designed alloy compositions,falling in the favored glass-forming region deduced from three binary metal sub-systems.Interestingly,at some alloy compositions,the crystal-amorphous-crystal transformations were observed back and forth while varying the irradiation doses.In addition,at the alloy composition of Fe25Hf67Nb8,a metastable FCC phase was formed through an HCP-FCC structural phase transformation and it had a large lattice constant identified to be a=4.51 .Besides,the formation mechanism of non-equilibrium alloy phases was also discussed in terms of thermodynamics of solids and atomic collision theory.
