Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density o...Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.展开更多
Electronic structures in two kinds of boron structures are investigated by the first-principle density func- tional theory （DFT） calculations. One structure is from theoretical prediction, and the other is from expe...Electronic structures in two kinds of boron structures are investigated by the first-principle density func- tional theory （DFT） calculations. One structure is from theoretical prediction, and the other is from experimental in- vestigation. Binding energy calculations suggest that the boron structure designed from theory is more stable than that made by experiment. Elastic constants calculations show that both structures are mechanically stable. The electronic structure results show that the theoretical designed structure exhibits semi-metal behavior, while the other structure exhibits metMlic character. No magnetic phenomenal is discovered from them. All the calculations are carried out by the first principles calculation through the MatC1oud platform, which is developed by our research group.展开更多
Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the...Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer dis- tance of two graphene sheets and the intercalated capacity of Li ions is discussed, It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.展开更多
The electronic structure, atomic geometry and energetic properties of ceramic nanomultilayer have been systematically studied with first principles density functional theory calculations based on the generalized gradi...The electronic structure, atomic geometry and energetic properties of ceramic nanomultilayer have been systematically studied with first principles density functional theory calculations based on the generalized gradient approximations. It is found that the interface structure and adhesion, which determine the mechanical and thermal properties, are sensitive to the surface mor- phology. We also provide an analysis of adhesion of ZrO2/A1203 interface as a function of thickness of each layer. With the in- crease of ZrO2 thickness, both covalence and ionicity of the interfacial bonds are enhanced, which results in more strongly coupled interfaces while the ionic interaction decreases for thicker Al2O3 layers, which results in weakly coupled interfaces. A first-principles calculation method has been proposed to design nanomultilayer materials to achieve the demanded adhesion.展开更多
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.
基金Supported by National Natural Science Foundation of China under Grant No.11547177
文摘Electronic structures in two kinds of boron structures are investigated by the first-principle density func- tional theory （DFT） calculations. One structure is from theoretical prediction, and the other is from experimental in- vestigation. Binding energy calculations suggest that the boron structure designed from theory is more stable than that made by experiment. Elastic constants calculations show that both structures are mechanically stable. The electronic structure results show that the theoretical designed structure exhibits semi-metal behavior, while the other structure exhibits metMlic character. No magnetic phenomenal is discovered from them. All the calculations are carried out by the first principles calculation through the MatC1oud platform, which is developed by our research group.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50802089 and 51072183)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China (Grant No. [2008] 890)the Natural Science Foundation of Zhejiang Province (Grant No. Y4090280)
文摘Litbium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Re- sults show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer dis- tance of two graphene sheets and the intercalated capacity of Li ions is discussed, It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.
文摘The electronic structure, atomic geometry and energetic properties of ceramic nanomultilayer have been systematically studied with first principles density functional theory calculations based on the generalized gradient approximations. It is found that the interface structure and adhesion, which determine the mechanical and thermal properties, are sensitive to the surface mor- phology. We also provide an analysis of adhesion of ZrO2/A1203 interface as a function of thickness of each layer. With the in- crease of ZrO2 thickness, both covalence and ionicity of the interfacial bonds are enhanced, which results in more strongly coupled interfaces while the ionic interaction decreases for thicker Al2O3 layers, which results in weakly coupled interfaces. A first-principles calculation method has been proposed to design nanomultilayer materials to achieve the demanded adhesion.
