The homogeneous glass sample for the (1-x)As 2S 3-xCdBr 2,where x=0.015,0.035, 0.05, was prepared by the conventional melt-quenched method.Amorphous (1-x)As 2S 3-xCdBr 2 alloys were determined by X-...The homogeneous glass sample for the (1-x)As 2S 3-xCdBr 2,where x=0.015,0.035, 0.05, was prepared by the conventional melt-quenched method.Amorphous (1-x)As 2S 3-xCdBr 2 alloys were determined by X-ray diffraction, thermal comprehensive analysis and Raman scattering. The glass transition temperature (T g) decreases a bit with the addition of CdBr 2. Based on the experimental data, the microstructure is considered to be the discrete molecule species of AsBr 3 and Cd-S atomic bonds or clusters are homogeneously dispersed in a disordered polymer network formed by AsS 3 pyramids interlinked by sulfur bridges.展开更多
The preparation of new types of poly(imide-urea)s (PIUs) with high thermal stability and improved solubility was investigated. Three series of aromatic poly(imide-urea)s (PIUOa-c, PIUSa-c, and PIUNa-c) bearing pendent...The preparation of new types of poly(imide-urea)s (PIUs) with high thermal stability and improved solubility was investigated. Three series of aromatic poly(imide-urea)s (PIUOa-c, PIUSa-c, and PIUNa-c) bearing pendent benzoxazole, benzothiazole or benzimidazole rings were prepared by one-pot polycondensation reaction of three bis(imide-carboxylic acid)s, 2-[3,5-bis(N-trimellitimidoyl)-phenyl]benzoxazole (1O), 2-[3,5-bis(N- trimellitimidoyl)-phenyl]benzothiazole (1S), or 2-[3,5-bis(N-trimellitimidoyl)-phenyl]benzimidazole (1N) with various kinds of aromatic diamines (a-c). The effects of the benzazole pendent groups on the polymer properties such as solubility and thermal stability were investigated by comparison of the polymers. All of the resulting polymers exhibited excellent solubility in common polar solvents. The glass transition temperature of the polymers determined by DSC thermograms were in the range 192℃ - 236℃. The temperatures at 10% weight loss from their TGA curves were found to be in the range 390℃ - 441℃ in nitrogen.展开更多
2-D and 3-D micro-architectured multiphase thermoelastic metamaterials are designed and analyzed using a parametric level set method for topology optimization and the finite element method.An asymptotic homogenization...2-D and 3-D micro-architectured multiphase thermoelastic metamaterials are designed and analyzed using a parametric level set method for topology optimization and the finite element method.An asymptotic homogenization approach is employed to obtain the effective thermoelastic properties of the multiphase metamaterials.Theε-constraint multi-objective optimization method is adopted in the formulation.The coefficient of thermal expansion(CTE)and Poisson’s ratio(PR)are chosen as two objective functions,with the CTE optimized and the PR treated as a constraint.The optimization problems are solved by using the method of moving asymptotes.Effective isotropic and anisotropic CTEs and stiffness constants are obtained for the topologically optimized metamaterials with prescribed values of PR under the constraints of specified effective bulk modulus,volume fractions and material symmetry.Two solid materials along with one additional void phase are involved in each of the 2-D and 3-D optimal design examples.The numerical results reveal that the newly proposed approach can integrate shape and topology optimizations and lead to optimal microstructures with distinct topological boundaries.The current method can topologically optimize metamaterials with a positive,negative or zero CTE and a positive,negative or zero Poisson’s ratio.展开更多
Copper sulfide thin films are deposited onto different substrates at room temperature using the thermal evaporation technique. X-ray diffraction spectra show that the film has an orthorhombicchalcocite （7-Cu2S） phas...Copper sulfide thin films are deposited onto different substrates at room temperature using the thermal evaporation technique. X-ray diffraction spectra show that the film has an orthorhombicchalcocite （7-Cu2S） phase. The atomic force microscopy images indicate that the film exhibits nanoparticles with an average size of nearly 44 nm. Specrtophotometric measurements for the transmittance and reflectance are carried out at normal incidence in a spectral wavelength range of 450 nm-2500 nm. The refractive index, n, as well as the absorption index, k is calculated. Some dispersion parameters are determined. The analyses of el and e2 reveal several absorption peaks. The analysis of the spectral behavior of the absorption coefficient, c~, in the absorption region reveals direct and indirect allowed transitions. The dark electrical resistivity is studied as a function of film thickness and temperature. Tellier＇s model is adopted for determining the mean free path and bulk resistance.展开更多
Two poly（aryl ether）s containing naphthyl moieties were prepared from bis（3,5-dimethyl-4-hydroxyphenyl）naphthyl methane （monomer 1） via nucleophilic aromatic substitution polycondensation with bis（4-fluoropheny...Two poly（aryl ether）s containing naphthyl moieties were prepared from bis（3,5-dimethyl-4-hydroxyphenyl）naphthyl methane （monomer 1） via nucleophilic aromatic substitution polycondensation with bis（4-fluorophenyl） ketone and bis（4-fluorophenyl） sulfone. The structures of these polymers were confirmed by 1H NMR. The Mn values of the two polymers were 96,200 and 88,600, respectively. The polymers exhibited good thermal stabilities with 5% mass loss at T 〉 400 and high glass-transition temperature （Ts） of T 〉 250 ℃. Moreover, the resultant polymers were amorphous determined by wide angle X-ray diffraction （WAXD）. ？2009 Lei Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All fights reserved.展开更多
文摘The homogeneous glass sample for the (1-x)As 2S 3-xCdBr 2,where x=0.015,0.035, 0.05, was prepared by the conventional melt-quenched method.Amorphous (1-x)As 2S 3-xCdBr 2 alloys were determined by X-ray diffraction, thermal comprehensive analysis and Raman scattering. The glass transition temperature (T g) decreases a bit with the addition of CdBr 2. Based on the experimental data, the microstructure is considered to be the discrete molecule species of AsBr 3 and Cd-S atomic bonds or clusters are homogeneously dispersed in a disordered polymer network formed by AsS 3 pyramids interlinked by sulfur bridges.
文摘The preparation of new types of poly(imide-urea)s (PIUs) with high thermal stability and improved solubility was investigated. Three series of aromatic poly(imide-urea)s (PIUOa-c, PIUSa-c, and PIUNa-c) bearing pendent benzoxazole, benzothiazole or benzimidazole rings were prepared by one-pot polycondensation reaction of three bis(imide-carboxylic acid)s, 2-[3,5-bis(N-trimellitimidoyl)-phenyl]benzoxazole (1O), 2-[3,5-bis(N- trimellitimidoyl)-phenyl]benzothiazole (1S), or 2-[3,5-bis(N-trimellitimidoyl)-phenyl]benzimidazole (1N) with various kinds of aromatic diamines (a-c). The effects of the benzazole pendent groups on the polymer properties such as solubility and thermal stability were investigated by comparison of the polymers. All of the resulting polymers exhibited excellent solubility in common polar solvents. The glass transition temperature of the polymers determined by DSC thermograms were in the range 192℃ - 236℃. The temperatures at 10% weight loss from their TGA curves were found to be in the range 390℃ - 441℃ in nitrogen.
文摘2-D and 3-D micro-architectured multiphase thermoelastic metamaterials are designed and analyzed using a parametric level set method for topology optimization and the finite element method.An asymptotic homogenization approach is employed to obtain the effective thermoelastic properties of the multiphase metamaterials.Theε-constraint multi-objective optimization method is adopted in the formulation.The coefficient of thermal expansion(CTE)and Poisson’s ratio(PR)are chosen as two objective functions,with the CTE optimized and the PR treated as a constraint.The optimization problems are solved by using the method of moving asymptotes.Effective isotropic and anisotropic CTEs and stiffness constants are obtained for the topologically optimized metamaterials with prescribed values of PR under the constraints of specified effective bulk modulus,volume fractions and material symmetry.Two solid materials along with one additional void phase are involved in each of the 2-D and 3-D optimal design examples.The numerical results reveal that the newly proposed approach can integrate shape and topology optimizations and lead to optimal microstructures with distinct topological boundaries.The current method can topologically optimize metamaterials with a positive,negative or zero CTE and a positive,negative or zero Poisson’s ratio.
文摘Copper sulfide thin films are deposited onto different substrates at room temperature using the thermal evaporation technique. X-ray diffraction spectra show that the film has an orthorhombicchalcocite （7-Cu2S） phase. The atomic force microscopy images indicate that the film exhibits nanoparticles with an average size of nearly 44 nm. Specrtophotometric measurements for the transmittance and reflectance are carried out at normal incidence in a spectral wavelength range of 450 nm-2500 nm. The refractive index, n, as well as the absorption index, k is calculated. Some dispersion parameters are determined. The analyses of el and e2 reveal several absorption peaks. The analysis of the spectral behavior of the absorption coefficient, c~, in the absorption region reveals direct and indirect allowed transitions. The dark electrical resistivity is studied as a function of film thickness and temperature. Tellier＇s model is adopted for determining the mean free path and bulk resistance.
基金supported by Natural Science Foundation of Guangdong Province(No.7301357)Science and Technology Projects of Shenzhen City(No.200724).
文摘Two poly（aryl ether）s containing naphthyl moieties were prepared from bis（3,5-dimethyl-4-hydroxyphenyl）naphthyl methane （monomer 1） via nucleophilic aromatic substitution polycondensation with bis（4-fluorophenyl） ketone and bis（4-fluorophenyl） sulfone. The structures of these polymers were confirmed by 1H NMR. The Mn values of the two polymers were 96,200 and 88,600, respectively. The polymers exhibited good thermal stabilities with 5% mass loss at T 〉 400 and high glass-transition temperature （Ts） of T 〉 250 ℃. Moreover, the resultant polymers were amorphous determined by wide angle X-ray diffraction （WAXD）. ？2009 Lei Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All fights reserved.
