In this work, we synthesized high-quality In As nanowires by a convenient chemical vapor deposition method,and developed a simple laser heating method to measure the thermal conductivity of a single In As nanowire in ...In this work, we synthesized high-quality In As nanowires by a convenient chemical vapor deposition method,and developed a simple laser heating method to measure the thermal conductivity of a single In As nanowire in air. During the measurement, a focused laser was used to heat one end of a freely suspended nanowire, with its other end embedded into a carbon conductive adhesive. In order to obtain the thermal conductivity of In As nanowires, the heat loss in the heat transfer process was estimated, which includes the heat loss through air conduction, the heat convection, and the radiation loss. The absorption ratio of the laser power in the In As nanowire was calculated. The result shows that the thermal conductivity of In As nanowires monotonically increases from 6.4 W m-1K-1to 10.5 W m-1K-1with diameters increasing from 100 nm to 190 nm, which is ascribed to the enhanced phonon-boundary scattering.展开更多
NiCr micron-resistor was designed and prepared by magnetron sputtering and lithography on the substrate of silicon with different powers. It is found that there exists a big gap in the TCR between the annealed group a...NiCr micron-resistor was designed and prepared by magnetron sputtering and lithography on the substrate of silicon with different powers. It is found that there exists a big gap in the TCR between the annealed group and the un-annealed group. A series of tests were made to figure out the reasons lying behind the gap in the TCR between the annealed group and the un-annealed group. UV reflection results show that there is no increase in the concentration of free electrons after annealing. However, the data obtained from XRD reveal that the annealing does not have an obvious influence on the strain of thin films, but really increases the grain size of thin films. Therefore, the grain boundary scattering plays a dominant role in explaining the obvious difference in the TCR. Finally through appropriate methods, a micron-resistor for heating-up with a low TCR value was obtained.展开更多
A two-variable earthquake model on a quenched random graph is established here. It can be seen as a generalization of the OFC models. We numerically study the critical behavior of the model when the system is nonconse...A two-variable earthquake model on a quenched random graph is established here. It can be seen as a generalization of the OFC models. We numerically study the critical behavior of the model when the system is nonconservative： the result indicates that the model exhibits self-organized criticality deep within the nonconservative regime. The probability distribution for avalanche size obeys finite size scaling. We compare our mode/with the mode/ introduced by Stefano Lise and Maya Paczuski [Phys. Rev. Lett. 88 （2002） 228301], it is proved that they are not in the same universality class.展开更多
When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder...When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder are investigated by using rotational isomeric state model. Using the average conformational energy and entropy and the average length, we can determine the elastic force f, or the fraction of the energy term to the total force f(e)/f where f(e) = partial derivative /partial derivative < r > and f = partial derivative /partial derivative < r >. Comparisons with experimental data are also made. The results of these microscopic calculations are discussed in terms of the macroscopic phenomena of rubber elasticity.展开更多
Electronic and optical properties of single-walled zinc oxide （ZnO） nanotubes are investigated from the firstprinciples calculations. Electronic structure calculations show that ZnO nanotubes are all direct band gap...Electronic and optical properties of single-walled zinc oxide （ZnO） nanotubes are investigated from the firstprinciples calculations. Electronic structure calculations show that ZnO nanotubes are all direct band gap semiconducting nanotubes and the band gaps are relatively insensitive to the diameter and chirality of tubes. The origin of the common electronic band gaps of ZnO nanotubes is explained in terms of band-folding from the two-dimensional band structure of graphite-like sheet. Moreover, the optical properties such as dielectric function and energy loss function spectra of different ZnO nanotubes are very similar, relatively independent of diameter and chirality of tubes. The calculated dielectric function and loss function spectra show a moderate optical anisotropy with respect to light polarization.展开更多
BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals (NCs) have been grown on SrTiO3 (001) substrate using laser molecular beam epitaxy (L-MBE). In situ reflection high-energy electron diffraction (RHEED) was emp...BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals (NCs) have been grown on SrTiO3 (001) substrate using laser molecular beam epitaxy (L-MBE). In situ reflection high-energy electron diffraction (RHEED) was employed to investigate the process of lattice strain in the self-organization of Ni NCs and the epitaxial growth of BaTiO3/SrTiO3 superlattices. The results indicated that the strain from large lattice mismatch drove the self-organization of Ni NCs. Also, the layer-by-layer growth of BaTiO3/SrTiO3 superlattices Keywords: Nanocrystal;Superlattices;Self-organization 1. Introduction Oxide artificial superlattices, especially (001) oriented BaTiOsuperlattices and the island growth of Ni NCs were controllable ac-curately. The fine alternation of the two processes would provide a possible route to engineer controllably the nano-composite microstructure.展开更多
Based on the template formed from monodispersed polystyrene (PS) latex, a modified fast sol-gel process was employed to synthesize a three-dimensional ( 3-D ) ordered macroporous silica material after removing the tem...Based on the template formed from monodispersed polystyrene (PS) latex, a modified fast sol-gel process was employed to synthesize a three-dimensional ( 3-D ) ordered macroporous silica material after removing the template by calcination at high temperature. It was indicated that there existed highly ordered packed pores within the whole silica material by SEM morphology observation. It was also found that the pores were interconnected. The pore size could be controlled mainly by varying the particle size of the latex ranging from 101 to 102 nm. The formation process of the ordered pores was also preliminarily discussed.展开更多
Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force fe/f as a function of strain for polyethylene (PE). Calculated fe/f values are in good...Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force fe/f as a function of strain for polyethylene (PE). Calculated fe/f values are in good agreement with those obtained experimentally. Results show that the behavior of fe/f is mainly contributed from intramolecular interaction of chemical structure, and that the internal energy contribution is strain-dependent.展开更多
基金the National Basic Research Program of China (No. 2012CB932703)the NSF of China (Nos. 11374092 and 11204073)+2 种基金the Research Fund for the Doctoral Program of Higher Education (Nos. 20110161110034, 20110161120027)the Fundamental Research Funds for Central Universities (Nos. xjj2011001 and 2012jdgz04)the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (2013)
文摘In this work, we synthesized high-quality In As nanowires by a convenient chemical vapor deposition method,and developed a simple laser heating method to measure the thermal conductivity of a single In As nanowire in air. During the measurement, a focused laser was used to heat one end of a freely suspended nanowire, with its other end embedded into a carbon conductive adhesive. In order to obtain the thermal conductivity of In As nanowires, the heat loss in the heat transfer process was estimated, which includes the heat loss through air conduction, the heat convection, and the radiation loss. The absorption ratio of the laser power in the In As nanowire was calculated. The result shows that the thermal conductivity of In As nanowires monotonically increases from 6.4 W m-1K-1to 10.5 W m-1K-1with diameters increasing from 100 nm to 190 nm, which is ascribed to the enhanced phonon-boundary scattering.
文摘NiCr micron-resistor was designed and prepared by magnetron sputtering and lithography on the substrate of silicon with different powers. It is found that there exists a big gap in the TCR between the annealed group and the un-annealed group. A series of tests were made to figure out the reasons lying behind the gap in the TCR between the annealed group and the un-annealed group. UV reflection results show that there is no increase in the concentration of free electrons after annealing. However, the data obtained from XRD reveal that the annealing does not have an obvious influence on the strain of thin films, but really increases the grain size of thin films. Therefore, the grain boundary scattering plays a dominant role in explaining the obvious difference in the TCR. Finally through appropriate methods, a micron-resistor for heating-up with a low TCR value was obtained.
文摘A two-variable earthquake model on a quenched random graph is established here. It can be seen as a generalization of the OFC models. We numerically study the critical behavior of the model when the system is nonconservative： the result indicates that the model exhibits self-organized criticality deep within the nonconservative regime. The probability distribution for avalanche size obeys finite size scaling. We compare our mode/with the mode/ introduced by Stefano Lise and Maya Paczuski [Phys. Rev. Lett. 88 （2002） 228301], it is proved that they are not in the same universality class.
基金This research was financially supported by the National Natural Science Foundation of China and the National Basic Research Project "Macromolecular Condensed State" from STCC
文摘When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder are investigated by using rotational isomeric state model. Using the average conformational energy and entropy and the average length, we can determine the elastic force f, or the fraction of the energy term to the total force f(e)/f where f(e) = partial derivative /partial derivative < r > and f = partial derivative /partial derivative < r >. Comparisons with experimental data are also made. The results of these microscopic calculations are discussed in terms of the macroscopic phenomena of rubber elasticity.
基金supported by the National Natural Science Foundation of China (Grant No 10674070)the Program for New Century Excellent Talents in University,China (Grant No NCET-04-0779)Changjiang Scholars and Innovative Research Team in University,China (Grant No IRT0534)
文摘Electronic and optical properties of single-walled zinc oxide （ZnO） nanotubes are investigated from the firstprinciples calculations. Electronic structure calculations show that ZnO nanotubes are all direct band gap semiconducting nanotubes and the band gaps are relatively insensitive to the diameter and chirality of tubes. The origin of the common electronic band gaps of ZnO nanotubes is explained in terms of band-folding from the two-dimensional band structure of graphite-like sheet. Moreover, the optical properties such as dielectric function and energy loss function spectra of different ZnO nanotubes are very similar, relatively independent of diameter and chirality of tubes. The calculated dielectric function and loss function spectra show a moderate optical anisotropy with respect to light polarization.
文摘BaTiO3/SrTiO3 superlattices with embedded Ni nanocrystals (NCs) have been grown on SrTiO3 (001) substrate using laser molecular beam epitaxy (L-MBE). In situ reflection high-energy electron diffraction (RHEED) was employed to investigate the process of lattice strain in the self-organization of Ni NCs and the epitaxial growth of BaTiO3/SrTiO3 superlattices. The results indicated that the strain from large lattice mismatch drove the self-organization of Ni NCs. Also, the layer-by-layer growth of BaTiO3/SrTiO3 superlattices Keywords: Nanocrystal;Superlattices;Self-organization 1. Introduction Oxide artificial superlattices, especially (001) oriented BaTiOsuperlattices and the island growth of Ni NCs were controllable ac-curately. The fine alternation of the two processes would provide a possible route to engineer controllably the nano-composite microstructure.
文摘Based on the template formed from monodispersed polystyrene (PS) latex, a modified fast sol-gel process was employed to synthesize a three-dimensional ( 3-D ) ordered macroporous silica material after removing the template by calcination at high temperature. It was indicated that there existed highly ordered packed pores within the whole silica material by SEM morphology observation. It was also found that the pores were interconnected. The pore size could be controlled mainly by varying the particle size of the latex ranging from 101 to 102 nm. The formation process of the ordered pores was also preliminarily discussed.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 29874035 and 20074041), the "863" High Technology Project, and the Special Funds for the State Major Basic Research Project (Grant No. G1999064800).
文摘Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force fe/f as a function of strain for polyethylene (PE). Calculated fe/f values are in good agreement with those obtained experimentally. Results show that the behavior of fe/f is mainly contributed from intramolecular interaction of chemical structure, and that the internal energy contribution is strain-dependent.
