研制高性能隔热材料对发展航空、建筑、运输等领域具有重要意义。二氧化硅(SiO2)纤维具有低密度、低热导、抗氧化的优点, 是一种极具发展潜力的隔热材料。然而, SiO2纤维的热导率有待进一步降低, 如何进一步提升其隔热性能是一个重要课题。本文从SiO2纤维的隔热机理出发, 首先分析了不同形貌(实心、中空、多孔)SiO2纤维的制备方法及研究现状, 并总结了SiO2纤维与有机材料、无机材料等复合的研究进展。同时, 简述了隔热材料目前的主要应用领域, 最后展望了SiO2纤维基隔热材料在未来的发展方向。

Considering the changes of the geometric shielding effect in a molecule as the incident electron energy varing, an empirical fraction, which is dependent on the incident electron energy, is presented. Using this empirical fraction, the total cross sections (TCSs) for electrons scattering from complex polyatomic molecules C2F4 and SO2 are calculated over a wide energy range from 30 to 5000 eV together with the additivity rule model at Hartree-Fock level. In the TCS calculations, the atoms are presented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption contributions. The quantitative TCSs above 100 eV are in good agreement with those obtained by experiments and other theories. It is proved that the empirical fraction, which exhibits the TCS contributions of shielded atoms in a molecule at different energies, is reasonable.

The total (elastic plus inelastic) cross sections for positron scattering from N2 and CO2 over the incident energy range from 30 to 3000eV are calculated using the additivity rule model at Hartree-Fock level. A complex optical model potential modified by incorporating the concept of bonded atom, which takes into account the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross section of positron-molecule scattering. The calculated total cross sections are in good agreement with those reported by experiments and other theories over a wide energy range.

The accurate dissociation energy and equilibrium geometry of the b3Π state of 7LiH molecule is calculated using a symmetry-adapted-cluster configuration-interaction method in full active space. And the calculated results are 0.2580 eV and 0.1958 nm for the dissociation energy and equilibrium geometry, respectively. The whole potential energy curve for the b3Π state is also calculated over the internuclear separation range from about 0.10 to 0.54 nm. The results are fitted by the Murrell-Sorbie function. It is found that the Murrell-Sorbie function form, which is mainly used to fit the ground-state potential energy function, is well suitable for the excited triplet b3Π state. The vertical excitation energy from the ground state to the b3Π state is calculated to be 4.233 eV. Based on the analytic potential energy function, the harmonic frequency of 610.88 cm^(-1) about this state is firstly estimated. Compared with other theoretical results, this work is the most complete effort to deal with the analytic potential energy function and the harmonic frequency of this state.

Total cross sections (TCSs) of electrons scattering from triatomic molecules over the energy range from 30 to 5000 eV are investigated employing a new semi-empirical formula. The TCSs of electrons scattering from triatomic molecules SO2, NO2, and CO2 are calculated. The quantitative TCSs are in good agreement with those obtained by experiments. It is shown that the results derived from the semi-empirical formula are much closer to the measurements than other calculations.

A complex optical model potential correlated by the concept of bonded atoms, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the absolute differential cross sections, the integrated and momentum transfer cross sections for electrons scattered by O2 at intermediate and high energies by using additivity rule model at Hartree-Fock level. In the study, the complex optical model potential is composed of static, exchange, correlation polarization plus absorption contributions. The quantitative absolute differential cross sections, the integrated and momentum transfer cross sections are obtained. Compared with available experimental data, this approach presents good results. It is shown that the additivity rule model together with the complex optical model potential correlated by the concept of bonded atoms is completely suitable for the calculations of the absolute differential cross sections, the integrated and momentum transfer cross sections.

A model complex optical potential rewritten by the conception of bonded atom, which considers the overlapping effect of electron cloud, is employed to calculate the total (elastic + inelastic) cross sections with simple molecules (N_(2), O_(2), NO_(2), NO, N_(2)O) consisting of N & O atoms over an incident energy range of 100 - 1600 eV by the use of additivity rule at Roothaan-Hartree-Fock level. In the study, the complex optical potential composed of static, exchange, correlation polarization plus absorption contributions firstly uses bonded-atom conception. The qualitative results are compared with experimental data and other calculations wherever available and good agreement is obtained. The total cross sections of electronmolecule scattering above 100 eV can be successfully calculated.