制备高分子一维准晶可能性的探讨

本文首次探讨了制备高分子一维准品的可能性,并以苯乙烯—富马腈二单体共聚反应为例具体地分析了这种可能性。     

Anti-plane problem analysis for icosahedral quasicrystals under shear loadings

The present paper is concerned with the longitudinal shear elasticity of three-dimensional icosahedral quasicrystals. By virtue of the Dugdale hypothesis along with the method of complex potential theory, it involves two defect problems of the icosahedral quasicrystals. The first one is the calculation of stress intensity factors and the size of the cohesive force zone in a half-infinite crack. Meanwhile, the crack tip tearing displacements can be exactly derived. The other is the demonstration of the generalized stress intensity factors induced by a sharp V-notch as an extension of a crack. The generalized E-integral around the notch tip gives the energy release rate when the V-notch degenerates into a crack. Apart from their own usefulness in carrying out some simplified crack analyses, the results obtained in this work can particularly serve as a basis for fracture mechanics of anti-plane defect problems of icosahedral quasicrystals.     

Scatterer radius dependence of focusing properties in two-dimensional photonic quasicrystal flat lens

The focusing properties of a germanium decagonal photonic quasicrystal flat lens with different scatterer radii have been analyzed. For different wavelengths and polarization modes, the lenses have different scatterer radius thresholds resulting in different focusing properties. For a point source of light in the transverse-electric mode, we found dual-focusing occurs along the symmetry axis within a range of scattering radii. As scatterer radius increases, the dual-focusing image power and far-field-focusing image quality diminish, whereas near-field-focusing image quality, dual-focusing image distance, and the summed object-image distance all increase.     

Simple quasicrystal model of liquid and its applications: calculations of enthalpy of vaporisation and adsorption energy in slit nanopore

Physical properties of liquids are important to both theoretical study and engineering designs. These properties are determined by the spatial configuration of liquids. Based on the main characteristics of short-range order of liquid configuration, a simple quasicrystal model of liquid with close-packed body-centred cubic structure is proposed to simulate the spatial structure of liquids. Then the bonding potential energy of liquid molecule is analytically expressed with Lennard-Jones intermolecular potential. Enthalpy of evaporation can be calculated with this model, which has obvious physical meaning and the calculated values agree with experimental data. Based on the fact that liquid in a confined nano-space are distributed in layers, the characteristics of liquids in slit nanopores can also be described with this simple model. The potential profiles of liquid molecules in slit nanopores and the heat of adsorption can be well reproduced with this quasicrystal model of liquid. This model can capture the main characteristics of liquid. It provides a simple method to describe the physical mechanism and directly estimate the characteristic parameters of simple liquid systems.     

MOVING SCREW DISLOCATION IN CUBIC QUASICRYSTAL

The elasticity theory of the dislocation of cubic quasicrystals is developed. The governing equations of anti-plane elasticity dynamics problem of the quasicrystals were reduced to a solution of wave equations by introducing displacement functions, and the analytical expressions of displacements, stresses and energies induced by a moving screw dislocation in the cubic quasicrystalline and the velocity limit of the dislocation were obtained. These provide important information for studying the plastic deformation of the new solid material.     

Fundamental solutions of critical wedge angles for one-dimensional piezoelectric quasicrystal wedge

Two problems of a one-dimensional (1D) piezoelectric quasicrystal (QC) wedge are investigated, i. e., the two sides of the wedge subject to uniform tractions and the wedge apex subject to the concentrated force. By virtue of the Stroh formalism and Barnett-Lothe matrices, the analytical expressions of the displacements and stresses are derived, and the generalized solutions for the critical wedge angles are discussed. Numerical examples are given to present the mechanical behaviors of the wedge in each field. The results indicate that the effects of the uniform tractions and the concentrated force on the phonon field displacement are larger than those on the phason field.     

The formation and stability of quasicrystal in Al80Mn14Si6 under high static pressure

Abstract

The method of quenching in fusing state under high static pressure (MQFSHP) was applied for the first time to prepare the quasicrystal icosahedral phase of Al₈₀Mn₁₄Si₆ alloy. The pressure was from 2.8GPa to 3.1GPa and the cooling rate during quenching was of about 100°C/s. Some sharp electron diffraction spots showing an arrangement with a five-fold symmetry axis and noncrystalline ring have been observed in electron diffraction experiment.

The crystallization temperature of I phase obtained from high pressure(HP) is close to that of rapid cooling ribbon, but the cooling rate of the sample obtained is lower than that of rapid cooling ribbon.     

Determination of the chemical states of impurities in natural kyanite by the ionoluminescence technique

Ionoluminescence (IL) of natural kyanite crystals was studied during 120 MeV Au⁹⁺ ion irradiation in the fluence range 1.50?12 × 10¹¹ ions/cm². The IL spectrum exhibits sharp peaks at ～689, 694, 705, 713 and 716 nm, along with a broad emission peak at 530 nm recorded for all samples investigated. The sharp emission peaks at 689 and 694 nm are attributed to R₂ and R₁ lines of Cr³⁺ impurities, and they are related to the transition ²E_g → ⁴A_2g. The peaks at 705–716 nm are attributed to Fe³⁺ impurities and are related to the transition ⁴T_1g → ⁶A_1g. It was observed that up to a given fluence, the IL peak intensity grows, reaches a maximum and gradually decreases with increase of Au⁹⁺ ion fluence. The decrease in IL intensity might be attributed to disorder produced by dense electronic excitation under swift heavy ion irradiation. The stability of the chemical species was studied both with and without irradiation by means of FTIR spectroscopy. The results confirm that the Si?O?Al, Al?O and Si?O (2ν₃) type species are destroyed due to amorphization.     

Microstructural evolution in Al–Mn–Cu–(Be) alloys

This study investigates the effects of alloying elements on the microstructural evolution of Al-rich Al–Mn–Cu–(Be) alloys during solidification, and subsequent heating and annealing. The samples were characterised using scanning electron microscopy, energy dispersive X-ray spectroscopy, synchrotron X-ray diffraction, time-of-flight secondary-ion mass spectroscopy, and differential scanning calorimetry. In the ternary Al₉₄Mn₃Cu₃ (at%) alloy, the phases formed during slower cooling (≈1?K?s^?1) can be predicted by the known Al–Mn–Cu phase diagram. The addition of Be prevented the formation of Al₆Mn, decreased the fraction of τ₁-Al₂₉Mn₆Cu₄, and increased the fraction of Al₄Mn. During faster cooling (≈1000?K?s^?1), Al₄Mn predominantly formed in the ternary alloy, whereas, in the quaternary alloys, the icosahedral quasicrystalline phase dominated. Further heating and annealing of the alloys caused an increase in the volume fractions of τ₁ in all alloys and Be₄Al (Mn,Cu) in quaternary alloys, while fractions of all other intermetallic phases decreased. Solidification with a moderate cooling rate (≈1000?K?s^?1) caused considerable strengthening, which was reduced by annealing for up to 25% in the quaternary alloys, while hardness remained almost the same in the ternary alloy.     

Solidification of tin on quasicrystalline surfaces

A two-phase alloy of β-Sn and Al₆₃Cu₂₅Fe₁₂ quasicrystal produced by melt-spinning was annealed and aged to form various microstructures of tin in a quasicrystalline (QC) or microcrystalline (MC) matrix. The morphology and structure of the interfaces was studied by scanning and transmission electron microscopy and was related to melting and solidification behavior of tin studied by differential scanning calorimetry. In a MC matrix the tin phase occurred as nanoparticles and solidified with an undercooling of about 35°C. In a QC matrix, tin formed intergranular layers on faceted matrix grains. Tin showed multiple solidification peaks in undercooling ranging from 8°C to 43°C, indicating several distinct nucleation sites which compete with each other and are selected kinetically. The interfacial energy (depending on the structural state of the matrix) had a more dominating effect on the solidification of tin than the size, shape and the distribution of the tin particles. It was also concluded that solidification of tin is easier on quasicrystalline surfaces than on aluminum.