Deformation Of Crystal Structure Research Articles

３次元結晶構造内部の変形と破壊の可視画像化

Monitoring internal deformation and fracture of three-dimensional crystal structures under three-dimensional stress is very important. However, observing these phenomena solely by laboratory experiment is difficult. Several experimental results are available, but they are insufficient, since only the surfaces of the crystal structures could be observed. In an effort to obtain data beyond the limitations of laboratory experiment, we have been pursuing the development of computational simulation. This system enables us to analyze internal deformation and fracture of three-dimensional crystal structures with flaking and slipping on crystal grain boundaries. During this process we discovered the lack of useful visualization software, which is vital in evaluating the computational simulation results. In the present study we succeeded in developing visualization software which enables us to display and analyze internal deformation and fracture with flaking and slipping on crystal grain boundaries in an arbitrary cross section of three-dimensional crystal structures. The software development environment that we used is Direct3D “Retained Mode” in Microsoft DirectX7.

Slip line analysis in Ni 3Al by atomic force microscopy

Ni{sub 3}Al intermetallic compounds are well known to exhibit, within a certain range of temperature, an anomalous behavior of their flow strength. This positive temperature dependence of the flow strength has been the subject of extensive experimental study concerning its mechanical properties and dislocation microstructures, which have yielded many possible models. When a crystal is sheared by dislocations that are moving on a slip plane, steps are produced at the intersection of this plane and the crystal surface. As a result, these steps, usually called slip lines or slip traces, are intimately associated with both the crystal structure and plastic deformation, and may give significant information about the processes that create the traces. The purpose of this paper is to report a preliminary analysis of slip traces on Ni{sub 3}Al single crystals by using an AFM. The overall features of the slip traces are first examined, then the possibility of using AFM observations for demonstrating the occurrence of cross-slip on the slip traces is investigated.

STUDY ON THE INTERFACE STRUCTURE: DIAMOND THIN FILM EPITAXY ON (001) SILICON SUBSTRATE

An interesting interface structure between diamond film and silicon substrate has been observed. That is, according to the deformation of the diamond film crystal structure, a strictly 3:2 matching of the two lattices across the interface is obtained. This result clearly indicates that misfit dislocations at the interface and "epitaxial tilting" are not the only two ways to overcome the 1.5% residual misfit.

Thermal Decomposition of Sepiolite and Variations in Pore Structure With and Without Acid Pre-treatment

Sepiolite is a high surface area clay mineral containing channels of molecular dimensions. In industrial applications as an adsorbent or catalyst support, the mineral should have thermal stability. In this study, the effect of heat treatment on sepiolite structure was investigated. Thermal decomposition of raw sepiolite and acid pre-activated sepiolite samples were carried out with a thermogravimetric analyser. Approximately 24% weight loss was observed till 900°C. This value decreased to 14% for acid pre-treated samples. The surface area value of the original sepiolite was 148 m2 g−1, and it increased to 263 m2 g−1 at 100°C. Further increase in temperature caused channel plugging and crystal structure deformation, as a result the surface area values showed a decrease with temperature. On the other hand, acid pre-treatment caused a change in pore size distribution by increasing the surface area 2·5 times. Acid pre-treatment also restricted the possible crystal structure deformations during temperature changes. While the surface area of the original mineral which was heated up to 900°C was 60 m2 g−1, the corresponding value of the acid pre-treated sepiolite was 360 m2 g−1.

Surface damage in single-crystal Mn-Zn ferrite

The depth of the damaged surface layer and the changes of hysteresis loop caused by surface processing in Mn0.53Zn0.35Fe2.12O4 single crystal are measured. The results obtained are treated as a consequence of the crystal structure deformation at the surface and coherent limited domain wall movement.

Crystal structure and local deformation in K2M2++(SO4)3– compounds of the langbeinite-type

Crystal structure and local deformation in K₂<i>M</i>₂⁺⁺(SO₄)₃– compounds of the langbeinite-type

Correction of dipole field due to lattice deformation of a perovskite-type crystal

Correction of Lorentz field coefficients in a Perovskite-type crystal is discussed by considering orthorhombic deformation of a simple cubic lattice. If one considers the deformation of crystal structure from the simple cubic lattice a 3 to the orthorhombic lattice a(1 + Δ 1) × a(1 + Δ 2) × a(1 + Δ 3), a change of the internal field at some respective points caused by the dipole interaction is calculated as follows. The internal electric fields at (000), ( 1 2 1 2 1 2 ) etc. are given by the equations E n(000) = { 4 3 π + S n(000) + 2.1563 (Δ 1 + Δ 2) − 16.8793Δ 3} p a 3 E n( 1 2 1 2 1 2 ) = { 4 3 π + S n( 1 2 1 2 1 2 ) − 10.0622(Δ 1 + Δ 2) + 7.5578Δ 3} p a 3 etc. where S' n s represent the Lorentz correction terms and p is the dipole moment placed at the lattice points. By applying the results the quantitative discussions are possible for many phenomena accompanied by the lattice deformation, namely, ferroelectricity, piezoelectricity, photoelasticity and so on. As an example calculations are made to estimate the birefringences of the BaTiO 3 and WO 3 crystals.