Macroscopic properties of sandstone are commonly attributed to the degradation of its microstructure during heating treatment processes. However, few previous studies have focused on comprehensive observations on how the microstructure of sandstone changes with temperature. In this study, a kind of sandstone containing quartz, albite, calcite, and laumontite (little), was collected from Linyi (Shandong Province, China) to observe the microstructure degradation changes with temperature by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and thermo-gravimetric analyses (TGA). Firstly, 10 groups of sandstone samples were heated from 25 • C to 900 • C. Then, some core micro-parameters including lattice constant, full width at half maximum (FWHM), micro-strain, dislocation density, TGA curve changes and failure characteristic of the mineral were analyzed comprehensively. Finally, the underlying mechanism causing the microscopic thermal damage at different temperature intervals was also discussed. The results showed that: (1) quartz, the framework component of this sandstone, underwent an α-to β-phase change over the temperature range from 400 • C to 600 • C. This phenomenon caused the lattice constant, micro-strain, dislocation density and TGA curve to decrease sharply during this interval, leading to the microstructure deterioration of sandstone; (2) calcite underwent a decomposition reaction between 600 • C and 800 • C, and resulted in the XRD pattern peak, lattice constant, micro-strain and TGA curve dropping continuously. It destroyed further the internal microstructure of sandstone and produced numerous inter-granular cracks around quartz crystals; (3) further examination found that the decomposition reactions of minerals presented non-synchronized characteristics due to the different sensitivities of minerals to temperature, which led to thermal stress, thermal fracturing of minerals, and thermal reactions happening in different temperature intervals.
We present measurements of the (e, 2e) cross sections of xenon for transitions leading to the 5p 3/2 and 5p 1/2 states of the residual ion using an incident polarized electron beam in coplanar asymmetric kinematics and in the intermediate energy regime. The results show that the spin up-down asymmetry for the 5p 3/2 and 5p 1/2 transitions can be understood as an analogue of the so-called fine-structure effect in inelastic scattering. However, our present measurements also point to significant contributions from relativistic effects in the electron-atom system under certain conditions. The measured spin up-down asymmetry is analysed using the density matrix formalism. This approach reveals that different exchange interactions contribute to the fine-structure effect for ionization. The contribution of relativistic interactions in the observed parameters is also investigated by using a semirelativistic DWBA model to evaluate the scattering amplitudes.
Spin resolved (e,2e) experiments provide an extremely sensitive test of theories of electron impact ionization and many-body Coulomb effects. We present here results for (e,2e) collisions with xenon which show the first experimental evidence of the fine structure effect in electron impact ionization, analogous to the well known effect in electron impact excitation of atoms by polarized electrons. Comparison with distorted-wave Born-approximation calculations shows the sensitivity of the results to details of the target atom wave functions as well as the treatment of relativistic effects. PACS numbers: 34.80.Dp, 34.80.Nzwhere s " J and s # J are, respectively, the ͑e, 2e͒ differential cross sections to the final ion state of angular momentum J for incident electrons with spin up and spin down perpendicular to the scattering plane. Experimentally, A J is determined from the relation
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