The meso-structure mineral composition and fracture mechanism of uniaxial compressed mudstone samples at high temperature were analyzed by XRD and scanning electron microscopy. The effect of temperature on mudstone composition and fracture mechanism were studied from a meso-structural perspective, and the relationship between meso-structure and macro-mechanical characteristics at high temperature was revealed. The findings demonstrated that the fluctuation in diffraction intensity of kaolinite in the mudstone caused the fluctuation in its mechanical properties. The overall structure underwent a phase change around 600 ℃, which led to the sudden change in the mechanical properties of mudstone samples. When the temperature reached 600 ℃, the crystalline state worsened and kaolinite disappeared; however, some illite was produced, indicating that the chemical reaction of the structure and sudden drop of bearing capacity of the mudstone. Mudstone fracturing at high temperature involves mainly intergranular and transgranular fractures, which are typical in micro-brittle tensile failure. Considering the macro-fracture characteristics of mudstone, the results suggested that macro-fracture under external force corresponds to the meso-fracture.
The solution behavior, including solubility, reactivity and sedimentation, of ZnO and ZnS in a Na_2CO_3-NaCl molten salt used for Sb smelting was investigated in the temperature range of 700-1000 oC. The saturated amount of dissolved ZnO in the molten salt remained constant at 0.02% and was unaffected by temperature; additionally, ZnO did not react with the molten salt. In contrast, the saturated amount of dissolved ZnS in the eutectic molten salt increased with increasing temperature, and the content of ZnS was 0.53% at 1000 oC. In addition, ZnS reacted with Na_2CO_3 above 900 oC to give ZnO. The sedimentation rates of these three species in the molten salt followed the order of Sb>ZnS>ZnO. It was thus concluded that ZnO is an appropriate sulfur-fixing agent for low-temperature Sb smelting in a Na_2CO_3-NaCl molten medium, and that the optimal smelting temperature is below 900 oC.
The experimental tests for limestone specimens at 700 °C in uniaxial compression were carried out to inves- tigate the mechanical effects of loading rates on limestone by using a MTS810 rock mechanics servo- controlled testing system considering the loading rate as a variable. The mechanical properties of limestone such as the stress-strain curve, variable characteristics of peak strength and the modulus of elasticity of limestone were studied under the strain rates ranging from 1.1 10à5 to 1.1 10à1 sà1. (1) Sharp decreases were shown for the peak strength and elastic modulus of limestone from 1.1 10à5 to 1.1 10à4 sà1 at 700 °C as well as a downward trend was shown from 1.1 10à4 to 1.1 10à1 sà1 with the rise of the strain rate. (2) The peak strain increased from 1.1 10à5 to 1.1 10à4 sà1, however, there was no obvious changes shown for the peak strain of limestone from 1.1 10à4 to 1.1 10à1 sà1. These results can provide valuable references for the rock blasting effect and design of mine.
Tang FurongMao XianbiaoZhang LianyingYin HuiguangLi Yan
