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[en] Highlights: • The alkaline cation nature and amount control the shrinkage values at room temperature. • Shaping of geopolymers in complex geometries is possible. • The chemical composition of geopolymer induces three behaviors after heating. • M/Al ratio (M = Na, K) controls fire resistance of geopolymers at high temperature. This paper presents results from experimental studies on the thermal resistance and dilatometry analysis of various geopolymer formulations, which were prepared by mixing alkaline solutions, metakaolin and reinforcements. Nine compositions were tested by dilatometric analysis and thermal resistance at high temperature (800 °C). Structural and microstructural analysis was conducted to verify the geopolymerization, and differential thermogravimetric analysis was performed to evaluate the nature of water, depending on the formulation. Some key parameters were identified as critical parameters that influenced the geopolymer properties, such as the nature (Na or K) and the molar concentration of the alkaline cation ([M] < 16 mol/L), the molar concentration of silicon ([Si] < 39 mol/L) and the alkaline metal to aluminum ratio (M/Al < 0.65). Finally, it was possible to arrange the various formulations in a ternary scheme as functions of the metal, aluminum and silicon concentrations. This scheme may represent a roadmap for controlling the thermal resistance of geopolymer materials.
[en] There are many indicators to measure the performance of power cable materials, among which flame retardancy, conductivity and environmental protection are the most important. In experiment 1, the flame retardancy of sample cables was studied by thermogravimetric analysis, and an analytical method for flame retardancy of cable materials was provided. In experiment 2, the environmental protection performance of the sample cable was analyzed by cytotoxicity test. Finally, a reasonable prospect and forecast for the new power cable in the future is given. (paper)
[en] Water splitting by Sulfur iodine (54) cycle is one of the promising thermochemical processes for hydrogen production due to its high efficiency. The decomposition of H2SO4 to produce SO2 is the reaction with the highest energy demand in the S-I cycle and it shows a large kinetic barrier. Sulfuric acid being highly corrosive and its endothermic decomposition needs elevated temperatures (>850 °C). The total operating pressure in the whole process reach upto 6 MPa. Henceforth, before the scale-up of this process plant there is a need to explore various materials of construction under very harsh acidic environments and phase changing conditions. Corrosion studies on possible material (metals/ alloys/) of construction have been studied in detail and the most corrosion resistant materials were chosen to construct a pilot-scale sulfuric acid decomposition plant section and was fabricated, installed and commissioned at Indian Institute of Technology (IIT), Delhi. (author)
[en] With the advancements of materials science and technology, organic materials found significant applications in aerospace industry. But under the orbital thermal and vacuum environment, organic materials can outgas and the outgassed products and induced environment often degraded performances of spacecraft or its subsystem. In this article, the typical impacts of outgassing environment on spacecraft are explained briefly. Then the outgassing theory, test method, identification of compounds and control measures were reviewed in detail. The need for transient and long-term outgassing model is discussed. The standard test methods of E595 and E1559 are compared. The promising new techniques such as infrared spectrometry and/or mass-spectrometry with thermogravimetric analysis is proposed for the identification of outgassed compounds. The vacuum bakeout and molecular absorber for outgassing control are reviewed and for the last more research work is needed. (paper)