Sample decomposition method selection is crucial for accurate determination of silicon carbide (SiC). According to the properties of SiC, it is stable and insoluble in hydrofluoric acid, sulfuric acid, and other acids, but can be dissolved in molten alkalis. In this study, two different melting reagents were used: a mixture of Naâ‚‚O + KOH and KNO₃ + KOH. After leaching with hot water and acidification using hydrochloric and nitric acids, an insoluble residue was observed by the naked eye, indicating that these reagents were not effective in decomposing SiC. Therefore, the potassium fluorosilicate volumetric method could not be applied. Based on the decomposition capability of the mixed solvents, a high-temperature melting approach was chosen. The decomposition temperature and time were set at 1050°C and 1100°C, respectively, and the results were consistent. This paper adopts 1050°C. During the decomposition process, the sample was observed every 10 minutes. A two-dimensional motion mixer showed that after 30 minutes, the sample became clear, indicating complete decomposition. Thus, 30 minutes was selected as the optimal time. Leaching acidity plays an important role in the analysis of SiC. Due to the tendency of silicic acid to polymerize, the acidity during leaching should be kept below 2 mol/L. In this study, the leaching procedure used for determining SiOâ‚‚ in ores was adopted, which involves leaching with 100 mL of hydrochloric acid (1+6). For the color development reaction involving the silicon molybdenum heteropoly acid, the acidity is typically controlled at C(Hâº) = 0.1–0.6 mol/L. To ensure accuracy, the color development acidity was regulated using a reagent blank solution based on daily analysis of SiOâ‚‚ in refractories. Interference from other elements must also be considered. In addition to SiC, the main components of silicon carbide-containing refractory products include SiOâ‚‚, Alâ‚‚O₃, CaO, MgO, Feâ‚‚O₃, TiOâ‚‚, MnO, Crâ‚‚O₃, Pâ‚‚Oâ‚…, and free carbon. SiOâ‚‚ can be removed by volatilization with hydrofluoric acid, while free carbon can be burned off in a high-temperature furnace. Non-ferrous metal oxides like Crâ‚‚O₃ can be eliminated through reference preparation. Pâ‚‚Oâ‚… and Feâ‚‚O₃ can be masked using oxalic acid, although this method is not suitable for phosphate-bonded refractories. Other components did not interfere significantly with the analysis. The reliability of the results and the applicability of the method are also important factors. Since no standard samples were available, the results obtained from pure SiC only reflect the recovery rate. Synthesizing samples that exactly match real samples is difficult. Therefore, this study employed the gravimetric analysis method, which does not require a standard sample, and followed the decomposition procedure described in the paper. The results from the perchloric acid dehydration method were compared with those obtained using the proposed method. The method is applicable for determining SiC in SiC materials and has a wide range of applications. It can be used for analyzing refractory products containing 1% or more SiC. For samples with SiC content above 30%, the allowable difference can be controlled below 0.3%. If the differential photometric method is used for SiC contents exceeding 30%, the sample weight and fractionation rate remain unaffected, and the allowable difference can be kept below 0.5%. This method is simple to perform, has minimal interference, and the resulting sample solution can also be used for the determination of Alâ‚‚O₃, CaO, MgO, and Feâ‚‚O₃. Pneumatic Upward Expansion Valve expansion valve,upward expansion valve,Pneumatic upward expansion valve,expansion valve Pneumatic,upward expansion valve Pneumatic,Pneumatic expansion valve Jiangsu Tanggong Automatic Control Equipment Co., Ltd. , https://www.tgcontrolequipment.com
Experimental Study on SiC Composition in Refractory Products