Sorption of gases by crystalline and molten 12CaO.7Al2O3 |
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| Affiliation: | 1. Institute of Agro-Environmental and Forest Biology, National Research Council of Italy, Via Salaria Km 29,300, 00015 Monterotondo Scalo, Roma, Italy;2. Centro Sviluppo Materiali SpA, Via di Castel Romano 100, 00128 Roma, Italy;1. College of Materials Science and Engineering, Beijing University of Technology, Key Laboratory of Functional Materials, Beijing, 100124, China;2. School of Materials Science and Engineering, Hefei University of Technology, Hefei, 230009, China;1. Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, PR China;2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, PR China;3. Faculty of Electrical and Computer Science, Ningbo University, Ningbo 315211, PR China;4. Department of Chemistry, Tsinghua University, Beijing 100084, PR China;5. Shimazu China Co. LTD., Shanghai 200233, PR China |
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| Abstract: | In order to explain the role of gases in the stabilization of the structure of 12CaO.7Al2O3 a mass-spectrometric study was carried out in vacuum of 10−9 atm and in the temperature range of 900° – 1346°C, using polycrystalline samples obtained from the crystallization of melts soaked at 1500°C. It has been demonstrated by thermodynamic analysis of partial pressures of H2O, CO2, CO and O2 measured over the samples that the gases CO2, CO and O2 were sorbed by the specimens in molten state and were encapsulated during its crystallization, while the water vapours further penetrated into the zeolitic structure of the crystals at the time of their cooling. High values of isosteric heat of desorption of gases CO2, CO, and O2, such as 70–80 K-cal/mole, show that the desorption of these gases takes place due to the breakdown of the crystal lattice, while the removal of water with isosteric heat of desorption of about 11 K-cal/mole occurs as a result of its escape through the ‘windows’ in the cellular structure of the crystal. Based on these experimental results a structural model of the melt formed from 12CaO.7Al2O3 crystals has been developed. |
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