MgO has been shown to facilitate the precipitation of MgO-rich crystalline phases within the MgO-CaO-Al_(2)O_(3)-SiO_(2)(MCAS)glassy inclusion system,which possesses a high liquidus temperature and a significant Young...MgO has been shown to facilitate the precipitation of MgO-rich crystalline phases within the MgO-CaO-Al_(2)O_(3)-SiO_(2)(MCAS)glassy inclusion system,which possesses a high liquidus temperature and a significant Young’s modulus.The underlying linkage between the structural evolution and the crystallization characteristics of the MCAS system was systematically investigated using molecular dynamics simulation and thermodynamic calculation.The results revealed that Mg^(2+) ions played a dual role,constructing networks through the formation of tricluster oxygens while consuming bridging oxygens(BOs)in a mechanism similar to Ca^(2+) ions.However,despite this dual role,the network connectivity was still decreased with the increase in MgO/(MgO+Al_(2)O_(3))(M/(M+A))and CaO/(CaO+SiO_(2))(C/(C+S))ratios,primarily due to the reduction in BOs.This microscopic structural evolution resulted in a reduction in viscosity and an enhancement of crystallization ability.Furthermore,the remarkable diffusion capability of Mg^(2+) ions,coupled with the increased proportion of 6-coordinated Mg^(2+)ions,unveiled the mechanism underlying the precipitation of MgSiO_(3) and Mg_(2)SiO_(4) crystals,which exhibited high Young’s moduli of 165.23 and 196.67 GPa,respectively.To prevent the precipitation of MgO-rich crystalline phases,it was crucial to maintain the M/(M+A)ratio below 0.42 and the C/(C+S)ratio below 0.16 within the MCAS system.展开更多
The adsorption behavior of water on ZSM-5 was simulated by using the grand canonical ensemble Monte Carlo (GCEMC) method.The geometric structure and properties of ZSM-5 were first analysed by the Connolly surface meth...The adsorption behavior of water on ZSM-5 was simulated by using the grand canonical ensemble Monte Carlo (GCEMC) method.The geometric structure and properties of ZSM-5 were first analysed by the Connolly surface methods and Solvent surface methods.Simulation results showed that Connolly free volume and the volume of water molecular inaccessible in zeolite gradually decreased with decreasing zeolite ratio nSi/nAl.ZSM-5 zeolite was strongly hydrophobic under low pressure conditions,and its adsorption capacity would increase with increasing pressure.Desorption curves had a certain lag,and this proved the existence of capillary rally phenomenon.The adsorption capacity of ZSM-5 zeolite exchanged by K+,Na+,Ca2+ had a significant change,and increased with increasing aperture size.The adsorption capacity of zeolite increased with Si atoms replaced by Ti atoms in zeolite matrix,while it would decrease with increasing number of Al atoms replaced by Ti atoms.At the same adsorption capacity,the absorption heat reduced with increasing nSi/nAl ratio or aperture size.展开更多
基金support from the National Key R&D Program of China(Grant Nos.2023YFB3709900 and 2023YFB3709903)the National Natural Science Foundation of China(Grant Nos.52174293 and U22A20171)+1 种基金the High Steel Center(HSC)at North China University of TechnologyUniversity of Science and Technology Beijing(USTB).
文摘MgO has been shown to facilitate the precipitation of MgO-rich crystalline phases within the MgO-CaO-Al_(2)O_(3)-SiO_(2)(MCAS)glassy inclusion system,which possesses a high liquidus temperature and a significant Young’s modulus.The underlying linkage between the structural evolution and the crystallization characteristics of the MCAS system was systematically investigated using molecular dynamics simulation and thermodynamic calculation.The results revealed that Mg^(2+) ions played a dual role,constructing networks through the formation of tricluster oxygens while consuming bridging oxygens(BOs)in a mechanism similar to Ca^(2+) ions.However,despite this dual role,the network connectivity was still decreased with the increase in MgO/(MgO+Al_(2)O_(3))(M/(M+A))and CaO/(CaO+SiO_(2))(C/(C+S))ratios,primarily due to the reduction in BOs.This microscopic structural evolution resulted in a reduction in viscosity and an enhancement of crystallization ability.Furthermore,the remarkable diffusion capability of Mg^(2+) ions,coupled with the increased proportion of 6-coordinated Mg^(2+)ions,unveiled the mechanism underlying the precipitation of MgSiO_(3) and Mg_(2)SiO_(4) crystals,which exhibited high Young’s moduli of 165.23 and 196.67 GPa,respectively.To prevent the precipitation of MgO-rich crystalline phases,it was crucial to maintain the M/(M+A)ratio below 0.42 and the C/(C+S)ratio below 0.16 within the MCAS system.
文摘The adsorption behavior of water on ZSM-5 was simulated by using the grand canonical ensemble Monte Carlo (GCEMC) method.The geometric structure and properties of ZSM-5 were first analysed by the Connolly surface methods and Solvent surface methods.Simulation results showed that Connolly free volume and the volume of water molecular inaccessible in zeolite gradually decreased with decreasing zeolite ratio nSi/nAl.ZSM-5 zeolite was strongly hydrophobic under low pressure conditions,and its adsorption capacity would increase with increasing pressure.Desorption curves had a certain lag,and this proved the existence of capillary rally phenomenon.The adsorption capacity of ZSM-5 zeolite exchanged by K+,Na+,Ca2+ had a significant change,and increased with increasing aperture size.The adsorption capacity of zeolite increased with Si atoms replaced by Ti atoms in zeolite matrix,while it would decrease with increasing number of Al atoms replaced by Ti atoms.At the same adsorption capacity,the absorption heat reduced with increasing nSi/nAl ratio or aperture size.
