In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration pro...In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was investigated.Composition of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa method.According to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal conditions.The DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide cement.The three stages correspond to different activation energies.Therefore,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.展开更多
Sodium dihydrogen phosphate (NaH_(2)PO_(4)) and potassium dihydrogen phosphate (KH_(2)PO_(4)) were selected as additives for magnesium oxysulfate (MOS) cement.The phase composition and the microstructure of MOS cement...Sodium dihydrogen phosphate (NaH_(2)PO_(4)) and potassium dihydrogen phosphate (KH_(2)PO_(4)) were selected as additives for magnesium oxysulfate (MOS) cement.The phase composition and the microstructure of MOS cement were characterized using X-ray diffraction (XRD),thermogravimetric analysis (TG-DSC),Flourier transform infrared spectroscopy (FT-IR),mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM).It is found that both NaH_(2)PO_(4) and KH_(2)PO_(4) lead to an increase in the compressive strength and an improvement in the volume stability of MOS cement.The XRD,MIP and SEM results show that the addition of NaH_(2)PO_(4) or KH_(2)PO_(4) does not change the phase composition of MOS cement but promotes the formation of strength phase of 5Mg(OH)_(2)·MgSO_(4)·7H_(2)O (5·1·7 phase).This phase brings a considerable improvement in the microstructure of MOS cement,which has a positive effect on the properties of MOS cement.展开更多
基金Fund by the National Natural Science Foundation of China (No.51778101)the General Program (Key Program,Major Research Plan)of National Natural Science Foundation of China+2 种基金the National Key R&D Program (No.2020YFC1909304)the National Program on Key Basic Research Project of Chinathe Joint Fund Project of National Natural Fund of China (U1908227)。
文摘In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was investigated.Composition of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa method.According to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal conditions.The DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide cement.The three stages correspond to different activation energies.Therefore,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.
基金Supported by the Key Research and Development and Transformation Plan of Qinghai Province-Special Project for Transforming Scientific and Technological Achievements(No.2019-NN-159)。
文摘Sodium dihydrogen phosphate (NaH_(2)PO_(4)) and potassium dihydrogen phosphate (KH_(2)PO_(4)) were selected as additives for magnesium oxysulfate (MOS) cement.The phase composition and the microstructure of MOS cement were characterized using X-ray diffraction (XRD),thermogravimetric analysis (TG-DSC),Flourier transform infrared spectroscopy (FT-IR),mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM).It is found that both NaH_(2)PO_(4) and KH_(2)PO_(4) lead to an increase in the compressive strength and an improvement in the volume stability of MOS cement.The XRD,MIP and SEM results show that the addition of NaH_(2)PO_(4) or KH_(2)PO_(4) does not change the phase composition of MOS cement but promotes the formation of strength phase of 5Mg(OH)_(2)·MgSO_(4)·7H_(2)O (5·1·7 phase).This phase brings a considerable improvement in the microstructure of MOS cement,which has a positive effect on the properties of MOS cement.
