Given the complexity of the thermo-hydro-chemically coupled phase transition process of hydrates,real-time in-situ observations are required.Thermometry maps are particularly essential in analyzing the heat transfer p...Given the complexity of the thermo-hydro-chemically coupled phase transition process of hydrates,real-time in-situ observations are required.Thermometry maps are particularly essential in analyzing the heat transfer process during the growth and dissociation of crystal hydrates.In this study,we present the temporally and spatially resolved thermometry of the formation of tetrahydrofuran hydrates based on the temperature dependence of the chemical shift of the water proton.Images of temperature changes were synchronously obtained using a 9.4 T^(1)H magnetic resonance imaging(MRI)system to predict the saturation level of the aqueous solution,phases of the solid hydrates,and the positive temperature anomaly of the exothermic reaction.It was observed that variations in the MRI signal decreased while the temperature rise differed significantly in space and time.The results predicted in this study could have significant implications in optimizing the phase transition process of gas hydrates.展开更多
Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature de...Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress-strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol^（-1）in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A ＊60 % peak efficiency occurs at 800-850 °C/0.001-0.010 s^（-1）. The other peak efficiency of ＊60 % occurs at C950 °C/0.001-0.010 s^（-1）, which can be considered to be the optimum condition for high-temperature working of this alloy.However, at strain rates of higher than 1.000 s^（-1）and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52025066,52006024,81701774,61771423,U21B2065)the Fundamental Research Funds for the Central Universities(Grant No.DUT22LAB130)。
文摘Given the complexity of the thermo-hydro-chemically coupled phase transition process of hydrates,real-time in-situ observations are required.Thermometry maps are particularly essential in analyzing the heat transfer process during the growth and dissociation of crystal hydrates.In this study,we present the temporally and spatially resolved thermometry of the formation of tetrahydrofuran hydrates based on the temperature dependence of the chemical shift of the water proton.Images of temperature changes were synchronously obtained using a 9.4 T^(1)H magnetic resonance imaging(MRI)system to predict the saturation level of the aqueous solution,phases of the solid hydrates,and the positive temperature anomaly of the exothermic reaction.It was observed that variations in the MRI signal decreased while the temperature rise differed significantly in space and time.The results predicted in this study could have significant implications in optimizing the phase transition process of gas hydrates.
基金financially supported by the Project of Introducing Talents of Discipline to Universities‘‘111’’Project(No.B08040)
文摘Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress-strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol^（-1）in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A ＊60 % peak efficiency occurs at 800-850 °C/0.001-0.010 s^（-1）. The other peak efficiency of ＊60 % occurs at C950 °C/0.001-0.010 s^（-1）, which can be considered to be the optimum condition for high-temperature working of this alloy.However, at strain rates of higher than 1.000 s^（-1）and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.
