The lattice thermal conductivity(κ_(latt))of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth.MgSiO_(3)akimotoite is stable at the bottom of the mantle transition zo...The lattice thermal conductivity(κ_(latt))of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth.MgSiO_(3)akimotoite is stable at the bottom of the mantle transition zone;it transitions to MgSiO_(3)perovskite(MgPv).Inκ_(latt)this work,we carry out a study of the of MgSiO_(3)akimotoite for pressures up to 25 GPa and temperatures up to 2500 K,based onκ_(latt)first-principles calculations combined with lattice dynamics theory.At 300 K and 25 GPa,the of MgSiO_(3)akimotoite is 37.66 W m^(-1)K^(-1),κ_(latt)larger than that of MgPv(13.46 W m^(-1)K^(-1)),which implies that the phase transition explains the reduction in.At 300 K,the pressureκ_(latt)κ_(latt)dependence of is 0.68 W m^(-1)K^(-1)GPa-1,stronger than that of MgPv(0.48 W m^(-1)K^(-1)GPa-1).The azimuthal anisotropy in of MgSiO_(3)akimotoite decreases from 45.5%at 0 GPa to 28.94%at 25 GPa,while the variation trend is opposite to that of MgPv.In MgSiO_(3)κ_(latt)akimotoite,Fe incorporating in the mineral leads to a decrease in and an increase in azimuthal anisotropy.Along the geotherm,theκ_(latt)of MgSiO_(3)akimotoite is lower than that of ringwoodite,which would suggest that MgSiO_(3)akimotoite slows down heat conduction at the bottom of mantle transition zone.These findings are useful for determining the thermal structure of,and understanding heat transfer in,the interior of the Earth.展开更多
Transparent glass-ceramics containing MgSiO_(3)and/or Mg_(2)SiO_(4)nanocrystals were prepared.Effects of MgO/SiO_(2)ratio on crystallization properties of MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals were investigated.When ...Transparent glass-ceramics containing MgSiO_(3)and/or Mg_(2)SiO_(4)nanocrystals were prepared.Effects of MgO/SiO_(2)ratio on crystallization properties of MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals were investigated.When the MgO/SiO_(2)ratio is relatively low,crystallization of MgSiO_(3)is favored,whereas a higher MgO/SiO_(2)ratio tends to promote the crystallization of Mg_(2)SiO_(4).Glass-ceramics are transparent in the visible range due to the small size of the precipitated nanocrystals.Replacing SiO_(2)with MgO results in an increase in Vickers hardness,and the Vickers hardness can be further enhanced through the precipitation of MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals.The findings presented herein are meaningful for the preparation of highly transparent glass-ceramics containing MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41474067,12174352).
文摘The lattice thermal conductivity(κ_(latt))of mantle minerals plays a crucial role in the heat flow and temperature distribution within the Earth.MgSiO_(3)akimotoite is stable at the bottom of the mantle transition zone;it transitions to MgSiO_(3)perovskite(MgPv).Inκ_(latt)this work,we carry out a study of the of MgSiO_(3)akimotoite for pressures up to 25 GPa and temperatures up to 2500 K,based onκ_(latt)first-principles calculations combined with lattice dynamics theory.At 300 K and 25 GPa,the of MgSiO_(3)akimotoite is 37.66 W m^(-1)K^(-1),κ_(latt)larger than that of MgPv(13.46 W m^(-1)K^(-1)),which implies that the phase transition explains the reduction in.At 300 K,the pressureκ_(latt)κ_(latt)dependence of is 0.68 W m^(-1)K^(-1)GPa-1,stronger than that of MgPv(0.48 W m^(-1)K^(-1)GPa-1).The azimuthal anisotropy in of MgSiO_(3)akimotoite decreases from 45.5%at 0 GPa to 28.94%at 25 GPa,while the variation trend is opposite to that of MgPv.In MgSiO_(3)κ_(latt)akimotoite,Fe incorporating in the mineral leads to a decrease in and an increase in azimuthal anisotropy.Along the geotherm,theκ_(latt)of MgSiO_(3)akimotoite is lower than that of ringwoodite,which would suggest that MgSiO_(3)akimotoite slows down heat conduction at the bottom of mantle transition zone.These findings are useful for determining the thermal structure of,and understanding heat transfer in,the interior of the Earth.
基金Funded by the National Natural Science Foundation of China(Nos.52202026,and 62175192)the Natural Science Foundation of Hubei Province(No.2022CFB762)。
文摘Transparent glass-ceramics containing MgSiO_(3)and/or Mg_(2)SiO_(4)nanocrystals were prepared.Effects of MgO/SiO_(2)ratio on crystallization properties of MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals were investigated.When the MgO/SiO_(2)ratio is relatively low,crystallization of MgSiO_(3)is favored,whereas a higher MgO/SiO_(2)ratio tends to promote the crystallization of Mg_(2)SiO_(4).Glass-ceramics are transparent in the visible range due to the small size of the precipitated nanocrystals.Replacing SiO_(2)with MgO results in an increase in Vickers hardness,and the Vickers hardness can be further enhanced through the precipitation of MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals.The findings presented herein are meaningful for the preparation of highly transparent glass-ceramics containing MgSiO_(3)and Mg_(2)SiO_(4)nanocrystals.
