scholarly journals Self-consistent thermodynamic parameters of pyrope and almandine at high-temperature and high-pressure conditions: Implication on the adiabatic temperature gradient

2021 ◽  
pp. 106789
Author(s):  
Chang Su ◽  
Yonggang Liu ◽  
Dawei Fan ◽  
Wei Song ◽  
Guang Yang
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Temperature Gradient ◽  
Thermodynamic Parameters ◽  
Adiabatic Temperature ◽  
Self Consistent ◽  
Adiabatic Temperature Gradient

scholarly journals Self-Consistent Thermodynamic Parameters of Diopside at High Temperatures and High Pressures: Implications for the Adiabatic Geotherm of an Eclogitic Upper Mantle

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1322
Author(s):  
Chang Su ◽  
Dawei Fan ◽  
Jiyi Jiang ◽  
Zhenjun Sun ◽  
Yonggang Liu ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Thermodynamic Parameters ◽  
Upper Mantle ◽  
High Pressures ◽  
Potential Temperature ◽  
Theoretical Data ◽  
Adiabatic Temperature ◽  
Depth Range ◽  
Self Consistent ◽  
Adiabatic Temperature Gradient

Using an iterative numerical approach, we have obtained the self-consistent thermal expansion, heat capacity, and Grüneisen parameters of diopside (MgCaSi2O6) over wide pressure and temperature ranges based on experimental data from the literature. Our results agree well with the published experimental and theoretical data. The determined thermodynamic parameters exhibit nonlinear dependences with increasing pressure. Compared with other minerals in the upper mantle, we found that the adiabatic temperature gradient obtained using the thermodynamic data of diopside is larger than that of garnet while lower than that of olivine, when ignoring the Fe incorporation. Combining our results with thermodynamic parameters of garnet obtained in previous studies, we have estimated the adiabatic temperature gradient and geotherm of an eclogitic upper mantle in a depth range of 200–450 km. The results show that the estimated adiabatic temperature gradient of the eclogite model is ~16% and ~3% lower than that of the pyrolite model at a depth of 200 km and 410 km, respectively. However, the high mantle potential temperature of the eclogite model leads to a similar temperature as the pyrolite model in a depth range of 200–410 km.

scholarly journals 19. Convection Zones and Coronae of White Dwarfs

1971 ◽  
Vol 42 ◽  
pp. 130-135 ◽  
Author(s):  
K. H. Böhm ◽  
J. Cassinelli
Keyword(s):  
Chemical Composition ◽  
Temperature Gradient ◽  
White Dwarf ◽  
White Dwarfs ◽  
Convection Zone ◽  
Adiabatic Temperature ◽  
Turbulent Convection ◽  
Cool White Dwarfs ◽  
Adiabatic Temperature Gradient

Outer convection zones of white dwarfs in the range 5800 K ≤ Teff ≤ 30000 K have been studied assuming that they have the same chemical composition as determined by Weidemann (1960) for van Maanen 2. Convection is important in all these stars. In white dwarfs Teff < 8000 K the adiabatic temperature gradient is strongly influenced by the pressure ionization of H, HeI and HeII which occurs within the convection zone. Partial degeneracy is also important.Convective velocities are very small for cool white dwarfs but they reach considerable values for hotter objects. For a white dwarf of Teff = 30000 K a velocity of 6.05 km/sec and an acoustic flux (generated by the turbulent convection) of 1.5 × 1011 erg cm−2 sec−1 is reached. The formation of white dwarf coronae is briefly discussed.

Studies on HPHT synthesis and N defects of N-rich B-doped diamonds

CrystEngComm ◽  
2018 ◽  
Vol 20 (44) ◽  
pp. 7109-7113 ◽  
Author(s):  
Xinyuan Miao ◽  
Liangchao Chen ◽  
Hongan Ma ◽  
Chao Fang ◽  
Longsuo Guo ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Temperature Gradient ◽  
Single Crystal ◽  
High Quality ◽  
Temperature Conditions ◽  
Ni Content ◽  
Growth Method

In this paper, high-quality N-rich single crystal diamonds with different boron additive contents were synthesized in NiMnCo alloy with high Ni content by the temperature gradient growth method under HPHT (high pressure and high temperature) conditions.

Effect of Ni70Mn25Co5 or Fe55Ni29Co16 on the Growth of Type-II a Large Diamonds with Al as Nitrogen Getter

2011 ◽  
Vol 266 ◽  
pp. 89-92
Author(s):  
Shang Sheng Li ◽  
Ning Luo ◽  
Xiao Lei Li ◽  
Tai Chao Su ◽  
You Mou Zhou ◽  
...  
Keyword(s):  
Growth Rate ◽  
High Pressure ◽  
High Temperature ◽  
Temperature Gradient ◽  
Nitrogen Concentration ◽  
Type Ii ◽  
High Quality ◽  
Quality Type ◽  
Temperature Gradient Method ◽  
Large Diamond

With adopting Al as the nitrogen getter in Ni70Mn25Co5 or Fe55Ni29Co16 catalyst, High-quality type-Ⅱa large diamonds have been grown under the conditions of about 5.5GPa and 1580K by using the temperature gradient method. While Al(2.0wt%) is added in the Fe55Ni29Co16, the nitrogen concentration(Nc) in the diamond is less than 1ppm. While Al(4.0wt%) is added in the Ni70Mn25Co5, the Nc in the diamond is highly arrived at 48ppm. The different of solubility of nitrogen in both catalyst at high pressure and high temperature is the basic reason of the different effect of eliminating nitrogen of Al. It can be shown in experamentals that Al is a less efficient nitrogen getter in Ni70Mn25Co5 than in Fe55Ni29Co16. While Al(2.0wt%) is added in the Fe55Ni29Co16, the high-quality type-Ⅱa large diamond, in which nitrogen is less than 1ppm and which the size was arrived at 3.3mm, had grown by decreasing the growth rate of diamond.

Synthesis and characterization of boron and nitrogen co-doped diamond crystals under high pressure and high temperature conditions

CrystEngComm ◽  
2017 ◽  
Vol 19 (31) ◽  
pp. 4571-4575 ◽  
Author(s):  
Meihua Hu ◽  
Ning Bi ◽  
Shangsheng Li ◽  
Taichao Su ◽  
Qiang Hu ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Temperature Gradient ◽  
Gradient Method ◽  
Synthesis And Characterization ◽  
Temperature Conditions ◽  
Diamond Crystals ◽  
Temperature Gradient Method ◽  
Co Doped

In this study, diamond crystals co-doped with boron and nitrogen were synthesized via a temperature gradient method at 5.3–5.8 GPa and 1300–1550 °C by adding B and N dopants to a system of carbon and an Fe-based solvent catalyst.

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