Reaction mechanism of metal and pyrite under HPHT conditions and improvement of the properties

2022 ◽  
Author(s):  
Yao Wang ◽  
Dan Xu ◽  
Shan Gao ◽  
Qi Chen ◽  
Dayi Zhou ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
Reaction Mechanism ◽  
First Principles ◽  
Room Temperature ◽  
First Principles Calculations ◽  
Mine Wastewater ◽  
Al Addition ◽  
Thermal Stability Of ◽  
Pyrite Tailings

Abstract Pyrite tailings are the main cause of acid mine wastewater. An idea was put forward to more effectively use pyrite, and it was modified by exploiting the reducibility of metal represented by Al under high-pressure and high-temperature (HPHT) conditions. Upon increasing the Al addition, the conductivity of pyrite were effectively improved, which is nearly 734-times higher than that of unmodified pyrite at room temperature. First-principles calculations were used to determine the influence of a high pressure on the pyrite lattice. The high pressure increased the thermal stability of pyrite, reduced pyrite to high-conductivity Fe7S8 (pyrrhotite) by Al, and prevented the formation of iron. Through hardness and density tests the influence of Al addition on the hardness and toughness of samples was explored. Finally the possibility of using other metal-reducing agents to improve the properties of pyrite was discussed.

scholarly journals Simultaneous tuning of the magnetic anisotropy and thermal stability of $$\alpha ^{''}$$-phase Fe$$_{16}$$N$$_{2}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. Odkhuu ◽  
S. C. Hong
Keyword(s):  
Thermal Stability ◽  
Magnetic Anisotropy ◽  
First Principles ◽  
Alpha Phase ◽  
Formula Unit ◽  
First Principles Calculations ◽  
A Value ◽  
Valence Electrons ◽  
Re Elements ◽  
Thermal Stability Of

AbstractSimultaneously enhancing the uniaxial magnetic anisotropy ($$K_u$$ K u ) and thermal stability of $$\alpha ^{''}$$ α ′ ′ -phase Fe$$_{16}$$ 16 N$$_{2}$$ 2 without inclusion of heavy-metal or rare-earth (RE) elements has been a challenge over the years. Herein, through first-principles calculations and rigid-band analysis, significant enhancement of $$K_u$$ K u is proposed to be achievable through excess valence electrons in the Fe$$_{16}$$ 16 N$$_{2}$$ 2 unit cell. We demonstrate a persistent increase in $$K_u$$ K u up to 1.8 MJ m$$^{\text {-}3}$$ - 3 , a value three times that of 0.6 MJ m$$^{\text {-}3}$$ - 3 in $$\alpha ^{''}$$ α ′ ′ -Fe$$_{16}$$ 16 N$$_{2}$$ 2 , by simply replacing Fe with metal elements with more valence electrons (Co to Ga in the periodic table). A similar rigid-band argument is further adopted to reveal an extremely large $$K_u$$ K u up to 2.4 MJ m$$^{\text {-}3}$$ - 3 in (Fe$$_{0.5}$$ 0.5 Co$$_{0.5}$$ 0.5 )$$_{16}$$ 16 N$$_{2}$$ 2 obtained by replacing Co with Ni to Ga. Such a strong $$K_u$$ K u can also be achieved with the replacement by Al, which is isoelectronic to Ga, with simultaneous improvement of the phase stability. These results provide an instructive guideline for simultaneous manipulation of $$K_u$$ K u and the thermal stability in 3d-only metals for RE-free permanent magnet applications.

scholarly journals Thermal stability of a nanocrystalline HfNbTiZr multi-principal element alloy processed by high-pressure torsion

2020 ◽  
Vol 168 ◽  
pp. 110550 ◽  
Author(s):  
Pham Tran Hung ◽  
Megumi Kawasaki ◽  
Jae-Kyung Han ◽  
János L. Lábár ◽  
Jenő Gubicza
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Principal Element ◽  
Thermal Stability Of

scholarly journals The thermal stability of FAPbBr3 nanocrystals from temperature-dependent photoluminescence and first-principles calculations

RSC Advances ◽  
2020 ◽  
Vol 10 (72) ◽  
pp. 44373-44381
Author(s):  
Xiaozhe Wang ◽  
Qi Wang ◽  
Zhijun Chai ◽  
Wenzhi Wu
Keyword(s):  
First Principles ◽  
First Principle ◽  
First Principles Calculations ◽  
Temperature Dependent ◽  
Time Resolved ◽  
First Principle Calculations ◽  
Steady State Time ◽  
Time Resolved Photoluminescence ◽  
Thermal Stability Of ◽  
Temperature Dependent Photoluminescence

The thermal properties of FAPbBr3 perovskite nanocrystals (PNCs) is investigated by use of temperature-dependent steady-state/time-resolved photoluminescence and first-principle calculations.

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