scholarly journals Theoretical investigations on the phase transition of pure and Li-doped AlH3

RSC Advances ◽  
2017 ◽  
Vol 7 (67) ◽  
pp. 42024-42029 ◽  
Author(s):  
Zheng Mei ◽  
Feng-Qi Zhao ◽  
Si-Yu Xu ◽  
Xue-Hai Ju
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Aluminum Hydride ◽  
Enthalpy Change ◽  
Free Energy Change ◽  
Gibbs Free Energy Change ◽  
Α Phase ◽  
Theoretical Investigations

The calculated Gibbs free energy change and enthalpy change for the γ → α phase transition and heat capacity indicate that the aluminum hydride synthesized in experiments is Li-doped.

Theoretical Thermodynamic Analysis and Phase Analysis of AZ91D/Flyash Composites

2014 ◽  
Vol 788 ◽  
pp. 604-607
Author(s):  
Hong Chao Chu ◽  
Si Rong Yu ◽  
Cui Xiang Wang ◽  
Qi Lou
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Minimum Principle ◽  
Solution Treatment ◽  
Entropy Change ◽  
Treatment Temperature ◽  
Free Energy Change ◽  
Energy Change ◽  
Solution Treatment Temperature ◽  
Gibbs Free Energy Change

The thermodynamic calculation is valuable for judging the feasibility of a reaction. In the present paper, the enthalpy change (∆HR), entropy change (∆SR) and Gibbs free energy change (∆GR) among various components in AZ91D Mg alloy-Cenosphere composites (FAC/AZ91D) were calculated. Through the calculation, we obtained the relationships between the Gibbs free energy changes and temperatures. The difficulty degree of every potential reaction could be directly reflected by the correlation curve between the temperature and the Gibbs free energy change. The analysis result provided the theoretical basis for the reaction temperature and the solution treatment temperature of the FAC/AZ91D system. At the same time, the analysis based on the minimum principle of the reaction free energy revealed the final components (MgO, Mg2Si and MgAl2O4), which was partially similar to the result of XRD analysis (MgO, Mg2Si and Mg17Al12).

Gibbs free energy change of a discrete chemical reaction event

2020 ◽  
Vol 152 (8) ◽  
pp. 084116
Author(s):  
Carlos Floyd ◽  
Garegin A. Papoian ◽  
Christopher Jarzynski
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Chemical Reaction ◽  
Free Energy Change ◽  
Energy Change ◽  
Gibbs Free Energy Change ◽  
Reaction Event

Behavior of Intermediate CaTiO3 in Reduction Process of TiO2 by Calcium Vapor

2013 ◽  
Vol 551 ◽  
pp. 25-31 ◽  
Author(s):  
Jin Gang Jia ◽  
Bao Qiang Xu ◽  
Bin Yang ◽  
Dong Sheng Wang ◽  
Heng Xiong ◽  
...  
Keyword(s):  
Free Energy ◽  
Titanium Oxide ◽  
Gibbs Free Energy ◽  
Reduction Process ◽  
Free Energy Change ◽  
Energy Change ◽  
Flow Sheet ◽  
Gibbs Free Energy Change ◽  
Crystal Water ◽  
Calcium Vapor

Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor.

Intergranular Crack Nucleation in Bicrystalline Materials Under Fatigue

1996 ◽  
Vol 63 (3) ◽  
pp. 788-795 ◽  
Author(s):  
H. M. Shodja ◽  
Y. Hirose ◽  
T. Mura
Keyword(s):  
Free Energy ◽  
Crack Initiation ◽  
Gibbs Free Energy ◽  
Cyclic Deformation ◽  
Intergranular Crack ◽  
Crack Nucleation ◽  
Free Energy Change ◽  
Gibbs Free Energy Change ◽  
Cycle Number ◽  
Pile Up

During cyclic deformation of polycrystalline materials, as substantiated by many experimental observations, due to existence of high stress concentration at the interfaces the preferential site of crack nucleation is intercrystalline. Accordingly, it is assumed that the highly localized cyclic deformation persistent slip band (PSB) occurs along the grain boundary (GB) which results in intergranular crack initiation. In the present work the irreversible accumulation of dislocations are used to characterize PSB by means of double pile-up which are composed of vacancy and interstitial dipoles. We shall give the mechanism and a quantitative remedy of ratcheting of plastic deformation peculiar to fatigue deformation. In a manner conceptually analogous to Griffith theory (1921), the critical number of cycles to failure and hence the S-N curves for crack initiation is obtained by considering the free energy of the system. The Gibbs free energy change ΔG increases with the fatigue cycle number due to cyclic increment of elastic strain energy which in turn stems from cyclic pile-up of dislocations along the slip planes. The Gibbs free energy change attains its maximum value at a critical cycle number beyond which the state of dislocation dipole accumulation becomes energetically unstable. In our theory we postulate that this critical state is the onset of crack initiation. We shall give a quantitative value for the fatigue limit and analyze the dependence of the S-N curve on several important physical parameters such as grain size; surface energy; yield strength; width of the PSB; and the ratio of the shear modulus of the bicrystalline material.

Blinking Suppression in Highly Excited CdSe/ZnS Quantum Dots by Electron Transfer under Large Positive Gibbs (Free) Energy Change

ACS Nano ◽  
2018 ◽  
Vol 12 (9) ◽  
pp. 9060-9069 ◽  
Author(s):  
Elizabeth Mariam Thomas ◽  
Sushant Ghimire ◽  
Reiko Kohara ◽  
Ajith Nair Anil ◽  
Ken-ichi Yuyama ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Electron Transfer ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Free Energy Change ◽  
Energy Change ◽  
Gibbs Free Energy Change

An Improved Model for Predicting Fatigue Crack Initiation Life of GH4169

2010 ◽  
Vol 29-32 ◽  
pp. 468-473
Author(s):  
Dong Lei ◽  
Ge Li ◽  
Bin Kai Shi ◽  
Jian Hua Zhao
Keyword(s):  
Free Energy ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Gibbs Free Energy ◽  
Fatigue Crack Initiation ◽  
Free Energy Change ◽  
Gibbs Free Energy Change ◽  
Plastic Energy ◽  
Crack Initiation Life ◽  
Improved Model

An improved model has been developed to predict fatigue crack initiation life using the criterion of minimizing the Gibbs free energy change considering plastic energy. The prediction process was described in this paper and used to predict the fatigue crack initiation life of notched GH4169 superalloy rolled bar at room temperature and 450°C. The results are acceptable for fatigue crack initiation life prediction in engineering experience and show that the improved model for predicting fatigue crack initiation life as an extension of the concept of minimizing the Gibbs free energy change considering plastic energy is adoptable to some superplastic materials such as GH4169.

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