scholarly journals Diffusivities and Atomic Mobilities in bcc Ti-Mo-Zr Alloys

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1909 ◽  
Author(s):  
Weimin Bai ◽  
Guanglong Xu ◽  
Mingyue Tan ◽  
Zhijie Yang ◽  
Lijun Zeng ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Diffusion Flux ◽  
Chemical Diffusion ◽  
Metallic Biomaterials ◽  
Mobility Database ◽  
Thermo Calc Software ◽  
Bcc Structure ◽  
Diffusion Couple Technique ◽  
Micro Analysis ◽  
Zr Alloys

β-type (with bcc structure) titanium alloys have been widely used as artificial implants in the medical field due to their favorable properties. Among them, Ti-Mo alloy attracted numerous interests as metallic biomaterials. Understanding of kinetic characteristics of Ti alloys is critical to understand and manipulate the phase transformation and microstructure evolution during homogenization and precipitation. In this work, diffusion couple technique was employed to investigate the diffusion behaviors in bcc Ti-Mo-Zr alloys. The diffusion couples were prepared and annealed at 1373 K for 72 h and 1473 K for 48 h, respectively. The composition-distance profiles were obtained via electron probe micro-analysis (EPMA). The chemical diffusion coefficients and impurity diffusion coefficients were extracted via the Whittle-Green method and Hall method. The obtained diffusion coefficients were assessed to develop a self-consistent atomic mobility database of bcc phase in Ti-Mo-Zr system. The calculated diffusion coefficients were compared with the experimental results. They showed good agreement. Simulations were implemented by Dictra Module in Thermo-Calc software. The predicted composition-distance profiles, inter-diffusion flux, and diffusion paths are consistent with experimental data, confirming the accuracy of the database.

Structure and Soft-Packed Cell Performance of Nano-Particle LiFePO4 Prepared by Spray-Drying Method

2020 ◽  
Vol 1003 ◽  
pp. 268-274
Author(s):  
Ling Li Zuo ◽  
Lin Chen ◽  
Shuo Yin ◽  
Ji Yun Liu ◽  
Cheng Lu ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electrochemical Properties ◽  
Spray Drying ◽  
Diffusion Coefficients ◽  
Rate Capability ◽  
Chemical Diffusion ◽  
Nano Particle ◽  
Drying Method ◽  
Capacity Retention ◽  
Lithium Ions

Well-crystallized and nanosized LiFePO4/C composite have been successfully synthesized by spray-drying under N2 atmosphere. The morphology, physical and electrochemical properties of the LiFePO4/C were tested and analyzed. The charge transfer resistances (Rct) and chemical diffusion coefficients of lithium ions (DLi+) in LiFePO4/C was systematically tested by EIS. The results show that the lithium ions diffusion coefficients obtained from EIS is 1.58×10-14 cm2·s-1. The assembled soft-packed cell with LiFePO4/C show better rate capability and cycling stability. The average capacity retention of LiFePO4/C soft-packed cell decreases to 100%, 98.9%, 96.5%, 92.4%, and 90.3% when current rate increases to 0.3, 0.5, 1, 2, and 3C, respectively. The capacity retention after 80 cycles is retained at more than 99%.

scholarly journals The choice of a thermodynamic formulation dramatically affects modelled chemical zoning in minerals

2021 ◽  
Author(s):  
Lucie Tajcmanova ◽  
Yury Podladchikov ◽  
Evangelos Moulas
Keyword(s):  
Mantle Convection ◽  
Diffusion Flux ◽  
Chemical Diffusion ◽  
Irreversible Processes ◽  
Dynamic Processes ◽  
Positive Entropy ◽  
Admissibility Condition ◽  
Chemical Zoning ◽  
Natural Processes ◽  
The Earth

<p>Quantifying natural processes that shape our planet is a key to understanding the geological observations. Many phenomena in the Earth are not in thermodynamic equilibrium. Cooling of the Earth, mantle convection, mountain building are examples of dynamic processes that evolve in time and space and are driven by gradients. During those irreversible processes, entropy is produced. In petrology, several thermodynamic approaches have been suggested to quantify systems under chemical and mechanical gradients. Yet, their thermodynamic admissibility has not been investigated in detail. Here, we focus on a fundamental, though not yet unequivocally answered, question: which thermodynamic formulation for petrological systems under gradients is appropriate – mass or molar?  We provide a comparison of both thermodynamic formulations for chemical diffusion flux, applying the positive entropy production principle as a necessary admissibility condition. Furthermore, we show that the inappropriate solution has dramatic consequences for understanding the key processes in petrology, such as chemical diffusion in the presence of stress gradients.</p>

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