scholarly journals A Mechanistic Study of Clustering and Diffusion of Molybdenum and Rhenium Atoms in Liquid Sodium

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1430
Author(s):  
Zhixiao Liu ◽  
Mingyang Ma ◽  
Wenfeng Liang ◽  
Huiqiu Deng
Keyword(s):  
Ab Initio Molecular Dynamics ◽  
Liquid Sodium ◽  
Mechanistic Study ◽  
Concentration Effects ◽  
Heat Transfer Medium ◽  
Binding Force ◽  
Temperature Heat ◽  
Higher Temperature ◽  
And Diffusion ◽  
Temperature And Concentration Effects

Liquid Na is widely used as the heat transfer medium in high-temperature heat pipes based on Mo-Re alloys. In this study, ab initio molecular dynamics are employed in order to understand the interactions between the Na solvent and Mo or Re solute in the liquid phase. Both the temperature and concentration effects on the clustering and diffusion behaviors of solute atoms are investigated. It is found that Mo2 and Re2 dimers can be stabilized in liquid Na, and the higher temperature leads to a stronger binding force. Pure Re and Mo-Re mixed solutes can form tetramers at the highest concentration. However, for the pure Mo solute, Mo4 is not observed. The diffusivities of a single solute atom and clusters are calculated. It is found that the Mo species diffuse faster than the Re species, and the diffusivity decreases as the cluster size increases.

Rational direct synthesis of [Fe(Htrz)2(trz)](BF4) polymorphs: temperature and concentration effects.

2021 ◽  
Author(s):  
Marlene Palluel ◽  
Liza el Khoury ◽  
Nathalie Daro ◽  
Sonia Buffière ◽  
Michaël Josse ◽  
...  
Keyword(s):  
Memory Effect ◽  
Spin Crossover ◽  
Direct Synthesis ◽  
Large Temperature ◽  
Concentration Effects ◽  
Temperature Range ◽  
Temperature And Concentration Effects

The [Fe(Htrz)2trz](BF4) compound is probably the most studied in the spin crossover (SCO) community since it exhibits switching properties with a large temperature range of memory effect, just above room...

Validation of a Code and Effect of Turbulence Model on Predicting Thermal Stratification Phenomena in the Upper Plenum of SFR

2018 ◽  
Author(s):  
Shibao Wang ◽  
Dalin Zhang ◽  
Chenglong Wang ◽  
Ping Song ◽  
Jing Chen ◽  
...  
Keyword(s):  
Thermal Stratification ◽  
Structural Integrity ◽  
High Heat ◽  
Scaled Model ◽  
Cylindrical Coordinate ◽  
Order Scheme ◽  
Higher Temperature ◽  
Turbulent Models ◽  
Thermal Hydraulic Analysis ◽  
And Diffusion

Thermal stratification phenomena occurring in the upper plenum during a scram transient have an important influence on the structural integrity and the passive safety of sodium-cooled fast breeder reactor (SFR). A two-dimensional thermal-hydraulic analysis code was developed under cylindrical coordinate based on conservation laws of mass, momentum and energy. Block-structured grids were generated to resolve the problems with complicated geometric properties. A second-order scheme based on midpoint rule was applied for the discretization of convection and diffusion terms. Two RANS-type turbulent models, i.e. the standard k–ε model (SKE) and the realizable k–ε model (RKE), are available in this code. A sodium test with scaled model, characterized by large aspect ratio, of a Japanese prototype SFR was used for the validation, mainly from the viewpoints of vertical temperature profiles and rising characteristics of the stratification interface. Results showed that this code could reproduce overall basic behaviors of thermal stratification. The sodium with higher temperature stayed largely stagnant in the upper region under buoyancy effect. Due to the high heat conductivity of sodium, momentum transportation made its leading function. Thus, the RKE model which accounts for the mean deformation rate gave better outcomes than the SKE model.

Atomic packing and diffusion in Fe85Si2B9P4 amorphous alloy analyzed by ab initio molecular dynamics simulation

2015 ◽  
Vol 117 (17) ◽  
pp. 17B705 ◽  
Author(s):  
Yaocen Wang ◽  
Akira Takeuchi ◽  
Akihiro Makino ◽  
Yunye Liang ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Amorphous Alloy ◽  
Ab Initio ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Atomic Packing ◽  
And Diffusion

EFFECT OF ENVIRONMENT AND EQUIPMENT ON PRODUCTIVITY OF ALFALFA LEAFCUTTER BEES (HYMENOPTERA: MEGACHILIDAE) IN SOUTHERN ALBERTA, CANADA

1996 ◽  
Vol 128 (1) ◽  
pp. 47-56 ◽  
Author(s):  
K.W. Richards
Keyword(s):  
Environmental Variables ◽  
Total Cell ◽  
Significant Positive Effect ◽  
Megachile Rotundata ◽  
Southern Alberta ◽  
Temperature Heat ◽  
Leafcutter Bee ◽  
Nesting Material ◽  
Higher Temperature ◽  
Positive Effect

AbstractFour indicators of productivity and quality for the alfalfa leafcutter bee, Megachile rotundata (Fab.), were examined over a 3-year period and the influence of different shelter designs, nesting materials, and 34 environmental variables evaluated. A higher percentage of cocoons per total cells was produced in polystyrene nesting material than in pinewood nesting material. Both nesting materials had similar percentages of tunnels capped or containing cells and total numbers of cells per hive. Shelters with conspicuous orientation patterns or silhouettes had more tunnels capped per hive, tunnels with cells, and greater total cell production per hive than did other shelter designs. The time of maximum bee production varied greatly among the 3 years. Many environmental variables, especially those associated with higher temperature, heat units, and mean actual temperature, had a significant positive effect on bee productivity and cell quality. The information contained in this study may help delineate those climatic areas where this valuable alfalfa pollinator can be most effective, and may assist beekeepers in making management decisions that will improve their operations.

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