Abstract
Molybdenum-rhenium alloys are usually used as the wall materials for high-temperature heat pipes using liquid sodium as heat-transfer medium. The corrosion of Mo in liquid Na is a key challenge for heat pipes. In addition, oxygen impurity also plays an important role in affecting the alloy resistance to Na liquid. In this article, the adsorption and diffusion behaviors of Na atom on Mo (110) surface are theoretically studied using first-principles approach, and the effects of alloy Re and impurity O atoms are investigated. The result shows that the Re alloy atom can strengthen the attractive interactions between Na/O and the Mo substrate, and the existence of Na or O atom on the Mo surface can slower down the Na diffusion by increasing diffusion barrier. The surface vacancy formation energy is also calculated. For the Mo (110) surface, the Na/O co-adsorption can lead to a low vacancy formation energy of 0.47 eV, which indicates the dissolution of Mo is a potential corrosion mechanism in the liquid Na environment with O impurities. It is worth noting that Re substitution atom can protect the Mo surface by increasing the vacancy formation energy to 1.06 eV.
Highlights
Alkali metal heat pipes (HPs) are initially designed for heat transfer in space nuclear power systems, of which the operating temperature is typically from 800 K to 1800 K
In order to find out the thermodynamically most stable surface structure of bcc-Mo, the surface energy is calculated by the following equation: σ = ( Eslab − n × Ebulk )/(2A)
Where A is the surface area and n is the number of atoms in the slab model, Eslab is the total energy of the surface, Ebulk is the energy per Mo atom of the ground state structure
Summary
Alkali metal heat pipes (HPs) are initially designed for heat transfer in space nuclear power systems, of which the operating temperature is typically from 800 K to 1800 K. HPs using alkali metals are promising in advanced energy and power systems such as highefficiency waste heat utilization [1], hypersonic vehicles [2], and molten salt reactors [3]. A heat pipe consists of a sealed shell, wick structure and a vapor chamber containing working fluid, which is normally filled after the shell is evacuated [4]. Heat transfer in a heat pipe is achieved passively by the phase change and the circulation of the working fluid [5]. Different types of working fluid and shell material are adopted in heat pipes used under different working conditions. The type of heat pipe can be divided into four main types according to their working temperature: low temperature heat pipe (−270~0 ◦ C), normal temperature heat pipe (0~200 ◦ C), medium temperature heat pipe (200~600 ◦ C)
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