Physical properties of α-Fe upon the introduction of H, He, C, and N

Abstract

The effects of impurities of H, He, C, and N in α-Fe are investigated in terms of electronic structures using the density functional theory. Calculations reveal that H and He are stable at the T-site while C and N are stable at the O-site within α-Fe. The local strain field by H, He, C, and N in α-Fe cause structural elongation. Furthermore, the decrease of magnetic moment of Fe upon the introduction of C and N are found where the charge transfer is responsible. H, He, C, and N affect the electronic structure of α-Fe and change the fundamental physical properties of α-Fe.

Tuning the Deoxygenation of Bulk-Dissolved Oxygen in Copper

“…The incorporation of desired impurities (or dopants) into the bulk has been studied extensively to modify or achieve desired bulk properties. − In contrast, the fundamental understanding on the reversed process, that is, removal of impurities, is very limited. Macroscopically speaking, the removal of impurities from a material is usually time-consuming, energy intensive, and very costly.…”

The effect of point defects on diffusion pathway within α-Fe

“…C and N atoms are seen to be stable at the octahedral site of Fe [11]. The diffusion barrier of C and N is reported to be greatly affected by the introduction of a vacancy into Fe [9].…”

“…The He atom is calculated to be stable at the tetrahedral site in Fe without a vacancy [11]. He is dissolved in endothermic matter in Fe without vacancy; therefore, He tends to diffuse easily due to the stress coming from the surrounding Fe atom.…”

Selective Growth of Noble Gases at Metal/Oxide Interface

“…9−11 In general, noble gases have low solubility, making the defect site behave as a trapping site. 12 However, the location and the role of noble gases at the metal/ oxide interface are not well understood, thereby making it difficult to determine whether noble gases stay at the interface or grow toward the metal or oxide sites.…”

“…The metal/oxide interface in structural materials has been extensively investigated as it plays a key role for the thermal stability and mechanical strength of oxide dispersed metal. − In addition, the presence of noble gases at such interfaces generates scientific and engineering interest as changes in the properties of these materials could be a result of noble gases at the interfaces. In particular, He and Ar gases are two common noble gases seen in metal/oxide interfaces where He atoms are induced by transmutation reactions and Ar atoms are introduced during material processing under fully saturated Ar gases in order to prevent oxidation. , Such noble gases are considered to play a crucial role in material fracturing and embrittlement where they generally form few nanometers of noble gas bubbles during the annealing process. , It is also reported that trapping He gases in Y–Ti based oxides is effective compared to trapping He in an Fe matrix in regards to preventing material fractures. − In general, noble gases have low solubility, making the defect site behave as a trapping site . However, the location and the role of noble gases at the metal/oxide interface are not well understood, thereby making it difficult to determine whether noble gases stay at the interface or grow toward the metal or oxide sites.…”