Effect Of Hydrogen Environment Research Articles

DFT Atomic‐Scale Insight into Pt/Cu Single Atom Alloy Clusters Supported on γ‐Al2O3: The Effect of Hydrogen Environment

Single atom alloy (SAA) clusters formed by anchoring single atoms in small supported host clusters are emerging as catalysts with high performance. In this work, density functional theory (DFT) calculations and ab‐initio molecular dynamics (AIMD) simulations are performed to study the stability and the structure evolution of γ‐alumina‐supported platinum/copper SAA clusters of sub‐nanometer size in hydrogen environment. Due to the strong dynamic nature of both Cu cluster and anchored Pt single atom and their evolving interaction with the support, different isomers with different geometric and energetic properties are predicted. Extensive sampling through AIMD simulations reveals strong effect of hydrogen on the location of Pt single atom and strong variation of the cluster shape, evolving from 3D to concave and planar shapes wetting the alumina support. Interfacial site location of Pt single atom is found to be hydrogen coverage dependent. When the hydrogen coverage increases, the Pt single atom located preferentially at the interfacial site is pulled up by hydrogen atoms toward the upper surface Cu layers. The interaction of Pt/Cu cluster with alumina is predicted to decrease with increasing hydrogen coverage. Finally, electronic structure analysis reveals dramatic effect of hydrogen on the metallic nature of the catalysts.

Effect of hydrogen environment on the separation of Fe grain boundaries

A density-functional theory based empirical potential was used to explore the energies of different types of Fe grain boundaries and free surfaces in thermodynamic equilibrium with a hydrogen environment. The classical model for calculating the ideal work of separation with solute atoms is extended to account for every trapping site. This yields the lowest-energy structures at different hydrogen chemical potentials (or gas pressures). At hydrogen gas pressures lower than 1000 atm, the reduction of the reversible work of separation is less than 33% and it increases to 36% at a gas pressure of 5000 atm. Near the hydride formation limit, 5 × 104 atm, the reduction is 44%. Based on the magnitude of these reductions for complete decohesion, and accounting for experimental observations of the microstructure associated with hydrogen-induced intergranular fracture of Fe, it is posited that hydrogen-enhanced plasticity and attendant effects establish the local conditions responsible for the transition in fracture mode from transgranular to intergranular. The conclusion is reached that intergranular failure occurs by a reduction of the cohesive energy but with contributions from structural as well as compositional changes in the grain boundary that are driven by hydrogen-enhanced plasticity processes.

Study on Effect of Hydrogen Environment on Stress Corrosion Cracking of Retaining Ring in Hydrogen-Cooled Generator

Study on Effect of Hydrogen Environment on Stress Corrosion Cracking of Retaining Ring in Hydrogen-Cooled Generator

Study on Effect of Hydrogen Environment on Stress Corrosion Cracking of Retaining Ring in Hydrogen-Cooled Generator

In hydrogen-cooled generator, the quality of hydrogen environment directly affects generator’s operating especially the retaining ring. In order to research the relationship between the hydrogen environment and stress corrosion of material, the metallographic analysis is held for retired retaining ring of a power plant. There were intergranular and transcrystalline cracks, similar with hydrogen embrittlement. Designed generating system of occurrence for wet hydrogen, hydrogen charging is operated to retaining ring material used in tensile test, and then observed fracture by scanning electron microscope. The results showed that fracture was including cleavage, dimple and secondary crack caused by hydrogen-induced lagging plastic deformation.

1316 水素雰囲気内で摩擦される各種プラスチックの摩擦摩耗特性(OS01-3 + GS04 機械要素とトライボロジー + トライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

1316 水素雰囲気内で摩擦される各種プラスチックの摩擦摩耗特性(OS01-3 + GS04 機械要素とトライボロジー + トライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

Fatigue Characteristics of Low Carbon Steel in Hydrogen Gas Environment

In order to investigate the effect of hydrogen environment on fatigue crack growth characteristics of a low carbon steel JIS S10C, fatigue crack growth tests were conducted in a low pressure hydrogen gas environment. Fatigue crack growth rate in hygrogen gas is higher than that in nitrogen gas. It seems that a crack in the range of low growth rate prefers to propagate along the grain boundaries under hydrogen environment while in the range of high growth across the grains accompanied by brittle striation patterns or river patterns. It is important to clarify how hydrogen affects the crack growth behavior of different stages of crack growth.

3513 SUS304鋼微小穴材における疲労き裂の停留・伝ぱに及ぼす水素雰囲気の影響(S20-3 水素ガス雰囲気での疲労特性,S20 材料強度特性に及ぼす水素の影響)

3513 SUS304鋼微小穴材における疲労き裂の停留・伝ぱに及ぼす水素雰囲気の影響(S20-3 水素ガス雰囲気での疲労特性,S20 材料強度特性に及ぼす水素の影響)

3512 A6061-T6の摩擦撹拌溶接継ぎ手の疲労き裂伝ぱに及ぼす水素ガス雰囲気の影響(S20-3 水素ガス雰囲気での疲労特性,S20 材料強度特性に及ぼす水素の影響)

3512 A6061-T6の摩擦撹拌溶接継ぎ手の疲労き裂伝ぱに及ぼす水素ガス雰囲気の影響(S20-3 水素ガス雰囲気での疲労特性,S20 材料強度特性に及ぼす水素の影響)

オーステナイトステンレス鋼の疲労特性に及ぼす水素雰囲気の影響(金属組織と強度評価 OS.1)

オーステナイトステンレス鋼の疲労特性に及ぼす水素雰囲気の影響(金属組織と強度評価 OS.1)

SUS304のフレッティング疲労強度に及ぼす水素雰囲気の影響(材料力学(転がり・摩擦・摩耗))

SUS304のフレッティング疲労強度に及ぼす水素雰囲気の影響(材料力学(転がり・摩擦・摩耗))

SUS304鋼の微小穴材の疲労き裂発生および疲労き裂伝ぱに及ぼす水素雰囲気の影響(金属組織と強度評価 OS.1)

SUS304鋼の微小穴材の疲労き裂発生および疲労き裂伝ぱに及ぼす水素雰囲気の影響(金属組織と強度評価 OS.1)

Effect of hydrogen environment on the notched tensile properties of T-250 maraging steel annealed by laser treatment

In the present work, slow displacement rate tensile tests were performed to find out the influence of ageing condition and hydrogen-charging on the notched tensile strength and fracture characteristics of T-250 maraging steel aged at various conditions. The influence of embrittling species in the environment on the notched tensile strength was accessed by comparing the measured properties in air, gaseous hydrogen and H 2S-saturated solution. The hydrogen diffusivity, permeation flux and apparent solubility of various specimens determined by electrochemical permeation method, were correlated well with the microstructures and mechanical property. The results indicated that the peak-aged (H900) specimen was highly sensitive to hydrogen embrittlement even in gaseous hydrogen. In contrast, the microstructures of over-aged (H1100) specimen comprising of reverted austenite and incoherent precipitates could trap large amount of hydrogen atoms, resulting in decreased hydrogen permeability and hydrogen embrittlement susceptibility. The solution-annealed specimen had the highest diffusion coefficient and the lowest quantity of trapped hydrogen among the specimens, showing high susceptibility to sulfide stress corrosion cracking. In the presence of notches, hydrogen atoms were prone to segregate and trap at grain boundaries, resulting in the formation of intergranular fracture.

Effect of Hydrogen Environment during Loading on Delayed Fracture of Ultrahigh Strength Maraging Steel

Etude experimentale sur des eprouvettes de traction entaillees en acier 15% Co-6,5% Mo-18% Ni-1,1% Ti. En atmosphere d'hydrogene, la rupture differee est tres lente. La difference du degre de fragilite s'explique par l'adsorption d'hydrogene et par la deformation plastique. La rupture est probablement controlee par l'adsorption