Search results for "Metallurgy"
showing 10 items of 1419 documents
The co-reactant role during plasma enhanced atomic layer deposition of palladium
2020
Atomic layer deposition (ALD) of noble metals is an attractive technology potentially applied in nanoelectronics and catalysis. Unlike the combustion-like mechanism shown by other noble metal ALD processes, the main palladium (Pd) ALD process using palladium(ii)hexafluoroacetylacetonate [Pd(hfac)2] as precursor is based on true reducing surface chemistry. In this work, a thorough investigation of plasma-enhanced Pd ALD is carried out by employing this precursor with different plasmas (H2*, NH3*, O2*) and plasma sequences (H2* + O2*, O2* + H2*) as co-reactants at varying temperatures, providing insights in the co-reactant and temperature dependence of the Pd growth per cycle (GPC). At all te…
Effects of ball-milling on the hydrogen sorption properties of LaNi5
2009
Abstract Pressure–composition isotherms of LaNi 5 alloys were studied as function of ball-milling time. Results indicate that ball-milling convert a part of the LaNi 5 to a non-absorbing state—a state which does not absorb hydrogen under conditions where un-milled LaNi 5 powders absorb and transform to LaNi 5 H 6 , in addition to particle size reduction and creation of defects. The non-absorbing fraction in the milled sample is found to grow with increase in the ball-milling time. The resistance to the hydride formation of the long-time ball-milled LaNi 5 samples is found to continue even after a 1-h high vacuum annealing at around 1000 K. This indicates that the hydrogen-absorption-resist-…
Electrochemical Investigation of Hydrogen Evolution and Absorption Phenomena in Nickel Based Electrodes
1996
Due to its potential for industrial applications, hydrogen absorption in metals has attracted continuous interest. Understanding the hydrogen chemistry in metals is crucial due to the significance of hydrogen-metal interactions in important industrial and technical applications such as catalysis, H-fuel containment, corrosion and embrittlement of metals and rechargeable metal hydride batteries [1–2].
Relation between grain size and hydrogen diffusion coefficient in an industrial Pd–23% Ag alloy
1999
Abstract The diffusion mechanism of hydrogen in an industrial cold worked Pd–23% Ag alloy is investigated according to its grain size. The microstructural parameters are determined by X-ray diffraction analysis and the diffusion parameters are determined using the galvanostatic electrochemical permeation technique. Two diffusion mechanisms are displayed. For apparent grain size below 40 nm the hydrogen atoms diffuse in the grain boundaries. For grain size above 100 nm, an intergranular diffusion mechanism occurs. For intermediate grain size both mechanisms coexist. Furthermore, the diffusion in the grain boundaries is not faster than the diffusion in the bulk, as generally observed for pure…
Use of Hydrogen Molybdenum Bronze in Vacuum‐Deposited Perovskite Solar Cells
2019
Herein, the dehydration of a hydrogen molybdenum bronze (HYMoO3), converting it to molybdenum oxide (MoOX), is explored toward the development of perovskite solar cells (PSCs) for the first time. H0.11MoO3 bronze is synthesized, characterized, and deposited on indium tin oxide (ITO) under different concentrations and annealing conditions for in situ conversion into MoOX with appropriate oxygen vacancies. Vacuum‐deposited PSCs are fabricated using the as‐produced MoOX hole injection layers, achieving a power conversion efficiency of 17.3% (average) for the optimal device. The latter has its stability and reproducibility tested, proving the robustness and affordability of the developed hole t…
Comparison of resistance to damage of unalloyed carbon steels under the influence of hydrogen
2018
One of the most commonly used construction material in industry is unalloyed steel S235 and S355. These types of steel are used for construction of ships, bridges, coastal construction, welded tanks, and in buildings. Due to the operating conditions, these types of steel may undergo hydrogen degradation in the process of manufacturing of welded structures or when operating the structures. This paper presents the results of study into resistance of selected types of non-alloy structural steels to hydrogen degradation. Tests were carried out to determine changes in mechanical properties in the static trials of stretching without hydrogen, and after saturation with hydrogen. Parallel fractogra…
Study of the Hydrogen Embrittlement Sensitivity of an X4CrNiMo 16.5.1 Stainless Steel and the Associated Electron Beam Weld
2015
X4CrNiMo 16.5.1 steel (commercial name APX4) is a low carbon martensitic stainless steel known for its remarkable mechanical characteristics and its good resistance to corrosion. The use of APX4 in the manufacture of high pressure gas vessels requires a thorough understanding of its resistance to Hydrogen Embrittlement (HE) as the gas can contain traces of hydrogen, and martensitic steels, and their welds, are generally very sensitive to HE. This paper deals with the first part of this study, involving the characterization of the microstructure and the mechanical properties of each zone of the electron beam weld (melted zone and four different heat affected zones), and the investigation of …
Influence of the external stretching on hydrogen electromigration in palladium
2002
Abstract Electromigration and diffusion of hydrogen in palladium depending on unit elongation were investigated. It was found that the obtained experimental results cannot be described by means of a single flux of hydrogen, which diffuses in a gradient of electric field. In order to effectively explain the obtained results, a theoretical model was elaborated. It assumed the existence of the following two fluxes of hydrogen in the stretched metal: • Ji—of migration, according to the interstitial mechanism, and • Ji-d—of migration, according to the interstitial-defective mechanism. Dependence of effective valences and diffusion coefficients for both mechanisms of transportation were determine…
Rapid nanocrystallization of soft-magnetic amorphous alloys using microwave induction heating
2009
The crystallization of Fe73Nb3Cu1Si16B7 alloy during microwave heating was investigated in situ using synchrotron radiation powder diffraction. The phase transformation comprises a primary nanocrystallization stage and a final microcrystallization step. We provide evidence for a strong enhancement of the transformation kinetics. Microwave heating occurs as a result of both ohmic and magnetic losses induced by eddy currents, which defines a volumetric microwave induction heating process. Nanocrystallization is completed within 5 s, while full crystallization is achieved in less than 10 s.
Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation
2015
Abstract A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp 3 bonds percentage and possible diamond crystal formation were investigated ‘in-depth’ and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp 3 percent in the low power irradiated areas and similarly ‘in the depth’ of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an ‘in-depth’ (but not…