Kinetics of subsurface hydrogen adsorbed on niobium: Thermal desorption studies

2002 ◽  
Vol 17 (10) ◽  
pp. 2698-2704 ◽  
Author(s):  
A. L. Cabrera ◽  
J. Espinosa-Gangas ◽  
Johan Jonsson-Akerman ◽  
Ivan K. Schuller
Keyword(s):  
Heat Treatment ◽  
Carbon Monoxide ◽  
Thermal Desorption ◽  
Hydrogen Adsorption ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Desorption ◽  
X Ray Diffraction ◽  
Surface Sites ◽  
Adsorption Desorption ◽  
Kinetics Of

The adsorption/absorption of hydrogen and the adsorption of carbon monoxide by niobium foils, at room temperature, was studied using thermal desorption spectroscopy. Two hydrogen desorption peaks were observed with a maximum at 404 and 471 K. The first hydrogen desorption peak is regarded as hydrogen desorbing from surface sites while the second peak, which represents desorption from surface sites stronger bound to the surface, also has a component—due to its tailing to higher temperatures—of hydrogen diffusing from subsurface sites. Carbon monoxide adsorption was used to determine the number of surface sites, since it does not penetrate below the surface. Two carbon monoxide desorption peaks are observed in these experiments: at 425 and 608 K. The first peak is regarded as the adsorption of molecular carbon monoxide, and the second, as carbon monoxide dissociated on the niobium surface. The crystallographic orientation of the foils was determined by x-ray diffraction and showed a preferential (110) orientation of the untreated foil due to the effect of cold rolling. This preferential orientation decreased after hydrogen/heat treatment, appearing strong also in the (200) and (211) orientations. This change in texture of the foils is mainly due to the effect of heat treatment and not to hydrogen adsorption/desorption cycling. The kinetics of hydrogen and CO desorption is compared with that of Pd and Pd alloys.

Surface Interactions in Pd-Nb System and Their Relation to Basic Questions and Practical Catalysis

1997 ◽  
Vol 62 (4) ◽  
pp. 575-580 ◽  
Author(s):  
Tomas Jirsak ◽  
Vladimír Nikolajenko ◽  
Zlatko Knor
Keyword(s):  
Carbon Monoxide ◽  
Thermal Desorption ◽  
Room Temperature ◽  
Thermal Desorption Spectroscopy ◽  
Surface Interactions ◽  
Lower Number ◽  
Adsorption Properties ◽  
Adsorption Sites ◽  
Adsorption Desorption ◽  
Adsorption Capability

Room temperature adsorption-desorption properties of Pd overlayers of various thicknesses were studied by thermal desorption spectroscopy of carbon monoxide. Pd overlayers were deposited on clean and oxidized Nb foil (NbOx/Nb). Adsorption properties of Pd overlayers deposited on clean Nb at temperature 350-400 K were not influenced by annealing in the temperature range 400 K to 600 K. Annealing above this temperature caused the decrease in the area of the Pd surface. It became probably smoother, exhibiting lower number of adsorption sites for CO. Non-annealed Pd overlayers deposited on the oxide carrier (NbOx/Nb) at temperatures between 350 and 400 K possessed the same adsorption capability as Pd deposited directly on Nb. Pd atoms thus neither massively penetrated into the oxide layer nor were encapsulated by NbOx.

The Kinetics of Hydrogen Desorption From Zirconium Hydride

2013 ◽  
Author(s):  
Mingwang Ma ◽  
Ruiyun Wan ◽  
Yuan Wang ◽  
Yanlin Cheng ◽  
Li Liang ◽  
...  
Keyword(s):  
Thermal Desorption ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Desorption ◽  
Pressure Effects ◽  
Zirconium Hydride ◽  
Desorption Kinetics ◽  
Desorption Process ◽  
Exponential Factor ◽  
Predict Weight Loss ◽  
Kinetics Of

Thermal desorption spectroscopy (TDS) was used to study the thermal desorption kinetics of zirconium hydride films, which were deposited on molybdenum substrates and thermally charged with gas phase hydrogen. The observed desorption peaks were attributed to phase transforming steps. The activation energy and pre-exponential factor for desorption kinetics was estimated as 116 kJ/mol and 8762 s−1 according to Kissinger relation, respectively. A simulation of TDS spectra was made, which showed that the desorption process followed a first order kinetics. The kinetic parameters were then utilized to predict weight loss behavior at a temperature profile. Pressure effects that can potentially reduce the desorption rate were discussed.

Kinetics of hydrogen desorption from palladium and ruthenium-palladium foils

1995 ◽  
Vol 10 (3) ◽  
pp. 779-785 ◽  
Author(s):  
A.L. Cabrera ◽  
Erie Morales ◽  
J.N. Armor
Keyword(s):  
Carbon Monoxide ◽  
Hydrogen Adsorption ◽  
Bulk Diffusion ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Uptake ◽  
Hydrogen Desorption ◽  
Activation Energies ◽  
Absolute Temperature ◽  
Pd Alloy ◽  
Second Peak

The absorption of hydrogen and carbon monoxide at room temperature by palladium and 5% ruthenium-palladium foils was studied using thermal desorption spectroscopy. It was found that hydrogen readily diffused in the palladium and desorbed as one broad peak at about 650 K. Plots of the In (rate) versus inverse absolute temperature indicate that the desorption order is n = 1.25 and the activation energy is about 8.5 Kcal/mol. Carbon monoxide is adsorbed, as two different states, on the surface of the foil and complete coverage is quickly reached below 100 L. Hydrogen also diffuses in 5% ruthenium-palladium foil but to a lesser degree. Two hydrogen desorption peaks are observed in the Ru-Pd alloy. The desorption traces can be fitted with two peaks and the desorption orders are n = 2 for the first peak and n = 1.25 for the second peak. Activation energies of 10.7 and 5.6 Kcal/mol are obtained for the first and second hydrogen peaks, respectively. The first hydrogen desorption peak is regarded as hydrogen desorbing from the surface sites while the second peak is regarded as hydrogen diffusing from below the surface. Activation energies for bulk diffusion were obtained from hydrogen uptake measurements using a sensitive microbalance. These energies corresponded to 4.4 Kcal/mol for Pd foil and 4.9 Kcal/mol for the Ru-Pd alloy. Discussion about the relation between these results with prior studies of hydrogen adsorption on Pd single crystal is included. The appearance of a fractional order for hydrogen desorption is also discussed.

The Role of Cr in H Desorption Kinetics in Rapidly Solidified Al

2014 ◽  
Vol 783-786 ◽  
pp. 264-269 ◽  
Author(s):  
Iya I. Tashlykova-Bushkevich ◽  
Keitaro Horikawa ◽  
Goroh Itoh
Keyword(s):  
High Temperature ◽  
Thermal Desorption ◽  
High Purity ◽  
Thermal Desorption Spectroscopy ◽  
Secondary Phase ◽  
Hydrogen Desorption ◽  
Oxide Surface ◽  
Desorption Kinetics ◽  
Hydrogen Trapping ◽  
Rapidly Solidified

Hydrogen desorption kinetics for rapidly solidified high purity Al and Al-Cr alloy foils containing 1.0, 1.5 and 3.0 at % Cr were investigated by means of thermal desorption analysis (TDA) at a heating rate of 3.3°C/min. For the first time, it was found that oxide inclusions of Al2O3 are dominant high-temperature hydrogen traps compared with pores and secondary phase precipitates resulted in rapid solidification of Al and its alloys. The correspondent high-temperature evolution rate peak was identified to be positioned at 600°C for high purity Al and shifted to 630°C for Al-Cr alloys. Amount of hydrogen trapped by dislocations increases in the alloys depending on Cr content. Microstructural hydrogen trapping behaviour in low-and intermediate temperature regions observed here was in coincidence with previous data obtained for RS materials using thermal desorption spectroscopy (TDS). The present results on hydrogen thermal desorption evolution indicate that the effect of oxide surface layers becomes remarkable in TDA measurements and show advantages in combinations of both desorption analysis methods to investigate hydrogen desorption kinetics in materials.

scholarly journals Adsorption of malic acid at the hydroxyapatite/aqueous NaCl solution interface

2021 ◽  
Author(s):  
Władysław Janusz ◽  
Ewa Skwarek
Keyword(s):  
Zeta Potential ◽  
Malic Acid ◽  
Particle Sizes ◽  
Nacl Solution ◽  
X Ray Diffraction ◽  
Radioisotope Method ◽  
X Ray ◽  
Solution Interface ◽  
Adsorption Desorption ◽  
Kinetics Of

AbstractThe aim of the study was the basic incidence on the phenomenon of adsorption that occurs at the hydroxyapatite/malic acid interface, leading to a change in the surface properties of hydroxyapatite, Analytical methods used in the research: X-ray diffraction (XRD) as well as by the, adsorption–desorption of nitrogen (ASAP), potentiometric titration. The specific adsorption of malic acid ions at the hydroxyapatite interface was investigated by means of the radioisotope method. The zeta potential of hydroxyapatite dispersions was determined by electrophoresis with Zetasizer Nano ZS90 by Malvern. The particle sizes of hydroxyapatite samples were analyzed using Masteriszer 2000 Malvern. Studies on the kinetics of malic acid on hydroxyapatite from a solution with an initial concentration of 1 mmol/dm3 have shown that the adsorption process is initially fast, followed by a slow adsorption step. An increase in the pH of the solution causes a decrease in the malic acid adsorption as a result of competition with hydroxyl ions. The presence of adsorbed malic acid was confirmed by the FTIR measurements. The effect of malic acid adsorption on the zeta potential and particle size distribution of hydroxyapatite in the NaCl solution was investigated.

scholarly journals Hydrogen desorption kinetics of MgH2 synthesized from modified waste magnesium

2014 ◽  
Vol 32 (3) ◽  
pp. 385-390
Author(s):  
Aysel Kantürk Figen ◽  
Bilge Coşkuner ◽  
Sabriye Pişkin
Keyword(s):  
Hydrogen Desorption ◽  
Nitrogen Atmosphere ◽  
Desorption Kinetics ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Xrf Scanning ◽  
Isothermal Kinetic ◽  
Kinetics Of

AbstractIn the present study, hydrogen desorption properties of magnesium hydride (MgH2) synthesized from modified waste magnesium chips (WMC) were investigated. MgH2 was synthesized by hydrogenation of modified waste magnesium at 320 °C for 90 min under a pressure of 6 × 106 Pa. The modified waste magnesium was prepared by mixing waste magnesium with tetrahydrofuran (THF) and NaCl additions, applying mechanical milling. Next, it was investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) techniques in order to characterize its structural properties. Hydrogen desorption properties were determined by differential scanning calorimetry (DSC) under nitrogen atmosphere at different heating rates (5, 10, and 15 °C/min). Doyle and Kissenger non-isothermal kinetic models were applied to calculate energy (Ea) values, which were found equal to 254.68 kJ/mol and 255.88 kJ/mol, respectively.

Preparation and Catalytic Performance of Ti(SO4)2/γ-Al2O3 Catalysts for Oligomerization of 1-Butene

2013 ◽  
Vol 634-638 ◽  
pp. 696-700
Author(s):  
Lin Jiu Xiao ◽  
Peng Li ◽  
Yong Gang Sheng
Keyword(s):  
Heat Treatment ◽  
Physicochemical Properties ◽  
Heat Treatment Temperature ◽  
Catalytic Performance ◽  
Treatment Temperature ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
Isothermal Adsorption ◽  
X Ray ◽  
Adsorption Desorption

A series of Ti(SO4)2/γ-Al2O3 catalysts were prepared by impregnation method and the catalytic performance of these catalysts in 1-butene oligomerization was investigated. The heat treatment temperature played great influences on the catalytic performance of these catalysts in the oligomerization. 90.1 wt.% conversion of 1-butene and 92.2 wt.% selectivity of dimers were obtained on Ti(SO4)2/γ-Al2O3(450) catalyst at 80 °C, 1.0 Mpa and LHSV=0.6 h−1. The heat treatment temperature determined the crystallinity of TiOSO4 and specific surface area of these catalysts, which affected the catalytic performance of these catalysts in 1-butene oligomerization. In addition, the physicochemical properties of these catalysts were comparatively characterized by powder X-ray diffraction (XRD), N2 isothermal adsorption-desorption techniques.

scholarly journals Crystal structure change in multilayer GeH flakes by hydrogen desorption under ultrahigh vacuum environments

2021 ◽  
Author(s):  
Mai Itoh ◽  
Masaaki ARAIDAI ◽  
Akio OHTA ◽  
Osamu Nakatsuka ◽  
Masashi Kurosawa
Keyword(s):  
Crystal Structure ◽  
Mass Loss ◽  
Thermal Desorption ◽  
Ultrahigh Vacuum ◽  
Thermal Desorption Spectroscopy ◽  
Hydrogen Desorption ◽  
Structure Change ◽  
Spectroscopy Analysis ◽  
Free Standing ◽  
Short Time

Abstract To confirm the feasibility of the theoretically proposed method of forming free-standing germanene [Araidai et al., J. Appl. Phys. 128, 125301 (2020).], we have experimentally investigated hydrogen desorption properties from the hydrogen-terminated germanane (GeH) flakes. Thermal desorption spectroscopy analysis revealed that hydrogen desorption occurred during the heating under an ultrahigh vacuum environment, corresponding to mass loss of 1.0 wt%. Moreover, we have found that using an ultrahigh vacuum ambient and short-time annealing for hydrogen desorption is a key to sustain the crystal structures.

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