Thermal Desorption Spectra Of Hydrogen Research Articles

Numerical interpretation of thermal desorption spectra of hydrogen from high-carbon ferrite-austenite dual-phase steel

The peak in the thermal desorption spectra of hydrogen from a high-carbon ferrite-austenite dual-phase steel shifts to the high-temperature side as the amount of charged hydrogen increases. However, the hydrogen-trapping state and the peak formation process are unclear. We interpreted the spectra by reproducing them using the previously reported model. Introducing a diffusion barrier from the ferrite phase to the austenite phase and excluding hydrogen entering the austenite phase shows that the peak is attributed to the carbide trap site when the amount of charged hydrogen is comparatively small and hydrogen trapped by the interface trap site increasingly influences the peak as the amount of charged hydrogen increases. We also found that the thickness dependence of the peak for the interface trap site could be attributed to a different reason than the conventional diffusion-determining process.

On the Problem of “Super” Storage of Hydrogen in Graphite Nanofibers

This article is devoted to some fundamental aspects of “super” storage in graphite nanofibers (GNF) of “reversible” (~20–30 wt.%) and “irreversible” hydrogen (~7–10 wt.%). Extraordinary results for hydrogen “super” storage were previously published by the group of Rodriguez and Baker at the turn of the century, which been unable to be reproduced or explained in terms of physics by other researchers. For the first time, using an efficient method of processing and analysis of hydrogen thermal desorption spectra, the characteristics of the main desorption peak of “irreversible” hydrogen in GNF were determined: the temperature of the highest desorption rate (Tmax = 914–923 K), the activation energy of the desorption process (Q ≈ 40 kJ mol−1), the pre-exponential rate constant factor (K0 ≈ 2 × 10−1 s−1), and the amount of hydrogen released (~8 wt.%). The physics of hydrogen “super” sorption includes hydrogen diffusion, accompanied by the “reversible” capture of the diffusant by certain sorption “centers”; the hydrogen spillover effect, which provides local atomization of gaseous H2 during GNF hydrogenation; and the Kurdjumov phenomenon on thermoelastic phase equilibrium. It is shown that the above-mentioned extraordinary data on the hydrogen “super” storage in GNFs are neither a mistake nor a mystification, as most researchers believe.

On the real possibility of “super” hydrogen intercalation into graphite nanofibers

In this work, data of Rodriguez-Baker et al. and some others were analyzed and interpreted in relation to the long-term, i.e., about 25 years, problem of “super” storage (intercalation) of “reversible” (at 300 K) hydrogen (∼38 ± 10 wt.%, i.e., the atomic ratio (H/C) ≈ 7 ± 3)), along with “irreversible” hydrogen (∼11 ± 3 wt.% ((H/C) ≈ 1.5 ± 0.4)) into graphite nanofibers (GNFs). For a more in-depth study of the a problem, an effective methodology of processing and analyzing the thermal desorption spectra of hydrogen and the related thermogravimetric data was modified and used. It was shown that the above noted extraordinary data on the “super” storage of hydrogen in GNFs are neither an error nor a hoax, as most researchers believed. The necessary conditions were determined to reproduce this extraordinary data. It has also been shown that the Rodriguez-Baker team can reproduce “normal,” i.e., typical results obtained by other researchers on hydrogen storage in GNFs.

Atomistic State of Hydrogen in Electrochemically Deposited Cu Films

Electro and electroless deposition of Cu films are widely used in the print circuit boards production. These electrochemical Cu deposition process are accompanied with the simultaneous hydrogen evolution, and the hydrogen co-deposition sometimes causes the voids and blisters1). However, the detail mechanism of such hydrogen-induced phenomena have not been clarified. We previously reported that the primary cause of the room-temperature grain growth observed in electrodeposited Cu films was the formation of superabundant vacancies induced by the hydrogen co-deposition2). In this study, the atomistic state of hydrogen co-deposited in the Cu films obtained by electro and electroless deposition and the influence of hydrogen on the microstructure of Cu films were investigated.Cu films were electrodeposited from six different baths (sulfate bath, additive-containing bath, chloride bath, pyrophosphate bath, EDA bath, and EDTA bath) and electrolessly deposited from an EDTA bath. The amount and atomistic state of hydrogen in the Cu films were analyzed by thermal desorption spectroscopy (TDS). The microstructural analysis of the Cu films was performed by X-ray diffraction (XRD) and transmission electron microscopy (TEM).In the electrodeposited Cu films with high hydrogen concentrations (x = H/Cu = 5.4 ~ 98.2×10-4), the room-temperature grain growth proceeded with the desorption of hydrogen during 7 ~ 21 days after deposition2). A pronounced desorption peak at 600 ~ 700 K due to the break-up of vacancy-hydrogen clusters3) was observed in the thermal desorption spectra of hydrogen from these Cu films.In the thermal desorption spectra of hydrogen from electrolessly deposited Cu films, a pronounced peak at around 420 K and a small peak at 600 ~ 700 K were observed and the hydrogen concentration was x = 13.6×10-3. From the XRD measurements, the lattice expansion of about 0.14% was observed in the as-deposited Cu films, which was reduced with the desorption of hydrogen at room temperature after 7 days. These results suggest that the desorption peak at 420 K may be assigned to the desorption of hydrogen from the regular interstitial sites. In the TEM images of these Cu films, many nano-voids distributed in the crystal grains were observed. We consider that the hydrogen molecules trapped in the nano-voids should be desorbed at high temperature above 900 K. The high-temperature TDS measurements will be performed. References 1) T. Sharma, A. E. Landry, A. Leger, D. A. Brown, T. Bernhard, S. Zarwell, F. Brüning, and R. Brüning, Thin Solid Films, 666, 76 (2018).2) N. Fukumuro, H. Yoshida, T. Yamazaki, Y. Fukai, and S. Yae, J. Japan. Inst. Met. Mater., 80, 736 (2016).3) Y. Fukai, M. Mizutani, S. Yokota, M. Kanazawa, Y. Miura, and T. Watanabe, J. Alloy. Comp., 356-357, 270 (2003).

Numerical Interpretation of Hydrogen Thermal Desorption Spectra for Iron with Hydrogen-Enhanced Strain-Induced Vacancies

We obtained thermal desorption spectra of hydrogen for a small-size iron specimen to which strain was applied during charging with hydrogen atoms. In the spectra, a shoulder-shaped peak in the high-temperature side was enhanced compared with the spectra of the specimen to which only strain was applied. We also observed that the peak almost disappeared by aging processes at ≥ 373 K. Then, assuming that the shoulder-shaped peak results from hydrogen atoms released by vacancies, we simulated the thermal desorption spectra using a model incorporating the behavior of vacancies and vacancy clusters. The model considered up to vacancy cluster {{V_9}}, which is composed of nine vacancies, and employed the parameters based on atomistic calculations, including the H trapping energy of vacancies and vacancy clusters that we estimated using the molecular static calculation. As a result, we revealed that the model could, on the whole, reproduce the experimental spectra, except two characteristic differences, and also the dependence of the spectra on the aging temperature. By examining the cause of the differences, the possibilities that the diffusion of clusters of {V_2} and {V_3} is slower than the model and that vacancy clusters are generated by applying strain and H charging concurrently were indicated.

Studying the thermal desorption of hydrogen in some carbon nanostructures and graphite

The methodology of the approximation and interpretation of thermal desorption spectra (TDS) of hydrogen in some carbon nanostructures and graphite has been developed and applied for such materials.The methodology is based on a definite approximation by the symmetrical Gaussians of the hydrogen thermal desorption spectra, obtained by using one single heating rate, for carbon materials and nanomaterials, and a definite processing of the Gaussians, in the approximation of the first-order reactions and the second-order ones. It results in determining (with a satisfactory accuracy, for the further physical analysis), from TDS data of one single heating rate, the activation energies and pre-exponential factors of the rate constants of desorption processes corresponding to the main TDS peaks with different temperatures of the maximum desorption rate. The developed methodology contains several successive steps of its implementation, including the use of several “criterions of truth” and the final verification and/or modification of the results, with the help of numerical modeling methods. This technique is not less informative, but much less time-consuming in experimental terms compared to the generally accepted classical Kissinger method, which demands using of several heating rates, and has strict limits of applicability. Furthermore, the methodology allows one to reveal physics and atomic mechanisms of the main desorption processes through thermodynamic analysis of the obtained peak characteristics and comparison with the corresponding independent experimental and theoretical data.The purpose of such a methodology is to further reveal the weakly studied physics of the main states of hydrogen in carbon materials and nanomaterials, and not the thorough detailed mathematical description of the spectra. For this case, both the large difference and the large spread of the known experimental and theoretical values of the thermodynamic characteristics of the main desorption processes, important for hydrogen storage problems, are also taken into account.

Study of correlation between the steels susceptibility to hydrogen embrittlement and hydrogen thermal desorption spectroscopy using artificial neural network

Steels are the most used structural material in the world, and hydrogen content and localization within the microstructure play an important role in its properties, namely inducing some level of embrittlement. The characterization of the steels susceptibility to hydrogen embrittlement (HE) is a complex task requiring always a broad and multidisciplinary approach. The target of the present work is to introduce the artificial neural network (ANN) computing system to predict the hydrogen-induced mechanical properties degradation using the hydrogen thermal desorption spectroscopy (TDS) data of the studied steel. Hydrogen sensitivity parameter (HSP) calculated from the reduction of elongation to fracture caused by hydrogen was linked to the corresponding hydrogen thermal desorption spectra measured for austenitic, ferritic, and ferritic-martensitic steel grades. Correlation between the TDS input data and HSP output data was studied using two ANN models. A correlation of 98% was obtained between the experimentally measured HSP values and HSP values predicted using the developed densely connected layers ANN model. The performance of the developed ANN models is good even for never-before-seen steels. The ANN-coupled system based on the TDS is a powerful tool in steels characterization especially in the analysis of the steels susceptibility to HE.

On the kinetic analysis of the hydrogen thermal desorption spectra for graphite and advanced carbon nanomaterials

This study is devoted to a further development and application of our previous results, including the method of kinetic analysis of the hydrogen thermal desorption spectra (TDS) processes in materials heating with only one rate. As shown in this study, from such TDS data, the activation energies (Q) and the per-exponential factors (K0) of the rate constants (K) of the hydrogen desorption processes can be determined (evaluated with the enough accuracy) with the help of our method, including the standard deconvolution of TDS spectra by “pure” (that’s symmetrical) Gaussian curves (peaks), along with the identification (interpretation) of the peaks, and revealing their atomic mechanisms. Some critical aspects of using the pure Gaussian curves approach, and/or the first order reactions Kissinger approach (that’s is asymmetrical curves), especially for the diffusion controlling cases, along with approaches of Polanyi–Wigner equation of the first-order processes (that’s asymmetrical curves) and the second order processes (that’s symmetrical curves) are taken into account, as well. As an example, such a treatment and identification (interpretation) of TDS data on deuterium TDS spectra for graphite exposed to high flux plasma at high temperatures have been performed.

Surface vs diffusion in TDS of hydrogen

The paper addresses the numerical simulation of conditions in which the measurement of thermal desorption spectra of hydrogen (TDS) is carried out. Plane steel samples of 10 mm thickness were used as the specimens for simulation. The skin effect which is observed with standard hydrogen charging of samples was accounted for the initial conditions. The standard diffusion of hydrogen was simulated according to Fick’s law. Solution of the Fick’s equation is obtained by finite element methods using the developed code. The resulting solutions show that standard hydrogen charging can lead to the appearance of an additional TDS peak, even without taking into account the traps. New interpretation of the TDS method for hydrogen dissolved in a solid was suggested.

Simulation of thermal desorption spectrum of hydrogen from austenite embedded in the martensite matrix

Thermal desorption spectra of hydrogen of martensite (or ferrite), austenite and a composite of them in which austenite is a minor phase are simulated using McNabb–Foster theory. Whereas the peak temperature of desorption rate is markedly dependent upon the specimen thickness in all specimens, it did not decrease below a certain limit in thin martensite specimens where hydrogen desorption is controlled by detrapping of hydrogen from the trap site. The peak temperature in the two-phase specimen depends strongly upon the thickness of austenite if the initial amount of hydrogen in the ferrite matrix can be ignored, becoming close to or lower than the room temperature for the austenite thickness less than ∼10 μm. For larger austenite particles the release rate of hydrogen from the austenite governs the peak temperature. For small particles such as interlath retained austenite the release time of hydrogen from the particle is so short that re-capture of hydrogen at matrix dislocations and martensite/austenite interfaces can enhance the peak of martensite and/or cause an independent peak at a higher temperature.

EFFECT OF IRRADIATION WITH PULSED ION BEAM ON THE MICROSTRUCTURE OF TiH 2

Titanium has long been of interest as hydrogen storage material since titanium has a high affinity to hydrogen isotopes. Titanium deuteride or tritide is an important nuclear material used in the field of nuclear technology. Investigations concerning hydrogen–titanium system seem to mainly focus on the hydrogen thermal desorption spectra so as to study hydrogen desorption kinetics from metal hydride and to determine the rate–controlling step, but little is known on the evolution of its compositional changes under a much more un–equilibrium condition. In the past two decades, the intense pulsed ion beam (IPIB) technique has received extensive attention as a tool for surface modification of materials. Compared with conventional ion implantation, IPIB irradiation into materials possesses a higher energy density with shorter pulse width and be typical of more intense thermal–mechanical effect. From such a point of view, considering the features of extreme high heating and cooling rate of IPIB, IPIB as a method to evaluate the stability characteristics of titanium hydride film is utilized in order to determine a predictable behavior of the film’s evolution under an extreme un–equilibrium external condition. In current study, TiH2 films irradiated by intense pulsed ion beam have been investigated by using scanning electronic microscopy, surface profilometer, X–ray diffraction and slow positron annihilation, in order to evaluate the effect of irradiation with pulsed ion beam on the microstructure of TiH2. Three sets of TiH2 films are irradiated several shots * D} <2bj ^SG 11205136 mlL-C : 2013–03–18, ml['-C : 2013–07–20 j3 : ℄ n, , 1987 W, %e DOI: 10.3724/SP.J.1037.2013.00122 1270 p ` AE x 49 * at energy density ranging from 0.1 J/cm to 0.5 J/cm. No noticeable phenomenon of melting and change of phase structures have occurred to samples under irradiation of 0.1—0.3 J/cm. However, phenomenon of melting and indication of cracking has been detected on the surface after energy density reaches 0.5 J/cm. Besides, desorption of hydrogen from the film, and a titanium hydride with a body centered tetragonal structure (bct), seldom reported by researchers and formed under extreme conditions, has also been identified only after energy density of IPIB reaches 0.5 J/cm. S parameter of slow positron annihilation reflects that the crystal defect structures have been greatly changed by IPIB irradiation, in which S parameter reaches a large value at 0.3 J/cm with 1 shot, while a small one at 0.5 J/cm with 5 shots.

Numerical Modeling of Thermal Desorption Spectra of Hydrogen: A Review of Thermal Desorption Models

Numerical modeling of thermal desorption spectra of hydrogen, which is used for identifying the hydrogen state in metals, is reviewed. The previously proposed models are described in the historical perspective by categorizing them according to the rate-determining processes of hydrogen detrapping and diffusion in the thermal desorption spectra. The range of validity of each model is also described.

拡散支援脱離モデルによるSi(100)表面からの水素熱脱離スペクトル

拡散支援脱離モデルによるSi(100)表面からの水素熱脱離スペクトル

A Numerical Study on the Validity of the Local Equilibrium Hypothesis in Modeling Hydrogen Thermal Desorption Spectra

We present a systematic benchmark study on different numerical models for analyzing hydrogen thermal desorption spectra, by focusing on the adoption of the local equilibrium hypothesis in these models. We find that the direct numerical method of the full set of the extended mass conservation equations is only able to predict the experimental behavior of thermal desorption spectra for pure iron in the thin specimen limit, while other models incorporating the local equilibrium hypothesis fail to predict this behavior.

Adsorption of hydrogen on the Pd(100)-p(2×2)-p4g-Pd3Ti surface

Abstract Ti/Pd(1 0 0) surface alloy has p(2 × 2)-p4g symmetry. Hydrogen adsorption removes the lateral distortion of the first layer atoms to yield c(2 × 2). We studied the hydrogen adsorption by thermal desorption experiment and self-consistent total-energy calculation based on density-functional theory. Thermal desorption spectra of hydrogen from this surface are composed of two components: a relatively broad peak shifting from 355 to 345 K with increasing coverage and a sharp desorption peak at 380 K. The former is assigned to hydrogen desorption occurring on the c(2 × 2) domains. The shape and peak temperature of the latter is similar to the sharp hydrogen desorption peaks reported on the p(2 × 2)-p4g surfaces of Al/Pd(1 0 0) and H/Cu(1 0 0). It is suggested that the sharp desorption peak may be intrinsic to hydrogen desorption from the p(2 × 2)-p4g surfaces. The nature of the hydrogen adsorption site is discussed.

Hydride formation and thermal desorption spectra of hydrogen of cathodically charged single-phase gamma titanium aluminide

The authors have previously reported thermal desorption spectra of hydrogen obtained from cathodically charged two-phase (Ti{sub 3}Al ({alpha}{sub 2}) + TiAl ({gamma})) titanium aluminides by means of thermal desorption spectroscopy (TDS), in which hydrogen ion current (H{sub 2}{sup +}) corresponding to hydrogen evolution rate during heating was measured by a quadrupole mass spectrometer in an ultra-high vacuum condition. Several accelerated hydrogen evolutions (TDS peak temperatures) have been observed in a series of TDS measurement, and then the authors have suggested that these peaks were dependent on the microstructures ({alpha}{sub 2} and {gamma} phases) as well as dissociation of the hydride phase which formed during cathodic charging. A comparison with the TDS spectra from other series of titanium aluminides, such as a single-phase {gamma} alloy, might give clearer views of the microstructural dependence on hydrogen evolution kinetics. In this paper, hydride formation, hydrogen uptake and hydrogen evolution kinetic of a cathodically charged single-phase {gamma} titanium aluminide are investigated, and these results are compared with the previous ones obtained in two-phase ({alpha}{sub 2} + {gamma}) titanium aluminides.

Effect of surface oxide layers on deuterium permeation through stainless steels with reference to outgassing reduction in ultra- to extremely high vacuum

Hydrogen is a dominant outgassing species from stainless steel vacuum chambers in ultra- to extremely high vacuum. Oxidation of stainless steel surfaces has been known to reduce the outgassing. The oxide layer formed on the stainless steel surface is expected to serve as a diffusion barrier for hydrogen diffusing from the bulk. In the present study the effects of oxidation on the outgassing rate, on hydrogen thermal desorption spectra, on surface contamination and on deuterium permeation and diffusion characteristics through the stainless steels are summarized. Discussion is given to the role of the surface oxide layer in outgassing reduction as well as to the effect of thickness and chemical compositions on reduction in hydrogen permeability and diffusion. The surface oxide formed in the present study appears to serve as the diffusion barrier for hydrogen and is found to decrease the deuterium permeability to 1 2 – 1 3 of the unoxidized one by lowering the diffusion coefficient. The most effective oxide is proposed to be Cr-rich oxide with 100–200Å thickness.

Self-discharge behaviour of sealed Ni-MH batteries using MmNi3.3+xCo0.7Al1.0−x anodes

The thermodynamic and kinetic factors controlling self-discharge behaviour of the Ni-MmNi3.3+xCo0.7Al1.0−x (x = 0.0, 0.2) sealed cells have been investigated.A modified sealed cell is employed to measure the charge retention of the anode and cathode separately in the Ni-MmNi3.3+xCo0.7Al1.0−x (x = 0.0, 0.2) sealed cells. It is found that the charge retention of the MmNi3.3+xCo0.7Al1.0−x electrode is the same as the total charge retention and is much smaller than the Ni cathode in air at 1 atm and 30°C.From the results of hydrogen thermal desorption spectra with respect to open-circuit time, it is confirmed that the cause of the self-discharge for the MmNi3.3+xCo0.7Al1.0−x anode is due to the desorption of hydrogen from the metal hydride electrode owing to the pressure difference between the hydrogen partial pressure in the sealed cell and the equilibrium hydrogen pressure of the metal hydride alloy. Also, it is found that the self-discharge behaviour of Ni-MH cells is not correlated with the type or structure of the MH anode.As a diffusion barrier for hydrogen, MmNi3.3Co0.7Al1.0 alloy is encapsulated with Cu (which has lower hydrogen diffusivity than MH alloy); however the charge retention of the Ni-MmNi3.3Co0.7Al1.0 sealed cell is not improved because hydrogen is desorbed through cracks rather than the Cu-coated layer.The charge retention of the Ni-MmNi3.3Co0.7Al1.0 sealed cell is greatly improved by applying 1 atm of hydrogen gas. This pressure is higher than the equilibrium hydrogen pressure of the metal hydride and decreases the driving force for hydrogen desorption from the MH electrode.

Calculations of thermal desorption spectra of hydrogen molecule and hydrocarbon molecule from graphite using the mass balance equations

The thermal desorption spectra of hydrogen molecules and hydrocarbon molecules emitted from graphite have been theoretically calculated using the solution of the mass balance equations, in which the rate constants of thermal detrapping, retrapping, local molecular recombination, and hydrocarbon formation are included. It is shown that the peak temperature of the thermal desorption spectra of both hydrogen and hydrocarbon molecules is a function of the speed of temperature rise and the initial concentration of retained hydrogen. From the former result it is shown that the relation between the peak temperature and the peak time obtained experimentally gives the effective rate constant of local molecular recombination for hydrogen molecule emission and the rate constant on thermal detrapping for hydrocarbon molecule emission. Finally, the thermal desorption spectra are numerically calculated and compared with the experimental results.

Atomic hydrogen solubility in thin gold films and its influence on hydrogen thermal desorption spectra from the surface

Atomic hydrogen solubility in thin gold films within the temperature interval 250–380 K has been studied, and the exothermic heat of the solution (9 kJ/mol H) has been determined. The influence of predissolved hydrogen concentration on TD spectra from the surface has been shown.