Hydrogen Isotope Permeation Research Articles

Proton permeation and selective separation of hydrogen isotopes through fullerene nanocages (X12Y12): A DFT insights

To resolve the problem of mobile electrolytes for the permeation of hydrogen isotopes in fuel cells, we have studied herein heteronuclear fullerene nanocages (Al12N12, Al12P12, B12N12, and B12P12) for the separation and permeation of hydrogen isotopes. The separation and permeation of fullerene nanocages for hydrogen isotopes are studied at ωB97XD functional of DFT along with 6–31g (d,p) pople basis set. Zero-point energy (ZPE) is calculated for Protium (H+) and its heavier isotopes including deuterium (D+) and tritium (T+). The Arrhenius equation is employed to calculate the selectivity of protium to deuterium (H+/D+) and deuterium to tritium (H+/T+) isotopes. The selectivity is calculated by using the zero-point energy difference (ZPE) of protium (H+) to its heavier isotopes. The proposed fullerene nanocages estimated better selectivity for proton isotopes. The phosphide-based nanocages (Al12P12, B12P12) provide superior selectivity values of H+/D+ and H+/T+ compared to nitrogen-based nanocages (Al12N12, B12N12). This study provides insights into separation pathways for proton isotopes through nanocages for many industrial applications in the energy sector.

Effects of Carbon Deposition on Deuterium Plasma-Driven Permeation Through Tungsten-Coated RAFM Steel

In steady-state operation of fusion reactors, eroded materials and contaminations, especially carbon (C), may deposit on the surface of plasma-facing components. In this work, the effects of C deposition on hydrogen isotope permeation behavior through tungsten (W)–coated reduced activation ferritic/martensitic (RAFM) steel were systematically investigated by plasma-driven permeation (PDP) measurements in the temperature range of 633 to 893 K. A C deposition layer with thickness of ~200 nm was prepared by magnetron sputtering to simulate the formation of C impurities in the first-wall area of tokamaks. The implantation depth of incident deuterium (D) ions was estimated to be <10 nm at incident energy of 114 eV. Deuterium effective diffusion coefficients (Deff’s) for W-coated RAFM steel with/without a C layer were obtained. It was found that the C layer tended to increase Deff in the low-temperature region of ~675 to 820 K. At high temperature, however, Deff was measured be lower than that without a C layer. Nevertheless, the addition of a C layer had no significant effect on Deff compared to the W coating alone with respect to bare RAFM steels. For steady-state D-PDP flux, it was found that the C layer significantly decreased D permeation flux at low temperature. But, the permeation flux difference between the samples with/without a C layer became smaller with increasing temperature, indicating that the influence of C deposition on D permeation was negligible at high temperature. Similar D-PDP behavior was detected as increasing the incident ion flux by means of increasing plasma discharge power. Surface reemission of absorbed D as well as the D concentration gradient throughout the sample was found to be influenced by C deposition; therefore, D permeation flux changed correspondingly.

Hydrogen permeation in iron-chromium-aluminum (FeCrAl) alloys and the effects of microstructure and surface oxide

Iron–chromium–aluminum (FeCrAl) class alloys are candidates for use as cladding for accident-tolerant fuels and moderators. In this context, hydrogen isotope permeation in FeCrAl alloys is an important material property. In the present work, the apparent permeability, effective diffusivity, and apparent solubility of hydrogen in the FeCrAl alloys C26M and Kanthal D (KD) were measured with gas-driven hydrogen permeation. Permeation measurements were conducted at temperatures of 400 to 700 °C and at gas-driven pressures from 1 to 100 kPa. In particular, the effect of grain size on hydrogen transport was studied with KD samples with three different microstructures: nanocrystalline (NC), ultra-fine grained (UFG), and coarse-grained (CG). The UFG and NC specimens had higher apparent activation energies (73.4 kJ mol-1 and 65.2 kJ mol-l, respectively) for hydrogen permeability than the CG sample (46.9 kJ mol-1). An aluminum oxide layer formed on the primary- and secondary-side surfaces of all samples subjected to permeation experiments which demonstrated the propensity of FeCrAl alloys to form these innate oxide permeation barriers.

Hydrogen interactions with intrinsic point defects and hydrogen diffusion in tungsten doped Al2O3

In light of the extensive use of tungsten (W) in fusion experimental devices and the importance of hydrogen isotopes permeation, based on the first principle approaches we study the effects of W doping on the formation energies of intrinsic point defects, hydrogen interactions with such defects, and hydrogen diffusion in bulk of α-Al2O3. Our investigation demonstrated that W doping enhances the formation of oxygen and aluminum vacancies (Vo and VAl) in α-Al2O3. In W doping α-Al2O3, hydrogen primarily exists in the form of Ho− (hydrogenation of the bulk VO3−) and Hi− (H interstitial) defects, while it hardly occupies VAl. Hydrogen is firmly trapped by Vo with a formation energy −3.35eV, and Hi− diffusion become extremely challenging because W doping significantly raises the Hi− diffusion barrier to 4.44 eV. Our findings indicate that W doping is beneficial for hydrogen permeation resistance in α-Al2O3.

HYDROGEN BARRIER COATINGS AND THEIR PERMEATION RESISTANCE

This review discusses the state of the art in hydrogen permeation for a variety of coatings. Hydrogen ingress into structural materials can be detrimental due to corrosion and embrittlement. To enable safe operation in applications requiring protection from hydrogen isotopes, recent advances in material design and performance characterization of barrier coatings to prevent hydrogen isotope absorption ingress and permeation are summarized. Alternative coating concepts can provide greater resistance to hydrogen isotope permeation along with other improved properties such as mechanical strength and thermal resistance. The information presented here focuses on recent findings of promising hydrogen barriers including oxides, nitrides, carbon, carbide, MAX phases, and metals and their mechanical strength, hydrogen uptake, and radiation resistance.

Deuterium permeation studies through bare and Er2O3 coated SS 316L

Hydrogen isotope permeation through the structural walls of a fusion reactor poses concern for both fuel loss and safety. A primary focus in the International Thermonuclear Experimental Reactor (ITER) is the reduction of hydrogen isotopes, particularly tritium permeation through structural materials. In this work, an experimental setup has been developed to study the permeation of deuterium through thin samples such as bare and erbia (Er2O3) coated 100 µm thick stainless steel (SS 316 L). Permeation results through a bare SS 316 L sample yielded deuterium diffusivity and permeability of SS 316 L. Erbia coating on SS 316 L was developed using dip coating technique and its performance was tested as a permeation reduction barrier (PRB). A permeation reduction factor of ∼87 and 359 have been achieved with coating thickness ∼ 100 and ∼200 nm respectively. No measureable permeation flux was obtained for coating thickness of 492 nm. These results indicate the effectiveness of erbia coating in reducing deuterium permeation through SS 316 L.

Multi-layer structured AlN/Er2O3 coating: Enhanced thermal stability and hydrogen isotope permeation resistance

AlN/Er2O3 multi-layer coatings, as a novel hydrogen isotope permeation barrier for nuclear reactor and hydrogen energy field, were prepared by magnetron sputtering coupled with metal-organic decomposition on the surface of reduced activation ferrite/martensitic steel. The thickness of the Er2O3 layers was adjusted by spin coating several times, the adhesion of the layers was tested with a micron scratch tester, and the microstructure and surface composition of the layers were analyzed by TEM and XPS. The results indicate the absence of evident crack holes on the coating surface, uniform distribution of elements without segregation, and satisfactory densification. In comparison with the individual Er2O3 coating, the multi-layer coating incorporating AlN as the interlayer exhibits enhanced adhesion strength, which could effectively mitigate the thermal mismatch phenomenon of Er2O3 under high temperature conditions. Electrochemical hydrogen permeation and high temperature gas pressure driven deuterium permeation tests demonstrated that the permeability resistance of the AlN/Er2O3 coating does not linearly increase with its thickness. The hydrogen permeation reduced factor of the coating reaches its maximum value when the thickness of the Er2O3 coating is 1500 nm.

Deuterium permeation and retention behavior in copper-based brazing filler materials

Copper-based brazing filler materials are commonly employed in vacuum brazing techniques to achieve joining of plasma-facing components for ITER. In this work, gas-driven permeation (GDP) and thermal desorption spectroscopy (TDS) experiments have been performed to study the hydrogen isotopes permeation and retention behavior in two types of brazing filler materials (CuMnNi and CuGeNi metals). Experimental results show that CuMnNi filler exhibits the similar deuterium (D) permeability with CuMnNi filler but lower diffusion coefficients than CuGeNi filler. Three distinct peaks are observed between 380 K and 980 K for CuMnNi filler. However, no evident desorption peak is observed for CuGeNi filler. CuGeNi filler may be considered as a potential brazing filler material for reducing tritium inventory.

Deuterium permeation performance of V4Cr4Ti/RAFM steel joint with in-situ formed carbide interlayer during diffusion bonding

Vanadium alloy (V4Cr4Ti) is a structural material used in future fusion reactors owing to its inherent advantages of high-temperature strength and neutron irradiation resistance. Oxygen pickup and high hydrogen isotope permeability are the two major concerns for their application in various types of blankets. To solve these issues, a bimetallic joint was designed with a CLF-1 layer of reduced-activation ferritic/martensitic (RAFM) steel to resist corrosion and a CLF-1/V4Cr4Ti bonding interface to suppress hydrogen isotope permeation. Samples were prepared from joints bonded via solid-state diffusion under hot isostatic pressing (HIP). Deuterium (D) gas permeation tests were performed at various temperatures in the range 400–600 °C at 100 kPa. After deuterium permeation tests, the thermal desorption spectra (TDS) of the samples were analyzed. And the permeation behavior of deuterium atom across the joints was schematically discussed. The results showed that bonding with steel could be an effective solution for resisting hydrogen isotope permeation through the V4Cr4Ti alloy. Thermal desorption spectrum (TDS) analysis of the tested samples revealed a desorption peak temperature equivalent to that of TiC. The formation of a 1 µm-wide B2 ordered α'- [Fe, (V, Ti)] phase layer, together with a large number of dispersed carbides around the interface, played a significant role in the deuterium permeation resistance. In addition, microstructural changes in the steel base material after the 900 °C bonding process were beneficial for suppressing deuterium diffusion.

Hydrogen isotope permeation and retention behavior in the RAFM steel manufactured by laser powder bed fusion

Laser powder bed fusion (LPBF) has emerged as a promising additive manufacturing technique for producing complex components across various industries. This method is particularly instrumental in fabricating reduced activation ferritic/martensitic (RAFM) steel, a candidate structural material for the tritium breeding blanket. Hydrogen transport behaviors in the conventional RAFM steel have been largely investigated; however, they are not well understood in the LPBF-RAFM steel. In this work, we studied the hydrogen isotope permeation and retention behavior in the RAFM steel fabricated by LPBF, utilizing the deuterium gas driven permeation and thermal desorption spectroscopy experiments. The results show that the hydrogen isotope permeability of the LPBF-RAFM steel is close to the conventionally fabricated RAFM steel, but the diffusion coefficient is greatly lower and the retention is markedly higher in the LPBF-RAFM steel compared to the conventional RAFM steel. The large number density of microvoids and TiC precipitates in the LPBF-RAFM steel could be the predominant factors that result in the decrease in hydrogen isotope diffusion coefficient and the increase in the total amount of deuterium retention.

Improving hydrogen isotope permeation resistance of (TiVAlCrZr)O multi-component metal oxide coating by O+ Ion implantation

Oxygen vacancy can greatly affect the performance of metal oxide to hydrogen isotope permeation resistance. In this work, we report a new strategy to improve the permeation resistance by oxygen ion implantation. A (TiVAlCrZr)O multi-component metal oxide film was prepared as a tritium permeation barrier on a 316 L substrate by RF magnetron sputtering deposition, and then implanted by oxygen ions to fill the oxygen vacancies inside. The grazing incidence X-rays (GIXRD) analysis showed that the pristine and the oxygen-implanted coatings were in an amorphous phase. The deuterium permeation resistance of the four coatings was tested by a gas-driven device. The result showed that the pristine coating had a permeation reduction factor (PRF) of 5,610 at 500 °C, while there was a 13.6 times of increase in PRF with an oxygen concentration of 11.4 at.% with the best-reported value of 76,500, and more oxygen ions implanted, the better the deuterium permeation resistance of the coating. The GIXRD showed that after the test the pristine coating remained amorphous, while some crystals were formed in the oxygen-implanted coating with an oxygen concentration of 11.4 at.%. Oxygen ion implantation enhanced the deuterium permeation resistance by filling the oxygen vacancies and forming of more stable state of amorphous multi-component metal oxide, which is expected to be a new type of deuterium permeation barrier.

A novel method for preparing α-Al2O3 (Cr2O3)/Fe–Al composite coating with high hydrogen isotopes permeation resistance

α-Al2O3 as a preferred material for hydrogen isotopes permeation barrier (HIPB) can effectively prevent hydrogen embrittlement in structural steel and has higher thermal stability. However, its application is limited by the issue that it is hard to prepare α-Al2O3 at relatively low temperature and its formation temperature is too high (>1000 °C) to damage the mechanical properties of structural steel. To overcome this issue, this paper presents a novel method (combining Al electrodeposition, aluminizing, Cr deposition and air oxidation) for the preparation of α-Al2O3 (Cr2O3)/Fe–Al composite coating on 316 L stainless steel for the first time. The formation temperature of α-Al2O3 was successfully reduced to 800 °C. The post-oxidation samples were characterized by SEM, XPS, XRD, EDS and TEM. The results showed that the oxide film was composed of highly crystalline α-Al2O3 and Cr2O3 nanoparticles, where the later were diffusely distributed in the internal α-Al2O3 film. And there was an epitaxial growth relationship between α-Al2O3 and Cr2O3. The low-temperature formation of the α-Al2O3 film was due to the fact that the Cr2O3 nanoparticles formed during the oxidation process acted as templates and nucleation sites, which reduced the nucleation barrier of α-Al2O3. Deuterium permeation tests showed that its deuterium permeation reduction factor (DPRF) was 8892 at 500 °C, which met the standard for practical application.

Thermal-assisted resistive sensor based on the PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere

The detection of hydrogen isotopes is not only the premise of ensuring safety of hydrogen energy, but also has very important application value and scientific significance in the field of fusion energy. Therefore, it is imperative to develop efficient and reliable hydrogen isotope sensors. Herein, a thermal-assisted resistive sensor is constructed based on the hydrogen isotope effect of PdCr alloy thin film for sensitive detection of hydrogen isotopes in helium atmosphere. The permeation of hydrogen isotopes in palladium lattice is facilitated through thermal effect to improve the dynamic response capability of sensor. The research results show that the response time of sensor to hydrogen and deuterium is reduced from 192 s to 113 s–17 s and 10 s respectively. However, the sensitivity deteriorated by about 40% at 110 °C compared with room temperature. Meanwhile, the PdCr alloy thin film resistive sensor represents a remarkable linear response in a range of 0.1%–4% hydrogen and deuterium, with correlation coefficients of 0.9971 and 0.9998 respectively. And the response difference of hydrogen and deuterium may be utilized to discriminate hydrogen isotopes. Furthermore, the sensor exhibits prominent selectivity, extraordinary working stability and a wide range of 100ppm-100%. Therefore, this work presents a feasible approach to design high-performance resistive hydrogen isotope sensors for the development of hydrogen energy and fusion energy.

Hydrogen isotope permeation through interfaces and permeability of tungsten layers

The estimation of the hydrogen isotope flux through a fusion reactor wall component is important for the material selection and in order to guarantee a safe and economical reactor operation. Since the permeation flux through a component cannot be measured directly, due to the large size of such a component, the deuterium permeability of various fusion materials were investigated in the last years. In order to investigate, if an interface, meaning a change of materials in a component, has an influence on the permeation flux, combined material systems in laboratory scale are studied. The combined materials systems are produced by applying a thin W or Cu layer on a polished bulk steel or CuCrZr substrates by magnetron sputter deposition. In a previous study (Houben et al., 2022), the combined material system of Cu coated steel was investigated. The conclusion was that the interface has a minor influence on the permeation flux compared to the large influence of the layer microstructure. In order to investigate, if the minor influence of the interface is valid in general, the systems W coated steel and CuCrZr are studied in this publication. By heating the substrate during W sputter deposition, a crack-free W layer is produced and crack propagation in the W layer at elevated temperature is prevented. The W layer permeabilities are obtained for both W coated substrates and are similar, but compared to the W bulk permeability from literature the W layer permeabilities are several orders of magnitude larger.The main conclusion from these studies is that in all investigated combined material systems the influence of the interface on the permeation flux is minor compared to the large influence of the microstructure. Therefore, for a reliable estimation of the permeation flux through a fusion reactor component it is crucial to characterize the applied materials. Especial for coatings the measurement of the layer permeability is important, since the layer permeability of a material can be very different compared to the permeability of a bulk material.

Thermochemically synthesized α‐Al2O3 composite coating with high bonding strength and deuterium permeation resistance

AbstractHydrogen isotope permeation in structural steels can cause severe issues, including steel brittleness, fuel loss, and radioactive pollution in fusion reactors. To tackle this issue, we report a simple synthesis of α‐Al2O3/AlPO4 composite coating by the thermochemical reaction method to serve as an effective barrier hampering hydrogen isotope permeation. This coating was formed at 500°C and composed of α‐Al2O3 and AlPO4 phases. A relatively uniform and compact structure with thickness of ∼35 μm made its corrosion resistance reaching above 3000 times that of the 321 steel substrate. With just one‐side coated, the α‐Al2O3/AlPO4 coating achieved a considerable deuterium permeation reduction factor of 1935 at 450°C, three orders of magnitude higher than 321 steels. What's more, after the deuterium permeation test, no pores or cracks were generated. The excellent bonding between the coating and the substrate was resulted from the formation of CrxPy at their interface induced by Cr diffusion from the substrate. The results obtained from the current study shed new light on seeking reliable and viable ceramic coatings to tackle hydrogen permeation issues.

Effect of He seeding on hydrogen isotope permeation in tungsten by H-D mixed plasma exposure

Effect of He seeding on hydrogen isotope permeation in tungsten by H-D mixed plasma exposure

The effects of heavy-ion irradiation on electrical properties and hydrogen isotope permeation behavior of ceramic coatings

Tritium permeation through structural materials in fusion reactor blanket systems is a crucial problem in terms of fuel efficiency and radiological safety. A tritium permeation barrier has been developed using ceramic coatings for several decades to mitigate tritium leakage. Recent studies are focused on irradiation effects on microstructure and hydrogen isotope permeation behavior of the coatings. However, most of the analytical methods used in these studies were destructive and time-consuming, which is undesirable to apply to the actual reactor components. Here, we report the influence of irradiation damage on electrical properties and deuterium permeation behaviors of ion-irradiated zirconium oxide coatings fabricated by metal organic decomposition to develop a convenient approach for coating characterization. The undamaged and irradiated coatings decreased the deuterium permeation flux by a factor of more than 1000 in comparison with an uncoated substrate at 300 °C. The irradiated coatings had lower permeation flux than the undamaged coatings, suggesting that irradiation-induced grain growth reduced deuterium permeation. While the undamaged coating degraded in the measurement at around 450 °C, the irradiated coatings kept high permeation reduction performance after the measurement at 600 °C. The total electrical conductivities of the irradiated coatings were up to two orders of magnitude higher than those of the undamaged one below 400 °C and then increase linearly with inverse temperature. The dominant influence on the electrical conductivity was irradiation defects at low temperatures and the inherent conduction performance of the coating at high temperatures. Our results show that electrochemical impedance measurements are useful even for submicron-thick ceramic thin coatings and confirm the irradiation effects on electrical conductivity, especially in the low-temperature range.

Density functional theory study of formation and diffusion of hydrogen, deuterium, and tritium in Pd-V intermetallic compounds

Permeation of hydrogen isotopes in palladium/vanadium bimetallic membranes is known to deteriorate over time because of Pd-V interdiffusion. Intermetallic compounds may form in the interdiffusion region. Density functional theory is employed to study how Pd-V compounds may affect the permeation. Three compounds Pd8V, α-Pd2V, and PdV4 are explored in this study. Formation and migration energies of hydrogen, deuterium, and tritium are calculated and subsequently compared to the data in pure Pd and V metals. The calculations show that both the formation and migration energies in the compounds are higher than in the pure metals. Thus, the permeation of these isotopes in the compounds is lower than in the pure metals. In addition, the least permeable compound is the one near the middle of the composition range, i.e. the α-Pd2V. The results provide atomistic insight for the permeation reduction in Pd/V membranes as interdiffusion progresses.

Effect of Cr2O3 nanosheet insertion on the deuterium permeation behavior of a Cr-Zr-O coating

In this study, a Cr2O3 nanosheet (Cr2O3 NS) inserted Cr-Zr-O coating was developed as a hydrogen isotope permeation barrier. The Cr2O3 NSs, fabricated by rapid heat treatment, were amorphous with a thickness of only several nanometers. These Cr2O3 NSs were then incorporated into a Cr-Zr-O multi-metal oxide composite coating via a dip-coating method to form a coating. The effect of the Cr2O3 NS concentration on the morphology, microstructure and deuterium permeation resistance of the coating was studied. With the addition of 1.0 g l−1 Cr2O3 NSs, compared with the Cr-Zr-O coating without NSs, the permeation reduction factor of the resultant coating was enhanced from 249 °C to 575 °C at 500 °C. The coating, with a thickness of nearly 193 nm, achieved a comparable deuterium resistance that was above two orders of magnitude higher than the steel substrate. The results show that ceramic NSs can serve as effective fillers for enhancing the coating performance when functioning as a hydrogen isotope barrier.

Electronic property and effective diffusion coefficient calculation model of hydrogen isotopes in multicomponent steel 2.25Cr1Mo from first-principles calculations

Chrome-molybdenum (2.25Cr1Mo) ferritic steel is one of the primary materials used in heat exchanger pipes in the steam generators of high-temperature gas-cooled reactors (HTGRs). Studying the tritium diffusion mechanism in 2.25Cr1Mo ferritic steel is of vital importance for the prediction and interpretation of tritium activity concentration in the reactor. However, the permeation of hydrogen isotopes in these alloys remains difficult to predict owing to the lack of understanding of the microscopic interactions between hydrogen isotopes and multicomponent alloys. In this study, the electronic and diffusion properties of the hydrogen isotopes in 2.25Cr1Mo alloy were investigated using first-principles calculations. Hydrogen preferentially intercalated into tetrahedral interstitial sites rather than octahedral ones in 2.25Cr1Mo alloy. The Cr and Mo dopants induced strong repulsion between H and the matrix. Interaction between H and 2.25Cr1Mo exhibited a combination of ionic and covalent bonds with electrons transferred from the steel to H atom. Dopants acted as scattering centers with local interaction with H and expanded the preventive effect of H diffusion to the second-nearest tetrahedral interstitials with a high energy barrier. The effective H diffusion coefficient in the alloy was calculated by an approximate model based on the volumetric ratio of the components for the first time. The obtained pre-exponential factor and activation energy agreed well with the experimental results. The current research provides a reliable way to determine the effective diffusion coefficient of hydrogen isotopes in multielement alloys, which can accelerate R&D of tritium-resistant materials in both fusion and fission reactors.