Hydrogen Getter Research Articles

Fabrication of powder high-entropy TiZrHfNbTa alloy by calcium-hydride method: Synthesis kinetics and structure evolution

High-entropy alloys are currently considered as prospective hydrogen storage materials and getters, which can be utilized to create a high vacuum in specialized devices. To provide high sorption properties, it is crucial to use highly porous materials or powders that makes powder metallurgy an attractive and suitable method. In the current work, a powder high-entropy alloy TiZrHfNbTa was obtained by reducing transition metal oxides with calcium hydride. The mechanism and features of the calcium-hydride synthesis of the high-entropy alloy have been studied. Phase composition has shown to be dependent on holding time at a temperature of 1200 °C. The powder’s structure comprises four BCC solutions based on Nb, Ta, TiZrHf, and TiZrHfNb, when holding time is up to two hours. Prolonged holding leads to more homogeneous structure, and the final product possesses two BCC phases: Ti0.21Zr0.24Hf0.24Nb0.25Ta0.06 (BCC-I: ∼75 wt%) and Ti0.15Zr0.05Hf0.08Nb0.10Ta0.62 (BCC-II: ∼25 wt%). The analysis of BCC-I formation kinetics with the aid of the Avrami equation has shown that a quite prolonged time of around 48 hours is necessary to achieve a single-phase structure of the powder due to the presence of tantalum, which impedes homogenization. Parameter n in the Avrami equation has been determined to be 0.361.

Suppression of Enhanced Magnesium Diffusion During High‐Pressure Annealing of Implanted GaN

Activation of ion‐implanted p‐type dopants in gallium nitride has demonstrated great progress utilizing high pressures to enable novel and traditional device architectures; however, such conditions consistently exhibit anomalously enhanced diffusion up to several microns in very short periods of time for device relevant concentrations. Here, this diffusion is shown to be modulated by unintentional hydrogen content within the anneal ambient and thus controllable by inclusion of a high‐temperature hydrogen getter. Furthermore, diffusion is also shown to be greatly suppressed using co‐implanted oxygen at low concentrations while simultaneously maintaining characteristics of p‐type material in photoluminescence. Subsequently, after annealing at 1300 °C for 30 min in 3.8 kbar of nitrogen pressure, the magnesium concentration in the diffusion tail is suppressed by 28% at 1–1.5 μm in depth using a hydrogen getter alone, which reduces hydrogen uptake by 45% and fully suppressed at >1 μm in depth using co‐implantation alone and further reduced with concurrent use of a hydrogen getter. Co‐implantation alone reduces the in‐diffused magnesium dose by 60% compared to reference samples.

Porous Silicone Rubber Composite Supported 1,4-Diphenylethynyl Benzene for Hydrogen Absorption with Pd/C Catalyst.

Hydrogen is a dangerous gas as it reacts very easily with oxygen and may explode; therefore, the accumulation of hydrogen in confined spaces is a safety hazard. Composites consisting of unsaturated polymers and catalysts are a common getter, where the commonly used polymer is 1,4- diphenylethynyl benzene (DEB). Silicone rubber (SR) is a good carrier for hydrogen-absorbing materials due to its excellent chemical stability and gas permeability. In this work, polysiloxane, water, and a emulsifier are ultrasonically injected into a uniform emulsion, and the hydrogen getter DEB-Pd/C (Palladium on carbon) is then added. Under the catalysis of platinum (Pt), the cross-linking agent undergoes a hydrosilylation reaction to cross-link polysiloxane in emulsion to form silicone rubber. Then, the water was removed by freeze-drying, and the loss of water constructed a porous frame structure for silicone rubber, thus obtaining porous silicone rubber. The difference in hydrogen absorption performance between porous silicone rubber and ordinary silicone rubber was compared. It was found that, with the increase in water in the emulsion, the porous frame of silicone rubber was gradually improved, and the hydrogen absorption performance was improved by 243.4% at the highest, almost reaching the theoretical saturated hydrogen absorption capacity. Porous silicone rubber was prepared by emulsion mixing, which provided a new idea for further improving the hydrogen absorption performance of silicone rubber.

Additively Manufactured Silicone Polymer Composite with High Hydrogen Getter Content and Hydrogen Absorption Capacity.

Hydrogen getters consisting of 1,4-bis[phenylethynyl] benzene (DEB) and a carbon-supported palladium catalyst (Pd/C) have been used to mitigate the accumulation of unwanted hydrogen gas in a sealed system. Here, we report the formulation of a composite resin consisting of silicone polymer plus DEB-Pd/C as an active getter material and the additive manufacturing of silicone getter composites with a high getter content (up to 50 wt %). NMR and DSC studies suggest no reaction between the silicone polymer resin and DEB even at elevated curing temperatures (75 °C). Getter composites with varying amounts of getter and filler were formulated, and their rheological properties were studied. The two composite resins with good printability parameters and different getter contents were chosen to make 3D-printed samples. The hydrogen absorption capacity of these samples was studied at a low hydrogen pressure of 750 mTorr of pure hydrogen. The getter composite with 50 wt% of getter showed normalized DEB conversion of 83%, with the hydrogen adsorption capacity of 100.2 mL of H2 per gram of polymer getter composite.

Preparation and properties of nitrogen-doped reduced graphene oxide loaded palladium/1,4-bis(phenylethynyl)benzene irreversible hydrogen getters

Preparation and properties of nitrogen-doped reduced graphene oxide loaded palladium/1,4-bis(phenylethynyl)benzene irreversible hydrogen getters

Ultrathin flexible hydrogen getter films with excellent hydrogen uptake and mechanical properties

The incorporation of DEB-Pd/C into polymers provides a possible solution to obtain various composite materials with customized properties. In this work, we selected SEBS as a substrate to prepare an ultra-thin flexible DEB-Pd/C@SEBS composite film. The mechanical properties and hydrogen uptake properties of composite films with different DEB-Pd/C contents and different thicknesses were investigated. The results show that these films possess excellent H2 uptake and mechanical properties. We speculate that the microphase separation structure of these films results in high gas permeability and diffusion rate, which make the material have good compatibility. In addition, these films can be cut and bent into any shape, which can be applied to hetero-slit space easily and conveniently.

Synthesis of novel graphene-based targeted hydrogen getter nanocomposites and their properties

The getter setting is critical for maintaining a high vacuum environment in the annular space of multilayer insulation in the cryogenic vessel. To maximize the sorption of residual gases, particularly hydrogen, an efficient targeted hydrogen getter must be designed. In this study, PdO nanoparticles and Alkyne-PVA were loaded onto graphene oxide to create an efficient and cost-effective targeted hydrogen getter. Raman, XRD, XPS, SEM, TEM, and other characterization methods were used to investigate the microstructure and morphology of the intermediate and Alkyne-PVA-(GO-PdO) nanocomposites. The “Getter Sorption Properties Test System” was used to evaluate the hydrogen sorption properties of the nanocomposites. The results show that the super high specific surface area and efficient network structure of GO can be used as a good substrate material for the loading of PdO nanoparticles and Alkyne-PVA, and that the nanocomposites prepared with reasonable ratios of PdO nanoparticles and Alkyne-PVA have excellent hydrogen sorption performance, and have promising application prospects. The simultaneous use of unsaturated hydrocarbon branched chain and Pd element to the construction of a low-temperature vacuum annular space hydrogen getter in this work is critical to the commercial popularization of hydrogen getters.

Impact of yttrium hydride formation on multi-isotopic hydrogen retention by a getter trap for the DONES lithium loop

Compliance with imposed hydrogen concentration limits in the lithium loop of the DEMO-Oriented Neutron Source (DONES) requires the installation of an yttrium-based hydrogen trap. To determine an appropriate H-trap design, it is essential to have access to a numerical tool capable of simulating hydrogen transport in the DONES lithium loop connected to an yttrium pebble-bed. In the past, a simplified model was created that allows such calculations when hydrogen concentrations in the lithium are low. However, in certain DONES operating phases, the concentration in the lithium is high and in a range where yttrium dihydride (YH2) formation is likely. Due to the anticipated great impact of YH2 formation on the H-trap performance a new model is developed that includes the mechanism of hydride formation. It is based on a mathematical reproduction of complete pressure-composition isotherms of the Li–H and Y–H systems. Thus, the conditions that trigger YH2 formation are determined and the variation of hydrogen solubility in different yttrium hydride phases is deduced. An approximate concentration-dependent relationship of hydrogen diffusivity in yttrium is derived and incorporated into the model. Simulations are performed to analyze the dynamics of the concentration decrease during purification of the lithium circuit prior to the experimental DONES phase by varying design parameters of the trap. It is found that hydride formation greatly increases the hydrogen gettering capacity of the H-trap and limits the maximum concentration in the lithium. Indeed, YH2 formation may be purposefully triggered to exploit its beneficial properties for DONES. Simulations of the hydrogen purification process during the experimental phase of DONES show that the H-trap must be replaced at least every 28 days to meet tritium limits. This work sets the conditions for the required pebble-bed mass of the H-trap at a given temperature to comply with the DONES safety requirements. Finally, the model is validated by numerical reproduction of experimental results.

Evaluation of Hydrogen Gettering Rates Correlated to Surface Composition and Texture of Nickel-Plated Zircaloy Getters of Different Heat Treatment Procedures.

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures.

Deuterium concentration profiles at the rolled joints of CANDU fuel channels

A diffusion model is proposed to explain high concentrations of hydrogen isotopes seen in some rolled joints of CANDU reactors. Predicted concentration profiles emanating from the rolled joints into the Zr-2.5Nb pressure tubes suggest an early ingress event happens within the first six months of operation in some tubes. This event is consistent with gettering of hydrogen from the 403 stainless steel end-fittings by the pressure tubes.

Suppression of impurities absorption and heterophase inclusions in Ge-As-S glasses

Strong absorption from the impurities and background scattering induced by heterophase inclusions are major issue in the applications of Ge-As-S glass in mid-infrared (MIR). Here, we report that, the absorption of impurities sourced from raw materials can be removed effectively by oxygen getters and hydrogen getters under static vacuum distillation, leading to almost disappearance of the absorption at 3.11 μm due to SH, <4.08 ppm at 4.01 μm due to SH and < 11.03 ppm at 7.5 μm due to As-O, respectively, in Ge10As28S62. The impurities of H2O and CO2 can be further eliminated to near zero by dynamic distillation. On the other hand, the heterophase inclusions, originating from raw materials of sulfur, arsenic and germanium, the silica-container and deoxidizer of Mg, can be eliminated thoroughly by dynamic distillation and optimized melting temperature. We draw the fibers using unpurified and purified glasses and found that, comparing with the fiber loss of 2.87 dB/m at unpurified glass, the optical loss can be decreased to about 1.86 dB/m in purified glass without any visible particles or heterophase inclusions. All the results pave the way of developing low loss Ge-As-S glass fiber for high power laser delivery.

Hydrogen Uptake Kinetics of 1,4-Bis(phenylethynyl)benzene Rubberized O-Rings: Measurements, Modeling, and Comparison with Additional Forms of Organic Getters

A class of molecules called “hydrogen getters” can react with, or scavenge, H2 in applications where the hydrogen presence and/or buildup are not desirable. One such “getter”, 1,4-bis(phenylethynyl)benzene or DEB, can be incorporated into a silicone matrix in the form of an O-ring for added flexibility, environmental resiliency, and convenient use as a gasket in sealed applications. However, the performance and kinetics of this DEB-loaded rubberized O-ring have not yet been characterized. In this work, the hydrogen uptake kinetics of the rubberized DEB O-ring were extracted by the isoconversional analysis from isothermal isobaric data under conditions of 13,332 Pa H2 and 305–325 K. The isoconversional and cylindrical diffusion approximations were then used to predict and model the hydrogen uptake of rubberized DEB O-rings under any arbitrary condition, as illustrated in this work for the simple case of a constant rate of hydrogen generation/input. In comparison with other Pd/carbon-based/organic getter systems, these rubberized DEB O-rings provide a type of hydrogen getter material with enhanced flexibility and catalyst protection in applications where an O-ring seal is needed.

Three-dimensional layered porous graphene aerogel hydrogen getters

Organic getters are often introduced into sealed systems to remove the excessive reactive hydrogen gas. In this work, the formable graphene aerogel hydrogen getters are prepared by integrating the alkyne-containing molecules (e.g., DEB) into the palladium-loaded three-dimensional layered porous graphene aerogel (Pd-GA). The performance of Pd-GA/DEB composite materials in reducing reactive hydrogen gas is examined at pressures of 0.1–1 bar at a temperature of 25 °C, and the hydrogen consumption is measured as a function of time. Results suggest that the hydrogen uptake capability of Pd-GA/DEB getters increases with the loading of Pd particles on the GA and the content of Pd 0 . The highest hydrogen absorption capacity is up to 215.5 cm 3 /g, and the hydrogenation rate of DEB molecules is 89.3%. This study promotes the fundamental understanding of solid-phase catalytic hydrogenation and the applications of 3D layered porous graphene aerogel in hydrogen absorption. • A compressible and strong graphene aerogel (GA) was prepared by a gentle method. • The palladium (Pd) nanoparticles were uniformly supported on the GA. • The formable hydrogen getters were fabricated by integrating Pd-GA with DEB. • The highest hydrogen absorption capacity of Pd-GA/DEB was up to 215.5 cm 3 /g. • The GA can effectively disperse metal particles and accelerate hydrogen diffusion.

Intermetallic alloys as hydrogen getters

Metal hydrides were discovered in the fifties and since then have been widely studied and developed, mainly for energy applications (batteries, hydrogen storage, compression.). In addition to these uses, other properties are considered such as sensors, actuators, or scavengers. This paper proposes a review of intermetallic-based materials for hydrogen gettering. The different chemistries (Zr- or Ti-based compounds) are described in terms of alloying elements and gettering properties. Various aspects, including the activation process, surface coating and resistance to impurities, are also discussed. Finally, new processes and other possible applications are discussed for these materials.

Hydrogenation aging mechanisms of a porous composite with polyethylene as matrix and 1,4-bis(phenylethynyl)benzene as hydrogen getter

Although 1,4-bis(phenylthynyl)benzene (DEB) blended with a carbon supported palladium catalyst (Pd/C) is one of the most widely used irreversible hydrogen getter in a closed environment, it is hard to form and easy to burn. To overcome these deficiencies of this powdery DEB-Pd/C hydrogen getter, a DEB-Pd/C/LDPE porous hydrogen absorbing composite has been developed in our group. In the present work, hydrogen absorption aging mechanisms of this porous hydrogen absorbing composite samples are investigated by using a accelerated aging test method, their hydrogen absorption performances are measured by hydrogen absorption experiments, and their aging mechanisms are studied by X-ray diffraction, attenuated total reflection-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and field emission transmission electron microscope. The results show that both the hydrogen absorption rate and the hydrogen absorption capability of each aging composite sample decrease with the increasing of storage time. The results also show that the decrease of its hydrogen absorption rate is mainly attributed to both the surface migration of its DEB and the surface oxidation of its Pd catalyst, and the decrease of its hydrogen absorption capacity is mainly attributed to the surface migration of its DEB.

Sorption properties of novel-fashioned low-cost hydrogen getters in a high-vacuum-multilayer insulation structure

In a high-vacuum-multilayer insulation structure (HVMLIS), H2 is released into the vacuum jacket by manufactured materials, resulting in the deterioration of the insulation vacuum. Palladium oxide (PdO), which is expensive, is typically used as an H2 getter in HVMLIS. However, PdO generates sparks by vigorously reacting with H2, which are a potential threat to HVMLIS. Therefore, in this work, silver-exchanged zeolite is optimised to obtain an inexpensive and safe Ag–Z getter and a silver molecular sieve (SMS) together with a low-temperature active material getter (AMG). Moreover, an experimental platform was designed to test the H2 sorption properties of the three getters and compare them with traditional PdO. The experiment revealed that the cumulative sorption capacities of PdO, Ag–Z, SMS and AMG were 184.8, 63.1, 124.9 and 5.28 mL/g, respectively. However, the costs of SMS, Ag–Z and AMG were only ~7.37%, 5.08% and 6.13% of the cost of PdO, respectively, indicating that SMS is a promising alternative to PdO, which is expensive. Simultaneously, the microstructure of the H2 getters was analysed via X-ray powder diffraction. Further, PdH0.706 and Pd2H1.5 were obtained in addition to Pd, after H2 was absorbed by PdO. Ag+ was reduced to Ag in SMS, and Cu8O was produced by the reaction of CuO in AMG. These findings provide a basis for the subsequent optimisation of the H2 getters.

Hydrogen absorption properties of Ce23Mg4Ni7 alloy at medium vacuum

Ce–Mg–Ni alloys have a high affinity for hydrogen, and are typical examples of compounds that form hydrides. These hydrides may be formed in medium vacuum by using a hydrogen getter. In this study, Ce23Mg4Ni7 ternary alloy was fabricated by vacuum induction melting. The hydrogen absorption kinetics of the alloy were tested using an automatic Sievers device, and its hydride microstructure was observed via a transmission electron microscopy (TEM). The results indicate that the ternary phase, Ce23Mg4Ni7, is the main phase of the alloy, and the alloy absorbed hydrogen to form a Ce23Mg4Ni7Hx hydride. Under a hydrogen pressure of 5000 Pa at 50 °C, the equilibrium pressure of the system can be reduced to less than 10 Pa. By the eighth time of backfilling to compensate for hydrogen, the equilibrium pressure is reduced to 1 × 10−2 Pa. The Langmuir absorption equation was used to fit the hydrogen absorption results of the alloy, and it was shown that the saturated hydrogen absorption capacity of the alloy is 55.72 mL, and the absorption coefficient is 0.0078 at 50 °C.

Gettering of Hydrogen by Zircaloy Fuel Cladding in Simulated Used Fuel Containers in a Deep Geologic Repository

Hydrogen redistribution and ingress were found to occur between metals proposed for manufacturing containers to store used nuclear fuel in deep geologic repositories. Zircaloy fuel cladding was found to getter hydrogen from steel, and through steel and copper, presumably after disappearance of metal-oxide barriers to hydrogen transport in anoxic conditions expected in-service. Long-term implications for changes in fracture toughness and delayed hydride cracking of the fuel cladding are discussed.

Uptake Rate of Hydrogen Getter for Effectively Removing Outgassed H2 from Microelectronic Packages

Abstract Hydrogen absorption kinetic properties of palladium foil-based getter elements have been studied by manometric method based pressure amplitude measurement. The getter H2 uptake rate can be simply converted by pressure amplitude change, and can be fairly described by a mixed gas sorption modeling analysis. It has been found that the sorption rate of Pd-based getter element has a maximum rate of 40 ppm/min at initial absorption stage but it gets slowly down to 0.5ppm/min when approaching maximum sorption capacity, determined by a getter foil thickness. Based on different H2 outgassing rates of metal and polymer based package materials, a safety factor based methodology has been proposed for down selecting an appropriate getter element that can effectively removing outgassed H2 from microelectronic packages.

Polymer Framework with Continuous Pores for Hydrogen Getters: Molding and a Boost in Getter Rate

The hydrogen getter consisting of 1,4-bis­[phenylethynyl]­benzene (DEB) and a carbon-supported palladium catalyst (Pd/C) is limited by its powder forms in practical application. Development of the molded DEB-Pd/C is thus highly demanded. To solve the contradiction between molding and hydrogen-getter rate, herein, we prepared a porous polymer matrix composite for DEB-Pd/C by a facile one-phase removal method of their cocontinuous polymer matrices. Such a porous composite exhibits excellent hydrogen-getter activities. More interestingly, under low hydrogen partial pressure, the porous composite had a faster getter rate than that of powder getters. The significantly enhanced activity is attributed to the confinement effects of the continuous pore structure of the polymer frameworks, which further indicates its promise as a highly active and flexible supporting framework for hydrogen absorption or other gas–solid reactions.