Ball Milling In Hydrogen Research Articles

Development of Magnesium-Based Material with Hydrogen-Storage Capacity of 7 wt.

TiCl₃ was chosen as an additive to increase hydriding and dehydriding rates of Mg. In our previous works, we found that the optimum percentage of additives that improved the hydriding and dehydriding features of Mg was approximately ten. Specimens consisting of 90 wt% Mg and 10 wt% TiCl₃ (named Mg-10TiCl₃) were prepared by high-energy ball milling in hydrogen. The specimens' hydriding and dehydriding properties were then studied. Mg-10TiCl₃ had an effective hydrogenstorage capacity (the quantity of hydrogen absorbed in 60 min) of approximately 7.2 wt% at 593 K under 12 bar H₂ at the second cycle. After high-energy ball milling in hydrogen, Mg-10TiCl₃ contained Mg, β-MgH₂, and small amounts of γ-MgH₂ and TiH1.924. TiH1.924 remained undercomposed even after dehydriding at 623 K in a vacuum for 2 h. The hydriding and dehydriding properties of Mg-10TiCl₃ were compared with those of other specimens such as Mg-10Fe₂O₃, Mg-10NbF5, and Mg-5Fe₂O₃-5Ni, for which the hydrogen-storage properties were previously reported.

200 NL H2 hydrogen storage tank using MgH2–TiH2–C nanocomposite as H storage material

MgH2-based hydrogen storage materials are promising candidates for solid-state hydrogen storage allowing efficient thermal management in energy systems integrating metal hydride hydrogen store with a solid oxide fuel cell (SOFC) providing dissipated heat at temperatures between 400 and 600 °C. Recently, we have shown that graphite-modified composite of TiH2 and MgH2 prepared by high-energy reactive ball milling in hydrogen (HRBM), demonstrates a high reversible gravimetric H storage capacity exceeding 5 wt % H, fast hydrogenation/dehydrogenation kinetics and excellent cycle stability. In present study, 0.9 MgH2 + 0.1 TiH2 +5 wt %C nanocomposite with a maximum hydrogen storage capacity of 6.3 wt% H was prepared by HRBM preceded by a short homogenizing pre-milling in inert gas. 300 g of the composite was loaded into a storage tank accommodating an air-heated stainless steel metal hydride (MH) container equipped with transversal internal (copper) and external (aluminium) fins. Tests of the tank were carried out in a temperature range from 150 °C (H2 absorption) to 370 °C (H2 desorption) and showed its ability to deliver up to 185 NL H2 corresponding to a reversible H storage capacity of the MH material of appr. 5 wt% H. No significant deterioration of the reversible H storage capacity was observed during 20 heating/cooling H2 discharge/charge cycles. It was found that H2 desorption performance can be tailored by selecting appropriate thermal management conditions and an optimal operational regime has been proposed.

Effect of Various Additives on the Hydrolysis Performance of Nanostructured MgH2 Synthesized by High-Energy Ball Milling in Hydrogen

Effect of Various Additives on the Hydrolysis Performance of Nanostructured MgH2 Synthesized by High-Energy Ball Milling in Hydrogen

Increase in the dehydrogenation rates and hydrogen-storage capacity of Mg-graphene composites by adding nickel via reactive ball milling

Ni was added to increase the dehydrogenation rates of graphene-added Mg with a composition of 95 wt% Mg + 5 wt% graphene (named Mg-5graphene). For this, samples with a composition of 95 wt% Mg + 2.5 wt% Ni + 2.5 wt% graphene (named Mg-2.5Ni-2.5graphene) were prepared by ball milling in hydrogen. Mg-2.5Ni-2.5graphene had significantly higher initial hydrogenation and dehydrogenation rates, with significantly larger quantities of hydrogen absorbed and released over 60 min, than Mg-5graphene. Mg-2.5Ni-2.5graphene exhibited a very high effective hydrogen-storage capacity of approximately 7 wt% at the second cycle (n = 2). We believe that the increase in the Mg crystallite size, leading to a decrease in the grain boundaries, with cycling contributed partly to decreases in the hydrogenation and dehydrogenation rates as n increases. We attributed the partial transformation of graphene into C60 fullerene to the processing of reactive ball milling and the introduction of heat during cycling.

Hydrogen storage behavior of magnesium catalyzed by nickel-graphene nanocomposites

In present study nanocomposites of Graphene Like Material (GLM) and nickel containing 5–60 wt % Ni were prepared by a co-reduction of graphite oxide and Ni2+ ions. These nanocomposites served as effective catalysts of hydrogenation-dehydrogenation of magnesium based materials and showed a high stability on cycling. Composites of magnesium hydride with Ni/GLM were prepared by high-energy ball milling in hydrogen. The microstructures and phase compositions of the studied materials were characterized by XRD, SEM and TEM showing that Ni nanoparticles have size of 2–5 nm and are uniformly distributed in the composites. The kinetic curves of hydrogen absorption and desorption by the composites were measured using a Sievert's type laboratory setup and were analyzed using the Avraami – Erofeev approach. The re-hydrogenation rate constants and the Avraami exponents fitting the kinetic equations for the Mg/MgH2+Ni/GLM composites show significant changes as compared to the Mg/MgH2 prepared at the same conditions and this difference has been assigned to the changes in the mechanism of nucleation and growth and alteration of the rate-limiting steps of the hydrogenation reaction. The composites of Mg with Ni/GLM have a high reversible hydrogen capacity exceeding 6.5 wt % H and also show high rates of hydrogen absorption and desorption and thus belong to the promising hydrogen storage materials.

Synthesis of nanocrystalline Ce13Fe81B6 alloy through mechanically driven disproportionation-recombination process

Nanocrystalline Ce13Fe81B6 alloy powder was synthesized by mechanically driven disproportionation-recombination processing. The microstructure transformation of the alloy during different processing stages was characterized by XRD and TEM. The magnetic properties of the nanocrystalline powder were measured by VSM. The results showed that the Ce2Fe14B matrix phase of the Ce13Fe81B6 alloy was disproportionated into the nanostructured CeH2.51, α-Fe, and Fe2B phases by ball milling in hydrogen for 20 h, and that these nanostructured phases could be desorbed and recombined to nanocrystalline Ce2Fe14B phase again by subsequent vacuum annealing, with the remanence, coercivity, and maximum energy product of the as-synthesized alloy powders achieving 8.1 kGs, 6.02 kOe, and 8.51 MGOe, respectively.

Kinetics and thermodynamics of hydrogenation-dehydrogenation for Mg-25%TM (TM = Ti, Nb or V) composites synthesized by reactive ball milling in hydrogen

0.75Mg−0.25TM−H (TM = Ti, Nb or V) samples were mechano-chemically synthesized by reactive ball milling. The detailed reaction mechanism during hydrogen release and uptake was investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) experiments. The thermodynamic and kinetic properties have been studied by Sievert's method. On the base of calculated values of the Gibbs free energy for reaction of hydrogen absorption (ΔG < 0) it reveals that hydrogenation reaction could thermodynamically proceed at room temperature, which is experimentally confirmed for all of the studied composites. It is clearly shown that β-MgH2 forms at RT under conditions of experiment. Comparative analysis of the MgTi, MgV and MgNb systems makes it possible to establish that the most effective additive facilitating hydrogen uptake, particularly at RT, is vanadium. It provides the degree of conversion into hydride phase α = 0.86 for the first minute of hydrogenation. In contrast, additives of Nb and Ti provide only α = 0.62 and 0.36, respectively, following the 30 min of exposure. However, this study reveals that for the dehydrogenation process, titanium is the best among the examined additives, which is evidenced by lowest value of activation energy Ea = 53.6 kJ/mol of the hydrogen desorption.

Hydrogen Sorption of Pure Mg and Niobium (V) Fluoride-Added Mg Alloys Prepared by Planetary Ball Milling in Hydrogen

Hydrogen Sorption of Pure Mg and Niobium (V) Fluoride-Added Mg Alloys Prepared by Planetary Ball Milling in Hydrogen

Magnesium-based hydrogen storage nanomaterials prepared by high energy reactive ball milling in hydrogen at the presence of mixed titanium–iron oxide

An experimental study was undertaken on the preparation, by High Energy Reactive Ball Milling in Hydrogen (HRBM), of hydrogen storage materials on the basis of Mg mixed with FeTiO3, and their further characterisation (SEM, TEM, XRD, volumetric H2 absorption studies, TDS). It was shown that the addition of ⩾5wt.% of FeTiO3 dramatically improves H absorption in Mg and reduces the temperature of further H desorption. Subsequent addition of carbon, including Graphite (G), Activated Carbon (AC) and Multi-Wall Carbon Nanotubes (MWCNT) results in some slowing of the H absorption down but significantly improves re-hydrogenation performances of the material, which in time is able to re-absorb about 5wt.% H in less than 5–7min (15bar H2/250°C). These improvements were associated with the reduction of FeTiO3 to yield nanoparticles of Fe and TiFe(Hx).

Kinetics of mechanically activated disproportionation of NdFeB alloy during reactive milling in hydrogen: Experimental studies, mechanism and modelling

The process of solid–gas reaction milling in hydrogen was applied to achieve full disproportionation and microstructure nanocrystallization of NdFeB alloy. The NdFeB alloy was disproportionated by room-temperature reactive ball milling in hydrogen, with the mechanical energy serving as the driving force. The reaction progress during milling was examined by hydrogen absorption measurement, and the corresponding microstructure change was characterized by X-ray diffraction (XRD). The mechanism of mechanically activated hydrogenation–disproportionation reaction of NdFeB alloy was investigated. The disproportionation kinetics of an as-cast Nd16Fe76B8 (atomic ratio) alloy during reaction milling was experimentally studied by in-situ monitoring of the hydrogen absorbed by the alloy in the vial. On the assumption that the impact energy to activate the reaction plays a role analogous to that of the thermal energy for the conventional thermally activated process, a theoretical model for the kinetics of the mechanically assisted disproportionation was proposed. By fitting the experimental data with the theoretical model, the kinetic equation and the energy utilization efficiency under different milling conditions were obtained. The effect of milling parameters and hydrogen pressure on the disproportionation kinetics was evaluated and the underlying mechanisms were discussed by referring to the mechanical energy input intensity and the Gibbs free energy change for the reaction.

Magnesium–carbon hydrogen storage hybrid materials produced by reactive ball milling in hydrogen

Time-resolved studies uncovered kinetics and mechanism of Mg–hydrogen interactions during High energy reactive ball milling in hydrogen (HRBM) in presence of various types of carbon, including graphite (G), activated carbon (AC), multi-wall carbon nanotubes (MWCNT), expandable (EG) and thermally-expanded (TEG) graphite. Introduction of carbon significantly changes the hydrogenation behaviour, which becomes strongly dependent on the nature and amount of carbon additive. For the materials containing 1wt.% AC or TEG, and 5wt.% MWCNT, the hydrogenation becomes superior to that for the individual magnesium and finishes within 1h. Analysis of the data indicates that carbon acts as a carrier of the “activated” hydrogen by a mechanism of spill-over. For Mg–G the hydrogenation starts from an incubation period and proceeds slower. An increase in the content of EG and TEG above 1wt.% results in the deterioration of the hydrogenation kinetics. The effect of carbon additives has roots in their destruction during the HRBM to form graphene layers encapsulating the MgH2 nanoparticles and preventing the grain growth. This results in an increase of absorption–desorption cycle stability and a decrease of the MgH2 crystallite size in the re-hydrogenated Mg–C hybrid materials (40–125nm) as compared to Mg alone (180nm).

Desorption–recombination kinetics and mechanism of a mechanically milled nano-structured Nd16Fe76B8 alloy during vacuum annealing

The process of mechanically activated disproportionation by ball milling in hydrogen and subsequent desorption–recombination has been proved to be a promising method to produce nanocrystalline NdFeB-type magnets. Aiming to install higher magnetic properties of NdFeB-type magnet, it is crucial to select properly and optimize the desorption–recombination processing temperature and time to achieve a fully recombined microstructure with homogeneous nano-sized Nd2Fe14B grains. Thus, the desorption–recombination kinetics of the as-disproportionated Nd16Fe76B8 (atomic ratio) alloy during vacuum annealing was experimentally investigated using Mössbauer effect, X-ray diffraction and transmission electron microscopy. The effect of processing time and temperature on the desorption–recombination kinetics to form Nd2Fe14B was elucidated and the underlying mechanisms were discussed by referring to the thermal energy input intensity and the Gibbs free energy change for the reaction. The optimum magnetic properties were achieved by vacuum annealing at 780°C for 30min due to a fully recombination microstructure with uniform grains of 50–55nm in average size. Furthermore, by applying chemical equation for Mössbauer spectra, the transformed fraction of Nd2Fe14B phase during desorption–recombination process was determined, which increased as f=1-exp(−ktn) with n falling in the range of 0.91–0.97. The kinetic equation, the rate constant, the reaction order exponent, and the activation energy for the desorption–recombination reaction to form Nd2Fe14B during vacuum annealing were obtained by fitting the experimental data with the JMAK theory, and thus the kinetics of desorption–recombination can be quantified and evaluated.

MC simulation of desorption–recombination reaction and grain growth of nano-structured disproportionated NdFeB alloy

The process of mechanically activated disproportionation by ball milling in hydrogen and subsequent desorption–recombination has been proved to be a promising method to produce nanocrystalline NdFeB-type magnets. To ensure a fully recombinated microstructure with homogeneous nano-sized Nd2Fe14B grains, the desorption–recombination processing temperature and time should be properly selected or optimized. Thus, Monte Carlo (MC) simulation was performed to elucidate the effect of processing temperature on the kinetics of the recombination reaction to form Nd2Fe14B phase as well as the growth of the recombinated Nd2Fe14B grains. Based on the recombination reaction and grain growth mechanism of the disproportionated NdFeB alloy, a modified Monte Carlo (MC) model was introduced to simulate the kinetics of the reaction and grain growth behavior under various desorption–recombination processing conditions. The results show that the kinetics of both the recombination reaction and the growth of the newly formed Nd2Fe14B grains accelerate with increasing temperature. In particular, the recombination reaction of the disproportionated stoichiometrical Nd2Fe14B (atomic ratio) alloy can be completed in 30min at 800°C, with the grain size of the recombinated Nd2Fe14B phase being 35nm in average. After the finish of the recombination reaction, the growth of the Nd2Fe14B grains will proceed, with the growth rate or kinetics depending on the processing temperature. This paper presents an effective way to simulate the reaction progress and the grain growth during the desorption–recombination processing of nano-structured as-disproportionated NdFeB alloy, which is useful for process control and optimization.

Nanostructured Metal Hydrides for Hydrogen Storage Studied by In Situ Synchrotron and Neutron Diffraction

AbstractThis work was focused on studies of the metal hydride materials having a potential in building hydrogen storage systems with high gravimetric and volumetric efficiencies of H storage and formed / decomposed with high rates of hydrogen exchange. In situ diffraction studies of the metal-hydrogen systems were explored as a valuable tool in probing both the mechanism of the phase-structural transformations and their kinetics. Two complementary techniques, namely Neutron Powder Diffraction (NPD) and Synchrotron X-ray diffraction (SR XRD) were utilised. High pressure in situ NPD studies were performed at D2 pressures reaching 1000 bar at the D1B diffractometer accommodated at Institute Laue Langevin, Grenoble. The data of the time resolved in situ SR XRD were collected at the Swiss Norwegian Beam Lines, ESRF, Grenoble in the pressure range up to 50 bar H2 at temperatures 20-400°C.The systems studied by NPD at high pressures included deuterated Al-modified Laves-type C15 ZrFe2-xAlx intermetallics with x = 0.02; 0.04 and 0.20 and the CeNi5-D2 system. D content, hysteresis of H uptake and release, unit cell expansion and stability of the hydrides systematically change with Al content.Deuteration exhibited a very fast kinetics; it resulted in increase of the unit cells volumes reaching 23.5 % for ZrFe1.98Al0.02D2.9(1) and associated with exclusive occupancy of the Zr2(Fe,Al)2 tetrahedra.For CeNi5 deuteration yielded a hexahydride CeNi5D6.2 (20°C, 776 bar D2) and was accompanied by a nearly isotropic volume expansion reaching 30.1% (∆a/a=10.0%; ∆c/c=7.5%). Deuterium atoms fill three different interstitial sites including Ce2Ni2, Ce2Ni3 and Ni4. Significant hysteresis was observed on the first absorption-desorption cycle. This hysteresis decreased on the absorption-desorption cycling.A different approach to the development of H storage systems is based on the hydrides of light elements, first of all the Mg-based ones. These systems were studied by SR XRD. Reactive ball milling in hydrogen (HRBM) allowed synthesis of the nanostructured Mg-based hydrides.The experimental parameters (PH2, T, energy of milling, ball / sample ratio and balls size), significantly influence rate of hydrogenation. The studies confirmed (a) a completeness of hydrogenation of Mg into MgH2; (b) indicated a partial transformation of the originally formed -MgH2 into a metastable -MgH2 (a ratio / was 3/1); (c) yielded the crystallite size for the main hydrogenation product, -MgH2, as close to 10 nm. Influence of the additives to Mg on the structure and hydrogen absorption/desorption properties and cycle behaviour of the composites was established and will be discussed in the paper.

Synthesis of Mg 15Fe materials for hydrogen storage applying ball milling procedures

The effects of different synthesis procedures on the microstructure and hydrogen uptake characteristics of the Mg 15Fe materials were studied. The applied processes of synthesis consisted basically on ball milling in argon atmosphere followed by a hydriding reaction. Two mill devices with distinct milling modes were employed, i.e. a low energy mill (LEM) (Magneto Uni-Ball-Mill II) and a high energy mill (HEM) (Fritsch Planetary Mill, P6). The HEM sample showed better Mg–Fe mixing degree than the sample obtained from the LEM process due to the small particles of Fe resulting from the larger amount of mechanical energy transferred to the materials by the HEM device. The better Mg–Fe contacting was responsible for the higher hydrogen capacity and faster hydrogen uptake rate of the high energy milled material. Therefore, the HEM procedure was more effective than the LEM. The hydrogen uptake properties of the HEM synthesized material were compared with other Mg-based materials obtained via inert and reactive ball milling without a subsequent activation step. This study showed that Mg 15Fe mixture of powders synthesized via reactive ball milling in hydrogen (RBM–LEM) has higher hydrogen capacity (5.5 wt% H) and faster kinetics than samples with the same composition milled in argon (LEM – 1.65 wt% H and HEM 1.87 wt% H). Nevertheless, a superior hydrogen capacity (6.5 wt% H) were obtained by adding LiBH 4 to Mg 15Fe via HEM in argon atmosphere.

Mechanically Activated Disproportionation and Microstructure Nanocrystallization of a Nd&lt;SUB&gt;14&lt;/SUB&gt;Fe&lt;SUB&gt;66.9&lt;/SUB&gt;Co&lt;SUB&gt;11&lt;/SUB&gt;B&lt;SUB&gt;7&lt;/SUB&gt;Zr&lt;SUB&gt;0.1&lt;/SUB&gt;Ga&lt;SUB&gt;1.0&lt;/SUB&gt; Permanent Magnetic Alloy

In order to obtain nano-structured as-disproportionated microstructure in partially Co-substituted NdFeB-type alloys, the Nd14Fe66.9GCo11B7Zr0.1Ga1.0 alloy was disproportionated by room-temperature reactive ball milling in hydrogen, with the mechanical energy serving as the driving force. The reaction progress during milling was examined by hydrogen absorption measurement, and the corresponding microstructure change was characterized by X-ray diffraction (XRD), Mössbauer spectrometry, and transmission electron microscopy (TEM), respectively. The results show that the Nd2(Fe, Co)14B matrix phase in the alloy can be mechanically disproportionated by a two-stage reaction. Firstly, the Nd2(Fe, Co)14B matrix phase in the alloy is hydrogenated into Nd2(Fe, Co)14BH(x), until the value of x achieves about 2.9 when a full hydrogenation is achieved. After that, the Nd2(Fe, Co)14BH(x) phase is gradually disproportionated into alpha-Fe(Co), NdH2.7, and (Fe, Co)2B phases upon further milling in hydrogen. The as-disproportionated phases NdH2.7, (Fe, Co)2B, and alpha-Fe(Co), are typically nano-structured, with an average grain size of about 10 nm, which lays the basis for synthesizing nanocrystalline Nd2(Fe, Co)14B grains via a subsequent desorption-recombination treatment.

In situ synchrotron X-ray diffraction studies of hydrogen desorption and absorption properties of Mg and Mg–Mm–Ni after reactive ball milling in hydrogen

Reactive ball milling in hydrogen was applied to synthesize nanocrystalline Mg- and Mg8Mm20Ni-based hydrides with crystallite size below 10 nm. These hydrides were studied by in situ synchrotron X-ray diffraction performed at the Swiss–Norwegian Beam Lines of the European Synchrotron Radiation Facility, Grenoble. Characterization of the phase-structural and microstructural state of the constituents during the reversible processes of synthesis and decomposition of the hydrides upon application of hydrogen pressure or vacuum at temperatures 20–350 °C and kinetics of hydrogen uptake was performed. Details of the mechanism of the phase-structural transformations were provided by high time resolution of the synchrotron X-ray diffraction data, high sensitivity in determining formation of the phase constituents, excellent accuracy in yielding the crystallographic characteristics and in probing the microstructural evolution of the constituents formed.

Microstructure nanocrystallization of a Mg–3 wt.%Al–1 wt.%Zn alloy by mechanically assisted hydriding–dehydriding

In order to develop nanocrystalline microstructure in Mg alloy powders, the mechanically assisted hydriding–dehydriding process was proposed, and a pioneering experimental study was performed on a Mg–3 wt.%Al–1 wt.%Zn (AZ31 Mg) alloy. Firstly, the as-cast alloy was hydrided by room-temperature ball milling in hydrogen. Then, a thermal dehydriding treatment was carried out under vacuum. The microstructure change due to hydriding/dehydriding was examined by XRD and TEM, respectively. The results show that the alloy can be mechanically hydrided at ambient temperature, with the polycrystalline Mg phase transformed into nano-structured MgH 2. After a subsequent thermal dehydriding at 350 °C, the MgH 2 is turned into Mg again, and nanocrystalline alloy powders are thus obtained.

Hydrogen reaction kinetics of Mg-based alloys synthesized by mechanical milling

The influence of mechanical milling of Mg-based mixtures on the structure and hydrogen sorption properties was investigated by measuring the rate of hydrogen absorption, nuclear magnetic resonance and X-ray diffraction. In order to separate different factors responsible for hydrogenation kinetics, we compare the results of milling of both pure Mg and the mixture of Mg with different metallic and oxide additives in argon at 77 K and in hydrogen atmosphere at room temperature, with the milling tools made of steel and brass. It was established that the role of grain size and different catalytic additives is considerable only for an initial formation of MgH 2 phase during mechanical activation in hydrogen. The most important effect of mechanical activation at the late stages of milling consists of the formation of a special structural state of the hydrogen-containing phase, independently on the type of the catalyst. The observed enhancement of the proton spin-lattice relaxation rate in the samples prepared by ball milling in hydrogen is attributed to the effect of paramagnetic centers which are an intrinsic feature of such a structural state.

Preparation, microstructure, and magnetic properties of a nanocrystalline Nd 12Fe 82B 6 alloy by HDDR combined with mechanical milling

Nanocrystalline Nd 12Fe 82B 6 (atomic ratio) alloy powders with Nd 2Fe 14B/ α-Fe two-phase structure were prepared by HDDR combined with mechanical milling. The as-cast Nd 12Fe 82B 6 alloy was disproportionated via ball milling in hydrogen, and desorption–recombination was then performed. The phase and structural change due to both the milling in hydrogen and the subsequent desorption–recombination treatment was characterized by X-ray diffraction (XRD). The desorption–recombination behavior of the as-disproportionated alloy was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The morphology and microstructure of the final alloy powders subject to desorption–recombination treatment were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The results showed that, by milling in hydrogen for 20 h, the matrix Nd 2Fe 14B phase of the alloy was fully disproportionated into a nano-structured mixture of Nd 2H 5, Fe 2B, and α-Fe phases with average size of about 8 nm, and that a subsequent desorption–recombination treatment at 760 °C for 30 min led to the formation of Nd 2Fe 14B/ α-Fe two-phase nanocomposite powders with average crystallite size of 30 nm. The remanence B r, coercivity H c, and maximum energy product (BH) max of such nanocrystalline Nd 12Fe 82B 6 alloy powders achieved 0.73 T, 610 kA/m, and 110.8 kJ/m 3, respectively.