Browse
Submit Data
Databases
API
Help

Dataset Information

8 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Comments on "Evidence of the hydrogen release mechanism in bulk MgH₂".

ABSTRACT: The effect of an electron beam induced dehydrogenation of MgH₂ in the transmission electron microscope (TEM) is largely underestimated by Nogita et al., and led the authors to a misinterpretation of their TEM observations. Firstly, the selected area diffraction (SAD) pattern is falsely interpreted. A re-evaluation of the SAD pattern reveals that no MgH₂ is present in the sample, but that it rather consists of Mg and MgO only. Secondly, the transformation of the sample upon in-situ heating in the TEM cannot be ascribed to dehydrogenation, but is rather to be explained by the (nanoscale) Kirkendall effect, which leads to the formation of hollow MgO shells without any metallic Mg in their cores. Hence, the conclusions drawn from the TEM investigation are invalid, as the authors apparently have never studied MgH₂.

SUBMITTER: Surrey A

PROVIDER: S-EPMC5384078 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Comments on "Evidence of the hydrogen release mechanism in bulk MgH2".

Surrey Alexander A Nielsch Kornelius K Rellinghaus Bernd B

Scientific reports 20170407

The effect of an electron beam induced dehydrogenation of MgH2 in the transmission electron microscope (TEM) is largely underestimated by Nogita et al., and led the authors to a misinterpretation of their TEM observations. Firstly, the selected area diffraction (SAD) pattern is falsely interpreted. A re-evaluation of the SAD pattern reveals that no MgH2 is present in the sample, but that it rather consists of Mg and MgO only. Secondly, the transformation of the sample upon ...[more]

PMID: 28387219

Similar Datasets

Evidence of the hydrogen release mechanism in bulk MgH2.

Project description:Hydrogen has the potential to power much of the modern world with only water as a by-product, but storing hydrogen safely and efficiently in solid form such as magnesium hydride remains a major obstacle. A significant challenge has been the difficulty of proving the hydriding/dehydriding mechanisms and, therefore, the mechanisms have long been the subject of debate. Here we use in situ ultra-high voltage transmission electron microscopy (TEM) to directly verify the mechanisms of the hydride decomposition of bulk MgH2 in Mg-Ni alloys. We find that the hydrogen release mechanism from bulk (2??m) MgH2 particles is based on the growth of multiple pre-existing Mg crystallites within the MgH2 matrix, present due to the difficulty of fully transforming all Mg during a hydrogenation cycle whereas, in thin samples analogous to nano-powders, dehydriding occurs by a 'shrinking core' mechanism.

| S-EPMC4327414 | biostudies-literature

Study of the Hydrogen Storage Properties and Catalytic Mechanism of a MgH2-Na3AlH6 System Incorporating FeCl3.

Project description:In this work, the catalytic effects of FeCl3 toward the hydrogen storage properties of the MgH2-Na3AlH6 composite were investigated for the first time. The temperature-programed desorption results indicated that the onset temperature of the hydrogen release of a 10 wt % FeCl3-doped MgH2-Na3AlH6 composite was ∼30 °C lower than that of the undoped MgH2-Na3AlH6 composite. The addition of FeCl3 into the MgH2-Na3AlH6 composite resulted in improved absorption and desorption kinetics performance. The absorption/desorption kinetics measurements at 320 °C (under 33 and 1 atm hydrogen pressure, respectively) indicated that within 10 min, the doped sample absorbed ∼4.0 wt % and desorbed ∼1.5 wt % hydrogen. By comparison, the undoped sample absorbed only ∼2.1 wt % and desorbed only ∼0.6 wt % hydrogen under the same conditions and time. Comparably, the apparent activation energy value of the doped composite is 128 kJ/mol, which is 12 kJ/mol lower than that of the undoped composite (140 kJ/mol). The formation of the new species of MgCl2 and Fe in the doped composite was detected from X-ray diffraction analysis after heating and absorption processes. These two components were believed to play a vital role in reducing the decomposition temperature and kinetics enhancement of the MgH2-Na3AlH6 composite.

| S-EPMC8320109 | biostudies-literature

Synthetic nanocomposite MgH2/5 wt. % TiMn2 powders for solid-hydrogen storage tank integrated with PEM fuel cell.

Project description:Storing hydrogen gas into cylinders under high pressure of 350?bar is not safe and still needs many intensive studies dedic ated for tank's manufacturing. Liquid hydrogen faces also severe practical difficulties due to its very low density, leading to larger fuel tanks three times larger than traditional gasoline tank. Moreover, converting hydrogen gas into liquid phase is not an economic process since it consumes high energy needed to cool down the gas temperature to -252.8?°C. One practical solution is storing hydrogen gas in metal lattice such as Mg powder and its nanocomposites in the form of MgH2. There are two major issues should be solved first. One related to MgH2 in which its inherent poor hydrogenation/dehydrogenation kinetics and high thermal stability must be improved. Secondly, related to providing a safe tank. Here we have succeeded to prepare a new binary system of MgH2/5 wt. % TiMn2 nanocomposite powder that show excellent hydrogenation/dehydrogenation behavior at relatively low temperature (250?°C) with long cycle-life-time (1400?h). Moreover, a simple hydrogen storage tank filled with our synthetic nanocomposite powders was designed and tested in electrical charging a battery of a cell phone device at 180?°C through a commercial fuel cell.

| S-EPMC5643390 | biostudies-literature

MgH2 nanoparticles confined in reduced graphene oxide pillared with organosilica: a novel type of hydrogen storage material.

Project description:Hydrogen is a promising alternative fuel that can push forward the energy transition because of its high energy density (142 MJ kg-1), variety of potential sources, low weight and low environmental impact, but its storage for automotive applications remains a formidable challenge. MgH2, with its high gravimetric and volumetric density, presents a compelling platform for hydrogen storage; however, its utilization is hindered by the sluggish kinetics of hydrogen uptake/release and high temperature operation. Herein we show that a novel layered heterostructure of reduced graphene oxide and organosilica with high specific surface area and narrow pore size distribution can serve as a scaffold to host MgH2 nanoparticles with a narrow diameter distribution around ∼2.5 nm and superior hydrogen storage properties to bulk MgH2. Desorption studies showed that hydrogen release starts at relatively low temperature, with a maximum at 348 °C and kinetics dependent on particle size. Reversibility tests demonstrated that the dehydrogenation kinetics and re-hydrogenation capacity of the system remains stable at 1.62 wt% over four cycles at 200 °C. Our results prove that MgH2 confinement in a nanoporous scaffold is an efficient way to constrain the size of the hydride particles, avoid aggregation and improve kinetics for hydrogen release and recharging.

| S-EPMC11306994 | biostudies-literature

Oxygen Vacancy-Rich 2D TiO2 Nanosheets: A Bridge Toward High Stability and Rapid Hydrogen Storage Kinetics of Nano-Confined MgH2.

Project description:MgH2 has attracted intensive interests as one of the most promising hydrogen storage materials. Nevertheless, the high desorption temperature, sluggish kinetics, and rapid capacity decay hamper its commercial application. Herein, 2D TiO2 nanosheets with abundant oxygen vacancies are used to fabricate a flower-like MgH2/TiO2 heterostructure with enhanced hydrogen storage performances. Particularly, the onset hydrogen desorption temperature of the MgH2/TiO2 heterostructure is lowered down to 180 °C (295 °C for blank MgH2). The initial desorption rate of MgH2/TiO2 reaches 2.116 wt% min-1 at 300 °C, 35 times of the blank MgH2 under the same conditions. Moreover, the capacity retention is as high as 98.5% after 100 cycles at 300 °C, remarkably higher than those of the previously reported MgH2-TiO2 composites. Both in situ HRTEM observations and ex situ XPS analyses confirm that the synergistic effects from multi-valance of Ti species, accelerated electron transportation caused by oxygen vacancies, formation of catalytic Mg-Ti oxides, and stabilized MgH2 NPs confined by TiO2 nanosheets contribute to the high stability and kinetically accelerated hydrogen storage performances of the composite. The strategy of using 2D substrates with abundant defects to support nano-sized energy storage materials to build heterostructure is therefore promising for the design of high-performance energy materials.

| S-EPMC9287516 | biostudies-literature

Evidence for the Fulde-Ferrell-Larkin-Ovchinnikov state in bulk NbS2.

Project description:We present measurements of the magnetic torque, specific heat and thermal expansion of the bulk transition metal dichalcogenide (TMD) superconductor NbS2 in high magnetic fields, with its layer structure aligned strictly parallel to the field using a piezo rotary positioner. The upper critical field of superconducting TMDs in the 2D form is known to be dramatically enhanced by a special form of Ising spin orbit coupling. This Ising superconductivity is very robust to the Pauli paramagnetic effect and can therefore exist beyond the Pauli limit for superconductivity. We find that superconductivity beyond the Pauli limit still exists in bulk single crystals of NbS2 for a precisely parallel field alignment. However, the comparison of our upper critical field transition line with numerical simulations rather points to the development of a Fulde-Ferrell-Larkin-Ovchinnikov state above the Pauli limit as a cause. This is also consistent with the observation of a magnetic field driven phase transition in the thermodynamic quantities within the superconducting state near the Pauli limit.

| S-EPMC8209018 | biostudies-literature

Microstructural Study of MgB2 in the LiBH4-MgH2 Composite by Using TEM.

Project description:The hampered kinetics of reactive hydride composites (RHCs) in hydrogen storage and release, which limits their use for extensive applications in hydrogen storage S1and energy conversion, can be improved using additives. However, the mechanism of the kinetic restriction and the additive effect on promoting the kinetics have remained unclear. These uncertainties are addressed by utilizing versatile transmission electron microscopy (TEM) on the LiBH4-MgH2 composite under the influence of the 3TiCl3·AlCl3 additives. The formation of the MgB2 phase, as the rate-limiting step, is emphatically studied. According to the observations, the heterogeneous nucleation of MgB2 relies on different nucleation centers (Mg or TiB2 and AlB2). The varied nucleation and growth of MgB2 are related to the in-plane strain energy density at the interface, resulting from the atomic misfit between MgB2 and its nucleation centers. This leads to distinct MgB2 morphologies (bars and platelets) and different performances in the dehydrogenation kinetics of LiBH4-MgH2. It was found that the formation of numerous MgB2 platelets is regarded as the origin of the kinetic improvement. Therefore, to promote dehydrogenation kinetics in comparable RHC systems for hydrogen storage, it is suggested to select additives delivering a small atomic misfit.

| S-EPMC9182164 | biostudies-literature

Intermittent bulk release of human cytomegalovirus

Project description:Human Cytomegalovirus (HCMV) significantly remodels host cell processes and membranes to enable effective production of virus progeny. Nascent capsids exit the nucleus and undergo a final morphogenesis process in the cytoplasm where they associate with tegument and membranes. During this process called secondary envelopment, fully assembled virions are formed which are wrapped inside of host vesicles. Both the origin of the receiving membrane as well as the dynamic organization of the envelopment and exocytosis process are not well understood. Enveloped virus particles can be both found individually wrapped in small vesicles but also as accumulations in multivesicular bodies (MVBs). While individually wrapped particles are believed to exit the cell by exocytosis, it is unclear if particles in MVBs ever leave the cell or are actually targeted for lysosomal degradation. Using a novel correlative light and electron microscopy workflow that allows three-dimensional imaging of whole cells, we present evidence that HCMV capsids can bud into MVBs, generating large intracellular accumulations of enveloped virions. Immunofluorescence and fusion assays suggest that these MVBs are positive for markers of the exosomal pathway. Time-lapse as well as functional live-cell imaging showed that MVBs fuse with the plasma membrane and release patch-like accumulations of virus particles. Our data suggests a so far undescribed envelopment and exocytosis pathway of HCMV, possibly involving the late-endosome/exosome pathway, leading to the intermittent bulk release of virus particles.

2022-06-23 | PXD023444 | Pride

Intrinsic Bulk Quantum Oscillations in a Bulk Unconventional Insulator SmB6.

Project description:The finding of bulk quantum oscillations in the Kondo insulator SmB6 proved a considerable surprise. Subsequent measurements of bulk quantum oscillations in other correlated insulators including YbB12 lent support to our discovery of a class of bulk unconventional insulators that host bulk quantum oscillations. Here we perform a series of experiments to examine evidence for the intrinsic character of bulk quantum oscillations in floating zone-grown single crystals of SmB6 that have been the subject of our quantum oscillation studies. We present results of thermodynamic, transport, and composition analysis experiments on pristine floating zone-grown single crystals of SmB6 and compare quantum oscillations with metallic LaB6 and elemental aluminum. These results establish the intrinsic origin of quantum oscillations from the insulating bulk of floating zone-grown SmB6. The similarity of the Fermi surface in insulating SmB6 with the conduction-electron Fermi surface in metallic hexaborides is at the heart of a theoretical mystery.

| S-EPMC7593550 | biostudies-literature

Intermittent bulk release of human cytomegalovirus.

Project description:Human Cytomegalovirus (HCMV) can infect a variety of cell types by using virions of varying glycoprotein compositions. It is still unclear how this diversity is generated, but spatio-temporally separated envelopment and egress pathways might play a role. So far, one egress pathway has been described in which HCMV particles are individually enveloped into small vesicles and are subsequently exocytosed continuously. However, some studies have also found enveloped virus particles inside multivesicular structures but could not link them to productive egress or degradation pathways. We used a novel 3D-CLEM workflow allowing us to investigate these structures in HCMV morphogenesis and egress at high spatio-temporal resolution. We found that multiple envelopment events occurred at individual vesicles leading to multiviral bodies (MViBs), which subsequently traversed the cytoplasm to release virions as intermittent bulk pulses at the plasma membrane to form extracellular virus accumulations (EVAs). Our data support the existence of a novel bona fide HCMV egress pathway, which opens the gate to evaluate divergent egress pathways in generating virion diversity.

| S-EPMC9352052 | biostudies-literature