Damage-tolerance strategies for nacre tablets.

Nacre, a natural armor, exhibits prominent penetration resistance against predatory attacks. Unraveling its hierarchical toughening mechanisms and damage-tolerance design strategies may provide significant inspiration for the pursuit of high-performance artificial armors. In this work, relationships between the structure and mechanical performance of nacre were investigated. The results show that other than their brick-and-mortar structure, individual nacre tablets significantly contribute to the damage localization of nacre. Affected by intracrystalline organics, the tablets exhibit a unique fracture behavior. The synergistic action of the nanoscale deformation mechanisms increases the energy dissipation efficiency of the tablets and contributes to the preservation of the structural and functional integrity of the shell.

The remarkably improved hydrogen storage performance of MgH2 by the synergetic effect of an FeNi/rGO nanocomposite.

Magnesium hydride (MgH2) has been considered as a promising hydrogen storage material for buildings that are powered by hydrogen energy, but its practical application is hampered by poor kinetics and unstable thermodynamics. Herein, we describe a feasible method for preparing FeNi nanoparticles dispersed on reduced graphene oxide nanosheets (FeNi/rGO), and we confirmed that excellent catalytic effects increased the hydrogen storage performance of MgH2. 5 wt% FeNi/rGO-modified MgH2 began to release hydrogen at 230 °C and liberated 6.5 wt% H2 within 10 min at 300 °C. As for the hydrogenation process, the dehydrogenated sample absorbed 5.4 wt% H2 within 20 min at 125 °C under a hydrogen pressure of 32 bar. More importantly, a hydrogen capacity of 6.9 wt% was maintained after 50 cycles without compromising the kinetics during each cycle. A unique catalytic mechanism promoted synergetic effects between the in situ-formed Mg2Ni/Mg2NiH4, Fe, and rGO that efficiently promoted hydrogen dissociation and diffusion along the Mg/MgH2 interface, anchored the catalyst, and prevented MgH2 from aggregation and growth.

Excellent catalysis of Mn3O4 nanoparticles on the hydrogen storage properties of MgH2: an experimental and theoretical study.

Recently, transition metal oxides have been evidenced to be superior catalysts for improving the hydrogen desorption/absorption performance of MgH2. In this paper, Mn3O4 nanoparticles with a uniform size of around 10 nm were synthesized by a facile chemical method and then introduced to modify the hydrogen storage properties of MgH2. With the addition of 10 wt% Mn3O4 nanoparticles, the MgH2-Mn3O4 composite started to release hydrogen at 200 °C and approximately 6.8 wt% H2 could be released within 8 min at 300 °C. For absorption, the completely dehydrogenated sample took up 5.0 wt% H2 within 10 min under 3 MPa hydrogen even at 100 °C. Compared with pristine MgH2, the activation energy value of absorption for the MgH2 + 10 wt% Mn3O4 composite decreased from 72.5 ± 2.7 to 34.4 ± 0.9 kJ mol-1. The catalytic mechanism of Mn3O4 was also explored and discussed with solid evidence from X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) studies. Density functional theory calculations revealed that the Mg-H bonds were elongated and weakened with the doping of Mn3O4. In addition, a cycling test showed that the hydrogen storage capacity and reaction kinetics of MgH2-Mn3O4 could be favourably preserved in 20 cycles, indicative of promising applications as a solid-state hydrogen storage material in a future hydrogen society.

Effect of Thickness of Molybdenum Nano-Interlayer on Cohesion between Molybdenum/Titanium Multilayer Film and Silicon Substrate.

Titanium (Ti) film has been used as a hydrogen storage material. The effect of the thickness of a molybdenum (Mo) nano-interlayer on the cohesive strength between a Mo/Ti multilayer film and a single crystal silicon (Si) substrate was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and nano-indenter. Four groups of Si/Mo/Ti multilayer films with different thicknesses of Mo and Ti films were fabricated. The XRD results showed that the introduction of the Mo layer suppressed the chemical reaction between the Ti film and Si substrate. The nano-indenter scratch results demonstrated that the cohesion between the Mo/Ti film and Si substrate decreased significantly with increasing Mo interlayer thickness. The XRD stress analysis indicated that the residual stress in the Si/Mo/Ti film was in-plane tensile stress which might be due to the lattice expansion at a high film growth temperature of 700 °C and the discrepancy of the thermal expansion coefficient between the Ti film and Si substrate. The tensile stress in the Si/Mo/Ti film decreased with increasing Mo interlayer thickness. During the cooling of the Si substrate, a greater decrease in tensile stress occurred for the thicker Mo interlayer sample, which became the driving force for reducing the cohesion between the Mo/Ti film and Si substrate. The results confirmed that the design of the Mo interlayer played an important role in the quality of the Ti film grown on Si substrate.

Catalytic Effect of Facile Synthesized TiH1.971 Nanoparticles on the Hydrogen Storage Properties of MgH2.

Abstract: Catalytic doping plays an important role in enhancing the hydrogen storage performance of MgH2, while finding an efficient and reversible catalyst remains to be a great challenge in enhancing the de/rehydrogenation properties of MgH2. Herein, a bidirectional nano-TiH1.971 catalyst was prepared by a wet chemical ball milling method and its effect on hydrogen storage properties of MgH2 was studied. The results showed that all the TiH1.971 nanoparticles were effective in improving the de/rehydrogenation kinetics of MgH2. The MgH2 composites doped with TiH1.971 could desorb 6.5 wt % H2 in 8 min at 300 °C, while the pure MgH2 only released 0.3 wt % H2 in 8 min and 1.5 wt % H2 even in 50 min. It was found that the smaller the size of the TiH1.971 particles, the better was the catalytic effect in promoting the performance of MgH2. Besides, the catalyst concentration also played an important role and the 5 wt %-c-TiH1.971 modified system was found to have the best hydrogen storage performance. Interestingly, a significant hydrogen absorption amount of 4.60 wt % H2 was evidenced for the 5 wt %-c-TiH1.971 doped MgH2 within 10 min at 125 °C, while MgH2 absorbed only 4.11 wt% hydrogen within the same time at 250 °C. The XRD results demonstrated that the TiH1.971 remained stable in cycling and could serve as an active site for hydrogen transportation, which contributed to the significant improvement of the hydrogen storage properties of MgH2.

Superior catalytic effects of FeCo nanosheets on MgH2 for hydrogen storage.

Magnesium hydride (MgH2) is considered as a promising hydrogen storage material for "hydrogen economy" due to its high capacity; however, its stable thermodynamics and slow kinetics hinder its practical applications. Transition metal catalysts attract intense interest in modifying MgH2 systems. Herein, FeCo nanosheets with a thickness of 50 nm were successfully prepared and confirmed to have superior catalytic effects on MgH2. The nano-FeCo-catalyzed MgH2 started to release hydrogen at 200 °C which ended at 320 °C, while the hydrogen desorption process of pure MgH2 occurred at 350-420 °C. Besides, the dehydrogenated FeCo-containing sample could rapidly take up 6.7 wt% H2 within 1 min at 300 °C. Furthermore, after doping with nano-FeCo, the activation energy of hydrogen desorption and absorption was dramatically reduced to 65.3 ± 4.7 kJ mol-1 and 53.4 ± 1.0 kJ mol-1, respectively. In a word, our findings may provide references for designing and producing nano-level intermetallic catalysts for the research area of hydrogen storage or other energy-related research.