Hydrogen absorption/desorption properties of Li–Al–N–H composite

Li₃AlH₆ and LiNH₂ at a 1:3 molar ratio were mechanically milled to yield a Li–Al–N–H composite. The hydrogen storage properties of the composite were studied using thermogravimetry, differential scanning calorimetry, mass spectrometry, and X-ray diffraction. Addition of LiNH₂ lowered the decomposition temperature of Li₃AlH₆. The Li–Al–N–H composite began to release hydrogen at around 110 °C, which was 90 °C lower than the initial desorption temperature of Li₃AlH₆. About 7.46 wt% of hydrogen was released from the composite after heating from room temperature to 500 °C. A total hydrogen desorption capacity of 8.15 wt% was obtained after accounting for hydrogen released in the ball-milling process. The resulting dehydrogenated composite absorbed 3.56 wt% of hydrogen at 400 °C under a hydrogen pressure of 110 bar. The hydrogen absorption capacity and kinetic properties of the Li–Al–N–H composite significantly improved when CeF₃ was added to the composite. A maximum hydrogen absorption capacity of 4.8 wt% was reached when the composite was doped with 2 mol% CeF₃.     

Modulating Hydrogen Adsorption via Charge Transfer at the Semiconductor–Metal Heterointerface for Highly Efficient Hydrogen Evolution Catalysis

Designing and synthesizing highly efficient and stable electrocatalysts for hydrogen evolution reaction (HER) is important for realizing the hydrogen economy. Tuning the electronic structure of the electrocatalysts is essential to achieve optimal HER activity, and interfacial engineering is an effective strategy to induce electron transfer in a heterostructure interface to optimize HER kinetics. In this study, ultrafine RhP₂/Rh nanoparticles are synthesized with a well-defined semiconductor–metal heterointerface embedded in N,P co-doped graphene (RhP₂/Rh@NPG) via a one-step pyrolysis. RhP₂/Rh@NPG exhibits outstanding HER performances under all pH conditions. Electrochemical characterization and first principles density functional theory calculations reveal that the RhP₂/Rh heterointerface induces electron transfer from metallic Rh to semiconductive RhP₂, which increases the electron density on the Rh atoms in RhP₂ and weakens the hydrogen adsorption on RhP₂, thereby accelerating the HER kinetics. Moreover, the interfacial electron transfer activates the dual-site synergistic effect of Rh and P of RhP₂ in neutral and alkaline environments, thereby promoting reorganization of interfacial water molecules for faster HER kinetics.     

Replacing C?C Unit with B←N Unit in Isoelectronic Conjugated Polymers for Enhanced Photocatalytic Hydrogen Evolution

Three linear isoelectronic conjugated polymers PCC , PBC , and PBN are synthesized by Suzuki-Miyaura polycondensation for photocatalytic hydrogen (H₂) production from water. PBN presented an excellent photocatalytic hydrogen evolution rate (HER) of 223.5 µmol h⁻¹ (AQY₄₂₀ = 23.3%) under visible light irradiation, which is 7 times that of PBC and 31 times that of PCC . The enhanced photocatalytic activity of PBN is due to the improved charge separation and transport of photo-induced electrons/holes originating from the lower exciton binding energy (E_b), longer fluorescence lifetime, and stronger built-in electric field, caused by the introduction of the polar B←N unit into the polymer backbone. Moreover, the extension of the visible light absorption region and the enhancement of surface catalytic ability further increase the activity of PBN . This work reveals the potential of B←N fused structures as building blocks as well as proposes a rational design strategy for achieving high photocatalytic performance.     

Vesicular Lipidic Systems,Liposomes, PLO,and Liposomes–PLO: Characterization by Electronic Transmission Microscopy

Situations exist in which rapid administration of treatment, as well as maintenance of efficient concentrations for the longest possible time, turns out to be essential. In view of the previous treatment, the elaboration of liposomes, PLO (pluronic lecithin organogel), and the mixture of both is described, as well as their characterizations by electronic transmission microscopy, with the aim of finding out precisely the type of structure for both controlled release systems, its composition, size, homogeneity, and integrity. The period of study has been 90 days. Multilaminar and unilaminar vesicles smaller than 1 μm in diameter were seen in the liposomes, PLO, and liposomes–PLO formulations on transmission electron microscopic (TEM) observation. The technique of characterization reveals the progressive aggregation of the liposomas along the period of study. However, all the vesicles of PLO maintain a defined structure and only a light aggregation 60 days after the elaboration. Changes of morphology and aggregation of liposomas decreased after the incorporation of cholesterol (CH) to the liposomal matrix. The best results were obtained with the formulas liposomes–PLO, which maintain their individuality and integrity during the whole period of study. The combined formulation of liposomas and PLO showed an increase of stability of both lipid systems.     

Density function theory investigation on the thermodynamic properties of the Li–N–H system

The electronic structures and formation enthalpies of compounds in the Li–N–H system have been studied by using the density functional theory. In order to evaluate the competition between each reaction in the system, the chemical potential phase diagrams of compounds in the Li–N–H system have been computed and discussed. Our calculations show that for LiNH₂, Li⁺ combines with [NH₂]^- by an ionic bond. For Li₂NH, the N–H bond displays covalent characteristics. The calculated formation enthalpy of compounds in the Li–N–H system is in agreement with previous results, the LiNH₂ is −212.27 kJ mol⁻¹, LiH is −91.66 kJ mol⁻¹, Li₂NH is −243.14 kJ mol⁻¹, Li₄NH is −309.72 kJ mol⁻¹, Li₃N is −189.11 kJ mol⁻¹, and NH₃ is −102.27 kJ mol⁻¹, respectively. Using the chemical potential phase diagrams, six reversible reactions are discussed. It is found that Li₄NH takes part in the three reversible reactions and some NH₃ formed in the system react with other compounds in the Li–N–H system. These reversible reactions are confirmed by the proposed mechanism from experiments.     

Porous Host–Guest MOF-Semiconductor Hybrid with Multisites Heterojunctions and Modulable Electronic Band for Selective Photocatalytic CO2 Conversion and H2 Evolution

Optimizing catalysts for competitive photocatalytic reactions demand individually tailored band structure as well as intertwined interactions of light absorption, reaction activity, mass, and charge transport.  Here, a nanoparticulate host–guest structure is rationally designed that can exclusively fulfil and ideally control the aforestated uncompromising requisites for catalytic reactions. The all-inclusive model catalyst consists of porous Co₃O₄ host and Zn_xCd_1-xS guest with controllable physicochemical properties enabled by self-assembled hybrid structure and continuously amenable band gap. The effective porous topology nanoassembly, both at the exterior and the interior pores of a porous metal–organic framework (MOF), maximizes spatially immobilized semiconductor nanoparticles toward high utilization of particulate heterojunctions for vital charge and reactant transfer. In conjunction, the zinc constituent band engineering is found to regulate the light/molecules absorption, band structure, and specific reaction intermediates energy to attain high photocatalytic CO₂ reduction selectivity. The optimal catalyst exhibits a H₂-generation rate up to 6720 µmol g⁻¹ h⁻¹ and a CO production rate of 19.3 µmol g⁻¹ h⁻¹. These findings provide insight into the design of discrete host–guest MOF-semiconductor hybrid system with readily modulated band structures and well-constructed heterojunctions for selective solar-to-chemical conversion.     

Transformations Induced by Mechanochemical Activation in the Al–Fe3O4 System

The physicochemical transformations induced by mechanochemical and thermal treatments of Al–Fe₃O₄ mixtures under Ar atmosphere have been investigated. This reaction system underwent a self-sustained reaction after 37 min of high-energy milling, yielding -Fe and -Al₂O₃. The mixtures activated for shorter times showed the same reaction when thermally treated in Ar atmosphere, at approximately 660°C. Depending on the heating conditions, the reaction did or did not occur in a self-sustained way. The influence of the processing parameters on the synthesis and properties of the different materials obtained has been analyzed.     

Modulating Electronic Structure with Copper Doping to Promote the Electrocatalytic Performance of Cobalt Disulfide in Li–O2 Batteries

Introducing heteroatom into catalyst lattice to modulate its intrinsic electronic structure is an efficient strategy to improve the electrocatalytic performance in Li–O₂ batteries. Herein, Cu-doped CoS₂ (Cu–CoS₂) nanoparticles are fabricated by a solvothermal method and evaluated as promising cathode catalysts for Li–O₂ batteries. Based on physicochemical analysis as well as density functional theory calculations, it is revealed that doping Cu heteroatom in CoS₂ lattice can increase the covalency of the Co S bond with more electron transfer from Co 3d to S 3p orbitals, thereby resulting in less electron transfer from Co 3d to O 2p orbitals of Li–O species, which can weaken the adsorption strength toward Li–O intermediates, decrease the reaction barrier, and thus improve the catalytic performance in Li–O₂ batteries. As a result, the battery using Cu–CoS₂ nanoparticles in the cathode exhibits superior kinetics, reversibility, capacity, and cycling performance, as compared to the battery based on CoS₂ catalyst. This work provides an atomic-level insight into the rational design of transition-metal dichalcogenide catalysts via regulating the electronic structure for high-performance Li–O₂ batteries.     

Phase formation in the Ti–Al–Mo–N system during the growth of adaptive wear-resistant coatings by arc PVD

Ti–Al–Mo–N coatings have been grown by arc PVD at different bias voltages, V_b, applied to the substrate and partial pressures of nitrogen reaction gas, p(N₂), in the working chamber. The coatings have a nanocrystalline structure, with an average grain size on the order of 30–40 nm and a layered architecture made up of alternating layers based on a (Ti,Al)N nitride and Mo-containing phases of thickness comparable to the grain size. It has been shown that the phase composition of the coatings depends on V_b and p(N₂): raising the energy of deposited ions by increasing V_b from–120 to–140 V, as well as raising p(N₂) from 0.3 to 0.5 Pa, leads to a more complete molybdenum nitride formation during coating growth, which causes a transition from (Ti,Al)N–Mo–Mo₂N compositions to (Ti,Al)N–Mo₂N. Measurements of the binding energy of Mo 3d photoelectrons in metallic Mo and the Mo₂N nitride by X-ray photoelectron spectroscopy have shown that the transition from the former phase to the latter is accompanied by a negligible energy shift.     

Simultaneously Improved Bendability and Strength of Al–Mg–Si–Cu–Zn Alloys by Controlling the Formation and Evolution of Primary Fe-Rich Phase

In present work, the formation, evolution, and distribution of the primary Fe-rich phase in an Al–Mg–Si–Cu–Zn–Fe–Mn alloy are coupling controlled by ultrasonic melt treatment (USMT) and thermomechanical processing (TMP). It is shown in the results that the size of grains and Fe-rich phase in the as-cast state can be greatly reduced by the applied optimum USMT at 680 °C. Additionally, the transformation rate of β-Fe-rich phase to α-Fe-rich phase can be also enhanced. After the coupling control of USMT and TMP, the number density and distribution uniformity of multiscale Fe-rich particles can be greatly increased or improved, which contributes to the fine-grained recrystallization microstructure and weakened texture. Finally, compared with the 6xxx series Al alloys (such as AA6016 and AA6111), the alloy sheet in the pre-aging state exhibits substantially improved bendability and strength (the plastic strain ratio and tensile strength are 0.67 and 304 MPa, respectively). The effect of USMT on the formation and transformation of primary Fe-rich phase and the mechanisms of improved bendability and strength are deeply discussed.     

Characterisation of the system Li–Na0.90Fe0.90Ti1.10O4 by electrochemical techniques

The electrochemical insertion of lithium has been studied in order to determine, from the potential–composition curves, the domains of single-phase (or solid solution) and two-phase regions in the Li–Na_0.90Fe_0.90Ti_1.10O₄ (Li–NFTO) phase diagram. For this, the step potential electrochemical spectroscopy technique was applied to analyse the Li–NFTO system over a potential range from 3.1 to 1 V vs. lithium. In this voltage range 0.9 lithium ions/formula can be intercalated. Between 0≤x≤0.38, where the variable x is referred as x in Li_xNFTO, a solid solution is obtained. This process takes place in the potential range from 3 to 1.7 V. On the other hand, for x values greater than 0.38 a two-phase domain is developed, which finishes with the complete transformation of Li_0.38NFTO to a compound of formal composition Li_0.90NFTO. This second reduction falls into a lower potential range (1.7–1.3 V).     

Lead-Free Halide Perovskite Cs3Bi2xSb2–2xI9 (x ≈ 0.3) Possessing the Photocatalytic Activity for Hydrogen Evolution Comparable to that of (CH3NH3)PbI3

Lead-free perovskites Cs₃Bi_2xSb_2–2xI₉ (x = 0.1, 0.3, 0.5, 0.7, 0.9) are prepared by a co-precipitation method and their photocatalytic performance for hydrogen production is studied in aqueous HI solution. Compared with the lead-based perovskite (CH₃NH₃)PbI₃, Cs₃Bi_2xSb_2–2xI₉ has a better catalytic performance under air mass 1.5 G (AM 1.5 G) simulated sunlight (100 mW cm⁻²), powders of Cs₃Bi_0.6Sb_1.4I₉ (100 mg) loaded with Pt nanoparticles show < H₂ evolution rate of 92.6 µ mol h⁻¹, which greatly exceeds that of (CH₃NH₃)PbI₃ powders loaded with Pt nanoparticles (100 mg catalyst, 4 µ mol h⁻¹). The Cs₃Bi_2xSb_2–2xI₉ has a high stability, with no apparent decrease in catalytic activity after five consecutive H₂ evolution experiments. The doping of Sb in Cs₃Bi_2xSb_2–2xI₉ effectively reduces the contribution of Bi³⁺ on the conduction band, attenuating the effect of Bi vacancy on band structure. Compared with pure Cs₃Bi₂I₉ and Cs₃Sb₂I₉, Cs₃Bi_2xSb_2–2xI₉ has fewer midgap states and better optical absorption, which greatly enhances its performance for the hydrogen evolution reaction.     

Effect of carbon content on the microstructure and properties of W–Si–C–N coatings fabricated by magnetron sputtering

A series of W–Si–C (4–5 at.%)–N nanocomposite coatings with different C contents have been deposited on Si wafer substrates by reactive magnetron sputtering of W–Si–C composite target in Ar + N₂ mixed atmosphere. Microstructure characteristics and mechanical properties of W–Si–C–N coatings were investigated in this paper. Results exhibited that W–Si–C–N coatings possess nanocomposite microstructure where nano-crystallites W₂(C, N) embedded in amorphous matrix of Si₃N₄/CNx/C. As the C content increased, the hardness and Youngs’ modulus of the W–Si–C–N coatings first increased and then decreased, reaching the maximum value of approximate 36 GPa and 382 GPa, respectively, for coatings containing 11.1 at.% C. All the coatings are in compressive stress state, ranging from 0.8 to 2.0 GPa. In addition, friction coefficient of the W–Si–C–N coatings considerably decreased with the increase of C content.     

Regulating the Electronic Structure of Bismuth Nanosheets by Titanium Doping to Boost CO2 Electroreduction and Zn–CO2 Batteries

The electrochemical carbon dioxide reduction reaction (E-CO₂RR) to formate is a promising strategy for mitigating greenhouse gas emissions and addressing the global energy crisis. Developing low-cost and environmentally friendly electrocatalysts with high selectivity and industrial current densities for formate production is an ideal but challenging goal in the field of electrocatalysis. Herein, novel titanium-doped bismuth nanosheets (Ti Bi NSs) with enhanced E-CO₂RR performance are synthesized through one-step electrochemical reduction of bismuth titanate (Bi₄Ti₃O₁₂). We comprehensively evaluated Ti Bi NSs using in situ Raman spectra, finite element method, and density functional theory. The results indicate that the ultrathin nanosheet structure of Ti Bi NSs can accelerate mass transfer, while the electron-rich properties can accelerate the production of *CO₂⁻ and enhance the adsorption strength of *OCHO intermediate. The Ti Bi NSs deliver a high formate Faradaic efficiency (FE_formate) of 96.3% and a formate production rate of 4032 µmol h⁻¹ cm⁻² at −1.01 V versus RHE. An ultra-high current density of −338.3 mA cm⁻² is achieved at −1.25 versus RHE, and simultaneously FE_formate still reaches more than 90%. Furthermore, the rechargeable Zn–CO₂ battery using Ti Bi NSs as a cathode catalyst achieves a maximum power density of 1.05 mW cm⁻² and excellent charging/discharging stability of 27 h.     

Evolution of damage during the fatigue of 3D woven glass-fibre reinforced composites subjected to tension–tension loading observed by time-lapse X-ray tomography

The development of fatigue damage in a glass fibre modified layer-to-layer three dimensional (3D) woven composite has been followed by time-lapse X-ray computed tomography (CT). The damage was found to be distributed regularly throughout the composite according to the repeating unit, even at large fractions of the total life. This suggests that the through-thickness constraint provides a high level of stress redistribution and damage tolerance. The different types of damage have been segmented, allowing a quantitative analysis of damage evolution as a function of the number of fatigue cycles. Transverse cracks were found to initiate within the weft after just 0.1% of life, followed soon after (by 1% of life) by longitudinal debonding cracks. The number and extent of these multiplied steadily over the fatigue life, whereas the spacing of transverse cracks along with weft/binder debonding saturated at 60% of life and damage in the resin pockets occurred only just before final failure.     

Microstructure and properties of the Si3N4/silica aerogel composites fabricated by the sol–gel method via ambient pressure drying

Si₃N₄ particle reinforced silica aerogel composites have been fabricated by the sol–gel method via ambient pressure drying. The microstructure and mechanical, thermal insulation and dielectric properties of the composites were investigated. The effect of the Si₃N₄ content on the microstructure and properties were also clarified. The results indicate that the obtained mesoporous composites exhibit low thermal conductivity (0.024–0.072 Wm^− 1 K^− 1), low dielectric constant (1.55–1.85) and low loss tangent (0.005–0.007). As the Si₃N₄ content increased from 5 to 20 vol.%, the compressive strength and the flexural strength of the composites increased from 3.21 to 12.05 MPa and from 0.36 to 2.45 MPa, respectively. The obtained composites exhibit considerable promise in wave transparency and thermal insulation functional integration applications.     

Fatigue life estimation under multiaxial random loading by means of the equivalent Lemaitre stress and multiaxial S–N curve methods

In this paper, the frequency domain formula of equivalent Lemaitre stress taking into account the hydrostatic stress effect is first introduced, and the corresponding method for estimating fatigue life under multiaxial random loading is developed based on multiaxial S–N curve. The proposed method is systematically validated with the random bending-torsion fatigue tests and numerical simulations. It has been shown that the hydrostatic stress has a significant influence on multiaxial fatigue life; the results predicted by the proposed method agree well with the experiment, and are more accurate than those obtained for the equivalent von Mises stress method.