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The structural, electronic, and thermodynamic properties of titanium hydride TiH 2 have been investigated using the principles of density functional theory based on the coherent potential approximation (CPA) integrated in the AkaiKKR package, with the aim of reducing the high stability and decomposition temperature to create an ideal material for hydrogen storage, thereby meeting DOE (the U.S. Department of Energy) standard conditions (formation enthalpy ΔH = −40 kJ/mol.H 2 and a decomposition temperature T des from 289 to 393 K).This study focuses particularly on the effects of titanium vacancy creation and the application of uniaxial deformation on the compound. The results show that with 12% of titanium vacancies, the formation energy increase from −122.34 kJ/mol.H 2 to −40.97 kJ/mol.H 2 and the temperature of desorption decreases from 936.045 K to 313.49 K, while −8% compressive uniaxial deformation achieve the value −41.42 kJ/mol.H 2 and 316.97 K. • Enhancing the hydrogen storage properties of titanium hydride by vacancy defects. • 12% titanium vacancies reduce the enthalpy of formation to −40.973 kJ/mol.H 2 and T des to 313.49 K. • 8% compressive uniaxial deformation decreases formation enthalpy to −41.42 kJ/mol.H 2 and T des to 316.97 K. [ABSTRACT FROM AUTHOR]

[Display omitted] The scientific paper presents studies of the radiation-protective features of a polymer composite material for protection against space radiation based on poly-tetra-fluoro-ethylene, Bi 2 O 3 bismuth oxide, WC tungsten carbide, B 4 C boron carbide, TiH 1.7 titanium hydride shot. The composite provides for a high degree of protection against ionizing radiation, including protection against exposure to secondary neutrons: macroscopic fast neutrons removal cross-section (E > 2 MeV) 0.1331–0.1414 cm−1, thermal-velocity neutrons removal cross-section (E < 0.4 eV), cm−1 0.1183–0.1257 cm−1. A shield made of the tailored composition of the proposed 6 cm thick polymer composite attenuates the intensity of neutron radiation by more than 50 % at energies from 0.1 to 5 MeV, in particular, the greatest attenuation of the neutron radiation intensity occurs at an energy of 0.1 MeV with a sharp increase in attenuation when passing through a 2 cm thick shield and complete absorption occurs passing through a 6 cm thick shield. This material can be used to protect astronauts and radio-electronic equipment from the effects of adverse or harmful space factors, including exposure to secondary neutrons, and this material can also be used to protect crews of ships with mobile nuclear reactors such as atomic submarines and nuclear-powered icebreakers. [ABSTRACT FROM AUTHOR]

MgH 2 is a promising hydrogen storage material and its hydrogen desorption kinetics can be enhanced by introducing catalysts. To deeply understand synergetic effect of multiple phases on hydrogen desorption of MgH 2 , the formation mechanism of catalytic phases and their effect on hydrogen storage properties were studied in a MgH 2 - 5 wt% TiF 3 - 15 wt% NiCp 2 composite. The experimental results demonstrate that the nano-sized Mg 2 NiH 4 , TiH 2 and MgF 2 phases can be formed in situ after sample preparation and activation. The in situ formed phases provide a synergetic effect on hydrogen absorption and desorption during subsequent cycling, leading to the significant enhancement of hydrogen desorption kinetics and cycle durability. This work provides guidance for the design and preparation of novel Mg-based materials with excellent hydrogen storage properties. [Display omitted] • Mg 2 NiH 4 , TiH 2 and MgF 2 can be formed in MgH 2 - 5 wt% TiF 3 - 15 wt% NiCp 2 composite. • Mg 2 NiH 4 , TiH 2 and MgF 2 provide a synergetic effect on hydrogen desorption of MgH 2. • Dehydrogenation activation energy of MgH 2 -TiF 3 -NiCp 2 composite is 76.2 kJ mol−1. • MgH 2 -TiF 3 -NiCp 2 composite has a capacity retention rate of 91% after thirty cycles. [ABSTRACT FROM AUTHOR]

Experimental hydrogen loadings in titanium thin films were compared to the Mintz-Bloch model. 500 nm titanium thin films were deposited with an electron-beam evaporator onto sapphire substrates and were capped with a 10 nm palladium thin film. The titanium films were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and loading temperatures of 100 °C, 150 °C, 200 °C and 250 °C. Comparisons of X-ray diffractions of loaded and unloaded films showed the presence of titanium hydride in loaded films. The experimental loadings were compared to the Mintz-Bloch model where the Mintz-Bloch model overpredicted experimental loadings. This was due to the Mintz-Bloch assuming that hydride forms immediately upon hydrogen exposure in the metal. However, the difference between the experimental loading kinetics and Mintz-Bloch model was reduced as loading temperatures increased until the temperature reached 250 °C where some titanium hydride outgassing occurred. • Hydrogen loading of titanium thin films was successfully demonstrated at 100 °C, 150 °C, 200 °C, and 250 °C. • Pressure drops from Sievert apparatus show hydrogen absorption of stoichiometric ratio of 2 hydrogen atoms per titanium atom. • Hydrogen absorption in titanium was confirmed with X-ray diffraction of titanium hydride peak. • Loading kinetics of titanium films compared to Mintz-Bloch model and showed good correlation. [ABSTRACT FROM AUTHOR]

The proton exchange membrane electrolysis cell (PEMEC) is a green and efficient method for producing hydrogen. The flow field structure is a critical factor affecting the performance of electrolysis. However, conventional processing of flow channels is complex and expensive, a novel PEMEC structure utilizing three-dimensional titanium meshes as flow distributors instead of flow channels is proposed. It is found to exhibit higher current density, pressure, hydrogen concentration, and lower temperature than the traditional parallel flow fields. The current density is improved by 88.2 mA/cm2 and the energy consumption is reduced by 0.15 kW h N−1·m−3 at 1.9 V. Based on the uniformity index, the new structure is found to improve the current and temperature uniformity by 20.6% and 13.4%, respectively, when compared to the parallel flow field structure. Additionally, the physical properties of the mesh layers are studied in terms of their influence on electrolysis performance. The increase in porosity and decrease in thickness can enhance the performance of the cell. The results show that a structure with titanium meshes is more beneficial for improving the heat and mass transfer performance and optimizing uniform distribution than the parallel channels, which provides a new direction for the design of electrolysis cell structures. • A novel PEMEC structure with Ti meshes as flow distributors is proposed. • The new structure improves current and temperature uniformity by 20.6% and 13.4%, respectively. • The energy consumption is reduced by 0.09 kW h N−1·m−3 at 1.7 V. • Increasing porosity and decreasing thickness of mesh layers can improve the performance. [ABSTRACT FROM AUTHOR]

The fracture mechanism of hydrogen charged Ti–6Al–4V has been investigated through a multianalytical approach. The difference in hydrogen solubility between β phase (high solubility) and α phase (low) governs the formation and growth pattern of titanium hydrides, and determine the fracture mode of Ti–6Al–4V. Depending on the hydrogen charging extent, the penetration of hydrogen and distribution of hydrides can be divided into three stages. In the initial stage hydrogen diffuses mainly into the β phase, as judged from its increase in Volta potential, and with no hydrides formed. Failure analysis after tensile tests exhibits plastic behavior and a fracture surface with mainly dimples. In the subsequent transition stage, hydrides are formed at the α/β interfaces and along α grain boundaries. More initial cracks occur in the brittle hydrides and the fracture surface transforms from dimple to quasi-cleavage. In the final stage a layer of uniformly distributed hydride is produced on the surface and within the α phase. Supported by nanoindentation measurements, the plasticity of the charged sample diminishes with hydrogen charging time, and an intergranular-transgranular mixed fracture is observed. Overall, the study forms clear evidence that the distribution and cracks of hydrides influence the fracture mode of the Ti-6A-4V alloy. • Hydrides form at α/β interface, grow along α grain boundaries, and occupy α grains. • Cracks initiate and propagate through soft-brittle hydrides. • The presence and distribution of hydrides determine the mode of fractures. • Hydrogen permeation increases the Volta potential difference between β and α phases. [ABSTRACT FROM AUTHOR]

The suppression effects of melamine polyphosphate, titanium dioxide and melamine cyanurate powders on titanium hydride dust explosions were studied using a 1.2 L standard Hartmann tube system, a 20-L spherical vessel testing system, a simultaneous thermal analyzer and a field emission scanning electron microscope. The experimental results showed that the three solid suppressants could effectively decrease the explosion parameters such as flame luminescence intensity, flame propagation velocity and maximum explosion pressure, et al. Because of the different suppression characteristics of the suppressants, their suppression effects on the particles combustion temperatures were significantly different. To completely suppress the dust explosion of titanium hydride, the inerting ratio of the melamine polyphosphate powders was the smallest when compared with those of the titanium dioxide and melamine cyanurate powders. In addition, the field emission scanning electron microscope was used to analyze the residues of a dust explosion. The testing results showed that the thermal decomposition residues of melamine polyphosphate powders were coating on the surface of the unburned titanium hydride particles to make them lose reactivity, that was why the suppression effect of melamine polyphosphate powders was the most effective when compared with titanium dioxide and melamine cyanurate powders. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of NaAlH 4 as a practical hydrogen storage material has seen extensive progress. However, it is still difficult to control the hydrogen storage properties of NaAlH 4 and in particular its hydrogen thermodynamics. Herein, we demonstrate the potential of core-shell NaAlH 4 @Ti nanostructures in altering the hydrogen storage properties of NaAlH 4. To this aim, a facile solvent evaporation method was developed to enable the making of freestanding NaAlH 4 nanoparticles and their individual encapsulation within a Ti shell. These core-shell nanostructures enabled: (i) an effective confining environment for NaAlH 4 and its dehydrogenation products, and (b) fast hydrogen kinetics due to a weakening of the Al–H bond and the shorter diffusion lengths. At 180 °C, a reversible hydrogen storage capacity of 4.4 mass% was observed. More remarkably, this core-shell approach enabled a shift in the equilibrium plateau pressure, therefore demonstrating the possibility to control the hydrogen thermodynamics of NaAlH 4 at the nanoscale. [Display omitted] • Core-shell NaAlH 4 @Ti nanostructures have been successfully synthesized. • This enables fast NaAlH 4 hydrogen kinetics and a reversible hydrogen storage capacity of 4.4 mass%. • This also enables a shift in the plateau pressure and control over the hydrogen thermodynamics of NaAlH 4. [ABSTRACT FROM AUTHOR]

MAX phases are new type of easily machinable cermets, demanded in modern materials science as construction materials. One of the most widely studied and promising representatives of the titanium-based MAX phases are hexagonal Ti 2 AlC and Ti 3 AlC 2. Current methods of their synthesis are unsuitable for their mass production. The creation and development of new methods and technologies for their producing are urgent tasks of materials science. The modern technologies are required providing high quality and productivity, cost-effective, environmentally friendly and easily scaled methods. In 2007, in our Laboratory of High-Temperature Synthesis of the IChPh of Armenian NAS, the Hydride Cycle method (HC) for synthesis of refractory alloys and intermetallic compounds was elaborated. The gist of this method is the use of the synthesized by Self-propagating High-temperature Synthesis mode (SHS) transition metal hydrides as starting materials. In the present work, for the first time, the HC method was applied in the synthesis of Ti 2 AlC and Ti 3 AlC 2 MAX phases. Preliminarily, HCP TiC 0.45 H 1.07÷1.17 , FCC TiC 0.5 H 0.22÷0.73 and TiC 0.67 H 0.31-0.39 titanium carbohydrides were synthesized in the SHS mode and used as starting reagents. The present work was set to study the effect on the phase composition and structure of the synthesized MAX phases of conditions of HC. The analysis methods, used to certify the synthesized MAX phases, were: chemical, differential-thermal, X-ray phase. The microstructures of the samples were snapshot on SEM Prisma E scanning electron microscope. The work resulted in the synthesis in HC of single-phase Ti 2 AlC and Ti 3 AlC 2 MAX phases with unit cell parameters [а = 3.0553; c = 13.6459; c/a = 4.466; P6 3 /mmc] and [a = 3.0552; c = 18.7396; c/a = 6.132], respectively. This work demonstrated advantages of HC over the traditional methods of MAX phases synthesis. [ABSTRACT FROM AUTHOR]

The formation of the Ti substituted Mg 2 Ni alloys, a promising hydrogen storage material for various applications is studied in detail. Mg 1.95 Ti 0.05 Ni alloy and ribbons are successfully prepared by vacuum arc melting and melt spinning methods. The phases, microstructures, and thermal behavior of the alloys and ribbons are characterized by XRD, SEM, TEM, DTA/TG. Sievert-type apparatus is used to study hydrogen sorption properties. Apart from the dominant Mg 2 Ni phase, the formation of MgNi 2 , Mg, and Ni 3 Ti phases is seen in both Mg 1·95 Ti 0·05 Ni alloy and ribbons. During the initial three cycles, Mg 1·95 Ti 0·05 Ni ribbons showed 2 wt % hydrogen storage capacity. To explain the atomic-scale influence of Ti dopant in the studied alloys and hydrides, FP(L)APW + lo method based on Density Functional Theory (DFT) is applied to Mg 2-x Ti x Ni (x = 0.25 and 0.5) alloys and Mg 2-x Ti x NiH 4 (x = 0.25 and 0.5) hydrides. An increase in the Ti dopant on the Mg site leads to the hydrides destabilization. Bader's charge density topology analysis provides insight into the charge transfer and bonding between the constituent atoms. • Partial substitution of a low amount of Ti was carried out in Mg 2 Ni intermetallic alloy. • The melting temperatures of the intermetallic Mg 2 Ni phases in Mg 1·95 Ti 0·05 Ni alloy and ribbons are about 725 °C. • Hydrogen storage capacity of Mg 1·95 Ti 0·05 Ni ribbons reaches 2 wt% at 350 °C. • Ti reduces the stability of the hydride by weakening the binding energy. [ABSTRACT FROM AUTHOR]

Interfacial solar driven water evaporation (ISDWE) and photocatalytic pollutant degradation (PPD) have been considered as efficient and green technologies for tackling the water crisis. Here, through hydrothermal treatment of TiH 1.924 /Ti powders, we designed a hybrid material composed of partially oxidized TiH 1.924 and TiO 2 nanosheets with outstanding ISDWE and PPD performances. Titanium suboxides can be formed inside the compound of partially oxidized TiH 1·924 /TiO 2 nanosheet, and induce efficient solar-thermal transformation. Meanwhile, TiO 2 nanosheet is conducive to reducing the water vaporization enthalpy, ensuring adequate water supply, and enlarging the surface area for evaporation. Due to the synergies between partially oxidized TiH 1.924 and TiO 2 nanosheet, the water evaporation rate achieved 1.70 kg m−2•h−1 under solar radiation of 1.0 kW m−2, which is higher than most reported titanium compounds. The investigation on the PPD performance showed that the photothermal effect and band alignment collaboratively improved the photodegradation of rhodamine B by partially oxidized TiH 1·924 /TiO 2 nanosheets. The excellent PPD property can promote the long-term ISDWE application of partially oxidized TiH 1·924 /TiO 2 nanosheets by avoiding the dye accumulation. This study may provide valuable information for developing advanced composites, ISDWE and PPD technologies. [ABSTRACT FROM AUTHOR]

Mechanism of Hydrogen-induced defects and cracking in Ti and Ti–Mo alloy was systematically analyzed from the perspective of microstructure. Results show that more hydrogen atoms can be dissolved in Ti–Mo alloy due to the existence of β phase, and the precipitation amount of hydride is reduced under the same hydrogen charging conditions. The analysis of positron annihilation results show that the solid solution of Mo element reduces the hydrogen induced defect concentration in the alloy and inhibit the combination of hydrogen and defects. At the same time, Mo atom can affect the electronic structure of Titanium hydrides, and then reduce the bonding between titanium atoms and hydrogen atoms, thereby reducing the formation of brittle titanium hydride. The reduction of hydride and hydrogen induced defect concentration significantly decrease the hardening rate of Ti–Mo alloy, thereby effectively reducing the hydrogen embrittlement sensitivity of titanium and inhibiting its hydrogen absorption cracking tendency. • The formation of β phase in Ti–Mo alloy improves the solubility of hydrogen, thereby reducing the precipitation of hydride. • The solid solution of Mo can affect the electronic structure of titanium hydride and weaken the bonding between Ti–H. • The solid solution of Mo can reduce the concentration of hydrogen-induced defects in Ti–Mo alloy. • Reducing the concentration of hydride and hydrogen induced defect can inhibit hydrogen absorption cracking tendency. [ABSTRACT FROM AUTHOR]

The study belongs to the field of hydrogen materials science. A neutron diffraction study of titanium carbohydride TiC 0.50 H y was carried out in the range of hydrogen concentration у = 0.50 ÷ 0.60. It is shown that high-temperature titanium carbohydride TiC 0·50 H 0.50 of equiatomic composition has a face-centered cubic lattice (sp. gr. Fm 3 ¯ m), where hydrogen atoms are located in tetrahedral interstices. It has been established that in this alloy in vacuum, the phenomenon of hydrogen thermal emission is observed - complete removal of hydrogen with preservation of the FCC lattice of the TiС 0.50 interstitial alloy. For the first time in the Ti–C–H system, a first-order concentration phase transition FCC (sp. gr. Fm 3 ¯ m) → HCP (sp. gr. Pm 3 ¯ 1) in TiC 0.50 H y carbohydride at a hydrogen concentration y > 0.50 was discovered without changing the octahedral environment of carbon atoms and tetrahedral the surroundings of hydrogen atoms by Ti atoms. The HCP phase in vacuum is heat-resistant at temperatures T < 600 K. The unit cell volume of the hcp phase is two times smaller than the unit cell volume of the FCC phases TiC 0.50 H y and TiH 2 of equiatomic composition. The results of studying the fcc phase of the equiatomic composition of TiC 0·50 H 0.50 can be used to prepare a high-temperature hydrogen reservoir in hydrogen energy. The HCP phase can be used as a biological protective material in transport nuclear power plants and on nuclear submarines instead of titanium dihydride TiH 2. [ABSTRACT FROM AUTHOR]

Hydrogen metallurgy, as a green metallurgical technology, is one of the effective ways to reduce carbon emissions. The generation of titanium suboxides (Ti n O 2n-1 , 3 ≤ n ≤ 9) during the hydrogen reduction of ilmenite results in abundant hydrogen and heat loss. In this study, the ability of titanium suboxides to reduce ilmenite is systematically analyzed and confirmed. Thermodynamic calculations reveal that these titanium suboxides exist stably and reduce ilmenite when the reaction temperature exceeds 1100 K. Validation experiments indicate that Ti 3 O 5 can be used to reduce ilmenite to iron and rutile. Furthermore, by controlling the reduction time and holding operation in an inert atmosphere, the discovery of metallic iron particles generated inside unreacted ilmenite. This shows that titanium suboxides can reduce ilmenite, and also the metallization rate of iron is increased. This study has great guideline significance for the clean and green production of ilmenite. • The mechanism of hydrogen reduction of ilmenite is expounded. • Stable existence of titanium suboxides at reaction temperatures exceed 1100 K. • Titanium suboxides can reduce ilmenite is confirmed. • The metallization rate can be increased by holding operation. [ABSTRACT FROM AUTHOR]

Titanium hydride is widely considered as an important hydrogen storage material due to its high capacity, stability and low cost. The microstructure of titanium hydride, which is usually induced by the hydrogenation of titanium, strongly influences its storage performance. However, the relationship between the hydrogenation conditions and the derived microstructure of titanium hydride is still unclear, limiting the development of its structure design strategy. In this work, the microstructure of titanium hydride is correlated with its hydrogenation conditions through the thermodynamics and kinetics. By evaluating the effects of the hydrogenation temperature, pressure and cooling rate, three classes of the hydrogenation processes were clarified: kinetic-limited, continuous and stepwise. Besides, according to the SEM and FIB-STEM results, these different processes are confirmed to greatly vary the bulk microstructure. It is concluded that a fast and continuous transition induces a broken bulk morphology, while a stepwise process leads to a larger bulk grain size. In summary, this study presents a framework for designing titanium hydride structures by modifying phase transition processes through careful adjustment of hydrogenation parameters, namely, a condition-process-structure relationship. This relationship offers crucial guidance in managing the grain refinement or coarsening of hydrides within hydrogen storage components and metallurgical applications. • Effect of hydrogenation conditions on the microstructure of TiD x was studied by electron microscopy. • Marked SEM shows the surface morphology of TiD x exhibited negligible change after hydrogenation. • FIB-STEM shows that the cross-section morphology of TiD x varies significantly according to the hydrogenation conditions. • Three classes of the hydrogenation processes were clarified as kinetic-limited, continuous and stepwise. • Fast and continuous phase transition fractures bulk, while a stepwise one induces relative larger grains. [ABSTRACT FROM AUTHOR]

Interstitial hydrogen atoms in titanium usually deteriorate the mechanical properties of titanium by brittle hydride phase or hydrogen-enhanced localized plasticity. In this study, hydride was used as the second phase to improve the tensile strength and elongation of TA1 pure titanium. The continuous coarse hydride network is precipitated in TA1 pure titanium after the hydrogen-charged. Then pulse current treatment is used to decompose the original coarse hydride network and reduce the size and number of hydride strips. Finally, a small uniform hydride network is formed in TA1 pure titanium. The results of tensile experiments indicate that the tensile strength of hydrogen-charged TA1 pure titanium treated by pulse current increases from the 286.4 MPa to 316.1 MPa and the elongation increases from the 47.6 % to 56.8 %. The improvement of mechanical properties demonstrate that the small and uniform hydrides can significantly improve the mechanical properties of TA1 pure titanium. In hydrogen-charged TA1 pure titanium treated by pulse current, the increment of strength is mainly caused by hard phase hydrides, and the increase in plasticity is attributed to the role of twins in coordinating deformation during plastic deformation. This study manifests that in addition to being used as a temporary alloying element to optimize the microstructure of titanium, hydrogen can also be directly act as a second phase in titanium to improve the mechanical properties. • Hydride was used for the first time to improve the tensile strength and elongation of Ti. • Hydride and deformation twin are the essential mechanism of tensile properties improvement of Ti. • Interstitial hydrogen has the potential to improve the mechanical properties of titanium. [ABSTRACT FROM AUTHOR]

In this study, it is revealed for the first time that ultra-high-speed impact can trigger in-situ dehydrogenation at the impact interface of titanium hydride (TiH). This phenomenon leads to a phase transformation from brittle TiH to ductile Ti, causing a shift in the ductile-to-brittle transition from the impact interface to the particle interior. Inspired by this unique behavior, and considering the mechanical interactions between particles during the spray process, TiH powders were used as feedstock to successfully produce a large-scale random cellular structure through cold spray. A systematic investigation of the deposition process revealed that unbroken TiH particles interact with dehydrogenated ones, resulting in only the ductile portion of the TiH particle being deposited, while the brittle interior is spalled off, consequently forming the "walls" of the cellular structures. This work highlights the potential of TiH powders to advance cold spray technology, particularly in the creation of complex cellular structures. [Display omitted] [ABSTRACT FROM AUTHOR]

TiH 2 has gradually gained attention in powder metallurgy because of its unique properties. This study systematically investigated the porosity, density, mechanical tensile properties, and fracture toughness of sintered samples of TiH 2 as a powder metallurgy starting material. The results showed that, compared with hydrogenation-dehydrogenation titanium (HDH Ti), the density, elongation, and fracture toughness of the sintered TiH 2 samples significantly improved. In addition, the contributions of grain size, porosity, and oxygen content to the yield strength of the samples are discussed, and the results revealed that a lower oxygen content and porosity are the main reasons for the differences in the mechanical properties between HDH Ti and TiH 2. Finally, the experimental results are combined with first-principles calculations and simulations to construct a TiH 2 phase transition model. The contribution of H atoms to the TiH 2 phase transition energy barrier and activation sintering densification was investigated and elucidated, revealing the TiH 2 sintering densification mechanism from the perspective of phase transition. The derived results contribute to a deeper understanding of the intrinsic mechanism of TiH 2 activation sintering densification, which is highly important for the development of advanced titanium materials. • The fracture toughness of TiH 2 sintered sample is higher than HDH Ti. • Lower yield strength of TiH 2 is attributed to grain size and oxygen content. • Higher density of TiH 2 sintered materials is related to grain growth. • H atom reduces TiH 2 phase transition barrier (δ →α). • Revealed the densification mechanism from the perspective of phase transition. [ABSTRACT FROM AUTHOR]

Pathogenic wound infections remain a major global health challenge. When skin tissue is wounded, some colonizing pathogenic bacteria secrete large amounts of hyaluronidase (HAase) to degrade the extracellular matrix (ECM), enabling their diffusion and proliferation. Current clinical techniques for detecting infection rely on basic visual cues or analysis of wound fluids, enabling only reactive treatment once severe signs manifest. Herein, we present the use of a closed-loop patch (CLP) for advanced wound management. The patch contains a bio-inspired sensor based on an engineered hyaluronic acid (HA) hydrogel that detects HAase secreted by invading pathogens. This detection triggers a quantifiable change in the capacitance of the interdigital electrode and achieving in-time detection of Staphylococcus aureus (S. aureus) infection in a murine wound model before obvious visual signs appear. In response, the release of titanium hydride (TiH 1.924) nanodots from hydrogel decomposition can eradicate pathogens under ultrasound (US) irradiation. Concurrently, the product, HA fragments further promoted cell migration and angiogenesis to significantly improve wound healing by ∼14.6-fold rates in 12 days. Overall, the CLP provides a sensory act-treat effect according to the wound status, which facilitate the closed-loop integration of monitoring and rehabilitation. This strategy may provide additional possibilities for the design of future wound management systems. [Display omitted] • The CLP achieved in-time detection of S. aureus infection before obvious visual signs appear. • THgel decomposition releases TiH 1.924 nanodots that eradicate bacteria under US irradiation. • THgel decomposition releases HA fragments that improving wound healing rates. • The CLP integrates monitoring and rehabilitation, facilitating closed-loop wound management systems. [ABSTRACT FROM AUTHOR]

• The failure of titanium tank utilized for production and storage of molten Na 2 S was studied. • The hydride-induced embrittlement was identified as the failure cause of titanium tank. • The side products of H 2 , H 2 S, and Na 2 SO 3 lead to the formation of titanium hydride structure. • The effect of Na 2 CO 3 addition into the reactive media as a preventive action was investigated. The corrosion failure of a titanium tank operating under high temperature of 220 °C for the production and storage of molten Na 2 S was thoroughly analyzed in this study. The various material characterization methods, such as visual inspection, microscopic observation, chemical analysis, and mechanical assessment, demonstrated that hydride-induced embrittlement plays a considerable role in the failure of the titanium tank. The key finding was that side products of H 2 , H 2 S, and Na 2 SO 3 cause the destruction of the passive oxide film and, thus, provide the conditions for the absorption and penetration of atomic hydrogen, resulting in the formation of brittle TiH 2 and subsequent flaking on the surface. To failure prevention of the titanium tank in such environments, the selection of tank material from Monel® 400, blowing nitrogen gas into the system, and loading Na 2 CO 3 into the reactive media were proposed. By complementary electrochemical investigations, it was clarified that Na 2 CO 3 can stabilize the passive oxide film on the titanium surface and, therefore, enhance the resistance of the titanium tank against corrosion and failure. Notably, the present study can provide helpful references for enhancing the safety maintenance management of similar types of equipment. [ABSTRACT FROM AUTHOR]

Hydride induced embrittlement is one of the main causes for the stress corrosion crack of titanium alloys. The formation process of the hydride at atomic level remains controversial as it is not accessible directly by experiments. In the present work, the formation of titanium hydride is investigated by using a first principles method. By calculating the formation energies of TiH m with various types of H occupation state in HCP and FCC Ti matrix, we show that there exists phase equilibrium between α-Ti-H solid solution and δ/ε hydrides with χ and γ hydrides appearing as metastable phases. The energy barrier for the HCP → FCC structure transformation for the formation of the hydrides decreases with increasing H:Ti ratio m. The structure transformation is accompanied with spontaneous shift of half amounts of the H atoms from the octahedral to the tetrahedral interstices. The energy barrier for the migration of the remaining half of the H atoms from the octahedral to the tetrahedral interstices reduces with increasing m and approaches to a constant value. The hydrostatic compressive stress acting on TiH m , resulted from the H-induced lattice dilation tendency and the constraint of the surrounding matrix, does not facilitate the HCP → FCC transformation and the migration of the H atoms. The present work sheds light on the hydride formation process at atomic level. [Display omitted] [ABSTRACT FROM AUTHOR]

This study explores the delaying of the formation of helium bubbles and blisters in pure titanium by hydrogen pre-implantation. Titanium, implanted with helium (40 KeV, 5 × 1017 ions/cm²), exhibited large bubbles that cause exfoliation after heat treatment, whereas hydrogen pre-implantation inhibited bubble growth at room temperature and reduced the exfoliation after heat treatment. In the samples pre-implanted with hydrogen, we found evidence of helium diffusion delay by: (a) a fourfold reduction in bubble pressure (b) faceted cavities in the samples (c) a smaller increase in titanium lattice parameters (d) a 16-fold reduction in average bubble size and a sixfold reduction in bubble area fraction (e) a more than twofold decrease in exfoliation (f) a tendency toward the formation of larger bubbles as a result of heat treatment. We believe that it is reasonable to assume that the inhibition of helium diffusion between tetrahedral interstitial lattice sites takes place because of the occupation of the intermediate octahedral sites by hydrogen atoms. Evidence for the opposite effect, that is inhibition of the diffusion of hydrogen in the presence of helium, is found in the retention of hydrogen in the specimens at elevated temperatures. This retention allowed the existence of titanium hydride after heat treatment at 680 °C. The present study sheds light on the intricate interplay between hydrogen and helium in titanium, providing insights into mechanisms that can potentially mitigate helium-induced damage in materials. [ABSTRACT FROM AUTHOR]

First-principles density functional theory (DFT) calculations were performed to investigate the effect of ternary alloying on the hydrogenation properties of the TiFe system. Al, Be, Co, Cr, Cu, Mn and Ni were selected as substitutional elements for Fe sites, in the light of their reported enhancement of activation, kinetic and thermodynamic properties. The use of special quasi-random structures to account for disordering of solute elements in the sub-lattice allowed a quantitative assessment of substitutional effects on the hydrogenation behaviour of single-phase TiFe 1-x M x alloys, up to a solute concentration as high as 40 at.%. The energy of monohydride formation obtained by DFT calculations, approximated to the enthalpy of formation, was discussed in terms of changes in lattice parameter and hence plateau pressure. Based on the consistency between DFT calculations and earlier experimental results, a linear relationship between monohydride formation energy/enthalpy and plateau pressure was proposed as a simple method to predict the value of one of these physical properties from the other. The obtained correlation could therefore turn out to be a helpful tool to predict the ab/desorption plateau pressure of unexplored vast multi-component systems from DFT calculation, or, the other way around, could allow to estimate the formation enthalpy from only one pressure-composition-isotherm (PCI) measurement hence without the need of Van't Hoff plot. [Display omitted] • The hydrogenation properties of TiFe 1-x M x alloys are studied by DFT calculations. • Al, Be, Co, Cr, Cu, Mn and Ni are selected as substitutional elements for Fe sites. • Special quasi-random structures are used to consider disordering of solute elements. • Substitutional effects are assessed quantitatively for actual alloy compositions. • A simple relationship correlates monohydride formation energy and plateau pressure. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction depends on the accumulation of electrons on the catalytic center to enable the two-electron processes involved in water reduction. This work reports on the modification of inexpensive nickel (Ni) composite electrodes with engineered semiconductor heterojunctions based on earth-abundant transition metals that show superior hydrogen generation activity in the presence of a non-toxic electrolyte (K 2 CO 3). This is, small amounts of cobalt (Co) or copper (Cu) oxides can improve the reactivity of composite electrodes formed by deposition of titanium (Ti) or niobium (Nb) semiconductors onto Ni surfaces. In general, modified Nb-based semiconductors show better performance and their enhanced activity can be understood in terms of modified surface potentials upon formation of semiconductor-Ni heterojunctions. Photoelectrochemical activity can be detected in the presence of Cu oxides, where hydrogen generation onset potential is reduced under UV–Vis light irradiation. The study demonstrates that small composition changes can greatly affect the activity of Nb-based Ni composite electrodes, showing exciting new applications for Nb-based materials. [Display omitted] • Small amounts of Co or Cu species greatly affect Nb-based Ni composite electrodes activity. • Similar Cu loadings suggest electrode enhanced activity depends on the semiconductor. • Cu oxides-Nb phosphate heterojunction shows the highest catalytic activity. • Cu species induce slight photoelectrochemical effects. [ABSTRACT FROM AUTHOR]

Porous Mo 2 Ti 2 AlC 3 was synthesized by reactive synthesis of the mixed powder of molybdenum, aluminum, titanium hydride and graphite at 1500 °C. The effects of sintering temperature on the phase transition and pore structure parameters of porous Mo 2 Ti 2 AlC 3 were deeply discussed, and the pore forming mechanism in the sintering process was further deduced. The results showed that the pore formation of porous Mo 2 Ti 2 AlC 3 consists of the following aspects: (i) At 500 °C, stearic acid was completely pyrolyzed; (ii) At 700 °C, titanium hydride was completely decomposed into titanium and hydrogen via endothermic reaction; (iii) The partial diffusion effect of aluminum in the formation of TiAl and Mo 3 Al intermetallic compounds; (iv) The solid-solid reaction of titanium and molybdenum with graphite generated TiC and Mo 2 C; (v) TiC, Mo 2 C, Ti 2 AlC, Mo 3 Al and graphite further reacted to form Mo 2 Ti 2 AlC 3 ,where pore formation was mainly controlled by (iii) and (v). In addition, the corrosion resistance and mechanical properties of porous Mo 2 Ti 2 AlC 3 were also explored. [ABSTRACT FROM AUTHOR]

The influence of electrochemical charging of hydrogen at j = −5 mA/cm2 for 6, 12, 48 and 96 h on the structural and the mechanical behavior of wrought and electron beam melting (EBM) Ti–6Al–4V alloys containing 6 wt% β and similar impurities level was investigated. The length of the α/β interphase boundaries in the EBM alloy was larger by 34% compared to that in the wrought alloy. The small punch test (SPT) technique was used to characterize the mechanical behavior of the non-hydrogenated and hydrogenated specimens. It was found that the maximum load and the displacement at maximum load of the wrought alloy remained nearly stable after 6 h of charging, showing a maximum decrease of ∼32% and 11%, respectively. Similarly, hydrogenation of the EBM alloy resulted in a gradual degradation in mechanical properties with charging time, up to ∼81% and 86% in pop-in load and displacement at the "pop-in" load, respectively. The mode of fracture of the wrought alloy changed from ductile to semi-brittle with mud-cracking in all hydrogenated specimens. In contrast, the mode of fracture of the EBM alloy changed from a mixed mode ductile-brittle fracture to brittle fracture with star-like morphology. The degraded mechanical properties of the EBM alloy are attributed to its α/β lamellar microstructure which acted as a short-circuit path and enhanced hydrogen diffusion into the bulk as well as δ a and δ b hydride formation on the surface. In contrast, a surface layer with higher concentration of δ a and δ b hydrides in the wrought alloy served as a barrier to hydrogen uptake into the bulk and increased the alloy resistivity to hydrogen embrittlement (HE). This study shows that EBM Ti–6Al–4V alloy is more susceptible to mechanical degradation due to HE than wrought Ti–6Al–4V alloy. [Display omitted] • Hydrogen effects on electron beam melting (EBM) and wrought Ti–6Al–4V are compared. • Electrochemical hydrogenation and the small punch test (SPT) are employed. • The EBM alloy is more susceptible to hydrogen embrittlement than the wrought alloy. • The fracture mode changes dramatically due to exposure to hydrogen. • Different hydrogen effects arise from different microstructures and oxygen content. [ABSTRACT FROM AUTHOR]

The impact of mechanochemical activation and methods of addition of non-hydrolyzing salts of NaCl, NH 4 Cl, NH 4 Br и MgCl 2 ∙(either dry powder or solution) on the reaction rate and yield of hydrogen production upon magnesium hydride oxidation by water was investigated. It was established that addition of halides increases the hydrogen yield from 22% to 99% (of theoretical value) while the rate of hydrogen production has increased from ∼220 to 1700 mL/min g (MgH 2). The addition of dry salts during the mechanochemical treatment of the hydride always results in much higher reaction rate compared to the use of the same salt solutions. It was observed that activation by NH 4 Cl and MgCl 2 results in bell-shaped change in the hydrogen release rate. Of all evaluated halide salt activators, the greatest overall yield (∼99%) was achieved in the presence of 0.17 M NaCl solution. The reaction rate at these conditions was rather slow; it took up to 4 h to complete the oxidation. The highest rate of oxidation, when 94% of theoretical yield was achieved in 3 min, was observed in the presence of 0.85 M NH 4 Br. [Display omitted] • Non-hydrolysable halides enhance H 2 generation by MgH 2 oxidation with water. • Performance of salts depends on adding techniques. • Paired combination of salts gives no additional effect. • The highest reaction rate and H 2 yield was observed for NH 4 Br. [ABSTRACT FROM AUTHOR]

Thermal decomposition of titanium hydrides in electrochemically hydrogenated electron beam melting (EBM) and wrought Ti–6Al–4V alloys containing 6 wt% β is compared. Differential scanning calorimetry (DSC) is used to identify phase transitions. High-temperature X-ray diffraction (HTXRD) is used to identify phases and determine their contents and crystallographic parameters. Both alloys are found to contain α H (hcp) and β H (bcc) solid solutions, as well as δ a (fcc) and δ b (fcc) hydrides after hydrogenation. δ a is found to decompose between room temperature and 350 °C to α H (in both alloys) plus either β H and δ b (wrought alloy) or δ b only (EBM alloy). δ b fully decomposes at either 450 °C (wrought alloy) or 600 °C (EBM alloy) to α H plus H 2 desorption (which starts at 300 and 350 °C in the wrought and EBM alloys, respectively). In the case of the wrought alloy, β H is also formed in this decomposition reaction due to faster diffusion of hydrogen. The non-continuous, finer needle-like morphology of the β-phase in the as-printed EBM alloy combined with its smaller lattice constants seem to inhibit hydrogen diffusion into the bulk alloy through the β-phase, thus triggering δ a dissociation into δ b (rather than to β H +δ b) and δ b decomposition into α H (rather than to α H + β H). Hydrogen incorporation in the α H phase results in its expansion in the c direction in both alloys. HTXRD allows to conclude that both δ a and δ b hydrides decompose up to 600 °C. Hydrogen peaks measured at higher temperatures are due to hydrogen desorption from the hydride that is decomposed from the sample's bulk and/or hydrogen desorption from β H and/or α H during heating. These findings indicate that the EBM Ti–6Al–4V alloy might be more prone to hydrogen damage at elevated temperatures than its wrought counterpart when both have a similar β-phase content. • Dehydrogenation of hydrogenated EBM and wrought Ti–6Al–4V alloys is compared. • The kinetics and products of hydride decomposition are different in the two alloys. • The differences result from different microstructures of the origin alloys. • Decomposition of δ a to δ b is reported here for the first time. • The EBM alloy may be more prone to hydrogen damage at elevated temperatures. [ABSTRACT FROM AUTHOR]

In a recent study, it was observed that electrochemical charging with hydrogen produces microvoids both in wrought and in additively manufactured, electron beam melted (EBM) Ti–6Al–4V alloys. This result is surprising since titanium forms stable hydrides and has an exothermic heat of hydrogen solution. By comparison, hydrogen bubble formation is typically observed only in metals and alloys with an endothermic heat of hydrogen solution that do not form hydrides. Here, we evaluate possible mechanisms for the formation of microvoids and bubbles in Ti-based alloys. Additional experimental work confirms that voids do not form in electrochemically hydrogenated, single-phase, pure wrought Ti, whereas they do form in the wrought Ti–6Al–4V alloy hydrogenated under the same conditions. In commercially pure Ti (CP–Ti), hydride is formed from the surface inward, and the surface is brittle and heavily cracked and disintegrated. By contrast, in the two-phase alloy, hydrides are formed also deeper in the bulk, and microvoids are evident both adjacent to the surface and along interphase boundaries. Alongside the forming hydride, the surface integrity is maintained, although some cracks are formed due to microvoid coalescence. While the incorporation of hydrogen into the alloy causes a large increase in its volume, we note that the precipitation of hydride from a supersaturated solution causes a net contraction. We suggest that the mechanism that best reflects the experimental evidence of microvoids formation is a manifestation of the contraction that results from hydride precipitation from a hydrogen-supersaturated alloy. • Microvoids are observed in wrought Ti–6Al–4V after electrochemical hydrogenation. • Such voids do not form in wrought, single-phase, CP-Ti. • Such voids are abnormal in hydride-forming metals with exothermic heat of solution. • Shrinkage due to hydride precipitation is suggested as leading to void formation. • Multiphase and fast diffusion paths into the bulk alloy promote void formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • TiH 2 powder demonstrated sintered density higher than Ti HDH powder. • Powder of small particle size or narrow PSD resulted in higher sintered density. • Low oxygen content can be obtained in TiH 2 - based sintered samples. • TiH 2 -based sintered samples exhibited better balance of strength and ductility. In the powder metallurgy of titanium and titanium alloys, titanium powders produced through hydrogenation/dehydrogenation (HDH) approach and titanium hydride powder are extensively used. The choice of initial powder greatly influences the properties and performance of as-sintered materials. In the present study, comparative experiments were performed on two powders of various sizes to elucidate the peculiarities of their densification process and the characteristics (as-sintered density, impurity content, and tensile properties) of the processed materials. As expected, the sintering performance of both powder-type compacts were greatly affected by the specific surface and contact areas, so finer powders and higher compaction pressures were used to achieve higher densities upon sintering. However, the systematic results clearly indicated the advantage of using titanium hydride powder as a starting material in titanium powder metallurgy. At equal size, compaction, and sintering parameters, materials processed from titanium hydride powder had higher density and lower impurity content, thereby providing better balance of tensile properties compared with materials processed from HDH titanium powder. This advantage is explained by the higher relative density of green compacts made of brittle titanium hydride powder and by the higher sintering ability of such compacts activated by powder-released hydrogen. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) simulations are utilized to study the absorption and diffusion of hydride ions along four types of titanium nitride grain boundaries: open and compact structures of Σ5 (210)[001] and Σ5 (310)[001]. The absorption energy into bulk vacancies ranges from approx. −0.7 eV in TiN 0.7 to −0.38 eV for a single vacancy in TiN, and shows a minor dependence on the hydrogen content in the structure. The absorption energy for vacancy sites at the grain boundaries ranges from −0.44 eV to −0.66 eV. Hydrogen absorption into interstitial sites at the grain boundaries is less favourable, in part due to a positive and fairly large zero-point energy contribution, with absorption enthalpies between −0.09 eV and 0.06 eV. The interstitial diffusion barriers are 1.34 eV and 0.83 eV in the open Σ5 (310) and Σ5 (210) grain boundaries, respectively. In the compact grain boundaries, the migrating hydrogen species changed oxidation state from a hydride ion (H0.5−) to a proton (H0.3+) at the transition state as it formed bonds to nitrogen along the diffusion path. The diffusion barriers are larger than in the corresponding open structures: 1.75 eV and 1.02 eV in the compact Σ5 (310) and Σ5 (210) structures, respectively. The considered grain boundaries and diffusion pathways cannot explain the fast interfacial hydride ion transport reported for hydrogen separation membranes based on TiN x thin films with columnar microstructure. [Display omitted] [ABSTRACT FROM AUTHOR]

The mechanism of hydrogen embrittlement in grade 2 titanium was studied by a combined micro and nanoscale approach. Insights into the hydrogen related deformation and degradation mechanisms were acquired via a unique characterisation procedure, correlating the topological observations on the fracture surface after tensile testing to the dislocation arrangement underneath. Focused ion beam lift-out was employed to extract a subsurface slice perpendicular to the fracture surface. High resolution characterisation provided information about the dislocation configuration and active hydrogen-assisted degradation mechanism. A high hydrogen content forms a brittle titanium hydride phase, failing via hydride cleavage. At a moderate hydrogen quantity, hydrogen in solid solution is responsible for a ductility decrease via the hydrogen-enhanced localised plasticity mechanism. [Display omitted] • Investigation of hydrogen embrittlement in titanium at micro and nanoscale. • Distribution of dislocations reveals hydrogen dependent deformation mode. • Indications of degradation via hydrogen enhanced localised plasticity mechanism. • Material degradation via brittle hydride cleavage at high hydrogen concentrations. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement is a prevalent issue that restricts the use of titanium as a structural material. To comprehend the hydrogen embrittlement mechanism, it is necessary to investigate the intrinsic mechanical properties of hydrides in titanium. In this study, a fragile to strong transition is observed in δ -TiH 2 at 423 K. The in situ high temperature nuclear magnetic resonance measurements reveal that the occupancy of hydrogen atoms undergo a transition from octahedral sites to tetrahedral sites at the same temperature. Further first-principles calculations reveal that the decrease in the generalized stacking fault energy, resulting from the modification in the hydrogen atom occupancy, is the primary reason for the enhancement in the mechanical properties of δ -TiH 2. This study suggests comprehending hydride fracture toughness through the lens of hydrogen atom occupancy, providing a novel research perspective on the hydrogen-induced embrittlement mechanism in titanium alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • titanium spontaneously reacts with hydrogen at room temperature. • reaction starts under pressure when the surface oxide layer is broken. • titanium alloys react faster than pure titanium. • stoichiometric TiH 2 is formed. Surface wear-activated spontaneous reactions of titanium and its alloys with hydrogen at room temperature are shown in this work. Titanium powder, intensively mixed under hydrogen pressure in a planetary mill, without any grinding media, reacts readily with hydrogen gas with the formation of stoichiometric titanium dihydride. The reaction, once initiated, proceeds spontaneously even without movement of the milling vial with a similar reaction rate. The moment of initiation of the reaction seems to be related to the removal of oxide impurities from the surface of the titanium particles and is strongly correlated with milling velocity. According to thermogravimetric measurements and X-ray diffraction (XRD) phase analysis, titanium is fully converted to TiH 2. Titanium alloys were found to react in the same manner. Ti-5553 (β) reacts more easily than grade 5 Ti (Ti-Gd5) (α'), which is more reactive than grade 2 Ti (Ti-Gd2). The titanium alloy particles maintain their shape and coherency after hydrogenation. The method seems to be extremely cost-effective in the synthesis of titanium hydride and also allows the production of hydrogenated alloyed powders in spherical form, which can potentially be applied in the additive manufacturing of titanium foams. The results also show a significant risk of using titanium alloys in a hydrogen atmosphere at room temperature. It seems that after losing the protective oxide layer, parts made of pure titanium or its alloys may undergo catastrophic destruction after losing strength and ductility upon full conversion to hydride. [ABSTRACT FROM AUTHOR]

[Display omitted] • High density dislocations inhibit hydrogen atoms diffusion. • Different types of hydrides were identified by CDB spectrum and theoretical calculations. • Hydrogen concentration decreases with increasing dislocation density. This work aims to elucidate the interaction between hydrogen atoms and pre-introduced dislocations in commercially pure titanium (CP-Ti). Positron annihilation spectroscopy supplemented by the first-principle calculations was utilized to reveal the effects of dislocation densities on the formation of hydride types and the concentration of hydrogen-induced defects in CP-Ti. Results show that, in the hydrogen-charged sample with 40 % deformation, hydrogen-induced damage gradually decreases when the hydrogen enters the sample at a depth of about 350 nm. This finding suggests that the high-density dislocations present in deformed specimens effectively trap hydrogen atoms and inhibit their diffusion, which ultimately mitigate damage within the samples. γ-TiH and δ-TiH 2 hydrides are observed in the hydrogen-charged sample. The thermal desorption spectroscopy results show that the desorption amount of deuterium decreases from 1.14 × 1018 D/cm2 to 5.10 × 1017 D/cm2 with an increase in dislocation density because dislocations inhibit the diffusion of deuterium. In samples with higher deformation, the high dislocation density inhibits the formation of δ-TiH 2 hydrides and promotes the formation of γ-TiH hydrides, which significantly reduce the hardening of samples. These results provide insight into the interaction of hydrogen with pre-introduced defects and provide strong theoretical support for the development and improvement of more damage-resistant materials. [ABSTRACT FROM AUTHOR]

The formation of titanium hydrides is closely related to the hydrogen embrittlement in titanium and its alloy. In this work, a comprehensive study on the stable and metastable structures of TiH x (x=0.5, 1, 1.5 and 2) has been performed by means of first-principles calculations in combination with the evolutionary algorithm. The structural features, dynamical stability and elastic properties of these searched titanium hydrides have been systematically investigated. The influence of temperature on the structure stability and phase transition of the Ti 2 H, TiH, Ti 2 H 3 and TiH 2 phases is considered using the quasi-harmonic approximation theory. Our calculations predict that Ti 2 H, Ti 2 H 3 and TiH 2 undergo temperature-driven phase transitions. The reason that the theoretical calculation overestimates the critical temperature of the tetragonal to cubic phase transition in TiH 2 within the quasi-harmonic approximations approach is also explored and discussed. The thermodynamic stability of these TiH x (x=0.5, 1, 1.5 and 2) structures is further analyzed over the temperature range of 0–1100 K. TiH 2 is the only stable structure in the Ti–H system and Ti 2 H, TiH, and Ti 2 H 3 are thermodynamically metastable within 900 K. [Display omitted] [ABSTRACT FROM AUTHOR]

Titanium and aluminum couplings are susceptible to both corrosion and wear during their service life. When the passive film on the titanium surface is worn off, the galvanic effect will affect the corrosion-wear interaction, and tribocorrosion mechanism is altered accordingly. A combination of electrochemical techniques (Potentiostatic and Potentiodynamic Polarization), characterization of wear scar morphology (Scanning Electron Microscope, SEM and a 3D profilometer), and analysis of wear debris composition (Surface-Enhanced Raman Spectroscopy, SERS) were employed to clarify the tribocorrosion mechanism. The results show that the wear effect is predominant for the tribocorrosion of TC18 titanium alloy, and the corrosion-induced wear increment mainly comes from the ploughing effect of regenerated passive film. When the titanium alloy is coupled with aluminum, the corrosion acceleration is weak, while the cathodic reaction increases due to the negative shift of the corrosion potential. This results in the regenerated passive film containing a higher proportion of easily sheared low-valent titanium oxides and titanium hydrides, promoting the wear rate. • The tribocorrosion mechanism of TC18 titanium alloy is mainly controlled by wear. • The wear increment under applied potential comes from the ploughing effect of regenerated passive film. • Al has little effect on the corrosion acceleration of worn TC18 but it promotes wear rate. • With Al coupled, the enhanced cathodic reaction changes the surface state of wear scar. • More easily-sheared low valence titanium oxides and titanium hydroxide are formed in wear scar. [ABSTRACT FROM AUTHOR]

We investigated hydrogen some properties of magnesium hydrides substituted with titanium by a first principles calculation. In order to evaluate effect of different substitution concentration and configuration on desorption temperature and bulk modulus, we constructed five systems such as Mg 4 Ti 2 H 12 , Mg 8 Ti 2 H 20 , Mg 16 Ti 2 H 36 , Mg 14 Ti 4 H 36 and Mg 12 Ti 6 H 36 by using 1 × 1 × 3, 1 × 1 × 5 and 3 × 3 × 1 super cell of pure magnesium hydride. Among the investigated systems, Mg 14 Ti 4 H 36 system showed the best performance as hydrogen storage material in the complex viewpoints of substitution energy, desorption temperature and bulk modulus. In addition to, our results demonstrated that not only substitution concentration but also configuration plays vital effect on material's property of magnesium hydrides. Bader charge analysis explained the reason why desorption temperature is fallen down by substitution with titanium. • Overall bonding strength is weakened by titanium substitution. • Mg 4 Ti 2 H 6 has too low desorption temperature for dehydrogenation. • Proper substitution configuration is necessary for good property. • Mg 14 Ti 4 H 36 is a good candidate as hydrogen storage material. • Single substitution has advantages compared with co-substitution. [ABSTRACT FROM AUTHOR]

[Display omitted] Possible models for the arrangement of hydrogen atoms in the sites of the cubic lattice of titanium oxyhydride TiO y H p with vacancies in the metallic and nonmetallic sublattices are considered for the first time. It has been established that interstitial H atoms in oxyhydrides occupy vacant octahedral sites 4(b) of the oxygen sublattice. No displacement of H atoms in tetrahedral sites 8(c) is observed. [ABSTRACT FROM AUTHOR]

Titanium tetra hydride is considered for hydrogen storage purposes. Firstly, formation energy, hydrogen desorption temperature and gravimetric hydrogen density of TiH 4 is computed. Secondly, an ab initio constant pressure molecular dynamic simulation under pressure is performed to reveal behaviour of TiH 4 for the first time. The result exhibits two phase transitions successively. C2/m phase of TiH 4 transforms into C2/c phase at 40 GPa simulation pressure. Then, elastic constants of phases are determined to examine mechanical stability of phases. Based on the evolution of elastic constants, it is found that C2/m phase fulfils Born stability criteria for a monoclinic structure, indicating that C2/m phase is mechanically stable whereas C2/c phase is not mechanically stable. Additionally, several critical parameters which are important for hydrogen storage such as brittleness and ductility, Young and Shear modulus are obtained and analysed. In addition, electronic structures of phases are calculated and evaluated. Finally, dynamic stability from phonon dispersion curves is examined. C2/m phase is also found to be dynamically stable. Image 1 [ABSTRACT FROM AUTHOR]

The study focuses on hydrogen desorption characteristics of lithium hydride (LiH), sodium hydride (NaH), calcium hydride (CaH 2), and titanium hydride (TiH 2) which permits a possible path regarding challenging goals of US DOE standards. This research reported the consequences of enrichment in hydrogen uptake 7.02 wt% in lithium hydride, 7.71 wt% in sodium hydride, 5.91 wt% in calcium hydride, and 5.00 wt% in titanium hydride using silicon as an additive when evaluated with the help of volumetric technique. The ball milling process with silicon additive for LiH, NaH, CaH 2 , and TiH 2 shows depletion in dehydrogenation temperatures 523 K, 453 K, 488 K, and 463 K respectively. Similarly, the reduction in the activation energies reported due to ball milling process with silicon additive are 37 kJ/mol for lithium hydride, 42 kJ/mol for sodium hydride, 56 kJ/mol for calcium hydride and 45 kJ/mol for titanium hydride compared with crystalline powder samples of the respective materials. The outcome of Fourier-transform infrared spectroscopy of milled hydride samples after decomposition intimate rapid decrease in transmittance intensities due to hydrogen release because of the destabilization effect caused by silicon additive. The porosity and sponginess in high-resolution Transmission electron microscopy images after dehydrogenation reveals the hydrogen desorption from the sample materials. • TG-DTA for isothermal decomposition of LiH, NaH, CaH 2 & TiH 2 with 10% Si additive. • Reduction in dehydrogenation temperature & activation energy values by Si additive. • Characterization of samples by FTIR & TEM spectroscopy methods for validation. [ABSTRACT FROM AUTHOR]

Titanium hydride potassium perchlorate (THPP), which is one of the most commonly utilized pyrotechnic initiators, can fail or deviate from the desired performance when subjected to aging. The aging process is known to change its composition as well as its thermochemical kinetics; however, the variation in the performance of THPP in terms of its combustion behavior has not been addressed. This experimental paper reports new correlations between the ignition and combustion characteristics of THPP. A thermal analysis, along with morphological observations, conducted on aged samples revealed that aging caused progressive oxidation of the fuels and subsequent decomposition of the oxidants. The reaction kinetics extracted using the isoconversional method pointed to a decrease in the activation energy due to thermal aging while the opposite was noted in the case of hygrothermal aging. In particular, an increase in the activation energy limited the range of ignition temperature and decreased the reactivity, thereby increasing both the ignition delay time and burn time. Such altered characteristics due to aging could lead to an inconsistent performance of the pyrotechnic initiators. [ABSTRACT FROM AUTHOR]

The results of the calorimetric studies of thermal dissociation of titanium, zirconium, magnesium, and palladium hydrides performed in recent years are presented. The multiplet character of thermal dissociation characteristic of all these hydrides is shown. A good correlation between the course of differential scanning calorimetry curves and the results of thermogravimetry has been demonstrated. The discrete nature of the decomposition processes is established. A sequence of mechanisms occurring during the heating of transition metal dihydrides in a medium with a low partial pressure of hydrogen has been proposed: rearrangement in the hydride phase; destruction of metal - hydrogen bonds to form a solid solution supersaturated with hydrogen; diffusion of hydrogen to the interface of solid phase - environment; molization of hydrogen at the exit from the solid phase. [ABSTRACT FROM AUTHOR]

We studied the effect of oxidation temperature and initial hydrogen concentration on the occurrence of cubic (δ) to tetragonal (ε) phase transformation induced by thermal oxidation of titanium hydride powders in air. X-ray diffraction analysis indicates that δ → ε transformation occurs during oxidation at 400 °C, but not at lower (300 °C) or higher (500 °C) oxidation temperatures. The relative amounts of hydrogen loss during oxidation were determined by temperature-programmed desorption mass spectrometry (TPD-MS). The findings suggest that oxygen stabilizes the tetragonal phase (ε), and that the δ/ε phase composition following oxidation depends on both oxygen and hydrogen concentrations. For high oxidation temperatures (500 °C), some degree of hydride decomposition leads to a decrease in H concentration and to destabilization of the tetragonal phase after cooling down to room temperature. Image 1 • δ → ε phase transformation may occur through powder oxidation treatment in air. • Dissolved oxygen stabilizes the tetragonal (ε) phase. • The extent of δ → ε conversion strongly depends on the oxidation temperature. • Oxygen and hydrogen concentrations affect the δ/ε composition following oxidation. • At high temperatures (~500 °C) oxidation is accompanied by partial dehydrogenation. [ABSTRACT FROM AUTHOR]

The hydrogen behavior in electrochemically charged electron beam melting (EBM) and wrought Ti–6Al–4V alloys with a similar β-phase content of ~6 wt% was compared. Hydrogenation resulted in the formation of microvoids, either adjacent to the surface or along interphases, their coalescence, and emanation of microcracks around them. The microstructure of the EBM alloy displayed a discontinuous arrangement of β-phase particles in the short-transverse direction, a smaller lattice constant of the β-phase, and more α/β interphase boundaries, making the EBM alloy more susceptible to hydrogen embrittlement. The hydrogenated alloys were composed of α H (hcp) and β H (bcc) solid solutions as well as δ a (fcc) and δ b (fcc) hydrides with lattice parameters that have not been reported before. These hydrides were transformed from the primary α-phase. No major microstrain difference was observed between the EBM and wrought alloys, either before or after hydrogenation. Microstrains in the α and β phases increased following hydrogenation; they were larger in the β H and δ a phases compared to the α H and δ b phases. A post-treatment that would increase the size of the β particles is suggested to improve the resistance of EBM Ti–6Al–4V to hydrogen-induced damage. Image 1 • Hydrogen behavior in electrochemically charged EBM and wrought Ti–6Al–4V alloys is compared. • The EBM alloy is more prone to hydrogen-induced cracking at interphase boundaries. • The surfaces of hydrogenated alloys consist of both solid solutions and hydrides. • The δ a and δ b (fcc) hydrides transform from the α (hcp) phase. • These hydrides and their lattice constants have not been reported before. [ABSTRACT FROM AUTHOR]

• Titanium hydride was deoxidized using a calcium reductant. • The process was shortened by combining the dehydrogenation and deoxidation process. • The oxygen in powder by advanced process was same as the previous process. • The powder prepared by advanced process has increased oxidation resistance. In a previous study, we prepared a low-oxygen titanium powder from titanium scrap through Hydrogenation-Dehydrogenation and deoxidation in a solid-state (DOSS) process with calcium. In this study, an advanced deoxidation in a solid-state process applied titanium hydride as a raw material is proposed to shorten the time of the previous DOSS process. Compared to the previous DOSS process, the total process time was shortened, and the same oxygen reduction rate was obtained. In addition, it was confirmed that the low-oxygen titanium powder prepared this by advanced DOSS process has a superior oxidation resistance than the titanium powder obtained by the previous study. [ABSTRACT FROM AUTHOR]

Upgraded titania slag (UGS) is a titanium-rich material with over 90 wt% titanium dioxide and some minor elements such as Fe, Al, Cr, and Si, which is mainly used for preparing TiO 2 and TiCl 4. In this study, UGS was directly reduced with magnesium powder in a hydrogen atmosphere. Titanium alloy hydride powder with the oxygen content of 0.032 wt% was obtained. The minor elements of Fe, Si, Al, and Cr from the UGS were kept in the final powder with the main phase of TiH 1.924 (δ), and minor intermetallic phases of HFe 2 Ti, Ti 5 Si 3 H 0.9 and Cr 1.8 TiH 5.3. EDS elemental mapping results indicated that HFe 2 Ti and Ti 5 Si 3 H 0.9 intermetallics formed bright phase islands in the matrix. The reduction mechanism and the reaction sequence were discussed based on the thermodynamic modelling with the assistance of HSC chemistry software. The possibility of hydrogen reduction of titanium oxides was discussed as well. Unlabelled Image • A dense titanium alloy hydride powder was obtained directly from Upgraded Titania Slag. • The beneficial elements in UGS were kept for the future alloy-design use. • The oxygen level of <0.035 wt% was achieved and met the standard specification. • Hydrogen did not work as a reducing agent but as an aid destabilizing Ti-O. [ABSTRACT FROM AUTHOR]

Titanium hydride powder was used to completely or partly replace the spherical titanium powder in order to reduce the cost. The microstructure and mechanical properties after debinding and sintering were investigated. The results showed that with the addition of the titanium hydride powder, the microstructure gradually changed. The fabricated alloy was a titanium matrix composite reinforced with in-situ TiC particles. With the increase in the proportion of titanium hydride powder, the catalytic debinding percentage decreased, which led to an increase in the concentration of carbon and oxygen, and hence, there was a decrease in the tensile strength and elongation though the density of titanium MIM samples increased. The hardness and wear resistance increased as compared with those for pure titanium materials in the market. These results provide a promising method for reducing the cost of titanium MIM, and development of great industrial application prospects. Unlabelled Image • Composite reinforced by in-situ TiC phase was fabricated during sintering. • TiC is beneficial to the improvement of strength and wear resistance of samples. • The cost of Ti MIM can be reduced by adding titanium hydride powder. [ABSTRACT FROM AUTHOR]