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Dental implant alloys made from titanium and zirconium are known for their high mechanical strength, fracture toughness and corrosion resistance in comparison with commercially pure titanium. The aim of the study was to investigate possible differences in the surface chemistry and/or surface topography of titanium and titanium-zirconium surfaces after sand blasting and acid etching. The two surfaces were compared by X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, scanning electron microscopy and profilometry. The 1.9 times greater surface hydrogen concentration of titanium zirconium compared to titanium was found to be the major difference between the two materials. Zirconium appeared to enhance hydride formation on titanium alloys when etched in acid. Surface topography revealed significant differences on the micro and nanoscale. Surface roughness was increased significantly (p<0.01) on the titanium-zirconium alloy. High-resolution images showed nanostructures only present on titanium zirconium., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Titanium is a metal with excellent physical and chemical properties. Although it is highly abundant in the earth's crust, the difficulty of its extraction makes it expensive and restrict its application on a large scale. It has become a world problem to develop a titanium smelting method with low cost and short process. In this research, TiH1.924 powder with a low oxygen content was produced by hydrogen-assisted magnesiothermic reduction at 650 °C for 2 hours. By optimizing the thermodynamic calculation method of Ti–O–H solid solution, the thermodynamic data of Ti–O, Ti–H, and Ti–O–H with different oxygen contents have been calculated. The results showed that the hydrogen in Ti–O–H has destabilizing effect on the oxygen in Ti–O lattice. Therefore, under hydrogen atmosphere, Mg can break the thermodynamic limit of deoxidation of Ti–O solid solution, obtaining a low oxygen content reduction product. In order to further reduce the oxygen content in the product, the mechanism of secondary oxidation of the titanium hydride product was investigated, leading to the conclusion that higher hydrogen content in titanium hydride can obviously enhance its anti-oxidation property. The research can provide theoretical support for the deep reduction of TiO2 using low-cost Mg powder to obtain titanium powder with a low oxygen content. [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 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]

Some results concerning the hydrogen effect at electrolytic saturation at a current density of j = 1500 and 3500 A/m2 for 3 h at room temperature on the temperature dependence of the yield stress σ0.1(T) and the shape memory effect (SME) under tension of the [011]-oriented Ti-50.55%Ni (at.%) alloy single crystals are presented. It was shown that hydrogen is in a solid solution and forms particles of titanium hydride TiH2 after hydrogenation at j = 1500 and 3500 A/m2, respectively. Both hydrogen in the solid solution and TiH2 particles led to a decrease in the Ms temperature of the onset of the forward martensitic transformation (MT) upon cooling and the Md temperature (Md is the temperature at which the stresses for the onset of the stress-induced MT are equal to the stresses for the onset of plastic flow of the high-temperature B2 phase), and increased the yield stress σ0.1 of the B2 phase at the Md temperature compared to hydrogen-free crystals. It was found that the SME under stress depends on the tensile stress level and current density. The maximum SME εSME = 10 ± 0.2% at σex = 200 MPa and εSME = 10.5 ± 0.2% at σex = 300 MPa was observed in the hydrogen-free crystals and after hydrogenation at j = 1500 A/m2, respectively, which exceeded the theoretical value of lattice deformation ε0 = 8.95% for the B2-B19′ MT in [011] orientation under tension. At j = 1500 A/m2, the physical reason for the excess of the SME of the theoretical ε0 value was due to the increase in the plasticity of B19′ martensite upon hydrogenation. At j = 3500 A/m2, εSME = 8.0 ± 0.2%, and it was less than ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. The decrease in SME after hydrogenation at j = 3500 A/m2 was associated with the interaction of two types of B19′-martensite: oriented under stress and non-oriented, formed near TiH2 particles. It was shown that the redistribution of hydrogen in the bulk of the crystals during long-term holding for 168 h at 263 K after hydrogenation at j = 1500 A/m2 increases the SME relative to crystals without long-term holding: 3.5 times at 50 MPa and 1.8 times at 100–150 MPa. After long-term holding, εSME = 9.5 ± 0.2% at 150 MPa, which exceeds the theoretical value ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. [ABSTRACT FROM AUTHOR]

The development of titanium (Ti) powder production process is important because Ti powder metallurgy (PM) is a promising method that can result in large cost savings by reducing material loss and the number of steps in the conventional manufacturing process of Ti metal and its alloys. This study investigated the process of producing Ti hydride powder directly from titanium tetrachloride (TiCl4) using magnesium (Mg) metal and hydrogen gas (H2). The experiments were conducted at 10731173K when the TiCl4 feeding rate was in the range of 19.1657.42 g·min-1 with the use of cooling gas as Ar or H2 gas. A mixture of Ti and Ti hydride (TiH1.5) was obtained in an iron (Fe) crucible by the dehydrogenation of Ti hydride as the TiCl4 reduction proceeded. The concentration of oxygen (O) decreased with a decrease in the specific surface area and/or an increase in the proportion of TiH1.5 in the powder. As a result, the concentration of O of the mixture of Ti and TiH1.5 decreased to 0.116 mass% under a certain condition. [ABSTRACT FROM AUTHOR]

The negative infl uence of oxygen, nitrogen, and carbon admixtures in titanium hydride production is shown. The procedures were developed for determination in titanium hydride of the content of carbon admixtures in ceramic crucibles, and of oxygen and nitrogen in graphite crucibles by stepwise heating. Removal of the gas phase and part of the adsorbed layer of admixtures from the titanium hydride allows reducing the amount of oxygen and nitrogen admixtures in it by approximately 3 times. A procedure was developed for determination of hydrogen content in titanium hydride by burning this compound in a fl ow of gaseous oxygen with н2 о formation. Recommendations are provided as regards the instruments to be used for analysis of titanium hydride for hydrogen content. The problem of formation of titanium hydride with superstoichiometric hydrogen content is considered. The papers published on this subject do not provide a convincing proof of the existence of such hydrides. [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]

The results of spectrometry with an ASD FieldSpec 3 FR spectroradiometer at wavelengths ranging from 350 to 2500 nm for hydrogenated amorphous and crystalline titanium and zirconium diborides are presented. The results were used to determine changes in the spectral characteristics of hydrogen in bulk and film TiB2 and ZrB2. The spectrometry was performed with the contact method using a Unit Contact Probe. The bulk test samples and spraying targets were prepared by the powder metallurgy method. X-ray diffraction identified that the samples had crystalline structure. Thin films of titanium and zirconium diborides were produced by magnetron sputtering of TiB2 and ZrB2 targets in an argon atmosphere. The structure of the films was studied using an EMP-100 electron diffractometer employing the transmission method at a residual pressure of ~7 ∙ 10–3 Pa. The electron diffraction patterns showed a strong 'halo' at the center, being indicative of amorphous structure of the films, promoting hydrogen transfer process. The samples were hydrogenated from the gas phase at a hydrogen pressure of 0.1 MPa and a temperature of 870 K. A critical analysis of published methods for the quantitative determination of hydrogen in high-temperature borides was provided. The spectrometry method is advantageous in that it is fast, precise, nondestructive, and surface-sensitive, and the entire spectrum is displayed in real time. The intensities of the Brackett Bβ and Balmer Hβ hydrogen lines for crystalline and amorphous TiB2 were compared, and the absorption of hydrogen by the crystalline sample was found to be 4.1 times higher than that by the amorphous one. In polycrystalline TiB2, lines with a halfwidth of 200–300 nm were observed at 500 and 750 nm, which was explained by the subbarrier tunneling of hydrogen atoms between neighboring interstitials, ranging, in particular, for many lattice parameters. The absorbed hydrogen amount in the amorphous film was 1.4 times higher than on the starting film. Magnetron sputtering of ceramic targets was known to lead to the introduction of impurities several tens of nanometers in size (short-range crystalline ordering) into the film, to which the hydrogen penetration process was sensitive. The presence of hydrogen atoms resulted in spectral bell-like curves, partially overlapping each other. By analogy with metal amorphous alloys, the shape of these curves could be explained by quasi-interstices. In the amorphous titanium diboride, a bell-like Balmer Hβ curve was observed, confirming short-range crystalline ordering. Correlation between the hydrogen absorption and the lattice energy and bonding energy of Me–B atoms was established. When hydrogen was absorbed by crystalline titanium and zirconium diborides, TiB2 was found to absorb higher amounts of hydrogen because of lower lattice energy and Ti–B atomic bond energy. As the spectroradiometer method is prompt and informative, we can recommended it for the identification of hydrogenated amorphous and crystalline ceramic materials. [ABSTRACT FROM AUTHOR]

The technique of SHS (self-propagating high-temperature synthesis) makes it possible to synthesize titanium hydride efficiently. Titanium powder synthesized through SHS hydrogenation and dehydrogenation in a vacuum furnace is experimentally studied. We examine the change in the microstructure and phase and chemical composition in hydrogenated and dehydrogenated titanium sponge. The titanium sponge is hydrogenated in a high-pressure SHS reactor at a hydrogen pressure of 3 MPa. It is established that SHS hydrogenation leads to a decrease in the content of oxygen and carbon impurities. After hydrogenation, the sponge contains a single-phase δ-titanium hydride having a tetragonal lattice. The particles have a shattered shape. It is confirmed that the titanium hydride obtained contains a higher amount of hydrogen (4.64 wt %). The hydrogenated titanium sponge is mechanically ground using a ball mill to bring the particle size within the range of 40–250 µm. Titanium hydride powder is dehydrogenated in a vacuum furnace at 850°C for 220 min. After dehydrogenation, titanium contains a single-phase α-titanium powder having a hexagonal close-packed lattice. There is no change observed in size and shape of the particles. The process studied makes it possible to obtain high-quality titanium powder having a required particle size distribution to be applied in various areas of powder metallurgy. [ABSTRACT FROM AUTHOR]

Some results concerning the hydrogen effect at electrolytic saturation at a current density of j = 1500 and 3500 A/m2 for 3 h at room temperature on the temperature dependence of the yield stress σ0.1(T) and the shape memory effect (SME) under tension of the [011]-oriented Ti-50.55%Ni (at.%) alloy single crystals are presented. It was shown that hydrogen is in a solid solution and forms particles of titanium hydride TiH2 after hydrogenation at j = 1500 and 3500 A/m2, respectively. Both hydrogen in the solid solution and TiH2 particles led to a decrease in the Ms temperature of the onset of the forward martensitic transformation (MT) upon cooling and the Md temperature (Md is the temperature at which the stresses for the onset of the stress-induced MT are equal to the stresses for the onset of plastic flow of the high-temperature B2 phase), and increased the yield stress σ0.1 of the B2 phase at the Md temperature compared to hydrogen-free crystals. It was found that the SME under stress depends on the tensile stress level and current density. The maximum SME εSME = 10 ± 0.2% at σex = 200 MPa and εSME = 10.5 ± 0.2% at σex = 300 MPa was observed in the hydrogen-free crystals and after hydrogenation at j = 1500 A/m2, respectively, which exceeded the theoretical value of lattice deformation ε0 = 8.95% for the B2-B19′ MT in [011] orientation under tension. At j = 1500 A/m2, the physical reason for the excess of the SME of the theoretical ε0 value was due to the increase in the plasticity of B19′ martensite upon hydrogenation. At j = 3500 A/m2, εSME = 8.0 ± 0.2%, and it was less than ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension. The decrease in SME after hydrogenation at j = 3500 A/m2 was associated with the interaction of two types of B19′-martensite: oriented under stress and non-oriented, formed near TiH2 particles. It was shown that the redistribution of hydrogen in the bulk of the crystals during long-term holding for 168 h at 263 K after hydrogenation at j = 1500 A/m2 increases the SME relative to crystals without long-term holding: 3.5 times at 50 MPa and 1.8 times at 100–150 MPa. After long-term holding, εSME = 9.5 ± 0.2% at 150 MPa, which exceeds the theoretical value ε0 = 8.95% for B2-B19′ MT in [011] orientation under tension.

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 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]

Titanium and its alloys could be called the "streetwalker" among commercially applied metals, because its poor nobility allows it to "pick-up" anything. Titanium is one of the metals that forms very stable borides, carbides, nitrides, oxides, and even hydrides. The solubility of nitrogen and oxygen in the hexagonal crystal structure of (metallic) titanium is very high; on the other end limited quantities of boron, carbon, and hydrogen can be dissolved. In the present contribution, we report on a significant increase in the solid solution limit of hydrogen in hexagonal close-packed (h.c.p.) titanium, where the h.c.p. crystal lattice is stabilized by deliberate interstitial alloying with high quantities of nitrogen or oxygen atoms. The presence of nitrogen/oxygen prevents the hydrogen-induced transformation of the h.c.p. titanium lattice to a face-centered cubic (f.c.c.) titanium lattice that occurs if no oxygen or nitrogen is present. The hydrogen content that can be accommodated at room temperature in h.c.p. titanium is as high as an unprecedented 50 at. pct from about 0 at. pct and causes an anisotropic expansion of the hexagonal lattice. This finding showcases that there could be an unexploited potential for combining large quantities of interstitials in titanium-based lattices. [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]

A hydride-forming element titanium (Ti) was selected as an additive to improve the hydrogen uptake and release properties of MgH2. The hydrogen uptake and release properties of three Ti-added MgH2 alloys [named MgH2-xTi (x = 6, 12, and 15)] prepared by milling in hydrogen (reactive mechanical grinding) were investigated and those of MgH2-12Ti were studied in more detail because it had the highest initial hydrogen uptake and release rates and the largest quantities of hydrogen absorbed and released for 60 min. At the cycle number, n, of one (n = 1), MgH2-12Ti absorbed 4.01 wt.% H for 2.5 min and 6.39 wt.% H for 60 min at 573 K in 12 bar H2, having an effective hydrogen storage capacity of 6.39 wt.%. MgH2-12Ti released 0.44 wt.% H for 2.5 min and 1.86 wt.% H for 60 min at 593 K in 1.0 bar H2. γ-MgH2, TiH1.924, and MgO were formed during reactive mechanical grinding. We believe that the brute forces and tensile, compressive, or shear stresses, which are applied to the materials during reactive mechanical grinding, introduce imperfections, fabricate cracks, expose fresh and clean surfaces, decrease the particle size, and disperse the additive among the particles. The γ-MgH2, TiH¹.924, and MgO formed during reactive mechanical grinding and their pulverization during reactive mechanical grinding are believed to make these effects stronger. [ABSTRACT FROM AUTHOR]

Method for nondestructive analysis of stoichiometric content in titanium hydrides using neutron filtered beams at the Kyiv research reactor is presented. Method is based on analysis of total neutron cross sections σt(obs) of titanium hydride samples observed in experiment using transmission technique. Computer calculations for finding optimal energies and widths of neutron beams for this method were carried out. It was shown that the measurements and further analysis of the observed total neutron cross sections σt(obs) for the titanium hydride samples may allow to receive the relation value metal/hydrogen in hydride with accuracy ∼ 1.0 % using neutron filtered beam with average energy 2 keV. Presented method can be applied for the investigation of hydrides of any other metals.

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]

The electrolytic hydrogen precharging process is used to analyze the influence of hydrogen on the microstructure, corrosion resistance, and mechanical properties of pure titanium. The results demonstrate that two types of titanium hydrides (δ‐TiHx and ϵ‐TiH2) are detected by electron backscatter diffraction (EBSD), and the volume fraction of titanium hydrides, the local strain caused by hydrogen precipitation, and the thickness of hydrides layer increase with the increase in precharging time. It is noteworthy that the formation of hydrides layer has a protective effect on general corrosion, but the local strain caused by hydrides precipitation leads to the destruction of corrosion resistance, as a result the corrosion resistance of pure titanium increases first and then decreases with the increase in hydrogen precharging time. Moreover, with the precipitation of hydrides, the fracture mode changes from ductile failure to duplex‐ and multimode failure, resulting in the decrease in ultimate tensile strength (UTS) and elongation. Therefore, the mechanical and electrochemical properties of the precharged samples first increase and then decrease with the increase in precharging time, reaching their optimum values at 10 h, and the critical precharging time is determined to be 75 h when comparing those properties with pure titanium. [ABSTRACT FROM AUTHOR]

A titanium/ruthenium heteromultimetallic polyhydride complex [(Cp'Ti)2(Cp*Ru)2(µ‐H)6] (3) (Cp' = C5Me4SiMe3, Cp* = C5Me5) was obtained from the reaction of [Cp'Ti(CH2SiMe3)3] (1) with [Cp*Ru(µ‐H)4RuCp*] (2) under H2. Complex 3 can readily react with N2 to give an imido/nitrido complex [(Cp'Ti)2(Cp*Ru)2(µ‐NH)(µ‐N)(µ‐H)3] (4) via N–N bond cleavage and N–H bond formation. The result demonstrates that the heteromultimetallic hydride complexes can serve as a platform for dinitrogen activation. [ABSTRACT FROM AUTHOR]

Hydrogen saturated samples of technically pure titanium have been studied by the electron-positron annihilation method (EPA), coupled with the thermoelectric power measurements performed in these samples saturated by different amount of hydrogen. The structure of the hydrogenated samples was additionally investigated by X-ray diffraction. The complete coincidence of the moment of occurrence of a change in the structure of hydrogenated titanium depending on the amount of introduced hydrogen has been established. The intensity of positron annihilation drops with increasing hydrogen concentration in α-titanium to 0.04 wt % and then remains unchanged up to values of 0.05 wt % () -titanium to increases afterwards. At the same time, a sharp change in the values of the thermoelectric power occurs in this range. In the region of 0.05%, the annihilation rate stabilizes and begins to increase, while the thermoelectric power begins to decrease slowly. The inflection point on the dependence of thermoelectric power on hydrogen concentration corresponds to the onset of the formation of titanium -hydrides. An increase in the positron lifetime is observed in the concentration range of 0.05–0.08 wt %, then the lifetime stays stable up to concentrations of 0.08–0.12 wt %. A transition from () to () phase is formed in this range. Next, the positron lifetime increases, as does the number of defects, while the thermoelectric power gradually drops (to a concentration of 0.24 wt %). This is followed by a stabilization mode of all the above parameters to 0.35 wt %. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V is one of the most widely used titanium alloys. However, it is susceptible to hydrogen embrittlement, e.g. due to hydride formation. Hydrogen permeability through Ti-based alloys is affected by the rapid formation of hydride or oxide surface layers as well as by trapping in the bulk alloy. Here, we analyze and compare the electrochemical hydrogen permeation (EHP) through wrought and electron beam melted (EBM) Ti-6Al-4V alloys. Hydrogen diffusion coefficients are calculated from the permeation current transients. The effective diffusion coefficient of hydrogen in the wrought alloy is found to be an order of magnitude higher than in the AM'ed alloy. The different microstructures of the wrought and EBM alloys are found to play an important role in hydrogen distribution and phase transformation in the alloy. In the EBM alloy, hydrogen is distributed more uniformly and, consequently, more pronounce phase transformations occur, eventually leading to brittle cracking. In the wrought alloy, on the other hand, hydrogen is distributed unevenly in the bulk of the membrane, forming hydride clusters, most probably at α/β interphase boundaries. These findings suggest that the EBM Ti-6Al-4V alloy is more susceptible to HE than its wrought counterpart. • Electrochemical hydrogen permeation (EHP) in wrought and EBM Ti6Al4V is studied. • A different permeation behavior is related to microstructure and hydride distribution. • A careful EHP procedure is established for Ti and its alloys. • Hydrogen diffusivity in the wrought alloy is an order of magnitude higher. • The EBM alloy is more susceptible to hydrogen embrittlement and cracking. [ABSTRACT FROM AUTHOR]

• Rare earths (RE) are used in permanent magnets that are crucial to Europe's successful green and digital transition • Direct recycling of sintered magnets involves less energy-intensive processing steps than pyro- or hydrometallurgy. • Automated sorting and disassembly pilots have been developed to enable commercial recycling of NdFeB type magnets • Hydrogen-assisted direct recycling can produce high quality powders enabling the production of high performance N45 + magnets • Processes have been developed to separate oxidised grain boundary phase from the hard-magnetic phase of the recycled powders. • Demonstrator applications from direct recycled magnets that have similar properties with a much better environmental impact • Design for Recycling criteria have been developed to facilitate the recycling of NdFeB magnets. Rare Earths (RE) permanent magnets are essential components for Europe's successful green and digital transition However, the entire value chain of RE magnetic materials depends on imports, which are highly vulnerable in current global supply chain models. To mitigate this situation, EU Regulation plans that at least 15 % of the EU's annual consumption of permanent magnets should be covered by recycling capacities by 2030. Researchers in the EU H2020 project SUSMAGPRO consortium have shown that hydrogen can be used as a very efficient recycling method to extract NdFeB magnet powder from various EOL Components in the IP protected Hydrogen-based Processing of Magnet Scrap (HPMS). On exposure to hydrogen the sintered NdFeB magnets break down into a friable, demagnetised, hydrogenated powder containing an interstitial hydride of Nd 2 Fe 14 BH X (10 µm) and smaller particles (<1 µm) from the grain-boundary phase NdH 2.7. This process delivers a sustainable source of magnetic material for the production of sintered, polymer bonded and metal-injection moulded magnets. The paper will present numerous results along the whole value chain of magnet recycling, including automatic dismantling of magnet containing products, magnets extraction, HPMS recycling, production of recycled magnets and demonstrator testing. It will also discuss best practices and bottlenecks of the processes as an outlook for successful design-for-recycling of future applications. [ABSTRACT FROM AUTHOR]

Hydrogen behavior in metals and alloys is of great importance since the hydrogen-metal systems used for absorption of nuclear radiation in thermonuclear energy production. Titanium hydride (TiH2) employed widely as a material for hydrogen storage due to its high capacity for hydrogen isotopes. The hydrogen thermal desorption of titanium hydrides with different concentrations is studied by density functional theory methods for determining the cohesion energy of H in TiH x as a function of the hydrogen concentration, and stability TiH x sample with high-level H is determined. For macro-kinetic simulation of hydrogen behavior in TiH x we use the open hydrodynamic package OpenFOAM. Using such simulations, we can model the hydrogen thermal desorption under the action of an ion beam. • Cohesion energy was calculated using DFT methods for delta-TiHx (1.5 < x < 2.5). • The stability of titanium hydride was calculated for ultra-high H concentration. • The diffusion model using in the work takes into account the hydrogen sub-lattice. [ABSTRACT FROM AUTHOR]

In this work, the hydrogen sorption kinetics as well as the hydrogen effect on phase transformations, structure and properties of additively manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy using electron beam melting (EBM) were studied. In situ X-ray diffraction complex was used to analyze phase transitions in the EBM Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy under hydrogenation in gas atmosphere. The EBM mode is found to affect significantly on the microstructure and the rate of hydrogen sorption by Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy during hydrogenation at a temperature of 650 °C. The measurements have shown that the highest rate of hydrogen absorption is observed in samples manufactured at the beam current of 3 mA and the scanning speed of 150 mm/s. Hydrogenation of the samples leads to redistribution of alloying elements in the titanium alloy resulted in the formation of aluminum-rich α 2 -Ti 3 Al intermetallic phase and hydrides precipitation. • Titanium Ti-6.5Al-3.5Mo-1.5Zr-0.3Si parts were manufactured by electron beam melting. • The phase transformations [α+β].→[α(α 2)+β+δ]→[β+δ] occur under hydrogenation at 650 °C. • Hydrogen sorption depends on microstructure, β phase distribution and crack formation. • Hydrogenation causes hardening of the alloy due to hydrides and intermetallic precipitations. [ABSTRACT FROM AUTHOR]

In this study we compared the microstructural changes in the presence of hydrogen of Ti-6Al-4V alloy prepared by two different additive manufacturing (AM) methods: electron beam melting (EBM) and selective laser melting (SLM). Cathodic hydrogenation of AM Ti-6Al-4V resulted in significant expansion of β Ti phases due to the solute hydrogen, increasing of micro-strains, and α → titanium hydride/β H transformation. It was shown that SLM Ti-6Al-4V with acicular martensitic structure is more prone to hydrogen-induced phase transformation and hydrogen-assisted damage, compared to EBM. Moreover, it was revealed that different hydrogen charging environments cause different microstructural changes in EBM Ti-6Al-4V. Unlike cathodic hydrogen charging, gaseous hydrogen charging at elevated temperature reduced the process-induced micro-strains and promoted Al redistribution within the EBM Ti-6Al-4V. This resulted in massive precipitation of brittle α 2 -Ti 3 Al intermetallic compound, which act as a strong hydrogen trapping site aside from the Ti hydride phase. • SLM Ti-6Al-4V is more prone to hydrogen-induced phase transformation, comparing to EBM. • CHC increases micro-strains, expands the lattice, and causes α → β H /Ti-hydride transformation. • GHC decreases micro-strains and causes massive precipitation of α 2 -Ti 3 Al phase. • α 2 -Ti 3 Al phase serves as an irreversible hydrogen trapping site. [ABSTRACT FROM AUTHOR]

In this study, the effects of phase composition and hydrogen content on the compactibility of the titanium hydride powders are investigated. The crushing strength and the XRD patterns were performed. From the results of the green density, it is clear that the compressibility of the unsaturated hydride titanium powder is higher than that of TiH2. The results of the compression tests indicate that the crushing strength of unsaturated hydride titanium powder is markedly higher than that of the TiH2 and pure Ti. The relative mass fraction of each phase of the unsaturated hydride titanium powder was analyzed by Rietveld refinement of the XRD patterns. The phase composition with high compactibility of the unsaturated hydride titanium powder contains a lot of TiH1.5 and a small amount of α-Ti and TiH. There is a suitable range for each phase: TiH1.5 (70-73 wt.%), α-Ti (13-18 wt.%) and TiH (11-15 wt.%). [ABSTRACT FROM AUTHOR]

We perform the experimental investigation of the interaction of hydrogen with Ті-Al-V-Fe, Al-V-Fe, and Ті-Al-Mo-Fe master alloys used for the production of titanium alloys from powder mixtures based on hydrogenated titanium. It is shown that hydrogen released from hydrogenated titanium in the course of heating of these mixtures may temporarily saturate powder master alloys depending on their chemical composition and pressure and temperature conditions. This phenomenon leads to the appearance of bulk effects and affects the defectiveness of the crystal structure and diffusion processes responsible for the synthesis of alloys from powder mixtures. In the case of heating of the master alloys in hydrogen, we establish the temperature ranges of hydrogen sorption depending on the chemical compositions of alloys and, in the course of subsequent heating in a vacuum chamber, the temperature ranges of its desorption. The presence of titanium in the compositions of master alloys activates their interaction with hydrogen. At the same time, in the presence of significant total amount of aluminum and iron, these alloys become inert in hydrogen. [ABSTRACT FROM AUTHOR]

Magnesium hydride is extensively examined as a hydrogen store due to its high hydrogen content and low cost. However, high thermodynamic stability and sluggish kinetics hinder its practical application. To overcome this last drawback, different Ti amounts ( y = 0, 0.025, 0.05, 0.1, 0.2 and 0.3) were added to magnesium to form (1-y)MgH 2 +yTiH 2 nanocomposites (NC) by reactive ball milling under hydrogen gas. Thermodynamic stability of the MgH 2 phase in NCs was determined using a manometric Sieverts rig. Reversible hydrogen capacity and reaction kinetics were determined at 573 K over 20 sorption cycles under a limited reaction time of 15 min. On increasing Ti amount, reaction kinetics are enhanced both in absorption and desorption leading to a higher reversibility for hydrogen storage with the MgH 2 phase. However, titanium increases the molar weight of NCs and forms irreversible titanium hydride. The highest reversible capacity (4.9 wt% H) was obtained for the lowest here studied TiH 2 content ( y = 0.025). [ABSTRACT FROM AUTHOR]

Transition metal hydrides are of great practical interest due to high volume concentration of hydrogen. Titanium dihydride is a typical representative of such materials. Safe and reliable application of the dihydride requires established values of hydrogen diffusion rates. Experimental studies of the matter provide somewhat controversial results, therefore we investigate the process from first principles. We calculate hydrogen diffusion rates in representative compounds ( T i H 1.75 and T i H 2.0 ) and demonstrate that the dominant diffusion mechanism depends on temperature and composition. [ABSTRACT FROM AUTHOR]

Method for nondestructive analysis of stoichiometric content in titanium hydrides using neutron filtered beams at the Kyiv research reactor is presented. Method is based on analysis of total neutron cross sections σt(obs) of titanium hydride samples observed in experiment using transmission technique. Computer calculations for finding optimal energies and widths of neutron beams for this method were carried out. It was shown that the measurements and further analysis of the observed total neutron cross sections σt(obs) for the titanium hydride samples may allow to receive the relation value metal/hydrogen in hydride with accuracy ~ 1.0 % using neutron filtered beam with average energy 2 keV. Presented method can be applied for the investigation of hydrides of any other metals. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structures of two dinuclear titanocene hydride complexes are reported. Both complexes, namely bis(ŋ5-(di-para-tolylmethyl)cyclopentadienyl)titanium hydride dimer, [(ŋ5- C20H19)2Ti(μ-H)]2 (2a) and bis(ŋ5-2- adamantylcyclopentadienyl)- titanium hydride dimer, [(ŋ5-C15H19)2Ti (μ-H)]2 (2b), are formed via activation of molecular hydrogen by the corresponding bis (ŋ5,ŋ1-pentafulvene)titanium complexes 1a and 1b at ambient temperatures and pressures in high yields. The hydride complexes 2a and 2b exhibit planar [Ti2H2] cores and as a result of the heterolytic cleavage of molecular hydrogen, substituted Cp Ligands were formed during the reaction. [ABSTRACT FROM AUTHOR]

In order to improve the detonation performance of emulsion explosives, a new type of emulsion explosives with TiH2 powders is developed. The influences of the amount of sensitizers GMs and energetic additives TiH2 on explosion characteristics of emulsion explosives are studied to determine the optimum compositions. Underwater explosion and brisance testing experiments show that, compared to traditional GMs sensitized emulsion explosives, the shock wave specific impulse I and total energy E of GMs-TiH2 sensitized emulsion explosives are improved significantly, and the effect of TiH2 powders on improving the explosion power of emulsion explosives is better than that of Ti powders. The brisance of GMs-TiH2 emulsion explosives is 23.80 mm compression of lead block, 7.7 mm more than that of the emulsion explosives sensitized by GMs alone. Therefore, the hydrogen containing material TiH2 could be a promising energetic additive for developing high-power emulsion explosives. [ABSTRACT FROM AUTHOR]

Controllable helium-containing TiH 2 phase films were prepared on Si (100) substances by magnetron sputtering with hydrogen-helium-argon mixed gas, in order to investigate the helium behavior in titanium tritide. The TiH x He films were characterized by ion beam analysis (IBA) in which elastic recoil detection (ERD) and Rutherford backscattering spectrometry (RBS) methods are included, X-ray diffraction (XRD) and scanning electron microscope (SEM). It is found that with the increase in the relative hydrogen flow rate (Q H : Q Ar ) under the fixed helium flow and sputtering pressure, the hydrogen concentration in TiH x He films increases at first, and then decreases. Though the hydrogen concentration in TiH x He films can be greatly increased by increasing the total sputtering pressure, excessive sputtering pressure will deteriorate the crystallization quality. Although the helium concentration mainly relies on the relative helium flow rate of mixed gas during sputtering, the increase of the relative helium flow rate will reduce the concentration of hydrogen in films at fixed sputtering pressure dramatically. Fortunately, suitable relative hydrogen flow and sputtering pressure can maintain a high concentration of hydrogen in the films. Thus TiH x He films with controllable hydrogen and helium content can be achieved. [ABSTRACT FROM AUTHOR]

Spherical nanocrystalline TiH 2 powder was synthesized by calciothermic reduction of TiO 2 with CaH 2 at low temperature. Reduction was performed in solid state either by reactive milling in H 2 or via pre-milling in Ar with subsequent heat treatment in H 2 . Reactively milled powders are pyrophoric on exposure to air. Leaching of the side product CaO was only successful from the pre-milled and heat treated powders. As synthesized TiH 2 is stable in air and desorbs H 2 below 600 °C forming nanocrystalline Ti. Therefore it is suitable to prepare ultra finegrained cp-Ti. [ABSTRACT FROM AUTHOR]

The recycling process of the machined chips from the commercial Ti-6%Al-4%V (Ti-64) alloys to raw powders was established through the combination of brittle TiH2 compounds formation via heat treatment in hydrogen gas atmosphere and fragmentation by ball milling technique. TG-TDA and XRD analysis obviously suggested the hydride and dehydride behavior of pure Ti and TiH2 powders. The suitable heat treatment temperature at 873 K or more in H2a-Ar mixed gas successfully caused the formation of TiH2 compounds, and resulted in the fragmentation of Ti-64 machined chips to powders with a median particle size of 120 μm, which were completely consolidated by pressing. In addition, the original machined chips never remained in the ball-milled machined chips after heat treated over 873 K. The green compact after vacuum sintering at 1273 K showed a relative density of about 93%, larger than that of the sintered material in using the commercial Ti-64 powders. [ABSTRACT FROM AUTHOR]

In this research, DTA and TGA curves of titanium hydride powder in air with the heating rates of 5, 10, 20, 25, 30ºC/min were drawn, and XRD patterns of titanium hydride powder during heating rate 10ºC/min were prepared. Results showed that hydrogen comes out of titanium hydride in air during seven stages. And, by increasing heating rate, the mechanism of hydrogen emission from titanium hydride is almost fixed. Upon computation of activation energy of these stages, it was revealed that the mechanism does change at different temperatures. According to DTA curve at 10ºC/min, at temperatures lower than 460ºC, the mechanism is controlled by internal diffusion, at temperatures between 460-650ºC, it is controlled by physicochemical process, and at temperatures higher than 650ºC, it is controlled by chemical reaction. By increasing heating rate, the mechanism is changed at higher temperatures.

Ti–6Al–4V alloy parts were obtained by laser powder bed fusion (L-PBF) process. The influence of electrochemically charged hydrogen on the microstructure, phase identification, and mechanical properties of as-charged Ti–6Al–4V alloy parts from printing and deposition directions was studied. The impact of hydrogen desorption on L-PBF Ti–6Al–4V alloy parts was characterized with oxygen nitrogen hydrogen analyzer, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that as-built Ti–6Al–4V alloy was composed of a unique structure of a kind of equiaxed α (hcp) + intergranular β (bcc) dual-phase. The average surface roughness values for R a and R q were 10.1 ± 1.0 μm and 12.6 ± 1.3 μm, respectively. After electrochemically charged hydrogen, the phase in the part was composed of a solid solution of hydrogen in α-phase, and δ-TiH 2 and δ-TiH x hydride phases. The mechanical properties of as-printed Ti–6Al–4V alloy part from deposition direction were higher than those of as-built part from printing direction. After electrochemically charged hydrogen, the hydrogen content in the as-built Ti–6Al–4V alloy part increased significantly. The mechanical properties of the as-charged parts from printing and deposition directions were decreased significantly. The susceptibility to hydrogen embrittlement significantly depended on the orientation of additively manufactured Ti–6Al–4V alloy parts, the as-printed part from deposition direction had a higher resistance to hydrogen embrittlement compared with printing direction. After electrochemically charged hydrogen, Ti–6Al–4V alloy parts from printing direction was prone to brittle fracture and form the microcracks in α phase or along α/β interface in the as-built part. [ABSTRACT FROM AUTHOR]