TiH2 Research Articles

Titanium Hydride Growth and Tix Fe Intermetallic Particle Dissolution on Grade-2 Titanium Under Simulated Crevice Corrosion Conditions

ASTM Grade-2 titanium (Ti-2) is a commercially pure grade of titanium with a combination of high strength, excellent ductility, and elite corrosion resistance. That determines its use in diverse and demanding applications, including use as components in flue-gas desulphurization plants, exhaust systems in the automotive industry, and multiple components in marine equipment.Crevice corrosion and hydrogen embrittlement are the common failure mechanisms for Ti-2 components. Crevice corrosion involves the development of occluded cell corrosion conditions characterized by a solution consisting of low [O2] and low pH. Under these conditions, the hydrogen evolution reaction (HER) becomes the dominant cathodic reaction. The HER drastically affects crevice propagation and leads to the formation of titanium hydride (TiHx) phases. Such phases are responsible for Ti-2 hydrogen embrittlement by decreasing Ti ductility, leaving it susceptible to hydrogen-induced cracking under tensile stress even after cessation of crevice corrosion. Due to the roles of microstructural features in these processes, the hydrogen absorption and hydride formation behaviour of Ti-2 will vary on the surface and in the bulk material. Improving our understanding of the HER and hydride formation on titanium is crucial due to their importance in material failure scenarios.Iron, present as an impurity in Ti-2, has been shown to affect titanium's corrosion behaviour drastically1. Due to the formation of TixFe intermetallic particles (IMPs), iron affects crevice corrosion behaviour, HER kinetics, and hydride formation. With the much higher exchange current density of iron (io = 2.0-3.0 x 10-6 A/cm2)2,3 compared to titanium (io = 5.0-6.3 x 10-9 A/cm2)2,4, it is probable that the HER and hydride formation will preferentially occur on IMPs. Given the influence of TiHx on corrosion behaviour and the extreme applications of Ti-2, it is crucial to develop a relationship between our understanding of TiHx formation and microstructure.This research aims to develop a relationship between Fe content in Ti, the resulting microstructure, and their effect on hydride formation, leading to improved material selection criteria, alloy development, and performance. This study investigates the initiation and propagation mechanism of TiHx formation on Ti-2 over a 24-hour period. Hydrides were grown galvanostatically in a simulated crevice corrosion environment. The surface was analyzed at various time intervals using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), focused ion beam (FIB) milling, X-ray diffraction (XRD), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). By visualizing TiHx within the matrix using FE-SEM, we determined that titanium hydride formation initiates at IMPs and then the hydride grows in all directions around these sites. After reaching a depth of ~ 5 µm below the surface of the IMP, the vertical hydride growth ceases, but the hydride continues to spread laterally across the Ti grain face until it reaches full surface coverage. Under steady-state conditions, the hydride is present as a uniformly distributed layer across the surface, with a thickness of ~ 5 µm. The electrochemical potential values during the galvanostatic hydride growth process and the amount of hydride detected using XRD support the hypothesis that the hydride proliferates before reaching a limited thickness. Elemental maps obtained using ToF-SIMS validate the observation that hydrides initiate at IMPs and confirm that the features observed in FE-SEM are hydrides. Furthermore, the amount and type of hydrogen-containing species were measured to elucidate the dynamics of TiHx formation. References He X, Noël JJ, Shoesmith DW. Effects of iron content on microstructure and crevice corrosion of Grade-2 titanium. Corrosion. 2004;60(4):378-386.Trasatti S. Work function, electronegativity, and electrochemical behaviour of metals. III. Electrolytic hydrogen evolution in acid solutions. J Electroanal Chem. 1972;39(1):163-184.Abd Elhamid MH, Ateya BG, Weil KG, Pickering HW. Calculation of the Hydrogen Surface Coverage and Rate Constants of the Hydrogen Evolution Reaction from Polarization Data. J Electrochem Soc. 2000;147(6):2148.Bockris JO, Reddy AKN. Modern Electrochemistry. Plenum Press; 1970.

An Experimental Study on Deuterium Production from Titanium Hydride Powders Subjected to Thermal Cycles

An extensive multi-year experimental study was conducted to investigate the potential production of deuterium from titanium hydride TiHx powders subjected to specific thermal cycles. Mass spectrometry was performed, focusing on the variation in signal intensities at m/z = 2, 3, 4, 18, 19, 20, and 21, corresponding to fragments primarily involving deuterium, during the degassing of titanium hydride powders as the sample temperature was raised from room temperature to approximately 1100 °C. The results reveal an anomaly in the deuterium-to-hydrogen ratios, with the analysis indicating an increase in deuterium concentration by a factor of approximately 280 compared to its natural concentration on Earth. Three independent methods confirmed the excess deuterium. Simultaneously, flow calorimetry was performed during the degassing process, which did not show any measurable excess heat produced in the configuration used. This study was motivated by our novel theoretical predictions, based on the standard electroweak theory with gauge symmetry, suggesting the generation of slow neutrons within metal hydrides when exposed to coherent excitations. Our findings align with direct measurements of neutron emission by TiHx powders under cavitation in liquid water, as recently published by Fomitchev-Zamilov.

Isotope-dependent site occupation of hydrogen in epitaxial titanium hydride nanofilms

Hydrogen, the smallest and lightest element, readily permeates a variety of materials and modulates their physical properties. Identification of the hydrogen lattice location and its amount in crystals is key to understanding and controlling the hydrogen-induced properties. Combining nuclear reaction analysis (NRA) with the ion channeling technique, we experimentally determined the locations of H and D in epitaxial nanofilms of titanium hydrides from the analysis of the two-dimensional angular mappings of NRA yields. Here we show that 11 at% of H are located at the octahedral site with the remaining H atoms in the tetrahedral site. Density functional theory calculations revealed that the structures with the partial octahedral site occupation are stabilized by the Fermi level shift and Jahn-Teller effect induced by hydrogen. In contrast, D was found to solely occupy the tetrahedral site owing to the mass effect on the zero-point vibrational energy. These findings suggest that site occupation of hydrogen can be controlled by changing the isotope mixture ratio, which leads to promising manifestation of novel hydrogen-related phenomena.

High speed impact induced dehydrogenation of titanium hydride and formation of cellular structure via cold spray

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.

MICROSTRUCTURE AND WEAR BEHAVIOR CHARACTERIZATION OF STIR-CAST ALUMINUM 6063 ALLOY AND ITS FOAM: A COMPARATIVE STUDY

In this research work, aluminum 6063 alloy foam was synthesized through stir casting using varying amounts of titanium hydride as a foaming agent. A comparative microstructural and wear behavior analysis of stir-cast aluminum 6063 alloy and its foam is presented. The oxide and aluminide phases present as intermetallic compounds in the stir-cast aluminum 6063 alloy foam ensure the stability of the synthesized foam. In order to optimize the effect of wear parameters on the tribological properties of stir-cast aluminum 6063 alloy foam, the L933 orthogonal array (OA) was designed and modeled statistically. The tribological properties of stir-cast aluminum 6063 alloy and its foam were evaluated by pin-on-disc tests. The optimal tribological properties of the synthesized foam are 0.29 coefficient of friction, 8.6 N frictional force, and 0.00025 mm3/N-m specific wear rate. The tribological properties of stir-cast aluminum 6063 alloy foam are superior to those of aluminum 6063 alloy and comparable to other aluminum foams described in the literature.

Covalent Carbide Interconnects Enable Robust Interfaces and Thin SEI for Graphite Anode Stability under Extreme Fast Charging.

Carbonaceous and carbon-coated electrodes are ubiquitous in electrochemical energy storage and conversion technologies due to their electrochemical stability, lightweight nature, and relatively low cost. However, traditional reliance on conductive additives and binders leads to impermanent electrical pathways. Here, a general approach is presented to fabricate robust electrodes with a progressive failure mechanism by introducing carbide-based interconnects grown via carbothermal conversion of (5 wt%) titanium hydride nanoparticles. This method concurrently enhances both electrical and mechanical properties within the electrode architecture. The resulting chemical bonding between active materials establishes a novel mechanism to maintain stable electrical pathways during cycling. Employed as Li-ion battery anodes, these electrodes exhibit improved cyclability, achieving 80% capacity retention after 800 fast-charge cycles at moderate loading (1 mAh cm- 2). High loading cells with areal capacity of 3 mAh cm-2 show significantly improved cycle lifeover the same number of cycles. This performance improvement is attributed to the absence of significant impedance growth and a thinner solid electrolyte interphase (SEI) layer formed at high current densities (4C) as demonstrated by X-ray photoelectron spectroscopy and transmission electron microscopy studies. The enhanced conductivity facilitates SEI formation, lowering ionic impedance and mitigating lithium plating, ultimately leading to the reported extended cycle life.

Mechanical energy absorption capacity of the porous Ti-6Al-4V alloy under quasi-static and dynamic compression

Porous materials are very efficient in absorbing mechanical energy in different applications. In the present study, porous materials based on the Ti-6(wt.%)Al-4V alloy were manufactured with the use of two different powder metallurgy methods: i) blended elemental powder approach using titanium hydride (TiH2) as well as V-Al master alloy powders and ii) using hydrogenated Ti-6-4 pre-alloyed powder. The powder compacts were sintered with additions of ammonium bicarbonate as a pore-holding removable agent. The emission of hydrogen from hydrogenated powders on vacuum sintering and the resulting shrinkage of powder particles permitted the control of the sintering process and creation of anticipated porous structures. Mechanical characteristics were evaluated under quasi-static and dynamic compressive loading conditions. Dynamic compression tests were performed using the direct impact Hopkinson pressure bar technique. All investigations aimed at characterizing the mechanical energy-absorbing ability of the obtained porous structures. The anticipated strength, plasticity, and energy-absorbing characteristics of porous Ti-6-4 material were evaluated, and the possibilities of their application were also discussed. Based on the obtained results, it was found that porous Ti-6-4 material produced with a blended elemental powder approach showed more promising energy absorption properties in comparison with pre-alloyed powder.

Ti-decorated B-doped biphenylene: A hydrogen storage sponge at room temperature

It has always been a difficult problem to design Kubas-type hydrogen storage materials that make hydrogen molecules activate but do not dissociate. Density functional theory calculations confirm that Ti decorated B-doped biphenylene is the first two-dimensional room-temperature hydrogen storage sponge reported so far. The hydrogen adsorption energy of Ti-decorated B-doped biphenylene is in the range of −0.29 ∼ −0.51 eV with hydrogen storage capacity is 6.58–9.13 wt%. What's very interesting and exciting is that the Kubas interaction between Ti sites and H2 can be regulated by changing the electron occupation state of the dx2-y2 orbitals of Ti, and this regulation can be realized through the uniaxial lattice strain in the XOY plane. The average hydrogen adsorption energy of tensile Ti-decorated B-doped biphenylene ranges between −0.34 ∼ −0.66 eV, while −0.22 ∼ −0.48 eV for compressed one. This process makes the reversible hydrogen storage as simple and feasible as a sponge absorbing water. This study provides clear structural for the transformation mechanism to form a folded structure and also provides an important precedent model.

Correlating the microstructure of titanium hydride with its hydrogenation conditions via thermodynamics and kinetics

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.

Enhancing hydrogen storage properties of titanium hydride TiH2 with vacancy defects and uniaxial strain: A first-principles study

The structural, electronic, and thermodynamic properties of titanium hydride TiH2 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.H2 and a decomposition temperature Tdes 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.H2 to −40.97 kJ/mol.H2 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.H2 and 316.97 K.

Compressor‐Driven Titanium and Magnesium Hydride Systems for Thermal Energy Storage: Thermodynamic Assessment

ABSTRACTMetal hydrides enable excellent thermal energy storage due to their high energy density, extended storage capability, and cost‐effective operation. A metal hydride‐driven storage system couples two reactors that assist in thermochemical storage using cyclic operation. Metal hydride reactors, operating at both low and high temperatures, serve for the storage of hydrogen and thermal energy, respectively. The integration of efficient thermal energy storage technology is known to enhance the efficiency of solar thermal systems. In this regard, during the peak hours of solar energy, the high‐temperature supply heat can be utilized to store hydrogen gas in the low‐temperature reactor, which simultaneously facilitates energy storage in the high‐temperature reactor. Moreover, the temperature and energy released from the reactors are highly dependent on the pressure of the gas. As a result, installing a compressor between the low and high‐temperature metal hydride reactors can help generate additional outputs, such as a cooling effect. This paper conducts a thermodynamic analysis to assess the system's performance, considering parameters such as thermal storage efficiency, coefficient of performance (COP), and COPCCH (combined cooling and heating based COP). Moreover, the performance analysis was carried out for two cases, that is, high‐temperature titanium hydride (TiH2) and magnesium hydride (MgH2). The results show that MgH2 and TiH2 achieve a maximum COPCCH of 1.08 and 0.9, respectively, and system storage efficiency of 76.15% and 74.34%, respectively. In spite of having lower efficiency than MgH2, the TiH2‐based system has the ability to recover heat at a very high temperature.

Coating Titanium Transport Layers for Enhanced Short and Long Term Performance in PEM Water Electrolysis Cells

The ageing of titanium porous transport layers (PTL) affects the longevity of polymer electrolyte membrane water electrolysis systems by the formation and thickening of a weakly conductive oxide layer. The evolving oxygen on the anode in combination with the high electrical potential provides a challenging environment in which a low electrical contact resistance to the catalyst layer (CL) needs to sustain over a long period. One previous approach is a precious metal coating of the PTL with platinum or iridium [1], which can prevent oxidation of the titanium. A cost-effective alternative is a hydrochloric acid treatment, which forms titanium hydride (TiH). [2] Titanium nitride (TiN) promises better electrical conductivity with similar corrosion resistance, but has not yet been tested as a coating. The same is true for niobium, which performed well as a coating for stainless steel bipolar plates. [3] In our studies, all these candidates face the same conditions aside an untreated PTL in one unique series of measurements. All types are repeated three times to ensure reproducibility. The mean polarization curves (figure 1 left) show that the two precious metals, iridium and platinum, significantly improve the cell voltage at a current density of 2A/cm² by 80mV and 95mV, respectively. Titanium hydride achieves an even higher reduction of 100mV without the use of precious metals. The high frequency resistance plots in figure 1 right determine that the improvement of up to 20% or 30mΩ∙cm² is attributable to a reduced contact resistance to the CL. This assumption is proven by the fact that a PTL that is only coated with iridium on the side facing the CL behaves identically to a PTL that is coated on both sides. The ohmic losses in contact with the BPP are therefore negligible in these experiments. Titanium nitride and niobium coated PTLs behave in the same way as the reference measurement. In addition to the measurements shown, long-term experiments (>1000 hours) are currently running for all types of coating, and corrosion measurements in sulphuric acid are being carried out in parallel. The joint results will determine the suitability of the various coatings for long-term use in electrolysers.[1] Liu, C., Shviro, M., Gago, A. S., Zaccarine, S. F., Bender, G., Gazdzicki, P., Morawietz, T., Biswas, I., Rasinski, M., Everwand, A., Schierholz, R., Pfeilsticker, J., Müller, M., Lopes, P. P., Eichel, R.-A., Pivovar, B., Pylypenko, S., Friedrich, K. A., Lehnert, W., Carmo, M., Exploring the Interface of Skin-Layered Titanium Fibers for Electrochemical Water Splitting. Adv. Energy Mater. 2021, 11, 2002926. https://doi.org/10.1002/aenm.202002926[2] Bystron, T., Vesely, M., Paidar, M. et al. Enhancing PEM water electrolysis efficiency by reducing the extent of Ti gas diffusion layer passivation. J Appl Electrochem 48, 713–723 (2018). https://doi.org/10.1007/s10800-018-1174-6[3] Stiber, S., Hehemann, M., Carmo, M., Müller, M., Ayers, K.E., Capuano, C., Danilovic, N., Morawietz, T., Biswas, I., Gazdzicki, P., Heger, J.-F., Gago, A.S. and Friedrich, K.A. (2022), Long-Term Operation of Nb-Coated Stainless Steel Bipolar Plates for Proton Exchange Membrane Water Electrolyzers. Adv. Energy Sustainability Res., 3: 2200024. https://doi.org/10.1002/aesr.202200024 Figure 1

Elastoplastic and Electrochemical Characterization of xTiB2 Strengthened Ti Porous Composites for Their Potential Biomedical Applications

The microstructure, elastoplastic properties, and corrosive response of induced porous Ti-TiH2 materials reinforced with TiB2 particles were investigated. Samples were fabricated using CP-Ti Grade1, Titanium Hydride (TiH2), TiB2 powders (0, 3, 10, and 30 vol.%), and ammonium bicarbonate salt (40 vol.%) as a space holder. Composites were fabricated using the Powder Metallurgy technique under high-vacuum conditions (HVS) at 1100 °C. Scanning electron microscopy, X-ray diffraction, nanoindentation tests, and electrochemical assays were used to investigate the pore formation, pore distribution, phase formation, elastoplastic properties, and electrochemical behavior of the compounds, respectively. With a mean pore diameter of 50–900 µm and Young’s modulus of less than 100 GPa, which is close to the properties of human bone, the pore structures of the compounds processed here are shown to be a potential biomaterial for osseointegration. In addition, their H/Er and H3/Er2 ratios for the reinforced samples are higher than those of the unreinforced sample (1.5 and 4 times higher than the unreinforced sample, respectively), suggesting a better wear resistance of the Ti-TiH2/xTiB2 composites. Electrochemical experiments demonstrated that the Ti-TiH2/xTiB2 composites exhibited superior passivation properties compared to the Ti-TiH2 sample. Additionally, the corrosion rates exhibited by the 3 and 10 vol.% of TiB2 samples were found to be within an acceptable range for potential biomedical applications (29.26 and 185.82 E-3 mm·y−1). The elastoplastic properties combined with the electrochemical behavior place the Ti-TiH2/3-10TiB2 composites as potential candidates for the biomedical application of CP-Ti.

Operando visualization of porous metal additive manufacturing with foaming agents through high-speed x-ray imaging

Porous metals find extensive applications in soundproofing, filtration, catalysis, and energy-absorbing structures, thanks to their unique internal pore structure and high specific strength. In recent years, there has been an increasing interest in fabricating porous metals using additive manufacturing (AM), leveraging its unique advantages, including improved design freedom, spatial material control, and cost-effective small-batch production. In this study, we conducted pioneering operando visualization of AM porous metal using a laser powder bed fusion (L-PBF) setup combined with a high-speed synchrotron x-ray imaging system. Single track printing experiments using Ti6Al4V (Ti64) combined with titanium hydride (TiH2) and sodium carbonate (Na2CO3) as foaming agents, with varying mixing ratios were performed under different processing conditions. The results elucidate the dynamic development of porosity formation. The average pore size is significantly influenced by the particle size of foaming agents when pore coalescence is absent. For all foaming agent content tested in the current study, the number of pores is found to be more sensitive to changes in laser power than in laser scanning speed. Increasing linear energy density (increasing laser power or reducing laser scanning speed) promotes the foaming agent activation thereby porosity formation. However, high linear energy density skews pore distribution towards the surface despite forming deeper melt pools. In addition, the impact of additional factors including foaming agent’s laser absorptivity and decomposition kinetics with respect to AM time scales should be carefully considered to avoid ineffective activation of foaming agents during the AM of porous metals.

A closed-loop patch based on bioinspired infection sensor for wound management

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 (TiH1.924) 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.

The Effect of Implantoplasty on the Fatigue Behavior and Corrosion Resistance in Titanium Dental Implants.

Implantoplasty is a technique increasingly used to remove the biofilm that causes peri-implantitis on dental implants. This technique of mechanization of the titanium surface makes it possible to eliminate bacterial colonies, but it can generate variations in the properties of the implant. These variations, especially those in fatigue resistance and electrochemical corrosion behavior, have not been studied much. In this work, fatigue tests were performed on 60 dental implants without implantoplasty, namely 30 in air and 30 in Hank's solution at 37 °C, and 60 with implatoplasty, namely 30 in air and 30 in Hank's solution at 37 °C, using triaxial tension-compression and torsion stresses simulating human chewing. Mechanical tests were performed with a Bionix servo-hydraulic testing machine and fracture surfaces were studied by scanning electron microcopyElectrochemical corrosion tests were performed on 20 dental implants to determine the corrosion potentials and corrosion intensity for control implants and implantoplasty implants. Studies of titanium ion release to the physiological medium were carried out for each type of dental implants by Inductively Coupled-Plasma Mass Spectrometry at different immersion times at 37 °C. The results show a loss of fatigue caused by the implantoplasty of 30%, observing that the nucleation points of the cracks are in the areas of high deformation in the areas of the implant neck where the mechanization produced in the treatment of the implantoplasty causes an exaltation of fatigue cracks. It has been observed that tests performed in Hank's solution reduce the fatigue life due to the incorporation of hydrogen in the titanium causing the formation of hydrides that embrittle the dental implant. Likewise, the implantoplasty causes a reduction of the corrosion resistance with some pitting on the machined surface. Ion release analyses are slightly higher in the implantoplasted samples but do not show statistically significant differences. It has been observed that the physiological environment reduces the fatigue life of the implants due to the penetration of hydrogen into the titanium forming titanium hydrides which embrittle the implant. These results should be taken into account by clinicians to determine the convenience of performing a treatment such as implantoplasty that reduces the mechanical behavior and increases the chemical degradation of the titanium dental implant.

Reaction path search for propane dehydrogenation and metathesis on titanium hydride

Abstract The reaction mechanisms of C3H8 dehydrogenation and subsequent metathesis on a TiH2 surface were investigated using an automated reaction path search method. The predicted pathway suggests that dehydrogenation could occur at the H vacancies present on the TiH2 surface. The propylidene species formed by the initial dehydrogenation reaction are crucial intermediates in butane formation; this compound is in turn required by the subsequent metathesis reaction on the surface of the metal hydrides.

Insights into the formation of titanium hydrides from first principles calculations

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 TiHm 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 TiHm, 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.

Hydrogen storage properties of Ti-doped C20 nanocage and its derivatives: A comprehensive density functional theory investigation

We have innovatively designed and assessed the hydrogen storage properties of a single Ti-doped C20 nanocage and its B, N or B and N heteroatom substituted derivatives with the help of the density functional theory approach for the first time to the best of our knowledge. Out of fifteen designed structures by substituting heteroatoms, only 8 structures are found to be suitable for Ti doping and H2 adsorption viz. C20, C12N8, C12B8, C12B4N4, C10B5N5, C10B10, B10C10 and B10N10. Their formation energy and cohesive energy values confirm the stability of all the structures. Ti atom binds more strongly with B, N or B and N heteroatom substituted C20 nanocage than unsubstituted C20 nanocage which is necessary to avoid clustering for multiple Ti doped nanocages. Among the eight Ti doped nanocages considered, H2 molecules strongly interact with Ti-doped C12B4N4 nanocage. The binding strength of Ti atom with nanocages decreases during the hydrogen adsorption process. The obtained H2 adsorption energy values for all the structures are within the range of 0.2–0.7 eV, which is conducive to reversible hydrogen storage. Calculated Gibbs free energy-corrected H2 adsorption energy values at different temperature and pressure indicate favorable H2 adsorption over the entire pressure range at room temperature. For Ti doped C20, C12N8, C12B8, C10B5N5, C10B10, B10N10, and B10C10 nanocages, H2 adsorption is thermodynamically favorable below 360, 350, 300, 285, 235, 277, and 251 K, respectively at 1 atm pressure. From PDOS analysis, it is observed that the 1s orbital of H overlaps with 3d orbital of Ti atom. The highest H2 desorption temperature is observed for the C12B4N4Ti nanocage, and the lowest for C10B10Ti, aligning well with the calculated adsorption energy values. As H2 desorption temperature is high, the stability of Ti-doped nanocages at high temperature (634 K) is confirmed using ab initio molecular dynamics simulations. Bader's quantum theory in atoms in molecules is used to prove the weak non-covalent interaction between all the atoms.

Energy release characteristics of PTFE/Al/TiH2 reactive jet with different TiH2 content

Titanium hydride (TiH2), a promising high-energy additive, is doped into PTFE/Al to optimize the energy output structure of the reactive jet and strive for better aftereffect damage ability to the target. Six types of PTFE/Al/TiH2 reactive liners with different TiH2 content are prepared by the molding and sintering method. The energy release characteristics of PTFE/Al/TiH2 reactive jet are tested by the transient explosion energy test, and are characterized from pressure and temperature. The reaction delay time, pressure history, and temperature history of the energy release process are obtained, then the actual value of released energy and reaction efficiency of the reactive jet are calculated. The results show that the peak pressure and temperature of the PTFE/Al/TiH2 jet initially increase and then decrease with increasing TiH2 content. When the TiH2 content is 10%, the actual value of released energy and reaction efficiency increased by 24% and 6.4%, respectively, compared to the PTFE/Al jet. The reaction duration of the reactive material is significantly prolonged as the TiH2 content increased from 0% to 30%. Finally, combined with the energy release behaviors of PAT material and the dynamic deformation process of liner, the enhancement mechanism of TiH2 on energy release of the reactive jet is expounded.