Low Hydrogen Content Research Articles

P‐34: Study on the Properties of Silicon‐Nitride Thin Films Deposited by PECVD

We have deposited silicon nitride (SiNx) film by plasma‐enhanced chemical vapor deposition at 230°C. The high‐quality SiNx with low hydrogen content, high compactness and low stress was achieved successfully by adjusting the pressure and silane‐ammonia gas flow ratio. The Refractive index, thickness and stress were tested by ellipsometer. The chemical bonding including Si‐N, Si‐H and N‐H in those films was analyzed by Fourier Transform Infrared Spectroscopy. The compactness was characterized by the etch rate of the film under plasma etching gas SF6 and O2.

Study of the hydrogenation effect on the structure and flattening of tubular samples of PT-7M titanium alloy

In this work, we analyze the effect of hydrogen embrittlement on the performance of PT-7M titanium alloy products. The above examples show that PT-7M titanium alloy products with a high hydrogen content are prone to cracking, the probability of their destruction increases. In the initial state, the samples were annealed in vacuum at 680 о. Hydrogenation of the samples was carried out by the diffusion method at room temperatures to concentrations of 0.002, 0.005 and 0.01 % (by mass) in a Siverts laboratory setup. The hydrogen content in the samples was determined on a highly sensitive G8 Galileo gas analyzer. To assess the effect of hydrogen embrittlement on the plastic properties and tendency to crack formation, the samples were tested for flattening. The structural state of the alloy was analyzed, which showed that hydride phases were observed to increase with increasing hydrogen concentration. The effect of structural changes in the alloy on the microhardness was studied. The X-ray diffraction analysis also showed the presence of hydride precipitates in the PT-7M alloy. Using the CAE ANSYS engineering complex, a numerical simulation of the stress-strain state of samples was carried out during a flattening test. The simulation results showed that the maximum stresses during flattening exceed the tensile strength. One of the reasons for the hydride phase precipitation is high stresses, which is also confirmed by the results of flattening tests and metallographic analysis: in local zones with an increased level of stresses in the material structure, a higher concentration of the TiHx hydride phase. Flattening tests also showed that the cause of cracking during flattening testing is the presence of brittle hydrides in the structure of the material: cracks are formed by the destruction of hydride phases. In the initial state and with a low hydrogen content (up to 0.002 mass %) no cracks were found in the samples. Thr research was conducted within the framework of the grant RNF No. 19-19-00332 "Development of scientifically substantiated approaches, hardware and software facilities for monitoring of damage of construction materials, based on the artificial intellect approaches to provide safe operation of technical objects in the Arctic conditions".

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

The Effect of Biodegradable Waste Pyrolysis Temperatures on Selected Biochar Properties.

Biochars produced during biodegradable waste pyrolysis are products with a wide range of environmental applications. The effect of impact biochars depends on their properties which determine the course of specific processes. The main aim of the study was to investigate the effect of pyrolysis temperature on selected properties of biochar produced from various plant wastes (beech wood chips, walnut shells, wheat-rye straw), the valorization of which is of key importance for the implementation of the circular economy. Biochars were produced at temperatures of: 400 °C, 500 °C, 600 °C and 700 °C in a nitrogen atmosphere. An increase in the pyrolysis temperature caused a drop in the biochar production yield. As the temperature increased, higher carbon content and lower hydrogen content could be seen in the products obtained. An increase in the pH and total organic carbon (TOC) values also found. The influence of temperature on ash content, observed in the case of BWS (biochar from walnut shell) and BWRS (biochar from wheat and rye straw), did not occur in the case of BWC (biochar from beech wood chips). Another parameter that demonstrated a growing tendency with increasing temperature was the BET specific surface area (except for biochars from wheat and rye straw). An increase in pyrolysis temperature caused a decrease in the diversity and density of the surface functional groups of biochars. The influence of the type of precursor used in the production of biochar on the presence of surface functional groups was demonstrated. The presence of intense stretching vibrations of C–O bonds, having a potential impact on the sorption capacity of biochars, was determined in the FTIR spectra of BWC600 and BWC700 biochars, this feature, combined with the large BET surface area, may affect the sorption potential of these biochars. The presence of this type of high-intensity vibrations was also observed in the spectra of biochar BWRS600 and BWRS700. This can compensate for the low BET surface value and play an important role when using these biochars in sorption processes for organic and inorganic compounds.

Effect of heating rate on gasification and phosphorus recovery for palm oil mill effluent in supercritical water

This study investigated the effects of the heating rate on the simultaneous production of gas and inorganic phosphorus (IP) from palm oil mill effluent in supercritical water (600 °C, 25 MPa). The heating rate was controlled by modulating the preheater lengths (1, 2, and 4 m) and flow rates (2 and 3 g/min). Faster heating rates were obtained using shorter-length preheaters, even at identical flow rates. Although the increased heating rate resulted in a higher carbon gasification efficiency and lower hydrogen content, it also reduced the amount of precipitated IP. As the effect of flow rate, which determined the residence time in the reactor, was much smaller than that of the heating rate, it can be concluded that the primary reactions of this process are completed in the preheater. This finding can help to guide the optimization of the POME recycling process.

The effect of hydrogen addition on the amplitude and harmonic response of azimuthal instabilities in a pressurized annular combustor

The present work introduces an annular combustion chamber operated at intermediate pressures. The combustor is operated with CH4-H2 blends leading to a variety of azimuthal combustion instabilities. The influence of the hydrogen content, the air mass flow rate and the equivalence ratio on the instabilities is investigated over a wide range of operating conditions with mean chamber pressures from 1.5 to 3.3 bar. This leads to a range of exit boundary conditions, from partially to fully reflecting. It is found that pure methane and methane-hydrogen mixtures with low hydrogen contents result in stable combustion. However, when the hydrogen content reaches 25% by volume high-amplitude instabilities are excited, which exhibit higher order harmonics with significant pressure amplitude contributions. Such harmonic response was not previously observed in atmospheric annular combustors. The amplitudes decrease slightly when the H2 content is increased further. The harmonic response is found to be amplitude dependent with fewer significant harmonic contributions occurring at low-amplitudes and a cut-on amplitude of the fundamental mode at which higher harmonics become significant. The interaction between the harmonic components of the pressure amplitudes is shown to follow a quadratic relationship. The modal response was analyzed and it was found that all high-amplitude instabilities feature clockwise spinning modes whereas lower-amplitude instabilities feature counter clockwise spinning modes. Finally, a low- and high-amplitude case were investigated in detail and phase-averaged images are discussed. The low-amplitude instabilities result in flame dynamics similar to those observed in atmospheric combustors previously whereas the high-amplitude instabilities exhibit large oscillations in the flame height and intensity. A characterization of the boundary conditions is also provided for numerical simulations which includes temperature measurements, acoustic characterization and cold flow velocity profiles.

Utilization of Agave durangensis leaves by Bacillus cereus 4N for polyhydroxybutyrate (PHB) biosynthesis

Lignocellulosic wastes may provide a means to economize polyhydroxybutyrate (PHB) production. This study has proposed the use of Agave durangensis leaves obtained from the artisanal mezcal industry as a novel substrate for this aim. Results revealed an increase in PHB biosynthesis (0.32 g/L) and improvement in %PHB (16.79–19.51%) by Bacillus cereus 4N when A. durangensis leaves used as carbon source were physically pre-treated by ultrasound for 30 min (ADL + US30’) and thermally pre-treated (ADL + Q). Chemical analyses and SEM studies revealed compositional and morphological changes when A. durangensis leaves were physically pre-treated. Also, elemental analysis of growth media showed that carbon/nitrogen ratios of 14–21, and low nitrogen, hydrogen, and protein content were well-suited for PHB biosynthesis. Confocal microscopy revealed morphological changes in the bacterial cell and carbonosome structure under the influence of different substrates. Finally, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) analyses showed that homopolymeric PHB with a high thermal-resistance (271.94–272.89 °C) was produced. Therefore, the present study demonstrates the potential use of physically pre-treated A. durangensis leaves to produce PHB. These results promote the development of a circular economy in Mexico, where lignocellulosic wastes can be employed to produce value-added biotechnological products.

A model to determine the effects of low proportion of hydrogen and the flame kernel radius on combustion and emission performance of direct injection spark ignition engine

The only product of hydrogen combustion is water, so it is very clean. In this paper, the effects of low hydrogen content and FKR on the performance of the GDI engine are mainly studied. The simulation results show that adding less than 3% hydrogen in the GDI engine can improve the BP and BT of the engine under typical urban conditions such as 1500 rpm and 2000 rpm. As the hydrogen volume fraction and the FKR increase, the LFS of the mixture increases, resulting in a shorter ignition delay, combustion delay, and 10–90 % MFB. However, an increase in FKR results in a decrease in the BP and BT. In terms of fuel economy, the BSFC decreases as the hydrogen content increases, but as FKR increases, the BSFC increases. In terms of emissions, the proportion of hydrogen increases, HC and NOx emissions increase, and CO and CO2 emissions decrease. Therefore, adding hydrogen to the GDI engine while adjusting the FKR can improve the dynamic performance of the engine and reduce CO and CO2 exhaust emissions.

Numerical study on the reaction mechanism of CO2 hydrogenation in atmospheric-pressure dielectric barrier discharge

Recently, the catalytic conversion of greenhouse gases by plasma technology has attracted more and more attention. In this paper, a two-dimensional fluid model is developed to study the reaction mechanism of plasma CO2 hydrogenation in atmospheric-pressure dielectric barrier discharge (DBD). The effect of varying volume ratio of CO2/H2 on reaction mechanism of CO2 hydrogenation is studied carefully, such as temporal and spatial density distributions of main radicals and ions, dynamics of streamer propagation, and generation and loss pathways of H, CO, and CH3OH. It is found that H, O, and CO are the three most abundant species, and lower hydrogen content in gas mixture promotes streamer propagation and the formation of conduction current in plasma column. Besides, H is mainly produced by electron-impact dissociation of H2 (e + H2 ⇒ e + 2H); O and CO are dominantly produced by electron-impact dissociation of CO2 (e + CO2 ⇒ e + CO + O). Interestingly, H addition reaction to the intermediate species CH3O (CH3O + H ⇒ CH3OH) is found to be the main reaction pathway for methanol formation. Finally, a schematic overview of dominant reaction pathways for plasma CO2 hydrogenation in atmospheric DBD is presented, which ultimately leads to a better understanding of the intrinsic reaction mechanism.

Gas-phase hydrodeoxygenation (HDO) of guaiacol over Pt/Al2O3 catalyst promoted by Nb2O5

Pt/xNb2O5/(100-x)Al2O3 (x = 0, 5, 20, 100, wt.%) catalysts were tested on the gas phase hydrodeoxygenation (HDO) of guaiacol (2-methoxyphenol, C7H8O2), model compound representative of the lignin-derived portion of the bio-oil produced after pyrolysis or HTL. The physicochemical properties of the catalysts were analyzed by XRD, N2 physisorption, CO chemisorption, and temperature programmed desorption of isopropylamine. The catalytic performances were evaluated in a continuous flow system at atmospheric pressure with the aim of reducing the oxygen content of the guaiacol molecule as an upgrading step of the biomass processing. The influence of H2 partial pressure, temperature, space velocity, and pure supports performance on both activity and selectivity was determined. The Pt/Nb2O5 catalyst exhibited superior oxygen removal. Niobia addition enhanced the selectivity towards phenol while Pt/Al2O3 formed mainly catechol. The interaction between Pt and NbOx species probably enables oxophilic sites formation which enhances DDO reaction towards phenol formation and less deactivation even at low hydrogen content.

Energy recovery from sewage sludge: Product characteristics, heating value prediction and reaction kinetics

Energy recovery from sewage sludge was carried out by using microwave and conventional torrefaction. The microwave torrefaction was carried out by using a laboratory-scale microwave oven that provides single-mode microwave irradiation at 2.45 GHz, and the amount of sewage sludge for each experiment was approximately 20 g. The efficiency of microwave heating can be substantially promoted at higher power level, resulting in higher heating rate and maximum temperature. According to higher energy yield and heating value of torrefied sewage sludge, the optimum power level for bioenergy produced by microwave torrefaction of sewage sludge should be 200 W. Because of lower mass yield and temperature required to obtain the same yield, microwave heating can be more effective than conventional heating for sewage sludge torrefaction. The elemental composition of torrefied sewage sludge at 400 W was similar to that of anthracite, and its low hydrogen and oxygen contents could prevent excessive formation of smoke. Two correlations were obtained to predict the HHV of SS based on proximate and elemental compositions. With the recovery of liquid and gas products as bioenergy, the energy return on investment for microwave torrefaction of sewage sludge can be up to 16.4, much higher than the minimum value required for a sustainable society. Because of lower activation energy but higher pre-exponential factor, microwave heating can be approximately five times faster than conventional heating.

Insights into magnesium borohydride dehydrogenation mechanism from its partial reversibility under moderate conditions

Magnesium borohydride, Mg(BH4)2, is a potential hydrogen storage material because of its high hydrogen capacity and favorable thermodynamic stability comparing to other borohydrides. Although various intermediates, which influence the hydrogen storage properties, have been explored during the hydrogen desorption process of Mg(BH4)2, the in-depth dehydrogenation mechanism is still unclear. Herein, partial reversibility of Mg(BH4)2 and its dehydrogenation mechanism are investigated by isothermal cycles. It is found that Mg(BH4)2 can release 7.06 wt% H2 at 270°C for 3-day duration. After rehydrogenation, 3.61 wt% H2 is released during the second dehydrogenation. In the third and fourth cycles of hydrogen desorption, 3.54 and 3.24 wt% H2 are released, respectively. By carefully analyzing de/rehydrogenated samples with nuclear magnetic resonance and Fourier transform infrared spectrometer methods, the MgB5H9, MgB2H6, MgB8H8, MgB9H9, and MgB12H12 borohydride intermediates can be confirmed. Among the intermediates, MgB5H9 and MgB9H9 possess reversibility to Mg(BH4)2, whereas MgB8H8 and MgB12H12 are irreversible under the current hydrogen absorption conditions of 120 bar hydrogen backpressure. Considering the content change trend of these intermediates during hydrogen de/absorption cycles, the partial dehydrogenation mechanism of Mg(BH4)2 is proposed. In general, there are two different kinds of borohydride intermediates consisting in the hydrogen de/absorption processes: the metastable kind, MgBxHy (x < y), and the stable kind, MgBzHz. During the early phase of dehydrogenation, Mg(BH4)2 tends to first decompose into MgBxHy, which possesses relatively high hydrogen content. Later, MgBzHz with relatively low hydrogen content will be transformed from both Mg(BH4)2 and MgBxHy and become the majority of the dehydrogenation products. Finally, MgBzHz will polymerize into intermediates with high ‘z’ values during further hydrogen desorption process, eventually MgB12H12. Such partial dehydrogenation mechanism of Mg(BH4)2 is assumed to be promoted to the general dehydrogenation process of Mg(BH4)2. Furthermore, the discovery of the reversible intermediates including MgB5H9 and MgB9H9 sheds light on the method of thermodynamically controlling the dehydrogenation conditions to selectively form reversible intermediates, for the purpose of enhancing the reversible properties of Mg(BH4)2.

On the role of traps in the microstructural control of environmental hydrogen embrittlement of a 7xxx series aluminum alloy

The nature of hydrogen traps and hydrogen embrittlement (HE) behavior of a 7xxx series aluminum alloy with different microstructural characteristics were investigated. Hydrogen trapped by Al lattice, dislocations, soluble second phase particles, and vacancies. Hydrogen-induced intergranular fracture occurred in the specimen with high hydrogen trapping at dislocations, due to a large amount of weakly bounded hydrogen to dislocations. HE resistance was firstly obtained by controlling distribution of soluble second phase particles, resulting in a lower hydrogen content resides at dislocations. However, an excessive increase in second phase particles led to HE sensitivity of the alloy due to hydrogen-induced decohesion at the particles.

Quantitative strengthening evaluation of powder metallurgy Ti–Zr binary alloys with high strength and ductility

Titanium is well-known for its high strength, good corrosion resistance, and biocompatibility. For further improvement of its mechanical properties, it is alloyed with other elements, such as zirconium. In this study, pre-mixed pure Ti powder and ZrH2 particles were employed to prepare extruded Ti–Zr alloys with a low hydrogen content via dehydrogenation after sintering. The Zr solutes were uniformly dissolved in the α-Ti matrix by applying the optimal conditions for homogenization and water-quenching heat treatment. The synthesized Ti–Zr alloys consisted of the equiaxed fine α-Ti grains via dynamic recrystallization during extrusion. When the ZrH2 particle content was less than 10 wt%, the extruded Ti–Zr alloys showed a large tensile elongation of more than 25% at room temperature with a yield stress of approximately 850 MPa. In the case of Ti–10% ZrH2 powder, the mean α-Ti grain size was 2.7 μm, which was smaller than that of extruded pure Ti (3.5 μm). By applying the Hall–Petch equation for grain refinement and Labusch model for Zr solid solution to quantitatively estimate the increase in the yield stress, it was clarified that both factors had an equal effect for Ti–5 and –10 wt% ZrH2 powder even with the dominance of solid-solution strengthening by Zr solutes for alloys with small Zr content.

Impact of Insulators and Their Deposition Method on the Reliability of AlInGaN-Based UVB LEDs

AlInGaN-based light emitting diodes (LEDs) emitting in the ultraviolet (UV) wavelength range around 310nm were fabricated using 300nm thick SiNx or SiO2 layers deposited by different types of plasma enhanced chemical vapor deposition (PECVD) for electrical insulation. The composition, deposition technique, and thermal treatment of the insulator were varied and its influence on the breakdown voltage, step coverage, and degradation behavior of the UVB LEDs was studied. LEDs with SiNx layers deposited by PECVD in a capacitively coupled (CC) deposition process at high temperatures showed the highest conformity, highest breakdown voltages, but also the fastest degradation. The degradation was reduced by annealing the wafers after the insulator deposition. If the SiNx or SiO2 was deposited by inductively coupled IC-PECVD instead, the conformity and breakdown voltages decreased. Insulators deposited by IC-PECVD showed a high rate of sudden failures during the first 1,000h of operation. Studies of the hydrogen content in the SiNx layer showed that the insulator with the highest hydrogen content (SiNx by CC-PECVD) resulted in the fastest degradation, while that with the lowest hydrogen content (SiO2 by IC-PECVD) showed a slower degradation.

Combustion Characteristics of Fluoropolymer Coated Boron Powders

ABSTRACT The problem of sluggish combustion reactivity of Boron (B) can be overcome by inclusion of fluoropolymers. In this paper, three commercial fluoropolymers; PVDF (59 wt% F), Viton (66 wt% F) and THV (72 wt% F) coated (Ca. 4 wt%) B powders (Ca. 1-µm in size) were prepared and their combustion characteristics have been investigated. Among the fluoropolymer-coated powders, THV coated B provided the highest average improvement in heat of oxidation, reactivity in terms of pressure generation and combustion temperature followed by Viton and PVDF coated B. The sequence of reactivity enhancement has been explained by the variances in gasification efficiencies of the boric oxide shell, induced by the thermal decomposition of the respective fluoropolymer coatings. THV with higher fluorine and lower hydrogen content, supposedly promotes better gasification of the boric oxide shell by releasing more fluorine rich alkanes/alkenes during thermal decomposition. However, PVDF predominantly produces HF, which apparently less effective in gasification of the boric oxide shell, resulting in limited improvement of the measured properties.

Assessment of Combustion and Gasification Behavior in a Bubbling Fluidized Bed Reactor: A Comparison between Biomass with and without Chemical Additives

During the storage of biogenic materials for energy utilization, destructions by microbial attacks are inevitable. Besides material degradation, self-ignition of wood chip piles also occurs consistently. Treating the feedstock with, for example, mineral additives such as Dolomite can inhibit the microbial destructions, though such treatment may affect the thermochemical conversion of the fuel particles. This study therefore demonstrates the effect of mixing 4 wt % calcium hydroxide with wood chips used as feedstock in a 20 kW (fuel input) bubbling fluidized bed reactor. The reactor consists of a 100 mm (inner diameter) cylindrical column with 1.0 m height, where both gasification and combustion modes can be applied. Six different tests within equivalence ratios of 0.1–1.1 are conducted, and in each run, both fluidization behavior and quality of the product gas at different reaction temperatures (750–900 °C) are analyzed and compared with the results from wood chips of the same particle size but without the additive. The results show that there is no significant difference in the product gas composition, but evidence shows that the chemical additive impacts on the bed pressure drop over the equivalence ratio tested. The gasification window is increased and the energy value of the product gas is higher with a lower hydrogen content. During the combustion, both the exit gas temperature and oxygen concentration are lower, suggesting that additional light molecules such as water vapor are released during the conversion of biomass mixed with additive.

A Density Functional Theory Study of the Hydrogen Absorption in High Entropy Alloy TiZrHfMoNb.

The high entropy alloy is promising for hydrogen storage, especially in regard to its adjustable hydrogen storage properties. Despite several experimental investigations, there still lacks a detailed atomic-level understanding of the hydrogenation process. In this study, based on first-principles calculations, the hydrogen behaviors and microstructural evolution in high entropy alloy TiZrHfMoNb during the hydrogen absorption are investigated systematically. At low hydrogen content, hydrogen atoms prefer to occupy the octahedral interstitial sites of the BCC phase, which is different from that in BCC pure metals; when the hydrogen content reaches 1.08 wt %, the BCC TiZrHfMoNb hydrides transform into FCC phase, and hydrogen atoms are more favorable to occupy the tetrahedral interstitial sites. Further radial distribution function (RDF) analysis indicates that the enhanced disorder of <hydrogen-hydrogen> bonds and decreased lattice distortion of the metal structure destabilize the BCC TiZrHfMoNb hydride and eventually induce the BCC → FCC phase transformation, which is quite different from that in conventional alloys; the difference originates from the severe lattice distortion in high entropy alloy. The phonon spectra of different TiZrHfMoNb hydrides show that the hydride with a H/M ratio of 2 dynamically has a stable lattice, corresponding to a hydrogen storage capacity of 1.94 wt %. The present study demonstrates that the high entropy alloys have unique hydrogen absorption ability, which may advance the related experimental and theoretical studies.

Formation and suppression of hydrogen blisters in tunnelling oxide passivating contact for crystalline silicon solar cells

The formation of hydrogen blisters in the fabrication of tunnelling oxide passivating contact (TOPCon) solar cells critically degrades passivation. In this study, we investigated the formation mechanism of blisters during the fabrication of TOPCons for crystalline silicon solar cells and the suppression of such blisters. We tested the effects of annealing temperature and duration, surface roughness, and deposition temperature on the blister formation, which was suppressed in two ways. First, TOPCon fabrication on a rough surface enhanced adhesion force, resulting in reduced blister formation after thermal annealing. Second, deposition or annealing at higher temperatures resulted in the reduction of hydrogen in the film. A sample fabricated through low-pressure chemical vapor deposition at 580 °C was free from silicon–hydrogen bonds and blisters after the TOPCon structure was annealed. Remarkably, samples after plasma-enhanced chemical vapor deposition at 300, 370, and 450 °C were already blistered in the as-deposited state, despite low hydrogen contents. Analysis of the hydrogen incorporation, microstructure, and deposition mechanism indicate that in plasma-enhanced chemical vapor deposition (PECVD) deposition, although the increase of substrate temperature reduces the hydrogen content, it risks the increase of porosity and molecular-hydrogen trapping, resulting in even more severe blistering.

NANOINDENTATION OF HYDROGEN ENRICHED Zr-1Nb ZIRCONIUM ALLOY NUCLEAR FUEL CLADDINGS

Zirconium alloys are being commonly used as a material of choice for nuclear fuel claddings in water cooled nuclear reactors for decades due to their good corrosion resistance and low neutron absorption. However, the increasing operation conditions of next generation nuclear reactors (Gen-V) in terms of higher temperatures, pressures and higher neutron flux requires evaluation of further Zr cladding usability. The embrittlement of Zr claddings due to hydrogen pickup from reactor coolant is one of the issues for its potential use in Gen-IV reactors. Nanoindentation is an effective tool for analysis of the change of mechanical properties of hydrogen enriched Zr claddings from localised material volume. Zirconium alloy Zr-1Nb (E110) with experimentally induced hydrides was analysed by the means of nanoindentation. Zirconium hydrides were formed in the material after exposure in high temperature water autoclave. The optimized methodology of surface preparation suitable for nanoindentation is described and the resulting surface quality is discussed. The nanoindentation measurements were performed as an array of 10x10 indents across areas with hydrides. Depth dependent hardness and reduced modulus values measured by nanoindentation were compared between the material with no hydrogen content, low hydrogen content (127 ppm H) and high hydrogen content (397 ppm H). Complementary microhardness measurements at HV 0.1 were performed on all materials for bulk material hardness comparison.