Phase Abundance Research Articles

The effect of phase contents on the properties of yttria stabilized zirconia dental materials fabricated by stereolithography-based additive manufacturing

The aim is to investigate the impact of phase contents on mechanical properties, translucency, and aging stability of additively manufactured yttria partially stabilized zirconia ceramics. For that purpose, we evaluated two PSZ materials. The first type was prepared utilizing commercially available 5 mol% yttria-stabilized zirconia(5Y-PSZ), while the second type, denoted as 3Y+8Y-PSZ ceramics, was fabricated by blending 3 mol% and 8 mol% yttria-stabilized zirconia powders. Compared to 5Y-PSZ (39.90 wt% tetragonal phases and c/a2 = 1.0141), 3Y+8Y-PSZ is characterized by a greater abundance of tetragonal phases (47.68 wt%), which display higher tetragonality (c/a2 = 1.0165) and lower yttrium oxide content (2.25mol%). As a result, the 3Y+8Y-PSZ demonstrates elevated strength (816.52 MPa) and toughness (4.32 MPa m1/2), accompanied by reduced translucency(CR:0.47) and it exhibits greater susceptibility to aging. The phase contents, yttrium oxide content, and lattice parameters in the tetragonal phase play a crucial role in determining the mechanical properties, translucency, and aging stability of PSZ ceramics.

A Log‐Ratio‐Based Algorithm for Petrologic Mass‐Balance Problems and Uncertainty Assessment

AbstractWe provide a new algorithm for mass‐balance calculations in petrology and geochemistry based on the log‐ratio approach championed initially by John Aitchison (e.g., Aitchison, 1982, https://doi.org/10.1111/j.2517-6161.1982.tb01195.x; Aitchison, 1984, https://doi.org/10.1007/bf01029316) along with the underlying principles, mathematical frameworks, and data requirements. Log‐ratio Inversion of Mixed End‐members (LIME) is written in MATLAB and calculates phase proportions in an experiment or rock given a bulk composition, the composition of each phase, and the associated compositional uncertainties. An important advantage of LIME is that performing the mass‐balance calculation in inverse log‐ratio space constrains phase proportions to be between 0 and 100 wt.%. Further, the resulting LIME phase proportions provide realistic estimates of uncertainty regardless of data distribution. These two characteristics of LIME improve upon standard multiple linear regression techniques, which may yield negative values for phase proportions if non‐constrained or report oversimplified symmetric errors. Primary applications of LIME include estimating phase abundances, calculating melting and metamorphic reaction stoichiometries, and checking for open system behavior in phase equilibria experiments. The technique presented here covers whole‐rock analysis, mineralogy, and phase abundance, but could be extended to isotopic tracers, trace element modeling, and regolith component un‐mixing. We highlight the importance of uncertainty estimations for phase abundances to the fields of petrology and geochemistry by comparing our results from LIME to previously published mass‐balance calculations. Furthermore, we present case studies that demonstrate the role of mass‐balance calculations in determining magma crystallinity and defining melting reactions.

Bacterial community and sensory quality from coffee are affected along fermentation under carbonic maceration

The diversity and activity of the indigenous microorganisms in coffee are essential for obtaining safe and good-quality coffee. The use of fermentation under carbonic maceration in coffee fruits showed a positive correlation between the bacterial community and sensory score. Thus, the objective of this study was to evaluate the bacterial diversity in coffee cherries during fermentation under carbonic maceration and their correlations with coffee-quality. Next-generation sequencing and Specialty Coffee Association protocol were used in this study. Predominance of Leuconostoc sp. and Lactobacillus sp. during fermentation was observed. Leuconostoc sp. had higher relative abundance in the initial phase of fermentation and at 18 and 28 °C than Lactobacillus sp. Furthermore, the greatest microbial diversity occurred at 38 °C and after 72 h. At this temperature, the relative abundance of Lactobacillus correlated positively with sensorial score. Thus, an increase in temperature and fermentation time favors Lactobacillus spp and coffee sensory quality.

Synchrotron x‐ray diffraction for sealed Mars Sample Return sample tubes

AbstractThe joint NASA‐ESA Mars sample return campaign aims to return up to 31 sample tubes containing drilled sedimentary and igneous cores and regolith. The titanium alloy tubes will initially still be sealed when they are retrieved. Several types of measurement will be carried out on sealed samples in the pre‐basic characterization phase of scientific investigation. We show that powder x‐ray diffraction (XRD) analysis can be successfully carried out on sealed samples using an x‐ray source at the I12 beamline of Diamond Light Source synchrotron. Our experiment used an analog sample tube and a Martian regolith analog (Icelandic basaltic sand). The titanium walls of the tube analog give strong but few diffraction peaks, making identification of the major constituent mineral phases feasible. A more significant constraint on quantification of mineral phase abundances by this XRD technique is likely to be the grain size of the sample. This technique opens up the possibility of initial mineralogical analysis of samples returned from Jezero crater without opening the sample tubes and the potential changes to the sample that entails.

Structures and electrochemical performances of La0.7Sm0.3MgNi3·6Co0.4 + xwt.%Ni (x = 0,5,10,15,20) alloys applied to Ni-MH battery

The La–Mg–Ni–Co-based AB2-type alloys, namely La0.7Sm0.3MgNi3·6Co0.4xwt.%Ni (x = 0,5,10, 15, 20), were synthesized through ball milling. The study focused on investigating the impact of Ni content on the structures and electrochemical properties. The structures of the samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Transmission electron microscope (TEM). It has been demonstrated that the experimental samples consist of a primary phase, LaMgNi4, and a secondary phase, LaNi5. The abundance of phases undergoes significant changes with variations in Ni content, while the phase composition remains constant. The results indicate that a rise in Ni concentration results in an elevation of the LaNi5 phase and a reduction of the LaMgNi4 phase. Additionally, ball milling and the addition of nickel contribute to the refinement of the alloy grains. As the nickel concentration reached 20 wt%, the cycle retention rate(S30) of the composite alloy electrode achieved its maximum value of 73.42 %. In addition, the electrochemical kinetic test findings demonstrated that the maximum D value of the hydrogen diffusion system was 1.807 × 10−10 cm2/s and that the maximum current density of the composite hydrogen storage alloy electrode was 723 mA/g when x = 0 wt%.

Compositional tuning of A2B7-type La0.7–xYxMg0.3Ni3.5 alloys for gaseous hydrogen storage

Rare earth-based superlattice alloys have great potential for gaseous hydrogen storage, as well as successful application as nickel-metal hydride batteries anodes. In this work, Y substitution was carried out to adjust the gaseous hydrogen storage properties of A2B7-type La0.7Mg0.3Ni3.5 alloys. The results indicate a multiphase structure in the alloys comprised of the main rhombohedral Gd2Co7 and PuNi3 phases, with a small amount of CaCu5 phase. Moreover, the Y substitution results in higher abundance of the Gd2Co7 phase. The alloy La0.42Y0.28Mg0.3Ni3.5 exhibits a hydrogen storage capacity of 1.55 wt% at 298 K and a desorption plateau pressure of 0.244 MPa. In addition, this alloy demonstrates a stable cycle life by a capacity retention of 94.2% after 50 cycles, with the main capacity degradation occurring during the initial 20 cycles. This work accentuates the potential of the La–Y–Mg–Ni-based superlattice alloys for applications in solid-state hydrogen storage.

Metal Deportment in Complex Secondary Raw Materials: The Case of Vanadium in Basic Oxygen Furnace Slags

With the increasing demand for metalliferous and mineral raw materials and the consequent depletion of the global natural resource base, the possible utilization of secondary raw material sources is receiving more and more attention. In the present study, we present results from a detailed vanadium deportment study of three basic oxygen furnace slag (BOS) samples known to containing elevated bulk concentrations of vanadium. Complementary analytical methods that were used to quantify the abundance and composition of V-containing phases include SEM-based automated mineralogy, X-ray fluorescence analysis, and X-ray powder diffraction as well as electron probe microanalysis. The vanadium deportment was quantified using Monte-Carlo simulations of the data obtained from automated mineralogy and electron microprobe analysis. The total V concentrations identified by XRF are between 1.7 and 2.2 wt.% V. The most important hosts of vanadium are larnite-, brownmillerite- and portlandite-solid solutions. In two samples Ca carbonates also significantly contribute to the V deportment, while wuestite, lime, and native iron do not contribute significantly to the vanadium deportment. A thorough consistency check identifies considerable uncertainties in the density of the V-bearing phases as the most likely reason to explain remaining discrepancies between measured and calculated V values.

Compilation of Henry's law constants (version 5.0.0) for water as solvent

Abstract. Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles. Therefore, it is necessary to understand their distribution between the phases. According to Henry’s law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution. Henry’s law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format. The compilation contains 46 434 values of Henry’s law constants for 10 173 species, collected from 995 references. It is also available on the internet at https://www.henrys-law.org (last access: October 2023). This article is a living review that supersedes the now obsolete publication by Sander (2015).

EPMA maps unveil the actual chemical variations and crystallisation sequence of pyroxene and plagioclase solidified from a basaltic liquid at variable cooling rates

Crystal-chemical variations of pyroxene (px) and plagioclase (plg) have been analysed by X-ray electron-microprobe (EPMA) mapping to quantify their actual chemical dispersions. These phases were experimentally crystallised from a basaltic liquid (B100, MORB from Iceland) at cooling rates of 1, 7, 60 and 180 °C/h from 1300 °C down to 800 °C. Experiments were run at ambient conditions applying defined temperature paths mirroring characteristic cooling rates from innermost to outermost portions of metre- to centimetre-thick lavas, dikes and bombs emplaced under submarine to subaerial conditions. As the cooling rate increases from 1 to 180 °C/h, the run-products become progressively enriched in pyroxene and depleted in plagioclase, while spinel is invariably low (few area%) and glass is significant only at 180 °C/h. An increase of cooling rate generally leads to enrichment of Al2O3 and depletion of MgO in px, while the opposite behaviour is observed for plg; these trends are mirrored by calculated cations (apfu: atom per formula unit) and components. Average variations as a function of cooling rate are similar to those already observed through classical analysis performed by single point EPMA. However, the actual chemical distributions of CaO versus MgO, Al2O3 and FeOtot oxides unveil the presence of a wider range in pyroxene chemistry. In particular, one px (px-1, CaO-rich, diopsidic type) is present at all the applied cooling rates; a very low CaO-px (px-2, pigeonite or orthopyroxene type) is detected at 1 °C/h; and, finally, once more population of px (px-3, CaO-poor diopsidic type) appears at 60 and 180 °C/h. By contrast, plg analyses yield invariably identical compositions. Textural variations as a function of cooling rate and geothermometric estimations indicate that px-1 crystallised at high-T (or low ΔT), while plg mainly grew in the residual melt produced by the saturation of px. If only textures were evaluated, this order of segregation would like remain unrecognised since px at low cooling rates is smaller than plg. The abundance of phases, their crystal-chemical features, and their order of segregation can be regarded through a theoretical framework of a time-temperature-transformation (TTT) diagram. The most significant chemical variations are displayed by MgO and Al2O3 for both px and plg, which faithfully capture the evolution of cooling conditions. The chemical compositions of px-1 is close to the thermodynamic equilibrium only at 1 °C/h. As the cooling rates increase, the px chemistry indicates disequilibrium conditions. Finally, this study shows that as ΔT/Δt increases, the most abundant px (px-1) and plg are forced towards compositions that become progressively closer to those of the parental liquid.

Characterization of mineral precipitation in artificially fractured chalk during flooding experiments for IOR research

Natural fractures in carbonate reservoirs are essential to effectively transport hydrocarbon in an otherwise low permeable matrix. However, they can reduce the wanted effect of water injection and Improved Oil Recovery (IOR), as the injected water mainly runs through the fractures. We have investigated chemical and textural alteration in and adjacent to an artificial fracture with an aperture of 2.25 (±0.05) mm in Upper Cretaceous chalk from the St. Vaast Formation (Mons Basin, Belgium). The sample has been injected mainly with 0.219 M MgCl₂ under reservoir conditions over two months. The fracture aperture reduced averagely by 76%. The analysis performed by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) show that, magnesite is the dominating precipitate in the fracture with sizes ranging from 0.5 to 5 μm. The abundance of magnesium phases in the fracture fill was also confirmed by Scanning Electron Microscopy (SEM) coupled with Energy-dispersive X-ray spectroscopy (EDS) and bulk geochemistry (Inductively Coupled Plasma Mass Spectrometry ICP-MS). Besides magnesite, phyllosilicates were observed by TEM and Helium Ion Microscopy combined with Secondary Ion Mass Spectrometry (HIM-SIMS). The newly formed material, precipitates, and possible reworked minerals are characterized by magnesite crystals being covered occasionally by phyllosilicates. This material has formed a distinct area bounded to the surrounding matrix. The final diameter of the precipitate measures about 2.75 (±0.15) mm, which indicates an incremental widening of the original fracture aperture. Calcite along fracture wall dissolved. Effluent concentration supports dissolution by an increase in Ca2⁺ and precipitation of magnesite by the loss of Mg2+. As either silica or aluminium is a component of the fluids, the origin of these elements is necessarily from the matrix of the chalk. It is yet unknown if phyllosilicates precipitated or was reworked, or both. Formation and concentration of magnesite and phyllosilicates in reservoir fractures can reduce fracture permeability over time and lead to subsequent propagation through the matrix of the reservoir rock. This in-depth mineralogical study of artificial fracture changes has the utmost importance for the implementation of techniques in fractured reservoirs.

Lithium isotope separation by precipitation method coupled with solvent extraction with 1-Hydroxy-4-(p-toluidino) anthraquinone

This paper reported a novel chelating agent and a green precipitation-extraction separation strategy for lithium isotope enrichment. 1-Hydroxy-4-(p-toluidino) anthraquinone and anisole were used as chelating agent and diluent, respectively. Three phases including organic phase, aqueous phase and precipitation could be preparated. The experiment indicated that excess sodium hydroxide was helpful to promote the single-stage precipitation rate and equilibrium time. The isotope result indicated that 6Li was concentrated in the aqueous phase and 7Li was concentrated in precipitation phase. The maximum single-stage lithium isotope speration factor reached to 1.013 ± 0.001. By doing thermodynamic analysis of the reaction, the free energy change (ΔG), enthalpy change (ΔH) and entropy change(ΔS) of the separation process were −8.97 J mol−1, −21.37 J mol−1 and −0.0438 J mol−1 K−1 at 283 K. The results of DFT simulation and wave function analysis indicated that a lithium ion combined with a chelating agent anion formed a stable six-member ring between two oxygen, which was more stable than sodium ions combined with chelating agent anions (the Gibbs free energy of the lithium ions reaction was more negative). As interaction analysis result showed, the Li-O bond in complex interaction was significantly stronger than the Li-O bond interaction in aqueous phase, which was the theroy that led to the enrichment of 7Li in organic phase. In the activated carbon treatment experiment, it was found that part of lithium chelator solved in aqueous phase, which resulted in that the lithium abundance of aqueous phase hardly changed. In order to increase the abundance of 6Li in aqueous phase, it is necessary to add adjuvant to reduce the water solubility of lithium chelate. Overall, an economical and environmental-friendly precipitation method with a certain application prospect for lithium isotope separation was proposed, and the direction of improving the separation performance was pointed out in this paper.

The potential of Sudanese Refractory Gold Ores Characterization and Pre-treatment in Ariab Mines (VMS) in Red Sea (Sudan)

This laboratory work demonstrates the ability to characterize and pre-treat Sudanese refractory gold ores at Ariab mines to extract the gold with optimal parameters. Characterization studies were performed by AAS, XRF and XRD analysis to assess the abundance of elements and mineral phases. In addition, the acidity of the ore was examined to estimate the effective amount of lime. The ore was subjected directly to cyanidation without any pre-treatment. High oxidation reagent processes were carried out to pre-treat the ore. Chemical analysis results show the gold grade to be 1.37 g/t. In addition, the ore contained 51.78% Fe2O3, 43.40% SO3, 2.39% CuO, 1.47% SiO2, 0.35% Cr2O3, 0.17% CaO, 0.08% As2O3, 0.06% ZnO and 0.06% MnO. The XRD result shows that the ore phases are Pyrite (FeS2), Chatkaite (Cu6Fe+2Sn2S2) and Quartz (SiO2). The investigations of direct cyanidation elucidated that the ore can consume a high amount of cyanide with unsatisfactory recoveries for gold (Exgold ≤39.41%). The influence of the cyanide concentration, pulp density (% by weight), leaching time hr, agitator speed and pH were examined in direct cyanidation experiments. In pre-treatment experiments, the effect of hydrogen peroxide (H2O2) and concentrations on gold recovery was studied. The pre-treatment of the ore with H2O2 achieved a good impact on the gold extraction performance. The higher gold extraction was obtained at hydrogen peroxide (H2O2) 300 ppm, cyanide concentration 3500 ppm, leaching time 10 hr, pH=10.5 and pulp density 40%.

Effect of Mischmetal Addition on Microstructure and Mechanical Properties of As-Cast and As-Rolled Mg–Sn–Ca Alloys

The microstructures and mechanical properties of Mg–3Sn–0.1Ca–xMM (mischmetal, x = 0.3, 0.6, and 0.9 wt.%) alloys were investigated. Optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) were used to characterize the microstructures and phase constitutions of the cast and rolled alloys. Room temperature tensile tests were conducted to obtain the mechanical properties and macro-textures to evaluate the texture weakening effect results of the MM. The results show that an abundance of second phase formed, confirmed as the (Ca,MM)MgSn phase, and the volume fraction increased with the increasing MM addition. The tensile yield strength of the as-cast alloys increased with the MM addition, but the elongation decreased. All of the rolled Mg–3Sn–0.1Ca–xMM alloys showed a strong basal texture, and only slightly decreased in intensity after annealing treatment due to the particle-stimulated nucleation of recrystallization. The as-annealed Mg–3Sn–0.1Ca–0.6MM alloys exhibited the highest tensile strengths of 266.5 ± 3.3 MPa and 136.1 ± 3.7 MPa, which are mainly ascribed to grain refinement strengthening, Orowan strengthening and texture strengthening.

Understanding molecular abundances in star-forming regions using interpretable machine learning

ABSTRACT Astrochemical modelling of the interstellar medium typically makes use of complex computational codes with parameters whose values can be varied. It is not always clear what the exact nature of the relationship is between these input parameters and the output molecular abundances. In this work, a feature importance analysis is conducted using SHapley Additive exPlanations (SHAP), an interpretable machine learning technique, to identify the most important physical parameters as well as their relationship with each output. The outputs are the abundances of species and ratios of abundances. In order to reduce the time taken for this process, a neural network emulator is trained to model each species’ output abundance and this emulator is used to perform the interpretable machine learning. SHAP is then used to further explore the relationship between the physical features and the abundances for the various species and ratios we considered. H2O and CO’s gas phase abundances are found to strongly depend on the metallicity. NH3 has a strong temperature dependence, with there being two temperature regimes (<100 K and >100 K). By analysing the chemical network, we relate this to the chemical reactions in our network and find the increased temperature results in increased efficiency of destruction pathways. We investigate the HCN/HNC ratio and show that it can be used as a cosmic thermometer, agreeing with the literature. This ratio is also found to be correlated with the metallicity. The HCN/CS ratio serves as a density tracer, but also has three separate temperature-dependence regimes, which are linked to the chemistry of the two molecules.

Effects of deep cryogenic treatment on microstructure, mechanical, and corrosion of ZK60 Mg alloy

This study aims to investigate the effects of deep cryogenic treatment combined with traditional heat treatment on the microstructural characteristics, mechanical properties, and corrosion performance of ZK60 magnesium alloy. Quasi-in-situ TEM testing also indicates that deep cryogenic treatment induces the formation of ultra-fine zinc-rich precipitates in the magnesium matrix. After solid solution treatment, materials with cryogenic treatment will retain significant internal stress, which promotes the subsequent precipitation of rod-like β′1 during aging. Microstructural analysis reveals that deep cryogenic treatment before solution treatment and artificial aging can significantly enhance the length and density of rod-like β′1 precipitates. The treated material shows improved strength while maintaining its original elongation rate. Due to the nanoscale precipitation-induced micro galvanic effect, the aged samples exhibit a higher corrosion rate. The abundance of micrometer-sized second phases in the untreated sample does not significantly accelerate the material's corrosion rate. The solution-treated samples show the weakest micro galvanic effect and the best corrosion resistance.

Understanding lanthanum effects on the structure and properties of LaxY1−xMgNi4 hydrogen storage alloys

This study mainly concentrated on investigating the effects on the crystal structure, hydrogen storage, and electrochemical properties of LaxY1−xMgNi4 (x = 0, 0.25, and 0.5) alloys. The refined X-ray diffraction patterns reveal the substitution by La results in a change in the phase composition and abundance of the compound and an increase in the lattice constants. La can increase the maximum hydrogen absorption capacity while decreasing the hydrogen absorption and desorption plateaus. However, increasing the La content leads to incomplete hydrogen desorption. In electrochemistry, La addition can improve the activation property, while the electrodes with higher Y content show better cycling stability. The La0 25Y0.75MgNi4 alloy exhibits a maximum capacity for discharge of ∼400 mAh g−1 @10 mA g−1. Its superior electrochemical kinetic performance is attributed to a higher hydrogen diffusion coefficient and exchange current density. Therefore, by optimizing the La content, the tested alloys' hydrogen storage, and electrochemical performance can be improved.

Clean fabrication strategy of diamond crystals containing nanocomposite films for corrosion and wear protection of AISI-321 alloy

This study focused on the synthesis of Niobium/Hexagonal-Diamond/Amorphous-Carbon (Nb/H-D: a-C) films on AISI-321 alloy. The substrate heating used as a vital deposition parameter to tailor structure of the films in an unbalanced magnetron (UB-M) sputtering system for the first time. The substrate heater temperature (Th) ranged between (RT) to 150 °C. The results indicated that increasing the substrate heater temperature promoted the abundance of hexagonal diamond (H-Diamond) crystals through the solid phase separation. Therefore, the film deposited at the highest temperature (150 °C) demonstrated the highest plenty of H-Diamond. Electrochemical impedance spectroscopy (EIS) measurements (after 2, 8, 24, 72, and 168 h immersion) and polarization tests (after 168 h immersion) disclosed that increasing the substrate heater temperature positively affects the corrosion resistance of (Nb/H-D: a-C) films. The results proved that the film deposited at the highest temperature of 150 °C, demonstrated the exceptional corrosion protection efficiency of 99.69 %. Moreover, this film presented acceptable low-frequency impedance (|Z|10KHz) and total resistance (Rt) values of >108 Ω·cm2 and >117 MΩ·cm2 at all immersion times in 3.5 wt% NaCl solution. The highest abundance of the H-Diamond phase, with remarkable chemical inertness at higher substrate heater temperatures, can be an effective reason for elevating anti-corrosion performance of the films. Additionally, as the substrate heater temperature enhanced from RT to 150 °C, mechanical properties illustrated an remarkable increment trend (increasing hardness from 20 to 32.7 GPa and the elasticity modulus from 407 to 470 GPa). Moreover, the anti-wear performances of the films significantly improved with increasing substrate heater temperature, reducing the wear rate from 9.4 × 10−6 to 9 × 10−7 mm3/N·m. These results are mainly attributed to the highest abundance of the superhard H-Diamond phase in the film deposited at higher substrate heater temperature. In conclusion, the (Nb/H-D: a-C) film synthesized at 150 °C represented a promising candidate for tailoring the electrochemical and anti-wear performances of AISI-321 alloy.

The phase structures and electrochemical properties of (La, Mg)(Ni, Co)3.7M0.1 (M = Zr, Cr, Al, Mn, Ni) hydrogen storage alloys

A5B19 phase were obtained by using the La-Ni and Mg-La precursors instead of La, Mg and Ni pure metal to prepare the La0.85Mg0.15Ni2.65Co1.05M0.1 alloys (M = Ni, Zr, Cr, Al, Mn). Rietveld refinement of XRD shows that there are (La, Mg)5Ni19 (Ce5Co19 + Pr5Co19), and LaNi5 phases in the La0.85Mg0.15Ni2.65Co1.05M0.1 alloys, and the elements of Mn or Cr and Al or Zr can respectively promote the formation of Pr5Co19 phase and (La, Mg)2Ni7 phase. Electrochemical tests reveals that the maximum discharge capacity (Cmax) of the alloys correspondingly change with the abundance of A5B19 phase which possesses higher hydrogen storage capacity. The elements of Al and Zr can improve the cycling stability, but decrease the high-rate dischargeability. This result can be due to the properties of the surface oxide film which can reduce corrosion and decrease the surface catalytic activity. The kinetics analysis revealed that the kinetics performance of alloy of M = Al is mainly affected by I0, and that of the other alloys benefits from both I0 and D.

A Computational Investigation into the Hydrogenation of NO on Water Ice Surfaces to Rationalize the NO:HNO:NOH Disparity in Space

Molecules possessing NO bonds are important precursors in biology; however, in the interstellar medium (ISM), such bonds are observed in relatively low abundance. NO and HNO are two species detected concurrently within the ISM that contain this bond in its simplest form. However, NO is observed to be approximately 200 times more abundant than HNO, which is curious due to the ubiquity of hydrogenated species in the ISM. In the present work, we use computational techniques to determine whether (i) HNO can be formed from NO on cold dust grain surfaces and (ii) if formed, HNO is able to desorb from the surface. Dust grains, which at low (10 K) temperature are primarily coated in water ice, are modeled using both hexagonal and amorphous ice models. A strong thermodynamic driving force is calculated for NO hydrogenation to HNO on the water ice surfaces, suggesting facile formation of HNO. Interestingly, the formation of NOH is also a thermodynamic possibility. Investigation into the reaction kinetics showed no barrier to hydrogenation in either scenario on the hexagonal ice surface; however, on the more astronomically relevant amorphous ice, barriers of 0.53 eV (51 kJ mol–1) and 0.77 eV (74 kJ mol–1) are observed for the formation of HNO and NOH, respectively. Comparison of the adsorption energies showed NO to bind to the surface the weakest (< –0.2 eV/–19 kJ mol–1), followed by HNO (< –0.6 eV/–58 kJ mol–1), and then NOH (< –1.50 eV/–144 kJ mol–1). This suggests that, once formed, HNO is likely to remain adsorbed to the surface, thus accounting for the lower gas phase abundance observed compared to NO. NOH, if formed, will be even less likely to desorb in appreciable amounts and hence remains undetected. Combined, the results suggest that hydrogenated species are possible to be formed from NO on ice surfaces and are likely to remain bound to the surface, supporting the experimental observations.

Numerical Simulations Reproduce Field Observations Showing Transient Weakening During Shear Zone Formation by Diffusional Hydrogen Influx and H2O Inflow

AbstractExposures on Holsnøy island (Bergen Arcs, Norway) indicate fluid infiltration through fractures into a dry, metastable granulite, which triggered a kinetically delayed eclogitization, a transient weakening during fluid‐rock interaction, and formation of shear zones that widened during shearing. It remains unclear whether the effects of grain boundary‐assisted aqueous fluid inflow on the duration of granulite hydration were influenced by a diffusional hydrogen influx accompanying the fluid inflow. To better estimate the fluid infiltration efficiencies and the parameter interdependencies, a 1D numerical model of a viscous shear zone is utilized and validated using measured mineral phase abundance distributions and H2O‐contents in nominally anhydrous minerals of the original granulite assemblage to constrain the hydration by aqueous fluid inflow and diffusional hydrogen influx, respectively. Both hydrations are described with a diffusion equation and affect the effective viscosity. Shear zone kinematics are constrained by the observed shear strain and thickness. The model fits the phase abundance and H2O‐content profiles if the effective hydrogen diffusivity is approximately one order of magnitude higher than the diffusivity for aqueous fluid inflow. The observed shear zone thickness is reproduced if the viscosity ratio between dry granulite and deforming, reequilibrating eclogite is ∼104 and that between dry granulite and hydrated granulite is ∼102. The results suggest shear velocities &lt;10−2 cm/a, hydrogen diffusivities of ∼10−13±1 m2/s, and a shearing duration of &lt;10 years. This study successfully links and validates field data to a shear zone model and highlights the importance of hydrogen diffusion for shear zone widening and eclogitization.