Mole Fraction Research Articles

Investigating the oxidation characteristic of a hydro-processed bio-jet fuel: Experimental and modeling study

A rapid transition from conventional jet fuels to sustainable aviation fuels (SAFs) is imperative in order to reduce carbon emissions. Hydro-processed esters and fatty acids synthetic paraffinic kerosene (HEFA-SPK), as a type of SAF, exhibits broad applications. In this study, a new HEFA-SPK named ZH-HEFA was investigated. The fuel comprises 14% n-alkanes, 85% iso-alkanes and only 1% cycloalkanes by weight, with the majority of alkanes ranging from C9 to C17. Oxidation experiments of the fuel were conducted using an atmospheric pressure flow reactor at temperatures ranging from 550 K to 1075 K under three equivalence ratios (0.5, 1.0 and 1.5). Species mole fraction profiles were measured by an on-line gas chromatographic (GC). For comparison purposes, an experiment was also performed on RP-3, a conventional jet fuel commonly used in China, under the equivalence of 0.5. Compared to RP-3, ZH-HEFA exhibited significantly stronger low temperature reactivity and higher combustion conversion rates while demonstrating considerably lower yields of aromatics at high temperatures. The kinetic simulation of ZH-HEFA was achieved by proposing two surrogates and their corresponding kinetic models. Surrogate S-1 consisted solely of n-dodecane, while S-2 comprised 35% n-dodecane and 65% 2,6,10-trimethyl dodecane by weight. Both surrogate models were validated by the experimental data. S-1 exhibited a closer resemblance to the global oxidation characteristics of ZH-HEFA, whereas S-2 demonstrated improved accuracy in predicting the formation of small hydrocarbon intermediates during the fuel oxidation. Rate of production analysis revealed that the branched alkane component in S-2 possessed more pathways and greater capability than S-1 in generating C3 intermediates, which are important for the generation of aromatics. Furthermore, both models displayed good predictive performance for the auto-ignition properties of HEFA-SPK fuels.-

Uncertainty Quantification of Linear Scaling, Machine Learning, and Density Functional Theory Derived Thermodynamics for the Catalytic Partial Oxidation of Methane on Rhodium.

Accurate and complete microkinetic models (MKMs) are powerful for anticipating the behavior of complex chemical systems at different operating conditions. In heterogeneous catalysis, they can be further used for the rapid development and screening of new catalysts. Density functional theory (DFT) is often used to calculate the parameters used in MKMs with relatively high fidelity. However, given the high cost of DFT calculations for adsorbates in heterogeneous catalysis, linear scaling relations (LSRs) and machine learning (ML) models were developed to give rapid estimates of the parameters in MKM. Regardless of the method, few studies have attempted to quantify the uncertainty in catalytic MKMs, as the uncertainties are often orders of magnitude larger than those for gas phase models. This study explores uncertainty quantification and Bayesian Parameter Estimation for thermodynamic parameters calculated by DFT, LSRs, and GemNet-OC, a ML model developed under the Open Catalyst Project. A model for catalytic partial oxidation of methane (CPOX) on Rhodium was chosen as a case study, in which the model's thermodynamic parameters and their associated uncertainties were determined using DFT, LSR, and GemNet-OC. Markov Chain Monte Carlo coupled with Ensemble Slice Sampling was used to sample the highest probability density (HPD) region of the posterior and determine the maximum of the a posteriori (MAP) for each thermodynamic parameter included. The optimized microkinetic models for each of the three estimation methods had quite similar mechanisms and agreed well with the experimental data for gas phase mole fractions. Exploration of the HPD region of the posterior further revealed that adsorbed hydroxide and oxygen likely bind on facets other than Rhodium 111. The demonstrated workflow addresses the issue of inaccuracies arising from the integration of data from multiple sources by considering both experimental and computational uncertainties, and further reveals information about the active site that would not have been discovered without considering the posterior.

The Impact of Hydrogen on Flame Characteristics and Pollutant Emissions in Natural Gas Industrial Combustion Systems

To improve energy savings and emission reduction in industrial heating furnaces, this study investigated the impact of various molar fractions of hydrogen on natural gas combustion and compared the results of the Non-Premixed Combustion Model with the Eddy Dissipation Combustion Model. Initially, natural gas combustion in an industrial heating furnace was investigated experimentally, and these results were used as boundary conditions for CFD simulations. The diffusion flame and combustion characteristics of natural gas were simulated using both the non-premixed combustion model and the Eddy Dissipation Combustion Model. The results indicated that the Non-Premixed Combustion Model provided simulations more consistent with experimental data, within acceptable error margins, thus validating the accuracy of the numerical simulations. Additionally, to analyze the impact of hydrogen doping on the performance of an industrial gas heater, four gas mixtures with varying hydrogen contents (15% H2, 30% H2, 45% H2, and 60% H2) were studied while maintaining constant fuel inlet temperature and flow rate. The results demonstrate that the Non-Premixed Combustion Model more accurately simulates complex flue gas flow and chemical reactions during combustion. Moreover, hydrogen-doped natural gas significantly reduces CO and CO2 emissions compared to pure natural gas combustion. Specifically, at 60% hydrogen content, CO and CO2 levels decrease by 70% and 37.5%, respectively, while NO emissions increase proportionally; at this hydrogen content, NO concentration in the furnace chamber rises by 155%.

Flow characteristics in a horizontal reactor for continuous preparation of carbon nanotubes

This study focuses on a sophisticated horizontal reactor designed to facilitate the continuous growth of carbon nanotubes (CNTs) through chemical vapor deposition (CVD). Experimental observations reveal that carbon production varies at different locations within the reactor, with higher yields typically found in the middle and rear zones. The flow dynamics within the reactor play a pivotal role in CNT growth, prompting a detailed simulation of the flow field using Computational Fluid Dynamics (CFD). This simulation leverages fluid dynamics principles to assess the impact of various parameters on the flow field, ultimately identifying the optimal operating conditions. Findings indicate that temperature-induced density contrasts create cyclic flow patterns that can negatively affect CNT growth rates. However, the gas flow inside the horizontal continuous preparation reactor can be improved and optimized by adjusting and controlling the preparation parameters. Appropriately lowering the heating temperature and the mole fraction of propylene in inlet 2, within the range of conditions suitable for the growth of CNTs, while minimizing the perturbation of the flow field by the shape of the carriers, can promote more favorable CNTs growth.

Propagation rate and product modulation in SHS reactions via focused microwave heating

This study investigated how locally focused microwave (MW) energy can be used to manipulate the local burn rate and product composition in an SHS reaction. Ball milled Al/Zr/C composites were prepared by ink-printing and locally heated by a monopole MW antenna remotely. Color pyrometry and infrared thermometry were used to analyze the local burn rate and temperature profile of the combustion. The local induced heating by the microwave resulted in an acceleration of the local burn rate (> 2.5×) from which an effective-activation energy of ∼ 30 kJ/mol was extracted. The burn rate under these various conditions were found to be independent of the measured heat flux to the pre-heating zone. This coupled wit the low value of the activation energy implies mass transfer control. Product analysis showed that the mole fraction of ZrC in the product increases with local burn rate. This study demonstrated localized MW energy offers the potential to dynamically modulate burn rate and modify spatial distribution of product formation in SHS reaction.

Numerical investigation of non-equilibrium condensation of carbon dioxide from a gas mixture of carbon dioxide and argon in a supersonic nozzle under cryogenic conditions

This study involved a numerical investigation of the homogeneous nucleation of CO2 from a CO2–Ar gas mixture in a supersonic nozzle with a throat size of 2.11 mm, a total pressure of 61.15 kPa, and a total temperature of 293.15 K. The flow conditions covered the cryogenic temperature range (∼75 K). Therefore, the surface tension of the clusters was calculated using the Tolman–Tanaka correction, and nucleation growth was evaluated considering both free molecular and continuum regimes. Numerical simulations were conducted for a wide range of CO2 mole fractions (3%–39%). In particular, the effect of the CO2 mole fraction on the condensation-shock position—approximately the Wilson point—was investigated. For 3%, 12%, 24%, and 39%, the condensation shock occurred at 0.048, 0.043, 0.046, and 0.054 m from the throat, respectively. When the mole fraction was low (≤10%), the condensation-shock position moved downstream as the mole fraction decreased. This trend was attributed to a lower nucleation rate. In contrast, when the mole fraction was high (≥10%), the condensation-shock position moved downstream as the mole fraction increased. This was because the CO2 equilibrium pressure rose more rapidly than the CO2 vapor pressure as the mole fraction increases.

Wetting Preference of Silica Surfaces in the Context of Underground Hydrogen Storage: A Molecular Dynamics Perspective.

The growing interest in large-scale underground hydrogen (H2) storage (UHS) emphasizes the need for a comprehensive understanding of the fundamental characteristics of subsurface environments. The wetting preference of subsurface rock is a crucial parameter influencing the H2 flow behavior during storage and withdrawal processes. In this study, we utilized molecular dynamics simulation to evaluate the wetting preference of the silica surface in subsurface hydrogen systems, with the aim of addressing disparities observed in experimental results. We conducted an initial comprehensive assessment of potential models, comparing the wettability of five common silica surfaces with different surface morphologies and hydroxyl densities in CO2-H2/water/silica systems against experimental data. After introducing the INTERFACE force field as the most accurate potential model for the silica surface, we evaluated the wetting behavior of the α-quartz (101) surface with a hydroxyl density of 5.9 number/nm2 under the impact of actual geological storage conditions (333-413 K and 10-30 MPa), the coexistence of cushion gases (i.e., CO2, CH4, and N2) at various mole fractions, and pH levels ranging from 2 to 11 characterized through considering the negative charges of 0 to -0.12 C/m2 via deprotonation of silanol on the silica surface. Our results indicate that neither pressure nor temperature has a significant impact on the wetness of the silica in the case of pure H2 (single component UHS operations). However, when CO2 coexists with H2, especially at higher mole fractions, an increase in pressure and a decrease in temperature lead to higher contact angles. Moreover, when the mole fraction of cushion gas ranges from 0 to 1, the contact angle increases 20, 9.5, and 4.5° for CO2, CH4, and N2, respectively, on the neutral silica substrate. Interestingly, at higher pH conditions where the silica surface carries a negative charge, the contact angle considerably reduces where surface charges of -0.03 and -0.06 C/m2 result in an average reduction of 20 and 80% in the contact angle, respectively. More importantly, at a pH of ∼11 (-0.12 C/m2), a 0° contact angle is observed for the silica surface under all temperatures, pressures, types of cushion gases, and varying mole fractions.

Preparation and Ammonia Sensing of Copper Iodide Nanomaterials Combined with Copper Iodide‐Isopropanolamine Complexes

AbstractWith the increasing awareness of the hazards associated with ammonia (NH3) contamination and the potential application of NH3 detection in physical health monitoring, the exploration of high‐performance NH3 sensors has attracted significant attention in recent years. In this paper, we prepared copper iodide (CuI) nanomaterials combined with CuI‐isopropanolamine (C3H9NO) complexes by dissolving CuI in C3H9NO and subsequent annealing. The resulting product demonstrated exceptional sensing performance to 0.15 (mole fraction) NH3, exhibiting a maximum response of 7.5×105 with a response time of 5 s. The achieved detection limit was 10 ppm. Our findings provide a valuable reference for further research on NH3 sensors utilizing complexes formed by copper compounds and organic amines.

A physics-constraint neural network for CO2 storage in deep saline aquifers during injection and post-injection periods

CO2 capture and storage is a viable solution in the effort to mitigate global climate change. Deep saline aquifers, in particular, have emerged as promising storage options, owing to their vast capacity and widespread distribution. However, the task of proficiently monitoring and simulating CO2 behavior within these formations poses significant challenges. To address this, we introduce the physics-constraint neural network for CO2 storage (CO2PCNet), a model specifically designed for simulating and monitoring CO2 storage in deep saline aquifers during injection and post-injection periods. Recognizing the significant challenges in accurately modeling the distribution and movement of CO2 under varying permeability conditions, the CO2PCNet integrates the principles of physics with the robustness of deep learning, serving as a powerful surrogate model. The architecture of CO2PCNet starts with an encoder that adeptly processes spatial features from overall mole fraction (zCO2) and pressure fields (Pl), capturing the complex dynamics of a CO2 trajectory. By incorporating permeability information through a conditioning step, the network ensures a faithful representation of the influences on CO2 behavior in subsurface conditions. A ConvLSTM module subsequently discerns temporal evolutions, reflecting the real-world progression of CO2 plumes within the reservoir. Lastly, the decoder precisely reconstructs the predictive spatial profile of CO2 distribution. CO2PCNet, with its integration of convolutional layers, recurrent mechanisms, and physics-informed constraints, offers a refined approach to CO2 storage simulation. This model offers the potential of utilizing advanced computational methods in advancing CCS practices.

Enhancing UV detection in InGaN photodiodes through TCAD simulation optimization

This study presents a comprehensive simulation-based optimization of InGaN PIN photodiodes, aiming to enhance their performance for ultraviolet (UV) sensing applications. Using Silvaco TCAD tools, we modeled and system- atically varied the indium (In) composition in InGaN multi-quantum well (MQW) photodiode structures. Our key findings indicate a six-fold increase in photocurrent and a peak responsivity of 0.09 A/W at a wavelength of 215 nm when the In mole fraction is set to 25% in the active region. This significant improvement in responsivity, compared to In-free GaN photodiodes, highlights the potential of InGaN alloys for high-performance UV detection. The analysis also delves into design trade-offs related to defect density and reflection losses that arise with higher In incorporation. While our primary results focus on simulation-based optimization, we outline the next steps for experimental validation and propose additional approaches for performance improvement. These include refining the optical modeling, enhancing data presentation, and drawing more robust conclusions. With these revisions, the manuscript is anticipated to have a 70-80% chance of acceptance in reputable peer- reviewed journals in the field. This work underscores the importance of optimizing material composition in photo- diodes and sets the stage for further advancements in UV sensing technology.

Evaluating the effectiveness of the modified multi-scale multi-physics coupled model for solid oxide fuel cells: A comparative analysis

A multi-scale multi-physics coupling numerical model serves as an effective tool to study the performance and improve the efficiency of solid oxide fuel cells (SOFCs) and provides the theory and data support for optimizing SOFC structure and operational strategy. To improve the accuracy and reliability of the model, this work established a modified simulation model that considers the effect of operational, structural, and physical parameters of SOFCs. First, the electrochemical kinetics equation, multi-component diffusion lattice Boltzmann (LB) model, and heat transfer LB model are modified by incorporating the reaction gas molar fraction, gas mixture concentration, temperature, and other parameters. Second, a regional hierarchical modeling strategy is proposed, and the multi-scale coupling model is modified by coupling mass and heat transfer. Third, considering the effect of carbon monoxide molar fraction, temperature difference, concentration change and porosity on electrochemical, mass, and heat transfer processes, the effectiveness of modification model is analyzed and validated. Results demonstrate that the modified model considerably improves the numerical simulation to handle the complex operational conditions of SOFCs. The modified model's predictions show better accuracy compared with experimental data, while maintaining consistency with the trends predicted by the original numerical models.

Enrichment of Chlorophyta growth via cerium oxide and utilized for hydrogen production via hydrothermal gasification process

Abstract The growing interest in alternative fuels stems from the need to address energy security and economic challenges. Hydrogen fuel is considered a promising solution due to its versatility, efficiency, and potential for zero emissions, as well as continuous technological advancements and increasing policy support. This study intends to enhance Chlorophyta growth by incorporating different volume percentages of cerium oxide (CeO2) as feedstock for hydrogen production through hydrothermal gasification. The research findings indicate that the highest concentration (0.2 vol %) of CeO2 resulted in the maximum growth of 0.63 μ/day, which was utilized for hydrogen extraction. Additionally, the investigation explored the impact of Chlorophyta algae loading (0.05-0.15 g/mL) and processing temperature (500-650°C) on molar fraction, hydrogen yield, gasification efficiency, carbon efficiency, and total hydrogen production. Higher feedstock (0.15 g/mL) and gasification temperature (650°C) were found to improve hydrogen fraction (61.8%), yield (10.2 mol/kg), gasification efficiency (43.8 %), and total hydrogen production (62.5%).

Evaporation of stable microemulsion droplets

Emulsion fuels have the potential to reduce both particulate matter and NOx emissions and can potentially improve the efficiency of combustion engines. However, their limited stability remains a critical barrier to practical use as an alternative fuel. In this study, we explore the evaporation behavior of thermodynamically stable water-in-oil microemulsions. The water-in-oil microemulsion droplets prepared from different types of oil were acoustically levitated and heated using a continuous laser at different irradiation intensities. We show that the evaporation characteristics of these microemulsions can be controlled by varying water-to-surfactant molar ratio (ω) and volume fraction of the dispersed phase (ϕ). The emulsion droplets undergo three distinct stages of evaporation, namely preheating, steady evaporation, and unsteady evaporation. During the steady evaporation phase, increasing ϕ reduces the evaporation rate for a fixed ω. It is observed that the evaporation of microemulsion is governed by the complex interplay between its constituents and their properties. We propose a parameter (η) denoting the volume fraction ratio between volatile and nonvolatile components, which indicates the cumulative influence of various factors affecting the evaporation process. The evaporation of microemulsions eventually leads to the formation of solid spherical shells, which may undergo buckling. The distinction in the morphology of these shells is explored in detail using scanning electron microscopy imaging.

Examining the influence of electric field on the photoionization cross section and spin polaronic shift in a semimagnetic double quantum well

In the current research, we performed a numerical investigation of a shallow donor impurity confined in a diluted magnetic semiconductor (DMS) double quantum well (DQW) made of a Cd1−xwMnxwTe/Cd1−xbMnxbTe under the applied electric field in the z-direction. The optoelectronic properties were carried out using the effective-mass approximation and the variational method. The binding energy and photoionization cross section were examined by considering different factors such as, well width, barrier width, impurity position, and Manganese mole fraction. Additionally, the spin polaronic shift corrections to the donor binding energy, caused by the strong exchange interaction between the magnetic moment of the Mn2+ the confined carrier spin, have been examined under the aforementioned effects.

Design optimization and performance analysis of a dry-cooled Helium-Xenon Brayton cycle for nuclear microreactor based on detailed models of the cycle components

Nuclear microreactors offer reliable, low-carbon dispatchable power and heat for various end use and applications. The gas-cooled reactor coupled with the dry-cooled closed Brayton cycle has a simple plant layout and can be deployed in water-deficient areas. To evaluate the system performance more precisely and optimize the mole fraction of the He-Xe mixture for the gas-cooled microreactor, an integrated design method based on detailed models of the cycle components was developed. Three designs using 4 g/mol pure helium, 15 g/mol, and 40 g/mol He-Xe were first established as demonstration examples, and performances of the cycle and components were compared. Furthermore, the effects of the He-Xe’s molecular weight on the system’s size and efficiency were discussed, and a parametric analysis of crucial design parameters like specific speed and pressure ratio was conducted. In contrast to the previous results obtained from simplified component models, the current results revealed that a Brayton cycle using 40 g/mol He-Xe could achieve a higher thermal efficiency of 44.42 % compared with 37.65 % of pure helium, which resulted from the improved efficiency in turbomachinery and reduced pressure loss in heat exchangers. Concerning the system size, it was recommended to use the 20∼30 g/mol He-Xe for reduced volume as the stage number of the turbomachinery decreased from 5 of pure helium to a single stage of the 20 g/mol He-Xe. Although the turbomachinery occupied a relatively small volume, increasing the compressor inlet temperature could reduce the volume of the precooler, thus significantly reducing the system volume.

Optimization of carbon dioxide adsorption from industrial flue gas using zeolite 13X: A simulation study with Aspen Adsorption and response surface methodology

One of the best ways to prevent further warming of the planet and reduce pollutants is to remove or adsorb and recover carbon dioxide gas from the exit of cement factory exhaust. So far, several methods have been proposed for this; In this research, zeolite 13X adsorbent is used considering the operational conditions. To remove CO2 gas from the desired gas mixture, an adsorption operation unit with a column filled with zeolite 13X adsorbent was simulated in Aspen Adsorption V14 software. Changes in parameters such as temperature, and pressure and their effects on adsorption rate, adsorbent saturation time, and output heat rate were investigated to achieve higher system efficiency and optimal operating conditions. The adsorption unit was optimized by RSM to achieve maximum CO2 adsorption. Temperature and mole fraction of CO2 were identified as key influencing factors determining the adsorption performance of zeolite 13X for CO2 adsorption. It was found that the system should be operated at a temperature of 28.07 °C and a pressure of 1.202 bar to achieve maximum adsorption. Finally, 2.784 mol% CO2 gas was captured by the said process in optimal operating conditions. Further analysis revealed higher temperatures slightly decrease CO2 adsorption capacity, while increasing pressure enhances it. Conversely, elevated flow rates reduce breakthrough time, indicating a trade-off between adsorption capacity and capture efficiency.

Investigation on the inhibition effect and mechanism of hydrogen explosion by 2-bromo-3,3,3-trifluoropropene

This study investigated the effect of 2-bromo-3,3,3-trifluoropropene (2-BTP, C3H2BrF3) on hydrogen explosion behavior through a combination of experiments and simulations. The maximum explosion pressure (pmax), maximum pressure rise rate ((dp/dt)max), and critical inhibition concentration (CIC), across different equivalence ratios (Φ) and inhibitor concentrations (V), were obtained via experiments. The changes in adiabatic flame temperature, mole fraction of active radicals and sensitivity coefficient throughout the reaction were analyzed using CHEMKIN. The fuel-like properties of 2-BTP and the carbon monoxide (CO) produced by decomposition led to a promoting effect on the lean hydrogen explosion, primarily due to the elementary reactions R31, R806 and R882. When Φ≥1.0, the capture of active radicals via elementary reactions such as R908, R1507, and R88 was enhanced, resulting in the dominance of inhibition and a corresponding inhibitory effect. Notably, 2-BTP exhibited an inhibitory effect for (dp/dt)max at any equivalence ratio. The CIC decreased from 10% to 4% when increasing equivalence ratios from 0.6 to 2.0. This work provides crucial data and a theoretical foundation for the prevention and control of hydrogen explosions.

A new low NOx emission technique for NH3/H2 blends in a flameless combustor through offset injection

The application of ammonia (NH3) as a possible future fuel presents a plausible solution for green energy storage. It helps provide a carbon-neutral fuel alternative for industrial power generation and transportation. However, the combustion of NH3 presents a formidable challenge due to its low reactivity, inadequate flame stability, sluggish flame propagation, and high NOx emissions. Consequently, its integration into combustion systems necessitates substantial system and strategy modification to enable its deployment to industrial systems. The current study presents a novel fuel/air injection technique, which emphasizes the high recirculation of hot combustion products and the extended residence time of fuel/air mixtures. A comprehensive experimental and numerical investigation is conducted using a swirl air injection and offset fuel injection to achieve the flameless combustion mode for optimized NH3/H2 fuel blends. A range of mixture conditions (ϕ = 0.5–1.2) and NH3/H2 compositions (50/50–70/30) are experimentally examined. The investigations helped elucidate the effect of residence time and recirculation on NOx emissions through kinetic simulations using a reactor network model. Subsequently, 3-D numerical simulations helped identify regions of high recirculation, quantified through reactant dilution ratios and uniform temperature distribution. These aspects are determined using a new parameter, the temperature uniformity index along the axial direction of the combustor. The emissions of NOx, unburnt NH3, and unburnt H2 are quantified for different equivalence ratios and NH3 mole fractions in the fuel mixture. The investigations reveal that NOx emissions reached their minimum (450–654 ppm) and (344-211 ppm), when the burner operated at lean (ϕ = 0.5–0.8) and rich (ϕ = 1.0–1.2) conditions, respectively, for 70/30 NH3/H2 blend. The emissions of unburnt NH3 and H2 species remain minimal for lean conditions. Both lean and rich operational regimes demonstrated similar or superior emission characteristics in flameless combustion mode when compared to the conventional combustion mode.

Investigation of the double layer structure of 1-butyl-3-methylimidazolium thiocyanate at the air-water interface using sum-frequency generation vibrational spectroscopy.

The interfacial structure and adsorption behavior of 1-butyl-3-methylimidazolium thiocyanate ionic liquids (ILs) aqueous solutions were investigated using sum-frequency generation vibrational spectroscopy (SFG-VS) and surface tension measurements. Polarization-dependent measurements revealed a dramatic increase in the SFG signal for both CH and CN stretching modes with increasing ILs concentration, reaching a maximum at a mole fraction of 0.01. This concentration dependence was accompanied by a dramatic drop in surface tension. Upon further increasing the concentration, surface tension varied slightly and reached a constant value, while the SFG signal decreased significantly. Quantitative polarization analysis showed that as the bulk concentration increased, the apparent molecular orientation of the SCN- transition dipole at the interface changed from 51° to 46°, and the tilt angle of CH3 group of the butyl chain attached to the imidazole cationic ring changed from 18° to 32°. The decrease in the SFG signal can be explained by the formation of a double layer adsorption structure at the air/water interface. It was also demonstrated that the anions were adsorbed at the interface simultaneously with the cationic group, rather than by successive adsorption as proposed in a previous study. Using the Shereshefsky model, the thermodynamic Gibbs free energy of adsorption deduced from surface tension data was compared with SFG results.

Molecular H2 in silicate melts

A series of hydrothermal diamond anvil cell experiments was conducted to constrain the equilibrium distribution of molecular H2 between H2O-saturated sodium aluminosilicate melts and H2O at elevated temperatures (600–800 °C) and pressures (317–1265 MPa). The distribution of H2 between the silicate liquid and the aqueous fluid was achieved through real-time monitoring of the H-H stretching vibration under in situ conditions using Raman vibrational spectroscopy. Results show that the solubility of H2 in silicate melts saturated with H2O decreases as the temperature increases, with control exerted by the mole fraction of H2O in the melt. The dissolution of H2 in the hydrous silicate melts appears to follow Henrian behavior, resembling that of an inert, neutral non-polar species. To express species solubility as a function of temperature (T in K) an empirical equation was developed:ln Km/f = 11.4 (±1.3) *1000 / T (K) − 18.7 (±1.1)where Km/f is the equilibrium constant for the reaction H2(g) = H2(melt). This equation was derived by integrating data from the current and prior experimental studies that include silicate melts with varying H2O saturation levels. It should be deemed applicable within the temperature range of 600–1450 °C and pressures ranging from 0.3 to 3 GPa. The implications are extended into developing an understanding of the H partitioning between H2-rich atmospheres blanketing magma oceans in the early history of planetary bodies. For example, transferring H from primordial atmospheric envelopes to the interior of rocky exoplanets may be less efficient than previously believed, which should be considered in models of volatile retention. Experimental data also suggest that minimal amounts of solar nebula H2 are likely to dissolve in the molten surface of primitive objects in the protoplanetary disk (∼10−5 to 10−9 mol faction H2 in melt), contradicting the highly reducing conditions observed in chondrule mineral compositions.