Vapor Species Research Articles

Influence of Water Vapor on High Temperature Oxidation Behavior of Type 310 Stainless Steel

Oxidation behavior of 310 stainless steel (SS) was investigated in both dry and water vapor-containing air, respectively, at 800 ~ 1000 °C . The roles of water vapor on oxidation rate and scale microstructure were explored. After the exposure test, the specimen was examined by X-ray diffraction (XRD) for corrosion product identification. The cross-section image of each specimen after oxidation test was examined using a scanning electron microscope (SEM), where the scale chemical composition was analyzed with the attached energy dispersive spectrometer (EDS). The experimental results showed that oxidation of 310 SS followed parabolic oxidation kinetics in dry air, while a higher weight gain was found in moisture air at the early stage of exposure test showing accelerated oxidation. However, a lower weight gain was measured in water vapor-containing air at 1000 °C as compared with that in dry air for a prolonged exposure. XRD and cross-section SEM examination revealed that the oxidation product mainly consisted of an outer compact Cr2O3 and an inner spinel when exposed in dry air. In moisture air at 1000 °C, however, degradation of the passive film occurred due to the change of point defect structure while the oxidation product was mainly spinel. Moreover, the reaction of Cr2O3 with H2O resulted in the formation of CrO2(OH)2 vapor species which subsequently led to the formation of a loose scale structure and caused an increased oxidation rate.

High Temperature Mass Spectrometric Study of Vaporization of The Oxycarbide Ceramics Based on the MAX-Phases

In the present study, the vaporization processes of the carbide materials with the Ti2SiC, Ti3SiC2, Ti2AlC, Ti3AlC2, Zr2AlC, Zr3AlC2 chemical compositions containing the MAX-phases as well as the oxycarbide systems based on these materials with the addition of hafnia were examined by the Knudsen effusion mass spectrometric method up to the temperature 2200 K. It was established that the main vapor species over the samples with the Ti2AlC, Ti3AlC2, Zr2AlC, and Zr3AlC2 compositions at the temperature 1500 K was atomic aluminum. The samples containing silicon were less volatile compared to the carbide materials with aluminum and transferred into vapor at temperatures exceeding 1900 K to form gaseous Si, Si2, SiC2, and Si2C. The addition of hafnia to the carbides under study led to the formation of oxygen-containing vapor species, particularly Al2O and SiO, and to decrease in the total vapor pressure over the systems formed. It was shown that the samples of the oxycarbide Ti2SiC-HfO2 system were the least volatile materials, and, among the oxycarbide systems containing aluminum, the lowest volatility was observed for the samples of the Zr2AlC-HfO2 system in the case of the hafnia content up to 10 mol. % and of the Ti2AlC-HfO2 system for the higher HfO2 concentration.

Thermodynamics of gaseous strontium and calcium cerates studied by Knudsen effusion mass spectrometry and estimation of relative electron ionization cross-section for CeO2(g).

Ceria-based systems are of great interest because of their unique properties. Such systems may be used as anode materials for SOFCs or in oxygen sensors. Theexploitation of these materials often requires high temperatures. In such conditions, the partial or complete evaporation of materials is possible. Therefore, knowledge of the values of partial pressures and thermodynamic properties is essential to predict and/or prevent possible consequences and accidents. Knudsen effusion mass spectrometry was used to determine partial pressures of vapor species over the SrO-CeO2 and CaO-CeO2 systems. Measurements of partial pressures were performed with a MS-1301 mass spectrometer. Vaporization was carried out using molybdenum or tungsten effusion cells. A theoretical study of gaseous strontium and calcium cerates was performed by several quantum chemical methods: density functional theory (DFT) M06, DFT PBE0, and MP2. The minimum value of relative electron ionization cross-section for CeO2 was estimated. In the temperature range of 2218-2249 K above the SrO-CeO2 system and of 2128-2208 K above the CaO-CeO2 system, gaseous M, MO, MO, CeO2, O, O2 and MCeO3 (M = Sr, Ca) were found. Energetically favorable structures of gaseous SrCeO3 and CaCeO3 were found, and vibrational frequencies were evaluated in the "rigid rotor-harmonic oscillator" approximation. On the basis of the equilibrium constants of gaseous reaction MO + CeO2 = MCeO3, the standard formation enthalpy of gaseous SrCeO3 (-913 ± 26 kJ/mol) and of gaseous CaCeO3 (-917 ± 26 kJ/mol) at 298 K were determined. The estimated value of relative electron ionization cross-section for CeO2 is in agreement with the general rule applicable for dioxides. The stability of SrCeO3 and CaCeO3 gaseous species was confirmed by KEMS. Gas-phase reactions involving gaseous SrO (CaO) and CeO2 with gaseous SrCeO3(CaCeO3) were studied. Enthalpy of formation reaction of gaseous SrCeO3(CaCeO3) from gaseous SrO (CaO) were evaluated theoretically, and the obtained value is in agreement with the experimental one.

(Digital Presentation) Reactive Evaporation of Cr Vapors from Chromia-Alkaline Oxide Mixtures Generated in 800℃ Air and Subsequent Condensation Onto Aluminosilicate Fibers

This research aims to improve fundamental understanding of the reactive evaporation and condensation of Chromium (Cr) vapors, which are generated from Cr containing alloys used in many high-temperature (>500℃) process environments and can form potentially problematic condensed hexavalent (Cr(VI)) species downstream. This study focuses on the effects of alkaline oxides present in the Cr source on the resultant Cr evaporation and condensation. Vapor species were generated by flowing high-temperature (800℃) air containing 3% water vapor over chromia (Cr2O3) and mixtures of chromia with calcium oxide (CaO) or magnesium oxide (MgO) powders. Lab-grade quartz and alumina fiber samples were positioned downstream from the Cr-alkaline oxide source where the temperature decreases (<500℃) to collect condensed vapor species. Total condensed Cr and ratios of oxidation states were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES) and diphenyl carbazide (DPC) colorimetric/direct UV-VIS spectrophotometric analyses. Preliminary results indicate a decrease in partial pressures of generated Cr vapor species as well as a decrease in condensed Cr species on the aluminosilicate fibers when alkaline oxides are present in the Cr source compared to a pure Cr source. These results also indicate presence of hexavalent Cr (Cr(VI)) species condensed on all samples investigated. Computational thermodynamic equilibrium modelling corroborated the experimental results showing partial pressures of produced vapor species in the presence of alkaline oxides as well as stabilities of condensed Cr compounds on the fiber samples. Comparative results and analyses are presented and discussed to help inform mechanistic understanding and future related research and engineering efforts. Figure 1

A novel phase-field lattice Boltzmann framework for diffusion-driven multiphase evaporation

Heat transfer and phase change phenomena, particularly diffusion-driven droplet evaporation, play pivotal roles in various industrial applications and natural processes. Despite advancements in computational fluid dynamics, modeling multiphase flows with large density ratios remains challenging. In this study, we developed a robust and stable conservative Allen–Cahn-based phase-field lattice Boltzmann method to solve the flow field equations. This method is coupled with the finite difference discretization of vapor species transport equation and the energy equation. The coupling between the vapor concentration and temperature field at the interface is modeled by the well-known Clausius–Clapeyron correlation. Our approach is capable of simulations under real physical conditions and is compatible with graphics processing unit architecture, making it ideal for large-scale industrial simulations. Three validation test cases are conducted to demonstrate the consistency of the presented model, including simulations of Stefan flow, the evaporation of suspended droplets containing water, acetone, and ethanol in the air, and the evaporation of a water sessile droplet on a flat surface. The results show that the model is able to predict the behavior and characteristics of each case accurately. Notably, our numerical results exhibit a maximum relative error of approximately 1% in simulations of Stefan flow. In the case of suspended droplet evaporation, the observed maximum difference between the calculated wet bulb temperatures and those derived from psychrometric charts is approximately 0.9 K. Moreover, our analysis of the sessile droplet reveals a good agreement between the results obtained by our model for the evaporative mass flux and those obtained from the existing models in the literature for different contact angles.

A high temperature engine materials test facility.

Gas turbine engines subject materials to extreme conditions. Their high temperature materials and co-developed coatings must survive combustion gas temperatures currently approaching 1800 °C, large thermal gradients, severe thermal shock, and static and fatigue inducing applied stresses, all the while operating in highly reactive, high-pressure, high-speed combustion gas flows containing significant partial pressures of water vapor, oxygen, and other reactive species for many tens of thousands of hours. We describe the design and development of a test facility for the study of materials under individual and combinations of test parameters similar to those experienced within legacy and future engines. A hydraulic load frame capable of applying static or cyclic tension-compression stresses up to 400 MPa to flat-dog bone-shaped test specimens is integrated within an environmental test chamber capable of sustaining gas pressures from 0.1 to 1.2 MPa (1-12 atm). An adjustable0.1-2 kW power CO2 laser whose 10.6 µm wavelength radiation is strongly absorbed by ceramic coating materials is used to heat sample surfaces to temperatures of 1800 °C and above, while rear surface air jet cooling establishes through-thickness thermal gradients. Rapid laser heating in conjunction with transiently applied front and/or rear-side air cooling is used to create hot or cold thermal shock effects. This is accompanied by the impingement of a high pressure (up to 1.3 MPa) reactive gas jet upon the sample with speeds up to 300m/s by preheating dry air, mixing it with steam to the desired humidity, heating to 850 °C, and then expanding it through a converging nozzle. Thermal imaging pyrometers measure specimen front and back surface temperature fields, while environmental test chamber view ports permit digital image correlation and strain mapping.

High‐temperature Mass Spectrometric Study and Modeling of the Thermodynamic Properties of the TiO2‐SiO2‐ZrO2 System

AbstractDevelopment of the advanced materials based on the TiO2‐SiO2‐ZrO2 system is hindered by lack of the information on its thermodynamic properties and phase equilibria. In the present study, the samples in the TiO2‐SiO2‐ZrO2 system were prepared by solid‐state synthesis and analyzed by X‐ray microanalysis, fluorescence, and diffraction techniques. The thermodynamic properties in this system were evaluated by Knudsen effusion mass spectrometric (KEMS) method and optimized within the generalized lattice theory of associated solutions (GLTAS). The main vapor species over the silica‐containing samples vaporized from the tungsten cell at the temperature 1973 K were SiO, O, WO2, and WO3. The vapor over the samples in the TiO2‐ZrO2 system at 2356 K was composed mainly of TiO, TiO2, O, WO2, and WO3. The activity of components in the samples and the partial pressures of the identified vapor species were determined. At 1973 K, the TiO2‐SiO2‐ZrO2 system is characterized by positive deviations from the ideality. The observed weak dependence of the SiO2 activity on the SiO2 content suggests the presence of a broad field of immiscibility on the phase diagram in the concentration range 40–100 mol . % SiO2. The thermodynamic data on the TiO2‐SiO2‐ZrO2 system obtained by KEMS can be of great value for calculation of the phase equilibria.

A flow-batch lab-in-syringe foam microextraction platform for the simultaneous preconcentration and in situ membraneless gas-liquid separation of mercury prior to cold vapor atomic absorption spectrometry

Herein, the proof-of-concept of a novel lab-in-syringe (LIS) foam microextraction platform is presented as a front-end to cold vapor atomic absorption spectrometry (CVAAS) for the simultaneous preconcentration and membraneless gas-liquid separation (GLS) of inorganic mercury in biological samples. The proposed method is based on the on-line formation of the ammonium pyrrolidine dithiocarbamate complex with mercury that was retained in the pores of polyurethane foam immobilized on the piston of the LIS system. Metal complex elution and in situ mercury vapor generation are accomplished inside the microsyringe in a flow-batch format, while the separation of vapor species is achieved via the membraneless GLS found at the top of the syringe’s barrel. Under optimized operation conditions, for 90 s preconcentration time, the limit of detection was 0.02 μg L−1 and the repeatability (RSD) was 3.8% (at the 0.5 μg L−1 concentration level), within a working range extending up to 4.0 μg L−1. The practicality of the novel manifold was demonstrated using the Blue Applicability Grade Index, while the accuracy of the method was evaluated using certified reference materials and spiked samples.

Vaporization processes and thermodynamic properties of the SrO-ZrO&lt;sub&gt;2 &lt;/sub&gt; system at high temperatures

Vaporization processes and thermodynamic properties of the SrO-ZrO2 system in the concentration range from 10 to 90 mol% SrO were studied by high-temperature differential mass spectrometry. Evaporation of the studied samples were carried out from tungsten Knudsen effusion cell. Partial pressures of vapor species in the temperature range of 1975-2800 K were determined. The values of SrO and ZrO2 activities, as well as Gibbs energies and excess Gibbs energies in the composition range from 90 to 45 mol% SrO were obtained at the temperature of 1940 K and from 45 to 10 mol% SrO at the temperature of 2123 K. It is established that in the SrO-ZrO2 system minor negative deviations from ideal behavior are observed.

Determination of activities and condensation temperatures of GaO1.5 and InO1.5 in anorthite-diopside eutectic melts by Knudsen Effusion Mass Spectrometry

The group 13 elements Ga and In are overabundant in bulk silicate Earth (BSE) when compared to lithophile elements of similar 50% nebular condensation temperature Tc50. To understand whether evaporation from silicate melts provides a more accurate description of volatility during the later stages of planetary accretion, namely, at higher temperatures and oxygen fugacities than in the solar nebula, knowledge of the activities of GaO1.5 and InO1.5 in silicate melts and their stable gaseous species are required. To this end, we doped anorthite-diopside (An-Di) eutectic glasses with ∼1000 and ∼10,000 ppm of Ga and In and determined their equilibrium partial pressures above the silicate liquid by Knudsen Effusion Mass Spectrometry (KEMS) using Ir cells at 1550–1740 K over the log(fO2) range ΔIW+1.5 to ΔIW+2.5 (IW = iron-wüstite buffer). We detect Ga0 and In0 as the dominant vapour species and determine activity coefficients of γ(GaO1.5) = 0.036(6) at 1700 K and of γ(InO1.5) = 0.017(12) at 1674 K. Using these activity coefficients, we calculate partial pressures of Ga and In, together with those of similarly volatile elements, K and Zn and show that their relative volatilities from An-Di eutectic melts are in the in order Ga > K ∼ In > Zn, different from those predicted from their Tc50 under nebular conditions but in line with their relative abundances in the BSE. This substantiates the view that the abundances of volatiles in BSE, such as Ga and In, may have been set by evaporation from silicate melts under oxidising conditions at later stages of planetary accretion. Moreover, chondrules likely never underwent significant evaporation during melting and their volatile-depleted nature is likely inherited from the earliest solid condensates.

The Influence of Water Concentration on High-Temperature Reactive Evaporation and Condensation of Cr in 800°C Air

Deleterious reactive evaporation of chromium from stainless steels commonly used in solid oxide electrochemical systems is well-documented; however, interactions between Cr vapor species and surrounding interfaces during complex and dynamic system exposures is poorly understood. Understanding the interactions between Cr vapor species and downstream components during operation is critical for improving system performance and safeguarding environmental, health and safety, as many condensed Cr compounds contain toxic and carcinogenic hexavalent chromium Cr(VI). Furthermore, the interactions between volatilized Cr species and surrounding interfaces are dependent upon dynamic chemical environments. The objective of this study is to systematically investigate and report on condensation pathways of Cr vapors within representative system environments with variable water concentrations. To accomplish this objective, an experimental platform was designed to generate Cr vapor species from the reactive evaporation of chromia (Cr2O3) powder with high-temperature (>1100 K) air/H2O mixtures, and expose downstream ceramic insulation materials (e.g., aluminosilicate fibers) at reduced temperatures (<600 K). Insulation material chemical compositions investigated include pure silica (SiO2) and alumina (Al2O3) to combinations thereof with and without inclusions of alkaline earth metals (e.g., Ca, Mg, Sr). Materials are studied as a function of exposure conditions using complementary materials characterization tools such as SEM-EDX, XPS, and diphenyl carbazide reactions to assess Cr(VI) concentrations. Reactive evaporation of Cr from chromia occurs in the presence of oxygen and/or water vapor to form various Cr-containing vapor species. Thermodynamic data reveals an equilibrium partial pressure increase of several orders of magnitude at elevated (>500 K) temperatures for all Cr vapor species. In the presence of water vapor, the partial pressure of Cr oxyhydroxide (CrO2(OH)2(g)) is greater by many several orders of magnitude and becomes the dominant species up to ~1500 K. The research objective is to explore effects of water vapor in air on Cr condensation and speciation on different ceramic insulation materials. The experimental setup thus far has exposed aluminosilicate fibers to volatilized Cr species from Cr oxide powder at 1100 K for 150 hours under varying water vapor conditions: 0 vol%(dry), 3 vol%, and 10 vol% H2O. Preliminary results show an increase in Cr(VI) formation on fibers exposed to volatile Cr species as water vapor content increases. See Figure 1 for an overview of the experimental concept, Cr(VI) test kit, and preliminary results for dependency on water vapor. Analyses of these results will be presented and discussed in context of potential implications for SOFC/SOEC systems. Figure 1

Determination of thermochemical properties of stainless steels type D-9 and T-91 using Knudsen Effusion Mass Spectrometry

High temperature vaporisation thermodynamic studies over D-9 and T-91 stainless steel samples were carried out in the temperature range 1202–1529 K and 1232–1530 K respectively, by using Knudsen Effusion Mass Spectrometry (KEMS). These studies revealed that both the alloys undergo incongruent vaporisation. Cr(g), Mn(g), Fe(g) and Ni(g) were the neutral vapour species observed over the D-9 alloy. Cr(g), Mn(g) and Fe(g) were the neutral vapour species observed over the T-91alloy. Partial pressure-Temperature relations were derived using KEMS for the first time. Apparent enthalpies of vaporisation data were deduced by second law method. Chemical activities of all the major metallic elements (Fe, Cr, Ni and Mn) in the commercial grade D-9 austenitic stainless steel were determined in the temperature range of 1202–1529 K. In case of T-91 ferritic steel, chemical activities of Fe, Cr and Mn were determined in the temperature range of 1232 -1530 K.

Correlation of Volumetric Vaporsorption and Vapor Sensing Phenomenon of Flower-Like MoS2-Based Sensor

An innovative approach is reported with an aim to effectively correlate room temperature alcohol vapor (methanol, ethanol, and 2-propanol) sensing performance of flower-like MoS2 sphere-based devices with the corresponding vacuum volumetric vaporsorption study. Hydrothermally derived flower-like MoS2 sphere-based resistive devices were tested to detect the above species and the steady-state characteristics of the sensor (response magnitude and baseline drift) were directly and effectively correlated with the corresponding physisorption measurements carried out using Quantachrome Autosorb iQ. Response magnitude of the sensing layers having different porosity and effective surface area was duly predicted from the volume of adsorbed vapor species on the respective surfaces. Moreover, the baseline drift of the sensors was directly correlated with the amount of target species that remain chemisorbed. Considering rising and falling (transient characteristics) edges of the dynamic response curve, it was found that response time is predominantly governed by the physisorption phenomena, while the recovery is determined by both the mechanism (physidesorption and chemidesorption), though later having relatively lower influence. The highest response magnitude ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 77%) was achieved for sensor originated from the highest deposition time (24 h) toward methanol. It was duly correlated with its highest Brunauer–Emmett–Teller (BET) surface area (10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{{2}}$ </tex-math></inline-formula> /g) as well as its highest methanol adsorption at room temperature (116 cm3/g) among the lot. The highest baseline drift ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12^{\circ }{)}$ </tex-math></inline-formula> of 24-h deposited device was explained in the light of the highest open-loop gap (30 cm3/g).

Exhaust Gases as Fluxing Agents for Palladium: Formation Enthalpies and Vapor Pressures of PdO, PdO2, Pd(CO)n (n = 1–3), Pd(NO)n (n = 1,2), Pd(OH)n (n = 1,2), HOPdNO, and 21 Other Species under Automotive Catalyst Aging Conditions

Catalyst deactivation by precious metal sintering is a major driver of cost in automotive emission control catalysts. In order to develop strategies to mitigate sintering and maintain higher activity from lower precious metal loading, it is necessary to first develop a more complete understanding of the sintering process. In particular, it is of interest to identify the mobile intermediates that are responsible for sintering via Ostwald ripening and the extent to which the identities and concentrations of these intermediates depend upon the composition of the contacting atmosphere during catalyst use. In this work, first-principles thermodynamic calculations have been conducted on a series of small palladium-containing molecules to assess the potential of these molecules to form over palladium catalysts in the presence of automotive exhaust and serve as mobile carriers during Ostwald ripening. Among the results obtained, three stand out: (1) while exposure to reducing atmospheres in general does not enhance palladium mobility, exposure to carbon monoxide in particular leads to a multiple order of magnitude increase in palladium mobility driven primarily by the formation of Pd(CO)2; (2) under hydrothermal aging conditions, the most abundant vapor species is neither Pd nor PdOx but PdOH; and (3) combination of the latter with traces of nitric oxide enables a significant increase in palladium mobility via the formation of HOPdNO. The impact of surface adsorption on stabilization of mobile intermediates is also considered; a simple non-specific adsorption model indicates that surface stabilization enhances Pd(OH)2 formation under hydrothermal aging conditions.

Numerical prediction of ash deposit growth burning pure coal and its blends with woody biomass in a 1.5 MWTH combustor

The present work applies an original ash deposition model to a 1.5 MWTH combustor burning pure coal and its blends with woody biomasses (15 wt% biomass and 85 wt% coal). Previously, this model was validated with eleven (11) different solid fuels burning at a 100 kW down fired combustor, and this is the first scale-up study under industrially relevant conditions at 1.5 MWTH. The model does not require CFD modeling but considers four essential deposition mechanisms: inertial impaction, thermophoresis, condensation, and eddy impaction. The model employs the melt fraction stickiness model (MFSM), which includes a novel approach to determine sticking efficiency. The thermodynamic package of FactSage calculates the equilibrium composition of vapor species and the melt fraction of ash deposit and fly ash particles. Burning the fuels of this research produces NaCl and KCl, which are the main alkali vapor species for ash deposit formation on the clean surface of a heat exchanger. Condensation of such alkali vapor species expedites the ash deposit growth. The model suggests that cofiring woody biomass with coal makes slight changes at ash deposit growth at the locations farther to the burner. However, the predicted ash deposit growth for coal versus its blends at the closer location to the burner is significant. The present work substantiates that a numerical non-CFD model can be used for different scales of combustors and a wide range of solid fuels. Based on a novel approach in predicting ash deposit growth, the modeling results are consistent with the experimental data from a 1.5 MWTH combustor, paving the way for its commercial application.

Evaluating the Value of CrIS Shortwave-Infrared Channels in Atmospheric-Sounding Retrievals

The Cross-track Infrared Sounder (CrIS), in low Earth orbit since 2011, makes measurements of the top of atmosphere radiance for input into data assimilation (DA) systems as well as the retrieval of geophysical state variables. CrIS measurements have 2211 narrow infrared channels ranging between 650 and 2550 cm−1 (~3.9–15.4 μm) and capture the variation in profiles of atmospheric temperature, water vapor, and numerous trace gas species. DA systems derive atmospheric temperature by assimilating CO2-sensitive channels in the CrIS longwave (LW) band (650–1095 cm−1). Here, we investigate if CO2-sensitive channels in the shortwave (SW) band (2155–2550 cm−1) can similarly be applied. We first evaluated the information content of the CrIS bands followed by an assessment of the performance degradation of retrievals due to the loss of individual CrIS bands. We found that temperature profile retrievals derived from the CrIS SW band were statistically both well-behaved and as accurate as a retrieval utilizing the CrIS LW band. The one caveat, however, is that the higher CrIS instrument noise in the SW band limited its performance under certain conditions. We conclude with a discussion on the implications our results have for channel selection in retrieval and DA systems as well as the design of future space instruments.

Global Three-Dimensional Emission Inventory for Launch Vehicles from 2009 to 2018

Launch vehicles enable Earth observation, terrestrial navigation, communication, and space exploration. In doing so, they emit chemicals including carbon dioxide, water vapor, chlorine, alumina, black carbon, and other species that contribute to climate change and ozone depletion. With commercial launches increasing and new engines being developed, the impact of rocket launches must be reassessed. This work introduces a global three-dimensional inventory of stoichiometric emissions from rocket launches between 2009 and 2018. We calculate fuel burned and emissions as functions of altitude using publicly available data and a physics-based trajectory model. We estimate that 140 kt of carbon dioxide were emitted in total, and that 79 kt of water vapor, 5 kt of chlorine, and 8 kt of alumina were emitted above the tropopause between 2009 and 2018. All those emissions were produced in the Northern Hemisphere, of which 65% were from Russian and American launches. The number of launches and emissions of carbon dioxide are increasing over time, whereas water vapor and chlorine emissions have decreased since 2009 with the retirement of the space shuttle. Our results constitute the first global, spatially resolved inventory of launch emissions; and they are a critical step toward fully understanding the environmental effects of launch vehicles.

Coupled chemical–CFD modeling of unsealed dry storage of advanced test reactor spent fuel

Given the current lack of long-term disposal for spent nuclear fuel storage in the United States, the current inventory of advanced test reactor (ATR) fuel at Idaho National Laboratory (INL) is expected to be stored in a dry storage facility for an extended storage period. As part of an effort to understand the conditions during a 50-year period, a three-dimensional computational fluid dynamics (CFD) of the unsealed canisters packed with spent fuel in the storage facility was constructed, this CFD model is coupled with radiolytic chemical reactions associated with water vapor and other species. The coupled model is simulated over a range of sensitivity parameters for the fuel decay heat, relative humidity, and oxyhydroxide film thickness for undried and fully-dried fuel. The most important parameter was the initial fuel decay heat. Over the range of cases, the hydrogen and nitric acid concentrations are low enough no significant impact is expected.

High-temperature mass spectrometric study and modeling of ceramics based on the Al2 O3 -SiO2 -ZrO2 system.

Materials based on the Al2 O3 -SiO2 -ZrO2 system are promising for a wide range of high-temperature technological applications, such as thermal barrier coatings in the aviation and space industry or advanced materials in nuclear power reactors. Experimental studies of the ceramics based on this system by the Knudsen effusion mass spectrometric (KEMS) method are of significant interest in designing technological processes for the synthesis and exploitation of the Al2 O3 -SiO2 -ZrO2 materials. Samples of ceramics in the Al2 O3 -SiO2 -ZrO2 system, including the Al2 O3 -ZrO2 and SiO2 -ZrO2 binaries, were prepared by solid-state synthesis. Analysis of the samples was performed by X-ray fluorescence and diffraction techniques. The vapor composition and thermodynamic properties of the components in this system were determined by KEMS. The derived thermodynamic functions were optimized within the generalized lattice theory of associated solutions (GLTAS). In the temperature range 1900-2600 K, the SiO, Al,AlO, Al2 O, ZrO, ZrO2 , and O vapor species were identified over the samples in the systems under study. For the thermodynamic properties to be determined correctly, the samples of the Al2 O3 -SiO2 -ZrO2 system had to be vaporized at temperatures less than 2000 K, where data could be obtained only for the SiO species. The SiO2 activities obtained were taken as the experimental basis for the modeling within the GLTAS approach. This allowed evaluation of the component activities and excess Gibbs energy, and assessment of the relative number of bonds of different types. At 1920 K, the Al2 O3 -SiO2 -ZrO2 system is characterized by negative deviations of its thermodynamic properties from the ideal behavior. The consistency of the obtained modeling results was illustrated by comparison of the values derived from the data for the ternary and the boundary binary systems and thereby indicates the reasonable uniformity of the energy parameters of the lattice model derived in the calculations, which may be used in further modeling of multicomponent systems.

Thermodynamic assessment of lithium halide reciprocal salt systems for energy applications

Lithium halides are of interest because of their unique applications as fuel or coolants in molten salt reactors (MSRs) and electrolytes in thermally activated batteries. Because iodine is an important fission product for MSRs, the Molten Salt Thermal Properties Database-Thermochemical (MSTDB-TC) is being expanded to include relevant iodide reciprocal salt systems. In this work, we assess the thermochemical properties of lithium halide pseudobinary systems based on reported experimental phase diagrams, eutectic temperatures, and enthalpies of mixing. Within the framework of the modified quasi-chemical model in the quadruplet approximation (MQMQA), extrapolations to the related pseudoternary and pseudoquaternary systems have been performed. The pseudoquaternary representations of phase equilibria, enthalpy, entropy, and heat capacity are represented in the resultant models. Of interest for generating source terms for accident analysis is the ability to compute the vapor pressures of the dominant iodide species for the systems at any composition. An example of such calculations is provided for the LiF-LiI system at xLiI = 0.01 and xLiI = 0.70, in this case indicating that the LiI vapor species are predominant.