Cuckoo searching optimal composition of multicomponent alloys by molecular simulations
Not provided.
Materials Science↗
SEARCH · Search NASA
Results for “Compositional simulation”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Manufacturing and characterization of continuous fiber-reinforced thermoplastic tape overmolded long fiber thermoplastic
Light-weight construction, design freedom, integration of functions, and compelling cost element are desired by Original Equipment Manufacturers (OEMs) and their suppliers. The emergence of overmolding of continuous-discontinuous reinforcement enables design freedom and ability to tailor stiffness, strength, and damage tolerance for structural applications. In this work, long fiber thermoplastics (LFT) are overmolded with continuous fiber-reinforced thermoplastic (CFRTP) tape are combined using extrusion compression molding process to evaluate the structural performance. The CFRTP tape overmolded LFT samples were characterized using nondestructive and destructive techniques to track fiber alignment, fiber distribution, manufacturing defects, interfacial bonding of the tape – LFT and effect of CFRTP tape on LFT. Mode 1 fracture toughness, G 1c for tape overmolded LFT was higher by 25–30% compared to literature reported G 1c . This response was attributed to excellent fiber distribution, good fiber wetting, and absence of voids at the interface. Three-point bend test indicated that CFRTP tape overmolded LFT composites were better able to resist damage under the bending load compared to constituent LFT composite. Flexural strength of the overmolded composite was higher by 119–142%, and modulus higher by 77–65% compared to constituent LFT composite. Simulated flexural results accurately represents the mechanical behavior of composites. Here, the penetration energy of tape overmolded LFT composites determined by LVI test was in the range of 27.66–30.15 J, which is significantly higher than constituent LFT composite, 7.76 J. CFRTP tape overmolded LFT composite exhibits progressive fiber fracture, matrix cracking, and interfacial debonding failure, whereas, constituent LFT composite showed catastrophic fiber fracture.
42 ENGINEERING↗
Development and evaluation of a silver mordenite composite sorbent for the partitioning of xenon from krypton in gas compositions
A new engineered form composite sorbent for the selective separation of xenon from krypton in simulant composition off-gas streams resulting from the reprocessing of used nuclear fuel has been developed and evaluated. A sodium mordenite powder was incorporated into a macroporous polymer binder, formed into spherical beads and successfully converted to a 9 wt.% silver form composite sorbent. The final engineered form sorbent retained the characteristic surface area indicative of sodium mordenite powder. The sorbent was evaluated for xenon adsorption potential with capacities measured as high as 30 millimoles of xenon per kilogram of sorbent achieved at ambient temperature and 460 millimoles of xenon per kilogram sorbent at 220 K. Xenon/krypton selectivity was calculated to be 22.4 with a 1020 µL/L xenon, 150 µL/L krypton in a balance of air feed gas at 220 K. Furthermore, adsorption/desorption thermal cycling effects were evaluated with results indicating sorbent performance was not significantly impacted while undergoing numerous adsorption/desorption thermal cycles.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Damped Ly α absorbers and atomic hydrogen in galaxies: the view of the GAEA model
ABSTRACT Using the GAEA semi-analytic model, we analyse the connection between Damped Ly α systems (DLAs) and H i in galaxies. Our state-of-the-art semi-analytic model is tuned to reproduce the local galaxy H i mass function, and that also reproduces other important galaxy properties, including the galaxy mass–gas metallicity relation. To produce catalogues of simulated DLAs we throw 105 random lines of sight in a composite simulated volume: dark matter haloes with log$(\frac{M_{200}}{ {\rm M}_{\odot }}) \ge 11.5$ are extracted from the Millennium Simulation, while for $9.2 \le \log (\frac{M_{200}}{ \mathrm{M}_{\odot }})\lt 11.5$ we use the Millennium II, and for $8 \le \log (\frac{M_{200}}{\mathrm{M}_{\odot }}) \lt 9.2$ a halo occupation distribution model. At 2 < z < 3, where observational data are more accurate, our fiducial model predicts the correct shape of the column density distribution function, but its normalization falls short of the observations, with the discrepancy increasing at higher redshift. The agreement with observations is significantly improved increasing both the H i masses and the disc radii of model galaxies by a factor of 2, as implemented ‘a posteriori’ in our 2M−2R model. In the redshift range of interest, haloes with $M_{200} \ge {10}^{11} \, \mathrm{M}_{\odot }$ give the major contribution to ΩDLA, and the typical DLA host halo mass is $\sim \!{10}^{11} \, \mathrm{M}_{\odot }$. The simulated DLA metallicity distribution is in relatively good agreement with observations, but our model predicts an excess of DLAs at low metallicities. Our results suggest possible improvements for the adopted modelling of the filtering mass and metal ejection in low-mass haloes.
Di Gioia, Serafina↗
Characterizing the Effect of Capillary Heterogeneity on Multiphase Flow Pulsation in an Intermediate–Scale Beadpack Experiment using Time Series Clustering and Frequency Analysis
An intermediate-scale beadpack drainage experiment was conducted to investigate how simple layered lamination heterogeneity affects CO 2 flow. Two simple layers of capillary barriers are manually packed in the tank and slow drainage was carried out using analog fluids to mimic the capillary- and gravity-dominated CO 2 upward migration process in deep saline aquifers. Nonwetting phase saturation time series clustering analysis and frequency analysis have been conducted on the experimental data. Additionally, modified invasion percolation numerical simulations were done on a digital model of the beadpack to compare to experimental results. Results show that capillary barriers can lead to strong pulsation behavior, which in turn can cause unexpected early breaching through other barriers. The inlet pressure is found to be able to respond to saturation changes in far regions of the domain, indicating that the wetting phase can transmit pressure changes from the other phase. Although static simulations were not able to capture all the dynamic behavior observed in the experiment, Monte Carlo composite simulation results combining many different realizations can better illustrate how the nonwetting phase will behave in the heterogeneous domain. Furthermore, our results suggest the need for CO 2 storage site selection with preference given to aquifers with more capillary barriers with finer grain sizes to avoid flow pulsation and to retard plume upward migration.
58 GEOSCIENCES↗
Standard High Solids Vessel Design De-inventory Simulant Qualification
The Hanford Tank Waste Treatment and Immobilization Plant (WTP) is working to develop a Standard High Solids Vessel Design (SHSVD) process vessel. To support testing of this new design, WTP engineering staff requested that a Newtonian simulant be developed that would represent the de-inventory (residual high-density tank solids cleanout) process. Its basis and target characteristics are defined in 24590-WTP-ES-ENG-16-021 and implemented through PNNL Test Plan TP-WTPSP-132 Rev. 1.0. This document describes the de-inventory Newtonian carrier fluid (DNCF) simulant composition that will satisfy the basis requirement to mimic the density (1.18 g/mL ± 0.1 g/mL) and viscosity (2.8 cP ± 0.5 cP) of 5 M NaOH at 25 °C.1 The simulant viscosity changes significantly with temperature. Therefore, various solution compositions may be required, dependent on the test stand process temperature range, to meet these requirements. Table ES.1 provides DNCF compositions at selected temperatures that will meet the density and viscosity specifications as well as the temperature range at which the solution will meet the acceptable viscosity tolerance.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Standard High Solids Vessel Design Non-Newtonian Simulant Qualification
The Hanford Tank Waste Treatment and Immobilization Plant (WTP) is working to develop a Standard High Solids Vessel Design process vessel. To support testing of this new design, WTP engineering staff requested that a non-Newtonian simulant be developed that would represent the Most Adverse Design Condition (MADC), denoted as MADC-4, with respect to mixing performance as specified by WTP. The majority of the simulant requirements are specified in 24590-PTF-RPT-PE-16-001, Rev. 0, and a discussion of suggested non-Newtonian rheological parameters for the simulant was provided in WTP RPT-241, Rev. 0. This document describes the simulant composition that will satisfy the basis requirement along with ancillary testing to assess the rheological behavior of the simulant depending on the formulation approach used, simulant aging, and the effects of dilution. From this data, a simulant recipe to meet the basis is recommended. The simulant recipe was designed to meet a target rheology (as expressed by Bingham model parameters) of 34.5 ± 1.5 Pa [yield stress] and 33.5 ±1.5 cP [consistency] at 25 °C.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Chemical Composition Analysis of Simulated Waste Glass T10-G-16A
In this report, SRNL provides chemical composition analyses of a simulated LAW glass designated T10-G-16A.The measured chemical composition data are reported and compared with the targeted values for each component. No issues were identified in reviewing the analytical data.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Crystalline Silicotitanate ion exchange media long-term storage evaluation
Crystalline Silicotitanate a (CST) ion exchange media is produced in an engineered form, known as IONSIV™ IE-911. This material has been tested extensively for use in removing 137 Cs from Savannah River Site (SRS) and Hanford site tank waste. This inorganic material is highly selective for removing cesium ions, even in the presence of high concentrations of sodium and potassium ions and is tolerant of the harsh conditions of the varying tank chemistries. A batch of caustic washed IE-911 that had been produced by the supplier and received at SRS in 2001 was tested to verify that it was still in good condition after the extended storage. This testing involved standard batch contacts to measure the removal of Cs from simulated tank waste. This report describes the results of testing performed to verify that the IE-911 matches the performance of previous batches of this media. To confirm that the performance of IE-911 is similar to previous batches and that no degradation had occurred during storage, batch contact testing was performed using SRNL’s standard methodology using a non-radioactive SRS Average Waste Simulant composition utilized in previous studies. Batch contact kinetics testing was also conducted to determine cesium loading on this batch versus time. The cesium equilibrium loading isotherm in SRS simulant at 23°C was compared to ZAM isotherm model predictions and previous test results with IE-911 media. The measured and predicted distribution coefficients and cesium loading (“Q”) are shown in Table ES-1. The physical properties of the material were also determined, including density, moisture content, and particle size.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Gasification of coal, Chenopodium Album biomass, and co-gasification of a coal-biomass mixture by thermogravimetric-gas analysis
Gasification studies were performed on sub-bituminous coal of the province Centro in Boyacá state of Colombia, vegetable biomass Chenopodium album (cenizo) and co-gasification of coal-biomass mixtures agglomerated with paraffin in a thermogravimetric analyzer. Biomass synergistically promoted thermochemical transformation of the coal was observed. Experimental results were compared to equilibrium composition simulations. Ash fusibility tests of the coal-biomass mixture were carried out, which allowed to clarify its behavior, such as dry or fluid ash according to own chemical composition, during the gasification process. The experimental tests allowed determining the differences in thermal decomposition, between coal, cenizo and coal-biomass blend, which are attributable to the physicochemical properties of each one solid fuel. During the tests, gas chromatography analyses were performed to establish the compositions of the syngas. The syngas obtained from biomass had the highest concentration of CO and the lowest H 2 ; the coal and the coal-biomass mixture were slightly minor respectively. Concentrations of CH 4 , CO 2 and C 2 H 4 were similar between coal and biomass. This result is consistent with the higher calorific value of the coal syngas. The production of syngas from the coal-biomass mixture had the lowest contents of H 2 and CO due to synergistic phenomena that occur with the fuel mixture. The co-gasification of the mixture gave the highest syngas production, carbon conversion, and thermal efficiency. These results indicate the viability of co-gasification of coal- Chenopodium album agglomerated mixtures. In gasification of non-agglomerated mixtures of coal-cenizo, the biomass can be burned directly without producing syngas.
09 BIOMASS FUELS↗
Validating compositional fluid flow simulations using 4D seismic interpretation and vice versa in the SECARB Early Test—A critical review
We report on strengths and weaknesses of 4D seismic interpretation as a technique for monitoring carbon dioxide that was injected as part of a large scale test associated with commercial enhanced oil recovery (EOR) at Cranfield Field, Mississippi, USA. The goals of the monitoring effort are 1) to make measurements to verify that the CO 2 is contained in the reservoir according to operational designs and model predictions, and 2) that if there are deviations, to provide data which can be used to update the earth models and determine if any mitigation is needed. Our work uses a compositional numerical simulation to model CO 2 flow in the reservoir and compares the results with estimates of changes in seismic properties between a pre-injection and a survey after more than 2 million metric tons injected. The complicated physics of the problem in Cranfield field present challenges to seismic interpretations. These findings reflect partial agreement between the results of the numerical simulation and the seismic interpretations. Possible causes of discrepancies among the fluid flow model and multiple interpretations of the same seismic data sets performed with different work flows illuminates the types of uncertainties that should be considered to achieve the goals of monitoring.
4D seismic↗
Chemical Composition Analysis of Simulated Waste Glass T10-G-16A
In this report, SRNL provides chemical composition analyses of a simulated LAW glass designated T10-G-16A. The measured chemical composition data are reported and compared with the targeted values for each component. No issues were identified in reviewing the analytical data. The measured concentrations of Al 2 O 3 , CaO, Na 2 O, and SiO 2 in T10-G-16A deviated from the targeted composition. It is of potential interest to note that these deviations result in a glass composition that is shifted toward the SiO 2 corner of the Al 2 O 3 -Na 2 O-SiO 2 phase diagram, away from the nepheline phase field. The results of these analyses will be used in developing a better understanding of the properties and performance of this glass.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Characterisation of sludge for pyrolysis conversion process based on biomass composition analysis and simulation of pyrolytic properties
Highlights: • Characterisation of different types sewage sludge for pyrolytic properties. • Developed analytical procedure to categorise and quantify composition of sludge. • Observed qualitative similarity and quantitative variation on properties of sludge. • Correlated organic components with thermochemical properties of sludge. • Coupled model compounds selection and composition analysis for simulation study. - Abstract: Pyrolytic behaviour of sludge is highly complex and obscure because of its heterogeneous and diverse composition. Therefore, an analytical procedure is proposed to categorise and quantify the main constituents in sludge. In addition, a simulation study of sludge characteristics is carried out to complement the composition analysis and to improve our understanding on the relationship between composition of sludge and its corresponding properties. Different types of sludge samples were collected at different treatment stages from four Water Reclamation Plants in Singapore in two separate batches. Model compounds are selected to represent components identified and are used in simulation of pyrolytic properties of sludge. Constituents of sludge are adequately categorised, quantified and characterised in this study. Qualitative similarities and quantitative variations on characteristics of different sludge samples were identified. Comparison among the samples collected with the simulation provided insights on how differences in organic composition of sludge affected its properties.
09 BIOMASS FUELS↗
Low Activity Waste Tuning Feed Material Testing; Qualification and Transition Testing (Final Report)
The primary objective of this work was to collect data to support processing of the proposed LAW tuning feed composition at the WTP. This was achieved through assessment of the modified LAWB83 feed and glass composition by feed rheology testing and by processing selected LAW feeds through a DM100 melter to confirm that the tuning feed material can be fed to the melter with acceptable commercial or hazards risk. The testing also confirmed that transitions from the startup frit to the LAWB83 tuning feed and then to the cold commissioning simulant composition can be performed without causing any significant melter performance issues.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Simplified predictive models for CO 2 sequestration performance assessment
CO2 sequestration in deep saline formations is increasingly being considered as a viable strategy for the mitigation of greenhouse gas emissions from anthropogenic sources. In this context, detailed numerical simulation based models are routinely used to understand key processes and parameters affecting pressure propagation and buoyant plume migration following CO2 injection into the subsurface. As these models are data and computation intensive, the development of computationally-efficient alternatives to conventional numerical simulators has become an active area of research. Such simplified models can be valuable assets during preliminary CO2 injection project screening, serve as a key element of probabilistic system assessment modeling tools, and assist regulators in quickly evaluating geological storage projects. We present three strategies for the development and validation of simplified modeling approaches for CO2 sequestration in deep saline formations: (1) simplified physics-based modeling, (2) statisticallearning based modeling, and (3) reduced-order method based modeling. In the first category, a set of full-physics compositional simulations is used to develop correlations for dimensionless injectivity as a function of the slope of the CO2 fractional-flow curve, variance of layer permeability values, and the nature of vertical permeability arrangement. The same variables, along with a modified gravity number, can be used to develop a correlation for the total storage efficiency within the CO2 plume footprint. Furthermore, the dimensionless average pressure buildup after the onset of boundary effects can be correlated to dimensionless time, CO2 plume footprint, and storativity contrast between the reservoir and caprock. In the second category, statistical “proxy models” are developed using the simulation domain described previously with two approaches: (a) classical Box-Behnken experimental design with a quadratic response surface, and (b) maximin Latin Hypercube sampling (LHS) based design with a multidimensional kriging metamodel fit. For roughly the same number of simulations, the LHS-based metamodel yields a more robust predictive model, as verified by a k-fold cross-validation approach (with data split into training and test sets) as well by validation with an independent dataset. In the third category, a reduced-order modeling procedure is utilized that combines proper orthogonal decomposition (POD) for reducing problem dimensionality with trajectory-piecewise linearization (TPWL) in order to represent system response at new control settings from a limited number of training runs. Significant savings in computational time are observed with reasonable accuracy from the PODTPWL reduced-order model for both vertical and horizontal well problems – which could be important in the context of history matching, uncertainty quantification and optimization problems. The simplified physics and statistical learning based models are also validated using an uncertainty analysis framework. Reference cumulative distribution functions of key model outcomes (i.e., plume radius and reservoir pressure buildup) generated using a 97-run full-physics simulation are successfully validated against the CDF from 10,000 sample probabilistic simulations using the simplified models. The main contribution of this research project is the development and validation of a portfolio of simplified modeling approaches that will enable rapid feasibility and risk assessment for CO2 sequestration in deep saline formations.
54 ENVIRONMENTAL SCIENCES↗
Defense Waste Processing Facility Nitric-Glycolic Flowsheet Chemical Process Cell Chemistry: Part 2
The conversions of nitrite to nitrate, the destruction of glycolate, and the conversion of glycolate to formate and oxalate were modeled for the Nitric-Glycolic flowsheet using data from Chemical Process Cell (CPC) simulant runs conducted by Savannah River National Laboratory (SRNL) from 2011 to 2016. The goal of this work was to develop empirical correlation models to predict these values from measurable variables from the chemical process so that these quantities could be predicted a-priori from the sludge or simulant composition and measurable processing variables. The need for these predictions arises from the need to predict the REDuction/OXidation (REDOX) state of the glass from the Defense Waste Processing Facility (DWPF) melter. This report summarizes the work on these correlations based on the aforementioned data. Previous work on these correlations was documented in a technical report covering data from 2011-2015. This current report supersedes this previous report. Further refinement of the models as additional data are collected is recommended. The glass REDOX depends on the concentrations of nitrate and manganese (oxidants), and of glycolate, formate, oxalate, carbon, and antifoam (reductants) in the melter feed. The waste sludge contains nitrite, nitrate, manganese (Mn), and oxalate. Virtually all of the nitrite is converted to nitrate or NO+NO 2 +N 2 O gases in the CPC. The portion of the nitrite converted to nitrate increases the amount of nitrate in the sludge. The amount of glycolate in the final melter feed depends on the amount of the glycolic acid feed that is destroyed. Similarly, the amounts of formate and oxalate formed during the decomposition of glycolic acid are required. The material balance on carbon was found to not close in most cases. Generally, there was less carbon at the end of testing compared to the inputs. The most uncertain product variable was glycolate, so material balances were performed where the glycolate concentration was adjusted, usually upward, to close the balance. Correlation versus the original, as-measured, data was generally poor, but correlation against the material balance adjusted values was greatly improved. It was also shown that the correlation of the measured REDOX versus the predicted REDOX was much better when the material balance adjusted glycolate values were used. Three data series were primarily used during the regressions of the data; these series were 1) Sludge Batch 9 NG flowsheet simulant runs NG51-62 (SB9-NG); 2) Scaled Runs + Bounding Hydrogen Runs (SR+BH); and 3) Runs GN43-50 and 57 (43-50,57). The glycolate destruction was found to correlate with acid stoichiometry (AS), percent reducing acid (PRA), and for some data series, headspace to simulant volume ratio (HSV), mercury (Hg), and nitrate. Although glycolate destruction for pairs of data series (e.g., [SB9-NG] and [SR+BH]) were found to depend on HSV, the combination of all three data series was not found to have significant dependence on this variable. The best model for glycolate destruction depended on AS, nitrate, and Hg. This model predicted the product glycolate compositions of the data to within 92-106%. The conversion of glycolate to formate was high when noble metals and Hg were not present, with values up to 100%. When noble metals and Hg were present, this conversion ranged from zero to 7%, and was dependent on AS. Lower AS gave higher conversions to formate. The conversion to oxalate was found to depend on the AS and the initial concentration of nitrite. An alternative fit versus AS and the form of ruthenium (Ru) used is a possible alternative. This fit was somewhat less statistically significant. This second model predicts that more oxalate is formed when Ru-nitrosyl nitrate is used rather than Ru chloride. The conversion of glycolate to oxalate ranged from zero to 6%. The conversion of nitrite to nitrate depended primarily on AS and PRA, with HSV and Hg being significant when these variables were varied. For multiple series of data, nitrite was also needed to SRNL-STI-2017-00172 5HYLVLRQ viL distinguish between data series, and the effect of HSV became insignificant. The best model for nitrite to nitrate conversion depended on AS, PRA, nitrite, and Hg. The 95% confidence intervals on the predicted values of glycolate destruction, glycolate to oxalate conversion, and nitrite to nitrate conversion were used to determine the uncertainty in the predicted REDOX when starting with only the composition of the sludge, AS, and PRA. Using the 95% confidences on an individual value (that is the confidence in getting a particular value for one single test as opposed to what the mean would be for multiple tests), the uncertainty in the predicted REDOX was calculated. The uncertainty in the actual product composition glycolate, oxalate, formate, and nitrate concentrations translated to an uncertainty in the REDOX value of ±0.1,which is approximately the uncertainty claimed in the REDOX model itself.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Precipitation of Epsilon Particles in Metal Doped Ceria Irradiated with Energetic Ions
Metallic particles precipitated from fission products in oxide fuel matrix (e.g., UO{sub 2}) have a great impact on the thermal and mechanical properties of the fuel. A burn-up of 40 MWd/kg U results in the conversion of 4% of the uranium to approximately 3% fission products and 1% transuranium elements. Epsilon phase is the major metallic phase of the precipitates with a hexagonal-closed packed (HCP) crystal structure. It can exist in a variety of metallic forms in UO{sub 2}, but typically, it consists of five metals: Mo, Pd, Rh, Ru and Tc. Epsilon particles can form over a wide range of stoichiometries in the five metal system. Simulated compositions with Re as a surrogate for Tc have been investigated as a waste form for {sup 99}Tc, an isotope with a long half-life of 2.13 10{sup 5} years and a high solubility under oxidizing conditions in addition to Mo in the corrosion process. There is a pressing need to understand the factors influencing the formation and growth of the metallic phase in fuel. Efforts are currently underway to perform careful neutron irradiation of nuclear fuel under controlled conditions in a test reactor, recover metallic phases that may be present, and characterize the resulting structure and chemistry. Due to the long duration, high cost and radiological concerns associated with neutron irradiation and sample characterizations, ion irradiation studies of a surrogate material with a full control of the processing parameters can emulate different stages of the particle precipitation, which can add a tremendous value to reactor-based studies. This presentation reports our recent ion irradiation results on the metallic particle precipitation under various irradiation and thermal annealing conditions.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Temperature-Dependence of Corrosion of Ni-Based Superalloys in Hot CO 2 -Rich Gases Containing SO 2 Impurities
Future power plants will require Ni-based superalloys resistant to high-temperature corrosion in CO 2 -rich environments containing impurities. In this work, several commercially available Ni-based alloys (617, 230, 625, 263, 740H) were exposed at 600°C, 650°C, 750°C and 1 atm to 95% CO 2 , 4% H 2 O, 1% O 2 without/with 0.1% SO 2 to simulate compositions expected in a direct-fired supercritical CO 2 power cycle. The results indicate no effect of SO 2 at 750°C, a small negative effect at 650°C, and a large negative effect at 600°C. Alloys exposed at the higher temperatures (650–750°C) formed thin Cr-rich oxide scales, whereas the lowest temperature (600°C) resulted in thicker scales consisting of non-protective oxides and sulfates. Thermodynamic analysis indicates this increased corrosion is associated with a transition in the stable compounds in contact with the gas. Understanding the factors that affect this transition will aid in the selection or design of alloys for future CO 2 -based power systems.
36 MATERIALS SCIENCE↗