The moisture absorption behavior of two fiber reinforced composite materials was evaluated in a unidirectional manner The flat materials were exposed to varying humidity and temperature conditions inside of an environmental chamber in order to determine their effective moisture equilibrium (M m ) and moisture absorption rate (D z ). Two-ply (thin) and four-ply (thick) materials were utilized to obtain M,,, and Dz, respectively. The results obtained from laboratory work were then compared to modeling data to better understand the material properties. Predictions capabilities were built to forecast the maximum moisture content, time required for saturation, and the moisture content at any given humidity and temperature. A case study was included to demonstrate this capability. Also of interest were cubed samples to investigate directionality preferences in water immersion studies. Several coatings were evaluated for their water permeation properties. Further dissemination authorized to the Department of Energy and DOE contractors only; other requests shall be approved by the originating facility or higher DOE programmatic authority.
The supercritical carbon dioxide (S-CO2) Brayton Cycle has gained significant attention in the last decade as an advanced power cycle capable of achieving high efficiency power conversion. Sandia National Laboratories, with support from the U.S. Department of Energy Office of Nuclear Energy (US DOE-NE), has been conducting research and development in order to deliver a technology that is ready for commercialization. Root cause analysis has been performed on the Recompression Loop at Sandia National Laboratories. It was found that particles throughout the loop are stainless steel, likely alloy 316 based upon the elemental composition. Deployment of a filter scheme is underway to both protect the turbomachinery and also for purposes of determining the specific cause for the particulate. Shake down tests of electric resistance (ER) as a potential in-situ monitoring scheme shows promise in high temperature systems. A modified instrument was purchased and held at 650°C for more than 1.5 months to date without issue. Quantitative measurements of this instrument will be benchmarked against witness samples in the future, but all qualitative trends to date are as to be expected. ER is a robust method for corrosion monitoring, but very slow at responding and can take several weeks under conditions to see obvious changes in behavior. Electrochemical noise was identified as an advanced technique that should be pursued for the ability to identify transients that would lead to poor material performance.
The performance of Y2O3-stabilized ZrO2 (YSZ), Y2O3, and Al2O3 plasma sprayed coatings are investigated for their ability to prevent attack of Haynes 230 by a near-eutectic Cu-Mg-Si metallic phase change material (PCM) in a closed environment at 820 °C. Areas where coatings failed were identified with optical and scanning electron microscopy, while chemical interactions were clarified through elemental mapping using electron microprobe analysis. Despite its susceptibility to reduction by Mg, the Al2O3 coating performed well while the YSZ and Y2O3 coating showed clear signs of failure. Due to a lack of reliable melting in the PCM, these results are attributed to the evolution of gaseous Mg leading to the formation of MgO and MgAl2O4.
The supercritical carbon dioxide (S - CO2) Brayton Cycle has gained significant attention in the last decade as an advanced power cycle capab le of achieving high efficiency power conversion. Sandia National Laboratories, with support from the U.S. Department of Energy Office of Nuclear Energy (US DOE - NE), has been conducting research and development in order to deliver a technology that is rea dy for commercialization. There are a wide range of materials related challenges that must be overcome for the success of this technology. At Sandia, recent work has focused on the following main areas: (1) Investigating the potential for system cost re duction through the introduction of low cost alloys in low temperature loop sections, (2) Identifying material options for 10MW RCBC systems, (3) Understanding and resolving turbine degradation, (4) Identifying gas foil bearing behavior in CO 2 , and (5) Ide ntifying the influence of gas chemistry on alloy corrosion. Progress in each of these areas is provided in this report.
The systematic development of microstructure, solidification characteristics, and heat of solidification with composition in copper-silicon-magnesium alloys for thermal energy storage is presented. Differential scanning calorimetry was used to relate the thermal characteristics to microstructural development in the investigated alloys and clarifies the location of one of the terminal three-phase eutectics. Repeated thermal cycling highlights the thermal storage stability of the transformation through multiple melting events. In conclusion, two near-terminal eutectic alloys display high enthalpies of solidification, relatively narrow melting ranges, and stable transformation hysteresis behaviors suited to thermal energy storage.
Dish-Stirling systems are a strong candidate to meet cost production goals for solar thermal power production. Thermal energy storage improves the capacity factor of thermal power systems; copper-silicon-magnesium eutectic alloys have been investigated as potential latent heat storage materials. This work examines the ability of commercially available plasma spray coatings to serve as protective barriers with these alloys, while highlighting mechanistic insights into materials for latent heat storage systems. Computed tomography was leveraged as a rapid screening tool to assess the presence of localized attack in tested coatings.