Browsing by Author "Singh, Prabhakar"
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Item Advanced Glass Seal for Electrochemical Oxygen Separation-Compression Device(49th International Conference on Environmental Systems, 2019-07-07) Reisert, Michael; Aphale, Ashish; Hong, Junsung; Mahapatra, Manoj; Singh, PrabhakarGlass-based sealing materials are preferred for hermetic sealing of high temperature electrochemical devices due to flexibility in tuning the thermophysical properties by formulation chemistry. Ease of manufacturing and application are the other major advantages of glass seals and a number of glass systems have been reported as sealants for solid oxide electrochemical systems. Recent developments in sealing materials for oxygen separation and compression will be presented with focus on chemical and structural stability of electrode–seal and electrolyte–seal interfaces. The similarities and contrasts between the sealing materials for oxygen compressors and fuel/electrolysis cell systems will be discussed. Seal properties will be discussed with regards to constituent materials such as glass network formers, modifiers, additives, and intermediate oxides.Item Capture of Trace Airborne Contaminants: Application to Electrochemical Systems(49th International Conference on Environmental Systems, 2019-07-07) Aphale, Ashish; Reisert, Michael; Hong, Junsung; Heo, Su Jeong; Hu, Boxun; Singh, PrabhakarTerrestrial and space environments, commonly encountered for life support and in-situ resource utilization (ISRU), contain a number of trace (ppm-ppt) levels of intrinsic and extrinsic impurities originating from source atmospheres as well as reaction byproducts from processing (chemical, thermal and electrochemical) systems. We present our research work on the removal of trace contaminants such as Cr, S, Si, B etc. from the air stream by the use of “getters”. The concept of “getters” along with underlying thermochemical understanding of materials chemistry will be discussed. The “getter” architecture, which provides a safe, robust, fire-resistant means of capturing gaseous impurities, will be discussed in detail. The basis for materials selection and reaction processes will be presented and experimental results obtained in our laboratory will be highlighted. Approaches for enhancing the capacity and lifetime of “getters” will also be discussed.Item Carbon Resistant Electrode for Direct Utilization of Hydrocarbon Fuels in Elevated Temperature Solid State Electrochemical Systems(49th International Conference on Environmental Systems, 2019-07-07) Hu, Boxun; Belko, Seraphim; Hong, Junsung; Aphale, Ashish; Reisert, Michael; Kumar, Rajesh; Dongare, Avinash; Singh, PrabhakarDirect utilization of hydrocarbon fuels in elevated temperature solid state electrochemical systems offers potential for improvement in electrical performance, better thermal management in the cell and stack as well as use of simpler balance of plant. Above systems, however, remain prone to carbon deposition in the fuel electrode resulting in structural and electrical performance degradation. We present our research findings on high entropy alloys (HEA) which have demonstrated carbon-free operation in the presence of gaseous and liquid hydrocarbons. Compared to Ni based conventional electrode material that showed extensive deposition of filamentary carbon and pulverization of nickel granular structure, HEA showed resistance to carbon formation. Research findings based on thermochemical models and implications of carbon-free operation for NASA specific missions will be highlighted for power generation, electrolysis and in-situ resource utilization.Item Carbon-Based Regenerable Sorbents for the Combined Carbon Dioxide and Ammonia Removal for the Primary Life Support System (PLSS)(44th International Conference on Environmental Systems, 2014-07-13) Wójtowicz, Marek A.; Cosgrove, Joseph E.; Serio, Michael A.; Manthina, Venkata; Singh, Prabhakar; Chullen, CindaResults are presented on the development of reversible sorbents for the combined carbon dioxide and trace-contaminant (TC) removal for use in Extravehicular Activities (EVAs). Since ammonia is the most important TC to be captured, data on TC sorption presented in this paper are limited to ammonia, with results relevant to other TCs to be reported at a later time. The currently available life support systems use separate units for carbon dioxide, trace contaminants, and moisture control, and the long-term objective is to replace the above three modules with a single one. Furthermore, the current TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal, which is non-regenerable, and the carbon-based sorbent under development in this project can be regenerated by exposure to vacuum at room temperature. The objective of this study was to demonstrate the feasibility of using carbon sorbents for the reversible, concurrent sorption of carbon dioxide and ammonia. Several carbon sorbents were fabricated and tested, and multiple adsorption/vacuum-regeneration cycles were demonstrated at room temperature, and also a carbon surface conditioning technique that enhances the combined carbon dioxide and ammonia sorption without impairing sorbent regeneration.Item Solid State Electrochemical Oxygen Separation and Compression(49th International Conference on Environmental Systems, 2019-07-07) Reisert, Michael; Aphale, Ashish; Taylor, Dale; Graf, John; Singh, Prabhakar; Hu, Boxun; Heo, Su Jeong; Hong, JunsungCeramic and solid-state electrochemical oxygen separation and compression systems offer the ease of producing high purity and high pressure oxygen from a variety of gaseous streams representative of ambient and constrained system exposure conditions (terrestrial and space). The electrochemical cells utilize exclusive oxygen ion conducting ceramic membranes (doped fluorites) and operate in a 550-850 °C temperature range. Advanced perovskites synthesized from non-noble and non-strategic materials serve as electrodes for both oxygen reduction and evolution. A number of electrochemical cells, connected in series using dense, electronically-conducting perovskite interconnects form the basis of a “cell stack” for increased oxygen production. The robust solid-state device provides a means of oxygen separation/compression, operating favorably in environments without reducing atmospheres (unlike terrestrial fuel/electrolysis cells). Thermochemical-electrochemical principles for oxygen separation and compression will be discussed. Materials for the construction of cells and stack along with fabrication techniques will be examined and the basis for material selection will be described. Approaches for the electrochemical performance improvement will also be discussed.