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Carbon Dioxide Gas Sensors
Current bulk or thick film solid electrolyte CO<sub>2</sub> sensors are expensive, difficult to batch fabricate, and large in size. In contrast, this new amperometric, solid-state, oxide-based electrolyte CO<sub>2</sub> microsensor is affordable, easy to fabricate, and is so small that it could easily be integrated onto a substrate the size of a postage stamp. The basic composition of the sensor is identical to a previously designed NASA Glenn technology in which a solid electrolyte of Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> is deposited between interdigitated electrodes on an alumina substrate and is covered by Na<sub>2</sub>CO<sub>3</sub>/BaCO<sub>3</sub>. Unlike its predecessor, however, this innovation includes an additional layer of nanocrystalline SnO<sub>2</sub> sol gel, an electron donor type (N-type) semiconductor, on top of the Na<sub>2</sub>CO<sub>3</sub>/BaCO<sub>3</sub> . This new layer provides a greater number of electrons for reduction reaction at the working electrode to detect CO<sub>2</sub>. As a result, overall performance is enhanced, and this new state-of-the-art sensor has the ability to operate at temperatures as low as 375&deg;C. This low temperature capability significantly decreases the amount of power required to operate the sensor, opening the door to a multitude of new applications that were previously unattainable.
mechanical and fluid systems
Spacecraft Atmosphere Carbon Dioxide (CO<sub>2</sub>) Capture via Deposition
Spacecraft Atmosphere Carbon Dioxide (CO<sub>2</sub>) Capture via Deposition is an air revitalization architecture that utilizes the different physical phase-change properties of International Space Station (ISS) cabin-like constituents (nitrogen, oxygen, carbon dioxide, water vapor, and various trace contaminants) to selectively separate constituents of interest, such as carbon dioxide and trace contaminants. As the main target constituent is CO<sub>2</sub>, which does not condense in atmospheric conditions, this architecture is referred to as CO<sub>2</sub> deposition, or CDep. The technology addresses future CO<sub>2</sub> removal and life support system needs using a completely different technical approach than currently employed on the ISS. Instead of using a sorbent, this technology utilizes cooling to directly freeze CO<sub>2</sub> out of the atmosphere. Specifically, it involves forcing a phase change of CO<sub>2</sub> from the cabin atmosphere by solidifying it onto a cold surface. The technology for spacecraft atmosphere CO<sub>2</sub> capture uses sequential heat exchangers to cool airflow from the spacecraft atmosphere, and uses deposition coolers that can operate in a deposition mode, in which CO<sub>2</sub> from the airflow is deposited to generate said CO<sub>2</sub> depleted air, and a sublimation mode in which deposited CO<sub>2</sub> is sublimated into CO<sub>2</sub> gas. The system can alternately cycle between the deposition mode and the sublimation mode. A deposition system can also remove humidity in addition to CO<sub>2</sub> via a multi-stage process, and can also significantly assist in controlling the trace contaminants.
mechanical and fluid systems
ISS as seen by STS-124; Photo Credit: NASA on the Commons, https://www.flickr.com/photos/nasacommons/35201127816/in/album-72157648186433655/
Liquid Sorbent Carbon Dioxide Removal System
NASA's Liquid Sorbent Carbon Dioxide Removal System was designed as an alternative to the current CO2 removal technology used on the International Space Station (ISS), which uses solid zeolite media that is prone to dusting, has a low absorption capacity, and requires high regeneration temperatures and frequent maintenance. Motivated by CO2 removal systems on submarines, NASA innovators began investigating the use of liquid sorbents. Liquid sorbents have a capacity four times greater than solid zeolites, require low regeneration temperature, and need fewer unreliable moving mechanical parts than solid based systems. While submarine CO2 scrubbers spray an adsorbing chemical directly into the air stream and allow the liquid to settle, NASA's new system uses a capillary driven 3D printed microchannel direct air/liquid contactor in a closed loop system. The Liquid Sorbent Carbon Dioxide Removal System is robust and reliable, while being low in weight, volume, and power requirements. The system is capable of reaching equilibrium when the liquid sorbent surface is being regenerated at a rate equal to the rate of absorption into the liquid.
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