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Miniaturized Schottky Diode Sensors for Hydrogen and Hydrocarbon Detection at High Temperatures

The sensors have application in fuel leak detection, environmental monitoring, fire detection, security monitoring, and engine emission monitoring. John H. Glenn Research Center, Cleveland, Ohio A miniaturized Schottky diode hydrogen and hydrocarbon sensor with the structure of catalytic metal-metal oxide-silicon carbide (SiC) has been developed. The major innovation of this work is the use of the metal oxide, palladium oxide (PdOx), as a barrier layer between the catalytic metal and the SiC in the gas-sensing structure. A major advantage of adding a PdOx barrier layer between the gate metal and the SiC is to prevent and alleviate chemical reactions between the gate metal and the SiC. Without the PdOx barrier layer, the gate metal and the substrate can easily form metal silicides at high temperature, leading to diode structure disruption. The metal oxide barrier layer can be incorporated into a gas-sensing structure by standard deposition techniques in a controlled manner. This oxide naturally forms with Pd in Pd-based gas sensor systems and can disrupt the gas sensor structure when formed in situ in an uncontrolled manner. However, purposely including this oxide in the Schottky barrier structure produces a stable barrier layer that enables a stable and sensitive gas sensor structure.

Posted in: Physical Sciences, Sensors, Briefs

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Analog Ceramic Isolated Voltage Sensor

John H. Glenn Research Center, Cleveland, Ohio Galvanic isolated monitoring of voltages for launch vehicle, missiles, and space-deployed systems can be very challenging. Radiation exposure makes use of optics-based sensors difficult, as they can latch-up and become corrupted by the radiation environment; such devices can moreover be thermally challenged. Magnetic transformer-based methods of isolated voltage measurement require shielding to prevent stray magnetic interference from degrading or corrupting the readings; moreover, magnetic-based solutions are unable to measure voltages down to DC levels.

Posted in: Physical Sciences, Sensors, Briefs

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Flexible and Erectable Magnetic Field Response Sensors

Langley Research Center, Hampton, Virginia The means to make a flexible and/or erectable magnetic field response sensor, a geometrically fixed capacitor mounting frame, a wireless dipstick, and an elastically flexible capacitor support have been developed. Either the capacitor mounting frame or the flexible, erectable magnetic field response sensor can be developed to take measurements in hazardous conditions, or in containers with environmentally harmful contents, such as a gasoline storage tank.

Posted in: Physical Sciences, Sensors, Briefs

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Miniature Amperometric Solid Electrolyte Carbon Dioxide Sensor with Low Detection Limit

This sensor is applicable to fire detection, personal health monitoring, and environmental monitoring. John H. Glenn Research Center, Cleveland, Ohio A miniaturized amperometric electro-chemical (solid electrolyte) carbon dioxide (CO2) sensor using a novel and robust sensor design has been developed and demonstrated. Semiconductor microfabrication techniques were used in the sensor fabrication, and the sensor is fabricated for robust operation in a range of environments. The sensing area is 1.0 × 1.1 mm. The sensor is operated by applying voltage across the electrodes and measuring the resultant current flow at temperatures from 450 to 600 °C. Linear responses were achieved to the CO2 concentrations from 1% to 4%, and to the natural logrithmic concentrations of the CO2 from 0.02% to 1%. This CO2 sensor has the advantage of being simple to batch-fabricate, small in size, low in power consumption, easy to use, and fast with response time.

Posted in: Physical Sciences, Sensors, Briefs

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Multi-Step DRIE Process to Fabricate Silicon-Based THz Components

Commercial applications include airport screening systems, explosives detectors, nondestructive testing, and wireless communications. NASA’s Jet Propulsion Laboratory, Pasadena, California Terahertz (THz) frequency radiometers, spectrometers, and radars are promising instruments for the remote sensing of planetary atmospheres such as Mars, Venus, Jupiter, and Saturn, and their moons such as Titan, Europa, Ganymede, and others. For these long-term planetary missions, severe constraints are put on the mass and power budget for the payload instruments.

Posted in: Manufacturing & Prototyping, Briefs

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Plasma Reduction of Lunar Regolith for In-Space Fabrication

Plasma processing effectively produced agglutinate and glassy spherules — analog particles similar to those found on the lunar surface. Marshall Space Flight Center, Alabama The in situ production of vital gases and raw materials on the lunar surface is an integral part of NASA’s exploration vision. Development of processes for extraction of oxygen and metallics from the lunar regolith will be vital not only for life support on the lunar surface, but also for spacecraft propulsion to travel further beyond low Earth orbit. This will have a direct impact on cost reduction associated with minimizing the raw material mass from Earth. Aside from utilization of in situ resources, one of the significant limitations of current simulant is the lack of constituents, such as agglutinates. These agglutinates are typically mineral fragments of the lunar regolith that are held together by glass and, depending on location, may constitute 60% to 70% of the lunar regolith.

Posted in: Manufacturing & Prototyping, Briefs

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Method for Determining Self-Reacting Friction Stir Weld Schedules

This new process is quicker and more effective. Lyndon B. Johnson Space Center, Houston, Texas This invention establishes a process to define a viable self-reacting friction stir weld (SR-FSW) schedule (parameter settings) for a given material combination. The focus of this process results in a SR-FSW schedule that is insensitive to intentional changes or normal process variation in pin force at a given rotation and travel speed. Viable is defined as a weld schedule that is usable in a production environment and is able to accommodate normal production variations.

Posted in: Manufacturing & Prototyping, Briefs

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