Time filter

Source Type

Westerville, OH, United States

Rettie A.J.E.,University of Texas at Austin | Lee H.C.,University of Texas at Austin | Marshall L.G.,University of Texas at Austin | Lin J.-F.,University of Texas at Austin | And 6 more authors.
Journal of the American Chemical Society

Bismuth vanadate (BiVO4) is a promising photoelectrode material for the oxidation of water, but fundamental studies of this material are lacking. To address this, we report electrical and photoelectrochemical (PEC) properties of BiVO4 single crystals (undoped, 0.6% Mo, and 0.3% W:BiVO4) grown using the floating zone technique. We demonstrate that a small polaron hopping conduction mechanism dominates from 250 to 400 K, undergoing a transition to a variable-range hopping mechanism at lower temperatures. An anisotropy ratio of ∼3 was observed along the c axis, attributed to the layered structure of BiVO4. Measurements of the ac field Hall effect yielded an electron mobility of ∼0.2 cm2 V -1 s-1 for Mo and W:BiVO4 at 300 K. By application of the Gärtner model, a hole diffusion length of ∼100 nm was estimated. As a result of low carrier mobility, attempts to measure the dc Hall effect were unsuccessful. Analyses of the Raman spectra showed that Mo and W substituted for V and acted as donor impurities. Mott-Schottky analysis of electrodes with the (001) face exposed yielded a flat band potential of 0.03-0.08 V versus the reversible H2 electrode, while incident photon conversion efficiency tests showed that the dark coloration of the doped single crystals did not result in additional photocurrent. Comparison of these intrinsic properties to those of other metal oxides for PEC applications gives valuable insight into this material as a photoanode. © 2013 American Chemical Society. Source

Courts S.S.,Lake Shore Cryotronics, Inc.

The model DT-670-SD cryogenic diode temperature sensor, manufactured by Lake Shore Cryotronics, Inc. has been used on numerous aerospace space missions since its introduction nearly 15 years ago. While the sensing element is a diode, it is operated in a non-standard manner when used as a temperature sensor over the 1.4-500 K temperature range. For this reason, the NASA and MIL-type test and performance standards designed to ensure high reliability of diode aerospace parts don't properly define the inspection and test protocol for the DT-670-SD temperature sensor as written. This requires each aerospace application to develop unique test and inspection protocols for the project, typically for a small number of sensors, resulting in expensive sensors with a long lead time. With over 30 years of experience in supplying cryogenic temperature sensors for aerospace applications, Lake Shore has developed screening and qualification inspection and test protocols to provide "commercial off-the-shelf (COTS)" DT-670-SD temperature sensors that should meet the requirements of most high-reliability applications including aerospace. Parts from acceptance and qualified lots will be available at a base sensor level with the ability to specify an interchangeability tolerance, calibration range, mounting adaptor, and/or lead extension for final configuration. This work presents details of this acceptance and qualification inspection and test protocol as well as performance characteristics of the DT-670-SD cryogenic temperature sensors when inspected and tested to this protocol. © 2015 Elsevier Ltd. All rights reserved. Source

Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 599.78K | Year: 2011

The innovative, high transmission band-pass filter technology proposed here is an improvement in multilayer metal-mesh filter design and manufacture for the far IR to submillimeter ranges. The proposed metal-mesh filters can tolerate cryogenic temperatures (down to 4K and below) and a wide vibration/shock spectrum, making them launch-capable and durable for long periods in space. In addition, the proposed band-pass filters are light weight, as they employ no heavy substrates. The proposed 2?5 mm thickness (mostly the mounting frame) allows insertion into tight spaces and standard filter wheels. The thin, light weight, vacuum compatible design can be incorporated into almost any detector setup. Large sizes can be manufactured for newer instruments with larger diameter beams.

Lake Shore Cryotronics, Inc. | Date: 2011-08-31

Sensors operate by resolving changes in orientation of a wavelength dependent structure with respect to a reference direction determined by an incident light beam, resulting in very high sensitivity and dynamic range. Said sensors are wavelength encoded, can be multiplexed in a single light path such as an optical fiber, yet are decoupled mechanically from the fiber, resulting in high stability.

Optical fiber anchors accomplishing low creep confinement or fixing of a section of optical fiber in an assembly compact enough to be used conveniently as an anchor or as an enabling part of a strain or temperature sensor while retaining low optical losses and the original buffer coating to prevent the fiber from being exposed to abrasion and other influences that could lead to breakage. A rigid body is used that is mechanically stiff and hard enough to prevent the fiber from cutting into it or distorting the medium or substrate when subjected to stress, even over a long period of years. Trapping can be accomplished by molding the bent fiber into the substrate or body, adhesively bonding or soldering the optical fiber into a confining curved groove in a body or substrate.

Discover hidden collaborations