MartÃnez, Luis Javier Huang, Ningfeng Ma, Jing Lin, Chenxi Jaquay, Eric Povinelli, Michelle LĪ new photonic crystal structure is generated by using a regular graphite lattice as the base and adding a slot in the center of each unit cell to enhance field confinement. We conclude that the calibrated graphite thermometer> is ambiguous in active tectonic settings.ĭesign and optical characterization of high- Q guided-resonance modes in the slot- graphite photonic crystal lattice. Microstructural observations show that brittle processes caused the documented mechanical modifications of the aggregate graphite crystallinity. Our results demonstrate structural disorder of graphite, manifested as changes in the Raman spectra. The degree of structural order both in the starting and resulting materials was analyzed by Raman microspectroscopy. We sheared highly crystalline graphite powder at normal stresses of 5 and 25 megapascal (MPa) and aseismic velocities of 1, 10 and 100 µm s-1. To examine the possibility of mechanical modifications of graphite structure and the potential impacts on graphite thermometry>, we performed laboratory deformation experiments.
However, discrepancies between temperatures indicated by graphite crystallinity versus other thermometers have been documented in deformed rocks. Thus, the degree of graphite crystallinity, or its structural order, has been calibrated as an indicator of the peak metamorphic temperatures experienced by the host rocks. Graphitization, or the progressive maturation of carbonaceous material, is considered an irreversible process. Kirilova, Martina Toy, Virginia Rooney, Jeremy S. Structural disorder of graphite and implications for graphite thermometry Optical test results showed 6nm cry0 deformation from ambient to 30 degrees Kelvin and little to no change in its surface figure due to cry0 cycling. A lightweighted 0.2-diameter polished SuperSic mirror was tested at cryogenic temperature at NASMSFC. It exhibits exceptional polishability for reflective optics with high strength, stiffness, and excellent thermal conductivity. SuperSiC has excellent thermal properties and cryogenic stability.
SuperSiC, a low areal density material, developed by POCO Graphite, have been used as mirror substrate for high energy lasers, laser radar systems, surveillance, telescopes, scan mirrors and satellites. SuperSiC 0.25m Mirror Cryogenic Test ResultĮng, Ron Stahl, Phil Hogue, Bill Hadaway, James The test technique and results are discussed. The surface figure of the mirror was measured before and after cry0 cycling. It was tested for cryogenic (cryo) survivability to 20deg Kelvin in SOMTC's X-ray Calibration and Cryogenic Test Facility. The mirror is a Poco Graphite CVD Si clad SiC substrate. Recently a lightweight mirror technology was tested at Marshall Space Flight Center's Space Optic Manufacturing Technology Center (MSFC, SOMTC). Thus, it would appearmore » that the observed weight changes were dominated in most cases by the removal of volatiles rather than by the evaporation of carbon.« less The weight loss per hour, for pre-dried graphite coupons, was in most cases higher with short holding times than for prolonged exposure. Scanning electron microscopy revealed no change in the surface morphology of the samples before and after heating, indicating that the loss of material occurred in a uniform, rather than a localized, fashion.
A loss in weight was observed in all cases, but there appeared to be no simple relationship between the holding temperature and the weight loss observed. Poco AXF 5 Q graphite coupons were heated at temperatures ranging from 1900 K to 2400 K. A study of the high temperature behavior of graphite
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