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Title: Temperature-dependent diffuse reflectance spectroscopy of plasma-sprayed Cr-doped α-alumina using supercontinuum laser illumination and CO_2 laser heating

Authors:
ORCiD logo; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1389902
Grant/Contract Number:
NE0008189
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Applied Optics
Additional Journal Information:
Journal Volume: 56; Journal Issue: 27; Related Information: CHORUS Timestamp: 2017-09-13 12:05:20; Journal ID: ISSN 1559-128X
Publisher:
Optical Society of America
Country of Publication:
United States
Language:
English

Citation Formats

Brupbacher, Michael C., Zhang, Dajie, Buchta, William M., Airola, Marc B., Brown, David M., Thomas, Michael E., and Spicer, James B.. Temperature-dependent diffuse reflectance spectroscopy of plasma-sprayed Cr-doped α-alumina using supercontinuum laser illumination and CO_2 laser heating. United States: N. p., 2017. Web. doi:10.1364/AO.56.007618.
Brupbacher, Michael C., Zhang, Dajie, Buchta, William M., Airola, Marc B., Brown, David M., Thomas, Michael E., & Spicer, James B.. Temperature-dependent diffuse reflectance spectroscopy of plasma-sprayed Cr-doped α-alumina using supercontinuum laser illumination and CO_2 laser heating. United States. doi:10.1364/AO.56.007618.
Brupbacher, Michael C., Zhang, Dajie, Buchta, William M., Airola, Marc B., Brown, David M., Thomas, Michael E., and Spicer, James B.. 2017. "Temperature-dependent diffuse reflectance spectroscopy of plasma-sprayed Cr-doped α-alumina using supercontinuum laser illumination and CO_2 laser heating". United States. doi:10.1364/AO.56.007618.
@article{osti_1389902,
title = {Temperature-dependent diffuse reflectance spectroscopy of plasma-sprayed Cr-doped α-alumina using supercontinuum laser illumination and CO_2 laser heating},
author = {Brupbacher, Michael C. and Zhang, Dajie and Buchta, William M. and Airola, Marc B. and Brown, David M. and Thomas, Michael E. and Spicer, James B.},
abstractNote = {},
doi = {10.1364/AO.56.007618},
journal = {Applied Optics},
number = 27,
volume = 56,
place = {United States},
year = 2017,
month = 9
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on September 15, 2018
Publisher's Accepted Manuscript

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  • Real time, {ital in} {ital situ} temperature measurements during chemical downstream etching of silicon wafers have been performed using a diffuse reflectance spectroscopy based sensor [Weilmeier {ital et} {ital al}., Can. J. Phys. {bold 69}, 422 (1991)]. The spectrometer has a spatial resolution of 1 cm{sup 2}, updates the temperature every 2 s, and has a temperature resolution of better than 1{degree}C. The thermal time constant the wafers and the thermally regulated electrostatic chuck (10{degree}C{lt}{ital T}{lt}90{degree}C) varied between 7 and 30 s depending on clamping and backside gas pressure. The exothermic etch process is accompanied by increases in the siliconmore » wafer temperature consistent with the thermal conductivity conditions and with the etch chemistry. The temperature uniformity across the wafers was better than 2{degree}C during the entire etch process. {copyright} {ital 1996 American Vacuum Society}« less
  • In situ {sup 13}C NMR spectroscopy and diffuse reflectance infrared spectroscopy (DRIFTS) have been used to characterize the adsorbed states of isoprene on both {gamma}-Al{sub 2}O{sub 3} and Cu/{gamma}-Al{sub 2}O{sub 3} catalysts. Both techniques have been shown to be quite complementary and provide very fine information. Isoprene molecules are physisorbed only at room temperature on alumina. On reduced copper-alumina, isoprene is mainly physisorbed, but a few chemisorbed species are evidenced. Taking into account the {sup 13}C NMR line-width variations and the IR results, an adsorption model is proposed for Cu/{gamma}-Al{sub 2}O{sub 3}: reduced copper induces a selective orientation for themore » physisorbed isoprene molecules. The chemisorbed species detected by DRIFTS is attributed to a {pi}-complex of isoprene with Cu{sup +} sites on the reduced copper-alumina spinel surface. The physisorbed species is the precursor of this {pi}-complex, and this view agrees with the selectivity of isoprene hydrogenation on copper catalysts.« less
  • Surface species formed by the deposition of Co{sub 2}(CO){sub 8} on partially dehydroxylated aluminas were identified by diffuse reflectance IR spectroscopy (DRIFT). CO{sub 2}(CO){sub 8} decomposes when it interacts with the surface of alumina, giving rise to smaller surface species, such as Co(CO){sub 4}{sup {minus}} and Co{sup 2+}(CO){sub x} in which cobalt is supposed to be in octahedral coordination, as well as to larger Co{sub 6} species. The behavior of these species and the formation of new ones, a divalent cobalt carbonyl, in which cobalt is in tetrahedral coordination, and one unidentified, were studied by heating the sample gradually untilmore » {nu}(CO) due to carbonyl species had disappeared. CO{sup 2+}(CO){sub x} with cobalt in octahedral coordination is the first surface species to disappear. Tetrahedrally coordinated divalent cobalt carbonyl, in turn, was found to be the most stable of the cobalt carbonyl surface species. As side reactions, bicarbonates, carbonates, and formates have been formed. A bicarbonate species has been proposed to be formed simultaneously with the disproportionation of CO{sub 2}(CO){sub 8}. Liberating CO reacts with O{sup {minus}} sites, forming monodentate carbonate, which turns to bidentate carbonate species during heating. At higher temperatures, hydrogen releases and reacts with CO forming formate species. The authors proposed the disproportionation of Co{sub 2}/(CO){sub 8} for the main initial surface reaction on alumina 200. Besides the disproportionation, other initial reactions, such as a formation of Co{sub 6} species, exist on aluminas with more Lewis acid/basic sites. Formation of co{sub 6} species and bicarbonates was found to be competitive reactions, most probably they adsorb at similar sites.« less
  • The absorption and fluorescence of o-, m-, and p-distyrylbenzenes on surfaces of polycrystalline silica and alumina were investigated in the adsorbed state. Time-resolved diffuse reflectance transient absorption spectra were recorded following pulsed nanosecond laser excitation at 354 nm. In each case, a long-lived transient was detected and assigned to radical-cation absorption, and in two cases a short-lived transient was observed and assigned to triplet-triplet absorption. The radicals were also detected by ESR spectroscopy after laser excitation. Experimental observations of the laser fluence dependence of the radical-ion formation efficiency are consistent with a mechanism involving the sequential absorption of two photonsmore » during the same laser pulse. It is shown that model calculations for one- and two-photon excitation processes give predictions that are in good agreement with the measurements of the triplet-state and radical-ion production, respectively.« less