Luminescence of polymorph crystalline and glassy SiO2, GeO2: A short review

Trukhin, A.N.

doi:10.1016/j.jnoncrysol.2009.01.040

Cited by 9 publications

(8 citation statements)

References 26 publications

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“…It can be concluded that the efficiency of heat transfer was improved by between 5 and 7% by using quartz as compared to glass. This enhancement of the heat transfer was caused by the radiative properties of quartz glass during the absorption and transmission process, as analyzed by Trukhin (2009). Moreover, it is seen that the heat transfer is increased with the increase of the Reynolds number.…”

Section: Resultsmentioning

confidence: 85%

Thermal Performance of Carbon Nanotube Nanofluids in Solar Microchannel Collectors: an Experimental Study

Ahlatli¹,

Maré²,

Estellé³

et al. 2016

IJTech

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Many studies show that nanofluids, especially with carbon nanotubes, improve heat transfer. Other studies show that a nanofluid is a good candidate for solar systems because of its good absorptivity. We are facing an increasing number of miniaturized and more powerful systems. Especially in microelectronics, small heat sinks with high heat transfer are being developed, called micro-channel heat sinks (MCHS). In this paper, the heat transfer behavior of carbon nanotube-water nanofluid in a microchannel solar collector is studied experimentally. The exchanger is composed of 16 micro-channel hydraulic diameters of 1 mm and a glass or quartz cover with a surface area of 25 cm 2 . Solar radiation is simulated by a halogen lamp. The experimental set-up includes a solar meter, pressure, and temperature sensors, and it is allowed to control the flow. The nanofluid is a solution of water containing a 0.01%, 0.05%, 0.1%, and 0.5% weight fraction, respectively, of the carbon nanotubes, which are 9.2 nm in diameter and 1.5 µm in length. Viscosity and density are measured experimentally. The evolution of efficiency and the pressure drop are presented according to the Reynolds number and are compared with the results obtained with distilled water.

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Section: Resultsmentioning

confidence: 85%

Thermal Performance of Carbon Nanotube Nanofluids in Solar Microchannel Collectors: an Experimental Study

Ahlatli¹,

Maré²,

Estellé³

et al. 2016

IJTech

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“…As previously stated [1,[3][4][5]7], we connect the luminescence of a single crystal of stishovite with similar luminescence (also two bands, blue and UV) in as-received oxygen deficient silica glass [13][14][15][16][17] and an analogous luminescence center in α-quartz crystal induced [9][10][11][12] with damaging radiation (γ, neutron and dense electron beam). That means similar defects are observed in these materials.…”

Section: Discussionmentioning

confidence: 82%

“…Previous research [7] of stishovite luminescence was not able to definitively answer the question of whether the luminescence center exists in the form of one of the three materials considered in this research, or if it was created with ionizing irradiation. To resolve this we investigated some virgin single crystals.…”

Section: Introductionmentioning

confidence: 83%

“…The excitation was made from one side of the holder and detection from the other, so that the possible luminescence of contamination on the surface of the holder was excluded. Pure silica glass samples of different manufactures as well as pure γ-irradiated and non-irradiated α-quartz crystals, studied in detail previously [7,[9][10][11][12], were used for comparison.…”

Section: Methodsmentioning

confidence: 99%

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Luminescence of silicon Dioxide — silica glass, α-quartz and stishovite

Trukhin¹,

Šmits

Chikvaidze

et al. 2011

Open Physics

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Abstract:This paper compares the luminescence of different modifications of silicon dioxide -silica glass, α-quartz crystal and dense octahedron structured stishovite crystal. Under x-ray irradiation of pure silica glass and pure α-quartz crystal, only the luminescence of self-trapped exciton (STE) is detected, excitable only in the range of intrinsic absorption. No STE luminescence was detected in stishovite since, even though its luminescence is excitable below the optical gap, it could not be ascribed to a self-trapped exciton. Under ArF laser excitation of pure α-quartz crystal, luminescence of a self-trapped exciton was detected under two-photon excitation. In silica glass and stishovite mono crystal, we spectrally detected mutually similar luminescences under single-photon excitation of ArF laser. In silica glass, the luminescence of an oxygen deficient center is presented by the so-called twofold coordinated silicon center (L.N. Skuja et al., Solid State Commun. 50, 1069(1984). This center is modified with an unknown surrounding or localized states of silica glass (A.N. Trukhin et al., J. Non-Cryst. Solids 248, 40 (1999)). In stishovite, that same luminescence was ascribed to some defect existing after crystal growth. For α-quartz crystal, similar to silica and stishovite, luminescence could be obtained only by irradiation with a lattice damaging source such as a dense electron beam at a temperature below 80 K, as well as by neutron or γ-irradiation at 290 K. In spite of a similarity in the luminescence of these three materials (silica glass, stishovite mono crystal and irradiated α-quartz crystal), there are differences that can be explained by the specific characteristics of these materials. In particular, the nature of luminescence excited in the transparency range of stishovite is ascribed to a defect existing in the crystal after-growth. A similarity between stishovite luminescence and that of oxygen-deficient silica glass and radiation induced luminescence of α-quartz crystal presumes a similar nature of the centers in those materials.

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“…8 the x-ray excited emission spectrum of stishovite is compared with the cathodoluminescence spectrum of pure α-quartz [14]. …”

Section: Comparison Of Stishovite Luminescence With That Of Irradiatementioning

confidence: 99%

Luminescence of SiO2 and GeO2 crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article)

Trukhin¹

2016

Low Temperature Physics

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Luminescence properties of SiO 2 in different structural states are compared. Similar comparison is made for GeO 2 . Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are that for α-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in the crystal with rutile structure. In rutile structured SiO 2 (stishovite) and GeO 2 (argutite) the main luminescence is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses specific two bands, one of which has a slow decay (for SiO 2 in the blue and for GeO 2 , in green range) and another, a fast ultraviolet (UV) band (4.75 eV in SiO 2 and at 3 eV in GeO 2 ). In silica and germania glasses, the luminescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in the visible range and another in the UV range. The defect luminescence of glasses was studied in details during last 60-70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the corresponding pure nonirradiated crystals with α-quartz structure is absent. Only irradiation of a α-quartz crystal by energetic electron beam, γ-rays and neutrons provides defect luminescence analogous to glasses and crystals with rutile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects. PACS

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Luminescence of polymorph crystalline and glassy SiO2, GeO2: A short review

Cited by 9 publications

References 26 publications

Thermal Performance of Carbon Nanotube Nanofluids in Solar Microchannel Collectors: an Experimental Study

Thermal Performance of Carbon Nanotube Nanofluids in Solar Microchannel Collectors: an Experimental Study

Luminescence of silicon Dioxide — silica glass, α-quartz and stishovite

Luminescence of SiO2 and GeO2 crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article)

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