Measurement of Infrared Absorption Coefficients of Molten Glasses

Abstract

In this article, a method based on the "submerged mirror" technique to measure the absorption coef cient of molten glass is presented. Infrared light, which is modulated by Michelson's interferometeric setup, passes through the molten glass and is collected by a mercury-cadmium-telluride (MCT) or a silicon detector. The signal is processed by a Fourier transform infrared (FTIR) spectrometer to yield the spectral intensity of the infrared light. The processes are repeated with different thicknesses of molten glass layer. The spectral absorption coef cient is calculated from the apparent transmittance. Tests of the apparatus have been made with distilled water, for which the results agree well with existing data. Measurements were carried out for a number of calcia-alumina-silicate glasses at temperatures ranging from 1,200 to 1,300 C.Radiative heat transfer is an important-if not the most dominant-mode of heat transfer during the drawing of E-glass through bushings. For optimal control of the ber drawing process, the radiative heat losses must be accurately determined and/or tailored, which requires detailed and accurate knowledge of the glass's absorption coef cient at high temperature.Methods to measure optical properties of liquids can be broadly classi ed into emission techniques [1, 2], acousto-optics [3], ellipsometry [4,5], Kramers-Kronig transforms [6,7], pole-t procedures [8], transmission techniques [9-13], and submerged-mirror techniques [14,15].An error analysis using representative errors in emissivity measurements shows that emission techniques are very sensitive to temperature measurement errors. The use of acousto-optics requires microphones that can withstand temperatures greater than 1,000°C, which have not been developed yet. The performance-to-cost ratio of setups in ellipsometric methods justify their use only for high-accuracy measurements of the complex index of refraction. Kramers-Kronig transforms need measurements over a wide spectral range to achieve reasonable accuracy. Mackenzie [10] and Greenberg [9] have performed transmission measurements by holding a thin lm of liquid with platinum

Optical Properties of Sodium Chloride Solution within the Spectral Range from 300 to 2500 nm at Room Temperature

“…The Kramers–Kronig transform method requires experimental measurement over a wide spectral range to ensure scientific accuracy. 16,–18 Although the ellipsometry method is very convenient to obtain the refractive index n, some limitations will be introduced into acquiring the absorption index k of transparent materials that absorb less of the incident light. For example, there is considerable difficulty in the characterization of low absorption coefficients (α < 100 cm −1 ) using the ellipsometry method.…”

Radiative thermal conduction of molten tin sulfide estimated from its optical emission spectrum

“…Not all materials are equally affected when interacting with such thermal radiation from the waste-heat source. 22,23,[32][33][34][35][24][25][26][27][28][29][30][31] While conservation of energy requires that the sum of absorptivity, transmissivity, and reflectivity is equal to 1 for matter, each material has a different share of each mode of interaction with radiation. A bulk material qualified as opaque, such as a metal, exhibits high absorptivity but lacks transmissivity, preventing penetration of radiation into it.…”

“…The techniques used for measuring optical properties 22,23,[32][33][34][35][24][25][26][27][28][29][30][31] of Equation 3 can be broadly categorized into 1) emission, 2) transmission, 3) reflection, 4) submerged-mirror, and 5) ellipsometry. Such variety of techniques that are already verified by different materials suggests an easy access to optical properties of molten semi-conductors.…”

Measurement method for high-temperature infrared optical constants of ZnS crystal materials in a multi-layer structure

“…Such materials include semi-transparent solids (for example, quartz glass, zinc sulfide, Ge, CaF 2 , ceramics, aerogel and coatings), hydrocarbon liquid fuels, and combustion gases. The radiation properties or optical constants of semi-transparent materials are important physical parameters in scientific research and engineering applications [1][2][3][4][5][6][7][8]. For example, the radiation properties of quartz glass are needed for optical performance evaluations and for designs of optical windows in applications especially for harsh thermal environments.…”

“…Although some research works in the subject of optical constants were engaged on many kinds of semi-transparent thin films, there are few studies reported on the measurements of high-temperature optical constants for ZnS crystal materials. It's well known that the submerged-mirror technique [1] to measure optical properties of liquids can just provide a meaningful reference for high-temperature radiation property measurements for ZnS materials. The ZnS plate may be put in an optical heating cavity equipped with the optical windows and was heated to the desired temperature using the conduction or convection heating modes.…”