IR Pyrometry Research Articles

Effect of oxygen concentration on combustion behavior of single coal pellets from three different ranks in a concentrating photothermal reactor

Comparative combustion studies were performed in a concentrating photothermal platform (room temperature chamber type experimental bench with less volumetric reactions) on coal pellets (>6mm) from three different ranks: bituminous coal, sub-bituminous coal, and lignite. The combustion of single coal pellet in 21 ~ 50% oxygen concentration was observed with IR pyrometry and high-speed cinematography to obtain temperature–time–size histories. Based on the combined mass measurement and gaseous product analysis, a comprehensive understanding of the effects of oxygen concentration on single coal pellet combustion behaviours was developed. Distinctive three-stage processes were proposed with characteristical temperature and cinematography variations. No obvious flame duration was detected in 21% or 30% O2 while transient but luminous flames were clearly observed in 40% and 50% O2 and formed notable temperature peaks in the second stage during combustion of all the three ranks coal pellets. Volume and density both changed non-linearly during combustion and such processes were accelerated with the increase of oxygen concentration. High concentrations of CO and CH4 were detected due to the suppression of volumetric reactions. CO accounted for about 9.3% of the gaseous products and consistently exhibited two peaks with the first peak independent from oxygen concentration. Three-stage combustion process was further validated by CO2/CO ratio and the effective reaction orders of oxygen concentration were 1.91 (bituminous coal), 1.81 (sub-bituminous coal) and 1.26 (lignite).

The Potential of IR Pyrometry for Monitoring Interpass Temperature in Wire + Arc Additive Manufacturing

The Potential of IR Pyrometry for Monitoring Interpass Temperature in Wire + Arc Additive Manufacturing

Investigations Regarding the Influence of Surface Topography on Emissive Properties of Material

In the paper analysis of surface topography influence on emissivity of metals was shown. This was performed for infrared band comprising wavelength region of 7.5 13 micrometers. Appropriate characterization and description of object emissivity has a crucial influence on accuracy of IR system for remote temperature measurement, e.g. IR thermography or pyrometry. These properties depend on many factors, including surface topography of material, where especially cavities play a very important role. In references so far emissivity are discussed mainly as influence of type of material (metal, dielectric), its temperature, wavelength or direction of emission. In the paper characterizing emissivity of construction materials in connection with 3D surface topography.

Thermal conductivity measurement of AlN films by fast photothermal method

Aluminum nitride (AlN) films were deposited by reactive direct current Magnetron Sputtering (dcMS) on Si (100) substrates, with different thicknesses, in Ar-N2 gas mixture. The films were characterized by X-ray diffraction (XRD), profilometry, scanning electron microscopy and UV-Visible Ellipsometry. The effect of the thickness on the thermal conductivity of AlN films was investigated using a fast IR pyrometry device. The XRD measurements show that AlN films are texturated along (002) direction. Moreover, X-ray rocking curve measurements indicate that the crystalline quality of the AlN is improved with the increase of film thickness. Optical analyses by IR spectroscopy and UV-Visible Ellipsometry demonstrate a high optical band gap of pure AlN films with semi-transparent behaviour in the IR range (1 to 7 μm). The effective thermal conductivity of the AlN films is strongly dependent on the film thickness. An effective thermal conductivities between (80 ± 05) and (175 ± 15) W.m−1.K−1 were measured for 260 and 8000 nm thick AlN film.

Online Control by IR Pyrometry of Nanostructured Multilayer CrCx/CrN Coatings Grown by MOCVD

Online control of a deposition process is an important issue since it permits to check that everything is going well and it can contribute to elucidate the growth mechanism of the film. Results concerning real time analysis by IR pyrometry during CVD of nanostructured multilayer CrCx/CrN coatings are presented. The temporal variation of the emitted signal depends on the optical properties of the deposited material. In the case of CrCx coating, the emissivity behaves as for metal-like material: the resulting pyrometric signal changes sharply before stabilizing. With CrN, damped oscillations due to interferences resulting from multi reflection at interfaces are observed in the early stages. The signal recorded during deposition of CrCx/CrN multilayer coating is the combination between the two precedent phenomena: it perfectly follows the multilayer stacking as shown by comparison with TEM and SIMS profile analyses.

Online Control by IR Pyrometry of Nanostructured Multilayer CrCx/CrN Coatings Grown by MOCVD

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Use of IR pyrometry to measure free-surface temperatures of partially melted tin as a function of shock pressure

Equilibrium equation of state theory predicts that the free-surface release temperature of shock-loaded tin will show a plateau at 505 K in the stress range from 19.5 to 33.0 GPa, corresponding to the solid-liquid, mixed-phase region of tin. In this paper we report free-surface temperature measurements on shock-loaded tin from 15 to 31 GPa using multiwavelength optical pyrometry. The shock waves were generated by direct contact of detonating high explosive with a tin sample, and the stress in the sample was determined by free-surface velocity measurements using photon Doppler velocimetry. We measured the emitted thermal radiance in the near IR region at four wavelengths from 1.5 to 5.0 μm. Above 25 GPa the measured free-surface temperatures were higher than the predicted 505 K, and they increased with increasing stress. This deviation may be explained by hot spots and/or variations in surface emissivity, and it may indicate a weakness in the use of a simple analysis of multiwavelength pyrometry data for conditions, such as above the melt threshold, where hot spots or emissivity variations may be significant. We are continuing to study the discrepancy to determine its cause.

Metrological questions of the measurement of surface temperature by a noncontact IR-pyrometry method

This paper discusses how the accuracy with which the surface temperature is measured by IR pyrometry is affected by a number of methodological and metrological factors. It is shown that, when the temperature of rough metallic surfaces is being measured, the emissivity of the samples should be considered effective, since it depends on the ambient temperature and the aperture of the pyrometer. A discussion is given of how the absorption of IR radiation by the atmosphere affects the accuracy of the measurements.

In situ IR pyrometric analysis during thermal treatment in air of TiO xN y coatings

IR pyrometry is an original diagnostic tool for in situ analysis of surface transformations of coatings or bulk materials during the thermal treatment under reactive atmosphere such as high temperature oxidation. Significant oscillations of the pyrometric signal were observed during annealing in air of TiO 1.5N 0.5 coatings in the temperature range 673–823 K. This is due to interferences resulting from multi-reflections at the interfaces of a transparent growing film. This reveals the formation of a TiO 2 thin film on the top of the TiO 1.5N 0.5 coating. Modeling of the time dependence of the IR pyrometric signal allows the determination of the oxide layer thickness, transformation rate and optical properties of the films under the growth conditions. The progressive oxidation of a compact amorphous TiO 1.5N 0.5 coating from the external surface to the substrate interface was supported by SIMS, XRD and reflectance analyses.

Diagnostic in TCOs CVD processes by IR pyrometry

Infra red pyrometry is a sensitive, simple and low-cost technique commonly used for the measurement of the deposition temperature in CVD processes. We demonstrate in this work that this optical technique can be used as diagnostic tool to provide fruitful informations during the growth under atmospheric pressure of TiO 2 films on various substrates chosen as an example of transparent oxide. Significant variations of the pyrometric signal were observed during the deposition of TiO 2 thin films due to interferences in the growing film resulting from multi-reflections at the interfaces and scattering induced by the surface roughness. Modeling of the time dependence of the IR pyrometric signal allows simultaneously the determination of the layer thickness, the growth rate, surface roughness and refractive index of the thin films under the growth conditions. This diagnostic technique can be used for various transparent thin films grown on opaque substrates and is well adapted to control CVD processes operating either under atmospheric or low pressure and more generally any thermal treatment processes.

Diagnostic in CVD processes by IR pyrometry

The control of CVD processes requires in situ analysis techniques and real time monitoring to identify the chemical species involved in the mechanism, to determine the growth kinetics and more generally to detect and analyze the dynamics of any event occurring during the growth of the film. We demonstrate through four representative examples that IR pyrometry allows to answer to the last two items, which make it an attractive diagnostic tool for CVD processes, simple to use, sensitive at nanometric scale, economic and being able to operate either under atmospheric or low pressure. Thus, we monitored the initial stages of the growth of conducting diffusion barriers CrC x N y on Si and as a second example, we have followed their heat treatment to detect possible phase transformations. The case of MOCVD of Fe reveals the high sensitivity of this diagnostic technique. Indeed, the abrupt changes of the pyrometric signal correlate remarkably to changes in the growth mode. Lastly, the characteristic oscillations due to multireflexions at the interfaces observed in the first stages of the growth of transparent TiO 2 film allow the real time determination of the growth rate. These examples show the great diagnostic potentialities of IR pyrometry for the optimization and the control of CVD processes.

Influence of reflected radiation of high velocity oxy-fuel spraying torch on long wavelength IR pyrometry temperature measurement

High velocity oxy-fuel (HVOF) torch radiations were measured in the 8–14 μm spectral band as a function of successively oxygen and methane (CH 4) flow rates. Experienced flow rates were varied respectively from 250 to 450 Nl/min for oxygen and from 100 to 150 Nl/min for methane. Prediction about the effects of the reflected HVOF torch radiation on the measured temperature was detailed. Extraneous radiant energy coming from the HVOF torch was found to have drastic effects on temperature measurement under some special input conditions. In such a case, a correction of the measured temperature for reflected HVOF radiant energy has to be performed for low target temperature or low target emissivity.

In‐Situ Optical Pyrometry in the CVD of Metallic Thin Films for Real Time Control of the Growth

AbstractIn‐situ temperature measurement is essential in CVD in order to control the temperature of the growing films. This is frequently achieved by optical pyrometry because it is a sensitive, convenient, and inexpensive technique that can be used in corrosive atmospheres. In this work, in‐situ IR pyrometry has been used, not for direct measurement of the temperature, but for real time monitoring of the early stages of the growth of metallic‐type thin films, selected as a model system. Significant variations in the pyrometric signal were observed during the metal–organic (MO) CVD of CrCxNy thin films due to changes of emissivity of the film/substrate system. The pyrometric signal (or emissivity) depends predominantly on the nature, thickness, and surface roughness of the growing film. As a result, fruitful information as to the formation of an interphase, or the existence of an induction period, can be obtained in real time by this detection technique. Radiation pyrometry can be used as a surface diagnostic tool for the growth of a large variety of thin film materials that exhibit an emissivity sufficiently different from that of the substrate.

Real time monitoring of the growth of metallic thin films by in situ pyrometry

In situ temperature measurement is an integral part of dwosition processes and optical pyrometry is a useful technique to control the temperature of the growing film. In this work, in situ IR pyrometry has been used for real time monitoring of the early stages of the growth of metallic-type thin films selected as model system. Significant variations of the pyrometric signal were observed during MOCVD of CrC x N y films due to changes of emissivity of the film/substrate system. The pyrometric signal (or emissivity) depends predominantly on the nature, the thickness and the surface roughness of the growing film. As a result, fruitful informations as the formation of an interphase or the existence of an induction period can be obtained in real time by this technique. IR pyrometry can be used as surface diagnostic tool for a large variety of thin film materials that exhibits an emissivity sufficiently different from the substrate.

High heat flux simulation experiments with improved electron beam diagnostics

Plasma facing materials such as beryllium, carbon or tungsten are subjected to intense heat loads during off-normal plasma operation. To simulate these events, electron beam experiments are performed routinely to investigate the thermomechanical performance of the materials. In these tests, main emphasis has been laid on the material damage such as melting, cracking, and degradation of the materials' properties. On the other hand, severe thermal loads are also associated with the release of particles from the loaded surface (metallic droplets or carbon dust) which might contaminate the plasma in future fusion devices. To investigate these phenomena in high heat flux simulation tests, extensive diagnostics are required to evaluate the actual material loading and to characterize the resulting material damage. Among these are measurements of the electrical current through the test coupons and high-speed IR pyrometry.

Fast Thermography for HT-7U Superconducting Tokamak

A 30 channel fast IR pyrometry array has been proposed for HT-7U superconducting tokamak, which has a 0.5 μs time response, a 10 mm diameter spatial resolution and a 5°C temperature resolution. The temperature range is from 250°C to 1200°C. The two dimensional temperature profiles of the first wall during both major and minor disruptions could be measured with an accuracy of about 1% of measuring temperature, which is adequate for tokamak experiments. This offers a very useful tool for disruption study, especially for the research of divertor physics and edge heat flux on HT-7U superconducting tokamak.

Differential IR pyrometry of surface-heating nonuniformity

Differential IR pyrometry of surface-heating nonuniformity