Abstract: Laser-assisted machining (LAM), in which the material is locally heated by an intense laser source prior to material removal, provides an alternative machining process with the potential to yield higher material removal rates, as well as improved control of workpiece properties and geometry, for difficult-to-machine materials such as structural ceramics. To assess the feasibility of the LAM process and to obtain an improved understanding of governing physical phenomena, a laser assisted machining facility was developed and used to experimentally investigate the thermal response of a rotating silicon nitride workpiece heated by a translating CO 2 laser. Using a focused laser pyrometer, surface temperature history measurements were made to determine the effect of rotational and translational speed, as well as the laser beam diameter and power, on thermal conditions. The experimental results are in good agreement with predictions based on a transient three-dimensiona numerical simulation of the heating process. With increasing workpiece rotational speed, temperatures in proximity to the laser spot decrease, while those at circumferential locations further removed from the laser increase. Near-laser temperatures decrease with increasing beam diameter, while energy deposition by the laser and, correspondingly, workpiece surface temperatures increase with decreasing laser translational speed and increasing laser power. In a companion paper (Rozzi et al., 1998), the detailed numerical model is used to further elucidate thermal conditions associated with laser heating and to assess the merit of a simple, analytical model which is better suited for on-line process control.

Abstract: The absorptance of material at the laser wavelength and as a junction of temperature, ranging from room temperature to the removal point, significantly affects the efficiency of the laser machining process. A priori predictions of a laser machining process, using either simplistic or sophisticated models, require knowledge of the material's absorptance behavior. An experimental apparatus for such measurements is described. The device consists of a specimen mounted inside an integrating sphere, heated rapidly by a CO 2 or a Nd:YAG laser. Reflectances are measured with a small focused probe laser (Nd:YAG or CO 2 ), while specimen surface temperatures are recorded by a high-speed pyrometer. Experimental results have been obtained for wavelengths of 1.06 μm (Nd:YAG) and 10.6 μm (CO 2 ) for graphite, alumina, hot-pressed silicon nitride, sintered α-silicon carbide, as well as two continous-fiber ceramic matrix composites (SiC-based). Data are presented for temperatures between room temperature and the ablation/decomposition points.

Abstract: The present invention discloses a high temperature pyrometer 20 which is suitable, in particular, for temperature measurement in a gas turbine. The pyrometer comprises a flexible lightguiding measuring probe 21 with a microlens 22 resistant to high temperatures and with an optic fiber 24 composed of quartz or sapphire, said microlens and said fiber being provided with a gold sheathing 25, 26 and/or a protective capillary 27, 28. The heat radiation is evaluated in a remote detector 32 having measuring electronics 33 connected to it. The pyrometer 20 is distinguished by compactness, high temperature capability, flexibility, versatile installability and high measuring accuracy. The invention also relates to a development of the pyrometer 20 for gas turbines, to a gas turbine with a pyrometer 20 according to the invention, and to a method for monitoring a gas turbine with the aid of a pyrometer 20. Explanations are given of ways in which the measuring probe 21 can be fitted in guide blades 34, 48 and by means of which accurate temperature measurements are possible on moving and guide blades 34, 35, 48, 49 in low pressure and high pressure turbines. The operating safety and the efficiency of gas turbines can thereby be increased.

Abstract: Quantification of infrared (IR) radiation is a convenient, non-contact method for making the base metal temperature measurements needed for on-line feedback controls. However, the problem of interference from the arc is a complicating factor in applying IR temperature sensing to welding. The objective of this research is to implement and test a top-face, non-contact temperature measurement system based on optical pyrometry. Investigations relating to the development of an infrared temperature measurement system are described. An apparatus consisting of a fiberoptic cable, a silicon photodiode/power meter and a computer data acquisition system were configured and used for the tests. Results of the experiments showed that radiation from both the arc and the hot tungsten electrode were important sources of interference in the IR emissions from the base metal. Attenuation of the interfering radiation using a band-pass optical filter and a specially-designed gas cup was investigated. Finally, the sensing system was calibrated using thermocouple measurements of actual base metal temperature.

Abstract: The thickness and surface roughness of diamond films grown on a Ti–6Al–4V alloy in a microwave plasma reactor was measured in situ using optical pyrometry. The growing film results in oscillations of the apparent temperature with time, which can be explained by interference effects caused by reflections from the film/air and film/substrate interfaces. The equation governing the transmittance of the diamond/metal system has been derived by taking into account the complex index of refraction of an absorbing substrate. The apparent temperature was modeled using this relation for the transmittance in order to extract the time dependence of film thickness, surface roughness, and the true temperature of the substrate. The growth rate was observed to exhibit two regimes: an initial period of slowly increasing growth followed by a growth rate that was about 50% higher. The surface roughness increased at a nearly uniform rate but quickly reached a saturation roughness for long deposition times (high surface roughn...

Abstract: This document describes the realization and dissemination of the International Temperature Scale of 1990 (US-90) above 700 "C at the National Institute of Standards and Technology (NIST). By using fundamental principles of blackbody physics, the US-90 scale is first fixed at the freezing point of gold (T90 = 1064.18 "C) and is then extended to temperatures between 700 "C and 2700 "C by determining the ratio of the spectral radiance of a tungsten ribbon filament lamp to that of a gold fixed-point blackbody at a wavelength of 655.3 nm. A description of the facilities in the NIST Radiance Temperature Calibration Laboratory is given, along with a discussion of the wavelength calibration, size of source, and linearity issues. The use and calibration of radiance temperature standards are explained. Values of stability and uncertainties in the scale are reported. The expanded uncertainties (k = 2) at 800 "C and 2300 "C are 0.6 "C and 1.4 "C for ribbon filament lamps, 4 "C and 7 "C for disappearing filament optical pyrometers, and 2 "C and 3 "C for infrared radiation thermometers.

Abstract: Pure Si and Ge, and their alloys were stably levitated and melted using an electromagnetic levitator combined with a laser heating unit. A temperature measurement method using a mono- or multicolor pyrometer for the semiconductor was discussed, and a calibration method for a monocolor pyrometer was developed by deriving their spectral emissivities at each melting point. The maximum undercooling was measured as a function of composition. This result corresponded well with the calculated value using the classical theory of steady state nucleation in binary metallic melts.

Abstract: Sami D. Alaruri, MEMBER SPIE Lisa Bianchini Andrew J. Brewington Allison Engine Company Rolls Royce Aerospace Group P.O. Box 420, M/S W03A Indianapolis, Indiana 46206-0420 Abstract. A method that employs an integrating sphere and a singlewavelength (1.6-mm) pyrometer to measure the spectral effective emissivities of YSZ thermal barrier coatings in the temperature range (;650 to 1050°C) is described. The effective spectral emissivities for two YSZ samples are measured as a function of the heat cycle duration. An increase in the emissivity of the YSZ samples is observed after the first heat cycle. Such an increase is attributed to the diffusion of aluminum and aluminum oxide from the bond-coat into the YSZ layer. The average effective spectral emissivity measured for YSZ after the first heat cycle was 0.72960.013. © 1998 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(98)03002-5]

Abstract: A method and device for detecting an incorrect position of a semiconductor wafer during a high-temperature treatment of the semiconductor water in a quartz chamber which is heated by IR radiators, has the semiconductor wafer lying on a rotating support and being held at a specific temperature with the aid of a control system. Thermal radiation which is emitted by the semiconductor wafer and the IR radiators is recorded using a pyrometer. The radiation temperature of the recorded thermal radiation is determined. The semiconductor wafer is assumed to be in an incorrect position if the temperature of the recorded thermal radiation fluctuates to such an extent over the course of time that the fluctuation width lies outside a fluctuation range ΔT which is regarded as permissible.

Abstract: A radiation pyrometer in conjunction with a two-stage light gas gun has been used to measure shock temperatures of soda-lime glass in the pressure range 54–109 GPa. This pyrometer consists of two parts, i.e., an optical multichannel analyzer which measures the radiation spectrum over the visible range (∼450 nm window) and a four-channel photomultiplier tube system which records the time-varying behavior of shock temperatures. The measured radiation spectra are compared with the Planck function to estimate the shock temperatures and emissivities. Obtained spectra are well fit by the Planck function with moderate emissivities, indicating that relatively homogeneous thermal radiation is the main component of radiation. Obtained shock temperatures range from 2800 (100) to 5700 (300) K and they seem to represent shock temperatures of liquefied soda-lime glass (melt). The Hugoniot is well described by a linear relation, us=0.14(21)+1.92(5)up km/s. It is deduced that the radiation from liquids under shock compre...

Abstract: The temperature of the laser spot or at least its direct vicinity is measured with local resolution, with the temperature measurement spot (2,2') covered by at least one pyrometer being smaller than the laser spot. The temperature measurement spot synchronously follows the motion of the laser spot over the workpiece surface. Several controllers or control loops are used for sequential control of the laser output power.

Abstract: The initial growth of diamond films in a microwave plasma reactor has been studied using in situ two-color infrared pyrometry. Analysis of the observed oscillations of the apparent temperature has yielded the substrate temperature and also the instantaneous film growth rate and rms surface roughness σ. Two distinct regimes of growth have been clearly identified: an initial period of rapidly increasing σ before the diamond nuclei coalesce, followed by a slower increase of σ with thickness as the continuous film grows further. The differing initial roughnesses and emissivities of Si and Mo substrates have been shown to have important effects on the growth of diamond.

Abstract: Sb doped sol-gel SnO2 single layers (thickness ≈100 nm) were prepared from alcoholic solution and deposited via a dip coating process on fused silica substrates. The coatings have been sintered at a typical rate of 10–15 cm2/s by CO2 laser irradiation. The laser spot was scanned in one direction at a speed of 15,000 cm/s and the sample was moved in a perpendicular one at a speed up to 250 mm/s. The temperature of the topmost 10 μm layer was monitored by a fast pyrometer (μs resolution). The following properties of the coatings have been determined: the electrical resistivity ρ, the carrier density n, and mobility μ, the structure, the thickness, the mesoscopic and micromorphology and the density. The sintering by CO2 laser radiation is mainly a thermal driven process. At T ≈500°C it allows to obtain coatings with a smaller resistivity (6.8×10−3 Ωcm) than those produced by conventional furnace firing (ρel≈2.9×10−2 Ωcm). The results are discussed in terms of particle size and packing density.

Abstract: A method for calibrating an optical pyrometer to an external reference point. By changing the focus of the optical pyrometer without physically moving the pyrometer, calibration of the optical pyrometer can be accomplished without modifying the semiconductor operation. Broadly speaking, the present invention contemplates an apparatus for calibrating an optical pyrometer. The apparatus includes a first optical source in a heating chamber with an optical port, an optical pyrometer, a mirror, and a second optical source. The optical pyrometer is positioned to receive light rays from a first optical source residing inside the heating chamber. The second optical source is located external to the heating chamber. The second optical source serves as an external reference point. The external location of the second optical source allows for calibration of the optical pyrometer without modification of the heating chamber or the first optical source residing inside the heating chamber. The mirror is positioned between the heating chamber and the optical pyrometer. The mirror is situated in such a way as to permit the optical pyrometer to receive light rays from the second optical source.

Abstract: A combined pyrometer-multimeter instrument 1 comprises a multimeter with apparatus for determining the temperature of a surface by non-contact measurement of radiation received at a distance. The instrument may have an apparatus for determining temperature of that surface by direct contact eg a thermocouple 6. The non-contact apparatus may have optical viewing sighting means and projected laser beam sighting means, and means for determining emissivity of the surface. Provision may be made for recording data, eg a data logger. Audio output may be provided eg by speech synthesis in accordance with temperature determinations. Conveniently, the instrument is adapted for holding in the hand eg by a pistol-grip handle, and/or for mounting on a tripod. Temperatures derived respectively from infrared radiation and from direct contact may have separate displays. The instrument may have means for control by vocal command. Separate multimeter, pyrometer and thermocouple devices may communicate by cable, wireless or infrared.

Abstract: The pyrometer includes a light-guiding probe (21) for detecting thermal radiation and transferring it to a detector (33). The probe includes an optical fibre (24) with a micro-optical sensor head (22). The fibre and the sensor head are resistant to high temperatures. The fibre and the sensor head have a flexible covering. A gas turbine for generation of electricity is also claimed. A method for monitoring a gas turbine using the high-temperature pyrometer is also claimed.

Abstract: Emissivity is a measure of how well a real surface can radiate energy as compared with a blackbody. This characteristic radiative number is usually determined by means of optical pyrometry. By contrast an indirect measurement method has been developed which enables the determination of the normal spectral emissivity of various materials at a specific wavelength. A heat flow induced in a test body by the absorbed irradiation of a laser beam may be correlated with the spectral emissivity of its surface. The theory of the measuring principle is discussed and the feasibility of the method evaluated by means of practical experiments utilizing a thermopile built up using a thick film technique.

Abstract: A pyrometric method was developed earlier for the simultaneous in situ measurement of the temperature and the size of combusting fuel particles in entrained flow reactors The temperature measurement is based on two-color pyrometry and the particle sizing on the proportionality of the measured radiative flux and the cross-sectional area of a particle at a known temperature This particle-sizing method needs a discrimination procedure to confirm that the detected particle is valid for particle sizing We report on a novel method for particle discrimination based on coaxial reference optics The new method has several advantages compared with the method presented earlier, including the measurement in turbulent flow fields

Abstract: Experiments were performed to investigate the behavior of lead near its critical point Emission spectra of shocked lead samples during unloading into helium at different initial pressures were measured by an optical multichannel analyzer (OMA), as well as by a fast optical pyrometer To describe the obtained experimental data, a model of a thin mixture layer was suggested, in which helium emits due to the presence of external electrons from lead

Abstract: of EP0898158The pyrometer includes a light-guiding probe (21) for detecting thermal radiation and transferring it to a detector (33). The probe includes an optical fibre (24) with a micro-optical sensor head (22). The fibre and the sensor head are resistant to high temperatures. The fibre and the sensor head have a flexible covering. A gas turbine for generation of electricity is also claimed. A method for monitoring a gas turbine using the high-temperature pyrometer is also claimed.

Abstract: Thermal radiation calorimetry has been applied to measure the thermal conductivity and the specific heat capacity of an isolated solid specimen simultaneously The system, in which a disk-shaped specimen and a flat heater are mounted in a vacuum chamber with the specimen heated on one face by irradiation, is presented A theoretical formulation of the simultaneous measurement at quasi-steady state is described in detail Noncontact temperature measurement of both specimen surfaces has been performed using pyrometers and a thermocouple set in the gap between the heater and the specimen Pyroceram 9609 specimens, whose surfaces were blackened with colloidal graphite, were used in the measurement The largest error involved in the noncontact temperature measurement is ±2°C in the range from 450 to 650°C The resultant values of the specific heat capacity and the thermal conductivity deviate by about 10% from the recommended values for the Pyroceram specimen

Abstract: The present invention provides a method of forming titanium silicide by subjecting a silicon substrate having titanium formed thereon to a thermal process, such as rapid thermal process. The silicon substrate and the titanium are being heated to at least a selected annealing temperature, which is the minimum temperature on and after which the titanium silicide displays generally constant sheet resistivity and resistance non-uniformity. The selected annealing temperature is determined by heating the silicon substrate and the titanium from an initial temperature to a final temperature to create titanium silicide and measuring the sheet resistance and/or resistance non-uniformity at selected temperature intervals between the initial temperature and the final temperature. The temperature on and after which the sheet resistance and resistance non-uniformity is generally constant is the selected annealing temperature. The temperature of the silicon substrate and titanium can be measured by an optical sensor such as an optical pyrometer. The selected annealing temperature can be used to calibrate the optical sensor for more accurate measurement of the temperature during the thermal process.

Abstract: A method employing an integrating sphere and a single wavelength (1.6 μm) pyrometer for measuring the spectral effective emissivities of superalloys in the temperature range (∼650-1050°C) is described. The spectral effective emissivities for five superalloys, namely, MARM-247, MARM-509, CMSX-4, Inconel-718, N-155, and two Rene-N6 samples coated with YSZ thermal barrier coating were measured. Correcting the pyrometer measurements for the variations in the object emissivity would reduce the uncertainty in the temperature measurements to <±1%.

Abstract: It is shown that the heated body temperature can be measured from the energy distribution of photoelectrons appearing in the photoelectric device which serves simultaneously as detector and analyser of the body radiation spectrum. The effective wavelengths of this temperature measuring technique cannot be chosen arbitrarily because they are functions of the temperature and must be measured. A technique for measuring the series of values of the effective wavelengths , which is necessary for estimation of the procedural error , has been proposed. The latter depends on the type of spectral characteristic of the photodetector, the energy photoelectron dispersion D in a retarding field and the emissivity of a heated surface . The formulae for the procedural error calculation are obtained and the latter has been shown to be less than that for measuring the temperature by conventional optical pyrometry methods and almost independent of temperature; -3 K for tungsten (when T = 1200-2600 K) and -5 K for platinum (when T = 1200-1800 K). The calculated results have been proved by series of experiments. A photoemissive pyrometer based on this method can be employed for temperature measurements when the exact meaning of a changeable emissivity is unknown as it takes place, for example, at pulse heating processes.

Abstract: The true and apparent temperature of samples during the deposition of III-V layers by molecular beam epitaxy changes as a result of the variation in spectral emissivity ϵ with layer thickness. Taking into account the infrared optical properties of these materials, we modelized the variations of the true sample temperature and the apparent temperature (as determined by pyrometric measurement) during the growth. We limited our study to deposits involving at least one absorbing material (at the pyrometer wavelength), for example GaSb, InAs or InSb. We showed that our simple model can agree reasonably with experiments in the 400−500 °C temperature range.