A new experimental device for infrared spectral directional emissivity measurements in a controlled atmosphere is presented. The sample holder, which permits to measure spectral directional emissivity up to 1050K, is placed inside a stainless steel sample chamber that can be evacuated or filled with different gases. The signal detection is carried out by means of a Fourier transform infrared spectrometer. The experimental results focus on the capability of the device to perform emissivity measurements as a function of temperature, emission angle, and in situ surface state evolution. A careful study of the sample temperature homogeneity and the measurement method has been done, including the background radiation, the apparatus response function, and temperature differences between the sample and the blackbody radiator. As a consequence, a compact expression for the sample emissivity that generalizes those previously obtained for the direct radiometric measurement method is found. The error assessment shows that the main contribution to the emissivity uncertainty is related to the sample temperature. The overall uncertainty at intermediate temperature is estimated to be around 3% at short wavelengths. Emissivity measurements of Armco iron were used in order to check the accuracy of the experimental device. The experimental results show an excellent fit with direct emissivity data accessible in the literature, as well as with the theoretical emissivity obtained from the Hagen-Rubens relation.

The martensitic transformation temperatures and the types of martensitic phases have been determined in a wide concentration range of technological interest for Cu-Al-Ni shape-memory alloys (SMAs) A stability diagram of martensitic phases as a function of alloy concentration has been determined. It is found that when the aluminum content increases, the transformation changes from ␤ 3 ⇒ ␤ Ј 3 to ␤ 3 ⇒ ␥ Ј 3 , with an intermediate concentration range where both martensites coexist due to a ␤ 3 ⇒ ␥ Ј 3 ϩ ␤ Ј 3 transformation. On the other hand, an increase of nickel content stabilizes the martensite ␤ Ј 3 , changing from a mixed ␤ 3 ⇒ ␥ Ј 3 ϩ ␤ Ј 3 to a single ␤ 3 ⇒ ␤ Ј 3 transformation. Furthermore, linear relationships between M s and Al and Ni concentrations have been obtained for all types of martensitic phases.

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Emissivity measurements are of great interest for both theoretical studies and technological applications. Emissivity is a property that specifies how much radiation a real body emits as compared to a blackbody. The emissivity determination of a sample should be an easy task: a simple comparison between the sample and blackbody radiation at the same temperature. Unfortunately, when measuring the emissivity, some practical problems arise due to the differences between the true emitted radiation and the detected quantity. To clarify this point, an analysis of different direct methods for emissivity measurement is presented. Furthermore, a method that includes multiple reflections is developed. The systematic errors associated with each method are computed theoretically as a function of wavelength, sample temperature, and emissivity, and the surrounding enclosure temperature and emissivity. In general, the error is very high for small sample enclosures, but it strongly decreases when the enclosure area increases. Although at short wavelengths all the analyzed methods produce similar errors, noticeable differences appear under other conditions, and methods considering more radiation terms do not always produce lower errors.

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Temperature measurement of cutting tools used in machining processes has great technological importance, and it is interesting in a large number of industrial applications because wear is directly related to this variable. The influence of emissivity on the temperature measurement using radiation thermometers and the dependence of the measured temperature on the emissivity as a function of the surface roughness and the oxidation state is studied in this paper. Emissivity is measured using the direct radiometric method for uncoated P10 tungsten carbide inserts. Theoretical temperature shifts produced by changes in emissivity are estimated for several types of radiation thermometers, and these shifts are compared to the experimental temperature measurements carried out in the orthogonal turning process of cylindrical samples of 42CrMo4 steel with different machinability grades.

In order to design a device to carry out direct emissivity measurements, a key point is the analysis of all the uncertainty components that give rise to the combined standard uncertainty. This will permit to choose the most appropriate measurement method to minimize the uncertainty, and also to identify the sources of the largest errors. If the experimental device is already in use, the complete uncertainty characterization, in addition to the emissivity uncertainty calculation, will permit the improvement of the device capabilities. Thus, a guideline to the experimentalists working in this subject is provided. In this work, a complete study of the uncertainty components in direct emissivity determination is carried out. First of all, the emissivity measurement method and the uncertainty estimation methodology are introduced. After that, the influence of the uncertainties of each of the magnitudes used to obtain the emissivity is analyzed theoretically. The most important error sources depending on the measuring parameters have been identified. Finally, as a practical example, the error sources on a low emissivity sample are experimentally studied. In this case, it has been found that, at intermediate temperatures and short wavelength, the emissivity uncertainty is determined by the uncertainty in the sample temperature, whereas at long wavelength, the factor determining the emissivity uncertainty is the temperature uncertainty of the surroundings.