DEVELOPMENT OF A BENCH TOP INSTRUMENT FOR MEASURING HIGH TEMPERATURE SURFACE EMISSIVITY

FOR SURFACES AT HIGH TEMPERATURE THE EMITTED SPECTRUM OF ELECTROMAGNETIC RADIATION IS THE MOST CONVENIENT PROBE OF TEMPERATURE, IF THE SPECTRAL EMITTANCE OF THE SAMPLE IS KNOWN. THIS PROPOSAL SUGGESTS THE APPLICATION OF FOURIER TRANSFORM (FT) SPECTROSCOPY TO THE MEASUREMENT OF SPECTRAL EMITTANCE. THE OBJECTIVE OF PHASE I IS TO DEMONSTRATE THE DETERMINATION OF SPECTRAL EMITTANCE EMPLOYING A FI-IR SPECTROMETER COUPLED TO A MODERATE TEMPERATURE FURNACE. MEASUREMENTS WOULD BE MADE OF THE RADIANCE FROM SAMPLES IN A THIN WALL FURNACE AND OF THE INTEGRATED SPECULAR AND DIFFUSE REFLECTION IN A MORE CONVENTIOAL FURNACE. THE RESULTS OF THE TWO METHODS WILL BE COMPARED AND THE ERRORS CONSIDERED. MEASUREMENTS WOULD BE MADE AT TEMPERATURES UP TO 2000 DEG R BETWEEN 1.7 AND 20 MICRONS AND NEARLY NORMAL INCIDENCE. IN PHASE II, AN INSTRUMENT WILL BE CONSTRUCTED BASED ON THE RESULTS OF THE TWO METHODS. AMONG THE CONCEPTS TO BE CONSIDERED FOR THE FINAL DESIGN ARE THE USE OF BOTH REFLECTION AND EMISSION MEASUREMENTS. THE REFLECTION METHOD WOULD DETERMINE THE SPECTRAL EMITTANCE ON A HOT SAMPLE WHOSE TEMPERATURE, AT THE MEASUREMENT POINT, MAY BE IMPRECISELY KNOWN. THE EMISSION MEASUREMENT, MADE SIMULTANEOUSLY WOULD DETERMINE THE TEMPERATURE, BASED ON THE MEASURED SPECTRAL EMITTANCE. THE PHASE II PROGRAM WOULD RESULT IN AN INTEGRATED, AUTOMATED, BENCH TOP, RESEARCH PROTOTYPE INSTRUMENT FOR EVALUATION.