Facility for assessing spectral normal emittance of solid materials at high temperature.

Area of Science:

• Materials Science and Engineering
• Renewable Energy Technologies
• Optical Physics

Background:

• Spectral emittance is crucial for developing advanced materials for solar absorption and renewable energy applications.
• Accurate measurement of spectral emittance at high temperatures is essential for material characterization and performance prediction.

Purpose of the Study:

• To design, build, and validate a novel experimental facility for measuring directional spectral emittance.
• To investigate the spectral emittance of ultra-refractory ceramics (hafnium carbide and tantalum diboride) at high temperatures (up to 1200 K).
• To evaluate the accuracy of estimating high-temperature spectral emittance from room-temperature reflectance measurements.

Main Methods:

• Development of a new experimental setup for directional spectral emittance measurements in the 2.5–20 μm range.
• Testing the facility using hafnium carbide and tantalum diboride samples under controlled high-temperature conditions (up to 1200 K).
• Comparison of experimental results with quasi-monochromatic measurements from a solar furnace and with calculations based on room-temperature reflectance.

Main Results:

• The new facility successfully measured spectral emittance in a controlled environment up to 1200 K.
• Experimental data for hafnium carbide and tantalum diboride showed good agreement with previous measurements.
• Calculated spectral emittance from room-temperature reflectance showed a similar trend but underestimated the experimentally measured high-temperature emittance.

Conclusions:

• The developed experimental facility is reliable for measuring directional spectral emittance of materials at elevated temperatures.
• High-temperature spectral emittance measurements are critical and cannot be accurately predicted solely from room-temperature reflectance data.
• The findings provide valuable data for materials used in solar energy and other high-temperature applications.