Investigators: Ared Cezairliyan, Tsuyoshi Matsumoto, John McClure, Louis Phillips and Daniel Josell

Technical Description:

This project is involved with the development of new techniques for the accurate measurements, primarily at high temperatures, of selected thermophysical properties of materials, in both solid and liquid phases, utilizing rapid (millisecond- and microsecond- resolution) pulse-heating (volume and surface) techniques.

Technical Objectives:

• Develop new techniques for the accurate measurements of selected thermophysical properties of solid materials at high temperatures (up to their melting region) utilizing millisecond-resolution resistive self-heating techniques.

• Develop new techniques for the accurate measurements of selected thermophysical properties of liquid materials at high temperatures (several hundred degrees above their melting region) utilizing microsecond-resolution resistive self-heating techniques.

• Develop a laser pulse technique for the accurate measurement of thermal diffusivity of multilayered thin films at high temperatures.

Anticipated Outcome:

• Advancement of the state-of-the-art of thermophysical measurements at high temperatures.

• Generation of accurate bench-mark data on selected key materials.

• Development of high-temperature thermophysical standards.

Accomplishments for FY 1995:

• Completed development of a novel high-speed laser polarimetry technique for measurements of normal spectral emissivity of metals and alloys at high temperatures (up to the melting region) in millisecond-resolution pulse-heating experiments.

• Validated operation of the new technique by performing simultaneous measurements of normal spectral emissivity (at 633 nm) with the new laser polarimetry technique and a conventional method involving spectral radiometry.

• Obtained accurate data on normal spectral emissivity (at 633 nm) of molybdenum and tungsten in the temperature range 2000 K - 2800 K.

• Introduced significant improvements (automation) in the millisecond-resolution system by incorporating a new computer-controlled, fast-acting, high-current, solid-state switch.

• Modified existing laser pulse thermal diffusivity measurement system to permit delivery of very short pulses (50 ns). Conducted preliminary experiments on pure molybdenum and thin multilayered specimens composed of molybdenum and alumina in order to assess operational characteristics of the system. Prepared computer programs to process the experimental data and analyze the thermal diffusivity results.

Impacts and Technical Highlights:

• NIST developed a new technique, the first and the only one of its kind, for the measurement of normal spectral emissivity of metals and alloys at high temperatures in rapid pulse-heating experiments. This technique will enable measurement of the true temperature of a specimen where it is either very difficult or impossible to have a blackbody configuration for the specimen to permit direct radiometric measurements of its true temperature.

• An accurate knowledge of thermal diffusivity will play an important role in the selection, use, and assessment of thin films and specifically thermal barrier coatings in high temperature applications, such as in jet engine blades.

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Last modified: Mon Jan 06 09:46:15 1997 Metallurgy Webmeister