Microscopic two-color infrared imaging of Ni Al reactive particles and pellets

Abstract

Non-contact temperature measurements using infrared detection are widely used for observing combustion in reactive materials. The most common method used is multicolor ratio pyrometry, where point measurements are taken at different wavelengths and the ratios are used to estimate temperatures. It is desirable to perform spatially and temporally resolved measurements at high speeds. We report a new design that employs optical elements coupled with a high-speed infrared camera. The system has a spatial resolution of 14 micrometers/pixel and can go as high as 3900 frames per second, while simultaneously obtaining images at two different wavelengths. The system was calibrated with a black body source to permit calculation of emissivities in addition to temperatures. Reactions were observed in single particles of mechanically activated nickel-aluminum and their pellets fabricated by cold pressing. The particles were ignited using a CO 2 laser heated hot plate at 670 K, whereas the pellets were ignited using an electrical spark. The particles show multiple reaction stages corresponding to melting of aluminum and peritectic decomposition of NiAl 3 and Ni 2 Al 3 , with maximum temperatures reaching 1450 K, before thermal losses quench further reactions. Particles within a reacting pellet go through the same stages, but continue reacting due to the additional heating from the neighboring particles and reach

A coupled in-situ measurement of temperature and kinematic fields in Ti-6Al-4V serrated chip formation at micro-scale

“…Small scale calibration of IR cameras remains a challenging task for the thermography community. Either a specific lens is designed for microscopic observation, and calibration is then classical [49], or the camera is used without lens and the incoming radiation is focused on the detector array [31]. However, the approach presented in this latter work performs the calibration of the thermal flux ratio at two different wavelengths (bichromatic thermography), not an absolute one.…”

“…and its two subsequent relations dΨ dt = k dθ dt and ∇Ψ = k ∇θ (30) the heat diffusion equation Eq. 28 = w ch (31) where the left hand side term I(Ψ) is called the inertial term and the right one D(Ψ) is called diffusive term. Imaged zone The key point here is that the available experimental data do not read the third dimension of the temperature fileds (along z).…”