FT-IR spectrometry in materialography

Fourier transform infrared (FT-IR) spectroscopy was utilized in the analysis of various materials as a complementary technique to scanning electron microscopy during microstructural characterization. Applications included: (1) the identification of resin and filler additives in organometallic cements; (2) differentiation between resin type, and quantification of their degree of conversion; (3) identification of the fracture pathway in resin-bonded glass-filled resin composites; (4) characterization of resin degradation due to air and ethanol exposure; (5) detection of thin lubricating oil films on stainless steel; (6) characterization of the oxidation of stainless steel as a function of temperature and exposure time at room temperature; and (7) characterization of the aqueous corrosion of stainless steel during exposure in 0.1M sodium chloride. The results presented include scanning electron micrographs for the relevant structural details together with the FT-IR absorbance versus wavenumber spectra for the phase or component of interest. FT-IR techniques included diffuse reflectance, microtransmission with the FT-IR microscope, and polarization-modulated external reflection-absorption techniques. The results showed (1) that polymethyl methacrylate and alumina are additives in some dental cements; (2) that one type of bonded composite fractures entirely through the adhesive bonding resin; and (3) that ethanol degradation of resin occurs via an increase in the concentration of carbonyl C  O bonds. The extreme sensitivity with the external reflection technique was demonstrated by (1) the continued detection of thin oil films on polished stainless steel after numerous attempts to wipe the oil from surface; (2) the ability to differentiate the surface of stainless steel due to different exposure times to room temperature air; and (3) the ability to distinguish corroded surfaces after immersion for varying times in a chloride solution.