Characterization of ceramic coatings by Raman microscopy
Ingénierie et Architecture
Thermal spraying is one of the most reliable technology for adding layers, and involve the projection of small softened particles onto a prepared surface where they form a continuous coating. Combined thermal and kinetic energy cause the particles to "splat" onto the surface, and onto each other, producing a cohesive coating of successive ceramic or polymer layers onto metal, ceramic or polymer substrates.
Plasma sprayed ceramic coatings are specifically useful for their wide variety of industrial applications. During freezing, these coatings undergo quenching (shrinking). In addition, the coefficients of thermal expansion (CTE) of the coating and the substrate materials are different. These two effects subject the coating to residual stress: a stressed coating can either crack significantly or peel off completely, thus initiating coating failure. Hence, residual stress is an important factor in determining coating cohesion and adhesion.
Stress measurement in plasma sprayed coating using Raman and FTIR spectroscopy constitute a novel approach that involves deep understanding of thermal spraying Raman and FTIR spectroscopy. Dr. P.P. BANDYOPADHYAY, an expert on thermal spraying[1], was the Visiting Scientist of this SNF Scientific Exchange Project leaded by Dr. P. BRODARD, an expert in Raman & FTIR microscopy[2].
[1] Characteristics of plasma sprayed coatings produced from carbon nanotube doped ceramic powder feedstock, S. C. Jambagi, S. Kar, P. Brodard, P. P. Bandyopadhyay, Materials and Design, 112 (2016) 392.
[2] Raman spectroscopy assisted residual stress measurement of plasma sprayed and laser remelted zirconia splats and coatings, B. Das, P. Brodard, P.P. Bandyopadhyay, Surface & Coatings Technology, 378 (2019) 124920.