Radiation-assisted phosphorous diffused polyimide as low thermal emissivity material

Radiation enhanced diffusion of phosphorous into the surface layer of polyimide is shown to be effective in lowering its thermal emissivity in the range of wavelengths between 8 and 14 μm. The effect of the fluence of irradiation on the value of emittance has been studied and lowest emissivity was associated with the formation of nanoclusters on the surface. The variation in the dielectric constant of the irradiated polyimide has been monitored as a function of irradiation. Increase in the value of dielectric constant is correlated to the corresponding value of the thermal emittance. Semiempirical calculations, using Fresnel’s relation, are used to validate the measurements. Elemental concentration of phosphorous in the surface region of the film and its morphology has been studied by energy dispersive X-ray analysis using scanning electron microscope.