Prevention of spontaneous combustion of cellulose with a thin protective Al 2 O 3 coating formed by atomic layer deposition

We have studied properties of thin protective coating layers of Al2O3, grown by atomic layer deposition (ALD) technique on surfaces of cellulose fibrous materials, using scanning electron microscopy (SEM), scanning transmission microscopy (STEM), energy dispersive x-ray spectroscopy (EDS), high- resolution transmission microscopy (HR-TEM), x- ray diffraction (XRD) and thermal gravimetry (TGA). A minimum thickness of about 50 nm was required to completely inhibit oxygen diffusion into the material and prevent self-ignition at elevated temperatures. No substantial differences were found in morphology or protection performance of Al2O3 coatings produced by thermal or plasma-enhanced ALD (PEALD) methods. However, PEALD technique has shown almost a double growth rate, while, at the same time, it was successfully applied at temperatures as low as 40 °C without degrading quality of the coating.