Portable near-infrared (NIR) spectroscopy enabled the nondestructive estimation of internal moisture gradients in Eucalyptus sp. wood subjected to natural and kiln drying. Freshly cut wood was processed into beams, and samples were collected radially, from the heartwood to the sapwood. NIR spectra were obtained using a portable spectrometer, while moisture content was determined gravimetrically at levels of approximately 40%, 30%, and 20%. Partial least squares regression (PLS-R) models were developed to predict the moisture distribution in the wood. The models successfully detected the spatial variation of moisture in the radial surfaces, revealing persistent internal moisture gradients in both drying methods. Wood density strongly influenced prediction performance; denser samples showed greater agreement between NIR estimates and laboratory measurements. The results demonstrate that portable NIR spectroscopy is a promising tool for the rapid, nondestructive monitoring of internal moisture distribution during wood drying, with potential applications in process control and quality assessment.
In this study, the effect of binary mixtures of colloidal nanosilica suspensions on the supraparticle formation in superheated steam drying at 300 degrees C is investigated. It is shown that the single droplet drying kinetics and the final supraparticle morphology can be modified by the addition of smaller nanoparticles into a suspension of larger nanoparticles. It was found that the presence of smaller nanoparticles slows down the evaporation of single droplets, delays crust formation, and produces smaller supraparticles. Comparison of the average supraparticle porosity of the bidisperse structures with the porosity data of corresponding monodisperse systems shows a general decrease in porosity. Analysis of the SEM images reveals that at a volume mixing ratio of 25 vol% of small nanoparticles, stable supraparticles are obtained for all initial solids concentration, and at high initial solids concentrations (30 wt%) stable supraparticle were formed at all mixing ratios.
