Examination of Water Phase Transitions in Black Spruce by Magnetic Resonance and Magnetic Resonance Imaging

Abstract

This study examines the phase transitions of water in wood by magnetic resonance and magnetic resonance imaging.The goal was to observe and understand the behavior of water below 0 C in wood.The species studied, black spruce (Picea mariana Mill.), presented one abrupt phase change that occurred at about 3 C, which was attributed to the phase transition of free water.A more diffuse change occurred below 60 C, which was attributed to a phase transition of bound water.A recently developed portable unilateral magnetic resonance instrument is demonstrated as a powerful tool in the study of water in wood.This portable magnet used a bulk spin-spin relaxation time measurement that quantifies observable bound and free water in wood.Imaging was used to verify the unilateral magnetic resonance results and to better understand realistic freeze-thaw behavior of log samples in the field.A ring boundary behavior during the thawing process was observed, and likewise there were differences in the thawing behaviors of heartwood and sapwood samples.