中文摘要：

本文以榆木（Elm）为试材,利用低场核磁共振技术,通过分析试件在各含水率阶段的分层含水率和横向弛豫时间T2,研究经微波干燥木材中水分的状态和迁移规律。研究表明：初含水率为50%的试件存在3种状态水,分别是结合水和存在于不同位置的两种自由水。含水率干燥到纤维饱和点以上时,主要进行自由水移动和向结合水的转化过程,自由水的T2值减小,结合水的T2值增大,厚度方向存在内高外低的含水率梯度场;当含水率干燥到20%以下时,不存在自由水,结合水的T2值随着含水率的降低而减小,木材内水分分布相对均匀,随着微波功率的增加,出现内层含水率低于表层的情况。

英文摘要：

In this paper,the LF-NMR technique was used to monitor the rules of moisture state and mobility in wood samples of elm during microwave drying.Study of the moisture content profiles and the state of T2 during different moisture content period showed that there were three kinds of water state in the sample that moisture content was 50%,bound water and two kinds of free water located in different position.When the moisture content was above FSP,the free water mainly moved and transformed to the bound water,and the T2 value of free water decreased accompanying with the increased the T2 value of bound water.The results showed that the moisture gradients presented a similar pattern with higher moisture content in the center and lower moisture content on the surface layer.There was no free water in samples when the moisture content below 20%,and the T2 value of free water showed a tendency of dropping,with the reduced moisture content.Meanwhile,the moisture content profiles inside the samples were flat.With the increased of the microwave power,the moisture content of the inner layers which was slightly lower than that on the surface layer occurred in the samples.