利用TD-NMR技术研究杨木高温干燥过程水分分布
收稿日期: 2015-09-21
修回日期: 2016-07-11
网络出版日期: 2016-09-05
基金资助
国家自然科学基金资助项目（30800866，31160141）.
Water Distribution in Poplar during High-Temperature Drying Process Studied by Time-Domain Nuclear Magnetic Resonance
Received date: 2015-09-21
Revised date: 2016-07-11
Online published: 2016-09-05
木材中水分状态变化和迁移对木材的物理性质有重要影响．通过时域核磁共振技术（TD-NMR）可以从分子层面解读木材与水分的关系，可以为木材干燥、木制品加工提供理论依据和实践参考．该研究以北京杨为研究对象，通过对高温干燥过程中木材内部水分变化的自由感应衰减（FID）曲线和横向弛豫时间（T2）进行测定与分析，探究木材干燥过程中水分状态变化及迁移过程．研究结果表明，FID和T2信号量与木材含水率高度线性相关，由此可以计算木材在干燥过程中任意时刻的含水率．通过对干燥过程中水分T2分布的分析表明：心材试件在干燥过程中，长弛豫时间自由水（c状态水分）的拟合面积出现了先减小后增大然后再减小的趋势，而边材试件中则不存在这种现象．在北京杨心材试件中含量最多的是弛豫时间为10 ms数量级的水分，而在边材试件中各状态水分含量差异较小，含量最多的是弛豫时间为100 ms数量级的水分．在高温干燥过程中，边材试件内各状态水分百分含量减少的速度快于心材，各试件中自由水的蒸发速度明显快于结合水．
关键词： 时域核磁共振(TD-NMR); 水分分布; 横向弛豫时间(T2); 北京杨; 高温干燥
高玉磊 , 李新宇 , 雷鹏 , 张明辉 . 利用TD-NMR技术研究杨木高温干燥过程水分分布[J]. 波谱学杂志, 2016 , 33(3) : 479 -490 . DOI: 10.11938/cjmr20160313
Moisture in wood affects its physical properties. Time-domain nuclear magnetic resonance (TD-NMR) technique can be used to monitor water state changes and migration, providing a powerful tool to study changes of water in wood during drying and product processing. In this study, water states and migration in Beijing poplar were monitored by TD-NMR during high-temperature drying. Free induction decay (FID) and transverse relaxation time (T2) of water were measured. The results showed that both FID and T2 signals were linearized with moisture content, hence the moisture content in the whold drying process can be calculated. Free water with long relaxation time in heart wood showed a trend of first decrease and then increase and decrease again at last, this phenomenon did not happen in the sap wood. In the heart wood, the most abundant moisture is the water with magnitude of 10 ms relaxation time. But the moisture content of each water state has small difference in sap wood, and the most abundant moisture is the water with magnitude of 100 ms relaxation time. During high temperature drying process, the moisture percentage decrease faster in sap wood than that in heart wood, and the evaporation rate of free water is significantly faster than the bound water.
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