Low permeability of wood causes problems during drying of timber. This study evaluated the effects of microwave (MW) pretreatment on the conventional drying behavior and mechanical damages of Chinese fir lumber. MW pretreatment of lumber was performed at applied MW energy of 43 kWh/m3, and then, the samples were dried in a laboratory drying kiln. The results showed that the drying rate was effectively increased after MW pretreatment. The moisture content (MC) deviation in thickness and residual stress indexes of MW-pretreated samples were significantly decreased in comparison with the control samples, and the appearance quality of wood samples was not clearly affected by the MW pretreatment. Scanning electron microscope (SEM) micrographs demonstrated that pit membranes were damaged after MW pretreatment, and the micro-cracks in radial section as well as detachments between ray parenchyma cells and tracheids were also observed. Consequently, new pathways for moisture migration during drying process were formed after MW pretreatment, which contributed to the improved permeability of Chinese fir lumber and decreased drying time.

中文翻译：

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微波预处理对50 mm厚度杉木木材干燥的影响

木材的低渗透性在木材干燥期间引起问题。这项研究评估了微波（MW）预处理对杉木木材常规干燥行为和机械损伤的影响。在施加的MW能量为43 kWh / m3的条件下对木材进行MW预处理，然后在实验室干燥炉中干燥样品。结果表明，MW预处理后，干燥速率得到了有效提高。MW预处理样品的厚度和残余应力指数的水分含量（MC）偏差与对照样品相比显着降低，并且MW预处理对木材样品的外观质量没有明显影响。扫描电子显微镜（SEM）显微照片显示，微波预处理后，凹坑膜被破坏，观察到放射状微裂纹以及射线实质细胞与气管之间的分离。因此，MW预处理后形成了干燥过程中水分迁移的新途径，这有助于提高杉木木材的渗透性并减少干燥时间。