木材高强微波处理及其结构失效机制研究进展

Research progress on high-intensity microwave treatment and failure mechanism of wood

木材高强微波处理技术作为一种绿色、高效、快捷的木材预处理手段,能通过引发木材中弱相结构的破坏失效,改变木材材性,并为木材功能性改良提供良好的先决条件;因此,木材高强微波处理技术已逐渐成为优质木材资源紧缺背景下,实现速生材实木化利用,缓解我国木材供需矛盾的重要方式。由于微波作用下引发的木材弱相结构破坏是木材高强微波处理中的关键环节,直接影响处理效果,所以为了进一步完善木材高强微波处理基础理论体系,精准调控微波处理效果,并扩大其在木材加工领域中的应用范围,有必要结合木材多尺度结构特征,深入阐明高强微波处理过程中木材多尺度弱相结构的失效机制。笔者在介绍高强微波处理技术发展、应用现状及其对木材关键性能影响的基础上,结合木材弱相结构概念,对近年来有关微波作用下木材多尺度结构失效机制的研究进行综述,并通过总结现有研究的经验与不足,对今后相关研究的开展提出了建议与展望,以期为深入阐明木材高强微波处理技术机理及实现该技术的大范围、可控化应用提供新思路。

Wood is the only renewable and degradable biomass material among the major building materials and has a lot of unique and excellent properties, which leads it to play a vital role in our daily life and economic development. However, the durable wood resources in our country are far from sufficient, resulting in the unavoidable cultivation of the fast-growing wood. Unfortunately, the fast-growing wood is not comparable in quality to durable wood and is difficult to be utilized directly, mainly due to its special growth and structural features. As an environment-friendly, efficient, and fast method for wood pretreatment, the high-intensity microwave treatment can change the properties of fast-growing wood and provide a good precondition for wood modification by causing the failure of weak structures in wood. Briefly speaking, microwaves can heat the water in the wood, generating high-temperature and high-pressure steam within the wood cells. With the rise of the temperature and pressure, the weak structures, which are most prone to failure in wood, will be destroyed. Consequently, under the background of the shortage of high-quality wood resources, the high-intensity microwave treatment has been widely used in many fields of the wood industry and gradually become an effective way to achieve the solid utilization of fast-growing wood as well as alleviate the contradiction between wood supply and demand in China. Given that the damage of weak structures is the key point in the high-intensity microwave treatment and directly determines the treatment effects, it’s necessary to clarify the failure mechanism of wood multi-scale weak structures in the treatment. Meanwhile, this will also improve the theoretical system of wood high-intensity microwave technique as well as benefit the accurate control and wide applications of the wood microwave treatment. On the basis of introducing the existing researches and applications of the wood high-intensity microwave technique, combined with the concept of the weak structure of wood, this study reviewed studies on the failure mechanism of the multi-scale structures in microwave-treated wood. In addition, by summarizing the experience and shortcomings of previous researches, some suggestions and prospects were proposed in this paper, which is supposed to provide new methods and ideas for carrying out further studies on the failure mechanism of wood multi-scale structures during the high-intensity microwave treatment.