Effects of Microwave Treatment on Microstructure of Chinese Fir
Microwave (MW) treatment is an effective method to increase refractory wood permeability, thereby reducing drying time and defects. The extent of modification depends on the damage extent of the wood microstructure. In this study, MW intensities of 43 kWh/m<sup>3</sup> (low intensity) an...
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MDPI AG
2020-07-01
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| Series: | Forests |
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| Online Access: | https://www.mdpi.com/1999-4907/11/7/772 |
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| author | Xiang Weng Yongdong Zhou Zongying Fu Xin Gao Fan Zhou Feng Fu |
| author_facet | Xiang Weng Yongdong Zhou Zongying Fu Xin Gao Fan Zhou Feng Fu |
| author_sort | Xiang Weng |
| collection | DOAJ |
| description | Microwave (MW) treatment is an effective method to increase refractory wood permeability, thereby reducing drying time and defects. The extent of modification depends on the damage extent of the wood microstructure. In this study, MW intensities of 43 kWh/m<sup>3</sup> (low intensity) and 57 kWh/m<sup>3</sup>(high intensity) were adopted to treat Chinese fir lumber. Microstructural changes in wood samples were observed using scanning electron microscopy (SEM) and pore structure was characterized using mercury intrusion porosimetry (MIP). Results were as follows: After low-intensity MW treatment, parts of the bordered pit membranes in tracheids were damaged, and micro-fibrils on the margo were ruptured, while the torus basically remained intact. Micro-cracks were observed at both ends of the cross-field pit apertures, propagating to the cell walls of tracheids. The middle lamellar between ray parenchyma cells and longitudinal tracheids cracked, and the width of cracks was in the range of 1–25 μm. After high-intensity MW treatment, damage to the wood microstructure was more severe than that in the low-intensity MW treatment, with macro-cracks having a width range of 100–130 μm being generated. In addition, on the fracture surface of macro-cracks, the bordered pit membranes in tracheids fell off, cross-field pit membranes disappeared and the ray parenchyma cells were seriously damaged, exhibiting fracture of the tracheid walls. Both low-intensity and high-intensity MW treatment can increase the pore diameter corresponding to the margo capillaries (peak value increased from 674.7 nm to 831.8 nm and 1047.6 nm, respectively). The number of pores in the tracheid lumen diameter range also significantly increased. These results provide a theoretical support forMW treatment processes’ improvement and high-value utilization of Chinese fir. |
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| id | doaj.art-0aa5843addbc441cae3e5ccc7e44dd7f |
| institution | Directory Open Access Journal |
| issn | 1999-4907 |
| language | English |
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| publishDate | 2020-07-01 |
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| series | Forests |
| spelling | doaj.art-0aa5843addbc441cae3e5ccc7e44dd7f2023-11-20T07:14:03ZengMDPI AGForests1999-49072020-07-0111777210.3390/f11070772Effects of Microwave Treatment on Microstructure of Chinese FirXiang Weng0Yongdong Zhou1Zongying Fu2Xin Gao3Fan Zhou4Feng Fu5Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, ChinaResearch Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, ChinaResearch Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, ChinaResearch Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, ChinaResearch Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, ChinaResearch Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, ChinaMicrowave (MW) treatment is an effective method to increase refractory wood permeability, thereby reducing drying time and defects. The extent of modification depends on the damage extent of the wood microstructure. In this study, MW intensities of 43 kWh/m<sup>3</sup> (low intensity) and 57 kWh/m<sup>3</sup>(high intensity) were adopted to treat Chinese fir lumber. Microstructural changes in wood samples were observed using scanning electron microscopy (SEM) and pore structure was characterized using mercury intrusion porosimetry (MIP). Results were as follows: After low-intensity MW treatment, parts of the bordered pit membranes in tracheids were damaged, and micro-fibrils on the margo were ruptured, while the torus basically remained intact. Micro-cracks were observed at both ends of the cross-field pit apertures, propagating to the cell walls of tracheids. The middle lamellar between ray parenchyma cells and longitudinal tracheids cracked, and the width of cracks was in the range of 1–25 μm. After high-intensity MW treatment, damage to the wood microstructure was more severe than that in the low-intensity MW treatment, with macro-cracks having a width range of 100–130 μm being generated. In addition, on the fracture surface of macro-cracks, the bordered pit membranes in tracheids fell off, cross-field pit membranes disappeared and the ray parenchyma cells were seriously damaged, exhibiting fracture of the tracheid walls. Both low-intensity and high-intensity MW treatment can increase the pore diameter corresponding to the margo capillaries (peak value increased from 674.7 nm to 831.8 nm and 1047.6 nm, respectively). The number of pores in the tracheid lumen diameter range also significantly increased. These results provide a theoretical support forMW treatment processes’ improvement and high-value utilization of Chinese fir.https://www.mdpi.com/1999-4907/11/7/772microwave treatmentChinese firmicrostructurepore structure |
| spellingShingle | Xiang Weng Yongdong Zhou Zongying Fu Xin Gao Fan Zhou Feng Fu Effects of Microwave Treatment on Microstructure of Chinese Fir Forests microwave treatment Chinese fir microstructure pore structure |
| title | Effects of Microwave Treatment on Microstructure of Chinese Fir |
| title_full | Effects of Microwave Treatment on Microstructure of Chinese Fir |
| title_fullStr | Effects of Microwave Treatment on Microstructure of Chinese Fir |
| title_full_unstemmed | Effects of Microwave Treatment on Microstructure of Chinese Fir |
| title_short | Effects of Microwave Treatment on Microstructure of Chinese Fir |
| title_sort | effects of microwave treatment on microstructure of chinese fir |
| topic | microwave treatment Chinese fir microstructure pore structure |
| url | https://www.mdpi.com/1999-4907/11/7/772 |
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