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    仲翔, 张少军, 马尔妮. 不同含水率状态下木材细胞壁孔径分布变化[J]. 北京林业大学学报, 2021, 43(11): 128-136. DOI: 10.12171/j.1000-1522.20210260
    引用本文: 仲翔, 张少军, 马尔妮. 不同含水率状态下木材细胞壁孔径分布变化[J]. 北京林业大学学报, 2021, 43(11): 128-136. DOI: 10.12171/j.1000-1522.20210260
    Zhong Xiang, Zhang Shaojun, Ma Erni. Variation in pore size distribution of wood cell wall under different moisture states[J]. Journal of Beijing Forestry University, 2021, 43(11): 128-136. DOI: 10.12171/j.1000-1522.20210260
    Citation: Zhong Xiang, Zhang Shaojun, Ma Erni. Variation in pore size distribution of wood cell wall under different moisture states[J]. Journal of Beijing Forestry University, 2021, 43(11): 128-136. DOI: 10.12171/j.1000-1522.20210260

    不同含水率状态下木材细胞壁孔径分布变化

    Variation in pore size distribution of wood cell wall under different moisture states

    • 摘要:
        目的  探究由水分所引发的木材细胞壁孔隙结构变化规律与机制,为木材的热质转移、渗透性以及木材改性提供理论指导。
        方法  将杨木和杉木分别制成5 mm(径向) × 5 mm(弦向) × 1 mm(轴向)的木片,基于氮气吸附法、差示扫描热孔计法考察试样在绝干状态、气干状态、纤维饱和状态和饱水状态4种典型水分状态下的孔径分布、比表面积、孔体积等特征参数,并对比不同状态和不同树种间的孔隙结构差异。
        结果  木材细胞壁孔径大多在10 nm以下,尤其以4 nm以下为主,10 nm以上孔隙相对较少;随着含水率的提升,木材细胞壁孔径分布曲线显著升高,从气干状态到纤维饱和状态,杨木和杉木的孔径分布最大值分别增加了52.73%和58.62%,而从纤维饱和状态到饱水状态,两者分别增加了435.24%和470.43%。
        结论  在木材由绝干状态逐渐吸湿,以及吸水至饱水状态的过程中,木材细胞壁孔隙体积呈明显增大趋势。在木材达到饱水状态后,细胞壁孔隙体积增大至极限,但由于自由水的冰点下降,其在−2 ℃左右产生大量吸热信号进而干扰测量结果,故此时差示扫描热孔计法所测得的孔径分布参考范围有限。不同树种间孔隙分布差异不明显。

       

      Abstract:
        Objective  This work was conducted to investigate the changing tendency and mechanism of pore structure in wood cell wall induced by water, so as to provide theoretical guidance for heat and mass transfer within wood, wood permeability and wood modification.
        Method  Poplar wood and fir wood were prepared into wood slices of 5 mm (R) × 5 mm (T) × 1 mm (L) . Based on nitrogen sorption method and differential scanning thermoporosimetry, the characteristic parameters of pore size distribution, specific surface area, pore volume were investigated at four typical moisture content states including oven-dry state, air-dry state, fiber saturation state and saturated state. The pore structure differences between different states and different tree species were compared.
        Result  The pore size of wood cell wall was mostly less than 10 nm, especially below 4 nm, with relatively few pores above 10 nm. With the increase of moisture content, the pore size distribution curve of wood cell wall rose significantly. From air-dry state to fiber saturation state, the maximum pore size distribution of poplar wood and fir wood increased by 52.73% and 58.62%, respectively, furtherly from fiber saturation state to saturated state, those values increased by 435.24% and 470.43%, respectively.
        Conclusion  As the wood gradually changes from oven-dry state to saturated state, the pore volume of wood cell wall becomes higher obviously. When the wood reaches saturated state, the volume of cell wall pores reaches the maximum. However, due to the signal interference from a large amount of free water, the detecting range of pore size distribution measured by the differential scanning thermoporosimetry is limited. There is no obvious difference in pore distribution among different tree species in this study.

       

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