Al-Qararah Ahmad M, Ekman Axel, Hjelt Tuomo, Kiiskinen Harri, Timonen Jussi, Ketoja Jukka A
VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044 VTT, Finland.
Department of Physics and Nanoscience Center, , P.O. Box 35, FI-40014 University of Jyvaskyla, Finland.
J Microsc. 2016 Oct;264(1):88-101. doi: 10.1111/jmi.12420. Epub 2016 May 9.
Recent developments in making fibre materials using the foam-forming technology have raised a need to characterize the porous structure at low material density. In order to find an effective choice among all structure-characterization methods, both two-dimensional and three-dimensional techniques were used to explore the porous structure of foam-formed samples made with two different types of cellulose fibre. These techniques included X-ray microtomography, scanning electron microscopy, light microscopy, direct surface imaging using a CCD camera and mercury intrusion porosimetry. The mean pore radius for a varying type of fibre and for varying foam properties was described similarly by all imaging methods. X-ray microtomography provided the most extensive information about the sheet structure, and showed more pronounced effects of varying foam properties than the two-dimensional imaging techniques. The two-dimensional methods slightly underestimated the mean pore size of samples containing stiff CTMP fibres with void radii exceeding 100 μm, and overestimated the pore size for the samples containing flexible kraft fibres with all void radii below 100 μm. The direct rapid surface imaging with a CCD camera showed surprisingly strong agreement with the other imaging techniques. Mercury intrusion porosimetry was able to characterize pore sizes also in the submicron region and led to an increased relative volume of the pores in the range of the mean bubble size of the foam. This may be related to the penetration channels created by the foam-fibre interaction.
利用泡沫成型技术制造纤维材料的最新进展引发了在低材料密度下对多孔结构进行表征的需求。为了在所有结构表征方法中找到有效的选择，使用二维和三维技术来探索由两种不同类型纤维素纤维制成的泡沫成型样品的多孔结构。这些技术包括X射线显微断层扫描、扫描电子显微镜、光学显微镜、使用电荷耦合器件（CCD）相机的直接表面成像和压汞法。所有成像方法对不同类型纤维和不同泡沫特性的平均孔径描述相似。X射线显微断层扫描提供了关于片材结构最广泛的信息，并且与二维成像技术相比，显示出不同泡沫特性的更明显影响。二维方法略微低估了含有孔隙半径超过100μm的硬化学热磨机械浆（CTMP）纤维的样品的平均孔径，而高估了所有孔隙半径低于100μm的含有柔性硫酸盐纤维的样品的孔径。使用CCD相机的直接快速表面成像与其他成像技术显示出惊人的高度一致。压汞法也能够表征亚微米区域的孔径，并导致在泡沫平均气泡尺寸范围内孔隙的相对体积增加。这可能与泡沫 - 纤维相互作用产生的渗透通道有关。
