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Carmichael’s Concise Review


Coming Events 2018


Microscopy & Microanalysis 2018 August 5–9, 2018


Baltimore, MD www.microscopy.org


Denver X-Ray Conference August 6–10, 2018


Westminster, CO www.dxcicdd.com


XRM2018: 14th International Conference on X-ray Microscopy August 19–24, 2018


Saskatoon, Canada www.xrm2018.com


EMAS 2018 - Microbeam Analysis in the Earth Sciences September 4–7, 2018 Bristol, UK


www.microbeamanalysis.eu/events/event/51-emas- 2018-microbeam-analysis-inthe-earth-sciences


Imaging Interactions with Fluorescence: From Nano-To-Micro Scale September 5–7, 2018 Diepenbeek, Belgium


www.uhasselt.be/NanoMacroImaging-2018


ESP 2018 ECP 2018: 30th European Congress of Pathology September 8–12, 2018 Bilbao, Spain


www.esp-congress.org


International Microscopy Congress IMC19 September 9–14, 2018


Sydney, Australia www.imc19.com


4th International Conference on BioTribology


September 26–29, 2018 Montreal, Canada


www.elsevier.com/events/conferences/ international-conference-on-biotribology


2019


Microscopy & Microanalysis 2019 August 4–8, 2019


Portland, OR www.microscopy.org 2020


Microscopy & Microanalysis 2020 August 2–6, 2020


Milwaukee, WI www.microscopy.org 2021


Microscopy & Microanalysis 2021 August 1–5, 2021


Pittsburgh, PA www.microscopy.org 2022


Microscopy & Microanalysis 2022 July 31–August 4, 2022


Portland, OR www.microscopy.org 2023


Microscopy & Microanalysis 2023 July 24–28, 2023


Minneapolis, MN www.microscopy.org


More Meetings and Courses Check the complete calendar near the back of this magazine.


8


Synthetic structural materials with exceptional mechanical performance suffer from either large weight and adverse environmental impact (for example, steel and alloys) or complex manufacturing processes and therefore high cost (for example, polymer-based biomimetic composites). Recently a large multi-disciplinary team led by Teng Li and Liangbing Hu at the University of Maryland, College Park, demonstrated a relatively simple method for processing natural wood into densified wood that has remarkable structural characteristics [1]. This is a two-step process that first involves a chemical treatment with sodium hydroxide and sodium sulfite. This treatment partially removed two components of the cell walls, lignin and hemicellulose, but did not appreciably remove cellulose. The second step was mechanical pressing at 100° C, which leads to a reduction in thickness of the wood by about 80%.


Scanning electron microscopy (SEM) of natural wood reveals many lumina (tubular channels 20–80 μ m in diameter) oriented along the direction of wood growth ( Figure 1a ). SEM of densified wood showed fully collapsed lumina ( Figure 1b ). The open spaces between the cell walls in natural wood are completely eliminated resulting in a unique laminated structure with cell walls tightly intertwined with each other. The densely packed and intertwined wood cell walls in the densified wood at the microscale level led to a high degree of alignment of cellulose nanofibers and therefore drastically increased the interfacial area among nanofibers. At the molecular level, owing to the many hydroxyl groups in cellulose molecular chains, relative sliding among densely packed wood cell walls involves an enormous number of repeating events of hydrogen-bond formation, breaking and reformation, which is probably responsible for the enhanced properties of the densified wood.


Imaging Wood Stronger Than Steel


Stephen W. Carmichael Mayo Clinic , Rochester , MN 55905 carmichael.stephen@mayo.edu


Figure 1 : (a) SEM image of the cross section of natural basswood perpendicular to tree growth direction. (b) SEM image of the cross section of densifi ed basswood (super wood) perpendicular to tree growth direction.


doi: 10.1017/S155192951800069X 2018 July


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