Microstructural features assessment of different waterlogged wood species by NMR diffusion validated with complementary techniques |
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| Affiliation: | 1. Department of Earth Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy;2. National Research Council - Institute for Complex Systems (CNR-ISC) c/o Physics Department Sapienza University of Rome, Rome, Italy;3. Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM) Bologna, P. Gobetti 101, 40129 Bologna, Italy;4. Consiglio Nazionale delle Ricerche - Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN) Bologna, P. Gobetti 101, 40129 Bologna, Italy;5. Department of Mathematical and Computational Sciences, Physics Science and Earth Sciences (MIFT), University of Messina, Messina 98166, Italy;6. Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Piazza del Viminale 1, 00184 Rome, Italy;1. Department of Cardiology, Boston Children''s Hospital and Department of Pediatrics, Harvard Medical School, Boston, MA, USA;2. Department of Computer Science, Technical University of Munich, Garching, Germany;3. Philips Healthcare, Gainesville, FL, USA;1. Department of Radiology, Kawasaki Medical School, 577 Matsushima, Kurashiki-city, Okayama 701-0192, Japan;2. Department of Pathology, Kawasaki Medical School, 577 Matsushima, Kurashiki-city, Okayama 701-0192, Japan;3. Department of Radiology, Radiolonet Tokai, Asaoka-cho 3-86-2, Chikusa-ku, Nagoya-city, Aichi 464-0811, Japan;4. Philips Japan, Konan 2-13-37, Minato-ku, Tokyo 108-8507, Japan;5. Department of Urology, Kawasaki Medical School, 577 Matsushima, Kurashiki-city, Okayama 701-0192, Japan;1. Division of Clinical Radiology Service, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan;2. Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa 920-0942, Japan |
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| Abstract: | Wood is a hygroscopic, multi-scale and anisotropic natural material composed of pores with different size and differently oriented. In particular, archaeologically excavated wood generally is waterlogged wood with very high moisture content (400%–800%) that need to have a rapid investigation at the microstructural level to obtain the best treatment with preservative agents. Time-dependent diffusion coefficient D(t) quantified by Pulse Field Gradient (PFG) Nuclear Magnetic Resonance (NMR) techniques provides useful information about complex porous media, such as the tortuosity (τ) describing pore connectivity and fluid transport through media, the average-pore size, the anisotropic degree (an). However, diffusion NMR is intrinsically limited since it is an indirect measure of medium microstructure and relies on inferences from models and estimation of relevant diffusion parameters. Therefore, it is necessary to validate the information obtained from NMR diffusion parameters through complementary investigations. In this work, the structures of five waterlogged wood species were studied by PFG of absorbed water. D(t) and τ of water diffusing along and perpendicular to vessels/tracheids main axes together with relaxation times and an were quantified. From these parameters, the pore sizes distribution and the wood microstructure characterization were obtained. Results among wood species were compared, validated and integrated by micro-imaging NMR (μ-MRI), environmental-scanning electron-microscope (ESEM) images, wood dry density and imbibition times measurement of all woods. The work suggests that an vs τ rather than the estimated pore size diversifies and characterize the different wood species. As a consequence diffusion-anisotropy vs tortuosity could be an alternative method to characterize and differentiate wood species of waterlogged wood when high resolution images (μ-MRI and ESEM) are not available. Moreover, the combined use of D(t) and micro-MRI expands the scale of dimensions observable by NMR covering all the interesting length scales of wood. |
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