Wood is a natural porous material with pores size between 0-400 μm and its structures [1,2] vary according to the species and to the anatomical direction observed. Wood is also a hygroscopic material in which water molecules diffuse and the diffusion coefficient is vehicle of information about pores dimension and distribution. Aim of this work was to characterize archaeological waterlogged wood by non-destructive nuclear magnetic resonance diffusion, relaxometry, imaging and cryoporometry in order to investigate the samples at different length scales (nanometer, micrometer and sub-millimeter scale). The work is divided in two steps. In the frst step, the molecular diffusion protocol was validated by studying fve soaked modern woods (four hardwoods and one softwood) and measuring the diffusion coefficient along x axis (i.e. perpendicular to the main axis of vessels/tracheids) with a 400 MHz Bruker-Avance spectrometer. By introducing data correction to remove the diffusion of water through semi-permeable membranes (cell walls) [3], pores diameter was estimated. In the second step, the characterization of the porosity and microstructure of a small and archaeological submerged wood excavated in Naples and belonging to the 5th century A.D. was carried out. Relaxation times T 1 and T 2 were quantifed and magnetic resonance images were acquired by using a 300 MHz or 400 MHz spectrometer while cryoporometry was performed at 500 MHz using spin-echo and CPMG experiments over the temperature range 180-294 K, increasing temperature in 76 steps of 1.5 K [4]. T 1 and T 2 provided preliminary information about water compartments, wood density and porosity. T 2 and T 1-weighted images with an in-plane resolution of 18 x 18 μm 2 allowed to observe anatomical and physiological elements under the micrometer and sub-millimeter scale while T 2 *-weighted images highlighted the presence of paramagnetic impurities due to the decay. Thanks to the magnetic resonance images it was possible to get a complete and non-destructive virtual histology in the three anatomical sections of wood (Fig. 1).
NMR PROTOCOL FOR MULTISCALE CHARACTERIZATION OF ARCHAEOLOGICAL WATERLOGGED WOOD / Stagno, Valeria; Mailhiot, Sarah; Telkki, Ville-Veikko; Capuani, Silvia. - (2020), pp. 105-105. (Intervento presentato al convegno CCR Young Professionals Forum 2020 tenutosi a Torino).
NMR PROTOCOL FOR MULTISCALE CHARACTERIZATION OF ARCHAEOLOGICAL WATERLOGGED WOOD
Valeria Stagno
Primo
Writing – Original Draft Preparation
;
2020
Abstract
Wood is a natural porous material with pores size between 0-400 μm and its structures [1,2] vary according to the species and to the anatomical direction observed. Wood is also a hygroscopic material in which water molecules diffuse and the diffusion coefficient is vehicle of information about pores dimension and distribution. Aim of this work was to characterize archaeological waterlogged wood by non-destructive nuclear magnetic resonance diffusion, relaxometry, imaging and cryoporometry in order to investigate the samples at different length scales (nanometer, micrometer and sub-millimeter scale). The work is divided in two steps. In the frst step, the molecular diffusion protocol was validated by studying fve soaked modern woods (four hardwoods and one softwood) and measuring the diffusion coefficient along x axis (i.e. perpendicular to the main axis of vessels/tracheids) with a 400 MHz Bruker-Avance spectrometer. By introducing data correction to remove the diffusion of water through semi-permeable membranes (cell walls) [3], pores diameter was estimated. In the second step, the characterization of the porosity and microstructure of a small and archaeological submerged wood excavated in Naples and belonging to the 5th century A.D. was carried out. Relaxation times T 1 and T 2 were quantifed and magnetic resonance images were acquired by using a 300 MHz or 400 MHz spectrometer while cryoporometry was performed at 500 MHz using spin-echo and CPMG experiments over the temperature range 180-294 K, increasing temperature in 76 steps of 1.5 K [4]. T 1 and T 2 provided preliminary information about water compartments, wood density and porosity. T 2 and T 1-weighted images with an in-plane resolution of 18 x 18 μm 2 allowed to observe anatomical and physiological elements under the micrometer and sub-millimeter scale while T 2 *-weighted images highlighted the presence of paramagnetic impurities due to the decay. Thanks to the magnetic resonance images it was possible to get a complete and non-destructive virtual histology in the three anatomical sections of wood (Fig. 1).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
