E53 Determining the moisture content of wood by free-induction-decay (FID NMR) signal Maks Merela*, Igor Serša, Urša Mikac and Primož Oven
MOISTURE DETERMINATION methods methods • Determination by oven dry method (SIST EN 13183-1:2003) • E Estimation by electrical resistance method (SIST EN 13183- i i b l i l i h d 2:2003) • Estimation by capacitance method (EN 13183-3:2005) y p ( ) • Standard Test Method for Moisture in Wool by Distillation With Toluene (ASTM D2462 - 90(2008) • Using the Karl Fischer titration method (the Reaction of Iodine with Water) (ASTM D6869 – 03) • Measurement of MC in wood with a CT scanner Measurement of MC in wood with a CT scanner • Optimal Signal Conditioning in the NIR Moisture Meter • Neutron Imaging MC determination g g • Method and apparatus for colorimetric analysis (US Patent 4005983) • and … d Nuclear Magnetic Resonance MC determination •
NMR BACKGROUND NMR BACKGROUND • at magnetic resonance method we operate with magnetic properties of atoms which nuclei have ti ti f t hi h l i h magnetic dipole (hydrogen atom) • method detects different concentrations of h d hydrogen atoms t VERY CONVINIANT FOR WATER DETECTION
Because of its heterogeneous structure and moisture content WOOD is a very appropriate material for NMR studies
NMR EQUIPEMENT • magnetic field: 2,35 T
SAMPLE PREPARATION • FID signal: • FID signal: -detection in 15 sec. -and weighting of a sample and weighting of a sample sample in RF coil
OVEN DRY METHOD MC in wood is defined as: ratio between the mass of water ( m w ) in the sample ti b t th f t ( ) i th l and mass of oven dry sample ( m 0 ): − m m [ [ ] ] m = = ⋅ ⋅ = = ⋅ ⋅ g 0 w MC MC 100 100 100 100 % % m m 0 0
RESULTS NMR FID signal vs. mass of water 30.000 30.000 NMR FID = 100137 * mass of water + 452,84 R 2 = 0,9982 25.000 20.000 gnal R FID sig 15.000 NMR 10.000 5.000 0 0 0 0,05 0,1 0,15 0,2 0,25 mass of water (g) • NMR FID signal is linear proportional to mass of water • NMR FID signal is not dependant on tree species
Linear relation between FID and mass of water: = ⋅ w + NMR FID 100 137 m 452 , 84 m w for our experimental setup can be expressed as: − NMR NMR FID FID 452 452 , 84 84 = m w 100 100 137 137 = − m m m m m m w g o ⎛ ⎞ − from FID signal NMR FID 452 , 84 ⎜ ⎜ ⎟ ⎟ = = − m m m m ⎜ ⎜ ⎟ ⎟ we get m without we get m 0 without 0 g ⎝ ⎠ 100 137 oven drying
[ [ ] ] = m OVEN DRY ⋅ 100 % w MC METHOD EQ METHOD EQ. m 0 − NMR FID 452 , 84 = m w 100 137 ⎛ ⎞ − NMR FID 452 , , 84 ⎜ ⎜ ⎟ ⎟ = − m m ⎜ ⎟ 0 g ⎝ ⎠ 100 137 FINAL RESULT IS: − [ ] NMR FID 452 , 84 = ⋅ NMR MC 100 % ⎡ ⎡ ⎤ ⎤ ⎛ ⎛ ⎞ ⎞ − NMR NMR FID FID 452 452 , , 84 84 ⎜ ⎜ ⎟ ⎟ ⋅ − ⎢ ⎢ ⎥ ⎥ 100 137 m ⎜ ⎟ g ⎝ ⎠ ⎣ 100 137 ⎦
RESULTS Oven dry method vs. NMR MC determination 140% R 2 = 0,996 120% 100% Grav. MC 80% 60% 40% 20% 0% 0% 20% 40% 60% 80% 100% 120% 140% NMR MC experimental data of samples (different wood species and size) excellent agreement between both methods ( R 2 = 0,9961).
CONCLUSIONS: ☺ NMR based method enables accurate and simple ☺ NMR b d th d bl t d i l moisture content determination ☺ ☺ method can be universally used for any NMR setup th d b i ll d f NMR t ☺ once the system is calibrated, MC of any sample, not only of wood, can be determined from its FID l f d b d t i d f it FID amplitude and its weight ☺ method could therefore be used for laboratory and ☺ th d ld th f b d f l b t d industrial purposes to obtain MC quickly and accurately at the site of the use t l t th it f th Di Disadvantages: d t - method can be used only for small samples - price of the equipment i f th i t
3D MR SCANING OF A LIVING BRANCH
RESULTS MR IMAGING AND MC DISTRIBUTION DETERMINATION K OAK li h light microscopy i 2D MR image MC surface plot ECH BEE
REZULTATI MOISTURE GRADIENT DETERMINATION Beech (88 %) 300 %) content (% 250 ost (%) 200 150 150 vlažno Moisture c 100 50 M 0 0 1 2 3 4 5 Branch diameter (mm) premer vejice (mm) 300 Oak (91 %) 250 %) content (% ažnost (%) 200 150 Moisture c vla 100 50 M 0 0 1 2 3 4 5 6 7 premer vejice (mm) Branch diameter (mm)
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