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NIR SPECTROSCOPIC MONITORING OF WATER ADSORPTION/DESORPTION PROCESS 3. Result and Discussion 3.1. Decomposition of NIR spectra Variation of the NIR spectra with water adsorption onto wood was analyzed basing on three structural forms of water molecules: free water molecules (S0), molecules with one OH group engaged in hydrogen bonding (S1) and molecules with two OH groups engaged in hydrogen bonding (S2) [4]. Curve fitting was undertaken to separate the NIR difference spectra using OPUS (ver. 4.0, Bruker Optik GmbH). Fig. 1 shows the difference and the decomposed spectra of water in the modern sample. An areal integral for each component, AI(Sn), was calculated using Eq. (1), where Sn is one of the structural form of water molecule (n=0,1,2), and DA(ν) is the difference absorbance at a wavenumber ν. AI( S n ) = DA( ν ) dν (1) ∫ 3.2. Adsorption/desorption isotherm for the modern and archaeological wood Fig. 2 shows the adsorption/desorption isotherms of the modern and archaeological wood samples. Both samples show hysteresis loops. The equilibrium moisture content of the archaeological samples is reduced compared to modern samples at each RH level. This is due to the decrease with ageing of hemicellulose of which OH groups form hydrogen bonding with ambient water molecules. Difference absorbance 0.6 0.4 0.2 0 5400 S1 S0 5200 Difference spectrum of water in modern wood S2 5000 Wavenumber(cm -1 ) Fig. 1. Difference and decomposed spectra of water in the modern hinoki wood sample. 4800 200 Moisture content (%) 20 10 0 Modern wood Archaeological wood Desorption Adsorption 20 40 60 80 100 RH (%) Fig. 2. Adsorption/desorption isotherm for the modern and archaeological hinoki wood samples. 3.3. Spectroscopic interpretation of the mechanism of water adsorption by wood Fig. 3 plots the variation of the areal integral (AI(Sn)) (a) and the peak wavenumber (νp(Sn)) (b) for three water components in the NIR difference spectra of the modern sample versus RH. The archaeological sample shows the same tendencies. For the sake of simplicity, we assumed that an areal integral derived from the spectral decomposition is proportional to the amount of the adsorbed water molecules. S1 and S2 components show the hysteresis loop, which is not evident for the S0 component . The variation of AI(Sn) and νp(Sn) can be explained by classifying the RH range into following three stages: Stage I (RH=0-40 %), Stage II (RH=40-90 %) and Stage III (RH=90-100 %). Table 1 summarizes the spectroscopic characteristics. In Stage I, the water molecules interact with wood substance more strongly than in the other stages since a monomolecular layer of water is formed. It is therefore suggested that most of monomolecular layer is composed of the S2 component. The wavenumbers, νp(S0) and νp(S1) showed almost the same value both in the adsorption and desorption processes at Stage I. This suggests that the water molecules adsorbed in wood substance consist predominantly of two of the structural forms, namely, S2 and S0 (or S1) components. The S0 component is very likely to exist when adjacent water molecules are sparse so that the S0 component increased with an increase of RH at this stage. On the other hand, the S0 component decreased gradually at the RH more than 40 % possibly because of an expansion of the upper layers. In Stage II, the water molecules interact with adjacent water molecules, because two or more layers (multilayers) are formed on wood surface. The areal integral, AI(S0) decreased with an increase of RH. This might be due to the three-dimensional (inter-layer) expansion of water molecules and the increase of bonding force within water molecules. The shift of νp(S0) and νp(S2) to higher and lower wave numbers, respectively, may also be caused by the inter-layer expansion of water molecules.
WOOD SCIENCE FOR CONSERVATION OF CULTURAL HERITAGE AI (S n) ν p (S n) (cm -1 ) 200 150 100 50 0 5250 5200 5150 5100 5050 StageⅠ StageⅡ StageⅢ S0 S1 S2 Desorption desorption S0 S1 S2 201 (a) Adsorption adsorption 5000 0 20 40 60 RH (%) 80 100 Fig. 3. Variations of the S0, S1 and S2 components with RH for the modern hinoki wood sample. Bulk water (or capillary condensed water) is observed at Stage III, where the water molecules exist in not only adsorbed but also bulk states. The increase of the S1 and S2 components in this RH range is directly associated with the increase of bulk water. Stage I Stage II Stage III Table 1: Adsorbed water condition in wood derived from NIR spectra. 0-40 % 40-90 % 90-100 % Areal intgral AI(S AI(S0) 0) = AI(S AI(S1) 1) < AI(S AI(S2) 2) AI(S AI(S0) 0)
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Proceedings e report 67
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Wood science for conservation of cu
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SUMMARY Introduction ..............
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WOOD SCIENCE FOR CONSERVATION OF CU
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INTRODUCTION These proceedings of a
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(A) MATERIAL PROPERTIES
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SORPTION OF MOISTURE AND DIMENSIONA
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VIBRATIONAL PROPERTIES OF TROPICAL
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CREEP PROPERTIES OF HEAT TREATED WO
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MEASUREMENT OF THE ELASTIC PROPERTI
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ELASTIC PROPERTIES OF MINUTE SAMPLE
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4. Results Young's modulus (10^4 Mp
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PREDICTION OF LINEAR DIMENSIONAL CH
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DIMENSIONAL CHANGE OF UNRESTRICTED
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DIMENSIONAL CHANGE OF UNRESTRICTED
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AGEING OF WOOD - DESCRIBED BY THE A
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90 30 0 3,0E-03 - 2,0E 2,0E-03 - 1,
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4. Application HYGRO-LOCK INTEGRATI
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RESEARCH ON THE AGING OF WOOD IN RI
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RESEARCH ON THE AGING OF WOOD IN RI
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Xylarium Database RESEARCH ON THE A
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AGING WOOD FROM CULTURAL PROPERTIES
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AGING WOOD FROM CULTURAL PROPERTIES
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STRENGTH AND MOE OF POPLAR WOOD (PO
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STRENGTH AND MOE OF POPLAR WOOD ACR
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STRENGTH AND MOE OF POPLAR WOOD ACR
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PHOTODEGRADATION AND THERMAL DEGRAD
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ROMANIAN WOODEN CHURCHES WALL PAINT
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DISINFECTION AND CONSOLIDATION BY I
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3. Results and discussion WOOD SCIE
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FUNGAL DECONTAMINATION BY COLD PLAS
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STUDIES ON INSECT DAMAGES OF WOODEN
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TERMITE INFESTATION RISK IN PORTUGU
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BIODETERIORATION OF CULTURAL HERITA
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4. Causes of biodeterioration WOOD
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DEGRADATION OF MELANIN AND BIOCIDES
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MOULD ON ORGANS AND CULTURAL HERITA
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Page 153 and 154: WOOD SCIENCE FOR CONSERVATION OF CU
Page 157 and 158: RESEARCH STUDY ON THE EFFECTS OF TH
Page 159 and 160: 4. Methodology WOOD SCIENCE FOR CON
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Page 165 and 166: NON DESTRUCTIVE IMAGING FOR WOOD ID
Page 167 and 168: METHODS OF NON-DESTRUCTIVE WOOD TES
Page 173 and 174: MEASUREMENT AND SIMULATION OF DIMEN
Page 179 and 180: IN THE HEART OF THE LIMBA TREE (TER
Page 189 and 190: 3. Conclusions WOOD SCIENCE FOR CON
Page 191 and 192: 2. Materials and methods WOOD SCIEN
Page 197 and 198: 3. Chemometrics WOOD SCIENCE FOR CO
Page 201 and 202: 3. Results and discussion WOOD SCIE
Page 203: NIR SPECTROSCOPIC MONITORING OF WAT
Page 207 and 208: NUMERICAL SIMULATION OF THE STRENGT
Page 209 and 210: 3. Methods and models WOOD SCIENCE
Page 213 and 214: SIMPLE ELECTRONIC SPECKLE PATTERN I
Page 217 and 218: 5. Conclusions WOOD SCIENCE FOR CON
Page 221 and 222: Average r adiated presure field (dB
Page 223 and 224: EXPERIMENTAL AND NUMERICAL MECHANIC
Page 229 and 230: EFFECT OF THERMAL TREATMENT ON STRU
Page 235 and 236: The aims of this work are to: WOOD
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Page 239 and 240: 4. Conclusions chrome yellow WOOD S
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EUROPEAN TECHNICAL COMMITTEE 346 -
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THE WRECK OF VROUW MARIA - CURRENT
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ROMANIAN ARCHITECTURAL WOODEN CULTU
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RESSURREIÇÃO DE CRISTO - PANEL FR
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ON 18 TH- AND 19 TH- CENTURY SACRIS
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ON 18TH- AND 19TH- CENTURY SACRISTY
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DEFIBRING OF HISTORICAL ROOF BEAM C
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EXAMINATION AND CONSERVATION OF TWO
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EXAMINATION AND CONSERVATION OF TWO
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THE CONSEQUENCES OF WOODEN STRUCTUR
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CONSEQUENCES OF WOODEN STRUCTURES C
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WHAT ONE NEEDS TO KNOW FOR THE ASSE
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load (KN) Samples 6 5 4 3 2 1 WOOD
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STRUCTURAL BEHAVIOUR OF TRADITIONAL
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INVESTIGATION ON THE UTILIZATION OF
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3. Results and discussions WOOD SCI
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Abadlia ......................... 3
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ANNEX 1: FACTS ABOUT COST ACTION IE
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Keynote presentations WOOD SCIENCE
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Finito di stampare presso Grafiche
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