CHARACTERIZATION OF WOODEN ARTEFACTS BY VIBRATIONAL SPECTROSCOPY

Transcription

1 RER 8015 Using Nuclear Techniques for the Characterization and Preservation of Cultural Heritage in the European Region Regional Training Course on Demonstration of Techniques for Cultural Heritage Protection, 9-13 May 2011, Bucharest, Romania CHARACTERIZATION OF WOODEN ARTEFACTS BY VIBRATIONAL SPECTROSCOPY Ioana Stănculescu 1,2, Mihaela M. Manea 1, Marian Vîrgolici 1, Constantin D. Negut, Mihalis Cutrubinis 1, Valentin I. Moise 1, Corneliu C. Ponta 1 1 IRASM Irradiation Technology Center, Horia Hulubei National Institute for Physics and Nuclear Engineering, 407 Atomistilor Str., Magurele, , Romania 2 University of Bucharest, Faculty of Chemistry, Department of Physical Chemistry, 4-12 Regina Elisabeta Bd., Bucharest, , Romania, istanculescu@nipne.ro

2 TOPICS Vibrational spectroscopy techniques Fourier Transform Infrared spectroscopy (FTIR) Fourier Transform Raman spectroscopy (FT-Raman) Vibrational spectroscopy py analysis of gamma irradiated : 300 years old historical wood tempera painted wooden panels

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5 ARMONIC OSCILLATOR MODEL OF A DIATOMIC MOLECULE The frequency of the atoms periodic motion is the vibration frequency (ν).

6 A molecule with N atoms has 3N-6 normal modes of vibration; linear molecules have only 3N-5 normal modes of vibration. A molecular vibration is excited when the molecule absorbs a quantum of energy, E, corresponding to the vibration's frequency, ν. E = hν, where h is Planck constant. Characteristic vibration frequencies are used for chemical bonds identification.

7 JABLONSKI DIAGRAM

8 BRUKER VERTEX 70 FT-IR/RAMAN SPECTROMETER FTIR transmission measurements in KBr pellets Mobile MIR specular reflectance probe for non contact, in situ measurements FT-Raman measurements with Nd:YAG laser, excitation wavelength of 1064 nm and power between 1 and 500 mw (LN2 detector) Optic fiber mobile RAMPROBE for non contact in situ measurements (LN2 Ge detector) TGA-IR analysis by coupling with NETZSCH STA 409 PC Luxx simultaneous thermal analyzer OPUS 6.5 software

9 LIGNOCELLULOSIC STRUCTURE OF WOOD

10 APPLICATIONS OF INFRARED SPECTROSCOPY IN WOOD CHARACTERIZATION Wood species identification: blue and magenta- conifers, red maple tree Transmitt tance [%] ν (C-H) ν (C=O) ν (C=C) δ (C-H) 30 ν(o-h) ν (C-O) Wavenumber cm-1

11 APPLICATIONS OF INFRARED SPECTROSCOPY IN WOOD CHARACTERIZATION Determination of biological or photophysical decay state No. Wood Ratio lignin/carbohydrate Ratio carbonyl/carbohydrate I 1505 /I 1375 I 1505 /I 1158 I 1738 /I 1375 I 1738 /I pine, 70 years pine, new oak, 100 years oak, 40 years acacia, 50 years 6 hornbeam, 40 years Determination of lignin content: % lignin = x x 2, where x C =C band area of 1505 cm -1

12 FT-RAMAN SPECTRA OF PINE (ORANGE) AND HORNBEAM WOOD (BLACK) Rama an Intensity Wavenumber cm-1

13 TGA-IR 3D plot of wood pyrolysis under inert atmosphere

14 FTIR spectra of pyrolysis products resulted in inert atmosphere by wood thermal decomposition: conifers-red,blue; maple tree-green Units Absorbance Wavenumber cm-1

15 VIBRATIONAL SPECTROSCOPY STUDY OF GAMMA-IRRADIATED HISTORICAL WOODEN ARTEFACTS Experimental models of 300 years old historical pinewood were irradiated at IRASM Co60 gamma irradiator with 6, 12, 25, 50 and 100 kgy. The samples were divided in six batches, five of them being subjected to artificially induced accelerated degradation in air tight inert containers (2 batches in dry atmosphere and 3 batches in humid atmosphere ) for 1, 2 or 3 weeks at 80 C).

16 The church of Dretea, 1672

17 N f D t h h 1742 Nave of Dretea church, 1742, The Sixtin Chapel of the Astra Museum wooden churches

18 Wood accelerated degradation experiments, in dry (left) and humid (right) atmosphere

19 ance Units Absorba MIR reflectance spectra variations of unirradiated (green) and irradiated (red) wood samples are very small Wavenumber cm

20 Factor 3: 13.19% Baseline corrected and normalized spectra were used for sample clusterization with Principal Components Analysis. PCA analysis failed to classify irradiated (black) and unirradiated samples P30 P08 P17 Factor 4: % P*29 P31 P36 P*05 P*11 P05 P10 P15 P09 P*26 P16 P*15 P*21 P26 P*03 P*09 P03 P35 P*27 P20 P12 P27 P14 P01 P07 P11 P19 P23 P*33 P*14 P24 P34 P25 P*06 P*02 P*12 P*32 P26 P*23 P*30 P*16 P*24 P*34 P*20 P*35 P13 P*36 P*08 P08 P29 P06 P*10 P33 P02 P*22 P*17 P*04 P21 P32 P18 P*18 P22 P04 P*28 P

21 FT-IR transmission spectra shows small differences between artificially degraded in dry (red) and humid (blue) atmospheres and non-aged (green) samples Absorban nce Units Wavenumber cm

22 Baseline corrected and normalized spectra were used for sample clusterization with Principal Components 0.04 Analysis % Factor 4: P34D25H3 P36D100H3 p17d50h1 P30D100H2 p15d12h1 p18d100h1 P35D50H3 P27D12H2 P26D6H2 p14d6h1 P31D0H3 p4d25 p5d50 P33D12H3 p16d25h1 P25D0H2 p13d0h1 P29D50H2 p3d12 P32D6H3 P28D25H2 p2d6 p6d p1d Factor 1: 76.43% Projection of the cases on the factor plane; PCA analysis of the FTIR data of humid (1, 2, and 3 weeks) aged (blue) and non aged (black) wood

23 Projection of the cases on the factor plane ; PCA analysis of the FTIR data of dry (red), humid (black) conditions aged and non aged (blue) wood p13d0h1p12d100d1 p11d50d1 p4d25 p10d25d % Factor 3: p5d50 p1d0 p3d12 p2d6 p6d100 p17d50h1 p16d25h1 p9d12d1 p18d100h1 p7d0d1-10 p8d6d1-15 p14d6h1 p15d12h Factor 1: 45.50%

24 FT-Raman spectra of dry (red) aged wood samples had lower intensity bands than humid (blue) conditions aged samples, due probably to trapped electrons. Raman I Intensity Wavenumber cm

25 Thermal analysis revealed slight changes in thermal stability of wood samples. The time of accelerated degradation was not sufficient to probe significant modification of thermal stability below an absorbed irradiation dose of 12 kgy. TG /% DTG /(%/min) 100 [1.2] [4.2] [7.2] [3.2] [5.2] [2.2] [6.2] Peak: 60.2 C, %/min Mass Change: % Peak: 72.4 C, %/min Change: % Peak: 70.0 C, %/minmass Change: % C Peak: Peak: 59.8 Peak: C, C, C, %/min Mass Change: % %/min Mass Change: % %/min Mass Change: % Peak: 67.3 C, %/min Mass Change: % [1.2] P01-C1-0kGy-DSC-S-2K-Air dsv TG DTG [2.2] P24-C8-100kGy-aged2wks-RH0%-80C-DSC-S-2K-Air dsv TG DTG [3.2] P19-C8-0kGy-aged2wks-RH0%-80C-DSC-S-2K-Air dsv TG DTG [4.2] P20-C8-6kGy-aged2wks-RH0%-80C-DSC-S-2K-Air dsv TG DTG [5.2] P21-C8-12kGy-agd2wks-RH0%-80C-DSC-S-2K-Air dsv TG DTG [6.2] P22-C8-25kGy-aged2wks-RH0%-80C-DSC-S-2K-Air dsv TG DTG [7.2] P23-C8-50kGy-aged2wks-RH0%-80C-DSC-S-2K-Air dsv TG DTG Residual Mass: % (594.0 C) Residual Mass: % (593.6 C) Residual Mass: % (594.0 C) Residual Mass: 1.19 % (593.8 C) Residual Mass: % (593.7 C) Residual Mass: 2.00 % (593.8 C) Residual Mass: 0.06 % (594.1 C) Mass Change: % Mass Change: % 20 Peak: C, %/min Peak: C, %/min Mass Change: % -2.5 Peak: C, %/minmass Change: % Mass Change: % Peak: C, %/min Mass Change: % Peak: C, %/min Mass Change: % Peak: C, %/min Mass Change: % Peak: C, %/minmass Change: % Peak: C, %/min Mass Change: % Peak: C, %/minmass Change: % Peak: C, %/min [3.2] Mass Change: % -3.0 [1.2] [5.2] Peak: C, %/minmass Change: % Peak: C, %/min [4.2] [7.2] [2.2] [6.2] 0 Peak: C, %/minmass Change: % Peak: C, %/min Temperature / C TG/DTG curves (Air, 2 K/min) of aged samples- 2 weeks at 80 C and 0 % RH

26 The main DTG peak temperature variation with radiation absorbed dose for inert atmosphere nonaged ag2w80c0rh ag3w80c100r DT TG peak (C C) Absorbed dose (kgy)

27 The main DTG peak temperature variation with radiation absorbed dose for oxidative atmosphere 366 nonaged ag2w80c0rh ag3w80c100r DT TG peak (C C) Absorbed dose (kgy)

28 CONCLUSIONS I Vibrational spectra provided information about very small changes in the molecular structure of wood components due to γ- irradiation and accelerated degradation. PCA was useful for sample clustering, based on changes in the FT- IR spectra, which may be correlated with the irradiation dose or ageing treatment. Further interpretation of data is envisaged. A5 C decrease of main DTG decomposition temperature, after 20 kgy absorbed radiation dose was observed in both inert and oxidative atmosphere. A 6 C increase of main DTG decomposition temperature, below 12 kgy absorbed radiation dose was observed in oxidative atmosphere.

29 SPECTROSCOPIC EVALUATION OF PAINTED LAYER STRUCTURAL CHANGES INDUCED BY GAMMA RADIATION IN EXPERIMENTAL MODELS Experimental models prepared by Conservation- Restoration Department of Bucharest National University of Arts (Romania), consisted of small rectangular a (3x10 cm) pieces pecesof wood covered ed by a ground layer (chalk in mixture with bone glue) and pigments pg : ultramarine (Na 8-10Al 6S 6O 24S 2-4), red lead (Pb 3 O 4 ), chrome yellow (PbCrO 4 ), mars red (synthetic Fe 2O 3), raw sienna (iron oxides H2O), lead white (PbCO 3 ) 2 Pb(OH) 2 mixed with tempera (18% aqueous solution of yolk egg). The ratio of pigment to yolk egg emulsion was 1:2 in weight.

30 Experimental models of tempera painted wooden panels: from left to right top row: ultramarine, lead white, chrome yellow bottom row: raw sienna, red lead, red mars; Notations: +V - varnished paint layer side; d-35 Gy/min dose rate irradiated experimental models; D Gy/min dose rate irradiated experimental models; u - unirradiated experimental models.

31 Gamma irradiation i A SVST Co-60/B gamma irradiator was used for irradiation. Irradiation was carried out in the presence of air at room temperature. An ECB dosimetric system was used for dose measurements. e e All values of dose are expressed as absorbed dose in water. The dosimetric system has traceability to High Dose Reference Laboratory RISØ Denmark. Samples were prepared in three series: one unirradiated, used as a reference, and two irradiated at 11 kgy but using two dose rates: 35 Gy/min (d) and 245 Gy/min (D).

32 FTIR spectra of unirradiated, unvarnished raw sienna (orange) and red lead (red) paint layers and egg yolk (black). Absorbance Units Wavenumber cm-1

33 FTIR spectra of dammar varnish (black), unvarnished raw sienna painted layer (red) and varnished (orange). Absorbance Units Wavenumber cm-1

34 FTIR spectra of raw Sienna experimental model paint layer: unirradiated (black), d irradiated (orange) and D irradiated (red). There are two curves for each color because the spectra of varnished and unvarnished regions are shown. Absorbance Units Wavenumber cm-1

35 FT-Raman spectra of chrome yellow; unirradiated (black), d irradiated (orange) and D irradiated (red); There are two curves for each color because the spectra of varnished and unvarnished regions are shown Raman Inten nsity Wavenumber cm-1

36 Average spectrum, the standard deviation (stdev) and mean distance (md) were calculated with the OPUS software. n - the number of original spectra, y i - absorbance and y- mean absorbance value. The following stdev,, md values were obtained: chrome yellow 0.169, 0.149; mars red 0.126, 0.112; raw sienna 0.128, 0.114; red lead 0.173, 0.149; lead white 0.295, 0.239; ultramarine 0.098, Lead white has the biggest deviations and this is consistent with the observed colour non-uniformity of the samples. Chrome yellow and red lead have comparable next biggest values. This approach gives near values of stdev and md for Pb based pigments (lead white, chrome yellow and red lead) and Fe based pigments (mars red and raw sienna).

37 CONCLUSIONS II The FTIR spectra analysis permitted, in the case of raw sienna and chrome yellow paint layers experimental models, the rapid identification of dammar varnished and unvarnished samples by the most intense band of dammar from 1705 cm -1. Mineral pigments used in the historical paintings proved to be stable at irradiation. The most important changes in the FTIR spectra were e observed for raw Sienna samples: for the higher dose rate the egg yolk protein oxidation peaks and the CH stretching bands due to lipids degradation products increase in intensity.

38 Acknowledgements IAEA, RER/8/015 project Using Nuclear Techniques for the Characterization and Preservation of Cultural heritage Artefacts in the European Region ANCS Romania, DELCROM project //irasm.ro/delcrom/ ro/delcrom/ /

39 THANK YOU FOR YOUR ATTENTION!