Personne : Stevanovic-Janezic, Tatjana
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Stevanovic-Janezic
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Tatjana
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Université Laval. Département des sciences du bois et de la forêt
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ncf10532859
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Publication Restreint An investigation of thermochemical changes in Canadian hardwood species during wood welding(Springer, 2013-02-09) Erakovic, Sanja; Cloutier, Alain; Stevanovic-Janezic, Tatjana; Diouf, Papa Niokhor; Prado, Maria; Pizzi, Antonio; Royer, Mariana; Belleville, BenoîtThermochemical changes during wood-dowel welding were investigated in two Canadian hardwood species commonly used for indoor appearance applications: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). The original reference wood sample and the welded interface between two bonded wood pieces, a dowel and a substrate, were compared to explain differences in mechanical properties between species. Pyrolysis gas chromatography–mass spectrometry (Py-GC/MS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used. The gases emitted during wood welding were determined by Py-GC/MS and gas chromatography coupled with a thermal conductivity detector and a flame ionization detector (GC-TCD/FID). Results showed that thermal welding of birch and maple woods degrades hemicelluloses and affects lignin polymer through depolymerisation. Welding effectiveness is therefore directly associated with the properties of the original wood constituents, primarily lignin and carbohydrates. The lignin-related changes at the welded interface were greater for sugar maple than for yellow birch, corroborating mechanical property differences observed between the two species. The gases proportions were similar for both species and no harmful gases were detected in the smoke released during welding process.Publication Accès libre Chemical changes induced in Pinus radiata and Eucalyptus nitens following the densification process(Pulp and Paper Technical Association of Canada, 2015-01-31) Cloutier, Alain; Stevanovic-Janezic, Tatjana; Chavez, Romina; Koumba, Georges; Bustos, CeciliaDensification of wood leads to improvement of its mechanical properties. Specimens of Pinus radiata and Eucalyptus nitens wood were densified using heat, steam, and pressure to improve their mechanical properties and thus enhance their utilization. At a maximum steam pressure of 550 kPa and a maximum press hydraulic pressure ranging from 4.5 to 9 MPa, selected temperatures of 160°C, 180°C, and 200°C were used to check the mechanical properties and to identify the chemical composition of wood samples before and after densification. Densified wood samples showed markedly reduced hygroscopicity. The chemical changes in the wood constituents occurring during densification were characterized using FT-IR, Py-GC/MS, and XPS. According to the densification process between pine and eucalyptus, the results obtained showed that the densification effects were better for Eucalyptus nitens than for Pinus radiata. The FT-IR analysis revealed a high condensation index for pine lignin and the low condensation index for eucalyptus lignin, indicating easier formation of C-C linkages by densification in pine lignin. Py-GC/MS analyses were performed to follow the lignin/carbohydrate ratio, and these revealed major carbohydrate losses during densification at the highest temperature.