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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Voici les éléments 1 - 8 sur 8
  • Publication
    Accès libre
    Fuel properties of sugar maple and yellow birch wood in relation with tree vigor
    (North Carolina State University, 2016-05-01) Cloutier, Alain; Stevanovic-Janezic, Tatjana; Achim, Alexis; Nguyen, Quy Nam
    The fuel properties of wood obtained from sugar maple (SM) and yellow birch (YB) of temperate hardwood stands located in the Province of Québec, Canada were studied to see how tree vigor affects the chemical composition and calorific value of the wood. This study focused on the physical and chemical properties of wood with the aim of using the material for the production of solid biofuels. Specific items measured included the wood’s calorific values, and the levels of extractives, ash, and lignin. Changes in chemical composition were found among tree vigor classes. The low vigor trees had higher extractives, ash, and lignin contents than the vigorous trees. Total extractives ranged between 4.88 and 7.32% in SM, and between 3.35 and 5.12% in YB. Klason lignin ranged between 21.46 and 23.53% in SM, and between 18.60 and 21.51% in YB. Ash content ranged between 0.38 and 0.97% in SM, and between 0.26 and 0.47% in YB. The combined effects of higher lignin content that could contribute to a better self-bonding of particles and of higher extractives content that could facilitate the pelletization process makes the low vigor trees more suitable for conversion into solid biofuels. The higher amounts of extractives and lignin present in the low vigor sugar maple and yellow birch trees could also have a positive role in maintaining the high calorific values of this wood despite higher ash content.
  • Publication
    Restreint
    Pressurized hot water treatment of sugar maple and yellow birch wood particles for high quality fuel pellet production
    (Elsevier, 2017-02-01) Cloutier, Alain; Stevanovic-Janezic, Tatjana; Achim, Alexis; Nguyen, Quy Nam
    This study was conducted with the aim of converting low quality hardwoods into high quality fuel pellets by using hot water as a pretreatment method. Hardwood particles from sugar maple and yellow birch trees were first pretreated with hot water at 150 °C, 175 °C and 200 °C for 30 min in a batch reactor. The solid fractions following hot water treatment were then compacted into pellets using a single pelletizer. The produced pellets exhibited a number of enhanced properties as compared to those obtained from untreated wood particles. The increases in density and energy content of pellets reached approximately 30% and 40%, respectively. Compressive strength was increased by three times or more. Results also indicated that pellets of high water resistance were obtained using material treated with hot water at a temperature of about 200 °C for both sugar maple and yellow birch wood. In addition, considerable reduction in friction in the die was observed when treated wood particles were used.
  • Publication
    Accès libre
    Surface chemical changes of sugar maple wood induced by thermo-hygromechanical (THM) treatment
    (MDPI, 2019-06-17) Fu, Qilan; Laghdir, Aziz; Cloutier, Alain; Stevanovic-Janezic, Tatjana
    The aim of this study was to investigate the effects of heat and steam on the chemical properties of thermo-hygromechanical (THM)-densified sugar maple wood. The THM densification process was performed at two different temperatures (180 °C and 200 °C) with and without steam. The functional groups, surface chemical composition and internal structure and components of the control and densified samples were investigated using attenuated total reflection Fourier transform infrared (ATR-FTIR), X-ray photoelectron (XPS) spectroscopy and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). The obtained results suggest that the THM densification treatment resulted in significant chemical changes on the wood surface. The results of the ATR-FTIR spectra confirmed the decomposition of hemicelluloses and the relative increase of cellulose and lignin contents on the wood surface. The Py-GC/MS and XPS results show an increase of the oxygen/carbon atomic (O/C) ratio, which indicated that chemical substances containing oxygenated functionality were formed through the densification process. The densification treatment favored the depolymerization of hemicelluloses and cellulose as indicated by an increased anhydrous sugar (levoglucosan) release during the pyrolysis process. Densification also facilitated the cleavage of the lignin side chains, resulting in increased phenyl units with short chains released during the pyrolysis process.
  • Publication
    Restreint
    Effect of process parameters and raw material characteristics on physical and mechanical properties of wood pellets made from sugar maple particles
    (Pergamon, 2015-07-03) Cloutier, Alain; Stevanovic-Janezic, Tatjana; Achim, Alexis; Nguyen, Quy Nam
    The aim of the current study was to investigate the influence of process parameters and raw material characteristics on physical and mechanical properties of wood pellets made from particles of sugar maple trees of different vigor. Pellets were made in a single pelletizer while controlling temperature (75, 100 and 125 °C), moisture content (8.1, 11.2 and 17.2%), compression force (1500, 2000 and 2500 N) and particle size (<0.25, 0.25–0.5 and 0.5–1.0 mm). Particle size was the most important factor influencing friction in the die, followed by moisture content, compression force and temperature. Moisture content was the most important factor affecting pellet density, followed by temperature, compression force and raw material particle size. Temperature was the most important factor for pellet compression strength, followed by compression force, particle size and moisture content. Friction in the die decreased with increasing particle size and moisture content of the material and increased with increasing compression force. It decreased initially with increasing temperature from 75 °C to 100 °C, and then increased with temperature. Density and strength of pellets increased with temperature and compression force, decreased with increasing particle size, and decreased with increasing moisture content. Pelletizing should be performed at 100 °C to minimize friction and a moisture content of 11.2% to maximize density and compression strength of the pellets. Wood particles from sugar maple trees of low vigor were more suitable for making wood pellets in terms of friction in the pelletizer and compression strength than those from vigorous trees.
  • 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, Cecilia
    Densification 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.
  • 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, Benoît
    Thermochemical 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
    Restreint
    Determination of optimal wood-dowel welding parameters for two North American hardwood species
    (VSP, 2012-08-10) Cloutier, Alain; Stevanovic-Janezic, Tatjana; Pizzi, Antonio; Belleville, Benoît; Blanchet, Pierre
    Rotational wood-dowel welding has been shown to rapidly produce wood joints of considerable strength without any adhesive. The technique offers an opportunity to increase productivity and reduce costs in the furniture industry. The objective of the study was to define optimal wood-dowel welding parameters for two North American hardwood species frequently used for indoor appearance products: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). Optimized parameters for individually studied species were determined using a rotational wood-dowel welding machine designed for the technique. A comparative analysis of wood-dowel welding parameters was performed. The investigated parameters for both species were grain orientation, rotational speed, and insertion speed. Temperature profile measurements at the interface during rotational wood-dowel welding were also carried out. Optimal welding mechanical properties were determined from the dowel withdrawal strength using a standard tensile strength test. Results revealed a significant interaction between species, rotational speed, and insertion speed. Sugar maple produced wood joints with higher withdrawal strength than yellow birch. The best results for sugar maple and yellow birch were obtained with a rotational speed of 1000 rpm. A 25 mm s−1 insertion speed produced significantly stronger welded joints in sugar maple than at 12.5 mm s−1. For yellow birch, a 16.7 mm s−1 insertion speed provided the best results. Both species and rotational speed had a significant effect on peak temperature at the interface during welding. Peak welding temperatures with optimal parameters were 244 and 282 °C for sugar maple and yellow birch, respectively.
  • Publication
    Restreint
    Effects of hot water treatment of raw bark, coupling agent, and lubricants on properties of bark/HDPE composites
    (Elsevier Science Publishers, 2012-06-13) Cloutier, Alain; Soulounganga, Patrice; Stevanovic-Janezic, Tatjana; Koubaa, Ahmed; Ngueho Yemele, Martin Claude; Wolcott, Michael P.
    Hot water treated and untreated black spruce bark (BSB) and trembling aspen bark (TAB) fibers were combined with high density polyethylene (HDPE) to produce bark thermoplastic composites by extrusion. Bark fibers of three size categories (fine, medium, and coarse) were used at contents of 50% and 60% based on oven dry weight. The effects of hot water treatment of raw bark and the addition of coupling agent (MAPE) and lubricants (OP-100, talc) on the flexural and tensile properties of bark/HDPE composites were investigated. Results showed a significant impact of hot water treatment on tensile properties of composites made with BSB and on tensile and flexural strength of composites made with TAB. The addition of coupling agent and lubricants significantly improved the flexural and tensile strength properties of bark/HDPE composites but reduced toughness and strain.