XPS characterization of wood chemical composition after heat-treatment

Abstract

XPS was used to characterize the chemical changes occurring after drying or applying a heat-treatment to beech wood samples. Our results indicate that the surface of this air-exposed material could be strongly affected either by the ambient atmosphere during storage or by the complex atmosphere in the oven during drying or heat-treatment. However, the O/C ratio measured after removal of a thin slice of a few millimetres of an untreated sample is in reasonable agreement with that calculated from the wellestablished chemical composition of beech. Through this methodology (equivalent to scraping for hard materials) it is expected to get a realistic characterization of the wood. The reliability and repeatability of the XPS measurements have been checked and the method applied to the study of the chemical changes of the beech samples subjected to heat-treatment. Heating at 240°C induces a significant decrease of the O/C ratio from 0.55 before to 0.44 after the treatment. Heat-treatment induces also a decrease of the C 2 carbon contribution (carbon atom bound to a single non-carbonyl oxygen) associated with an increase of the C 1 carbon contribution (carbon atoms bound only to carbon or hydrogen atoms), in agreement with chemical modifications reported previously in the literature. Thanks to the small analysed area of the equipment used in this study, different spots were analysed to demonstrate the presence or absence of a gradient of chemical composition due to thermal degradation or migration of extractives from within the wood structure to its surface. At the scale of our observations, the different wood samples investigated (dried or heat treated) appear to be homogeneous.

Changes in Surface Properties of Heat-Treated Phyllostachys pubescens Bamboo

“…Changes in chemical functional groups on the bamboo surface are an impetus for changes in bamboo surface free energy after heat treatment. XPS, which was used in these tests, is commonly applied to investigate the surface chemical composition of lignocellulose materials (Nguila et al 2006;Tuong et al 2011).…”

Surface Characteristics of Poplar Wood with High-Temperature Heat Treatment: Wettability and Surface Brittleness

“…The chemical or physical characteristics of wood surfaces affect the gluing and coating processes, while the decorative surface of wooden wares attracts consumers to purchase them. Existing studies have shown that chemical, physical, and structural properties of a heat-treated wood surface also change during heat treatment (Inari et al 2006;Popescu et al 2011;Popescu et al 2013;Li et al 2015). Wood surfaces turn out to be warmer and more attractive because of the formation of degradation products from hemicelluloses, changes in extractives, and the formation of oxidation products such as quinones (Dubey et al 2012;Wastiels et al 2012).…”

“…Mitsui et al (2008) studied the variation of the molecular structure of heat-treated wood using NIR spectroscopy and found that the hydroxyl groups in the cellulose became degraded in the following order: amorphous, semi-crystalline, and crystalline regions. XPS results showed that the oxygen/carbon ratio (O/C) of beech decreased from 0.55 before treatment to 0.44 after treatment at 240 °C (Inari et al 2006).…”

“…Nevertheless, the effect of heat treatment on the surface properties of plantation poplar timbers, especially wettability and surface brittleness, has rarely been studied. Wood surface changes can affect the distribution of adhesives on the wood surface, the penetration of adhesive into the porous wood structure, the curing of adhesives, and finally, the bonding strength (Boonstra et al 2006a,b;Inari et al 2006;Sernek et al 2007;Dilik and Hiziroglu 2012). Exact knowledge of heat-treated poplar wood's surface characteristics, including wettability, surface hardness, roughness, and abrasive resistance, is essential to optimize coating, painting, and gluing processes.…”

Chemical Analysis of Densification, Drying, and Heat Treatment of Scots pine (Pinus sylvestris L.) through a Hot-Pressing Process

“…High temperature treatment as a physical modification is achieved through the heat treatment of wood under high temperatures (160 to 250 °C) with lumber pyrolysis in shielded gas environments (Inari et al 2006;Boonstra et al 2007;Korkut et al 2008;Kocaefe et al 2013). This method effectively enhances the dimensional stability by relieving internal stress and improves the decay resistance (Park et al 2014).…”