关键词：
木材热处理;白蜡木;材色;傅里叶红外光谱分析;X射线光电子能谱分析
摘 要：
以白蜡木(Fraxinus americana)为试材,在常压过热蒸汽条件下进行热处理,对热处理材和对照材的明度(L*)和色度(a*,b*)指标进行比较,借助傅里叶红外光谱仪(FT-IR)和X射线光电子能谱仪(XPS)对试材细胞壁化学组分的主要基团和元素变化进行分析,以探索热处理对木材材色的调节机理。结果表明:随着处理温度的增加,热处理材和对照材的总体色差不断增大,色差值与木材内部C和O元素的浓度比高度相关,表明热处理材的材色能较为准确地指示木材内部化学组分的变化。热处理材的明度指标随热处理温度的升高呈阶梯式下降,明度值的变化与木材中羧基的浓度线性相关,表明半纤维素是影响热处理材明度的主要因素。热处理材的色度指标变化规律没有明度指标显著,随着处理温度的升高,a*值先增加后降低,试材的b*值随着处理温度的升高总体上呈下降趋势。热处理使木素中的羰基等发色基团数量发生变化,是使热处理材的色度指标发生变化的一个主要原因。
译 名：
Mechanism of color change of heat-treated white ash wood by means of FT-IR and XPS analyses
作 者：
DING Tao;PENG Wenwen;LI Tao;College of Materials Science and Technology,Nanjing Forestry University;
关键词：
wood heat treatment;;Fraxinus americana;;wood color;;Fourier transform infrared spectroscopy;;X-ray photoelectron spectroscopy
摘 要：
Heat treatment changes the color of wood and is considered a potential way for modifying the low-cost wood species to replace imported tropical hardwood.However,the color change of heat-treated wood and the mechanism behind it are still not fully understand.In this study,white ash(Fraxinus americana) was thermally treated at 190℃ or 210℃ with atmospheric steam.The lightness(L*),red/green color(a*) and yellow/blue color(b*) of the heattreated and the control samples were measured by using a colorimeter.The Fourier transform infrared spectroscopy(FT-IR) and X-ray photoelectron spectroscopy(XPS) analyses were applied to investigate the changes of the main functional groups and elements in the wood cell walls.The objective is to explore the underlying reasons for the heatinduced wood color changes.The results showed that the color difference between the control and heat-treated samples increased with the climbing treatment temperature and was negatively correlated with the ratio of element C to element O in the wood,indicating that color was an effective indicator revealing the chemical changes of wood components and can be used to predict the property changes of the heat-treated wood.The lightness of the heat-treated wood decreased significantly with the rise of treatment temperature,and showed a linear relationship with the carboxyl group content in the wood,indicating that hemicelluloses played an important role in determining the lightness of wood.Hemicelluloses were subjected to pronounced degradation during the heat treatment and the dark degradation products may contribute to the darkened appearance of the heat-treated wood.Contrary to lightness,the a* and b* values showed less clear change tendency after the heat treatment.The values of a* increased firstly and then decreased with the increasing treatment temperature.The values of b* declined with the rising of treatment temperature.These twocolor parameters were less influenced by the polysaccharides in the wood,and it was the reaction type and extent of lignin that greatly determined the color characteristics of the heat-treated wood.Heat treatment caused the change of the chromophoric groups in the lignin,such as conjugated carbonyl groups,and simultaneously induced the condensation reaction of the lignin.The color changes of the heat-treated wood were probably the results of these reactions.
