考古木材的保存保护需要基于其主要化学组分的降解状况, 制定科学的保护方案, 如加固剂的选用、 处理时间与温度的控制等。 选取徐州万达汉代墓群出土四个棺木作为样品; 经鉴定, 树种分别为硬松（Pinus subgen. Diploxylon sp.）、 楠木（Phoebe sp.）、 梓木（Catalpa sp.）和榉木（Zelkova sp.）。 采用衰减全反射傅立叶红外光谱及热重分析, 快速表征考古木材和对应现代材的化学性质和热解特性。 研究结果表明: 考古硬松、 考古楠木、 考古梓木以及考古榉木的红外光谱中1 730 cm-1附近来自于半纤维素乙酰基上CO伸缩振动的吸收峰几乎消失, 而1 500 cm-1附近木素苯环骨架伸缩振动吸收峰的相对峰强提高, 这反映出古木半纤维素降解严重, 而木素留存较好。 古木综纤维素样品中均未发现半纤维素中酰氧键（—COO）位于1 238 cm-1附近的特征峰, 而除现代楠木综纤维素外, 其余现代材综纤维素红外谱图中均检测到此峰, 这表明与纤维素相比, 古木中半纤维素降解更严重, 也说明楠木的半纤维素含有较少的酰氧键。 与古木酸不溶木素样品相比, 现代健康材酸不溶木素1 459 cm-1附近甲基与亚甲基的C—H弯曲振动的吸收峰强度较高, 说明现代健康材酸不溶木素中有更多的甲基与亚甲基, 木素大分子中含有更多的侧链。 古木酸不溶木素的红外谱中1 028 cm-1附近的木素中仲醇与脂肪醚结构的吸收峰强度低于现代材, 说明古木的酸不溶木素含有较少的C—O键。 比较不同树种古木和现代材的热解行为, 发现古木热解速率均减缓, 快速热解段起始温度提前, 残炭率提高。 古木与现代材热解行为的差异, 主要与古木综纤维素大量降解, 木素相对含量的提高有关。 在4个古木样品中, 考古楠木的残炭率最低, 这表明考古楠木木素相对含量较低, 综纤维素保存较好, 其天然耐久性在4个树种中最好。 此外, 由于古木酸不溶木素中含有较少的侧链以及甲氧基使得其热解速率变慢。 以上结果表明, 红外光谱与热重分析均可用于分析考古木材的降解状况, 能为及时制定文物保护方案提供科学依据。

The conservation and protection of archaeological wood requires scientific protection schemes based on the knowledge of the main chemical components degradation process, such as the selection of reinforcements, treatment time and temperature. In this paper, four coffin samples were selected, which were excavated from Xuzhou Wanda Han dynasty tombs. These wood samples were identified as four different wood species, namely the hard pine (Pinus sp.), phoebe (Phoebe sp.), catalpa (Catalpa sp.) and zelkova (Zelkova sp.). By Attenuated Total Reflection Fourier Transform IR (ATR-FTIR) and Thermal Gravimetric Analysis (TGA), the chemical properties and fast pyrolysis behavior of the archaeological wood and corresponding sound woods are characterized. The results showed that the absorption peaks of CO stretching vibration from the acetyl group in the infrared spectrum of the archaeological pine, phoebe, catalpa and zelkova almost disappeared near 1 730 cm-1, while the relative peak intensity of the lignin benzene ring skeleton around 1 500 cm-1 was increased. These results reflect the serious degradation of hemicellulose in archaeological wood, while lignin preserved better. The absorption peak of acyloxy bond (—COO) at 1 238 cm-1 in hemicellulose was not found in the samples of archaeological wood holocellulose, but it was detected in the infrared spectra of all modern wood holocellulose except modern phoebe holocellulose, which indicated that the hemicellulose in archaeological wood suffered degradation more seriously than cellulose, and this result indicated that the acyloxy bonds content in phoebe hemicellulose was low. Compared with the acid-insoluble lignin samples of archaeological wood, the intensity of absorption peak near 1 459 cm-1 (methyl and methylene C-H bending vibration) is stronger than that of archaeological wood, indicating that there are more methyl, methylene and side chains in acid-insoluble lignin of modern wood. In the ATR-FTIR spectra of archaeological acid-insoluble lignin, the absorption peak intensity of lignin in the vicinity of 1 028 cm-1 is lower than that of modern health wood, indicating that the acid-insoluble lignin of archaeological wood contains few C—O bonds. Comparing the pyrolysis behavior of archaeological wood and referenced wood of different tree species found that the archaeological wood has slower pyrolysis rate, low initial temperature of the rapid pyrolysis stage and higher residue mass. The difference in pyrolysis behavior between archaeological wood and modern wood is mainly related to the massive degradation of holocellulose and the increase of relative lignin content in the archaeological wood. Among the four archaeological wood samples, the residual mass rate of archaeological phoebe is the lowest, which indicates that the relative content of lignin in archaeological phoebe is lower and holocellulose preserved better. Hence, its natural durability is the best among the four tree species. In addition, the pyrolysis rate of archaeological acid-insoluble lignin is slower than reference acid-insoluble lignin due to the low amount of side chains and methoxy groups. The above results show that both infrared spectroscopy and thermogravimetric analysis can be used to analyze the degradation progress of archaeological wood, and provide a scientific basis for the timely conservation of cultural relic.