摘要: 目的探究考古木材与现代木材在水分吸附热力学方面的不同及原因，旨在提高出土饱水木质文物的尺寸稳定性，可以为出土饱水考古木材的保护研究提供理论依据、�/sec> 方法以古代与现代柏木为研究对象，分别采用扫描电子显微镜和傅里叶红外光谱表征试材的微观形貌和化学基团；利用动态水分吸附分析分别测�?5�?0 ℃下的试材吸湿和解吸等温吸附曲线，并基于Hailwood-Horrobin水分吸着理论进行拟合，结合Clausius-Clapeyron公式分别计算试材的微分吸着�?i>Q _S、自由能变化Δ G及微分吸着熵Γ�i>S，分析考古试材与现代试材在吸附热力学量的差异、�/sec> 结果与现代木材相比，考古木材的细胞壁腐朽明显，产生大量细胞壁孔洞，并有菌丝体的存在。考古木材纤维素、半纤维素降解严重，而木质素相对含量升高，且极性基团−OH、−COOH含量减少。在一定温度下，考古木材的平衡含水率大于现代木材，耋�i>Q _S、Γ�i>S值均低于现代木材，并在含水率5%处产生拐点，该拐点对应单分子层吸着水达到饱和；另一方面，考古木材和现代木材的Δ G值差异不大；考古木材在吸湿平衡态下 Q _S、Γ�i>G�?/i>Δ S值小于解吸平衡态的值、�/sec> 结论考古木材在经历长时间腐蚀后，细胞壁结构产生腐朽；与现代木材相比，考古木材纤维素、半纤维素降解程度最大，考古木材对水分的吸着减少；考古木材的吸湿性大于现代木材，而热力学值偏低；考古木材存在热力学吸湿滞后现象、�/sec>

关键诌�
• 考古木材/
• 柏树/
• 微观结构/
• 水分/
• 吸附热力�?/a>

Abstract: ObjectiveThis research was carried out to explore the differences and reasons of moisture sorption thermodynamics between archaeological wood and recent wood, and provide a theoretical basis for the protection and research of excavated archaeological wood, and be conducive to improving the dimensional stability of the unearthed moisture-saturated wooden relics. MethodAncient and recent cypress ( Cupressussp.) were used as research objects, and the microscopic morphology and chemical groups of the wood samples were characterized by scanning electron microscope and Fourier transform infrared spectroscopy, respectively. The adsorption and desorption isotherms for both wood at 25 and 50 � were measured by dynamic vapor sorption, and fitted based on the Hailwood-Horrobin moisture sorption theory. The differential adsorption heat Q _S, Gibbs free energy change Δ Gand differential adsorption entropy Δ Sof the wood samples were calculated by Clausius-Clapeyron formula to analyze the discrepancy of sorption thermodynamics between archaeological and recent wood. ResultCompared with recent wood, the cell wall of archaeological wood was decayed obviously. A large number of cell wall pores and mycelia were found. The cellulose and hemicellulose were degraded seriously with increased relative content for lignin. The content of polar group −OH and −COOH decreased. Under certain temperature conditions, the equilibrium moisture content of archaeological wood was higher than that of recent wood, while the values of Q _Sand Δ Swere lower than that of recent wood, and an inflection point occurred at the moisture content of 5%, corresponding to a saturation of the monolayer water. On the other hand, there was little difference in Δ Gbetween archaeological wood and recent wood. The values of Q _S, Δ Gand Δ Sof archaeological wood in hygroscopic equilibrium state were lower than those in desorption equilibrium state. ConclusionIn this study, it was found that the cell wall structure of archaeological wood decayed after a long time of corrosion. Compared with recent wood, the degradation degree of cellulose and hemicellulose in archaeological wood was the greatest. And the moisture sorption of archaeological wood reduced. Under certain temperature conditions, the hygroscopicity of archaeological wood was higher than that of recent wood, but its thermodynamic values were lower. There were thermodynamic sorption hysteresis of archaeological wood.

Key words:
• archaeological wood/
• Cupressussp./
• microstructure/
• moisture/
• sorption thermodynamics

�?nbsp; 1考古木材和现代木材的SEM国�/p>

Figure 1.SEM images of archaeological wood and recent wood

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�?nbsp; 2考古木材与现代木材的红外光谱国�/p>

Figure 2.FTIR spectra of archaeological wood and recent wood

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�?nbsp; 3考古木材与现代木材在1 550 ~ 1 800 cm^�?（a）�? 200 ~ 1 550 cm^�?（b）�?50 ~ 1 200 cm^�?（c）波数范围内的分峰拟合曲纾�/p>

Figure 3.Deconvolution of the “fingerprint� region for archaeological wood and recent wood FTIR spectrum 1 550 � 1 800 cm^�?(a), 1 200 � 1 550 cm^�?(b), 850 �? 200 cm^�?(c)

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�?nbsp; 4考古木材与现代木材的等温吸附曲线

Figure 4.Adsorption isotherms of archaeological wood and recent wood

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�?nbsp; 550 ℃下考古木材的吸湿和解吸等温吸附曲线

Figure 5.Adsorption and desorption isotherms of archaeological wood at 50 ℂ�/p>

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�?nbsp; 6考古木材与现代木材中水分的微分吸着热（Q_S）随含水率（MC）的变化曲线

Figure 6.Variation curves of differential heat of sorption (Q_S) of moisture in archaeological wood and recent wood against moisture content (MC)

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�?nbsp; 7考古木材（a）与现代木材（b）中水分的自由能变化（Γ�i>G）随含水率的变化曲线

Figure 7.Variation curves of free energy change (ΔG) of moisture in archaeological wood (a) and recent wood (b) against moisture content

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�?nbsp; 8考古木材与现代木材中水分的微分吸着熵（ΔS）随含水率的变化曲线

Figure 8.Variation curves of differential entropy of sorption (ΔS) of moisture in archaeological wood and recent wood againstmoisture content

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�?nbsp; 950 ℃下考古木材吸湿与解吸过程中皃�i>Q_S（a）、Γ�i>G（b）、Γ�i>S（c）随含水率的变化曲线

Figure 9.Variation curves ofQ_S(a), ΔG(b), ΔS(c) in archaeological wood against moisture content during moisture adsorption and desorption at 50 ℂ�/p>

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�?nbsp; 1考古木材、现代木材在25�?0 ℃下不同相对湿度下的吸湿滞后

Table 1.Moisture sorption hysteresis of archaeological wood and recent wood under different relative humidities at 25 and 50 ℂ�/p>

相对湿度 Relative humidity	滞后� Hysteresis rate
	25 ℃考古木材 25 �?archaeological wood	50 ℃考古木材 50 �?archaeological wood	25 ℃现代木杏�br/>25 �?recent wood	50 ℃现代木杏�br/>50 �?recent wood
0.1	0.62	0.74	0.63	0.71
0.2	0.63	0.72	0.64	0.73
0.3	0.64	0.72	0.65	0.74
0.4	0.66	0.73	0.67	0.76
0.5	0.68	0.75	0.70	0.78
0.6	0.71	0.77	0.73	0.81
0.7	0.76	0.81	0.77	0.84
0.8	0.82	0.86	0.84	0.89
0.9	0.91	0.94	0.93	0.95

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