基于氮气吸附法的古代丝织品纳米孔隙研究方法初探

Preliminary research on a new method for the nanoporous structure of ancient silk fabrics based on the nitrogen adsorption method

孔隙不仅是纤维骨架的一部分,也是外界物质进出的重要通道。目前,关于古代丝织品纳米孔隙结构的相关研究极少,仅有孔径一项评价指标,较为单一。实验采用红外光谱法和电子顺磁共振波谱法研究古代丝织品的降解特征,在此基础上采用低温氮气吸附法表征蚕丝纤维内部固有的孔隙结构,首次从孔形、孔径分布、比表面积、孔体积、平均孔径、分形维数等多个角度对古代丝织品的微观孔隙结构进行综合研究。研究结果表明:与现代丝织品相比,清代黄山样品、北宋南陵样品及战国郴州样品的劣化程度依次加深。孔结构分析显示,所有样品中同时含有狭缝形孔和圆筒形孔,孔隙具有连续性,表明蚕丝内部存在复杂的多级结构。其中,劣化程度较高的北宋和战国样品内部存在更多的大孔或开放性孔隙。Barrett-Joyner-Halenda(BJH)法和非定域密度泛函(NLDFT)法的研究结果显示,样品孔隙以介孔为主,孔径主要分布在20 nm以下,最可几孔径基本稳定在2.8 nm左右,为蚕丝内部的有序孔。比表面积和孔体积的研究结果表明,劣化程度较轻的黄山样品具有较高的比表面积,其孔体积的增加主要来源于小孔,南陵样品和郴州样品孔体积的增加主要来源于大孔。分形维数的结果显示样品中至少存在三种具有自相似性的孔隙结构,孔隙的复杂度由高到低依次为:黄山样品、现代样品、郴州样品和南陵样品。基于氮气吸附法的研究,初步建立起丝织品纳米孔隙评价指标,为古代丝织品文物孔隙结构的理论研究和保护策略的制定提供了新的视角。

Pores are not only a part of the fiber skeleton,but also an important channel for external substances to enter and exit.At present,there are few studies of the nanoporous structure of ancient silk fabrics,and the pore size is the only evaluation index,showing the lack of various evaluation indexes.In this study,the degradation characteristics of ancient silk fabrics were studied using infrared spectrometry and electron paramagnetic resonance(EPR)spectrometry.The low-temperature nitrogen adsorption method was used for the characterization of the pore structure within silk fibers,and the microscopic pore structure was studied with regard to pore shape,pore size distribution,specific surface area,pore volume,average pore size and fractal dimension.The results show that compared with modern silk fabrics,deterioration of the Huangshan sample(Qing Dynasty),the Nanling sample(Northern Song Dynasty)and the Chenzhou sample(Warring States Period)is more and more serious in sequence.Analysis of the pore structure shows that there are both cylindrical pores and slit pores in all the samples with a wide range of pore size distribution,indicating that the pore distribution is continuous and there are complex multistage structures in the silk fiber.Among these,the adsorption capacities of the Northern Song and Warring States samples are much higher than those of the modern and Qing Dynasty samples,suggesting that there are more macropores or open pores in them.The results of the Barrett-Joyner-Halenda(BJH)and nonlocal density functional theory(NLDFT)methods show that pores of the samples are mainly mesoporous,with the pore size mainly distributed below 20 nm and the inherent aperture inside the silk fiber being about 2.8 nm.The data of specific surface area and pore volume show that the Huangshan sample with less deterioration has a higher specific surface area and the increase of its pore volume mainly comes from small pores,while the increases of pore volume of the Nanling and Chenzhou samples mainly come from large pores.In addition,the data of fractal dimension show that there are at least three kinds of self-similar pore structures in the samples and the order of pore complexity from high to low is the Huangshan,modern,Chenzhou and Nanling samples.According to the nitrogen adsorption method-based research,nanoporosity evaluation indexes of silk have preliminarily been established,which provides a new perspective for the theoretical research on the pore structure of ancient silk fabrics and the formulation of conservation strategies.