摘要
为了真正实现古陶瓷完整器的元素成分无损分析,就要建造能容纳常规大小古陶瓷样品的真空靶室,以及建立弯曲表面古陶瓷的定量分析方法。本文报道了本实验室QuanX型能谱仪真空靶室改造的整体设计和加工,以及针对弯曲表面古陶瓷样品定量分析的处理方法。大量的测量工作表明所改装的能谱仪完全适应古陶瓷完整器的元素成分无损分析的需要,同时证明古陶瓷样品在较低真空条件下的测量分析是完全无损的;所提出表面弯曲古陶瓷的定量分析处理方法具有简便易行,精确度较高的特点。
This article mainly describe the whole design of vacuum chamber connected to the QuanX model ED - XRF and the quantitative analysis method to the samples with curve surface, which are two major difficulties in the project of non - destructive analysis on intact porcelain vessel.
The first change in the equipment is out of our own design, but completed in the factory of TN Spec-trace Company, which can guarantee the analysis of porcelain vessel with any dimension in air condition. The varied instrument is regarded as a standard new type product due to the reasonable design; it is still far from ideal analysis with elements Na and Mg unable to be detected.
The design of the vacuum chamber was based on volume consideration; it is better to find the balance between analysis requirement and cost together with technical difficulty. It should be noticed that the cost will soar at the chamber volume of about 40cm × 40cm × 40cm, because the vacuum chamber has to be established in new structure to ensure the safety at that volume, furthermore some other technical problem may also emerge due to the big volume. On the other hand, a statistic on volume distribution was made to be sure that more than 90 percent porcelain vessels have the volume less than 40cm × 30cm × 35cm quantitatively. Thus a chamber with 40cm x 30cm x 37cm volume is designed for non - destructive analysis.
The big vacuum chamber can just make it possible to perform non - destructive analysis on intact porcelain vessel, some assistant gadgets are also designed to make the analysis convenient, such as: a camera is fixed to watch the analyzed sample surface; a shank can draw the sample frame within 10 cm range, thus offer the possibility of linear scanning analysis for some special samples; a watching window not only offer observation of sample but also guarantee the safety of putting sample vessel into the chamber.
XRF techniques are usually used for the manufacture in industry, there in nearly no sample with curve surface in those analyses, thus the quantitative analysis on the sample with curve surface was ig- nored before. With the development of scientific researches on ancient ceramics, some methods were proposed to give quantitative analysis on samples with curve surface, but limited quantitative effect can be got.
By careful examining the formula of XRF calculation, it is found that the content C; calculated from intensity may greatly differ from the content C/ gained from the convergence formula due to curve surface, so that the fundamental parameter method can hardly be applied to those sample with curve surface. If the factor A used in C; calculation formula is replaced by A'varying with convergence condition, the further calculation can be easily processed.
If EC method is employed in calculation, a new spectra process is proposed to complete the quantitative analysis on the sample with curve surface. Since the total content of Al and Si can be usually more than 90% in most samples, there are almost equal peak area counts in different ancient porcelain samples. The spectra of ancient porcelains with curve surface can be normalized to the spectra with normal surface, the intensity obtained form the normalized spectra are used to get the analysis results. To achieve better quantitative results, it should be normalized to 100% .
With both methods, rather satisfied results were obtained on the sample with curve surface.
By enlarging the volume of vacuum chamber, adding some assistant accessories, improving the quantitative analysis on porcelain sample with curve sample, a set of new measuring system is established . The intact ancient porcelain vessels can be totally non - destructively analyzed in relatively low vacuum, which is proved by hundreds of analyses on various kinds of ancient porcelain vessels.
出处
《文物保护与考古科学》
2002年第B12期284-297,共14页
Sciences of Conservation and Archaeology
基金
国家文物局文物科研项目
编号:200011
关键词
无损分析
古陶瓷
靶室
X荧光分析
Non-destructive analysis, Ancient porcelain, Vacuum chamber, XRF
