tailieunhanh - Volume 10 - Materials Characterization Part 3

Tham khảo tài liệu 'volume 10 - materials characterization part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Applicable to various samples including solids Relatively rapid and easy to learn Semiquantitative results can be obtained from many samples without use of standards most standards may be kept for long periods of time because most applications are for solids Instrumentation is relatively inexpensive Limitations Detection limits for bulk determinations are normally a few ppm to a few tens of ppm depending on the x-ray energy used and the sample matrix composition For thin-film samples detection limits are approximately 100 ng cm2 Not suitable for elements of atomic number less than 11 unless special equipment is available in which case elements down to atomic number 6 may be determined Capabilities of Related Techniques Inductively coupled plasma optical emission spectroscopy and atomic absorption spectrometry have better detection limits for most elements than x-ray spectrometry and are often better choices for liquid samples elements of low atomic number can be determined using these techniques X-ray spectrometry or x-ray fluorescence is an emission spectroscopic technique that has found wide application in elemental identification and determination. The technique depends on the emission of characteristic x-radiation usually in the 1 - to 60-keV energy range following excitation of atomic electron energy levels by an external energy source such as an electron beam a charged particle beam or an x-ray beam. In most sample matrices x-ray spectrometry can detect elements at concentrations of less than 1 pg g of sample 1 ppm in a thin film sample it can detect total amounts of a few tenths of one microgram. Initially x-ray spectrometry found wide acceptance in applications related to metallurgical and geochemical analyses. More recently x-ray spectrometry has proved valuable in the analysis of environmental samples in the determination of sulfur and wear elements in petroleum products in applications involving forensic samples and in measurements of electronic and .