Director Standard Reference Materials : Homogeneity Characterization of NBS Spectrometric Standards IV : Preparation and Microprobe Characterization of W-20 % Mo Alloy Fabricated by Powder Metallurgical Methods
A significant problem of the National Bureau of Standards Standard Reference Materials program is the provision of standards suitable in homogeneity for use with microanalytical techniques such as the spark source mass spectrograph and the electron probe microanalyzer. An interim approach to the problem has been the extended homogeneity characterization of selected existing standards. This paper describes the preparation and evaluation of the first NBS standard tested specifically from the beginning for application to electron probe microanalyzers. The standard designated SRM 480 is a tungsten-20 weight percent molybdenum alloy prepared by a powder metallurgy process. Based on the results of about 1500 determinations for both tungsten and molybdenum by electron probe microanalysis, the material was found to be of high homogeneity at about the micrometer level of spatial resolution. The coefficient of variation for molybdenum was 2.5% and that for tungsten 1.5%. Correction of relative intensity ratios to obtain concentrations is discussed in terms of input parameter uncertainties such as mass absorption coefficients, and electron backscatter factors. The result of studies for atomic number correction and effects on operating voltage on the microprobe absorption correction., will be given. It is concluded that SRM 480 should be a valuable addition to any microprobe laboratory doing quantitative analysts.
NIST Standards for Microanalysis and the Certification Process
The National Institute of Standards and Technology (NIST) has been involved in the development of standards for microanalysis since the middle of the 1960s. Certification of “traceable” standards that can be sold to other laboratories is time-consuming and costly, especially when the extent of microheterogeneity within each specimen becomes part of the uncertainty assigned to the certified values. The process of certification of microanalysis standards and the improvements that have facilitated the process with the development of automation and computerization are reviewed.
XCIII. The high-frequency spectra of the elements
(1913). XCIII. The high-frequency spectra of the elements. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science: Vol. 26, No. 156, pp. 1024-1034.