Standard Reference Materials:Homogeneity Characterization of NBS Spectrometric Standards II:Cartridge Brass and Low-Alloy Steel

摘要

Most modern instrumental methods of analysis depend on the use of known standards of composition for cali¬bration. Newer analytical techniques such as the solids mass spectrometer, laser probe and, especially, the electron probe microanalyzer have reduced the amount of a sample which can be analyzed quantitatively to a range of about 0.1 micrograms to as little as 0.00005 micro¬grams. As a corollary to these microanalytical advances, homogeneity requirements have become severe for the analytical standards. This paper describes a continu¬ation of the NBS effort to more fully characterize existing standards as to suitability for the new micro-analytical techniques [1], An NBS cartridge brass sample in both the wrought (NBS-1102) and chill cast forms (NBS-C1102), as well as an NBS low-alloy steel sample (NBS-463), have been investigated by means of electron probe microanalysis and optical metallography. Some seventeen elements are contained, in the brass while twenty-five elements are in the steel. Results for ten elements in the steel are presented while results for six elements in the brass are given. In the steel, Fe, Ni, Cu, and Si are essentially distrib¬uted homogeneously at micron levels while Mn, Ta, Nb, Zr, S, and Cr are not. In the brass, Cu and Zn are distributed homogeneously at micron levels while Pb, S, Al, and Si are not. Electron probe microanalyzer results indicate that both NBS-1102 and NBS-C1102 brass are suit¬able for use as a calibration standard for electron probe microanalysis as well as other microanalytical techniques such as the solids mass spectrometer. The results for brass have been corroborated by a number of laboratories using the electron probe analyzer.