National Institute for Occupational Safety and Health

“ The settled dust may be ground and/or wet sieved to best match the airborne dust exposure. Wet-sieving is done with a 10-μm sieve, 2-propanol, and an ultrasonic bath, followed by evaporation of excess alcohol, drying in an oven for 2 h, and overnight storage in a dessicator. Deposit the end product on a filter or pack in a conventional XRD powder holder and follow step 10. NOTE: For quantitative determination of percent boron carbide, weigh out, in triplicate, 2 mg of the respirable or sieved dust, transfer to a 50-mL beaker, add 10 mL 2-propanol, and continue with steps 6 and 7. ”

“ Calculate the normalized intensity, Îx = I x · N/I r. Determine the net normalized intensity, ˆI Ag , of an interference-free silver peak on the sample filter following the same procedure. Use a short scan time for the silver peak (e.g., 5% of scan time for analyte peaks) throughout the method. Scan each field blank over the same 2- θ range used for B 4C and silver peaks. These analyses serve only to verify that contamination of the filters has not occurred. The analyte peak should be absent. The normalized intensity of the silver peak should match that of the media blanks. ”

“ The primary titanium diboride peak interferes with the secondary silver peak. Niobium oxide interferes with the tertiary boron carbide peak. Silver chloride, found as an impurity in the silver filter, may interfere with some low-intensity boron carbide peaks. When peak overlaps are not severe, a smaller receiving slit or chromium X-radiation may be used; however, a new calibration graph will be necessary. The presence of some elements in the sample (iron, in particular) can result in appreciable X-ray fluorescence, leading to high background intensity. ”