A significant change is reported in mean particle size and shape characteristics of carbon black due to specimen contamination while under examination in electron microscopes. The effect is described for a number of well‐known commercial blacks and examples are given in graphical form to illustrate expected variations in mean particle size with continued bombardment at normal focusing intensities. The effect is observed in other materials but is more pronounced in carbon black. Suggestions are made for minimizing the effect.
End of preview. The entire article is 9 pages. Rent for Free