Abstract
I HAVE succeeded in showing recently that the comparatively coarse particles of any powder are suitable for structure investigation by means of electron diffraction1. For this purpose a mineral or other substance is ground carefully in a small mortar. The powder obtained is placed in a sedimentation air tube like that described by Gonell2. When blowing the slow jet of air through the heap of powder disposed at the bottom of this sedimentation tube, only the coarsest particles will return, while the minute ones will move with the air blast to the top of the tube where there is a big receiver. By placing there a suitable holder, for example, a loop of wire with a thin celluloid film for the transmission method, or a support for the reflection method, one can collect the particles, the sizes of which depend on the speed of the air blast. It is possible also to collect the smallest particles at the bottom of the tube. For this purpose it is necessary to blow the air for a few minutes only until the smoke appears at the top of the tube, and then to wait, in the case of a tube of one metre in length, in general about 10–15 minutes. Then all particles larger than 0.1–1.0 in size are precipitated at the bottom of the tube, the remaining being still suspended in the air. To collect the latter on the holder it is sufficient to wait in the case mentioned above about half an hour, after which the process had to be repeated a few times to accumulate a layer of sufficient thickness. It may be noted that the diffraction haloes from the celluloid film disappear completely only when the layer is thick enough. In this way I have obtained sometimes sufficiently clear diffraction patterns from specimens, which were otherwise quite unsuitable for electron diffraction, for example, ignited magnesia, sand, cements and tripolites. Mrs. L. I. Tatarinowa has proposed another method for preparing the specimens by drying on the celluloid film a drop of liquid with a fine suspension of the substance to be studied. This method, which gives sometimes excellent specimens for electron diffraction, has an especial advantage in that it requires only the minutest portion of substance. I have used successfully both these methods.
Similar content being viewed by others
Article PDF
References
C. R. Acad. Sci. U.S.S.R., No. 7–8, 461, March 1935.
Tonindustrie Z., No. 13, 243; 1929.
Phys. Rev., 47, 331; 1935.
Z. Krist., 75, 196; 1930.
Phys. Rev., 45, 657; 1934.
Z. techn. Phys. (Russian).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
SHISHACOW, N. Electron Diffraction by Vitreous Silica Powder. Nature 136, 514 (1935). https://doi.org/10.1038/136514a0
Issue Date:
DOI: https://doi.org/10.1038/136514a0
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.