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Experiments with Alternate Currents of High Potential and High Frequency by Nikola Tesla
page 80 of 127 (62%)
carborundum coating seems to be more durable than other coatings, not
only because the carborundum can withstand high degrees of heat, but
also because it seems to unite with the carbon better than any other
material I have tried. A coating of zirconia or any other oxide, for
instance, is far more quickly destroyed. I prepared buttons of diamond
dust in the same manner as of carborundum, and these came in
durability nearest to those prepared of carborundum, but the binding
paste gave way much more quickly in the diamond buttons: this,
however, I attributed to the size and irregularity of the grains of
the diamond.

It was of interest to find whether carborundum possesses the quality
of phosphorescence. One is, of course, prepared to encounter two
difficulties: first, as regards the rough product, the "crystals,"
they are good conducting, and it is a fact that conductors do not
phosphoresce; second, the powder, being exceedingly fine, would not be
apt to exhibit very prominently this quality, since we know that when
crystals, even such as diamond or ruby, are finely powdered, they lose
the property of phosphorescence to a considerable degree.

The question presents itself here, can a conductor phosphoresce? What
is there in such a body as a metal, for instance, that would deprive
it of the quality of phosphorescence, unless it is that property which
characterizes it as a conductor? for it is a fact that most of the
phosphorescent bodies lose that quality when they are sufficiently
heated to become more or less conducting. Then, if a metal be in a
large measure, or perhaps entirely, deprived of that property, it
should be capable of phosphorescence. Therefore it is quite possible
that at some extremely high frequency, when behaving practically as a
non-conductor, a metal or any other conductor might exhibit the
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