Abstract
Heretofore the observation of grain boundaries with the field emission microscope has been limited by the accidental and infrequent appearance of suitable specimens. A process for preparing polycrystalline tungsten samples by bending a tungsten wire, etching a tip at the bend and heating is described. Both large and small angle grain boundaries result. As many as five tungsten grains may share a cross section of less than one micron in diameter. All the parameters required to describe the geometry of the boundaries may be obtained experimentally. Detailed observations on the dislocation structure of boundaries with angles as great as 6° are potentially possible. However, the field emission intensity from the region immediately adjoining and including the grain boundary must first be increased appreciably. Possible methods for achieving improved electron emission from the grain boundary region are discussed.
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