Chromium particles

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Chromium has an atomic weight of 51.996, a density of 6.92, a melting point of 1890°C, and a boiling point of 2665°C; its evaporation temperature at a vacuum pressure of 1.3×10-2 Pa is 1157°C. Evaporation can be carried out by heating a conical basket or boat made of tungsten or tantalum; for small amounts of evaporation, a molybdenum boat can also be used for heating. Chromium granules are a type of sublimation material; when they evaporate in a vacuum, their surface oxidizes very easily. If an oxide film forms, it becomes difficult for them to evaporate from the surface. Therefore, sometimes chromium is electroplated onto as thick a tungsten wire as possible, and then the tungsten wire is heated in a vacuum to cause the chromium granules to evaporate. Chromium grains have good mechanical properties, and the chromium film deposited on a heated substrate bonds very firmly to the substrate. Taking advantage of this property of chromium films, extremely thin chromium films are often used as interlayer films, such as as underlying layers for Al and Au, to enhance the adhesion of these films to the substrate. Aitesi produces chromium granules, with the molecular formula Cr; they are mainly in granular form, appear light gray in color, and have a purity of 99.95% ； The commonly used particle sizes are 1-3 mm, 3-5 mm, and 5-10 mm.