Metal tungsten is a kind of non-ferrous metal, but it is not because metal tungsten has “color”, nor is it because tungsten has “appearance”.
Metal products are divided into non-ferrous metals and ferrous metals. Except for steel, manganese and other metals that are ferrous metals, the rest of the metals are non-ferrous metals; therefore, the so-called “non-ferrous” is to distinguish them from ferrous metals, even if they are white, such as silver, general Metal luster, such as tungsten molybdenum is also called non-ferrous metals.
Tungsten products have different colors or different appearances in different product stages.
Tungsten is a rare metal with a high melting point, which belongs to the VIB group of the sixth period (the second longest period) in the periodic table of elements. Tungsten is a silvery-white metal that looks like steel. Tungsten has a high melting point, low vapor pressure, and low evaporation rate. The chemical properties of tungsten are very stable, it does not react with air and water at room temperature, and it is insoluble in hydrochloric acid, sulfuric acid, nitric acid and alkali solutions. Aqua regia can only oxidize the surface and dissolve in the mixture of nitric acid and hydrofluoric acid. At high temperature, it can combine with chlorine, bromine, iodine, carbon, nitrogen, sulfur, etc., but not with hydrogen.
Natural tungsten ore comes in many colors.
- Wolframite: The colors are dark gray, light reddish brown, light brown black, brown and iron brown. Semi-metallic luster, metallic luster and resinous luster.
- Scheelite: the color is off-white, and there are also yellowish brown, green and light red. Greasy sheen.
Violet tungsten oxide is a powder that ranges in color from deep purple to pure purple. It is generally obtained by calcining ammonium paratungstate in a rotary kiln. There are differences in the morphology of purple tungsten oxide prepared under different parameter conditions. Among them, the color difference can be directly observed.
Violet tungsten oxide is made of ammonium paratungstate (APT), and is calcined in a rotary calciner. During the calcining process, an appropriate amount of NH3 is introduced to slightly reduce tungsten oxide to W02.72. During the preparation process, the furnace temperature, feed amount and furnace speed will all affect the properties of the product purple tungsten. Studies have shown that under the condition of constant process conditions, too high furnace temperature or too small feed amount and too long residence time of materials in the furnace may cause high WO2 phase content in purple tungsten oxide products; on the contrary, Then APT is not completely decomposed into purple tungsten oxide as W18049. Both the product phase composition and the degree of APT decomposition will affect the appearance and color of the product violet tungsten. The following is the result of detecting the phase formation of violet tungsten by colorimetry:
Depending on the specific preparation conditions, the appearance of violet tungsten changes between dark purple and pure purple, and purple is always the distinctive feature of the substance.
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