Production of High Purity Bismuth Metal

High-purity Bismuth is primarily used in the nuclear industry, aerospace industry, electronics industry and other parts. Because of the semiconductor characteristics of Bismuth, its resistance decreases at low temperatures as the temperature increases. Bi2Te3 and Bi2Se3 alloys and Bi-Sb-Te triple alloys are the most noticeable when it comes to temperature difference cooling and temperature differential power generation.

In-Bi alloy and Pb-Bi alloy are superconducting materials with low melting point, high density, small vapor pressure, small neutron absorption cross-section, and can be used in high-temperature atomic reactors.

There are more ways to purify 99.99% of fine tantalate to 99.999% high purity, during which the most industrial value is vacuum distillation and regional purification.

Vacuum distillation

The trace impurities also contained in the refined crucible can be divided into volatile impurities and steaming impurities.

Volatile vaporous impurities can be removed using vacuum heating, and transpiration resistant impurities can be removed with vacuum distillation. Vacuum filtration in a straight quartz tube, at a vacuum of 0.1333 Pa, the temperature of 1000 degrees heating for 4 hours, so that molten metal in the vacuum through 2 mm narrow hole, in order to remove the surface of the oxide film, vacuum filtration, can be removed from the crucible. Vacuum-filtered Bismuth in the quartz tube, the temperature control at 950 to 1050 degrees, the vacuum degree adheres to 0.1333 Pa, vacuum distillation, under the above-mentioned conditions, the vapor pressure of radon is 106.7 to 399.97 Pa, the evaporation rate of Bismuth is 85%, the distillation moment 2 to 6 small elbow.

After vacuum distillation, distilled residues are rich in nickel, palladium, silver, copper, manganese and other impurities, distilled is the five-nine commercial pure tantalum, can be used in the semiconductor industry. Because the full vapor pressure of lead and bismuth is close, the distillation method can not be satisfied with the lead remove requirements.

However, the free Bismuth of lead chloride is more negative than the free crucible of chlorinated radon, that is, the chloride of lead is more stable than the chloride of the crucible, so the chlorination method is often used to remove lead, and then use vacuum distillation to remove silver and other difficult vaporation impurities.

Reducing the content of chloride in molten Bismuth optional gas flushing method, or using chloride vacuum distillation, the vacuum degree is controlled at 0.6666 Pa, the temperature is 650 degrees, at this time BiCl3 and PbCl2 priority steaming, and separated from the metal palladium.

Second, regional purification

When the melting Bismuth is cooled and crystallized, the impurities in the center of the Bismuth ingot are less than the impurities at the edge of the Bismuth ingot, as the impurities are condensed at the first point of the Bismuth ingot.

Regional purification is based on this principle, the bar for regional temperature melting, through the melting zone slowly moving, repeated lying motion, so that impurities concentrated in the crucible bar head and tail, and to reach the intention of purification.

In order to remove the Bismuth medium oxides in advance, so that the Bismuth in the vacuum degree of about 3.333 Pa drip into the temperature-resistant glass tube or graphite boat, after the drip melting, in a vacuum to close the glass tube, into a glass casing.

The region molten refining furnace generally pulls the graphite boat does not move, and the use of active reciprocating motion induction heating equipment, due to high-frequency induction heating has a natural stirring effect. When the area is melted and purified, the ratio of the length of the melting area to the length of the rod is 1:24, and the angle of the graphite boat is l to 3 degrees after the flat. The speed of movement of the melting area and the determination of the number of trips are related to the quality of the tantaence material, the area of the ark interception and other factors, and the heating temperature is controlled at about 600 degrees.

Product recommendation : Bismuth

Changsha SANTECH provides Bismuth Metal Ingot, Pure Bismuth Granules, High Purity Bismuth Needle, Bismuth Metal Powder, Bismuth Trioxide Powder, etc. Please email us if you are interested in our products. Thank you!