At low temperatures, the powder is black and when heated to 1000°C it turns gray. Tantalum is a high melting point metal that has a melting point next to tungsten. Its stability to oxidants is higher than tungsten, similar to platinum. It slowly oxidizes in humid air, starts to oxidize when heated to 150-300°C, and accelerates to oxidation above 600°C, forming volatile Re2O7. It burns at 400°C to generate Re2O7 white smoke in oxygen atmosphere. And volatile.
Pure ammonium perrhenate can be obtained by reducing ammonia gas. The purity of hydrogen is greater than 99.9%, the hydrogen speed is 5 liters, and the reduction temperature is:
The first stage of 500 °C, insulation 1.5 hours;
The second stage, 800°C, holds 1.5 hours of incubation.
After the first stage of reduction is completed, the material is pushed until the cooling zone is cooled for 20 minutes, removed, ground in an agate mortar, and sifted through a 180-mesh sieve. After all sifting, the vessel is loaded into the furnace for the second stage of reduction. During the grinding, it is necessary to pay attention to the spontaneous combustion of the powder, after the second stage of reduction, under the protection of hydrogen in the furnace, after 20 minutes of cooling, it can be baked to obtain the powder.