Study on the properties and process of rhenium powder prepared by hydrogen reduction

Rhenium powder is prepared by hydrogen reduction in a tubular push-boat furnace using ammonium perrhenate. The effects of process parameters, including ammonium perrhenate particle size, reduction temperature, hydrogen flow rate, and boat loading amount, on rhenium powder morphology, particle size, and oxygen content are investigated.Furthermore, vacuum deoxidation treatment is performed on the rhenium powder, and the effects of reduction temperature on its metallic impurity content are analyzed.The results show that after primary hydrogen reduction at 350 ℃, ammonium perrhenate is primarily converted into rhenium powder,with only trace amounts of intermediate oxides remaining; after secondary reduction, ammonium perrhenate is completely transformed into rhenium powder.Ammonium perrhenate undergoes significant particle refinement during reduction; however,the particle size of the rhenium powder primarily depends on that of the raw ammonium perrhenate.Rhenium powder prepared from medium and large-sized ammonium perrhenate mainly consists of irregular flaky particles, along with a small amount of fine particles.Ultra-fine ammonium perrhenate (approximately 5 μm) yields rhenium powder composed of micro-nano particles after reduction.Reduction temperature is the primary factor affecting the oxygen content in rhenium powder; as the reduction temperature increases, oxygen content in rhenium powder decreases. However, higher reduction temperature also enhances the tendency of rhenium powder to sinter and agglomerate. To obtain rhenium powder with lower oxygen content, vacuum degassing is performed on the rhenium powder in a vacuum furnace, where oxygen content is reduced by reducing the oxygen partial pressure in the furnace atmosphere.Under a vacuum pressure below 10?3 Pa, the secondary reduced rhenium powder (0.160% O) is treated at 900 °C for 2 h, lowering its oxygen content to 0.063%. During the high-temperature reduction of ammonium perrhenate, impurities from the furnace tube and boat may be introduced into the rhenium powder. The content of metallic impurities in the rhenium powder is independent of the reduction temperature and remains extremely low.