A low-cost, efficient, and industrially feasible pathway for large scale preparation of tungsten nanopowders. (January 2019)

• Record Type: Journal Article
• Authors: Sun, Guo-Dong; Wang, Kai-Fei; Song, Cheng-Min; Zhang, Guo-Hua
• Is Part Of: International journal of refractory metals & hard materials. Volume 78(2019)
• Page Start: 100
• Page End: 106
• Publication Date: 2019-01
• Subjects: Tungsten -- Nanopowders -- Carbothermic reduction -- Hydrogen reduction -- Low cost -- Industrial feasibility; Heat resistant alloys -- Periodicals; Refractory materials -- Periodicals; Metallography -- Periodicals; Alliages réfractaires -- Périodiques; Matériaux réfractaires -- Périodiques; Métallographie -- Périodiques; Heat resistant alloys; Metallography; Refractory materials; Periodicals; Electronic journals; 669.73
• DOI: 10.1016/j.ijrmhm.2018.08.013
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: Tungsten (W) is the most commonly used high-temperature refractory metal in many critical fields such as aerospace, military and electronic industries etc. This paper proposes a low-cost, efficient, and industrially feasible pathway for large scale preparation of tungsten nanoparticles via the combination of carbothermic reduction and hydrogen reduction processes. The new strategy involves the preparation process of pre-reduction W powder by reducing commercial WO3 with insufficient carbon black at 1050 °C or 1150 °C to avoid the residue of carbon, and the deep reduction process of pre-reduction W powder by hydrogen 725 °C. By this process, most of the oxygen in WO3 was reduced by carbon, and W particles with a much smaller size could be obtained owing to the absence of the volatile tungsten oxide, such as WO2 (OH)2, which leads to the serious increase of particle size during the hydrogen reduction process. Tungsten nanoparticles with average particle sizes of about 40 nm and 75 nm have been successfully synthesized at 1050 °C and 1150 °C, respectively, with the residual carbon content as low as about 0.01%. This process can be readily extended to a large-scale industrial production of W nanopowders. Additionally, this new strategy has great potential to prepare other pure metals (or nanopowders) from their metal oxides via combining of carbothermic reduction (main process) and further reduction of other reducing agents. Highlights: Pre-reduced nano W powders were prepared by reducing WO3 with insufficient carbon. Growth of W nanoparticles can be controlled in carbothermic reduction process. A minor amount of remained WO2 can reduce the residual carbon to as low as 0.01%. A deep deoxidation by H2 at 725 °C could reduce the minor amount of WO2 to W.