# Preparation of Ultrafine W Powder via H2 Reduction of Carbon-Containing WO3: Influences of Reduction Temperature and C/WO3 Molar Ratio

## TL;DR

This study explores how to make ultrafine tungsten powder using hydrogen reduction of carbon-containing tungsten trioxide, focusing on temperature and carbon ratios.

## Contribution

The paper introduces a method to produce smaller tungsten particles by optimizing reduction parameters and carbon content.

## Key findings

- Higher reduction temperatures initially decrease then increase tungsten particle size, with a minimum at 770 °C.
- Increasing the C/WO3 molar ratio decreases the reaction rate and also initially reduces particle size, with a minimum at 1.0.
- Carbon-containing WO3 produces smaller tungsten particles than pure WO3 due to nucleating and synergistic effects.

## Abstract

Ultrafine W powder is a key material for manufacturing high-performance W-based products. In this study, ultrafine W powder was prepared via the H2 reduction of carbon-containing WO3, and the parameters of reduction temperature (740–830 °C) and C/WO3 molar ratio (0.5–2.5) were mainly considered. The results demonstrated that, with the increase in reduction temperature, the reaction rate gradually increased, while the particle size of W powder exhibited a trend showing an initial decrease and then increase, with a minimum value of 146 nm at 770 °C. The results also showed that, with the increase in C/WO3 molar ratio, the reaction rate gradually decreased, while the particle size of W powder also first decreased and then increased, with its minimum value at a C/WO3 molar ratio of 1.0. The reduction pathways of H2 reduction of WO3 to W was given as WO3→WO2.9→WO2.72→WO2→W. Due to the co-actions of nucleating agent and the synergistic reduction effect, the particle size of W powder obtained by reducing carbon-containing WO3 was smaller than that obtained by reducing pure WO3, and a possible reaction mechanism was proposed.