Micro-Spherical Tungsten-Molybdenum Alloy Particles Using APT by Spray Drying

Tungsten‑molybdenum (W-Mo) alloy is of considerable interest in recent years as a high temperature material for a various of applications, ranging from electric, electronic, nuclear reactor to space vehicle, due to its outstanding properties including high melting point, low thermal expansion, high thermal conductivity, and excellent mechanical strength at elevated temperature, etc.

To boost its properties for wider applications, micro-spherical tungsten‑molybdenum alloy material was fabricated using ammonium paratungstate (APT) by spray drying combined with microwave assisted calcination.

The experimental design of spherical tungsten‑molybdenum alloy material is as below:

Using ammonium paratungstate hydrate [(NH4)10W12O41] (AR, Tianjin Chemical Reagent Factory, China), and ammonium molybdenum [(NH4)6Mo7O24] (AR, Tianjin Chemical Reagent Factory, China) as starting materials. Two precursors were mixed together with different Mo equivalent (20 wt%, 40 wt%, 60 wt% and 80 wt%, respectively). Then, the mixture was completely dissolved in high-purity water to be the spray drying precursor.

A commercial spray drying machine (B290, Buchi, Switzerland) was used to prepare the spherical (NH4)10W12O41-(NH4)6Mo7O24 particles. A two-fluid nozzle was used as the atomizer. The temperatures at the inlet and outlet of the spray dryer were 140 °C and 85 °C, respectively. The atomization pressure was 0.6 MPa, and the feed rate of the precursor was 4 ml/min.

The spraying dried (NH4)10W12O41-(NH4)6Mo7O24 particles need further heat treatment to be the W-Mo alloys powder. Firstly, the spraying dried powder was calcined in N2/H2 (Vol 5:1) at 650 °C for 2 h followed by cooling under N2/H2 in a self-made microwave tube furnace. Then, the 1st-calcined powder was continued ignited in N2/H2 (Vol 5:1) at 850 °C for 2 h followed by cooling under N2/H2 in the self-made microwave tube furnace. Well-dispersed micro-spherical W-Mo alloys particles were synthesized.

In conclusion, micro-spherical tungsten‑molybdenum alloy material was fabricated using ammonium paratungstate (APT) by spray drying combined with microwave assisted calcination. The size distribution of as-prepared W-Mo alloys particles was between 1 and 8 μm, and the average size was about 3 μm. The as-synthesized W-Mo alloy powder shows good sintering property.

• < Prev
• Next >