A Preparation of Purple Tungsten Oxide with Nano-Needle Shape

As a semiconductor material (with a band gap of 2.4 to 2.8 eV), tungsten oxide has an extremely wide range of applications in photoelectrochemistry.  Among them, purple tungsten oxide (W18O49) has attracted special attention from researchers because of its unique properties and structure.  

Monoclinic purple tungsten has the largest oxygen defect structure. Compared with yellow tungsten (WO3) and blue tungsten (WO2.9), purple tungsten has a special surface structure and the highest chemical activity, and is suitable for ultrafine particle tungsten powder.  Production of various nano-scale tungsten compounds.  On the other hand, purple tungsten can be used as a carrier for treating cancer cells in biomedicine; it can shield light waves from near-infrared light to achieve intelligent heat insulation; it can also be applied to photocatalytic degradation of organic pollutants.  Purify the environment.  At present, the preparation method of the purple tungsten powder is generally obtained by using ammonium paratungstate as a raw material to be calcined by introducing ammonia gas into a rotary kiln.  The purple tungsten powder prepared by such a conventional method has a large particle size and a large amount of impurities, and it is difficult to obtain a high purity purple tungsten.  

Some scholars have used hydrothermal synthesis to prepare nano-zinc tungsten. This method mixes WCl6 with ethanol and reacts at 180°C for 24 h in the reaction vessel. Although nano-scale purple tungsten can be obtained, it takes a long time to react and each time purple is obtained.  The quality of tungsten is small.  Therefore, it is necessary to develop a new high-efficiency and simple preparation method of nano-tungsten tungsten to provide high-quality raw materials for the preparation of ultra-fine powders such as ultra-fine tungsten powder and tungsten carbide.

In order to achieve the above purposes, researchers have directly used ammonium metatungstate as raw material to prepare ultra-fine purple tungsten.

The process includes:

ammonium metatungstate ((NH4)6H2W12O40), ammonium nitrate (NH4NO3), adjuvant sulfur Urea (CN2H4S).  The selected raw materials are formulated into a solution according to a certain ratio, stirred until completely dissolved, and heated at a constant temperature of 200 ° C. After the solution is evaporated to dryness, a vigorous redox reaction occurs in several tens of seconds, and a large amount of gas is released to form purple tungsten, and the obtained powder is  It has a nano-needle shape with a diameter of 30 to 100 nm and a length of 0.5 to 5 μm.  The process has the characteristics of short process and low cost, and the prepared nano-needle-shaped purple tungsten has high purity, large specific surface area, good dispersibility and excellent performance, and is more suitable for mass production than conventional processes.

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