Tungsten Oxide Ammonia Sensor

Tungsten oxide is a transition metal oxide n-type semiconductor. As a functional material, in recent years, a large number of studies have found that tungsten-based oxides does not only can be applied as catalysis, electrochromism, battery electrodes, solar absorbing materials and invisible materials, but also has the semiconductor characteristics of heat-sensitive, pressure-sensitive and gas-sensitive.

The application and research of tungsten oxide nanocrystalline films in gas sensors, photocatalysis, photoconductivity, etc. are attracting more and more attention. In the field of semiconductor gas sensors, tungsten oxide based materials have been considered as one of the most effective oxide gas sensing materials for detecting NOx, SOx, NH3, H2S and so on.

The tungsten oxide nanowire gas sensing material is prepared by the following method:

(1) Dissolving 1.0 to 1.5 g of sodium tungstate in 24 to 30 ml of deionized water, and magnetically stirring in an ice water bath for 1 hour to form a colorless transparent sodium tungstate solution;

(2) Slowly add 3.5 to 4 ml of 3 M/L hydrochloric acid to the solution in (1) and stir for 0.5 hour, then slowly add 4.6 to 5.2 ml of 0.3 M/L of oxalic acid and continue stirring for 0.5 hour. Then a light yellow micelle solution is formed;

(3) Transferring 28 to 30 ml of the micelle solution in (2) into a 50 ml reaction vessel and adding 25 to 30 g of potassium sulfate to stir uniformly, and then hydrothermally treating at a temperature of 180 ° C for 12 to 14 hours;

(4) The hydrothermal product in step (3) was repeatedly washed with deionized water and absolute ethanol, and then sufficiently dried in an air atmosphere at 65 ° C to obtain a tungsten oxide nanowire.

The tungsten oxide nanowire ammonia sensor is prepared by the following method:

(1) Preparation of gas sensitive material slurry

The tungsten oxide nanowires prepared as described above are mainly composed of ethyl cellulose and terpineol as a binder, and a glass frit is added to enhance the adhesion between the sensitive material and the alumina substrate. The above materials are mixed and stirred evenly to prepare ammonia sensitive material slurry.

(2) Sintering of components

The slurry in the above (1) was applied on an alumina substrate connected with a silver electrode and a lead, and sufficiently dried in air at 70 ° C, and sintered at a temperature of 300 to 500 ° C in a box furnace for 1~2 hours. Finally a tungsten oxide nanowire ammonia sensor element was obtained.

(3) Component aging

The ammonia sensitive element sintered in the above (2) was aged at 300 ° C for 72 hours to prepare an ammonia sensor to be tested.

The tungsten oxide gas sensor has very low energy consumption during the whole preparation process, and the prepared tungsten oxide nanowire has a large specific surface area, and the tungsten oxide ammonia sensor prepared by the nanowire has a strong sensation to very low concentration of ammonia (1 to 100 ppm). High sensitivity, good repeatability and high stability.

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