Tungsten trioxide is a transition metal oxide, with a semiconductor character, has great potential for gas-sensitive materials, sensitive to a variety of gases, especially toxic gases.
Tungsten Trioxide Gas Sensitive Performance Test
In recent years, with the emergence of nanotechnology, it was found that nano-tungsten trioxide has a higher sensitivity and response speed. There are three main methods for preparing nano tungsten trioxide, gas phase method, liquid phase method and solid phase method. In general, hydrothermal method has become the most widely used method for the preparation of nano WO3 by virtue of its economical, low cost and easy operation.
Commonly used to produce gas-sensing elements of tungsten trioxide mainly nanorods, nano-plate, nano-plate rod-like mixed structure and other forms, as will eventually become what form, are generally in the process of hydrothermal synthesis by adjusting the parameters formed by the results, therefore, even with the same hydrothermal method of nano-tungsten trioxide, often because of different regulators, the temperature is different, and makes the operation of a wide variety of the final nano-structure is also different.
Some scholars use water from tungsten trioxide thermal method, in order to verify the gas sensing properties of the above-mentioned three kinds of structure, using citric acid as acidifier, ammonium metatungstate will be mixed and sodium sulfate, were dissolved into distilled water, according to a certain percentage of the mixed solution by adding citric acid, by adding the amount of citric acid to adjust the reduction of rod, plate, plate-like mixed structure of three kinds of structure of nano-tungsten trioxide.
Through the test of the three structures, the following conclusions are obtained. The specific surface area of BET of nano plate, nano plate rod and nano rod WO3 is 17.55 m2/g, 11.01 m2/g, 10.57 m2/g, respectively, it can be seen that the specific surface area is nano plate > nano plate rod > nano rod. It can be said that the specific surface area is the key to determine the sensitivity of nano-tungsten trioxide, so the results will be clear at a glance.
In the atmosphere of three acetone, the same concentration of ammonia and formaldehyde, gas sensing properties of tungsten trioxide nano plate is the best, this is mainly due to the nano tungsten trioxide plate has a high specific surface area, can significantly change the effective resistance of the crystal and increase the active site of gas reaction. For gas sensitive reactions, the more active sites of metal oxides are, the more sensitive the gas sensitivity is, and the selectivity and sensitivity of gas sensors are higher.
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