2021年12月15日星期三

Preparation of Nano Tungsten Trioxide by Hydrothermal Synthesis

Nano tungsten trioxide is a typical N-type semiconductor gas sensing material, which has a large specific surface area, stable chemical properties, a variety of toxic gases have good sensitivity, can effectively improve sensitivity and responsiveness of gas sensors effectively reduce the harmful effects of harmful gases on human health.

tungsten trioxide hydrothermal reactor image

The preparation of nano tungsten trioxide by hydrothermal method can overcome the problems that the nano rods prepared in the prior art have larger diameters, uneven distribution of rods and other forms of particles. 

Using ammonium metatungstate as tungsten source, citric acid as the profile control agent, according to a certain proportion in the mixed solution, adding concentrated hydrochloric acid solution was adjusted by drops in pH magnetic stirring at room temperature is equal to 1.5, half an hour so that the magnetic stirring solution mixing, the mixed solution was transferred to a hydrothermal reaction kettle PTFE capacity of 100 mL in seal, placed in an oven and incubated at 180 ° C for 18 h. After completion of the hydrothermal reaction, the precipitate was collected by centrifugation, washed with deionized water and acetone, and centrifuged three times to remove residual Na2SO4 and organic impurities in the precipitate. The cleaned precipitate was placed in a watch glass, dried in an oven at 80 ° C for 24 h, and finally ground in an agate mortar to obtain a powder.

Through SEM and TEM observation, it is concluded that the best technological conditions for preparing nano structured WO3 are citric acid content of 2 mol, P H value of the system 1.5, hydrothermal reaction 180 degrees, and hydrothermal reaction time of 1D. The prepared nanorod WO3 nanorods have a maximum length of about 2.5 um, a diameter of about 30-60 nm, a maximum aspect ratio of about 1:80 and a growth direction of the nanorods of [002].

The gas sensor made of nano rod tungsten trioxide has the best working temperature of 350 ℃, 300 ℃, 325 ℃ and 250 ℃ in the gas of ethanol, acetone, ammonia and formaldehyde respectively. When the gas concentration is 1000 ppm sensitivity reached the maximum, respectively 21.29,10.82,24.32 and 9.68; Gas sensors for the four gases minimum detection concentrations were 100ppm, 50ppm, 25ppm and 100ppm, gas sensitivity is good, but to be higher than the working temperature of 150 ℃ to play a good gas sensitivity performance, so in the future to find the right of the material on the nano tungsten oxide doping is to improve the performance of gas sensors the main way.

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