Monoclinic Tungsten Trioxide Effect on Gas Sensing

Monoclinic tungsten trioxide prepared by nanometer tungsten trioxide through hydrothermal method and calcination treatment, which is characterized by higher non-symmetry axis and the second symmetry axis, the symmetry plane is more than one. Monoclinic tungsten trioxide has a strong heterogeneity, which has three principal refractive index.

Taking Na₂WO₄• 2H₂O as raw materials, DL- malic acid as supplement aid, in this context, which can be synthesized in a three-dimensional spherical shape containing precursor (WO₃ • xH₂O). It shows that the addition of malic acid dose of WO₃ • xH₂O morphology and crystalline phase having a significant impact. Thus gas test shows that the optimum operating temperature of three samples reaches to 250 ℃, and square-shaped monoclinic tungsten trioxide shows the highest sensitivity, which mainly due to its unique and innovative three-dimensional porous structure. At 300 ℃ optimum operating temperature is the lowest detectable concentration of material, which can reach 0.1ppm, material optimum calcination temperature is determined as 500 ℃,the sensitivity of 5ppm acetone sample gas reaches to 7.9; at 95% relative humidity conditions , the sensitivity of 5ppm acetone resistance remains 5.72.

In tests of different gases (such as acetone, methanol, ethanol, ammonia, etc.) in the gas sensing of different working conditions, monoclinic tungsten trioxide gas shows high selectivity and sensitivity. Taking Na2WO₄ • 2H₂O as raw materials, which are used by Na₂C₂O₄, Na₂SO₄ and H₂C₂O₄ supplement. The hydrothermal conditions is 24 hours, at 180 ℃. Experimental results show that the solution plays the role in Na +, SO₄₂-, C₂O₄₂-, HC2O₄- ions and H₂C₂O₄ nano WO₃ crystal nucleation and growth process. The results show that three different adjuvants does not effect on crystal of product system. Subsequent tests show Na₂C₂O₃ assisting synthesis of WO₃nanorods at 320 ℃ for certain concentrations to gas sensing, which mainly due to its high degree of dispersion and crystallinity.

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