Study On The Effect Of Acid Ions On The Gas Sensing Properties Of Tin Based Nanomaterials

With the development of The Times, the progress of the society, modern industry produces a great deal of gases, automobile exhaust emissions increase, family generally use natural gas, coal gas, liquefied petroleum gas. On the one hand, these cause serious air pollution and damage to the ecological environment there; on the other hand, there are some security risks, such as fire, explosion and poisoning. So at this moment, it is in urgent need of a means to be used for the detection of various gases, especially ambient gas, then the gas sensors emerged and immediately became people's research hot spot. People found nano metal oxide and metal composite oxide semiconductor materials have gas-sensitive characteristics, but these pure single-phase material because of their own nature, as the sensing material with low sensitivity, poor selectivity, slow response and recovery and other shortcomings, not well used in practical. To enhance the gas performance of the material, often through the preparation of special appearance, carrying on the doping and so on to realize.In order to guarantee that removed the disturbance of other foreign ions, this paper used the dissolution-pyrolysis method to prepare nano SnO₂ and different Zn salts to prepare nano Zn2SnO₄. Several acid ions were introduced into the preparation proceeding, to research the impact of these ions on the gas-sensitive properties of materials, and analyse the obtained results. Experimental results showed that different acid ions consequences were different.1. Different acids including H₂SO₄, HNO3 and HCl were added into the precursors with the wt% (acid/SnO₂) 3, 5 and 7, then after 500℃and 600℃calcination respectively. XRD analysis showed that the obtained powders were rutile nanometer SnO₂, through the gas test, it could be found that the gas response of the acid doped-SnO₂ to some gases were much higher than the pure SnO₂.The gas response of the 3 wt% H₂SO₄-doped SnO₂ (calcined at 500℃) to 5ppm H₂S could reach 46.8, to 50ppm H₂S achieved 156.7, at the working temperature 175℃. And under the same conditions, pure SnO₂ almost exhibited no sensitivity.The gas response of the 3 wt% HNO3-doped SnO₂ (calcined at 500℃) to 10ppm Cl₂ reached 316.5, to 100ppm Cl₂ was 587.2, at the working temperature 175℃, and meanwhile the pure SnO₂ had the gas responses 89.1 and 66.8, respectively.The gas response of the 3 wt% HNO3-doped SnO₂ (calcined at 600℃) to 100ppm Cl₂ was 375, at the working temperature 175℃, while pure SnO₂ was only 57.7.2. Through dissolution-pyrolysis routine, and according to the molar ratio 1:1 of Sn and Zn, ZnSO₄, Zn(HO3)2 and Zn(CH3COO)2 were added into the precursor, after calcination at 400℃, 500℃, 600℃and 700℃, respectively, nanometer Zn2SnO₄ powders were obtained. The specific results of the gas test were listed below.Mixed ZnSO₄ with the precursor, calcined at 700℃,ZnO/SnO₂/Zn2SnO₄ mixture was synthesized. Compared with other gases, the mixture powder had a good gas sensing behavior to 100ppm H2S, the gas response reached 94.5, at the working temperature 210℃.Using Zn(HO₃)₂ as the zinc source and calcined at 700℃, SnO₂/Zn2SnO₄ mixture was obtained. Through the gas test found that the gas response of this oxide mixture powder to 100ppm H2S could achieve 199.2 and had a good selectivity, at the working temperature 290℃.Took Zn(CH₃COO)₂ as the raw material and after 700℃calcination, ZnO/SnO₂/Zn2SnO₄ mixture was made. It showed a relatively high gas response to H2S than other gases, the gas response to 100ppm H2S was 110.5, when the working temperature was 290℃.