The Preparation Of Nano-SnO₂ And The Properties On Its Gas-solid Interface

Through summarizing the related references, reviweing the development of the gas sensor and the study of SnO₂ semiconductor gas sensor, in order to improve the properties of SnO₂ semiconductor gas sensor and to broaden its testing range, we establish this study on the preparation of SnO₂ and Zn adulterated SnO₂ materials and their sense organs used in the TMA gas sensor. The TMA gas is one of the major odor gases. It is important to determine the TMA gas quickly and conveniencely by the high sensitive gas senor in inspecting and protecting the environment. This study is made up of the following four parts:Nano-SnO₂ is prepared by the gel-gridding method and the homogeneous precipitated method. Compared to the gel-gridding method, the homogeneous precipitated method has more advantages such as simpler method, bigger rate of production, so we chose the homogeneous precipitated method as the major preparation method. Further we study on the relationships among the ratioes of the reactants, the time of the reaction and the concertration of the dispersant. Finally we selecte the prefered experiment conditions of the homogeneous precipitated method: the mol ratio between the reactants of SnCl₄ and urea is 1:20, the reaction time is 8 hour, and the consentration of the PEG4000 dispersant is 5wt%. By these congditions, we prepare nano-SnO₂, also Zn adulterated SnO₂ are prepared. The mol contents of the adulterated Zn in SnO₂ are 1%, 2% and 3%.These particles are characterized by SEM, XRD, and their isoelectric points are measured. The results show that by the gel-gridding methold, the average rate of production is 51.5%, the second size of SnO₂ is about 60nm; by the homogeneous precipitated method, the average rate of production is 82.3%, the first size of SnO₂ is about 8nm, and its second size is about 80nm, also 2ZnO ·SnO₂ is partly formed when Zn is adulterated, its structure type belongs to spinel. All particles in water solution are with negative charges, the isoelectric points are about between pH 3.07 and pH 3.36. All results show that through the two methods, we can get nano particles with equally sizes and uniform distributings.These particles are rubbed and spreaded on the surfaces of the electrodes. Then through the processes of activation and aging, the lateral-heating sense organs are made. These sense organs are put in the gas sensitive testing system to test separately their resistances in the air (Ra), and in the atmosphere of TMA gas (Rg), then we get...