Study On The Detection Characteristics Of Hydrogen And Acetylene Gas Sensors Based On Thorium Sulfide Composite Materials

Dissolved gas analysis(DGA)is a simple and effective method to diagnose potential faults of oil-immersed power transformers.High performance gas sensor technology has always been the direction of on-line monitoring of dissolved gas in transformer oil.As a narrow band gap of two-dimensional gas sensitive material,Molybdenum sulfide(MoS₂)owns high specific surface area,high porosity and high power conversion efficiency.It's worth mentioning that the compound preparation could significantly improve the gas sensitive material response values and on specific gas selectivity.Firstly,we start from theoretical modeling,takeing H₂ and C₂H₂ gas as the detection target and the MoS₂ gas-sensitive material as the detection substrate,establish the gas adsorption model of different composites respectively based on the first principles.We select the optimal composite combination form through simulation calculation.Then,gas-sensitive materials with excellent microcosmic morphology were prepared in the laboratory by step hydrothermal method.Based on the gas-sensitive detection platform,the gas-sensitive properties of materials with different composite proportions were explored.The main reasons for the aging of materials were speculated by observing the change of microcosmic morphology.Finally,we change the energy of the material incentive form,using optical excitation MoS₂ based gas sensors to detect target gas.The improvement of MoS₂ material aging phenomenon was explored under the excitation light.The main research of this paper is as follows:1 The gas sensitivity mechanism of different MoS₂ matrix composites was analyzed by the first principle simulation.The supercell model of single MoS₂(001)with Sn and Znatoms was constructed,and the formation energy,charge transfer of composite atoms and state density of single MoS₂ crystal were calculated.The results show that the composite formation of Znatom is smaller than Sn atom,the charge transfer is larger than Sn atom,and the band gap of MoS₂ crystal is relatively narrower.Then,the adsorption models of H₂ and C₂H₂ gas were established for two composite models and pure MoS₂(001)crystals,and the adsorption energy,charge transfer of gas,differential charge density and state density of the adsorbed gas were calculated.The results show that H₂ and C₂H₂ gas molecules transfer the most electrons and adsorb the most energy on the Znmodel.After comprehensive comparison of the simulation results,the Znatomic composite model,namely ZnO-MoS₂ composite material,was selected to carry out the following gas sensitivity research.2 ZnO-MoS₂ materials with different composite proportions were prepared and their sensitivity to H₂ and C₂H₂ gases was measured systematically.The preparation of MoS₂ matrix material was optimized by the method of step by step hydrothermal method from the microscopic morphology.Then ZnO nanoparticles were uniformly deposited on the matrix material.The crystal phase structure of the prepared material was determined by various means of phase characterization.The sensitive material is assembled as side-heat sensors,which were tested the working temperature,the concentration characteristics and response recovery characteristic under two kinds of gas.The results show that the composite with the composite ratio of Zn:Mo=1:2 has the best gas sensitivity to the two gases.The response characteristics of the composite material to C₂H₂ gas better verify the accuracy of the simulation calculation in chapter two.3 The causes of aging to material response values were analyzed by comparing different aging schemes.Since the gas-sensitive material has a long pre-heating process before detection,the thermal energy excitation cannot be regulated.The control test group with no light and no air contact was set respectively in the aging process.The results show that the response values of the three aging schemes are all attenuated below 2.Light and air molecules have little effect on the attenuation of the response value during the aging process.The microstructure of the material was seriously agglomerated after aging,which thus speculated that the main factor causing material aging may be energy incentives.4 The gas sensitivity and aging improvement of the material under light excitation were detected.The intelligent algorithm was used to solve the cross sensitivity phenomenon and to correct the nonlinear attenuation of the response value caused by aging.The energy excitation was replaced by light,and the gas-sensitive properties of the composite were measured.Under light excitation,the response value of the material decreases as well as the response speed is accelerated.The slow decay rate of response value under photoaging can realize reliable detection within 40 days.The obtained multidimensional data were intelligently classified by using the deep confidence neural network.The test sample data showed that the H₂ and C₂H₂ gas could be detected with high accuracy,and the maximum prediction error under each aging cycle was less than 10%.