Preparation Of Nanometer Copper Oxide And Study On Its Gas Sensitivity

As an important device for detecting gas concentration and types,gas sensor has become indispensable in today’s society.CuO is widely studied as a sensitive material for C₂H₅OH,NH₃,H₂,CH₃COCH₃,NO₂ and H₂S.In this paper,three-dimensional（3D）flake-like CuO samples and sea urchin-like CuO samples were prepared by hydrothermal method,and the structure and morphology of each sample were characterized to explore the gas sensing characteristics of samples about NO₂ gas,and the main reasons for the difference in sensitivity were analyzed.On this premise,in order to further improve the gas sensing properties of CuO samples,such as poor stability and long response/recovery time,different doses of surfactants CTAB,PVP and PEG were added to the preparation process,and the effects of surfactants on the structure,morphology and gas sensing properties of CuO materials were analyzed.The main conclusions are as follows:1)Using CuCl₂ as copper source,3D flower-like CuO samples were prepared by hydrothermal method by changing hydrothermal temperature and Cu²⁺:OH^-to characterize the structure and morphology of CuO samples.Gas sensing elements based on different samples were prepared.The gas sensitivity was measured when the concentration of NO₂ gas was 2ppm-20 ppm at 100℃.When the concentration of NO₂ gas was 2 ppm,different samples were obtained.Response/recovery time of gas sensor corresponding to product.The results showed that the sensitivity of CuO samples was up to 50%when the concentration of NO₂ was 20 ppm at the optimum hydrothermal parameters(Cu²⁺concentration:0.05 mol/L,NaOH concentration:0.02 mol/L,[Cu²⁺]:[OH^-]=5:26,hydrothermal temperature:140℃,reaction time:10 h).For 2 ppm,the response time of NO₂ is 18 s and the recovery time is 21 s.2)On the basis of the hydrothermal optimization process,different doses of surfactants CTAB,PVP and PEG were added to obtain three-dimensional flower-like CuO samples with different structure,size and morphology.The phase composition was analyzed by XRD,and the morphology of the samples was analyzed by SEM.Finally,CuO semiconductor gas sensor was fabricated using these samples as sensitive materials.Through the analysis of gas sensitive test results,it is found that different doses and different kinds of surfactants have great influence on the structure and morphology of CuO.With the addition of surfactants,the response/recovery time of CuO material is greatly shortened,and the resistance value of material is more stable.3)Sea urchin-like CuO samples were prepared by changing hydrothermal temperature with Cu（NO₃）₂ as copper source.The morphology of CuO samples was characterized.Gas sensing elements based on different samples were prepared.Sensitivity curves and recovery response curves of the sensors were measured and plotted.The results show that the response/recovery time of the prepared CuO sample is short and the hydrothermal parameters(hydrothermal Cu²⁺concentration:0.04 mol/L,hydrothermal NaHCO₃ concentration:0.08 mol/L,hydrothermal temperature:60℃,reaction time:4 h,annealing temperature:400℃,annealing time:90 min)are optimized.On the basis of optimizing the process,different doses of surfactant PEG were added to the preparation,which dispersed the thin slices of sea urchin-like CuO structure into fine spine clusters.With the increase of PEG dosage,the density of fine spine increased.The sensitivity of sample No.31 prepared by adding 0.75 g surfactant PEG is 66%when the concentration of NO₂ is 20 ppm,and the response/recovery time of each sample is very short when the concentration of NO₂ is 2 ppm.