Nanoscale Nickel-Containing Powders for Use in CO and NO 2 Gas Sensors
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Nanoscale Nickel-Containing Powders for Use in CO and NO2 Gas Sensors M. V. Kuznetsova, *, A. V. Safonova, **, D. A. Bobreshova, ***, O. V. Belousovab, ****, and Iu. G. Morozovb, ***** aAll-Russian
Research Institute for Problems of Civil Defense and Emergencies, Ministry of Emergency Situations, Moscow, 121352 Russia bMerzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] ****e-mail: [email protected] *****e-mail: [email protected] Received November 22, 2019; accepted December 30, 2019
Abstract—This paper investigates the physicochemical characteristics and gas-sensitivity mechanisms of nickel oxide (NiO) and nickel ferrite (NiFe2O4) obtained by levitation-jet synthesis LJS). Properties of synthesized materials were examined using various spectroscopic methods. XPS showed that the presence of Ni3+ ions in samples reduced significantly with an increase in the specific surface area of the powders and a decrease in the average diameter of their particles. In this regard, it can be concluded that the number of uncompensated Ni2+ vacancies in such samples also decreases and the concentration of O2– vacancies, on the contrary, increases significantly. The Raman spectra of nanoscale NiO lacked a magnon band, which is usually observed at v = 1500 cm–1, whereas the spectrum of nanoferrite sample had a pronounced 2M band, which indicates an increase in spin correlation. According to the analysis of UV spectra of the samples, there is an increase in reflectivity values with an increase in wavelength for large nanoparticles when compared to the corresponding values for small particles. In this regard, we suggested that Ni-based oxide nanoparticles are semiconductors with an indirect transition to band-gap energy, and this is in sharp contrast to the data obtained earlier by other researchers. The gas sensitivity of nanoscale powders was investigated in relation to carbon monoxide and nitrogen dioxide at operating temperatures of 350–500°C. An evaluation of the results made it possible to conclude that the operating characteristics of the sensors that we propose are superior in a number of parameters to the similar characteristics of sensors made of commercial powders, as well as of powders obtained by other synthetic methods. Keywords: levitation-jet synthesis, nanoparticles, nickel oxide, nickel ferrite, gas-sensing properties, gas sensors, carbon monoxide, nitrogen dioxide DOI: 10.3103/S1067821220050089
INTRODUCTION In recent decades, gas sensors created based on metal oxide semiconductors (MOS) using various laboratory or industrial technologies have been the subject of intensive research with a view to their possible application for monitoring and controlling production processes, as well as for assessing the quality of the environment [1]. Moreover, such sensors have been used in many technological pro
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