NO₂ Sensing Behavior of Compacted Chemically Treated Multi-Walled Carbon Nanotubes

This article is devoted to the investigation of the sensing behavior of chemically treated multi-walled carbon nanotubes (MWNTs) at room temperature. Chemical treatment of MWNTs was carried out with a solution of either sulfuric or chromic acids. The materials obtained were investigated by transmission electron microscopy, scanning electron microscopy, Raman-spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The active layer of chemiresistive gas sensors was obtained by cold pressing (compaction) at 11 MPa of powders of bare and treated multi-walled carbon nanotubes. The sensing properties of pellets were investigated using a custom dynamic type of station at room temperature (25 ± 2 °C). Detection of NO2 was performed in synthetic air (79 vol% N2, 21 vol% O2). It was found that the chemical treatment significantly affects the sensing properties of multi-walled carbon nanotubes, which is indicated by increasing the response of the sensors toward 100–500 ppm NO2 and lower concentrations

Room-Temperature NO₂ Gas Sensors Based on Granulated Carbon Nanofiber Material

Room-temperature gas sensors based on granulated carbon nanofiber material were investigated for the detection of NO2. The granulated material consisting of intertwined carbon nanofibers was synthesized by the decomposition of CH4 over the Ni/Al2O3 catalyst in a vibro-fluidized bed reactor. Carbon material was investigated using transmission electron microscopy, Raman spectroscopy, low-temperature nitrogen adsorption, and X-ray photoelectron spectroscopy. Investigation of the gas sensors towards NO2 at room temperature (25 ± 2 °C) was carried out in a dynamic flow-through setup in the range from 1 to 500 ppm. A comparison of the sensitivity gas sensor to NH3 and CH4 was also given. The sensor based on non-treated carbon nanofiber material showed the response ΔR/R0 of 5.1 % to 10 ppm of NO2. It was found that the sensor response to NO2 decreased when increasing the relative humidity. The effect of the relative humidity was more pronounced for low concentrations of nitrogen dioxide and decreases with a further increase in them

Electrical properties of compacted carbon nanomaterials

In this paper, the electrical properties of various compacted carbon nanomaterials were investigated. Compacted carbon nanomaterials (carbon nanofibers, multi-walled carbon nanotubes) were compacted into cylindrical samples and the electrical properties were measured in a frequency range from 50 Hz to 1MHz

Electrical properties of epoxy composites based on carbon black

In this work, AC electrical properties of epoxy composites based on carbon black (CB) were determined depending on the loading of filler. The measurements were carried out within a frequency range 20 Hz – 1 MHz. The loading of carbon black was 0–5 wt.% in composites. The conductivity increased when increasing the content of carbon black and the maximum values were observed at 5 wt.% CB. The maximum value of permittivity was at 0.75 wt.% CB and it can be considered as percolation threshold