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The mesoporous pebble-like NiCo2O4 nanostructures were smoothly obtained via a simple hydrothermal route and the succeeding annealing treatment. Various techniques, including XRD, SEM, TEM, Raman spectra, FTIR, and MH curves have been used to study the obtained products. The obtained results exhibited that the morphology of spinel NiCo2O4 could be...
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... Further information about the chemical bonding of NiCo 2 O 4 was examined using Raman spectroscopy, the results of which are presented in Fig. 2. The Raman spectra of the NiCo 2 O 4 samples displayed four peaks at 187, 474, 520 and 672 cm −1 , which are mainly associated with the F 2g , E g , F 2g , and A 1g vibration modes of spinel NiCo 2 O 4 , respectively. These observed Raman peaks corroborate to the Co-O and Ni-O vibrations, strongly supporting previous NiCo 2 O 4 reports [26][27][28]. In addition, the observed lower F 2g and higher A 1g Raman modes are mainly associated with the tetrahedral and octahedral sites of NiCo 2 O 4 , respectively [28,29]. ...
In this article, the potential of solution-processed spinel nickel-cobaltite (NiCo2O4) nanostructures as chemiresistive sensors for detecting ethanol (C2H5OH) is demonstrated. Various techniques were used to characterize the structure, composition, and morphology of the as-synthesized NiCo2O4 samples prior to gas sensing studies. By adjusting the reaction time, cubic crystalline NiCo2O4 structures with different surface morphologies were obtained, including upright-standing nanoplatelets enclosed by nanoneedle-type structures. These nanoneedle-type structures are composed of numerous interconnected nanoparticles with diameters of ∼4–8 nm. These unique structural and morphological characteristics enable the NiCo2O4 nanostructures to exhibit excellent sensing properties towards C2H5OH gas at 140 °C, with significant changes in their resistance values observed upon exposure to 10–1000 ppm C2H5OH. Notably, the NiCo2O4 sample processed for 9 hours, with a specific surface area of 48.19 m²/g, was recognized as the most promising sensor among the various NiCo2O4 samples, showing a maximum response of 54.4% towards 200 ppm C2H5OH, with good repeatability and complete recovery characteristics. Additionally, we also investigated and discussed various sensing characteristics of the NiCo2O4 sensors, including their gas concentration dependent response, selectivity, temperature dependent response, reproducibility and stability. Moreover, the sensing interactions between NiCo2O4 and C2H5OH gas molecules were elucidated through the use of an energy band diagram, providing valuable insights into the sensing mechanism of these sensors. Overall, this research provides a practical and simple strategy for synthesizing spinel oxide nanostructures and demonstrates their potential in C2H5OH sensing applications.
The effects of the glycine content (ϕ) and annealing temperature on the phase composition and morphology of NiCo2O4 spinel samples manufactured by solution combustion synthesis (SCS) reactions were studied. With small amounts of glycine in the precursor, the major phase in the thus-prepared samples was nickel cobalt oxide; when ϕ ≥ 0.7 metallic nickel was in addition formed in the samples, and it was only at ϕ ≥ 1.4 that NixCo3 – xO4 spinels, where x < 1, started to form. The highest-nickel sample (Ni0.72Co2.22O4) was prepared at ϕ = 2.2. An increase in annealing temperature from 400 to 700°С was accompanied by a decrease in nickel amount in the NixCo3 – xO4 spinel crystal structure to x = 0.07–0.13 and an increase in nickel amount in double oxide samples.
In this current research article, nickel oxide (NiO) nanoparticles were synthesised by hydrothermal process. The stability of structural and magnetic properties of NiO nanoparticles has been examined by shock wave loading experiment. In the present experiment, authors employed the shock waves with Mach number 2.2, and different shock pulses such as 100 and 200 pulses were loaded on the test samples. The test sample's molecular and crystalline structure stabilities are scrutinized by FTIR and PXRD techniques. SEM and VSM techniques are utilized to understand the surface and magnetic behaviour of NiO nanopar-ticles. The obtained crystallographic structure, molecular structure and surface changes are not showing any significant changes, but in magnetic properties, the value of the saturated magnetization has gradually reduced by the impact of shock waves. The obtained results of NiO nanoparticles have stable crystalline properties against the impact of shock waves; hence, the test material is suggested to the aerospace and military including high-temperature and high-pressure operation conditions.
