Richa Srivastava

Synthesis and characterization of ZnO–TiO2 nanocomposite and its application as a humidity sensor

A detailed study is reported of the synthesis and characterization of a ZnO–TiO2 nanocomposite and its application as a humidity sensor. Variations of resistance with relative humidity have been observed. The sensitivity of the sensor at different temperatures has also been calculated. Scanning electron micrographs and X-ray diffraction patterns of the sensing material were obtained at different temperatures. The minimum size of nanoparticles is found to be 50 nm at room temperature (19°C). The highest sensitivity observed at room temperature was 18 MΩ/%RH. Kelvin radii, which are the radii of pores, have also been studied; their average value at ambient temperature (19°C) is found to be 8.35 Å.

Ferrite Materials: Introduction, Synthesis Techniques, and Applications as Sensors

ABSTRACT The present review summarizes, in a detailed introduction, the synthesis techniques, structures, classifications, uses, properties, and applications of ferrite materials in the fields of sensors. Morphological and structural studies of ferrite materials were performed. A great advantage of ferrites is their porosity, which is necessary for a sensor. These pores serve as humidity or gas adsorption sites and the sensitivity of sensor depends on the size of these pores. The variation in sensitivity with operating temperature at different concentrations of gas for sensing elements CuFe2O4, CdFe2O4, and ZnFe2O4 is discussed. In addition, resistivity–humidity a characteristic and sensitivity for the MgFe2O4 and Mg0.9Sn0.1Fe2O4 corresponding to different values of percentage of relative humidity is discussed.

Nanostructured ZnFe2O4 thick film as room temperature liquefied petroleum gas sensor

In the present work, thick film of nanostructured zinc ferrite was prepared by screen printing method and its liquefied petroleum gas (LPG) sensing properties were investigated. The structural and surface morphological characterisations of the sample were analysed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The minimum crystallite size of ZnFe2O4 calculated from Scherrers formula is found to be 4 nm. SEM images exhibit the porous nature of the sensing material with a number of active sites. Optical characterisation of the film was carried out by ultraviolet–visible spectrophotometer. The estimated value of band gap of the film was found 1.91 eV. The LPG sensing properties of the zinc ferrite film were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the film were measured with the exposure of LPG as a function of time. The maximum values of sensitivity and percentage sensor response were found 16 and 1785, respectively, for 5 vol.% of LPG. These experimental results show that nanostructured zinc ferrite is a promising material for LPG sensor.

Synthesis and Characterization of ZnO/ZnNb2O6 Nanocomposite and Its Application as Humidity and LPG Sensor

ABSTRACT The present article reports the synthesis and characterization of ZnO/ZnNb2O6 nanocomposite and its humidity and liquefied petroleum gas (LPG) sensing behavior at room temperature. Pellets from the powder of synthesized material were calcined at 150, 300, 450, and 550°C for 3 h and tested for their humidity and LPG sensing ability separately. Each heat-treated pellet was exposed to humidity under controlled conditions, and variations in resistance with variations in humidity were measured. Similarly, heat treated pellets were exposed to LPG and variations in resistance were recorded. Electrical sensitivities of sensing material at different temperatures were also evaluated. After chemical mixing of niobium oxide with zinc oxide, the average sensitivity of a sensor increased from 8 to 19 MΩ/% relative humidity (RH) over the range from 10 to 95% RH at room temperature and in the case of LPG sensing, the maximum sensitivity was 12.

Humidity Sensor: An Overview

ABSTRACT The present review provides a detailed introduction, properties, types, applications, uses, and requirements of a humidity sensor. Humidity affects mankind directly or indirectly. Therefore, there is an urgent need to precisely measure and control humidity in various environments. The role and various methods for measurement of humidity are included. The detailed working principle of a resistive type humidity sensor based on metal oxides is also explained.

Synthesis and Characterization Techniques of Nanomaterials

ABSTRACT Earlier studies have shown that nanomaterials are the most promising materials for modern development of science and technology. In this brief review, attention will be focused on a detailed introduction, the synthesis methods to prepare ceramic nanoparticles, and various characterization techniques.

Flame Synthesis of Carbon Nanotubes using Camphor and its Characterization

ABSTRACT This paper emphasizes the primitive study of flame synthesis of carbon nanotube using camphor and its characterization. Flame of camphor was deposited on a conical cap of the chamber through a condensation process, and it was collected from the mid portion of the cap after 6 h, at room temperature 25°C. The collected material was mixed with 10% PVA for proper adhesion of molecules. The pelletization of this powder was done by applying uniaxial pressure of 5 tons. This pellet was used as a sensing element and was investigated using Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). SEM studies show carbon nanotubes like leaf veins with some fatty materials. Average diameter of carbon nanotubes using Debye-Scherrers formula was found to be 30 nm.

Experimental Investigation on Humidity Sensing of Nanostructured Ferric Oxides

Nanostructured ferric oxides (A and B) were synthesized via chemical precipitation method using two different precipitating agents i.e. ammonium hydroxide and sodium hydroxide. X-ray diffraction proved the formation of ferric oxide. Crystallite sizes of the materials A and B were 40 and 18 nm respectively. Surface morphology of sample B reveals that it has more adsorption sites in comparison to A. Further the pellets and thick films of materials A and Bwere prepared and investigated with the exposition of humidity from 10%RH to 90 %RH. It was found that the thick film prepared with material B was most sensitive among all having maximum average sensitivity 8.12 MΩ/%RH. Good sensitivity, less hysteresis, and reproducibility identify that fabricated humidity sensor (B) is promising for the device application.

P1.0.5 Comparative humidity sensing based on Fe2O3 synthesized via different methods

Ferric oxide nanomaterial was synthesized by two hydrothermal precipitation methods as B1 and B2. Pellets as sensing elements were subjected to specially designed humidity chamber and variations in resistance with relative humidity (%RH) were measured. Pellet prepared from B2 reveal maximum average sensitivity 6.61 MΩ/%RH. Structural analysis confirmed the formation of Fe2O3 with α-phase and rhombohedral structure. Average crystallite size of materials for B1 and B2 were found 40 and 18 nm respectively. SEM images show more porosity (largest surface area) of material for B2. TEM image of material for B2 shows uniform distribution of particles having average particle sizes are around 2 nm. Optical and thermal properties were investigated by using UV-visible absorption spectroscopy and Differential scanning calorimetric techniques.

Experimental Investigation on Moisture Sensing Behavior of La2O3 with La(OH)3 at Nanoscale

ABSTRACT This article reports the moisture-sensing behavior of a nanostructured La2O3 and La(OH)3. Pellets of this material were prepared and used as a sensing element after successive thermal annealing for 2 h at different temperatures of 200, 400, 600, and 800°C. After each annealing step, this sensing element was placed in a conductivity holder and exposed to humidity. Variations in resistance with relative humidity were recorded. The sensing material was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). A close look of the scanning electron micrographs confirms that the sensing element annealed at 400°C was more porous and uniform than the other samples. The maximum average sensitivity obtained was 19 MΩ/% relative humidity (RH) and results were found to be reproducible. The crystallite size of the sensing material was found to be in the range of 30–140 nm. The mass loss of the sensing material at different temperatures was also studied.