SYNTHESIS AND IMPLEMENTATION OF NiZnFe 2 O 4 FERRITES TO DESIGN EMBEDDED SYSTEM FOR HUMIDITY MEASUREMENT
2 ABSTRACT: Along with magnetic properties, the spinel ferrites exhibit promising electrical properties, deployment of which results into evolution of new area of applications as the electronic sensor materials. The electrical properties significantly depend upon the environmental compositions, for which it has been exposed. The electrical resistance of these sensor materials varies not only with gas concentration but also with change in water vapour concentration. With the view to develop an embedded technology based smart sensor module for humidity measurement a sensor material NixZn1-xFe2O4 are synthesized by chemical method and characterized by XRD and IR tools. The x-ray powder diffraction reveals the formation of single phase spinel ferrite, which is also supported by the IR absorption bands attributed to tetrahedral (A) site and octahedral (B) sites. Employing embedded philosophy, the sensor module is designed about AVR ATmega8L microcontroller for humidity measurement. The thick film of materials under investigation, prepared by screen painting technique, is used to sense the concentration of water molecules. Analog part of the system is wired about highly precise instrumentation amplifier AD620. Deployment of on-chip ADC of 10-bit resolution causes to increase in the preciseness of the results. The system is calibrated to the humidity in RH%. The data shown by the system under investigation reveals close match with the standard data.
ELECTRICAL AND MAGNETIC CHARACTERIZATION OF NANO CRYSTALLINE NI-ZN FERRITE SYNTHESIZED BY CO-PRECIPITATION ROUTE
Abstract Nickel zinc ferrite nanoparticles Ni1−xZnxFe2O4 (x=0.25, 0.5, 0.75, 1) have been prepared by the chemical co-precipitation route. The samples were characterized by X-ray diffraction (XRD), DC electrical resistivity, dielectric constant and low field AC magnetic susceptibility. The powder XRD patterns confirm the single phase spinel structure for the synthesized materials. The crystallite size was calculated from the most intense peak (3 1 1) using the Scherrer formula. The crystallite size was found within the range 7–15 nm. The crystallite size decreases with increasing zinc concentration. DC electrical resistivity decreases as the temperature increases indicating that the samples have semiconductor like behavior. DC electrical resistivity of the samples at room temperature was found to vary from 1.67×109 to 4×109 Ω cm with zinc concentration. The activation energy and drift mobility were calculated from DC electrical resistivity measurements. The dielectric constant for all the compositions has been studied as a function of frequency in the range from 500 Hz to 1 MHz at room temperature. The dielectric constant follows the Maxwell–Wagner interfacial polarization. AC magnetic susceptibility measurements were carried out as a function of temperature to measure the transition temperature, which was found to decrease with zinc concentration. The decrease of transition temperature has been explained by the distribution of cations on A and B sites.
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.