Barbara Lipowska; Bronisław Psiuk; Mirosław Cholewa
Abstract
Cellular SiC/iron alloy composite with a spatial structure of mutually intersecting skeletons created with a porous ceramic preform has not been obtained before, despite promising spectrum of potential uses. We tested the possibility of obtaining such material using a SiC material with an oxynitride ...
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Cellular SiC/iron alloy composite with a spatial structure of mutually intersecting skeletons created with a porous ceramic preform has not been obtained before, despite promising spectrum of potential uses. We tested the possibility of obtaining such material using a SiC material with an oxynitride bonding and grey cast iron. Porous ceramic preforms were made by pouring the gelling ceramic suspension over a foamed polymer base which was next fired. The obtained samples of materials were subjected to macroscopic and microscopic observations as well as investigations into the chemical composition in microareas. It was found that the minimum width of a channel in the preform, which in the case of pressureless infiltration enables molten cast iron penetration, ranges from 0.10 to 0.17 mm. It was also found that the ceramic material applied was characterized by good metal wettability. Were the channels are wide enough for the metal penetration we observed that the ceramics/metal contact area always has a transition zone in which mixing of both components takes place.
S. Bhagat; K. Amar Nath; K.P. Chandra; R.K. Singh; A.R. Kulkarni; K. Prasad
Abstract
Lead-free pseudo-binary compounds (1-x)Ba(Fe1/2Nb1/2)O3–xBaTiO3; (0 ≤ x ≤ 1) have been synthesized at 1200°C using conventional ceramic technique and characterized by X-ray diffraction, scanning electron microscopy, dielectric and vibration sample magnetometer studies. The crystal structure ...
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Lead-free pseudo-binary compounds (1-x)Ba(Fe1/2Nb1/2)O3–xBaTiO3; (0 ≤ x ≤ 1) have been synthesized at 1200°C using conventional ceramic technique and characterized by X-ray diffraction, scanning electron microscopy, dielectric and vibration sample magnetometer studies. The crystal structure of the compounds is found to be monoclinic with the space group P2/m except for BaTiO3 for which it is tetragonal (P4/mmm). The incorporation of BaTiO3 significantly reduces the dielectric loss and improve the frequency and temperature stability of the dielectric properties of Ba(Fe1/2Nb1/2)O3. Compound 0.25Ba(Fe1/2Nb1/2)O3-0.75BaTiO3 exhibited a low value of temperature coefficient of capacitance (< ±3%) in the working temperature range (up to +85°C), room temperature dielectric constant equal to 282 and low loss tangent (~10-2) which meets the specifications for “Z5D” of Class II dielectrics of Electronic Industries Association. Hence, this composition might be a suitable candidate for capacitor applications. Besides, magnetic studies indicated the possibility of magneto-electric coupling in the system.
Ansu Kumar Roy; K. Amar Nath; K. Prasad; Ashutosh Prasad
Abstract
The present study addresses the problem of quantitative prediction of effective complex relative permittivity and ac conductivity of (Bi0.5Na0.5)0.94Ba0.06TiO3-Polyvenylidene Fluoride (BNBT06-PVDF) 0-3 composite samples (prepared by solution cast method at an elevated temperature) having 10, 20 and 30 ...
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The present study addresses the problem of quantitative prediction of effective complex relative permittivity and ac conductivity of (Bi0.5Na0.5)0.94Ba0.06TiO3-Polyvenylidene Fluoride (BNBT06-PVDF) 0-3 composite samples (prepared by solution cast method at an elevated temperature) having 10, 20 and 30 volume percentage of BNBT06 powder. SEM micrographs of the fractured surfaces showed that the particle distribution in the grains is not strictly homogeneous. Some areas of agglomeration of particles in the grains are also seen in the micrographs. EDAX patterns confirmed the presence of different constituent elements of the composite samples. The resulting data for room temperature real and imaginary parts of relative permittivity as well as real part of ac conductivity showed an increasing trend with increasing volume fraction of the ceramic filler. The 30 vol. % of BNBT06-PVDF composite had the highest dielectric constant of 75.3 and dielectric loss of ~6.09 i.e., loss tangent ~0.08. Among the dielectric mixing models presented, Rother-Lichtenecker model showed the best fit to the experimental data for the test composite. Similar equations for effective ac conductivity in terms of conductivity of the constituent phases of the composite were proposed in the present work to be fitted to find that none except Rother-Lichtenecker equation fitted the experimental data well. First order exponential growth type of equation applicable to all the three properties fitting the experimental data excellently is also proposed in the present work.
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