Engineering Sciences and Technology - Publications

Permanent URI for this collection

https://dspace.uohyd.ac.in/handle/1/18

Browse

Browsing Engineering Sciences and Technology - Publications by Subject "A. Sintering"
  • Item
    Effect of sintering temperature on structural, dielectric, piezoelectric and ferroelectric properties of sol-gel derived BZT-BCT ceramics
    ( 2016-03-01) Chandrakala, E. ; Paul Praveen, J. ; Hazra, Binoy Krishna ; Das, Dibakar
    The effects of sintering temperature on the structural, dielectric, piezoelectric and ferroelectric properties of sol-gel derived lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) piezoelectric ceramics have been reported in this manuscript. BZT-BCT ceramics sintered at 1550 °C for 2 h resulted in homogeneous and highly dense microstructure with ∼96-97% of the theoretical density and grain size of ∼10 μm. The results indicated a strong influence of the sintering temperature on the structural, dielectric, piezoelectric and ferroelectric properties of BZT-BCT ceramics. BZT-BCT ceramics sintered at 1550 °C for 2 h resulted in high piezoelectric charge coefficient d33∼617 pC/N, large planar electromechanical coupling factor kp∼54%, large piezoelectric voltage constant g33∼11.5 mV m/N, high dielectric constant εr∼5000, and a low tan δ∼0.019. The correlation of dielectric, piezoelectric and ferroelectric properties of the BZT-BCT ceramics with sintering temperature has been explained on the basis of grain size effect and motion of the 90° domain walls.
  • Item
    Influence of applied pressure during field-assisted sintering of Ti(C,N)-WC-FeAl based nanocomposite
    ( 2015-03-01) Archana, M. S. ; Srikanth, V. V.S.S. ; Joshi, S. V. ; Joardar, J.
    Ti(C,N)-WC-FeAl based nanocomposites are processed by field-assisted sintering at 1500 °C. The phase and microstructural evolution during the process under the influence of different applied pressures of 30, 50 and 100 MPa are studied using x-ray diffraction and scanning electron microscopy. Lattice parameters of (Ti,W)(C,N) solid solution and binder phases after sintering are found to vary with applied pressure. The nanocomposite grains are observed to possess a core-rim microstructure. Microstructural variations in terms of type, size and fraction of "core-rim" structure as a function of applied pressure are investigated. The hardness and indentation fracture toughness values are in the range of 17.6-18.4 GPa and 5.9-6.8 MPam, respectively. These values are comparable with those reported for Ti(C,N)-based composites with metal binder.
  • Item
    Magneto-electric properties of in-situ prepared xCoFe < inf > 2 < /inf > O < inf > 4 < /inf > -(1-x)(Ba < inf > 0.85 < /inf > Ca < inf > 0.15 < /inf > )(Zr < inf > 0.1 < /inf > Ti < inf > 0.9 < /inf > )O < inf > 3 < /inf > particulate composites
    ( 2016-11-15) Reddy, Monaji Vinitha ; Paul, J. Praveen ; Sowmya, N. Shara ; Srinivas, A. ; Das, Dibakar
    Magneto-electricparticulate composites, [xCoFe2O4– (1-x)(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3](x=30, 40, 50 wt%), were synthesized in-situ by a modified sol-gel method. This novel synthesis method has led to uniform distribution of the magnetostrictive and piezoelectric phases in the composite samples and improved magnetoelectric properties. Using autocombustion method CFO nanoparticles were synthesized and were added to the precursor gel of BCZT, further the composite powders were calcined at 800 °C and sintered at 1300 °C. Composite containing 50 wt% CFO showed a maximum magnetostriction (λmax) of ~88 ppm and strain sensitivity (dλ/dH) of ~41×10−9 Oe−1. 40CFO-60BCZT composite showed a high piezoelectric voltage constant (g33) of 8×10−3 V m/N. All the composites showed magnetoelectric effect and the maximum magnetoelectric coupling coefficient (dE/dH=αME) was measured ~161 mV/cm. Oe for 40CFO-60BCZT sample at its resonance frequency. The effect of microstructure on the magnetoelectric properties of [(x)CFO-(1-x)BCZT] composites has been studied and reported in this investigation as a function of its piezoelectric (BCZT)/ferrite (CoFe2O4) content.
  • Item
    Studies on ionic conductivity of stabilized zirconia ceramics (8YSZ) densified through conventional and non-conventional sintering methodologies
    ( 2011-12-01) Rajeswari, K. ; Suresh, M. Buchi ; Hareesh, U. S. ; Rao, Y. Srinivasa ; Das, Dibakar ; Johnson, Roy
    Densification studies of 8 mol% yttria stabilized zirconia ceramics were carried out by employing the sintering techniques of conventional ramp and hold (CRH), spark plasma sintering (SPS), microwave sintering (MWS) and two-stage sintering (TSS). Sintering parameters were optimized for the above techniques to achieve a sintered density of > 99% TD. Microstructure evaluation and grain size analysis indicated substantial variation in grain sizes, ranging from 4.67 μm to 1.16 μm, based on the sintering methodologies employed. Further, sample was also sintered by SPS technique at 1425 °C and grains were intentionally grown to 8.8 μm in order to elucidate the effect of grain size on the ionic conductivity. Impedance spectroscopy was used to determine the grain and grain boundary conductivities of the above specimens in the temperature range of RT to 800 °C. Highest conductivity of 0.134 S/cm was exhibited by SPS sample having an average grain size of 1.16 μm and a decrease in conductivity to 0.104 S/cm was observed for SPS sample with a grain size of 8.8 μm. Ionic conductivity of all other samples sintered vide the techniques of TSS, CRH and MWS samples was found to be ∼0.09 S/cm. Highest conductivity irrespective of the grain size of SPS sintered samples, can be attributed to the low densification temperature of 1325 °C as compared to other sintering techniques which necessitated high temperatures of ∼1500 °C. The exposure to high temperatures while sintering with TSS, CRH and MWS resulted into yttria segregation leading to the depletion of yttria content in fully stabilized zirconia stoichiometry as evidenced by Energy Dispersive Spectroscopy (EDS) studies. © 2011 Elsevier Ltd and Techna Group S.r.l.