For this study,we synthesized Aurivillius Bi_(5)Ti_(3)FeO_(15) ceramic using the generic solid-state reaction route and then performed roomtemperature X-ray diffraction to confirm that the compound had a single phase ...For this study,we synthesized Aurivillius Bi_(5)Ti_(3)FeO_(15) ceramic using the generic solid-state reaction route and then performed roomtemperature X-ray diffraction to confirm that the compound had a single phase with no impurities.The surface morphology of the prepared sample was observed to contain microstructural grains approximately 0.2–2μm in size.The dielectric properties of the sample were determined as a function of frequency in a range of approximately 100 Hz to 1 MHz at various temperatures(303 K≤T≤773 K).Nyquist plots of the impedance data were found to exhibit a semi-circular arc in the high-temperature region,which is explained by the equivalent electrical circuit(R_(1)C_(1))(R_(2)QC_(2)),where R_(1) and R_(2) represent the resistances associated with the grains and grain boundaries,respectively,C_(1) and C_(2) are the respective capacitances,and Q is the constant phase element(CPE),which accounts for non-Debye type of behavior.Our results indicate that both the resistance and capacitance of the grain boundaries are more prominent than those of the grains.The alternating current(ac)conductivity data were analyzed based on the Jonscher universal power law,which indicated that the conduction process is dominated by the hopping mechanism.The calculated activation energies of the relaxation and conduction processes were very similar(0.32 to 0.53 eV),from which we conclude that the same type of charge carriers are involved in both processes.展开更多
Cobalt(Co)-modified brownmillerite KBiFe_(2)O_(5)(KBFO;[KBiFe_(2(1−x))Co_(2x)O_(5)(x=0,0.05)])polycrystalline is synthesized following the solid-state reaction route.Rietveld refinement of X-ray diffraction data confi...Cobalt(Co)-modified brownmillerite KBiFe_(2)O_(5)(KBFO;[KBiFe_(2(1−x))Co_(2x)O_(5)(x=0,0.05)])polycrystalline is synthesized following the solid-state reaction route.Rietveld refinement of X-ray diffraction data confirmed the phase purity of KBFO and KBiFe_(1.9)Co_(0.1)O_(5)(KBFCO).The optical bandgap energy(Eg)of KBFO decreased from 1.59 to 1.51 eV because of Co substitution.The decrease in bandgap can be attributed to the tilting of the Fe–O tetrahedral structure of KBFCO.The observed room-temperature Raman peaks of KBFCO shifted by 3 cm^(−1) toward a lower wavenumber than that of KBFO.The shift in Raman active modes can be attributed to the change in the bond angles and bond lengths of the Fe–O tetrahedral structure and modification in response to oxygen deficiency in KBFO because of Co doping.Compared with that of KBFO,the frequency-dependent dielectric constant and dielectric loss of KBFCO decrease at room temperature,which is a consequence of the reduction in oxygen migration and modification in response to vibrational modes present in the sample.展开更多
Ply-by-ply failure analysis of symmetric and anti-symmetric laminates under uniform sinusoidal transverse dynamic loading is performed for a specified duration.The study investigates the first ply failure load,followe...Ply-by-ply failure analysis of symmetric and anti-symmetric laminates under uniform sinusoidal transverse dynamic loading is performed for a specified duration.The study investigates the first ply failure load,followed by the detection of successive ply failures and their failure modes using various failure theories.Some of the well-established failure theories,mostly used by the researchers,are considered for the failure prediction in laminates.The finite element computational model based on higher order shear deformation displacement field is used for the failure analysis and the complete methodology is computer coded using FORTRAN.The ply-discount stiffness reduction scheme is employed to modify the material properties of the failed lamina.The failure theories used in the analysis are compared according to their ability to predict failure load,failed ply,failure mode and progression of failure.The failure analysis is performed for both the cross-ply and angle-ply laminates with all edges simply supported and clamped.The significance of fibre orientation and stacking sequence in terms of the strength of a laminate and failure progression is also highlighted.展开更多
基金Anil Kumar Singh acknowledges the Board of Research in Nuclear Science(BRNS)Mumbai(Sanction No.2012/37P/40/BRNS/2145)+1 种基金the UGC-DAE Consortium for Scientific Research,Mumbai(Sanction No.CRS-M-187,225)the Science and Engineering Research Board(SERB),New Delhi(Sanction No.SR/FTS/PS-187/2011)for funding.
文摘For this study,we synthesized Aurivillius Bi_(5)Ti_(3)FeO_(15) ceramic using the generic solid-state reaction route and then performed roomtemperature X-ray diffraction to confirm that the compound had a single phase with no impurities.The surface morphology of the prepared sample was observed to contain microstructural grains approximately 0.2–2μm in size.The dielectric properties of the sample were determined as a function of frequency in a range of approximately 100 Hz to 1 MHz at various temperatures(303 K≤T≤773 K).Nyquist plots of the impedance data were found to exhibit a semi-circular arc in the high-temperature region,which is explained by the equivalent electrical circuit(R_(1)C_(1))(R_(2)QC_(2)),where R_(1) and R_(2) represent the resistances associated with the grains and grain boundaries,respectively,C_(1) and C_(2) are the respective capacitances,and Q is the constant phase element(CPE),which accounts for non-Debye type of behavior.Our results indicate that both the resistance and capacitance of the grain boundaries are more prominent than those of the grains.The alternating current(ac)conductivity data were analyzed based on the Jonscher universal power law,which indicated that the conduction process is dominated by the hopping mechanism.The calculated activation energies of the relaxation and conduction processes were very similar(0.32 to 0.53 eV),from which we conclude that the same type of charge carriers are involved in both processes.
基金UGC-DAE CSR,Mumbai(Sanction No.CRS-M-187,225)Board of Research in Nuclear Science(BRNS),Mumbai(Sanction No.2012/37P/40/BRNS/2145)Science and Engineering Research Board(SERB),New Delhi(Sanction No.SR/FTP/PS-187/2011)for funding and fellowships.
文摘Cobalt(Co)-modified brownmillerite KBiFe_(2)O_(5)(KBFO;[KBiFe_(2(1−x))Co_(2x)O_(5)(x=0,0.05)])polycrystalline is synthesized following the solid-state reaction route.Rietveld refinement of X-ray diffraction data confirmed the phase purity of KBFO and KBiFe_(1.9)Co_(0.1)O_(5)(KBFCO).The optical bandgap energy(Eg)of KBFO decreased from 1.59 to 1.51 eV because of Co substitution.The decrease in bandgap can be attributed to the tilting of the Fe–O tetrahedral structure of KBFCO.The observed room-temperature Raman peaks of KBFCO shifted by 3 cm^(−1) toward a lower wavenumber than that of KBFO.The shift in Raman active modes can be attributed to the change in the bond angles and bond lengths of the Fe–O tetrahedral structure and modification in response to oxygen deficiency in KBFO because of Co doping.Compared with that of KBFO,the frequency-dependent dielectric constant and dielectric loss of KBFCO decrease at room temperature,which is a consequence of the reduction in oxygen migration and modification in response to vibrational modes present in the sample.
文摘Ply-by-ply failure analysis of symmetric and anti-symmetric laminates under uniform sinusoidal transverse dynamic loading is performed for a specified duration.The study investigates the first ply failure load,followed by the detection of successive ply failures and their failure modes using various failure theories.Some of the well-established failure theories,mostly used by the researchers,are considered for the failure prediction in laminates.The finite element computational model based on higher order shear deformation displacement field is used for the failure analysis and the complete methodology is computer coded using FORTRAN.The ply-discount stiffness reduction scheme is employed to modify the material properties of the failed lamina.The failure theories used in the analysis are compared according to their ability to predict failure load,failed ply,failure mode and progression of failure.The failure analysis is performed for both the cross-ply and angle-ply laminates with all edges simply supported and clamped.The significance of fibre orientation and stacking sequence in terms of the strength of a laminate and failure progression is also highlighted.
