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Chaudhary R.K.,Indian Institute of Technology Kanpur | Baskey H.B.,Special Materials Group | Srivastava K.V.,Indian Institute of Technology Kanpur | Biswas A.,Indian Institute of Technology Kanpur
IET Microwaves, Antennas and Propagation | Year: 2012

In this study, (Zr 0.8Sn 0.2)TiO 4-epoxy composites are synthesised, characterised and used in dielectric resonator antenna applications. (Zr 0.8Sn 0.2)TiO 4 and epoxy are mixed in five different ratios, that is, 50:50, 60:40, 70:30, 80:20 and 90:10 with small amount of hardner (HY 951). The crystal structure and cell parameters of (Zr 0.8Sn 0.2)TiO 4 are confined by Rietveld analysis. The complex permittivity of the composite is measured at different microwave frequencies in X-band (8.2-12.4 GHz). It has been found that the permittivity is reduced by increasing the percentage of epoxy in composite system. The optimised weight percentage ratio of (Zr 0.8Sn 0.2)TiO 4 and epoxy composite material are used in a two-layer rectangular dielectric resonator antenna using coaxial excitation for obtaining wideband performance. The effects of the antenna parameters like length, width and probe length are investigated using Ansoft's high-frequency structure simulator (HFSS) software. The agreement between simulated and experimental data is very good. The proposed design provides the measured impedance bandwidth of 58.7% (at resonance frequency 8.40 GHz) from 6.45 to 11.38 GHz for reflection coefficient (S 11) of less than -10 dB with a measured average gain of 6.99 dB in the frequency range of 6.0-11.5 GHz. The radiation patterns are consistent throughout the operational bandwidth. © 2012 The Institution of Engineering and Technology.


Chaudhary R.K.,Indian Institute of Technology Kanpur | Baskey H.B.,Special Materials Group | Srivastava K.V.,Indian Institute of Technology Kanpur | Biswas A.,Indian Institute of Technology Kanpur
2011 IEEE Indian Antenna Week - Workshop on Advanced Antenna Technology, IAW 2011 | Year: 2011

In this study, (Zr 0.8Sn 0.2)TiO 4-Epoxy composite have been synthesized and characterized at X-band frequencies. (Zr 0.8Sn 0.2)TiO 4 and Epoxy are mixed in five different ratios, i.e. 50:50, 60:40, 70:30, 80:20 and 90:10 with small amount of hardner (HY 951). The complex permittivity of the composite is measured at different microwave frequencies in X-band (8.2-12.4 GHz). It is found that the permittivity is reduced by increasing the percentage of epoxy in the composite. The optimized ratio of (Zr 0.8Sn 0.2)TiO 4 and Epoxy composite material have been used in two layer rectangular dielectric resonator antenna using coaxial excitation. The proposed design provides the measured impedance bandwidth of 58.7% (at resonance frequency 8.40 GHz) from 6.45 to 11.38 GHz for reflection coefficient (S 11) less than -10dB with absolute gain of 6.7 dB. The radiation patterns are consistent throughout the operational bandwidth. © 2011 IEEE.


Tyagi S.,Indian Institute of Technology Roorkee | Baskey H.B.,Special Materials Group | Agarwala R.C.,Indian Institute of Technology Roorkee | Agarwala V.,Indian Institute of Technology Roorkee | Shami T.C.,Special Materials Group
Transactions of the Indian Institute of Metals | Year: 2011

Mixture of cobalt ferrite and strontium hexaferrite nanocrystals i.e. SrFe 12O 19/CoFe 2O 4 exhibiting super paramagnetic nature were synthesized by modified flux method. The resulting precursors were heat treated (HT) at 900 and 1200°C for 4 h in nitrogen atmosphere. During heat treatment, transformation proceeds as instantaneous rate of nucleation and three dimensional growth with activation energy of 135.835 kJ/mole. The hysteresis loops showed a hike in saturation magnetization from 1.045 to 84.362 emu/g with an increase in HT temperature. The 'as synthesized' particles have size in the range of 10-20 nm with spherical shape. Further, these spherical shape particles tend to change their morphology to hexagonal plates with increase in HT temperatures. The relative complex permittivity and permeability of the composite powder are investigated. The minimum reflection loss of the composite powder reaches to-27.6 dB at 10.8 GHz which suits its application in RADAR absorbing materials. © 2011 TIIM, India.


Tyagi S.,Indian Institute of Technology Roorkee | Baskey H.B.,Special Materials Group | Agarwala R.C.,Indian Institute of Technology Roorkee | Agarwala V.,Indian Institute of Technology Roorkee | Shami T.C.,Special Materials Group
Transactions of the Indian Institute of Metals | Year: 2011

Zinc ferrite and strontium hexaferrite; SrFe 12O 19/ZnFe 2O 4 (SrFe 11.6Zn 0.4O 19) nanoparticles having super paramagnetic nature were synthesized by simultaneous co-precipitation of iron, zinc and strontium chloride salts using 5 M sodium hydroxide solution. The resulting precursors were heat treated (HT) at 850, 950 and 1150°C for 4 h in nitrogen atmosphere. The hysteresis loops showed an increase in saturation magnetization from 1.040 to 58.938 emu/g with increasing HT temperatures. The 'as-synthesized' particles have size in the range of 20-25 nm with spherical and needle shapes. Further, these spherical and needle shaped nanoparticles tend to change their morphology to hexagonal plate shape with increase in HT temperatures. The effect of such a systematic morphological transformation of nanoparticles on dielectric (complex permittivity and permeability) and microwave absorption properties were estimated in X band (8.2-12.2 GHz). The maximum reflection loss of the composite reaches -26.51 dB (more than 99% power attenuation) at 10.636 GHz which suits its application in RADAR absorbing materials. © 2011 Indian Institute of Metals.


Tyagi S.,Indian Institute of Technology Roorkee | Baskey H.B.,Special Materials Group | Agarwala R.C.,Indian Institute of Technology Roorkee | Agarwala V.,Indian Institute of Technology Roorkee | Shami T.C.,Special Materials Group
Ceramics International | Year: 2011

Nickel and zinc substituted strontium hexaferrite, SrFe11Zn 0.5Ni0.5O19 (SrFe12O 19/NiFe2O4/ZnFe2O4) nanoparticles having super paramagnetic nature are synthesized by co-precipitation of chloride salts using 7.5 M sodium hydroxide solution. The resulting precursors are heat treated (HT) at 900 and 1200 °C for 4 h in nitrogen atmosphere. During heat treatment, transformation proceeds as a constant rate of nucleation and three dimensional growth with an activation energy of 176.79 kJ/mol. The hysteresis loops show an increase in saturation magnetization from 1.042 to 59.789 emu/g with increasing HT temperatures. The 'as-synthesized' particles with spherical and needle shapes have size in the range of 20-25 nm. Further, these spherical and needle shaped nanoparticles tend to change their morphology to hexagonal plate and pyramidal shapes with increase in HT temperatures. The effect of such a systematic morphological transformation of nanoparticles on dielectric (complex permittivity and permeability) and microwave absorption properties are estimated in X band (8.2-12.2 GHz). The maximum reflection loss of the composite reaches -29.62 dB (99% power attenuation) at 10.21 GHz which suits its application in RADAR absorbing materials. © 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

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