Finite size effect and influence of temperature on electrical properties of nanocrystalline Ni–Cd ferrites

Batoo, Khalid Mujasam,Kumar, Shalendra,Lee, Chan Gyu,Alimuddin, Chan Gyu Elsevier 2009 Current Applied Physics Vol.9 No.5

<P><B>Abstract</B></P><P>Electrical conductivity and dielectric measurements have been investigated for four different average grain sizes ranging from 3 to 7nm of nanocrystalline Ni<SUB>0.2</SUB>Cd<SUB>0.3</SUB>Fe<SUB>2.5−</SUB><I><SUB>x</SUB></I>Al<I><SUB>x</SUB></I>O<SUB>4</SUB> (0.0⩽<I>x</I>⩽0.5) ferrites. The impedance spectroscopy technique has been used to study the effect of grain and grain boundary on the electrical properties of the Al doped Ni–Cd ferrites. The analysis of data shows only one semi-circle corresponding to the grain boundary volume suggesting that the conduction mechanism takes place predominantly through grain boundary volume in the studied samples. The variation of impedance properties with temperature and composition has been studied in the frequency range of 120Hz–5MHz between the temperatures 300–473K. The hopping of electrons between Fe<SUP>3+</SUP> and Fe<SUP>2+</SUP> as well as hole hopping between Ni<SUP>3+</SUP> and Ni<SUP>2+</SUP> ions at octahedral sites are found to be responsible for conduction mechanism. The dielectric constant and loss tangent (tan<I>δ</I>) are found to decrease with increasing frequency, whereas they increase with increasing temperature. The dielectric constant shows an anomalous behavior at selected frequencies, while the temperature increases, which is expected due to the generation of more electrons and holes as the temperature increases. The behavior has been explained in the light of Rezlescu model.</P>

Study of dielectric and ac impedance properties of Ti doped Mn ferrites

Khalid Mujasam Batoo,샤런드라쿠마르,이찬규,Alimuddin 한국물리학회 2009 Current Applied Physics Vol.9 No.6

We have reported dielectric and ac impedance properties of Ti doped Mn1+xFe2-2xO4 (0 ≼ x ≼ 0:5) ferrites prepared by solid-state reaction method, using dielectric and impedance spectroscopy in the frequency range of 42 Hz–5 MHz, between the temperatures (300K–473K). The dielectric constant and dielectric loss (tand) decreases with increasing frequency but these parameters increase with increasing temperature. The dielectric loss tangent curves exhibit dielectric relaxation peaks at high frequencies (3.6 kHz– 5 MHz), which are attributed to the coincidence of the frequency of charge hopping between the localized charge states and the external field. The dielectric properties have been explained on the basis of space charge polarization according to Maxwell–Wagner’s two-layer model and the hopping of charge between Fe2+ and Fe3+ as well as between Mn3+ and Mn2+ ions at B-sites. The complex impedance analysis has been used to separate grain and grain boundary in studied samples. Two semicircles corresponding to grain and grain boundary have been observed at low temperature, while only one semicircle has been seen at high temperatures. The resistance of grain and grain boundary both increase with Ti4+ doping.

Influence of Al doping on electrical properties of Ni–Cd nano ferrites

Khalid Mujasam Batoo,샤런드라쿠마르,이찬규,Alimuddin 한국물리학회 2009 Current Applied Physics Vol.9 No.4

We have reported the structural and electrical properties of nano particles of Al doped Ni0.2Cd0.3Fe2.5O4 ferrite using X-ray diffraction, dielectric spectroscopy and impedance spectroscopy at room temperature. XRD analysis confirms that the system exhibits polycrystalline single phase cubic spinel structure. The average particle size estimated using Scherrer formula for Lorentzian peak (311), has been found 5(±) nm. The results obtained show that real (ε'), imaginary (ε'') part of the dielectric constant, loss tangent (tanδ), and ac conductivity (σac) shows normal behaviour with frequency. The dielectric properties and ac conductivity in the samples have been explained on the basis of space charge polarization according to Maxwell–Wagner two-layer model and the Koop’s phenomenological theory. The impedance analysis shows that the value of grain boundary impedance increases with Al doping. The complex impedance spectra of nano particles of Al doped Ni–Cd ferrite have been analyzed and explained using the Cole–Cole expression.

Finite size effect and influence of temperature on electrical properties of nanocrystalline Ni–Cd ferrites

Khalid Mujasam Batoo,이찬규,샤런드라쿠마르,Alimuddin 한국물리학회 2009 Current Applied Physics Vol.9 No.5

Electrical conductivity and dielectric measurements have been investigated for four different average grain sizes ranging from 3 to 7 nm of nanocrystalline Ni0.2Cd0.3Fe2.5-xAlxO4 (0.0 ≼ x ≼ 0.5) ferrites. The impedance spectroscopy technique has been used to study the effect of grain and grain boundary on the electrical properties of the Al doped Ni–Cd ferrites. The analysis of data shows only one semi-circle corresponding to the grain boundary volume suggesting that the conduction mechanism takes place predominantly through grain boundary volume in the studied samples. The variation of impedance properties with temperature and composition has been studied in the frequency range of 120 Hz–5 MHz between the temperatures 300–473 K. The hopping of electrons between Fe3+ and Fe2+ as well as hole hopping between Ni3+ and Ni2+ ions at octahedral sites are found to be responsible for conduction mechanism. The dielectric constant and loss tangent (tand) are found to decrease with increasing frequency, whereas they increase with increasing temperature. The dielectric constant shows an anomalous behavior at selected frequencies, while the temperature increases, which is expected due to the generation of more electrons and holes as the temperature increases. The behavior has been explained in the light of Rezlescu model.

A magnetic nanocomposite produced from camel bones for an efficient adsorption of toxic metals from water

Alqadami, Ayoub Abdullah,Khan, Moonis Ali,Otero, Marta,Siddiqui, Masoom Raza,Jeon, Byong-Hun,Batoo, Khalid Mujasam Elsevier 2018 Journal of cleaner production Vol.178 No.-

<P><B>Abstract</B></P> <P>A new, simple, clean, and green procedure for the production of a magnetic nanocomposite (MBBC) from waste camel bone biochar was here described. MBBC particles were in the nano-size range (∼12 nm), having characteristics of both hydroxyapatite and magnetite. The produced nanocomposite was characterized by FT-IR, XRD, TG, SEM, TEM, BET, XRD, Zeta potential and XPS analyses. MBBC exhibited a paramagnetic behavior, having a saturation magnetization of 50.20 emu/g and a mesoporous structure with a BET surface area of 162 m<SUP>2</SUP>/g. The FT-IR spectrum of MBBC displayed doublet peaks at 573–601 cm<SUP>−1</SUP> (corresponding to Fe–O vibrations) and a peak at 1046 cm<SUP>−1</SUP> (associated with HPO<SUB>4</SUB>), which support the successful formation of MBBC. The maximum adsorption capacities of MBBC, as for the Langmuir isotherm model fittings, were 344.8, 322.6 and 294.1 mg/g for Pb(II), Cd(II) and Co(II), respectively. MBBC showed rapid heavy metals adsorption rates, accomplishing ∼75% adsorption within 5 min. After adsorption accomplishment, MBBC particles were magnetically separated from treated water and heavy metals from saturated MBBC were efficiently desorbed by elution with 0.01 M HCl. Under such elution, the MBBC stability against acid leaching of Fe was proved. Hence, it could be inferred that the production of MBBC from waste camel bones and its utilization for the removal of heavy metals from water is a novel approach within the cleaner production concept.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A magnetic nanocomposite (MBBC) was produced from waste camel bone biochar. </LI> <LI> MBBC was ∼12 nm particle size, paramagnetic and mesoporous with 162 m<SUP>2</SUP>/g BET area. </LI> <LI> Pb(II), Cd(II) and Co(II) adsorption capacities on MBBC were 345, 323 and 294 mg/g. </LI> <LI> Metals recovery from saturated MBBC was maximum (85–90%) with 0.01 M HCl. </LI> <LI> Deniable leaching of Fe occurred from MBBC during desorption with 0.01 M HCl. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>