Murtaza Saleem

Uptake of Uranium Ions by Molecular Sieve

Adsorption of uranium on molecular sieve (X-type) has been studied as a function of shaking time, amount of adsorbent, pH, concentration of adsorbate and temperature. Uranium adsorption obeys the Langmuir and Dibinin-Rudushkevich isotherms equations. The values of AH° and ΔS° were calculated from the slopes and intercepts of plots between In KD versus MT. The results show endothermic heat of adsorption but negative free energy value indicating that the process of uranium adsorption on molecular sieve is favoured at high temperature. The influence of various cations and anions on uranium adsorption were also studied. Table 1. Instrumental conditions for measuring Uranium concentration

Enhanced magnetization of sol-gel synthesized Pb-doped strontium hexaferrites nanocrystallites at low temperature

Effect of Pb doping on the structural and low temperature magnetic properties of SrPbxFe12-xO19 (x = 0, 0.1, 0.2, 0.3, and 0.4), synthesized by sol-gel autocombustion technique, has been investigated. The powder samples were sintered at 800°C for 2 h in order to develop the stable hexagonal phase, characteristic of the SrFe12O19 structure. The consequences of Pb substitution (at iron sites) on various structural parameters like lattice constants, unit cell volume, crystallite size, and porosity have been discussed. Fourier transform infrared frequency bands were utilized to determine the formation of tetrahedral and octahedral clusters of M-type ferrites. Hexagonal texture of the grains, a characteristic of the hexagonal crystal structure of SrFe12O19, was refined by Pb substitution. The magnetic properties, determined using a vibrating sample magnetometer, revealed that saturation magnetization decreased, while coercivity was increased with the increase of Pb contents. However, the increased squareness ratio and hence the energy product motivate the utilization of these ferrite compositions where hard magnetic characteristics are required.The increased values of saturation magnetization were observed at reduced temperature of 200 K, attributable to the better spin alignments of individual magnetic moments at low temperature.

Room Temperature Magnetic Behavior of Sol-Gel Synthesized Mn Doped ZnO

Mn doped ZnO nano-crystallites were synthesized by state of the art sol-gel derived auto-combustion technique. As-burnt powder was investigated with different characterization techniques to explore the properties of Mn doped ZnO dilute magnetic semiconductor. X-ray diffraction measurements indicate that Mn doped ZnO retain wurtzite type hexagonal crystal structure like ZnO. Compositional and morphological studies were carried out by energy dispersive X-ray analysis and scanning electron microscopy, respectively. Temperature dependent resistivity of the sample exhibited the semiconducting behavior of the DMS material. Room temperature magnetic properties determined by vibrating sample magnetometer, revealed the presence of ferromagnetic and diamagnetic contributions in Mn doped ZnO.

Effect of Co substitution on the structural, electrical, and magnetic properties of Bi0.9La0.1FeO3 by sol-gel synthesis

Cobalt (Co)-doped Bi0.9La0.1FeO3 multiferroics were synthesized by a sol-gel method based on the autocombustion technique. As-synthesized powder was examined using various characterization techniques to explore the effect of Co substitution on the properties of Bi0.9La0.1FeO3. X-ray diffraction reveals that Co-doped Bi0.9La0.1FeO3 preserves the perovskite-type rhombohedral structure of BiFeO3, and the composition without Co preserves the original structure of the phase; however, a second-phase Bi2Fe4O9 has been identified in all other compositions. Surface morphological studies were performed by scanning electron microscopy. Temperature-dependent resistivity of the samples reveals the characteristic insulating behavior of the multiferroic material. The resistivity is found to decrease with the increase both in temperature and Co content. Room temperature frequency-dependent dielectric measurements were also reported. Magnetic measurements show the enhancement in magnetization with the increase in Co content.

Multiferroicity in sol–gel synthesized Sr/Mn co-doped BiFeO3 nanoparticles

A simple and cost effective sol–gel auto-combustion technique was used to synthesize Bi0.9Sr0.1Fe1−xMnxO3 (x = 0, 0.05, 0.10, 0.15 and 0.20) multiferroics. Rietveld’s refined X-ray diffraction patterns validated the synthesis of pure phase bismuth ferrite nanoparticles adopting a rhombohedrally distorted ABO3 type perovskite structure with space group R3c. Morphology of the prepared samples manifested the improved crystallinity with increasing Mn contents in BiFeO3. Uniformly distributed multi-shaped grains having varying sizes were formed after combustion which would affect the microstructural related properties of the parent compound. Energy dispersive X-ray spectroscopy confirmed the presence of the relevant elements in the prepared compositions according to their stoichiometric ratio. Enhanced saturation magnetization was observed with increasing doping concentration in the parent compound. Improved polarization versus electric field loops were observed in Mn and Sr co-doped BiFeO3 nanoparticles. All the properties in the present research work have been explained on the basis of dopants and their concentrations, phase purity, microstructure and grain sizes.

Origin of Ferromagnetism in Al and Ni Co-doped ZnO Based DMS Materials

Zn0.95Ni0.05O and Zn0.90Ni0.05Al0.05O compositions of nanocrystallites are synthesised using the well recognised auto-combustion technique. The x-ray diffraction patterns demonstrate the phase pure characteristic wurtzite-type crystal structure with space group P63mc in both the compositions. The elemental incorporation of Ni and Al contents into the ZnO structure is confirmed by energy dispersive x-ray analysis. The micrographs of scanning electron microscopy show an approximate ordered morphology. The electrical resistivity is observed to decrease with the rising temperature, depicting the characteristic semiconductor behaviour of the samples. The lower values of resistivity and ferromagnetic interactions in the Al-doped sample correspond to an increase of carriers density. It is observed that the carrier mediated mechanism is mainly responsible for ferromagnetism in ZnO-based diluted magnetic semiconductors.

Adsorption of UO22+ ions on activated charcoal : pH effect

The adsorption of UO22+ ions on activated charcoal was studied as a function of pH. The adsorption mechanism of UO22+ ions has been discussed in terms of hydrolyzed species formed in aqueous solution at different pH values.

Structural and Magnetic Studies of Zn0.95Co0.05O and Zn0.90Co0.05Al0.05O

Single-phase Zn0.95Co0.05O and Zn0.90Co0.05Al0.05O samples were prepared by a novel combustion method. X-ray diffraction studies exhibit the pure phase wurtzite structure of doped ZnO. Energy dispersive x-ray analysis confirms the incorporation of dopants into the host material. Scanning electron microscopy shows the ordered morphology in both of the samples. Temperature-dependent resistivity analysis describes the expected semiconducting behavior that is similar to the parent ZnO materials. Room-temperature magnetic measurements reveal the absence of ferromagnetism in Co-doped ZnO, while the Co and Al co-doped sample displays apparent room-temperature ferromagnetic behavior. The decrease of resistivity and presence of ferromagnetic behavior in Al-doped ZnCoO system corroborate the significant role of free carriers.

Phase Pure Synthesis and Morphology Dependent Magnetization in Mn Doped ZnO Nanostructures

Zn0.95Mn0.05O nanostructures were synthesized using sol gel derived autocombustion technique. As-burnt samples were thermally annealed at different temperatures (400, 600, and 800°C) for 8 hours to investigate their effect on structural morphology and magnetic behavior. X-ray diffraction and scanning electron microscopic studies demonstrated the improvement in crystallinity of phase pure wurtzite structure of Mn doped ZnO with variation of annealing temperature. Energy dispersive X-ray elemental compositional analysis confirmed the exact nominal compositions of the reactants. Electrical resistivity measurements were performed with variation in temperature, which depicted the semiconducting nature similar to parent ZnO after 5 at% Mn doping. Magnetic measurements by superconducting quantum interference device detected an enhanced trend of ferromagnetic interactions in thermally annealed compositions attributed to the improved structural morphology and crystalline refinement process.

Carriers‐assisted Enhanced Ferromagnetism in Al‐doped ZnMnO Nano‐crystallites

Zn 0.95−x Al x Mn0.05O (x=0, 0.03, 0.05, and 0.07) dilute magnetic semiconductor materials have been synthesized by sol‐gel auto‐combustion technique. The effect of Al doping on the structural, electrical, and magnetic properties has been investigated. X‐ray diffraction studies demonstrate the existence of single phase characteristic hexagonal wurtzite type crystal structure, similar to the host ZnO, in all the synthesized compositions. Although, the microscopic images revealed that the grains were clustered, yet some individual grains could be seen to have hexagonal texture. Electrical resistivity was observed to decrease with the rise of temperature up to 450 °C, depicting the characteristic semiconductor behavior. Room temperature ferromagnetic behavior was observed in all the compositions. The value of saturation magnetization increased with the increase of Al concentration in ZnMnO system referred to the gradual enhancement of free carriers.