Elements Of X Ray Diffraction

When collimated beams of low energy ions are used to bombard materials, the surface often develops a periodic pattern or “ripple” structure. Different types of patterns are observed to develop under different conditions, with characteristic features that depend on the substrate material, the ion beam parameters, and the processing conditions. Because the patterns develop spontaneously, without applying any external mask or template, their formation is the expression of a dynamic balance among fundamental surface kinetic processes, e.g., erosion of material from the surface, ion-induced defect creation, and defect-mediated evolution of the surface morphology. In recent years, a comprehensive picture of the different kinetic mechanisms that control the different types of patterns that form has begun to emerge. In this article, we provide a review of different mechanisms that have been proposed and how they fit together in terms of the kinetic regimes in which they dominate. These are grouped into regions of behavior dominated by the directionality of the ion beam, the crystallinity of the surface, the barriers to surface roughening, and nonlinear effects. In sections devoted to each type of behavior, we relate experimental observations of patterning in these regimes to predictions of continuum models and to computer simulations. A comparison between theory and experiment is used to highlight strengths and weaknesses in our understanding. We also discuss the patterning behavior that falls outside the scope of the current understanding and opportunities for advancement.

Making waves: Kinetic processes controlling surface evolution during low energy ion sputtering

The demand for portable gas sensors is increasing following the progress in the electronics industry; there is an equal need to increase the quality of gas sensors. Spinel ferrites have been used as electronic materials for more than 50 years and offer a suitable ceramic base for the gas sensor market. They are simple, low cost, and compared to other gas sensors have structural and compositional versatility. This review highlights the recent developments and shows the potential of the spinel ferrites on gas sensor technology. Sensing mechanisms for a range of gasses and humidity are explained for n-type, p-type, mixed and substituted spinel ferrite gas sensors. The change in conduction mechanism is discussed outlining electronic and chemical sensitization that both increase the conductivity. Some cation substitutions are shown to change the oxidation state, thereby increasing sensitivity, but noble metals are shown to chemically sensitize spinel ferrites. This review surveys synthesis methods for producing spinel ferrites and discusses future prospects for further improvements.

Spinel ferrite oxide semiconductor gas sensors

Synthesis and characterization of zinc/iron oxide composite nanoparticles and their antibacterial properties

We report the design and synthesis of small-sized zwitterion-coated gadolinium-embedded iron oxide (GdIO) nanoparticles, which exhibit a strong T1 contrast effect for tumor imaging through enhanced permeation and retention effect and the ability to clear out of the body in living subjects. The combination of spin-canting effects and the collection of gadolinium species within small-sized GdIO nanoparticles led to a significantly enhanced T1 contrast effect. For example, GdIO nanoparticles with a diameter of ∼4.8 nm exhibited a high r1 relaxivity of 7.85 mM–1·S–1 and a low r2/r1 ratio of 5.24. After being coated with zwitterionic dopamine sulfonate molecules, the 4.8 nm GdIO nanoparticles showed a steady hydrodynamic diameter (∼5.2 nm) in both PBS buffer and fetal bovine serum solution, indicating a low nonspecific protein absorption. This study provides a valuable strategy for the design of highly sensitive iron-oxide-based T1 contrast agents with relatively long circulation half-lives (∼50 min), efficien...

Engineered iron-oxide-based nanoparticles as enhanced T1 contrast agents for efficient tumor imaging.

Magnetic resonance study of Ce and Gd doped NiFe2O4 nanoparticles

In the present work, structural, morphological, magnetic and optical properties of nickel ferrite thin films having different thickness are reported. All the films were deposited on Si (100) substrate by pulsed laser deposition technique. Thicknesses of the films determined by x-ray reflectivity vary from 62 to 176nm as the deposition time varies from 16 min to 40 min. The films were characterised by x-ray diffractogram, Fourier transform infrared (FTIR) and Raman spectroscopy for structural and phase confirmation. FTIR and Raman spectra confirm mixed spinel nature of nickel ferrite. Surface morphology is studied by Atomic force microscopy. All the films have granular nature. Magnetic properties were studied by vibrating sample magnetometer and magnetic hysteresis curves were recorded for all the films at room temperature and at10K. At 10K, saturation magnetisation was found to increase while coercivity deceases with thickness. The results are explained on the basis of anisotropy induced by cation inversion and strain. Optical properties were studied by UV-vis reflectance spectra. The value of optical band gap (5.7eV) was found to be independent of thickness of the film. Copyright © 2011 VBRI press.

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Structural, Magnetic And Optical Studies Of nickel Ferrite Thin Films

Zinc ferrite nanoparticles of different sizes ranging from 12 to 62 nm were synthesized by using the nitrate route. These nanoparticles were irradiated by a 100 MeV oxygen beam at two fluences: 1 × 1013 and 5 × 1013 ions/cm2. It was observed that modes corresponding to cubic spinel phase were retained after the irradiation in all the systems. The variation in the parameters of various modes follows phonon confinement, while this effect seems to violate in irradiated specimen. It was found that the irradiation-induced changes in the modes F2g(2) and F2g(3) depend on whether the crystallite size of the pristine sample is less than, equal to or greater than the phonon confinement length, while this length is not dominant for the irradiation-induced changes in the mode A1g. The changes in various parameters of the modes are attributed to the combined effect of the restructuring of the chemical species and ion-induced defects. Copyright © 2011 John Wiley & Sons, Ltd.

Micro-Raman investigation of nanosized zinc ferrite: effect of crystallite size and fluence of irradiation

We have studied the role of Dy3+ doping on the XRD, TEM, FTIR, and dielectric and electrical properties of CoFe2O4 at room temperature. Cubic spinel phase of CoFe2−xDyxO4 ( <path id="x1D465" d="M536 404q0 -17 -13.5 -31.5t-26.5 -14.5q-8 0 -15 10q-11 14 -25 14q-22 0 -67 -50q-47 -52 -68 -82l37 -102q31 -88 55 -88t78 59l16 -23q-32 -48 -68.5 -78t-65.5 -30q-19 0 -37.5 20t-29.5 53l-41 116q-72 -106 -114.5 -147.5t-79.5 -41.5q-21 0 -34.5 14t-13.5 37
q0 16 13.5 31.5t28.5 15.5q12 0 17 -11q5 -10 25 -10q22 0 57.5 36t89.5 111l-40 108q-22 58 -36 58q-21 0 -67 -57l-19 20q81 107 125 107q17 0 30 -22t39 -88l22 -55q68 92 108.5 128.5t74.5 36.5q20 0 32.5 -14t12.5 -30z"> = 0.00, 0.05, 0.10, and 0.15) was synthesized by using different sintering temperatures (300, 500, 700, and 900°C). The two absorption bands ν1 and ν2 are observed in Fourier transform infrared spectroscopy (FTIR) spectra corresponding to the tetrahedral and octahedral sites, which show signature of spinel structure of the sample. For the sample sintered at 300°C, the dielectric constant is almost unchanged with the frequency at the particular concentrations of = 0.00 and 0.05. Similar result is obtained for the sample sintered at 500°C ( = 0.10, 0.15), 700°C ( = 0.05, 0.10, and 0.15), and 900°C ( = 0.05, 0.10). An increase in the dielectric constant was observed for the undoped cobalt ferrite sintered at 500, 700, and 900°C. The values of electrical resistivity of the materials vary from ~105 to 109 Ω-cm.

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H.M. Agrawal

Papers

Magnetic resonance study of Ce and Gd doped NiFe2O4 nanoparticles

Structural, Magnetic And Optical Studies Of nickel Ferrite Thin Films

Micro-Raman investigation of nanosized zinc ferrite: effect of crystallite size and fluence of irradiation

FTIR and Electrical Study of Dysprosium Doped Cobalt Ferrite Nanoparticles

Qualitative soil mineral analysis by EDXRF, XRD and AAS probes