In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Experiments have been performed to further the development of natural fiber reinforced composites as a replacement for glass fiber composites. Untreated and treated surfaces of natural fibers were characterized using FTIR, XPS, and ESEM. Changes in the peaks in the FTIR spectrum at 1730, 1625 and 1239 cm −1 indicated that the alkali treatment removes hemicellulose and lignin from natural fiber surfaces. ESEM indicated the presence of silane on treated hemp and kenaf. XPS shows that hemp has a lower O/C ratio than kenaf. Water absorption experiments were also conducted to determine saturation mass gain. Alkali treated fiber composites absorbed more water than silane treated or untreated composites. The natural fiber composites absorbed more water than the glass fiber composites. Hemp composites, in general, performed worse in flexural testing than kenaf composites.

Characterization of natural fiber surfaces and natural fiber composites

We discuss the generation of high-density and high-temperature plasmas by focusing high peak power laser radiation onto a solid target. Emphasis will be put on the process of laser ablation and on its basic, physical mechanisms. A survey will be given of the main experimental techniques, namely optical emission and absorption spectroscopy, mass spectrometry, time-of-flight and charge collection measurements, devised to characterize laser-produced plasmas. The fundamental theoretical and numerical approaches developed to analyse laser-target interaction, plasma formation, as well as its expansion will also be reviewed, and their predictions compared with the experimental findings. Although the main emphasis of the review will be on metal target ablation, reference and comparison to results on multicomponent targets will also be frequently given.

https://iopscience.iop.org/article/10.1088/0953-4075/32/14/201/pdf

Characterization of laser-ablation plasmas

Physical and electrical properties of Zr–Cu substituted strontium hexaferrite nanoparticles synthesized by co-precipitation method

Scanning force microscopy (SFM) has been used for the determination of friction, phase transformation, piezoelectric behavior (in the contact mode), polarization state, and dielectric constant (in the noncontact mode) of nanometer regions of lead zirconate titanate (PZT) films. The use of the SFM tip in the contact mode, to polarize different nanoregions of the PZT film and to apply an oscillating field thereon, led to effective piezoelectric coefficients and piezoelectric loops. The measured effective piezoelectric coefficient was shown to depend appreciably on both the tip contact force and the quality of the tip-to-film electrical contact. In the noncontact mode, application of an ac signal (with a frequency ω) across the tip—PZT film—electrode system produced an oscillation of the tip at frequencies ω (fundamental or first harmonic) and 2ω (second harmonic). The signals at ω and 2ω were related to the state of polarization and the dielectric constant of the PZT film, respectively. Analysis of the comb...

Characterization of ferroelectric lead zirconate titanate films by scanning force microscopy

Mössbauer and magnetic studies of PbFe12−xCrxO19 hexagonal ferrites

AlVO4 is a relatively new sensor material derived from V2O5/Al2O3 mixtures to selectively detect NO and NO2 gases. Previous studies carried out in order to determine its structural, absorptive and sensory properties indicate that the AlVO4 is not the only single phase. This work deals with the synthesis of the compound by the ceramic and the nitrate decomposition methods, and by the sol gel route. The Rietveld refinement of the compound was carried out in order to determine its crystal structure. Single phase of AlVO4 was successfully obtained via the nitrate decomposition and the sol gel methods. Thereafter, films prepared by the sol gel route were deposited on alumina and Si/SiO2/Pt substrates and characterized by SEM and X-ray diffraction. The electric characterization of the AlVO4 on alumina substrate film is also presented.

Preparation and characterization of AlVO4 compound

Experimental study of the Hopkinson effect in fine BaFe12O19 particles

The transport of material from target to substrate has been monitored in the pulsed laser deposition of Pb(Ti0.48Zr0.52)O3 films on p‐doped Si(100) using two in situ diagnostics, namely plume fluorescence spectroscopy and plume ion mass spectrometry. The as‐grown PZT films are specular, with thicknesses which decrease from 350 to 250 nm on a radius 5 mm from the center and show a dielectric hysteresis with typical remanent polarizations and coercive fields of 0.2 μC/cm2 and 124 kV/cm, respectively. The analysis of the plume fluorescence emission and ionic yield indicates that oxidation of the ablated material occurs during transport from target to substrate and that, in order to grow ferroelectric thin films, the substrate should be located in the region of the plume where the relative concentrations of metal oxides and clusters increase.

F. Leccabue

Papers

Mössbauer and magnetic studies of PbFe12−xCrxO19 hexagonal ferrites

Preparation and characterization of AlVO4 compound

Experimental study of the Hopkinson effect in fine BaFe12O19 particles

In situ diagnostics of pulsed laser deposition of ferroelectric Pb(Ti0.48Zr0.52)O3 on Si

Magnetic properties and phase formation of SrMn2Fe16O27 (SrMn2-W) hexaferrite prepared by the coprecipitation method