Investigations of lanthanum doping on magnetic properties of nano cobalt ferrites

The magnetic properties of nano-crystallite cobalt lanthanum ferrite (CoLa_xFe_2-x O₄) with varied quantities of lanthanum (x = 0, 0.1, 0.15, 0.2, 0.25, 0.3) prepared by co-precipitation method have been studied by vibrating sample magnetometer (VSM) and LCR meter. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the size, structure, and morphology of the ferrite samples. The average crystallite size varied from 17.83 nm to 49.99 nm. All the samples, although, in nano range, show significant hysteresis. The saturation magnetization (M_s) values decreased from 60.57 emu/g to 30.15 emu/g. The remanence (M_R) fell from 10.85 emu/g to 6.39 emu/g. Doping with lanthanum La³⁺ ions modulates significantly the magnetic properties of cobalt spinel ferrites without sacrificing the ferromagnetic character.     

Effect of Gd doping on magnetic, electric and dielectric properties of MgGdxFe2−xO4 ferrites processed by solid state reaction technique

MgGd_xFe_2−xO₄ (x = 0.0, 0.05, 0.1 and 0.15) ferrites, with improved dc resistivity, initial permeability, saturation magnetization, and extremely low relative loss factor, have been synthesized by solid state reaction technique. The microstructures, electric, dielectric and magnetic properties have been investigated by means of X-ray diffraction, Keithley 2611 system, impedance analyzer and VSM respectively. The addition of Gadolinium in Mg ferrite has been shown to play a crucial role in enhancing the electric, dielectric and magnetic properties. The dc resistivity is increased by two orders of magnitude as compared to Mg ferrite. Saturation magnetization has been increased by two times and remnant magnetization has been increased by more than three times due to the doping of Gd³⁺ ions in Mg ferrite. The relative loss factor was found to have very low values and is of the order of 10⁻⁴-10⁻⁵ in the frequency range 0.1-30 MHz. The variations of electric, dielectric and magnetic properties of the samples have been studied as a function of frequency and Gd³⁺ ions concentration measured at room temperature. High resistivity and improved magnetic properties can be correlated with better compositional stoichiometry and the replacement of Fe³⁺ ions by Gd³⁺ ions. The mechanisms responsible to these results have been discussed in this paper.     

The Role of Water in Air-jet Texturing (A Critical Review)

This paper presents a brief summary of the results of the role of water in air-jet texturing from a number of authors. The explanations of the results put forward by the authors have been reviewed and some have been analysed.     

Nanograins dependent dielectric constant, tunability, phase transition, impedance spectroscopy and leakage current of (Pb1 − xSrx)TiO3 thin films

Nanostructured (Pb_1 − xSr_x)TiO₃ (PST) (x = 0.1, 0.2 and 0.3) thin films have been prepared by chemical solution deposition process using spin coating technique. The solution as such was deposited on Pt/Ti/SiO₂/Si substrates and annealed at 650 °C/3h. Nanograins dependent dielectric properties of PST films show dielectric constant up to the higher frequency region, low losses, large tunability and phase transition at small temperature. The impedance data has been fitted by Cole-Cole model to study the effect of grain boundaries on the dielectric properties. The current-voltage characteristics have been measured to study leakage current in PST films and described by Poole-Frenkel emission model. It is suggested that the key carrier transport process in PST films is emission of electrons from a trap state near the metal-film interface into a continuum of states associated with each conductive dislocation. The activation energy value for carrier transport in PST films is obtained from temperature-dependent current-voltage characteristics.     

Experimental study on vibration and damping of curved panel treated with constrained viscoelastic layer

This paper presents experimental investigation on the damping effects of constrained layer damping treatment on a curved panel. Vibration attenuation of the curved panel is achieved by attaching constraining layer damping patches at the optimal locations. The placement strategies of constrained layer patches are devised using the modal strain energy (MSE) method. Locations for application of damping patches are those, where modal strain energy is maximum for the particular mode. The treatment is then applied to the elements that have highest MSE in order to target specific modes of vibrations. Extensive experiments are conducted by making number of separate samples of viscoelastic and constrained layer damping patches for each configuration to damp different modes simultaneously or independently. The experimental results demonstrate utility of the modal strain energy technique as an effective tool for selecting the locations of the constrained layer damping treatment to achieve desired damping characteristics over a broad frequency band.     

Grape waste as a biosorbent for removing Cr(VI) from aqueous solution

Grape waste generated in wine production is a cellulosic material rich in polyphenolic compounds which exhibits a high affinity for heavy metal ions. An adsorption gel was prepared from grape waste by cross-linking with concentrated sulfuric acid. It was characterized and utilized for the removal of Cr(VI) from synthetic aqueous solution. Adsorption tests were conducted in batch mode to study the effects of pH, contact time and adsorption isotherm of Cr(VI), which followed the Langmuir type adsorption and exhibited a maximum loading capacity of 1.91 mol/kg at pH 4. The adsorption of different metal ions like Cr(VI), Cr(III), Fe(III), Zn(II), Cd(II) and Pb(II) from aqueous solution at different pH values 1-5 has also been investigated. The cross-linked grape waste gel was found to selectively adsorb Cr(VI) over other metal ions tested. The results suggest that cross-linked grape waste gel has high possibility to be used as effective adsorbent for Cr(VI) removal.     

Arsenic removal using hydrous nanostructure iron(III)-titanium(IV) binary mixed oxide from aqueous solution

The synthetic bimetal iron(III)–titanium(IV) oxide (NHITO) used was characterized as hydrous and nanostructured mixed oxide, respectively, by the Föurier transform infra red (FTIR), X-ray diffraction (XRD) pattern and the transmission electron microscopic (TEM) image analyses. Removal of As(III) and As(V) using the NHITO was studied at pH 7.0 (±0.1) with variation of contact time, solute concentration and temperature. The kinetic sorption data, in general, for As(III) described the pseudo-first order while that for As(V) described the pseudo-second order equation. The Langmuir isotherm described the equilibrium data (303 (±1.6) K) of fit was well with the Langmuir model. The Langmuir capacity (q_m, mg g^?1) value of the material is 85.0 (±4.0) and 14.0 (±0.5), respectively, for the reduced and oxidized species. The sorption reactions on NHITO were found to be endothermic and spontaneous, and took place with increasing entropy. The energy (kJ mol^?1) of sorption for As(III) and As(V) estimated, respectively, is 9.09 (±0.01) and 13.51 (±0.04). The sorption percentage reduction of As(V) was significant while that of As(III) was insignificant in presence of phosphate and sulfate. The fixed bed NHITO column (5.1 cm × 1.0 cm) sorption tests gave 3.0, 0.7 and 4.5 L treated water (As content ≤ 0.01 mg L^?1) from separate As(III) and As(V) spiked (0.35 ± 0.02 mg L^?1) natural water samples and from high arsenic (0.11 ± 0.01 mg L^?1) ground water, respectively when inflow rate was (0.06 L h^?1).     

Development of UHMWPE modified PP/PET blends and their mechanical and abrasive wear behavior

In this study, polypropylene and polyethylene terephthalate blend were modified by incorporating different percentages of ultrahigh molecular weight polyethylene (UHMWPE) ranging from 1 to 5 phr. Modified blends were prepared by melt mixing the PP/PET blend and UHMWPE. Ultimate tensile strength of UHMWPE filled blend was determined at 10, 20, 50, and 100 mm/min cross head speeds of testing. It was found that increase of cross head speed from 10 to 100 mm/min increases the tensile strength of PP/PET/UHMWPE blends. Maximum ultimate tensile strength is exhibited by the blend containing 2 phr UHMWPE. Breaking strain of the UHMWPE modified and unmodified PP/PET blend increased with the increase of cross head speed due to the highly entangled chain structure of UHMWPE. Shore A hardness of the filled blends also increased from 341 to 356, which is highest for 2 phr UHMWPE. High stress abrasive wear of UHMWPE modified blend was determined by using Suga abrasion tester, model NUS‐1 Japan. Wear rate of the PP/PET(90/10) blends having 1, 2, and 5 phr of UHMWPE was determined at different loads such as 1, 3, 5, and 7 N and sliding distances from 6.4 m to 25.6 m. Wear rate values show that UHMWPE has prominent effect on abrasive wear of PP/PET blends. Addition of 2 and 5 phr UHMWPE improved the wear resistance of PP/PET blends at different loads, which has been explained on the basis of improved bonding as compared with pure PP/PET blend and increased hardness. Maximum abrasive wear rate reduction was achieved by adding 2 phr UHMWPE in PP/PET(90/10) blend. POLYM. COMPOS. 28:267–272, 2007. © 2007 Society of Plastics Engineers     

Characterization of molten salt doped with different size nanoparticles of Al2O3

This paper aims to study the effect on the characteristics of molten salt because of the dispersion of different size nanoparticles of Al₂O₃. The eutectic mixture of 54 wt% KNO₃ and 46 wt% NaNO₃ was selected as the base salt. Five different size nanoparticles of Al₂O₃, 80, 135, 200, 300, and 1000 nm, were dispersed into the base salt at a mass concentration of 1% to make the nanomaterials by a two‐step method, respectively. Thermal properties of the base salt and the samples with Al₂O₃ nanoparticles, including the melting point temperature, fusion heat, specific heat capacity, and thermal diffusivity, were measured with differential scanning calorimeter (DSC) and Xenon Flash Apparatus (XFA). On the basis of the measured specific heat capacities and thermal diffusivities, their thermal conductivities in the solid state were calculated at discrete specified temperatures. The results showed that the dispersions of 200‐ and 135‐nm Al₂O₃ nanoparticles could enhance the average solid and liquid specific heat capacities by up to 17.2% and 19.7%, respectively. The research on thermal diffusivity and thermal conductivity also verified that the influences of different size nanoparticles were different. Although no new strong intensity peaks or peak position variations were found in the diffraction patterns of the two samples with 80‐ and 1000‐nm nanoparticles of Al₂O₃, the larger deviations in the lower wavenumber region still meant possible crystalline structure variation because of the dispersion of Al₂O₃ nanoparticles. Scanning electronic microscope (SEM) images showed the inhomogeneity and the agglomeration of dispersed nanoparticles in the base salt, and the formation of a nanolayer around the nanoparticles could be a possible explanation to the thermal‐physical property variation.