Influence of Grain Size to Resistivity Relaxation of La0.7Sr0.3MnO3 Nanoparticles

2015 ◽  
Vol 1123 ◽  
pp. 260-263
Author(s):  
Christian Fredy Naa ◽  
Didier Fasquelle ◽  
Manuel Mascot ◽  
Suprijadi ◽  
Sparisoma Viridi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Material ◽  
Grain Size ◽  
Sol Gel ◽  
Resistivity Ratio ◽  
Grain Sizes ◽  
Relaxation Measurements ◽  
Different Temperatures ◽  
Different Grain Size ◽  
The Magnetic Field

The resistivity relaxation in magnetic material is one of the important characteristics for reliable device operations. It also provides insight to the physics of magnetic material. Furthermore, this characteristic is related to the micro structural of the material. In this paper, the resistivity relax- ation of different grain sizes of La0.7Sr0.3MnO3(LSMO) nanoparticles has been studied. The LSMO nanoparticles was synthesized by sol-gel method and to obtain different grain size, the samples were sintered at different temperatures ranging from 800◦C to 1100◦C. The resistivity relaxation measurements were recorded for 500-1500s under the influence of magnetic field in range 25-110mT in room temperature. Under the influence of magnetic field, the resistivity of all samples were slowly de- creases as a function of time following logarithmic behavior. Moreover, no saturation was observed in the measurement time span. The resistivity ratio ρ(t)/ρ(0) as a function of time t was fitted by using logarithmic model. It is shown that resistivity relaxation depends on the grain size and the strength of the magnetic field.

Ionic conductivity in nanocrystalline Gd doped ceria

2008 ◽  
Vol 1122 ◽  
Author(s):  
Gianguido Baldinozzi ◽  
David Simeone ◽  
Dominique Gosset ◽  
Mickael Dollé ◽  
Georgette Petot-Ervas
Keyword(s):  
Grain Size ◽  
Ionic Conductivity ◽  
Sol Gel ◽  
Doped Ceria ◽  
Narrow Size Distribution ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Sizes ◽  
The Impact

AbstractWe have synthesized Gd-doped ceria polycrystalline samples (5, 10, 15 %mol), having relative densities exceeding 95% and grain sizes between 30 and 160 nm after axial hot pressing (750 °C, 250 MPa). The samples were prepared by sintering nanopowders obtained by sol-gel chemistry methods having a very narrow size distribution centered at about 16 nm. SEM and X-ray diffraction were performed to characterize the sample microstructures and to assess their structures. We report ionic conductivity measurements using impedance spectroscopy. It is important to investigate the properties of these systems with sub-micrometric grains and as a function of their composition. Therefore, samples having micrometric and nanometric grain sizes (and different Gd content) were studied. Evidence of Gd segregation near the grain boundaries is given and the impact on the ionic conductivity, as a function of the grain size and Gd composition, is discussed and compared to microcrystalline samples.

Effects of Ca2+-Doping on the Crystal Lattice of α-Fe2O3

2014 ◽  
Vol 975 ◽  
pp. 116-121
Author(s):  
Bruna da Costa Andrade ◽  
José Cleverton da Conceição Passos ◽  
Marcelo Andrade Macedo
Keyword(s):  
Magnetic Field ◽  
Electrical Resistivity ◽  
Crystal Lattice ◽  
Coercive Field ◽  
Calcium Concentration ◽  
Sol Gel ◽  
Impedance Analysis ◽  
Hematite Phase ◽  
Sol Gel Process ◽  
The Magnetic Field

Samples of CayFe12-yO19 (0 ≤ y ≤ 1.0) were prepared by a proteic sol–gel process with hematite phase and clusters of M-type calcium hexaferrite. Impedance analysis showed that the resistivity increased with calcium concentration in the 0.0 < y ≤ 0.2 range, but decreased for y > 0.2. The saturation of the electrical resistivity occurred at 7.5 × 106 Ω·cm for Ca0.9Fe11.1O19. The plot of magnetization as a function of the magnetic field showed high values of saturation magnetization (40 emu/g) with low remanence (6.7 emu/g) and coercive field (320 Oe).

Effect of Annealing Atmosphere on the Morphology of Copper Oxide Thin Films Deposited on TiO2 Substrates Prepared by Sol-Gel Process

2013 ◽  
Vol 594-595 ◽  
pp. 113-117 ◽  
Author(s):  
Dewi Suriyani Che Halin ◽  
Ibrahim Abu Talib ◽  
Abdul Razak Daud ◽  
Muhammad Azmi Abdul Hamid
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Grain Size ◽  
Copper Oxide ◽  
Spin Coating ◽  
Sol Gel ◽  
Annealing Atmosphere ◽  
Oxide Thin Films ◽  
Different Temperatures ◽  
Xrd Patterns

Copper oxide films were prepared via sol-gel like spin coating starting from methanolic solutions of cupric chloride onto the TiO2 substrates. Films were obtained by spin coating under room conditions (temperature, 25-30 °C) and were subsequently annealed at different temperatures (200-400 °C) in oxidizing (air) and inert (N2) atmospheres. X-ray diffraction (XRD) patterns showed crystalline phases, which were observed as a function of the annealing conditions. The film composition resulted single or multi-phasic depending on both temperature and atmosphere. The grain size of film was measured using scanning electron microscopy (SEM) and the surface roughness of thin films was characterized by atomic force microscopy (AFM). The grain size of which was annealed in air at 300 °C was 30.39 nm with the surface roughness of 96.16 nm. The effects of annealing atmosphere on the structure and morphology of copper oxide thin films are reported.

Development and Application of Multi-Modular Roll Magnetic Separator

2012 ◽  
Vol 472-475 ◽  
pp. 912-916
Author(s):  
Ding Guo Huang ◽  
Song Liu ◽  
Hong Guang Jiao ◽  
Fei Yue Wang
Keyword(s):  
Magnetic Field ◽  
Magnetic Material ◽  
Permanent Magnet ◽  
Magnetic Force ◽  
Economic Benefits ◽  
Magnet System ◽  
Magnetic Separator ◽  
Perfect Performance ◽  
One Machine ◽  
The Magnetic Field

This new dry magnetic separator has a special structure. It has many magnetic roll which are staggered like a stairsteps. It can finish the task of separating different minerals with only this one machine. And also it can make the different magnetic material which are in the same mineral separate at the same time. The permanent magnet system is made of large fan-shaped magnet. The magnet pole N and S are staggered and has perfect performance of magnetic separation. And the magnetic force is made full use by going-up dynamic separation. And also it gives an analysis of stress in the magnetic field. It also shows that its separation idex is better, the economic benefits are obvious, and it has broader prospects of popularization and application.

SOME OBSERVATIONS ON ROCK MAGNETISM

Geophysics ◽  
1958 ◽  
Vol 23 (2) ◽  
pp. 285-298 ◽  
Author(s):  
Lynn G. Howell ◽  
Joseph D. Martinez ◽  
E. H. Statham
Keyword(s):  
Magnetic Field ◽  
Magnetic Material ◽  
Magnetic Susceptibility ◽  
Transition Temperature ◽  
Iron Ore ◽  
Rock Magnetism ◽  
Bedding Plane ◽  
Metamorphic Rocks ◽  
The Magnetic Field ◽  
Red Bed

It seems that in general the plane of maximum magnetic susceptibility lies in the bedding plane for sediments and in the plane of foliation for metamorphic rocks; there is, also, a tendency for the remanent vector to lie in the plane of foliation in the latter. In the case of chemical deposits, the question is raised as to whether the hematite crystal growth is controlled by the magnetic field. Since pure hematite crystals are paramagnetic along the ternary axis, the remanent vector lies in the basal plane perpendicular to this axis, which being the plane of ferromagnetism, is also the plane of maximum susceptibility. We have investigated chemically deposited hematite in the Clinton iron ore of Silurian Age. Although the remanent vector lies close to the plane of maximum susceptibility, this plane, unfortunately, is also the bedding plane. Several other hematite‐bearing formations show a direction of magnetization close to the bedding plane. Measurements of magnetization and susceptibility anisotropy of samples cooled below the transition temperature for hematite have been made with no conclusive results other than indications of the presence of hematite in some cases. Samples from the Hazel formation of pre‐Cambrian Age have been investigated. The planes of maximum susceptibility for this slightly metamorphosed red bed dip at various angles, and thus a system of microfractures containing magnetic material is suggested as a possible explanation. Pole locations for the Clinton iron ore and the Hazel are presented.

Grain Size Effects on the Oxidation of Fe-33Ni-19Cr Alloy at 700°C

2014 ◽  
Vol 699 ◽  
pp. 151-156
Author(s):  
Noraziana Parimin ◽  
Esah Hamzah ◽  
Astuty Amrin
Keyword(s):  
Grain Size ◽  
Annealing Temperature ◽  
Oxidation Kinetic ◽  
Solution Treatment ◽  
Oxidation Behaviour ◽  
Solution Annealing ◽  
X Ray ◽  
Average Grain Size ◽  
Different Temperatures ◽  
Different Grain Size

The effect of different grain size on the oxidation of Fe-33Ni-19Cr alloy was discussed. The present paper focuses on the oxidation behaviour in dry air at temperature of 700oC with respect to oxidation kinetics. Solution treatment was applied to Fe-33Ni-19Cr alloy by means of different solution annealing temperature to alter the average grain size of the specimens. Solution heat treatments were carried out on Fe-Ni-Cr alloys at three different temperatures, namely, 1000oC, 1100oC and 1200oC. The results showed that the average grain size increased with increase in solution annealing temperature that was significantly affecting the oxidation kinetic of the materials. Optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were employed in this study to analyse the oxidation behaviour of solution-annealed samples. Smaller grain size improves the protective oxidation behaviour by enhancing spallation resistance and reducing oxidation rate. Spallation resistance correlates with a reduction in texture of the oxide layers.

scholarly journals Characterization of mechanical properties of barium titanate ceramics with different grain sizes

2018 ◽  
Vol 36 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Tomasz Trzepiecinski ◽  
Magdalena Gromada
Keyword(s):  
Grain Size ◽  
Compressive Strength ◽  
Barium Titanate ◽  
Testing Machine ◽  
Compression Tests ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Uniaxial Testing ◽  
Different Grain Size ◽  
Titanate Ceramics

AbstractIn this paper, three BaTiO3 powders of various particle size distributions were obtained as a result of mechanical activation in the mixer mill. Green barium titanate pellets and cylindrical specimens were fabricated by both uniaxial and isostatic pressing methods. As a result of the application of different maximal sintering temperatures, the obtained materials were characterized by various average grain sizes: 0.8 μm, 20 μm and 31.0 μm. The basic properties of sintered pellets and cylinders were determined and the influence of materials average grain size on their Young’s modulus and compressive strength were determined through compression tests in a uniaxial testing machine, Zwick/Roell Z100. The elastic properties were similar for tested materials with a different grain size. However, the microstructure of BaTiO3 strongly influenced the compressive strength.

An Experimental Study of Magnetic Damping Effect on Temperature Gradient Induced Natural Convection in Liquid Gallium

2004 ◽  
Author(s):  
B. Xu ◽  
B. Q. Li ◽  
D. E. Stock
Keyword(s):  
Magnetic Field ◽  
Natural Convection ◽  
Liquid Gallium ◽  
Horizontal Magnetic Field ◽  
Magnetic Damping ◽  
Damping Effect ◽  
Different Temperatures ◽  
Hot Film ◽  
The Magnetic Field ◽  
Good Agreement

The results of an experimental investigation of natural convection driven flow of liquid gallium are presented. The gallium contained by a rectangular box with two opposite ends held at different temperatures and is subject to a uniform horizontal magnetic field. The objective of this study was to examine the damping effect of a magnetic field on the natural convection in a liquid metal. A hot film anemometry was used to measure the velocity profile and a thermocouple was used to measure the temperature field. The hot-film probe was calibrated over a narrow range of temperatures in a rotating container fill with liquid gallium. The velocity and temperature profiles are compared with previous numerical simulations and reasonably good agreement was found. The damping effect of the external magnetic field was observed in both the temperature and the velocity profiles and found to increase as the strength of the magnetic field increases.

Conjugate Heat Transfer Analysis of Circular Microtube Under Time Varying Heat Source

2005 ◽  
Author(s):  
Abdullatif A. Gari ◽  
Muhammad M. Rahman
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Magnetic Material ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transient Heat Conduction ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Heating And Cooling ◽  
The Magnetic Field

When a magnetic field is applied to a magnetic material it releases energy. It has been proven experimentally that this temperature rise could be as high as 20 K when a magnetic field of 10 T is applied. Heat is generated when the magnetic field is applied and cooling is produced when the magnetic field is released. The purpose of this study is to explore transient heat transfer coefficient when a fluid is circulated in the substrate through microchannels. Equations for the conservation of mass, momentum, and energy were solved in the fluid region. In the solid region, the transient heat conduction equation was solved. Gadolinium and water were picked as the magnetic material and working fluid respectively. The results are represented by plotting the variations of heat transfer coefficient and Nusselt number with time at various sections of the tube. The effects of the magnetic field strength, diameter of the microtube in the substrate, and Reynolds number were studied. It was found that the heat transfer coefficient changes with time in a periodic fashion when heating and cooling are generated in the system by repeated introduction and relaxation of the magnetic field. The results of this study will be useful for the development of microtube heat exchangers for a compact magnetic refrigerator.

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