• Title/Summary/Keyword: cation distribution

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Magnetic Properties and Cation Distribution of Phosphorous-Doped $Co-{\gamma}-{Fe_2} {O_3}$ Particles

  • Na, J.G.;Han, D.H.
    • Journal of Magnetics
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    • v.1 no.1
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    • pp.51-54
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    • 1996
  • The effects of additional P-doping on the magnetic properties, thermal stability and cation distribution of Co-doped ${\gamma}-{Fe_2} {O_3}$have been investigated by means of magnetic annealing and measurements with vibration sample magnetometer and torque magnetometer. It is found that the P-doping promotes the coercivity and its magnetic-thermal stability, which may be attributed to increase of the cubic magneto-crystalline anisotropy constant, $K_1$ and the activation energy, E, for cation rearrangement, respectively. The cation distribution of P and Co-substituted iron oxide was calculated from the variation of the saturation magnetization with P-doping on the basis of the Neel model. It was found that the most of P ions in the iron oxides occupied the B-site of spinel lattice.

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Theoretical and Experimental Studies on the Kinetics of Cation Redistribution Processes in Complex Oxides

  • Shi, Jianmin;Becker, Klaus-Dieter
    • Journal of the Korean Ceramic Society
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    • v.47 no.1
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    • pp.39-46
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    • 2010
  • The kinetics of cation reequilibration have been studied theoretically and experimentally in complex oxides after an external perturbation of equilibrium by temperature jumps. A general kinetic model for cation redistribution amongst non-equivalent sites in complex oxides is derived based on a local homogeneous point defect mechanism involving cation vacancies. Temperature-jump optical relaxation spectroscopy has been established to investigate cation kinetic processes in spinels and olivines. The kinetic model satisfactorily describes the experimental absorbance relaxation kinetics in cobalt containing olivines and in nickel containing spinels. It is found that the kinetics of cation redistribution in complex oxides shows a strong temperature- and composition-dependence. Activation energies for cation redistribution in Co-Mg olivines are found to range between 200 and 220 kJ/mol whereas an energy barrier of about 230 kJ/mol is observed in the case of nickel gallate spinel.

Effect of Preparation on Structure and Magnetic Properties of ZnFe2O4

  • Niyaifar, Mohammad
    • Journal of Magnetics
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    • v.19 no.2
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    • pp.101-105
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    • 2014
  • In this work, Zinc ferrite nanoparticles have been prepared by various methods, conventional (ZC), mechanochemical processing (ZM) and Sol-Gel (ZS) method, to compare their structural and magnetic properties. The cation distribution obtained from XRD shows the degrees of inversions are 4%, 14.8%, and 16.4% from the normal $ZnFe_2O_4$ structure. Fourier transform infrared spectroscopy (FT-IR) confirms changes in cation distribution of $ZnFe_2O_4$ fabricated by sol-gel and mechanochemical processing. The $^{57}Fe$ M$\ddot{o}$ssbauer spectra of the samples were recorded at room temperature. The spectra exhibit a line broadening. The magnetic properties of the samples were studied by vibration sample magnetometer (VSM) at room temperature and the results show that the sample ZM has ferrimagnetic behaviour.

Preparation and Physical Characterizations of Superparamagnetic Maghemite Nanoparticles

  • Yoon, Sunghyun
    • Journal of Magnetics
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    • v.19 no.4
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    • pp.323-326
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    • 2014
  • Superparamagnetic maghemite nanoparticles were prepared by chemical co-precipitation, followed by a temperate oxidation stage, and investigated using FE-SEM, XRD, TGA, VSM, and M$\ddot{o}$ssbauer spectroscopy. Through SEM image and XRD analysis, its average particle size was found to be 13.9 nm. While VSM magnetic measurement showed typical superparamagnetic behavior at room temperature, M$\ddot{o}$ssbauer spectroscopic investigation revealed that non-vanishing magnetic hyperfine structure were retained. Cation distribution estimated from M$\ddot{o}$ssbauer spectroscopy confirmed the formation of maghemite nanophase in the sample.

Influence of Alkali Metal Cation Type on Ionization Characteristics of Carbohydrates in ESI-MS

  • Choi, Sung-Seen;Kim, Jong-Chul
    • Bulletin of the Korean Chemical Society
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    • v.30 no.9
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    • pp.1996-2000
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    • 2009
  • Alkali metal salts were introduced to enhance the ionization efficiency of glucose and maltooligoses in electrospray ionization-mass spectrometry (ESI-MS). A mixture of the same moles of glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose was used. Salts of lithium, sodium, potassium, and cesium were employed as the cationizing agent. The ionization efficiency varied with the alkali metal cation types as well as the analyte sizes. Ion abundance distribution of the [M+$cation]^+$ ions of the carbohydrates varied with the fragmentor voltage. The maximum ion abundance at low fragmentor voltage was observed at maltose, while the maximum ion abundance at high fragmentor voltage shifted to maltotriose or maltotetraose for Na, K, and Cs. Variation of the ionization efficiency was explained with the hydrated cation size and the binding energy of the analyte and alkali metal cation.

Size dependence of Cation Distribution in Magnetic Nanoparticles (자성 나노입자에서 양이온 분포의 크기 의존성)

  • Cho, Jun-Hee;Ko, Sang-Kil;Lee, Hwan;Ahn, Yang-Kyu;Song, Ki-Chang;Choi, Eun-Jung
    • Journal of the Korean Magnetics Society
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    • v.16 no.1
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    • pp.60-65
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    • 2006
  • In order to investigate the dependence of the particle size on the cation distribution in the spinel structure, Mossbauer spectra were taken in the presence of an external magnetic field f3r the magnetic nanoparticles prepared by using a microemulsion method. The crystals are found to have a cubic structure. The results show that as the particle sizes decrease, $Fe^{3+}$ ions migrate from the octahedral site to tetrahedral site.

Intercalation of Ca-montmorillonite with Decylammonium Ion and n-Alcanol (Decylammonium 이온과 n-Alcanol 분자에 의한 Ca-montmorillonite의 Intercalation)

  • 최진호;김창은;형경우
    • Journal of the Korean Ceramic Society
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    • v.20 no.3
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    • pp.205-210
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    • 1983
  • The determination of charge density and charge distribution in montmorillonite are discussed. The method is based on cation exchange of the inorganic interlayer cations against decylammonium ion and molecular intercalation of n-alcanol. The results obtained from Yougil-bentonite show that charge density of 0.37 per unit formula and cation exchange capacity of 102.5 meq/100g.

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Characteristics of Physical and Adsorption of Korean Traditional Charcoal (우리나라 전통 숯의 물리.화학적 특성)

  • Kim, Joon-Tae;Kim, Sun-Hwa;Kim, Hae-Jin
    • Journal of environmental and Sanitary engineering
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    • v.21 no.4 s.62
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    • pp.77-86
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    • 2006
  • The water purification was very important in Korea which has not sufficient water resource and while adsorption method among the various methods to eliminate the water pollutants has been widely used by activated carbon. This study was conducted the basic experiment for hall distribution, pH, conductivity, electronic microscope, cation exchange and inorganic materials the adsorption capacity of Korean traditional charcoal which has similar characteristics to activated carbon of organic pollutants. As a result of observing Korean traditional charcoal with electronic microscope, it was found that it has porous structure, oak charcoal has circular structure, pine charcoal has square structure and bamboo charcoal has hexagonal structure, which has high void fraction per unit area because of its thin cell wall structure. As a result of experimenting hall distribution, hall distribution of bamboo high temperature charcoal is high as 0.269cc/g and has the greatest inorganic contents and cation exchange capacity(CEC) which are the important factor of chemical adsorption.