• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.260-260
• /
• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.183-183
• /
• 2014

Recently, multiferroic materials gain much attention due to their fascinating fundamental physical properties. These materials offer wide range of potential applications such as data storage, spintronic devices and sensors, where both electronic and magnetic polarizations can be coupled. Among single-phase multiferroic materials, $BiFeO_3$ is typical because of the room-temperature magnetoelectric coupling in view of long-range magnetic- and ferroelectric-ordering temperatures. However, $BiFeO_3$ is well known to have large leakage current and small spontaneous polarization due to the existence of oxygen vacancies and other defects. Furthermore the magnetic moment of pure $BiFeO_3$ is very weak owing to its antiferromagnetic nature. Recently, various attempts have been performed to improve the multiferroic properties of $BiFeO_3$ through the co-doping at the A and the B sites, by making use of the fact that the intrinsic polarization and magnetization are associated with the lone pair of $Bi^{3+}$ ions at the A sites and the partially-filled 3d orbitals of $Fe^{3+}$ ions at the B sites, respectively. In this study, $BiFeO_3$, $Bi_{0.9}Ho_{0.1}FeO_3$, $BiFe_{0.97}Ni_{0.03}O_3$ and $Bi_{0.9}Ho_{0.1}Fe_{0.97}Ni_{0.03}O_3$ bulk compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Ho_2O_3$, $Fe_2O_3$ and $NiO_2$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ for 24 h to produce the samples. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ and sintered in air for 1 h. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent and temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer and superconducting quantum-interference device.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.250-250
• /
• 2012

Recently, multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and potential technological applications in magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because of its very interesting magnetoelectric properties for application to spintronics. Enhanced ferromagnetism was found by Fe-site ion substitution with magnetic ions. In this study, $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Fe_3O_4$ and NiO powders were mixed with the stoichiometric proportions, and calcined at $450^{\circ}C$ for 24 h to produce $BiFe_{1-x}Ni_xO_3$. Then, the samples were directly put into the oven, which was heated up to $800^{\circ}C$ and sintered in air for 20 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The Raman measurements were carried out with a Raman spectrometer with 514.5-nm-excitation Ar+-laser source under air ambient condition on a focused area of $1-{\mu}m$ diameter. The field-dependent magnetization and the temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The x-ray diffraction study demonstrates the compressive stress due to Ni substitution at the Fe site. $BiFe_{0.95}Ni_{0.05}O_3$ exhibits the rhombohedral perovskite structure R3c, similar to $BiFeO_3$. The lattice constant of $BiFe_{0.95}Ni_{0.05}O_3$ is smaller than of $BiFeO_3$ because of the smaller ionic radius of Ni3+ than that of Fe3+. The field-dependent magnetization of $BiFe_{0.95}Ni_{0.05}O_3$ exhibits a clear hysteresis loop at 300 K. The magnetic properties of $BiFe_{0.95}Ni_{0.05}O_3$ were improved at room temperature because of the existence of structurally compressive stress.

• Journal of Food Hygiene and Safety
• /
• v.25 no.2
• /
• pp.118-121
• /
• 2010

A HPLC-MS/MS method was developed for simultaneous determination of six sweeteners (acesulfame-K, cyclamate, saccharin, sucralose, stevioside, aspartame) in children's favorite foods. The procedure involves an extraction of the six sweeteners with 50% methanol solution, sample clean-up using the Carrez clearing reagent and filtering with cartridge filter. The HPLC separation was performed on a Hypersil Gold (150 mm ${\times}$ 2.1 mm 5 um) column using the water/acetonitrile mobile phase (95:5). Mass spectrometric analysis was carried out using the TSQ Quantum Ultra operated in negative and positive ESI/SRM. With this method, good linear relationship, sensitivity and reproducibility were obtained. The spike recoveries of six sweeteners for 2 kinds of foods spiked into 0.4 mg/ kg ranged from 87.4 to 114.7%. The detection limits were above 0.02 mg/kg. The method has been applied to determination of six sweeteners in children's favorite foods.

• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.1-8
• /
• 2005

In this study, $TiO_2$ powders were prepared by hydro-thermal synthesis with titanium tetra isopropoxide. The prepared $TiO_2$ and the commercial $TiO_2$(P-25, Degussa) were by impregnating $H_2PtCl_6$ solution or the leached solution from the waste catalytic converter of automobile. Modified photocatalysts were analyzed by ICP-AES, UV-DRS, XRD, SEM. And band-gap energy of modified photo-catalyst was found to decreased to 1.76eV and basic structure was changed upon modification by leached solution. Modified photocatalysts were coated on the wallpaper after using mixed solution with adhesive materials(PVC). And then to know the modified photo catalysts tested the reactivity and quantum efficiency in the mixed gas with NO as reactants in the photo catalytic reactor. In the gas phase, photo-catalytic activity of NO was the highest for modified P-25 catalysts(P-25(w)) that P-25(w) was impregnated by leached solution of wasted catalytic converter.

• Journal of the Korean Magnetics Society
• /
• v.17 no.1
• /
• pp.47-50
• /
• 2007

[ $ZnCr_2O_4$ ] shows geometrically frustrated magnet. Recently, $CoCr_2O_4$ has been investigated for multiferroic property and dielectric anomalies by spin-current model. Polycrystalline $CoCr_2O_4$ and $CoCrFeO_4$ compounds was prepared by wet-chemical process. Crystallographic and magnetic properties of $CoCr_2O_4$ and $CoCrFeO_4$ were investigate by using the x-ray diffractometer(XRD), vibrating sample magnetometer(VSM), superconducting quantum interference device magnetometer(SQUID), and $M\"{o}ssbauer$ spectroscopy. The crystal structure was found to be single-phase cubic spinel with space group of Fd3m. The lattice constants of $CoCr_2O_4$ and $CoCrFeO_4$ $a_0$ were determined to be 8.340 and 8.377 ${\AA}$, respectively. The ferrimagnetic transition temperature for the both samples were observed at 97 K and 320 K. The $M\"{o}ssbauer$ absorption spectra at 4.2 K show that the well developed two sextets are superposed with small difference of hyperfine field($H_{hf1}=507\;and\;H_{hf2}=492\;kOe$). Isomer shift values($\delta$) of the two sextets are found to be 0.33 and 0.34 mm/s relative to the Fe metal, respectively, which are consistent with the high spin $Fe^{3+}$ charge state.

• Journal of the Korean Magnetics Society
• /
• v.16 no.1
• /
• pp.102-106
• /
• 2006

Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers. in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. We have synthesized magnetite $(Fe_3O_4)$ nanoparticles using chemical coprecipitation technique with sodium oleate as surfactant. Nanoparticle size can be varied from 2 to 8nm by controlling the sodium oleate concentration. Magnetite phase nanoparticles could be observed from X-ray diffraction. Magnetic colloid suspensions containing particles with sodium oleate and chitosan have been prepared. Nanoparticles, both oleate-coated and chitosan-coated, have been characterized by several techniques. Atomic farce microscope (AFM) was used to image the coated nanoparticles. Magnetic hysteresis measurement were performed using a superconducting quantum interference device (SQUID) magnetometer at room temperature to investigate the magnetic properties of the magnetite nanoparticles. The SQUID measurements revealed superparamagnetism of nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.14-15
• /
• 2010

Recently there has been growing interest in topological insulators or the quantum spin Hall (QSH) phase, which are insulating materials with bulk band gaps but have metallic edge states that are formed topologically and robust against any non-magnetic impurity [1]. In a three-dimensional material, the two-dimensional surface states correspond to the edge states (topological metal) and their intriguing nature in terms of electronic and spin structures have been experimentally observed in bulk Bi1-xSbx single crystals [2,3,4]. However, if we want to know the transport properties of these topological metals, high purity samples as well as very low temperature will be needed because of the contribution from bulk states or impurity effects. In a recent report, it was also shown that an intriguing coupling between the surface and bulk states will occur [5]. A simple solution to this bothersome problem is to prepare a topological metal on an ultrathin film, in which the surface-to-bulk ratio is drastically increased. Therefore in the present study, we have investigated if there is a method to make an ultrathin Bi1-xSbx film on a semiconductor substrate. From reflection high-energy electron diffraction observation, it was found that single crystal Bi1-xSbx films (0${\sim}30\;{\AA}A$ can be prepared on Si(111)-$7{\times}7$. The transport properties of such films were characterized by in situ monolithic micro four-point probes [6]. The temperature dependence of the resistivity for the x=0.1 samples was insulating when the film thickness was $240\;{\AA}A$. However, it became metallic as the thickness was reduced down to $30\;{\AA}A$, indicating surface-state dominant electrical conduction. Figure 1 shows the Fermi surface of $40\;{\AA}A$ thick Bi0.92Sb0.08 (a) and Bi0.84Sb0.16 (b) films mapped by angle-resolved photoemission spectroscopy. The basic features of the electronic structure of these surface states were shown to be the same as those found on bulk surfaces, meaning that topological metals can be prepared at the surface of an ultrathin film. The details will be given in the presentation.

• Journal of Animal Science and Technology
• /
• v.61 no.4
• /
• pp.192-203
• /
• 2019

A study was conducted to determine the influence of feed form and microbial enzyme supplementation on energy utilization, bone quality, and amino acid and mineral digestibility of broiler chickens. Four hundred and eighty Ross 308, day-old broiler chickens were randomly assigned to eight diets formulated from commonly used ingredients in Tanzania. A 2 (pellet or mash) ${\times}$ 4 (control, Axtra XB, Quantum Blue (QB) and Axtra XB + QB enzyme) factorial array in a completely randomized design having six replicates per treatment (10 birds per replicate) was used. Birds were raised in climate-controlled rooms in a 3-phase; starter (0-10 days), grower (11-24 days) and finisher (25-35 days). Apparent metabolizable energy (AME), metabolizable energy intake, net energy of production, energy retained as protein (REp), and efficiency of metabolizable energy use for energy and protein retention were higher (p < 0.05) in birds fed pelleted diets. The AME and REp was higher (p < 0.05) with enzyme supplementation. Ash content, weight, length, width and breaking strength of tibia bones were highest (p < 0.05) in birds on pelleted diets. Tibia bone traits were improved (p < 0.05) when enzymes were included, particularly in a combination of QB and Axtra XB. However, potassium, magnesium, and zinc contents were highest (p < 0.05) when QB was supplemented. Digestibility of all amino acids was higher (p < 0.05) in birds supplied with pellets and with enzyme supplementation for most amino acids, except for serine. There was a positive interaction (p < 0.05) between feed form and enzymes on lysine and phenylalanine digestibility. Digestibility of Ca, P, K, S, Zn, and Fe was higher (p < 0.05) in birds fed pelleted diets, while those on mashed diets had higher (p < 0.05) digestibility of Cu and B. The digestibility of P, K, and Zn was highest (p < 0.001) when QB was added, while Ca, P, S, and B digestibility was highest when a combination of Axtra XB + QB was applied. Pelleted diets with or without enzymes improved energy utilization, digestibility of amino acids, and minerals, and increased bone strength in broiler chickens.

• The Korean Journal of Pain
• /
• v.6 no.2
• /
• pp.192-198
• /
• 1993

In 1984, a magnetic resonance spectrometer(magnetic resonance analyser, MRA $I_{TM}$) was developed by Sigrid Lipsett and Ronald J. Weinstock in the USA, Biomedical applications of the spectrometer have been examined by Dr. Hoang Van Duc(pathologist, USC), and Nakamura, et al(Japan). From their theoretical views, the biophysical functions of this machine are to analyse and synthesize a healthy tissue and organ resonance pattern, and to detect and correct an abnormal tissue and organ resonance pattern. All of the above functions are based on Quantum physics. The healthy tissue and organ resonance patterns are predetermined as standard magnetic resonance patterns by digitizing values based on peak resonance emissions(response levels or high pitched echo-sounds amplified via human body). In clinical practice, a counter or neutralizing resonance pattern calculated by the spectrometer can correct a phase-shifted resonance pattern(response levels or low pitched echo-sounds) of a diseased tissue and organ. By administering the counter resonance pattern into the site of pain and trigger point, it is possible to readjust the phase-shifted resonance pattern and then to alleviate pain through regulation of the neurotransmitter function of the nervous system. For assessing clinical effectiveness of pain relief with MRA $I_{TM}$ this study was designed to estimate pain intensity by the patient's subjective verbal rating scale(VRS such as graded to no pain, mild, moderate and severe) before application of it, to evaluate an amount of pain relief as applied the spectrometer by the patients subjective pain relief scale(visual analogue scale, VAS, 0~100%), and then to observe a continuation of pain relief following its application for managing acute and chronic pain in the 102 patients during an 8 months period beginning March, 1993. An application time of the spectrometer ranged from 15 to 30 minutes daily in each patient at or near the site of pain and trigger point when the patient wanted to be treated. The subjects consisted of 54 males and 48 females, with the age distribution between 23~40 years in 29 cases, 41~60 years in 48 cases and 61~76 years in 25 cases respectively(Table 1). The kinds of diagnosis and the main site of pain, the duration of pain before the application, and the frequency of it's application were recorded on the Table 2, 3 and 4. A distinction between acute and chronic pain was defined according to both of the pain intervals lasting within and over 3 months. The results of application of the spectrometer were noted as follows; In 51 cases of acute pain before the application, the pain intensities were rated mild in 10 cases, moderate in 15 cases and severe in 26 cases. The amounts of pain relief were noted as between 30~50% in 9 cases, 51~70% in 13 cases and 71~95% in 29 cases. The continuation of pain relief appeared between 6~24 hours in two cases, 2~5 days in 10 cases, 6~14 days in 4 cases, 15 days in one case, and completely relived of pain in 34 cases(Table 5~7). In 51 cases of chronic pain before the application, the pain intensities were rated mild in 12 cases, moderate in l8 cases and severe in 21 cases. The amounts of pain relief were noted as between 0~50% in 10 cases, 51~70% in 27 cases and 71~90% in 14 cases. The continuation of pain relief appeared to have no effect in two cases. The level of effective duration was between 6~12 hours in two cases, 2~5 days in 11 cases, 6~14 days in 14 cases, 15~60 days in 9 cases and in 13 cases the patient was completely relieved of pain(Table 5~7). There were no complications in the patients except a mild reddening and tingling sensation of skin while applying the spectrometer. Total amounts of pain relief in all of the subjects were accounted as poor and fair in 19(18.6%) cases, good in 40(39.2%) cases and excellent in 43(42.2%) cases. The clinical effectiveness of MRA $I_{TM}$ showed variable distributions from no improvements to complete relief of pain by the patient's assessment. In conclusion, we suggest that MRA $I_{TM}$ may be successful in immediate and continued pain relief but still requires several treatments for continued relief and may be gradually effective in pain relief while being applied repeatedly.