• Korean Journal of Materials Research
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• v.20 no.12
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• pp.654-660
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• 2010

The influences of Na and K content on the crystal phase, the microstructure and the electrical property of $BaTiO_3$-based thermistors was found to show typical PTC effects. The crystal phase of powder calcined at $1000^{\circ}C$ for 4hrs showed a single phase with $BaTiO_3$, and the crystal structure was transformed from tetragonal to cubic phase according to added amounts of Na and K. In XRD results at $43^{\circ}\sim47^{\circ}$, the $(Ba_{0.858}Na_{0.071}K_{0.071})(Ti_{0.9985}Nb_{0.0015})O_{3-\delta}$ showed (002) and (200) peaks but the $(Ba_{0.762}Na_{0.119}K_{0.119})(Ti_{0.9975}Nb_{0.0025})O_{3-\delta}$ showed (002), (020) and (200) peaks. In sintered bodies, those calcined at $600^{\circ}C$ rather than at $1000^{\circ}C$ were dense, and for certain amounts of Na and K showed rapid decreases in grain size. In relative permittivity, the curie temperature due to the transformation of ferroelectric phase rose with added Na and K but decreased in terms of relative permittivity. In the result of the R-T curve, the sintered bodies have curie temperatures of about $140^{\circ}C$ and the resistivity of sintered bodies have scores of $\Omega{\cdot}cm$; the jump order of sintered bodies was shown to be more than $10^4$ in powder calcined at $1000^{\circ}C$.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.413-418
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• 2005

Perovskite $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3[PNN-PZT]$ ceramics were synthesized by conventional ceramic processing technique. In order to modify piezoelectric properties for sensor application in this system, NiO addition was considered to provide $Ni^{+2}$ as an acceptor, which was known to occupy with B site in the structure. The effect of NiO addition up to $8\;mol\%$ on the following piezoelectric properties as well as sintering properties was investigated. When NiO added more than $1\;mol\%$, average grain size was decreased and second phase was found to form. Moreover, the second phase caused decrease in relative dielectric constant $(\varepsilon_{33}T/\varepsilon0)$, electro-mechanical coupling factor $(k_p)$, and piezoelectric charge constant $(d_{33})$, while increasing mechanical quality factor $(Q_m)$. When $1\;mol\%$ NiO was added, density, dielectric properties and piezoelectric properties were abruptly increased.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.27-33
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• 2001

The growth characteristics of 4-fold grain which was appeared in KLN deposition on $Pt/Ti/SiO_2/Si(100)$ substrate was studied by varying process variables. Substrate temperature, sputtering pressure, rf power were selected as process variables, and experiment was carried out near optimum fabrication condition. When using K and Li enriched target, the optimum fabrication conditions were substrate temperature of $600^{\circ}C$, sputtering pressure of 150mTorr, rf power of 100 W and its surface morphology is sensitively varied by small deposition condition changes. KLN is composed of elements which have large difference of boiling point. And it is difficult to fabricate thin film at high temperature and high vacuum deposition condition. Furthermore the phenomenon during deposition process can not be explained by using Thorton's model which explains the relation between thin film structure and melting point of thin film materials. These phenomenon can be explained using boiling point of elements which consist of thin film material.

• Korean Journal of Weed Science
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• v.9 no.3
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• pp.221-229
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• 1989

This study is conducted to evaluate the effect of KIM-112 (Ca-3, 5-diode-4-propyonly-cyclohexane-1-carboxylate) application at 13, 8 and 3 days before heading for the possibility of lodging prevention, growing pattern of several organisms, growth and yield in paddy rice. KIM-112 was the most effective in reducing elongation of the third internode when it was applied at 13 days before heading(13DBH) and the second internode when it was applied at 8DBH and 3. KIM-112 gradually inhibited internode elongation of rice with increase in dosage starting from 1.0ga.i./10a. The culm length shortened by 7-17% at 3DBH. The maximum distribution of leaf blade at canopy structure was positioned higher on KIM-112 application than on untreated. Lodging index decreased by 8-47% on KIM-112 application and field lodging degree(0-5) was 5 at untreated but KIM-112 application was only 1.3-2.0 of 3 DBH and was little lodging of 8-13 DBH. Ripened grain ratio of KIM-112 application were higher than those of untreated. Yield increased by 27-37% at KIM-112 application.

• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.13-18
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• 1997

The effects of the various raw material composition and sintered temperature on the physical properties of Ni-Zn ferrite have been investigated. They turned out to be spinel structure by X-ray diffraction and the size of grain from microscope was from 6 ${\mu}{\textrm}{m}$ to 16 ${\mu}{\textrm}{m}$. As the sintering temperature was increased from 1030 $^{\circ}C$ to 1070 $^{\circ}C$, the initial permeability and magnetic induction has increased and the both of Q factor and coercive force has decreased. The coercive force and curie temperature were almost the same at each specimen. Their values were about 0.20 Oe and 220 $^{\circ}C$. The frequency of specimen will used in the range from 400 kHz to 20 MHz. The basic composition of $Ni_{0.14}Zn_{0.64}Cu_{0.22}Fe_2O_4$ (specimen B) sintered at 1050 $^{\circ}C$ shows the best results at magnetic induction($B_r & B_m$).

• Journal of the Korean Vacuum Society
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• v.22 no.2
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• pp.79-85
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• 2013

Rare earth ions, either $Eu^{3+}$ or $Dy^{3+}$-doped $CaMoO_4$ phosphors were synthesized by using the solid-state reaction method. The crystalline structure of all the phosphor powders, irrespective of the type and concentration of activator ions, was found to be a tetragonal system with the main diffraction peak at (112) plane. For $Eu^{3+}$-doped $CaMoO_4$ phosphors, the grain particles showed an increasing tendency and the pebble-like patterns with a very homogeneous size distribution in the range of 0.01~0.10 mol of $Eu^{3+}$ ions concentration, and the excitation spectra were composed of a broad band centered at 311 nm and weak multiline peaked in the range of 360~470 nm. The dominant emission spectrum was the strong red emission centered at 618 nm due to the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ ions. For $Dy^{3+}$-doped $CaMoO_4$ powders, excitation spectra showed a charge transfer band centered at 303 nm and relatively weak bands resulting from the transitions of $Dy^{3+}$ ions and the main yellow emission spectrum was observed at 578 nm, which was assigned to the $^4F_{9/2}{\rightarrow}^7H_{13/2}$ transition of $Dy^{3+}$ ions.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.312-312
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• 2012

Magnesium oxide has become focus for research activities due to its use in magnetic tunnel junctions and for understanding of do ferromagnetism. Theoretical investigations on such type of system indicate that the presence of defects greater than a threshold value is responsible for the magnetic behaviour. It has also been shown experimentally that by decreasing the film thickness and size of nanoparticles, enhancement/increase in magnetization can be achieved. Apart from the change in dimension, swift heavy ions (SHI) are well known for creating defects and modifying the properties of the materials. In the present work, we have studied the irradiation induced effects in magnesium oxide thin film deposited on quartz substrate via X-ray absorption spectroscopy (XAS). Magnesium oxide thin films of thickness 50nm were deposited on quartz substrate by using e-beam evaporation method. These films were irradiated by 200 MeV Ag15+ ion beam at fluence of $1{\times}10^{11}$, $5{\times}10^{11}$, $1{\times}10^{12}$, $3{\times}10^{12}$ and $5{\times}10^{12}ions/cm^2$ at Nuclear Science Centre, IUAC, New Delhi (India). The grain size was observed (as studied by AFM) to be decreased from 37 nm (pristine film) to 23 nm ($1{\times}10^{12}ions/cm^2$) and thereafter it increases upto a fluence of $5{\times}10^{12}ions/cm^2$. The electronic structure of the system has been investigated by X-ray absorption spectroscopy (XAS) measurements performed at the high energy spherical grating monochromator 20A1 XAS (HSGM) beamline in the National Synchrotron Radiation Research Center (NSRRC), Taiwan. Oxides of light elements like MgO/ZnO possess many unique physical properties with potentials for novel application in various fields. These irradiated thin films are also studied with different polarization (left and right circularly polarized) of incident x-ray beam at 05B3 EPU- Soft x-ray scattering beamline of NSRRC. The detailed analysis of observed results in the wake of existing theories is discussed.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.166-176
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• 1994

Ni base superalloys are composed of solid sohltion hardening elements(Co, Cr. Mo. W and so on) and $\gamma '$ precipitation hardening elements(A1, Ti, Nb, Ta and so on). To Improve the mechanical properties and oxidation resistanre of superalloys, rare earth elements(%r, Hf, Y and so on) are added to the inner substrate, or are used as coating materials. Their pffects on the growth rate and adhes~on of oxide are changed according to the kinds of oxides such as $AI_2O_3$ and $Cr_2O_3$. The effect of yttrium on the oxidation rate, grain size of oxide, internal structure, and crack resistance was investigated for two kinds of Ni-base superalloys. One in AF'115 superalloy containing Hf and the other is MA6000 superalloy containing $Y_2O_3$. They werr owid~zed at high temperature after yttrium surface modification using ion coater. Yttrium coating on the AF115 and MA6000 superalloys results in a marked change in the growth of the inner oxide. For AF115 superalloy, the degree of gram boundary segregation of $Cr_2O_3$, and prefer en^ tial oxidation of Hf are decreased, and the shape of inner oxidation layer was changed from triangle to plate type. For MA6000 superalloy, $Cr_2O_3$ oxide scale was transformed as outer oxidation layer of CrZOI and inner oxidation layer of $Cr_2O_3$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.1
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• pp.57-63
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• 2011

Changes in food preferences and dietary habits of Korean prone to decrease consumption of the traditional energy source, rice. The exceeding condition of rice production in Korea is now not only impacting on the profit structure of farmers but also threatening food security. Although there have been several efforts to increase rice consumption rate, by developing various processed foods using rice flour, grain hardness of rice has been the most significant limiting factor. In this study, we addressed the suitability of the Namil(SA)-flo1, a mutant rice line has floury endosperm, in terms of producing rice flour by using dry-milling method, which is lower cost and more eco-friendly than other available methods such as wet-milling. Rice flour of the Namil(SA)-flo1 exhibited superior physico-chemical characteristics to any other check varieties including the wild type, Namil, in terms of distribution of granule sizes and content of damaged starch.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.2
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• pp.77-85
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• 2018

This study was performed to understand the effects of filling stage temperature on the characteristics of starch and storage protein and the quality of rice grains. Eight early maturing rice varieties were cultivated in Cheolweon (latitude $38^{\circ}15^{\prime}N$) and Suwon (latitude $37^{\circ}16^{\prime}N$) areas in Korea. Rice grown in Suwon, with relatively high ripening period temperatures, showed significantly reduced head rice ratio and eating qualities, higher protein and lower amylose contents than rice grown in Cheolweon. In rice that ripened under high temperature conditions, the starch contained significantly less short-chain amylopectin (DP < 12) but more intermediate- (DP 13-24) and long- (DP > 25) chain amlylopectin compared to rice that ripened under normal conditions. In addition, the electrophoretic pattern of rice storage protein under high- temperature conditions revealed decreased prolamin and increased glutelin contents.