• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.357-360
• /
• 2000

Ferroelectric 0.05PZN-xPZT(90/10)-(0.95-x)PZT(10/90) (x=0.65, 0.85) specimens were fabricated by the mixed-oxide method and cold-pressing method using sol-gel derived PZT(90/10) and PZT(10/90) powders. All specimens show a uniform ferroelectric grain without the presence of the pyrocholre phase. Average grain size increased with an increase in sintering temperature, the value for the x=0.65 specimen sintered at 125$0^{\circ}C$ was 14.4${\mu}{\textrm}{m}$. The dielectric constant and dielectric loss of the x=0.65 specimen sintered at 125$0^{\circ}C$ were 1247, 2.05%, respectively. All specimens showed fairly good temperature and frequency stability of dielectric constant with the range from -2$0^{\circ}C$ to 6$0^{\circ}C$ and 100Hz to 10MHz. The coercive electric field and the remanent polarization of x = 0.65 specimen sintered at 125$0^{\circ}C$ were 8.5 kV/cm and 13 $\mu$C/cm$^2$, respectively.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1020-1029
• /
• 1998

The reaction-bonded TiC-Ni/Si/Co composites were prepared by the melt infiltration of Co, Si, and Ni me-tal into the TiC preforms. The miocrostructure reaction composition and mechanical properties were in-vestigated. In the case of the melt infiltrated with Co and Ni TiC grain shape was changed from angular to spherical shape with the average grain size of ∼5$\mu\textrm{m}$. In the case of the melt infiltrated with Co/Si or Ni/Si, Si was reacted with TiC particles and formed SiC particles. The bending strength of both specimens which have atomic ratio of 3 were 710 MPa and 515 MPa respectively. In the case of the melt infiltrated with Ni/Si/Co,. nonstoichiometric TiC was formed and its bending strength decreased to 420 MPa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.212-216
• /
• 2000

ZnO varistors for distribution surge arrester (18kV, 5kA) were developed and tested microstructure and electrical characteristics. Microstructure of ZnO varistor was consisted of ZnO grain, spinel phase and Bi-rich phase. Average grain size of ZnO varistor was $\mu\textrm{m}$ Reference voltage and lightning impulse residual voltage of ZnO varistor exhibited a good haracteristics above 5.5kV and below 11.56kV, respectively. Consequently, discharge capacity which is the most important characteristics of ZnO varistor for surge arrester exhibited excellent properties above 70kA at twice high-current impulse test. Moreover, variation rate of reference voltage and lightning impulse residual voltage showed below 5% and 2% after high-current impulse test, respectively. Leakage current and watt loss of ZnO varistor will not increase during accelerated aging test at stress condition, such as 3.213kV/$115^{\circ}C$/1000h.

• Journal of Powder Materials
• /
• v.12 no.5 s.52
• /
• pp.362-368
• /
• 2005

The structural and magnetic properties of nanostructued Fe-20 ;wt.%Si alloy powders were investigated. Commercial Fe-20 wt.%Si alloy powders (Hoeganaes Co., USA) with 99.9% purities were used to fabricate the nanostructure Fe-Si alloy powders through a high-energy ball milling process. The alloy powders were fabricated at 400 rpm for 50 h, resulting in an average grain size of 16 nm. The nanostructured powder was characterized by fcc $Fe_{3}Si$ and hcp $Fe_{5}Si_3$ phases and exhibited a minimum coercivity of approximately 50 Oe.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.296-299
• /
• 2003

In this paper, $0.10Pb(Sb_{1/2}Sn_{1/2})O_3-0.25PbTiO_3-0.65PbZrO_3$ ceramics were fabricated by the mixed-oxide method. The sintering temperature and time were $1230^{\circ}C$ and 2[hr], respectively. The structural, dielectric and piezoelectric properties with addition of NiO were studied. The crystal structure of a specimen was rhombohedral. As a result of SEM, the average grain size were decreased with increasing the contents of NiO. But the grains of the specimens doped with 0.4wt% NiO were increased, due to deposits of excess NiO at grain boundaries in the liquid phase. Relative dielectric constant and dielectric loss of the specimen doped with 0.1wt% NiO were 701 and 0.026, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.591-592
• /
• 2005

PTC Thermistors specimens were fabricated by added $MnO_2$ as donors, and $Nb_2O_5$ as acceptors and sintered $1250^{\circ}C$/2hrs. Average grain size decreased with increased in added $MnO_2$, and increased with added in $Nb_2O_5$. But, appeared liquid phase as $Bi_2O_3$ and $TiO_2$, affect to grain growth. XRD result, peak strength waslowed then crystallization not well, but, secondary phase were not showed all specimens. All specimens resistance were so high, about $40M\Omega$ over, couldn't measured to those resistance and doesn't appear PTCR effect.

• Journal of the Korean Society of Food Culture
• /
• v.15 no.2
• /
• pp.101-110
• /
• 2000

This study was carried out to investigate the consumer recognition and consumption of Misitgaru(the traditional powder of roast grain). Data were collected from the 605 housewives(average age, 42.9 years old) residing in Chonbuk area by the self-administered questionnaire. The results from this study were as follows. The respondants were generally concerned regarding Misitgaru as a between-meal snack(33%). And there were recognition on Misitgaru as a weaning food(17%), health food(16%), and substitute food(14%). Of the respondants, good consumers of the Misitgaru were high ratio in age below 30 years old and in number of family member between 6 to 7. Among the demographic variables, age, educational level and housing form especially affected the purchasing place and educational level affected the kinds of mixing cereals. The higher the educational level, the more the kinds of mixing cereals. The methods of storage were significantly different according to age and income level. The older in age and higher in income level, the higher the storage at room temperature.

• Journal of the Korean institute of surface engineering
• /
• v.49 no.4
• /
• pp.376-381
• /
• 2016

The effects of ICP (Inductively Coupled Plasma) power, ranging from 0 to 200 W, on the crystal structure, microstructure, surface roughness and mechanical properties of magnetron sputtered VN coatings were systematically investigated with FE-SEM, AFM, XRD and nanoindentation. The results show that ICP power has a significant influence on coating microstructure and mechanical properties of VN coatings. With the increasing of ICP power, coating microstructure evolves from a porous columnar structure to a highly dense one. Average crystal grain size of single phase cubic fcc VN coatings was decreased from 10.1 nm to 4.0 nm with increase of ICP power. The maximum hardness of 28.2 GPa was obtained for the coatings deposited at ICP power of 200 W. The smoothest surface morphology with Ra roughness of 1.7 nm was obtained from the VN coating sputtered at ICP power of 200 W.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.412-415
• /
• 2004

PTC Thermistors specimens were fabricated by added $MnO_2$ as donors, and $Nb_2O_5$ as accepters and sintered $1250^{\circ}C/2hrs$. Average grain size decreased with increased in added $MnO_2$, and increased with added in $Nb_2O_5$. But, appeared liquid phase as $BaTiO_3$ and $TiO_2$, affect to grain growth. XRD result, peak strength waslowed then crystallization not well, but, secondary phase were not showed all specimens. All specimens resistance were so high, about $40M{\Omega}$ over, couldn't measured to those resistance and doesn't appear PTCR effect.

• Korean Journal of Metals and Materials
• /
• v.48 no.11
• /
• pp.1009-1013
• /
• 2010

Extremely dense WC with a relative density of up to 99% was obtained within five minutes under a pressure of 80 MPa using the High-Frequency Induction Heated Sintering method. The average grain size of the WC was about 71 nm. The advantage of this process is not only rapid densification to obtain a neartheoretical density but also the prohibition of grain growth in nano-structured materials. The hardness and fracture toughness of the dense WC produced by HFIHS were $2660kg{\cdot}mm^{-2}$ and $7.2MPa{\cdot}m^{1/2}$, respectively.