• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.334-339
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• 2004

Microstructures and mechanical properties of SPSed monolithic HAp, HAp-Ag, and HAp-ZrO$_2$sintered bodies were investigated by the XRD, SEM, and TEM techniques. The nano-sized HAp powders were successfully synthesized by precipitation of Ca(NO$_3$)$_2$4$H_2O$ and (NH$_4$)HPO$_4$solution. In the HAp-Ag composite, the shrinkage cavities were observed at the interfaces between HAp and large sized Ag particles due to the mismatch of their thermal expansion coefficients. However, no found the defect at the interfaces between HAp and fine-sized Ag particles. In the HAp-ZrO$_2$composite. nano-sized ZrO$_2$particles were almost dispersed at the grain boundaries of HAp phase. The fracture toughness of HAp-Ag and HAp-ZrO$_2$ composites were increased due to the plastic deformation and phase transformation mechanisms of the dispersed fine Ag and ZrO$_2$phase in the HAp matrix, respectively.

• Journal of Sensor Science and Technology
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• v.7 no.2
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• pp.131-139
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• 1998

$CdS_{0.67}Se_{0.33}$ single crystal was grown by vertical sublimation method of closed tube physical vapour deposition. The (0001) growth plane of oriented single crystals was confirmed from the back-ref1ection Laue patterns. From the Hall effects by van der Pauw method, the as-grown $CdS_{0.67}Se_{0.33}$ single crystals were found to be n-type semiconductors. The mobility appeared to be decreased by lattice scattering at temperature range from 150K to 293K and by impurity scattering at temperatures ranging from 30K to 150K In order to explore its applicability in photoconductive cells, we measured the ratio of photo-current to dark-current (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time respectively. The results indicated that for the samples annealed in Cu vapour the photoconductive characteristics are best. We obtained sensitivity of 0.99, the value of pc/de of $1.84{\times}10^{7}$, the MAPD of 323mW and the rise and decay time of 9.3 ms and 9.7 ms, respectively.

• Archives of design research
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• v.15 no.2
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• pp.213-222
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• 2002

A transfer paper, is needed in the third firing, is usually utilized for industrial ceramics in order to produce tablewares or promoting products. Products may have the same form, however; the price might be different by what kinds of design have transferred. We need to fully understand these methods in order to create high value and quality. Remodeling, the so-called second architecture, results from social Needs for renovation of structures and changing functions. Tile satisfying the need for a custom-made design which fits the features of a space. Most importantly, the remodeler must make an individual design ordered for the customer with an emphasis on economy and time efficiency. Tiles currently in the market are mass-produced using an automated system with a high-priced mold. It is difficult to find tiles of distinct design that are made in a small quantity. We need to develop a method for making various kinds of tile designs that would be marketed for the remodeling industry. In this study, after designing a certain wall with the tiffs in the space, 1 will talk about developing a method to make transfer paper to produce individual tiles for the space. 1 hope that the functional and aesthetic effect on remodeling will gain in popularity, and that we will foster a new demand for tiles in harmony with the other materials mentioned in this study.

• Korean Journal of Poultry Science
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• v.48 no.4
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• pp.327-335
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• 2021

Riemerella anatipestifer (RA) can cause septicemia, polyserositis, and ataxia in ducks. It can also colonize the upper respiratory tract of healthy ducks. These differences in pathogenicity are probably the result of diverse mechanisms of virulence in different strains. Since serum resistance is a feature frequently found in systemic pathogens, 130 RA strains having different clinical origins were tested. A variety of serum susceptibility levels were detected. Pharynx strains from healthy ducks were mainly susceptible to the bactericidal effect of the serum, while systemic strains were serum resistant. Heat-treatment of the sera abolished the bactericidal activity, indicating that complement is a key factor in this effect. In an attempt to associate serum-resistance to surface determinant genes of the bacteria, we screened for six genes involved in lipopolysaccharide synthesis and membrane proteins in RA. Of these, three genes (AS87_09335, AS87_00480, and AS87_05195) encoding outer membrane proteins might be implicated in serum resistance statistically. The results indicate that serum resistance is a virulence mechanism in RA.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.4
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• pp.172-179
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• 2006

When $Al_2O_3-MoO_3$ mixture is reduced, $MoO_3$ is only reduced to Mo at $900^{\circ}C$. But a compound between $Al_2O_3$ and Mo is not formed up to $1300^{\circ}C$. In the case of $Al_2O_3-MoO_3-MnO_2$ mixture, an intermediate compound $Mn_2Mo_3O_8$ is firstly formed at $900^{\circ}C$ and changes to $MnAl_2O_4$ at $1100^{\circ}C{\sim}1300^{\circ}C$. $Al_2O_3/Mo/MnO_2$ composite are manufactured by a selective reduction process in which Mo is only reduced in the powder mixture of $Al_2O_3,\;MoO_3\;and\;MnO_2$ oxide. For $Al_2O_3/Mo$ composite, the average grain size was not changed with increasing Mo content because of inhibition of grain growth of $Al_2O_3$ matrix in the presence of Mo particles. Fracture strength increased with increasing Mo content due to phenomenon of grain growth inhibition of $Al_2O_3$ matrix. Hardness decreased because of a lower hardness value of Mo, whereas fracture toughness increased. For $Al_2O_3,\;Mo\;and\;MnO_2$ composite, grain growth was facilitated by MnOB and it showed a lower fracture strength because of grain growth effect with increasing Mo and $MnO_2$ content. Hardness decreased because of the grain growth of matrix and coalesced Mo particles to be located in grain boundary, whereas fracture toughness increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.5-9
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• 2008

Cordierite has a very low thermal expansion coefficient, but has problem that it has a weak mechanical strength and is apt to be attacked by acid such as sulfur for using as a diesel particulate filter support. The physical properties of $ZrTiO_4$ modified with $SiO_2,\;Al_2O_3$, MoOx, $Cr_2O_3\;and\;Nb_2O_5$ were investigated with XRD, SEM, UTM and thermal expansion, etc. in this paper. $ZrTiO_4$ powder was synthesized as a monoclinic structure with processes that starting materials of $TiO_2\;and\;ZrO_2$ were mixed with ball mill and calcined above $1240^{\circ}C$ for 3 hr. Additive modified $ZrTiO_4$ specimens for flexural strength and thermal expansion measurement were obtained by mixing $ZrTiO_4$ powder with additives, pressing and firing at $1300^{\circ}C$ for 3 hr. The porosity of additive modified $ZrTiO_4$ decreased monotonically with increasing additive content by 5 wt% regardless of additive types and saturated for further increase of additive by 10wt. The flexural strength of $Al_2O_3$ (5, 10 wt%) modified $ZrTiO_4$ shows a large increase, but that of other additives modified $ZrTiO_4$ decreased. The thermal expansion coefficient of additive modified $ZrTiO_4$ except $Nb_2O_5$ decreased continuously with the content of additive. In particular, the lowest thermal expansion coefficient of $ZrTiO_4$ was obtained for the additive of $SiO_2$.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.3
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• pp.145-152
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• 2002

The composition of primary minerals in the rocks and secondary minerals of clay fractions of the soil developed on the cinder cones in the foot of Halla Mt., Jeju Island was investigated. The effects of parent materials on the physico-chemical properties and mineralogical characteristics were evaluated by XRD, DTA with the chemical composition of $H^+$ saturated clays. The main rock-forming minerals of a residual cinder cones were plagioclase with subsidiary minerals of hematite, gibbsite and quartz in the red cinder cone and of augite, quartz, feldspars and olivine in black cinder cone. It is demonstrated that ignition loss and sesquioxides content were higher in the red cinder soil than black cinder, which was resulted in the intermittent eruption of volcanic activity. For the chemical analysis of whole soils, $SiO_2/Al_2O_3$ ratio was increased from 2 to 3, but Ignition loss is decreased and $K_2O$ content are very low with increasing the soil depth in regard to the composition and kinds of clay minerals. No clay formation from micas mineral were in volcanic ashes. Dominant clay minerals of the cinder cone soils as a black and red cinder cone soil were allophane with some quartz and feldspars, while vermiculite, illite, kaolin were coexisted as a subsidiary minerals. But the red cinder cones soils had more hematite and gibbsite of the clay fractions than the black soils with magnetite. The exothermic pick of DTA at about $660^{\circ}C$ for cinder cone soils might be corresponded the oxidation magnetite to hematite reation. With regarding to the compositions of mineral detected by X-ray diffractogram and the properties of minerals by D.T.A thermogram, the dominant clay mineral was allophane of the cinder cone soils with some ferrous compounds, red colour of the cinder cone soils which are originated in hematite.