• 약학회지
• /
• 제22권1호
• /
• pp.22-26
• /
• 1978

The purposes of this investigation were to study the characteristic properties of bismuthoxynitrate formed by hydrolysis of bismuthnitrate according to various reaction conditions and to propose the property difference between synthesized pearl pigment and bismuthsubnitrate as pharmaceuticals by means of X-ray diffraction, IR, DTA and TGA. The pearl pigment could be obtained by reaction of bismuth nitrate-diluted nitric acid solution with cold water (5.deg.) agitation at lower pH. The pearl pigment was BiO. NO$_{3}$. 2H$_{2}$O. in composition and crystalline form was thin plate of monoclinic system and its combination with water was assumed to be hydrated hydrous form between Bi-H$_{2}$O bond. On the other hand, bismuthsubnitrate was 5BiO.4NO$_{3}$.6H$_{2}$O in composition and crystalline form was pillar of rhombic system and the bond between Bi and H$_{2}$O molecules was assumed to be hydrous form. The different properties between two compounds in structure are presumed to be caused by the hydrolysing conditions of bismuthnitrate respectively.

• 한국세라믹학회지
• /
• 제29권9호
• /
• pp.719-728
• /
• 1992

ZrO2/Al2O3-Mullite composites were prepared by infiltration of the silica sol to the porous ZrO2/Al2O3 bodies. The porous ZrO2/Al2O3 bodies for infiltration were fabricated using ZrO2 (20wt%)/Al2O3 composite powders synthesized by the emulsion-hot kerosene drying method. The preparation of silica sols was conducted by the hydrolysis-peptization of an alcoholic TEOS solution. When ZrO2/Al2O3-Mullite and ZrO2/Al2O3 composites were sintered at 1$650^{\circ}C$ for 4 hrs, both of them showed an excellent sinterability. As the amount of mullite added in the composites increased, the ratio of the tetragonal phase of zirconia to the monoclinic phase at the room temperature became higher. It was known that values of the fracture toughness of the ZrO2/Al2O3-Mullite composites were about 5.48 MPa.m1/2 much larger than that of the ZrO2/Al2O3 system.

• 한국세라믹학회지
• /
• 제30권7호
• /
• pp.563-570
• /
• 1993

Spherical, monosized gadolinium compound was prepared by the reaction of Gd(NO3)3 solution with decomposition products of urea in the solution at evaluated temperature. Chemical composition and calcination characteristics of spherical gadolinium compound prepared were investigated by X-ray IR and TG-DTA. The approximate chemical composition of the spherical particle precipitated was Gd(OH)CO3.1.5H2O. Gd(OH)CO3.1.5H2O was calcined to monoclinic type Gd2O3 at 115$0^{\circ}C$ via cubic type Gd2O3 near $600^{\circ}C$. The effects of various parameters such as pH, temperature, concentration ratio of urea to gadolinium precusor, ageing time, and others material (CCl3COOH and HOCNH2) in stead of urea as precipitating agent on the properties of the resulting precipitates were studied systematically.

• 한국세라믹학회지
• /
• 제30권7호
• /
• pp.571-577
• /
• 1993

The effect of $\alpha$-Al2O3 seeding on preparation of zirconia/alumina gel fragment prepared by sol-gel processing was characterized through XRD, SEM, TG/DTA and IR analysis. Aluminum isopropoxide and zirconium butoxide were used as starting materials. $\alpha$-Al2O3 seeding restrained grain growth of alumina and zirconia, and decreased tetragonal to monoclinic phase transformation of zirconia on cooling. Therefore, fine zirconia-toughened alumina composite having the relative sintered density of about 98% of theoretical at 140$0^{\circ}C$ for 2h could be obtained.

• 한국세라믹학회지
• /
• 제31권10호
• /
• pp.1176-1180
• /
• 1994

The sliding wear behavior of the plasma-sprayed zirconia containing 3 mol% yttria was investigated after the annealing at room temperature to 80$0^{\circ}C$ in various concentrations of humid atmosphere as laboratory, humid, dry argon atmosphere. Both of the friction coefficient and the wear loss increased with increasing temperature up to 80$0^{\circ}C$. Surface morphology of the worn samples changed with annealing temperature. The change of monoclinic/tetragonal (m/t) x-ray peak intensity ratio effected the wear behavior. The m/t ratio had maximum value at 20$0^{\circ}C$ and decreased with increased temperature in laboratory and humid atmosphere. In argon atmosphere the m/t ratio had no maximum value and decreased with increasing temperature. At all the annealing temperature humid atmosphere had more the m/t ratio value than any other atmosphere. The change of toughness was showed the inversed result of m/t ratio change. The results indicated that the resudial stress which was induced by the different amount of phase transformation takes a detrimental role in wear behavior.

• 한국세라믹학회지
• /
• 제28권7호
• /
• pp.549-555
• /
• 1991

Mullite-zirconia (0∼4 mol% yttria) composites were obtained by In-situ sintering of zircon and alumina mixture, and their mechanical properties were studied in conjuction with microstructure observation. Martensitic transformation temperature (Ms) of zirconia dispersed in the mullite matrix decreased with Y2O3 contents and was about 600$^{\circ}C$ for ZrO2 containing 4 mol% Y2O3. On cooling of this composites, tetragonal to monoclinic phase transformation induced microcracks at the grain boundary of mullite matrix. The microcracks seemed to absorb the fracture energy in stress field during mechanical tests. Therefore, toughening mechanisms of this composite were considered to nucleation and extension of microcrack, and crack deflection mechanism due to the difference of thermal expansion coefficient between matrix and dispersed phase.

• 한국세라믹학회지
• /
• 제45권2호
• /
• pp.126-131
• /
• 2008

In this study, we prepared zirconia gel by the sol-gel method and investigated its photoluminescence properties by varying pyrolysis temperature. The addition of acetic acid into a Zr-alkoxide solution resulted in forming the bidentate ligands with Zr ions and producing a stable gel. At the pyrolysis temperature of $350^{\circ}C$, the zirconia nanocrystals with tetragonal structure gradually appeared in the gel. The PL intensity of the zirconia gel increased with increasing the pyrolysis temperature up to $350^{\circ}C$, but decreased above the temperature. Concurrently, its PL peak wavelength continuously shifted from ${\sim}440\;nm$ to ${\sim}550\;nm$ with the temperature. The PL characteristics of the zirconia gels were closely associated with decomposition of residual organic groups, the formation of the zirconia nanocrystals, and the tetragonal to monoclinic phase transformation.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
• /
• pp.1510-1513
• /
• 2005

The luminescent properties of $Eu^{3+}$ and $Sm^{3+}$ doped potassium tungstate phosphor were investigated. The $K_{4-3x}(WO_4)_2:Eu_x$, $Sm_y$ phosphor was produced by firing the mixed precursors, followed by re-firing with a flux. The re-firing process provided the clean surface to the particles. The excitation spectra showed that the strong absorption in the region of ultra violet light occurred due to the high europium doping concentration. The incorporation of europium to potassium tungstate was easier, compared to other host materials. The excitation spectra could be controlled by the small addition of samarium. The increase of energy absorption around 405nm was assigned to the $Sm^{3+}$ ions. The comparison between real x-ray diffraction and simulated one revealed that the crystal structure of $K_{4-3x}(WO_4)_2:Eu_x,Sm_y$ phosphor is monoclinic with a space group, C2/c.

• 한국세라믹학회지
• /
• 제33권3호
• /
• pp.332-338
• /
• 1996

This study was investigated on the recycle feasibility of the waste AC(Ammonium Carbonate) solution produ-ced in a commercial AUC(Ammonium Uranyl Carbonate) conversion plant. AUC particles were produced with the AC solution which was prepared with AC solid-agent instead of ammonia and carbon-dioxide gases. As the results particles of monoclinic shapes has been obtained regardless of the pH change if the carbonate concentration is sufficient in the mother liquore. Also a lot of twinned or aggregated particles were formed in case of the increase of pH in the reaction system but not affected in the change of temperature. Consequen-tly the characteristics of the particles which converted for AUC were produced withAC solution to UO2, particles specific surface area shape sintered density and others were similar to that of the particles which were produced with gases only when the pellets are fabricated in the nuclear fuel manufacturing process So the waste AC solution which is produced in the commercial AUC conversion plant is possible to recycle.

• 한국세라믹학회지
• /
• 제33권3호
• /
• pp.355-361
• /
• 1996

Yttria stabilized zirconia (YSZ) thin films were prepared by the electrochemical vapor deposition (EVD) method on the porous Al2O3 substrates. Y2O3 mol% of thin film was linearly increased with yttrium mole fraction of vapor phase. As yttrium mole fraction(Zyc13=0.18) increased dense and faceted thin films were enhanced. However as the yttrium mole fraction (Zyc13=0.04) decreased porous thin films with monoclinnic phase prevailed. With increasing pressure difference of substrate sides penetration depth decreased porosity and amount of monoclinic phase in the films increased.