• Journal of the Korean Ceramic Society
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• v.33 no.9
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• pp.1057-1063
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• 1996

Y2O3-CeO2-ZrO2 powders were prepared from water-soluble salts using a coprecipitation method. The forming process of oxide and the characteristics of the calcined powders treated in different drying conditions were investigated. The oxidation was occurred at the temperature of around 40$0^{\circ}C$ and the main crystallization of ZrO2 around $600^{\circ}C$. On calcination at $600^{\circ}C$ heating lamp-dried powders consisted of agglomerates of globular morphology with average agglomerate size of 2.27${\mu}{\textrm}{m}$ and specific surface area of 68.3m2/g and spray dried powders contained dense spheric particles with average agglomerate size of 1.35${\mu}{\textrm}{m}$ and specific surface area of 11.0m2/g which exhibited low agglomeration tendency. Removal of the water by a freeze-drying technique produced calcined powders containing flake-like secondary particle structures with wide agglomerate size distri-bution of 0.1-60${\mu}{\textrm}{m}$ and specific surface area of 24.5${\mu}{\textrm}{m}$. The 20 MPa-pressed density (36.8-41.4% T,D) of calcined powders did not nealy depend on drying methods whilst compaction ratio of calcined powders derived from freeze-drying was the highest ( 6.24) among three drying methods. On continuous heating up to 150$0^{\circ}C$ the sinterability of calcined powders derived from heating lamp-drying was superior to those derived from spray-and freeze-drying. The final sintered density of calcined powders was the highest (96% T,D at 150$0^{\circ}C$) in case of heating lamp-drying.

• The Journal of the Petrological Society of Korea
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• v.26 no.4
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• pp.327-339
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• 2017

The Cretaceous Myeongseongsan Granite in the northwestern Gyeonggi Massif consists of a major pale pink-colored biotite monzogranite and a minor white-colored biotite alkaligranite. Low Sr and high Ba concentrations, negative Eu-anomalies in REE plot, negative Sr anomalies in spider diagram, a negative correlation between Sr and Rb, and positive correlations between Sr and Ba and $Eu/Eu^*$ indicate that a fractional crystallization of both plagioclase and K-feldspar played a significant role during magma evolution. The Myeongseongsan Granite is plotted in I-& S-type granites on I, S, A-type granite classification scheme. While the biotite monzogranite is plotted in unfractionated I-& S-type granite, the biotite alkaligranite is plotted in fractionated I-& S-type granite, which indicates that the biotite alkaligranite is a more differentiated product. In order to elucidate the nature of the protoliths of the peraluminous Myeongseongsan magma, we plotted in $Al_2O_3/TiO_2$ vs. $CaO/Na_2O$ and Rb/Sr vs. Rb/Ba diagrams, and they suggest that the Myeongseongsan Granite was derived from clay-poor metagreywackes and meta-psammites or their igneous counterparts. Whole-rock zircon saturation temperature indicates that the Myeongseongsan magma was melted at $740-799^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1076-1084
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• 1995

A mixture of aluminum isopropoxide (Al(OC3H7i)3) solution and sodium hydroxide (NaOH) solution was hydrolyzed in the range between pH 1~14. the powder obtained from sol-gel process was calcined at several temperatures and crystallization behaviors of various samples were investigated. The hydrolyzed sols of pH 1~6 wre clear, or near clear. On the other hand, powder precipitated from sols of pH 7~14. The sample obtained from pH 3 solution crystallized via complicated route, and $\beta$-Al2O3 and $\beta$"-Al2O3 phases appeared at lower temperature than samples from other pH conditions. And the quantity of remained $\beta$"-Al2O3 phase after heat treatment at 150$0^{\circ}C$ was more than samples from other pH conditions. After sintering, ionic conductivities were 1.3$\times$10-4S.cm-1 to 0.76$\times$10-4S.cm-1.0-4S.cm-1.

• Advances in nano research
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• v.10 no.3
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• pp.211-219
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• 2021

The evaluation of the corrosion resistance of titanium with a TiO2 nanotubes top layer was carried out (TiO2 NT). These nanostructures were evolved into anatase nanoparticles without heat treatment in an aqueous medium, which is a novel phenomenon. This work analyzes the layer between the nanotube bottom and the substrate, which is thin and still susceptible to corrosion. The bottom of TiO2 nanotubes having Fluor resulting from the synthesis process changed between amorphous to crystalline anatase with a crystallite size of about 4 nm, which influenced the corrosion rates. Four kinds of samples were evaluated. A) NT by Ti anodizing; B) NTSB for Ti plates, either modifying its surface or anodizing the modified surface; C) NT-480 for anodized Ti and heat-treated (480℃) for reaching the anatase phase; D) NTSB-480 for Ti plates, first, modifying its surface using sandblast, after that, anodizing the modified surface, and finally, heat-treated to 480℃ to compare with samples having induced crystallization and passivation. Four electrochemical techniques were used to evaluate the corrosion rates. The surfaces having TiO2 nanotubes with a sandblast pre-treatment had the highest resistance to corrosion.

• Korean Journal of Materials Research
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• v.6 no.8
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• pp.852-857
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• 1996

Crystallization characteristics of titanium oxide thin film during post-annealing of reactive sputter deposition were studied. Amorphous phases of as-deposited films were crystallized into rutile after annealing at $900^{\circ}C$ and anatase at $500^{\circ}C$, respectively when $O_2$ concentration during sputtering was more than 15%. However, rutile was the only phase obtainable after annealing if %$O_2$ was less than 10%. For these films, Magneli phase($Ti_nO_{2n-1}$) were crystallized below $500^{\circ}C$ at first place due to slow oxidation of nonstoichiometric films but $500^{\circ}{\sim}600^{\circ}C$ anatase with nonstoichiometry was crystallized for a short period. It was, therefore, concluded that crystal growth can proceed without phase transition if stoichiometric phase is formed at the first stage of crystallization, and that rutile, the most stable phase, was resulted from any oxygen deficient nonstoichiometric films.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.11-21
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• 1999

For microelectronic packaging application, the crystallizable glass powder in CaO-$A1_2O_3-SiO_2-B_2O_3$system was mixed with various amounts of alumina inclusions (\approx 4 $\mu \textrm{m}$), and its sintering behavior, crystallization behavior, and dielectric constant were examined in terms of vol% of alumina and the reaction between the alumina and the glass. Sintering of the CASB glass powder alone at $900^{\circ}C$ resulted in full densification (99.5%). Sintering of alumina-filled composite at $900^{\circ}C$ also resulted in a substantial denslfication higher than 97% of theoretical density, In this case, the maximum volume percent of alumina should be less than 40%. XRD analysis revealed that there was a partial dissolution of alumina into the glass. This alumina dissolution, however, did not show the particle growth and shape accommodation. Therefore, the sintering of both the pure glans and the alumina-filled composite was mainly achieved by the viscous flow and the redistribution of the glass. Alumina dissolution accelerated the crystallization initiation time at $1000^{\circ}C$ and hindered the densification of the glass. Dielectric constants of both the alumina-filled glass and the glass-ceramic composites were increased with increasing alumina content and followed rule of mixture. In case of the glass-ceramic matrix composites showed relatively lower dielectric constant than the glass matrix composite. Furthermore, as alumina content increased, crystallization behavior of the glass was changed due to the reaction between the glass and the alumina. As alumina reacted with the glass matrix, the major crystallized phase was shifted from wollastonite to gehlenite. In this system, alumina dissolution strongly depended on the particle size: When the particle size of alumina was increased to 15 $\mu\textrm{m}$, no sign of dissolution was observed and the major crystallized phase was wollastonite.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.296-296
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• 2007

Ferroelectric neodymium-substituted $Bi_4Ti_3O_{12}$(BTO) thin films have been successfully deposited on Pt/Ti/$SiO_2$/Si substrate by a sol-gel spin-coating process and the effect of crystallization temperature on their microstructure and ferroelectric properties were studied systematically. $Bi(TMHD)_3$, $Nd(TMHD)_3$, $Ti(O^iPr)_4$ were used as the precursors, which were dissolved in 2-methoxyethanol. The thin films were annealed at various temperatures from 600 to $720^{\circ}C$ in oxygen ambient for 1 hr, which was followed by post-annealed for 1 hr after depositing a Pt electrode to enhance the electrical properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the crystallinity and surface morphology of layered perovskite phase, respectively. The crystallinity of the BNT films was improved and the average grain size increased as the crystallization temperature increased from 600 to $720^{\circ}C$ at an interval of $40^{\circ}C$. The polarization values of the films were a monotonous function of the crystallization temperature. The remanent polarization value of the BNT thin films annealed at $720^{\circ}C$ was $24.82\;{\mu}C/cm^2$ at an applied voltage of 5 V.

• Transactions on Electrical and Electronic Materials
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• v.4 no.5
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• pp.24-27
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• 2003

We have been investigated phase-change with temperature and electric field in chalcogenide Ge$_2$Sb$_2$Te$\sub$5/ thin film. T$\sub$c/(crystallization temperature) is confirmed by measuring the resistance with the varying temperature on the hotplate. We have measured I-V characteristics with Ge$_2$Sb$_2$Te$\sub$5/ chalcogenide thin film. It is compared with I-V characteristics after impress the variable pulse. The pulse has variable height and duration.

• Journal of Magnetics
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• v.4 no.2
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• pp.60-64
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• 1999

The addition of Co into $Nd_4Fe_{77.5-x}Co_x(HfGa)_yB_{18.5}(0$\leq$x$\leq$5, y=0, 0.5)4 was found to enhance the magnetic properties of $Fe_3B/Nd_2Fe_{14}B$ nanocomposite magnets. The enhancement resulted from the fact that Co retarded the crystallization of $\alpha$-Fe or Fe3B but accelerated that $Nd_2Fe_{14}B$. The decreased interval between the onset of crystallization temperature of Fe3B and $Nd_2Fe_{14}B$. phases enabled the grain growth of each phase to be uniform dufing a post annealing of the melt spun ribbons. The addition of 3~5 at. % Co into ternary composition $Md_4Fe_{77.5}B_{18.5}$ increased the coercivity (iHc) from 3.27 to 3.54 kOe with the enhanced remanence value (4$\pi$Mr) around 11.54 kG. From the ribbon magnets of Nd4Fe71.5Co5Hf0.5B18.5 made at 26 m/sec and annealed at 68$0^{\circ}C$ for 10 min, the magnetic properties of Br=11.54 kG, iHc=3.54 kOe, and (BH)max=14.35 MGOe were obtained from volume production line.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.120-122
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• 2003

We have been investigated phase-change with temperature and electric field in chalcogenide $Ge_2Sb_2Te_5$ thin film. $T_c$(crystallization temperature) is confirmed by measuring the resistance and conductivity with the varying temperature on the hotplate. We have measured I-V characteristics with $Ge_2Sb_2Te_5$ chalcogenide thin film. It is compared with I-V characteristics after impress the variable pulse. The pulse has variable height and duration that used voltage and current source.