• 한국세라믹학회지
• /
• 제16권1호
• /
• pp.21-25
• /
• 1979

This study is proposed to find an appropriate body for high expansion glass ceramics of ${Na}_2O-{Al}_2O_3-{SiO}_2$ system. The compositions of basic glasses are selected to be melted easily and to be crystallized into nepheline with various contents of alumina. The crystallization temperatures of basic glasses are determined by DTA. The crystals in the basic glasses developed by heat treatment are investigated by X-ray diffraction analysis, and thermal properties such as expansion coefficients, fusion points are measured. We find, therefore,that crystallization temperatures, crystal phases and thermal properties are affected by content of alumina.

• 한국세라믹학회지
• /
• 제28권6호
• /
• pp.488-494
• /
• 1991

In this study, the effects of catalyst and DCCA content were investigated in order to determine the optimum conditions of monolithic silica gel formation through sol-gel process. Formamide, oxalic acid, glycerol and dimethylformamide are used as DCCA. To observe the phenomena in drying and heat-treating of gels, we examined structural exchange of gels using FT-IR, TG-DTA and XRD. Monolithic gels were obtained by adding formamide and dimethylformamide as DCCA. According to the heat treatment schedule, silica glass is prepared by heat-treatment up to 1050$^{\circ}C$.

• Tribology and Lubricants
• /
• 제7권2호
• /
• pp.61-66
• /
• 1991

The frictional and wear characteristics of non-asbestos friction materials made of four different fibers (carbon, aramid, ceramic and glass) have been investigated at elevated temperature using High Frequency Friction Tester. On the basis of the experimental results, friction and wear phenomena of four different non-asbestos fibers were caused by lattice layer film of carbon, polymeric transfer film of aramid, abrasion of ceramic and adhesion of glass fiber under each contact junction. The surface analysis of the worn specimens and counter parts after tests were observed using Scanning Electron Microscope and Optical Microscope.

• 한국세라믹학회지
• /
• 제25권1호
• /
• pp.1-6
• /
• 1988

The IR edge absorption of the important pure components of ZrF4-based glasses, including two previously uncharacterized components(ZrF4 and AlF3), has been measured. Values of the glass IR edge absorption coefficients have been calculated from these results, assuming additivity, and are compared with experimental glass absorption coefficients. The calculated ${\alpha}$ values are about a factor of two lower than the experimental values for ZrF4-based glasses, and the ZrF4 makes the largest contribution to the calculated ${\alpha}$ value.

• 한국세라믹학회지
• /
• 제23권4호
• /
• pp.85-89
• /
• 1986

Electrical conductivity have been measured as function of temperature in MgO.$P_2O_5$ glasses containing small amounts of water. Conduction was due to the contribution of $H^+$ and the mobility of protons in the glass increased linearly with increasing its concentration. The conductivity was pro-portional to the square of the proton concentration and the activation energy decreased linerly with increasing logarithm of the proton concentration, And $$\sigma$_0$ and $A_0$ was independent of the proton concentration but not on glass compositions.

• 한국세라믹학회지
• /
• 제27권6호
• /
• pp.783-789
• /
• 1990

Shaped crystal growth apparatus were made for sapphire ribbon single crystal growth. Sapphire ribbon single crystal are grown by EFG(Edge-defined Film-fed Growth) methdo for use as watch-glass and SOS(Silicon-On-Sapphire) devices. Sapphire ribbon crystals were grown to be 40min wide, 1.8mm thick, 96mm long. Therelationshiops between growth striation and surface roughness, with various growth rates, were investigated and compared. It was found that sapphire ribbon crystal is suitable for watch-glass by measuring the transmittance in the visible light region.

• 한국세라믹학회지
• /
• 제21권4호
• /
• pp.349-354
• /
• 1984

The purpose of present study is to find the structure crystallization mechanism and physical properties in $TiO_2$ containing lead zinc borosilicate glass system. The experiments such as differential thermal analysis infrared spectral analysis. X-ray diffraction analysis and thermal expansion measurements have been done. Differential thermal analysis of coarse and fine glass powder showed bulk nucleating mechanism for high $TiO_2$ containing glasses and surface nucleation mechanism for low $TiO_2$ containing glasses. The prepared glasses crystallized to crystalline mixture of PbO.2ZnO. $B_2O_3$ .4PbO.2ZnO.$5B_2O_3$and 2PbO.ZnO.$B_2O_3$ when heat-treated in the range of 480 and 51$0^{\circ}C$ and crystallized to PbTiO3 when heat-treated at $600^{\circ}C$. Obtained crystalline phase of $PbTiO_3$ in glass matrix strongly affects to thermal expansion coefficient and the value of crystallized glass varied 68.0 to $107.1{\times}10-7$/$^{\circ}C$ depending on the amount of $TiO_2$added. Infrared spectral analysis showed that [$BO_3$] triangle and [$BO_3$] tetrahedral units were coexisted in the glass with high content of PbO.

• 한국세라믹학회지
• /
• 제31권11호
• /
• pp.1337-1345
• /
• 1994

Glasses in the system of 45CaO-25TiO2-30P2O5 containing 1 mole% of M2O(M=Li, Na, K) were melted and crystallized. And their crystal phases were Ca3(PO4)2, CaTi4(PO4)6, and TiO2. Porous glass-ceramics with skeleton of two crystal phase CaTi4(PO4)6 and TiO2 were prepared by selective leaching of Ca3(PO4)2 with 0.1 N-HCl. Glass transition temperature(Tg) and crystallization temperature(Tc) were decreased by addition of 1 mole% alkali metal oxide. Pore size of porous glass-ceramics was increased with increasing heat treatment temperature and its dependence on heat treatment temperature was decreased with addition of Na2O and K2O. It was found that porous glass-ceramics of parent glass and containing 1mole% M2O(M=Li, Na, K) composition had maximum specific surface area, porosity and maximum of crystallzed phase by heat treatment at 80$0^{\circ}C$, 76$0^{\circ}C$, 78$0^{\circ}C$, 80$0^{\circ}C$ respectively.

• 한국세라믹학회지
• /
• 제31권6호
• /
• pp.629-636
• /
• 1994

The ferrimagnetic glass-ceramics in the system Fe2O3-CaO-SiO2 for hyperthermia were investigated. Glasses could be prepared up to the content of 40 wt% of Fe2O3 and below the weight ratio of 1.0 of CaO/SiO2. The maximum saturation magnetization and the maximum coercive force were 29.85 emu/g and 340.1 Oe respectively, for a glass 40Fe2O3.20CaO.40SiO2 composition heat-treated at 95$0^{\circ}C$ for 8 hours. And for a glass 40Fe2O3.30CaO.30SiO2 composition the maximum saturation magnetization and the maximum coercive force were 18.47 emu/g and 374.4 Oe heat-treated at 1,00$0^{\circ}C$ and 90$0^{\circ}C$ for 8 hours respectively. The maximum hysteresis loss was 1,726.3 cal/g for a glass 40Fe2O3.20CaO.40SiO2 composition heat-treated at 95$0^{\circ}C$ for 8 hours. It was found that the ferrimagnetic Fe2O3.CaO.SiO2 glass-ceramics was little injurious to human body as results of biocompatibility test and biotoxicity test.

• 한국세라믹학회지
• /
• 제26권4호
• /
• pp.559-567
• /
• 1989

Bioglasses have been known to be as one of the promising biomateials, which can be used for replacing defective hard and soft tissue. There have been many reports on biological results for this type of glass, but no systematic work has carried out on the structures and properties of the bioglass itself. In the present study, the effect of P2O5 in bioglasses on their structures and properties was examined. Infrared and Raman spectroscopy for the glass structural analysis, differential thermal and X-ray diffraction analysis for the crystallization of the bioglass were performed, and several physical properties were measured. When the glasses were heat-treated, Na2O.2CaO.3SiO2 was the major crystalline phase and $\beta$-NaCaPO4 crystal was found for the glass with high P2O5 content. The added P2O5 in the glasses enhanced the polymerization of silicate glass structure and it changed the chain-like glass structure to a sheet-like structure, and some P2O5 may stay as phosphate monomer. With addition of P2O5 in the glass the density of the glasses decreased, but not much changes in their thermal expansion coefficient, softening point and microhardness were observed.