• 한국레이저가공학회지
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• 제14권1호
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• pp.25-29
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• 2011

Micromachining of photosensitive glass by UV exposure, heat treatment, and etching processes is reported. Like photoresist, the photosensitive glass is also classified into positive and negative types by development characteristics. For the positive type, the exposed area is crystallized and etched away during the etching process in HF solution, whereas the unexposed area is crystallized and etched away for the negative type. The crystallized area of the photosensitive glass has an etch rate approximately 30~100 times faster than that of the amorphous area so that it becomes possible to fabricate microstructures in the glass. Based on the unique properties of glass such as high optical transparency, electrical insulation, and chemical/thermal stability, the glass micromachining technique introduced in this work could be widely applied to various devices in the fields of electronics, bio engineering, nanoelectonics and so on.

• 한국세라믹학회지
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• 제23권3호
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• pp.67-77
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• 1986

various properties and manufacturing conditions were investigated in order to synthesize the glass-ceramics of $CaO-P_2O_5$ system for bioceramics. Compositions of easy unidirectional crystallization were between 47.5 and 50, 0mol% CaO For the glass rods prepared by pulling them to about 3 times the original rod length unidirectional crystallization was easier than original glass rods. These samples were crystallized in the axial direction at 15${\mu}{\textrm}{m}$/min in an electric furnace with a temperature gradient of about 3$0^{\circ}C$/cm at 57$0^{\circ}C$. Bending strengths of surface and unidirectionally crystallized samples were investigated with various CaO/$P_2O_5$ molar ratios. The bending strengths of unidirectionally crystallized samples were larger than those of surface -crystallized samples and the value of 47.5CaO.52.5 $P_2O_5$ was 1650kg/$cm^2$. XRD patterns showed that major phase is $\beta$-Ca(PO3) with minor phase 2CaO.$P_2O_5$ Relative crystal-linity of surface-crystallized sample was inversely propertional to the bending strenth. SEM of fracture surface of unidirectionally crystallized samples revealed an unidirectionally aligned structures.

• 한국세라믹학회지
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• 제56권6호
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• pp.526-533
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• 2019

Indialite/cordierite glass-ceramics demonstrate excellent microwave dielectric properties such as a low dielectric constant of 4.7 and an extremely high quality factor Qf of more than 200 × 10³ GHz when crystallized at 1300℃/20 h, which are essential criteria for application to 5G/6G mobile communication systems. The glass-ceramics applied to dielectric resonators, low-temperature co-fired ceramic (LTCC) substrates, and direct casting glass substrates are reviewed in this paper. The glass-ceramics are fabricated by the crystallization of glass with cordierite composition melted at 1550℃. The dielectric resonators are composed of crystallized glass pellets made from glass rods cast in a graphite mold. The LTCC substrates are made from indialite glass-ceramic powder crystallized at a low temperature of 1000℃/1 h, and the direct casting glass-ceramic substrates are composed of crystallized glass plates cast on a graphite plate. All these materials exhibit excellent microwave dielectric properties.

• 한국군사과학기술학회지
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• 제13권1호
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• pp.120-125
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• 2010

For application of transparent bulletproof materials, the SLS(soda-lime-silicate) glass was heated by 2-step crystallization. The DTA curve for SLS glass revealed the nucleation and crystal growth temperature at about $575^{\circ}C$ and $675^{\circ}C$, respectively. The crystallized glass was heated at various conditions(temperature, time). As a result, the maximum nucleation and crystal growth rates were $3.8\times10^5/mm^3{\cdot}hr$ at $575^{\circ}C$ and 20.58nm/min at $680^{\circ}C$, respectively. The bending strength, fracture toughness and vickers hardness were 451.7MPa, $0.9388MPa{\cdot}m^{1/2}$, and $693.9H_v$ which were 201%, 31%, and 22% higher than parent glass, respectively. Surface image and transmittance of crystallized SLS glass were analyzed by optical microscopy and UV/VIS/NIR spectrophotometer. Transmittance of crystallized SLS glass at visible-range(200~800nm) was not changed.

• 한국세라믹학회지
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• 제21권4호
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• pp.349-354
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• 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
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• 제40권3호
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• pp.255-261
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• 2003

생체활성 유리를 알루미나 기판에 코팅하고 이를 유사 생체 용액에 반응시켰을 때 코팅 유리층 표면에 생성된 수산화 아파타이트 형성 거동 변화에 대하여 연구하였다. 알루미나에 코팅된 생체 활성 유리를 여러 온도에서 열처리하였을 때 다양한 종류의 결정상이 나타났으며, 특히 110$0^{\circ}C$에서 열처리하였을 때는 $\beta$-wollastonite와 apatite, 120$0^{\circ}C$에서 열처리하였을 때는 $\alpha$-wollastonite와 apatite가 생성되었다. 이들 시편을 tris-완충용액에 반응시켰을 때, $\alpha$-wollastonite 결정의 부식 속도가 $\beta$-wollastonite의 부식 속도보다 빨랐다. 그리고 이들 시편을 유사 생체 용액과 반응시켰을 때는 두 코팅층 표면에서 수산화 아파타이트가 형성되었는데, 그 형성 속도는 $\alpha$-wollastonite가 포함된 시편에서 더 빨랐다.

• 한국결정성장학회지
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• 제1권2호
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• pp.94-103
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• 1991

ZnO함량이 45~60mol%인 ZnO-$P_2O_5$계 유리를 $1200^{\circ}C$에서 용융한 후 열처리하여 결정화시켰다. 기초유리와 결정화시킨 시료의 기계적 성질, 전기적 성질 등을 X선 회절, FTIR, 밀도, 열팽창, 전기전도도, 미세경도 등을 측정하여 검토하였다. X선 회절분석 결과 ZnO의 함량이 45~55mol%인 결정화 유리에서는 주결정상이 메타인산아연[$Zn(PO_3)_2$]이었으며ZnO가 60mol%인 시료는 피로인산아연($Zn_2P_2O_7$)으로 나타났다. 열팽창계수와 직류전기전도도는 ZnO가 50~60mol%인 시료에서 결정상 방향에 따라 각기 다른 값을 나타났으며 이는 배향성 결정상이 존재함을 시사한다.

• 한국군사과학기술학회지
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• 제13권6호
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• pp.1127-1132
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• 2010

Borosilicate glass was prepared in the composition of 81% $SiO_2$, 4% $Na_2O$, 2% $Al_2O_3$, 13% $B_2O_3$. The albite phase($NaAlSi_3O_8$) increased with the $ZrO_2$(0~10wt.%) addition. For measurement of glass transition temperature($T_g$), crystallization temperature($T_{c,max}$) measured by differential thermal analysis. The $T_g$ and $T_{c,max}$ were $510{\sim}530^{\circ}C$ $650{\sim}670^{\circ}C$, respectively. The crystallized glass was heated at various conditions(temperature, time). After nucleation at $550^{\circ}C$ for 2hours prior to crystal growth at $650^{\circ}C$ for 4hours, the resulting Vickers hardness, fracture toughness and bending strength were about $736H_v$, $1.0779MPa{\cdot}m^{1/2}$, and 493MPa, which were 17%, 45% and 149% higher than parent borosilicate glass, respectively. Crystal size and transmittance of crystallized borosilicate glass were analyzed by FE-SEM, EDX and UV-VIS-NIR spectrophotometer. Transmittance of crystallized borosilicate glass was decreased with increasing $ZrO_2$(wt%) at visible-range. The results prove that light-weight bulletproof can be fabricated by the crystallization of borosilicate glass.

• 한국세라믹학회지
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• 제54권5호
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• pp.395-399
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• 2017

The thermal properties and crystallization behavior of calcium phosphate glass fabricated using eggshell were examined. Nature eggshell has several impurities in the main component of $CaCO_3$. To manufacture calcium phosphate glass, washed eggshell was dissolved in aqua-regia while adding a solution of isopropyl alcohol, D. I. water and phosphoric acid. The calcined precursor was melted at $1000^{\circ}C$, and the glass ($T_g$ : $540^{\circ}C$) was crystallized at $620{\sim}640^{\circ}C$, which temperature range is relatively low compared to the crystallization temperature of other general types of calcium phosphate glass. The calcium phosphate glass using eggshell was successfully crystallized without any additional nucleating agents due to the multiple effects of impurities such as $Fe_2O_3$, $Al_2O_3$, SrO and $SiO_2$ in the eggshell. The main crystalline phase was ${\beta}-Ca(PO_3)_2$ and a biocompatible material, hydroxyapatite, was also observed. The crystallization process was completed under the condition of a holding time of only 1 h at the low temperature.

• 한국세라믹학회지
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• 제33권8호
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• pp.855-862
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• 1996

The nucleation and the crystal growth rates of Ge-Se-Te chalcogenide glass by two step heat-treatment and its effect on the mechanical optical properties and water-resistance were determined. The maximum nuclea-tion and crystal growth rate were 2.1$\times$103/mm3 .min at 28$0^{\circ}C$ and 0.4${\mu}{\textrm}{m}$/min at 33$0^{\circ}C$ respectively. When the crystal volume fraction with crystal size $1.5mutextrm{m}$ was about 4% the (hardness and fracture toughness were about 117kg/mm2 and 6.0 MPa.mm1/2)respectively. The weight loss of crystallized glass in water was lower than parent glass($25^{\circ}C$ for 32 hrs : 0.03% 8$0^{\circ}C$ for 16 hrs : 0.1%) as 0.01% at $25^{\circ}C$, 0.03% at 8$0^{\circ}C$ for 16 hrs : 0.1%) at $25^{\circ}C$ 0.03% at 8$0^{\circ}C$ respectively. The IR-transmittance decreased with increasing crystal size and crystal volume fraction. The IR-transmittance of crystallized glass with the crystal size of $1.5mutextrm{m}$ (crystal volume fraction : 4%) presented 56% which was about 4% lower than that of parent glass.