EAF dust가 첨가된 결정화 유리의 물리적 특성

강승구,Kang, Seung-Gu 한국결정성장학회 2008 한국결정성장학회지 Vol.18 No.6

$Fe_2O_3$, ZnO 등이 주성분인 EAF dust를 $30{\sim}70\;wt%$ 첨가한 규산염계 유리 및 결정화유리를 제조하고, 시편내부에 생성된 상 및 미세구조와 물리적 특성과의 관계를 고찰하였다. 또한 제조된 유리와 결정화유리의 결정화 거동을 상분석 및 미세구조 관찰을 통하여 분석하였다. EAF dust가 30 wt% 첨가된 용융체의 경우 전형적인 비정질 XRD 패턴을 나타냈으며, 그 이상 첨가된 용융체에는 미용해 된 결정상이 일부 존재하였다. 모든 결정화유리에서는 franklinite, willemite 그리고 augite 결정상이 형성되었다. 결정화유리의 비중은 같은 조성의 유리에 비하여 높았고, EAF dust 함량에 따라 함께 증가하였다. 또한 결정화 유리의 열적 및 기계적 특성이 유리보다 우수하게 나타났다. 즉 유리는 EAF dust 첨가량과 함께 열팽창 계수가 증가하였으나 결정화유리에서는 반대로 감소하였다. 또한 EAF dust 첨가량에 따라 비커스 경도는 유리 및 결정화유리 모두 증가되었으며 같은 조성에서 결정화 유리의 경도값이 항상 더 높게 나타났다. The glass and glass-ceramics containing EAF dust $30{\sim}70\;wt%$ were fabricated and the dependance of physical properties upon crystal phases and microstructure formed was studied. The crystallization behavior of glass and glass-ceramics containing various contents of EAF dust composing of mainly $Fe_2O_3$ and ZnO was analyzed by crystal identification and microstructure observation. The glass specimen with EAF dust 30 wt% showed a typical amorphous pattern in XRD results and the specimen with above 30 wt% EAF dust had some un-dissolved crystals which was originated from EAF dust. The all glass-ceramics had franklinite, willemite and augite crystal phases. The density of glass-ceramics was higher than that of same composition glass, and it increased with EAF dust contents. In addition, the thermal and mechanical properties of glass-ceramics were always higher than those of glasses. In other words, the thermal expansion coefficient of glass increased with EAF dust contents while it decreased for the glass-ceramics. The vickers hardness for the glass and glass-ceramics increased with EAF dust content, the glass-ceramics always being higher those of glass of same composition.

Negative Effect of Rapidly Resorbing Properties of Bioactive Glass-Ceramics as Bone Graft Substitute in a Rabbit Lumbar Fusion Model

이재협,유현승,Jun-Hyuk Seo,이도윤,장봉순,이춘기 대한정형외과학회 2014 Clinics in Orthopedic Surgery Vol.6 No.1

Background: Bioactive glass-ceramics have the ability to directly bind to bones and have been widely used as bone graft substitutes due to their high osteoconductivity and biocompatibility. CaO-SiO2-P2O5-B2O3 glass-ceramics are known to have good osteoconductivity and are used as bone graft extenders. Methods: This study aimed to evaluate the effects of the resorbing properties of glass-ceramics in bone fusion after producing and analyzing three types of CaO-SiO2-P2O5-B2O3 glass-ceramics with high osteoconductivity that had enhanced resorption by having an increased B2O3 content. The three types of CaO-SiO2-P2O5-B2O3 glass-ceramics with B2O3 contents of 8.0, 9.0, and 9.5 weight % were designated and grouped as P20B80, P10B90, and P5B95, respectively. Glass-ceramic types were tested for fusion rates and bone formation by employing the lumbar 5–6 intertransverse process fusion model in 51 New Zealand male rabbits. Bioactivity was assessed by soaking in simulated body fluid (SBF). Results: In vitro study results showed sufficient hydroxycarbonate apatite layer formation occurred for P20B80 in1 day, for P10B90 in 3 days, and for P5B95 in 5 days after soaking in SBF. For the rabbit lumbar spine posterolateral fusion model, the autograft group recorded a 100% fusion rate with levels significantly higher than those of P20B80 (29.4%), P10B90 (0%), and P5B95 (14.3%), with high resorbing properties. Resorbing property differences among the three glass-ceramic groups were not significant. Histological results showed new bone formation confirming osteoconductivity in all three types of glass-ceramics. Radiomorphometric results also confirmed the resorbing properties of the three glass-ceramic types. Conclusions: The high resorbing properties and osteoconductivity of porous glass-ceramics can be advantageous as no glass-ceramics remain in the body. However, their relatively fast rate of resorption in the body negatively affects their role as an osteoconductive scaffold as glass-ceramics are resorbed before bony fusion.

결정화 유리 개발 및 응용

김선욱(Sun Woog Kim),황종희(Jonghee Hwang) 한국세라믹학회 2020 세라미스트 Vol.23 No.3

Glasses have become a significant part of our daily life as they are widely used in the buildings and the mobile phone displays. Among the functional glass materials, glass-ceramics are widely used in recent times and are distinguished due to their special properties. Glass-ceramics are polycrystalline solids prepared by controlled crystallization of glass. They are used as tough glass-ceramics, biocompatible glass-ceramics, and low thermal expansion glass-ceramics. Among the glass-ceramics, low thermal expansion glassceramics has received much attention due to their excellent thermal, mechanical, and optical properties and commercially used as cook top panels and telescope mirrors. In this work, we reviewed the general theory and application of glass-ceramics.

제강분진이 첨가된 규산염계 결정화유리의 미세구조 분석

김환식,강승구,Kim, H.S.,Kang, S.G. 한국결정성장학회 2006 한국결정성장학회지 Vol.16 No.5

제강분진(EAF dust, 이하 더스트)이 첨가된 규산염계 유리 프리트를 용융하여 유리 시편을 제조하고, 이를 열처리하여 결정화 시킨 후 표면 및 내부의 미세구조를 관찰하였다. 제조된 유리의 DTA 분석결과 결정화온도($T_c$)는 $850^{\circ}C$ 부근이었으며 이로부터 열처리 온도를 $950^{\circ}C$로 정하였다. XRD 분석결과 더스트가 50wt% 들어간 유리시편은 비정질 상태였으나 70wt% 들어간 유리시편은 spinel 결정상이 나타났다. 결정화유리시편은 spinel 및 willemite 결정상이 함께 나타나며 더스트의 첨가량이 증가할수록 willemite 결정상이 증가하였다. 더스트의 함유량이 50wt%인 유리시편의 경우 연마된 절단면이 거울 표면같이 매끄러운 상태였으나 70wt% 첨가된 경우에는 유리질의 모상(glass matrix)내에 최대 10mm 크기의 spinel 결정상이 존재하였다. 결정화유리시편의 경우에는 자유표면에 $2{\sim}5{\mu}m$ 크기의 ZnO 결정입자들이 생성되었고, 내부에는 유리상, spinel 그리고 willemite 결정상이 혼재하였다. 더스트가 50wt% 첨가된 유리는 결정입자가 존재하지 않았으나 70wt% 첨가된 유리시편에는 14%의 결정이 존재하였다. 더스트가 50 및 70wt% 첨가된 결정화유리시편의 결정화도는 각각 19 및 43% 이었다. 결정화 전후 시편들을 TCLP 용액에 18시간 담근 후 SEM을 통하여 미세구조를 관찰했을 때 유리시편에는 균열이 발생하였으나, 결정화유리시편의 경우 침식흔적은 나타났으나 균열은 존재하지 않았다. Microstructures of free surface and interior of glass-ceramics obtained by heat treating silicate glass specimen containing electric arc furnace dust(EAF dust) were observed. The crystallization temperature, $T_c$ of glassy specimen was measured around $850^{\circ}C$ from the result of different thermal analysis so heat treatment temperature to obtain glass-ceramic specimen was selected as $950^{\circ}C$ for 1 hr. Glass specimens containing 50 wt% dust were amorphous, while glass specimens containing 70 wt% dust showed spinel crystal peaks in XRD results. In case of glass-ceramic specimens, spinel crystalline phase was appeared with willemite, and willemite crystal peak intensity increased with increasing dust contents. The fractured surface of glass specimens containing 50 wt% dust was smooth like mirror surface, but that containing 70 wt% dust showed spinel crystals of 10 ${\mu}m$ size in glass matrix. In case of glass-ceramic specimens, ZnO crystal particles of $2{\sim}5{\mu}m$ size were produced in free surface and glassy phase, spinel and willemite crystal phases existed in interior. There were no crystals in glasses containing 50 wt% dust, while glass containing 70 wt% dust had 14 vol% crystals. Crystallinity of glass-ceramic specimens containing 50 and 70 wt% dust were 19 and 43%, respectively. When microstructures of glass and glass-ceramic specimens were observed through SEM after TCLP experiment, glass specimens showed flaking phenomenon while glass-ceramic specimens showed a slight corrosion evidence without any cracks.

Properties of Glass-Ceramics in the System CaO-TiO2-SiO2 with the Additives of Al2O3, ZrO2 and B2O3 for Use in the Solid Oxide Fuel Cells.

Lee, Jun-Suk,Park, Min-Jin,Shin, Hyun-Ick,Lee, Jae-Chun The Korean Ceramic Society 1999 The Korean journal of ceramics Vol.5 No.4

Glasses in the system $CaO-TiO_2-SiO_2-Al_2O_3-ZrO_2-B_2O_3$ were investigated to find the glass seal compositions suitable for use in the planar solid oxide fuel cell (SOFC). Glass-ceramics prepared from the glasses by one-stage heat treatment at $1,000^{\circ}C$ showed various thermal expansion coefficients (i,e., $8.6\times10^{-6^{\circ}}C^{-1}$ to $42.7\times10^{-6^{\circ}}C^{-1}$ in the range 25-$1,000^{\circ}C$) due to the viscoelastic response of glass phase. The average values of contact angles between the zirconia substrate and the glass particles heated at 1,000-$1,200^{\circ}C$ were in the range of $131^{\circ}\pm4^{\circ}$~$137^{\circ}\pm9^{\circ}$, indicating that the glass-ceramic was in partial non-wetting condition with the zirconia substrate. With increasing heat treatment time of glass samples from 0.5 to 24 h at $1,100^{\circ}C$, the DC electrical conductivity of the resultant glass-ceramics decreased from .$14\times10^{-5}\Omega^{-1}\textrm{cm}^{-1}\; to\; 4.0\times10^{-5}\Omega^{-1}\textrm{cm}^[-1}$ at $800^{\circ}C$. Isothermal hold of the glass sample at $1100^{\circ}C$ for 48h resulted in diffusion of Ca, Si, and Al ions from glass phase into the zirconia substrate through the glass/zirconia bonding interface. Glass phase and diffusion of the moving ion such as $Ca^{2+}$ in glass phase is responsible for the electrical conduction in the glass-ceramics.

Physico-mechanical behaviour of alkali and alkaline earth metal-containing mica glass–ceramics: a comparative evaluation

Amit Mallik 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.5

Mica glass–ceramics are known for their superior mechanical strength, fracture toughness and machinability. Crystallization, microstructure and mechanical behaviour of alkali and alkaline earth metal-containing mica glasses based on K 2 O/SrO/ BaO·4MgO·Al 2 O 3 ·6SiO 2 ·2MgF 2 composition were investigated by diff erential thermal analysis, X-ray diff raction, scanning electron microscopy and microhardness indenter. A distinct crystallization exotherm was observed in the diff erential thermal analysis curve.The crystallization peak corresponded to the formation of K-fl uorphlogopite for K-glass, Sr-fl uorphlogopite for Sr-glass, and Ba-fl uorphlogopite for Ba-glass. XRD results revealed that the above-mentioned formations were the major phases, while alpha hexacelsian, enstatite, and mullite were the minor phases in K-, Sr-, and Ba-glass–ceramics. SEM results indicated that the “house of cards” microstructure appeared in Sr-glass–ceramics at lower crystallization temperature than in the K- and Ba-glass–ceramics. The physico-mechanical properties of Ba- and Sr-glass–ceramics were compared with K-glass ceramics, and it was found that Ba-glass–ceramics possessed superior crystallization, microstructure and mechanical strength than the other two glass ceramics.

Micro/Millimeter-Wave Dielectric Indialite/Cordierite Glass-Ceramics Applied as LTCC and Direct Casting Substrates: Current Status and Prospects

Ohsato, Hitoshi,Varghese, Jobin,Vahera, Timo,Kim, Jeong Seog,Sebastian, Mailadil T.,Jantunen, Heli,Iwata, Makoto The Korean Ceramic Society 2019 한국세라믹학회지 Vol.56 No.6

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.

유리 및 결정화 유리 골 시멘트에서 DCPD의 형성 및 수산화 아파타이트로의 전환

임형봉,김철영,Lim, Hyung-Bong,Kim, Cheol-Young 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.1

The glass in the system of CaO-$SiO_2-P_2O_5$ and the corresponding glass-ceramics are prepared for bone cements and the behaviors of the hardening and hydroxyapatite formation were studied for the glass and glass-ceramic powders. The glass crystallized into apatite, $\alpha$-wollastonite and $\beta$-wollastonite depending on the glass composition when they were heat-treated at $950^{\circ}C$ for 4 h. A DCPD (dicalcium phosphate dihydrate : $CaHPO_4{\cdot}2H_2O$) was developed when the prepared glass and glass-ceramic powders were mixed with 3M-$H_3PO_4$ solution. The DCPD (Ca/P=1.0) transformed to HAp (Ca/P=1.67) when the bone cement was soaked in simulated body fluid (SBF), and this HAp formation strongly depended on the releasing capacity of $Ca^{2+}$ ions from the glass and glass-ceramic cements. The glass-ceramic bone cement containing $\alpha$-wollastonite crystals showed faster transformation of DCPD to HAp than other glass-ceramics containing $\alpha$- and $\beta$-wollastonite crystals. No hydroxyapatite was observed when the glass-ceramic bone cement containing apatite crystals (36P6C) was soaked in SBF even for 1 month, because no $Ca^{2+}$ ion can be released from the stable apatite crystals.

Chemical durability of wollastonite glass-ceramics derived from waste glass and sludge bottom ash

윤순도,이종운,윤연흠,양형식 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.1

Wollastonite glass-ceramics was prepared by using the milling and sintering process with a mixture of two different powders. As a solution to environmental and waste recycling problems, powder mixtures consisting of dry sludge bottom ash and waste glass powder were used to make Wollastonite glass-ceramics. The chemical durability, crystallinity, morphological properties and chemical compositions of the specimens before and after acid immersion were observed by field emission-scanning electron microscopy (FE-SEM) and an energy dispersive X-ray spectrometer (EDS). Various mechanical properties, such as density, compressive strength, bending strength and Vickers hardness were also investigated. Various heat treatment temperatures [850, 950 and 1050 oC] were used to obtain glass-ceramics before and after the acid immersion of the optimum chemical durability and to find adequate mechanical properties for practical usage. As the heat-treatment temperature was increased from 850 oC to 1050 oC, the mechanical properties improved, especially the glass-ceramics in a dense acicular type of crystals of the Wollastonite phase at 1050 oC, in particular, and all specimens before and after acid immersion, in general. Wollastonite glass-ceramics was prepared by using the milling and sintering process with a mixture of two different powders. As a solution to environmental and waste recycling problems, powder mixtures consisting of dry sludge bottom ash and waste glass powder were used to make Wollastonite glass-ceramics. The chemical durability, crystallinity, morphological properties and chemical compositions of the specimens before and after acid immersion were observed by field emission-scanning electron microscopy (FE-SEM) and an energy dispersive X-ray spectrometer (EDS). Various mechanical properties, such as density, compressive strength, bending strength and Vickers hardness were also investigated. Various heat treatment temperatures [850, 950 and 1050 oC] were used to obtain glass-ceramics before and after the acid immersion of the optimum chemical durability and to find adequate mechanical properties for practical usage. As the heat-treatment temperature was increased from 850 oC to 1050 oC, the mechanical properties improved, especially the glass-ceramics in a dense acicular type of crystals of the Wollastonite phase at 1050 oC, in particular, and all specimens before and after acid immersion, in general.

Effect of glass cooling rate on the crystallization behavior and structure of Al2O3-SiO2-Na2O-CaF2 oxyfluoride glass-ceramics

Mengxuan Li,Jinxin Zou,Guangping Guo,Jianxiang Liu,Guicheng Wang 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.5

The glass cooling rate during molding process has significant effect on the crystallization behavior and structural uniformityof Al2O3-SiO2-Na2O-CaF2 oxyfluoride glass-ceramics. Abaqus Finite Element Analysis indicated that at room temperaturecooling environment, the cooling rate of 8mm thick glass was notably lower than that of 3 mm thick glass. The interiortemperature of 8 mm thick precursor glass was still above 710 oC even after the sample was cooled for 15 s, which caused theformation of “crystal stones” in precursor glass. The microstructure of oxyfluoride glass and glass-ceramics with differentthickness was analyzed by using DTA, XRD, IR and SEM. Since the 8 mm thick glass was cooled slowly, the initial crystalnucleation generated in the interior of glass, mixed crystal phases were formed in the interior after heat treatment, while singleCaF2 crystal phase formed on the surface. On the contrary, there was only uniform CaF2 crystal phase generating in the 3mm thick precursor glass after heat treatment, as a result of high cooling rate during molding process. Besides, the mechanismand ways to optimize the structure uniformity of glass ceramics were also be discussed.