• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.11
• /
• pp.712-717
• /
• 2014

Glass ceramic has a high mechanical strength and low sintering temperature. So, it can be used as a thick film substrate or a high strength insulator. A series of glass ceramic samples based on MgO-$Al_2O_3-SiO_2-ZrO_2$ (MASZ) were prepared by melting at $1,600^{\circ}C$, roll-quenching and heat treatment at various temperatures from $900^{\circ}C$ to $1,400^{\circ}C$. Dependent on the heat treatment temperature used, glass ceramics with different crystal phases were obtained. Their nucleation behavior, microstructure and mechanical properties were investigated with differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vicker's hardness testing machine. With increasing the heat treatment temperature of MASZ samples, their hardness and toughness initially increase and then reach the maximum points at $1,300^{\circ}C$, and begin to decrease at above this temperature, which is likely to be due to the softening of glass ceramics. As the content of $ZrO_2$ in MAS glass ceramics increases from 7.0 wt.% to 13 wt.%, Vicker's hardness and fracture toughness increase from $853Kg/mm^2$ to $878Kg/mm^2$ and $1.6MPa{\cdot}m^{1/2}$ to $2.4MPa{\cdot}m^{1/2}$ respectively, which seems to be related with the nucleation of elongated phases like fiber.

• Journal of the Korean Ceramic Society
• /
• v.41 no.2
• /
• pp.143-150
• /
• 2004

Biaxial flexure strength (ball-on-3-ball) and fracture toughness (indentation microfracture) of heat-pressable glass-ceramics for dental use were investigated in this study. Crystal phase and microstructure of glass-ceramics were analyzed by XRD. SEM, and TEM. Crack propagation in specimens was not effectively arrested by dispersed crystalline particles. However, higher degree of crystallization probably contributes to strengthening of glass-ceramics. Better clinical reliability can be expected from lithium disilicate glass-ceramic because of its significantly higher biaxial flexure strength and fracture toughness.

• Journal of the Korean Ceramic Society
• /
• v.47 no.4
• /
• pp.325-328
• /
• 2010

Varying quantities of a high-thermal-expansion glass, 50CaO-20ZnO-$20B_2O_3-10SiO_2$ (CZBS), were added to alumina and sintered at $875^{\circ}C$ for 2 h for low temperature co-firing ceramic (LTCC) applications. As the amount of glass addition increased from 40 wt% to 70 wt%, the apparent density of the sintered product increased from 88.8% to 91.5%, which was also qualitatively confirmed by microstructural observation. When the glass addition was very high, e.g., 70 wt%, an apparent formation of secondary phases such as $CaZn_2AlZnSiAlO_7$, $Ca_2Al(AlSi)O_7$, $Ca_2Al_2SiO_7$, $Ca_2ZnSi_2O_7$ and ZnO, was observed. Both the dielectric constant and the coefficient of thermal expansion increased with the glass addition, which was qualitatively consistent with the analytical models, while the experimental values were lower than the predicted ones due to the presence of pores and secondary phases.

• Journal of Korean Society for Atmospheric Environment
• /
• v.19 no.1
• /
• pp.57-66
• /
• 2003

TiO$_2$ sol was prepared by sol-gel method, and this sol was coated in ceramic and glass bead by dip-coating method. The coated catalyst was applied to degrade benzene in the gas phase by exposing to UV -lamp (365 nm) in a batch reactor. The removal efficiency of the benzene was compared by changing various conditions such as the kind of chemical additives, the coating beads (ceramic and glass), solution pH, the initial concentration of TiO$_2$ sol, UV intensity, and benzene concentration. The physical structure of TiO$_2$ sol used in this study was found to be pu-rely anatase type from XRD analysis. The results showed that ceramic bead was effective as the coating agent rath-er than glass bead. The significant change in the benzene removal efficiency of benzene did not occur with chang-ing coating frequency and the initial concentration of TiO$_2$ sol. The removal efficiency of benzene increased with increasing UV intensity, and with acidic treatment of TiO$_2$-coated ceramic bead.

• Journal of the Korean Academy of Esthetic Dentistry
• /
• v.25 no.2
• /
• pp.98-108
• /
• 2016

In recent days, perhaps the biggest driver in new material development is the desire to improve restorations esthetics compared to the traditional metal substructure based ceramics or all-ceramic restorations. Each material type performs differently regarding strength, toughness, effectiveness of machining and the final preparation of the material prior to placement. For example, glass ceramics are typically weaker materials which limits its use to single-unit restorations. On the other hand, zirconia has a high fracture toughness which enables multi-unit restorations. This material requires a long time sintering procedure which excludes its use for fast chair side production. Hybrid ceramic material developed for CAD/CAM system is contained improved nano ceramic elements. This new material, called a Resin Nano Hybrid Ceramic is unique in durability of function and aesthetic base compositions. The new nano-hybrid ceramic material is not a composite resin. It is also not a pure ceramic. The material is a mixture of both and consists of nano-ceramic fillers. Like a composite, the material is not brittle and is fracture resistant. Like a glass ceramic, the material has excellent polish retention for lasting esthetics. The material is easily machined by chair side or in a dental lab side, could be an useful restorative option.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.23 no.4
• /
• pp.180-188
• /
• 2013

The glass of E-glass fiber composition was fabricated by using refused coal ore which is obtained as by-product from Dogye coal mine in Samcheok. We used silica-alumina refused coal ore which has low carbon content relatively, and the amount of refused coal ore has been changed from 0 to 35 % in batch composition. E-glass was fabricated by the melting of mixed batch materials at $1550^{\circ}C$ for 2 hrs with different refused coal ore composition of 0~35 %. We obtained a transparent and clear glass with high visible light transmittance value of 81~84%, thermal expansion coefficient of $5.39{\sim}5.61{\times}10^{-6}/^{\circ}C$ and softening point of $851{\sim}860^{\circ}C$. The glass fiber samples were also obtained through fiberizing equipment at $1150^{\circ}C$, and tested chemical resistance and tensile strength to evaluate the mechanical property as a reinforced glass fiber of composite material. As the result, we identified the properties of E-glass fiber by using refused coal ore are plenty good enough compare to that of normal E-glass without refused coal ore, and confirmed the possibility of refused coal ore as for the raw material of E-glass fiber.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.5 s.182
• /
• pp.170-176
• /
• 2006

Multi-layered laminate made of ceramic/composite have been developed to prevent penetration by high velocity impact. In this study, three-layered plates consisted of 1) cover layer (glass fiber reinforced polymer), 2) $Al_{2}O_{3}$, ceramic plate, and 3) backing plate (glass fiber reinforced polymer) were fabricated with various conditions and tested for their ballistic protection characteristic. The ceramic composite laminates, with thin backing plate, were completely penetrated by armor piercing projectile. The plate with inserted rubber between ceramic and backing plate showed excellent ballistic protection, though completely penetrated by the second shoot.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.226-231
• /
• 2007

This paper studied on the impact fracture modeling techniques of spherical dome with MACOR glass-ceramic. The glass ceramic material has bigger compressive strength than the tensile strength and endure well at high temperature. The fracture simulation under shock perssure was performed by the finite element method with nonlinear code LS-Dyna. The simulation was carried out by 3 type dome models under step impact pulse shape. 4-node shell element and 8-node solid element were used for analysis.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2000.04a
• /
• pp.111-111
• /
• 2000

In order to form a uniform oxidation layer and spinel crystalline phase that has been help strong bonding in Kovar(Fe-29Ni-17Co)-to-glass sealing, the humidified nitrogen and nirtogen/hydrogen mixture was used as an oxidation atmosphere. Kovar oxidation was diffusion-controlled reaction and the activation energy was 25~32 kcal/mol at $600~900^{\circ}C.$ After oxidation at $600^{\circ}C, $ the oxidation layer was under 1 $\mu\textrm{m}$ thickness and crystalline phase was spinel which was found to be suitable for the Kovar-to-glass sealing. The Kovar-to-glass seal was carried out at $1010^{\circ}C$ and humidified nitrogen/hydrogen mixture atmosphere. Sealing properties were tested by Leak tester and SEM.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.6
• /
• pp.168-174
• /
• 2007

A ceramic glass mold was developed for micro hot-embossing and replicated polymer parts are fabricated. The glass-ceramic micro mold could be fabricated with a laser process and a wet etching process and the fabrication time could be saved a lot. Various polymer micro structures can be obtained by hot-embossing. The process parameters such as ho-embossing temperatures or pressures were investigated and optimized. This process can be applied for fabrication of micro structures for flip-chips or micro fluidic channels for bio-engineering. The advantages and disadvantages of this process are discussed, too.