• Korean Journal of Materials Research
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• v.34 no.1
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• pp.12-20
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• 2024

This study successfully prepared high-porosity aluminosilicate fibrous porous ceramics through vacuum suction filtration using aluminosilicate fiber as the primary raw material and glass powder as binder, with the appropriate incorporation of glass fiber. The effects of the composition of raw materials and sintering process on the structure and properties of the material were studied. The results show that when the content of glass powder reached 20 wt% and the samples were sintered at the temperature of 1,000 ℃, strong bonds were formed between the binder phase and fibers, resulting in a compressive strength of 0.63 MPa. When the sintering temperatures were increased from 1,000 ℃ to 1,200, the open porosity of the samples decreased from 89.08 % to 82.38 %, while the linear shrinkage increased from 1.13 % to 10.17 %. Meanwhile, during the sintering process, a large amount of cristobalite and mullite were precipitated from the aluminosilicate fibers, which reduced the performance of the aluminosilicate fibers and hindered the comprehensive improvement in sample performance. Based on these conditions, after adding 30 wt% glass fiber and being sintered at 1,000 ℃, the sample exhibited higher compressive strength (1.34 MPa), higher open porosity (89.13 %), and lower linear shrinkage (5.26 %). The aluminosilicate fibrous porous ceramic samples exhibited excellent permeability performance due to their high porosity and interconnected three-dimensional pore structures. When the samples were filtered at a flow rate of 150 mL/min, the measured pressure drop and permeability were 0.56 KPa and 0.77 × 10^-6 m² respectively.

• The Korean Journal of Ceramics
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• v.1 no.4
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• pp.209-213
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• 1995

The electrical conductivity was investigated in two series of alkali aluminosilicate glass melts, $25R_2O(R: Na and K)-xAl2O3-(75-x)SiO_2$ at temperatures ranging from 1000 to 140$0^{\circ}C$. The dependences of conductivity or activation energy on $Al_2O_3/R_2O$ of both series in the molten state showed a same behavior. These results in the molten state were compared with previous studies for sodium alkali aluminosilicate glasses in the molten and solid state, and explained in terms of the binding state: $[-O]-R^+\; and\; [AlO_4]-R^+$.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.488-493
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• 2010

Geopolymer is a term covering a class of synthetic aluminosilicate materials with potential use in a number of areas, but mainly as a replacement for Portland cement. In this study, geopolymers with fly ash and meta kaolin were prepared using KOH as an alkali activator and water glass. The effect of water glass on the microstructures and the compressive strength of the geopolymer was investigated. As the amount of water glass increased, the dissolved inorganic binder particles in the geopolymers increased due to polymerization, resulting in a dense microstructure. The meta kaolin-based geopolymer showed a better extent of polymerization and densification than that of the fly ash-based geopolymer. XRD data also suggested that polymerization in meta kaolin-based geopolymers should be active resulting in the formation of an amorphous phase with an increasing amount of water glass. The compressive strength of the geopolymer was also dependent on the amount of water glass. The compressive strength of the geopolymers from both fly ash and meta kaolin increased with an increasing amount of water glass because water glass improved the extent of polymerization of the inorganic binder and resulted in a dense microstructure. However, the addition of water glass to the geopolymer did not seem to be effective for the improvement of compressive strength because the meta kaolin-based geopolymer mainly consisted of a clay component. For this reason, the fly ash-based geopolymer showed a higher value of compressive strength than the meta-kaolin geopolymer.

• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.221-225
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• 2007

The possibility of improving amplification characteristics and lowering the melting point of bismuth-doped aluminosilicate glass as a new amplification material, which has broadband near-infrared emission at 1300 nm regions, was investigated. Spectroscopic analysis of bismuth-doped aluminosilicate glass shows that the addition of an alkali metal oxide, $Li_{2}O$ increases FWHM of fluorescence spectrum but decreases fluorescence intensity, while $GeO_{2}$ composition increases both FWHM of fluorescence spectrum and fluorescence intensity. Also, excellent optical amplification gain characteristics in a $GeO_{2}$-added sample were observed.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.700-706
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• 2016

Etch rate, surface roughness and microstructure as plasma resistance were evaluated for six kinds of oxide glass with different compositions. Borosilicate glass (BS) was found to be etched at the highest etch rate and zinc aluminum phosphate glass (ZAP) showed a relatively lower etch rate than borosilicate. On the other hand, the etching rate of calcium aluminosilicate glass (CAS) was measured to be similar to that of sintered alumina while yttrium aluminosilicate glass (YAS) showed the lowest etch rate. Such different etch rates by mixture plasma as a function of glass compositions was dependent on whether or not fluoride compounds were formed on glass and sublimated in high vacuum. Especially, in view that $CaF_2$ and $YF_3$ with high sublimation points were formed on the surface of CAS and YAS glasses, both CAS and YAS glasses were considered to be a good candidate for protective coating materials on the damaged polycrystalline ceramics parts in semi-conductor and display processes.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.481-486
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• 2008

The different degrees of blackening were observed at the inner surface of borosilicate, soda-lime, and aluminosilicate glass tubes having different sodium (Na) contents. The sodium contents ($Na_2O$) within the borosilicate, soda-lime, and aluminosilicate glass tubes were found to be 4%, 14%, and 0.06%, respectively. The degree of blackening was shown to increase as the sodium content within the glass of the fluorescent lamp containing Ne+Ar+Hg gas mixture. Higher degree of blackening was observed from the inner surface of the glass tube coated with $Y_2O_3$. The blackening was found to be originated from the amalgam of $NaHg_2$ generated by the chemical reaction between the mercury ions within the discharge gas and sodium within the glass tube during operation.

• Journal of the Korean Ceramic Society
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• v.47 no.3
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• pp.216-222
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• 2010

Portland cement has been restricted in applications to ecological area because of its environmental harmfulness and the $CO_2$ emission during a production process. Geopolymer materials attract some attention as an inorganic binder due to their superior mechanical and eco-friendly properties. In this study, geopolymer-based cement was prepared by using aluminosilicate minerals (flyash, meta-kaolin) with alkaline-activators and its compressive strength with concentration of alkaline-activators was investigated. Aluminosilicate-based geopolymers were obtained by mixing aluminosilicate minerals, alkaline solution (NaOH or KOH with different concentration) and water-glass under the vigorous stirring for 20 min. Compressive strength after curing at $30^{\circ}C$ for 3 days increased with the concentration of alkaline-activator due to the enhanced polymerization of the aluminosilicate materials and dense microstructure. Aluminosilicate-based geopolymer cement using KOH as an alkaline-activator showed high compressive strength compared with NaOH activator. In addition, geopolymer cement using fly-ash as a raw material showed higher compressive strength than that of meta-kaolin.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.501-506
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• 2017

Surface morphology and optical properties such as transmittance and haze effect of glass etched by physical and chemical etching processes were investigated. The physical etching process was carried out by pen type sandblasting process with $15{\sim}20{\mu}m$ dia. of $Al_2O_3$ media; the chemical etching process was conducted using HF-based mixed etchant. Sandblasting was performed in terms of variables such as the distance of 8 cm between the gun nozzle and the glass substrate, the fixed air pressure of 0.5bar, and the constant speed control of the specimen stage. The chemical etching process was conducted with mixed etching solution prepared by combination of BHF (Buffered Hydrofluoric Acid), HCl, and distilled water. The morphology of the glass surface after sandblasting process displayed sharp collision vestiges with nonuniform shapes that could initiate fractures. The haze values of the sandblasted glass were quantitatively acceptable. However, based on visual observation, the desirable Anti-Glare effect was not achieved. On the other hand, irregularly shaped and sharp vestiges transformed into enlarged and smooth micro-spherical craters with the subsequent chemical etching process. The curvature of the spherical crater increased distinctly by 60 minutes and decreased gradually with increasing etching time. Further, the spherical craters with reduced curvature were uniformly distributed over the etched glass surface. The haze value increased sharply up to 55 % and the transmittance decreased by 90 % at 60 minutes of etching time. The ideal haze value range of 3~7 % and transmittance value range of above 90 % were achieved in the period of 240 to 720 minutes of etching time for the selected concentration of the chemical etchant.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3250-3259
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• 2022

A new approach to the use of rice straw as a difficult-to-recycle agricultural waste was proposed. Potassium aluminosilicate was obtained by spark plasma sintering as an effective material for subsequent immobilization of ¹³⁷Cs into a solid-state matrix. The sorption properties of potassium aluminosilicate to ¹³⁷Cs from aqueous solutions were studied. The effect of the synthesis temperature on the phase composition, microstructure, and rate of cesium leaching from samples obtained at 800-1000 ℃ and a pressure of 25 MPa was investigated. It was shown that the positive dynamics of compaction was characteristic of glass ceramics throughout the sintering. Glass ceramics RS-(K,Cs)AlSi₃O₈ obtained by the SPS method at 1000 ℃ for 5 min was characterized by a high density of ~2.62 g/cm³, Vickers hardness ~ 2.1 GPa, compressive strength ~231.3 MPa and the rate of cesium ions leaching of ~1.37 × 10^-7 g cm^-2·day^-1. The proposed approach makes it possible to safe dispose of rice straw and reduce emissions into the atmosphere of microdisperse amorphous silica, which is formed during its combustion and causes respiratory diseases, including cancer. In addition, the obtained is perspective to solve the problem of recycling long-lived ¹³⁷Cs radionuclides formed during the operation of nuclear power plants into solid-state matrices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.67-73
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• 2017

Recently, macroporous ceramic materials with high electrical conductivity and mechanical strength are urgently needed for semiconductor and display manufacturing devices. In this work, we obtained electro-conducting macroporous aluminosilicate ceramics having surface resistivity of 108~1,010 ohm by dispersing electro-conducting carbon in ceramic matrix. By addition of 0.5~3.0 wt% frit glass, chemical bonding between grains was strengthened, and flexural strength was enhanced up to 160 MPa as a result. We evaluated the characteristics of present ceramics as vacuum chuck module for liquid crystal display display manufacturing devices.