• Korean Journal of Materials Research
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• v.29 no.11
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• pp.727-733
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• 2019

In this study, the glass melting properties are evaluated to examine the possibility of using refused coal ore as replacement for ceramic materials. To fabricate the glass, refused coal ore with calcium carbonate and sodium carbonate in it (which are added as supplementary materials) is put into an alumina crucible, melted at $1,200{\sim}1,500^{\circ}C$ for 1 hr, and then annealed at $600^{\circ}C$ for 2 hrs. We fabricate a black colored glass. The properties of the glass are measured by XRD (X-ray diffractometry) and TG-DTA (thermogravimetry-differential thermal analysis). Glass samples manufactured at more than $1,300^{\circ}C$ with more than 60 % of refused coal ore are found by XRD to be non-crystalline in nature. In the case of the glass sample with 40 % of refused coal ore, from the sample melted at $1,200^{\circ}C$, a sodium aluminum phosphate peak, a disodium calcium silicate peak, and an unknown peak are observed. On the other hand, in the sample melted at $1,300^{\circ}C$, only the sodium aluminum phosphate peak and unknown peak are observed. And, peak changes that affect crystallization of the glass according to melting temperature are found. Therefore, it is concluded that glass with refused coal ore has good melting conditions at more than $1,200^{\circ}C$ and so can be applied to the construction field for materials such as glass tile, foamed glass panels, etc.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.59-66
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• 2015

A new concept of an inorganic foaming process at low temperature was demonstrated for the production of inorganic thermal insulating materials with the properties of flexible light-weight, the advantages of organic-based thermal insulation material. The foaming process was proceeded by establishing a skeleton of the foam body by using inorganic fibrous sepiolite and aluminum silicate. A cavity was formed by the expansion of fibrous skeleton body, by the gas which was generated from foaming agent at low temperature. Then the multi-vesicular expanded perlite with low thermal conductivity was filled into the cavity in a skeleton of the foam body. Finally through these overall process, a new inorganic foamed body could be obtained at low temperature without the hot melting of inorganic materials. In order to achieve this object, various preparations such as fibrous sepiolite fibrillation process, heat treatment process of the fibrous slurry were needed, and the optimal compositional condition of slurry was required. The foam body produced showed the properties of flexible light-weight thermal insulation materials such as bulk density, yield strength, flexural strength, and high heat resistance.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.187-192
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• 2000

We prepared $SiO_2-Na_2O-R_mO_n$ thin films based on economics of water glass and investigated optical, mechanical properties of product thin films. Coating sol stabilized with 1 N HCl and 1 N $NH_4OH$, was fabricated by using water glass and calcium nitrate, and aluminum nitrate as starting materials. As-coated films on stainless steel, Si wafer and soda-lime-silica glass by spinning were finally annealed at 500, 750 and $900^{\circ}C$. Micro hardness and nitrogen content in film surface of annealed films were measured by Knoop hardness tester and EDX, respectively. Field Emission Scanning Electron Microscope (FE-SEM) and UV-VIS spectroscopy were adopted to analyze surface morphology and thickness and reflectance of our films.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.48-52
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• 2014

The Mg-enriched magnesium aluminum silicate (MAS) glass is known for its higher mechanical strength and chemical resistance. Among such glasses, cordierite ($Mg_2Al_4Si_5O_{18}$) is well known to have a low thermal expansion and low melting point. Polycrystalline engineering ceramics such as alumina can be strengthened by a surface modification with low thermal expansion materials. The present study involves the synthesis of cordierite by a sol-gel process and investigates the effect of glass penetration on the surface of alumina. The cordierite powders were prepared from $Al(OC_3H_7)_3$, $Mg(OC_2H_5)_2$ and tetraethyl orthosilicate by hydrolysis and condensation reaction. The cordierite powders were characterized by X-ray diffraction (XRD, Rigaku), scanning electron microscope (SEM, JEOL: JSM-5610), energy dispersive spectroscopy (EDS, JEOL: JSM-5610), and universal testing machine (UTM, INSTRON). The X-ray diffraction patterns showed that the synthesized particles were ${\mu}$-cordierite calcined at $1100^{\circ}C$ for 1 h. The shape of synthesized cordierite was changed from ${\mu}$-cordierite to ${\alpha}$-cordierite with increasing calcination temperature. Synthesized cordierite was used for surface modification of alumina. Cordierite powders penetrated deeply into the alumina sample along grain boundaries with increasing temperature. The results of surface modification tests showed that the strength of the prepared alumina sample increased after surface modification. The strength of a surface modified with synthesized cordierite increased the most, to about 134.6MPa.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.378-382
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• 2018

It is a known fact that the cement production is responsible for almost 5% of total worldwide $CO_2$ emission, the primary factor affecting global warming. Geopolymers are valuable as ordinary Portland cement (OPC) substitutes because geopolymers release 80% less $CO_2$ than OPC and have mechanical properties sufficiently similar to those of OPC. Therefore, geopolymers have proven attractive to eco-friendly construction industries. Geopolymers can be fabricated from aluminum silicate materials with alkali activators such as fly ash, blast furnace slag, and so on. Integrated gasification combined cycle (IGCC) slag has been used for fabricating geopolymers. In general, IGCC slag geopolymers are fabricated with finely ground and sieved (<128 mesh) IGCC slag. The grinding process of as-received IGCC slag is one of the main costs in geopolymer production. Therefore, the idea of using as-received IGCC slag (before grinding the IGCC slag) as aggregates in the geopolymer matrix was introduced to reduce production cost as well as to enhance compressive strength. As-received IGCC slag (0, 10, 20, 30, 40 wt%) was added in the geopolymer mixing process and the mixtures were compared. The compressive strength of geopolymers with an addition of 10 wt% as-received IGCC slag increased by 19.84% compared to that with no additional as-received IGCC slag and reached up to 41.20 MPa. The enhancement of compressive strength is caused by as-received IGCC slag acting as aggregates in the geopolymer matrix like aggregates in concrete. The density of geopolymers slightly increased to $2.1-2.2g/cm^3$ with increasing slag addition. Therefore, it is concluded that a small addition of as-received IGCC slag into the geopolymer can increase compressive strength and decrease the total cost of the product. Moreover, the direct use of as-received IGCC slag may contribute to environment protection by reducing process time and $CO_2$ emission.

• Korean Journal of Materials Research
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• v.34 no.3
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• pp.175-183
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• 2024

Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a binder because of its good adhesive properties and heat resistance. Since Davidovits developed Geopolymer matrix composites (GMCs) based on the binder properties of geopolymer, they have been utilized as flame exhaust ducts and aircraft fire protection materials. Geopolymer structures are formed through hydrolysis and dehydration reactions, and their physical properties can be influenced by reaction conditions such as concentration, reaction time, and temperature. The aim of this study is to examine the effects of silica size and aging time on the mechanical properties of composites. Commercial water glass and kaolin were used to synthesize geopolymers, and two types of silica powder were added to increase the silicon content. Using carbon fiber mats, a fiber-reinforced composite material was fabricated using the hand lay-up method. Spectroscopy was used to confirm polymerization, aging effects, and heat treatment, and composite materials were used to measure flexural strength. As a result, it was confirmed that the longer time aging and use of nano-sized silica particles were helpful in improving the mechanical properties of the geopolymer matrix composite.

• Journal of the Mineralogical Society of Korea
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• v.29 no.3
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• pp.155-165
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• 2016

Understanding the effect of boron content on atomic structures of boron-bearing multicomponent silicate melts is essential to reveal the atomistic origins of diverse geochemical processes involving silica-rich magmas, such as explosive volcanic eruption. The detailed atomic environments around B and Al in boron-bearing complex aluminosilicate glasses yield atomistic insights into reactivity of nuclear waste glasses in contact with aqueous solutions. We report experimental results on the effect of boron content on the atomic structures of sodium borate glasses and boron-bearing multicomponent silicate melts [malinkoite ($NaBSiO_4$)-nepheline ($NaAlSiO_4$) pseudo-binary glasses] using the high-resolution solid-state NMR ($^{11}B$ and $^{27}Al$). The $^{11}B$ MAS NMR spectra of sodium borate glasses show that three-coodrinated boron ($^{[3]}B$) increases with increasing $B_2O_3$ content. While the spectra imply that the fraction of non-ring species decreases with decreasing boron content, peak position of the species is expected to vary with Na content. Therefore, the quantitative estimation of the fractions of the ring/non-ring species remains to be explored. The $^{11}B$ MAS NMR spectra of the glasses in the malinkoite-nepheline join show that four-coordinated boron ($^{[4]}B$) increases as $X_{Ma}$ [$=NaBSiO_4/(NaBSiO_4+NaAlSiO_4)$] increases while $^{[3]}B$ decreases. $^{27}Al$ MAS NMR spectra of the multicomponent glasses confirm that four-coordinated aluminum ($^{[4]}Al$) is dominant. It is also observed that a drastic decrease in the peak widths (full-width at half-maximum, FWHM) of $^{[4]}Al$ with an addition of boron ($X_{Ma}=0.25$) in nepheline glasses. This indicates a decrease in structural and topological disorder around $^{[4]}Al$ in the glasses with increasing boron content. The quantitative atomic environments around boron of both binary and multicomponent glasses were estimated from the simulation results of $^{11}B$ MAS NMR spectra, revealing complex-nonlinear variation of boron topology with varying composition. The current results can be potentially used to account for the structural origins of the change in macroscopic properties of boron-bearing oxide melts with varying boron content.

• Journal of the Mineralogical Society of Korea
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• v.20 no.3
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• pp.223-229
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• 2007

The mechanism of hydrothermally synthesizing Na-A zeolite from siliceous mudstone at a $Na_2O/SiO_2$ ratio of 0.6, a $SiO_2/Al_2O_3$ 2.0 and a $H_2O/Na_2O$ 119 has been observed by IR, DTA, XRD and SEM. This mudstone is a tertiary periodic sedimentary rock and widely spreads around the Pohang area. In the early hydrothermal synthesis at $80^{\circ}C$ in an autoclave, sodium silicate and sodium aluminate were found to be preferentially reacted to generate Na-A type zeolite. Gibbsite and bayerite were also formed due to the presence of extra aluminum oxide in the feedstock. As reaction time in-creased up to 50 h, residual sodium aluminatewas reacted with siliceous mudstone, causing the Na-A zeolite crystal to grow and the hydroxylsodalite to generate. Therefore, in the $14{\sim}50\;h$ synthetic time, Na-A zeolite and hydroxylsodalite were formed. Also, if reaction time passed over 50 h, a part of the Na-A zeolite was finally redissolved and reacted with hydroxylsodalite to synthesize Na-P zeolite, generating porous surface of Na-A zeolite and disappearing hydroxylsodalite.

• Korean Journal of Soil Science and Fertilizer
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• v.11 no.2
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• pp.75-80
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• 1979

Ammonium desorption from 16 soils treated with $(NH_4)_2HPO_4$ solution (2000 ppm $NH_4$) was investigated by seven extractions with 0.01M $CaCl_2$. 1. There were 2 to 4 steps alternately appeared with fast and slow mode. 2. Desorption equation, log y=b-ax where y is desorption amount, b a constant indicating adsorption maximum, a retention constant, and x extraction number, was held for each step. 3. Desorption rate (100${\times}$desorption / adsorption) was 65% for the average of 15 soils, maximum 87% in Gimcheon series, minimum 32% in Samgag series. Yongho series (a peat soil) showed 156% indicating the release of large quantity of indigenous soil ammonium. 4. Desorption rate was negatively correlated with initial adsorption and in this relation the tested soils were classified into 3 groups. 5. The cumulative desorption curve was approaching almost to maximum in all tested soils with seven extractions. The final retention amount, ranged from 25% of CEC (Gimhae series) to 502% (Samgag Series). 6. Amount and rate of desorption did not have any significant relation with Langmuir adsorption maxima of ammonium, CEC and contents of clay, available phosphorus and organic matter. 7. The above results may indicate that adsorption and desorption of ammonium is closely related with iron, aluminum silicate and adsorption and desorption characteristics of accompanied anions.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.173-183
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• 2012

The nature of surface deformation of Tono granite was investigated using a confocal laser scanning microscope (CLSM) under water-saturated stress relaxation conditions. A new apparatus was developed for this experiment, enabling continuous measurements of stress-strain and simultaneous observations of surface deformation by CLSM. The amounts of grain contact deformation and intra-granular surface deformation were calculated using a finite element method. The results reveal that intense grain contact deformation and intra-granular surface deformation occurred during the period of stress relaxation, and that the intensity of this deformation increased with increasing applied stress. Finite element method (FEM) results show that the strain of grain boundary was greater than strain of inter-granular surface. Contour maps of these local strains were compiled for individual grains and their boundaries, revealing intense deformation at the boundaries between biotite and quartz under compressional stress. This result was a consequence of the mechano-chemical effect of biotite and quartz minerals. Biotite in granite has a layered structure of iron-magnesium-aluminum silicate sheets that are weakly bonded together by layers of potassium ions. In contrast, quartz occurs as stable spherical grains.