• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.151-156
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• 2010

Porous mullite/alumina composites have been fabricated by a freeze casting technique using TBA-based coal fly ash/alumina slurry. After sintering, unidirectional macropore channels aligned regularly along the TBA ice growth direction were developed; simultaneously, small sized micropores fromed in the outer walls of the pore channels. The physical and mechanical properties (e.g. porosity and compressive strength) of the sintered porous composites were roughly dependant of processing conditions, due to the complexity of the factors affecting them. However, with increasing solid loading and sintering temperature, the compressive strength generally increased and the porosity decreased. After sintering $1500^{\circ}C$ for 2 h, the porous specimen (porosity: 52.1%) showed a maximum compressive strength of 70.0 MPa.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.86-91
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• 2010

Among various fuel cells, solid oxide fuel cells (SOFCs) offer the highest energy efficiency, when taking into account the thermal recycling of waste heat at high temperature. However, the highest efficiency and lowest pollution for a SOFC can be achieved through the sophisticated control of its constituent components such as electrodes, electrolytes, interconnects and sealing materials. The electrochemical conversion efficiency of a SOFC is particularly dependent upon the performance of its electrode materials. The electrode materials should meet highly stringent requirements to optimize cell performance. In particular, both mass and charge transport should easily occur simultaneously through the electrode structure. Matter transport or charge transport is critically related to the configuration and spatial disposition of the three constituent phases of a composite electrode, which are the ionic conducting phase, electronic conducting phase, and the pores. The current work places special emphasis on the quantification of this complex microstructure of composite electrodes. Digitized images are exploited in order to obtain the quantitative microstructural information, i.e., the size distributions and interconnectivities of each constituent component. This work reports regarding zirconia-based composite electrodes.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.771-778
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• 1996

Utilization of fly ash by-produced from coal fired power plants and classified as general waste became very important problem to solve in the environmental protection and recycling of waste materials. The possibility of large scale substitution of fly ash as a raw material for bricks and wet tiles was highly expected because the chemical compositions of fly ash were mostly Al2O3 and SiO2 and the properties of it were very similar with clay. Accordingly in order to investigate the substitutional limit these specimens were substituted from 0 to 100 wt% fly ash by 20wt% increment for clay. Fly ash-clay bodies were fired at 1200, 1250 and 130$0^{\circ}C$ and then their properties were measured, It was found that these specimens sintered at 125$0^{\circ}C$ had a good bending strength. Especially when these sintered bodies were added to 20, 40 and 60 wt% fly ash the bending strength of those were 201 , 205 and 191kg.cm2 respectively with the water absorption below 1%, This showed that fly ash could be substituted ab 60 wt% in this experiment.

• Resources Recycling
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• v.27 no.5
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• pp.61-68
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• 2018

The aluminum dross is oxide generated on the surface of the molten metal during the aluminum melting process and it is divided into white dross and black dross according to presence of the Salt flux. White dross has high metal content and is recycled via the melting process. Black dross is largely berried, because the it has a low metal content and difficulty in separating the components. Black dross contains a salt components such as NaCl and KCl, and inorganic materials such as $Al_2O_3$ and MgO, and it is necessary to study the technology to recover and recycle such valuable resources. In this study, a process for recycling aluminum black dross was proposed. The inorganic and soluble substances present in the black dross were separated through crushing-dissolution-solid/liquid separation-decompression evaporating. By controlling the ratio of water and black dross, the recovery condition of the separated product was optimized and we confirmed the highest Salt flux recovery efficiency 91 wt.% at black dross:water ratio 1:9. Finally, Through the synthesis of zeolite using recovered ceramic material, the materialization possibility of black dross was confirmed.

• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.343-349
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• 2004

Laser-aided debonding has advantages in that the heat produced is localized and controlled, the debonding tool is not heated, and it can be used for the removal of various types of ceramic brackets, regardless of their design. However, the range of safe power usage for laser-aided debonding has not vet been confirmed. The Purpose of this study was to evaluate the histologic changes of pulpal tissue in a rabbit's incisor after Nd-YAG laser-aided ceramic bracket debonding at different levels of power. The result were as follows: 1. At 3-5W Nd-YAG laser power level and 3 seconds of exposure time, the ceramic bracket debonding procedure was not easy. At 5W of power a tie-wing fracture occurred on one bracket during debonding using Weingart plier. The histologic section of pulp represented no adverse changes. 2. At 7-13 W power level and less than 5 seconds of exposure time, the debracketing procedure was done easily and bracket facture did not occur. The histologic section of pulp represented mild and reversible changes. All the results were reversible and no pulpal degeneration or necrosis occurred. Considering the results, it appears that the laser-aided debonding technique is a safe method that does not result in irreversible pulpal changes, softens bracket bonding resin within a saie range of power and exposure time, and is useful for ceramic bracket recycling by lowering the tie- wing fracture rate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.2
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• pp.87-91
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• 2011

The purpose of this study is to develop ceramic glazes for the pottery production by utilizing wasted white porcelain, celadon porcelain and bone china thrown away from the areas of Icheon and Yeoju. Most of Korean pottery manufacturers are located in the both areas. According to the XRF analysis, the wasted white porcelain contains over 67 % of silica. It is enough to make a transparent glaze without adding silica. The wasted celadon porcelain contains much $Fe_2O_3$, which is suitable for producing a celadon glaze. The wasted bone china contains 22 % of $P_2O_5$, which is suitable for making a milky white bone china glaze. As a result, it is expected that production of pottery glaze using the wasted porcelains will reduce pollution problems comes from the landfill, and obtain economic effects in terms of resources recycling. It is also expected to be utilized as alternative materials of imported ones.

• Smart Structures and Systems
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• v.24 no.4
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• pp.541-552
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• 2019

Construction development and greenhouse gas emissions have globally required a strategic management to take some steps to stain and maintain the environment. Nowadays, recycled aggregates, in particular ceramic waste, have been widely used in concrete structures due to the economic and environmentally friendly solution, requiring the knowledge of recycled concrete. Also, one of the materials used as a substitute for concrete cement is wollastonite mineral to decrease carbon dioxide (CO2) from the cement production process by reducing the concrete consumption in concrete. The purpose of this study is to investigate the effect of wollastonite on the mechanical properties and durability of conventional composite concrete, containing recycled aggregates such as compressive strength, tensile strength (Brazilian test), and durability to acidic environment. On the other hand, in order to determine the strength and durability of the concrete, 5 mixing designs including different wollastonite values and recovered aggregates including constant values have been compared to the water - cement ratio (w/c) constant in all designs. The experimental results have shown that design 5 (containing 40% wollastonite) shows only 6.1% decrease in compressive strength and 4.9% decrease in tensile strength compared to the control plane. Consequently, the use of wollastonite powder to the manufacturing of conventional structural concrete containing recycled ceramic aggregates, in addition to improving some of the properties of concrete are environmentally friendly solutions, providing natural recycling of materials.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.2
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• pp.110-116
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• 2003

This study was executed to evaluate the utilization and efficiency of the ceramic biocarrier as the promoter of decomposing on the organic matters for the composting using with pig manure by analyzing of the physico-chemical properties during composting. The treatments of this experiment were consisted of the control(C),microorganism(M), M with natural zeolite(M+Z), M with synthesized zeolite(M+SZ), and M with ceramic biocarrier(M+CZ). The process term of composting was conducted for 30days in the rapidly fermented machine(as pilot system). The results of the physico-chemical properties of the composts were as follows. The changes of temperature during composting was not relative with the microorganism and zeolite materials used in the composts. At all of the treatments were similar to changing of temp. from the initial stage to the final stage. But the added microorganism treatments were higher than control. And the entire pH value of treatments were appeared the same that above temperature result, also the M+CZ and M+SZ treatment among the treatment were higher. At the results of T-C, T-N and C/N ratio, in case of T-C value, the M+CZ treatment was highly more decreased than others. However at the T-N value, there were not the differences from the each treatment. And the C/N ratio was changed according to the changes of T-C and T-N value. Especially, at the M+CZ aud M+SZ treatments were remarkably reduced by about 21.4-23.3 value. In the result of G.I for evaluating of the compost humidity, the M+CZ and M+SZ treatments were close up approximately 110 value compared with the control(G.I value 100). Therefore, the examined ceramic biocarrier amended with compost-promoting-bacteria could be applied to the production of many high quality fertilizers. It is also expected that the results of this researches could be applied to the recycle of the organic wastes based on the experimental results of ceramic biocarrier and compost-promoting-bacteria application.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1123-1131
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• 2001

The sintering behaviors of the renewed $Al_2$O$_3$ceramics were investigated as functions of the addition amount and particle size of recycling $Al_2$O$_3$powder, such as crushed powder of structural $Al_2$O$_3$ceramics and waste $Al_2$O$_3$adsorbent, were investigated. Pure $Al_2$O$_3$sample was fabricated by sintered at 1,$650^{\circ}C$ for 5h and it was crushed into powder (-40${\mu}{\textrm}{m}$and +40${\mu}{\textrm}{m}$ in particle size) by thermal shock treatment and crushing. Then, 10~50wt% of crushed $Al_2$O$_3$powder and waste $Al_2$O$_3$adsorbent were mixed with pure $Al_2$O$_3$powder and were subjected to re-sintering to renewed $Al_2$O$_3$sample. The density and the 3-point bending strength increased with increasing the sintering temperature without regard to the addition amount and particle size of recycling $Al_2$O$_3$powder, and that of the samples at the same sintering temperature decreased with increasing the addition amount and particle size of recycling $Al_2$O$_3$powder. Samples over 200 Mpa of 3-point bending strength were obtained by mixing ~30wt% of crushed $Al_2$O$_3$powder(-40${\mu}{\textrm}{m}$), ~20wt% of crushed $Al_2$O$_3$powder (+40${\mu}{\textrm}{m}$) and 10wt% of waste $Al_2$O$_3$adsorbent. 5~20wt% of waste glass powder containing renewed $Al_2$O$_3$samples for densification were fabricated by sintered at 1200~1$650^{\circ}C$ for 5h. The temperature of maximum density and 3-point bending strength decreased with increasing the addition amount of waste glass powder, however, these samples at above 140$0^{\circ}C$ showed lower density and bending strength than renewed $Al_2$O$_3$samples. The addition of waste glass powder did not improved the densification of renewed $Al_2$O$_3$sample.

• Resources Recycling
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• v.29 no.6
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• pp.65-72
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• 2020

Black dross is a dark gray dross generated during the aluminum recycling process that uses flux, and contains NaCl, KCl, Al2O3, MgO, etc. Black dross is separated into soluble substances (NaCl, KCl) and insoluble substances (Al2O4, MgO) through the dissolution process. Soluble materials can be reused as salt flux, and Al2O3 and MgO can be upcycled to various ceramic materials through the synthesis process. In this study, Mayenite was synthesized using Al2O3 and MgO recovered from black dross, and the synthesis was performed according to the mixing ratio and reaction temperature. It was confirmed that when Mayenite was synthesized using black dross (spinel) and CaCO3, precursors were changed to Mg0.4Al2.4O4 and CaO at 700 ℃, and to Ca12Al14O33 (Mayenite) after 800 ℃. In the mixing conditions experiment, it was confirmed that the Mayenite XRD peak increased with increase of the CaCO3 content, and the Mg0.4Al2.4O4 XRD peak decreased. As a result of the BET analysis of the synthesized powder, the surface area decreased as the fine particles were grown and agglomerated in the process of generating mayenite.