• 한국세라믹학회지
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• 제22권2호
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• pp.11-16
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• 1985

The semiconducting ceramics having positive temperature coefficient of resistivity in he family of 0.25mol% $Sb_2O_3$ doped barium titanates were prepared with AST ($4Al_2O_3$.$9SiO_2$.$3TiO_2$) and $MnO_2$ as additives and these electrical properties were investigated. The PTCR characteristic in these ceramic materials was improved by the addition of AST and $MnO_2$ because the addition of AST decreased the room temperature resistivity and controlled grin size due to the formation of a liquid phase during sintering and the addition of $MnO_2$ improved by forming acceptor level on the intergranular layer. On dependence on the switching time as switching temperature was increased the initial power and switching time increased.

• Carbon letters
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• 제7권1호
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• pp.27-33
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• 2006

Carbon-ceramic composites were fabricated by using fly ash and PANOX fibers as reinforcement. Fly ash, because of its small size particles e.g. submicron to micron level can be effectively dispersed along with fibrous reinforcements. Phenolic resin was used as carbon precursor. Both dry as well as wet methods were used for forming composites. The resulting composites were characterized for their microstructure, thermal and mechanical properties. The microstructure and mechanical properties of composites are found to be dependent on type of the fly ash, fibrous reinforcements as well as processing parameters. The addition of fly ash improves hardness and the fibers, which get co-carbonized on heat treatment, increase the flexural strength of the carbon-ceramic composites. Composites with dual reinforcement exhibit about 30-40% higher strength as compared to the composites made with single reinforcement, either with fly ash as filler or with chopped fibers.

• 한국세라믹학회지
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• 제46권3호
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• pp.306-312
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• 2009

The size of various alumina ceramics used in semiconductor and display industry is also required to increase with increase in wafer and panel size. In this research, large alumina ceramics was fabricated by filter pressing of alumina slurry using commercial powder and thereafter sintering at $1600^{\circ}C$ in gas furnace. The characteristics of large alumina ceramics thereby were compared to those of small alumina ceramics prepared by pressure forming such as uniaxial pressing and CIP. Careful control of properties of alumina slurry and filter pressing made the fabrication of large alumina ceramics possible, and its characteristics were equivalent to those of small alumina ceramics. The large alumina ceramics, prepared by sintering the green body of 63% relative density at $1600^{\circ}C$, exhibited both dense microstructure corresponding to 98.5% of relative density and 99.8% of high purity as in starting powder.

• 한국세라믹학회지
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• 제47권6호
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• pp.503-508
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• 2010

$Eu^{2+}$-doped $\beta$-SiAlONs ($Si_{6-z}Al_zO_zN_{8-z}:Eu_y$) are recognized as promising phosphor materials to build an white LED for lighting application due to its excellent absorption/emission efficiency in the long wave length region. In this research, the fabrication of $\beta$-SiAlON:Eu plate phosphor by sintering was investigated with fixed Eu content(y) and varied composition of the host lattice(z). The addition of the activator $Eu_2O_3$ lead to enhanced densification by forming the transient liquid phase. The refinement of a composition by the calculated lattice parameter indicated that the measured composition of the fabricated specimens is nearly same to that of designed one. The single phase $\beta$-SiAlON:Eu plate with relative density of 96.4% was achieved by addition of 2 wt% CaO, which implies the possibility of full densification by adjusting the processing variables.

• 전기학회논문지
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• 제57권3호
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• pp.429-432
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• 2008

Much studies have been concentrated to develop the fabrication technique for high critical current density but still there are a lot of gap which should be overcome for large scale application of superconducting materials at liquid nitrogen temperature. The improvement of the critical current can be achieved by forming the nano size defect working as a flux pinning center inside the superconductor. In this paper, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of superconductor.

• 한국세라믹학회지
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• 제43권12호
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• pp.829-832
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• 2006

In this study, the influence of the magnetic field on ferrite slurry's injection time during the slurry forming process was investigated. The evaluation system of the slurry's injection time under the strong magnetic field was designed with FEM and manufactured. Studied parameters were the applied magnetic field, the input pressure of the slurry, and the supplying tube materials. As the results, the injection time was increased with the external magnetic field strength and rapidly decreased with increasing the input pressure of the slurry. Also the injection time was decreased when the supplying tube was manufactured with the magnetic material having the higher magnetic permeability than the ferrite.

• 한국세라믹학회지
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• 제52권6호
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• pp.473-478
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• 2015

Green bodies of earthenware tile were prepared from a mixture of earthenware tile powder and SiC as forming agents by applying a conventional process. Granule powder for tile samples was prepared using the spray drying method with commercial earthenware raw material with a quantity of SiC of 0.3 wt%. The applied pressure was $250kg{\cdot}f/m^2$ and the firing temperature was $1050-1200^{\circ}C$. The effects of the SiC particle size and sintering temperature on the open porosity and total porosity were investigated and the correlative mechanism was also discussed. While total porosity was not significantly changed by decreasing the SiC particle size, the open porosity showed a gradual decrease, which represents an increase of the closed porosity. As the sintering temperature increased, coarsening was made among the pores due to excessive oxidation. The volume shrinkage and bending strength were demonstrated for the sintered tile samples. The sintered bulk density was also measured to determine the weight reduction value.

• 한국세라믹학회지
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• 제46권6호
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• pp.662-667
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• 2009

Porous SiC candle filter preforms were fabricated by extrusion and ramming process. To fabricate SiC candle filter preform, commercially available 85 ${\mu}m\;{\alpha}-$-SiC powder and 44 ${\mu}m$ mullite, CaC$O_3$ powder were used as the starting materials. The candle type preforms were fabricated by vacuum extrusion and ramming process, and sintered at $1400{^{\circ}C}$ 2 h in air atmosphere. The effect of forming method on porosity, density, strength (flexural and compressive strength) and microstructure was investigated. Also, corrosion test of the sintered candle filter specimens as forming method was performed at $600{^{\circ}C}$ in IGCC syngas atmosphere. The sintered SiC filter which was formed by ramming process has more higher density and exhibit higher strength than extruded filter. Its maximum density and 3-point bending strength were 2.00 g/$cm^3$ and 45 MPa, respectively.

• 한국분말재료학회지
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• 제27권6호
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• pp.490-497
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• 2020

The 3D printing process provides a higher degree of freedom when designing ceramic parts than the conventional press forming process. However, the generation and growth of the microcracks induced during heat treatment is thought to be due to the occurrence of local tensile stress caused by the thermal decomposition of the binder inside the green body. In this study, an alumina columnar specimen, which is a representative ceramic material, is fabricated using the digital light process (DLP) 3D printing method. DTG analysis is performed to investigate the cause of the occurrence of microcracks by analyzing the debinding process in which microcracks are mainly generated. HDDA of epoxy acrylates, which is the main binder, rapidly debinded in the range of 200 to 500℃, and microcracks are observed because of real-time microscopic image observation. For mitigating the rapid debinding process of HDDA, other types of acrylates PETA, PUA, and MMA are added, and the effect of these additives on the debinding rate is investigated. By analyzing the DTG in the 25 to 300℃ region, it is confirmed that the PETA monomer and the PUA monomer can suppress the rapid decomposition rate of HDDA in this temperature range.

• 한국세라믹학회지
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• 제51권6호
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• pp.549-553
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• 2014

$CoSb_3$-based skutterudite compounds are candidate materials for thermoelectric power generation in the mid-temperature range (600 - 900 K) because their thermoelectric properties can be enhanced by doping and filling. The joining property of thermoelectric module electrodes containing thermoelectric materials is of great importance because it can dominate the efficiency of the thermoelectric module. This study examined the properties of $CoSb_3$/Al/Ti/CuMo joined by the spark plasma sintering technique. Titanium thin foil was used to prevent the diffusion of copper into $CoSb_3$ and Aluminum thin foil was used to improve the adhesion between $CoSb_3$ and Ti. The insertion of an Aluminum interlayer between the Ti and $CoSb_3$ was effective for joining $CoSb_3$ to Ti by forming an intermediate layer at the Al-$CoSb_3$ boundary without any micro cracks. Specifically, the adhesion strength of the Ti/Al/$CoSb_3$ joining interface showed a remarkable improvement compared with our previous results, without deterioration of electrical property in the interface.