• Journal of Powder Materials
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• v.21 no.2
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• pp.102-107
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• 2014

A high temperature dilatometer attached to a graphite furnace is built and used to study the sintering behavior of $B_4C$. Pristine and carbon doped $B_4C$ compacts are sintered at various soaking temperatures and their shrinkage profiles are detected simultaneously using the dilatometer. Carbon additions enhance the sinterability of $B_4C$ with sintering to more than 97% of the theoretical density, while pristine $B_4C$ compacts could not be sintered above 91% due to particle coarsening. The shrinkage profiles of $B_4C$ reveal that the effect of carbon on the sinterability of $B_4C$ can be seen mostly below $1950^{\circ}C$. The high temperature dilatometer delivers very useful information which is impossible to obtain with conventional furnaces.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.78-82
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• 2000

Although alumina aggregates have been used as refractory aggregates due to the improved mechanical properties of refractories as a result of the low contraction of alumina aggregates, the aggregates have a difficulty in fabrication due to its low sinterability. Two types of alumina aggregates and a fused alumina aggregate containing transient liquid forming additives are prepared to investigate the sintering characteristics of aggregates. $Al_2O_3$rich composition in the $Al_2O_3$-MgO-$SiO_2$(-$TiO_2$) system is chosen for the transient liquid phase sintering and the final recrystallized bonding phase between grains inside the fused alumina aggregates is found to be a needle-like mullite phase. The flexural strength of alumina bars, reaction-bonded using the paste having a composition of $Al_2O_3$-MgO-$SiO_2$-$TiO_2$, is about 78 MPa, which is one half value of that of pure alumina.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.234-238
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• 2008

The efficiency of fiber reinforced CMC(ceramic matrix composite) on the SiC materials have been investigated, in conjunction with the fabrication process by liquid phase sintering and the characterization. LPS-$SiC_f$/SiC composites was studied with the detailed analysis such as the microstructure, sintered density, flexural strength and fracture behavior. The applicability of carbon interfacial layer has been also investigated in the LPS process. Submicron SiC powder with the constant total amount and composition ratio of $Al_2O_3,\;Y_2O_3$ as sintering additives was used in order to promote the performance of the SiC matrix material. LPS-$SiC_f$/SiC composites were fabricated with hot press under the sintering temperature and applied pressure of $1820^{\circ}C$ and 20MPa for 1hr. The typical property of monolithic LPS-SiC materials was compared with LPS-$SiC_f$/SiC composites.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.365-368
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• 2003

Small amounts of additives such as mol % 0.13 NiO and mol % 0.01 $CaCO_3$were added to Cu-Zn-Mg ferrites. Basic composition of the Cu-Zn-Mg ferrites was $Cu_{Cu}$X/$Fe_{0.054}$ /$Zn_{0.486}$$Mg_{0.407}$ $Fe_{1.946}$ $O_4$(group A) and $Cu_{0.263}$$Fe_{0.027}$ $Zn_{0.503}$ $Mg_{0.262}$ $Fe_{1.973}$ $O_4$(group B). Specimens were sintered at different temperatures (1010, 1030, $1050^{\circ}C$) for 2 hours in air followed by an air cooling. Then, effects of various composition and sintering temperatures on the microstructure and the magnetic properties such as inductions, coercive forces, and initial permeabilities of the Cu-Zn-Mg ferrites were investigated. The average grain size increased with the increase of sintering temperature. The magnetic properties obtained from the aforementioned Cu-Zn-Mg ferrite specimens were 1,724 gauss for the maximum induction, 1.0 oersted for the coercive force, and 802 for the initial permeability. These magnetic properties indicated that the specimens could be utilized as the core of IFT (intermediate frequency transformer) and antenna in the amplitude modulation.

• Journal of the Korean Ceramic Society
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• v.40 no.3
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• pp.309-316
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• 2003

EAF(Electric Arc Furnace) Dust classified as special wastes containing heavy metal contaminants may cause to damage an environment such as underground water contamination if they were not treated properly. The possibility of producing the porous sintered body made from EAF Dust/clay composition system was studied. Mixing of EAF Dust and clay was carried out using wet-mixing process and two different sintering methods such as rapid and normal heat treatment were tried. By observing density, porosity and microstructure of sintered bodies, it was found that the bloating phenomenon depend on the contents of C, where the liquid phase occur or not during the sintering process. To obtain a light-aggregate of porous body due to bloating, the rapid heating was better than the normal heating at sintering process.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.91-97
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• 2019

The effect of different Ni-containing additives on the sintering behavior and electric conductivity of the proton conducting electrolyte $BaCe_{0.35}Zr_{0.5}Y_{0.15}O_{3-{\delta}}$ (BCZY5) was investigated. Ni-doped, NiO-added, and $BaY_2NiO_5$(BYN)-added (all 4 mol%) BCZY5 samples were prepared by the solid state synthesis method and sintered at $1400^{\circ}C$ for 6 h. Among the three samples, the onset of densification was observed at the lowest temperature for NiO-added BCZY5, which is attributed to the formation of an intermediate phase at a low melting temperature. The BYN-added sample, where no consumption of the constitutional elements of the electrolyte was expected during sintering, exhibited the highest electrical conductivity whereas the doped sample had the lowest conductivity. The electrical conductivities at $500^{\circ}C$ under humid argon atmosphere were measured to be 2.0, 4.8, and $6.2mS{\cdot}cm^{-1}$ for Ni-doped and NiO- and BYN-added samples, respectively.

• Journal of the Korean Ceramic Society
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• v.16 no.1
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• pp.3-12
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• 1979

The effects of sintering temperature and sintering atmosphere on magnetic properties and microstructuresof Mn-Zn ferrites have been studied. Mixture of 52.8mole% $Fe_2O_3$, 26.4mole% MnO, 15.1mole0% ZnO and 5.7mole% NiO was prepared, and 0.1mole% CaO, 0.02mole% $SiO_2$ were added as minor additives. After calcining and ball milling the powder was granulated for compacting. The specimens were sintered at $1, 250^{\circ}$, $1, 300^{\circ}$and 1, 35$0^{\circ}C$ in the various atmosphere of $N_2$, $N^_2\DIV0.6% O_2$, $N_2＋2.7% O_2$, $N_2＋4.1% O_2$, $N^2＋8.2% O_2$ and air for 3 hours and cooled in $N_2$ atmosphere. The grian growth rate and densities increase as sintering temperature and oxygen content of atmosphere increase. At the sintering temperature of $1, 250^{\circ}C$ the initial permeabilities increase as oxygen content of atmosphere increase. At the sintering temperature of$ 1, 300^{\circ}$and $1, 350^{\circ}$ the initial permeabilities show maximum values at $N_2＋4.1% O_2$ atmosphere. The secondary peaks of initial permeabilities are observed between 100$^{\circ}$and 20$0^{\circ}C$, and the positions of secondary peaks move to higher temperature as oxygen content of atmosphere increases. Q-factors decrease as sintering temperature increases and oxygen content of atmosphere decreases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.454-457
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• 2010

The influence of CuO addition on what of the $(Ba,Sr)TiO_3$ ceramics was studied. The sintering temperature of $(Ba,Sr)TiO_3$ ceramics was lowered by the addition of CuO additives. The 1 - 5 wt% CuO were selected and employed as the sintering aids. Low-Temperature Co-fired Ceramic technologies are popular technologies used in the manufacture of microwave devices. In this study, crystalline and electrical properties of CuO doped $(Ba,Sr)TiO_3$ ceramics were investigated to determine the low temperature sintering properties. The addition of CuO to $(Ba,Sr)TiO_3$ lowered the sintering temperature from $1350^{\circ}C$ to $1150^{\circ}C$. The dependence of the sintering temperature shrinkage rate and mechanism of CuO doped $(Ba,Sr)TiO_3$ ceramics are investigated and discussed. Also, the crystalline structure of CuO - doped $(Ba,Sr)TiO_3$ ceramics is discussed by the X-ray diffraction (XRD) method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.3
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• pp.128-132
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• 2007

[ $B_4C$ ] ceramics were fabricated by spark plasma sintering process and their sintering behavior, microstructure and mechanical properties were evaluated. Relative density of $B_4C$ ceramics were obtained by spark plasma sintering method reached as high as 99% at lower temperature than conventional sintering method, in addition, without any sintering additives. The mechanical properties of $B_4C$ ceramics was improved by a methanol washing process which can be removed $B_2O_3$ phase from a $B_4C$ powder surface. This improvement results ken the formation of homogeneous microstructure because the grain coarsening was suppressed by the elimination of $B_2O_3$ phase. Particularly, fracture toughness of the sintered specimen using a methanol washed powder improved over 30% compared with the specimen using an as-received commercial powder.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.559-569
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• 2010

The liquid-phase sintering method was used to prepare a glass lens forming core composed of SiC-$Al_2O_3-Y_2O_3$. Spark plasma sintering was used to obtain dense sintered bodies. The sintering characteristics of different SiC sources and compositions of additives were studied. Results revealed that, owing to its initial larger surface area, $\alpha$-SiC offers sinterability that is superior to that of $\beta$-SiC. A maximum density of $3.32\;g/cm^3$ (theoretical density [TD] of 99.7%) was obtained in $\alpha$-SiC-10 wt% ($6Al_2O_3-4Y_2O_3$) sintered at $1850^{\circ}C$ without high-energy ball milling. The maximum hardness and compression stress of the sintered body reached 2870 Hv and 1110 MPa, respectively. The optimum ultra-precision machining parameters were a grinding speed of 1243 m/min, work spindle rotation rate of 100 rpm, feed rate of 0.5 mm/min, and depth of cut of $0.2\;{\mu}m$. The surface roughnesses of the thus prepared final products were Ra = 4.3 nm and Rt = 55.3 nm for the aspheric lens forming core and Ra = 4.4 nm and Rt = 41.9 for the spherical lens forming core. These values were found to be sufficiently low, and the cores showed good compatibility between SiC and the diamond-like carbon (DLC) coating material. Thus, these glass lens forming cores have great potential for application in the lens industry.