• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.558-563
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• 1996

Fracture strength of $Si_{3}N_{4}/20$ vol% SiC nanocomposites with fifferent sintering additives was measured. Strength of nanocomposites with 6 wt% $Y_{2}O_{3}$ and 2 wt% $Al_{2}O_{3}$ as sintering additives was higher at room temperature but significant strength degradation at elevated temperature was occured due to the softening of grain boundary phase. Fracture strength of 8 wt% $Y_{2}O_{3}$ doped sample was higher than that of $Al_{2}O_{3}$ added sample at $1400^{\circ}C$. The retention of high temperature strength in 8 wt% $Y_{2}O_{3}$ doped sample can be attributed to high softening temperature and crystallization of grain boundary glassy phase.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.669-674
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• 2020

Liquid-phase-sintered (LPS) SiC materials were briefly examined with their microstructure and mechanical property. Especially, effect of high-temperature exposure on the tendency of fracture toughness of LPS-SiC were introduced. The LPS-SiC was fabricated in hot-press by sintering powder mixture of sub-micron SiC and sintering additives of Al₂O₃-Y₂O₃. LPS-SiC represented dense morphology and SiC grain-growth with some amount of micro-pores and clustered additives as pore-filling. The strength of LPS-SiC might affected by distribution of micro-pores. LPS-SiC tended to decrease fracture toughness depending on increasing exposure temperature and time.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.836-842
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• 1998

In this experiment well-know additives for Mn-Zn ferrites CaO and {{{{ { SiO}_{2 } }} were added at various content and their effects on microstructures and magnetic properties with sintering atmosphere were examined. By adding up to 0.04wt% {{{{ { SiO}_{2 } }} and and 0.06wt% CaO the sintered density was increased and then decreased gra-dually. Higher sintered density and initial permeability were observed by adding both CaO and {{{{ { SiO}_{2 } }} than by adding CaO or {{{{ { SiO}_{2 } }} alone. Without any additives initial permeability and tan$\delta$/${\mu}$ decreased at 1000kHz as oxidation degree(${\gamma}$) increased.

• 연구논문집
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• s.30
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• pp.111-119
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• 2000

Sintering of alumina powder was studied in the presence of Y-Si oxide and oxynitride additives. The main crystalline phase of the sintering aids pre-reacted at $1400^{\circ}C$ was $\alpha$ - $Y_2$$SiO_2$>$O_7$. Y-N apatite was co-existed in the Si-40N sintering aid because of its high content of N. During the sintering process, liquid phases were formed by the reaction between additives and alumina, and these liquid phases promote the densification of alumina. SEM micrographs showed that uniform grain growth occurred in the system with oxide additive(Si-0N). In the case of oxynitride additive system(Si-20N and Si-40N), bimodal microstructure was observed due to the exaggerated grain growth, As the nitrogen content in the additive system increased the exaggerated grain growth occurred extensively. Bloating, which seemed to be originated by the liberation of $N_2$ gas, occurred un the Si-40N oxynitride additive system.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.629-635
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• 1997

The effects of the annealing atmospheres(O2, N2) and sintering additives that Bi2O3 is a major composition on the microwave dielectric and sintering propertie of (1-x)CaTiO3-xLaAlO3 system were investigated. The annealing atmospheres and the increase of annealing time after sintering did not affect the relative dielectric constant($\varepsilon$r) and temperature coefficient of resonant frequency($\tau$f) of (1-x)CaTiO3-xLaAlO3 system. However, the Q.f0 values of (1-x)CaTiO3-xLaAlO3 were very sensitive to annealing atmospheres. As the annealing time increased under O2 atmosphere the Q.f0 values of (1-x)CaTiO3-xLaAlO3 enhanced untill 10 hrs in 0.3$\leq$x$\leq$0.6 region, but degraded over that time. The increasing rate of Q.f0 value increased wth increasing x. On the other hand, as the annealing time increased under N2 atmosphere the Q.f0 values were constant in x$\leq$0.6 region, increased gradually in x$\geq$0.7 region. When 0.97Bi2O3-0.03Al2O3 and 0.76Bi2O3-0.24NiO of 3wt% as sintering additives were added to (Ca0.5La0.5) (Ti0.5Al0.5)O3 (x=0.5) the sintering temperature of 1$600^{\circ}C$ was lowered to 140$0^{\circ}C$, and the relative dielectric constant($\varepsilon$r) and temperature coefficient of resonant frequency($\tau$f) were not nearly changed. The addition of 0.97Bi2O3-0.03Al2O3 and 0.76Bi2O3-0.24NiO of 3wt% to (Ca0.5La0.5)(Ti0.5Al0.5)O3 made the Q.f0 values to be lower about 15% and 34%, respectively.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.911-916
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• 1998

By using {{{{ { { {Y }_{3 }Al }_{5 }O }_{12 } }} (YAG) and SiO2 as sintering additives the effect of the composition of sintering ad-ditives on microstructure and mechanical properties of the hog-pressed and subsequently annealed SiC ma-terials were investigated. Microstructures of sintered and annealed materials were strongly dependent onthe composition of sintering additives. The average diameter and volume fraction of elongated grains in an-nealed materials increased with the SiO2/YAg ratio while the fracture toughness increased with the SiO2/YAg ratio. The average MPa.{{{{ { m}^{1/2 } }} respectively. Typical strength and fracture toughness of an annealed material with SiO2/YAg ra-tionof 0.67 were 371 MPa and 5.6 MPa.{{{{ { m}^{1/2 } }} respectively.

• The Korean Journal of Ceramics
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• v.1 no.1
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• pp.45-54
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• 1995

Four kinds of silicon nitride based ceramic materials have been hot pressed. Effect of the sintering additives on the phase transformation, microstructural development and mechanical properties was investigated. While sintering under the same condition a big difference among the microstructures of the specimens, they appeared alike if sintered to have a similiar $\alpha$-$\beta$ phase ratio. The specimen of the stoichiometric $\alpha$-$\beta$ sialon composition showed very limited amount of the intergranular glassy phase and a significant degree of the residual stress. It exhibited almost no strength degradation up to $1300^{\circ}C$, and the strength of the specimen degraded more as its composition deviated from the stoichiometry.

• Journal of the Korean Ceramic Society
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• v.44 no.2 s.297
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• pp.79-83
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• 2007

To fabricate a thick, porous yttria-stabilized zirconia without cracking and warping, a method for the simultaneous control of the porosity and shrinkage was designed. As a pore former, a potato starch was used. For the control of shrinkage the oxidation of Al metal particles was used. For the sintering of the above powder mixtures, a partial sintering technique was used at $1300^{\circ}C$ for 10 min in air. Upon adding the additives, high open porosity above 53% and a low shrinkage level were obtained. As a result cracking and warping of the sintered body were deterred. This outcome most likely resulted from the compensation of sintering shrinkage due to the volume expansion caused by oxidation of the Al metal particles during heat-treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1990.10a
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• pp.71-77
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• 1990

This paper is studied on the sintering characteristics of Ni-Zn ferrites. The specimen ferrites was composed of 20 mol% NiO, 30mol% ZnO, 50 mol% Fe$_2$O$_3$, and 0.0025 mol%, 0.005 mol%, 0.01 mol% Nb$_2$O$\_$5/, Bi$_2$O$_3$, V$_2$O$\_$5/, wee used as minor additives. Sintering was carried out at 1100$^{\circ}C$. As results from the experiments, the high value of initial permeability of 6X10$^2$∼9X10$^2$ can be achieved at 500KHz∼1000KHz. The value of loss factor 1X10￣$^2$∼2X10$^2$ can be achieved at 500KHz∼1000KHz. The lowest 1/(${\mu}$XQ) value was obtained in the specimen with the addition of 0.005mol% fracyion for V$_2$O$\_$5/.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.197.1-197
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• 2003