Hwang, Jin-Geun
(The Center of Biomedical Materials and Biotechnology, The Center of Green Materials Technology, Department of Materials Science and Engineering, Andong National University)
,
Oh, Kyung-Sik
(The Center of Biomedical Materials and Biotechnology, The Center of Green Materials Technology, Department of Materials Science and Engineering, Andong National University)
,
Chung, Tai-Joo
(The Center of Biomedical Materials and Biotechnology, The Center of Green Materials Technology, Department of Materials Science and Engineering, Andong National University)
,
Kim, Tae-Heui
(The Center of Biomedical Materials and Biotechnology, The Center of Green Materials Technology, Department of Materials Science and Engineering, Andong National University)
,
Paek, Yeong-Kyeun
(The Center of Biomedical Materials and Biotechnology, The Center of Green Materials Technology, Department of Materials Science and Engineering, Andong National University)
The low-temperature sintering behavior of AlN was investigated through a conventional method. $CaF_2$, CuO and Cu were selected as additives based on their low melting points. When sintered at $1600^{\circ}C$ for 8 h in $N_2$ atmosphere, a sample density > 98% was ob...
The low-temperature sintering behavior of AlN was investigated through a conventional method. $CaF_2$, CuO and Cu were selected as additives based on their low melting points. When sintered at $1600^{\circ}C$ for 8 h in $N_2$ atmosphere, a sample density > 98% was obtained. The X-ray data indicated that eutectic reactions below $1200^{\circ}C$ were found. Therefore, the current systems have lower liquid formation temperatures than other systems. The liquid phase showed high dihedral angles at triple grain junctions, indicating that the liquid had poor wettability on the grain surfaces. Eventually, the liquid was likely to vaporize due to the unfavorable wetting condition. As a result, a microstructure with clean grain boundaries was obtained, resulting in higher contiguity between grains. From EDS analysis, oxygen impurity seems to be well removed in AlN lattice. Therefore, it is believed that the current systems are beneficial for reducing sintering temperature and improving oxygen removal.
The low-temperature sintering behavior of AlN was investigated through a conventional method. $CaF_2$, CuO and Cu were selected as additives based on their low melting points. When sintered at $1600^{\circ}C$ for 8 h in $N_2$ atmosphere, a sample density > 98% was obtained. The X-ray data indicated that eutectic reactions below $1200^{\circ}C$ were found. Therefore, the current systems have lower liquid formation temperatures than other systems. The liquid phase showed high dihedral angles at triple grain junctions, indicating that the liquid had poor wettability on the grain surfaces. Eventually, the liquid was likely to vaporize due to the unfavorable wetting condition. As a result, a microstructure with clean grain boundaries was obtained, resulting in higher contiguity between grains. From EDS analysis, oxygen impurity seems to be well removed in AlN lattice. Therefore, it is believed that the current systems are beneficial for reducing sintering temperature and improving oxygen removal.
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제안 방법
In order to identify such an additive, CaF2, Cu and CuO were investigated due to their low melting points as well as the oxygen gettering effect. In this study, densification, microstructure evolution, and thermal conductivity were examined for samples sintered at the low temperature of 1600℃. Based on the results, the present systems showed favorable characteristics for improving the low-temperature sintering behavior of AlN.
Microstructures were observed on fractured surfaces with SEM (VEGA II LMU, TESCAN). To observe grain boundary phases, HRTEM (TECNAI 30F, FEI) and energy dispersive spectroscopy (EDS) were performed. TEM samples were prepared using FIB (focused ion beam: LYRA3, TESCAN).
대상 데이터
A mixed powder composed of CaF2, Al2O3, and CuO or Cu was added to the AlN as an additive. Two kinds of sample powder were prepared: (1) 86AlN-2.8CaF2-8.4Al2O3-2.8Cu(S1), and (2) 86AlN-2.8CaF2-8.4Al2O3-2.8CuO(S2). The compositions were empirically determined and represented in wt.
To observe grain boundary phases, HRTEM (TECNAI 30F, FEI) and energy dispersive spectroscopy (EDS) were performed. TEM samples were prepared using FIB (focused ion beam: LYRA3, TESCAN). The thermal conductivity of each sample was calculated based on thermal diffusivity and heat capacity using laser flash technique at 298 K.
이론/모형
Sintered densities were obtained by the Archimedes method using distilled water as an immersion medium. Every density datum was determined by an average of three similar specimens.
성능/효과
Every density datum was determined by an average of three similar specimens. Based on the rule of mixture considering the densities of 3.26 g/cm3 for AlN, 3.18 g/cm3 for CaF2, 3.95 g/cm3 for Al2O3, 6.31 g/cm3 for CuO, and 8.96 g/ cm3 for Cu, the theoretical densities of samples S1 and S2 are determined to be 3.32 and 3.31 g/cm3 , respectively. Linear shrinkage and weight loss were calculated by the difference in dimension and mass between sintered and green bodies, respectively.
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