• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1436-1438
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• 2001

The $\beta$-SiC + $ZrB_2$ ceramic electroconductive composites were pressureless-sintered and annealed by adding 12wt% $Al_2O_3$ + $Y_2O_3$ (6 : 4wt%) powder as a function of sintering temperature. The relative density showed the highest value of 81.1% at 1900$^{\circ}C$ sintering temperature. The phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H), $TiB_2$, $Al_5Y_2O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest value of 230 MPa for composites sintered at 1900$^{\circ}C$. The vicker's hardness and the fracture toughness showed the highest value of increased with increasing sintering temperature and showed the highest of 9.88 GPa and 6.05 $MPa{\cdot}m^{1/2}$ at 1900$^{\circ}C$. The electrical resistivity was measured by the Pauw method from 25$^{\circ}C$ to 700$^{\circ}C$. The electrical resistivity of the composites showed the PTCR (Positive Temperature Coefficient Resistivity).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.118-122
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• 2001

The ${\beta}-SiC+TiB_2$ ceramic electroconductive composites were pressureless-sintered and annealed by adding 12wt% $Al_2O_3+Y_2O_3$(6 : 4wt%) powder as a function of sintering temperature. The relative density is over 78.83% of the theoretical density and increased with increasing sintering temperature. The phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H), $TiB_2$, $Al_5Y_2O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest of 140 MPa for composites sintered at $1900^{\circ}C$. The vicker's hardness increased with increasing sintering temperature and showed the highest of 4.07 GPa at $1900^{\circ}C$. Owing to YAG, the fracture toughness showed the highest of 4.07 $MPa{\cdot}m^{1/2}$ for composites at $1900^{\circ}C$. The electrical resistivity was measured by the Pauw method from $25^{\circ}C$ to $700^{\circ}C$. The electrical resistivity of the composites showed the PTCR(Positive Temperature Coefficient Resistivity).

• 한국재료학회지
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• 제21권6호
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• pp.352-356
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• 2011

[ $Zn_{2(1-x)}Mn_xSiO_4$ ]$0.07{\leq}x{\leq}0.15$) green phosphor was prepared by solid state reaction. The first heating was at $900^{\circ}C-1250^{\circ}C$ in air for 3 hours and the second heating was at $900^{\circ}C$ in $N_2/H_2$(95%/5%) for 2 hours. The size effect of $SiO_2$ in forming $Zn_2SiO_4$ was investigated. The temperature for obtaining single phase $Zn_2SiO_4$ was lowered from $1100^{\circ}C$ to $1000^{\circ}C$ by decreasing the $SiO_2$ particle size from micro size to submicro size. The effect of the activators for the Photoluminescence (PL) intensity of $Zn_2SiO_4:Mn^{2+}$ was also investigated. The PL intensity properties of the phosphors were investigated under vacuum ultraviolet excitation (147 nm). The emission spectrum peak was between 520 nm and 530 nm, which was involved in green emission area. $MnCl_2{\cdot}4H_2O$, the activator source, was more effective in providing high emission intensity than $MnCO_3$. The optimum conditions for the best optical properties of $Zn_2SiO_4:Mn^{2+}$ were at x = 0.11 and $1100^{\circ}C$. In these conditions, the phosphor particle shape was well dispersed spherical and its size was 200 nm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.894-896
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• 1999

The $\beta$-SiC+$ZrB_2$ ceramic composites were pressureless-sintered and annealed by adding 4, 8, 12wt% $Al_{2}O_{3}+Y_{2}O_{3}$(6 : 4wt%) powder as a liquid forming additives at $1800^{\circ}C$ for 4h. The relative density is over 79.3% of the theoretical density and phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H, 4H), $ZrB_2$, $Al_{5}Y_{2}O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest of 301.33MPa for composites added with 8wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed the highest of $3.6979MPa{\cdot}m^{1/2}$ for composites added with 8wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. The electrical resistivity was measured by the Pauw method from $25^{\circ}C$ to $700^{\circ}C$. The electrical resistivity of the composites showed the PTCR(Positive Temperature Coefficient Resistivity).

• 전기학회논문지
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• 제56권9호
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• pp.1602-1608
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• 2007

The composites were fabricated, respectively, using 61[vol.%] SiC-39[vol.%] $TiB_2$ and using 61[vol.%] SiC-39[vol.%] $ZrB_2$ powders with the liquid forming additives of 12[wt%] $Al_2O_3+Y_2O_3$ by hot pressing annealing at $1650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H, 3C), $TiB_2$, $ZrB_2$ and $YAG(Al_5Y_3O_{12})$ crystal phase on the Liquid-Phase-Sintered(LPS) $SiC-TiB_2$, and $SiC-ZrB_2$ composite. $\beta\rightarrow\alpha-SiC$ phase transformation was occurred on the $SiC-TiB_2$ and $SiC-ZrB_2$ composite. The relative density, the flexural strength and Young's modulus showed the highest value of 98.57[%], 249.42[MPa] and 91.64[GPa] in $SiC-ZrB_2$ composite at room temperature respectively. The electrical resistivity showed the lowest value of $7.96{\times}10^{-4}[\Omega{\cdot}cm]$ for $SiC-ZrB_2$ composite at $25[^{\circ}C]$. The electrical resistivity of the $SiC-TiB_2$ and $SiC-ZrB_2$ composite was all positive temperature coefficient resistance (PTCR) in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$. The resistance temperature coefficient of composite showed the lowest value of $1.319\times10^{-3}/[^{\circ}C]$ for $SiC-ZrB_2$ composite in the temperature ranges from $100[^{\circ}C]$ to $300[^{\circ}C]$ Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

• 공업화학
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• 제24권4호
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• pp.382-390
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• 2013

소다석회 조성의 폐 병유리를 대상으로 효율적인 재활용방안을 찾기 위해서 발포화에 적절한 조성의 조절을 통해 직접 보온단열재 발포유리블럭을 제조할 수 있는 공정을 조사하였다. 폐 병유리의 직접 발포화를 위해 첨가되는 성분 및 조성은, 폐 유리분말 100중량부에 대하여 $SiO_2$ 10중량부, $Na_2SO_4$ 0.5중량부, $B_2O_3$ 3.0중량부, 그리고 발포제로서 카본 블랙류 탄소재 0.3중량부이다. 발포공정은 턴넬키른에서 진행하며, 발포소성 조건은 폐 유리분말의 입도는 -325 mesh, 발포소성온도는 $830{\sim}850^{\circ}C$, 발포시간은 30~35 min이 바람직하다. 상기 조건하에 제조된 발포체는 밀도가 $0.17{\sim}0.21g/cm^3$, 열전도도 $0.06{\pm}0.005kcal/h{\cdot}m{\cdot}^{\circ}C$, 수분 흡수율 1.1~1.5%, 압축강도는 $20{\sim}30kgf/mm^2$의 물성을 나타내었다.

• 한국재료학회지
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• 제16권12호
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• pp.719-724
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• 2006

Ultrafine mullite powder was prepared from aluminium-secbutoxide and tetraethyl orthosilicate(TEOS) in the molar $Al_2O_3/SiO_2$=3/2. Sol-gel method by partial hydrolysis technique, as it were, first, TEOS was partially hydrolysized and then mixed with Al-secbutoxide for complete hydrolysis was used. X-ray diffraction, infrared spectroscopy and transmission electron microscopy, etc. confirmed that the mullite powder prepared by this method is in the stoichiometric $Al_2O_3/SiO_2$ ratio. Al-Si spinel was formed at $980^{\circ}C$ and ultrafine mullite powder with about 20 nm particle size was obtained above $1,200^{\circ}C$. Also mullite powders calcined at $1,600^{\circ}C$ had a stoichiometric composition, $3Al_2O_3{\cdot}2SiO_2$ and the lattice constants of the mullite powders calcined above $1,200^{\circ}C$ were almost coincided with theoretical values.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1303-1304
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• 2007

The composites were fabricated, respectively, using 61[vol.%]SiC-39[vol.%]$TiB_2$ and using 61[vol.%]SiC-39[vol.%]$ZrB_2$ powders with the liquid forming additives of 12[wt%] $Al_{2}O_{3}+Y_{2}O_{3}$ by hot pressing annealing at $1650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. ${\beta}{\rightarrow}{\alpha}$-SiC phase transformation was occurred on the SiC-$TiB_2$ and SiC-$ZrB_2$ composite. The relative density, the flexural strength and Young's modulus showed the highest value of 98.57[%], 226.06[Mpa] and 86.38[Gpa] in SiC-$ZrB_2$ composite at room temperature respectively. The electrical resistivity showed the lowest value of $7.96{\times}10^{-4}[{\Omega}{\cdot}cm]$ for SiC-$ZrB_2$ composite at $25[^{\circ}C]$. The electrical resistivity of the SiC-$TiB_2$ and SiC-$ZrB_2$ composite was all positive temperature coefficient resistance (PTCR) in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$. The resistance temperature coefficient of composite showed the value of $6.88{\times}10^{-3}/[^{\circ}C]$ and $3.57{\times}10^{-3}/[^{\circ}C]$ for SiC-$ZrB_2$ and SiC-$TiB_2$ composite in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$.

• 농업과학연구
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• 제2권1호
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• pp.61-100
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• 1975

수도재배(水稻栽培)에 있어 작중토(作中土)의 유효규산함량(有效珪酸含量), ppm과 유기물함량(有機物含量)% 비(比) $SiO_2$/O.M. 근거(根據)한 N 적량(適量) 추정식(推定式) $Nkg/10a=(4.2+0.096\;SiO_2/O.M.).F$에서 N시비량(施肥量)을 추정(推定) 시용(施用)할 때의 적정(滴定) 가리(加里) 시용량(施用量) 추정식(推定式) $K_2Okg/10a=(K_O/\sqrt{Ca+Mg}-Ks/\sqrt{Ca+Mg})\sqrt{Ca+Mg}{\cdot}47{\cdot}BD$ 단 (但) $K_O/\sqrt{Ca+Mg}=0.03158+0.0007658\;SiO_2/O.M.$ $K_S/\sqrt{Ca+Mg}=Kme/100g/\sqrt{(Ca+Mg)}me/100g$의 타당성(妥當性) 여부(如否)를 판단(判斷)하기 위하여 3수준(水準)의 규회석처리(珪灰石處理)를 주구(主區)로하여 작토중(作土中)의 $SiO_2$/O.M. 비(比)를 증대(增大) 시키고 각주구별(各主區別)로 적정가리시용량(適正加里施用量) 추정식(推定式)에서 추정(推定)한 $K_2O$ 시용량(施用量)과 이에30%를 증비(增肥)하는구(區) 및 적정가리시용추정치(適正加里施用推定値)와는 관계(關係)없이 $K_2O\;8kg/10a$를 시용(施用)하는 3개수준(個水準)의 $K_2O$ 처리구(處理區)를 설정(設定)하여 수도품종(水稻品種) Akibare를 재배(栽培)하는 포장시험(圃場試驗)을 수행(遂行)하고 토양(土壤), 식물체분석(植物體分析) 및 수도(水稻)의 생육(生育)과 수량(收量) 및 수량구성요소(收量構成要素)들을 조사(調査)한 성적(成績)들을 종합검토(綜合檢討)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 작토중(作土中) 유효규산함량(有效珪酸含量) ppm과 유기물함량(有機物含量)%비(比), $SiO_2$/O.M.에 근거(根據)한 수도(水稻)에 대(對)한 N적량추정식(適量推定式)에서 추정(推定)한 N시용량(施用量)은 수도품종(水稻品種) Akibare의 생육(生育) 및 수량면(收量面)에서 볼 때 과량(過量)이었으며 토양(土壤) 및 식물체(植物體) 분석치(分析値)들에서 검토(檢討)한 결과(結果) $SiO_2$/O.M. 비조절(比調節)의 기본원리(基本原理)는 합당(合當)하나 그 식(式)의 상수(常數) 또는 F값은 변동(變動)되여야 한다고 판단(判斷)되였다. 2. 작토중(作土中)의 K활성도(活性度) 치환성(置換性) 염기 me/100 g비(比) $K/\sqrt{Ca+Mg}$를 조절(調節)하기 위한 $K_2O$ 시비량(施肥量) 추정식(推定式)에서 추정(推定)한 $K_2O$ 시용량(施用量)은 수도품종(水稻品種) Akibare의 생육(生育) 및 수량면(收量面)에서 과량(過量)이였으며 토양(土壤) 및 식물체(植物體) 분석치(分析値)들에서 검토(檢討)한 결과(結果) 조절기준(調節基準)되는 $K_O/\sqrt{Ca+Mg}$의 설정식(設定式) 즉(卽) $K_O/\sqrt{Ca+Mg}=0.03158+0.0007658\;SiO_2/O.M.$의 원리(原理)는 합리적(合理的)이나 기상수(其常數)의 변동(變動)이 필요(必要)하며 $K_S/\sqrt{Ca+Mg}$에 있어서도 토양(土壤)의 K공급능(供給能)을 고려(考慮)할수 있는 새로운 조절기준(調節基準)이 설정(設定)되어야 한다고 판단(判斷)되였다. 3. 수도(水滔)에 대한 $K_2O$ 시용량(施用量) 추정식중(推定式中)의 $K_S/\sqrt{Ca+Mg}$ 조절(調節) 기준(基準)은 K 공급능(供給能)을 대표(代表)할수 있는 작토중(作土中)의 치환성(置換性) Kme/100g에 근거(根據)해서 마음과 같이 설정(設定)함이 보다 합리적(合理的)임을 수도품종(水稻品種) Akibare의 천상수량 $K_2O$ 흡수량면(吸收量面)에서 밝힐수 있었다. 즉 $K_S/\sqrt{Ca+Mg}=0.037+0.78Kme/100g$.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1165-1166
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• 2006

An experiment was carried out to investigate the effect of Ba Stearate as a reducing agent on the magnetic and physical properties of anisotropic $BaFe_2-W$ type ferrite magnets. It was found that the magnetic properties of $BaO{\cdot}8.5Fe_2O_3$ were improved by adding 0.3 wt% of Ba Stearate, 0.5 wt% of $SiO_2$, and 0.5 wt% of CaO together. The optimum conditions for making magnets were as follows; semisintering condition: $1350^{\circ}C{\times}4.0$ h in nitrogen gas atmosphere, drying condition: $180^{\circ}C{\times}2.0$ h in air, sintering condition: $1160^{\circ}C{\times}1.5$ h in nitrogen gas atmosphere. Magnetic and physical properties of a typical sample were $J_m$ = 0.46 T, $J_r$ = 0.43 T, $H_{cJ}$ = 182.3 kA/m, $H_{cB}$ = 177.2 kA/m, $(BH)_{max}$ = 33.8 kJ/$m^3$, $T_C$ = $495^{\circ}C$ and $K_A$ = $2.65{\times}10^5\;J/m^3$ and $H_A$ = 1332 kA/m.