• 한국결정성장학회지
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• 제29권2호
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• pp.45-49
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• 2019

본 연구에서는, 탄소성분으로서 탄화왕겨, 제지슬러지, 커피찌꺼기와 실리카 분말로부터, 비교적 미세한 탄화규소 결정질 응집체를 합성하였다. 탄소성분들과 실리카의 혼합물로부터 탄화규소 응집체를 얻기 위한 주요 반응물질은 열탄화환원 반응에 의해 생성된 일산화규소 기체로 추정되었다. 탄화왕겨, 제지슬러지, 커피찌꺼기와 실리카 분말의 혼합물로부터 열탄화환원반응법을 거쳐 생성된 탄화규소 결정질 응집체들에 대한 XRD 회절패턴으로부터 결정상을 분석하였고, FE-SEM과 FE-TEM을 통한 미세구조, 결정구조 분석이 이루어졌다. 탄화왕겨, 제지슬러지, 그리고 실리카 분말의 시료의 경우, XRD 분석에서는 $35^{\circ}$ 부근의 (111) peak은 비교적 높은 강도를 나타내었다. 탄화왕겨, 제지슬러지, 커피찌꺼기와 실리카 분말의 혼합물로부터 합성된 시료들에 대해 FE-SEM 관찰을 통하여 $1{\mu}m$ 이하의 미세입자들을 관찰하였으며, TEM 측정 결과에서는 탄화규소 결정질상의 (110) 회절패턴들을 확인하였다.

• 한국세라믹학회지
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• 제28권6호
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• pp.465-470
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• 1991

AlN powder was synthesized by carbothermal reduction and nitridation of aluminum hydroxides precipitated in 5∼11 pH range from Al2(SO4)3$.$18H2O aqueous solution. Nitridation reactivity of hydroxide, which depends on precipitation pH, reaction temperature and time, was examined by XRD analysis at 1200∼1350$^{\circ}C$ and compared with that of commercial ${\alpha}$-Al2O3. Hydroxides obtained at higher pH could be more easily nitridated and, considering DTA/TG and BET results, the reason seems to be specific surface area difference of reactants depending on the content of decomposed structural water and the transition rate from transition-Al2O3 to ${\alpha}$-Al2O3.

• 한국세라믹학회지
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• 제33권4호
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• pp.455-463
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• 1996

Aluminium nitride (AlN) powder was prepared by using aluminium (III) complexes with dibasic carboxylate ligands(adipato)(hydroxo) aluminium(III) and (hydroxo)(succinato)aluminium (III) as a precursor. The AlN pow-der was obtained by calcining the complexes without mixing any carbon source under a flow of ammonia at 120$0^{\circ}C$ Contary to the conventional carbothermal reduction and nitridiation the process of decarboniza-tion of the residual carbon was not required because of the reaction of ammonia with carbon at temperature >100$0^{\circ}C$. Fine AlN powder was also prepared by calcining a mixture of an (adipato)(hydroxo)aluminium(III) complex and carbon under a flow of nitrogen at 140$0^{\circ}C$ The AlN powders prepared were ultrafine and their morphology was almost the same as that of powders of two precursors.

• 한국세라믹학회지
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• 제26권2호
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• pp.167-170
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• 1989

Al2O3/SiC composite-material was synthesized by the birth-spread mechanism through the carbothermal reduction reaction of SiO2 in Ha-Dong Kaolin with carbon powder under H2 gas atmosphere at 1300~140$0^{\circ}C$. Average diameter of synthesized SiC whiskers were 1${\mu}{\textrm}{m}$ and aspect ratio (c/a) was 10~100. Al2O3 particles and SiC whiskers were mixed homogeneously in the reacted pellet.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2019년도 정기학술대회 발표논문집
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• pp.83-83
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• 2019

Increasing the CO₂ concentration in the atmosphere induce high temperature and rising sea levels. So the technology that capture and reuse of the CO₂ have been recently become popular. Among other methods, CRR(CO2₂ reduction reaction) is typical method of CO₂ reusing. Electrocatalyst can show more higher efficiencies in CRR than photocatalyst because it doesn't use nature source. Nowadays, finding high efficient electrocatalyst by controlling electronic (affected by stoichiometry) and geometric (affected by atomic arrangement) factors are very important issues. Mono-atomic electro-catalyst has limitations on controlling binding energy because each intermediate has own binding energy range. So the Multi-metallic electro-catalyst is important to stabilize intermediate at the same time. Carbon monoxide(CO) which is our target product and important feedstock of useful products. Au is known for the most high CO production metal. With copper, Not only gold/copper has advantages which is they have FCC packing for easily forming solid solution regardless of stoichiometry but also presence of adsorbed CO on Cu promotes the desorption of CO on Au because of strong repulsion. And gold/copper bi-metal catalyst can show high catalytic activity(mass activity) although it has low selectivity relatively Gold. Actually, multi-metallic catalyst structure control method is limited in the solution method which is takes a lot of time. In here, we introduce CTS(carbo thermal shock) method which is using heat to make MMNP in a few seconds for making gold-copper system. This method is very simple and efficient in terms of time(very short reaction time and using carbon substrate as a direct working electrode) and increasing reaction sites(highly dispersed and mixing alloy structures). Last one is easy to control degree of mixing and it can induce 5 or more metals in one alloy system. Gold/copper by CTS can show higher catalytic activity depending on metal ratio which is altered easily by changing simple variables. The ultimate goals are making CO₂ test system by CTS which can check the selectivity depending on metal types in a very short time.

• 한국세라믹학회지
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• 제38권9호
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• pp.846-852
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• 2001

2차원적 몬테 칼로 시뮬레이션을 사용하여, 화학적 기상 반응법에 의한 탄화규소 전환층의 생성에 미치는 온도의 영향을 조사하였다. 화학적 기상 반응법은 실리카의 열탄화 환원법에 근거하며, 흑연 기판의 탄소와 실리카 반응기체와의 화학적 반응에 의하여 탄화규소 전환층을 형성하는 방법이다. 탄화규소는 반응기체의 확산 및 반응과 같은 열적활성화 과정을 통하여 생성되기 때문에 탄화규소 전환층의 형성은 온도에 크게 의존함을 알 수 있다. 본 연구에서는 몬테 칼로법을 사용하여 삼각격자로 배열된 2차원적인 계에서 흑연 기판의 미세 기공을 따라 확산된 반응기체와 탄소와의 반응에 의해서 탄화규소가 형성되는 과정을 시뮬레이션을 행하였다. 반응 온도를 1900K, 2000K, 2100K, 2200K로 조건을 달리하여 시뮬레이션 하였으며, 그 계산 결과를 실험 결과와 비교하여 재현성을 검토하고 탄화규소 전환층의 두께와 화학적 조성 구배에 대한 반응 온도의 영향을 검증하기 위한 것이다.

• 한국세라믹학회지
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• 제26권1호
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• pp.100-108
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• 1989

Aluminum hydroxides were prepared by the alkoxide hydrolysis method using Al-isopropoxide as a starting material and NH4OH as a catalytic agent. When Al-isopropoxide was hydrolyzed in a H2O-NH3 system, only Al(OH)3 was obtained over all pH values. However, AlOOH was formed besides Al(OH)3 when Al-isopropoxide was hydrolyzed in a H2O-NH3-isopropyl alcohol system. The AlOOH/Al(OH)3 ratio was increased as the isopropyl alcohol content was increased. The hydroxides, Al(OH)3 and AlOOH, obtained in this study and the commerical products, $\alpha$-Al2O3 and AlOOH were subjected to the carbothermal reduction and nitridation reaction to product AlN powder, using carbon black as a reducing agent under N2 atmosphere at various temperatures. AlN was synthesized from the obtained Al(OH)3 and the commercial AlOOH at 145$0^{\circ}C$, however, synthesized from the obtained AlOOH and the commercial alpha-alumina at 135$0^{\circ}C$. The temperature difference is assumed to be attributed to the reactivity of those powders. AlN powder prepared from the Al-isopropoxide was observed to have the narrower particle size distribution than that prepared from the commercial $\alpha$-Al2O3 or AlOOH.

• 한국세라믹학회지
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• 제28권2호
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• pp.130-140
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• 1991

The powders of the system Si3N4-Y2O3-AlN were prepared using Si(OC2H5)4 and YCl3.6H2O together with commercial AlN powder. $\alpha$-Si3N4 was prepared by the carbothermal reduction and nitridation of the hydrolyzed gel at 135$0^{\circ}C$ for 10h in N2 atmosphere. YCl3.6H2O was observed to be changed to Y2O3 during the reaction. $\alpha$-Sialon(X=0.2, 0.4, 0.6) ceramics were obtained by hot-pressing the Si3N4-Y2O3-AlN mixture at 178$0^{\circ}C$ for 1h under 30 MPa. The content of $\alpha$-Sialon increased with increasing metal solubility(x value) and $\alpha$-Sialon single phase was obtained at the metal solubility of 0.6. With increasing metal solubility, flexural strength, fracture toughness and thermal shock resistence were decreased, while the microhardness was increased. Large elongated $\beta$-Si3N4 grains were mainly observed at lower metal solubility. Mechanical prorerties of the sintered ceramics with X=0.2 were measured as follows : flexural strength ; 650 MPa, fracture toughness ; 3.63 MN/m3/2, hardness ; 14.7 GPa, thermal shock resistence temperature ; 58$0^{\circ}C$.

• 한국결정성장학회지
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• 제26권5호
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• pp.188-192
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• 2016

본 연구에서는, 실리카 분말과 왕겨의 혼합체로부터 탄화된 물질로부터, 탄화규소 (SiC) 분말이 합성되었다. 탄화왕겨와 실리카의 열탄화환원 반응을 통해 얻어진, SiC 시료는 XRD 회절 패턴, FE-SEM 및 FE-TEM을 통해 분석되었다. 시료들은 XRD 패턴에서, $35^{\circ}$ 부근의 (111) peak는 매우 높은 intensity를 나타내었고, $60^{\circ}$, $72^{\circ}$ 부근의 (220), (311) peak 등 탄화규소 결정상에 대한 peak pattern이 명확하게 관찰되었다. Ar 분위기에서 탄화왕겨와 실리카의 혼합비율이 6 : 4인 혼합물로부터 합성된 시료는 XRD 패턴에서 잔류카본이 검출되지 않았으며, hexagonal 결정상의 비율이 비교적 낮고, cubic SiC 결정상이 주도적으로 나타내었다. 탄화왕겨와 실리카의 혼합비율이 6 : 4인 경우에 합성된 시료는 $5{\mu}m$ 이하의 미세한 입자들이 관찰되었으며, TEM 분석결과에서, SiC 결정질상의 (110) 회절패턴 형태를 나타내었다.

• 한국세라믹학회지
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• 제48권5호
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• pp.368-372
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• 2011

Aluminum nitride (AlN) has excellent thermal conductivity, whereas it has some disadvantage such as low sinterability. In this study, the effects of sintering additive content and sintering condition on thermal conductivity of pressureless sintered AlN ceramics were examined on the variables of 1~3 wt% sintering additive ($Y_2O_3$) content at $1900^{\circ}C$ in $N_2$ atmosphere with holding time of 2~10 h. All AlN specimens showed higher thermal conductivity as the $Y_2O_3$ content and holding time increase. The formation of secondary phases (yttrium aluminates) by reaction of $Y_2O_3$ and $Al_2O_3$ from AlN surface promoted the thermal conductivity of AlN specimens, because the secondary phases could reduce the oxygen contents in AlN lattice. Also, thermal conductivity was increased by long sintering time because of the uniform distribution and the elimination of the secondary phases at the grain boundary by the evaporation effect during long holding time. A carbothermal reduction reaction was also affected on the thermal conductivity. The thermal conductivity of AlN specimens sintered at $1900^{\circ}C$ for 10 h showed 130~200W/mK according to the content of sintering additive.