• 분석과학
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• 제11권3호
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• pp.156-160
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• 1998

다양한 탄소재와 Si를 함유하는 화합물로부터 SiC를 합성하였고, XRD 분석으로부터 구조적 특성 연구와 DSC 분석에 의한 열역학적 연구를 통하여 졸-겔법과 carbothermal 반응법을 비교연구하였다. 졸-겔법보다는 carbothermal 반응법에 의한 합성이 SiC의 형성을 뚜렷하게 하였다. X-선 회절결과로부터 여러가지 탄소재의 SiC 형성 정도는 두 방법 모두 석유 코크스, 활성탄, 인조흑연의 순으로 증가함을 알 수 있었다. 그리고 DSC 분석결과로부터 발열반응에 대한 엔탈피 변화량은 carbothermal 반응법의 경우 활성탄, 석유 코크스, 인조흑연의 순으로 감소하였고, 흡열반응에 대한 변화량은 역순으로 증가하였다. 그러나 졸-겔법의 경우 발열반응에 대한 엔탈피 변화량은 석유 코크스, 활성탄, 인조흑연의 순으로 감소하였다.

• Fibers and Polymers
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• 제6권2호
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• pp.103-107
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• 2005

An attempt was made to correlate the polymerization temperature and rheological and thermal properties of acrylonitrile (AN)-acrylamide (AM) copolymers. The copolymers were synthesized at different polymerization temperature. The copolymer structure was characterized by gel permeation chromatography (GPC) and Infrared spectrum (IR). The rheological and thermal properties were investigated by a viscometer and differential scanning calorimeter-thermogrametric (DSC-TG) analysis, respectively. When the polymerization temperature increased from $41^{\circ}C\;to\;65^{\circ}C$, the molecular weight $(\bar{M}_w)$ of copolymers decreased from 1,090,000 to 250,000, while its conversion increased from $18\%\;to\;63\%$, and the polymer composition changed slightly. To meet the requirements of carbon fibers, the rheological and thermal properties of products were also investigated. It was found that the relationship between viscosity and $\bar{M}_w$ was nonlinear and the viscosity index (n) decreased from 3.13 to 2.69, when the solution temperature increased from $30^{\circ}C\;to\;65^{\circ}C$. This suggests the dependence of viscosity upon $\bar{M}_w$ is higher at lower solution temperature. According to the result of activation energy, the sensivity of viscosity to solution temperature is higher for AN-AM copolymers synthesized at higher polymerization temperature. The result of thermal analysis shows that the copolymers obtained at higher polymerization temperature are easier to cyclization evidenced from lower initiation temperature. The weight loss behavior changed irregularly with polymerization temperature due to irregular change of liberation heat.

• 자원리싸이클링
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• 제26권3호
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• pp.39-46
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• 2017

탄소환원질화법을 이용하여 질화알루미늄(Aluminum Nitride: AlN)을 제조하는 연구를 실험실 규모로 수행하였다. 고품위 알루미나 분말과 탄소(carbon black)를 배합하여 흑연 도가니에 장입하고, 노내 분위기를 진공으로 한 다음 질소 가스를 흘려주어 온도($1,600{\sim}1,700^{\circ}C$), 시간(0.5~6 hr), $N_2$유량($4.7{\times}10^{-6}{\sim}20{\times}10^{-6}m^3/sec$), 장입 시료층 높이(0.5~20 mm)를 변화시키면서 AlN을 합성하였다. 실험결과, 고순도 알루미나와 탄소 혼합물을 질소 분위기의 $1600{\sim}1700^{\circ}C$ 온도 범위에서 반응시킬 때 반응 온도가 높을수록 생성된 AlN의 1차 입자 크기가 커지고, 반응 활성화 에너지는 382 kJ/mol로 화학 반응이 율속 단계로 판단되었다. 시험 제조한 AlN들의 산소 함량은 0.71~0.96 wt%였고, 질소는 30.7~35.1 wt%로서 상용 제품과 근접한 결과를 나타내었다.

• 한국진공학회지
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• 제17권6호
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• pp.576-581
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• 2008

각종 전자 방출원 및 디스플레이 응용분야에서 우수한 가능성을 보이고 있는 이중벽 탄소나노튜브를 Tetra Hydro Furan(THF) 열분해 방법으로 대량합성 하였다. 본 연구에서는 Fe-Mo 금속이 MgO 담지체에 담지된 촉매에 THF 를 공급하여 이중벽 탄소나노튜브를 합성하였다. 이 합성된 이중벽 탄소나노튜브는 비정질 탄소파티클이 없는 고순도로 합성되었으며, 탄소나노튜브 다발의 직경은 12 - 20 nm 로 균일하게 분포하였고, 성장 길이는 수십 마이크로미터 였다. TEM 분석 결과 이중벽 탄소나노튜브 5 - 10 가닥이 뭉쳐있는 다발 형태로 존재하였고, 합성된 이중벽 탄소나노튜브의 Raman spectrum 분석 결과 내부 직경이 0.9 - 1.5 nm, 외부 직경이 1.6 - 2.2 nm 의 직경 분포를 갖는 이중벽 구조의 탄소나노튜브가 합성되었음을 확인 할 수 있었다. 본 연구에서 사용된 THF 가 이중벽 탄소나노튜브를 합성하는데 적합한 탄소공급원임을 제시한다.

• 한국재료학회지
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• 제31권9호
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• pp.525-531
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• 2021

Carbon-encapsulated Ni catalysts are synthesized by an electrical explosion of wires (EEW) method and applied for CO₂ methanation. We find that the presence of carbon shell on Ni nanoparticles as catalyst can positively affect CO₂ methanation reaction. Ni@5C that is produced under 5 % CH₄ partial pressure in Ar gas has highest conversions of 68 % at 350 ℃ and 70 % at 400 ℃, which are 73 and 75 % of the thermodynamic equilibrium conversion, respectively. The catalyst of Ni@10C with thicker carbon layer shows much reduced activity. The EEW-produced Ni catalysts with low specific surface area outperform Ni catalysts with high surface area synthesized by solution-based precipitation methods. Our finding in this study shows the possibility of utilizing carbon-encapsulated metal catalysts for heterogeneous catalysis reaction including CO₂ methanation. Furthermore, EEW, which is a highly promising method for massive production of metal nanoparticles, can be applied for various catalysis system, requiring scaled-up synthesis of catalysts.

• 대한금속재료학회지
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• 제48권4호
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• pp.335-341
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• 2010

High-quality single-walled carbon nanotubes (SWCNTs) were synthesized by catalytic decomposition of $C_2H_2$ using Fe-Mo/MgO catalyst at $800^{\circ}C$. The as-synthesized SWCNTs typically occurred in the form of a bundle with a diameter of 10~20 nm together with amorphous carbon and catalytic impurities, which were removed by a two-step purification process consisting of oxidation and an acid treatment. The oxidation step, using an $O_2$-Ar mixture at $380^{\circ}C$ for 5 hr in a vertical-type furnace and a $HNO_3$ treatment at $100^{\circ}C$ for one hour, was utilized to remove the amorphous carbon particles. Subsequently, metallic catalysts were removed in HCl at room temperature for 5 hr under magnetic stirring. The SWCNT suspension was prepared by dispersing the purified SWCNTs in an aqueous sodium dodecyl benzene sulfonate solution with horn-type sonication. This was then air-sprayed on glass to fabricate CNT field emitters. The samples had a turn-on field value of 4 V/${\mu}m$ and a current density of 0.67 mA/$cm^2$ at 9 V/${\mu}m$. Increasing the HCl treatment time improved the field emission properties.

• 공업화학
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• 제35권3호
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• pp.260-265
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• 2024

반도체 웨이퍼 운반용 tray에 사용하기 위한 반도체 대전방지용 물질을 합성하기 위해 탄소나노튜브를 포함하는 폴리(메틸메타크릴레이트)(PMMA)와 폴리우레탄(PU)의 in-situ polymerization이 설계되고 진행되었다. 새롭게 합성된 복합체는 상업용 장치 제조 공정을 모방한 조건에서 열적특성과 전기전도성 특성을 평가하였다. 이들의 관련 성능을 비교한 결과, 탄소나노튜브를 함유하고 있는 PMMA와 PU 모두 탄소나노튜브 함량이 올라갈수록 열적인 특성이 향상되었으며, 전기전도성 역시 함량이 올라갈수록 증가하는 우수한 성능을 나타내었다. In-situ polymerization을 통한 복합체의 morphology는 FE-SEM을 통하여 확인한 결과 상용성이 우수한 상태로 확인되었다. 탄소나노튜브를 포함하는 PMMA와 PU 모두 반도체 대전방지용 물질로서 사용할 수 있는 우수한 표면저항 값인 10³ Ω/□의 특성 결과를 확인할 수 있었다.

• 한국결정성장학회지
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• 제23권6호
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• pp.296-301
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• 2013

Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under the thermal chemical vapor deposition system. A 304-type stainless steel was used as a substrate with nickel powders as the catalyst. The surface of the substrate was pretreated using a sand paper or a mechanical drill to enhance the production yield of the carbon coils. The characteristics of the deposited carbon nanomaterials on the substrates were investigated according to the surface state on the stainless steel substrate. The protrusion induced by the grooves on the substrate surface could enhance the formation of the carbon nanomaterials having the coils geometries. The cause for the enhancement of the carbon coils formation by the grooves was suggested and discussed with the surface energies for the interaction between as-growing carbon elements. Finally, we could obtain the massive production yield of the carbon coils by the surface pretreatment using SiC sand papers on the several tens grooved stainless steel substrate.

• 한국분말재료학회지
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• 제24권3호
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• pp.248-253
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• 2017

In this study, we investigate the effect of the diffusion barrier and substrate temperature on the length of carbon nanotubes. For synthesizing vertically aligned carbon nanotubes, thermal chemical vapor deposition is used and a substrate with a catalytic layer and a buffer layer is prepared using an e-beam evaporator. The length of the carbon nanotubes synthesized on the catalytic layer/diffusion barrier on the silicon substrate is longer than that without a diffusion barrier because the diffusion barrier prevents generation of silicon carbide from the diffusion of carbon atoms into the silicon substrate. The deposition temperature of the catalyst and alumina are varied from room temperature to $150^{\circ}C$, $200^{\circ}C$, and $250^{\circ}C$. On increasing the substrate temperature on depositing the buffer layer on the silicon substrate, shorter carbon nanotubes are obtained owing to the increased bonding force between the buffer layer and silicon substrate. The reason why different lengths of carbon nanotubes are obtained is that the higher bonding force between the buffer layer and the substrate layer prevents uniformity of catalytic islands for synthesizing carbon nanotubes.

• Carbon letters
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• 제28권
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• pp.60-65
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• 2018

Linear carbon chains (LCCs) encapsulated inside the hollow cores of carbon nanotubes (CNTs) have been experimentally synthesized and structurally characterized by Raman spectroscopy and transmission electron microscopy. However, in terms of electronic conductivity, their transportation mechanism has not been investigated theoretically or experimentally. In this study, the density of states and quantum conductance spectra were simulated through density functional theory combined with the non-equilibrium Green function method. The encapsulated LCCs inside (5,5), (6,4), and (9,0) single-walled carbon nanotubes (SWCNTs) exhibited a drastic change from metallic to semiconducting or from semiconducting to metallic due to the strong charge transfer between them. On the other hand, the electronic change in the conductance value of LCCs encapsulated inside the (7,4) SWCNT were in good agreement with the superposition of the individual SWCNTs and the isolated LCCs owing to the weak charge transfer.