Large-area graphene of the order of centimeters was deposited on copper substrates by low-pressure chemical vapor deposition (LPCVD) using hexane as the carbon source. The effect of temperature and the carrier gas flowrates on the quality and uniformity of the as-deposited graphene was investigated using the Raman analysis. The film deposited at 870 °C with a total carrier gas flowrate of 50 sccm is predominantly single-layer with very low defects according to the Raman spectra. The 2D/G peak intensity ratios obtained from the Raman spectra of samples from three different locations of graphene deposited on a whole copper catalyst was used to calculate the large-area uniformity. Based on the results, a very high uniformity of 89.6% was calculated for the graphene deposited at 870 °C. The uniformity was observed to decrease with increasing temperature. Similar to the thickness uniformity, the electrical conductivity values obtained as a result of I–V measurements and water contact angle measurements were found to be close to each other for the graphene deposited under the same deposition conditions.

High-quality β-silicon carbide (SiC) coatings are expected to prevent the oxidation degradation of carbon fibers in carbon fiber/silicon carbide (C/SiC) composites at high temperature. Uniform and dense β-SiC coatings were deposited on carbon fibers by low-pressure chemical vapor deposition (LP-CVD) using silane (SiH4) and acetylene (C2H2) as source gases which were carried by hydrogen gas. SiC coating layers with nanometer scale microstructures were obtained by optimization of the processing parameters considering deposition mechanisms. The thickness and morphology of β-SiC coatings can be controlled by adjustment of the amount of source gas flow, the mean velocity of the gas flow, and deposition time. XRD and FE-SEM analyses showed that dense and crack-free β-SiC coating layers are crystallized in β-SiC structure with a thickness of around 2 micrometers depending on the processing parameters. The fine and dense microstructures with micrometer level thickness of the SiC coating layers are anticipated to effectively protect carbon fibers against the oxidation at high-temperatures.

Si3N4가 추진기관 연소조건 하에서 흑연의 산화와 마모를 효과적으로 방지하는 다층 코팅재료로 쓰일 수 있도록 하기 위하여 저압화학기상증착법(LPCVD)으로 Si3N4를 코팅할 때의 증착특성에 대해 연구하였다. 흑연 위에 pack cementation방법으로 SiC를 코팅하고 그 위에 저압화학기상증착법으로 Si3N4를 코팅 하였으며, 증착온도와 반응기체입력비를 변화시키면서 이에 따른 증착속도와 표면형상의 변화를 관찰하였다. 증착속도는 증착온도가 높아짐에 따라 처음에는 증가하다가 최대값을 나타낸 후 감소하는 경향을 나타냈으며, 그레인의 크기는 증착온도가 높아짐에 따라 작아지는 경향을 보였다. 한편, 반응기체의 입력비가 20≤NH3/SiH4≤40인 조건에서는 증착속도의 변화나 표면형상의 변화를 관찰할 수 없었다. 증착온도 800~1300˚C 범위에서 증착된 Si3N4가 비정질상인 것을 XRD로 확인할 수 있었으며 1300˚C, 질소 분위기에서 2시간 동안 열처리하여 결정상인 Si3N4를 인을 수 있었다.