• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.1137-1139
• /
• 1999

저가의 우수한 성능을 갖는 적외선 영상표시 소자 구현에 적합한 마이크로 볼로미터를 MEMS 기술을 사용하여 제작하였다. 작은 열질량을 갖는 마이크로미터 단위의 열적고립 구조(thermal isolation structure) 제작은 폴리이미드(PI2611)를 희생층으로 사용하여 최종적으로 ashing공정 단계에서 폴리이미드를 제거하여 마이크로 볼로미터 구조를 완성하였다. 이 때의 구조층으로는 PECVD 질화실리콘($SiN_x$) 박막, 감지층으로 산화바나듐($VO_x$) 박막을 사용하였다. 본 연구에서는 폴리이미드 패턴 형성시 건식식각 공정조건 변수에 따라서 패턴의 기울기를 조절하여 폴리이미드 측면에서 발생되는 불 균일한 박막 증착과 패터닝 문제를 개선하였다. 또한 저응력의 질화실리콘 박막을 사용하여 잔류응력에 의한 열적고립 구조의 뒤틀림 현상을 완화하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.176.1-176.1
• /
• 2013

TCO (Transparent Conductive Oxide)는 투명 전도성 산화물 높은 투과율과 낮은 비저항 가지고 있어서 최근 사용된 평판디스플레이 LCD(liquid crystal display), PDP (Plasma Display Panel), OLED (Organic Light Emitting Display) 에 많이 사용되고 있다. 현재 양산화 되고 있는 ITO (Indium tin Oxide)는 좋은 전도율과 높은 투과율로서 가장 많이 쓰인다. 하지만 ITO중에 Indium Oxide는 치명적인 독성을 가지고 있으며 In의 저장량이 적어 시간이 갈수록 가격이 비싸지는 등 여러 가지 단점을 가지고 있다. 그것에 비해 AZO (aluminum-doped zinc oxide)는 독성이 없고 가격도 저렴하여 ITO의 단점을 보완 할 수 있는 물질이다. AZO 증착은 현재 sol-gel, CVD(chemical vapor deposition), Sputter, 등으로 사용되고 있으며 현재 많은 연구가 진행되고 있다. 본 실험에서는 PEN 기판을 사용하였으며, 플라즈마의 열적 데미지로 인한 기판의 변형 등 여러 가지 문제를 해결하기 위하여 박막의 열적 변형이 적고, 고밀도 플라즈마로 양질의 박막 증착이 가능한 FTS (Facing Target Sputtering)방법을 사용하여 AZO박막을 증착시키고 구조적, 전기적, 광학적인 특성을 평가 하였다. 측정 분석 결과 AZO는 가시광 영역에 높은 투과율이 요구되는 Flexible display 표시장치와 OLED, PDP, 유기태양전지 등 많은 영역에 사용이 가능 할 것이라 사료된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.10
• /
• pp.720-727
• /
• 2019

Resonating thermal lags of solid fuel with heat transfer oscillations generated by boundary layer oscillation is the primary mechanism of the occurrence of the LFI (Low Frequency Combustion Instability) in hybrid rocket combustion. This study was experimentally attempted to confirm that how the boundary layer was perturbed and led to the LFI. Special attention was also made on oxidizer swirl injection to investigate the contribution to combustion stabilization. Also the overall behavior of fluctuating boundary layer flow and the occurrence of the LFI was monitored as swirl intensity increased. Fluctuating boundary layer was successfully monitored by the captured image and POD (Proper Orthogonal Decomposition) analysis. In the results, oscillating boundary layer became stabilized as the swirl intensity increases. And the coupling strength between high frequency p', q' diminished and periodical amplification of RI (Rayleigh Index) with similar frequency band of thermal lag was also decreased. Thus, results confirmed that oscillating axial boundary layer triggered by periodic coupling of high frequency p', q' is the primary mechanism to excite thermal resonance with thermal lag characteristics of solid fuel.

• Composites Research
• /
• v.31 no.5
• /
• pp.260-266
• /
• 2018

This study investigates thermal and mechanical characterization of Hafnium carbide coating on the $C_f-C$ composites. The hafnium carbide coatings by vacuum plasma spray on the C/C-SiC composites are prepared to evaluate oxidation and wear resistance. We perform the thermal durability tests by thermal cycling at $1200^{\circ}C$ for 10cycles in air and investigates the weight change of each cycle. We also evaluate the wear and indentation behavior using tungsten carbide ball indenter as a mechanical evaluation. As a result, the HfC coating is beneficial to reduce of weight loss during thermal cycling test and improve the elastic property of C/C-SiC composite. Especially, the HfC coating improves the wear resistance of C/C-SiC composite.

• Polymer(Korea)
• /
• v.30 no.6
• /
• pp.519-524
• /
• 2006

Poly(4-vinyl pyridine) (PVP) and its copolymers, poly(4-vinyl pvridine- co-acrylamide) and poly(4-vinyl pyridine-co-allylamine), were synthesized and evaluated for application to organic solder-ability preservatives (OSP). The copolymers were synthesized by radical polymerization of vinyl pyridine in the presence of acrylamide or allylamine as a comonomer. Various kinds of polymers with different chemical composition were synthesized by varying the feed ratio of monomers and their low $M_w$ polymers can be obtained by adding 2-mercaptoethanol as a chain transfer agent during poly-merization. All the polymers showed good adhesion properties on Cu pad when they were spin-coated. Especially, allylamine -containing copolymers showed both good adhesion and solubility properties. Also, they exhibited better thermal stability than PVP homopolymer and such thermal properties were changed depending on the chemical composition and their $M_w$, which were evidenced by the measurement of oxygen induced temperature (OIT). From the OIT measurement, poly(4-vinyl pyridine- co-allylamine) was thermally stable up to $230^{\circ}C$ for 70 min in the 100% oxygen environment. As a result, allylamine-containing copolymers can be considered as a promising OSP coating material that has excellent thermal and adhesive properties applicable to the present microelectronic package processes.

• Journal of the Korean Electrochemical Society
• /
• v.23 no.1
• /
• pp.1-10
• /
• 2020

DSA (Dimensionally Stable Anode) electrodes are physically, thermally and electrochemically stable and are mainly Ti electrodes coated by Ru, Ir and Ta. DSA electrodes have been used in many industrial fields such as chlor-alkali, electrochemical water treatment, water electrolysis, etc. This review paper summarizes the study on the applications using DSA electrodes published in the recent 5 years. It suggests that the researches are intensively required on effective screening of electrodes materials, optimal designing of electrode structures and economical manufacturing of large area electrodes. It is expected that these studies will contribute to the further research and development on advanced DSA electrodes. In addition, the enhancement of DSA electrodes significantly leads to expand the type of the application using electrochemical processes in industry.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.3
• /
• pp.705-711
• /
• 2000

A thin film oxide semiconductor micro gas sensor array which shows only 60 mW of power consumption at an operating temperature of $300^{\circ}C$ has been fabricated using microfabrication and micromachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double-layer structure of $0.1\mum\; thick\; Si_3N_4 \;and\; 1 \mum$ thick phosphosilicate glass (PSG) prepared by low-pressure chemical-vapor deposition (LPCVD) and atmospheric-pressure chemical-vapor deposition (APCVD), respectively. The sensor array consists of such thin film oxide semiconductor sensing materials as 1 wt.% Pd-doped $SnO_2,\; 6 wt.% A1_2O_3-doped\; ZnO,\; WO_3$/ and ZnO. Baseline resistances of the four sensing materials were found to be stable after the aging for three days at $300^{\circ}C$. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials.

• Resources Recycling
• /
• v.12 no.5
• /
• pp.29-35
• /
• 2003

$\beta$-Sialon is synthesized by carbo-thermal reduction and nitriding (CTRN) method, using the Fly ash from power plant. $\beta$-Siaion is synthesized at $1,450^{\circ}C$ for 10 hours, and sintered at $1,550 ^{\circ}C$ for 3 hours in nitrogen atmosphere. The XRD analytical results show that the sintered $\beta$-Sialon contains $SiO_2$ and $FeSi_{x}$ of inter-metallic compound. The sintered $\beta$-Sialon is stable against the oxidation at the temperature of 1,31$0^{\circ}C$ for 20 hours. The weight of the sample increases rapidly by oxidation reaction at $1,360^{\circ}C$. The oxide scale is consisted with mullite phase when it is oxidized at the temperature of $1,360 ^{\circ}C$ for 10 hours.

• Polymer(Korea)
• /
• v.25 no.6
• /
• pp.866-875
• /
• 2001

In this work, thermal decomposition mechanism based on kinetic parameters and thermal stability of carbon fiber-reinforced carbon matrix composites (C/C composites), have been studied under high temperature oxidative conditions with addition of tetra-ethylorthosilicate (TEOS) as an oxidation inhibitor. Thermogravimetric analysis (TGA) was executed to evaluate the thermal decomposition mechanism and thermal stability of C/C composites in the temperature range of 30 ～ $850^{\circ}C$. As a result, the kinetic parameters of the composites impregnated with TEOS, i.e., activation energy for thermal decomposition ($E_d$), order of reaction (n) , and pre-exponential factor (A) were evaluated as 136 kJ/mol, 0, and 2.3$\times$$10^9s^{-1}$, respectively. Especially, the IPDT and $E_d$ of C/C composites impregnated with TEOS were improved largely compared with the composites impregnated without TEOS, due to the formation of $SiO_2$ on composite surfaces, resulting in interrupting the oxygen attack to carbon active site in the composites.

• Journal of the Korean Vacuum Society
• /
• v.21 no.5
• /
• pp.242-248
• /
• 2012

Valence band of a vacuum-reduced $TiO_2$ (001) surface has been carefully examined using synchrotron x-ray photoelectron spectroscopy to investigate variation of the gap state upon oxidation and thermal diffusion of $Ti^{3+}$ interstitials from the bulk. We compare our results with that obtained from $TiO_2$ (110) and aim to address a crystal-face dependency in the oxidation and diffusion rates of $Ti^{3+}$ interstitials. We find very similar behaviors in the oxidation and thermal diffusion rate of $Ti^{3+}$ interstitials between the two crystal faces suggesting a negligible crystal-face dependency in this case.