가연성(可燃性)물질의 중량 연소속도 측정에 관한 실험적 연구

박영조,한응교,김상욱,박원영 한국산업안전학회 1987 한국안전학회지 Vol.2 No.1

A study was performed on combustion rates of three kinds of combustible substances under a few different combustion conditions. To measure the combustion rates by meight method, I contrived an apparatus using a sensitive load cell. The experimental results by the combustion tests of various combustible substances shows that the combustion circumstances, eg., air supply condition and the existence of flammable oil. And it is found that the time constant T in case of oil absence is smaller than that in case of oil existence, and the time constant T in case of enforced air-entrained condition is greater that in case of natural air-entrained condition.

The Effect of Processing Variables and Composition on the Nitridation Behavior of Silicon Powder Compact

박영조,김해두,Hyung-Woo Lim,Eugene Choi 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.8

The effect of compositional and procesing variables on a nitriding reaction of silicon powder compact and subsequent post sin-substantially at low temperatures, while the formation of a liquid phase between the nitriding agent and the sintering additive sat a high temperature caused a negative catalyst effect resulting in a decreased nitridation rate. A liquid phase formed by sol elyan additive, however, was found to have no effect on nitridation for the additive amount used in this research. The original si teof a decomposing pore former was loosely filled by a reaction product (Si3N4), which provided a specimen with nitriding gas pas-sage. For SRBSN (Sintered RBSN) specimens of high porosity, only a marginal dimensional change was measured after post sin-tering. Its engineering implication for near-net shaping ability is discussed.

5083-H113 알루미늄合金의 表面균열進展擧動과 균열닫힘 現象

박영조,김정규,신용승,김영운 대한기계학회 1987 대한기계학회논문집 Vol.11 No.2

본 논문에서는 작은 인공결함을 가진 표면균열의 진전거동을 밝히기 위하여 용접성이 좋고 강도도 적당하며 내식성이 좋아 해양구호무재 및 용접구호물재로서 널 리 사용되는 5083-H113 알루미늄합금을 준비하고 이재료의 피로표면균열 진전거동에 미치는 응력비의 영향을 균열닫힘과 함께 검토하였다. The propagation and closure behavior of surface crack initiated at a sharply notched specimens were investigated in 5083-H113 aluminium alloy under constant amplitude of tension load by the unloading elastic compliance method. The crack shape (aspect ratio) was found to be approximately semicircular during the crack was being small and to be changed to semi-elliptical during it was being long. The propagation rate of a surface crack initiated from notch root decelerated with increasing crack length when the crack was small and then accelerated when it was large. The effect of stress ratio was large in lower .DELTA.K range, but the effective stress intensity factor range .DELTA.K$_{eff}$ was found to diminish the difference of the crack propagation rate. By considering the increase in crack closure stress with crack length and examining the microphotographs, plasticity-induced and roughness-induced crack closure mechanisms were predominant in the range of this study.y.

파워디바이스용 고열전도율 질화규소 기판 소재

박영조,고재웅,김진명,이재욱,김해두 한국세라믹학회 2012 세라미스트 Vol.15 No.5

환경정화용 다공성 세라믹스

박영조,윤희숙,이재욱,송인혁,김해두,Park, Yeong-Jo,Yun, Hui-Suk,Lee, Jae-Uk,Song, In-Hyeok,Kim, Hae-Du 재료연구소 2009 機械와 材料 Vol.21 No.2

산업이 고도화 되는 과정에서 필연적으로 환경오염 문제가 발생하고 있는데, 그 중에서도 에너지 고효율화를 위해 고온 고압 등의 극한환경 하의 공정이 증가하면서 다공질 세라믹스를 이용한 촉매기술 또는 포집 분리기술에 대한 필요성이 부각되고 있다. 다공성 세라믹 소재가 유효하게 대응 가능한 대기오염과 관련하여 오염물질 및 오염의 실태를 살펴보고, 각종 다공성 세라믹스의 제조방법과 이에 따른 소재특성을 소개하고 시장의 현황과 전망을 정리하였다. 다공성 세라믹 소재의 활용과 관련해서는 오염물질을 입자상물질과 가스상물질로 대별하여 대표적인 사용처와 소재를 수록하였으며, 차세대 신개념 필터로 연구 중인 반응소결 질화규소에 대해 언급하였다.

Characterization of Pore Structures for Porous Sintered Reaction-Bonded Silicon Nitrides with Varied Pore-Former Content

박영조,송인혁,김해두 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.11

The effect of pore former content on both porosity and pore structure was investigated for porous sintered reaction-bonded silicon nitrides (SRBSNs). A spherical PMMA with d50=8 μm was employed as a pore-former. Its amount ranged from 0 to 30 part. Porous SRBSNs were fabricated by post-sintering at various temperatures where the porosity was controlled at 12~52%. The strong tendency of increasing porosity with PMMA content and decreasing porosity with sintering temperature was observed. Measured pore-channel diameter increased (0.3→1.1 μm) with both PMMA content and sintering temperature. The effect of pore former content on both porosity and pore structure was investigated for porous sintered reaction-bonded silicon nitrides (SRBSNs). A spherical PMMA with d50=8 μm was employed as a pore-former. Its amount ranged from 0 to 30 part. Porous SRBSNs were fabricated by post-sintering at various temperatures where the porosity was controlled at 12~52%. The strong tendency of increasing porosity with PMMA content and decreasing porosity with sintering temperature was observed. Measured pore-channel diameter increased (0.3→1.1 μm) with both PMMA content and sintering temperature.

Fabrication of β-SiAlONs by a Reaction-Bonding Process Followed by Post-Sintering

박영조,노은아,김해두,고재웅 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.5

A cost-effective route to synthesize β-SiAlONs from Si mixtures by reaction bonding followed by post-sintering was investigated. Three different z values, 0.45, 0.92 and 1.87, in Si6-zAlzOzN8-z without excess liquid phase were selected to elucidate the mechanism of SiAlON formation and densification. For RBSN (reaction-bonded silicon nitride) specimens prior to post-sintering, nitridation rates of more than 90% were achieved by multistep heating to 1400℃ in flowing 5%H₂/95%N₂; residual Si was not detected by XRD analysis. An increase in density was acquired with increasing z values in post-sintered specimens, and this tendency was explained by the presence of higher amounts of transient liquid phase at larger z values. Measured z values from the synthesized β-SiAlONs were similar to the values calculated for the starting compositions. Slight deviations in z values between measurements and calculations were rationalized by a reasonable application of the characteristics of the nitriding and post-sintering processes.

The Effect of the Sintering Additives on the Fabrication and Thermal Conductivity of Porous SinteredRBSN

박영조,김해두 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.7

investigated in this study. Regardless of the liquid phase content, elongated large grains of a typical morphology evolved in t hepost-sintered specimens. Phase analysis revealed a complete phase transformation into β-Si3N4 in both porous systems. Oxyni-tride second phases (melilite) precipitated in the latter, while those were free in the former containing less amount of liqui dphase. The post-sintering condition that yielded a favorable microstructure for a filter application was achieved when the spec i-mens were soaked at 1800o 3N4 ceramics is dominated by theporosity more than this factor is influenced by the addition of Al 2O3.

The Effect of Si3N4 Addition on Nitriding and Post-Sintering Behavior of Silicon Powder Mixtures

박영조,고재웅,이재욱,김해두 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.4

Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with Si3N4 content, while the highest extent of nitridation was measured in Si3N4-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the Si3N4-free specimen. On the other hand, pores from the decomposed pore former were retained in the Si3N4-added specimen. Introduction of small Si3N4 particles (d50= 0.3 μm) into a powder compact consisting of large silicon particles (d50= 7 μm) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to Si3N4 size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body.

아버님 보옵소서

박영조 문예운동사 2015 문예운동 Vol.- No.127