• 한국분말재료학회지
• /
• 제12권4호
• /
• pp.273-278
• /
• 2005

Nanostructured TiN/$TiB_2$/$TiSi_2$ and TiN/$TiB_2$/$Ti_5Si_2$ composite powders have been prepared by mechanochemical reaction from mixtures of Ti, BN, and $Si_3N_4$ powders. The raw materials have reacted to form a uniform mixture of TiN, $TiB_2$ and $TiSi_2$ or $Ti_5Si_3$ depending on the amount of $Si_3N_4$ used in the starting mixtures, and the reaction proceeded through so-called mechanically activated self-sustaining reaction (MSR). Fine TiN and $TiB_2$ crystallites less than a few tens of nanometer were homogeneously dispersed in the amorphous $TiSi_2$ or $Ti_5Si_3$ matrix after milling for 12 hours. These amorphous matrices became crystalline phases after annealing at high temperatures as expected, but the original microstructure did not change significantly.

• 한국재료학회지
• /
• 제5권7호
• /
• pp.869-879
• /
• 1995

TiAi intermetallic compound has been extensively studied for possible high temperature structural applications because of its high specific strength at high temperature, high creep resistance, and good oxidation resistance at elevated temperatures. In addition to its good properties, an economic manufacturing routes should be developed for this material to be used more extensively. One of the promising route in manufacturing TiAl intermetallics is the Self-propagating High-temperature Synthesis (SHS) method. Thus in this study, an attempt was made to study the mechanism of the SHS process in TiAl synthesis. The composition of the sample was Ti-(45, 50, 53)at% Al and the microstuctures of the products were analyzed using optical microscope and scanning electron microscope. When the phases formed at the main SHS reaction of whicyh combustion temperature is higher than the melting temperature of aluminum were identified as TiAl and Ti$_3$Al ; Ti$_3$Al cores surrounded by TiAl phase. In order to increase the combustion temperature, carbon was added 5 and 10at.%. When the carbon content was 10at.%, the heat of the reaction was large enough to melt the phase formed and that is consistent with the theoretical calculation results of the adiabatic temperature. The combution temperatue, which was measured by a computer data acquisition system, increased with the carbon content. The phases formed from the reaction involving the carbon added were indentified as TiAl and Ti$_2$AlC using XRD. The vickers hardness of the reaction product increased with the carbon content.

• 한국자기학회지
• /
• 제9권2호
• /
• pp.78-84
• /
• 1999

고온연소합성법(self-propagating high temperature synthesis)을 이용하여(Ni, Zn)Fe2O4 분말을 제조하고 초기 분말의 크기와 산소압에 따른 생성물의 미세조직과 자기적 특성을 조사하였다. (Ni, Zn) 페라이트 분체는 다양한 입도의 Fe, Fe2O3, NiO, ZnO의 원료 분말을 n-hexane 용액에서 습식으로 spex mill을 사용하여 5분 혼합하고 12$0^{\circ}C$ 진공로에서 24시간 건조한 후 0.5~10기압의 산소압에서 고온연소합성 반응으로 제조하였다. 성형 압력이 없는 경우 평균 연소온도와 연소속도는 최대 약 125$0^{\circ}C$와 9.8mm/sec였으며 산소압과 ZnO입도가 감소하면 감소하였다. 고온연소합성된 시료는 다공질 구조를 갖고 있으며 X-선 회절 시험으로 시편들의 spinel구조를 관찰하였다. ZnO입도와 산소압이 증가하면 보자력, 최대자화, 잔류자화, 각형비 및 큐리 온도는 각각 13.24Oe, 43.88emu/g, 1.27emu/g, 0.0034emu/gOe, 37.8$^{\circ}C$에서 11.83Oe, 68.87emu/g, 1.23emu/g, 0.00280emu/gOe, 439.$^{\circ}C$와 7.99Oe, 75.84emu/g, 0.791emu/g, 0.001937emu/gOe, 53.8$^{\circ}C$로 변화하였다. 산소압에 따른 겉보기 활성화에너지를 고려하면 페라이트의 연소합성 반응은 ZnO입도와 산소압에 크게 의존한다.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2005년도 생물공학의 동향(XVI)
• /
• pp.18-18
• /
• 2005

Photoinduced electron transport process in nature such as photoelectric conversion and long-range electron transfer in photosynthetic organisms are known to occur not only very efficiently but also unidirectionally through the functional groups of biomolecules. The basic principles in the development of new functional devices can be inspired from the biological systems such as molecular recognition, electron transfer chain, or photosynthetic reaction center. By mimicking the organization of the biological system, molecular electronic devices can be realized $artificially^{1)}$. The nano-fabrication technology of biomolecules was applied to the development of nano-protein chip for simultaneously analyzing many kinds of proteins as a rapid tool for proteome research. The results showed that the self-assembled protein layer had an influence on the sensitivity of the fabricated bio-surface to the target molecules, which would give us a way to fabricate the nano-protein chip with high sensitivity. The results implicate that the biosurface fabrication using self-assembled protein molecules could be successfully applied to the construction of nanoscale bio-photodiode and nano-protein chip based on electrical detection.

• 한국연소학회지
• /
• 제8권1호
• /
• pp.17-24
• /
• 2003

The conventional regenerative system has a high thermal efficiency as well as energy saving using the high preheated combustion air. in spite of these advantages, it can not avoid high nitric oxide emissions. Recently, flameless combustion has received much attention to solve these problems. In this research, numerical analysis is performed for flow-combustion phenomena in the self regenerative burner. In this analysis we used Fluent 6.0 code. the that is developed for commercial use, Methane gas is used as a fuel and two-step reaction model for methane and Zeldovich mechanism for NO generation are used. the velocity of the preheated combustion air is used as a parameter and we analyze the characteristics of flow-field, temperature distributions and NO emissions. Due to the increased recirculation rate, the maximum temperature of flame is significantly increased and NOx emissions is reduced.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.620-623
• /
• 2001

The peculiarities of using Self-propagating High-temperature Synthesis (SHS) and solid state phase synthesis for production of high temperature superconductor materials are discussed. Oxide superconductors with general formula $ReBa_2$$Cu_3$$O_{7-x}$ (Re= Y, Yb, Sm, Nd) have been made with using barium oxide initial powder instead of traditional barium carbonate. X-ray powder diffraction showed a single phase orthorhombic perovskite structure was produced in all reactions. Phenomena observed during the grinding of the reactant mixture are presented. Mechano-chemical activation - as a pretreatment of the reactant mixture - strongly influences the kinetic parameters, the reaction mechanism, and the composition and structure of the final product.

• 한국전기전자재료학회논문지
• /
• 제15권3호
• /
• pp.275-280
• /
• 2002

The peculiarities of using Self-propagating High-temperature Synthesis (SHS) and solid-stave chase synthesis for production of high temperature superconductor materials were discussed. Oxide superconductors with general formula of $ReBa_2Cu_3O_{7-x}$ (Re=Y, Sm) haute been made by using barium oxide initial powder instead of traditional barium carbonate. Phenomena observed during the grinding of the reactants mixture are presented. Mechano-chemical activation - as a pre-treatment of the reactants mixture - strongly influences the kinetic parameters, the reaction mechanism, and the composition and structure of the final product.

• 자원리싸이클링
• /
• 제12권6호
• /
• pp.3-7
• /
• 2003

산화철의 제조에는 기존의 습식화학제조법과 건식화학제조법이 있는데, 모두 환경에 영향을 미치는 화학물질을 대량으로 사용하여 산화철을 제조하는 기술이다. 본 기술보고에서는 환경친화적 제조법으로 스크랩을 원료로 박테리아를 이용하여 산화철을 제조하는 생화학적 기술과 자전고온합성법을 이용하여 산화철을 제조하는 신개념의 산화철제조 기술을 소개하였다.

• Macromolecular Research
• /
• 제17권12호
• /
• pp.987-994
• /
• 2009

Palladium nanoparticles having cubic silsesquioxanes (POSS) (Pd-POSS) were produced by the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$ in methanol at room temperature. Functionalized multiwalled carbon nanotubes (MWNT-COOH) were prepared by acid treatment of pristine MWNTs. The hybrid nanocomposites of Pd-POSS and MWNT-COOH (Pd-MWNT nanocomposites) were synthesized by self-assembly method via ionic interaction between positively charged Pd-POSS and negatively charged MWNT-$COO^-$. The spherical aggregates of Pd-POSS with a diameter of 40-60 urn were well attached to the surfaces of MWNT-COOH on Silicon wafer. The composition, structure, and surface morphology of Pd-MWNT nanocomposites were studied by UV-vis spectrophotometer, energy dispersive spectrum (EDX), scanning electron microscopy (SEM), and atomic force microscope (AFM).

• Nuclear Engineering and Technology
• /
• 제46권3호
• /
• pp.281-290
• /
• 2014

In order to properly quantify fission reactor neutronics parameter uncertainties, we have to use covariance data and sensitivity profiles consistently. In the present paper, we establish two consistent methodologies for uncertainty quantification: a self-shielded cross section-based consistent methodology and an infinitely-diluted cross section-based consistent methodology. With these methodologies and the covariance data of uranium-238 nuclear data given in JENDL-3.3, we quantify uncertainties of infinite neutron multiplication factors of light water reactor and fast reactor fuel cells. While an inconsistent methodology gives results which depend on the energy group structure of neutron flux and neutron-nuclide reaction cross section representation, both the consistent methodologies give fair results with no such dependences.