• Journal of Magnetics
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• 제14권4호
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• pp.150-154
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• 2009

The effect of Ga and, Nb addition on the kinetics and mechanism of the disproportionation of a Nd-Fe-B alloy were investigated by isothermal thermopiezic analysis (TPA) using $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ (x=0 and 0.3, y= 0 and 0.2) alloys. The addition of Ga and Nb retarded the disproportionation kinetics of the Nd-Fe-B alloy significantly, and increased the activation energy of the disproportionation reaction. The disproportionation kinetics of the $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys measured under an initial hydrogen pressure of 0.02 MPa were fitted to a parabolic rate law. This suggested that during the disproportionation of $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys with an initial hydrogen pressure of 0.02 MPa, a continuous disproportionation product is formed and the overall reaction rate is limited by the diffusion of hydrogen atoms (or ions).

• Journal of Microbiology and Biotechnology
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• 제8권3호
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• pp.287-290
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• 1998

Acarbose effectively inhibited the synthesis of dextran, and the inhibition pattern was a noncompetitive type with a $K_i$ value of 1.35 mM. It also inhibited the disproportionation reaction of dextransucrase with isomaltotriose and decreased the efficiency of the maltose acceptor reaction. Increased concentration of dextransucrase or maltose in reaction digests, however, decreased the degree of inhibition by acarbose.

• 한국표면공학회지
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• 제29권5호
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• pp.478-481
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• 1996

Disproportionation reaction is very important and interesting reaction to be applied to such surface treatment as metal, alloy, compound coating, a surface etching and so on. In gaseous system, the reaction of Al chloride is applied to Al and Al alloy coating, and the similar reaction of Ti chloride is also used for Ti, Ti alloy and Ti compound coating. As for aqueous system, this reaction is utilized to such metal coat as Sn etc. and metal etching such as Cu, Fe and so on. Also in molten salts system, this reaction has many application for surface treatment like metal, alloy and compound coatings for corrosion, wear, heat resistance and so forth. For instance, carbide film, nitride film, boride film, alloy film, quite new different film from the components of substrate material are coated in single and multiple component film system by the disproportionation reaction.

• 한국분말재료학회지
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• 제17권1호
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• pp.23-28
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• 2010

HDDR treated anisotropic Nd-Fe-B powders have been widely used for the sheet motors and the sunroof motors of hybrid or electric vehicles, due to their excellent magnetic properties. Microstructural alignment of HDDR treated powders are mostly depending on the hydrogen reaction in disproportionation step, so the specific method to control hydrogenation reaction is required for improving magnetic properties. In disproportionation step, hydrogenation pressure and reaction time were controlled in the range of 0.15~1.0 atm for 15~180 min in order to control the micorstructural alignment of $Nd_2Fe_{14}B$ phase and, at the same time, to improve remanence of HDDR treated magnet powders. In this study, we could obtain a well aligned anisotropic Nd-Fe-B-Ga-Nb alloy powder having high remanence of 12 kG by reducing hydrogen pressure down to 0.3 atm in disproportionation step.

• Journal of Magnetics
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• 제15권4호
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• pp.155-158
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• 2010

The HDDR (hydrogenation, disproportionation, desorption, and recombination) process can be used as an effective way of converting a no coercivity Nd-Fe-B ingot material, with a coarse $Nd_2Fe_{14}B$ grain structure, to a highly coercive one with a fine grain structure. Careful control of the HDDR process can lead to an anisotropic powder with good $Nd_2Fe_{14}B$ grain texture; the most critical step for inducing texture is disproportionation. The critical conditions (hydrogen pressure and temperature) for the disproportionation reaction of fully hydrogenated $Nd_{12.5}Fe_{81.1-(x+y)}B_{6.4}Ga_xNb_y$ (x = 0 or 0.3, y = 0 or 0.2) alloys, in different atmospheres of pure hydrogen and a mixed gas of hydrogen and argon, was investigated with TPA (thermopiezic analyser). From this, the hydrogen pressure-temperature diagram showing the critical conditions was established. The critical disproportionation temperature of the fully hydrogenated $Nd_{12.5}Fe_{81.1-(x+y)}B_{6.4}Ga_xNb_y$ alloys was slightly increased as the hydrogen pressure decreased in both pure hydrogen and mixed gas. The critical disproportionation temperature of the hydrogenated alloys was higher in the mixed gas than in pure hydrogen. Addition of Ga and Nb increased the critical disproportionation temperature of the fully hydrogenated Nd-Fe-B alloys.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2217-2222
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• 2009

The transition structures for the epoxidations of ethylene and the disproportionations by the dioxiranes of phosphines, phosphites and sulfides were studied with density function theory methods using the Becke3LYP functional and 6-311+G(2d,p) basis set. When the dioxiranes have methyl substituents rather than hydrogen substituents, the reaction barriers ($E_{TS}$) become higher in their epoxidations of ethylene by the steric hindrance, but become lower in their disproportionations of phosphines, phosphites and sulfides, which indicates that the nature of the dioxiranes seems to be electrophilic and in their disproportionations the reaction barriers are effected both by the electrophilicity and the steric hindrance. The steric factors in the disproportionations were calculated and more bulky substituents at dioxiranes may be necessary to retard the disproportionation and to enhance the epoxidation.

• 대한화학회지
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• 제25권3호
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• pp.166-171
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• 1981

알루미늄을 추출시킨뒤 양이온 교환에 의해 세공크기를 조절한 모더나이트 촉매상에서 트리메틸벤젠의 이성질화 반응에 대한 형상선택성을 조사했다. 반응온도가 높아짐에 따라 동종간 주고 받기 반응은 크게 증가했고 이성질화 반응에는 큰 변화가 없었다. 1,2,4-트리메틸벤젠의 반응에서 반응시간이 경과함에 따라 1,3,5-트리메틸벤젠과 동종간 주고 받기 생성물이 급격히 감소하였다. 반응생성물의 분포, 특히 이성질화 생성물의 분포로 미루어보아 Ba-모더나이트 촉매의 유효세공의 지름은 약 8.1과 8.6${\AA}$사이값을 갖는 것으로 생각되었다.

• KSBB Journal
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• 제14권6호
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• pp.713-717
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• 1999

Lipomyces starkeyi ATCC 74054를 UV로 돌연변이하여 선발한 JLC26의 효소적인 특성을 알아보았다. 효소는 70% ammonium sulfate로 침전시키고, CM-Sepharose column chromatography로 부분 정제하였다. 이때 얻어진 각 효소 specific activity는 amylase 활성의 경우는 5367 unit/mg이었고 dextranase 활성의 경우는 3045 unit/mg이었다. 효소의 최적 pH와 온도는 5.5와 37$^{\circ}C$였으며, pH 2.5-5.5와 4-55$^{\circ}C$에서 안정성을 보였다. 부분 정제된 효소는 amylase와 dextranase 활성을 동시에 보이는 100 KDa의 크기를 가지는 하나의 단백질이었다. 이 효소는 maltotriose 기질과 반응할 때 disproportionation reaction 현상을 보여 가지구조를 지닌 panose와 ${\alpha}(1{\rightarrow}6)$glucosylmaltotriose을 생산하였다. 이 균은 starch 배지에서 키워 amylase와 dextranase 활성을 동시에 지니는 효소를 생산함으로써 dextran과 mutan은 구성된 치태를 분해하는 효소재료로의 이용성이 기대된다.

• 충청수학회지
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• 제27권2호
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• pp.319-325
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• 2014

In this paper, we investigate chemical hyperstructures of chemical reactions for iron and indium using hyperstructure theory.

• Journal of Microbiology
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• 제39권4호
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• pp.331-333
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• 2001

The production of oilgosaccharides using Penicillium citrium cells at high sugar concentrations was investigated at 50$\^{C}$ and pH 5.0. Both 1-kestose and neokestose were produced form sucrose, while both nystose and tetrasaccharide were produced from 1-kestose. However, no reaction product was obatined from neogructo-oligosaccharides such as neokestos. Based on these experimental rsults, a hypothetical reaction route was proposed to illustrate how neofructor-oilgosaccharids are formed from 1-kestose.