• 한국주조공학회지
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• 제5권3호
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• pp.13-18
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• 1985

Decarburization phenomena were investigated at $800^{\circ}C$ by the $PH_2O/PH_2$ + Ar gas mixture in the case iron range which contains Si, Mn and Cr as an alloying elements. Dissociation of cementite in a matrix which contains graphitizer as Si begins at the carbon rich cementite dendrite arms. Several primary austenite $({\gamma})$ skeletons are surrounded by those nucleated graphite nodules, and that forms a limited area of nucleation region. Decarburization reactions at $800^{\circ}C$ in Fe-C, Fe-Mn-C and Fe-Cr-C alloy are followed by parabolic rate law under the gas mixture of $PH_2O/PH_2=0.01$ and the modified rate const. ${\kappa}$ were in the range of $1{\sim}6{\times}10^{-10}cm^2/s$.

• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.3973-3978
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• 2011

The reductive pinacol coupling reaction of aldehydes or ketones creating a new C-C bond has been a major tool to produce 1,2-diol compounds. The reaction mechanism is known to be composed of sequential three steps (activation, coupling, and dissociation). In this work, we studied the dissociation step of half-titanocene-based catalytic systems. Cp and $Cp^*$ derivatives of the pinacolato-bridged dinuclear complex were synthesized and evaluated as possible models for intermediates from the coupling step. We monitored $^1H$-NMR spectra of the reaction between the metalla-pinacol intermediates and $D_2O$. New reaction routes of the dissociation step including oxo- and pinacolato-dibridged dinuclear complexes and oxo-bridged multinuclear complexes have been suggested.

• 대한화학회지
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• 제27권5호
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• pp.311-319
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• 1983

Anilinium ion, o-toluidinium ion, phenol 및 o-chlorophenol의 해리상수를 10∼40$^{\circ}C$온도범위와 1~2000 bar의 압력범위에서 분광광도법으로 측정하였다. phenols에서는 일반적인 약산에서처럼 온도와 압력이 증가할수록 해리상수가 증가하였으나 anilinium ions의 해리상수는 온도가 증가할수록 증가하였고, 압력이 증가할수록 감소하였다. 해리상수의 압력이 증가할수록 해리상수가 증가하나 anilinium ions와 같이 하전의 증감이 없으면 해리상수는 감소한다. 이들 해리상수값에서 열역학적 파라미터, ${\Delta}H^{circ}$,${\Delta}G^{circ}$, ${\Delta}S^{circ}$,${\Delta}V^{circ}$ 및 ${\beta}$를 계산하고 해리반응의 성질을 고찰하였다.

• 대한화학회지
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• 제31권5호
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• pp.400-405
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• 1987

세가지 아미노산 즉 글리신, 알라닌 및 트립토판의 두가지 해리상수를 전도도법을 이용하여 온도(15 ~ 35$^{\circ}$C)와 압력(1~2,500bar)을 변화시키면서 측정하였다. 두가지 해리상수는 온도가 높아지면 모두 증가했으나 압력이 높아지면 첫째 해리상수는 증가하고 둘째 해리상수는 트립토판을 제외하면 감소하였다. 이와같은 현상은 반응의 열역학적 성질을 이용하여 설명하였으며 나아가서 반응의 특성을 알아보기 위해서 Hammett의 법칙을 적용하고 반응의 치환기 상수와 압력에 따른 반응상수를 계산하였다. 아미노산의 해리상수의 특성을 치환 효과로 설명하였고 반응의 유형을 반응상수로서 알아보았다.

• 한국세라믹학회지
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• 제32권11호
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• pp.1255-1261
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• 1995

Mullite-spinel-zirconia composites were prepared by reaction sintering of calcined alumina and magnesia, and zircon powders. The influence of calcining temperature on densification processes and on mechaical properties of subsequently sintered compacts was investigated. The mullite was formed by the reaction of $\alpha$-Al2O3 and amorphous SiO2 at firing temperatures over 141$0^{\circ}C$. The mullitization proceeded more rapidly in the specimen calcined at 110$0^{\circ}C$ than at either 120$0^{\circ}C$ or 130$0^{\circ}C$. Microstructures before and after the mullitization (or mullite dissociation) showed different morphologies, and their effects on mechanical properties were significant. The flexural strength and fracture toughness of the specimen calcined at 130$0^{\circ}C$ and subsequently fired at 145$0^{\circ}C$ were 316 MPa and 4.2Mpa.m1/2, respectively.

• 대한화학회지
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• 제31권5호
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• pp.395-399
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• 1987

루신의 해리상수를 전도도법을 이용하여 온도(15 to 40$^{\circ}$C)와 압력(1~2,500bar)을 변화시키면서 측정했다. 루신의 두가지 해리상수는 온도가 높아지면 모두 증가하였다. 그러나 압력이 높아지면 첫째 해리상수는 증가하였으나 둘째 해리상수는 낮은 온도에서는 감소하고 높은 온도에서는 증가했다. 이들 해리상수를 이용하여 해리반응의 열역학적 성질들을 계산하고 이들 성질로부터 해리반응의 특성을 알아보았다.

• 한국세라믹학회지
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• 제20권1호
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• pp.13-18
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• 1983

The investigations have been carried out to study the characteristics of limestone using in Korean cement industry with prime interests in the dissociation and thermal phase changes of limestone between 90$0^{\circ}C$ and 140$0^{\circ}C$ The range of decomposition temperature of limestone was 840-87$0^{\circ}C$ and it was considered that the temperature was lowered by impurities in the limestone. The more the impurities and the finer the grain size of quartz in limestone the lower temperature was applied in forming $C_2S$ mineral the temperature of about 100$0^{\circ}C$. The major clinker minerals such as $C_3S$, $C_2S$, $C_3A$ and $C_4AF$ were formed in most of limestone when the firing temperature was up to 130$0^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.267-270
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• 2002

Photodissociations of o-, m-, and p-iodotoluene radical cations were investigated by using Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry. Iodotoluene radical cations were prepared in an ICR cell by a photoionization charge-transfer method. The time-resolved one-photon dissociation spectra were obtained at 532 nm and the identities of $C_7H_7^+$ products were determined by examining their bimolecular reactivities toward toluene-$d_8$. The two-photon dissociation spectra were also recorded in the wavelength range 615-670 nm. The laser power dependence, the temporal variation, and the identities of $C_7H_7^+$ were examined at 640 nm. The mechanism of unimolecular dissociation of iodotoluene radical cations is elucidated: the lowest barrier rearrangement channel leads exclusively to the formation of the benzyl cation, whereas the direct C-I cleavage channel yields the tolyl cations that rearrange to both benzyl and tropylium cations with dissimilar branching ratios among o-, m-, and p-isomers. With a two-photon energy of 3.87 eV at 640 nm, the direct C-I cleavage channel results in the product branching ratio, [tropylium cation]/[benzyl cation], in descending order, 0.16 for meta >0.09 for ortho >0.05 for para.

• 대한화학회지
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• 제16권2호
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• pp.59-63
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• 1972

In connection with two electron binding energy of each bond of saturated hydrocarbons, C-C bond fission and hydrogen abstraction from C-H bond are discussed by means of two center Huckel method. A beautiful correlation could be noticed between the observed bond dissociation energy and the calculated bond energy except for n-butane. Bond dissociation energies between C-C bond were also related to C-C bond fission. We could also find a very close relation between the relative easiness of hydrogen abstraction and the calculated binding energy of C-H bond. In other words, C-H bonds of tertiary hydrogen have been noticed as most weakely bonded and hence the tertiary hydrogen would most easily from the paraffins. In addition, the C-H binding energy is discussed applying ionic character of C-H bond which is derived from its dipole moment (0.4D)

• 대한화학회지
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• 제12권4호
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• pp.150-154
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• 1968

2,3,4-Pentanetrionetrioxime was synthesized from 2,4-pentanedione(or acetylacetone) and its acid dissociation constants were determined in 50%(v/v) dioxane-water solvent mixture at $20{\pm}0.1^{\circ}C$. The color reactions of the ligand with divalent metal ions, Fe(II), Ni(II), Co(II), Cu(II), and Mn(II) were studied.