Microstructure and Mechanical Properties of CoCrFeMnNiSnx High‑Entropy Alloys

X. Y. Gu,Y. N. Dong,Y. X. Zhuang,J. Wang 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.3

The objective of this study is to investigate the effect of Sn content on the microstructure and mechanical properties of theCoCrFeMnNiSnxhigh entropy alloys. The microstructure and mechanical properties of the alloys have been studied by X-raydiffraction, scanning electron microscopy, room-temperature compressive tests and Vickers hardness tests. It has been foundthat Sn has a great effect on the microstructure and mechanical properties of the alloys. The CoCrFeMnNi alloy has a simpleFCC phase structure, while a few white precipitations (MnNi2Sn-like) are observed in the Sn0.03and Sn0.07alloys. With furtheradditions of Sn, the microstructure of Sn0.1,Sn0.3and Sn0.5changes to a typical dendrite structure, the dominated dendriteregion has a lattice of FCC structure which is enriched with Cr, Co and Fe, and the interdendritic region is enriched withMn, Ni and Sn. The volume of the MnNi2Sn-like phase increases with Sn content increasing. The addition of Sn enhancesthe formation of the MnNi2Sn-like phase in the CoCrFeMnNiSnxalloys, and improves the hardness and strength of as-castalloys, but reduces the ductility of the alloys. The strengthening mechanism of alloys was solid solution strengthening andformation of the MnNi2Sn-like phase. In the CoCrFeMnNiSn0.03and CoCrFeMnNiSn0.07alloys, the solid solution is thedominant mechanism. With the Sn content increasing, the second phase strengthening is the dominant mechanism.

Correlation of the Rates on Solvolysis of 2,2,2-Trichloroethyl Chloroformate Using the Extended Grunwald-Winstein Equation

고한중,강석진 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.5

The solvolysis rate constants of 2,2,2-trichloroethyl chloroformate (Cl3CCH2OCOCl, 3) in 30 different solvents are well correlated with the extended Grunwald-Winstein equation, using the NT solvent nucleophilicity scale and the YCl solvent ionizing scale, with sensitivity values of 1.28 ± 0.06 and 0.46 ± 0.03 for l and m, respectively. The activation enthalpies (ΔH≠) are 10.1 to 12.8 kcal·mol−1 and the activation entropies (ΔS≠) are −27.8 to −36.8 cal·mol−1·K−1, which is consistent with the proposed bimolecular reaction mechanism. The kinetic solvent isotope effect (kMeOH/kMeOD) of 2.39 is also in accord with SN2 mechanism probably assisted by general-base catalysis.

Kinetic Studies of the Solvolyses of 4-Nitrophenyl Phenyl Thiophosphorochloridate

고한중,강석진 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

Rates of solvolyses of 4-nitrophenyl phenyl thiophosphorochloridate (4-NO2PhOP(S)(Cl)OPh, 1) in ethanol,methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone, and 2,2,2-trifluroethanol (TFE) are reported. Thermodynamic parameters were determined at several temperatures in three representative solvents. The extended Grunwald-Winstein equation was applied to 29 solvents and the correlation coefficient (R) showed 0.959. The sensitivities (l = 1.37 and m = 0.62) are similar to those obtained for diphenyl thiophosphorochloridate ((PhO)2PSCl, 2), diphenyl phosphorochloridate ((PhO)2POCl, 3), diphenyl phosphinic chloride (Ph2POCl, 4), and diphenyl thiophosphinic chloride (Ph2PSCl, 5). The solvolytic reaction mechanism of 4-nitrophenyl phenyl thiophosphorochloridate (1) is suggested to be proceeded a SN2 process as previously reported result. The activation enthalpies are shown as slightly low as ΔH≠ = 9.62 to 11.9 kcal·mol-1 and the activation entropies are shown as slightly high negative value as ΔS≠ = ‒34.1 to ‒44.9 cal·mol-1·K-1 compared to the expected SN2 reaction mechanism. Kinetic solvent isotope effects are accord with a typical SN2 mechanism as shown in the range of 2.41 in MeOH/ MeOD and 2.57 in H2O/D2O solvent mixtures

A Kinetic Study on Solvolysis of Diphenyl Thiophosphorochloridate

고한중,강석진,Dennis N. Kevill 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.2

Rates of solvolyses of diphenyl thiophosphorochloridate ((PhO)2PSCl, 1) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone and 2,2,2-trifluoroethanol (TFE) are reported. For four representative solvents, studies were made at several temperatures and activation parameters were determined. The 30 solvents gave a reasonably precise extended Grunwald-Winstein plot, correlation coefficient (R) of 0.989. The sensitivity values (l = 1.29 and m = 0.64) of diphenyl thiophosphorochloridate ((PhO)2PSCl, 1) were similar to those obtained for diphenyl phosphorochloridate ((PhO)2POCl, 2), diphenylphosphinyl chloride (Ph2POCl, 3) and diphenylthiophosphinyl chloride (Ph2PSCl, 4). As with the previously studied of 3~4 solvolyses, an SN2 pathway is proposed for the solvolyses of diphenyl thiophosphorochloridate (1). The activation parameters, ΔH≠ (= 11.6~13.9 kcal․mol-1) and ΔS≠ (= -32.1 ~ -42.7 cal․mol-1․K-1), were determined, and they were in line with values expected for an SN2 reaction. The large kinetic solvent isotope effects (KSIE, 2.44 in MeOH/MeOD and 3.46 in H2O/D2O) are also well explained by the proposed SN2 mechanism.

Analysis of the Solvolysis of Anthraquinone-2-Carbonyl Chloride in Various Mixed Solvents

고한중,강석진 대한화학회 2018 대한화학회지 Vol.62 No.4

The solvolyses of anthraquinone-2-carbonyl chloride (1) were studied kinetically in 27 pure and various mixed solvents. The analysis using the extended Grunwald-Winstein equation in the solvolyses of anthraquinone-2-carbonyl chloride (1) obtained the l value of 2.11 ± 0.11, the m value of 0.54 ± 0.06, and the correlation coefficient of 0.955. The solvolysis reaction of 1 might proceed via an associative SN2 mechanism enhancing bond making than bond breaking in the transition state (TS). This interpretation is further supported by a relatively large solvent kinetic isotope effect (SKIE, 2.27).

Rate-Product Correlations for the Solvolysis of 5-Nitro-2-Furoyl Chloride

최호준,고한중,Dildar Ali,양기열,구인선 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.10

The solvolysis rate constants of 5-nitro-2-furoyl chloride (5-NO2(C4H2O)-2-COCl, 1) in 27 different solvents are well correlated with the extended Grunwald-Winstein equation, using the NT solvent nucleophilicity scale and YCl solvent ionizing scale, with sensitivity values of 1.20 ± 0.05 and 0.37 ± 0.02 for l and m, respectively. The activation enthalpies (ΔH≠) were 5.63 to 13.0 kcal·mol−1 and the activation entropies (ΔS≠) were −25.9 to −43.4 cal·mol−1·K−1, which is consistent with the proposed bimolecular reaction mechanism. The solvent kinetic isotope effect (SKIE, kMeOH/kMeOD) of 2.65 was also in accord with the SN2 mechanism and was possibly assisted using a general-base catalysis. The product selectivity (S) for solvolysis of 1 in alcohol/water mixtures was 1.2 to 11, which is also consistent with the proposed bimolecular reaction mechanism.

Correlation of Rates of Solvolysis of Diphenylacetyl Chloride Using Extended Grunwald–Winstein Equation

고한중,강석진 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.10

Rate constants for solvolysis involving the displacement of chloride from the carbonyl carbon of diphenylacetyl chloride ((C6H5)2CHCOCl, 1) in ethanol, methanol, aqueous binary mixtures incorporating ethanol, methanol, acetone, 2,2,2-trifluoroethanol (TFE), and 1,1,1,3,3,3-hexafluoro-2-propanol, and binary mixtures of TFE with ethanol are reported. The kinetic data obtained from the reactions in 34 different solvents and solvent mixtures gave an extended Grunwald–Winstein correlation with the l value of 0.76 ± 0.06, the m value of 0.34 ± 0.04, and the correlation coefficient (R2) of 0.932. The appreciable values for both l and m suggest that the bond formation is ahead of the bond breaking with an SN2 mechanism, and the l/m ratio of 2.2 is also in the range of values found for SN2 reaction. This interpretation is further supported by the activation parameters, i.e., relatively small positive ΔH≠ (7.7–16.3 kcal/mol) values and large negative ΔS≠ (−24.6 to −53.4 cal/mol/K) values, and the solvent kinetic isotope effect (1.62).

Rate and Product Studies on the Solvolyses of Allyl Chloroformate

고한중,강석진 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.12

The solvolysis rate constants of allyl chloroformate (CH2=CHCH2OCOCl, 3) in 30 different solvents are well correlated with the extended Grunwald-Winstein equation, using the NT solvent nucleophilicity scale and YCl solvent ionizing scale, with the sensitivity values of 0.93 ± 0.05 and 0.41 ± 0.02 for l and m, respectively. These l and m values can be considered to support a SN2 reaction pathway. The activation enthalpies (ΔH≠) were 12.5 to 13.4 kcal·mol−1 and the activation entropies (ΔS≠) were −34.4 to −37.3 cal·mol−1·K−1, which is also consistent with the proposed bimolecular reaction mechanism. The solvent kinetic isotope effect (SKIE, kMeOH/kMeOD) of 2.16 was also in accord with the SN2 mechanism. The values of product selectivity (S) for the solvolyses of 3 in alcohol/water mixtures was 1.3 to 3.9, which is also consistent with the proposed bimolecular reaction mechanism.

Mechanistic Studies of the Solvolyses of Cyclohexanesulfonyl Chloride

강석진,고한중 대한화학회 2019 대한화학회지 Vol.63 No.4

In this study, the solvolysis of cyclohexanesulfonyl chloride (1) was studied by kinetics in ethanol-water, methanol- water, acetone-water, and 2,2,2-trifluoroethanol (TFE)-water binary solvent systems. The rate constants were applied to the extended Grunwald-Winstein equation, to obtain the values of m = 0.41 and l = 0.81. These values suggested SN2 mechanism in which bond formation is more important than bond breaking in the transition state (TS). Relatively small activation enthalpy values (11.6 to 14.8 kcal·mol-1), the large negative activation entropy values (-29.7 to -38.7 cal·mol-1·K-1) and the solvent kinetic isotope effects (SKIE, 2.29, 2.30), the solvolyses of the cyclohexanesulfonyl chloride (1) proceeds via the SN2 mechanism.

Solvolyses of N-Methyl-N-phenylcarbamoyl Chlorides with Electron Acceptor Substituents in A Queous Binary Mixtures

구인선,안선경,양깅열,고한중,최문호,이익춘,Gu, In Seon,An, Seon Gyeong,Yang, Yeol,Go, Han Jung,Choe, Mun Ho,Lee, Ik Chun Korean Chemical Society 2001 Bulletin of the Korean Chemical Society Vol.22 No.8

Solvolyses of N-methyl-N-phenylcarbamoyl chlorides in aqueous binary mixtures of acetone, ethanol, methanol and in water, D2O, and 50% D2O-CH3OD are investigated at 25.0 $^{\circ}C.$ The Grunwald-Winstein plots of first-ord er rate constants for N-methyl-N-phenylcarbamoyl chlorides with YCl (based on 2-adamantyl chloride) show a dispersion phenomenon. The ring parameter (I) has been shown to give considerable improvement when it is added as an hI term to the original Grunwald-Winstein and extended Grunwald-Winstein correlations for the solvolyses of N-methyl-N-phenylcarbamoyl chlorides. This study has shown that the magnitude of l, m and h values associated with a change of solvent composition is able to predict the dissociative SN2 transition state. The kinetic solvent isotope effects determined in deuterated water are consistent with the proposed mechanism of the general base catalyzed and/or a dissociative SN2 mechanism channel for N-methyl-N-phenylcarbamoyl chlorides solvolyses.