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Limin Wang - One of the best experts on this subject based on the ideXlab platform.
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direct determination of kinetic fragility indices of glassforming liquids by differential scanning calorimetry kinetic versus thermodynamic fragilities
Journal of Chemical Physics, 2002Co-Authors: Limin Wang, V Velikov, Charles AngellAbstract:A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. “Steepness indexes” m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50–150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its Nitrogen Derivative decahydroisoquinoline, and find the latter two to be th...
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direct determination of kinetic fragility indices of glassforming liquids by differential scanning calorimetry kinetic versus thermodynamic fragilities
Journal of Chemical Physics, 2002Co-Authors: Limin Wang, V Velikov, C A AngellAbstract:A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. “Steepness indexes” m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50–150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its Nitrogen Derivative decahydroisoquinoline, and find the latter two to be the most fragile liquids known, m =145 and 128 respectively. Surprisingly, of the liquids studied, decalin has the smallest increase in heat capacity at the glass transition. By contrast, the strongest liquid, glycerol, has the largest increase. However, the thermodynamic fragility of decalin, assessed from the scaled rate of increase of the excess entropy above Tg, is found to be high, due to the unusually small value of the excess entropy at Tg. Conversely, the entropy-based fragility for glycerol is the lowest. Thus the correlation of kinetic and entropy-based thermodynamic fragilities reported in recent work is upheld by data from the present study, while the basis for any correlation with the jump in heat capacity itself is removed.
C A Angell - One of the best experts on this subject based on the ideXlab platform.
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direct determination of kinetic fragility indices of glassforming liquids by differential scanning calorimetry kinetic versus thermodynamic fragilities
Journal of Chemical Physics, 2002Co-Authors: Limin Wang, V Velikov, C A AngellAbstract:A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. “Steepness indexes” m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50–150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its Nitrogen Derivative decahydroisoquinoline, and find the latter two to be the most fragile liquids known, m =145 and 128 respectively. Surprisingly, of the liquids studied, decalin has the smallest increase in heat capacity at the glass transition. By contrast, the strongest liquid, glycerol, has the largest increase. However, the thermodynamic fragility of decalin, assessed from the scaled rate of increase of the excess entropy above Tg, is found to be high, due to the unusually small value of the excess entropy at Tg. Conversely, the entropy-based fragility for glycerol is the lowest. Thus the correlation of kinetic and entropy-based thermodynamic fragilities reported in recent work is upheld by data from the present study, while the basis for any correlation with the jump in heat capacity itself is removed.
V Velikov - One of the best experts on this subject based on the ideXlab platform.
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direct determination of kinetic fragility indices of glassforming liquids by differential scanning calorimetry kinetic versus thermodynamic fragilities
Journal of Chemical Physics, 2002Co-Authors: Limin Wang, V Velikov, Charles AngellAbstract:A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. “Steepness indexes” m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50–150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its Nitrogen Derivative decahydroisoquinoline, and find the latter two to be th...
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direct determination of kinetic fragility indices of glassforming liquids by differential scanning calorimetry kinetic versus thermodynamic fragilities
Journal of Chemical Physics, 2002Co-Authors: Limin Wang, V Velikov, C A AngellAbstract:A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. “Steepness indexes” m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50–150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its Nitrogen Derivative decahydroisoquinoline, and find the latter two to be the most fragile liquids known, m =145 and 128 respectively. Surprisingly, of the liquids studied, decalin has the smallest increase in heat capacity at the glass transition. By contrast, the strongest liquid, glycerol, has the largest increase. However, the thermodynamic fragility of decalin, assessed from the scaled rate of increase of the excess entropy above Tg, is found to be high, due to the unusually small value of the excess entropy at Tg. Conversely, the entropy-based fragility for glycerol is the lowest. Thus the correlation of kinetic and entropy-based thermodynamic fragilities reported in recent work is upheld by data from the present study, while the basis for any correlation with the jump in heat capacity itself is removed.
Charles Angell - One of the best experts on this subject based on the ideXlab platform.
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direct determination of kinetic fragility indices of glassforming liquids by differential scanning calorimetry kinetic versus thermodynamic fragilities
Journal of Chemical Physics, 2002Co-Authors: Limin Wang, V Velikov, Charles AngellAbstract:A calorimetric method of obtaining directly the fragility of liquids from the fictive temperatures of variably quenched glasses, is outlined. “Steepness indexes” m, have been determined for a group of molecular liquids of diverse character, and vary in the range 50–150. The values obtained mostly agree well with those from earlier studies using dielectric relaxation, heat capacity spectroscopy, and viscosity data. In our method there is the advantage that the fragility is determined from the relaxation process that is basic to the calorimetric glass transition temperature measurement, namely, that of the enthalpy. The calorimetric measurements also yield the liquid and glass heat capacities, and entropies of fusion, permitting relationships between thermodynamic and kinetic responses to be examined simultaneously. We study glycerol, dibutylphthallate, 9-bromophenanthrene, salol, orthoterphenyl, propylene carbonate, decalin and its Nitrogen Derivative decahydroisoquinoline, and find the latter two to be th...
Dias G.h.m. - One of the best experts on this subject based on the ideXlab platform.
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Synthesis Of The Iron(ii)-Nitrogen Complex: Concepts Of Reactivity And Back-bonding For Undergraduate Chemistry Students [síntese De Complexo Ferro(ii)-nitrogênio: Abordagem Dos Conceitos De Reatividade E Retro-doação Para Alunos De Graduação Em Química]
2015Co-Authors: Pissetti F.l., Nono R.s., Gushikem Y., Dias G.h.m.Abstract:There has been a considerable interest in coordination complexes of molecular Nitrogen (N2), partly due to a possible relationship between such complexes and the Nitrogen activation process in nature. The present paper describes the synthesis and infrared spectroscopic characterization of an iron-Nitrogen Derivative with ethylenediamine-N,N, N′,N′-tetraacetate (edta) as an experiment for an undergraduate course. The topics covered here include synthesis, reactivity and spectroscopy
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Synthesis Of The Iron(ii)-Nitrogen Complex: Concepts Of Reactivity And Back-bonding For Undergraduate Chemistry Students [síntese De Complexo Ferro(ii)-nitrogênio: Abordagem Dos Conceitos De Reatividade E Retro-doação Para Alunos De Graduação Em Química]
2015Co-Authors: Pissetti F.l., Nono R.s., Gushikem Y., Dias G.h.m.Abstract:There has been a considerable interest in coordination complexes of molecular Nitrogen (N2), partly due to a possible relationship between such complexes and the Nitrogen activation process in nature. The present paper describes the synthesis and infrared spectroscopic characterization of an iron-Nitrogen Derivative with ethylenediamine-N,N, N′,N′-tetraacetate (edta) as an experiment for an undergraduate course. The topics covered here include synthesis, reactivity and spectroscopy.303723726Yandulov, D.M., Schrock, R.R., (2003) Science, 301, p. 76Hidai, M., (1999) Coord. Chem. Rev, 186, p. 99Allen, A.D., Senoff, C.V., (1965) J. Chem. Soc., Chem. Commun, p. 621Senoff, C.V., (1990) J. Chem. Educ, 67, p. 368Fryzuk, M.D., Johnson, S.A., (2000) Coord. Chem. Rev, 200, p. 379Pool, J.A., Lobkovsky, E., Chirik, P.J., (2004) Nature, 427, p. 527MacLachlan, E.A., Fryzuk, M.D., (2006) Organometallics, 25, p. 1550Shriver, D.F., Atkins, P.W., Langford, C.H., (1990) Inorganic Chemistry, , Oxford University Press: OxfordTuczek, F., Lehnert, N., (1998) Angew. Chem., Int. Ed, 37, p. 2636Bassalote, M.G., Lopez-Alcala, J.M., Vizcaino, M.C.P., Gonzalez-Vilchez, F., (1986) Inorg. Synth, 24, p. 207Nakamoto, K., (1997) Infrared and Raman Spectra of Inorganic and Coordination Compounds, , 5th ed, John Wiley & Sons: New YorkLopez-Alcala, J.M., Puerta, M.C., Gonzalez-Vilchez, F., (1984) Polyhedron, 3, p. 623Chatt, J., Dilworth, R., Richards, R.L., (1978) Chem. Rev, 78, p. 6Gushikem, Y., (2005) Quim. Nova, 28, p. 15