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Philippe Espeau - One of the best experts on this subject based on the ideXlab platform.
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kinetics of the solid solid transformations for the piracetam trimorphic system incidence on the construction of the p t Equilibrium Phase Diagram
The Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Anne Spasojevic De Bire, Camille Alzina, Nicolas Guiblin, Philippe EspeauAbstract:Abstract The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the (solid + solid) transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
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Kinetics of the solid+solid transformations for the piracetam trimorphic system: Incidence on the construction of the p–T Equilibrium Phase Diagram
Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Camille Alzina, Nicolas Guiblin, Anne Spasojevic - De Biré, Philippe EspeauAbstract:The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the solid-solid transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
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Kinetics of the (solid + solid) transformations for the piracetam trimorphic system: Incidence on the construction of the p–T Equilibrium Phase Diagram
The Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Anne Spasojevic De Bire, Camille Alzina, Nicolas Guiblin, Philippe EspeauAbstract:Abstract The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the (solid + solid) transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
Yohann Corvis - One of the best experts on this subject based on the ideXlab platform.
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kinetics of the solid solid transformations for the piracetam trimorphic system incidence on the construction of the p t Equilibrium Phase Diagram
The Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Anne Spasojevic De Bire, Camille Alzina, Nicolas Guiblin, Philippe EspeauAbstract:Abstract The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the (solid + solid) transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
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Kinetics of the solid+solid transformations for the piracetam trimorphic system: Incidence on the construction of the p–T Equilibrium Phase Diagram
Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Camille Alzina, Nicolas Guiblin, Anne Spasojevic - De Biré, Philippe EspeauAbstract:The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the solid-solid transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
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Kinetics of the (solid + solid) transformations for the piracetam trimorphic system: Incidence on the construction of the p–T Equilibrium Phase Diagram
The Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Anne Spasojevic De Bire, Camille Alzina, Nicolas Guiblin, Philippe EspeauAbstract:Abstract The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the (solid + solid) transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
Nicolas Guiblin - One of the best experts on this subject based on the ideXlab platform.
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kinetics of the solid solid transformations for the piracetam trimorphic system incidence on the construction of the p t Equilibrium Phase Diagram
The Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Anne Spasojevic De Bire, Camille Alzina, Nicolas Guiblin, Philippe EspeauAbstract:Abstract The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the (solid + solid) transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
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Kinetics of the solid+solid transformations for the piracetam trimorphic system: Incidence on the construction of the p–T Equilibrium Phase Diagram
Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Camille Alzina, Nicolas Guiblin, Anne Spasojevic - De Biré, Philippe EspeauAbstract:The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the solid-solid transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
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Kinetics of the (solid + solid) transformations for the piracetam trimorphic system: Incidence on the construction of the p–T Equilibrium Phase Diagram
The Journal of Chemical Thermodynamics, 2016Co-Authors: Yohann Corvis, Anne Spasojevic De Bire, Camille Alzina, Nicolas Guiblin, Philippe EspeauAbstract:Abstract The three common polymorphs of piracetam have been characterized by associating thermal analysis, X-ray diffraction and densimetry. DSC experiments showed that the (solid + solid) transition temperature between Forms II and I and between Forms III and I is scan-rate dependent. The transition temperatures decrease when the DSC scan rate decreases and the thermodynamic temperatures were confirmed by isothermal X-ray diffraction. These new results in terms of temperature and enthalpy of transition allow us to propose a new Equilibrium Phase Diagram establishing the relative thermodynamic stability of the three common polymorphs of piracetam as a function of the temperature and the pressure. The Diagram suggests that Form II presents a small stability domain located just above the stability domain of Form I. As a consequence, Form I should transform into Form II, which itself can turn into Form III when placed under pressure.
P. Conflant - One of the best experts on this subject based on the ideXlab platform.
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bi17yb7o36 and biybo3 two new compounds from the bi2o3 yb2o3 Equilibrium Phase Diagram determination
Materials Research Bulletin, 2004Co-Authors: Michel Drache, Pascal Roussel, J.p. Wignacourt, P. ConflantAbstract:Abstract Synthesis and thermal behavior investigation of Bi 1− x Yb x O 1.5 materials (0.166 ≤ x ≤ 0.666) have been realized, in order to obtain the low temperature Equilibrium Phases. A plot of the Bi 2 O 3 –Yb 2 O 3 Equilibrium Phase Diagram is proposed. Two new compounds, structurally related to the δ-Bi 2 O 3 variety, are evidenced. Bi 17 Yb 7 O 36 ( x = 0.292) crystallizes in an orthorhombic cell with a = 16.259(2), b = 10.705(1), c = 5.487(1) A. It transforms into the cubic δ-Bi 2 O 3 type variety over 855 °C. Only this cubic form, easily quenchable in a metastable form, was reported up to now as a composition of a δ solid solution domain (δ). A narrow domain of orthorhombic solid solution (e) could exist (0.275 ≤ x ≤ 0.305). A second compound BiYbO 3 crystallizes in a triclinic cell with a = 8.487(1), b = 8.419(1), c = 9.928(1) A, α = 86.03(1), β = 111.29(1), γ = 74.25(1)°. At 970 °C, a peritectoid transformation into a mixture of δ and Yb 2 O 3 -based solid solution (Yb 2 O 3 -s.s.) occurs; this latter disappears at about 1200 °C. This last event is easily reversible on cooling, whereas the first one is very sluggish. Consequently, for the composition domain x > 0.35, the samples cooled from the high temperature are generally constituted of a mixture of δ-type Phase and Yb 2 O 3 -s.s.
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Bi17Yb7O36 and BiYbO3: two new compounds from the Bi2O3–Yb2O3 Equilibrium Phase Diagram determination
Materials Research Bulletin, 2004Co-Authors: Michel Drache, Pascal Roussel, J.p. Wignacourt, P. ConflantAbstract:Abstract Synthesis and thermal behavior investigation of Bi 1− x Yb x O 1.5 materials (0.166 ≤ x ≤ 0.666) have been realized, in order to obtain the low temperature Equilibrium Phases. A plot of the Bi 2 O 3 –Yb 2 O 3 Equilibrium Phase Diagram is proposed. Two new compounds, structurally related to the δ-Bi 2 O 3 variety, are evidenced. Bi 17 Yb 7 O 36 ( x = 0.292) crystallizes in an orthorhombic cell with a = 16.259(2), b = 10.705(1), c = 5.487(1) A. It transforms into the cubic δ-Bi 2 O 3 type variety over 855 °C. Only this cubic form, easily quenchable in a metastable form, was reported up to now as a composition of a δ solid solution domain (δ). A narrow domain of orthorhombic solid solution (e) could exist (0.275 ≤ x ≤ 0.305). A second compound BiYbO 3 crystallizes in a triclinic cell with a = 8.487(1), b = 8.419(1), c = 9.928(1) A, α = 86.03(1), β = 111.29(1), γ = 74.25(1)°. At 970 °C, a peritectoid transformation into a mixture of δ and Yb 2 O 3 -based solid solution (Yb 2 O 3 -s.s.) occurs; this latter disappears at about 1200 °C. This last event is easily reversible on cooling, whereas the first one is very sluggish. Consequently, for the composition domain x > 0.35, the samples cooled from the high temperature are generally constituted of a mixture of δ-type Phase and Yb 2 O 3 -s.s.
Yu. V. Medvedev - One of the best experts on this subject based on the ideXlab platform.
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The chemistry of the compound semiconductor-intrinsic insulator interface
Russian Chemical Reviews, 1994Co-Authors: N. N. Berchenko, Yu. V. MedvedevAbstract:Processes leading to the growth of intrinsic insulators (oxides, sulfides, and fluorides) on the surfaces of semiconductors of the III-V, II-VI, and IV-VI groups as well as their solid solutions are analysed with the aid of classical thermodynamics. Their Phase compositions, found from the Equilibrium Phase Diagram, are compared with the compositions found as a result of experimental studies of the semiconductor-insulator interface. It is shown that there is a relation between the characteristic features of the Equilibrium Phase Diagram (in particular the segregation of a metal or nonmetal at the interface), the type of intrinsic lattice defects, and the electrophisical properties of the interface. The possible ways of creating an ideal compound semiconductor-insulator interface are considered. The bibliography includes 171 references.
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THERMODYNAMIC STABILITY OF GAAS SULFUR PASSIVATION
Applied Physics Letters, 1994Co-Authors: Yu. V. MedvedevAbstract:The solid‐state part of the Ga‐As‐S‐O quaternary Equilibrium Phase Diagram has been established from thermodynamic calculations. It is shown that GaS forms a chemically stable interface with GaAs, while As2S3 tends to react with GaAs and the reaction results in elemental As segregation at the GaAs/native sulfide interface. A recently developed chemical vapor deposition of GaS provides, hence, an ideal chemical passivation of GaAs.