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DSC and XRD

in contrast, is sensitive both to phase transitions within polymorphs and to polymorphic transformations, and the equipment needed is [Pg.745]

The misinterpretation or underutilization of data obtained using either XRD or DSC alone can be overcome by using both techniques in a given investigation (ten Grotenhuis, 1999). [Pg.746]


Mesomorphic dendrimers containing electroactive units have potential for construction of dendrimer based molecular switches. Deschenaux et al. reported [154] the synthesis and liquid-crystalline properties of a novel dendrimer containing six mesomorphic ferrocene units. Apart from exhibiting a broad enantiotropic smectic A phase as determined by polarized optical microscopy, DSC, and XRD studies, thermogravimetry revealed the excellent thermal stability of the macromolecule. [Pg.64]

Kaneniwa et al. (1988) studied the transformation of phenylbuta eftram to thea-form in ethanol at 4C by DSC and XRD. The reaction was essentially complete in 4 days. Kaneniwa et al. (1985) also studied the transformation kinetics of indomethacin polymorphs in ethanol and Lt the data to nine different kinetic models. The data Ltthe Avrami equation best, which assumes two-dimensional nuclear growth. The transformation ofdfferm to they-form was a function of temperature with an activation energy of 14.2 kcal/mol. [Pg.545]

Even when DSC and XRD are both used, quite separate instruments are involved. This leads to difficulties in reconciling results owing to differences in sample thermal history/conditioning, sample dimensions and sample temperature control and uniformity. These difficulties can be entirely overcome by coupling XRD and DSC together in the same instrument and making both types of measurement simultaneously on the same sample. [Pg.746]

Coupling of DSC and XRD has considerable potential for improving the control of polymorphism in the processing of fat-based foods (Ollivon et al., 2001 Allais et al., 2003). [Pg.746]

Fig. 15 Theoretical phase diagram of PF2/6 as a function of M for T > Tg and the compilation of the corresponding experimental results. M defines low (LMW, M < M ) and Mn high (HMW, Mn > M ) regimes. The solid line shows the theoretical Nem-Hex phase transition. The Hex-Nem transitions based on DSC and XRD measurements are marked by solid triangles and open circles, respectively. The grid-lines correspond to the Mn of experimentally studied materials. The vertical bar at 90-130 °C for Mn = 8 kg/mol shows the position of occasionally seen Hex traces. Reprinted with permission from [24]. (2005) by the American Physical Society... Fig. 15 Theoretical phase diagram of PF2/6 as a function of M for T > Tg and the compilation of the corresponding experimental results. M defines low (LMW, M < M ) and Mn high (HMW, Mn > M ) regimes. The solid line shows the theoretical Nem-Hex phase transition. The Hex-Nem transitions based on DSC and XRD measurements are marked by solid triangles and open circles, respectively. The grid-lines correspond to the Mn of experimentally studied materials. The vertical bar at 90-130 °C for Mn = 8 kg/mol shows the position of occasionally seen Hex traces. Reprinted with permission from [24]. (2005) by the American Physical Society...
To illustrate the interrelationship of these techniques, a summary of the multidisciplinary approach for the characterization of materials is presented. DSC, TGA, and XRD analyses are initially employed to characterize some of the basic physical properties of the material. DSC analysis of several lots of material produces curves that exhibit endothermic maxima at different temperatures, suggesting the existence of multiple crystal forms. Whereas DSC is utilized to identify the thermal properties of these materials, XRD is the definitive technique utilized to determine the presence of crystal forms. If XRD analysis shows that different powder diffraction patterns exist, corroborating evidence has been generated confirming that the lots of material under investigation comprise different crystal forms. In most cases, DSC and XRD... [Pg.240]

The evolution of microstructure with plastic deformation in (3-PP during compression is examined by DSC and XRD techniques. Figure 11.13a and b shows the DSC traces of a-PP and (3-PP specimens after deformation to various... [Pg.320]

It should be stressed that the analytical methods surveyed above achieve their optimum effectiveness and lead to deeper insights into polymorphism and pseudopolymorphism when used in combination. A simple illustration is the combined use of dissolution rate analysis and crystal structure analysis of two polymorphs. Used individually, these techniques would produce merely data, whereas the combined approach could lead to an explanation for the differences in dissolution rates based on differences in crystal packing. Some reported studies utilise a wide range of techniques, permitting a comprehensive analysis of a polymorphic system, while others may use only two, but nevertheless effective, complementary techniques (e.g. DSC and XRD). The following examples selected from the recent literature illustrate this point. [Pg.192]

The diermal decomposition in air of NiC204 2H20, has been investigated [73] by means of TG/DTG-DTA, DSC and XRD. TG/DTG-DTA curves showed that the decomposition proceeds through two well-defined steps with DTA peaks closely corresponding to the mass loss obtained. XRD showed that the final solid decomposition product was NiO. [Pg.458]

Five different TiyCuH compositions were studied by DSC and XRD methods. The exothermic transition temperatures, Tx. kinetic activation energies, E, and heats of transition, AH, were determined from the DSC... [Pg.200]

Lamellar arrangements were detected by polarised light microscopy. DSC and XRD confirmed that chains of emulsifier were in the crystalline state. Ternary systems with liquid paraffin were isotropic, homogenous o/w creams for a wide composition range. Incorporation of 50 mol % cholesterol lead to the separation of a gel-liquid crystalline phase within the layer [174]. The transition energies, derived from DSC, decreased linearly with increasing cholesterol concentration. Optical microscopy should be used to confirm phase separation in creams [175]. [Pg.1006]


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