Academic literature on the topic 'Polymorphic phase transformation kinetic'
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Journal articles on the topic "Polymorphic phase transformation kinetic"
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Spivak L. V., Kirchanov V. S., and Shchepina N. E. "Polymorphic transformations in iodine titanium." Physics of the Solid State 64, no. 11 (2022): 1784. http://dx.doi.org/10.21883/pss.2022.11.54208.400.
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Based on the analysis of differential scanning calorimetry data, the possibility of classifying the observed endothermic or exothermic transformations as phase transformations of the first oder is considered. Two approaches have been implemented. The first is based on the correspondence between the temperatures of the maximum conversion rate and the temperatures of the extrema on the second derivative of the differential scanning calorimetry signal with respect to temperature. In the second approach, the phase transformation is considered as a kind of kinetic reaction of a chemical process with the determination of some parameters included in the kinetic equations. In this case, the order parameter of such reaction n is obtained from the analysis of the differential scanning calorimetry signal shape in the region of phase transformation registration temperatures. Using the example of experiments carried out during thermal cycling of titanium iodide samples, it is shown that both the first and second approaches make it possible to fairly adequately attribute the processes that cause calorimetric effects on the dependences of differential scanning calorimetry to first-order phase transitions. In particular, the obtained results of differential scanning calorimetry during heating and cooling of iodide titanium show that polymorphic transformations in it are realized by various mechanisms depending on the rate of thermal cycling and the thermal history of the metal. Keywords: activation energy, titanium, calorimetry, polymorphism, structure, approximation.
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Purba, Elida. "DETERMINATION OF REACTION KINETICS USING ONLINE X-RAY DIFFRACTION." Indonesian Journal of Chemistry 8, no. 3 (June 17, 2010): 337–41. http://dx.doi.org/10.22146/ijc.21588.
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X-ray diffraction (XRD) is a powerful technique for the study of polymorphism and polymorphic phase transformations. Monitoring of phase transformation directly has been very limited to-date. The XRD system used in this study was used to determine the rate of transformation of pure glutamic acid a form to b form in a solution mediated phase. On every run starting from the pure a form, the transformation process was monitored continuously at fixed temperature, and separate experiments were performed as a function of temperature. The operating temperature was varied from 36 to 57 °C with 10% w/w solid concentration. Data were taken every 200 seconds until the transformation was completed. This paper is concerned with a study of the transformation of the alpha (a) form of L-glutamic acid (L-GA) to the beta (b) form in order to determine the kinetic reaction. The rate constant (k), activation energy (Ea) and pre-exponential factor (A) were obtained. Sensitivity tests were also carried out to examine minimum detection limit when both a and b present in the mixture. In addition, effect of particle size on XRD patterns was also determined. The results show that XRD gives useful information to observe polymorphism for pharmaceutical industry. Keywords: XRD, polymorphism, glutamic acid, reaction kinetics
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Sadigh, Babak, Luis Zepeda-Ruiz, and Jonathan L. Belof. "Metastable–solid phase diagrams derived from polymorphic solidification kinetics." Proceedings of the National Academy of Sciences 118, no. 9 (February 22, 2021): e2017809118. http://dx.doi.org/10.1073/pnas.2017809118.
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Nonequilibrium processes during solidification can lead to kinetic stabilization of metastable crystal phases. A general framework for predicting the solidification conditions that lead to metastable-phase growth is developed and applied to a model face-centered cubic (fcc) metal that undergoes phase transitions to the body-centered cubic (bcc) as well as the hexagonal close-packed phases at high temperatures and pressures. Large-scale molecular dynamics simulations of ultrarapid freezing show that bcc nucleates and grows well outside of the region of its thermodynamic stability. An extensive study of crystal–liquid equilibria confirms that at any given pressure, there is a multitude of metastable solid phases that can coexist with the liquid phase. We define for every crystal phase, a solid cluster in liquid (SCL) basin, which contains all solid clusters of that phase coexisting with the liquid. A rigorous methodology is developed that allows for practical calculations of nucleation rates into arbitrary SCL basins from the undercooled melt. It is demonstrated that at large undercoolings, phase selections made during the nucleation stage can be undone by kinetic instabilities amid the growth stage. On these bases, a solidification–kinetic phase diagram is drawn for the model fcc system that delimits the conditions for macroscopic grains of metastable bcc phase to grow from the melt. We conclude with a study of unconventional interfacial kinetics at special interfaces, which can bring about heterogeneous multiphase crystal growth. A first-order interfacial phase transformation accompanied by a growth-mode transition is examined.
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An, Ji-Hun, Guang Jin Choi, and Woo-Sik Kim. "Polymorphic and kinetic investigation of adefovir dipivoxil during phase transformation." International Journal of Pharmaceutics 422, no. 1-2 (January 2012): 185–93. http://dx.doi.org/10.1016/j.ijpharm.2011.10.049.
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Хлебникова, Ю. В., Д. П. Родионов, Л. Ю. Егорова, and Т. Р. Суаридзе. "Кристаллографические особенности структуры alpha-фазы гафния и сплавов гафний--титан." Журнал технической физики 89, no. 1 (2019): 86. http://dx.doi.org/10.21883/jtf.2019.01.46968.86-18.
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AbstractThe structure of a hafnium crystal undergoing β → α (bcc → hcp) polymorphic transformation upon gradual cooling and the structure of Hf_55Ti_45 and Hf_30Ti_70 alloys formed under various kinetic conditions of polymorphic transformation are studied. The structure of the α phase in cast hafnium is shown to consist of lath crystals grouped into packets. The misorientations between separate laths in a packet are less than 1°. The Hf–Ti alloys in the cast state exhibit a mixed structure consisting of α-phase crystals of several morphological types. A structure of packet martensite is observed in the Hf–Ti alloys after quenching. Each packet includes laths of several crystallographic orientations. There is no regular alternation of differently orientated laths in the packet. The same set of α-phase orientations within an initial β-phase grain is observed independently of the cooling rate of the Hf–Ti alloys upon β → α polymorphic transformation. The misorientation of substructural elements within an α-phase crystal in the Hf–Ti alloys is ~5° for the cast state and ~2.2° after quenching.
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Kerschhofer, Ljuba, Catherine Dupas, Ming Liu, Thomas G. Sharp, William B. Durham, and David C. Rubie. "Polymorphic transformations between olivine, wadsleyite and ringwoodite: mechanisms of intracrystalline nucleation and the role of elastic strain." Mineralogical Magazine 62, no. 5 (October 1998): 617–38. http://dx.doi.org/10.1180/002646198548016.
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AbstractKinetic models and rate equations for polymorphic reconstructive phase transformations in polycrystalline aggregates are usually based on the assumptions that (a) the product phase nucleates on grain boundaries in the reactant phase and (b) growth rates of the product phase remain constant with time at fixed P-T. Recent observations of experimentally-induced transformations between (Mg,Fe)2SiO4 olivine (α) and its high pressure polymorphs, wadsleyite (β) and ringwoodite (γ), demonstrate that both these assumptions can be invalid, thus complicating the extrapolation of experimental kinetic data. Incoherent grain boundary nucleation appears to have dominated in most previous experimental studies of the α–β–γ transformations because of the use of starting materials with small (<10–20 µm) grain sizes. In contrast, when large (0.6 mm) olivine single crystals are reacted, intracrystalline nucleation of both β and γ becomes the dominant mechanism, particularly when the P-T conditions significantly overstep the equilibrium boundary. At pressures of 18–20 GPa intracrystalline nucleation involves (i) the formation of stacking faults in the olivine, (ii) coherent nucleation of γ-lamellae on these faults and (iii) nucleation of β on γ. In other experiments, intracrystalline nucleation is also observed during the β-γ transformation. In this case coherent nucleation of γ appears to occur at the intersections of dislocations with (010) stacking faults in β, which suggests that the nucleation rate is stress dependent. Reaction rims of β/γ form at the margins of the olivine single crystals by grain boundary nucleation. Measurements of growth distance as a function of time indicate that the growth rate of these rims decreases towards zero as transformation progresses. The growth rate slows because of the decrease in the magnitude of the Gibbs free energy (stored elastic strain energy) that develops as a consequence of the large volume change of transformation. On a longer time scale, growth kinetics may be controlled by viscoelastic relaxation.
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Zeng, Guang, Stuart D. McDonald, Jonathan J. Read, Qinfen Gu, and Kazuhiro Nogita. "Kinetics of the polymorphic phase transformation of Cu6Sn5." Acta Materialia 69 (May 2014): 135–48. http://dx.doi.org/10.1016/j.actamat.2014.01.027.
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Спивак, Л. В., В. С. Кирчанов, and Н. Е. Щепина. "Полиморфные превращения в йодидном титане." Физика твердого тела 64, no. 11 (2022): 1820. http://dx.doi.org/10.21883/ftt.2022.11.53341.400.
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Based on the analysis of differential scanning calorimetry data, the possibility of classifying the observed endothermic or exothermic transformations as phase transformations of the first oder is considered. Two approaches have been implemented. The first is based on the correspondence between the temperatures of the maximum conversion rate and the temperatures of the extrema on the second derivative of the differential scanning calorimetry signal with respect to temperature. In the second approach, the phase transformation is considered as a kind of kinetic reaction of a chemical process with the determination of some parameters included in the kinetic equations. In this case, the order parameter of such reaction n is obtained from the analysis of the differential scanning calorimetry signal shape in the region of phase transformation registration temperatures. Using the example of experiments carried out during thermal cycling of titanium iodide samples, it is shown that both the first and second approaches make it possible to fairly adequately attribute the processes that cause calorimetric effects on the dependences of differential scanning calorimetry to first-order phase transitions. In particular, the obtained results of differential scanning calorimetry during heating and cooling of iodide titanium show that polymorphic transformations in it are realized by various mechanisms depending on the rate of thermal cycling and the thermal history of the metal.
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Botoshansky, M., A. Ellern, N. Gasper, J. O. Henck, and F. H. Herbstein. "Structural, Thermodynamic and Kinetic (Hysteresis) Aspects of the Enantiotropic First-Order Phase Transformations of N-Anilinophthalimide and N-(N'-Methylanilino)phthalimide." Acta Crystallographica Section B Structural Science 54, no. 3 (June 1, 1998): 277–90. http://dx.doi.org/10.1107/s0108768197012135.
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The crystal structures of the orthorhombic and monoclinic polymorphs of N-anilinophthalimide (m.p. of monoclinic polymorph 457 K) have been determined by X-ray diffraction at 293 K and were found to have only small differences between the molecular conformations in the two phases, but quite different molecular arrangements. There is very weak N—H...O hydrogen bonding in the orthorhombic phase and weak N—H...O hydrogen bonding in the monoclinic phase. The thermal motion in the crystals of both phases has been analyzed and their thermal expansion determined. The enthalpies of solution in a number of solvents have been calculated from the solubility measurements of Chattaway & Lambert [(1915), J. Chem. Soc. 107, 1773–1781], which also give the temperature and enthalpy of the enantiotropic `orthorhombic to monoclinic' phase transformation (Tc = 283 K; ΔH transf = 1.54 kJ mol−1). The phase-transformation endotherm in a DSC (differential scanning calorimetry) trace from the orthorhombic polymorph occurs only at ∼310 K on heating and there is no corresponding exotherm on cooling; the DSC trace gives ΔH transf = 1.62 kJ mol−1 and ΔH fus = 26.9 kJ mol−1. This phase transformation is an example of the common type (occurrence ∼95%) where ΔV transf = (V monoclinic − V orthorhombic) is positive. Analogous (but less complete) results have been obtained for the monoclinic and triclinic polymorphs of N-(N′-methylanilino)phthalimide (m.p. of triclinic polymorph 398 K). There were only minor differences between the molecular conformations in the two phases, but the molecular arrangements were quite different. This `monoclinic to triclinic' phase transformation also has ΔV transf = (V triclinic − V monoclinic) positive. The solubility (and other) measurements of Chattaway & Lambert (1915) gave Tc = 328.43 K and ΔH transf = 4.17 kJ mol−1. A DSC trace for the monoclinic crystals shows a broad endotherm at ∼372–376 K on heating, but there is no corresponding exotherm on cooling; ΔH transf = 3.6 kJ mol−1 and ΔH fus = 21.7 kJ mol−1. These two compounds provide further examples of molecular crystals with a large hysteresis in their first-order enantiotropic solid-state phase transformations, the transformation to the high-temperature phase occurring well above Tc and the low-temperature phase not being recovered on cooling below Tc . Presumably the hysteresis must be ascribed to as-yet unknown features of the nucleation processes.
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An, Ji-Hun, Wonno Youn, Alice Kiyonga, Changjin Lim, Minho Park, Young-Ger Suh, Hyung Ryu, Jae Kim, Chun-Woong Park, and Kiwon Jung. "Kinetics of the Solution-Mediated Polymorphic Transformation of the Novel l-Carnitine Orotate Polymorph, Form-II." Pharmaceutics 10, no. 4 (October 1, 2018): 171. http://dx.doi.org/10.3390/pharmaceutics10040171.
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Research studies related to the polymorphs of l-Carnitine orotate (CO), a medication used for the treatment and prevention of liver diseases, are insignificant or almost nonexistent. Accordingly, in the present study, l-Carnitine orotate (CO) was prepared for investigating CO polymorphs. Here, a reactive crystallization was induced by reacting 1g of l-Carn (1 equivalent) and 0.97 g of OA (1 equivalent) in methanol (MeOH); as a result, CO form-I and CO form-II polymorphs were obtained after 1 h and 16 h of stirring, respectively. The characterization of CO polymorphs was carried out utilizing Powder X-ray diffraction (PXRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and solid-state Nuclear Magnetic Resonance Spectroscopy (solid-state CP/MAS 13C-NMR). The solution-mediated polymorphic transformation (SMPT) of CO polymorphs was investigated in MeOH at controlled temperature and fixed rotational speed. The results revealed that CO form-I is a metastable polymorph while CO form-II is a stable polymorph. From the same results, it was confirmed that CO form-I was converted to CO form-II during the polymorphic phase transformation process. Moreover, it was assessed that the increase in temperature and supersaturation level significantly promotes the rate of nucleation, as well as the rate of mass transfer of CO form-II. In addition, nucleation and mass transfer equations were employed for the quantitative determination of SMPT experimental results. Lastly, it was suggested that CO form-II was more thermodynamically stable than CO form-I and that both polymorphs belong to the monotropic system.
Dissertations / Theses on the topic "Polymorphic phase transformation kinetic"
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Svärd, Michael. "Structural, Kinetic and Thermodynamic Aspects of the Crystal Polymorphism of Substituted Monocyclic Aromatic Compounds." Doctoral thesis, KTH, Teknisk strömningslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-33836.
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This work concerns the interrelationship between thermodynamic, kinetic and structural aspects of crystal polymorphism. It is both experimental and theoretical, and limited with respect to compounds to substituted monocyclic aromatics. Two polymorphs of the compound m-aminobenzoic acid have been experimentally isolated and characterized by ATR-FTIR spectroscopy, X-ray powder diffraction and optical microscopy. In addition, two polymorphs of the compound m-hydroxybenzoic acid have been isolated and characterized by ATR-FTIR spectroscopy, high-temperature XRPD, confocal Raman, hot-stage and scanning electron microscopy. For all polymorphs, melting properties and specific heat capacity have been determined calorimetrically, and the solubility in several pure solvents measured at different temperatures with a gravimetric method. The solid-state activity (ideal solubility), and the free energy, enthalpy and entropy of fusion have been determined as functions of temperature for all solid phases through a thermodynamic analysis of multiple experimental data. It is shown that m-aminobenzoic acid is an enantiotropic system, with a stability transition point determined to be located at approximately 156°C, and that the difference in free energy at room temperature between the polymorphs is considerable. It is further shown that m-hydroxybenzoic acid is a monotropic system, with minor differences in free energy, enthalpy and entropy. 1393 primary nucleation experiments have been carried out for both compounds in different series of repeatability experiments, differing with respect to solvent, cooling rate, saturation temperature and solution preparation and pre-treatment. It is found that in the vast majority of experiments, either the stable or the metastable polymorph is obtained in the pure form, and only for a few evaluated experimental conditions does one polymorph crystallize in all experiments. The fact that the polymorphic outcome of a crystallization is the result of the interplay between relative thermodynamic stability and nucleation kinetics, and that it is vital to perform multiple experiments under identical conditions when studying nucleation of polymorphic compounds, is strongly emphasized by the results of this work. The main experimental variable which in this work has been found to affect which polymorph will preferentially crystallize is the solvent. For m-aminobenzoic acid, it is shown how a significantly metastable polymorph can be obtained by choosing a solvent in which nucleation of the stable form is sufficiently obstructed. For m-hydroxybenzoic acid, nucleation of the stable polymorph is promoted in solvents where the solubility is high. It is shown how this partly can be rationalized by analysing solubility data with respect to temperature dependence. By crystallizing solutions differing only with respect to pre-treatment and which polymorph was dissolved, it is found that the immediate thermal and structural history of a solution can have a significant effect on nucleation, affecting the predisposition for overall nucleation as well as which polymorph will preferentially crystallize. A set of polymorphic crystal structures has been compiled from the Cambridge Structural Database. It is found that statistically, about 50% crystallize in the crystallographic space group P21/c. Furthermore, it is found that crystal structures of polymorphs tend to differ significantly with respect to either hydrogen bond network or molecular conformation. Molecular mechanics based Monte Carlo simulated annealing has been used to sample different potential crystal structures corresponding to minima in potential energy with respect to structural degrees of freedom, restricted to one space group, for each of the polymorphic compounds. It is found that all simulations result in very large numbers of predicted structures. About 15% of the predicted structures have excess relative lattice energies of <=10% compared to the most stable predicted structure; a limit verified to reflect maximum lattice energy differences between experimentally observed polymorphs of similar compounds. The number of predicted structures is found to correlate to molecular weight and to the number of rotatable covalent bonds. A close study of two compounds has shown that predicted structures tend to belong to different groups defined by unique hydrogen bond networks, located in well-defined regions in energy/packing space according to the close-packing principle. It is hypothesized that kinetic effects in combination with this structural segregation might affect the number of potential structures that can be realized experimentally. The experimentally determined crystal structures of several compounds have been geometry-optimized (relaxed) to the nearest potential energy minimum using ten different combinations of common potential energy functions (force fields) and techniques for assigning nucleus-centred point charges used in the electrostatic description of the energy. Changes in structural coordinates upon relaxation have been quantified, crystal lattice energies calculated and compared with experimentally determined enthalpies of sublimation, and the energy difference before and after relaxation computed and analysed. It is found that certain combinations of force fields and charge assignment techniques work reasonably well for modelling crystal structures of small aromatics, provided that proper attention is paid to electrostatic description and to how the force field was parameterized. A comparison of energy differences for randomly packed as well as experimentally determined crystal structures before and after relaxation suggests that the potential energy function for the solid state of a small organic molecule is highly undulating with many deep, narrow and steep minima.QC 20110527
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Sheridan, Andrew Keith. "Kinetics and temperature- and pressure-induced polymorphic phase transformations in molecular crystals." Thesis, King's College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322597.
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Chan, Fung Choy. "Powder X-ray diffraction studies of structural and kinetic aspects of polymorphism." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327050.
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Shimobayashi, Norimasa. "High Temperature Transmission Electron Microscopy of the Polymorphic Phase Transformation in Ca-poor Pyroxenes." 京都大学 (Kyoto University), 1989. http://hdl.handle.net/2433/86417.
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Ray, Kamal Kanti. "Characterization of phase state, morphological, mechanical and electrical properties of nano- and macro-dimensional materials." Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/7017.
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The importance of studying the physico-chemical properties of nano-dimensional materials has gained significant attention in the fields of semiconductors, pharmaceuticals, materials science, and atmospheric chemistry owing to the differences in physical properties between macro- and nano-dimensional solids. Nonetheless, direct studies of physical properties of materials at nanoscale is limited in part due to their inherent size constraints and experimental limitations. However, development of atomic force microscopy (AFM) led to the implementation of methods to characterize a wide range of physical properties, including – but not limited to – mechanical properties, electrical properties, viscoelastic properties, and surface tension. Herein, the dissertation focuses on AFM-based method development for characterization of atmospheric particles as well as understanding the relationship between structure and physical properties of organic solids at both macro- and nano-dimensions.
In the atmospheric chemistry realm, the combined aerosol effect on the climate and environment has significant uncertainty in part due to lack of direct characterization of their physico-chemical properties. The difficulty in assessing the physical and chemical properties arises due to the presence of diversified aerosol sources, which in turn influences the size, morphology, phase states and chemical compositions. Sea spray aerosols (SSAs) are the second-largest source of aerosols in the atmosphere. Studying SSAs – especially in submicrometer-dimensions – requires high-resolution microscopy techniques such as AFM. AFM can be used for imaging of individual aerosols, quantifying organic volume fraction for core-shell morphologies, measuring water uptake, quantifying surface tension of individual droplets, and measuring mechanical and viscoelastic properties of materials. Herein, we employed AFM-based morphology and force spectroscopy studies to correlate the 3D morphology, phase state, and viscoelastic properties of selected single-component chemical systems found in sea spray aerosol (SSA). We established a quantitative framework toward differentiation of the solid, semisolid and liquid phase states of individual particles by utilizing both relative indentation depth (RID) and viscoelastic response distance (VRD) data obtained from the force−distance plots. Moreover, we established a semi-quantitative and quick phase assessment by measuring the aspect ratio (AR) that refers the extent of particle spreading as a result of impaction. Overall, the established AFM-based quantitative and semi-quantitative phase identification method can be utilized to assess the phases of aerosols irrespective of chemical identity.
Next, we investigated the factors that may control the electrical and mechanical properties of pharmaceutical and organic semiconducting materials in nano- and macro-dimensions. Understanding the structure-property relationship of materials, especially in the nano-dimension, is necessary for proper drug design and development of organic semiconducting materials. In this context, cocrystals provide a means to modulate the physico-chemical properties of organic solids. For example, the modulation of the mechanical properties is important in the pharmaceutical industry for improving the tabletability. The mechanical properties may be affected by packing arrangement, interaction strength and type, and atomic and chemical composition. Herein, we report the influence of alkane and alkene functional groups on the mechanical properties of organic solids based on salicylic acid (SA). The approach affords both isostructural and polymorphic solids. The isostructural alkane functional solid exhibits a two-fold larger Young’s modulus (YM) compared to the cocrystal with the alkene, where the YM refers to the stiffness of the material. Here, the higher YM values are attributed to the presence of a bifurcated weak C-H···O interactions involving the alkane and neighboring SA molecules. On the other hand, in the case of alkene polymorphisms, molecular packing with column arrangement shows higher YM values compared to the herringbone arrangements. Thus, functional groups and crystal arrangements influence the stiffness of the solid organic cocrystals.
Moreover, we report the modulation of mechanical properties of salicylic acid (SA) through cocrystallization by variation of propane and butane functionality with bipyridine coformers. We show that the variation of propane and butane functionality in bipyridine coformer with salicylic acid leads to synthesis of cocrystal and salt-cocrystal, respectively. The AFM nanoindentation study revealed that the Young’s modulus values follow the order salicylic acid < cocrystal << salt-cocrystal. The highest Young’s modulus values of the salt-cocrystal, among the studied systems, are attributed to the presence of strong N+–H···O– and O–H···O– interactions. On the other hand, higher Young’s modulus values of the propane-based cocrystal compared to the macro-dimensional salicylic acid are attributed to the stronger O–H ···N hydrogen bonding. Thus, homologous alkane functional groups can influence the mechanical properties of the organic solid crystals.
Additionally, in situ solid-solid polymorphic phase transformation and nucleation of a metastable and elusive polymorph of SA cocrystals in combination with 4,4’-bipyridine were studied. Understanding the solid-solid phase transformations and nucleation mechanisms are important for proper control over the parameters associated with the synthesis of targeted crystalline solids with desired crystal structure. Using in situ powder X-ray diffraction (PXRD) and terahertz time domain spectroscopy (THz-TDS) data we showed that the Form II polymorph transforms to Form I over time. AFM imaging and nanoindentation techniques were utilized to follow and quantify in real-time the solid-solid polymorphic transformation of the metastable Form II to the thermodynamically stable Form I on a single crystal basis. AFM in situ single crystal data revealed that the metastable Form II has a rod-shaped morphology and relatively high elasticity (Young’s modulus), which transforms to prism-shaped nanocrystals of much smaller sizes with significantly reduced elasticity. The AFM imaging reveals that the single crystals on the order of 80-150 nm to undergo catastrophic changes in morphology that are consistent with cracking and popping owing to a release of mechanical stress during the transformation. The nucleation mechanism for the polymorphic transformation is not spatially localized and occurs over the entire crystal surface. The higher mechanical properties of the metastable Form II is due to the presence of the additional interlayer C-H···O interactions.
Furthermore, we have studied the electrical properties of boron-based cocrystals. More specifically, cocrystallization of a nonconductive 2,4-difluorophenylboronic ester catechol adduct of a 4,4’-bipyridine (BEA) host with two aromatic semiconducting guests (pyrene and tetrathiafulvalene) generated conductive cocrystals with variable charge carrier mobilities. Charge carrier mobilities of the cocrystals with either pyrene or tetrathiafulvalene were measured using conducting probe AFM (CP-AFM). The incorporation of π-rich aromatic guests through face-to-face and edge-to-face π-contacts results in electrically conductive cocrystals. The cocrystal with tetrathiafulvalene as a guest shows approximately 7 times higher charge carrier mobility than the cocrystal with pyrene.
Overall, the current dissertation demonstrates the AFM-based method development and applications towards materials characterization to measure the morphological, electrical, mechanical, and phase-states at both nano- and macro-dimensions. The high spatial precision of the methods developed enables us to better understand the controlling factors for materials design and processing across nano- and macro-dimensions.
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Venturato, Giulia. "Modelling the Influence of Phase Transformation Kinetics in 22MnB5 Hot Stamping." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3424888.
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Sheet metal forming has gained, over the last years, more and more importance since the automotive industry is demanding very specific characteristic for the new generation of components of the car body-in-white. The requirements of more lightness for enhancing the fuel saving is becoming a key factor for the design of new components, but the lightness must be coupled with a high mechanical resistance to grant the passengers’ safety. One of the most effective ways to meet these requirements has been the use of new generations of High Strength Steels (HSS), whose mechanical properties can be enhanced by thermal treatments. Direct hot stamping has represented an effective solution to do that, due to the possibility to shorten the process chain of many sheet metal parts typical of the car body-in-white. Thinner sheets have been used for the manufacturing of many automotive parts, granting the desired lightness and high resistance, to obtain the crashworthiness necessary to protect the passengers of the vehicle. Hot stamping is, nowadays, widely applied in the automotive industry, but the research in this field is still of high interest between the academic environment. This is because the process involves a large series of parameters that have to be accurately understood to enhance the performances and the complexity of the stamped parts. Since the initial heating to the last quenching step, the material undergoes a series of microstructural and mechanical transformations, whose optimization and right timing govern the final characteristic of the final component. In parallel to the industrial development work, a large branch of academic and scientific research is focused on the numerical modelling of the process which reveals of fundamental importance for the process design and optimization.
The present work stands in the framework of the researches in the field of the hot stamping process. The material investigated in this work is the AluSi® pre-coated quenchable steel 22MnB5, well known with the commercial name of Usibor 1500P®. The complete characterization of this material aims to fill the lack in literature about testing in hot condition the material flow stress of all the microstructural phases, proposing a fitting model capable to describe the mechanical behaviour in the FE models. The formability in hot conditions is studied as well, analysing the effect of the temperature and microstructure on the resultant Forming Limit Curve (FLC). The phase transformation kinetics was studied, confirming the literature and giving the motivation for this work. Finally, the damage criterion Generalized Incremental Stress-State dependent damage MOdel (GISSMO) was calibrated. The whole experimental activity was coupled with numerical simulations, for the necessary data analysis and calibration.
The work presented in this thesis has been carried out at the DII laboratories of the University of Padova, from October 2016 to September 2019 under the supervision of Prof. Andrea Ghiotti. This work was carried out within the framework of the University Research Project “Advanced CAE method to predict failure and material properties in hot forming” ref. 2014-4050 URP Award developed in cooperation with Ford Motor Company GMBH.La deformazione di lamiere sta guadagnando, negli ultimi anni, sempre più importanza dal momento che l’industria automobilistica sta richiedendo caratteristiche molto specifiche per la nuova generazione di componenti per la scocca. Le richieste di leggerezza per aumentare il risparmio di carburante sta diventando un fattore chiave per il design di nuovi componenti, ma la leggerezza deve necessariamente essere accoppiata con l’alta resistenza meccanica per garantire la sicurezza dei passeggeri. Uno dei metodi più efficaci per incontrare tali richieste è stato l’utilizzo della nuova generazione di acciai alto resistenziali (HSS), le cui proprietà meccaniche possono essere migliorate grazie ai trattamenti termici. Lo stampaggio a caldo diretto rappresenta una soluzione efficace per questo scopo, grazie alla possibilità di accorciare la catena di processo di molti componenti metallici della scocca dell’auto. Lamiere più sottili vengono impiegate per la produzione di molte parti dell’auto, garantendo le desiderate leggerezza e alta resistenza, per ottenere la resistenza agli urti necessaria a proteggere i passeggeri del veicolo. Lo stampaggio a caldo è, oggigiorno, ampiamente applicato nell’industria automobilistica, ma la ricerca in questo campo è ancora di alto interesse nell’ambiente accademico. Questo è dovuto al fatto che lo stampaggio a caldo coinvolge un’ampia serie di parametri che devono essere accuratamente compresi per migliorare il potenziale del processo e la complessità delle parti stampate. A partire dal primo stage di riscaldamento all’ultima fase di tempra, il materiale subisce una serie di trasformazioni microstrutturali e meccaniche, la cui ottimizzazione e il loro corretto timing controlla le caratteristiche finali del componente. Parallelamente al lavoro di ricerca sperimentale, una grande branca della ricerca è volta allo studio delle simulazioni numeriche che sono di fondamentale importanza per simulare il processo e ottimizzarne ogni step. Il presente lavoro si inquadra nella ricerca nell’ambito dello stampaggio a caldo. Il materiale studiato in questo lavoro è l’acciaio temprabile 22MnB5 rivestito da AluSi®, conosciuto commercialmente con il nome di Usibor 1500 P®. La completa caratterizzazione del materiale ha come scopo di coprire le mancanze nella letteratura nell’ambito dei test ad alta temperatura sulla reologia di tutte le microstrutture, proponendo un modello di fitting per rappresentare i dati nei modelli FE. La formabilità ad alta temperatura è altresì soggetto di studio, analizzando gli effetti della temperatura e della microstruttura nella risultante curva limite di formabilità (FLC). La cinetica di trasformazione di fase è stata oggetto di studio, confermando i dati presentati in letteratura e fornendo le basi per questo lavoro. Infine, il nuovo modello di danneggiamento Generalized Incremental Stress-State dependent damage MOdel (GISSMO) è stato calibrato. L’intera attività sperimentale è stata affiancata alle simulazioni numeriche, per la necessità dell’analisi e calibrazione dei dati. Il lavoro presentato in questa tesi è stato portato avanti nei laboratori del Dipartimento di Ingegneria Industriale, DII, dell’università di Padova, da ottobre 2016 a settembre 2019 sotto la supervisione del prof. Andrea Ghiotti. Questo lavoro è parte del progetto di ricerca dell’Università chiamato “Advanced CAE method to predict failure and material properties in hot forming” ref. 2014-4050 URP Award, sviluppato in collaborazione con Ford Motor Company GMBH.
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Xiong, Wei. "Thermodynamic and Kinetic Investigation of the Fe-Cr-Ni System Driven by Engineering Applications." Doctoral thesis, KTH, Termodynamisk modellering, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96707.
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This work is a thermodynamic and kinetic study of the Fe-Cr-Ni system as the core of stainless steels. The Fe-Cr, Fe-Ni and Cr-Ni systems were studied intensively using both computational and experimental techniques, including CALPHAD (CALculation of PHAse Diagrams), phase field simulation, ab initio modeling, calorimetry, and atom probe tomography. The purpose of this thesis is to reveal the complexity of the phase transformations in the Fe-Cr-Ni system via the integrated techniques. Due to the importance of the binary Fe-Cr system, it was fully reassessed using the CALPHAD technique by incorporating an updated description of the lattice stability for Fe down to zero kelvin. The improved thermodynamic description was later adopted in a phase field simulation for studying the spinodal decomposition in a series of Fe-Cr binary alloys. Using atom probe tomography and phase field simulation, a new approach to analyze the composition amplitude of the spinodal decomposition was proposed by constructing an amplitude density spectrum. The magnetic phase diagram of the Fe-Ni system was reconstructed according to the results from both ab initio calculations and reported experiments. Based on the Inden-Hillert-Jarl magnetic model, the thermodynamic reassessment of the Fe-Ni system demonstrated the importance of magnetism in thermodynamic and kinetic investigations. Following this, the current magnetic model adopted in the CALPHAD community was further improved. Case studies were performed showing the advantages of the improved magnetic model. Additionally, the phase equilibria of the Fe-Cr-Ni ternary were discussed briefly showing the need of thermodynamic and kinetic studies at low temperatures. The “low temperature CALPHAD” concept was proposed and elucidated in this work showing the importance of low temperature thermodynamics and kinetics for designing the new generation of stainless steels.QC 20120612
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Feng, Zhiyao. "The Deformation-induced Martensitic Phase Transformation in Low Chromium Iron Nitrides at Cryogenic Temperatures." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1526306156203016.
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Moscu, Corcodel Alina. "Structural transformation under reaction conditions of supported PtSn nanoparticles characterized by in situ DRIFTS and kinetic modeling." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10177.
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La réaction d’oxydation sélective du CO par O2 en présence d’un excès d’hydrogène (PROX) est considérée comme une étape de purification essentielle de l’H2 à utiliser dans des piles à combustible. L’objectif de cette thèse est de mieux comprendre le mécanisme de cette réaction sur des catalyseurs bimétallique s à base de Pt et Sn. Des catalyseurs modèles Pt et Pt-Sn ont été synthétisés en deux étapes : (i) formation de nanoparticules (NP) métalliques colloïdales en suspension suivi par ( ii) l’imprégnation de ces particules sur des supports. L’adsorption du CO suivit par spectroscopie FT-IR en réflexion diffuse (DRIFTS) a été utilisée pour caractériser ces solides après une réduction permettant de reformer des phases d’alliage PtSn. L’analyse DRIFTS permet de caractériser la nature des sites de Pt présents, soit dans l’alliage, soit dans des phases pures de Pt. La chaleur d’adsorption du CO sur la phase d’alliage a été mesurée par DRIFTS, pour la première fois, et apparait bien plus faible que celle sur le Pt seul. De manière surprenante, la ségrégation de l’alliage en présence de CO/H 2 à des températures inférieur es à 175°C a été mise en évidence. Des mesures in situ DRIFTS de la réaction d’oxydation préférentielle du CO (PROX) indiquent que l’alliage se transforme rapidement en Pt et SnOx de par la présence de l’O2. Aucune indication de la présence d’alliage n’a jamais pu être obtenue sous PROX, indiquant que les meilleures propriétés catalytiques associés aux phases Pt-Sn sont dues à leur habilité à générer une nouvelle phase active Pt+SnOx lors de leur ségrégation. Un modèle microcinétique du PROX sur Pt+SnOx a été développé sur la base de ceux pertinents à l’oxydation du CO et PROX sur Pt seul, permettant une modélisation satisfaisante des données. Ce travail montre l’intérêt du couplage des méthodes spectroscopiques et cinétiques pour la compréhension de la structure des catalyseurs « au travail » et des mécanismes de réactions complexesThe selective oxidation of CO in the presence of a large excess of H2 (PROX) is considered as a crucial step in the purification of H 2 to be used in low-temperature fuel cells, which are clean sources of energy. The objective of this thesis was to better understand the reaction mechanisms taking place over promising catalysts based on Pt and Sn. Model Pt-Sn catalysts were prepared by a two-step method: (i) synthesis of metallic nanoparticules (NP) in a colloidal suspension followed by (ii) the deposition of these NPs onto a support. The first step of the method enabled to produce well-controlled Pt-Sn NPs in terms of size and composition. However, the NPs were partly destroyed during the deposition step followed by calcination, due to the reoxidation of Sn. The adsorption of CO followed by diffuse reflectance spectroscopy (DRIFTS) was used to characterize the nature of these solids following a reduction, which was able to regenerate an alloyed phase. The DRIFTS analysis enabled to discriminate between Pt in an alloyed phase and Pt on monometallic surfaces. The heat of CO adsorption measured by DRIFTS appeared to be much lower than that associated with the pure Pt phase. Surprinsingly, a segregation of Pt and Sn was observed under a CO/H2 mixture below 175°C. In situ analysis by DRIFTS of the PROX reaction indicated that the Pt-Sn alloy rapidly decomposed in the presence of O2, forming an intimate mixture of Pt and SnOx. No evidence of the presence of Pt -Sn alloyed phases could be obtained under PROX conditions, suggesting that the superior catalytic activity of the Pt –Sn materials were related to the Pt+SnOx mixture. A detailed PROX microkinetic model was developed over Pt+SnOx, based on those relevant to CO oxidation and PROX over pure Pt. This work epitomises the benefits in combining in situ spectroscopic study with kinetic modelling to better understand the structure of catalysts “at work” and reaction mechanisms
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Wang, Bincheng. "Ultrahigh Density Magnetic Recording Media: Quantitative Kinetic Experiments and Models of the A1 to L10 Phase Transformation in FePt and Related Ternary Alloy Films." Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/72.
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L10 ordered FePt continues to be of interest for ultrahigh density magnetic recording media, in particular, heat assisted magnetic recording (HAMR) media. However, when deposited at room temperature, the alloy film forms in the chemically disordered A1 state, requiring a post-deposition anneal at high temperatures or for long times, or deposition onto heated substrates at temperature ≥ 400 °C to form the ordered L10 phase. It has been of interest to identify ternary alloying additions that can reduce the post deposition annealing or the elevated deposition temperatures, and to examine the impact of deposition at elevated temperatures on the transformation kinetics.
Binary and ternary alloy films were sputter deposited from elemental targets at nominally room temperature at two different thicknesses of 1 micron and 500 nm. The latter films were used for composition analysis using energy dispersive X-ray spectrometry (EDS). The transformation from the A1 phase to the L10 phase was studied by differential scanning calorimetry (DSC) using freestanding micron-thick films. The kinetic ordering temperature (KOT), defined as the peak temperature of the DSC trace at a heating rate of 40 °C/min, was used to evaluate the impact of alloy composition and alloying additions on the ordering transformation
The nine ternary alloying elements and composition ranges are: 0.0 - 2.6 at.% Mg, 0.7 – 12.2 at.% V, 2.2 – 16.3 at.% Mn, 1.6 – 21.5 at.% Ni, 1.3 – 17.3 at.% Cu, 0.0 – 16.7 at.% Ag, 1.9 – 13.8 at.% Au, 1.2 – 12.9 at.% B and 1.4 at.% C. Compared with binary FePt, Cu additions have no impact on the (KOT), whereas all the other additions except C result in an increase of KOT. Additional experiments are necessary to better evaluate the impact of C additions. Elevated temperature deposition experiments showed that higher deposition temperatures result in faster transformation only for binary films with > 46 at.% Pt.
The time-temperature-transformation (TTT) and isothermal transformation curves for binary FePt and ternary Fe46.7Cu2.4Pt50.9 films were calculated using the Michaelsen- Dahms (MD), k2(T), k2(T)N(T) and a new continuous nucleation model, k2(T)N(T,t). The model that most closely agrees with all available experimental data is the k2(T) model.
Books on the topic "Polymorphic phase transformation kinetic"
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H, Drummond Charles, and United States. National Aeronautics and Space Administration., eds. Comments on "Kinetic Study on the Hexacelsian-Celsian Phase Transformation". [Washington, DC: National Aeronautics and Space Administration, 1992.
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Bansal, Narottam P. Comments on "Kinetic Study on the Hexacelsian-Celsian Phase Transformation". [Washington, DC: National Aeronautics and Space Administration, 1992.
Find full textBook chapters on the topic "Polymorphic phase transformation kinetic"
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Yoo, Han-Ill. "Kinetics of Phase Transformation: Initial Stage." In Lectures on Kinetic Processes in Materials, 173–214. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-25950-1_5.
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Yoo, Han-Ill. "Kinetics of Phase Transformation: Later Stage." In Lectures on Kinetic Processes in Materials, 215–45. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-25950-1_6.
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Chen, Ying. "Kinetic Monte Carlo Modeling of Martensitic Phase Transformation Dynamics." In Handbook of Materials Modeling, 1265–85. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-319-44677-6_100.
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Chen, Ying. "Kinetic Monte Carlo Modeling of Martensitic Phase Transformation Dynamics." In Handbook of Materials Modeling, 1–21. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-42913-7_100-1.
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Begand, Sabine, Thomas Oberbach, Wilfried Glien, and J. Schneider. "Kinetic of the Phase Transformation of ATZ Compared to Biograde Y-TZP." In Bioceramics 20, 763–66. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-457-x.763.
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"13. Kinetics and hysteresis in high-temperature polymorphic transformations under pressure." In Phase Transitions in Solids Under High Pressure, 357–81. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742: CRC Press, 2013. http://dx.doi.org/10.1201/b15943-15.
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"14. Hysteresis and kinetics of low-temperature polymorphic transformations under pressure." In Phase Transitions in Solids Under High Pressure, 382–423. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742: CRC Press, 2013. http://dx.doi.org/10.1201/b15943-16.
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Fang, H., M. Wong, and Y. Bai. "A new kinetic model for steel specific heat during phase transformation." In From Materials to Structures: Advancement through Innovation, 807–11. CRC Press, 2012. http://dx.doi.org/10.1201/b15320-144.
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Wei, S., and A. W. ,. Jr Castleman. "Reaction Dynamics in Femtosecond and Microsecond Time Windows: Ammonia Clusters as a Paradigm." In Chemical Reactions in Clusters. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195090048.003.0009.
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The last decade has seen tremendous growth in the study of gas phase clusters. Some areas of cluster research which have received considerable attention in this regard include solvation (Lee et al. 1980), (Armirav et al. 1982), and reactivity (Dantus et al. 1991; Khudkar and Zewail 1990; Rosker et al. 1988; Scherer et al. 1987). In particular, studies of the dynamics of formation and dissociation, and the changing properties of clusters at successively higher degrees of aggregation, enable an investigation of the basic mechanisms of nucleation and the continuous transformation of matter from the gas phase to the condensed phase to be probed at the molecular level (Castleman and Keesee 1986a, 1988). In this context, the progressive clustering of a molecule involves energy transfer and redistribution within the molecular system, with attendant processes of unimolecular dissociation taking place between growth steps (Kay and Castleman 1983). Related processes of energy transfer, proton transfer, and dissociation are also operative during the reorientation of molecules about ions produced during the primary ionization event required in detecting clusters via mass spectrometry (Castleman and Keesee 1986b), providing further motivation for studies of the reaction dynamics of clusters (Begemann et al. 1986; Boesl et al 1992; Castleman and Keesee 1987; Echt et al. 1985; Levine and Bernstein 1987; Lifshitz et al. 1990; Lifshitz and Louage 1989, 1990; Märk 1987; Märk and Castleman 1984, 1986; Morgan and Castleman 1989; Stace and Moore 1983; Wei et al. 1990a,b). The real-time probing of cluster reaction dynamics is a facilitating research field through femtosecond pump-probe techniques pioneered by Zewail and coworkers (Dantus et al. 1991; Khundkar and Zewail 1990; Rosker et al. 1988; Scherer et al. 1987). Some real-time investigations have been performed on metal, van der Waals, and hydrogen-bonded clusters by employing these pump-probe spectroscopic techniques. For example, the photoionization and fragmentation of sodium clusters have been investigated by ion mass spectrometry and zero kinetic energy photoelectron spectroscopy in both picosecond (Schreiber et al. 1992) and femtosecond (Baumert et al. 1992, 1993; Bühler et al. 1992) time domains. Studies have also been made to elucidate the effect of solvation on intracluster reactions.
Conference papers on the topic "Polymorphic phase transformation kinetic"
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Chauvin, Camille, Frédéric Zucchini, and David Palma de Barros. "Study on phase transformation in Tin under dynamic compression." In 2019 15th Hypervelocity Impact Symposium. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/hvis2019-027.
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Abstract We propose to study experimentally the polymorphic transition of Tin under dynamic compression. These transformations have been investigated for a long time through usual velocity measurements under shock from ambient condition. At CEA Gramat we have improved our understanding of such phase transformations through both experimental and theoretical means. Experimental velocity measurements have long suggested that non equilibrium behavior and kinetics is an important part of the dynamic compression response of materials undergoing phase transformations. Empirical kinetic models can in many cases reproduce the experimental velocity profiles, but without clearly identifying the nature of the transition. For nearly two decades, the CEA Gramat operates several gas guns for shock loading and high pulsed power (HPP) drivers dedicated to Isentropic Compression Experiments (ICE) up to several GPa. These experimental devices and associated diagnostics (velocimetry and temperature measurements and x-ray diffraction experiments) help to begin to study kinetics under dynamic transition in a more rigorous manner. We have used these experiments to examine various compression paths and have used the results to improve equation of state (EOS) models incorporated in our numerical codes. The latter can be used to run simulations starting with ambient initial conditions, then load metallic materials from various non ambient initial temperatures. This can significantly extend the range of our studies into previously unexplored thermodynamic paths. We propose to describe our preheating devices for gas gun experiments and our HPP driver, and to present our preliminary results on shock loading and on isentropic compression at various initial temperatures, to explore the phase diagram of Tin. In addition, we present the design of promising testing on X-ray diffraction under shock to help to develop a more physical kinetic model relying on nucleation and growth mechanisms, which are implemented in our continuum level codes.
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Kharlamov, Y., J. A. Chattha, and M. Kharlamov. "The Effects of Deposition Parameters and Gaseous Detonation Equipment Design on the Coating Formation." In ITSC2005, edited by E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p1139.
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Abstract By use of up-to-date methods of gaseous detonation spraying it is possible to obtain coatings with wide range of thermal and kinetic energy of sprayed particles and their state (liquid, solid, semiliquid, with change of their chemical and phase composition duration of stay in impulse hot gaseous detonation jet, etc.). The philosophy of gas detonation sprayed coating structure and properties control include next basic methods: (1) change of values and ratio of thermal and kinetic energy of sprayed particles; (2) governing of thickness and sizes of single layers of coating (“coating spot“), D-Gun rate of fire, and relative velocity of moving of D-Gun and workpart; (3) change of dispersion and shape of powder particles; (4) regulation of thermal cycle of coating in process of spraying by use preliminary, concomitant or post spraying heating or cooling; (5) use of variable spraying modes for obtaining of individual layers and zones of coating (change of composition and flow rate of gases and powder, D-Gun fire rate, powder dispersion, distance of spraying, etc.); (6) settlement of ratio between percentage of amorphous, microcrystalline and crystalline phases, metastable and equilibrium phases by selection of rational conditions of spraying; (7) control of degree of physico-chemical transformations into powder particles (polymorphic transformations, dissociation, oxidation, interaction between components of composite powders, etc.), change of time of particles stay into gas products flow, composition and parameters of gaseous medium, etc.; (8) alloying of sprayed powders as for assurance of necessary properties of coatings as for improvement of their inclination to coating formation (oxidation resistance into high temperature gas flow, inclination of seizure, etc.); (9) use of composite powders; (10) spraying at mode with powder particles which have premelting temperature at time of coating formation; (11) treatment of sprayed coatings (thermal, thermo-chemical, thermo-mechanical, etc.); (12) control of coating macrostructure by successive deposition of layers, bands and spots of coatings with smooth or abrupt change of composition, deposition of discrete coatings; etc.
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Wu, Xiaodong, Jianshen Wu, Guojun Sun, and Caoyin Xie. "One-dimensional modeling of shape memory alloy with improved kinetic relation for phase transformation." In SPIE's 8th Annual International Symposium on Smart Structures and Materials, edited by Vittal S. Rao. SPIE, 2001. http://dx.doi.org/10.1117/12.436499.
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Santhanakrishnan, Soundarapandian, Fanrong Kong, and Radovan Kovacevic. "A thermo-kinetic phase transformation model for multi-pass laser heat treatment by using high power direct diode laser." In ICALEO® 2010: 29th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing. Laser Institute of America, 2010. http://dx.doi.org/10.2351/1.5062083.
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Zhao, Fulong, Qianfeng Liu, and Hanliang Bo. "Parameter Analysis of the Static Droplets Phase Transformation Under the Pressure Variation Condition." In 2016 24th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icone24-60028.
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The steam-water separator is a vital important plant in the steam generator, whose function is to remove transported small droplets in the vapor stream and provide the high quality saturated steam for the steam turbine. The performance of the steam-water separator in the steam generator has a great impact on the safety and economy of the nuclear power station. The steam-water separation mechanism is far from maturity as a result of the complexity of the separator structure and the interaction of the steam, droplets together with the liquid film. Our research team tries to build a new research route about the steam-water separation mechanism from the microcosmic behavior aspects of the droplets including the production, movement, collision, extinction as well as the phase transformation. When the droplets move during the steam-water separator, the pressure could decrease continuously due to the resistance and the structure variation, which may break the liquid-vapor equilibrium and make the droplets evaporate and then could greatly influence the steam-water separating characteristics. This paper builds a hydrodynamic-kinetic model on the static droplets phase transformation under the pressure variation condition based on the physics phenomenon description of the droplets evaporation as well as the mechanism explanation. Through different kinds of calculations by change of the time step, the model has been proved to be independent on the time step. In order to make sure that the new model is correct, this paper compares the calculation results with the experimental ones and finds that the calculation results are in wonderful accordance with the existing experimental data. The relative errors between the calculation results and the experimental ones are between ± 5%. At last, this paper conducts the detailed sensitivity analysis of different relative parameters, which are useful for the understanding of the process of the droplets evaporation as well as could deepen the comprehension of the droplets phase transformation mechanism under the condition of the pressure change. The calculation results show that the evaporation characteristics of the static droplets under the pressure variation condition are predominantly influenced by the initial pressure, the ultimate pressure of the environment, as well as the difference of the initial and ultimate pressure. In addition, the initial radius of the droplets and the environment temperature can have a great impact on the droplets evaporation characteristics This model could provide the theoretical reference for further study of the process of the droplets phase transformation during transport in the steam-water separator as well as the steam-water separating performance of the separator, which can guide the design of the steam-water separation plants.
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Duong, Nick H., J. Ma, Muhammad P. Jahan, Shuting Lei, and Murali Sundaram. "FEM Investigation of Phase Transformation in Vibration Assisted Nano Impact Machining by Loose Abrasives (VANILA)." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87274.
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In this paper, a numerical study of a nanomachining process, Vibration Assisted Nano Impact machining by Loose Abrasives (VANILA), has been conducted. In the VANILA process, an atomic force microscope (AFM) is used as a platform and the nano abrasives (diamond particles) are injected in slurry between the silicon workpiece and the vibrating AFM probe. The vibration of the AFM probe generates kinetic energy for the abrasives to impact the silicon workpiece and result in nanoscale material removal. In addition, silicon usually experiences phase transformation when subject to high pressure at nano-scale. The commercial Finite Element Method (FEM) software package Abaqus is employed to simulate the phase transformation experienced by the silicon workpiece in this VANILA process under different machining parameters such as impact speed, impact angle and coefficient of friction between the nano-abrasive and silicon workpiece. It is found that the machining parameters (impact speed, impact angle, and coefficient of friction) have substantial influence on the phase transformation of silicon workpiece in the nanomachining VANILA. Phase volumes for Si-VII, Si-VIII, and Si-X increase as the impact speed increases from 100 m/s to 200 m/s. Phase volume of Si-X increases as the friction coefficient increases. For Si-VII and Si-VIII, the phase volumes decrease as friction coefficient increases from 0.05, 0.3 and 0.5. In addition, the phase volumes for Si-VII, Si-VIII, and Si-X usually increase as the impact angles increases from 20° to 90°. However, for impact speed of 150 m/s and frictional coefficient of 0.05, the Si-VII phase volume increases first as impact angle increases from 20° to 70° and then decreases as the impact angle increases from 70° to 90°.
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Ji, Pengfei, Yiming Rong, Yuwen Zhang, and Yong Tang. "Molecular Dynamics Investigation of Phase Change Induced by Ultrafast Laser Irradiation." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70143.
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Irradiated by ultrafast laser pulse, the phase change phenomena in aluminum film are investigated via molecular dynamics simulation. The embedded-atom method potential is employed to describe atomic interactions. The laser heating is modeled by adding a kinetic energy term to the laser pulse irradiated atom at each time step. The resolidification is realized by thermal conduction to cool down locally melted atoms. The temporal and spatial distribution of atomic motion is recorded to compute the temperature evolution and structure change during melting and resolidification processes. The interface between solid and liquid is identified via Ackland analysis. Due to the temperature difference, diffraction profile of the resolidified aluminum is found different from the aluminum before laser irradiation. The simulation results provide helpful information on the atomic scale temperature variation and structure transformation underlying ultrafast laser induced phase change.
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Agboola, Babatunde O., Theocharis Baxevanis, and Dimitris C. Lagoudas. "Thermodynamically Consistent Thermomechanical Modeling of Kinetics of Macroscopic Phase Transition in SMA Using Phase Field Theory." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7555.
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Experimental observations have shown that polycrystalline NiTi wires, strips and tubes develop inelastic strain via nucleation and growth of macroscopic martensitic domains under mechanical loading. These domains consist of almost fully-transformed grains, which result from micro-domains that are formed at the grain-size level. Evolution of these macroscopic domains via transformation front propagation is accompanied by complex interactions between mechanical work, latent heat, heat transfer, and loading rates. These interactions could affect the performance reliability or controllability of the material when deployed. Therefore, modeling effort is necessary to describe these interactions so as to improve the design and application of SMA devices. A 3-D thermodynamically consistent thermomechanical macroscopic model, which is able to describe phase transition kinetics in shape memory alloys, is proposed in this work. The model employs a Ginzburg-Landau-type kinetic law resulting from the notion of configurational forces associated with the gradient of an order parameter (a field variable). As a first attempt to demonstrate the capability of the model, 1-D simplification of the model is implemented within a finite element framework. Kinetics of phase transition and the effects of heat production associated with the thermomechanical coupling on the stress-strain response of an SMA are examined. In particular, the roles of external loading rate and heat transfer boundary conditions on the stress-strain response are investigated for displacement-controlled loading. Results obtained are in good agreement with experimental trends.
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Bailey, Neil S., and Yung C. Shin. "Optimization of Laser Hardening Processes for Industrial Parts With Complex Geometry via Predictive Modeling." In ASME 2009 International Manufacturing Science and Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/msec2009-84012.
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A predictive laser hardening model for industrial parts with complex geometric features has been developed and used for optimization of hardening processes. A transient three-dimensional thermal model is combined with a three-dimensional kinetic model for steel phase transformation and solved in order to predict the temperature history and solid phase history of the workpiece while considering latent heat of phase transformation. Further, back-tempering is also added to the model to determine the phase transformation during multitrack laser hardening. The integrated model is designed to accurately predict temperature, phase distributions and hardness inside complex geometric domains. The laser hardening parameters for two industrial workpieces are optimized for two different industrial laser systems using this model. Experimental results confirm the validity of predicted results.
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Acuna, Andres, Antonio Ramirez, Ravi Menon, Per-Åke Björnstedt, and Leonardo Carvalho. "Developing a Weld Overlay Specification for Hyper Duplex Stainless Steel." In ASME 2021 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/pvp2021-62042.
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Abstract Hyper Duplex Stainless Steels (HDSS) are dual phase, ferritic-austenitic materials with a remarkable yield strength (≥ 700 MPa) and corrosion resistance (PREN/W > 49). It has been developed as an alternative to super-duplex stainless steels, where higher mechanical and corrosion performance is required. Unfortunately, such highly alloyed materials are susceptible to brittle intermetallic phase formation, such as the sigma phase. Understanding the intermetallic formation is essential to obtain its optimal properties and define advantages and limitations for a welding specification. Overlay experiments on three-layered HDSS deposited over a carbon steel plate using 1.1kJ/mm and 1.65kJ/mm shown a clear austenite/ferrite phase ratio difference between the first and last layer. The last deposited layer has a larger ferrite volume fraction and chromium nitride presence. However, no sigma phase was found on the overlay conditions. A sigma phase kinetic model was developed using Thermocalc Prisma, experimentally adjusted, and validated by physical simulation in a series of isothermal heat treatment tests. The additivity rule was used to calculate continuous-cooling-transformation (CCT) curves from the adjusted temperature-time-transformation (TTT) curves. The kinetic model predicts no sigma precipitation for cooling rates faster than 4°C/s. Physical simulation with controlled cooling rates validated the model. Also, the thermal history analysis of the overlay experiments has shown no sigma was expected due to the total time and temperature transformation and cooling rates not reaching the calculated CCT.
Reports on the topic "Polymorphic phase transformation kinetic"
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Carlson, L. W., J. M. Grazier, D. J. Holcomb, S. T. Montgomery, and D. H. Zeuch. Uniaxial Compression Experiments on PZT 95/5-2Nb Ceramic: Evidence for an Orientation-Dependent, ''Maximum Compressive Stress'' Criterion for Onset of the F(R1)()A(O) Polymorphic Phase Transformation. Office of Scientific and Technical Information (OSTI), January 1999. http://dx.doi.org/10.2172/3862.
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Zeuch, D. H., S. T. Montgomery, and D. J. Zimmerer. The effects of non-hydrostatic compression and applied electric field on the electromechanical behavior of poled PZT 95/5-2Nb ceramic during the F{sub R1} {yields} A{sub 0} polymorphic phase transformation. Office of Scientific and Technical Information (OSTI), October 1995. http://dx.doi.org/10.2172/135537.
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