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First-order Phase Transition (first-order + phase_transition)
Selected AbstractsComment on "The Magnetocaloric Effect of LaFe11.6Si1.4, La0.8Nd0.2Fe11.5Si1.5, and Ni43Mn46Sn11 Compounds in the Vicinity of the First-Order Phase Transition"ADVANCED MATERIALS, Issue 37 2009Lluís Mañosa The aim of the present comment is to show that when both calorimetric and magnetization measurements are properly executed, there is no significant discrepancy in the entropy values obtained from the two methods, thus validating the use of the Maxwell relations, which is the most commonly used technique in the study of the magnetocaloric effect. [source] Reply to "Comment on the Magnetocaloric Effect of LaFe11.6Si1.4, La0.8Nd0.2Fe11.5Si1.5, and Ni43Mn46Sn11 Compounds in the Vicinity of the First-Order Phase Transition"ADVANCED MATERIALS, Issue 37 2009Jun-Ding Zou The magnetocaloric effect (MCE) of Ni43Mn46Sn11 in the vicinity of a first-order martensitic phase transition is discussed by using magnetic measurements, heat capacity measurements and differential scanning calorimetry (DSC) measurements. The results confirm that the MCE of Ni43Mn46Sn11 obtained by magnetic measurements (via the Maxwell relation) may be seriously overestimated and Ni-Mn-Sn alloys should be treated carefully. [source] Erratum: The Magnetocaloric Effect of LaFe11.6Si1.4, La0.8Nd0.2Fe11.5Si1.5, and Ni43Mn46Sn11 Compounds in the Vicinity of the First-Order Phase TransitionADVANCED MATERIALS, Issue 37 2009Jun-Ding Zou No abstract is available for this article. [source] The Magnetocaloric Effect of LaFe11.6Si1.4, La0.8Nd0.2Fe11.5Si1.5, and Ni43Mn46Sn11 Compounds in the Vicinity of the First-Order Phase TransitionADVANCED MATERIALS, Issue 6 2009Jun-Ding Zou The magnetocaloric effect is discussed in terms of the thermodyna mic Maxwell relation and its necessary conditions. The origin of the sharp "spikes" that appear in entropy-change curves is discussed. The Maxwell relation and heat-capacity measurements are then used to determine the entropy change and are applied to the discussion of LaFe11.6Si1.4, La0.8Nd0.2Fe11.5Si1.5, and Ni43Mn46Sn11 compounds. [source] Unprecedented "One-Finger-Push"-Induced Phase Transition With a Drastic Color Change in an Inorganic Material,ADVANCED MATERIALS, Issue 21 2007M. Gaudon A drastic color transition from green to brownish-red in the CuMo1,xWxO4 system occurs during a first-order phase transition. This study shows that it is possible to control this transition in terms of temperature or pressure with respect to the tungsten content (see figure). Hence, the use of these compounds for new applications as temperature indicators or shock detectors is feasible. [source] Amphiphilic PEG/alkyl-grafted comb polylactidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2007Xuwei Jiang Abstract Amphiphilic polylactides (PLAs) with well-defined architectures were synthesized by ring-opening polymerization of AB monomers (glycolides) substituted with both a long chain alkyl group and a triethylene glycol segment terminated in either a methyl or benzyl group. The resulting amphiphilic PLAs had number average molecular weights >100,000 g/mol. DSC analysis revealed a first-order phase transition at , 20 °C, reflecting the crystalline nature of the linear alkyl side chains. Polymeric micelles were prepared by the solvent displacement method in water. Dynamic light scattering measurements support formation of a mixture of 20-nm-diameter unimolecular micelles and 60-nm particles comprised of an estimated 25 polymer molecules. UV,vis characterization of micelles formed from acetone,water solutions containing azobenzene confirmed encapsulation of the hydrophobic dye, suggesting their potential as new amphiphilic PLAs as drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5227,5236, 2007 [source] Model of a superconducting singular Fermi liquid with a first-order phase transitionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2004Ryszard Gonczarek Abstract Model of s -wave and d -wave superconductivity in a singular Fermi liquid with a divergent scattering amplitude for particles with the same quasi-momenta and opposite spins is formulated and presented with regard to a narrow, nearly half-filled conduction band. The ground state and other eigenstates for the superconducting phase are found. Thermodynamic functions are obtained by the use of the Bogolubov method. The gap equation along with the equation for the chemical potential is derived in a general form and solved in a self-consistent manner for s -wave pairing. Above a certain temperature there are two solutions of the gap equation, however only for the greater one the superconducting phase remains stable. It is shown that the system undergoes a first-order phase transition between the superconducting and the normal phase. The critical temperature and the heat of the transition are found. The temperature dependence of the entropy and the specific heat of the system is also presented. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phase transitions in Sm1,xSrxMnO3 single crystals (0 , x , 0.8)PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003V. Yu. Abstract Magnetic and electrical properties of Sm1,xSrxMnO3 (0 , x , 0.8) single crystals have been studied and the T , x phase diagram has been revised. The compensation points of spontaneous weak ferromagnetic moment have been observed for pure SmMnO3 and for low doped compositions (0 , x < 0.05). For 0.4 , x , 0.475 the ferromagnetic ordering occurs as a first-order phase transition. It is shown that in a magnetic field the temperature of this transition increases and the transition becomes broader, which results in the appearance of a critical point (Tcr , 193 K, Hcr , 68 kOe for x = 0.45). Another transition, accompanied by a reduction of magnetization and noticeable anisotropy of magnetization curves, has been observed at low temperature Ts , 40 K. Below the Neel temperature, a pure antiferromagnetic state without spontaneous magnetization has been observed for 0.5 , x , 0.575, while for 0.6 , x , 0.675 an additional low-temperature transition to a new phase with a non-zero weak-ferromagnetic moment has been found. [source] Nanocomposites of silver nanoparticle and dinonylnaphthalene disulfonic acid-doped thermoreversible polyaniline gelPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Ashesh Garai Silver/polyaniline-dinonylnaphthalene disulfonic acid (PANI-DNNDSA) gel nanocomposites are prepared from the reduction of silver salt by polyaniline in formic acid medium. Scanning electron micrographs (SEM) indicate the presence of three-dimensional fibrillar network structure and the silver nanoparticles remain dispersed within the PANI-DNNDSA fibrillar network. Differential scanning calorimetric (DSC) study shows reversible first-order phase transition characterizing the composite to behave as a thermoreversible gel. Transmission electron micrographs (TEM) show a decrease of nanoparticle size with increasing AgNO3 concentration. Wide angle X-ray scattering (WAXS) patterns show lamellar structure in the gel as well as in the gel metal nanocomposites (GMNCs) and the two melting peaks in the DSC patterns correspond to the melting of monolayer and bilayer crystals produced from the interdigitation of DNNDSA tails anchored from PANI chains within the PANI lamella. The above melting points are greater in the GMNCs than that of pure gel indicating the formation of complex melting thermogram with crystallites produced from the anchored surfactants tails at the surface of Ag nanoparticles. The GMNCs show a higher thermal stability than that of pure PANI-DNNDSA gel. PANI-DNNDSA gel has an emission peak at 354 nm but fluorescence quenching occurs in the GMNCs and the emission peak becomes red shifted. Also in the UV,vis spectra the , band-polaron band transition peak shows a red shift and the DC conductivity increases with increasing Ag nanoparticle concentration in the GMNCs. The current (I),voltage (V) characteristic curves indicate Ohmic nature of conductivity of the gel and the current at the same voltage increases appreciably with increasing Ag nanoparticle concentration. These GMNCs are easily processible due to its thermoreversible nature. So, an easily processible, thermally stable and highly conducting DNNDSA-doped PANI-Ag gel nanocomposite with interesting photoluminescent property has been successfully developed suitable for optoelectronic applications. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] High-pressure crystal structure of the non-linear optical compound BiB3O6 from two-dimensional powder diffraction dataACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2009R. E. Dinnebier Our recently proposed method for automatic detection, calibration and evaluation of Debye,Scherrer ellipses using pattern-recognition techniques and advanced signal filtering was applied to the two-dimensional powder diffraction data of the non-ferroelectric, non-centrosymmetric non-linear optical (NLO) compound ,-BiB3O6 as a function of pressure. At ambient conditions, ,-BiB3O6 crystallizes in the space group C2 (phase I). In the pressure range between P = 6.09 and 6.86,GPa, it exhibits a first-order phase transition into a structure with the space group C1 (P1) [phase II at P = 8.34,GPa: a = 7.4781,(6), b = 3.9340,(4), c = 6.2321,(6),Å, , = 93.73,(1), , = 102.93,(1), , = 90.76,(1)°, and V = 178.24,(3),Å3]. Non-linear compression behaviour over the entire pressure range is observed, which can be described by two Vinet relations in the ranges from P = 0.0 to 6.09,GPa, and from P = 6.86 to 11.6,GPa. The extrapolated bulk moduli of the high-pressure phases were determined to be K0 = 38,(1),GPa for phase I, and K0 = 114,(10),GPa for phase II. The crystal structures of both phases were refined against X-ray powder diffraction data measured at several pressures between 0.0 and 11.6,GPa. The structural phase transition of ,-BiB3O6 is mainly characterized by a reorientation of the [BO3]3, triangles, the [BO4]5, tetrahedra and the lone electron pair which is localized at Bi3+, in order to optimize crystal packing. [source] Following an isosymmetric phase transition by changes in bond lengths and anisotropic displacement parameters: the case of meta -carboxyphenylammonium phosphiteACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2009El-Eulmi Bendeif Crystal structure studies in the 100,345,K temperature range were performed to relate the molecular structure changes of meta -carboxyphenylammonium phosphite (m -CPAMP) to its first-order phase transition at Tc = 246,(2),K. Thermal displacement parameters and most bond distances show an abrupt jump at the transition. Such a structural change is related to collective effects leading to competition between intra- and intermolecular interactions. [source] Mechanism of the first-order phase transition of an acylurea derivative: observation of intermediate stages of transformation with a detailed temperature-resolved single-crystal diffraction methodACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2003Daisuke Hashizume The process of the first-order solid-to-solid phase transition of 1-ethyl-3-(4-methylpentanoyl)urea (1) was observed by means of a detailed temperature-resolved single-crystal diffraction method, which resembles watching a series of stop-motion photographs. The transition consists of two elementary processes, one supramolecular and the other molecular. Crystal structures from before and after the phase transition are isostructural. The straight-ribbon-like one-dimensional hydrogen-bonding structure is formed and stacked to form a molecular layer. The geometry of the layer is retained during the phase transition. The relative position of the layer with its neighbours, on the other hand, changes gradually with increasing temperature. The change is accelerated at the temperature representing the start of the endotherm seen in the DSC curves of (1). The structural variation yields void space between the neighbouring layers. When the void space grows enough that the crystal is unstable, the 3-methylbutyl group on the last of the molecules turns into a disordered structure with drastic conformational changes to fill up the void space. The phase transition process is well supported with simple force-field calculations. A crystal of 1-(4-methylpentanoyl)-3-propylurea (2), which shows no solid-to-solid phase transitions, was also analysed by the same method for comparison. [source] Modified Rachford-Rice equations including interfacial contributions and their application to the nucleation processAICHE JOURNAL, Issue 7 2010Bernardo Carreón-Calderón Abstract The Rachford-Rice expressions [Rachford HH, Rice JD, Petroleum Trans AIME 1952;195:327-328] have been modified to include interfacial contributions in the calculation of the equilibrium coexistence between two macroscopic phases. It is shown that two-phase equilibrium states for first-order phase transitions from nucleation to the presence of evolved macroscopic phases can be characterized by using these generalized expressions. Thus, this new treatment allows the determination of the critical inclusion of nucleation of the so-called dispersed phase in a way similar to the determination of incipient new-phase formation points of a saturated phase on the binodal curve. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Driving force in first-order phase transitions and its application to gas hydrate nucleation from a single phaseAICHE JOURNAL, Issue 9 2009Bernardo Carreón-Calderón Abstract Classical nucleation theories of general application are taken as starting point to analyze the driving force for multicomponent gas hydrate nucleation from a single homogeneous phase. It is shown that the ratio between the specific surface energy and the critical radius of nucleation has a single value irrespective of the analyzed driving force expression. From this result, two driving force expressions for multicomponent gas hydrate nucleation are derived in the context of the so-called generalized nucleation theory, and it is demonstrated that the driving force for gas hydrates can be estimated using the same information given for the determination of the incipient formation points of the dispersed phase from a saturated phase. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Phase Transitions in Pb(Mg1/3Nb2/3)O3,PbTiO3 Studied by Low-Frequency Internal Friction MeasurementJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007Feng Yan The low-frequency internal friction (0.1 Hz Quantum phase transition in a spin-½ XX chain with three-spin and uniform long-range interactionsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2005Ping Lou Abstract A spin-½ XX chain with three-spin and uniform long-range interactions among the z components of the spins is constructed. Based upon the model, using the Jordan,Wigner transformation, the thermodynamic quantities and spin transports of the system are evaluated exactly. The phase diagram together with the key parameters characterizing quantum phase transitions is presented. It is noted that, similarly to classical first-order phase transitions, there are also the metastable states "supercooled" and "superheated" in the first-order quantum phase transitions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]
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