Zeitschriftenartikel: „Phase change hysteresis“

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Meyers, Jeremy P. „Hysteresis and Phase Change in Electrochemical Materials“. ECS Transactions 16, Nr. 13 (18.12.2019): 167–73. http://dx.doi.org/10.1149/1.2987768.

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Aiki, T., E. Minchev und T. Okazaki. „Mathematical models for phase change problems with hysteresis effect“. Nonlinear Analysis: Theory, Methods & Applications 63, Nr. 5-7 (November 2005): e1185-e1198. http://dx.doi.org/10.1016/j.na.2005.03.089.

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3

Zastawna-Rumin, Anna, Tomasz Kisilewicz und Umberto Berardi. „Novel Simulation Algorithm for Modeling the Hysteresis of Phase Change Materials“. Energies 13, Nr. 5 (05.03.2020): 1200. http://dx.doi.org/10.3390/en13051200.

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Latent heat thermal energy storage (LHTES) using phase change materials (PCM) is one of the most promising ways for thermal energy storage (TES), especially in lightweight buildings. However, accurate control of the phase transition of PCM is not easy to predict. For example, neglecting the hysteresis or the effect of the speed of phase change processes reduces the accuracy of simulations of TES. In this paper, the authors propose a new software module for EnergyPlus™ that aims to simulate the hysteresis of PCMs during the phase change. The new module is tested by comparing simulation results with experimental tests done in a climatic chamber. A strong consistency between experimental and simulation results was obtained, while a discrepancy error of less than 1% was obtained. Moreover, in real conditions, as a result of quick temperature changes, only a partial phase transformation of the material is often observed. The new model also allows the consideration of the case with partial phase changes of the PCM. Finally, the simulation algorithm presented in this article aims to represent a better way to model LHTES with PCM.

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Hu, Yue, Rui Guo, Per Kvols Heiselberg und Hicham Johra. „Modeling PCM Phase Change Temperature and Hysteresis in Ventilation Cooling and Heating Applications“. Energies 13, Nr. 23 (06.12.2020): 6455. http://dx.doi.org/10.3390/en13236455.

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Applying phase change material (PCM) for latent heat storage in sustainable building systems has gained increasing attention. However, the nonlinear thermal properties of the material and the hysteresis between the two-phase change processes make the modelling of PCM challenging. Moreover, the influences of the PCM phase transition and hysteresis on the building thermal and energy performance have not been fully understood. This paper reviews the most commonly used modelling methods for PCM from the literature and discusses their advantages and disadvantages. A case study is carried out to examine the accuracy of those models in building simulation tools, including four methods to model the melting and freezing process of a PCM heat exchanger. These results are compared to experimental data of the heat transfer process in a PCM heat exchanger. That showed that the four modelling methods are all accurate for representing the thermal behavior of the PCM heat exchanger. The model with the DSC Cp method with hysteresis performs the best at predicting the heat transfer process in PCM in this case. The impacts of PCM phase change temperature and hysteresis on the building energy-saving potential and thermal comfort are analyzed in another case study, based on one modelling method from the first case study. The building in question is a three-room apartment with PCM-enhanced ventilated windows in Denmark. The study showed that the PCM hysteresis has a larger influence on the building energy consumption than the phase change temperature for both summer night cooling applications and for winter energy storage. However, it does not have a strong impact on the yearly total energy usage. For both summer and winter transition seasons, the PCM hysteresis has a larger influence on the predicted percentage of dissatisfied (PPD) than the phase change temperature, but not a strong impact on the transition season average PPD. It is therefore advised to choose the PCM hysteresis according to whether it is for a summer night cooling or a winter solar energy storage application, as this has a significant impact on the system’s overall efficiency.

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Frame, James D., Nicolas G. Green und Xu Fang. „Modified Maxwell Garnett model for hysteresis in phase change materials“. Optical Materials Express 8, Nr. 7 (28.06.2018): 1988. http://dx.doi.org/10.1364/ome.8.001988.

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Szilard, D., W. J. M. Kort-Kamp, F. S. S. Rosa, F. A. Pinheiro und C. Farina. „Hysteresis in the spontaneous emission induced by VO2 phase change“. Journal of the Optical Society of America B 36, Nr. 4 (07.03.2019): C46. http://dx.doi.org/10.1364/josab.36.000c46.

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Green, Nicolas G., und Xu Fang. „A Modified Maxwell Garnett Model: Hysteresis in phase change materials“. Journal of Physics: Conference Series 1322 (Oktober 2019): 012038. http://dx.doi.org/10.1088/1742-6596/1322/1/012038.

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8

Serikawa, Mao, Kensaku Mabuchi, Makoto Satoh, Yoshinobu Nozue, Yoshihiko Hayashi und Masahiro Yokoyama. „Measurement of full-scale phase change material products considering hysteresis“. Applied Thermal Engineering 192 (Juni 2021): 116895. http://dx.doi.org/10.1016/j.applthermaleng.2021.116895.

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Abrahams, S. C., J. Ravez, H. Ritter und J. Ihringer. „Structure–property correlation over five phases and four transitions in Pb5Al3F19“. Acta Crystallographica Section B Structural Science 59, Nr. 5 (25.09.2003): 557–74. http://dx.doi.org/10.1107/s0108768103011509.

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The calorimetric and dielectric properties of Pb5Al3F19 in the five phases stable under ambient pressure are correlated with structure for fuller characterization of each phase. The first-order transition between ferroelectric phase V and antiferroelectric phase IV at T V,IV = 260 (5) K exhibits a thermal hysteresis of 135 (5) K on heating, with a maximum atomic displacement Δ(xyz)max = 1.21 (6) Å; the transition from phase IV to ferroelastic phase III at 315 (5) K is also first order but with a thermal hysteresis of 10 (5) K and Δ(xyz)max = 0.92 (7) Å; that from phase III to paraelastic phase II at 360 (5) K is second order without hysteresis and has Δ(xyz)max = 0.69 (4) Å; and the transition from phase II to paraelectric phase I at 670 (5) K is second or higher order, with Δ(xyz)max = 0.7 (4) Å. The measured entropy change ΔS at T V,IV agrees well with ΔS as derived from the increased configurational energy by Stirling's approximation. For all other phase transitions, 0.5 ≥ ΔS > 0 J mol−1 K−1 is consistent with an entropy change caused primarily by the changes in the vibrational energy. The structure of phase III is determined both by group theoretical/normal mode analysis and by consideration of the structures of phases II, IV and V reported previously; refinement is by simultaneous Rietveld analysis of the X-ray and neutron diffraction powder profiles. The structure of prototypic phase I is predicted on the basis of the atomic arrangement in phases II, III, IV and V. The introduction of 3d electrons into the Pb5Al3F19 lattice disturbs the structural equilibrium, the addition of 0.04% Cr3+ causing significant changes in atomic positions and increasing T IV,III by ∼15 K. Substitution of Al3+ by 20% or more Cr3+ eliminates the potential minima that otherwise stabilize phases IV, III and II.

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Li, Yan Shan, Shu Jun Wang, Hong Yan Liu, Wan Gang Zheng, Huan Qing Ma und Fan Bin Meng. „Recent Advances in Form-Stable Phase Change Materials of Polyethylene Glycol“. Advanced Materials Research 850-851 (Dezember 2013): 164–68. http://dx.doi.org/10.4028/www.scientific.net/amr.850-851.164.

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The polyethylene glycol is a kind of phase change energy storage material with small thermal hysteresis effect, the phase change enthalpy and phase transition temperature varies with its different molecular weight. This article summarizes polyethylene glycol as research progress of phase change energy storage material, which mainly discusses the preparation methods and outlook about form-stable phase change materials.

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Hsu, Ting-Heng, Chieh-Hsuan Chung, Feng-Ju Chung, Chun-Che Chang, Ming-Chang Lu und Yu-Lun Chueh. „Thermal hysteresis in phase-change materials: Encapsulated metal alloy core-shell microparticles“. Nano Energy 51 (September 2018): 563–70. http://dx.doi.org/10.1016/j.nanoen.2018.06.021.

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Afremov, Leonid L., und Ilia G. Iliushin. „The Effect of Mechanical Stresses on the Coercive Force of the System of Two-Phase Interacting Nanoparticles“. Solid State Phenomena 215 (April 2014): 89–94. http://dx.doi.org/10.4028/www.scientific.net/ssp.215.89.

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Within the framework of the two-phase grain model (by the example of γ-Fe203 cobalt coated particles) a theoretical analysis of the effect of uniaxial mechanical stresses on the magnetization of the system of hetero-phase interacting nanoparticle was held. It is shown that stretching leads to reduction when compression increases the coercive force Hc and doesnt change the residual saturation magnetization Irs of the system of interacting particles. "Smoothing" the hysteresis loop and "lowering" the magnetization curve, the magnetostatic interaction between particles decreases both Hc, and Irs, giving the fact that hysteresis characteristics of an ensemble of interacting nanoparticles change much more in stretching than in compression.

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Longbiao, Li. „A thermomechanical fatigue hysteresis-based damage evolution model for fiber-reinforced ceramic–matrix composites“. International Journal of Damage Mechanics 28, Nr. 3 (19.04.2018): 380–403. http://dx.doi.org/10.1177/1056789518772162.

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In this paper, a thermomechanical fatigue hysteresis-based damage evolution model for fiber-reinforced ceramic–matrix composites has been developed. Upon unloading and reloading, the fiber/matrix interface debonded length, interface counter-slip length, and interface new-slip length change with increasing or decreasing applied stress, which affects the stress–strain fatigue hysteresis loops and fatigue hysteresis-based damage parameters. The reloading/unloading stress–strain relationships when fiber/matrix interface partially or completely debonding are determined as a function of interface debonding/sliding, peak stress, applied cycle number, and thermal cycle temperature. The relationships between thermomechanical fatigue loading parameters (i.e. peak stress, applied cycle number, and thermal cyclic temperature), fiber/matrix interface debonding/sliding lengths, and fatigue hysteresis-based damage parameters (i.e. fatigue hysteresis dissipated energy, fatigue hysteresis modulus, and fatigue peak strain) have been established. The effects of fiber volume fraction, peak stress, matrix cracking space, and thermal cyclic temperature range on damage evolution under the out-of-phase thermomechanical cyclic loading have been discussed. The differences in damage evolution between in-phase/out-of-phase thermomechanical fatigue and isothermal fatigue loading at the same peak stress have been analyzed. The damage evolution of cross-ply SiC/magnesium aluminosilicate composite under the out-of-phase thermomechanical and isothermal fatigue loading has been predicted.

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Brener, R., und H. Shechter. „Intramolecular Rotational Phase-Transition in Bulk and Adsorbed Fe(CO)5 on (0001) Graphite*“. Zeitschrift für Naturforschung A 43, Nr. 10 (01.10.1988): 855–58. http://dx.doi.org/10.1515/zna-1988-1004.

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Abstract Mossbauer spectroscopy results on bulk iron pentacarbonyl Fe(CO)5 and as adsorbate on (0001) graphite display a sharp transition at ~ 110K. related to intramolecular hindered rotations of CO-ligands, with no associated structural changes. The hysteresis in the temperature dependence of the quadrupole splitting and the abrupt change in the spectral intensity suggest a cooperative first-order phase transition.

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Christie, R. J., P. K. Wu, P. Photinos und S. C. Abrahams. „Phase transitions and ferroelectricity in NaSb3F10“. Journal of Applied Crystallography 42, Nr. 1 (28.11.2008): 58–62. http://dx.doi.org/10.1107/s0021889808036182.

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Atomic coordinate analysis allows materials with appropriate but previously unrecognized dielectric properties to be predicted as new ferroelectrics if their crystal structure is known. An earlier such prediction that NaSb3F10is ferroelectric is confirmed herein without ambiguity. Its spontaneous polarizationPsis found to exhibit reproducible dielectric hysteresis at room temperature, withPs≃ 60 µC m−2, under the application of a field of 0.3 MV m−1or greater. The pyroelectric coefficient 〈p〉 = 17 (5) µC m−2 K−1at 298 K. NaSb3F10undergoes a phase transition atTC≃ 461 K, on correction for thermal hysteresis, with entropy change ΔS= 5.7 (3) J mol−1 K−1. The colorless crystals melt atTm ≃ 515 K and decompose above ∼600 K. The thermal hysteresis of ∼35 K inTC, on heating and cooling at 5–25 K min−1, is typical of first-order phase transitions. The space group in ferroelectric phase III isP63, and that in phase II is predicted to beP6322, a nonpolar supergroup ofP63; the supergroup expected in the prototypic nonferroic phase I isP63/mmc. The space group of phase III isnota direct subgroup of phase I. The dielectric permittivity ∊′ at 1 kHz increases over an order of magnitude between 300 K and a major inflection atTC, continuing to increase steadily thereafter toTm.

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Suleimenov, I. E., O. Guven, G. A. Mun, Ch Uzun, O. A. Gabrielyan, Sh B. Kabdushev, L. Agibaeva und A. Nurtazin. „Hysteresis Effects During the Phase Transition in Solutions of Temperature Sensitive Polymers“. Eurasian Chemico-Technological Journal 19, Nr. 1 (19.06.2017): 41. http://dx.doi.org/10.18321/ectj501.

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It is demonstrated, for the first time,that well-known phase transitions induced by changes in temperature in solutions of polymers containing both hydrophilic and hydrophobic functional groups could be followed by noticeable hysteresis effects. A<br />well-known phase transitions accompanied by a sharp change in fluid properties, in particular its optical density can be induced by many external influences, including temperature changes occurring in the solutions of polymers containing both<br />hydrophilic and hydrophobic functional groups. Since intensification subsequent hydrophobic interactions, leading to loss of solubility of the polymer molecules, resulting, in particular, a significant increase in the turbidity of the medium and are accompanied by a pronounced hysteresis phenomena. Hysteresis phenomena in the processes of molecular-scale play an important theoretical and practical interest in linkage with the development of advanced nano-level technology. In particular, the issue of the development of molecular "trigger" switches, and other analog electronic systems, implemented on submolecular level was actively discussed. In fact, under the same physical conditions of the environment of macromolecules system can be in two different states, which resolves the issue of programming such molecules. State of these polymers depends on their way of formation and thermodynamic variables. Observed effect could be utilized directly for information recording into the structure on the basis of stimulus-sensitive macromolecular chains. In fact, it is a first step towards creating memory of quasi-biological elements.

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Bu, Wen Shao, Lei Lei Xu, Xian Bo Wang und Xin Win Niu. „Double-Hysteresis Current Control Strategy of PWM Rectifier“. Applied Mechanics and Materials 433-435 (Oktober 2013): 1037–44. http://dx.doi.org/10.4028/www.scientific.net/amm.433-435.1037.

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to hold the merits of the traditional hysteresis controller, and at the same time, hold back the change of switching frequency and reduce the switching power loss in hysteresis control of PWM rectifier, based on the relationship between line currents and switching status, an improved algorithm of double-hysteresis current control method for three-phase voltage-type PWM converter was proposed. In the strategy, the position of reference voltage vector can be detected by double hysteresis, PLL circuit can detect the output of switching states. The proposed algorithms not only hold the merits of traditional hysteresis, such as quick current response and current limited capacity, but also, it can overcome the drawback of non-fixed switching frequency of traditional hysteresis. The algorithm has been simulated and verified by MATLAB/simulink platform, and the system operates stably.

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Szilard, Daniela, Patrícia P. Abrantes, Felipe A. Pinheiro, Felipe S. S. Rosa, Carlos Farina und Wilton J. M. Kort-Kamp. „Optical Forces on an Oscillating Dipole Near VO2 Phase Transition“. Universe 7, Nr. 6 (22.05.2021): 159. http://dx.doi.org/10.3390/universe7060159.

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We investigate optical forces on oscillating dipoles close to a phase change vanadium dioxide (VO2) film, which exhibits a metal-insulator transition around 340 K and low thermal hysteresis. This configuration emulates the interaction between an illuminated nanosphere and an interface and we employ a classical description to capture its important aspects. We consider both electric and magnetic dipoles for two different configurations, namely with the dipole moments parallel and perpendicular to the VO2 film. By using Bruggeman theory to describe the effective optical response of the material, we show that the thermal hysteresis present in the VO2 transition clearly shows up in the behavior of optical forces. In the near-field regime, the force on both dipoles can change from attractive to repulsive just by heating (or cooling) the film for a selected frequency range. We also verified that the optical forces are comparable to the Casimir-Polder force in a similar system, revealing the possibility of modulating or even changing the sign of the resultant force on an illuminated nano-object due to the presence of a thermochromic material. We hope that this work contributes to set the grounds for alternative approaches to control light-matter interactions using phase-change materials.

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Kozlovskiy, Artem, Jumat Kargin, Malik Kokarev und Daut Mukhambetov. „Study of the iron nanoparticles phase transformation during thermal annealing“. Chemical Bulletin of Kazakh National University, Nr. 1 (31.03.2017): 16–25. http://dx.doi.org/10.15328/cb796.

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Change in structural properties and phase composition of nanoparticles based on iron oxide was researched in the paper. As a result of conducted studies it was found that during heat treatment oxide phases of (γ-Fe2O3) and α-Fe2O3 maghemite were formed in oxygen atmosphere. Researches of powder array magnetization were showed that the hysteresis loop movement had the form characteristic for ferromagnetic materials. Additionally, loops obtained at different directions of the magnetic field have different characters, which indicate the magnetic anisotropy presence in the samples.

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Nikitin, Sergey, Andrey Smirnov, Anatoly Bogdanov und Ioulia Ovchenkova. „The transformation of the magnetostructural phase transition with Ti addition in Gd5Si2Ge2“. EPJ Web of Conferences 185 (2018): 05006. http://dx.doi.org/10.1051/epjconf/201818505006.

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The magnetic, thermal expansion and magnetostriction measurements of Gd5-xTixSi2Ge2 (x=0, 0.05, 0.1) compounds have been carried out in wide range of fields and temperatures. It is found that Ti addition leads to the disappearance of the structural transformation, the change of the order of the phase transition and the decrease of the hysteresis. The large positive magnetostriction associated with the structural phase transition in Gd5Si2Ge2 changes to the small negative one associated with the magnetic phase transition in Gd4.9Ti0.1Si2Ge2. The linear dependence of volume magnetostriction on the square of magnetization obtained for all investigated compounds is explained using the thermodynamic theory.

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Маширов, А. В., И. И. Мусабиров, М. С. Аникин, М. А. Сёмкин, В. Митюк, Р. Ю. Гайфуллин, В. В. Коледов und В. Г. Шавров. „Гомогенизационный отжиг и магнитные свойства образца фазы Лавеса GdNi-=SUB=-2-=/SUB=-“. Физика твердого тела 63, Nr. 12 (2021): 1994. http://dx.doi.org/10.21883/ftt.2021.12.51655.13s.

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The paper shows the effect of homogenization annealing on the ferromagnet-paramagnet phase transition in the GdNi2 alloy. In the cast sample, at the Curie point, a temperature hysteresis is observed, which in an external magnetic field of 13.5 T can be at least 3 degrees. The data of scanning electron microscopy of the electropolished samples showed a decrease in the impurity phase of GdNi and practically no temperature hysteresis of the phase transition in the annealed GdNi2 sample. The value of the isothermal change entropy DSm = - 18.931 J/(kg*K) for an annealed sample of the GdNi2 alloy at the Curie point of 75 K in a magnetic field of 13.5 T.

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Hsieh, C. K., und Chang-Yong Choi. „A General Analysis of Phase-Change Energy Storage for Solar Energy Applications“. Journal of Solar Energy Engineering 114, Nr. 4 (01.11.1992): 203–11. http://dx.doi.org/10.1115/1.2930007.

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A unified approach is developed for the analysis of one, two, or three-phase melting or solidification of a semi-infinite medium with or without subcooling or superheating and imposed with constant, monotonic, or cyclic temperature or flux conditions. A source and sink method is presented in which a sink front is used to characterize a melt front while a source front is used to characterize a freeze front. An integrodifferential equation is then derived for the interface position which is linearized locally for numerical solution. This position is, in turn, used as input for the determination of the temperature distribution and energy storage and release in different phases of the medium. The numerical solution presented in this paper has shown to be unique, convergent, stable, and accurate. The analysis has been applied to the study of phase change in a subcooled paraffin wax imposed with a cyclic temperature condition. Test results yield some interesting phenomena related to the merging of phase-change fronts and hysteresis of energy storage and release, among others, which have not previously been reported in the literature. Their relations to the energy storage and release are particularly stressed in the paper.

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Ivanov, Igor, und Oksana Ivanova. „Phase Transitions in Ion-Exchange Materials during the Water Vapor Sorption“. EPJ Web of Conferences 248 (2021): 01003. http://dx.doi.org/10.1051/epjconf/202124801003.

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Water vapor sorption process on ion-exchange materials was investigated using a model taking into account the mutual influence of variations in hydration energy and osmotic effect. At realistic parameter values, phase transitions of the first kind of the thin adsorbed liquid film and thick adsorbed liquid film type can occur. Possible reasons and criteria of the phase transitions that led to stepwise change of ionite resistance were discussed. The phase transitions obtained in this work manifest themselves as hysteresis loops on water vapor adsorption-desorption experimental isotherms. Hysteresis was observed experimentally both at high and at low values of relative air humidity. It was explained using different models: for high and low humidity separately. The present work made it possible to explain these critical phenomena using single mathematical model.

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Chen, Xin, Vladimir Shvartsman, Doru C. Lupascu und Q. M. Zhang. „Comment on “Giant pyroelectric energy harvesting and a negative electrocaloric effect in multilayered nanostructures” by G. Vats, A. Kumar, N. Ortega, C. R. Bowen and R. S. Katiyar, Energy Environ. Sci., 2016, 9, 1335“. Energy & Environmental Science 14, Nr. 3 (2021): 1612–14. http://dx.doi.org/10.1039/d0ee02548h.

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In the ferroelectric phase, the change of polarization with temperature from partially switched polarization hysteresis loops has no relation with the electrocaloric effect (ECE) and hence cannot be used in Maxwell relation to deducing ECE.

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Rezaeealam, Behrooz, und Behzad Norouzi. „Investigating Ferroresonance Phenomenon in a Single-Phase Transformer with the Effect of Magnetic Hysteresis“. Indonesian Journal of Electrical Engineering and Computer Science 2, Nr. 2 (01.05.2016): 248. http://dx.doi.org/10.11591/ijeecs.v2.i2.pp248-258.

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<p>Ferroresonance is a non-linear phenomenon and very dynamic in the power quality problems. This phenomenon should be carefully analyzed so that preventive measures could be taken before its appearance and prevent injury and damage to electrical power appliances. Ferroresonance is seen more in the middle-voltage networks with supplying unloaded or slightly loaded transformers by cables. The materials used in the manufacture of transformer cores are creates a major role in their dynamic behavior. In this article are used from two types magnetic material GOES and NGOES in the transformer core of single phase. The physical behavior of these materials is considered during the core hysteresis. For modeling the hysteresis loop has been used from Jiles-Atherton method. By using the finite element method and with help COMSOL Multiphysics Software, transformer is simulated in two space dimensions. Laboratory test the transformer core hysteresis loop is described and shows which the Jiles-Atherton model is one of the best known models of hysteresis. The results shows which use of GOES materials in the transformer core is cause Significant reduction the core losses in comparison with the NGOES materials. Also change of ferroresonance mode and the severity its occurrence are the results of changing the material used in the transformer core.</p>

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Kakimoto, Kenichi, Tatsuro Hotta und Hitoshi Ohsato. „Phase Transition and Structural Analysis of (Li,Na,K)NbO₃ Lead-Free Piezoelectric Ceramics“. Key Engineering Materials 421-422 (Dezember 2009): 3–8. http://dx.doi.org/10.4028/www.scientific.net/kem.421-422.3.

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Structural characterization of various (Li,Na,K)NbO3 solid solutions with different Li contents has been carried out by temperature-variable Raman scattering measurement. It was found that there was no clear thermal hysteresis between orthorhombic-tetragonal phase transition in the heating/cooling processes for (Li,Na,K)NbO3 ceramics with Li content of 6 wt% and above, although a noticeable thermal hysteresis is observed in the Raman spectra and dielectric constant measurement for the other specimens with lower Li contents. It is presumed that the structural change of (Li,Na,K)NbO3 cell tends to become insensibility against temperature as the Li content increases above 6.0 mol%.

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Li, Yongtao, Shiyou Zheng, Fang Fang, Hanping Zhang, Qingan Zhang und Dalin Sun. „Pressure hysteresis in the TiMn1.5Vx-H2 (x = 0.1–0.5) system“. Journal of Materials Research 24, Nr. 9 (September 2009): 2886–91. http://dx.doi.org/10.1557/jmr.2009.0338.

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The structural characteristics of TiMn1.5Vx (x = 0.1–0.5) alloys and the hysteresis phenomenon in the TiMn1.5Vx-H2 system have been studied. The TiMn1.5Vx alloy consists mainly of the C14 Laves phase plus some of the BCC solid solution phase, depending on x. The lattice parameters of the C14 Laves phase increase slightly as x increases from 0.1 to 0.2 but are invariant with a further increase in x up to 0.3–0.5. The pressure-composition isotherms clearly show a pressure hysteresis in the TiMn1.5Vx-H2 system which decreases with an increase in the x value mainly due to the equilibrium pressure change for hydride formation. The free energy loss during hydride formation is related to not only the volume expansion, but also the elastic strain in the TiMn1.5Vx alloy itself, that is, prior to hydrogen absorption.

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Han, Xi, Yang Bai und Li Jie Qiao. „The Electrocaloric Effect of BaTiO₃ Ceramics Using Hydrothermal Synthesized Nano-Sized Starting Powders“. Advanced Materials Research 624 (Dezember 2012): 138–41. http://dx.doi.org/10.4028/www.scientific.net/amr.624.138.

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The electrocaloric effect (ECE) of barium titanate ceramics with hydrothermal synthesized nano-sized starting powders was investigated. The Curie point and latent heat of the phase transition were characterized by a differential scanning calorimeter (DSC). The P-E hysteresis loops were measured in the temperature range from 30-160oC and ECE adiabatic temperature change was obtained according to the Maxwell relation. A double hysteresis loop is observed at the temperature slightly above the Curie point, which indicates a good consistency of phase transition similar to single crystal. It is also proved by the sharp endothermic peak of phase transition in DSC curves. It exhibits a high ECE of ΔTmax=1.3K under a low applied field of 10kV/cm, which is much higher than that of the sample using micron-sized starting powders.

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Liu, Lu, Xuelai Zhang, Xiaofeng Xu, Yi Zhao und Shihua Zhang. „The research progress on phase change hysteresis affecting the thermal characteristics of PCMs: A review“. Journal of Molecular Liquids 317 (November 2020): 113760. http://dx.doi.org/10.1016/j.molliq.2020.113760.

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Aharrouch, Rachid, Karima El Kihel, Mohamed Madani, Nabil Hachem, Amer Lafhal und Mohammed El Bouziani. „Magnetic properties and hysteresis behavior of a ferrimagnetic mixed spin-3/2 and spin-5/2 Ising nanowire“. Multidiscipline Modeling in Materials and Structures 16, Nr. 5 (19.03.2020): 1261–76. http://dx.doi.org/10.1108/mmms-11-2019-0194.

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PurposeThe purpose of this paper is to study the magnetic properties and the hysteresis behavior of a ferrimagnetic cubic Ising nanowire with mixed spins S = 3/2 and S = 5/2 in which the atoms are placed alternately.Design/methodology/approachIn order to investigate the effects of the exchange interactions and crystal field on the magnetic properties and hysteresis behavior of the nanowire, we have used the Monte Carlo simulation. More precisely, we have plotted the thermal variations of the sublattice and total magnetizations for different values of the Hamiltonian parameters, and we have presented the corresponding phase diagrams. In addition, the influence of an external magnetic field is examined by plotting the variations of hysteresis loops with the change of temperature and crystal field.FindingsAll phase transition found in this study are of second-order and the critical temperatures increase linearly with the increase of the exchange interactions. The compensation temperatures appear only for some domains of crystal field D and exchange interaction JB of the sublattice (B). Moreover, when studying the hysteresis behavior, the system can show one or double hysteresis loops.Originality/valueThe authors consider that this research is consistent with the scientific axis of the journal which benefits a great esteem in our country and in the world. In addition, the results are of technological interest.

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Mouro, João, Paolo Paoletti, Michele Basso und Bruno Tiribilli. „Measuring Viscosity Using the Hysteresis of the Non-Linear Response of a Self-Excited Cantilever“. Sensors 21, Nr. 16 (19.08.2021): 5592. http://dx.doi.org/10.3390/s21165592.

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A self-oscillating microcantilever in a feedback loop comprised of a gain, a saturator, and an adjustable phase-shifter is used to measure the viscosity of Newtonian fluids. Shifting the signal of the loop with the adjustable phase-shifter causes sudden jumps in the oscillation frequency of the cantilever. The exact position of these jumps depends on whether the shift imposed by the phase-shifter is increasing or decreasing and, therefore, the self-excited cantilever exhibits a hysteretic non-linear response. This response was studied and the system modeled by a delay differential equation of motion where frequency-dependent added mass and damping terms accounted for the density and the viscosity of the medium. Experimental data were obtained for solutions with different concentrations of glycerol in water and used to validate the model. Two distinct sensing modalities were proposed for this system: the sweeping mode, where the width of the observed hysteresis depends on the viscosity of the medium, and the threshold mode, where a sudden jump of the oscillation frequency is triggered by an arbitrarily small change in the viscosity of the medium.

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Samulionis, Vytautas, Juras Banys und Yulian Vysochanskii. „Ultrasonic Relaxation in Phase Transition Region in Ferroelectric Semiconductors of Sn₂P₂S₆Family“. Solid State Phenomena 184 (Januar 2012): 345–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.184.345.

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The paper presents recent results of ultrasonic investigation of Sn2P2S6 family ferroelectric crystals and their solid solutions in the temperature range 100-300 K. It was shown that in Sn2P2(S,Se)6 crystals the critical ultrasonic velocity slowing down for longitudinal waves propagating along main crystallographic directions is quite sharp and large. The relative change of longitudinal ultrasonic velocity along z-axis at the phase transition gradually increased from 10 % in pure Sn2P2S6 till 25 % for sample with 0.4 content of Se. Such large velocity change causes the large ultrasonic attenuation anomaly. The increase of relaxation time: τ=τ0/(TC-T) leads to the increase of attenuation. Prefactor τ0 was shown to be very small and the critical attenuation anomaly arises in the narrow temperature range close to phase transition. In the 0.4 Se sample the phase transition is of the first order because small thermal hysteresis exists. The ultrasonic velocity behaviour in the ferroelectric phase was described using Landau theory and free energy expansion including sixth order terms. For (Sn,Pb)2P2S6 system the critical ultrasonic anomalies were smaller and the phase transition temperature substantially decreased (for 0.45 Pb sample the phase transition point was at Tc =140 K). The ultrasonic anomalies at phase transition in (PbxSn1-x)2P2S6 have large hysteresis showing that transition is of the first order, far from the critical point.

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Moś, Joanna E., Karol A. Stasiewicz, Katarzyna Matras-Postołek und Leszek R. Jaroszewicz. „Thermo-Optical Switching Effect Based on a Tapered Optical Fiber and Higher Alkanes Doped with ZnS:Mn“. Materials 13, Nr. 21 (09.11.2020): 5044. http://dx.doi.org/10.3390/ma13215044.

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The paper investigates the effect of thermo-optic switching resulting from the hybrid combination of a tapered optical fiber (TOF) with alkanes doped with nanoparticles of zinc sulfide doped with manganese (ZnS:Mn NP). Presented measurements focused on controlling losses in an optical fiber by modification of a TOF cladding by the alkanes used, characterized by phase change. Temperature changes cause power transmission changes creating a switcher or a sensor working in an ON-OFF mode. Phase change temperatures and changes in the refractive index of the alkane used directly affected power switching. Alkanes were doped with ZnS:Mn NPs to change the hysteresis observed between ON-OFF modes in pure alkanes. The addition of nanoparticles (NPs) reduces the difference between phase changes due to improved thermal conductivity and introduces extra nucleating agents. Results are presented in the wide optical range of 550–1200 nm. In this investigation, hexadecane and heptadecane were a new cladding for TOF. The higher alkanes were doped with ZnS: Mn NPs in an alkane volume of 1 wt.% and 5 wt.%. The thermo-optic effect can be applied to manufacture a thermo-optic switcher or a temperature threshold sensor.

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LI, TONG, YONGSHENG DU, HUI YAN und DUNBO YUD. „OBSERVATION OF PHASE SEPARATED La0.5Sr0.5MnO3 FILM“. International Journal of Modern Physics B 20, Nr. 05 (20.02.2006): 551–57. http://dx.doi.org/10.1142/s0217979206033437.

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La 0.5 Sr 0.5 MnO 3 films on (001) LaAlO 3 were prepared by RF magnetron sputtering using powder target and were studied by SQUID and XPS. The XPS results show the formation of Mn 3+ and Mn 4+, indicating the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) clusters. SQUID measurement of LSMO on LAO and Si also support an interaction between them at low temperatures, resulting in the shift of hysteresis loops. Large coercivities at low temperature can be attributed to the pinning of both FM and AFM clusters and small coercivities at high temperature to the depinning of both FM and AFM phases, resulting from the thermal motion at higher temperatures which help to overcome the energy barrier and change the magnetic alignments.

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Song, Zhao, Zongbin Li, Bo Yang, Haile Yan, Claude Esling, Xiang Zhao und Liang Zuo. „Large Low-Field Reversible Magnetocaloric Effect in Itinerant-Electron Hf1−xTaxFe2 Alloys“. Materials 14, Nr. 18 (11.09.2021): 5233. http://dx.doi.org/10.3390/ma14185233.

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First-order isostructural magnetoelastic transition with large magnetization difference and controllable thermal hysteresis are highly desirable in the development of high-performance magnetocaloric materials used for energy-efficient and environmental-friendly magnetic refrigeration. Here, we demonstrate large magnetocaloric effect covering the temperature range from 325 K to 245 K in Laves phase Hf1−xTaxFe2 (x = 0.13, 0.14, 0.15, 0.16) alloys undergoing the magnetoelastic transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state on decreasing the temperature. It is shown that with the increase of Ta content, the nature of AFM to FM transition is gradually changed from second-order to first-order. Based on the direct measurements, large reversible adiabatic temperature change (ΔTad) values of 2.7 K and 3.4 K have been achieved under a low magnetic field change of 1.5 T in the Hf0.85Ta0.15Fe2 and Hf0.84Ta0.16Fe2 alloys with the first-order magnetoelastic transition, respectively. Such remarkable magnetocaloric response is attributed to the rather low thermal hysteresis upon the transition as these two alloys are close to intermediate composition point of second-order transition converting to first-order transition.

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Al-Janabi, Ali, und Miroslava Kavgic. „Application and sensitivity analysis of the phase change material hysteresis method in EnergyPlus: A case study“. Applied Thermal Engineering 162 (November 2019): 114222. http://dx.doi.org/10.1016/j.applthermaleng.2019.114222.

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Feng, Ying, Zhi Li, Subhash Rakheja und Hui Jiang. „A Modified Prandtl-Ishlinskii Hysteresis Modeling Method with Load-dependent Delay for Characterizing Magnetostrictive Actuated Systems“. Mechanical Sciences 9, Nr. 1 (23.04.2018): 177–88. http://dx.doi.org/10.5194/ms-9-177-2018.

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Abstract. The actuating precision of a micro-positioning system, driven by a magnetostrictive actuator, is adversely limited by its nonlinearities, particularly the output-input hysteresis, which are further affected by the operating load and input frequency. In this paper, the output-input properties of a magnetostrictive actuated system are experimentally characterized considering a wide range of operating frequencies and loads. The measured data revealed that the hysteresis behaviour is strongly affected with a change of operating load, and a modified Prandtl-Ishlinskii model with load-dependent delay is subsequently formulated to describe the nonlinear characteristics of the magnetostrictive actuated system in terms of major and minor loop hysteresis, and output magnitude and phase responses. The proposed model integrates a load-delay function related to the load mass with the Prandtl-Ishlinskii hysteresis model so as to fully describe the coupled nonlinear delay effects of the system output. The validity of the proposed model is demonstrated through comparisons with the experimental data for a range of operating loads and frequencies. It is shown that the proposed model can accurately describe the load-dependent hysteresis effects of the magnetostrictive actuated system up to certain input frequencies.

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Wu, Yuan Yuan, und Yi Long. „Magnetocaloric Effect of LaFe_11.5Si_1.5C_0.2 Sinters Prepared by SPS Process“. Advanced Materials Research 849 (November 2013): 212–17. http://dx.doi.org/10.4028/www.scientific.net/amr.849.212.

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In order to make high performance magnetic refrigeration materials, Spark Plasma Sintering (SPS) process was introduced in the preparation of LaFe11.5Si1.5C0.2 materials. Results show that the size of the starting powder has a significant influence on the magnetic entropy change than the sintered temperature does. Finer starting powder induce a decomposition of 1:13 phase into α-Fe phase during sintered process. By controlling the particle size, the decomposition can be decreased. The maximum magnetic entropy change value of the sinters with the size of sutible starting powder is as same as the parent compound. Also, the hysteresis loss of the sinters decreased.

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Endo, Takatsugu, Kozo Fujii und Keiko Nishikawa. „Crystal Polymorphism of 1-Butyl-3-methylimidazolium Hexafluorophosphate: Phase Diagram, Structure, and Dynamics“. Australian Journal of Chemistry 72, Nr. 2 (2019): 11. http://dx.doi.org/10.1071/ch18422.

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The ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), is one of the most representative ILs. Despite its relatively simple ion structure and popularity, [C4mim]PF6 shows complex and confusing thermal phase behaviours, which stem from crystal polymorphism associated with cation conformational change and large thermal hysteresis. To the best of our knowledge, [C4mim]PF6 is the most investigated IL in terms of phase diagram, whereas full understanding has not yet been achieved due to its complexity. Here we review the current status of understanding of the phase diagram and structure/dynamics of each crystalline phase. Presently, depending on temperature and pressure, five structurally different polymorphic crystals have been reported as α, β, γ, δ, and δ’ in addition to some unspecified phases implied by calorimetric studies. Particularly for the α, β and γ phases, the structure and dynamics are well investigated by Raman, NMR, and X-ray scattering techniques.

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Delville, Remi, Hui Shi, Richard D. James und Dominique Schryvers. „Special Microstructures and Twin Features in Ti₅₀Ni_50-X(Pd,Au)_X at Small Hysteresis“. Solid State Phenomena 172-174 (Juni 2011): 105–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.105.

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The breaking of symmetry due to atomic displacements in the austenite-martensite phase transformation generally leads to their crystallographic incompatibility. Energy minimizing accommodation mechanisms such as martensite twinning have been recently shown to be a source of hysteresis and irreversible plastic deformation. Compatibility between the two phases can however be achieved by carefully tuning lattice parameters through composition change. A dramatic drop in hysteresis and novel microstructures such as a lowering of the amount of twin lamella are then observed. Related theoretical and simulation works also support the existence of such microstructures including peculiar self-accommodating configurations at near-compatibility. We present the transmission electron microscopy (TEM) study of these novel microstructures for the alloy systems Ti50Ni50-xPdxand Ti50Ni50-xAuxwhere the composition was systemically tuned to approach perfect compatibility. High resolution imaging of the interface between austenite and martensite supplies evidences of compatibility at the atomic level.

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Maheshwari, Priya, Sandeep Kumar Sharma, Dhanadeep Dutta, Kathi Sudarshan und P. K. Pujari. „Phase Transition of Water Confined in Saponites Using Positron Annihilation Spectroscopy“. Materials Science Forum 733 (November 2012): 111–14. http://dx.doi.org/10.4028/www.scientific.net/msf.733.111.

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The temperature dependent Positron lifetime and Doppler broadening spectroscopy have been carried out to study the phase transition of water confined in interlamellar spaces of saponite clay in the temperature range 300K-200K. The change in slope/discontinuity in S-parameter and Ps lifetime as a function of temperature is an indication of phase transition. Two phase transition temperatures viz. above and below the bulk freezing temperature have been observed for water confined in saponite clay. This indicates the presence of two regimes of water confined in interlamellar spaces. The freezing-melting cycle is also marked by significant hysteresis.

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Shirinyan, Aram S. „Two-phase equilibrium states in individual Cu–Ni nanoparticles: size, depletion and hysteresis effects“. Beilstein Journal of Nanotechnology 6 (28.08.2015): 1811–20. http://dx.doi.org/10.3762/bjnano.6.185.

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In isolated bimetallic nanoscale systems the limit amount of matter and surface-induced size effects can change the thermodynamics of first-order phase transformation. In this paper we present theoretical modification of Gibbs free energy concept describing first-order phase transformation of binary alloyed nanoparticles taking into account size effects as well as depletion and hysteresis effects. In such a way the hysteresis in a form of nonsymmetry for forth and back transforming paths takes place; compositional splitting and the loops-like splitted path on the size dependent temperature–composition phase diagram occur. Our calculations for individual Cu–Ni nanoparticle show that one must differentiate the solubility curves and the equilibrium loops (discussed here in term of solidification and melting loops). For the first time we have calculated and present here on the temperature–composition phase diagram the nanomelting loop at the size of 80 nm and the nanosolidification loop at the size of 25 nm for an individual Cu–Ni nanoparticle. So we observe the difference between the size-dependent phase diagram and solubility diagram, between two-phase equilibrium curves and solubility curves; also intersection of nanoliquidus and nanosolidus is available. These findings lead to the necessity to reconsider such basic concepts in materials science as phase diagram and solubility diagram.

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Gawin, Dariusz, Francesco Pesavento, Marcin Koniorczyk und Bernhard A. Schrefler. „Non-equilibrium modeling hysteresis of water freezing: Ice thawing in partially saturated porous building materials“. Journal of Building Physics 43, Nr. 2 (11.06.2019): 61–98. http://dx.doi.org/10.1177/1744259119855100.

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This article presents a novel mathematical model of hygro-thermal processes in a porous material, partially saturated with liquid water, exposed to temperatures below the freezing point of pore water. Water–ice phase transition is modeled by means of a kinetic approach considering water supercooling and thermodynamic non-equilibrium of the phases, what allows taking into account a hysteresis of ice content during freezing–thawing of moist porous materials. The model equations are solved for two numerical examples. The first one deals with laboratory differential scanning calorimetry test of a cement mortar saturated with water and exposed to temperatures below the freezing point of water (down to −40°C). The results are used for experimental validation of the proposed model, confirming its accuracy and practical usefulness. In the second example, the mesh refinement test is performed and the influence of the solid–liquid water phase change model parameters on the simulation results for a 1D model problem concerning water freezing–thawing are analyzed and discussed.

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Gogotsi, Yury G., Vladislav Domnich, Sergey N. Dub, Andreas Kailer und Klaus G. Nickel. „Cyclic Nanoindentation and Raman Microspectroscopy Study of Phase Transformations in Semiconductors“. Journal of Materials Research 15, Nr. 4 (April 2000): 871–79. http://dx.doi.org/10.1557/jmr.2000.0124.

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This paper supplies new interpretation of nanoindentation data for silicon, germanium, and gallium arsenide based on Raman microanalysis of indentations. For the first time, Raman microspectroscopy analysis of semiconductors within nanoindentations is reported. The given analysis of the load-displacement curves shows that depth-sensing indentation can be used as a tool for identification of pressure-induced phase transformations. Volume change upon reverse phase transformation of metallic phases results either in a pop-out (or a kink-back) or in a slope change (elbow) of the unloading part of the load-displacement curve. Broad and asymmetric hysteresis loops of changing width, as well as changing slope of the elastic part of the loading curve in cyclic indentation can be used for confirmation of a phase transformation during indentation. Metallization pressure can be determined as average contact pressure (Meyer's hardness) for the yield point on the loading part of the load-displacement curve. The pressure of the reverse transformation of the metallic phase can be measured from pop-out or elbow on the unloading part of the diagram. For materials with phase transformations less pronounced than in Si, replotting of the loaddisplacement curves as average contact pressure versus relative indentation depth is required to determine the transformation pressures and/or improve the accuracy of data interpretation.

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Klimeš, Lubomír, Pavel Charvát, Mahmood Mastani Joybari, Martin Zálešák, Fariborz Haghighat, Karthik Panchabikesan, Mohamed El Mankibi und Yanping Yuan. „Computer modelling and experimental investigation of phase change hysteresis of PCMs: The state-of-the-art review“. Applied Energy 263 (April 2020): 114572. http://dx.doi.org/10.1016/j.apenergy.2020.114572.

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Shrestha, Ramesh, Yuxuan Luan, Sunmi Shin, Teng Zhang, Xiao Luo, James S. Lundh, Wei Gong et al. „High-contrast and reversible polymer thermal regulator by structural phase transition“. Science Advances 5, Nr. 12 (Dezember 2019): eaax3777. http://dx.doi.org/10.1126/sciadv.aax3777.

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In comparison with the advancement of switchable, nonlinear, and active components in electronics, solid-state thermal components for actively controlling heat flow have been extremely rare. We demonstrate a high-contrast and reversible polymer thermal regulator based on the structural phase transition in crystalline polyethylene nanofibers. This structural phase transition represents a dramatic change in morphology from a highly ordered all-trans conformation to a combined trans and gauche conformation with rotational disorder, leading to an abrupt change in phonon transport along the molecular chains. For five nanofiber samples measured here, we observe an average thermal switching ratio of ~8× and maximum switching ratio of ~10×, which occurs in a narrow temperature range of 10 K across the structural phase transition. To the best of our knowledge, the ~10× switching ratio exceeds any reported experimental values for solid-solid and solid-liquid phase transitions of materials. There is no thermal hysteresis observed upon heating/cooling cycles.

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Kojima, Takashi, und Masataka Koishi. „Mechanisms of Mechanical Behavior of Filled Rubber by Coarse-Grained Molecular Dynamics Simulations“. Tire Science and Technology 48, Nr. 2 (07.01.2020): 78–106. http://dx.doi.org/10.2346/tire.20.160117.

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ABSTRACT: We reproduced mechanical behaviors, such as the reinforcement effect, hysteresis, and stress softening, of filled rubber under cyclic deformations using coarse-grained molecular dynamics simulations. We measured polymer density distribution in the nonload equilibrium state and conformational changes in polymer chains during deformation for dispersed and aggregated filler structures. We found that the polymer–filler attractive interactions increase the polymer density in the vicinity of fillers and decrease the polymer density in the other regions. The polymer bonds that connect polymer particles away from fillers are extended when the polymer density decreases. This alteration increases the modulus of the polymer phase, and the reinforcement effect appears. For aggregated filler structures, the polymer chains interacting with adjacent fillers act as a bridge between these fillers and increase the modulus, especially when the strain is low. To test the mechanisms of hysteresis and stress softening, we measured the changes in the polymer paths. A polymer path is the minimal path of polymer networks between two fillers; in other words, it is the “bridge” that connects two fillers. We found that the polymer paths increase in length, especially during primary loading, because of polymer adsorption/desorption on the filler surface to adjust the change of filler positions. It was also found that the influence of the filler structure diminishes in the first loading. During subsequent unloading, a long path does not become a short path again but will be folded even though the filler distance reduces. Hence, the change in the polymer paths in the second cycle is smaller than that in the first cycle because the polymer path is just unfolded. We confirmed the hysteresis and stress-softening result from these conformational changes. In this article, we also discuss the recovery mechanism for stress softening and the history dependence.

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JAAFAR, ADNAN, SAFWAN AREKAT, AHMED AL-SAIE und MOHAMED BOUOUDINA. „STRUCTURE AND MAGNETIC PROPERTIES OF NANOSIZED BaFe2O4 MATERIAL“. International Journal of Nanoscience 09, Nr. 06 (Dezember 2010): 575–77. http://dx.doi.org/10.1142/s0219581x10007289.

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A mixture of BaO and Fe 2 O 3 was mechanically alloyed followed by subsequent annealing. XRD spectra and magnetization hysteresis curves were obtained for both as-milled and annealed samples. XRD pattern of the as-milled powder indicates the formation of an initial amorphous phase. Upon annealing up to 900°C, the material crystallizes into monoferrite BaFe 2 O 4 phase, accompanied by a dramatic change of the magnetic properties. Moreover, the Ms ≈ 5.8 emu/g , Hc ≈ 1.2 kOe , Mr ≈ 2.4 emu/g and an average crystallites size around 23 nm.

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Tóth, László Zoltán, Lajos Daróczi, Elena Panchenko, Yuri Chumlyakov und Dezső László Beke. „Acoustic Emission Characteristics and Change the Transformation Entropy after Stress-Induced Martensite Stabilization in Shape Memory Ni53Mn25Ga22 Single Crystal“. Materials 13, Nr. 9 (08.05.2020): 2174. http://dx.doi.org/10.3390/ma13092174.

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Measurements have been carried out to compare stress-induced martensite stabilization aged (SIM-aged) and as grown shape memory Ni53Mn25Ga22 single crystals with the means of simultaneous differential scanning calorimetry (DSC) and acoustic emission (AE). Contrary to expectations, the position of the hysteresis practically did not change, whilst the width of the hysteresis increased, and the forward and reverse transitions became sharper in the SIM-aged sample. The energy distributions of acoustic hits showed regular power law behaviour and the energy exponents were slightly different for heating and cooling; this asymmetry had different signs for the SIM-aged and as grown samples. During heating, in accordance with the sharper transitions observed in the DSC runs, two well-marked jumps could be seen on the plot of cumulative number of the acoustic emission events. Therefore, these were attributed to high sudden jumps in the phase transition during heating observed in the DSC. The effect of the SIM-aging on the transformation entropy was also investigated and it was found that it was about 36% less in the case of the SIM-aged sample.

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Schaper, Andreas K., Michael Schosnig, Ali Kutoglu, Werner Treutmann und Helmut Rager. „Transition from the incommensurately modulated structure to the lock-in phase in Co-åkermanite“. Acta Crystallographica Section B Structural Science 57, Nr. 4 (24.07.2001): 443–48. http://dx.doi.org/10.1107/s0108768101006930.

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The adaptation of the incommensurate structure modulation in Ca2CoSi2O7 (dicalcium cobalt disilicate) single crystals to decreasing temperature has been examined using in situ high-resolution transmission electron microscopy and electron diffraction. The transition from the incommensurate to the commensurate lock-in phase of Co-åkermanite exhibits a pronounced hysteresis of a highly strained metastable state with a characteristic microdomain morphology. A network of domain walls surrounding single orientation domains develops out of the room-temperature tartan pattern, the domains increase in size and their alignment changes from crystallographic to random. At 100 K the phase transition becomes almost complete. In parallel, the evolution of the modulation structure can be described by a change from a loose arrangement of octagonal tilings into a close-packed configuration of overlapping octagons in the commensurate low-temperature lock-in phase. Thereby, the octagon represents the ordered distribution of low-coordinated Ca clusters within a nanodomain extending over 4 × 4 subunits, on average [Riester et al. (2000). Z. Kristallogr. 215, 102–109]. The modulation wavevector was found to change from q 1,2 = 0.295 (a* ± b*) at 300 K to q 1,2 = 0.320 (a* ± b*) at 100 K.

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