Hysteresis Width Research Articles

Time-dependent creep fatigue damage evolution in C/SiC composite: Theory and analytical prediction

In this paper, the time-dependent damage evolution in carbon fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) under creep fatigue loading at elevated temperature was analyzed using a micromechanical approach. Synergistic effects of creep fatigue peak stress level and damage in the matrix and the interface on time-dependent damage evolution in C/SiC composites were analyzed. Next, relationships of time-dependent creep fatigue damage mechanisms, damage parameters, environmental temperature and duration were determined. Then, the effects of composite constituent properties, creep fatigue damage state, environmental temperature, and duration on time-dependent damage evolution in C/SiC composites were analyzed. Furthermore, time-dependent composite strain response and interface debonding and oxidation state in C/SiC composite under different creep fatigue peak stress levels were predicted. Under creep fatigue loading, the composite internal damage evolution contributed to the increased time/temperature-dependent composite peak strain. Hysteresis-based damage parameters were developed and utilized to monitor C/SiC composite internal damage evolution. Under creep fatigue loading, the hysteresis area and width increased with oxidation duration to a peak value and remained constant, and the hysteresis modulus decreased with oxidation duration.

One-way coupled numerical model utilizing Viscoelastic Maxwell model for MR damper

Describing the hysteresis behavior of magnetorheological (MR) shock absorber significantly facilitates the developers before manufacturing and control processes. However, most of the models developed to describe the phenomenon have been required experimental data of the manufactured absorber. In this study, the hysteresis behavior for a shock absorber has been characterized by developing a three-dimensional coupled numerical model that adapts Viscoelastic Maxwell Model to momentum equations of fluid flow. The viscosity of the MR fluid, which depends on the magnetic flux density, has been calculated with the Herschel-Bulkley model at each node of the fluid domain, coupled with the magnetic field analysis. The hysteresis relationship between force and velocity has been obtained from time-dependent CFD analyses on the deformed grid. It has been observed that the hysteresis behavior of the MR shock absorber has been attained with a good agreement when the data obtained from the developed numerical model are compared with the experimental data. In addition, besides estimating the hysteresis widths in the force-velocity curves, all effects and changes in time in the flow domain have been observed thanks to the model.

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Slow Phase Transition-Induced Scan Rate Dependence of Spin Crossover in a Two-Dimensional Supramolecular Fe(III) Complex

Realization of high luminous transmittance and solar modulation ability of VO2 films by multistep deposition and in-situ annealing method

Novel VO2(x nm)/VO2(x nm)/VO2(x nm) (x = 10, 14, 16, 20) trilayer films are proposed and prepared on quartz glass substrates via multistep devotion and in-situ annealing by pulsed laser deposition. The bottom, intermediate and top VO2 layers are distinguished by different thickness and annealing time. The characterization of FESEM and AFM showed that grain size and surface roughness of VO2 films increase gradually from the bottom to top layer. The trilayer structure has little effect on phase transition temperature of VO2, but hysteresis width can be tuned in the range of 11–27 °C. The luminous transmission and solar modulation ability of VO2(16 nm)/VO2(16 nm)/VO2(16 nm) trilayer film were remarkably enhanced to 55.7% and 8.0%. The results suggested that such an enhancement can be attributed to the well matching of grain size of the bottom, intermediate and top VO2 layers. The study in this work provide a simple and promising strategy for designing high-quality VO2-based smart windows without additional functional layers.

Competition between Hydrogen and Anagostic Bonds in Ruthenocene Phases under High Pressure

High pressure favors anagostic bonds CH···Ru, which leads to a new polymorph of ruthenocene RuCp2, where Cp denotes the cyclopentadienyl ring [C5H5]−. Ruthenocene can be isothermally compressed in its ambient-pressure phase α up to 3.9 GPa, when it transforms to the new phase, β. The transition between phases α and β proceeds with an exceptionally wide hysteresis extending between 0.7 and 3.9 GPa. The transition destroys single crystals of RuCp2, but a single crystal of polymorph β can be obtained by high-pressure nucleation (above 3.9 GPa) and its isochoric growth continued above 1.0 GPa. On decompression, phase β transforms back to phase α at 0.7 GPa. The structures of phases α (space group Pnma) and β (space group Pcmb) have been determined by X-ray diffraction in the pressure range from 0.1 MPa up to 3.9 GPa. The eclipsed conformation of α-RuCp2 is retained in phase β, which contrasts with the conformational phase transitions in ferrocene and nickelocene. The lattice dimensions and molecular orientations in ruthenocene polymorphs are clearly related, which leads to the characteristic twinning-like oriented growth of the crystals of concomitant phases.

Regulation of phase transition temperature and preparation for doping-VO2 smart thermal control films

Vanadium dioxide (VO2) is considered one of the most promising smart thermal control materials due to its insulator-metal temperature (IMT) reversible phase transition, accompanied by large changes in its optical properties. However, as the crystal defects on IMT change and the optical property of VO2 is still unclear, the preparation of doped VO2 films by magnetron sputtering is still a great challenge. In this work, the IMT of 41 kinds of doping-VO2 systems were studied by high throughput calculation based on density functional theory (DFT). It was found that the IMT increased with the decrease of the β angle in M phase and expansion of cell volume difference of M-phase and R-phase for IIA elements, VIIA elements, transition elements, and rare earth element doped VO2, and increased with the increase of the β angle in M phase and a decrease of cell volume difference of M-phase and R-phase for IA, IVA, VA, and VIA element doped VO2. According to the rule, the IMT, electronic structures, and optical properties of W doped VO2 were studied based on DFT. The results show that IMT and bandgap decrease with the increase of W6+ ion concentration, which is due to the increased cell volume difference of M-phase and R-phase in W doped VO2; each doped atom can reduce the IMT of 20.2 °C, and the IMT of V0.98W0.02O2 is close to room temperature (Tc ≈ 27 °C). The rate of infrared emissivity (∆ɛ) of V0.98W0.02O2 is about 0.2 at 8–14 μm (0.088–0.155 eV) and the average solar absorption (αs) of M phase and R phase is about 0.53 and 0.59 at 0.3–1.5 μm (0.496–4.13 eV), respectively. Finally, radio frequency magnetron sputtering was used to achieve precise doping, which solved the problem of oxygen partial pressure in reactive magnetron sputtering, and V1-xWxO2 films with IMT close to room temperature and narrow hysteresis width were prepared. This is due to the fact that higher W doping content will greatly increase the density of defect-induced nucleation sites and promote nucleation. At the same time, the experimental results of IMT were consistent with the calculated results, which proved the reliability of the calculation. This will provide a theoretical basis for the development of new thermal control materials and a new method for the preparation of doping-VO2 films in the future.

Study on the halide effect of MA4PbX6·2H2O hybrid perovskites – From thermochromic properties to practical deployment for smart windows

Thermochromic smart windows empowered by the unique material properties and reversible thermochromism of dihydrated methylammonium lead halide hybrid perovskites (MA4PbX6·2H2O; X: halide) have risen as novel yet promising candidates for thermochromic smart windows, in which the halide plays a crucial role to the functionality and performance. In this study, the effects of halide types and mixing ratios on the thermochromic properties and practical deployment of MA4PbX6·2H2O halide hybrid perovskites are comprehensively studied by extensive fabrication and characterization processes as well as fundamental and applicational investigation tools. The potential perovskite compositions for thermochromic smart window applications are identified with respect to the desired optical properties (i.e. luminous transmittance and solar modulation ability) and transitional properties (i.e. transition temperature, hysteresis width and transition time). Moreover, thermal-regulating performance of the applicable candidate mixed halide hybrid perovskite MA4PbI5Br1·2H2O is demonstrated in a model-house field investigation. This work provides not only an inclusive database of the thermochromic properties of MA4PbX6·2H2O halide hybrid perovskites, but also an application manual about their deployment for thermochromic smart windows, facilitating the development of smart windows and sustainable buildings.

Guest-Induced Multistep-to-One-Step Reversible Spin Transition with Enhanced Hysteresis in a 2D Hofmann Framework.

The interplay of host-guest interactions and controlled modulation of spin-crossover (SCO) behavior is one of the most exploited topics regarding data storage, molecular sensing, and optical technologies. In this work, we demonstrate the experimental approach of tuning the SCO behavior via controlled modulation of the spin-state cooperativity in a 2D Hofmann coordination polymer, [FeIIPd(CN)4(L)2]·1.3MeOH (1·1.3MeOH; L = methyl isonicotinate). Removal of the solvent changes the four-step transition to a complete one-step spin transition with an enhanced hysteresis width (∼20 K). Structural analysis of solvated (1·1.3MeOH) and partially desolvated (1·0.3MeOH) compounds reveals that the crystal system changes from a monoclinic C2/c space group to an orthorhombic Imma space group, where the FeII sites are present in a more symmetrically equivalent environment. Consequently, the axial ligand-field (LF) strength and face-to-face interactions of the ligands were increased by removing the guest, which is reflected in the highly cooperative SCO in 1 (desolvated compound). Also, the shift of the CN bond stretching frequencies and decrease of their relative intensities from the variable-temperature Raman spectroscopic measurements further corroborate the SCO behavior. Besides, theoretical calculations reveal that the singlet (1Γ) LF terms decrease by removing guest molecules, enhancing the molecular population in the low-spin state at low temperature, as experimentally observed for 1. Notably, fine tuning of the SCO behavior via host-guests interactions provides a great opportunity to design potential chemosensors.

A trinuclear {FeIII2FeII} complex involving both spin and non-spin transitions exhibits three-step and wide thermal hysteresis

A trinuclear {FeIII2FeII} complex involving both spin and non-spin transitions exhibits three-step and wide thermal hysteresis

Large easy-axis magnetic anisotropy in a series of trigonal prismatic mononuclear cobalt(ii) complexes with zero-field hidden single-molecule magnet behaviour: the important role of the distortion of the coordination sphere and intermolecular interactions in the slow relaxation

A N6-tripodal ligand allows the preparation of a family of prismatic mononuclear cationic CoIIcomplexes with SMM behavior. Their axial anisotropy, magnetic relaxation and hysteresis width are modulated by the anion effects on the crystal structure.

Evolution of Transformation Strain During Partial Transformation Cycling of an NiTi Shape Memory Alloy

This paper deals with how the magnitude of transformation strain changes on partial transformation cycling of an NiTi shape memory alloy. A near-equiatomic NiTi shape memory alloy was allowed to undergo partial thermal cycling keeping the stress constant at 100 MPa for various upper cycle temperatures (between austenite start and austenite finish), using a custom-built thermomechanical cycling test setup. The displacement and the temperature of the sample during cycling were measured using a LASER extensometer and an optical pyrometer, respectively. The test results show that the recovery strain and thermal hysteresis width decrease with increasing number of cycles during partial cycling. In addition, martensite start and martensite finish temperatures increase during the initial cycles, whereas austenite start and austenite finish temperatures decrease during the initial cycles, followed by their saturation.

SPIN-CROSSOVER IRON(II) COORDINATION COM­POUNDS: FABRICATION OF FUNCTIONAL MATERIALS AND THEIR INTEGRATION INTO MICRO- AND NANOCONSTRUCTIONS

Development of micro- and nanosized spin-crossover (SCO) materials has become an important research direction within the past decade. Such an interest is associated with high perceptive of practical application of these materials in nanoelectronic devices. Therefore, researches working in the field of SCO put considerable efforts to obtain SCO complexes in various functional forms, such as nanoparticles, thin films, etc. Fabrication of these materials is realized through different chemical and/or lithographical approaches, which allow to adjust size, shape and even organization of nanoobjects.
 In this review theoretical background of SCO phenomenon is described, additionally different classes of coordination compounds exhibiting spin crossover are covered. It is demonstrated that electric field, temperature and light irradiation can be effectively used for switching and control of spin state in nanosized SCO systems. Cooperative SCO with transition close to room temperature, wide hysteresis loop and distinct thermochromic effect is most often observed for Fe(II) coordination complexes. Therefore, Fe(II) SCO compounds form one of the most perspective classes of compounds for obtaining functional materials. It is shown that integration of Fe(II) compounds into micro- and nanohybrid devi­ces allows to combine unique functional pro­perties in one material due to synergy between SCO and physical properties (luminescent, electrical, etc.) of the other component. As a result, SCO compounds are interesting not only from the fundamental point of view, but also from practical, thanks to the possibility of integration of SCO Fe(II) complexes as active materials in devices of different configurations.
 It is expected that obtaining of new Fe(II) coordination polymers with unique SCO cha­racteristics will favor the development of new functional materials and devices on their basis in the nearest future.

ECAP based regulation mechanism of shape memory properties of NiTiNb alloys

NiTiNb is a kind of wide hysteresis shape memory alloy with great application potential in aerospace. However, the mechanism of improving the shape memory properties of the NiTiNb alloy by tailoring grain size and grain boundary type has not been well identified. Accordingly, taking equal channel angular pressing (ECAP) as the grain refinement method, this paper focused on the regulation mechanism of grain size and grain boundary type on the shape memory properties. First, grain refinement structures with a special distribution of low- and high- angle grain boundaries (LAGBs and HAGBs) were prepared by ECAP with different passes. Then, the mechanism of the grain boundary on the shape memory properties was first revealed. It was found that many LAGBs appeared in NiTiNb alloy after ECAP, and with increasing of ECAP passes, the LAGBs were transformed into the HAGBs, achieving grain refinement. The stress-induced transformation produced (001) compound twins in the dense sub-microcrystalline region surrounded by LAGBs, leading to a non-monotonic variation of transformation strain with decreasing grain size. Meanwhile, with the decrease of grain size (or the increase of grain boundary content), the transformation hysteresis temperature and recovery stress of the NiTiNb alloy increased simultaneously. To obtain better shape memory characteristics, we can tailor the type and distribution of specific grain boundaries through the design of ECAP.

High-Pressure Polymorphs Nucleated and Stabilized by Rational Doping under Ambient Conditions.

High-pressure polymorphs can be obtained and stabilized at ambient pressure by utilizing dopants with more voluminous molecules, inducing internal strain in the structures. This effect has been confirmed for doped resorcinol and imidazole derivatives by nucleating and stabilizing their high-pressure phases under ambient conditions. The dopant molecular volume and concentration, as well as the bulk modulus of the polymorph in the binary system, are related to the stability region in the single-component phase diagram. High-pressure isothermal and isochoric recrystallizations yielded pure single crystals of resorcinol ε above 0.20 GPa and a new polymorph ζ above 0.70 GPa. These recrystallizations of pure resorcinol revealed within 1 GPa of the p–T phase diagram the boundaries and the stability regions of four resorcinol polymorphs α, β, ε, and ζ, contrary to the compression experiments on ambient-pressure polymorphs α and β, when the high-pressure phases were hidden behind the wide hysteresis extending to nearly 5 GPa. The hysteresis, originating from the H-bonding networks, hinders the formation of polymorphs ε and ζ when polymorphs α and β are compressed without melting or dissolving the crystals. Polymorph ζ is the only known resorcinol structure built of hydrogen-bonded layers.

Electrical Characterization and Study of Current Drift Phenomena and Hysteresis Mechanism in Junctionless Ion-Sensitive Field-Effect Transistor

A comprehensive study of the drain current drift mechanism and hysteresis phenomena in fabricated p-channel junctionless ion-sensitive field-effect transistor (JL-ISFET) has been investigated for the first time. The current drift measurements have been performed through transient analysis of drain current, under different pH and liquid-gate bias (Vlg). Further, time-dependent gate-capacitance (CG) has also been analyzed to see the effect of hydroxyl ions (OH−) in the sensing film (Al2O3). The hysteresis has also been investigated for different pH loop (7 → 3 → 7 → 11 → 7 and 7 → 11 → 7 → 3 → 7) and times (960s, 1500s, and 1920s). It has been observed that the drift of JL-ISFET occurs because of chemical modification of the sensing film, due to OH−. The proposed device exhibits a threshold voltage sensitivity of 58.2 mV/pH that is near the Nernstian limit. Further, the hysteresis width and maximum drain current drift are measured as \(\sim \) 1.3 mV and 2.4 μ A (\(\sim \) 75%), respectively.

Pressure Tunable Electronic Bistability in Fe(II) Hofmann-like Two-Dimensional Coordination Polymer [Fe(Fpz)2Pt(CN)4]: A Comprehensive Experimental and Theoretical Study.

A comprehensive experimental and theoretical study of both thermal-induced spin transition (TIST) as a function of pressure and pressure-induced spin transition (PIST) at room temperature for the two-dimensional Hofmann-like SCO polymer [Fe(Fpz)2Pt(CN)4] is reported. The TIST studies at different fixed pressures have been carried out by magnetic susceptibility measurements, while PIST studies have been performed by means of powder X-ray diffraction, Raman, and visible spectroscopies. A combination of the theory of elastic interactions and numerical Monte Carlo simulations has been used for the analysis of the cooperative interactions in TIST and PIST studies. A complete (T, P) phase diagram for the compound [Fe(Fpz)2Pt(CN)4] has been constructed. The critical temperature of the spin transition follows a lineal dependence with pressure, meanwhile the hysteresis width shows a nonmonotonic behavior contrary to theoretical predictions. The analysis shows the exceptional role of the total entropy and phonon contribution in setting the temperature of the spin transition and the width of the hysteresis. The anomalous behavior of the thermal hysteresis width under pressure in [Fe(Fpz)2Pt(CN)4] is a direct consequence of a local distortion of the octahedral geometry of the Fe(II) centers for pressures higher than 0.4 GPa. Interestingly, there is not a coexistence of the high- and low-spin (HS and LS, respectively) phases in TIST experiments, while in PIST experiments, the coexistence of the HS and LS phases in the metastable region of the phase transition induced by pressure is observed for a first time in a first-order gradual spin transition with hysteresis.

High-frequency magnetic response of superferromagnetic nanocomposites

Studies of the dynamical response of thin-film composites of magnetic nanoparticles embedded in dielectric matrices to the oscillatory magnetic field of the microwave-frequency range are performed using numerical simulations. Four soft-magnetic systems; (Co)0.42(MgF2)0.58, (Fe65Co35)0.57(SiO2)0.43, (Fe65Co35)0.75(Al2O3)0.25, (Fe65Co35)0.6(Al2O3)0.4, typical of a class of ”high-frequency ferromagnetic nanocomposites” are simulated. The necessary micromagnetic parameters are extracted from data within the model of random magnetic anisotropy (RMA). Those materials are candidates for use in micro-converters of power (inductors and transformers) due to their high saturation magnetization, high resistivity, and absence of intra-grain magnetic domains. Thus, they are able to create a high magnetic flux at low power losses. The simulations allow for an inspection into details of the spatial distribution of the oscillating magnetization. We predict noticeable differences in the ferromagnetic resonance (FMR) in different composites which are related to the shape of the static hysteresis. Operating ranges of the driving-field amplitude are related to the hysteresis width. Next to FMR, we analyze the magnetic response via the oscillatory motion of domain walls in a longitudinal field. Besides the response to the alternating field of a constant direction, we study the magnetization dynamics driven by in-the-plane-rotating field. Such a field can drive the magnetization rotations which are a strong-response (nonlinear) mode potentially useful for efficient power conversion.

Optimizing VO2 film properties for use in SAW devices

The aim of this study is to optimize the conditions for producing thin VO2 films for their use in SAW devices. We used the pulsed laser deposition (PLD) method to produce VO2 films. We used a metallic vanadium target. The dependence of the oxygen pressure during PLD on the resistive metal–insulator transition (MIT) on substrates of [Formula: see text]-sapphire and LiNbO3 YX/128[Formula: see text] was studied. The resulting films had sharp metal–insulator temperature transitions on [Formula: see text]-Al2O3. The most high-quality films showed resistance change by four orders of magnitude. At the lower point of the hysteresis, the resistance of these samples was in the range of 50–100 [Formula: see text]. The synthesized VO2 films had a sharp temperature transition and a relatively small width of thermal hysteresis. The SAW damping during its passage through a VO2/ZnO/LiNbO3 YX/128[Formula: see text] film at the metal–insulator phase transition temperature was studied. Attenuation SAW decreases with increasing temperature from 52 dB/cm to 0 dB/cm.

Regulation of the phase transition temperature and hysteresis width by changing the composition of Eu1–xLaxFe3(BO3)4 solid solution

A detailed study of the structural phase transition in ${\mathrm{Eu}}_{1\text{--}x}{\mathrm{La}}_{x}{\mathrm{Fe}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{4}$ mixed crystals as a function of composition is reported. By analyzing a frequency shift of an electronic f-f transition in high-resolution optical spectra of ${\mathrm{Eu}}^{3+}$ ions, we detected a decrease in the phase transition temperature ${T}_{\mathrm{s}}$ from 87.05 to 12.2 K (upon cooling) and a simultaneous increase in thermal hysteresis $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{s}}$ from 0.29 to 4.7 K with increasing $x$ from $x=0$ to $x=0.12$. A rectangular hysteresis loop was observed. The experimental ${T}_{\mathrm{s}}(x)$ and $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{s}}(x)$ dependences are described within the developed analytical model utilizing linear decrease in ${T}_{\mathrm{s}}$ with $x$ and treating the increase in $\mathrm{\ensuremath{\Delta}}{T}_{\mathrm{s}}$ in terms of the impurity-related decrease in the interaction between some local order parameters. We argue that ${R}_{1\ensuremath{-}x}{R}_{x}^{\ensuremath{'}}{\mathrm{Fe}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{4}$ solid solutions, where $R$ and $R$\ensuremath{'} are different rare-earth elements, can be used to implement optical storage devices and switches operating at any chosen temperature between 0 and 450 K. It is found that the changes in the composition and, correspondingly, structural phase transition parameters do not affect the magnetic phase transformation. ${\mathrm{Eu}}_{0.88}{\mathrm{La}}_{0.12}{\mathrm{Fe}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{4}$ demonstrates the structural phase transition at about 12 K, well below the N\'eel temperature ${T}_{\mathrm{N}}=32\phantom{\rule{0.16em}{0ex}}\mathrm{K}$.

Substrate Temperature-Dependent Structural, Optical, and Electrical Properties of Thermochromic VO2(M) Nanostructured Films Grown by a One-Step Pulsed Laser Deposition Process on Smooth Quartz Substrates

Thermochromic M-phase vanadium dioxide VO2(M) films with different morphologies have been grown directly on smooth fused quartz substrates using low deposition rate pulsed laser deposition without posttreatment. When the substrate temperature was increased in the range 450°C–750°C, better (011) texturization of VO2(M) films was observed along with an enhancement of their crystallinity. Morphology evolved from small-grained and densely packed VO2(M) grains at 450°C to less packed micro/nanowires at 750°C. Mechanisms behind the crystallinity/morphology evolution were discussed and correlated with the effect of the temperature on the diffusion of the adatoms as well as on the V5+ valence states content in VO2(M) films. Resistivity measurements as a function of temperature revealed that the insulator-to-metal transition features of VO2(M) films (i.e., transition temperature (TIMT), resistivity variation (ΔR), hysteresis width (ΔH), and transition sharpness (ΔT)) are strongly dependent on the processing temperature. In terms of optical properties, it was found that the open (i.e., porous) structure of the films achieved at high temperature induced an improvement of their luminous transmittance. Simultaneously, the enhancement of the films crystallinity with the temperature resulted in better IR modulation ability. The present contribution provides a one-step process to control the morphology of VO2(M) films grown on smooth quartz substrates for applications as switches, memory devices, and smart windows.