Pronounced Hysteresis Loops Research Articles

Desorption hysteresis in organic-rich formations: Implications for long-term carbon dioxide sequestration and hydrogen recovery factor

This study explores the potential of organic-rich formations for geo-storage of hydrogen and carbon dioxide using a novel molecular simulation workflow combing Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) to delineate the interplay between pore structure, kerogen maturity, and the resulting adsorption–desorption behavior. The investigation utilizes two representative kerogen models – immature (II-A) and overmature (II-D) – to account for the inherent heterogeneity of organic-rich formations. The simulations demonstrate a direct correlation between kerogen maturity and gas sorption capacity. The overmature model, with its larger intermolecular spaces, exhibits a higher capacity for both H2 and CO2 compared to the immature one. Notably, CO2 displays a significantly stronger affinity towards the organic material, resulting in a much higher sorption capacity compared to H2 for both kerogen types. The key finding lies in the contrasting desorption profiles for H2 and CO2. H2 desorption exhibits minimal hysteresis, suggesting readily recoverable gas with minimal trapping within the kerogen structure. This signifies the potential for efficient H2 storage with minimal losses during retrieval stages. Conversely, CO2 desorption displays a pronounced hysteresis loop, indicating significant gas retention within the formation even at lower pressure. This behavior aligns perfectly with the objective of CO2 sequestration, where minimizing leakage risk is paramount. These contrasting effects of hysteresis on H2 storage and CO2 sequestration highlight the unique suitability of organic-rich formations for both applications. Additionally, the study suggests a potential link between kerogen maturity and the magnitude of the hysteresis loop. Such insights could be instrumental in selecting optimal formations for targeted geo-storage operations.

Transient simulation of the electrical hysteresis in a metal/polymer/metal nanostructure.

The time-dependent quantum transportation through a metal/polymer/metal system is theoretically investigated on the basis of a Su-Schrieffer-Heeger model combined with the hierarchical equations of motion formalism. Using a non-adiabatic dynamical method, the evolution of the electron subspace and lattice atoms with time can be obtained. It is found that the calculated transient currents vary with time and reach stable values after a response time under the bias voltages. However, the stable current as the system reaches its dynamical steady state exhibits a discrepancy between two sweep directions of the bias voltage, which results in pronounced electrical hysteresis loops in the current-voltage curve. By analyzing the evolution of instantaneous energy eigenstates, the occupation number of the instantaneous eigenstates, and the lattice of the polymer, we show that the formation of excitons and the delay of their annihilation are responsible for the hysteretic current-voltage characteristics, where electron-phonon interactions play the key factor. Furthermore, the hysteresis width and amplitude can also be modulated by the strength of the electron-phonon coupling, level-width broadening function, and temperature. We hope these results about past condition-dependent switching performance at a sweep voltage can provide further insight into some of the basic issues of interest in hysteresis processes in conducting polymers.

Adaptable photonic artificial neurons for attention-based object identification

The human visual system, reflected by its unique attention-dependent object recognition, holds remarkable potential. However, emulating the capabilities of the human visual system using typical two-terminal photodetectors is challenging. This is because these devices, which respond directly to optical and/or electrical stimuli, do not possess the adaptive and selective features inherent in bio-neuronal systems. In this study, we present a report of adaptable, attention-dependent object recognition utilizing gallium oxide-based photodetectors. The device demonstrates a pronounced hysteresis loop opening with an on/off ratio of less than 10 while maintaining ultra-low dark current levels below 10−10 A in its current-voltage curves. Notably, the on/off ratio can dynamically adjust to multilevel, > 102, and even rise to 103 under ultraviolet illumination. The observed results are attributed to the charge trapping and detrapping processes, as evidenced by detailed photocurrent mapping. Moreover, when subjected to simultaneous optical and electrical stimuli, the current first rises and subsequently falls post-peak, exhibiting neuron-like dynamics. These dynamics are subsequently used to emulate attention-based object identification by designing 3 × 3 array. Our findings present proof-of-concept photodetectors that emulate bio-neuronal object recognition systems, suggesting considerable potential for breakthroughs in areas like surveillance, remote sensing, medical imaging, and machine vision.

Symmetric bipolar resistive switching in copper oxide nanostructure/ITO lateral device under exposure to atmospheric oxygen and application in artificial synaptic devices

Capacitively coupled resistive switching behaviour was observed in a planar-geometry two-terminal device based on nanostructures of copper oxide as active material and indium tin oxide (ITO) as electrodes. When tested in ambient atmosphere, current-voltage I−V characteristic was found to be symmetric with pronounced hysteresis loop signifying two different states of resistance, namely the low resistive state (LRS) and high resistive state (HRS). Capacitive effect was apparent in the low voltage regime due to the presence of offset voltage at zero current and offset current at zero bias. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of native oxygen vacancies in copper oxide. Additionally, exposure to atmospheric oxygen played the dominant role in creation of excess vacancy sites by electrochemical reaction near positive electrode. Creation of excess density of oxygen vacancy near the electrodes in conjunction with trapping and detrapping of electrons from these defect sites is perceived as the prime mechanism for the observed switching behaviour. The device ON/OFF ratio, ION/IOFF∼1.5 was found to be stable over at least 100 continuous cycles. When tested under vacuum, the device I−V characteristics was linear in shape without any hysteresis signifying ohmic transport. Analysis of ultraviolet photoelectron spectroscopy (UPS) showed the Fermi energy level of copper oxide is at ∼ 4.69 eV, which is in a close match with the work function of ITO-electrode. The essential synaptic characteristics such as learning and forgetting curves and paired pulse facilitation (PPF) are established. The nonlinearity factors (NLF) are very low indicating the copper oxide-based devices are promising candidates for neuromorphic applications.

Spin state bistability in (Mn, Zn) doped Fe(phen)2(NCS)2 molecular thin film nanocrystals on quartz

Spin state bistability within high spin (HS) and low spin (LS) state is investigated in undoped and (Zn, Mn) doped spin crossover (SCO) complex Fe(phen)2(NCS)2 thin films (thickness ∼ 300 nm) deposited by dip-coating technique at room temperature on the quartz substrate. The X-ray diffraction studies clearly show the formation of crystalline structure of SCO complexes. The growth of the thin films was indisputably confirmed by electron microscopy and optical studies. The optical absorption peak between 535-557 nm was clearly observed, and that corresponds to 1A1g → 1T1g ligand field absorption in undoped and metal-doped (Zn, Mn) SCO thin films. The high spin (HS) state of the SCO films at room temperature was confirmed by Raman spectra. The bistability of spin states is clearly revealed by the well pronounced thermal hysteresis loop in magnetization measurements. The spin transition temperature (T1/2) and loop width are found to be critically dependent on metal doping and suggested the possibility of tuning these parameters in spin-crossover thin films to design future spin-based devices.

Antifogging Properties of Spinodal Porous Structures for Optical Application.

For the optical applications of antifogging, equilibrium amounts of adsorbed water with humidity were measured on bulk glasses having spinodal pores of 4, 10, 15, 20, and 50 nm. The kinetics of adsorption toward a saturated state and desorbing reversely from the saturated state were investigated on a 15 nm sample that was etched sufficiently to suppress the influence of the silica gel left in the pores. To clarify the role of the pores, the relative humidity (RH) was transformed to Kelvin's diameter, φ. There were pronounced hysteresis loops in the adsorption amounts against humidity, in which adsorption occurred at higher humidities and desorption took place at humidities corresponding to sizes of pores confirmed by mercury intrusion porosimetry. On the basis of weather data in Tokyo, the antifogging coating having pores larger than 12 nm in size was proposed with an emphasis on the recovery of antifogging. Antifogging was further discussed in terms of the capabilities of adsorption related to the thickness of the porous layer and the kinetics of adsorption with a degree of supersaturation at RH100%.

Low field magnetotransport behavior of barium hexaferrite/ferromagnetic manganite bilayer

Adding functionalities to existing ferroelectric/ferromagnetic materials showed promising results with exciting physical mechanisms. Pure and bilayer films of strong ferromagnetic oxides, viz, BaFe12O19 (BaM) and La0.67Sr0.33MnO3 (LSMO), were fabricated by pulsed laser deposition. Polycrystalline samples of dense structure, uniform thickness, and monodispersed grain distributions were used to form capacitor-like stack geometry for dielectric and magneto-dielectric (MD) measurements. High dielectric constants at moderately high frequencies with increased relaxation times were observed for the bilayer film and are attributed to the BaM/LSMO strained interface, while Maxwell–Wagner polarization plays an insignificant role. Modeling of dielectric loss tangents and AC conductivity revealed localized carrier hopping between Fe ions in the bilayer film. Pronounced hysteresis loops with a small coercive field and increased saturation magnetization values of BaM/LSMO bilayers, as compared with BaM/Pt, are demonstrated at 300 K; where the role of mixed valence Mn ions in +3 and +4 states at the bottom LSMO electrode is highlighted. MD measurements with varying magnetic fields showed magnetically tunable, large MD coupling values (∼287%) for BaM/LSMO/Pt. The phenomenally high MD values are discussed based on ionic polarization, colossal magnetoresistance of LSMO, and magnetostriction at the BaM/LSMO interface. Our findings propose significant applications of ferromagnetic oxide bilayers in the emerging field of magneto-dielectric coupling devices.

Soybean Hull Insoluble Polysaccharides: Improvements of Its Physicochemical Properties Through High Pressure Homogenization

Soybean hull is an agroindustrial waste which has not been fully studied as a food ingredient. The aims of this work were to obtain insoluble fibers from soybean hull and to evaluate the effect of high pressure homogenization (HPH) on its physicochemical properties. Hull insoluble polysaccharides (HIPS) were obtained in a single step, as the insoluble residue after pectin removal. FTIR showed bands corresponding to cellulose and hemicellulose in HIPS, and thermogravimetric analysis showed two degradation events at 236.3 °C and 325.6 °C, corresponding to cellulose and hemicellulose, respectively. HIPS dispersions (pH 3.00) were subjected to HPH by three cycles at increasing pressures (up to 1000 bar), obtaining soybean hull nanofibers. SEM images show that HPH at 1000 bar reduced the dimensions of the fiber bundle from 30 to 90 μm in length and 9–15 μm in diameter to nanofibers of 10–30 μm in length and 100–400 nm in diameter. AFM further confirms a heterogeneous distribution of sizes in HIPS800 and HIPS1000, evidencing the presence of individual nanofibers with diameters around 50 ± 10 nm and 40 ± 10 nm, respectively, with several μm in length. Furthermore, an increase in water holding capacity from 2.1 to 61 gwater/gdry matter and viscosity from 0.39 to 34,945 Pa.s were achieved as HPH at 1000 bar treatment was applied. HPH increased the interfacial area and promoted the interconnection of fibers in a hydrated gel-like structure. This explains flow behavior, which was extensively studied in this work: three-region viscosity profile (shear-thinning, plateau or shear-thickening and shear-thinning) and a pronounced hysteresis loop. Oscillatory rheology was used to study the viscoelastic behavior of HIPS dispersions. HIPS are a source of nanofibers, easy to obtain through a single step of chemical treatment followed by the application of high pressures. It is remarkable that the use of few chemical solvents is favorable from an environmental point of view. This work also suggests a potential application of HIPS to improve physicochemical and structural properties in acidic foods.

Experimental Comparison of Nonlinear Optical Properties Between Graphene Oxide and Reduced Graphene Oxide

We delineate a comparative investigation between dispersed graphene oxide (GO) and reduced graphene oxide (RGO) by experimentally measuring their principal/nonlinear optical parameters. We show that the nonlinear refractive index of RGO is larger than that of GO while the nonlinear absorption coefficient of RGO is almost negligible. We particularly organize an experimental plan using GO and RGO inks included in a Mach–Zehnder interferometer and illuminated by a light beam with the wavelength 650 nm. We obtain that the lower threshold input power and more pronounced hysteresis loops are obtained for RGO in comparison to GO. We infer that the contribution of nonlinearity is majorly refractive in RGO rather than absorptive. In return, GO shows a larger absorptive nonlinearity compared to RGO in consequence of the larger nonlinear absorption coefficient. Although GO seems to be appropriate for the saturable absorption-based applications, we deduce that partially reduced GO is more preferred since it can appear as an active electrode providing then an ultrathin electric double layer required for ultrashort pulse generation. Our results indicate that RGO is also suitable for the electro-optical applications like the modulation through which the Fermi energy is to be tuned with a low bias voltage. As well, we propose RGO for all-optical applications like the optical switching for which the highly nonlinear response is required.

New Class of Type III Porous Liquids: A Promising Platform for Rational Adjustment of Gas Sorption Behavior.

Porous materials have already manifested their unique properties in a number of fields. Generally, all porous materials are in a solid state other than liquid, in which molecules are closely packed without porosity. "Porous" and "liquid" seem like antonyms. Herein, we report a new class of Type 3 porous liquids based on rational coupling of microporous framework nanoparticles as porous hosts with a bulky ionic liquid as the fluid media. Positron annihilation lifetime spectroscopy (PALS) and CO2 adsorption measurements confirm the successful engineering of permanent porosity into these liquids. Compared to common porous solid materials, as-synthesized porous liquids exhibited pronounced hysteresis loops in the CO2 sorption isotherms even at ambient conditions (298 K, 1 bar). The unique features of these novel porous liquids could bring new opportunities in many fields including gas separation and storage, air separation and regeneration, gas transport, and permanent gas storage at ambient conditions.

Adsorption on Nanopores of Different Cross Sections Made by Electron Beam Nanolithography.

Adsorption on nanoporous matrices is characterized by a pronounced hysteresis loop in the adsorption isotherm, when the substrate is loaded and unloaded with adsorbate, the origin of which is a matter of immense debate in the literature. In this work, we report a study of argon adsorption at 85 K on nonconnecting nanopores with one end closed to the surrounding where the effects of different pore cross sections fabricated by electron beam lithography (EBL) are investigated. A polymethylmethacrylate (PMMA) resist is deposited on the electrodes of a sensitive quartz crystal microbalance without degradation of the resonance quality factor or the long-term and short-term stabilities of the device even at cryogenic temperatures. Four different pores' cross sections: circular, square, rectangular, and triangular, are produced from EBL, and the isotherms for these pore shapes exhibit pronounced hysteresis loops whose adsorption and desorption branches are nearly vertical and have almost the same slopes. No difference is observed in the hysteresis loops of the isotherms for the pores with triangular and square cross sections, whereas the hysteresis loop for the pore with circular cross sections is much narrower, suggesting that they are more regular than the other pores. All of these observations suggest that the hysteresis behavior resulted mainly from microscopic geometric irregularities present in these porous matrices.

Memristive device based on a depletion-type SONOS field effect transistor

State-of-the-art SONOS (silicon-oxide-nitride-oxide-polysilicon) field effect transistors were operated in a memristive switching mode. The circuit design is a variation of the MemFlash concept and the particular properties of depletion type SONOS-transistors were taken into account. The transistor was externally wired with a resistively shunted pn-diode. Experimental current–voltage curves show analog bipolar switching characteristics within a bias voltage range of ±10 V, exhibiting a pronounced asymmetric hysteresis loop. The experimental data are confirmed by SPICE simulations. The underlying memristive mechanism is purely electronic, which eliminates an initial forming step of the as-fabricated cells. This fact, together with reasonable design flexibility, in particular to adjust the maximum RON/ROFF ratio, makes these cells attractive for neuromorphic applications. The relative large set and reset voltage around ±10 V might be decreased by using thinner gate–oxides. The all-electric operation principle, in combination with an established silicon manufacturing process of SONOS devices at the Semiconductor Foundry X-FAB, promise reliable operation, low parameter spread and high integration density.

Comparison of two different modeling approaches to describe the non‐linear viscoelastic behavior of filled rubber material

AbstractThis contribution presents the characterisation of an incompressible carbon black‐filled elastomer as one characteristical example for highly filled rubber material. The material model is developed with respect to uniaxial tension data. The experiments show that a strongly pronounced non‐linear viscoelastic material behavior is present and the most important characteristic is the extremely long relaxation time which has to be taken into account. These long relaxation times are also visible in cyclic tests, where a pronounced hysteresis loop appears even for the slowest possible strain rates [1,2].In the material's characterization two different model approaches are realized. As a first approach the behavior is represented by a pure viscoelastic model. Since all the deformations are reversible for a stress‐free relaxation, no plasticity parts are included in the model. In order to display the non‐linearities process‐dependent material parameters have to be applied. Hence, the resulting coupling of different material parameters yields a complex parameter identification.For a more effective identification process, a second approach is provided describing the interaction of the filler particles. The friction of the fillers during deformation results in a statical hysteresis, which does not depend on the strain rate. Therefore, special attention is turned towards the behavior of the hysteresis loops that are observed, similar to the description of Vandenbroucke et al. [3]. Therein, in a rheological model, some Prandtl‐elements, consisting of a friction element and a spring are added to the classical viscoelastic model. This results in a model, which does not need any process‐dependency. Hence, the identification process can be simplified. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Stable Pentagonal Bipyramidal Dy(III) Single-Ion Magnet with a Record Magnetization Reversal Barrier over 1000 K.

Single-molecule magnets (SMMs) with a large spin reversal barrier have been recognized to exhibit slow magnetic relaxation that can lead to a magnetic hysteresis loop. Synthesis of highly stable SMMs with both large energy barriers and significantly slow relaxation times is challenging. Here, we report two highly stable and neutral Dy(III) classical coordination compounds with pentagonal bipyramidal local geometry that exhibit SMM behavior. Weak intermolecular interactions in the undiluted single crystals are first observed for mononuclear lanthanide SMMs by micro-SQUID measurements. The investigation of magnetic relaxation reveals the thermally activated quantum tunneling of magnetization through the third excited Kramers doublet, owing to the increased axial magnetic anisotropy and weaker transverse magnetic anisotropy. As a result, pronounced magnetic hysteresis loops up to 14 K are observed, and the effective energy barrier (Ueff = 1025 K) for relaxation of magnetization reached a breakthrough among the SMMs.

An Experimental and Modeling Study of the Adsorption Equilibrium and Dynamics of Water Vapor on Activated Carbon

In this work, the adsorption of water vapor on a commercial activated carbon is studied by means of static and dynamic measurements. To this end, two customized setups are used, which are able to deal with the challenges associated with adsorption measurements under humid conditions. In the first part, the equilibrium of water vapor on activated carbon during adsorption and desorption at 45 °C is characterized. The equilibrium adsorbed amount of water vapor exhibits a pronounced hysteresis loop, requiring the use of an isotherm model with hysteresis to describe the data. In the second part, fixed-bed experiments for both adsorption and desorption conditions at three feed velocities are presented. These dynamic experiments are described by a nonisothermal detailed column model, which considers the linear driving force model for mass transfer and axial dispersion. Heat and mass transfer coefficients are estimated so as to describe the fixed-bed experiments. The results from the static and dynamic measuremen...

Microscopic theory of cooperative spin crossover: Interaction of molecular modes with phonons.

In this article, we present a new microscopic theoretical approach to the description of spin crossover in molecular crystals. The spin crossover crystals under consideration are composed of molecular fragments formed by the spin-crossover metal ion and its nearest ligand surrounding and exhibiting well defined localized (molecular) vibrations. As distinguished from the previous models of this phenomenon, the developed approach takes into account the interaction of spin-crossover ions not only with the phonons but also a strong coupling of the electronic shells with molecular modes. This leads to an effective coupling of the local modes with phonons which is shown to be responsible for the cooperative spin transition accompanied by the structural reorganization. The transition is characterized by the two order parameters representing the mean values of the products of electronic diagonal matrices and the coordinates of the local modes for the high- and low-spin states of the spin crossover complex. Finally, we demonstrate that the approach provides a reasonable explanation of the observed spin transition in the [Fe(ptz)6](BF4)2 crystal. The theory well reproduces the observed abrupt low-spin → high-spin transition and the temperature dependence of the high-spin fraction in a wide temperature range as well as the pronounced hysteresis loop. At the same time within the limiting approximations adopted in the developed model, the evaluated high-spin fraction vs. T shows that the cooperative spin-lattice transition proves to be incomplete in the sense that the high-spin fraction does not reach its maximum value at high temperature.

Adsorption in alumina pores open at one and at both ends.

We have studied adsorption in regular, self-ordered alumina pores open at both ends or only at one end. The straight, non-connected pores have diameters ranging from 22 to 83 nm, with a relative dispersion below 1% in the pore size. Adsorption isotherms measured in open pores with a torsional microbalance show pronounced hysteresis loops characterized by nearly vertical and parallel adsorption and desorption branches. Blocking one end of the pores with glue has a strong influence on adsorption, as expected from classical macroscopic arguments. However, the experimental measurements show an unexpectedly rich phenomenology dependent on the pore size. For large pores (Dp ≥ 67 nm), the isotherms for closed end pores present much narrower hysteresis loops whose adsorption and desorption boundaries envelop the desorption branches of the isotherms for the corresponding open pores of the same size. The loop for small closed end pores (Dp = 22 nm) is slightly wider than that for open pores while the adsorption branches coincide. For large pores, in contrast, the desorption branches of pores with the same Dp overlap regardless of the pore opening. These observations are in agreement with our grand canonical Monte Carlo (GCMC) simulations for a cylindrical pore model with constrictions, suggesting that the alumina pores could be modeled using a constricted pore model whose adsorption isotherm depends on the ratio of the constriction size to the pore size (Dc/Dp).

Giant Stretchability and Reversibility of Tightly Wound Helical Carbon Nanotubes

There is a surging interest in 3D graphitic nanostructures which possess outstanding properties enabling them to be prime candidates for a new generation of nanodevices and energy-absorbing materials. Here we study the stretching instability and reversibility of tightly wound helical carbon nanotubes (HCNTs) by atomistic simulations. The intercoil van der Waals (vdW) interaction-induced flattening of HCNT walls prior to loading is constrained by the defects coordinated for the curvature formation of helices. The HCNTs exhibit extensive stretchability in the range from 400% to 1000% as a result of two distinct deformation mechanisms depending on the HCNT size. For small HCNTs tremendous deformation is achieved by domino-type partial fracture events, whereas for large HCNTs this is accomplished by stepwise buckling of coils. The formation and fracture of edge-closed graphene ribbons occur at lower temperatures, while at elevated temperatures the highly distributed fracture realizes a phenomenal stretchability. The results of cyclic stretching-reversing simulations of large HCNTs display pronounced hysteresis loops, which produce large energy dissipation via full recovery of buckling and vdW bondings. This study provides physical insights into the origins of high ductility and superior reversibility of hybrid CNT structures.

Magnetic and optical investigations on LaFeO3 powders with different particle sizes and corresponding ceramics

Abstract The optical and magnetic properties of nano-LaFeO3 powders prepared by a starch assisted soft-chemistry synthesis and corresponding ceramics have been investigated. Magnetic measurements on LaFeO3 powders with crystallite sizes of 37–166 nm show pronounced magnetization hysteresis loops. Measurements at 300 K reveal that the coercivity (Hc) of 19–32 kOe depends on the crystallite size, whereas the low remanence values (Mr) of roughly 0.2 emu/g and the maximal magnetization (Mmax) at 90 kOe of 1.05–0.85 emu/g are only slightly changing. Investigations at 10 K reveal a loop shift (exchange bias) up to 12 kOe in the negative direction depending on the crystallite size. Ceramic bodies, sintered at ≥ 1300 °C possess a considerably reduced hysteresis loop. Hc is decreased up to 3.0 kOe, whereas Mr and Mmax are slightly increasing. None of the samples reaches saturation at 90 kOe indicating an anti-ferromagnetic ordering of the spins. The optical band gaps of the LaFeO3 samples were determined by means of diffuse reflectance spectra. For all LaFeO3 powders similar band gaps of 2.65 eV were observed. However, ceramics with grain-size significantly larger than 250 nm show smaller band gap values up to 2.12 eV.

Low-cycle Fatigue Behaviors of an As-extruded Mg–12%Gd–3%Y–0.5%Zr Alloy

Cyclic deformation and fatigue behaviors of Mg–12%Gd–3%Y–0.5%Zr (wt%, GW123K) alloy were investigated at room temperature under axial cyclic loading in strain controlled condition. It is shown that conventional extruded GW123K alloy maintained cyclic stability at strain amplitudes ranging from 2 × 10 −3 to 10 −2 . The pronounced symmetric hysteresis loops were also observed during cyclic loading. Fracture surface observations indicated that fatigue cracks mainly initiated at large Gd-riched phase or at inclusion clusters at surface or subsurface, and grain boundary (GB) and slip bands (SBs) are also preferential sites for micro-crack incubation.