Phase Transitions In Materials Research Articles

A sequential delivery system based on MoS2 nanoflower doped chitosan/oxidized dextran hydrogels for colon cancer treatment

A sequential delivery system based on MoS2 nanoflower (MoS2 NF) doped chitosan (CS)/oxidized dextran (OD) hydrogels is developed for the treatment of colon cancer. 5-Fluorouracil (5-FU) is combined with polyethylenimine (PEI) decorated MoS2 NF via electrostatic attraction and hydrogen bonding, and the obtained 5-FU/PEI/MoS2 is encapsulated by 1-tetradecanol (TD), a commonly used phase transition material. The resultant TD/5-FU/PEI/MoS2 (TFPM) is then co-encapsulated with methotrexate (MTX) in the CS/OD hydrogels generated via Schiff base reaction and electrostatic attraction. Because the electrostatic attraction between CS and OD is pH-sensitive, MTX and TD/5-FU/PEI/MoS2 can be easily released from the hydrogels at pH 7.4. MoS2 is an outstanding photothermal agent, and the generated hyperthermia under near infrared (NIR) irradiation can lead to the melting of TD and the consequent release of 5-FU encapsulated. More importantly, the generated hyperthermia under NIR irradiation can realize the chemo-photothermal synergistic tumor therapy. Finally, the practicability of the developed sequential delivery system is demonstrated by cytotoxicity test.

Low-Power Dynamic Circuit Design With Steep-Switching Hybrid Phase Transition FETs (Hyper-FETs)

Dynamic logic circuits suffer from leakage current during their evaluation period causing output voltage degradation. Although the keeper transistor is added to protect the output node from leakage, it comes with a considerable area and power penalty. In this article, we propose a novel design topology of a low-power dynamic logic circuit based on steep-switching hybrid phase transition FETs (Hyper-FETs). A Hyper-FET utilizes a phase transition material that exhibits selective insulator-to-metal transition enabling it to overcome the fundamental Boltzmann’s limit. The characteristic feature of the Hyper-FET also includes a higher ON–OFF ratio than the conventional counterpart. We utilize this unique advantage to alleviate the leakage issue in the dynamic circuits. We use a compact model of the phase transition material calibrated with experimental data of a single crystal VO2. For the baseline transistor, we use the predictive technology model of 14-nm FinFET. We comprehensively analyze the effects of different material parameters to explore the scope of further performance improvement. From our analysis, we deduce a range of insulating and metallic state resistance of the phase transition material (PTM) for optimum performance. We also examine the effect of process variation by performing the Monte Carlo variation analysis. Our analysis indicates that the leakage problem of the dynamic circuits is substantially improved as the phase transition material provides an additional high resistance with the pull-down network. We also observe that our design can outperform the conventional dynamic logic circuit even under random process variation.

Switchable Wideband Terahertz Absorber Based on Refractory and Vanadium Dioxide Metamaterials

Achieving actively tunable metamaterial absorption is a significant development direction. Phase-transition materials have attracted growing interest for the use in nanophotonics owing to their flexibility. In this work, we firstly demonstrate a wideband terahertz refractory absorber that achieves more than 90% absorptance in the range of 1.71--3.31 THz. The metal composing the structure is refractory metal, which could function in high-temperature conditions and complex electromagnetic environment. Then, we incorporate phase-change material vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) film to this refractory absorber, realizing high reflection of more than 93% in the metallic state, while the wideband perfect absorption peak over 98% is obtained in the insulating state. Calculated results show that metamaterial absorber obtains switchable functions. Furthermore, the tunable absorber has polarization-insensitive behavior. So, our designed absorber with dynamic tunable characteristics provides flexibility to adjust the absorption performance and has significant value in application. The proposed architecture offers a novel method for creating dynamic and multi-functional photonic devices in phase-change materials.

A review on phase change materials: Development, Types, and Applications

Heat-storage materials that can be used to transition from one phase to another are known as phase change materials (PCM). This review article aims to highlight the history, iterations, and future value-adding of PCM in the sciences and engineering industries. This study discusses the many types of phase transition materials, as well as their encapsulations and applications. The study also includes findings from many experiments conducted around the world in order to offer a complete picture of overall advancement in the field of PCM.

Review on latent thermal energy storage using phase change material

One of the appealing technologies that contributes to raising the energy storage density is latent heat thermal energy storage. The heat of fusion is isothermally stored at a temperature representing the temperature at which a phase-change material transitions between phases. The current research provides a review of how phase transition materials are used in melting and solidification. Generally, the range of working temperature extends from -20 °C to 200 °C for solidification and melting applications. The first range (-20 to 5 °C) is employed for commercial and domestic refrigeration. The second range (5 to 40 °C) is utilized to lower the energy requirements for air-conditioning applications. The applications includes in third range (40 to 82 °C) are solar collector and heating of water. Applications of absorption cooling, waste electricity generations, and heat recovery are operated at high temperature range (82 to180 °C). There are various types of PCMs for all the above temperature ranges. The present review paper will discuss the application field, Geometry, PCM type, heat transfer augmentation technique and their effects on the performance. The conclusions are mentioned to give more insight about the PCM behavior in various applications.

Lattice thermal conductivity switching via structural phase transition in ferromagnetic VI3

The realization of reversible thermal conductivity through ferromagnetic ordering can improve the heat management and energy efficiency in magnetic materials-based devices. VI3, as a new layered ferromagnetic semiconductor, exhibits a structural phase transition from monoclinic (C2/m) to rhombohedral () phase as temperature decreases, making it a suitable platform to investigate thermal switching in magnetic phase transition materials. This work reveals that the thermal switching ratio of VI3 can reach 3.9 along the a-axis. Mechanical properties analysis indicates that the C2/m structure is stiffer than the one, causing the larger phonon velocity in C2/m phase. Moreover, due to the fewer phonon branches in C2/m phase, the number of phonon--phonon scattering channels in C2/m phase is smaller compared to that of phase. Both the larger phonon velocity and the longer phonon lifetime lead to larger lattice thermal conductivity in C2/m phase. This study uncovers the mechanical and thermal properties of VI3, which provides useful guides for designing magnetic materials-based devices such as thermal switch.

Multifunctional and tunable ultra-broadband linear to circle polarization converter based on VO2-integrated material

Considering that the metastructures (MSs) previously proposed usually perform in a single state, herein, a multifunctional and tunable ultra-broadband linear to circle (LTC) polarization converter based on phase transition material vanadium dioxide ( V O 2 ) is proposed in the terahertz (THz) region. By manipulating the temperature, the function of the LTC polarization conversion (PC) can be conveniently switched between transmission and reflection states. When the environment temperature is low, V O 2 presents the insulating state, and the MS can achieve ultra-wideband LTC PC from 0.57–0.83 THz with a relative bandwidth (RB) of 37.3%. When the temperature exceeds 68°C, LTC PC with the frequency bandwidth of 0.83–1.20 THz and 0.83–1.17 THz can be obtained in a reflection state when electromagnetic waves propagate forward and backward, whose RBs are 36.4% and 34.0%, respectively. Meanwhile, a broadband linear to linear (LTL) PC can also be realized in the range of 1.19–1.41 THz for the forward incident wave and 1.16–1.37 THz for the backward incident wave. The designed MS offers an effective method to realize four different functions and has tremendous potential value in realizing THz modulation devices, electromagnetic cloaking, and communication systems.

Graphene-based H-shaped biosensor with high sensitivity and optimization using ML-based algorithm

In this paper, a biosensing absorber based on phase transition material is presented. Different phases of the Ge2Sb2Te5 (GST) substrate have been studied for the suggested absorber with controllable characteristics. The structure has been examined to determine the infrared absorption characteristics. The detection of varying volumes of hemoglobin and urine biomolecules is studied. The graphene-GST material is utilized for spectrum tuning. The tuning for two distinct phases of GST material, amorphous GST and crystalline GST is examined. The results for aGST and cGST are reported in the form of absorption. Different amounts of hemoglobin and urine biomolecules are used to tune these two GST stages. Based on the wavelength shifts at these various concentrations, the sensitivity is computed. The highest achievable sensitivity for hemoglobin and urine biomolecules is 1500 nm/RIU and 1667 nm/RIU. The developed model is observed for various geometrical parameters and incidence angles, from which it is determined that the suggested structure is insensitive to wide angles between 0° and 60°. For urine biomolecules, the aGST design is more sensitive than the cGST design, but similar results are achieved for hemoglobin biomolecules. Experiments are conducted with Machine Learning-based regression models to minimize the simulation time and resource requirements of biosensor design. The findings of the trials indicate that a regression model can accurately estimate the absorption values for intermediate wavelengths with an R2 score of 0.9999.

Nanoscale Friction across the First-Order Charge Density Wave Phase Transition of 1T-TaS2.

Nanotribology using atomic force microscopy (AFM) can be considered as a unique approach to analyze phase transition materials by localized mechanical interaction. In this work, we investigate friction on the lamellar transition metal dichalcogenide 1T-TaS2, which can undergo first-order charge density wave (CDW) phase transitions. Based on temperature-dependent atomic force microscopy under ultrahigh vacuum conditions (UHV), we can characterize the general friction levels across the first-order phase transitions and for the different phases. While structural and electronic properties for different phases appear to be of minor influence on friction, a distinct peak in friction is observed during the phase transition when cooling the sample from the nearly commensurate CDW (NC-CDW) phase to the commensurate CDW (C-CDW) phase. By performing systematic measurements as a function of load, scan velocity, and scan time, a recently proposed friction mechanism can be corroborated, where the AFM tip gradually induces local transformations of the material close to the spinodal point in a thermally activated and shear-assisted process until the surface is fully "harvested". Our results demonstrate that repeated nanomechanical stress can trigger local first-order phase transitions constituting a so far little explored mechanical energy dissipation channel.

Dissipation losses limiting first-order phase transition materials in cryogenic caloric cooling: A case study on all-d-metal Ni(-Co)-Mn-Ti Heusler alloys

Ni-Mn-based Heusler alloys, in particular all-d-metal Ni(-Co)-Mn-Ti, are highly promising materials for energy-efficient solid-state refrigeration as large multicaloric effects can be achieved across their magnetostructural martensitic transformation. However, no comprehensive study on the crucially important transition entropy change Δst exists so far for Ni(-Co)-Mn-Ti. Here, we present a systematic study analyzing the composition and temperature dependence of Δst. Our results reveal a substantial structural entropy change contribution of approximately 65 J(kgK)-1, which is compensated at lower temperatures by an increasingly negative entropy change associated with the magnetic subsystem. This leads to compensation temperatures Tcomp of 75 K and 300 K in Ni35Co15Mn50-yTiy and Ni33Co17Mn50-yTiy, respectively, below which the martensitic transformations are arrested. In addition, we simultaneously measured the responses of the magnetic, structural and electronic subsystems to the temperature- and field-induced martensitic transformation near Tcomp, showing an abnormal increase of hysteresis and consequently dissipation energy at cryogenic temperatures. Simultaneous measurements of magnetization and adiabatic temperature change ΔTad in pulsed magnetic fields reveal a change in sign of ΔTad and a substantial positive and irreversible ΔTad up to 15 K at 15 K as a consequence of increased dissipation losses and decreased heat capacity. Most importantly, this phenomenon is universal, it applies to any first-order material with non-negligible hysteresis and any stimulus, effectively limiting the utilization of their caloric effects for gas liquefaction at cryogenic temperatures.

Three-Dimensional Perovskite Phase Transition Materials with Switchable Second Harmonic Generation Properties Introduced by Homochiral (1S,4S)-2,5-Diazabicyclo[2.2.1]-heptane.

Switchable second harmonic generation (SHG) materials have potential applications in information storage, signal processing, and so on because they can switch between SHG-on and SHG-off states. In this work, we designed and synthesized three organic-inorganic hybrid Rb halide three-dimensional (3D) perovskite materials [1S,4S 2,5-2.2.1-H2dabch]RbX3·0.5H2O (X = Cl, 1; Br, 2; I, 3) based on the chiral 1S,4S-2,5-diazabicyclo[2.2.1]heptane (1S,4S-2,5-2.2.1-dabch). The selection of homochiral organic cations ensures that the compounds 1∼3 crystallize in the noncentrosymmetric and chiral space group P212121, which further leads to reversible SHG responses of the three compounds. Through differential scanning calorimetry (DSC) and dielectric measurements, it revealed that the phase transition point of the compounds 1∼3 increased with RbCl, RbBr, and RbI. This is because the hydrogen interaction H···X between the inorganic framework [RbX3]n and the organic cation [1S,4S-2,5-2.2.1-H2dabch]2+ is increased with the order of I > Br > Cl. This study can provide an effective molecular design strategy for the exploration and construction of temperature-tunable SHG switching materials.

Magnetic properties and cryogenic magnetocaloric effect in monoclinic RE8.66(BO3)2(B2O5)O8 (RE = Er, Tm) compounds

Researchers in cryogenic magnetic refrigeration have never stopped pursuing magnetic refrigerants with lower ordering temperatures and larger magnetocaloric effects. Rare earth borates have been found to be potential cryogenic magnetocaloric materials due to their low phase transition temperatures and considerable magnetic entropy changes. Here, two rare earth borates RE8.66(BO3)2(B2O5)O8 (RE = Er, Tm) were successfully fabricated, and the crystallographic and magnetic parameters as well as cryogenic magnetocaloric effects were systematically evaluated. The compounds are deemed to crystalize in a monoclinic structure belonging to space group C2/m. They are both second-order phase transition materials without any long-range order above 2 K. These monoclinic rare earth borates, especially for Er8.66(BO3)2(B2O5)O8, show more considerable low-field magnetocaloric effects than rare earth orthoborates. For ΔH = 1 and 2 T, the values of −ΔSMmax are 5.1 and 11.2 J/(kg K) for Er8.66(BO3)2(B2O5)O8, 3.0 and 5.3 J/(kg K) for Tm8.66(BO3)2(B2O5)O8, respectively. Therefore, they are regarded as potential candidates for cryogenic magnetic refrigeration.

Targeted regulation and optimization of multifunctional phase transition materials by novel void occupancy engineering.

As an innovative form of stimulus-response materials, organic-inorganic hybrid phase transition materials have become a wonderful contender in the field of functional electronic equipment due to their versatile structure, intensive functions and straightforward preparation. However, the targeted regulation and optimization of the electrical/optical response, along with the establishment of regular structure-performance relationships, pose significant challenges in meeting the diverse demands of practical applications over an extended period. Herein, we conducted a systematic investigation into the role of lattice void occupancy in regulating phase transition temperature (Tp) and related optical/electrical bistability. By taking hybrid material [TMEA][Cd(SCN)3] featuring a flexible ammonium cation [TMEA]+ (TMEA = ethyltrimethylammonium) as the prototype, we successfully synthesized three phase transition materials, namely [DEDMA][Cd(SCN)3], [TEMA][Cd(SCN)3] and [TEA][Cd(SCN)3] (DEDMA = diethyldimethylammonium, TEMA = triethylmethylammonium, and TEA = tetraethylammonium), and the excellent regulation of the physical properties of these compounds was achieved through subtle engineering of void occupancy. More strikingly, [TEA][Cd(SCN)3] exhibits remarkable bistable properties in terms of dielectric and nonlinear optical responses (with second-harmonic generation intensity reaching 2.5 times that of KDP). This work provides a feasible avenue to reasonably customise organic-inorganic hybrid phase transition materials and finely adjust their intriguing functionalities.

Switchable multifunctional terahertz metamaterial with slow-light and absorption functions based on phase change materials

Terahertz (THz) wave usually refers to the electromagnetic wave with a frequency between 0.1—10.0 THz. It has potential applications in wireless communication, biomedical image processing, nondestructive testing, military radar, and other fields. However, owing to function limitation of the natural material, multifunctional terahertz devices are difficult to design and fabricate, which becomes a bottleneck for THz technology. The emergence of metamaterials fills the gap in the electromagnetic materials in the THz frequency band, and now they are widely used in THz functional devices, such as THz modulators, THz absorbers, THz filters, THz sensors, and THz slow-light devices. However, the above-mentioned THz devices all have a single function. For practical application, multifunction integrated THz devices have broader application prospects. As is well known, the Ge&lt;sub&gt;2&lt;/sub&gt;Sb&lt;sub&gt;2&lt;/sub&gt;Te&lt;sub&gt;5&lt;/sub&gt; (GST) is a typical phase transition material. Under excitation of light or electronic field, GST can realize a reversible phase transition between insulating state and metallic state. In order to achieve a switchable multifunctional THz device, in this work we design a THz metamaterial based on the phase transition material GST and realize a switchable function with slow-light and absorption functions. The THz metamaterial consists of a microstructure layer, which is composed of gold rings arranged periodically, and a GST thin film spaced by an SiO&lt;sub&gt;2&lt;/sub&gt; dielectric layer. When GST is in an insulating state, the two gold rings are coupled to each other under the excitation of the THz pulse. Then, we can observe the EIT-like effect. The THz pulses propagating in the metamaterial we proposed can be slowed down, and a maximum group delay of the THz pulse can reach 3.6 ps. However, when GST is in a metallic state, we can observe two absorption peaks in the spectrum of the proposed THz metamaterial, and the absorption rate is 97% at a frequency of 0.365 THz and 100% at a frequency of 0.609 THz. Furthermore, we also investigate the polarization properties of the proposed THz metamaterial, and find that it has polarization insensitive characteristic. When the polarization angle of the incident THz light pulse changes from 0° to 90°, the slow-light and absorption properties of the THz metamaterial are unaffected. The proposed THz metamaterial has potential applications in THz biomedical image processing, THz optical switching, and THz optical buffer.

An Electrostatic Locking Mechanism For Tendon-driven Surgical Robot

Variable stiffness surgical robots are capable of adapting to different surgical scenarios, providing enhanced stability during minimally-invasive surgeries. Prevalent methods for achieving variable stiffness, such as lockable mechanisms, granular jamming, and phase transition materials, have inherent weaknesses including difficulties in downsizing and issues related to excessive temperatures. In this paper, a novel lockable mechanism based on electrostatics is proposed, along with a tendon-driven surgical robot prototype that utilizes this locking mechanism to achieve variable stiffness. The proposed mechanism involves the installation of graphite electrode sheets at each joint, with silica gel being used as the dielectric material. By applying a high voltage to the electrode sheets, adjacent joints automatically absorb and restrict relative sliding, effectively preventing joint rotation and ensuring complete joint locking. An electrostatic adhesive braking force model for the robot is presented. Simulations and experiments conducted based on the robot prototype have been carried out to validate the locking capability of the proposed mechanism and the accuracy of the electrostatic adhesive braking force model.

MINIMIZATION OF ANNUAL ENERGY CONSUMPTION BY INCORPORATING PHASE CHANGE MATERIALS INTO BUILDING COMPONENTS: A COMPREHENSIVE REVIEW

Building envelopes are essential for supplying buildings with appropriate energy and thermal comfort performance. Recent research on novel strategies and methodologies applies improved solutions in this area. With a specific focus on phase transition materials, the primary methods used in this area are examined to find contemporary and efficient procedures. Due to phase change materials' (PCMs') enhanced capacity to store and release heat during phase transition, this technology is expanding rapidly and is utilized in various building components. This study emphasizes the value of PCMs in building envelope systems, particularly on the roof and exterior wall applications. In what follows an overview and discussion of PCM types, general and desirable qualities, and potential uses is presented. The thermal behavior of PCM is described using incorporation techniques and procedures, influential parameters, basic numerical tools, and modeling equations. A thorough review based on current research has been carried out to highlight the potential of PCM with the best approaches in various places. In addition to various research pauses for future investigations, the primary findings of PCM thermal performance have been discussed, taking into account the decreased cooling/heating load, energy savings, and increased thermal comfort.

Dielectric and optical properties of a new organic–inorganic hybrid phase transition material

Dielectric and optical properties of an organic–inorganic hybrid phase transition material.

Захист сонячних батарей від перегрівів за допомогою критичних терморезисторів на основі діоксиду ванадію

The overheating caused by electrical loads is one of the essential factors impairing the reliability of photovoltaic components of solar cells. The most common technical solution to this problem is to use such additional elements as bypass diodes. However, the practice of installing such diodes in parallel with a chain of solar cells has shown that this approach does not eliminate hot spots completely, and thus characteristics of the solar cells deteriorate at a faster pace. One of the possible solutions to this problem is to use critical thermistors based on metal-semiconductor phase transition materials, such as vanadium dioxide. Structurally, such thermal protection is implemented by adding a separate photovoltaic element with a thermistor protection element that is in thermal contact with it. This study investigated the effectiveness of such a solution to prevent local overheating in photovoltaic components of solar cells. Glass-ceramic materials based on vanadium dioxide and vanadium-phosphate glass of the V2O5—P2O5 system were used as thermistor elements, which abruptly change the electrical resistance by 1.5—2.0 orders of magnitude in the temperature range around 700С. The research results showed that the considered protective elements can function as reusable (self-healing) fuses against electrothermal overloads in solar batteries. Considering the relative simplicity and low cost of the manufacturing technology of glass-ceramic materials with a metal-semiconductor phase transition, the described approach to preventing overheating of photovoltaic cells of solar cells in situations with higher reliability requirements appears to be promising.

Effect of Pd(II) uptake on high-temperature phase transitions in a hybrid organic-inorganic perovskite semiconductor.

Hybrid organic-inorganic perovskites (HOIPs) have been widely studied for their interesting functions and potential applications. Here, we report a novel sulfur-containing hybrid organic-inorganic perovskite based on a one-dimensional ABX3-type compound: [C3H7N2S]PbI3 ([C3H7N2S]+ is 2-amino-2-thiazolinium) (1). Compound 1 undergoes two high-temperature phase transitions at 363 K and 401 K, respectively, showing a band gap of 2.33 eV, and has a narrower band gap compared to other one-dimensional materials. Moreover, by introducing thioether groups into the organic component, 1 has the ability to uptake Pd(II) ions. Compared with previously reported low-temperature isostructural phase transition sulfur-containing hybrids, the molecular motion of 1 becomes more intense under the stimulation of high temperature, leading to changes in the space group during the two phase transitions (Pbca → Pmcn → Cmcm), which are no longer the previous isostructural phase transitions. Significant changes in the phase transition behavior and semiconductor properties before and after metal absorption make it possible to monitor the absorption process of metal ions. The study of the effect of Pd(II) uptake on phase transitions may be helpful to reveal the mechanism of phase transitions more deeply. This work will broaden the hybrid organic-inorganic ABX3-type semiconductor family and pave the way for the development of organic-inorganic hybrid-based multifunctional phase transition materials.

Захист сонячних батарей від перегрівів за допомогою критичних терморезисторів на основі діоксиду ванадію

The overheating caused by electrical loads is one of the essential factors impairing the reliability of photovoltaic components of solar cells. The most common technical solution to this problem is to use such additional elements as bypass diodes. However, the practice of installing such diodes in parallel with a chain of solar cells has shown that this approach does not eliminate hot spots completely, and thus characteristics of the solar cells deteriorate at a faster pace. One of the possible solutions to this problem is to use critical thermistors based on metal-semiconductor phase transition materials, such as vanadium dioxide. Structurally, such thermal protection is implemented by adding a separate photovoltaic element with a thermistor protection element that is in thermal contact with it. This study investigated the effectiveness of such a solution to prevent local overheating in photovoltaic components of solar cells. Glass-ceramic materials based on vanadium dioxide and vanadium-phosphate glass of the V2O5—P2O5 system were used as thermistor elements, which abruptly change the electrical resistance by 1.5—2.0 orders of magnitude in the temperature range around 700С. The research results showed that the considered protective elements can function as reusable (self-healing) fuses against electrothermal overloads in solar batteries. Considering the relative simplicity and low cost of the manufacturing technology of glass-ceramic materials with a metal-semiconductor phase transition, the described approach to preventing overheating of photovoltaic cells of solar cells in situations with higher reliability requirements appears to be promising.