Structural Phase Change Research Articles

Effects of structural phase changes on the luminescence of Eu-doped (1-x)BaTiO3-xCaZrO3

We investigated the structural and luminescent properties of Eu3+-doped (1-x)BaTiO3-xCaZrO3 (BCTZ:Eu). The changes in the structural symmetry of BCTZ:Eu with CaZrO3 substitution and Eu3+ doping was determined using Rietveld refinement of the X-ray diffraction patterns. Under ultraviolet photoexcitation, the specimens exhibited typical red-orange emission peaks resulting from the f–f transitions from Eu3+ ions. The intensities and asymmetry ratios of the emission intensities, as well as Stark splitting of the emission bands from Eu3+ were found to be strongly dependent on the structural phase transformation of BCTZ from tetragonal to rhombohedral. These findings suggest that BCTZ:Eu possesses a great potential for multifunctional devices that have both ferroelectric and luminous properties.

In Operando Optical Tracking of Oxygen Vacancy Migration and Phase Change in few Nanometers Ferroelectric HZO Memories

AbstractFerroelectric materials offer a low‐energy, high‐speed alternative to conventional logic and memory circuitry. Hafnia‐based films have achieved single‐digit nm ferroelectricity, enabling further device miniaturization. However, they can exhibit nonideal behavior, specifically wake‐up and fatigue effects, leading to unpredictable performance variation over consecutive electronic switching cycles, preventing large‐scale commercialization. The origins are still under debate. Using plasmon‐enhanced spectroscopy, a non‐destructive technique sensitive to <1% oxygen vacancy variation, phase changes, and single switching cycle resolution, the first real‐time in operando nanoscale direct tracking of oxygen vacancy migration in 5 nm hafnium zirconium oxide during a pre‐wake‐up stage is provided. It is shown that the pre‐wake‐up leads to a structural phase change from monoclinic to orthorhombic phase, which further determines the device wake‐up. Further migration of oxygen ions in the phase changed material is then observed, producing device fatigue. These results provide a comprehensive explanation for the wake‐up and fatigue with Raman, photoluminescence and darkfield spectroscopy, combined with density functional theory and finite‐difference time‐domain simulations.

A Polymorphic Memtransistor with Tunable Metallic and Semiconducting Channel.

Modulating semiconducting channel potential has been used for electrical switching in transistors without biological plasticity operations that are critical for energy-efficient neuromorphic computing. To achieve efficient data processing, alternative transport mechanisms, such as tunneling and thermionic emission, have been introduced with 2D materials. Here, a polymorphic memtransistor based on atomically thin Mo0.91 W0.09 Te2 is presented, where the lattice and electronic structures of the lateral device channel can be tuned as either metallic (1T') or semiconducting (2H) phases by electrical gating. The structural and electronic phase change of the channel material, optimized in Mo0.91 W0.09 Te2 , is explored using transport and optical measurements at the device scale. Based on the phase transition, the polymorphic memtransistor demonstrates a high on/off ratio (up to 105 ), low subthreshold swing (down to 80mV dec-1 ), and various memristive behaviors, which are distinguished from traditional phase-change memory, transistors, and passive memristors for diverse neuromorphic and in-memory computing.

Structural-Phase Changes of the Fe3C/Fe7C3/P-Phase/Cam Mechanocomposite at Heating

The effect of the action of temperature on the structure and phase composition of anFe3C/Fe7C3/P-phase/Cam composite obtained by mechanosynthesis of Fe–75 at % C has been studied by the methods of X-ray diffraction, Mössbauer spectroscopy, thermogravimetric analysis, and differentialscanning calorimetry. It is shown that the structural and phase changes at heating have a multistage character.In the temperature range 315–400°C crystallization of the paramagnetic P-phase with generation of Fe3Cand/or Fe7C3 occur. In the course of heating to higher temperatures, complete decomposition of carbideFe7C3 (in the range 450–550°C) and partial decomposition of Fe3C (at 600°C and above) are observed. Aftercooling from 800–1000°C the mechanocomposite consists of α-Fe, cementite Fe3C, and graphite. The phasetransformations are accompanied by the processes of composite oxidation with the formation of Fe3O4 oxide and its subsequent reduction. The P-phase is a disorded amorphous carbide Fe1 – xCx, which is characterized by magnetic ordering at the temperature of liquid nitrogen.

Structural-Phase Changes of the Fe3C/Fe7C3/P-Phase/Cam Mechanocomposite at Heating

Structural-Phase Changes of the Fe3C/Fe7C3/P-Phase/Cam Mechanocomposite at Heating

Antiferroelectric orthorhombic P-to-R phase transition induced exotic electrocaloric effect in NaNbO3-based lead-free ceramics

Phase transition is expected in designing high-performance electrocaloric effect (ECE). However, hidden antiferroelectricity in NaNbO3-based ceramics complicates ECE evolution as compared to conventional ferroic materials. Therefore, a NaNbO3−xBi0.5Li0.5TiO3 (x = 0.08, 0.10, and 0.12) system is introduced to explore ECE performance in P (Pbma), Q (P21ma), and R (Pnma) phases since a Bi0.5Li0.5TiO3 dopant plays a Janus role in stabilizing ferroelectric Q (x = 0.08 and 0.10) and inducing the antiferroelectric (AFE) relaxor R phase (x = 0.12). Rietveld refinement reveals a phase structure change from the P/Q to R state. Bi0.5Li0.5TiO3 addition makes a downshift of P-to-R transition temperature accompanied by an increase in relaxation property, as certified by dielectric analysis/piezoelectric force images, in situ XRD/Raman spectra, and ferroelectric tests. Additionally, a square P–E loop evolves into less-sharp and finally changes into a slant one with increasing Bi0.5Li0.5TiO3 content. ECE is directly measured, and its peak value increases from 0.15 K for x = 0.08 and 0.21 K for x = 0.10 and finally to 0.11 K for x = 0.12 composition. Interestingly, dual ECE peaks appear in x = 0.10, and it is probably contributed by R relaxor polar nanodomains. This work not only clarifies actual ECE behavior in AFE orthorhombic (P/R) NaNbO3-based ceramics but also fulfills understandings of AFE P-to-R transitions in modulating ECE.

Synthesis of bio-nanocomposite coating (silver-multi wall carbon nano tubes) by electroless plating method

Silver-multi wall carbon nanotube (Ag-MWCNTs) nano-composite coating was prepared using electroless deposition technique on stainless steel (316L) sheets. Majority of the literature and researches on this issue focuses on the macro and microscale effects of the bath composition as well as process parameters upon the composite coatings microstructure. So far, few researches have studied the bath composition influence upon the structure of phase, microstructure, and surface morphology; therefore, the current investigation compared the influences of the MWCNTs nanoparticles incorporation at various concentrations (0.1, 0.3, and 0.5 g/l) on the phase structure, microstructure and surface morphology. The phase structure changes were evaluated via X-ray Diffraction (XRD) analysis. The surface morphology (nanoparticles distribution into silver coating) was investigated via Scanning Electron Microscopy (SEM). The chemical composition of the nano-composite coating surface was studied via EDS analysis. In the present work, electroless deposition technique was used successfully in synthesis of silver-based MWCNTs nano-composite, so the EDS results showed that the main elements of the nano-composite coating are carbon, silver and oxygen that are distributed homogeneously over the surface of samples, while the SEM analysis results showed the coating is uniform and covers the stainless steel 316L substrate, also that the distribution of MWCNTs nanoparticles into the Ag matrix coating is more uniform. The XRD analysis results manifested the composition and crystal structure of the nano-composite coating consisted of Ag and MWCNTs fully crystalline structure.

Novel resource utilization approach of spent catalyst from flue gas denitrification: Preparing high quality titanium-bearing pellets

Spent titanium-based catalyst is a waste generated by the selective catalytic reduction (SCR) denitrification process, whose generation is dramatically increasing in the iron and steel industry year by year. A novel approach was proposed in this work to prepare titanium-bearing pellets by using spent catalyst. The influences of spent catalyst addition on the comprehensive properties of pellets were studied. The corresponding relationship between the change of phase structure and the spent catalyst pellets' strength was investigated. The results demonstrated that the spent catalyst could be adsorbed on the surface of ore particles physically and chemically, improving the adhesion of particles inside the pellet and the hydrophilicity, thus obtaining good comprehensive performance of the green pellets. When adding 5.0 wt% spent catalyst, the bentonite dosage could be reduced by 50%, and the strength of roasted pellets could meet the requirement of large blast furnaces. The consolidation mechanism of the spent catalyst pellets indicated that TiO2 reacted with FeO first to generate FeTiO3 in the preheating process and further oxidized to form Fe2TiO5 in the roasting process. The unreacted TiO2 would appear in the roasted pellets and inhibit recrystallization and polycrystalline growth of Fe2O3 grains, resulting in the reduction of compressive strength. Overall, high-quality titanium-bearing pellets could be obtained when the amount of spent catalyst was less than 5.0 wt%. This study thus provided an alternative route to resource utilization of spent catalysts in iron and steel enterprises.

Performance enhancement of modified asphalt via coal gangue with microstructure control

The efficient application of coal gangue into asphalt pavement materials not only improves pavement service performance, but also relieves environmental pressure of accumulation. However, the compatibility of coal gangue powder with asphalt pavement materials promises further strengthens, calling for enhanced processing schemes of coal gangue. Firstly, modified materials were successfully prepared by modulating the coal gangue powder. A series of microscopic experiments were conducted to characterize the phase structure, microstructure, thermal stability, adsorption capacity, and functional group change characteristics of different types of coal gangue powder. Then, three kinds of coal gangue powders were applied to the matrix asphalt by melt blending method, and the composite's rheological properties and aging resistance were also studied. Finally, the modification mechanism of the composite was discussed from the micro level. The research showed that the specific surface area of intercalated and activated coal gangue powder increased about 1.45 times and 1.25 times, respectively, compared with ordinary coal gangue powder. The physical adsorption capacity of gangue powder can be improved by chemical intercalation or high-temperature activation. The high-temperature resistance and anti-aging performance of asphalt can be affected by enhancing the interaction between coal gangue powder and the asphalt matrix. The design of coal gangue modified asphalt materials with different structural characteristics promotes the development of sustainable and durable pavement.

Review of effective techniques for surface engineering material modification for a variety of applications

<abstract> <p>The status of current advances in modifying surfaces for the protection of materials is reviewed in this research. The main goal of material selection is to improve and reinforce surface functionalities. A few examples of surface modification techniques include sol-gel, cladding, electroplating, plasma and thermal spraying, physical deposition of vapors (PVD), vapor chemical deposition (CVD) and beam electron physical vapor deposition (EB-PVD). Strengthening by flame, induction, laser or electron beam is one type of surface modification procedure. Other types include plasma-immersed ion implantation and ion implantation at high energies, as well as diffusion treatments like carburizing and nitriding. Friction control, improved surface corrosion and wear resistance and changes to a component's mechanical or physical qualities are all possible using surface modification methods. The study also contains contemporary research in laser therapy, PVD, EB-PVD, thermal spraying and ion implantation. Additionally, magnetron sputtering (MS) is a widely used and successful approach for thin film coating in the current study. It is crucial to remember that each approach has a distinct set of restrictions, and the method's parameters might change based on the one that is selected, such as deposition targets, overall vacuum substrate temperature, reactive or mixed gas type, pressure percentage and bias voltage, which all have impacts on the PVD technique's layer qualities. Phase formation, change in phase, hardness and film structure of monolayer and multilayer films formed on the substrate under various circumstances also cause variations in the characteristics. Additionally, ion implantation enhances the surface characteristics of layers by implanting ions such as N<sup>+</sup>, B<sup>+</sup>, C<sup>+</sup>, etc. The study shows that the higher layers of multilayer enhance the degree of hardness and lower friction coefficients. To enhance the protection of thermal resistance, a thermal spraying barrier coating was coated on substrate nickel-base alloys, and the surface materials' texture, hardness and wear rate were altered by laser beam. Additionally, a heat pipe's performance was improved by a factor of 300 by adding a tiny coating of gold.</p> </abstract>

New insight of in-situ generation of composite cathode by converting Na3V2(PO4)3@C to improve aqueous zinc-ion batteries’ performance

The NASICON-structure Na3V2(PO4)3 is attracted lots of attention due to its three-dimensional ion diffusion channels, high discharging platform and small volume deformation, which has become the most potential cathode material candidates for aqueous zinc-ion batteries. Nevertheless, we found that [email protected] undergoes a structural phase change which is converted to composite (V2O5, NaV3(PO4)3, Zn3V4(PO4)6) after 50 cycles in this study. Here, we exploited the in-situ generation of composite by cycling the [email protected] batteries at 60 °C for only 1 cycle ([email protected] °C) to promote the performance of cathode material for aqueous zinc-ion batteries. The [email protected] ℃ display a high capacity of 164 mA h g−1 at 100 mA g−1 and excellent rate performance (155 mA h g−1 at 1000 mA g−1) are realized. This is the first reported in-situ generation of composite as a cathode material for aqueous zinc-ion batteries so far. This work breaks the original conventional thinking to present new insight to developing cathode materials for zinc energy storage.

Cathodoluminescence and optical absorption spectroscopy of plasmonic modes in chromium micro-rods

Manipulating light at the sub-wavelength level is a crucial feature of surface plasmon resonance (SPR) properties for a wide range of nanostructures. Noble metals like Au and Ag are most commonly used as SPR materials. Significant attention is being devoted to identify and develop non-noble metal plasmonic materials whose optical properties can be reconfigured for plasmonic response by structural phase changes. Chromium (Cr) which supports plasmon resonance, is a transition metal with shiny finished, highly non-corrosive, and bio-compatible alloys, making it an alternative plasmonic material. We have synthesized Cr micro-rods from a bi-layer of Cr/Au thin films, which evolves from face centered cubic to hexagonal close packed (HCP) phase by thermal activation in a forming gas ambient. We employed optical absorption spectroscopy and cathodoluminescence (CL) imaging spectroscopy to observe the plasmonic modes from the Cr micro-rod. The origin of three emission bands that spread over the UV–Vis-IR energy range is established theoretically by considering the critical points of the second-order derivative of the macroscopic dielectric function obtained from density functional theory (DFT) matches with interband/intraband transition of electrons observed in density of states versus energy graph. The experimentally observed CL emission peaks closely match the s–d and d–d band transition obtained from DFT calculations. Our findings on plasmonic modes in Cr(HCP) phase can expand the range of plasmonic material beyond noble metal with tunable plasmonic emissions for plasmonic-based optical technology.

Above room temperature dielectric switchable organic co-crystal [C4H4O4]⋅[C3H9N] with Hirshfeld surface analyses

A new co-crystal [C 4 H 4 O 4 ]∙[C 3 H 9 N] was synthesized, where [C 4 H 4 O 4 ]=fumaric acid and [C 3 H 9 N]= isopropylamine. A reversible phase change happened at 352/357 K and it belongs to a homogenous phase change. Hirshfeld surface analyses reveal that three interactions of H⋅⋅⋅H, H⋅⋅⋅O and H⋅⋅⋅C contribute to more than 90% the total forces. Dielectric anomalies were also observed accompanied with structural phase change. • The forces of the H⋅⋅⋅H, H⋅⋅⋅O and H⋅⋅⋅C bond interactions by Hirshfeld surface analyses are different at the high and low dielectric states. We report a new dielectric phase change co-crystal [C 4 H 4 O 4 ]⋅[C 3 H 9 N] 1 , among which [C 4 H 4 O 4 ] is fumaric acid and [C 3 H 9 N] is isopropylamine / IPA. Single-crystal X-ray measurements show space group of 1 belongs to monoclinic P 2 1 / c space group, and a homogeneous phase change occurs. Hirshfeld surface analyses reveal that three interactions of H⋅⋅⋅H, H⋅⋅⋅O and H⋅⋅⋅C contribute more than 90 % to the total forces, and the forces of the three bonds are different at different phases. \

Poly (Vinylidene Difluoride) Polymer in 1-Ethyl-3-methylimidazolium Acetate and Acetic Acid Containing Solvents: Tunable and Recoverable Solvent Media to Induce Crystalline Phase Transition and Porosity

In this report, 1-ethyl-3-methylimidazolium acetate, [EMIM][AcO] ionic liquid (IL) and acetic acid (AA) comprised solvents were used for the thermal treatment of poly (vinylidene difluoride), PVDF. Here, besides the various combinations of IL and AA in solvents, the pure IL and AA were also applied as a solvent upon thermal treatments. The samples obtained after the treatment were analysed for structural and crystalline phase changes, porosity, and molecular weight distribution with various analytical techniques. The Kamlet-Taft parameters measurement of the IL and AA containing solvents with different solvatochromic dyes was also performed to examine their solvent properties and correlate with the properties of the treated PVDF materials. The treatment of PVDF with pure IL results in the formation of highly carbonaceous material due to extensive dehydroflurination (DHF) as well as possibly successive cross-linking in the polymer chains. Upon IL and AA combined solvent treatment, the neat PVDF which composed of both α- and β crystalline phases was transformed to porous and β-phase rich material whereas in case of pure AA the non-porous and pure α-phase polymeric entity was obtained. A combined mixture of IL and AA resulted in a limited the DHF process and subsequent cross-linking in the polymer chains of PVDF allowed the formation of a porous material. It was observed that the porosity of the thermally treated materials was steadily decreasing with increase in the amount of AA in solvents composition and solvent with an AA:IL mole ratio of 2:1 resulted in a PVDF material with the highest porosity amongst the applied solvents. A recovery method for the IL and AA combined solvent after the thermal treatment of PVDF was also established. Hence, with varying the type of solvents in terms of composition, the highly carbonaceous materials as well as materials with different porosities as well as crystalline phases can be obtained. Most importantly here, we introduced new IL and AA containing recoverable solvents for the synthesis of porous PVDF material with the electroactive β-phase.

Non-Destructive Testing by Magnetic Noise Method of the Quality of Heat Treatment of Steel Samples Obtained by Additive Technology

The manufacture of products using additive technologies is accompanied by the unpredictable appearance of inhomogeneity of properties, anisotropy, residual stresses, porosity, and other defects. Therefore, there is a great relevance of non-destructive quality control of products obtained by additive technologies. The purpose of the paper is the experimental investigation of the possibility of testing and evaluation of the quality of heat treatment of three-dimensional and cast samples by non-destructive control methods.The low-alloy steel 09G2S samples, which was obtained by casting and selective laser sintering different modes of subsequent heat treatments were studied. The method of the Barkhausen effect and the instrumented indentation method for measuring the material hardness were applied.It was experimentally established that both methods are highly sensitive to annealed and normalized three-dimensional samples and their rejection. Compared to the hardness measurement method, which is mainly associated with phase-structural changes, the magnetic noise method due to selectivity to other controlled parameters is additionally sensitive to cast samples (at the same time the microstructures of cast and normalized three-dimensional samples are close to each other according to X-ray data).The magnetic noise method can be used as one of the physical methods for evaluation the quality and control of the heat treatment of 3D samples at the manufacturing stage when testing their types and modes, as well as sorting samples.

Elucidating MnO2 Reaction Mechanism By Multi-Modal Characterization in Aqueous Zn-MnO2 Batteries

Aqueous Zn-ion batteries has attracted great attention in recent years, as a promising candidate for grid energy storage applications. An aqueous system offers intrinsic safety, high ionic conductivity contributing improved power capability and raw materials that are more earth abundant and environment friendly. Numerous promising reports haven been focusing on the Zn/MnO2 system owing to its low cost, moderate discharge potentials and with improved reversibility in the mild aqueous electrolyte. However, many questions remain unanswered regarding its reaction mechanism. The different reaction mechanisms including Zn+2 insertion, H+ insertion, chemical conversion reaction including the combined intercalation and conversion reaction mechanism, and the dissolution-deposition of the manganese oxide.In this work, we aim to unravel the reaction mechanism by a systematic multimodal synchrotron characterization. This work discusses the galvano-static charge-discharge process of aqueous Zn-MnO2 batteries using operando measurements, which provides us with a direct insight into the phenomenon and can be directly correlated to the battery's electrochemical response. The multimodal techniques include operando X-ray diffraction to study the structural phase change of the cathode active material, operando X-ray absorption spectroscopy to probe the local structure changes and transmission X-ray microscopy studies to observe the key morphological events. Overall, this multimodal approach gives us an insight into the reaction mechanism enabling us to better design Zn-MnO2 batteries for practical applications.

Microstructure and enhanced tensile properties of AlCo CrFeNi high entropy alloys with high Co content fabricated by laser melting deposition

AlCoxCrFeNi (x = 2.2, 2.8) high entropy alloys (HEAs) were successfully prepared by multi-layer and multi-channel laser melting deposition (LMD). The tensile properties of the LMD-fabricated AlCoxCrFeNi HEAs were investigated. The phase evolution of these alloys was examined by X-ray diffraction and compared with existing models. The microstructure of the alloys was characterized using scanning electron microscopy and electron backscatter diffraction. It is found that Co element can promote the phase transformation from BCC phase to FCC phase in the as-deposited AlCoxCrFeNi HEAs, and the volume fraction of FCC phase increases from 51.4% to 74.6% as the Co content increases from 36.2 at% to 40.8 at%. With the increase of Co content, the grain size of BCC phase in the alloys decreases and a larger amount of fine needle-like BCC phase appears in the FCC matrix. Tensile testing shows that higher Co content in the deposited AlCoxCrFeNi alloy can enhance its plasticity without significantly compromising its ultimate strength. As the Co content increases, the fracture strain increases from 5.9% to 15.4%, while the yield strength reduces from 450 MPa to 360 MPa and the ultimate tensile strength increases from 734 MPa to 739 MPa. The variations in tensile properties of the AlCoxCrFeNi alloy result from phase structure changes and microstructure evolution. Through this research, it is demonstrated that enhancement of the tensile properties of the LMD-fabricated AlCoCrFeNi HEAs can be realized by increasing the content of Co element.

Crystalline Phase Changes due to High-Speed Projectiles Impact on 304L Steel

High yield 304L steel is well known for its employment in manufacturing. The quenched and tempered low-carbon alloy has a minimum yield strength of 40-50 ksi. Also, 304L offers good corrosion resistance and weldability. Traces of Chromium and Nickel in 304L give it the desired corrosion resistance properties. So, it is an ideal candidate for pressure vessels and the petrochemical industry applications. The physical characteristics and molecular structure of 304L steel are also well known; however, little is known about the high-velocity impact on this metal alloy’s crystalline structure and material phase changes. The effects of high-speed velocity impact on the crystalline structure and material phase changes due to impacts are studied herein experimentally. The high-speed impact on the crystalline structure’s inevitable phase change is examined, let alone the atomic reorganization resulting from the impact on the 304L steel. The effects of an impact on the crystalline structure are assessed by impacting 304L steel plates (15.4 x 15.4 x1.27 cm) with Lexan projectiles. A two-stage light gas gun accelerates these projectiles to a velocity of 6.70 km/s at the point of the impact. The impacted plates’ surfaces are prepared for the Electron Back Scatter Diffraction (EBSD) microscope inspection. Nine regions on each impacted plate area are examined and analyzed. Each part (90x90) square microns were cut off the test samples, keeping with the required surface finish standards. These regions are selected from the area immediately under the impact crater to locations not physically affected by the impact. Observations of collected EBSD images show that the predominant phase is Body-Centered Cubic (BCC); Face-Centered Cubic (FCC) and Hexagonal-Close-Packed (HCP) phases are also indexed. Since these crystalline structures are the most expected lattice formations, the samples are post-impact examined for molecular structure allocation changes. The results were then tabulated according to the region’s relative impact crater. Previous research, A36 steel results show that post-impact inspection of HCP phase chage, in iron specifically, is completely and rapidly reversible during impact. However, in this study, traces of HCP were found at some locations in all post-impact stages. This study also indicates that the BCC crystalline structure remained the dominant phase structure after impact, and it is valid with all test samples and all levels of shock loading. High pressure and the temperature quickly affect the target material at 6.70 km/sec velocity. The damage zone develops within 5 microseconds at this velocity due to impacting momentum

The achieving enhanced piezoelectric performance of KNN-based ceramics: Decisive role of multi-phase coexistence induced by lattice distortion

Multi-phase coexistence induced by phase boundary regulation is an efficient approach to promote the performance of (K, Na)NbO3 ceramics. Here, [(1-x) (K0.5Na0.5)(Nb0.965Sb0.035)O3 - x (Bi0.5Na0.5)HfO3, x = 0, 0.01, 0.02, 0.03, 0.04, 0.05] [(1-x) KNNS - x BNH] lead-free piezoceramics are prepared through solid-state sintering method. The changes of internal phase structure are analysed by systematic measurements, from which the coexistence of rhombohedral-tetragonal (R-T) multi-phase is confirmed at x = 0.04. The lattice distortion caused by BNH doping induces the coexistence of R-T multi-phase, consequently achieving the best comprehensive properties at x = 0.04 (d33 = 353 pC/N, TC = 285 ℃, εr = 6517, Pr = 15.3208 μC/cm2), which is due to the reduced domain wall energy and more easily deflected domains in the R-T multi-phase coexistence zone. This work is helpful to understand the essence of the multi-phase coexistence caused by doping to improve the piezoelectric performance.

Grid structure phase change composites with effective solar/electro-thermal conversion for multi-functional thermal application

Phase change materials (PCMs) have high energy storage density and stable phase transition temperature, and are one of the most promising thermal storage and management materials. However, the PCMs’ shape instability, poor light absorption, low electrical and thermal conductivity seriously hinder their multi-functional application. Herein, a three-dimensional carbon aerogel with grid structure, large porosity, and hierarchical porous structure was prepared from resource-rich plant straw for supporting PCMs. Polyethylene glycol (PEG) as thermal energy guest was encapsulated into carbon aerogel by simple vacuum impregnation. The obtained PEG/carbon aerogel composites show high loading rate of PCMs（＞97%), high thermal storage density (＞185 J g−1), stable shape, and effective solar/electro-thermal conversion. The grid structure carbon aerogel as efficient thermal and electron transfer pathways guarantee effective solar/electro-thermal conversion of composites. PEG encapsulated in each lattice as a thermal functional unit realizes the thermal storage and management. Especially, grid-structure composites realized fast and uniform electro-thermal conversion and storage under low voltage. This work provides a feasible, economic, and large-scale preparation strategy for the multi-functional PCMs. The multi-functional composites have broad application prospects in solar energy capture and storage, waste power recycling, building energy saving, smart thermal management and so on.