Phase-change Alloys Research Articles

Characteristics, Encapsulation Strategies, and Applications of Al and Its Alloy Phase Change Materials for Thermal Energy Storage: A Comprehensive Review

AbstractAmong metal‐based phase change materials (PCMs), Al and its alloys have garnered significant attention due to their high latent heat and high thermal conductivity. However, challenges such as leakage, corrosion, and oxidation have limited their widespread application. Numerous researches have demonstrated that encapsulating Al and its alloy PCMs is one effective way to address these problems. This review provides a comprehensive overview of the characteristics, encapsulation strategies, and applications of Al and its alloy PCMs. First, the advantages and thermal properties of Al and its alloy PCMs are introduced, and their problems are then discussed. Subsequently, various encapsulation strategies that are expected to solve the above problems are summarized and compared. Additionally, the applications of Al and its alloy PCMs in solar thermal energy storage, catalysis, and electric vehicles are reviewed. Finally, current challenges, potential solutions, and the key direct of future study are presented.

Thermal and cyclic performance of aluminum alloy composite phase change microcapsules for high-temperature thermal energy storage

Al alloys are suitable for high-temperature applications such as solar thermal power generation and industrial heat utilization. However, addressing the challenges of high-temperature corrosion and material failure in Al alloys is of paramount importance. In practical industrial applications, there is a need to develop encapsulation techniques applicable to a wider range of Al alloy types and phase change temperature ranges, exploring the universality of the technology and the diversity of application scenarios. In this study, a dual encapsulation was conducted on binary and ternary Al alloys (including Al-Ni, Al-Mg, Al-Si-Mg, and Al-Mg-Zn). Aiming at thermal energy storage, four composite phase change microcapsules (CPCM) were successfully prepared and subjected to material characterization, thermal performance analysis, and thermal cyclic tests in air environments. After 2000 thermal cycles, no cracks were observed on the surface of the four CPCMs, and the microstructure remained intact. The components of the CPCMs maintained good chemical compatibility. Among the four types of CPCMs, the Al-Si-Mg CPCMs exhibited the best thermal cyclic stability, with a latent heat reduction rate of 19.5 % after 2000 cycles. The experimental results indicated that the dual encapsulation strategy was effective for various types of Al alloy PCMs, thereby expanding the application of Al alloys in high-temperature thermal storage. Furthermore, Al alloys with more regular morphology and lower active metal content exhibited better thermal performance and cyclic capability, making them more suitable candidates for high-temperature thermal storage applications.

Preparation and erosion resistance of SiC-based ceramic-PCM sensible-latent heat composite heat storage materials

Alloy phase change materials (PCM) are key materials in latent heat storage systems for solar thermal power generation, however, their application is limited by the high corrosion and oxidation problems of alloys. To reduce the erosion problem of alloy PCM, SiC-based ceramic encapsulated flake graphite (EG) modified Al-Cu28-Si6 alloy was used to successfully prepare composite PCM with high compatibility and oxidation resistance. Adopting static erosion test method, the composite PCM was subjected to 50 thermal cycles (25–1000 °C holding time of 10 h was recorded as 1 cycle). The results showed that SiC-based ceramics have excellent corrosion resistance to composite PCM with 10 wt% EG added, which due to the excellent reticulation and encapsulation of EG. Based on the Young-Laplace equation and the contact angle, the erosion resistance mechanism of silicon carbide ceramic alloys has been revealed. SiC-based ceramic-PCM sensible heat-latent heat composite heat storage material was expected to be used for high-temperature heat storage in solar thermal power generation.

Microencapsulation of Zn-10 mass% Al alloy phase change material via dry synthesis method

Thermal energy storage (TES) via latent heat storage (LHS) using metal alloy phase change material (PCM) offers advantages in medium-to-high temperature operation around 400 °C and high heat storage capacity. Microencapsulation of alloys as PCMs can mitigate issues of reactivity and improve handling properties of PCM. This research presents the novel development of microencapsulated PCM (MEPCM) with a core of Zn–10 mass% Al that operates around 400 °C. The MEPCMs were synthesized using high-speed impact blending (HIB), where fine AlOOH particles mechanically coat the surface of Zn–10 mass% Al alloy microspheres, resulting in robust surface modification. Subsequent heat-oxidation treatment at 800 °C was performed to obtain stable oxide coating. The HIB treatment resulted in an AlOOH coating containing Zn nanoparticles, which the heat-oxidation process transformed into α-Al2O3 and ZnO nanoparticles. The MEPCMs exhibited heat storage densities, including latent and sensible heat (ΔT=200 °C), that were 1.9 times higher than the capacity of solar salt, which is commonly used as a sensible heat storage material. Furthermore, the MEPCMs maintained their shape and latent heat capacity after 300 and 1000 cyclic tests. These superior MEPCM characteristics hold the potential to significantly advance the development of LHS-based TES systems operating around 400 °C, with applications in energy generation and industrial processes.

Thermal Performance Analysis of Aluminum Alloy Phase Change Panels for Regions with Hot Summers and Warm Winters

Thermal Performance Analysis of Aluminum Alloy Phase Change Panels for Regions with Hot Summers and Warm Winters

Sandwich-structured In–Ga alloy phase change thermal pad with low thermal resistance and leakage prevention

Sandwich-structured In–Ga alloy phase change thermal pad with low thermal resistance and leakage prevention

Thermal stability, glass-forming ability, and fragility nature of phase-change alloys of Se90Pb10−xSnx (0 ≤ x ≤ 8) system

Thermal stability, glass-forming ability, and fragility nature of phase-change alloys of Se90Pb10−xSnx (0 ≤ x ≤ 8) system

Macroencapsulated Al-Si phase change materials for high temperature latent thermal energy storage

This research investigated the encapsulation of Al-Si alloy phase change materials (PCMs) for efficient thermal storage at high temperature. Two strategies, the direct powder formation route and in situ powder alloying formation route, were employed successfully. In the direct powder formation route, Al-Si alloy powders were spheroidized into spheres and encapsulated within Al2O3 powder shells with the help of organic binder, which were finally sintered at high temperature, forming Al-Si@Al2O3 capsules with cavities. Isostatic pressing at 50 MPa and 200 MPa were applied to the Al-Si cores, in order to optimize the cavity size. In the in situ powder alloying formation route, Al and Si powders were used as raw materials, which could be in situ transferred to Al-Si alloy inside the capsule during the sintering formation process. With the powders as the raw materials, the final capsules obtained after sintering could provide a buffer cavity inside the capsules, which could accommodate the volumetric expansion of the PCMs during melting, thereby mitigating the potential leakage and rupture of the capsules. Investigations into the melting-solidification cycles revealed the remarkable durability of the Al-Si phase change capsules. Isostatic pressure treatment decreased internal ineffective cavities, improving the heat storage density of the capsules. The Al-12Si(Ar)-200 MPa capsule exhibited superior thermal storage performance, enduring up to 1300 cycles. The Al-12Si core had a melting enthalpy of 479 J/g, while the thermal storage density of the phase change capsule within the temperature range of 500 °C–700 °C reached 496 J/g. The results underscore the significant potential of macroencapsulated Al-Si PCM, positioning it as a promising candidate for high-temperature thermal storage applications.

A novel flexible catheter with integrated magnetic variable stiffness and actuation

Flexible instruments offer significant advantages over traditional rigid instruments in ophthalmic surgery, because they can achieve larger working space and minimize the risk of damage caused by contact with eye tissues. However, it also needs to be rigid to achieve sufficient surgical operation force and stability. In this study, we propose a novel flexible catheter with integrated magnetic variable stiffness and actuation, based on electromagnetic induction heating and phase change alloy. The experimental results show that the catheter can switch from rigid to flexible modes in 11 s, and it takes 10 s to switch from flexible to rigid modes in room temperature. The bending stiffness of the catheter is 930.23°N mm2 in rigid mode and 74.42°N mm2 in flexible mode. In addition, the catheter can limit the axial force below 0.08°N in flexible mode, while withstand a force greater than 1.08°N in rigid mode. The catheter is equipped with a magnetic tip that can safely navigate in flexible mode with maximum bending angle of 106 degrees. The phantom experimental results demonstrated the potential clinical value of the proposed catheter.

Reconfigurable phase change chalcogenide grating couplers with ultrahigh modulation contrast

In photonic integrated circuits, efficient coupling of light between fibers and waveguides is challenging due to mode area mismatch. In-plane grating couplers (GC) have become popular for their low cost, easy alignment, and design flexibility. While most GC designs have fixed coupling efficiencies, with a view to emerging adaptive neuromorphic and quantum integrated circuits and interposers that need ultra-compact memory/modulation components, we introduce a CMOS-compatible GC based on phase-change chalcogenide alloy germanium antimony telluride. The GC design optimized utilizing inverse design techniques achieves over 50% coupling efficiency at 1550 nm when amorphous, and near-zero efficiency when switched to a crystalline state. This design is non-volatile, reversible, and provides ultra-high transmission modulation contrasts of up to 60 dB. While the operational range can be adjusted across the telecommunication band by modifying the GC's etch depth or thickness. We show that such devices do not need global switching of their entire phase change volume and can achieve maximum modulation contrasts through switching precisely positioned phase change inclusions hinting at low-power and ultrafast modulation potential.

Terahertz-infrared spectroscopy of Ge2Sb2Te5 films on sapphire: Evolution of broadband electrodynamic response upon phase transitions

Phase-change alloy Ge2Sb2Te5 (GST) forms a favorable material platform for modern optics, photonics, and electronics thanks to a pronounced increase in conductivity with thermally induced phase transitions from amorphous (a-GST) into cubic (c-GST) and then hexagonal (h-GST) crystalline states at the temperatures of ≃150 and ≃300°C, respectively. Nevertheless, the data on broadband electrodynamic response of distinct GST phases are still missing, which hamper the design and implementation of related devices and technologies. In this paper, a-, c-, and h-GST films on a sapphire substrate are studied using broadband dielectric spectroscopy. For all GST phases, complex dielectric permittivity is retrieved using Drude and Lorentz models in the frequency range of 0.06–50 THz or the wavelength range of ≃5000–6 μm. A contribution from the free charge-carriers conductivity and vibrational modes to the broadband response of an analyte is quantified. In this way, the Drude model allows for estimation of the static (direct current—DC) and dynamic (at 1.0 THz) conductivity values, caused by motions of free charges only, which are as high as σDC≃15 and 40 S/cm and σ1.0THz≃8.8 and 28.6 S/cm for the c- and h-GSTs, respectively. This overall agrees with the results of electrical measurements of GST conductivity using the four-point probe technique. The broadband electrodynamic response models obtained for the three GST phases are important for further research and developments of GST-based devices and technologies.

Micro-encapsulation of a low-melting-point alloy phase change material and its application in electronic thermal management

The application of liquid metal (LM) with high thermal conductivity in electronic thermal management is an emerging hotspot, but leakage of LM can cause environmental pollution and lead to corrosion of electronic equipment, thereby affecting the safety of its operation. Moreover, large temperature fluctuation will be caused for the limited thermal storage capacity of LM. To solve the above problems, it is urgent to develop LM-based microcapsules with high thermal conductivity and high thermal storage capacity. Herein, a novel micro-encapsulated phase change material (MEPCM) with an internal void, composed of liquid metal Sn–Bi–In core and PMMA shell, was firstly fabricated via liquid phase micro-encapsulation method. The results showed that microcapsules maintained good morphology and efficient thermal storage capacity (246.46 J cm−3) after 300 thermal cycles, 97.12% of that before the cycle (253.77 J cm−3). Subsequently, the MEPCM-based composite was prepared by mixing MEPCM into thermal gel. The enthalpy of 50 wt% MEPCM composite was 126.72 J cm−3, and the thermal conductivity of it was 3.23 W m−1·K−1, while that of thermal gel was 0.98 W m−1·K−1. Then the 50 wt% MEPCM-based composite was applied for LED chip, and the temperature of chip was 71.1 °C, 11.2 °C lower than that of thermal gel. Therefore, MEPCM-based composites with high thermal conductivity and thermal storage capacity are considerably potential for electronic thermal management.

Flexible core–shell structured Al-Cu alloy phase change materials for heat management

The development of core–shell structured phase change materials (PCMs) with tunable melting points has been attracted much attention for thermal storage of solar energy, and a flexible shell is crucial for their practical applications. Herein, we prepared microencapsulated Al-Cu alloy PCMs (MEPCMs) with a flexible shell by a deposition-oxidizing calcination method. The Cu nanoparticles are chemically deposited on the surface of Al powders by a rapid replacement reaction, which further promotes the formation of Al-Cu alloy microspheres and the oxidation of Al to form Al2O3 shell during oxidation calcination. The prepared MEPCMs show excellent thermal cyclic performance and tunable melting point (549–592 °C). The presence of a thin film between the Al2O3 shell and Al-Cu alloy core may act as a buffer to accommodate volume change during melting-freezing process, obtaining a flexible core–shell structure. The heat storage density of Al-Cu alloy MEPCMs decreases by only 0.09% after 100 melting-freezing cycles, indicating high thermal cycling stability. In addition, the microencapsulated Al-Cu alloys present high latent heat (208.6–222.3 J·g−1) and relatively high thermal conductivity (∼1.8 W·(m·K)−1), which makes it attractive for application in high-temperature thermal storage systems.

Spin Glass Behavior in Amorphous Cr2 Ge2 Te6 Phase-Change Alloy.

The layered crystal structure of Cr2 Ge2 Te6 shows ferromagnetic ordering at the two-dimensional limit, which holds promise for spintronic applications. However, external voltage pulses can trigger amorphization of the material in nanoscale electronic devices, and it is unclear whether the loss of structural ordering leads to a change in magnetic properties. Here, it is demonstrated that Cr2 Ge2 Te6 preserves the spin-polarized nature in the amorphous phase, but undergoes a magnetic transition to a spin glass state below 20K. Quantum-mechanical computations reveal the microscopic origin of this transition in spin configuration: it is due to strong distortions of the CrTeCr bonds, connecting chromium-centered octahedra, and to the overall increase in disorder upon amorphization. The tunable magnetic properties of Cr2 Ge2 Te6 can be exploited for multifunctional, magnetic phase-change devices that switch between crystalline and amorphous states.

Bioinspired bistable dielectric elastomer actuator based on low-melting-point alloy phase change regulation

Soft bistable actuators that exhibit flexibility, fast response, and low energy consumption are key components for applications such as fast grippers, shape reconfiguration actuators, and deployable soft robots. Inspired by the structure of rhododendron leaves, we designed a bistable dielectric elastomer actuator (BDEA) by integrating a dielectric elastomer with a low-melting-point alloy. The developed BDEA can operate reversibly between two stable states through the synergistic application and control of high voltage and Joule heating. The transition process between the two stable states of the actuator was elucidated using finite element analysis. The bending angles of the actuator in the two deformation directions were measured, and grasping experiments were performed. The experimental results show that the direction and magnitude of deformation of the bistable actuator can be tuned to conform to the shape of the target object. The developed BDEA has enhanced shape adaptability and higher bearing capacity compared to conventional soft actuators.

Polarization-multiplexed metaholograms with erasable functionality

The unprecedented capability of metasurfaces in pixel-wise-level accurate light manipulation has enabled the realization of polarization-multiplexed metasurface holograms in a single or multiple channel. However, most metasurfaces are static and unable to realize active or tunable wave control in many scenarios. We introduce an erasable functionality for multi-channel metasurface holograms based on active phase tuning, which is realized using the nonvolatile chalcogenide phase change alloy of GeSbSeTe (GSST). Upon the incidence of linearly or circularly polarized waves, polarization-dependent holograms constructed using amorphous GSST (a-GSST) elliptical pillars are achieved because of the complete phase control. The a-GSST holograms feature a subwavelength spatial resolution for all elliptical pillars, with local transmittances ranging from 66% to 90%. Benefiting from the amorphous-to-crystalline phase transition of GSST, the hologram functionality can be completely erased because the crystallized pillars cannot provide the effective propagation modes required by the anisotropic phase modulations in the operating wavelength range. The unique properties of the proposed polarization-multiplexed holograms with erasable functionality offer more degrees of freedom and have potential applications in many fields, such as anti-counterfeiting, encryption, and holographic sources.

One-step crystallization in (Ge2Sb2Te5)90Ga10 thin film

Owing to data storage ability of chalcogenide based Ge2Sb2Te5 phase change alloy, this composition has been tremendously explored for its application in memory devices. Upon annealing, this composition exhibit two step crystallization, i.e, amorphous -to- fcc, and then from fcc -to- hcp phase. To address the issue of power consumption in such phase transitions, the present study is reporting one-step crystallization in (Ge2Sb2Te5)90Ga10 thin film, i.e., from amorphous -to- fcc phase which is confirmed by optical transmission contrast studies. Thus, the results poses the promising data storage applicability of (Ge2Sb2Te5)90Ga10 thin film in phase change memory devices.

Geodesic Convolutional Neural Network Characterization of Macro-Porous Latent Thermal Energy Storage

Abstract High-temperature latent heat thermal energy storage with metallic alloy phase change materials (PCMs) utilize the high latent heat and high thermal conductivity to gain a competitive edge over existing sensible and latent storage technologies. Novel macroporous latent heat storage units can be used to enhance the limiting convective heat transfer between the heat transfer fluid and the PCM to attain higher power density while maintaining high energy density. 3D monolithic percolating macroporous latent heat storage unit cells with random and ordered substructure topology were created using synthetic tomography data. Full 3D thermal computational fluid dynamics (CFD) simulations with phase change modeling was performed on 1000+ such structures using effective heat capacity method and temperature- and phase-dependent thermophysical properties. Design parameters, including transient thermal and flow characteristics, phase change time and pressure drop, were extracted as output scalars from the simulated charging process. As such structures cannot be parametrized meaningfully, a mesh-based Geodesic Convolutional Neural Network (GCNN) designed to perform direct convolutions on the surface and volume meshes of the macroporous structures was trained to predict the output scalars along with pressure, temperature, velocity distributions in the volume, and surface distributions of heat flux and shear stress. An Artificial Neural Network (ANN) using macroscopic properties—porosity, surface area, and two-point surface-void correlation functions—of the structures as inputs was used as a standard regressor for comparison. The GCNN exhibited high prediction accuracy of the scalars, outperforming the ANN and linear/exponential fits, owing to the disentangling property of GCNNs where predictions were improved by the introduction of correlated surface and volume fields. The trained GCNN behaves as a coupled CFD-heat transfer emulator predicting the volumetric distribution of temperature, pressure, velocity fields, and heat flux and shear stress distributions at the PCM–HTF interface. This deep learning based methodology offers a unique, generalized, and computationally competitive way to quickly predict phase change behavior of high power density macroporous structures in a few seconds and has the potential to optimize the percolating macroporous unit cells to application specific requirements.

Spectroscopic study of nitrogen incorporation in Ge, Sb, and Te elemental systems: A step toward the understanding of nitrogen effect in phase-change materials

Nitrogen doping in chalcogenide materials represents a promising way for the improvement of material properties. Indeed, N doping in GeSbTe phase-change alloys have demonstrated to greatly enhance thermal stability of their amorphous phase, necessary to ensure the data retention of the final phase-change memory device. Although it is suggested that the N doping in such alloys leads to the preferential formation of Ge-N bonds, further questions concerning the bonding, in particular, Sb-N and Te-N, and the structural arrangement remain unclear. In this paper, we present a study of as-deposited elemental Ge, Sb, and Te systems and their nitrides (i.e., GeN, SbN, and TeN alloys), using a large range of N content from 0 up to about 50 at. %. The as-deposited alloys are investigated by Fourier transform infrared and Raman spectroscopy. We identify the active vibrational modes associated with the formation of Ge-N, Sb-N, and Te-N bonds, highlighting the impact of N incorporation on the structure of these elemental systems. We further qualitatively compare the GeN, SbN, and TeN experimental spectra with the “ab initio” simulations of the related ideal nitride structures. Finally, the analysis of elemental nitride layers is extended to N-doped GeSbTe alloys, providing deeper understanding of nitrogen bonding in such ternary systems, employed in memory technology.

A Novel Intelligent Fan Clutch for Large Hybrid Vehicles

To solve the problems of complex structure, poor reliability, and low intelligence of existing fan clutches for large hybrid vehicles, this paper proposes a new adaptive shape memory alloy intelligent fan clutch for large hybrid vehicle motor cooling. Based on the pure shear shape memory alloy thermodynamic effects, the relationship between shape memory alloy spring recovery force and temperature has been established; based on the shape memory alloy spring thermal drive characteristics and clutch construction dimensions, clutch torque transmission equations have been established. The shape memory alloy fan clutch transmission characteristics were quantitatively analyzed in terms of temperature, torque, rotational speed, and slip rate. The results show that the shape memory alloy fan clutch model based on the finite element method (FEM) and the established transmission model can accurately describe the mechanical characteristics of the shape memory alloy phase change process and the clutch torque transmission characteristics. When the clutch input speed is 3000 rad/min and the temperature is 100 °C, the output torque is 19.04 N·m, the speed is 2877.2 rad/min, and the slip rate is 4.3%. Due to the shape memory effect of shape memory alloy, the clutch can intelligently adjust the fan speed by sensing the ambient temperature. A fan clutch can satisfy the heat dissipation requirement of a large hybrid vehicle’s transmission system under complicated road conditions.