Low Thermal Conductivity Research Articles

A novel colorless flexible polymer aerogel with stable amine linkage enabled superior formaldehyde removal and multifunctional application

Massive formaldehyde emissions have seriously endangered environment and human health, while predictably polymer aerogel is a promising candidate for formaldehyde (FA) removal, whereas low FA adsorption capacity, high volume shrinkage, and mechanical brittleness restrict its further development. Herein, based on “rigid-soft combination” polycondensation strategy, trifunctional 1,3,5-benzenetricarboxaldehyde (BTC) and polyetheramine Jeffamine T403 are selected as building blocks to construct a novel amine-linked polymer aerogel (rBTA) with hierarchical micro-nano porous structure via mild sol-gel method and freeze-drying process. Stable amine linkages in rBTA are formed by NaBH4 reduction of imine bonds, improving acid/alkali resistance and chemical stability greatly, and creating numerous active amine sites for reaction with FA. Formation of robust 3D covalent network facilitates to simultaneously achieve ultra-low-shrinkage (5.4%), high specific compressive modulus (5.32 kN·m·kg-1), remarkable mechanical durability/fatigue-resistance, flexibility, and machinability. Benefiting from synergistic physical-chemical adsorption effect, FA adsorption capacity and removal ratio of rBTA reach as high as 459.84 mg·g-1 and 97.87%, respectively. Colorless rBTA is further ground into powders for preparing polyoxymethylene (POM)/rBTA composite without affecting its color and formaldehyde emission amount at 60/230°C effectively decreases by 66.87%/79.55%. Furthermore, rBTA exhibits hydrophobicity, low thermal conductivity, and high solar reflectance, being successfully applied in emulsion separation, thermal insulation, and energy-efficient buildings fields.

HNTs Improve Flame Retardant and Thermal Insulation of the PVA/CA Composite Aerogel.

Porous materials are widely used in construction, batteries, electrical appliances, and other fields. In order to meet the demand for flame-retardant and thermal insulation properties of organic porous materials, in this work, poly(vinyl alcohol)/calcium alginate/halloysite nanotube (PVA/CA/HNTs) aerogels with a hierarchical pore structure at micrometer-nanometer scales were prepared through freeze-drying using PVA as the substrate. The cross-linking reactions of PVA with H3BO3 and sodium alginate (SA) with CaCl2 constructed a double cross-linking network structure within the aerogel. And the HNTs were incorporated as reinforcing agents. The experimental results showed that the PVA/CA/HNTs aerogels had excellent flame-retardant and thermal insulation properties, and the heat release rate (HRR) and total heat release (THR) were effectively reduced compared to the PVA/CA aerogel. In addition, PVA/CA/HNTs aerogels had a high limiting oxygen index (LOI 60%) and low thermal conductivity (0.040 W/m·K). While their surface was subjected to a flame (800-1000 °C) for 25 min, the temperatures of the back surface were still lower than 80 °C. The low thermal conductivity of HNTs with hollow nanotube-like structures and the excellent flame-retardant properties of CA contributed to this phenomenon. The presence of HNTs and CA facilitated the formation of a dense carbon layer during combustion, enhancing the flame retardancy for PVA. In addition, the interpenetrating cross-linking network and the unique nanopores of HNTs collectively established a hierarchical pore structure within the gel, effectively impeding substance and heat exchange between the substrate and external environment. As the flame-retardant and thermal insulating material, PVA/CA/HNTs aerogels have a promising development prospect and potential in the fields of construction, transportation, electronics, and electrical appliances.

Thermoelectric properties of superionic Li0.11Cu1.89S compound

Copper sulfide is a multifunctional material. Copper sulfides are known to be used in photo-electric converters, in plasmonics, in active electrodes of batteries and supercapacitors, etc. The excellent thermoelectric properties of copper sulfide are well-known too. The purpose of this study is to investigate the thermoelectric performance of nanocomposite copper sulfide contained monoclinic Cu2S and tetragonal Cu1.96S phase. According to scanning electron microscopy, the average particle size of the synthesized powder was about 373 nm. The Li0.11Cu1.89S sample showed an electronic conductivity of 50–180 S/cm, a Seebeck coefficient of 0.04–0.31 mV/K in the range of 300–700 K, and high power factor 5.8 μW K−2cm−1 at 672 K. Total thermal conductivity decreases with increasing temperature from 0.61 to 0.22 W∙K−1m−1 in the range of 300–700 K. Such low thermal conductivity and high power factor made it possible to achieve an extremely high dimensionless thermoelectric figure of merit ZT = 1.76 at 672 K, which allows to consider the Li0.11Cu1.89S alloy as a promising thermoelectric material.

“Cocktail-like” double-layered polyimide/alumina composite aerogels via side-direction freezing method as designable high-temperature thermal insulations

The extremely low thermal conductivity, low density, and high-temperature stability of polyimide (PI) aerogels are promising candidates for thermal insulation applications. In this work, the layered PI/Al2O3 composite aerogels (PACAs) were developed, inspired by the biomimetic idea of a “cocktail” layered structure to enhance the service temperature of PI. By exploiting the density difference between the water-soluble polyimide acid (PAA) solution and Al2O3 slurry, we successfully fabricated PACAs with a macro-scale layered structure through side-direction freezing and thermal imidization processes. The PACAs exhibit significant anisotropic structural characteristics, with pore channels presenting a honeycomb structure in the Z-direction, effectively suppressing heat transfer along this direction. Both PI and Al2O3 aerogels demonstrate anisotropic properties in different directions, with the PI aerogel achieving excellent thermal insulation with a thermal conductivity of 0.0197 W/(m·K) along the Z-direction. By adjusting the relative thickness of the PI and Al2O3 layers, optimal thermal insulation performances were achieved at temperatures of 300 °C, 600 °C, and 900 °C. These results showcase the innovative advantages of the layered structure in enhancing thermal insulation while leveraging the low thermal conductivity of PI and the high-temperature tolerance of Al2O3.

Boosting the thermoelectric performance of Bi2S3 by CeCl3 addition and hydrothermal synthesis

Bi2S3 is a potential thermoelectric material due to its high Seebeck coefficient (S), low thermal conductivity (κ) and environmentally friendly elemental composition. However, pristine Bi2S3 suffers from a low thermoelectric performance primarily owing to the intrinsic low electrical conductivity (σ). In this work, we employ CeCl3 doping to promote the σ of Bi2S3 by a hydrothermal method. Doping 1.0 % mol CeCl3 provides more electrons to increase the carrier concentration to 2.73 × 1019 cm−3 of Bi2S3 at room temperature, which leads to significant high σ and power factor of 242 μW m−1 K−2 at 573 K. In addition, the formation of micro–nano pores in the doped Bi2S3 bulk samples contribute to the phonon scattering as well as the reduction of lattice thermal conductivity. A peak ZT of ∼0.31 at 623 K is obtained in the Bi2S3 bulk sample doped with 1.0 % mol CeCl3, which is almost twice as high as the pristine Bi2S3. Simultaneously, the Vickers hardness of 1.0 % mol CeCl3 doped Bi2S3 samples achieves to approximately 1.28 GPa, which is enhanced by nearly 40 % compared to pristine Bi2S3. This study has provided a facile method for realizing high thermoelectric performance and high mechanical property of Bi2S3 materials.

Investigating the effect of nanobubble-based cutting fluid on tool wear and cutting forces in milling of Inconel 718

Machining of Nickel-Based Superalloys (NBSAs) is characterized by rapid work hardening, low thermal conductivity, and extreme abrasive behavior. Due to such characteristics of NBSAs, the machining of materials like Inconel 718 (IN718) results in extensive tool wear and high cutting forces. The present study employs nanobubble-based cutting fluid during machining of IN718 and investigates its effect on tool wear and cutting forces. The trochoidal milling experiments were conducted on an IN718 workpiece with nanobubble-based and normal cutting fluid at varying surface speeds. The evolution of tool flank wear area and peak resultant cutting force were recorded and compared to evaluate the effectiveness of nanobubble-based cutting fluid over normal cutting fluid. The results showed that nanobubble-based cutting fluid lowers the tool wear rate by enhancing heat dissipation and reducing abrasion wear. However, higher cutting forces were observed with nanobubble-based cutting fluid due to increase in hardness of the workpiece. Also, it is realized that using nanobubble-based cutting fluid can significantly improve the lifespan of the tool, leading to sustainable manufacturing.

Thermal optimization of PCM‐based heat sink using fins: A combination of CFD, genetic algorithms, and neural networks

AbstractSustainable development requires focusing on renewable energy, such as solar power, due to the limited availability of fossil fuels. Solar energy, available only during daylight, can be stored in thermal batteries using phase change materials (PCM). However, PCM has low thermal conductivity, slowing its melting process. Fins have been added to enhance heat diffusion, but their optimal design requires further study. This research examines an annular chamber with fixed inner and outer wall temperatures and explores fin configurations. Two series of evenly spaced fins (four and five) were analyzed, with melting times calculated using CFD simulations. Larger fins reduce melting time but limit PCM storage. Effectiveness, defined as the PCM space over melting time, was used to evaluate performance. Higher boundary temperatures decreased melting time but did not always increase effectiveness. The study also used artificial neural networks (ANN) combined with a genetic algorithm to predict optimal conditions. The configuration with five fins, a 90°C boundary temperature, a fin length of 45 mm, and a thickness of 5.4 mm achieved the highest effectiveness of 4.7, showing that smaller fins at lower temperatures are more efficient.

Extending the Transient Plane Source Scanning method for determining the specific heat capacity of low thermal conductivity materials through a numerical study

In contrast to the conventional Transient Plane Source (TPS) method, the Transient Plane Source Scanning (TPSS) technique allows for the direct determination of the specific heat capacity and requires the use of a specially designed sample holder for accurate measurements. While this method correctly determines the specific heat capacity of samples with moderate and high thermal conductivity, it tends to underestimate the values for those with low thermal conductivity. This paper demonstrates that the underestimated specific heat capacity results from heat loss during the measurement process. To precisely quantify the heat loss, a numerical model based on the finite element method was developed, with key material properties tuned based on measurement data. This model can closely describe the curve of measured thermal response, thereby enabling the precise determination of the specific heat capacity. Consequently, this study introduces a novel approach that incorporates numerical simulation to enhance TPSS measurements of poorly conducting samples, providing a reliable alternative for determining specific heat capacity.

Properties of CaO-MgO-SiO2 insulating refractories prepared from phosphorus tailings

CaO-MgO-SiO2 insulating refractories were prepared using phosphorus tailings through in-situ pore-forming technology in this work, aiming to achieve the efficient utilization of solid waste phosphorus tailings. microsilica was used to react with free CaO generated by the decomposition of dolomite from phosphorus tailings during the calcination in order to prevent the hydration of CaO in the materials. The influence of microsilica addition and heating temperature on the properties of insulating refractories prepared from phosphorus tailings was investigated. The results showed that CaO-MgO-SiO2 insulating refractories with 8.8 wt% microsilica addition exhibited excellent comprehensive performance after heating at 1300 °C for 3 h. The insulation refractories prepared from phosphorus tailings were anti-hydration, had lower thermal conductivity, and could be used as insulation refractories for high-temperature kilns.

The DFT prediction of comprehensive properties of antiperovskites Mg6CX4 (X = S, Se, Te) and effects of defects and surface adsorption

It is important to search potential materials to meet ever-increasing demand in various fields. In order to understand the new hexagonal antiperovskites material Mg6CX4 (X=S, Se, Te), their mechanical, electronic and optical properties were studied based on density functional theory (DFT). The structural stability has been confirmed by the elastic constant criteria, formation energy, phonon dispersion spectra and ab-initio molecular dynamics (AIMD) simulation performed at 300K. Besides, the Poisson's ratios over 0.26 demonstrate the ductility of the studied materials. They all have direct electronic band structures with bandgaps of 0.977eV for Mg6CS4, 0.809eV for Mg6CSe4 and 1.274eV for Mg6CTe4, respectively. The calculated melting temperatures are all around 1000K, which indicates the potential for high-temperature application. Therefore, Mg6CTe4 fits most for absorber in solar cells due to its proper bandgap and dispersive band edge. The antiperovskites exhibit high and broad light absorption in visible and near ultraviolet region with absorption coefficient greater than 104cm-1, which inidcates a broad applicable prospect in optoelectronic field. Mg6CTe4 is also a candidate for efficient solid-state refrigeration due to its lowest thermal conductivity as 0.0046W/(K•m). The defect analysis suggest that oxygen defects are the most favorable and have complex effects on bandgaps. The high bandgap sensitivity to surface adsorbates implies potential application in gas detector.

Nano-Enhanced Graphite/Phase Change Material/Graphene Composite for Sustainable and Efficient Passive Thermal Management.

Passive battery thermal management systems (BTMSs) are critical for mitigation of battery thermal runaway (TR). Phase change materials (PCMs) have shown promise for mitigating transient thermal challenges. Fluid leakage and low effective thermal conductivity limit PCM adoption. Furthermore, the thermal capacitance of PCMs diminishes as their latent load is exhausted, creating an unsustainable cooling effect that is transitory. Here, an expanded graphite/PCM/graphene composite that solves these challenges is proposed. The expanded graphite/PCM phase change composite eliminates leakage and increases effective thermal conductivity while the graphene coating enables radiative cooling for PCM regeneration. The composite demonstrates excellent thermal performance in a real BTMS and shows a 26% decrease in temperature when compared to conventional BTMS materials. The composite exhibits thermal control performance comparable with active cooling, resulting in reduced cost and increased simplicity. In addition to BTMSs, this material is anticipated to have application in a plethora of engineered systems requiring stringent thermal management.

The influence of the elemental valence on the thermophysical properties of high entropy (La0.2Sm0.2Eu0.2Yb0.2Y0.2)2(Ce0.5Zr0.5)2O7 coatings for thermal barrier application

Commercial yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are no longer sufficient for the stringent demands in the high operating temperature and excellent thermophysical properties of the high-performance gas turbines and aviation engines. High entropy ceramics, distinguished by their superior thermophysical properties, have risen as a potential substitute for TBCs. However, the realm of atmospheric plasma spraying (APS) in the creation of these advanced TBCs remains relatively unexplored. In this work, three distinct high-entropy (La0.2Sm0.2Eu0.2Yb0.2Y0.2)2(Ce0.5Zr0.5)2O7 coatings were developed through the meticulous alteration of spraying power. The effects of spraying power on the microstructure, valence states of constituent elements and thermophysical properties of the coatings were deeply investigated. The results indicated that all the as-sprayed coatings exhibit a defect fluorite structure. Spraying power does have a significant impact on the thermophysical properties of the coatings. With the decrease in spraying power, the thermal conductivity of the coatings shows a progressive reduction, whereas the coefficient of thermal expansion (CTE) exhibits a gradual increase. This trend is closely related to valence states of constituent elements in the coatings. The resulting coating exhibits a low thermal conductivity of 0.54 W⋅m-1⋅K-1, a high CTE of 11.22×10-6·K-1 and a superior phase stability at elevated temperatures.

ОЦЕНКА ТЕПЛОПРОВОДНОСТИ ПОКРЫТИЙ НА ОСНОВЕ АЛЮМИНИДОВ ЖЕЛЕЗА

It is shown that the formation of a coating from FeAl/Fe3Al/Fe(Al) iron aluminides on the steel surface of the hopper of the anode mass mixer reduces its sticking to the walls of the funnel during loading. The latter is due to the maintenance of a high temperature of the anode mass due to the low thermal conductivity of the coating in contact with it.

Effect of Al2O3 nano/micro powder ratio on microstructures and properties of microporous MgO-MgAl2O4 refractory aggregates

In this work, the microporous MgO-MgAl2O4 refractory aggregates were prepared by in-situ decomposition synthesis method. The effect of Al2O3 nano/micro powder ratio on the microstructures and properties was studied under the premise that the fixed total content of Al2O3 was 15wt%. The results demonstrated that the aggregates were composed of microporous MgO microparticles with nano pores as well as MgAl2O4 grains located among them. The ratio not only influenced the volume expansion through changing the lattice constant of in-situ MgAl2O4, but also affected the formation of two different positions of MgAl2O4 bonds, thereby influencing the microstructures and properties. When the ratio was 4:6, the combined effect of the shrinkage of MgO microparticles and the expansion of in-situ MgAl2O4 grains promoted the formation of the bonds between MgAl2O4 grains and MgO microparticles, as well as among the MgAl2O4 grains, which resulted in the best comprehensive properties of the microporous MgO-MgAl2O4 refractory aggregates, characterized by micro-nano pores, an apparent porosity of 26%, a flexural strength of 23.2 MPa, a flexure strength after thermal shock of 20.4 MPa and a low thermal conductivity of 2.99 W/(m·K) at 800°C.

Lightweight, ultrahigh-strength and flame-retardant cellulose aerogel crosslinked with a reactive P/N-rich curdlan derivative.

Cellulose aerogel, recognized for its eco-friendliness, bio-sustainability and excellent thermal insulation property, holds immense potential as an insulation material. However, the application of cellulose aerogel has been hindered by its inherent drawbacks, particularly its low strength and flammability. In this study, a reactive P/N-rich curdlan derivative (NT) was synthesized and characterized. Lightweight, ultrahigh-strength and flame-retardant composite aerogels were then prepared by slow freezing, freeze-drying and chemical crosslinking methods. Composite aerogel crosslinked with 30% NT exhibited exceptional thermal insulation property with a low thermal conductivity of 33.9mW/(m·K), which rivaled the value of petroleum-based thermal insulation materials. It possessed an ultrahigh compressive modulus (0.786MPa) at low density (21.6mg/cm3), which supported >12,000 times its weight. It also displayed superior flame-retardant property, with a limiting oxygen index of up to 33.1% and a V-0 rating in the UL-94 test. This study provides a new insight into the high-value utilization of natural polysaccharide and an innovative solution to the problem of low strength and flammability of cellulose aerogel. Cellulose aerogels with ultrahigh strength, superior flame retardancy and thermal insulation property possess a promising application in the fields of construction, aerospace and thermal protective clothing as high-performance thermal insulation materials.

Thermally insulated C/SiC/SiBCN composite ceramic aerogel with enhanced electromagnetic wave absorption performance

Thermal insulation and electromagnetic wave (EMW) absorption integrated materials with lightweight are highly desirable in hypersonic vehicles and military application, as they provide both aerodynamic heat resistance and EMW stealth capability. Herein, a C/SiC/SiBCN ceramic composite aerogel was developed using a novel strategy combining in situ chemical vapor deposition of SiC nanofibers with the polymer-derived ceramic (PDC) aerogel method. The microstructure, phase composition, thermal insulation, mechanical properties and EMW absorption performances of the composite aerogel were thoroughly investigated. The resulting C/SiC/SiBCN composite aerogel with three impregnation-pyrolysis cycles demonstrates improved mechanical properties, with the compressive strength increasing from 0.21 MPa to 0.48 MPa compared to pure SiBCN aerogel. Additionally, the composite aerogel shows a low thermal conductivity of 0.049 W/mK and a low density of 0.116 g/cm3. Moreover, the C/SiC/SiBCN composite aerogel exhibits outstanding EMW absorption properties, achieving a minimum reflection loss of -45.7 dB and an effective bandwidth of 5.3 GHz. Owing to the integration of EMW absorption and thermal insulation properties, the C/SiC/SiBCN composite aerogel offers promising potential for developing integrated microwave absorption and thermal insulation materials for high-speed vehicles.

Low Thermal Conductivity of Epidote and Its Cooling Effect on the Oceanic Crust

AbstractEpidote is a potential water carrier in subducting oceanic crust, and it is involved in temperature records from blueschist and eclogite exhumed from subduction zones. Thermal conductivity (κ) and thermal diffusivity (D) of epidote were measured at 303–1,473 K and 0.5–3.0 GPa using the transient plane‐source method. κ and D values decreased with temperature before dehydration, but increase anomalously with temperature after dehydration, and finally decreased with crystallization of the decomposition products. Thermal conductivity and thermal diffusivity of epidote exhibited a positive pressure dependence. The obtained κ and D values of epidote were significantly smaller than those of nominally anhydrous minerals and other hydrous minerals. X‐ray computed tomography analysis revealed that the pores inside the recovered samples were partially connected. κ and D values were dominated by conductive heat transport before dehydration, while the anomalous increase in the thermal parameters after dehydration may have been caused by the fluid inside the connected pores. Using variable thermal conductivity obtained in this study, the thermal structures of warm subducting slabs associated with epidote‐blueschist and epidote‐eclogite facies were modeled. Our estimations revealed that the temperatures of warm slabs below the forearc with the epidote‐blueschist and epidote‐eclogite facies may be lower 7–10 and ∼40–50 K compared to those determined using a constant thermal conductivity value. This implies that the presence of epidote‐blueschist and epidote‐eclogite could reduce the temperature of the slab, which may alter the dehydration depth of the slab.

Investigation of thermal transport mechanism of silicone-modified phenolic matrix nanocomposites with different pyrolysis degrees

Polymeric nanocomposites with low thermal conductivity show promising applications for next-generation thermal protection materials used in re-entry vehicles due to their lightweight, high char yield, and excellent ablation-oxidation resistance. However, the thermal conductivity of polymeric nanocomposites varies with the pyrolysis degree of the polymer matrix in aerodynamic environments, which significantly affects thermal protection and structural applications but is challenging to identify experimentally. Herein, non-equilibrium molecular dynamics simulations combined with experiments were implemented to determine the dependence of thermal conductivities on pyrolysis degree and microstructures for polymeric nanocomposites. We further explore the thermal transport mechanism through various contributions to the morphology. The results show that the thermal conductivity of the polymer matrix can be increased by a factor of 4.44 (from 0.27 W/m/K to 1.47 W/m/K) as the pyrolysis degree increases from 0 to 100%, and the thermal conductivity depends nonlinearly on the pyrolysis degree and temperature. Molecular dynamics simulations found that the side chains of the polymer matrix are rapidly scissored with the increasing pyrolysis degrees, and the structural ordering of the residual solids containing sp2 hybridization is enhanced, exhibiting graphene-like microtopological features, which reduces phonon scattering and makes thermal transport more efficient. This work provides insight into the linkage between the thermal transport properties and the pyrolysis degree of polymeric nanocomposites, which is valuable for improving the thermal transport performance and modeling ablation response for polymeric nanocomposites.

Innovative preparation of polyimide/polysulfone amide (PI/PSA) membrane-pore-like nanofibers with biomimetic penguin feather shaft structure and thermal insulation performances

The white-browed penguin can survive in extreme environments due to its unique feather structure. The feather shafts of penguins are porous, separated by the membrane-pore-like structure made of keratin fiber membranes. The feather branches are densely arranged around the feather shafts. This unique structure provides inspiration for researchers. In this work, we developed a simple method to construct polyimide/polysulfone amide (PI/PSA) membrane-pore-like structure nanofibers resembling penguin feather shafts and studied the effects of different low-boiling point solvents (tetrahydrofuran (THF), ethyl acetate (EA), and acetone (AC)) on the morphology, tensile properties, and thermal insulation properties of PI/PSA membrane-pore-like structure nanofibers. Comprehensive characterization was also performed using scanning electron microscope, total reflection infrared spectrometer, X-ray diffractometer, universal testing machine, thermal conductivity meter, pore size analyzer, thermal gravimetric analyzer, infrared thermal imaging instruments, and thermocouple testing instruments. The results showed that when the mass ratio of THF to N, N-dimethylacetamide (DMAC) was 20/80, the prepared PI/PSA membrane-pore-like structure nanofibers exhibited excellent thermal insulation properties, with a low thermal conductivity of 0.0436 W·m−1·K−1, a breaking strength of 7.72 ± 2.64 MPa, and a breaking elongation of 8.19 ± 4.07 %. The biomimetic membrane-pore-like structure with excellent thermal insulation properties is expected to be applied in various fields, such as heat-protective clothing and architectural coatings in harsh environments.

Recent Advances in High-Entropy Ceramics: Synthesis Methods, Properties, and Emerging Applications

High-entropy ceramics (HECs) represent an emerging class of materials composed of at least five different cations or anions in near-equiatomic proportions, garnering significant attention due to their extraordinary functional and structural properties. While multi-component ceramics have played a crucial role for many years, the concept of high-entropy materials was first introduced eighteen years ago with the synthesis of high-entropy alloys, and the first high-entropy nitride films were reported in 2014. These newly developed materials exhibit superior properties over traditional ceramics, such as enhanced thermal stability, hardness, and chemical resistance, making them suitable for a wide range of applications. High-entropy carbides, borides, oxides, oxi-carbides, oxi-borides, and other systems fall within the HEC category, typically occupying unique positions within phase diagrams that lead to novel properties. HECs are particularly well suited for high-temperature coatings, for tribological applications where low thermal conductivity and similar heat coefficients are critical, as well as for energy storage and dielectric uses. Computational tools like CALPHAD streamline the element selection process for designing HECs, while innovative, energy-efficient synthesis methods are being explored for producing dense specimens. This paper provides an in-depth analysis of the current state of the compositional design, the fabrication techniques, and the diverse applications of HECs, emphasizing their transformative potential in various industrial domains.