High Thermal Properties Research Articles

Hierarchical Modeling of the Thermal Insulation Performance of Novel Plasters with Aerogel Inclusions

Silica aerogel possesses a significantly lower thermal conductivity compared to still air at room temperature, thanks to its high porosity and advanced thermal and physical properties. It is extensively investigated for its potential use as an insulation material, usually being incorporated into other matrix materials, such as cement plasters, to enhance the overall thermal performance with minimal weight load. The development of lightweight thermal insulation materials is a key step in reducing energy consumption in hot and cold environments during construction and in thermal equipment. The superior insulation capabilities of aerogels stem from their nanostructured SiO2 framework, which induces nanoscale rarefaction effects on the enclosed air near the SiO2 structure. This study reconstructed the nanostructured SiO2 network of modern aerogels using microscopy imaging and the literature data and integrated it into sophisticated heat transfer simulations at a microscopic level to predict its thermal performance. The simulation assumed conduction as the primary energy dissipation mechanism, incorporating local rarefaction effects based on kinetic theory approaches. SiO2 aggregates were modeled as interconnected strings of spherical beads, with variations in the aggregate size explored in a parametric study. Nanoscale rarefaction phenomena, such as slip wall and Knudsen diffusion, prevalent at these grain sizes and structures, were incorporated to refine the modeling approach. The degree of the aerogel content relative to the effective properties of the multiphasic material was then investigated systematically along the multilayered mortar thickness and on a representative multiphasic layer at the mesoscopic level. The results quantify the significant decrease in the thermal conductivity of the heterogeneous material as the porosity of the aerogel increased. The insulation performance of this aerogel incorporated into cement plasters was assessed with this hierarchical approach and validated against experimental data, providing insights for the optimization of the fabrication process and potential applications in construction.

Excellent broadband sound absorption in composites manufactured by embedding piezoelectric polymer aerogels in porous ceramics

Challenges remain in the design and manufacture of acoustic devices with excellent broadband sound absorption performance. Herein, an efficient acoustic absorber with hierarchical pore structure and additional acoustic-electrical energy conversion mechanism is reported in which combined zirconia porous ceramics and P(VDF-TrFE) piezoelectric aerogels. Reticular cross-scale pore structure enables sound waves to propagate and dissipate effectively. The vibrations generated by piezoelectric aerogels under acoustic excitation further consume sound waves through converting acoustic energy into electrical energy based on the local piezoelectric and triboelectric effect, which improves the medium and low-frequency sound absorption capability. The average sound absorption coefficient of the prepared acoustic composites reaches 0.87 while the noise reduction coefficient is 0.54. Furthermore, the composites also possess low density, high compressive strength, good hydrophobicity and thermal insulation properties for applications. Therefore, this innovative strategy offers new design ideas for the next generation of high-performance acoustic materials with promising applications in transportation and industrial construction.

Preparation and Performance Study of Thermally Conductive Silicone Adhesive Applying in Flip Chip Ball Grid Array

A thermally conductive silicone adhesive UB-5715 was prepared using vinyl silicone oil of medium viscosity, hydrogen-containing silicone oil and micron alumina powder. The results revealed that UB-5715 demonstrated superior thermal and mechanical properties. Specifically, its thermal decomposition temperature exceeded 400 °C, the thermal conductivity coefficient surpassed 1.80 W/m·K, the thermal resistance was under 12.0 °C·cm2/W, the shear strength reached achieved was over 5.00 MPa. Meanwhile, after being subjected to uHAST for 384 hours, thermal cycle for 1000 times and heat aging for 1000 hours respectively, UB-5715 still maintained its high thermal conductivity coefficient and mechanical properties. The thermal conductivity coefficient still exceeded 1.70 W/m·K, shear strength still surpassed 5.00 MPa, the tensile modulus remained below 100 MPa, the linear expansion coefficient was less than 160 ppm/°C, and its comprehensive performance met the reliability requirements for advanced packaging process substrates and heat dissipation cover assemblies.

Aromatic Poly(dithioacetal)s: Spanning Degradability, Thermostability, and High Refractive Index Towards Eco-friendly Optics.

In the quest for eco-friendly optics, high refractive index polymers (HRIPs) with degradability have been one of the desirable optical materials for realizing eco-friendly and efficient lighting technologies. However, it has been challenging for HRIPs to simultaneously realize thermostability, high refractive index (RI), visible transparency, and efficient degradability, all of which are essential for their practical use. In this context, we herein focus on aromatic poly(dithioacetal)s, composed of visible-transparent yet degradable dithioacetal moieties and rigid phenylene sulfide spacers, exhibiting moderately high Tg (> 60 °C), high RI (> 1.7), and colorless film features. In addition, poly(dithioacetal)s can balance (1) high stability under the operating conditions even upon heating and (2) quantitative degradability that can selectively yield cyclic low-molecular-weight products that can be further repolymerized upon further addition of an acid catalyst. These results provide a key concept for high refractive index polymers that allow on-demand degradability and recyclability without compromising their high potential thermal and optical properties.

Physicochemical, techno-functional, and thermal properties of Kabuli chickpea's aquafaba extracted by optimized microwave-assistive process

Aquafaba, a liquid by-product from the soaking and cooking of legumes, is often discarded in canning processes despite its rich protein, carbohydrate content, and functional properties. This study investigates the impact of microwave irradiation pretreatment on the extraction efficiency and the physicochemical, techno-functional, and thermal properties of Kabuli chickpea aquafaba. The findings revealed that increased microwave irradiation time and power led to a reduction in foaming ability and extraction efficiency but significantly enhanced the soluble protein content, density, dry matter, and foam stability of aquafaba. Optimal extraction was achieved with 5 min of irradiation at 900 W, yielding the highest extraction efficiency (175.3 %), protein concentration (1779.12 mg kg-1), density (1.019 g/mL), dry matter (4.11 %), foaming ability (341.21 %), and foam stability (49.56 %). Thermogravimetric analysis and FT-IR spectroscopy confirmed that microwave pretreatment improved the thermal stability of aquafaba without altering its chemical structure. Microwave-assisted extraction improves the quality and functionality of aquafaba, offering a sustainable alternative to waste disposal in the food industry. While the initial investment in microwave technology may be high, it transforms aquafaba from a waste by-product into a valuable resource, leading to significant profitability for canning industries. Given the high techno-functional, physicochemical, and thermal properties of aquafaba, it appears to be a suitable alternative to more expensive ingredients like egg whites and a promising substitute in vegan products.

Influence of solid loading on microstructure evolution and thermal conductivity of aluminum nitride ceramics fabricated by digital light processing 3D printing

Efficient thermal management is essential to reduce hot spot temperature of high-power opto-electronic components and improve their working efficiency. In this work, AlN ceramics with high density and thermal conductivity properties were fabricated using a joint process of digital light processing (DLP) 3D printing and micro-pressure-assisted sintering method. Effects of solid loading on microstructure evolution and thermal properties of the ceramics were systematically discussed. AlN ceramic mini-channel heat sinks were designed and fabricated using the optimized DLP 3D printing and sintering parameters. The thermal management performances of the ceramic heat sinks were evaluated by investigating the optoelectronic property of the encapsulated laser diode module. Results indicated that the laser diode module could be long-timely operated at full driven power. This study provided a new strategy for fabricating high performance AlN ceramics with complex configurations and highlighted the technical potential of AlN ceramic heat sink with compact coolant channels.

2D Embedded Ultrawide Bandgap Devices for Extreme Environment Applications.

Ultrawide bandgap semiconductors such as AlGaN, AlN, diamond, and β-Ga2O3 have significantly enhanced the functionality of electronic and optoelectronic devices, particularly in harsh environment conditions. However, some of these materials face challenges such as low thermal conductivity, limited P-type conductivity, and scalability issues, which can hinder device performance under extreme conditions like high temperature and irradiation. In this review paper, we explore the integration of various two-dimensional materials (2DMs) to address these challenges. These materials offer excellent properties such as high thermal conductivity, mechanical strength, and electrical properties. Notably, graphene, hexagonal boron nitride, transition metal dichalcogenides, 2D and quasi-2D Ga2O3, TeO2, and others are investigated for their potential in improving ultrawide bandgap semiconductor-based devices. We highlight the significant improvement observed in the device performance after the incorporation of 2D materials. By leveraging the properties of these materials, ultrawide bandgap semiconductor devices demonstrate enhanced functionality and resilience in harsh environmental conditions. This review provides valuable insights into the role of 2D materials in advancing the field of ultrawide bandgap semiconductors and highlights opportunities for further research and development in this area.

High thermal and mechanical properties of carbon fiber network reinforced copper matrix composites achieved by configuration design and interface engineering

Constructing three-dimensional (3D) fillers within the matrix represents a highly promising strategy for achieving excellent comprehensive performance. In this study, the possibility of implementing 3D network configuration in carbon fiber/copper (CF/Cu) composites is explored. A novel composite structure was developed through template-electrodeposition and hot-pressing sintering techniques, incorporating a 3D CF network within the Cu matrix. Additionally, tungsten carbide (WC) coating was applied to the CF surface using molten salt method. Research findings indicate that the 3D CF networks establish continuous heat flow channels within the Cu matrix, while the WC coating mitigates the interfacial thermal resistance by improving CF-Cu interface bonding. The 3D-CF(WC)/Cu composite obtained through the synergistic strengthening of configuration design and interface engineering exhibits excellent thermal and mechanical properties. The thermal conductivity (TC), coefficient of thermal expansion (CTE), and bending strength of the 3D-CF(WC)/Cu composite in the in-plane direction are 457.4 ± 9.0 W m−1 K−1, 6.9 ± 0.4 × 10−6 K−1, and 281.9 ± 5.2 MPa, respectively; and in the through-plane direction are 400.8 ± 8.9 W m−1 K−1, 6.1 ± 0.4 × 10−6 K−1, and 263.1 ± 5.6 MPa, respectively. This research provides a novel approach to develop carbon reinforced metal matrix thermal management composites.

Cellulose, cellulose nanofibers, and cellulose acetate from Butia fruits (Butia odorata): Chemical, morphological, structural, and thermal properties

Cellulose possesses numerous advantageous properties and is a precursor to compounds and derivatives. The objective of this study was to isolate and characterize cellulose from Butia fruits and simultaneously produce cellulose nanofibers and cellulose acetate from the isolated cellulose. Cellulose extraction was performed using a combination of alkaline and bleaching treatments, while the production of cellulose nanofibers and cellulose acetate was achieved through acid hydrolysis and acetylation, respectively. The materials were characterized by their chemical composition, size distribution, zeta potential, morphology, relative crystallinity (XRD), functional groups (FTIR), molecular structure (NMR), and thermal stability (TGA). The Butia crude fibers presented 49.4 % cellulose, 4.5 % hemicellulose, 25.4 % lignin, and 1.3 % ash. The cellulose nanofibers presented an average diameter ranging from 13.7 to 93.1 nm and exhibited a high degree of crystallinity (63.3 %). FTIR, XRD, 13C, and 1H NMR analyses confirmed that the isolation processes effectively removed amorphous regions from the cellulose nanofibers and confirmed the cellulose acetylation process. As demonstrated, cellulosic materials derived from Butia fruit exhibit promise for various applications, including their potential use as reinforcing agents in polymer matrices, due to their high extraction yield, thermal properties, and crystallinity.

Investigation of Wire-Arc Directed Energy Deposition of Copper for use in e-Mobility applications.

Abstract Additive manufacturing of pure copper is interesting for utilising high electrical and thermal conductivity properties for electrical as well as thermal applications. Wire-arc directed energy deposition is beneficial for producing large parts with less material wastage and is suitable for relatively less abundant resources like copper. The present study explores the feasibility and properties of parts produced using CuSn1 feedstock alloy and this process. Metallographic analysis and micro-hardness tests were conducted. The relative density of 99.99% is achieved, the micro-hardness is 64 HV0 1 and the grain sizes are observed to be growing along the build direction.

Enhancing flame retardancy in 3D printed polyamide composites using directionally arranged recycled carbon fiber

Combining recycled carbon fiber (rCF) and 3D printing technology has shown great potential for fabricating functional prototypes and production parts used in the aerospace and automotive industries. However, it is still a challenge to design flame-retardant 3D printed parts with high mechanical properties and flame-retardant rating. In the work, a flame-retardant polyamide (PA)-based composite for material extrusion 3D printing was prepared by utilization of rCF, polyhedral oligomeric silsesquioxanes (POSS), and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene (DOPO)-based flame retardant. The 3D-printed composites have high thermal stability, mechanical properties, and excellent flame retardancy with a V-0 rating. With the benefits of material extrusion 3D printing, directionally arranged rCF in 3D printed composites could effectively inhibit the fire spread, extend the time to ignition (TTI), reduce the total heat release (THR) and total smoke release (TSR) of 3D printed composites. The directional flame-retardant mechanism is mainly the thermal conductivity mechanism of the condensed phase and the promotion of stable ordered carbon layer formation. It provides a promising path for designing high-performance flame-retardant materials.

High toughness, flexible and thermally conductive fluorine rubber composite films reinforced by hexagonal boron nitride flakes for thermal management

The rapid advancement of electronic information technology has generated a substantial demand for polymer-based thermal management materials. In order to address the challenges of heat dissipation and avoid signal interference, it is essential to develop polymer-based thermal management materials with both high thermal conductivity and low dielectric properties. Herein, hexagonal boron nitride flakes (h-BNFs) with a high aspect ratio and some hydroxyl groups were prepared using the high pressure homogenization technique. Subsequently, h-BNF/fluorine rubber (h-BNF/FKM) composite films were fabricated through a simple and scalable blade coating method. During the blade coating process, most of the h-BNFs can align with their (002) crystal planes paralleling to the horizontal direction. In addition, the rest of the h-BNFs will randomly distribute and overlap with each other, combining with the horizontally aligned h-BNFs to form a distinctive three-dimensional packing network. This unique network structure enables the h-BNF/FKM composite films to have thermal conductivities of up to 0.44 W/(m·K). Moreover, the introduction of h-BNFs can effectively reduce the dielectric constants and dielectric losses of FKM films. More importantly, the h-BNF/FKM composite films also exhibit outstanding mechanical toughness, excellent flexibility, good adhesion and improved flame-retardancy, providing promising applications in the electronic device thermal management.

Growth behavior of anisotropic monometallic MOFs derivatives with the high absorbing and thermal properties

The growth behavior and morphological characteristics of metal-organic frameworks (MOFs) should be considered as important factors in understanding their structure. Therefore, MOFs with atypical shapes, heterogeneous structures or abnormal properties that grow anisotropic can serve as components and templates for further directed assembly or conversion into MOF derivatives with excellent performance in electromagnetic wave absorption. Cobalt (Co) and nickel (Ni) metals have good magnetic properties and are common materials for the preparation of monometallic MOF-derived. In this study, various MOF materials with anisotropic properties, such as rod-like, flower-like, and braided, were prepared by adjusting the molar ratio of Co and Ni solvent to the organic ligand. Due to the rich inter-facial polarization and strong magnetic coupling network of the magnetic composites, Ni-MOF-b (Ni-MOF with braided shape) was prepared for the first time when the molar ratio of nickel nitrate to linker was 1:1.2. The Ni-C-b was obtained after pyrolysis of Ni-MOF-b, the minimum reflection loss of Ni-C-b was –50.7 dB at 4.0 mm. In addition, the thermal conductivity of the film prepared with Ni-C-b as filler is 2.2 W/mK. The film with integrated good heat dissipation and wave absorbing properties provides a research idea for the design of multifunctional integrated film.

Effects of high temperature wettability and thermal properties of glass with different Al/Ga ratios on p+ emitter metallization

Ag-Al paste is a key material of n-type silicon-based solar cells. The uneven Ag/Al spike on the transmitter surface after metallization is easy to cause local short circuit, which is a bottleneck that limits its application. The glass play an indispensable role in the surface metallization of the emitter. The influence of high temperature wettability and thermal properties of glass on the metallization of p+ emitter was studied from the point of view of ionic radius by adjusting the ratio of Al/Ga. The results indicated that when the Al/Ga ratio is 2:3, an abundance of free oxygen improved the O/Si ratio within the glass network structure, facilitating the depolymerization of siloxane anion clusters into simpler structural units in the silicate network structure. Al ions preferentially combine with free oxygen to formed [AlO4]. The entrapment of free oxygen by [BO3] units tended to form more [BO4] units with increased thermal stability. The glass sample demonstrated minimal difference between left and right contact angles. The glass wet the Si wafer steadily and evenly throughout the melting process. The formation of a continuous dense glass layer increased the contacts between the metal electrode and the emitter. Not only a mass of silver crystals were deposited on the emitter surface, but also small and dense Ag/Al spikes were distributed. Excellent metallization contacts were formed with the p+ emitter, which improved the solar cell's photoelectric conversion efficiency.

Integrated Supervisory Control and Data Acquisition System for Optimized Energy Management: Leveraging Photovoltaic and Phase Change Material Thermal Storage

ABSTRACTReliable energy sources are crucial for both economic growth and quality of life. In developing countries, where expensive fuels are often the primary energy source, governments are exploring innovative solutions like small‐scale, IoT‐based projects to achieve energy independence in buildings. This research investigates the integration of renewable energy technologies, statistical modeling, cloud computing, and IoT to develop a self‐managing energy system for buildings. The system prioritizes renewable sources, specifically monocrystalline solar cells with 20% efficiency for photovoltaic (PV) energy and flat plate collectors with 90% efficiency and minimal energy loss for thermal energy. Thermal energy is stored in paraffin wax, chosen for its high storage efficiency and thermal properties. The system also utilizes an absorption chiller with a high coefficient of performance (COP) to provide cooling using solar thermal energy. The building's energy loads are categorized as A, B, C, and D, each utilizing both PV and thermal energy. A SCADA system oversees the operation, monitoring the on–off status of these loads. The system is designed for continuous operation, with simulations conducted using Anaconda Jupyter Notebook and Python. This model aims to offer a sustainable and efficient energy solution for buildings, meeting energy demands while optimizing energy use.

Green synthesis of soybean oil-derived UV-curable resins for high-resolution 3D printing

With the rapid development of 3D printing technology, it has penetrated various fields. In the context of global oil resource scarcity and increasing emphasis on environmental protection, developing high-performance bio-based 3D printing materials is a crucial means to overcome the limitations of petroleum resources and achieve sustainability. This paper proposed a "green" development method for high-performance, sunlight-curable vat photopolymerization 3D printing resins based on soybean oil and itaconic anhydride. Utilizing bio-based itaconic anhydride to replace traditional petroleum-based materials, a novel UV-curable prepolymer, IPESO, with 80.37 % high bio-carbon (Cbio) content and no volatile substances was synthesized. Simultaneously, a series of resins, IPESO-ETPTAx, with high mechanical and thermal properties were obtained utilizing ethoxylated trimethylolpropane triacrylate (ETPTA) as a diluent. Samples printed with IPESO-ETPTA40 achieve a high resolution of 40 µm on the xy-axis. This advanced material has broad application prospects in the field of vat photopolymerization 3D printing and provides a new strategy for the development of plant oil-based vat photopolymerization 3D printing resins.

Polymer alloys with high thermal properties consisting of polyfunctional benzoxazine derived from an oligonuclear phenolic compound and bismaleimide

Polymer alloys with high thermal properties consisting of polyfunctional benzoxazine derived from an oligonuclear phenolic compound and bismaleimide

High thermal stability and mechanical properties of nanosized-Fe-reinforced aluminum matrix composites via deformation-driven metallurgy

Fine-grained aluminum, characterized by high performance and lightweight, is highly susceptible to grain coarsening leading to instability at elevated temperatures. The introduction of the Fe element has shown extraordinary potential to enhance thermal stability, marked by its low solubility and diffusion rate within the Al matrix. In light of this, Fe nanoparticles were exploited to reinforce fine-grained aluminum via deformation-driven metallurgy based on the principle of severe plastic deformation. The inherent mechanisms of dynamic recovery and recrystallization associated with thermo-mechanical properties facilitated the consolidation of ultrafine-grained Al–Fe nanocomposites, resulting in homogeneous dispersion both intragranularly and intergranularly of the reinforcements with an average particle size of 200.2 ± 4.6 nm. These dispersed Al–Fe nanophases with stable structures refined grains and pinned grain boundaries to hinder migration, which significantly enhanced the thermal stability of the composites. The average grain size remained substantially constant after thermal exposure at 300 °C for 100 h, with variability maintained within a 0.20 μm threshold. The mechanical properties remained substantially unchanged, exhibiting an ultimate tensile strength of 480 ± 9 MPa and elongation of 14.8 ± 0.4 %.

Enhancing Durability of Concrete and Mortar with Ceramic Waste: A Comprehensive Review

The construction industry continually seeks sustainable materials to enhance the durability of structures while minimizing environmental impact. Ceramic waste, a by-product of the ceramic manufacturing process, presents a promising alternative. Traditionally used for tiles, sanitary ware, and bricks, ceramic materials are valued for their high strength, aesthetic appeal, and thermal insulation properties. The study indicates that ceramic waste enhances the durability of construction materials due to its inherent properties, such as low water absorption and high abrasion resistance. Additionally, utilizing ceramic waste addresses environmental concerns associated with landfill disposal, which include soil and water contamination, greenhouse gas emissions, and the depletion of landfill space. Incorporating ceramic waste into construction materials not only offers environmental benefits by reducing landfill waste and conserving natural resources but also provides economic advantages through cost-effective waste management and material production. This research explores the incorporation of ceramic waste into construction materials, emphasizing the enhanced durability properties like water absorption, Chloride test, UPV test, Electrical resistivity test, freezing and thawing test, drying shrinkage test and sulphate attack test of concrete and mortar mix while highlighting the dual benefits of improved material performance. The results of water absorption increases with ceramic amount increment, resistance to chloride ion rises to 20% replacement, drying shrinkage and electrical resistivity decreases with increase in amount of ceramic waste, freezing and thawing & sulphate attack showed that ceramic waste material used as aggregate increases, mass loss reduces due to freezing and thawing cycles and the amount of ceramic waste material used increases, compressive strength increases up to a certain limit when immersion in sulphuric acid solution.

Structural analysis of selective laser melted copper-tin alloy

Additively manufactured complex geometries from copper alloys with high thermal and mechanical properties have drawn the attention of researchers. The present contribution explores the additive manufacturing (AM) of copper-based alloys from powder particles intended for heat sink and heat exchange applications. Selective laser melting (SLM) parameters featuring low laser beam power (160 W), moderate scanning speed (320 mm/s), and high energy density (200 J/mm³) were employed to fabricate dense components from CuSn10 particles. The present work deal with structural analysis and precision investigation of microfabrication, particularly in Struts, Tubes, and Fins. Mechanical properties (compression and hardness) for Strut structure, differential pressure evaluations for Tube structure, and analyses of thermal and electrical conductivities for Fin structure were investigated. The results showed an improvement in strength compared to those of pure copper, facilitating ease of AM. The obtained results affirm the feasibility of AM, demonstrating the successful creation of complex and combined solid-porous structures using SLM process from Cu alloys. A comprehensive structural investigation and characterization of the Cu–Sn alloy is presented here, aiming to establish a standardized approach for analysing Cu alloys. The results indicate that small-scaled structures fabricated via CuSn10 alloy exhibits a thermal conductivity of 34.3 W·m⁻¹·K⁻¹, an electrical conductivity of 4.72×10⁶ S/m, a hardness of 119 HV-50, a uniform surface roughness of 6 µm, and can withstand a force loading of 1 kN.