Al2O3 Filler Research Articles

Electrospun nanofiber surface-modified polyethylene separator for enhanced cycling stability and low-temperature performance of sodium-ion batteries

Sodium-ion batteries (SIBs) are emerging as promising low-cost and long-cycle energy storage systems. However, the poor wettability of the conventional polyolefin separators with polar electrolytes leads to low ionic conductivity and high battery resistance, causing rapid capacity decay. Herein, we propose using a polyethylene (PE) separator coated with a nanofiber composited of poly(vinylidene fluoride) (PVDF) and Al2O3 filler via electrospinning. Compared to the standard PE separators, this composite separator offers much improved electrolyte wettability, mechanical strength, and electrochemical stability. Electrochemical tests demonstrate that the Na[Ni1/3Fe1/3Mn1/3]O2||hard carbon pouch cells based on the PVDF-Al2O3/PE composite separator exhibit a capacity retention of 95.1% after 800 cycles at 1C. Additionally, the separator significantly enhances low-temperature discharge performance and cycling stability. Characterizations based on Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction confirm the successful integration of Al2O3 nanoparticles into the PVDF matrix, resulting in a homogeneously dispersed and well-connected structure, which improves ion transport efficiency and stability, thereby effectively boosting battery performance. This research highlights the potential of PVDF-Al2O3 nanofiber composite separators for advanced SIBs with high reversibility, a wide operating temperature range, and long cycling life.

Low-cost and rapid preparation of high-performance carbon fiber reinforced ceramic matrix composites by molding-in situ densification

Carbon fiber reinforced ceramic matrix composites (CFCMCs), demonstrated huge demand of braking and transmission systems for heavy-loading equipment. However, high production cost, cumbersome preparation process and long preparation cycle severely limited its application and industrialization in the defense industry. In this work, a molding-in situ densification process was proposed to prepare AlN-modified CFCMCs under the synergistic effects of Al and Al2O3 fillers, facilitating a significant reduction in the preparation steps and treating temperature. The existence of active Al fillers was conducive to inducing the formation of Al-Si alloy melt and increasing contact area between Si and C to reduce the temperature of the Si-C reaction and promote the densification of composite materials. Meanwhile, the addition of Al2O3 effectively limited long-range flow of the alloy melt, further inhibiting severe volume deformation of the composites and the generation of large pores. When the maximum heat treatment temperature reached 1300 °C, the preparation cycle of AlN-modified CFCMCs reduced as low as 23–28 h after the molding-in situ densification process, which was roughly decreased by a 50 % drop. The compressive and flexural strength of AlN-modified CFCMCs achieved 308.51 MPa and 115.68 MPa, respectively. This molding-in situ densification strategy provided a pathway toward to achieve low-cost and rapid preparation of high-performance CFCMCs for the scale-up application in the fields of defense and military industry.

Enhancing wind turbine blade protection: Solid particle erosion resistant ceramic oxides-reinforced epoxy coatings

In recent days, it is crucial for the globe to shift fossil fuel energies to renewable energies such as hydroelectric, wind, solar, tidal, geothermal, etc. to mitigate global warming issues. Wind energy has been regarded as one of the renewable energy sources to rely on in the future. In this aspect, wind turbine blade maintenance is quite a challenge in tropical areas like India. One of the main reasons why wind turbine blades get damaged and produce less energy is solid particle erosion. In the present work, epoxy nanocomposite coatings reinforced with Al2O3, ZrO2, and CeO2 nanoparticle fillers have been applied on glass fiber reinforced polymer (GFRP) substrates using a simple spray coating method. These nanoparticles have been prepared in-house by solution combustion synthesis (SCS) route using urea, glycine, and oxalyl dihydrazide fuels, respectively. X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy have been used to characterize the materials and coatings. Epoxy coatings with different Al2O3, ZrO2, and CeO2 nanoparticle concentrations have been subjected to solid particle erosion resistance tests at impinging angles of 30°, 60°, and 90°. ZrO2 and CeO2 nanoparticle-reinforced epoxy coatings show much better resistance to solid particle erosion than Al2O3-reinforced coatings. Estimated average erosion rates are 17 and 11.3 × 10−3 mm3 g−1, respectively, for epoxy coatings with 20 and 40 wt% ZrO2 nanoparticles. However, GFRP substrate and neat epoxy (EP) coating show much higher erosion rates with respect to nanoparticles-reinforced epoxy coatings. To ascertain a correlation between H3/E2 and the solid particle erosion rates of the coatings, nanoindentation tests have been carried out. Tensile strength and initial modulus of all the coatings are found to be directly proportional to the average erosion rates, whereas, elongation at break shows an inverse relationship with the average erosion rate. This correlation of mechanical properties with solid particle erosion performance can play a critical role in the development of realistic simulation of protective coatings for wind turbine blades.

Preparation of thermally conductive polyimide/aluminum oxide/boehmite composite separators for enhancing lithium‐ion battery safety and performance

AbstractThis study endeavors to enhance the safety of lithium‐ion batteries (LIBs) by synthesizing a polyamide acid (PAA)/Al2O3 composite spinning solution using 4,4′‐diaminodiphenyl ether (ODA) and pyromellitic anhydride (PMDA) as monomers, and nano‐Al2O3 as a thermal conductivity filler. Subsequently, the PAA/Al2O3 fiber membrane is fabricated via electrostatic spinning, followed by gradient heating imidization to produce a polyimide (PI)/Al2O3 composite membrane. This membrane is then dipped into a boron nitride (BM) slurry to ultimately yield an organic–inorganic PI/Al2O3/BM composite separator with superior flame‐retardant and thermal conductivity properties. The thermal stability, flame retardancy, electrolyte wettability, mechanical integrity, and cycle rate performance of the composite membranes are rigorously evaluated. The results demonstrate that the PI/5% Al2O3/BM composite membrane exhibits the most favorable overall performance, with no shrinkage observed at 200°C and no significant changes after sustained ignition for 10 s. The incorporation of the thermal conductivity Al2O3 filler significantly enhances the heat transfer properties of the composite separator. The room temperature ionic conductivity reaches 2.786 mS cm−1 after electrolyte absorption, and the initial discharge capacity of the assembled battery is 156.28 mAhg−1. Following 100 charge/discharge cycles at 0.2C, the capacity retention rate is 97.7%, and at a discharge rate of 5C, the capacity retention rate is 74.9%.

Multi‐layer graphene nanosheets bridging binary aluminium oxide for the synergistic enhancement of thermal conductivity and electrical insulation of silicone resin composite

AbstractThe flexible polymer composites usually require high intrinsic thermal conductivity fillers for the applications in thermal management, such as the well‐known graphene, which can, in turn, compromise their electrical insulation properties. Here, the authors developed the silicone resin (SR) composites filled with multi‐layer graphene nanosheets (MGN) and binary alumina (Al2O3), and the microstructure of composites exhibits the dominant skeleton of large‐sized Al2O3 filler and branching of small‐sized Al2O3 fillers features by the size matching effect of optimal binary Al2O3. The introduction of supplementary MGN fillers further increases the face‐to‐face contact probability and bridges the isolated binary Al2O3, which contributes to the high thermal conductivity of 3.0 W·m−1·K−1 under these synergistic effects. The dense and connected ‘Al2O3‐MGN‐Al2O3’ thermal conductive pathway is successfully built, as supported by the numerical simulation and Agari model fitting. Meanwhile, the electrical conductivity caused by MGN can be blocked by the surrounding insulation Al2O3 filler network, exhibiting a high volume resistivity of 1.7 × 1015 Ω · cm. Moreover, the Al2O3/MGN/SR composite films effectively transfer the heat and diminish the hot‐spot temperature by 53.5°C in cooling light emitting diode chip module application.

Core-shell engineering of graphite nanosheets reinforced PVDF toward synchronously enhanced dielectric properties and thermal conductivity

Polymer composites integrating high dielectric permittivity (ε′) but low loss, large breakdown strength (Eb) and thermal conductivity (TC), have attracted widespread attention in electronic devices and power systems. To simultaneously achieve these properties in graphite nanosheet (GNS)/poly(vinylidene fluoride, PVDF), the GNS were first encapsulated by a layer of aluminum oxide (Al2O3), and then incorporated into PVDF, and the resulting PVDF nanocomposites’ dielectric properties and TC were explored in terms of the Al2O3 shell thickness and filler loading. The insulating Al2O3 shell serves as a barrier layer for the formation of leakage current and long-distance electron migration thus resulting in much lower dielectric loss and conductivity of the GNS@Al2O3/PVDF. It effectively mitigates the dielectric mismatch between the filler and host matrix, further introduces more traps that can capture charge carriers, and increases the barrier height for electron detrapping subsequently preventing the growth of electric trees and elevating the Eb. Moreover, the Al2O3 interlayer alleviates both the phonon density state and phonon impedance mismatches between the filler and matrix and facilitates the interfacial phonon transport thus leading to improved TC. The dielectric parameters and TC of the GNS@Al2O3/PVDF can be simultaneously modulated by optimizing the Al2O3′s thickness. This work offers an effective approach for designing and fabricating the polymeric nanodielectrics concurrently integrating high ε′ but low loss, enhanced Eb, and TC for prospective applications in power equipment and microelectronic devices.

Preparation and properties of Al2O3 modified epoxy-glass fiber composites

The present study intends to use Al2O3 as thermal conductivity filler, epoxy resin as matrix, and glass fiber as reinforcement material, and prepare Al2O3 modified epoxy-glass fiber composite materials through vacuum diversion flow and hand paste molding. By changing the amount of Al2O3, performance tests and comparison are conducted. The results show that when the content of Al2O3 filler is 2 %, the comprehensive mechanical properties are the best, the thermal conductivity is increased by about 20 %, the specific heat capacity is increased by about 30 %, and the combustion time is also increased by 10 s.

Polycarbonate-based composite polymer electrolytes with Al2O3 enhanced by in situ polymerized electrolyte Interlayers for all-solid-state lithium-metal batteries

Lithium-metal batteries (LMBs) have attracted significant attention as promising energy storage devices due to their high energy density. However, the practical application of LMBs is hindered by issues such as dendrite growth and electrolyte decomposition, which lead to poor cycling stability. To address these challenges, this study focuses on investigating the performance of poly(ethylene carbonate) (PEC)-based composite polymer electrolytes (CPEs) with an in situ polymerized poly(vinyl ethylene carbonate) (PVEC)-based electrolyte interlayer. The electrolytes were optimized by incorporating lithium bis(fluorosulfonyl)imide (LiFSI) salt, lithium bis(oxalato)borate (LiBOB) and lithium nitrate (LiNO3) additives, as well as Al2O3 filler. The objective was to improve the compatibility and cycling stability of LMBs by enhancing the electrolyte/electrode interfacial properties. Remarkably, the Li||Li symmetric cell utilizing the optimized CPE exhibited outstanding stability, operating for 700 h without short-circuiting at 0.1 mA cm−2, indicating excellent interfacial compatibility. Additionally, the Li||LiFePO4(LFP) cells using the same electrolyte demonstrated impressive performance, delivering initial discharge capacity of 159.32 mAh g−1 at 0.1 C with retention and coulombic efficiency close to 100 % after 100 cycles at 60 °C. This paper highlights the effectiveness of utilizing polymer electrolyte interlayers and additives like LiNO3 in CPEs to enhance the interfacial compatibility and cycling stability of LMBs.

Directional thermal transport feature in binary filler-based SiR composites with horizontally oriented h-BN

Efficiently thermal management in electronic devices calls for creating polymer composites that have superior thermal transport abilities. Compared with single-filler composites, hybrid-filler composites have gained significant attention as they not only utilize the advantages of each filler individually but also allow for the potential cooperation in constructing filler networks between them. Differing from the previous research on hybrid-filler size, geometry, composition, and content and their impact on thermal conductivity (TC) in composites, this study aims to examine the spatial distribution effects of hybrid-fillers. A binary-filler strategy comprising of anisotropic 2D h-BN and 0D isotropic S–Al2O3 has been proposed, with the primary h-BN filler aligned to filly utilize its anisotropy and intrinsic TC properties. Furthermore, positioning a small quantity of S–Al2O3 between adjacent parallel h-BN considerably improves TC in the non-oriented direction of silicon rubber (SiR) composites. A special focus is given to the influence of the interstitial S–Al2O3 filler on the individual through-plane TC (λ⊥) and in-plane TC (λ⫽) variation of the binary-filler hybrid SiR composites, which are perpendicular and parallel to the oriented h-BN. When incorporating 40 vol% h-BN and 5 vol% S–Al2O3, the binary SiR composites exhibit the highest concurrent λ⫽ and λ⊥ values of 14.581 and 2.132 W/m·K, respectively. The corresponding effects on the ductility, hardness, and dielectric properties of the SiR composites were explained. Moreover, the use of commercially available TC fillers, along with the effortless preparation method, enables the potential to produce h-BN based TIMs materials on a large scale for thermal management usage.

Effect of alumina fillers on physical and mechanical properties of luffa/groundnut shell natural fiber reinforced polymer composites

AbstractThis study aims to investigate the physical and mechanical properties of epoxy composites reinforced with hybrid luffa waste and groundnut shell waste natural fibers and to evaluate the effect of different filler loadings of alumina on the mechanical behavior of the hybrid composites. The luffa fibers were made to undergo mercerization in 10% NaOH solution. All the treated fibers and the alumina fillers were characterized using X‐ray diffraction analysis (XRD). The study used three different filler loadings of alumina (Al2O3) (5%, 10%, and 15% by volume) and three different fractions of treated luffa‐waste groundnut shell hybrid fibers (10%, 30%, and 50% by volume). The composites were fabricated using the hand layup technique, and the prepared test specimens were subjected to mechanical and physical properties testing as per ASTM standards. The experimental findings indicated that the inclusion of Al2O3 filler improved the physical and mechanical characteristics of the natural fiber‐reinforced hybrid composites. The results showed that the composites with 30 vol. % fibers (1:1 luffa fiber: groundnut shell fiber) and 10 vol. % Al2O3 content showed enhanced tensile, flexural, shear, and impact strength and hardness. Besides, a good synergy between the alumina fillers, natural fibers, and the polymer matrix was observed in the surface morphology of the composite specimen. The developed composites can be used in low and medium‐load‐bearing structural and non‐structural applications.Highlights Development of hybrid polymer composites with luffa and novel groundnut shell fibers Hybridization of alumina ceramic particles with natural fiber hybrid composites Assessment of physical and mechanical properties of the polymer composites

Fiber Bragg grating detection of gel time and residual strain of curing in epoxy resins

AbstractThe curing shrinkage of epoxy resin can generate residual strains and internal stresses that reduce the material's strength and life. In this paper, a thermocouple‐compensated fiber grating detection method for the gel time and residual strain in epoxy resin is proposed. The strain evolution and glass transition temperature of E51/W93 epoxy systems with different Al2O3 contents cured at 30°C are detected by fiber Bragg gratings and DSC tests. The generation mechanism of residual strain in epoxy resin filled with Al2O3 fillers is studied. The gel time, gel temperature and residual strain of epoxy resin can be measured by this method. The results show that the cure shrinkage of epoxy is affected by chemical shrinkage, thermal expansion or shrinkage, and demolding, resulting in residual strain of the material after curing. Moreover, the glass mold has a great interference with the curing shrinkage of epoxy. The Al2O3 filler can prolong the gel time of E51/W93 epoxy systems, and reduce the exothermic peak temperature of curing. When the content of Al2O3 filler exceeds 44.44 wt.%, the low proportion of epoxy and the thermal conductivity of the filler make the curing shrinkage of epoxy during the heating stage mainly affected by chemical shrinkage. The glass transition temperature of the epoxy with Al2O3 content of 70.59 wt.% is the maximum, and the residual strain is at a low level. This method is helpful to analyze the curing shrinkage characteristics of materials, and is of great significance for evaluating the properties of epoxy cured products and guiding the optimization of material parameters.Highlights A method for measuring the gel time and residual strain of curing in epoxy resin is proposed. The study focuses on the detection of key parameters during the curing of epoxy resins with different Al2O3 contents. The aim is to analyze the curing shrinkage and residual strain generation mechanism of epoxy resin filled with different contents of Al2O3.

Optimized machine learning with hyperparameter tuning and response surface methodology for predicting tribological performance in bio‐composite materials

AbstractThis study investigates the influence of NaOH treatment on tribological behavior in hybrid fiber‐reinforced composites, specifically employing Banana fiber with Al2O3 filler in an epoxy matrix. Through design of experiments (DOE), disc speed, wear duration, and NaOH treatment are analyzed for specific wear rate (SWR) and coefficient of friction (COF). To advance the understanding of wear characteristics, the study leverages advanced machine learning, using Python‐powered artificial neural networks (ANN), is integrated with innovative ANN hyperparameter optimization. Optimized parameters (1050 rpm, 60 s, 5% treatment) significantly minimize SWR (12.38 × 10−5 mm3/Nm) and COF (0.2). Scanning electron microscopy (SEM) analysis reveals improved interfacial adhesion and identifies micro‐cracks as the primary wear mechanism. This work contributes to a profound understanding of wear in hybrid composites, offering a fine‐tuned predictive model for optimizing tribological behavior and advancing material science and engineering.Highlights Reduced SWR, COF in composites via NaOH optimization. DOE: Explored disc speed, duration, NaOH impact. Advanced machine learning techniques enhanced wear prediction. Innovative: ANN hyperparameter optimization. Optimal Parameters: 1050 rpm, 60 s, 5% treatment.

Electrical and Mechanical Performances for Low-Density Polyethylene Nano Composite Insulators

Low-density polyethylene (LDPE) metal oxide nanocomposites are used as high-voltage insulation in AC cables to reduce space charging and other issues. Nanoparticles such as SiO2, MgO, and ZnO are used as fillers in polyethylene matrix to achieve good electrical, thermal, and mechanical properties such as space charge reduction, increased surface and volume resistance, and high dielectric stress bearing capabilities. LDPE/Al2O3 compounds are prepared at concentrations of 1%, 3%, 5%, and 7% for nanofillers and at concentrations of 10%, 20%, 30%, and 40% for micro fillers. The dielectric strength of the LDPE/Al2O3 sample was measured at different temperatures to determine the effect of temperature on the dielectric strength value. To check the various properties of the samples, the tensile strength test has been applied. The Whale Optimization Algorithm (WOA) was used to calculate the optimal Al2O3 filler percentage for the best dielectric strength value.

Tribological and mechanical properties of nanofilled glass fiber reinforced composites and analyzing the tribological behavior using artificial neural networks

AbstractThis study investigates the effects of filler content and type on the mechanical (tensile strength and impact resistance) and tribological properties of woven glass fiber‐reinforced composites (WGFC) produced using three different nanofillers (MgO, CuO, and Al2O3) at various loading levels (0.7, 1.4, and 2.8 wt%). Additionally, analyses of the artificial neural network algorithm were reported for the predictions of wear rate, mass loss, and coefficient of friction (COF) by given applied load, sliding distance, filler ratio, and filler type. The composites were fabricated using the hand lay‐up method. The filled composites were characterized using Fourier Transform Infrared (FTIR) spectroscopy, and the worn surfaces of the samples after the wear test were analyzed using Scanning Electron Microscopy (SEM). The wear resistance of the composite samples improved at 0.7 wt% CuO and 1.4 wt% MgO filler contents. At 200 m sliding distance and 1.4 wt% filler ratio, the highest wear ratio was determined as 55 mm3/m × 10−3 in the Al2O3‐filled composite, and the lowest was determined as 31 mm3/m × 10−3 in the MgO‐filled composite. At 1.4% filler ratio and 15 N load, the lowest friction coefficient was determined as 0.45 μ in MgO‐filled composite, and the highest was 0.56 μ in Al2O3‐filled composite. Al2O3 filler increased the mass loss and wear rate of the composite material. In Charpy impact tests, the maximum impact energy of 13.9 J/m2 was obtained with a 2.8 wt% Al2O3 filler content. Tensile tests showed an increase in tensile strength for all filler contents compared to unfilled composites. The highest tensile strength of 242.1 MPa was achieved with 0.7 wt% CuO reinforcement.Highlights In all applied wear parameters and filler ratios, the Al2O3 filler adversely affected the wear resistance of the composite, while the MgO filler showed the best performance in terms of wear resistance. All types and ratios of fillers increased the tensile strength compared to the unfilled composite. Contrary to its negative effect on wear, the Al2O3‐filled composites exhibited the highest impact resistance. The prediction analysis of the tribological behavior of composite material using ANN reveals that the Levenberg–Marquardt algorithm fits very well.

Characterisation of Nano Aluminium Oxide Filled Hybrid Cotton Glass FRP Composite Structures

Natural fiber-based composite manufacturing is now an expanding field of study, and it is the preferred option not only because of its exceptional qualities such as light weight, rigidity, low density and superior mechanical properties, but also because it is affordable, biodegradable, fully or mostly recyclable and renewable. A Glass Fibre is a type of Reinforced Polymer (GFRP) made of tiny glass fibers embedded in a plastic matrix. Hybridization of natural and synthetic fibres has to be done to overcome the shortfall of these fibres. When compared to single Fibre Reinforced Polymer (FRP) composites, fibre-reinforced hybrid composites offer improved mechanical, thermal, and damping characteristics. The goal of this research is to see how Nano Aluminum Oxide (Al2O3) fillers affect the characteristics of hybrid cotton-glass FRP composites. The vacuum bagging technique was used to make nano Al2O3 particles - hybrid cotton-glass FRP composites out of glass fibre chopped strand mat, cotton fabric, epoxy resin, and nano-Al2O3 fillers. The nano Al2O3 fillers were integrated in different weight (wt.) ratios in the FRP and the effect on tensile, flexural and impact properties were examined.

Enhanced thermal conductivity of electrically insulating polydimethylsiloxane composites with boron nitride nanosheet and aluminum oxide for thermal management on flexible electronics

AbstractWith the trend of integration and miniaturization of stretchable electronics, thermal management has been a crucial issue. Developing novel materials with high thermal conductivity (TC) and flexibility is urgent. Herein, we report a stretchable polydimethylsiloxane (PDMS)/boron nitride nanosheet (BNNS)@spherical aluminum oxide (Al2O3) composite with high TC and electrical insulation prepared by a two‐step strategy of sucrose‐template and hot‐pressing. An effective foam‐pressing route benefits the composites to form a three‐dimensional thermally conductive networks, improving the in‐plane TC value of the resultant composite to 4.03 W/(mK) at the filler mass fraction of 35.7 wt% and enhancing to 4.66 W/(mK) under 40% stretching ratio. Meanwhile, the composites can be restored to their former state and retain thermally conductive stability with repeated bending and twisting tests. Moreover, the composites were applied in LED with stretching, exhibiting good heat dissipation performance. These results demonstrate this PDMS composite can be potentially utilized as a high‐performance material to solve thermal management problems in flexible electronics.Highlights The heat conduction network is prepared by sucrose‐template and hot‐pressing. BNNS@P‐Al2O3 fillers are self‐assembled via the electrostatic interaction. The composites exhibit good thermal conduction and superior flexibility. The thermal conductivity of the composite increases after stretching. The composites can retain thermal conductive stability after deformation.

Pengaruh Penambahan Filler Al2O3 dan TiO2 pada Resin Polyester terhadap Sifat Fisik dan Mekanik

Polyester composites have been developed to have high strength and light density, but the fracture occurs due to very little plastic deformation or low strain values, pre-failure detection is difficult in these composites due to the rapid propagation of cracks in the composite system. To increase the strength and delay failure, the addition of filler in the form of Al2O3 and TiO2 particles is carried out. The use of particles as fillers in polymer composite materials is increasingly being developed. In this study, Al2O3 and TiO2 particles (0%, 2%, 4%, 6%, 8%, 10% vol.) were added in polyester matrix BQIN EX 157. by casting method; the liquid homogeneous mixture was carefully poured into a simple mould to be air dried. The composites were cut to serve as specimens for density test, mechanical tests such as tensile and compressive tests. The results showed a density of 1.23 g/cm3, a maximum strength of 47 MPa for 2% additional Al2O3 filler, (tensile, decreasing ̴11%) and 120 MPa (compressive) for a maximum of 2% additional Al2O3 (compressive, decreasing ̴3%) with TiO2 filler. The decrease in strength was caused by uneven particle dispersion, voids and agglomeration that occurred during the casting process.

Dry-Contact Thermal Interface Material with the Desired Bond Line Thickness and Ultralow Applied Thermal Resistance.

Efforts to directly utilize thixotropic polymer composites for out-of-plane thermal transport applications, known as thermal interface materials (TIMs), have been impeded by their mediocre applied thermal resistance (Reff) in a sandwiched structure. Different from traditional attempts at enhancing thermal conductivity, this study proposes a low-bond line thickness (BLT) path for mitigating the sandwiched thermal impedance. Taking the most common TIM, polydimethylsiloxane/aluminum oxide/zinc oxide (PDMS/Al2O3/ZnO), as an example, liquid metal is designed to on-demand localize at the Al2O3-polymer and Al2O3-filler interface regions, breaking rheological challenges for lowering the BLT. Specifically, during the sandwiched compression process, interfacial LM is just like the lubricant, dexterously promoting the relaxation of immobilized PDMS chains and helping fillers to flow through mitigating the internal friction between Al2O3 and adjacent filler. As a result, this TIM first time exhibits a boundary BLT (4.28 μm) that almost approaches the diameter of the maximum filler and performs an ultralow dry-contact Reff of 4.05 mm2 K/W at 40 psi, outperforming most reported and commercial dry-contact TIMs. This study of the low-BLT direction is believed to point to a new path for future research on high-performance TIMs.

The effects of multiple‐sized compound fillers on the thermal, electrical, and processing properties of epoxy composites

AbstractThe efficient filling of the multiple‐sized compound fillers can effectively increase the thermal conductivity of the polymer composite. However, determining the specific proportion of the compound fillers with different sizes is hard. This article proposes a random distribution model and the closest packing model to calculate the proportion of the compound fillers and prepare the epoxy composites with different compound fillers. By elaborately designing epoxy composites containing 75 wt% (48 vol%) ternary compound Al2O3 fillers, its thermal conductivity reached 1.640 W/(m·K). In addition, the volume resistivity for all prepared Al2O3/epoxy composites was higher than 1016 Ω cm. Besides, the electrical and dielectric properties of the epoxy composite with multiple‐sized compound fillers were comparable or superior to the composite with single‐sized fillers. Last but not least, the viscosity of the ternary compound Al2O3/epoxy mixture was significantly lower than the single‐sized Al2O3/epoxy mixture, which is beneficial for improving the processability of the epoxy composite. The results of this article will guide the development and utilization of epoxy composites with high thermal conductivities.Highlights A random distribution model and the closest packing model were proposed. The thermal conductivity of the designed epoxy composites reached 1.640 W/(m·K). The compound filler can effectively improve the processability of the composite.

Obtaining thermal resistance of mold compounds using a package structure model with a heat-generating test element group: Comparison of the thermal conductivity and glass transition temperature of epoxy mold compounds

Epoxy mold compounds (EMCs) with thermal conductivity of 0.8–4 W/m∙K and a glass transition temperature (Tg) of 150–270 °C were prepared using epoxy resins with various network structures and SiO2 and Al2O3 fillers. The test structure was fabricated using a heat-generating test element group (TEG) chip and an EMC in which the thermal conductivity and Tg varied. The TEG chip has two types of measurement pad: one for sensing the surface temperature and the other for heating the chip surface. The thermal resistance of the package structure model decreased from 14 °C/W to 4 °C/W from 0.8 to 4 W/m∙K, with the thermal conductivity of the mold compound having the same Tg. The thermal resistance of the package structure model decreased from 7.5 °C/W to 5.5 °C/W by increasing the Tg of the mold compound having the same thermal conductivity from 150 °C to 270 °C. Control over the thermal conductivity of the EMCs appeared to have a greater effect than the Tg on the thermal resistance of the package structure model using a TEG. The liquid EMC with a thermal conductivity of 4 W/m∙K provided the lowest thermal resistance (4 °C/W) among the EMCs examined.