Thermal Conductivity Constant Research Articles

Surface micro-welding strategy of h-BN assembled microspheres for composites with desirable thermal conductivity and a low dielectric constant

As electronic devices strive for higher integration and faster signal transmission, the demand rises for polymer composites with high thermal conductivity (TC) and low dielectric constant (εr). However, high TC composites often come with a high filler content, leading to a reduction in processibility and dielectric properties. Herein, by surface micro-welding strategy, we fabricated cohesive h-BN microspheres (SBO) with a quasi-hollow structure. The pre-constructed micro-nano network of h-BN inside the microsphere serves as a continuous pathway for heat transfer, while the internal space of the microsphere is divided into numerous gas chambers, establishing a foundation for low εr. Benefiting from this structure, the TC of the prepared composite is 2.12 W/m·K, and its εr is remarkably low at 3.24 (103 Hz), effectively balancing the TC and dielectric properties at a high filler loading. Furthermore, this designed structure significantly reduces the viscosity of the composite (measured 309 Pa s with a filler content of 50 wt% at 1s−1) due to the smooth surface of the microsphere. This strategy offers a facile approach for fabricating composites characterized by desirable TC, low εr and excellent processibility, showcasing promising prospects for advancement in the realm of microelectronics.

Highly Anisotropic Thermally Conductive Dielectric Polymer/Boron Nitride Nanotube Composites for Directional Heat Dissipation.

An ideal dielectric material for microelectronic devices requires a combination of high anisotropic thermal conductivity and low dielectric constant (ɛ') and loss (tan δ). Polymer composites of boron nitride nanotubes (BNNTs), which offer excellent thermal and dielectric properties, show promise for developing these dielectric polymer composites. Herein, a simple method for fabricating polymer/BNNT composites with high directional thermal conductivity and excellent dielectric properties is presented. The nanocomposites with directionally aligned BNNTs are fabricated through melt-compounding and in situ fibrillation, followed by sintering the fibrous nanocomposites. The fabricated nanocomposites show a significant enhancement in thermal properties, with an in-plane thermal conductivity (K‖) of 1.8 Wm-1K-1-a 450% increase-yielding a high anisotropy ratio (K‖/K⊥) of 36, a 1700% improvement over isotropic samples containing only 7.2 vol% BNNT. These samples exhibit a 120% faster in-plane heat dissipation compared to the through-plane within 2 s. Additionally, they display low ɛ'of ≈3.2 and extremely low tan δ of ≈0.014 at 1kHz. These results indicate that this method provides a new avenue for designing and creating polymer composites with enhanced directional heat dissipation properties along with high K‖, suitable for thermal management applications in electronic packaging, thermal interface materials, and passive cooling systems.

High thermal conductivity and low dielectric polyimide nanocomposites using diamine-assisted mechanochemical exfoliation boron nitride and in-situ polymerization under pressure

Advanced integrated circuit materials demand polymer composites with exceptional thermal conductivity and low dielectric constant to minimize power consumption and improve signal transmission. However, conventional methods of improving the thermal conductivity of composites by incorporating thermal conductive fillers result in an increase in dielectric constant, producing a huge challenge in simultaneously achieving enhanced thermal conductivity and low dielectric constant. Herein, a brick-and-mortar structure has been successfully constructed through in-situ polymerization of the diamine-assisted mechanochemical exfoliated (DAME) boron nitride (BN) with trifluoromethyl-containing PI and microporous polyhedral oligomeric silsesquioxane (POSS) under pressure. The DAME functionalized BNNS (f-BN) exhibit high aspect ratios, few lattice defects, high yields and excellent dispersion in the POSS/PI matrix. Notably, the obtained 40 wt% f-BN/POSS/PI nanocomposite exhibits a high in-plane thermal conductivity of 17.76 W m−1 K−1 with a 488% enhancement compared to 40 wt% hBN/POSS/PI, and simultaneously maintains low dielectric constant of 2.76 and low dielectric loss of 0.0042 at 1 MHz close to the pure POSS/PI matrix. Density functional theory is utilized to reveal the possible chemical reactions between f-BN and diamine, and the impacts of interfacial functionalization on the thermal conductivity and dielectric properties of nanocomposites are illustrated by molecular dynamics simulations. Furthermore, the DAME method demonstrates good universality among polyimide matrices, and shows excellent practical implementation as a thermal interface material and flexible printed circuit board. This material provides a promising solution for integrated circuits by successfully addressing the challenge of combining low dielectric constant and high thermal conductivity in microelectronic systems.

Determination of Thermal Conductivity Constant for Spray-Dried Mung Bean Protein Isolate using Series-Parallel “Block” Method and Central Composite Design

The efficient production of mung bean protein isolate (MBPI) is essential for sustainable food processing, yet it is energy-intensive due to drying phase required to convert raw mung beans into a fine powder. This work was carried out to calculate the thermal conductivity constant (k) of protein (A), moisture (B) and residual carbohydrate (C) of spray-dried MBPI. The protein slurry was prepared by dissolving MBPI in water at the ratio of 1:3, 1:4, and 1:5 prior to spray drying. The protein slurry was then spray dried at three different inflow temperatures of 140, 160, and 180 °C. A Series and Parallel Combination "Block" Model in tandem with a Central Composite Design (CCD) were selected to calculate the thermal conductivity constant of A, B and C. Eight arrangement components on A, B, and C component, measurements were derived from the initial three data points by utilizing the CCD method, in the preliminary study. By utilizing the series-parallel approach and statistical combination, there are a total of forty study arrangements. The thermal conductivity of MBPI with arrangements of A, B, and C (pABC); and a series of combinations of A and C in parallel to B (sAC pB) ranged from 0.1964-0.224 Wm-1 ℃ -1, with R2 = 98.73%-99.42%. Therefore, the energy requirement of spray drying process for MBPI could be predicted by the thermal properties of each component selected in the protein isolate.

Alkylated modified boron nitride nanosheets/polyimide composite films with advanced thermal conductivity and low dielectric constant

Owing to the rapid development of the latest micro-electronic devices, polymer composite materials that combine high thermal conductivity and low permittivity have aroused the interest of researchers. However, it is a huge challenge to balance the above parameters. In this work, hexagonal boron nitride (h-BN) powder was ultrasonically exfoliated to obtain alkylated boron nitride nanosheets (Alkyl-BNNS). Then, a series of polyimide (PI) composites were synthesized with different amounts of Alkyl-BNNS. Attributed to more robust interfacial non-covalent interactions between Alkyl-BNNS and polymer chains to inhibit interfacial polarization, Alkyl-BNNS can be scattered well in PI substrate. Thus, the obtained PI composite behaved a high thermal conductivity of 6.21 W/(mK) and a low dielectric constant (3.23) under the load of 20 wt%. Besides, Alkyl-BNNS/PI composites have efficient thermal management capability, low water absorption, favorable electrical resistance, and prominent tensile strength. Importantly, these composite films are expected to be excellent candidates in the field of microelectronics.

Morphological engineering of SiO2 interlayer towards meliorative dielectric and thermal properties in β‐SiCw@SiO2/PVDF composites

AbstractPolymers with high thermal conductivity (TC) and dielectric constant (ε) but low dielectric loss show enormously potential applications in electrical power systems. To enhance the ε and TC while significantly suppressing the loss of β‐silicon carbide whisker (β‐SiCw)/polyvinylidene fluoride (PVDF), in this study, SiO2 shells with different morphologies were constructed on the superficies of β‐SiCw via a facile oxidation method in air atmosphere. The SiO2 shell’ morphology on the TC and dielectric performances of the β‐SiCw@SiO2/PVDF are systematically explored as a function of the frequency and filler loading. The β‐SiCw@SiO2/PVDF demonstrate astonishingly restricted loss and meliorative TC when compared to the β‐SiCw/PVDF because the SiO2 shell not only suppresses the β‐SiCw from direct contact with one another and impedes the long‐distance charges migration thereby resulting in rather low loss and leakage conductivity, but also restrains the thermal interfacial resistance via increased interfacial compatibility and interactions. The concurrent enhancement effect in the ε and TC but low loss of the composites is more evident in the crystalline SiO2 interlayer with a high TC compared with amorphous one. These results provide insight into the exploration of composite nanodielectrics with large TC and ε but low loss for applications in electrical power systems.Highlights Core@shell structured β‐SiCw@SiO2/PVDF were obtained by a facile oxidation. The great reduction in both loss and conductivity is attributed to the SiO2 shell. Crystalline SiO2 shell can improve the composites' thermal conductivity. The SiO2 shell prevents long‐range carrier migration.

Excellent Thermal and Dielectric Properties of Hexagonal Boron Nitride/Phenolic Resin Bulk Composite Material for Heatsink Applications

In the present paper, we report polymer composites based on phenolic resin filled with hexagonal boron nitride; hot compression molding coupled with solution-based mixing were used to manufacture the composites. The paper presents experimental results on the physical and physicochemical properties of the obtained composites: thermal stability in air and argon, dielectric constant and dielectric loss tangent, active electrical resistance, thermal conductivity (mean and anisotropy), and mechanical strength. It is shown that the proposed technique of composite manufacturing, including the application of high-process pressures, makes it possible to obtain materials with high anisotropy of thermal conductivity, extremely high-filler content, and excellent dielectric properties, all of which are very important for prospective highly efficient lightweight heatsink elements for electronic devices. Experimental values of thermal conductivity and dielectric constant were analyzed using known mathematical models. Experimental values for thermal conductivities (up to 18.5 W·m−1·K−1) of composites at filler loadings of 65–85 vol.% are significantly higher than published data for bulk boron nitride/polymer composites.

Simultaneously Improved Thermal Conductivity and Dielectric Properties of NBR Composites by Constructing 3D Hybrid Filler Networks

AbstractThis work aims to address the heat accumulation issue in electronic components during high‐frequency operation through the preparation of novel thermally conductive composites. First, polydopamine (PDA) and in‐situ growth of silver (Ag) nanoparticles are applied for the surface modification of graphene oxide (GO) and carbon nanotube (CNT) to prepare pGO@Ag and pCNT@Ag hybrid filler, respectively. Then, nitrile butadiene rubber (NBR) is chosen as the polymeric matrix and simultaneously incorporated with both pGO@Ag and pCNT@Ag to prepare polymeric composites with excellent thermal conductivity (TC) and dielectric constant (ɛr). Due to the construction of 3D heat conduction networks by utilizing 2D pGO@Ag and 1D pCNT@Ag, the fabricated NBR composites achieved the maximum TC of 1.0112 W/(mK), which is 636% higher than that of neat NBR (0.1373 W (mK)−1). At the filler loading of 9 vol%, the TC of pGO@Ag/pCNT@Ag/NBR composite is 152% that of GO/CNT/NBR composite (0.6660 W (mK)−1). Moreover, due to electron polarization effect of GO and CNT and micro‐capacitor effect of Ag nanoparticles, a large ɛr of 147.12 is attained at 10 Hz for NBR composites. Overall, the development of dielectric polymer materials with high TC is beneficial for enhancing the service life and safety stability of the electronic components.

Constructing “sesame‐biscuit” structured hybrids with SiC and Ag particles for enhancing thermal conductivity and dielectric constant of elastomer composites

AbstractWith the development of multifunctional and miniaturized integrated circuits, polymeric materials with large dielectric constant and high thermal conductivity have major significance in modern electronic industry. In this work, “sesame‐biscuit” structured thermally conductive hybrids were prepared by polydopamine (PDA) modification and in‐situ electroless silver (Ag) plating on the surface of silicon carbide (SiC), referred as SiC‐P‐Ag. Then, the SiC‐P‐Ag was incorporated into epoxidized natural rubber (ENR) matrix to yield polymeric composites (ENR/SiC‐P‐Ag) with excellent thermal and dielectric properties. It was found that PDA improved the interfacial compatibility and reduced the interface thermal resistance between SiC and ENR matrix. In addition, the formation of heat conduction channels and conductive Ag nanoparticles caused an increase in thermal conductivity of the 50 vol% ENR/SiC‐P‐Ag composite to 0.5655 W/(mK), which was 540% that of the pure ENR (0.1048 W/(mK)). Meanwhile, the 50 vol% ENR/SiC‐P‐Ag composite showed a low AC conductivity of 2.98 × 10−11 S/cm and a high dielectric constant of 35 at 10 Hz. It is noteworthy that this simple and efficient route for preparing ENR/SiC‐P‐Ag composites can also be applied in other fillers for simultaneously enhancing dielectric constant and thermal conductivity of polymeric composites.

Are MXenes suitable for soft multifunctional composites?

MXenes are a family of two-dimensional (2D) nanomaterials known for their high electrical and thermal conductivity, as well as high aspect ratios. Recent research has focused on dispersing MXenes within compliant polymer matrices, aiming to create flexible and stretchable composites that harness MXenes' exceptional conductivity and aspect ratios. Experimental findings demonstrate the potential of MXene polymer composites (MXPCs) as flexible electrical, thermal conductors, and high dielectric materials, with promising applications in soft matter engineered systems. However, the 2D structure of MXene inclusions and their relatively large elastic modulus can impart increased stiffness to the polymer matrix, posing limitations on the mechanical flexibility of these functional materials. Here, we introduce a modeling platform to predict the mechanics and functionality of MXene elastomer composites and assess their suitability as soft multifunctional materials. Our investigation primarily focuses on understanding the influence of MXenes' size, layered structure, and percolation arrangements on the effective properties of the resulting composites. Through our model, we successfully determined the elastic modulus, thermal conductivity, and dielectric constant of MXene elastomer composites, and our results exhibit strong agreement with those obtained through finite element analysis. By utilizing this framework, we can theoretically identify the necessary microstructures of MXenes and guide the experiments, enabling the creation of MXPCs with the desired synergistic mechanical and functional properties.

Fluorine-terminated functionalized liquid metal/silicon carbide binary nanoparticles for polyvinyl alcohol composite films with high in-plane thermal conductivity and ultra-low dielectric constant

Highly thermally conductive and low dielectric constant are among the most sought-after properties of flexible polymer-based thermal-management materials (TMMs). However, it remains a formidable challenge to develop efficient thermal dissipation materials with fascinating comprehensive performance. In this work, we present an interfacial engineering strategy using trifluoropropyltriethoxysilane (TFPTES) to act as a thermal linker at granular silicon carbide-liquid metal (SiC-LM) binary interfaces (SiC-LM@F) in the polyvinyl alcohol (PVA) matrix, in which the LMs merely partially anchored to the surface of binary filler by a controllable ball milling technology. The strong hydrogen bonding and/or compact “shoulder-to-shoulder” contact between the binary components and matrix interfaces confer an expressway for the propagation of interfacial phonons. For this, the developed PVA/SiC-LM@F composite film demonstrates a high in-plane TC of 10.2 W m−1 K−1 and ultra-low dielectric constant of 1.49 at 106 Hz at 40 wt% SiC-LM@F loading content, which is more superior to those of the other counterparts in this experiment. Additionally, the obtained PVA/SiC-LM@F composite film also reveals favorable tensile strength, excellent electric insulation, and efficient cooling capacity. This interfacial engineering strategy is expected to offer a versatile solution to the design and construction of advanced thermal-management materials (TMMs).

The particle size effect of Halexylon Salicornicum on thermal conductivity and dielectric constant of polyester resins- Halexylon Salicornicum composites

Iraq is home to the Halexylon Salicornicum plant (HS). This study modifies thermal conductivity and dielectric constant of unsaturated polyester resin using HS as filler (UPE). Different HS filler particle sizes, including 6.5 mm (raw HS), 1.18mm, 250 m, 125 m, 75 m, and 50 m, are used to create HS- UPE composites. HS filler loading levels (1, 3, 5, 7, 10, 15, 20 and 25) (wt percent). All HS- UPE composites' thermal conductivity and dielectric constant are investigated. Study is done on how changes in frequency (from 500 Hz to 1 MHz) affect the dielectric constant of all composites. The thermal conductivity of HS- UPE composites falls as the concentration of HS filler increases and particle size reduces; it is at its lowest level at 25% weight. At 50 m particle size, the impact of particle size on heat conductivity of composites is clearly visible. When HS filler concentration rises and particle size falls, the dielectric constant of HS- UPE composites increases; it reaches its maximum value at 25% wt and 50m RH particle. On 50 m RH-RTV silicone composites, frequency variation has little impact.

Synchronously improved thermal conductivity and dielectric constant for epoxy composites by introducing functionalized silicon carbide nanoparticles and boron nitride microspheres

Polymer-based dielectrics with high thermal conductivity and superb dielectric properties hold great promising for advanced electronic packaging and thermal management application. However, integrating these properties into a single material remains challenging due to their mutually exclusive physical connotations. Here, an ideal dielectric thermally conductive epoxy composite is successfully prepared by incorporating multiscale hybrid fillers of boron nitride microsphere (BNMS) and silicon dioxide coated silicon carbide nanoparticles (SiC@SiO2). In the resultant composites, the microscale BNMS serve as the principal building blocks to establish the thermally conductive network, while the nanoscale SiC@SiO2 as bridges to optimize the heat transfer and suppress the interfacial phonon scattering. In addition, the special core–shell nanoarchitecture of SiC@SiO2 can significantly impede the leakage current and generate a great deal of minicapacitors in the composites. Consequently, favorable thermal conductivity (0.76 W/mK) and dielectric constant (∼8.19) are simultaneously achieved in the BNMS/SiC@SiO2/Epoxy composites without compromising the dielectric loss (∼0.022). The strategy described in this study provides important insights into the design of high-performance dielectric composites by capitalizing on the merits of different particles.

Enhanced Sinterability, Thermal Conductivity and Dielectric Constant of Glass-Ceramics with PVA and BN Additions.

With the rapid development of the microelectronics industry, many efforts have been made to improve glass-ceramics’ sinterability, thermal conductivity, and dielectric properties, which are essential components of electronic materials. In this study, low-alkali borosilicate glass-ceramics with PVA addition and glass-BN composites were prepared and successfully sintered at 770 °C. The phase composition, density, microstructure, thermal conductivity, and dielectric constant were investigated. It was shown that PVA addition contributes to the densification process of glass-ceramics (~88% relative density, with closed/open pores in the microstructure) and improves the thermal conductivity of glass material from 1.489 to 2.453 W/K.m. On the other hand, increasing BN addition improves microstructures by decreasing porosities and thus increasing relative densities. A glass-12 wt. % BN composite sample exhibited almost full densification after sintering and presented apparent and open pores of 2.6 and 0.08%, respectively. A high thermal conductivity value of 3.955 W/K.m and a low dielectric constant of 3.00 (at 5 MHz) were observed in this material. Overall, the resulting glass-ceramic samples showed dielectric constants in the range of 2.40–4.43, providing a potential candidate for various electronic applications.

Application of Arrhenius chemical process on unsteady mixed bio-convective flows of third-grade fluids having temperature-dependent in thermo-rheological properties

This article presents the unsteady mixed convective flow of third-grade fluid flow comprising nanoparticles and gyrotactic microorganisms past a stretching sheet. The fluid flow is assumed to be laminar and incompressible. The fluid flow is considered to be highly magnetized by applying a strong magnetic field. Newtonian viscous dissipation, chemical reactions, and Arrhenius activation energy are taken into consideration. The transformed system of equations is solved by HAM. Convergence analysis of the HAM is displayed with the help of figures. The relations of physical factors with fluid flow profiles are displayed with the help of figures and tables. It is reported that the greater material and mixed convection factors have escalated the fluid’s velocity. The higher Eckert number and thermal conductivity constant have augmented the thermal function, while the higher Prandtl number has reduced the temperature profile. The greater activation energy factor has augmented the concentration profile, while the augmenting chemical reaction and Schmidt number have reduced the concentration profile. In the streamlines of the steady and unsteady flows, there is also a significant difference in behavior.

Poly(vinylidene fluoride)/Mica nanocomposite: A potential material for photovoltaic backsheet application

Solar backsheet is the protective layer of the photovoltaic module that plays a vital role in protecting the module from harsh environmental conditions. Various properties such as mechanical, electrical, optical and chemical properties are critical in improving the service life and performance of the module. Poly(vinylidene fluoride) (PVDF) is recognized as the most suitable polymer for single-layer backsheets. However, it is difficult to optimize all the properties; hence, researchers are focused on fabricating the backsheet made of PVDF composites. In this study, PVDF/nano-mica nanocomposite (PVDF-MX) films were fabricated through the film casting method at different loading of nano-mica. Various properties such as mechanical, thermal, dielectric, optical properties and wettability characteristics of PVDF-MX films have been investigated. Addition of nano-mica increased γ-phase of PVDF, while the degree of crystallinity decreased. The strong interaction between the nano-mica and PVDF chain resulted in increased tensile strength, thermal conductivity, wettability and dielectric constant. UV–visible spectroscopy analysis showed that the opacity of PVDF films increased upon the addition of nano-mica. On the other hand, PVDF-MX films displayed excellent stability when exposed to high temperatures and UV radiations. Furthermore, augmentation of hydrophobicity of PVDF-MX films effectively resisted moisture absorption. Improved properties of PVDF-MX films could be a potential material as a single-layered solar backsheet application and showed satisfying properties for long-term stability.

Bioinspired modification strategy to improve thermal conductivity and dielectric constant of natural rubber composite for thermal management applications

AbstractNatural rubber (NR) composites filled with modified aluminum nitride (AlN) particles were successfully fabricated with high thermal conductivity and dielectric constant. To boost the interfacial interactions form thermal conductive networks between AlN and NR matrix, a mussel‐inspired polydopamine and γ‐(2,3‐epoxypropoxy)propy trimethoxysilane (KH560) grafting were combined to yield AlN‐PDA‐KH560. The double‐layer structure led to good filler dispersion of AlN‐PDA‐KH560 with decreased interfacial thermal resistances. As a result, the largest thermal conductivity in 30 phr AlN‐PDA‐KH560/NR was reached to 0.48 W/m K, which was 2.28 times larger than pure NR. Furthermore, the 30 phr AlN‐PDA‐KH560/NR composite also had relatively high dielectric constant (3.95 at 103 Hz) and low dielectric loss (~0.01 at 103 Hz), benefiting for long time operation and thermal diffusion. This strategy provides a facile, low‐cost, and scalable method to fabricate high electrical and thermal conducting composites for strong potential in thermal management for electronic devices.

Physical property and interface binding energy calculation of polyimide/boron nitride nanosheets thermally conductive composite insulating materials

As an insulating material, polyimide (PI) has low intrinsic thermal conductivity and high dielectric constant under high temperature conditions, which causes surface charge accumulation and severely limits the performance of insulation. In this paper, by adapting two-dimensional boron nitride nanosheets (BNNSs), a new type of material model with a PI-BNNS composite structure was established based on a molecular dynamics (MD) simulation method. Meanwhile, the thermal parameter, mechanical parameters, and electrical parameters of models with different doping concentrations at different temperatures were calculated. The results showed that the filling of BNNSs significantly improved the comprehensive performance by changing dielectric constant, breakdown field strength, thermal conductivity and so on. Furthermore, to reveal the microcosmic mechanism of the doping effect, the interfacial interaction intensity was analyzed by calculating the surface binding energy between PI/BNNS. With increasing doping ratio, the van der Waals interaction significantly increased, thus improving the phonon transfer capacity from electron movement to lattice vibration, leading to the mechanical properties and thermal conductivity of the materials significantly improved with increasing doping ratio. The increase in surface binding energy also leads to a deeper trap to capture the charge and produces charge shielding layers to improve the breakdown strength of the system.

Phonon propagation in isotopic diamond superlattices

The out-of-plane thermal conductivity and elastic constant of epitaxial [100] $^{12}\mathrm{C}/^{13}\mathrm{C}$ superlattice diamonds with layer thicknesses of 1, 30, and 100 nm are evaluated by picosecond ultrasound spectroscopy. The measured elastic constants of the superlattices are equivalent to those of single-layer diamond thin films. This result confirms our success in synthesizing superlattice specimens with few defects at the interfaces. Therefore, the phonon transport behavior is governed by the mass difference, not the interfacial defects. The measured thermal conductivity of the superlattices is lower than that of a pure $^{12}\mathrm{C}$ isotope diamond thin film. We estimated the lattice thermal conductivity using the lattice dynamics calculation, attributing the lowered thermal conductivity to the decrease in the phonon group velocity in superlattices. We further consider the effect of mini-umklapp scattering in the superlattice, which explains the dependence of the thermal conductivity on the layer thickness. We reveal that the mini-umklapp scattering effect becomes significant only for an isotope diamond superlattice because of the high Debye temperature and large relative mass difference.

The particle size effect of rice husk on thermal conductivity and dielectric constant of RTV Silicon rice husk composites

The rice husk (RH) is a wide agricultural resource by-product of rice milling process in Iraq. In this work, RH is used as filler to modified thermal conductivity and dielectric constant of RTV silicone. RH-RTV silicone composites are prepared with different RH filler particle sizes, they are equal to 6.5mm (raw RH), 1.18mm, 250 μm, 125 μm, 75 μm, and 50μm. The levels of RH filler loading (1, 3, 5, 7, 10, 15 and 20) (wt %). The thermal conductivity and dielectric constant of all RH-RTV silicone composites are studied. The effect of varying frequency (from 500 Hz to 1 MHz) on dielectric constant all composites is studied. The thermal conductivity of RH-RTV silicone composites decrease with RH filler concentration increases and particle size decreases, thermal conductivity has minimum value at 20%wt. The particle size effect on thermal conductivity of composite is very observably at 50μm particle. The dielectric constant of RH-RTV silicone composites is increased when RH filler concentration increases and particle size decreases, thy have maximum value at 20%wt and 50μm RH particle. The varying of frequency is low effect on 50μm RH-RTV silicone composites.