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1.
《Ceramics International》2022,48(11):15483-15492
In this work, a new kind of double layers modified alumina-based hybrid (silver@copper@alumina (Ag@Cu@Al2O3) hybrid) was successfully synthesized through the two-step layer-by-layer process. First, copper (Cu) nanoparticles were assembled onto alumina (Al2O3) particles by reduction of Cu2+. Second, Ag@Cu@Al2O3 hybrids were assembled via Ag deposition on the surface of Cu@Al2O3 particles. The obtained Ag@Cu@Al2O3 hybrids served as thermally conductive fillers to greatly boost the thermal conductivity of poly (dimethylsiloxane) (PDMS). The thermal conductivity reached 1.465 W m?1 K?1 at 85 wt% filler loading. The thermal conductivity of PDMS matrix was increased more than 7 times by the addition of Ag@Cu@Al2O3 hybrid, which was much higher than single layer modified alumina-based hybrids (Ag@Al2O3 and Cu@Al2O3 hybrids) and virgin Al2O3 particle. The effect of double layers modified filler, single layer modified filler and virgin filler on the thermal conductivity of PDMS matrix was discussed in detail and the mechanism of these fillers for improving thermal conductivity was studied through Foygel's thermal conduction model. Otherwise, electric, mechanical and thermal properties of Ag@Cu@Al2O3/PDMS composites were also further tested and analyzed.  相似文献   

2.
In this work, a multi-contact Al2O3@AgNPs hybrid thermal conductive filler was synthesized by in-situ growth method to fill high thermal conductivity polydimethylsiloxane (PDMS)-based composites to prepare TIMs. And the thermal conductivity, electrical conductivity, and mechanical properties of the composite materials were studied. During the synthesis process of the multi-contact hybrid filler, different concentrations of silver ions were reduced to generate silver nanoparticles and attached to the surface of Al2O3. Al2O3@AgNPs/PDMS thermally conductive composites were prepared by changing the filler addition. Using SEM, XPS, and XRD is used to characterize the morphology and chemical composition of Al2O3@AgNPs hybrid filler. The thermal conductivity of PDMS-based composites with different AgNPs content under 70 wt% filler loading was studied. The results show that the thermal conductivity of PDMS-based composites filled with 7owt%Al2O3@3AgNPs/PDMS multi-contact hybrid filler is 0.67 W/m·K, which is 3.72 times that of pure PDMS, and is higher than that of unmodified Al2O3 with the same addition amount. /PDMS composite material has a high thermal conductivity of 24%. This work provides a new idea for the design and manufacture of high thermal conductivity hybrid fillers for TIMs.  相似文献   

3.
In this work, a facile strategy is proposed to concurrently enhance both in-plane and through-plane thermal conductivity of injection molded polycarbonate (PC)-based composites by constructing a dense filler packing structure with planar boron nitride (BN) and spherical alumina (Al2O3) particles. The state of orientation of BN platelets is altered with the presence of Al2O3, which is favorable for improving both in-plane and through-plane thermal conductivity of subsequent moldings. Rheological analysis showed that the formation of intact thermal conductive pathways is crucial to the overall enhancement of thermal conductivity. Both in-plane and through-plane thermal conductivity of PC/BN(20 wt%)/Al2O3(40 wt%) composites reached as high as 1.52 and 1.09 W mK−1, which are 485% and 474% higher than that of pure PC counterparts, respectively. Furthermore, the prepared samples demonstrated excellent electrical insulation and dielectric properties which show potential application in electronic and automotive industries.  相似文献   

4.
《Ceramics International》2023,49(18):30204-30213
As an excellent two-dimensional insulating material with high thermal conductivity, high temperature stability and high hardness, hexagonal boron nitride(h-BN) is widely applied in semiconductor manufacturing, aerospace, metallurgical manufacturing and other cutting-edge fields. However, the unique surface structure of h-BN leads to poor lubricity and easy agglomeration, which limits the application of h-BN especially in the field of electronic packaging. To address key issues boosted above, this study designed and prepared the BN@Fe3O4 magnetic insulating particles and doped it into the reduced viscosity epoxy resin to prepare the composites. By selecting appropriate external magnetic field strength and BN@Fe3O4 particles’ content, a novel 3D structure of fillers like dominoes in epoxy resin composite was successfully constructed. The microstructure of the BN@Fe3O4 particles and composites were analyzed, the thermal conductivity, the mechanical and the electrical properties of composites were simultaneously tested. Results manifested that the core-shell structures with BN as core and Fe3O4 as shell was successfully prepared, linking through the PDA middle layer between the BN core and Fe3O4 shell. Under the influence of magnetic orientation, the BN@Fe3O4 magnetic particles were preferred an out-of-plane oriented in the epoxy resin composites, resulted an enormously enhanced on thermal conductivity of composites. At a magnetic field strength of 60 mT and 25 vol% BN@Fe3O4 content, the thermal conductivity of BN@Fe3O4/EP composites is as lofty as 1.832 W/(m K), which is 1023.46% higher than that of pure epoxy resin. Meanwhile, the thermal stability has also been slightly improved, the elastic modulus and insulation performances remain at the same level.  相似文献   

5.
《Ceramics International》2023,49(18):30248-30256
The thermal conductivity of polymer composites could be improved through the orientation of fillers in specific directions. Here, a novel strategy to fabricate BN/Ag nanowires@Ni/epoxy composites (BN/Ag NWs@Ni/EP) to dynamically improve the in-plane or out-of-plane thermal conductivity of the composites in real-time by changing the direction of the magnetic field was investigated. The thermal conduction path was constructed by Ag NWs bridging between BN flakes. Ag NWs@Ni would be oriented in the in-plane or out-of-plane direction by changing the direction of the magnetic field. The out-of-plane or in-plane thermal conductivities of the composites were 0.824 and 0.723 W m−1K−1 at 40 wt% BN/Ag NWs@Ni content, and the corresponding TCEs were 429% and 359% respectively when Ag NWs@Ni was oriented in the out-of-plane or in-plane direction. Meanwhile, BN/Ag NWs@Ni/EP exhibited good mechanical and dielectric properties, which were beneficial for its industrial application in electronic packaging. This strategy provides the possibility for the applications that required the adjustment of the heat conduction direction in real-time.  相似文献   

6.
The addition-type liquid silicone rubber (ALSR) co-filled with spheroidal Al2O3 and flaky BN was prepared by the mechanical blending and hot press methods to enhance the thermal, electrical, and mechanical properties for industrial applications. Morphologies of ALSR composites were observed by scanning electron microscopy (SEM). It was found that the interaction and dispersion state of fillers in the ALSR matrix were improved by the introduction of BN sheets. Thermal, electrical, and mechanical performances of the ALSR composites were also investigated in this work. The result indicated that the thermal conductivity of ALSR can reach 0.64 W m−1 K−1 at the loading of 20 wt% Al2O3/20 wt% BN, which is 3.76 times higher than that of pure ALSR. The addition of Al2O3 particles and BN sheets also improve the thermal stability of ALSR composites. Moreover, pure ALSR and ALSR composites showed relatively lower dielectric permittivity (1.9–3.1) and dielectric loss factor (<0.001) at the frequency of 103 Hz. The insulation properties including volume resistivity and breakdown strength were improved by the introduction of flaky BN in the ALSR matrix. The volume resistivity and characteristic breakdown strength E0 are 6.68 × 1015 Ω m and 93 kV/mm, respectively, at the loading of 20 wt% Al2O3/20 wt% BN. In addition, the mechanical characteristics including elongation at break and tensile strength of ALSR composites were also enhanced by co-filled fillers. The combination of these improved performances makes the co-filled ALSR composites attractive in the field of electrical and electronic applications.  相似文献   

7.
《Ceramics International》2023,49(5):7987-7995
Monolithic Al2O3 and Al2O3-graphene-SiC hybrid composites were prepared by spark plasma sintering (SPS) under vacuum atmosphere. The results show that the hybrid composites were almost completely dense (>97%). SiC content has a significant effect on the microstructure of the composites. With the increase of SiC content, the average grain size of alumina decreased gradually. The addition of SiC to alumina changed fracture mode from inter-granular fracture to mixed fracture mode of inter-granular fracture and trans-granular fracture. The Al2O3-0.4 wt%graphene-5 wt% SiC hybrid composite has the highest bending strength and hardness, which were 57% and 19.22% higher than those of the monolithic alumina, respectively. The room temperature (RT) thermal conductivity of the monolithic Al2O3 (25.5 W/m·K) was the highest. The thermal conductivity and thermal diffusivity coefficient of the composites decreased with the increase in temperature, while the specific heat of monolithic alumina and composites increased with the increase in temperature and additives. These properties were related to the microstructure of materials and the possible transport mechanisms were discussed.  相似文献   

8.
《Ceramics International》2021,47(20):28252-28259
Oxide ceramics are considered as promising high temperature solar absorber materials. The major aim of this work is the development of a new solar absorber material with promising characteristics, high efficiency and low-cost processing. Hence, this work provides a comparative and inclusive study of densification behavior, microstructure features, thermal emissivity and thermal conductivity values of the two new high temperature solar absorbers of ZrO2/Fe2O3 and Al2O3/CuO ceramics. Ceramic composites of ZrO2/(10–30 wt%) Fe2O3 and Al2O3/(10–30 wt%) CuO were prepared by pressureless sintering method at a temperature of 1700 °C/2hrs. Identification of the solar to thermal efficiency of the composites was evaluated in terms of their measured thermal emissivity. Thermal efficiency and heat transfer homogeneity were investigated in terms of thermal conductivity and diffusivity measurement. The results showed that both composites exhibited comparable densification behavior, homogenous and harmonious microstructure. However, Al2O3/10 wt% CuO composite showed higher thermal and solar to thermal efficiencies than ZrO2/Fe2O3 composites. It gave the lowest and the best thermal emissivity of 0.561 and the highest thermal conductivity of 15.4 W/m. K. These values proved to be the best amongst all those of the most known solar absorber materials made from the expensive SiC and AlN ceramics. Thus, Al2O3/CuO composites have succeeded in obtaining outstanding properties at a much lower price than its other competitive materials. These results may strongly identify Al2O3/CuO composites as promising high-temperature solar absorber materials instead of ZrO2 and the other carbide and nitride ceramics.  相似文献   

9.
《Ceramics International》2023,49(18):29639-29646
The high coefficient of thermal expansion (CTE) of polymeric composites can cause large deformation under temperature changes, affecting coupling with devices made of other materials in radio frequency (RF) communication systems and limiting their application in RF systems. In order to obtain polyphenylene sulphide (PPS)-based composites with low CTE, a series of PPS-based composites containing different loadings of ceramic powders (including Zr2WP2O12, BN, AlN, Al2O3) were fabricated by melt extrusion method using PPS with 40 wt% glass fibre (GF) as matrix material. The experimental results showed that the PPS composites with Zr2WP2O12 (ZWP) as a filler had a lower CTE compared to the samples with other fillers at the same filler loading. The CTE of PPS/GF/ZWP steadily decreased with increasing ZWP addition. At 20 vol% ZWP loading, a 67% (about 18 ppm/°C) reduction of CTE compared to the PPS/GF was achieved. The addition of ZWP powder to PPS/GF also led to an improvement in the dielectric loss of the composite. When the ZWP content is 20 vol%, the dielectric loss of the composites is about 0.0035, which is 24.4% lower than PPS/GF. Hence, the PPS/GF/ZWP composites have great potential for applications in RF communication systems.  相似文献   

10.
《Ceramics International》2022,48(22):33571-33579
The construction of high thermal conductivity polymer composites by the orientation of fillers is of great significance in electronic devices. Herein, a novel strategy to prepare boron nitride-Ni nanoparticles/epoxy resin composites (hmBN-Ni/EP) through the synergistic effect of magnetic field and hot-pressing on the orientation of BN-Ni fillers has been reported. hmBN-Ni/EP composites have better BN orientation in the in-plane direction than other BN-based/EP composites obtained by hot-pressing or magnetic field orientation only. The thermal conductivity of hmBN-Ni/EP reached 2.42 W m?1 K?1 at 30 wt% BN-Ni loading, which was 1145% higher than pure EP. The enhancement of thermal conductivity of hmBN-Ni/EP was attributed to the high in-plane orientation of BN-Ni through the synergistic effect of magnetic field orientation and hot-pressing. Meanwhile, the as-prepared hmBN-Ni/EP composites showed good insulation and mechanical properties which were facilitated to its industrial application in electronic packaging. This work provided a new strategy for better orientation of BN-Based fillers in polymer matrix by combining the magnetic field orientation and hot-pressing.  相似文献   

11.
Microsized or nanosized α‐alumina (Al2O3) and boron nitride (BN) were effectively treated by silanes or diisocyanate, and then filled into the epoxy to prepare thermally conductive adhesives. The effects of surface modification and particle size on the performance of thermally conductive epoxy adhesives were investigated. It was revealed that epoxy adhesives filled with nanosized particles performed higher thermal conductivity, electrical insulation, and mechanical strength than those filled with microsized ones. It was also indicated that surface modification of the particles was beneficial for improving thermal conductivity of the epoxy composites, which was due to the decrease of thermal contact resistance of the filler‐matrix through the improvement of the interface between filler and matrix by surface treatment. A synergic effect was found when epoxy adhesives were filled with combination of Al2O3 nanoparticles and microsized BN platelets, that is, the thermal conductivity was higher than that of any sole particles filled epoxy composites at a constant loading content. The heat conductive mechanism was proposed that conductive networks easily formed among nano‐Al2O3 particles and micro‐BN platelets and the thermal resistance decreased due to the contact between the nano‐Al2O3 and BN, which resulted in improving the thermal conductivity. POLYM. ENG. SCI., 50:1809–1819, 2010. © 2010 Society of Plastics Engineers  相似文献   

12.
Polypyrrole (PPy) nanolayers were introduced on the surface of alumina (Al2O3) particles via admicellar polymerization. The properties of silicone rubbers (SRs) filled with PPy-coated Al2O3 and pristine Al2O3 as thermally conductive fillers were studied and compared. The results demonstrate that the addition of PPy-coated Al2O3 leads to a better interfacial compatibility but lower cross-linking density of the composites than pristine Al2O3. The improvement in the compatibility and the decrease in the cross-linking density are paradoxes in affecting mechanical properties. The improvement in the compatibility shows a slight predominance on the strength at low-filler contents. Lower cross-linking density of modified-Al2O3/SR composites led to a better processing performance and a higher maximum filler loading amount than the pristine Al2O3/SR composites, which is beneficial to increasing the thermal conductivity and maintaining a relatively good strength. The PPy-coated Al2O3/SR composite with 83 wt% filler content has a thermal conductivity of 1.98 W/(m K) and a tensile strength of 2.9 MPa, and the elongation at break was 63%. Functionalized fillers by admicellar polymerization used in the fabrication of filler/SR composites not only improve the interfacial compatibility but also optimize and expand the functions of the composites, which has great significance for the production and application of thermally conductive SR in some branches of industry (automotive, electrical engineering, etc.) in the future.  相似文献   

13.
Natural rubber (NR) composites highly filled with nano‐α‐alumina (nano‐α‐Al2O3) modified in situ by the silane coupling agent bis‐(3‐triethoxysilylpropyl)‐tetrasulfide (Si69) were prepared. The effects of various modification conditions and filler loading on the properties of the nano‐α‐Al2O3/NR composites were investigated. The results indicated that the preparation conditions for optimum mechanical (both static and dynamic) properties and thermal conductivity were as follows: 100 phr of nano‐α‐Al2O3, 6 phr of Si69, heat‐treatment time of 5 min at 150°C. Furthermore, two other types of fillers were also investigated as thermally conductive reinforcing fillers for the NR systems: (1) hybrid fillers composed of 100 phr of nano‐α‐Al2O3 and various amounts of the carbon black (CB) N330 and (2) nano‐γ‐Al2O3, the particles of which are smaller than those of nano‐α‐Al2O3. The hybrid fillers had better mechanical properties and dynamic performance with higher thermal conductivity, which means that it can be expected to endow the rubber products serving under dynamic conditions with much longer service life. The smaller sized nano‐γ‐Al2O3 particles performed better than the larger‐sized nano‐α‐Al2O3 particles in reinforcing NR. However, the composites filled with nano‐γ‐Al2O3 had lower thermal conductivity than those filled with nano‐α‐Al2O3 and badly deteriorated dynamic properties at loadings higher than 50 phr, both indicating that nano‐γ‐Al2O3 is not a good candidate for novel thermally conductive reinforcing filler. POLYM. COMPOS., 37:771–781, 2016. © 2014 Society of Plastics Engineers  相似文献   

14.
《Ceramics International》2021,47(24):34794-34801
Ho2O3 was employed to improve the microstructural densification and performances of pressureless sintered corundum–mullite ceramic composites. This study investigated the influences of Ho2O3 addition on the microstructure, physical properties and thermal shock resistances of the composites. The results indicated that sample AH5 (80 wt% Al2O3, 20 wt% coal series kaolin, and 5 wt% additional Ho2O3), which was sintered at 1550 °C, showed the best comprehensive properties. In this Al2O3-rich and SiO2-poor system, a reaction between the Ho2O3 and Al2O3–SiO2 system produced an Ho2O3–Al2O3–SiO2 liquid phase. This liquid phase increased the microstructural densification and resulted in a lower sintering temperature. The generation of mullite and holmium disilicate during thermal shocks improved the thermal shock resistance. The high bending strength and satisfactory thermal shock resistance of the as-prepared corundum–mullite ceramic composites showed their potential for use in heat transmission pipelines.  相似文献   

15.
《Polymer Composites》2017,38(9):1902-1909
In this paper, in order to investigate and predict the synergistic effect of the tetra‐needle‐shaped zinc oxide whisker (T‐ZnO) and boron nitride (BN) hybrid fillers in the thermal conductive high‐density polyethylene (HDPE) composites, the filler networks were studied through dynamic rheological measurement. Moreover, the crystallinity of the HDPE in the composites, and the thermal and electrical conductivity of the composites were also investigated. It was found that when the ratio of the BN and T‐ZnO in hybrid fillers was 20:10, the HDPE/hybrid fillers composite not only had the highest thermal conductivity but also can maintain the electrically insulating. Furthermore, the gel point of the HDPE/hybrid fillers composites was 11.2 wt%, and it was close to the 10 wt%. Therefore, the synergistic effect of the T‐ZnO and BN hybrid fillers in the HDPE/hybrid fillers composites can be successfully predicted through dynamic rheology date. Simultaneously, the Scanning electron microscope results showed that the T‐ZnO and BN particles can contact each other to form the thermal conductive paths so that the thermal conductivity of the HDPE can be enhanced through addition of the hybrid fillers. In addition, it was also found that the improved thermal conductivity of the HDPE/hybrid fillers composites was not because of a change in the crystallinity of the HDPE in the HDPE/hybrid fillers composites. POLYM. COMPOS., 38:1902–1909, 2017. © 2015 Society of Plastics Engineers  相似文献   

16.
Aluminum oxide (Al2O3) particles and silicon carbide (SiC) whiskers improved the thermal conductivity of high-density polyethylene (HDPE). To improve the dispersion of inorganic fillers in the matrix, 5 wt% of maleic anhydride-modified polyethylene was added into HDPE as a compatibilizer, and the hybrid matrix was denoted as mHDPE. The thermal conductivity, heat resistance, and tensile properties of resulting HDPE composites were characterized. The results showed that the thermal conductivity reached its maximum value of 0.8876 W/(m K) at 1/4 weight ratio of Al2O3/SiC, which was 110.3, 54.8, and 8.8% higher than that of pure HDPE, mHDPE/Al2O3, and mHDPE/SiC composites, in the order given, indicating that hybrid fillers have synergistic effect on the thermal conductivity of HDPE composites. Moreover, they also have a synergistic effect on the heat resistance and Young’s modulus. As the SiC content increases, the heat resistance of the composites increases at first and then falls, and the maximum VST is reached at an Al2O3/SiC weight ratio of 3/2, which is 5.4 °C higher than that of HDPE. The maximum Young’s modulus of the composites (1160 MPa) is obtained at an Al2O3/SiC weight ratio of 1/4, and the yield strength increases gradually as the SiC whiskers’ content increases.  相似文献   

17.
The silicone rubber with good thermal conductivity and electrical insulation was obtained by taking vinyl endblocked polymethylsiloxane as basic gum and thermally conductive, but electrically insulating hybrid Al2O3 powder as fillers. The effects of the amount of Al2O3 on the thermal conductivity, coefficient of thermal expansion (CTE), heat stability, and mechanical properties of the silicone rubber were investigated, and it was found that the thermal conductivity and heat stability increased, but the CTE decreased with increasing Al2O3 fillers content. The silicone rubber filled with hybrid Al2O3 fillers exhibited higher thermal conductivity compared with that filled with single particle size. Furthermore, a new type of thermally conductive silicone rubber composites, possessing thermal conductivity of 0.92 W/mK, good electrical insulation, and mechanical properties, was developed using electrical glass cloth as reinforcement. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2478–2483, 2007  相似文献   

18.
Various thermally conductive fillers including aluminum oxide(Al2O3), magnesium oxide(MgO), β-silicon carbide particle(β-SiCp) and β-silicon carbide whisker(β-SiCw) were used to prepare polystyrene thermal conductivity composites. Experimental results showed that, for given filler loading, the thermal conductivity of the composites was higher for PS flake than that of PS particle, and the thermal conductivity was optimal by powder blending method. The SiCw filler was more favorable to improve the thermal conductivity of the composites; a much higher thermal conductivity of 1.18 W/mK could be achieved for the composite with 40 vol% SiCw, about six times higher than that of native polystyrene. The experimental thermal conductivity values were in agreement with those predicted by lower bound of Maxwell-Eueken model. For given SiC loading, the thermal conductivity increased with the increasing shape parameter of n. The SiCw was much easier to form the thermal conductivity chains and network than that of SiCp.  相似文献   

19.
《Polymer Composites》2017,38(10):2221-2227
Graphene nanoplatelets (GNPs) have attracted considerable attention in the field of thermal management materials due to their unique structure and exceptional thermal conductive properties. In this work, we demonstrate a significant synergistic effect of GNPs, alumina (Al2O3), and magnesia (MgO) in improving the thermal conductivity of polycarbonate/acrylonitrile‐butadiene‐styrene polymer alloy (PC/ABS) composites. The thermal conductivity of the composites prepared through partial replacement of Al2O3 and MgO with GNPs could increase dramatically compared with that without GNPs. The maximum thermal conductivity of the composite is 3.11 W mK−1 at total mass fraction of 70% with 0.5 wt% GNPs loading. It increases 60% compared with that without GNPs (1.95 W mK−1). The synergistic effect results from the compact packing structure formed by Al2O3/MgO and the bridging of GNPs with Al2O3/MgO, thus promoting the formation of effective thermal conduction pathways within PC/ABS matrix. More importantly, together with the intrinsically high thermal conductivity of GNPs, boosted and effective pathways for phonon transport can be created, thus decrease the thermal resistance at the interface between fillers and PC/ABS matrix and increase the thermal conductivity of composites. POLYM. COMPOS., 38:2221–2227, 2017. © 2015 Society of Plastics Engineers  相似文献   

20.
In this study, synthetic graphite, carbon fiber, and carbon nanotube were used as thermal conductive fillers and ethylene‐propylene‐diene (EPDM) as matrix. Oriented EPDM/filler composites were prepared with two‐roll mill, and the effects of orientation and content of carbon based fillers on thermal conductivity and tensile strength of the composites were investigated. Parallel thermal conductivity of the oriented composites is significantly higher than normal thermal conductivity of the oriented composites. Especially, at 31.6% graphite content, parallel thermal conductivity of oriented composites is 7.14 W/mK. Very high thermal conductivity was achieved for oriented EPDM/graphite composites. Orientation of the fillers using two‐roll mill significantly improves the thermal conductivity in the orientation direction. For all the EPDM/filler composites, tensile strength of orientation direction is higher than that of normal direction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41000.  相似文献   

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