Structural Design Of Thermal Conductive Material With Different Dimensions And Research On The Performance Of Fabricated Composites

The demands of effective heat dissipation have boomed due to the microminiaturization and intelligentization of consumer electronics.Traditional thermal design,as a mature heat dissipation solution for industrial electronics,could not satisfy the heat dissipation requirements of contemporary terminal products.The low-cost and lightweight polymers widely used in electronic packaging have poor heat transferability.Developing materials with higher heat transferability had been an urgent issue to improve the computing speed,functionality,reliability,and lifespan of electronics.As a result,new heat-dissipating polymer composites as an economical and reliable passive cooling solution had become an effective way to solve the mismatch between the huge demand and lack of high thermal conductivity materials.In this work,the heat transfer network was constructed by different dimensional materials after analyzing current researches of heat-dissipating polymer composites.These designs are expected to improve the thermal conductivity of polymer composites.Concurrently,the relevant thermal conductivity model based on the effective medium theory was optimized.While improving the heat-dissipating capacity of the fabricated composites,it also took into account the electrical insulation,thermal stability and mechanical properties.Not only that,the heat flow and temperature distribution in the microscopic area of composites was also simulated by the Abaqus finite element method.The distribution and location of hot spots in different heat transfer designs were visually analyzed.The following thesis was studied:1.The SiCnw network was composed of one-dimensional(1D)silicon carbide nanowires(SiCnw).The longitudinal location of the rigid SiCnw was transformed in axial load,forming a transverse heat conduction network in the preformed polyvinylidene fluoride(PVDF).The integrity of the SiCnw lateral network can be effectively tailored by preparing PVDF/SiCnw composites with different thicknesses.When the thickness of the prepared PVDF/SiCnw composite was 0.1 mm and the SiCnw content was 30 wt%,a SiCnw lateral network with good integrity can be obtained and the in-plane thermal conductivity reached 13.31 W/(m·K).According to the experiments,the theoretical model of nanowires overlap and distribution affecting the thermal conductivity of composites was meliorated.2.1D SiCnw and two-dimensional(2D)graphene are used to design 1D-2D structures.The bonded 1D-2D structure with graphene and SiCnw was prepared.In axial load,a thermal conductive network with good integrity was constructed to greatly improve the in-plane thermal conductivity(30.49 W/(m·K))of the fabricated composite.But the through-plane thermal conductivity of the composite was only 0.28 W/(m·K).For achieving the improvement of through-plane thermal conductivity,the non-bonded 1D-2D structure was composed of vertically oriented graphene with the magnetic field response and SiCnw.The non-bonded 1D-2D structure increased the through-plane thermal conductivity of the composite to 0.71 W/(m·K).But the in-plane thermal conductivity of the composite was only 0.31 W/(m·K).The result indicated SiCnw might effectively construct the interlayer phonon pathway of graphene in the bonded 1D-2D structure.Further considering the reliability and safety of composites used as electronic packaging materials,breakdown-resistant barium titanate particles were introduced to effectively improve breakdown voltage(2.19 kV,and 169.5%)of the composite containing the bonded 1D-2D structure.3.Zero-dimensional(0D)SiC particles and 2D reduced graphene oxide(rGO)were used to design 0D-2D structures.With the help of GO assisted method,aminated SiC particles and GO electrostatically self-assembled into GO@SiC 0D-2D structures.The ratio of GO to aminated SiC particles of the 0D-2D structures was optimized to achieve a full coverage GO@SiC structure in which aminated SiC particles completely covered GO layer.The results showed that when the ratio of GO to aminated SiC particles was 1:100,GO was almost completely covered by aminated SiC particles in the GO@SiC100.The performances of the prepared composites,including thermal conductivity,electrical conductivity,and mechanical property,confirmed that 1:100 was the optimal ratio of GO and aminated SiC particles.The fully covered rGO@SiC structure was formed by the GO@SiC structure by thermal reduction to achieve a higher heat transferability of composites.The results showed that the fully covered rGO@SiC structure with an aminated SiC particle size of 600 nm was conducive to heat transfer of the composite(1.02 W/(m·K)),and its electrical conductivity is also maintained at 1.1 8×10-12 S/cm.4.The above experiment designs showed the construction of a bonded network could effectively improve the heat transferability of composites.Combining with the recent development of new heat transfer materials,a three-dimensional(3D)network of boron phosphide(BP)crystals with chemical bonds was synthesized using nickel foam as the template.The epoxy composite containing 3D-BP had a good isotropic thermal conductivity(2.01 W/(m·K))and 980.5%higher than pure epoxy.At the same time,the thermal expansion coefficient of the composite reached as low as 26.95 × 10-6/?,much lower than epoxy of 60.69×10-6/?.5.The Abaqus finite element method was used to simulate 2D heat transfer of composites containing different thermally conductive structures,which is constructed by materials of different dimensions.The heat transfer procedure in the composites was effectively analyzed under uniform conditions.The structure and distribution of the thermally conductive filler inside the composite were analyzed.Effective theoretical guidance was provided for future experimental design.