RESUMEN
Good solid-liquid mixing homogeneity and liquid level stability are necessary conditions for the preparation of high-quality composite materials. In this study, two rotor-stator agitators were utilized, including the cross-structure rotor-stator (CSRS) agitator and the half-cross structure rotor-stator (HCSRS) agitator. The performances of the two types of rotor-stator agitators and the conventional A200 (an axial-flow agitator) and Rushton (a radial-flow agitator) in the solid-liquid mixing operations were compared through CFD modeling, including the homogeneity, power consumption and liquid level stability. The Eulerian-Eulerian multi-fluid model coupling with the RNG k-ε turbulence model were used to simulate the granular flow and the turbulence effects. When the optimum solid-liquid mixing homogeneity was achieved in both conventional agitators, further increasing stirring speed would worsen the homogeneity significantly, while the two rotor-stator agitators still achieving good mixing homogeneity at the stirring speed of 600 rpm. The CSRS agitator attained the minimum standard deviation of particle concentration σ of 0.15, which was 42% smaller than that achieved by the A200 agitators. Moreover, the average liquid level velocity corresponding to the minimum σ obtained by the CSRS agitator was 0.31 m/s, which was less than half of those of the other three mixers.
RESUMEN
Design and fabrication of oriented thermal management materials has great significance in meeting the requirements of high-power heat dissipation device applications. To synchronously improve the structure stability and thermal management performance, in this study, large-scale silicon carbide (SiC) nanowires were deposited on the graphite film (GF) surface to reinforce the aluminum-based laminar composites. Highly thermally conductive SiCnws-GF multiscale architecture reinforced Al laminar composites with enhanced interlayer bonding strength were achieved by an innovative pressure infiltration strategy. The embedding of the silicon carbide nanowires not only improved the thermal conductivity of the laminar composites but also enhanced the interface bonding strength between the Al matrix and the SiCnws-GF multiscale structure robustly. The interlaminar shear strength of the SiCnws-GF reinforced Al laminar composites was 134.1 MPa, which was 2.4 times the value of GF reinforced Al composites. The in-plane thermal conductivity of the best-performing SiCnws-GF reinforced Al laminar composites was 868.9 W (m K)-1, which was 16.9% higher than the value of the GF reinforced Al laminar composites. The outstanding interlaminar shear strength and superior thermal conductivity of the SiCnws-GF reinforced Al laminar composites revealed that a potential and competitive thermal management material was obtained.
RESUMEN
Uniform and dense carbon nanotubes (CNTs) were grown on the surface of the graphite film (GF) by a plasma-enhanced chemical vapor deposition process. The synthesized CNTs can act as a bridge between GF and Al matrix to enhance the interface performance and improve thermal properties of the GF/Al laminated composite simultaneously. A layer-by-layer CNTs-GF/Al composite with both increased mechanical property and thermal management capability was fabricated through an optimized pressure infiltration process, which was time- and energy-saving. The results show that the interface of the laminated composite is well bonded and no interface product such as Al4C3 is generated. Additional investigations reveal that the growth of CNTs is an effective way to improve the thermal conductivity and reduce the coefficient of thermal expansion of the GF reinforced Al composites. Overall, the best-performing CNTs-GF/Al composites with a CNTs-GF volume fraction of 51.42% show an increase of 47.99% in thermal conductivity and 26.44% in interlaminar shear strength, making them promising thermal management laminated materials.