No abstract

Poor flowability of printable powders and long preparation cycles are the main challenges in selective laser sintering (SLS) of chopped carbon fiber reinforced silicon carbide composites (SiC composites) with complex structures. In this study, we develop an efficient and novel processing route in the fabrication of lightweight SiC composites via SLS of phenolic resin (PR) and Cf powders with the addition of α-SiC particles combined with one-step reactive melt infiltration (RMI). The effects of α-SiC addition on the microstructural evolution of the Cf/SiC/PR printed bodies, Cf/SiC/C green bodies, and derived SiC composites were investigated. The results indicate that the added α-SiC particles play an important role in enhancing the flowability of raw powders, reducing porosity, increasing the reliability of the Cf/SiC/C green bodies, and contributing to improving the microstructure homogeneity and mechanical properties of the SiC composites. The maximum density, flexural strength, and fracture toughness of the SiC composites are 2.749±0.006 g⋅cm −3 , 266±5 MPa, and 3.30±0.06 MPa•m 1/2 , respectively. The coefficient of thermal expansion (CTE) of the SiC composites is approximately 4.29×10 −6 K −1 from room temperature (RT) to 900 °C, and the thermal conductivity is in the range of 80.15-92.48 W•m −1 •K −1 at RT. The high-temperature strength of the SiC composites increase to 287±18 MPa up to 1200 °C. This study provides a novel as well as a feasible tactic for the preparation of high-quality printable powders as well as lightweight, high strength, and high thermal conductivity SiC composites with complex structures by SLS and RMI.

Belonging to the family of SiC-based composites, Al/SiC has excellent mechanical and thermal properties, making it irreplaceable in high-power electronic devices, key cooling components of 5G base station, electric vehicles, high-speed brake pads, space probe operation devices, and other related fields featured by high technologies. The fabrication of Al/SiC composites is typically difficult when a high-volume fraction of the SiC matrix phase is required to be added. The melt infiltration method, which can achieve near-net forming, has been recognized to be a favorable method for preparing Al/SiC composites due to the disadvantage of traditional processing. How to obtain a high-quality silicon carbide (SiC) ceramic green body is key for the high-quality melt infiltration method. Selective laser sintering technology provides a new opportunity for a high-quality ceramic forming process. It is rapid and efficient, by realizing large-scale and complicated-shape without cast molding. In the present investigation, the SiC green body was obtained by selective laser sintering technique, with the thermoplastic phenolic resin as binder and the content of which to be as low as 15% (in volume), for the subsequent procedure to fabricate composite materials. However, low binder content also renders low flexural strength. As the resin content increases to 25% (in volume), the strength of the SiC green body was 3.77 MPa and a strength increment of 702.1% was measured for the SLSed SiC green body. Spray drying was applied for purpose of more spherical powder. Yet due to porous microstructure in spray-dried powder, the porosity of the SiC green body was high (71.18%) which resulted in deteriorated strength of the green body.