Enhanced mechanical and microwave absorption properties of SiCf/SiC composite using aluminum powder as active filler

• Published in: Journal of alloys and compounds 2019-06, Vol.790, p.58-69
• Main Authors: Duan, Shichang, Zhu, Dongmei, Dong, Jie, Lu, Xiaoke, Ding, Donghai, Zhou, Wancheng, Luo, Fa
• Format: Article
• Language: English
• Subjects: Active filler; Aluminum; Aluminum carbide; Bend strength; Ceramic fiber reinforced ceramics; Complex permittivity; Composite materials; Densification; Dielectric loss; Dielectric properties; Fillers; Impedance matching; Infiltration; Mechanical and dielectric properties; Microwave absorption; Modulus of rupture in bending; Pyrolysis; SiCf/SiC composites; Silicon carbide
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.03.171

SiCf/SiC composites have been recognized as an ideal structural and microwave absorbing materials, however the use of SiCf/SiC composites still restricted at the stage of laboratory research due to their poor mechanical and microwave absorbing properties. In this study, both the bending strength and the complex permittivity for microwave absorbing purpose were successfully improved with the addition of aluminum fillers during the Precursor Infiltration and Pyrolysis (PIP) process of SiCf/SiC composites. The effects of aluminum powder content on the microstructural evolutions of polycarbosilane (PCS) derived SiC matrix, mechanical and dielectric properties of composites were investigated. The results confirm that the flexural strength of composite reaches the maximum value of 317 MPa when the aluminum content is 10 wt% owing to the higher densification and the generation of β-SiC and Al4C3. The values of ε′ and ε′′ can be reduced to suitable levels with good impedance matching and dielectric loss when the aluminum content is 5 wt% attributed to the reduction of free carbon in the matrix. Furthermore, the reflection loss values of composites can be as low as −56 dB and the optimal bandwidth below −10 dB is 3.4 GHz when incorporating 5 wt% aluminum powders. •Aluminum as active filler can adjust dielectric property of SiCf/SiC composite.•Aluminum added in the mixed precursors can promote the crystallization of SiC.•The mechanical properties of SiCf/SiC composites can be greatly improved.•An optimum microwave absorption performance was obtained by adding aluminum.