Spark Plasma Sintering of Functionally Graded Silicon Carbide for Lightweight Armour Applications
C.M. O'Brien (TU Delft - Mechanical Engineering)
V. Popovich – Mentor (TU Delft - Mechanical Engineering)
M.J.M. Hermans – Graduation committee member (TU Delft - Mechanical Engineering)
Erik Carton – Mentor (TNO)
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Abstract
Silicon carbide (SiC) is a promising technical ceramic widely used in defence systems due to its high hardness, low density, and excellent thermal stability, and is thus found in personal protective systems and structures. For processing, the densification of SiC remains a challenge as a result of its covalent bonding and limited self-diffusion during sintering. Finding methods of enhancing SiC sintering while reducing the weight of the final product is an intriguing area of research with potential for next-generation protective applications.
This study focuses on the use of boron carbide (B4C) as a sintering additive and the configuration of processing parameters to investigate how this affects the microstructural development and resulting mechanical properties of spark-plasma sintered (SPS) SiC. Starting powders were characterised by X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD). Samples containing varying B4C contents were fabricated by SPS and subsequently characterised through density measurements, optical and electron microscopy, ultrasonic testing, hardness testing, and fracture toughness measurements.
The results demonstrate that B4C acts as an effective sintering aid for SiC, producing a significant increase in densification at low additions while also enabling controlled variations in porosity through compositional adjustment to be achieved. The increased density resulted in improved elastic properties and hardness, indicating that porosity was the dominant factor governing mechanical performance. Microstructural analysis revealed discrete B4C particles distributed throughout the SiC matrix and confirmed strong interfacial bonding within bilayer structures. Functionally graded SiC-based ceramics were successfully fabricated through engineered density gradients, with no evidence of interfacial delamination observed.
These findings aid in understanding the effects of SPS processing parameters on the microstructure and the resulting mechanical properties. This knowledge is highly relevant for the design of novel structural and protective systems, where high hardness, low weight and thermal stability are pivotal.