Silicon carbide (SiC) is an extremely durable material with superior corrosion and oxidation resistance, making it an excellent candidate for aerospace applications such as engine hot-end components.
SiC ceramic-metal composites are denser than metals and possess high specific tensile strength and stiffness, as well as being capable of withstanding high temperatures – an advantage which helps improve aircraft and space vehicle performance as well as decrease emissions.
High-temperature oxidation resistance
Silicon carbide ceramic matrix composites (CMC) represent an innovative solution to light water reactor cladding tubes. While capable of withstanding extreme temperature conditions and radiation exposure, CMC materials present several unique challenges when applied for nuclear use, including oxidation cracking, and sintering issues that must be overcome to make these materials suitable for nuclear application.
This research is dedicated to the creation of a new CMC fabrication process with improved high-temperature oxidation resistance. Using liquid-phase precursors and redox reactions to produce ceramic material, as well as silicate-hafnium compounds that limit oxygen diffusion, this new process produced samples with superior resistance against high temperature oxidation while providing good phase stability as measured by XPS analysis.
The CF/HfC-SiCN CMCs successfully survived one-hour isothermal oxidation at 1700 degC in steam with minimal changes to structural integrity and only slight color variation of surface areas; as shown in Figure 6. Morphologies of heated clad segments can be found in Figure 6, while XRF analysis revealed intact ceramic coatings on all the CFs while Table S2 provides elemental composition information of all samples oxidized during oxidation.
High strength
Silicon Carbide (SiC) is a ceramic material with superior mechanical strength and toughness, as well as resistance to high temperatures and corrosion, making it an attractive material choice. Unfortunately, its brittleness limits its use for structural applications; this issue can be solved by reinforcing monolithic SiC with fiber reinforcement, creating a ceramic matrix composite (CMC). Doing this improves both its performance and durability.
Traditional ceramic fabrication techniques such as hot pressing and sintering have long been employed to produce CMCs, though these processes are only effective at producing those reinforced with discontinuous phase (particulates or chopped fibers). Continuous fiber CMCs require alternative approaches.
CMCs can be manufactured through various techniques, including chemical and physical treatment. Such treatments can enhance reinforcing phase adherence to matrix structures while decreasing crack propagation risk at high temperature, protecting fibers from environmental damage that might reduce their longevity in harsh environments. Furthermore, a laser-based manufacturing technique has recently been created which allows for the fabrication of high-performance ceramic fiber composites without using furnace technology.
High tensile strength
Silicon Carbide (SiC) is an extremely durable material suitable for demanding applications. However, its brittleness prevents it from replacing more ductile metallic counterparts in many instances. This disadvantage can be overcome by reinforcing monolithic SiC with continuous or woven fiber reinforcement – known as ceramic matrix composites – to significantly enhance physicochemical and thermomechanical properties as well as durability of ceramics.
Studies on CMCs at high temperatures have utilized various methodologies, such as bending and fracture toughness testing, to investigate their mechanical behavior in high temperature conditions. Results from these tests demonstrate that these CMCs can tolerate significant displacement without fracture, while also possessing strong tensile strength properties.
Additive manufacturing technologies AFP and RMI offer promising production methods for these materials, as they enable carbon fiber-reinforced carbon-SiC matrix composites with superior thermal stability at elevated temperatures to be produced using additive manufacturing techniques such as reactive melt infiltration. Furthermore, these composites have demonstrated outstanding oxidation resistance, tensile strength at 1000 degC as well as large strain to rupture ratios and high impact toughness ratings.
Corrosion resistance
Silicon carbide ceramics are widely recognized for their superior corrosion resistance and thermal shock tolerance, lightweight design, biocompatibility and resistance to fatigue – qualities which make them suitable for aerospace and military use as well as medical device devices.
CMCs consist of multiple components, with the matrix system serving as their core. Reinforcing material and pores comprise this component. A second key feature is the fiber-matrix interface (FMI), which determines their morphology and properties – formed through deposition of gaseous precursors into fiber preform pore networks during CVI processes.
CMCs are composed of ceramic matrix materials like mullite or alumina, while their fibers typically feature silicon carbide fibers. Silicon carbide fibers have proven particularly helpful in improving fracture toughness and elongation at elevated temperatures, leading to new applications of these advanced materials. CMC strength at elevated temperatures results from neck formation between SiC particles that prevent stress concentration.
High thermal expansion
Silicon carbide is an ideal material for ceramic matrix composites due to its superior oxidation resistance, thermal shock stability and creep resistence properties. Furthermore, it makes an excellent candidate for high temperature mechanical testing applications; however, special processing and molding methods must be utilized in order to attain the desired properties – often at great expense in terms of production costs and scaleability as well as special equipment and skilled operators being necessary for successful usage.
This study explored the effects of different forming and molding techniques on the high-temperature mechanical properties of SiC CMCs. CMCs were made using an ultrahigh concentration (66 vol%) SiC slurry that was densified using precursor impregnation and pyrolysis (PIP), yielding PRCs with excellent thermomechanical properties up to 2000 degC in argon.
The composites had higher tensile strength than pure carbon and their load-displacement curve showed no evidence of brittle fracture. Furthermore, PRCs demonstrated effective fiber pull-out behavior which is essential in high performance applications like brake pads and pads, clutches and furnace charging plates. Furthermore, CMCs demonstrated very low thermal expansion rates as well as good tribological behavior.