Silicon carbide (SiC) is an advanced ceramic material consisting of silicon and carbon. Naturally occurring as the rare mineral moissanite, SiC powder production began mass-scale manufacturing as early as 1893.
NASA Glenn researchers have developed a cutting-edge processing method that significantly decreases power requirements, temperatures and processing times to create stronger SiC tows that can be used in metal matrix composites for aerospace as well as civil industrial applications.
High Strength
Silicon carbide ceramic fiber is an outstanding reinforcement material for metal, polymer, and ceramic matrix composites, providing high strength and stiffness at low density while still retaining its properties even at very high temperatures. Understanding its mechanical behavior is paramount to accurately predict composite behavior and customize properties accordingly; hence single fiber tensile tests are used to characterize its behavior; with scanning electron microscopy used to examine tensile fractured SiC fiber while EDS/XRD analysis provides information on elemental composition along radial distribution lines.
AFRL engineers have developed innovative silicon carbide fiber technology designed for use in gas turbine engine components. This unique process creates stronger fibers designed to withstand extreme environments that exist when gas turbines operate; additionally, damaged or poor-quality fibers may be repaired or even made whole again through healing processes.
NicalonTM is a continuous SiC fiber with exceptional strength and modulus, offering increased performance in ceramic, polymer, and metal matrix composites (CMC, PMC, and MMC). Specialty Materials’ Hi-Nicalon Type S fiber offers enhanced thermal stability as well as higher crystallinity; its enhanced thermal stability provides higher creep resistance with up to 1400 degC creep resistance maintaining strength throughout. Used across a range of industries including aerospace applications it has also been qualified as part of this new material family.
High Modulus
Silicon carbide ceramic fibers can maintain their mechanical properties even at high temperatures, making them an excellent choice for use in metal, ceramic and polymer matrix composites. Their resistance to chemical corrosion, oxidation, fatigue and creep makes them particularly well suited to aerospace applications while their heat tolerance makes them suitable for gas turbine engines.
Silicon carbide ceramic fibers exhibit increasing tensile strengths with increasing fiber length, due to decomposition of SiCxOy amorphous phase at their core section, leading to carbon-rich regions at the boundaries of crystalline SiC grains. Furthermore, their flexural modulus increases with an increase of bulk species such as SiO2 or Si3N4. This corresponds with increased thermodynamic stability due to higher Young’s moduli values.
Goodfellow provides engineers with an assortment of silicon carbide ceramic fibers to choose the optimal variation for their application. Each type varies in terms of its tensile strength, modulus and density – and variations available include:
High Corrosion Resistance
Silicon carbide fiber is an advanced ceramic material composed of silicon and carbon that boasts exceptional properties such as temperature oxidation resistance, hardness, high strength, thermal stability, corrosion resistance and low density. As one of the ideal aerospace high-temperature resistant, reinforcing and stealth materials available today, its applications span across numerous fields in civil industries including aviation, military weapons and equipment, sports equipment and automobiles.
Metal matrix composite materials reinforced with silicon carbide fibers possess superior specific strength, stiffness, thermal expansion coefficient and electrical conductivity compared to their metallic counterparts, making them superior in many applications. Unfortunately, however, their performance in harsh environments is often compromised by corrosion; corrosion increases surface flaws while degrading tensile strength under in-service loads reducing lifetime and leading to catastrophic failure of these materials.
In this work, autoclave tests were used to investigate the influence of surface morphology and elemental composition on hydrothermal corrosion mechanisms of isolated SiC fibers. Tensile strength measurements before and after corrosion tests for commercial Hi-Nicalon (type S) and LCVD SiC fiber with various stoichiometric formulations and pre-treatments was measured – changes were also analyzed in linear density of fiber strands; results demonstrated that corrosion degraded strength but did not lead to its failure.
High Temperature Resistance
Silicon carbide ceramic fibers have the unique capability of withstanding very high temperatures without suffering structural degradation, making them a superior material choice for ceramic matrix composites (CMC) used in aerospace applications. SiC fiber-reinforced CMCs outshone nickel-based superalloys as components able to withstand long exposure to hot temperatures (gas turbine blades for instance) due to being twice as strong and 20% more heat resistant while being two thirds lighter compared with their alloy counterparts.
silicon carbide’s thermal stability and chemical purity has led to its widest application as a material for wafer tray supports and paddles in semiconductor furnaces, lightweight kiln furniture (posts, firing rings, pusher slabs and setter plates), wear-resistant parts as well as resistance heating elements in electric furnaces as well as core material of varistors and thermistors for electronic circuitry applications. It has even found applications as resistance heating elements.
In order to establish the resistance of silicon carbide fibers at high temperatures, a study was undertaken by measuring electrical current flowing through them at various temperature points. Two different fiber types: Sylramic-iBN and Hi-Nicalon were evaluated. Resistance measurements were then conducted within a furnace by passing fiber tows through an adjustable temperature profile and recording their voltage over time; an isothermal resistance-temperature relationship was thus established.