Silicon Carbide Foam

Silicon carbide foam is a multipurpose material with numerous uses. It boasts great tensile strength and electrical conductivity while resisting corrosion from acids and alkalis.

Foam-structured SiC is an innovative new catalyst carrier material, proven to possess excellent mechanical and thermal properties as well as high porosity and surface area. This material offers several advantages over its predecessors like silica, alumina ceramics and activated carbon.

High-Porosity

Foam ceramics feature special three-dimensional network structures and high porosity with relatively low bulk density, making them excellent materials for filtering corrosive liquids and environmental pollutants, heat transfer, energy absorption and pressure resistance applications. Furthermore, they can also serve as filter media in transportation equipment, machinery national defense applications.

There are various fabrication techniques for producing porous silicon carbide (SiC) ceramics. These methods include replica techniques, sacrificial template methods and foaming methods; foaming typically employs organic compounds that decompose without leaving residue during firing such as poly(methyl methacrylate) microbeads as placeholders to form part of the final ceramic’s porosity.

The open-celled SiC foams produced are porous with an average porosity of 73.4 vol% due to the presence of surfactants that reduce gas-liquid interfacial tension and prevent bubble thinning and rupture, as well as having an impressive flexural strength of up to 1.6 MPa.

To create open-celled foams, liquid allylhydridopolycarbosilane was cross-linked with borane dimethylsulfide (BDMS, boron source) to form solid boron-modified polycarbosilane which was mixed in a 20:80 ratio with PMMA microbeads for warm pressing before being pyrolyzed at 1000 degC in argon to form SiC foams with defined pores and microstructure that were identified through scanning electron microscopy (SEM) analysis as well as mercury porosimetry measurements.

High-Temperature Durability

Silicon Carbide (SiC), commonly referred to as Carborundum, is an extremely hard chemical compound consisting of silicon and carbon. Naturally occurring as moissanite gem, SiC is mass-produced as powders and crystals for use as an abrasive material due to its wide bandgap semiconductor properties and high temperature resistance.

SiC foam open-cell ceramic abrasives with porosities exceeding 80% and cell sizes that range from microns to millimeters are commercially used in applications ranging from molten metal filtration, radiant burners, catalyst supports, kiln furniture and cleaning lines with hardness build-up or mill scale accumulation. Foam ceramic abrasives also make an excellent solution for line cleaning services that have difficulty reaching harder materials due to hardness build-up or mill scale accumulation.

Foams with Si-H groups make ideal preceramic precursors, whereby they are combined with aerogel precursors to create final ceramics. Their XRD and FTIR spectra demonstrate that these Si-H groups have formed crosslinks with divinyl benzene aromatic rings to guarantee mechanical stability and form preceramic composites that adhere to this theory.

Foamed abrasives have an extraordinary tensile strength compared to that of alumina at 280 MPa and 440 GPa respectively, providing remarkable strength and durability during high temperature applications where other materials easily degrade or decay. Thermal fatigue experiments on Si-SiC over Al2O3 foams at 800 and 1000 degC reveal this advantage, with less macrocracks developing across fracture surfaces as a result of thermal fatigue fatigue experiments on Si-SiC foams abrasives over Al2O3 thermal fatigue tests at 800 and 1000 degC thermal fatigue studies provide evidence of this superior performance when exposed to extreme temperatures (800 and 1000 degC respectively). Thermal fatigue experiments show this advantage to be superiority over Al2O3 in terms of resilience; thermal fatigue tests conducted under conditions where other materials would quickly degrade; thermal fatigue tests conducted under conditions that prove its use over its aluminum counterpart, where other materials would easily degrade or decompose when subjected to temperatures (800 and 1000 degC), with less frequent macro-cracks appearing across fracture surfaces due to lower temperature exposure.

High-Conductivity

Silicon carbide is an exceptional material known for its resistance to harsh chemical environments. With a specific density of 3.21 g/cm3, silicon carbide stands out as a denser material than ceramics but less dense than some metals. Furthermore, this versatile material features good moldability and tensile strength characteristics which allow it to easily fit various applications.

This feature makes carbon fibre important in several applications, including those requiring high-temperature durability and strength, with its ability to resist physical damage from impact and pressure as well as its exceptional hardness rating of Mohs 9, providing it with excellent abrasion resistance – something essential when used for line pigging.

Foam ceramics also boast high thermal conductivities compared to other ceramic materials, which makes them especially helpful in applications involving phase change materials (PCMs). Their cells and ligaments allow effective transference of heat between fluids flowing through it thereby increasing coupling rates and thus efficiency.

Foam ceramics are known for their electrical conductivity. This quality comes from their reticulated vitreous carbon core that has been encased in silicon carbide, complementing its high mechanical strengths and temperature tolerance. Furthermore, Duocel (r) foam pigs feature high surface areas which accelerate fluids flow thereby helping reduce line downtime and cleaning costs; their electrical conductivity remains consistent at higher temperatures as well.

High-Temperature Corrosion Resistance

Silicon carbide foam offers excellent high temperature corrosion resistance, making it the ideal material choice for applications such as thermal protection systems and furnace/reactor racking. This is due to its low thermal expansion coefficient, high mechanical strength, and nondeforming behavior when exposed to elevated temperatures. In addition, its special network structure increases surface area within pores so as to absorb more liquid and gas molecules quickly without allowing any to flow freely and cause contamination.

Additionally, its excellent moldability and processing with diamond tools make it ideal for producing complex parts with large dimensions and intricate shapes. Furthermore, it does not suffer corrosion by acids and alkalis when filtering liquid, thus avoiding deposits on its surface from acidic and alkaline solutions and dramatically cutting maintenance time and costs for systems using this material.

Silicon Carbide Foam boasts an enhanced heat transfer coefficient due to its special space network structure, making it suitable for applications including heat treating electronic components, fluidized bed bottom plates, humidifiers and water boilers. Furthermore, the material enhances collection efficiency of diesel engine oil fumes making it a viable choice for exhaust collectors.

Low-Pressure Sintering

Silicon carbide ceramic foam sintering can be completed under atmospheric pressure without needing high temperature or inert atmosphere, significantly lowering production costs of enterprises. Furthermore, this ceramic foam does not readily corrode in acid or alkali environments when filtering liquid, therefore not polluting filtered metal liquid. As a result of its design characteristics and filterability features, large size or complex shape products can easily be produced through this method of sintering.

Silicon nitride and SiAlON ceramics are normally pressureless sintered using a vacuum furnace; however, when using low additive compositions that release nitrogen during heating and sintering, nitrogen volatilisation occurs; therefore requiring high-pressure applications to effectively prevent volatilisation during heating and sintering.

To address these challenges, we developed the low pressure sintering (LPS). This technique uses atmospheric gas pressure above a threshold value to prevent nitrogen loss during sintering and can produce much higher densities than traditional methods.

LPS also facilitates fast sintering cycles and near net shaped products, giving LPS an advantage over reaction bonded methods currently used to make large and complex silicon carbide ceramics. Furthermore, this process allows dissimilar materials to sinter together more readily allowing novel composites to form that could increase recycling rates through taking waste material which would normally be thrown away and combining it with ceramic material creating novel composites with unique and desirable properties.

Low-Pressure Filtration

Silicon carbide ceramic foam filters can be used for molten metal filtration to eliminate nonmetallic inclusions from aluminum liquid and purify it, greatly improving casting quality, decreasing scrap losses, and improving production efficiency. Foam filters come in three grades of filter porosity: 10, 20, or 30 ppi depending on your operating conditions and desired filtration effects. It is crucial that you select an effective filter suited to these operating conditions for maximum filtration impact.

Foam ceramics offer superior characteristics compared to other traditional materials used for molten metal filtration: higher porosity, thermal conductivity, mechanical strength, oxidation resistance and corrosion resistance. Furthermore, their uneven surfaces contain numerous micropores that create an intricate network structure, greatly expanding contact area between phases. With such properties silicon carbide ceramic foam is emerging as the next-generation catalyst carrier replacing traditional silica, alumina and activated carbon catalyst carriers.

Foam ceramics can be coated with nanowires to extend their functions and performance in challenging separation applications. When immersed in molten aluminum, a nanowire-coated filter displays high collection efficiency for ions while its open-cell foam struts develop hair-like textures for even higher collection efficiency. Furthermore, nanowires can be arranged so they form an uninterrupted filter surface to facilitate high-efficiency, low-pressure aerosol filtration – ideal for use in chemical industrial furnaces, steam generators, radiant burners and high-pressure adiabatic burners – as they boast small size, fuel saving operation as well as wide power regulation range, stable combustion and low pollutant emissions compared with their counterparts.