Silicon carbide ceramic filters are essential components in various industrial processes that require the filtration of liquid metal to remove impurities and ensure high-quality products. Their open pore structure offers both excellent mechanical strength and temperature resistance.
To achieve a more desirable rheology, previous formulations using alumina and fused silica were switched out for fumed silica; this switch resulted in better flow properties as well as increased room temperature strength and high-temperature strength.
Rheology
Silicon carbide (SiC) is an advanced ceramic material composed of silicon and carbon. Found naturally as the extremely rare mineral moissanite, SiC is now mass-produced as synthetic silica for industrial uses such as abrasives and other high-performance applications. SiC has many desirable characteristics including very low thermal expansion coefficient, high hardness, resistance to chemical corrosion, excellent strength at elevated temperatures and good electrical conductivity – qualities which have made it indispensable in national defense, automobile engineering, information electronics and space technology applications.
This invention provides a ceramic foam filter composed of silicon carbide (20-35%), zirconium oxide (10-20%), fused silica (10-20%) and binder (1-10%) applied as a slurry to a polyurethane sponge and sintered between 1100-1450 deg C. This new formulation significantly enhances its rheological characteristics and allows for the addition of an antifouling agent; furthermore providing improved chemical stability, mechanical strength and superior permeability compared to traditional oxide ceramics such as alumina and zirconia.
In order to identify an ideal formulation, an experiment was conducted where fumed silica replaced both alumina and fused silica in an experiment. The results demonstrated that this new composition produced filters which were approximately two times stronger at room temperature compared to prior art silicon carbide filters; additionally, their high temperature strength was more than two and one half times greater.
Strength
Silicon Carbide Ceramic Foam Filters have numerous applications. They’re especially beneficial when purifying molten metal casting alloy to ensure high quality castings while avoiding thermal shock, while they’re ideal for use in metallurgy as they can withstand both high temperatures and harsh chemicals.
Foam filters are composed of ceramic slurry containing both fused silica and colloidal silica; adding colloidal silica can improve its thixotropic characteristics and primeability, reduce inclusions in molten metal, provide laminar flow for better cleaning purposes, and help increase thixotropy characteristics of the mixture.
Silicon Carbide Ceramic Foam Filters’ high-temperature strength can be determined by the combination of fumed silica and alumina present within their composition, with various amounts being tested until an optimal formulation was found which offers both room temperature and high-temperature strength.
Ideal slurry formulations contain large quantities of alumina and fumed silica for maximum strength, yet it may still contain some fused silica without significantly impacting its high temperature strength. This is because adding some fused silica makes the mixture easier to machine, which may prove helpful in certain circumstances.
Breakage
Silicon carbide is a strong, tough material. Its low thermal expansion and high hardness make it suitable for a variety of industrial applications, from armored vests to brakes. But one of its most important roles is in filtration. Its porous structure allows it to capture contaminants and meet drinking water regulatory standards. It also improves efficiencies and reduces costs by reducing the number of treatment steps required.
Until recently, ceramic foam filters were prepared by firing a suspension of silica powder and a pore-forming agent in an open hearth furnace. These materials were used in various molten metal production processes to filter impurities and entrapped gases. The resulting ceramic foam had high mechanical strength, inertness to molten metal and chemicals, and stable pore sizes.
In the past, it was necessary to use alumina binder in the preparation of the slurry that was used to make these ceramic foam filters. This resulted in a lower temperature resistance and a reduction in the hot strength of the filter. The invention of alumina-free ceramic foam filters has allowed for a significant increase in the strength, particularly the hot strength, of these products.
These new filters are made from recrystallized silicon carbide (R-SiC), a material that Saint-Gobain Performance Ceramics & Refractories has been developing and producing for decades. In fact, this unique material forms the core of our innovative Crystar FT membrane system designed for liquid purity, security and sustainability.
Maintenance
Silicon carbide ceramic foam filters are essential components in many industrial processes that require molten metal filtration, helping produce superior end products by filtering out impurities that could otherwise contaminate them. They have excellent mechanical strength and are resistant to chemicals and metals – qualities which make them suitable for casting of copper alloys among many other uses.
Silicon carbide ceramic filters are created by mixing silica powder with binder and then sintering it to form a porous ceramic, which can then be used to filter liquids from solids such as mud, organic material and bacteria – eventually yielding clean water suitable for drinking or other applications. Ceramics make an effective material for liquid filtration due to their high specific surface area and low pore size – this makes ceramics superior compared to alternatives such as glass-like silica.
Maintaining a silicon carbide ceramic foam filter on an ongoing basis is essential to its proper operation, including cleaning, replacing worn parts as they wear down, and repairing any damages that occur. Maintenance schedules will depend on usage patterns; maintenance could range anywhere from weekly to monthly visits.