Silicon carbide ceramic is an ideal material for applications requiring high dimensional stability across changing temperatures, while remaining chemically inert and offering good thermal conductivity.
Explore Saint-Gobain Hexoloy(r), our range of sintered refractory ceramics designed specifically for copper furnaces – hot face bricks and burner blocks as well as bell and bosh bricks!
High chemical inertness
Silicon carbide is inert to most chemicals at high temperatures and boasts an extremely low coefficient of expansion, making it the perfect material to use when dealing with aggressive chemistry. Furthermore, its inertness extends its lifespan and makes it resistant to oxidation and corrosion for longer than other materials.
Chemically inert and thermal shock resistant, sinterable SiC is also resistant to temperature variations within a kiln environment without cracking or degrading. Furthermore, its high thermal conductivity enables effective heat distribution within the kiln for improved firing results and energy efficiency.
Saint-Gobain Performance Ceramics & Refractories leverages SiC’s physical properties to craft innovative technical ceramic solutions for use across numerous industry applications, such as kiln furniture, burner nozzles, sliding earings, process components for semiconductor industry processes, passive armor for security & defense use and particulate filters. Hexoloy SE SiC extruded components made using pressure-less sintering of submicron powder are utilized in high purity applications and customized to meet customer requirements; these components are 50% harder than tungsten carbide yet impervious to contamination.
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Sintered Silicon Carbide (SSiC) is an extremely hard ceramic material produced through various production methods, such as dry pressing, casting and extrusion. SSiC can be found in applications ranging from ballistic-resistant ceramic armor for vehicles and aircraft to friction-free ultra-high purity applications like Hexoloy SA which has been engineered as an extremely hard and dense SSiC material that reduces any risk of contamination in ultra-purity settings.
Recent trends in semiconductor manufacturing industry include an ongoing decrease in acceptable levels of metallic contamination on processed wafers. Therefore, high purity materials have become an increasing requirement for kiln furniture. But existing siliconized SiC materials fall short of these specifications. Torti et al’s report in “High Strength Silicon Carbide for Use In Severe Environments” (1973) revealed that hot pressed SSiC bodies containing 95-98% SiC had poor thermal shock resistance – not surprising given their lower thermal conductivity compared to pure SiC. Achieve better thermal conductivity can be obtained by silicifying converted graphite SiC bodies that contain at least 71%vol %SiC.
High specific stiffness
Specific stiffness of silicon carbide is an integral characteristic for high-performance applications like ballistics and aerospace. In these fields, material must resist rotational forces while remaining temperature stable – these requirements are precisely met by Saint-Gobain’s Hexoloy sintered silicon carbide material.
Dynamic tensile behavior of ceramic materials can often be investigated through plate impact experiments (also referred to as spalling tests). When these experiments take place, an intense tensile stress is created when release waves from impactor and target collide, creating an immense tensile strain which quickly leads to damage and dynamic fracture.
To determine the defect population of both grades of silicon carbide used in this study, quasi-static four-point bending tests were carried out on specimens with dimensions of 5mm in height and 3mm width. The results indicate that PS-S grade, due to its more dispersed microstructure, has the lowest Weibull modulus and higher strain rate sensitivity than PS grade.
The characteristic time (tc) for sintering processes depends upon both their strain rate and defect population size, with it decreasing exponentially with increasing strain rate until reaching only few microseconds at very high strain rates.
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Silicon carbide’s hardness, rigidity, and thermal conductivity make it a suitable material for mirror surfaces on astronomical telescopes. Furthermore, its heat tolerance enables it to withstand high temperatures without expanding or contracting during extended space missions that occupy orbit for extended periods.
Hexoloy(r) SE silicon carbide is produced through pressure-less sintering submicron sic powder through an exclusive extruding process, yielding a fully sintered ceramic with a density of over 98% theoretical. It stands out among industrial ceramics as one of the hardest options with outstanding wear resistance against both rotational and sliding forces.
Saint Gobain silicon carbide stands out with its low thermal expansion and specific stiffness properties that enable it to serve as a lightweight structural component in industrial metrology equipment, such as CMM bridges and Z axes, positioning systems and CMM probes due to its ability to withstand high speed and precision measurements. Furthermore, its light weight and low thermal expansion also allow it to be utilized in temperature-critical applications like nuclear reactor oxidizing environments as well as its chemical inertness which makes it suitable for ceramic bearings and pistons among many other uses.
High oxidation resistance
Over time, metallurgical applications have become more demanding, necessitating high strength, thermal conductivity, and oxidation resistance from their products. Refractory products must meet these increasingly stringent criteria under higher load weights and shorter firing cycles – placing greater strain on them to meet this higher standard of performance. Enhanced nitride- and oxynitride-bonded silicon carbide compositions have been developed specifically to meet these challenges, providing extended life for immersion tubes in aluminum galvanizing furnaces or brick bottoms of reduction cells.
These new materials are made by reactant-sintered synthesis of alpha SiC powder, Si metal and carbonaceous material, then sintered under pressureless conditions to form their shape. They offer superior thermal conductivity with little or no porosity at maximum operating temperature of 1,350degC.
Saint-Gobain has also engineered an oxynitride-bonded silicon-carbide material known as Silit(r). To produce it, starting charge mixture containing particulate SiC is mixed with boron and carbon before siliconizing to form a refractory body. Boron helps increase volume change resistance under oxidative stress exposure to steam at 900degC, creating significantly greater resistance than standard nitride-bonded silicon carbides.
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