What is silicon carbide honeycomb ceramic?

Silicon carbide honeycomb ceramics are honeycomb-shaped ceramics whose primary component is silicon carbide (SiC).

Silicon carbide (SiC) ceramic honeycomb not only exhibits excellent room-temperature mechanical properties—such as high flexural strength, outstanding oxidation resistance, good corrosion resistance, high wear resistance, and a low coefficient of friction—but also boasts the best high-temperature mechanical performance (including strength and creep resistance) among known ceramic materials. Materials sintered by hot pressing, pressureless sintering, and hot isostatic pressing can maintain their high-temperature strength up to 1600°C, making them the ceramic materials with the highest high-temperature strength. Moreover, their oxidation resistance is the best among all non-oxide ceramics. The main drawback of silicon carbide (SiC) honeycomb ceramics is their relatively low fracture toughness, indicating greater brittleness. To address this issue, in recent years, composite ceramics based on SiC honeycomb ceramics have emerged one after another, including fiber- (or whisker-) reinforced composites, composites strengthened by dispersed heterogeneous particles, and gradient-function materials, all of which have significantly improved the toughness and strength of the original monolithic material. Silicon carbide (SiC) honeycomb ceramics have found extensive applications in various industrial sectors, including petroleum, chemical engineering, microelectronics, automotive, aerospace, aviation, papermaking, laser technology, mining, and nuclear energy.

Silicon carbide honeycomb ceramics are a new type of ceramic product with a honeycomb-like structure that has been developed in recent years. From their initial use in catalytic converters for small automobiles to their widespread application today in industries such as chemical engineering, power generation, metallurgy, petroleum, electronics, and mechanical engineering, these ceramics are becoming increasingly prevalent, and their future prospects are quite promising.

The silicon carbide honeycomb ceramic for automotive applications involves a high-purity silicon carbide honeycomb ceramic collector designed for the efficient capture of particulate matter emitted by diesel engines. Pure silicon carbide is selected as the porous ceramic aggregate, and nano-sized silicon carbide is used as a sintering aid. The ratio of ceramic aggregate to sintering aid is controlled within the range of 100:1 to 15. A combination of organic substances such as methyl cellulose and tung oil, along with an appropriate amount of water, is employed as a binder and plasticizer; the ratio of organic substances to water is maintained between 1:1 and 1:3. The extrusion molding process is used to produce green bodies. By adjusting the proportions and amounts of organic binders and plasticizers, the non-solid-phase content is controlled within the range of 13% to 31%. First, the green bodies are heated using microwave heating followed by oven drying to remove moisture. Subsequently, conventional heating methods are applied to eliminate the organic components from the green bodies. Finally, atmospheric-pressure sintering is carried out. By varying the average size of micron-sized particles, adjusting the dosage of nano-sized sintering aids, and modifying the firing temperature, the pore structure of the honeycomb ceramic material can be regulated and altered to achieve a interconnected network-like distribution of pores.

Honeycomb ceramics consist of numerous equally sized pores arranged in various shapes. Currently, the maximum pore density has reached 20 to 40 pores per square centimeter, with a density ranging from 4 to 6 grams per cubic centimeter and a water absorption rate as high as over 20%. Thanks to their porous, thin-walled structure, these ceramics significantly increase the geometric surface area of the support material and greatly enhance their resistance to thermal shock. Among currently produced products, the mesh-like pores are predominantly triangular or quadrilateral in shape. Triangular pores exhibit much better load-bearing capacity and have a higher pore density than quadrilateral ones—a feature that is particularly important for catalytic supports. As the number of pores per unit area increases and the wall thickness of the pores decreases, the thermal-shock resistance of ceramic supports improves, and the temperature at which thermal-shock failure occurs also rises. Therefore, honeycomb ceramics must reduce their coefficient of thermal expansion and increase the number of pores per unit area. The coefficient of thermal expansion is a key performance indicator; currently, overseas standards specify α25-1000℃ ≤ 1.0 × 10⁻⁶ ℃⁻¹, which represents a certain gap compared to domestic levels. However, this gap is steadily narrowing. Initially, the raw materials used for manufacturing honeycomb ceramics mainly included kaolin, talc, aluminum powder, and clay. Today, however, the range of raw materials has expanded dramatically—particularly with the use of diatomaceous earth, zeolites, expanded clays, and refractory materials. As a result, honeycomb ceramics are finding increasingly broad applications and are continually improving in performance.

In addition to honeycomb ceramics used for sintering and shaping, non-sintered honeycomb ceramics have also emerged, significantly enhancing the catalytic performance and activity. Moreover, the external dimensions have evolved from the smallest spherical-ring shapes to larger-sized pillars, as well as square and circular forms. Depending on the mold design, honeycomb ceramics can be fabricated in various sizes, shapes, and structures. For instance, molecular sieve catalysts used in the petrochemical industry for air adsorption and drying in oil refining processes can reach dimensions of up to 0.8 meters in length and 0.25 meters in width, with a pore density of up to 25 pores per square centimeter. Significant changes have occurred in terms of raw materials, manufacturing processes, and mechanical engineering—especially in the production technology, which has seen substantial improvements. As catalysts, honeycomb ceramics must not crack during the manufacturing and shaping process; organic components must be completely removed. In addition to wear resistance, these ceramics are required to possess a certain level of mechanical strength and be capable of being regenerated and reused multiple times.

The main products of honeycomb ceramics include dozens of items such as thermal storage packing materials, activated carbon, activated alumina, molecular sieves, ceramic balls, tower packing, and catalysts. The thermal capacity of the honeycomb ceramic used for thermal storage packing materials exceeds 1000 J/kg·K, and its operating temperature is ≥1700℃. In kilns such as heating furnaces, baking ovens, soaking furnaces, and cracking furnaces, this material can save more than 40% of fuel, increase production by over 15%, and reduce flue gas temperatures to below 150℃.

After activated carbon powder or granules are shaped into honeycomb ceramic structures, their capacity for water purification and wastewater treatment is significantly enhanced. This is particularly true in the pharmaceutical industry, where they excel at dehydrating, decolorizing, and removing impurities from antibiotics, hormones, vitamins, nucleic acid injections, various injectable drugs, and other pharmaceutical products.

Honeycomb ceramic packing boasts advantages such as a larger specific surface area and superior strength compared to other shaped packings. This enables more uniform gas-liquid distribution, reduces bed resistance, and delivers enhanced performance. Additionally, it has a longer service life and performs exceptionally well as packing material in the petrochemical, pharmaceutical, and fine chemical industries.

Honeycomb ceramics offer greater advantages when used as catalysts. Utilizing honeycomb ceramic materials as a support and employing unique coating materials made from precious metals, rare-earth metals, and transition metals, these catalysts exhibit high catalytic activity, excellent thermal stability, long service life, and high mechanical strength.

Honeycomb ceramics used in catalytic cracking are gradually replacing existing products. Catalytic cracking uses heavy distillates—ranging from 200 to 500°C—as feedstock (including vacuum distillates, straight-run light diesel oil, coker wax oil, and others), with silicoaluminate catalysts. The reaction temperature typically falls between 450 and 550°C (varying depending on the reactor type). This process boasts high production volumes—each large-scale catalytic cracking unit processes over a million tons of oil per year—and demands stringent technical conditions. For instance, the catalyst must be regenerated every few minutes or even seconds upon contact with the oil, and the fluidized-bed catalyst is fed at a rate of 10 tons per minute or more. As catalytic activity improves, stricter regeneration conditions become necessary to accelerate the regeneration process—for example, temperatures ranging from 600 to 650°C, or even up to 700°C. Consequently, catalyst consumption is substantial: approximately 0.3 to 0.6 kg of catalyst is consumed per ton of feedstock. Catalysts with poor mechanical strength suffer even greater consumption. Therefore, even slight improvements in catalyst activity, selectivity, and stability would have significant practical implications for production. For this very reason, honeycomb ceramic catalysts are constantly being refined and upgraded, and market demand continues to grow. These catalytic cracking catalysts are increasingly being replaced by honeycomb ceramic catalysts; honeycomb ceramic catalysts with larger dimensions and higher pore densities are now emerging and demonstrating strong growth potential.