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Materials of technical ceramics

Ceramic materials are non-metallic inorganic materials. Sembach has a wide range of different materials available, so that a wide variety of requirement profiles can be met by making the right choice. The customer's specifications determine the ideal material. It's good to know that Sembach has a high level of experience with its competent engineers and technicians.

Aluminum oxide (Al₂O₃) is a key material in our production range, manufactured from synthetic raw materials with purity levels of 80% to over 99%. It is characterized by outstanding properties:

  • Excellent hardness
  • High to maximum strength
  • High to very high thermal conductivity
  • Very good electrical insulation properties
  • Excellent wear resistance
  • Very good chemical corrosion resistance
  • Good thermal shock resistance
  • High to highest fire resistance

The further development A100 offers even better hardness and wear resistance. Thanks to an optimized raw material preparation process and special polishing techniques, A100 has an extremely fine-grained structure with a purity of more than 99.97 %. This results in increased density, hardness and strength as well as a flawless surface, ideal for demanding applications in textile machinery and other areas.

Mixed oxides, in particular ZTA (zirconia toughened alumina), consist of aluminum oxide and zirconium oxide in various mixing ratios, typically 20 % ZrO₂ and 80 % Al₂O₃. The addition of zirconium oxide significantly improves the fracture hardness and strength of the material, which is due to the “transformation reinforcement”. This reinforces the crack resistance by generating residual compressive stresses that prevent cracks from propagating or splitting.

The material properties vary depending on the mixing ratio, but in general mixed oxides combine the hardness of Al₂O₃ and the toughness of ZrO₂ . They offer

  • Good tribological properties
  • Very high strength with high hardness
  • Very good corrosion resistance
  • High fracture toughness
  • High wear resistance
  • Good surface quality

Mixed oxides are used in mechanically highly stressed components such as plain bearings and pump shafts.

Zirconium oxide, a high-performance ceramic, offers exceptional properties, for example in medical technology. It is mainly produced from electro-melted or chemically precipitated raw materials and is available in two types: MgO-stabilized (Mg-PSZ) and Y2O3-stabilized (Y-TZP). The material properties according to DIN VDE 0335/DIN EN 60 672 include

  • Excellent tribological properties
  • Outstanding strength
  • Very low thermal conductivity
  • High corrosion resistance
  • High wear resistance
  • Very high fracture toughness
  • High thermal expansion
  • Depending on the composition, a good oxygen ion conductivity can be achieved
  • Very high surface quality

It is used in various industries such as the textile industry and medical device technology, for thread guides, drawing cones, components in plain bearing technology and for knives, scalpels and tweezers.

Steatite, made from 90% soapstone, is a magnesium silicate with high workability and strength. Fired at 1,300 to 1,400°C, the actual steatite material is only created during sintering. This occurs during sintering through crystal formation, melting and dissolution processes. Under the name STEALAN, we offer joint-sealed high-frequency steatite with very good properties, including

  • High mechanical and thermal load capacity
  • Good heat insulator
  • Best electrical insulation properties
  • Low shrinkage, therefore good dimensional stability
  • Complicated components are easy to manufacture
  • Resistant to ageing for years
  • Resistant to UV radiation
  • Manufactured from very inexpensive raw materials, ensuring a very good price-performance ratio

Our customers use STEALAN for controller parts, switches, insulating bushings, axles, bushings and more.

Superpyrostat, a porous high-frequency steatite, is soft-fired and impresses with its good workability. Fired at 800 to 1,100°C and made mainly from soapstone, clays and fluxes, it offers

  • Strength and porosity specifically adjustable
  • High contact resistance
  • good machinability
  • Low shrinkage, therefore good dimensional stability
  • Complicated components are easy to manufacture
  • Manufactured from very inexpensive raw materials, ensuring a very good price-performance ratio

Our customers use Superpyrostat for high-performance cartridges and seals in lambda sensors.

Cordierite is characterized by excellent temperature properties, as it hardly shows any changes even when exposed to heat. Made from natural raw materials such as soapstone, clay, kaolin, corundum and mullite and fired at temperatures of 1,300 to 1,400°C, it offers

  • Very small defined thermal expansion
  • therefore very high thermal shock resistance
  • Good insulation properties
  • Low shrinkage, therefore good dimensional stability
  • Manufactured from very inexpensive raw materials, ensuring a very good price-performance ratio

Application examples include spark arrester plates, expansion rods for thermostats, burner nozzles for auxiliary car heaters and heating conductor supports for demanding temperature tasks.

Pyrostat, a cordierite ceramic, is characterized by selectively adjustable porosity, regulated by sintering temperatures of 1,200 to 1,300°C. It is primarily used in applications with high heat resistance and is available in three quality grades: C511, C520 and C530, each with guaranteed thermal shock resistance.

The advantages of Pyrostat include

  • High heat resistance
  • Very small defined thermal expansion
  • in combination with the adjusted porosity, this results in extremely good thermal shock resistance
  • Manufactured from very inexpensive raw materials, ensuring a very good price-performance ratio

Examples of applications include heating plates, sectional heating elements, tubes for heating cartridges and heating conductor supports.

The high-performance ceramic silicon nitride (Si₃N₄) is an extremely resilient lightweight material with outstanding properties for high-temperature applications and demanding environments. We manufacture prototypes and large series parts economically using injection molding, dry pressing and 5-axis milling machine processing.

Silicon nitride is unrivaled in terms of hardness, flexural strength, fracture toughness and wear resistance.

  • low density of 3.2 to 3.3 g/cm³
  • High flexural strength (up to 1,000 MPa)
  • High wear resistance
  • Good friction coefficients (extremely low sliding friction)
  • High temperature resistance
  • High creep resistance
  • High fracture toughness (7 MPam1/2)
  • low coefficient of thermal expansion and the associated
  • High thermal shock resistance (“thermal shock resistance”)
  • Operating temperatures of up to 1,300° C
  • Good resistance to corrosion, aggressive chemicals and molten metals (such as aluminum and magnesium)

Silicon nitride is used in combustion engines, power units, energy and chemical engineering systems, seals, sliding rings, pump impellers, guides, cutting tools, foundry and forming tools as well as welding nozzles and carrier plates for silicon wafer processing.