High Performance Technical Ceramics with a Wide Range of Properties for Use in Diverse Applications by CeramTec

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Background

The term "high-performance ceramics" refers to a variety of often highly-specialized ceramic materials. These materials demonstrate a unique spectrum of mechanical, electrical, thermal and biological/chemical characteristics. High-performance ceramics are invariably used in situations where other materials, such as plastic or metal, cannot withstand the extremely high loads.

There are truly a multitude of applications for high performance ceramics, due to the specific characteristics or qualities that each ceramic material has. Although in most cases these qualities cannot be seen by end users of CeramTec products, they play an important and often crucial role.

Machinable Ceramics

GRADE A LAVA exhibits good electrical and heat resistance. It is excellent in applications where close tolerances must be held. This material is available in a variety of shapes and sizes.

Steatites

Steatites used in place of aluminas are a cost-effective way to meet performance requirements. They are easier to form and fire at lower temperatures.

Steatites grade 645 L423C has good electrical properties. It is especially well suited for complicated pressed pieces.

Steatite grade 665 L533C has low dielectric loss. It makes excellent insulators for radio frequency applications.

Steatite grade Frequenta® also has low dielectric loss, but has been developed for superior strength and low thermal conductivity for higher temperature applications.

Cordierites

Cordierites have low coefficients of thermal expansion and excellent resistance to thermal shock. They offer a range of thermal expansion, mechanical strength and porosity criteria. They excel as cost-effective extruded and dry-pressed forms.

Cordierite grade 447 offers excellent thermal shock resistance with high continuous porosity, suitable for applications such as welding tile.

Cordierite grade 547 offers very good thermal shock resistance with improved flexural strength due to its semivitreous properties. It is able to withstand rapid temperature fluctuations, such as those found in oil burner applications.

Cordierite grade 701 also offers very good thermal shock resistance, good flexural strength and 0-1% porosity due to its vitrified properties. This cordierite can self-glaze. It is suitable for applications such as commercial heater supports.

Cordierite grade Sikor® S and Sikor® E offer higher compressive strength with slightly lower thermal shock resistance.

Alumina Ceramics

Aluminas exhibit good mechanical properties such as hardness, compressive and tensile strength and elastic modulus. They perform well at elevated temperatures.

Rubalit® 702 alumina is a state-of-the-art material for the manufacture of metal-film resistors. With an alumina content of 85%, it provides extreme hardness and high thermal conductivity. Practical applications have shown that Rubalit® 702 is capable of diffusing as much heat as the cap and film. Its extreme hardness necessitates laser trimming of the film material

Alumina grade 771 (94%) offers good electrical and mechanical properties. It is easily metallized by the moly process.

Alumina grades 614/698 (96%) is a high-strength alumina with good mechanical properties and good wear and chemical resistance. It also features excellent electrical properties. 614 is white; 698 is pink.

Rubalit® A1896 (96%) is an alumina ceramic with an optimum price/performance ratio. Its outstanding properties are low density, low weight, high corrosion and wear resistance, excellent electrical isolation, and anti-friction properties for sliding materials such as sintered metal and carbon.

Alumina grade Rubalit® 708S (96%) features high strength and thermal conductivity. It provides outstanding results when used on commercially available thick-film pastes and metallization systems.

Alumina grade 975 (99.5%) offers unique technology by virtue of its optimal dispersion of the MgO phase with the alumina grains. With virtually no transgranular porosity in its microstructure, 975 exhibits high density, superior wear resistance and moderate flexural strength. Another advantage is its highly uniform white color compared to conventional 99.5% aluminas. The material's white color remains consistent under either reducing or oxidizing conditions.

Alumina grade Rubalit® 710 (99.6%) produces optimum results and is considered the material of choice for thin-film technology. Its characterizing features are high strength and thermal conductivity.

Alumina grade Rubalit® A1999.5 (99.7%) is mechanically stronger, features a higher heat conductivity, and is more corrosion resistant. This high-purity alumina ceramic with carbon materials is especially suitable for plain bearings and seal rings.

Alumina grade 433 (99.9%) exhibits high hardness. Its fine, equiaxial microstructure provides excellent sliding and abrasive wear resistance. This material is ideal for corrosive conditions. A higher degree of surface finish (approaching 0.2 µin., Ra) is available for applications such as textile guides and mechanical seals.

Toughened Alumina Ceramics

Toughened alumina grade 950 has a combination of high strength (from zirconia) and high hardness (from the alumina phase). It has excellent wear resistance, both in sliding and abrasive conditions. This material offers a good compromise between toughened zirconia and alumina. It is a good choice for applications that require higher strength but lower hardness compared with alumina (e.g., textile wear parts). Produced with total dispersion of the zirconia phase in the alumina phase, 950 offers consistent performance, lot to lot.

Toughened alumina grade 965 has high fracture toughness and strength. Its fine dispersion of zirconium oxide gives very uniform microstructure and properties. This material is good for nozzles where thermal stresses are high.

Aluminum Nitride Ceramics

ALUNIT® aluminum nitride offers an extremely high thermal conductivity of 180 W/mK and outstanding electrical insulation properties. It is the high-end supplement to our Rubalit® alumina range. The thermal expansion coefficient of this material is comparable to silicon. Its electrical and mechanical characteristics are similar to alumina. Like Rubalit® alumina, ALUNIT aluminum nitride is non-toxic and environmentally compatible, presenting no disposal problems.

Titania Ceramics

Titania grade 192/193 is an excellent material for textile and other structural applications, where superior surface finishes are required with high chemical resistance. Titania grade 193 is identical except it is metallic gray in color and conducts static electricity.

Zirconia Ceramics

Tetragonal zirconia exhibits high flexural strength and superior low temperature stability. It features higher impact strength and erosive wear resistance as compared to alumina.

848 TTZP (yellow) zirconia is recommended for applications where high fracture toughness is required, with higher elastic modulus.

ZN 40 is a zirconia ceramic with an excellent surface finish and a higher strength than alumina. Its good crack resistance and anti-friction properties, combined with steel-like thermal expansion attributes, make this material an ideal partner for bearing composites working at elevated temperatures.

If the characteristics of these materials do not meet your requirements, we will draw upon our experience with hundreds of custom formulations and bodies to match the requirements of your application. Examples are alumina tapes for microelectronic applications and leachable materials for ceramic cores.

Silicon Carbide Ceramics

Rocar® silicon carbide is an extremely lightweight silicon carbide ceramic. It permits a reduction in mass forces at high speeds, and is considered remarkable for its hardness, excellent resistance to corrosion and sudden changes in temperature, excellent anti-friction properties, and higher heat conductivity over steel. The various types of Rocar silicon carbide include sintered and silicon infiltrated silicon carbide.

CD 101 is a zirconia reinforced silicon carbide designed for maximum hardness.

Silicon Nitride Ceramics

SL 200 B is a silicon nitride ceramic especially suitable for components exposed to mechanical stress and engine-specific applications even at elevated temperatures. It is recognized for its high strength and crack resistance, as well as its resistance to sudden changes in temperature.

Aluminum Titanite Ceramics

Alutit® is an aluminum titanate, which is produced in a special reaction-sintering process, consists of high-purity aluminum oxide and titanium oxide. It offers excellent resistance to sudden changes in temperature, good heat insulation, low elasticity module, and good chemical resistance.

Piezoceramics

Piezoceramics require very little energy and their shape potential is almost unlimited. Such properties allow this material to be used in widely-ranging apparatus and mechanical engineering applications.

Sonox® piezoceramic materials are classified in two groups according to their chemical composition.

Group 1 (Sonox P 4, P 8, and P88) is designed to withstand high electrical control voltages and intense mechanical (pressure) loads. They feature low dielectric loss, dielectric constants between 1000 and 1600, and high Q values (between 500 and 2000). Materials of this type are well suited for high-performance ultrasonic applications in the 20 kHz to several MHz range.

Group 2 (Sonox P 5, P 51, and P 53) are highly sensitive materials characterized by dielectric constants in the 1000 to 4000 range and low Q factors that are < 100. They are used in a wide range of sensor applications, as well as for actuators.

Metallized Substrates

CeramTec's metallized Rubalit® alumina and ALUNIT aluminum nitride ceramic substrates feature excellent mechanical, electrical, and thermal characteristics. These products, which are metallized onsite in our own facilities, provide superior adhesion, wettability, and excellent performance consistency in soldering baths. Their base layer design is tungsten, screen-printed with a minimum layer thickness of 6 µm. An electroless nickel layer (approximately 2 µm) assures a good solder flow.

Source: CeramTec North America

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