Glassy carbon, is a kind of pure carbon material, which combines the performance of glass and ceramic together with graphite. While, different with Graphite, the glassy carbon is with the structure just like that for Fullerene, which makes it with it`s own performances. Glassy carbon can be machined to glassy carbon rod, plate and tube, as well as different shapes of glassy carbon crucibles.
The glassy carbon can be used in vacuum or inert gas environment at 3000°C . Compared with other ceramic or metal thermal resistance materials, the strength of the glassy carbon can be strengthened as temperature becomes higher, and reached at max. 2700K, at 2700K, the glassy carbon is twice the strength as that at room temperature. Compared with ceramic and metal materials, glassy carbon won`t get embrittlement even at high temperatures, and with higher thermal shock resistance. So, it can be heated or cooled down in short time. Furthermore, the glassy carbon is with light weight, low thermal absorption and low thermal expansion, so, it can be used almost in all high temperature applications. The typical sample is used as a protection tube of high temperature meter, material loading system and high temperature furnace spare parts.
Due to its exceptional properties, glassy carbon is very advantageous for many different applications in the chemical industry. It offers a high corrosion resistance which makes it suitable for the chemical analysis. Compared with conventional laboratory equipment fabricated in platinum, gold and other corrosion resistant metals, special ceramics and fluoric plastics, equipment manufactured from affords a number of major advantages:
♦Resistance against all wet decomposition agents，
♦No memory effects (uncontrolled adsorption and desorption of elements)，
♦No contamination of the analytical sample，
♦Resistance against acid and alkaline melts，
♦Non-porous, glassy surface，
♦Main products include crucibles, beakers, boats and dishes for fuming-off, evaporating, melting and decomposition etc.
Melting crucibles of glassy carbon are applied in the dental technology for melting noble metal and titanium alloys. melting crucibles are notable for the following properties:
♦High thermal conductivity
♦Much longer service time than graphite crucibles
♦No adhesion of noble metal melts
♦Resistance to thermal shock
♦Suitability for all noble metal and titanium alloys
♦Use in induction-heated casting centrifuges
♦Generates a protective atmosphere over the metal melt
♦No melting salt required
High purity, extreme corrosion resistance, no particle generation, electrical conductivity and good mechanical properties make glassy carbon to an ideal material for the semiconductor production. Glassy carbon crucibles and boats are used for zone melting of semiconductor components, gallium arsenide synthesis, and monocrystal growth by the Bridgman or Czochralsky method. Glassy carbon is used for parts in ion implanting systems and electrodes for plasma etching systems due to its extreme resistance. The high X-ray transmission of glassy carbon is advantageous for the X-ray lithography. Glassy carbon wafers are used as substrate materials for X-ray masks.
Glassy carbon is resistant against biological systems and shows an excellent compatibility with blood and tissue. Good mechanical properties at low density, high purity and biocompatibility make glassy carbon to an interesting material for medical technology and biotechnology. Glassy carbon has a high X-ray transmission due to its low atomic number which is important for applications in the medical radio technology.
High temperature resistance, inert behavior, good thermal conductivity and high purity are some characteristics of glassy carbon which are advantageous when used as a material for vessels in metallurgy, monocrystal growth and ultrapure materials technology. The vessels can be used as susceptors in induction furnaces. Dental metal melting technology, zone melting of semiconductor components, gallium arsenide synthesis, monocrystal growth by the Bridgman or Czochralsky method and the synthesis of fluorescent compounds are a few typical industrial applications.
Melting vessels of show a demolding with a very high surface quality, no contamination by foreign elements and due to the hardness and wear resistance no carbon traces in the melting substance. Metal melts which do not form carbides have no wetting effect. Its good thermal shock resistance allows rapid heating and cooling times and red-hot crucibles do not crack when placed on cold surfaces.
Glassy carbon shows due to the low atomic number of carbon a high transparency for X-rays. This is advantageous for many applications e.g. X-ray windows for synchrotron beamlines or masks for X-ray lithography.
Glassy carbon is an ideal material for components in the glass industry. Glassy carbon is high temperature resistant in inert gas or vacuum up to 3000°C. Unlike all other ceramic and metallic high temperature materials, glassy carbon increase in strength with a rise in temperature up to 2700 K. It shows at 2700 K compared to room temperature the double strength. Glassy carbon has an extremely high resistance to thermal shock. Therefore short heating and cooling times are possible without any problems. Glassy carbon shows no wetting by molten glass. Due to the hard and smooth surface glassy carbon doesn’t show any particle generation like other carbon materials which would cause contaminations. Further advantages are the smooth surface, low thermal conductivity and low thermal expansion.
High temperature resistance in inert gas or vacuum up to 3000°C
Glassy carbon SIGRADUR? is high temperature resistant in inert gas or vacuum up to 3000°C. Unlike all other ceramic and metallic high temperature materials, glassy carbon increase in strength with a rise in temperature up to 2700 K. Glassy carbon shows at 2700 K compared to room temperature the double strength. Compared to ceramic and metallic materials, glassy carbon shows even at high temperatures no embrittlement.
Glassy carbon is made of pure carbon. The other materials besides carbon in it are extremely low in content, when heated over 2000°C, ?At these high temperatures the most foreign elements vaporize and only pure carbon remains. Due to the high purity glassy carbon is suitable for applications in the chemical analysis, semiconductor technology and ultra pure materials technology. Glassy carbon shows no memory effects which is advantageous in the ultratrace analysis.
Extreme corrosion resistance
Glassy carbon has an extreme corrosion resistance. Due to the closed microstructure glassy carbon doesn't form intercalation compounds. This gives extremely high resistance to corrosion by acid and alkaline agents and melts. Strong oxidizing substances like oxygen over 600°C and hot melts and acids with a powerful oxidizing action are the only substances to attack glassy carbon. But even here tests showed that glassy carbon is the most oxidation resistant carbon material.
Due to the high purity the catalytic action of foreign elements (reaction centres) concerning oxidation and corrosion is limited to a minimum. Glassy carbon shows a higher corrosion resistance to oxidizing substances like nitric acid, perchloric acid or oxygen. The oxidation speed of glassy carbon in boiling 65% nitric acid is 24 fold lower than glassy carbon.
Impermeability to gas and liquid, no open porosity
Glassy carbon is an impermeable material comparable with silica glass. The helium permeability as determined by the vacuum drop method is only 10-11?cm2?s-1. Thus glassy carbon is an ideal material for the vacuum technology.
No wetting by melts
Glassy carbon shows no wetting by many saline, metallic and ceramic melts. This is advantageous in the metallurgy, ultra pure materials technology and glass industry.
High hardness and strength
The mechanical properties of glassy carbon, like hardness and strength, are comparable with these of high-performance ceramics. Unlike all other ceramic and metallic high temperature materials, glassy carbon increase in strength with a rise in temperature up to 2700 K. Glassy carbon shows at 2700 K compared to room temperature the double strength.
Glassy carbon has despite the high strength a very low density. E.g. charging equipment made of glassy carbon has due to the low mass a very low thermal absorption which enables short heating and cooling times. Also for light weight constructions and high dynamic stressed units glassy carbon is used due to its low density.
High surface quality, no particle generation
Glassy carbon has a very high surface quality and can be polished. Due to the hard and smooth surface glassy carbon doesn't show any particle generation like other carbon materials. Therefore it is very suitable for the semiconductor and glass industry.
Low thermal expansion
Glassy carbon has a very low and isotropic thermal expansion comparable with silica glass. Therefore it retains its shape under heat which is very advantageous for all high temperature applications.
Extreme resistance to thermal shock
In comparison to the most ceramic and metallic materials glassy carbon has an extremely high resistance to thermal shock. Therefore short heating and cooling times are possible without any problems.
Isotropy of physical and chemical properties
Glassy carbon is an isotropic material. Due to its fullerene-related microstructure glassy carbon has no directional material properties.
Good electrical conductivity
Glassy carbon is electrical conductive and thus suitable for e.g. the electrochemistry and sensor technology. Melting crucibles can be heated inductively.
Glassy carbon is resistant against biological systems and shows an excellent compatibility with blood and tissue. Good mechanical properties at low density, high purity and biocompatibility make glassy carbon SIGRADUR? to an interesting material for medical technology and biotechnology.