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Overview of glassy carbon crucibles
Glassy carbon is high-temperature resistant in inert gas or vacuum environments up to 3,000 °C. Unlike all other ceramic and metallic high-temperature materials, glassy carbon increases in strength with a rise in temperature up to 2,400 °C. Glassy carbon is thus twice as strong at 2,400 °C as it is at room temperature.
The material does not become fragile at high temperatures and has a high degree of resistance to thermal shocks. Repeated high-level heating and cooling are not problematic.
Principal characteristics of glassy carbon crucible
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Low heating and smelting times, as the metal melts faster and more homogeneously. Glassy carbon crucibles have a longer life-span than those made of ceramics or ordinary graphite.
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Glassy carbon crucibles are not porous.
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Its high degree of purity, the low specific surface area and the isotropic structure of a carbon crucible give rise to a slight oxidation which produces protective gas above the smelted metal helping to prevent the formation of oxide on the molten metal.
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Uniform casting is possible without wetting the surfaces of the crucible. This property remains intact throughout the life-span of the product.
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With their high resistance to thermal shocks, crucibles made of glassy carbon will not crack even when placed on cold surfaces when still hot.
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Glassy carbon crucibles can be used in induction heating.
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Glassy carbon crucibles are ideally suited for smelting palladium alloys and other alloys containing a percentage of noble metals. Glassy carbon crucibles are also used with rare metals and titanium alloys.
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Glassy carbon crucibles are not to be used for the smelting of steel or ferrous alloys.
Available standard products of glassy carbon crucibles
- Cylindrical crucible
- Conical crucible (high angle)
- Conical crucible (low angle)
- Lid
- Crystal growth crucible
- Crucible with dispensing spout
- Boat, incinerating dish
Other types of glassy carbon crucibles are also available
- Bars, 1 to 10 mm diameter
- Plates, 0.5 to 6 mm thickness
- Films, 60 to 180 μm thickness
- Tubes upon request
- Powders
Technical data of glassy carbon crucibles
|
References |
Grade K |
Grade G (crucibles) |
|
|
Density |
g/cm³ |
1.54 |
1.42 |
|
Open porosity |
% |
0 |
0 |
|
Max. temperature (vacuum or inert gas) |
°C |
1,000 |
3,000 |
|
Electrical resistivity |
Ohm.cm |
50.10-4 |
45.10-4 |
|
Young’s modulus |
GPa |
35 |
35 |
|
Flexural strength |
MPa |
210 |
260 |
|
Compressive strength |
MPa |
580 |
480 |
|
Vickers hardness |
HV |
340 |
230 |
|
Thermal expansion (20/200°C) |
10-6.K-1 |
3.5 |
2.6 |
|
Thermal conductivity |
W/m.K |
4.6 |
6.3 |
|
Permeability coefficient |
% |
1.10-11 |
1.10-9 |
We can machine parts out of glassy carbon from your plans. Contact us for more informations.
FAQs that can help you in this category
Graphite can withstand different temperatures depending on the atmosphere in which it is used. Its working environment directly affects its thermal performances.
In a vacuum or an inert atmosphere, graphite can withstand extremely high temperatures, even above 2,000°C. If oxygen is not present, the material retains excellent thermal and structural stability.
In air or an oxidising atmosphere, however, the maximum working temperature is lower. At around 400 to 500°C and above; graphite starts to oxidise gradually on contact with oxygen, leading to a degradation of its properties and loss of material.
Choosing the right graphite grade and considering the atmospheric conditions in which the graphite will be used is absolutely necessary to obtain the performance and lifetime needed for a given application.
The Final Advanced Materials team is at your disposal to help you choose the most suitable graphite solution based on your thermal and environmental constraints.
Due to its layered crystalline structure, graphite has excellent electrical and thermal conductivity properties.
This organisation facilitates the movement of electrons and the propagation of heat within the material.
However, graphite also has anisotropic properties: its conductivity varies depending on the direction of the crystalline layers. Conductivity is thus higher in the direction parallel to the layers than in the direction perpendicular to them.
Parameters such as the graphite's purity and density also influence its electrical and thermal characteristics. All these characteristics therefore determine the level of conductivity of the material.
Despite these variations graphite remains an excellent thermal and electrical conductor, which is particularly suited to many demanding industrial environments.
The Final Advanced Materials team is at your disposal to help you choose the most suitable graphite for your technical requirements.
Graphite is an excellent solution for aggressive chemical environments.
Due to its great chemical stability, it resists most acids and bases, including at high concentrations.
Unlike metals, graphite does not rust and does not dissolve in most corrosive environments, making it a material which is particularly suitable for demanding applications.
However, there are certain limitations which be taken into account. In the presence of oxygen and high temperature, graphite is subject to oxidisation which can impair its properties. In addition, in fluorinated environments, in particular in the presence of hydrofluoric acid, a direct chemical reaction with carbon can occur.
The choice of graphite and working conditions therefore depends on the application's chemical and thermal environment.
The Final Advanced Materials team is at your disposal to help you choose the best graphite for your technical requirements.
A graphite-loaded cement is a particularly suitable solution for repairing graphite parts.
Its chemical compatibility with the material, along with its thermal expansion and electrical conductivity, which are similar to those of graphite, make it a preferred solution for this type of application.
Ceramic-loaded cements are particularly recommended for localised repairs which do not require high a mechanical strength.
The Final Advanced Materials team is at your disposal to help you choose the best solution for your technical constraints.
Graphite naturally possesses lubricating properties which is one of its most widely acknowledged characteristics.
Due to its layered structure, where the different layers easily slide over one another, it is an excellent solid lubricant.
However, its performance can vary depending on the working environment. In an inert atmosphere or in a vacuum, its effectiveness diminishes due to the scarcity of gas and moisture, elements which make it easier for the graphite layers to slide over one another.
However, in an oxidising, high-temperature atmosphere the main challenge is its natural oxidisation, which can impair the graphite’s properties.
The choice of graphite therefore depends directly on the working conditions and on the constraints specific to your application.
The Final Advanced Materials team is at your disposal to help you select the graphite solution which is most effective and best suited to your needs.