Carbon graphite is a compound formed by mixing an amorphous carbon with graphite. You can find it in a variety of shades ranging between black and steel-gray.
Features of Carbon Graphite
You will find some very distinct features specific to the carbon graphite you want to use. Let us list down a brief description of some of them:
Resistance to Temperature
Carbon graphite can perform exceptionally well in oxidizing applications with temperatures between 200°C and 600°C. They can equally work well in non-oxidizing applications having temperatures of around 3000°C.
Due to their low coefficient of thermal expansion, they are perfect for cryogenic temperature applications of between -35°C and -270°C. They can retain their shape and size in such conditions with just a slight variation.
Resistance to Corrosion
Carbon graphite can withstand very many corrosive elements. You can use them in applications having sulfur dioxide, petroleum among very many other chemicals without impacting it.
This is because the carbon atoms in them are strongly held together by covalent bonds forming hexagonal structures. The strength of these bonds resists any form of corrosion from such chemicals.
Self-Lubricating
The Van der Waals forces that bind the graphene layers inside the carbon graphite are very weak. This means that the graphene layers can easily rub off on another surface in contact with the carbon graphite.
The carbon graphite fills any rough surface between them by creating a dynamic film. This makes it possible for it to lubricate against itself even in dry environment applications.
Porosity
When the carbon graphite is baked during manufacturing, hydrocarbons are eliminated in outgassing process. The extreme heat pushes this gas out leaving a porous network in the amorphous carbon structure.
The porous network means we can easily impregnate it with additives such as resins and metals. They will reinforce your carbon graphite in terms of its mechanical and chemical properties.
How Carbon Graphite Is Made
We can create carbon graphite by combining amorphous carbon with graphite. Remember that these two both types of carbon have different physical and mechanical traits.
The desirable traits of amorphous carbon include resistance to wear, physical strength, and hard. You will find a weak and soft structure in graphite that makes it self-lubricating.
The two are first mixed with and then coal tar pitch is added as a binder. The mixture is then placed into molds of your desired shape and then compressed.
After compression molding, these parts have to be roasted at extremely high temperatures. This process is carried out to enable the coal tar pitch to carbonize.
This forms a solid strong component having both carbon and graphite. It is resistant to compression and shows no effect when exposed to extremely heavy load tests.
The carbon graphite is then placed in an oven and baked at very high temperatures. This leads to outgassing where the hydrocarbons are expelled from the solid structure.
This is where the carbon graphite achieves its porosity from the network of holes created. You basically have a structure that looks like a solid black sponge.
To enhance the chemical and mechanical properties, we can impregnate these holes with metal, resins and many other fillers. Depending on the application, they will improve its thermal properties and strengthen it.
Carbon Graphite Vs Graphite
Carbon graphite and graphite may be all made of carbon but they are two different elements. For starters, we know that graphite is entirely made of carbon atoms structured in a particular design.
This makes it an allotrope of carbon just like diamond. On the other hand, you get graphite carbon by mixing amorphous carbon and pure graphite using a binder.
This fuses both the physical and mechanical properties of both components. This makes carbon graphite superior in physical and mechanical qualities to graphite.
Benefits Of Carbon Graphite
When you use carbon graphite in your application, you stand to gain various benefits mainly from its properties. We can take a deep dig at some of them below:
High Temperature Range Application
You can use graphite electrodes in a wide range of temperatures from non-oxidized, oxidized and cryogenic applications. This gives it an operation from around -270°C to temperatures slightly above 3000°C.
Wet and Dry Environments
Since they are self-lubricating, you don’t have to add any lubrication where the application has dry conditions. This lubrication can also not be washed away unlike oil and grease in wet environment applications.
Dimensionally Stable
Carbon graphite’s coefficient of thermal expansion is very low meaning temperature has no significant impact on its size. This means that it does not expand/contract or deform easily in extreme temperature conditions.
Wear Resistant
You can be assured of excellent performance of your carbon graphite because it does not wear out easily. This is because of its excellent thermal properties combined with the fact that it can self-lubricate.
Corrosion Resistance
Being that it is chemically inactive, you can easily apply it in corrosive environments. It is also protected from effects of oxidation through porous impregnants such as salt.
High Thermal Conductivity
This means that your carbon graphite can dissipate or transfer heat generated in your application from friction. Materials having a low thermal conductivity normally transfer operational heat at a very low rate.
Carbon Graphite for Specialty Parts
If you have ever been in a situation where you had to replace a specialty part, then carbon graphite must had been an option. Most people prefer carbon graphite as a replacement for such because of several reasons.
Besides having excellent natural self-lubricating properties, carbon graphite can withstand high temperatures and corrosion. Additionally, it is both strong and hard therefore ensuring durability for your part.
Since it is thermally stable, you can comfortably use it in areas prone to both corrosion and chemical effects. If you are to improve its versatility, you can easily impregnate it with oxidation inhibitors or even resins.
If you can machine it with precision, you can get parts that have run out of stock. You can even have the most obscure part machined with a guarantee that it will stand the test of time.
Applications of Carbon Graphite
Carbon graphite is a versatile material that you can use in very many applications across various industries. This is major because of its ability to withstand high temperatures, self-lubricate, and with good thermal properties.
We can analyze its application based on the components that we can make out of it. Some of them include:
- Ball valve seats
- Various types of bushes and bearings
- Making vanes used in various industrial pumps
- Fabricating specialty parts
- Various seals such as mechanical seal faces and seal rings in cryogenic applications
- Wear plates
Conclusion
Carbon graphite can offer a wide variety of advantages when used in your applications. With their carbonaceous bonding that can withstand high temperatures, they combine various elements of carbon and graphite.
It takes the self-lubricating trait of graphite and blends it with carbon’s strength and wear resistance. They can be enhanced with various impregnants to give you a formidable material having excellent chemical and mechanical traits.
More Resources:
Graphite – Source: WIKIPEDIA
Graphite Properties – Source: BRITANNICA
