Graphite is unique because of its fascinating combination of softness and high strength.
The hardness of graphite is a crucial factor that you should consider when determining suitability for different mechanical applications.
Whether you want to use graphite in industrial, aeronautical, space exploration or any other industry, it is important to understand facts hardness of graphite material.
How Hard is Graphite?
Graphitehas a Mohs hardness between 1 and 2 and this makes it be grouped as a soft material. Graphite’s atomic structure is organized in layers of carbon atoms.
These atoms are held together by weak van der Waals forces and this permits them to slide over each other with much ease.
Carbon atoms are covalently bonded creating a planar hexagonal network.
Additionally, covalent bonds contrast the weak interlayer forces. As a result, it provides stability and strength to the layers. Remember, the fact that graphite layers can slide over each other maker it a perfect options for your lubrication applications.
Additionally, the soft nature makes graphite for pencil a common application. Graphite pencils are popular for normal writing and other artistic work.
Although graphite is soft, it has high strength and thermal resistance making it applicable in several industries like the aerospace, electronics and manufacturing industries.
Understanding Graphite Hardness Scale
The Mohs hardness scale is a common system for determining material hardness.Looking at the system, you will realize it ranges from 1 which represents the softest material (talc) to 10 which represents the hardest material(diamond).
Relating Graphite Hardness to Mohs Hardness Scale
Graphite leans on the softest side ranging between 1 and 2. Although this range implies that graphite is vulnerable to scratching or being indented, it does not determine the material’s resilience. You will realize this is quite evident in high-temperature environments.
Graphite’s hardness can change depending on whether it is in natural graphite or synthetic graphite. Additionally, other variables such as impurity and structural integrity also affects the graphite hardness.
Natural graphite is mined from the earth therefore may contain several impurities like silicates or oxides. These impurities impact the general hardness of the material.
You can also find natural graphite in many forms flake, amorphous and vein graphite. Each of these forms has distinct structural properties. Flake graphite has a better crystalline structure that causes better lubrication characteristics while still maintaining softness.
Synthetic graphite is a result of high-temperature processing of carbon precursors. You can control the hardness of synthetic graphite by adjusting the temperature, pressure and time. This way you can tailor synthetic graphite to suit different applications such as aerospace and electronic components.
Of course, this is attributed to the different degrees of hardness.
You can also introduce additives when manufacturing different graphite products. For instance, mixing clay to graphite to make pencil leads.
The amount of clay to graphite impacts the hardness of the lead. The higher the clay proportion the harder your lead will be. On the other hand, the higher the graphite proportion the softer and darker your pencil will be.
Factors Affecting Graphite Mohs Hardness
· Crystalline Structure
Graphite comes in many forms. Depending on graphite type, the space between layers or defects within the lattice structure impacts the material hardness.
A crystalline structure whose layers are aligned and intact, will definitely have higher hardness.
· Impurities
Impurities can occur naturally or can be introduced during graphite manufacturing. Impurities can create an abrasive structure by raising the Mohs hardness from the normal range which is between one and two.
Softer impurities such as clay however reduce the hardness of graphite making it even softer than pure graphite.
· Purity of Graphite
You can remove impurities from graphite making it have more consistent and predictable hardness properties. High-purity synthetic graphite is manufactured at different levels of hardness ensuring uniformity in performance.
· Temperature and Pressure during Formation
Graphite can be formed naturally over geological timescales or synthetically in controlled environments. These conditions can impact its hardness.
Environments with high pressure can compress the carbon atoms within graphite making the material even harder.
High temperatures equally influence the atomic structure of graphite. Therefore, it is possible for you to obtain required properties like increased hardness for specific industrial applications.
· Graphite Type
Natural graphite, because of its impurities and the geological conditions that they are formed happens to have more variations in hardness.
Vein, flake and amorphous are the three forms of natural graphite. Vein has more crystallinity than amorphous and thus may exhibit more hardness.
Synthetic graphite is produced in controlled environments. You can control its hardness to meet the industry’s requirements.
· Additives and Processing Techniques
In some instances, you can add additives during graphite processing to enhance its hardness and other characteristics.
For example, aerospace industries, carbon-carbon composites created from synthetic graphite can be designed for greater mechanical strength and hardness.
Additionally, you can add materials like ceramic reinforcements that can enhance your graphite’s resistance to wear.
Comparing Hard Carbon vs. Graphite
- Atomic structure: Graphite has a layered structure and crystalline nature while hard carbon has an amorphous structure and an Isotropic nature.
- Hardness: Graphite has a low Mohs hardness that is between 1 and 2 making it a soft material. On the other hand, hard carbon is harder than graphite since it has a more rigid structure.
- Electrical and thermal conductivity: Graphite has high electrical and thermal conductivity while hard carbon has lower electrical and thermal conductivity than graphite because of its amorphous structure.
- Electrochemical applications: Graphite anodes are used in lithium-ion batteries while hard carbon anodes are used in sodium-ion batteries.
- Wear resistance and durability: Graphite has low wear resistance compared to hard carbon.
- Thermal stability: Graphite has higher thermal stability as compared to hard carbon.
FAQs
1. What makes Graphite Harder or Softer?
The structure and purity of your graphite are some of the primary factors that determine its hardness. Natural graphite’s hardness depends on impurities while synthetic graphite hardness can be altered.
2. Why is Graphite Hard to Break?
Despite graphite being soft, it has high tensile strength along its planar layers. This helps it not to fracture when pressure is applied parallel to these layers offering durability.
3. What is the Graphite Pencil Hardness?
Graphite pencil hardness is grouped using a pencil grading scale where soft is represented by B to hard is represented by H. H grade pencils contain more clay proportion to graphite.
Conclusion
It is crucial to understand the hardness of your graphite to tailor its applications and suitability in various industrial applications.
At East Carbon, we will help you get high quality graphite with specific hardness for your unique application requirements – send us inquiry now.
