To understand the resistivity of carbon, it’s important to know about its various allotropes and how resistivity can differ based on the arrangement of carbon atoms within a material.
Carbon Allotropes Offering Different Resistivity Of Carbon
Carbon is tetravalent, meaning, it can form four bonds with other elements to create complex structures. Thanks to this tetravalency, we see diversity in life and materials in this universe.
Long chains of carbon can thus form this way resulting in distinct formations. This versatility produces carbon allotropes, the most common of which are diamond, graphite, amorphous carbon, and nanocarbon.
Each of these allotropes has unique properties and is used differently in industry.
What Is Resistivity?
Resistivity is a constant applied in the formula R = ⍴L/A, where
R = Electrical Resistance
⍴ = Resistivity
L = Length
A = Area
It’s an inherent property of the material and helps determine whether the substance has high or low electrical resistance. The formula shows us that resistivity is dependent on three main elements and is directly proportional to resistance and cross-sectional area.
The reciprocal of this is electrical conductivity (σ) given by the formula ⍴ = 1/σ.
Resistivity’s Relationship With Temperature
The relationship is demonstrated by a formula complex in appearance but easy to understand. It’s ⍴(T) = ⍴₀(1 + ɑ[T – T₀)], where
⍴ = Resistivity at temperature T (unknown)
⍴₀ = Resistivity at a known temperature (T₀)
Ɑ = temperature coefficient of resistivity (varies by material)
A temperature change has different effects on resistivity based on the material used.
Metals such as copper or silver show an increase in resistivity as temperature increases. This is because atomic vibrations result in more electrons scattering around, thereby reducing conductivity.
Semiconductors such as silicon and graphene, however, decrease their resistivity with an increase in temperature.
Insulators such as glass and diamond have a slight decrease in resistivity with a drop in temperature, but it remains high because of few free electrons, an important element for conductivity.
For carbon materials such as graphite and amorphous carbon, the change in resistivity with temperature varies by form. For instance, graphite resistivity decreases with increasing temperature because higher temperatures allow for more free electrons.
Why Is Resistivity Important In Industrial And Scientific Settings?
Understanding the resistivity of materials helps us differentiate between good, moderate, and bad conductors.
To comprehend how usage varies depending on this constant, let’s compare the resistivity of different elements and allotropes at 20 degrees Celsius, starting with the common carbon allotropes.
Diamond: 10¹² to 10¹⁶
Graphite: 10⁻⁵ to 10⁻³
Amorphous Carbon: 10⁻¹ to 10³
Copper: 1.724 ✕ 10⁻⁸
Aluminum: 2.65 ✕ 10⁻⁸
We can deduce from the direct proportionality of resistivity and resistance that metals like copper and aluminum have weak resistivity and resistance and therefore higher conductivity.
Carbon allotropes, on the other hand, have weaker conductivity, and out of these, graphite has the highest conductivity.
Industrial Applications Of Carbon Allotropes
Graphite
Despite its lack of visibility, graphite has many industrial applications, especially in the steel industry.
In the automotive industry, it’s used in clutch materials, gaskets, and brake linings.
Other than that, it’s a component in electric motor carbon brushes, lubricants, insulation, and fire retardants.
Diamond
While diamonds are insulators at room temperature, their thermal conductivity ensures surprisingly varied utilizations in the industry.
In the electronics industry, for instance, diamonds act as a heat sink by absorbing and dispersing it. This prevents overheating.
The medical industry also has diamond applications. They’re used in cosmetic procedures like dermabrasion. They’re also needed to make optical components like lenses.
In our modern world, we’ve also discovered the benefits of diamonds in scientific fields like quantum computing and particle physics.
Amorphous Carbon
This allotrope of carbon has a more disordered structure than other carbon forms but this disorder is key to its success in manufacture.
Amorphous carbon is hard and wear-resistant. This makes it ideal for coating automotive parts and medical devices.
Its low friction reduces wear and tear when operating mechanical parts.
Additionally, It’s resistant to corrosion and therefore perfect for the aerospace industry where parts often encounter harsh environments.
Metals Like Copper
Copper has high conductivity, is malleable, and is resistant to corrosion. It’s therefore not hard to imagine how perfect it is for electrical circuits.
Aside from its use in electrical wiring and cables, it’s also used to produce generators, solar panels, piping, motors and batteries, as a catalyst in many chemical processes such as hydrogenation, and medical devices such as surgical instruments.
Carbon Black, A Low-Quality Amorphous Carbon
Carbon black is reinforcing, UV-resistant, and conductive, thereby making this fine powder suitable for many purposes such as making rubber, coatings, and plastics.
However, it’s not environmentally friendly since it’s made from burning petroleum products like oil and diesel. Considering that the world is aware of the hazards of pollution, its continuous use is detrimental to your reputation and health.
We at CFI Carbon Products have transformed our amorphous carbon recipe by using coal to give you Austin Black 325. The product with low specific gravity is versatile, cost-effective, and emits less CO2.
Our company is more eco-friendly and we deliver the best products to ensure sustainability and improved processes.
If you’d like to know more about our innovative approach to making the industry better, reach out to us!
