Diamond-like Carbon

Diamond-like Carbon (DLC) is applied to surfaces for the benefits it offers and is used in a diverse array of applications and industries.

Key Characteristics of DLC:

Low friction surface � Wear and corrosion resistant � Diffusion resistant � Biocompatible � Anti-thrombogenic

Diameter, a company exploiting advanced materials, offers DLC coatings to a wide variety of surfaces, tailored to industry specifications. Our coatings offer superior adhesion and performance. We have extensive experience in the thin-film area, with over 17 years experience of developing and optimising proprietary processes.

What is Diamond-like Carbon?

Carbon is a very versatile element. It owes its versatility to the different ways carbon atoms can bond to each other and to other elements. In graphite, carbon atoms bond strongly to each other within a plane but weakly between adjacent planes. Graphite is soft, electrically conducting and opaque. In diamond the bonding is strong in all directions. Diamond is the hardest known material, electrically insulating and transparent from the far ultra-violet to the far infra-red. Diamond films with excellent protective properties can be produced by vacuum deposition but the optimum substrate temperature for coating is about 900�C which severely limits the range of substrates to which diamond can be applied.

Near room temperature, an amorphous carbon containing coating can be produced in which a proportion of the carbon atoms are bonded as in diamond and which resemble diamond in many ways - hence diamond-like carbon.

Applications of DLC

A rapidly growing variety of applications for DLC coatings are being found in mechanical engineering and bio-engineering. Diamond-like carbon is deposited at low temperature and can coat a wide range of metals, ceramics, glasses, and plastics

Key characteristics of DLC:

• Low friction surface
• Hard but flexible therefore wear resistant
• Chemically inert therefore corrosion resistant
• Atomically dense therefore diffusion resistant
• Biocompatible and anti-thrombogenic

Coating Properties:
 

• Unlike other coating processes PACVD process creates excellent adhesion to the substrate through the formation of surface carbides.
• Hardness. 900-4000 Hv.
• Coating thickness. 10nm-4.0µm.
• Density. 1.6-2.2 g/cm 3
• Refractive Index. 1.5-3.1
• Thermal conductivity. 700W/m-K
• Chemical stability. Inert
• Heat resistance. Cont. 250°C – intermittent 350
• Friction. 0.2 Mu typically but can be 0.04 Mu. Depending upon substrate.
   

The Coating Process

Diamond-like carbon is produced when carbon is deposited under energetic bombardment. The instantaneous local high temperature and pressure induce a proportion of the carbon atoms to bond as diamond. These conditions obtain during plasma assisted chemical vapour deposition (PACVD). Components to be coated are placed on an electrode which is capacitively coupled to a radio frequency source. In a cleaning stage, an inert gas such as argon is introduced.

The argon is ionised by the RF field and the positive ions bombard and clean the substrates. The cleaning stage is followed by the deposition stage in which a carbon containing gas such as acetylene is introduced to provide the energetic carbon ions.