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Ceramic Coatings
Thermic Edge Ltd is the sole manufacturer of high purity Cubic Silicon Carbide (SiC3) and Cubic Titanium Carbide (TiC3) ceramic coatings, that can be applied to purified graphite, ceramics and refractory metal components.
These very high purity sic and titanium carbide coatings are mainly intended for use in the semiconductor and electronics industries, for protecting wafer carriers, susceptors, and heating elements from corrosive and reactive environments such as MOCVD and EPI processes, used for wafer processing and device manufacture. The coatings are also suitable for vacuum furnaces and sample heating in high vacuum, reactive, and Oxygen environments.
Thermic Edge’s state-of-the-art machine shop allows us to offer a complete solution including the manufacture of the base graphite, ceramic or refractory metal component, and the SiC3 or TiC3 ceramic coating. We also offer a coating-only service for customer-supplied parts.
SiC3 is our trade name for our high purity cubic Silicon Carbide ceramic coating. It is applied to components to protect them from Oxidation or reaction with other gasses at high temperature. The SiC3 coating is applied using a high temperature, very high purity Chemical Vapour Deposition (CVD) reactor.
SiC3 coating is an electrical insulator, incredibly hard and has good corrosion and oxidation resistance. It can withstand temperatures up to 1600C at atmospheric pressure.
SiC3 Cubic Silicon Carbide ceramic coating can be applied to the following materials:-
SiC3 Cubic Silicon Carbide ceramic coating can be used at high temperature in the following environments:-
SiC3 Cubic Silicon Carbide coating has the following advantages over conventional SiC coatings:
This very high purity coating is mainly intended for use in the semiconductor and electronics industries, for protecting wafer carriers, susceptors, and heating elements from corrosive and reactive environments such as MOCVD and EPI processes, used for wafer processing and device manufacture. The coating is also suitable for vacuum furnaces and sample heating in high vacuum, reactive, and Oxygen environments.
SiC3 coating is an electrical insulator, incredibly hard, and has good corrosion and oxidation resistance. It can withstand temperatures up to 1600C at atmospheric pressure.
| Property | Value |
| Density | 3200 kg.m-3 |
| Crystal structure | 3C (cubic;β) |
| Porosity | 0% (helium leak tight) |
| Crystal Size | 1 – 5 µm |
| Visual Appearance | Grey, Satin to dull |
| Thermal Expansion (RT -400°C) | 4.2 x 10-6m.K-1 |
| Thermal Conductivity (@20°C) | 200 W.m-1.K-1 |
| Elastic Modulus | 450GPa |
| Electrical Resistivity (@20°C) | 1MΩ.m |
This table shows the impurities of SiC3 coating
The lowest limit of detection with this method. Testing carried out by EAG Laboratories using Glow Discharge Mass Spectroscopy.
Our Thermic Edge SiC3 Coating (TEC) is extremely high purity when compared to Silicon Carbide coatings supplied by other companies (C1 and C2)
A typical surface roughness profile is shown here.
The typical surface roughness parameters are Ra = 0.8µm, Rz = 5µm and Rt = 8µm.
Thermic Edge Coatings (TEC) deposits a high purity silicon carbide coating on various materials. The cubic, SiC3, coating has excellent corrosion protective properties at low, medium and high temperature. Typically the coating finds application in semiconductor industry, LED and solar production and aerospace. Materials coated are graphite, carbon composites, various ceramics and refractory metals.
The coating can only protect the underlying material effectively when the coating covers all areas visible to the environment, when it adheres well to the material and does not crack after the coating process.
A well adhering coating is therefore essential and the process carried out by TEC accomplishes this on various materials. The process is carried out at high temperature using ultrapure gases amongst which hydrogen which cleans the surface by removing oxides and other contaminants which might hinder good adhesion. During the initial stages of the process there is a trade-off between deposition and etching which further cleans the interface between underlying material and coating.
And of course in many applications graphite is used as the underlying material which has a high porosity. The TEC process penetrates the pores in the graphite very well and gives it a further enhancement for the adhesion. This is very well demonstrated in the figure below.
Use of graphite coated parts in high end applications depends on overall coverage of the graphite. This is important for the outside surfaces as well as for small and larger holes (blind, through). The small hole in the satellite disc is a good example and sufficient coating on the inside is important.
At TEC we made a small graphite sample with small holes drilled into the side with a handheld drill. This is for a first assessment only and further testing will commence the coming weeks. The test piece is shown below and after drilling and coating smaller parts were broken of the piece to examine the hole internals.
SEM analysis of a hole shows clearly that the coating penetrates into the small hole dia1.2mm x 5.5mm deep (see right).
At the bottom of the hole (diameter approximately 1.2 mm; depth 5.5 mm) there is still a layer of 10 µm present. Coating of the small satellite disc hole is therefore no problem and at least 60 % of the top layer thickness is expected at the bottom of the hole.
Use of graphite coated parts in high end applications depends on overall coverage of the graphite. This is important for the outside surfaces as well as for small and larger holes (blind, through). The small hole in the satellite disc is a good example and sufficient coating on the inside is important.
At TEC we made a small graphite sample with small holes drilled into the side with a handheld drill. This is for a first assessment only and further testing will commence the coming weeks. The test piece is shown below and after drilling and coating smaller parts were broken of the piece to examine the hole internals.
SEM analysis of a hole shows clearly that the coating penetrates into the small hole dia1.2mm x 5.5mm deep (see right).
At the bottom of the hole (diameter approximately 1.2 mm; depth 5.5 mm) there is still a layer of 10 µm present. Coating of the small satellite disc hole is therefore no problem and at least 60 % of the top layer thickness is expected at the bottom of the hole.
A large group of materials based on carbon fibres are referred to as carbon composites. It covers a wide range of materials with various characteristics based on the production process. What the materials have in common is the carbon fibre which is moulded (short fibres) or woven (long fibres) into various structures and impregnated to densify the structure. The properties of the fibre vary very much in the length of the fibre and perpendicular to the fibre. Especially the thermal expansion differs and makes it very difficult to coat a composite structure without cracking and/or delamination.
TE has gained some experience with coating carbon composite parts developed for high-temperature applications. Due to the large difference in thermal expansion and variations in different directions cracks appear. A good example is given right. The width of the crack in the horizontal direction is much larger than in the vertical direction indicating a different orientation of the fibre. Once the material is heated and close to the SiC3 deposition temperature most of the cracks will be closed and could protect the underlying material.
The most promising ceramics to be coated with SiC3 are silicon-based ceramics such as SiC, SiSiC, Si3N4, etc. The reason being that the thermal expansion of those materials fits very well with the SiC3 coating. The purpose of a top coating on those ceramics is to improve corrosion resistance and to block the diffusion of impurities from the base material. In the semiconductor industry, SiSiC boats and other parts are mostly coated by the ceramics supplier themselves. In that case, the coating prevents preferential attack and erosion of silicon from the base material.
So far alumina has proven difficult to coat as well as quartz due to its very low thermal expansion.
Tungsten and molybdenum have been coated successfully with SiC3 coating. Depending on the dimensions and shape up to 250 µm can be applied. The coating adheres very well and the system has a long-term stability at high temperature. The SiC3 coating can prevent oxidation of the underlying base material in oxidising environments.
TiC3 is our trade name for our high purity cubic Titanium Carbide ceramic coating. It is applied to graphite components to protect them from vaporisation in high vacuum (HV) and Ultra High Vacuum (UHV) at high temperature and reaction with other gasses at high temperature. The TiC3 coating is applied using a high temperature, very high purity Chemical Vapour Deposition (CVD) reactor.
TiC3 coating is a very good electrical conductor and can withstand very high temperatures up to 3000C. It has a very low vapour pressure, enabling it to operate at high temperature in high vacuum and Ultra High Vacuum (UHV). It is incredibly hard and has good corrosion resistance. It does not like oxygen however and will readily react with O2.
TiC3 Cubic Titanium Carbide ceramic coating can only be applied to high expansion graphite products, as it has a CTE of about 7x10e-6 mm/C
TiC3 Cubic Titanium Carbide ceramic coating can be used at high temperature and also very high vacuum in the following environments:-
| Property | Value |
| Density | 4930 kg.m-3 |
| Crystal Structure | 3C (cubic; β) |
| Porosity | 0% (helium leak tight) |
| Crystal Size | 2-10 µm |
| Visual Appearance | Light grey, Satin |
| Thermal Expansion (RT – 400°c) | 7.7 X 10-6M.k-1 |
| Thermal Conductivity (@20°C) | 50 W.m-1K-1 |
| Elastic Modulus | 420GPa |
| Electrical Resistivity (@20°C) | 0.02Ω.m |
| Hardness (Vickers) | 3500 HV |
An XRD Diagram is shown here.
The peaks shown in the diagram perfectly match the 3C crystal structure.
Surface and fracture as observed with Scanning Electron Microscope are shown below
The porosity of graphite is covered very well, and the coating penetrates the open porosity and enhances a very good adherence of the coating on the graphite surface. Adherence on sharp edges is good but in all cases a radius of at least 0.2 mm is advised.
Use of graphite coated parts in high end applications depends on overall coverage of the graphite. This is important for the outside surfaces as well as for small and larger holes (blind, through). The small hole in the satellite disc is a good example and sufficient coating on the inside is important.
At TEC we made a small graphite sample with small holes drilled into the side with a handheld drill. This is for a first assessment only and further testing will commence the coming weeks. The test piece is shown below and after drilling and coating smaller parts were broken of the piece to examine the hole internals.
SEM analysis of a hole shows clearly that the coting penetrates into the small hole dia1.2mm x 10.0 mm deep (see right).
At the bottom of the hole (diameter approximately 1.2 mm; depth 5.5 mm) there is still a layer of 10 µm present. Coating of the small satellite disc hole is therefore no problem and at least 60 % of the top layer thickness is expected at the bottom of the hole.
Currently we can coat components up to dia360 x 500mm.
Thermic Edge Coatings (TEC) deposits a high purity Titanium carbide coating on graphite. The cubic, TiC3, coating has excellent corrosion protective properties at low, medium and high temperature. Typically the coating finds application in semiconductor industry, vacuum furnaces and aerospace. Materials coated are graphite, carbon composites, various ceramics and refractory metals.
The coating can only protect the underlying material effectively when the coating covers all areas visible to the environment, when it adheres well to the material and does not crack after the coating process.
A well adhering coating is therefore essential and the process carried out by TEC accomplishes this on various materials. The process is carried out at high temperature using ultrapure gases amongst which hydrogen which cleans the surface by removing oxides and other contaminants which might hinder good adhesion. During the initial stages of the process there is a trade-off between deposition and etching which further cleans the interface between underlying material and coating.
Graphite is used as the underlying material which has a high porosity. The TEC process penetrates the pores in the graphite very well and gives it a further enhancement for the adhesion.
This table shows the impurities of TiC3 coating
Lowest limit of detection with this method. Testing carried out by EAG Laboratories using Glow Discharge Mass Spectroscopy.
At Thermic Edge, we pride ourselves on being at the forefront of the Vacuum Heating Technology Industry. We provide a complete service, our bespoke and versatile ranges give you the tools necessary for any inert, HV or UHV application.
This website uses cookies to ensure you get the best experience. Please see our Privacy Policy for more information.