• Refractory Metals
  • Technical Ceramics
  • Ceramics Selection Guide
  • Element Materials
  • Materials & Their Properties
  • Graphite & CCC Selection Guide

Refractory Metals

Here at Thermic Edge we offer refractory metals, professionally machined, at an affordable price. Thermic Edge boasts a vast variety of materials and refractory metals such as tungsten. All refractory metals are high quality, professionally pre-machined in factory, being very inexpensive to you: the customer. The materials are factory manufactured to the highest quality, highest duty, with the best prices in the UK to date.

Thermic Edge offers a range of raw and machined refractory metals. These metals include:

Tungsten Products:

  • Tungsten Rod/Wire/Bar/Sheet/Plate/Boat/Crucible/Tube/Foil/Disc/Electrode
  • Pure Tungsten Electrodes
  • Yttriated Tungsten Electrodes
  • Zirconiated Tungsten Electrodes
  • Lanthanated Tungsten Electrodes
  • Thoriated Tungsten Electrodes
  • Tungsten Heavy Alloys (W-Ni-Cu)
  • Tungsten Heavy Alloys (W-Ni-Fe)
  • Tungsten Silver
  • Tungsten Heavy Allow WNiCu WNiFe
  • Tungsten Alloy Radiation Shielding Material
  • WNiFe Alloy Rod
  • Tungsten Custom-Shaped Commodities

Molybdenum Products:

  • Molybdenum Foil/Sheet/Plate/Wire/Rod/Electrode/Crucible/Tube/Boat/Disc
  • Molybdenum Rolled Plate
  • Spray Molybdenum Wire
  • Molybdenum Lantanum (Mo-La)
  • TZM
  • Molybdenum Copper Alloy
  • Molybdenum Custom-Shaped Commodities

Technical Ceramics

Our range of technical ceramics we specialise in consists of two distinct groups Machinable and Non-Machinable. Machinable ceramics can be conventionally machined with varying degrees of difficulty depending on type and grade of material.

Thermic Edge offers a range of materials suitable for use in high vacuum and at high temperature. We can offer raw material or machined components to suit any requirement. Our range of materials includes Technical Ceramics, Ceramic textiles, Graphite based materials (such as: Carbon, Graphite, Carbon Carbon Composites) and also Refractory Metals. We have given a general over view of the materials below, with a selection and properties guide at the end of each section.

Materials & Ceramics

The Machinable ceramics include: Boron Nitride, BNS26 (Boron Nitride Silica), Pyrolytic Boron Nitride (PBN), Macor (Machinable glass ceramic), Shapal (Machinable Aluminium Nitride), BNP2 (lower cost shapal alternative, available in larger blocks).

Macor – one of the most common machinable ceramics, it is a machinable glass ceramic and easily machined with conventional metal working tools. It is an ideal prototyping material for use in a high vacuum environment at low or high temperature. Continuous use temperature is 800 C (No load to 1000C), with good dimensional stability and the coefficient of thermal expansion matches most metals. Negatives are poor thermal shock resistance and low strength (10% the compressive strength of Alumina).

MGC1000 – Lower cost alternative to Macor.

Shapal – is machined with diamond tooling and has high mechanical strength and high thermal conductivity. It has very good resistance to thermal shock and is based on the world’s first translucent aluminium nitride ceramic. Shapal ceramic unique characteristics make it suitable for a wide range of applications in the vacuum and nuclear industries. It has zero porosity, low out gassing rates, is not affected by most etch plasmas or ionizing radiation and easily joins to its self or other materials.

ABN1000 – Ceramisis’s much lower cost alternative to Shapal, with similar properties, but has virtually zero expansion coefficient and available in larger block size.

Boron Nitride – Boron nitride is a unique material, it offers outstanding thermal conductivity, excellent dielectric strength, very good thermal shock resistance, is self-lubricating and is easily Machinable. This material is an advanced synthetic ceramic available in powder, solid, liquid and aerosol spray forms. In an oxidizing atmosphere it can be used up to 900°C. However, in an inert atmosphere some grades can be used as high as 3000°C. Grades are available with a very low porosity and ultra-high strength for use in semiconductor processing and mechanical applications. There can be very large differences in the performance, properties and chemical composition of the different grades of boron nitride, so great care must be taken to choose the correct grade for any specific application. Our Boron Nitride grades can be described as follows:-

  • BN100 – Hot Pressed Low cost boron nitride grade mixed with a binder (Calcium borate) to add strength. Although this grade can be used at high temperatures, it is not suitable for high temperature (above 900C) use in high vacuum, as the calcium borate has a low vapour pressure and will evaporate out of the material under high vacuum and temperature, causing great damage to the vacuum environment.
  • BN200 – Isostatically pressed boron nitride without any binder. Available in large blocks and has very good strength and low porosity.
  • BN300 – Diffusion bonded very high purity boron nitride. Has lower strength than BN200 but higher purity makes it more suitable for UHV or very high temperature applications. Price is also higher than BN200.

BNS26 – is a boron nitride silica composite ceramic, it is a unique material combining Boron Nitride with Silica, essentially giving some of the best properties of both Macor and Boron Nitride. BNS26 is a hydrophobic advanced ceramic and is resistant to moisture (unlike boron nitride). It is suitable for the most severe electrical applications, is an excellent refractory material up to 1400C, and has excellent resistance to thermal shock. It is an ideal material for heater element supports and bases.

PBN – Pyrolytic Boron Nitride, not strictly a technical ceramic, it is made by chemical vapour deposition, depositing PBN onto a mould or substrate. It is only available in very thin sections, typically 1-2mm thick (Max 4mm thick), and can be post machined. It is mainly used for crucibles, it is very inert with zero porosity and a good electrical insulator. It is also ideal for UHV applications.

 

The Non-Machinable ceramics include: Alumina (Aluminium Oxide), Aluminium Nitride, Silicon Carbide, Silicon Nitride, Quartz, Zirconia

Alumina, Zirconia- Alumina and zirconia are hard wearing materials used for many applications. Once fired and sintered, they can only be machined using diamond-grinding methods. Alumina’s combination of hardness, high temperature operation and good electrical insulation makes it useful for a wide range of applications. Zirconia is similar to alumina in many of its properties but offers significant improvement in fracture toughness. It is particularly useful in applications where the mechanical strength of alumina is not sufficient.

We supply alumina components manufactured to our customer’s drawings in 4-6 weeks. Alumina is 10 times stronger than Macor and has good thermal shock resistance. It is ideal for use in high temperature high vacuum and UHV environments.

Aluminium Nitride, Silicon Nitride- Aluminium nitride has very high thermal conductivity, high mechanical strength and combined with its excellent electrical insulation properties is an ideal heat sink material for many electrical and electronic applications. Silicon nitride is an extremely hard material and is very useful for applications in which physical wear is of great importance. Silicon nitride also has very good thermal shock characteristics.

Silicon Carbide- is a very hard wearing material, again requiring diamond-grinding methods to process once fired. Although not exclusively, carbides are used mainly for applications in which physical wear is a major consideration. They are amongst the hardest materials available. Solid SiC is ideal for use as heating elements in UHV or in oxygen environment up to 1500C although price is very high compared to SiC coated Graphite elements.

Quartz – We supply quartz plates for element cover plates, rods and tubes for use as element supports. Partial machining is possible to put holes and slots into the quartz plates, rods and tubes, making them ideal for use as tungsten element supports (bespoke tungsten elements are also produced by Ceramisis). Quartz is ideal for use in UHV and has very low thermal conductivity it is also transparent to infra-red, and so is slow to heat, making it an ideal material for element supports, covers and sample holders.

Ceramics Selection Guide

The tables below are only to be considered as a guide and should not be denoted as specification. Machined in high density graphite can't be machined after conversion.

Non-Machinable Ceramics

Material Units unless stated Alumina   92% Alumina    96% Alumina    99% Alumina    99.5% Quartz Sapphire BeO Zirconia
Yttizia
Stabalised
Colour White White Off white Off white Clear Clear Whte White
Density g/cc 3.6 3.7 3.9 3.9 2.2 4 2.9 8
Porosity % 0 0 0 0 0 0 0
Poissons ratio 0.3
Thermal conductivity Wm/K 16.7 24.8 30 30 1.48 35-40 260 2
Dielectric strength Kv/mm 10 17 10-25 25-40 15-50 10
dielectric constant 9.8 9.9 9-10 3.8 7.5-11.5 7
Dielectric loss tangent 1MHz 0.0003
Flexural strength Mpa 345 358 380 380 80 800 200 800
Compressive strength Mpa 2200 2300 3000 3000 1100 2100 1750 2000
Hardness Vickers 1100 1150 9 Mohs 1400 1000 1850 1200 1350
Resistivity ohm/cm >10e14 >10e14 >10e14 >10e14 10e8 10e16 >10e14 >10e9
Max use temp °C 1500 1600 1700 1650 1200 2000 1700 1500
Max use temp in air °C 1500 1600 1700 1650 1200
Max use temp in vacuum °C 1500 1600 1700 1650 1200
Thermal expansion (CTE) general or parallel to grain in non isostatic materials /°C 8.5x10e-6 7.9x10e-6 5.4x10e-6 5.8x10e-6 8x10e-6 10x10e-6
CTE Perpendicular to grain in non isostatic materials /°C
Specific heat capacity J/Kg.K 800 900 880 700 750 1200 400
Easily Machinable No No No No No No No
Material Zirconia
Mgo
Stabalised
Aluminium Nitride Silicon Nitride Silicon
Nitride
hot pressed
Silicon Carbide  SSiC Silicon Carbide  SiSiC Silicon Carbide  RBSiC Silicon Carbide  converted Boron Carbide
Colour Cream Fawn Grey Grey Black Black Grey Black
Density 5.6 3.3 2.5 3.3 3.1 3.02 2.7 >2.48
Porosity 0 0 0 0 0 0
Poissons ratio 0.31 0.2 0.28 0.24
Thermal conductivity 2.5 180 15 20 110 45 14
Dielectric strength 20
dielectric constant 9 10
Dielectric loss tangent 0.001
Flexural strength 545 360 200 850 400 250 90 300-500
Compressive strength 1700 550 3000 2200 300 3000-5000
Hardness 910 1100 1100 1500 2400 2740-3430
Resistivity >10e10 >10e14 >10e14 >10e10 5x10e7 1.00E+11
Max use temp 1000 1600 1800 1500 1600 1380 1650 2450
Max use temp in air
Max use temp in vacuum 1600
Thermal expansion (CTE) general or parallel to grain in non isostatic materials 10x10e-6 3.8x10e-6 3.1x10e-6 3.3x10e-6 3.0x10e-6
CTE Perpendicular to grain in non isostatic materials
Specific heat capacity 400 800 1100 800 1100
Easily Machinable No No No No No No No Yes*/No No

 

Machinable Ceramics

Material Units unless stated Silicon Carbide  converted Boron Nitride BN100 Boron Nitride BN200 Boron Nitride BN300 Boron Niride Silica BNS26 Macor
Colour White Off White White White White
Density g/cc 1.9 2.2 1.85 2.52
Porosity % 15 0.6 13 6.7 0
Poissons ratio
Thermal conductivity Wm/K 30 28 71 para       121 perp 11 para  29 perp 1.46
Dielectric strength Kv/mm 1.7 1.7 2
dielectric constant 6
Dielectric loss tangent 1MHz 0.004
Flexural strength Mpa 64 para  34 perp 94
Compressive strength Mpa 30 113 345
Hardness Vickers 18 250 Knoop
Resistivity ohm/cm >10e14 10e12 >10e14 >10e16 10e17
Max use temp °C 900 1900 2000 1400 800
Max use temp in air °C 850 900 900 1200 800
Max use temp in vacuum °C 850 1900 2000 1400 800
Thermal expansion (CTE) general or parallel to grain in non isostatic materials /°C 2.95x10e-6 parallel 8x10e-6 0.57x10e-6 parallel 3.0x10e-6 parallel 12.3x10e-6
CTE Perpendicular to grain in non isostatic materials /°C 0.87x10e-6 perpendicular 0.46x10e-6 perpendicular 0.1x10e-6 perpendicular
Specific heat capacity J/Kg.K 1468 1960 1500 1550 790
Easily Machinable Yes*/No Yes Yes Yes Yes Yes
Maximum block size cm 49×40.6×24.5 dia27 x 40 25×4.6×4.5 49×40.6×24.5 30x30x5.5
Material MGC1000 PBN Shapal ABN1000 Graphite GP25 BN ZSBN
Colour White White Cream Cream Black Grey
Density 2.6 2.15 2.9 2.9 1.83
Porosity 0 0 0 0 10
Poissons ratio
Thermal conductivity 1.71 43-60 90 92.6 69
Dielectric strength 56 40
dielectric constant 7.1 7.1
Dielectric loss tangent
Flexural strength >108 243 para       198 perp 294 300 75
Compressive strength >508 1176 1070 170
Hardness 23000 692 Knoop 390 3.42-4.91 Knoop 79 shore
Resistivity >10e16 >10e13 >10e14 >10e14 0.0015
Max use temp 800 2200 1900 1900 2600 1800
Max use temp in air 800 900 1000 1020 500
Max use temp in vacuum 800 2200 1900 1900 2200 1800
Thermal expansion (CTE) general or parallel to grain in non isostatic materials 4.4x10e-6 0.57x10e-6 parallel 5.7x10e-6
CTE Perpendicular to grain in non isostatic materials 0.46x10e-6 perpendicular
Specific heat capacity 790
Easily Machinable Yes Yes Yes Yes Yes
Maximum block size 30.5×30.5×8 dia30 x 30 49x49x15

High Density Graphite and Carbon-Carbon Composite

High Density Graphite and Carbon-Carbon Composite for heating elements, high temperature and high vacuum applications.

Graphite

High density graphites and Carbon Carbon Composites (CCC) are ideal materials for in vacuum heating elements. Chemically the same, high density graphite and carbon carbon composite materials are very inert, get stronger with temperature, has low expansion coefficient and will not seize after heating. High density graphite is brittle but inexpensive and machined conventionally from large blocks, therefore very large sized graphite elements can be produced in a variety of shapes and sizes. Our high strength ultra-fine grained graphite enables small very intricate elements to be manufactured also. Graphite has a low expansion coefficient and is not degraded by constant heating and cooling, and also gets stronger as its temperature increases.

Its low resistivity means it requires high current power supplies and therefore large feedthroughs and cables which can be expensive. It can operate over 2000 °C in an inert atmosphere or in vacuum and <500°C if oxygen is present. Graphite elements have the ability to take very high power density, and therefore very fast ramp up times can be achieved. Its relatively high specific heat capacity means that cool down times in vacuum can be quite long. Apart from reacting with oxygen from 500C, graphite is otherwise very inert and can therefore operate in very corrosive or aggressive atmospheres without degradation. Particle contamination and open porosity can be a problem with graphite, but this can be overcome with coatings, or impregnations detailed below. Graphite elements are suitable for UHV applications, but must undergo initial out-gassing process due to its open porosity.

Carbon-Carbon Composite

Carbon Carbon Composite is much stronger than graphite and is not brittle due to its fibrous grain structure. Carbon Carbon Composite elements can therefore be made in very thin sections, typically 1mm thick, which overcome a number of the problems associated with high density graphite elements. Thin carbon carbon composite elements have a much higher resistance than high density graphite elements, allowing lower current, higher voltage power supplies to be used, and smaller power feedthroughs and cables, thereby reducing costs. The lower mass of the thin carbon carbon composite elements means that they heat up much quicker and also cool down much faster in vacuum. Carbon Carbon composite is produced in sheets (typically 1m²) of various thicknesses from 1.0mm to 30mm. Modern CNC machining techniques mean that carbon carbon composite elements can be produced very cheaply. We stock standard designs of carbon carbon composite elements from Ø1″ to Ø6″ which are manufactured in quantity and therefore very cost effective. Carbon carbon composite also has extremely low thermal conductivity which is beneficial in reducing heat loss through the power contact points, thereby increasing element uniformity. This low thermal conductivity also means that carbon carbon composite is ideal for use as a heat shield, both in vacuum and also in inert atmosphere.

For larger sized elements it will be necessary for the graphite element or carbon carbon composite element to be supported, as these materials do not have the rigidity to support themselves without sagging. Ceramisis can supply a range of ceramic materials suitable for supporting graphite elements and carbon carbon composite elements. Ceramisis can also manufacture ceramic bases with a recess machined to the same pattern as the element. A high thermal conductivity ceramic lid can then be fixed in position, completely encapsulating the graphite element. This not only supports the element but also protects it from deposition product, and eliminates high temperature arcing in low vacuum.

To electrically insulate graphite elements it is also possible to apply a SiC coating. This can be applied by CVD or by painting and firing. The CVD method has better and more uniform adhesion, and can withstand up to 1400C. It is however very expensive and the surface tension of the coating does apply a high stress to the graphite element meaning the element can distort and thin section elements are not strong enough to be coated. The paint on SiC coating is inexpensive and easy to apply but has a maximum operating temperature of 1100C. Other coatings can be applied to graphite and carbon carbon composite to seal the porosity and reduce particle count. These coatings are pyrolytic graphite, vitreous carbon, and pyrolytic boron nitride. These coatings can improve oxidation resistance, reduce particle count and improve chemical resistance of the graphite element. Pyrolytic graphite coating is the only coating that can be applied to carbon carbon composite. The table below details the properties and applications for each coating.

Silicon Carbide, Pyrolytic Graphite, Vitreous Carbon and PBN Coatings, Plus Vitreous Carbon Impregnation On Graphite

To stop the problems of out gassing, particle contamination and oxidation that occurs with high density graphite and carbon carbon composite elements, there are various coatings that can be applied as follows:

Pyrolytic Graphite Coating ( PG ): 

This can be applied by a CVD method to high density graphite and carbon carbon composite elements (see picture right). It is still electrically conductive, but it totally seals the surface porosity and therefore traps any particles. Pyrolytic graphite coating is chemically the same as high density graphite and ccc and so will still react chemically in the same way and with oxygen at 500°C.

PG coating is preferred by some for UHV applications, because it seals the open porosity of the graphite. However should the coating have a pin hole then the underlying graphite will take forever to outgas and thus act as a virtual leak. We therefore recommend uncoated graphite for UHV, as without the coating the graphite can initially outgas freely. PG coating would only be recommended for UHV if particle contamination was an issue.

Vitreous Carbon Coating / Impregnation:

Vitreous carbon surface treatment is a cheap alternative to pyrolytic graphite coating, and is produced by vitrifying a resin applied to the surface of the high density graphite component. It seals in the particles but does not totally seal the porosity, although it can be drastically reduced. Vitreous carbon coating is better at sealing the porosity than the impregnation and gives a nice black glassy appearance to the component. It is chemically the same as high density graphite and so will still react chemically in the same way and with oxygen at 500°C.

Silicon Carbide Coating ( SiC ):

Is a dark grey coating applied by a CVD method to specific grades of high density graphite. This silicon carbide ( SiC ) coating is an electrical  insulator and therefore cannot be applied to the electrical contact points on the element (see picture right). We can supply a SiC paint that can be applied to connection points after connection has been made. This paint is then thermally cured. The silicon carbide coating can operate in oxygen environments up to 1500°C and can resist some chemically corrosive environments better than graphite.

Pyrolytic Boron Nitride Coating ( PBN ):

This white Pyrolytic Boron Nitride coating can be applied to very specific grades of high density graphite (see picture right) to seal the porosity and improve the oxidation and chemical resistance of the element. It will oxidise at 900°C if oxygen is present, but can withstand 2000°C in an inert atmosphere or vacuum (with N2 present).

Materials

And their Properties

Plain graphite elements:

  • <500°C in Oxygen, >2000°C in vacuum or inert atmosphere, low cost but brittle with >12% open porosity.

Carbon Carbon Composite (Carbon Fibre) elements:

  • Properties are same as for plain graphite but is strong and not brittle.

Solid Pyrolytic Graphite (PG) elements:

  • <500°C in Oxygen, >2000°C in vacuum or inert atmosphere. Impervious, very high strength and rigidity.

Vitreous Carbon impregnation on graphite elements:

  • <500°C in Oxygen, >2000°C. Low cost impregnation to reduce particle emission. Does not reduce porosity of base material.

Vitreous Carbon coating on graphite elements:

  • <500°C in Oxygen, >2000°C. Low cost coating to reduce particle emission and reduce porosity of base material.

Pyrolytic Graphite (PG) coating on Graphite or CCC elements:

  • <500°C in Oxygen, >2000°C in vacuum or inert atmosphere. This coating seals the porosity of the base material, eliminating particle emissions and greatly reducing out-gassing.

Silicon Carbide (SiC) coating on Graphite elements:

  • <1400°C in Oxygen or in vacuum or inert atmosphere, seals porosity of the base material, and improves chemical resistance. Coating is an electrical insulator. Exposed graphite power connection points should be outside hot zone and cooled below 500C if O2 present.

Pyrolytic Boron Nitride (PBN) coating on Graphite elements:

  • <900°C in Oxygen, >2000°C in vacuum or inert atmosphere (with N2 present). Seals porosity of the base material, and improves chemical resistance. Coating is an electrical insulator.

Solid Silicon Carbide (SiC) elements:

  • <1500°C in Oxygen or in vacuum or inert atmosphere, has open porosity and is an electrical conductor, and has good chemical resistance. Can be coated with CVD SiC to seal porosity and give electrical insulation. Advantages over SiC coated graphite are that it has no exposed graphite to oxidise, plus has much higher resistivity, requiring lower current power supply. Negatives are that it is very expensive.

NOTICE: AREA IN DEVELOPMENT

In the meantime, please do refer to the contact section down below if you have a query about the Graphite & CCC selection guide. We are trying our hardest to bring the website to an official release; thank you for your patience.

Carbon-Carbon Composite Selection Guide

G & CCC Selection guide

Refractory Metals

Here are images of the product materials in the refractory metals range at Thermic Edge

Contact

  • This field is for validation purposes and should be left unchanged.
Responsive website designed & developed by
×