Sapphire

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Almath Crucibles offer a variety of sapphire tubes.

Sapphire tubes are ideal for protecting high-temperature thermocouples in corrosive environments, are 100% gas tight and will operate up to 2000C.

These tubes are not always held in stock – please check current delivery times with us if this is critical
Different diameters and lengths are available on request. Please ask
We can also offer custom-made sapphire products. Please request a quotation

Typical Applications

High-temperature protection tubes
Kiln furniture
Electrical insulators/substrates
Engineering ceramics in turbine engine parts
Infrared-transmitting windows

Material properties

Please note that the information set forth herein is offered for comparison only, and is not to be construed as absolute engineering data or constituting a warranty or representation for which we assume legal responsibility.

Chemical Resistance	-
Acids – Concentrated	Good
Acids – dilute	Good
Thermal Diffusivity, 25°C	Good
Continuous Operating Temperature	Good
Maximum No Load Temperature	Good

Electrical Properties	-
Dielectric constant	7.5-11.5
Dielectric strength (kV mm-1)	15-50
Volume resistivity @25 ̊C (Ohm-cm)	>10(14)

Mechanical Properties	-
Compressive strength (MPa)	2100
Hardness – Knoop (kgf mm-2)	2000
Hardness – Vickers (kgf mm-2)	1600-1800
Tensile modulus (GPa)	350-390

Physical Properties	-
Apparent porosity (%)	0
Density (g cm-3)	3.985
Refractive index	1.71-1.79
Useful optical transmission range (nm)	150-5500
Water absorption – saturation (%)	0

Thermal Properties	-
Coefficient of thermal expansion @20-1000 ̊C (x10-6 K-1 )	5.8
Melting point ( ̊C)	2050
Specific heat @25 ̊C ( J K-1 kg-1 )	750
Thermal conductivity @20 ̊C (W m-1 K-1 )	35-40
Upper continuous use temperature ( ̊C)	1800-1950

DATA MEASUREMENTS – All data measurements are typical and made at room temperature unless otherwise noted
THERMAL SHOCK RESISTANCE – Tests are run by quenching samples into water from various elevated temperatures. The change in temperature where a sharp decrease in flexural strength is observed is listed as ‘delta Tc’
CHEMICAL RESISTANCE – Although all alumina and zirconia ceramics are highly resistant to chemical attack, it is recommended that specific applications are discussed with Almath Crucibles to ensure optimum ceramic selection

View our full range of Sapphire products.

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Contact us to discuss a custom Sapphire solution.

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Almath Crucibles Ltd.

Epsom Building,
The Running Horse,
Burrough Green,
Newmarket, Suffolk
CB8 9NE

ISO 9001:2015 registered
(CQS Cert #GB2001792)

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