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Thermal Conductivity & Coefficient of Expansion

Thermal conductivity is the propensity for any material to transfer heat from one point to another. Of course for heat to "flow," it is necessary for a difference of temperature to exist within a continuous section of the material. Thermal conductivity is analogous to electrical conductivity. Similarly, thermal resistance is the inverse of thermal conductivity as electrical resistance is the inverse of electrical conductivity.

Coefficient of expansion is the rate at which a material will grow in length with an increase in temperature. Most material grow in a fairly linear fashion, particularly within a defined range of temperatures. A positive coefficient of expansion indicates that the material gets longer as its temperature increases. Most metals are like that. Ice is a well-known example of a negative coefficient of expansion, since it contracts in length with increasing temperature (in other words, ice expands as it gets colder).


SubstanceThermal Conductivity
(W/cm·°C)
Coefficient of
Thermal Expansion
(ppm/°C)
Density
(g/cm3)
Specific Thermal Conductivityb
(W/cm·°C)
Air (still)0.0003   
Alumina0.276   
Alumina (85%)0.118   
Aluminum2.1650.232.70.81
Beryllia (99.5%)1.969   
Beryllia (97%)1.575   
Beryllia (95%)1.161   
Beryllium1.772   
Beryllium-Copper1.063   
Boron Nitride0.394   
Brass (70/30)1.220   
Copper3.9370.178.90.45
Copper/Invc/Copper1.640.0848.4.020
Copper/Mod/Copper1.820.0609.90.18
Copper/Mod-Cu/Copper2.45-2.800.60-0.109.40.26-0.30
Diamond (room temp)6.299   
Epoxy0.002   
Epoxy (thermally conductive)0.008   
FR-4  (G-10)0.003   
GaAs0.591   
Glass0.008   
Gold2.913   
Heatsink Compound0.004   
Helium (liquid)0.000307   
Invar0.110.0138.10.014
Iron0.669   
Kovar0.170.598.30.020
Lead0.343   
Magnesium1.575   
Mica0.007   
Molybdenum1.299   
Monel0.197   
Mylar0.002   
Nickel0.906   
Nitrogen (liquid)0.001411   
Phenolic0.002   
Platinum0.734   
Sapphire (a-axis)0.32   
Sapphire (c-axis)0.35   
Silicon (pure)1.457   
Silicon (0.0025 Ω-cm)1.457   
Silicon Carbide0.90   
Silicon Dioxide (amorphous)0.014   
Silicon Dioxide (quartz, a-axis)0.059   
Silicon Dioxide (quartz, c-axis)0.11   
Silicone Grease0.002   
Silicone Rubber0.002   
Silicon Nitride0.16 - 0.33   
Silver4.173   
Stainless Steel (321)0.146   
Stainless Steel (410)0.240   
Steel (low carbon)0.669   
Teflon0.002   
Tin0.630   
Titanium0.2190.0864.40.016
Tungsten1.969   
Water0.0055   
Zinc1.024   
 

a: Approximate values from 0 °C to 100 °C
b: Thermal conductivity divided by specific gravity
    (introduced by Dr. Carl Zweben & K.A. Schmidt)
c: Invar
d: Molybdenum


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    BSEE - KB3UON

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