Thermal Conductivity Table for Common Materials

Thermal conductivity is one of the properties of materials that controls their capacity to carry heat. This quality is essential for many industrial and scientific uses, from the optimisation of heat exchangers to building materials. What a variety of materials do when subjected to heat is fundamental to optimizing operations and protecting industrial machinery. Alfa Chemistry provides the table below that summarises the thermal conductivity of the most common materials you will ever come across.

Materials	Thermal Conductivity (W/mK)
Water	0.598
Air	0.025
Ice	2.22
Glass	1.05
Boron carbide	30
Graphite	200
Carbon fiber	100
Polyethylene	0.5
Polypropylene	0.2
Carbon dioxide	0.0166
Brick	1.31
Porcelain	1.5
Tungsten carbide	110
Diamond	1000
Graphene	4000
PET	0.3
Polycarbonate	0.2
Carbon monoxide	0.024
Sand	0.25
Limestone	1.3
Elektron 21	116
Duralumin	140
Zirconium-tin alloy	18
Austenitic stainless steel	20
Mild steel	50
Gray iron	53
TZM alloy	126
Inconel	6.5
ETP	394
Cupronickel	40
Zamak 3	113
Ruby	40
Uranium dioxide	8.68
Polystyrene	0.12
Polyvinyl chloride	0.2
Nitrous oxide	0.042
Concrete	0.5
Granite	3.2
Pure titanium	22
6061 alloy	150
Zirconium-niobium alloy	18
Martensitic stainless steel	24
High-carbon steel	50
White iron	15-30
Mo-25 Re alloy	70
Hastelloy	10.2
Brass	120
Aluminium bronze	59
Soft tin solder	50
Salt	7
Kevlar	0.04
Polyamide-Nylon	0.2
Rubber	0.5
Methan	0.034
Stone wool	0.3
Quartz	3
Ti-6Al-4V	6.7
7068 alloy	190
Chromoly steel	41
Duplex stainless steel	19
Tool steel	26
Ductile iron	36
Tungsten-rhenium alloy	70
Stellite	14.8
Bronze	75
Beryllium copper	115
Amalgam	23
Sugar	0.15
Wax	0.2
Coal	0.2
Asphalt concrete	0.75
Propane	0.017
Glass wool	0.03
Aerogel	0.01
Rose gold	300
Yellow gold	320
White gold	250
PH stainless steel	18
High-speed steel	41
Malleable iron	40
Pure tungsten	170
Invar	12
Constantan	21.2
Nickel silver	40
Galistan	16.5
Oak wood	0.17
Pine wood	0.12
Gasoline	0.16
Diesel fuel	0.13
Acetylene	0.024

What is Thermal Conductivity?

Thermal conductivity (k), measured in watts per meter per Kelvin (W/m·K), quantifies a material's ability to conduct heat. It is very important for the thermal system efficiency. Materials that are very thermally conducting wick heat well, and those that are less thermally conductors are great insulators, blocking the flow of heat. For solids, liquids, and gases, the way in which heat is transferred depends upon what type of substance they are, so their thermodynamics are not the same.

Thermal Conductivity in Solids

Metals: High Conductivity Due to Electron Movement

Metals generally exhibit high thermal conductivity due to the presence of free-moving electrons. These electrons transfer heat more effectively than phonons (the quanta of lattice vibrations). This property makes metals, such as copper, aluminum, and silver, ideal for heat conduction in electrical and mechanical systems. The high electron mobility within metallic structures leads to enhanced heat transfer efficiency, which is crucial in electronics, heat exchangers, and cookware.

Non-Metals: Lattice Vibrations Dominate Heat Transfer

In non-metallic solids, heat conduction is primarily governed by phonons, which are vibrations of the atomic lattice. The efficiency of heat transfer is influenced by the material's atomic structure, with crystalline solids generally exhibiting higher thermal conductivity than amorphous materials. For example, diamond, a crystalline form of carbon, has the highest thermal conductivity among known materials, surpassing even metals like aluminum and copper.

Material	Thermal Conductivity (W/m·K)
Diamond	1000
Graphite	119
Quartz	8.7
Glass	1

The thermal conductivity of non-metals can be significantly lower than metals, as seen with materials like glass and certain polymers. For instance, graphite has relatively high thermal conductivity, making it suitable for high-temperature applications like heat shields and battery technology.

Thermal Conductivity in Liquids

Unlike solids, where heat conduction is driven by the interaction of atoms in a rigid lattice, liquids conduct heat primarily through molecular diffusion. The distance between molecules in a liquid is greater than in a solid, which reduces the efficiency of heat transfer. However, liquids tend to have higher thermal conductivities than gases due to their denser molecular structure.

Liquid	Thermal Conductivity (W/m·K)
Water	0.606
Ethanol	0.171
Mercury	8.3
Liquid Sodium	142

Water, for example, is commonly used in cooling systems due to its relatively high thermal conductivity compared to other liquids. Liquid metals, such as mercury, are used in specialized high-temperature applications where efficient heat dissipation is crucial.

Thermal Conductivity in Gases

Gases have much lower thermal conductivities than solids or liquids due to the larger distance between molecules and the lower frequency of collisions. As a result, gases are poor conductors of heat. The thermal conductivity of gases depends on their molecular weight, temperature, and pressure. Lighter gases, such as hydrogen and helium, typically exhibit higher thermal conductivity than heavier gases.

Gas	Thermal Conductivity (W/m·K)
Hydrogen	0.442
Helium	0.151
Air	0.026
Carbon Dioxide	0.016

Hydrogen, with its small molecular size, has a relatively high thermal conductivity. In contrast, gases like carbon dioxide and air have much lower conductivities, which is why air is often used as an insulator in various industrial applications.

Applications of Thermal Conductivity

Several factors influence the thermal conductivity of materials, including:

• Temperature: Thermal conductivity typically increases with temperature in metals, as electron mobility improves. However, in non-metals, it may decrease due to the increased scattering of phonons at higher temperatures.
• Pressure: In gases, thermal conductivity increases with pressure because the frequency of molecular collisions rises, leading to more efficient heat transfer.
• Material Structure: The atomic or molecular structure plays a significant role in determining thermal conductivity. Crystalline materials tend to have higher conductivities due to their ordered structure, whereas amorphous materials, such as glasses, exhibit lower thermal conductivities.
• Phase of Matter: As a general rule, solids are much better conductors than liquids and gases. However, within each phase, the specific material and its properties determine its efficiency in transferring heat.