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Boron and Silicon – Comparison – Properties

This article contains comparison of key thermal and atomic properties of boron and silicon, two comparable chemical elements from the periodic table. It also contains basic descriptions and applications of both elements. Boron vs Silicon.

boron and silicon - comparison

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Boron and Silicon – About Elements


Significant concentrations of boron occur on the Earth in compounds known as the borate minerals. There are over 100 different borate minerals, but the most common are: borax, kernite, ulexite etc. Natural boron consists primarily of two stable isotopes, 11B (80.1%) and 10B (19.9%). In nuclear industry boron is commonly used as a neutron absorber due to the high neutron cross-section of isotope 10B. Its (n,alpha) reaction cross-section for thermal neutrons is about 3840 barns (for 0.025 eV neutron). Isotope 11B has absorption cross-section for thermal neutrons about 0.005 barns (for 0.025 eV neutron). Most of (n,alpha) reactions of thermal neutrons are 10B(n,alpha)7Li reactions accompanied by 0.48 MeV gamma emission.


Silicon is a hard and brittle crystalline solid with a blue-grey metallic lustre, it is a tetravalent metalloid and semiconductor.

Boron in Periodic Table

Silicon in Periodic Table

Source: www.luciteria.com

Boron and Silicon – Applications


Nearly all boron ore extracted from the Earth is destined for refinement into boric acid and sodium tetraborate pentahydrate. In the United States, 70% of the boron is used for the production of glass and ceramics. The major global industrial-scale use of boron compounds (about 46% of end-use) is in production of glass fiber for boron-containing insulating and structural fiberglasses, especially in Asia. Boron is added to boron steels at the level of a few parts per million to increase hardenability. Higher percentages are added to steels used in the nuclear industry due to boron’s neutron absorption ability (e.g. pellets of Boron Carbide). Boron can also increase the surface hardness of steels and alloys through boriding. Boron carbide and cubic boron nitride powders are widely used as abrasives.


Most silicon is used industrially without being purified, and indeed, often with comparatively little processing from its natural form. Silicon is a vital ingredient in aluminum, steel, and iron alloys. It is added as a fluxing agent for copper alloys. In the form of clay and sand, it is used to manufacture bricks and concrete; it is a valuable refractory material for high-temperature work, for example, molding sands for castings in foundry applications. Silica is used to make fire brick, a type of ceramic. Silicate minerals are also in whiteware ceramics, an important class of products usually containing various types of fired clay minerals (natural aluminium phyllosilicates). An example is porcelain, which is based on the silicate mineral kaolinite. Traditional glass (silica-based soda-lime glass) also functions in many of the same ways, and also is used for windows and containers. Hyperpure silicon metal and doped hyperpure silicon (doping with boron, phosphorous, gallium, or arsenic) are used in solar cells, transistors and semiconductors.

Boron and Silicon – Comparison in Table

Element Boron Silicon
Density 2.46 g/cm3 2.33 g/cm3
Ultimate Tensile Strength N/A 170 MPa
Yield Strength N/A 165 MPa
Young’s Modulus of Elasticity N/A 150 GPa
Mohs Scale 9.5 7
Brinell Hardness N/A N/A
Vickers Hardness 49000 MPa N/A
Melting Point 2079 °C 1410 °C
Boiling Point 3927 °C 3265 °C
Thermal Conductivity 27 W/mK 148 W/mK
Thermal Expansion Coefficient 5-7 µm/mK 2.6 µm/mK
Specific Heat 1.02 J/g K 0.71 J/g K
Heat of Fusion 50.2 kJ/mol 50.55 kJ/mol
Heat of Vaporization 508 kJ/mol 384.22 kJ/mol