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.
|Phase at STP||Solid|
|Ultimate Tensile Strength||N/A|
|Young’s Modulus of Elasticity||N/A|
|Vickers Hardness||49000 MPa|
|Melting Point||2079 °C|
|Boiling Point||3927 °C|
|Thermal Conductivity||27 W/mK|
|Thermal Expansion Coefficient||5-7 µm/mK|
|Specific Heat||1.02 J/g K|
|Heat of Fusion||50.2 kJ/mol|
|Heat of Vaporization||508 kJ/mol|
|Electrical resistivity [nanoOhm meter]||~E15|
|Magnetic Susceptibility||−6.7e-6 cm^3/mol|
Applications of Boron
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.
Production and Price of Boron
Raw materials prices change daily. They are primarily driven by supply, demand and energy prices. In 2019, prices of pure Boron were at around 2500 $/kg.
Economically important sources of boron are the minerals colemanite, rasorite (kernite), ulexite and tincal. Together these constitute 90% of mined boron-containing ore. Turkey and the United States are the largest producers of boron products. Turkey produces about half of the global yearly demand.
Mechanical Properties of Boron
Strength of Boron
In mechanics of materials, the strength of a material is its ability to withstand an applied load without failure or plastic deformation. Strength of materials basically considers the relationship between the external loads applied to a material and the resulting deformation or change in material dimensions. In designing structures and machines, it is important to consider these factors, in order that the material selected will have adequate strength to resist applied loads or forces and retain its original shape. Strength of a material is its ability to withstand this applied load without failure or plastic deformation.
For tensile stress, the capacity of a material or structure to withstand loads tending to elongate is known as ultimate tensile strength (UTS). Yield strength or yield stress is the material property defined as the stress at which a material begins to deform plastically whereas yield point is the point where nonlinear (elastic + plastic) deformation begins.
See also: Strength of Materials
Ultimate Tensile Strength of Boron
Ultimate tensile strength of Boron is N/A.
Yield Strength of Boron
Yield strength of Boron is N/A.
Modulus of Elasticity of Boron
The Young’s modulus of elasticity of Boron is N/A.
Hardness of Boron
In materials science, hardness is the ability to withstand surface indentation (localized plastic deformation) and scratching. Brinell hardness test is one of indentation hardness tests, that has been developed for hardness testing. In Brinell tests, a hard, spherical indenter is forced under a specific load into the surface of the metal to be tested.
Brinell hardness of Boron is approximately N/A.
The Vickers hardness test method was developed by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers hardness test method can be also used as a microhardness test method, which is mostly used for small parts, thin sections, or case depth work.
Vickers hardness of Boron is approximately 49000 MPa.
Scratch hardness is the measure of how resistant a sample is to permanent plastic deformation due to friction from a sharp object. The most common scale for this qualitative test is Mohs scale, which is used in mineralogy. The Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly.
Boron is has a hardness of approximately 9.5.
See also: Hardness of Materials
Boron – Crystal Structure
A possible crystal structure of Boron is rhombohedral structure.
In metals, and in many other solids, the atoms are arranged in regular arrays called crystals. A crystal lattice is a repeating pattern of mathematical points that extends throughout space. The forces of chemical bonding causes this repetition. It is this repeated pattern which control properties like strength, ductility, density, conductivity (property of conducting or transmitting heat, electricity, etc.), and shape. There are 14 general types of such patterns known as Bravais lattices.
See also: Crystal Structure of Materials
Crystal Structure of Boron
Thermal Properties of Boron
Boron – Melting Point and Boiling Point
Melting point of Boron is 2079°C.
Boiling point of Boron is 3927°C.
Note that, these points are associated with the standard atmospheric pressure.
Boron – Thermal Conductivity
Thermal conductivity of Boron is 27 W/(m·K).
The heat transfer characteristics of a solid material are measured by a property called the thermal conductivity, k (or λ), measured in W/m.K. It is a measure of a substance’s ability to transfer heat through a material by conduction. Note that Fourier’s law applies for all matter, regardless of its state (solid, liquid, or gas), therefore, it is also defined for liquids and gases.
Coefficient of Thermal Expansion of Boron
Linear thermal expansion coefficient of Boron is 5-7 µm/(m·K)
Thermal expansion is generally the tendency of matter to change its dimensions in response to a change in temperature. It is usually expressed as a fractional change in length or volume per unit temperature change.
Boron – Specific Heat, Latent Heat of Fusion, Latent Heat of Vaporization
Specific heat of Boron is 1.02 J/g K.
Heat capacity is an extensive property of matter, meaning it is proportional to the size of the system. Heat capacity C has the unit of energy per degree or energy per kelvin. When expressing the same phenomenon as an intensive property, the heat capacity is divided by the amount of substance, mass, or volume, thus the quantity is independent of the size or extent of the sample.
Latent Heat of Fusion of Boron is 50.2 kJ/mol.
Latent Heat of Vaporization of Boron is 508 kJ/mol.
Latent heat is the amount of heat added to or removed from a substance to produce a change in phase. This energy breaks down the intermolecular attractive forces, and also must provide the energy necessary to expand the gas (the pΔV work). When latent heat is added, no temperature change occurs. The enthalpy of vaporization is a function of the pressure at which that transformation takes place.
Boron – Electrical Resistivity – Magnetic Susceptibility
Electrical property refers to the response of a material to an applied electric field. One of the principal characteristics of materials is their ability (or lack of ability) to conduct electrical current. Indeed, materials are classified by this property, that is, they are divided into conductors, semiconductors, and nonconductors.
See also: Electrical Properties
Magnetic property refers to the response of a material to an applied magnetic field. The macroscopic magnetic properties of a material are a consequence of interactions between an external magnetic field and the magnetic dipole moments of the constituent atoms. Different materials react to the application of magnetic field differently.
See also: Magnetic Properties
Electrical Resistivity of Boron
Electrical resistivity of Boron is ~E15 nΩ⋅m.
Electrical conductivity and its converse, electrical resistivity, is a fundamental property of a material that quantifies how Boron conducts the flow of electric current. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity.
Magnetic Susceptibility of Boron
Magnetic susceptibility of Boron is −6.7e-6 cm^3/mol.
In electromagnetism, magnetic susceptibility is the measure of the magnetization of a substance. Magnetic susceptibility is a dimensionless proportionality factor that indicates the degree of magnetization of Boron in response to an applied magnetic field.
Application and prices of other elements