material science
Atomic Weight: The weighted average mass of the atoms in a naturally occurring sample of an element, typically expressed in atomic mass units (amu). It is approximately equal to the number of protons and neutrons in an atom's nucleus.
Dipoles: A pair of equal and opposite electrical charges or magnetic poles separated by a distance. In the context of molecules, dipoles refer to molecules that have a distribution of charge, leading to partial positive and negative ends (e.g., water molecules).
Electronegative: Refers to the tendency of an atom to attract electrons in a chemical bond. The higher the electronegativity, the stronger the atom pulls electrons towards itself (e.g., fluorine is highly electronegative).
Electropositive: Describes elements or atoms that tend to lose electrons and form positive ions (cations) in chemical reactions. Metals like sodium or calcium are electropositive.
Primary Bond: Strong bonds that hold atoms together in a molecule or compound. These include covalent, ionic, and metallic bonds.
Secondary Bond: Weaker interactions between molecules or atoms that are not based on the sharing or transfer of electrons. These include van der Waals forces, hydrogen bonds, and dipole-dipole interactions.
Allotropy: The existence of different forms of the same element in the same physical state, with atoms arranged differently (e.g., carbon exists as graphite, diamond, and graphene).
Amorphous Solid: A solid in which atoms or molecules are not arranged in a regular, repeating pattern. Glass is a common example of an amorphous solid.
Anisotropy: The property of being directionally dependent, meaning the material's properties vary when measured in different directions. For instance, crystalline materials may have different mechanical properties along different axes.
Coordination Number: The number of nearest neighbor atoms or ions surrounding a central atom or ion in a crystal structure.
Isotopic: Refers to atoms of the same element that have the same number of protons but different numbers of neutrons, leading to different atomic masses (e.g., carbon-12 and carbon-14).
Noncrystalline Solid: A solid that lacks a regular atomic structure, often referred to as an amorphous solid. Examples include glasses and certain polymers.
Polycrystalline: A material composed of many small crystals or grains, which are randomly oriented. Metals are often polycrystalline.
Polymorphism: The ability of a material to exist in more than one crystal form. For example, carbon can exist as diamond, graphite, or graphene.
Alloy: A mixture of two or more elements, typically metals, designed to achieve specific properties that are different from those of the individual elements.
Microstructure: The structure of a material as observed under a microscope, including the arrangement of grains, phases, and defects. The properties of a material often depend on its microstructure.
Interstitial Solid Solution: A solid solution in which smaller atoms (called interstitials) fit into the interstices or gaps between the host atoms in a crystal lattice (e.g., carbon in iron to form steel).
Solid Solution: A homogeneous mixture of two or more elements that form a single phase. The solute atoms are dispersed within the solvent's crystal structure.
Substitutional Solid Solution: A type of solid solution where atoms of the solute replace the atoms of the solvent in the crystal lattice (e.g., copper and zinc form brass).
Carburizing: A heat treatment process that introduces carbon into the surface of steel to harden it, typically by heating the steel in a carbon-rich environment.
Interdiffusion: The process by which atoms of two or more elements mix together when they come into contact, often occurring in alloys or during heat treatments.
Interstitial Diffusion: The diffusion of atoms through the interstitial spaces (gaps) in a crystal lattice, often involving small atoms like hydrogen, carbon, or nitrogen.
Self Diffusion: The movement of atoms within a pure material, typically observed in crystalline solids. It occurs without the addition of foreign atoms and is driven by thermal energy.
Vacancy Diffusion: The diffusion mechanism where atoms move by hopping into vacant sites in a crystal lattice, typically occurring in metals and other crystalline materials.