scioly material science

metals

ability to conduct electricity, their shiny appearance, and their mechanical properties like malleability and ductility. Metals readily form positive ions, which means they tend to lose electrons in chemical reactions, resulting in positively charged particles.

metallic bond

-"sea" of delocalized electrons around a lattice of positively charged metal ions. The free electrons act as a glue, holding the structure together, and giving metals their characteristic properties, such as electrical conductivity, malleability, and the ability to conduct heat

-two main types of alloys: interstitial and substitutional

Substitutional alloy

-forms when elements with atoms of similar atomic radii are mixed, and the atoms of one element replace the atoms of another element

-usually made up of metals

Interstitial alloys

-form when the elements being mixed have different atomic radii and the smaller atoms fill in the interstitial spaces (holes) in the lattice structure of the larger atoms

-usually made up of metals and nonmetals

low hardness (metals)

-positive metal ions are surrounded by a "sea" of electrons, they can move past each other without breaking the bonds that hold the material together

-malleabile

high elastic modulus (metals)

-stiffness, or resistance to being deformed under stress

-require a significant amount of force to bend or stretch

-ideal for construction

low thermal expansion (metals)

-expand very little when subjected to heat

-important in applications where dimensional stability is critical, such as in precision engineering and the construction of machinery

metal expansion formula

ΔL = αLΔT, where α is the coefficient of linear thermal expansion, L is the initial length, and ΔT is the change in temperature.

high ductility (metals)

-ability of a material to be stretched into a wire without breaking

corrosion (metals)

-occurs when metals react with elements like oxygen, leading to the formation of oxides or other compounds

high density (metals)

-high mass per unit volume

-body-centered cubic (BCC), face-centered cubic (FCC), or hexagonal close-packed (HCP)

BCC (body centered cubic)

-coordination number of 8

-one atom in center and each of the corners of the cube

FCC (face centered cube)

-coordination number of 12

-one atom in the center of the face of the cube, one atom in each of the corners

HCP (hexagonal close packed

-coordination number of 12

-hexagon shaped, one atom at each of the corners and one in the center of the face. three atoms in between the two faces

degree of crystallinity

-degree of structural order in a solid material

-crystalline: high degree of order, strength and rigity

-semi-crystalline: has cystalline and amorphous regions, flexibilty with strenth

-amorphous: flexible but less strong (glass)

magnetic properties of metals

-diamegnetism: weak repulsion from a magnetic field

-paramagnetism: stronger magnetic properties, unpaired electrons create magnetic dipoles that align with an external magnetic field, although this alignment disappears when the field is removed

-ferromagnetism: magnetic moments that align without an external field, permanent magnet,

grain structure (microscopic view of metals)

-small randomly oriented crystals

-smaller grains result in stronger metal

-an be observed by sanding and polishing the metal surface, revealing the pattern of grains

-crucial in determining the metal's hardness, strength, and resistance to deformation.

metal forms (microscopic view of metals)

-combines the properties of metals with the lightweight nature of foams

-consist of a metal matrix filled with a large number of gas-filled pores

-sponge-like appearance

-strength and electrical conductivity

-excellent energy absorption capabilities

ceramics

-typically stiff, strong, and hard, but they are also brittle, meaning they are more likely to fracture under stress

-excellent insulators of heat and electricity

-lack the ductility and malleability of metals

polymers

-made up of long chains of repeating molecular units called monomers

-low in density and are not as stiff or strong, making them more flexible and easier to deform

-extremely ductile and can be stretched to great lengths without breaking

-do not react easily with other substances

-nonmagnetic and poor conductors of electricity, but they can if they have a backbone of alternating double and single bonded carbon atoms

composites

-materials made by combining two or more different materials to achieve properties that are not possible with a single material

metals in nature

native state- metals exist in their pure, elemental form, often as nuggets or grains, typically less reactive

combined state- are found as part of minerals, where they are chemically bonded with other elements

mining

surface mining- ores are extracted from the surface of the earth using heavy machinery

subsurface mining- ores are extracted from beneath the earths surface

after mining, the metal needs to be seperated from the material through smelting or chemical reduction

Pyrometallurgy- use of high temperatures to convert the ore into a raw metal

hydrometallurgy- aqueous chemistry to convert the ore into a raw metal

electrolysis- used if the metal cannot be easily reduced through traditional methods

hotworking (manufacturing technique)

-a metal is deformed at a temperature above its recrystallization point

-allows the metal to be shaped without cracking

-forging: a metal piece is hammered or pressed into a desired shape

-rolling: the metal is passed between rollers to reduce its thickness and improve its surface finish

casting (manufacturing technique)

-molten metal is poured into a mold to form a specific shape as it cools and solidifies

-allows for the production of complex shapes that would be difficult or impossible to achieve through other manufacturing methods

-sand casting: sand is used to create the mold

-die casting: involves forcing molten metal into a mold under high pressure

Powder metallurgy (manufacturing technique)

-involves compacting powdered metal into a desired shape, followed by heating it to bond the particles together without melting the metal

-useful for producing complex shapes or for materials that are difficult to work with using traditional methods, such as those with high melting points or low ductility

-allows for precise control over the material's properties, such as density and porosity