INTRO TO MATERIALS Flashcards
electrostatic interactions between molecules. are usually much weaker than the intramolecular forces
intermolecular forces
When the electronegativity difference between bonded atoms is moderate to zero, i.e., usually less than 1.9, the bonding electrons are shared between the bonded atoms, as illustrated in Fig. 3.9.4. The attractive force between the bonding electrons and the nuclei is the [] that holds the atoms together in the molecules. The [] is usually weaker than the metallic and the ionic bonds but much stronger than the intermolecular forces.
covalent bond
Metals tend to make the [] with each other. Metals also tend to have lower electronegativity values. So, when the average electronegativity of the bonded atom is low and the electronegativity difference between them is also low, they tend to make a [].
metallic bond
is the ability of the material to conform to its intended purpose
performance
Polar molecules have permanent dipoles, one end of the molecule is partial positive (δ+) and the other is partial negative (δ-). The polar molecules have electrostatic interactions with each other through their δ+ and δ- ends called [], though these interactions are weaker than ionic bonds. The polar molecules orient in a way to maximize the attractive forces between the opposite charges and minimize the repulsive forces between the same charges
dipole-dipole interactions
[] stress is the stress state caused by an applied load that tends to elongate the material along the axis of the applied load, in other words, the stress caused by pulling the material. [] or [] is a limit state of [] stress that leads to tensile failure in the manner of ductile failure or brittle failure.
tensile strength
Tensile
ultimate tensile strength
Relatively weak, tend to be
Soft, have low melting points
Molecular solids
is the method by which a material undergo for its manufacture.
process
a physical object that is made of one or more substance(s)
materials
Held together by the intermolecular forces: dispersion forces, dipole–dipole interactions, and hydrogen bonds
Molecular solids
Held together by a delocalized “sea” of collectively shared valence electrons
Metallic solids
[] tend to have lower electronegativity and [] have higher electronegativity.
Metals
nonmetals
are composed of one or more metallic elements
metals
There is the electrostatic interaction between cation and anion, i.e., the same charges attract each other, and opposite charges repel each other. The cations and anions orient themselves in a 3D crystal lattice in such a way that attractive interactions maximize and the repulsive interactions minimize. [] are usually weaker than metallic bonds but stronger there the other types of bonds.
Ionic bonds
the ability of a material to return to its previous shape after stress is released.
Elasticity
a material can be plastic deformed and shaped when cold. A [] material can be plastic shaped with hammering or rolling without fracture.
Malleability
is a material trait in terms of the kind and magnitude of response to a specific imposed stimulus.
property
the resistance to compressive stress which is caused by an applied load that acts to reduce the length of the material along the axis of the applied load, in other words, a resistance from squeezing the material.
Compressive Strength
forces caused by correlated movements of the electrons in interacting molecules, which are the weakest of intermolecular forces and are categorized as van der Waals forces.
london dispersion or dispersion forces
When the electronegativity difference is low, usually less than 1.9, the bond is either [] or []
metallic or covalent.
The forces holding ions together in ionic solids are electrostatic forces. Opposite charges attract each other. These are the strongest intermolecular forces. [] hold many ions in a crystal lattice structure.
Ionic forces
the resistance to the stress state caused by the combined energy of a pair of opposing forces acting along parallel lines of action through the material, in other words, the stress caused by faces of the material sliding relative to one another. An example is cutting paper with scissors or stresses due to torsional loading.
shear strength
a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion.
Hardness
composed of two (or more) individual materials which come from the metal, ceramic and/or polymers.
composites
Extremely hard, unique property as
semiconductor
Covalent-network solids
employed in components implanted into the human body for replacement of diseased or damaged body parts.
biomaterials
Big changes occur in the property with a small change in the crystal dimension
Nanomaterials
Held together by the mutual attraction between cations and anions (ion-ion)
Ionic solids
compounds between metallic and nonmetallic elements (most frequently oxides, nitrides, and carbides)
ceramics
chemical bonds holding the atoms together in the molecules.
intramolecular forces
MATERIALS CLASSIFICATION:
polymers, metals, ceramics, composites
Solids in which the dimensions of individual crystals have been reduced to the order of 1–100 nm
Nanomaterials
Held together by an extended network of covalent bonds
Covalent-network solids
Stronger and have higher melting points than molecular solids, more flexible than metallic, ionic, or covalent-network solids.
polymers
usually relates to the arrangement of its internal components.
structure
Contain long chains of atoms, where the atoms within a given chain are connected by covalent bonds and adjacent chains held to one another largely by weaker intermolecular forces
polymers
materials with dimensions on the order of a nanometer
nano engineered materials
When the electronegativity difference between the bonded atoms is large, usually more than 1.9, the bond is []. Generally, a bond between a metal and a nonmetal is [].
ionic
MECHANICAL PROPERTIES OF MATERIALS:
Tensile Strength
Shear Strength
Compressive Strength
Elasticity
Hardness
Malleability
Plasticity
materials that are able to sense changes in their environments and then respond to these changes in predetermined manners
smart materials
is designing or engineering the structure of a material to produce a predetermined set of properties on the basis of its structure–property correlations.
MATERIALS ENGINEERING
a weak attraction that results when a polar molecule induces a dipole in an atom or in a nonpolar molecule by disturbing the arrangement of electrons in the nonpolar species.
Induced Dipole
+ions arranged in a well-defined 3D arrangement called crystal lattice with some of the outermost electrons roaming around in the whole piece of the [], forming a sea of electrons around the metal atoms, as illustrated in Fig. 3.9.2. The attraction between +ions and the sea of free moving electrons is the [] that holds the atoms together in a piece of []. The [] is usually the strongest type of chemical bond.
metallic bond
are electrostatic interactions involving a partially charged dipole of one molecule and a fully charged ion.
ion-dipole
have electrical properties that are intermediate between the electrical conductors and insulators
semiconductors
ADVANCED MATERIALS:
semiconductors, biomaterials, smart materials, nano engineered materials
involves the investigation on why materials behave the way they do, how they were made and how they can be improved.
MATERIALS SCIENCE AND ENGINEERING
involves investigation of the relationships that exist between the structures and properties of materials.
MATERIALS SCIENCE
the ability of a solid material to undergo permanent deformation, a nonreversible change of shape in response to applied forces.
Plasticity
Hard, brittle, electrically and thermally
insulated
Ionic solids
Nonmetals tend to make a [] with each other. Nonmetals also have higher electronegativities. So, when the average electronegativity of the bonded atom is high and the electronegativity difference between them is low, they tend to make a [].
covalent bond
between a partially positively charged hydrogen in one molecule and a partially negatively charged oxygen, nitrogen, or fluorine in a nearby molecule.
h bonding
Good electrical conductor, relatively
strong but not brittle, high melting points
Metallic solids
mostly composed of organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements and are characterized by very large molecular structures, often chain-like in nature that have a backbone of carbon atoms.
polymer
