Materials Exam

metal examples

stainless steel, cobalt alloys, titanium alloys

metal applications

joint replacements, dental root implants, orthopedic fixation (bone plates)

metallic bonding

orderly atomic packing and a crystalline structure characterized by a 3D array. exhibits metallic bonding where valence electrons are delocalized and shared by all atoms. this makes metals ductile, meaning they deform when a load is applied and can easily form alloys with other metals. good electrical and thermal conductors because electric field triggers movement of electrons, which generates energy. non-directional

ceramics examples

aluminum oxide, zirconia, and calcium phosphates

ceramics applications

femoral ball liners, acetabular cup liners, dental implants, and bone fillers

ionic bonding

often in ceramics. non-directional so the magnitude of bond is equal in all directions. strong electrostatic forces which makes ceramics hard (able to withstand forces) and brittle (bonds and lattices break with too much force). high melting and boiling points.

ceramics structure

crystalline materials, possessing an orderly atomic packing in 3D arrays, though some can be amorphous. vacancies exist for both cations and anions, and electroneutrality must be maintained when impurities are present

synthetic polymer examples

silicones, polyethylene, polyvinyl chloride, polyurethanes, and polyactides

synthetic polymer advantages and disadvantages

positive: mass produced and able to tailor for the application

negative: treatment to improve integration

natural polymer examples

collagen, gelatin, elastin, silk, and polysaccharides

natural polymer advantages and disadvantages

positive: derived from the body and have similar properties to biological tissues

negative: feasibility, low mechanical processes, and pathogen removal

polymer applications

UHMWPE cup liner, some joint replacement articulating surfaces, spinal cages, biodegradable bone plates for low-load regions, biodegradable sutures, and tissue engineering scaffolds

covalent bonding

common in polymeric materials. directional, meaning bonds will remain in the aligned manner. this contributes to the toughness of the material (ability to absorb energy without rupture). lower melting and boiling points and electrical conductivity in comparison to ionic or metallic bonds. strong forces within molecules and weaker forces between them.

biomaterials attributes

biocompatibility, sterilizability, physical characteristics, manufacturability

biocompatibility

noncarcinogenic, nonpyrogenic, nontoxic, nonallergenic, blood compatible, non-inflammatory

sterilizability

not destroyed by typical sterilization techniques such as autoclaving, dry heat, radiation, and ethylene oxide

physical characteristics

strength, elasticity, and durability

manufacturability

machinable, moldable, extrudable

crystalline materials

orderly atomic packing, 3D arrays, metals, most ceramics, and some polymers.

lattice

periodic and geometric arrangement of atoms or ions in space (fundamental unit of crystal structure). specific atom, ion, or molecule is known as the motif or basis of the crystal structure

amorphous

no packing order which occurs during rapid cooling. most polymers and some ceramics

single crystal

a crystalline solid that exhibits only one orientation of arrangement

polycrystalline

solids that exhibit more than one orientation

simple cubic

CEL: a=2R

APF: 0.52

FCC

CEL: 2R(square root 2)

ATP: 0.74

BCC

CEL: 4R/(square root 3)
APF: 0.68

vacancies

vacan atomic sites in a structure (temperature dependent). exist in ceramics for both cations and anions. electrneutrality (charge balance) must be maintained when impurities are present

self-interstitials

extra atoms positioned between atomic sites in a monoatomic crystal. exists for cations but not as common for anions because anions are large relative to the interstitial sites

shottky defect

a paired set of cation and anion vacancies

frenkel defect

a cation vacancy/cation interstitial pair

edge dislocation

extra half plane of atoms inserted in a crystal structure

screw dislocation

spiral planar ramp resulting from shear deformation

dislocations

provide a pathway/mechanism for plastic deformation (irreversible change in shape arising from force). presence of slip accounts for the difference in theoretical/measured strength of metals. result in metal ductility and influence electronic and optical properties

grain

a region of space possessing the same crystallographic orientation

grain boundary

intersection of two regions of different orientation

area defects

effects malleability (ability to deform under compressoforce) and ductility (tensile force). less malleable and ductile because boundaries provide rigid structure which prevents atoms from moving. influenced by heating (more malleable) and cooling (more grain boundaries which makes it stronger)

self diffusion

the movement of identical atoms in a pure metal

vacancy diffusion

atoms exchange with vacancies. applies to substitutional impurities. rates depend on number of vacancies and activation energy to exchange

interdiffusion

in an alloy, atoms tend to migrate from regions of high to low concentration

interstitial

smaller atoms can diffuse between larger atoms. more rapid than vacancy diffusion

biomedical applications of diffusion

chemical protective clothing, nutrient transport/tissue engineering, controlled release/drug delivery, and contact lenses