Lecture 2A Flashcards
What kinds of properties make metals ideal for use as biomaterial in the body, and conversely what are the problems associated with the long term in vivo applications of metals within the body?
Metals are dense with high melting/boiling points, good heat conduction, good electrical conduction, malleable, ductile, lustrous.
Metals can cause allergic reactions, inflammation, or loosening of the implant.
Name three metals used as bio-metallic implants.
Stainless Steel.
Titanium.
Cobalt Alloys.
Name three applications for metals as implants.
Bone and joint replacement.
Dental Implants.
Cardiovascular Devices.
Surgical Instruments.
Distinguish between ionic and covalent bonding. What bonding is more prevalent in metallic structures?
Ionic bonding occurs between cations and anions and requires electron transfer.
Covalent bonding is the sharing of electrons.
Ionic bonding is more prevalent in metallic structures.
State and describe two types of imperfections of metallic structures.
Point defects such as: vacancy, interstitial, and substitutionary atoms.
Line defects such as dislocations.
Area defects such as grain boundaries.
State the difference between crystalline and non-crystalline materials.
Crystalline material are atoms packed in periodic, 3D arrays.
No crystalline material atoms have no periodic packing.
Define unit cell as it relates to metallic lattice structure of a metal.
A unit cell is the smallest repetitive volume which contains the complete lattice pattern of a crystal.
Name and schematically draw a structure that represents a way that microstructure of metallic atoms could be arranged.
Simple Cubic.
What information does the characterization technique XRD give.
X-Ray diffraction helps determine crystal structure of the atom by the measurement of angles, spacing, and intensity from detector.
Name and describe two types of metallic crystal defects.
Point defects: such as vacancies and extra atoms.
Line defects: such as dislocations.
Define alloy and describe ways that alloys could be formed.
Alloys is a metal comprised of two or more elements, at least one of which is metallic.
Metals do not mix but can combine with substitution or interstitial.
Differentiate between elastic and plastic deformation of metals.
Elastic deformations are reversible and plastic deformations are permanent and won’t go back to their original shape.
Define and describe in detail any two of the following mechanical properties of metals. Young's modulus. Ductility. Toughness. Hardenss.
Toughness is defined as the energy to break a unit volume of material. This can be found by finding the area under the stress/strain curve.
Hardness is the resistance to permanently indenting the surface. When a metal has large hardness, it can reduce cracking or deforming as well as better wear properties of the metal.
What are the two fundamental types of dislocations?
Dislocation Motion.
Single Crystal Slip.
State and describe two types of fracture mechanisms.
Ductile Fracture: occurs with plastic deformation (One piece, large deformation).
Brittle Fracture: little or no plastic deformation, catastrophic (Many pieces, small deformation).
What is creep?
Creep is a sample deformation at a constant stress vs. time.
What are the 4 types of material or classifications of materials used for biomaterials?
Polymers.
Metals.
Composites.
Ceramics.
State and describe in detail two mechanisms of strengthening in metals.
Alloying: small impurities tend to concentrate at dislocations; reduce mobility of dislocation therefore increasing strength.
Cold Work: room temperature deformation by forging, rolling, drawing, or extrusion that can increase yield strength, tensile strength; although decrease ductility.
State and describe two types of diffusion mechanisms.
Vacancy Diffusion: atoms exchange with vacancies.
Interstitial Diffusion: smaller atoms can diffuse between atoms.
