1. MASE 542/Chem 442
Ceramics and Glasses

2. stable attachment to connective tissue
Medical applications
Inorganic / non-metallic
Diagnostics, thermometers, tissue culture flasks
Fiber optics for biosensors and endoscopy
Porous carriers for biomolecules
Enzymes, antigens, antibodies
Naturally inert and chemically resistant
Resistant to microbial attack, pH change, temp
Ceramics used in dentistry for dentures, glass filled ionomer cement and crowns
Implants
Generally used to replace skeletal hard connective tissues
Require stable attachment
CERAMICS AND GLASSES ARE GENERALLY USED TO REPAIR OR REPLACE SKELETAL HARD CONNECTIVE TISSUES.
stable attachment to connective tissue

3. Ceramic Glass Inorganic compounds
contain metallic and non-metallic elements
inter-atomic bonding is ionic/covalent
generally formed at high temperatures.
Glass
An inorganic product of fusion that has cooled to a rigid condition without crystallization
An amorphous solid.
Lacking detectable crystallinity
only short-range atomic order
glassy or vitreous

4. Crystal versus Glassy Ceramics
Crystalline ceramics have long-range order, with components composed of many individually oriented grains.
Glassy materials possess short-range order, and generally do not form individual grains.
Most of the structural ceramics are crystalline.

5. Glass-ceramic: Polycrystalline solids prepared by the controlled crystallization (devitrification) of glasses.
Bioactive material: A material that elicits a specific biological response at the interface of the material, resulting in the formation of a bond between the tissues and the material.

6. Common Ceramics
Alumina, Zirconium, Hydroxyapatite, Calcium phosphates, Bioactive glasses are common
Porous ceramic materials
exhibit much lower strengths
extremely useful as coatings for metallic implants. 
The coating aids in tissue fixation of the implant by providing a porous surface for the surrounding tissue to grow into and mechanically interlock. 
Certain ceramics are considered bioactive ceramics if they establish bonds with bone tissue.

7. Ceramic Material Properties
• Composition • Microstructure • Phase state – Crystal structure – Defect structure – Amorphous structure – Pore structure • Surface – Flatness – Finish – Composition – Porosity • Shape and processing
Microstructure is affected by
The Thermal processes

8. Atomic Bonding in Ceramics
-- Can be ionic and/or covalent in character.
-- % ionic character increases with difference in
electronegativity of atoms.
• Degree of ionic character may be large or small:
CaF2: large
SiC: small
Adapted from Fig. 2.7, Callister & Rethwisch 8e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by
Cornell University.)

9. Factors that Determine Crystal Structure
1. Relative sizes of ions – Formation of stable structures:
--maximize the # of oppositely charged ion neighbors. - +
unstable - + - +
Adapted from Fig. 12.1, Callister & Rethwisch 8e.
stable
stable
2. Maintenance of
Charge Neutrality :
--Net charge in ceramic
should be zero.
--Reflected in chemical
formula:
CaF 2 : Ca 2+
cation F -
anions + A m X p
m, p values to achieve charge neutrality

10. Coordination # and Ionic Radii
cation
anion
• Coordination # increases with
To form a stable structure, how many anions can
surround around a cation?
Adapted from Fig. 12.2, Callister & Rethwisch 8e.
Adapted from Fig. 12.3, Callister & Rethwisch 8e.
Adapted from Fig. 12.4, Callister & Rethwisch 8e.
ZnS
(zinc blende)
NaCl
(sodium
chloride)
CsCl
(cesium r
cation
anion
Coord #
< 0.155 2
linear 3
triangular 4
tetrahedral 6
octahedral 8
cubic
Adapted from Table 12.2, Callister & Rethwisch 8e.

11. table_12_03
table_12_03

12. Computation of Minimum Cation-Anion Radius Ratio
Determine minimum rcation/ranion for an octahedral site (C.N. = 6)
a = 2ranion

13. Example Problem: Predicting the Crystal Structure of FeO
• On the basis of ionic radii, what crystal structure
would you predict for FeO?
Cation
Anion Al 3+ Fe 2 + Ca 2+ O 2- Cl - F
Ionic radius (nm)
0.053
0.077
0.069
0.100
0.140
0.181
0.133
• Answer:
based on this ratio,
-- coord # = 6 because
0.414 < < 0.732
-- crystal structure is NaCl
Data from Table 12.3, Callister & Rethwisch 8e.

14. Processing of Ceramics
1. Compounding
Mix and homogenize ingredients into
a water based suspension = slurry
a solid plastic material containing water = clay
2. Forming
The clay or slurry is made into parts by pressing into mold (sintering). The fine particulates are often fine grained crystals.
3. Drying
The formed object is dried, usually at room temperature to the so-called "green" or leathery state.
4. Firing
Heat in furnace to drive off remaining water. Typically produces shrinkage, so producing parts that must have tight mechanical tolerance requires care.
Porous parts are formed by adding a second phase that decomposes at high temperatures forming the porous structure.

15. Metal- Ceramic Comparison

16. fig_01_05
fig_01_05

17. Advantages of Ceramics:
inert in body (or bioactive in body)
Chemically inert in many environments
high wear resistance (orthopedic & dental applications)
high modulus (stiffness) & compressive strength
Comparable to metals
esthetic for dental applications

18. Disadvantages of Ceramics
brittle (low fracture resistance, flaw tolerance)
low tensile strength (fibers are exception)
poor fatigue resistance (relates to flaw tolerance)

19. TABLE 2 Types of Bioceramic–Tissue Attachment and Their Classification
Example
Al2O3 (Single crystal
and polycrystalline)
Al2O3 (Polycrystalline)
Hydroxyapatite-coated
porous metals
Bioactive glasses
Bioactive glass-ceramics
Hydroxyapatite
Calcium sulfate (Plaster
of Paris)
Tricalcium phosphate
Calcium-phosphate salts
Type of attachment
1. Dense, nonporous, nearly inert
ceramics attach by bone growth into
surface irregularities by cementing the device into the tissues or by
press-fitting into a defect
(“morphological fixation”).
2. For porous inert implants, bone
ingrowth occurs that mechanically
attaches the bone to the material
(termed “biological fixation”).
3. Dense, nonporous surface-reactive
ceramics, glasses, and glass-ceramics attach directly by chemical bonding with the bone (termed “bioactive fixation”).
4. Dense, nonporous (or porous)
resorbable ceramics are designed to be slowly replaced by bone.