Ceramics Flashcards
What are the useful properties of Ceramics? (7 things)
- High melting points
- good resistance to heat
- good chemical stability (they don’t oxidise)
- very high elastic modulus
- very high hardness
- light
- high compressive strength
What are the less useful properties of ceramics? (3 things)
- Brittle
- Sensitive to microcracks
- Tensile strength is low
What is Morphological Fixation?
Cementing the device into tissue or press fitting into defects
What is biological fixation?
Ceramics attach by bone ingrowth
What is Bioactive fixation?
Ceramics attach by chemical bonding with bone
What is Resorbable fixation?
Ceramics are slowly replaced by bone
What are the 4 different types of ceramics?
Non-porous, porous, non-porous bioactive, resorbable
What is sintering?
Compacting and forming of a powder by pressure or heat without reaching the melting point
What is hot isostatic pressing
using an inert gas (argon) to create high pressure on the material
What are examples of a non-porous ceramic?
Aluminium Oxide, Zirconia
Tell me everything you know about aluminium oxide?
- A non-porous ceramic
- Single crystal alumina
- Strength increases with grain size
- Elastic modulus 360 - 380 GPa
- low friction and wear properties
What are some applications of aluminium oxide?
- Femoral Heat
- Bone screws and plates
- Knee prosthesis
- Dental crowns and bridges
Tell me everything you know about Zirconia?
- Non-porous
- 2nd hardest material known
- complex tetragonal crystal structure
- higher fracture toughness than aluminium oxide
- Youngs modulus of 250GPa
- you can make a smooth surface
What have been the historical problems with Zirconia?
A change in the processing of the material leads to a slight change in the structure which lead to failure of 400 femoral heads
What is glass?
Amorphous solid that lacks detectable crystallinity
an inorganic product of fusion that has cooled to a rigid condition without crystallisation
What are some examples of bioactive ceramics or glasses?
Bioactive glass and Calcium hydroxyapatite
What is Calcium Hydroxyapatite?
The primary structural component of bone
what is bioglass?
A glass that can bind to bone
it is very sensitive to composition
made of silicon oxide, calcium oxide and sodium oxide
Applications of Calcium Hydroxyapatite
- Coatings for metallic implants
- Bone filler
- Provides a scaffold and encourages the filling of bone defect by naturally forming bone
What is an Example of Resorbable Ceramics?
Calcium Phosphate
Calcium Phosphate
- Abundant in nature and in living systems
- The phase depends on the ratio of calcium to phosphate
- the most stable phase of calcium phosphate is hydroxyapatite
How is Calcium Phosphate resorbed
- Physiologic dissolution
- Physically Disintegration into small particles as a result of preferential chemical attack of grain boundaries
- Biological factors, phagocytosis causes a decrease in local pH concentration
What is an example of a non-porous ceramic
Pyrolytic Carbon
Tell me everything you know about Pyrolytic Carbon?
- Similar structure to graphite
- made by heating to very high temps in the absence of oxygen
- used as a coating material
