Chapter 1 - Introduction to Nanotech Flashcards
What does nano mean?
comes from the greek work ‘dwarf’
expressed as 10-9
(molecular and atomic scale)
What is the range of length that classifies something as nano?
1-100nm range of at least 1 dimension
What is the equation for the surface area of a sphere?
4pi()r^2
What is the equation for the volume of a sphere?
(3/4)pi()r^3
What is nanoscience?
The natural progression of science exploring the nature of matter between atoms and molecules (defined by quantum mechanics) and condensed matter (defined by solid state chemistry/physics)
What is nanotechnology?
Working at the atomic, molecular, and supramolecular levels (1-100nm) to understand and create materials
What are nanomaterials?
Materials for which at least 1 dimension is in the nanorange.
These materials could be natural, incidental or manufactured and contain particles in an unbound state or as an aggregate or as an agglomerate. For at least 50% of these particles in the number size distribution must be on the nanoscale
What can nanomaterials be made of?
- metals
- ceramics
- polymers
- composites
What are some ancient examples of nanomaterials?
gold and silver NPs were used due to their colour properties as far back as the 4th century
- 11th century, gold + silver used in stained glass panels
- 4th century - roman cup appears red from the outside due to small amount of gold nanoparticles in the material
Who was the father of nanomaterials?
Michael Faraday
- created gold colloids with sheets of gold leaf using chemicals
Who is Richard Adolf Zsigmondy
- first to observe and perform size measurements of nanoparticles with sizes down to 10 nm using an ultramicroscope
Who invented the scanning tunneling microscope?
Gerd Binnig and Heinrich Rohrer in early 1980s
- used to manipulate single atoms when desired (but need very low tempt to immobilize them - ~-269C)
What are nanoparticles?
groups of atoms at the nanoscale
- are called molecules if they also have a defined stoichiometry (but NPs have an approximate stoichiometry)
- all 3 dimensions are in the nanoscale
What are nanoclusters?
clusters are particles containing a very small number of atoms such that it is no longer possible to clearly distinguish “bulk” atoms from hose at the surface
- general rule is a few hundred atoms or smaller
- they part a definite stoichiometry
- they are stable and follow the number of atoms according to the magic numbers equation (atoms packing around in a hard sphere)
- stoichiometric and around a few nm
What are nanocrystallites?
nanoscale size material that has crystalline order.
Crystal structure is not necessarily characteristics of the corresponding bulk material (may have different one)
Why are Nanomaterials so attractive?
Experiences changes in properties:
1. hardness
2. strength
3. wear resistance
4. frictional coefficient
5. corrosion resistance
6. magnetic properties
7. electrical properties
8. hydrogen diffusion
9. electrocatalytic properties
How does size influence internal and external size effects in nanomaterials?
internal or intrinsic size effects: change of the properties related to the particles (ex. melting T, hardness, band gap, ect.) irrespective of external disturbances
external size effects: arise always in the presence of interactions between physical fields and decreasing building units (particles, grains, domains) when the size becomes comparable with the length of the physical phenomena (free length of electrons, phonons, coherent length, ect.) ex. reflects different wavelength when the size decreases
What happens to the grains as size decreases?
Grain size decreases, thus increasing the volume fraction of grain boundaries (increase in interfaces and triple junctions)
What are the 2 categories for all approaches to make nanomaterials?
- top-down: break things down to nanoscale
- bottom-up: build up from atoms or molecules
