Transcript smart_materials_1 - Aldercar High School

SUMMARY - Descriptions
IONS
ONLY
IONIC
Crystals
Dissolve in water
eg sodium chloride (salt)
SIMPLE MOLECULAR
Usually Gases
eg CO2, H2O
MOLECULES
ONLY
METALLIC
Strong malleable solids
IONS +
Don’t dissolve
FREE
eg copper
ELECTRONS
ATOMS
joined into
GIANT
MOLECULE
S
GIANT MOLECULAR
Hard strong solids
Don’t dissolve
eg diamond
(graphite – special case)
SUMMARY - PROPERTIES
Structure Property
Reason
Ionic
HIGH mpt/bpt
CONDUCT: Solid NO
Molten YES Dissolved YES
Strong bonds between IONS
Ions can’t move
Ions can move to carry current
Covalent – LOW mpt/ bpt (often gas at
room temp). Soft when solid
Simple
molecular
CONDUCT: Never
Bonds between MOLECULES
very weak.
Molecules aren’t charged
Covalent – HIGH mpt/bpt. Hard & strong Strong bonds between all ATOMS
giant
No free charges/electrons
molecular
CONDUCT: Never
Covalent graphite
HIGH mpt/bpt
Soft & slippery
CONDUCT: YES (fairly well)
Strong bonds between ATOMS
Weak bonds between LAYERS
Free electrons between layers
Metallic
HIGH mpt/bpt. Hard & strong Strong bonds between IONS
Malleable
Regular structure, layers slide
CONDUCT: YES (very well) Free electrons between ions
Structure of an Alloy
1. Draw this picture.
2. What 2 things are
obvious from it?
Different size atoms
Irregular structure
This makes alloys HARDER than pure metals.
Smart Materials
Smart materials' 'are materials that have
one or more properties that can be
significantly changed in a controlled
fashion by external stimuli, such as
stress, temperature, moisture, pH,
electric or magnetic fields.
Smart Liquids
When a magnetic field is
applied to the fluid it becomes semi-solid
and when the field is removed, the fluid
returns to a free-flowing liquid.
•
http://www.youtube.com/watch?v=kL8R8SfuXp8
Shape Memory Alloys
A shape memory alloy is an
alloy that "remembers" its original,
cold, forged shape, and which returns to
that shape after being deformed by applying
heat.
http://www.youtube.com/
watch?v=fsBHF_j2FJ4
Exam Question
Nanomaterials
Are very small but how small?
Human hair 9 micrometers is
equivalent to 0.000009 m
40 microns
9 microns
0.000000009 m is 9 nm or 0.009
micrometers
0.25 nanometers is the average length of a
bond between atoms!!!
Very Small Can Make
Properites Very Different
Some Potential Uses
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Filtration
Catalysis
Tissue engineering
Drug delivery
Diagnostics
Memory storage
Quantum computers
Optoelectronics
Quantum dots
Nanotubes
• Cylindrical carbon molecules have novel properties that
make them potentially useful in many applications in
nanotechnology, electronics, optics and other fields of
materials science, as well as potential uses in architectural
fields. They exhibit extraordinary strength and unique
electrical properties, and are efficient thermal conductors.
Their final usage, however, may be limited by their potential
toxicity and controlling their property changes in response to
chemical treatment.