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Novel Properties of Nanomaterials - Coggle Diagram
Novel Properties of Nanomaterials
Wettability
Ability of a liquid to maintain contact with a solid surface due to intermolecular interactions like covalent bonding or Van der waals force when brought together
Degree of wettability is determined by force balance between adhesive and cohesive
an example of good wetting is nearer to the left while poor wetting is nearer to the right
Surface Tension
Molecule net force 0 due to bulk being pulled equally in every direction by neighboring liquid molecules
But molecules exposed at surface have no neighboring molecules in all directions to provide a balanced net force. so, they are pulled inwards by neighboring molecules creating an internal pressure which is surface tension
Contact angle: angle formed by interaction between the water droplet and solid surface
Contact Angle
4 Contact Angle Terms:
Superhydrophobic: θ ≤ 10
Hydrophilic surface: θ ≤ 10
Hydrophobic surface: θ ≤ 10
Superhydrophobic surface: θ ≤ 10°
-High contact angle (hydrophobic and superhydrophobic) = wetting of surface is unfavorable so the fluid will minimize contact with surface and form a compact liquid droplet
-Low contact angle(hydrophilic) = high wettability
Self-cleaning lotus leaf
The surface of Lotus leaf has a superhydrophobic surface that allows it to pick up dirt particles by water droplets, minimizes droplet's adhesion surface.
This is due to microscopic and nanoscopic bumps on surface.
Property is dependent on:
Contact area = smaller contact area lead to lower surface energy and poorer wettability and better self-cleaning effect.
Contact angle = larger contact area cause water droplet to bead up leading to better self-cleaning effect.
Sliding angle (minimum inclination angle necessary for droplet to slide off surface) = smaller sliding angle means water droplet roll down easier and pick up more dirt particles and better self-cleaning effect.
Surface Energy
Amount of free energy required to create a unit area of "new" surface on a material
E = γ · S
S.I Unit: E= Joules, γ = J/m^2, S = m^2
E becomes significant in nanoscale regime due to large surface area
Hydrophobic surface has low surface energy due to water droplet repelling tendency= high contact angle
Hydrophilic surface has high surface energy due to water droplet attracting tendency= low contact angle
Photocatalytic Nanomaterial
Nanosized particle that work as a catalyst to break down chemicals into byproducts without presence of sunlight, they themselves remain the same in the reaction.
Light source: Ultraviolet Light.
Electrons react with oxygen in sample to form O2-
Holes react with surface hydroxyl groups to form hydroxyl radicals
Radical species attack dirt particles and break down.
Object coated with photocatalytic nanomaterial like nanocrystalline titanium dioxide/Titania (TiO2-colourless)
It undergoes a chemical reaction and will break down and dirt particles loosen due to chemical exposure= photocatalytic stage
Reaction causes object's surface to become superhydrophilic and water droplets spread evenly across surface and washes away any dirt or debris on surface = superhydrophilic stage
Superhydrophobic :
~ high static water contact angle, low sliding angle needed for water droplet to slide off surface, carrying away dirt
Superhydrophilic
~ low static water contact angle, high sliding angle that spreads water droplets that carries away dirt.
Real-Life Applications of Self-Cleaning
Nepenthes pitcher plants.
Self-cleaning aquarium glass by Diamond Shell(Australia company)
Nanocomposites
Made up of more than one type of constituent materials.
Contain matrix and reinforcement.
Matrix surrounds and supports reinforcement materials by maintaining their positions.
Reinforcements enhance matrix properties which provide mechanical and physical properties.
Made up of bulk materials in conventional composites.
Example: abalone shell and chalk. Made up of calcium carbonate but different mechanical properties.
Mechanical Properties
Composites containing nanomaterials is better than bulk materials in terms of mechanical properties due to their nanosized particles.
Nanomaterials have high surface-area-to-volume ratio that promotes facilitative bonding with matrix material which result in superior mechanical performance.
The calcium carbonate (aragonite) platelets have interlocking atoms that stack upon one another to form nanostructure.
Mechanical Properties
Toughness - can deform plastically and absorb a lot of energy before breaking. Large area under graph of stress-strain.
Stiffness
high Young's Modulus that required large forces and stresses to stretch them.
Strong materials can withstand large stresses and may stretch but require large force to break them.
~ Jaeger-Fratzl Model
Em: Young's Modulus of mineral platelets
Gp: shear modulus of protein matrix
: volume concentration of mineral platelets
p: aspect ratio(width over thickness) of mineral platelets
Types of Nanocomposites
Ceramic-matrix nanocomposites
Main part contain ceramic - chemical compound from group of oxides, nitrides, borides in forms of powders
Reinforcements: Metals
Metal-matrix nanocomposites
Main part contain metal which is melted to incorporate reinforcements
Reinforcements: ceramic powders like boron nitride, carbon nitride
Polymer-matrix nanocomposites
Main part contain polymer in form of pellets which is also melted to incorporate reinforcements
Ceramic polymeric, metal oxide and Carbon-based nanomaterials are incorporated within polymeric network to get desired properties.
Real Life Applications of Nanomaterials
Biomedical like cancer therapy, drug delivery, drug release and sunscreens.
Industrial like industrial catalysts, conductive polymers.
Environment like waste water.
Energy like solar cells and fuel cells.
