Introduction to Nanomaterials

• Nano is 1nm = 10^-9 m.
• Nanomaterials are materials with atom sizes ranging from 1nm to 100nm.
• Nanoscience studies the basic properties of materials and compounds with at least one dimension on the nanoscale.
• Nanotechnology involves creating (design, production, devices) materials with structural features at nanometer scale.

Surface to Volume Ratio

• Nanomaterials have a larger surface to volume ratio compared to bulk materials.
• Considering an atom as a sphere, surface area = 4πr², volume = (4/3)πr³.
• Surface area to volume ratio (S/V) = (4πr²)/((4/3)πr³) = 3/r.
• As the radius of an atom decreases, the surface area to volume ratio increases.

Significance of S/V

• Nanoparticles become more reactive due to the increased surface area to volume ratio.
• Materials inert in bulk form become reactive in their nanoform.
• Increased efficiency in machines.

General Properties

• Particle size is in the range of 1nm-100nm.
• A 1nm particle has approximately 25 atoms.
• Larger surface to volume ratio.

Learner Outcomes

• Apply fundamental knowledge of crystal parameters to analyze basic engineering problems.
• Apply fundamental knowledge of non-crystalline solids for various applications.
• Apply fundamental knowledge of magnetic and dielectric materials in various technical fields by analyzing their intrinsic behaviors.
• Use basic knowledge of nanomaterials and their characterization techniques to identify their applications in societal issues.

Optical Properties

• Nanomaterials show optical absorption.
• They also show scattering of light.
• The frequency of emission can be tailored.
• Shows Blueshift in frequencies.

Electrical Properties

• Conductivity differs from bulk materials.
• Due to energy level changes, band gap changes at the nanoscale.

Magnetic Properties

• Easier to show ferromagnetic behavior.
• Saturation magnetization increases.
• Magnetic moment increases.
• Unstable magnetization due to superparamagnetic behavior.

Mechanical Properties

• Hardness and strength are high.
• Show more wear resistance, erosion resistance and last longer.
• Less elastic properties.

Applications

• Nanobiology.
• Nanoelectronics.
• Nanomaterial engineering.
• Nano-energy and environment.
• Nanomedicine.
• Nanofilters.
• Nanocatalysts.
• Nanosensors.

Two Main Approaches

• Top-down approach involves carving out nanosized particles from a bulk material through successive cutting.
• Ball milling and sputtering are examples of top-down approaches.
• Bottom-up approach involves building nanomaterials atom by atom, molecule by molecule, or cluster by cluster.
• Chemical vapor deposition and sol-gel methods are examples of bottom-up approaches.

Ball Milling

• Small, hard balls rotate inside a container to crush bulk materials into nanomaterials.

Ball Milling Parts

• Tank with a lid.
• Hardened steel or tungsten carbide balls.
• Impeller.
• Rotating shaft.

Ball Milling working

• Balls and particles are put inside and the container is closed with lid.
• When the container rotates around its central axis, the material is forced to press against the wall.
• Milling balls impact energy on collision and produce nano sized particles.

CVD - Chemical Vapor Deposition can be used for

• Preparation of metal nanoparticles

Chemical Vapor Deposition Principle

• Precursor molecules are adsorbed to the substrate surface, forming new bonds and new compounds.

Chemical Vapor Deposition Parts

• An oven which requires quartz tube
• Temperature controller
• Quartz boat in which the substrate is kept
• Gas in-let and gas outlet

Chemical Vapor Deposition Working

• A chemical compound is first vaporized and fragmented under suitable temperature and pressure.
• These fragments are called precursors.
• Precursor molecules float to the reactor en route to the hot substrate and diffuse over the substrate.
• A fraction of diffused precursor molecules get adsorbed to the substrate surface.
• When those molecules find enough energy to overcome the bond energy, they decompose into new fragments, forming new bonds and new compounds.

Chemical Vapor Deposition can be used for

• Preparing carbon nanomaterials.