CS代写 LECTURE 11

Emerging Materials: Nanomaterials
Resources, Processes & Materials Engineering
LECTURE 11

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Lecture Focus
ENGINEERED NANOMATERIALS
• Nanorods
• Nanosheets
• Nanocrystals • Composites
Reproduced from “Materials and Man’s Needs”, National Academy of Sciences, Washington D.C., 1974.

Lecture Outline
NANOMATERIALS
Nanomaterials
• Overview
• Classification
Nanomaterial Synthesis Approaches
Physics at Nanoscale
• Surface effects
• Properties at nanoscale
Applications • Food
• Electronics
Top – Down Approach
Bottom – Up Approach

What is a nanometer?
A nanometre is one billionth of a metre.
TASK: Human hair diameter is about
10 micrometers. What is the diameter
1nm=10-9 m

Nanoscience & Nanotechnology
Nanomaterials can be defined as materials possessing, at minimum, one external dimension measuring 1-100nm.
Nanoscience is the study of structures and materials on an ultra-small scale, and the unique and interesting properties these materials demonstrate.
Nanotechnology, is the design, production and application of structures, devices and systems at the nanoscale.

Early Nanotechnology
Further reading “Tiny Is Beautiful: Translating ‘Nano’ Into Practical” by on The New York Times 22nd Feb 2005. [(accessed on 10 May 2022)]; Available online:
13th Century: “Damascus” saber blades contained carbon nanotubes and cementite nanowires
https://www.nytimes.com/2005/02/22/science/tiny-is-beautiful-translating-nano-into-practical.html

Analyzing Historical Context
“There’s plenty of room at the bottom” lecture by at the annual American Physical Society meeting, Caltech (1959).
(1974) Prof. used the term “nanotechnology” for the first time in a scientific publication to explain precision engineering in semiconductor processes.

Significance of Nano-scale and Growth Outlook
• The ability to see nano-sized materials has opened up a world of possibilities in a variety of industries and scientific endeavors.
• The global market for nanotechnology should grow from USD $5.2 billion in 2021 to USD $23.6 billion by 2026, at compound annual growth rate (CAGR) of 35.5% for the period of 2021-2026. .
$34 billion AUD by 2026

Classification of Nanomaterials
CLASSIFICATION
Natural Nanomaterials Synthetic Nanomaterials
0-Dimensional Nanomaterials 1-Dimensional Nanomaterials 2-Dimensional Nanomaterials

A nanomaterial made by nature through (bio)geochemical or mechanical processes, without direct or indirect connection to a human activity or anthropogenic process.
• Nanoparticles including combustion products, forest fires, volcanic ash (65% SiO2, 18% Al2O3, 5% Fe2O3, 2% MgO, 4% CaO, 4% Na2O, and 0.1% S), ocean spray, and the radioactive decay of radon gas.
• Bacteria such as Shewanella and Lactobacillus species responsible for the fermentation of milk proteins.
• Coronavirus(125nm)responsibleforSARSdisease.

Two general categories: “incidental” and “engineered” nanoparticles.
• Incidental nanoparticles are the byproducts of human activities; have poorly controlled sizes and shapes.
ØSoot nanoparticles (consist mainly of carbon) are commonly found in atmosphere.
• Engineered nanoparticles are specifically designed and deliberately synthesized by human beings. They have very precisely controlled sizes, shapes, and compositions.
ØCarbon nanomaterials such as fullerenes, carbon nanotubes, and graphene.
ØSun block that contains combinations of ZnO & TiO2 nanoparticles including products from Neutrogena, Boots, Avon, The Body Shop, L’Oréal, Nivea..

Regardless of a nanomaterial’s origin, their size and shape, and not just their chemical composition and atomic structure, are fundamental to their properties; this makes them distinct from materials existing at the macroscale.
(3D) – Not a nanomaterial
3D graphenes

Nanomaterials of Zero Dimension (0D)
• A0Dstructureisthesimplestblockthatcanbeusedforthedesignofnanomaterials.
• Allthreedimensionsareinthenanometerregimeandhaveadiameterlessthan100nm. • Nanoparticles,nanocrystals,andnanoclusterscorrespondtothisgroup.
shutterstock.com/g/KaterynaKon

Nanomaterials of One Dimension (1D)
• They have a variable length, conserving two dimensions (height and width) in the nanometer regime; to these correspond the nanowires and nanotubes.
ZnO nanotubes from https://doi.org/10.1098/rsos.180510

Nanomaterials of Two Dimension (2D)
• Theyhavetwooftheirdimensionsnotconfinedtothenanometerregime. • Theyexhibitplatelikeshapes,nanosheets
Phosphorene

Learning Outcome Check
q What is the difference between (i) nanomaterials (ii) nanoscience and (iii) nanotechnology?
q What are the different classifications of nanomaterials, based on (a) source and (b) structure?
q Given a range of nanomaterials, sort them according to source/structure. q Give an example each of the following nanomaterials: 0D, 1D, 2D and 3D.

Nanomaterial Synthesis Approaches
Top – Down Approach

Nanomaterial Synthesis Approaches
Top – Down Approach

Nanomaterial Synthesis Approaches
Bottom – Up Approach
Physical Techniques
Physical Vapour Deposition (PVD)
• Sputtering
• Evaporation (laser, e-beam)
• Plasma arcing
• Laser ablation
Chemical Techniques
Chemical Vapour Deposition (CVD)
• PECVD (Plasma-enhanced CVD)
• RF- PECVD (Radio Frequency Plasma Enhanced CVD)
• MPE-CVD (Microwave Plasma-enhanced CVD) Self Assembled Monolayer
• Electrolytic deposition
• Pyrolysis

Nanomaterial Synthesis Approaches
Bottom – Up Approach

Surface Area to Volume Ratio (SAVR)
• The surface area to volume ratio for a material or substance made of nanoparticles has a significant effect on the properties of the material.
• Materials made up of nanoparticles have a relative larger surface area when compared to the same volume of material made up of bigger particles.
TASK: Compare the SAVR for spherical particles of radius 30, 15, 3 and 1. Compare the SAVR for cubic particles of side 30, 15, 3 and 1.
SAVR Ratio= !” SAVR Ratio= $#

Surface Effects
Decrease in Surface to Volume Ratio

Surface Effects

Properties of Nanomaterials
q CHEMICAL
• Materialsthatareinertintheirbulkform
become reactive at the nanoscale.
• Alteredmeltingpointsofconventional materials in nano regime
• Semiconductorsandmanymetalsshow large changes in optical properties as a function of particle size.

Chemical Properties
• Chemicallyinert;
• Regardedasapoorcatalyst;
• Each gold atom is surrounded by twelve
other atoms;
• Even the gold atoms at the surface have six adjacent gold atoms.
• GoldNPsbelow10nminsize;
• Greatcatalystforoxidizingcarbonmonoxide;
• Gold forms crystalline shapes;
• Theexposedatomsatthecornersofthe crystal are more reactive.
“When Gold is not noble”
Haruta M. When gold is not noble: catalysis by nanoparticles. Chem Rec. 2003;3(2):75-87.
https://doi.org/10.1002/tcr.10053

Optical Properties
• Yellowincolour,shinybecauselightreflects off their surfaces;
• Photons of light can’t get through the electron clouds at the surface, therefore aren’t absorbed by the electrons bound to atoms in metals;
• Photons are reflected back to the eye and which gives it that shiny bling quality.
Electroncloudatthesurfaceresonateswith different wavelengths of light depending upon their frequency;
BasedonNPsize,theelectroncloudwillbein resonance with a particular wavelength of light and absorb that wavelength;
90nmsizeparticlesabsorbcoloursonthered and yellow end of the colour spectrum: blue- green NP;
30nmsizeparticlesabsorbbluesandgreens, resulting in a red appearance.

Melting Temperature
Crystal Size Decreases (Bulk to Nano)
ETotal = EBulk + ESurface
Surface atoms require less energy to move because they are in contact with fewer atoms
of the substance.
Surface Energy Increases
Melting Point Decreases

Learning Outcome Check
q Briefly describe the synthesis of nanomaterials with respect to Top-Down and Bottom-Up approaches.
q Calculate surface area to volume ratio (SAVR) for a sphere of radius r, and a cube of length a.
q List 3 size-dependent properties of materials that change from bulk to nanosize particles. For each property, give an example.

Applications of Nanomaterials
Food Industry
The ripeSense® sensor works by reacting to the aromas released by the fruit as it ripens. The sensor is initially red and graduates to orange and finally yellow.
Biomedical Industry
Gold nanoparticles as hyperthermia therapy: Au NPs produce heat when excited by light at certain wavelengths. When light is applied to a tumor containing gold nanoparticles, the particles rapidly heat up, killing tumor cells in a treatment also known

Applications of Nanomaterials
Textile Industry
Silver nanoparticles are added to clothing for their powerful ability to kill bacteria and fungi, and to prevent the nasty odors they cause
Reinforced silk and other fibers with carbon nanotubes to improve strength and produce “electronic yarn”
Electronics
Snapdragon 865 chip by Qualcomm used in android phones today / A13 bionic chip in iPhone 11 and beyond is based on a 7nm lithography process(N7P) and contains 8.5 billion transistors.
silvertech – xsilverfiber.com

Learning Outcome Check
q Give an example of applications of nanotechnology in the following :
q Electronic q Biomedical

Lecture Summary
ü Overview to nanomaterials and nano- technology
ü Impact in the real world: Growth outlook ü Classification of Nano-materials
Ø Based on Source a) Natural
b) Synthetic
ØBased on Structure a) 0- Dimension
b) 1- Dimension
c) 2- Dimension
üNanomaterial Synthesis Approach Ø Top – Down Approach
Ø Bottom – Up Approach üSurface Effects
üProperties of Nanomaterials Ø Chemical
üApplications of Nano-materials in various industries

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