Materials in Nanotechnology - UNESCO...Outline • Nanomaterial Synthesis Approaches –General...

Materials in Nanotechnology

Introduction to Nanoparticle

Synthesis and Applications

Terence Kuzma

Outline

• Nanomaterial Synthesis Approaches

– General overview (Lecture 1)

• Nanoparticle Synthesis

– Chemical Reduction Methods

– Attrition

– Pyrolysis (Lecture 2)

– RF Plasma (Lecture 3)

– Thermal decomposition

– Pulsed Laser Method

• Some Nanoparticle Applications

Nanomaterial Synthesis

Approaches• Top down approach starts with a bulk material and then

breaks it into smaller pieces using mechanical, chemical,

or any other form of energy. In some applications, it

could be described as relative large amounts of energy

to force materials into specific configurations. Examples

PVD such as sputtering or e-gun evaporation.

• The bottom up approach synthesizes the nanomaterials

from atomic or molecular species via chemical reactions

or self assembly. This allows the precursor particles to

grow in size or gradually assembling the atomic or

molecular precursors until the desired structure is

achieved.

Nanomaterials Synthesis

ApproachesThe bottom up approach examples that we will explore in

the section include pyrolysis, colloidal chemical methods,

attrition, RF plasma, and pulsed laser method.

These approaches feature advantages, and

disadvantages. There are trades off factors such as cost.

Cost factors could include raw material, environmental

factors, process system maintenance, particle filtration.

Again the specific approach will dictate size distribution,

environmental concerns, and material type. So selecting

an approach has many considerations.

Examples that we will explore in the section include

pyrolysis, colloidal chemical methods, attrition, pyrolysis,

RF plasma, and pulsed laser method.

Nanomaterials Synthesis

Approaches• Both top down and bottom up can be performed in the

gas or liquid phases, supercritical fluids, the solid state,

or in a partial vacuum.

• Key to both processes is the ability to be repeatable and

predictable in manufacturing the nanoscale product. The

process must control the particle size, particle shape,

size distribution, particle composition, and degree of

agglomeration.

• Another important consideration is assuring a desired

level of stability. Intuitively nanomaterials usually have

reactive surface energy, but this potential must be

enabled at the appropriate time. So often nanomaterials

are stabilized until the desired reaction is enabled.

Outline


– General overview



– Attrition

– Pyrolysis

– RF Plasma




Chemical Reduction Method

• Chemical reduction methods has the potential to be

scaled up even at room temperature. The chemical

reduction of meyal salts is the most common method for

the synthesis of nanoparticles. Generally, this approach

is very useful because it easy, and initially inexpensive.

Naturally liquid byproducts may be costly to dispose, and

this method is applicable to a limited number of

materials.

• Chemical reduction methods may utilize both organic

and inorganic reactants.

• Typically, a metal salt is reduced leaving nanoparticles

evenly dispersed in a liquid.

Typical nanoparticle for bio-application

Metal nano colloid

Reducing agents

Sodium citrate

NaBH4

Ascorbic acid

Capping agents

Thiols

Citrate

Polymers, PVA, PVP


• Aggregation is prevented by electrostatic repulsion or the

introduction of a stabilizing reagent that coats the particle

surfaces.

• Several reducing agents such as ascorbic acid, citric

acid, and their salts; alkali hydrides namely NaBH4,

NaB(C2H5)3H, and LIB(C2H5)3H along with various

capping agents such as polymers. These polymers

could include polyvinylpyrrolidone, organic ligands such

as quaternary amines, thiols, and surfactants help to

stabilize metal nanoparticles.

• Particle sizes range from 1-200nm and are controlled by

the initial concentrations of the reactants and the action

of the stabilizing reagent.


• Examples: Gold

– A common method for preparing colloidal gold

nanoparticles involves combining hydrogen

tetrachloroaurate (HAuCl4) and sodium citrate

(Na3C6H5O7) in a dilute solution.

– Upon dissociation, the citrate ions (C6H5O73-) reduce

Au3+ to yield 30-40 nm gold particles.

Half reaction equations:

• Au3+(aq) + 3e- Au(s)

• C6H5O73-(aq) +H2O(l) C5H4O4

2-(aq) + CO2(g) + H3O(aq) +

2e-

Example: Formation of Gold Nanoparticles

HAuCl4Gold

NPHAuCl4

Sodium

Citrate

Heat

http://mrsec.wisc.edu/Edetc/nanolab/gold/index.html

J. Chem. Ed. 2004, 81, 544A.

1. Heat a solution of chloroauric acid (HAuCl4) up to reflux (boiling). HAuCl4 is

a water soluble gold salt.

2. Add trisodium citrate, which is a reducing agent.

3. Continue stirring and heating for about 10 minutes.

• During this time, the sodium citrate reduces the gold salt (Au3+) to

metallic gold (Au0).

• The neutral gold atoms aggregate into seed crystals.

• The seed crystals continue to grow and eventually form gold

nanoparticles.

Red Color = Gold NP

Example: Formation of Gold Nanoparticles

Reduction of gold ions: Au(III) + 3e- → Au(0)

Nucleation of Au(0) seed crystals:Seed Crystal

10’s to 100’s of Atoms

Nanorods

Spherical

Nanoparticles

Isotropic

Growth

Anisotropic

Growth

Surface capped

with citrate anions

Adding surfactant to growth solution

caps certain crystal faces and promotes

growth only in selected directions.

Growth of nanoparticles:

Seed


• Examples: Molybdenum

– 1-5 nm molybdenum nanoparticles can be

created at room temperature by reducing

MoCl3 in a toluene solution in the presence of

sodium triethylborohydride (NaBEt3H).

– Reaction equation:

MoCl3 + 3NaBEt3H Mo + 3NaCl + 3BEt3 +

(3/2)H2


• Examples: Iron– The TEM image to the right shows

3nm Fe nanoparticles produced by

reducing FeCl2 with sodium

borohydride (NaBH4) in xylene.

– Trioctylphosphine oxide (TOPO) was

introduced as a capping agent to

prevent oxidation and aggregation

Phys. Chem. Chem. Phys., 2001, 3, 1661È1665

TEM image of Fe nanoparticles


• Examples: Silver– The reduction of AgNO3 by NaBH4 in

aqueous solution can produce small

diameter (<5nm) silver nanoparticles

– In one reported method, the reduction

takes place between layers of kaolinite, a

layered silicate clay material that functions

to limit particle growth.

– Dimethyl sulfoxide (DMSO) is used as a

capping agent to prevent corrosion and

aggregation of the Ag particles.

R. Patakfalvi et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 220 (2003) 45/54

Outline





– Attrition (Mechanical Milling)

– Pyrolysis

– RF Plasma




Attrition (Mechanical Milling)

• Attrition known as mechanical milling is routinely used in powder metallurgy and mineral processing industries. In this method mixtures of elemental or prealloyed powders are subjected to grinding under protective atmosphere in systems that are capable of high energy compressive impact forces.

• Macro or micro scale particles are ground in a ball mill, a planetary ball mill, or other size reducing mechanism.

• The resulting particles are separated by filters and recovered.

• Particle sizes range from tens to hundreds of nm.

• Broad size distribution and varied particle geometry.

• May contain defects and impurities from the milling process.

• Generally considered to be very energy intensive.

Cao, Guozhong. Nanostructures and Nanomaterials: Synthesis, Properties &

Applications. Imperial College Press. 2004

Attrition • For single-phase elemental powder or intermetalic

compound powder is milled the grain size of the powder continues to decrease until it reaches a desired level of 3-25nm.

• Some intermetallic compounds of the powder becomes amorphous beyond this point.

• Because the processes are low temperature newly formed grains grow very slowly.

• Mechanical attrition processes allow allow the preparation of alloys and composites that could be precluded by other manufacturing methods.

• High energy mechanical milling is a very effective process for synthesizing metal ceramic composites.

Attrition: Rotary Ball Mill

• A hollow steel cylinder containing tungsten balls and a solid precursor rotates about its central axis.

• Particle size is reduced by brittle fracturing resulting from ball-ball and ball-wall collisions.

• Milling takes place in an inert gas atmosphere to reduce contamination.

http://www.ktf-split.hr/glossary/image/ball_mill.gif

http://www.ktf-split.hr/glossary/image/ball_mill.gif

Attrition: Rotary Ball Mill• Rotary mills are likely to introduce impurities to the particle

surface. This could be to serve as a sintering aid, and may force eutectic liquid so as to introduce liquid phase sintering.

• Surface defects from milling may also increase surface defects that increase surface energy which may be favorable for densification in a nanocomposite.

• This is a popular method of making powdered metals with each particle having a predictable alloy ratio. This allows products that have consistent uniformity in the bulk. An example is CPM-3V steel. This steel is used for

cutting tools such as specially

knives. These knives have

outstanding edge retention

due to their homogeneity.

Attrition

Claudio L. De Castro, Brian S. Mitchell. Nanoparticles from Mechanical Attrition.

Department of Chemical Engineering, Tulane University, New Orleans, Louisiana, USA

• Attrition Examples




Part 2

Terence Kuzma

Outline





– Attrition

– Pyrolysis

– RF Plasma




Pyrolysis

• Pyrolysis is a popular method for creating

nanoparticles, especially oxides. A

precursor (liquid or gas) is forced through

an orifice at high pressure and burned.

• The resulting ash is collected to recover

the nanoparticles.

• Large volume of gas leads to high rate of

material synthesis

Pyrolysis: Material Applications

Images clockwise from top left:

1. Tire <www.Safercar.gov>

2. Paint cans <http://www.ndhealth.gov/wm/PollutionPreventionAndRecyclingProgram/

MercuryContainingDevicesProducts.htm>

3. Optical Fibers <https://lasers.llnl.gov/publications/photons_fusion/2009/january

_february.php>

4. Vitamans <www.fda.gov/AboutFDA/WhatWeDo/History/ThisWeek/ucm117726.htm>

5. Makeup <https://pa-online.pa.gov.sg/NASApp/sdsol/sdsol/common

/Bring_Out_Best_In_You.htm>

6. Ink Quil < http://www.orovalleyaz.gov/Town_Government/Town_Clerk/notary_services.htm>

Carbon Black

TiO2

SiO2

Tires

Inks

Paints

Makeup Flowing aid

Optical

fibers

Annual Production of

Flame made materials

• Carbon black – 8 million tons $8 billion

• TiO2 - 2.5 million tons, $5 billion

• SiO2 2.0 million tons, $2 billion

Pratsinis, Sotiris E., Functional Nanoparticles and Films Made in the Gas-

phase. Nano Science and Technology Institute, Cambridge. 2008

Flame Spray Pyrolysis (FSP)

• Versatile

• Large Variety

of precursors

• Controllable

• Scalable

Aggregation

Condensation

Coagulation

Nucleation

Droplet evaporation

Pyrolysis: System Overview

Xiao Q., Yiguang J., Stefan B. and Nan Y. Synthesis of Y2O3:Eu Phosphor Nanoparticles by

Flame Spray Pyrolysis. Princeton University, Princeton, NJ

Pyrolysis

Aggregates and Agglomerates:• Aggregate – An assemblage of particles rigidly joined together by chemical

or sinter-forces.

• Agglomerate – A loosely coherent assembly of particles and/or aggregates

held together by weak interactions

• Current aerosol instruments cannot distinguish between them.

Aggregates Agglomerates

Pyrolysis

Agglomerate Formation Sequence

Residence time

TiO2

Monomers

Transient Hard

Agglomerates

Spherical

Particles Hard Agglomerates Soft Agglomerates

Pyrolysis

Degree of agglomeration matters:

• Agglomerated

- Fillers

- Catalysts

- Lightguide preforms

- Particles for CMP

• Non-agglomerated

- Pigments

- Composites

- Electronics

• Distinction between hard and soft agglomerates is largely empirical.

• Controlled agglomeration can minimize post-grinding and other

costly separation techniques.



Pyrolysis

Regions of AgglomerationNon-Agglomerates

Hard Agglomerates

Soft Agglomerates



Pyrolysis

Impact of oxygen

• Aids in combustion

• Provides chemistry in the reaction

• Acts as a dilutent, cools the flame,

prevents agglomeration

• All of these variables can be decoupled by

burner design. Which is cheaper than

increasing oxygen flow.

Pyrolysis

Pyrolysis

Particle Size Controlled by O2 Flow

• Excess oxygen

makes the flame

burn cooler

resulting in

smaller diameter

particles

Pyrolysis

Particle Formation and Growth by Gas Phase Chemical

Reaction, Coagulation, Sintering and Surface Growth:

O2

TTIP

Molecules

TiO2

Molecules

TiO2

Particles

Ti

C3H7O

C3H7O

OC3H7

OC3H7

Titanium-Tetra-Iso-Propoxide

TiO2

Aggregates

Decreasing Temperature



Pyrolysis: Jet Design

CH4 CH4

CH4Air

AirAir

TiCl4 TiCl4TiCl4 TiCl4

Air Air

Pyrolysis: Jet DesignEffect of Oxidant Composition on TiO2 Morphology:

CH4

CH4

Oxidant

Oxidant

TiCl4TiCl4

Flame mixing B Flame mixing C

Pyrolysis: Nozzle Quenching



Vapor

• Flame length is controlled by

rapid quenching

• Prevents agglomeration by

inhibiting growth processes in the

early stages of growth.

• Provides precise control of

particle size

Desired

Pyrolysis: Nozzle QuenchingNozzle Quenching controls flame length and particle

size.

Pyrolysis: Nozzle QuenchingTiO2 Particle Size Control by Nozzle Quenching



Pyrolysis: Electrostatic Charging

• Particle size can also be controlled by generating an

electric field across the flame.

• A large electric field (hundreds of kV/m) is generated

between two plate electrodes situated on opposite sides

of the flame.

• Similar to nozzle quenching, the electric field limits

particle growth by reducing the residence time in the

high temperature region of the flame.

• In addition, the electric field charges the particles. This

results in electrostatic repulsion between newly formed

particles, preventing coagulation.

S. Vemury, S.E. Pratsinis, L. Kibbey, Electrically-controlled flame synthesis of nanophase TiO2, SiO2, and

SnO2 powders. JMR, Vol. 12, 1031-1042. 1997.

Pyrolysis: Electrostatic Charging

• Pyrolysis is a high yield method that can

fulfill the strong demand for nanoparticles.

• Can be customized to produce unique

nanoparticles.

• Broad distribution of particle sizes and

morphology, needs filtration/separation.

Pyrolysis: Advantages &

Disadvantages




Part 3

Terence Kuzma

Outline


– Colloidal Chemical Methods

– Attrition

– Pyrolysis

– RF Plasma

– Thermal Decomposition


• Nanoparticle Applications

RF Plasma Synthesis • The starting material is placed in a pestle and heated under vacuum

by RF heating coils.

• A high temperature plasma is created by flowing a gas, such as He,

through the system in the vicinity of the coils.

• When the material is heated beyond its evaporation point, the vapor

nucleates on the gas atoms which diffuse up to a cooler collector rod

and form nanoparticles.

• The particles can be passivated by introducing another gas such as

O2.

• In the case of Al nanoparticles the O2 forms a thin layer of AlO3

around the outside of the particle inhibiting aggregation and

agglomeration.

• RF plasma synthesis is very popular method for creating ceramic

nanoparticles and powders

• Low mass yield.

Poole, C., Owens, F. Introduction to Nanotechnology. Wiley, New Jersey. 2003

RF Plasma Apparatus


Outline



– Attrition

– Pyrolysis

– RF Plasma




Thermal Decomposition

• Thermal decomposition is the chemical decomposition of a substance into ins constituents by heating.

• A solid bulk material is heated beyond its decomposition temperature in an evacuated furnace tube.

• The precursor material may contain metal cations and molecular anions, or metal organic solids.

• Example: 2LiN3(s) 2Li(s) +3N2(g)

– Lithium particles can be synthesized by heating LiN3 in a quartz tube under vacuum.

– When heated to 375oC the nitrogen outgases from the bulk material and the Li atoms coalesce to form metal nanoparticles.


Thermal Decomposition Apparatus

Sample in Ta foil

Furnace

Evacuated

Quartz Tube

Turbo Molecular

Pump

Mechanical Pump

Outline



– Attrition

– Pyrolysis

– RF Plasma


– Pulsed Laser Methods


Pulsed Laser Methods

• Pulsed Lasers have been employed in the

synthesis silver nanoparticles from silver nitrate

solutions.

• A disc rotates in this solution while a laser beam

is pulsed onto the disc creating hot spots.

• Silver nitrate is reduced, forming silver

nanoparticles.

• The size of the particle is controlled by the

energy in the laser and the speed of the rotating

disc.



• Pulsed Lasers have also been employed to

aqueous media at room temperature without

reducing agents or organic ligands.

• As you recall capping agents are required for

gold particles, and the capping agents and

ligands can interfere with subsequent

processes. The un-encapsulated exposed gold

high catalytic activity, exclusion of toxic effects in

biomedical applications or an improved

sensitivity in analytical applications

Monophasic ligand-free alloy nanoparticle synthesis determinants during

pulsed laser ablation of bulk alloy and consolidated microparticles in water

Anne Neumeister , Jurij Jakobi , Christoph Rehbock , Janine Moysig and

Stephan Barcikowski

Pulsed Laser Methods• Pulsed lasers can also create homogeneous

particles without temperature segregation that

are typical of high temperature processes.

• Alloy nanoparticles (NPs) are of increasing

interest due to their beneficial properties in

contrast to their monometallic constituents.

• Alloy NPs benefit from the fact that their optical,

catalytic as well as magnetic properties are

tunable based on the elemental compositions of

the particles




Stephan Barcikowski

Pulsed Laser Methods• A well-studied bimetallic system is the

combination of Ag and Au which possess similar

lattice constants while the two elements are

completely miscible over the entire composition

range

• Both metals display intense and well-defined

surface plasmon resonance (SPR) bands in the

visible range and the optical absorption spectra

of Ag–Au alloy NPs generally exhibit one SPR

band whose maximum depends on the alloy

compositionMonophasic ligand-free alloy nanoparticle synthesis determinants during



Stephan Barcikowski


Phys. Chem. Chem. Phys., 2014, 16, 23671-23678

Pulsed Laser Methods• Incoming laser pulse is adsorbed by the bulk

material forming a plasma (C2).

• At point C1, the generation of an expanding

cavitation bubble, while crystalline NPs are

formed inside the cavitation bubble by

nucleation and coalescence

• At point B, coalescence and reaction of the

generated species with colloidal particles

• At point C, ablation and cavitation bubble

formation




Stephan Barcikowski

Pulsed Laser Apparatus for Ag

Nanoparticles


Outline



– Attrition

– Pyrolysis

– RF Plasma


– Pulsed Laser Methods


Nanoparticle Applications: ZnO

• Zinc Oxide has opaque and antifungal

properties.

• Used as UV blocking pigments in sunscreens,

cosmetics, varnishes, and fabrics

• Incorporated in foot powders and garden

supplies as an antifungal.

• ZnO nanowires can improve the elastic

toughness of bulk materials

Nanoparticle Applications: TiO2

• Titanium Dioxide is used as an inorganic white

pigment for paper, paints, plastics, and whitening

agents.

• TiO2 nanoparticles are used as UV blocking

pigments in sunscreens, cosmetics, varnishes, and

fabrics.

• TiO2 has unique photocatalytic properties that make

it suitable for a number of advanced applications:

– Self-cleaning glass and antifogging coatings

– Photoelectrochemical cells (PECs)

– Detoxification of waste water

– Hydrolysis

Nanoparticle Applications: Fe

• 50-100nm Iron nanoparticles are used in

magnetic recording devices for both digital

and analog data.

• Decreasing the diameter to 30-40nm

increases the magnetic recording capacity

by 5-10 times per unit.

Nanoparticle Applications:

Iron Oxide• Iron Oxide nanoparticles have unique

magnetic and optical properties.

• Iron oxide nanoparticles can be

translucent to visible light while being

opaque to UV light.

• Applications include UV protective

coatings, various electromagnetic uses,

electro-optic uses, and data storage.


Iron Alloys• Iron-platinum nanoparticles have

increased magnetism and it is predicted

that 3nm particle can increase the data

storage capacity by 10 times per unit area.

• Iron-palladium nanoparticles 100-200nm in

diameter have been shown to reduce toxic

chlorinated hydrocarbons to nontoxic

hydrocarbon and chloride compounds.

SCIENCE VOL 287 17 MARCH 2000


Alumina• Alumina (Aluminum Oxide) is used in

Chemical Mechanical Polishing (CMP)

slurries, as well as ceramic filters.

• Nano-alumina is used in light bulb and

fluorescent tube coatings because it emits

light more uniformly and allows for better

flow of fluorescent materials.

Nanoparticle Applications: Ag

• Silver has excellent conductivity and has

been used as an antimicrobial material for

thousands of years.

• Silver’s anti-microbial potential increase

with increased surface area.

• Applications include biocides, transparent

conductive inks, and antimicrobial plastics,

and bandages.

Nanoparticle Applications: Gold

• Gold nanoparticles are relatively easy to produce compared to other types of nanoparticles due to its high chemical stability.

• Uses for gold nanoparticles are typically catalytic and include DNA detection and the oxidation of carbon monoxide.

• Gold has superior conductivity allowing gold nanoparticles to be used in various probes, sensors, and optical applications.


• The First Response® home pregnancy test uses 1µm polystyrene sphere and 50nm gold particles coated with an antibody to human chorionic gonadotropin (hCG), a hormone produced during pregnancy.

• When urine containing hCG comes in contact with the polystyrene-gold-antibody complex, the nanoparticles coagulate into red clumps. Fluids pass through a filter where the clumps are caught yielding a pink filter.

• Suspended (un-coagulated) nanoparticles pass through the filter and no color change occurs.

Bangs, L. B. New Developments in Particle-based

Immunoassays. Pure & Appl. Chem. Vol. 68, No 10 p

1873-1879. 1996


Bangs, L. B. New Developments in Particle-based

Immunoassays. Pure & Appl. Chem. Vol. 68, No 10 p

1873-1879. 1996

Nanoparticle Applications: ZrO

• Zirconium Dioxide nanoparticles can

increase the tensile strength of materials

when applied as a coating.

• This has many possible applications in

wear coatings, ceramics, dies, cutting

edges, as well as piezoelectric

components, and dielectrics.

Sintering

• Sintering is the process of compacting and

forming a solid mass of material by heat and/or

pressure without melting it to the point of

liquefaction

• Sintering is possible with metals, ceramics,

plastics

• Atoms in the materials diffuse across the

boundaries of the particles, fusing the particles

together and creating one solid piece

Sintering

• Because the sintering temperature does not

have to reach the melting point of the material,

sintering is often chosen as the shaping process

for materials with extremely high melting points

such as tungsten and molybdenum

Sintering• Sintering occurs by diffusion of atoms through

the microstructure, this diffusion is caused by a

gradient of chemical potential

http://www.intechopen.com/books/sintering-applications/pulse-current-auxiliary-sintering

Sintering• The six common mechanisms are:

– Surface diffusion – Diffusion of atoms along the

surface of a particle

– Vapor transport – Evaporation of atoms which

condense on a different surface

– Lattice diffusion from surface – atoms from surface

diffuse through lattice

– Lattice diffusion from grain boundary – atom from

grain boundary diffuses through lattice

– Grain boundary diffusion – atoms diffuse along grain

boundary

– Plastic deformation – dislocation motion causes flow

of matter

Sintering

Synthesis and Thermoluminescent Characterization of Ceramics Materials,

Teodoro Rivera

Structural and Dielectric Properties of Glass – Ceramic Substrate With Varied Sintering Temperatures

Rosidah Alias

Sintering• Zirconium dental sintering

Sintering

https://3dprint.com/165438/sdm-employee-jay-lenos-garage/

Outline





– Attrition

– Pyrolysis

– RF Plasma




– END

Materials in Nanotechnology - UNESCO...Outline • Nanomaterial Synthesis Approaches –General...

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Transcript of Materials in Nanotechnology - UNESCO...Outline • Nanomaterial Synthesis Approaches –General...