Sheryl Ehrman
Particles!
Workshop materials
Screen printing technology
Aerosol processing of materials
7/28/09
Particles! workshop plan
• 3:30-3:45 Intro to workshop, introductions to each other
• 3:45-4:30 Introduction to particle technology
– Particle technology basics
– Air pollution
• 4:30-5:15 Laboratory tours - flame reactor, metal powder
reactor
• 5:15-5:45 Where are the particles, conductive pastes activity
• 5:45-6:45 dinner
• 6:45-7:45 How are the circuit boards printed? Screen printing
activity. Important powder properties, flowability activity
• 7:45-8:45 Details about our process to make the powders,
design activities
• 8:45-9 Wrap up and clean up
http://www.eickmeyer.com/Gebrauchtliste/05-1/Siebdruckmaschine-Thieme520.jpg
http://www.zanafilla.net/screen_printer_mid.jpg
http://www.gsiglasers.com/UserFiles/Images/Market%20Sectors/Electronics/prec
ision_cutting.jpg
http://images.pennnet.com/articles/smt/thm/th_0612smt_screen02.jpg
Particle processing – general
goals
Size,
composition
control
Avoid
agglomeration
Holy
grail
Quantity/cost
Our laboratory’s approach:
• develop processes for niche
applications
• only one or two of the objectives
required
• make use of aerosol approaches
when advantageous
Particles, how to make them
• Top down
– Milling
– Refining micron scale
patterning techniques
• Bottom up
– From atoms or molecules to clusters to particles
to macroscale materials
Methods of making fine particles
• Starting from molecular level
– From precursor
Aerosol
• Combustion synthesis
• Thermal or plasma synthesis
Solution phase synthesis
• Precipitation
• Sol gel
• Emulsion
– Evaporation/condensation
• Starting from cluster level
– Spray pyrolysis
– Electrospray
Aerosol example: Cu doped ceria
Water cooled substrate
for particle deposition
Rotameters
CH4
O2
N2
Burner
Compressed Air
Metal acetate precursors
0.3 mol /l in water
Nebulizer
R.K. Pati, S. Hou, O. Akhuemonkhan, I.C. Lee, D. Chu, S.H. Ehrman, submitted (2006)
Solution phase example: Fe nanoparticles
8.75
9.50
•Precipitation of iron from iron chloride in
presence of sodium borohydride and trace
amount of palladium ions as seeds
•Polyacrylic acid added as dispersing agent
K.C. Huang and S.H. Ehrman, Langmuir, in press (2006)
Why the emphasis on aerosol
processes in our lab?
• Advantages in some cases:
–
–
–
–
–
Rapid
Simple, less steps required
No solvents
Amenable to continuous processing
Potential for scalablity
Disadvantages
• Poor size control
• Poor control of aggregation
• Difficult to make non-oxides
– Interesting alternatives - sodium coated metal
nanoparticles (Axelbaum, Zachariah) in aerosol
process
• May battle thermodynamics in mixed
systems
Aerosol manufacturing, $$
Product
Volume,
tons/yr
Market
$/yr
Process
Carbon black
8M
8B
Flame
Titania
2M
4B
Flame
Fumed silica
0.2 M
2B
Flame
Zinc oxide
0.6 M
0.7 B
Hot wall furnace
Fe, Pt, CeO2
0.02 M
0.3 B
Hot wall furnace,
spray pyrolysis
Ref: K. Wegner, S.E. Pratsinis, Chem. Eng. Sci. 51, 4581 (2003)
Metal powders for conductive pastes
DuPont uses 400,000 kg of precious metal
per year to make their pastes
Prices:
Silver - 13.90/ounce
Gold - 950/ounce
Palladium - 260/ounce
Copper - 2.50/pound
Nickel - 7.54/pound
General Aerosol Process Schematic
Feed #1
Preparation
Feed #2
Preparation
.
.
.
•
•
•
•
Vaporization
Pumping/Compression
Addition of additives
Preheating
Feed #N
Preparation
Schematic developed by R. Bertrum Diemer, DuPont
© R.B. Diemer, Jr. 2005
General Aerosol Process Schematic
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Feed #N
Preparation
Aerosol
Reactor
•
•
•
•
•
•
Mixing
Reaction Residence Time
Particle Formation/Growth Control
Agglomeration Control
Cooling/Heating
Wall Scale Removal
© R.B. Diemer, Jr. 2005
General Aerosol Process Schematic
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Aerosol
Reactor
Base Powder
Recovery
• Gas-Solid Separation
Feed #N
Preparation
© R.B. Diemer, Jr. 2005
General Aerosol Process Schematic
Vent or
Recycle Gas
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Treatment
Reagents
Aerosol
Reactor
Offgas
Treatment
Base Powder
Recovery
Feed #N
Preparation
© R.B. Diemer, Jr. 2005
Waste
• Absorption
• Adsorption
General Aerosol Process Schematic
Vent or
Recycle Gas
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Treatment
Reagents
Aerosol
Reactor
Offgas
Treatment
Base Powder
Recovery
Coarse
and/or Fine
Recycle
Powder
Refining
Feed #N
Preparation
•
•
•
Degassing
Desorption
Conveying
Waste
•
•
© R.B. Diemer, Jr. 2005
Size Modification
Solid Separations
General Aerosol Process Schematic
Vent or
Recycle Gas
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Treatment
Reagents
Aerosol
Reactor
Feed #N
Preparation
Formulating
Reagents
•
•
•
Base Powder
•
Recovery
•
Coarse •
Powder
and/or Fine•
Recycle
Refining
•
Offgas
Treatment
Product
Formulation
© R.B. Diemer, Jr. 2005
Waste
Coating
Additives
Tabletting
Briquetting
Granulation
Slurrying
Filtration
Drying
General Aerosol Process Schematic
Vent or
Recycle Gas
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Treatment
Reagents
Aerosol
Reactor
Feed #N
Preparation
Formulating
Reagents
•
Waste
•
•
•
Bags
Super Sacks
Jugs
Bulk
Base Powder
containers
Recovery
– trucks
Coarse
– tank cars
Powder
and/or Fine
Recycle
Refining
Offgas
Treatment
Product
Formulation
© R.B. Diemer, Jr. 2005
Packaging
Product
General Aerosol Process Schematic
Vent or
Recycle Gas
Feed #1
Preparation
Feed #2
Preparation
.
.
.
Treatment
Reagents
Aerosol
Reactor
Offgas
Treatment
Base Powder
Recovery
Powder
Refining
Feed #N
Preparation
Formulating
Reagents
Waste
Product
Formulation
Coarse
and/or Fine
Recycle
Packaging
Product
© R.B. Diemer, Jr. 2005
Particle Synthesis Setup
Reactor Furnace
(Lindberg)
Diffusion Dryer
(TSI Model 3062)
Temperature: 300 °C ~ 1000 °C
By-Pass
(R.T. control)
Atomizer
(RETEC)
Powder Collection
(X-ray Diffraction)
Compressed
Nitrogen
Precursors
0.3 M precursor in
water/alcohol solution
(10% by volume)
Colors of Copper Powders
300 °C
450 °C
600 °C
1000 °C
Cu·N
Cu·N +ETOH
Cu·Ac
Pure Cu
Cu·Ac + ETOH
Image J.-H. Kim
Other results with alcohol
• Can make phase pure
copper from copper nitrate
• Enable formation of copper
acetate at lower
temperatures
• Works for nickel nitrate too!
• ~ 0.1 mol % H2 estimated,
well below flammability limit
in air
Particle synthesis
(polydisperse)
Temperature also important
Polydisperse Copper Powders
Cu: 600 °C
Cu: 1000 °C
From copper nitrate with co-solvent
Scanning Electron Microscope Images, JH Kim
Spray pyrolysis processes
(adapted from Gurav et al., Aerosol
Sci. and Tech., 1993)
http://resources.metapress.com/pdf-preview.axd?code=t1r6110741380195&size=largest
Composition is a variable
What composition will give you a melting point
of 1100 K and the highest conductivity
possible?
What composition will give you a melting point
of 1250 K and the highest conductivity
possible?
Particle diameter is a variable
We want 1 micron diameter particles
droplet
Equations
dry salt
end particle
dd
dp
dd
Droplet diameter
dp
Particle diameter
CMp
Mass concentration
p
Density of copper nitrate
solid
Now we want to make lots of particles
Process scale up calculation
Wrap up
• Particle technology, it’s everywhere!
• One application, metal powders for
conductive pastes, everywhere too, big
business!
• Particle properties are important for
patterning the conductive pastes
• Lots of chemical engineering goes into
developing the process to make the metal
powders!
So what’s a micro or nanoparticle?
•
•
•
•
Micro: particle < 100 microns in diameter
Nano: particle < 100 nanometers in diameter
May form larger structures: agglomerates, films
These can be 100’s of microns in size
100 nm
500 nm
CuO/CeO2 nps
Size selected Cu nps
Top view of film of TiO2 nps
Cu microparticles
Particles are
everywhere!
• Pollen? Soot? Viruses?
Pollen
http://www.e-microscopy.com/upload/img/misc_pollen.jpg
Calicivirus
Polio Virus
All images Bar = 50 nm Photo Credit: F.P. Williams, U.S. EPA
More images for public use at http://www.epa.gov/nerlcwww/
http://www.mpbs.wnoz.us.edu.pl/moje_sadze/soot_b.jpg
Beneficial particles
http://www.aafa.org/pictures/dpi.jpg
http://www.sptimes.com/2002/03/29/photos/ht-sunscreen.jpg
http://www.mpbs.wnoz.us.edu.pl/moje_sadze/soot_b.jpg
http://www.nanophase.com/catalog/item.asp?ITEM_ID=41&DEPARTMENT_ID=38
Particles (nano) in the past
• Lampblack (carbon black) produced
in quantity by the ancient Chinese
• Pigments used by other civilizations
several hundred years BC in glass
and other ceramics
• Examples of nano in the not sodistant past…
Ref: Johnson, P. H., and Eberline, C. R., “Carbon
Black, Furnace Black”, Encyclopedia of Chemical
Processing and Design, J. J. McKetta, ed., Vol. 6,
Marcel Dekker, 1978, pp. 187-257.
Ref. G. Ulrich,Chemical and Engineering News, 1984
Particles in the lab
• Studies of reactions of halogen compounds in hydrogen flames,
late 1960’s, early 1970’s
• 1970’s application of this towards making optical fibers
• Bell Laboratories research
• “Modified Chemical Vapor Deposition”
Ref: Simpkins PG, Greenbergkosinki S., MacChesney JB, Journal of Applied Physics, 50 (9)
5676 (1979).
Particles in industry -
Vapor-phase axial
deposition of optical fiber preforms
start with rod
(preform) of
pure silica, SiO2
O2/H2 burner
produces nanoparticles
of silica + Ge, Ti,
B, P etc…
graphite furnace
to consolidate
fume
H2, O2, SiCl4 + GeCl4 + TiCl4...
consolidated
preform is
drawn into
optical fiber
Particles in the lab – Optical behavior
Size dependent optical properties
•
•
•
•
•
CdSe nanoparticles, synthesized in
solution
monodisperse size, different sizes in
each vial
illuminated with UV light
emitting different (size dependent)
wavelengths of visible light
phenomena result of size-dependent
quantum confinement
image: Felice Frankel, MIT
particles: Moungi Bawendi’s group at MIT, Department of Chemistry
Ref: Tobin JG, Colvin VL, Alivasatos AP, Phys. Rev. Let. 66 (21) 2786 (1991)
Murray CB, Norris DH, Bawendi MG, J. Am. Chem. Soc., 115 (19) 8706 (1993)
Particles in the market place
• Commercially available nanoparticles, for
example Qdots
• Can be functionalized to bind to specific
targets
• Used extensively today for
diagnostics in biotechnology
Here, dual labeled mouse fibroblasts. Actin
stained red. Nuclear membrane labeled with
red and green probes, appearing yellow.
Nano in the lab – electronic behavior
Single electron transistors
•
a single electron excess charge on a
particle markedly changes its conductive
properties
•
could eventually lead to orders of
magnitude decrease in device size
huge implications for computing
Difficulties:
nanoparticles
gold leads +
linker molecules
•
•
SiO2 insulating layer
Doped Si substrate
– stability at T >> 0 K ?
– manufacturing in quantity?
– how to pattern/order them?
after Klein et al., Nature, 389, 699 (1997)
Nano in the marketplace
• Still waiting on this one…
• Meanwhile… top down getting really small, sub 0.2
micron feature size in an integrated circuit
• Two new nano issues
– Polishing at nano level between processing steps
– Small features -> contaminants = killer nano particles!!
http://www.semiconductor-technology.com/projects/rf/rf1.html
Nano in the marketplace
• Killer particles?
• Rule of thumb: particle > 1/3
of smallest feature size can
cause killer defect
• Defect detection
– Performance after production
– On-line, light scattering
• At these size scales, on-line
very challenging!
http://www.geek.com/news/geeknews/2006Jan/bch20060126034439.htm
In my lab, what do we do?
• As chemical engineers we develop processes for making
inorganic nanoparticles and nanoparticle based materials
• It’s a great time for chemical engineers to get involved
– Relevance of manufacturing to enabling this technology
– Ability to characterize improving rapidly