8/3/2019 nano retim
1/15
Processes for the production of nanoparticles
Production processes
in a li uid hase in a aseous hase
Precipitation process in homogeneous solution in surfactant based systems
Sol - gel process
Hydrothermal process
Aerosol process
Flame hydrolysis Spray pyrolysis
8/3/2019 nano retim
2/15
Educts
Agglomerate
Primary particle
Nucleus
Nanoparticles
Nucleus formation
Growth
Agglomeration
Deagglomeration
Critical supersaturation
Mixing of educts, temperature, etc.
Transport mechanism
diffusion or convection-controlled
Particle interaction
van-der-Waals attraction
electrostatical / sterical repulsion
Agglomerate structure
Euklidical geometry, fractals
Integration or diffusion-limitedparticle growth
Stabilisation of the nanoparticles against agglomeration !
8/3/2019 nano retim
3/15
gmax= 3
1
gsurf
Gibbs energy g
radius o nucleicritical radius of nuclei r*
gsurf = 4r2
g = (S- l) 3M 4 r3
Gibbs energy of nu-
cleus formation gConcentration of critical nuclei:
=
22
23*
)ln(3
16exp
SRTkT
MNN
O
Critical radius of nucleus:
MSlnRT
r* 2=
1 . r < r* nuclei dissolve
2. r > r*
nuclei are able to reduce
Gibbs energy by growing
Thermodynamics of nanoparticle formation
8/3/2019 nano retim
4/15
Model of LaMer and Dinegar (1950)
saturation concentration CSCS
supersaturationgrowth
nucleation critical u ersaturation C 0
rocess time
C0
nucleation
growth
+
++
++
++
fast homogeneous nucleation
growth process by diffusion
8/3/2019 nano retim
5/15
monomer, ions etc.
nucleation
growth
primary particles
Ostwald ripening
agglomeration andredispersion
agglomerates
Different approaches to synthesise nanoparticles in liquids
organic monomers inorganic salts inorganic monomers metal organic compounds
hydrolysis hydrolysis hydrolysis
polymerisation as
emulsion suspension
oligomerisation
polycondensation polycondensation polycondensation
particles in suspension particles in suspension particles in suspension particles in suspension
latex sol sol sol
examples:
PS 0.1 - 1000 m Al2O3 SiO2 Al2O3PMMA 0.3 - 1000 m TiO2 TiO2
MF 1.0 - 1000 m ZrO2 ZrO2Fe2O3
microparticles GmbH
8/3/2019 nano retim
6/15
Ag+ + Br - AgBr
Silver bromide
Chemical and physical processes for nano particle synthesis
Process: precipitation in homogeneous solution
synthesis of silver bromide
Chemical reaction:
Principle:precipitation (Controlled double jet precipitation CDJP - technique)
(gelatine)
KBrAgNO3ions
embryos
nuclei
primary particle
growth, coagulation, ...
growth
cluster formation
complex and cluster formation
colloids
8/3/2019 nano retim
7/15
Precipitation reactions in homogeneous solution
AgBr nanoparticle, produced by CDJ - technique at pBr 2,0 (a), 2,8(b), 4,0 (c)
8/3/2019 nano retim
8/15
Precipitation reactions in homogeneous solution
Images (transmission electron microscopy left - scanning electron microscopy right) of
CdS nanoparticles, produced in homogeneous solution at 26C by CDJ - technique
8/3/2019 nano retim
9/15
Precipitation reactions in homogenous solutions
Scanning electron microscopy image of aluminium(III)-oxide, 100C, left
Transmission electron microscopy image of chromium(III)-oxide, 75C, right,
produced by precipitation reaction in homogeneous solution
8/3/2019 nano retim
10/15
Generation of nanoscaled barium sulphate
Process: Precipitation in homogeneous solution Nucleation - Growth
Goal: Nanoscaled particle size distribution (as monodisperse as possible, stabilised)
Theoretical basics and experimental approach:
Chemical reaction: 42
4
2 BaSOSOBa + Concentration of reactants: 0.01 mol/L 0.5 mol/L
Concentration based initial supersaturation SC: 500 25,000Molar ratio of reactants R: 1 10 (excess of Ba
2+ions)
Stabilisation: electrostatic (excess of Ba2+
ions)
sterical (0.03 g dispersing agent / g BaSO4)
Dispersing agent: Melpers 0030:- 30 % w/w PolyethercarboxylateProcess parameter: concentration based initial supersaturation SC
molar ratio of reactants R
feed rate and mixing
concentration of dispersing agent
L
SOBa
cK
ccS
24
2 =
+=24
2
SO
Ba
c
cR
Discontinuous stirred tank reactor
Stirrer rotational speed 800 min-1
Tank reactor volume 1000 ml
Characterisation of particle sizes
Dynamic light scattering
Scanning electron microscopy
Chair for Process Systems Engineering, Institute of ProcessEngineering, Otto-von-Guericke University Magdeburg
Petrova, A., Hintz, W., Tomas, J.: Investigation of the precipitation of barium sulphate nanoparticles, Chem. Eng. Technol. 31 (2008) 604-608
8/3/2019 nano retim
11/15
Particle size distributions during the precipitation process of BaSO4
Influence of the feed rate of potassium sulphate solution on theparticle size distribution Q0(d) of the precipitated BaSO4 particles
100 200 300 400 5000
20
40
60
80
100
ParticlesizedistributionQ0(d)in%
Particle diameter in nm
Feed rate of K2SO4
5 mL/min
10 mL/min
20 mL/min40 mL/min
80 mL/ min
Method:Dynamic light scatteringInstrument: Horiba LB 500
Educts: 0.2 mol/L, Sc=10,000, T= 25C0.03 g dispersing agent / g BaSO4
Mean agglomerate diameterd50,0
Feed rate of K2SO4
5 mL/min d50,0 = 227.8 nm
10mL/min d50,0 = 208.2 nm
20mL/min d50,0 = 178.9 nm
40 mL/min d50,0 = 121.5 nm
80 mL/min d50,0 =105.3 nm
8/3/2019 nano retim
12/15
Method:Dynamic light scatteringInstrument: Horiba LB 500
Educts: 0.05 mol/L - 0.5 mol/L, R=1
Sc = 2,500 25,000, 25C
0.03 g dispersing agent / g
Mean agglomerate diameter:
Sc =2,500 d50,0 = 208.9 nm
Sc = 5,000 d50,0 = 151.4 nmSc = 10,000 d50,0 = 123.9 nm
Sc = 15,000 d50,0 = 109.0 nm
Sc =20,000 d50,0 = 101.4 nm
Sc = 25,000 d 50,0 = 82.5 nm
Particle size distributions during the precipitation process of BaSO4
50 100 150 200 250 300 350 400
0
20
40
60
80
100
Particlesiz
edistribution
Q0(d)in%
Particle diameter d in nm
Initial supersaturation Sc
Sc = 2,500 Sc = 5,000 Sc = 10,000 Sc = 15,000 Sc = 20,000 Sc = 25,000
Influence of the initial supersaturation Sc on the particle
size distribution Q0(d) of the precipitated BaSO4
8/3/2019 nano retim
13/15
10 100 1000 10000
0
20
40
60
80
100
Particlesizedis
tributionQ0(d)in%
Particle diameter d in nm
Molar ratio R
R = 1
R = 2
R = 4
R = 6
R = 8
R = 10
Method:Dynamic light scatteringInstrument : Horiba LB 500
Educts: 0.2 mol/L barium chloride0.05 mol/L-0.5 mol/L sulphate
Sc = 2,500 Sc = 8,000, 25C
without dispersing agent
Mean agglomerate diameter:
R = 1 d50,0 = 3,781.3 nm
R = 2 d50,0 = 506.0 nm
R = 4 d50,0 = 155.8 nm
R = 6 d50,0 = 121.9 nm
R = 8 d50,0 = 100.9 nm
R = 10 d 50,0 = 92.9 nm
Particle size distribution during the precipitation process of BaSO4
Influence of the molar ratio R on the particle size distributionQ0(d) of the precipitated BaSO4 particles
+=24
2
SO
Ba
c
cR
8/3/2019 nano retim
14/15
Structure of precipitated barium sulphate agglomerates
Scanning electron microscopy image of barium sulphate agglomerates (without dispersing agent)
Method: Scanning electron microscopy (SEM), concentration of reactants: 0.5 mol/L, R= 1, Sc = 25,000,
T = 25 C, addition of barium chloride to potassium sulphate, 80 mL/min, without dispersing agent
8/3/2019 nano retim
15/15
10 100 1000 10000
0
20
40
60
80
100
ParticlesizedistributionQ
0(d)in%
Particle diameter d in nm
with 0.02 g dispersing agent /g BaSO4 (DLS)no dispersing agent (DLS): agglomerates
no dispersing agent (SEM): primary particles
Particle size distributions Q0(d) of precipitated BaSO4, with and
without dispersing agent, sizes were determined with dynamic light
scattering (DLS) and scanning electron microscopy (SEM)
Particle size distributions during the precipitation process of BaSO4
Method:Dynamic light scattering
Scanning electron microscopy
Educts: 0.5 mol/L, R=1, Sc =25,000
25 C, 80 mL/min
with/without dispersing agent (0.02 g/g)
Mean agglomerate diameter:
with dispersing agent:
d50,0 = 82.0 nm
without dispersing agent:
d50,0 = 1,498.2 nm (DLS)
d50,0 = 79.0 nm (SEM)
Top Related