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1
Lecture
Nanoceramics
Prof. Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Properties of nanoceramics:
Transparent ceramics and
coatings
2Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Lecture:
Overview of nanomaterials
ceramics
Methods of producing nanopowders
Phenomena in disperse systems
Consolidation of nanopowders
Properties of nanoceramicsTransparent ceramics and coatings
3Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
opaque ceramic translucent ceramic
4Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
TRANSPARENT CERAMICS
nanooptics nanoelectronics other
5Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
MULTIFUNCTIONAL CERAMICS
PZT - PbZrO3,
PLZT - (Pb,La)(Zr,Ti)O3
transparent and
piezoelectric
for sensor applications
YSZ - ZrO2 with stabilizer
transparent and ion conductive
for fuel cells, fiber optics, EUV-
litography
YAG - Y3Al5O12 with
activator
transparent and durable
for Laser Technology and
Turbine Blade Construction
Corundum - Al2O3
transparent and chemically
and mechanically resistant
for optical and armour
protection inserts
6Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
The microstructural units (grains, pores, interfaces) of
the ceramic are smaller than about 100 nm, because
light is scattered with about 1/4 of the shortest
wavelength.
7Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
8Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
9Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
10Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
11Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Part of the incident light is reflected by all transparent materials. The
reflection is based on the abrupt change of the refractive index at the
interface of two media. Submicrostructured surfaces can
significantly reduce reflection. The surface structures, which are
smaller than the light wavelength, cannot be perceived visually - the
structures cause a continuous transition of the refractive index at the
surface and thus reduce the reflection.
12Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
13Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
14Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
15Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
0I
IT
transmission
the intensity I of a light wave after passing
through a possibly selectively weakening
medium of thickness d in relation to the
intensity I0 of the original light wave
is a constant, the absorption coefficient is
16Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
transmission
The transmission in a disc after a
simplification of drilling and Huffmann
The real-in-line transmission to Peelen and
Metselaar
(1-RS) multiple reflections at boundary surfaces according to an
mathematical series development according to G. Kortüm.
scattering factor, = scattering at grain boundaries and pores
Transmission without
scattering
17Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
At normal incidence, the reflection R1 on one surface is related to the material
refractive index n, given by
and the total reflection loss, including multiple
reflection, is
Therefore, the maximum transmission is as follows:
18Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
the actual inline transmission (RIT) of a fully dense transparent ceramic:
where n/n is the ratio of the refractive index difference between the polarization
perpendicular and parallel to the c-axis to the average index n, 2r is the grain size of
the ceramic, the wavelength of the incident light, and d is the thickness of the
sample. This equation implies that the RIT is closely related to n/n and r at a given
thickness. The smaller the values of n/n and r, the higher the RIT. If n/n is an
intrinsic property of materials, r is an extrinsic parameter that can be controlled by
material processing. Therefore, the grain size of the ceramic for given materials
should be small enough to achieve a high RIT. For example, the grain size of a high
density sintered Al2O3 must be about 0.5 mm for a RIT of 60 to 65% at = 640 nm
and d = 1 mm [Wang].
19Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
transmission
20Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
The most important requirement that nanoparticles have to meet is a small size.
Typically, particle diameters smaller than 50 nm are necessary to obtain optically
transparent materials. The reason for this is the strongly increasing scattered light
intensity with increasing particle size. This connection is described by the law of
Rayleigh:
I is the intensity of the transmitted beam, I0 the intensity of the input beam, r the
radius of spherical particles, np the refractive index of the particles and nm the
refractive index of the matrix. λ is the wavelength of the light, Φp the volume
fraction of the particles and x the optical path length. A high scattering intensity is
associated with a cloudy appearance of the nanocomposite material and thus with
a loss of quality of the material for optical applications.
21Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Distortion introduced into the incident laser beam as it propagates through the PLM. The dark lines shown
inside the PLM body are representative of local refractive index inhomogeneities and discontinuities
observed by the incident laser beam. The incident laser beam has a uniform circular shape and a
Gaussian intensity distribution. After passing the PLM sample, the transmitted beam has a distorted shape
due to mass scattering. [Sharma]
22Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Transparent Al2O3 ceramics
23Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG Arctube Ceramic Metal Halide, Toto
24Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd for laser applications
25Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
for laser applications
26Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
27Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
28Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
29Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
30Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
31Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
32Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
33Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
YAG:Nd
34Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Since 1999, Yanagitani and Yagi Group in Konoshima Chemical, Co., in cooperation
with the Ueda Group at the University of Konoshima, started the development of highly
transparent neodymium-doped YAG ceramics in vacuum sintering process, where the
starting materials were produced by nanocrystalline technology.
Compared to YAG single crystal, transparent ceramic laser materials have the following
advantages, namely:
(1) Ease of production;
(2) less expensive;
(3) Production of large and high concentrations;
(4) multilayer and multifunctional ceramic structure;
(5) Mass production etc.
The optical properties of Nd: YAG ceramics, such as absorption, emission and
fluorescence lifetime as well as thermal conductivity, are similar to those of Nd: YAG
single crystal.
35Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
36Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
37Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
38Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
39Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
40Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
The SSHCL (Solid-State Heat Capacity Laser)
requires slabs that are 2 centimeters thick
The SSHCL uses the world's
largest laser-quality
transparent ceramic amplifier
plates, measuring 10 x 10 x 2
centimeters [Konoshima
Chemical Co.].
Konoshima is the leader in polycrystalline YAG production
41Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Transparent ceramics are produced by forming a nanopowder with a desired
shape and then sintering the sample in a vacuum to form an aggregate of
microcrystals [Konoshima ].
42Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Production method used by Konoshima (1)
Transparent ceramics are produced by shaping a nanopowder of constituents
into the desired shape, then sintered in vacuum (heated below the melting point)
to form an aggregate of microcrystals with optical and thermal properties almost
identical to those of a monocrystal.
The precipitate of a solution of yttrium, neodymium and aluminium salts with the
addition of a solution of ammonium bicarbonate is then filtered, washed and
dried.
The co-precipitated amorphous carbonate is agglomerated to particles of about
10 nanometers.
43Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Production method used by Konoshima (2)
In a process known as slip casting, a suspension of the fine powder is poured
into a plaster mould and allowed to settle.
The green compact (preform) still contains many pores and is only 40 to 45
percent dense. The preform structure is then sintered in a vacuum at high
temperature for many hours. This sintering process involves the diffusion of
surface atoms, which causes the particles to fuse together and reduce the total
surface energy.
Some of the pores are squeezed out, and the structure shrinks, but retains its
overall shape. In addition, many physical and thermal properties are dramatically
improved during sintering.
44Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Production method used by Konoshima (3)
The precursor is heated to about 1100ºC to decompose the carbonates and form
particles of neodymium-doped yttrium aluminium garnet (Nd: YAG) about 100
nanometres in size. Highly agglomerated, the particles are treated with
ultrasound and then the large particles are removed to obtain a uniform small
size.
15-millimeter-diameter
samples of transparent
ceramic yttrium–
aluminum–garnet
[Livermore Res.].
45Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
46Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
47Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
48Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
Considering the experimental arguments, there are three conditions to obtain
optically transparent ceramics:
The material must be > 99.985% of theoretical density
no second phases must not be present in the microstructure
The material system must be optically isotropic or the average grain size must be
<200 nm.
Why nanopowders?
Sintering favoured by huge surface energy
the specific surface area increases with decreasing particle size
the surface energy increases with decreasing particle size (Kelvin Eqn.)
the sintering force increases with decreasing particle size
Transparent ceramics
Step 1: Preparation high purity powder
Step 2: High-temperature powder pre-pressing
Step 3: High Temperature Isostatic Presses (HIP) (to clear transparency)
49Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
50Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
51Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
Segregation on the grain boundaries
52Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
applications
defense
scintillator
smart gear
engineered materials
53Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
scintillators
Absorption coefficient of X-rays
4
effabs Z density, Zeff effective atomic
number of the material
54Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
The scintillator can be considered as a phosphor material for radiation that converts high-energy
particles, such as X-rays, X-rays and X-rays, into visible or UV light. The application of scintillator
has a great variety. It is usually combined with photodetectors and uses medical devices such as
X-ray CT, PET / SPECT, high energy physics, and a well-known example is baggage screening
in airports.
scintillators
55Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
scintillators
56Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
scintillators
57Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
scintillators
58Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
scintillators
59Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics
60Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Nano layer Thin layer Thick layer
61Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Nano layer Thin layer Thick layer
62Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Functions of thin layers
• tribological protection against wear / scratches
• reduction of friction / dry lubrication
• sterile and protection against corrosion / chemicals
• Color and glossyness
• anti-reflection
• electrical conductivity / insulation / electro-magnetic shielding
• bio compatibility / protection against microbes
• matrix for catalysts
• thermal conductivity / protection against heat and cold
• 3D surface structures / micro reactors / nano technology
• 2D surface structures
• protection against diffusion
• wettability / bonding agent / protection against dirt
• sensors / actuators
• photo voltaic
63Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Functions of nanolayers (ultrathin films)
Easy-to-clean surfaces
dirt resistant surface
protection against abrasion
scratch resistancy
antibacterial surfaces
corrosion protection
moisture protection
Acid / base resistant
high permanence
64Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
65Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
UV protection
66Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Light is reflected at both interfaces of an anti-reflective layer. The two reflected
waves of a certain wavelength can cancel each other out completely by
interference, if both the phase and amplitude conditions are fulfilled.
Clean layer
anti-reflection
Hardness
Colors
Substrate
67Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
Light is reflected at both interfaces of an anti-reflective layer. The two reflected
wave trains of a certain wavelength can cancel each other out completely by
interference, if both the phase and amplitude conditions are fulfilled.
68Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
The anti-reflection layer reduces the reflection.
69Dr. Julian Plewa
FH Münster
Applied Material Sciences
FB Chemical Engineering
Transparent ceramics and coatings
The anti-reflection layer reduces the reflection.