Lecture
Nanoceramics
Properties of nanoceramics: Transparent ceramics and coatings
Prof. Dr. Julian Plewa Applied Material Sciences 1 FH Münster FB Chemical Engineering Lecture: Overview of nanomaterials ceramics Methods of producing nanopowders Phenomena in disperse systems Consolidation of nanopowders Properties of nanoceramics Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 2 FH Münster FB Chemical Engineering opaque ceramic translucent ceramic
Dr. Julian Plewa Applied Material Sciences 3 FH Münster FB Chemical Engineering Transparent ceramics and coatings
TRANSPARENT CERAMICS
nanooptics nanoelectronics other
Dr. Julian Plewa Applied Material Sciences 4 FH Münster FB Chemical Engineering Transparent ceramics and coatings
MULTIFUNCTIONAL CERAMICS
PZT - PbZrO3, YSZ - ZrO2 with stabilizer PLZT - (Pb,La)(Zr,Ti)O3 transparent and ion conductive transparent and for fuel cells, fiber optics, EUV- piezoelectric litography for sensor applications
YAG - Y3Al5O12 with Corundum - Al2O3 activator transparent and chemically transparent and durable and mechanically resistant for Laser Technology and for optical and armour Turbine Blade Construction protection inserts
Dr. Julian Plewa Applied Material Sciences 5 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 6 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 7 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 8 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 9 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 10 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 11 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 12 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 13 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 14 FH Münster FB Chemical Engineering Transparent ceramics and coatings
transmission I T I0
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
Dr. Julian Plewa Applied Material Sciences 15 FH Münster 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 Transmission without Metselaar scattering
(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
Dr. Julian Plewa Applied Material Sciences 16 FH Münster 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:
Dr. Julian Plewa Applied Material Sciences 17 FH Münster 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].
Dr. Julian Plewa Applied Material Sciences 18 FH Münster FB Chemical Engineering Transparent ceramics and coatings
transmission
Dr. Julian Plewa Applied Material Sciences 19 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 20 FH Münster 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]
Dr. Julian Plewa Applied Material Sciences 21 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Transparent Al2O3 ceramics
Dr. Julian Plewa Applied Material Sciences 22 FH Münster FB Chemical Engineering Transparent ceramics and coatings
YAG Arctube Ceramic Metal Halide, Toto
Dr. Julian Plewa Applied Material Sciences 23 FH Münster FB Chemical Engineering Transparent ceramics and coatings
YAG:Nd for laser applications
Dr. Julian Plewa Applied Material Sciences 24 FH Münster FB Chemical Engineering Transparent ceramics and coatings
for laser applications YAG:Nd
Dr. Julian Plewa Applied Material Sciences 25 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 26 FH Münster FB Chemical Engineering Transparent ceramics and coatings
YAG:Nd
Dr. Julian Plewa Applied Material Sciences 27 FH Münster FB Chemical Engineering Transparent ceramics and coatings
YAG:Nd
Dr. Julian Plewa Applied Material Sciences 28 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 29 FH Münster FB Chemical Engineering Transparent ceramics and coatings
YAG:Nd
Dr. Julian Plewa Applied Material Sciences 30 FH Münster FB Chemical Engineering Transparent ceramics and coatings YAG:Nd
Dr. Julian Plewa Applied Material Sciences 31 FH Münster FB Chemical Engineering Transparent ceramics and coatings YAG:Nd
Dr. Julian Plewa Applied Material Sciences 32 FH Münster FB Chemical Engineering Transparent ceramics and coatings YAG:Nd
Dr. Julian Plewa Applied Material Sciences 33 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 34 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 35 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 36 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 37 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 38 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 39 FH Münster 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
Dr. Julian Plewa Applied Material Sciences 40 FH Münster 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 ].
Dr. Julian Plewa Applied Material Sciences 41 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 42 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 43 FH Münster 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.].
Dr. Julian Plewa Applied Material Sciences 44 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 45 FH Münster FB Chemical Engineering Transparent ceramics
Dr. Julian Plewa Applied Material Sciences 46 FH Münster FB Chemical Engineering Transparent ceramics
Dr. Julian Plewa Applied Material Sciences 47 FH Münster 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)
Dr. Julian Plewa Applied Material Sciences 48 FH Münster FB Chemical Engineering Transparent ceramics
Dr. Julian Plewa Applied Material Sciences 49 FH Münster FB Chemical Engineering Transparent ceramics
Dr. Julian Plewa Applied Material Sciences 50 FH Münster FB Chemical Engineering Transparent ceramics
Segregation on the grain boundaries
Dr. Julian Plewa Applied Material Sciences 51 FH Münster FB Chemical Engineering Transparent ceramics and coatings
applications
defense scintillator smart gear engineered materials
Dr. Julian Plewa Applied Material Sciences 52 FH Münster FB Chemical Engineering scintillators
Absorption coefficient of X-rays 4 density, Zeff effective atomic Z number of the material abs eff
Dr. Julian Plewa Applied Material Sciences 53 FH Münster FB Chemical Engineering scintillators
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.
Dr. Julian Plewa Applied Material Sciences 54 FH Münster FB Chemical Engineering scintillators
Dr. Julian Plewa Applied Material Sciences 55 FH Münster FB Chemical Engineering scintillators
Dr. Julian Plewa Applied Material Sciences 56 FH Münster FB Chemical Engineering scintillators
Dr. Julian Plewa Applied Material Sciences 57 FH Münster FB Chemical Engineering scintillators
Dr. Julian Plewa Applied Material Sciences 58 FH Münster FB Chemical Engineering Transparent ceramics
Dr. Julian Plewa Applied Material Sciences 59 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Nano layer Thin layer Thick layer
Dr. Julian Plewa Applied Material Sciences 60 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Nano layer Thin layer Thick layer
Dr. Julian Plewa Applied Material Sciences 61 FH Münster 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
Dr. Julian Plewa Applied Material Sciences 62 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Functions of nanolayers (ultrathin films)
Easy-to-clean surfaces corrosion protection dirt resistant surface moisture protection protection against abrasion Acid / base resistant scratch resistancy high permanence antibacterial surfaces
Dr. Julian Plewa Applied Material Sciences 63 FH Münster FB Chemical Engineering Transparent ceramics and coatings
Dr. Julian Plewa Applied Material Sciences 64 FH Münster FB Chemical Engineering Transparent ceramics and coatings
UV protection
Dr. Julian Plewa Applied Material Sciences 65 FH Münster 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
Dr. Julian Plewa Applied Material Sciences 66 FH Münster 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.
Dr. Julian Plewa Applied Material Sciences 67 FH Münster FB Chemical Engineering Transparent ceramics and coatings
The anti-reflection layer reduces the reflection.
Dr. Julian Plewa Applied Material Sciences 68 FH Münster FB Chemical Engineering Transparent ceramics and coatings
The anti-reflection layer reduces the reflection.
Dr. Julian Plewa Applied Material Sciences 69 FH Münster FB Chemical Engineering