prof. dr. J.T.M. (Jeff) de Hosson
Two routes are pursued in synergy.
(a) atomic and nano-meter scale:
This route focuses on the structural aspect as a central theme; i.e. it considers mainly the atomic scale with HRTEM and the effects of segregation on in-situ fracture using UHV small-spot SEM/SAM. We have concentrated on the question whether HRTEM image information can be interpreted in terms of the atomic structure and whether the latter will provide information of the bond-strength along the (segregated) heterophase interface between dissimilar materials, like a metal and a ceramic material. It is accurate to say that important properties of materials in high-technology structural and functional applications are strongly affected, even controlled, by the presence of solid interfaces. This part focuses on elucidation of the link between an important property of a metal-ceramic interface, namely the work of adhesion and the atomic structure. The basic idea is that the link between the atomic structure and the interface energy is provided by the interplay between atomic bonding and misfit that is present. In order to make the transition from this atomistic regime to a mesoscopic scale an anisotropic linear elasticity description is employed.
Over the last couple of years a strong impetus has been given to studies of nano-cluster/nano-structured thin metal layers. The appeal of these types of thin films stems from their novel magnetic and mechanical properties, which can be intrinsically different from their macrocrystalline counterparts. HRTEM techniques are used to provide a more direct link between microstructure and the magnetic properties of various alloys, whereas Lorentz microscopy and electron holography methodologies are explored to characterize the magnetic structure of nano-sized cluster films.
(b) Engineering scale
Interfaces between dissimilar materials are also important in the field of surface engineering. The second route that has been followed includes high-power laser systems to manufacture ceramic-layers on top of metallic substrates for tribological applications. Here the research lies in the field of surface engineering to obtain either a (pore less) ceramic layer that is firmly bonded to the underlying substrate (laser cladding) or to produce functionally graded materials (laser melt particle injection). One of the objectives of this research is to discover whether the interfaces are stable or undergo diffusional reactions, as the kinetics, rather than the equilibrium phase diagram, dominates. To emphasize the dynamic rather than the static behavior, in-situ heating and in-situ deformation studies have been carried out both in transmission- and in environmental scanning electron microscopy. Laser technology and in-situ microstructural research are forged together in an international collaboration (Philips, Fraunhofer, Merck, Pelikan, Sandvik, Xaarjet-MIT) on nano-sized ceramics in which the sol-gel concept is combined with inkjet technology and laser treatment of surfaces.
The main experimental tools to unravel the microstructural features are ultra-HRTEM (combined with PEELS, EDS and image filtering GIF2000TM), local probe microscopy (AFM and TOF-(I)AP-FIM), UHV-scanning electron/scanning Auger microscopy (SEM/SAM), environmental and high-resolution low-voltage scanning electron microscopy with electron backscatter diffraction /orientation imaging microscopy (EBSD/OIM). Properties, in particular those of thin films and coatings, with emphasis on mechanical properties, are studied using a Nano-indenter MTS XP, Instron Tensile machine + Messphysik Video extensometer +digital image correlation (DIC), CSM Scratch tester, CSM High-temperature tribo-tester, in-situ mechanical testing (tensile, compression, 3 and 4-point bending combined with heating) in an environmental SEM, straining+heating holder for TEM. Magnetic structure/properties are assessed using Lorentz Microscopy, Electron Holography and Magnetic Force Microscopy (MFM).
Characterization: microscopy and X-ray
Transmission electron microscopy
JEOL 4000 EX/II + PEELS, point-to-point resolution 0.165 nm (HRTEM, 400 kV)
JEOL 2010 FEG +EDAX+ GIF, spot size 0.5 nm (straining+heating holders, 200 kV)
JEOL 200 CX + EDAX (CTEM, 200 kV)
TEM preparation facilities, Ion milling, PIPS, Etching, Tenupol, Tripod, image simulation sofware.
Scanning electron microscopy
- Philips SEM-XL30s-FEG + EDAX + EBSP+OIM
Philips SEM-XL30-FEG +EDAX+EBSP+OIM
Philips ESEM-XL30-FEG+EDAX+ tensile/bending/hot stages
JEOL 7800F, FEG SEM+ scanning Auger microscopy+EDAX, UHV fracture stage
JEOL JXA8600 +EDAX/WDS superprobe-microprobe
Tescan LYRA- FEG
- VG-FIM 100 Poschenrieder
IAP/FIM - TOF – AP
Tescan LYRA- FEG- Focussed Ion beam
AFM/STM Dimension Veeco 3100 (Nanoscope)
micro Surf- confocal microscopy
Mahr Perthometer S2/6D2S profilometer
- Philips PW 1820 w goniometer
- Philips X’Prt PW 3040 y goniometer]
- Oxford Applied Research Nanocluster Source NC200U
- CW-CO2 laser Rofin Sinar Spectra Physics 820, 1.5 kWatt
- Nd-YAG laser system Rofin Sinar CW 20, 2 kWatt, coaxial laser clad system
- Nd-YAG laser Lumonics 300
- IPG 3kW Yt:YAG Fiber laser
- Teer UDP 400/4 magnetron sputtering rig
- LINAC electron accelerator (0.5 MeV,1mA)
- Heraeus furnace 1200 oC
- Thermolyne 1700 oC
- High presuure / gases atmosphere furnace 1700 oC
- Arc furnace
- Vacuum furnace
- Venticell furnace
- In- situ TEM picoindenter, Hysitron.
Nano-indenter MTS XP
MTS fatigue and tension/compression, furnace
Instron Tensile machine + Messphysik Video extensometer +Digital Image Correlation CCDs
Locan 320 Acoustic emission
Vickers hardness tester
Scratch tester CSM Revetest
High-temperature tribo tester CSM + Tribox software
Concise summary of projects supervised by the following project leaders :
Dr. YuTao Pei, M2i-RuG, y.pei rug.nl ,
Dr. Vasek Ocelik, M2i-RuG, v.ocelik rug.nl ,
Dr. David Vaichtein, RuG, D.I.Vainchtein rug.nl ,
Dr. Willem van Dorp, RuG, VENI-NWO, W.F.van.Dorp@rug.nl ,
Prof.dr. Jeff Th.M. De Hosson, RuG, j.t.m.de.hosson rug.nl ,
Visiting scientists: Dr. Tony Kazantzis (Thessaloníki), Prof.dr. Anatoly A. Turkin(National Science Center Kharkov Institute of Physics and Technology)
Design of microstructure for optimum performances of DLC-based
PhD student: Kalpak Shaha
Postdocs: Dr. ChangQiang Chen
Nano-structured coatings have recently attracted increasing interest because of the possibilities of synthesizing a surface protecting layer with unique physical-chemical properties that are often not attained in the bulk counterpart. On top of this, amorphous DLC-based nano-composite coatings exhibit not only excellent wear resistance and super-hardness but also low friction, which provide a solution to the stringent requirements on drive-line components in automotive industry such as prolonging the life in operation of the components and increasing the efficiency of the engines by reduction of friction. Within the framework of a novel experimental approach to the design and control of wear resistant nanocomposite coatings, the project is aimed at scrutinizing the deposition window of pulsed sputtering, optimization of nano-/micro-structure and tribo-chemistry in relation to the performances of DLC-based nanocomposite coatings. The project is in particular linked to the recently installed closed-field unbalanced magnetron
sputtering system (Teer UDP 4/350) .
In situ probing of size dependent properties of nano pillars.
PhD student: Alexey Kuzmin
The project is aimed at scrutinizing our hypotheses about the interplay between relevant length scales and size effects affecting the thermo-mechanical stability of devices. The hypotheses read:
· Upon decreasing size, when going from crystalline to metallic glassy materials, we move from a ‘smaller is stronger’ into a ‘smaller is tougher’ regime.
· Devices thinner than a critical thickness will not exhibit catastrophic failure depending on the specific materials design.
This proposal sets apart from the current work in this field by focusing on what is the interplay of the internal characteristic length scale, e.g. the size of the shear transformation zone, and the external dimensions of the amorphous material system, and how this could be tuned to yield an optimal performance. Understanding and controlling shear localization is one of the principal tasks in research on metallic glasses. However, a major drawback of experimental and theoretical research so far is that - not surprisingly- almost all of the microscopy work has been concentrated on static structures and as a consequence the mechanical response of amorphous materials is a subject area which is still shrouded with considerable confusion. Our approach is to concentrate on in situ TEM/SEM studies of amorphous systems (pillars) and amorphous-controlled nanocrystalline multilayers under compression/tension and load/displacement controlled conditions.
Nano texturing using Ultrashort Laser Pulses.
Postdoc: Dr. Jozef Obona
This project aims at developing processes for fabrication of surface structures on micro- and nano scale by the use of ultra short laser pulses. Surfaces structures will generate special contact surfaces in metal or ceramic for friction control in precision equipment. Laser textured surfaces can also generate specific properties e.g. wetting or optical and surface patterns that can be replicated in polymer surfaces. Furthermore, research will be conducted into the physical aspects of the interaction of ultra short laser pulses with materials. In general the results of this project will contribute to bridging the micro – nano manufacturing gap.
Many nano manufacturing processes are based on lithographic techniques that have driven the silicon wafer industry, but increasingly the new drive is for low cost, high precision products based on non-silicon materials like polymers, ceramics, and metals. The need to structure these materials in the size range 100 nm – 10 µm, has lead to the development of a new range of process technologies and laser micromachining is one of them. The project is carried out in close collaboration between our group and the Twente University group of prof. Bert Huis in ‘t Veld.
Design of novel nanoporous metallic actuators.
PhD students: Eric Detsi and Sergey Punzhin
Nanoporous metallic actuators have appeared recently and have the potential to outperform existing (dense) materials. The key feature is the materials’ nanostructural architecture, which links the overall behavior to the charge-induced surface stresses at the nanoscale. The opportunity lies in the unique combination of nanoscale surface properties, that can be tuned by an applied potential, and the design freedom offered by the three-dimensional nanostructural architecture. We propose to explore this opportunity through the concerted action of experiments and modeling, aimed at designing novel nanoporous metals with a superior actuation performance. In this project we synthesize novel nanoporous metals by exploiting the self-assembling properties of block copolymers at the nanoscale, characterize their microstructure and test their functionality.
Optimization of the microstructure and properties of laser deposited
PhD students: Mikhail Dutka and Ismael Hemmati
Postdoc: Dr.Ivan Furar
Laser surface engineering techniques (laser cladding, laser melt injection and laser surface / hardening/ remelting) embrace a body of methodologies offering relatively thick (0.3- 2 mm) coatings with excellent hardfacing, wear and corrosion resistant properties on inferior substrates. The principal objective of this project is to understand the basic relationships among the laser processing parameters, the resulting microstructure and the corresponding properties of the coatings. This allows the design of an optimal microstructure for the required applications.
Tunable self-organization of nanocomposite multilayers.
Postdocs: Dr. ChangQiang Chen and Dr. JianCun Rao
This work concentrates on the controlled growth and structure evolution of self-assembled nanocomposite multilayers that are induced by surface ion-impingement. The nanoscale structural and chemical information, especially at the growing front, has been investigated with high-resolution transmission electron microscopy. Concurrent ion impingement of growing films produces an amorphous capping layer of ~3 nm thicknesses where spatially modulated phase separation is initiated. The modulation of multilayers, controlled by the self-organization of nanocrystallites below the capping layer, is maintained and is also tunable through the entire film.
Self-healing of composite materials.
Postdoc: Dr. Huajie Yang
The project is aimed at designing new high temperature Ti-Al-C ceramic composites with high crack-healing ability. The novel approach leads to promising materials for a variety of high-temperature structural and functional applications. The crack-healing efficiency will be improved by enhancing the adhesive strength of oxidation products present within the crack openings to the base material via changing the chemical composition of the oxidation products with alloying elements such as B, Si, Cr, Mo and Zr added into the Ti-Al-C matrix. Also, the oxidation resistance and high temperature mechanical properties of Ti-Al-C high temperature ceramics will be tuned by these alloying elements in the Ti-Al-C matrix so as to form solid solution strengthening phase or/and second reinforcements. The project is carried out in collaboration with the Delft University of Technology (prof.dr. S. van der Zwaag, Dr. GuiMing Song, Dr. W. Sloof)
Ultra Low frictional coatings on rubber seals.
Postdoc: Dr. Diego Martinez-Martinez
Rubber seals are commonly used in lubrication system to prevent dirt and water entering the system and to avoid leakage of lubricants. Dynamic rubber seals operate in sliding contact mode at relatively high speed and under no or marginal lubrication condition. Under such a tough operational condition, contact seals are the major sources of friction of lubrication systems or bearings, which may take 50-70% of the total friction. Furthermore, rubber seals are subjected to severe wear leading to an increase of clearance, which is often the cause of loss of the function and failure of the lubrication system. Therefore, an advanced solution for dynamic rubber seals is stringent for bearings and automotive industries. Within the framework of a novel experimental approach to the design, deposition and characterization of wear resistant and low frictional DLC-based nanocomposite coatings on rubber seals, the project is aimed at developing a unique coating system on a rubber seal having low dry-sliding friction coefficient (< 0.25), high wear resistance, good adhesion to rubber surface and high flexibility and strain tolerance to follow large deformation of rubber substrate.
Superplasticity and interfaces in coarse grained metallic systems.
PhD student: ZhengGuo Chen
Visiting scientist: Dr. Tony Kazantzis
The mechanical properties, the anisotropy and the dislocation microstructures of two coarse-grained aluminum alloys were investigated by a combination of uniaxial tension and transmission electron microscopy.They exhibited optimum superplasticity at 10-2 s-1 and at T equal to 425°C and above 475°C with maximum elongations close to or above 300% depending on the specimen orientation.We will analyze the secondary necking instabilities that are associated with a large volume fractions of soft grains.They produce microstructures that exhibit maxima in the cube and Goss component of the deformed grains and a slight grain refinement.The deformation lies between the five power law and the power law breakdown.At the secondary necking instabilities, the average dislocation velocity increases, most dislocations break away form their solute atmospheres and thermally activated deformation occurs with high activation energies.Grain boundary sliding is prohibited due to the presence of coherent precipitates that pin effectively the grain boundary motion.
Interfaces in flexible multilayers.
Postdoc: Dr.ir. Willem Pier Vellinga
The project deals with time dependent properties and fatigue of flexible electronics that may be used in technology for modular ultra light and ultra thin, easy-to-wear electronic products such as lighting and signage devices, reusable and disposable sensor devices, foldable solar panels and displays. Roll-to-roll production processes will enable to make these devices in large sizes and quantities at competitive costs. It is important to understand the nature of the mechanical deformation that these multimaterial. Multilayer laminates may experience during production and intended use, as well as the associated (time-dependent) stress distributions and their effects on the reliability and durability of the devices. Dynamic and cyclic (fatigue) deformation modes are of course relevant for these devices, especially near room temperature and at varying degrees of humidity. The response to cyclic mechanical loading (fatigue) will ultimately determine the usefulness of flexible electronics.The roject is carried out in collaboration with the Eindhoven University of technology (Prof. Bert de With)
Interfaces and domains in ferroelectrics and multiferroics.
PhD researcher: Sriram Venkatesan
The piezoelectric and dielectric properties of ferroelectric perovskites can be greatly enhanced by reducing the symmetry elements, in particular by eliminating the “easy axis” along which the polarization vector is usually constraint. The objective of this project is to create such systems artificially by controlling the growth at the nanoscale. In particular, we study the critical thickness for ferroelectricity and local variation in surface charge ordering at an atomic scale in transition-metal (perovskite) oxides with electron-holography techniques and scanning probe microscopy. The use of High Resolution TEM together with electron holography to provide information about both the atomic order, the structural domains and defects (dislocations) and the local electric polarization in ferroelectric (multi-ferroic) thin films, which together define the ferroelectric and ferromagnetic response of these films. (Togetherwith dr. B.J. Kooi) .
Tailoring metallic-organic interfaces.
PhD student: Enne Faber
PostDoc: Dr.ir. Willem Pier Vellinga
Metal-polymer laminates of electrolytic chromium coated steel plate are increasingly used for packaging of food and beverages. From a materials point-of-view there are a number of challenges since the polymer coated sheet is subjected to severe loading conditions during forming, e.g. deep-drawing and wall ironing (DWI). Damage is introduced during production, but also during the subsequent content sterilization procedure and it is obvious that this damage may become apparent during the prolonged shelf-life of the product. The main objective of this project is to improve product reliability using insight in micro-scale deformation mechanisms at the polymer-steel interface and the interplay between micro-deformation and de-adhesion. The microstructural evolution near the interface and its interrelation with the evolution of the interface geometry and interface bonding is key to understand and model the behaviour of the laminates. This project aims to clarify the microscopic processes that determine polymer-metal adhesion during forming. Deformation and delamination processes on multiple scales will be studied numerically and experimentally in a concerted action between Eindhoven University of Technology (TU/e –Dr. P. Schreurs, Prof. M. Geers) and University of Groningen ..
Mathematical and computational analysis of roughening- smoothing transitions
Visiting scientist: Prof.dr. A.A. Turkin( National Science Center "Kharkov Institute of Physics and Technology")
The present collaborative project is devoted to computer modeling of kinetics of formation and properties of nanocomposite coatings based on amorphous diamond-like carbon (DLC). Because of unique combination of mechanical, tribological and physical properties DLC-coatings are used in numerous advanced applications. We focus on an analysis of smoothening mechanism of the thin film grown with p-DC magnetron sputtering. Roughness evolution has been described by the linear stochastic equation which contains the second- and fourth-order gradient terms. It turns out that the thin film roughness can be controlled by adjusting the waveform, frequency and width of DC pulses. The transition from the roughening regime of coating growth to the smoothening one will be studied. The dramatic decrease in the surface roughness when the frequency is changed from 100 kHz to 350 kHz is explained by a strong increase of atomic diffusivity along the surface because of increase of Ar+ ion flux to the substrate.
Focused beam induced nanostructures
Veni-NWO project: Dr.Willem van Dorp
Focused beam induced chemistry promises to be play an important role in future lithography. With beam induced chemistry, two- or three-dimensional patterns are defined in a single step by dissociating adsorbed gas molecules with charged particles. As it is a one-step process, it does in principle not require any pre- or postprocessing, in contrast to for instance resist-based electron beam lithography (EBL). Currently, EBL is the main patterning technique that gives access to the 200 to ~10nm regime and the fabrication of a functional structure typically requires at least several processing steps. Focused beam induced chemistry has the potential to make it easier and faster to define complex patterns or patterns with details smaller than 10nm. The project concentrates on focused ion beam induced deposition (FIBID) and focused electron beam induced deposition (FEBID). A dsorbed precursor molecules are dissociated by a focused beam and under the influence of the charged particles, the precursor molecules are fragmented. in collaboration with TuDelft (group prof.dr.ir. P. Kruit and Dr. C.W. Hagen)
Electrical switching dynamics in phase-change random access memory.
Joint PhD student: Jasper Oosthoek
In this project the emphasis is on the reversible amorphous-crystalline phase transformation in so-called Phase-change Random Access Memories (PRAMs), that have potential for future universal memory, is proposed. The basis for the PRAM is a large differencein electrical resistivity between the amorphous and crystalline phase that enables two or multi-level memory states. Using electrical (Joule) heating, nano-second switching between the states is possible. Phase-change materials have become well known from their application in rewritable CD and DVD formats, where carried out in close collaboration with NXP and Philips in Eindhoven . Fundamental problems remain that hamper a technological breakthrough of the concepts of PRAM in general. We address the various questions by analyzing PRAM cells after different switching conditions and as a function of the number of switching cycles using TEM (joint efforts with dr. B.J. Kooi) .
H-storage and nano clusters
Joint PhD student: Gopi Krishnan
In this project the emphasis lies on the high surface to volume ratio of nano clusters for the uptake of H by metallic systems. A main challenge is to design a system for fast uptake but alsofast release of H.High resolution electron microscopy is the principal experimental method to perform a careful analysis of the various crystallographic phases formed. (joint efforts with dr. B.J. Kooi and dr. G. Palasantzas)
Dynamic surface roughening and the Casimir force in MEMS/NEMS.
Joint PhD student: Peter van Zwol
The aim of the proposed research is to scrutinize the influence of random roughness and its dynamic scaling on the Casimir effect, which arise from the perturbation by conducting plates of zero point vacuum fluctuations of the electromagnetic field. When the proximity between material objects becomes of the order of several nanometers, a regime is entered in which dispersive surface forces that are quantum mechanical in nature, namely, van der Waals (for separations< 10 nm) and Casimir forces (or retarded van der Waals; for separations >> 10 nm) become operative (joint efforts with dr. G. Palasantzas).
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