Novel Materials: Characterisation and Processing

Forming and machining of the nano-crystalline alloys

Gy. Krállics a, M. Horváth b, J. Nyirő b

a Department of Materials Science and Engineering, Budapest University of Technology and Economics, H-1521 Budapest, Bertalan L. u.7., Hungary
b Department of Manufacturing Engineering, Budapest University of Technology and Economics, H-1111 Budapest, Egry József u. 1, Hungary

Abstract

Equal-Channel Angular Pressing (ECAP) is an effective tool for producing ultra fine grained materials. repeated application of ECAP, the rotation of the sample along the longitudinal axis of the billet allows to carry out different routes of deformation. The applied route has a strong influence on the texture, microstructure and mechanical behaviour of ECAP processed metals. In the present study ECAP was successfully applied to produce ultra fine-grained microstructure in a commercial Al-Mg-Si alloy (AI 6082). The mechanical investigations of the ECAP deformed specimens revealed that after 4 ECAP passes the material had a very high strength but a significantly decreased ductility. Further ECAP processing to 8 passes by route C increased ductility dramatically and strength slightly. This indicates that the anisotropy of the structure of ECAP deformed materials may play an important role in achieving good ductility. We made an ultra-precision manufacturing that we analyzed the changing of structure of nano-crystalline materials and the surface roughness for the effect of machining. After manufacturing we prepared an analysis with AFM (Atomic Force Microscope). The results provided that the quality of the ultra-precision finished surface of the processed sample improved dramatically after eight passes.

Keywords: Equal channel angular pressing, high strength and ductility, nano-sized microstructure, surface quailty

Modelling and design of GaN based piezoelectric MEMS

C.R. Bowen a, D.W.E. Allsopp b, R. Stevens a, P.Shields c, W.N. Wang c

a Materials Research Centre, Department of Mechanical Engineering, University of Bath, Bath, UK, BA2 7AY
b Department of Electronic and Electrical Engineering, University of Bath, Bath, UK, BA2 7AY
c Department of Physics, University of Bath, Bath, UK, BA2 7AY

Abstract

The conditions encountered in aerospace, in automotive and many industrial applications present a challenge for semiconductor based sensor technologies. High temperatures (>180C) or ionising radiation inhibit the use of silicon transistors. This limits the scope for integrating silicon based sensors and MEMS with conventional electronics. The challenge of extreme environments requires a new approach. We examine here a solution based on GaN, a material with properties that offer wide ranging novel functionality and unexplored scope for integrating advanced sensor devices into single integrated systems for reliable operation in a wide range of extreme environments.

Keywords: GaN, piezoelectric, MEMS, sensor, actuator

Indirect Tooling Based on Micromilling, Electroforming and Selective Etching

P.T. Tang a, J. Fugl a, L. Uriarte b, G. Bissacco a & H.N. Hansen a

a Dept. of Manufacturing Engineering and Management (IPL), Technical University of Denmark, Produktionstorvet, bldg. 427S, DK-2800 Kgs. Lyngby
b Fundacion Tekniker, Avda. Otaola 20, 20600, Eibar, Spain

Abstract

The tool inserts used for injection moulding or hot-embossing of polymer micro-components, are the most important and expensive and crucial part of this important mass-production process. In this paper a new fabrication scheme is introduce, consisting of a combination of micro-milling, electroforming and selective etching. The basic concept is to exploit the benefit of true 3D-machining in a soft substrate such as aluminium with the excellent replication capabilities of nickel electroforming. The term indirect machining covers the fact that the master that is produced by machining a positive structure, i.e. the opposite of what is needed for the actual mould insert.

Keywords: micromilling, electroforming, selective etching, tooling, injection moulding

Systematic Interaction of Sedimentation and Electrical Field in Electrophoretic Deposition

S. Bonnas a,b, J. Tabellion b, H.-J. Ritzhaupt-Kleissl a, J. Haußelt a,b

a Institute for Materials Research III, Forschungszentrum Karlsruhe, 76021 Karlsruhe, Germany
b Laboratory for Materials Processing, Department of Microsystems Engineering (IMTEK),University of Freiburg, 79110 Freiburg, Germany

Abstract

The systematic interaction of sedimentation and electrical field in electrophoretic deposition allows the tailoring of specific properties of deposited green bodies. This technique permits a selective deposition of the nanosized fraction of conventional powders with broad or non-monomodal particle size distribution, thus making preceding classification obsolete. Potential applications are coatings with a very smooth surface or the replication of microstructures or moulds which are filled with nanosized particles and subsequently with coarser particles as support in one process step. Also graded structures can be fabricated with regard to particle size distribution, porosity and composition (e.g. zirconia toughened alumina). In this paper, the interaction of sedimentation and electrical field in electrophoretic deposition is described focussing on the characterisation of both processes, sedimentation and electrophoretic deposition. In addition the effectiveness of the combined process will be shown.

Keywords: electrophoretic deposition, sedimentation, particle size distribution, zirconia

Particle size dependent viscosity of polymer-silica-composites

T. Hanemann a,b, R. Heldele a, J. Hausselt a,b

a Forschungszentrum Karlsruhe, Institut f. Materialforschung III, D-76021 Karlsruhe, Germany
b Albert-Ludwigs-Universität Freiburg, Institut f. Mikrosystemtechnik (IMTEK), D-79110 Freiburg, Germany

Abstract

In this paper the influence of micro- and nanosized particles on the flow behaviour of unsaturated polyester resinsilica-composites will be compared. Commercially available micro-sized quartz filler and different hydrophilic or hydrophobic nanosized Aerosils were investigated with respect to the change of the viscosity as well as the flow activation energy with filler load. Apart from particle size and specific surface area the polarity of the filler's surface has a strong impact on the resulting flow behaviour and the accessible maximum filler load. The dependence of the relative viscosity upon the filler load was described using different empirical approaches as established in thermoplastic or wax based feedstock systems containing porcelain, alumina or PZT.

Keywords: Polymer-ceramic-composites, rheological properties, nanosized particles

Micro EDM parameters optimisation

S. Bigot a, J. Valentinčič b,c, O. Blatnik b, M. Junkar b

a Manufacturing Engineering Centre, Cardiff University, Cardiff, UK, e-mail: bigots@cf.ac.uk
b Faculty of Mechanical Engineering, University of Ljubljana, Slovenia, e-mail: lat@fs.uni-lj.si
c Corresponding author

Abstract

Electrical discharge machining (EDM) is an important process in the field of micro machining. However, a number of issues remain to be solved in order to successfully implement it in an industrial environment. One of these issues is the processing time. This paper investigates the optimisation of machining parameters for rough and fine machining in micro EDM. In one case, the parameters are selected to achieve the highest material removal rate (MRR). In the other case, the best surface roughness is targeted. Some of the main difficulties linked with micro EDM are caused by the high wear occurring on the electrode. The study focuses on a specific combination of electrode and workpiece material and proposes a typical method for micro EDM process optimisation.

Keywords: micro EDM, micromachining, roughing, finishing, micro holes and cavities

Micro EDM parameters optimisation

R. Jurischka a, A. Schoth a, C. Müller a, D. Thiebaud b, R. Gallera b, H. Reinecke a

a Department of Microsystems Engineering IMTEK, Laboratory for Process Technology University of Freiburg, 79110 Freiburg, Germany
b Sarix SA, Micro EDM Technology, 6616 Losone, Switzerland

Abstract

Today, microfluidic devices are becoming more and more important in life science, chemical analytic, and medical areas. For these applications disposable and low cost articles are highly convenient. Polymers are ideally suited for these applications due to their material properties and their applicability for high volume production with high accuracy. In this study, we optimized the μEDM-milling technology to fabricate mold inserts made from steel, including microfluidic structures, with an excellent surface quality. The microfluidic structures have channel dimensions down to 18 μm, aspect ratios of up to 4 and a surface roughness Ra Keywords: micro replication, injection molding, microfluidic, EDM, milling, steel, tool

Characterization of Molecularly Imprinted Polymers as Novel Materials for Biochemical Sensors

Neda Haj Hosseini a,b, Cristina Rusu a , Anatol Krozer a, Sjoerd Haasl a, Kristina Reimhult a, Jan-Olof Lindgren a, Peter Enoksson b, Lei Ye c

a Imego AB, Arvid Hedvallsbacke 4, 411 33 Göteborg, Sweden
b MC2, Chalmers Univ. of Technology, 411 33 Göteborg, Sweden
c Applied Biotechnology, Lund Univ., PO Box 11, 221 00 Lund, Sweden

Abstract

We study the behavior of Molecularly Imprinted Polymers (MIP) as novel synthetic receptor layers in biochemical sensors. Electropolymerization was used as an easy to implement method for polymer deposition and integrated impedance spectroscopy to monitor MIP behavior towards target molecules. Contrary to what is reported in the literature we consider that it is neither easy nor reliable to attribute the impedance changes to target binding/elution. However, alternative and/or more precise characterization methods are needed to track nano-scale changes in MIPs. Thus we are developing an optical set-up for detection of static deflections on the micro-cantilevers as a result of surface stress induced by changes in MIPs. Using an optical set-up, changes in the deflection of MIP-covered microcantilevers when exposed to the target molecules could be measured.

Keywords: Molecularly Imprinted Polymers, Impedance Spectroscopy, Micro-cantilevers, Biochemical sensors

Structuring of phosphorescent pigments by two-step hot embossing for signaletic applications

M. Sahli a,b,c, F. Legay a, C. Roques-Carmes a, C. Khan Malek b, J.C. Gelin c

a Laboratoire de Microanalyse des Surfaces (LMS), ENSMM, 25030 Besançon cedex, France.
b Laboratoire FEMTO-ST, CNRS UMR 6174, Département LPMO, 25044 Besançon cedex, France.
c Laboratoire FEMTO-ST, CNRS UMR 6174, Département LMARC, 25030 Besançon cedex, France.

Abstract

The hot embossing process is carried out in order to complement the panel of methodologies associated with the utilization of phosphorescent pigments for photoluminescent safety systems. The basic material, in compound form, is a strontium aluminate doped with Eu2+ and Dy3+ ions. Materials with these specific properties are protected from mechanical contact as well as from interactions with the environment, particularly atmospheric humidity to which these pigments are sensitive. Transparent structures with phosphorescent small-sized cavities were manufactured by a two-step hot embossing process developed for this application. The novelty of this work lies in applying the hot-embossing process to this new class of materials for safety applications. The modelling associated with this application allows the description of the velocity distribution in the various parts of the mould during the hot embossing process. Moreover it explains the interest of using sequential steps for testing signaletic applications.

Keywords: Molecularly Imprinted Polymers, Impedance Spectroscopy, Micro-cantilevers, Biochemical sensors

An Ultrathick SU-8 UV Lithographic Process and Sidewall Characterization

K Jiang1, C-H Lee and P Jin

Centre for MicroEnigineering and NanoTechnology, The University of Birmingham, Birmingham, U.K. B15 2TT

Abstract

This paper presents a UV lithographic process for fabrication of ultrathick SU-8 micro structures and sidewall surface characterization. The UV lithographic process has enabled the thickness of the SU-8 structures to be increased from 240 um given in the datasheet to 1000 um, and thus massively increases the application range. In developing the UV lithographic process, the best softbake and UV exposure times have been searched and tested in experiments. The UV light transmission spectrum has been analyzed. Then the best results have been produced on the research basis. The straight sidewall and 40:1 aspect ratio SU-8 structure images are presented in the paper. As SU-8 microstructures are suitable for microfluidics and bio-compatible, the sidewall surface roughness is characterized using AFM. The roughness contour of the sidewall shows that the surface topography is similar throughout the depth. The average roughness Ra is 46.46 nm. Other surface parameters, such as Rq, Rp-p, Rpk and Rsk, are also obtained and analysed. The implication of the smooth surface roughness of SU-8 structures to their applications is discussed in terms of transmission efficiency, the changes in friction to flowing liquid in a microchannel and the changes in the surface tension and capillary effect.

Keywords: Ultrathick SU-8, UV lithography, sidewall surface roughness, softbake

Fabrication of nano-dimensional features in FOTURAN using focused ion beam technology

P.T. Docker, J Teng, P. D. Prewett, K. C. Jiang1

MicroEngineering and Nano technology Group, Department of Mechanical Engineering and Manufacturing University of Birmingham, Birmingham, B15 2TT, UK

Abstract

This paper details the findings of work carried out to determine the feasibility of manufacturing nano-dimensional features in photoetchable glass (Foturan TM) using focused ion beam technology. To date the standard processing techniques for producing features (UV lithography and UV lasers) in this material are limited by grain structure giving minimum feature size typically 10 microns. Focused ion beam technology (FIB) offers two potential advantages: there is no additional processing such as wet etching in hydrofluoric acid and there is the potential to manufacture nanodimensional features, smaller than the micron scale which can be achieved using UV patterning with wet etch. This relies on the high resolution of the FIB system - Keywords: Photoetchable glass, Foturan, Nano-scale features, Focused ion beam patterning.

Influence of the process parameters on themicrostructure of screenprinted Ba0.6Sr0.4TiO3 (BST60) thick-films on alumina-substrates

F. Paul ∗, J.R. Binder, A. Berto, G. Link, H.-J. Ritzhaupt-Kleissl

Forschungszentrum Karlsruhe, Institute for Materials Science III, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

Abstract

This article briefly discusses some aspects of the influence of process parameters on the microstructure of screenprinted BST60 thick-films on polycristalline alumina substrates. The focus of the experiments is directed toward the reduction of porosity by means of preparation without using sintering additives or composite techniques. The influence of paste composition, sintering temperature, cold isostatic compaction and microwave sintering on the morpholgy of the thick-films has been examined. The conclusion drawn from these results is, that the porosity of the films cannot be reduced by variation of paste composition or sintering temperature alone. Cold isostatic compaction of the green films leads to an improved homogeneity of the films, but not to a considerable reduction of porosity. Additional sintering by microwave might offer the possibility to reduce porosity of BST thick-films.

Keywords: BST, thick-film, screen printing, ceramic powder, microstructure, microwave sintering

Self-assembled nanostructured polymer films from concentrated solutions of block copolymers

N. Didier a, P. Panine b

a Ecole Nationale Supérieure de Physique de Grenoble, 38 402 St-Martin d'Hères, France
b European Synchrotron Radiation Facility, 38 043 Grenoble, France

Abstract

We are presenting in this paper a simple method to orient auto-assembling systems. We detail the production process of oriented nanostructured polymer films by shearing a concentrated solution of block copolymers. The most appropriate tool to simulate the applied strains during the film formation is a rheometer with a cone-plate geometry. We use the technique of Small Angle X-ray Scattering (SAXS) on the high brilliance beamline ID02 of the European Synchrotron Radiation Facility (ESRF) to analyse in situ the structure at large scale. By coupling on-line rheology with SAXS (Rheo-SAXS), we can determine simultaneously the structure and its stability associated with the shear rate. Hence, the solution is spread using a film applicator within the same mechanical strain deformation scheme. Once dried, films are observed by SAXS. Finally, a detailed analysis of orientation distribution function obtained from the SAXS diffusion pattern on each film provides a quantitative value of the level of alignment of the polymeric chains.

Keywords: block copolymer, shearing, orientation, nanostructure.