First Prize Winner:

167/M07 A Novel Prediction Method for Fabrication of Orthopedic Implants by Bio-Functional “Alumina-Zirconia” Composites
H. Sarraf (Sp), J. Havrda, Institute of Chemical Technology of Prague (CZ)

Today, most of the orthopedic implants consist of metallic, polymeric or ceramic components applied for increasing the quality of life of the patients which there are many advantages and disadvantages considering the need of an aging population and growing demand, implants should exhibit a lifetime more than 30 years. This demonstrates the need for more wear-resistant and biocompatible materials such as ceramics. From this point of view, this present work focuses on the investigation and preparation of a novel prediction method based on nano particle-sized colloidal processing which has been developed and used to produce high quality and biocompatibility alumina-toughened zirconia composites. The investigation was rather comprehensive, accounting for all processing steps from suspension preparation, consolidation, drying and sintering. The ultimate goal was to establish as clearly as possible relationships between colloidal processing and microstructures, i.e. how colloidal processing controls or modifies the microstructure. This new method caused high homogeneous, defect free and developed and controlled microstructure of (ATZ) bio-ceramic composites and with desired mechanical properties which the results of this work present the necessary basis for the development of compositional gradient composites that combine e.g. the advantages of the high wear resistance of alumina and the high fracture toughness of zirconia. ATZ composites could be good choice for preparing implants and could extend the lifetime of the artificial hips. In the future a new generation of bio-functional gradient material in the scale of a nano-sized microstructure could be developed and acquire a niche on the biomaterials market.

Second Prize Winner:

95/D04 Diffusion of Dithiophosphates in Rubber Compounds
C. Rosca (Sp), University “Politehnica” of Timisoara (Romania); U. Giese, R.H. Schuster, Deutsches Institut für Kautschuktechnologie e.V., Hannover (Germany); T. Früh, Rhein Chemie Rheinau GmbH, Mannheim (Germany); I. Manoviciu, University “Politehnica” of Timisoara (Romania)

Diffusion of compound ingredients before, during and after vulcanization is recognized as an important factor in the overall properties of complex rubber products, especially if different mixtures or blends with incompatible rubbers are used. The physical properties of elastomers are determined mainly by the chemical nature of the polymer, plasticizers, processing aids, the reinforcement through active fillers and the different types of crosslinks and crosslink density formed during vulcanization [1, 2].
Objective of the work is the characterization of the diffusion behavior of the accelerator, di- (2-ethyl) hexylphosphoryltrisulfid (SDT), between different rubber mixtures of tires.
In this work a special IR-Spectroscopy method was employed for the calculation of the diffusion coefficient. The experimental arrangement consists of a two layer sandwich: a ”reservoir” (the mixture A + 5phr SDT) and a ”film” (mixture A). The preparation was carried out by means of Ultramicrotome. The FT-IR Microscopy using transmission mode was a useful tool to characterize the diffusion process. The diffusion coefficient was calculated by means of analysis of concentration-distance curves.
Well-known methods like time lag method (ATR-FT-IR spectroscopy) and swelling investigations were used for comparison. The results for diffusion coefficients calculated using these different methods show a good correlation.

Finalists:

92/C07 Investigation on the Arc Erosion Behavior of AgMeO and AgNi Composites
N. Jeanvoine (Sp), F. Mücklich, Universität des Saarlandes, Saarbrücken (Germany)

The arc erosion behavior of silver matrix composite contact materials was investigated. Two material systems have been tested: silver-metal oxide and silver-nickel. The first system consists of SnO2 and CdO particles reinforced silver matrix composites. The second system consists of silver-nickel composites with different contents of nickel fibers. Pure silver and nickel samples were used as references. The craters caused by single electrical discharges on the surface were qualitatively and quantitatively examined using white light interferometry and scanning electron microscopy. In addition to single-spark tests, 2D FEM-simulations of the crater formation were conducted.
It was found that silver matrix composite materials exhibit a better erosion resistance, regarding the crater size, than pure silver. Reinforcement mechanisms were proposed for each system. For silver-metal oxide materials, the stabile oxide particles (SnO2) increase the effective viscosity of the melt, reducing the material lost by the ejection of molten particles. For silver-nickel materials, the depth and the volume of the craters decrease as the nickel content increases. Because of their physical and thermodynamic properties, nickel shows a better erosion resistance than silver. On the one hand, the nickel fibers reinforce the silver matrix according to a mixing rule. On the other hand, they reduce the motion of the melt, decreasing the flow and the particle ejection of molten silver.
The CdO particles don’t provide an effective reinforcement. Because of their low sublimation temperature they strongly modify the behavior of the plasma. According to the cathode spot theory a model was proposed to explain this phenomenon.

356/E39 Bonded Ferromagnetic Fibre Arrays
C. Shortall (Sp), A.E. Markaki, T.W. Clyne, Department of Materials Science & Metallurgy, Cambridge (UK)

Extensive effort has been devoted recently to the mechanical behaviour of highly porous metals. Unfortunately, much of this work is being done on material which is very brittle, particularly under tensile loading. This is partly due to unavoidable stress localisation effects, but these are often exacerbated by severe inhomogeneities and gross defects and by the presence of embrittling constituents in the cell walls (sometimes introduced deliberately to facilitate processing). A promising approach to the generation of highly porous, permeable material with relatively high strength is to strongly bond together an assembly of fibres or wires. The properties of such a material can be controlled by tailoring the fibre / wire properties (material, diameter, sectional shape) and architecture (volume fraction, orientation distribution, inter-joint spacing). However, to ensure adequate material strength, it is essential that suitably robust necks between adjacent fibres / wires should be generated.
Such arrays have further attractive features. For instance, porosity and permeability facilitate rapid temperature changes or penetration of in-growing tissue. Furthermore, macroscopic and local shape changes can be generated by inducing fibre bending, for example, by the imposition of a magnetic field.
Accelerated sintering techniques (brazing) are used to consolidate the fibre / wire arrays into strong, porous material and are investigated through experimental and modelling studies.

248/E23 Secrets of the Damascus Steel

Kientzl (Sp), G. Szocs, L. Nemeth, S. Arvay, Budapest University of Technology and Economics (H); J. Dobranszky, Research Group for Metals Technology of the Hungarian Academy of Sciences, Budapest (Hungary)

Damascus steel is one of the most famous material of the world, everyone have heard about it but nearly noone knows what it is exactly and what are the causes of its advanced properties.
The aim of the work was to collect all the information about this topic and to find the people who make this type of steel. The main aim was to create some Damascus blades of our own, based on the information collected from the literature.
The presentation is going to be about how to make Damascus steel with modern equipments and methods. There are several methods of blade creation that have been tried. Blades and workpieces were created from the most famous kinds of this material. These were examined by scanning electron microscope, optical microscope, tensile, impact and hardness testing. The results of the experiments of the different steel types have been compared.
Finally the results of our work: some complete pieces of Damascus blade and lots of experimental data which shows the difference between the raw material and the forged and heat treated steel.

70/G03 Influence of Zirconia Powder Surface on Rheological Behaviour of Thermoplastic Ceramic Suspensions

J. Hrazdera (Sp), M. Trunec, Brno University of Technology (CZ)

The work deals with rheological behaviour of thermoplastic suspensions, filled with 20-50 vol.% of ceramic powder. There were used three zirconia powders with different specific surface area (6,5 – 123 m2.g) for susupension preparation. Thermoplastic binder contained copolymer EVA, paraffin and stearic acid. Rheological behaviour was measured in the temperature range of 100 – 150 °C and shear rate range of 100 – 1000 s-1 by capillary rheometer. Viscosity of the suspensions increased with increasing specific surface area of the powder. Behaviour of binder and suspensions was pseudoplastic, and it was described by power law. Both, power law exponent and activation energy of viscous flow of the suspensions, were linearly decreasing with increasing specific surface area of the powder. Maximum amount of the powder with specific surface area of 123 m2.g was determined 25 vol.%. Changes of rheological behaviour in dependence on the powder specific surface area were discussed.

93/D04 Study of the Influence of Microwaves in the Mechanism of Vulcanisation and de Devulcamisation of Natural Rubber Using Model Compound Vulcanisation
B. Vega Sánchez (Sp), N. Agulló, S. Borrós, Universitat Ramon Llull, Barcelona (E)

Today the accumulation of tires represents one of the most important environmental problems related to rubber. For years recycling processes have obtained low quality materials which cannot be used to make new tires. The development of recycling procedures should be studied to improve the properties of the devulcanizated rubber in order to obtain high quality recycled tires.
There is no doubt about the efficiency of microwave irradiation to vulcanize rubber. The direct application of microwaves in combination with uniform heating allow to vulcanize rubber reducing extraordinarily times of reaction. Furthermore, some studies have shown the affinity of microwave irradiation to break selectively sulphur bounds and then make possible a real recycling process but there is a lack of information about the mechanism of microwave-assisted vulcanization and devulcanization processes.
In the present work, a new microwave reactor has been used to study the mechanism of microwave-heating vulcanization to make possible the devulcanization process and study also its mechanism. To simplify the study we have used model compound vulcanisation (MCV) using squalene as model of natural rubber, which has a similar structure but a low molecular weight, which makes easier its analyses. The effect of several accelerators in microwave vulcanization reaction has been tested. The accelerator evolution, the degree of cross-link and the reversion process has been determined by HPLC-UV, HPLC-MS, HPSEC and MALDI-TOF. The results have shown that microwave vulcanization is 10 times faster than thermal vulcanization. Some differences have been detected in the amount of the intermediates formed in the reaction and in the sulphur transfer to the squalene chain, which has allow the study of mirowave-assinted vulcanisation and devulcanization mechanism.

358/L24 Adhesion of Plasma Electrolytic Oxidation Coatings
A. Plati (Sp), J.A. Curran, T.W. Clyne, University of Cambridge (UK)

The Plasma Electrolytic Oxidation (PEO) process is a relatively new technique for growing thick, dense, ceramic coatings on metals such as aluminium and magnesium. PEO coatings may be used in applications where severe temperature changes and high mechanical loads occur. Strong adhesion of the coatings to the substrate is required to prolong coating lifetimes and to maintain coating integrity in such environments.
The microstructure and composition of the interface between PEO coatings and aluminium substrates was investigated using Scanning Electron Microscopy and Transmission Electron Microscopy. Four-point bend delamination tests, full fragmentation and indentation tests were conducted in order to measure the interfacial fracture toughness. The curvature of the coatings upon debonding was measured and fluorescence spectroscopy was used to assess the residual stresses.

It was shown that PEO coatings have low residual stresses and are highly adherent to the metal substrates.

252//L14 Microscopical Characterisation of Diamond Seed-layers on Ir/ SrTi03 Deposited Using the Bias Enhanced Nucleation (BEN) Technique
P. Bernhard (Sp), C. Ziethen, Johannes Gutenberg Universität, Mainz (Germany); M. Schreck, S. Gsell, T. Bauer, Universität Augsburg (Germany); G. Schönhense, Johannes Gutenberg Universität, Mainz (Germany)

The growth of diamond films of macroscopic dimensions without grain boundaries (quasi single-crystal diamond films) for the use as wafer material in future novel electronic devices is a topic of great interest in today’s diamond material research.
The Bias Enhanced Nucleation (BEN) process [1] performed on Ir/ SrTiO3 substrates was found to be a promising concept to reach this aim. Characteristic for this process is the accumulation of the diamond nuclei in island-like seed-layers with negligible nucleation outside. A question still to be answered is the internal structure of these ultrathin islands and its variation during the subsequent growth step.
In this work we therefore focussed our interest on the characterisation of these seed-layers using different analytical techniques. On the one hand X-ray Photoemission Electron Microscopy (X-PEEM) [2] was used to gain laterally resolved information about the chemical bonding structure. On the other hand, Scanning Electron Microscopy (SEM) and small spot Auger Electron Spectroscopy (AES) were used to determine the thickness of the seed-layers by measuring the attenuation of the Iridium Auger line intensity (due to the Auger electron inelastic mean free path).
The measurements showed that the carbon seed-layers with thicknesses of around 1 - 2 nm already possess a diamond structure.
Further information about the depth profile of the diamond seed layer was attained by using the SEM and AES techniques on a sample which had been patterned by Focused Ion Beam (FIB) before.

228/A12 Life-time Estimation of General Singular Stress Concentrators
J. Klusák (Sp), S. Seitl, P. Hutar, L. Nahlik, Academy of Sciences, Brno (CZ)

Under the assumptions of linear elastic fracture mechanics the behaviour of cracks and general singular stress concentrators is studied and compared. The stress distribution in the vicinity of singular stress concentrators is analysed. Based on these studies a special methodology of life-time estimation of a general stress concentrator is suggested. The method allows us to formulate conditions of crack initiation in general singular stress concentrators. The results generally contribute to better understanding of the failure and increase reliability of life estimations of structures.
Acknowledgement
The project has been realized with state financial support through the Grant Agency of the Czech Republic by grants 106/03/P054, 101/04/P001, 106/04/P084 and 106/01/0381.