Papers by Author: Omer Van der Biest

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Authors: Dongtao Jiang, Jef Vleugels, Omer Van der Biest, Wei Dong Liu, Raf Verheyen, Bert Lauwers
Abstract: Electrically conductive and wear resistant Si3N4-based composites were developed in order to facilitate electrical discharge machining (EDM). The microstructural and mechanical properties of Si3N4-based composites with different amounts of TiC0.5N0.5, fabricated by hot pressing at 1650°C for 1 hour, are investigated and evaluated. The hardness of the micron-sized TiC0.5N0.5 powder based composites increased with increasing TiC0.5N0.5 content from 20 up to 40 vol. %, whereas the bending strength decreased. The fracture toughness reached a maximum at 30 vol. % TiC0.5N0.5 and exhibits a strong anisotropy with respect to the hot-pressing direction. The EDM behaviour of the composites is strongly influenced by the TiC0.5N0.5 content. The composites with a higher TiC0.5N0.5 content have a lower material removal rate but a better surface quality.
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Authors: Guy Anné, Kim Vanmeensel, Jef Vleugels, Omer Van der Biest
Abstract: Complex shaped functionally graded alumina and zirconia based femoral ball-heads for biomedical applications were shaped by electrophoretic deposition (EPD). A composition gradient in alumina and zirconia was engineered to obtain a pure alumina surface region and a homogeneous alumina/zirconia core with intermediate continuously graded regions to generate appropriate thermal residual stresses after sintering. The gradient profiles were designed to obtain maximum compressive surface stresses and minimal tensile stresses in the core of the component to increase the strength and wear properties when compared to pure alumina components.
213
Authors: Guy Anné, Kim Vanmeensel, Jef Vleugels, Omer Van der Biest
Abstract: Due to their excellent properties of high strength, biocompatibility and stability in physiological environments, ceramics are investigated as bone substitute materials. In this way ceramic components have been used for total hip replacement components since the early 1970s. Alumina and zirconia monoliths are mainly used for these components. However, zirconia can undergo low temperature degradation in aqueous environment and alumina is brittle. To increase the strength, functionally graded Al2O3/ZrO2 ball-heads and acetabular cup inserts were made in this work by electrophoretic deposition (EPD). A composition gradient in alumina and zirconia was engineered to obtain a pure alumina surface region and a homogeneous alumina/zirconia core with intermediate continuously graded regions to generate thermal residual stresses at the surface after sintering. Experimental work revealed that a sequence of counter-electrodes was necessary to EPD complex shaped functionally graded material (FGM) components. To obtain deposits with a shape different from the deposition electrode, the deposit was grown up to the counter-electrode and the design of the counter-electrodes was supported by electrical field calculations to generate a constant electric field at the surface of the deposition electrode
213
Authors: Bram Neirinck, Jan Fransaer, Omer Van der Biest, Jef Vleugels
Abstract: Recent developments demonstrated that liquid templates in the form of solid particles stabilized emulsions can be used to produce porous materials. The use of such emulsions offers the possibility to control the porous properties over a wide range of pore sizes and porosities for a variety of materials. In addition, the liquid nature of the template enables the formed products to be sintered without a low temperature debinding step. In this work, the electrophoretic deposition (EPD) of these liquid templates for the production of porous alumina is reported. The experimental parameters needed to obtain stable emulsions, their influence on the final porous properties, as well as the influence of the deposition parameters are discussed.
299
Authors: Annabel Braem, Bram Neirinck, Omer Van der Biest, Jef Vleugels
Abstract: A new powder metallurgical processing route for porous Ti coatings on Ti-6Al-4V substrates based on the electrophoretic deposition (EPD) of TiH2 suspensions is presented. After dehydrogenation and sintering in vacuum, coatings with a fully interconnected porosity (up to 51%, interconnective pore channels (IPC) of 2-50 µm) and high adhesion strength (up to 47 MPa) are obtained. Further evaluation of these coatings for potential use in biomedical implants shows that EPD Ti coatings are significantly less prone to bacterial adhesion compared to state-of-the-art vacuum plasma sprayed (VPS) coatings, while still allowing substantial bone ingrowth. Using EPD, the coating process can easily be transferred to complex-shaped implant components.
144
Authors: L. Vandeperre, Omer Van der Biest
2013
Authors: Jef Vleugels, Omer Van der Biest
273
Authors: K.Y. Sastry, Ludo Froyen, Jef Vleugels, Omer Van der Biest, R. Schattevoy, K. Hummert
Abstract: Melt-spun flakes and air atomised powder of a multi-component Al-Si-Fe-X alloy were consolidated by field assisted (FAST) or spark plasma sintering (SPS) in vacuum using steel dies and punches. Experiments were carried out at 350, 400, 450 and 500°C under applied loads ranging from 81 to 283 MPa. The resulting compacts were microstructurally and mechanically characterized. Ultimate strength values up to 1000 MPa and plastic strains up to 20% were observed during compression tests. The effect of the powder shape on the sintering behaviour is compared. The effect of process parameters such as temperature and applied load on the densification and mechanical properties is discussed. It was found that compacts sintered from melt-spun flakes resulted in a higher strength and ductility than compacts produced from air-atomized powder, sintered under identical conditions.
1409
Authors: Andrey Maximenko, Omer Van der Biest
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