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Vienna, Austria

Ligon-Auer S.C.,Vienna University of Technology | Ligon-Auer S.C.,Christian Doppler Laboratory | Schwentenwein M.,Lithoz GmbH | Gorsche C.,Vienna University of Technology | And 5 more authors.
Polymer Chemistry | Year: 2016

Photo-curable resins based on multifunctional acrylate monomers are commonly applied as thin films (e.g. protective coatings, printing inks, etc.) and in recent years are also used for the fabrication of bulk objects such as dental fillings and 3D-printed parts. While rapid curing and good spatial resolution are advantages to these systems, brittleness and poor impact resistance due to inhomogeneous polymer architecture and high crosslink density are serious drawbacks. By comparison, epoxy thermoset resins suffered many years ago from similar problems, but since then are found in ever demanding applications thanks to a variety of approaches to increase polymer toughness. Based on these successes, researchers have tried to translate strategies for toughening epoxy resins to photopolymer networks. Therefore, this review surveys relevant scientific papers and patents on the development of crosslinked epoxy-based polymers and also photo-curable polymers based on multifunctional acrylates with improved toughness. Strategies developed to reduce brittleness include working with monomers, which intrinsically give tougher polymers, particulate additives, and alternate forms of polymerization and polymer architecture (e.g., dual-cure networks, interpenetrating networks, thiol-ene chemistry). All of these strategies have advantages and yet application specific rigours must also be considered before and during formulation development. © The Royal Society of Chemistry 2016. Source

Schwentenwein M.,Lithoz GmbH | Homa J.,Lithoz GmbH
International Journal of Applied Ceramic Technology | Year: 2015

In this study, a new process for additive manufacturing (AM) of dense and strong ceramic objects is described. The lithography-based ceramic manufacturing (LCM) technique is based on the selective curing of a photosensitive slurry by a dynamic mask exposure process. The LCM technique is able to produce strong, dense and accurate alumina ceramics without virtually any geometrical limitations. With over 99.3% of a theoretical alumina density, four-point bending strength of 427 MPa, and very smooth surfaces, the LCM process distinguishes itself from other AM techniques for ceramics and provides parts with very similar mechanical properties as conventionally formed alumina. © 2014 The American Ceramic Society. Source

Zanchetta E.,University of Padua | Cattaldo M.,University of Padua | Franchin G.,University of Padua | Schwentenwein M.,Lithoz GmbH | And 4 more authors.
Advanced Materials | Year: 2016

The first example of the fabrication of complex 3D polymer-derived-ceramic structures is presented with micrometer-scale features by a 3D additive manufacturing (AM) technology, starting with a photosensitive preceramic precursor. Dense and crack-free silicon-oxycarbide-based microparts with features down to 200 μm are obtained after pyrolysis at 1000 C in a nitrogen atmosphere. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Homa J.,Lithoz GmbH | Schwentenwein M.,Lithoz GmbH
Ceramic Engineering and Science Proceedings | Year: 2014

While Additive Manufacturing (AM)-technologies are already state-of-the-art in plastics processing or metalworking, the ceramic industry has been reluctant to implement this kind of technology due to insufficient quality of the parts produced by this means. Additive manufactured ceramics used to lack essential material properties such as density or strength, which hindered the application of such parts as technical ceramics. In this paper a new AM-technology, the Lithography-based Ceramic Manufacturing (LCM)-process, is presented. This technique is based on the selective curing of a photosensitive slurry by a mask exposure process. During the structuring, a photopolymer matrix is generated, which temporarily acts as scaffold and binder for the ceramic particles and is later on removed at elevated temperatures. Due to this approach, this novel technique achieves high green densities and thus, enables the production of strong, dense and accurate ceramic parts without any geometrical limitations. The parts produced using this technology have very similar mechanical properties as classical formed ceramic parts; for alumina a theoretical density of over 99.3 % and four-point bending strength of over 430 MPa has already been realized. These characteristics render the LCM-process an innovative and capable production method, especially in the case of complex shaped structures, customized parts or small series production. Copyright © 2015 by The American Ceramic Society. Source

Schwentenwein M.,Lithoz GmbH | Homa J.,Lithoz GmbH
CFI Ceramic Forum International | Year: 2014

In the field of ceramic processing, there is a strong need for the introduction of additive manufacturing (AM) technologies. Tools for ceramic injection molding (CIM) are expensive and require significant lead times which severely restrict the suitability of CIM for the production of small scale series or customized products. These are actually perfect conditions for the implementation of AM technologies; however, so far no adequate prototyping technology was available. The main reason for that are the high demands on high-performance ceramics - these materials are used where other materials fail, thus the quality and the reliability of the parts are crucial. In this paper a novel AMT-approach is presented, which is capable of producing strong, dense and accurate ceramic parts via a photopolymerization process, namely the Lithography-based Ceramic Manufacturing (LCM). For alumina a theoretical density of over 99, 4 % and 4-point bending strength of 430 MPa could already be realized. Moreover, due to its layer-by-layer approach, the LCM technology provides the opportunity to shape highly complex and intricate geometries that cannot be realized by conventional means. Holes with a diameter of 200 urn and a wall thickness of down to 150 μn could be realized by this technology to date. These characteristics render the LCM technology a capable addition to conventional processing techniques in the field of ceramics. Source

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