92. DKG Jahrestagung & Symposium Hochleistungskeramik

19. – 22. März 2017  –  TU Berlin

Das FGK präsentiert sich breit aufgestellt mit folgenden Themen auf der DKG-Tagung:

 

Synthesis and fabrication study of translucent lead-free perovskite ceramics with high density for electro-optical applications

J. Werner¹, K. Koch¹, N. Kratz¹, D. Rytz², S. Schwung², C. Voß¹

¹ FGK – Forschungsinstitut für Anorganische Werkstoffe -Glas/Keramik- GmbH, Höhr-Grenzhausen

² FEE – Forschungsinstitut für mineralische und metallische Werkstoffe –Edelsteine/Edelmetalle- GmbH, Idar-Oberstein

Potassium tantalate niobate (KTa_1-xNb_xO₃; KTN) and barium strontium titanate ((Ba,Sr)TiO₃; BST) exhibit potential as alternative materials for the lead-containing materials with high electro-optical effects such as Pb_1-xLa_x(Zr_yTi_1-y)_1-x/4O₃ (PLZT). The technical applications are still limited due to the difficulties of single crystal growth: The process leads to local concentration fluctuation, the resulting inhomogeneity influence the linear electro-optical properties and the Curie temperature, another powder synthesis and production process is required. For the production of highly translucent electro-optic ceramics pure powder with a narrow grain-size distribution and homogeneous composition have to be produced. Among others powders were synthesized via solid-state synthesis and sol-gel process. The powders were uniaxially pressed and pressureless sintered at varying temperatures. Correlations between the different powder preparation techniques, the obtained grain size distributions and sintering densities as well as the microstructural characteristics and optical properties will be discussed.

The authors thankfully acknowledge financial funding of the project “OptoCer – Processing of lead-free perovskite ceramics for electro optic applications” by the Rhineland-Palatinate Ministry of Education, Science, Youth and Culture under the grant No. 961-386261/1159K.

 

Poster Presentation: Aging behavior of architectural ceramics – Frost resistance

S. Sänger¹, S. Link¹, M. Engels¹, M. Ruppik², D. Schnabel²

¹ FGK – Forschungsinstitut für Anorganische Werkstoffe – Glas/Keramik – GmbH

² IZF – Institut für Ziegelforschung Essen E.V.

Ceramics as building material promise longevity. However, ceramics are exposed to aging effects and weathering, especially by usage in exterior areas. This limitation is, in particular, due to the impact of frost strain after water immersion. These aging effects result in a weakening of the structural integrity of the material. Defects like pores, grains and other inhomogeneities, generate intrinsic stress or local weakening. Saturation with pore water, while cooling down to freezing temperature, is the basic condition for frost damage. The damage mechanisms depend on parameters like porosity and material strength. In cooperation with the Brick and Tile Research Institute (IZF), the FGK investigates the freeze-thaw behavior of saturated architectural ceramics In this collaborative industrial research project, the IZF investigates the correlations of mechanisms associated with bricks and roofing tiles, while FGK focuses on floor and wall tiles, using idealized to fully synthetic raw materials and among other analytical procedures primarily low temperature dilatometry. To understand influences of phase composition of the ceramics, different material systems and mixtures were sintered to same porosity and tested on fracture toughness and water absorption capacity over a number of freeze-thaw cycles, while documenting expansion and contraction phenomena. The influence of the amount of glass phases was investigated by adding defined amounts of feldspar or glass frit to a ceramic, while keeping a constant water absorption capacity. Furthermore, the influences of pore shape have been evaluated, by using divers forming processes.

The authors thankfully acknowledge financial funding of the project “Frost-TTDil – Evaluation on fracture mechanisms of architectural ceramics out of synthetic and idealized raw materials by cyclic freeze-thaw exposure and low temperature dilatometry“ by the Federal Ministry of Economic Affairs and Energy (BMWi) through the cooperative industrial research initiative (IGF) under the grant No. IGF 18937 N.

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Investigation of the synthesis and fabrication of a high purity YVO₄ ceramics for optical applications

C. Volk, N. Kratz, J. Werner

Yttrium orthovanadate (YVO₄) single crystal is an excellent polarizer as well as laser host material with high optical transparency in the region 400 – 5000 nm¹. High tech applications of YVO₄ are still limited due to different crystal growth difficulties, so an alternative production method is required. For the fabrication of highly translucent ceramics phase pure raw materials with narrow grain size distributions are essential.  Therefore high purity YVO₄ with a small grain size of approx. 100 nm was synthesized by a wet chemical precipitation via a continuously working micro-jet reactor technique. For a better compressibility the powder was calcined at higher temperatures up to 925 °C to induce grain coarsening. Subsequently the calcined powder was uniaxially pressed and pressureless sintered in air at different temperatures up to 1450 °C. High densities > 98.5 % of the theoretical density were achieved. To further increase the densities the samples were hot isostatically pressed followed by an annealing process. Thus, translucent samples with densities > 99.5 % of the theoretical density could be obtained. The density results and the microstructural properties will be shown. Furthermore, correlations between the obtained grain size and distribution as well as the microstructure and the translucency will be considered.

The authors thankfully acknowledge financial funding for their work on ceramics for laser applications and ceramic phosphor converted LEDs by the Rhineland-Palatinate Ministry of Education, Science, Youth and Culture under the grants  0810-68503 and 965-52207-6/40.

¹ Erdei, S. et al., “Growth Studies of YVO₄ Crystals (II). Changes in Y-VO- stoichiometry”, Crystal Research & Technology, Vol. 29, Issue 6. Pages 815-828, 1994

 

The potential of optical 3D topography measurements for quality control and functional evaluation of ceramic surfaces

M. Engels

This contribution addresses the practical use of surface topography measurements for the characterization of ceramic surfaces in regard to their functional characteristics. The background and the potential of the optical 3D measurements will be highlighted, including the interpretation of topography and roughness values from the profile analysis. Examples of evaluation possibilities will be shown, addressing the aspects of quality assessment of surfaces, machining, surface investigation in regard to defects, processing influences and surface improvements for different applications. Special attention will be given to the use of topography measurements for the functional evaluation of ceramic tiles: within the framework of the European SlipSTD Project the topography measurement was adapted as an objective tool to establish fundamental knowledge concerning the influence on surface characteristics on slip resistance of ceramic tiles and its implications regarding the applicability of slip testing methods on different surfaces. Especially the use of topography in current investigations and developments into durability aspects of slip resistance and cleaning properties, as required by the European Regulation for Building Products, and the development of reliable reference systems for slip testing will be showcased.

 

 

Production and application of grinding beads consisting of ceramic composite material, used in high-energy ball mills

J. Karbaum¹, M. Zwick¹, A. Müller², K. Scheidt²

¹ Forschungsinstitut für Anorganische Werkstoffe – Glas/Keramik – GmbH

² Sigmund Lindner GmbH

In relation to a previous research project in cooperation with SiLi GmbH, it was succeeded to sinter ceramic composite material consisting of 60 vol.-% ZrO₂ and 40 vol.-% WC pressureless in nitrogen atmosphere. Subsequently investigations have been performed to specify the influencing effects on the sintering behavior. The results gained within the examinations have shown that it is necessary to create an in situ atmosphere while sintering. This is realizable under certain conditions in the high-temperature furnace and favors the sinter behavior which leads to a dense ceramic material. The received results showed the connection between the sinter atmosphere and the generation of different material phases. Consequently the ceramic properties are influenced by the sinter atmosphere in general.

Furthermore the manufacturing process of the ceramic grinding beads consisting of WC/ZrO₂ material has been optimized. This developed product is applied in high-energy ball mills. The grinding beads were investigated by different analysis regarded to products already available on the market. The presented results clarify the dependency of the energy and cost efficiency to the applied ceramic material used in the grinding process.

The authors thankfully acknowledge financial funding of the projects “New materials for high wear resistant ceramic grinding beads with high material density, used in agitator bead mills for energy-efficient grinding and dispersing” and “Development of core-shell grinding beads for wet milling, used for finest grinding with low contamination” by the Federal Ministry of Economics and Technology under grant no. KF2344205AG1 and no. KF2344211AG4.