Time filter

Source Type

Rheinbach, Germany

Kollenberg W.,WZR Ceramic Solutions GmbH
Keramische Zeitschrift | Year: 2014

Additive Manufacturing has become very popular during the last years. Laser Sintering of metals is close to industrial serial production. Ceramic components can be produced by Stereolithography on a small scale, with properties comparable to injection molding. 3D printing is used to produce customized kiln furniture, bone structures or design objects. By using particle filled inks a lot of new options are possible: dense microstructure, locally reinforced microstructures, and combination of different properties or colors. This technique is called multi-material 3D printing. FDM and 3D extrusion can be used to manufacture near-net-shape semi-finished ceramic products. Source

Kluthe C.,Bonn-Rhein-Sieg University of Applied Sciences | Kollenberg W.,WZR Ceramic Solutions GmbH
Materialwissenschaft und Werkstofftechnik | Year: 2013

Micro-scaled alumina filled preceramic papers are used to produce paper-derived alumina ceramics. The thin (0.6-0.7mm) and porous ceramics fabricated by this process can be, besides other possible applications, potentially utilized as setter plates on cordierite kiln furniture to avoid contact between the cordierite and powder metal substrate during sintering. The SiO2 of the cordierite causes objectionable reactions with the powder metal. For this application it is important to investigate the thermal shock behaviour of the paper-derived alumina ceramics especially focusing the residual strength, because fast cooling is a common technique in the metal sintering industry to avoid cost and save production time. Two differently processed types of paper were investigated: calendered (additionally roll-pressed) and uncalendered paper. Their remaining strength has been measured by the B3B- test after thermal shocks of a temperature difference ΔT = 100 K up to ΔT = 1000 K to evaluate the critical temperature difference ΔTC and the type of crack growth according to the method of Hasselman. In order to determine the cyclic thermal shock behaviour, at a temperature difference ΔT of 400 K and 600 K the ceramics have been quenched up to 5 times. The results of these investigations have been compared to the properties of tape casted alumina ceramics, a material already commercially used as setter plates. The initial strength of calendered paper-derived ceramics was 240 MPa. After quenching at a temperature difference ΔT = 600-700 K, 50% strength decrease was observed. Temperature differences of more than 800 K caused >90% strength reduction. Uncalendered paper-derived ceramics have 185 MPa strength. Between thermo shocks of temperature differences ΔT = 700-800 K, 50% of the strength reduction was measured. With thermo shocks of a temperature difference ΔT = 800 K only 10% of the initial strength remains. Generally the uncalendered ceramics showed a more stable crack growth than the calendered samples. Cyclic shocking at 400 K causes strength losses for both kinds of paper. But they differ in magnitude. While uncalendered paper only lost 7% strength, calendered paper strength was reduced by 20%, compared to their initial strength. This observation gets even more significant by shocking about 600 K. Calendered ceramics start with a higher initial strength and end up with a lower residual strength than the uncalendered ceramics. Only 30 MPa remain after five cycles of shocking, while the uncalendered paper-derived ceramics have 90 MPa remaining strength. Uncalendered ceramics show a better thermal stress resistance, which can be correlated to their higher porosity and therefore their increased crack deflection in the microstructure. Tape-casted alumina ceramics show a lower initial strength and lesser thermal shock resistance against simple and cyclic shocking. SEM pictures of the tape-casted alumina ceramics show large amounts of small, spherical shape pores, while paper-derived alumina microstructures show long cylindrical pores left by pyrolized cellulose fibres. Considering these results, paper-derived ceramics are a serious alternative to tape casted ceramics for an application as setter plates. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Tirone M.,Ruhr University Bochum | Rokitta K.,WZR Ceramic Solutions GmbH | Schreiber U.,University of Duisburg - Essen
Lithos | Year: 2016

A lava sample from the Tertiary Westerwald volcanic field was selected for a detailed study using various analytical techniques in combination with petrological, thermodynamic and diffusion modeling to extract information related to the thermochronological evolution of a magmatic event before eruption. The lava sample contains large olivine phenocrysts which are compositionally zoned and two coexisting but chemically distinct melts, a host melt with basaltic composition and small spherical pockets of a less abundant trachytic melt (globules). The sample was analyzed by electron microprobe, x-ray fluorescence (XRF) X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The primary melt of the host lava was determined using the program PRIMELT2.XLS. Partial fractional crystallization of olivine was modeled using the program alphaMELTS. Timescale and cooling rate were retrieved by fitting the measured Fe-Mg zoning along two directions in four olivine grains from the host lava using a 3-D numerical diffusion model. The measured variation of Ca is also consistent with a chemical diffusion process, while a numerical growth model applied to the same olivines does not appear to explain the Fe-Mg zoning. Chemical zoning of major elements in the melt globules were reproduced with a multicomponent diffusion model. The results of this study show that the host magma fractionated about 9% of olivine in a first stage, then the crystallization proceeded without further separation of mineral phases. Modeling of diffusion in the olivine crystals suggests that this second stage lasted at least ~. 5 yrs and the temperature of the melt decreased from 1120-1150 °C to 1090 °C during this time. According to the results of the multicomponent diffusion model applied to the melt globules, the coexistence of the two melts was extremely short (less than few hours), possibly recording the assimilation of the globules during eruption or cooling of the whole system on the surface. © 2016 Elsevier B.V. Source

Kollenberg W.,WZR Ceramic Solutions GmbH
Keramische Zeitschrift | Year: 2015

Additive Manufacturing becomes more and more important to ceramic industry. For industrial production Lithography and 3D-Printing are available today. Additive Manufacturing is cost-effective, if only small numbers of components are needed. Expenses for molds are saved, storage of molds is not necessary and customers can be served quicker and much more flexible. Any change in design can be realized on short call. The term "series production" becomes a new meaning with Additive Manufacturing. Here it is not necessary to produce a large number of equal components, to reduce costs. Different parts can be produced in one batch, coming to "series production of single parts". Source

Kollenberg W.,WZR Ceramic Solutions GmbH | Nikolay D.,WZR Ceramic Solutions GmbH
Keramische Zeitschrift | Year: 2012

After developing paper derived ceramics (called PT-Keramik®) on a laboratory and pilot-plant scale, now the industrial application is reported. There are currently 3 different PT-Keramik® types available: stoneware, cordierite and alumina. This article deals with basics about producing PT-Keramik®, relevant characteristics as well as examples for applications. © Copyright 2012 Expert Fachmedien GmbH. Source

Discover hidden collaborations