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Journal of Ceramic Science and Technology 4/2013
Vol. 4, No. 4 · December 2013
Evaluating Porosity in Cordierite Diesel Particulate Filter Materials, Part 1 X-Ray Refraction
A. Kupsch, A. Lange, M.P. Hentschel, Y. Onel, T. Wolk, A. Staude, K. Ehrig, B. R. Müller, G. Bruno
Pages 169-176 · DOI: 10.4416/JCST2013-00021
Bi-continuous porous ceramics for filtration applications possess a particularly complicated microstructure, with porosity and solid matter being intermingled. Mechanical, thermal, and filtration properties can only be precisely estimated if the morphology of both solid matter and porosity can be quantitatively determined. Using x-ray absorption and refraction, we quantitatively evaluate porosity and pore orientation in cordierite diesel particulate filter ceramics. Porosity values turn out to agree with mercury intrusion measurements, while pore orientation factors agree with published crysta …
Effect of In Situ-Formed Cerium Hexaaluminate Precipitates on Properties of Alumina -24 Vol% Zirconia (1.4Y) Composites
F. Kern
Pages 177-186 · DOI: 10.4416/JCST2013-00014
In situ-platelet-reinforced zirconia-toughened alumina ceramics have become established materials, successfully replacing alumina and zirconia in hip implants. While the beneficial effect of the in situ toughening seems undoubted, this toughening mechanism is still not fully understood.A nanocomposite ZTA containing 24 vol% partially stabilized zirconia (1.4Y-TZP) was reinforced with 10 vol% cerium hexaaluminate (CA6) by reacting in situ-reduced ceria with alumina during hot pressing. The mechanical properties, evolution of microstructure and phase composition of the CA6-containing ZTA were co …
Influence of Ta2O5 Doping on the Microstructure, Physical and Mechanical Properties of α-Alumina Ceramics
S.M. Naga, A.M. Hassan, M. Awaad, F. Bondioli
Pages 187-192 · DOI: 10.4416/JCST2013-00017
The effects of Ta2O5 addition on the densification behavior, microstructure and mechanical properties of Ta2O5-doped alumina ceramics were investigated. The Ta2O5 addition to the alumina matrix was varied from 0.25 wt% to 0.75 wt%. In order to optimize the sintering temperature, the powders of each composition were uniaxially pressed at 220 MPa into discs and rectangular bars, which were then pressureless-sintered at a temperature ranging from 1500 to 1650 °C for 1 h. The phase constitution and microstructure of the sintered ceramic bodies were characterized with an X-ray diffractometer and a …
Investigation of the Mechanical Properties and Machinability of Fluorphlogopite-Gehlenite Glass-Ceramics
B. Eftekhari Yekta, Z. Hamnabard
Pages 193-196 · DOI: 10.4416/JCST2013-00019
The gradual addition of CaO to a SiO2-Al2O3-B2O3-MgO-K2O-F glass-ceramic composition led to the precipitation of gehlenite crystals and the formation of a potassium-calcium solid solution of fine mica crystals. The above additions almost tripled the bending strength and led to a ∼ 1.5-fold increase in the fracture toughness of the glass-ceramic specimens. When the amount of CaO reached 30 weight parts, the microhardness of glass-ceramic specimens was considerably reduced while their machinability was improved.
E. Zschippang, H. Klemm, M. Herrmann, S. Höhn, B. Matthey, U. Guth, A. Michaelis
Pages 197-206 · DOI: 10.4416/JCST2013-00012
Si3N4-SiC and Si3N4-SiC-MeSi2 (Me = Nb, Mo, W, Zr) composites were densified by means of hot pressing at 1840 °C. Additional heat treatment was performed at 1900 °C in a gas pressure furnace at 1900 °C. The hot-pressed and heat-treated composites were investigated with X-ray diffraction, scanning electron microscopy and measurements of their electrical resistivity. The electrical resistivity of the hot-pressed Si3N4-SiC composite was about 104 Ωcm. The addition of silicides yielded a decrease in composite resistivity to values of about 101-10-2 Ωcm. The subsequent heat treatment results in a f …
Measurement of the Volume Expansion of SiC Refractories Induced by Molten Salt Corrosion
E. de Bilbao, P. Prigent, C. Mehdi-Souzani, M.-L. Bouchetou, N. Schmitt, J. Poirier, E. Blond
Pages 207-2012 · DOI: 10.4416/JCST2013-00011
Corrosion tests of oxide-bonded SiC-based refractory cylinders with molten salts (mainly CaSO4, K2SO4) were performed at high temperature to enable better understanding of the corrosion mechanisms operating in these materials. Salt pellets were placed on the upper surface of small refractory cylinders. After they had been melted, the corrosive product soaked into the pores of the refractory cylinders and partially corroded the SiC phase. SEMEDS analyses showed that CaSiO3 was the main new phase formed, growing from SiC aggregates into the pores. The shapes of the initial and corroded cylinders …
Effect of Temperature Path on the Poling of Commercial Hard PZT Ceramics and its Implication for Mass Production
S. Esslinger, P. Neumeister, A. Schönecker
Pages 213-216 · DOI: 10.4416/JCST2013-00018
In order to identify process parameters for the efficient poling of hard piezoelectrics in mass production, the effect of temperature modification during poling is investigated for a commercial hard PZT in the temperature range from 25 °C to 150 °C. While an electric field is applied, the temperature of the specimens was kept constant or the specimens were heated or cooled. The resulting piezoelectric performance was evaluated on the basis of the planar coupling factor at room temperature. An optimal poling temperature associated with maximum piezoelectric performance was found for poling with …
