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Journal of Ceramic Science and Technology 1/2011
Vol. 2, No. 1 · January 2011
Technology for the Obtainment of Transparent MgAl2O4 Spinel Parts
A. Goldstein, A. Goldenberg, M. Vulfson
Pages 1-8 · DOI: 10.4416/JCST2010-00018
The objective of the work was the establishment of a procedure allowing the obtainment of high-optical-transparency MgAl2O4 polycrystalline parts that exhibit a fine microstructure (average grains size lower than 5 μm). The technology had to be relevant for industrial-scale production. A nano powder, commercially available in large quantities, at a reasonable price, was used as raw material. It was determined that by applying a suitable combination of powder processing and green-bodies-forming procedure, a configuration favorable for advanced densification can be derived from the selected powd …
Gas Permeance and Selectivity of Perovskite-Titania Membranes
A.L. Ahmad, N.A. Abdullah Sani, S.H.S. Zein
Pages 9-14 · DOI: 10.4416/JCST2010-00026
Defect-free titania membranes doped with different concentrations of SrCo0.8Fe0.2O3 perovskite were successfully prepared using a sol-gel technique combined with a wet impregnation process. The titania membranes were immersed in a perovskite solution, dried, and calcined to obtain perovskite affixed inside the porous titania membranes. The phase transformation of titania and perovskite was investigated by varying the calcination temperature from 300 to 500 °C. The effect of perovskite concentration on the titania membrane morphology is described in detail. The results showed that calcination a …
Calcium aluminate (CaAl2O4) powder was prepared with a sol-gel technique using calcium nitrate tetrahydrate and aluminium sec-butoxide as precursors and ethyl acetoacetate as chelating agent. The dried gel and thermally treated samples were characterized by means of simultaneous Differential Thermal and Thermo-Gravimetric Analysis (DTA/TGA), Fourier Transform Infrared spectroscopy (FTIR), and X-Ray Diffraction (XRD). From the results obtained, the thermal evolution of the prepared gel, the crystallization behaviour and crystallization kinetics are discussed. It has been established that the de …
New Si/B/N/C Ceramics from a Silaborazine-Type Single-Source Precursor
H. Cakmak, M. Jansen
Pages 23-30 · DOI: 10.4416/JCST2010-00044
A new chloro-substituted monocyclic silaborazine derivative with a B/Si-ratio of 2, namely 1,1,3,5-tetrachloro-2,6-dimethyl-4-hydride-1-silaborazine (TDSB), has served as a single-source precursor for the synthesis of amorphous Si/B/N/C ceramics via the well-known „polymer route”. Accordingly, ammonia and methylamine were used as cross-linking reagents for polymerization of TDSB, leading to highly homogeneous pre-ceramic polymers, which were characterized with spectroscopic methods. In addition, subsequent thermal degradation of as-obtained polyborocarbosilazanes was monitored by means of DTA/ …
Nanoscopic Metal Fluorides as Promising Sintering Aids for High-Performance Alumina Ceramics
Ch. Stosiek, H. Ludwig, U. Reichel, G. Scholz, E. Kemnitz
Pages 31-38 · DOI: 10.4416/JCST2010-00023
Nanoscopic aluminium fluoride and magnesium fluoride were investigated as sintering additives for high-purity alumina ceramic production.
Nanoscopic magnesium fluoride has been found to be an excellent sintering additive. It enables an effective limitation of grain growth compared to standard ceramic production, thus resulting in ceramics with high density, sub-μm grain size and low concentration of defects, which are perfect preconditions for an improvement of mechanical strength, transparency as well as optical properties. As a result, transparent corundum ceramics with a Vickers hardness of …
Synthesis of PLLA-HA Hybrid Composites with Bone-Like Structure
J. Zhang, D. Jiang, Z. Chen, Q. Lin, Z. Huang
Pages 39-46 · DOI: 10.4416/JCST2010-00030
Many studies are currently underway to make synthetic bone-like materials with compositions of polymeric materials and hydroxyapatite (HA). In this paper, we report on the biomimetic preparation of poly-L-lactic acid (PLLA)/HA composites. Initially, HA nanorods with well-oriented organization were prepared with a simple hydrothermal method using dodecyl phosphate, a type of surfactant with a phosphorus head group, as the templating agent. The precipitate clusters consisting of hydroxyapatite nanorods exhibited a well-ordered microstructure. Subsequently, the obtained precipitates were disperse …
Properties of Injection Moulded Alumina-Toughened Zirconia
F. Kern, R. Gadow
Pages 47-54 · DOI: 10.4416/JCST2010-00019
Alumina-toughened zirconia (ATZ) materials are suitable materials for a variety of biomedical applications owing to their high strength, toughness and hydrothermal stability. The prospect of being able to offer ceramic implants to a broader group of patients requires a more cost-efficient near-net-shape manufacturing approach. Small and complex-shaped components can be efficiently mass-produced by means of ceramic injection moulding (CIM) with high surface quality and low dimensional tolerances. Compared to the state-of-the-art cold and hot isostatic pressing cycles commonly used for implant p …
Sintering and Mechanical Properties of AlMgB14 Composite Materials
M. Herrmann, R. Bodkin, N. J. Coville, I. Sigalas, M. Thiele
Pages 55-60 · DOI: 10.4416/JCST2010-00020
Different AlMgB14 composite materials were prepared from pre-reacted AlMgB14 and starting elemental powders by hot pressing. Only slightly different densification behaviours were found for the two types of starting materials. Full densification without decomposition was achieved only with a hot pressing pressure of 75 MPa. Different additives were tested to improve densification. The influence of the additives on the densification was found to be minor. A strong increase in hardness was observed for materials with Si, TiC, WC, TiB2 additions. The carbides react with the AlMgB14 during sinterin …
Sintering Behaviour of Multilayer Hydroxyapatite Laminates
E. Hahn, J. Hum, J. Will, K. Zuo, D. Jiang, P. Greil
Pages 61-68 · DOI: 10.4416/JCST2010-00034
Aqueous tape-cast slurries of hydroxyapatite with a solid loading of 32 vol% were prepared from various fractions of aggregated (mean particle size 4.7 – 5.6 μm) and dispersed powder (mean particle size 0.17 – 0.29 μm). Multilayer laminates were prepared and the shrinkage and density of the laminates sintered at 1250 °C were measured. While fractional density in the green laminates remains almost constant at 0.52, a pronounced increase in fractional sintered density from 0.96 to > 0.99 was observed with decreasing fraction of aggregated powder. Residual pore size and pore number density wer …
Microstructure and Mechanical Properties of Hot-Pressed Alumina – 5 vol% Zirconia Nanocomposites
F. Kern
Pages 69-74 · DOI: 10.4416/JCST2010-00038
Zirconia-toughened alumina (ZTA) ceramics are known to combine the hardness and abrasion resistance of alumina with an additional toughness increment introduced by zirconia. Toughening occurs by transformation toughening and/or microcracking depending on the grain size and stabilizer content of zirconia. In this study ZTA with 5 vol% unstabilized nanozirconia was manufactured by means of a mixing and milling technique and consolidated by hot pressing at 1350 – 1600 °C. Variation of the sintering conditions leads to nanocomposites with different microstructural features, such as grain sizes and …
