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Journal of Ceramic Science and Technology 2/2013
Vol. 4, No. 2 · July 2013
Influences of Cation Disorder in Commercial Spinel Powders Studied by 27Al MAS NMR on the Sintering of Transparent MgAl2O4 Ceramics
A. Krell, E. Brendler
Pages 51-58 · DOI: 10.4416/JCST2012-00029
At the Stockholm Conference of the European Ceramic Society 2011 it was shown that, together with the particle size of raw powders and the homogeneity of particle coordination in the green bodies, the real structure of the lattices is a third major influence on sintering, which may differ significantly even at fixed stoichiometry. Antisite defects govern the whole defect chemistry of MgAl2O4 and should, therefore, affect diffusion and sintering. This possibility is investigated here with solid state 27Al MAS nuclear magnetic resonance measurements of the occupancy of octahedral and tetrahedral …
The Effect of Different La-Containing Starting Materials on the Synthesis, Sintering, and Li+-Conductivity of Li3xLa2/3-xTiO3
A.C. Sutorik, C. Cooper, M.D. Green, J. Wolfenstine, G. Gilde
Pages 59-68 · DOI: 10.4416/JCST2012-00035
Li3xLa2/3-xTiO3 is a promising ceramic electrolyte for high energy density Li-batteries. The material is usually prepared from solid state reactions between Li2CO3, La2O3, and TiO2, but the hydroscopic nature of La2O3 leads to inconsistencies in formulation and synthetic outcome which can impact the phase formation and corresponding Li-conductivity of the final ceramic. To address this issue, La carbonate and hydroxides have been evaluated as starting materials for solid state synthesis of Li3xLa2/3-xTiO3 powders and sintered ceramic. The different La-starting materials are all prepared from p …
Water Uptake of Tape-Cast Cathodes for Lithium Ion Batteries
U. Langklotz, M. Schneider, A. Michaelis
Pages 69-76 · DOI: 10.4416/JCST2012-00036
High-performance ceramic-based cathodes (e.g. NMC, LFP) are the backbone of lithium ion batteries. The production of cathodes is based on ceramic manufacturing technologies (powder processing, slurry, tape casting). The minimization of the water content in the fabricated battery is a crucial point in its manufacturing.
This work is focused on the kinetics of water uptake in tape-cast cathode materials (NMC, LFP). The cathode foils were exposed to atmospheres with varying humidity and the water content was determined by means of coulometric Karl-Fischer titration. Conversely, the tendency of th …
Synthesis, Characterization and Luminescence Properties of Pr3+-Doped C12A7 and C3A
E. Tõldsepp, E. Feldbach, M. Kirm
Pages 77-84 · DOI: 10.4416/JCST2012-00039a
This paper presents comparative results of luminescence studies on complex wide-band-gap calcium aluminates 12CaO·7Al2O3 (C12A7, Eg∼7.0 eV) and 3CaO·Al2O3 (C3A, Eg∼6.5 eV) doped with Pr3+ ions. Doped C12A7 ceramics and C3A powders were prepared via self-propagating combustion synthesis followed by different thermal treatments. Time-resolved VUV spectroscopy of C3A:Pr3+ revealed fast interconfigurational 5d-4f emission of Pr3+ in the region of 3 eV – 4.5 eVwith lifetimes of ∼ 17 ns upon direct excitation of Pr3+ 5d levels, and ∼ 30 ns upon interband transitions. Acceleration of decay times (∼ …
Thermomechanical properties of Thermal Barrier Coatings (TBCs) are strongly influenced by coating defects, such as delaminations and pores, thus making it essential to have a fundamental understanding of microstructure-property relationships in TBCs to produce a desired coating. Object-Oriented Finite element analysis (OOF) has been shown previously as an effective tool for evaluating thermal and mechanical material behaviour, as this method is capable of incorporating the inherent material microstructure as input to the model. In this work, OOF was used to predict the thermal conductivity and …
Nanospecific Guidance in REACH: A Comparative Physical-Chemical Characterization of 15 Materials with Methodical Correlations
W. Wohlleben, L. Ma-Hock, V. Boyko, G. Cox, H. Egenolf, H. Freiberger, B. Hinrichsen, S. Hirth, R. Landsiedel
Pages 93-104 · DOI: 10.4416/JCST2012-00045
The REACH legislation deals with the Registration, Evaluation, Authorization and Restriction of Chemical substances in Europe. Here we provide a comparative physical-chemical characterization with standardized methods that adhere to the recent REACH guidance for nanomaterials. The suite of materials comprises two pigment-size reference materials, and 13 engineered nanomaterials, thereof four from the OECD sponsorship program. We report for each material on 20 endpoints for physical-chemical properties. Since toxicological effects and occupational exposures have already been reported for severa …
Characterisation of SiCN Coatings on Substrates of Hf and Nb
C. Delpero, W. Krenkel, G. Motz
Pages 105-112 · DOI: 10.4416/JCST2012-00041
Refractory metals like Hf and Nb have high hardness and melting points above 2000 °C which make them attractive candidates for high-temperature applications. In this work it was investigated whether these metals can be used as a basis for the development of metal-ceramic composite materials. Because of the tendency of the metals to form carbide and nitride phases, a preceramic SiCN-precursor was chosen for the synthesis of the ceramic coating. During pyrolysis a functionally graded intermediate layer consisting of metal carbide and nitride is formed by reaction with the precursor elements, whi …
Ordered mesoporous silicon-based non-oxide ceramics are attracting increasing interest thanks to their outstanding high-temperature stability and their anticipated robustness. In this category of materials, periodic ordered silicon-boron-carbon-nitrogen (Si/B/C/N) frameworks represent an excellent opportunity for use in harsh environments in key fields like heterogeneous catalysis and/or hydrogen storage. In this review, the nanocasting approach to these materials is summarized on the basis of the synthesis of boron-modified polysilazanes, the solution infiltration of carbonaceous and silica t …
Nanomaterials and Ceramic Nanoparticles – Use without Side-Effects?
M. Roesslein, V. Richter, P. Wick, H. F. Krug
Pages 123-130 · DOI: 10.4416/JCST2012-00038
It is expected that ceramic nanoparticles will be more intensely used in various technical, medical and biological fields in the near future. But their interaction with biological objects has not yet been completely understood. Within the scientific community, NGOs and the public, there is considerable concern about possible side-effects on health and environment. In an investigation of the behaviour of nanoparticles in a biological environment or nano-toxicological effects, three crucial phenomena have to be analysed in detail: material properties, surface state/surface reactions and uptake/t …
