Results of a study for the medical applications of micro- and nanowires are described. The magnetic characteristics of glass-coated Fe-based cast amorphous microwires (with a positive magnetostriction constant) are proposed. The residual stress distributions in this type of microwires determine the domain structures and the switching field behavior. These wires are characterized by a rectangular hysteresis loop and can be used in measuring and identification engineering. A model that describes the process of the reversal magnetization of an amorphous microwire with the help of a large Barkhausen jump is proposed. The model is estimated with regard to the optimization of the signal-to-noise ratio. The results obtained do not contradict the existing physical concepts concerning a domain wall motion and are more general and realistic than the previous models.

Many types of glass contain lanthanoides; among them, special glass for optical applications is the one with the highest content of lanthanoides. The precise determination of the lanthanoides' concentration is performed by inductively coupled plasma-optical emission spectrometry (ICP-OES). However, up to now, there are no established standard processes guaranteeing a uniform approach to the lanthanoide analysis. The knowledge of the lanthanoides' concentrations is necessary on the microscale in some cases, especially if a suitable separation and recycling procedure is to be applied. Here, the analysis is performed by energy-dispersive X-ray (EDX) or wavelength-dispersive X-ray (WDX) analytics in the scanning electron microscope.

Die elektrochemische Stabilitat von verschiedenen Elektrodenmaterialien, die zur Entfernung von Eisen aus Kalk-Natron-Glasschmelzen verwendet werden sollen, wurde untersucht. Als Elektrodenmaterialien wurden Kohlenstoff, Molybdan, Platin und Zinnoxid eingesetzt. Die Untersuchungen wurden bei einer Temperatur von 1400 degrees C unter realitatsnahen Bedingungen, d.h. bei Atmosphare mit einem Sauerstoffpartialdruck, ahnlich wie in einer Glaswanne, durchgefuhrt. Nach verschiedenen Reaktionsdauern wurden die Elektroden sowie die Grenzflache zum Glas mittels visueller Inspektion sowie REM/EDX charakterisiert.Investigations on the electrochemical stability of several materials, which are used as electrodes for the removal from iron in soda lime glass melts, are presented. Carbon, molybdenum, platinum, and tin oxide were studied as electrode materials. The experiments were carried out at a temperature of 1400 degrees C with oxygen partial pressures typical for glass melting tanks. After different reaction times both the electrode surfaces as well the interface region of the glass close to the interface was characterized visually as well as with SEM/EDX.

Glas ist fur kunftige Schlusseltechnologien wie Solar-, Informations- und Kommunikationstechnologien unverzichtbar. In der vorliegenden Arbeit wurde die Entfernung von Eisen aus Kalknatronglasschmelzen mittels elektrochemischer Verfahren untersucht. Durch eine Variation der Elektrodenmaterialien und der Elektrolysebedingungen (Temperatur, Spannung) war es moglich, Eisen aus der Glasschmelze direkt zu entfernen. Dabei zeigte sich allerdings, dass fur eine effiziente Entfernung von erheblichen Mengen Eisens ein optimales Design der Schmelzanlage notwendig ist.Glass is an essential material for future key technologies such as solar and information technologies. The removal of iron from melts of soda lime glass using in situ electrochemistry was investigated. By selecting the proper electrode materials and the electrolysis conditions (temperature, voltage), it was possible to directly remove iron from the molten glass. However, it was found that for an efficient removal of significant amounts of iron an optimum design of the melting furnace is needed.

Tracer surface exchange and tracer diffusion of oxygen were investigated in nanocrystals of the ionic conductor CeO2+10%Gd2O3. The use of nano size powders has the advantage that these parameters can be determined on a relatively short time scale even at low temperatures at which their values are low. Two complementary methods were used, a novel one based on SIMS performed on nano powder samples and a residual gas analysis method based on analyzing the composition of the gas-phase (which exchanges tracer material with the powder). The former, SIMS, measurements are novel because of the morphology of the oxide samples, namely powder rather than dense layers or bulk. Isotope surface exchange was found to be the limiting step with diffusion occurring rather rapidly in the small grains used. The values measured for the surface exchange coefficient Ktr are 2.3×10−13 and 9.0×10−13cm/s at 337 and 437°C, respectively for grains of nominally 5nm size. It is found that Ktr increases with increasing grain size.

Chapter 4 Diffusion in Ceramics Günter Borchardt, Günter Borchardt Tu Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, GermanySearch for more papers by this authorKarsten Gömann, Karsten Gömann University of Tasmania, Central Science Laboratory, Private Bag 74, Hobart, TAS 7001, AustraliaSearch for more papers by this authorMartin Kilo, Martin Kilo Tu Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, GermanySearch for more papers by this authorHarald Schmidt, Harald Schmidt Tu Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, GermanySearch for more papers by this author Günter Borchardt, Günter Borchardt Tu Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, GermanySearch for more papers by this authorKarsten Gömann, Karsten Gömann University of Tasmania, Central Science Laboratory, Private Bag 74, Hobart, TAS 7001, AustraliaSearch for more papers by this authorMartin Kilo, Martin Kilo Tu Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, GermanySearch for more papers by this authorHarald Schmidt, Harald Schmidt Tu Clausthal, Institut für Metallurgie, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, GermanySearch for more papers by this author Book Editor(s):Prof. Dr. Ralf Riedel, Prof. Dr. Ralf Riedel TU Darmstadt, Institut für Materialwissenschaft, Petersenstr. 23, 64287 Darmstadt, GermanySearch for more papers by this authorProf. Dr. I-Wei Chen, Prof. Dr. I-Wei Chen University of Pennsylvania, School of Engineering, 3231 Walnut Street, 19104-6272 Philadelphia, PA, USASearch for more papers by this author First published: 20 February 2008 https://doi.org/10.1002/9783527631926.ch4 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: General Introduction Simple Oxides Diffusion in Complex Oxides Diffusion in Non-Oxide Ceramics References Ceramics Science and Technology: Volume 1: Structures RelatedInformation

Cubic scandia-stabilised zirconia (ScSZ) has a very high oxygen ion conductivity, significantly higher than the more common yttria-stabilised zirconia (YSZ). However, its practical use is hindered by an ordered rhomboedric phase being present at low temperature which is unique for zirconias. The occurrence of this phase can be suppressed by co-doping scandia-stabilised with ternary metal oxides.It is the aim of this study to investigate the influence of co-doping with various cations on the ionic conductivity, and on the phase transition towards lower temperatures. To do that, we prepared scandia-stabilised zirconia containing 10 mol%Sc2O3 and up to 1.0 mol% Gd2O3, CaO, or CeO2, respectively, using a sol-gel method starting with nitrates of the metals. Powders were sintered at 1500 degrees C to obtain dense material with grain sizes in the range of 0.5 to 1.0 mu m.An addition of more than 0.5 mol% Gd2O3 significantly decreased the transition temperature of the phase transition between cubic and rhombohedral.The low temperature AC conductivity, measured in the range of 400 to 950 degrees C, was highest for ScSZ containing 1 mol% CeO2. The Arrhenius plot was strongly curved, indicating association or ordering of oxygen vacancies, which were explained with literature models. (C) 2010 Elsevier B.V. All rights reserved.

Silica segregation at two grain junctions or in amorphous triple junction pockets can influence creep by altering the grain‐boundary diffusion coefficient. Although the addition of silica to superplastic yttria‐stabilized tetragonal zirconia enhances ductility, differences in reported creep parameters have limited critical identification of rate controlling mechanisms. The present study on a pure 3 mol% yttria‐stabilized tetragonal zirconia (3YTZ) and 3YTZ with 0.39 or 3.9 wt% silica involved a detailed characterization of creep over a wide range of experimental conditions and also tracer diffusion measurements. The data broadly show transitions in creep stress exponents from n∼1 to ∼2 to ∼3 with a decrease in the stress. The data at high stresses are consistent with Coble diffusion creep, and creep at lower stresses is attributed to interface‐controlled diffusion creep. Measurements indicated that silica does not have any significant influence on grain boundary or lattice diffusion, and this is consistent with the observation that 3YTZ and 3YTZ with 0.39% or 3.9% silica exhibit essentially identical creep behavior in the Coble creep regime. Silica influences the interface control process so that the transitions in stress exponents are pushed to lower stresses with an increase in silica content.

The possibility of fast nitrogen ion conduction in solids is reviewed. Promising electrolytes based on three different base compounds are in the focus of this contribution: Zirconium oxide nitrides, tantalum oxide nitrides and mayenite-based materials. All aspects ranging from preparation methods, crystal structures (ideal and defect structure, also at elevated temperatures), transport properties (ionic and electronic conductivity, transference numbers, diffusion) and correlations between structure and physical properties are presented and discussed, in part also in relation to theoretical calculations. Fluorite-type quaternary oxide nitrides of zirconium are proven to be the first known materials with high nitrogen ion mobility. They can be described as fast mixed oxygen/nitrogen conductors but are limited due to the low maximum nitrogen/oxygen ratio achievable. Corresponding phases based on stabilized tantalum oxide nitrides have a superior N/O ratio but show poor thermal stability. For the development of a pure nitrogen ion conductor a different approach has also been investigated: Some cage compounds, in particular mayenite, allow the substitution of oxygen anions not tightly bound in the framework by nitrogen ions. Some of the obtained N-containing phases exhibit an outstanding electrical conductivity at low temperatures. Possible devices and applications such as a new type of a nitrogen sensor and an ammonia-producing fuel cell are introduced and discussed.

Oxygen uptake and oxygen diffusion in Mayenite (Ca12Al14O33) were investigated using the stable tracer O-18(2). Mayenite contains one intrinsic, highly mobile oxygen anion. It was shown that for high temperatures (above 700 degrees C), the diffusion goes through a interstitialcy mechanism, where the interstitial oxygen anion knocks out a lattice oxygen anion. The activation enthalpy for this process is around 0.9 eV, suggesting that the ionic migration is very fast.

Oxygen diffusion coefficients in SrZrO3 polycrystals were determined using the isotopic exchange method with O-18 as oxygen tracer. Diffusion treatments were performed at different temperatures between 1173 K and 1473 K. Oxygen diffusion profiles were established by secondary ion mass spectroscopy (SIMS). Classical diffusion equations were used to fit experimental results and to determine bulk diffusion (D-vol) and surface exchange (k) coefficients of oxygen in SrZrO3 polycrystalline materials. From these values, bulk diffusion and grain boundary diffusion coefficients as well as oxygen surface exchange coefficients were determined. The activation energy of oxygen diffusion in the bulk is 2.1 eV, while for the diffusion in the grain boundary, 1.8 eV was found. The surface exchange reaction has an activation enthalpy of 1.2 eV. (c) 2009 Elsevier B.V. All rights reserved.

The Nd3+ cation diffusion into transparent polycrystalline YAG (Y3Al5O12) was investigated as a function of temperature and silica content. Thin neodymium oxide layers were deposited on sintered YAG substrates prior to annealing under air at temperatures from 1400 to 1600 degrees C. Bulk and grain boundary neodymium diffusion coefficients were measured by secondary ion mass spectrometry. The experimental results show that silica addition increases the diffusivity of Nd3+ by a factor 10 whatever the diffusion path, probably as a result of extrinsic point defects formation, especially rare-earth vacancies.The experimental diffusion data were used to elucidate the sintering mechanism of Nd:YAG ceramics in the temperature range 1450-1550 degrees C. Firstly, it appeared that the intermediate stage of solid-state sintering should be controlled by the rare-earth diffusion along the grain boundary with an activation energy of about 600 U mol(-1). Secondly, grain growth mechanism at the final stage of liquid-phase sintering was investigated for silica-doped Nd:YAG samples. Thus, the grain growth should be limited by the reaction at interfaces at a temperature lower than 1500 degrees C, with an activation energy of about 880 kJ mol(-1). At higher temperature, it seems to be limited by the ionic diffusion through the intergranular liquid phase, with an activation energy of 250 kJ mol(-1). (C) 2009 Elsevier Ltd. All rights reserved.

Dense CeO2 layers of 350 nm thickness, with columnar grains of size 25 nm, were RF-sputtered on silicon. O-18 isotope exchange in the temperature range from 200 to 575 degrees C showed surface exchange at CeO2 as the rate-determining step, while diffusion through the polycrystalline thin layer was fast. The surface exchange coefficients controlled by surface or grain boundary processes were found to be k(s) = 2.7 x 10-8 exp(-0.3eV/kT)cm s(-1) or k(gb) = 1 x 10(-9) exp(-0.3eV/kT)cm s(-1.) Comparison with literature data on doped ceria revealed that surface exchange could be dominated by grain boundary processes. A lower limit for the diffusion coefficient was determined as 10(-15) cm(2) s(-1) at 575 degrees C. (c) 2007 Elsevier B.V. All rights reserved.

Mechanical creep of scandia stabilized zirconia containing 10 mol% Sc2O3 was measured. The activation enthalpy is 4.4 eV, revealing that the creep process is cation-diffusion-controlled, and creep can be correlated to known cation-diffusion coefficients. In particular, the creep exponent is 2, meaning that it is grain-boundary sliding controlling the creep process. (C) 2008 Elsevier B.V All rights reserved.

Zeitschrift für anorganische und allgemeine ChemieVolume 634, Issue 11 p. 2053-2053 Poster Oxygen Transport in O- and N-doped Mayenit Martin Kilo, Corresponding Author Martin Kilo martin.kilo@tu-clausthal.de TU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldTU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldSearch for more papers by this authorStefan Behrens, Stefan Behrens TU Berlin, Institut für Chemie, Sekr. C2,Search for more papers by this authorMartin y, Martin y TU Berlin, Institut für Chemie, Sekr. C2,Search for more papers by this author Martin Kilo, Corresponding Author Martin Kilo martin.kilo@tu-clausthal.de TU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldTU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldSearch for more papers by this authorStefan Behrens, Stefan Behrens TU Berlin, Institut für Chemie, Sekr. C2,Search for more papers by this authorMartin y, Martin y TU Berlin, Institut für Chemie, Sekr. C2,Search for more papers by this author First published: 28 August 2008 https://doi.org/10.1002/zaac.200870090AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume634, Issue11September 2008Pages 2053-2053 RelatedInformation

Zeitschrift für anorganische und allgemeine ChemieVolume 634, Issue 11 p. 2025-2025 Poster Preparation and Oxygen Transport in Doped Scandia-stabilised Zirconia Hussein Abbas, Corresponding Author Hussein Abbas TU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldTU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldSearch for more papers by this authorMartin Kilo, Corresponding Author Martin Kilo martin.kilo@tu-clausthal.de TU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldTU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldSearch for more papers by this author Hussein Abbas, Corresponding Author Hussein Abbas TU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldTU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldSearch for more papers by this authorMartin Kilo, Corresponding Author Martin Kilo martin.kilo@tu-clausthal.de TU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldTU Clausthal, Fakultät für Natur- und Materialwissenschaften, Robert-Koch-Str. 42, 38678 Clausthal-ZellerfeldSearch for more papers by this author First published: 28 August 2008 https://doi.org/10.1002/zaac.200870033AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume634, Issue11September 2008Pages 2025-2025 RelatedInformation

Zirconia powders doped with different amounts of dopants (CeO2, Gd2O3, and CaO) were synthesized by a citrate technique. X-ray diffraction for samples sintered at 1500 °C revealed that the zirconia ceramics were stabilized in the cubic phase above 12 mole % CaO and 10 mole % Gd2O3, while tetragonal zirconia is obtained above 15 mole % CeO2. Relative densities up to 99.5% were obtained. The effect of dopant concentration on the lattice parameter, average crystallite size, microstrain was studied. The cubic lattice parameter increases nearly linearly with increasing the concentration in case of CaO and Gd2O3. The tetragonal lattice parameters a t and c t increase nearly line- arly with increasing the concentration of CeO2. The average crystallite size was found to be larger than 600 nm for the samples investigated.

Cation doped zirconium oxynitrides (for example zirconium oxide doped with yttrium oxide and nitrogen, \''YZrON\''), having a fluorite-based structure, are suggested to have fairly high nitrogen diffusivity, besides their high oxygen mobility. In the present work, the tracer-diffusion of nitrogen and oxygen was measured in single crystalline \''YZrON\''. Results are compared to the migration pathways and migration enthalpies of nitrogen and oxygen ions as determined by elastic neutron diffraction studies. Excellent agreement of the measured activation enthalpies of nitrogen diffusion (about 2 eV) and oxygen diffusion (about 1 eV) determined by the two methods is found.

Anion diffusion was simulated in the system (Y0.2Zr0.8)-(O1.72N0.15) with the molecular dynamics (MD) technique using the program DL_POLY, employing empirical potentials of the Buckingham type. To describe nitrogen migration, nitrogen potentials had to be developed, assuming the interaction of charged nitrogen shells with a mass of 0.15 amu with cores. Comparing experimental and simulated anion diffusivities, the diffusion coefficients were found to be of similar order. However, nitrogen diffuses five times slower than oxygen according to the computer simulation, while experimentally, the difference is reported to be smaller. Calculated activation enthalpies were 1.2 and 1.4cV, respectively, for the two elements, with pre-exponential factors of 10(-5) and 10(-4) cm(2)/s, respectively.