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Article
Mineralogical and Physical Changes during Sintering of Plastic Red Clays from Sanaga Swampy Valley, Cameroon
The sintering behavior and mechanical properties of four alluvial clays sampled from the Sanaga River (sampling sites: Nanga-Eboko, Mbandjock, Batschenga, and Ebebda), central region of Cameroon were investiga...
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Article
Mullite Plasma Spraying for In Situ Repair of Cracks in Mullite Refractories: Simultaneous Optimization of Porosity and Thickness by Statistical Design of Experiments
We report a laboratory-scale study about the suitability of the plasma spraying process for “in situ” repair of cracks in mullite refractories of industrial furnaces. The “design of experiments” approach is us...
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Article
Magnetic Properties of Nanosized Ba2Mg2Fe12O22 Powders Obtained by Auto-combustion
We studied the magnetic properties of nanosized Ba2Mg2Fe12O22 powder obtained by citrate auto-combustion synthesis. The powder consists of agglomerates with mean crystallite size of 100 nm. The magnetic propertie...
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Article
The rocker bone: a new kind of mineralised tissue?
In some Ophidiiform fishes, the anterior part of the swimbladder is thickened into a hard structure called the “rocker bone”, which is thought to play a role in sound production. Although this structure has be...
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Article
Magneto-transport characterization of Dy123 monodomain superconductors
We consider textured materials of the DyBa2Cu3O7 type seeded with a Nd123 seed as initiator. They are grown with an excess 20% Dy211 phase on a Dy2O3 substrate. We report chemical characterization, electrical res...
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Article
Low-field magnetoresistance in La0.7Ca0.3MnO3 manganite compounds prepared by the spray drying technique
Calcium-substituted lanthanum manganite compounds were synthesized by the spray drying technique. This method—whose main advantages are versatility, high reproducibility and scalability—yields small grain mate...
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Article
Synthesis and characterization of new inorganic polymeric composites based on kaolin or white clay and on ground-granulated blast furnace slag
Alkali activation of dehydroxylated kaolin or clay yielded high-strength polymeric materials, so-called geopolymers. They were synthesized by mixing the aluminosilicate with solutions of sodium metasilicate an...
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Article
Preparation of BaZrO3 powders by a spray-drying process
The potential use of barium zirconate for the manufacture of corrosion-resistant substrates emphasizes the need for a simple, inexpensive, and easily scalable process to produce high-quality powders with well-...
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Article
Simultaneous measurements of thermal diffusivity, thermal conductivity and thermopower with application to copper and ceramic superconductors
A home made experimental set-up allows us to measure the thermal conductivity, the thermopower and the thermal diffusivity simultaneously in the temperature range (20-300 K). Therefore the specific heat can be...
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Chapter
Dysprosium Substitution in Bi-Based 2223 Materials: The Role of the Superconducting Layer Charge Distribution for Inducing a Structural Phase Transition
The chemical synthesis of dysprosium doped Bi-based 2223 high-Tc superconducting materials prepared by either a “two-powder process” or a “crystalline-glassy matrix precursor” method has been examined. In both ca...
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Article
Two Peak Effect in GMR: A Chemical Effect?
We show that the synthesis conditions have a dramatic influence on the resistivity behavior of calcium and sodium doped LaMnO3. Several samples prepared by lowtemperature techniques exhibit a double-peaked curve ...
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Article
Effect of Synthesis Process and Substrate on Electrical and Thermal Transport Properties of Bi-2212
Resistivity, thermoelectric power, and thermal conductivity have been measured for a Bi-2212 system synthesized from a glassy precursor, either with a commercially Al2O3 substrate or with a homemade BaZrO3 substr...
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Article
Anomalous temperature behavior of the resistivity in lightly doped manganites around a metal-insulator phase transition
An unusual temperature and concentration behavior of the resistivity ρ(T, x) in La0.7Ca0.3Mn1−2x CuxO3 is observed at slight Cu do** (0≤x≤0.05). Namely, the introduction of copper results in a splitting of the ...
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Article
A sharp decrease of resistivity in La0.7Ca0.3Mn0.96Cu0.04O3: Evidence for Cu-assisted coherent tunneling of spin Polarons
Nearly a 50% decrease of the resistivity ρ(T, x) is observed upon just 4% Cu do** at the Mn site of La2/3Ca1/3Mn1−x CuxO3. When the observed phenomenon is attributed to a decrease of the spin-polaron energy E σ
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Chapter
Fluctuation Contributions to the Transport Properties of Hg1.4 Ba2Ca2Cu3O8+δ and Bi2Sr1.8Ca1.2Cu2O8 Polycrystalline Superconductors
After some discussion on the precision and originality of the measurement methods used in order to measure the electrical resistivity and simultaneously the thermopower and the thermal conductivity as a functi...
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Article
Non Trivial Processes for Obtaining Bi-Based High Tc Superconductors
Dysprosium doped Bi-based 2212 ceramics were synthesized by a melt-texturing growth process in a 1.2T magnetic field, applied perpendicularly to the main axis of a cylindrically shaped sample. The materials we...
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Article
Magnetotransport Studies of Bi-Based 2212 and 2223 High Critical Temperature Superconductors
When a magnetic field is superimposed on a superconducting sample the electric and temperature gradients allow one to observe phenomena called excess electrical resistivity, excess thermoelectric power, Nernst...
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Article
Directional solidification by appropriate chemically active single crystal seed: An alternative way of generating large superconducting 123 single domain
A Dy2O3 single crystal has been used as a seed for the growth of isothermally melt-textured Dy-123 material. The nucleation-controlled step has been observed to be related to the heterogeneous nucleation of 211 p...
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Article
Microstructure development in isothermally melt-textured 123–211 composite materials
Microstructures of isothermally melt-textured 123–211 composite materials have been examined during the solidification process from quenched specimens. The distribution of 211 particles, the superconducting 12...
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Article
Field percolation and high current density in 80/20 DyBa2Cu3O7 − x/Dy2BaCuO5 bulk magnetically textured composite ceramics
We measured the AC susceptibility of magnetically textured (123) 80%/211(20%) DyBaCuO composite in a special set-up in order to enhance the intergrain contribution. The synthesis process led to very clean “wea...
