Materials Literature
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The crystal structure of the PbMg$_{1/3}$Ta$_{2/3}$O$_3$ (PMT) relaxor ferroelectric was studied under hydrostatic pressure up to $\sim 7$ GPa by means of powder neutron diffraction. We find a drastic pressure-induced decrease of the lead displacement from the inversion centre which correlates with an increase by $\si…
This Comment corrects two separate errors which previously appeared in the calculation of vibrational mode frequencies of tin spheres embedded in a silica matrix. The first error has to do with the vibrational frequency of a free elastic sphere. The second error has to do with the effect on the vibrational frequencies…
November 2002, "Magister", Supervisors : Dr. H. Bouzar (Tizi-Ouzou, Algeria) with the collaboration of Dr. V. Pierron-Bohnes and Dr. C. Goyhenex (Strasbourg, France). Mouloud Mammeri University, Tizi-Ouzou (Algeria) and Louis Pasteur University, Strasbourg (France).
We study the effects of magnetoelastic coupling on the degenerate ground state of the spin-1/2 antiferromagnetic Heisenberg model for the regular triangular spin cluster. Static displacement of spins spontaneously lifts the degeneracy of the ground state through the distance dependence of exchange coupling, i.e., a sp…
The electrospinning of polymer melts can offer an advantage over solution electrospinning, in the development of layered tissue constructs for tissue engineering. Melt electrospinning does not require a solvent, of which many are cytotoxic in nature, and the use of nonwater soluble polymers allows the collection of fi…
Chemisorption from the gas or liquid phase can result in a measurable resistance change in a metallic material when at least one dimension is smaller than the mean free path for electrons. Here we report on the fabrication of single nanoporous gold nanowires and demonstrate that adsorption of an alkanethiol can be mon…
The atomic geometry and electronic structure of diamond surfaces, both clean and with various hydrogen and oxygen terminations, have been studied using ab initio density-functional-theory calculations. Calculated ionization potentials and estimated electron affinities are presented for the different surfaces, while bu…
In view of the recent finding that the bimetallic AuPt nanoparticles prepared by molecular-capping-based colloidal synthesis and subsequent assembly on carbon black support and thermal activation treatment exhibit alloy properties, which is in sharp contrast to the bimetallic miscibility gap known for the bulk counter…
Quantum dots have emerged as an important class of material that offers great promise to a diverse range of applications ranging from energy conversion to biomedicine. Here, we review the potential of using quantum dots and quantum dot conjugates as sensitizers for photodynamic therapy (PDT). The photophysics of singl…
Monodisperse lead telluride (PbTe) nanocrystals ranging from approximately 4 to 10 nm in diameter are synthesized to provide quantum dot building blocks for the design of novel materials for electronic applications. Two complementary synthetic approaches are developed that enable either (1) isolation of small quantiti…
A combination of high-resolution scanning tunneling microscopy and density functional theory is utilized to study the interaction of water with the reduced TiO2(110)-(1 x 1) surface. As the direct product of water dissociation in oxygen vacancies, paired hydroxyl groups are formed. These pairs are immobile and stable…
Oxides with the cubic fluorite structure, e.g., ceria (CeO2), are known to be good solid electrolytes when they are doped with cations of lower valence than the host cations. The high ionic conductivity of doped ceria makes it an attractive electrolyte for solid oxide fuel cells, whose prospects as an environmentally…
The aberrations of a spherical lens composed of left-handed materials are studied in this letter. Five Seidel aberrations (spherical, coma, astigmatism, field curvature, and distortion) as a function of the refractive index n and shape factor q of the lens are considered. Our numerical calculations show that the negat…
Variable-angle ellipsometry has been used to characterize oligothiophene crystals with principal axes inclined at an angle to the surface normal. The results allow deducing with high sensitivity the orientation of the molecules in these anisotropic and absorbing organic solids, thus allowing one to follow the evolutio…
A new electric furnace has been designed and fabricated for measurements of the high‐resolution synchrotron radiation powder diffraction profiles from materials at high temperatures up to 1807 K in air, suitable for the multiple‐detector system installed at the BL‐4B 2 experimental station of the Photon Factory, Tsuku…
A high-brightness electron beam of more than 1011Asr−1m−2 was achieved from a graphite nanoneedle cathode, which was fabricated by simple hydrogen plasma etching of a graphite rod. A field emission was obtained at a high residual pressure of 10−6Torr. The performance of this cold cathode was demonstrated by the fabric…
Epilithic algae of the River Danube were investigated alongside the river from the source streams Breg and Brigach up to the end of the Hungarian stretch. Beside the data acquisition about the species composition of epilithic algae, diatom-based water quality analysis was performed with the aid of the widely used Euro…
We present a direct observation of nanoscale ferroelectric domain pinning centers in lithium niobate crystals. A high-voltage atomic force microscope has been used to tailor nanodomain structures in LiNbO3 crystal with high defect concentration. Domain pinning and depinning events have been captured following thermall…
We report the effects of biaxial strain on the charge ordering temperature Tco of the mixed-valent manganite perovskite oxide Pr0.5Ca0.5MnO3. Thin films were grown on SrTiO3, which has a 1.3% larger in-plane lattice parameter. Other substrates were used for comparison. Transport measurements combined with data from el…
AlN–SiC ceramics composed of AlN–SiC solid solutions were fabricated by pressureless sintering without sintering additives. The microstructure and electrical properties of the AlN–SiC ceramics were investigated for compositions between 0 and 75 mol% AlN. The AlN–SiC ceramics had a porous structure, and a 2H polytype w…