Materials Literature
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As a missing link of the tourmaline classification, an X-site vacant analogue of olenite was synthesized from three different starting compositions in the system Al2O3-B2O3-SiO2-H2O (ABSH) over the PT-range 4–40 kbar, 450–700 °C, however never as a single phase product; dumortierite with either quartz or with jeremeje…
One of the most interesting properties of quantum dots is the possibility to tune the band gap as a function of their size. Here we explore the possibility of changing the lifetime of the lowest-energy excited state by altering the surface passivation. We show that a moderately electronegative passivation potential ca…
Polarized single-crystal Raman scattering and powder infrared absorption spectra of Fdd2 orthorhombic natural natrolite (Na1.88 K0.02 Ca0.04 )(Al1.96 Si3.03 O10)⋅2.03 H2O from Khibiny, Kola peninsula, were measured. Using short-range models, lattice-dynamical calculations were performed for an idealized natrolite stru…
A photopyroelectric technique has been applied to the study of specific heat and thermal conductivity of homeotropically aligned mixtures of small quartz spheres (aerosil) and octylcyanobiphenyl (8CB) with concentration 0</=rho(s)</=0.04 g/cm(3). Thermal conductivity data show that, even at these very low concentratio…
The new mineral pillaite, Pb9Sb10S23ClO0.5, an oxy-chloro-sulfosalt, has been found at Buca della Vena mine in the Apuan Alps, northern Tuscany, Italy. It crystallized in small fractures of dolomitic lenses in massive Fe- Ba ore, together with many Pb-Sb sulfosalts, among which the oxy-sulfosalt scainiite. Pillaite oc…
A new band assignment of the IR spectrum of mullite is proposed on the basis of FTIR powder spec- troscopy of Al-Si, Al-Ge, and Ga-Ge compounds and polarised FTIR single-crystal spectroscopy of oriented ultrathin Czochralski-grown Al-Si 2:1-mullite slabs. The structural parameters of the mullite compounds were obtaine…
Within the one-dimensional tight-binding minibands and on-site Coloumbic interaction approximation, the absorption spectrum and coherent wavepacket time evolution in an optically excited semiconductor superlattice driven by dc-ac electric fields are investigated using the semiconductor Bloch equations. The dominating…
The magnetization at low temperatures for Nd0.5Sr0.5MnO3 and Nd0.5Ca0.5MnO3 samples showed a rapid increase with decreasing temperatures, contrary to a La0.5Ca0.5MnO3 sample. Specific heat measurement at low temperatures showed a Schottky-like anomaly for the first two samples. However, there is not a straight forward…
The accurate charge density of MgB2 was observed at room temperature(R.T.) and 15K by the MEM(Maximum Entropy Method)/Rietveld analysis using synchrotron radiation powder data. The obtained charge density clearly revealed the covalent bonding feature of boron forming the 2D honeycomb network in the basal plane, on the…
We perform high resolution X-ray diffraction on GaMnAs mixed crystals as well as on GaMnAs/GaAs and GaAs/MnAs superlattices for samples grown by low temperature molecular beam epitaxy under different growth conditions. Although all samples are of high crystalline quality and show narrow rocking curve widths and pronou…
Oxidation of SiC produces SiO2 while CO is released. A `reoxidation' step at lower temperatures is, however, necessary to produce high-quality SiO2. This step is believed to cleanse the oxide of residual C without further oxidation of the SiC substrate. We report first-principles calculations that describe the nucleat…
A core-softened model of a glass forming fluid is numerically studied in the limit of very low temperatures. The model shows two qualitatively different behaviors depending on the strength of the attraction between particles. For no or low attraction, the changes of density as a function of pressure are smooth, althou…
Specimens of tobermorite 11Å from Wessels mine, South Africa, an 'anomalous' tobermorite, and from Bašcenov, Urals, Russia, a 'normal' tobermorite, have been studied through X-ray diffraction. Their structural disorder, evidenced by the diffuseness of the reflections with k odd, has been dealt with through an OD app…
Techniques from graph theory are applied to analyze the bond networks in proteins and identify the flexible and rigid regions. The bond network consists of distance constraints defined by the covalent and hydrogen bonds and salt bridges in the protein, identified by geometric and energetic criteria. We use an algorith…
Abstract ZrB2-SiC composites are considered a class of promising materials for aerospace applications such as nose and leading edges of re-entry vehicles. Results on such materials obtained by hot isostatic pressing have confirmed their high resistance to the oxidation at temperature up to 2000°C. Ongoing work has sho…
Fe3O4-Nanopartikel, die beschichtet sind mit 2-Carboxyterthiophen (TTP-COOH), ordnen sich über π-π-Wechselwirkungen zu einheitlichen Mikrokügelchen an (siehe schematische Darstellung). Die Wechselwirkung zwischen den Partikeln ist relativ schwach: Durch Ultraschall lassen sich die Aggregate in monodisperse Nanopartike…
Epoxy and glass matrix Terfenol-D composites have been produced by using a cold and hot compression-molding technique, respectively. The static and dynamic magnetic and magnetomechanical properties of samples with a volume fraction Vf in the range of 10% to 82% have been investigated as functions of bias field, freque…
Luminescence due to the radiative recombination of localized biexcitons has been observed at low temperature (5 K) in ZnO/Zn0.74Mg0.26O multiquantum wells grown by laser-molecular-beam epilaxy on a lattice-matched ScAlMgO4 substrate (0001). The emission components due to the recombination of localized excitons and bie…
Temperature dependent dielectric constant measurements have been performed on 〈001〉 oriented 0.7 Pb(Mg1/3Nb2/3)O3–0.3 PbTiO3 crystals. These investigations have revealed an irreversible secondary transformation between a normal ferroelectric state and a relaxor ferroelectric state with increasing temperature. The resu…
Mg-doped Ba0.96Ca0.04Ti0.84Zr0.16O3 (BCTZ) thin films have been proposed as a promising material for microelectronic device applications based on high dielectric materials. Perovskite polycrystalline Mg-doped BCTZ thin films were fabricated on a Pt/Ti/SiO2/Si substrate by metalorganic decomposition method. Dielectric…