Materials Literature
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A new dendron with peripheral long alkyl chains and containing five C(60) units in the branching shell has been prepared and attached to a Fréchet-type dendron functionalized with ethylene glycol chains. The peripheral substitution of the resulting globular dendrimer with hydrophobic chains on one hemisphere and hydro…
The electronic structure, stability, electron-phonon coupling, and superconductivity of the nonoxide perovskite ${\mathrm{MgCNi}}_{3}$ are studied using density functional calculations. The band structure is dominated by a Ni d derived density of states peak just below the Fermi energy, which leads to a moderate Stone…
Several synthetic pathways of mesostructured porous silica using nonionic surfactants or copolymers have been reported since the discovery of this new family of materials. We developed a process, which we call a two-step synthesis, that allows us to synthesize MSU-X mesoporous silica, with very good reproducibility an…
The selective catalytic reduction of NO x (NO + NO 2 ) at low temperature with ammonia has been investigated with natural manganese ore, pure manganese dioxide, and manganese dioxide supported alumina. The catalysts showed high activities for NO x reduction with NH 3 in the presence of O 2 at temperatures below 250 °C…
In this paper the kinetics of the pozzolanic reaction between lime (calcium hydroxide) and sugar cane straw ash with 20 and 30% of clay burned at 800 and 1000 C is studied. A simple experimental technique where the conductivity is the experimental variable was used. A calibration curve was established for correlating…
In recent years it has become possible to study the properties of nanocrystalline metals through atomic-scale simulations of systems with realistic grain sizes. A brief overview of the main results is given, such as the observation of a reverse Hall-Petch effect - a softening of the metal when the grain size is reduce…
The effect of porosity in a wide range of mesopore diameters ( d p = 20−330 Å) on the dispersion and reducibility of cobalt species in mesoporous silicas is examined using nitrogen adsorption, X-ray diffraction, thermogravimetric analysis, and in situ X-ray absorption. It is shown that modification of mesoporous silic…
We report first-principles total-energy electronic-structure calculations in the density-functional theory performed for hexagonally bonded honeycomb sheets consisting of B, N, and C atoms. We find that the ground state of BNC sheets with particular stoichiometry is ferromagnetic. Detailed analyses of energy bands and…
In-situ-AFM-Messungen belegen, dass die Auflösung von Calciumphosphatkristallen in Gegenwart polymerer Additive nach Regeln stattfindet, die typisch für das jeweilige Muster funktioneller Gruppen auf dem Polymer sind. So ergeben Poly(natriumaspartat), Polylysin und Albumine durch unterschiedliches Abtragen der Kristal…
Stern- und Blockpolymere können durch lebende Radikalpolymerisationen hergestellt werden. Aus Lösungen dieser Makromoleküle entstehen beim Gießverfahren unter feuchten Bedingungen isoporöse, honigwabenartige Filme (siehe rasterelektronenmikroskopische Aufnahme). Dabei zeigt sich, dass der Porendurchmesser nicht nur vo…
Photoinduced anisotropy in amorphous selenium ( a-Se) has been studied by in situ x-ray absorption fine structure spectroscopy. It is found that upon irradiation with linearly polarized light the chainlike fragments in a-Se are oriented with their c-axis perpendicular to the polarization plane of the inducing light. T…
The acoustic signal from the sonochemical production of H2O2 in water, as measured by the intensity and the width of the second harmonic, show a sensitive and correlated dependence to the presence of small amounts (millimolar range) of an anionic surfactant (SDS) in water. The graphic shows the link from the ultrasoni…
Two BaxSr1−xO3, films with different contents of Ba (Ba0.25Sr0.75O3 and Ba0.75Sr0.5O3), separated by a MgO film, are used to fabricate planar varactors with low temperature coefficient of capacitance (TCC), high tunability and low losses. The TCC of the varactors are small in the temperature interval between the diele…
The synthesis, crystal structure, and magnetic characterization of a high-spin cluster comprising eight iron ions are presented in this contribution. The cluster has formula [(tacn)6Fe8O2(OH)12Br4.3(ClO4)3.7]·6H2O (Fe8pcl), where tacn is the organic ligand 1,4,7-triazacyclononane. It can be considered a derivative of…
The triple-barrier coupled quantum dots have been fabricated in individual single-wall carbon nanotubes by depositing a narrow SiO2 layer in between metallic source–drain contacts. The current–voltage characteristics at 4.2 K with different gate voltages before the SiO2 deposition have indicated the formation of a sin…
It is well known that chemical etching of strontium titanate (SrTiO3) results in titanium-terminated (B site) surfaces. In this letter, we describe a facile method for generating strontium-terminated surfaces in SrTiO3. We demonstrate that a substrate treatment consisting of a low-power oxygen ashing followed by annea…
Etching edges: In situ measurement by atomic-force microscopy (AFM) is employed to investigate the dissolution of calcium phosphate crystals in the presence of different polymeric additives. The dissolution occurs in a way that is dependent on the pattern of functional groups on each polymer. The influence of poly(sod…
Das größte bisher bekannte Wolframatoarsenat(III), [AsW65O217(H2O)7]26− 1, wurde aus wässriger, saurer Lösung in Form seines Kaliumsalzes in guter Ausbeute isoliert und durch Einkristall-Röntgenstrukturanalyse, 183W-NMR- und FT-IR-Spektroskopie sowie Elementaranalyse charakterisiert. Die kompakte Struktur von 1 mit id…
A series of molybdenum and tungsten organometallic oxides containing [Ru(arene)]2+ units (arene =p-cymene, C6Me6) was obtained by condensation of [[Ru(arene)Cl2]2] with oxomolybdates and oxotungstates in aqueous or nonaqueous solvents. The crystal structures of [[Ru(eta6-C6Me6]]4W4O16], [[Ru(eta6-p-MeC6H4iPr]]4W2O10],…
A new topology within the family of metallohelicates has been revealed by the crystal structure of the complex [Mn3(HL)3] (see picture). The novel oxygen-based pentadentate ligand H3L reacts with Mn(OAc)2 to produce this unique triple-stranded helicate with an unprecedented asymmetric arrangement of the metal ions alo…