Materials Literature
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A metalloporphyrin has been synthesized carrying a beta-cyclodextrin group on tetrafluorophenyl rings at the four meso positions of the porphyrin. It performs the selective hydroxylation of an androstanediol derivative with complete positional selectivity and 187 turnovers.
Catalytic activity tests in combination with characterization studies (using CO temperature programmed reduction, electron paramagnetic resonance, and Fourier transform infrared) have been performed with the aim of establishing which are the main factors influencing the reactivity of an oxidized Pt/CeO 2 /Al 2 O 3 cat…
The crack healing and strength behavior of an alumina‐silicon carbide (Al 2 O 3 ‐SiC) nanocomposite (Al 2 O 3 + 5 vol% 0.2 μm SiC particles) has been studied, as a function of the crack size and the annealing environment. Results show that annealing treatments can significantly increase the indentation strength. The a…
Abstract Model identification and control were studied for the seeded batch crystallization of an organic, industrial photochemical. The growth and nucleation kinetics are described by empirical power‐law expressions in relative supersaturation, and an additional model describing crystal shape dynamics is proposed. Th…
The phonon density of states of aluminum nitride was determined by time-of-flight neutron spectroscopy using a polycrystalline sample. The observed phonon excitation spectrum consists of a broadband centered at about 35 meV, a small gap in the 75--80 meV region, and two sharp bands at approximately 85 and 92 meV. A ri…
Photovoltaic effects in CdSe quantum dot (QD) films have been studied using surface photovoltage spectroscopy and complementary methods. The results show that, contrary to previous studies, nonnegligible electric fields can exist in QD films. As a result, driftlike currents must be considered, in addition to the well‐…
The electrosynthesis of tetrathiafulvane-derivatized polythiophenes (PT-TTFs) from bithiophenic precursors such as that shown in the Figure (m = 3 or 5) is reported. The lower oxidation potential of bithiophene compared to thiophene is suggested to account for the ease of electropolymerization. Highly electroactive, s…
The mechanical properties of Si 3 N 4 /SiC nanocomposite materials that contained nanosized intercrystalline SiC dispersions that originated from different starting powders and were made via different fabrication routes were studied in the temperature range of 1400°‐1550°C. The strength retained at 1400°C was between…
Excellent candidates for high remanent permanent magnets are nanoscaled composite materials consisting of soft magnetic $\ensuremath{\alpha}$-Fe grains embedded into a hard magnetic ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ environment. The magnetic properties of such permanent magnets sensitively depend on the…
The interaction of oxygen with the ordered Ni3Al (111) surface has been investigated in the temperature range from 300 to 1000 K using high-resolution electron-energy-loss spectroscopy (HREELS) and low-energy electron diffraction (LEED). The “2×2” LEED pattern of the clean Ni3Al (111) surface indicates a bulklike term…
Three-dimensional (3D) simulations of meso-phase formation in block copolymer melts under simple steady shear are performed in the framework of dynamic density-functional theory. The most stable ``perpendicular'' lamellar ordering is observed. The difference between 2D and 3D ordering in a model system is described. L…
Silver sulfide Ag 2 S nanocrystals have been synthesized in reverse micelles and coated with thioalkyl chains with different lengths. With short chains (≤C 8 ) and very long ones (≥C 16 ) the particles cannot be extracted from micelles. For short alkyl chains, this is due to disorder at the interface. For longer chain…
The fabrication of dense Si 3 N 4 /SiC nanocomposite materials that contained 2.5‐30 wt% SiC via gas‐pressure sintering and hot pressing was investigated. The SiC particles originated from admixed commercial SiC powders, SiCN powders produced by plasma synthesis, in situ reaction pyrolysis of carbon‐coated Si 3 N 4 pa…
X-ray-absorption fine-structure measurements from the Mn and La $K$ edges of samples of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ $(x=\stackrel{\ensuremath{\rightarrow}}{0}1)$ are presented as a function of temperature. In the insulating state, distortions of the Mn-O environment are found…
For applications of carbon nanotubes in electronic components site-specific assembly of nanotubes onto patterned substrates is required. The Figure shows, as an example, a surface modification that favors attachment of nanotubes to an electrode (Au/Pd). The adsorbed nanotube (gray) has a partial surfactant shell and t…
Abstract The crystal structures of rare-earth metal sesquisulfides and some related compounds (Tm 5 S 7 , Tm 8 S 11 , Tm 15 S 22 ) of orthorhombic or monoclinic symmetry with the mirror plane perpendicular to the translation of 3.7 Å – 4.1 Å have been studied using an analysis of close-packed atomic nets. The cation a…
We have found that a film of amorphous selenium exposed to simultaneous action of two different (Kr+ and Ar+) lasers whose photon energies are on different sides of the optical band gap, crystallizes more slowly than the one exposed to only one of the above. A decisive role of the polarization of the two laser beams h…
In this paper the physical mechanisms and fundamental methods of obtaining nanometer-size atomic clusters in semiconductors are discussed, along with the possibility of controlling the properties of these clusters and those of the resulting cluster-containing materials. A number of electronic properties of semiconduct…
Acoustic cavitation generates very large localized pressures and temperatures, and thus provides a mechanism whereby physical and biological effects are produced in a high-intensity acoustic field. In this work, we studied the influence of the temporal form of a pressure pulse waveform on the destructive effects of tr…
Abstract Electrically conductive elastomer foams were prepared by in situ vapor phase copolymerization of pyrrole and N‐methylpyrrole within preformed polyurethane foams. The conductive polymer is formed within the dense polymer phase of the foam, and the conductivity of the composite foam ranged from 10 −1 to 10 −7 S…