Materials Literature
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Hollow silica microspheres were synthesised at room temperature from a vortexed mixture of water and droplets of tetraethoxysilane (TEOS) containing 10 mol% aminopropyltriethoxysilane: droplets stabilized with the surfactant cetyltrimethylammonium bromide produced silica shells, 30.6 µm in mean diameter, whereas repla…
Fully undoped oligo(3,4-ethylenedioxythiophene)s have been synthesized from polycondensation of the corresponding dibromomonomer in the presence of a catalytic Ni(0)-based complex in N,N-dimethylacetamide (DMA). HPLC analysis indicated that the material is constituted of three main oligomers which have also been clear…
Phosphorus-containing epoxy-based epoxy–silica hybrid materials with a nanostructure were obtained from bis(3-glycidyloxy)phenylphosphine oxide, diaminodiphenylmethane, and tetraethoxysilane in the presence of the catalyst p-toluenesulfonic acid via an in situ sol–gel process. The silica formed on a nanometer scale in…
An overview is given on the generation of metal nanoparticles dispersed within amphiphilic polymeric systems, ranging from nonionic polymers and polyelectrolytes to amphiphilic diblock copolymers. Such materials are receiving increased attention, since they offer tremendous options for the development of composites po…
A modified cellular automaton model (MCA) was developed in order to simulate the evolution of dendritic microstructures in solidification of alloys. Different from the classical cellular automata in which only the temperature field was calculated, this model also included the solute redistribution both in liquid and s…
Two-dimensional hexagonally ordered CMK-3 carbons were synthesized using SBA-15 templates calcined at a temperature of 1153 K, whereas a disordered carbon was obtained using SBA-15 calcined at 1243 K, demonstrating that the pores connecting ordered mesopores in SBA-15 silica persist up to ca. 1153 K, but are eliminate…
Cyclic deformation of ultra-fine grain (UFG) materials processed by severe plastic deformation is reviewed in light of recent experimental results and common concepts of fatigue. High strength bulk metals with a characteristic structural element size of 200–300 nm were obtained through the so-called equal-channel angu…
Density functional theory has been used to study the adsorption of hydroxyl at low and high coverages and also to investigate the nature of the intermediate in the H2O formation reaction on Pt(111). At low coverages [1/9 of a monolayer (ML) to 1/3 ML] OH binds preferentially at bridge and top sites with a chemisorptio…
There has been great demand for shape memory alloy (SMA) actuators within the field of micro-machines. However, the thermomechanical behavior of SMA actuators is too complicated to accurately predict their response. Moreover the tracking control accuracy of SMA actuators is limited due to the inherent hysteresis nonli…
Hydrothermal powders of BaTiO 3 and (Ba,Ca)(Ti,Zr)O 3 contain large amounts of protons in the oxygen sublattice. The proton defects are compensated by vacancies on metal sites. When the powder is annealed, water is released and the point defects disappear in the temperature range of 100°–600°C. Metal and oxygen vacanc…
Dextran has recently been investigated as an alternative to poly(ethylene glycol) (PEG) for low protein-binding, cell-resistant coatings on biomaterial surfaces. Although antifouling properties of surface-grafted dextran and PEG are quite similar, surface-bound dextran has multiple reactive sites for high-density surf…
A novel molecule, containing two photochromic dithienylethene moieties linked to a fluorescent bis(phenylethynyl)- anthracene residue has been prepared, and shows a reversible change in its fluorescence quantum yield from 0.001 to 0.83, and a corresponding increase in laser emission intensity, on exposure to UV light.
Soil organic matter (OM) and mineral surfaces are intimately related, affecting the dynamics of each and their reactivity with many environmentally important substances. We examined the coverage of mineral surfaces by OM in acid soils of Massachusetts. Specific surface areas are controlled by a combination of clay and…
When subjected to alternating stresses, most materials degrade, e.g., suffer premature failure, due to a phenomenon known as fatigue. It is generally accepted that in brittle materials, such as ceramics, fatigue can only take place in toughened solids, i.e., premature fatigue failure would not be expected in materials…
Metallic nanowires protected from oxidation and corrosion by a sheath of polyaniline have been prepared in arrays on an alumina membrane support. The cobalt wire/polyaniline tubule nanocomposite structures (see Figure), which are produced by using the polyaniline tubules as a template for the growth of the metal wires…
The resistivity rho(dc) of manganites is studied using a random resistor-network, based on phase separation between metallic and insulating domains. When percolation occurs, both as chemical composition or temperature vary, results in good agreement with experiments are obtained. Similar conclusions are reached using…
The highly compact and globular shape, as well as the uniform size and plurifunctionality of dendrimers make them ideal molecular building blocks for a wide range of interfacial materials involving self-assembled monolayers, Langmuir films, multilayers, and other surface-confined assemblies. Moreover, the study of the…
Polypropylene (PP) composites with high filler content have been prepared with surface-treated fillers. The effect of the filler is twofold; nucleation of crystallization occurs, though the PP is also adsorbed onto the filler thereby retarding its motion. Differential scanning calorimetry has been used to study the cr…
Thermal diffusivity and optical absorption have been investigated for porous silicon, at room temperature, using photoacoustic spectroscopy. The experimental results obtained conform well with the existing studies recently published. The value obtained for thermal diffusivity is 0.045 ± 0.002 cm²/s.The absorption onse…
In this work, the application of the X-ray multiple diffraction technique using synchrotron radiation at Laboratório Nacional de Luz Síncrotron (LNLS) to study KDP phase transition induced by electric field is discussed. A Huber three-axis (omega, phi, 2theta) diffractometer mounted on a table which rotates around the…