Materials Literature
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Structural, magnetic and theoretical studies show that the bimetallic pentalene complex, Mn(2)(C(8)H(4)(1,4-Si(i)Pr(3)))(2), contains both high and low spin Mn(ii) in two very different sites.
OBJECTIVE: The objective of this study was to demonstrate that severe mechanical processing of industrial aciniform aggregates results in some fracture of large aggregates and minimal liberation of "primary particles." METHODS: Carbon black and amorphous silica were subjected to uniaxial compression, mixing into rubbe…
In semicrystalline polymers, important toughening is obtained with dispersions of rubber particles. However, adding rubber most often induces a substantial loss in elastic modulus. In the present study, we investigate how to avoid such softening by using ABC triblock copolymers with low rubber content. A polyamide-12…
Advanced TiC∕a-C:H nanocomposite coatings have been produced via reactive deposition in a closed-field unbalanced magnetron sputtering system (Hauzer HTC-1000 or HTC 1200). In this paper, we report on the tribological behavior of TiC∕a-C:H nanocomposite coatings in which ultralow friction is tailored with superior wea…
A bentonita, composta predominantemente pelo argilomineral montmorilonita que lhe confere as propriedades físicas concentra a maior parte das reservas nacionais (62%) no Estado da Paraíba. A transformação da bentonita em argila organofílica consiste em um procedimento laboratorial simples e pode ser realizada através…
Subnanometric ZnO clusters confined in different micropore zeolites are studied by steady-state and nanosecond time-resolved photoluminescence (PL) spectroscopy. The microsecond-scale lifetime is observed at room temperature for ZnO clusters confined in zeolites, which is significantly different from that of macrocrys…
The time dependences after poling of the mechanical quality factor Q m , electromechanical coupling coefficient k 31 and dielectric constant K have been investigated for both “soft” and “hard” lead zirconate titanate (PZT) ceramics. A significant increase of Q m with time was observed for “hard” PZTs, however “soft” o…
The gelation kinetics of aqueous solutions of poly(vinyl alcohol) (PVA) during freezing at −13 °C has been investigated with time-resolved small angle neutron scattering. Crystallization of PVA takes place inside an unfrozen liquid microphase that forms in the matrix of ice crystals and follows a first-order kinetics…
Methanol can be reformed with water, at ambient temperature, using photocatalysis, and this reaction represents a possible low energy, more sustainable pathway to hydrogen production than (for instance) steam reforming. The requirements for the catalysts are rather strict since titania itself is almost inactive for an…
We have measured the second-order nonlinear optical susceptibilities of an SrB 4 O 7 crystal and have determined its electromechanical coupling coefficients, piezoelectric charge and voltage constants, and bulk acoustic wave velocities by a resonance method using high- Q resonators. In addition, the dielectric permitt…
The collagen is the most common protein in mammalians. Thus its interaction with small molecules and particularly amino acids is of interest. Owing to the high degree of order of collagen fibers in a tendon, the 1H-1H and 1H-13C dipolar interactions and the 2H quadrupolar interaction of small molecules interacting wit…
The microstructure evolution in copper electrodeposits at room temperature (self-annealing) was investigated by means of x-ray diffraction analysis and simultaneous measurements of the electrical resistivity as a function of time. In situ studies were started immediately after deposition of the various thick layers an…
Sulfonated poly(ethylene oxide) (PEO)-grafted polyurethane (PU) (PU-PEO-SO(3)) prepared by bulk modification was used to coat both PU heart valves and vascular grafts, and their in vivo biocompatibility was evaluated using a canine shunt method. The two devices were implanted for up to 39 days and retrieved at specifi…
The radioluminescence (RL) properties of Ce-doped silica glasses prepared by sol−gel method were investigated as a function of the dopant amount in a wide range of concentrations (Ce:Si molar ratios from 1 × 10 - 5 to 5 × 10 - 2 ). The effects of xerogel densification temperature and of a postdensification thermal tre…
In this work we used quantum mechanics hybrid models (QM/QM) to investigate the high-temperature polymerization of styrene with the aim of elucidating its elementary chemistry. High and low quality quantum mechanics calculations were performed at the B3LYP/6-31g(d,p) and PM3 levels, respectively. Reaction kinetic cons…
Two different synthetic routes were used to synthesize three nanostructured cerium (IV) oxide powders: Two samples were obtained by precipitation from a basic solution of cerium nitrate and treated at 523 and 923 K, respectively, the third one was prepared by a microwave-assisted heating hydrolysis method and treated…
Low temperature photoluminescence and optical absorption studies on 200MeV Ag+15 ion irradiated Co-implanted ZnO thin films were studied. The Co clusters present in as implanted samples were observed to be dissolved using 200MeV Ag+15 ion irradiation with a fluence of 1×1012ions∕cm2. The photoluminescence spectrum of…
We have investigated the effect of hydrogen on the resistivity, Hall mobility, and carrier density of ITO films on glass substrates using a low-pressure plasma sputtering method. It was found that a certain hydrogen content in the Ar plasma leads to improvement in the resistivity relating to an increase in the electro…
A self-consistent dynamic model allowing the prediction of AC discharge activities leading to flashover on ice-covered insulator surface is presented. This model takes into account the effects of a number of parameters including insulator geometry and applied water conductivity. The instantaneous variations of major p…
A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft charac…