Materials Literature
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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…
The work hardening of metals subjected to complex processing paths is different from that in monotonic deformation. Changes in the deformation mode can promote transients in the strain-hardening rate, leading to anomalous softening or hardening of the material. This paper investigates the influence of strain path chan…
In this work we investigated the influence of formamide on the acid-catalyzed sol-gel process by Fourier transform infrared spectroscopy (FTIR). Three silica sols were studied: Sol catalyzed with nitric acid without formamide, sol catalyzed with nitric acid containing formamide and sol catalyzed with a mixture of nitr…
Gaseous pollution control, solid and liquid waste treatments have been commercialized based on incineration, catalysis, adsorption, disposal with landfill, etc. More recently technology based on plasmas has become significant due to the advantages such as lower costs, higher treatment and energy efficiencies, smaller…
The fundamental parameters approach is used to simulate the instrument contribution to the X-Ray diffraction profile. This procedure eliminates the need to experimentally prepare a reference sample of the studied crystalline material when using the Warren-Averbach method to investigate microstrutural parameters. The W…
A series of polyurethane/PMMA simultaneous interpenetrating networks (SINs) with various hard segment contents (X) in the polyurethane phase (X = 15.5 to 36.5% in polyurethane) and wide range of polyurethane (PU) to polyacrylate (PA) ratio (PU/PA = 20:80 to 80:20) were prepared, and the damping and mechanical properti…
The addition of glass phase can control the grain boundary structure and hence the mechanical properties of tetragonal zirconia polycrystals (TZP). To reveal the effect of the glass dopant on the high-temperature deformation behavior of TZP, SiO2-doped TZP, (SiO2–Al2O3)-doped TZP, (SiO2–MgO)-doped TZP and undoped TZP…
Fracture toughness testing becomes a very important parameter for mechanical design and maintenance of parts and structures. This work presents the design and construction of a machine device to perform the pre-crack nucleation on SE(B) specimens for fracture toughness testing. Employing this device, it is possible to…
The purpose of this work was to analyze water sorption by polymerized acrylic resins under different pressure, temperature and time treatments. A thermo-cured acrylic resin was used as the denture base (Classico Ltda.) and ethylene glycol di-methacrylate as a cross-linking agent, with processing carried out in a water…