Materials Literature
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This work proposes a procedure to estimate the dynamic damped behavior of fiber reinforced composite beams in flexural vibrations. A set of experimental dynamic tests were carried out in order to investigate the natural frequencies and modal shapes. These results are used to evaluate the damping factors by the program…
One of the most important compounds that are used in structural ceramics is alumina. During the last years, a variety of synthesis methods have been developed to obtain raw materials with suitable characteristics in terms of particle composition, size and shape. Controlled precipitation method (CP) allows to reach the…
A new Peltier system is introduced which offers new dimensions in temperature precision for parallel-plate and cone-and-plate measuring geometries in the temperature range from −30°C to +130°C. The use of an additional actively Peltier controlled hood (pat. pent.) reduces the temperature gradient across the sample to…
Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was st…
Rheological properties of aqueous suspensions (48 vol%) of zircon-alumina mixtures containing different amounts of polyelectrolyte as dispersant were studied. Slip casting in a plaster mold and pressure filtration at 8 MPa experiments were performed to correlate the rheological properties of the suspensions with the r…
Lanthanum-modified lead zirconate titanate (PLZT) ceramics were obtained with high transmittance in the visible range by a combination of an inexpensive chemical processing and hot pressing. Optical, microstructural, pyroelectric, ferroelectric and dielectric properties characterized in this study attested the applica…
Polypropylene with special properties can be obtained by metallocenic catalysts. These catalytic systems represent the beginning of a new age in polyolefins technology. In this work, the influence of the addition of a syndiotactic polypropylene (s-PP) on the processability and mechanical properties of a commercial iso…
The present work reports an investigation of the influence of the radial spacing between cathodes on the iron sintering process by hollow cathode electrical discharge, with surface enrichment of the alloying elements Cr and Ni. Pressed cylindrical samples of 9.5 mm diameter and density of 7.0 ± 0.1 g/cm³ were prepared…
The susceptibility of a duplex stainless steel UNS S31803 to thermal embrittlement at 475 °C was evaluated by means of mechanical tests (impact energy and hardness), magnetic measurements (hysteresis and thermomagnetic analysis) and scanning electron microscopy. The results show that the material undergoes severe embr…
Two new one-dimensional single azide-bridged metal(II) compounds [[M(5-methylpyrazole)4(N3)]n](ClO4)n(H2O)n [M = Co (1a), Ni (2a)] were prepared by treating an M(II) ion with stoichiometric amount of sodium azide in the presence of four equivalents of the 3(5)-methylpyrazole ligand. The isostructural compounds 1a and…
The preparation of spherical phosphor europium-doped yttrium oxide (Y 2 O 3:Eu) particles using a copolymer of N -isopropylacrylamide (NIPAM)] and acrylic acid (AAc) is described. The resulting phosphor particles have smaller particle diameters (<0.1 μm) compared to both commercial Y 2 O 3:Eu phosphors and spherical p…
Abstract A novel method of protein encapsulation is proposed. Preformed protein aggregates are covered with polyelectrolyte layers by means of layer‐by‐layer adsorption. The polyelectrolyte membrane prevents protein leakage out of the capsule. Using chymotrypsin as a model enzyme the capsule wall selective permeabilit…
Impregnating the cores of triblock-copolymer nanotubes with Fe2O3 renders them superparamagnetic. The resultant polymer/Fe2O3 hybrid nanofibers (see TEM image) have interesting properties in magnetic fields. The nanofibers align themselves in the magnetic-field direction, and mixtures of the nanofibers and nanotubes u…
The crystallization behavior of organometallic‐precursor‐derived amorphous Si‐C‐N ceramics was investigated under N 2 atmosphere using X‐ray diffractometry (XRD), transmission electron microscopy (TEM), and solid‐state 29 Si nuclear magnetic resonance (NMR) spectroscopy. Amorphous Si‐C‐N ceramics with a C/Si atomic ra…
Three novel Si‐C‐B‐N ceramic compositions, namely Si 2.9 B 1.0 C 14 N 2.9 , Si 3.9 B 1.0 C 11 N 3.2 and Si 5.3 B 1.0 C 19 N 3.4 , were synthesized using the polymer‐to‐ceramic transformation of the polyorganoborosilazanes [B(C 2 H 4 Si(Ph)NH) 3 ] n , [B(C 2 H 4 Si(CH 3 )NH) 2 –(C 2 H 4 Si(CH 3 )N(SiH 2 Ph))] n , and […
The mechanical properties of ceramic foams obtained through a novel process that uses the direct foaming and pyrolysis of preceramic polymer/polyurethane solutions were investigated. The elastic modulus, flexural strength, and compressive strengths were obtained for foams in the as‐pyrolyzed condition; values up to 7.…
The half-metallicity of ${\mathrm{CoS}}_{2},$ important for its possible use in spintronic applications, is investigated by means of density functional full-potential linearized augmented plane wave calculations within both the local spin-density approximation (LSDA) and the generalized gradient approximation (GGA). I…