CeraMat

Three-phase composites in the system Al2O3–YAG–ZrO2 (AYZ) were produced by doping the surface of commercial alumina nanopowders with inorganic precursors of the second phases. Materials with three different compositions were prepared, in which 5, 20 and 33 vol.% of each second phase were respectively present. Pure crystalline phases were obtained in the final composites, as assessed by X-ray diffraction. Green bodies were produced by slip casting and uniaxial pressing.

Electrospun polyamide-6 membranes containing titanium dioxide (TiO2) photocatalyst were prepared and characterized. By tailoring the electrospinning parameters it was possible to obtain membranes having two different thicknesses, namely 5 and 20 µm, in which TiO2 particles were homogeneously dispersed. As a comparison, hybrid films made with polyamide-6 matrix and TiO2 filler were successfully produced, with inorganic/organic ratios of 10 and 20 wt%.

Barium titanate—acrylic hybrids with ceramic contents ranging between 10 and 70 wt% were successfully prepared by means of photopolymerization. These composites presented a homogeneous distribution of the ceramic particles within the organic matrix. In addition, an almost complete acrylic double-bond conversion took place. Basic electrical properties of the composites were investigated by dielectric spectroscopy.

In this work, the 45S5 bioactive glass was synthesized through an aqueous sol–gel method. Characteristic functional groups were evidenced by Fourier transform infrared spectroscopy, the thermal behaviour was investigated by thermogravimetric and differential thermal analysis, crystallization kinetics and phase evolution were followed by X-ray diffraction measurements. The sintering behaviour of the sol–gel derived 45S5 was then studied by dilatometry and the microstructural evolution was followed step-by-step, interrupting the thermal cycle at different temperatures.

Materials having nanometric dimensions are able to improve their functional properties, which allow their exploitation in highly performing sensors. Materials with at least one dimension smaller than 100 nm are classified as nanostructured.

This paper deals with the uniaxial compression behavior of porous ceramics within a wide range of porosity, varying from 30 to 75 vol%. The load–displacement curves recorded on porous alumina samples showed a transition between a typical brittle behavior at porosity fractions below 60 vol% and a damageable, cellular-like behavior, at higher porosity fractions. This transition in fracture mode was confirmed by in situ compression tests in an X-ray tomograph.

Al2O3-10 vol.% YAG and Al2O3-10 vol.% ZrO2 bi-phase composites as well as Al2O3-5 vol.% YAG-5 vol.% ZrO2 tri-phase composite were developed by controlled surface modification of an alumina powder with inorganic precursors of the second phases. Green bodies were produced by dry pressing and slip casting and then sintered at 1500 °C. In particular, slip casting led to fully dense, defect-free, and highly homogenous samples, made of a fine dispersion of the second phases into the micronic alumina matrix, as observed by SEM.

The free sintering of ceramic powders into fully dense nanostructured materials is still a challenging process, even more complex when nanostructured transition alumina is used as starting powder. In this paper, biphasic (Alumina–YAG) and triphasic (Alumina–YAG–ZrO2) composite powders were produced by doping the same nanocrystalline transition alumina with inorganic precursors of the second-phases, which were subsequently yielded under controlled thermal treatments.

Epoxy/BaTiO3 hybrid materials are prepared as good candidates for organic capacitors. The hybrid system is cured by using camphorquinone and a iodonium salt through a free-radical promoted cationic polymerization using a long-wavelength tungsten halogen lamp. The cured films are fully characterized. Morphological characterization shows a well-dispersed inorganic phase within the organic matrix. Electrical characterization demonstrates a linear increase of the dielectric constant with increasing filler content, while low dielectric loss values are obtained.

This paper deals with the preparation and characterization of nanocomposite (NC) materials, comparing different technologies for sample fabrication, in view of their possible application as piezoelectric sensors. Those NCs consist on BaTiO3 nanoparticles embedded into a polyvinylidene fluoride matrix, where both the ceramic and the polymeric phases could exhibit ferroelectricity.