Improvement Of Insulation Properties Research Articles

Mortar and concrete composites with recycled plastic: A review

Valorization of waste plastic as concrete aggregates has become an opportunity. Some advantages are plastic waste recycling, consumption reduction of natural aggregates and improvement of concrete properties. This paper presents a review on addition of recycled plastic waste to cement composites and influence on their properties. Forty five international papers were selected from scientific peer-reviewed journals. The critical items analyzed were: plastic characteristics, mix proportion design and concrete properties. The last item includes fresh and hardened concrete properties, durability performance and thermal conductivity. Although some properties were negatively influenced by the plastics, this paper focuses on the variables that mitigate these effects. The improvement of insulation properties with plastic is widely analyzed, but further research is recommended. As conclusion, application of plastic waste would be useful on both, technical and environmental dimensions and this paper could be used as a helpful tool for studying and designing mortars and concrete composites with recycled plastic.

Tailoring transport properties through nonstoichiometry in BaTiO3–BiScO3 and SrTiO3–Bi(Zn1/2Ti1/2)O3 for capacitor applications

The ceramic perovskite solid solutions BaTiO3–BiScO3 (BT–BS) and SrTiO3–Bi(Zn1/2Ti1/2)O3 (ST–BZT) are promising candidates for high-temperature and high-energy density dielectric applications. A-site cation nonstoichiometry was introduced in these two ceramic systems to investigate their effects on the dielectric and transport properties using temperature- and oxygen partial pressure-dependent AC impedance spectroscopy. For p-type BT–BS ceramics, the addition of excess Bi led to effective donor doping along with a significant improvement in insulation properties. A similar effect was observed on introducing Ba vacancies onto the A-sublattice. However, Bi deficiency registered an opposite effect with effective acceptor doping and a deterioration in the bulk resistivity values. For n-type intrinsic ST–BZT ceramics, the addition of excess Sr onto the A-sublattice resulted in a decrease in resistivity values, as expected. Introduction of Sr vacancies or addition of excess Bi on A-site did not appear to affect the insulation properties in air. These results indicate that minor levels of nonstoichiometry can have an important impact on the material properties, and furthermore it demonstrates the difficulties encountered in trying to establish a general model for the defect chemistry of Bi-containing perovskite systems.

Resistivity Enhancement and Transport Mechanisms in (1 − x)BaTiO3–xBi(Zn1/2Ti1/2)O3 and (1 − x)SrTiO3–xBi(Zn1/2Ti1/2)O3

Ceramics of composition (1−x)BaTiO3–xBi(Zn1/2Ti1/2)O3 (BT‐BZT) were prepared by solid‐state synthesis; they have been shown to exhibit excellent properties suited for high‐temperature dielectric applications. The X‐ray diffraction data showed a single‐phase perovskite structure for all the compositions prepared (x ≤ 0.1 BZT). The compositions with less than 0.075 BZT exhibited tetragonal symmetry at room temperature and pseudo‐cubic symmetry above it. Most notably, a significant improvement in insulation properties was measured with the addition of BZT. Both low‐field AC impedance and high‐field direct DC measurements indicated an increase in resistivity of at least two orders of magnitude at 400°C with the addition of just 0.03 BZT (~107 Ω‐cm) into the solid solution as compared to pure BT (~105 Ω‐cm). This effect was also evident in dielectric loss data, which remained low at higher temperatures as the BZT content increased. In conjunction with band gap measurements, it was also concluded that the conduction mechanism transitioned from extrinsic for pure BT to intrinsic for 0.075 BZT suggesting a change in the fundamental defect equilibrium conditions. It was also shown that this improvement in insulation properties was not limited to BT‐BZT, but could also be observed in the paraelectric SrTiO3–BZT system.

Characterization of some properties on boards produced with bark of <i>Pinus pinaster</i> Ait. and produced with expanded vermiculite

The search for new applications to use boards requires innovation of their pro-perties. The improvement of insulation properties, the possibility to regulate the environmental conditions, the improvement of fire resistance and the increase of physical and mechanical properties allow a more diverse use of boards. Using new components in the production of boards and/or component materials also called composites (1), enables the improvement of these properties. This publication analyses different physical and mechanical properties of various types of single-layer boards produced either based on expanded vermiculite particles bonded with soluble silicate glasses (2) or based on lignocelluloses particles bark of Pinus pinaster Ait., agglutinated with cement derivatives of magnesium (3), the latter included in the classification of the norm (4). Commercial wood wool boards (5) are used as reference material.