The importance of promising composites in modern materials science is constantly increasing. The use of various fillers or additives is associated with their influence not only on the defining properties of the composite, but also on physical and mechanical characteristics of the material. In this case, the distribution of the additive and its wetting with a polymer play an important role. The problem highlighted in this article is the influence of different copper-containing fillers (copper (II) sulphate powder, micro-sized copper (II) oxide powder, and nano-structured copper (II) oxide-based hollow microspheres) on the technological and physical–mechanical properties of the composites based on polylactic acid (PLA). The hollow microspheres of copper (II) oxide have been obtained by ultrasonic spray atomization via pyrolysis of copper (II) nitrate. The structure of the copper-based additives has been studied using X-ray diffraction, scanning electron microscopy, and static light scattering. For the PLA-composites, scanning electron microscopy, differential scanning calorimetry, stress-strain properties testing, and density analysis have been performed. The plasticizing effect of polycaprolactone and polyethylene glycol has been studied for the highly filled PLA/CuSO4 composite. The samples of PLA with over 2 wt.% of CuO microspheres have a full volume-filling and percolation structure of the additive’s particles. Due to the regular spherical shape of the particles and a lower specific volume, CuO hollow microspheres are uniformly distributed in the PLA matrix acting as a structuring and reinforcing modifier. Differential scanning analysis showed heterogeneous crystallization on CuO particles with an increase in the degree of crystallinity and the melting point of the polymer. It has been shown that the pre-masterbatching technology and adding plasticizers to obtain PLA composites contribute minimizing defects and enhance mechanical properties.
The paper addresses the issue of recycling granulated blast-furnace slag (gBFS) as a source for production of cement-free binder materials for further usage in rare-earth metals production for radioactive waste disposal. The use of the vortex layer activator was provided as main technique allowing to produce high-dispersed chemically activated binders. The paper examines the effect of processing conditions on the physical-chemical and mechanical properties of the resulting BFS-based cement-free materials and gBFSbased concretes.
Low-temperature (350 °C) vitrification in a KNO3-NaNO3-KHSO4-NH4H2PO4 system, containing various additives to improve the chemical durability of the obtained material, was investigated. It was shown that a glass-forming system with 4.2–8.4 wt.% Al nitrate admixtures could form stable and transparent glasses, whereas the addition of H3BO3 produced a glass–matrix composite containing BPO4 crystalline inclusions. Mg nitrate admixtures inhibited the vitrification process and only allowed obtaining glass–matrix composites with combinations with Al nitrate and boric acid. Using ICP and low-energy EDS point analyses, it was recognized that all the obtained materials contained nitrate ions in their structure. Various combinations of the abovementioned additives favored liquid phase immiscibility and crystallization of BPO4, KMgH(PO3)3, with some unidentified crystalline phases in the melt. The mechanism of the vitrification processes taking place in the investigated systems, as well as the water resistance of the obtained materials, was analyzed. It was shown that the glass–matrix composites based on the (K,Na)NO3-KHSO4-P2O5 glass-forming system, containing Al and Mg nitrates and B2O3 additives, had increased water resistance, in comparison with the parent glass composition, and could be used as controlled-release fertilizers containing the main useful nutrients (K, P, N, Na, S, B, and Mg).
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