Piotr Bazarnik

The influence of carbon fillers on the thermal properties of polyurethane foam

The aim of this work was to investigate the influence of different types of carbon filler on the thermal stability and flammability of rigid polyurethane foams. As a filler, multi-walled carbon nanotubes and graphite fakes were used. Scanning electron microscopy was used to observe the structure of foam and dispersion of nanofiller in polymer matrix. Thermal stability of these composites was determined by thermogravimetry analysis. Test was carried out under both nitrogen and air atmosphere. The degradation products were evaluated by thermogravimetry (TG) combined with infrared spectroscopy (TG–IR) measurements. The activation energy was measured by the Flynn–Wall–Ozawa method from the TG curves. Flammability tests like limiting oxygen index and smoke density were also measured. No significant changes in the thermal stability of the composites were observed. The activation energy of sample containing carbon filler increased. Based on TG–IR, one can notice that there were no differences in the emitted volatile products during thermal degradation. Carbon filler enhanced fire retardancy of polyurethane foam; however, graphite gives better results.

The Strength and Ductility of 5483 Aluminium Alloy Processed by Various SPD Methods

Grain size refinement is an efficient way to improve mechanical strength and thus make light metals even lighter in terms of specific strength. However, the strength improvement is at the expense of ductility. Therefore, a better understanding of microstructural factors influencing both parameters is of prime importance for further development of ultrafine grained materials. In this work, we report results obtained for 5483 aluminium alloy which was subjected to several severe plastic deformation (SPD) methods, i.e. equal channel angular pressing (ECAP), Hydrostatic Extrusion (HE) and the combination of the two. Detailed microstructural analysis revealed significant difference in the grain size and grain boundary characteristics between samples obtained following different routes. It was found that although the grain size is a prime microstructural parameter determining mechanical strength, second order factors such as grain size distribution and distribution of grain boundary misorientation angles also play a significant role.

Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique

The presented paper investigates the relationship between the microstructure and thermal properties of copper-silicon carbide composites obtained through hot pressing (HP) and spark plasma sintering (SPS) techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal-ceramic boundary. It is the product of silicon dissolving process in copper occurring at an elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

Thermal stability and mechanical properties of HPT-processed CP-Ti

A grade 2 commercial pure titanium was processed by high-pressure torsion (HPT) at room temperature to 20 turns. X-ray analysis showed that an ω phase formed during HPT processing but disappeared immediately during 10 minutes post-HPT short-term annealing even at a very low temperature of 473 K. The thermal stability of HPT-processed microstructural evolution was studied by electron backscatter diffraction (EBSD). After short-term annealing at lower temperatures (473 and 673 K), the disc centre had relative higher hardness value than the edge area, and it was found that the centre retained the feature of deformed microstructure whereas the edge showed recovery / recrystallization of the microstructure. Short-term annealing at higher temperatures (873 and 973 K) led to almost uniformly distributed hardness and microstructures in the disc centre and edge areas. Grain structures and hardness measurements indicate complete recrystallization occurred at 873 K.

Influence of carbon nanotubes on mechanical properties and structure of rigid polyurethane foam

In this work, the influence of carbon nanotubes addition on foam structure and mechanical properties of rigid polyurethane foam/nanotube composites was investigated. Scanning electron microscopy was performed to reveal the foam porous structure and distribution of carbon nanotubes. To determine the mechanical properties, three point bending tests were carried out.