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The thermal stability and degradation, near-to-surface mechanical properties, and scratch resistance and damage mechanism of poly(etheretherketone) (PEEK)/reduced graphene oxide (RGO) nanocomposite coatings are analyzed and discussed in terms of their nanosheet content and microstructure. Although RGO modified the thermal stability and degradation of the polymeric matrix, for instance, by slightly reducing the onset degradation temperature, its addition was not a limiting factor in the PEEK processing. Respecting the microstructural features induced by the nanosheets, the nanocomposite coatings were found to exhibit (i) a partially exfoliated and large-scale co-continuous morphology related to RGO nanosheets whose basal planes were mainly aligned with the coating surface, (ii) a dendritic morphology of PEEK domains related to transcrystallinity, (iii) and irregular domains associated with the deposition of PEEK particles wrapped by the nanosheets. The changes provoked by RGO in the morphology and PEEK crystalline phase influenced the near-to-surface mechanical properties, scratch resistance, and scratch damage mechanism of the nanocomposite coatings. Within this context, the interlayer strength between the nanosheets in the large-scale co-continuous morphology and PEEK transcrystallinity had an important effect. Furthermore, the random-bumpy surface texture formed by the irregular PEEK domains together with the conformal cracking damage mechanism was decisive in the scratch response of the PEEK/RGO nanocomposite coatings. The comprehensive characterization carried out in this work concludes that PEEK/RGO electrophoretic coatings are suitable for a variety of applications requiring tribo-mechanical resistance. [ABSTRACT FROM AUTHOR]

The effect of the chemical composition on the morphology and microstructure of poly(ether ether ketone) (PEEK)/reduced graphene oxide (RGO) nanocomposite coatings is analyzed. RGO induced three main morphological features in the nanocomposites: (i) a large-scale co-continuous morphology related to nanosheets whose basal planes were mainly aligned with the coating surface, (ii) a dendritic morphology of PEEK domains, and (iii) irregular domains related to the deposition of PEEK particles wrapped by the nanosheets. The development of these morphological features was influenced by the RGO content, allowing the modification of the surface roughness. RGO also induced changes in the melting and non-isothermal crystallization of the polymeric matrix and promoted transcrystallinity in PEEK that, in turn, was a key factor in the development of the final microstructure. In addition, polymer chain mobility was observed to be hindered at high nanofiller concentrations, increasing the glass transition temperature, and diminishing the recrystallization of the polymeric matrix. [ABSTRACT FROM AUTHOR]

The simulation of the electrical resistance sintering (ERS) of hardmetal powders has been studied. The ERS process can produce a quick consolidation of electrical conductive powders by the simultaneous application of pressure and electrical current. A model of the process has been developed, integrating three actions, namely, thermal, mechanical and electrical, and taking into account the nature of both the powders and the die where powders are placed. The model has been implemented in COMSOL Multiphysics, a finite element commercial program. This paper deals with the model fundamentals and hardmetal particular aspects, such as modelling properties of mixed powders and its thermal behaviour. Other parameters in the model have been tuned to optimally fit the initial experimental data. To check simulation results, measurable parameters have been monitored during experimental tests with WC–6 wt% Co. Once the model was completed and put to work, results are discussed. [ABSTRACT FROM AUTHOR]