Microstructural and Mechanical Characterization of Colloidal Processed WC/(W5Vol%Ni) via Spark Plasma Sintering

This study investigates the sintering behaviour and properties of WC-based composites in which WC was mixed with W5vol%Ni in concentrations of 10vol% and 20vol%. Colloidal processing in water and spark plasma sintering were employed to disperse the WC particles and facilitate sintering. The addition of W5vol%Ni improved the sintering process, as evident from a lower onset temperature of shrinkage determined through dilatometric studies. All samples exhibited the formation of tungsten monocarbide (W₂C), with a more pronounced presence in the WC/20(W5vol%Ni) composite. Sintering reached its maximum rate at 1550 °C and was completed at 1600 °C, resulting in a final density exceeding 99.8%. X-ray diffraction analysis confirmed the detection of WC and W₂C phases after sintering. The observed WC content was higher than expected, which may be attributed to carbon diffusion during the process. Macro-scale mechanical characterisations revealed that the WC/10(W5vol%Ni) composite exhibited a hardness of 18.9 GPa, while the WC/20(W5vol%Ni) composite demonstrated a hardness of 18.3 GPa. Increasing the W5vol%Ni binder content caused a decrease in mechanical properties due to the formation of W₂C phases. This study provides valuable insights into the sintering behavior and properties of WC/W5vol%Ni composites, offering potential applications in extreme environments.

Free-Standing Faradaic Motors Based on Biocompatible Nanoperforated Poly(lactic Acid) Layers and Electropolymerized Poly(3,4-ethylenedioxythiophene)

The electro-chemo-mechanical response of robust and flexible free-standing films made of three nanoperforated poly(lactic acid) (pPLA) layers separated by two anodically polymerized poly(3,4-ethylenedioxythiophene) (PEDOT) layers has been demonstrated. The mechanical and electrochemical properties of these films, which are provided by pPLA and PEDOT, respectively, have been studied by nanoindentation, cyclic voltammetry, and galvanostatic charge-discharge assays. The unprecedented combination of properties obtained for this system is appropriated for its utilization as a Faradaic motor, also named artificial muscle. Application of square potential waves has shown important bending movements in the films, which can be repeated for more than 500 cycles without damaging its mechanical integrity. Furthermore, the actuator is able to push a huge amount of mass, as it has been proved by increasing the mass of the passive pPLA up to 328% while keeping the mass of electroactive PEDOT unaltered.