Nanocarbon-Based Fibrous Substances That Are Safe For Use

A methodology is presented to investigate safety aspects of processes for the manufacturing and machining of metallic fiber-reinforced composites. The aim is to establish application-safe processes by identifying risks of releasing potentially hazardous dusts at an early stage and by selecting suited protective measures. In the application investigated here, composites made of copper (Cu) with carbon nanotubes (CNT) or carbon nanofibers (CNF) are produced and processed. As electrical conductors and as thermally conductive contact materials, they benefit from the properties of the added carbon materials. On the one hand, tangled carbon nanotubes with diameters of approx. 20 nm and rigid CNFs with diameters of approx. 100 nm were used. For both types of fibers, the dust release propensity of the dry powder was first determined in the laboratory by morphologically characterizing, classifying and quantifying the dust produced in a vibrofluidization process. To assess the fiber exposure of employees, the airborne fiber number concentrations were then measured at the workplaces for producing and machining both composite materials. A new measurement protocol for aerosols containing nanoscale fibers was applied, which is currently being validated in a project funded by the German Social Accident Insurance (DGUV).