Material Manufacturing: New Weld Wire Reduces Failures from Hydrogen Damage
Oak Ridge National Laboratories, along with several other federal agencies, has developed a new alloy for welding applications in hopes of improving weld strength. While there are few details on the specifics of the new alloy, the welding wires created aim to reduce the effectiveness of hydrogen attack along welds.
The mechanisms of hydrogen damage are not well understood, but there are two common pathways in which hydrogen can lead to or further cracking in alloys. The localized cracking leads to a weak spot in the component, which will eventually lead to failure of the component, often below expected stress values.
The role of temperature on defect diffusion and nanoscale patterning in graphene
Jesse said, “It heals locally, like the (fictitious) liquid-metal T-1000 in Terminator 2: Judgment Day.”
Graphene is of great scientific interest due to a variety of unique properties such as ballistic transport, spin selectivity, the quantum hall effect, and other quantum properties. Nanopatterning and atomic scale modifications of graphene are expected to enable further control over its intrinsic properties, providing ways to tune the electronic properties through geometric and strain effects, introduce edge states and other local or extended topological defects, and sculpt circuit paths. The focused beam of a scanning transmission electron microscope (STEM) can be used to remove atoms, enabling milling, doping, and deposition. Utilization of a STEM as an atomic scale fabrication platform is increasing; however, a detailed understanding of beam-induced processes and the subsequent cascade of aftereffects is lacking. Here, we examine the electron beam effects on atomically clean graphene at a variety of temperatures ranging from 400 to 1000 °C. We find that temperature plays a significant role in the milling rate and moderates competing processes of carbon adatom coalescence, graphene healing, and the diffusion (and recombination) of defects. The results of this work can be applied to a wider range of 2D materials and introduce better understanding of defect evolution in graphite and other bulk layered materials.