Nanoporous metals are a point of interest in academia and industry due to its chemical, mechanical and optical properties that enables their use in catalysis, micro-actuation, and energy production and storage. This study investigates the influence of ligament size of nanoporous copper powders (NPC) on the enhancement of its low-temperature sinterability. Powders were fabricated via both acidic and alkaline chemical dealloying of Cu33Al67 gas atomized powders enabling the tunability of ligament sizes from 20 to 150 nm. This metastable material was studied using differential scanning calorimetry (DSC) to identify its stability range and its recrystallization temperature. A broad exothermic peak has been observed on the temperature range from 95 to 270 oC which is attributed to the activation of thermal coarsening of nanosized ligaments. This phenomenon is mainly attributed to the thermal instability of ligaments similar to the thermal instability (i.e. the Gibbs-Thompson effect) of nanoparticles that are subjected to the minimization of curvature (i.e. energy reduction) upon heating. Additionally, SEM and FIB studies revealed the necking between neighboring particles at reduced sintering temperatures (300-500 oC). To exploit the benefits of low-temperature sinterability and understand the role of the native oxide in the sintering process, powders were casted into a rectangular mold and sintered in both inert and reducing atmosphere. Its electrical conductance was monitored during sintering and correlated to the thermal decomposition temperature of different copper oxides. Better understanding of its low-temperature sinterability represents a step towards constructing conductive nanoporous electrodes for applications in electrocatalysis, multi-material integration printing with polymers, and beyond.

Harvesting the low-temperature sinterability of nanoporous copper for the fabrication of electrically conductive porous parts

ACS Spring 2022

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