Hierarchical‐Porous Copper Foams by a Combination of Sponge Replication and Freezing Techniques

Abstract

Open‐porous copper foams with additional strut porosity are manufactured by two different manufacturing routes. The first is based on the Schwarzwalder sponge replication technique. The second method is a combination of Schwartzwalder sponge replication and freezing technique in which an additional strut porosity is generated inside the struts of the sponge‐replicated foams by freezing at −20 °C for 24 h and subsequent sublimation. Thermal processing of both types of foams is conducted at 500 and 900 °C for 6 h in a hydrogen‐containing atmosphere to reduce copper oxides and to facilitate the sintering process of the copper powder particles. Despite significant shrinkage of both foam series after thermal processing, hollow struts and lamellar pores keep their shape and do not collapse. The influences of the additional lamellar pores and thermal processing temperature on the cellular structure, porosity, specific surface area, yield strength, absorbed energy, and thermal conductivity are studied. The additional strut porosity generated by the freezing step significantly increases the specific surface area of the copper foams by a factor of 2 in comparison to the sponge replicated foams.

Manufacturing of Open-Cell Aluminium Foams: Comparing the Sponge Replication Technique and Its Combination with the Freezing Method

“…In this work, the foams had a random lamellar pore orientation, which may have increased the strength characteristics, despite the high porosity of the strut, via a load sharing mechanism [ 38 , 39 ]. This behaviour of the mechanical properties has also been observed for copper foams [ 23 ].…”

“…In refs. [ 21 , 22 , 23 ], ceramic and copper foams manufactured by this combination were also characterized by a similar lamellar pore orientation behaviour.…”

“…It was found that this combination of methods increased the total specific surface area of the foams from 70 to 200 cm 2 g −1 due to the additional formation of lamellar pores. In [ 23 ], the production of metal foams based on copper powder made by this combination of methods was presented for the first time, which also showed the positive effect of the additional lamellar strut pores on the specific surface area and the mechanical properties of the foams. Despite the high density of copper powder and its rapid settling in suspension, the copper foams had lamella pores along with the entire sample.…”

Recent Advances in the Development of Highly Conductive Structured Supports for the Intensification of Non-adiabatic Gas-Solid Catalytic Processes: The Methane Steam Reforming Case Study

“…More recently, an alternative approach has been proposed, which consists in the combination of sponge replication and freezing techniques using PU templates for the production of porous open-cell copper foams using an aqueous copper dispersion (Sutygina et al, 2021). Foams were effectively produced, and the relevance of processing conditions (temperature and atmosphere) on final structure properties was thoroughly discussed.…”

Assessment of the flow behavior and structural performance of open-cell aluminum foams at critical flow conditions of pressure and temperature

“…Nowadays, open-cell Al foams are in increasing demand. Owing to the properties offered by Al as base metal, in addition to their porous interconnected structure, open-cell Al foams can be tailored in a wide range of applications, e.g., lightweight materials with high stiffness [3], metallic foam panels for sound and energy absorption [3], in vibration damping and electromagnetic shielding [13], as well as in heat exchangers, filters, catalyst carriers, and electrodes in aluminum-air batteries, where the combination of thermal/electrical conductivity and liquid/gas permeability is needed [14]. The functionality and possible uses of open-cell Al foams are strongly associated with their pores' shape, size, distribution, and physical interconnection.…”