Open-cell aluminum foams were manufactured by a sponge replication technique having a total porosity of ~90%. The influence of the thermal processing conditions such as atmosphere and temperature on the cellular structure, phase composition porosity, thermal conductivity, and compressive strength of the foams was studied. It was found that the thermal processing of aluminum foams in Ar at temperatures up to 800 °C led to aluminum foams with a reduced strut porosity, a lower amount of aluminum oxide, a higher thermal conductivity, and a higher compression strength, compared to foams thermally processed in air. These results were explained by the lower amount of aluminum oxide after thermal processing of the foams.

In the current study, the properties of the CrxN coatings deposited on the Inconel 718 superalloy using direct current reactive magnetron sputtering are investigated. The influence of working pressure on the microstructure, mechanical, and tribological properties of the CrxN coatings before and after high-temperature hydrogen exposure is studied. The cross-sectional scanning electron micrographs indicate the columnar structure of the coatings, which changes from dense and compact columns to large columns with increasing working pressure. The Cr/N ratio increases from 1.4 to 1.9 with increasing working pressure from 300 to 900 mPa, respectively. X-ray diffraction analysis reveals a change from mixed hcp-Cr2N and fcc-CrN structure to approximately stoichiometric Cr2N phase. After gas-phase hydrogenation, the coating deposited at 300 mPa exhibits the lowest hydrogen absorption at 600 °C of all investigated coatings. The results indicate that the dense mixed cubic and hexagonal structure is preferential for hydrogen permeation resistance due to the presence of cubic phase with higher packing density in comparison to the hexagonal structure. After hydrogenation, no changes in phase composition were observed; however, a small amount of hydrogen is accumulated in the coatings. An increase of coating hardness and elastic modulus was observed after hydrogen exposure. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient up to 20%–30%. The best value of 0.25 was reached for hydrogen exposed CrxN coating deposited at 300 mPa.

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.

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