Thermal efficiency of metal foams on pool boiling

This paper presents an experimental work on pool boiling using HFE-7100 at saturated conditions, under atmospheric pressure, and copper and nickel foams as the heating surface with four different thicknesses varying between 0.5 mm and 3 mm, followed by an analysis of the effect of foam fin-efficiency based on Ghosh model. All foams showed a better heat transfer coefficient (HTC) than the plain surface; however, as the heat flux increased, the HTC from the thicker nickel foams decreased due to the bubble vapor flow inside the foam. On the other hand, the thinner nickel foam showed better HTC at high heat fluxes with a maximum enhancement of 120%. The foam efficiency presented a similar tendency with the HTC, i.e., as the thickness decreases the efficiency increases; however, as compared with copper foams with a similar area but different porous diameter, the copper foams are 40% more efficient than the nickel ones due to the foam material, which has a thermal conductivity 4.5 times higher.

Carbon Paper as Current Collectors in Graphene Hydrogel Electrodes for High-Performance Supercapacitors

Current collectors are an important component of electrodes, functioning as conductive media by collecting currents from active materials and then exporting them to the external circuit. Common current collectors for graphene hydrogel (GH)-based supercapacitors are nickel foams or metal foils (platinum, gold, and aluminium, etc.). Here, hydrothermally synthesized GH was directly pressed on carbon paper and used as electrodes (denoted as GHE) for supercapacitors. With a mass loading of 2.7 mg·cm−2 at an active area of 0.64 cm2, the GHE-based supercapacitors revealed a high gravimetric capacitance of 294 F·g−1 at a current density of 1.18 A·g−1. When increasing the current density to 28.24 A·g−1, 66% (193 F·g−1) of the initial capacitance was maintained for the GHE-based supercapacitors. High performance for GHE-based supercapacitors was attributed to large specific surface area and good electrical conductivity of GH, and its intimate contact with carbon paper.

The morphology controlled growth of Co11(HPO3)8(OH)6 on nickel foams for quasi-solid-state supercapacitor applications

Co11(HPO3)8(OH)6 microstructures with different morphologies growing on NF were synthesized under different conditions, and the flower-like sample presents excellent electrochemical properties.