Flash cold sintering of Nb₂O₅: polarity and electrolyte effects

Abstract

We report on a novel consolidation technique based on the combination of a liquid (cold sintering) and electricity (flash sintering). The evolution of hydrogen from electrolysis of the solvent triggered the Flash Cold Sintering (FCS) event without need for external heating. Electrochemical effects became pronounced in the presence of acetic acid solution as the electrolyte had an increased conductivity compared to pure water. By adjusting the acetic acid molar concentration to 0.5 M and by inverting the polarity during FCS a 5 mm diameter 0.8 mm thick Nb 2 O 5 sample was evenly sintered up to 99% in 100 s at a temperature as low as 350°C. Conventional sintered counterparts achieved a 95% relative density when dwelled for 240 min at 1400°C. The inherent complexity of the proposed FCS approach resulted in enhanced densification and weakly translucent samples.

Influence of structural and surface properties of Nb2O5 pellets on methylene blue adsorption and adsorbent reuse capacity

“…However, heat treatment had no significant effects on apparent porosity or apparent density. These findings can be explained by the fact that pellet specimens did not undergo densification, given that the sintering temperature of Nb 2 O 5 is above 1250 °C [37]. It can also be seen from Table II that the average porosity of samples was about 46%.…”

Flash Sintering Research Perspective: A Bibliometric Analysis

“…It has proved to be an effective technique for the sintering of ceramic coatings on metallic substrates. The combination of FS with Cold Sintering has resulted in Cold Flash Sintering (CFS), where the presence of relatively small amounts of liquids, such as water of acetic acid, on the pellets are used as electrolytes and enables the flash event even at room temperature [90,91]. Last but not least, the efforts made by the pioneers in the field, Prof. Raj and others, have been relevant by spreading the topic through the scientific community by inviting visitors to their labs, collaborating with other groups, giving lectures, and organizing successful International Conferences on the topic "Electromagnetic/Electric Fields in materials processing" such as those held on 2016 and 2019 in Tomar (Portugal) or the symposiums arranged by the Materials Research Society (MRS).…”

Cold sintering process of hydroxyapatite derived from natural bone and co-precipitation method: a comparative study

“…In CSP, the initial powder is mixed with a solvent that partially dissolves the particles to facilitate the mass transport of powders at low temperatures under a uniaxial pressure [7]. The cold sintering process (CSP) is used for sintering numerous ceramics and composite materials made from extremely different materials, like polymer/ceramics [12][13][14][15][16][17][18][19][20][21][22]. However, Hassan and Ryu have recently reported the synthesis of high-density iodine-substituted Hydroxyapatite without adding any solvent via CSP, which obviously does not conform to the classical dissolution−precipitation mechanism.…”