Mechanism of Bi−Ni Phase Formation in a Microwave‐Assisted Polyol Process. Issue 11 (1st October 2020)

• Record Type: Journal Article
• Authors: Smuda, Matthias; Damm, Christine; Ruck, Michael; Doert, Thomas
• Is Part Of: ChemistryOpen. Volume 9:Issue 11(2020)
• Page Start: 1085
• Page End: 1094
• Publication Date: 2020-10-01
• Subjects: intermetallic phases -- nanoparticles -- polyol processes -- microwave assisted synthesis -- reduction reactions; Chemistry -- Periodicals; 540; 540.5
• DOI: 10.1002/open.202000236
• Languages: English
• ISSNs: 2191-1363

Abstract

Abstract: Typically, intermetallic phases are obtained in solid‐state reactions or crystallization from melts, which are highly energy and time consuming. The polyol process takes advantage of low temperatures and short reaction times using easily obtainable starting materials. The formation mechanism of these intermetallic particles has received little attention so far, even though a deeper understanding should allow for better synthesis planning. In this study, we therefore investigated the formation of BiNi particles in ethylene glycol in a microwave‐assisted polyol process mechanistically. The coordination behavior in solution was analyzed using HPLC‐MS and UV‐Vis. Tracking the reaction with PXRD measurements, FT‐IR spectroscopy and HR‐TEM revealed a successive reduction of Bi 3+ and Ni 2+, leading to novel spherical core‐shell structure in a first reaction step. Bismuth particles are encased in a matrix of nickel nanoparticles of 2 nm to 6 nm in diameter and oxidation products of ethylene glycol. Step‐wise diffusion of nickel into the bismuth particle intermediately results in the bismuth‐rich compound Bi3 Ni, which consecutively transforms into the BiNi phase as the reaction progresses. The impacts of the anion type, temperature and pH value were also investigated. Abstract : The intermetallic phase formation by a microwave‐assisted polyol process was investigated for the Bi−Ni system, revealing a core‐shell diffusion mechanism. Species in solution prior to the reduction as well as influences of anion type, pH value and temperature were investigated.