Open AccessMechanism of Bi−Ni Phase Formation in a Microwave‐Assisted Polyol Process
Author(s) -
Smuda Matthias,
Damm Christine,
Ruck Michael,
Doert Thomas
Publication year - 2020
Publication title -
chemistryopen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 29
ISSN - 2191-1363
DOI - 10.1002/open.202000236
Subject(s) - ethylene glycol , intermetallic , polyol , materials science , nanoparticle , dehydrogenation , crystallization , chemical engineering , nickel , bismuth , reaction mechanism , particle (ecology) , phase (matter) , nanotechnology , chemistry , catalysis , organic chemistry , metallurgy , alloy , composite material , engineering , polyurethane , oceanography , geology
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 Bi 3 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.