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The Influence of Shear Stress on Crystallization in an Ultrasound Levitator
Author(s) -
Sacher S.,
Krammer G.
Publication year - 2007
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/ceat.200700222
Subject(s) - materials science , crystallization , shear stress , particle size , shear (geology) , precipitation , calcium carbonate , particle size distribution , suspension (topology) , crystal (programming language) , shear rate , particle (ecology) , chemical engineering , mineralogy , composite material , chemistry , rheology , geology , meteorology , oceanography , physics , mathematics , homotopy , computer science , pure mathematics , engineering , programming language
Industrial precipitation processes often use chemical agents to influence crystal morphology and size distribution. This experimental study deals with the investigation of physical parameters including an alternative method to affect crystal growth, thus, avoiding the presence of additives as intrinsic impurities. The influence of shear stress acting on growing crystals within a droplet is investigated in an ultrasound levitator. An ultrasound levitator enables the suspension of a single droplet against gravity and the study of containerless precipitation with specific mechanical forces acting on crystals. The levitator is used as a three‐phase reactor with precipitation from the gas and liquid, and as a reactor for precipitation from two different solutions. Calcium carbonate is used as a model system. The variation of temperature and the amount of applied shear stress leads to different amounts of calcium carbonate morphologies. An increase in the shear stress results in more rounded or spherical crystals. The intensity of the shear stress also influences the particle size distributions of the precipitated crystals, i.e., with increasing shear stress, particle size distributions are shifted to smaller sizes.