TY - JOUR

T1 - The effect of ball mass on the mechanochemical transformation of a single-component organic system

T2 - anhydrous caffeine

AU - Michalchuk, Adam A.L.

AU - Tumanov, Ivan A.

AU - Boldyreva, Elena V.

N1 - Publisher Copyright: © 2018, The Author(s).

PY - 2018/10/1

Y1 - 2018/10/1

N2 - Abstarct: Mechanochemical methodologies, particularly ball milling, have become commonplace in many laboratories. In the present work, we examine the effects of milling ball mass on the polymorphic conversion of anhydrous caffeine. By investigating a single-phase system, the rate-limiting step of particle–particle contact formation is eliminated. It is found that larger milling balls lead to considerably faster conversion rates. Modelling of the transformation rate suggests that a single, time-independent rate constant is insufficient to describe the transformation. Instead, a convolution of at least two rate-determining processes is required to correctly describe the transformation. This suggests that the early stages of the transformation are governed only by the number of particle–ball collisions. As the reaction proceeds, these collisions less frequently involve reactant, and the rate becomes limited by mass transport, or mixing, even in originally single-phase systems, which become multi-phase as the product is formed. Larger milling balls are less hindered by poorly mixed material. This likely results from a combination of higher impact energies and higher surface areas associated with the larger milling balls. Such insight is important for the selective and targeted design of mechanochemical processes.

AB - Abstarct: Mechanochemical methodologies, particularly ball milling, have become commonplace in many laboratories. In the present work, we examine the effects of milling ball mass on the polymorphic conversion of anhydrous caffeine. By investigating a single-phase system, the rate-limiting step of particle–particle contact formation is eliminated. It is found that larger milling balls lead to considerably faster conversion rates. Modelling of the transformation rate suggests that a single, time-independent rate constant is insufficient to describe the transformation. Instead, a convolution of at least two rate-determining processes is required to correctly describe the transformation. This suggests that the early stages of the transformation are governed only by the number of particle–ball collisions. As the reaction proceeds, these collisions less frequently involve reactant, and the rate becomes limited by mass transport, or mixing, even in originally single-phase systems, which become multi-phase as the product is formed. Larger milling balls are less hindered by poorly mixed material. This likely results from a combination of higher impact energies and higher surface areas associated with the larger milling balls. Such insight is important for the selective and targeted design of mechanochemical processes.

KW - COCRYSTALLIZATION

KW - IN-SITU

KW - MECHANICAL ACTIVATION

KW - MECHANOSYNTHESIS

KW - PHASE-TRANSFORMATIONS

KW - POLYMORPH CONTROL

KW - POWDER MIXTURES

KW - RAMAN-SPECTROSCOPY

KW - TEMPERATURE

KW - X-RAY-DIFFRACTION

UR - http://www.scopus.com/inward/record.url?scp=85045746777&partnerID=8YFLogxK

U2 - 10.1007/s10853-018-2324-2

DO - 10.1007/s10853-018-2324-2

M3 - Article

C2 - 30996469

AN - SCOPUS:85045746777

VL - 53

SP - 13380

EP - 13389

JO - Journal of Materials Science

JF - Journal of Materials Science

SN - 0022-2461

IS - 19

ER -