2. Materials and methods
2.1. Sample preparation
The material used in this work is a fluidized cracking catalyst (FCC)
powder supplied by Grace Davison (Columbia, MD). The tracer powder
is created by dying the FCC powder with Sharpie ink. First, the top of the
H.N. Emady et al. / Powder Technology 286 (2015) 392–400 393
Sharpie is broken off and the ink packet is removed. Acetone is used to
rinse the ink from the top as well as the ink packet into a beaker. After
the ink from the beaker is poured onto the powder, the acetone is
used again to wash out all of the excess ink from the beaker. Approximately
30 mL of acetone is used per Sharpie. Following the addition of
ink with acetone into the powder bed, the components are fully
mixed together in the beaker using a glass stirring rod until the powder
is consistently dyed. After one Sharpie's worth of ink is mixed with the
powder completely, another is added. This process is repeated until the
desired dye strength is achieved. Dye strength is measured by the number
of Sharpies used to dye 100 mL of powder. Dye strengths of 3–6 dyeing
procedures were prepared and tested.
Samples of the dyed powder were used to create mixtures with undyed
powder. For example, 0.05 g of colored powder mixed with 49.95 g
of un-dyed powder forms a sample that is 0.1% colored by mass. Continuing
with this process, mixtures of 0.1–1%, 1–10%, and 10–100% by
mass dyed powder were generated with ten equal increments for
each percentage range. This wide range of samples aids in determining
the extent of variations in powder concentration that the measurement
device can detect.