Assignment A

Your report will illustrate how magnetic particles can be added to water to increase the viscosity of the suspension while controlling the settling velocity within the suspensions. Each group is tasked to include the behavior of suspensions that have solid concentrations between 0.01-0.50 volume fraction. In the first part of your report define terminal velocity and settling velocity. Then define the relative viscosity and apparent viscosity of a suspension. Explain why terminal velocity is used instead of the initial velocity or the velocity before the particles have accelerated due to gravity to the terminal velocity. Then as a measure of the time scales required provide the calculation for the time for each of the following particles to settle 0.1 m for

a.) 0.1,1.0,5.0,10 micron diameter silica sphere in water

b.) 0.25 ,1.0 ,2.0 ,5.0 ,10.0 micron diameter polystyrene sphere in water

c.) 10,20,30,40 micron diameter glass sphere in decane

d.) 50 micron, 500 micron, 1 mm, 2 mm diameter water droplet in air In the second part of your report discuss each of the following options for use as a magnetic fluid and the drawback of settling. (Assume the density of all of these particles for simplicity is 7900 kg/cubic meters.)

1. Iron Cobalt Nanoparticles (5-8 nanometer diameter) $100/g

2. Magnetite Powder (250-300 nanometer diameter) $10/g

3. Iron Carbonyl Sintered Powders (3-10 micrometer diameter) $1/g Give values for the viscosity and sedimentation velocity at volume fractions of 0.01, 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50. Make a table assuming 10 g of magnetic fluid is required for the application or end use. In the table give the the cost per fluid using each of the three options and the volume fractions. Then report on the maximum viscosity, minimum cost, and optimum composition that can be achieved for each particle choice