MAGNETIC HILLS

T A S K : A small amount of a ferrofluid placed in an inhomogeneous magnetic field forms hill-like structures. Investigate how the properties of these structures depend on relevant parameters.

BY ANASTASIA GUENOVA

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AGENDA• O R I G I N S O F F E R R O F LU I D• S Y N T H E S I S O F F E R R O F LU I D• H O M E - M A D E F E R R O F LU I D• C O LO R E D F E R R O F LU I D• N U M B E R O F S P I K E S A S A

F U N C T I O N O F D I S TA N C E T O M A G N E T

• I N V E S T I G AT I O N

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ORIGINS OF FERROFLUID• Ferrofluid is a liquid that becomes strongly

magnetized in the presence of a magnetic field

• Invented in 1963 by Steve Papell • A collection of superparamagnetic

nanoparticlesComposed of nanoscale particles (diameter usually 10 nanometers or less) of magnetite, hematite or some other compound containing iron, that are suspended in a liquid

• Ferrofluids lose their magnetic properties at a sufficiently high temperature (also known as the Curie temperature)

Steve Papell invented ferrofluid for NASA in

1963

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SYNTHESIS OF AQUEOUS FERROFLUIDStep 1: Add 4.0 mL of 1M FeCl3 and 1.0 mL of 2M FeCl2 solution to a 100 or 150 mL beaker.

Step 2: Continue stirring throughout the addition of 50 mL of 1.0 M aqueous NH3

Step 3: Let the magnetite settle. You can speed the settling process by putting a magnet under the container.Step 4: Decant (pour off) and discard the clear liquid without losing a substantial amount of solid. This works best if you keep a magnet under the container.

Step 5: Transfer the solid to a weighing boat with the aid of a few squirts from a wash bottle.

Step 6: Use a strong magnet to attract the ferrofluid to the bottom of the weighing boat.

Step 7: Pour off and discard as much clear liquid as possible, again keeping the magnet under the weighing boat.

Step 8: Add 1-2 mL of 25% tetramethylammonium hydroxide. Use a strong magnet to attract the ferrofluid to the bottom of the weighing boat. Pour off and discard the dark liquid. You are done!

HOMEMADE FERROFLUID

WHAT YOU HAVE TO DO:1. A bar magnet

5. A sponge 4. Vegetable

oil

3. A shallow dish

2. Iron filings

WHAT YOU NEED:

STEP 2STEP 1 STEP 35

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COLORED FERROFLUIDFollowing the same steps from the previous section, one further color ferrofluid for an added effect and interesting observations.

Step 1: Get a glowstick.

Step 2: Extract the luminescent liquid into a petri dish.

Step 3: Mix the luminescent liquid with the ferrofluid. Use a magnet to stir well.

The end result.

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NUMBER OF SPIKES AS A FUNCTION OF DISTANCE TO MAGNET

0 1 7 10 29 58 1060

0.51

1.52

2.53

3.54

4.54.1

3.53

2.5 2.3

1.71.2

Number of spikes

Dist

ance

bet

ween

the

ferro

fluid

and

th

e m

agne

t

BASED ON MY OWN RESEARCHThe experiment

was done using 2.5 ml store-bought ferrofluid and a neodymium magnet with 203N of power

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INVESTIGATION The factors which I found would affect the distance at which spikes formed:

The strength of the magnetThe magnetic strength of the fluidThe orientation of the magnet as it approaches the dish

When I pull the magnet away, the spikes disappear?That’s because individual particles of magnetite behave as tiny magnetic domains. Therefore, in the absence of a magnetic field and as a result of thermal agitation, the particles’ magnetic domains become randomly oriented relative to one another and the spikes disappear.

Why don’t the magnetic spikes stick together?That’s because in ferrofluids there must be something that acts as a dispersing agent (surfactant). This agent must adhere to the particles, surround them completely, and create a net repulsion between them. This means they can’t stick together.

What happens when you put a metal coin in the petri dish?Putting a metal coin in the ferrofluid allowed me to observe some interesting structures. As I brought the magnet closer to the ferrofluid, the coin stood on its side and the ferrofluid climbed on top of it.

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REFERENCES1. U N I V E R S I T Y O F W I S C O N S I N . M A D I S O N

M A T E R I A L S R E S E A R C H S C I E N C E A N D E N G I N E E R I N G C E N T E R

2. N A T I O N A L H I G H M A G N E T I C F I E L D L A B O R AT O R Y

3. W I K I P E D I A T H E F R E E E N C Y C L O P E D I A

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THANK YOU FOR YOUR ATTENTIONI F Y O U H AV E A N Y Q U E S T I O N S , P L E A S E D O N ’ T B E S H Y T O E - M A I L M E O N : G U E N O VA . A N A S TA S I A @ G M A I L . C O M