Lab 2 synthesis of aqueous ferrofluid by Hanna Thomson PDF

Preview

Summary

synthesis of aqueous ferrofluid to study it's behavior and response to varying strengths of applied magnetic fields lab report by Hanna Thomson...

Description

Hanna Thomson Lab 2: ferrofluids W 2pm chem314

Lab 2: Synthesis of Aqueous Ferrofluid Methods and Background The purpose of this lab was to synthesize ferrofluid and observe its properties and characteristics. Ferrofluid is a liquid magnetic material initially invented by NASA as a way to attract rocket fuel in an environment that lacks gravity, such as outer space, by applying an electric field to it. In our case, ferrofluid refers to the iron (ferrous) nanoparticles suspended in an organic solvent such as NH3, and stabilized by a surfactant (tetramethylammonium hydroxide). The magnetic nanoparticles are about 10nm in diameter or less to overcome charge-charge interaction between particles and aggregating together interrupting the magnetic properties ferrofluid displays, which is another reason why tetramethylammonium hydroxide is used to coat all the individual particles and prevent clumping or interactions.

Figure 1: chemical reaction used for synthesis of ferrofluid. Image obtained from http://whatwhen-how.com/nanoscience-and-nanotechnology/magnetic-nanoparticles-in-fluid-suspensionferrofluid-applications-part-1-nanotechnology/

Hanna Thomson Lab 2: ferrofluids W 2pm chem314

Above in figure one is the chemical reaction used for the synthesis of aqueous ferrofluid, where two moles of iron (III) chloride are reacted with one mole of iron (II) chloride and eight moles of ammonia as well as four moles of water to produce iron (III) tetroxide and eight moles of ammonium chloride. The iron (III) tetroxide are the observed magnetic nanoparticles, which are suspended in the eight moles of ammonium chloride solvent. The ferrofluid presents magnetic properties due to the crystal structures of iron (II) and iron (III). Iron (III) possesses 25% of an octahedral structure as well as 12.5%, and iron (II) possesses only 25%. Due to iron (III) electron spins being aligned anti-parallel, iron (III) does not display magnetic properties. However iron (II) electrons are aligned parallel to each other so it does display magnetic properties, which is why ferrofluid is deemed “superparamagnetic” meaning the substance reacts in the presence of an electric field but is able to turn its magnetism on and off due to its properties. There are two other materials that show similar behaviors as our synthesized ferrofluid, both being MnFe2O4 and CoFe2O4 due to similar crystal structure arrangements and electron spin states. Upon synthesizing ferrofluid, we found it displays a stronger magnetic behavior after the addition of 1-2mL of tetramethylammonium hydroxide because now all the nanoparticles are stabilized and suspended in aqueous solution not allowed to aggregate together, disrupting any van der waals interactions happening between them. The strength of the magnet also affected the behavior of our ferrofluid, we observed that a stronger magnet attracted the particles more aggressively and a weaker magnet showed less of a magnetic attraction towards the fluid. This is because introducing a weak magnetic field to the particles will only weakly attract the particles

Hanna Thomson Lab 2: ferrofluids W 2pm chem314

towards the magnet, and adding a strong magnetic field will align the nanoparticles more strongly to the magnetic field.

Procedure We began by making a 10mL solution from a 2M HCl solution using concentrated 12M HCl, and then a 4mL of a 1M solution of FeCl3 in 2M HCl, as well as a 1mL of a 2M solution of FeCl2 in 2M HCl. We then checked the iron solutions to ensure that the iron didn’t oxidize by taking 1M FeCl3 in 2M HCl and we observed an orange color if the iron was in the correct oxidation state. And taking 2M FeCl2 in 2M HCl we observed a light green/amber color if the iron was again in the correct oxidation state. We proceeded by taking 4.0mL of 1M FeCl3 and 1.0mL of 2M FeCl2 and adding both solutions to a 100mL beaker, mixing iron (II) and iron (III) in to one solution. Next we prepared 50mL of a 1M NH3 solution from concentrated ammonium hydroxide. While stirring the solutions in the 100mL beaker, we added 1mL of the 1M NH3 solution every 10 seconds and continuously stirring until all of the NH3 had been added. This allowed the iron nanoparticles to be suspended in an aqueous solvent. After stirring we allowed the mixture to settle and placed a strong magnet under the beaker to pull all of the magnetic particles to the bottom of the beaker to isolate the magnetic ferrofluid from the clear solution. We decanted the remaining transparent liquid from the beaker in to the waste container by simply pouring it out and keeping the magnet under the bottom of the beaker.

Hanna Thomson Lab 2: ferrofluids W 2pm chem314 After decanting the clear liquid we transferred the remaining solid to a weighing boat and placed a magnet underneath again, and repeated the same step as above. We then were supposed to add 1-2mL of 25% tetramethylammonium hydroxide to suspend the ferrofluid in the liquid, however we skipped this step and observed another labs demonstration that had used the tetramethylammonium hydroxide stabilizer, and recorded our observations. The tetramethylammonium hydroxide would act as our surfactant coating the individual nanoparticles and not allowing them to aggregate together and preventing any interactions between the charged particles, allowing our ferrofluid to behave better. Data and Calculations Dilution calculations: General dilution formula: M 1V1=M2V2 1.) 10mL of 2M HCl (10mL)(2M)=(12M)(V2): V2=1.67mL of HCl 2.) 4mL of 1M FeCl3 in 2M HCl (4mL)(1M)=(2M)(V2): V2= 2mL of 2M HCl 3.) 1mL of 2M solution FeCl2 in 2M HCl (1mL)(2M)=(2M)(V2): V2= 1mL 2M HCl 4.) 50mL 1M NH3 from 14.5M NH3OH (50mL)(1M)=(14.5M)(V2): V2=3.45mL NH3OH Chemical table: Chemical name

Hydrochloric acid

Chemic

Molecul

Freezin

Meltin

Density

al

ar

g point

g point

(g/mL)

formul

weight

(C)

(C)

a HCl

(g/mol) 36.46 Depen ds on

Depen ds on

1.2

Hazards

PPE

Corrosive/s

Gloves/gogg

kin

les

Hanna Thomson Lab 2: ferrofluids W 2pm chem314 Iron (III) chloride Iron (II) chloride Ammonium hydroxide Ammonia

FeCl3 FeCl2 NH3OH

NH3

Tetramethylammon

N(CH-

ium hydroxide

3

[M] 162.2 306 126.751 677 35.046 -91.5

17.031

91.15

-77.73

67

[M] 318 1023 24.7

2.9 3.16 880

irritation corrosive corrosive Skin/throat

-

-33.34

kg/m3 0.73kg/

irritation irritation

-

NA

m3 1.015

Skin

-

)4+OH-

irritation

Observations: 

Dilutions already prepared



1M FeCl3 in 2M HCl appeared orange/amber color=not oxidized



2M FeCl2 in 2M HCl appeared light green/orange color=not oxidized



Upon addition of 1M NH3 solution a black deep red color started to appear before dissolving, then persisted upon addition of almost all ammonia



Solid settled to the bottom and separated from clear liquid after approximately 15 seconds



No tetramethylammonium hydroxide left in lab, step skipped so magnetic attraction of particles to magnetic field was not as strong

Conclusion The purpose of this lab was to synthesize aqueous ferrofluid and study its magnetic properties and observe the effects of applying a magnetic field near it. FeCl2 and FeCl3 were mixed with NH3 and tetramethylammonium hydroxide to produce a magnetic ferrofluid, which in response to a magnetic field displays “spikes” where the magnetic iron nanoparticles align themselves with the direction of the electric field. This has to do with the

Hanna Thomson Lab 2: ferrofluids W 2pm chem314 nanoparticles being “superparamagnetic” meaning they have magnetic properties but the magnetism is not a permanent state. In iron (III) chloride, the crystal structure allows for the electrons to be aligned anti-parallel to each other, iron (III) does not possess magnetic properties which is why it is mixed with am iron (II) solution which does possess magnetic properties due to the electrons in the crystal structure being aligned parallel to each other. Overall our ferrofluid was relatively weak due to a few experimental reasons, one being that we did not have any tetramethylammonium hydroxide, and another depended on the strength of the magnet used to test it. A weaker magnet did not attract the ferrofluid very effectively, but the stronger magnet did induce a better behavior from our uncoated magnetic nanoparticles. Citations 1.) schaller, chris. CC8. Ligand Field Theory. https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_(Inorgan ic_Chemistry)/Organometallic_Chemistry/Ligand_Binding_in_Coordination_Complexes/CC8._Lig and_Field_Theory (accessed Mar 12, 2019). 2.) berger, patricia; adelman, nicholas b; beckman, katie j; campbell, jean d; ellis, arthur b; lisensky, george c. preparation and properties of an aqueous ferrofluid. http://homes.nano.aau.dk/tgp/ferrofluid.pdf (accessed Mar 12, 2019). 3.) Magnetic Nanoparticles in Fluid Suspension: Ferrofluid Applications Part 1 (Nanotechnology). http://what-when-how.com/nanoscience-and-nanotechnology/magnetic-nanoparticles-in-fluidsuspension-ferrofluid-applications-part-1-nanotechnology/ (accessed Mar 12, 2019). 4.) Ferrofluid. https://en.wikipedia.org/wiki/Ferrofluid (accessed Mar 12, 2019)....