LAB 2-Synthesis of Aqueous Ferrofluid PDF

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Rita Ayisi Chem 314 F 8-10:50am 1/24/2020 Lab partner: Tatiana

Lab 2: Synthesis of Aqueous Ferrofluid Methods and Background The purpose of this lab was to examine the magnetic properties of ferrofluid and synthesize it with the help of iron (III) chloride, iron (II) chloride, ammonia and 25% tetramethylammonium hydroxide. Ferrofluids (magnetic fluid) is a fluid that is strongly magnetized by a magnetic field1. These types of fluid are described as a solution and a suspension that reacts to the magnetic field. This solution is made of nano-size particles up to 100 times smaller than the wavelength of light with a diameter of 10nm2. Iron oxides such as magnetite (Fe3O4) and hematite (Fe2O3) are the common materials used in synthesizing these magnetic particles. The liquid is pulled toward the magnetic field by the attraction of the nanoparticles. However, the nanoparticles can burst from the carrier fluid forming a cloud of dust when exposed to a strong magnetic force. A hydrocarbon which is a surfactant coating is placed on the surface to stop the clumping of the nanoparticle via van der Waals forces. The position and strength of the magnetic field cause the ferrofluid to flow. Ferrofluids have an important role in the reduction of friction which is effective in transportation and electronics. For example, ferrofluid can be applied in electronics to increase the performance of a speaker. It also has an advantage in the field of medicine as it can assist deliver a drug to the body. The importance of ferrofluid in medicine was discussed in the article “preparation and properties of an Aqueous Ferrofluid.” It states the effective of artificial heart implantation with ferrofluid. The main part of the ferrofluid is the crystalline magnetite nanoparticles which are named based on its structure. The magnetic property is due to its antiparallel electron spins which move around the structure. Superparamagnetic is one of the ferrofluid properties where the fluid reacts to the magnetic field. However, in this type of ferrofluid, its magnetism move quickly due to the sizes of the particles. For ferromagnetism, strong interaction with the magnetic field is observed even after the removal of an outside force. The net magnetic moment of this ferrofluid is due to the unpaired electrons. With its small sensitivity to the magnetic field, paramagnetic lose its

magnetic properties when an external force is removed. The realignment of the electrons is due to its unpaired electrons. And for diamagnetism, they have a weak sensitivity to the magnetic field and magnetic properties are lost after the removal of the external force. With this, their electrons are paired so there is no net magnetic moment. To chemically stabilize the magnetic nanoparticles, a surfactant such as a tetramethylammonium hydroxide is important. Surfactant is an agent that promotes adhering to the nanoparticles by forming a net repulsion which stabilizes the colloid. The formation of the magnetite particles was achieved by the addition of ammonium hydroxide. The formation of spikes was due to the decanting of the clear liquid. 25% of tetramethylammonium hydroxide was used to stabilize the formed nanoparticle and observed under a magnet. The liquid was decanted to enable the formation of spikes. Less decanting of the liquid will cause a loss of spikes in the magnetite.

Experimental Procedure First, 4 mL of 1 M iron (III) chloride and 1 mL of 2 M iron (II) chloride were added to 100 mL beaker. Then 50 mL of 1 M ammonia solution was prepared using 6 M NH4OH. The 50 mL solution of 1M NH3 solution was then poured into the 100 mL beaker containing the FeCl3 and FeCl2 solutions while stirring it manually with a glass rod. The solution was continuously stirred over a period of about 5 minutes while adding approximately 1 mL of NH3 to the solution mixture every second. The addition that is faster than the solution can be mixed or slower than the particles grow large was all avoided. The stirring was stopped after the addition of all the 50 mL of 1 M NH3 solution. The solution was then left to settle by placing the beaker under a strong magnet. After some minutes, the clear liquid was poured off without losing a chunk amount of the solid. The solid was then transferred into a weighing boat with the aid of a few squirts of deionized water from a wash bottle. A strong magnet was used to attract the ferrofluid to the bottom of the weighing boat. The clear liquid was then poured away while keeping the magnet under the weighing boat. The solid was then rinsed with deionized water from a wash bottle and the clear liquid was discarded. The magnetite was then transferred into the weighing boat after washing and 1-2 mL of 25% tetramethylammonium hydroxide was added to it. Magnetite with the 25% tetramethylammonium hydroxide was gently stirred with a glass rod for at least a minute to

suspend the solids in the liquid. A strong magnet was again used to attract the ferrofluid to the bottom of the weighing boat. The dark liquid was discarded and the magnet was moved again to pour off any liquid. The ferrofluid was then moved around under the weighing boat and the physical properties were observed. The distance of the magnetite was observed and recorded by moving the magnet.

Data and Observations Data Table

Chemical Name

Chemical

Molecular

Density

Boiling point

Formula

weight

Ammonium Hydroxide

NH5O

35.05 g/mol

0.9 g/cm3

38-100

Hydrochloric acid

HCI

36.45 g/mol

1.18 g/mL

Less than 100 -30

Iron (III) chloride

FeCl3

162.20 g/mol

2.80 g/mL

------

point

Color observations for FeCl3 and FeCl2

Compound

Observed color

2 M FeCl2 in 2 M HCl

light Green

1 M FeCl3 in 2 M HCl

Orange

Observed color change with the addition of 1M NH3 mL of 1M of Ammonia added

Freezing

Observed color change

-60

-----

1 mL

A changed from yellow greenish color to brown color was observed.

13 mL

A color change from yellow to orange was observed.

24 mL

A color change from orange to dark red was observed.

37 mL

A color change from scarlet red to brown was observed.

42 mL

A color change from brown to black was observed.

50 mL

An opaque dark black color was observed.

Results and calculations ❏ When the magnet was moved under the weighing boat, spikes were observed in the ferrofluid. ❏ The ferrofluid takes the shape of the magnetic when moved under the weighing boat. ❏ No spikes in the ferrofluid with the removal of the magnet.

Volume of NH3 needed (30 g NH3 / 100 mL sol’n) x (1 mol NH3 /35.0 g NH3 ) x 1000 mL = 8.5714 mol NH3

M1V1 =M2V2 (8.5714 mol) V1 = 1 M (50 mL) V1 = 5.833 mL NH3 Conclusion The objective of this lab was to make ferrofluids and observed the physical properties in a weighing boat with the help of a magnet. The first part was the preparation of magnetite nanoparticle (ferrofluids) with FeCl3, FeCl2, and NH4OH. The nanoparticles were then stabilized with the addition of 25% tetramethylammonium.

Tetramethylammonium was the surfactant added to the magnetite to stabilize the nanoparticles due to its van der Waals forces which restricted the aggregation of the ferrofluid. The coating on the nanoparticle was formed by the ionic interaction between the hydroxide anion and the tetramethylammonium cation. However, the magnetite was successfully suspended in the solution due to the electrostatic repulsion among the tetramethylammonium cation. The chemical reaction in the synthesis of Fe3O4 was: 2FeCl3 + FeCl2 + 8NH3 + 4H2O -------> Fe3O4 +8NH4Cl. The reducing and oxidizing agent in this equation is iron. Magnetite which was the final product was held together by ionic interaction, which formed crystals and spikes when placed on the magnet. The arrangement of the unpaired electrons in the molecule is due to ferromagnetism which forms from the permanent magnetic dipole which was observed in this experiment. However, MnFeO4 and CoFe2O also have similar behavior to that of ferrofluid with inverse spinel structure which can be used to make ferrofluid. The magnetic properties were observed by the formation of spikes when placed under a magnet in which identified the magnetic properties of ferrofluid. But the removal of the magnet causes the loss of spikes. The spike formation in the experiment was due to the strength of the magnetic field. A stronger magnet with a higher magnetic field has increased downward gravity and tension. To conquer the force of gravity and surface tension, a stronger magnet is required for an experiment. Due to this result, the formation of spikes in the ferrofluid would not be formed with a weak magnet. The formation of spikes was not only due to the strength of the magnet but the distance of the magnet. This experiment teaches the relevance of the magnetic properties of ferrofluid and the stabilization of nanoparticles with surfactants such as tetramethylammonium hydroxide It can be concluded that the strength and distance of the magnet affect the formation of spikes in the ferrofluid.

References ThomasSep, G.P. “What Is Ferrofluid? A Guide to the Theory, Properties and Applications of Magnetic Fluid.” AZoM.com, 20 May 2019, www.azom.com/article.aspx?ArticleID=6726. Berger, P.; Adelman, N. B.; Beckman, K. J.; Campbell, D. J.; Ellis, A. B.; Lisensky, G. C. Journal of Chemical Education, 1999, 76, 943

Magnetic Properties.” Chemistry LibreTexts, 23 Feb. 2019, chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supple mental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/Atomic _and_Molecular_Properties/Magnetic_Properties....