Ferrofluid. DIY ferrofluid with a laser printer cartridge How to make a liquid magnet at home

To a person who is far from scientific discoveries, who said goodbye to physics or chemistry at school, many things seem unusual. Using in everyday life, for example, electrical appliances, we do not think about how exactly they work, taking the benefits of civilization for granted. But when it comes to something that goes beyond everyday perception, even adults are amazed, like children, and begin to believe in miracles.

How, besides magic, can one explain the phenomenon of the appearance of three-dimensional figures, flowers and pyramids, magical pictures that replace each other from a seemingly ordinary liquid? But it's not magic, science gives a rationale for what is happening.

What is ferrofluid?

We are talking about ferrofluid - a colloidal system consisting of water or other organic solvent containing the smallest particles of magnetite, and any material that contains iron. Their dimensions are so small that it is even hard to imagine: they are ten times thinner than a human hair! Such microscopic indicators of size allow them to be evenly distributed in the solvent using thermal motion.

For the time being, while there is no external influence, the liquid is calm, resembling a mirror. But one has only to bring a directed magnetic field to this "mirror" and it comes to life, showing the viewer amazing three-dimensional pictures: magical flowers bloom, moving figures grow on the surface, changing under the influence of the field.

Depending on the strength and direction of the magnetic field, the pictures change before our eyes - from light, barely noticeable ripples that appear on the surface of the liquid, through needles and peaks that change sharpness and slope and grow into flowers and trees.

The ability to create color pictures with the help of illumination, truly bewitching the observer, reveals an unknown world before him.

Unfortunately, metal particles, although they are called ferromagnetic, are not ferromagnetic in the full sense, since they cannot retain the resulting shape after the disappearance of the magnetic field. Because they do not have their own magnetization. In this regard, the use of this discovery, which, by the way, is not entirely new - it was made by the American Rosenzweig back in the middle of the last century, has not found wide application.

How to make and where is ferrofluid used?

Ferrofluids are used in electronics, in the automotive industry, and I would like to believe that their widespread use is not far off, and with the development of nanotechnology, they will be widely used. In the meantime, this is mostly fun for the admiring public, spoiled by various kinds of spectacles.

Three-dimensional pictures make you follow them with bated breath, doubt whether this is a montage, and look for an explanation of what is happening, at least on the Internet. Who knows, maybe a little boy, who today watches the metal “living” colors and figures with his mouth open, tomorrow will find a fundamentally new application for this phenomenon, making a revolution in science and technology. But this is tomorrow, but for now - watch and enjoy!

Ferrofluid, he is magnetic fluid- an extremely mysterious and curious contraption. I first saw it about ten years ago, in the Paris Museum of Science and Technology, where one of the exhibits was a tightly closed glass vessel with an oily black liquid inside. Nearby lay a pair of magnets. When they were brought up in a vessel, the liquid reacted, rising like a hedgehog and forming a picture of a rather menacing type of spikes repeating the shape of a magnet. There was also a brief description of what it is and what it is eaten with. Then I learned this name - ferrofluid. Of course, he passionately desired, but then there were absolutely no ideas where to get it, no opportunities for this. And now, ten years later...

Ferrofluid, in fact, is a suspension of nanoparticles of a ferromagnet (usually magnetite), about 10 nm in size (rarely larger), mixed in a surfactant (an organic solvent such as oleic acid, or water), which forms a kind of film around the nanoparticles, not letting them slip. Under the influence of a magnetic field, the particles line up along its lines, forming these characteristic needles. In principle, it is unlikely that I will be able to describe the properties of a ferrofluid better than in Wiki, so I send those who want to know more theory there.

I found the treasured jar I was looking for on Ebee, as well as many other things. The price tag was not very encouraging, but there were practically no alternatives (by the way, it is four times more expensive on supermagnete.de), so I had to order it. And now, a month later, I finally have a jar. 8 ounces of that weird black crap.
The first thing that was discovered was that she was wildly dirty. If a drop of ferrofluid gets on light-colored clothes, this stain will not be removed by ANYTHING. And it is very, very desirable to wear gloves when working with him. Second, she squirts wildly. Drops were found in the most unpredictable places. And the third - due to the combination of the first two properties of this jar, it will last for a very short time 🙁

Actually, as it turned out after several experiments, in order to obtain really interesting patterns of particle distribution, it is necessary to have powerful electromagnets and figures with a complex edge shape (such as drills, gears, etc.), and in a good way the electromagnet must be wound on this very object. Amusements with permanent magnets are curious, but, firstly, my magnets are rather weak for obtaining large pictures, and, secondly, this is entertainment for about five minutes, since the behavior of the liquid turns out to be rather monotonous.

Nevertheless, so far we have managed to come up with a more or less colorful option for using permanent magnets with ferrofluid: you need to bring the magnet not from below, but from above (of course, through a layer of glass or plastic), and then you can observe how a column grows from the center of the bowl with ferrofluid , and the glass under the magnet begins to bulge with needles of flowing liquid. In addition, the gravitational force pulling the liquid down noticeably increases the length of the needles.

Ferrofluid is extremely difficult to photograph with high quality. Due to its very sharp glossy reflection of light and complete blackness in any at least somewhat noticeably thick layer (by the way, it is brown in a very thin layer), it turns out to be difficult to photograph the borders of the spikes. But in the end, I figured out what to do: shoot with a shutter speed of five seconds, and during this time wave a flashlight, illuminating the hedgehog from the adhering ferrofluid from different sides.

By the way, you can try to make a ferrofluid with your own hands. Since I have not tried it yet, I will not go into details, but when I get there, I will certainly write down what and how. The main difficulty lies in the need to centrifuge the suspension, but you can try to get by with improvised means, because there is still no centrifuge.

I would like to specifically mention ferrofluid sculptures. This is what I will strive for and what I want to get from him in the end. A very bewitching sight, especially levitating ones.

The term "ferrofluid" usually refers to a fluid that is attracted by a magnet, that is, it reacts to a magnetic field. Moreover, in strong magnetic fields, this liquid can lose its fluidity, becoming like a solid body. Many have heard of such substances, but most consider such substances to be exotic and expensive high-tech products, available only to a select few lucky ones. This is true, but only partly. Sometimes a lower quality, but more than affordable product, made in a few minutes literally from garbage, is quite enough.

"Professional" magnetic fluids

A "professional" magnetic fluid is usually a colloidal solution of the smallest particles of a magnetic material, that is, a suspension of solid particles in a fluid that is stable and does not settle over time. Most often, magnetite (Fe 3 O 4) is used as a magnetic material, and the size of its particles is usually from 2 to 30 nanometers (however, there are also mentions of larger particles - up to 10 micrometers). To prevent sticking and settling of magnetic particles, various types of surface-active substances (surfactants) are used, depending on the type of base liquid that forms the basis of the colloidal solution. In turn, the choice of the base fluid is determined by the intended purpose of the finished product and the desired set of its properties (viscosity, density, heat resistance, thermal conductivity, etc.). In addition to water, the most popular base fluids for technical applications are kerosene and liquid industrial oils, for biomedical applications - various types of organic liquids.

Because of the magnetite particles, ferrous fluids are usually opaque black solids. To reduce the viscosity, the concentration of magnetite can be reduced, but this, of course, also reduces the magnetic properties of the liquid. The use of other magnetic fillers instead of magnetite can give the liquid a color other than black (usually different shades of yellow-brown), but none of these liquids can boast of crystal transparency.

The complexity of obtaining "real" magnetic fluids is impressive - for example, for mechanical grinding of particles to the desired size, experimenters needed 1000 hours of operation of a ball mill (1.5 months without a break!). Other methods are also quite exotic, for example, the grinding of particles by the electrocondensation method is based on the creation of a voltaic arc in a liquid between electrodes immersed in it, the gap between which is filled with the material to be ground. There are also purely chemical methods, however, even there they cannot do without repeated centrifugation of the reaction products. But the result is worth it: the liquids obtained in this way can retain their properties for many years.

The simplest chemical method is described here: http://nauka.relis.ru/34/0211/34211036.htm. A detailed consideration of the problem from strict scientific positions can be found on this site: http://magneticliquid.narod.ru/authority/008.htm.

DIY magnetic fluid

Manufacture of magnetic fluid by chemical means

To do this, you must have the following equipment and chemical glassware.

Pharmacy scales with a set of weights.
Two flasks (round or flat bottom).
Beaker.
Filter paper and funnel.
A strong enough magnet, preferably ring (from the speaker).
A small (laboratory) electric stove.
Porcelain glass for 150–200 ml.
Thermometer with temperature measurement range up to 100°С.
indicator paper.
To obtain a better ferrofluid, you will need a small benchtop centrifuge (4000 rpm). However, with moderate requirements for the final product, you can do without centrifugation or try to replace centrifugation with long settling.

In addition, the following reagents are required.

Salts of bi- and trivalent iron (chlorine FeCl 2, FeCl 3 or sulfate FeSO 4, Fe 2 (SO 4) 3).
Ammonia water 25% concentration (ammonia).
Sodium salt of oleic acid (oleic soap) as a surfactant. You can try to replace oleic acid with detergents with low foaming.
Distilled water. Instead of distilled water, you can use water that has been purified through a reverse osmosis system (including household water, but provided that this system does not have an “improving” post-cartridge that enriches already purified water with salts and microelements). Purified drinking water in bottles from the store will not work - it is usually “improved” with various microadditives; for the same reasons, natural spring and artesian water is not suitable.

Here is a summary of this technique. The figures are given per 10 grams of the solid magnetic phase (magnetite) in the ferrofluid.

The brownish-orange solution will instantly turn into a black suspension. Add some distilled water and place the flask with the resulting mixture on a permanent magnet for half an hour.

Before proceeding with manufacturing, I advise you to look at the page http://wsyachina.narod.ru/technology/magnetic_liquid.html, the same technique is described there, and at the end the author of the page shares his experience. In particular, he used the most common "Fairy" (dishwashing liquid) as a surfactant. The main thing is to pay special attention to the safety recommendations and take the necessary care!

Manufacture of magnetic fluid mechanically

Meanwhile, almost everyone can make a liquid that is quite acceptable for some applications and reacts to a magnetic field - without any reagents and in just a few minutes. Once again, I emphasize - only for some applications, and its quality is significantly worse than that obtained by chemical means. In particular, the consistency of the product turns out to be such that it can rather be called not a “liquid”, but a “slurry”. Moreover, the deposition time of magnetic particles is quite short - usually from several seconds to several minutes. But no chemistry and exotic technologies - only sifting and mixing. By the way, when people first became interested in magnetic fluids in the middle of the 20th century, their very first samples were obtained in exactly this way.

In order to make such a "magnetic slurry", you just need to collect the required amount of fine steel filings. The finer the better, therefore the most suitable is the steel dust remaining after the work of the "grinder" or grindstone. Dust is collected by a magnet (not too strong - not so much to prevent a large residual magnetization, but so that the iron filings do not tend to it so intensely and carry less non-magnetic dust with them). Then, to filter out dirt and large fractions, the collected can be sifted through a cloth (say, placed in a cloth bag and shaken over a spread newspaper; a magnet is again placed on the newspaper a little to the side, this time a stronger magnet is better, which catches steel dust particles that have slipped through the fabric, and fine non-magnetic dirt flies straight down past the magnet; large dirt particles and large steel filings cannot pass through the fabric and remain inside the pouch). The denser the fabric, the finer the sifted dust will be, but the longer it will take to shake the bag. To mechanize the process, you can try to blow dust particles through the fabric of the bag with the exhaust of a vacuum cleaner, but this will already require the preparation of devices for directing, deflecting and damping the air stream that has come out of the bag (say, from empty plastic bottles from drinking water, preferably with a wide neck and a volume of 5-8 liters). Therefore, it is worth thinking about the “mechanized” version only with sufficiently large volumes of the manufactured “product”, measured in liters, and for several grams of magnetic fluid, which is quite sufficient for most experiments and many practical applications, this is unlikely to be justified. Of course, centrifuging in a liquid will provide much better separation of particles, but a dense cloth and a vacuum cleaner can be found in almost every home, but for some reason centrifuges of several thousand revolutions per minute are not so widespread. If the collected dust is sufficiently clean and homogeneous, and the requirements for the quality of the “magnetic slurry” are quite low, then sifting can be omitted altogether.

I emphasize once again - the steel particles should be as small as possible. To obtain fine steel dust, a fine-grained (lapping) grinding wheel should be used. As a guide, we can offer the following - with a careful examination with the naked eye, it is impossible to determine the shape of dust particles; on white paper, they look like tiny dots. If you can determine the shape and orientation of the sawdust, then such sawdust is too large, it will settle very quickly and will be almost immobile! But such large sawdust is convenient to use in dry form to study the magnetic field lines. The criterion should be considered the size when the directions “along” and “across” are distinguishable in oblong-shaped sawdust - with normal vision, this usually corresponds to sizes on the largest side of 0.05–0.1 mm or more, i.e. such sawdust, at least one of the dimensions, is larger than 50 .. 100 micrometers.

The selected steel dust is filled with a liquid that wets the metal well. This can be ordinary water - preferably saturated with surfactants, i.e. soap or other detergent (foaming is harmful here, so it should be as small as possible!). But in order to avoid rapid corrosion of iron dust particles, which can simply “eat” them in a few days, it is better to use liquid engine oil for steel. Household is quite suitable - what is used to lubricate sewing machines. Alternatively, you can use a brake fluid that retains its properties over a very wide temperature range. However, it should be remembered that the brake fluid is very hygroscopic (although this is not so important here), and in an open vessel, volatile fractions evaporate from it, which are by no means beneficial to health - therefore, it is better to work with it in a well-ventilated area or in the open air.

The concentration of steel dust in the liquid must be, on the one hand, not too high, so that the liquid does not become too thick and viscous, and on the other hand, not too low, otherwise the movement of magnetic particles will not be able to entrain any noticeable volume of liquid. It is selected empirically by gradually adding sawdust to the liquid, thoroughly mixing and checking with a magnet. It is better to leave a slight excess of the base liquid than to receive its deficiency, since in the latter case the mobility of the resulting substance decreases very noticeably.

The mobility of the particles of such a magnetic fluid is determined by the force of wetting the metal with the liquid, which “isolates” the metal particles from each other and ensures their relatively free movement. Surfactants (surfactants) wet the surface of dust particles even better, which is why they are used in “professional” formulations. In strong magnetic fields, the force of mutual attraction of particles can exceed the force of wetting, and then the particles will begin to directly contact each other, and the liquid will “harden”, becoming something like wet sand. The specific value of the critical strength of the magnetic field depends both on the magnetic properties of the metal used, and on the force of wetting the metal with the base liquid or surfactant, as well as on the temperature of the liquid and the size of the metal particles (larger ones “stick together” faster, since they have a smaller specific surface area per unit mass ; in addition, large sawdust easily settles to the bottom, while especially small dust particles can be maintained in suspension by the Brownian movement of the molecules of the base liquid). When the magnetic field is removed, the mobility of the liquid will be restored if the residual magnetization is not too large.

Finally, it must be said that the magnetic fluid from iron dust is not only very thick, but also has high abrasive properties, so it is problematic to pump it through any tubes, but it can easily damage the bearings and working surfaces of the pumps pumping it (optimal pump type is a gear displacement pump similar to oil pumps in automobile engines). The abrasive action is significantly reduced if the clearance between mutually moving parts exceeds the size of the largest particles by at least one and a half to two times. In this situation, a pair of materials "hard metal - durable elastic plastic" are very resistant to wear. Plastic should be exactly elastic, like hard rubber or fluoroplastic, but not as hard as textolite or ebonite (and of course, be chemically resistant to the base fluid).

However, in many cases these features of the "magnetic fluid" are not fundamental, and many effects are manifested in it in the same way as in "real" magnetic fluids. In particular, a magnet pressed to the bottom, after being released, successfully floats to the center of the liquid even many minutes after the completion of the deposition of magnetic particles (however, in a settled liquid, this ascent can last several minutes or even hours). If the same magnet, on the contrary, is placed on the surface, then it will sink, again tending to the center of the liquid (more precisely, to the center of the area occupied by metal particles).

And the last remark. Light shaking or tapping on the wall of the vessel significantly increases the mobility of the "slurry". If you don’t feel like shaking your hands, then any source of weak vibration will do - up to a subwoofer speaker, to which you need to apply a powerful low-frequency signal (although housemates may not like it very much)! On such an impromptu "vibration stand", even settled and inactive "slurry" shows good fluidity. ♦

Ferrofluid - what is it and how to make a ferrofluid yourself

The ability to create color pictures with the help of illumination, truly bewitching the observer, reveals an unknown world before him.

How to make and where is ferrofluid used?

An incredible thing, this is visual physics, you need to show such experiments at school to students, introducing them to science through visual experiments, especially since you can make such a liquid at home!

That's for sure, we would have such a teacher-chemist - I would not skip a single lesson! Yes, I would sign up for an elective and an after-school program, if only to conduct such experiments and experiments!

It looks very nice, in medieval Europe for this they would obviously have been burned at the stake, like a heretic and a sorcerer!

A ferrofluid is a liquid that is strongly polarized in the presence of a magnetic field.

Experiments with ferrofluid

Ferrofluids are used in the manufacture of hard drives. It is applied to the rotating axles of the discs, thereby preventing the ingress of debris from the outside.

VF is also used in tweeters, to remove heat from the voice coil and to suppress resonance.

VF has found application in the aerospace and defense industries, medicine, optics, electronics and mechanical engineering, and much more.

How to make ferrofluid at home

oil (sunflower, machine or any other);
toner for a laser printer (the developer must be present in the composition).

The ingredients must be mixed, obtaining a liquid in density resembling sour cream.

why not use the metal powder right away?

It's not gonna go. To achieve the effect of "thorns", the body must be in a liquid state.

Sky, tried it with fine powder or guess?

there is a lot of resin in the toner, which will have to be separated somehow ... in general, the toner does not roll!

Not okay. just messed up the bathroom.

Class! You can think of a liquid splashing to the music!

the magnet must be attached to the column at a distance of 10-20 cm and turn it on loudly

finally got it fucked up! cool topic!

I made it this class)))))

My toner does not react at all to magnets, what's the matter?

Apparently you have a one-component toner (there is one plastic in it). It is necessary to purchase a toner that contains a developer (metal powder)

should try

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Ferrofluids are colloidal systems consisting of nanometer-sized ferromagnetic or ferrimagnetic particles suspended in a carrier liquid, which is usually an organic solvent or water. To ensure the stability of such a liquid, ferromagnetic particles are associated with a surface-active substance (surfactant), which forms a protective shell around the particles and prevents them from sticking together due to van der Waals or magnetic forces.

Ferrofluids:

Magnetic fluids are colloidal solutions - substances that have the properties of more than one state of matter. In this case, the two states are the solid metal and the liquid in which it is contained. This ability to change state under the influence of a magnetic field allows the use of ferrofluids as sealants, lubricants, and may also open up other applications in future nanoelectromechanical systems.

The first way to get magnetic fluid:

Almost everyone can make a liquid that reacts to a magnetic field with their own hands - without any reagents and in just a few minutes . Of course, its quality is significantly worse than that obtained by chemical means. In particular, the consistency of the product turns out to be such that it can rather be called not a “liquid”, but a “slurry”. Moreover, the deposition time of magnetic particles is quite short - usually from several seconds to several minutes. But no chemistry and exotic technologies, only sifting and mixing. In order to make "magnetic slurry", you just need to collect the required amount of small steel filings . The finer the better, therefore the most suitable is the steel dust remaining after the work of the "grinder" or grindstone.

Dust is collected by a magnet (not too strong - not so much to prevent a large residual magnetization, but so that the iron filings do not tend to it so intensely and carry less non-magnetic dust with them).

Then, to filter out dirt and large fractions, it can be collected through a cloth on a newspaper. . The denser the fabric, the finer the sifted dust will be, but the longer it will take to shake the bag.

Figure No. 1 - Iron filings and a magnet

But! In order to avoid rapid corrosion of iron dust particles, which can simply “eat” them in a few days, it is better to use liquid engine oil for steel. . Household is quite suitable - what is used to lubricate sewing machines.

The concentration of steel dust in the liquid must be, on the one hand, not too high, so that the liquid does not become too thick and viscous, and on the other hand, not too low, otherwise the movement of magnetic particles will not be able to entrain any noticeable volume of liquid. It is selected empirically by gradually adding sawdust to the liquid, thoroughly mixing and checking with a magnet. . It is better to obtain a slight excess of the base liquid than its deficiency, since in the latter case the mobility of the resulting substance decreases very noticeably.

The specific value of the critical strength of the magnetic field depends both on the magnetic properties of the metal used, and on the strength of wetting of the metal with the base liquid or surfactant, as well as on the temperature of the liquid and the size of the metal particles. When the magnetic field is removed, the mobility of the liquid will be restored if the residual magnetization is not too large.

The second way how to make magnetic fluid:

Magnetic fluid can be made even easier. There are dielectric magnetic toners (DM toners) for laser printers. DM-Toner is a substance consisting of resin and magnetized iron oxide. In this case, surfactants can be dispensed with.

For 50 ml of magnetic toner, you need to take 2 tablespoons of very pure vegetable oil.

Thoroughly mix the toner with the oil, that's all - the magnetic fluid is ready.

P.S.: I tried to clearly show and describe not tricky tips. I hope that at least something will be useful to you. But this is not all that is possible to invent, so go ahead and study the site

It has been 52 years since NASA employee Steve Papell invented ferrofluid. He solved a very specific problem: how to force the liquid in the rocket fuel tank to approach the hole from which the pump pumped fuel into the combustion chamber under conditions of weightlessness. It was then that Papell came up with a non-trivial solution - to add some kind of magnetic substance to the fuel in order to control the movement of fuel in the tank with the help of an external magnet. This is how ferrofluid was born.

Papel used magnetite (Fe 3 O 4) as a magnetic substance, which he crushed (ground in a mixture with oleic acid) for many days using a special technology. A stable colloidal suspension was obtained, in which tiny particles of magnetite 0.1-0.2 microns in size stably existed. Oleic acid in this system played the role of a surface modifier, which prevented magnetite particles from sticking together. Patent S. Papella US 3215572 A (Low viscosity magnetic fluid obtained by the colloidal suspension of magnetic particles) is open and can be viewed on the Internet. The classic composition of a ferrofluid is 5% (by volume) of magnetic particles, 10% of a surface modifier (oleic, citric or polyacrylic acids, etc.). The rest is an organic solvent, including liquid oils.

Interest in magnetic fluids has revived in recent years, and today they have already found many applications. If such a liquid is applied to a neodymium magnet, then the magnet will slide over the surface with minimal resistance, that is, friction will decrease sharply. On the basis of ferromagnetic fluid in the United States, radar-absorbing coatings are made for aircraft. And the creators of the famous Ferrari use magnetorheological fluid in the suspension of a car: by manipulating a magnet, the driver can make the suspension stiffer or softer at any time. And these are just a few examples.

Magnetic fluid is an amazing material. It is worth placing it in a magnetic field, as separate magnetic particles are combined and lined up along the field lines of force, turning into a completely solid substance. Today, magic tricks with magnetic fluid, which, when in contact with a magnet, turns into hedgehogs or cacti, flawless in terms of symmetry, are shown on many entertainment shows. Of course, you can buy ferrofluid, but it's much more interesting to make it yourself.

We wrote about how to get a self-hardening magnetic fluid, which will allow you to examine the structures formed by magnetic particles under a microscope (Chemistry and Life, 2015, No. 11). And here is another recipe for a homemade ferromagnetic fluid. Take 50 ml of laser printer toner. This powder consists of at least 40% magnetite, the particle size of which is 10 nanometers or less. The toner also necessarily contains a surface modifier so that the nanoparticles do not stick together. To 50 ml of toner, add 30 ml of vegetable oil (two tablespoons) and mix thoroughly, sparing no time for this process. You will get a black homogeneous liquid, similar to sour cream. Now pour it into a flat glass container with sides so that the layer thickness is at least a centimeter. Bring a magnet under the bottom of the container, and in this place a hard hedgehog will immediately appear in the liquid. It can be moved with a magnet. If you bring the magnet to the surface of the liquid or to the side, the liquid will literally jump out towards the magnet, so be careful. To avoid this trouble, you can put the magnetic fluid in a small glass conical flask, filling it halfway or a little less. Tilt the flask so that a layer of liquid forms along its wall, and hold the magnet close to the glass.

Success depends on the strength of the magnet (you can buy a small neodymium magnet in stores) and the quality of the toner. In the latter case, you must be sure that it contains magnetic powder.