|WikiProject Physics||(Rated C-class, Low-importance)|
|A fact from Ferrofluid appeared on Wikipedia's Main Page in the Did you know? column on 19 March 2004. The text of the entry was as follows: "Did you know Wikipedia:Recent additions/2004/March.||
- 1 Major revisions needed
- 2 CSI: NY
- 3 Add
- 4 Take your pic
- 5 Copied
- 6 Diagram
- 7 How to section
- 8 Possible vandalism alert
- 9 Clarification needed
- 10 History
- 11 Idea
- 12 What if you Froze a ferrofluid whilst the magnet was present?
- 13 Role of surfactant in a ferrofluid
- 14 paramagnetism versus superparamagnetism
- 15 Needs Fix
- 16 the shape and nature
- 17 Human Reaction
- 18 Surfactants again
- 19 Please note: incorrect reference
- 20 Curie temp
- 21 Brownian Motion
- 22 Jennifer's Body
- 23 History Section
- 24 Removing equation on resistance of a ferrofluid
- 25 Normal-Field Instability
- 26 Image caption
Major revisions needed
This page is need of some heavy editing since it contains a lot of errors. I was about to start, when I realized it was more work than I asked for. The structure of the article is quite bad and there is a lot of duplicate sentences and plain fact errors. Also most of the chemistry in the article is way off. Hematite is an antiferromagnetic phase and can not be used to form ferrofluids. The physics and chemistry of ferrofluids and magnetorheological fluids are a firmly established research fields and ferrofluids deserves a decent wikipedia entry. I will try to do what I can to tidy up/edit this page in the coming weeks and add some of the great references in on the topic astrolux (talk) 19:40, 5 July 2010 (UTC) —Preceding unsigned comment added by Astrolux (talk • contribs) 19:36, 5 July 2010 (UTC)
I watched the 4th season's 15th episode "DOA for a Day". in the episode, ferrofluid is identified because it is "sensitive to sound". While I strongly beleive this is inaccurate, can anyone specifically discount this. —Preceding unsigned comment added by 18.104.22.168 (talk) 01:39, 20 October 2008 (UTC)
I think someone combined two sections that should not be together:
- They are used in loudspeakers to sink heat between the voice coil and the magnet assembly, and to damp the movement of the cone. They reside in what would normally be the air gap around the voice coil, held in place by the speaker's magnet. Using electromagnets and sensors, the fluid's viscosity can be controlled dynamically. This allows hundreds of watts of mechanical power to be controlled with a few watts of electrical power, which is much more efficient than other methods of vibration control, such as piezoelectric crystals.
to my understanding, ferrofluid does not change viscosity under different magnetic fields, and is not used in that way to damp speakers. i think MR fluid is used to damp car shocks in that way, but it's not the same kind of damping. - Omegatron 02:49, Jul 8, 2004 (UTC)
Actually a ferrofluids viscosity does change under the influence of a magnetic field. It is easy to see why. At zero field the particles are free to move as they like. When a magnetic field is applied this is no longer the case since the particles are forced to align in a specific direction. The stronger the field, the less free the particles are to freely move, which translates to a viscosity change.Abiermans (talk) 10:04, 19 December 2007 (UTC)
A ferrofluid is a stable colloidal suspension of ferromagnetic mono-domain particles in a liquid carrier. To avoid agglomeration due to attractive dipole-dipole or Van der Vaals forces each particle is coated by long-chain molecules or by an electrostatic layer (see figure). Due to the smallness of the particles (diameter ~ 10nm) the properties of ferrofluids are substantially affected by thermal Brownian motion. When exposed to a magnetic field, a ferrofluid behaves like a paramagnetic gas of high permeability (Rosensweig).
--Light current 07:58, 4 February 2006 (UTC)
Also, ferrofluids DOES damp the electric coil in a loudspeaker in a way, so that unwanted resonances taking place in that coil are damped. It translates into overall improvement of the sound quality. References : http://mrsec.wisc.edu/Edetc/background/ferrofluid/index.html http://www.popsci.com/diy/article/2009-09/making-ferrofluids-work-you - Narayanarora —Preceding undated comment added 10:08, 6 January 2012 (UTC).
Just added link to MRC page.
Take your pic
I have provided a number of images which I believe to be higher quality and more informative than the ones currently used on the article. Feel free to make use of them. --Gmaxwell 01:19, 13 July 2006 (UTC)
- Whoa! — Omegatron 02:33, 13 July 2006 (UTC)
- I don't speak Slovak. Using Babel, I've asked a Wikipedian who does to speak to the author of the website. --Eyrian 23:52, 11 November 2006 (UTC)
|It is requested that a physics diagram or diagrams be included in this article to improve its quality. Specific illustrations, plots or diagrams can be requested at the Graphic Lab.
For more information, refer to discussion on this page and/or the listing at Wikipedia:Requested images.
How to section
Can I remove the tag? It's really not a big deal. — Omegatron 05:36, 2 January 2007 (UTC)
Possible vandalism alert
This is very confusing to me. First it is stated:
Ferrofluids are composed of nanoscale ferromagnetic particles
Later we read:
Ferrofluids have numerous optical applications due to their refractive properties; that is, each grain, a micromagnet, reflects light
When I link to the micromagnet hyperlink, I am taken to the article on magnets. So the second quote is saying that ferrofluids are composed of particles, each of which is a magnet. That is, each particle exhibits a magnetic moment (I guess is the way you say it) without an external magnetic field being applied. But if that is true, why is the first quote "Ferrofluids are composed of nanoscale ferromagnetic particles" and not "Ferrofluids are composed of nanoscale magnetic particles"? —The preceding unsigned comment was added by 22.214.171.124 (talk) 08:51, 18 February 2007 (UTC).
This may answer your optical applications questions: http://www.nanomagnetics.us - Look at the image gallery and John Shearers microscope images from the research link.Pinestone —Preceding unsigned comment added by Pinestone (talk • contribs) 12:01, 11 March 2008 (UTC)
How/When/Why was Ferrofluid developed and by whom? Answer that question and this will be a better entry --CPQD 00:45, 25 February 2007 (UTC)
This is just an idea, but someone might want to increase the size of the pictures on the topic page, by a little bit.
What if you Froze a ferrofluid whilst the magnet was present?
Would this make the particles freeze in their new alignment? making the fluid a ferromagnet as long as it was frozen? I'd guess so, cos it would be like the heat and beat method of making iron ferromagnets. Does anyone know for sure? Tom Michael - Mostly Zen (talk) 22:39, 25 February 2007 (UTC)
- Nothing would happen during "normal" freezing. You have to understand that "freezing" is just fixing the particles in place. It does nothing to stabilize the field of the particle. They are so small that they will fluctuate happily even when frozen. Otoh, if your cryostatically freeze them (i.e. going down to Liquid He temperatures), you might get below the superparamagnetic limit of the particles. In that case, they would act as an ferromagnet. 126.96.36.199 11:15, 4 June 2007 (UTC)
If you freeze a ferrofluid all the individual particles will be fixed in space position wise as someone mentioned. 'How' you freeze the ferrofluid is irellevant. There are two ways in which a ferrofluid looses any net magnetization after an applied field is removed. One way is physical rotation of the individual particles, this results in complete randomness and no net field. The other way is rotation of the magnetic moment inside each individual particle. While you can prevent the first mechanism by freezing, you can't stop the second mechanism from taking place, no matter how cold you make it. Also, don't forget that the particles are not touching each other in a (frozen) ferrofluid. A frozen ferrofluid therefor can have a net magnetization but this field will not last if the external field is removed, you can't make a permanent magnet by freezing a ferrofluid in a magnetic field and then turning the external field off. Someone correct me if I am wrong please.Abiermans (talk) 21:58, 12 December 2007 (UTC)
Role of surfactant in a ferrofluid
I think the information above is not correct. Making a stable ferrofluid requires solving of two problems. The first problem is settling of the particles in a magnetic or gravitational field. This problem is solved by making the magnetic particles very small, typically 10nm or smaller so that they can be kept in suspension by Brownian motion. The second problem is clumping together of the magnetic single domain particles, these particles are magnets afterall. That problem is solved by coating the particles with a surfactant. Steric repulsion prevents the particles from agglomorating. The surfactant addition has nothing to do with settling in the way it is described. This should be changed in the article. I am not sure I am comfortable editing the article.Abiermans (talk) 22:21, 12 December 2007 (UTC)
Dear Abiermans, I think you have a valid point about surfactants preventing agglomeration of ferro-particles and so, I think that section should be changed a bit. Before deleting some of the text that emphasized Brownian motion, I considered that a large surface area ball of miceles around a ferroparticle would get bumped around more frequently and this could help to keep the particle in suspension. Or perhaps the impacts would all get averaged out: more impacts but from opposing/self canceling directions? I don't know enough about Brownian motion to know. I considered surfactant action in terms of micels and I thought I understood the whole story, but, I don't understand how nanospheres of soy lecithin could prevent agglomeration of ferroparticles. I made some changes to this section, feel free to re-edit if you think I've missed something.
Hi Electricmic Thanks for the reply, I have taken the liberty of editing the article a bit. I rewrote part of the section on the surfactants and added the fact that ferrofluids contain either ferromagnetic OR ferrimagnetic particles. Let me know if the current version is acceptable.Abiermans (talk) 23:20, 14 December 2007 (UTC)
Hey AbermansWow! That's great. Very clearly stated. The very next paragraph still has a reference to nano-sphere surfactants. "Whether or not the surfactant is nanosphere-based or micelle-based, " I still don't understand the nanoshpere based surfacant's function in maintaining colloidal stability. Also, this sentence is now a bit out of sorts as it references a previous sentence that has been removed. I'd like to delete it but I don't understand the issue enough to be confident that I'd be improving the article. Thanks for your contributions.Electricmic (talk) 07:48, 15 December 2007 (UTC)
Hi Electricmic Well, the surfactants are nanoscale particles but I don't think there are nano-sphere surfactants because you need a polar(non polar) head and non-polar(polar) tail construction. Not entirely sure how to accomplisch that when you have a sphere.Abiermans (talk) 19:05, 17 December 2007 (UTC)
Does anyone know how the non polar surfactant tail interacts with the carrier liquid? Is this considered a bond or just a weak attraction? What is the method of attraction between the non polar side of the surfactant and the carrier liquid?Electricmic (talk) 08:04, 15 December 2007 (UTC)
paramagnetism versus superparamagnetism
Ferrofluids are not referred to as "superparamagnetic" because their magnetic susceptibility is large. They are "superparamagnetic" because they exhibit paramagnetic behavior even when at temperatures below the Curie or the Néel temperature. At least this is my understanding of ferrofluid behavior. —Preceding unsigned comment added by Abiermans (talk • contribs) 23:28, 14 December 2007 (UTC)
- I rewrote the paramagnetism page but I am not quite sure how to include this. I think there is a big problem in nomenclature here. Maybe the macroscopic response of a ferrofluid can be called (super)paramagnetic, but can the material be called that? Surely within each single domain the thing is ferromagnetically ordered! I think the statement ferrofluids display paramagnetism is incorrect. Ferrofluids display superparamagnetism and then explain that the latter requires ferro-ordering at the domain level, I'd think.
the shape and nature
- From what little I know, the peculiar shapes are caused by the liquid's reaction to the magnetic field lines. 188.8.131.52 (talk) 06:21, 2 March 2008 (UTC)
- Yeah, it's good idea (I can't write about it because I don't know reactions of human body for psychical contact with this amazing substance as is ferrofluid)
- 184.108.40.206 (talk) 21:06, 21 October 2008 (UTC)
Please note: incorrect reference
Magnetic viewing film is NOT in any way related to ferrofluid, and the reference should be removed. "It is a translucent thin flexible sheet, coated with micro-capsules containing nickel flakes suspended in oil" Nickel flakes are not nano-scale matter and is misleading and confusing for the reader.~~Pinestone 10:48, Sept 24, 2009 (EST)~~
- You seem to have misunderstood the purpose of See also sections: They're purely for navigation purposes, not content. Readers of this article might reasonably be expected to have an interest in reading one or more of the articles listed there; therefore, someone listed the article in See also. No direct connection is implied or expected as a result. WhatamIdoing (talk) 03:41, 30 September 2009 (UTC)
The sentence below sounded wrong to me so I will change it. Shouldn't the Curie temperature of a ferrofluid be independent of the carrier liquid and surfactant?
"However, ferrofluids lose their magnetic properties at sufficiently high temperatures, known as the curie temperature. The specific temperature required varies depending on the specific compounds used for the nano-particles, surfactant, and carrier fluid." Electricmic (talk) 05:06, 22 October 2009 (UTC)
I think Brownian Motion is a red-herring in this discussion. Even if there were no such thing as Brownian Motion the steric repulsion of the micels would keep the nanoparticles in suspension. Also, a strong magnet pulls the magnetite with forces far greater than the gravitational weight of each particle. "Weight" is another red-herringin this discussion. Who will word-smith a better paragraph than what we currently have (below)? "These surfactants prevent the nanoparticles from clumping together, ensuring that the particles do not form aggregates that become too heavy to be held in suspension by Brownian motion. The magnetic particles in an ideal ferrofluid do not settle out, even when exposed to a strong magnetic, or gravitational field." Electricmic (talk) 13:10, 22 October 2009 (UTC)
I think even mentioning it is completely irrelevant, but that seems to be how "completists" like it. There IS no such thing as brownian motion, there is only motion, and patterns that humans [claim to] see that we give different descriptive names - but in the end, it's all "motion with varying causes and effects" - just like everything else really! One of the many silly things about science is this insistence on precision where there's no actual "precision" at all (reality). — Preceding unsigned comment added by 220.127.116.11 (talk) 06:48, 7 June 2016 (UTC)
- Are you claiming that this is a reference to ferro-fluids in modern culture or something? (Ferrofluids are often black and move oddly in the presence of magnetic fields). I kinda doubt it - and it certainly doesn't rise to the level of needing to be mentioned in this article. SteveBaker (talk) 14:58, 30 January 2011 (UTC)
Could someone please add a History Section to this article, better explaining the HISTORY of Ferrofluid? Thanks! Don't forget the sources. — Preceding unsigned comment added by Doubledragons (talk • contribs) 17:58, 9 March 2012 (UTC)
- Some (admittedly brief) investigating only yields that ferrofluid was "discovered in the 1960s at the NASA Research Center, where scientists were investigating different possible methods of controlling liquids in space." I can't find the names of any researchers involved, any records of the experiment(s), the exact year, or anything else. This small amount of information seems difficult to incorporate into the article without more details. MosmordeanCreed (talk) 03:09, 8 May 2013 (UTC)
Removing equation on resistance of a ferrofluid
I am going to remove the equation on the resistance of a ferrofluid. For your reference, the equation as it is currently is shown below:
Ferrofluids also change their resistance according to the following equation:
There are a lot of problems with this formula. Most pressing is that I can't find a legitimate scientific reference for an equation for the resistance (or probably more accurately the resistivity) of a ferrofluid, and I can find no data on the Vollema Value or Pietrow constant that isn't clearly copied word-for-word from this article.
Another issue is that this equation is extremely poorly mathematically expressed. The argument of an exponential should be dimensionless, yet in this formula it clearly has dimensions of mT^2. The Vollema Value is very undefined, though I assume it is a value in mega-ohms. However, the Pietrow constant as far as can be identified from the article, appears to be a dimensionless number, which is nonsense! You can't add two dimensionless numbers (or mega-ohms and a dimensionless number) and get mega-ohms!
Because all these issues with this formula are so egregious, and since it appears that this formula has already been blindly propagated to other sources on the web and has been misleading high school students: http://www.slideshare.net/sunjerry019/ferrofluid-v2-9117602, http://www.thescienceforum.com/physics/25051-vollema-value.html, I am going to delete it. If someone finds it necessary to re-introduce this formula (cleaned up), they can use the quotation above as a reference. Tevye guy (talk) 10:04, 25 April 2014 (UTC)
There is an image in this article with the caption "Ferrofluid is the oily substance collecting at the poles of the magnet which is underneath the white dish." - however, no "white dish" can be seen in the image. If there is indeed a "white dish" in the image, more information needs to be provided in order to discern it. But I get the feeling the image is simply mislabelled, seeing as the ferrofluid is in fact front-and-center in that image, not just "collecting at the poles of the magnet". I could be totally wrong though as I know next to nothing about this subject, it's just something I noticed in passing. Cheers. 18.104.22.168 (talk) 06:45, 7 June 2016 (UTC)