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New Magnesium-Alloy Foam From NYU's Nikhil Gupta Floats On Water

Posted by timothy on from the floating-on-sand-is-old-hat dept.

Jason Koebler writes: A new class of magnesium-alloy syntactic foam, which is made out of hollow particles to lower its weight and density is one of the strongest metals for its weight and density ever developed, which makes it ideal for use in boats. Developed by Nikhil Gupta at NYU Polytechnic University, the alloy is 44 percent stronger than similar, aluminum-based foams, and each individual sphere within the foam can withstand pressure of more than 25,000 pounds per square inch before breaking, which is roughly 100 times the pressure exerted by water coming out of a firehose. Gupta's foams are currently used by the Navy and he suspects this one will be ready for use in warships within three years.

101 comments

  1. Robin by Archangel+Michael · · Score: 2

    Holey Floating Metal Batman!

    --
    Agent K: A *person* is smart. People are dumb, stupid, panicky animals, and you know it.
  2. Navy? Warships? by idontgno · · Score: 5, Interesting

    How flammable is this foamed magnesium alloy?

    A warship full of foamed magnesium would go up like a flare. It even incorporates its own oxidizer in the foam, in the air spaces. Unless they're forming the voids with inert gas.

    Unless they've paid some special attention to the flammability issue, a combat vessel made with this stuff would make the Forrestal look like a birthday candle.

    --
    Welcome to the Panopticon. Used to be a prison, now it's your home.
    1. Re:Navy? Warships? by gstoddart · · Score: 2

      Well, it does say it's currently used by the Navy ... so one presumes whatever they use it for they've done testing.

      At least, you hope they have. :-P

      "Admiral, the ships hull is on fire .... Ensign bring me my brown pants"

      --
      Lost at C:>. Found at C.
    2. Re:Navy? Warships? by Mr+D+from+63 · · Score: 1

      ANd what are its other durability properties, like brittleness/flexibility/fracture toughness? . Ability to withstand piercing? Just because it can withstand tensile or compressive stress doesn't make it a good solution for ships.

    3. Re:Navy? Warships? by gstoddart · · Score: 4, Insightful

      Surprisingly, these materials aren't all that expensive, according to Gupta--the raw materials are common, and there are many factories that make syntactic foams. The difficulty is in the basic science of creating them and evaluating their properties. Gupta's lab has all sorts of machines to bend, twist, compress, pull, and otherwise stress-test a material.

      "If there's a way to break something, we can do it here," he told me.

      From the sounds of it, this aint his first rodeo, and has already thought of this stuff.

      Maybe, just maybe, the man isn't an idiot?

      --
      Lost at C:>. Found at C.
    4. Re:Navy? Warships? by OzPeter · · Score: 4, Insightful

      ANd what are its other durability properties, like brittleness/flexibility/fracture toughness? . Ability to withstand piercing? Just because it can withstand tensile or compressive stress doesn't make it a good solution for ships.

      Given that TFA says that the Navy is using this foam for the deck of the USS Zumwalt, I'm betting that they have already thought up and answered more questions that the average slashdotter could have envisaged - and that they are happy with all of the answers.

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    5. Re:Navy? Warships? by NatasRevol · · Score: 5, Informative

      Science fact: magnesium != magnesium alloy

      --
      There are two types of people in the world: Those who crave closure
    6. Re:Navy? Warships? by TWX · · Score: 4, Interesting

      Fun fact... We bought a barbecue grille several years ago that we really liked. Used it for about year before we got a recall notice. We figured that there are three reasons to issue a recall; the product has a minor flaw that's too much of a pain for the manufacturer to correct in the field so it's cheaper to recall the product, or stupid people are hurting themselves by failing to follow directions or otherwise use the product in a safe fashion so it's just easier to recall the product (think lawn darts), or the product has a fundamental flaw that makes it unsafe and unrepairable at any reasonable expense.

      We're both pretty handy; I work on a lot of machines for fun and my wife has a Bachelor's Degree in Mechanical Engineering from MIT, so we figured if it was the first or second reason for a recall (ie, minor, correctable flaw or else improper usage) we could simply work around the issue and continue to use the grille. When we researched the recall more throughly we discovered that it was the third failure mode; the grille housing itself was made out of magnesium! Several owners had, through the course of cleaning the grille, scraped the oxidized layer off of the inside, exposing fresh magnesium, which ultimately ignited and burned the grille into the pavement. I had just thoroughly cleaned our grille when we got the recall notice but hadn't used it yet, and as we were loading it into the truck to take it back to the store I saw where the metal edge of my brush had gouged through the paint and oxide to expose fresh material.

      For all I know they've concocted a magnesium alloy for these ships that's both good at handling the corrosive effects of saltwater (along with magnesium's reactivity) and have managed to mitigate the dangers of exposure to fire or explosion, much in th way that sodium hexafluoride (the gas whose density can lower the pitch of one's voice as demonstrated on Mythbusters many seasons ago) is relatively safe compared to fluorine gas, but I'd still be nervous that some other failure mode hasn't been discovered that could be catastrophic down the road.

      --
      Do not look into laser with remaining eye.
    7. Re:Navy? Warships? by gurps_npc · · Score: 1
      The secret to much of modern technology is paint. We take materials and cover them with other materials to get the best properties of each, creating micro layers.

      I am absolutely positive that they will paint the magnesium foam with non-flammable, water proof substances to keep both water and flame away from the core.

      Two or three layers of protective coatings, and the only way the foam touches water or fire is if it is penetrated by a weapon that would sink the boat no matter what it was made of.

      At the very least, it could be used on internal structure points, if not the hull itself.

      --
      excitingthingstodo.blogspot.com
    8. Re:Navy? Warships? by Mr+D+from+63 · · Score: 2

      Surprisingly, these materials aren't all that expensive, according to Gupta--the raw materials are common, and there are many factories that make syntactic foams. The difficulty is in the basic science of creating them and evaluating their properties. Gupta's lab has all sorts of machines to bend, twist, compress, pull, and otherwise stress-test a material.

      "If there's a way to break something, we can do it here," he told me.

      From the sounds of it, this aint his first rodeo, and has already thought of this stuff.

      Maybe, just maybe, the man isn't an idiot?

      I didn't say it wasn't thought of. It just is not discussed and that interests me if there is going to be some discussion of a real world use.

      If there is going to be a press article about its use in ships, how about talking about more than one property? Is that unreasonable to ask?

    9. Re:Navy? Warships? by Mr+D+from+63 · · Score: 1

      Given that TFA says that the Navy is using this foam for the deck of the USS Zumwalt, I'm betting that they have already thought up and answered more questions that the average slashdotter could have envisaged - and that they are happy with all of the answers.

      Great, and I don't presume they haven't. If they want to talk about it being used in ships, why just talk about one property? I guess many /.ers like yourself only care about the hyped property, but I want to know what the other properties of this material are and I assume many others do to. Why write an article and leave out so much potentially interesting information? Laziness, lack of thoroughness?

    10. Re:Navy? Warships? by Andy+Dodd · · Score: 3, Informative

      Interesting question. It looks like it isn't air-in-magnesium - it's hollow air-filled SiC beads inside magnesium.

      (TFA doesn't mention the SiC part directly, but you can find more info in the linked research paper from TFA.)

      --
      retrorocket.o not found, launch anyway?
    11. Re:Navy? Warships? by sribe · · Score: 1

      Just curious: Perfect Flame from Lowe's?

    12. Re:Navy? Warships? by SuseLover · · Score: 1

      No, the air spaces aren't necessarily filled with air or gas containing oxygen, it could possibly be filled with a relatively inert gas such as nitrogen, helium, etc. or even a gas that retards fire.

      The potential problem with this material is that a magnesium fire can rip the O2 it needs straight from the H2O bonds in water. You cannot extinguish a Mg fire with water, that would be adding fuel to the fire. A vessel made of this floating in water means that it is floating its own fuel.

    13. Re:Navy? Warships? by Mr+D+from+63 · · Score: 1

      Since the material is described as a foam, I assume the construction technique will be to sandwich it between metal sheets, so maybe it is not as exposed anyhow.

    14. Re:Navy? Warships? by OzPeter · · Score: 0

      I guess many /.ers like yourself only care about the hyped property,

      Slow down skippy, you'r projecting there.

      but I want to know what the other properties of this material are and I assume many others do to. Why write an article and leave out so much potentially interesting information? Laziness, lack of thoroughness?

      While the first FA looked like a frat boy wannabe reporter, the second FA was a link to the published paper about the material properties of this foam. And if that isn't enough of you then there is always google - or a materials science degree at a reputable school.

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    15. Re:Navy? Warships? by Mr+D+from+63 · · Score: 0

      or we could discuss it here. I posed the inquiry to start that discussion. Sorry if you are not interested. You've made it clear.

    16. Re:Navy? Warships? by flopsquad · · Score: 4, Funny

      Slow clap from a Materials Engineer.

      --
      Nothing posted to /. has ever been legal advice, including this.
    17. Re:Navy? Warships? by Comrade+Ogilvy · · Score: 1

      To look at the failure modes of the material is a known thing since the sinking of the HMS Sheffield in the Falklands War. One of the reasons that ship sunk so quickly is the fire softened the aluminum superstructure, causing the various firebreaks to fail. (With the electrical system down and no way to provide substantial water, that ship was probably doomed anyway. But the concern was a similarly damaged ship even with a working water system might be doomed anyway.)

    18. Re: Navy? Warships? by Anonymous Coward · · Score: 0

      Yes, that's unreasonable to ask.
      http://www.smbc-comics.com/index.php?id=3732

    19. Re:Navy? Warships? by mlts · · Score: 1

      I'm curious about its properties as an insulation. It might be useful as both an insulator and as a load bearing material, either alone, or perhaps as a composite.

    20. Re:Navy? Warships? by ShanghaiBill · · Score: 0

      To look at the failure modes of the material is a known thing since the sinking of the HMS Sheffield in the Falklands War.

      The other lesson from the Sheffield, is that your computer should never be programmed to assume an incoming missile is friendly just because it was originally manufactured by one of your allies.

    21. Re:Navy? Warships? by TWX · · Score: 1

      Yep.

      Ours was the model with two distinct compartments. A normal-sized one and a smaller one next to it. Part of why we liked it so much was that the small compartment was perfect for a meal for two, heated up faster and didn't use as much propane as the big compartment.

      Ended up replacing it with a Kenmore with a wide side surface. Doesn't cook quite as well as the Perfect Flame, but won't spontaneously ignite either.

      --
      Do not look into laser with remaining eye.
    22. Re:Navy? Warships? by Mr+D+from+63 · · Score: 2

      You would think a 'foam' would be both good for both temperature and sound insulation. Sound insulation on a big ship would probably be a welcome quality as well.

    23. Re:Navy? Warships? by mlts · · Score: 1

      If it has as good structural strength as TFA states, this would be very useful for automobile or RV applications:

      1: Rodents are not going to chew through it, which can make it useful for walls.

      2: If it is good at handling deformation resistance, it might be able to be used in car doors for better safety in T-bone wrecks.

      3: If it is resistant to tools, it might be useful to slow down the meth-heads who like using a long screwdriver as a master key in RV storage lots.

      This technology has a lot of promise... maybe even in aerospace applications.

    24. Re:Navy? Warships? by ShanghaiBill · · Score: 5, Informative

      Syntactic foams have many very good properties. They use hollow ceramic beads embedded in a metal matrix. The beads are usually filled with an inert gas, most commonly nitrogen, often at far higher than 1 atm pressure. They are not particularly flammable, because the ceramic doesn't burn, and the pressurized N2 released during combustion retards the flame. It is also possible to embed halogenated frame retardants in the beads. They are strong in compression because the foam can absorb shock. They handle compression, tension, and shearing well because the beads inhibit crack propagation, sort of like how a missing link stops a zipper from unzipping. They resist heat conduction and melting better than solid metals. And, of course, they are light.

    25. Re:Navy? Warships? by Mr+D+from+63 · · Score: 1

      "structural strength" can have different meanings. Concrete has great structural strength when it comes to compressive forces, but is quite brittle and breaks if not re-inforced. Its not mentioned in the article and not clear to me from the source what the other critical properties are, or if they are addressed through construction/manufacturing techniques like sandwiching.

      Meth head resistance might be a new concept they haven't though of!

    26. Re:Navy? Warships? by Mr+D+from+63 · · Score: 1

      That is an interesting general description of this material class. The quote "They handle compression, tension, and shearing well" still leaves me questioning how well, as 'well" is a relative term. It kind of tells me they are only marginally good at it, which was my initial concern. Maybe this specific material is better in that regard?

      I would think this material on its own may not the solution for a ship deck, but possibly a layer.

      The low heat capacity and conductivity would seem to be quite nice for a ship deck that is being hit by the hot sun all day.

    27. Re:Navy? Warships? by adolf · · Score: 1

      Remedy: Consumers should immediately stop using the product and contact L G Sourcing to receive free replacement burners and, depending on the model of the grill owned, a free replacement lid.

      Consumer Contact: For additional information, contact the firm toll-free at (888) 840-9590 anytime

      Just curious, but: If you liked the grill, and did the homework, why didn't you just -- you know -- fix it? For free, even?

      --
      Kid-proof tablet..
    28. Re:Navy? Warships? by Krishnoid · · Score: 1

      Just curious, but: If you liked the grill, and did the homework, why didn't you just -- you know -- fix it? For free, even?

      And give up the opportunity to set the grill itself on fire and watch it burn even underwater?

    29. Re:Navy? Warships? by TWX · · Score: 1

      Wrong model.

      Not my video, but this is a single-chamber version of what we had. The base of the chamber is magnesium too. If one has to replace the lid and the base, one may as well just replace the grille.

      --
      Do not look into laser with remaining eye.
    30. Re:Navy? Warships? by TWX · · Score: 1

      Here is our model.

      --
      Do not look into laser with remaining eye.
    31. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      I wonder if they have enough mass to slow the spread of the flame

    32. Re:Navy? Warships? by Megol · · Score: 1

      Igniting magnesium isn't easy. IME igniting titanium is much easier. Aluminium burns well too (in fact it is often used as rocket fuel in pulverized form). And most steels can be made to burn with some effort.

      But we aren't talking about pure magnesium, we are talking about some specific alloy. Some additives are know to reduce fire hazards, one of which is calcium (itself a very reactive metal).

      And we are talking about product development - and you have to be pretty arrogant to think they don't know how to do their work. They do.

    33. Re:Navy? Warships? by sribe · · Score: 1

      Ours was the model with two distinct compartments.

      I have a very similar one, but it was not recalled. I kind of wish it had been--cooks very unevenly, and corrodes out more rapidly than it should, so it's going to die an early death, but of course out of warranty.

    34. Re:Navy? Warships? by drinkypoo · · Score: 1

      The secret to much of modern technology is paint.

      Thankfully, that's becoming less true as we move into more use of Aluminum, because paint always fails eventually and it sucks when your car's last line of defense is paint because they didn't think a corrosion coating was necessary because the paint was so awesome.

      I bought an Aluminum car specifically because paint sucks.

      --
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    35. Re:Navy? Warships? by DerekLyons · · Score: 0

      For all I know they've concocted a magnesium alloy for these ships that's both good at handling the corrosive effects of saltwater (along with magnesium's reactivity) and have managed to mitigate the dangers of exposure to fire or explosion, much in th way that sodium hexafluoride (the gas whose density can lower the pitch of one's voice as demonstrated on Mythbusters many seasons ago) is relatively safe compared to fluorine gas, but I'd still be nervous that some other failure mode hasn't been discovered that could be catastrophic down the road.

      Why do you assume that just because it's on a ship, it's routinely exposed to seawater? (Very little of a Navy ship is actually routinely exposed to seawater.) And why do you assume the foams claimed by the summary (but not supported anywhere in the article) to be in use by the Navy are magnesium?

    36. Re:Navy? Warships? by TWX · · Score: 1

      For exposure to seawater, because seawater is used to fight fires at-sea because of its abundance? Because the salty air and high humidity at sea means that even those parts that are not in direct contact with the ocean water will still be exposed? Because storms tends to create waves that splash water all over the place, including places that are not normally wet and even places that effort is made to keep water out of?

      For the foam metals being magnesium, "New Magnesium-Alloy Foam From NYU's Nikhil Gupta Floats On Water"

      --
      Do not look into laser with remaining eye.
    37. Re:Navy? Warships? by TWX · · Score: 1

      Makes me wonder if the magnesium was good for more even heating. If they switched materials in their castings to make it safe without redesigning the housings that could explain worse performance.

      --
      Do not look into laser with remaining eye.
    38. Re:Navy? Warships? by DerekLyons · · Score: 1

      For exposure to seawater, because seawater is used to fight fires at-sea because of its abundance?

      Which does not constitute routine exposure. Materials not routinely exposed to salt water on warships recieve no especial protection against it.
       

      Because the salty air and high humidity at sea means that even those parts that are not in direct contact with the ocean water will still be exposed? Because storms tends to create waves that splash water all over the place, including places that are not normally wet and even places that effort is made to keep water out of?

      The first isn't nearly as true as you might think, especially for larger warships. (Which are air conditioned and humidity controlled.) The second is also essentially not true for anything much beyond any openings to the weather deck.

    39. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      Yup, Nitrogen's only relatively inert. Once ignited, it is difficult to extinguish, being able to burn in nitrogen (forming magnesium nitride), carbon dioxide (forming magnesium oxide, and carbon) and water (forming magnesium oxide and hydrogen).

    40. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      From the paper:

      "Development of new alloys and processing methods has resulted in mitigating the limitations of magnesium such as flammability and corrosion, enabling applications in a variety of weight sensitive structures. Magnesium alloys and their properties have been studied extensively in existing literature, with AZ91D in particular being of great interest. AZ91D is a cast Mg-alloy, mainly containing 9 wt.% aluminum, 1 wt.% zinc and 0.3 wt.% manganese."

      The particles mixed into the alloy are silicon carbide.

      http://www.sciencedirect.com/science/article/pii/S0734743X15000767

    41. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      As it turns out, alloys do not behave the same as their constituent atomic parts. That's why we don't all explode any time we eat something full of sodium.

    42. Re:Navy? Warships? by khallow · · Score: 1

      But if they are calling it a magnesium alloy, then elemental magnesium is a principle component and flammability is an issue.

    43. Re:Navy? Warships? by TWX · · Score: 1

      I was under the impression that Group 2 Alkaline earth metals react with water relatively readily, though not as readily as the Group 1 Alkali metals. It would seem that if water causes a reaction that reacts-away the compound, that would be a bad thing to expose to water even incidentally.

      --
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    44. Re:Navy? Warships? by NatasRevol · · Score: 1

      Go learn some science.

      --
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    45. Re:Navy? Warships? by NatasRevol · · Score: 1

      Well, I do have an (unused) degree in that as well.

      --
      There are two types of people in the world: Those who crave closure
    46. Re:Navy? Warships? by gurps_npc · · Score: 1

      I counted corrosion coating as paint. Basically I meant any kind of thin layer put on top of the main structure.

      --
      excitingthingstodo.blogspot.com
    47. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      Sounds like he's already had some.

      Given that the Navy has already demonstrated problems with aluminum (!) flammability, anything made
      with magnesium ought to be automatically suspect. If it can be ignited, it is highly likely that few or no
      conventional firefighting equipment is capable of putting it out once ignited. Having this as a deck
      material might present a few problems.

    48. Re:Navy? Warships? by NatasRevol · · Score: 1

      Again, you have no fucking idea what you're talking about.

      Here's a very basic example for you.

      Hydrogen burns. If you combine it with oxygen, it doesn't.

      Get it yet?

      --
      There are two types of people in the world: Those who crave closure
    49. Re:Navy? Warships? by WolfWithoutAClause · · Score: 1

      I don't agree, aluminium is not easy to ignite at all in any kind of sustained way, unless you melt it and turn it into a spray, or you powder it (but then a lot of powders are pretty damn flammable), or you use high oxygen partial pressures.

      Whereas, magnesium is not that hard to ignite, and it self sustains at normal atmospheric oxygen partial pressures.

      --

      -WolfWithoutAClause

      "Gravity is only a theory, not a fact!"
    50. Re:Navy? Warships? by khallow · · Score: 1

      Water is not an alloy of hydrogen. Similarly, a magnesium containing oxide is not an alloy of magnesium. As I noted before, magnesium alloy implies a large portion of elemental magnesium. And oxygen will be present because this ship will be used on Earth in an oxygen rich atmosphere.

    51. Re:Navy? Warships? by CanadianMacFan · · Score: 1

      Well, in this case you are making a molecule and not an alloy to get the change in properties. However I wouldn't worry about the Magnesium burning up because it is in an alloy like you were trying to demonstrate. For an example of how properties can change take a look at copper and tin. They are both very easy to shape but combine them together you get bronze which is very tough.

    52. Re:Navy? Warships? by jbengt · · Score: 1

      Stiff foams typically aren't any good at absorbing sound.

    53. Re:Navy? Warships? by flopsquad · · Score: 1

      Well, I do have an (unused) degree in that as well.

      Same boat! Well, unused in the sense that I'm using it for patent law and not engineering.

      Back when I was doing research, I actually spent some time working with metal oxide foams. We followed a general rule that the Navy probably follows, too: the material is a failure if it spontaneously bursts into flame in its intended operating environment.

      --
      Nothing posted to /. has ever been legal advice, including this.
    54. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      I'm sorry your wife is such a dummy.

    55. Re:Navy? Warships? by Anonymous Coward · · Score: 0

      Well, in this case you are making a molecule and not an alloy to get the change in properties

      There is no clear line between a molecule and an alloy, it is more of a continuum. In the case of magnesium alloys, it is leaning pretty far toward molecules because of the electronegativity of magnesium, making it not so much a solid solution like more common aluminum and iron alloys.

    56. Re:Navy? Warships? by Anonymous Coward · · Score: 1

      Water is not an alloy of hydrogen. Similarly, a magnesium containing oxide is not an alloy of magnesium.

      No, but some alloys are closer to molecules than to a solid solution, and that occurs a lot with magnesium alloys.

      As I noted before, magnesium alloy implies a large portion of elemental magnesium.

      And yet there are many magnesium alloys with ignition temperature above their melting point and above the boiling point of pure magnesium. And that is without getting into the fire retardant nature of metal foams that use ceramic beads in the cells.

    57. Re:Navy? Warships? by Mr+D+from+63 · · Score: 1

      Yeah, after I thought about it a bit, they are low mass and stiff, so they probably transfer sound quite well.

    58. Re:Navy? Warships? by khallow · · Score: 1

      And yet there are many magnesium alloys with ignition temperature above their melting point and above the boiling point of pure magnesium.

      Which isn't relevant when you have fires with temperatures hotter than these temperatures. A warship would have (or have inflicted on it) a variety of means to achieve these elevated temperatures. I don't see here direct discussion of the actual concern, the high reactivity of magnesium.

      I get that the original poster was being bombastic, but I still don't buy that magnesium alloys are as stable in hot fires as you imply. It's worth noting in particular that warships have, and have inflicted on them, a variety of means for achieving temperatures hotter than what you mention.

      And that is without getting into the fire retardant nature of metal foams that use ceramic beads in the cells.

      Which is where most criticism of idontgno started. I already had read some of that before I had posted the first time.

    59. Re:Navy? Warships? by khallow · · Score: 1

      Let's try this post again.

      And yet there are many magnesium alloys with ignition temperature above their melting point and above the boiling point of pure magnesium. Which isn't relevant when you have fires with temperatures hotter than these temperatures. A warship would have (or have inflicted on it) a variety of means to achieve these elevated temperatures. I don't see here direct discussion of the actual concern, the high reactivity of magnesium. I get that the original poster was being bombastic, but I still don't buy that magnesium alloys are as stable in hot fires as you imply. And that is without getting into the fire retardant nature of metal foams that use ceramic beads in the cells. Which is where most criticism of idontgno started. I already had read some of that before I had posted the first time.

    60. Re:Navy? Warships? by khallow · · Score: 1
      Ugh, and again.

      And yet there are many magnesium alloys with ignition temperature above their melting point and above the boiling point of pure magnesium.

      Which isn't relevant when you have fires with temperatures hotter than these temperatures. A warship would have (or have inflicted on it) a variety of means to achieve these elevated temperatures. I don't see here direct discussion of the actual concern, the high reactivity of magnesium.

      I get that the original poster was being bombastic, but I still don't buy that magnesium alloys are as stable in hot fires as you imply. It's worth noting in particular that warships have, and have inflicted on them, a variety of means for achieving temperatures hotter than what you mention.

      And that is without getting into the fire retardant nature of metal foams that use ceramic beads in the cells.

      Which is where most criticism of idontgno started. I already had read some of that before I had posted the first time.

    61. Re:Navy? Warships? by Solandri · · Score: 1

      Science fact: magnesium != magnesium alloy

      Science fact: alloy = mixture of different elemental metals, not a chemical compound.

      So yes, magnesium alloy = magnesium. The presence of other metals in the alloy can limit the magnesium's exposure to the air and thus reduce flammability. But if you scratch it up or grind it into a powder, you're going to get pieces of raw magnesium.

      Syntactic foam is mostly hollow ceramic beads though. We used the stuff as floatation for our deep-diving robot submersible to achieve neutral buoyancy (the ceramic withstands pressure in deep-ocean dives and is cheaper than glass floatation spheres). I imagine the alloy is used to bind the beads together, so the alloy content is probably around 25% by volume, which reduces the fire danger further.

    62. Re:Navy? Warships? by Anonymous Coward · · Score: 1

      Which isn't relevant when you have fires with temperatures hotter than these temperatures.

      "These temperatures" are also on par with the ignition temperature of common steels too. What isn't relevant is the concern over it being magnesium at that point. There are all sorts of issues high temperature fires cause on metal structures, but not specific to magnesium alloys, and focusing on the magnesium part does make one sound like they are no familiar with the materials at all, as already pointed out.

      I don't see here direct discussion of the actual concern, the high reactivity of magnesium.

      Because that reactivity is far lower in even common alloys, even when magnesium composes more than 95% of the alloy...

    63. Re:Navy? Warships? by Anonymous Coward · · Score: 1

      Science fact: alloy = mixture of different elemental metals, not a chemical compound.

      This isn't a fact at all, especially as you get away from the common aluminum and iron alloys. The chemistry involved can get quite messy, and you can get varying strength in bonding varying all the way to something resembling a salt or to something with strong covalent bonds. Chemical bonds are not in neat, completely separate categories like shown in old, low level textbooks.

      But if you scratch it up or grind it into a powder, you're going to get pieces of raw magnesium.

      Even with more boring alloys, you have a solid solution, which like a liquid solution, means breaking off a piece still results in a just a smaller piece of the same solution. And sometimes corrosion resistance can be greatly enhanced with just a percent or two of an additional metal, and unaffected by scratching the surface.

      So yes, magnesium alloy = magnesium.

      Considering magnesium alloys can raise the ignition temperature form just under 500 C to over 1200 C, no they are not equal.

    64. Re:Navy? Warships? by dbIII · · Score: 1
      Many metal foams so far have been very tough, and there's plenty of tests for it. One of the easiest is to cut a little bar out of the stuff, slice a notch of standard size and shape in it, then hit it with a weight on a pendulum and see how far the weight swings up after it breaks the sample. Tests are often done at low temperatures to see how that material will handle at sub-zero temperatures - not a difficult thing to do since the mid point of the metal bar is the only thing that needs to be cold at the time of the test.

      Ability to withstand piercing?

      Hardness is very easy to measure directly (it's also usually related to compressive strength, but hardness tests are easy). The old Rockwell test would work well with this stuff - just press a hardened steel ball into the surface with a known weight/force and see how far it sinks in, which via a conversion (which the testing machines typically do for you) gives you a hardness number. Being a composite of air and alloy just means doing a lot of tests over a fair bit of surface until you get a representative number instead of a chance of an outlier.

      make it a good solution for ships.

      It will probably burn far more than the Sheffield did, but that's pretty obvious given the material so such a problem would be in the forefront of the minds of the designers.

    65. Re:Navy? Warships? by dbIII · · Score: 1

      If they want to talk about it being used in ships, why just talk about one property?

      Because it's a magazine reporter :(

    66. Re:Navy? Warships? by dbIII · · Score: 1

      Cool stuff. I was working with metal powder. Nitrogen gas is useful stuff to have around. Reducing in a furnace with a hydrogen atmosphere - interesting and you get to keep track of where all the exists are and make sure the corridoors are clear.

    67. Re:Navy? Warships? by dbIII · · Score: 1

      I think Snopes had a thing on that. If it was real perhaps it was a US made radar and IFF system, because a British one would never tag something French as friendly.
      Considering how it was flying very fast at wavetop height direct line of sight would only give a very short time to react either way.

    68. Re:Navy? Warships? by Anonymous Coward · · Score: 1

      Yes, sure you did. I mean

      I guess many /.ers like yourself only care about the hyped property

      is a perfect way to start a discussion. Not.

    69. Re:Navy? Warships? by khallow · · Score: 1

      Because that reactivity is far lower in even common alloys, even when magnesium composes more than 95% of the alloy...

      That sounded interesting, but when I read up on it, I saw that those alloys didn't actually have significantly lower reactivity. They have significantly lower surface reactivity, which is a good thing, but when they burn, they burn hot. The problem is that when it starts to burn in reaction with air in an environment well over both the melting points and ignition points of the alloy, it's 95% or more magnesium and that generates a lot more heat per unit volume (and mass) than steel would.

      This is where the observation that a considerable portion of your material is ceramic spheres with pressurized nitrogen or halogen gases becomes relevant.

  3. What about fire? by Anonymous Coward · · Score: 0

    I'd wonder about this foam's use in a boat, since I remember the high-school demo where the teacher lit a magnesium ribbon on fire.

  4. Uhhh by maz2331 · · Score: 1

    Magnesium is very incompatible with water, and could corrode away very quickly if it got wet. Plus it is rather flammable, with water accelerating its burning. I'm not sure that I'd want a lot of this on a warship that can be expected to be hit by enemy fire. It would go up like a flare.

    1. Re:Uhhh by Em+Adespoton · · Score: 4, Informative

      "magnesium alloy"

      As a comparison, Inox, or "stainless steel" is a steel alloy. Steel is very incompatible with water, and could corrode away very quickly if it got wet. And yet, add that chromium to create a new alloy, and suddenly you've got a slightly softer metal that doesn't oxidize.

      See also: transparent aluminium, silicon vs silicone, etc.

  5. Just what we needed... by Anonymous Coward · · Score: 0

    ... a new unit of measure. Pressure described as scalar multiples of "the pressure exerted by water coming out of a firehose."...

    1. Re:Just what we needed... by forty-2 · · Score: 1

      How many libraries of congress could you lift with that much pressure?

      --
      never drink kool-aid from a big vat
  6. 250 psi? by FF-Loucks · · Score: 1

    In the US, 250 psi would be a bit much for the pressure coming out of a fire hose. 100 psi would be much more typical nozzle pressure. We test our hoses to around 300 psi, but I'd hate to be the nozzle man at 250 psi. (to get 250 psi at the nozzle, you'd have to be pulling a 2 1/2" hose) Depending on hose length, you'd be looking at somewhere around 300 GPM at 250 psi on a 2 1/2" hose.

    1. Re:250 psi? by gstoddart · · Score: 2

      to get 250 psi at the nozzle, you'd have to be pulling a 2 1/2" hose

      In my best John Wayne voice ... that's just how some of us do things, there Pilgrim.

      Oh, did you mean diameter? Never mind then.

      --
      Lost at C:>. Found at C.
  7. Even a brick will float ... by BarbaraHudson · · Score: 1

    Even a brick will float if you coat it with silicone. And you can boil an egg in a paper bag. News at 11.

    --
    "Transparent" is a shit show that trades on every stereotype going. A man in drag is NOT a transsexual.
    1. Re:Even a brick will float ... by Anonymous Coward · · Score: 0

      TIL

    2. Re:Even a brick will float ... by ChrisMaple · · Score: 1

      Bricks have a specific gravity in the range of 1.75 - 2.4. They'll float in a pool of mercury, but not in water..

      --
      Contribute to civilization: ari.aynrand.org/donate
    3. Re:Even a brick will float ... by ceoyoyo · · Score: 1

      Well, that's irrelevant. And also wrong: regular silicone generally has a density of 1.1 - 2 or so and brick is even more dense, so no, a brick won't float no matter how much silicone you coat it with.

    4. Re:Even a brick will float ... by Anonymous Coward · · Score: 0

      A coat made of silicone foam 3 inches thick.

  8. VW Bonfire by WillgasM · · Score: 1

    Anybody ever been to a party where someone throws an old VW engine block on the bonfire?

    1. Re:VW Bonfire by Anonymous Coward · · Score: 0

      https://www.youtube.com/watch?v=PSnYQddXTcU

  9. They're kind of cheating by Karmashock · · Score: 1

    ... I mean, the metal isn't actually lighter than water... it just has lots of bubbles in it. I mean... I could tie a helium balloon to a brick... but I'm not actually making the brick lighter am I?

    You could foam anything anything and make it lighter.

    --
    I've decided to stop wasting my time responding to AC trolls/sockpuppets... so if you want a response from me... login.
    1. Re:They're kind of cheating by Mr+D+from+63 · · Score: 1

      You could foam anything anything and make it lighter.

      But the trick is that its also very strong. Its easy to achieve one property requirement, the more you add the harder it gets.

    2. Re:They're kind of cheating by mspohr · · Score: 1

      You could foam anything anything and make it less dense

      --
      I don't read your sig. Why are you reading mine?
    3. Re:They're kind of cheating by Karmashock · · Score: 1

      yeah but if I made a steel trellis, that wouldn't be considered a new type of metal.

      --
      I've decided to stop wasting my time responding to AC trolls/sockpuppets... so if you want a response from me... login.
  10. Zeppelins float in air by Anonymous Coward · · Score: 0

    Zeps were made from aluminium too and they floated in air. What is so fancy about floating in water?

  11. Other options by JustNiz · · Score: 1

    They should make a lump of phosphorus foam and try floating it on water.

    1. Re:Other options by HiThere · · Score: 1

      You could probably do that in a similar way, i.e., use a phosphorous allow, form it into small beads filled with a non-reactive medium (say nitrogen) and embed it in a matrix. I doubt, however, that it would have any useful properties. I'm rather certain that, unless it was your goal in the design, it wouldn't have any spectacular ones.

      FWIW, Titanium ribbons will burn so furiously that they will not only burn in nitrogen as well as oxygen, they will actually pull oxygen away from water. (Well, ok, so wil phosphorous, but phosphorous won't touch nitrogen.)

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
  12. Boats are already floating metal by monkeyxpress · · Score: 2

    The idea of a metal-air hybrid object that has a density less than water is already quite well developed. It is typically called a boat or ship. Some of them even have integrated air-cell buoyancy systems in the form of polystyrene blocks.

    Indeed based on his claims, it would appear this material (apparently "one of the strongest metals for its weight ever developed") would be much more important to the aviation industry.

    1. Re:Boats are already floating metal by just+another+AC · · Score: 1

      A lighter metal means ship weighs less for a given size. Most of the weight of a ship is the metal. Air compartments below the waterline will help buoyancy but at the expense of ship size (and hence drag).

      Reduced boat weight means reduced displacement which means greater carrying capacity / increased efficiency / higher top speed.

      Given the size of the worldwide shipping industry and the size of the naval military this is quite an important breakthrough.

  13. 170MPa is about half the strenght of bamboo by viking80 · · Score: 1

    A fiberglass boat is stronger. Fiberglass is orders of magnitude stronger.

    --
    don't cut it off www.mgmbill.org
  14. Sodium hexaflouride? by PeterM+from+Berkeley · · Score: 1

    I think you mean sulfur hexaflouride.

    --PM

    1. Re:Sodium hexaflouride? by TWX · · Score: 1

      Yes. My mistake.

      --
      Do not look into laser with remaining eye.
  15. Oblig. xkcd by Anonymous Coward · · Score: 0

    Umm...

    https://xkcd.com/678/

  16. Not always, in face not often at all by dbIII · · Score: 1

    No. As an example steel normally contains iron carbides instead of free carbon in solution.
    Some are as you state but most alloys used are not just solutions of one element dissolved in another.