One of the authors in a related paper[1] is Hyun-Tak Kim. He has many publications in peer-reviewed journals[2]. One even has > 1500 citations[3].
I can't tell if there is a catch anywhere, this seems pretty legitimate. Also, unlike some previous claims that required sophisticated setup to reproduce, this seems dead simple. I think we will hear from other researchers very soon.
1. Superconductor Pb10-xCux(PO4)6O showing levitation at room temperature and
atmospheric pressure and mechanism: https://arxiv.org/pdf/2307.12037.pdf
The actual picture of (poor) levitation in the paper you linked is pretty compelling. This isn’t a complex, noisy measurement showing something that’s related to superconductivity — this is a magnet and a supposed superconductor repelling each other.
As far as I know, that’s possible with permanent magnets (and it would be weird, but not impossible, if the group instead synthesized a novel ferromagnet and didn’t notice), electrets (seems pretty unlikely here), very extreme amounts of static charge (again, seems unlikely), and actual superconductivity (would be awesome).
Random bits of cooked oxides, ceramics, and such don’t float on a magnet.
Believe it or not, the levitation effect can be found in non-superconducting materials with a high diamagnetic constant such as pyrolytic carbon. Induced magnetic fields are created by "effective currents," which can occur in zero-resistance systems that are not called superconductors (because they can't conduct across a significant distance, only around a tiny loop) like molecular or atomic orbitals.
Copper and a magnet can certainly interact. Drop a magnet through a copper pipe and the eddy currents will induce a field that's opposed to the magnet causing a damping effect. Maybe something like this is going on where movement of the magnetic field is inducing an opposed magnetic field in the copper, and thus interacting.
Anyhow it will be interesting. if It can generate a field of 1.5-2 Tesla you could have more efficient solenoids and probably motors.
Yeah, that thing does really want to stay in a constant level on the magnetic field. That would dispel every other explanation on the GP, as it's not simply being repelled or attracted.
I found that video very compelling. If it was eddy current, the float standoff distance would have decayed. It sure looked to me like there was no decay at all, and wow! if true.
Eddy currents can be induced in non-superconducting materials that make it look like levitation, but the catch is that there has to be relative motion between the magnet and the object 'levitating' to generate the currents in the first place.
But in this sample video, the standoff distance doesn't appear to be slowly dropping at all, which would rule out eddy currents as a source of the behavior. If you continue watching the linked video to 13:27, he talks about how and why superconductors levitate.
I would say that this type of levitation where it sort of half levitates is quite common. I taught YBaCuO superconductor experiments for a few years. That Meisner effect would get full marks in my institution!
>As far as I know, that’s possible with permanent magnets (and it would be weird, but not impossible, if the group instead synthesized a novel ferromagnet and didn’t notice)
As far as I know a stable arrangement of permanent magnets levitating is impossible without a baring surface to keep them aligned. (i.e. free floating levitation is not possible without active control)
* ferromagnetic - attracted to one pole of a magnet but not the other (in a given orientation), this is what everybody thinks of when they think of "magnets"
* paramagnetic - attracted to both poles, i.e. stuff that sticks to magnets
* diamagnetic - repelled by both poles, except in superconductors, this effect is very weak compared to the forces experienced involving ferro-ferro or fero-paramagnetic materials.
There isn't another category, everything fits in to one of those buckets.
Saying
>Just so everyone is on the same page, static passive diamagnetic levitation is possible with materials like pyrolytic graphite.
is a bit deceptive, as what people know as "magnetic" materials are ferromagnetic.
That's not quite true. There is a Halbach array with a bunch of compensation coils that will nicely center as long as it is moving, no active control or bearing required.
stationary. Hence the 'as long as it is moving' bit above. Because the motion allows for the coils to generate enough of a current to drive the compensation. So you need a support system to bring the assembly up to a certain minimum speed above which it will stably levitate.
I wonder how long you could get one of those to spin in a vacuum.
Halbach arrays with compensating coils have been proposed for some interesting applications, such as low loss flywheels for electrical storage. I don't know if that ever got commercialized but I do recall that some prototypes were made by a US company. I can't find a reference to it though.
Its not a dirty secret, but just like the rules on chemicals under the organic certification, if you can show that there's no way to do what you want to do with lead-free, you can get an exemption. I suspect that "significantly lowers the cost of power generation" would outweigh "contains lead".
> if you can show that there's no way to do what you want to do with lead-free
The bar is even lower than that. For example, bullets are still made of lead, not because it's necessary, but because it's cheap, and despite the fact that it contaminates the meat of the hunted animal with lead.
Tangentially, the US Army has completely stopped using lead in bullets. Their 5.56 NATO ammo has copper where the lead used to be (i.e., inside a brass jacket) which reduces performance because copper is only 2/3 as dense as lead.
First, terms - brass is not used to "jacket" a bullet. Brass is used as the case material for the cartridge. Steel, and nickel plated steel are some times also used here. "Jacketing" (as in, Full Metal Jacket) refers to the material that wraps around the exterior of the projectile. As far as I'm aware, the material used here is almost always copper, or a copper alloy (cupronickel).
The US standard bullet is the M855. It's a lead core with a soft soft steel penetrator at the tip, that's jacketed with copper.
There's an advanced version of the M855, the M855A1, which is an entirely steel slug, jacketed with copper. This bullet has better terminal performance at longer ranges, and slightly better armour piercing capabilities.
The US army standard training round is the M193. It is a lead bullet jacketed with copper. Interestingly, it in many ways has better terminal performance than the M855 because this is the bullet the M16 and M4 rifles were designed around, and the M855 only exists because of NATO politics.
There are no bullets in the US inventory, to my knowledge, that use a copper core. Copper is simply far too expensive to be used at that scale, and, as you pointed out, reduces the weight of the projectile which has negative effects on terminal performance.
"Why are bullets jacketed in copper" you might be wondering here - when rifle cartridges were invented, they still used black powder, and all bullets were lead. When smokeless powder was invented, it became possible to have more explosive power per unit of volume. However, this had two negative effects - one, the lead projectile would either disintegrate, or became entirely inaccurate, at the speeds it was accelerated to. Second, the force of the bullet against the rifling of the barrel was rubbing away metal from the bullet, leaving lead deposits which fouled the gun and made it inaccurate. All steel bullets solved this problem, but increase the wear on the barrel. The solution was to coat (jacket) each bullet in a thin layer of copper, which was stiff enough to withstand the force of friction in air, while also softer than the steel barrel and reduced wear and tear on the rifles
M855 has a lead plug behind a steel penetrator. M855A1 has a copper plug behind a steel penetrator. So, I stand by my "copper where the lead used to be". I never said there wasn't a steel penetrator.
>For general issue, the U.S. Army adopted the M855A1 round in 2010 to replace the M855. The primary reason was pressure to use non-lead bullets. The lead slug is replaced by a copper alloy slug . . . The U.S. Marines adopted the Mk318 in early 2010 due to delays with the M855A1. This was a temporary measure until the M855A1 was available for them, which occurred in mid-2010"
As you probably know, most combat soldiers in the US Army and Marines carry a rifle (usually an M4 these days IIUC) that fires 5.56×45mm NATO, so it is probably the ammo type that the US military uses the most of.
This post is a master class in why you shouldn't get all your information from Wikipedia. Press releases are not reality.
Yes the M855A1 was developed and started operational testing in 2010. However, it wasn't available to anyone who wasn't forward deployed until...my memory says 2015. The M855 is still used on post because a) it's cheap, and ballistically similar to the M855A1 and b) the production lines at Lake City are still geared for them
The Marine corps didn't formally adopt the M855A1 until 2017/2018. Brass didn't like it because it broke the feed ramps on machine guns. There was a big procurement SNAFU about this.
I get that you're trying to be snide because you were so publicly wrong, but your tone here really just makes you sound like you're trying to sound smart about something you know nothing about. Something to consider. Frantic googling does not an expert make.
You're right about the copper core on the new model A1 - I thought it was steel entirely with thin jacket. I would argue that when, by weight, the majority of the bullet is steel, my original point still holds.
I worded my original assertion the way I did (lead replaced with copper) so that it would be true even if the majority of the bullet is steel.
>I get that you're trying to be snide because you were so publicly wrong, but your tone here really just makes you sound like you're trying to sound smart
Right back at you. I don't think I'm motivated by trying to sound smart, but rather by curiosity about the subject. Well, OK, half by wanting to sound smart (and win arguments) and half by curiosity.
In particular, I'm still curious about whether ammunition containing lead is still routinely used by the US military--if you still want to talk about it. I realize Wikipedia can be totally wrong. So far I haven't succeed in wringing information out of Google Search that would corroborate or support your assertion. When's the last time you (or someone you know to usually tell the truth) has observed M855 being used by the US military in significant quantities?
Answering without doxxing myself is harder than I thought. The last time I was on a US military range, which to be fair was right before the pandemic so things probably have changed - we drew green tip (M855) from the range master. My understanding was that a) the steel targets were getting beat up by A1 and there wasn't any money to replace them and b) we weren't a combat group so we didn't rate the good shit.
EDIT TO ADD:
I don't know if that qualifies as "quantities" and anecdotes are just that, but that's been my experience.
Thanks for taking the time to set me straight on that. I didn't realizes I was posting misinformation when I wrote, "the US Army has completely stopped using lead in bullets".
>The US army standard training round is the M193. It is a lead bullet jacketed with copper. Interestingly, it in many ways has better terminal performance than the M855 because this is the bullet the M16 and M4 rifles were designed around
As I understood the standard M4 with 1:7 barrel can't shoot M193 accurately
Copper bullets date back to the 80s, they're not a new development. Copper bullets have higher penetration despite having less mass, which makes them better against armored targets, and NATO still held on to lead for so long just because it's cheaper.
They date back further than that. In WW1, French troops were mostly shooting full copper/bronze shot. The reason was that it was cheaper and easier to mass-produce solid copper bullets than it was to increase the production of jacketed bullets by a similar amount, and with Germany excluded from naval trade, there was suddenly a lot more copper available on the market.
Yeah, I just mentioned in another comment that there already exist exemptions such as server/networking hardware:
"Lead in solders for servers, storage and storage array systems, network infrastructure equipment for switching, signalling, transmission, and network management for telecommunications"
Lead is used everywhere. Not in paint anymore but you can buy lead weights at hardware stores. Don't grind it up and put it in your muni water supply, but it's a household substance that is harmful if ingested, like many others.
Both lead solder and lead-free solder are commonplace. Lead is standard in aerospace and military applications, while lead-free is standard in most products sold in the EU.
It's more about producing toxic waste and contaminating the environment - no one's licking the solder joints in their electronics either, but you still have to use lead-free solder.
Compared to refining traditional conductors and recycling/disposing of used electronics?
> you still have to use lead-free solder
One, fumes. Two, people touch their solder and then grab a cookie.
We're premature. The results need to be proven. But the benefits of RTP superconductors is mindblowingly high enough that risks from lead contamination (far from a novel problem, I might add) can be safely ignored.
Soldering temperatures don't produce significant lead fumes. The fumes you see are flux fumes (which are also bad to inhale).
IMO, the most dangerous thing about lead solder is cleaning the iron. Both the common methods (damp sponge and brass wool) create many tiny little balls of solder that are hard to see and bounce about all over the place. Because of the high density of lead they're less affected by air resistance than you might expect, and they roll easily, so they can move surprising distances. They can easily end up caught in clothing, and from there fall into food. This will result in much higher lead ingestion than just touching solder then touching food.
I personally always use lead-free solder. If you have a good temperature controlled soldering iron it's nearly as easy to use as leaded solder.
Lead-free through-hole soldering is easy and practical. Unfortunately, for SMT prototyping (including reflow soldering), lead-free work is no longer that easy. Another problem, even in through-hole devices, is when you have large metal parts - a tough problem for RF/microwave circuits full of SMA and BNC connectors, backed by 1 or even 2 layers of solid ground planes, providing excellent a heatsink and a lot of cursing during work and rework. With lead-free solder, I found the iron needs to be cranked up to 420°C for a usable experience (but a larger iron tip may reduce that to a more reasonable level), and I don't know what temperature does it take to desolder them.
The last time I checked, low-temperature bismuth-tin alloy is only available as solder paste, unfortunately not available as flux-core solder wires (they're not really a good choice for connectors to begin with as the alloy is brittle, but I only need it to survive before the next prototype...)
It's trivial to experimentally demonstrate that solder fume contains almost no lead, the quantity is negligible. Claiming the contrary is the electronics equivalent of saying HTML is a programming language. Please don't do that again. The fume is indeed toxic, but it's due to the VOCs from the flux core, not the lead in the alloy.
A more solid (no pun intended) argument can be the hazards of debris. Furthermore, in my opinion, a newer and more serious problem of leaded solder today, in a workshop setting, is its use in solder paste. Solder paste and a reflow oven are required for prototyping any circuit boards with surface-mount components (SMT) - basically any modern circuit board today. Solder paste is a tube of toothpaste-like chemical mixture that contains tiny, micrometer-sized metal particles, mixed with sticky flux. If they're used without care, a solder paste spill is a sure way to contaminate the floor or work surface of your workspace. The sticky paste is also hard to wash away from skin.
Unfortunately, reflow soldering of surface-mount components can be really challenging, even more so when doing it by hand. Thus, classic lead-tin alloy is often used to reduce difficulties of assembly during workshop prototyping due to its technically superior properties. Switching to lead-free is only possible when you have a tightly-controlled and consistent work flow.
If you want lead-free, for small-scale prototyping and rework, a non-toxic bismuth-tin alloy is sometimes a good alternative to standard SAC305 lead-free solder thanks to its low melting temperature, which is one main reason that makes most lead-free alloys difficult to use (it even has considerable popularity in mass production of LED devices, as they are heat-sensitive). But its surface tension is slightly different, weakening the self-alignment effect of components during reflow soldering, increasing the chance of defective joints - a concern in prototyping. Its brittle nature also increases failure rates in the field, among other caveats.
> Solder paste and a reflow oven are required for prototyping any circuit boards with surface-mount components (SMT) - basically any modern circuit board today.
This is incorrect. You can easily do small scale work with almost all SMT components without solder paste. Solder paste is required for automated assembly processes. But almost anything done by hand can also be done with conventional solder.
Source: I worked as an electronics designer for a few years, and assembled prototypes and small production batches by hand with SMT parts (0603's, TTSOPS, etc) every day.
The one exception is BGA devices, because the solder pads are underneath the device. But doing those by hand requires precise alignment that is difficult enough that few people do it. Also, for smaller BGA devices with fewer pins, skilled operators can still solder them in place with a heat gun by covering the pads with solder and flux and just melting them into place.
I know two people (one of which is here on HN) who do fairly large BGAs by hand, I wonder if that skill is really that rare. I couldn't do it myself though, I did try but for some reason I can't make it work reliably enough to risk it on stuff that matters.
> This is incorrect. You can easily do small scale work with almost all SMT components without solder paste. Solder paste is required for automated assembly processes. But almost anything done by hand can also be done with conventional solder.
I disagree. I don't consider 0603 passives and TSSOP packages "modern" anymore. Of course these components can be hand soldered with ease (possibly at top quality with the aid of a microscope). Unfortunately, the industry is gradually abandoning TSSOP and QFP in favor of DFN, QFN, and LFCSP in recent years. For anything that does high-speed signaling or multiplexing above 1 Gbps (which is old by computer's standard) like USB 3.0, PCIe 1/2, QFN goes without the need for a mention (short of using BGA). But the thing is, even in simpler ICs like DC-DC controllers, you can see the same trend. Simple RFICs are another source of heavy users of these packages, reduced circuit parasitics is certainly a factor.
These packages are all leadless, and frequently with thermal pads at the bottom. An older term for leadless packages is BTC - Bottom Termination Components. [1] After a few successive and multiple failed QFN soldering attempts, I switched to ordering stencil, solder paste, and a hot plate. It worked perfectly on my first attempt, so I never looked back.
Unless you have top 10% soldering skills, which I don't (experienced smartphone repair technicians seems to have mastered the art of QFN), I found solder paste is required for maintaining your sanity with leadless packages. Furthermore, without reflow soldering, prototype assembly can be very time-consuming and takes hours, especially when you need 3 or more prototypes.
Occasionally, leadless packages also have optional difficulties turned on, completely eliminating the possibility of hand soldering, such as multiple bottom pads for different nets (to minimize parasitic inductance), or having two layers of contacts, one row on the exterior and on row on the interior.
> You can easily do small scale work with almost all SMT components without solder paste. [...] The one exception is BGA devices
And DFN, and QFN, and LFCSP, and...
Thanks to industrial and automotive users, some ICs still have QFP versions for these markets (due to their vibration resistance) that are friendly for hand operation, but you have to pay a premium.
Finally, even plain-old QFP chips have bottom thermal pad these days (in that case, you can manually apply a blob of solder on the PCB and reflow again with a hot air gun, but manually apply a drop of paste is easier to work with).
---
[1] But these days it would make people think it's some kind of a Bitcoin mining ASIC. BTW, the last time I've checked, these ASICs are indeed QFN, so one can say they're BTC BTC chips...
It's like fundamental best practice to always wash your hands thoroughly with soap if you handle leaded solder.
You might want to read more in the links I shared about the harmful effects of lead before "whatabouting" to other problems of electronics recycling/waste.
and yes, it's entirely possible this application would get an exemption from usual restrictions on lead. For example in the EU directive, one of the exemptions is:
> Lead in solders for servers, storage and storage array systems, network infrastructure equipment for switching, signalling, transmission, and network management for telecommunications
> fundamental best practice to always wash your hands thoroughly with soap if you handle leaded solder
But people don't, particularly students, and sometimes they also let their irons run too hot at which point fumes become an issue. Also, there is an easy alternative, so why not.
If the choice is lead superconductor or not, nobody is going to pause on a use case because there is lead. If they do, and if this is real, please let me know--I'd love to have them as competition.
> might want to read more in the links I shared about the harmful effects of lead before "whatabouting" to other problems of electronics recycling/waste
The point is, whether a RTP superconductor does or doesn't contain lead is irrelevant to its adoption. The advantages are too large. What current directives say are, similarly, irrelevant.
Oh, sure. You could have just said that then. You instead originally said something about "no one licks the insides of the computers", which isn't the reason lead in electronics/PCBs/etc. is restricted, and what I was pointing out.
Usually people who are making the argument you were making with the words you were using are signalling that lead is "lump of rock from center of nuclear reactor" dangerous. Honest to god, a lot of people believe this
Why is this being downvoted into oblivion? It's a completely valid, good-faith point explaining why lead has restrictions on its uses other than "someone might lick it"... It would be nice if people actually responded and vocalized their disagreement or described the flaws in my reasoning, rather than just suppressing my message.
As for how to avoid lead poisoning, coat the lead with a thin layer of some substance, perhaps a plastic or rubber that doesn’t affect its magnetic capabilities.
Or perhaps they can galvanize it with safer metal, leaving a really small part exposed.
I think people are talking about RoHS rather than practical danger. Since RoHS is incredibly strict about quantities, e.g. if you can mechanically seperate a piece of the widget, that's what gets measured.
Cobalt is way more toxic than lead and yet every consumer grade lithium ion battery contains it. The fact something is toxic is not that important. What is that we manage the end of life for the products it contains responsibly.
I mean, modulo edge cases, lead is a lot scarier than CO2; it's only because of the ridiculously obscene quantities of CO2 being produced that it's a more immanent threat. There's obviously not enough information yet to weigh the value/consequences of the amount of lead used here, but if your measure of whether something is a good idea for mitigating carbon emissions is just "it's not carbon emissions", you're going to find yourself kicking a can a bit down the road, or (much) worse.
Maybe they could pack it into epoxy encapsulated modules of standard size, so you could always reuse it in another motor or transformer or what have you, assuming you were willing to disassemble the scrapped gadget?
If you think carbon dioxide is scary, wait for your cup of Pepsi.
(Low toxicity of CO2 is actually one of the reasons it is not treated seriously enough).
> Superconductor Pb10-xCux(PO4)6O showing levitation at room temperature and atmospheric pressure
Is it late April Fools joke?
It can’t be true.
Edit: I am not surprised it levitates. I am astonished by how much it will reshape our world if it is real room-temp and ambient-pressure superconductor. Also is easy to produce. Just too good to be true.
Levitation is to be expected for any superconductor when it's in a superconducting state; that part is banal. The big question is whether it's actually a superconductor at RTP. Their results are strong enough that it's unlikely to be a mistake, though fraud is possible too (although it is so easily uncovered given the simplicity of preparing the material and the strength of the reported effects that fraud seems almost pointless since it'll be uncovered immediately).
The recipe in the paper is so simple that it's giving me Pons-Fleischmann vibes. It reads more like an entry from an alchemist's journal, reproducible with chemicals and equipment you could buy on eBay or Amazon.
I wonder if anyone has tried to contact one of the authors to confirm the paper is legitimate (i.e. someone isn't spoofing the author's names in order to create chaos).
Silicon is one of the most abundant elements on Earth and for thousands of years humans had no idea what would be possible with very controlled etching of it.
Mildly-topical Terry Pratchett amusement quote, since it involves a society that has overlooked the power of silicon plus the potential of superconductivity:
> Detritus blinked. There was a tinkle of falling ice. Odd things were happening in his skull. Thoughts that normally ambulated sluggishly around his brain were suddenly springing into vibrant, coruscating life. And there seemed to be more and more of them.
> 'My goodness,' he said, to no-one in particular.
> This was a sufficiently un-troll-like comment that even Cuddy, whose extremities were already going numb, stared at him.
> 'I do believe,' said Detritus, 'that I am genuinely cogitating. How very interesting!'
> 'What do you mean?'
> More ice cascaded off Detritus as he rubbed his head.
> 'Of course!' he said, holding up a giant finger. 'Superconductivity!'
> 'Wha'?'
> 'You see? Brain of impure silicon. Problem of heat dissipation. Daytime temperature too hot, processing speed slows down, weather gets hotter, brain stops completely, trolls turn to stone until nightfall, ie, colder-temperature,however,lowertemperatureenough,brain operatesfasterand—'
> [...] Detritus sat down again. Life was so simple, when you really thought about it. And he was really thinking. He was seventy-six per cent sure he was going to get at least seven degrees colder.
Assuming the lift is there or the magnets are strong enough, it would be plausible to have an electromagnetic hover skate park where you could pay by the hour, and possibly even future X-game like events where the boards and riders could move in any direction they can get acceleration in.
I want them to have enough current passing through them in a rod shape that it will run the current against the Earth's magnetic field to cause vertical movement.
Not so fast... These superconductors although revolutionary loose superconductivity in high magnetic fields (or with high currents).
If this proves true I'd see their use more in electronic circuits. Novel sensors etc rather than classic high power high field uses people dream about when the words "room temperature superconductivity" gets thrown about.
MRI will get much cheaper, but you still need a good upper critical field and a proper access control (Zone 2/3/4) protocol. So probably not in very small buildings.
From what I can tell this material can't provide higher than 0.3T. We've had permanent magnet MRI at 0.3T but the drawbacks vs superconducting magnets are weight and lack of active shielding.
With room temperature superconductivity doesn't it become possible to turn the magnet on and off far more easily? MRIs would be much safer if they were only energized during the actual imaging process.
They are already superconducting and using liquid helium to cool. They have failure modes of spilling gas out into the room (patient and operators have to evacuate.)
Superconductors will typically levitate if placed above a magnet, and vice versa. Magnets are weird--superconductors even more so. I assume that's what they were referring to?
Edit: Judging by Fig 4, which has a large object conspicuously labeled "magnet", that's probably what they're referring to.
This whole experiment is quite reminiscent of an experiment I did in high school. We synthesized a high temperature superconductor (IIRC it was YBCO) by grinding some powders together with a mortal and pestle and baking the result. And we stuck it in a little cup of LN2 and floated a magnet on it. It really works!
This group used somewhat nastier powders, they had to cook parts of it in a vacuum, and they floated the result on a magnet instead of vice versa. And it only floated a bit. But they did it without any cooling!
I would guess that it'll take a month or two to repro the procedure. The paper was uploaded in the last week, so we're still probably a few weeks out on peer review.
I can't tell if there is a catch anywhere, this seems pretty legitimate. Also, unlike some previous claims that required sophisticated setup to reproduce, this seems dead simple. I think we will hear from other researchers very soon.
1. Superconductor Pb10-xCux(PO4)6O showing levitation at room temperature and atmospheric pressure and mechanism: https://arxiv.org/pdf/2307.12037.pdf
2. Google Scholar: https://scholar.google.com/citations?user=_P8mux4AAAAJ&hl=en
3. Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging: https://scholar.google.com/citations?view_op=view_citation&h...