Making YBCO superconductor-----make money online

today on applied science we're going to

talk about superconductors you've

probably seen this cool demo of

levitating a magnet above a

high-temperature superconductor like

this and as it turns out making

superconductor is completely possible in

home shop and involves quite a lot of

fun stuff we've got spontaneously

combusting mixtures you've got hydraulic

pressing and we've got kilns with oxygen

flooding but first let's check out some

of the properties of the finished

product that I've made here the material

that we're making today is called ybco

for you tree embarr um Kapoor oxide and

this is a high-temperature

superconductor but high-temperature is

relative we still have to get it down to

liquid nitrogen temperatures so very

cold but not quite as cold as liquid

helium which is what some

superconductors require the

low-temperature ones ybco is a black

ceramic material and I'm making it in

little disks like this the shape of it

comes from the crucible in which I'm

making this and it's kind of a you know

it's a fairly dense thing it feels

basically like a floor tile or something

it's really just kind of a normal

feeling ceramic and it's pretty brittle

in this form too you can break this with

just a pair of pliers it's really not

that strong and if we break it you can

see a little bit of crystalline

structure inside the magnetic levitation

occurs because of an effect called flux

pinning and basically the crystal is not

completely perfect there's little

pinholes where the magnetic fields can

get through the superconductor and when

we drop a magnet on top the magnetic

field is forced through these little

pinhole defects and then can't get back

out because the little pinhole is

surrounded by a superconductor and

there's a current that flows through

there and so it's basically like a

little solenoid coil holding the magnet

in just that spot pretty neat effect for

visual interest I thought it would be

fun to put some of these colored

ferrofluids on the levitating magnet you

know can I have a levitating droplet of

fluid with the spikes coming out and

everything but as it turns out the

colorant in these colored ferrofluids

are just like a surface thing I put some

dust or something in there so if you go

into the bottle

The Dropper you don't actually get the

color out it's still black ferrofluid in

there but nonetheless still a cool

effect and then also a neat thing to do

is to drop a iron filings on top of this

and the momentum of the art of the

falling iron filings gets caught up into

the magnet and causes it to spin around

and it looks pretty cool and I also got

some high-speed video of this one of the

best tests for a superconductor is the

magnetic levitation like we've been

looking at but I also wanted to measure

the electrical resistance of my

superconductor to see if the transition

temperature agreed with the literature

so I came up with a setup to do that a

while ago Charles PAC sent me his great

temperature lager here and because this

is an open source device I was able to

download the firmware and modify it for

doing a superconductor transition

temperature measurement so what we have

here is a combination of both devices

we've got the Keithley doing a 4 wire

resistance measurement and the idea here

is it's got a hundred milliamps flowing

through the outer two probes and then

it's checking the voltage between the

inner two probes

and figuring out the resistance that way

and even at a hundred milliamps the

voltage drop between these two inner

probes is very small but what we're

doing is instead of measuring

temperature with this fourth Channel on

the data logger

it's basically piggybacking on the the

two sense electrodes and capturing that

tiny voltage and recording it and since

100 milliamps everything lines up so

twenty eight millionths of real

resistance corresponds to two hundred

and eighty-two units in this thing's

storage system it ends up being I think

tens of micro volts or something and at

the same time that we're recording the

voltage on the sample with this channel

we're also recording temperature from

real type K thermocouples here so the

whole setup allows us to measure

temperature and then the resistance

based on this sensitive setup so you can

see the results of the data collection

here it's actually pretty good I

wouldn't worry about the absolute

numbers quite so much

liquid nitrogen is only negative 196 I

think Celsius and you can see that my

measured temperature values go lower

than that which is not really possible

that's because type K thermocouples

aren't really the best way to measure

liquid nitrogen temperatures but it is

what I have on hand and it's actually

surprisingly close considering

everything else you can see for

comparison that a regular piece of metal

just gets to be a better and better

conductor the colder it gets

but the superconductor is special in

that it's getting to be a better

conductor as it gets colder and then

suddenly when it hits this transition

temperature it becomes a full

superconductor and the resistance really

does drop to zero it doesn't transition

to like a another regime where it's

getting better and better it really goes

to out to real zero attaching the leads

to the piece of superconductor was not

at all easy in fact the dumbest way to

do it ended up being the most effective

I basically just took this you know

heavy alligator clip and just bit onto

it like that and that's it that actually

worked really well some other things

that I tried were silver based epoxy

this seemed like it would have been a

great way to attach you know a small

wire but it doesn't work at all as soon

as the thing gets cold we lose contact

I'm not really sure if the epoxy is

shrinking and just making poor contact

with the ceramic or what but that

doesn't work and then I also was clever

thought I was being clever and made

these four wire Kelvin probes out of

pogo pins and they're nice and

spring-loaded and they have like a

really long travel and everything these

don't make contact either I put a lot of

pressure on it and between the springs

freezing up from the liquid nitrogen

pressure temperatures and just the small

surface area there those don't make

contact either so just clamp on with big

alligator clips I also tried to film an

experiment where I showed the magnetic

flux lines being excluded from the

superconductor when it becomes

superconducting and this didn't work but

it's actually correctly showing me

what's going on so this is actually how

I found out that high-temperature

superconductors are type 2

superconductors like ybco actually let a

lot of magnetic flow

through them it's just through this flux

pinning that all these weird magnetic

levitation effects happen

type 1 superconductors at really low

temperatures like pure mercury for

example as a type 1 superconductor those

actually exclude magnetic flux lines and

this experiment I'm gonna try to do this

if I ever get access to liquid helium

the iron filings should move away from

the superconductor showing that the flux

lines are going around it rather than

through it but type 2 superconductors

the flux lines do go through they just

get concentrated into these defects if

you search the internet for recipes to

make ybco superconductor you'll find

that the most common method is called

the shake and bake method and it's

called this because you basically just

put the three ingredients together get

REME oxide barium carbonate and copper

oxide together in a mortar pestle you

shake it up you grind it up and then you

put it in a kiln and you heat it up to

about 950 degrees C the baked part of

the shake and bake then you take it out

and you grind it up and you shake it

again and then you put it back in the

kiln and you take it out and then you

grind it up and shake it and put it back

in the kiln and you do this three or

four times the problem is that when it's

in the kiln it spends about a day at 950

degrees C and then another whole day to

cool down so this whole process can take

about a week and if it doesn't work at

the end like is what happened to me it's

very difficult to debug the process

because changing it requires another a

few days or a week to even find out if

the change you made works or not in any

case the main problem with the

shake-and-bake method is that we really

want these three ingredients to be in

like atomic contact with each other I

mean we want to make crystals that have

atrium barium and copper in them and so

to make that crystal structure the atoms

really kind of need to be almost

touching the problem is that even if

these are super finely ground powders

and we put them in a mortar and pestle

and grind them I mean that the chunks of

material have got to be like you know

millions or billions of atoms big right

so you're only going to form ybco at the

place where these chunks are touching

each other and so the point of

regrinding it and firing and regrinding

it and firing it is that you keep

the chunks open and letting more and

more surface area together so I actually

never got this to work I'm sure it can

if with enough grinding like they talked

about sitting there with a mortar and

pestle for like 30 minutes of straight

grinding and I admit I never got to that

level but anyway I found a much more fun

and effective method of doing this the

pyrophoric process involves finding

compounds of yttrium copper and barium

that are soluble in water and then we

boil the thing down to make this sludge

that ignites and since the three

chemicals are all soluble they were all

in you know intimate contact with each

other because they were in solution so

we don't have this problem of big chunks

of of powder like not getting together

close enough in this case it's easy to

find barium nitrate which is soluble in

water and copper nitrate which is

soluble in water if we could find it

really nice rate that would be great but

typically it's it's hard to find so what

we do instead is add a little bit of

nitric acid to the water and then add

the yttrium oxide and that will dissolve

it into the water the reason that we use

nitrates one is because it's soluble and

also because there are oxidizers and so

since we want this process to generate

its own heat we're going to use these as

oxidizers and the fuel is actually going

to be citric acid also soluble in water

so we put all these things together and

then as we cook it we boil off the water

and end up with a very thick sludge I

should point out that this releases some

really nasty fumes and so I have sort of

a makeshift fume hood it's actually a

very efficient fume extractor and it

blows the exhaust out the roof of the

garage here after maybe an hour or two

of slow boiling the sludge is getting

hotter and hotter because the water

content is going down and the heat input

is about the same so as the water goes

away that you know the temperature

starts going up and eventually it gets

to the ignition temperature and self

ignite

it's a really cool-looking process it

doesn't explode it's just a very quick

burning sort of like burning black

powder out in air in fact black powder

is very similar we've got a nitrate and

a fuel and we're burning it in an open

container so it doesn't explode it just

burns very quickly and I got some

high-speed footage of this too this was

actually an interesting shot because the

amount of infrared light coming off of

the combustion was so high it was

overpowering the camera and so I had to

add an extra little infrared filter in

front of it but then also I had to have

the fume extractor going because it was

blowing you know nitric acid fumes and

ash and everything out of there too so I

had the the tube setup and the camera

aiming in there and it was it was kind

of an interesting shot after the

combustion is done we're left with this

really loose sort of brown ash it's very

lightweight

in fact it's so lightweight that some of

it just sort of floats out from the hot

gases being released during the

combustion I tested some of this in

liquid nitrogen to see if it was

superconducting and of course it isn't

we'll talk about why in a minute but at

least all the ingredients have been

mixed together perfectly because they

were all in solution and then in the

heat of that fireball all of them got

forged together into ybco but

unfortunately it's not quite enough just

to have all the ingredients in the right

place at the right time we also have to

get more oxygen injected into this thing

and then also cool it down very slowly

so that it forms nice big crystals I

later found out that you don't have to

hydraulically press these if you want to

make a pellet just putting them loosely

into a crucible or a dish in aluminum

oxide dish and putting that in the

furnace and heating it up to about 950

is good enough you'll actually get a

perfectly fine hard disc out of it that

way that's that's mechanically fine

however if you do want a really nice

puck shape without any cracks or

anything in it you might need to

hydraulically press it and I tried this

a little bit and had some success

not a whole lot the pressing die is the

geometry that I have is not very good

and so the diode is Jama but anyway I

did make a few pellets this way and they

were kind of ok so after we're left with

the pellet of this pressed brown powder

or just sort of loosely tapped down into

a crucible the kiln serves two jobs here

one of them is to get the crystal

structure as uniform as possible just by

cooling it slowly and the other job is

to get more oxygen injected into the

ybco crystals despite all the literature

on the internet about ybco it's actually

difficult to figure out the exact

temperature ranges and times needed to

do this you would think it would be

pretty well-established by now but

there's actually a fair bit of

disagreement on the internet about

what's going on with all this stuff so I

can report what worked for me basically

heating up to 960 degrees C and then

decreasing the temperate holding for

about maybe one or two hours and then

decreasing at 1 degree C per minute over

the over the down to room temperature

with oxygen flowing in it's what ended

up working for me at first I had just a

thin stainless steel tube that was

allowing the oxygen into the kiln and I

was using a pretty high rate kind of

about 50s CCM standard cubic centimeters

a minute and then I realized that could

be a whole lot more efficient with the

oxygen and also have a better chance of

getting the oxygen into the crystal by

making like a little container within

the kiln so I drilled a hole in the

bottom of a crucible and then put it

used it as a lid basically and put it on

top of the crucible that was going into

the kiln holding the powder so that way

the oxygen would sort of be forced to

hang out with the powder that I was

trying to oxygenate in there and I ended

up using a flow rate of about 10 SEC M

another major problem that I had was

that my kilns thermometer was not quite

accurate enough to get the proper

temperature for doing this process so

most of the literature says you need to

be around 940 to 960 even as high as a

thousand degrees C to get ybco crystals

into the annealed state and then start

cooling down slowly from there and so

originally I was setting my kiln to 940

and none of my samples were working I

did this probably you know 5 10 times

and none of them were any good and

eventually I realized that

a temperature that the kilns reported

temperature was not quite right so you

can see inside this kiln the stock

temperature sensor is up there and near

the roof and I'm mostly interested in

the temperature inside this little

crucible within the kiln

thing so I added another thermometer or

another type K thermocouple and had that

set up with my data logger and that's

how I got the profile to see what the

actual temperature was inside there but

I didn't realize I had this problem and

then after I did realize it I used these

pyro metric cones to figure out if the

temperature at the base of the kiln here

is really what it says they are these

cones are designed to calibrate the

temperature of your kiln are tested and

they are made from a specific material

that begins to soften at a very specific

temperature range so this one is set to

go at just under a thousand degrees C

and it's kind of a it's kind of a hard

material it's actually very brittle I'll

just break this one just so you can see

it just snaps right off it's it feels

kind of like a ceramic but it's a little

bit lighter weight it's kind of like a

choco most or something like that and

the idea is that you put one in your

kiln and then start raising the

temperature and keep checking on it

looking in there and checking on the

state of this thing and when it's folded

over then you know you've reached the

right temperature so a very good way to

calibrate your thermometers so basically

as it turned out when I was setting my

kiln to 940 it was really only about

9:10 at the floor of the kiln and none

of those samples came out working so it

definitely needs to be hotter than that

I think 950 or 960 is fine and then in

the reading I've done since then I think

maybe the best temperature profile is to

go from 960 down to maybe 500 and then

you hold there for another 8 hours and

then from 500 down to room temperature

and you generally want to go pretty slow

like a degree per minute fortunately but

you need a temperature controller that

can adjust the temperature slowly enough

basically and that that's not so easy 1

degree C is actually the minimum rate of

travel for my temperature controller the

point of stopping it

500 like this is to get as much oxygen

in there as possible so the like you say

there's these two stages where there's

setting of the crystals and there's like

this maximum oxygenation which happened

at different temperatures the liquid

nitrogen that I used in this experiment

is indeed homemade I used my DIY liquid

nitrogen generator kind of an Express

mode so instead of having the original

power supply with the digital control

I've got this big very act that my dad

gave me and I've connected it directly

up to the cryocooler and then I have a

clamp meter here to monitor the current

going into the cooler and a power meter

to monitor the you know a number of

watts going into the system totally and

then I also have this kind of makeshift

air dryer here which is just a bunch of

silica gel and the the intake hose goes

to the bottom of this column of silica

gel while reading some of these papers

about making ybco

a lot of times you'll see something like

use a flow of 2 ml per minute of oxygen

but that doesn't mean just get a big

kiln and then stick a tube in aside and

get 2 ml per minute of oxygen going in

there it almost certainly means use a

vacuum tube furnace like this where

there's a quartz tube that goes all the

way through the middle and it gets hot

of course in the middle but you can

connect process gas or even a vacuum

pump to the outside and I've kind of

wanted one of these for a while because

there's a lot of other experiments you

can do with it that are pretty cool

and I didn't end up needing this since I

got the ybco working in my small

tabletop furnace but this is a

indication of what's to come on the

channel I'm going to use this to make

all kinds of cool stuff and it's it's

not built yet so maybe that'll even be

its own video is putting this together

ok see you next time bye

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