Turquoise Energy Ltd. News #18
Copyright 2009 Craig Carmichael - August 3rd 2009
July in Brief
newsletter articles are posted on the Turquoise Energy
Ltd. website. Only these highlight/contents blips are included in the
email. Complete newsletter:
Electric Hubcaptm Car Drive
Project Detailed Report
Torque Converter Project
* A quick test
Ceramic Motor Coil Cores Project Started
* Some test cores made and tested -
no positive results yet.
Turquoise Battery Project Detailed Report
* Manganese negative electrode - fell
As expected, I wasn't able to get much done on the energy projects in
the first half of July, and only some work in the last half. I put
considerable time into cutting,
planing and shipping hardwood for a few sales. August also will
have some major chunks of time cut out of it.
I did manage to make and test a few
microcrystalline motor coil cores.
In the last half, I continued the
cores and put
together my conception of a "production version" wiring box/motor
controller. On the 29th I finally tried it out. It worked! Has anyone
done a stand alone motor controller/equipment box that
encloses all the wiring for such a motor installation before? It seems
to simplify a lot of installation "loose ends". I revised the manual
for making them and uploaded it to the web site.
* * * * *
The car hybridizing project has been underway now for a year and a half
since January 2008, so perhaps it's a good time to recap the main items
of the project so far:
* The Motor went from a hazy conception for small, light,
high-torque wheel motors to practical, safe voltage, working prototype Electric
HubcapTM units that run well and that
can, in principle, be made even at home with auto and-or trailer
mechanical parts and bearings.
Instructions for making them have been placed on the web.
The Turquoise Motor Controller
likewise went somewhat fitfully from hazy concepts to a practical and
unit built with the required techniques and specs. A new concept was
evolved for clean, safe installations: the motor controller is an
internal component of a compact central wiring and equipment box,
housing all the various electrical components and inside which all the
wires terminate, similar to AC house wiring. An instruction manual for
making them, just updated, is on the web site.
* The Turquoise Battery has gone from poorly
understanding the various essentials of making a workable battery to
some exciting advanced concepts of great promise, which have not yet
been put together into a superior, economical, "life-time" battery with
higher power and energy density. Such a battery would do much to
improve the practicality of hybridizing a car.
* The Magnetic Torque Converter. Directly driving a car wheel,
though it moved a car on level pavement, proved to have insufficient
torque to be
electromagnets that push the supermagnets don't have nearly as much
magnetic flux as the supermagnets do,
hence the supermagnet strength force I expected isn't in fact
available. A motor
otherwise much larger than necessary, or perhaps motors on all four
wheels, would be necessary. Instead of that or using an inefficient
reduction gear system, I'm planning, and
started to make, a magnetic torque converter, as a new and superior
means of accomplishing the required torque magnification. The output
have the supermagnet strength force that the motor doesn't have
* The new Microcrystalline Motor Coil Cores project is intended
the motor. If the project is successful, three benefits will be to
reduce iron losses to a trivial level for improved motor
efficiency, to reduce motor weight, and to make the coils even easier
making the motor more economical. A fourth potentially possible benefit
may be to increase saturation flux, perhaps allowing a motor with a
potentially higher peak power for its size and weight.
Such cores are especially applicable to axial flux motors
where the coils are made separately and bolted onto a backing plate.
This may help explain why they aren't in use now in other new motors,
in which the laminates are part of the structure of the motor.
putting a test
piece of aluminum,
on top of the "stator" piece, on top of the magnet rotor. Nothing was
on an axle; the magnet
rotor remained stationary throughout. I rotated the
stator directly above it with my hands. Sure enough the test piece
tried to stay stationary with the magnet rotor underneath,
only following the turning of the stator, which it was resting on - or
sliding on, at about 1/3 the speed
it was moving. I expect that if it was a rotor on bearings
it would have turned only a
little with the stator.
I had been wondering what I was going to do about getting
copper coil winding wire if more than one or two more motors were to be
made here, and for testing microcrystalline coil cores. The price seems
to have about doubled in the last three years to about 14 $/pound. But
I've acquired over
100 pounds of it at a very low cost from someone retiring from
the motor repair business.
It was tedious
to unravel - long wound loops of 5, 6 or 7 various size wires stashed
into open boxes,
from abandoned or revised motor/generator rewinding projects. The
potential was there for creating great hopeless tangles, but luckily
they'd been little disturbed and I've done it before and was very
careful. I spent at least
ten hours on it, tying one
end to a tree and carefully unravelling the loops across the yard and
the house, then extracting the wires one at a time. Some coils were up
to about 235 feet long, but I now have mostly separate loops of #14
wire, carefully taped and the size labelled. It was a tremendous cost
savings over new wire. There's
enough for over 20 Electric Hubcap type motors, 24 or 36 volts. As
I'm now experimenting with microcrystalline coil cores, I may want
quite a bit of wire for test coils, and I can now use it freely as
Compact, High Current Rated Plugs, Sockets
Having enquired and searched the electrical supplies
stores for physically
small, high current plugs and sockets and found nothing, around three
months ago I finally made a thin profile plug and socket for the motor.
I find there actually are good units available... at the
electronics store!, where I didn't think to look for high power stuff.
They're called Power Pole Connectors from Anderson Power
Products. They're all rated for 600 volts, and they come in sizes
rated from 30 amps to 180 amps. Interestingly, the "plug" and the
"socket" are identical, just flip one of them over and they plug in
There are some dual and multiple units, but also there are
single contact units that lock and "stack" together into any desired
These are in stock at Queale Electronics. The plastic bodies come in
lots of colours.
Making the motors and installations simple and
straightforward is key to spreading the designs. Where
other motors need a factory and almost every part is custom made, much
of the Electric Hubcap can be assembled from brake disks, trailer axles
and bearings and other common, off the shelf parts - of which these are
just one more example.
Having designed and made the new motor controller circuit
and circuit board in
June, in July I made the "wiring and equipment box" enclosure I've had
in mind for some time, with
the motor controller being a side of the enclosure that can be removed
by unscrewing it from the inside. This allows it to be removed for
or replacement without dismounting the wiring enclosure or disturbing
the wiring. Co-incidentally, it also provides for easier access inside
the wiring box as the front and one side can both be removed.
The electrical components are inside the box, and
all the wiring terminations are enclosed.
The new motor controller
10" tall x 6" wide x 4.5" deep.
Totally enclosed wiring & electrical equipment
Laying out the several box mounted components (power
switch or breaker, power "solenoid" relay, filter capacitors, heavy
wire terminals) in the 10" x 8" box, it appeared the box could have
been made as narrow as
5-1/2", say 6" for comfort, with good two-sides access. It's surprising
how hard it is to find a convenient cranny in a car, near the wheel and
big enough for the wiring/motor controller box, so size is important.
In fact, an eight inch width doesn't fit well where I want
it to in my
own car, so I cut the box down to 6" wide. It looked like everything
would fit great, but I found the 200 amp breaker I chose for a main
power switch didn't quite fit in front of the solenoid relay (which
turns on the power from the car key) as I'd planned, and everything had
to be rearranged. It all fit in the box, but not as happily as
(I must look again for physically smaller
know I saw some on the web at one point.) There are also high current
battery switches for marine use, but they lack a safety circuit breaker
function. With the breaker, at least if a screwdriver gets in and
shorts the 36 volt bus to ground or something, it'll probably trip off
before anything blows up.
On July 29th I finally had everything ready, including a
couple of wooden "feet" for clamping the motor onto a workbench, and I
tried it out at 12 volts. Bizarre things happened. Then I checked and
found I hadn't rewired the control box with the switches and speed
control for the new motor controller - I thought I had. Once that was
done, everything worked flawlessly, to my great relief. And I could use
the frequency meter to get the RPM! It's a big plus knowing the RPM.
Then I went up to 24 volts. Still worked great. The next
day I got up the courage to try 36 volts. Still worked great! Phew!
New controller running motor on bench
found out a few things about the motor and the
particular setup on the bench. People have asked for specs. Here are a
few based on the tests - not the ones of most interest though.
The motor seemed to use more power to turn the same speed
as the voltage went up. There's probably some magnetic subtleties to
check out here.
And I noticed the motor needed more power to
go clockwise than counterclockwise. I thought I'd determined that the
timing wasn't that
critical!, but what else could it be but a timing issue? Then I tried
spinning it by hand: sure enough, for some reason there was more
actual friction turning it clockwise! (Perhaps I should grease those
|Amps turning CCW @ 620 RPM (no load)
|Watts CCW (V * A)
|Amps CW @ 620 RPM (no load)
|Watts CW (V * A)
|8.6 (580 RPM - maxed out)
noticed that the motor ran more smoothly at the lower
voltages. That was probably related to my
uneven magnet spacings and the air gap, which was also uneven.
These things are all adjustable. They'll bear some testing
At 12 volts (being wound for 36) it would just hit 620
RPM going counterclockwise. At one point (with more volts) I turned it
to 1000 RPM. That was pretty scary -- an open, large diameter motor
whirring away on a table in front of me. Bits picked up here and there
by the magnets
over time were flying off and hitting me. But the whirring
magnets were fanning a good breeze, which is exactly what's needed for
cooling the coils in real use. I didn't try to find out what
full speed was at 24 or 36
Later I straightened the alignment and evened the
gap around the rotor and tried it again. The final and
a bit wider gap, silly though it may sound to anyone familiar with
motors, was about 1/2 inch. The currents were somewhat lower for the
same RPM speeds.
|Amps turning CCW @ 620 RPM (no load)
|Watts CCW (V * A)
|Amps CW @ 620 RPM (no load)
|Watts CW (V * A)
|8.3 (just makes it to 620 RPM)
So! Comparing the two tables, the idling efficiency goes
increased gap, and the lower the supply voltage the less energy it uses
to idle at a given speed! I should try changing the PWM rate and see
what difference it makes. I used a
lower frequency than the chip maker recommended.
I may want to try some thinner supermagnets, eg 3/8" or
1/4". Then I can put on 18 evenly spaced for smoother operation and
reduce the air gap. Or maybe I should just try evenly spacing 12
"normal" size magnets next time. (If only epoxy wasn't so hard to get
off, I think I'd try redoing this rotor.)
Actually, the guy I've been ordering magnets from was down
to his last few, and he sent me some 2" x 2" x 1/2" because he was
short of 1" x 2" x 1/2". The next rotor may just have six of those! and
it'll probably run smoother than this one.
Then I checked at 1000 RPM. E = 1/2 mv2, and
1000 RPM2 / 620 RPM2 = 2.6, so that's almost
three times the rotational energy, but it took only somewhat more watts
to keep it spinning than 620 RPM:
|Amps turning CCW @ 1000 RPM (no load)
|Watts CCW (V * A)
Of course, all this is just the idling motor. A more pertinent question
is how it does with a heavy load, and I still have no ready means of
testing that except to get it to run the car.
I found a "bug" in the motor controller chip: if you flip
the direction switch while the motor is still turning, it comes to a
grinding halt even if no thrust is being asked for from the PWM control
pot. It probably deliberately turns on all the low side MOSFETs at
once, shorting all three wires together. This "instant stop" "feature",
which isn't even mentioned in the datasheets, will prevent regenerative
braking!, which is accomplished by telling the motor to run backwards
to the direction it's going -- precisely the condition where the chip
internally shorts everything out. I had planned that regenerative
braking could be added later by a fairly simple external control
It's probably pointless now, but perhaps later if the
Electric Hubcap is catching on, ON semiconductor could be approached
and asked if they would do an ammended version of the MC33033 chip. In
fact, at such a hypothetical time, perhaps they could be asked for a
modified chip for the express purpose of powering 3-phase electric
vehicle motors with regenerative braking, so that no external circuit
would be required.
Magnetic Torque Converter Project:
Torque Leverage Without Gears
I didn't have time for any actual fabrication work. I hope
to concentrate on this project in August.
Microcrystalline Electromagnet Coil Cores
Again I've had an idea for something in a field I haven't
worked in before. But if microcrystalline cores that carry enough flux
density for motors can be made, they have potential advantages:
1. They're easier to make than spray painting, fitting together, and
varnishing or casting. And they'd make the coils easier to wind. Easier
and less manual labour ultimately reduces the cost of the motors.
2. They probably would have lower iron losses than laminates, in fact
probably trivial losses, making the motors more efficient.
3. They're lighter - half the weight. This will save almost a kilogram
per motor. (Of course, that's out of 20+ Kg. Still, trimming a bit here
and there can add up.)
4. Cooling air flutes or holes could be cut or cast
I was also hoping a successful finished formulation will
transfer magnetic flux effectively but without itself being attracted
to magnets. Non-cogging coils would have special implications, for
example in windplant and other
generators where it is important that the propeller or other driving
force not be magnetically
"stuck" in one place in a light breeze. My ocean wave powered generator
would probably have worked if not for the cogging of the generator in
Of course there are also potential down sides:
1. They may be more fragile. That's why I'm using the porcelain-like
clay and adding feldspar for strength. Like porcelain toilets, I expect
they will prove to be "tough enough" for their intended use. (Two of
the latest and best cores, just fired, fell off a table onto a wooden
floor and didn't chip or break.)
2. They may saturate magnetically at a lower flux. If the available
flux density is too low, the idea won't be viable for high power motors.
3. They are likely to have a lower flux density than iron even in
working range, that is, to be much more effective than an air core but
not as good as iron.
two and three could
limit the power available from the motor. I'm still learning and
the last word isn't in. If the best I can do is better
than air but not good enough for high power motors, but is also
to magnets, they could still improve (eg) air-core windplant
generators, reducing the size, the number of supermagnets and the
amount of copper wire required.
I made several test cores to compare, and I came up with a
methodology of construction.
say at the top these procedures are just my current best conception
(July 20th) of
how to make them and what should go into them at this early period in
the development and testing.
First, iron oxide,
custer (potassium) feldspar, ilmenite and Laguna borate are mixed into
the clay, as
much "stuff" as it seems the clay can hold. The iron oxide should be
ferrous (FeO), which seems to be the most magnetic, or magnetite (Fe3O4).
Ferric oxide (Fe2O3- red rust) appears to be
non-magnetic, or at least not attracted to magnets.
Boron is a flux, and the borate is used as a frit to lower
the firing temperature of the clay. And, the Laguna borate
(specifically Laguna) has aluminum (mentioned in connection with
microcrystalline cores), iron and titanium oxides. I found out after
making a few coils that cone 5 (~2150 F) is hot enough to destroy of
modify some "dielectric" properties, doubtless also magnetic
properties. Now I'm trying cone 05 and other lower temperatures,
1800-2000 F. Boron is also the third ingredient in "NIB" (Nd-Fe-B)
local pottery supply actually happens to have some neodymium
oxide, too. But I'm not sure what either neodymium or boron might be
good for magnetically, in electromagnets!
Materials of an early test core, all from the pottery supply store.
On the plastic is the clay, ferric oxide, feldspar, and the plastic
"Wedging" (mixing) the ingredients. Another reason not to use ferric
oxide: It's really messy!
Careful as I was, and though I wiped and mopped, the table and floor
are still reddish.
Then, the clay is pressed into the mold.
two mounting bolt holes are "drilled" out by hand
with a piece of 3/8" brass tube with "teeth" filed into one end. Each
plug of clay is pushed out of the tube with a pencil. (A 1/2" tube
might be better - the holes shrink during firing and again with each
coat of glaze laminating.)
mold, a 1.2" long piece of 2" ABS plumbing pipe, is
placed into a pipe-joiner piece, and a pipe piece that just fits inside
the mold piece is pressed down to eject the core evenly on all sides
from the mold. (The 1.2" length allows for clay shrinkage, in drying
and again in firing,
to just over 1".
The 2" diameter should be a little larger as well to end up with 2"
grams of materials proved to be virtually enough to make two cores, so
I did, using a leftover bit of rather similar clay from the previous
"top up" the second one.)
Then it's typical pottery procedure: dry it, dry it some
more, eg, in the oven at 225 degrees (F), to drive out any remaining
so it won't explode in the kiln, then put it in the kiln and fire it to
cone 5 (2150(?) Farenheit).
There you have the core of the core. If you had a pottery
supply pre-mix the ingredients, and machines to squeeze the clay
through an extruder mold, cutting the extruded clay into sections as it
comes out, you could make hundreds of uniform motor coil cores in an
hour and would need a bunch of dryers and kilns to process them all.
An interesting observation is that a raw core with ferric
oxide (red rust) isn't attracted to a magnet, while a ferrous oxide
(black powder) core is. However, after firing, neither core is
attracted to the magnet.
Now the core is laminated with two layers of
with differing magnetic properties. The reason is to optimally
direct the magnetic flux, emanating from the coil wire, into the core
and out its top and bottom ends. The process is to dip it in mixes of
sodium silicate (AKA "water glass") with the desired mineral
silicate hardens with heat by releasing its water at about water
boiling temperature. Thus it forms a "glaze", glueing the powder in it
onto the core. (Think of raw egg white - it starts wet, but if it dries
onto something, it's hard stuff to scrape off.)
First you dip the core in sodium silicate with ilmenite
powder mixed into it. Ilmenite is a mineral composed of blended iron
and titanium oxides. That provides a coating or layer with
ferromagnetic and paramagnetic properties, titanium being paramagnetic.
Paramagnetic materials will line up, magnetize, in
the presence of a magnetic field, but as soon as the external field is
removed, the crystals (or was it some sub-crystalline unit? No matter!)
re-orient randomly, losing their magnetism.
This is placed in an oven at about 250 (F) degrees for a
few minutes (15?) to set the sodium silicate. There's no smoke or
fumes. When sodium silicate is heated
above the boiling point of water, it hardens, casting
the layer in place.
Thus you have the core, glazed with ilmenite "icing".
Next dip is
a coating of Rutile (again, in
preferably "Niobic Rutile". Rutile is a mineral, mostly titanium oxide,
with iron, niobium and tantalum oxides as frequent "significant
impurities". Niobium is
paramagnetic and in superconducting has "the greatest magnetic
penetration depth of any element". Tantalum is the element below it and
has similar properties. I can't find any specifically "niobic
rutile" for sale on the web, so the titanium and whatever happens to be
in what I buy at Victoria Clay Arts will have to do.
Now the coil wire is wound right on the core. (For
I'll need to make a new coil winder designed for this direct wrapping
method.) Since the skin of the core is fairly smooth and electrically
non-conductive, there's no need to insulate or protect the wire.
Another dip in
rutile, after heating, sets the coil wire in place on the core, thus
replacing motor varnish or
epoxy. (Tooo clean and simple!) The paramagnetic rutile and the mixed
magnetic ilemite help
magnetic field from the coil wires into the microcrystalline core.
Now, if only the price of copper wire hadn't doubled in
the last 3 years, we may, hopefully, be on the way to cheaper motor
coils as well as better!
First Test Coil Cores
Center: Test coil
12 o'clock: original nail gun finishing nails core
1: 12.5% ferric oxide with thin ilmenite coating. Some has chipped off
- perhaps it doesn't adhere to finger grease?
2: 12.5% ferrous oxide with a rather thick ilmenite coating. (This was
the first one, then I thinned the mix.)
3: 50-50 mix of ferric and ferrous with clear sodium silicate "glaze".
6: 25% ferrous oxide.
10: 28.6% ferric oxide
11: 37.5% ferric
First Test Results
The laminate (nail gun finishing nails) core repelled
(lifted or moved the
magnet) at the greatest distance, 1-13/16". The ones with 12.5% iron
oxide weren't much better than air core, 1-3/8" to 1-1/2". The one
with 25% FeO seemed better, 1-5/8". There were too many vague things in
the tests to be precise, and the outstanding conclusions were (a) that
adding more oxide seemed to be necessary and helpful, and (b) that a
setup, precisely repeatable and that would provide actual numeric
measurements for comparison, was required.
As a result, the next cores have much more ferric oxide
crammed into them, up to 37.5% by weight. Volume-wise, the pile of rust
powder looks bigger than the piece of clay. They make for very sandy,
gritty feeling clays. But I'll try 50% next...
When I went to fire my first cores, I plugged in my
"mini-kiln" outside with a long extension cord from the kitchen where I
have a timed outlet. I had added some kiln bricks to the outside of it
to improve the insulation, and I didn't want any burning paint fumes
from the (now presumably hotter) kiln exterior in the house. I
the kiln to hit cone 5 in about two to 2-1/2 hours. Four hours later
the sun was
going down and the cone was still standing straight! Then it dawned on
me that a 1440 watt unit was going to lose some voltage with that long
#16 cord. Sure enough: the voltage at the kiln's plug tested as 104.6
VAC! That worked out to 1094 watts, a 24% loss of power versus the
rated 1440 watts at 120 VAC -- it was never going to reach cone 5! But
probably sitting at cone 3 or 4 after about 2 hours, so I called it
That's a good thing to remember when the electric
lawnmower is "bogging down" using a long, light cord, too!
On the next firing, I
plugged in in the kitchen, but the voltage was still only 112. It
reached cone 5, but it took 3-1/2 hours.
started making up a test jig. The idea was to put the coil on a scale
with a supermagnet suspended above it. Then when the coil was
electrified, the repulsion from the magnet would make it "weigh more"
and the amount could be read on the scale.
But before I finished the jig, I realized that the scale I intended to
use was already 3/4 deflected just by the weight of the coil, and also
that there was an easier way to test them.
That way was to set the core on a supermagnet, then lower
a small piece of steel, suspended from a fish weighing scale, down onto
the core, and then see how much force it took to pull it off. The
results were disappointing, and also showed the variable nature of the
first test, as the 25% FeO core seemed no better here than the others:
|Steel Directly on magnet
|Laminated Core (nails)
|Air gap and all ceramic cores
On the 16th, I got some "granular magnetite" (Fe3O4
- mixed valence FeO and Fe2O3)
from the pottery store, which they hadn't had in on my previous visits,
and made a core with it. This oxide was specifically mentioned on a
couple of web pages talking about microcrystalline cores, including the
one that thought they might have potential as transformer etc cores.
I also added Gerstley Borate to this core, feeling that as boron is a
supermagnet material it might mystically add some valuable magnetic
property. Of course, if the core works I'll have to experiment further
to see whether the working ingredient is the magnetite, the borate, or
(Core composition #12: b-mix clay 100g, magnetite 74g, feldspar 25g,
betting using boron for supermagnets was discovered accidentally when
using borax flux in sintering the intended iron and neodymium?
I added the borate and got this surprising (to me) result
Yuk! Of course... boron is a flux!
With no promising results, I sort of thought I'd put the
cores project on hold and get back to other things. But I started
looking into the
subject of lower firing temperatures, eg for raku. I found this
paragraph in Wikipedia under "frit":
Also, frits can be added to high-tech ceramics.
Scientists have made
such frits by milling ZnO and H3BO3 with
zirconium beads, then heating this mixture to 1100°C, quenching it,
and grinding it.
This frit is then added to a Li2TiO3 ceramic
This addition is beneficial: the ceramic can sinter at a lower
temperature while still keeping its "microwave dielectric properties."
in order to retain "microwave dielectric" properties - which may also
apply to magnetic properties - the firing temperature has
to be lower. Having enough of "mix 12" with the borate left for
anothercore, I made it and fired it to cone 05 (which cones I happened
to have), about 1800(F) instead of cone 5 (2250(F)).
Topping up my remaining #12 mix with leftover #6, I made
another core with borate in it. This time I fired it to cone 05 (~1800
F) instead of cone 5 (~2150 F). It didn't melt down, and it was still
somewhat attracted to magnets after firing, unlike all the previous
cores. I coated it with ilmenite and rutile, but it still didn't
transfer flux better than air.
I was encouraged to start this project upon reading that
materials might be good replacements for laminates as transformer
cores. Perhaps I should go back to
the web and dig deeper for more info! (Now, where was that site again?)
I decided the Gerstley borate I'd been using was the wrong
stuff. Laguna borate had a bunch of additional minerals, mostly ones
indicated for "high-tech" microcrystalline ceramics. I also decided to
add some ilmenite to the core. I used the democratic process to
determine proportions: 20g feldspar, 20g ilmenite, 20g Laguna borate
and 20g magnetite. I started with 60g of clay but increased it to 80 as
the mix seemed weak. This was formula #13. The raw body seemed to have
no special magnetic properties, being weakly attracted and transfering
no more flux than air between the ends. This was fired to 2000 F, which
proved to be too hot. It bubbled and distorted and lost its magnetism.
The 1800 degrees firing seems better, but I can also try 1900.
Another idea is that the coils may need to be quenched in
water (or oil?) while they're still hot. This would cool them suddenly
greatly affect the size and nature of the resulting crystals. This will
be the subject of further experiments. I'm not looking forward to
pulling a glowing hot piece out of the kiln and dowsing it in water or
oil - the whole idea is making me very nervous!
Later I tried the quenching, from lower and higher firing
temperatures. It wasn't violent and nothing exploded, but again it
didn't produce any good results.
The next try will be to use even lower firing
temperatures, say 1700-1800 F, cone 07 or 08, with the paper clay.
That's about the lowest temperature one might expect to bisque fire at
and vitrify the clay. (Should make for quick firings!)
Since at the lowest temperatures I tried (05) the
magnetite seemed to retain some attraction to magnets, I'll try to stay
below what seems to be a threshold where it changes.
Then I'll try everything all over again at the lower
Near the beginning of the month I put together a manganese
dioxide electrode. In a salt electrolyte battery, I expect it would
convert to manganese chloride, reducing to manganese at
about -1.0 volts. (MnCl2 + 2e- <==> Mn + 2Cl-, or,
since that's probably soluble I expect it would be written: Mn++(aq)
<==> Mn(s) + 2Cl-. Mn valence goes from II to 0 either
way.) The MnO2
proved to be so conductive (a few kilo-ohms dry) that I decided to save
my little remaining monel powder and I put it in straight with no
additives, knowing it would only get more conductive as the electrode
charged to metallic manganese.
Manganese dioxide is the stuff of the positive electrode
in the regular dry cell and the non-rechargeable alkaline dry cell. (MnO2
<==> Mn2O3 , at +0.5v in salt, +0.15v in
But manganese has several interesting redox reactions, including the
reduction to metal at a good voltage for a negative electrode. In
alkali the reaction voltage is a little high (-1.55v)
hence zinc (~-1.25) is chosen as the highest available energy,
but in salt it looks like Mn should be good (-1.0v?).
One way to make a
battery rechargeable is to have reactions where none of the products of
charge or discharge are soluble . This is the attraction of alkaline
batteries (electrolyte KOH) with "OH-" electrolyte ions and forming
'X'OH (hydroxides) products: most hydroxides aren't soluble. In a
salt battery (eg KCl), 'X'Cl is formed instead, and most chloride salts
Another way is to trap or chelate the metal ions so they
aren't free to cross to the other electrode. Then the soluble 'X'Cl
reactions can be reversed.
I was going to use it with the previously made nickel tube
electrode as the positive. (One could, of course, try a
manganese-manganese battery!) I had the idea to roll up a piece of
watercolour paper with zirconium silicate ("zircon") powder as an ion
on inside a smooth tube, put in a center lead of nickel-brass, and fill
the tube with manganese oxide, compacting it down.
Then I slid it part way out of the tube and wrapped dental
floss around the paper to hold it all together.
As I put it in the battery, holding the center lead, the
whole electrode slipped off the lead and fell into the battery.
Subsequent attempts to reinsert the lead weren't very successful and
the wet paper mushed up.
So much for that electrode! Then I got onto the coil cores
didn't get any more battery work done.
The electrode in a perforated tube seems to be the most
successful so far, but if I'm to use that I think I need to find a
source of perforated nickel alloy tubes. Both making all the tiny holes
(which there should be 20 times as many of!) and the nickel
electroplating of the brass tube are tedious operations.
Also, the soldered-on terminal leads keep corroding off
(not a surprise), so it needs another way of attaching - hard solder,
perhaps, or a screw-on or crimp-on fitting.
On reviewing the reaction, I decided I should try to reduce the dioxide
(valence IV) into hydroxide (Mn(OH)2) or monoxide (MnO),
before I put it
into the battery. Otherwise it seems to me there'll be a big excess of
oxygen bubbling around in there!
I tried adding hydrogen peroxide to the powder. Sure
enough, it fizzes away. I presume, since nickel oxyhydroxide may be
reduced this way, that this should be converting the dioxide to the
hydroxide, releasing the excess oxygen (fizz).
My perspective on the likely chemistry is:
Ni(OH)2 + Cl- <==> NiOOH + HCl + e- [~ +1v: seems to be higher
than in alkali]
MnCl2 + 2e- <==> Mn + 2Cl- [~ -1v]