FulanoDetailMagnetohydrodynamic levitation for high-performance flexible pumps | PNAS
This one is just a flexible linear electromagnetic motor… Silicone and polyurethane rubber and polyethylene maintain their flexibility up to 100ºC.
Source: High Efficiency LSM with High Flux Densityfor Transportation
10 kilonewtons = 1000 kg
For the life of me I can’t find a f*cking flexible voice coil…
Soft Electromagnetic Artificial Muscles Using Liquid-Metal Coils and Bistable Housings
Multifunctional Magnetic Muscles for Soft Robotics | Nature Communications
Researchers develop soft electromagnetic actuators with medical potential
Sources: Versatile Ultrasoft Electromagnetic Actuators with Integrated Strain-Sensing Cellulose Nanofibril Foams Multi-object optimal design of electromagnetic artificial muscle structure | Semantic Scholar
Sources: Self-vectoring electromagnetic soft robots with high operational dimensionality | Nature Communications Energy and Force Optimization of a Network of Novel Electromagnetic Soft Actuators
Design optimization of a solenoid-based electromagnetic soft actuator with permanent magnet core
Soft Electromagnetic Sliding Actuators for Compliant Planar Motions Using Microfluidic Coil Arrays
Integrated Actuation and Sensing: Toward Intelligent Soft Robots | Cyborg and Bionic Systems
(PDF) Reconfigurable Magnetic Slime Robot: Deformation, Adaptability, and Multifunction
Soft and Deformable Sensors Based on Liquid Metals
Steel Heart- Artificial Heart Prototype
A unified understanding of magnetorheological elastomers for rapid and extreme stiffness tuning
Sources: Using Voice Coils to Actuate Modular Soft Robots: Wormbot, an Example Linbots: Soft Modular Robots Utilizing Voice Coils
(PDF) Electromagnetically driven elastic actuator
MagFlex: An Electromagnetic Soft Actuator for Safe Human-Robot Interaction | SpringerLink
Programmable Shape-Shifting Soft Robotic Structure Using Liquid Metal Electromagnetic Actuators
Magnetic shape memory alloy actuator
Magnetic shape-memory alloy - Wikipedia
Magnetic Fields #electromagnetism - YouTube Showing the direction of a magnetic field around a coil (maybe you could have an electric artificial muscle by having wires braided around a single electromagnet, just like in the video, but I simply cannot find any examples in real world to base myself upon)
Innovative grasping system with versatility and automation | Request PDF
Goddammit! This is so frustrating!
I can’t think of any reason on why a flexible soft voice-coil or solenoid actuator wouldn’t work, but I can’t find a single article that explores such an idea.
The examples I could find (listed above) are approximations of what I meant, maybe it can work, maybe it won’t.
3D modeling Actuators:
This is me from the future, in the cooling jacket section I explained how I could achieve a -70ºC cooling system using just air.
First, the objectives:
I will be working with electroadhesion to keep the build as simple as possible. So, besides the Motors, I need to decide how many pieces I will need to build in order to keep the whole mech customizable. Basically, what pieces I need to 3D model that will allow me to build everything like a lego.
- Rotor-Stator hybrid, I need to 3D model the slots and the cores.
- 3D models the phase connection, some axial motors have individual slots that are screwed into place and connected using electric fittings that work like wall plugs.
- 3D model the integrated incremental encoder. It would be interesting to add both optical, mechanical and hall encoders for redundancy and extra precision.
- 3D model the electrostatic bearings using the same principle of electroadhesion.
- 3D model the lego-like fittings.
- 3D model the lego-like fitting bars that will be the endoskeleton of the mech.
- 3D model of the cooling vessels, including the cooling jackets for cables, actuators, slip rings etc.
- 3D model of the electromechanical locking system so it doesn’t need energy while standing still.
Now that I’m talking about the Lego-like fittings, I do wonder: I want a mech with arms and legs with the same length?
Although the motors and bearings will fit into the cylinders that will be the limbs, the limbs can’t just have the same length and weight, can they?
- I will leave the cockpit and the hands for last because they will need very specific pieces that aren’t “mass-producible” like the “lego” pieces.
- I’m really having a hard time thinking on how I would make the hands, one thing is using linear actuators, other is using 30x30cm motors…
- I was researching a lot about robotic hands and how to make an actuation system for the hand, but there is no way around. I either make smaller motors specific for the fingers and wrists or I use solenoid actuators.
- Yes, Solenoid actuators aren’t that great, they have limited actuation distance and lower efficiency compared to brushless motors. But using only the hands and maybe wrists, it is good enough.
- … Now that I think about it, why didn’t I use a conventional solenoid for the artificial muscles?
- Why I’m like this?
- I calculated here and it seems like that a single coil with the proportions of a single slot of the motor (12 turns, 50 wires with 1mm of diameter and 0.653mm² of area) would barely lift a single newton (100 grams).
- You would need the coils of 50 to the full 99 slots in order to generate the full force that I was aiming that each motor would make.
- It would need as much material as the motors, but it would be easier to wind them all…
- One interesting detail: while the solenoid calculators tell otherwise, either arranging the solenoids in series or in parallel, TrainedGPT calculated that a solenoid with thinner wire, lower amperage and higher turn count would be weaker than the one with fewer turns, thicker wire and higher amperage solenoid.
- One problem is that the solenoids would need to be rigid, or else you would need double of actuators (and thus, double the weight) in order to have the same amount of range.
- Another detail is that it would output a fixed force and it would be fixed to a certain distance from the tip of the limb, while the motor can reach a better force output based on its torque.
- For example, supposedly, you could output 4000 kg with the solenoid array at a really high speed as fast as you can turn it on and off, but you would need to attach it to ⅓ of the limb’s length, making it output a maximum of 1333 kg of force. While the motor can output 10,000 to 30,000 newton meters of torque at a variable speed, but it can’t be as insanely as fast as the solenoid actuators.
The efficiency curve of solenoid actuators is very poor, however, if you switch the metal plunge to an electromagnetic plunge, it starts to work like a Voice coil.
- This image shows the efficiency curve between solenoids and voice coils.
- Now I don’t know how to continue again…
- I don’t like the irony of always finding a better solution every time I settle with a solution.
Well, I’ve decided: Voice Coils/Solenoids it is.
Although I gave up on the brushless motor, the subjects I learned about while trying to find out how to make it work are still relevant for voice coil actuators.
They will weigh just as much and maybe output way less force, but they are simpler to wind/build and simpler to control.
In the previous topic, I suggested working with rigid linear voice coils, but just now I remembered that there are multiple types of voice coil actuators. Including rotary ones.
This one is called a “bistable rotary solenoid”, but a rotary voice coil looks more like this:
Rotary voice coil motor RVCM - 180
Akshually🤓 this isn’t a motor, but a solenoid/voice coil because a motor is meant to rotate multiple times per second, unlike this one.
In either case, both of these designs are way simpler approaches of making an electric actuator instead of the “Xangô-99” that was supposed to have 99 slots and 66 poles.
And I think that the rotary voice coils will be useful in a few places while the linear ones will be useful in others.
Torso, shoulders, knees, elbows and feet could have linear actuators in configurations similar to a stewart platform with 4 actuators and the rotary ones would be reserved for motions that wouldn’t be possible to do. Like the arm rotation after the shoulder, the rotation at the base of the wrist, the rotation at the base of the ankle and the rotation of the thighs.
There would need to be a lot of parallel linear voice coils because of the thickness of the inner core.
… Or I could keep doing the same thing of the two mirrored stators facing each other, but instead of 99 slots, there are just 2 in each stator-rotor…
… Or I could keep it at 3 slots for better precision and range of motion…
But wasn't the 99 slot meant to give as much as possible? Are the 3 slots going to give as much torque and kv?
Or the number of slots won't affect it that much?
The TrainedGPT, Web-searchGPT and ChatGPT tend to always either assume that the idea is correct or that it won’t work. But a detail that I thought was interesting is that they agree that this motor would go up to 3000 rpm at 50 hertz at the cost of torque, so I think I would need to reduce the torque proportionally in order to reach the rpm I want.
- 3000 rpm / 30 = 100
- 50 hertz / 30 = 1.6hz
I couldn’t find a solid answer from GPT, but it is said that reducing the frequency in order to increase torque at the cost of rpm also decreases efficiency.
Taking efficiency curves into consideration, I should have considered that from the beginning.
… But ChatGPT (and a few forums) kinda let it to be understood that also increasing the gauge (wire thickness) and number of turns would also increase efficiency while increasing the torque at a given frequency.
- With all of that in mind, since I will lose efficiency anyway as long as I use lower slots-poles counts at lower frequencies, at least I should reconsider the weight-savings from doing that.
- The weight of 5.8 kilograms was the result of using 99 slots and 66 poles, the other slot-pole counts (24slot-20pole, 30slot-26pole, 36slot-30pole) all weighted around 2 to 3 kilograms. So I should use that weight of aluminum wire instead. No?
- At the end, I will need to build and test it to actually reach an answer.
I both feel like this was a huge waste of time and a genuinely necessary process and evolution in order to reach this conclusion.
One detail I’m actually afraid of: the structural strength of the motor.
We are talking about a resin infused ferrite core that will support 30,000 newton meters of torque.
How I’m sure that it won’t catastrophically fail?
I asked ChatGPT, and it said the core should have at least 20 to 300 MPa of sher and/or tensile strength (from where it took that number, I’m not aware). Ferrite cores have only 50 MPa of tensile strength.
So, I thought on the following:
If you are using ferrite powder for the soft magnetic core or an improvised iron/nickel/silicon steel core (like using wires of said materials), you will need to make holes so the graphene/glass fiber composite can give support to the structure. Like a honeycomb, where the holes are the structural material and the rest is the resin infused ferrite.
However, I would increase its dimensions from 30cm x 23cm to 30x30cm for compensation.
If you don’t really care about the performance of the magnetic field, you can just replace the core with the composite you intend on using. It will be just like an aircore motor.
Actually 3D modeling:
I’m still procrastinating, but for some reason, I feel like I’m missing something.
I keep looking through the project logs and saved links I have on my computer, but I always feel like I’m missing something, that I didn’t layed out the project just yet…
Well, anyway:
First I started using open source 3D models and aligned them, just to give a sense of scale. Left to right is a 3D model with roughly my height (185cm tall), the height of a mech that can fit in my room (265cm tall) and the height I was thinking of (380cm tall). At the end there is the electric motor’s mockup, one with 30x30cm, another with 24x30cm and finally with 15x30cm (the version where I cut the wiring in half).
In this one I just made the human sized model in a sitting position in order to visualize how they would fit in the 2.6 meter tall mech and the 3.8 meter tall one. Kinda campred.
In order to fit the pilot without any problem, you would need to make it 5 meters tall:
Out of curiosity, I tested how it would look if the mech was like that skeleton suit from the Avatar’s movie (the blue guys) or that mech from Appleseed.
It looks like sh1t.
I guess this one looks better and even more practical (the weird pose on the right is just showing that you could either keep the arms inside of the cockpit or the arms inside the mech’s limb).
In this one I made tubes that would be a mockup for the limbs, then I would add the motors afterwards just to see how much space they would occupy
Unfortunately, as you can see, on the 2.65 meter tall mech, the motors (either 30x30cm or 24x30cm) would be just too big.
I forgot to test the 15x30cm one:
I know that there are some motors overlapping, just pretend that they are behind each other, squeezing as much space as possible.
I will test it using voice coil actuators.
It is still a little bit cramped in there, but this looks way more viable than the motors.
Also, the dimensions of the voice coil actuators are 14cm of outer diameter, 10cm of inner diameter and 30cm of length. Weighing 6kg, but if you reduce the outer diameter to 12cm, it goes to 3kg. I`m also assuming that the moving rod will fill the interior of that space.
Now I will test the 3,8 meters tall mech:
From left to right: 30x30cm motors, 24x30cm motors, 15x30cm motors and voice coils.
Although the electric motors would be more efficient, they aren’t nearly as compact as the voice coils…
Out of curiosity, I added the electric motors to the 5 meter tall mech:
On the left it is the 15x30cm motors, on the right 30x30cm (in this case, pretend that the 30x30cm motors have double the weight and power output). It would still be too cramped for the mech.
At the start I wanted a mech to be able to lift 5 tons, then I reduced it to 1-3 tons and it still is a really hard amount to work with…
… I’m starting to question whether or not I should just reduce the carry weight to 500kg or around 300kg…
Out of curiosity, I reduced the power output from 300,000 watts to ¼ of it, 75,000 watts or even less, 50,000 watts. The motors ended up having around 15x15cm in dimensions.
Instead of lifting a maximum 3000 kilograms at 4 m/s to 12 m/s, it would lift 750 kilograms at 4 m/s to 12 m/s. And it would weigh around 1 to 0.5 kilograms with the aluminum wires alone.
- I will settle for this for the actuators: Voice Coils.
The rigid voice coils aren’t good for rotary motions, so it would be interesting to use the “Xangô-33” (the motor with 3 slots and weighting 3 kilograms) on said rotary joints.
Of course, you could simply use a system of pulleys to convert linear to rotary motion. Which I think I will use instead of making an entire electric motor…
Something like this? You would need to add another pulley below it for reverse motion.
hmmm…
Now what?
NOW I need to make the actual 3D model of the actuators with integrated encoders, cooling channels, casing and connectors.
I initially intended on making every brushless motor in the mech, both for arms and legs, with the same output (300,000 watts), but after this, it seems like I have no choice but to cut down by 3 times the strength of the upper body actuators.
Yes, I did say I would settle for the linear voice coil actuators, but… I just don’t know…
The 3D model I’ve made is more compact, even though it still weighs the same. But that is a rough estimation, the brushless motors could have more ferrite mass for its core and it would be easier to cool down.
I don’t have a proper way of predicting/calculating neither the motor nor the voice coil, but the motor has more available knowledge about it in case something doesn’t work the way I intended…
In any manner, I guess I will just 3D model everything and wonder about it later.
I will start with the brushless motor.
It will have 30cm of diameter, two mirrored stators with 3 slots, 5.8 kilograms of aluminum wire. I will reduce the weight, but I guess it will be easier by starting with it this way.
Every slot would have 6 turns with 4 layers for more or less 0.996 kilograms per slot, 0.996 x 3 slots x 2 stators = 5.9kg. 349,865mm³ is the volume of the coil
I’ve made the coil using the “Screw” modifier on Blender, and I will be forced to delete it because it is slowing the program too much. So in the final archive you will only see a solid C shape for mockup.
And of course, when I changed its shape, it got wider and smaller, meaning it would have a different number of turns and layers when wound around the slot.
My brother that lies in heaven, what the hell?
You have no fricking idea how hard it was to make a single slot on this thing, no matter what I did, nothing would make an arc. I mean, I’ve made an arc in the shape of the coil that would be wound around the slot, but for some reason Blender was saying that these two meshes had the same volume. So I had to make a new one just to be certain.
But when I tried to do it, every attempt was literally:
- I watch a tutorial showing how to do it.
- I repeat the same exact process on my end.
- It doesn’t work.
- repeat
The only way I got it to work was using a “Path” option from the “Curve” creation list using Shift+A, then I used a circle from the “Curve” option to use the Modifier “Curve” on the circle so the “Path” was a perfect circle, just so I could use the “Curve” modifier again with the “Array” modifier in a cube to make a continuous arc.
I finally finished the arc with the same dimensions and indeed, the blender was calculating the volume incorrectly. Now I need to redo the process again because the inside of the coil is bigger than the outside.
Well, to my surprise, it only reached 6cm of height, so the motor with the two stators would have 12cm of thickness in total (without the softcore).
I also added 10mm wide holes for structural support and 5mm wide holes for coolant flow.
The motor complete with both stators:
It ended up having 35cm of diameter because of the base.
Its volume is 1689641mm³, and assuming a density of the composite ferrite core to be around 4.5 g/cm³, so a single core would weigh… 7 kilograms.
7 kilograms x 3 cores x 2 stators = 42 kilograms.
Oh god.
I will have to reduce its dimensions and density.
The motor is reduced to ⅓ of its weight/size, the coils weigh more or less 2 kilograms and the ferrite core now weighs 4.3 kilograms. 4.3 x 3 slots x 2 stators = 25.8 kg.
Well… Dang it. Reducing its density it is. I will do that by adding less ferrite powder and more resin/polymer.
Now, reducing further to ⅓ of its size/weight for the arms:
The coils will have more or less 0.7 kilograms.
- I also forgot to make the coils of the motors 10 to 20% bigger/heavier. You see, electric motors are 80 to 90% efficient, meaning that they will deliver 10% to 20% less than the intended output. This being 290,000 watts or 90,000 for the case of 300 kilowatts and 100 kilowatts. I already fixed it in the 3D models, but you know what I mean.
- For reducing or increasing the output of the motors, I do think it would be better to increase/reduce the number of wires (in the case of 100 kw motor, reducing from 50 parallel wires to 20) and in the case of increasing/reducing the weight, it would be better to increase/reduce the number of turns of the coils.
Observation:
I don’t remember posting this anywhere, but here are some articles with the permeability of iron powder composites based on weight:
(PDF) Strain sensing capabilities of iron/epoxy composites
Enhancing the Low-Frequency Induction Heating Effect of Magnetic Composites for Medical Applications
A time discrete scheme for an electromagnetic contact problem with moving conductor
Another solution for the back-iron problem would be:
To use the halbach array with the electromagnets in order to concentrate in one direction.
US9558876B2 - Halbach array of electromagnets with substantially contiguous vertical and horizontal cores - Google Patents
Design and Simulation of Superconducting Lorentz Force Electrical Impedance Tomography (LFEIT) (PDF) Proposal and Challenge of Halbach Array Type Induction Coil for Cooktop Applications
There is the possibility of using an active magnetic shield.
- All about magnetic shielding Magnetic Shielding - Excel@Physics (for some reason my browser says this website isn’t safe) Actively shielded gradients - Questions and Answers in MRI On-scalp MEG system utilizing an actively shielded array of optically-pumped magnetometers Active magnetic radiation shielding system analysis and key technologies - ScienceDirect Closed bore XMR (CBXMR) systems for aortic valve replacement: Active magnetic shielding of x‐ray tubes | Request PDF A lightweight magnetically shielded room with active shielding | Scientific Reports Evaluation of Superconducting Magnet Shield Configurations for Long Duration Manned Space Missions Radiation Protection and Architecture Utilizing High Temperature Superconducting Magnets - NASA Reducing fringe fields - Questions and Answers in MRI Learn why magnetic shielding is a key part of MRI safety - MRI components Evaluation of Superconducting Magnet Shield Configurations for Long Duration Manned Space Missions
Surround the electromagnets with permanent magnets on all sides (or just weaker electromagnets with a similar force to permanent magnets), so the electromagnets are always interacting with another magnetic field.
A New Coreless Axial Flux Interior Permanent Magnet Synchronous Motor With Sinusoidal Rotor Segments | Semantic Scholar (PDF) Design Aspects, Winding Arrangements and Applications of Printed Circuit Board Motors: A Comprehensive Review A New Coreless Axial Flux Interior Permanent Magnet Synchronous Motor With Sinusoidal Rotor Segments | Semantic Scholar
(PDF) Improved Analytical Model for Electromagnetic Analysis of Axial Flux Machines With Double-Sided Permanent Magnet Rotor and Coreless Stator Windings (PDF) Performance analysis of a coreless permanent magnet brushless motor
Flux Barriers.
They are meant to enhance certain aspects of the electric motor, but they are normally used on synchronous reluctance motors.
There are papers about using them on BLDC motors, but I don’t think I can successfully design one by myself.
- As you can see, the flux barriers are meant to concentrate the magnetic flux, and most of them are in the rotor rather than in the stator. Probably because the part with permanent magnets has the weakest magnetic field in the machine, so I don’t know how well this would work for the stator. A Low-loss and Lightweight Magnetic Material for Electrical Machinery - PMC A Novel 12-Teeth/10-Poles PM Machine with Flux Barriers in Stator Yoke Reduction of cogging torque of single phase brushless DC motor using flux barrier Finite Element Analysis Of A Novel Brushless DC Motor With Flux Barriers Sensorless flux-weakening control of permanent-magnet brushless machines using third harmonic back EMF Optimization of novel flux barrier in interior permanent magnet-type brushless dc motor based on modified Taguchi method (PDF) Analysis of A Novel Consequent-Pole Flux Switching Permanent Magnet Machine with Flux Bridges in Stator Core https://www.semanticscholar.org/paper/Study-of-An-Improved-Yoke-Permanent-Magnet-Motor-Amirkhani-Mirsalim/49071efad47e9fa67a03d5d5aa136530252b59ee (PDF) Flux-Modulated Permanent Magnet Machines: Challenges and Opportunities
- Just don’t worry about it too much, even coreless ironless motors are around 80% efficient. Alternatives to stacked iron plates for electric motor cores? Cored Vs Coreless DC Motors – Progressive Automations
- I could also stop being a bitch and just switch to hydraulics/pneumatics, so I only need a single 300 kw (or more) BLDC motor.
I don’t know if this is a “solution” or not, but:
All ferromagnetic materials have densities from 6 g/cm³ and higher. So, at least 6 times denser than water. Thus, 1 liter of these materials would weigh 6 kilograms or more, unlike all the other low density materials I presented, such as polymers, carbon fibers, fiberglass etc.
Even ferrites (which are chemical compounds of iron and oxygen) have densities around 4.7 g/cm³, which, like I calculated before, is not low-dense enough.
I tried looking if metamaterials could work, but I couldn’t find anything.
Well, asking Web-SearchGPT and looking on the internet for days, it finally showed something interesting:
Nanofoam Exhibits Surprising Magnetic Properties | American Physical Society
The link above doesn’t link to the original article, so here it is: (PDF) Unconventional magnetism in all-carbon nanofoam
“Carbon nanofoam is structurally distinct from the other four known forms of carbon—graphite, diamond, fullerenes ( buckyballs), and nanotubes. With a density of about 0.002 g/cm³ (2 milligrams), comparable to that of aerogel, carbon nanofoam is one of the lightest known solid substances.
But what's most remarkable about the material, the researchers said, is that unlike other forms of carbon, the nanofoam is ferromagnetic, like a refrigerator magnet. However, at room temperature, the nanofoam's magnetization disappears a few hours after the material is produced.”
“...David Tománek of Michigan State University, who collaborated with the group on theoretical interpretation, believes that the carbon clusters in the foam are made up of nanotubes joined together into tetrapods. In these four-legged structures, some carbon atoms have a free electron, one that does not form a chemical bond. These unpaired electrons carry a magnetic moment that may lead to the magnetism."
So, this is still something in earlier stages, in fact, this article is from 2003.
And even then, it doesn’t delve if it has useful ferromagnetism. Just because you can detect it, doesn’t mean it is useful in the macroscale.
Also, while reading the various article's abstract text, it is mentioned that the ferromagnetism in carbon based materials is achieved at the nanoscale and at cryogenic temperatures.
Origin of magnetic moments in carbon nanofoam | Phys. Rev. B (2006, temperature from 2 kelvin, to 50 kelvin and even 300 kelvin [aka room temperature])
Strong paramagnetism and possible ferromagnetism in pure carbon nanofoam produced by laser ablation - ScienceDirect (2005, “maybe ferromagnetism at 90 kelvin” it was written)
Phys. Rev. B 71, 144424 (2005) - Theory of ferromagnetism in carbon foam (2005)
https://www.ingentaconnect.com/contentone/asp/jnn/2009/00000009/00000002/art00103 (2009, they use carbon nanotubes [not viable] and achieved a saturation of 0.11 emu/g, which is around 100 to 1000 times smaller than conventional metal ferromagnetic materials)
Investigation on magnetic carbon nanofoam composites (2010, they used 1% by weight of ferrite cobalt [CoFe2O4] in conjunction with the carbon nanofoam, so it obviously has some ferromagnetic property to it)
Unexpected magnetism in nanomaterials (2013) “Carbon nanofoam which contains graphite-like sheets with hyperbolic curvature as in schwarzite exhibits ferromagnetism. Carbon nanofoam produced by high-power laser ablation of glassy carbon in Ar atmosphere exhibits ferromagnetism up to 90 Kelvin (-185ºC)”
Phys. Rev. B 74, 214418 (2006) - Ferromagnetic behavior of carbon nanospheres encapsulating silver nanoparticles “showed weak ferromagnetic behavior up to at least room temperature with a coercive field of 389Oe at 2K and 103Oe at 300K”
Room-temperature ferromagnetism in graphite driven by two-dimensional networks of point defects | Nature Physics (2009, ChatGPT said that it has 10,000–17,000 times smaller saturation than conventional ferromagnetic materials)
Multilevel ferromagnetic behavior of room-temperature bulk magnetic graphite (2018, achieved a saturation of around 0.25 emu/g at room temperature, but the graph makes me think it was around 0.05 or something)
Synthesis and dye separation performance of ferromagnetic hierarchical porous carbon - ScienceDirect (2008, it achieved 11 emu/g, but it has 35% nickel per weight, so it doesn’t counts anyway)
Dunno if all of this was useless or not, but here is a few articles on how to make nano ferrite particles:
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