The end of microcoils?

[Magaro]

OK, here's a question for the metallurgists out there...what is the typical thickness of the oxide layer on Ni200 and Grade 1 titanium under the normal conditions of vaping? When I say normal conditions, I mean not being heated dull red or red hot but in the vicinity of 400 F.

The oxidation kinetics of titanium at 400F will be extremely sluggish. The oxide will develop very slowly. Why not conduct your own study? You could take some wire and put it in your kitchen oven (perhaps with and without an adjacent pan of distilled or deionized water to study the effect of humidity). The early stages of titanium thermal oxidation are readily visible to the naked eye. It think its unlikely that the wire will achieve full corrosion-protective coverage in any realistic time period at 400F. And the microstructure of the oxide film will be different than one formed at higher temperatures. Electrochemistry can be used to accelerate the oxidation, but I wouldn't advise doing that to a coil you intend to vape on given the chemicals used to create an effective electrolyte.

 

[awsum140]

Good idea, but exactly how would I measure the oxide thickness? I checked everywhere in the house and don't seem to have a scanning electron microscope.

I guess what I am getting at is the lack of solid data, available in a concise format, that can be used as a reference by the "casual" vaper.

 

[druckle]

The oxidation kinetics of titanium at 400F will be extremely sluggish. The oxide will develop very slowly. Why not conduct your own study? You could take some wire and put it in your kitchen oven (perhaps with and without an adjacent pan of distilled or deionized water to study the effect of humidity). The early stages of titanium thermal oxidation are readily visible to the naked eye. It think its unlikely that the wire will achieve full corrosion-protective coverage in any realistic time period at 400F. And the microstructure of the oxide film will be different than one formed at higher temperatures. Electrochemistry can be used to accelerate the oxidation, but I wouldn't advise doing that to a coil you intend to vape on given the chemicals used to create an effective electrolyte.

It would take a pretty accurate "ruler" to measure the oxide thickness wouldn't it?

 

[druckle]

Good idea, but exactly how would I measure the oxide thickness? I checked everywhere in the house and don't seem to have a scanning electron microscope.

I guess what I am getting at is the lack of solid data, available in a concise format, that can be used as a reference by the "casual" vaper.

Yeah, sorry. It's a great question but there's no easy way to get a good answer. Lot's of hard ways to get the answer but all are either very expensive or take a whole lot of time to do the work. Reality strikes I guesss..

 

[Magaro]

It would take a pretty accurate "ruler" to measure the oxide thickness wouldn't it?

The early stages of titanium oxidation are very highly correlated with specific changes in the visible color one perceives when looking at the oxide film in normal daylight. If this doesn't happen, then no significant oxidation has occurred.

 

[druckle]

The early stages of titanium oxidation are very highly correlated with specific changes in the visible color one perceives when looking at the oxide film in normal daylight. If this doesn't happen, then no significant oxidation has occurred.

Absolutely right. Those colors are interference colors related to the thickness and the wavelength of incident light. If someone were to accept "VERY THIN" as the answer they wouldn't be far wrong.

 

[Magaro]

I should mention that if you want to do your own "oven oxidation" experiment, be sure to start with a clean oven. Nasty organics in the atmosphere will certainly confound your results.

 

[HolmanGT]

I'm not a metallurgist and was hoping for a little more specific answer, LOL.

Awsum,

I would think there are so many variables involved in answering that question it would be almost impossible to answer. Also once it starts to oxidize it the oxidization process will slow down because the Ti is not as exposed to the oxygen.

Can I ask why you are interested in the thickness? Is it for voltage breakdown or heat insulation or ... ?

 

[awsum140]

I should mention that if you want to do your own "oven oxidation" experiment, be sure to start with a clean oven. Nasty organics in the atmosphere will certainly confound your results.

LOL. What I was really looking for was not, necessarily, an exact answer. I suspect, as a layman, that we are talking in terms of microns of thickness. Is that a correct "assumption"?

My interest stems from another thread where someone said, not in this specific wording, "how can an electrical connection be made to the coil if the oxide is an insulator?". My response, considered layman response, was that the oxide layer was extremely thin and easily displaced by the friction and abrasion of tightening the screw and that further oxidation of the actual connection is prevented because it is maintained in a relatively oxygen free, mechanically solid, environment.

 

[druckle]

LOL. What I was really looking for was not, necessarily, an exact answer. I suspect, as a layman, that we are talking in terms of microns of thickness. Is that a correct "assumption"?

YES

 

[druckle]

LOL. What I was really looking for was not, necessarily, an exact answer. I suspect, as a layman, that we are talking in terms of microns of thickness. Is that a correct "assumption"?

My interest stems from another thread where someone said, not in this specific wording, "how can an electrical connection be made to the coil if the oxide is an insulator?". My response, considered layman response, was that the oxide layer was extremely thin and easily displaced by the friction and abrasion of tightening the screw and that further oxidation of the actual connection is prevented because it is maintained in a relatively oxygen free, mechanically solid, environment.

Sounds like you are doing some very good thinking ! It's probably always good to retighten the connection now and then to do a little more abrasion and create higher contact forces both of which improve conductivity. It also upsets sneaky oxides that may creep in with time trying to confound your vape.

 

[Mad Scientist]

At 36 pages I guess I have little to add. Isn't this really just basic physics? I can vaporize nickel into virtual oblivian, condense it, form it back into a wire and vape with it -- without contracting metal fume fever. As long as I don't inhale the nickel atoms (or nickel oxide molecules) floating around before I can recondense enough nickel, I think I'm good. Dry burning a coil is dangerous? I'm not seeing it.

For vaping, the danger would seem to be approaching melting temperature of nickel or nickel oxide with resulting out gassing of each. Nickel melts at over 1000 F nickel oxide at over 3000 F. I'm sure I'm oversimplifying something, but I'm missing the need for any advanced metallurgy or chemistry for a simple physics question and I'm not too excited about needing studies either.

 

[Magaro]

LOL. What I was really looking for was not, necessarily, an exact answer. I suspect, as a layman, that we are talking in terms of microns of thickness. Is that a correct "assumption"?

My interest stems from another thread where someone said, not in this specific wording, "how can an electrical connection be made to the coil if the oxide is an insulator?". My response, considered layman response, was that the oxide layer was extremely thin and easily displaced by the friction and abrasion of tightening the screw and that further oxidation of the actual connection is prevented because it is maintained in a relatively oxygen free, mechanically solid, environment.

The "colored" films form at less than one micron thickness. They indicate the VERY early stages of oxidation.

 

[druckle]

At 36 pages I guess I have little to add. Isn't this really just basic physics? I can vaporize nickel into virtual oblivian, condense it, form it back into a wire and vape with it -- without contracting metal fume fever. As long as I don't inhale the nickel atoms (or nickel oxide molecules) floating around before I can recondense enough nickel, I think I'm good. Dry burning a coil is dangerous? I'm not seeing it.

For vaping, the danger would seem to be approaching melting temperature of nickel or nickel oxide with resulting out gassing of each. Nickel melts at over 1000 F nickel oxide at over 3000 F. I'm sure I'm oversimplifying something, but I'm missing the need for any advanced metallurgy or chemistry for a simple physics question and I'm not too excited about needing studies either.

Yeah, that's how I see it.

 

[awsum140]

Again, as a layman, what I am starting to think is that the metals seen, thus far, in vapor may very well be a result of the oxide coating coming off from repeated stress of heating and cooling. I don't think anyone is thinking that you're actually inhaling wire fumes, nowhere nearly hot enough even at cherry red (again, don't shoot me I'm just guessing).

It's the lack of solid data that's driving all of us casual vapers crazy.

 

[druckle]

Again, as a layman, what I am starting to think is that the metals seen, thus far, in vapor may very well be a result of the oxide coating coming off from repeated stress of heating and cooling. I don't think anyone is thinking that you're actually inhaling wire fumes, nowhere nearly hot enough even at cherry red (again, don't shoot me I'm just guessing).

It's the lack of solid data that's driving all of us casual vapers crazy.

Except for the case over heated "crappy" cartomizers the information I can glean from published work is that the metals seen are sourced from ambient air, given that the largest study I know of had metal content in the vapor stream equal or below that in the ambient air. It will be interesting to see additional studies but among the things I worry about metals (or oxides) in my vape are NOT on my list.

 

[Mad Scientist]

Again, as a layman, what I am starting to think is that the metals seen, thus far, in vapor may very well be a result of the oxide coating coming off from repeated stress of heating and cooling. I don't think anyone is thinking that you're actually inhaling wire fumes, nowhere nearly hot enough even at cherry red (again, don't shoot me I'm just guessing).

It's the lack of solid data that's driving all of us casual vapers crazy.

You're thinking along the right lines but you have to factor in the scale of what we're doing. Imagine a small piece of soft nickel wire weighing .1 gram heated to 450 F. Now blow on it. How long would you have to do that until the repeatedly formed layers of nickel oxide were continuously abraded away by the airflow and the .1 gram of nickel disappeared? I can't even guess how long. It would be measured in centuries if not geologic time. Vape for your entire life and you certainly will not get even .1 gram. We get trace elements of everything in everything. Someone saying they can detect nickel oxide in ecigs says nothing if they don't say how much per unit of something else (like ng / cubic liter of vapor or something).

Edit: meant cubic meter of vapor -- liter is already volume lol.

 

[AntC]

Had a long post going but I'm just gonna skip it and keep it basic: THANK YOU guys (or gals) for explaining this all to us. This is very important stuff and I truly appreciate the time the PhD's are spending to educate us. This is a REAL important topic, with REAL questions, and REAL answers. Thank you thank you thank you!!!

 

[awsum140]

I agree with the scale being minuscule at best, but the number of cycles can get really high. The amount would certainly seem to be extremely limited but no one has every actually tested to see what the amount really is in real world vaping conditions, especially like what we see today with the proliferation of sub-ohm, high powered (relatively) devices currently available being used by people that have no concept at all of what power levels are involved.

 

[MacTechVpr]

LOL. What I was really looking for was not, necessarily, an exact answer. I suspect, as a layman, that we are talking in terms of microns of thickness. Is that a correct "assumption"?

My interest stems from another thread where someone said, not in this specific wording, "how can an electrical connection be made to the coil if the oxide is an insulator?". My response, considered layman response, was that the oxide layer was extremely thin and easily displaced by the friction and abrasion of tightening the screw and that further oxidation of the actual connection is prevented because it is maintained in a relatively oxygen free, mechanically solid, environment.

Because basic oxidation needed for stable current flow is generally thin. Thin enough to be damaged by handling and compression and yes, certainly by a post screw. How thick is it exactly? Dunno. Done a lot of these and it varies by wire. Fatter wire requires more pulsing. A minimally strained wire will attain oxidation rapidly with uniform surface contact and a very few pulses at room air temp's. Humidity, altitude also affect the rate of oxidation. But I live in S FL where it's always humid. LOL Prolly a good thing. Also, I've found I get different results from mechs and APV's and among them. I agree it's a hard thing to predict and use the analogy…we all need to learn to fry our own eggs.

A tensioned micro will pulse end to end at low voltage very quickly. Begin to oxidize just as rapidly. Having built many on <15W VW for Kankers at ~1.8Ω (half max volt's) can tell you that typically the norm is <6 pulses to achieve insulation and res stability. A final red fire to assure uniformity. Not there. It's a fail. Too much surface imperfection or insurmountable gaps to ensure consistency and so there is observable wire temperature variation. But you wound one in less than 30 sec's so it's not a problem.

I state this here once again because I am so confident in these results having watched so many repeat them. Can only urge folks to try. Strain's a useful tool that cuts the time considerably for annealing. Once achieved micro's function in every way like a conventional open wind with the added concentration provided by the m.c.'s close geometry. The only caveat is that the oxidation must be adequate for the wire and power/voltage applied or current will overcome the insulating effect of the oxide layer.

How thick is thick? It's got to be thick enough to serve as an insulator. And that my friend is a learned process (or likely proprietary and valuable).

Not to say we all have to wind them. I have a lot of preferences myself. But strain's an important tool in any case for new vapers to certainly benefit from getting there quickly.

Good luck.