Origin of term: Valve Metal

The word "valve" is an old term used for diodes etc. It the way electricity flow is compared to water flow; a diode would be compared to a valve in a pipe.

"A Schottky diode structure is what is being implemented
with the valve metal and semiconductor oxide laminate."

could easily be inferred as:

"A Schottky diode structure is what is being implemented
with the metal (used to make the Valve) and semiconductor oxide laminate.

It is not a "name" per say but an adjective.

Hi Techno,

I'm not trying to be contrary, but a variable resistor is more like a valve in a pipe . The diode is more like a check valve.

Cheers,

Mike

"Outstanding!" ...

Thanks for the speedy clarification [both CSM_Eng & techno]... much appreciated.

T.M.D.

Hello ndt-tom

These are called "Valve Metals" because of the way they can self-grow nano-porous oxide films.

Refer: http://books.google.co.nz/books?id=P49DsqiWtwEC&pg=PA187&lpg=PA187&dq=%22valve+metal%22&source=web&ots=PbjikWza9B&sig=uwDazNOsb-X0WKgkxJWm1ULNpxA&hl=en

http://www3.interscience.wiley.com/cgi-bin/abstract/109621405/ABSTRACT?CRETRY=1&SRETRY=0

There are many other references to these metals, with the above explanation.

So in spite of the fact that W (Tungsten), Ta (Tantalum), Nb (Niobium, Zr (Zirconium) and similar metals were used in the manufacture of what were called "thermionic valves" because the electron flow went from the heated filament or cathode, through the vacuum towards the plate, which was charged with several hundred volts in a domestic receiver and thousands of volts in a transmitter.

The "thermionic valves", were called variously as "Vacuum Tubes" (Europe), "Electron Tubes" (US, Canada), "Valves" (UK, Australia, New Zealand)", that has nothing to do with these metals being called Valve Metals.

"Valve Metals" are called that, because of the way they can self-grow nano-porous oxide films.

Now you know.

Kind Regards....

You're saying that even though these metals were found to be useful in the design of "valves" that has nothing to do with their name? Instead, they're named after some property that has no reference to anything "valve"? (And, was nano-scale structure even detectable when these materials were named?) Sorry, the first two explanations have the ring of truth to them - yours does not.

Hello Guest,

Maxim:

Sincerity of belief is never a substitute for truth.

You are entitled to believe whatever you want, whether it is correct, or not.

You did ask for the explanation, and I assumed you wanted to know the correct reason behind the term "Valve Metals".

I shall use the original Term: "Thermionic Valve", as I explained in my earlier Post above rather than some variable term, dependent on which Country you learned about them, and so I did give the common variables in that earlier Post above

Back in the 1950's through to the 1990's I have worked with "Thermionic Valves", first as a hobby interest, then for a major New Zealand user of those "Thermionic Valves", and later on a commercial basis, for one of my Companies.

Please note the list given in that Topic Post written by ndt-tom:

<".....Al, W, Ti, Ta, Hf, Nb, Zr.....">

Note the interesting discrepancies:

Al = Aluminium (Aluminum for the US reader, refer here for the reason for spelling difference), has never to my knowledge been used as part of the structure of a "Thermionic Valve", but is a "Valve Metal".

Ti = Titanium has never to my knowledge been used as part of the structure of a "Thermionic Valve", but is a "Valve Metal".

Hf - Hafnium has never to my knowledge been used as part of the structure of a "Thermionic Valve", but is a "Valve Metal".

Please read my included "Valve Metals" list, from my earlier Post above:

<" W (Tungsten), Ta (Tantalum), Nb (Niobium, Zr (Zirconium) and similar metals">

The reason I did not include Al, Ti, and Hf from the list in the Topic Post by ndt-tom is simple:

Those metals were not ever used as connecting wires, or electrical structure assemblies at any time, during "thermionic valve" manufacture.

So, you didn't bother to type into Google's Search Engine the words (Important to type them between quote marks): "Valve Metal" = Results 1 - 10 of about 44,600 for "Valve Metal". (0.24 seconds).

Careful and diligent study will show that the Term: "Valve Metal" does refer as I described in my earlier Post above

I do agree with you that the Term "nanoscale" and "nanoporous" and the general term: "Nanotechnology" had yet to be coined for common use, even though "Thermionic Valves" had been invented and sold by the thousands of millions.

Interestingly, the first compound word using nano------ which I have been able to find, was in a book written in 1986, and published in 1987, is Engines of Creation - K. Eric Drexler

Of course, we are all free to believe what we choose, and as the Maxim goes: Sincerity of belief is never a substitute for truth.

Thank you for reading this Post, and the included Weblink references.

Kind Regards....

Sincerity of belief is never a substitute for truth.

But when faced with two mutually-exclusive truths, how do you decide? Both explanations cannot be correct. Just because a certain metal was never used in the commercial construction of a tube does not mean it was not found to be a "valve metal" and simply not used in production due to economic reasons. After a preponderance of the evidence presented, the simpler explaination still seems most likely.

Hello Guest,

I appreciate that you are probably a member but want to reply anonymously.

You are free to choose your belief, whether right or wrong.

The balance of evidence, all freely available, would prove my Posts above as correct.

Now I'm not going to get all upset and concerned about it.

Nor am I intending to kick the CR4 Saloon doors open, and start blazing away with my six-guns, like the gun-toting fellow in the picture at left.

If you want the real answer, then do your own research, the same way I did.

The "Thermionic Valve" origin of the Term: "Valve Metals", is not a scientifically reasoned Term, just a convenient fiction, which persons have latched onto, because it "sounds a credible explanation", instead of doing their own research.

Happy researching.

Kind Regards, from far away....

Well, I have to admit, you do sound very sincere...

Nope, I've read the posts and followed the links. The explaination from sparkstation sounds far to much like techo-babble designed to explain away a lay term that got attached to a technical process. It's far more likely that the suitability of these metals was determined experimentally and the actual molecular process discovered later.

Hi Sparkstation,

Al = Aluminium (Aluminum for the US reader, refer here for the reason for spelling difference)

I never knew! According to element name consistency, aluminium DOES sound better. Though every one will label me a heretic, I am going to pronounce it thus every chance I get.

Mike

Try saying it to the soundtrack of this:

http://en.wikipedia.org/wiki/Messiah_%28Handel%29#Hallelujah

Valve Metal seems to be a term that was coined by JAPANESE INVENTORS who mostly invent capacitors. A review of the US PTO records bears this out.

I think that the members of this metal list spontaneously form oxides readily and exist with such coatings when used, and that the oxides affect the bipolarity of the electrode (a nernst voltage exists, across the surface, or somehow e flow in one direction is NOT the same as in the other direction due to formation of the oxide layer), and thus "valve" action compared to other metals when used as capacitor plates. that is, before or after conditioning from use, the electrode behaves a little differently with respect to e flow direction. Not the same as a diode but a type of valve.

The former I am confident in, the latter conclusion is my best guess based on chemistry.

Sadly, I was unable to open your Wiley link, because their server believes my computer does not accept cookies (despite the fact that it does).

Perhaps you could quote, from that link, something that suggests the connection between the word "valve" and the oxide film that these metals form. These are not the metals commonly used in plumbing valves, for example, and without further information I cannot see a connection between the formation of this oxide layer and any "valve" of my experience -- with the exception of the the obvious usage in regards to electron valves (aka "tubes").

Your statement

"Valve Metals" are called that, because of the way they can self-grow nano-porous oxide films.

seems nonsensical without the benefit of something (which I assume your link provides) which makes a logical connection between "the way they can grow nano-porous oxide films" and the word "valve". (Why "valve" and not "anodizable" or "hard to weld"?)

The conventional wisdom is that these metals are grouped because they act in a similar way: namely that they form a thin, often protective oxide film. The most common of these is aluminum, which does not "rust" (and is a little tricky to weld) because of this protective oxide formation. To my knowledge, these metals were not called valve metals until after electron valves came into use. If you can quote something in the literature that makes the connection between oxide formation and the term "valve", (other than that these metals act like those used in electron valves) then I would feel better educated, and would be eternally grateful.

Hello Blink and other readers

I received a surprise when I returned to that link of Wiley, because it gave me the same response as you received.

My Browser (Firefox) has settings to allow Session Cookies", but it appears the Cookie/s which the Website wanted to instal in my PC were not really "Session Cookie/s at all, but ones of longer duration - so the website was not strictly honest, it appears.

It may have been some of my Security Applications, or Firewall refused to accept the "strange Cookie/s" from that website, and because the website could not place a wee spy into my PC, access was refused.

I have not taken that up with the Webmaster of that Site, because I had other things to do...............

It appears from looking at the site, that they like you to Register, perhaps gaining information and a possible fee - the last is presumed, because I did not try to Register.

However, there are ways of "Defeating that sort of webpage system", to locate the information required, and here is the article, copy/pasted, for your information:

Home / Polymers and Materials Science / General Materials Science

Materialwissenschaft und Werkstofftechnik Volume 20, Issue 9 , Pages 299 - 308 Published Online: 15 Sep 2004 Copyright © 1989 Verlag GmbH & Co. KGaA, Weinheim Save Title to My Profile Set E-Mail Alert

Save Article to My Profile Download Citation

Abstract | References | Full Text: PDF (828k) | Related Articles | Citation Tracking

Article The Valve Metal Character of Zirconium as inferred from anode potential measurements in mineral acid solutions Prof. Dr. S. Darwish, Dr. M. W. Khalil, Dr. M. A. Abdel Rahim, Porf. Dr. I. A. Ammar Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt Abstract A study on the value metal character of Zr in 0.1 M solutions of H 2SO4, HNO3, and H3PO4 has been performed using the anode potential as the primary variable in galvanostatic, potentiostatic, and capacity measurements. A method of surface pre-treatment, which suppresses both O2 evolution and metal dissolution, has been described. Kinetic parameters of oxide growth have been calculated. The results indicate that: (i) the high field approximation is applicable following an exponential law, and (ii) the height and activation distance of the energy barrier for ion transport through the oxide phase (Verwey model) are the same three acids. Measurements have been also made on the dielectric breakdown of oxide, and this occurs at potentials above 200 V. Direct capacity measurements give similar results as those based on reciprocal capacity calculated from galvanostatic experiments. It is concluded that the dominant anodic oxide species is ZrO 2 having a dielectric constant of 25. Open circuit potential measurements show that Zr is spontaneously oxidized in the three acids. Digital Object Identifier (DOI) 10.1002/mawe.19890200906 About DOI

Related Articles

• Find other articles like this in Wiley InterScience
• Find articles in Wiley InterScience written by any of the authors

Wiley InterScience is a member of CrossRef.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Now you should have access into the System, via the copy/pasted Hyperlinks.

For Example: Clicking on the "Find other articles like this on Wiley InterScience: gives:

Home / Advanced Search / Search Results

Search Results

There are 27787 results for documents like: "The Valve Metal Character of Zirconium as inferred from anode potential measurements in mineral acid solutions", by S. Darwish, M. W. Khalil, M. A. Abdel Rahim, I. A. Ammar
of which the first 500 are returned

View: 1-25 | 26-50 | 51-75 | 76-100 | 101-125 | Next >

Followed by all those first 500 references, which you may peruse, if you have the inclination, along with the spare time, and enjoy reading.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

I do believe that "Thermionic Valves" were called that, because the first "Thermionic Valve" was a Diode, and of course the current could pass in one direction only.

This relates well to the "Non-return Valve" in the Piping (Plumbing) Industry.

In the early days of electrical experimentation, similarities were drawn between hydrostatics and electricity.

Water Pressure - Electrical Potential = Voltage

Water Flow - Current Flow = Amperage

And so on.

Likewise, when the interesting Oxide Film on certain Metals was discovered, the Term "Valve Metals" was used, because of the "Hydrostatics/Electricity" similarities as referred to above.

The "Valve Metal" Term was not used because of similarity to a "Thermionic Valve" Diode, but the original similarity to a Valve of the non-return type, used in fluid (liquid or gas) installations.

After all, the study of water and liquid flow had been around centuries before Alessandro Volta who "discovered" the dry cell.

I place the word "discovered" in quote marks, because although Volta did discover it, he was not the first discoverer of the dry cell.

So that's not really the full story about the dry cell at all, because the Babylonians, Chinese and Egyptians, and probably the Mayas, all independently from each other, had discovered and used dry cells connected together as batteries, at least 2,000 years earlier than Alessandro Volta's "discovery" in 1800 (That's the basis for your further research, should you wish to do it)

Summary therefore:

The historic "Valves" term relates to valves for fluids = liquids (generally water) and gases.

Thus the first "Thermionic Valves" were called such.

Thus the trend continued, with the term: "Valve Metals".

Kind Regards from far away....

I appreciate your excellent explanation.

Either I was momentarily insane (not unlikely) or my browser had not refreshed the page for this thread (a possibility) when I made my comment to which you are replying; now, seemingly by magic, there are several intervening replies. Those intervening replies make your position clear, albeit ludicrous. Only kidding. Actually, your take on it makes great sense.

My concern was that you originally seemed to be stating that there was something valve-like in the way the oxide formed. But you are, in fact, saying that there is something valve-like (diode-like or rectifier-like) in the way the metal (and its oxide layer) performs. I agree whole-heartedly and completely.

Next time I find myself in NZ, I'll buy. Unfortunately, my frequency of visits has been extremely low (once every 40 years or so) but I certainly enjoyed my time there.

I was curious, so poked around, and found this:

In the early days of the growing electron-tube industry, the first electronic tubes (used as diodes) were named Fleming Valves. The term valve for an electron tube was more prevalent in England than in the United States. The early electron emitters were the hot filaments. Later, the cathode was added. To make an effective cathode a combination of a conducting metal and a substance that was a good electron emitter (thermionic emission) was required. It was found that certain metal and metal oxides were suitable. Thus the term valve metals.

From: http://www.padrak.com/ine/NEN_5_2_8.html

Yup - that's where I found it too. For some reason I could not get a link to work and was too lazy to retype the URL; probably should have - did not realize my post would look like my own words. Thanks, Ken!

My eternal gratitude for ALL contributions, here...

I believe that Sparkstation has recovered with aplomb from his first post (#4)...

As correct as it was, the overall post was semantically weak, due to his two quotes, following, having been emboldened in that post:

"These are called 'Valve Metals' because of the way they can self-grow nano-porous oxide films." and, at the end of the post (also emboldened):

"'Valve Metals' are called that, because of the way they can self-grow nano-porous oxide films."

Omitted from that first post of his was the quote that he provided in (his) Post#15 with the link to the original article (most enlightening):

"a valve metal is a metal which, when oxidized, allows current to pass if used as a cathode but opposes the flow of current when used as an anode."

This, above, was the type of definition being sought in the first place... and many "Thanks!", Sparkstation, for finding it! And thanks to RHABE for the useful learning-tool experiment as well! Bestest-Warmest Regards to one and all!

I note that cesium is not listed among the valve metals, but perhaps it should be.

Decades ago, I experimented with oxide coatings on cesium. (Actually, fluoride coating might have been better) The theory was that, with a very thin, half-monolayer, coating, the extremely polar thin film would enable thermal electrons to tunnel through, as a cathode, at room temperature. One would have a thermionic electron source with cheap, room temperature, heat, hence a free power source.

I never got my vacuum system clean enough to be able to get a half-monolayer oxide coating, and cesium is rather difficult to handle. (It comes in glass ampules which must be opened in a good vacuum, lest it go poof!) As far as I know, the theory was valid, but the execution was beyond my capabilities at the time.

I would be appreciative if anyone with experience with cesium would share it.

A W E S O M E ! . . . I knew that cesium was used in the most accurate atomic clock in the world... +/- 1 second in 20 million years... but I had never before heard just how volatile the material was.

Thanks for introducing that tidbit. "Incredible" how knowledge can snowball on us, eh?

Anybody have any "more-recent-input" on cesium... per esbuck's request?

stainless steel does not rust because of an oxide film, I recently spilt 80% sulphuric acid on a teaspoon which etched the surface leaving a "scar" but it has not rusted, I introduce this fact to allow others to speculate. We know that aluminium is a conductor and yet is a valve metal, could it be that stainless steel, although a compound has such properties? Very interesting thread. What is also interesting is the initial denial. Such folk wisdom where an explanation seems to fit takes some undoing, like removing a jigsaw puzzle piece which has been fitted with a hammer. I face such resistance with a friend on a number of topics. I have been unable to dissuade him from the belief that aluminium cookware is poisonous and that microwaves make food unhealthy. After years of this I recently gave up. For this reason I admire Sparkstation's persistence and congratulate him on his many informative posts and justified good answers.

ps In Uncle Tungsten (a wonderful book) the author, Oliver Sacks, describes wiping the surface of aluminium with mercury causing the aluminium to oxidise in air and rapidly transform into aluminium oxide powder. time to break open those tilt switches you all have on your shelves (I no longer have mine) and try it yourselves - and say what you found perhaps?

Hello HUX

<".....wiping the surface of aluminium with mercury causing the aluminium to oxidise in air and rapidly transform into aluminium oxide powder......">

That is one of the two reasons why mercury is totally banned from all aircraft, because after a short period of time, there would be holes, which would increase in size, until structural failure.

The other reason for mercury being banned in many places, is that even at room temperature, the vapour of mercury is extremely toxic, although it cannot be smelt by the human nose, plus it is readily absorbed through the skin - a good reason why not to "play with it", unless you have proper protection.

Refer: http://en.wikipedia.org/wiki/Mercury_poisoning

Kind Regards....

Did other kids of the 50's and 60's play with mercury as I did, rolling the little balls around, and "plating" coins with it?

Hello Blink

I did, and also had mercury amalgam tooth fillings too.

I do understand that some people are more susceptible to mercury poisoning than others - there appears to be a genetic link with that susceptibility.

I do know my general heath improved markedly, once that last mercury amalgam filling was replaced with the later filling material.

I discovered after early dentistry had filed my cavities with mercury amalgam fillings, that gold was the way to go.

A singular advantage of at least one gold filling or tooth cap, is that the body requires gold atoms in very small quantities, as a catalytic agent needed for certain enzymatic processes to work properly.

The gold may enter the body via food, wearing of gold jewellery, or a gold cap/filling of a tooth.

Interestingly, Platinum and Silver are also useful in extremely small amounts, to promote health, although it is important not to absorb too much, as metal poisoning may occur at higher levels.

Kind Regards....

Valve metals— Metals that form a compact, electronic

insulating passive layer when anodized in aqueous electrolyte,

exhibiting asymmetric _ conductivity: blocking

anodic reactions, except at very high voltages.Valvemetals

include aluminum,_titanium, tantalum, zirconium,

hafnium, and niobium. Some other metals, such as tin,

may exhibit valve-metal properties under specific conditions.

In _ electrochemical cells, valve metals function generally

as a _ cathode, but not generally as an _ anode

due to the insulating oxide layer that forms on the metal

surface under anodic conditions.This oxide is highly resistant

to the passage of current, and may serve for corrosion

protection. In most cases the oxide passivating films

are either amorphous, or composed of very small crystalline

domains (with high defect concentration) within

an amorphous matrix. The anodic oxide layers can be

grown up to 100 nm thick.

Valve metals are used in electronic components, such

as tantalum capacitors, microwave field-effect transistors,

gate materials, etc.

from Electrochemical Dictionary

I read through all the posts, but may have missed if someone already posted this, so my apologies if this has already been mentioned.

Since the OP was curious as to the origination of the term "valve metal" the way to best settle the discussion would be to find who coined the term and in what capacity it was originally used. So far as I am aware, the term 'valve metal' and 'valve electrode' were the english transliteration of the term (in german) 'Ventilelektrode' as coined by Gunterschulze in the early 1900's during his study of naturally and anodically created thin oxide films on these metals. The seminal book written by Guntershulze and Betz (Elektrolytkondensatoren, Guntershulze, A. and Betz, H, 1937. Krayn, Berlin) on this topic made these terms popular. I believe an english translation was published in '44 and '52. The terms made refference to the rectfying action of the oxide coated-electrode (forward direction: cathodic). Hope this helps. Sorry to resurrect and old dead thread, but I thought maybe I could shed some light.

I read with interest the contribution from the community on this topic. I have a question, however, regarding the quote:

"a valve metal is a metal which, when oxidized, allows current to pass if used as a cathode but opposes the flow of current when used as an anode."

How does it work in the electrochemical process where the coated titamium is used as an anode ? Does it resist the flow of current?

Thanks.