Does Karat determine particle size?

[burningsuntech]

I have processed memory sticks and plated circuitboard with the AP process.

I've noticed that the higher the karat gold, the more complete the foil or particle size and the lower the karat gold, the finer the particle size.

I'm thinking that the lower karat gold breaks up more easily because of the amount of base metals like copper or silver added to the gold to change its quality. Am I on track here or a bit derailed?

Also, if partical size is indeed smaller with lower quality gold, what would be the best filtering or decanting method for catching most, if not all the gold?

Thanks much, guys.

Sam

 

[Geo]

karat is a measurement of pure gold in an object. it is split into 24 equal parts. 1/24 would be 1K gold as an example. the gold doesnt change size but it can change volume and state of being (solid,liquid,gas).

 

[Palladium]

I've noticed that the higher the karat gold, the more complete the foil or particle size and the lower the karat gold, the finer the particle size.



Sam

It's not the karat that determines this, but the thickness of the plating. For all practical purposes gold used in electronics is pure and not karated.

 

[goldsilverpro]

I've noticed that the higher the karat gold, the more complete the foil or particle size and the lower the karat gold, the finer the particle size.



Sam

It's not the karat that determines this, but the thickness of the plating. For all practical purposes gold used in electronics is pure and not karated.

Ralph is right on the money, as usual. Most all the gold plating on escrap is at least 99% pure and most of this is at least 99.7% pure. In general, the thinner the gold, the more it will break up. Except for rare 18K gold contact points, there is no such thing as karat gold on escrap. If the plating looks pale, it's because it's so thin that you're seeing the nickel underneath it.

 

[burningsuntech]

I see. So the thickness of the plating determines how fine my particles are. I think the light bulb just went on. :idea:
Thanks for the input guys. Appreciate it.
Sam

 

[goldsilverpro]

I see. So the thickness of the plating determines how fine my particles are. I think the light bulb just went on. :idea:
Thanks for the input guys. Appreciate it.
Sam

Most of the gold plating you see is hardened with the addition of from 0.1% to 1% nickel or cobalt, mainly to improve wear resistance. About the only exception is the pure 99.99% pure gold plating that is used on certain parts, such as some ceramic CPU packages that must be heated for such things as die attach or lid mounting. At the high temperatures required, the only gold that wouldn't discolor is the high purity variety.

The hardened gold is stressed and, therefore, it contains many microcracks. Also, thin gold is quite porous and it's density is much less than the 19.3 written in the books. As the thickness increases, the cracks and the porosity start to fill in and the density increases. After dissolving the Ni and Cu underneath, thin hardened gold will break up into thousands of slivers. Thicker gold, say 30 microinches, will usually break up, but in larger pieces. Hardened gold 100 microinches or thicker will not break up, assuming the plating bath was in perfect working order when the object was plated.

Contamination (usually organic) in the plating bath will increase the stress in the deposit. We used to check hardened gold plating baths for excessive stress by first plating 1" x 4" polished brass panels to 100 microinches thick. Then the brass was dissolved in nitric. If the gold came off in one piece, that was excellent. If 3 or 4 large pieces, that was still quite good. If jillions of slivers, that was bad and the bath was either carbon treated to remove the organic contamination that was causing the excess stress or it was replaced with a new bath.

 

[butcher]

"The bath was either carbon treated to remove the organic contamination"

I am interested in learning more about how this carbon treatment was done,and possibly some details of the operation, Did the carbon also absorbed gold from the plating bath into this carbon, was the electrolyte run through carbon filters, or another method?.

Another question when gold is plated onto another metal like nickel base metal, is there some mixture where these two metals come together, like when we braze, solder or weld, where a portion of the two metals mix to form a bond of an alloy of the two metals in a fine thin layer where the two different metals meet, and join to form a strong bond?

Or is this bond determined by some other factor like the base metal plating in the silver mirror sticking to the pours in clean glass, or base metal plating sticking to the pours of plastic, or other materials before being plated with another metal like gold?

 

[goldsilverpro]

"The bath was either carbon treated to remove the organic contamination"

I am interested in learning more about how this carbon treatment was done,and possibly some details of the operation, Did the carbon also absorbed gold from the plating bath into this carbon, was the electrolyte run through carbon filters, or another method?.

Another question when gold is plated onto another metal like nickel base metal, is there some mixture where these two metals come together, like when we braze, solder or weld, where a portion of the two metals mix to form a bond of an alloy of the two metals in a fine thin layer where the two different metals meet, and join to form a strong bond?

Or is this bond determined by some other factor like the base metal plating in the silver mirror sticking to the pours in clean glass, or base metal plating sticking to the pours of plastic, or other materials before being plated with another metal like gold?

With gold plating baths, filter cartridges containing activated carbon are generally used. For more extreme contamination, activated carbon is mixed intimately with the hot solution. In both cases, some gold is adsorbed on the carbon so carbon treatment is avoided when possible for economic reasons. The best way to avoid organic contamination is to not introduce it into the bath in the first place.

The bonding or adhesion to the cathode is complicated and, for a thorough explanation, you would need to consult a good plating text. "Modern Electroplating" is the best one I know of. Basically, though, the first layer of atoms deposited fill in the surface crystal lattice of the substrate and become part of that crystal structure. If the lattices of the plating metal and the substrate metal are quite similar in geometry and dimensions, the basis structure is extended unchanged. If the two lattice structures are considerably different, the initial deposition will be like the substrate but will then shift towards the normal structure of the deposit metal.

 

[butcher]

Thank you for taking the time on those answers, so it is much as I suspected.

 

[Palladium]

I love it when Chris talks dirty ! :shock:
The simplicity ( Not to be confused with Shor ) of the way he states things has a certain elegance to it. In order to understand the over scope of the elegance you have to understand physics. I think the thing people most misunderstand about gold refining is it's not about chemistry, it's about physics. Big difference ! To know chemistry doesn't give but a narrow perspective into the world of physics, but to know physics reveals all the answers of chemistry and more. When we mix two metals together whether it be in solution, gas, or solid form they never in essence become a true solid as far as physics is concerned. In the material world people view objects as solids. In physics we learn that nothing is ever truly solid so no mater what everything must join to something else and at that junction we have a contact point. In solids these are known as grain surface boundaries where the atoms of two elements meet. These atoms form lattices that intersect. How these lattices form and intersect can determine characteristics of the solids, liquids, or gases. Material property science is a good field to study. If you have impurities in your metals then these can either be trapped in the lattice and contaminate the structure or can be push out to the surface of the lattice and become a stratified layer at a grain boundary making it week. This is true with iron we use for structural support. Get it right it's the strongest steel in the world. Get it wrong and it's the Titanic. Stratification is an example of pollutants not lining up in the lattice and being segregated into concentrated stratified layers. The way some metals are purified are done so because of this simple scientific principal. Anyway these boundaries can forum at the time the mixture of pure metals is melted and it cools forming a crystalline structure. Another example of this manipulation can been seen with heat treating a metal to conform to a desired crystalline structure for hardness or flexibility. Crystalline structures can be manipulated in many many ways. Now i think what butcher is referring to is plating. When atoms are joined by electrical plating the zones where the two metals meet is formed in a whole different way than when you melt two items to bond them atomically. The physics of the bonding of the atoms are very sensitive to foreign contaminates. Those contaminates can come from the solution, as Chris pointed out, or they can appear as say surface oxidation. That's why proper etching and cleaning is necessary so the contaminates don't become lodge as a layer between the two item your are trying to join. Then you have different fields of study about lattices such as creep and dielectric breakdown also know as whiskers to. Now iv'e done quiet a bit of jumping around, but my whole point is their is a lot more to gold refining than people see on the surface. I haven't even started to talk about precipitation and nucleation of the gold and how the basic fundamental principals of why gold refining is actually possible and how it really works is lost on the average person. I view gold refining in the essence of physics and by doing so you learn a whole new respect for something as elegant as the complexity of the system, but yet the simplicity of it all in it's simplest terms. Don't make me talk about black holes.

http://www.ndt-ed.org/EducationResources/CommunityCollege/Materials/Structure/metallic_structures.htm

 

[butcher]

Palladium,
I also like GSP's simple description of what seems to be a very complicated matter.

I am not to sure about them black holes, I have never seen any of them, never seen one of them big-foots either.

I did just a little reading of the material posted above, from what little I can gather the nickel can diffuse into or even through the crystal structure of the gold, and it can do this a bit easier with the electroplated gold than it does with the electrolytes plated gold.

It also seems in electronic materials they also use a wide variety of methods to apply the gold layers or solders, electroplating, pressure bonding, sputtering, high temperature bonding, and various other means...
With each of these methods there seems to be a little bit of differences in the bonds, but it supports my suspicions of how they might occur.

My thinking here is the gold at the bonding area is not solid, unless the gold is of fairly thick layers of gold to gold crystal bonding, and at the surface where gold and nickel or the other base metal meet, the metal crystals or surface is not flat or a pure flat surface of each of these metals, some cases a mix of dendrites like a thick forest of different trees mingled together, and in some cases can be somewhat of mixture of the metals...

If also the crystals of the two metals can diffuse or even mix, so when we dissolve the base metals away we could be left with fine gold particles, especially if the gold layer is thin or depending on how it was deposited, and the structure of the crystal lattice, this makes me also think that we could actually put these fine crystals of gold into solution easier at this layer or with thinly plated gold or depending on the structure of gold and base metals, (even in a the copper II chloride leach), (as the gold at this site would already be so fine), than it would be where when the gold is solid, as it would be in the thicker part of gold to gold bond, the gold would not be as easy to dissolve such as with the thicker foils, if this is so, the portion of gold dissolved here may also form the black powder of precipitated gold, as this fine gold precipitates back out of solution later.

This may also explain what I see sometimes see when adding dilute H2O2 solution, for a brief moment I have noticed a color change that looked like the yellow color of gold being dissolved, but quickly disappears back to the familiar green color.

If the nickel can diffuse I suspect the copper may also, or other base metals, or metal oxides involved, this may explain why it seems to be a bit of a challenge to get all of the base metals dissolved away from the gold, even with material such as the foils, and depending on the materials some seem more of a challenge than others.

 

[Palladium]

You got it!