Small micron sized silver spheres

[NobleMetalWorks]

I have been researching the different ways to precipitate silver from silver nitrate, in order to produce a silver spherical particle less than 8 microns in size.

While investigating all the complicated methods for precipitating fine gold powder from Silver Nitrate, I came across this document:

https://dl.dropbox.com/u/56505223/33-p1550.pdf

Obtaining the Ferrous Sulfate (Iron II Sulfate) Heptahydrate, does not seem to be a problem. However the methyl-2-pyrrolidone is expensive, and only seems to be used to produce a more compact silver sphere.

By applying different temperatures, you can produce different sized silver spheres. For my application, to make the powder as compact as possible, I think different sized spheres would be best, but not in random ratios. Does anyone have experience in calculating the sizes and ratio of each sphere size between 1. - 8. microns would be to achieve the maximum compactness of the resulting powder?

Would anyone have a suggestion as to what could be used instead of methyl-2-pyrrolidone, that would be more cost effective and encapsulate the silver spheres in the same way so as to achieve a more compact sphere?

Thank you for any help...

Scott

 

[NobleMetalWorks]

I found the information I needed on the size of the spheres that would compose an optimum density for what I intend to use the powder for. I am still interested in my other questions if anyone knows. Thank you...

Scott

 

[qst42know]

Have you looked at, flame spray, arc spray, or plasma spray?

It is usually used for building up metal surfaces in close proximity for restoration however without a surface to build on (at a distance) it could be used to produce spherical metals in mass quantity.

http://en.wikipedia.org/wiki/Thermal_spraying

 

[NobleMetalWorks]

Thank you, I appreciate the response...

I did a little reading about flame spraying, these are the issues I need to comply with in order to produce the type of fine silver powder I need.

Expense, I don't have a lot of money to invest in whatever process I use, I am really still building my business.

I need to create spheres of uniform size, and two different sizes so that when combined they would take up less space, and thus be denser

There is also vaporizing the metal under vacuum, but again the expense of the equipment, and I am not sure I would be able to control the size of the spheres.

With the process I posted above, I would be able to control the size of the spheres by temperature and reaction time. But I haven't attempted it yet so I'm not really sure what the end result will be. I am not even sure how I might go about measuring the results, or who I might be able to send a sample out to in order to get results.

Thank you for posting, I'm going to read more about the methods you proposed, I don't understand them as well, I think, as I should before I discount them.

Scott

 

[qst42know]

The simplest and the only device I have seen in person was a powder feeder attached to an oxy/acetylene rig. It was used to build up worn bearing journals for repair. The entire area where it was used was covered in metal dust that was slippery to walk on (spherical I would assume).

It might be capable of producing the fine silver spheres you need but I don't know for certain.

 

[glondor]

There are posts here somewhere that depict the results of making shot by pouring molten gold through a ring that has 4 pressure washer nozzles. The resulting shot was like fine sand. Some one will remember which member is doing this and may chime in and point you to it. It may be the cheapest way to go if the resulting micro shot is suitable for your purpose.

Key on "atomizer", "pressure washer"

 

[Merle]

There is also vaporizing the metal under vacuum, but again the expense of the equipment, and I am not sure I would be able to control the size of the spheres.

I have used thermal and ebeam vacuum evaporators (for semiconductor type processing), and these do not produce particles, rather a continuous, smooth film. Possibly at higher pressures (closer to atmosphere) there could be more collisions with gas molecules that might result in particle generation, but I am not aware of this.

I am not even sure how I might go about measuring the results, or who I might be able to send a sample out to in order to get results.

I have access to an SEM that I would offer my time (gratis) to examine samples for you. PM me if interested.

 

[NobleMetalWorks]

I have access to an SEM that I would offer my time (gratis) to examine samples for you. PM me if interested.

This forum never ceases to amaze me. Thank you so much for the offer, I am sending you a PM. That was very generous of you.

Scott

 

[glondor]

Dispersed uniform spherical silver particles were prepared in the absence of a protective colloid by rapidly mixing concentrated isoascorbic acid and silver-polyamine complex solutions. By varying the nature of the amine, temperature, concentration of reactants, silver/amine molar ratio, and the nature of the silver salt, it was possible to tailor the size of the resulting metallic particles in a wide range (80 nm to 1.3 μm). The silver spheres were formed by aggregation of nanosize subunits, the presence of which was detected by both electron microscopy and x-ray diffraction. Due to its simplicity, high metal concentration, and the absence of polymeric dispersants, the described method represents an advantageous route to manufacture cost-effectively dispersed uniform silver particles for electronic applications.


Preparation of silver spheres by aggregation of nanosize subunits

http://journals.cambridge.org/action/displayAbstract;jsessionid=71D122804BE1E42175B549DBEF5A8E6E.journals?fromPage=online&aid=7953147


http://ecadigitallibrary.com/pdf/CARTSUSA08/5_4a%20%20Halaciuga%20Clark%20Univ.pdf

 

[NobleMetalWorks]

Preparation of silver spheres by aggregation of nanosize subunits

http://journals.cambridge.org/action/displayAbstract;jsessionid=71D122804BE1E42175B549DBEF5A8E6E.journals?fromPage=online&aid=7953147


http://ecadigitallibrary.com/pdf/CARTSUSA08/5_4a%20%20Halaciuga%20Clark%20Univ.pdf

Thank you glondor,

The process you suggest can make even smaller spheres that are more dense and have a smoother surface. It seems like it produces a better, finer powder.

The way it reads, if I understand it correctly, the process would go something like this.

Dissolve silver nitrate in deionized water.

Dissolve a polyamine such as diethylenetriamine, in the Silver Nitrate solution


The solution is now a silver-polyamine complex


Dissolve Ascorbic Acid in cold deionized water, further chill with deionized ice, or cooling some other way.

Either vigorously stir, or use a magnetic stirrer, then slowly add the cold ascorbic acid solution.

Dependent upon the amount of ascorbic acid used

Dependent upon the amount of polyamine, and the type, you may control the size of the spheres.

Precipitation takes about 2-3 minutes to complete, and about another 20 minutes for the nano-particles to settle to the bottom.

After precipitation decant, filter, clean, dry. Since polyamine is an organic amino acid, the resulting powder should be incinerated by baking until red in a cast iron pan? Is there a better way at this step to incinerate without direct flame?

I have over simplified the process simply because I have not attempted to figure the correct measurements as of yet. I want to understand the process before I go through the hassle of figuring out the measurements, etc. Will someone correct me where I am wrong?

I am going to try both methods to see which results in a better product, but from what I have read, the nano spheres this process produces would be better suited to my needs.

Thank you

Scott

 

[qst42know]

After precipitation decant, filter, clean, dry. Since polyamine is an organic amino acid, the resulting powder should be incinerated by baking until red in a cast iron pan? Is there a better way at this step to incinerate without direct flame?

I think you might need a centrifuge to collect particles this size. The article describes silver small enough to make conductive ink. An iron skillet will undue all the precision lab work it takes to get to that point

 

[NobleMetalWorks]

After precipitation decant, filter, clean, dry. Since polyamine is an organic amino acid, the resulting powder should be incinerated by baking until red in a cast iron pan? Is there a better way at this step to incinerate without direct flame?

I think you might need a centrifuge to collect particles this size. The article describes silver small enough to make conductive ink. An iron skillet will undue all the precision lab work it takes to get to that point

It would have to be fired somehow, the organic amino acid would need to be incinerated.

According to the process, it takes 2 minutes to fully precipitate, and about 20 minutes for the solution to become clear, I assume this means the material would gravitate to the bottom of the flask/beaker, then to be collected as sponge. I am not so sure that filtering would capture the nano particles anyway, I think you would need to decant as much as possible, and maybe put in a vacuum desiccator, and then somehow incinerated to remove any leftover organic material. For my intended purpose I want to make sure that it's pure powder and has no leftover amino acids that could cause issues with the end product. I guess I could try it without incinerating and see if it affects the end product in a negative way.

Thank you

Scott

 

[qst42know]

Colloidal sized particles resist settling and filtration. Most try to avoid them for that reason. Quartz glass lab ware can be incinerated in.

Is this for making precious metal clay that was discussed in another thread?

 

[NobleMetalWorks]

Colloidal sized particles resist settling and filtration. Most try to avoid them for that reason. Quartz glass lab ware can be incinerated in.

Is this for making precious metal clay that was discussed in another thread?

This is exactly what it is intended for, yes.

I had thought about quartz lab glass

I just picked up a piece of equipment, not sure what it's called but it's the same company, IKA, that makes my hotplates so I believe it will be durable. It holds a beaker or other receptacle, and vibrates it. I hope this will settle the nano spheres better.

I also have a large vacuum desiccator, I figure I can evaporate off the liquids faster this way, then incinerate in the quartz as you suggested.

I have no idea how any of this will work in reality, I have never attempted anything like this before. So any suggestions or pointers would be appreciated.

Thank you

Scott

EDITED: I looked at patents that had to do with Mitsubishi Materials and PMC, then I looked at the people who were named on the patents, their associates, etc. I came across a patent filed by one of the people that was also on the PMC patent, that had to do with creating silver nano spheres. In the patent he talks about using two different size spheres so that a more compact, and correct sintering can be achieved. The spheres he was creating were all between .5 microns to 8.0 microns in size. It seems the sizes he was after were 1 micron and 3 microns. I would like to create spheres from .1 - 10.0 so that I can test which sizes in what combination works best.