What's new
What's new
By:
Advanced search…

Chemist who needs help designing an aluminum lid

R

RadChemist

Plastic
Joined
Jun 6, 2018
Hi everyone,

This is my first post here.

I am a Ph.D. student doing research in the field of radiochemistry. One of my projects involves radionuclide production through proton bombardment of enriched target materials in a cyclotron. A key component of my research is designing robust targets that are capable of withstanding high temperatures during irradiation.

Our current design features an aluminum target casing filled with layers of compressed target material, and a thin aluminum lid is fastened to the top with an epoxy adhesive.

I would like to move away from using any type of chemical adhesive and instead rely on some type of mechanical attachment (the simpler the better) since we've had contamination problems with epoxy in the past.

I've included three attachments of the design with dimensions.

Any help will be greatly appreciated!
 

Attachments

  • Dimensions.jpg
    Dimensions.jpg
    14.2 KB · Views: 317
  • Target holder.jpg
    Target holder.jpg
    4.2 KB · Views: 273
  • target holder and lid.jpg
    target holder and lid.jpg
    4.3 KB · Views: 293
I am not exactly sure what you are trying to accomplish but if the assembly is not moving around in use try a simple interference fit. Think old fashioned tin, like an Altoids container or the cap on a stick of deodorant.
 
Ignore the trolls.
Epoxy and other long chains will degrade under the energetic stream, beware of that.
Also, those high hydrogen compounds have a habit of absorbing neutrons and making deuterium.
That may be part of your epoxy problem...and of course simple thermal and mechanical issues.

Is this a reusable container?
Does it need to be.
If not then crimping or press fitting may be your best option.
It’s a fairly common technique.

What level of containment?
Pressure/vacuum requirements?
Venting requirements?
Environmental chemistry?

Other requirements?

This is a pre skinned cat, pick your knife carefully.
 
Hey you have to give this guy a bit of slack as he is from chemistry, which is a vast world unto itself and he cannot be expected to know everything. Remember many chemistry companies are bigger, older and have been more profitable for more years than anything us mechanical folks have come up with.

In answer to your question RadChemist, have you considered just threading the outside of the cap and inside of the container? Just a nice big coarse thread would be good. Thinking further, we have in fact done exactly what you're doing with our Technecium99 project, where sintered molybdenum targets get irradiated and convert to technecium. The targets are quite complex since to maximize exposed area, the beam hits the Moly target at an angle, and the target is water cooled on the back, so there is all sorts of plumbing, and the target is set up for production where you install and withdraw it remotely through a tube and then filter water through the front side after irradiation to get the Tc out. It turns out Tc is water soluble and Moly isn't. Chemistry is amazing. One key observation about this for you though is that they are fine with 18-8 stainless cap screws holding the target together. The steel obviously gets a bit activated but cools down fast enough. They do have multiple units though so each one has time to cool before the being opened up to have the moly replaced. But this does suggest you could put stainless cap screws around the rim of your target if you didn't want to thread the whole thing.

DM me if you want to talk in more detail.
 
RadChemist said:
One of my projects involves radionuclide production through proton bombardment of enriched target materials in a cyclotron.
Click to expand...

We were doing that in my dad's garage, but some guys in black coats came along and took everything. Just kidding.

Does your target need to be about the same size as it is now? I think some here don't realize that it's about 3/4" in diameter and 5/32" tall, total. Threading and then assembling would be tough. Using screws to hold together might be a better idea. Interference fit would be OK until you had to dis-assemble.

Just some thoughts.
JR
BTW, they didn't get everything. :D
 
I've done similar work at the Bates Linear Accelerator, and in other applications we used beryllium foil windows. If for your application Al is fine, try a slightly longer body with a shallow groove at the inside near the open end, then a slip-fit cap, and a stainless steel or other suitable wire ring that is deformed into the groove, and as it springs open in captures the cap in place.

You can form the ring with a couple of inward facing ears that could be gripped by pliers for removal, or just use a slight bend so the tip of a screwdriver could pry the ring out. You don't need a lot of force to contain the ring, so I would not recommend commercial retaining rings which in use require special tools and compression to use. Most commercial rings have square edges which could scrape off Al particles in use, a round wire ring shouldn't do this.
 
RadChemist said:
...robust targets that are capable of withstanding high temperatures during irradiation. ...Our current design features an aluminum target casing...
Click to expand...

I find it difficult to imagine aluminum (or epoxy adhesive) capable of withstanding high temperatures. How high is up? How hot is high?

Larry
 
JRIowa said:
We were doing that in my dad's garage, but some guys in black coats came along and took everything. Just kidding.

Does your target need to be about the same size as it is now? I think some here don't realize that it's about 3/4" in diameter and 5/32" tall, total. Threading and then assembling would be tough. Using screws to hold together might be a better idea. Interference fit would be OK until you had to dis-assemble.

Just some thoughts.
JR
BTW, they didn't get everything. :D
Click to expand...
Your name David Hahn?
The Radioactive Boy Scout | Harper's Magazine
 
digger doug said:
Why are we expected to do your job ?

How do think we all learned ?

google everything ?
Click to expand...

You know what digger????...why do you always second guess everything a newbie posts???
Do you ever just contribute to a thread without mentioning the poster to "do your own work" or "just google it" ???

Not everything is on google. Many things are filled with BS.

Maybe the OP did try everything he can think of and as last resort decided to seek advice.

Fucking GROW UP!!!
 
Rigor said:
You know what digger????...why do you always second guess everything a newbie posts???
Do you ever just contribute to a thread without mentioning the poster to "do your own work" or "just google it" ???

Not everything is on google. Many things are filled with BS.

Maybe the OP did try everything he can think of and as last resort decided to seek advice.

Fucking GROW UP!!!
Click to expand...

I believe that was and still is one of the main purposes of PM. Ask questions and get helpful replies.

To avoid a major problem with the apparently often conflicting advice offered the more (precise) information that can be given in the OP the better.

Things too like "How many will be made?" and/or "How much is willing to be spent?" can make a helluva difference to answers.
 
rcoope said:
Hey you have to give this guy a bit of slack as he is from chemistry, which is a vast world unto itself and he cannot be expected to know everything. Remember many chemistry companies are bigger, older and have been more profitable for more years than anything us mechanical folks have come up with.
Click to expand...

Yep, and one of the many reasons I switched fields. The bonus is there's plenty of smarter, far less-crusty individuals involved who are self aware enough to know when they don't know shit from tar.

RadChem, I'd put a small register on the lid to be press-fit into the bore. Then have two opposing notches in the lid on the sealing side to prise them apart w/a flat head screw driver. No threads, still sealed, easy to disassemble.
 
RC Mech said:
Yep, and one of the many reasons I switched fields. The bonus is there's plenty of smarter, far less-crusty individuals involved who are self aware enough to know when they don't know shit from tar.

RadChem, I'd put a small register on the lid to be press-fit into the bore. Then have two opposing notches in the lid on the sealing side to prise them apart w/a flat head screw driver. No threads, still sealed, easy to disassemble.
Click to expand...

Press fitting the alu/alum is a recipe for galling.
 
RC Mech said:
Should have stated "light" press fit. You'd be surprised at the range of lab apparatus that use Al/Al fits, 304SS/304SS threads, etc that don't gall in service.
Click to expand...

I’ve spent hundreds of hours with Swagelok SS fittings.
It takes care to get it right...and I still use nuke grade AS usually.
In this case it seemed he wanted to avoid other materials in the chamber.

Like I said, it’s a pre skinned cat, just pick the knife with care.
 
Tons of stuff is made with aluminum on aluminum threads and sliding fits. Things like camera lenses and accessories that screw on to them. I believe one common way to prevent galling is to anodize the aluminum after threading it. I think if even one of the threads, internal or external, is anodized then that will prevent the galling. I have made aluminum accessories that screwed onto a commercial camera lens and had no problems with them. They were not anodized, but the original lenses were. I suspect that plastic coat would also prevent galling, but it may not be OK for his temperatures.

Make a screw on lid and anodize it.



Limy Sami said:
That's the best idea so far, only don't make the retaining ring (or any lid come to that) from Alu, …..Alu on Alu threads tend to (will!) gall up solid.
Click to expand...
 
You must log in or register to reply here.

Similar threads

S
Draining a landslide, help needed designing push pipe
2 3 4
Replies
64
Views
16K
adama
A
P
Crystallizing a New Approach to Today’s Turning Needs
Replies
1
Views
7K
rabidchimp
rabidchimp
P
The Million-Dollar Job
Replies
1
Views
7K
Zonko
Z
P
Quality turn
Replies
0
Views
9K
PracticalMan
P








 

ABOUT PRACTICAL MACHINIST

With more than 10.6 million unique visitors over the last year, Practical Machinist is the most visited site for metalworking professionals. Practical Machinist is the easiest way to learn new techniques, get answers quickly and discuss common challenges with your peers. Register for the world’s largest manufacturing technology forum for free today to stay in the know.

Learn more about us.

STAY CONNECTED

Facebook Instagram YouTube LinkedIn Pinterest Twitter Tiktok

Register Become a forum member. Register today.

Sign Up Sign up for our e-newsletter.

© 2024 Copyright Practicalmachinist.com. All Rights reserved.

Back
Top