Cylindrical glass boll (sealed, containing solvent) for RF detector

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Discussion Overview

The discussion revolves around the creation of a glass micro capsule for use in a Nuclear Magnetic Resonance (NMR) probe, specifically designed to contain deuterated solvents while ensuring hermetic sealing. The context includes challenges related to the sealing process, material properties, and the need for precision in glassworking.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Max describes the need for a glass micro capsule to replace a plastic one, highlighting the dimensions and the requirement for it to be hermetically sealed.
  • Max expresses concerns about sealing methods due to the volatility of the solvents and the lack of precision in cutting glass without specialized equipment.
  • Mike suggests the involvement of a professional glass worker and proposes using a tapered tube with a mating stopper for sealing.
  • Max responds that some solvents may evaporate during the sealing process, complicating the task further, and notes the absence of professional glass workers in his area.
  • Another participant suggests that school lab technicians may have the necessary skills to assist with glassworking.
  • Further advice is given regarding the technique of sealing glass using a tapered piston and the potential methods for achieving a snug fit between glass parts.

Areas of Agreement / Disagreement

Participants generally agree on the need for skilled glassworking to achieve the desired results, but there is no consensus on the best method or available resources for accomplishing this task. The discussion remains unresolved regarding the practical steps to create the glass capsule.

Contextual Notes

Participants mention limitations related to the melting points of solvents and the precision required in glass cutting and sealing, which are not fully addressed in the discussion.

_maxim_
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Dear all,

here's my first request for a little help (maybe also in finding the proper subforum...)

I'm working as developer and scientific consultant in a lab for Nuclear Magnetic Resonance at high field (> 21 Tesla), and I have to create a suitable probe for checking the stability of a wide-bore cryomagnet.

This will be done by a simple RF detecting circuit which pilots a coil, and the coil is wound around a micro boll containing a deuterated solvent (D2O, CDCl3, DMSO-d6 and so on). The RF circuit is already operative and capable to read out the very tiny signal which arises from deuterium inside the strong magnetic field ( as a quick reference, see http://www.cis.rit.edu/htbooks/nmr/chap-7/chap-7.htm#7.1" ).

Now, about my request.
I need to substitute the plastic micro boll with a soldered glass micro capsule, containing one of the deuterated solvent (i.e. Acetone-d6).

The main problem is to have a regular cylinder in glass, with max external dimensions L x D= 8.2 x 4.6 mm (Length x Diameter), fully filled with the liquid, and with its bases hermetically sealed.

Started cutting a NMR sample tube, I have no any laser precision device in my lab, hence the quality of the cutting is very poor. The subsequent problem is solder the glass with highly flammable solvents (i.e. acetone), but the risk could be reduced using cryogenic liquids (i.e. liquid nitrogen).

Do you have any idea for realizing this glass capsule?

Any idea would be greatly appreciated
All best

Max
 
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It sounds like you need a professional glass worker.

As a suggestion, solder in a tapered tube with a mating (ground?) stopper, and seal it at the end while heat sinking the liquid.
 
Thanks Mike,

The point is that some solvent have quite low melting point and they vanish when one seals the cap.
Also, it seems there are no professional glass workers in my country. I asked to industries, but I am still waiting for an answer from a while.

I hope that physician people knows the way to build such a homemade device.

Cheers,
Max

P.S. maybe I have to move this question in another place?
 
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Some School Lab Technicians are very competent glass workers. Do you have a local High School or College?
 
Good call on the technicians. Some college chem labs still have old techs that can work glass.
As for the technique, it's based upon sealing a tube with a tapered piston and then flowing them together at the far end from the fluid. I've seen some amazingly snug fits between glass parts that are ground to fit together.
I'm not certain how the glass was tapered, but I suspect that tube was ground out with a tapered copper rod. Diamond chips seed into the surface of copper well, and if you go slow, it will grind away at your glass.
Then follow with more diamond compound and the glass rod grinding to fit into the tapered tube.
The first vacuum tight seals were made this way, and by adding a bit of mercury to wet the seal.
 

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