My notes on sealing tests using the Parkhomov cement formulation can be
seen at:
http://www.evernote.com/l/AXeKakT2sSpFMpLYlLx85OpP_c-MaaApbfs/
Dr Parkhomov has provided some additional details, which I will try in
the coming week. My conclusion so far is that a cement that contains
water as this one does will not seal the inside of a small-bore tube due
to shrinkage as the cement cures.
On 2/8/2015 9:56 AM, James Bowery wrote:
In an experiment where replication is everything, it takes a pretty
compelling reason to deviate from the exact protocol and the
justification for such deviation should be carefully documented prior
to the experimental run.
Where is this documentation for the justification for departure
from Parkhomov's protocol?
On Sun, Feb 8, 2015 at 11:02 AM, Bob Higgins <[email protected]
<mailto:[email protected]>> wrote:
I think estimations of the gas pressure inside the dogbone reactor
tube at failure are probably substantial over-estimates. We don't
really know how much volume was displaced by the Ni, so the volume
estimate for the chamber is probably only accurate +100%/-50%.
The volume of the system can and should be measured prior to start
of the experiment. This can be done with a calibrated piston
plumbed into the system. Decrease the volume by 1cc using the
piston and see how the pressure changes.
Second, there is a hot volume and a cold volume, but only one
pressure. Third, we don't know what is happening chemically
inside the hot chamber. Sure there is decomposition, but there
are probably also other hydride formations occurring at that
pressure and temperature (note that there was added zirconium).
Perhaps there was even ammonia formation which would reduce the
pressure; and this could condense in the cold side. Fourth, the
LiAlH4 weight added is probably only known +/- 20%.
The summary is we really won't know what the pressure profile was
in this experiment and we won't know until it is carefully
measured. There is no real point to the wild speculation. It
will just have to be measured.
On Sun, Feb 8, 2015 at 9:47 AM, Jones Beene <[email protected]
<mailto:[email protected]>> wrote:
Yes, that isthe good news- thatthe compression fitting works,
and if the problem relates to thermal stress, there is an easy
way to fix that also.
To minimize thermal stress – theheater wire could be
“feathered in” from both ends, whenit iswoundso that there is
an intermediate zone of heat which is less than the fully
woundwire, but greater thanthe unheated zone.The idea is to
spread out the areas of highest temperature gradient, to
reduce thermal stress.
*From:*_Bob Higgins_<mailto:[email protected]>
Ryan Hunt reports that the failure mode was NOT the
compression fitting giving way under pressure - the fitting
remained intact. This experiment was of the "easier
Parkhomov" design, posted previously where the seal was made
with a compression fitting, in this case with the use of a
soft aluminum ferrule at the suggestion of Alan Goldwater.
Alan's tests suggested the compression fitting would hold and
it did! \
