The absorption of hydrogen at grain boundaries and defects produces a macro
bubble of H and hence an internal pressure. It causes "hydrogen
embrittlement" resulting from the stress field around the bubbles and the
lower threshhold to crack propagation under a general stress field. It in
effect reduces the fracture toughness of the material where the H
accumulates. However the more ductile the matrix material is--for example a
nickel matrix--the better the fracture toughness will appear, and the more
margin there will be to a macroscopic rupture of the material accumulating
the H.
Small Nickel grains should work better, since the internal pressure is in a
more microscopic volume, and as the volume at a grain boundary increases due
to temperature, the pressure will not rise as rapidly since the proportional
increase in volume is greater than it would be for a larger grain boundary.
In addition a crack at a small grain boundary cannot propagate as far and
increase the macroscopic stress at the tip (of the crack) as much, as
happens with larger grains.
In any case maintaining strength of the matrix bonds is important as
temperature increases. Different alloys will change this matrix bond
strength. (Note that bonds at grain boundaries are different than those in
the crystal matrix and generally weaker.) And hydrogen that forms a matrix
bond with a metal (a metal hydride) generally will have weaker matrix bonds
and lower mechanical properties than the same metal without any hydride
formation.
Stress cycling (by either internal pressure or thermal variations) can
increase the size of defects at grain boundaries and cause eventual fatigue
failure; hence, repeated stress cycling would likely reduce the life of a
reactor by degrading its mechanical properties.
Bob
----- Original Message -----
From: "AlanG" <a...@magicsound.us>
To: <vortex-l@eskimo.com>
Sent: Saturday, March 14, 2015 9:30 AM
Subject: Re: [Vo]:Absorption of Hydrogen by Nickel
On 3/13/2015 7:26 PM, Axil Axil wrote:
I don't believe that nickel or titanium can be loaded with hydrogen. Is
such loading even possible?
This was demonstrated by Focardi e.al. and later described in several
papers, including
http://lenr-canr.org/acrobat/CampariEGphotonandp.pdf (1999)
and was replicated at CERN in 1996
http://www.lenr-canr.org/acrobat/CerronZebainvestigat.pdf
There's an excellent theoretical paper by Oriani at
http://lenr-canr.org/acrobat/OrianiRAthephysica.pdf (1993)
That analysis suggests that absorption in Ni occurs at grain boundaries,
surface defects (cracks) and lattice vacancies as recently discussed by
Storms and others. There are also findings that plastic deformation of the
lattice increases absorption by an order of magnitude, and that bulk
absorption occurs at ~600 bar. This is relevant because such high
pressures seem to be present in the Rossi/Parkhomov/MFMP fuel tubes.
