Looks like trying to find a needle in a haystack ;). It is indeed known that Hydrogen penetration is concentrated around grain boundaries. Crystallisation may play a role, however both Defkalion and Rossi's reactors are able to be turned off and on. In particular Rossi shows that his reactor seems to work way above the crystallisation temperature of Nickel. Cooling these reactors down slowly will re-crystallise the Nickel particles.
Likely very fine grains are only important in 'virgin' Nickel powder to allow certain speed of Hydrogen absorption during first operation of such load. Celani holds a patent application that combines oxidation and adding a silicate layer to significantly speed up absorption of Hydrogen. His process also includes rapid cooling, creating small grain sizes during re-crystallisation. On Sun, Mar 23, 2014 at 6:11 PM, Bob Cook <[email protected]> wrote: > Alain etal.-- > > This paper by Duncan etal. from ICCF-18 identified by Alain remind me of > an experience involving stress corrosion in Ni-Cr-Fe alloy 600 over 40 > years ago. The material specification being used to procure the Ni-Cr-Fe > material did not control the concentration of Niobium. It was not believed > to be an element that need to be controlled. However, some heats of > material were subject to stress corrosion and some were not. The ones > coming from one vendor were generally good and ones coming from another > vendor were not so good. It turned out that the vendor producing the good > heats--those that did not corrode--had added Nb in a very small > amount--several parts per million--to its heats, still meeting the > specification, since this element, Nb, was not controlled by the > specification. The small amount of Nb turned out to tie up carbon which > was allowed to a small extent per the specification. It reacted with the > carbon in the grain boundaries and prevented stress corrosion from > occurring. The micro stress patterns were changed and internal stress > small. The local energy necessary for the stress corrosion cracking did > not develop. > > Embrittlement is what happened in the welds of hulls of Liberty Ships that > broke up under stressing and fatigue during WW1. The welds were embrittled > by ionization of water in stick electrodes used to weld sections of the > hulls together. The migration of the hydrogen to local defects caused > internal pressure and the embrittlement. The lesson was: Do not to use wet > electrodes for welding steel. > > The devil is in the details. > > Separately, a good mechanism for controlling cracks may be the > introduction of water during alloying. Various small amount of crystals of > hydration can be added to a preparation of an alloy using powder metals > mixed and diced in a cryogenic ball-milling machine. (Such a device uses > liquid N-2 as the liquid in the ball milling process to get very > fine--maybe nano scale--particles of an alloy and the hydrated crystal. > The N-2 is nice, since it prevents the agglomeration of particles by > coating each particle with a layer of N-2. Very good mixing is possible. > The slurry mixture is poured into molds under a vacuum to keep stray atoms > out and the N-2 is allowed to evaporate under the vacuum and added > temperature and pressure. Pressure bonding is accomplished with the > hydrated crystal in the bonded metal lattice. During the heating > and pressure bonding process, the water of hydration changes to O-2 and > H-2, the O-2 reacts to form a metal oxide and the hydrogen collects in > defects to form an internal pressure and embrittlement. The metal atoms > bond together being very pure with little on no excess heat and whatever > pressure it takes. (He may be used in the pressure bonding process once > the N-2 is off gassed.) There is no oxide reduction necessary to get the > metal to bond well.. The small amount of O-2 reacts locally at the point > where the crystal of hydration ends up in the mix. The grains are very > small and well controlled in size considering the amount of water of > hydration used in the mix. For magnetic materials like Ni and Pd these > boundaries may even be oriented in a desired direction during bonding. > > Deuterated water of hydration crystals may be a good sauce in this mix for > Pd, giving pockets of D-2 at the grain boundaries without preloading. > > Anybody wanting a patent on this process idea should get to work. (smile) > > Bob >
