Historical research guide · 0504 · 2007
Anomalous effects in hydrogen-charged palladium — A review
G.K. Hubler
In one minute
Graham Hubler, writing from the US Naval Research Laboratory, reviews fifteen years of one stubborn measurement: electrochemical cells that push electrical energy into a palladium cathode loaded with deuterium and get more heat back out than they put in. He counts more than ten groups worldwide reporting excess heat in about a third of their runs, in episodes lasting hours to days at 50 to 200 percent above input, and notes that the effect has not faded in frequency or size as the methods improved. His explanation for the wave of failed replications in 1989 and 1990 is metallurgy: palladium swells and cracks as it takes up hydrogen, cracks give the gas a way back out, and almost nobody reached the loading ratio above 0.90 that the effect seems to need. Now that Vittorio Violante’s group can make foils which load that high every time, Hubler argues, the material is finally reproducible enough to study properly — and he lists seven in-situ experiments that could find the mechanism.
Connection
This is the review chapter 12 needs before the NASA Glenn lattice work: a materials scientist at a US Navy laboratory laying out why the palladium–deuterium heat results held up, why the first replications failed for reasons that had nothing to do with the physics, and exactly which measurements would settle the mechanism. Chapter 1 gets its model of a replication ledger from it — the effect is counted, the criticisms are answered one by one, and the open question is named as an experiment rather than a verdict.
From the source
More than ten groups worldwide have reported excess heat in about one third of their experiments, using open or closed electrochemical cells with a solid palladium cathode and deuterium-containing electrolyte, or deuterium gas loading of palladium powders; the significant events last for hours to days and run 50 to 200 percent above the electrical input.Abstract; Table 1, twelve named groups from Arata to Violante
The failure of most 1989 and 1990 replications is a materials problem rather than an absent effect: palladium cracks under a roughly 4 percent volume change on loading, the internal surfaces of those cracks recombine hydrogen and let it back out, and without alloying or mechanical toughening, an optimum grain size and gentle gradual loading the ratio stays below 0.9.Section 2, the four-point list of loading procedures
Three conditions are necessary though not sufficient for excess heat: deuterium loading above 0.90 atoms per palladium atom, high current density of about 250 milliamps per square centimetre, and a dynamic trigger that imposes a deuterium flux — a temperature step, a current step, or roughly 10 milliwatts of continuous helium–neon laser light on the cathode surface.Section 3, the three-line condition list and the following paragraph
Two recent cells are shown in detail: an ENEA cell with heavy water and lithium deuteroxide produced 8 percent excess power over the run once the calorimeter loss is accounted for, and an Energetics Technologies cell using an ENEA palladium foil produced about 2.2 watts net, 50 percent above input, averaged over twelve days after a three-day incubation.Section 4, Figures 3 and 4
The two stored-energy criticisms do not survive the data: a chemical battery cannot explain incubation times as short as a few minutes in small-volume cathodes, and integrated-energy experiments detect no endothermic phase that would signal charging beforehand, while recombination of hydrogen and oxygen is already recovered continuously inside the closed cells that show the effect.Section 4, the numbered criticisms 1 to 4 and Hubler’s replies
Hubler names the programme that would find the mechanism: seven in-situ measurements on the now-reproducible loaded foils — tensile stress, high-energy X-ray scattering past the 0.76 ratio already reached, neutron scattering of the deuterium sub-lattice and its phonons, radioactive isotope spectroscopy for chemical effects on nuclear decay, Mössbauer spectroscopy, perturbed angular correlations, and nuclear acoustic resonance — and states that no individual can do them, only a funded team.Section 5, experiments 1 to 7; Section 6, closing paragraph
The way in
https://doi.org/10.1016/j.surfcoat.2006.03.062How to cite it
G.K. Hubler (2007) Anomalous effects in hydrogen-charged palladium — A review doi:10.1016/j.surfcoat.2006.03.062