Modeling excess heat in NiH
Peter Hagelstein1 and Irfan Chaudhary2
1Massachusetts
Institute of Technology
2University of Engineering and Technology, Lahore
NiH
Before looking at expts…
•Excess heat seen in NiH experiments
•Effect first reported in electrolysis experiments by Mills and
Kneizys (1991)
•Excess heat in gas loading experiments reported by Piantelli
et al (1994)
•NiH is not PdD
•Differences are important
NiH lattice structure (fcc)
Ni
H
Phase diagram
Note: 400 Mpa = 3948 atm
Pressure vs loading
1 GPa
104
100 MPa
103
p (atm)
102
101
100
10-1
0.0
0.2
0.4
0.6
D/Pd
0.8
1.0
X-ray diffraction data in
electrochemical loading
Juskenas et al, Electrochimica Acta 43 1903 (1998)
No evidence for
intermediate a
values for loadings
in the a-b phase
region. Observed
only is the change
in volume
occupied by bphase NiH.
Recall electron density near
vacancy in Pd…
0.25
3
(e/Angstrom )
0.20
0.15
T
0.10
O
D2
0.05
V
0.00
-3
-2
-1
0
1
s [111] (Angstrom)
2
3
[100] Displacement of D2 in PdD Supercell
Monovacancy
L Dechiaro,
Quantum Espresso
DFT calculation
Electron density even higher in Ni (which is why H
doesn’t load well). But electron density reduced near a
vacancy, and can form H2. Ni is closest analog of Pd for
H2/D2 formation near vacancy. Expect issues for
vacancy creation and HD molecule formation to be
similar.
Vacancies made more readily
Temperature (K)
1000
5
10
25
10 25
5
xv=1%
800
1%
600
NiH
400
PdH
200
0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
H to Me site ratio
0.8
0.9
1.0
Ni phonon modes
D. A. Dimitrov et al Phys. Rev. B 60 6204 (1999)
Issues with the development of optical phonon modes in
gas loading since H concentration is low
Donor-receiver model
HD
Phonon
mode
3He
AZ*
AZ

Donor system
Receiver system
More Pxs with D added
0.7
0.6
Pxs(W)
0.5
500 mW
Pin = 1000 mW
0.4
200 mW
0.3
0.2
0.00
0.02
0.04
0.06
0.08
D/H
M. R. Swartz, G. M. Verner, and A. H. Frank, Proc. ICCF9 p. 335 (2002).
More issues
•HD/3He transition fine for donor
•Reduced mass smaller than for D2/4He system
1
1
1



m1 m2
 DD
MD

 MH
2
 HD
•So tunneling is orders of magnitude larger
•Deuterium natural abundance is 1/6240 of hydrogen
•DE = 5.49 MeV, so need to exchange few quanta
2
 MH
3
Take away message
•Excess heat seen in NiH
•Electrochemical systems, gas systems
•Harder to load
•Easier to make vacancies
•HD formation good
•Donor-receiver model happy
•Is some D in H
•Larger interaction matrix element since Gamow factor smaller
Piantelli experiment
Piantelli experiment
Ni rod:

10 cm


9 cm

0.5 cm diameter
S Focardi, R Habel, and F Piantelli, Il Nuovo Cimento, 107A 163 (1994)
Calibration
Data showing Pxs
Input power: 140? W
Excess power: 20 W
T vs Pin for Pxs = 0, 20, 50W
1998 Piantelli experiment
S Focardi, V Gabbani, V Montalbano, F Piantelli, S Veronesi,
Il Nuovo Cimento 111 1233 (1998)
Calibration curves
T1
T3
T2
T4
Excitation of the sample
DT1 = 381.7
Approx:
Pin = 60 W
Pxs = 20 W
DT1 = 467.4
Pressure-composition isotherms
•NiH is like PdH…
1 atm = 105 Pa
Solubility of H at low pressure
Uptake of H2 after several
loading cycles
Thinking about result
•Bulk Ni does not load much (5-20x10-5) near 1 atm
•Need O(6000 atm) to pressure-load bulk Ni with H2
•But some loading observed nonetheless in Piantelli expts
•Number of H atoms absorbed is several times O(3x1021)
•Number of Ni atoms in sample (1994) is O(4x1023)
•Loading in Cammarota replication from H2 absorption is NiH0.2
•Must be (non-bulk) special sites (defects or impurities)
•But not enough impurities in Cammarota version!
X-ray diffraction data in
electrochemical loading
Juskenas et al, Electrochimica Acta 43 1903 (1998)
No evidence for
intermediate a
values for loadings
in the a-b phase
region. Observed
only is the change
in volume
occupied by bphase NiH.
Diffusion of H
•Diffusion of H in Ni is much slower
than in Pd
D = D0 e-DE/kT
D0 = 7.04x10-3 cm2/sec
DE = 409 meV
D(300K) = 9.5x10-10 cm2/sec (NiH)
D(300K) = 5.5x10-7 cm2/sec (PdD)
•Elevated temperature D in NiH is
similar to D in PdD at 300 K
PdD diffusion model at 300 K
DD cm2/sec
10-6
10-7
10-8
0.0
0.2
0.4
0.6
D(oct)/Pd(location)
0.8
1.0
Excitation of the sample
DT1 = 381.7
Approx:
Pin = 60 W
Pxs = 20 W
DT1 = 467.4
H outgassing with
temperature rise
g-emission events
S Focardi and F Piantelli, “Produzione de energia e reazioni nucleari in sistemi NiH
a 400 C” (2000)
New elements in Miley expts
G. H. Miley and P. J. Shrestha, Slides presented at ICCF12 (2005).
New elements in Piantelli expt
•Low H loading in NiH gas systems
•Not enough H for good optical phonon mode
•NiH systems so far probably work based on acoustic mode
excitation
•Ni then participates strongly in vibrations
•Coupling of energy through nuclear excited states in Ni
•Some long-lived ones will have fission decay pathways
•Lattice-induced fission produces new elements
•Eats up significant amount of produced energy
Wish list for Santa
•Measurements of 3He in gas phase
•And correlation with energy (is Q-value 5.5 MeV?)
•Quantitative assay of Ni disintegration products
•More experiments with HD/3He branch in Pd codep expts
•Two-laser experiments in Ni to shed light on acoustic mode
operation
•Like to have NiX alloy with lower electron density
Take away message
•NiH excess heat discovered by Mills and Kneizys (1991)
•Gas loaded excess heat by Piantelli group (1994)
•H doesn’t load well in Ni
•Indirect evidence for vacancy generation in Piantelli
experiment
•Excess power stimulated by H flux
•High temperature operation favors 3He diffusion
•Excess heat stays on after flux initiation (consistent with
nuclear energy going into acoustic phonon modes
•Acoustic mode operation connected with transmutation