On Dec 10, 2007, at 5:37 AM, Charles M. Brown wrote:
Vorts,
Could the electron affinity transporter based on H2 or CO2 or H20
be simplified to use an array of LaB6 (a stable low work function
material) orthogonal needles facing a flat anode with a nanometer
scale gap in a vacuum?
First, let me say the key is not using a vacuum, but rather having
the gap be about equal to the mean free path. The transport is
actually carried out by molecules. It is not possible yet, to my
knowledge, to achieve a zero work function cathode. Cold cathodes
still require significant (in this context) voltages. The electron
affinity pile can only produce very small voltages per stage, limited
by the kinetic energies of the molecules doing the transporting plus
other factors. The more transport molecules available per second,
the higher the transport current. It is thus important to balance
the operating pressure with the gap size. The nice thing about a
nanometer scale gap is, the smaller gap, the higher the optimum
operating pressure, and thus max current available.
The key is achieving electron exchange with the transport molecule.
Nano-needle emitters should help with this. It may be that a
piezoelectric effect could help with this too. I discussed the piezo-
kinetic approach to second law violating somewhat here:
http://mtaonline.net/~hheffner/SLVN.pdf
There would be preferential electron transport from the needle to
the plate. A variant, which I hereby put in the public domain, is
to have a 3 ? 7 angstrom insulating solid that electrons can tunnel
through instead of a vacuum. This is also a variant of a diode
array where Schottky anodes abut n type semiconductors. It is
difficult for me to decide between the two.
Tunneling is a two way street. Use of differential affinities is key
to the transport idea. Electrons indeed do tunnel in the exchange
process, but the differing orbital characteristics between the
transporter and electrode atoms is key to achieving a one-way
transport. Those differences provide the ratchet.
I was unimpressed with Feynman's dismissal of diodes as thermal /
electrical ratchets which he mentioned in passing as doomed to fail
after doing most of his presentation with his paddle wheel /
ratchet wheel / pawl device which he taught was doomed to fail.
I believe that a variation with multiple unsprung pawls would
rectify the Brownian motion driven ratchet wheel's rotation. Having
at least one pawl in blocking position would stop the wrong way
rotation while the pawls would move at random without pounding the
incline. The probability of no blocking decreases exponentially to
the number of pawls.
Yes, but so does the energy required to obtain a single cog
movement. Something that may be of use to consider is the fact the
energy distribution is the same for large and small molecules.
Momentum, however, is much larger for large molecules in a gas than
the small. Any ratchet effect that can make use of large momenta
will work better with large gas molecules, and likely not require the
same degree of miniaturization as well. One of the best inorganic
molecules I've located along these lines is UF6, but there are likely
much better inorganic molecules for the job, and they can be
engineered for their electron transport characteristics too.
Horace Heffner
http://www.mtaonline.net/~hheffner/
