[NewCandle] New prospective matrix material for high temp LENR

[Keith Nagel]

Hey Horace,

Thanks for taking the time to abstract some of the
background info from the thesis; that was very helpful.

Why I made the connection to the cermets was the use of
zirconia in many of the compositions. As you say, typical
cermet compositions have a metal component of at most
20% say, where with these compositions metal values are
closer to 50%. Greater conductivity would surely result,
making for a more efficient cathode ( I sort of had in
mind using thin films of the cermet over a metal substrate
to reduce conductivity losses ).

This new material method described in your linked thesis
certainly has some promise for LENR usage;
the codeposition type of experiment I have conducted over the
years were predicated on the belief that dendritic growth of the active
metal
on the cathode was important for creating an active LENR site.
This is quite distinct from the approach
of codeposition with boron and the like ( techniques long
used in the metal plating industry ) to toughen the resulting
active metal film and allow for greater hydrogen isotope loading.
The latter approach being more appropriate to the F&P model
of LENR.

So having a bulk matrix of dendrites preformed in the cathode
where the whole is structurally stable could be very beneficial.
Getting the hydrogen _in_ there is another matter.

Now if we could just get this guy to try making a palladium
alloy...

K.

-----Original Message-----
From: newcandle-bounces at ipdiscover.com
[mailto:newcandle-bounces at ipdiscover.com]On Behalf Of Horace Heffner
Sent: Sunday, December 28, 2008 12:47 PM
To: New energy for the new world.
Subject: Re: [NewCandle] New prospective matrix material for high temp
LENR



On Dec 28, 2008, at 10:06 AM, Keith Nagel wrote:

> Indeed. I too have wondered whether cermet materials could
> be used for LENR type reactions, or just as novel electrodes
> for hydrogen generation.
>
> http://en.wikipedia.org/wiki/Cermet
>
> I am not too up on the vanguard of materials science to know where
> the thesis you linked fits in with the field; I gathered from a
> quick scan of the paper that the ductility of the alloy was the
> novelty but there could be more. That kind of dendritic growth
> is common in alloys in general; I've been reading much on
> ferromagnetic
> alloys and SEM photos often show the familiar frond shaped growths.
> But perhaps a cermet with the metal component forming dendrites
> is new??? Does that account for the ductility?
>
> K.

The advancement is in composite metallic glasses, not cermets.

 From Wiki:

"A cermet is a composite material composed of ceramic (cer) and
metallic (met) materials. A cermet is ideally designed to have the
optimal properties of both a ceramic, such as high temperature
resistance and hardness, and those of a metal, such as the ability to
undergo plastic deformation. The metal is used as a binder for an
oxide, boride, carbide, or alumina. Generally, the metallic elements
used are nickel, molybdenum, and cobalt. Depending on the physical
structure of the material, cermets can also be metal matrix
composites, but cermets are usually less than 20% metal by volume."

My impression, from the various examples given, is that cermets have
high resistance, and thus may not make good cathodes. "The metal is
used as a binder for an oxide, boride, carbide, or alumina."  They
are not metallic glasses and don't appear to be amenable to cold
rolling and thermoplastic forming.  Their main application appears to
be high temperature environments.

The glasses developed act more like metals than ceramics, and a low
cost thermoformable glass replacement for metallic titanium is even
available.  Starting on page 121:

"6.2 Background on Nanostructure-Dendrite Composites

Recently, titanium-based nanostructure-dendrite composites have been
reported which are said to exhibit increased toughness over bulk
metallic glasses (BMGs) and other nanostructured materials (see [1]).
This work has spawned an
entirely new field of nanoeutectic-oriented metallurgy, with dozens
of publications touting the benefits of such materials over BMGs
(see, for instance, [2–14]). However, upon further investigation of
this new field, we note that uniaxial compression tests are typically
the only mechanical tests used to characterize the perceived
toughness and enhanced plasticity of the nanostructured composites.
The geometry of the compression test, where closing stresses and
friction arrest slip, has resulted in the overstatement of toughness
in these new materials. It appears that the nanostructure-dendrite
composites are very similar to BMG composites, but with a eutectic
matrix that failed to form a glass during rapid cooling. The
crystallized matrix, or nanostructured eutectic as it is often
called, is typically comprised of brittle [***** note the prior word!
****] intermetallics, and fails with no apparent plasticity in
bending or tension tests. When nanostructure-dendrite composites are
loaded in an unconfined manner, as with the uniaxial tension test,
cracks move unimpeded through the brittle matrix and global ductility
is absent. In contrast, if the matrix is frozen as a glass, the
length scale of the deformation is larger, allowing microstructural
stabilization mechanisms to become possible. In the current work, we
demonstrate several new titanium-based glass-dendrite composites, all
of which exhibit at least 5 percent tensile ductility, low cost, and
densities comparable to high-performance crystalline titanium alloys
(4.97–5.15 g/cm3). We observe a remarkable similarity in mechanical
properties (such as tensile ductility, yield strength, and fracture
toughness) between the new glassy-composites and high-strength
crystalline titanium alloys (such as Ti-6Al-4V) — all with a
significantly lower Young’s modulus. The current work demonstrates
that titanium-based BMG composites can be competitive with
crystalline titanium alloys for structural applications where high
strength and toughness are a necessity."

Page 123: "In the case where the glass matrix does not vitrify into a
bulk glass, a brittle nanostructure-dendrite composite forms,
accompanied by a large increase in G. Based on nearly two decades of
research with BMGs, we note that a crystallized or partially
crystallized metallic glass is always more brittle than a fully
amorphous one."

"While the glass-dendrite composites have been shown to exhibit up to
~ 13% tensile ductility [14], nanostructure-dendrite composites fail
in an apparently brittle manner with no global ductility. Shear bands
that form in the nanostructured eutectic matrix develop into
catastrophic cracks at much shorter lengths than in BMGs, leading to
failure on a continuous path through the matrix. The crystalline
phases act as nucleation sites for shear bands, which typically form
at lower stresses than in monolithic glasses. Despite claims of
increased toughness and ductility in several publications on
nanostructure-dendrite composites, tension tests are noticeably
absent [1–14]. "

With this background, now to more specifically answer your questions.

The key to making high toughness composites with all the other
required features is the creation of *soft* crystal dendrites, i.e.
dendrites having a low shear modulus, lower than the glass in which
they are imbedded.

P 34: "The advancement that allowed in-situ alloys to exhibit tensile
ductility while ex-situ alloys do not is the understanding that the
inclusions need to be softer than the glass matrix [23]. This
fundamental concept was experimentally demonstrated in 2001, with the
alloy Zr56.2Ti13.8Nb5Cu6.9Ni5.6Be12.5 (LM2), but the concept was
largely overlooked."

Much of the rest of the work relates to how to form metallic glasses.
The result is summed up on P. 14: "We have observed that the two most
important criteria for bulk glass formation are deep eutectics and
atomic size mismatch."

P. 133: "The low processing temperatures of the composites allow for
rapid prototyping of parts and a cost savings over crystalline
titanium alloys. "

Best regards,

Horace Heffner
http://www.mtaonline.net/~hheffner/





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