A route to room-temperature superconductivity?
Robert Clark
other metals becomes superconducting at higher temperatures when
compressed:
Superconductivity: boron goes it alone.
Jul 12, 2001
"Boron - one of the lightest elements in the periodic table - becomes
a superconductor when it is squeezed, according to a team led by
Russell Hemley of the Carnegie Institute of Washington in the US. They
found that boron loses its resistance to electrical current below 6
kelvin and at a pressure of 160 gigapascals. Now theorists must
explain why the 'transition temperature' of boron rises as the
pressure increases, in contrast with other metals (M I Eremets et al
2001 Science 293 272)."
http://physicsworld.com/cws/article/news/2642
Reports
Superconductivity in Boron.
Mikhail I. Eremets, Viktor V. Struzhkin, Ho-kwang Mao, Russell J.
Hemley.
Science 13 July 2001: Vol. 293. no. 5528, pp. 272 - 274.
http://www.sciencemag.org/cgi/content/full/293/5528/272
As shown in Fig. 4 in this Science report, the dependence on
pressure of the temperature of transition to superconductivity is
remarkably linear at high pressures. If this holds up we can estimate
how much pressure would be required for boron to be superconducting at
liquid nitrogen temperature 77K and at room temperature 300K.
The report shows that the rate at which the transition temperature
increases according to pressure is .05K/GPa and that the transition
temperature is 11 K at 250 GPa. Then to get to a superconducting
transition temperature of 77 K would require a pressure of 1,570 GPa.
And to get to room-temperature superconductivity would require a
pressure of 6,030 GPa.
However, diamond anvils crack at around 400 GPa = 4 megabars. So to
test this would require new materials or methods to attain these
ultrahigh pressures. One possibility might be "tetracarbon" which from
theoretical calculations has been claimed to be 40 times harder than
diamond:
Newsgroups: sci.astro, sci.physics, sci.energy, sci.materials,
sci.chem
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 8 Sep 2006 11:35:49 -0700
Local: Fri, Sep 8 2006 1:35 pm
Subject: 'Tetracarbon', 40 times harder than diamond?
http://groups.google.com/group/sci.astro/browse_thread/thread/ff42a43c596088a8
Bob Clark
tadchem
> Scientists using diamond anvils have found that boron in contrast to
> other metals becomes superconducting at higher temperatures when
> compressed:
ERROR:
Eve Wikipedia knows that boron is a nonmetal - http://en.wikipedia.org/wiki/Boron
Did you do *any* fact checking, ever, in your life?
>
> Superconductivity: boron goes it alone.
> Jul 12, 2001
A six-year-old report?
This is a Usenet NEWSgroup - go find an OLDgroup.
> "Boron - one of the lightest elements in the periodic table - becomes
> a superconductor when it is squeezed, according to a team led by
> Russell Hemley of the Carnegie Institute of Washington in the US. They
> found that boron loses its resistance to electrical current below 6
> kelvin and at a pressure of 160 gigapascals. Now theorists must
> explain why the 'transition temperature' of boron rises as the
> pressure increases, in contrast with other metals (M I Eremets et al
> 2001 Science 293 272)."http://physicsworld.com/cws/article/news/2642
>
> Reports
> Superconductivity in Boron.
> Mikhail I. Eremets, Viktor V. Struzhkin, Ho-kwang Mao, Russell J.
> Hemley.
> Science 13 July 2001: Vol. 293. no. 5528, pp. 272 - 274.http://www.sciencemag.org/cgi/content/full/293/5528/272
>
> As shown in Fig. 4 in this Science report, the dependence on
> pressure of the temperature of transition to superconductivity is
> remarkably linear at high pressures. If this holds up we can estimate
> how much pressure would be required for boron to be superconducting at
> liquid nitrogen temperature 77K and at room temperature 300K.
Extrapolation is not something part of good data analysis. It is an
activity that careful scientists engage in to a very limited degree,
and only while writing grant proposals. Extrapolations are generally
done by engineers (when they haven't got the data they need) and
journalists (when they are trying to engage an audience).
> The report shows that the rate at which the transition temperature
> increases according to pressure is .05K/GPa and that the transition
> temperature is 11 K at 250 GPa.
Ten data points for Tc scattered from 4 °K to 11 °K hardly justifies
extrapolation to 77 °K, a leap of 66 ° from a data set spanning only 7
°. That would be like trying to predict the GNP of the US in 2007
based on data from 1935 through 1941.
> Then to get to a superconducting
> transition temperature of 77 K would require a pressure of 1,570 GPa.
It must take an awful big pile of animal excrement to generate that
much pressure.
> And to get to room-temperature superconductivity would require a
> pressure of 6,030 GPa.
Now the pile of manure grows in height by nearly 4 times, producing 64
time the mass.
> However, diamond anvils crack at around 400 GPa = 4 megabars. So to
> test this would require new materials or methods to attain these
> ultrahigh pressures. One possibility might be "tetracarbon" which from
> theoretical calculations has been claimed to be 40 times harder than
> diamond:
There is an old chemists' joke about a chemist who tried to develop an
acid so powerful it would eat through absolutely anything. He
couldn't find a container to put it in.
Tom Davidson
Richmond, VA
Robert Clark
> On Nov 22, 6:29 pm, Robert Clark <rgregorycl...@yahoo.com> wrote:
>
> > Scientists using diamond anvils have found that boron in contrast to
> > other metals becomes superconducting at higher temperatures when
> > compressed:
>
> ERROR:
You're starting to talk like Uncle Al. That's not a good thing.
Yes, boron is a non-metal. I was following the news release. That
statement in the news release would have been more accurately phrased
as "Now theorists must explain why the 'transition temperature' of
boron rises as the
pressure increases, in contrast to the metals that have been known to
undergo superconductivity."
The report is 6 years old. The ONLY reason why this has not been
tested to see if it extends to higher pressures is the lack of stable
methods of achieving such ultra high pressures.
I'm suggesting the possibility is so important that means of
extending the high pressure realm should be investigated.
Bob Clark
Robert Clark
> other metals becomes superconducting at higher temperatures when
> compressed:
>
> Superconductivity: boron goes it alone.
> Jul 12, 2001
> "Boron - one of the lightest elements in the periodic table - becomes
> a superconductor when it is squeezed, according to a team led by
> Russell Hemley of the Carnegie Institute of Washington in the US. They
> found that boron loses its resistance to electrical current below 6
> kelvin and at a pressure of 160 gigapascals. Now theorists must
> explain why the 'transition temperature' of boron rises as the
> pressure increases, in contrast with other metals (M I Eremets et al
> 2001 Science 293 272)."http://physicsworld.com/cws/article/news/2642
>
> Reports
> Superconductivity in Boron.
> Mikhail I. Eremets, Viktor V. Struzhkin, Ho-kwang Mao, Russell J.
> Hemley.
>
> As shown in Fig. 4 in this Science report, the dependence on
> pressure of the temperature of transition to superconductivity is
> remarkably linear at high pressures. If this holds up we can estimate
> how much pressure would be required for boron to be superconducting at
> liquid nitrogen temperature 77K and at room temperature 300K.
> The report shows that the rate at which the transition temperature
> increases according to pressure is .05K/GPa and that the transition
> temperature is 11 K at 250 GPa. Then to get to a superconducting
> transition temperature of 77 K would require a pressure of 1,570 GPa.
> And to get to room-temperature superconductivity would require a
> pressure of 6,030 GPa.
> test this would require new materials or methods to attain these
> ultrahigh pressures. One possibility might be "tetracarbon" which from
> theoretical calculations has been claimed to be 40 times harder thandiamond:
>
> Newsgroups: sci.astro, sci.physics, sci.energy, sci.materials,
> sci.chem
> From: "Robert Clark" <rgregorycl...@yahoo.com>
> Date: 8 Sep 2006 11:35:49 -0700
> Local: Fri, Sep 8 2006 1:35 pm
>
> Bob Clark
The maximum pressure attainable by the diamond anvil method is
typically given around 360 GPa, 4 megabars:
Diamond anvil cell.
http://en.wikipedia.org/wiki/Diamond_anvil
However, recently there have been produced synthetic diamonds 50%
harder than natural diamond:
Large diamonds made from gas are the hardest yet.
Posted on: Wednesday February 25, 2004.
http://www.physlink.com/News/022504CVDDiamonds.cfm
The researchers state these could be used to produce pressures at
least up 200 GPa. However, conceivable they could be used to create
pressures 50% higher than the maximum for natural diamonds, so perhaps
to 540 GPa.
Then the range to test the linear increase of transition temperature
of superconductivity with pressure for boron could be doubled.
Bob Clark
Robert Clark
> other metals becomes superconducting at higher temperatures when
> compressed:
>
> Superconductivity: boron goes it alone.
> Jul 12, 2001
> "Boron - one of the lightest elements in the periodic table - becomes
> a superconductor when it is squeezed, according to a team led by
> Russell Hemley of the Carnegie Institute of Washington in the US. They
> found that boron loses its resistance to electrical current below 6
> kelvin and at a pressure of 160 gigapascals. Now theorists must
> explain why the 'transition temperature' of boron rises as the
> pressure increases, in contrast with other metals (M I Eremets et al
> 2001 Science 293 272)."http://physicsworld.com/cws/article/news/2642
>
> Reports
> Superconductivity in Boron.
> Mikhail I. Eremets, Viktor V. Struzhkin, Ho-kwang Mao, Russell J.
> Hemley.
>
> As shown in Fig. 4 in this Science report, the dependence on
> pressure of the temperature of transition to superconductivity is
> remarkably linear at high pressures. If this holds up we can estimate
> how much pressure would be required for boron to be superconducting at
> liquid nitrogen temperature 77K and at room temperature 300K.
> The report shows that the rate at which the transition temperature
> increases according to pressure is .05K/GPa and that the transition
> temperature is 11 K at 250 GPa. Then to get to a superconducting
> transition temperature of 77 K would require a pressure of 1,570 GPa.
> And to get to room-temperature superconductivity would require a
> pressure of 6,030 GPa.
> However, diamond anvils crack at around 400 GPa = 4 megabars. So to
> test this would require new materials or methods to attain these
> ultrahigh pressures. One possibility might be "tetracarbon" which from
> theoretical calculations has been claimed to be 40 times harder than
> diamond:
>
> Newsgroups: sci.astro, sci.physics, sci.energy, sci.materials,
> sci.chem
> From: "Robert Clark" <rgregorycl...@yahoo.com>
> Date: 8 Sep 2006 11:35:49 -0700
> Local: Fri, Sep 8 2006 1:35 pm
>
> Bob Clark
Another possibility might be to use strong magnetic fields that
induce a high outward pressure on materials at high intensity to
counteract the very high compressive forces on the anvil.
This magnetic field generation method might work when you consider
that the main reason why static magnetic fields are limited in
intensity to about 30 tesla or so is because the intense fields cause
the wires to fall apart. See this page for a formula on the forces
produced by the magnetic field:
Magnetic Properties of Ferromagnetic Materials.
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/magprop.html#c2
It is quite possible to generate gigabar pressures in the wires
containing the current for example. The idea then would be to induce
the very high outward pressure in the diamond or metal in the anvil so
it would be able to withstand the high pressure far above what it
would normally take to crack it.
You might want to use a metal now rather than diamond in the anvil
since metals would more easily carry the high currents required to
generate the high magnetic fields. The metals would not be as hard as
diamond but the hope is this would be outweighed by the outward
pressure produced by the magnetic field.
Some recent research also has suggested that osmium might be
comparable to diamond in resistance to compression, though not in
hardness:
Osmium is Stiffer than Diamond.
27 March 2002
http://focus.aps.org/story/v9/st16
Bob Clark
John Schutkeker
news:86989d1f-90ab-4e5b...@y43g2000hsy.googlegroups.com:
Well, it may be room temperature superconductivity, but if it isn't also
"room pressure" superconductivity, then it is still no more useful than
low temp SC.
Mark Thorson
>
> Well, it may be room temperature superconductivity, but if it isn't also
> "room pressure" superconductivity, then it is still no more useful than
> low temp SC.
Not true. If you could get to RTSC with a diamond-anvil
pressure cell, you could put a SQUID magnetometer in there
that would be useful for lots of stuff. Maybe even a
Josephson junction CPU chip that would run Vista XP Pro
at a reasonable speed. What killed IBM's Josephson junction
project was the crazy way materials would break down when
cycled repeatedly to cryogenic temperatures.
Phil Hobbs
I agree that a room-temperature SQUID would be a very useful device,
even though it wouldn't be nearly as good as a low-temperature SQUID.
Hypres used to make a 100-GHz sampling scope based on SQUIDs, but it
needed liquid helium. Pretty amazing device for its time, though.
RE the IBM Josephson project:
They stayed with Pb junctions for too long, and those had the
temperature cycling problem in spades, just as you say. They eventually
went to niobium edge junctions, which survived very well, but by then it
was clear that the speed advantage wasn't enough to justify the
requirement for cryogenic temperatures. (I wasn't on the project, I'm
about 10 years too young, but I know a bunch of the people who worked on
it.)
Cheers,
Phil Hobbs
IBM T. J. Watson Research Center
Yorktown Heights NY
Robert Clark
> other metals becomes superconducting at higher temperatures when
> compressed:
>
> Jul 12, 2001
> "Boron- one of the lightest elements in the periodic table - becomes
> a superconductor when it is squeezed, according to a team led by
> Russell Hemley of the Carnegie Institute of Washington in the US. They
> kelvin and at a pressure of 160 gigapascals. Now theorists must
> pressure increases, in contrast with other metals (M I Eremets et al
> 2001 Science 293 272)."http://physicsworld.com/cws/article/news/2642
>
> ReportsSuperconductivityinBoron.
> Mikhail I. Eremets, Viktor V. Struzhkin, Ho-kwang Mao, Russell J.
> Hemley.
>
> As shown in Fig. 4 in this Science report, the dependence on
> pressure of the temperature of transition tosuperconductivityis
> remarkably linear at high pressures. If this holds up we can estimate
> liquid nitrogen temperature 77K and at room temperature 300K.
> The report shows that the rate at which the transition temperature
> increases according to pressure is .05K/GPa and that the transition
> temperature is 11 K at 250 GPa. Then to get to a superconducting
> transition temperature of 77 K would require a pressure of 1,570 GPa.
> pressure of 6,030 GPa.
> However,diamondanvils crack at around 400 GPa = 4 megabars. So to
> test this would require new materials or methods to attain these
> ultrahigh pressures. One possibility might be "tetracarbon" which from
> theoretical calculations has been claimed to be 40 times harder thandiamond:
>
> Newsgroups: sci.astro, sci.physics, sci.energy, sci.materials,
> sci.chem
> From: "Robert Clark" <rgregorycl...@yahoo.com>
> Date: 8 Sep 2006 11:35:49 -0700
> Local: Fri, Sep 8 2006 1:35 pm
>
> Bob Clark
I was doing a search on arxiv.org for articles on boron
superconductivity and found some articles discussing the fact that
diamond becomes superconducting when doped with boron:
Origin of Superconductivity in Boron-doped Diamond.
http://front.math.ucdavis.edu/0404.0547
Then what might be happening with the boron superconductivity is that
under the very high pressure of the diamond anvil, boron is infused
into the diamond, thus acting as a dopant.
Apparently for this boron superconductivity to be observed, the high
pressure still has to be applied, i.e., the diamond anvils still have
to be in contact with the boron. Then it's possible the drop in
resistance is coming from the lack of resistance in the diamond
immediately surrounding the boron sample because of the boron infused
in the diamond.
Bob Clark
Robert Clark
>
> Then what might be happening with theboronsuperconductivity is that
> under the very high pressure of the diamond anvil,boronis infused
> into the diamond, thus acting as a dopant.
> pressure still has to be applied, i.e., the diamond anvils still have
> resistance is coming from the lack of resistance in the diamond
> immediately surrounding theboronsample because of theboroninfused
> in the diamond.
>
> Bob Clark
This report shows the transition temperature Tc does increase with
increasing boron content over the range it has been tested:
Dependence of the superconducting transition temperature on the doping
level in single crystalline diamond films.
http://front.math.ucdavis.edu/0408.0517
You can see though in Fig.2 the transition temperature tested so far
is quite low only to 2K. Also, unlike the pressure case you can see
the dependence is not linear in Fig. 2. Judging from the graph it
could be continuing to increase like a square-root or log graph or it
could level off far earlier than the 77K and 300K temperature.
There are several methods for doping the diamond other than by high
pressures. For instance there is "ion implantation" that accelerates
charged ions electrostatically to high speeds to be embedded in a
crystal lattice.
I don't why this hasn't been tried to get even higher doping levels
of boron. Perhaps it takes a very high power level to get the high
doping concentrations.
Bob Clark
Robert Clark
> >diamondbecomes superconducting when doped withboron:
>
> > Origin ofSuperconductivityinBoron-dopedDiamond.http://front.math.ucdavis.edu/0404.0547
>
> > Then what might be happening with theboronsuperconductivity is that
> > under the very high pressure of thediamondanvil,boronis infused
> > Apparently for thisboronsuperconductivity to be observed, the high
> > to be in contact with theboron. Then it's possible the drop in
> > resistance is coming from the lack of resistance in thediamond
> > immediately surrounding theboronsample because of theboroninfused
> > in thediamond.
>
> > Bob Clark
>
> This report shows the transition temperature Tc does increase with
> increasing boron content over the range it has been tested:
>
> Dependence of the superconducting transition temperature on the doping
>
> You can see though in Fig.2 the transition temperature tested so far
> is quite low only to 2K. Also, unlike the pressure case you can see
> the dependence is not linear in Fig. 2. Judging from the graph it
> could be continuing to increase like a square-root or log graph or it
> could level off far earlier than the 77K and 300K temperature.
> pressures. For instance there is "ion implantation" that accelerates
> charged ions electrostatically to high speeds to be embedded in a
> crystal lattice.
> I don't why this hasn't been tried to get even higher doping levels
> of boron. Perhaps it takes a very high power level to get the high
> doping concentrations.
>
> Bob Clark
This report found superconductivity in boron-doped diamond up to 11
K:
Advantage on Superconductivity of Heavily Boron-Doped (111) Diamond
Films.
http://front.math.ucdavis.edu/0503.0303
Interestingly it found the superconductivity extended to higher
temperatures on diamond faces oriented in one direction (111) than in
another (100). This might be related to the fact that diamond is
stronger in one direction than in others. A good test of this would be
to try in the third direction (110).
Also, interesting is that the temperature Tc leveled off with
increasing boron concentration for the (100) direction but continued
to increase up to the highest doping level tried for the (111)
direction, nearly 5% boron. This is shown in Fig. 5 in the report.
Intriguingly the graph of Tc for the (111) direction appears to be
increasing exponentially with the boron content.
If the direction dependent effect is due to the difference in
strength according to direction that suggests another explanation for
the origin of the diamond superconductivity. It may be that in fact
the superconductivity in the diamond is because of the boron kept at
high pressure within the diamond lattice at high doping levels. The
lower strength directions are not able to keep the boron at sufficient
pressure to maintain the superconductivity in the boron.
Further evidence of this is that superconductivity was also observed
in silicon carbide doped with boron. Silicon carbide is another hard,
high strength material.
Superconductivity in Boron-doped SiC.
Journal of the Physical Society of Japan
Vol. 76 No. 10, October, 2007, 103710 (4 pages)
http://jpsj.ipap.jp/link?JPSJ/76/103710/
And this report suggests the superconductivity in the boron doped
diamond arises from filaments within the diamond:
Superconductivity in polycrystalline boron-doped diamond synthesized
at 20 GPa and 2700 K
J. Appl. Phys. 99, 033903 (2006) (7 pages)
"Bulk sample (~7.5 mm3) of boron-doped diamond containing 2.6(0.6)
at.% B was synthesized by means of direct reaction between boron
carbide and graphite in multianvil apparatus at 20 GPa and 2700 K.
Electrical resistance of the sample of B-doped polycrystalline diamond
was measured in the temperature interval from 10 mK to 300 K and
revealed a transition to superconducting state at 2.4-1.4 K. Our
results imply that increase of synthesis pressure from 8-9 GPa
[Ekimov et al., Nature 428, 542 (2004)] to 20 GPa does not
significantly affect boron content in diamond but decreases the
temperature of the transition to superconducting state. We observed
sharpening of the temperature interval of the transition to
superconducting state in magnetic field that may suggest that
superconductivity in our samples could arise from filaments of zero-
resistant material."
http://link.aip.org/link/?JAPIAU/99/033903/1
Good tests of this hypothesis would be to see if the
superconductivity occurred with other boron-doped high strength
materials and seeing if the superconductivity depended on the
directions the materials had their highest strength.
Some possibilities: boron nitride, aggregated diamond nanorods,
ultrahard fullerite, Rhenium diboride, and beta carbon nitride.
Bob Clark
John Schutkeker
news:474CACE4...@sonic.net:
Bzzzzt, wrong answer! You don't honestly think that they won't break
down equally unpleasantly when cycled repeatedly to diamond anvil
pressures, do you?
A liquid nitrogen refrigerator is an infinitely cheaper, and much
larger, place to build complex widgets, than a diamond anvil. What we
really need to bridge the gap between liquid nitrogen temp
superconductors and room temp superconductors is a dry ice temperature
superconductor (-60F, IIRC), because dry ice refrigerators are even
cheaper than liquid nitrogen refrigerators. ?:D
IMO, what makes Josephson Junction computers uninteresting is that
they're not a better mousetrap, just a different mousetrap.
Phil Hobbs
> Mark Thorson <nos...@sonic.net> wrote in
> news:474CACE4...@sonic.net:
>
>> John Schutkeker wrote:
>>> Well, it may be room temperature superconductivity, but if it isn't
>>> also "room pressure" superconductivity, then it is still no more
>>> useful than low temp SC.
>> Not true. If you could get to RTSC with a diamond-anvil
>> pressure cell, you could put a SQUID magnetometer in there
>> that would be useful for lots of stuff. Maybe even a
>> Josephson junction CPU chip that would run Vista XP Pro
>> at a reasonable speed. What killed IBM's Josephson junction
>> project was the crazy way materials would break down when
>> cycled repeatedly to cryogenic temperatures.
>
> Bzzzzt, wrong answer! You don't honestly think that they won't break
> down equally unpleasantly when cycled repeatedly to diamond anvil
> pressures, do you?
>
> A liquid nitrogen refrigerator is an infinitely cheaper, and much
> larger, place to build complex widgets, than a diamond anvil.
Larger, sure, but all we're talking about putting in it is a SQUID. You
can make those lithographically on one half of the anvil, and then
assemble it with a big preload, using some sort of
temperature-compensated mount. It ought never to have to be
disassembled, so in principle there's no cycling involved. (That of
course assumes that the metal seal on the cell didn't ever leak.)
The key thing about cryogenics is that they need constantly power and
continual babysitting.
Cheers,
Phil Hobbs
John Schutkeker
news:13m0a99...@corp.supernews.com:
> John Schutkeker wrote:
>> Mark Thorson <nos...@sonic.net> wrote in
>> news:474CACE4...@sonic.net:
>>
>>> John Schutkeker wrote:
>>>> Well, it may be room temperature superconductivity, but if it isn't
>>>> also "room pressure" superconductivity, then it is still no more
>>>> useful than low temp SC.
>>> Not true. If you could get to RTSC with a diamond-anvil
>>> pressure cell, you could put a SQUID magnetometer in there
>>> that would be useful for lots of stuff. Maybe even a
>>> Josephson junction CPU chip that would run Vista XP Pro
>>> at a reasonable speed. What killed IBM's Josephson junction
>>> project was the crazy way materials would break down when
>>> cycled repeatedly to cryogenic temperatures.
>>
>> Bzzzzt, wrong answer! You don't honestly think that they won't break
>> down equally unpleasantly when cycled repeatedly to diamond anvil
>> pressures, do you?
>>
>> A liquid nitrogen refrigerator is an infinitely cheaper, and much
>> larger, place to build complex widgets, than a diamond anvil.
>
> Larger, sure, but all we're talking about putting in it is a SQUID.
> You can make those lithographically on one half of the anvil, and then
> assemble it with a big preload, using some sort of
> temperature-compensated mount.
I knew you were going to say this, and now we've descended to the nadir
of bickering about what's complex and what isn't. According to my
definition, anything under the purview of "professional science" is by
definition complex. Other categories, like industrial, commercial,
hobbyist and amateur science are by definition easier.
Both steps you described above are intricate and difficult to implement,
and I shudder to think about the complexity of any steps you've left
out. I'm not saying that it can't be done, but just that it's not
*obviously* competitive with other ideas, for research dollars. Other
ideas can provide any or all of the following benefits - quicker
payoff, more important area of research, less effort, cheaper equipment.
> It ought never to have to be
> disassembled, so in principle there's no cycling involved. (That of
> course assumes that the metal seal on the cell didn't ever leak.)
Sure, but the same was true of the IBM experiment. Theoretically, once
you've got your widget working, it's reasonable to require that the user
never allow it to return to ambient temp & pressure. In practice, this
is yet another headache for the user, and it only takes a couple like
that to make them throw up their hands and say "It just ain't worth the
hassle." ;(
> The key thing about cryogenics is that they need constantly power and
> continual babysitting.
I'm sure that the anvil requires no less power or babysitting than the
cryo, and cryo setups are much more familiar to lab people than the
anvil. Familiarity = low cost + ease of use.
Robert Clark
...
> K:
>
> Advantage onSuperconductivityof Heavily Boron-Doped (111) Diamond
> Films.http://front.math.ucdavis.edu/0503.0303
>
> temperatures on diamond faces oriented in one direction (111) than in
> another (100). This might be related to the fact that diamond is
> stronger in one direction than in others. A good test of this would be
> to try in the third direction (110).
> Also, interesting is that the temperature Tc leveled off with
> increasing boron concentration for the (100) direction but continued
> to increase up to the highest doping level tried for the (111)
> direction, nearly 5% boron. This is shown in Fig. 5 in the report.
> Intriguingly the graph of Tc for the (111) direction appears to be
> increasing exponentially with the boron content.
> If the direction dependent effect is due to the difference in
> strength according to direction that suggests another explanation for
> thesuperconductivityin the diamond is because of the boron kept at
> high pressure within the diamond lattice at high doping levels. The
> lower strength directions are not able to keep the boron at sufficient
> Further evidence of this is thatsuperconductivitywas also observed
> in silicon carbide doped with boron. Silicon carbide is another hard,
> high strength material.
>
> Journal of the Physical Society of Japan
>
> And this report suggests thesuperconductivityin the boron doped
> diamond arises from filaments within the diamond:
>
> at 20 GPa and 2700 K
> J. Appl. Phys. 99, 033903 (2006) (7 pages)
> "Bulk sample (~7.5 mm3) of boron-doped diamond containing 2.6(0.6)
> at.% B was synthesized by means of direct reaction between boron
> carbide and graphite in multianvil apparatus at 20 GPa and 2700 K.
> Electrical resistance of the sample of B-doped polycrystalline diamond
> was measured in the temperature interval from 10 mK to 300 K and
> revealed a transition to superconducting state at 2.4-1.4 K. Our
> results imply that increase of synthesis pressure from 8-9 GPa
> [Ekimov et al., Nature 428, 542 (2004)] to 20 GPa does not
> significantly affect boron content in diamond but decreases the
> temperature of the transition to superconducting state. We observed
> sharpening of the temperature interval of the transition to
> resistant material."http://link.aip.org/link/?JAPIAU/99/033903/1
>
> Good tests of this hypothesis would be to see if thesuperconductivityoccurred with other boron-doped high strength
> materials and seeing if thesuperconductivitydepended on the
> directions the materials had their highest strength.
> Some possibilities: boron nitride, aggregated diamond nanorods,
> ultrahard fullerite, Rhenium diboride, and beta carbon nitride.
>
> Bob Clark
Another possibility might be the superhard nanocomposites recently
discovered:
=====================================
Newsgroups: sci.astro, sci.physics, sci.energy, sci.materials,
sci.chem
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 28 Aug 2006 11:07:14 -0700
Local: Mon, Aug 28 2006 1:07 pm
Subject: New super hard composites to 40 GPa tensile strength?
Some recent research show thin film coatings reaching up to 40 GPa in
tensile strength:
Superhard and Functional Nanocomposites Formed by Self-Organization.
Rev.Adv.Mater.Sci. 5(2003) 6-16.
http://www.ipme.ru/e-journals/RAMS/no_1503/veprek/veprek.html
Limits to the strength of super- and ultrahard nanocomposite coatings.
J. Vac. Sci. Technol. A 21(3), May/Jun 2003, pp. 532-544.
http://web.mit.edu/durint/PDF/VeprekEtAl2003.pdf
These coatings of micron-scale size have been found to rival diamond
in hardness.
There does not appear to be a limit to the length of these coatings.
However, the authors note it is uncertain if the hardness and derived
tensile stength measurements will extend to macro scale samples.
Also, the authors did not measure the tensile strength directly but
computed it from their measurements of the materials hardness.
Even if the strength measurements do not scale up to macro scale
sizes, their tensile strength at the micron-scale could allow them to
be used for hydrogen storage if used in the form of microspheres.
Bob Clark
=====================================
zzbu...@netscape.net
> Scientists using diamond anvils have found that boron in contrast to
> other metals becomes superconducting at higher temperatures when
> compressed:
>
> Superconductivity: boron goes it alone.
> Jul 12, 2001
> "Boron - one of the lightest elements in the periodic table - becomes
> a superconductor when it is squeezed, according to a team led by
> Russell Hemley of the Carnegie Institute of Washington in the US. They
> found that boron loses its resistance to electrical current below 6
> kelvin and at a pressure of 160 gigapascals. Now theorists must
> explain why the 'transition temperature' of boron rises as the
> pressure increases, in contrast with other metals (M I Eremets et al
> 2001 Science 293 272)."http://physicsworld.com/cws/article/news/2642
That's not too difficult to explain.
Since when you're working in the gigapascal range, you're
no longer working with pressure in the usual sense.
You're working with compression,
Which is the only reason lasers, wires, and capacitors even work.
> Reports
> Superconductivity in Boron.
> Mikhail I. Eremets, Viktor V. Struzhkin, Ho-kwang Mao, Russell J.
> Hemley.
> Science 13 July 2001: Vol. 293. no. 5528, pp. 272 - 274.http://www.sciencemag.org/cgi/content/full/293/5528/272
>
> As shown in Fig. 4 in this Science report, the dependence on
> pressure of the temperature of transition to superconductivity is
> remarkably linear at high pressures. If this holds up we can estimate
> how much pressure would be required for boron to be superconducting at
> liquid nitrogen temperature 77K and at room temperature 300K.
> The report shows that the rate at which the transition temperature
> increases according to pressure is .05K/GPa and that the transition
> temperature is 11 K at 250 GPa. Then to get to a superconducting
> transition temperature of 77 K would require a pressure of 1,570 GPa.
> And to get to room-temperature superconductivity would require a
> pressure of 6,030 GPa.
> However, diamond anvils crack at around 400 GPa = 4 megabars. So to
> test this would require new materials or methods to attain these
> ultrahigh pressures. One possibility might be "tetracarbon" which from
> theoretical calculations has been claimed to be 40 times harder than
> diamond:
>
> Newsgroups: sci.astro, sci.physics, sci.energy, sci.materials,
> sci.chem
> From: "Robert Clark" <rgregorycl...@yahoo.com>
> Date: 8 Sep 2006 11:35:49 -0700
> Local: Fri, Sep 8 2006 1:35 pm
> Subject: 'Tetracarbon', 40 times harder than diamond?http://groups.google.com/group/sci.astro/browse_thread/thread/ff42a43...
>
> Bob Clark