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PetTastic
2013-Sep-26, 05:16 PM
Recently, I have seen several articles about experiments confirming the existence of element number 115.

I while back people were talking about runaway fusion in core collapse supernova temporarily dumping large amounts of energy either as antimatter or super heavy elements.

The existence of ununpentium suggests there is an island of stability around 115 protons and that fusion reactions producing these elements absorbs large amounts of energy, and large numbers of smaller atoms.

So, for plausible science fiction purposes, would it be reasonable to say:
During a particular type core collapse, runaway fusion stores large amounts of energy in super heavy elements, until the levels build-up to the point that energy released by decay exceeds the energy absorbed by fusion.

Or is this just silly?

kzb
2013-Sep-26, 05:56 PM
The island of stability is now thought to be around the isotope 120-300. Maybe there is still some hope these isotopes have long half-lives and are made in supernovae. But whether a substantial fraction of the mass or energy could end up there, well who knows. There does not seem to be any evidence of it.

ShinAce
2013-Sep-26, 06:05 PM
The difficulty in producing element 115 is with the number of neutrons required.

There is a theoretical island of stability around 120. There is another theory involving magic numbers of neutrons and protons(creating filled shells similar to electron shells). 115 has the possibility of a filled shell, but we don't have the means of creating it with enough neutrons to investigate this 'stable' isotope.

A supernova would likely run into the same problem. It has the required energy in daughter nuclei, but would still have difficulty getting enough neutrons into the reaction to create a somewhat stable 115.

It's like having all the manpower in the world, but not a single brick. You can't build without the needed materials. I'm guessing that's why anti-matter might be invoked. If you could have enough energy to create (115+excess anti-neutrons), it would balance out.

Swift
2013-Sep-26, 08:55 PM
One of Poul Anderson's Polesotechnic League books had a somewhat similar idea as a plot element; IIRC, there was a planet that had been in a distant orbit around a star that went nova, and deposited a bunch of island of stability atoms on the surface of this planet.

Jens
2013-Sep-26, 10:51 PM
The existence of ununpentium suggests there is an island of stability around 115 protons and that fusion reactions producing these elements absorbs large amounts of energy, and large numbers of smaller atoms.


Just as a clarification, "discovery" here doesn't mean that they discovered this element as existing in nature. They simply produced it, and then detected its presence not by observing it directly (it decays too quickly) but by detecting the decay products. So 115 and other super heavy elements would probably be produced in a supernova, but within milliseconds they would decay into lighter elements.

Jens
2013-Sep-26, 10:57 PM
Also, just to be clear, 115 has not been officially discovered yet. It was first produced in 2003 or 2004, but not officially recognized by IUPAC. Now a second team has also confirmed its production so they are hoping that it will be recognized officially.

PetTastic
2013-Sep-26, 10:58 PM
Thanks for the help.
I was looking at a subplot where unscrupulous aliens are involved in extremely antisocial methods of gold production.
Fission products of element 115 being a semi-plausible route to gold (pinch of salt required).

I was looking at the uranium or plutonium + neutrons -> Americium.
Americium + calcium -> ununpentium
A half-life of 220ms + a bit of gravitational time dilation sounds a semi-plausible route to dumping lots of energy in a core collapse.

Nowhere Man
2013-Sep-26, 11:12 PM
One of Poul Anderson's Polesotechnic League books had a somewhat similar idea as a plot element; IIRC, there was a planet that had been in a distant orbit around a star that went nova, and deposited a bunch of island of stability atoms on the surface of this planet.

Mirkheim.

Fred

kzb
2013-Sep-27, 11:46 AM
Thanks for the help.
I was looking at a subplot where unscrupulous aliens are involved in extremely antisocial methods of gold production.
Fission products of element 115 being a semi-plausible route to gold (pinch of salt required).

I was looking at the uranium or plutonium + neutrons -> Americium.
Americium + calcium -> ununpentium
A half-life of 220ms + a bit of gravitational time dilation sounds a semi-plausible route to dumping lots of energy in a core collapse.

Only value of gold is due to its rarity, so it would be self-defeating to produce planetary masses of the stuff.

How about this instead: it's not gold that is the valuable product, it is the superheavy isotope itelf. Supernovae might be the only way of producing it economically.

Imagine that one or more superheavy isotopes turn out to have both long half-lives and are fissionable. Furthermore, the critical mass is much smaller than currently known fissionable nuclides, and the energy per unit mass is also significantly greater. What you have here is not gold, but something more valuable: interstellar transport fuel. It could be used itself, or it could be the fission trigger for a fusion reaction.

I don't think this scenario is actually disallowed by present knowledge either. Of course it could be eventually disallowed by advances in science, but then a lot of SF has fallen foul of that.

BigDon
2013-Sep-27, 12:40 PM
Only value of gold is due to its rarity,

Sez the guy who has never been around masses of it...

It does things to you. Odd things that you obviously haven't experienced. I guarantee if you were chatting it up with the guys at work and I walked in and laid a polished ingot on your desk everybody would shut up and pay attention.

You don't get that effect with an ingot of aluminum.

Swift
2013-Sep-27, 01:25 PM
You don't get that effect with an ingot of aluminum.
You might have in 1885 (http://en.wikipedia.org/wiki/Hall-H%C3%A9roult_process#History).

Prior to the Hall–Héroult process, elemental aluminium was made by heating ore along with elemental sodium or potassium in a vacuum. The method was complicated and consumed materials that were in themselves expensive at that time. This meant the cost to produce the small amount of aluminium made in the early 19th century was very high, higher than for gold or platinum. Bars of aluminium were exhibited alongside the French crown jewels at the Exposition Universelle of 1855, and Emperor Napoleon III of France was said to have reserved his few sets of aluminium dinner plates and eating utensils for his most honored guests.

PetTastic
2013-Sep-27, 03:13 PM
I am dropping the whole subplot anyway. It was far too dull.
They wanted the gold as a zero-g building material, for hostile environments, like near a supernova remnant, full of nasty isotopes.
Would you prefer to be behind a wall of alluminum or a wall of gold, while mining a hot nebula?

Darrell
2013-Sep-30, 03:53 PM
Only value of gold is due to its rarity, so it would be self-defeating to produce planetary masses of the stuff.

Not so. Gold has many very useful applications, due to its intrinsic physical properties, for which it is better suited, except for price, than most, in some cases any, other materials. The value of gold would certainly drop if it were no longer rare, but it would still be a valuable resource. You'll find gold used in applications where performance is considered to be more important than the added cost. Like satellites and space stations, high end electronics of all sorts, etc.

cjameshuff
2013-Oct-03, 11:03 PM
Despite its inflated cost due to its appeal for other uses, about 10% of world gold production goes to industrial uses. It's not just in high-end electronics. Gold plating is very widely used in electrical contacts, even in low-cost electronics. I'm currently working with a blood glucose meter. The test strips, little disposable use-once bits of plastic...use gold conductors and contacts. For reliable low-resistance contact on one end, and chemical inertness on the other.

Bottom-end electronics so cheap they place un-packaged chips directly on the board under a dollop of epoxy generally must gold-plate the board so they can properly bond the wires. Those wires are themselves very often gold. Gold has unique properties that make it useful for the wire-bonding process used to connect to silicon chips...aluminum and copper can be used, but with relative difficulty.

And on the high end, gold coatings and conductors are very widely used in test and lab equipment. Gold's seeing quite a bit of use in nanotech, and as a catalyst for certain exotic processes.

ShinAce
2013-Oct-04, 02:48 PM
I actually see very few quality connectors plated with gold. Typically, they're plated with nickel for its corrosion+wear resistance.

Gold is easy to rub off.

cjameshuff
2013-Oct-04, 04:56 PM
I actually see very few quality connectors plated with gold. Typically, they're plated with nickel for its corrosion+wear resistance.

Gold is easy to rub off.

Gold's even more corrosion resistant, and its softness makes for low resistance, highly repeatable contacts. Wear resistance can be improved with alloys...commonly with nickel.

A quick check of my desk shows not a single USB connector that doesn't have gold plated contacts. SD card connectors? Gold plated. The signal-carrying contacts on my oscilloscope's connectors, CPU pins/pads, RAM module pads, etc...almost universally gold plated.

Connector shields are generally nickel plated. A nickel plate is often used under the gold plate (the common ENIG process is electroless nickel under immersion gold). I've generally only seen nickel used as a cheaper but lower-quality alternative, though it might also see more use in applications with high cycle counts.

Grashtel
2013-Oct-06, 11:34 AM
I am dropping the whole subplot anyway. It was far too dull.
They wanted the gold as a zero-g building material, for hostile environments, like near a supernova remnant, full of nasty isotopes.
Would you prefer to be behind a wall of alluminum or a wall of gold, while mining a hot nebula?
Is the setup mass or volume limited? If its mass limited then aluminium, the added thickness will help catch secondary radiation and the lower atomic mass will cut down on bremsstrahlung radiation production, an even better choice would be something rich in low atomic mass elements like water/ice or plastic

PetTastic
2013-Oct-07, 02:29 AM
Is the setup mass or volume limited? If its mass limited then aluminium, the added thickness will help catch secondary radiation and the lower atomic mass will cut down on bremsstrahlung radiation production, an even better choice would be something rich in low atomic mass elements like water/ice or plastic

Alluminum looks tricky to refine in space. Hydrogen impurities make it brittle.

Also, I was assuming the hot plasma of a nebula would be highly corrosive, and the alluminum would not develop a stable oxide layer like on earth.
In the lab gold recrystalises when exposed to radiation, expelling impurities as the crystals grow, making it almost self-repair radiation damage.

cjameshuff
2013-Oct-07, 03:49 AM
Alluminum looks tricky to refine in space. Hydrogen impurities make it brittle.

Why would it get more hydrogen impurities in space? You can't find a single source of aluminum ore on Earth that isn't surrounded by hydrogen compounds, even the air contains water vapor. In space, you'd need to specifically hunt down bodies with deposits of ices to find anything with hydrogen, and would likely be processing the aluminum in vacuum.



Also, I was assuming the hot plasma of a nebula would be highly corrosive, and the alluminum would not develop a stable oxide layer like on earth.

The hot plasma of a nebula is still hard vacuum. The worst you could expect would be some eventual surface contamination. Considering that oxygen is likely to be one of the more abundant elements in the nebula, if the density of the nebula is high enough, you'd probably eventually get the usual oxide coat, maybe with some carbon compounds mixed in.

Low Earth orbit is within the upper reaches of the atmosphere...there's a lot of monatomic hydrogen and oxygen there, probably at higher densities than you're going to find in any nebula. Long-term exposure does actually pose some concern for some materials, and several experiments have been run testing such things.



In the lab gold recrystalises when exposed to radiation, expelling impurities as the crystals grow, making it almost self-repair radiation damage.

That doesn't sound like self repair to me, it sounds like inclusion formation and a dramatic drift of physical properties as crystal size and composition changes. Not that you'd want to be using gold as a structural material anyway. And you obviously have to have thick enough shielding that the inner side isn't exposed to much radiation. Even if you have so much radiation that it substantially physically weakens the outer portions of the shielding, you'll still have a substantial thickness that is unaffected.

Gold really isn't a good radiation shield. Dense heavy metals tend to produce a lot of secondary radiation and aren't that great from a mass standpoint, their main benefit is that they can be made relatively thin. Aluminum's a decent radiation shield, it produces some secondary radiation but can double as a structural material. Carbon's better, though graphite in particular can absorb and store dangerous amounts of energy from some kinds of radiation, releasing it later as heat. Carbon compounds with lots of hydrogen such as polyethylene are some of the best practical materials found.

I'm with Grashtel, for a given mass of shielding I'd rather have aluminum than gold, and I'd rather have polyethylene than aluminum. Best would be a layered composite like graded-Z shielding (http://en.wikipedia.org/wiki/Radiation_protection#Graded-Z_shielding).

PetTastic
2013-Oct-07, 03:55 PM
I was wrong about aluminium becoming brittle when absorbing hydrogen, it looks like it is one of the few metals that is relatively immune.

Space is a hydrogen environment. Everything is saturated to equilibrium point with hydrogen.
Away from Earth, most space enviroment don't contain enough oxygen to restore the oxide layer if it is being eaten away by hot ionised hydrogen.

Most metals recrystallise when exposed to radiation, but gold looks to be one that deforms the least, aluminuim looks quite bad because any contamination will form harder crystals then the pure metal, pushing it aside.

cjameshuff
2013-Oct-07, 04:52 PM
Space is a hydrogen environment. Everything is saturated to equilibrium point with hydrogen.
Away from Earth, most space enviroment don't contain enough oxygen to restore the oxide layer if it is being eaten away by hot ionised hydrogen.

Equilibrium with a good vacuum. And hydrogen won't reduce aluminum oxide...it goes the other way around. If you disrupt the oxide coating, aluminum will take the oxygen from water, releasing the hydrogen as a gas. Notice how asteroids aren't coated with metallic aluminum, elemental silicon, etc.



Most metals recrystallise when exposed to radiation, but gold looks to be one that deforms the least, aluminuim looks quite bad because any contamination will form harder crystals then the pure metal, pushing it aside.

It takes very high levels of radiation or extreme amounts of time for physical changes like this to be an issue. And why is it a problem if the outermost layers of your shielding recrystallize a bit? It'll still shield radiation just as well.

PetTastic
2013-Oct-08, 07:15 PM
This is getting a bit off topic, but who cares.

Interstellar asteroids will have surface temperatures, down as low as 3.8K.
That is way below both the tripple point and melting point of hydrogen.
Any asteroid worth mining will have enough surface gravity, to have all its voids filled with hydrogen frost.
(The idea of gravitational cooling is interesting. Hot atoms have enough enery to escape, cooler atoms/particles fall back.)

Room temperature hydrogen will not effect aluminium oxide, but in much of the interstellar medium, the hydrogen has kinetic energies equivalent to 8000 kelvin or more, ample to either punch through to oxide layer or decomposes it.

Radiation-induced crystallisation is one of PetTastics pet subjects.
To make atoms or molecules mobile in a crystal the photon only needs to overcome the energy of fusion.
For ice (6 kJ/mol) this is less than 1 electron volt, red/geen light light will do it easy.
For nontransparent substances, you need photons with enough energy to penetrate.
For stressed, deformed or crystals with an impurity gradient, the process is fast. Crystal surfaces migrating at 100 microns per hour (80cm per year) using classroom safe radiation sources. (That paper was 30 years ago, so the meaning of classroom safe may have changed)