- 3525 - SUPERCONDUCTIVITY - at room temperatures? Superconductivity could bring us near free electricity, levitated train travel, MRIs in every doctors office and who knows what else. The challenge is getting superconductivity to work at high enough temperatures that it can be commercially produced.
---------------- 3525 - SUPERCONDUCTIVITY - at room temperatures?
- We are making progress. Superconductivity is occurring at ever higher temperatures. When we know why, a breakthrough will be imminent ,and, that physicists with be eminent.
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- Superconductivity is a property of metals to carry electricity with zero resistance. No loss of power. No losses due to heat. It is amazing. The only problem is it occurs in materials frozen to near Absolute Zero, - 273 Centigrade.
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- A loop of this material at 4 Kelvin would carry an electric current for ever without adding any additional energy to keep it going. Several loops of this material could create an electromagnet that would not draw any power once it was started.
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- If we could get superconductivity to work at room temperatures we could have transmission lines that would send electricity across the country with zero power loss. We could have trains on magnetic railroad tracks that would levitate the entire train and send it along with little to no power to keep it running.
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- Magnetic Resonance Imaging could be available in every doctors office because MRIs could be cheap and readily available. Airport screening also comes to mind. So, what is stopping superconductors from going commercial?
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- Superconductivity only works at very low temperatures, close to Absolute Zero. It takes liquid helium to cool material down to these temperatures. Liquid helium is very expensive to produce.
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- Superconductivity was first discovered in Mercury in 1911. At 4 degrees Kelvin electric current would flow in the frozen metal with no resistance. Once current was started it is still flowing today. But, it took liquid helium coolant to get to those temperatures.
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- From that day on the search has been on to find materials that are resistance - free to electron flow at increasingly higher temperatures. Higher than 4 degrees Kelvin.
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- In 1954 Niobium - Tin was found to be superconductive at 18 Kelvin.
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- Nioblum is an element with 41 protons and 41 electrons. Abbreviated Nb in the Periodic Table and Nb(41) to designate the atomic number which is the number of protons. Tin is Sn (50). Tin has 50 protons in the atomic nucleus. The 50 electrons are in shells of 2 + 8 + 18 + 18 + 2 + 2 = 50
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- In 1986 a copper oxide was found superconductive at 35 Kelvin. LaBaCuO is the copper oxide. It is a compond of Lanthanum (57), and Barium (56), and Cu is Copper (29) and Oxygen (8)
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- In 2008 LaOFeAs was the first iron-based superconductor at 26 Kelvin.
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- Fe = Iron(26) As = Arsenic (33). Iron was not expected to be a good superconductor material because of its rich magnetic properties. “Cooper Pairs” of electrons are what creates super conduction and a strong magnetic field will break down Cooper Pairs. So, iron was not used in the research for a long time. This material is a surprise and shows that we do not understand superconductivity well enough.
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- In 2001 Magnesium Diboride was superconductive at 39 Kelvin.
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- Magnesium(12) shells are 2+8+2 = 12 was discovered in 1808. When combined with water is forms milk of magnesia. It is lightweight (12) and is used in building airplanes. It burns brightly in fireworks. It is essential fertilizer for most plants. Diboride, I do not know what that is.
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- In 2008 SmFeAsO was superconductive at 55 Kelvin. Sm = Samarium (62).
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- In 1987 Yttrium Barium Copper Oxide was superconductive at 92 Kelvin.
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- Yttrium is Y(39). Barium is Ba(56). 92 Kelvin was a temperature above the boiling point of liquid Nitrogen and liquid Nitrogen was a lot cheaper coolant to use than liquid Helium.
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- In 1995 Thallium doped Mercury cuprate went superconductive at 138 Kelvin. Thallium is Ti(81) and Mercury is Hg(80)
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- In 2010 everyone is still trying to produce the record high temperature superconductor material. The closer we can get to room temperature the cheaper and more successful a commercial application becomes.
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- How do these “high” temperature superconductors work? What is the physics that is going on?
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- We are still trying to figure this out. There seem to be two classes of superconductivity. One is iron-based discovered in 2008 at 55 Kelvin , and, the other is copper-oxide based discovered in 1986 found to work up to 138 Kelvin. These copper-oxide materials are called “ cuprates”. The problem with them is that although they operate at the highest temperatures cuprates are brittle and very hard to form into wires.
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- The physics theory we are working with is that superconductivity occurs because under certain conditions electrons can pair up in what is called “Cooper Pairs“. The pairing prevents electrons from bouncing off atoms in the lattice structure and loosing energy.
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- Somehow a negatively charged electron passing through a lattice structure of positively charged ions pulls nearby ions close creating a region of positive charge. The positive region attracts another electron to come through the lattice and pair with the first electron. At high temperatures, above 30 Kelvin, the heat energy, or vibration of atoms, is thought to break Cooper pairs apart. Superconductivity would therefore stop above 30 Kelvin temperatures.
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- When it was discovered that the cuprates of Lanthanum, Copper Oxygen, Barium, a brittle ceramic material, worked at 35 Kelvin some new theories about how superconductivity was working had to be found. La(57) Cu(29) O(8) Ba(56).
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- The process of doping these compounds seemed to make a difference. By replacing some of the atoms swapping out other atoms changed the number of electrons making superconductivity occur more easily.
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- Iron-arsenic compounds can come in two types, paramagnetic and anti-ferromagnetic. When anti-ferromagnetic the material’s magnetic fields of individual atoms line up in alternating directions. Anti-ferromagnetic material combined with doping seemed to raise the temperatures where superconductivity could occur.
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- A lecture at SSU on 11-15-10: Dr. Pei-Chun Ho, a scientist at Fresno State University gave a lecture on her experimentation at Fresno with the superconductivity:
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------------------ Pr Os4 Sb12
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----------------- Pr = Praseodymium (59) has 59 protons and an atomic weight of 140.91
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----------------- Os = Osmium (76) with 76 protons and atomic weight of 190.
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- Os 4 is an isotope of Osmium with the nucleus also having 4 neutrons. Osmium has electrons in the shells of 2 + 8 + 18 + 32 + 8 + 6 +2 = 76. The metal was discovered in 1803 named of the Greek word meaning smell. It combines with oxygen to produce a toxic odor. It is one of the hardest metals, along with Iridium. It is the least compressible element, along with Carbon. Its extreme hardness is used in pens, photograph needles, instrument pivot points, electrical contacts.
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---------------- Sb = Antimony (51) with 51 protons and an atomic weight of 121.75.
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- Antimony is a brittle, hard metal used in ceramics its electons are in shells : 2 + 8 + 18 + 18 + 2 + 3 = 51. Sb12 is an isotope with 12 neutrons in the nucleus.
- Another compound being studied is BaFe2As2P
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--------------- Ba = Barium(56) weight 137.34
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--------------- Fe2 = Iron (26) weight 55.85, plus 2 neutrons
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--------------- As2 = Arsenic (33) weight 74.9, plus 2 neutrons
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--------------- P = Phosphorus (15) weight 30.97
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- This material exhibits both anti-ferromagnetic and paramagnetic properties depending on degrees of doping. It is superconductive at 45 Kelvin.
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- You can imagine how complex these compounds are to work with. The crystalline structures are geometrically challenging to grow and to understand. Doping alters the lattice structures. Atoms come together in complex ways. Electrons navigate in the shells and somehow they find a combination where navigation is resistant - free.
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- Electricity flows freely, no loss of power, no thermal energy generated. There is a Nobel Prize for sure in someone’s future if they can discover the combination of materials that work at very high temperatures, above 273 Kelvin. And, to the physicists that can explain how this happens?
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- Cooper Pairs are being challenged as the only idea. There is really basic fundamental research at the Quantum Mechanical level involved here. That is why superconductivity is weird. If you are not confused you really do not understand the problem.
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March 29, 2022 SUPERCONDUCTIVITY - at room temperatures? 1224 3525
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