High Temperature Superconductivity

1. High Temperature Superconductivity http://www.rise.org.au/info/Tech/scon/image001.jpg Allen Moussa

2. Single crystal X-ray diffraction technique can be used to determine crystal structure, a collimator is used to narrow the X-ray beam as show in the image • When X-rays reflect off layers in a crystal they produce patterns of destructive and constructive interference on photographic film (see image) • X-rays have a small enough wavelength to allow the atomic spacing between planes in crystals to act as a diffraction grating single crystal x-ray diffraction X-rays produce an interference pattern after reflecting off several layers of atoms in a pure crystal. The superposition of many reflected waves results in a pattern of bright spots on the photographic film, this pattern is analyzed. http://www.teachnet.ie/dkeenahan/images/xrayCrystalDiffraction.jpg

3. SEM - Scanning electron microscope • High powered electron beams are fired at the surface of the sample in a raster like fashion providing a 3D image of the surface • Electrons are reflected from the surface of the crystal when hit by the beam, this causes the emission of X-rays which are then detected • The electron beam causes the sample to displace inner-shell electrons,a higher energy electron fills the shell and energy is released http://media-2.web.britannica.com/eb-media/88/113688-004-B14FDB14.gif

4. powder x-ray diffraction • This technique requires the sample to be grounded into a finely powdered material and placed onto a diffractometer • Involves diffraction of a monochromatic X-ray beam from a sample containing an enormous number of tiny crystals having random orientation • A detector moves around the crystal to measure the intensity of X-rays at different angles, and plots a relative intensity pattern at these different positions http://folk.ntnu.no/krill/mineralogee/7-filer/xrd.gif

5. advances leading to HTS - ceramics • Heike Onnes the ‘farther of superconductivity’ began experimentation with pure metals such as mercury • Ceramic materials are normally insulators, although in 1986 a layered ceramic compound (Ba-La-Cu oxide)was created that superconducted at the highest temperature then known, 30 K • The problem with ceramics is that they are hard and brittle making it a challenge to make long, flexible wires out of them • Improvements in transmission electron microscopy have led to increased understanding of the crystalline structure of high temperature superconductors The Meissner effect can be used to identify properties of different types of HTS, by analyzing the HTS critical magnetic field strength http://www.magnet.fsu.edu/education/tutorials/magnetacademy/superconductivity101/images/superconductivity-meissner.jpg

6. advances leading to HTS - BCS theory • High temperature superconductors are made from ceramic materials largely containing copper oxide • The discovery of HTS meant that liquid nitrogen could now be used as opposed to liquid helium which is expensive to produce • BSC provided a firm understanding of the mechanism underlying low temperature superconductivity which eventually led to HTS At critical temperatures electrons attract the positive ions and create a region of excess positive charge, which than attracts another nearby electron, these two electrons are now cooper pairs http://www.cartage.org.lb/en/themes/sciences/physics/SolidStatePhysics/Superconductivity/Fundamentals/fig5.gif

7. Superconductor applications - maglev train • Maglev (magnetic levitation) trains use the Meissner effect, they use superconducting magnets in the train and levitation coils attached to the side track • High temperature superconductors are now being used and this means that liquid nitrogen can be utilized, which lowers the operating cost significantly • Since there is no friction with the track air resistance is the only force slowing the train, the front has a streamlined design to reduce drag Image 1 Image 2 In image 1 the levitation coils attached to the track have north and south polarities due to Lenz’s law that they must oppose the change in flux caused by the moving superconducting magnets In image 2 a substation constantly reverses the polarity of the levitation coils so that each superconducting magnet is either being repelled of pulled along the track http://www.rtri.or.jp/rd/maglev/html/english/maglev_frame_E.html http://www.rtri.or.jp/rd/maglev/html/english/maglev_frame_E.html

8. Superconductor applications - SQUID • SQUID magnetometers are so sensitive that they can detect magnetic fields caused by electrical currents produced by the brain • SQUIDs use a superconducting ring to resists changes in flux from the external environment and give recordings of magnetic field strength • SQUIDs provide a safer method to analyze electrical currents in the brain, this has allowed researchers to further understand the brain differences between individuals with a disorders and those without http://superconductors.org/uses.htm#squid1

9. future applications - computers http://www.superconductors.org/Uses.htm

10. future applications - transmission of electricity http://www.azom.com/Details.asp?ArticleID=942#_What_are_the

11. future applications - motors and generators http://www.superconductors.org/Uses.htm

12. future applications - superconducting magnetic energy storage http://www.accel.de/pages/2_mj_superconducting_magnetic_energy_storage_smes.html

13. Bibliography • http://folk.ntnu.no/krill/mineralogee/7.htm • Physics Contexts 2 - Textbook • http://serc.carleton.edu/research_education/geochemsheets/techniques/SXD.html • http://www.trifieldmeter.com/magdone.htm • http://www.azom.com/Details.asp?ArticleID=1123#_What_is_SMES • http://www.eere.energy.gov/de/supercon_magnetic.html • http://en.wikipedia.org/wiki/Superconducting_magnetic_energy_storage#Technical_challenges • Mac os x dictionary application • http://en.wikipedia.org/wiki/High_temperature_superconductor • http://en.wikipedia.org/wiki/X_ray_diffraction • http://superconductors.org/History.htm • http://science.uniserve.edu.au/school/curric/stage6/phys/ideas/ • http://www.hsc.csu.edu.au/physics/core/implementation/9_4_4/944net.html • http://www.ornl.gov/info/reports/m/ornlm3063r1/contents.html • http://www.cartage.org.lb/en/themes/Sciences/Physics/SolidStatePhysics/Superconductivity/Fundamentals/fundamentals.htm • http://www.tlchm.bris.ac.uk/webprojects2000/igrant/hightctheory.html • http://www.hscphysics.edu.au/home • http://hyperphysics.phy-astr.gsu.edu/HBASE/Solids/hitc.html • http://www.howstuffworks.com/framed.htm?parent=superconductivity.htm&url=http://www.ornl.gov/reports/m/ornlm3063r1/contents.html • http://www.walter-fendt.de/ph14e/singleslit.htm • http://www.amsc.com/aboutus/super_fact.cfm • http://www.wmi.badw-muenchen.de/FG538/projects/P4_crystal_growth/index.htm • http://inventors.about.com/od/sstartinventions/a/superconductors_4.htm • Get smart Physics - written by Winston Grossley • Alasdair Hey - the physics guy