Superconductors
Part One: What is a superconductor ?
A superconductor is a material that, in a specific environment, displays the property of superconductivity, which is characterized by two traits
The material drops to having ZERO electrical resistance
The material expels magnetic flux fields (Meissner effect)
The classical interpretation of superconductivity is such that the material displays perfect conductivity (zero electrical resistance), but the occurrence of the Meissner effect indicates that superconductivity is more complex
The Meissner effect
Superconductors currently have applications in cutting edge computer chip research, as well as in MRI machines
MRI machines can use superconducting materials to sustain high electrical currents (and hence sustain extremely high magnetic fields)
The stronger a magnetic field, the higher quality imagery the machine can provide to doctors
more low energy water molecules are affected
fewer low energy water molecules will be excited by radio waves
higher resolution imagery
Superconductor Environments
Superconductors currently only exist at extremely low temperatures, such that a “high temperature superconductor” is classified as displaying those characteristic properties at temperatures above 30K (−243.15 °C)
liquid nitrogen boils at 77K
liquid helium boils at 4.2K
As of 2015, the highest critical temperature recorded for a superconducting material was 203K (for H2S), although high pressures of ~90gPa were required
90 gPa = 888231 atm = 13.05 x10^6 psi
Superconducting materials have a characteristic critical magnetic field
this basically means that the material is only able to expel magnetic fields to an extent, provided they are weaker than the critical magnetic field
when a material displays superconductivity, you can force it back to normal phase by subjecting it to a high enough magnetic field
Room Temperature superconductors
In recent days, many commentators have become excited by two papers that claim to document the production of a new superconductor that works at room temperature and ambient pressure. Scientists in Korea said they had synthesized a new material called LK-99 that would represent one of the biggest physics breakthroughs of recent decades.
copper doped lead phosphate system
critical temperature observed to be greater than 400K (127 °C)
“A real, working room-temperature superconductor which works at ambient pressure would be one of the holy grails of modern physics, unlocking major new developments in energy, transportation, healthcare, and communications,” said Mohammad Yazdani-Asrami of the University of Glasgow’s James Watt School of Engineering.
applications of room temperature superconductors
cheap MRI machines
don’t need a constant supply of liquid helium
national average cost of an MRI exam is $1325
drive down cost to patients and capital costs to hospitals
more compact and efficient motors
zero electrical resistance implies zero heat losses across a current
low loss power transmission
no heat losses from conductivity
