Superconductivity, and especially room temperature superconductivity, has been a holy grail of sorts, which the scientific community has sought for decades. Superconductors are materials which are capable of conducting electricity for an indefinite period of time without exhibiting resistance. This lack of resistance could revolutionize electricity transmission through a grid’s power lines, where as much as 10 percent to 15 percent of electricity dissipates as resistive heat loss. Currently, superconductors are used in limited applications including magnetic resonance imaging (MRI) machines, which provide medical imaging of patients by pulsing radio wave energy through a magnetic field created with the use of superconducting magnets. Superconducting magnets are also used to keep particles perfectly aligned for high-energy physics experiments, such as are conducted at the Large Hadron Collider at CERN.
The discovery of superconductivity dates back to 1911 when Dutch physicist Heike Kamerlingh Onnes observed the phenomenon in mercury, but research and development in the field started heating up in the late 1980s. On July 28th, 1987, then-U.S. President Ronald Reagan unveiled an 11-point initiative to accelerate the commercial development of superconductors in America. This initiative, which included a call for the U.S. Patent and Trademark Office to expedite patent grants related to superconductor technologies, was encouraged by research performed by that year’s co-winners for the Nobel Prize in Physics, J. Georg Bednorz and K. Alexander Müller. Bednorz and Müller demonstrated superconductivity in ceramic materials which were a full 12°C (53°F) warmer than previously known. This temperature was still only 35 degrees greater than absolute zero, but the discovery jump-started development activities in the superconductivity sector, with many scientists hoping that the idea of room temperature conductivity could eventually be realized.
The incredible energy demands required to turn known materials into superconductive ones has made widespread development of superconductivity an elusive goal. But superconductivity is once again in the news thanks to recent news out of Cornell University, which indicates that after nearly two decades of research the world’s first self-assembling gyroidal superconductor has been realized. The gyroid configuration, resulting in a complex cubic structure containing various spirals as well as two separate interpenetrating volumes, could create superconductors with entirely novel property profiles.
The Cornell research team was able to create the self-assembling gyroidal superconductor with the use of niobium nitride (NbN), a known superconducting material. Like many inventions, this discovery was aided by a bit of good luck in the form of failure. Researchers first heated NbN to a temperature of 700°C (1292°F) and cooled it to room temperature before testing it as a superconductor, but the NbN failed to exhibit superconducting capabilities. The same material was then heated to 850°C (1562°F), cooled to room temperature and tested, which is when the NbN self-assembled into a gyroidal superconductor. When the research team later tried to create the same effect by heating the NbN material directly to 850°C, they found that the gyroidal configuration wouldn’t form without the previous heating and cooling steps. Without performing the same test on a failed material, the Cornell scientists wouldn’t have come across this breakthrough, which the team published in a late January issue of Science Advances.
This latest step forward in the development of organic superconductors comes months after another major advance in superconducting, which has brought the scientific world one step closer to the reality of room temperature superconductivity. Research conducted at the Max Planck Institute for Polymer Research and the Johannes Gutenberg University, both situated in Mainz, Germany, has led to the development of a material made from hydrogen sulfide (H2S) that can conduct electricity without resistance at temperatures as high as -70°C (-94°F), a temperature which is about 19°C warmer than the coldest known temperatures recorded in Antarctica. To stabilize the molecular bonds between hydrogen and sulfur, the hydrogen sulfide material was placed under extremely high pressures of up to 1.5 million bar, about half of the pressure that exists within the Earth’s core.
The Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, is also focused on superconductor developments and researchers there have recently demonstrated the use of laser pulses directed at a material to make it superconductive at higher temperatures. Researchers focused on the use of carbon and potassium buckyballs, which are known superconductors when chilled to a temperature of -253°C (-423°F). When the buckyballs were pulsed with mid-infrared optical laser light, they became superconductive at a higher temperature of -173°C (-279°F). Perhaps most interestingly, the laser pulses caused the buckyball material to vibrate at lower temperatures and lose its superconductive abilities, indicating that laser pulse-enabled superconductivity is specifically well-suited for high temperature applications.
Ironically, despite the use of superconducting magnets in MRI machines, magnetic fields themselves can be disruptive to superconducting materials. Atoms in superconductors are cooled and pressurized to form weakly bonded electron pairs, but those weak bonds are broken when exposed to magnetic forces. Physicists performing research at the High Field Magnet Laboratory (HFML) in Nijmegen, Netherlands, found that ultrathin layers of molybdenum sulfide (MoS2) are superconducting at low temperatures and in a high magnetic field. The internal high magnetic field of MoS2 is much higher than the external magnetic forces that can be produced by the HFML, which established a world record in 2014 when it produced a continuous magnetic field of 37.5 teslas, the highest such magnetic field produced by a non-superconducting magnet.
Around the globe, researchers are also looking into the use of novel materials to serve as superconductors. In recent months, phosphine (PH3) has been the subject of experiments which have hypothesized that the material, commonly experienced in the form of a flammable gas, has superconducting abilities. Research conducted by chemists at the University of Buffalo, and published late January in the Journal of the American Chemical Society, has resulted in the knowledge that the structures into which phosphine breaks down under high pressures, and not phosphine itself, are superconducting.
Elsewhere, experiments focused on graphene, a two-dimensional form of atom which already possesses low electrical resistance, have looked into the potential of adding lithium atoms to change the distribution of electrons in graphene and give it superconducting capabilities. This research was published last year by the Proceedings of the National Academy of Sciences for the United States (PNAS). However, the process by which graphene can be doped with lithium again requires incredibly low temperatures of about -265°C (-445°F), and the resulting graphene requires even lower temperatures than that to transition into its superconducting state.
Room temperature superconductivity is still a dream, but research continues. Taking a look at the patents issued in recent months by the U.S. Patent and Trademark Office, we have come across a few recently patented technologies in the field of superconducting. The world’s largest chemical producer, BASF SE (ETR:BAS) of Ludwigshafen, Germany, has increased its IP holdings in this sector with the recent issue of U.S. Patent No. 9257628, entitled Process for Producing Nanoparticles and Their Use in the Production of High-Temperature Superconductors. It protects a process for producing nanoparticles having a metal compound by preparing a water-in-oil (w/o) microemulsion with at least one metal precursor in a dispersed polar phase with the aid of a surfactant and adding a base as a precipitant to a continuous nonpolar phase. This process allows the production of nanoparticles of transition metal compounds which are mostly free of disturbing associated materials such as water or compounds from ionic surfactants which may prevent the formation of a homogenous high-temperature superconductor layer.
The British industrial power systems holding company Rolls-Royce (LON:RR) has been developing its own superconductor tech, as is evidenced by the issue of U.S. Patent No. 9231444, which is titled Superconductor Winding. It discloses a superconducting electrical machine having a superconducting winding at least partially surrounded by a magnetic flux guide which includes a binder loaded with a magnetic material, a pole face portion and a back iron portion having different loadings of magnetic material by volume; the magnetic flux guide has a relative magnetic permeability of between 5 and 20, and the pole face portion has a lower bulk relative permeability than the back iron portion. This innovation seeks to eliminate saturation effects which increase the magnetic field in superconductor windings which limits the performance of the machine.
Further highlighting the global nature of superconductor development is U.S. Patent No. 9177700, titled Precursor for a Nb3Sn Superconductor Wire, Method for Manufacturing the Same, Nb3Sn Superconductor Wire, and a Superconducting Magnet System, issued last November to Japanese company SH Copper Products Co. It claims a precursor for a Nb3Sn (niobium-tin) superconductor wire to be manufactured by an internal diffusion method and comprising a plurality of niobium-based single core wires coated with a copper-based coating, a plurality of tin-based single core wires coated with a copper-based coating and a cylindrical diffusion layer comprised of tantalum or niobium in which the plurality of niobium-based single core wires and tin-based single core wires are disposed in a specific ratio. This innovation address a shortcoming of internal diffusion methods to produce superconductor wires which increase the magnetic coupling of niobium-tin filaments, which in turn increases alternative current losses.