Sustainable Component Found For Superconducting Technologies

AZO Materials, AZOnetwork - news, posted on May 2 2023

Magnesium diboride (MgB2), a low-cost, non-toxic superconductor, is employed in electric motors, field magnets, and generators. However, making nanoscale boron (B) particles which are used to fabricate MgB2, is expensive. Now, scientists are hoping to address this problem by using high-energy ultra-sonication in 2-propanol, a highly viscous solvent, to create impurity-free, nm-sized B particles.

This approach is affordable and allows the fabrication of bulk MgB2 using high critical current density, a requirement for the sustainable generation of high-performance superconducting magnets.

Magnesium diboride (MgB2) is a binary compound that acts as a superconductor, which is a substance that provides no resistance to the electric current passing through it—at a moderate temperature of approximately 39 K (-234 °C). This temperature can be obtained with the use of comparatively cheaper neon coolants or liquid hydrogen.

Additionally, MgB2 is lightweight, cheap, and non-toxic, and its precursors—magnesium (Mg) and boron (B)—are abundant. Consequently, it can substitute traditional low-temperature superconductors that need costly liquid helium for cooling and exchange magnets depending on neodymium, a rare element, along with boron and iron.

MgB2 has an extensive range of applications, along with the generation of coils and magnets for nuclear magnetic resonance, magnetic resonance imaging, fault current limiters, magnetic drug delivery, electric motors, and transportation. As per studies, MgB2 is a good candidate for polycrystalline superconducting magnets as it features a high trapped magnetic field (TF) and good critical current density (Jc).

However, it suffers from poor magnetic flux pinning. To improve pinning, it is necessary to tune the pinning centers in MgB2—the boundaries of small crystals or grains that comprise MgB2. To end this, scientists have revealed how nano-sized B particles can be employed as B precursors to fabricate nano-sized MgB2 grains with high Jc and strong grain boundary pinning.

B nanoparticles are now generated by pyrolysis, ball milling, and sintering. However, these techniques suffer from limitations like poor cost-effectivity and low purity output, requiring improved substitutes.

To end this, a team of researchers headed by Prof. Muralidhar Miryala from Shibaura Institute of Technology (SIT), Japan, have found high-energy ultra-sonication as a cheaper substitute for refining coarse B powder that is dispersed in 2-propanol up to nanoscale sizes. Journal of Alloys and Compounds published this study on April 14th, 2023.

"In this technique, ultrasonic vibrations impart high speeds to B particles in the solvent, leading to collisions. The resulting friction and shear tearing, compression, and energy release by the collapse of tiny air bubbles produced during collision break down B particles to nanometer sizes."

-Prof. Muralidhar Miryala, Shibaura Institute of Technology

With 2-propanol as the solvent for B, the scientists ultrasonically refined affordable commercial B powder for 45 minutes to create oxide-free nm-sized B particles. Then, they used them to fabricate bulk MgB2 with limited oxide and without carbon impurities, exhibiting superconductivity at approximately 38.5 K.

Moreover, it established high Jc values of 500 and 380 kA cm-2 at 10 K and 20 K, respectively. The latter of these Jc values marked an enhancement of 80% compared to that for bulk MgB2 prepared from low-cost B powder and was at par with that for costly commercial B powder. The observed upsurge in Jc was owing to improved grain boundary pinning in MgB2 as showed by microstructural analysis, and theoretically reinforced by the Dew–Hughes theory.

Schematic of 2D axisymmetric Field Cooled magnetization simulation for MgB2 bulk with radius rB

FC magnetization simulations to estimate the trapped field values in P45 bulk with 10, 20, 30 and 40 mm diameter and 10 mm thickness.

Ultimately, the scientists conducted field cooling magnetization simulations, forecasting that a 10 mm-thick and 40-mm wide MgB2 disk prepared from ultrasonically refined B powder can show a high TF of 2.5 teslas. “These findings bring MgB2 superconducting magnets, which can be fabricated in the form of tapes, wires, and films, a step closer to their commercialization,” predicts Prof. Miryala.

Undeniably, with a sustainable and economical technique for producing high-performance MgB2 superconductors, the current work could reveal the possibility of MgB2 super magnets!

news link: https://www.azom.com/news.aspx?newsID=61216

Article link: https://www.sciencedirect.com/science/article/pii/S0272884222021162

DOI:10.1016/j.jallcom.2023.170146

Ref: Srikanth, A. S., et al. Tuning of grain boundaries in MgB2 by boron ultra-sonication in 2-propanol – A way to low-cost high-Jc bulk superconducting magnets, Journal of Alloys and Compounds, 955, 170146, 2023.

Authors: A. Sai Srikanth, M. Santosh, M. Jirsa, M. Muralidhar*

University: SIT

The sound of water: New refining technique makes cheaper superconductors a reality

EUREKALERT! AAAS ; NEWS RELEASE 19-JUL-2022

Superconductors could potentially phase out bulk magnets in machinery ranging from MRIs and CT scanners to electric motors. The catch? Conventional high-temperature superconductors are made up of expensive rare earth metals and have a long and complicated fabrication process. This has caused attention to shift to superconductors manufactured from magnesium diboride (or MgB2), which is lightweight, cheap, and easier to fabricate and mold into intricate shapes.

Previous research has shown that using nanoscale boron to make MgB2 results in better magnetic characteristics. However, commercial nanoscale boron is expensive. Ball milling, a popular method for refining boron introduces impurities which hinder the superconductor’s performance. Thus, there is a need for a low-cost method for the nanoscale refining of boron. Now, in a paper published in Ceramics International (version available online on 14 June 2022), a team of researchers from Shibaura Institute of Technology (SIT), led by Professor Muralidhar Miryala, solved this problem by outlining an all-new, low-cost, and efficient method for refining boron.

The team used a technique called ultrasonication, a technique that employs ultrasound waves to agitate particles in a sample. First, they placed commercially available crystalline boron in distilled water. This was then subjected to ultrasonic sound waves of 20 kHz. The researchers subjected the crystalline boron to the ultrasonic treatment for varying periods of time to see which time period would be ideal. The resulting superconductor samples were checked for impurities, microstructure, and magnetic properties.

“We found that our samples of MgB2 were around 95% pure, which is much higher than the ball milling method that only produced 75% purity. The samples had a refined microstructure and had a 35% improvement than other methods. All of this was achieved with only 30 minutes of ultrasonic treatment”, says Prof. Miryala. This makes this new method of ultrasonication using distilled water extremely efficient at refining boron without having to use expensive materials. It brings down the cost of making MgB2 superconductors while also improving their magnetic characteristics.

According to Prof. Miryala, “Although ultrasonication as a method has been explored before for refining, previous attempts have used ethanol or hexane. This increases the cost of the process. The use of distilled water brings down the cost while still being as good or even better than the previous mediums.”

A schematic view of ultrasonication, depicting the process of refining large boron particles to obtain nano-grained sintered MgB2 bulk.

Overall, this study represents a huge step forward in making superconductors easily available for commercial purposes in devices. In addition, the study also brings into focus the ultrasonication technique, which is currently in its early stages of development. “This new technique will create more avenues of research. Other researchers can work on the optimization of this method to bring out its complete potential as well as apply this technique in their respective fields,” comments Prof. Miryala.

The researchers are confident that their findings will make cheap superconductors a reality soon enough!

News Link: https://www.eurekalert.org/news-releases/959173

Article link: https://www.sciencedirect.com/science/article/pii/S0272884222021162

DOI: https://doi.org/10.1016/j.ceramint.2022.06.115

Ref: Sai Srikanth Arvapalli et. al., Novel ultra-sonic boron refinement in distilled water for cost-efficient fabrication of MgB2 bulk ceramic superconductors, Ceramics International, 48 (19), 28102-28111, 2022.

Authors: Sai Srikanth Arvapalli, Muralidhar Miryala*, Naomichi Sakai, Masato Murakami, Milos Jirsa

University: SHIBAURA INSTITUTE OF TECHNOLOGY

On the Road to Practical, Low-cost Superconductors with Unexplored Materials

Researchers from Japan report advantages of high temperature superconductivity in a mixed rare-earth elements systems prepared using trending techniques

Superconductors have tremendous appeal in power transmission applications due to their zero resistance. However, to bring classical metallic superconductors into superconducting state requires liquid helium as a coolant, which is costly. Now, scientists from Japan take things to the new level by demonstrating high temperature superconductivity in mixed rare-earth barium copper oxides fabricated using a popular technique, opening doors to their low-cost, industrial scale production for real-world applications.

Superconductors are something like a miracle in the modern world. Their unique property of zero resistance can revolutionize power transmission and transport (e.g., Maglev train). However, most of the conventional superconductors require cooling down to extremely low temperatures that can only be achieved with liquid helium, a rather expensive coolant. Material scientists are now investigating “high-temperature superconductors” (HTSs) that can be cooled to a superconducting state by using the significantly cheaper liquid nitrogen (which has a remarkably higher temperature than liquid helium).

Title: Trapped field values under applied fields of 1 and 0.5 T at 77K as a function of x for (Gd0.33Y0.33-xEr0.33+x)-123 samples (left). After maximum external field application, a part of it stays trapped in the superconducting bulk, making it a powerful permanent magnet (right).

Caption: Scientists systematically optimized the composition of (Gd0.33Y0.33-xEr0.33+x)-123 samples by tuning the ratio of Y and Er in the 211 precursor (specifically, x = 0, 0.05, 0.1, 0.15, and 0.2). The sample corresponding to x=0.2 showed the highest trapped field

Currently, a prospective HTS material for such an exploration is (RE)Ba2Cu3Oy, RE-123, where RE stands for “Rare Earth” elements such as yttrium (Y), gadolinium (Gd), erbium (Er), neodymium (Nd), or europium (Eu). These materials in the single-crystalline form are able to overcome physical constraints that weaken superconductivity, thereby opening doors to a variety of engineering applications.

In a recent study published in the Journal of Alloys and Compounds (doi: 10.1016/j.jallcom.2021.160535), a team of scientists (Sunsanee Pinmangkorn, Arvapalli Sai Srikanth,....) from Shibaura Institute of Technology, Japan, led by Prof. Muralidhar Miryala, a pioneer in the area of HTS, developed single-crystalline bulk superconductors that can trap magnetic fields within them in a manner similar to how ferromagnets (iron, nickel, cobalt) retain the magnetic field. “The trapped field is one of the most relevant parameters in many practical applications of bulk RE-123 and is related to the bulk diameter,” explains Prof. Miryala.https://www.eurekalert.org/news-releases/803131

Among the several techniques available for fabricating bulk RE-123, the team went for an infiltrated growth (IG) technique, in which solid (RE)BaCuO5 (RE-211) reacts with a Ba-Cu-O liquid phase to form the superconducting RE-123. Prof. Miryala lays down the motivation behind their approach: “IG technique produces RE-123 bulks without homogeneities, can be performed in air, and scaled up to industrial levels. Moreover, it provides a fertile ground for exploring ternary RE elements systems, which have not been studied until now.”

Recently, the team investigated the ternary (Gd0.33Y0.33-xEr0.33+x)-123 bulk system, optimizing its composition by tuning the ratio of Y and Er in the 211 precursor (specifically, x = 0, 0.05, 0.1, 0.15, and 0.2). The team characterized the superconducting phases in the samples using X-ray diffraction and measured the trapped field and superconducting transition temperature (Tc). Finally, they carried out microstructural and chemical analysis using field-emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDX).

The XRD proved the single-crystalline nature of the RE-123 bulks, with Tc values in the range (91.5-92) K, which were significantly above the boiling point of liquid nitrogen (77K), and the highest trapped field of 0.53 tesla was observed in (Gd0.33Y0.13Er0.53)-123 (x=0.2). FESEM and EDX identified finely dispersed (Gd, Y, Er) -211 particles in all samples, with an Er-rich precipitates distribution for x=0.2, the sample which also showed the best superconducting performance.

“The findings in our study provides a notion of how to implement a low-cost production of high-performance (Gd, Y, Er)BCO bulks for real-life applications such as magnetic levitation, superconducting bearing, flywheel energy storage, magnetic resonance imaging, rotary motors, drug delivery, and water purification,” comments a contemplative Prof. Miryala.

Looks like a superconducting future may not be too far!