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Unlikely Superconductor Posted on 21 Mar 09:05

Weird Superconductor Leads Double Life

Understanding strontium titanate’s odd behavior will aid efforts to develop materials that conduct electricity with 100 percent efficiency at higher temperatures.
By Glennda Chui
March 20, 2018

Until about 50 years ago, all known superconductors were metals. This made sense, because metals have the largest number of loosely bound “carrier” electrons that are free to pair up and flow as electrical current with no resistance and 100 percent efficiency – the hallmark of superconductivity.

Then an odd one came along – strontium titanate, the first oxide material and first semiconductor found to be superconducting. Even though it doesn’t fit the classic profile of a superconductor – it has very few free-to-roam electrons – it becomes superconducting when conditions are right, although no one could explain why.

Now scientists have probed the superconducting behavior of its electrons in detail for the first time. They discovered it’s even weirder than they thought. Yet that’s good news, they said, because it gives them a new angle for thinking about what’s known as “high temperature” superconductivity, a phenomenon that could be harnessed for a future generation of perfectly efficient power lines, levitating trains and other revolutionary technologies.

The research team, led by scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, described their study in a paper published Jan. 30 in the Proceedings of the National Academy of Sciences.

"If conventional metal superconductors are at one end of a spectrum, strontium titanate is all the way down at the other end. It has the lowest density of available electrons of any superconductor we know about,” said Adrian Swartz, a postdoctoral researcher at the Stanford Institute for Materials and Energy Science (SIMES) who led the experimental part of the research with Hisashi Inoue, a Stanford graduate student at the time.

“It’s one of a large number of materials we call ‘unconventional’ superconductors because they can’t be explained by current theories,” Swartz said. “By studying its extreme behavior, we hope to gain insight into the ingredients that lead to superconductivity in these unconventional materials, including the ones that operate at higher temperatures.”

Dueling Theories

According to the widely accepted theory known as BCS for the initials of its inventors, conventional superconductivity is triggered by natural vibrations that ripple through a material’s atomic latticework. The vibrations cause carrier electrons to pair up and condense into a superfluid, which flows through the material with no resistance – a 100-percent-efficient electric current. In this picture, the ideal superconducting material contains a high density of fast-moving electrons, and even relatively weak lattice vibrations are enough to glue electron pairs together.

But outside the theory, in the realm of unconventional superconductors, no one knows what glues the electron pairs together, and none of the competing theories hold sway.

To find clues to what’s going on inside strontium titanate, scientists had to figure out how to apply an important tool for studying superconducting behavior, known as tunneling spectroscopy, to this material. That took several years, said Harold Hwang, a professor at SLAC and Stanford and SIMES investigator.

“The desire to do this experiment has been there for decades, but it’s been a technical challenge,” he said. “This is, as far as I know, the first complete set of data coming out of a tunneling experiment on this material.” Among other things, the team was able to observe how the material responded to doping, a commonly used process where electrons are added to a material to improve its electronic performance.

‘Everything is Upside Down’

The tunneling measurements revealed that strontium titanate is the exact opposite of what you’d expect in a superconductor: Its lattice vibrations are strong and its carrier electrons are few and slow.

“This is a system where everything is upside down,” Hwang said.

On the other hand, details like the behavior and density of its electrons and the energy required to form the superconducting state match what you would expect from conventional BCS theory almost exactly, Swartz said.

“Thus, strontium titanate seems to be an unconventional superconductor that acts like a conventional one in some respects,” he said. “This is quite a conundrum, and quite a surprise to us. We discovered something that was more confusing than we originally thought, which from a fundamental physics point of view is more profound.”

He added, “If we can improve our understanding of superconductivity in this puzzling set of circumstances, we could potentially learn how to harvest the ingredients for realizing superconductivity at higher temperatures.”

The next step, Swartz said, is to use tunneling spectroscopy to test a number of theoretical predictions about why strontium titanate acts the way it does.

SIMES is a joint SLAC/Sanford institute. Theorists from SIMES and from the University of Tennessee, Knoxville also contributed to this study, which was funded by the DOE Office of Science and the Gordon and Betty Moore Foundation’s Emergent Phenomena in Quantum Systems Initiative.

Citation: A. Swartz et al., PNAS, 30 January 2018 (10.1073/pnas.1713916115)

For questions or comments, contact the SLAC Office of Communications at communications@slac.stanford.edu.


SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, Calif., SLAC is operated by Stanford University for the U.S. Department of Energy's Office of Science.

SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. 

 


IKO ADDING NEW DUST PROTECTION FOR LINEAR LINEUP Posted on 28 Feb 12:52

Dust protection. A dust protective C-Wiper can be mounted to the outside of the end seal, ensuring operation in environments where metal chips are spattering. After 1,000 km of operation, the C-Wiper prevented foreign substances from entering the slide unit with no damage to the end seal.

Maintenance-free. The MX specification integrates IKO's proprietary C-Lube lubrication system. As the cylindrical rollers circulate, lubricant is distributed to the loading area through the rollers along the track rail. Lubrication is properly maintained in the loading area for over 12,500 miles, reducing valuable time spent lubricating hard to reach parts.

High load capacity. The MX models utilize rows of cylindrical rollers to provide a greater contact area than slides that use steel balls. They also maintain high rigidity in every direction. As a result, bearings deliver high load capacities––up to 674 kN for dynamic loads and 1,300 kN for static loads.

Mounting dimensions are compatible with MH and LWH ball type series. If you want to transition from a ball type to a roller type, your mounting dimensions do not need to change.

For more information, visit http://ikont.com/catalogs/linear-motion-rolling-guide-series/blue/1559E_MX_LRX.pdf

MX

About IKO

IKO is a world leader in needle roller bearings and linear motion rolling guides and was the first Company in Japan to initiate technical developments on the needle roller bearing. Compared with traditional ball bearings and other roller bearings, the needle roller bearing is small in size and light, but offers a very high load capacity. Needle roller bearings help to make the overall equipment more compact, thus saving money and resources. IKO has also developed a range of linear motion rolling guide units for applications that require extremely high levels of precision, such as semiconductor manufacturing equipment. 


NSK's NEW SUPER SPIN TOP Posted on 28 Feb 12:47

NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President and CEO: Toshihiro Uchiyama) Group company, NSK Micro Precision Co., Ltd. (Brand name: ISC), has developed a unique spinning top that incorporates several super smooth precision bearings. The top can stay upright and spin for about 8 minutes even on rough surfaces (weighted ring model). The top is on sale today.

See it on YouTube® https://youtu.be/TUIvatHdwhs New Window

In Japan, koma-asobi (top spinning) is a traditional game that has been enjoyed for over four centuries. Children often play with tops during the New Year's holiday, and some claim they bring good luck. The shape of the traditional spinning top has evolved over the years, but the core physical principles of play have not. With a playful spirit, and dedication to excellence, NSK Micro Precision endeavored to further evolve the spinning top, ultimately arriving at a completely game-changing design. The new top features the high precision bearings favored by Yo-yo world champions, and the central shaft doesn't rotate. This allows the top to spin for about 8 minutes on most surfaces, far longer than your average top (typically 2-3 minutes on unsmooth surfaces).

This new toy follows NSK Micro Precision's hit fidget spinner, the Saturn Spinner, which sold out on the first day. The company hopes that these toys will spark the interest of children and adults alike in the mysteries of science and technology.

NSK Spintop On Sale Now

Available January 10, 2018
Price 16,800 Yen (incl. tax, weight ring model)
Vendor Spin Gear Yo-yo Shop New Window

Product Features

Normally, spinning tops are made from a single piece of material, and the top body and center axis portion rotate as one when spun. The tip of the center portion touches the ground, so friction between the two surfaces gradually slows the top until it falls. In contrast, the NSK Micro Precision spintop has two precision bearings on the central shaft, so the shaft effectively moves separate from the body. When spinning the top, only the body rotates, so rotation-slowing friction doesn't affect the body as with regular tops. This unique shaft and bearing combination allows the top to spin unhindered, even on rough surfaces. It also enables the top to be picked up and even inverted.

Product Features

NSK Micro Precision Co., Ltd., an NSK Group company, develops, manufactures, and sells miniature ball bearings (deep groove, angular). The company's products are used in computer components, dental and medical instruments, monetary devices, fishing gear, and a wide variety of other applications.

NSK Micro Precision has employed its expertise in bearings to develop fidget spinners, yo-yos, and spinning tops as its contribution to showing the cool side of Japan's manufacturing. The company also supports the World Yo-yo Contest and the Japan Open Yo-yo Championship (JOYC).

Contact: NSK Micro Precision Co., Ltd. Headquarters
TEL:03-5283-7420
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