Archive for December 6th, 2011

December 6, 2011

Molybdenite

molybdenite semiconductor

molybdenite memory

Molybdenite [mo-lib-de-nite] is a mineral (molybdenum disulfide, MoS2). Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure, which consists of a sheet of molybdenum atoms sandwiched between sheets of sulfur atoms. The Mo-S bonds are strong, but the interaction between the sulfur atoms at the top and bottom of separate sandwich-like tri-layers is weak, resulting in easy slippage as well as cleavage planes.

Molybdenite occurs in high temperature hydrothermal ore deposits. Important deposits include the disseminated porphyry molybdenum deposits at Questa, New Mexico and the Henderson and Climax mines in Colorado. Molybdenite flakes are being researched for their potential use in low power semiconductors.

December 6, 2011

Tweel

tweel

The Tweel (a portmanteau of tire and wheel) is an experimental tire design developed by the French tire company Michelin. The tire uses no air, and therefore cannot burst or become flat.

Instead, the Tweel’s hub connects to flexible polyurethane spokes which are used to support an outer rim and assume the shock-absorbing role of a traditional tire’s pneumatic properties.

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December 6, 2011

Airless Tire

Bridgestone Air-Free

Non-pneumatic tires (NPT), or Airless tires, are tires that are not supported by air pressure. They are used on some small vehicles such as riding lawn mowers and motorized golf carts. They are also used on heavy equipment such as backhoes, which are required to operate on sites such as building demolition, where tire puncture is likely. Tires composed of closed-cell polyurethane foam are also made for bicycles and wheelchairs. Airless tires generally have higher rolling friction and provide much less suspension than similarly shaped and sized pneumatic tires. Other problems for airless tires include dissipating the heat buildup that occurs when they are driven. Airless tires are often filled with compressed polymers (plastic), rather than air.

Michelin is currently developing an integrated tire and wheel combination, the ‘Tweel,’ that operates entirely without air. The automotive engineering department at Clemson University is developing a low energy loss airless tire with Michelin through the NIST ATP project. Resilient Technologies and the University of Wisconsin’s Polymer Engineering Center are creating a ‘non-pneumatic tire,’ which is basically a round polymeric honeycomb wrapped with a thick, black tread. The initial version of the tire is for the Humvee.

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