Category Physics

A nanophotonic incandescent light bulb demonstrates the ability to tailor light radiated by a hot object. Credit: Ognjen Ilic

How photonics can reshape the spectrum of light, and rehabilitate Edison’s light bulb along the way. The incandescent bulb is an example of a high temperature thermal emitter. It is very useful, but only a small fraction of the emitted light (and therefore energy) is used: most of the light is emitted in the infrared and in this context wasted. Now, MIT researchers describes another way to recycle light emitted at unwanted infrared wavelengths while optimizing the emission at useful visible wavelengths.

While as a proof-of-concept the research group built a more energy-efficient incandescent light bulb, the same approach could also be used to improve the performance...

Stanford researchers are using spiky nanoparticles of graphene-coated nickel to create a lithium-ion battery that shuts down when it’s too hot, then quickly restarts when it cools (1µ =1 micrometer). Credit: Zheng Chen, Stanford University

The new technology could prevent the kind of fires that have prompted recalls and bans on a wide range of battery-powered devices, from recliners and computers to navigation systems and hoverboards. “People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries,” said Prof. Zhenan Bao, chemical engineering, Stanford. It “can be shut down and revived over repeated heating and cooling cycles without compromising performance.”

A typical Li-ion battery consists of 2 electrodes and a liquid or gel electrolyte that c...

a) Coated rods are arranged along a sub­strate, like angled teeth on a comb. b) The teeth are then inter­laced. c) When indium and galium come into con­tact, they form a liquid. d) The metal core of the rods turns that liquid into a solid. The resulting glue pro­vides the strength and thermal/​electrical con­duc­tance of a metal bond. From “Advanced Mate­rials & Processes,” Jan­uary 2016

Experts in nanotechnology have developed a glue that binds metal to metal to glass to you-name-it, sets at room temp, and requires little pressure to seal. “MesoGlue was founded by Huang and two of his PhD stu­dents: They had a dream of a better way of sticking things together...

Coincidence spectrometer employed in the present work. The HPGe crystal (yellow) is located in close geometry to the target. Both the target and the HPGe detector are surrounded by a 16-segment NaI(Tl) annulus (green). The five-sided plastic scintillators used to reject cosmic-ray muons are not shown.

Stars shine because nuclear reactions in their interiors convert mass to energy at a rate of many million tons/ s. At the same time, these nuclear reactions change the composition of the matter in the stellar interior. Thermonuclear fusion takes place quiescently in stars that are much older than the Sun, and also explosively in novae and supernovae. To explain how stars work, we need to measure the rates of the important nuclear reactions...