Laser Treatments Yield Smoother Metal Surfaces

Ever since the Bronze Age, metals have been cast in different shapes for different applications. Smooth surfaces that are resistant to corrosion are crucial for many of the present-day uses of cast metals, ranging from bio-implants to automotive parts. Yingchun Guan, from the A*STAR Singapore Institute of Manufacturing Technology (SIMTech) and her co-workers have shown how different laser-processing methods improve metal surfaces and protect them against corrosion1.
Laser processing involves scanning a high-intensity laser beam multiple times across the surface of a metal. Each scan by the laser beam ‘writes’ a track in the surface, which partially melts the metal. Consecutive tracks can overlap — the degree to which affects how well the melting caused by these tracks will smooth the surface of the metal. The scanning speed can also affect the surface melt.

Optical microscope cross-sections of the alloy surface show that increases in laser beam overlap during processing reduces the number of small cracks (top left, 25% overlap; top right, 50%; bottom left, 75%; and bottom right, 90%). (Credit: Copyright Elsevier 2013)

 

 Credit: The Agency for Science, Technology and Research (A*STAR),

Water Glides Freely Across 'Nanodrapes' Made from the World's Thinnest Material

Engineering researchers at Rensselaer Polytechnic Institute have developed a new drape made from graphene—the thinnest material known to science—which can enhance the water-resistant properties of materials with rough surfaces. These “nanodrapes” are less than a nanometer thick, chemically inert, and provide a layer of protection without changing the properties of the underlying material. The team of researchers, led by Rensselaer Professor Nikhil Koratkar, demonstrated how droplets of water encounter significantly less friction when moving across a surface covered with a nanodrape. - 

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Engineering researchers have developed a new drape made from graphene —- the thinnest material known to science —- which can enhance the water-resistant properties of materials with rough surfaces. (Credit: RPI)

Credit: Rensselaer Polytechnique Institute

Rensselaer

Bright, Laser-Based Lighting Devices

As a modern culture, we crave artificial white lights -- the brighter the better, and ideally using less energy than ever before. To meet the ever-escalating demand for more lighting in more places and to improve the bulbs used in sports stadiums, car headlights and street lamps, scientists are scrambling to create better light-emitting diodes (LEDs) -- solid state lighting devices that are more energy efficient than conventional incandescent or fluorescent light sources. 

Just one thing stands in the way: "droop," the term for a scientific problem related to LEDs currently in use. Droop refers to the fact that LED efficiency falls as operating currents rise, making the lights too hot to power in large-scale applications. Many scientists are working on new methods for modifying LEDs and making progress toward cooler, bigger and brighter bulbs. 

Photograph of bright white light (right) achieved using lasers in combination with phosphors next to an image of the phosphor with no illumination. (Credit: K.Denault/UCSB)

 Credit: aipadvances

Wagon-Wheel Pasta Shape for Better LED Lights

One problem in developing more efficient organic LED light bulbs and displays for TVs and phones is that much of the light is polarized in one direction and thus trapped within the light-emitting diode, or LED. University of Utah physicists believe they have solved the problem by creating a new organic molecule that is shaped like rotelle – wagon-wheel pasta – rather than spaghetti.

The rotelle-shaped molecule – known as a “pi-conjugated spoked-wheel macrocycle” – acts the opposite of polarizing sunglasses, which screen out glare reflected off water and other surfaces and allow only direct sunlight to enter the eyes.

Images of molecules for light-emitting diodes on the left are compared with similar shaped pasta on the right. The upper left electron microscope image shows spaghetti-shaped organic polymers now used for organic light-emitting diodes, or OLEDs. The lower left image shows new molecules -- created by scientists at the University of Utah and two German universities -- that are shaped like wagon-wheel or rotelle pasta and emit light more efficiently than the spaghetti-shape polymers. (Credit: Molecule images by Stefan Jester, University of Bonn. Pasta images courtesy Wikimedia Commons. Wagon wheel pasta image has been released into the public domain by its author, Fazalmajid at the English project. Spaghetti image has been licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license)

 Credit: University of Utah