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Post Info TOPIC: Glass in Space


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RE: Glass in Space
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Scientists 3D-print transparent glass

Scientists in Germany have successfully 3D-printed transparent glass.
Dr Bastian Rapp and his team from the Karlsruhe Institute of Technology spent two and half years developing the method.
They hope to print anything from photographic lenses and fibre optics to glass structures for buildings and rooftops for cars.

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Is glass a true solid?

Does glass ever stop flowing? Researchers at the University of Bristol and Kyoto University have combined computer simulation and information theory, originally invented for telephone communication and cryptography, to answer this puzzling question.
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Willow Glass
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 Ultra-thin glass can 'wrap' around devices

A new type of flexible ultra-thin glass has been unveiled by the company that developed Gorilla Glass.
Dubbed Willow Glass, the product can be "wrapped" around a device, said the New York-based developer Corning.

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Metallic glasses
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There are more than five sides to this story: In metallic glasses, researchers find a few new atomic structures

Drawing on powerful computational tools and a state-of-the-art scanning transmission electron microscope, a team of University of Wisconsin-Madison and Iowa State University materials science and engineering researchers has discovered a new nanometer-scale atomic structure in solid metallic materials known as metallic glasses.
Published May 11 in the journal Physical Review Letters, the findings fill a gap in researchers' understanding of this atomic structure. This understanding ultimately could help manufacturers fine-tune such properties of metallic glasses as ductility, the ability to change shape under force without breaking, and formability, the ability to form a glass without crystallising.

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Glass
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MIT researchers find a way to make glass that's anti-fogging, self-cleaning and free of glare.

One of the most instantly recognisable features of glass is the way it reflects light. But a new way of creating surface textures on glass, developed by researchers at MIT, virtually eliminates reflections, producing glass that is almost unrecognisable because of its absence of glare - and whose surface causes water droplets to bounce right off, like tiny rubber balls.
The new "multifunctional" glass, based on surface nanotextures that produce an array of conical features, is self-cleaning and resists fogging and glare, the researchers say. Ultimately, they hope it can be made using an inexpensive manufacturing process that could be applied to optical devices, the screens of smartphones and televisions, solar panels, car windshields and even windows in buildings.

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Title: Nanotextured Silica Surfaces with Robust Super-Hydrophobicity and Omnidirectional Broadband Super-Transmissivity
Authors: Kyoo-Chul Park, Hyungryul J. Choi, Chih-Hao Chang, Robert E. Cohen, Gareth H. McKinley, and George Barbastathis

Designing multifunctional surfaces that have user-specified interactions with impacting liquids and with incident light is a topic of both fundamental and practical significance. Taking cues from nature, we use tapered conical nanotextures to fabricate the multifunctional surfaces; the slender conical features result in large topographic roughness whilst the axial gradient in the effective refractive index minimises reflection through adiabatic index-matching between air and the substrate. Precise geometric control of the conical shape and slenderness of the features as well as periodicity at the nanoscale are all keys to optimising the multi-functionality of the textured surface, but at the same time these demands pose the toughest fabrication challenges. Here we report a systematic approach to concurrent design of optimal structures in the fluidic and optical domains, and a fabrication procedure that achieves the desired aspect ratios and periodicities with few defects, and large pattern area. Our fabricated nanostructures demonstrate structural superhydrophilicity or, in combination with a suitable chemical coating, robust superhydrophobicity. Enhanced polarisation-independent optical transmission exceeding 98% has also been achieved over a broad range of bandwidth and incident angles. These nanotextured surfaces are also robustly anti-fogging or self-cleaning offering potential benefits for applications such as photovoltaic solar cells.

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Gorilla Glass
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An ultra-strong glass that has been looking for a purpose since its invention in 1962 is poised to become a multibillion-dollar bonanza for Corning Inc.
The 159-year-old glass pioneer is ramping up production of what it calls Gorilla glass, expecting it to be the hot new face of touch-screen tablets and high-end TVs.
Gorilla showed early promise in the '60s, but failed to find a commercial use, so it's been biding its time in a hilltop research lab for almost a half-century. It picked up its first customer in 2008 and has quickly become a $170 million a year business as a protective layer over the screens of 40 million-plus cell phones and other mobile devices.

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Glass
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Glass as a High Energy Density Dielectric Material
Materials researchers at Penn State University have reported the highest known breakdown strength for a bulk glass ever measured. Breakdown strength, along with dielectric constant, determines how much energy can be stored in an insulating material before it fails and begins to conduct electricity. A bulk glass with high breakdown strength and high dielectric constant would make an ideal candidate for the next generation of high energy density storage capacitors to power more efficient electric vehicles, as well as other portable and pulsed power applications.
The highest dielectric breakdown strengths for bulk glasses are typically in the 4-9MV/cm range. The breakdown strength for the tested samples were in the 12MV/cm range, which in conjunction with a relatively high permittivity, resulted in energy densities of 35 J/cm³, as compared to a maximum energy density of 10 J/cm³ for polypropylene, the most common dielectric for pulsed power applications.

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Glass in Space
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It's easy: mix together some materials like sand, limestone and soda. Heat them above 2000o F. Then cool the incandescent liquid carefully so that crystals cannot form.

That's how you make glass.

Craftsmen on Earth have followed this basic recipe for millennia. It works. "Now we know it works even better in space," says glass and ceramics expert Delbert Day, who has been experimenting with glass melts on space shuttles over the past twenty years. He is the Curators' Professor Emeritus of Ceramic Engineering at the University of Missouri-Rolla.
Going into those first experiments, he says, he expected to end up with a purer glass. That's because on Earth, the melts--the molten liquid from which glass is formed--must be held in some kind of container. That's a problem.
"At high temperatures these glass melts are very corrosive toward any known container" As the melt attacks and dissolves the crucible, the melt--and thus the glass--becomes contaminated.

In microgravity, though, you don't need a container. In Day's initial experiments, the melt--a molten droplet about ½ cm in diameter--was held in place inside a hot furnace simply by the pressure of sound waves emitted by an acoustic levitator.
With that acoustic levitator, "we could melt and cool and melt and cool a molten droplet without letting it touch anything". Containerless processing produced a better glass, and of even higher quality than theory had predicted.

When most people think of glass, they think of that transparent stuff in window panes. But glass doesn't have to be transparent nor is it always found in windows. Among researchers there's a different definition: "glass" is a solid material with an amorphous internal structure.
The atoms in solids are usually arranged in regular, predictable patterns, like bricks fitted into a wall. But if the atoms are just jumbled together in a disorganized way, like bricks dumped on the ground... that's glass.
The window glass that we're so familiar with is made mostly of silica--a compound of silicon and oxygen. It's essentially melted sand. But in theory, a melt of any chemical composition can produce a glass as long as the melt can be cooled quickly enough that the atoms don't have time to hook themselves up into patterns, or crystals.

In Earth-orbit, it turns out, these molten liquids don't crystallize as easily as they do on Earth. It's easier for glass to form. So not only can you make glass that's less contaminated, you can also form it from a wider variety of melts.

But why is that important? What's wrong with glass made of silica?

For windows silica is just fine. But glass made from other chemical compositions offers a panoply of unexpected properties. For example, there are "bioactive glasses" that can be used to repair human bones. These glasses eventually dissolve when their work is done. On the other hand, Day has developed glasses which are so insoluble in the body that they are being used to treat cancer by delivering high doses of radiation directly to a tumour site.

Another example: Glass made of metal can be remarkably strong and corrosion-resistant. And you don't need to machine it into the precise, intricate shapes needed, say, for a motor. You can just mould or cast it.
Also intriguing to space researchers is fluoride glass. A blend of zirconium, barium, lanthanum, sodium and aluminium, this type of glass (also known as "ZBLAN") is a hundred times more transparent than silica-based glass. It would be exceptional for fibre optics.

A fluoride fibre would be so transparent, says Day, that light shone into one end, say, in New York City, could be seen at the other end as far away as Paris. With silicon glass fibres, the light signal degrades along the way.
Unfortunately, fluoride glass fibres are very difficult to produce on Earth. The melts tend to crystallize before glass can form.

The reason, is that gravity causes convection or mixing in a melt. In effect, gravity "stirs" it, and, in a process known as shear thinning, the melt becomes more fluid. This same process works in peanut butter: the faster you stir it, the more easily it moves.

In melts that are more fluid, like those stirred by gravity, the atoms move rapidly, so they can get into geometric arrangements more quickly. In thicker, more viscous melts, the atoms move more slowly. It's harder for regular patterns to form. It's more likely that the melt will produce a glass.

In microgravity, melts may be more viscous than they are on Earth.

While this theory has not yet been confirmed, some experimental results suggest that it is correct. NASA researcher Dennis Tucker worked with fluoride melts on the KC-135, a plane that provides short bursts of near zero-gravity interspersed with periods of high gravity.

"He did some glass-melting experiments, trying to pull thin fibres out of melts. During the low-gravity portion of the plane's flight, when g was almost zero, the fibres came out with no trouble. But during the double-gravity portion of the plane's flight, the fibre that he was pulling totally crystallized"

That result, could be explained by shear thinning. "A melt in low gravity doesn't experience much shear. But as you increase g, there'll be more and more movement in the melt." Shear stresses increase. The effective viscosity of the melt decreases. Crystallization becomes more likely.
Day is currently planning his next experiment in space--onboard the International Space Station--which he hopes will confirm his ideas. He'll be melting and cooling identical glass samples in the same way on Earth and in microgravity. Then he'll count the number of crystals that appear in each sample. If shear-thinning exists, he says, there will be fewer crystals in the space-melted samples than in the ones produced on Earth.

Eventually, Day hopes to take these lessons learned from space and apply them to glass production on the ground. Metallic glasses. Bioactive glasses. Super-clear fibre optics. The possible applications go on and on.... which makes the value of this research crystal clear.

From NASA



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