Glass Is Not What We Thought

Scientists discover that glass doesn't flow like a liquid. Something to ponder on while you're cleaning those windows.

Fossil Amber Challenges Theories About Glass - Scientists discover that glass doesn't flow like a liquid: In a finding that could help answer fundamental questions about how glass forms, scientists have discovered that the structure of amber barely changes even after tens of millions of years. "What we found was that in 20 million years, the amber changed density by only 2.1 percent. What we found challenges the way we look at glasses," said Gregory McKenna, a professor of chemical engineering at Texas Tech University.

The findings, detailed in a recent issue of the journal Nature Communications, are also further evidence that—contrary to what many students are taught in first-year chemistry courses—the stained glass windows in medieval cathedrals aren't thicker at the bottom because glass flows like a liquid and moves over time. "Those windows aren't flowing," McKenna said. "The glass makers were just smart enough to put the thicker ends at the bottom."

Fossilized Glass: In their new study, McKenna and his team focused on amber—fossilized tree resin—because its atoms are not arranged in any regular order. "In a crystal, everything is periodically arranged. If you know what's happening in one little bit, you can predict where the atoms are going to be everywhere else. In glass, things are much more disordered," explained Mark Ediger, an experimental chemist at the University of Wisconsin—Madison who was not involved in the study. Amber's noncrystalline nature thus makes it a good analog for studying glasses, which also have unordered atoms.

McKenna and his team were particularly interested in a phenomenon called the glass transition, which refers to the temperature at which a material transforms from a soft and flexible rubber-like state to a hard and brittle one. Despite decades of study, many aspects of the glass transition are still not well understood. For example, "what causes a liquid to slow so rapidly as it becomes a glass?" Ediger said. "And what's the best way to think about it?" The answers to these questions are of more than just academic interest. Glass transition is related to the performance of materials, and its properties are important for the design and manufacture of a whole host of glassy materials.

Beyond Window Glass: When laypeople talk about glass, they usually think of window glass, which is transparent and made primarily of silicate. But for scientists, any noncrystalline, or amorphous, solid is considered a glass. Under this broader definition, plastics can be transformed into glass, as can metals. Many modern technologies rely on glass. For example, modern planes such as the Airbus A380 and the 787 Dreamliner are built using glass-like resins and plastics.

"The current planes are probably fine because they have relatively high glass-transition temperatures and the airplanes don't get very hot, but imagine if you are building a supersonic transport and the whole airplane gets hot and remains hot for several hours," McKenna said. "At that point, you're pushing the limits of the materials, and working fairly close to the glass-transition temperatures. As the material changes, it could get more and more brittle, and you could conceivably have issues if you don't model them properly."

To better understand glass transitions, McKenna, along with colleagues Sindee Simon and Jing Zhao, experimented on 20-million-year-old Dominican amber. One of the tests they performed was called a stress-relaxation experiment, which involved taking strips of amber, stretching them out at different temperatures, and measuring the rate at which they relaxed back to their original states. The findings from this experiment provided clues about how the molecules inside the amber behave.

Because it takes a certain amount of force to distort the amber strips, measuring "the time it takes that force to go away tells you how fast the molecules inside the material can move," Ediger explained. The ancient amber provided a rare opportunity to study the glass transition in slow motion and at ambient temperatures. That's because the temperature at which a material gets frozen into the glassy state depends in part on how long it has to cool. "When you cool a liquid, the reason it becomes a glass is because the molecules are moving so slowly that at some temperature they get stuck, and then they cannot reach the state they should have at such low temperatures," Ediger said.

The longer a material takes to cool, the lower the temperature at which it turns to glass. "If I cool a liquid ten times more slowly, I'll get to a slightly lower temperature before I get stuck," Ediger said. With the fossil amber, McKenna and his team essentially had a glass that had cooled over a period of 20 million years—something impossible to replicate in a lab experiment. That allows scientists to "get way the heck down there in temperature"—down even to ambient air temperatures when amber would normally be frozen in a glass-like state—"and still have a liquid," Ediger said. "If we understood the properties of that material, then we would know a lot more about how glass formation occurs."

"To Be Continued"... Ediger said using fossil amber to study the glass transition was a creative idea and called the experiments by McKenna's team "beautifully done." "I'm not sure there's another lab in the world that could do the experiment with the needed precision," he added. McKenna and his team are already preparing to perform the same experiments with even older, 220-million-year-old amber from the Triassic period. "We are in the very early stages," McKenna said in a statement. "However, our research definitely is 'to be continued.'" The research was funded by the Division of Materials Research at the National Science Foundation.

New Feel Good Glass

Fraunhofer researchers have developed a window coating (not pictured) that lets in more light in the wavelengths that have a beneficial effect on our sense of well-being.

Window coating improves mood by letting more light in: With many of us spending more and more time indoors, it can be a struggle to get the amount of sunlight our bodies crave. Modern heat-insulating, sun-protection glazing doesn’t help, as it reflects a noticeable percentage of the incident sunlight in the part of the spectrum that governs our hormonal balance. Researchers at the Fraunhofer Institute for Silicate Research (ISC) have developed a coating for windows that lets in more light, in particular those wavelengths of light that have a beneficial effect on our sense of well-being.

While the human retina is most sensitive to light at the peak emission wavelength of sunlight, which brightens a room the most, Walther Glaubitt, a researcher at the Fraunhofer Institute for Silicate Research ISC in Würzburg, says our biorhythms aren’t affected by these wavelengths. Rather, it is blue light that has an impact on our sense of well-being.

According to Glaubitt’s team colleague Dr. Jörn Probst, this is because there are special receptors at the end of the nerve connection that connect the human retina to the hypothalamus – the control center for the autonomic control system – that are sensitive to blue light. These receptors convert the blue light into light-and-dark signals that are sent to the part of the brain that functions as our biological clock, where, amongst other things, the nerve impulses regulate melatonin levels.

Melatonin levels help regulate the sleep-wake cycle, with high levels of melatonin caused by a lack of light leading to problems sleeping and concentrating, as well as depression and other psychological impairments. Seasonal Affective Disorder, or SAD, can be one potential outcome from high melatonin levels.

The new coating, which Fraunhofer researchers developed with the help of industry partners, is particularly transmissive to light in the blue part of the spectrum - at wavelengths between 450 and 500 nanometers, but its transmissivity is increased across the entire range from 380 to 580 nanometers, which the researchers say is the portion of the spectrum responsible for promoting well-being. When applied to a window, the inorganic coating is barely perceptible as it is only 0.1 micrometers thick. It also has no effect on the heat-insulating properties of the window.

Currently, the ISC researchers have only applied the coating to the side of the glass that faces into the cavity between panes. They believe that coating both the inside and outside of the window will up the light transmissivity at 460 nanometers from the current 79 percent to around 98 percent.

UNIGLAS GmbH & Co. KG, which worked with Fraunhofer to bring the coating to market maturity, is set to launch a triple-glazing product featuring the coating, which is marketed under the name UNIGLAS | VITAL feel-good glass. This product boasts light transmissivity at 460 nanometers of 79 percent. However, this is with the coating only applied to the side of the glass facing into the cavity between panels. The ISC researchers believe that applying the coating to both the inside and outside of the windows, as they plan to do in the future, will result in windows with around 95 percent light transmissivity at 460 nanometers.

More news on this glass coating:

Science Blog

New glass coating makes you feel as if window is permanently open.

Feel-good glass for windows.

VITAL feel-good glass replaces pain with happy pane. 

Magnetic Soap Could Revolutionise Cleaning

A droplet containing the soap is attracted to the magnet at left.

Magnetic soap could help in oil spill clean-ups: An international team of scientists has demonstrated the first soap that responds to magnets. This means the soap and the materials that it dissolves can be removed easily by applying a magnetic field. Experts say that with further development, it could find applications in cleaning up oil spills and waste water.

Details of the new soap, which contains iron atoms, are reported in the chemistry journal Angewandte Chemie. It is similar to ordinary soap, but the atoms of iron help form tiny particles that are easily removed magnetically. "If you'd have said about 10 years ago to a chemist: 'Let's have some soap that responds to magnets', they'd have looked at you with a very blank face," said co-author Julian Eastoe of the University of Bristol. He told BBC News: "We were interested to see, if you went back to the chemical drawing board with the tool-kit of modern synthetic chemistry, if you could...design one."

Soap is made of long molecules with ends that behave differently: One end of the molecule is attracted to water and the other is repelled by it. The "detergent" action of soap comes from its ability to attach to oily, grimy surfaces, with the "water-hating" end breaking up molecules at that surface. The soap molecules then gather up into droplets in which all the "water-loving" ends face outward. Prof Eastoe and his team started with detergent molecules that he said were "very similar to what you'd find in your kitchen or bathroom" - one of which can be found in mouthwash. The team found a way to simply add iron atoms into the molecules. The droplets that the soap formed were attracted to a magnet, just as iron filings would be.

The soap could make for a far easier means of gathering oil from spills.

But single iron atoms would not behave as tiny individual magnets, so some other process had to be at work. To get a look at what was going on in the chemical process required a view at the molecular level. So the team sent their samples to the Institute Laue Langevin (ILL) in Grenoble, France, where an intense beam of the sub-atomic particles known as neutrons shed light on the matter. They saw that the iron particles were clumping neatly together into iron nanoparticles, tiny clumps of iron that could in fact respond to a magnetic field.

Prof Eastoe said the research was still at the laboratory stages but was already the subject of discussion. "The research at the University of Bristol in this field is about how we can take the ordinary and give it extraordinary properties by chemical design," he said. "We have uncovered the principle by which you can generate this kind of material and now it's back to the drawing board to make it better."

Scientists Produce World's First Magnetic Soap: Scientists from Bristol University have developed a soap, composed of iron rich salts dissolved in water, that responds to a magnetic field when placed in solution. The soap’s magnetic properties were shown with neutrons at the Institut Laue-Langevin to result from tiny iron-rich clumps that sit within the watery solution. The generation of this property in a fully functional soap could calm concerns over the use of soaps in oil-spill clean ups and revolutionise industrial cleaning products.

Scientists have long been searching for a way to control soaps (or surfactants as they are known in industry) once they are in solution to increase their ability to dissolve oils in water and then remove them from a system. The team at Bristol University have previously worked on soaps sensitive to light, carbon dioxide or changes in pH, temperature or pressure. Their latest breakthrough, reported in Angewandte Chemie, is the world’s first soap sensitive to a magnetic field.

Ionic liquid surfactants, composed mostly of water with some transition metal complexes (heavy metals like iron bound to halides such as bromine or chlorine) have been suggested as potentially controllable by magnets for some time, but it had always been assumed that their metallic centres were too isolated within the solution, preventing the long-range interactions required to be magnetically active.

The team at Bristol, lead by Professor Julian Eastoe produced their magnetic soap by dissolving iron in a range of inert surfactant materials composed of chloride and bromide ions, very similar to those found in everyday mouthwash or fabric conditioner. The addition of the iron creates metallic centres within the soap particles.

To test its properties, the team introduced a magnet to a test tube containing their new soap lying beneath a less dense organic solution. When the magnet was introduced the iron-rich soap overcame both gravity and surface tension between the water and oil, to levitate through the organic solvent and reach the source of the magnetic energy, proving its magnetic properties.

Once the surfactant was developed and shown to be magnetic, Prof Eastoe’s team took it to the Institut Laue-Langevin, the world’s flagship centre for neutron science, and home to the world’s most intense neutron source, to investigate the science behind its remarkable property.

When surfactants are added to water they are known to form tiny clumps (particles called micelles). Scientists at ILL used a technique called “small angle neutron scattering (SANS)” to confirm that it was this clumping of the iron-rich surfactant that brought about its magnetic properties.

Dr Isabelle Grillo, responsible of the Chemistry Laboratories at ILL: “The particles of surfactant in solution are small and thus difficult to see using light but are easily revealed by SANS which we use to investigate the structure and behaviour of all types of materials with typical sizes ranging from the nanometer to the tenth of micrometer.”

Up, up and away: This photo shows the magnetic soap rising up through the test tube.

The potential applications of magnetic surfactants are huge. Their responsiveness to external stimuli allows a range of properties, such as their electrical conductivity, melting point, the size and shape of aggregates and how readily its dissolves in water to be altered by a simple magnetic on and off switch. Traditionally these factors, which are key to the effective application of soaps in a variety of industrial settings, could only be controlled by adding an electric charge or changing the pH, temperature or pressure of the system, all changes that irreversibly alter the system composition and cost money to remediate.

Its magnetic properties also makes it easier to round up and remove from a system once it has been added, suggesting further applications in environmental clean ups and water treatment. Scientific experiments which require precise control of liquid droplets could also be made easier with the addition of this surfactant and a magnetic field.

Professor Julian Eastoe, University of Bristol: “As most magnets are metals, from a purely scientific point of view these ionic liquid surfactants are highly unusual, making them a particularly interesting discovery. From a commercial point of view, though these exact liquids aren’t yet ready to appear in any household product, by proving that magnetic soaps can be developed, future work can reproduce the same phenomenon in more commercially viable liquids for a range of applications from water treatment to industrial cleaning products.”

Peter Dowding an industrial chemist, not involved in the research: “Any systems which act only when responding to an outside stimulus that has no effect on its composition is a major breakthrough as you can create products which only work when they are needed to. Also the ability to remove the surfactant after it has been added widens the potential applications to environmentally sensitive areas like oil spill clean ups where in the past concerns have been raised.”