The latest research has laid the foundation for a better understanding of the optical properties of glass
glass materials can be seen everywhere. Whether someone is staring out of the window or through the intelligent scrolling screen, there is always a layer of glass between them, no matter what they are browsing
although glass has existed for at least 5000 years, there are still many unknowns about this material, such as the formation of some glasses and how they acquire certain properties. A better understanding of this may contribute to new technological innovations, such as scratch free coatings and glass materials with different mechanical properties
in the past few years, researchers at the University of Pennsylvania have been studying glass materials with stable properties. This closely aligned glass is produced by the deposition of vapor molecules on cold substrates
#160; "There is a big problem," said zahrafakhraai, an associate professor of chemistry at the University of Pennsylvania School of Arts and Sciences. "Is this similar to the same amorphous naturally aged glass, such as amber, that is, it is just a liquid cooled and formed over many years."
to answer these questions, fahkraai, doctoral student tianyiliu and chemistry professor patrickwalsh designed and synthesized a new special molecule, which is perfectly wrapped outside a spherical object. According to fakhraai, these unique molecules can be deposited without forming any substrate. Because of this, researchers hope that this kind of glass is amorphous and isotropic, which means that their constituent particles, whether they are atoms, colloids or grains, are arranged in a way that has no overall mode or order
surprisingly, researchers noticed that these stable glasses have birefringence, which means that the refractive index of light is different in the direction parallel to the substrate, which is impossible in circular materials. Their findings were published in the journal Physical Review Letters
when there is birefringence, light emitted in one direction will form beams in different directions. This effect is often used in liquid crystal displays: changing the direction of the material so that light interacts with it without recruiting several workshop technicians to produce optical effects. In most deposited glasses, this is the result of the alignment of molecules in a particular direction, as they condense from the vapor phase into a glassy state
the birefringence mode in stable glass is very strange. Fakhraai said that researchers do not want any directionality of circular molecular materials in the material
cooperated with physics professor jameskikkawa and doctoral student annemarieexarhos. The latter experimentally studied the orientation of molecules in photoluminescence properties. Chemistry professor josephsubotnick helped with simulation, aiming to find out the crystal structure and calculation, which allowed them to calculate the mathematical value of birefringence or the order of amorphous state. Researchers confirmed their hunch that there was no directionality in materials
although measured as zero order in glass, scientists still see birefringence, similar to the situation when up to 30% of molecules are completely ordered. Through their experiments, they found that this was due to the nature of each layer of the deposition layer, which made the molecules more closely packed in the direction perpendicular to the surface during the deposition process. The higher the density of glass, the higher the birefringence. This process can control the density by controlling the substrate temperature
#160; "We can prove that this is a unique property in this rapid process," fakhraai said. "This is a new structure, which is very unique, because you don't have any direction, but you can still average the molecular distance, and there is still a random, birefringent whole. This also teaches us a lot about how to actually enter these low state stages, but it also provides a method of engineering to control optical properties, without having to produce some ordered structures in the material.
because these pressure sources are These glasses have different mechanical properties due to different distribution on the plane, which may be helpful for coating technology. It may be possible to manipulate the direction of the glass or its delamination to give it certain properties, such as the formation of an anti scratch coating
#160; "We think that if we want to add something to the glass surface," fakhraai said, "it will form different toughness on this side. This may change its fracture mode or hardness or elastic properties. I want to understand how the shape, direction and packaging affect the mechanical properties of these coatings, which will be one of the most interesting places in future applications."
according to fakhraai, one of the most exciting parts of this study is the basic characteristics, which can now show that there can be high-density amorphous phases. She hopes that she and other researchers can study these systems to understand what happens in high aging glass
"this tells us that we can actually fill some materials to make glass materials with excellent aging resistance," fakhraai said. "This makes it possible to better understand the process of making stable glasses in our country
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