Researchers find a way to produce free-stand…

Researchers find a way to produce free-standing films of perovskite oxides

A team of researchers from Nanjing University in China, the University of Nebraska and the University of California in the U.S. has found a way to produce free-standing films of perovskite oxide. In their paper published in the journal Nature, the group describes the process they developed and how well it worked when tested. Yorick Birkhölzer and Gertjan Koster from the University of Twente have published a News and Views piece on the work done by the team in the same journal issue.

Birkhölzer and Koster point out that many new materials are made by going to extremes—making them really big or really small. Making them small has led to many recent discoveries, they note, including a technique to make graphene. One area of research has focused on ways to produce transition-metal oxides in a thinner format. It has been slow going, however, due to their crystalline nature. Unlike some materials, transition-metal oxides do not naturally form into layers with a top layer that can be peeled off. Instead, they form in strongly bonded 3-D structures. Because of this, some in the field have worried that it might never be possible to produce them in desired forms. But now, the researchers with this new effort have found a way to produce two transition-metal oxides (perovskite oxides strontium titanate and bismuth ferrite) in a thin-film format.

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New Frontiers for Recyclable Polymers Many …

New Frontiers for Recyclable Polymers

Many modern plastics, rubbers and ceramics cannot be recycled, but new polymers made from waste sulfur are promising to solve one of the planet’s biggest recycling problems – and even create new industries of the future. 

Researchers around the world have taken the next step to develop a range of these versatile and recyclable materials by controlling and improving their physical and mechanical properties to make them closer to scale up for manufacture. 

Sulfur polymers are already being used in next-generation batteries, IR imaging (such as night-vision lenses), environmental remediation, and agriculture, but it has been difficult to control the hardness, flexibility, colour and other key properties of these polymers.

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Jam-packed: A novel microscopic approach to …

Jam-packed: A novel microscopic approach to amorphous solids

A team led by The University of Tokyo developed a new method for understanding the structural organization of disordered collections of soft discs or spheres using a new approach: putting a focus on local mechanical properties that is fundamentally different from previous approaches to ordered crystals and disordered amorphous solids. In particular, the researchers focused packings resulted from the phenomenon of “jamming,” in which a free-flowing substance suddenly clogs as the density increases. The work may help with the design of more efficient industrial materials that are less likely to breakdown under external load.

Imagine you are sitting on the beach playing with the sand piles. But when you try to decorate the castle that you have just built, you are surprised to find that only a very small operation leads to its collapse. In this case, you’ve just discovered the “marginal stability” of amorphous solids, due to which the system loses its stability unexpectedly. While amorphous solids are ubiquitous in nature and have wide industrial applications, it can be a serious issue for our safety if they fall apart out of control. The structural organization of amorphous solids, which leads to marginal stability, is quite complex and still not completely understood. In fact, most scientists intend to understand amorphous solids using the established models of ordered crystals, but consensus has never been reached.

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Functional Natural and Synthetic Polymers H…

Functional Natural and Synthetic Polymers

Highly specialized polymers with specific functionality has attracted strong research interest worldwide. 

Generally, functionality is defined as the “quality of being suited to serve a purpose well” (according to the Oxford English Dictionary). 

In polymer science however, functionality is commonly used to describe various features of polymers, from individual chemical groups and their reactivity, to the unique properties of macromolecules arising as a consequence. 

“The growing literature on functional polymers encompasses the impressive levels of control that researchers have in tailoring polymer properties to make them practicably suited to serve a specific purpose” writes Dr. Markus Müllner, senior lecturer at the University of Sydney and Chair of the Royal Australian Chemical Institute, New South Wales Polymer group.

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Organic electronics: a new semiconductor in the carbon-nitride family

Teams from Humboldt-Universität and the Helmholtz-Zentrum Berlin have explored a new material in the carbon-nitride family. Triazine-based graphitic carbon nitride (TGCN) is a semiconductor that should be highly suitable for applications in optoelectronics. Its structure is two-dimensional and reminiscent of graphene. Unlike graphene, however, the conductivity in the direction perpendicular to its 2D planes is 65 times higher than along the planes themselves.

Some organic materials might be able to be utilised similarly to silicon semiconductors in optoelectronics. Whether in solar cells, light-emitting diodes, or in transistors – what is important is the band gap, i.e. the difference in energy level between electrons in the valence band (bound state) and the conduction band (mobile state). Charge carriers can be raised from the valence band into the conduction band by means of light or an electrical voltage. This is the principle behind how all electronic components operate. Band gaps of one to two electron volts are ideal.

A team headed by chemist Dr. Michael J. Bojdys at Humboldt University Berlin recently synthesised a new organic semiconductor material in the carbon-nitride family. Triazine-based graphitic carbon nitride (or TGCN) consists of only carbon and nitrogen atoms, and can be grown as a brown film on a quartz substrate.The combination of C and N atoms form hexagonal honeycombs similar to graphene, which consists of pure carbon.Just as with graphene, the crystalline structure of TGCN is two-dimensional.With graphene, however, the planar conductivity is excellent, while its perpendicular conductivity is very poor. In TGCN it is exactly the opposite: the perpendicular conductivity is about 65 times greater than the planar conductivity. With a band gap of 1.7 electron volts, TGCN is a good candidate for applications in optoelectronics.

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materialsscienceandengineering: Ceramics: Grad…


Ceramics: Grade A lava

A naturally occurring form of hydrous aluminum silicate, lava on its own is easily machinable. As such, when fired and processed as a ceramic (in the form of grade A lava), the resulting material is highly machinable. 

Grade A lava has good electrical and heat resistance, excellent resistance to thermal shock, and low thermal conductivity. Once fired in a kiln, lava also hardens significantly. Since lava is a natural material, however, the structure of the grains, color, and other natural properties are difficult to control and depend almost entirely on the raw material being mined. As such, the true processing conditions for creating grade A lava can vary. Generally, this material is not fired about 2000 F. 

Grade A lava is used in a variety of applications that tend to require materials that can withstand thermal cycling

Sources: ( 1 ) ( 2 ) ( 3 ) ( 4 ) ( 5 )

Image source.

The Hollow-Face Illusion.

The Hollow-Face Illusion.

Seen here with an Einstein mask, the Hollow-Face illusion is an example of the biases our brain uses.

This example is the bias of seeing a face normally in a convex manner, which the brain will counter cues of light, shade and depth to be able to picture this face in a convex way.

Via BBC and QI.

A polar-bear-inspired material for heat insu…

A polar-bear-inspired material for heat insulation

For polar bears, the insulation provided by their fat, skin, and fur is a matter of survival in the frigid Arctic. For engineers, polar bear hair is a dream template for synthetic materials that might lock in heat just as well as the natural version. Now, materials scientists in China have developed such an insulator, reproducing the structure of individual polar bear hairs while scaling toward a material composed of many hairs for real-world applications in the architecture and aerospace sectors. Their work appears June 6 in the journal Chem.

“Polar bear hair has been evolutionarily optimized to help prevent heat loss in cold and humid conditions, which makes it an excellent model for a synthetic heat insulator,” says co-senior author Shu-Hong Yu, a professor of chemistry at the University of Science and Technology of China (USTC). “By making tube aerogel out of carbon tubes, we can design an analogous elastic and lightweight material that traps heat without degrading noticeably over its lifetime.”

Unlike the hairs of humans or other mammals, polar bear hairs are hollow. Zoomed in under a microscope, each one has a long, cylindrical core punched straight through its center. The shapes and spacing of these cavities have long been known to be responsible for their distinctive white coats. But they also are the source of remarkable heat-holding capacity, water resistance, and stretchiness, all desirable properties to imitate in a thermal insulator.

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