Tag Archives: materials

Ultrathin, Ultralight NanoCardboard For Aerospace

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure. Now, a team of Penn Engineers has demonstrated a new material they call “nanocardboard,” an ultrathin equivalent of corrugated paper cardboard. A square centimeter of nanocardboard weighs less than a thousandth of a gram and can spring back into shape after being bent in half.

Nanocardboard is made out of an aluminum oxide film with a thickness of tens of nanometers, forming a hollow plate with a height of tens of microns. Its , similar to that of corrugated cardboard, makes it more than ten thousand times as stiff as a solid plate of the same mass.

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Nanocardboard is made out of an aluminum oxide film with a thickness of tens of nanometers, forming a hollow plate with a height of tens of microns. Its sandwich structure, similar to that of corrugated cardboard, makes it more than ten thousand times as stiff as a solid plate of the same mass. A square centimeter of nanocardboard weighs less than a thousandth of a gram and can spring back into shape after being bent in half.

Nanocardboard‘s stiffness-to-weight ratio makes it ideal for aerospace and microrobotic applications, where every gram counts. In addition to unprecedented mechanical properties, nanocardboard is a supreme thermal insulator, as it mostly consists of empty space. Future work will explore an intriguing phenomenon that results from a combination of properties: shining a light on a piece of nanocardboard allows it to levitate. Heat from the light creates a difference in temperatures between the two sides of the plate, which pushes a current of air molecules out through the bottom.

Igor Bargatin, Assistant Professor of Mechanical Engineering, along with lab members Chen Lin and Samuel Nicaise, led the study.

They published their results in the journal Nature Communications.

Source: https://phys.org/

New Materials For New Processors

Computers used to take up entire rooms. Today, a two-pound laptop can slide effortlessly into a backpack. But that wouldn’t have been possible without the creation of new, smaller processors — which are only possible with the innovation of new materials. But how do materials scientists actually invent new materials? Through experimentation, explains Sanket Deshmukh, an assistant professor in the chemical engineering department of Virginia Tech whose team’s recently published computational research might vastly improve the efficiency and costs savings of the material design process.

Deshmukh’s lab, the Computational Design of Hybrid Materials lab, is devoted to understanding and simulating the ways molecules move and interact — crucial to creating a new material. In recent years, materials scientists have employed machine learning, a powerful subset of artificial intelligence, to accelerate the discovery of new materials through computer simulations. Deshmukh and his team have recently published research in the Journal of Physical Chemistry Letters demonstrating a novel machine learning framework that trainson the fly,” meaning it instantaneously processes data and learns from it to accelerate the development of computational models. Traditionally the development of computational models are “carried out manually via trial-and-error approach, which is very expensive and inefficient, and is a labor-intensive task,” Deshmukh explained.

This novel framework not only uses the machine learning in a unique fashion for the first time,” Deshmukh said, “but it also dramatically accelerates the development of accurate computational models of materials.” “We train the machine learning model in a ‘reverse’ fashion by using the properties of a model obtained from molecular dynamics simulations as an input for the machine learning model, and using the input parameters used in molecular dynamics simulations as an output for the machine learning model,” said Karteek Bejagam, a post-doctoral researcher in Deshmukh’s lab and one of the lead authors of the study.

This new framework allows researchers to perform optimization of computational models, at unusually faster speed, until they reach the desired properties of a new material.

Source: https://vtnews.vt.edu/

Perovskite Could Convert Up To 44% Of Light Into Electricity

Perovskites are a family of crystals that show promising properties for applications in nano-technology. However, one useful property that until now was unobserved in perovskites is so-called carrier multiplication – an effect that makes materials much more efficient in converting light into electricity. New research, led by   (UvA-IoP) physicists Dr Chris de Weerd and Dr Leyre Gomez from the group of Prof. Tom Gregorkiewicz, has now shown that certain perovskites in fact do have this desirable propertyCrystals are configurations of atoms, molecules or ions, that are ordered in a structure that repeats itself in all directions. We have all encountered some crystals in everyday life: ordinary salt, diamond and even snowflakes are examples. What is perhaps less well-known is that certain crystals show very interesting properties when their size is not that of our everyday life but that of nanometers – a few billionths of a meter.

Perovskites – named after 19th century Russian mineralogist Lev Perovski – form a particular family of materials that all share the same crystal structure. These perovskites have many desirable electronic properties, making them useful for constructing for example LEDs, TV-screens, solar cells and lasers. A property which so far had not been shown to exist in perovskites is carrier multiplication. When semiconductors – in solar cells, for example – convert the energy of light into electricity, this is usually done one particle at a time: a single infalling photon results in a single excited electron (and the corresponding ‘hole’ where the electron used to be) that can carry an electrical current. However, in certain materials, if the infalling light is energetic enough, further electron-hole pairs can be excited as a result; it is this process that is known as carrier multiplication.

Until now, carrier multiplication had not been reported for perovskites. That we have now found it is of great fundamental impact on this upcoming material. For example, this shows that perovskite nanocrystals can be used to construct very efficient photodetectors, and in the future perhaps solar cells”, says De Weerd, who successfully defended her PhD thesis based on this and other research last week.

When carrier multiplication occurs, the conversion from light into electricity can become much more efficient. For example, in ordinary solar cells there is a theoretical limit (the so-called Shockley-Queisser limit) on the amount of energy that can be converted in this way: at most a little over 33% of the solar power gets turned into electrical power. In semiconductor nanocrystals that feature the carrier multiplication effect, however, a maximum efficiency of up to 44% is predicted.

The paper in which the researchers report on their findings was published in Nature Communications this week.

Source: http://iop.uva.nl/

Electric Car: How To Make Super-Fast Charging Batteries

Researchers have identified a group of materials that could be used to make even higher power batteries. The researchers, from the University of Cambridge, used materials with a complex crystalline structure and found that lithium ions move through them at rates that far exceed those of typical electrode materials, which equates to a much faster-charging battery. Although these materials, known as niobium tungsten oxides, do not result in higher energy densities when used under typical cycling rates, they come into their own for fast charging applications. Additionally, their physical structure and chemical behaviour give researchers a valuable insight into how a safe, super-fast charging battery could be constructed, and suggest that the solution to next-generation batteries may come from unconventional materials.

Many of the technologies we use every day have been getting smaller, faster and cheaper each year – with the notable exception of batteries. Apart from the possibility of a smartphone which could be fully charged in minutes, the challenges associated with making a better battery are holding back the widespread adoption of two major clean technologies: electric cars and grid-scale storage for solar power.

We’re always looking for materials with high-rate battery performance, which would result in a much faster charge and could also deliver high power output,” said Dr Kent Griffith, a postdoctoral researcher in Cambridge’s Department of Chemistry and the paper’s first author.

In their simplest form, batteries are made of three components: a positive electrode, a negative electrode and an electrolyte. When a battery is charging, lithium ions are extracted from the positive electrode and move through the crystal structure and electrolyte to the negative electrode, where they are stored. The faster this process occurs, the faster the battery can be charged. In the search for new electrode materials, researchers normally try to make the particles smaller. “The idea is that if you make the distance the lithium ions have to travel shorter, it should give you higher rate performance,” said Griffith. “But it’s difficult to make a practical battery with nanoparticles: you get a lot more unwanted chemical reactions with the electrolyte, so the battery doesn’t last as long, plus it’s expensive to make.

Nanoparticles can be tricky to make, which is why we’re searching for materials that inherently have the properties we’re looking for even when they are used as comparatively large micron-sized particles. This means that you don’t have to go through a complicated process to make them, which keeps costs low,” explained Professor Clare Grey, also from the Department of Chemistry and the paper’s senior author. “Nanoparticles are also challenging to work with on a practical level, as they tend to be quite ‘fluffy’, so it’s difficult to pack them tightly together, which is key for a battery’s volumetric energy density.”

The results are reported in the journal Nature.

Source: https://www.cam.ac.uk/

Strain Improves Performance of Atomically Thin Semiconductor

Researchers in UConn’s Institute of Materials Science significantly improved the performance of an atomically thin semiconductor material by stretching it, an accomplishment that could prove beneficial to engineers designing the next generation of flexible electronics, nano devices, and optical sensors.

In a study appearing in the research journal Nano Letters, Michael Pettes, assistant professor of mechanical engineering, reports that a six-atom thick bilayer of tungsten diselenide exhibited a 100-fold increase in photoluminescence when it was subjected to strain. The material had never exhibited such photoluminescence before.

The findings mark the first time scientists have been able to conclusively show that the properties of atomically thin materials can be mechanically manipulated to enhance their performance, Pettes says. Such capabilities could lead to faster computer processors and more efficient sensors.

The process the researchers used to achieve the outcome is also significant in that it offers a reliable new methodology for measuring the impact of strain on ultrathin materials, something that has been difficult to do and a hindrance to innovation.

Experiments involving strain are often criticized since the strain experienced by these atomically thin materials is difficult to determine and often speculated as being incorrect,” says Pettes. “Our study provides a new methodology for conducting strain-dependent measurements of ultrathin materials, and this is important because strain is predicted to offer orders of magnitude changes in the properties of these materials across many different scientific fields.”

Source: https://today.uconn.edu/

Tool Speeds Up Manufacturing Of Powered Wearable

People could soon power items such as their mobile phones or personal health equipment by simply using their daily movements, thanks to a new research tool that could be used by manufacturers.

In a new paper published by Nano Energy, experts from the Advanced Technology Institute (ATI) at the University of Surrey (UK) detail a new  methodology that allows designers of smart-wearables to better understand and predict how their products would perform once manufactured and in use.

The technology is centred on materials that become electrically charged after they come into contact with each other, known as triboelectric materials – for example, a comb through hair can create an electrical charge. Triboelectric Nanogenerators (TENGs), use this static charge to harvest energy from movement through a process called electrostatic induction. Over the years, a variety of TENGs have been designed which can convert almost any type of movement into electricity. The University of Surrey’s tool gives manufacturers an accurate understanding of the output power their design would create once produced.

This follows the news earlier this year of the ATI announcing the creation of its £4million state-of-the-art Nano-Manufacturing Hub. The new facility will produce plastic nanoscale electronics for wearable sensors, electronic tags and other electronic devices.

Ishara Dharmasena, lead scientist on this project from the University of Surrey, said: “The future global energy mix will depend on renewable energy sources such as solar power, wind, motion, vibrations and tidal. TENGs are a leading technology to capture and convert motion energy into electricity, extremely useful in small scale energy harvesting applications. Our work will, for the first time, provide universal guidance to develop, compare and improve various TENG designs. We expect this technology in household and industrial electronic products, catering to a new generation of mobile and autonomous energy requirements.”

Source: https://www.surrey.ac.uk/