au creat o sursă de energie personalizabilă, care poate fi tăiată, pliată sau întinsă fără a-și pierde funcția;cum au creat sursă de alimentare portabilă, un supercapacitor, care funcționează ca o baterie rapidă de încărcare și poate fi reîncărcată de mai multe ori.Supercapacitorul editabil este fabricat din material compozit din materiale compozite cu dioxid de mangan întărit. În timp ce dioxidul de mangan este un material obișnuit pentru supercapacitorii, structura nanofire superioară, întărită cu o rețea de nanotuburi de carbon și fibre de nanoceluloză, permite ca electrozii să reziste tulpinilor asociate în timpul procesului de personalizare.
Posted: Jan 30, 2018
A customizable, fabric-like power source for wearable electronics
(Nanowerk News) Scientists at Nanyang Technological University, Singapore (NTU Singapore) have created a customizable, fabric-like power source that can be cut, folded or stretched without losing its function.
A new power source developed by NTU Singapore scientists which can be customised into any shape, such as a Chinese character in this example. (Image: NTU)
Crucially, they have made their supercapacitor customizable or “editable”, meaning its structure and shape can be changed after it is manufactured, while retaining its function as a power source. Existing stretchable supercapacitors are made into predetermined designs and structures, but the new invention can be stretched multi-directionally, and is less likely to be mismatched when it is joined up to other electrical components.
The new supercapacitor, when edited into a honeycomb-like structure, has the ability to store an electrical charge four times higher than most existing stretchable supercapacitors. In addition, when stretched to four times its original length, it maintains nearly 98 per cent of the initial ability to store electrical energy, even after 10,000 stretch-and-release cycles.
Experiments done by Prof Chen and his team also showed that when the editable supercapacitor was paired with a sensor and placed on the human elbow, it performed better than existing stretchable supercapacitors. The editable supercapacitor was able to provide a stable stream of signals even when the arm was swinging, which are then transmitted wirelessly to external devices, such as one that captures a patient’s heart rate.
A black intricately designed supercapacitor powering a light. Such customisation of the power source opens up new possibilities for wearable electronics in future. (Image: NTU)
The authors believe that the editable supercapacitor could be easily mass-produced as it would rely on existing manufacturing technologies. Production cost will thus be low, estimated at about SGD$0.13 (USD$0.10) to produce 1 cm2 of the material.
The team has filed a patent for the technology.
Professor Chen said, “A reliable and editable supercapacitor is important for development of the wearable electronics industry. It also opens up all sorts of possibilities in the realm of the ‘Internet-of-Things’ when wearable electronics can reliably power themselves and connect and communicate with appliances in the home and other environments.
“My own dream is to one day combine our flexible supercapacitors with wearable sensors for health and sports performance diagnostics. With the ability for wearable electronics to power themselves, you could imagine the day when we create a device that could be used to monitor a marathon runner during a race with great sensitivity, detecting signals from both under and over-exertion.”
In the traditional method, electrodes are made into an unchangeable structure with predesigned stretchability. In contrast, the new supercapacitors that NTU scientists developed can be edited into different shapes and structures and stretched in different directions. (Image: NTU)
The editable supercapacitor is made of strengthened manganese dioxide nanowire composite material. While manganese dioxide is a common material for supercapacitors, the ultralong nanowire structure, strengthened with a network of carbon nanotubes and nanocellulose fibres, allows the electrodes to withstand the associated strains during the customisation process.
The NTU team also collaborated with Dr. Loh Xian Jun, Senior Scientist and Head of the Soft Materials Department at the Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR).
Dr. Loh said, “Customisable and versatile, these interconnected, fabric-like power sources are able to offer a plug-and-play functionality while maintaining good performance. Being highly stretchable, these flexible power sources are promising next-generation ‘fabric’ energy storage devices that could be integrated into wearable electronics.”
Lupta împotriva cariilor dentare primește ajutor cu un nou material inteligent nanocompozit.Cu unele reglaje fine, acest nou material „inteligent” ar putea crea o umplere mai puternică și mai puține excursii la dentist.
Posted: Jan 30, 2018
The fight against tooth decay gets help with a new nanocomposite smart material
(Nanowerk News) When patients go to the dentist to fill a cavity, they’re trying to solve a problem — not create a new one. But many dental patients get some bad news: bacteria can dig under their tooth-coloured fillings and cause new cavities, called recurrent caries. These recurrent caries affect 100 million patients every year and cost an additional US$34 billion to treat.
Now, a research collaboration between the Department of Materials Science & Engineering (MSE), Faculty of Dentistry, and the Institute of Biomaterials and Biomedical Engineering (IBBME) at the University of Toronto has resulted in a novel way to minimize recurrent caries.
In a recent paper published in the journal Scientific Reports („Drug self-assembly for synthesis of highly-loaded antimicrobial drug-silica particles”), professors Ben Hatton (MSE), Yoav Finer (Dentistry) and PhD student Cameron Stewart (IBBME) tackled the issue and proposed a novel solution: a filling material with tiny particles made by self-assembly of antimicrobial drugs, designed to stop bacteria in its tracks. These particles may solve one of the biggest problems with antibacterial filling materials: how do you store enough drug within the material to be effective for someone’s entire life?
“Adding particles packed with antimicrobial drugs to a filling creates a line of defense against cavity-causing bacteria,” says Hatton. “But traditionally there’s only been enough drug to last a few weeks. Through this research we discovered a combination of drugs and silica glass that organize themselves on a molecule-by-molecule basis to maximize drug density, with enough supply to last years.” This discovery of using antimicrobials which self-assemble means the team can pack 50 times as much of the bacteria-fighting drugs into the particles.
“We know very well that bacteria specifically attack the margins between fillings and the remaining tooth to create cavities,” says Finer. “Giving these materials an antimicrobial supply that will last for years could greatly reduce this problem.”
Looking ahead, the research team plans on testing these new drug-storing particles in dental fillings, monitoring their performance when attacked by bacteria and saliva in the complex environment in the mouth. With some fine-tuning, this new ‘smart’ material could create a stronger filling and fewer trips to the dentist.
Cercetătorii au demonstrat cum să creeze un aliaj de aluminiu super-puternic care rivalizează rezistența oțelului inoxidabil, un avans cu potențiale aplicații industriale.Acoperirile din aliaj de aluminiu-fier rezultat „nanotwinned” s-au dovedit a fi unul dintre cele mai puternice aliaje de aluminiu create vreodată, comparabile cu oțelurile cu rezistență ridicată.
Posted: Jan 26, 2018
New research yields super-strong aluminum alloy
(Nanowerk News) Researchers have demonstrated how to create a super-strong aluminum alloy that rivals the strength of stainless steel, an advance with potential industrial applications.
“Most lightweight aluminum alloys are soft and have inherently low mechanical strength, which hinders more widespread industrial application,” said Xinghang Zhang, a professor in Purdue University’s School of Materials Engineering. “However, high-strength, lightweight aluminum alloys with strength comparable to stainless steels would revolutionize the automobile and aerospace industries.”
New research shows how to alter the microstructure of aluminum to impart greater strength and ductility. Findings were detailed in two new research papers. The work was led by a team of researchers that included Purdue postdoctoral research associate Sichuang Xue and doctoral student Qiang Li.
A sample is readied for analysis using a transmission electron microscope. (Image: Marshall Farthing)
The new high-strength aluminum is made possible by introducing “stacking faults,” or distortions in the crystal structure. While these are easy to produce in metals such as copper and silver, they are difficult to introduce in aluminum because of its high “stacking fault energy.”
A metal’s crystal lattice is made up of a repeating sequence of atomic layers. If one layer is missing, there is said to be a stacking fault. Meanwhile, so-called “twin boundaries” consisting of two layers of stacking faults can form. One type of stacking fault, called a 9R phase, is particularly promising, Zhang said.
“It has been shown that twin boundaries are difficult to be introduced into aluminum. The formation of the 9R phase in aluminum is even more difficult because of its high stacking fault energy,” Zhang said. “You want to introduce both nanotwins and 9R phase in nanograined aluminum to increase strength and ductility and improve thermal stability.”
Now, researchers have learned how to readily achieve this 9R phase and nanotwins in aluminum.
“These results show how to fabricate aluminum alloys that are comparable to, or even stronger than, stainless steels,” he said. “There is a lot of potential commercial impact in this finding.”
Xue is lead author of the Nature Communications paper, which is the first to report a “shock-induced” 9R phase in aluminum. Researchers bombarded ultrathin aluminum films with tiny micro-projectiles of silicon dioxide, yielding 9R phase.
“Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nanometers in width,” Xue said.
The microprojectile tests were performed by a research group at Rice University, led by professor Edwin L. Thomas, a co-author of the Nature Communications paper. A laser beam causes the particles to be ejected at a velocity of 600 meters per second. The procedure dramatically accelerates screening tests of various alloys for impact-resistance applications.
“Say I want to screen many materials within a short time,” Zhang said. “This method allows us to do that at far lower cost than otherwise possible.”
Li is lead author of the Advanced Materials paper, which describes how to induce a 9R phase in aluminum not by shock but by introducing iron atoms into aluminum’s crystal structure via a procedure called magnetron sputtering. Iron also can be introduced into aluminum using other techniques, such as casting, and the new finding could potentially be scaled up for industrial applications.
The resulting “nanotwinned” aluminum-iron alloy coatings proved to be one of the strongest aluminum alloys ever created, comparable to high-strength steels.
“Molecular-dynamics simulations, performed by professor Jian Wang’s group at the University of Nebraska, Lincoln, showed the 9R phase and nanograins result in high strength and work-hardening ability and revealed the formation mechanisms of the 9R phase in aluminum,” Zhang said. “Understand new deformation mechanisms will help us design new high strength, ductile metallic materials, such as aluminum alloys.”
One potential application might be to design wear- and corrosion-resistant aluminum alloy coatings for the electronics and automobile industries.
Oamenii de stiinta de astazi raporteaza in ACS Applied Nano Materials ( „Nacre Mimetic cu Nanowire de argint incorporat pentru incalzire rezistiva” ) un material hibrid compus din imitatie de perle combinata cu nanofire de argint care functioneaza ca un incalzitor, cu beneficiul suplimentar de flexibilitate ridicata, sugerand un potential rol în dispozitive portabile.Nacre, altfel cunoscut sub numele de mama de perle, formează învelișul opalescent exterior al unei perle și învelișul interior al cochililor de moluscă. Oamenii de știință au fost mult timp interesați de acest material ușor, dar puternic pentru o gamă largă de aplicații, fabricând substanțe care imită pergul pentru utilizare ca agenți de întârziere a incendiilor, bariere de gaz și conductori.Materialul compozit a prezentat proprietăți excelente de încălzire, generând căldură, deoarece curentul electric a fost trecut prin nanofirele de argint, chiar și atunci când a fost îndoit în mod repetat sau când a fost laminat într-un tub. Într-un experiment de dovadă a conceptului, cercetătorii au plasat pe încălzitor un plasture cu hidrogel încărcat cu antibiotice sensibil la căldură. Întoarcerea la temperatură a declanșat o modificare a fazei în plasture, eliberând antibioticele.
Posted: Jan 24, 2018
Pearly material for bendable heating elements
(Nanowerk News) The iridescent shimmer of a string of pearls may one day be more than pretty adornment. Scientists now report in ACS Applied Nano Materials („Nacre Mimetic with Embedded Silver Nanowire for Resistive Heating”) a hybrid material consisting of imitation pearl combined with silver nanowires that works as a heater, with the added benefit of high flexibility, suggesting a potential role in wearable devices.
Nacre, otherwise known as mother of pearl, makes up the opalescent exterior coating of a pearl and the inner coating of mollusk shells. Scientists have long been interested in this lightweight, yet strong material for a range of applications, manufacturing substances that imitate nacre for use as fire retardants, gas barriers and conductors.
Flexible conductors made from silver nanowires and a flexible plastic substrate called polyethylene terephthalate (PET) are being developed in laboratories, but researchers are running into problems with adhesion between PET and the silver nanowires. So, Hongwei Duan and colleagues wanted to explore a nacre mimetic as the substrate for silver nanowires to develop a flexible resistive heater.
The researchers prepared the nacre mimetic from a synthetic nanoclay coated with a polyvinyl alcohol polymer that self-assembled upon water removal, generating a flexible transparent sheet. Then, they transferred silver nanowires from a filter membrane to the nacre mimetic sheet by hot pressing the pearly substrate against the membrane. The silver nanowires adhered to the new material better than to traditional flexible plastic substrates, resisting removal with scotch tape, a standard test of adhesion.
The composite material showed excellent heating properties, producing heat as electric current was passed through the silver nanowires, even when bent repeatedly or when rolled up into a tube. In a proof-of-concept experiment, the researchers placed a heat-sensitive antibiotic-loaded hydrogel patch onto the heater. Turning up the temperature triggered a phase change in the patch, releasing the antibiotics.
Ei au reușit să creeze primul metamaterial cuantic al lumii, care poate fi folosit ca element de control în circuitele electrice superconductoare .Metamaterialele sunt substanțe ale căror proprietăți sunt determinate nu atât de atomii din care sunt compuși, cât și de structura structurală a atomilor. Fiecare structură are sute de nanometri și are un set propriu de proprietăți care dispar atunci când oamenii de știință încearcă să separe materialul în componentele sale. De aceea, o astfel de structură se numește meta-atom (nu trebuie confundată cu atomii obișnuiți ai Mendeleev’s Periodic Table). Orice substanță constând din meta-atomi se numește meta-material.
Posted: Jan 23, 2018
Scientists develop quantum metamaterial from complex twin qubits
(Nanowerk News) An international team consisting of Russian and German scientists has made a breakthrough in the creation of seemingly impossible materials. They have managed to create the world`s first quantum metamaterial which can be used as a control element in superconducting electrical circuits (Nature Communications, „Magnetically induced transparency of a quantum metamaterial composed of twin flux qubits”).
Superconducting quantum metamaterial consisting of an array of 15 twin qubits embedded in a coplanar wave guide. An SEM image of twin flux qubits (above) and a whole structure (below) are shown. Each qubit consists of two superconducting loops sharing one common central Josephson junction (α-junction) and four identical Josephson junctions located on the outer parts of the loops. The α-junction allows the magnetic flux to tunnel between the loops. The inset is a schematic of a single meta-atom–the twin flux qubit; the phases on nodes are shown. (Image: NUST MISIS)
Metamaterials are substances whose properties are determined not so much by the atoms they consist of, but by the atoms’ structural arrangement. Each structure is hundreds of nanometers, and has its own set of properties that disappear when scientists try to separate the material into its components. That is why such a structure is called a meta-atom (not to be confused with the common atoms of Mendeleev`s Periodic Table). Any substance consisting of meta-atoms is called a meta-material.
Until recently, another difference between atoms and meta-atoms was that the properties of conventional atoms were described by quantum mechanics equations, while meta-atoms were described by classical physics equations. However, the creation of qubits led to the emergence of a potential opportunity to construct metamaterials consisting of meta-atoms whose state could be described quantum-mechanically. However, this research required the creation of unusual qubits.
„An international team of scientists from NUST MISIS, Karlsruhe Institute of Technology (Germany), and IPHT Jena (Germany), led by Professor Alexey Ustinov, head of the NUST MISIS Laboratory of Superconducting Metamaterials, has created the world`s first so-called „twin” qubit, as well as a metamaterial on its basis. Thanks to the outstanding properties of the new material, it will be possible to create one of the key elements in superconducting electronic devices”, said Alevtina Chernikova, Rector of NUST MISIS.
Kirill Shulga, a researcher at the NUST MISIS Laboratory of Superconducting Metamaterials and the first author of the project, noted that a conventional qubit consists of a scheme that includes three Josephson junctions. The twin qubit however is composed of five junctions that are symmetric to the Central axis (see diagram).
The energy of the ground state (a) and the transition energy hf01 of the twin qubit. The minimum point of the (b) plot corresponds to the transition of the central junction phase. (Image: NUST MISIS)
„Twin qubits were supposed to serve as a more complex system than the conventional superconducting qubits. The logic here is quite simple: a more complex (artificially complex) system, with a large number of degrees of freedom, has a higher number of factors that can influence its properties. When changing some external properties of the environment where our metamaterial is located, we can turn these properties on and off by turning the twin qubit from one state with certain properties to another with other properties”, he added.
This became apparent during the experiment, as the whole metamaterial consisting of twin qubits switched over between two different modes.
„In one of the modes, the chain of qubits transmits electronic radiation in the microwave range very well while remaining a quantum element. In another mode, it turns the superconducting phase by 180 degrees and locks the transmission of electromagnetic waves through itself. Yet it still remains a quantum system. So with the help of a magnetic field, such a material can be used as a control element in systems for quantum signals (separate photons) in circuits, from which developing quantum computers consist of”, said Ilya Besedin, an engineer at the NUST MISIS Laboratory of Superconducting Metamaterials and one of the project’s researchers.
It is hard to accurately calculate the properties of one twin qubit on a standard computer compared to the properties of a standard qubit. It is possible to reach the limit of complexity, a level close to or surpassing the capabilities of modern electronic computers, if qubits become several times more complex. Such a complex system can be used as a quantum simulator, i.e. a device that can predict or simulate properties of a certain real process or material.
As the researchers note, they had to sort out lots of theories to correctly describe the processes that occurs in quantum meta-materials.
Source: National University of Science and Technology MISIS
descriu dezvoltarea unui material catalitic ieftin și eficient pentru un tip de celulă de combustibil numită celulă de combustibil cu membrană din polimer electrolitic (PEMFC), care transformă energia chimică a hidrogenului în energie electrică și se numără printre cele mai promițătoare tipuri de celule de combustibil pentru motoarele electrice și electronice.Cercetătorii UC Riverside au dezvoltat un material catalitic ieftin și eficient pentru celulele de combustie din polimer electrolitic (PEM), care se numără printre cele mai promițătoare tipuri de celule de combustibil la motoarele electrice și electronice.Materialul pe care l-am creat poate permite producătorilor de automobile să transforme componentele structurale, cum ar fi hota sau șasiul, în elemente funcționale care ajută la alimentarea autovehiculelor”
Posted: Jan 22, 2018
Making fuel cells for a fraction of the cost
(Nanowerk News) Fuel cells have the potential to be a clean and efficient way to run cars, computers, and power stations, but the cost of producing them is limiting their use. That’s because a key component of the most common fuel cells is a catalyst made from the precious metal platinum.
In a paper published today in Small („Electrocatalytic N-Doped Graphitic Nanofiber – Metal/Metal Oxide Nanoparticle Composites”), researchers at the University of California, Riverside, describe the development of an inexpensive, efficient catalyst material for a type of fuel cell called a polymer electrolyte membrane fuel cell (PEMFC), which turns the chemical energy of hydrogen into electricity and is among the most promising fuel cell types to power cars and electronics.
Engineered carbon fibers embedded with active nanoparticles (top) can be fabricated into structural materials that are lightweight and flexible (bottom). (Image: UC Riverside)
The catalyst developed at UCR is made of porous carbon nanofibers embedded with a compound made from a relatively abundant metal such as cobalt, which is more than 100 times less expensive than platinum. The research was led by David Kisailus, the Winston Chung Endowed Professor in Energy Innovation in UCR’s Marlan and Rosemary Bourns College of Engineering.
Fuel cells, which are already being used by some carmakers, offer advantages over conventional combustion technologies, including higher efficiency, quieter operation and lower emissions. Hydrogen fuel cells emit only water.
Like batteries, fuel cells are electrochemical devices that comprise a positive and negative electrode sandwiching an electrolyte. When a hydrogen fuel is injected onto the anode, a catalyst separates the hydrogen molecules into positively charged particles called protons and negatively charged particles called electrons. The electrons are directed through an external circuit, where they do useful work, such as powering an electric motor, before rejoining the positively charged hydrogen ions and oxygen to form water.
A critical barrier to fuel cell adoption is the cost of platinum, making the development of alternative catalyst materials a key driver for their mass implementation.
Using a technique called electrospinning, the UCR researchers made paper-thin sheets of carbon nanofibers that contained metal ions – either cobalt, iron or nickel. Upon heating, the ions formed ultrafine metal nanoparticles that catalyzed the transformation of carbon into a high-performance graphitic carbon. Subsequently, the metal nanoparticles and residual nongraphitic carbon were oxidized, leading to a highly porous and useful network of metal oxide nanoparticles dispersed in a porous network of graphite.
UC Riverside researchers have developed an inexpensive, efficient catalyst material for polymer electrolyte membrane (PEM) fuel cells which are among the most promising fuel cell types to power cars and electronics. (Image: BEXIM (CC BY 4.0))
Kisailus and his team, collaborating with scientists at Stanford University, determined that the new materials performed as good as the industry standard platinum-carbon systems, but at a fraction of the cost.
„The key to the high performance of the materials we created is the combination of the chemistry and fiber processing conditions,” Kisailus said. „The remarkable electrochemical properties were primarily attributed to the synergistic effects obtained from the engineering of the metal oxide with exposed active sites and the 3D hierarchical porous graphitic structure.”
Kisailus said an added benefit of the catalytic nanocomposite was that its graphitic fiber nature provided additional strength and durability, which would enable it to serve as both a fuel cell catalyst and potentially as a structural component.
„An important challenge in making high-performance vehicles is reducing weight, both from the body of the vehicle as well as extra weight from the battery or fuel cell, without affecting safety or performance,” he said. „The material we created may enable automakers to turn structural components, such as the hood or the chassis, into functional elements that help power cars.”
Un material compozit nanostructurat dezvoltat la UC Santa Cruz a arătat o performanță impresionantă ca un catalizator pentru despicarea electrochimică a apei pentru a produce hidrogen. Un catalizator eficient și ieftin este esențial pentru realizarea promisiunii de hidrogen ca un combustibil curat și ecologic.
Posted: Jan 17, 2018
New nanocatalyst for hydrogen production
(Nanowerk News) A nanostructured composite material developed at UC Santa Cruz has shown impressive performance as a catalyst for the electrochemical splitting of water to produce hydrogen. An efficient, low-cost catalyst is essential for realizing the promise of hydrogen as a clean, environmentally friendly fuel.
Researchers led by Shaowei Chen, professor of chemistry and biochemistry at UC Santa Cruz, have been investigating the use of carbon-based nanostructured materials as catalysts for the reaction that generates hydrogen from water.
In one recent study, they obtained good results by incorporating ruthenium ions into a sheet-like nanostructure composed of carbon nitride. Performance was further improved by combining the ruthenium-doped carbon nitride with graphene, a sheet-like form of carbon, to form a layered composite.
„The bonding chemistry of ruthenium with nitrogen in these nanostructured materials plays a key role in the high catalytic performance,” Chen said. „We also showed that the stability of the catalyst is very good.”
The Front Cover shows the production of hydrogen gas when electrons and protons meet on ruthenium ion-complexed graphitic carbon nitride nanosheets supported on graphene surface. The image is based on an ancient Chinese legend of Niulang and Zhinü. Niulang was a human cowherd and Zhinü was a fairy from heaven. They fell in love with each other. Yet their love was banned by the fairy’s queen, who forcefully separated them by the Silver River. The lovers were only able to see each other once a year, on the 7th day of the 7th lunar month, with the help of a flock of magpies that formed a bridge.The new findings were published in ChemSusChem(„Ruthenium Ion-Complexed Graphitic Carbon Nitride Nanosheets Supported on Reduced Graphene Oxide as High-Performance Catalysts for Electrochemical Hydrogen Evolution”) and is featured on the cover of the January 10 issue. First author Yi Peng, a graduate student in Chen’s lab, led the study and designed the cover image.
Hydrogen has long been attractive as a clean and renewable fuel. A hydrogen fuel cell powering an electric vehicle, for example, emits only water vapor. Currently, however, hydrogen production still depends heavily on fossil fuels (mostly using steam to extract it from natural gas). Finding a low-cost, efficient way to extract hydrogen from water through electrolysis would be a major breakthrough. Electricity from renewable sources such as solar and wind power, which can be intermittent and unreliable, could then be easily stored and distributed as hydrogen fuel.
Currently, the most efficient catalysts for the electrochemical reaction that generates hydrogen from water are based on platinum, which is scarce and expensive. Carbon-based materials have shown promise, but their performance has not come close to that of platinum-based catalysts.
In the new composite material developed by Chen’s lab, the ruthenium ions embedded in the carbon nitride nanosheets change the distribution of electrons in the matrix, creating more active sites for the binding of protons to generate hydrogen. Adding graphene to the structure further enhances the redistribution of electrons.
„The graphene forms a sandwich structure with the carbon nitride nanosheets and results in further redistribution of electrons. This gives us greater proton reduction efficiencies,” Chen said.
The electrocatalytic performance of the composite was comparable to that of commercial platinum catalysts, the authors reported. Chen noted, however, that researchers still have a long way to go to achieve cheap and efficient hydrogen production.
Noul material a fost testat legat de plasa de rechin din Golful Watson din Sydney, arătând că nanomaterialele erau eficiente pentru a rezista la biofoluarea într-un mediu marin.Suprafețele antifoulare sunt deformabile și transparente, ceea ce face ca aplicarea lor să fie ideală pentru camerele și senzorii subacvatici. a dezvoltat straturi de acoperire nanostructurate care au proprietati antivegetative fara a folosi componente toxice.
Posted: Jan 17, 2018
Wrinkled nanocoatings could save billions in shipping and aquaculture
(Nanowerk News) A team of chemistry researchers from the University of Sydney Nano Institute has developed nanostructured surface coatings that have anti-fouling properties without using any toxic components.
Biofouling – the build-up of damaging biological material – is a huge economic issue, costing the aquaculture and shipping industries billions of dollars a year in maintenance and extra fuel usage. It is estimated that the increased drag on ship hulls due to biofouling costs the shipping industry in Australia $320 million a year.
Since the banning of the toxic anti-fouling agent tributyltin, the need for new non-toxic methods to stop marine biofouling has been pressing.
Leader of the research team, Associate Professor Chiara Neto, said: “We are keen to understand how these surfaces work and also push the boundaries of their application, especially for energy efficiency. Slippery coatings are expected to be drag-reducing, which means that objects, such as ships, could move through water with much less energy required.”
The Nepenthes pitcher plant traps a lubricating layer in the structure of its peristome. The nanowrinkles developed by the team function in the same way, trapping a lubricating layer that stops the adhesion of bacteria and other marine organisms, and could have drag-reducing properties. (click on image to enlarge)
The new materials were tested tied to shark netting in Sydney’s Watson Bay, showing that the nanomaterials were efficient at resisting biofouling in a marine environment.
The new coating uses ‘nanowrinkles’ inspired by the carnivorous Nepenthes pitcher plant. The plant traps a layer of water on the tiny structures around the rim of its opening. This creates a slippery layer causing insects to aquaplane on the surface, before they slip into the pitcher where they are digested.
Nanostructures utilise materials engineered at the scale of billionths of a metre – 100,000 times smaller than the width of a human hair. Associate Professor Neto’s group at Sydney Nano is developing nanoscale materials for future development in industry.
Biofouling can occur on any surface that is wet for a long period of time, for example aquaculture nets, marine sensors and cameras, and ship hulls. The slippery surface developed by the Neto group stops the initial adhesion of bacteria, inhibiting the formation of a biofilm from which larger marine fouling organisms can grow.
The interdisciplinary University of Sydney team included biofouling expert Professor Truis Smith-Palmer of St Francis Xavier University in Nova Scotia, Canada, who was on sabbatical visit to the Neto group for a year, partially funded by the Faculty of Science scheme for visiting women.
In the lab, the slippery surfaces resisted almost all fouling from a common species of marine bacteria, while control Teflon samples without the lubricating layer were completely fouled. Not satisfied with testing the surfaces under highly controlled lab conditions with only one type of bacteria the team also tested the surfaces in the ocean, with the help of marine biologist Professor Ross Coleman.
Test surfaces were attached to swimming nets at Watsons Bay baths in Sydney Harbour for a period of seven weeks. In the much harsher marine environment, the slippery surfaces were still very efficient at resisting fouling.
The antifouling coatings are mouldable and transparent, making their application ideal for underwater cameras and sensors.
Aliajele MXene sunt o clasă foarte recent descoperită de materiale 2D, care ar putea consta în oricare dintre milioane de aranjamente posibile ale metalelor de tranziție (precum molibden sau titan), carbon și azot. Aceste caracteristici se reflectă în denumirea „MXene” – „M” reprezintă atomi de metal, „X” reprezintă carbon și azot, în timp ce sufixul „ene” semnalează structura atomică 2D a materialelor.
Posted: Jan 16, 2018
Clever simulation scheme helps identify the most promising compositions of 2D materials
(Nanowerk News) A high-throughput scan of possible compositions for a new class of materials known as MXenes gives researchers invaluable direction for picking the best candidate from the millions of possible material recipes (ACS Nano, „High-throughput survey of ordering configurations in MXene alloys across compositions and temperatures”). The simulation study by researchers from the A*STAR Institute of High Performance Computing is a significant advancement in the field of MXenes, which have exciting potential in next-generation energy storage applications.
Two-dimensional (2D) materials are a relatively new class of materials that display a wide range of unusual properties associated with their ability to constrain the movement of electrons and energy in a 2D plane. The MXene alloys are a very recently discovered class of 2D materials, which could conceivably consist of any of millions of possible arrangements of transition metals (like molybdenum or titanium), carbon and nitrogen. These characteristics are reflected in the name ‘MXene’ — the ‘M’ represents metal atoms, the ‘X’ denotes carbon and nitrogen, while the ‘ene’ suffix signals the materials’ 2D atomic structure.
“Since MXenes are new, there’s still much to be learned about their structure and properties,” says Teck Leong Tan from A*STAR. “As MXene alloys are formed by mixing different types of transition elements at different compositions, the alloying possibilities in MXenes are huge. So we developed a high-throughput computational method to predict the probable structures and stable phases of different MXene alloys across all compositional ranges and temperatures.”
Although there are many possible MXene alloy compositions, most will not be stable. The challenge faced by material scientists has been how to efficiently sweep through the huge number of alloy configurations to identify those with the lowest formation energy and hence highest stability. Conventional ‘first principles’ calculation approaches are too computationally intensive for such a scan to be feasible.
“Our approach uses what’s called a cluster expansion method to ‘learn’ the effective interactions between atoms, thus enabling quick evaluation of the formation energies of millions of MXene alloy structures,” says Tan.
The scan, conducted in collaboration with Drexel University in the US, revealed that molybdenum-based MXenes mixed with vanadium, tantalum, niobium or titanium, appear to form the most stable ordered structures. Titanium however tends to form stable ‘asymmetric’ ordered structures that were previously not considered viable.
“Our scan allows us to predict the structures of MXene alloys that are yet to be fabricated and estimate the likelihood of their fabrication from a thermodynamics viewpoint. And for known MXene alloys, our predicted structures are consistent with experimental results.”
a prezentat un nou tip de adezivi subacvatici care sunt mai rezistenți decât clemele biologice naturale pe care mielurile le folosesc în mod normal pentru a adera la roci, creaturi de mare.Acest adeziv care blochează hidrogelul poate fi folosit ca un adeziv umed robust și versatil pentru o gamă largă de aplicații care necesită o aderență stabilă și puternică în diverse condiții umede
Posted: Jan 16, 2018
New insights into underwater adhesives
(Nanowerk News) A Korean research team, affiliated with Ulsan National Institute of Science and Technology (UNIST) has presented a new type of underwater adhesives that are tougher than the natural biological glues that mussels normally use to adhere to rocks, ships, and larger sea critters. This has attracted much attention as a technology that surpass the limits of conventional chemical-based adhesives that significantly lose adhesion capability when exposed to moisture or when reused.
Photograph of the fabricated flexible interlocking adhesive (left) and a SEM image (center) of the PEGDMA microhook arrays of the adhesive. Shown on right is the conceptual illustration of the reversible interlocking of the PEGDMA microhook arrays via the hydration-induced shape reconfiguration of the array for high adhesion under wet conditions. (Image: UNIST)
Wet adhesives are substances that are applied to the joining surfaces in the fluid state. According to the research team, stable adhesion between surfaces under wet conditions is highly desirable for many practical applications, particularly in the bioengineering and medical fields, where most surfaces are wet. However, limitations in complicated surface treatment and expensive protocols restrain the extensive use of these natural protein adhesives. Furthermore, they are typically permanent adhesives, and therefore, have limitations for application as a reversible and reusable adhesive.
Professor Jeong solved such issues using the simple hydrogel microstructures alone. In the study, the research team presented a wet-responsive, shape-reconfigurable, and flexible hydrogel adhesives that exhibit strong adhesion under wet environments based on reversible interlocking between reconfigurable microhook arrays.
The microhooks of the adhesive were designed to exhibit a unique structural configuration with protruding heads. The adhesion between the interlocked microhook arrays is greatly enhanced under wet conditions because of the hydration-triggered shape reconfiguration of the hydrogel microstructures. Furthermore, this water-responsive shape change was reversible and the microstructure can recover its original shape and size upon water removal by drying.
„These adhesives take the form of thin flexible films with bioinspired mushroom-shaped micropillars uniformly spread on the surface of microstructure,” says Hyun-Ha Park in the Ph.D. program of Mechanical Engineering, the first author of the study. „When the interlocked arrays are exposed to water, a notable volume expansion of a corresponding shape transformation of the hydrogel microhooks occurred by the swelling of the hydrogel, resulting in significantly increased wet adhesion both in the shear and normal directions.”
The research team notes, „In contrast to other wet binding systems, the current interlocking mechanism does not involve any complicated surface treatment or chemical moieties, thus allowing for a simple yet efficient route to strong and reversible wet adhesion in a cost-effective manner.”
„The surface of the conventional chemical adhesives softens or dissolves when exposed to moisture or water, which can lead to a significant decrease in adhesive bond strength or loss of adhesion over time,” says Professor Jeong. „In contrast to other wet binding systems, the current interlocking mechanism does not involve any complicated surface treatment or chemical moieties, thus allowing for a simple yet efficient route to strong and reversible wet adhesion in a cost-effective manner.”
„This wet-responsive and reversible hydrogel interlocking adhesive can serve as a robust and versatile wet adhesive for a broad range of applications which require stable and strong adhesion under diverse wet conditions,” Professor Jeong adds.
Source: Ulsan National Institute of Science and Technology
Efectul durității particulelor asupra comportamentului de penetrare a țesăturilor intercalate cu particule uscate și suspensii concentrate de lichide particulare
