Oamenii de stiinta din armata au dovedit o predictie veche de zeci de ani ca amestecarea TNT si nanoparticulele de aluminiu noi pot spori semnificativ performantele energetice. Această descoperire explozivă se așteaptă să extindă puterea de foc a armatei americane în luptă.
Cercetătorii de la Laboratorul de Cercetare US Army si Universitatea Texas Tech a demonstrat până la accesoriu 30 la suta in viteza de detonare a TNT exploziv prin adaugarea nanoparticule noi de aluminiu, în care învelișul de alumină nativă a fost înlocuită cu o sare oxidantă numită AIH sau iodat de aluminiu hexahidrat.
Posted: Jun 11, 2018
Scientists have a blast with aluminum nanoparticles
(Nanowerk News) Army scientists proved a decades-old prediction that mixing TNT and novel aluminum nanoparticles can significantly enhance energetic performance. This explosive discovery is expected to extend the reach of U.S. Army firepower in battle.
Researchers from the U.S. Army Research Laboratory and Texas Tech University demonstrated up to 30-percent enhancement in the detonation velocity of the explosive TNT by adding novel aluminum nanoparticles in which the native alumina shell has been replaced with an oxidizing salt called AIH, or aluminum iodate hexahydrate.
This is a single nanoparticle extracted out from a view of native aluminum particles at 150,000 magnification. The image highlights the amorphous oxide shell surrounding the crystalline core. (Image: U.S. Army Research Laboratory)
The structure of the AIH-coated aluminum nanoparticles was revealed for the very first time through high resolution transmission electron (TEM) microscopy performed by ARL’s Dr. Chi-Chin Wu, a materials researcher who leads the plasma research for the lab’s Energetic Materials Science Branch in the Lethality Division of Weapons and Materials Research Directorate.
Wu said this revolutionary research offers the potential for the exploitation of aluminum and potentially other metallic nanoparticles in explosive formulations to extend the range and destructive power of Army weapons systems, a key objective of the Army’s „Long Range Precision Fires” modernization priority.
„We believe these results show tremendous promise for enhancing the detonation performance of conventional military explosives with aluminum nanoparticles for the first time,” said ARL’s Dr. Jennifer Gottfried, a physical chemist who collaborated on the research.
„It is very exciting to advance science to a point where we can harness more chemical energy from metal particles at faster timescales. This is an exciting time for transforming energy generation technology,” said Dr. Michelle L. Pantoya, the J. W. Wright Regents Chair in Mechanical Engineering and Professor at Texas Tech University.
The team found that the crystalline aluminum core was effectively protected against unwanted oxidation by the AIH shell, which appears as protruding nodules on the aluminum surface. The enhanced reactivity due to this unique morphological feature and novel core-shell structure was demonstrated by laser-induced air shock from energetic materials experiments, an innovative laboratory-scale energetic testing method developed by Gottfried. This technique involves impacting the sample with a high-energy, focused laser pulse to violently break apart the explosive molecules. The interaction of the laser with the material forms a laser-induced plasma and produces a shock wave that expands into the surrounding air. The energy released from an explosive sample can then be experimentally determined by measuring the laser-induced shock velocity with a high-speed camera.
It was predicted decades ago that aluminum nanoparticles have the potential to enhance the energetic performance of explosives and propellants because of their high energy content and potential for rapid burning. This is because they have exceptionally large surface areas compared to their total volume and a very large heat of reaction. However, the surface of the aluminum nanoparticles is naturally oxidized in air to form a thick alumina shell, typically 20% by weight, which not only lowers the energy content of the nanoparticles by reducing the amount of active aluminum, it also slows the rate of energy release because it acts as a barrier to the reaction of the aluminum with the explosive. Therefore, replacing the oxide shell, as successfully achieved by TTU, can significantly improve the explosive performance.
These preliminary joint efforts have also led to a formal research collaboration under an ARL Director’s Research Award, the fiscal 2018 External Collaboration Initiative between Wu and TTU.
After publishing two papers in high-impact scientific journals in the past year, the team is poised to pursue additional energetics research with aluminum nanoparticles by working with the U.S. Army Research, Development and Engineering Command at Picatinny Arsenal, New Jersey, and the Air Force Research Laboratory.
Capacul de supresoare Magpul – 5,5 „este alcătuit dintr-un manșon din polimer rezistent la căldură suprapus peste un scut încălzit din oțel inoxidabil, care se montează direct pe corpul supresor cu cleme din oțel” care „minimizează transferul de căldură pentru a menține temperaturile de acoperire externe până la 1000 grade F mai rece decât suprafața supresorului și permite răcirea fluxului de aer în recipient. În plus, servește ca dispozitiv izolator termic îmbunătățit și dispozitiv de reducere a semnăturii, reducând în mod semnificativ distorsiunile mirajului la imaginea de vedere a shooterului, reducând probabilitatea de deteriorare a impactului asupra corpului supresor și diminuând șansele de accidentare accidentală a calității sau deteriorarea personalului sau echipament în timpul arderii armei și răcire
Magpul Suppressor Cover – 5.5″ for Round 5.56mm NATO Muzzle Cans (Silencers/Sound Suppressors) during Combat Ops: Lowers Outer Suppressor Heat and Thermal Signature! (Video!)
DefenseReview’s (DR) found that it’s often the little things that can make your life a lot better and/or easier. Assuming it works as advertised, the Magpul Suppressor Cover – 5.5″ (5.5 inches) is one of those products. When it comes to guns heat’s the enemy in a whole bunch of ways, particularly with rifle/carbines, and even more particularly with select-fire rifle/carbines, including those in 5.56mm NATO (5.56x45mm NATO) caliber. Anyway, the Magpul Suppressor Cover – 5.5″ (5.5 inches) is specifically designed to cover 1.5” outer diameter/5.5″-long round cans (silencers/sound suppressors) like the popular Surefire SOCOM556-RC2 muzzle can (silencer/sound suppressor), and it would appear to be very well designed for that purpose.
The the Magpul Suppressor Cover – 5.5″ consists of a “heat-resistant polymer sleeve overlaid onto a raised stainless steel heat shield that mounts directly to the suppressor body with steel clamps” that “minimizes heat transfer to keep external cover temperatures up to 1000 degrees F cooler than the surface of the suppressor and allows cooling airflow across the can. Additionally, it serves as an enhanced thermal insulator and signature reduction device, significantly mitigating mirage distortions to the shooter’s sight picture, reducing the likelihood of impact damage to the suppressor body, and lessening the chance of accidental heat-related injury or damage to personnel or equipment during weapon firing and cool down.” Sounds pretty good.
When you’re involved in a high-speed, low-drag dynamic combat op involving a lot of moving, and perhaps even climbing and/or repelling, the last thing you need is a hot suppressor burning through your clothing or skin. So, why make life any harder than it has to be?
Oh, and the the Magpul Suppressor Cover – 5.5″ even lowers your can’s thermal signature, and attenuates/mitigates the mirage effect on your sight picture. Handy.
The following are Magpul Suppressor Cover – 5.5″ features, straight from the company’s website:
– Extreme temperature protection that mitigates internal suppressor temperatures to safe levels
– Minimizes retained heat, allowing faster cooling than any other suppressor cover technology
– Reduces thermal signature of host firearm
– Mitigates mirage effects in sight picture
– Two stainless steel clamps provide a strong, rigid and reliable interface capable of sustained firing sessions and rough handling
– High temp polymer sleeve withstands brutal suppressor temperatures during extended periods of firing without deterioration
– High strength corrosion resistant stainless steel heat shield
Additional sizes for different can sizes and calibers are supposed to be avalable soon.
Anyway, DR like’s the this product, and looks forward to trying it out at some point. In the meantime, check out Defense Review’s video on it, below.
un sistem integrat de schelet de carbon care conectează o vesta de soldat și un rucsac, permițând îndepărtarea rapidă a rucsacului, după cum este necesar
Cercetătorii au demonstrat fabricarea pe scară largă a unui nou tip de peliculă electrozică transparentă pe bază de argint nanopatternat. Ecranele tactile cu ecran tactil și televizoarele cu ecran plat utilizează electrozi transparenți pentru a detecta atingerea și pentru a comuta rapid culoarea fiecărui pixe; cercetătorii raportează fabricarea unui film subțire transmițător transparent pe discuri de sticlă cu diametrul de 10 centimetri. Pe baza estimărilor teoretice care se potrivesc îndeaproape cu măsurătorile experimentale, ele calculează că electrozii subțiri de film subțire pot funcționa semnificativ mai bine decât cei utilizați pentru afișajele flexibile existente și ecranele touch.
Posted: Jun 07, 2018
Transparent, conductive films promising for developing flexible screens
(Nanowerk News) Researchers have demonstrated large-scale fabrication of a new type of transparent conductive electrode film based on nanopatterned silver. Smartphone touch screens and flat panel televisions use transparent electrodes to detect touch and to quickly switch the color of each pixel. Because silver is less brittle and more chemically resistant than materials currently used to make these electrodes, the new films could offer a high-performance and long-lasting option for use with flexible screens and electronics. The silver-based films could also enable flexible solar cells for installation on windows, roofs and even personal devices.
In the journal Optical Materials Express („Transparent and conductive electrodes by large-scale nano-structuring of noble metal thin-films”), the researchers report fabrication of a transparent conducting thin-film on glass discs 10 centimeters in diameter. Based on theoretical estimations that matched closely with experimental measurements, they calculate that the thin-film electrodes could perform significantly better than those used for existing flexible displays and touch screens.
The researchers used an approach called colloidal lithography to create a silver nanopattern that conducts electricity while letting light through the holes. The new transparent electrode films could be useful for solar cells as well as flexible displays and touch screens. (Image: Jes Linnet, University of Southern Denmark)
„The approach we used for fabrication is highly reproducible and creates a chemically stable configuration with a tunable tradeoff between transparency and conductive properties,” said the paper’s first author, Jes Linnet from the University of Southern Denmark. „This means that if a device needs higher transparency but less conductivity, the film can be made to accommodate by changing the thickness of the film.”
Finding a flexible alternative
Most of today’s transparent electrodes are made of indium tin oxide (ITO), which can exhibit up to 92 percent transparency – comparable to glass. Although highly transparent, ITO thin films must be processed carefully to achieve reproducible performance and are too brittle to use with flexible electronics or displays. Researchers are seeking alternatives to ITO because of these drawbacks.
The anti-corrosive nature of noble metals such as gold, silver and platinum makes them promising ITO alternatives for creating long-lasting, chemically resistant electrodes that could be used with flexible substrates. However, until now, noble metal transparent conductive films have suffered from high surface roughness, which can degrade performance because the interface between the film and other layers isn’t flat.
This scanning electron microscopy image shows a thin film of silver deposited over plastic nanoparticles. Dissolving the particles leaves a precise pattern of honeycomb-like holes that allow light to pass through, producing an electrically conductive and optically transparent film. (Image: Jes Linnet, University of Southern Denmark)
Transparent conductive films can also be made using carbon nanotubes, but these films don’t currently exhibit high enough conductance for all applications and tend to also suffer from surface roughness due to the nanotubes stacking on top of each other.
In the new study, the researchers used an approach called colloidal lithography to create transparent conductive silver thin films. They first created a masking layer, or template, by coating a 10-centimeter wafer with a single layer of evenly sized, close-packed plastic nanoparticles. The researchers placed these coated wafers into a plasma oven to shrink the size of all the particles evenly. When they deposited a thin film of silver onto the masking layer, the silver entered the spaces between the particles. They then dissolved the particles, leaving a precise pattern of honeycomb-like holes that allow light to pass through, producing an electrically conductive and optically transparent film.
Balancing transparency and conductivity
The researchers demonstrated that their large-scale fabrication method can be used to create silver transparent electrodes with as much as 80 percent transmittance while keeping electrical sheet resistance below 10 ohms per square – about a tenth of what has been reported for carbon-nanotube-based films with the equivalent transparency. The lower the electrical resistance, the better the electrodes are at conducting an electrical charge.
The researchers used colloidal lithography was used to create a thin film that was transparent and conductive thin film. (a) Schematic illustration of the fabrication process. (b) A single nanohole after the silver was deposited deposition and dissolving of the plastic particle. Scale bar: 200 nm. (c) Low magnification micrograph of deposited silver thin-film on homogenous particle monolayer, demonstrating large-scale feasibility. Scale bar: 50 microns. (d) Particle monolayer on substrate after spin-coating and a short (60 s) time in the plasma oven: Scale bar: 2 microns. (e) Particle monolayer after a long (3 min) time in the plasma oven, demonstrating that original particle positions are preserved even after significant size reduction. Scale bar: 10 microns. (Image: Jes Linnet, University of Southern Denmark) (click on image to enlarge)
„The most novel aspect of our work is that we accounted for both the transmission properties and the conductance properties of this thin film using theoretical analysis that correlated well with measured results,” said Linnet. „Fabrication problems typically make it hard to get the best theoretical performance from a new material. We decided to report what we encountered experimentally and postulate remedies so that this information could be used in the future to avoid or minimize problems that may affect performance.”
The researchers say that their findings show that colloidal lithography can be used to fabricate transparent conductive thin films that are chemically stable and could be useful for a variety of applications.
Oferind un mijloc inovator, ieftin și rapid de detectare a agenților de amenințare, o nouă tehnologie de detectare poate oferi avantaje semnificative pentru războinicii desfășurați
Datorită modificării grosimii care influențează și compoziția spectrală a luminii reflectate, materialul ar putea fi folosit ca nanosenzori colorimetrici. Datorită dimensiunilor extrem de mici și posibilei cuplări cu un laser și spectrometru miniaturizat, compozitul ar putea fi aplicat în viitor în sistemele de laborator pe cip sau chiar în celula umană.
Posted: Jun 05, 2018
Making composite material smart with precious metal
(Nanowerk News) Doping polymer brushes with gold nanoparticles results in a switchable composite material which changes its thickness depending on the pH value. The research by physicists at the TU Darmstadt, published in the journal Soft Matter („Making strong polyelectrolyte brushes pH-sensitive by incorporation of gold nanoparticles”), could be used to design chemical nanosensors in diagnostics or environmental analytics.
Polymer brushes are chains of large molecules which are densely grafted on a surface. Due to electrostatic forces, the chains extend from the surface and form a fur-like layer with a thickness of several hundred nanometres.
Currently, research focuses on the design of polymer systems responding to various environmental stimuli such as pH value, temperature or specific biomarkers. Physicists at TU Darmstadt and TU Berlin have shown for the first time how the thickness of a polymer brush can be made switchable by incorporating pH-sensitive gold nanoparticles.
“The combination of polymer chains and gold nanoparticles is promising, especially in medical diagnostics or environmental analytics,” says Dikran Boyaciyan. The 30-year-old PhD student works in the “Soft Matter at Interfaces” group led by professor Regine von Klitzing.
Physicist Dikran Boyaciyan synthesizes polymer brushes in the lab. (Image: Sebastian Keuth)
„This technology is still at an early stage of development. The primary objective is how the interaction between polymer systems and nanoparticles may be tuned and calibrated in a controlled environment,” Boyaciyan explains. Smart polymer materials could be used in chemical nanosensors which report on toxins or cancer cells, monitor parameters of organs or target the release of drugs inside the human body.
Boyaciyan tested two types of pH-insensitive polymers with respect to their prospect for long-term use as sensors: the non-ionic PNIPAM and the cationic PMETAC. The former was found unsuitable because of gold particles being washed out from the brush at high pH values. In the cationic PMETAC brush, however, the gold particles adhered unaffected by pH changes.
Furthermore, Boyaciyan was able to show how to make a reversible pH-switchable composite from PMETAC by incorporating gold nanoparticles and how its complex formation works. In an acidic environment, the particles lose their charge and both particle-particle interactions and particle-brush interactions occur. This leads to a swollen brush because of its chains being less confined.
In contrast, an alkaline environment causes negative charges on the particles and interactions with the positively charged brush are preferred. The chains collapse resulting in a thinner brush layer.
Because of the thickness change also influencing the spectral composition of the reflected light, the material could be used as colorimetric nanosensors. Due to the extremely small dimensions and possible coupling with a miniaturized laser and spectrometer the composite could, in future, be applied in lab-on-a-chip systems or even within the human cell.
reprezintă prima utilizare a unui material produs de ciuperci într-un dispozitiv electric subțire.Cercetatorii de la Universitatea de Stat din Oregon se uita la un pigment organic durabil, folosit de om in lucrari de arta de sute de ani, ca o posibilitate promitatoare ca material semiconductor.
Constatările sugerează că ar putea deveni o alternativă durabilă, ieftină și ușor fabricată la siliciu în aplicații electronice sau optoelectronice, unde nu sunt necesare capacitățile de înaltă performanță ale siliciului.
Optoelectronica este o tehnologie care lucrează cu utilizarea combinată a luminii și electronicii, cum ar fi celulele solare, iar pigmentul studiat este xylindein.
Posted: Jun 05, 2018
Fungi-produced pigment shows promise as semiconductor material
(Nanowerk News) Researchers at Oregon State University are looking at a highly durable organic pigment, used by humans in artwork for hundreds of years, as a promising possibility as a semiconductor material.
Findings suggest it could become a sustainable, low-cost, easily fabricated alternative to silicon in electronic or optoelectronic applications where the high-performance capabilities of silicon aren’t required.
Optoelectronics is technology working with the combined use of light and electronics, such as solar cells, and the pigment being studied is xylindein.
Chlorociboria Aeruginascens fungus on a tree log. (Image: Oregon State University)
„Xylindein is pretty, but can it also be useful? How much can we squeeze out of it?” said Oregon State University physicist Oksana Ostroverkhova. „It functions as an electronic material but not a great one, but there’s optimism we can make it better.”
Xylindien is secreted by two wood-eating fungi in the Chlorociboria genus. Any wood that’s infected by the fungi is stained a blue-green color, and artisans have prized xylindein-affected wood for centuries.
The pigment is so stable that decorative products made half a millennium ago still exhibit its distinctive hue. It holds up against prolonged exposure to heat, ultraviolet light and electrical stress.
„If we can learn the secret for why those fungi-produced pigments are so stable, we could solve a problem that exists with organic electronics,” Ostroverkhova said. „Also, many organic electronic materials are too expensive to produce, so we’re looking to do something inexpensively in an ecologically friendly way that’s good for the economy.”
With current fabrication techniques, xylindein tends to form non-uniform films with a porous, irregular, „rocky” structure.
„There’s a lot of performance variation,” she said. „You can tinker with it in the lab, but you can’t really make a technologically relevant device out of it on a large scale. But we found a way to make it more easily processed and to get a decent film quality.”
Ostroverkhova and collaborators in OSU’s colleges of Science and Forestry blended xylindein with a transparent, non-conductive polymer, poly(methyl methacrylate), abbreviated to PMMA and sometimes known as acrylic glass. They drop-cast solutions both of pristine xylindein and a xlyindein-PMMA blend onto electrodes on a glass substrate for testing.
They found the non-conducting polymer greatly improved the film structure without a detrimental effect on xylindein’s electrical properties. And the blended films actually showed better photosensitivity.
„Exactly why that happened, and its potential value in solar cells, is something we’ll be investigating in future research,” Ostroverkhova said. „We’ll also look into replacing the polymer with a natural product – something sustainable made from cellulose. We could grow the pigment from the cellulose and be able to make a device that’s all ready to go.
„Xylindein will never beat silicon, but for many applications, it doesn’t need to beat silicon,” she said. „It could work well for depositing onto large, flexible substrates, like for making wearable electronics.”
„And there are a lot more of the materials,” Ostroverkhova said. „This is just first one we’ve explored. It could be the beginning of a whole new class of organic electronic materials.”
O serie de acte și regulamente, care au fost sperate de Underwriters Laboratories DoD și Institutul Național al Justiției guvernează utilizarea armelor nebune de ceramică
