Institute for Nuclear Problems

Minsk, Belarus

Institute for Nuclear Problems

Minsk, Belarus
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News Article | January 20, 2016
Site: www.materialstoday.com

Antireflective coatings are used to cut surface glare in everything from eyeglasses and camera lenses to solar cells, TV screens and LED devices. Now, inspired by the eyes of moths, researchers from the Research Institute for Nuclear Problems of Belarusian State University in Belarus and Institut Jean Lamour-Université de Lorraine in France have developed a novel, low-cost, ultra-lightweight material that can act as an effective anti-reflective surface for microwave radiation. The eyes of moths are covered with a periodic, hexagonal pattern of tiny bumps smaller than the wavelength of the incident light. They act as a continuous refractive index gradient, allowing the moths to see at night and avoid nocturnal predators, like bats. This structure also makes the moth eye one of the most effective antireflective coatings in nature. It has already successfully been mimicked by scientists to produce high-performance antireflective coatings for visible light, albeit coatings that are often expensive to fabricate and difficult to customize. This new material cuts down reflections from microwaves rather than from visible light; blocking microwave reflection is important for conducting precise microwave measurements. As a consequence, the coating may be used as a radar-absorbing material in stealth technology, making an airplane invisible to radar, or in police traffic radar that uses microwaves to measure the speed of passing cars. Described in Applied Physics Letters, the new technology is based on a monolayer of hollow carbon spheres packed in two dimensions. The researchers have demonstrated that this monolayer is able to achieve almost perfect microwave absorption – near 100% absorption of microwaves in the Ka-band (26–37 gigahertz) frequency range, the first antireflective material to achieve this. "Based on the experimental and modeling results, we found that using hollow carbon spheres with larger spherical diameters and optimal shell thickness it is possible to achieve almost perfect microwave absorption," said Dzmitry Bychanok, the primary author and a researcher at the Research Institute for Nuclear Problems of Belarusian State University in Belarus. The novel coating material they produced can also be completely derived from biological resources, he added, which may make it greener, lower-cost, easier to fabricate and ultra-lightweight compared to conventional antireflective coatings. Hollow carbon spheres with a uniform diameter can be used to produce ordered periodic structures. To mimic the structure of moth eyes, the researchers compactly packed the hollow carbon spheres in two dimensions to form a hexagonal-patterned monolayer. This monolayer can then act as a strong, electrically conductive coating material. "You can picture the geometry of the hollow sphere monolayer as that of Christmas cake decoration balls compactly filled in a Petri dish – filling a flat surface with identical balls will lead to a spontaneous hexagonal self-ordering," Bychanok explained. "The spatial distribution of the hollow sphere monolayer is ideally hexagonal, but in practice it is more in-between cubic and hexagonal. The thickness of the monolayer is in the range of one to two millimeters." In the experiment, carbon hollow spheres were fabricated by a template method that utilized fish eggs or sugar-based polymer beads with certain diameters. Specifically, the researchers coated the bio-based template spheres with sugar, then ‘pyrolysed’ them – a chemical modification that involves thermally decomposing the resultant spheres in an inert atmosphere. This heating converts the sugar coating into char, while the inner template sphere is largely destroyed and decomposed into gas, leaving a hollow carbon sphere. Using theoretical modeling based on long-wave approximation and experimental measurements, the team studied the electromagnetic properties of monolayers produced by hollow spheres with different parameters, focusing on the Ka-band (microwave) frequency. Their results showed that, for electromagnetic applications requiring high absorption, the most effective hollow spheres are those with larger radii or diameters. Additionally, each value of hollow sphere radius has an optimum shell thickness to achieve the highest absorption coefficient. "Our study showed that the monolayer formed by spheres with a radius of 6mm and a shell thickness of about 5µm enables the highest microwave absorption coefficient, which is more than 95% at 30 gigahertz," said Bychanok. Bychanok said the work pointed out that moth-eye-like two-dimensional ordered structures based on hollow conducting spheres are promising systems for microwave radiation absorption applications. The team's next step is to investigate and develop three-dimensional periodic structures that can effectively manipulate microwave radiations. This story is adapted from material from the American Institute of Physics, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.


Silenko A.J.,Institute for Nuclear Problems
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The Proca-Corben-Schwinger equations for a spin-1 particle with an anomalous magnetic moment are added by a term describing an electric dipole moment, then they are reduced to a Hamiltonian form, and finally they are brought to the Foldy-Wouthuysen representation. Relativistic equations of motion are derived. The needed agreement between quantum-mechanical and classical relativistic equations of motion is proved. The scalar and tensor electric and magnetic polarizabilities of pointlike spin-1 particles (W bosons) are calculated for the first time. © 2013 American Physical Society.


Grubich A.O.,Institute for Nuclear Problems
Journal of Environmental Radioactivity | Year: 2012

Regardless of the surface area of the site, the spatial distribution of radioactive contamination of soils with 137Cs for Chernobyl fallout is described by a lognormal distribution. Moreover, the spatial pattern of the radioactive contamination of soil is random geometrical multifractal field. Due to that, any contamination spot, when studied in detail, decomposes into a multitude of small spots decomposing further into a multitude of smaller spots etc. Similar patterns are apparently characteristic for fallout of other radionuclides, the Fukushima fallout, as well as atmospheric fallout of non-radioactive dust and aerosols. © 2011 Elsevier Ltd.


Silenko A.Y.,Institute for Nuclear Problems
Physics of Particles and Nuclei Letters | Year: 2013

It is shown that, under the Wentzel-Kramers-Brillouin approximation conditions, using the Foldy-Wouthuysen (FW) representation allows the problem of finding a classical limit of relativistic quantum mechanical equations to be reduced to the replacement of operators in the Hamiltonian and quantum mechanical equations of motion by the respective classical quantities. © 2013 Pleiades Publishing, Ltd.


Silenko A.J.,Institute for Nuclear Problems | Silenko A.J.,Joint Institute for Nuclear Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The exact Foldy-Wouthuysen Hamiltonian is derived for a pointlike spin-1 particle with a normal magnetic moment in a nonuniform magnetic field. For a uniform magnetic field, it is exactly separated into terms linear and quadratic in spin. New unexpected properties of a particle with an anomalous magnetic moment are found. Spin projections of a particle moving in a uniform magnetic field are not integer, and the tensor polarization is asymmetric in the plane orthogonal to the field. Previously described spin-tensor effects caused by the tensor magnetic polarizability exist not only for nuclei but also for pointlike particles. © 2014 American Physical Society.


Silenko A.Y.,Institute for Nuclear Problems
Theoretical and Mathematical Physics | Year: 2013

Relativistic methods for the Foldy-Wouthuysen transformation of the "step-by-step" type already at the first step give an expression for the Hamilton operator not coinciding with the exact result determined by the Eriksen method. The methods agree for the zeroth and first orders in the Planck constant terms but do not agree for the second and higher-order terms. We analyze the benefits and drawbacks of various methods and establish their applicability boundaries. © 2013 Pleiades Publishing, Ltd.


Baryshevsky V.G.,Institute for Nuclear Problems
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

The use of spin rotation effect in bent crystals for measuring the magnetic moment of short-lived particles in the range of LHC and FCC energies is considered. It is shown that the estimated number of produced baryons that are captured into a bent crystal grows as ~γ3/2 with increasing particle energy. Hence it may be concluded that the experimental measurement of magnetic moments of short-lived particles using the spin rotation effect is feasible at LHC and higher energies (for LHC energies, e.g., the running time required for measuring the magnetic moment of Λc+ is 2÷16 hours). © 2016 The Author.


News Article | January 5, 2016
Site: phys.org

The eyes of moths are covered with a periodic, hexagonal pattern of tiny bumps smaller than the wavelength of the incident light. They act as a continuous refractive index gradient, allowing the moths to see at night and avoid nocturnal predators, like the bat. The physiology also makes the moth eye one of the most effective antireflective coatings in nature. It has already successfully been mimicked by scientists for developing high-performance antireflective coatings for visible lights—albeit coatings that are often expensive to fabricate and difficult to customize. The new material cuts down reflections from microwaves rather than from visible light—invisible energy from a different part of the energy spectrum. Blocking microwave reflection is an important application for precise microwave measurements, and the coating may be used as a radar absorbing material in stealth technology, a technique that makes make an airplane invisible to radar, or police traffic radar that uses microwaves to measure car speed. Described this week in the journal Applied Physics Letters from AIP Publishing, the new technology is based on a monolayer of hollow carbon spheres packed in two dimensions and has been demonstrated to be able to achieve almost perfect microwave absorption, i.e. near 100 percent absorption of microwaves in the Ka-band (26-37 gigahertz) frequency range, the first antireflective material to achieve this. "Based on the experimental and modeling results, we found that using hollow carbon spheres with larger spherical diameters and optimal shell thickness it is possible to achieve almost perfect microwave absorption," said Dzmitry Bychanok, the primary author and a researcher at the Research Institute for Nuclear Problems of Belarusian State University in Belarus. The novel coating material they produced can be completely derived from biological resources, he added, which may make it greener, lower-cost, easier to fabricate and ultra-lightweight compared to conventional antireflective coatings. How they Made the Material Hollow carbon spheres with uniform diameter can be used for producing ordered periodic structures. To mimick the structure of moth eyes, the researchers compactly packed hollow carbon spheres in two dimensions to form a hexagonal-patterned monolayer, which is a strong, electrically conductive coating material as well. "You can picture the geometry of the hollow sphere monolayer as that of Christmas cake decoration balls compactly filled in a Petri dish—filling a flat surface with identical balls will lead to a spontaneous hexagonal self-ordering," Bychanok explained. "The spatial distribution of the hollow sphere monolayer is ideally hexagonal, but in practice it is more in-between cubic and hexagonal. The thickness of the monolayer is in the range of one to two millimeters." In the experiment, carbon hollow spheres were fabricated by a template method based on fish eggs or sugar-based polymer beads with certain diameters. Specifically, the researchers coated the bio-based template spheres with sugar, then "pyrolysed" them—a chemical modification based on thermally decomposing the resultant spheres in inert atmosphere. During such heating, the sugar coating was converted into char at the surface of the spheres, while the inner template sphere was largely destroyed and decomposed into gas, leaving a hollow carbon sphere. Using theoretical modeling based on long-wave approximation and experimental measurements, the team studied the electromagnetic properties of monolayers based on different-parameter hollow spheres in Ka-band (microwave) frequency. The result showed that, for electromagnetic applications requiring high absorption, the most preferable hollow spheres are those with larger radii or diameters. Additionally, each value of hollow sphere radius has an optimum shell thickness to achieve the highest absorption coefficient. "Our study showed that the monolayer formed by spheres with a radius of six millimeters and a shell thickness of about five micrometers enables the highest microwave absorption coefficient, which is more than 95 percent at 30 gigahertz," said Bychanok. Bychanok said the work pointed out that moth-eye-like two-dimensional ordered structures based on hollow conducting spheres are promising systems for microwave radiation absorption applications. The team's next step is to investigate and develop three-dimensional periodic structures for an effective manipulation of microwave radiations. More information: "Hollow carbon spheres in microwaves: bio inspired absorbing coating" by D. Bychanok, S. Li,A. Sanchez-Sanchez, G. Gorokhov, P. Kuzhir, F.Y. Ogrin, A. Pasc,T. Ballweg, K.Mandel, A. Szczurek, V. Fierro and A. Celzard, Applied Physics Letters , Jan.5, 2015. DOI: 10.1063/1.4938537


News Article | January 6, 2016
Site: www.cemag.us

Antireflective coatings are used to cut surface glare in everything from eyeglasses and camera lenses to solar cells, TV screens, and LED devices. Now researchers from Research Institute for Nuclear Problems of Belarusian State University in Belarus and Institut Jean Lamour-Université de Lorraine in France have developed a novel, low-cost, ultra-lightweight material that could be used as an effective anti-reflective surface for microwave radiation based on the eyes of moths. The eyes of moths are covered with a periodic, hexagonal pattern of tiny bumps smaller than the wavelength of the incident light. They act as a continuous refractive index gradient, allowing the moths to see at night and avoid nocturnal predators, like the bat. The physiology also makes the moth eye one of the most effective antireflective coatings in nature. It has already successfully been mimicked by scientists for developing high-performance antireflective coatings for visible lights — albeit coatings that are often expensive to fabricate and difficult to customize. The new material cuts down reflections from microwaves rather than from visible light — invisible energy from a different part of the energy spectrum. Blocking microwave reflection is an important application for precise microwave measurements, and the coating may be used as a radar absorbing material in stealth technology, a technique that makes an airplane invisible to radar, or police traffic radar that uses microwaves to measure car speed. Described this week in the journal Applied Physics Letters from AIP Publishing, the new technology is based on a monolayer of hollow carbon spheres packed in two dimensions and has been demonstrated to be able to achieve almost perfect microwave absorption, i.e. near 100 percent absorption of microwaves in the Ka-band (26-37 gigahertz) frequency range, the first antireflective material to achieve this. “Based on the experimental and modeling results, we found that using hollow carbon spheres with larger spherical diameters and optimal shell thickness it is possible to achieve almost perfect microwave absorption,” says Dzmitry Bychanok, the primary author and a researcher at the Research Institute for Nuclear Problems of Belarusian State University in Belarus. The novel coating material they produced can be completely derived from biological resources, he added, which may make it greener, lower-cost, easier to fabricate and ultra-lightweight compared to conventional antireflective coatings. Hollow carbon spheres with uniform diameter can be used for producing ordered periodic structures. To mimic the structure of moth eyes, the researchers compactly packed hollow carbon spheres in two dimensions to form a hexagonal-patterned monolayer, which is a strong, electrically conductive coating material as well. “You can picture the geometry of the hollow sphere monolayer as that of Christmas cake decoration balls compactly filled in a Petri dish — filling a flat surface with identical balls will lead to a spontaneous hexagonal self-ordering,” Bychanok explains. “The spatial distribution of the hollow sphere monolayer is ideally hexagonal, but in practice it is more in-between cubic and hexagonal. The thickness of the monolayer is in the range of one to two millimeters.” In the experiment, carbon hollow spheres were fabricated by a template method based on fish eggs or sugar-based polymer beads with certain diameters. Specifically, the researchers coated the bio-based template spheres[JB1]  with sugar, then "pyrolysed" them — a chemical modification based on thermally decomposing the resultant spheres in inert atmosphere. During such heating, the sugar coating was converted into char at the surface of the spheres, while the inner template sphere was largely destroyed and decomposed into gas, leaving a hollow carbon sphere. Using theoretical modeling based on long-wave approximation and experimental measurements, the team studied the electromagnetic properties of monolayers based on different-parameter hollow spheres in Ka-band (microwave) frequency. The result showed that, for electromagnetic applications requiring high absorption, the most preferable hollow spheres are those with larger radii or diameters. Additionally, each value of hollow sphere radius has an optimum shell thickness to achieve the highest absorption coefficient. Our study showed that the monolayer formed by spheres with a radius of six millimeters and a shell thickness of about five micrometers enables the highest microwave absorption coefficient, which is more than 95 percent at 30 gigahertz,” says Bychanok. Bychanok says the work pointed out that moth-eye-like two-dimensional ordered structures based on hollow conducting spheres are promising systems for microwave radiation absorption applications. The team’s next step is to investigate and develop three-dimensional periodic structures for an effective manipulation of microwave radiations.


News Article | January 6, 2016
Site: www.rdmag.com

Antireflective coatings are used to cut surface glare in everything from eyeglasses and camera lenses to solar cells, TV screens and LED devices. Now researchers from Research Institute for Nuclear Problems of Belarusian State University in Belarus and Institut Jean Lamour-Université de Lorraine in France have developed a novel, low-cost, ultra-lightweight material that could be used as an effective anti-reflective surface for microwave radiation based on the eyes of moths. The eyes of moths are covered with a periodic, hexagonal pattern of tiny bumps smaller than the wavelength of the incident light. They act as a continuous refractive index gradient, allowing the moths to see at night and avoid nocturnal predators, like the bat. The physiology also makes the moth eye one of the most effective antireflective coatings in nature. It has already successfully been mimicked by scientists for developing high-performance antireflective coatings for visible lights -- albeit coatings that are often expensive to fabricate and difficult to customize. The new material cuts down reflections from microwaves rather than from visible light -- invisible energy from a different part of the energy spectrum. Blocking microwave reflection is an important application for precise microwave measurements, and the coating may be used as a radar absorbing material in stealth technology, a technique that makes make an airplane invisible to radar, or police traffic radar that uses microwaves to measure car speed. Described this week in the journal Applied Physics Letters from AIP Publishing, the new technology is based on a monolayer of hollow carbon spheres packed in two dimensions and has been demonstrated to be able to achieve almost perfect microwave absorption, i.e. near 100 percent absorption of microwaves in the Ka-band (26-37 gigahertz) frequency range, the first antireflective material to achieve this. "Based on the experimental and modeling results, we found that using hollow carbon spheres with larger spherical diameters and optimal shell thickness it is possible to achieve almost perfect microwave absorption," said Dzmitry Bychanok, the primary author and a researcher at the Research Institute for Nuclear Problems of Belarusian State University in Belarus. The novel coating material they produced can be completely derived from biological resources, he added, which may make it greener, lower-cost, easier to fabricate and ultra-lightweight compared to conventional antireflective coatings. How they Made the Material Hollow carbon spheres with uniform diameter can be used for producing ordered periodic structures. To mimick the structure of moth eyes, the researchers compactly packed hollow carbon spheres in two dimensions to form a hexagonal-patterned monolayer, which is a strong, electrically conductive coating material as well. "You can picture the geometry of the hollow sphere monolayer as that of Christmas cake decoration balls compactly filled in a Petri dish -- filling a flat surface with identical balls will lead to a spontaneous hexagonal self-ordering," Bychanok explained. "The spatial distribution of the hollow sphere monolayer is ideally hexagonal, but in practice it is more in-between cubic and hexagonal. The thickness of the monolayer is in the range of one to two millimeters." In the experiment, carbon hollow spheres were fabricated by a template method based on fish eggs or sugar-based polymer beads with certain diameters. Specifically, the researchers coated the bio-based template spheres with sugar, then "pyrolysed" them -- a chemical modification based on thermally decomposing the resultant spheres in inert atmosphere. During such heating, the sugar coating was converted into char at the surface of the spheres, while the inner template sphere was largely destroyed and decomposed into gas, leaving a hollow carbon sphere. Using theoretical modeling based on long-wave approximation and experimental measurements, the team studied the electromagnetic properties of monolayers based on different-parameter hollow spheres in Ka-band (microwave) frequency. The result showed that, for electromagnetic applications requiring high absorption, the most preferable hollow spheres are those with larger radii or diameters. Additionally, each value of hollow sphere radius has an optimum shell thickness to achieve the highest absorption coefficient. "Our study showed that the monolayer formed by spheres with a radius of six millimeters and a shell thickness of about five micrometers enables the highest microwave absorption coefficient, which is more than 95 percent at 30 gigahertz," said Bychanok. Bychanok said the work pointed out that moth-eye-like two-dimensional ordered structures based on hollow conducting spheres are promising systems for microwave radiation absorption applications. The team's next step is to investigate and develop three-dimensional periodic structures for an effective manipulation of microwave radiations.

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