Technology of Niat
OOC: Reference thread for all technologies and information about Niat. Posting is allowed, but please keep it to a minimum. You can always TG me about a question or something you have.
Technology
Nuclear Power:
Amidoxime for Uranium Extraction (http://forums.jolt.co.uk/showthread.php?p=12598202&posted=1#post12598202) (other metals included)
Nuclear Battery (http://forums.jolt.co.uk/showthread.php?p=12598205&posted=1#post12598205)
Solar Power:
Nanocrystal Solar Cells (http://forums.jolt.co.uk/showthread.php?p=12598188&posted=1#post12598188)
3-D Solar Cells (http://forums.jolt.co.uk/showthread.php?p=12598196&posted=1#post12598196)
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Quantum-Dot Leap
Tapping tiny crystals' inexplicable light-harvesting talent
Peter Weiss
One frustration of solar energy is that although it's free, clean, and inexhaustible, it's a major challenge to harvest efficiently. Consider what happens when photons of sunlight hit a solar cell: They strike electrons in semiconductor material and send them on their way as an electric current. Although many solar photons carry enough energy to theoretically unleash several electrons, they almost never free more than one.
The complex physics behind that limitation boils down to this: An electron loosed by absorbing a photon often collides with a nearby atom. But when it does, it's less likely to set another electron free than it is to create atomic vibrations that squander the electron's excess energy on heat.
For the past half century, the limit of one electron per solar photon seemed a regrettable fact of semiconductor physics. However, in recent tests of semiconductor bits only a few nanometers in diameter—entities known as nanocrystals or quantum dots—researchers have been surprised to find that photons at solar energies commonly unleash multiple electrons.
The number set loose depends on the dot's composition and—as a quirk of quantum mechanics—its size. Recent experiments on 8-nanometer-diameter lead selenide quantum dots have given the best results so far: Ultraviolet-light photons—albeit at a wavelength found sparingly in sunlight—released seven electrons apiece.
That leap in producing electrons could lead to major improvements in solar cell efficiencies, the researchers say, that is, if those electrons can be harvested from the cells. So far, evidence from prototype solar cells and photodetectors suggests that the newfound effect can indeed improve cells' power outputs.
"It's not just a pipedream to think about this [multiplication effect] giving you a real benefit in a solar cell device," says Richard D. Schaller of Los Alamos (N.M.) National Laboratory. Other technologies that might benefit include lasers that operate at useful wavelengths not attainable with other materials and solar water splitters that produce hydrogen for fuel cells (SN: 10/30/04, p. 282: Available to subscribers at http://www.sciencenews.org/articles/20041030/bob10.asp).
Whereas the new effect's practical potential is apparent, the means by which solar photons yield so many electrons is not. In a heated debate, some scientists argue that a previously unseen type of quantum mechanical entity must briefly form in each quantum dot. Others contend that an already well-understood process can account for the multiple-electron output.
"What's exciting here is this unexpected result," says Arthur J. Nozik of the National Renewable Energy Laboratory (NREL) in Golden, Colo. "This is very interesting new physics."
Size matters
In the electrical realm, semiconductors occupy a middle ground between insulators and conductors. Whereas atoms of insulators bind their electrons tightly, conductor atoms let those negatively charged particles roam free. In contrast, semiconductor atoms hold their electrons until given small energy boosts. Then, the electrons are available to flow as current.
If a photon strikes an electron in a semiconductor with more than the threshold amount of oomph, called the material's band-gap energy, the electron breaks loose. It leaves behind a vacancy, known as a hole, in the atom's electronic structure. Each free electron–hole pair created by a photon is called an exciton.
Despite the one-photon-one-exciton rule that solar-energy specialists had observed when photons hit the semiconductors in their power cells, physicists had known since the 1950s that photons at much higher energies could give rise to multiple excitons. They had observed, for instance, that X-ray photons trigger swarms of excitons in semiconductor materials.
Scientists also determined that such multiple-exciton production takes place by means of a process called impact ionization. Roughly speaking, an electron from an exciton strikes an electron bound to an atom, creating another exciton. If enough excess energy remains in the newly formed exciton, its electron can create yet another exciton, and so on. However, at the relatively low energies of solar photons, subtleties related to electron motion largely prevent the exciton-to-electron energy transfers, so only negligible impact ionization occurs, Nozik notes.
Quantum dots, which were first made in the 1970s, introduce another factor: size. Until the dots' debut, researchers knew what happened only when light struck larger pieces of semiconductor, such as those in a transistor or microchip.
The wavelike nature of electrons, as dictated by quantum mechanics, makes itself felt at the dot's minuscule dimensions. For instance, a dot has a larger band-gap energy than does the same semiconductor material in bulk, so the dot absorbs higher-energy, bluer light. Also, because a dot is often as small in diameter as the wavelength of an electron inside it, the dot immobilizes the electron.
About a decade ago, Nozik began to suspect that the smallness of quantum dots might make impact ionization a fruitful process at solar-radiation energies. For example, he figured that a dot's grip on an electron would nullify the motion-related subtleties that squelched the process at larger scales. So, he and his team set out to find an exciton boost in quantum dots of indium phosphide and indium arsenide.
Seven up
As it turns out, Nozik's crew was focused on the wrong quantum dots. At Los Alamos, however, Schaller and Victor I. Klimov had begun studying lead selenide nanocrystals as potential components in lasers.
When those researchers looked at the effect of high-energy blue light, they saw the first evidence of solar-energy photons creating more than one exciton apiece. In a 2004 report, the Los Alamos physicists reported that photons could generate as many as three excitons apiece in lead selenide quantum dots (SN: 4/24/04, p. 259: http://www.sciencenews.org/articles/20040424/fob2.asp).
Shifting gears, Nozik, NREL's Randy J. Ellingson, and their colleagues verified the Los Alamos findings about a year later. They also unveiled the first evidence for multiple excitons from another type of quantum dot, made of lead sulfide.
Curious whether the effect was peculiar to lead-based quantum dots, the Los Alamos researchers tested a quantum dot with a very different electronic structure. In the Dec. 19, 2005 Applied Physics Letters, they reported signs that cadmium selenide dots were producing two excitons apiece.
"The fact that they can see [multiple excitons] in that material suggests that maybe it happens in all quantum dots," comments physical chemist Philippe Guyot-Sionnest of the University of Chicago.
Extending their work on lead-based dots, the NREL researchers report in the March 15 Journal of the American Chemical Society that lead telluride dots produce up to three excitons from single solar-energy photons. Currently, the Los Alamos researchers are examining cadmium telluride nanocrystals.
In further studies of lead selenide dots reported in the March Nano Letters, the Los Alamos group has evidence that some ultraviolet-light photons can trigger seven excitons apiece. Even bigger hauls are likely, the team asserts.
Hypothetically, the number of excitons a photon creates corresponds to the energy of the photon divided by the dot's band-gap energy. That's because the photon must deliver one band-gap's worth of energy to each electron that it breaks free from an atom. Using a dot with a smaller band gap increases the expected number of excitons because less energy is needed to push each electron over the threshold, Klimov explains.
In practice, however, effects such as the distribution of photon energy between electrons and holes require that photons have more than the hypothetically required energy to produce a specific number of excitons. For instance, the NREL team finds that in lead selenide dots, a photon must have at least two and a half band gaps of energy to produce two excitons. Tests at Los Alamos indicate a minimum requirement of three band gaps.
Regardless of exactly how much photon energy is needed, even the most modest boost in solar cells—say, to two excitons per photon—"would be a major, major achievement," Nozik says.
Quick question
The mounting evidence for the quantum-dot effect has sparked debate. The dispute centers on this question: Can impact ionization account for what's going on or is there something at play that was previously unknown and thus more exciting? "Right now, there's a lot of fighting in the area of theory," notes Klimov.
In Klimov's tests and the NREL experiments, the process seems instantaneous because the multiple excitons appear so quickly—within less than 50 femtoseconds (fs), or thousandths of a trillionth of a second. However, impact ionization proceeds sequentially. That is, after a photon creates the first exciton, that exciton creates the second exciton, which in turn generates the third, and so on. Could that step-by-step process create seven excitons in less than 50 fs?
Theorist Alexander L. Efros of the Naval Research Laboratory in Washington, D.C., thinks not. In collaboration with Nozik's team, Efros has invoked quantum theory to propose that a photon hitting a quantum dot instantaneously creates a novel quantum object that's simultaneously both one and many excitons.
In a slightly less exotic interpretation, theorist Vladimir M. Agranovich of the Russian Academy of Sciences in Moscow, collaborating with Klimov and Schaller, suggests that a so-called virtual exciton springs into existence for a moment after the photon hits. Armed briefly with more energy than physics ordinarily permits, it spawns the multiple excitons simultaneously—a scenario that the physicists described in the December 2005 Nature Physics.
Disagreeing with such extraordinary scenarios, Alex Zunger, a theorist at NREL, says that his team's calculations indicate that impact ionization can account for the experimental findings.
Maybe yes, maybe no, says theorist Guy Allan of the Institute of Electronics, Microelectronics, and Nanotechnology in Lille, France. Creation of a new exciton takes a mere 0.1 fs, so 50 fs is plenty of time to make seven or more excitons, he says.
Yet he adds that calculations by him and his institute colleague Christophe Delerue account for a few excitons per photon from impact ionization, but not as many as the maximum observed in quantum dots. Says Allan, "There may be another process to discover."
Going dotty
If the mysterious multiple-exciton effect pans out in practical devices, solar cell efficiencies could soar, scientists say. Both the Los Alamos and NREL teams calculate a maximum of 42 percent conversion of solar power to usable electricity. Conventional cells, by contrast, operate at 15 to 20 percent efficiency.
Some researchers have made prototype photodetectors and solar cells from quantum dots. For instance, Difei Qi of Louisiana Tech University in Ruston and her colleagues mixed a conductive, photosensitive polymer known as MEH-PPV with lead selenide quantum dots. Under visible light, a device incorporating dots at only about 5 percent by weight generated 50 percent more current than expected if each photon yielded one exciton, the Louisiana team reported in the Feb. 28, 2005 Applied Physics Letters.
More recently, a Texas team working with Klimov and Schaller made experimental solar cells by blending 8-nm-diameter lead selenide quantum dots with another conductive polymer called polythiophene. "We see a dramatic increase in photocurrent at exactly three multiples of the band-gap energy," says Anvar A. Zakhidov of the University of Texas at Dallas in Richardson. That current ramp-up indicates that photons are producing multiple excitons, he reported last March in Baltimore at a meeting of the American Physical Society.
Despite such encouraging signs, before highly efficient solar cells appear, "there's a lot of work to be done," Nozik cautions.
Generating extra excitons might also have a major impact on equipment that uses solar energy to split water to extract its hydrogen for various uses—for instance, to energize fuel cells—Klimov says. Each water-splitting reaction requires four electrons, he notes, so the more electrons per solar photon the better.
Scientists have used quantum dots to make laser beams of wavelengths not available with natural dyes or crystals. The boost in exciton productivity could also make such lasers more efficient.
Efficiency could become a hallmark of many quantum-dot technologies. As oil prices soar to record levels, thrifty quantum dots promise to give solar energy in particular an even more powerful appeal.
http://www.sciencenews.org/articles/20060603/bob8.asp
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Nanocrystal solar cells or quantum dot solar cells, are solar cells based on a silicon substrate with a coating of nanocrystals.
Whilst previous methods of quantum dot creation relied on expensive molecular beam epitaxy processes, fabrication using colloidal synthesis allows for a more cost effective manufacture. A thin film of nanocrystals is obtained by a process known as “spin-coating”. This involves placing an amount of the quantum dot solution onto a flat substrate, which is then rotated very quickly. The solution spreads out uniformly, and the substrate is spun until the required thickness is achieved.
Quantum dot based photovoltaic cells based around dye-sensitised colloidal TiO2 films were investigated in 1991[1] and were found to exhibit promising efficiency of converting incident light energy to electrical energy, and were found to be incredibly encouraging due to the low cost of materials in the search for more commercially viable/affordable renewable energy sources.
Although research is still in its infancy and is ongoing, in the future quantum dot based photovoltaics may offer advantages such as mechanical flexiblity (quantum dot-polymer composite photovoltaics[2]) as well as low cost, clean power generation.[3]
http://en.wikipedia.org/wiki/Nanocrystal_solar_cell
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Niat Usage
Using third generation Nanocrystal solar cells Niat has begun to achieve the solar dream. Using large arrays of these highly efficient cells protected with a transparent protective film they are constructed in large arrays that make cells of 1 square meter in diameter by 2 cm thick that allows for cheap production of the panels. These panels are then lined on the top of buildings, or attached to the backs of billboards or various other structures to generate power when the sunlight reaches it. Often it feeds off the energy of other lights in cities to use the power to get back a small amount of the energy.
The military sees promise in this technology and has begun using the Nanocrystal solar cells as a way to reduce energy consumption and puts the panels over hangars and on the top of buildings. The material gives a grey appearance when it is coated that is not very reflective, but it produces three times the amount of energy conventional solar cells (Type Two/Generation Two). These solar cells are used for a duel purpose. They are rigged to electrolysis machines to produce hydrogen or are put directly into the electrical grid to reduce the demands of other sources of power in great numbers. The ability to use electrolysis is one of the Army’s chief interests in the technology as that ‘Solar Farms’ across the barren deserts or rocky mountains of Niat can be used as production plants for hydrogen fuel cells to power tanks and other vehicles.
This solar technology is expected to reduce the national energy demand by 40% in just a decade and solve one of the military’s key problems with petrol demand in typical gas-guzzler tanks and other vehicles that cannot share fuel do to engine problems. This technology greatly enhances the future of Niat as a green-nation and solves many problems that could not coexist otherwise.
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Unique three-dimensional solar cells that capture nearly all of the light that strikes them could boost the efficiency of photovoltaic (PV) systems while reducing their size, weight and mechanical complexity.
The new 3D solar cells capture photons from sunlight using an array of miniature "tower" structures that resemble high-rise buildings in a city street grid. The cells could find near-term applications for powering spacecraft, and by enabling efficiency improvements in photovoltaic coating materials, could also change the way solar cells are designed for a broad range of applications.
"Our goal is to harvest every last photon that is available to our cells," said Jud Ready, a senior research engineer in the Electro-Optical Systems Laboratory at the Georgia Tech Research Institute (GTRI). "By capturing more of the light in our 3D structures, we can use much smaller photovoltaic arrays. On a satellite or other spacecraft, that would mean less weight and less space taken up with the PV system."
The 3D design was described in the March 2007 issue of the journal JOM, published by The Minerals, Metals and Materials Society. The research has been sponsored by the Air Force Office of Scientific Research, the Air Force Research Laboratory, NewCyte Inc., and Intellectual Property Partners, LLC. A global patent application has been filed for the technology.
The GTRI photovoltaic cells trap light between their tower structures, which are about 100 microns tall, 40 microns by 40 microns square, 10 microns apart -- and built from arrays containing millions of vertically-aligned carbon nanotubes. Conventional flat solar cells reflect a significant portion of the light that strikes them, reducing the amount of energy they absorb.
Because the tower structures can trap and absorb light received from many different angles, the new cells remain efficient even when the sun is not directly overhead. That could allow them to be used on spacecraft without the mechanical aiming systems that maintain a constant orientation to the sun, reducing weight and complexity – and improving reliability.
"The efficiency of our cells increases as the sunlight goes away from perpendicular, so we may not need mechanical arrays to rotate our cells," Ready noted.
The ability of the 3D cells to absorb virtually all of the light that strikes them could also enable improvements in the efficiency with which the cells convert the photons they absorb into electrical current.
In conventional flat solar cells, the photovoltaic coatings must be thick enough to capture the photons, whose energy then liberates electrons from the photovoltaic materials to create electrical current. However, each mobile electron leaves behind a "hole" in the atomic matrix of the coating. The longer it takes electrons to exit the PV material, the more likely it is that they will recombine with a hole -- reducing the electrical current.
Because the 3D cells absorb more of the photons than conventional cells, their coatings can be made thinner, allowing the electrons to exit more quickly, reducing the likelihood that recombination will take place. That boosts the "quantum efficiency" – the rate at which absorbed photons are converted to electrons – of the 3D cells.
Fabrication of the cells begins with a silicon wafer, which can also serve as the solar cell’s bottom junction. The researchers first coat the wafer with a thin layer of iron using a photolithography process that can create a wide variety of patterns. The patterned wafer is then placed into a furnace heated to 780 degrees Celsius. Hydrocarbon gases are then flowed into furnace, where the carbon and hydrogen separate. In a process known as chemical vapor deposition, the carbon grows arrays of multi-walled carbon nanotubes atop the iron patterns.
Once the carbon nanotube towers have been grown, the researchers use a process known as molecular beam epitaxy to coat them with cadmium telluride (CdTe) and cadmium sulfide (CdS) which serve as the p-type and n-type photovoltaic layers. Atop that, a thin coating of indium tin oxide, a clear conducting material, is added to serve as the cell’s top electrode.
In the finished cells, the carbon nanotube arrays serve both as support for the 3D arrays and as a conductor connecting the photovoltaic materials to the silicon wafer.
The researchers chose to make their prototypes cells from the cadmium materials because they were familiar with them from other research. However, a broad range of other photovoltaic materials could also be used, and selecting the best material for specific applications will be a goal of future research.
Ready also wants to study the optimal heights and spacing for the towers, and to determine the trade-offs between spacing and the angle at which the light hits the structures.
The new cells face several hurdles before they can be commercially produced. Testing must verify their ability to survive launch and operation in space, for instance. And production techniques will have to scaled up from the current two-inch laboratory prototypes.
"We have demonstrated that we can extract electrons using this approach," Ready said. "Now we need to get a good baseline to see where we compare to existing materials, how to optimize this and what’s needed to advance this technology."
Intellectual Property Partners of Atlanta holds the rights to the 3D solar cell design and is seeking partners to commercialize the technology.
Another commercialization path is being followed by an Ohio company, NewCyte, which is partnering with GTRI to use the 3D approach for terrestrial solar cells. The Air Force Office of Scientific Research has awarded the company a Small Business Technology Transfer (STTR) grant to develop the technology.
"NewCyte has patent pending, low cost technology for depositing semiconductor layers directly on individual fullerenes," explained Dennis J. Flood, NewCyte’s president and CTO. "We are using our technology to grow the same semiconductor layers on the carbon nanotube towers that GTRI has already demonstrated. Our goal is to achieve performance and cost levels that will make solar cells using the GTRI 3D cell structure competitive in the broader terrestrial solar cell market."
http://www.physorg.com/news95520809.html
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Niat Usage
The ministry of solar power and technology of Niat (MSPTN) can enacted that the cells be used in combination with the third generation of solar cells (Nanocrystal solar cells) that this can be used to increase the overall efficiency of the Nanocrystal cells from 42% to nearly 95% that does not require mechanical movement of the solar arrays for maximum energy production. Using this technology to put the micro-towers on top of the solar cells they can be used to produce the current maximum energy output per area. Relying on this technology the solar farms can nearly double the output of energy they had initially planned for.
(More to be added later)
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The sea is a wealth resources
Environmental problems form an important theme throughout the world and to resolve them, nuclear power is regarded as an indispensable energy resource. In a country like Japan, however, which lacks in natural resources, uranium to fuel nuclear power plants must be imported.
The amount of economically mineable uranium in the earth is estimated at between 5 and 6 million tons, according to OECD/NEA-IAEA, 1995. If we continue to consume uranium at the present rate, its demand reportedly will exceed the supply in the near future, which will make it impossible to generate electricity using nuclear energy.
According ly, Japan has been working to develop fast breeder and nuclear fusion reactors. But before technology for these next-generation reactors can be perfected, there is a strong possibility that we will again meet an energy crisis. With this in the offing, I regarded the sea as potentially an infinite source of uranium.
Thus the amount of uaranium in seawater was calculated and the results showed that the Black Current off Japan carries approximately 5.2 million tons a year. This amount is equivalent to the earth's remaining inventory of this ore. At present, Japan consumes about 6,000 tons of uranium per year. So even if only 0.1 percent of what flows along Japan can be recovered, the domestic demand for uranium can be supplied, and that is why I have continued to propose taking advantage of the uranium in seawater as an energy resource.
Resources carried by the Black Current
Rare metals Annual Amount
Total
(unit: 10,000 tons) Annual amount per cross section
of Black Current(tons/m2)
Cobalt (Co) 16 0.005
Titanium(TI) 170 0.059
Vanadium(V) 340 0.119
Uranium(U) 520 0.182
Molybdenum(Mo) 1,580 0.553
*Average speed of Black Current:1.75m/s
*Average flow amount of BlackCurrent:50 millionsm3/s
Selective collection of uranium
When seawater evaporates, many kinds of salts remains. We know that there is only one uranium particle in 34 million other element particles. For this reason, we have been researching on uranium recovery from seawater over a decade ago to find the most effective technology. As a result, we chose a chemical fanction of amidoxime as the uranium adsorbent. Amidoxime reacts with uranium and is used as an analytical indicator for the element. Using radiation, the method for introducing the amidoxime group onto a nonwaver materials was eatablised. A patent for this technology was applied for Japan and elsewhere. Radiation is the key for this invention.
After establishing this rodiation processing, we developed the small scale equipment for uranium absorbent cloth in seawater. Adsorption experiments in seawater flow were done in cooperation with the Mutsu organization of JAERI, and the results proved that uranium can berecovered from the sea effectively using natural energy such as current and/or wave power. Moreover, 16 grams of uranium yellow cake, applicable as reactor fuel, can be separated and purified. This result, then, marks the world's first success for this system. From the standpoint of economy, it was also apparent that this technology has every potential for practical use, which means that it is a promising domestic energy resource for Japan in the long term.
If all nations take uranium from the sea, calculations inaieate that the balance of uranium concentration in the sea would not change as the amount seawater is estimated at a thousand times that in the earth. It was also proved that insoluble uranium on the sea bottom exceeds that in the water by a thousand times.
Experimental results show that vanadium in seawater can be recovered by using the same absorbent also, and its quantity is nearly twice that of uranium. The need for vanadium is expected to increase in the future as a substitute for titanium owing to its properties of great stability at high temperature and excellent corrosion resistance. But vanadium is mined only in the Republic of Kazakhstan and in South Africa. This rate metal can be easily extracted from seawater. Moreover, other useful elements such as cobalt, titanium, molybdenum, etc. can be recovered, too. All of this means that Japan has the potential to produce new resources. Based on the outcome of the initial experiment, research on a large-scale demonstration plant is under way this fiscal year.
www.jaeri.go.jp/english/ff/ff43/topics.html
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The polyethylene (PE) membrane was prepared by the radiation-induced grafting of acrylonitrile (AN) onto PE hollow fiber and by the subsequent amidoximation of cyano groups in poly-AN graft chains. The adsorption characteristics of the chelating hollow fiber membrane was examined as the solution of UO 2 2+ permeated across the chelating hollow fiber membrane. The inner and outer diameter increased with an increasing grafting yield, whereas, the pure water flux and pore diameter decreased with an increasing grafting yield. The adsorption of UO 2 2+ by the chelating hollow fiber membranes increased with an increasing amidoxime group. The adsorbed amount of UO 2 2+ in the uranyl acetate solution was higher than that in the uranyl nitrate solution. The adsorbed amount of UO 2 2+ is higher than that of Cu 2+ when the solution of UO 2 2+ and Cu 2+ permeated across the chelating membrane, respectively. The adsorption characteristics of UO 2 2+ by the amidoxime group-chelating fiber membrane in the presence of Na 1+ and Ca 2+ showed a high selectivity for UO 2 2+ even though there was a high concen-tration of Na 1+ and Ca 2+ in the inlet solution
http://taylorandfrancis.metapress.com/content/286b82q58hxay0w4/fulltext.pdf
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An electron beam grafted adsorbent was synthesized by post irradiation grafting of acrylonitrile (AN) on to a non-woven thermally bonded polypropylene (PP) sheet using 2 MeV electron beam accelerator. The grafted poly(acrylonitrile) chains were chemically modified to convert a nitrile group to an amidoxime (AMO) group, a chelating group responsible for metal ion uptake from an aqueous solution. The effect of various experimental variables viz. dose, dose rate, temperature, and solvent composition on the grafting extent was investigated. PP grafted with the amidoxime group (AMO-g-PP) was tested for its suitability as an adsorbent for removal of heavy metal ions such as Co2+, Ni2+, Mn2+, and Cd2+ from aqueous solution. Langmuir and Freundlich adsorption models were used to investigate the type of adsorption of these ions. The adsorption capacities of the adsorbent for the metal ions were found to follow the order Cd2+>Co2+>Ni2+>Mn2+. The kinetics of adsorption of these ions indicated that the rate of adsorption of Cd2+ was faster than that of other ions studied.
http://taylorandfrancis.metapress.com/content/w981242n6r354r17/fulltext.pdf
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In order to recover uranium ions from seawater, chelate-type resins with amidoxime and amidoxime/carboxylic acid groups were prepared by radiation-induced polymerization of acrylonitrile (AN) and AN/acrylic acid and by subsequent amidoximation of cyano group of poly(AN), respectively. The resins were characterized by FT–IR, FT–Raman, solid-state 13C-NMR, SEM, and elemental analysis, respectively. The adsorption rate of uranium ion by resins with the amidoxime/carboxylic acid group were higher than that of resins with the amidoxime group. The adsorption of uranium ions in artificial seawater to chelate-type resins was also examined.
nkinghub.elsevier.com/retrieve/pii/S0969806X03000720
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To improve the adsorption rate of uranium from seawater, hydrophilic amidoxime (AO) fibers were prepared by cografting of methacrylic acid (MAA) with acrylonitrile (AN) onto polypropylene fibers and subsequent conversion of the produced cyano group to an amidoxime group by reaction with hydroxylamine. An optimum amidoximation time of 0.75 h was selected at a weight ratio of AN to MAA (x/y) of 80/20. By varying x/y in the monomer mixture, cografted polymers were prepared. The value of x/y governed the AO group density and water content of the resultant fibrous adsorbents. As x/y increased, the AO group density of the fiber increased and its water content decreased. The AO/MAA adsorbent, based on the PP fibers prepared by cografting at an x/y of 60/40 and subsequent amidoximation, exhibited the highest uranium adsorption rate in the flow-through mode
linkinghub.elsevier.com/retrieve/pii/S0969806X0000298X
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ABSTRACT
A collector is disclosed that is made of a polyolefin fiber having amidoxime groups and that is capable of efficient adsorptive recovery of useful metals such as uranium, vanadium, cobalt and titanium which are dissolved in small quantities in seawater. In the presence of a polymerizable monomer having a hydrophilic group, a polymerizable monomer having a cyano group is grafted to a polyolefin fiber by radiation-initiated graft polymerization to form both a hydrophilic group and a cyano group in the same graft side chains, and the cyano groups in the graft side chains are reacted with hydroxylamine to be converted to amidoxime groups, thereby producing a collector capable of recovering dissolved metals from seawater.
BACKGROUND OF THE INVÈNTION
(a) This invèntion relates to a collector made of a polyolefinic fiber having an amidoxime group and a hydrophilic group and which is capable of efficient adsorptive recovery of useful metals such as uranium, vanadium, cobalt and titanium that occur dissolved in small quantities in seawater. The invèntion also relates to a process for producing the collector.
Seawater has various metals (see Table 1) dissolved in it and the present invèntion aims at recovering these dissolved metals by adsorption using a collector.
TABLE 1 Total estimated Concentration dissolved Dependency Rare metal in seawater, quantity, on overseas, sources (mg/ton) (.times.10.sup.8 tons) (%) Cobalt (Co) 0.1 1 100 Yttrium (Y) 0.3 3 100 Titanium (Ti) 1 15 100 Manganese (Mn) 2 30 90 Vanadium (V) 2 30 100 Uranium (U) 3 45 100 Molybdenum (Mo) 10 150 100 Lithium (Li) 170 2,330 100 Boron (B) 4,600 63,020 100 Strontium (Sr) 8,000 109,600 100
(b) The invèntion relates to a collector that is produced by introducing an amidoxime group, either alone or in combination with a hydrophilic group, into side chains grafted to a polyolefinic fiber substrate and which needs only to be anchored in seawater to accomplish efficient recovery of useful metals such as vanadium, cobalt, uranium and titanium that are dissolved in the seawater. The invèntion also relates to a cassette of such collectors and a method of collecting the above-mentioned useful metals from seawater using the cassette.
To produce the collector of the invèntion, a polymerizable monomer such as acrylonitrile (CH.sub.2.dbd.CHCN) that contains a cyan group (--CN) is grafted onto a polyolefinic fiber substrate by radiation-initiated graft polymerization so as to form grafted side chains and the cyan groups in these side chains are reacted with hydroxylamine (NH.sub.2 OH) or the like to be converted to amidoxime groups.
A plurality of the thus produced collectors may be sandwiched between nets and a plurality of the resulting assemblies are stacked in position at suitable spacings to construct a collector cassette. The cassette may be placed in a number of cages that are anchored in seawater to recover useful dissolved metals from it by adsorption.
(a) Conventionally, amidoxime groups are introduced into a polymer structure in accordance with the following scheme (1) by reacting the cyano group (--CN) with hydroxylamine (NH.sub.2 OH): ##STR1##
To synthesize a satisfactory amidoxime resin by introducing amidoxime groups into a polymer structure, the introduction of amidoxime groups into substrates typically made of the general-purpose polyacrylic fiber or polyacrylic beads produced by emulsion polymerization. However, these acrylic resins have suffered from deterioration in skeletal strength of the polymer on account of the introduction of hydrophilic amidoxime groups into the cyano groups in the polymer skeleton. With a view to preventing this problem, a review has been made to form crosslinks in the polymer structure. In fact, however, the increase in the degree of crosslinking is accompanied by a decrease in the rate of metal adsorption and this tradeoff has been an obstacle to the solution of the problem.
It is known that a collector that is capable of selective adsorptive recovery of dissolved metals from seawater can be produced by grafting acrylonitrile onto a polyethylene fiber under exposure to radiation and then reacting it with hydroxylamine to introduce amidoxime groups.
It is also known that a selective adsorbent of uranium dissolved in seawater can be produced from a substrate of a desired shape that is made of an inorganic material, an organic material or a composite thereof and into which both an amidoxime group and a hydrophilic group are introduced by radiation-initiated graft polymerization (see Japanese Patènt Publication No. 58775/1987) filed by one of present invèntors).
Under the circumstances, there has been a pressing need to improve the existing collectors and develop a material that is strong enough to withstand prolonged exposure to hostile weather conditions in ocean and which maintains high performance in collecting vanadium, uranium and other useful metals in seawater.
(b) In seawater, vanadium, uranium and many other rare metals that scarcely occur in Japan are contained dissolved but their concentrations are extremely low, only about 1.9 mg of vanadium per ton of seawater and about 3.3 mg of uranium.
Heretofore, uranium has been recovered from seawater by the following methods using an adsorbent; seawater is brought into contact with the particles of titanic acid to adsorb uranium from the seawater and fine air bubbles are attached to the particles of titanic acid, which are then floated on the seawater and separated therefrom to recover the uranium (Japanese Patènt Public Disclosure No. 61018/1979); calcium or carbonate ions are removed from seawater before uranium in the seawater is recovered by adsorption onto a hydrous metal oxide adsorbent (Japanese Patènt Public Disclosure No. 79111/1979); a collector produced by reacting a polyethyleneimine derivative with hydroxylamine is used to achieve adsorptive recovery of metal ions dissolved in seawater (Japanese Patènt Public Disclosure No. 48725/1987); and using a kalixarene derivative to recover uranium in seawater by adsorption (Japanese Patènt Public Disclosure No. 136242/1987).
Dissolved metals can also be recovered using chelate resins and conventional methods based on this approach include the following: a specified group is introduced into a chloromethylated crosslinked polystyrene, which is then reacted with hydroxylamine to produce an adsorbent resin that is used to recover dissolved metals from seawater by adsorption (Japanese Patènt Public Disclosure No. 84907/1984); a chelate resin having malonyl dihydroxamate residue is used as an adsorbent to recover dissolved metals by adsorption (Japanese Patènt Public Disclosure No. 83730/1984); and a chelate resin having functional groups of a specified structure in the molecule is used to recover dissolved metals by adsorption (Japanese Patènt Public Disclosure No. 11224/1985).
To date, the conventional methods of recovering uranium from seawater using adsorbents or those for recovering dissolved metals using chelate resins have not been implemented in practice since they are incapable of cost-effective collection of uranium and other rare metals. However, for Japan which is by no means rich in mineral resources, it has been long desired to exploit the metals that are dissolved in the surrounding sea.
http://www.uspatentserver.com/686/6863812.html
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A novel amidoxime-group-containing adsorbent of hollow-fiber form (AO-H fiber) was prepared by radiation-induced graft polymerization of acrylonitrile onto a polyethylene hollow fiber, followed by chemical conversion of the produced cyano group to an amidoxime group. Distribution of the amidoxime group was uniform throughout the hollow-fiber membrane. The fixed-bed adsorption column, 30 cm in length and charged with the bundle of AO-H fibers, was found to adsorb uranium from natural seawater at a sufficiently high rate: 0.66 mg uranium per g of adsorbent in 25 days.
http://www3.interscience.wiley.com/cgi-bin/abstract/109065700/ABSTRACT
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Niat Usage
Using this technology as a base for the uranium collection it is our plan to use this technology in a off-shore oil-rig production style form to extract uranium and other heavy metals from the sea water. Niat will incorporate these designs and use AO-H fiber containing the amidoxime group to pull heavy metals from the ocean and collect them at the rate of 1 g per 1 kg. Even though it is .1% effective it is cost-effective to pull a variety of metals at the expensive cost to ensure Niat’s future as a uranium producer and consumer.
For more information, look into the Abramorba Class Refinery.
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A battery with a lifespan measured in decades is in development at the University of Rochester, as scientists demonstrate a new fabrication method that in its roughest form is already 10 times more efficient than current nuclear batteries—and has the potential to be nearly 200 times more efficient. The details of the technology, already licensed to BetaBatt Inc., appears in today’s issue of Advanced Materials.
“Our society is placing ever-higher demands for power from all kinds of devices,� says Philippe Fauchet, professor of electrical and computer engineering at the University of Rochester and co-author of the research. “For 50 years, people have been investigating converting simple nuclear decay into usable energy, but the yields were always too low. We’ve found a way to make the interaction much more efficient, and we hope these findings will lead to a new kind of battery that can pump out energy for years.�
The technology is geared toward applications where power is needed in inaccessible places or under extreme conditions. Since the battery should be able to run reliably for more than 10 years without recharge or replacement, it would be perfect for medical devices like pacemakers, implanted defibrillators, or other implanted devices that would otherwise require surgery to replace or repair. Likewise, deep-space probes or deep-sea sensors, which are beyond the reach of repair, also would benefit from such technology.
Betavoltaics, the method that the new battery uses, has been around for half a century, but its usefulness was limited due to its low energy yields. The new battery technology makes its successful gains by dramatically increasing the surface area where the current is produced. Instead of attempting to invent new, more reactive materials, Fauchet’s team focused on turning the regular material’s flat surface into a three-dimensional one.
Similar to the way solar panels work by catching photons from the sun and turning them into current, the science of betavoltaics uses silicon to capture electrons emitted from a radioactive gas, such as tritium, to form a current. As the electrons strike a special pair of layers called a “p-n junction,� a current results. What’s held these batteries back is the fact that so little current is generated—much less than a conventional solar cell. Part of the problem is that as particles in the tritium gas decay, half of them shoot out in a direction that misses the silicon altogether. It’s analogous to the sun’s rays pouring down onto the ground, but most of the rays are emitted from the sun in every direction other than at the Earth. Fauchet decided that to catch more of the radioactive decay, it would be best not to use a flat collecting surface of silicon, but one with deep pits.
A layer of silicon riddled with pits, each of which would fill with the radioactive tritium gas, would be like dropping the sun into a deep well lined with solar panels. Almost all of the sun’s rays, no matter which way they were emitted, would strike a well wall. Only those rays that fired straight up and out of the well would be lost. With this reasoning, Fauchet devised a method to excavate pits into a microscopic piece of silicon.
The pits, or wells, are only about a micron wide (about four ten-thousandths of an inch), but are more than 40 microns deep. After the wells are “dug� with an etching technique, their insides are coated with a material to form a p-n junction just a tenth of a micron thick, which is the best thickness to induce a current. The Advanced Materials paper details how these wells were dug in a random fashion, yielding a 10-fold increase in current over the conventional design. The team is already working on a technique to create and line the wells in a much more uniform, lattice formation that should increase the energy produced by as much as 160-fold over current technology.
“Our ultimate design has roughly 160 times the surface area of the conventional, flat design,� says Fauchet. “We expect to be able to get an efficiency that very nearly matches, and we’re doing this using standard semiconductor industry fabrication techniques.�
Houston-based BetaBatt Inc. has formed to capitalize on the technology, and has recently been awarded a technology commercialization grant by the National Science Foundation (NSF). NSF funded the initial research as well. Collaborators on this research included one of Fauchet’s graduate students, Wei Sun, Nazir Kherani from the University of Toronto, Karl Hirschman from Rochester Institute of Technology, and Larry Gadeken from BetaBatt, Inc.
http://www.physorg.com/news4081.html
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Betavoltaics are generators of electrical current, in effect a form of battery, which use energy from a radioactive source emitting beta particles (electrons). A common source used is the hydrogen isotope, tritium. Unlike most nuclear power sources, which use nuclear radiation to generate heat, which then generates electricity (thermoelectric and thermionic sources), betavoltaics use a non-thermal conversion process.
The functioning of a betavoltaic device is somewhat similar to a solar cell, which converts photons (light) into electric current. In a betavoltaic, when an electron strikes a particular interface between two layers of material (a p-n junction), a current is generated.
Betavoltaics were invented over 50 years ago. In 2005 a new betavoltaic device using porous silicon diodes was proposed to increase their efficiency. This increase in efficiency is largely due to the larger surface area of the capture material. The porous silicon allows the tritium gas to penetrate into many pits and pores, greatly increasing the effective surface area of the device.
The primary use for betavoltaics is for remote and long-term use, such as spacecraft requiring electrical power for a decade or two. The recent progress in technology has prompted some to suggest using betavoltaics to trickle-charge conventional batteries in consumer devices, such as cell phones and laptop computers. As early as 1973, betavoltaics were suggested for use in long-term medical devices such as pacemakers.
Although betavoltaics use a radioactive material as a power source, it is important to note that beta particles are low energy and easily stopped by shielding, as compared to the gamma rays generated by more dangerous radioactive materials. With proper device construction (i.e.: shielding), a betavoltaic device would not emit any dangerous radiation. Leakage of the enclosed material would of course engender health risks, just as leakage of the materials in other types of batteries lead to significant health and environmental concerns.
Betavoltaic devices suffer internal damage to their components as a result of the energetic electrons. Additionally, as the radioactive material emits, it slowly decreases in activity (refer to half-life). Thus, over time a betavoltaic device will output less and less power. This decrease occurs over a period of many years. For tritium devices, the half-life is 12.32 years. In device design, one must account for what battery characteristics are required at end-of-life, and insure that the beginning-of-life properties take into account the desired useable lifetime.
http://en.wikipedia.org/wiki/Betavoltaics
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Direct Energy Conversion Technology BetaBatt is a Houston-based company in the business of developing long-lasting reliable power sources. The Company has researched and patented a novel 3D energy conversion architecture named the DECTM Cell, based on nano-scale porous silicon. The DECTM Cell is able to convert decay electrons to electricity 10 times more efficiently than conventional 2D devices using standard semiconductor manufacturing methods. The company's first commercial product, a quarter size battery with a 12-20 year lifespan and mission critical reliability, has performance characteristics that address current problems faced by medical implant, oil and gas, and remote sensing industries, as well as military and space organizations. Going forward, BetaBatt intends to apply its novel architecture to Micro-Electro Mechanical Systems (MEMS), Mesh Networks, Smart Dust and other micro/nano architectures requiring long-lasting reliable power sources.
Semiconductor devices based on Direct Energy Conversion (DECTM) technology will generate electric current from a radioelement source. The efficiency of the DECTM Cell stems from its single step capture-and-conversion method. DECTM Cells use energy produced from the decay of a radioactive isotope, not a chemical reaction. The Company's patented architecture - based on the same physical principles that are employed in solar cells - and the selection of beta emitters ensures a power source that emits no radiation and is safer than chemical batteries for a broad variety of industrial and medical applications.
A key innovation is the distribution of the beta emitter energy source throughout the DECTM Cell volume. This means that the current generation is not just a surface effect, but occurs everywhere within the active volume. Thus, DECTM current sources are extremely efficient, converting a large fraction of the available decay energy into electric current. The first and second generations of tritium-powered BetaBatteriesTM are expected to produce 50- and 125-micro-Watts per cubic centimeter of active device volume, respectively.
BetaBatteryTM current sources are long-lasting, based on the selection of the beta source. Tritium has a half-life (T½) equal to 12.3 years. This means that after 12.3 years, the current output will be half its original value and a tenth of the original after 40 years. This productive life is orders of magnitude longer than chemical batteries. The decline in output for DECTM power cells will be quite predictable and can be accommodated by appropriate electronics design for each specific application.
BetaBatteriesTM are far more reliable than chemical batteries, and have significantly longer life spans. They have about the same energy density as a lithium battery, but last ten or more times longer. BetaBatteriesTM can be stacked or scaled to meet application-specific requirements. When compared to chemical batteries, BetaBatteries are strongly differentiated by their intrinsic features:
Small or Big MEMS to "D" size
High Efficiency From Direct Energy Conversion
Green And Safe No harmful radiation, leaching, or contamination
Long Life 12 - 100+ years (depending on energy source)
Scalable Wide form factor variety
Extreme Environments 100°C to +150°C, shock tolerant
Manufacturable Well known semiconductor techniques
BetaBatteriesTM may be used in two ways:
In stand-alone mode for low current applications
Paired with chemical batteries for high current, limited duty cycle applications
BetaBatteriesTM increase shelf life and ensure readiness by acting as a trickle charger, thus enhancing capability, reliability and useful life.
The properties and performance characteristics of DECTM Cells make them particularly suitable for applications which benefit from a constant and sustained current and one or more of the following:
Battery replacement is difficult, costly or high risk
Mission-critical reliability
Size or form factor constraints
Performance in extreme or fluctuating environments (e.g., outer space)
A major advantage of DECTM power cells is their "always on" capability. This means they would be ideal for permanent or semi-permanent "install and forget" applications in remote or inaccessible locations. Another advantage is that DECTM technology is scalable. DECTM current sources could be used to power the smallest realizations of MEMS devices and sensors. By selecting appropriately-sized semiconductor wafers and connecting the resulting DECTM Cells together, a very wide range of BetaBatteryTM power levels can be delivered. Another advantage of DECTM technology is that the high efficiency of energy conversion gives rise to a very small amount of waste heat. This means that in the majority of applications there will not need to be any extra design effort nor auxiliary systems installed to remove excess heat.
Space-worthy DECTM technology has many advantages compared to Radioisotope Thermal Generators (RTGs) including high efficiency, little waste heat, low mass, no shielding requirements and a zero noise signature in all energy regions important for astrophysical investigations.
http://www.betabatt.com/
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Niat Usage
Using this technology Niat has begun to implement the nuclear battery reactors in far off military bases as a suitable way to provide backup power for emergency systems and use 1 cubic meter of cells to provide a constant 125W of energy to keep all communications available in a ‘install and forget’ setup so that even in the event of losing back up generators the ability to keep contact is ensured even in the worse-case scenario. This also allows for a safe non-toxic threat that provide a stable and long-lived battery that is ideal compared to chemical lithium batteries for a variety of devices. One stack of these cells can ensure satellite, phone and fiber optic transmission lines for a stranded base.
Another use is the ability to put them in troop devices and provide sensors for troops that do not have a short-life that can be used for the entire campaign without problems. These small cells can power communication and ID tags, watches and other gear such as water purification systems on the front lines that would have a normally large thermal signature or large size. Using these low-heat batteries it would help reduce the emissions and requirement for fuel to produce drinkable water for the troops. Effectively lightening the logistics load for an entire campaign by a large amount.
With all features implemented into as many sources as possible the military expects to reduce fuel consumption by 12% that would keep costs down and provide safe power generation without logistical support.