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  • richardmitnick 3:24 pm on July 21, 2014 Permalink | Reply
    Tags: , , , , Sandia Lab   

    From DOE Pulse: “Diamond plates create nanostructures through pressure, not chemistry “ 

    pulse

    July 21, 2014
    Darrick Hurst, 505.844.8009,
    drhurst@sandia.gov

    You wouldn’t think that mechanical force — the simple kind used to eject unruly patrons from bars, shoe a horse or emboss the raised numerals on credit cards — could process nanoparticles more subtly than the most advanced chemistry.

    Yet, in a recent paper in Nature Communications, Sandia National Laboratories researcher Hongyou Fan and colleagues appear to have achieved a start toward that end.

    three
    Sandia National Laboratories researcher Hongyou Fan, center, points out a nanoscience result to Sandia paper co-authors Paul Clem, left, and Binsong Li.
    (Photo by Randy Montoya)

    Their newly patented and original method uses simple pressure — a kind of high-tech embossing — to produce finer and cleaner results in forming silver nanostructures than do chemical methods, which are not only inflexible in their results but leave harmful byproducts to dispose of.

    Fan calls his approach “a simple stress-based fabrication method” that, when applied to nanoparticle arrays, forms new nanostructures with tunable properties.

    “There is a great potential market for this technology,” he said. “It can be readily and directly integrated into current industrial manufacturing lines without creating new expensive and specialized equipment.”

    Said Sandia co-author Paul Clem, “This is a foundational method that should enable a variety of devices, including flexible electronics such as antennas, chemical sensors and strain detectors.” It also would produce transparent electrodes for solar cells and organic light-emitting diodes, Clem said.

    The method was inspired by industrial embossing processes in which a patterned mask is applied with high external pressure to create patterns in the substrate, Fan said. “In our technology, two diamond anvils were used to sandwich nanoparticulate thin films. This external stress manually induced transitions in the film that synthesized new materials,” he said.

    The pressure, delivered by two diamond plates tightened by four screws to any controlled setting, shepherds silver nanospheres into any desired volume. Propinquity creates conditions that produce nanorods, nanowires and nanosheets at chosen thicknesses and lengths rather than the one-size-fits-all output of a chemical process, with no environmentally harmful residues.

    While experiments reported in the paper were performed with silver — the most desirable metal because it is the most conductive, stable and optically interesting and becomes transparent at certain pressures — the method also has been shown to work with gold, platinum and other metallic nanoparticles

    Clem said the researchers are now starting to work with semiconductors.

    Bill Hammetter, manager of Sandia’s Advanced Materials Laboratory, said, “Hongyou has discovered a way to build one structure into another structure — a capability we don’t have now at the nanolevel. Eight or nine gigapascal —the amount of pressure at which phase change and new materials occur — are not difficult to reach. Any industry that has embossing equipment could lay a film of silver on a piece of paper, build a conductive pattern, then remove the extraneous material and be left with the pattern. A coating of nanoparticles that can build into another structure has a certain functionality we don’t have right now. It’s a discovery that hasn’t been commercialized, but could be done today with the same equipment used by anyone who makes credit cards.”

    The method can be used to configure new types of materials. For example, under pressure, the dimensions of ordered three-dimensional nanoparticle arrays shrink. By fabricating a structure in which the sandwiching walls permanently provide that pressure, the nanoparticle array will remain at a constant state, able to transmit light and electricity with specific characteristics. This pressure-regulated fine-tuning of particle separation enables controlled investigation of distance-dependent optical and electrical phenomena.

    At even higher pressures, nanoparticles are forced to sinter, or bond, forming new classes of chemically and mechanically stable nanostructures that no longer need restraining surfaces. These cannot be manufactured using current chemical methods.

    Depending on the size, composition and phase orientation of the initial nanoparticle arrays, a variety of nanostructures or nanocomposites and 3-D interconnected networks are achievable.

    The stress-induced synthesis processes are simple and clean. No thermal processing or further purification is needed to remove reaction byproducts.
    This work was funded by the Department of Energy’s Office of Science. Other authors of the paper are from Cornell University and Los Alamos National Laboratory.

    See the full article here.

    DOE Pulse highlights work being done at the Department of Energy’s national laboratories. DOE’s laboratories house world-class facilities where more than 30,000 scientists and engineers perform cutting-edge research spanning DOE’s science, energy, National security and environmental quality missions. DOE Pulse is distributed twice each month.

    DOE Banner


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  • richardmitnick 1:14 pm on June 27, 2014 Permalink | Reply
    Tags: , , Sandia Lab   

    From Sandia Lab: “Diamond plates create nanostructures through pressure, not chemistry” 


    Sandia Lab

    You wouldn’t think that mechanical force — the simple kind used to eject unruly patrons from bars, shoe a horse or emboss the raised numerals on credit cards — could process nanoparticles more subtly than the most advanced chemistry.

    hf
    Sandia National Laboratories researcher Hongyou Fan, center, points out a nanoscience result to Sandia paper co-authors Paul Clem, left, and Binsong Li. (Photo by Randy Montoya)

    Yet, in a recent paper in Nature Communications, Sandia National Laboratories researcher Hongyou Fan and colleagues appear to have achieved a start toward that end.

    Their newly patented and original method uses simple pressure — a kind of high-tech embossing — to produce finer and cleaner results in forming silver nanostructures than do chemical methods, which are not only inflexible in their results but leave harmful byproducts to dispose of.

    Fan calls his approach “a simple stress-based fabrication method” that, when applied to nanoparticle arrays, forms new nanostructures with tunable properties.

    “There is a great potential market for this technology,” he said. “It can be readily and directly integrated into current industrial manufacturing lines without creating new expensive and specialized equipment.”

    Said Sandia co-author Paul Clem, “This is a foundational method that should enable a variety of devices, including flexible electronics such as antennas, chemical sensors and strain detectors.” It also would produce transparent electrodes for solar cells and organic light-emitting diodes, Clem said.

    The method was inspired by industrial embossing processes in which a patterned mask is applied with high external pressure to create patterns in the substrate, Fan said. “In our technology, two diamond anvils were used to sandwich nanoparticulate thin films. This external stress manually induced transitions in the film that synthesized new materials,” he said.

    The pressure, delivered by two diamond plates tightened by four screws to any controlled setting, shepherds silver nanospheres into any desired volume. Propinquity creates conditions that produce nanorods, nanowires and nanosheets at chosen thicknesses and lengths rather than the one-size-fits-all output of a chemical process, with no environmentally harmful residues.

    While experiments reported in the paper were performed with silver — the most desirable metal because it is the most conductive, stable and optically interesting and becomes transparent at certain pressures — the method also has been shown to work with gold, platinum and other metallic nanoparticles

    Clem said the researchers are now starting to work with semiconductors.

    Bill Hammetter, manager of Sandia’s Advanced Materials Laboratory, said, “Hongyou has discovered a way to build one structure into another structure — a capability we don’t have now at the nanolevel. Eight or nine gigapascal —the amount of pressure at which phase change and new materials occur — are not difficult to reach. Any industry that has embossing equipment could lay a film of silver on a piece of paper, build a conductive pattern, then remove the extraneous material and be left with the pattern. A coating of nanoparticles that can build into another structure has a certain functionality we don’t have right now. It’s a discovery that hasn’t been commercialized, but could be done today with the same equipment used by anyone who makes credit cards.”

    The method can be used to configure new types of materials. For example, under pressure, the dimensions of ordered three-dimensional nanoparticle arrays shrink. By fabricating a structure in which the sandwiching walls permanently provide that pressure, the nanoparticle array will remain at a constant state, able to transmit light and electricity with specific characteristics. This pressure-regulated fine-tuning of particle separation enables controlled investigation of distance-dependent optical and electrical phenomena.

    At even higher pressures, nanoparticles are forced to sinter, or bond, forming new classes of chemically and mechanically stable nanostructures that no longer need restraining surfaces. These cannot be manufactured using current chemical methods.

    Depending on the size, composition and phase orientation of the initial nanoparticle arrays, a variety of nanostructures or nanocomposites and 3-D interconnected networks are achievable.

    The stress-induced synthesis processes are simple and clean. No thermal processing or further purification is needed to remove reaction byproducts.

    This work was funded by the Department of Energy’s Office of Science. Other authors of the paper are from Cornell University and Los Alamos National Laboratory.

    See the full article here.

    Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.
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  • richardmitnick 10:35 am on June 17, 2014 Permalink | Reply
    Tags: , , , Sandia Lab   

    From Sandia Lab: “Novel nanoparticle production method could lead to better lights, lenses, solar cells” 


    Sandia Lab

    June 17, 2014
    Sue Holmes, sholmes@sandia.gov, (505) 844-6362

    Sandia National Laboratories has come up with an inexpensive way to synthesize titanium-dioxide nanoparticles and is seeking partners who can demonstrate the process at industrial scale for everything from solar cells to light-emitting diodes (LEDs).

    Titanium-dioxide (TiO2) nanoparticles show great promise as fillers to tune the refractive index of anti-reflective coatings on signs and optical encapsulants for LEDs, solar cells and other optical devices. Optical encapsulants are coverings or coatings, usually made of silicone, that protect a device.

    Industry has largely shunned TiO2 nanoparticles because they’ve been difficult and expensive to make, and current methods produce particles that are too large.

    Sandia became interested in TiO2 for optical encapsulants because of its work on LED materials for solid-state lighting.

    two
    Sandia National Laboratories researchers Dale Huber, left, and Todd Monson have come up with an inexpensive way to synthesize titanium-dioxide nanoparticles, which could be used in everything from solar cells to light-emitting diodes. (Photo by Randy Montoya) Click on the thumbnail for a high-resolution image.

    Current production methods for TiO2 often require high-temperature processing or costly surfactants — molecules that bind to something to make it soluble in another material, like dish soap does with fat.

    Those methods produce less-than-ideal nanoparticles that are very expensive, can vary widely in size and show significant particle clumping, called agglomeration.

    Sandia’s technique, on the other hand, uses readily available, low-cost materials and results in nanoparticles that are small, roughly uniform in size and don’t clump.

    “We wanted something that was low cost and scalable, and that made particles that were very small,” said researcher Todd Monson, who along with principal investigator Dale Huber patented the process in mid-2011 as “High-yield synthesis of brookite TiO2 nanoparticles.”

    Low-cost technique produces uniform nanoparticles that don’t clump

    Their method produces nanoparticles roughly 5 nanometers in diameter, approximately 100 times smaller than the wavelength of visible light, so there’s little light scattering, Monson said.

    “That’s the advantage of nanoparticles — not just nanoparticles, but small nanoparticles,” he said.

    Scattering decreases the amount of light transmission. Less scattering also can help extract more light, in the case of an LED, or capture more light, in the case of a solar cell.

    TiO2 can increase the refractive index of materials, such as silicone in lenses or optical encapsulants. Refractive index is the ability of material to bend light. Eyeglass lenses, for example, have a high refractive index.

    Practical nanoparticles must be able to handle different surfactants so they’re soluble in a wide range of solvents. Different applications require different solvents for processing.

    Technique can be used with different solvents

    “If someone wants to use TiO2 nanoparticles in a range of different polymers and applications, it’s convenient to have your particles be suspension-stable in a wide range of solvents as well,” Monson said. “Some biological applications may require stability in aqueous-based solvents, so it could be very useful to have surfactants available that can make the particles stable in water.”

    The researchers came up with their synthesis technique by pooling their backgrounds — Huber’s expertise in nanoparticle synthesis and polymer chemistry and Monson’s knowledge of materials physics. The work was done under a Laboratory Directed Research and Development project Huber began in 2005.

    “The original project goals were to investigate the basic science of nanoparticle dispersions, but when this synthesis was developed near the end of the project, the commercial applications were obvious,” Huber said. The researchers subsequently refined the process to make particles easier to manufacture.

    Existing synthesis methods for TiO2 particles were too costly and difficult to scale up production. In addition, chemical suppliers ship titanium-dioxide nanoparticles dried and without surfactants, so particles clump together and are impossible to break up. “Then you no longer have the properties you want,” Monson said.

    The researchers tried various types of alcohol as an inexpensive solvent to see if they could get a common titanium source, titanium isopropoxide, to react with water and alcohol.

    The biggest challenge, Monson said, was figuring out how to control the reaction, since adding water to titanium isopropoxide most often results in a fast reaction that produces large chunks of TiO2, rather than nanoparticles. “So the trick was to control the reaction by controlling the addition of water to that reaction,” he said.

    Textbooks said making nanoparticles couldn’t be done, Sandia persisted

    Some textbooks dismissed the titanium isopropoxide-water-alcohol method as a way of making TiO2 nanoparticles. Huber and Monson, however, persisted until they discovered how to add water very slowly by putting it into a dilute solution of alcohol. “As we tweaked the synthesis conditions, we were able to synthesize nanoparticles,” Monson said.

    The next step is to demonstrate synthesis at an industrial scale, which will require a commercial partner. Monson, who presented the work at Sandia’s fall Science and Technology Showcase, said Sandia has received inquiries from companies interested in commercializing the technology.

    “Here at Sandia we’re not set up to produce the particles on a commercial scale,” he said. “We want them to pick it up and run with it and start producing these on a wide enough scale to sell to the end user.”

    Sandia would synthesize a small number of particles, then work with a partner company to form composites and evaluate them to see if they can be used as better encapsulants for LEDs, flexible high-index refraction composites for lenses or solar concentrators. “I think it can meet quite a few needs,” Monson said.

    See the full article here.

    Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.


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