WO2017095925A1 - Mousses métalliques interconnectées à faible densité et procédés de fabrication - Google Patents

Mousses métalliques interconnectées à faible densité et procédés de fabrication Download PDF

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Publication number
WO2017095925A1
WO2017095925A1 PCT/US2016/064218 US2016064218W WO2017095925A1 WO 2017095925 A1 WO2017095925 A1 WO 2017095925A1 US 2016064218 W US2016064218 W US 2016064218W WO 2017095925 A1 WO2017095925 A1 WO 2017095925A1
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Prior art keywords
nanowires
nanowire
metal
density
foam
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PCT/US2016/064218
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English (en)
Inventor
Edward BURKS
Dustin GILBERT
Kai Liu
Sergei Kucheyev
Thomas Felter
Jeffrey COLVIN
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The Regents Of The University Of California
Lawrence Livermore National Security, Llc
Sandia Corporation
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Application filed by The Regents Of The University Of California, Lawrence Livermore National Security, Llc, Sandia Corporation filed Critical The Regents Of The University Of California
Publication of WO2017095925A1 publication Critical patent/WO2017095925A1/fr
Priority to US15/956,993 priority Critical patent/US20180311737A1/en
Priority to US16/001,766 priority patent/US20190085478A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/054—Nanosized particles
    • B22F1/0547—Nanofibres or nanotubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1121—Making porous workpieces or articles by using decomposable, meltable or sublimatable fillers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1143—Making porous workpieces or articles involving an oxidation, reduction or reaction step
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/006—Nanostructures, e.g. using aluminium anodic oxidation templates [AAO]
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/04—Wires; Strips; Foils
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/10—Copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2301/00—Metallic composition of the powder or its coating
    • B22F2301/25—Noble metals, i.e. Ag Au, Ir, Os, Pd, Pt, Rh, Ru
    • B22F2301/255—Silver or gold

Definitions

  • the technology of this disclosure pertains generally to nanoscale structure fabrication methods, and more particularly to an ultralow-density, nanostructured, monolithic pure metal foams and fabrication methods.
  • Nanoporous metal foams have a host of beautiful electrical
  • nanoparticles exist, there are relatively few synthetic processes for producing bulk, monolithic forms of nanostructured metals that have been developed.
  • Conventional methodologies for fabricating monolithic metallic nanoporous materials or foams have limited practical applications and are difficult to adapt to large scale production because of their complicated procedures and use of expensive materials.
  • selective dealloying of a binary alloy which involves selectively etching a less-noble metal from a bimetallic alloy.
  • the metallic alloy starting material contains two or more elements, one of which is readily susceptible to selective chemical or electrochemical etching that preferentially removes the element.
  • the dealloying process involves the removal of a substantial portion of the starting material to create porosity.
  • aluminum based alloys are often used with conventional chemical dealloying approaches because aluminum can be removed from the alloy with either a strong acid or a strong base.
  • the dealloying process also requires a starting alloy with a percolating network of pores or the formation of a network of pores to complete the etching process throughout the structure.
  • Immersion times in the acid or base are typically 2 to 5 days and times increase with the size of the starting structure.
  • nanoporous metal monoliths involve certain forms of combustion synthesis such as the thermal decomposition of transition-metal complexes containing high nitrogen energetic ligands.
  • nanostructured metal monolithic foams can be formed with a self-propagating combustion synthesis process utilizing metal complexes of the energetic high-nitrogen ligand, bistetrazole amine
  • BTA BTA
  • the BTA metal complexes are prepared by the reaction of monohydrated
  • bi(tetrazolato)amine or ammonium bi(tetrazolo)amine and a selected metal salt The product is collected and dried as a fine powder.
  • organic aerogels such as polysaccharide templates.
  • these approaches are usually better suited for use with metal oxides.
  • the present technology provides methods for fabricating low cost, ultralow density pure metal foams, with tunable densities between 50% and
  • the highly porous foam structures have scalable and macroscopic overall sizes, in the range of several millimeters or more. Such materials will provide an unprecedented platform for exploration of lightweight materials, coatings, photovoltaics, thermoelectrics, heat exchangers, hydrogen storage and catalysts, and could have
  • the fabrication methods begin with the selection of the type of metal nanowires that are preferably made from pure metals such as Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals. Combinations of compatible metal nanowires can also be formed in some embodiments.
  • the term nanowire is used in a general sense for a nanoscale element and is intended to include a variety of structures such as nanotubes, nanorods, nanowires and nanoribbons etc., that are either solid or hollow.
  • the nanowires are formed with a template and electrodeposition.
  • the characteristics of the nanowires are determined by the configuration of the template.
  • the electrodeposition process allows the synthesis of a wide variety of metallic nanowires as the building blocks for the foams. This is easily scalable for mass production and is cost-effective, which are highly advantageous features particularly compared to current lithography approaches in the art.
  • the selected metal nanowires are dispersed in a fluid that is suitable for lyophilization such as deionized water.
  • concentration or density of the nanowires within the freezable fluid can be controlled to tune the density of the final foam.
  • the dispersion may be prepared with the density of nanoscale metal wires tuned to a given application over a continuous range from 0.05 % to 50% by volume.
  • nanowires may oxidize or have otherwise reacted with the environment during formation or in storage. Such contamination can be removed before the foam formation.
  • nanowires may be placed into a solution of an acid such an L- ascorbic acid to treat the wire surfaces and remove oxides and other contaminants before being placed in the lyophilization fluid.
  • the tuned dispersion of treated nanowires is then used to fill shaped molds for freezing.
  • the molds can be essentially any shape and size.
  • the dispersion is dropped or injected directly into a cryogenic liquid such as liquid nitrogen to form spheres, cylinders, discs, cubes, rectangular prisms, sheets, or other forms.
  • the frozen molded forms are then placed into a vacuum chamber for lyophilization.
  • the frozen liquid sublimates under controlled conditions leaving a structure of interlocked nanowires.
  • This structure of loosely interlocked nanowires is processed further to bond the points of contact between the nanowires to form the final foam without significant increase in density.
  • the technology utilizes a sintering step, the oxidation and reduction or sintering of the nanowires to transform the foam from an interlocked structure (where the nanowires are touching) into an interconnected structure (where the nanowires are further bonded).
  • metallic foams with a wide range of tunable densities and characteristics is provided. Aspects of the final metal foam can be tuned by the selection of the length and the cross-sectional dimensions of the nanowire elements as well as the selection of the concentration or density of the nanowires in the nanowire dispersion.
  • Another aspect of the technology is to provide nanowire surface
  • An aspect of the technology is to provide a method for the creation of three dimensional, low and ultralow density foam structures through electrodeposition and a freeze-drying process
  • a further aspect of the technology is the creation of interconnected pure metallic foams that have low density (down to 0.05% of its bulk density) and are still mechanically stable.
  • Another aspect of the technology is to provide a pure metal foam that is particularly suited for producing x-ray emissions from laser illumination.
  • metallic foam structures with densities from about 20 g/cm 3 to about 1 mg/cm 3 are particularly useful as targets for high energy density lasers to generate bright x-rays.
  • FIG. 1 is a schematic flow diagram of a method of fabricating low density interconnected pure metal foams according to one embodiment of the technology.
  • FIG. 2 is a schematic flow diagram of an alternative embodiment of the method of fabrication of pure metal foams of interconnected nanowires according to the technology.
  • FIG. 3 is an indentation curve with loading and unloading portions for a 9 mg/cm 3 strengthened Cu cylindrical foam that was 2 mm in height and diameter. By measuring the initial slope of the unloading curve the modulus of the material can be extracted.
  • FIG. 4 is a relative modulus vs. relative density plot for various low density materials as compared to the foams of the present technology.
  • FIG. 1 through FIG. 4 to illustrate the fabrication system and methods. It will be appreciated that the methods may vary as to the specific steps and sequence and the systems and apparatus may vary as to structural details without departing from the basic concepts as disclosed herein. The method steps are merely exemplary of the order that these steps may occur. The steps may occur in any order that is desired, such that it still performs the goals of the claimed
  • FIG. 1 a flow diagram of one embodiment of a
  • the fabrication process generally begins with the preparation of a dispersion of metal nanowires in a freezable liquid.
  • a variety of fluids can be used to prepare the dispersion at block 20 of FIG. 1 .
  • the fluid that is used is preferably one that does not react with the type of metal forming the metal nanowires that have been selected for the foam.
  • the preferred fluid will also freeze and subsequently sublimate under controlled conditions and otherwise be suitable for lyophilization processes. Preferred fluids also will exert limited stresses on the dispersed wires upon freezing. Deionized water is particularly preferred but other solvents or pure substances that have a triple point may also be suitable freezable fluids for wire dispersions, for example, liquid C0 2 , iodine, arsenic, naphthalene and ammonium chloride.
  • the metal nanowires that are provided at block 20 are preferably made from pure metals or metal alloys.
  • Suitable metals for metal nanowire foams generally include Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals.
  • nanowire generally refers to nanoscale structures that have at least one cross-sectional dimension that is less than 1 m, (i.e. in the nanoscale range), and preferably about 500 nm or less, and more preferably, 200 nm or less.
  • Such nanoscale structures will typically have an aspect ratio of the length to the smallest cross-sectional dimension of greater than 1 , preferably, greater than 10, and in many cases, greater than 100.
  • the nanoscale structures are nanorods with length and diameter dimensions that produce aspect ratios of between 2 and 10. Accordingly, both the length and the cross-sectional dimensions of the nanowire element are variable.
  • the cross-section of the nanowire element may also have any
  • nanoscale wire element may be solid or hollow.
  • nanowire is intended to include a variety of structure such as nanotubes, nanorods, nanowires and nanoribbons etc.
  • the dispersion that is prepared at block 20 also has a nanowire
  • Wire density refers to number of nanowires per unit volume (e.g. pm 3 ).
  • the wire density of the final foam is determined, in part, by the concentration of nanowires in the nanowire dispersion volume that is initially prepared.
  • the dispersion may be prepared with essentially any density of
  • the preferred volume ratio of the fluid in the dispersion vs. the nanowire volume for example, ranges from 1 to 10,000.
  • the surfaces of the nanowires in the dispersion that is provided may be treated to ensure that the nanowires remain sufficiently metallic at block 30. This process is used to reduce any oxides that may be present in on the surfaces of the nanowires. Wires are then moved back into deionized water through fluid exchanges immediately prior to freezing at block 40 of FIG. 1 . [0044] For example, the nanowires may be placed into a solution of an acid such an L-ascorbic acid to treat the wire surfaces at block 30.
  • the wires may be moved into 100g/L L-ascorbic acid, for example, where they are soaked for 48 hours in order to reduce any oxide in the copper to ensure the wires are pure copper during the foam formation process and to strengthen the van der Waals attractions between the wires during the foam formation step.
  • this L-ascorbic acid treatment may not be necessary for silver, palladium, gold or platinum wires since they do not readily oxidize.
  • the nanowire surface treatment at block 30 may be the immersion of the nanowires into a volume of 0.25g/10mL polyvinyl-pyrrolidone (PVP) surfactant to separate the wires. The treated wires are then moved back to water through a fluid exchange process.
  • Alternative chemicals for such surface treatment may include oxalic acid for oxide removal and surfactants are Cetrimonium bromide (CTAB), Sodium dodecyl sulfate (SDS), and polyvinyl alcohol (PVA) for nanowire separation.
  • Lyophilization techniques may be employed at block 40 and block 50 to turn the resulting ice-wire structure into a freestanding, low-density foam composed of interlocked nanowires.
  • the wires In order to create a nanowire structure from the resulting wire-water solution at block 30, the wires must undergo a freeze-drying process to avoid collapse from the surface tension of the water. Once the wire-water solution has been created, the density of the final foam structure can be adjusted by changing the water to wire ratio.
  • the dispersion of treated nanowires and
  • freezable fluid may be placed into various shaped molds and frozen at block 40 of the method of FIG. 1.
  • thin copper molds for high thermal conductivity
  • solutions can also be dropped directly into liquid nitrogen or other cryogenic liquid in the form of droplets and then frozen as spheres at block 40.
  • Pipettes of varying diameters can be used to adjust the diameters of the spherical ice-wire structures.
  • Lyophilization techniques that are employed at block 50 normally work by reducing the surrounding pressure of wire-liquid material frozen at block 40, for example in a vacuum, to allow the frozen water in the material to sublimate (i.e. move directly from the solid phase to the gas phase).
  • the material is cooled to a temperature that is below the lowest temperature where the solid phase and liquid phase can coexist, called the triple point. This cooling ensures that the material will sublimate rather than melt during the drying steps.
  • the pressure is lowered and the material may be heated to an optimal point where the frozen material sublimates efficiently. Typically approximately 95% of the water sublimates away in the primary drying phase.
  • the pressure may be lowered further and the material temperature may also be increased to facilitate desorption of remaining water molecules from the material.
  • the freeze-drying steps of block 50 of FIG. 1 leave a free-standing structure of interlocked nanowires.
  • This interlocked structure is processed further at block 60 of FIG. 1 .
  • the process changes the structure from a loosely interlocked lattice of wires into a single interconnected pure-metal foam without a substantial increase in density.
  • the ice-wire structure preferably undergoes several oxidation-reduction cycles to physically coalesce the wires together at the intersections to form the final foam.
  • FIG. 2 a flow diagram of an alternative
  • FIG. 2 begins with the formation of a nanoporous membrane template at block 80.
  • This membrane template has pores or channels with controllable
  • Nanowires can be grown by electrodeposition into nanoporous templates of various sizes and types.
  • the preferred template materials include anodized aluminum oxide (AAO) membranes, polycarbonate membranes, porous mica membranes or nanochannel glass templates, to lengths of between approximately 1 pm to 100 pm and diameters from approximately 10 nm to
  • a working electrode is coated onto one side of the
  • a metal layer may be coated onto one side of the membrane by a variety of procedures such as by magnetron sputtering to cover the template pores and to be used as a working electrode during
  • Nanowires are then formed by electrodeposition in the membrane at block 100.
  • One preferred electrodeposition process is carried out in a three-electrode cell with electrolytes tailored to the particular metal that is to be deposited in the pores and channels of the template.
  • the working electrode on the membrane template deposited at block 90 is removed at block 1 10.
  • the working electrode may be removed by conventional etching procedures at block 1 10 that will dissolve the electrode.
  • the nanowires are then released from the membrane template by disintegration of the template at block 120.
  • the nanowires can be separated from template material by both chemical and mechanical methods such as by etching and sonication.
  • the released nanowires may be optionally agitated to separate and randomize the nanowires. It was found that during this template removal process the wires tended to clump together (long axes parallel to one another) due to van der Waals attractions between the wires. To disrupt this clumping, the containers could be shaken
  • nanowire surface treatments at block 140 may also be in the form of exposure to a surfactant.
  • the treated nanowires are then washed and dispersed in a suitable fluid for freeze drying (lyophilization) at block 150. Washing removes the unused surface treatments and other contaminants.
  • the washing and dispersion step at block 150 can also include concentrating or diluting the nanowires to a desired density, which will influence the characteristics of the final foam that is produced.
  • the prepared dispersion of treated nanowires is then frozen.
  • the dispersion can be placed in shaped molds to produce foams with a selected shape.
  • Spherical shaped foams can also be produced by placing drops of nanowire-fluid mixture into a cryogenic liquid such as liquid nitrogen.
  • This Lyophilization procedure can also be performed in commercially available freeze-drying machines.
  • the interlocked wire structure that remains after the removal of the frozen fluid at block 170 is processed further to form an interconnected pure-metal foam at block 180 of the method of FIG. 2.
  • the points of contact between nanowires of the interlocked nanowire structure are preferably sintered by heating the interlocked nanowire structure without melting the wires to the point of liquefaction or by exposing the structure to several oxidation-reduction cycles.
  • Example 1 In order to demonstrate the operational principles of the fabrication methods, several metal foams were prepared using the fabrication method shown schematically in FIG. 2. In this example, pure metal nanowire foams of Cu, Pd, Co and Ag were fabricated with a wide range of tunable densities.
  • Nanowires were grown by electrodeposition into nanoporous
  • templates of various sizes and types including anodized aluminum oxide (AAO) membranes and polycarbonate membranes, to lengths of between 5 pm and 40 pm and diameters from about 50 nm to 200 nm.
  • AAO anodized aluminum oxide
  • Magnetron sputtering was used to coat thick conductive layers (200 nm to 500 nm) on the backsides of the membranes for use as working electrodes.
  • thick conductive layers 200 nm to 500 nm
  • a 500 nm thick copper layer was coated onto the backside of the membrane to cover the template pores and to be used as a working electrode during electrodeposition.
  • silver, palladium, gold and platinum nanowires a 500 nm gold working electrode was used instead.
  • electrodeposition cell where metals were deposited potentiostatically into the pores to grow nanowires.
  • the electrodeposition of wires was carried out in a three-electrode cell with suitable electrolytes. In all cases, a platinum counter electrode was used along with an Ag + /AgCI reference electrode.
  • Potential was pulsed to help ensure uniform deposition (for example, from 0 mV to -200 mV at one second intervals for copper deposition).
  • the deposition current was monitored and growth was halted when an increase in current corresponding to the onset of over-deposition was detected.
  • Deposition potential was pulsed and electrolytes containing large amounts of metal ions were used to ensure deposition uniformity.
  • the deposition was carried out with an electrolyte composed of 238 g/L copper sulfate and 21 g/L sulfuric acid.
  • the electrolyte was composed of 15.6 g/L silver sulfate and 224 g/L potassium thiocyanate.
  • the deposition electrolyte was composed of 5 g/L PdCI 2 and 10 g/L HCI.
  • cobalt nanowires the electrolyte was composed of 50 g/L cobalt sulfate and 40 g/L boric acid.
  • the working electrodes of the templates were removed by floating the wire-filled AAO (working electrode side down) in an etchant solution.
  • a copper working electrode 7.9M nitric acid was used for 15 seconds.
  • a gold working electrode a solution containing 10 ml_ of water, 4 grams of potassium iodide and 2 grams of iodine was used.
  • the wire-filled membrane was then thoroughly rinsed in deionized water.
  • the template was then immersed in 6M NaOH and sonicated for 15 minutes to dissolve the AAO template and remove the nanowires. It was found that during this template removal process the wires tend to clump together (long axes parallel to one another) due to van der Waals
  • the wires In order to create a nanowire foam from the resulting wire-water solution, the wires must undergo a freeze-drying process to avoid collapse from the surface tension of the water. Once the wire-water solution has been created, the density of the final foam can be adjusted by changing the wire-water ratio. Densities from 200 mg/cm 3 to 8 mg/cm 3 were achieved using this process. To create spherical foams, droplets of this solution were placed directly into liquid nitrogen and frozen as spheres. Pipettes of varying diameters were used to adjust the diameters of foams from 2 mm to 5 mm. Ice-wire spheres were then moved into small baskets composed of a single loop of thin (127pm diameter) wire to support the structure during freeze-drying.
  • This wire was always made of the same material as the foam.
  • thin copper molds for high thermal conductivity
  • Frozen foams were placed in rough vacuum ( ⁇ 10mTorr) in order to sublimate out the ice from the sample, leaving a free-standing nanowire structures of interlocked nanowires.
  • Example 2 produced with the methods shown in Example 1 to quantify the enhanced strength of the interconnected Cu nanowire foams.
  • cylindrical Cu foams with a 2 mm height and diameter were fabricated and strengthened using the
  • the indenter tip was a 2 mm ruby sphere and measurements were conducted at room temperature and ambient laboratory humidity. The loading and unloading rate was kept constant at 100 m/m. A sample loading/unloading curve is shown in FIG. 3.
  • Loading/unloading curves were derived for a 9 mg/cm 3 strengthened Cu cylindrical foam with 2 mm in height and diameter. By measuring the initial slope of the unloading curve it was possible to extract the modulus of the subject material. The elastic modulus of each sample was extracted from the initial slope of the unloading curve using the Oliver-Pharr multipoint unloading method. For a spherical indenter tip contacting a flat surface the Elastic Modulus, E r can be calculated as:
  • S is the unloading stiffness of the sample,— taken here as the slope of the first 15% of the unloading curve of each sample;
  • A(h contact is the area of contact between the indenter tip and the sample at the depth of penetration below the plane of contact:
  • FIG. 4 is a relative modulus vs. relative density plot for various low density materials.
  • the graph of FIG. 4 includes the results of the Cu measurements as well as results from previous measurements of low and ultralow density materials.
  • results shown as open circles in FIG. 4 represent interlocked copper wire foams from previous results in the art for comparison.
  • the prior work shows a modulus of about 5 Pa.
  • the interconnected foams structure made from the same material produced by the current methods was found to have a modulus of 1200 Pa, an improvement in elastic modulus of three orders of magnitude at the same density.
  • FIG. 4 Also depicted in FIG. 4 are several other low and ultralow density materials whose modulus has been measured through nanoindentation for comparison.
  • Using the methods of the present technology it was possible to create a pure metallic foam whose relative modulus is comparable to strong materials such as C and Si aerogels at the same relative densities.
  • Ni microlattices have a much greater relative modulus than the interconnected Cu foams, but require an elaborate nanolithography process.
  • the nanowire foams produced by the methods described herein can be fabricated over large areas and volumes much more easily and cost-effectively as the methods rely only on electrodeposition and the samples are fabricated inside of macroscopic molds.
  • ultralow density metal foams are for use as high energy density laser targets due to their ability to be heated volumetrically that allows targets composed of high-Z elements to uniformly reach the extreme temperatures that are required for X-ray emission.
  • Gas targets, oxides, metal-doped aerogels and metal-lined cavities have been employed previously for reaching the necessary effective density.
  • the pure metal targets allow higher X-ray conversion efficiencies if the targets can be fabricated at densities low enough to allow volumetric heating while still maintaining mechanical stability.
  • each of 40 beams delivered 475 J of 351 nm laser light to the spherical foam sample. Of these beams, 20 beams were incident on each hemisphere of the spherical Cu targets and were focused 600 pm inside the sample.
  • ultralow density Cu, Ag, Co and Pd pure metal foams have been fabricated using nanowire starting material (made by
  • the densities of the foams can be tuned from as low as 8 mg/cm 3 , or 0.09% of the bulk density, to as high as 200 mg/cm 3 and beyond.
  • the Cu nanowire foams can be greatly strengthened through an oxidation and reduction process by transforming a loosely interlocked structure into a truly interconnected nanowire monolith.
  • the elastic modulus of such foams was found to increase by three orders of magnitude compared to that of an interlocked structure.
  • Such mechanically stable pure metal foams open up a wide range of applications, including high energy density laser targets.
  • Embodiments of the present technology may be described herein with reference to flowchart illustrations of methods and systems according to embodiments of the technology, and/or procedures, algorithms, steps, operations, formulae, or other computational depictions, which may also be implemented as computer program products.
  • each block or step of a flowchart, and combinations of blocks (and/or steps) in a flowchart, as well as any procedure, algorithm, step, operation, formula, or computational depiction can be implemented by various means, such as hardware, firmware, and/or software including one or more computer program instructions embodied in computer-readable program code.
  • blocks of the flowcharts, and procedures, algorithms, steps, operations, formulae, or computational depictions described herein support combinations of means for performing the specified function(s), combinations of steps for performing the specified function(s), and computer program instructions, such as embodied in computer-readable program code logic means, for performing the specified function(s).
  • each block of the flowchart illustrations, as well as any procedures, algorithms, steps, operations, formulae, or computational depictions and combinations thereof described herein can be implemented by special purpose hardware-based computer systems which perform the specified function(s) or step(s), or combinations of special purpose hardware and computer-readable program code.
  • present disclosure encompasses multiple embodiments which include, but are not limited to, the following:
  • a method for fabricating low density and ultralow density nanostructured metal foams comprising: (a) forming a dispersion of metal nanowires in a freezable fluid; (b) freezing the liquid dispersion to form an ice-nanowire structure; (c) sublimating the frozen liquid to expose a free standing nanowire foam; and (d) binding the nanowire foam structure at points of contact to form an interconnected metal foam monolith.
  • the metal nanowires are formed from a metal selected from the group of metals consisting of Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals.
  • dispersion contains wires diluted in volume by a factor of 2 to 10,000.
  • nanostructured metal foams comprising: (a) preparing a nanoporous membrane template; (b) applying an electrode to one side of the nanoporous membrane template: (c) forming nanowires within the nanoporous membrane template by electrodeposition; (d) releasing the formed nanowires from the membrane template; (e) forming a dispersion of metal nanowires in a freezable fluid; (f) freezing the liquid dispersion; (g) sublimating the frozen liquid to expose an interlocked nanowire structure; and (h) binding the interlocked nanowire structure at points of contact between nanowires to form an interconnected metal foam.
  • releasing of formed nanowires comprises: etching the membrane template to remove the electrode; disintegrating the membrane template to release nanowires; dispersing the released nanowires in a freezable fluid; and agitating released nanowires to separate and randomize nanowires in the freezable fluid.
  • nanoporous membrane template comprises an anodized aluminum oxide
  • AAO membrane a polycarbonate membrane, a porous mica membrane or a nanochannel glass membrane.
  • metal nanowires are formed from a metal selected from the group of metals consisting of Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh,
  • dispersion wherein the dispersion contains wires diluted in volume by a factor of 2 to 10,000.
  • a metallic foam structure comprising; (a) an interconnected
  • the network structure has a density from about 20 g/cm 3 to about 1 mg/cm 3 .
  • the metal nanowire network is formed from one or more metals selected from the group of metals consisting of Al, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Sb, La, Nd, Sm, Dy, Pt, Au, Pb, and Bi, and alloys based on one or more of these metals.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Nanotechnology (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Powder Metallurgy (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Abstract

L'invention concerne des mousses de métal pur à très faible densité, d'une densité approchant 0,1 % de la densité en vrac, et des procédés de synthèse faisant appel à des nanofils métalliques interconnectés. Des nanofils de diverses tailles et de divers métaux sont synthétisés par électrodéposition dans des gabarits nanoporeux tels que de l'oxyde ou polycarbonate d'aluminium anodisé. Les gabarits font l'objet d'une attaque chimique et les nanofils sont dispersés dans de l'eau par le biais d'un échange de fluide approprié. Des traitements de surface assurent que les nanofils demeurent suffisamment métalliques et physiquement séparés. Les solutions de fil-eau peuvent être déversées directement dans de l'azote liquide sous la forme de gouttelettes ou placées dans des moules de diverses formes. Une technique de lyophilisation est employée pour transformer le mélange résultant glace-fil en une mousse autoportante, à faible densité, composée de nanofils entremêlés. Enfin, un traitement de frittage ou d'oxydation du matériau en mousse à des températures élevées est utilisé pour relier les nanofils en une mousse métallique interconnectée, améliorant fortement la solidité de la structure.
PCT/US2016/064218 2015-11-30 2016-11-30 Mousses métalliques interconnectées à faible densité et procédés de fabrication WO2017095925A1 (fr)

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US16/001,766 US20190085478A1 (en) 2015-11-30 2018-06-06 Low-density interconnected ionic material foams and methods of manufacture

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Cited By (2)

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WO2018237337A1 (fr) * 2017-06-23 2018-12-27 Lawrence Livermore National Security, Llc Aérogels métalliques conducteurs ultralégers
WO2021022800A1 (fr) * 2019-08-02 2021-02-11 大连理工大学 Procédé de préparation de surface capable de préparer diverses structures de nanofils

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CN112404448A (zh) * 2019-08-23 2021-02-26 南京智融纳米新材料科技有限公司 三维网状纳米结构金属泡沫材料的低温规模化制备方法

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US20130285008A1 (en) * 2009-04-28 2013-10-31 Ben-Gurion University Of The Negev Research And Development Authority Nanowires, method of fabrication the same and uses thereof
US20140076373A1 (en) * 2007-10-04 2014-03-20 Timothy D. Sands Fabrication of nanowire array composites for thermoelectric power generators and microcoolers
WO2014057564A1 (fr) * 2012-10-11 2014-04-17 岩谷産業株式会社 Procédé de fabrication de nanoparticules sèches par lyophilisation
WO2015023760A1 (fr) * 2013-08-14 2015-02-19 Board Of Regents, The University Of Texas System Procédé de fabrication de nanofils de silicium et dispositifs contenant des nanofils de silicium

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6054495A (en) * 1996-02-20 2000-04-25 The United States Of America As Represented By The Secretary Of The Navy Synthesis of unagglomerated metal nano-particles at membrane interfaces
US20140076373A1 (en) * 2007-10-04 2014-03-20 Timothy D. Sands Fabrication of nanowire array composites for thermoelectric power generators and microcoolers
US20130285008A1 (en) * 2009-04-28 2013-10-31 Ben-Gurion University Of The Negev Research And Development Authority Nanowires, method of fabrication the same and uses thereof
WO2014057564A1 (fr) * 2012-10-11 2014-04-17 岩谷産業株式会社 Procédé de fabrication de nanoparticules sèches par lyophilisation
WO2015023760A1 (fr) * 2013-08-14 2015-02-19 Board Of Regents, The University Of Texas System Procédé de fabrication de nanofils de silicium et dispositifs contenant des nanofils de silicium

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018237337A1 (fr) * 2017-06-23 2018-12-27 Lawrence Livermore National Security, Llc Aérogels métalliques conducteurs ultralégers
US11938545B2 (en) 2017-06-23 2024-03-26 Lawrence Livermore National Security, Llc Ultralight conductive metallic aerogels
WO2021022800A1 (fr) * 2019-08-02 2021-02-11 大连理工大学 Procédé de préparation de surface capable de préparer diverses structures de nanofils

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