Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
  • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/44—Carbon
  • C09C1/48—Carbon black
  • C09C1/56—Treatment of carbon black ; Purification
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
  • A61P31/04—Antibacterial agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM

Definitions

• the invention relates generally to nanopowder synthesis processes, and more particularly to the controlled use of a precursor material (such as a precursor gas) to assist in the formation of unagglomerated nanoparticles of the powder. It also relates to novel nanomaterials comprised of carbon and metals produced by the process along with the fundamental processes the novel nanomaterials enable.
• a precursor material such as a precursor gas
• Nanopowders exhibit unique properties that are different than their micron counter-parts such as lower melting/sintering temperatures, higher hardness, increased optical transparency and increased reactivity. Many applications would like to benefit by exploiting these properties.
• the commercial availability of nanopowders has been limited to a few materials such as silica, carbon black and alumina.
• Several new processes are now producing nanopowders in commercial scale and have the ability to make a wide range of materials including silver, copper, gold, platinum, titanium and iron as well as others.
• the particles generally need to be unagglomerated. This aids in preserving the properties unique to the nanoscale and allows easier incorporation of the powder into most applications. Many of the new processes, especially with metals, cannot produce unagglomerated particles. Metal particles at this size have high surface energies and are consequently unstable. When two particles contact one another, the particles form a neck to decrease both the local curvature and surface area, consequently lowering the total surface energy. The result is the formation of hard agglomerates, or aggregates, of the nanopowder which are nearly impossible to break apart. Since the particles are fused to one another, they begin to act like a much larger particle and lose many of the desired characteristics of nanoparticles.
• the particles form a nanostructured material instead of a true nanopowder.
• Nano- sized particles have been shown to have reduced melting and sintering temperatures relative to the bulk material properties. This makes nanopowders very prone to aggregation at elevated temperatures.
• SFE sodium/halide flame and encapsulation technology
• This process uses a three-inch long flame inside a four-foot long tubular flow reaction furnace for sodium reduction of metal halides, such as boron trichloride and titanium tetrachloride, to produce metal and ceramic nanoparticles.
• the particles produced are 10 to 100 nm in diameter with a salt encapsulation.
• This system is an open loop process that requires continuous feed of the salt encapsulation solution and the combustion gases into the reaction furnace. Hence, it uses considerable gases and is not very efficient.
• this material requires an additional step to remove the salt encapsulation.
• the salt encapsulation can present chemical compatibility issues, especially in applications where ionic contamination is not well tolerated, even when the encapsulation is removed.
• Harima Electronic Material division of Harima Chemicals based in Tokyo, Japan uses a gas evaporation process to produce a nano-silver paste containing particles with an average size of 7 nm coated with an organic dispersing agent.
• This material has much of the same issues as Sol-Gel produced material in that the dispersant agent that is bonded to the particle's surface must be removed from the silver to have the silver reactive. Additionally, if the paste is dried to form a powder, the particles become aggregated.
• Amorphous morphology is generally not desirable for metal particles because the particles will crystallize over time and/or at temperature resulting in unstable reactivity of the particles.
• the microscopic quantities of particles were collected 3mm from the arc by drifting onto a substrate, again further demonstrating that the technology is not commercially feasible.
• the Solenoid process a pulsed solenoid is used in conjunction with a high power, pulsed plasma (500-5000+ V, 10,000-100,000+A, 0.1 - 10ms) process to produced unagglomerated nanoparticles in commercial quantities.
• the liner of the solenoid provides an uncontrolled precursor for coating the particles.
• the plasma created from the metal precursor materials used to make the nanopowders evaporates the liner. The amount of material removed from the liner is not controlled.
• the gas species evolved by the vaporization of the liner is not controlled and is dependent upon the liner composition and production conditions.
• the liner is restricted to materials that are compatible with this process and limits the choice of particle coating materials to a very short list of high strength, plasma tolerant and insulating materials. Hence, it is impossible to control the coating precursor concentration within this process.
• the material produced from the Solenoid process consisted of discrete metal particles surrounded by carbonaceous material. Because the silver is not tightly bound to the carbon material and there is no surface chemistry attached to the silver particles, they are very active. Specifically, 25nm silver nanoparticles were produced that have been shown to have good bacterial efficacy in a commercial topical wound dressing.
• the current invention overcomes the previous art problems and difficulties, by producing dry, unagglomerated coated nanopowders in commercial volumes in a controllable process.
• the particles are stable at room temperature and remain discrete.
• the new process can use a similar high-powered, pulsed plasma process as disclosed and described in United States Patent No. 6,777,639 ("the '639 Patent") and the '858 Patent Application, but without the complexity of the pulsed solenoid used in the Solenoid process.
• the current invention provides a high level and wide range of control of coating properties and coating precursors.
• the current invention produced far-reaching results and produced both non-agglomerated nanoparticles and novel nanomaterial compositions.
• the invention in the broad extent provides a novel method for synthesizing nanometals as well as a method for producing novel nano-materials.
• the synthesis process incorporates a system for automatically controlling the coating precursor material within the synthesis process.
• the controlled coating precursor system can be in multiple forms including a controlled gas, liquid or solid feed system or combination therein.
• the coating precursor may interact with the plasma, the particles or combinations therein.
• control of the coating precursor material is accomplished by using a gas injection control system to provide a controlled hydrocarbon precursor material that interacts with the synthesis process to produce highly unagglomerated nanometal particles.
• the hydrocarbon gas interacts with the plasma and nanomaterial precursor material to form carbonaceous materials that assists in keeping the nanoparticles unagglomerated. Additionally control of the agglomeration level is accomplished by control of the hydrocarbon gas species and quantity.
• a gas evolving system is used to introduce the hydrocarbon precursor into the system to control the amount of particle agglomeration.
• a solid or liquid precursor is used to evolve gas in a controlled manner into the synthesis process.
• the gas evolution may occur by interaction with the plasma or by an independent source such as heating the solid or liquid.
• a solid hydrocarbon precursor rod can be fed into the process in a controlled manner to evolve the hydrocarbon gas.
• the hydrocarbon gas is created by controlled injection of a liquid hydrocarbon precursor into the process to interact with the plasma.
• the hydrocarbon gas may also be created by controlled evaporation of the liquid precursor material.
• the process of the current invention produces novel materials.
• the novel materials are a composite of unagglomerated nanometals and a carbonaceous material.
• the carbonaceous material has been shown to contain a carbyne form of carbon.
• the material produced by the process has been shown to be effective against a wide range of bacteria.
• the silver material embodiment of the present invention has been shown to have bacterial efficacy against both gram positive and gram-negative bacteria.
• Figure 1 is a diagram of the pulsed power synthesis system embodiment of the present invention that is configured with an automated gas control system for the coating precursor material.
• Figure 2 is a TEM image of 77nm silver produced without any coating precursor.
• Figure 3 is a TEM image of a composition embodiment of the present invention (45nm silver produced using 44 ppm of acetylene gas).
• Figure 4 is a TEM image of another composition embodiment of the present invention (28nm silver produced using 440 ppm of acetylene gas).
• Figure 5 is a TEM image of another composition embodiment of the present invention (22nm silver produced using 4,400 ppm of acetylene gas).
• Figure 6 is a TEM image of another composition embodiment of the present invention (9nm silver produced using 44,000 ppm of acetylene gas).
• Figure 7 is a TEM image of another composition embodiment of the present invention (30nm silver produced using 8800 ppm of methane gas).
• Figure 8 are the XRD plots of 25nm material produced by the Solenoid process.
• Figure 9 are the XRD plots of another composition embodiment of the present invention (25nm material produced using 4400 ppm acetylene).
• Figure 10 are the XRD plots of another composition embodiment of the present invention (lOnm material produced using 44,000 ppm acetylene).
• Figure 11 are the XRD plots of the composition embodiment of the present invention of Figure 7 (the 30nm material produced using 8800 ppm methane).
• Figure 12 is a TEM image of the composition embodiment of the present invention of Figure 9 (25nm silver produced using 4,400 ppm acetylene), which shows the carbyne structures.
• Figure 13 is the EELS data of the composition embodiment of the present invention of Figures 9 and 12 (25nm silver produced using 4,400 ppm acetylene), which confirms the presence of carbynes and discrete silver particles.
• Figure 14 is a TEM image of the composition embodiment of the present invention of Figure 10 (lOnm silver produced using 44,000 ppm acetylene), which shows the carbyne structures and discrete silver particles.
• Figure 15 is a TEM image of the carbyne structures of the composition embodiment of the present invention of Figures 10 and 14 (lOnm silver produced using 44,000 ppm acetylene), which shows the presence of carbynes.
• Figure 16 is a TEM image of a prior art carbon/silver composite.
• Figure 17 is another TEM image of the same prior art carbon/silver composite of Figure 16.
• Figure 18 is another TEM image of the same prior art carbon/silver composite of Figures 16 and 17, which shows crystalline particles.
• Figure 19 is another TEM image of the same prior art carbon/silver composite of Figures 16-18, which shows crystalline particles.
• Figure 20 is a TEM image of the same prior art carbon/silver composite material of Figures 16-19, which shows only the carbon material.
• Figure 21 is a TEM image of the prior art carbon/silver composite material of Figures 16-20, which shows only the carbon material.
• Figures 22A-C are TEM images of a composition embodiment of the present invention (silver/carbon composite material made using 8800 ppm methane), which shows the presence of carbyne.
• Figure 23 shows EELS analysis of the composition embodiment of the present invention of Figures 22 A-C (silver/carbon composite material made using 8800 ppm methane), which confirms the presence of carbyne.
• Figures 24A-D are TEM images of another composition embodiment of the present invention (copper/carbon composite produced using 44,000 ppm acetylene), which shows the presence graphitic and fullerene carbon.
• Figure 25 is the EELS data of the composition embodiment of the present invention of Figures 24 A-D (copper/carbon composite produced using 44,000 ppm acetylene), which confirms the presence graphitic and fullerene carbon.
• Figures 26A-B are TEM images of another composition embodiment of the present invention (iron/carbon composite produced using 4,400 ppm acetylene), which shows the presence graphitic and fullerene carbon.
• Figure 27 is the EELS data of the composition embodiment of the present invention of Figures 26 A-B (iron/carbon composite produced using 4,400 ppm acetylene), which confirms the presence graphitic and fullerene carbon.
• Figures 28A-B are TEM images of another composition embodiment of the present invention (iron/silver/carbon composite/alloy material using acetylene).
• Figures 29 A-B are TEM images of another composition embodiment of the present invention (carbon material using carbon precursor material and acetylene gas). ⁇
• Figure 30 is a diagram of another pulsed power synthesis system of the present invention that is configured with an automated liquid control system for the coating precursor material.
• FIGS 3 IA-B are TEM images of another composition embodiment of the present invention (silver/carbon composite material using 10 gm heptaethiol).
• Figure 32 is a TEM image of another composition embodiment of the present invention (silver/carbon composite material using 20 gm heptaethiol).
• the current invention alleviates the problems of the previous systems and provides a unique system that has the ability to control the agglomeration of the particles and is versatile enough to handle different coating precursors.
• Figure 1 shows a detailed schematic of the current invention.
• the current invention uses a gas injection system with a continuous closed loop feedback concentration control system to control the hydrocarbon precursor to assist in forming the unagglomerated nanometals.
• the system is composed of the radial gun synthesis process 100 described in the '639 Patent, of which is incorporated by reference and which details have been omitted.
• the reaction vessel 101 is connected to the cyclone 102 via a collection pipe 103.
• the cyclone is used to remove larger particles, typically greater than 0.5 micron, which are collected in the cyclone hopper 104.
• the cyclone is connected to the dust collector 105 by a stainless steel pipe 106.
• Located within the dust collector is a filter 107 used to separate the powder from the gas stream.
• the bottom of the dust collector contains a packaging valve 108 which is connected to a packaging container 109 used to collect the powder.
• the outlet of the dust collector is connected to the inlet of a sealed blower 110.
• the outlet of the sealed blower is then connected to the reaction vessel 101 to form a closed loop system.
• gas bottles 120 are connected to a gas injection manifold, 121.
• the new invention incorporates a bottle of particle coating precursor gas 150, such as a hydrocarbon gas like acetylene or methane, connected to the gas injection valve 154. While the preferred embodiment uses hydrocarbon gases it is not limited to hydrocarbon gases and other gases such as silane can be used.
• a gas sensor 151 is connected to the outlet of the reaction vessel and pulls gas samples out of the reaction vessel.
• the gas sensor contains a set point controller 152 that uses the data from the gas sensor to maintain a predefined gas concentration.
• the system is vacuumed to remove any oxygen from the system and is then filled with the inert gases.
• the inert gases may be, but are not limited to argon, helium, nitrogen, and neon.
• the blower 110 is turned on and the gases are recirculated.
• the set point controller 152 is set to maintain a specific gas concentration, typically in the range of 1-500,000 ppm and more specifically in the range of 50-50,000 ppm, and then the hydrocarbon gas is injected into the system.
• the gas sensor 151 monitors the gas concentration and the set point controller causes the gas injection valve 154 to inject the hydrocarbon gas to maintain the specified concentration.
• the material synthesis is started and powder is produced. As powder is produced, the coating precursor material is consumed and additional coating precursor material is automatically added to the system.
• the blower 110 is continuously recirculating the gas within the closed loop.
• the powder moves with the gas through the cyclone 102 where larger particles are removed.
• the remaining powder continues to the dust collector 105 where it collects on the surface of the filter 107.
• the filter is back pulsed with compressed gas (not shown) to remove the powder and allow it to fall into the packaging container 109.
• the packaging valve 108 can be closed to seal the system and allow the packaging container with the powder to be removed.
• the gas that passes through the filter then flows into the blower and is sent back to the reaction vessel.
• the hydrocarbon gas interacts with the plasma. As the gas quenches, it may form solids, react with the metal vapor or may catalytically interact with the metal vapor and particles. The resulting product of the plasma and gas quench is the formation of highly unagglomerated metal nanoparticles. Additionally carbon structures, including amorphous carbon (soot), graphite, fullerenes, carbon nanotubes, diamond like carbon structures and carbyne structures and combinations thereof may be formed. The carbon may interact with the inert gases to form other compounds such as cyano derivatives in the case of nitrogen. Additionally, for some metals such as aluminum, compounds may be formed that contain carbide compounds. Consequently the hydrocarbon gas is being consumed and must be adjusted to maintain a specific gas concentration.
• While the current examples show materials produced using acetylene and methane, other gases such as alkanes (methane CH4, ethane C2H6, propane C3H8, butane C4H10, pentane C5H12, heptane C6H14, etc.), alkenes, alkynes at an appropriate but non-explosive vapor pressure could be used with the current invention. While the current examples use hydrocarbon gas, it is not necessarily limited to them. For example silane gas could be used to form a silicon matrix or borane gas could be used to form a boron matrix when a portion of the matrix gas does not form a compound with the metal precursor. One skilled in the art will also recognize that mixture of gases could also be used. In some cases it may be possible to form combinations of the metal particles, compounds of the metal and matrix gas and the matrix. Other gases such as organo-metallic gases such as ferrocene could also be used.
• alkanes methane CH4, ethane C2H6, propane
• the current invention has broad capabilities and demonstrated the ability to produce a wide array of material sizes, morphologies and compositions.
• the new invention was able to produce materials in the range of 8- 1 OOnm with precise and consistent control, far greater than the solenoid process.
• the solenoid process was able to produce material down to 25nm; however, it could not produce this material consistently.
• the new process was also able to produce new materials that contained higher carbyne contents and compositions that were pyrophoric and had different dispersibility characteristics. Additionally, the new process is capable of producing various materials including but not limited to metals, metal alloys and combinations of metals and metal alloys.
• Example 1 The following tests were performed using the system invention of the present Application.
• the radial gun synthesis technique as described above was used to produce the material.
• Acetylene and methane were used for the hydrocarbon gas. All size measurements are computed based on BET measurements and an equivalent sphere diameter model.
• Figure 2 shows the 77 nm silver produced with no hydrocarbon gas. It shows extensive necking between particles.
• Figure 3 shows the 45 nm silver produced by adding only a 44-ppm concentration of acetylene. The amount of agglomeration is substantially reduced.
• Figure 4 shows 28 nm silver produced by adding 440-ppm acetylene.
• Figures 5 and 6 show material produced at 4400 ppm and 44,000 ppm levels of acetylene. The material size produced was 22 nm and 9 nm, respectively. This shows a clear trend of decreasing particle size with increasing gas concentration. Additionally the particles are discrete and unagglomerated.
• embodiments of the invention have an average size of material in the range between about 8nm and about 45nm, and more specifically, can have a size of material in the range between about 8 nm and about 25nm, and even more specifically, can have a size of material in the range between about 8nm and 15 nm. Additional tests were performed using methane at 8800-ppm concentration using the same production conditions as above. The results of the material produced are shown in Figure 7. This material is also unagglomerated.
• the material from the current process has been analyzed to determine its uniqueness.
• TEM Static light scattering
• DLS dynamic light scattering
• ICP Inductively coupled plasma Optical Emission Spectroscopy
• XRD X-ray diffraction
• LECO Electron Energy Loss Spectrometry
• FTIR Fourier Transform Infrared
• GC/MS gas chromatography/mass spectroscopy
• the mean particle size is computed from an equivalent sphere diameter model based on the surface area measurements from the Monosorb BET.
• the Branauer, Emmett and Teller (BET) method for particle measurement uses gas adsorption to determine the specific surface area that is then used to compute a particle size based on an equivalent sphere model.
• the mean particle size in various liquids was determined by a Horiba LA910 SLS. In each SLS test, a 20 gm, 0.1% solution was prepared in a beaker and sonicated using a Misonix Sonicator 3000 with a 0.5-in probe for 2 minutes (4 minute elapsed) at 90% power, half duty cycle. The carbon content of each powder was measured based on LECO analysis.
• the material from the new process is distinguishable from the solenoid process. Additionally, for a given gas the carbon content increases with the amount of gas in the reaction chamber. Interestingly, for a given ambient precursor gas carbon content (4,400 ppm acetylene vs. 8,800 ppm methane) the carbon content in the materials is not the same. This indicates that the coating composition is different for the different gases.
• the composition of the produced material was determined from a host of tests including XRD, ICP and LECO. X- ray diffraction tests were performed to determine the material composition and crystal structure. The results are summarized in Table 3. The results confirm that the material is predominantly crystalline silver with a small amount of carbon. The crystallite size of the silver was also estimated from the XRD analysis and shows good correlation with the BET results indicating that the particles are discrete. The XRD analysis showed small amounts of carbon that was interpreted to be Fullerite structures. Figures 8-11 show the XRD data for the various materials.
• peaks indicated by 80Ia-1101a indicate the Face Centered Cubic (FCC) form of silver whereas peaks 803a-l 103a (thick lines) indicate the primitive hexagonal form of silver. These results confirm the material is highly crystalline.
• the peaks indicated by 805b- 1105b can be interpreted as fullerite. Later analysis using Scanning Transmission Electron Microscope (STEM), EELS and EDS indicate that this is a mixture of sp2-bonded (graphitic) and spl -bonded (carbyne) carbon.
• the metal content was also verified using ICP analysis which shows in excess of 99% silver on a metal basis. This means that of the metal in the sample, 99% is silver. It does not tell the total amount of metal in the sample. From the XRD analysis, the only materials present were carbon and silver. LECO analyses were performed to determine the carbon content in each of the samples. This is shown in the Table 4.
• the EELS analysis shows that under certain conditions the carbon has an sp2 and/or spl bonding structure.
• Carbon bonding structure with spl is referred to as carbyne.
• the carbyne structure is elemental carbon in a triply bonded form; rod-like molecule comprised mostly of alkyne (C ⁇ C) groups, more commonly referred to as spl - bonded chains of carbon atoms.
• C ⁇ C alkyne
• carbyloid which refers to individual types of carbon compounds collectively referred to as carbynes.
• allenic carbyne or ⁇ -carbyne.
• Polyyne consists of series of alternating single and triple carbon-carbon bonds (- C ⁇ C-O ⁇ C-). Also referred to as acetylenic carbyne or ⁇ -carbyne.
• the carbyne form of carbon is extremely difficult to produce and has only been produced in laboratories under very specialized conditions. It is generally considered unstable and hence it has been difficult to study.
• One embodiment of the invention produced by this unique process is a composite of metal particles interspersed within a carbon structure that appears to contain carbyne bonding (spl).
• This material can be produced in significant commercial scale quantities, more specifically, silver particles inter-dispersed within a carbon matrix containing carbyne structures.
• the morphology of the carbon structure appears to change based on the production conditions.
• One production condition using 4,400- ⁇ pm acetylene produces material with a specific surface area of 22 m2/g (BET) that is 97wt.% of silver and 3 wt. % carbon is shown in Figure 12. It shows discrete silver particles interspersed within a low-density carbon matrix.
• Figure 13 shows the EELS data, specifically the Carbon K-edge spectra, of the sample made using 4400ppm of acetylene.
• the spectra shows equivalent heights for the D*, 1301, and D*, 1305, peaks indicating the presence of spl bonding or carbynes.
• the same production conditions yielded a material with a specific surface area of 60 m2/g that is 70 wt.% silver and 30 wt.% carbon.
• the carbon structure in this material has a different morphology which appear to be "layers" of carbon deposited on the curved surface of the metal nanoparticles as shown in Figure 14a, 14b and 14c.
• FIG 14a The dark elements in figure 14a show discrete silver particles while the high crystallinity of the silver particles is shown in Figure 14c as evident by the presence of the lattice planes. For the most part, the silver particles are discrete and are interspersed within the carbon structure. Additionally, the TEM images show that the silver particles are much smaller than the material produced using 4,400 ppm of acetylene.
• Figure 15 shows a TEM of the carbynes structures produced using silver and 44,000 ppm of acetylene. When this composite material is exposed to the electron TEM beam, the silver particles are excited and expelled from the carbon matrix. This indicates that the silver particles are not tightly bond to the carbon.
• the material produced with the solenoid process is also shown in Figures 16-21. This material appears very different than the material produced with the 44,000 ppm of acetylene.
• the silver/carbon composite material was also produced using methane at a concentration that has approximately the same amount of carbon as one of the previous conditions. This material gave similar results exhibiting the intertwined layers of carbon with interspersed silver particles as shown in Figures 22A-C.
• the specific surface area was 19 m2/g and with a silver and carbon mass content of 98.5/1.5, respectively.
• Figure 23 shows the low loss EELS spectra for the carbon material in the methane silver sample. The peaks 2301 at 4.85 eV and 2305 at 19.5 eV indicate the presence of carbynes.
• the silver produced using methane did have one notable difference in that when larger quantities were exposed to air it was pyrophoric.
• the TEM images were taken from a small sample that was isolated before the material ignited.
• the material produced with acetylene gas was also pyrophoric but only at concentrations below about 500ppm. For comparison purposes, the solenoid material was not pyrophoric.
• the same production conditions were used to make a copper and carbon composite material.
• a material with a specific surface area of 44 m2/g and 20 wt% copper and 80 wt% carbon was produced as shown in Figures 24 A-D.
• the EELS K-edge spectra is shown in Figure 25.
• the high D * peak, 2505, relative to the D* peak, 2501 indicates the material contains a high presence of sp3 carbon (diamond like carbon or fullerene) structures.
• the D * peak, 2501 also indicates that there is some sp2 carbon or graphitic carbon.
• a novel material was synthesized using silver and iron as the precursor metals and acetylene gas as shown in Figures 28 A-B.
• the resulting material demonstrated some unique properties, one of which is that the material is magnetic and appears to be paramagnetic.
• the other unique property is that at certain production conditions the material is pyrophoric when exposed to air.
• Example 5 Graphite precursor material
• Other materials made with the current invention include a nickel and carbon composite and a nickel/silver and carbon composite.
• a nickel and carbon composite and a nickel/silver and carbon composite.
• precious metals such as gold, palladium and platinum can also be used to produce metal/carbon composite materials. These materials are of particular interest because of their catalytic nature, which is similar to silver but generally stronger. This would probably produce more of the carbyne structure.
• Other metals such as cobalt, aluminum, and other metals can also be used.
• the material produced with the new process will burn or oxidize when exposed to elevated temperatures, radiation or a flame. It is not clear if this is a pure oxidation reaction of the metal or a chemical reaction involving the carbon matrix.
• An alternative embodiment of the current invention involves feeding rods of polycarbonate or other solid material in the vicinity of the arc.
• materials such as polycarbonate, thermoplastics such as polyethylene, polypropylene, poly (vinyl chloride), polystyrene, acrylics, nylons and cellulosics, thermoset plastics such as polyamide, polybutadiene, polyether block amide (PEBA), polyetherimide, polyimide, polyurea, polyurethane (PUR), silicone and vinyl ester. Phenolic, melamine and urea formaldehyde could also be used.
• Fluropolymers such as polytetrafluorethylene (PTFE) and polyvinylidene fluoride (PVDF) may also be used. It is also possible to control the spatial location where the solid materials are introduced to again control at the point in the quench process where the coating is applied. However, the degree of spatial control would be much more restricted in the case of solids if one depends on the arc plasma to vaporize the material. Supplemental heating can be applied to a solid to induce vaporization at the desired location. An alternative would be to melt, vaporize, or decompose solids external to the reaction chamber and introduce droplets, sprays, or jets in the liquid or gas phase.
• pellet injector Another means of introducing solids into the arc region is the use of a pellet injector. This could either be a simple gravity or mechanically driven injector, or it could be a more sophisticated light gas gun (or similar). It would be possible to use helium as the propellant in a light gas gun to avoid introducing any contaminants.
• liquid evaporation is used to control the amount of hydrocarbon gas in the system.
• a test was conducted by the addition of 10 grams and 20 grams, respectively, of heptanethiol directly into the reaction vessel using the apparatus shown in Figure 30.
• the system is vacuumed and then filled with the inert gas.
• the ball valve 3025 isolating the liquid port 3026 is closed and the cap from the liquid port is removed.
• the liquid coating precursor, heptanethiol, is added into the liquid port 3026 and the cap 3027 replaced.
• the 2-in ball valve 3025 is opened and allows the heptanethiol to enter into the reactor 3001.
• the blower 3010 is turned on and run for 5-10 minutes to evaporate some of the liquid coating precursor.
• the reactor 3001 is then operated as normal. By controlling the amount of liquid in the system, the amount of vapor is consequently controlled.
• An alternative type of gas or liquid injection system consists of precisely located pulsed or continuous jets of secondary coating material(s) in the expansion region of the arc synthesized material. This allows controlling the point during the synthesis and quench that the coating material or materials are introduced. This allows partial decoupling of the condensation and coating processes, which allows coating nanoparticles of one material with a material with a higher melting temperature before any agglomeration could occur.
• the tests have been limited to a narrow range of hydrocarbons and a limited range of concentrations.
• This technology allows controlling the secondary matrix gas precursor concentration from less than a part per million to 100%. It is possible to introduce more than one material simultaneously by using multiple matrix precursor gases and liquids, as well as electrode materials. By controlling both the arc synthesis parameters and the gas concentration it is possible to independently control the primary particle size, secondary coating thickness, and degree of agglomeration.
• a plasma injector This could include Marshall guns, electrothermal injectors, and other means.
• coatings could be introduced in solid, liquid, gas, or plasma form resulting in the ability to produce nanomaterials with various coating properties.
• Another embodiment includes the simultaneous or staged injection of similar or dissimilar materials by any of the distinct means described above. For example, it is possible to inject a liquid spray of one coating material directly into the arc region while controlling a fixed background concentration of a second coating gas.
• the silver nanopowder is used as an antibacterial agent.
• Silver has long been known to have antimicrobial effects that are a function of the ions released by material. Silver ions can kill bacteria by interfering with respiration (Bragg, P.D. and Rainnie, DJ., "The effect of silver ions on the respiratory chain of Escerhichia coli.,” Can. J. Microbiol. 20, 883-889 (1974)), or by interacting with bacterial DNA (Modak K., and Fox C, "Binding of silver sulfadiazine in the cellular components of Pseudomonas aeruginosa,” Biochem. Pharm. 22: 2392-2404 (1973)).
• antibacterial static agents are considered to be materials which prevent growth. These materials typically have at least a Log 0 reduction. Materials are generally considered to have antibacterial properties if there is at least a Log 2 reduction and preferably a Log 3 reduction. Depending on standards, a "complete kill" is defined as between at least a Log 4 or at least a Log 6 percent reduction. While the current tests were performed for one hour, one skilled in the art will recognize the time sensitivity of these tests. Often, additional kill of the bacteria will occur with longer exposure times to the antibacterial agent.
• the two bacteria that were tested were chosen because they represent gram positive, S. aureus, and gram negative, E. coli, forms of bacteria.
• silver ions have been shown to be effective against gram-negative bacteria but have been shown to ineffective against gram-positive bacteria. This effect is attributed to the thicker peptidoglycan wall of the gram-positive bacteria.
• a unique property of the new silver materials is that they had good efficacy against both gram positive and gram-negative bacteria.
• wound dressing such as topical wound dressings, creams and ointments. It can be incorporated into various consumer electronics, such as cell phone screens, telephone receivers and keyboards; athletic gear such as shoes, clothing, underwear, protection pads, sweat bands, handle grips, tent surfaces or any other area where there is high moisture exposure such as sweating or water exposure; personal hygiene products such as soaps, deodorant, feminine hygiene pads and personal wipes; dental products such as toothbrushes and dental floss; water filters; humidifiers and wipes to give the item antibacterial properties.
• the high-current pulsed arc discharge with adjustable feedback-controlled concentration of coating precursor mixture has significant and far-reaching advantages over the competing processes.
• Either the arc discharge plasma pyrolyses the background gas or liquid vapor, or the hot particles or droplets of the primary material produced during condensation accomplish the same end.
• This secondary material gas then co-condenses with the primary material.
• the point at which the secondary material is pyrolysed, and other factors one or the other material will primarily or entirely reside on the surface of particles composed of the alternate material.
• the level of agglomeration and coating thickness can be controlled.
• the current invention delivers roughly 5,000 times more energy to the arc. This allows the current invention to produce orders of magnitude more material per unit time. The higher energy also produces a much hotter plasma with a more rapid quench which enables the synthesis of a much wider range of nanomaterials with superior properties.
• the new process results in co-condensed particles rather than forming a compound (e.g. metal carbide). It also allows precise control of gas concentration as well as gas mixing.
• the microarc experiments were performed with 1 atmosphere of pure methane, whereas the current invention controls the concentration to as low as 1 ppm in an inert gas background.
• the new nanoparticle coating process produces particles which are far less agglomerated than those produced with the microarc process and are much more crystalline and hence stable.
• the flame synthesis process is fundamentally a different process than the current invention and is much more restricted in choice of coating materials and doesn't afford nearly the ability to control the size of particles produced or the range of coating thickness.
• the coating process is an artifact of the solenoid protection armor and is restricted to materials which are compatible with this application. This fact constrains the choice of coating materials to a very short list of high strength, plasma tolerant, insulating, arc resistant materials. Additionally, the decomposition of the liner material results in a wide variety of gas species, the composition of the coating precursor cannot be accurately controlled. Control of the coating process is not possible with the solenoid process. Also the solenoid process introduces significant additional cost and complexity to the synthesis process because it requires a sophisticated solenoid magnet and a large pulsed power supply and control system. Additionally, the solenoid liner needs to be replaced on a periodic basis because it is being consumed.

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• 2005
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