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WO2017156430A1 - Nanostructures d'oxyde métallique et procédés de synthèse de nanostructures d'oxyde métallique - Google Patents

Nanostructures d'oxyde métallique et procédés de synthèse de nanostructures d'oxyde métallique Download PDF

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Publication number
WO2017156430A1
WO2017156430A1 PCT/US2017/021860 US2017021860W WO2017156430A1 WO 2017156430 A1 WO2017156430 A1 WO 2017156430A1 US 2017021860 W US2017021860 W US 2017021860W WO 2017156430 A1 WO2017156430 A1 WO 2017156430A1
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metal oxide
acid
aqueous
immersing
nanostructure
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PCT/US2017/021860
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English (en)
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Christopher C. Perry
Kevin E. NICK
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Loma Linda University Health
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Publication of WO2017156430A1 publication Critical patent/WO2017156430A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9016—Oxides, hydroxides or oxygenated metallic salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J25/00—Catalysts of the Raney type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/58—Fabrics or filaments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/06—Washing
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • C01G23/08—Drying; Calcining ; After treatment of titanium oxide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • 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
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C01P2004/16—Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00—Use of specific compounds during water treatment
    • C02F2305/08—Nanoparticles or nanotubes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • Metal oxide nanostructures have structural and physical properties that make the nanostructures suitable for many technological applications, such as solar fuel cell and battery technology, tissue engineering, and photocatalysis.
  • Ilmenite is an abundant titanium-iron oxide mineral that can be used as a starting material for making metal oxide nanostructures.
  • Embodiments of the disclosure relate generally to metal oxide nanostructures/ nanomaterials and processes of preparing the same.
  • methods of forming a metal oxide nanostructure are provided.
  • the method comprises: immersing a precursor metal oxide in an aqueous acid solution to form an acid-treated metal oxide;
  • the precursor metal oxide comprises a titanate.
  • the precursor metal oxide comprises ilmenite.
  • the precursor metal oxide comprises a powder.
  • the powder comprises particles between 2 to 10 ⁇ m in size. In some embodiments, the powder comprises particles under 5 ⁇ m in size.
  • the method further comprises a step of milling a precursor metal oxide (e.g., ilmenite) to form oxide powders having an average size (e.g., a median particle size or a mean particle size) of 10 ⁇ m or less.
  • a precursor metal oxide e.g., ilmenite
  • the aqueous acid solution comprises hydrochloric acid (HCl) or citric acid.
  • the aqueous acid solution comprises HCl at a concentration of about 2 M to about 10 M.
  • the step of immersing the precursor metal oxide in the aqueous acid solution is performed at a temperature and time sufficient to at least partially leach out a metal from the precursor metal oxide.
  • the precursor metal oxide comprises ilmenite and the step of immersing the precursor metal oxide in the aqueous acid solution is performed at a temperature and time sufficient to at least partially leach out iron from the precursor metal oxide. In some embodiments, the step of immersing the precursor metal oxide in the aqueous acid solution is performed at a temperature of at least about 80°C. In some embodiments, the step of immersing the precursor metal oxide in the aqueous acid solution is performed at a temperature of between 80°C and 100°C. In some embodiments, the step of immersing the precursor metal oxide in the aqueous acid solution is performed at for at least about 2 hours.
  • the step of immersing the precursor metal oxide in the aqueous acid solution is performed for about 2-4 hours. In some embodiments, the step of immersing the precursor metal oxide in the aqueous acid solution results in the formation of an acid-treated metal oxide that comprises at least about 90% titanium. [0006] In some embodiments, prior to the step of immersing the acid-treated metal oxide in an aqueous base solution, the acid-treated metal oxide is washed with an aqueous solution. In some embodiments, the washing comprises centrifugation and/or filtration. [0007] In some embodiments, the aqueous base solution comprises sodium hydroxide (NaOH) or potassium hydroxide (KOH).
  • the aqueous base solution comprises NaOH at a concentration of at least 2 M.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution is performed in a high pressure vessel (> 100 bar) at a temperature of about 100°C to about 140°C.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution is performed at a temperature of about 120°C.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution comprises autoclaving.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution comprises continuous stirring.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution is performed for at least about 36 hours.
  • the method prior to the drying step, the method further comprises washing the acid- and base-treated metal oxide in an aqueous solution.
  • the method prior to the drying step, the method further comprises washing the acid- and base-treated metal oxide in HCl.
  • the drying step comprises oven drying the acid- and base-treated metal oxide at a temperature of at least about 100°C for at least about one hour.
  • the method of forming nanostructures comprises: leaching a precursor metal oxide in an aqueous acid at a temperature and time sufficient to at least partially leach out iron;
  • the heating temperature is between 80°C and 95°C.
  • the method further comprises performing a sodium ion (Na+) exchange on the nanofibers after autoclaving.
  • the autoclaving temperature is above 120 °C.
  • the nanofibers are dried until all water is removed. In some embodiments, the drying is at a temperature of about 100°C for about 1 hour.
  • the precursor comprises powder between 2 to 10 ⁇ m in size. In some embodiments, the precursor comprises powder under 5 ⁇ m in size. In some embodiments, the precursor comprises metal oxide titanate powder or oxide mixtures of iron, copper, vanadium, and manganese.
  • the aqueous acid is HCl or citric acid. In some embodiments, the aqueous base is 2-10 M NaOH.
  • the nanostructure e.g., nanocomposite
  • the nanocomposite is a metal oxide nanofiber dominated by Ti and containing Na and a transition metal.
  • the nanocomposite is further doped with an element selected from the group consisting of d-block metals, lanthanoids, and actinoids.
  • nanostructures produced according to the methods described herein are provided. In some embodiments, the nanostructure is a nanofiber. In some embodiments, the nanostructure is a nanofiber comprising titanium dioxide (TiO 2 ).
  • the nanostructure is a nanocomposite.
  • the nanostructure is a nanocomposite comprising an oxide of titanium and at least one more transition metal (groups 8 to 12 that include Mn, Fe, Co, Ni, Cu, Zn, Ag, Pd, Pt, Ir, Au, Cd, Ru) and/or multiple element component alloys of transition metals (e.g. Au/Ag, Ni/Cd, Fe/Au, Ni/Pt, Pt/Ni), wherein titanium is the predominant metal in the nanocomposite.
  • the nanocomposite comprises an oxide of titanium and one or more of copper, iron, vanadium, or manganese.
  • compositions comprising such nanostructures (e.g., nanofibers or nanocomposites) are provided.
  • scaffolding for tissue engineering comprising such nanostructures are provided.
  • antimicrobial films comprising such nanostructures are provided.
  • photovoltaic cells comprising such nanostructures are provided.
  • high capacity storage battery components comprising such nanostructures are provided.
  • photocatalytic environmental remediation assemblies comprising such nanostructures are provided. BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG.1 illustrates a scanning electron microscopy image of Na x Fe y Ti (l-z) O z nanofibers synthesized via a two-step sequential process of acid (4M HCl) and base (10 M NaOH ⁇ 114 hrs) hydrothermal treatment of ball-milled ilmenite (FeTiO 3 ) powder.
  • FIGS. 2A-2B illustrate scanning electron microscope images of treated, ball-milled ilmenite powder after (A) acid (4 M HCl) treatment alone or (B) base (10 M NaOH) treatment alone.
  • FIG.3 illustrates an embodiment of a method for forming nanofibers.
  • 4A-4B illustrate that similar nanofibers form after sequential acid treatment (4 M HCl) and base treatment (10 M NaOH) of naturally occurring ilmenite obtained from ores in Canada and Pakistan. Following base treatment, the samples were washed in aqueous HCl and dried at 100°C. (A) 4 hours acid treatment followed by 48 hours base treatment. (B) 4 hour acid treatment followed by 36 hours base treatment. DETAILED DESCRIPTION OF THE INVENTION
  • the nanostructure is a metal oxide nanostructure, such as a nanostructure comprising a metal oxide of copper (Cu), iron (Fe), titanium (Ti), vanadium (V), or manganese (Mn).
  • the nanostructure is a metal oxide nanofiber, such as a nanofiber comprising a metal oxide of Cu, Fe, Ti, V, or Mn.
  • a metal oxide starting material e.g., ilmenite
  • ilmenite a metal oxide starting material
  • Embodiments of the disclosed methods have the advantage of easily being scaled up for the mass production of nanofiber or tubular nanostructures (e.g., titanate nanostructures), and thus are suitable for industrial applications.
  • the methods described herein use readily available starting materials and reagents.
  • the starting materials can be obtained from naturally occurring mineral sources such as ilmenite (FeTiO 3 ) which is cheap and abundant; large reserves of ilmenite of greater than 680 million tons exist.
  • Various embodiments of the disclosure are an unexpected improvement over the published methodologies, in which either base treatment or acid treatment was used, such as Tao et al., "Expanding the applications of the ilmenite mineral to the preparation of nanostructures: TiO 2 nanorods and their photocatalytic properties in the degradation of oxalic acid," Chemistry 2013, 19 (3), 1091-6; and Simpraditpan et al., A; "Effect of calcination temperature on structural and photocatalyst properties of nanofibers prepared from low- cost natural ilmenite mineral by simple hydrothermal method," Materials Research Bulletin 2013, 48 (9), 3211-3217, the entirety of each of which is hereby incorporated by reference.
  • nanostructure refers to a material that has a size in at least one dimension that is on the nanoscale. In some embodiments, a nanostructure has a size in at least one dimension of less than about 100 nm.
  • a nanostructure has a size in at least one dimension of between about 1 nm and about 100 nm.
  • a nanostructure is in the form of a nanofiber or a nanoplate (e.g., a fiber or a plate having a thickness of less than about 100 nm).
  • a nanostructure is in the form of a "nanocomposite,” which as used herein, refers to a composite of two or more materials in which at least one of the materials has a size in at least one dimension that is on the nanoscale (e.g., less than about 100 nm).
  • the term "precursor metal oxide” refers to a composition comprising an oxide of one or more metals.
  • the precursor metal oxide is a mineral or ore comprising an oxide of one or more metals, e.g., a naturally occurring mineral or ore such as ilmenite.
  • the precursor metal oxide comprises one or more additional components (e.g., a metal or an impurity) that is removed or separated from the metal oxide according to a method as described herein.
  • titaniumate refers to a compound comprising an oxide of titanium and at least one additional metallic element (including but not limited to copper, iron, manganese, and vanadium).
  • a titanate comprises an oxide of titanium and iron (e.g., FeTiO 3 ).
  • Conditional language such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include or do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments.
  • Conjunctive language such as the phrase “at least one of X, Y, and Z," unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc.
  • the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than or equal to 10% of, within less than or equal to 5% of, within less than or equal to 1% of, within less than or equal to 0.1% of, and within less than or equal to 0.01% of the stated amount. If the stated amount is 0 (e.g., none), the above recited ranges can be specific ranges, and not within a particular % of the value. For example, within less than or equal to 10 wt./vol. % of, within less than or equal to 5 wt./vol. % of, within less than or equal to 1 wt./vol. % of, within less than or equal to 0.1 wt./vol. % of, and within less than or equal to 0.01 wt./vol. % of the stated amount. III. METAL OXIDE NANOSTRUCTURES
  • metal oxide nanostructures are provided.
  • a metal oxide nanostructure is prepared according to a method described herein.
  • nanostructures are materials that have sizes in at least one dimension of between 1 nm and 100 nm (or between about 1 nm and about 100 nm), e.g., between about 1 nm and about 80 nm, between about 1 nm and about 60 nm, between about 1 nm and about 40 nm, between about 5 nm and about 75 nm, or between about 5 nm and about 50 nm.
  • a nanostructure has a size in at least one dimension of less than 100 nm, e.g., less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than 40 nm, less than 30 nm, or less than 20 nm.
  • a nanostructure has a diameter of between about 1 nm and about 100 nm, e.g., between about 1 nm and about 80 nm, between about 1 nm and about 60 nm, between about 1 nm and about 40 nm, between about 5 nm and about 75 nm, or between about 5 nm and about 50 nm.
  • a nanostructure has a diameter of less than 100 nm, e.g., less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than 40 nm, less than 30 nm, or less than 20 nm.
  • a nanostructure has a width of between about 1 nm and about 100 nm, e.g., between about 1 nm and about 80 nm, between about 1 nm and about 60 nm, between about 1 nm and about 40 nm, between about 5 nm and about 75 nm, or between about 5 nm and about 50 nm.
  • a nanostructure has a width of less than 100 nm, e.g., less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than 40 nm, less than 30 nm, or less than 20 nm.
  • thermally stable mixed metal oxide nanocomposites are disclosed.
  • the nanocomposites can be nano- metal oxides that contain two or more metals.
  • metal oxide nanofibers such as titanate nanofibers, can be formed, though the disclosure is not so limiting and it will be understood that the particular methods disclosed can be used for the formation of other types of nanofibers.
  • metal oxide nanomaterials such as TiO 2 /Fe 2 O 3 and FeTiO 3 can be formed. Small percentages of other transition metals can be incorporated into the nanostructures.
  • MMO mixed metal oxide
  • thermally stable nanomaterial mixed metal oxide nanostructures can be formed.
  • An example of a nanofiber formed from an embodiment of the disclosed method is shown in Figure 1, which is a scanning electron microscopy image of metal oxide nanofibers dominated by Ti, but also containing Na and Fe by Energy Dispersive Spectroscopy (EDS) analysis.
  • EDS Energy Dispersive Spectroscopy
  • the nanostructures can further be doped/incorporated with d-block-metals that exhibit catalytic properties (e.g., to the right of group 7) such as, for example, Ag, Au, Pt, Pd, Ru, Os, Cu, Ni, lanthanoids, and actinoids, though other types of doping can be used as well.
  • Doping nanostructures can refer to adding small amounts of other elements such as those listed above to the base MMO nanostructure.
  • doping with elements listed above can enhance any of the physical or electrical properties of the nanomaterial.
  • incorporation of doping metals can be performed in conjunction with the formation of MMO nanofibers.
  • the produced nanofibers can be 1-100 nm thick or any ranges within this range, e.g., 2-75 nm (or about 2 to about 75 nm) thick or 2-50 nm (or about 2 to about 50 nm) thick and microns in length.
  • the nanofibers can be longer than typically formed nanofibers known in the art.
  • other dimensions of nanofibers can be formed as well, and the particular dimensions do not limit the disclosure.
  • the nanostructure (e.g., nanofiber) that is formed comprises predominantly a single metal.
  • the nanostructure comprises predominantly titanium.
  • the term “predominantly” means that that metal makes up at least about 50% (e.g., at least 60%, at least 70%, at least 80%, at least 90%, or at least 95%) of the metals in the nanostructure; thus, as a non-limiting illustration, a nanostructure that comprises "predominantly titanium” means that titanium makes up at least about 50% of the metals in the nanostructure.
  • the nanostructure comprises at least 90% of a single metal (e.g., comprises at least 90% titanium). In some embodiments, the nanostructure comprises predominantly a single metal (e.g., titanium) and further comprises sodium.
  • the nanostructure further comprises residual or trace amounts of one or more other metals and/or minerals (e.g., which can be residual or trace amounts that remain after treating a precursor metal oxide such as ilmenite with acid treatment and base treatment).
  • the nanostructure comprises predominantly titanium, further comprises sodium, and further comprises residual or trace amounts of one or more of iron, manganese, zinc, or silicates, and/or is doped with one or more other metals (e.g., one or more transition metals, alkali metals, and/or alkaline earth metals).
  • MO metal oxide
  • a metal oxide nanostructure yield of greater than 50% can be achieved, though this can increase with greater time treatments as discussed herein.
  • the method comprises: immersing a precursor metal oxide in an aqueous acid solution to form an acid-treated metal oxide;
  • the immersing step comprises stirring; and drying the acid- and base-treated metal oxide to yield the metal oxide nanostructure.
  • the precursor metal oxide comprises an oxide mixture of two or more (e.g., two, three, four, five, six or more) transition metals, such as but not limited to titanium, iron, copper, vanadium, manganese, scandium, chromium, nickel, and zinc.
  • the precursor metal oxide comprises a titanate.
  • the precursor metal oxide comprises ilmenite, which is an oxide mineral comprising titanium-iron oxide (FeTiO 3 ).
  • the precursor metal oxide (e.g., ilmenite) is in a particulate form, e.g., a powder.
  • the powder comprises particles that have an average size (e.g., diameter) of less than about 5 ⁇ m. In some embodiments, the powder comprises particles that have an average size (e.g., diameter) of less than about 10 ⁇ m. In some embodiments, the powder comprises particles that have an average size (e.g., diameter) of greater than about 2 ⁇ m. In some embodiments, the powder comprises particles that have an average size (e.g., diameter) of between about 2 to about 10 ⁇ m.
  • the powder comprises a population of particles wherein at least about 50%, at least about 60%, at least about 70%, at least about 80%, or at least about 90% of the particles have an average size (e.g., diameter) of less than about 10 ⁇ m, e.g., less than about 5 ⁇ m.
  • the powder comprises a population of particles wherein at least about 50%, at least about 60%, at least about 70%, at least about 80%, or at least about 90% of the particles have an average size (e.g., diameter) of between about 2 to about 10 ⁇ m or of less than about 10 ⁇ m (e.g., less than less than about 5 ⁇ m).
  • the methods described herein comprise a step of milling a precursor metal oxide (e.g., ilmenite) to produce a powder.
  • a precursor metal oxide e.g., ilmenite
  • Methods of processing metal oxide ores such as ilmenite into powders are known in the art. See, e.g., WO 1995/008004.
  • the precursor metal oxide e.g., ilmenite
  • the precursor metal oxide is immersed in an aqueous acid solution that comprises a mineral acid or an organic acid.
  • the aqueous acid solution comprises a mineral acid, including but not limited to hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrobromic acid, perchloric acid, or hydroiodic acid.
  • the aqueous acid solution comprises hydrochloric acid.
  • the aqueous acid solution comprises an organic acid, including but not limited to citric acid, formic acid, acetic acid, carbonic acid, lactic acid, malic acid, oxalic acid, or benzoic acid.
  • the aqueous acid solution comprises citric acid.
  • the aqueous acid solution has a pH of less than about 5.
  • the aqueous acid solution has a concentration of at least about 2 M, e.g., about 2 M, about 3 M, about 4 M, about 5 M, about 6 M, about 7 M, about 8 M, about 9 M, or about 10 M. In some embodiments, the aqueous acid solution has a concentration of about 2 M to about 10 M, e.g., about 4 M to about 10 M or about 6 M to about 10 M. In some embodiments, the aqueous acid solution comprises HCl at a concentration of about 2 M to about 10 M. [0045] In some embodiments, the step of immersing the precursor metal oxide in an aqueous acid solution comprises heating the solution.
  • heating the aqueous acid solution may increase the amount of metals and/or impurities that are leached out of the precursor metal oxide into the aqueous acid solution.
  • the aqueous acid solution is heated to a temperature of at least about 80°C, e.g., at least 85°C, at least 90°C, or at least 95°C.
  • the aqueous acid solution is heated to a temperature of up to about 100°C.
  • the aqueous acid solution is heated to a temperature of about 80°C to about 100°C, e.g., about 80°C to about 95°C.
  • the precursor metal oxide is immersed in the aqueous acid solution for at least about 30 minutes, at least about 60 minutes, at least about 90 minutes, at least about 120 minutes, or longer. In some embodiments, the precursor metal oxide is immersed in the aqueous acid solution for at least about 1 hour, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 5 hours, at least about 6 hours, or longer. In some embodiments, the precursor metal oxide is immersed in the aqueous acid solution for about 1 hour to about 6 hours, e.g., about 2 hours to about 4 hours.
  • the step of immersing the precursor metal oxide in an aqueous acid solution comprises immersing the precursor metal oxide in the aqueous acid solution for a sufficient length of time to leach out at least some metal(s) and/or impurities from the precursor metal oxide such that at the end of the acid treatment step, the resulting product comprises predominantly a single metal.
  • the total metal composition of the resulting product comprises at least 60%, at least 70%, at least 80%, or at least 90% of a single metal.
  • the resulting product comprises predominantly titanium.
  • the precursor metal oxide comprises ilmenite and at the end of the acid treatment step, the resulting product comprises predominantly titanium (i.e., at least some of the iron in the ilmenite leaches out).
  • the total metal composition of the resulting product after acid treatment comprises at least 70%, at least 80%, at least 90%, or at least about 95% titanium.
  • up to about 30%, up to about 25%, up to about 20%, about 15%, up to about 10%, or up to about 5% of the total metal composition of the resulting product after acid treatment comprises a second metal.
  • the precursor metal oxide comprises ilmenite and at the end of the acid treatment step, the total metal composition of the resulting product comprises predominantly titanium (e.g., comprises at least 70%, at least 80%, at least 90%, or at least about 95% titanium) and further comprises up to about 30%, up to about 25%, up to about 20%, about 15%, up to about 10%, or up to about 5% of iron.
  • the amount of a second metal that is present in the acid-treated metal oxide may promote or enhance the formation of particular structures.
  • a lower amount of second metal (e.g., iron) present in the acid-treated metal oxide may promote or enhance the formation of fibrous structures (e.g., nanofibers) while a higher amount of second metal (e.g., iron) present in the acid-treated metal oxide may promote or enhance the formation of plate-like structures.
  • the conditions of the acid treatment step can be adjusted to increase or decrease the amount of second metal (e.g., iron) that is present in the acid-treated metal oxide at the end of the acid treatment step.
  • the acid-treated metal oxide is separated from the aqueous acid solution, and in some embodiments, the acid-treated metal oxide is washed to remove residual acid.
  • the acid-treated metal oxide is washed with an aqueous solution (e.g., deionized water or distilled water).
  • the washing is performed by filtration. In some embodiments, the washing is performed by centrifugation.
  • the acid-treated metal oxide is then immersed in an aqueous base solution.
  • the aqueous base solution comprises sodium hydroxide or potassium hydroxide.
  • the aqueous base solution has a concentration of at least about 2 M, e.g., about 2 M, about 3 M, about 4 M, about 5 M, about 6 M, about 7 M, about 8 M, about 9 M, or about 10 M.
  • the aqueous base solution has a concentration of about 2 M to about 10 M, e.g., about 5 M to about 10 M.
  • the aqueous base solution comprises NaOH at a concentration of at least 5 M.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution is performed at a temperature of about 100°C to about 140°C, e.g., about 100°C to about 120°C, about 110° to about 140°C, or about 120°C to about 140°C.
  • the step of immersing the acid-treated metal oxide in an aqueous base solution is performed at a temperature of at least about 110°C.
  • the acid-treated metal oxide in the aqueous base solution is heated under pressure, e.g., using an autoclave.
  • acid-treated metal oxide is then immersed in the aqueous base solution for at least about 12 hours, at least about 15 hours, at least about 18 hours, at least about 24 hours, at least about 30 hours, at least about 36 hours, at least about 42 hours, at least about 48 hours, at least about 54 hours, at least about 60 hours, at least about 72 hours, at least about 84 hours, or at least about 96 hours.
  • acid-treated metal oxide is then immersed in the aqueous base solution for about 12 hours to about 96 hours, e.g., for about 24 hours to about 60 hours, for about 36 hours to about 60 hours, or for about 36 hours to about 48 hours.
  • the acid-treated metal oxide in the aqueous base solution is stirred such that the acid-treated metal oxide sample remains suspended in the solution.
  • the stirring is performed using paddles or a stir bar.
  • the acid-treated metal oxide in the aqueous base solution is stirred continuously throughout the length of the base treatment step.
  • the step of stirring the acid-treated metal oxide sample in the aqueous base solution promotes or enhances the formation of fibers, e.g., longer fibers and/or a greater quantity of fibers.
  • the amount and/or size of a nanostructure (e.g., nanofiber) that is formed during the base treatment step may vary depending on conditions such as the concentration of base, the temperature, and the length of time of the base treatment step.
  • the conditions of the base treatment step e.g., concentration of base, temperature, length of time, and amount or speed of stirring
  • the method further comprises washing the acid- and base-treated metal oxide in an aqueous solution.
  • the acid- and base-treated metal oxide is washed with an aqueous solution (e.g., deionized water or distilled water). In some embodiments, the washing is performed by filtration. In some embodiments, the washing is performed by centrifugation. In some embodiments, prior to the drying step, the method further comprises washing the acid- and base-treated metal oxide in HCl to remove excess sodium ions that may be present in the sample. [0055] In some embodiments, the sample is dried for a length of time sufficient to remove substantially all liquids from the resulting nanostructures (e.g., nanofibers).
  • an aqueous solution e.g., deionized water or distilled water.
  • the washing is performed by filtration. In some embodiments, the washing is performed by centrifugation.
  • the method prior to the drying step, the method further comprises washing the acid- and base-treated metal oxide in HCl to remove excess sodium ions that may be present in the sample.
  • the sample is dried for a length of time sufficient
  • the sample is oven dried at a temperature of about 100°C or higher (e.g., at least about 100°C or at least about 110°C) for at least one hour (e.g., for at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 hours or more).
  • a person of ordinary skill in the art will appreciate that other methods of drying the sample can also be used.
  • one or more metals can be incorporated into the metal oxide nanostructure during the synthesis methods described herein.
  • the one or more metals are transition metals, alkali metals, and/or alkaline earth metals.
  • the one or more metals are transition metals that exhibit catalytic properties, such as but not limited to Ag, Au, Pt, Pd, Ru, Os, Cu, Ni, lanthanoids, and actinoids.
  • the one or more metals e.g., transition metals, alkali metals, and/or alkaline earth metals
  • the one or more metals are incorporated into the nanostructure by adding the one or more metals to the aqueous base solution into which the acid-treated metal oxide is immersed.
  • the methods described herein comprise immersing the acid-treated metal oxide in an aqueous base solution at a temperature of at least about 100°C, wherein the aqueous base solution comprises one or more transition metals, alkali metals, and/or alkaline earth metals.
  • the one or more metals e.g., transition metals, alkali metals, and/or alkaline earth metals, e.g., Ag or Au
  • the nanostructure e.g., nanofiber
  • Disclosed below with respect to Figure 3 is an exemplary method 300 for forming the advantageous nanostructures.
  • a metal oxide starting material can be provided 302.
  • the metal oxide starting material can be, for example, metal oxide titanate powder, such as those formed from an ilmenite (FeTiO 3 ) rock.
  • the starting material can be an oxide mixture of iron, copper, vanadium, and manganese, e.g., a powder.
  • the powder can be less than 5 um in size (or less than about 5 um in size).
  • the powder can be less than 10 um in size (or less than about 10 um in size).
  • the powder can be greater than 2 um in size (or greater than about 2 um in size).
  • the powder can be heated at a range of 80-95°C (or about 80 to about 95°C) in an aqueous acid to leach out iron 304 in the powder to better expose any titanium to the reaction.
  • the aqueous acid can be, for example, HCl or citric acid (e.g., 2-10 M HCl such as 4 M HCl or 10 M HCl), though other acids can be used as well.
  • the powder in the acid can be heated for >30 minutes (or > about 30 minutes) per 0.5 g (or about 0.5 g) of powder.
  • the acid treatment can occur for up to 4 hours (or up to about 4 hours).
  • the product formed from this acidic hydrothermal treatment can be known as the sample.
  • the temperature and time in the aqueous acid can be selected based on the materials used (e.g., the metal oxide starting material and/or the aqueous acid). For example, in some embodiments, metals may leach out at a higher temperature for some metal oxides compared to other metal oxides. Also, in some embodiments, metals may leach out faster in a relatively stronger acid compared to a relatively weaker acid. As yet another example, in some embodiments, metals may leach out faster with increasing temperature. Accordingly, the temperature and time in the aqueous acid can be selected to at least partially leach out the metal based on the starting composition and structure that can vary in a naturally occurring ore.
  • the acid-treated metal oxides can be autoclaved (e.g., heated under pressure) with an aqueous base 306.
  • the autoclave temperature can be above 120°C (or above about 120°C).
  • the autoclave temperature can be at least 150°C (or at least about 150°C).
  • the autoclave temperature can be 150°C or lower (or about 150°C or lower).
  • an example aqueous base can be a 2-10 M (or about 2– about 10 M) NaOH solution though other bases can be used as well.
  • the aqueous base can be greater than 2-10 M NaOH.
  • 20 mL (or about 20 mL) of base can be used per 0.5 g (or about 0.5 g) of sample.
  • the autoclaving in the aqueous base can be performed until nanofiber formation. In some embodiments, this step can last for 12 hours to 96 hours (3-5 days) (or about 12 hours to about 96 hours).
  • the temperature and time in the aqueous base can be selected based on the materials used (e.g., the metal oxide used and/or the aqueous base) and/or the desired shape, size, and quantity of the nanofibers to be produced. For example, in some embodiments, nanofibers may form at a higher temperature for some metal oxides compared to other metal oxides.
  • nanofibers may form faster in a relatively stronger base compared to a relatively weaker base.
  • nanofibers may form faster with increasing temperature.
  • longer and/or more nanofibers may form with longer time.
  • the temperature and time in the aqueous base can be selected to form the desired shape, size, and quantity of the nanofibers based on a number of variables. For example, longer times can produce longer nanofibers and more complete conversion of the starting materials.
  • the washing can be done with a centrifuge.
  • a sodium (Na + ) ion-exchange with HCl 310 can be performed which can remove sodium ions from the surface of the nanofibers to yield a more consistent final product.
  • the sample is suspended in 1 M HCl (or about 1 M HCL), although other acids may be used.
  • washing and vacuum filtering can be performed.
  • the resulting residue can then be oven dried 312. In particular, the residue can be oven dried at 100°C (or about 100°C) for one hour (or about one hour). The drying time can be long enough to remove water from the amount of material being processed. Thus, larger amounts of material may use longer drying times. Further, in some embodiments, additional drying time does not harm the product.
  • metal oxide nanostructures e.g., nanofibers and nanocomposites
  • Embodiments of the disclosure address the need for large scale synthesis of metal oxide nanofibers.
  • Non-limiting applications of metal oxide nanomaterials e.g. TiO 2 /Fe 2 O 3 , FeTiO 3
  • the methods described herein provide a sustainable, green approach to synthesizing metal oxide nanostructures that have application in these technologies.
  • the disclosure provides fuel cells, solar cells, photovoltaic cells, and high capacity storage battery components comprising a metal oxide nanostructure as described herein.
  • embodiments of the nanostructures e.g., nanofibers
  • the nanostructures described herein can be used was scaffolding for tissue engineering or in biomedical devices.
  • a non-limiting example is in stem cell research as 3-dimensional matrix containing nutrients for cellular and tissue growth.
  • Another example is in orthopedic medicine where the implant of these nanofibers can aid in tissue regeneration after joint replacement.
  • the nanostructures described herein can be used in the preparation of an anti-microbial coating or film, e.g., for food packaging.
  • Example 1 Generation of Titanium Dioxide Nanofibers
  • Ilmenite ore was obtained and milled into powder form.
  • the ilmenite powder was heated at a temperature of 80°C in an aqueous acid solution comprising 4 M HCl for four hours. After acid treatment, the resulting sample was washed by centrifugation and filtration to remove excess acid and dissolved impurities (e.g., metal ions such as Fe).
  • the sample was then immersed in an aqueous base solution comprising 10 M NaOH and was heated to 120° to 140°C under pressure by autoclaving. The sample was treated for 48 hours (for generating the nanofibers shown in Figure 4A) or for 36 hours (for generating the nanofibers shown in Figure 4B).
  • Figures 4A-B illustrate the nanofibers that were formed from a four hour acid treatment followed by a 48 hour base treatment ( Figure 4A) or from a four hour acid treatment followed by a 36 hour base treatment ( Figure 4B).
  • Figure 4A illustrates that the method described herein is robust and that similar products are obtained even when starting with materials found in nature that exhibit variation in composition. For example, ilmenite ore used in this example was obtained from Pakistan and Canada.
  • Ilmenite ore from Pakistan is known to contain more Si, Cr, Mn, V, and Fe than ilmenite ore from Canada, while the ore from Canada contains more Mg.

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Abstract

L'invention concerne des modes de réalisation de procédés de fabrication de nanostructures d'oxyde métallique, telles que des nanofibres ou des nanocomposites. Dans certains modes de réalisation, le procédé comprend un processus en deux étapes de traitement acide et basique.
PCT/US2017/021860 2016-03-11 2017-03-10 Nanostructures d'oxyde métallique et procédés de synthèse de nanostructures d'oxyde métallique WO2017156430A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150050494A1 (en) * 2012-03-19 2015-02-19 The Hong Kong University Of Science And Technology Incorporating Metals, Metal Oxides and Compounds on the Inner and Outer Surfaces of Nanotubes and Between the Walls of the Nanotubes and Preparation Thereof
US20150087506A1 (en) * 2013-09-25 2015-03-26 Instituto Mexicano Del Petroleo Nanostructured titania catalyst with stabilized acidity and process thereof
US20160030908A1 (en) * 2013-03-06 2016-02-04 Ecole Polytechnique Federale De Lausanne (Epfl) Titanium oxide aerogel composites

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150050494A1 (en) * 2012-03-19 2015-02-19 The Hong Kong University Of Science And Technology Incorporating Metals, Metal Oxides and Compounds on the Inner and Outer Surfaces of Nanotubes and Between the Walls of the Nanotubes and Preparation Thereof
US20160030908A1 (en) * 2013-03-06 2016-02-04 Ecole Polytechnique Federale De Lausanne (Epfl) Titanium oxide aerogel composites
US20150087506A1 (en) * 2013-09-25 2015-03-26 Instituto Mexicano Del Petroleo Nanostructured titania catalyst with stabilized acidity and process thereof

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