WO2006090151A1 - Process of forming a nanocrystalline metal alloy - Google Patents

Process of forming a nanocrystalline metal alloy Download PDF

Info

Publication number
WO2006090151A1
WO2006090151A1 PCT/GB2006/000633 GB2006000633W WO2006090151A1 WO 2006090151 A1 WO2006090151 A1 WO 2006090151A1 GB 2006000633 W GB2006000633 W GB 2006000633W WO 2006090151 A1 WO2006090151 A1 WO 2006090151A1
Authority
WO
WIPO (PCT)
Prior art keywords
metal
metal alloy
phase
fct
alloy
Prior art date
Application number
PCT/GB2006/000633
Other languages
French (fr)
Inventor
John Simon Owen Evans
Andrew Kenneth Hughes
Loc Huy Nguyen
Original Assignee
University Of Durham
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University Of Durham filed Critical University Of Durham
Publication of WO2006090151A1 publication Critical patent/WO2006090151A1/en

Links

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
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • 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
    • 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
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to a method of forming a metal or a metal alloy. Particularly, but not exclusively the present invention relates to a method of forming. a nanocrystalline metal alloy.
  • FePt nanoparticles are commonly synthesized by either the simultaneous decomposition of iron pentacarbonyl (Fe(CO) 5 ) and reduction of platinum acetylacetonate (Pt(acac)2) i n the presence of polyol reducing agents or by co- reduction of an iron and platinum salt- Both syntheses are performed in the presence of surfactant molecules to give particle size control. Particles synthesized according to these methods are generally reported to have an Fe/Pt disordered face centered cubic (fee) structure and are thus superparamagnetic in nature.
  • Fe(CO) 5 Due to the volatility of Fe(CO) 5 at the synthesis temperature, an excess is typically required to achieve materials with a 1:1 Fe: Pt ratio, and precise stoichiometry of materials under a certain set of reaction conditions can only be achieved empirically. Although the average stoichiometry of a large sample of FePt formed according to this method is likely to be 1:1, the stoichiometry at a nanoparticulate scale can differ considerably. Furthermore, the Fe and Pt may not be intimately admixed and may include a core of platinum and a covering of iron, or local clusters of iron and platinum.
  • Fe/Pt having close to a 1:1 Fe: Pt ratio can be converted from a face centred cubic (fee) phase to an ordered face centred tetragonal (fct) phase.
  • fee face centred cubic
  • fct face centred tetragonal
  • nanopartides having a low Fe: Pt ratio must combine with nanoparticles having a high Fe: Pt ratio to form an agglomerated Fe: Pt particle having an Fe: Pt ratio close to 1:1.
  • the nanoparticles typically have to be heated to temperatures of 550 0 C or more. At these annealing temperatures, the surfactants coating the particles break down leading to a reduction in interparticle spacing and agglomeration of the particles resulting in a dramatic increase in particle size.
  • reaction scheme 1 a method of forming a metal or metal alloy according to reaction scheme 1:
  • A represents a first metal
  • B represents a second metal
  • n is greater than zero
  • x is an integer of at least one
  • y is an integer of at least one.
  • the method of the present invention involves the simultaneous reduction of a first metal, and oxidation of a second metal.
  • the reduction of metal A proceeds only in the presence of metal B, thus assuring the stoichiometry of compound A x B y .
  • the metals forming A x B y are intimately mixed on an atomic scale by this method.
  • a and B represent the same metal.
  • a and B represent different metals.
  • a n+ represents any metal in a positive formal oxidation state capable of reduction by B n ⁇ .
  • A represents a transition metal; suitably a post transition metal or a late transition metal.
  • A represents Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, Au, Zn, Ga, Ge, As, Cd, In, Sn, Sb, Hg, Tl, Pb or Bi .
  • A represents Pt for magnetic application.
  • A represents Pd for catalytic applications.
  • B n ⁇ represents any metal in a negative formal oxidation state capable of oxidation by A n+ . More suitably B represents a transition metal. In one embodiment B represents V, Cr, Mn, Fe, Co, Ni, Mo, Ru, Rh, W, Re or Os . Advantageously B represents Fe, Co or Mn.
  • a n+ and B n ⁇ may be in the form of metal containing compounds.
  • the metal containing compound of A may be platinum acetylacetonate.
  • the metal containing compound of B includes one or more ligands know to stabilise low oxidation states.
  • ligands include carbonyl ligands, cyclopentadienyl ligands, arene ligands, alkene ligands, and phosphine ligands.
  • the metal containing compound of B may be in the form of a metal carbonyl such as Na 2 Fe(CO) 4 .
  • the metal containing compound of B includes V(CeHg) 2 " , Mn(C 5 (CH 3 ) 5)2 ' , or W(CO) 3 (C 5 H 5 ) " .
  • n is 1, 2 or 3.
  • n is 2.
  • x is 1, 2 or 3.
  • y is 1, 2 or 3.
  • the reaction proceeds according to reaction scheme 2 :
  • reaction may proceed according to reaction scheme 3 :
  • reaction scheme 4 may proceed according to reaction scheme 4:
  • reaction may proceed according to other similar reaction schemes.
  • Metal sources are present in both oxidized and reduced forms.
  • the electrons required to reduce metal A are located on metal B rather than on an additional species, and metal B acts as the reducing agent for metal A.
  • a x B y is formed when a specific, electron balanced ratio of the two metal precursors is present.
  • the reduction of metal A proceeds only in the presence of metal B and so the metals forming A x By will be intimately mixed on an atomic scale.
  • the ratio of metal to reducing agent is assured and thus the stoichiometry of A x B y is also assured.
  • the reaction proceeds only in the presence of A and B the stoichiometry of the compound formed is assured and predicatable at a nanoparticulate scale and this is in contrast to known methods.
  • the stoichiometry of the metal alloy formed according to the method of the present invention does not vary to any considerable degree within a sample of the metal alloy. Furthermore the metals forming the metal alloy of the present invention are intimately admixed at an atomic level.
  • the method of the present invention avoids problems inherent in prior art methods requiring simultaneous reduction or reduction/decomposition of two metal sources through the use of a separate reducing agent. Such prior art processes can potentially lead to either poorly defined stoichiometry or an inhomogenous structure in which, for example, a core of one metal forms first and is later coated by the second metal. In contrast, the metals of the metal alloy of the present invention are intimately, uniformly admixed.
  • the method of the present invention does not involve handling of the toxic liquid Fe(CO) 5 .
  • the reactants are mixed together at room temperature.
  • the reaction mixture may be heated after mixing.
  • the method includes the step of energising the reaction mixture.
  • the reaction mixture may be energised though the application of energy such as conventional thermal energy, microwave energy, UV energy, sonic energy, gamma irradiation or a combination thereof .
  • the reaction mixture is heated.
  • the reaction may be conventionally heated to a temperature of 300 0 C or more; suitably 300 0 C to 450 0 C.
  • the reaction mixture may be heated to a temperature of 300 0 C to 390 0 C.
  • reaction mixture may be energised through the application of microwave energy.
  • the reaction mixture may be heated to 100 to 400 0 C; suitably to 100 to 150 0 C.
  • reaction takes place under an inert atmosphere.
  • the reaction takes place in the presence of one or more solvents.
  • a range of solvents known in the art may be used.
  • one or more of the solvents is a hydrocarbon solvent.
  • the solvent is an aliphatic or aromatic hydrocarbon groups which may be substituted or unsubstituted with one or more of any substituted or unsubstituted alkane, alkene, alkyne or aromatic hydrocarbon groups and contains amine, amide, nitrile, halogen, ether, alcohol, thiol, acid (such as carboxylic or sulphonic acid), ester, aldehyde, ketone, phosphine or phosphine oxide.
  • the solvent may be a long chain hydrocarbon solvent such as nonadecane, docosane or tetracosane.
  • a long chain hydrocarbon solvent such as nonadecane, docosane or tetracosane.
  • suitable solvents include ethers, such as cyclic and polyethers, ionic liquids, mineral oils, silicone oils, glycols, including polyethylene glycols and supercritical fluids such as CO 2 and Xe.
  • the reaction may take place in the presence of one or more surfactants.
  • the surfactants suitably control the particle size of the metal or metal alloy formed.
  • a range of known surfactants may be used.
  • the surfactant is an aliphatic or aromatic hydrocarbon group which may be substituted or unsubstituted with one or more of any substituted or unsubstituted alkane, alkene, alkyne or aromatic hydrocarbon groups, and which may contain one or more amine, amide, nitrile, halogen, ether, alcohol, thiol, acid (such as carboxylic or sulphonic acid), ester, aldehyde, ketone, phosphine or phosphine oxide groups.
  • the surfactant is oleic acid, oleyl amine, trioctylphosphine or a combination thereof.
  • the use of oleic acid as surfactant will typically promote the formation of nanoparticles having a controlled particle size.
  • the use of oleic acid may also reduce the amount of sintering the nanoparticles exhibit on heating.
  • the use of oleyl amine or related amines as surfactant may promote the formation of fct nanoparticles .
  • the reaction takes place in the presence of one or more stabilisers.
  • Any known stabiliser may be used.
  • the stabiliser is an aliphatic or aromatic hydrocarbon group which may be substituted or unsubstituted with one or more of any substituted or unsubstituted alkane, alkene, alkyne or aromatic hydrocarbon groups, and which may contain one or more amine, amide, nitrile, halogen, ether, alcohol, thiol, acid (such as carboxylic or sulphonic acid) , ester, aldehyde, ketone, phosphine or phosphine oxide groups.
  • the stabiliser comprises a phosphine reagent, for instance a tertiary phosphine such as triphenyl phosphine or trioctyl phosphine.
  • a phosphine reagent for instance a tertiary phosphine such as triphenyl phosphine or trioctyl phosphine.
  • the presence of trioctylphosphine may promote the formation of nanoparticles having a particle size of 5 run or less.
  • the reaction includes a purification step involving the separation of metal alloy A x B y from any byproducts formed.
  • the purification step consists of dispersing and sonocating the product in a solvent, precipitating the product out, and centrifuging the product.
  • the purification process may be repeated.
  • the method may include the step of washing the nanoparticles with water to remove impurities such as Na 2 CO 3 .
  • the metal or metal alloy formed according to the method of the present invention suitably has a fee or fct structure.
  • the method includes the step of converting all or some of the metal or metal alloy from a fee to a fct phase.
  • the phase conversion step involves heating preformed A x B y to a temperature of 300 0 C or more; suitably 400 0 C to 450 0 C; more preferably 430 0 C to 450 0 C.
  • the metal or metal alloy A x B y is converted from a fee to a fct phase in solution.
  • the metal or metal alloy solution comprises a surfactant.
  • the surfactant may be any suitable surfactant such as those listed above.
  • metal alloys having a defined metal :metal ratio can be converted from a fee phase to a fct phase.
  • the metal alloy formed according to the method of the present invention has a uniform, controlled stoichiometry at a nanoparticulate level.
  • nanoparticles of the metal alloy of the present invention do not need to coalesce to form particles having a defined stoichiometry.
  • Nanoparticles of the metal alloy of the present invention can be converted from a fee phase to a fct phase without significant agglomeration, and the temperatures associated with the phase transition are significantly lower than for metal alloy formed according to known methods .
  • surface coatings such as solvents are less likely to be burnt off. The presence of a coating reduces the likelihood of the particles agglomerating.
  • phase type, particle size, chemical composition and magnetic properties of the metal alloy produced may be controlled by various parameters such as molar ratio of precursors, solvent type, molar ratio, concentration and type of solvent, surfactant and/or stabiliser added, the amount of energy transferred in the energising step, the agitation method used and/or the purification process used.
  • surfactants such as amine surfactants
  • a metal or metal alloy having a fct phase
  • the use of surfactants, such as amine surfactants may result in a metal or metal alloy having a controlled particle size.
  • the metal or metal alloy has a particle size of 2 to 10 nm; suitably 3 to 7 nm.
  • oleic acid typically results in particles having a relatively small particle size.
  • metal or metal alloy is formed having an average particle size of less than 3 nm; suitably less than 2 nm.
  • oleyl amine typically results in particles having a relatively large particle size.
  • metal or metal alloy is formed having an average particle size of more than 3 nm; suitably approximately 3 to 7 nm.
  • FePt particles having a fct structure and a particle size of from 4 to 6 nm could be obtained in tetracosane at temperatures from 350 to 390 0 C using various amine surfactants.
  • the FePt particle size was increased from 1.5 to 4 nm by changing the molar ratio from 1:1:1:1 olyl amine: oleic acid: Fe: Pt to 2:0:1:1.
  • the addition of triphenyl phosphine or trioctyl phosphine led to a reduction in particle size.
  • 2.7 nm particles could be prepared by microwave heating in the presence of oleyl amine and oleic acid.
  • PtRu and other binary nanoparticle alloys have been shown to be excellent catalysts for oxidation in fuel cell and other applications. Particle size, stoichiometry and atomic distribution have impact on catalytic properties .
  • a metal or metal alloy A x By obtainable from the process hereinbefore described.
  • a x B y is FePt.
  • a X B Y is FePd.
  • a x B y has a fee phase type.
  • a x B y has a fct phase type.
  • the size of the particles forming A x By is predictable and controllable.
  • the interparticulate spacing of A x B y remains great enough to reduce or prevent agglomeration of the particles upon heating to temperatures of 300 0 C and above; suitably 400 0 C and above.
  • the problems of agglomeration or decomposition at increased temperatures are, therefore, reduced or overcome.
  • a solution comprising A x B y .
  • the solution comprises A x B y and a surfactant.
  • the solution may consist solely of A x B y and a surfactant .
  • the solution is colloidal.
  • the solution comprises a surfactant such as any of those listed as suitable above.
  • a surfactant such as any of those listed as suitable above.
  • oleyl amine, oleic acid, trioctylphosphine or a combination thereof may be used.
  • the surfactant is oleyl amine.
  • Compound A x B y typically exhibits magnetic properties.
  • the nanoparticles of A x B y tend, therefore, to be attracted to each other and problems are associated with forming a solution of A x B y having dispersed particles .
  • Particular problems are associated with forming a solution of A x B y having substantially uniformly dispersed particles.
  • a stable dispersion can be formed from fct particles of the present invention prepared directly in solution using NMe 1J OH and ethanol .
  • a X B Y as a data storage apparatus; in particular for use as a magnetic data storage apparatus.
  • a magnetic data storage apparatus comprising A x B y .
  • the magnetic data storage apparatus comprises A x B y having fct phase type.
  • the magnetic data storage apparatus comprises A x B y in solid form.
  • a x B y as a surface coater .
  • the surface coater provides a magnetic coating on a substrate.
  • the substrate is typically formed from polymer, ceramic, metal or from a semiconductor such as silicon.
  • a x B y is in the form of a suspension.
  • a x B y as a catalyst; suitably for use as a high surface area catalyst.
  • a and B are admixed uniformly and intimately for use as a catalyst.
  • a x B y is in the fct phase type.
  • a x B y in sensing applications, such as a gas sensor (H 2 ) .
  • a x B y as a ferrofluid.
  • Figure 1 shows an X-ray diffraction pattern of the FePt product (LHNO59) formed according the method of Example 3;
  • Figure 2 shows the relationship between magnetisation and field for fct particles formed according to the method of Example 3.
  • Figure 3 shows the particle size proportion of FePt product (LHN063, LHN064, LHN069, LHN091, LHN098, LHN093, LHN094) formed according to the method of Example 4?
  • Figure 4 shows X-ray diffraction patterns of FePt product (LHN031) formed according to the method of Example 6 at varying temperatures;
  • Figure 5 shows an X-ray diffraction pattern of the fct FePt product (LHN079) formed according to the method of Example 9;
  • Figure 6 shows a TEM image of the FePt product (LHN079) formed according to the method of Example 9 after dispersion in NMe 4 OH/EtOH;
  • Figure 7 shows an X-ray diffraction pattern of the fee FePt product formed according to the method of Example 11;
  • Figure 8 shows an X-ray diffraction pattern of fee FePd formed according to the method of Example 11;
  • Figure 9 shows a HRTEM image of monodispersed fee FePt product formed according to the method of Example 11.
  • Example 1 FePt synthesis using oleic acid as surfactant (LHN052).
  • a mixture of platinum acetylacetonate (0.118 g, 0.3 mtnol) , disodium tetracarbonylferrate (0.104 g, 0.3 mmol) , oleic acid (0.2 ml, 0.6 mmol) and tetracosane (10 g) was placed in a 100 ml round bottom flask equipped with a N 2 in/outlet, condenser and thermal probe. The mixture was vacuumed down and purged with N 2 several times before the mixture was heated to around 6O 0 C causing the tetracosane to melt. The mixture was sonocated at 64 0 C for 1 hour to form a brown mixture.
  • the round bottom flask was placed onto a heating mantle which had previously been heated to a high temperature.
  • the round bottom flask was heated quickly during 30 min to 389 0 C.
  • the mixture was maintained at reflux between 389°C and 382 0 C for 1 hour to give a dark mixture.
  • the dark mixture was maintained under N 2 atmosphere and allowed to cool to around 50 0 C before the addition of 50 ml of hexane to dissolve the tetracosane.
  • the mixture was then sonocated at room temperature for 15 minutes followed by centrifugation to give a dark precipitate and a pale supernatant containing a significant amount of tetracosane.
  • the dark precipitate was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleic acid (0.5 ml), precipitated out through the addition of absolute ethanol (25 ml) and finally centrifuged to give a dark precipitate. The washing process was repeated twice and a black powder was obtained after the product was left to dry.
  • the sample was shown by powder X-ray diffraction to contain fee FePt phase with a particle size of under 3 nm.
  • Example 2 FePt synthesis using a mixture of oleic acid and oleyl amine as surfactant (LHN061 and LHN076) .
  • the method of Example 1 was repeated with slight variations in the amount of the various precursors and reaction times.
  • a summary of reaction conditions is shown in the table below:
  • the dark mixture formed through the method was maintained under N 2 atmosphere and allowed to cool down to around 5O 0 C before the addition of 50 ml of hexane to dissolve the tetracosane.
  • the mixture was then sonocated at room temperature for 15 minutes to give a mixture of a dark black product dispersion and a precipitated shiny solid.
  • the precipitated shiny solid was separated from the suspended phase by decanting.
  • the dark black suspension was then centrifuged to give a dark precipitate from which a pale supernatant containing a significant amount of tetracosane was decanted.
  • the black product was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleyl amine (0.5 ml), precipitated out by adding ethanol absolute (25 ml) and finally centrifuged to give a dark precipitate.
  • the washing process was twice repeated and a black powder was obtained after the product was left to dry at room temperature overnight . X-ray diffraction patterns of the dark black solid were obtained.
  • the dark shiny solid was also washed several times in hexane until the organic phase was clear and the solid was left to dry at room temperature overnight. X-ray diffraction patterns of the shiny black solid were obtained.
  • the dark black powder and the dark shiny solid obtained were shown through powder diffractometer patterns, to have similar fee FePt phase types.
  • the X-ray diffraction patterns of the two samples showed impurity peaks which were identified as peaks of Na 2 CO 3 . Na 2 C ⁇ 3 could be removed by washing with water.
  • the particle size of both FePt product fractions were under 3 run.
  • Example 3 FePt synthesis using oleyl amine or related amines as surfactant.
  • the dark mixture was maintained under N 2 atmosphere and allowed to cool to around 5O 0 C.
  • the reaction mixture tended to separate into 2 parts: a clear liquid phase formed mainly from tetracosane which crystallizes upon further cooling and a dark precipitate gathered on the vessel wall.
  • Hexane 50 ml was added to the reaction mixture followed by sonocation at room temperature for 15 minutes to disperse the dark solid into the organic phase. After centrifugation, the pale supernatant containing a significant amount of tetracosane was decanted from the dark solid.
  • the black solid was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleyl amine (0.5 ml), precipitated out through the addition of ethanol (25 ml) and finally centrifuged to give a dark precipitate. The washing process was repeated twice and a black powder was obtained after the product was left to dry at room temperature overnight. All 5 samples showed similar results of which the XRD pattern of LHN059 is representatively shown (see Figure 1) .
  • Figure 2 shows magnetic hysteresis loops of as synthesised FePt particles prepared in tetracosane at 289°C recorded at 10 and 290 K. Coercivity of approximately 1300 Oe at 290 K and 3100 Oe at 1OK was observed.
  • In situ powder diffraction experiments were performed as a sample of LHNO59 was heated from 300 to 903 K under a H 2 ZAr mixture. An increase in the degree of fct ordering was clear from around 650 K. At higher temperatures the order parameter rises significantly, rising to more than 0.8, as determined by Rietveld refinement of x-ray diffraction data. On heating above 750 K the particle size as determined by x-ray diffraction also rises sharply.
  • Example 4 FePt synthesis using various amines 2 3 The method of Example 1 was repeated with varying 4 amounts of precursors, and different reaction times 5 and washing processes . K summary of the reaction 6 conditions is shown in the table below: 7
  • the black product was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleyl amine (0.5 ml), precipitated out by adding absolute ethanol (25 ml) and finally centrifuged to give a dark precipitate.
  • Oleyl amine was added as some amines used in the reaction are solid at room temperature and are not highly soluble in the hexane and ethanol used during the washing process.
  • the dark precipitate was then dispersed and sonocated at room temperature in a mixture of absolute ethanol (40 ml) and H 2 O (20 ml) for 15 min before centrifugation to recover the dark precipitate.
  • the washing process was twice repeated using a mixture of hexane, ethanol and oleyl amine.
  • the product was left to dry at room temperature overnight to give a black powder.
  • Example 5 FePt synthesis using phosphine reagents as stabilizers
  • Example 6 FePt synthesis using a nonadecane solvent and oleic acid surfactant.
  • a mixture of platinum acetylacetonate (0.118 g, 0.3 mmol) , disodium tetracarbonylferrate (0.104 g, 0.3 mmol) and oleic acid (0.2 ml, 0.6 mmol) was placed in a 100 ml round bottom flask equipped with a N 2 in/outlet, condenser and thermal probe. The mixture was vacuumed down and purged with N 2 several times before nonadecane (20 ml) was injected. The mixture was sonocated at 64 0 C for 1 hour to form a brown mixture. The round bottom flask was placed into a heating mantle which had previously been heated to high temperature. The round bottom flask was heated quickly to reflux at 335 0 C for different time periods (1, 3 or 5 hours) to give a dark mixture.
  • the dark mixture was maintained under N 2 atmosphere and allowed to cool to around 50 0 C before the addition of 30 - 40 ml of hexane (to dissolve nonadecane) and absolute ethanol (-30 ml) to precipitate particles.
  • the volume of solvents was adjusted to avoid crystallization of nonadecane in the reaction mixture.
  • the mixture was then sonocated at room temperature for 15 minutes followed by centrifugation to give a dark precipitate and a pale supernatant.
  • the pale supernatant contained a significant amount of nonadecane which typically crystallized at room temperature.
  • the black product was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleic acid (0.5 ml), precipitated out by adding absolute ethanol (25 ml) and finally centrifuged to give a dark precipitate.
  • the washing process was repeated and a black powder was obtained after the product was left to dry at room temperature overnight.
  • Figure 4 shows x-ray diffraction patterns obtained from variable temperature powder diffraction experiments performed on FePt product (LHN031) prepared by this route.
  • Evidence for fct ordering in sample LHN031 can be observed from 703 K.
  • the order parameter as determined by Rietveld refinement of the x-ray data rises to 0.73. This ordering occurs without significant particle growth with the particle size (as determined by x-ray diffraction) remaining under 4 nm.
  • Example 7 FePt particles synthesized in oleyl amine and nonadecane (LHNlO4)
  • Example 6 The method of Example 6 was repeated, except oleic acid was replaced by oleyl amine .
  • a mixture of platinum acetylacetonate (0.118 g, 0.3 mmol) , disodium tetracarbonyl iron (0.104 g, 0.3 mmol) and oleic acid (0.2 ml, 0.6 mmol) was placed in a 100 ml round bottom flask equipped with an Ar in/outlet, condenser and thermal probe. The mixture was vacuumed down and purged with Ar several times before injection of nonadecane (10 ml) . The mixture was sonocated at 64°C for 1 hour to form a brown mixture.
  • the round bottom flask was placed on a heating mantle which had previously been pre-heated to a high temperature.
  • the round bottom flask was heated quickly to reflux at 335 0 C.
  • the reaction mixture was heated at reflux for 1 hour to give a dark mixture.
  • the purification process differed slightly to that used for Example 6.
  • the dark mixture was allowed to cool to around 50 0 C before addition of 30 - 40 ml of hexane to dissolve the nonadecane.
  • ethanol was not added at this stage.
  • the mixture was sonocated for 15 minutes at room temperature.
  • the sample was then centrifuged to give a dark precipitate.
  • a pale supernatant contained the major part of the nonadecane which crystallized at room temperature.
  • the black product was next dispersed and sonocated ( ⁇ 15 i ⁇ in) in a mixture of hexane (20 ml) and oleic acid (0.5 ml) .
  • the product was precipitated out through the addition of absolute ethanol (25 ml) and was then centrifuged to a give dark precipitate.
  • the dark precipitate was next washed and sonocated in a mixture of ethanol (40 ml) and water (20 ml) . After centrifugation the dark precipitate was twice washed in a mixture of hexane, oleyl amine and ethanol and a black powder was obtained after the product was left to dry overnight at room temperature.
  • LHN104 contained partially ordered fct FePt particles.
  • the particle size of the FePt particles was above 5 run.
  • Example 8 FePt particles synthesized in nonadecane with oleyl amine, C18-amine/ trioctylphosphine, (LHN119)
  • Example 7 The method of Example 7 was repeated using the reaction conditions summarised below. The purification process was also similar to that used in Example 7.
  • the XRD pattern of the sample formed showed the presence of FePt particles.
  • the particle size of sample LHN 119 was approximately half that of the sample formed according to the method of Example 7 (LHN104) . This decrease in particle size may be explained by the presence of trioctyphosphine which prevents particle growth during the reaction.
  • Example 9 Producing ordered fct FePt particles by annealing fee FePt particle in tetracosane at high temperature
  • Fee FePt particles were synthesised using the method of Example 1 but with solvent, surfactants and reaction times as detailed in Table 5. The particles were characterised by x-ray powder diffraction.
  • the three fee FePt samples described above were subsequently annealed in solution.
  • a mixture of fee FePt sample (50-150 mg) , oleyl amine (0.100 ml) and tetracosane (10 g) was placed in a 100 ml round bottom flask equipped with a N 2 in/outlet, condenser and thermal probe .
  • the mixture was vacuumed down and purged with N2 several times before melting tetracosane at around 6O 0 C.
  • the mixture was sonocated at 64 0 C for 1 hour to form a dark black dispersion.
  • the round bottom flask was placed in a heating mantle which had previously been heated to a high temperature.
  • the round bottom flask was quickly heated to reflux between 370 and 39O 0 C for 18 hours to give a dark mixture. Shorter reaction times would achieve similar results.
  • Example LHN059 The purification was similar to the process described in Example 3 (sample LHN059) .
  • LHN020, LHNO78 and LHNO77 formed LHN068, LHNO79 and LHN081 respectively. All 3 FePt samples formed according to the method of Example 9 exhibited similar results.
  • the XRD pattern of sample LHN079 is representative of the samples (see Figure 5) .
  • LHN068 and LHN079 were significantly larger than sample LHN081.
  • FIG. 6 shows the TEM of dispersed particles after redeposition on a TEM grid.
  • the reaction mixture was allowed to cool down to 60 0 C before the addition of -50 mL hexane.
  • the solution was then sonicated and centrifuged. Afterwards the product was washed four times: first with -20 mL hexane and 10 drops of surfactant, then with -40 mL ethanol and ⁇ 7 mL water. For each of the last two washing steps -20 mL hexane and 10 drops of surfactant were used. Every time the mixture was sonocated for 15 min at room temperature and -30 mL ethanol were added to obtain the particles (HB005) .
  • the product was separated by centrifugation then dispersed in hexane (20 ml) in the presence of appropriate surfactants and precipitated by adding ethanol (40 ml) . After centrifugation, the material was washed one more time in a similar solvent mixture, dried in air at room temperature and stored under N 2 -
  • Example 12 Producing fct Particles by Microwave Heating
  • a mixture of fee FePt nanoparticles (0.020 g) synthesized by conventional heating method and ball milled NaCl (0.400 g) were placed in 10 ml microwave vessel and oleyl amine (0.200 ml) added.
  • the reaction vessel was purged with N 2 , sealed and transferred into a microwave reactor. Reaction was typically carried out using control parameters of 300W max power, 250 0 C max temperature and 250 psi max pressure over a 15-20 min period. Rapid increase of pressure often took place and close monitoring was required to prevent excessive pressure build up.
  • the dark product mixture was allowed to cool to room temperature, washed with a mixture of water and absolute ethanol, and centrifuged. The dark black material was dried in air at room temperature and stored under N 2 .

Abstract

There is described a method of forming a metal or a metal alloy, in particular a method of forming a nanocrystalline metal alloy. The method involves the simultaneous reduction of a first metal and oxidation of a second metal wherein the second metal acts as a reducing agent. The metal or metal alloy formed has a predictable, controllable and uniform stoichiometry on the nanoscale.

Description

Process of Forming a Nanocrystalline Metal Alloy
The present invention relates to a method of forming a metal or a metal alloy. Particularly, but not exclusively the present invention relates to a method of forming. a nanocrystalline metal alloy.
Self-assembled face centred tetragonal FePt nanoparticles superlattices have recently been identified as promising candidates for magnetic storage applications because of their large uniaxial magnetocrystalline anisotropy [K1, s 7 X 106 J/m3] and good chemical stability. Calculations indicate that particles as small as 2.8 urn have a sufficiently high KUV (V=volume) product to be exploited for permanent data storage, leading to significant advances in hard disk drive areal densities over currently used materials.
Chemical routes using high temperature solution- phase-based conditions are the most practical and widely chosen fabrication methods to prepare monodisperse metal particles. FePt nanoparticles are commonly synthesized by either the simultaneous decomposition of iron pentacarbonyl (Fe(CO)5) and reduction of platinum acetylacetonate (Pt(acac)2) in the presence of polyol reducing agents or by co- reduction of an iron and platinum salt- Both syntheses are performed in the presence of surfactant molecules to give particle size control. Particles synthesized according to these methods are generally reported to have an Fe/Pt disordered face centered cubic (fee) structure and are thus superparamagnetic in nature. Due to the volatility of Fe(CO)5 at the synthesis temperature, an excess is typically required to achieve materials with a 1:1 Fe: Pt ratio, and precise stoichiometry of materials under a certain set of reaction conditions can only be achieved empirically. Although the average stoichiometry of a large sample of FePt formed according to this method is likely to be 1:1, the stoichiometry at a nanoparticulate scale can differ considerably. Furthermore, the Fe and Pt may not be intimately admixed and may include a core of platinum and a covering of iron, or local clusters of iron and platinum.
Only Fe/Pt having close to a 1:1 Fe: Pt ratio can be converted from a face centred cubic (fee) phase to an ordered face centred tetragonal (fct) phase. As noted above, although the average stoichiometry of a large sample of FePt formed according to known methods could be 1:1, the stoichiometry could differ considerably within individual particles of FePt. To convert the FePt from fee to fct phase, nanopartides having a low Fe: Pt ratio must combine with nanoparticles having a high Fe: Pt ratio to form an agglomerated Fe: Pt particle having an Fe: Pt ratio close to 1:1. To convert the Fe/Pt structure from a face centred cubic (fee) phase to an ordered face centered tetragonal (fct) phase (the so called Llo structure) , the nanoparticles typically have to be heated to temperatures of 5500C or more. At these annealing temperatures, the surfactants coating the particles break down leading to a reduction in interparticle spacing and agglomeration of the particles resulting in a dramatic increase in particle size.
Agglomeration of particles hinders the performance of such particles as high-density recording materials. Different methods have been attempted to lower the FePt phase transition temperature and avoid particle sintering or to establish a direct route to fct nanoparticles. Introduction of a third metal such as Cu, Ag, Zr, Au and Al into FePt alloys has lowered the phase transition temperature to around 4000C. However, the ternary nanoparticles retain the problems of agglomeration or decomposition on further annealing at higher temperatures. A direct synthesis of fct-FePt nanoparticles using a chemical route has been suggested involving the reduction of platinum and iron acetylacetonates in tetraethylene glycol at 3000C. This method leads to the formation of partial fct FePt alloys with a particle size of 5 to 10 run. The preparation of partially ordered FeS3Pt47 nanoparticles has been suggested by the simultaneous decomposition of Fe (CO) 5 and Pt(acac)2 in hexadecylamine at 3600C. These particles display small RT coercivity values.
According to a first aspect of the present invention there is provided a method of forming a metal or metal alloy according to reaction scheme 1:
xAn+ + yBn" > AXBY
where : A represents a first metal; B represents a second metal; n is greater than zero; x is an integer of at least one; and y is an integer of at least one.
In contrast to known methods, the method of the present invention involves the simultaneous reduction of a first metal, and oxidation of a second metal. The reduction of metal A proceeds only in the presence of metal B, thus assuring the stoichiometry of compound AxBy. The metals forming AxBy are intimately mixed on an atomic scale by this method.
In one embodiment A and B represent the same metal.
In one embodiment A and B represent different metals. Suitably An+ represents any metal in a positive formal oxidation state capable of reduction by Bn~ . More suitably A represents a transition metal; suitably a post transition metal or a late transition metal. In one embodiment A represents Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, Au, Zn, Ga, Ge, As, Cd, In, Sn, Sb, Hg, Tl, Pb or Bi . Advantageously A represents Pt for magnetic application. Alternatively A represents Pd for catalytic applications.
Suitably Bn~ represents any metal in a negative formal oxidation state capable of oxidation by An+. More suitably B represents a transition metal. In one embodiment B represents V, Cr, Mn, Fe, Co, Ni, Mo, Ru, Rh, W, Re or Os . Advantageously B represents Fe, Co or Mn.
In one embodiment of the present invention An+ and Bn~ may be in the form of metal containing compounds. Suitably the metal containing compound of A may be platinum acetylacetonate. Suitably the metal containing compound of B includes one or more ligands know to stabilise low oxidation states. Such ligands include carbonyl ligands, cyclopentadienyl ligands, arene ligands, alkene ligands, and phosphine ligands. The metal containing compound of B may be in the form of a metal carbonyl such as Na2Fe(CO)4. In one embodiment the metal containing compound of B includes V(CeHg)2 " , Mn(C5 (CH3) 5)2', or W(CO)3(C5H5)". Suitably n is 1, 2 or 3. Preferably n is 2. Suitably x is 1, 2 or 3. Suitably y is 1, 2 or 3. In one embodiment of the present invention the reaction proceeds according to reaction scheme 2 :
An+ + Bn~ > AB
Alternatively the reaction may proceed according to reaction scheme 3 :
An+ + 2Bn" > AB2
Alternatively the reaction may proceed according to reaction scheme 4:
An+ + 2B(n/2)" > AB2
Alternatively the reaction may proceed according to other similar reaction schemes.
Metal sources are present in both oxidized and reduced forms. The electrons required to reduce metal A are located on metal B rather than on an additional species, and metal B acts as the reducing agent for metal A. AxBy is formed when a specific, electron balanced ratio of the two metal precursors is present. The reduction of metal A proceeds only in the presence of metal B and so the metals forming AxBy will be intimately mixed on an atomic scale. The ratio of metal to reducing agent is assured and thus the stoichiometry of AxBy is also assured. As the reaction proceeds only in the presence of A and B the stoichiometry of the compound formed is assured and predicatable at a nanoparticulate scale and this is in contrast to known methods. The stoichiometry of the metal alloy formed according to the method of the present invention does not vary to any considerable degree within a sample of the metal alloy. Furthermore the metals forming the metal alloy of the present invention are intimately admixed at an atomic level.
The method of the present invention avoids problems inherent in prior art methods requiring simultaneous reduction or reduction/decomposition of two metal sources through the use of a separate reducing agent. Such prior art processes can potentially lead to either poorly defined stoichiometry or an inhomogenous structure in which, for example, a core of one metal forms first and is later coated by the second metal. In contrast, the metals of the metal alloy of the present invention are intimately, uniformly admixed.
Furthermore, unlike such prior art methods, the method of the present invention does not involve handling of the toxic liquid Fe(CO)5.
In one embodiment of the present invention the reactants are mixed together at room temperature. The reaction mixture may be heated after mixing. In one embodiment of the present invention the method includes the step of energising the reaction mixture. The reaction mixture may be energised though the application of energy such as conventional thermal energy, microwave energy, UV energy, sonic energy, gamma irradiation or a combination thereof .
Suitably the reaction mixture is heated. The reaction may be conventionally heated to a temperature of 3000C or more; suitably 3000C to 4500C. Alternatively, the reaction mixture may be heated to a temperature of 3000C to 3900C.
Alternatively the reaction mixture may be energised through the application of microwave energy. The reaction mixture may be heated to 100 to 4000C; suitably to 100 to 1500C.
Suitably the reaction takes place under an inert atmosphere.
In one embodiment of the present invention the reaction takes place in the presence of one or more solvents. A range of solvents known in the art may be used. Suitably one or more of the solvents is a hydrocarbon solvent. Suitably the solvent is an aliphatic or aromatic hydrocarbon groups which may be substituted or unsubstituted with one or more of any substituted or unsubstituted alkane, alkene, alkyne or aromatic hydrocarbon groups and contains amine, amide, nitrile, halogen, ether, alcohol, thiol, acid (such as carboxylic or sulphonic acid), ester, aldehyde, ketone, phosphine or phosphine oxide. In one embodiment the solvent may be a long chain hydrocarbon solvent such as nonadecane, docosane or tetracosane. Conventional literature routes to FePt in these hydrocarbon solvents may lead to violent and uncontrolled reactions. Other suitable solvents include ethers, such as cyclic and polyethers, ionic liquids, mineral oils, silicone oils, glycols, including polyethylene glycols and supercritical fluids such as CO2 and Xe.
In one embodiment of the present invention the reaction may take place in the presence of one or more surfactants. The surfactants suitably control the particle size of the metal or metal alloy formed. A range of known surfactants may be used. Suitably the surfactant is an aliphatic or aromatic hydrocarbon group which may be substituted or unsubstituted with one or more of any substituted or unsubstituted alkane, alkene, alkyne or aromatic hydrocarbon groups, and which may contain one or more amine, amide, nitrile, halogen, ether, alcohol, thiol, acid (such as carboxylic or sulphonic acid), ester, aldehyde, ketone, phosphine or phosphine oxide groups. Advantageously the surfactant is oleic acid, oleyl amine, trioctylphosphine or a combination thereof. The use of oleic acid as surfactant will typically promote the formation of nanoparticles having a controlled particle size. The use of oleic acid may also reduce the amount of sintering the nanoparticles exhibit on heating. The use of oleyl amine or related amines as surfactant may promote the formation of fct nanoparticles .
In one embodiment of the present invention the reaction takes place in the presence of one or more stabilisers. Any known stabiliser may be used. Suitably the stabiliser is an aliphatic or aromatic hydrocarbon group which may be substituted or unsubstituted with one or more of any substituted or unsubstituted alkane, alkene, alkyne or aromatic hydrocarbon groups, and which may contain one or more amine, amide, nitrile, halogen, ether, alcohol, thiol, acid (such as carboxylic or sulphonic acid) , ester, aldehyde, ketone, phosphine or phosphine oxide groups. Advantageously the stabiliser comprises a phosphine reagent, for instance a tertiary phosphine such as triphenyl phosphine or trioctyl phosphine. The presence of trioctylphosphine may promote the formation of nanoparticles having a particle size of 5 run or less.
In one embodiment of the present invention the reaction includes a purification step involving the separation of metal alloy AxBy from any byproducts formed. Suitably the purification step consists of dispersing and sonocating the product in a solvent, precipitating the product out, and centrifuging the product. The purification process may be repeated. The method may include the step of washing the nanoparticles with water to remove impurities such as Na2CO3.
The metal or metal alloy formed according to the method of the present invention suitably has a fee or fct structure.
In one embodiment the method includes the step of converting all or some of the metal or metal alloy from a fee to a fct phase.
Suitably all of the metal or metal alloy of the present invention is converted from a fee to a fct phase.
In one embodiment the phase conversion step involves heating preformed AxBy to a temperature of 3000C or more; suitably 4000C to 4500C; more preferably 4300C to 4500C.
In one embodiment the metal or metal alloy AxBy is converted from a fee to a fct phase in solution.
Suitably the metal or metal alloy solution comprises a surfactant.
The surfactant may be any suitable surfactant such as those listed above.
Only metal alloys having a defined metal :metal ratio can be converted from a fee phase to a fct phase. The metal alloy formed according to the method of the present invention has a uniform, controlled stoichiometry at a nanoparticulate level. In contrast to metal alloy formed according to known processes, nanoparticles of the metal alloy of the present invention do not need to coalesce to form particles having a defined stoichiometry. Nanoparticles of the metal alloy of the present invention can be converted from a fee phase to a fct phase without significant agglomeration, and the temperatures associated with the phase transition are significantly lower than for metal alloy formed according to known methods . At the reduced temperatures associated with the phase transition of the metal alloys of the present invention, surface coatings such as solvents are less likely to be burnt off. The presence of a coating reduces the likelihood of the particles agglomerating.
The phase type, particle size, chemical composition and magnetic properties of the metal alloy produced may be controlled by various parameters such as molar ratio of precursors, solvent type, molar ratio, concentration and type of solvent, surfactant and/or stabiliser added, the amount of energy transferred in the energising step, the agitation method used and/or the purification process used.
Typically the use of surfactants, such as amine surfactants, results in a metal or metal alloy having a fct phase. The use of surfactants, such as amine surfactants, may result in a metal or metal alloy having a controlled particle size. Typically the metal or metal alloy has a particle size of 2 to 10 nm; suitably 3 to 7 nm.
The use of oleic acid as surfactant typically results in particles having a relatively small particle size. Typically metal or metal alloy is formed having an average particle size of less than 3 nm; suitably less than 2 nm. The use of oleyl amine as surfactant typically results in particles having a relatively large particle size. Typically metal or metal alloy is formed having an average particle size of more than 3 nm; suitably approximately 3 to 7 nm.
For example, FePt particles having a fct structure and a particle size of from 4 to 6 nm could be obtained in tetracosane at temperatures from 350 to 3900C using various amine surfactants. The FePt particle size was increased from 1.5 to 4 nm by changing the molar ratio from 1:1:1:1 olyl amine: oleic acid: Fe: Pt to 2:0:1:1. The addition of triphenyl phosphine or trioctyl phosphine led to a reduction in particle size. 2.7 nm particles could be prepared by microwave heating in the presence of oleyl amine and oleic acid. PtRu and other binary nanoparticle alloys have been shown to be excellent catalysts for oxidation in fuel cell and other applications. Particle size, stoichiometry and atomic distribution have impact on catalytic properties .
According to a further aspect of the present invention there is provided a metal or metal alloy AxBy obtainable from the process hereinbefore described.
Preferably AxBy is FePt.
Alternatively AXBY is FePd.
Suitably AxBy has a fee phase type. Alternatively AxBy has a fct phase type.
In one embodiment the size of the particles forming AxBy is predictable and controllable.
Advantageously the stoichiometry of AxBy is predictable and uniform.
The interparticulate spacing of AxBy remains great enough to reduce or prevent agglomeration of the particles upon heating to temperatures of 3000C and above; suitably 4000C and above. The problems of agglomeration or decomposition at increased temperatures are, therefore, reduced or overcome.
According to a further aspect of the present invention there is provided a solution comprising AxBy. Suitably the solution comprises AxBy and a surfactant.
The solution may consist solely of AxBy and a surfactant .
Typically the solution is colloidal.
Suitably the solution comprises a surfactant such as any of those listed as suitable above. In particular oleyl amine, oleic acid, trioctylphosphine or a combination thereof may be used. Suitably the surfactant is oleyl amine.
Compound AxBy typically exhibits magnetic properties. The nanoparticles of AxBy tend, therefore, to be attracted to each other and problems are associated with forming a solution of AxBy having dispersed particles . Particular problems are associated with forming a solution of AxBy having substantially uniformly dispersed particles. Surprisingly a stable dispersion can be formed from fct particles of the present invention prepared directly in solution using NMe1JOH and ethanol .
According to a further aspect of the present invention there is provided the use of AXBY as a data storage apparatus; in particular for use as a magnetic data storage apparatus.
According to a further aspect of the present invention there is provided a magnetic data storage apparatus comprising AxBy. Suitably the magnetic data storage apparatus comprises AxBy having fct phase type. Suitably the magnetic data storage apparatus comprises AxBy in solid form.
According to a further aspect of the present invention there is provided the use of AxBy as a surface coater . In one embodiment the surface coater provides a magnetic coating on a substrate. The substrate is typically formed from polymer, ceramic, metal or from a semiconductor such as silicon. Suitably AxBy is in the form of a suspension.
According to a further aspect of the present invention there is provided the use of AxBy as a catalyst; suitably for use as a high surface area catalyst.
Preferably A and B are admixed uniformly and intimately for use as a catalyst.
According to a further aspect of the present invention there is provided the use of AxBy as a permanent magnet. Suitably AxBy is in the fct phase type.
According to a further aspect of the present invention there is provided the use of superparamagnetic AxBy in biomedical fields such as the use of AxBy as an NMR contrast agent, for hyperthermic treatment, targeted drug delivery or cell separation.
According to a further aspect of the present invention there is provided the use of AxBy in sensing applications, such as a gas sensor (H2) .
According to a further aspect of the present invention there is provided the use of AxBy in cell tagging or separation.
According to a further aspect of the present invention there is provided the use of AxBy as a ferrofluid.
The present invention will now be described by way of example only with reference to the accompanying figures in which;
Figure 1 shows an X-ray diffraction pattern of the FePt product (LHNO59) formed according the method of Example 3;
Figure 2 shows the relationship between magnetisation and field for fct particles formed according to the method of Example 3.
Figure 3 shows the particle size proportion of FePt product (LHN063, LHN064, LHN069, LHN091, LHN098, LHN093, LHN094) formed according to the method of Example 4? Figure 4 shows X-ray diffraction patterns of FePt product (LHN031) formed according to the method of Example 6 at varying temperatures;
Figure 5 shows an X-ray diffraction pattern of the fct FePt product (LHN079) formed according to the method of Example 9;
Figure 6 shows a TEM image of the FePt product (LHN079) formed according to the method of Example 9 after dispersion in NMe4OH/EtOH;
Figure 7 shows an X-ray diffraction pattern of the fee FePt product formed according to the method of Example 11;
Figure 8 shows an X-ray diffraction pattern of fee FePd formed according to the method of Example 11;
Figure 9 shows a HRTEM image of monodispersed fee FePt product formed according to the method of Example 11.
Example 1: FePt synthesis using oleic acid as surfactant (LHN052).
A mixture of platinum acetylacetonate (0.118 g, 0.3 mtnol) , disodium tetracarbonylferrate (0.104 g, 0.3 mmol) , oleic acid (0.2 ml, 0.6 mmol) and tetracosane (10 g) was placed in a 100 ml round bottom flask equipped with a N2 in/outlet, condenser and thermal probe. The mixture was vacuumed down and purged with N2 several times before the mixture was heated to around 6O0C causing the tetracosane to melt. The mixture was sonocated at 640C for 1 hour to form a brown mixture. The round bottom flask was placed onto a heating mantle which had previously been heated to a high temperature. The round bottom flask was heated quickly during 30 min to 3890C. The mixture was maintained at reflux between 389°C and 3820C for 1 hour to give a dark mixture. The dark mixture was maintained under N2 atmosphere and allowed to cool to around 500C before the addition of 50 ml of hexane to dissolve the tetracosane. The mixture was then sonocated at room temperature for 15 minutes followed by centrifugation to give a dark precipitate and a pale supernatant containing a significant amount of tetracosane. The dark precipitate was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleic acid (0.5 ml), precipitated out through the addition of absolute ethanol (25 ml) and finally centrifuged to give a dark precipitate. The washing process was repeated twice and a black powder was obtained after the product was left to dry.
The sample was shown by powder X-ray diffraction to contain fee FePt phase with a particle size of under 3 nm.
Example 2: FePt synthesis using a mixture of oleic acid and oleyl amine as surfactant (LHN061 and LHN076) . The method of Example 1 was repeated with slight variations in the amount of the various precursors and reaction times. A summary of reaction conditions is shown in the table below:
Figure imgf000021_0001
The dark mixture formed through the method was maintained under N2 atmosphere and allowed to cool down to around 5O0C before the addition of 50 ml of hexane to dissolve the tetracosane. The mixture was then sonocated at room temperature for 15 minutes to give a mixture of a dark black product dispersion and a precipitated shiny solid. The precipitated shiny solid was separated from the suspended phase by decanting.
The dark black suspension was then centrifuged to give a dark precipitate from which a pale supernatant containing a significant amount of tetracosane was decanted. The black product was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleyl amine (0.5 ml), precipitated out by adding ethanol absolute (25 ml) and finally centrifuged to give a dark precipitate. The washing process was twice repeated and a black powder was obtained after the product was left to dry at room temperature overnight . X-ray diffraction patterns of the dark black solid were obtained.
The dark shiny solid was also washed several times in hexane until the organic phase was clear and the solid was left to dry at room temperature overnight. X-ray diffraction patterns of the shiny black solid were obtained.
The dark black powder and the dark shiny solid obtained were shown through powder diffractometer patterns, to have similar fee FePt phase types. The X-ray diffraction patterns of the two samples showed impurity peaks which were identified as peaks of Na2CO3. Na2Cθ3 could be removed by washing with water. The particle size of both FePt product fractions were under 3 run.
Example 3: FePt synthesis using oleyl amine or related amines as surfactant.
Five reactions using oleyl amine as surfactant were performed in tetracosane at high temperature for different reaction times (LHN059, LHN062, LHN067, LHN071 and LHN089). The experimental method of Example 1 was repeated but the amount of the various precursors and reaction times were slightly altered as summarised in the table below:
Figure imgf000023_0001
Tabl e 2 : Experimental condi tion of reactions
The dark mixture was maintained under N2 atmosphere and allowed to cool to around 5O0C. The reaction mixture tended to separate into 2 parts: a clear liquid phase formed mainly from tetracosane which crystallizes upon further cooling and a dark precipitate gathered on the vessel wall. Hexane (50 ml) was added to the reaction mixture followed by sonocation at room temperature for 15 minutes to disperse the dark solid into the organic phase. After centrifugation, the pale supernatant containing a significant amount of tetracosane was decanted from the dark solid. The black solid was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleyl amine (0.5 ml), precipitated out through the addition of ethanol (25 ml) and finally centrifuged to give a dark precipitate. The washing process was repeated twice and a black powder was obtained after the product was left to dry at room temperature overnight. All 5 samples showed similar results of which the XRD pattern of LHN059 is representatively shown (see Figure 1) .
All samples contained a similar mixture of partially ordered fct FePt particles .
The appearance of (001) and (110) peaks at 22.8° and 32.7° (2-theta) respectively showed the existence of FePt particles having an fct phase type. Particle size, as determined by X-ray diffraction, varied from 6 to 8.5 run. Particle size may be controlled by the different interactions between the particle surface and head group of the surfactant.
Figure 2 shows magnetic hysteresis loops of as synthesised FePt particles prepared in tetracosane at 289°C recorded at 10 and 290 K. Coercivity of approximately 1300 Oe at 290 K and 3100 Oe at 1OK was observed. In situ powder diffraction experiments were performed as a sample of LHNO59 was heated from 300 to 903 K under a H2ZAr mixture. An increase in the degree of fct ordering was clear from around 650 K. At higher temperatures the order parameter rises significantly, rising to more than 0.8, as determined by Rietveld refinement of x-ray diffraction data. On heating above 750 K the particle size as determined by x-ray diffraction also rises sharply. 1 Rutherford Back Scattering (RBS) studies showed that 2 the chemical FePt ratio was 1:1. TEM indicates a 3 relatively narrow distribution of FePt particles 4 with dark clumps which form due to the ferromagnetic 5 properties of fct FePt particles. Particle size 6 calculation based on 153 random particles has shown 7 that the sample has a relatively narrow particle size distribution. The average particle size was
9 around 4.5 ran. 0 1 Example 4: FePt synthesis using various amines 2 3 The method of Example 1 was repeated with varying 4 amounts of precursors, and different reaction times 5 and washing processes . K summary of the reaction 6 conditions is shown in the table below: 7
Figure imgf000025_0001
9 Table 3 : Experimental condition of reactions 0 Synthesis was performed following the method of Example one. After heating the product was maintained under an inert N2 atmosphere and allowed to cool to around 5O0C. The product tended to separate into 2 parts : a clear liquid phase formed mainly from tetracosane which tended to crystallize upon further cooling and a dark precipitate gathered on the vessel wall. 50 - 100 ml hexane was added to the product followed by sonocation at room temperature for 15 minutes to disperse the dark solid into the organic phase.
After centrifugation, the pale supernatant was decanted from the dark solid. The black product was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleyl amine (0.5 ml), precipitated out by adding absolute ethanol (25 ml) and finally centrifuged to give a dark precipitate. Oleyl amine was added as some amines used in the reaction are solid at room temperature and are not highly soluble in the hexane and ethanol used during the washing process. The dark precipitate was then dispersed and sonocated at room temperature in a mixture of absolute ethanol (40 ml) and H2O (20 ml) for 15 min before centrifugation to recover the dark precipitate. The washing process was twice repeated using a mixture of hexane, ethanol and oleyl amine. The product was left to dry at room temperature overnight to give a black powder.
All samples formed showed similar properties. All samples contained partially ordered fct FePt particles and showed no crystalline impurities. The particle size for all samples determined by x- ray diffraction varied from 4 to 8 inn, except sample LHN098 which had a particle size of around 2.5 ran (see Figure 3) .
Example 5: FePt synthesis using phosphine reagents as stabilizers
Several phosphines (triphenyl phosphine, 3Ar-P and trioctyl phosphine, 3C8-P) were used in the synthesis of FePt particles in this Example. The method of Example 1 was repeated. A summary of the reaction conditions is shown in the table below:
Figure imgf000027_0001
Table 4: Experimental condition of reactions LHN116 and LHNl17 Samples LHN116 and LHN117 have XRD patterns including (001) and (110) peaks (indicative of fct ordering) at approximately 24° and 32° (2-theta) respectively. The particle size of samples formed with phosphine was significantly reduced. This observation can be explained by trioctyphosphine acting as a stabilizer to prevent particles from growing during reaction.
Example 6: FePt synthesis using a nonadecane solvent and oleic acid surfactant.
A mixture of platinum acetylacetonate (0.118 g, 0.3 mmol) , disodium tetracarbonylferrate (0.104 g, 0.3 mmol) and oleic acid (0.2 ml, 0.6 mmol) was placed in a 100 ml round bottom flask equipped with a N2 in/outlet, condenser and thermal probe. The mixture was vacuumed down and purged with N2 several times before nonadecane (20 ml) was injected. The mixture was sonocated at 640C for 1 hour to form a brown mixture. The round bottom flask was placed into a heating mantle which had previously been heated to high temperature. The round bottom flask was heated quickly to reflux at 3350C for different time periods (1, 3 or 5 hours) to give a dark mixture.
The dark mixture was maintained under N2 atmosphere and allowed to cool to around 500C before the addition of 30 - 40 ml of hexane (to dissolve nonadecane) and absolute ethanol (-30 ml) to precipitate particles. The volume of solvents was adjusted to avoid crystallization of nonadecane in the reaction mixture. The mixture was then sonocated at room temperature for 15 minutes followed by centrifugation to give a dark precipitate and a pale supernatant. The pale supernatant contained a significant amount of nonadecane which typically crystallized at room temperature. The black product was next dispersed and sonocated (-15 min) in a mixture of hexane (20 ml) and oleic acid (0.5 ml), precipitated out by adding absolute ethanol (25 ml) and finally centrifuged to give a dark precipitate.
The washing process was repeated and a black powder was obtained after the product was left to dry at room temperature overnight.
All four samples were shown by x-ray diffraction to have only fee FePt phase with a particle size of under 2 nm.
Figure 4 shows x-ray diffraction patterns obtained from variable temperature powder diffraction experiments performed on FePt product (LHN031) prepared by this route. Evidence for fct ordering in sample LHN031 can be observed from 703 K. By 903 K the order parameter as determined by Rietveld refinement of the x-ray data rises to 0.73. This ordering occurs without significant particle growth with the particle size (as determined by x-ray diffraction) remaining under 4 nm. It was also observed from study of the x-ray diffraction patterns of FePt product (LHN072, LHN073 and LHN104) prepared by this route that fct ordering can be achieved whilst maintaining small particles using the method of this invention.
Example 7 : FePt particles synthesized in oleyl amine and nonadecane (LHNlO4)
The method of Example 6 was repeated, except oleic acid was replaced by oleyl amine . A mixture of platinum acetylacetonate (0.118 g, 0.3 mmol) , disodium tetracarbonyl iron (0.104 g, 0.3 mmol) and oleic acid (0.2 ml, 0.6 mmol) was placed in a 100 ml round bottom flask equipped with an Ar in/outlet, condenser and thermal probe. The mixture was vacuumed down and purged with Ar several times before injection of nonadecane (10 ml) . The mixture was sonocated at 64°C for 1 hour to form a brown mixture. The round bottom flask was placed on a heating mantle which had previously been pre-heated to a high temperature. The round bottom flask was heated quickly to reflux at 3350C. The reaction mixture was heated at reflux for 1 hour to give a dark mixture.
The purification process differed slightly to that used for Example 6. The dark mixture was allowed to cool to around 500C before addition of 30 - 40 ml of hexane to dissolve the nonadecane. In contrast to Example 6 ethanol was not added at this stage. The mixture was sonocated for 15 minutes at room temperature. The sample was then centrifuged to give a dark precipitate. A pale supernatant contained the major part of the nonadecane which crystallized at room temperature. The black product was next dispersed and sonocated (~ 15 iαin) in a mixture of hexane (20 ml) and oleic acid (0.5 ml) . The product was precipitated out through the addition of absolute ethanol (25 ml) and was then centrifuged to a give dark precipitate. The dark precipitate was next washed and sonocated in a mixture of ethanol (40 ml) and water (20 ml) . After centrifugation the dark precipitate was twice washed in a mixture of hexane, oleyl amine and ethanol and a black powder was obtained after the product was left to dry overnight at room temperature.
X-ray diffraction showed LHN104 contained partially ordered fct FePt particles. The particle size of the FePt particles was above 5 run.
Example 8: FePt particles synthesized in nonadecane with oleyl amine, C18-amine/ trioctylphosphine, (LHN119)
The method of Example 7 was repeated using the reaction conditions summarised below. The purification process was also similar to that used in Example 7.
Na2Fe(CO)4 : 0.3 mmol Pt(acac)2 : 0.3 mmol Oleyl amine : 0.6 mmol Ci8_amine : 0 . 6 mmol Trioctylphosphine : 0 . 3 mmol Nonadecane : 15 ml Sonocation : 64 0C/ lhr Heating : 330 0C/ 2 hrs
The XRD pattern of the sample formed (LHN119) showed the presence of FePt particles. The particle size of sample LHN 119 was approximately half that of the sample formed according to the method of Example 7 (LHN104) . This decrease in particle size may be explained by the presence of trioctyphosphine which prevents particle growth during the reaction.
In situ high temperature diffraction experiments revealed clear evidence of ordering to the fct phase from temperatures as low as 653 K. Significant particle growth was only observed at higher temperatures.
Example 9: Producing ordered fct FePt particles by annealing fee FePt particle in tetracosane at high temperature
Fee FePt particles were synthesised using the method of Example 1 but with solvent, surfactants and reaction times as detailed in Table 5. The particles were characterised by x-ray powder diffraction.
Figure imgf000033_0001
Table 5: Experimental condition and structural properties of fee FePt particle's synthesis
The three fee FePt samples described above were subsequently annealed in solution. A mixture of fee FePt sample (50-150 mg) , oleyl amine (0.100 ml) and tetracosane (10 g) was placed in a 100 ml round bottom flask equipped with a N2 in/outlet, condenser and thermal probe . The mixture was vacuumed down and purged with N2 several times before melting tetracosane at around 6O0C. The mixture was sonocated at 640C for 1 hour to form a dark black dispersion. The round bottom flask was placed in a heating mantle which had previously been heated to a high temperature. The round bottom flask was quickly heated to reflux between 370 and 39O0C for 18 hours to give a dark mixture. Shorter reaction times would achieve similar results.
The purification was similar to the process described in Example 3 (sample LHN059) .
LHN020, LHNO78 and LHNO77 formed LHN068, LHNO79 and LHN081 respectively. All 3 FePt samples formed according to the method of Example 9 exhibited similar results. The XRD pattern of sample LHN079 is representative of the samples (see Figure 5) .
All three samples contained partially ordered fct FePt particles . The effective average cell parameter (as measured by fitting a simple fee model to subcell peaks) shows a small reduction on transforming from fee to fct phase.
The particle sizes of the samples could be controlled. LHN068 and LHN079 were significantly larger than sample LHN081.
In situ high temperature x-ray diffraction studies on LHN079 confirmed the partial fct order at room temperature. On heating under an Ar/H2 atmosphere an increase in particle ordering was observed from around 630 K. At high temperatures significant particle growth was observed.
Particles of the fct phase could be readily dispersed in NMe4OHVEtOH. Figure 6 shows the TEM of dispersed particles after redeposition on a TEM grid.
X-ray microanalysis and RBS data were consistent with a 1:1 particle stoichiometry. Example 10: Preparation of FePd
Palladium acetylacetonate (0.091 g, 0.3 mmol) and disodium tetracarbonylferrate (0.104 g, 0.3 mmol) were placed in a 100 mL two-neck flask connected to argon, a condenser and a thermometer. The flask was vacuumed down and purged with argon three times before tetracosane solvent (~20 mL) and oleylamine surfactant (1:1 molar ratio) were added. The mixture was then sonocated for 15 min at room temperature and heated to 371°C for 60 minutes.
The reaction mixture was allowed to cool down to 600C before the addition of -50 mL hexane. The solution was then sonicated and centrifuged. Afterwards the product was washed four times: first with -20 mL hexane and 10 drops of surfactant, then with -40 mL ethanol and ~7 mL water. For each of the last two washing steps -20 mL hexane and 10 drops of surfactant were used. Every time the mixture was sonocated for 15 min at room temperature and -30 mL ethanol were added to obtain the particles (HB005) .
Example 11: Use of Microwave Heating to produce FePt/FePd
In a typical reaction a mixture of Pt/Pd acetylacetonate (0.3 mmol), disodium tetracarbonylferrate (0.3 mmol) with appropriate amounts of surfactants and solvents (see table) was placed in a 100 ml thick walled glass vessel connected to a condenser and Ar input. The mixture was sonocated at 60 0C for 1 hr before transferring into a CEM300W Discover Focus Synthesis microwave apparatus with a 2.45 GHz operating frequency. Reaction was typically carried out using control parameters of 300W max power, 250 0C max temperature and 250 psi max pressure. After reaction the dark product mixture was allowed to cool to room temperature before adding 100 ml of absolute ethanol to precipitate dark particles . The product was separated by centrifugation then dispersed in hexane (20 ml) in the presence of appropriate surfactants and precipitated by adding ethanol (40 ml) . After centrifugation, the material was washed one more time in a similar solvent mixture, dried in air at room temperature and stored under N2-
Figure imgf000036_0001
An x-ray diffraction pattern of the fee FePt product, the fee FePd and monodispersed fee FePt product formed according to the method of Example 11 is shown in Figures 7, 8 and 9 respectively.
Example 12: Producing fct Particles by Microwave Heating
A mixture of fee FePt nanoparticles (0.020 g) synthesized by conventional heating method and ball milled NaCl (0.400 g) were placed in 10 ml microwave vessel and oleyl amine (0.200 ml) added. The reaction vessel was purged with N2, sealed and transferred into a microwave reactor. Reaction was typically carried out using control parameters of 300W max power, 250 0C max temperature and 250 psi max pressure over a 15-20 min period. Rapid increase of pressure often took place and close monitoring was required to prevent excessive pressure build up. After reaction, the dark product mixture was allowed to cool to room temperature, washed with a mixture of water and absolute ethanol, and centrifuged. The dark black material was dried in air at room temperature and stored under N2.

Claims

Claims
1. A method of forming a metal or metal alloy that can be expressed according to reaction scheme 1 :
xAn+ + yBn~ > AxBy
wherein : A represents a first metal; B represents a second metal; n is greater than zero; x is an integer of at least one,- and y is an integer of at least one.
2. The method as claimed in Claim 1 wherein A represents Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, Au, Zn, Ga, Ge, As, Cd, In, Sn, Sb, Hg, Tl, Pb or Bi.
3. The method as claimed in either one of Claims 1 and 2 wherein B represents V, Cr, Mn, Fe, Co, Ni, Mo, Ru, Rh, W, Re or Os.
4. The method of any preceding claim wherein n is 1, 2 or 3.
5. The method of any preceding claim wherein x is 1, 2 or 3 and y is 1, 2 or 3.
6. The method as claimed in any preceding claim wherein the reactants are energised through the application of thermal energy, microwave energy, UV energy, sonic energy, gamma irradiation or a combination thereof.
7. The method as claimed in any preceding claim wherein the reaction mixture is conventionally heated to a temperature of 300 to 39O0C.
8. The method as claimed in any one of Claims 1 to 6 comprising the step of heating the reaction mixture to 100 to 4000C through the application of microwave energy.
9. The method as claimed in any preceding claim wherein the reactants are mixed together in the presence of a surfactant, the surfactant comprising oleic acid, oleyl amine, trioctylphosphine or a combination thereof.
10. The method as claimed in any preceding claim wherein the reactants are mixed together in the presence of a stabiliser, the stabiliser comprising a phosphine reagent.
11. The method as claimed in any preceding claim wherein the method proceeds in solution to form metal or metal alloy AχBy in fct phase directly.
12. The method as claimed in any one of Claims 1 to 10 comprising the step of heating the metal or metal alloy formed to convert AxBy from a face centred cubic phase (fee) to a face centred tetragonal (fct) phase.
13. The method of Claim 12 wherein the metal or metal alloy is heated to 300 to 4500C to effect conversion of AxBy to a fct phase.
14. The method as claimed in either one of Claims 12 and 13 wherein the metal or metal alloy AxBy is converted in solution from a face centred cubic phase (fee) to a face centred tetragonal (fct) phase.
15. The method as claimed in Claim 14 wherein the metal or metal alloy AxBy solution comprises a surfactant.
16. A metal or metal alloy obtainable according to the method of any one of Claims 1 to 15.
17. The metal or metal alloy as claimed in Claim 16 wherein A represents Fe and B represents Pt or Pd.
18. The metal or metal alloy as claimed in either one of Claims 16 and 17 having a fee or fct phase.
19. A metal or metal alloy as claimed in any one of Claims 16 to 18 having a predictable, uniform stoichiometry at the nanoscale.
20. The metal or metal alloy as claimed in any one of Claims 16 to 19 having an average particle size of 2 to 10 run.
21. A colloidal solution comprising the metal or metal alloy as claimed in any one of Claims 16 to 20 and a surfactant .
22. The solution of Claim 21 wherein the surfactant is oleyl amine.
23. A dispersion comprising the metal or metal alloy as claimed in any one of Claims 16 to 20 in fct phase, NMe4OH and ethanol.
24. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 as a data storage apparatus .
25. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 as a catalyst.
26. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 as a surface coater.
27. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 as a permanent magnet.
28. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 as an WMR contrast agent.
29. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 in sensing applications.
30. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 in cell tagging or separation.
31. The use of the metal or metal alloy as claimed in any one of Claims 16 to 20 as a ferrofluid.
PCT/GB2006/000633 2005-02-23 2006-02-23 Process of forming a nanocrystalline metal alloy WO2006090151A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0503694.2A GB0503694D0 (en) 2005-02-23 2005-02-23 Process
GB0503694.2 2005-02-23

Publications (1)

Publication Number Publication Date
WO2006090151A1 true WO2006090151A1 (en) 2006-08-31

Family

ID=34401160

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2006/000633 WO2006090151A1 (en) 2005-02-23 2006-02-23 Process of forming a nanocrystalline metal alloy

Country Status (2)

Country Link
GB (1) GB0503694D0 (en)
WO (1) WO2006090151A1 (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008065537A2 (en) * 2006-11-28 2008-06-05 Toyota Jidosha Kabushiki Kaisha PRODUCTION METHOD FOR FePT-Fe-NANOCOMPOSITE METAL MAGNETIC
CN103785858A (en) * 2014-03-04 2014-05-14 北京化工大学 Method for preparing amorphous nanometer rhodium palladium alloy and catalytic application thereof
CN105170995A (en) * 2015-09-21 2015-12-23 陕西师范大学 Method for wrapping gold-silver alloy nanometer particles through silicon dioxide
CN105618786A (en) * 2016-01-22 2016-06-01 青岛大学 Preparation method for cage-shaped nanometer gold-silver alloy suitable for being used as organic dye catalyst
CN110560704A (en) * 2019-10-11 2019-12-13 东北大学 Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements
WO2021012954A1 (en) * 2019-07-23 2021-01-28 山东大学 Method for preparing silicon or germanium nanomaterials by decomposing ternary alloy, silicon or germanium nanomaterials and application

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030121364A1 (en) * 2002-01-02 2003-07-03 International Business Machines Corporation Metal salt reduction to form alloy nanoparticles

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030121364A1 (en) * 2002-01-02 2003-07-03 International Business Machines Corporation Metal salt reduction to form alloy nanoparticles

Non-Patent Citations (7)

* Cited by examiner, † Cited by third party
Title
CHEN M. & NIKLES D.E.: "Synthesis, self-assembly, and magnetic properties of FexCoyPt100-x-y nanoparticles", NANO LETTERS, ACS, WASHINGTON, DC,, vol. 2, no. 3, March 2002 (2002-03-01), U.S., pages 211 - 214, XP002354488 *
CHINNASAMY C. ET AL.: "Polyol-process-derived CoPt nanoparticles: Structural and magnetic properties", JOURNAL OF APPLIED PHYSICS, AMERICAN INSTITUTE OF PHYSICS. NEW YORK, vol. 93, no. 10, 15 May 2003 (2003-05-15), U.S., pages 7583 - 7585, XP012058224 *
JEYADEVAN B. ET AL.: "Direct synthesis of fct-FePt nanoparticles by chemical route", JAPANESE JOURNAL OF APPLIED PHYSICS, JAPAN SOCIETY OF APPLIED PHYSICS, TOKYO, vol. 42, no. 4a, 1 April 2003 (2003-04-01), JAPAN, pages L350 - L352, XP002355666 *
JEYADEVAN B. ET AL.: "Towards direct synthesis of fct-FePt nanoparticles by chemical route", JOURNAL OF APPLIED PHYSICS, AMERICAN INSTITUTE OF PHYSICS. NEW YORK,, vol. 93, no. 10, 15 May 2003 (2003-05-15), U.S., pages 7574 - 7576, XP012058221 *
JONG-II PARK, JINWOO CHEON: "Synthesis of "Solid Solution" and "Core-Shell" Type Cobalt-Platinum Magnetic Nanoparticles via Transmetalation Reactions", JOURNAL OF AMERICAN CHEMICAL SOCIETY, 25 May 2001 (2001-05-25), US, pages 5743 - 5746, XP002380647 *
SHOUHENG S. ET AL.: "COMPOSITIONALLY CONTROLLED FEPT NANOPARTICLE MATERIALS", IEEE TRANSACTIONS ON MAGNETICS, IEEE SERVICE CENTER, NEW YORK, vol. 37, no. 4, July 2001 (2001-07-01), NY/U.S., pages 1239 - 1243, XP001110475 *
SHOUHENG S. ET AL.: "MONODISPERSE FEPT NONOPARTICLES AND FERROMAGNETIC FEPT NANOCRYSTAL SUPERLATTICES", SCIENCE, AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE, vol. 287, no. 5460, 17 March 2000 (2000-03-17), U.S., pages 1989 - 1991, XP001089844 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008065537A2 (en) * 2006-11-28 2008-06-05 Toyota Jidosha Kabushiki Kaisha PRODUCTION METHOD FOR FePT-Fe-NANOCOMPOSITE METAL MAGNETIC
WO2008065537A3 (en) * 2006-11-28 2008-07-24 Toyota Motor Co Ltd PRODUCTION METHOD FOR FePT-Fe-NANOCOMPOSITE METAL MAGNETIC
CN103785858A (en) * 2014-03-04 2014-05-14 北京化工大学 Method for preparing amorphous nanometer rhodium palladium alloy and catalytic application thereof
CN103785858B (en) * 2014-03-04 2016-01-06 北京化工大学 A kind of preparation method of amorphous nano rothenio-palladium and catalytic applications thereof
CN105170995A (en) * 2015-09-21 2015-12-23 陕西师范大学 Method for wrapping gold-silver alloy nanometer particles through silicon dioxide
CN105618786A (en) * 2016-01-22 2016-06-01 青岛大学 Preparation method for cage-shaped nanometer gold-silver alloy suitable for being used as organic dye catalyst
WO2021012954A1 (en) * 2019-07-23 2021-01-28 山东大学 Method for preparing silicon or germanium nanomaterials by decomposing ternary alloy, silicon or germanium nanomaterials and application
CN110560704A (en) * 2019-10-11 2019-12-13 东北大学 Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements
CN110560704B (en) * 2019-10-11 2021-10-22 东北大学 Method for inductively synthesizing fct-FePt nano particles by doping low-melting-point elements

Also Published As

Publication number Publication date
GB0503694D0 (en) 2005-03-30

Similar Documents

Publication Publication Date Title
Fiévet et al. The polyol process: a unique method for easy access to metal nanoparticles with tailored sizes, shapes and compositions
US7029514B1 (en) Core-shell magnetic nanoparticles and nanocomposite materials formed therefrom
JP3989868B2 (en) Synthesis of magnetite nanoparticles and method for forming iron-based nanomaterials
JP3258295B2 (en) Method for producing transition metal nanoparticles
US7811545B2 (en) Process for large-scale production of monodisperse nanoparticles
US7527875B2 (en) Group of metal magnetic nanoparticles and method for producing the same
US6676729B2 (en) Metal salt reduction to form alloy nanoparticles
US7547347B2 (en) Synthesis of nano-materials in ionic liquids
Fereshteh et al. Effect of ligand on particle size and morphology of nanostructures synthesized by thermal decomposition of coordination compounds
JP2011052326A (en) Ultrafine composite metal particles and method for manufacturing the same
JPH10183207A (en) Ultrafine grain and production thereof
WO2006090151A1 (en) Process of forming a nanocrystalline metal alloy
JP2010512463A (en) Method for producing iron or iron oxide nanopowder particles
JP2003297617A (en) Method of manufacturing nano-sized ferromagnetic alloy particles
JP2012197473A (en) Method for synthesizing metal or alloy nanoparticle by supercritical hydrothermal reaction under reductive atmosphere
JP2011184725A (en) Method for synthesizing cobalt nanoparticle by hydrothermal reduction process
JP2016056431A (en) Method for producing palladium alloy nanoparticle
JP4528959B2 (en) Magnetic material and method for producing the same
JP6320533B2 (en) Method for producing uniform metal oxide nanoparticles with high reproducibility
JP4452847B2 (en) Manufacturing method of metal magnetic powder
KR100800586B1 (en) A process of manufacturing for Cu nanoparticles using pre-dispersed Na pastes
JP4861802B2 (en) Method for producing Fe / Pd composite nanoparticles
KR101174178B1 (en) Method for preparing nanoparticle of metal or metal oxide
JP2005330526A (en) Method for producing nanoparticle group
Rao et al. Synthesis of nanocrystals

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 06709865

Country of ref document: EP

Kind code of ref document: A1

WWW Wipo information: withdrawn in national office

Ref document number: 6709865

Country of ref document: EP