ES2300208A1 - Nanostructured oxide ceramic/n-w material, method for preparing and uses thereof - Google Patents

Abstract

The subject matter of the present invention is an nanostructured ceramic oxide/n-w composite material of nanometric size, 1 to 20 nm, with a tungsten content between 0.05 vol.% and 30 vol.%. Also described is the method for preparing the ceramic oxide/n-W material of the invention. This novel material can be useful in the manufacture of electronic components, catalysers, structural technical ceramics and pigments, dyes and coatings on metal substrates.

Description

Nanostructured Oxide Material ceramic / n-W, obtaining procedure and its Applications.

Technical sector

New materials as electronic components,  catalysts, structural technical ceramics, pigments and dyes, coatings on metal substrates, etc.

State of the art

Tungsten (W) is a metal with properties Intrinsic exceptional: high melting point (3422ºC), great hardness (3.43 GPa), the lowest thermal expansion coefficient of all metals (4.5 · 10-6 K-1) and one of the lower vapor pressures within them:

one

The alumina (8.5 10 - 6 K - 1) and the spinel (7.3 10 - 6 K - 1) are chemically very oxides stable, resistant to corrosion and have coefficients of thermal expansion very similar to tungsten (5.4 \ cdot 10 -6 K-1) which minimizes possible problems arising from the formation of residual stresses at the interface.

On the other hand, it is well known that metallic materials, in the nanometric range, have less ductility than the same micrometer particle size materials [Siegel RW, Nanostruct Mater ; 3 (1993) 1-18]. In the particular case of W, which has a high value of G (shear modulus), the expected Vickers hardness - taking into account the linear relationship between G and H_ {v} - can be increased in tungsten nanoparticles to values of the order of 30 GPa. This, together with the high values of H_ {v} that the alumina or spinel matrices possess, can result in ceramic / nanometal composite materials of much greater hardness than the corresponding microparticulate compounds [C. Pecharromán, F. Esteban-Betegón, JF Bartolomé, G. Richter, and JS Moya, Nanoletters , 4 [4]; (2004) 747-51].

In the field of catalysis, multiple metal and metal oxide systems supported on ceramic oxides have been studied for various applications since there are many catalytically active metals (V, Nb, Ta, Re, Rh, Rb, Co, Fe, Mn, Pt, Mo, etc.) with sizes between some nanometers and approximately 0.5 microns [Wong Michael S; Wachs Israel E; Knowles William V. Patent WO2005 / 002714 of 01/13/2005; J.-W. Yoon, T. Sasaki, N. Koshizaki, Thin Solid Films 483 (2005) 276-282; T. Sanders, M. Kirchhoff, U. Specht, G. Veser, AIChE Annual Meeting , Conference Proceedings (2005) 10004; X.-H. Yun, M.-X. Chen, J.-W. Shi, W.-F. Shangguan, Shanghai Jiatong Daxue Xuebao / Journal of Shanghai Jiatong University , 39 [11] (2005) 1886-1890; L. Bultel, P. Vernoux, F. Gaillard, C. Roux, E. Siebert, Solid State Ionics , 176 (7-8) (2005) 793-801; Y. Guo, G. Lu, X. Mo, Y. Wang, Chemistry Letters 33 [12] (2004) 1628-1629; G. Li, W. Li, M. Zhang, K. Tao, Catalysis Today 93-95 (2004) 595-601; H.-R. Chen, J.-L. Shi, L. Li, M.-L. Rouen, D.-S. Yan, Journal Of Chemical Engineering of Japan 36 [10] (2003) 1212-1215; XL Pan, N. Stroh, H. Brunner, GX Xiong, SS Sheng, Separation and Purification Technology , 32 [1-3] (2003) 265-270].

The variety of systems is so great that, today in day, catalysts of this type are found in processes so various as chemical industries, environmental protection (such as for example the catalytic converters of cars), in the reduction of NO_ {x} in energy plants, in refineries of oil, drug synthesis, petrochemical processes, etc.

On the other hand, there are abundant bibliographic references in the literature related to the processing of ceramic materials containing metal nanoparticles, such as Al 2 O 3 / Ni, Al 2 O 3 / Mo, Al 2 O_ {3} / Cr, Al_ {2} O_ {3} / Cu, etc. Most of these composite materials have been obtained from mixtures of powders (oxide and metal) that are homogenized by the classic wet routes [M. Nawa, T. Sekino, K. Niihara, Journal of Materials Science , 29 [12] (1994) 3185-3192], or from oxide mixtures with metal precursors (eg nitrates [T. Sekino, S. Etoh, Y.-H. Choa, K. Niihara, Materials Research Society Symposium-Proceedings , 501 (1998) 289-294 and ST Oh, JS Lee, K. Niihara, Scripta Mater . 44 (2001) 2117-2120] or acetylacetonate [ Y. Ji, JA Yeomans, Journal of the European Ceramic Society 22 (2002) 1927-1936] Other groups have obtained nanostructured alumina / metal powders using physical techniques such as laser abrasion [J. Naser, H. Ferkel, NanoStructured Materials , 12 (1999) 451-451], or by the sol-gel technique [P. Bhattacharya, K. Chattopadhyay, NanoStructured Materials , 12 (1999) 1077-1080].

In the case of alumina / nW powders, the work of Sekino et al [T. Sekino, K. Niihara, NanoStructured Materials , 6 (1995) 663-666 and T. Sekino, K. Niihara, NanoStructured Materials , 6 (1995) 663-666]. The authors obtain dense compounds of said material from homogeneous mixtures of alumina powders and tungsten oxide. The processing followed by these authors consists in completely dissolving the WO3 powder in an ammoniacal solution, to which the alumina powder and distilled water are subsequently added. The mixture is homogenized in a ball mill, then dried under vacuum and calcined at 500 ° C in air or Ar for 3 hours. The resulting powder is re-ground in ethanol for 24 hours and subsequently, reduced under H2 atmosphere. The authors do not mention the sizes or morphology of the alumina powder / nW obtained.

On the other hand, Yan et. to [H. Yan, BS Xu, Journal of Inorganic Materials 18 (5) 2003 1127-1130] report in the literature the preparation of nanostructured alumina powder / W by heterogeneous precipitation. In this specific case, it is a powder metallurgical processing. The authors start from Al (NO3) 3 • 9H2O and (NH4) 2003 as raw materials, subsequently add nanometric W powder and homogenize it by means of a simple mechanical mixture. They explain that they obtain the nanostructured powder by vacuum calcining the dry Al (OH) 3 / W gel at 1000 ° C for 1 h.

In the case of nanostructured powders of MgAl 2 O 4 / W no references found in the literature.

Description of the invention brief description

An object of the present invention constitutes it a composite nanostructured material, hereinafter oxide material / n-W ceramic of the invention, consisting of a nanostructured ceramic oxide / n-W material with a nanometric size of metal particle between 1 and 100 nm, preferably between 1 and 20 nm, which are strongly adhered to the oxidic substrate. This material nanostructured ceramic oxide / nW of the invention may present a tungsten content between 0.05% and 30% by volume, for example, 1%.

Another object of the invention is the procedure for obtaining the oxide material ceramic / n-W of the invention, hereinafter method of obtaining the invention, which comprises the following stages:

a) the oxidic powder is suspended in absolute ethanol, with a concentration in solids generally less than 85%, putting the whole set under agitation by any magnetic or mechanical device that favors dispersion,

b) in parallel, a solution of tungsten chloride in absolute ethanol (purity> 99%) with the concentration required to obtain the nanostructured powder with the desired metal concentration, the solution being heated by below 70 ° C,

c) once all tungsten chloride has been transformed into tungsten ethoxide W, (colorless solution) in the step b), is added in a controlled manner to the powder suspension a) oxidic which is kept under continuous agitation to favor the homogeneous mixing of both liquids,

d) the remaining solvent is removed by evaporation at a temperature, generally, less than 70 ° C and always under continuous agitation, being able to heat it on stove to 60 ° C for 24 hours until a dry powder is obtained,

e) subsequently, the dry powder of d), is sieve using a standard mesh, preferably below 63 microns, and calcined at temperatures between 500 ° C and 700 ° C, preferably at 600 ° C, for a period of time enough to eliminate organic components and favor Crystallization of tungsten oxide on the surface of the oxidic particles, preferably, for one hour, and

f) reduce tungsten oxide to tungsten metallic by a heat treatment between 750ºC and 1100ºC, preferably at 900 ° C, under hydrogen reducing atmosphere of the e) nanostructured powder between one hour and a half and two hours and half, preferably two hours, which produces the crystallization of metal nanoparticles on the surface of the oxidic particles.

Finally, another object of the present invention it is the use of the oxide material / n-W ceramic of the invention in the process, to illustrative title and without limiting the scope of invention, of products belonging to the following group: components electronics, catalysts, structural technical ceramics, pigments and dyes and coatings on substrates metallic

Detailed description

The invention faces the problem of provide new nanostructured materials intended for Products such as electronic components, catalysts, ceramics structural technique, pigments and dyes, coatings on metal substrates

The invention is based on the fact that the inventors have observed that it is possible to obtain a nanostructured powder of alumina / W and spinel / W of high purity, with a size of metal particles less than 100 nm, even less than 20 nm, and that are strongly adhered to the oxidic substrate, through a chemical procedure that favors the reaction of replacement between metal alkoxide and the OH groups that cover the surface of the oxidic particles (alumina or spinel) where M-OH schematically represents the surface of the oxidic particles with the presence of OH groups (alumina or spinel) In this way, a coating of the oxidic particles with the corresponding molecules organ-metal [W (OCH_2 -CH3) x] (see Figures 1 to the 3). On the other hand, the cost of this procurement procedure it is low due to the use of chloride during the process of synthesis. In summary, the procedure for obtaining the material ceramic oxide / n-W of the invention is based on two types of chemical reactions, namely:

i)

The that occurs in a first stage among tungsten chloride and the solvent medium (absolute ethanol), and

ii)

The reaction that occurs between the latter solution and the surface of the oxidic particles (alumina or spinel).

Therefore, an object of the present invention is  constitutes a composite nanostructured material, hereinafter ceramic oxide / n-W material of the invention, constituted by a nanostructured oxide material ceramic / n-W with a nano particle size metal between 1 and 100 nm, preferably between 1 and 20 nm, which are strongly adhered to the substrate oxidic This nanostructured ceramic oxide / nW material of the invention may have a tungsten content between 0.05% and 30% by volume, for example, 1%.

A particular object of the invention is constitutes the ceramic oxide / n-W material of the invention where the oxide, by way of illustration and without limiting the scope of the invention, belongs to the following group:

a) alumina, in any form crystallographic, namely?,??,?,?, \ kappa, \ rho, \ eta, \ theta and \ chi, with a grain size between 20 and 1000 nm [K. Wefers and C. Misra, Alcoa Laboratories, Oxides and Hydroxides of Aluminum (1987)],

b) alumina with any oxide that may enter in solid solution in your network - such as, for example, TiO2, Fe 2 O 3, Y 2 O 3, etc. - and, in particular, the chromite (Cr 2 O 3) whose solid solution with alumina is continues in the range between 0% and 100% by weight, Y

c) aluminum-magnesium spinel (MgAl 2 O 4) in any of its varieties (stoichiometric, rich in alumina or rich in magnesia), with a molar ratio that can range between 66 and 91%, for example 78%, and a grain size between 20 and 1000 nm [E. M. Levin, Phase Equilibrium diagrams for Ceramics, The American Ceramic Society Inc., Figs 259 and 260, (1964)].

The particle size of these ceramic oxides it can be nanometric (<200 nm) or micrometric (<10 um) (Example 1).

A particular embodiment of the invention is constitutes the ceramic oxide / n-W material of the invention in which the material is α-Al 2 O 3 / nW.

Another particular embodiment of the invention is constitutes the ceramic oxide / n-W material of the invention in which the material is spinel / nW.

Another object of the invention is the procedure for obtaining the oxide material ceramic / n-W of the invention, hereinafter method of obtaining the invention, which comprises the following stages:

a) the oxidic powder is suspended in absolute ethanol, with a concentration in solids generally less than 85%, putting the whole set under agitation by any magnetic or mechanical device that favors dispersion,

b) in parallel, a solution of tungsten chloride in absolute ethanol (purity> 99%) with the concentration required to obtain the nanostructured powder with the desired metal concentration, the solution being heated by below 70 ° C,

c) once all tungsten chloride has been transformed into tungsten ethoxide W, (colorless solution) in the step b), is added in a controlled manner to the powder suspension a) oxidic which is kept under continuous agitation to favor the homogeneous mixing of both liquids,

d) the remaining solvent is removed by evaporation at a temperature, generally, less than 70 ° C and always under continuous agitation, being able to heat it on stove to 60 ° C for 24 hours until a dry powder is obtained,

e) subsequently, the dry powder of d), is sieve using a standard mesh, preferably below 63 microns, and calcined at temperatures between 500 ° C and 700 ° C, preferably at 600 ° C, for a period of time enough to eliminate organic components and favor Crystallization of tungsten oxide on the surface of the oxidic particles, preferably, for one hour, and

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f) reduce tungsten oxide to tungsten metallic by a heat treatment between 750ºC and 1100ºC, preferably at 900 ° C, under hydrogen reducing atmosphere of the e) nanostructured powder between one hour and a half and two hours and half, preferably two hours, which produces the crystallization of metal nanoparticles on the surface of the oxidic particles.

Another particular object of the invention is constitutes the process of the invention where the oxidic powder of a) can be selected, by way of illustration and without limit the scope of the invention, among the following group:

a) alumina, in any form crystallographic, namely?,??,?,?, \ kappa, \ rho, \ eta, \ theta and \ chi with a grain size between 20 and 1000 nm,

b) alumina with any oxide that may enter in solid solution in your network - such as, for example, TiO2, Fe 2 O 3, Y 2 O 3 - and, in particular, chromite (Cr 2 O 3) whose solid solution with alumina is continuous in the range between 0% and 100% by weight, and

c) aluminum-magnesium spinel (MgAl 2 O 4) in any of its varieties (stoichiometric, rich in alumina or rich in magnesia), with a molar ratio that can range between 66 and 91%, for example, 78%, and a grain size between 20 and 1000 nm.

Another particular object of the invention is constitutes the process of the invention where the concentration of the tungsten chloride metal phase of b) may vary in function of the tungsten concentration desired in the ceramic material of the invention, for example, between 0.05 and 30% in volume of W, for example, in particular 1% (Example one).

Another particular embodiment of the invention is it constitutes the method of obtaining the invention where uses alumina (α-Al 2 O 3) as powder oxidic (Example 1).

Another particular embodiment of the invention is it constitutes the method of obtaining the invention where use spinel as an oxidic powder (Example 1).

Finally, another object of the present invention it is the use of the oxide material / n-W ceramic of the invention in the process, to illustrative title and without limiting the scope of invention, of products belonging to the following group: components electronics, catalysts, structural technical ceramics, pigments and dyes and coatings on substrates metallic

As catalyst the oxide material Ceramic / n-W of the invention can be used in a wide variety of processes as diverse as in the industry chemical, environmental protection (such as, for example, catalytic converters of automobiles), in reducing NO_ {x} in power plants, in oil refineries, in drug synthesis, in petrochemical processes, etc.

Description of the figures

Figure 1.- Scheme of the chemical reaction between tungsten chloride and absolute ethanol from stage b) of Process of the invention (Formula 1).

Figure 2.- Image of electron microscopy of Transmission (MET) of nanostructured powders α-Al 2 O 3 / nW. The size of the Metal particles are between 5 and 20 nm. The tungsten nanoparticles are monodispersed and firmly adhered to the oxidic particles.

Figure 3.- MET micrograph corresponding to spinel powder / nW. In this case, the particle size Metallic is between 3 and 20 nm.

Examples of realization Example 1 Obtaining nanostructured powders of Al 2 O 3 / nW and spinel / nW as particular embodiments of the oxide material ceramic / n-W of the invention

The starting raw materials are:

-

oxidic powder: Taimei alumina (α-Al 2 O 3, TM-DAR, Taimei Chemicals , Japan, average particle size 147 nm, purity> 99%) and aluminum magnesium spinel (AR-78 , Alcoa Industrial Chemicals , Germany) average particle size of 700 nm, purity> 99%, with 78% by weight of Al 2 O 3. Both alumina or spinel powder of high purity should be used, with a grain size in the range 0.1-1 µm,

-

Tungsten Chloride (WC16) [ Aldrich , Tungsten (V) Chloride, 99.9%], and

-

Absolute ethanol used as solvent medium ( Panreac 99.5% pure).

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For this, the following has been followed procedure, identical for both oxides (alumina and spinel), with the particularities of each case that below.

50 g of alumina were used (α-Al 2 O 3) and 20 g of spinel which they were suspended in 70 g and 60 g of absolute ethanol, respectively, in continuous magnetic stirring [step a)]. The solids concentration remained below 85%. In In parallel, 5.348 g of tungsten chloride (WCl6) were used for alumina and 2,402 g WCl6 for spinel in solution with the amount of absolute ethanol required (350 ml for alumina and 240 ml for the spinel) to transform the color yellow of the tungsten chloride powder solution in colorless, heating the solution below 70 ° C [step b)]. In these two particular embodiments the conditions are defined to establish a concentration of the metallic phase of tungsten 1% in the final ceramic material of the invention.

At the time of contact between chloride tungsten and absolute ethanol from step b) of the process of The invention produces the following chemical reaction (Formula 1; see Figure 1):

2

As noted in Formula (1) there is a evolution of hydrochloric acid (gas) that will not cease until the solution, initially yellow, becomes colorless, moment in which an ethoxide solution of W is achieved in absolute ethanol

Then, this solution is added drop by drop on the alumina and spinel suspension, respectively, gradually becoming the color solution off-white in blue [stage c)]. This solution was followed. stirring and heating (<70 ° C) to a viscous state to finally introduce the assembly in an oven at 60ºC for 24 hours [stage d)]. The dried product thus obtained was screened using a standard mesh below 63 microns and the powder is heat treated at 600 ° C for 1 hour [step e)]. Again the treated powder was screened below 63 microns and reduced by a tubular oven in H2 atmosphere at 900 ° C for 2 hours [stage f)].

In this way powders have been obtained nanostructured of α-Al2 O3 / nW in which the size of the metal particles is comprised between 5 and 20 nm (Figure 2), finding the nanoparticles of monodispersed tungsten and firmly adhered to particles oxidic as it appears from the study conducted by MET of the oxide / metal interface. Similarly it has been observed that in spinel powder / nW obtained particle size Metallic is between 3 and 20 nm (Figure 3). Finally, indicate that the nanostructured powders of Al 2 O 3 / nW and spinel / nW obtained have a tungsten content of 1% in volume, which has been determined by chemical analysis later and matches the amount of W programmed in the experiment.

Claims (12)

1. Composite nanostructured material characterized in that it is constituted by a ceramic oxide / nW material with a nanometric metal particle size between 1 and 100 nm, preferably between 1 and 20 nm, adhered to the oxidic substrate and with a tungsten content between 0 , 05% and 30% by volume. 2. Composite nanostructured material according to claim 1 characterized in that the oxide belongs to the following group: a) alumina, in any form crystallographic, namely?,??,?,?, \ kappa, \ rho, \ eta, \ theta and \ chi, with a grain size between 20 and 1000 nm, b) alumina with any oxide that may enter in solid solution in your network whose solid solution with alumina it is continuous in the range between 0% and 100% by weight, Y c) aluminum-magnesium spinel (MgAl 2 O 4) in any of its varieties (stoichiometric, rich in alumina or rich in magnesia), with a molar ratio that can range between 66 and 91%, for example, 78%, and a grain size between 20 and 1000 nm. 3. Composite nanostructured material according to claim 2 characterized in that the alumina of b) belongs to the following group: TiO 2, Fe 2 O 3, Y 2 O 3 and chromite (Cr 2) } O_ {3}). 4. Composite nanostructured material according to claim 2 characterized in that the ceramic oxide / nW material is a-Al2O3 / nW. 5. Composite nanostructured material according to claim 2 characterized in that the ceramic oxide / nW material is spinel / nW. 6. Procedure for obtaining the nanostructured material according to claims 1 to 5, characterized in that it comprises the following steps: a) the oxidic powder is suspended in absolute ethanol, with a concentration in solids generally less than 85%, putting the whole set under agitation by any magnetic or mechanical device that favors dispersion, b) in parallel, a solution of tungsten chloride in absolute ethanol (purity> 99%) with the concentration required to obtain the nanostructured powder with the desired metal concentration, the solution being heated by below 70 ° C, c) once all tungsten chloride has been transformed into tungsten ethoxide W, (colorless solution) in the step b), is added in a controlled manner to the powder suspension a) oxidic which is kept under continuous agitation to favor the homogeneous mixing of both liquids, d) the remaining solvent is removed by evaporation at a temperature, generally, less than 70 ° C and always under continuous agitation, being able to heat it on stove to 60 ° C for 24 hours until a dry powder is obtained, e) subsequently, the dry powder of d), is sieve using a standard mesh, preferably below 63 microns, and calcined at temperatures between 500 ° C and 700 ° C, preferably at 600 ° C, for a period of time enough to eliminate organic components and favor Crystallization of tungsten oxide on the surface of the oxidic particles, preferably, for one hour, and f) reduce tungsten oxide to tungsten metallic by a heat treatment between 750ºC and 1100ºC, preferably at 900 ° C, under hydrogen reducing atmosphere of the e) nanostructured powder between one hour and a half and two hours and half, preferably two hours, which produces the crystallization of metal nanoparticles on the surface of the oxidic particles. 7. Method according to claim 6 characterized in that the oxidic powder of a) is selected from the following group: a) alumina, in any form crystallographic, namely?,??,?,?, \ kappa, \ rho, \ eta, \ theta and \ chi, and with a size of grain between 20 and 1000 nm, b) alumina with any oxide that may enter in solid solution in your network and whose solid solution with alumina it is continuous in the range between 0% and 100% by weight, Y

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c) aluminum-magnesium spinel (MgAl 2 O 4) in any of its varieties (stoichiometric, rich in alumina or rich in magnesia), with a molar ratio that can range between 66 and 91%, for example, 78%, and a grain size between 20 and 1000 nm. Method according to claim 7, characterized in that the alumina of b) is selected from the following group: TiO 2, Fe 2 O 3, Y 2 O 3 and the chromite (Cr 2) O_ {3}). Method according to claim 7, characterized in that the concentration of the tungsten chloride metal phase of b) can vary depending on the concentration of tungsten in the material to be obtained, preferably, between 0.05 and 30% by volume of W, and for example, 1%. 10. Method according to claim 7, characterized in that alumina (α-Al 2 O 3) is used as the oxidic powder. 11. Method according to claim 7, characterized in that spinel is used as oxidic powder. 12. Use of nanostructured material according to claims 1 to 5 in the preparation of a product belonging to the following group: electronic components, catalysts, structural technical ceramics, pigments and dyes and coatings on metal substrates.