NIOBIUM NANOPARTICLE PREPARATION, USE AND PROCESS FOR OBTAINING THEREOF

Abstract

A preparation of niobium nanoparticles, its use, and a process for obtaining it by comminution, that is, a top-down process. The preparation of nanoparticles has a particular composition, purity, granulometric profile, and specific surface area, being useful in a variety of applications. Also taught is a process for obtaining nanoparticles of mineral species containing Niobium, through controlled comminution and without chemical reactions or contamination with reagents typical of the synthesis of nanoparticles. The preparation of niobium nanoparticles provides the large-scale production of niobium pentoxide nanoparticles with high purity, determined granulometric profile and very high specific surface area, enabling its use in practice in several industrial applications.

Claims

1. A preparation of nanoparticles comprising a content equal to or greater than 95 wt % Niobium particles, wherein 50% to 99% of particles (d50 to d99) are in the granulometric range of 5 to 1000 nanometers (nm).

2. The preparation of nanoparticles according to claim 1, wherein 90% to 99% of particles (d90 to d99) are in the granulometric range of 5 to 1000 nanometers (nm).

3. The preparation of nanoparticles according to claim 1, wherein the content is equal to or greater than 99 wt % niobium particles.

4. The preparation of nanoparticles according to claim 1, wherein the nanoparticles are niobium pentoxide.

5. The preparation of nanoparticles according to claim 1, wherein the particle size distribution profile is: d10: between 14 and 110 nm; d50: between 29 and 243 nm; and d90: between 89 and 747 nm.

6. The preparation of nanoparticles according to claim 1, wherein the particle size distribution profile is: d10 from 70 to 100 nm; d50 from 170 to 240 nm; d90 from 400 to 580 nm.

7. The preparation of nanoparticles according to claim 1, wherein the particle size distribution profile is: d50 from 10 to 178 nm; d80 from 10 to 300 nm; d90 from 10 to 400 nm.

8. The preparation of nanoparticles according to claim 1, wherein 90% to 99% of the particles (d90 to d99) are in the granulometric range between 100 and 1000 nm.

9. The preparation of nanoparticles according to claim 1, wherein 90% to 99% of the particles (d90 to d99) are in the granulometric range between 5 and 100 nm.

10. The preparation of nanoparticles according to claim 9, wherein the particle size distribution profile is: d10: between 9 and 27 nm; d50: between 16 and 67 nm; d90: between 33 and 94 nm.

11. The preparation of nanoparticles according to claim 1, wherein the specific surface area is from 0.5 to 150 m.sup.2/g.

12. The preparation of nanoparticles according to claim 11, wherein the average specific surface area is 40 to 70 m.sup.2/g.

13. A method for the preparation of particles or nanoparticles with adjusted rheological properties, adjusted degrees of packing or void fractions, adjusted fluidity of the final preparation a content equal to or greater than 95 wt % Niobium particles, wherein 50% to 99% of particles (d50 to d99) are in the granulometric range of 5 to 1000 nanometers (nm) comprising of nanoparticles preparation, comprising using as a starting material.

14. A method for the preparation of: stable colloidal compositions; steels, metallic and non-metallic alloys, ceramics and/or polymers; composite materials, electronic components, battery cells, energy storage systems, piezoelectric sensors and actuators, solar panels; glass, glass ceramics, transparent and translucent materials; catalysts as a content equal to or greater than 95 wt % Niobium particles, wherein 50% to 99% of particles (d50 to d99) are in the granulometric range of 5 to 1000 nanometers (nm) comprising of nanoparticles preparation, comprising using a starting material.

15. A process for obtaining niobium nanoparticles, comprising the steps of: feeding Niobium particles to a comminution equipment selected from: high-energy mill, ball mill and steammill; adjusting the comminution conditions selected from: in a high-energy mill: suspend particles to be comminuted in a liquid, in a concentration between 1% and 90% m/m, and stabilize the suspension until obtaining a stable colloidal suspension; placing said suspension and grinding balls with a selected diameter between 5 μm and 1.3 mm in the grinding chamber; adjust the mill rotation speed between 500 and 4500 rpm; and grinding the particles at a temperature below 60° C.; or in a jet mill with superheated fluid or steammill, feeding particles smaller than 40 micrometers; adjusting the speed of the air classifier between 1,000 and 25,000 rpm; adjusting the compressed steam pressure between 10 and 100 bar and temperature between 230 and 360° C.; and comminuting the particles until obtaining the desired granulometric profile.

16. The process according to claim 15, wherein the stabilization of the colloidal suspension is performed by: adjusting the pH of the polar liquid medium to the range from 2 to 13, and optionally adding surfactants; or add surfactants to the non-polar liquid medium.

17. The process according to claim 15, further comprising a pre-comminution step of the niobium particles before the feeding step to the comminution equipment, said pre-comminution being conducted until reaching a mean particle size of less than 40 micrometers.

18. The process according to claim 17, wherein the pre-comminution is performed in a ball mill, disk mill or high-energy mill or in a jet mill.

19. The process according to claim 15, further comprising the steps of: feeding a high-energy mill with micrometric niobium pentoxide (Nb.sub.2O.sub.5) particles; feeding said mill with a liquid and adjusting the pH in the range from 5 to 10; feeding said mill with balls with a selected diameter between 50 μm and 400 μm; adjusting the mill rotation speed between 2000 and 4000 rpm; and grinding the particles at a temperature below 60° C. until the desired granulometric profile is obtained.

20. The process according to claim 15, wherein the high-energy mill is of the agitated medium type and said spheres are selected from: Zirconia, Silicon carbide, alumina, said spheres being optionally stabilized with Yttria or Niobium Pentoxide, or combinations thereof.

21. The process according to claim 15, wherein the jet mill at superheated temperature or steammill is adjusted with the following parameters: rotation of the air classifier at 20,000 rpm; compressed steam pressure at 50 bar; and temperature of the superheated fluid of 280° C.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0062] The following figures are shown:

[0063] FIG. 1 shows the particle size distribution of an embodiment of Niobium (Nb.sub.2O.sub.5) nanoparticle preparation of the invention, showing the granulometric profile measured by the laser scattering method, using an Analysette 22 NanoTecplus brand FRITSCH. Shown are: granulometric distribution or equivalent diameter on the particle volumetric base in nanometers (horizontal axis), the relative fraction of the nanoparticles (vertical axis on the left) and cumulative fraction (vertical axis on the right).

[0064] FIG. 2 shows a photo of a sedimentation test as a function of the pH of the suspension formed by Nb.sub.2O.sub.5 particles in an aqueous solution adjusted with HCl or NaOH to change the pH of the medium. The different equilibrium pHs are shown in the numbered tubes: 2, 4, 9 and 12.

[0065] FIG. 3 shows a photo of a stabilization test tube as a function of time (shelf-life) used in the turbidimetry analysis in a TURBISCAN-type equipment, showing a tube containing a suspension of niobium nanoparticles at pH 9 after 6 hours of evaluation.

[0066] FIG. 4 shows the particle size distribution of niobium pentoxide comminuted as a function of grinding time in a high energy mill (sampling frequency). The equivalent diameter of the particles in nm is shown on the x-axis and the frequency in % on the y-axis.

[0067] FIG. 5 shows the particle size distribution as a function of the cumulative volume of the comminuted niobium pentoxide sample. The equivalent diameter in nm is shown on the x-axis and the cumulative volume in % on the x-axis.

[0068] FIG. 6 shows the cumulative distribution profile of Nb.sub.2O.sub.5 particles in alcohol as a dispersant at the inlet of a jetmill. The equivalent diameter in microns is shown on the x-axis, on the left y-axis the volume % and on the right y-axis the cumulative volume %.

[0069] FIG. 7 shows the cumulative particle distribution profile of Nb.sub.2O.sub.5 particles in alcohol as a dispersant at the outlet of a jetmill. The equivalent diameter in microns is shown on the x-axis, on the left y-axis the volume % and on the right y-axis the cumulative volume %.

[0070] FIG. 8 shows the curves corresponding to the granulometric distribution profile of the commercial product containing niobium pentoxide (curve A=input) and the pre-comminuted niobium pentoxide preparation (curve B). The equivalent diameter of the particles in micrometers is shown on the x-axis and the cumulative volume in % is shown on the y-axis.

[0071] FIG. 9 shows the curves corresponding to the granulometric distribution profile of the commercial product containing niobium pentoxide (curve A=input) and the pre-comminuted niobium pentoxide preparation (curve B). The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0072] FIG. 10 shows the curve corresponding to the particle size distribution profile of the preparation of niobium pentoxide nanoparticles (curve C) in the entire nanometer range, with particles between 74 and 747 nm. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0073] FIG. 11 shows the curve corresponding to the particle size distribution profile of the niobium pentoxide nanoparticle preparation (curve D) in the entire nanometer range, with particles between 20 and 206 nm. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0074] FIG. 12 shows the curve corresponding to the particle size distribution profile of the niobium pentoxide nanoparticle preparation (curve E) in the entire nanometer range, with particles between 8 and 89 nm. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0075] FIG. 13 shows the curves corresponding to the granulometric distribution profiles of three different preparations of pre-comminuted niobium pentoxide (curves C, D and E) in a single graph. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0076] FIG. 14 shows the curves corresponding to the granulometric distribution profiles of three different preparations of pre-comminuted niobium pentoxide (curves C, D and E) in a single graph. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

DETAILED DESCRIPTION OF THE INVENTION

[0077] The present invention solves several state-of-the-art problems and provides a preparation of niobium nanoparticles that concomitantly contemplates the following technical characteristics: particles predominantly or entirely in the nanometer granulometric range; high purity; an industrial-scale process that enables supply and use on an economic scale. Said preparation can also be called preparation of niobium nanoparticles.

[0078] In the present invention, the term “Niobium particles” encompasses various chemical entities containing Niobium, including Niobium metal, oxides, hydrates, hydrides, carbides, or nitrides of Niobium, Niobium iron or Niobium bonded to other metals or transition metals, or combinations thereof. It also includes Niobium Pentoxide.

[0079] The invention is also defined by the following provisions.

[0080] Preparation of nanoparticles comprising a content equal to or greater than 95 wt % Niobium particles, wherein 50% to 99% particles (d50 to d99) are in the granulometric range from 5 to 1000 nanometers (nm).

[0081] Preparation of nanoparticles comprising a content equal to or greater than 95 wt % Niobium particles, wherein 90% to 99% particles (d90 to d99) are in the granulometric range from 5 to 1000 nanometers (nm).

[0082] Preparation of nanoparticles as defined above comprising a content equal to or greater than 99 wt % Niobium particles.

[0083] Preparation of nanoparticles as defined above wherein the nanoparticles are Niobium Pentoxide.

[0084] Preparation of nanoparticles as defined above having particle size distribution d10: between 14 and 110 nm; d50: between 29 and 243 nm; and d90: between 89 and 747 nm.

[0085] Preparation of nanoparticles as defined above having a d10 particle size distribution from 70 to 100 nm; d50 from 170 to 240 nm; d90 from 400 to 580 nm.

[0086] Preparation of nanoparticles as defined above having d50 particle size distribution from 10 to 178 nm; d80 from 10 to 300 nm; d90 from 10 to 400 nm.

[0087] Preparation of nanoparticles as defined above in 90% to 99% particles (d90 to d99) are in the granulometric range from 100 to 1000 nm.

[0088] Preparation of nanoparticles as defined above wherein 90% to 99% particles (d90 to d99) are in the granulometric range from 5 to 100 nm.

[0089] Preparation of nanoparticles as defined above having particle size distribution d10: between 9 and 27 nm; d50: between 16 and 67 nm; d90: between 33 and 94 nm.

[0090] Preparation of nanoparticles as defined above having specific surface area between 0.5 and 150 m.sup.2/g.

[0091] Preparation of nanoparticles as defined above having an average specific surface area of 40 to 70 m.sup.2/g.

[0092] Use of nanoparticle preparation described above for adjusting the rheological properties of other particle or nanoparticle preparations, adjusting degrees of packing, fluidity, void fractions or other properties of the final preparation.

[0093] Use of the nanoparticle preparation described above for the preparation of: stable colloidal compositions; steels, metallic and non-metallic alloys, ceramics and/or polymers; electronic components, battery cells, energy storage systems, piezoelectric sensors and actuators, solar panels; glass, glass ceramics or other transparent and translucent materials; catalysts.

[0094] Process for obtaining niobium nanoparticles comprising the steps of: [0095] feeding niobium particles to a comminution equipment selected from: high-energy mill and steammill; [0096] adjusting the comminution conditions selected from: [0097] in a high-energy mill: [0098] to suspend particles to be comminuted in a liquid, in a concentration between 1 and 90% m/m, and stabilize the suspension until obtaining a stable colloidal suspension; and [0099] to place said suspension and grinding balls with a selected diameter between 5 μm and 1.3 mm in the grinding chamber; adjusting the mill rotation speed between 500 and 4500 rpm; and grinding the particles at a temperature below 60° C.; or [0100] in a jet mill with superheated fluid or steammill, feeding particles smaller than 40 micrometers; adjust the speed of the air classifier between 1,000 and 25,000 rpm; adjust the compressed steam pressure between 10 and 100 bar and temperature between 230 and 360° C.; [0101] comminuting the particles until obtaining the desired granulometric profile.

[0102] Process as described above in which the stabilization of the colloidal suspension to be placed in the grinding chamber of the high-energy mill is selected from: adjusting the pH of the polar liquid medium to the range between 2 and 13, and optionally adding surfactants; or the addition of surfactants in a non-polar liquid medium.

[0103] Process as described above, further comprising a pre-comminution step of the Niobium particles before the feeding step to the comminution equipment, said pre-comminution being conducted until reaching a mean particle size between 1 and 40 micrometers.

[0104] Process wherein said pre-comminution is performed in a ball mill, disk mill or high-energy mill.

[0105] Process wherein said pre-comminution is performed in a jet mill.

[0106] Process as described above in which the high-energy mill is of the agitated medium type and said spheres are selected from: Zirconia, Silicon carbide, alumina, said spheres optionally being stabilized with Yttria or Niobium pentoxide, or combinations thereof.

[0107] Process as described above wherein the operating pH in the mill is 6 to 10.

[0108] Process as described above wherein the operating temperature in the mill is 30 to 40° C.

[0109] In one embodiment, a preparation of niobium pentoxide (Nb.sub.2O.sub.5) nanoparticles with purity equal to or greater than 99% is provided.

[0110] In one embodiment, the niobium nanoparticle preparation of the present invention has a particle size between 5 and 1000 nanometers. In some embodiments, the preparation of nanoparticles of the invention comprises particles with defined particle size fractions, for example, a preparation with particles integrally between 100 and 1000 nm, a preparation with particles integrally between 5 and 100 nanometers, and preparations with particles in intermediate values and with granulometric fractions of defined value.

[0111] In some embodiments of the present invention, as is already the practice of the segment, the distribution of granulometric fractions is defined by d10, d50, d90 and occasionally d99, notations reflecting the accumulated % volume of particles corresponding to each notation, d10 referring to 10% of the particles volume, d50 to 50% of the volume and so on.

[0112] In some embodiments, the invention provides a preparation of Niobium particles in the granulometric range below 100 nanometers.

[0113] In some embodiments, the niobium pentoxide nanoparticle preparation has a granulometric distribution: d10: between 9 and 27 nm; d50: between 16 and 67 nm; and d90: between 33 and 94 nm.

[0114] In other embodiments, the niobium pentoxide nanoparticle preparation has a granulometric distribution: d10: between 14 and 110 nm; d50: between 29 and 243 nm; and d90: between 89 and 747 nm.

[0115] In some embodiments, the invention provides a preparation of Niobium particles with specific surface area between 50 and 148 m.sup.2/g.

[0116] In one embodiment, the niobium pentoxide nanoparticle preparation has a mean specific surface area of 62.07 m.sup.2/g.

[0117] In one embodiment, a preparation of niobium pentoxide nanoparticles with an average particle size (d50) of 16 nm is provided. In another embodiment, the niobium pentoxide nanoparticle preparation has a mean particle size (d50) of 29 nm. In another embodiment, the niobium pentoxide nanoparticle preparation has a mean particle size (d50) of 67 nm. In another embodiment, the niobium pentoxide nanoparticle preparation has a mean particle size (d50) of 178 nm.

[0118] The nanoparticle preparation of the invention is useful in several applications, including: preparation of stable colloidal suspensions; modulation or improvement of the mechanical properties of steels, metallic and non-metallic alloys, ceramics and/or polymers; doping of materials to modulate electromagnetic properties for use in electronic components, battery cells, energy storage systems, solar panels, sensors and piezoelectric actuators; the modulation of optical properties of glasses or other transparent materials; use as a component of catalysts.

[0119] In one embodiment, the use of the nanoparticle preparation of the invention provided stable liquid compositions or colloidal suspensions, wherein the nanoparticles remain in suspension for a long time, providing a long shelf-life.

[0120] The process for obtaining niobium nanoparticles differs from other congeners because it is a top-down process, without chemical reactions or mechanical-chemistry. The fact that pure or high-purity niobium particles are used for comminution provides the obtainment of high-purity nanoparticle preparations, since the process does not add impurities or lead to the formation of reaction products, as is the case with processes bottom-up, synthesis or state-of-the-art mechanical-chemicals.

[0121] The process of the invention comprises the steps of: [0122] feeding Niobium particles to a comminution equipment selected among: high energy mill; and steammill; [0123] adjusting the comminution conditions selected from: [0124] in a high-energy mill: [0125] suspending particles to be comminuted in a liquid, in a concentration between 1 and 90% m/m, and stabilize the suspension until obtaining a stable colloidal suspension; and [0126] placing said suspension and grinding balls with a selected diameter between 5 μm and 1.3 mm in the grinding chamber; adjusting the mill rotation speed between 500 and 4500 rpm; and grinding the particles at a temperature below 60° C.; [0127] in a jet mill at superheated temperature or steammill, feeding particles smaller than 40 micrometers; adjusting the speed of the air classifier between 1,000 and 25,000 rpm; [0128] adjusting the compressed steam pressure between 10 and 100 bar and temperature between 230 and 360° C.; and [0129] comminuting the particles until obtaining the desired granulometric profile.

[0130] Pre-process mean particle size reduction as demonstrated above is particularly useful for improving the performance of the subsequent comminution process in a high-energy mill, as demonstrated in examples 1-4 and 7, or in a steammill comminution process, described in example 6 below.

[0131] In one embodiment, the process involves wet milling in a high-energy mill and makes it possible, on an industrial scale, for the first time, to obtain niobium pentoxide particles predominantly or entirely in the nanometer granulometric range. In the embodiments in which the comminution is performed in high-energy wet mills, the stabilization of the colloidal suspension to be placed in the grinding chamber of the high-energy mill is a very important step, being selected from: adjusting of the polar liquid medium pH for the range between 2 and 13, and optionally adding surfactants; or adding surfactants in a non-polar liquid medium.

[0132] In one embodiment, a mill known from the state of the art is used, such as, for example, a high-energy mill with Yttria-stabilized Zirconia spheres (ZrO.sub.2+Y.sub.2O.sub.3), by adjusting specific parameters, including rotation time, pH and temperature. In one embodiment, the grinding medium includes Zirconia balls, ZTA (Alumina-reinforced Zirconia or Yttrium) and alumina. Preferably, zirconium spheres stabilized with 5% m/m Yttria are used.

[0133] In another embodiment, the process involves comminution by a jet mill with superheated steam (steammill), to which particles smaller than 40 microns are fed, the air classifier rotation being adjusted between 1,000 and 25,000 rpm, the compressed steam pressure between 10 and 100 bar, and the temperature between 230 and 360° C.

EXAMPLES

[0134] The examples shown herein are intended only to exemplify some of the various ways of performing the invention, however without limiting its scope.

Example 1—Niobium Pentoxide (Nb.SUB.2.O.SUB.5.) Wet Grinding Process in High-Energy Mill

[0135] In this embodiment, the preparation of niobium pentoxide nanoparticles was obtained by milling with adjustment of parameters that include rotation speed, pH, temperature.

[0136] Niobium pentoxide (Nb.sub.2O.sub.5) from a commercial source, with high purity and with granulometric distribution d90=68.425, d50=20.867 and d10=0.345 (μm) was fed to a high energy mill of the agitated medium type. Said mill operates with grinding balls/spheres from 5 μm to 1.3 mm in diameter, made of Yttria-stabilized Zirconia. In this embodiment, the size of said balls was 400 μm. The grinding conditions of the said material, to obtain the niobium nanoparticle powder (Nb.sub.2O.sub.5), included: rotation speeds between 1000 and 4500 rpm, temperatures below 40° C. maintained with the aid of a forced cooling system external to the said mill. After 30 to 120 minutes of operation under these conditions, a powder preparation containing niobium nanoparticles was obtained.

[0137] Different grinding conditions were tested to evaluate efficiency. Table 1 shows the test results on different milling parameters and times:

TABLE-US-00001 TABLE 1 Grinding efficiency and granulometric distribution (d10, d50 and d90) in micrometers (μm) Time (min) pH Technique T (° C.) d10 d50 d90 0 11.13 Fraunhofer 17 0.345 20.867 68.425 30 6.63 Mie 34.7 0.077  0.178  0.402 60 6.43 Mie 35 0.077  0.186  0.405 90 6.25 Mie 35.8 0.084  0.183  0.384 120 6.08 Mie 35.8 0.099  0.239  0.576

[0138] The data in table 1 show that under condition of a grinding time of 30 minutes, pH 6.63, with the size measurement technique by laser scattering according to the Mie model and on a volumetric basis, and a temperature of 34.7° C., nanoparticles with d10 of 0.077 were obtained; d50 of 0.178; and d90 of 0.402 (respectively 77 nm, 178 nm and 402 nm).

Example 2—Particle Size Measurement

[0139] The particle size distribution was measured by the laser scattering method, using the Analysette 22 NanoTecplus brand FRITSCH. As shown in FIG. 1, the preparation of niobium nanoparticles of the invention has a granulometric distribution integrally in the range of nanoparticles. FIG. 1 shows the particle size distribution or equivalent diameter of the particles in nanometers (horizontal axis), the relative fraction of the nanoparticles (left vertical axis) and cumulative fraction (right vertical axis). The figure shows that the niobium nanoparticles of this embodiment of the invention have an equivalent diameter between 10 and 1000 nanometers (nm), with 90% between 10 and 400 nm, 80% between 10 and 300 nm, 50% between 10 and 178 nm,

Example 3—Stable Colloidal Suspension—Stability Test of Niobium Particles as a Function of pH and in Aqueous Solution

[0140] The nanoparticle preparation obtained according to example 1 was used to obtain a stable colloidal suspension and stabilization tests as a function of pH were performed. FIG. 2 shows the results obtained in tubes numbered for the different tested pHs: 2, 4, 9, 12. As illustrated in FIG. 2, the results show the stability of the Niobium nanoparticles is very dependent on the pH of the medium, and that at pH 4 the particles reached their highest instability. It is also observed that at this pH 4 practically 100% of the particles sedimented, since the supernatant liquid in the test tube is completely free of solid particles with sizes that could suffer interference from the visible light of the environment. The supernatant liquid has the typical translucency of the aqueous solution used. It is also observed the accumulation of Niobium particles at the bottom of the tubes with pH 4, indicating the height of the sediment formed by the particles. At pH 9, the particles in that condition are less susceptible to sedimentation and showed greater stability.

Example 4—Liquid Compositions Containing Niobium Nanoparticles—Stability/Shelf-Life Tests

[0141] The preparation of nanoparticles according to examples 1 and 2 was submitted to the stability test as a function of time (shelf-life). FIG. 3 shows the result of said test, indicating that after 6 hours of turbidimetry testing in a TURBISCAN equipment, the particles at pH 9 remained stable and did not form sediments. This behavior is typical of stable nanometer particles.

Example 5— Niobium Pentoxide (Nb.SUB.2.O.SUB.5.) Wet Grinding Process in High-Energy Mill

[0142] A Labstar LS01 ball mill (Netzsch) was fed with micrometric particles of niobium pentoxide. Said process involves high-energy wet milling. The particle suspension was 17.7% m, consisting of approximately 3500 g of milli-Q water+10 M NaOH and 750 g of the solid sample which was prepared and stabilized in the mill mix tank at pH 9, titrated with 10 M NaOH. The grinding balls used were Yttria-stabilized zirconia, 400 μm in diameter. The filling of the grinding chamber was 80% vol and the suspension temperature below 40° C. The mill rotation speed was set to 3000 rpm and grinding was performed for 8 hours. To stabilize the suspension at pH 9, additions of 10 M NaOH were made during milling, samples were taken from time to time and particle sizes were measured.

[0143] The measurement of the particles was carried out in Fritsch equipment, model Analysette 22, with a unit for wet particle size measurements as an accessory. Particle size distribution measurements were made by static light scattering. The analysis medium was distilled water. An aliquot of the suspension with 17.7% m, during the milling process, was analyzed in ten repetitions by the equipment. The results in table 2 show the measurements (average of 10 measurements) and the DTP (particle size distribution) obtained in each grinding time under the conditions indicated above.

TABLE-US-00002 TABLE 2 Results of d10, d50 and d90 in nanometers. Sampling (time in hours) D10 (nm) D50 (nm) D90 (nm) 0.5 226 660 1366 1 207 449 919 1.5 193 450 943 2 181 382 778 2.5 180 358 711 3 165 336 601 3.5 159 298 540 4 153 286 519 6 138 261 503 7 138 261 503 8 119 243 476

[0144] Particle size distribution curves as a function of frequency and cumulative volume are shown in FIGS. 4 and 5.

[0145] FIG. 4 shows the particle size distribution of niobium pentoxide comminuted as a function of grinding time in a high-energy mill (sampling frequency). The equivalent diameter of the particles in nm is shown on the x-axis and the frequency in % on the y-axis.

[0146] FIG. 5 shows the particle size distribution as a function of the cumulative volume of the comminuted niobium pentoxide sample. The equivalent diameter in nm is shown on the x-axis and the cumulative volume in % on the y-axis.

Example 6—Comminution of Niobium Pentoxide by Jetmill

[0147] In the present example, a jet mill was used to pre-comminute the niobium pentoxide particles in order to improve the performance of the subsequent comminution process up to an integral granulometric distribution (d99) in the nanometer range.

[0148] A sample of niobium pentoxide, with an input particle size distribution profile d90% 69.4 μm; d50% 40.6 μm and d10% 13.4 μm, relative humidity 0.85% (Sartorius—20 min at 105° C.) and bulk density 1.62 g/cm.sup.3 was subjected to various comminution conditions in a jetmill, as summarized in Table 3.

TABLE-US-00003 TABLE 3 Comminution conditions in jetmill Tests # 1 2 3 Product 1 2 3 Classifier Speed Rpm 18,000 18,000 18,000 Grinding air pressure bar(g) 5.5 5.5 5.5 Fan capacity (%) 30 20 22 Inlet air temperature ° C. 28 27 28 Quantity of starting Kg 5 5 5 material Test time Min 30 30 30 Product flow kg/h 0.9 0.8 0.8 Nozzle diameter Mm 2.1 2.1 2.1 Nozzles distance Mm 80 80 80 Classifier pressure mbar(g) 0.12 0.11 011 Slit pressure mbar(g) 0.16 0.16 0.14 Classifier current A 1.53 1.52 1.54 Bulk density g/L 1.6 1.6 1.6 Final moisture % 0.8 0.8 0.8 Specific grinding energy kWh/kg 1.66 1.87 1.87 Specific air flow m.sup.3/kg 44.3 49.8 49.8 Dosage A/B 1% low 1% low 1% low Granulometry in Master % μm μm μm 3000 d10 1.41 1.44 2.77 d50 11.40 10.40 8.88 d90 31.10 28.50 22.30

[0149] FIG. 6 shows the cumulative particle distribution profile of Nb.sub.2O.sub.5 in alcohol as a dispersant in a jetmill (product 1 in table 3 above). The equivalent diameter in microns is shown on the x-axis, on the left y-axis the volume % and on the right y-axis the cumulative volume %. For this sample the residual weight is 1.14%, the specific surface area 1.536 m.sup.2/g, and the concentration 0.0020%. The particle distribution profile is dD90=31.1 μm; D50=11.4 μm; d10=1.41 μm.

[0150] FIG. 7 shows the cumulative particle distribution profile of Nb.sub.2O.sub.5 in alcohol as a dispersant in a jetmill (product 3 in table 3 above). The equivalent diameter in microns is shown on the x-axis, on the left y-axis the volume %, and on the right y-axis the cumulative volume %. For this sample the residual weight is 0.68%, the specific surface area 1.063 m.sup.2/g, and the concentration 0.0081%. The particle distribution profile is dD90=22.3 μm; D50=8.88 μm; d10=2.77 μm.

[0151] Reducing the average particle size as demonstrated above is particularly useful for improving the performance of the subsequent high-energy mill comminution process as demonstrated in Examples 1˜4 or the comminution process described in Example 7 below.

Example 7—Comminution of Niobium Pentoxide by Steammill

[0152] In this embodiment, Nb.sub.2O.sub.5 particles with the distribution profile according to FIG. 7 (example 6), dD90=22.3 μm; D50=8.88 μm; d10=2.77 μm were fed to a steammill.

[0153] Then, the air classifier rotation was adjusted to 20,000 rpm and the compressed steam pressure to 50 bar. The temperature of the superheated fluid was 280° C.

[0154] After operating under these conditions, a particle size distribution profile similar to that obtained in examples 1-2, FIG. 1, was obtained.

Example 8—High Purity and Defined Granulometric Distribution of Niobium Pentoxide (Nb.SUB.2.O.SUB.5.) Nanoparticle Preparations

[0155] In the present example, several embodiments of Niobium pentoxide nanoparticle preparations were obtained, with purity greater than 99%. Commercial niobium pentoxide, with the granulometric distribution described in Table 4, was pre-comminuted in a high-energy mill containing Yttria-stabilized zirconia spheres with a diameter of 400 μm, in liquid medium and the pH adjusted to 6.6. The mill rotation speed was 3500 rpm and the grinding of the particles was performed at a temperature below 40° C. Table 4 shows the particle size distribution (DTP) of input niobium pentoxide (commercial product) and output niobium pentoxide of a pre-comminution step.

TABLE-US-00004 TABLE 4 Input DTP (commercial product) and output after a pre-comminution. DTP for Niobium pentoxide diameter [μm] % cumulative Input Output 1.13 2.130 0.991 2.97 4.030 1.450 4.87 6.720 1.880 6.22 8.680 2.130 10.00 13.400 2.770 12.72 16.400 3.120 15.03 18.700 3.550 17.96 21.200 4.030 21.73 24.100 4.580 26.56 27.400 5.210 32.68 31.100 6.120 40.22 35.300 7.440 50.00 40.600 8.880 59.08 45.600 10.160 69.48 51.800 12.700 79.47 58.900 16.500 88.11 66.900 21.200 94.59 76.000 27.400 98.55 86.400 35.300 99.99 98.100 40.100

[0156] FIG. 8 shows the curves corresponding to the granulometric distribution profile of the commercial product containing niobium pentoxide (curve A=input) and the pre-comminuted niobium pentoxide preparation (curve B). The equivalent diameter of the particles in micrometers is shown on the x-axis and the cumulative volume in % is shown on the y-axis.

[0157] FIG. 9 shows the curves corresponding to the granulometric distribution profile of the commercial product containing niobium pentoxide (curve A=input) and the pre-comminuted niobium pentoxide preparation (curve B). The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis. The data show that the pre-comminution step allows obtaining a preparation containing niobium pentoxide microparticles with particles between 1 and 40 micrometers.

[0158] The average specific surface area S (m.sup.2/g) of the particles after the pre-comminution step was 0.32 m.sup.2/g.

[0159] In one embodiment, the pre-comminuted particles were then fed to a high-energy mill, applying conditions similar to those described in example 5, but with 200 μm Zr spheres and milled for different times, until obtaining each preparation of nanoparticles. Three different preparations of nanoparticles were obtained, each with a defined granulometric distribution as described in table 5.

TABLE-US-00005 TABLE 5 Particle size distribution of three different preparations (C, D and E) of niobium pentoxide nanoparticles. DTP for Niobium pentoxide diameter [μm] % cumulative C D E 1.13 0.074 0.021 0.009 2.97 0.082 0.024 0.010 4.87 0.098 0.027 0.012 6.22 0.104 0.029 0.012 10.00 0.119 0.033 0.014 12.72 0.131 0.036 0.016 15.03 0.138 0.038 0.017 17.96 0.145 0.040 0.017 21.73 0.159 0.044 0.019 26.56 0.175 0.048 0.021 32.68 0.192 0.053 0.023 40.22 0.212 0.058 0.025 50.00 0.243 0.067 0.029 59.08 0.282 0.078 0.034 69.48 0.322 0.089 0.038 79.47 0.376 0.104 0.045 88.11 0.413 0.114 0.049 94.59 0.455 0.125 0.054 98.55 0.550 0.152 0.066 99.99 0.747 0.206 0.089

[0160] FIG. 10 shows the curve corresponding to the granulometric distribution profile of the preparation of niobium pentoxide nanoparticles (curve C) integrally (d99.99) in the nanometer range, with particles between 74 and 747 nm. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0161] FIG. 11 shows the curve corresponding to the granulometric distribution profile of the preparation of niobium pentoxide nanoparticles (curve D) integrally (d99.99) in the nanometer range, with particles between 20 and 206 nm. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0162] FIG. 12 shows the curve corresponding to the particle size distribution profile of the niobium pentoxide nanoparticle preparation (curve E) integrally (d99.99) in the nanometer range, with particles between 8 and 89 nm. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0163] FIG. 13 shows the curves corresponding to the granulometric distribution profiles of the three different preparations of pre-comminuted niobium pentoxide from FIGS. 10-12 (curves C, D and E) in a single graph. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0164] FIG. 14 shows the curves corresponding to the granulometric distribution profiles of three different preparations of pre-comminuted niobium pentoxide (curves C, D and E) in a single graph. The equivalent diameter of the particles in micrometers is shown on the x-axis and the frequency in % is shown on the y-axis.

[0165] The nanoparticle preparations of this embodiment of the invention have a very high specific surface area, which enables their use in a very wide variety of applications. Table 6 shows the mean specific surface area data of the niobium pentoxide nanoparticle preparations.

TABLE-US-00006 TABLE 6 Mean specific surface area S of three different preparations of niobium pentoxide nanoparticles (C, D and E). S [m.sup.2/g] C D E Mean 7.44 26.85 62.07

[0166] It should be noted that in some fractions of preparation E, niobium pentoxide nanoparticles greater than 90 m.sup.2/g were obtained and one of the fractions resulted in 148.2 m.sup.2/g, values far above those never achieved in the prior art.

[0167] Those skilled in the art will know that through the use of classifiers, such as air classifiers or ultracentrifugation, the different granulometric fractions of each preparation can be separated, thereby enabling the obtaining of even narrower granulometric distribution profile curves in relation to those exemplified above.

Example 9—Preparations of Nanoparticles Resulting from the Combination of Integrally Nanometric Preparations of Niobium Pentoxide (Nb.SUB.2.O.SUB.5.)

[0168] In the present example, different nanoparticle preparations were obtained by combining the two nanoparticle preparations (preparations C and E) exemplified in example 8 above.

[0169] In one embodiment, a 1:1 mixture of Preparation C and Preparation E of Example 8 was obtained by simple homogenization.

[0170] In another embodiment, a 1:10 mixture of preparation C and preparation E of example 8 was obtained by simple homogenization.

[0171] In another embodiment, a 1:1 mixture of preparation D and preparation B (pre-comminuted) of example 8 was obtained by simple homogenization.

[0172] The resulting granulometric distribution profiles provide adjustment of the rheology of the preparations obtained, since the combinations of larger particles (preparations B or C) with smaller nanoparticles (preparations D or E) provide different degrees of packing, void fractions, fluidity and different behaviors in subsequent applications such as sintering, dispersion in viscous liquids and other applications.

[0173] Those skilled in the art will value the knowledge presented herein and will be able to reproduce the invention in the presented modalities and in other variants and alternatives, covered by the scope of the following claims.