Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F7/00—Compounds of aluminium
  • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
  • C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
  • C01F7/306—Thermal decomposition of hydrated chlorides, e.g. of aluminium trichloride hexahydrate
• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/50—Solid solutions
  • C01P2002/52—Solid solutions containing elements as dopants
  • C01P2002/54—Solid solutions containing elements as dopants one element only
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/60—Compounds characterised by their crystallite size
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer

Definitions

• the present invention relates to nanoparticles and their preparation, wherein the nanoparticles consist of Al 2 O 3 with fractions of oxides of the elements of the I. and II. Main group of the Periodic Table.
• Fine alumina powders are used in particular for ceramic applications, for matrix reinforcement of organic or metallic layers, as fillers, polishing powders, for the production of abrasives, as additives in paints and laminates as well as for other special applications.
• the production of the ultra-fine alumina powder is carried out either by chemical synthesis, mechanical comminution methods or thermophysical way.
• the aim of the present invention is therefore to produce nano-crystalline mixed oxides consisting of aluminum oxide and metal oxides of elements of the I. and II.
• Main group of the periodic table with a method that provides high yields in a short time with minimal energy input.
• the resulting product should be redispersible by simple means and thus be able to deliver stable nano-suspensions.
• the invention relates to nanoparticles consisting of 50 to 99.99% by weight of aluminum oxide and 0.01 to 50% by weight of oxides of elements of I. or II.
• the alumina in these mixed oxides is preferably present for the most part in the rhombohedral ⁇ -modification (corundum). Accordingly, the proportion of these mixed oxides of the I. or II. Main group may only be dimensioned so that the corundum lattice remains the claimed nanoparticles.
• the mixed oxides according to the present invention preferably have a crystallite size of less than 1 ⁇ m, preferably less than 0.2 ⁇ m and particularly preferably between 0.001 and 0.09 ⁇ m. Particles of this size according to the invention will be referred to below as nanoparticles.
• the mixed oxides according to the invention can be prepared by different processes described below.
• Such agglomerates can be prepared, for example, by various chemical syntheses. These are usually precipitation reactions (hydroxide precipitation, hydrolysis of organometallic compounds) with subsequent calcination. In this case, crystallization seeds are often added to the
• the desired molecules are obtained from chemical reactions of a Precursorgases or by rapid cooling of a supersaturated gas.
• the formation of the particles occurs either by collision or the constant in equilibrium
• Nanoparticles are formed here by the decomposition of Precursormolekülen in the flame at 1500 ° C - 2500 0 C.
• the use of AICI 3 has so far only produced the corresponding clay.
• large-scale reactor reactors are used for the synthesis of submicroparticles such as carbon black, pigmented TiO 2 , silicic acid and alumina. Small particles can also be formed from drops with the help of centrifugal force, compressed air, sound, ultrasound and other methods.
• the drops are then converted into powder by direct pyrolysis or by in situ reactions with other gases.
• spray and freeze drying should be mentioned.
• precursor drops are transported through a high temperature field (flame, oven), resulting in rapid evaporation of the volatile component or initiating the decomposition reaction to the desired product.
• the desired particles are collected in filters.
• the production of BaTiO 3 from an aqueous solution of barium acetate and titanium lactate can be mentioned here.
• grinding may also be trying to crush corundum and thereby generate ⁇ crystallites in the nano Bereicrrzu.
• the best grinding results can be achieved with stirred ball mills in a wet grinding.
• grinding beads must be used from a material that has a greater hardness than corundum.
• the nanoparticles must be released. This is preferably done by grinding or by treatment with ultrasound.
• this deagglomeration in the presence of a solvent and a coating agent preferably takes place of a silane which, during the milling process, saturates the resulting active and reactive surfaces by a chemical reaction or physical attachment, thus preventing reagglomeration.
• the nano-mixed oxide remains as small Obtained particles. It is also possible to add the coating agent after deagglomeration.
• agglomerates are used which, as described in Ber. DKG 74 (1997) no. 11/12, pp. 719-722, as previously described.
• the starting point here is aluminum chlorohydrate, which has the formula Al 2 (OH) x Cl y, where x is a number from 2.5 to 5.5 and y is a number from 3.5 to 0.5 and the sum of x and y is always 6 amounts to.
• This aluminum chlorohydrate is mixed with crystallization seeds as an aqueous solution, then dried and then subjected to a thermal treatment (calcination).
• aqueous solutions Preferably, one starts from 50% aqueous " solutions, as they are commercially available. Such a solution is mixed with nuclei which promote the formation of the ⁇ -modification of Al 2 O 3 . In particular, such nuclei cause a lowering of the temperature for the formation of the ⁇ -modification in the subsequent thermal treatment.
• nuclei As germs are preferably in question finely disperse corundum, diaspore or hematite. It is particularly preferable to use finely divided ⁇ -Al 2 O 3 -KeJiOe having an average particle size of less than 0.1 microns. In general, 2 to 3 wt .-% of germs based on the resulting alumina from.
• This starting solution additionally contains oxide formers in order to produce the oxides MeO in the mixed oxide.
• oxide formers especially the chlorides of the elements of the I. and II. Main group of the Periodic Table, in particular the
• the amount of oxide generator is such that the finished nanoparticles contain 0.01 to 50% by weight of the oxide Me.
• the oxides of the I. and II. Main group can be present as "" separate PhasePneberfdem A ⁇ umini ⁇ mox ⁇ d or with this real mixed oxides such as spinels, etc. form.
• the term "mixed oxides" in the context of this invention should be understood to include both types. This suspension of aluminum chlorohydrate, germs and oxide formers is then evaporated to dryness and subjected to a thermal treatment (calcination).
• This calcination is carried out in suitable devices, for example in push-through, chamber, tube, rotary kiln or microwave ovens or in a fluidized bed reactor.
• suitable devices for example in push-through, chamber, tube, rotary kiln or microwave ovens or in a fluidized bed reactor.
• the temperature for the calcination should not exceed 1400 ° C.
• the lower temperature limit depends on the desired yield of nanocrystalline oxide, on the desired residual chlorine content and the content ⁇ to ⁇ germs.
• the formation of the nanoparticles begins ⁇ ⁇ ⁇ ⁇ 500 ° C, however, in order to keep the chlorine content low and the yield of nanoparticles high, but you will work preferably at 700 to 1100 0 C, in particular at 1000 to 1100 ° C. ,
• agglomerates accumulate in the form of nearly spherical nanoparticles. These particles consist of Al 2 O 3 and MeO. The content of MeO acts as an inhibitor of crystal growth and keeps the crystallite size small. " As a result, the resulting nanoparticles, as obtained by the above-described calcination-preserving agents, clearly differ from the particles as obtained in the processes described in DE 199 22 492, WO 2004/089827 and WO 02/08124.
• the agglomerates are preferably comminuted by wet grinding in a solvent, for example in an attritor mill, bead mill or stirred mill.
• nanoparticles which have a crystallite size of less than 1 .mu.m, preferably less than 0.2 .mu.m, more preferably between 0.001 and 0.9 microns.
• the described method shows significant advantages, since the mixed oxides according to the invention form significantly softer agglomerates, which has a positive effect on the time required for deagglomeration and the wear in the mill. For example, after six hours of grinding, a suspension of nanoparticles with a d90 value of approximately 50 nm is obtained. Another possibility for deagglomeration is the use of ultrasound.
• Suitable solvents for deagglomeration are both water and alcohols and other polar solvents which are able to stably take up the released nanoparticles.
• an inorganic or organic acid such as HCl, HNO 3 , formic acid or acetic acid should be added to stabilize the resulting nanoparticles in the aqueous suspension.
• the amount of acid may be 0.1 to 5 wt .-%, based on the mixed oxide.
• Another possibility is to use nanoparticles by adding acrylates,
• Centrifuging be separated.
• the resulting fine fractions may then be dried by, e.g. by lyophilization, be converted into easily redispersible nanopowder.
• the deagglomeration by grinding or supply of ultrasonic energy is preferably carried out at temperatures of 20 to 100 ° C, more preferably at 20 to 90 ° C. Examples:
• Magnesium chloride mixture was crushed in a mortar, resulting in a coarse powder.
• the powder was calcined in a rotary kiln at 1050 0 C.
• the contact time in the hot zone was a maximum of 5 min.
• a white powder was obtained whose grain distribution corresponded to the feed material.
• a 50% aqueous solution of aluminum chlorohydrate was added with calcium chloride so that after calcination the ratio of alumina to calcium oxide is 99.5: 0.5%.
• the solution 2% nuclei are added to a suspension of Feinstkorund. After the solution has been homogenized by stirring, the drying is carried out in a rotary evaporator. The solid aluminum chlorohydrate-calcium chloride mixture was crushed in a mortar to form a coarse powder.
• the powder was calcined in a rotary kiln at 1050 ° C.
• the contact time in the hot zone was a maximum of 5 min.
• a white powder was obtained whose grain distribution corresponded to the feed material.
• An X-ray structure analysis shows that predominantly ⁇ -alumina is present.
• the images of the SEM image taken showed crystallites in the range 10 - 80 nm (estimate from SEM image), which are present as agglomerates.
• the residual chlorine content was only a few ppm.
• this calcium oxide-doped corundum powder were suspended in 160 g of water.
• the suspension was desagglomehert in a vertical stirred ball mill from. Netzsch (type PE 075).
• the grinding beads used consisted of zirconium oxide (stabilized with yttrium) and had a size of 0.3 mm.
• the pH of the suspension was monitored every 30 min and quenched by addition of dilute nitric acid to a pH of 4 to 4.5 h ⁇ t ⁇ fT7Nä ⁇ n ⁇ 6 ' ⁇ StirnlJel1 wIfräe ⁇ ie "Sü ⁇ pensiöTTvon derTMähipefle ⁇ separated and using an analytical Disc centrifuge from the company Brookhaven characterized with regard to particle size distribution. A d90 of 77 nm, a d50 of 55 nm and a d10 of 25 nm were found. The nanosuspension from the Mixed oxides are thus much finer than comparable suspensions of pure ⁇ -alumina.

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• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Oxygen, Ozone, And Oxides In General (AREA)

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• 2006
  • 2006-07-13 US US11/988,711 patent/US20090041656A1/en not_active Abandoned
  • 2006-07-13 ES ES06776216.1T patent/ES2677894T3/es active Active
  • 2006-07-13 EP EP06776216.1A patent/EP1907323B1/de not_active Not-in-force
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