JP2002500157A - Non-oxide ceramics with surface coating - Google Patents

Abstract

  (57) [Summary] The invention is based on BN having an average primary particle size of 0.1 to 50 nm, the surface of which is coated with at least one α-amino acid, or the elements Ti, Zr, Hf, Cr, Mo, W, V, Nb. The present invention relates to a non-oxide ceramic comprising a group of carbides, nitrides, borides and silicides of Ta, Si, Ge and Sn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a non-oxide ceramic, a material whose surface is coated with at least one α-amino acid, a method for producing the same, and a ceramic sintered material thereof (
The invention relates to ceramic sintered materials and their use for the production of layers.

[0002]

[Prior art]

According to EP-A-650,954, it has already been described that ceramic powders are used for the production of ceramic sintered materials and layers. However, they still have some disadvantages with regard to their processing properties, such as the redispersibility and the product properties of the products produced therefrom.

[0003] For example, if a suspension of these ceramic powders is used, they then sufficiently solidify the molded items.
2 shows a high degree of agglomeration of the primary particles, which means that a high sintering temperature is required for the compact.

The average primary particle diameter is 0.1 to 50 nm
From BN whose surface is coated with at least one α-amino acid and from the elements Ti, Zr, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge
And non-oxide ceramics comprising the group of carbides, nitrides, borides and silicides of Sn.

[0005] A surface coating is understood to mean that the α-amino acids are chemically or physically attached to the surface of the ceramic.

[0006] Suitable non-oxide ceramics are TiN, ZrN, TiC or SiC, especially TiN or TiC.

[0007] The surface-coated non-oxide ceramic is preferably a powder.

In the context of this application, an α-amino acid comprises an amino group and a carboxylic acid group bonded to the same carbon atom and has the formula

[0009]

Embedded image

[0010] Compounds with structural components of are understood.

In a preferred embodiment, the ceramic of the present invention is coated with an aliphatic α-amino acid. Arginine, cysteine, ornithine, citrulline, lysine, aspartic acid and asparagine can be mentioned as particularly preferred.

However, aromatic α-amino acids such as tyrosine, especially L-tyrosine, and heterocyclic α-amino acids are also useful.

The L-form of these amino acids is commonly used.

In a preferred embodiment, the ceramic of the present invention has a primary particle size of 0.5 to 30 nm.

[0015] The present invention also provides BN having an average primary particle diameter of 0.1 to 50 nm and carbides of the elements Ti, Zr, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge and Sn, Non-oxide ceramics consisting of a group of nitride, boride and silicide,
At least one α-amino acid in water and / or in an organic solvent at 20 to 150 ° C.
And then dried (in some cases, after filtration) at a temperature of less than 1 ° C., which is a non-oxide ceramic.

Non-Oxide Ceramics Used The average particle size of the non-oxide ceramics used in the method of the present invention can be measured using an electron micrograph. They are preferably from 0.1 to 50 nm, in particular from 0.5 to 30 nm. Primary particles of non-oxide ceramics preferably have a spherical structure.
They may also be their aggregates or aggregates (agg
regates) in which they are less than 500 nm,
Preferably the average particle size is less than 150 nm.

The non-oxide ceramic used may be crystalline or amorphous, and is preferably crystalline. These are described, for example, in US Pat. No. 5,472,47.

[0018]

[Outside 1]

It is obtained by the method. CVR (chemical vapor reaction)
reaction)) method is preferably used here, whereby particles of a very narrow particle distribution having a size not containing larger than granules and of high purity can be produced.

The characteristics of the non-oxide ceramics produced in this way are preferably in the form of their powder, but are completely free of individual particles (primary particles) substantially larger than the average particle diameter. (Lack). Thus, the powder preferably contains less than 1% of individual particles that differ from the average particle size by more than 20% and there are substantially no particles that differ by more than 50%.

The non-oxide ceramics used in the method of the present invention may be present in the form of their primary particles, aggregates or aggregates of primary particles or mixtures of the two. Aggregates or agglomerates are those in which several particles interact with each other via van der Waals forces or in which primary particles bind together during a preliminary step due to surface reactions or "sintering" Is understood.

The non-oxide ceramics used may have an extremely low oxygen content of less than 10% by weight, preferably <1% by weight, in particular <0.1% by weight, based on the solid.

[0023] Their high purity and surface purity are also characteristic. Depending on the method of manufacture, the non-oxide ceramics used are sensitive to air or pyrophoric.
ric). To remove this property, the non-oxide ceramics may be surface modified or oxidized or passivated in a defined manner by treating with a gas / vapor mixture prior to use in the method of the present invention. (Passivated).

Non-oxide ceramics in which the concentration of —O ⁻ NH ₄ ⁺ groups of the non-oxide ceramic is 50 to 1000, preferably 50 to 500, in particular 100 to 500 μeq / g, are particularly preferred in the process according to the invention. Used for

Therefore, the present invention relates to a method for producing a non-oxide ceramic from BN having an average primary particle size of 0.1 to 50 nm and a concentration of —O ^— NH ₄ ⁺ groups of 50 to 1000 μeq / g as well as the element Ti. , Zr, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge
And a non-oxide ceramic comprising the group of carbides, nitrides, borides and silicides of Sn.

The NH ₄ ⁺ groups are preferably located on the surface of the ceramic.

The ceramics of the present invention, ie those containing —O ^— NH ₄ ⁺ groups and containing α-amino acids, also preferably have one atom for all atoms present in the 5 nm thick surface layer of the ceramic particles. It has a Cl content of less than atomic%.

[0028] External particle layers of suitable thickness can be investigated, for example, using ESCA (electron spectroscopy for chemical analysis), in particular by XPS (X-ray photoelectron spectroscopy).

The —O ^— NH ₄ ⁺ group can be produced, for example, by reacting an —OH group on a ceramic surface with aqueous ammonia. For those parts,
H groups are obtained, for example, by oxidation or passivation of ceramic particles produced by the CVR method with an oxygen-containing gas. This produces a monomolecular oxide layer containing hydroxyl groups on the ceramic surface. The number of -OH groups is measured, for example, by conductivity titration. The number of —OH groups is, for example, for TiN particles obtained by the CVR method, about 300 μeq / g of the ceramic and the amount of —O ^— NH ₄ ⁺ groups after treatment with ammonia is of the same order. .

Therefore, the present invention also relates to an average primary particle size of from 0.1 to 50 nm and from BN and of the elements Ti, Zr, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge and Sn. Characterized in that at least one non-oxide ceramic of the group of carbides, nitrides, borides and silicides is treated with an aqueous ammonia solution at a temperature of from 20 to 150 ° C., optionally under pressure, The present invention also relates to a process for producing a ceramic containing an O ^- NH ₄ ⁺ group.

The ceramic used for this treatment is preferably obtained by using the CVR method, for example the same method as described in US Pat. No. 5,472,477.

In the CVR method, a gaseous reactant such as TiC for producing TiN is used.
l ₄ and NH ₃ are reacted in the reactor. The product is preferably free of vessel wall reactions (ex.
production). The method is particularly preferably performed in a microtubule reactor (tu).
in a laminar flow of reactants and products in a bulk reactor.

The reactants are then generally introduced into a coaxially arranged reactor. Obstacles are preferably incorporated into the otherwise severely laminar flow to thoroughly mix the reactants. This results in a Karman vortex street (Ka) with limited intensity and spread where sufficient mixing occurs.
rman vortex street).

Strongly very preferably, the reaction medium is suitably obscured by a layer of inert gas in order to avoid adhesion of the reaction partners on the walls of the reactor.

The NH ₃ treatment is preferably performed in an aqueous NH ₃ solution having a strength of 5 to 50% by weight. Particularly preferably, the reaction is performed at a temperature of 40 to 120 ° C.

In another preferred embodiment of this NH ₃ treatment, the treated ceramic is filtered off, optionally washed with water, and then dried.

Suitable drying methods are basically all methods that can be used for removing water. The following equipment, such as a fluidized bed dry
er), paddle dryer, spray dryer (spr)
ay dryer), drying cabinets and vacuum dryers may be used.

The present invention therefore also relates to non-oxide ceramics, preferably in powder form, obtainable by this NH ₃ treatment procedure.

If the process according to the invention for the production of α-amino acid coated ceramics is carried out in an organic solvent or a mixture of solvents, suitable organic solvents which may be mentioned are aliphatic C _1-. C ₄ alcohols such as methanol, ethanol, isopropanol, n- propanol, n- butanol, isobutanol or ter
t-butanol, aliphatic ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone or diacetone alcohol, polyols such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, trimethylolpropane, 100-4000 g / mol, preferably 400 Polyethylene glycol having an average molecular weight of -1500 g / mol, or glycerol, a monohydroxy ether, preferably a monohydroxyalkyl ether, in particular a mono C ₁ -C ₄ -alkyl glycol ether, such as ethylene glycol monoalkyl ether, monoethyl diethylene glycol monomethyl Ether or diethylene glycol monoethyl ether, diethylene glycol monobutyl ether , Dipropylene glycol monoethyl ether, thiodiglycol, triethylene glycol monomethyl ether or monoethyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-pyrrolidone, N-vinyl-pyrrolidone, 3-dimethyl-imidazolidone, dimethylacetamide and dimethylformamide. Mixtures of the solvents mentioned are also suitable.

The process of the present invention is preferably carried out at atmospheric pressure at a temperature from 60 ° C. to the boiling point of the particular solvent system used. The process is particularly preferably carried out under reflux. The method may be carried out at elevated temperature, with the application of an external pressure, in particular 2-10 bar.

The process according to the invention is particularly preferably carried out in water or an aqueous mixture of solvents.

Wet grinding of the ceramics used with at least some α-amino acids (
Wet-milling may also take place before or during the process of the invention, for example in a 2-roller milling device. Ceramics used in powder form or in the form of a water-moist compacted cake with some α-amino acids and water, preferably deionized water, may be used, for example, in stirred tanks, dissolvers and similar. With the aid of the apparatus, optionally after a pre-crushing procedure, it is generally beaten to obtain a uniformly ground suspension (ie, introduced and homogenized).

The milled suspension may contain some proportion of a low boiling solvent (boiling point <150 ° C.), which may optionally be removed by evaporation during the course of the subsequent milling procedure Is also good. However, it may also contain some proportion of high-boiling solvents or other additives, such as grinding aids, defoamers or wetting agents.

Wet-crushing of the ceramics used includes both pre-crushing and milling. The suspension concentration is preferably above that required for the final production stage. The required final concentration of solids is preferably prepared after the wet crushing procedure. After pre-crushing, grinding is performed to give the desired fine particle distribution. For example, compounders, roll mills, compounding screws, ball mills, rotor-stator mills, dissolvers, corundum disc mills, vibratory mills and 0.1-2 mm diameters Apparatus such as a stirred ball mill of particularly high speed, continuous or batch operation, comprising milling balls of the type described above are suitable for this milling procedure. The grinding balls may be made of glass, ceramic, or metal, such as steel. The milling temperature is preferably in the range of from 20 to 150 ° C., but is generally at room temperature and is optionally (op) optionally also used as a dispersant (grinding aid).
tional) It may be below the turbidity point of the surface active compound.

The α-amino acid is preferably 0.1 to 20 based on the amount of ceramic used.
Used in amounts by weight. An amount of 1 to 10% by weight is particularly preferably used.

After the process according to the invention, the excess α-amino acids may optionally be removed, for example by filtration of the surface-coated ceramics.

The excess α-amino acid may also be removed, for example, by centrifuging the suspension and then decanting the supernatant. Membrane filtration or microfiltration (microf
The illumination method is also suitable.

The surface-coated ceramics obtained by the process according to the invention, which are still wet, ie water-wet or solvent-wet, are subsequently dried. 20 to 150 ° C,
In particular, a drying temperature of 50-120 ° C is preferably used, where the use of reduced pressure is useful.

Drying can be suitably performed using a conventional drying apparatus such as a paddle dryer, a drying cabinet, a spray dryer, a fluidized bed dryer and the like. The residual water content after drying is preferably less than 2% by weight with respect to the ceramic.

The surface-coated ceramics obtained according to the invention are preferably produced as powders.

The ceramics according to the invention are preferably used for the production of ceramic composite materials consisting of non-oxide and / or oxide components, preferably in the form of their aqueous or solvent-containing suspensions. The suspension may be used in the production of a metal composite.

The invention therefore also relates to the surface-coated ceramics of the invention and to a suspension comprising water and / or an organic solvent.

The suspension according to the invention preferably comprises from 5 to 50% by weight, in particular from 10 to 35% by weight, based on the suspension, of an α-amino acid-coated ceramic according to the invention, from the suspension. From 50 to 95% by weight, in particular from 65 to 90% by weight, of water and / or organic solvents and optionally other additives.

Suitable other additives include, for example, cationic, anionic, amphoteric, and / or
Or non-ionic dispersants, such as the publication "Surfactants Europe, a collection of effective surfactants in Europe (Surfactants Europa,
A Directory of Surface Active Agent
s available in Europe "(Gordon Hollis (Gor
don Hollis), Royal Society of Chemis
try, Cambridge (1995)) and also pH regulators such as NaO
H, ammonia, aminomethylpropanol and N, N-dimethylaminoethanol.

Particularly preferred aqueous suspensions of the ceramics according to the invention have a pH of 7-10, in particular 8
-9 of these things. These aqueous suspensions are particularly preferably prepared by means of a slip casting method, with a green material.
ial) and layers. These green materials are then sintered to obtain a composite with improved mechanical properties.

Layers can also be prepared from the aqueous suspensions of the present invention by immersion or spreading. Layers produced in this way can be used, for example, for abrasion or cutting, drilling and milling of metals and ceramics.
ling) improve the material. Furthermore, an improved anti-corrosion layer can be achieved by this method.

Solvent-containing suspensions are preferably used for the pigmented plastics material.

The invention therefore also features that the ceramics of the invention surface-coated with α-amino acids are suspended in water and / or one or more organic solvents, preferably in the form of a powder. The present invention also relates to a method for producing the suspension of the present invention.

In a preferred embodiment of the method, the dispersion takes place in water, preferably in the presence of pH 7-10, especially NH ₃ . Dispersion can suitably be carried out using conventional equipment, such as a rotor-stator mixer, an ultrasonic device, a jet disperser or a high-pressure homogenizer.

The suspension containing the organic solvent is preferably prepared by adding the organic solvent to the aqueous suspension and removing the water by a suitable method, for example by distillation.

The present invention also provides a suspension of the present invention, optionally with another ceramic powder or ceramic suspension, before and after removal of the water and / or solvent dispersant, a green material or layer. Performing a manufacturing process and then sintering,
The present invention relates to a method for producing a ceramic sintered material.

In this connection, suitable further ceramics are, for example, those with a particle size of up to several μm. Al ₂ O ₃ , TiC, SiC and Si ₃ N ₄ can be mentioned especially as ceramics. Mixtures of these ceramics are outstandingly suitable for producing ceramic sintered materials or layers.

The ceramic suspension and the dried surface-coated ceramic powder obtained by the method of the present invention can be further processed in various ways for the purpose of producing green or sintered materials or layers. it can. For example, an extrusion material can be manufactured by sintering after extrusion to provide the final material. In this case, usually 20 to 80, preferably 30 to 70 and especially 4
0 to 60 parts by weight of a ceramic powder according to the invention (in itself or for example in the form of a suspension as described above), 10 to 70, preferably 20 to 60 and especially 30 to 5
0 parts by weight of dispersant medium and from 0.5 to 20, preferably 2 to 15, in particular 5
From 10 to 10 parts by weight of additives selected from binders, plasticizers and mixtures thereof are used per 100 parts by weight of the extruded material.

The binders and plasticizers mentioned are preferably modified celluloses (eg methylcellulose, ethylcellulose, propylcellulose and carboxy-modified cellulose), polyalkylene glycols (preferably having an average molecular weight of from 400 to 50,000, in particular Polyethylene glycol and polypropylene glycol), dialkyl phthalates (eg dimethyl phthalate, diethyl phthalate, dipropyl phthalate and dibutyl phthalate) and mixtures of these substances. Obviously, other binders and plasticizers such as polyvinyl alcohol can also be used.

[0065] The binders and plasticizers mentioned above are required to maintain adequate dimensional stability after the manufacture and molding procedure of the extruded material.

After very thorough stirring of the above-mentioned components (for example in a traditional stirrer), some dispersant is added until the extruded material has the desired solids content (preferably under reduced pressure). It may be removed again. The preferred solids content of the extruded material is at least 30% by volume
In particular, it is at least 40% by volume.

Other suitable molding procedures include electrophoresis, casting, slip compression casting and filter pressing and combinations of electrophoresis and casting, combinations of casting compression and filter pressing, and injection. Molding, fiber spinning
, A combination of gel casting and centrifuging. Dense mold articles of high basic density
Moulded items are obtained using these molding methods. Similarly,
It is also possible to use suspensions for coating purposes. Suitable coating methods include, for example, immersion, spin coating, doctoring, paint (
painting) and electrophoresis. Suitable substances are, for example, metals, ceramics, cemented carbides, glass and cement.

The green material or layer produced may then be dried and subjected to a sintering process. Surprisingly, it has been shown that the required compression occurs at relatively low temperatures. Even more surprisingly, no sintering aid was required. Sintering temperatures typically range from 0.4 to 0.6 of the melting or decomposition temperature. This is the usual temperature is about the melting or decomposition temperature, and the sintering aids and possibly pressure are also much lower than those disclosed in the prior art where required.

The resulting ceramic sintered material or layer has a particle size of less than 100 nm,
It is characterized as a nanoscale structure with a density of 95% and a high degree of hardness.

The ceramic sintered mold article of the present invention can be used for, for example, the following. -Bulk ceramics, for example grinding powder. -Decorative purposes, wear protection, tribological application
coatings for metals, ceramics and glasses, as corrosion protection, especially as a layer on cutting tools and for abrasives or grinding powders. -Components of the ceramic / ceramic composite. Al ₂ O ₃ , TiC, SiC and S
i3N4 is particularly suitable as a matrix material. -Components of the nanocomposite. -Sintering aids for coarse ceramics. Metal / ceramic composites in hard substance form. -Cermet. -For filtration purposes, e.g. micro / ultra / nan
o) —Pore layer for filtration and reverse osmosis.

[0071]

【Example】

The following examples serve to further illustrate the invention but do not limit it in any way.

Example 1 2 g of L-arginine was dissolved in 250 ml of a solvent mixture consisting of ethanol / water (1: 1). 10 g of solid TiN (U.S. Pat. No. 5)
, 472, 477, prepared by the CVR method according to the method of CVR, with a primary particle distribution of 0.5 to 30 nm), into this solution intensely mixed (magnetic stirrer) with inportion. )added. The suspension was heated under reflux (heating block) for 5 hours at a temperature of 90-100 ° C. Thereafter, the suspension was poured to a pore size of 0.45 μm and a glass frit.
Suction filtration through a round filter consisting of cellulose acetate / cellulose nitrate (frit) and washing with deionized water. Thereafter, the filter cake was dried in a drying cabinet at 70 ° C. for 10 hours.

5 g of the TiN powder thus modified were taken up in 50 ml of water and the pH was adjusted to 9 with a dilute ammonia solution. The suspension is then subjected to an ultrasonic device (ultraso).
nic finger (power: 200 watts) for 5 minutes.

To characterize the particles in the suspension, an aliquot was diluted with the above solution and the average particle size of the TiN was measured using the dynamic light scattering method (scattered light distribution). . A value of 145 nm was measured. The following mass distribution values were measured using ultracentrifugation (mass distribution).

[0075]

[Table 1]

(Note: Here, particles are understood as primary particles and aggregates (or aggregates)).

Example 2 15 g of solid TiN (produced by the CVR method, see Example 1, having a primary particle distribution of 0.5 to 30 nm) at a concentration of 10% (str)
) was added in portions with vigorous thorough mixing (magnetic stirrer) and heated at 80 ° C for 2 hours. Thereafter, the suspension was
And filtered through a round filter consisting of cellulose acetate / cellulose nitrate with a glass frit. Thereafter, the filter cake was dried in a drying cabinet at 70 ° C. for 10 hours.

The Cl content on the surface of the pretreated TiN particles could be reduced from 2.9 to 0.8 atomic%. Analysis was performed using ESCA (electron spectroscopy for chemical analysis) and XPS (X-ray photoelectron spectroscopy).

2 g of L-arginine were dissolved in 250 ml of a solvent mixture of ethanol / water (1: 1).

10 g of solid TiN pretreated with ammonia by the method described above was added to this solution.
Add in portions with strong mixing (magnetic stirrer). The suspension was heated under reflux (heating block) for 5 hours at a temperature of 90-100 ° C. Then the suspension is
. Suction-filtered through a 45 μm pore size and round filter made of glass frit cellulose acetate / cellulose nitrate and washed with deionized water. Thereafter, the filter cake was dried in a drying cabinet at 70 ° C. for 10 hours.

5 g of the TiN powder thus modified were taken up in 50 ml of water and the pH was adjusted to 9 with a dilute ammonia solution. Thereafter, the suspension was sonicated (power: 200).
Watts) for 5 minutes.

To characterize the particles in the suspension, an aliquot was diluted with the above solution and the average particle size of the TiN was measured using the dynamic light scattering method (scattered light distribution). 1
A value of 38 nm was measured. The following mass distribution values were measured using ultracentrifugation (mass distribution).

[0083]

[Table 2]

(Note: Here, particles are understood as primary particles and aggregates).

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Gonzales-Blanco, Euan German Day-50937 Cologne Kerpener Shijtraase 1a F-term (reference) 4G001 BA33 BA38 BB33 BB38 BC02 BC13 4G030 AA50 AA52 GA07 GA16

Claims (11)

[Claims] 2. The method according to claim 1, wherein the average primary particle size is from 0.1 to 50 nm, and the surface is coated with at least one α-amino acid.
, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge and Sn are non-oxide ceramics comprising a group of carbides, nitrides, borides and silicides. 2. The non-oxide ceramic according to claim 1, which is selected from the group consisting of TiN, ZrN, TiC and SiC. 3. The non-oxide ceramic according to claim 1, which is selected from the group consisting of TiN and TiC. 4. The non-oxide ceramics according to claim 1, wherein their surfaces are coated with arginine. 5. An average primary particle diameter of 0.1 to 50 nm, from BN or elements Ti, Zr, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge and Sn.
A non-oxide ceramic comprising a group of carbides, nitrides, borides and silicides of at least one α-amino acid in water and / or an organic solvent at 20 to 150 ° C.
The method for producing a non-oxide ceramic according to claim 1, wherein the non-oxide ceramic is treated at a temperature of and dried (in some cases, after filtration). 6. A BN having an average primary particle diameter of 0.1 to 50 nm and a non-oxide ceramic having a concentration of —O ^— NH ₄ ⁺ groups of 50 to 1000 μeq / g, or an element of Ti, Zr, Hf, Non-oxide ceramics comprising a group of carbides, nitrides, borides and silicides of Cr, Mo, W, V, Nb, Ta, Si, Ge and Sn. 7. Carbides, nitrides of Ti, Zr, Hf, Cr, Mo, W, V, Nb, Ta, Si, Ge and Sn from BN having an average primary particle diameter of 0.1 to 50 nm, The method according to claim 6, wherein at least one non-oxide ceramic consisting of a group of boride and silicide is treated with an aqueous NH ₃ solution at a temperature of 20 to 150 ° C. 8. A suspension comprising at least one non-oxide ceramic according to claim 1 and water and / or an organic solvent. 9. The method for producing a suspension according to claim 8, wherein the non-oxide ceramic according to claim 1 is suspended in water and / or an organic solvent. 10. The suspension according to claim 8, providing a green material or layer before or after removal of the dispersant (water and / or solvent), optionally together with other ceramic powders or suspensions. For producing ceramic sintered materials and layers, characterized in that they are treated and subsequently sintered. 11. A sintered ceramic material or layer obtained by the method according to claim 10.