Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
  • C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
  • C04B35/589—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride obtained from Si-containing polymer precursors or organosilicon monomers
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/12—Organo silicon halides
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
  • C07F7/02—Silicon compounds
  • C07F7/08—Compounds having one or more C—Si linkages
  • C07F7/12—Organo silicon halides
  • C07F7/121—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20
  • C07F7/127—Preparation or treatment not provided for in C07F7/14, C07F7/16 or C07F7/20 by reactions not affecting the linkages to the silicon atom

Definitions

• the present invention relates to a process for the preparation of silylalkylboranes with the structural feature Si-CB, new molecular silylalkylboranes, new molecular silylalkylborazines, new oligo- and polyborocarbosilazanes, a process for their preparation and their use, and high-carbon silicon boron carbide nitride ceramics and a process for their production ,
• non-oxidic multinary ceramics via the cross-linking of molecular precursors is of outstanding importance. Ceramic materials of high purity and with a homogeneous element distribution at the atomic level can currently only be produced in this way. Via conventional synthetic routes, e.g. Solid state reaction, such materials are not accessible.
• the nitride and carbide nitride ceramics with boron and silicon have become particularly important. They have high thermal stability and resistance to oxidation and show a pronounced inhibition of crystallization.
• the thermal resistance of the ceramics in this quaternary system can be increased by the additional incorporation of carbon in the ceramic network.
• Such materials are outstandingly suitable for high-temperature use under atmospheric conditions and can be used as bulk material, as ceramic fibers in composite materials, in the form of coatings or for microstructure processes.
• Patent DE 4 1 07 1 08 A1 describes the synthesis of the one-component precursor trichlorosilylaminodichloroborane (TADB, CI 3 Si-NH-BCI 2 ) which, after crosslinking with methylamine and subsequent pyrolysis in an inert gas stream, leads to a ceramic of the approximate composition SiBN 3 C. The carbon it contains comes from the methyl group of the cross-linking reagent methylamine.
• TADB trichlorosilylaminodichloroborane
• a disadvantage of this method is the low possibility of varying the carbon content, which can only be controlled here by a longer alkyl group in the crosslinking reagent.
• this alkyl group is lost in the form of volatile hydrocarbons during pyrolysis or leads to undesirable graphite deposits in the ceramic.
• Patent W098 / 45302 describes the production of high-carbon ceramics in the Si / B / N / C system from a one-component precursor which has a branched carbon bridge between the elements boron and silicon. In this way, more carbon-rich ceramics can be synthesized.
• a disadvantage of this process is that the one-component precursors have an alkyl group on the carbon bridge, which can be lost in the form of volatile hydrocarbons during pyrolysis.
• Another object was to provide amorphous Si / B / N / C ceramics with improved high temperature and oxidation resistance. This object is achieved according to the invention by a process for the preparation of a compound of the formula (I):
• R each independently represents a hydrocarbon with 1 to 20 C atoms, hydrogen, halogen, NR'R “or OR ', where R' and R" independently of one another represent hydrogen or a hydrocarbon with 1 to 20 C atoms and R 1 and R 2 independently represent a hydrocarbon with 1 to 20 C atoms, hydrogen, halogen, NR'R “or OR ', where R' and R" independently represent hydrogen or a hydrocarbon with 1 to 20 C atoms.
• X is halogen, reacted with a metal M, for example an alkali metal such as Na, K and in particular Li, an alkaline earth metal, in particular Mg, or a transition metal such as Cu, Zn, Cd, Hg.
• a metal M for example an alkali metal such as Na, K and in particular Li, an alkaline earth metal, in particular Mg, or a transition metal such as Cu, Zn, Cd, Hg.
• the radicals R, R 1 , R 2 , R 'and R can each independently represent a hydrocarbon radical with 1 to 20 C atoms, preferably with 1 to 10 C atoms.
• a hydrocarbon radical is a radical which is formed from the elements carbon and hydrogen. According to the invention, the hydrocarbon radical can be branched or unbranched, saturated or unsaturated. The hydrocarbon radical can also contain aromatic groups, which in turn can be substituted by hydrocarbon radicals. Examples of preferred hydrocarbon radicals are, for example, unbranched saturated hydrocarbon radicals.
• radicals R can also be branched saturated hydrocarbons, in particular branched C 1 -C 20 -alkyls, such as i-propyl, i-butyl, t-butyl, and further branched alkyl radicals.
• the radical R comprises one or more olefinically unsaturated groups.
• radicals examples include vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, butadienyl, pentadienyl, hexadienyl, heptadienyl, octadienyl, nonadeinyl and decadienyl.
• the radical R can also contain an alkyne group, ie a C C C bond.
• At least one radical R and preferably all radicals R contain an aromatic group, in particular an aromatic radical having 5 or 6 carbon atoms, such as a phenyl group or a phenyl group substituted by a hydrocarbon, such as methylphenyl, dimethylphenyl, trimethylphenyl , Ethylp enyl, or Propylphenyl.
• the aromatic radical preferably comprises from 5 to 20, in particular up to 10, carbon atoms.
• the hydrocarbon radicals R, R ⁇ R 2 , R 'and R can in each case be varied independently of one another.
• At least one radical R, R 1 , R 2 , R' or / and R" comprises and in particular all radicals R, R 1 , R 2 , R 'and / or R "a C, to C 20 - Alkyl group, in particular a CC 6 alkyl group, a phenyl group, a vinyl group or an allyl group or a hydrocarbon radical having 1 to 3 carbon atoms, in particular methyl, ethyl or propyl and most preferably methyl.
• the radical shark stands for a halogen atom and means in particular Cl, Br or I, it being preferred that at least one radical shark and preferably all radicals shark Cl ' .
• the compound (III) can be prepared directly from a compound of the formula (II) with a metal, as described above, if a metal with sufficient reactivity is used, e.g. Li, Na, K, Mg, Cu, Zn, Cd, Hg.
• a metal with sufficient reactivity e.g. Li, Na, K, Mg, Cu, Zn, Cd, Hg.
• the compound (III) wherein M is a metal which is not sufficiently reactive for efficient direct alkylation, e.g. Sn can also be produced in two stages. In the first stage, a compound (IM) is created with a directly reactive metal, which is then "re-metallized" with the non-directly reactive metal in a second stage.
• the metal can be used, for example, in the form of metal chips or preferably as a powder.
• R is as defined above and Y represents halogen, NR'R "or OR ', where R' and R" independently of one another are hydrogen or a hydrocarbon having 1 to 20 carbon atoms. It is also possible to first transfer the silylalkyl radical of the formula (III) to another metal and then to carry out the reaction with the borane.
• R can each independently have the meanings given for the general process, metalized in a Grignard reaction with magnesium powder and then reacted with the haloborane.
• the silane of the general formula (III) is preferably reacted with at least one alkyloxychloroborane YB (R 3 ) (R 3 ' ), in which Y is Cl and R 3 and R 3' independently of one another are a C 1 -C 20 alkoxy or Represent phenyloxy radical.
• the present invention therefore furthermore relates to the reaction of a compound of the general formula (V)
• R, R 1 and R 2 each independently represent hydrogen, halogen, a hydrocarbon radical having 1 to 20 carbon atoms, a radical N (R ') (R ") or a radical OR', in which R" and R 'independently of one another represent hydrogen or a hydrocarbon radical having 1 to 20 carbon atoms, and X denotes halogen.
• R 1 and R 2 each independently represent either hydrogen or halogen.
• the intermediates (R) 3 Si - C (R 1 ) (R 2 ) - B (OR ') (OR ") are separated from the reaction mixture with element chlorides or organic acid halides and in particular with boron trihalides without prior separation to
• the Grignard reaction is carried out using the dilution principle at temperatures below 50 ° C. in an aprotic, organic solvent which can be, for example, an acyclic or cyclic ether or a C 5 -C 8 alkane.
• an aprotic, organic solvent which can be, for example, an acyclic or cyclic ether or a C 5 -C 8 alkane.
• the solvent is removed by distillation and the product is either fractionally distilled at reduced pressure or purified by recrystallization.
• Other purification methods such as high performance liquid chromatography (HPLC) can also be used.
• the invention therefore furthermore relates to silylalkylboranes of the formula (I)
• R each independently represents hydrogen, halogen, a hydrocarbon radical having 1 to 20 C atoms, N (R ') (R ") or OR', where R 'and R" each independently represent hydrogen or a hydrocarbon radical having 1 to 20 C Represents atoms, and R 1 and R 2 each independently represent hydrogen, halogen, N (R ') (R ") or OR', where R 'and R" each independently represent hydrogen or a hydrocarbon radical having 1 to 20 carbon atoms ,
• R is preferably independently of each occurrence C r C 6 alkyl, vinyl, phenyl, hydrogen, halogen, organylamino groups N (R ') (R "), organyloxy groups OR' with R ', R" independently of one another C r C 6 alkyl , Vinyl, phenyl or hydrogen and R ⁇ R 2 independently of one another hydrogen or one of its isotopes or halogen.
• silylalkylboranes of the formula (I) according to the invention are compounds in which the Si
• Hydrocarbon residue are bound.
• Such compounds contain one or two hydrocarbon radicals on the Si atom, so that
• Carbon content of a ceramic made from such compounds can be further increased. Furthermore, such compounds have a reduced proportion of those reactive towards oligomerization or polymerization
• Halogen atoms As a result, oligomers or polymers with a low degree of crosslinking, in particular polymers that are essentially linear, can be produced. Furthermore, compounds of the formula (I) are preferred in which two halogen atoms or one on the boron atom
• Halogen atom and a hydrocarbon radical are bound.
• silanes used as starting products are commercially available.
• the borane used can, according to J. Chem. Soc. (1 957) 501-505 can be prepared from commercially available boranes.
• the invention further relates to silylalkylborazines having the formula (X):
• R each independently represents hydrogen, halogen, a hydrocarbon radical having 1 to 20 C atoms, N (R ') (R ") or OR', where R 'and R" each independently represent hydrogen or a hydrocarbon radical having 1 to 20 C Represents atoms, and R 2 and R 3 each independently represent hydrogen, halogen, N (R ') (R ") or OR', where R 'and R" each independently represent hydrogen or a hydrocarbon radical having 1 to 20 carbon atoms and R 4 each independently represents R 1 , Sn (R *) 3 or Si (R *) 3 , wherein R * each independently represents R 2 or a hydrocarbon radical having 1 to 20 carbon atoms.
• residues preferred or particularly preferred in the present silylalkylborazines correspond to the residues indicated as preferred herein for the silylalkylboranes.
• silylalkylborazines according to the invention are particularly suitable as precursor compounds and, after polymerisation and pyrolysis of the polymers, lead to new amorphous Si / B / N / C ceramics with improved, previously indi cate systems, high temperature and oxidation resistance. These new ceramics show practically none Loss of mass up to at least 2000 ° C or / and are stable to oxidation in pure oxygen up to at least 1400 ° C.
• silylalkylboranes according to the invention can be reacted with amines of the type N (R 4 ) 3 or the corresponding ammonium salts HN (R 4 ) 3 + A " to give the silylalkylborazines described, where R 4 each has the meanings given above.
• a " represents any one Anion and is in particular a halide, such as F “ , Cl “ , Br “ or J " , an S0 4 2 " group, a N0 3 " group or a nitrite, chlorate, perchlorate, carbamate, Tartrate, phosphate, pentaborate, chromate, citrate, hydrogen citrate, carbonate, hydrogen carbonate, triflate, acetate or benzoate group.
• a " is preferably a halide, particularly preferably chloride.
• the reaction of the silylalkylboranes with the amines or ammonium salts is preferably carried out with or without a solvent at temperatures between -100 ° C. and 200 ° C., more preferably at temperatures between 20 ° C. and 50 ° C.
• R 4 are each independently hydrogen, halogen, a hydrocarbon radical having 1 to 20 carbon atoms, N (R ') (R "), OR', where R 'and R" are each independently hydrogen or a hydrocarbon radical having 1 to 20 represents carbon atoms, represents Sn (R *) 3 or Si (R *) 3 , where R * each independently has the same meaning as R.
• R 4 are each independently hydrogen, halogen, a hydrocarbon radical having 1 to 20 carbon atoms, N (R ') (R "), OR', where R 'and R" are each independently hydrogen or a hydrocarbon radical having 1 to 20 represents carbon atoms, represents Sn (R *) 3 or Si (R *) 3 , where R * each independently has the same meaning as R.
• These borazines are in the presence of a suitable combination of catalyst, base and acid scavenger (for example a zeolite) with silanes of the above formula (III) or with silanes of the type
• R 1 each independently of one another denotes hydrogen, halogen, a hydrocarbon radical having 1 to 20 C atoms, N (R ') (R ") or OR', in which R 'and R" each independently represent hydrogen or a hydrocarbon radical having 1 represents up to 20 carbon atoms, and R 2 and R 3 each independently represent hydrogen, halogen, N (R ') (R ") or OR', where R 'and R" each independently represent hydrogen or a hydrocarbon radical having 1 to 20 C.
• X denotes hydrogen, halogen, Sn (R *) 3 or Si (R *) 3 where R * each independently has the same meanings as R for the silylalkylborazines.
• the invention also relates to oligo- and polyborocarbosilazanes obtainable from the molecular silylalkylboranes or silylalkylborazines according to the invention, characterized in that in the first coordination sphere each silicon atom has at least one carbon atom and this is bound to a boron atom, this boron atom being additionally bound to two nitrogen atoms.
• the oligo- or polyborocarbosilazanes have in particular the structural units Si-CBNBC-Si, Si-CBN-Si-C-Boder / and BC-Si-N-Si-CB on.
• the structural features given are - for better clarity - linear sequences, with Si of course always bound to four neighboring atoms, B and N always bound to three neighboring atoms and C each to three or four neighboring atoms.
• the corresponding hyphens have been omitted for clarity, but can be easily read by the person skilled in the art. Branches can occur on any atom.
• the invention also relates to a process for the preparation of such an oligo- or polyborocarbosilazane, in which a silylalkylborane of the formula (I) or a silylalkylborazine of the formula (X) with a compound R'R "NH, where R ', R" are each independent Hydrogen or a hydrocarbon radical having 1 to 20 carbon atoms, is reacted at temperatures from -100 ° C to 300 ° C.
• the oligo- or polyboro carbosilazanes can also be formed from the precursor compounds, in particular the abovementioned silylalkylboranes or silylalkylborazines, by direct polymerization of the one-component precursors, in particular by polycondensation at temperatures between -100 ° C. and 500 ° C. , The use of ammonia and / or amines is not necessary for direct polymerization.
• the invention also relates to a process by means of which the theological properties of the oligo- or polyborocarbosilazanes, which are obtained in the form of liquid, viscous or solid, partly soluble and meltable polymers, can be adjusted with ammonia or by heat treatment.
• the degree of crosslinking of the oligo- or polyborocarbosilazanes can be adjusted by the type of polymer formation.
• ammonia or amines are used, highly cross-linked structures are formed, while predominantly linear structures are obtained in direct polymerization by temperature treatment, for example at ⁇ 500 ° C., preferably at ⁇ 300 ° C.
• temperature treatment for example at ⁇ 500 ° C., preferably at ⁇ 300 ° C.
• oligo- or polyborocarbosilazanes with different, desired rheological properties can be produced in a targeted manner or the rheological properties of oligo- or polyborocarbosilazanes can be modified by an appropriate aftertreatment.
• the oligo- or polyborocarbosilazanes are obtained in the form of liquid, viscous or solid, partly soluble and meltable polymers, which can be subjected to various molding processes, e.g. B. casting, spinning into fibers, drawing of films, production of coatings by various coating processes such as dip (“dip-coating”) or centrifugal coatings ("spin-coating”) before they are converted to silicon boron carbide nitride ceramics, for example.
• Another object of the invention is a method for producing a silicon boron carbide nitride ceramic, in which an oligo- or polyborocarbosilazane according to the invention with the structural element Si-CB (N) -N or a silylalkylborane of the formula (I) or a silylalkylborazine of the formula (X) in pyrolyzed in an inert or ammonia-containing atmosphere at temperatures between -200 ° C and + 2000 ° C and then calcined in an inert or ammonia-containing atmosphere at temperatures between 800 ° C and 2000 ° C.
• the inert atmosphere can be selected from an inert gas atmosphere, for example an argon or helium atmosphere, a nitrogen atmosphere or an atmosphere from another inert gas which does not react with the reactants under the reaction conditions between 800 ° C and 1700 ° C.
• the oligo- or polyborocarbosilazanes are heated for several hours at temperatures between 30 and 1000 ° C. They are then preferably calcined in a nitrogen or argon atmosphere to remove hydrogen at temperatures between 1200 and 1600 ° C., with preferred heating rates of 1-100 K / min.
• the invention also relates to silicon boron carbide nitride ceramics produced by the process described above from the oligo- or polyborocarbosilazanes according to the invention.
• These ceramics preferably contain the N-Si-C-B-N structural element and in particular the structural unit Si-C-B-N-B-C-Si, Si-C-B-N-Si-C-B or / and B-C-Si-N-Si-C-B.
• the ceramics according to the invention can be obtained in the pyrolysis both crystalline and amorphous. It is preferably a silicon boron carbide nitride powder. Because of the particularly advantageous properties, ceramics are preferred in which the elements N, Si, C and B are present in an amount of more than 93% by weight, in particular more than 97% by weight.
• the ceramic according to the invention in particular has a low oxygen content of ⁇ 7% by weight, preferably ⁇ 3% by weight and in particular ⁇ 1% by weight or ⁇ 0.5% by weight.
• the crystallization of the amorphous material into a composite ceramic with at least one of the materials SiC, Si 3 N 4 , BN, C and B 4 C can be carried out by Storage at a temperature higher than 1 400 ° C.
• the constituents are essentially completely homogeneously distributed on the nanometer scale, that is to say they are present in a monodisperse distribution.
• the composite ceramics according to the invention are particularly notable for their high temperature resistance and can be wholly or partly crystalline, in particular as a powder.
• the oligo- or polyborocarbosilazanes, ceramics and composite ceramics can be used for the production of ceramic powders, ceramic coatings, ceramic moldings, ceramic foils, ceramic fibers or ceramic microstructures.
• silylalkylboranes, oligo- and polyborocarbosilazanes according to the invention can be used in chemical vapor deposition (CVD) or physical vapor deposition (PVD). Ceramic coatings or coatings can be produced by coating substrates using CVD or PVD.
• the gas phase deposition can be carried out as described in the prior art (see e.g. DE 1 96 358 48).
• Microstructures can be created, for example, by injection molding or lithographic processes.
• the ceramics are suitable for the production of composite materials.
• the ceramics are particularly preferably produced in the form of fibers, from which, for example, fabrics or braids are made, which can be used as fillers to increase the strength or toughness of other ceramics.
• the present invention further provides a process for the preparation of a compound of the formula (I)
• R represents a hydrocarbon having 1 to 20 C atoms, hydrogen, halogen, N (R ') (R ") or O (R'), where R 'and R" independently of one another are hydrogen or a hydrocarbon having 1 are up to 20 C atoms and R 1 and R 2 are independently hydrogen, halogen or a hydrocarbon with 1 to 20 C atoms.
• R in each case independently of one another is a hydrocarbon having 1 to 20 carbon atoms, hydrogen, halogen, N (R ') (R ") or O (R'), where R 'and R "independently of one another are hydrogen or a hydrocarbon having 1 to 20 carbon atoms.
• the present invention further provides a process for the preparation of a compound of the formula (I)
• each independently of one another represents a hydrocarbon having 1 to 20 C atoms, hydrogen, halogen, N (R ') (R ") or O (R'), where R 'and R" independently of one another are hydrogen or a hydrocarbon with 1 to 20 C atoms and R 1 and R 2 independently of one another are hydrogen, halogen or a hydrocarbon with 1 to 20 C atoms, characterized that a CH-acidic compound of the general formula (VIII)
• R is as defined above and X represents halogen, NR'R "or OR ', where R' and R" independently of one another are hydrogen or a hydrocarbon having 1 to 20 C atoms.
• An acidic ion exchanger or a zeolite can in particular be used as the acid scavenger in both of the above-mentioned processes.

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• 2001
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