DE19741459A1 - Polymeric ceramic precursor containing B, N, Si, H and C - Google Patents

Abstract

Polymeric ceramic precursors containing B, N, Si, H and C are prepared by: - (a) reacting a hydridosilylalkylborane component with a compound having at least two NH bonds; and - (b) removing volatile reaction products.- DETAILED DESCRIPTION - The compound containing NH bonds is selected from: - (a) ammonia and/or primary amines; - (b) polysilazanes of formula: R4(Si(R1)(R2)N(R3))nR4(I); and - (c) mixtures of these.- The hydrosilyl alkylborane component has the formula: HpB(-R6-Si(R7)(R8)(R9))3-p (II) - R1 and R2 independently at each occurrence = H, alkyl, alkenyl, alkynyl or optionally polymeric Si-containing residue; - R3 independently at each occurrence = H, Me or Et; - R4 independently = H or optionally substituted alkyl, or two groups R4 together may form a bond; and - n = at least 2; - with the proviso that at least two NH groups are present.- p = 0 or 1; - R6 = optionally cross linked alkylene residue; - R7, R8 and R9 independently at each occurrence = H or alkyl with the proviso that at least one of R7, R8 and R9= H.- INDEPENDENT CLAIMS are included covering: - (a) hydrosilylalkylboranes of formula (II); - (b) polymeric ceramic precursors including a structural element of formula: HpB(R15-Si(R11)(R12)(R13))3-p (III); - (c) a process for making ceramic materials by pyrolysis of the ceramic precursor compounds; - (d) ceramic materials made using the precursors; - (e) composites coated with B-containing polysilazanes (III) or with a ceramic material obtained from the precursor; and - (f) use of the precursor compounds in the preparation of Si-B-C-N ceramics.- p = 0 or 1; - R15 = optionally cross linked alkylene residue; - R11 = H and R12 and R13 independently at each occurrence = H, alkyl or NHR14 in which R14 = an optionally polymeric Si-containing residue; - or R11 = NHR14 and R12 and R13 each independently = H or NHR14; - USE - The ceramic precursor materials can be hot pressed into molded green bodies which are then converted into ceramic parts by pyrolysis treatment, or the ceramic material may be produced in the form of a composite material with a ceramic (precursor) coating layer.TF - TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - The reactants are reacted together: - (i) in the presence of a catalyst selected from bases, Group (VIII) transition metal carbonyl- and olefin complexes and/or Speyers catalyst; - (ii) in an organic solvent medium; and - (iii) at -10 to +30 degreesC.- CERAMICS AND GLASS - Ceramic materials are made by pyrolysis treatment of the polymeric ceramic precursor compound under an inert atmosphere.Preferably before pyrolysis the precursor compound is compacted e.g., by hot pressing at a pressure of at least 10 MPa

Description

The present invention relates to a method for producing polymeric ceramic precursors in the Si-B-C-N system as well as new ones Manufactured boron polysilazanes and their conversion into Ceramic materials.

Ceramics in the Si-B-C-N system are characterized by excellent High temperature stabilities. For example, the thermal Decomposition of Si-C-B-N ceramics generally in the range of more than 1600 ° C and often only at about 2000 ° C and more these ceramics other than materials such as Si-N-C ceramics High temperature materials are superior.

Molecular precursors for Si-B-C-N ceramics are usually described in Salt elimination reactions by aminolysis or ammonolysis containing boron Chlorosilanes or chlorosilylaminodichloroboranes synthesized, with the only chlorinated boron-containing chlorosilanes were used. A disadvantage of these methods is that the reaction is considered as By-product is a salt that can only be separated with great effort can be.

Methods are also known for the synthesis of Si-B-C-N precursors by reacting oligomeric silazanes with borane donor adducts or borazine. In both cases, polymers result in their polymeric Wear scaffolding borazine units.  

European patent application EP-A-0 536 698 describes a method for the preparation of a boron-substituted polysilazane in which the boron of a borane and via bar-carbon bonds to the polysilazane is bound. This bar substituted polysilazane is manufactured by Reacting a borane with a silazane ammonolysis product, which was obtained by reacting ammonia with a halogenated Silicon compound. In the examples there are implementations of such Ammonolysis product with dicyclohexylborane disclosed. One disadvantage of this The process is that the salt formed in the ammonolysis in the product is present and before the formation of Si-B-C-N ceramics with large Effort must be separated. There are polymeric ceramic precursors or precursors in which the boron atoms in the precursor are not are cross-linked, i.e. not with more than one silicon atom Carbon spacers are linked.

German patent application DE-43 20 783 discloses a process for the preparation of boron-containing polysilazanes by ammonolysis of a trisilylborane with the formula B [-C ₂ H ₄ -Si-Cl ₂ X] ₃ , in which X is a chlorine atom or an aliphatic radical with 1- 4 carbon atoms. A disadvantage of this process is again that NH ₄ Cl is formed during the ammonolysis, which has to be separated with great effort in order to produce a high-quality ceramic before further processing of the precursor. This process makes it possible to obtain boron-containing silazanes in which the boron atoms are each connected to 3 silicon atoms via -CH ₂ -CH ₂ - or -CH (CH ₃ ) spacers.

Riedel et al. (Nature: 1996, pages 796-798) describe the production a polymeric ceramic precursor, in a first step Dichloromethyl vinyl silane is reacted with dimethyl sulfide borane after Cleaning is subjected to ammonolysis in a second step and the by-product ammonium chloride is then separated off.  

A disadvantage of this method is that the removal of the salt from the polymeric ceramic precursor is associated with great effort. The polymeric ceramic precursor is characterized by a structure in which the boron atoms are each bonded to 3 silicon atoms via —C ₂ H ₄ spacers, which in turn are bonded to 2 nitrogen atoms and are substituted with a methyl group.

The object of the present invention was to develop a new method to provide for the production of Si-B-C-N precursors in which the Boron atoms are bound to nitrogen atoms via carbon spacers and cross-linked, and in which no difficult to separate Reaction by-products, such as salts, are obtained.

According to the invention, this object is achieved by a process for producing a polymeric ceramic precursor which contains the elements B, N, Si, H and C and which is characterized in that

• (a) a hydridosilylalkylborane component with a component that contains at least two NH bonds,
• (b) separating volatile reaction products and
• (c) the polymeric ceramic precursor wins.

The component containing at least two NH bonds is preferably selected from

• (a) ammonia and / or primary amines,
• (b) polysilazanes containing a structural element of the formula (I)
  R ⁴ [Si (R ¹ ) (R ² ) N (R ³ )] _n R ⁴ (I),
  where R ¹ and R ^{2 are} independently selected at each occurrence from H, alkyl, alkenyl, alkynyl and an optionally polymeric Si-containing radical, R ^{3 is} independently selected at each occurrence from H, CH ₃ and C ₂ H _5, R ⁴ independently of one another are H or an optionally substituted alkyl radical, or two R ⁴ radicals taken together are a bond, and n is an integer ≧ 2, with the proviso that at least two NH groups are present; and
• (c) mixtures thereof.

If the component containing NH groups comprises an amine, im general the use of amines with a low Carbon content preferred. Thus, preferred amines are used for Are suitable for use in the inventive method with a Lower alkyl group-substituted amines such as methylamine, ethylamine, Propylamine and the like. Methylamine is most preferred.

According to the invention, the NH group-containing component can additionally or instead of ammonia and / or the amine mentioned above comprise one or more polysilazanes of the formula (I) mentioned above. Polysilazanes with the radicals R ¹ to R ⁴ defined above have been found to be suitable for use in the present invention. In principle, the use of longer-chain aliphatic or aromatic radicals instead of the components defined for R ¹ to R ⁴ is also possible in the process according to the invention. In general, however, a high carbon content is not desirable in the ceramic materials resulting from the thermolysis of the polymer ceramic precursors.

The radicals R ¹ and R ² can, in each case independently of one another, be selected from alkenyl and / or alkynyl groups, preferably from C ₂ to C ₆ , and more preferably from C ₂ to C ₃ alkenyl or / and alkynyl groups. They therefore offer further potential for additional crosslinking reactions, either of unsaturated groups with one another or by adding a suitable reaction partner, such as, for example, B. a hydroboration agent.

If the radicals R ¹ and R ^{2 are} not unsaturated, reactive groups, they are preferably selected from H, CH ₃ and an optionally polymeric Si-containing radical. An example of a Si-containing radical is NHR ⁵ , where R ^{5 is} R ⁴ [Si (R ² ) N (R ³ )] _{m is} R ⁴ and m is an integer ≧ 1. In addition, there may be links between Si atoms and other structural elements.

With respect to R ³ , at least two of the R ³ radicals are H and the remaining R ³ are generally selected from H and CH ₃ and preferably essentially all R ^{3 are} H. In the case of cyclic polysilazanes, 2 R ⁴ are bonded together. Such cyclic polysilazanes are usually oligomers that normally have about 2-10 [-Si-N-] units in the ring structure. Linear polysilazanes usually comprise a higher number of repeat units, in this case R ^{4 is} preferably H.

Polysilazanes which are suitable for use in the process according to the invention are known in principle from the prior art or they can be prepared by a known process such as ammonolysis or aminolysis of appropriately substituted chlorosilanes. Examples of suitable polysilazanes which are suitable for use in the process according to the invention are [-Si (CH ₃ ) (H) -NH-] _x , [-SiH ₂ -NH-] _x and [-SiH (NH) _0.5 -NH-] _x .

According to the invention, the component containing at least two NH groups is reacted with a hydridosilylalkylborane component. The hydridosilylalkylborane component comprises at least one hydridosilylalkylborane, comprising a structural element of the formula (II)

HpB [-R ⁶ Si (R ⁷ ) (R ⁸ ) (R ⁹ )] _3-p (II)

wherein p is 0 or 1, R ^{6 is} an optionally cross-linked alkylene radical and R ⁷ , R ⁸ and R ^{9 are} independently selected from H and alkyl for each occurrence, with the proviso that at least one of R ⁷ , R ⁸ or R ⁹ H represents.

The compounds mentioned above can be prepared, for example, by ammonolysis or aminolysis of a corresponding chlorosilylborane. Alternatively, such compounds can be obtained by hydroboration of an Si compound comprising an alkenyl or alkynyl group. Examples of such Si compounds are, for example, vinylsilanes which can be substituted by lower alkyl groups. Compounds in which the carbon spacer between the B and Si atoms originates from a C ₂ to C ₆ group have been found to be suitable in practice. Preferred compounds have carbon spacers derived from a C ₂ to C ₃ group. Furthermore, compounds with C ₂ spacers are generally preferred over the corresponding compounds with C ₃ spacers.

The substituents of the hydridosilylalkylborane are further selected so that the carbon content of the component is kept low. For each occurrence, R ⁶ is preferably selected independently from C ₂ H ₄ and C ₂ H ₃ R ¹⁰ , where R ^{10 is} an optionally polymeric B-containing radical which is a crosslink to a boron atom of an analogous structural element and R ⁷ , R ⁸ and R ⁹ are independently selected from H and CH ₃ for each occurrence.

Examples of hydridosilylalkylboranes which have already proven advantageous in practice are hydridosilylethylboranes of the formulas B [C ₂ H ₄ -Si (CH ₃ ) ₂ H] ₃ , B [C ₂ H ₄ -Si (CH ₃ ) H ₂ ] ₃ and B [C ₂ H ₄ -SiH ₃ ] ₃ .

The ratio in which the hydridosilylalkylborane component with the Component containing NH bonds is reacted with one another is relative not critical and can depend on the desired degree of crosslinking to be chosen. As is obvious to a person skilled in the art, this is for  maximum crosslinking required amount of N-H bonds equal to that Amount of Si-H bonds present.

The reaction of hydridosilylalkylborane with ammonia, primary amine and / or NH groups-containing polysilazane is preferably carried out in the presence of a catalyst. Suitable catalysts for this are, for example, bases such as KH, LiNH ₂ , Me-Li or n-Bu-Li, transition metal carbonyl and olefin complexes of Group VIII and Speyers catalyst (hexachloroplatinate).

To carry out the implementation, the two reactants NH component and hydridosilylalkylborane preferably in one Solvent brought into contact with each other. Examples of suitable ones organic solvents are aromatic hydrocarbon solvents such as toluene.

The reaction is generally carried out at a temperature in the range of -10 to + 30 ° C, preferably at a temperature of about 0 to 25 ° C. For many implementations, a temperature of around 10 ° C has been found well suited. Furthermore, as is known to the person skilled in the art, to take the usual measures necessary for processing the above mentioned materials are appropriate. For example, the implementation in an inert gas atmosphere, such as an argon atmosphere perform.

After the reaction, the reaction product is obtained. Since at the Only hydrogen is produced and no difficult to separate, solid by-products in particular, however, is a costly insulation not mandatory. In general, only the emerging Hydrogen removed or let escape and that Reaction product of a polymeric ceramic precursor from the solvent severed. The separation takes place in a conventional manner, the  Is known to those skilled in the art, for example by increasing the temperature or / and create a vacuum.

The invention further relates to a hydridosilylalkylborane of the formula (II)

H _p B [R ⁶ -Si (R ⁷ ) (R ⁸ ) (R ⁹ ) _3-p (II)

where p is 0 or 1, R ^{6 is} an optionally cross-linked alkylene radical, R ⁷ and R ^{8 are} independently H and alkyl at each occurrence and R ^{9 is} H. R ⁶ is preferably a C ₂ to C ₆ and more preferably a C ₂ to C ₃ alkylene radical which optionally has a bond to a boron atom and thus to an analog structural element. For each occurrence, R ⁶ is preferably selected independently from C ₂ H ₄ and C ₂ H ₃ R ¹⁰ , where R ^{10 represents} a bond or crosslink to an analog structural element, and R ⁷ and R ⁸ are selected independently of each other for each occurrence H and CH ₃ .

In a preferred hydridosilylalkylborane of the present invention, R ⁷ and R ^{9 are} H and R ⁸ is CH ₃ . In another preferred hydridosilylalkylborane of the present invention, R ⁷ , R ⁸ and R ^{9 are} H. In the most preferred compounds, R ^{6 is also} C ₂ H ₄ or / and C ₂ H ₃ R ¹⁰ .

Another object of the present invention is a polymer Ceramic precursor, which is obtainable by the inventive method. These ceramic precursors contain the elements Si, B, C, N and H. In addition these elements can still be contaminated by other elements, that come from the implementation of preliminary stages, for example be. The content of foreign elements is generally based on a molar basis, less than 5%, preferably less than 2% and more preferably less than 0.5%.  

There is an advantage of the polymeric ceramic precursors according to the invention in that they are salt-free after their synthesis. They are therefore suitable as a raw material for the production of high quality ceramics.

Boron-containing ceramic precursors according to the invention are characterized by a structure in which boron atoms are bonded to at least 2 silicon atoms via a spacer. In the present invention, a spacer is understood to mean those hydrocarbon groups which result from the reaction of an alkenyl or alkynyl group and which, depending on the position at which the addition took place, have a linear spacer length of at least 1 carbon atom. These spacers are, for example, in the case of a vinyl group —CH ₂ CH ₂ - and —CH (CH ₃ ) -. In the case of an ethynyl group, the spacers are -CH (B) -CH ₂ -, -CH (CH ₂ (B)) - and -C (B) (CH ₃ ) -, where (B) is the link to an analogous structural element represents.

A polymeric ceramic precursor according to the invention can be represented as a compound comprising a structural element according to formula (III)

H _p B [R ¹⁵ -Si (R ¹¹ ) (R ¹² ) (R ¹³ )] _3-p (III)

where p is 0 or 1, R ^{15 is} an optionally crosslinked alkylene radical; R ^{11 is} H and R ¹² and R ^{13 are} independently H, alkyl or NHR ¹⁴ at each occurrence, where R ^{14 is} an optionally polymeric Si-containing residue; or R ^{11 is} NHR ¹⁴ and R ¹² and R ^{13 are} independently H or NHR ¹⁴ at each occurrence. The radical R ¹⁵ represents a crosslink to a boron atom of an analog structural element and NHR ¹⁴ represents a crosslink to a Si atom of an analog structural element.

In a preferred polymeric ceramic precursor, R ^{15 represents} a C ₂ to C ₆ , more preferably a C ₂ to C ₃ and most preferably a C ₂ alkylene radical which can be crosslinked with another structural unit.

In a highly preferred ceramic precursor, R ^{11 is} H and R ¹² and R ¹³ are H, CH _3, or NHR ¹⁴ independently at each occurrence.

Another object of the present invention are cross-linked boron-containing silazanes which, when ceramized, d. H. during further processing of these molecular precursors to ceramics by thermolysis have low mass loss. It has surprisingly turned out to be emphasized that molecular precursors in which the silicon atoms in a valence are bound to boron atoms via a carbon spacer, and the remaining valences are silazane bond and / or hydrogen, for Production of ceramics in the Si-B-C-N system are outstandingly suitable.

In a preferred polymeric ceramic precursor of this type, R ^{15 represents} a C ₂ to C ₆ , more preferably a C ₂ to C ₃ and most preferably a C ₂ alkylene radical which can be crosslinked with a further structural unit. Such a ceramic precursor is also preferred, wherein R ^{11 is} NHR ¹⁴ and R ¹² and R ^{13 are} H or NHR ¹⁴ independently at each occurrence. In one of the most preferred ceramic precursors, which has proven very suitable in practice, R ^{12 is} H and R ¹³ is NHR ¹⁴ . In another such ceramic precursor, R ¹² and R ^{13 are} NHR ¹⁴ .

The polymeric ceramic precursors according to the invention can be one Residual content of unreacted starting groups, such as vinyl groups, exhibit. This content is generally less than 10%, preferably ≦ 5% and more preferably ≦ 1%, based on the originally existing groups.

The ceramic precursors according to the invention are outstandingly suitable for the production of ceramic materials by means of thermolysis. In general, the advantageous properties increase with decreasing alkyl substitution or increasing H substitution and / or crosslinking ((NH) _0.5 substitution) of the Si atoms. It has been found that when the above-mentioned materials are thermolysed, a very small loss of mass occurs during the ceramization, which is generally also associated with a low crack formation in the ceramics produced.

Another object of the invention is a method for producing Materials by thermolysis treatment of a precursor, which thereby characterized in that the precursor comprises a polymeric ceramic stage, which is obtainable by a method according to the invention and / or a polymeric ceramic precursor of the present invention. For this, the Ceramic preliminary stage of a thermolysis treatment at elevated temperature subjected. The thermolysis treatment is preferably carried out by heating carried out to a temperature in the range of 1000 to 1300 ° C. The Ceramic precursor is left for a sufficient time at this temperature held to complete thermolysis of the starting product receive. The thermolysis is preferably carried out in an inert gas atmosphere, e.g. B. under an inert gas such as argon.

Before thermolysis, the polymeric ceramic precursor is generally in transferred a green body. This is generally done by compacting, and preferably by hot pressing. With hot pressing there is a pressure applied, which is sufficient to the precursor materials suitable compress, but while maintaining a residual porosity, so that the Gases generated during the thermolysis can still escape. A Pressure of about ≧) 5 MPa, generally of ≧ 10 MPa, has increased in Generally found to be useful. The pressure applied can also be significantly higher, for example up to 100 MPa in general however, at such high pressures, the materials are compressed to such an extent that the residual porosity is too low to allow the gases to escape allow during thermolysis. This can result in cracking to have.  

In hot pressing, a temperature of generally 80 to 250 ° C, preferably a temperature in the range of 130 to 140 ° C used. The temperature used should not be so high that the Material becomes plastic.

Yet another object of the present invention is a through Ceramic material obtainable as described above. The Ceramic materials according to the invention are distinguished by high Purity, since no salt is obtained in the synthesis of the precursors, as well as in Dependence on the precursors used by a very low Weight loss based on the mass of the used Ceramic precursor material. The thermal resistance of this Ceramic materials depend on the exact composition, but lies in the range of about 1600 to <typical for Si-B-C-N ceramics 2000 ° C.

Yet another object of the invention is a composite that is a boron-containing silazane according to the invention, or one thereof resulting ceramic material is coated. Suitable materials for Production of such composites are, for example, ceramic materials, such as oxides, carbides, nitrides and silicides, as well as carbons and optionally glasses and / or metals. An example of a The composite according to the invention is approximately one with the inventive Ceramic coated carbon fiber. The coating does not need to be continuous, d. H. it can only cover part of the surface of the Cover ceramics.

Another object of the invention is the use of a Hydridosilylalkylborane according to the invention for the production of polymers Ceramic precursors. Yet another object of the invention is that Use of polymeric ceramic precursors by the Methods of the invention are available, and / or from  Polymeric ceramic precursors according to the invention for the production of Si-B-C-N ceramics. Another subject is the use of a Method according to the invention for the production of ceramic layers. Due to the fact that in the implementation of the raw materials, So the NH component and the hydrosilylalkylborane, no solid By-products, such as a salt, are created The inventive method excellent for the production of Ceramic layers directly on a substrate. The substrate can also be a porous substrate that is infiltrated with the starting materials, whereby a ceramic material is obtained which is based on inner and / or outer Surfaces at least partially with one described above ceramic material according to the invention is coated.

Examples example 1

50 mmol tris (hydridosilylethyl) borane B [C ₂ H ₄ SiH ₃ ] ₃ were dissolved in a little toluene, this solution was cooled to 0 ° C. and saturated with NH ₃ . Thereupon about 0.5 mmol of methylithium were added dropwise and the introduction of ammonia was continued for 30 minutes. After a short time, the solutions began to cloud over due to the precipitation of the polymer B [C ₂ H ₄ Si (NH) _1.5 ] ₃ . When the reaction was complete, the colorless precipitates were decanted off and dried in a high vacuum at 25 ° C. to constant weight.

The colorless powders could be converted into amorphous ceramics in an argon atmosphere in approximately 85% ceramic yield by thermolysis (1100 ° C., heating rate 2 ° C./min). The tris (hydridosilylethyl) borane B [C ₂ H ₄ SiH ₃ ] _{3 was} reacted with CH ₃ NH ₂ under analogous conditions.

Example 2

50 mmol of tris (hydridosilylethyl) borane B [C ₂ H ₄ Si (CH ₃ ) H ₂ ] ₃ were dissolved in a little toluene, this solution was cooled to 0 ° C. and saturated with NH ₃ . Thereupon about 0.5 mmol of butyllithium were added dropwise and the introduction of ammonia was continued for 30 minutes. After a short time, the solutions began to cloud over due to the precipitation of the polymer B [C ₂ H ₄ Si (CH ₃ ) NH] ₃ . After the reaction had ended, the colorless precipitates were decanted off and these were dried to constant weight in a high vacuum at 25 ° C.

The colorless powders could be converted into amorphous ceramics in an argon atmosphere in about 73% ceramic yield by thermolysis (1100 ° C., heating rate 2 ° C./min). The tris (hydridosilylethyl) borane B [C ₂ H ₄ Si (CH ₃ ) NH] _{3 was} reacted with CH ₃ NH ₂ under analogous conditions.

Example 3 Synthesis of B [C ₂ H ₄ -SIH ₃ ] ₃

300 mmol (H ₂ C = CH) SiH ₃ were introduced into a solution of 80 mmol (CH ₃ ) S * BH ₃ in toluene, cooled to 0 ° C. The volatile constituents were then removed from the reaction mixture at 20 ° C./5 mbar.

Alternatively, the title compound could also be prepared starting from the corresponding tris (trichlorosilyl-ethyl) borane by reaction with LiAIH ₄ .

Claims (29)

1. A process for the preparation of a polymeric ceramic precursor which contains the elements B, N, Si, H and C, characterized in that

• (a) reacting a hydridosilylalkylborane component with a component which contains at least two NH bonds,
• (b) separating volatile reaction products and
• (c) the polymeric ceramic precursor wins.

2. The method according to claim 1, characterized in that the component containing NH bonds is selected from

• (a) ammonia and / or primary amines,
• (b) polysilazanes containing a structural element of the formula (I)
  R ⁴ [Si (R ¹ ) (R ² ) N (R ³ )] _n R ⁴ (I),
  where R ¹ and R ^{2 are} independently selected at each occurrence from H, alkyl, alkenyl, alkynyl and an optionally polymeric Si-containing radical, R ^{3 is} independently selected at each occurrence from H, CH ₃ and C ₂ H ₅ , R ⁴ independently of one another are H or an optionally substituted alkyl radical, or two R ⁴ radicals taken together are a bond, and n is an integer ≧ 2, with the proviso that at least two NH groups are present; and
• (c) mixtures thereof.

3. The method according to claim 2, characterized in that the amine (a) is CH ₃ NH ₂ . 4. The method according to claim 2 or 3, characterized in that in formula (I) R ¹ , R ³ and R ^{4 are} each H or two R ^{4 taken} together are a bond, and R ^{2 is} independently H, CH ₃ or is an optionally polymeric Si-containing radical. 5. The method according to any one of the preceding claims, characterized in that the hydridosilylalkylborane component is a structural element according to formula (II)
H _p B [-R ⁶ -Si (R ⁷ ) (R ⁸ ) (R ⁹ )] _3-p (II)
comprises, wherein p is 0 or 1, R ^{6 is} an optionally cross-linked alkylene radical and R ⁷ , R ⁸ and R ^{9 are} independently selected at each occurrence from H and alkyl, with the proviso that at least one of R ⁷ , R ⁸ or R ^{9 represents} H. 6. The method according to claim 5, characterized in that R ^{6 is} independently selected at each occurrence from C ₂ H ₄ and C ₂ H ₃ R ¹⁰ , where R ^{10 is} an optionally polymeric, B- and / or Si-containing radical, and that R ⁷ , R ⁸ and R ^{9 are} independently selected from H and CH ₃ for each occurrence. 7. The method according to any one of the preceding claims, characterized, that one carries out the reaction in the presence of a catalyst. 8. The method according to claim 7, characterized, that the catalyst is selected from bases, transition metal carbonyl and Group VIII olefin complexes and / or Speyers catalyst. 9. The method according to any one of the preceding claims, characterized, that one carries out the reaction in an organic solvent. 10. The method according to any one of the preceding claims, characterized, that the reaction at a temperature of -10 to + 30 ° C. carries out. 11. hydridosilylalkylborane according to formula (II)
H _p B [R ⁶ -Si (R ⁷ ) (R ⁸ ) (R ⁹ )] _3-p (II)
wherein p, R ⁶ , R ⁷ and R ^{8 are} as defined in claim 5 and R ^{9 is} H. 12. A hydrosilylalkylborane according to claim 11, wherein and R ⁷ and R ^{8 are} independently H or CH ₃ at each occurrence. 13. A hydrosilylalkylborane according to claim 12, wherein R ^{7 is} H and R ^{8 is} CH ₃ . 14. Hydrosilylalkylborane according to claim 12, wherein R ⁷ and R ^{8 are} H. 15. Polymeric ceramic precursor, characterized, that by a method according to one of claims 1 to 10 is available. 16. Polymeric ceramic precursor comprising a structural element according to formula (III)
H _p B [R ¹⁵ -Si (R ¹¹ ) (R ¹² ) (R ¹³ )] _3-p (III)
where p is 0 or 1, R ^{15 is} an optionally crosslinked alkylene radical; R ^{11 is} H and R ¹² and R ^{13 are} independently H, alkyl or NHR ¹⁴ at each occurrence, where R ^{14 is} an optionally polymeric Si-containing residue; or R ^{11 is} NHR ¹⁴ and R ¹² and R ^{13 are} independently H or NHR ¹⁴ at each occurrence. 17. A polymeric ceramic precursor according to claim 16, wherein R ^{15 is} independently at each occurrence C ₂ H ₄ or C ₂ H ₃ R ¹⁶ , wherein R ^{16 is} an optionally polymeric, B-containing radical, R ^{11 is} H and R ¹² and R ^{13 are} H, CH ₃ or NHR ¹⁴ independently for each occurrence. 18. A polymeric ceramic precursor according to claim 16, wherein R ^{15 is} C ₂ H ₄ or C ₂ H ₃ R ¹⁶ independently at each occurrence, wherein R ^{16 is} an optionally polymeric, B-containing radical, R ^{11 is} NHR ¹⁴ , and R ¹² and R ^{13 are} H or NHR ¹⁴ independently at each occurrence. 19. A polymeric ceramic precursor according to claim 18, wherein R ^{12 is} H and R ^{13 is} NHR ¹⁴ . 20. A polymeric ceramic precursor according to claim 18, wherein R ¹² and R ^{13 are} NHR ¹⁴ . 21. Process for the production of ceramic materials Pyrolysis treatment of a precursor,  characterized, that the precursor is a polymeric ceramic precursor according to one of the Claims 15 to 20 includes. 22. The method according to claim 21, characterized, that the pyrolysis treatment in an inert gas atmosphere carries out. 23. The method according to claim 21 or 22, characterized, that the polymeric ceramic precursor is compacted before pyrolysis. 24. The method according to claim 23, characterized, that the compression by hot pressing at a pressure ≧ 10 MPa executes. 25. Ceramic material, obtainable by a method according to one of the Claims 21 to 24. 26. Composite coated with a boron-containing polysilazane after one of claims 15-20 or a ceramic material according to claim 17. 27. Use of a hydridosilylalkylborane according to one of the claims 11 to 14 for the production of boron-containing silazanes. 28. Use of polymeric ceramic precursors according to one of the Claims 15 to 20 for the production of Si-B-C-N ceramics. 29. Use of a method according to one of claims 1 to 10 or / and 21 to 24 for the production of ceramic layers.