DE19947731B4 - Process for the production of a component from SiC ceramic and semifinished product produced therefrom - Google Patents

Abstract

method for producing a component made of SiC ceramic, in which an output body made of a cellulosic, treated with a pyrolyzable binder Provided material and pyrolyzed the thus prepared starting body and subsequently infiltrated with silicon which is at least partially reacted with carbon to SiC, characterized that a technical Semi-finished cellulose-containing cellular material in the form of shavings and / or in the form of one or more layers, which is bound with binder and pressed, wherein for adjustment of the structure of the component of the content of the binder of the technical semi-finished product less than 50 mass% is set and the porosity of the technical Semi-finished product to a maximum of 60% by volume. is set.

Description

The The present invention relates to a method of manufacture a component made of SiC ceramic, in which an output body of a cellulosic, treated with a pyrolyzable binder Provided material and pyrolyzed the thus prepared starting body and subsequently infiltrated with silicon which is at least partially reacted with carbon to SiC. Furthermore refers the invention to a produced by such a method Workpiece.

One Such component or the corresponding method is from Journal of the European Ceramic Society 18 (1998), pages 1961-1973, under the heading "Biomorphic Cellular Silicon Carbide Ceramics from Wood: I. Processing and Microstructure " publication experiments were carried out to get out of a course grown wood to produce a Siliziumkarbidkeramik. After the specified Procedure becomes the natural one Wood first dried, then at temperatures between 800 and 1,800 ° C in one nitrogen atmosphere pyrolyzed, resulting in a carbon preform. In these Carbon preform then becomes liquid Si at 1,600 ° C infiltrated under vacuum. This creates a SiC ceramic.

It is conceivable that with the above-stated procedure simple components can be produced. It can be seen that the Properties of the components due to the properties of natural Wood materials fluctuate greatly, which results in particular from that natural wood materials by growth and location factors very different in theirs Cell structures are constructed. Thus, a reproducible production of ceramic materials from such natural wood materials with under the individual components comparable properties barely possible.

The EP 0 151 213 describes a method for producing a reaction sintered silicon carbide body. A still deformable, even, first film of carbonaceous material and a still deformable, regularly profiled second film of carbonaceous material, which may be organic fiber materials, who arranged so flat on each other that form cavities; the films are bonded together at the contact lines, the structure is cured and, after the curing process, the structure is subjected to a burnout and coking process under an inert atmosphere and then, after coking, the structure is immersed in a molten silicon bath or organic Soaked silicon compounds and fumigated with vapors, and then that the structure is fired until the formation of silicon carbide.

outgoing from the prior art described above is the present Invention, the object of a method of the initially described Art, as well as a semi-finished product produced by this method, too create that has reproducible properties or reproducible Characteristics of the component guaranteed. Furthermore should the possibility be given the characteristics to the respective requirements, the be placed on a SiC ceramic component to adapt. The specified Procedure should allow very inexpensive To produce SiC ceramic components.

Is solved the task, starting from a method with the aforementioned Characteristics, in that a technical semi-finished product made of cellulosic, cellular material in the form of chips and / or in the form of one or more layer (s) is used, with Binder is bound and pressed, with the setting of the structure of the component of the content of the binder of the technical semi-finished product less than 50 mass% is set and the porosity of the technical Semi-finished product is set to a maximum of 60% by volume.

It is essential that a technical semi-finished product is used as the starting material for the produced component of SiC ceramic, which consists of components in the form of chips and / or one or more layer (s) of cellulosic material. Such chips and / or layers can be defined defined to create a technical semi-finished product. These starting materials, ie technical semi-finished products from chips and / or layers, are already available as materials very extensive and in great variety, since in particular when it comes to technical semi-finished wood materials, the materials can be used in the Building and furniture industry as well as in mold making. The properties of the herzustel sirloin component of SiC ceramic can also by the Amount of pyrolyzable binder containing the starting body can be adjusted. These pyrolyzable binders may already be present in the construction element which is being used immediately, ie an element which is commercially available as a prefabricated part, or the binder content may be defined to produce the starting body of chips and / or layers.

It is apparent that by the use of technical materials, in particular technical engineered wood, a technical semi-finished product can be built that meets the requirements of a high degree can be adapted to be produced component of SiC ceramic. As a parameter, To the properties of the SiC ceramic very strong, but still with very simple means to influence, the variations offer themselves the layer orientation, the binder used, the nature of the cellulosic material, such as in the form of chips and / or Layers that can be put together variably on. It continues possible, especially when technical woods as starting material for producing a technical semifinished product be used to use different hardwoods or softwoods, which are pressed with a binder to semi-finished sheet. In terms of hardwoods Beech, oak and maple are particularly suitable, while softwoods are found in the essential conifers are.

According to the proceedings, a first output body of cellulosic material bound with pyrolyzable binder, built up. This body is pressed, being the pressed one Blank advantageously already the end component approaching or can have corresponding final contours. But it is also possible this compressed body to work to its final form, what with usual, in the wood processing Industry-used tools is possible. The starting body or the technical semi-finished product can be built up in layers, with also layers of wood or of other cellulosic material, added can be to structure the semi-finished product. A key advantage is that the porosity in the technical semi-finished already by the used, cellulose-containing Starting material strongly influenced can be. In terms of wood as a cellulosic source material is of particular importance that the cell structure of the wood with the appropriate transport channels for water and nutrients (tracheids) and the medullary rays perpendicular to these transport channels for the later infiltration process can be used.

Of the output body from the defined constructed, technical semi-finished product is then pyrolyzed, preferably at temperatures between 800 to 1,600 ° C. In these pyrolyzed starting body, the highly porous with a very high percentage of carbons that continues translaminar pore channels is then then liquid under vacuum Silicon infiltrates. Such an infiltration process can be perform very easily, because the silicon has a very high capillary action with respect to Cell structure of the carbon body having. With appropriate holding time, preferably at the maximum Infiltration temperature, becomes a reaction of the liquid silicon with the present in the pyrolyzed starting body, amorphous Carbon allows, what then a microstructure made of SiC ceramic, which strongly depends on the initial structure of the technical semifinished product is dependent as starting body.

The cellulosic material should have a strong cellular structure, because with such a material, the pore channels in the starting body in Shape of a technical semi-finished product in the direction and size are affected can. It has been shown that a SiC ceramic, which is made of a technical semi-finished product, which has a very high proportion of translaminar pore channels, a quick and complete Si filling is possible. This results in a dense SiC ceramic with low residual porosity. If the proportion of pore channels too high It may happen that the SiC ceramics formed high Si contents and due to the high initial porosity Defects, e.g. Lunker, has. With too small pore channels can be observed that a uniform Si infiltration is difficult and there are areas of unreacted carbon can.

Of the Proportion of the carbon content of the binder used for this purpose will, the chips and / or layers of cellulosic material should at least 30%. This will provide sufficient carbon provided to you later when infiltrating liquid Silicon silicon carbide to form.

By the construction of a semifinished product of several layers, the arising stresses in the technical semifinished product, and thus in later SiC ceramic, from built or kept low. If a technical Semi-finished product is constructed, in which the layers have the same positional orientations with respect to their main fiber directions, it is achieved the existence relatively dense structure is present at high SiC levels. High strength, however, can be reach only in the main fiber direction.

For this reason, the semi-finished product used should at least two layers with different Have orientation with respect to their main fiber directions. Especially with such a layer orientation results in a semi-finished product which has high strengths parallel to the different positional orientations. In addition, due to the blocking effect of the individual layers during the pyrolysis, a crack structure supporting the Si infiltration results.

Around a technical semi-finished product, which forms the starting body of the SiC ceramic, in which every other layer with respect to their position orientation by 90 ° the previous layer is rotated, a uniform stress distribution achieved in the semi-finished product. Such semi-finished products (for example plywood) or the corresponding SiC ceramics can be used when a large-area component is needed, For example, in the form of a plate, or if the main load directions lie perpendicular to each other in the plane of the plate. something similar applies when the layers have a quasi-isotropic positional orientation; just a component made of such a SiC ceramic should then be used if high form faith about all process steps and uniform, quasi-isotropic Properties are required at the board level.

For one simple structure of a technical semi-finished offers such a having individual layers built up from plywood plies are. Such veneer layer layers can be peeled off a log, preferably with a thickness of ≤ 1.5 mm, more preferably ≤0.7 mm. These layers are then moistened, smoothed and dried so that flat Veneer layers arise. By peeling off a log remains the cell structure of the wood with the tracheids as transport channels for water also for nutrient and with the medullary rays perpendicular to the tracheids. There Nevertheless, a log due to a different structuring of the natural Growth, which is dependent on the year and location, can then These veneer layers are layered differently, so that a largely homo gener starting body with pore structures. Between the individual veneer layers can if necessary, chip material can be interposed to avoid the technical problem Build up semis. Individual layers may consist of individual, adjoining veneer sections be formed. This measure is particularly advantageous if the fiber orientation the Geometries of the component to be adapted.

As already mentioned, The individual layers should have a quasi-isotropic positional orientation to the formation of a uniform texture, caused by the thin Lying, support and at the same time thin-walled, spatial curved To be able to produce ceramic components.

The technical semi-finished products can be made of composite panels with a repeating Structure are constructed, preferably also in the form that the layers are constructed symmetrically to the plate center plane. Especially for one such a structure are plywood boards, as used in construction or furniture industry used be so on available in a wide variety Starting materials used can be. It should be noted that in addition to cellulosic material in the form of wood of various types also other cellulosic Materials that have a cellular structure can be used can.

One is an essential part of the technical semi-finished product as a starting body the binder used to the constituents of the starting body in Form of chips and / or one or more layer (s) to bind. The binder can one during the pyrolysis ceramic-forming polymer. Just such Binder brings with it the advantage that a certain amount of ceramics already present before the siliconization in the pyrolyzed molded body.

If as a binder, a Si-organic polymer is used results the advantage that after the infiltration of the pyrolyzed preform with liquid silicon the content of SiC in the microstructure can be increased. This has the advantage that the resulting Si contents or Implementation of the silicon can be reduced. Basically be used as a binder phenol. But it is also possible to use glue resin as To use binders. However, preference is given to the use of phenolic resin, as is achieved with such a binder that the technical Semi-finished by customary in the wood industry process and produced inexpensively can be as well as a high carbon yield during the Pyrolysis allows becomes. This can be the danger of destruction reduce the technical semi-finished product.

Care should be taken that the content of binder is <50% by mass or <25% by mass. If the binder content is set higher, the cellular structure may clog and high shrinkage stresses may occur during pyrolysis. Just below 25% by mass of the content of binder can be achieved that the cells of the cellulosic material remain free; it should However, care should be taken that the binder content is not less than 5%, otherwise a sufficient dimensional stability is no longer guaranteed.

Around to allow rapid pyrolysis of the technical semi-finished product without damage should the porosity of technical semi-finished products> 5% be. However, the upper limit of porosity should not exceed 60% be; is an optimal fraction of the porosity in the volume of the whole body determined by the choice of the type of wood and the binder and the desired fabric composition the SiC ceramic.

According to the method it is advantageous, the liquid Silicon by capillary action parallel to the cell structure of the technical Semi-finished infiltrate, as a result, a fast and uniform production also large components possible is.

Farther should the liquid Silicon at a temperature above 1420 ° C under inert gas or vacuum be infiltrated into the pyrolyzed technical semi-finished product, wherein a temperature range above 1,600 ° C is particularly preferred since thereby shortening the residence time in the furnace and the reaction of Si is accelerated to SiC with the pyrolyzed semifinished product.

For the process step The pyrolysis has come in handy proved, the pyrolysis of the technical semi-finished product in several successive Temperature steps with each cooling to room temperature to perform because thereby additional Segmentation cracks occur and thereby escape of gaseous degradation products even with large format and thick-walled components possible becomes. Furthermore should be the first temperature step of pyrolysis in a temperature range between 250 ° C and 300 ° C are carried out since from this temperature range, the highest mass loss rates during the Pyrolysis of usual technical semi-finished products occur.

Around the proportion of carbon, in the technical semi-finished product, before the Infiltration with liquid Silicon, increase, becomes this after a first pyrolysis of the technical semifinished product again fed binder, by vacuum or pressure infiltration, and then subjecting this technical semi-finished product to further pyrolysis.

Farther can the carbon in the technical semi-finished product after its pyrolysis be modified by that pyrolyzed, technical semi-finished product under vacuum or inert gas atmosphere Subjected to graphitization at a temperature of at least 1,600 ° C. becomes. Such a graphitization step must then be carried out when the reaction rate of SiC formation is increased should.

It has been shown that to prevent distortion during pyrolysis mechanical loads on the technical semi-finished product should be applied transversely to the main fiber direction with 10 ³ - 10 ⁵ N / m ² (0.001 - 0.1 MPa). By this measure, the technical semi-finished product largely retains its shape, despite possibly high volume shrinkage.

The technical semi-finished product can, before the pyrolysis, under slight pressure of <5 × 10 ⁶ N / m ² (5 MPa) are pressed to a density of <1.0 g / cm ³ . With this method step, the chips or layers are joined together and brought into the desired shape of the SiC component, taking into account the volume shrinkage occurring during pyrolysis. The slight pressure ensures that the cellular structure of the cellulosic semi-finished product is retained. In addition, prior to compression, the ingredients may be coated with the binder by conventional impregnation or spraying techniques, which has the advantage that the uniform coating can reduce the total binder content required and the cells during the process Pressing remain open.

It The aim is that the finished component made of SiC ceramic no or a minimum residual mass fraction should have on carbon, since free carbon oxidation resistance of the SiC ceramic. For this reason should be used for manufacturing such having a minimum residual mass fraction of carbon SiC ceramic silicon at least 2.35 times the mass of the pyrolyzed, technical Semi-finished products are added. This corresponds to the necessary silicon mass for one stoichiometric Silicon reaction.

Farther For the preparation of a <5% porosity SiC ceramic, silicon infiltration should be used to 3 - 4.2 times, based on the mass of the technical semi-finished product before the silicization set become.

A further, procedural variation lies in the fact that the chips, Layers and / or layers first be pyrolyzed, then be bonded with binder and siliconized after another pyrolysis become. Especially with such a procedural measure is ensured that the Volume shrinkage and the settling paths during pyroylse minimized become. This allows the technical semi-finished product largely in the final contour be brought to the SiC component, so that expensive processing steps the hard SiC ceramic omitted.

Instead of the liquid silicification of the pyrolyzed starting body can the silicon gas or vaporous under inert gas or vacuum at a temperature above 1600 ° C infiltrated become. Such infiltration of silicon over the gaseous or vaporous phase has the advantage that SiC components with high porosity (for example for thermal insulation, for filters) can be made with very precise SiC content. In contrast, should the silicon in liquid Phase always then infiltrated into the pyrolyzed, porous technical semi-finished product Be required if dense, possibly Si-containing SiC components are.

following Be exemplary embodiments of the invention.

In the drawings shows

1 schematically a technical semifinished product, which is made of pressed chips,

2 schematically a technical semi-finished product, which is composed of individual layers,

3 a schematic representation of the individual steps for producing a technical semifinished product as a starting body for a component made of SiC ceramic according to the invention,

4 to 7 various layer structures of the technical semi-finished product, each with different and changed positional orientations with respect to the main fiber directions,

8th a microstructure of a chipboard in the siliconized state in a 100-fold magnification, and

9 The microstructure of a plywood in the siliconized state in a 15-fold magnification.

As a starting body for the production of a component from a SiC ceramic, a technical semifinished product is provided which consists of components in the form of chips and / or layers or layers of cellulosic material. 1 shows such a technical semi-finished product 1 with a base in the direction of the xy plane, with individual chips being layered in the z-direction. The chips are bonded with a pyrolyzable binder, preferably with a phenolic resin.

On the other hand shows 2 a technical semi-finished product 1 as a starting body, which is composed of individual layers, which are stacked in the z-direction and bonded with a pyrolyzable binder. 3 shows a technical semi-finished product, which corresponds to the 2 is formed. This technical semi-finished product 1 is from three layers 2 wherein the bottom and top ply (if wood) have the same orientation of the major fiber directions indicated by the hatching, while the center ply has a major fiber direction of orientation at an angle of 90 ° the orientation of orientation in the upper or lower layer, in each case in the xy plane. The three layers 2 , which may have a thickness between 0.25 to 2.5 mm, and are each peeled off, for example, from a log, are previously dried and then with a binder 3 , namely phenolic resin, glued. During gluing may be on the top veneer layer 2 a pressure can be exerted, as indicated by the arrow, denoted by "p." In this way, a technical semi-finished product of almost any thickness, seen in the z-direction, can be built up from layers. For example, the choice of the wood type, the layer structure and the orientation of the main fiber directions and the binder used, the pressure exerted p and the compression time t, ie the time during which the pressure p is exerted, and the compression temperature T set the properties of the technical semi-finished product In view of the compression temperature T, it should be noted that complete crosslinking of the binder during the pressing operation is ensured to achieve a high C content during pyrolysis and intimate bonding of the individual layers.

Subsequently, the technical semi-finished product 1 at a temperature> 600 ° C, but not higher than 1,600 ° C, pyrolyzed. Liquid silicon is then infiltrated into the pyrolyzed semifinished product so that this liquid silicon reacts with carbon to form SiC. The infiltration temperature must be above 1420 ° C, so that it is ensured that the silicon is present in a sufficient, liquid state.

During the pyrolysis shrinkage of the technical semi-finished product is observed, even if individual veneer layers are used to the technical semi-finished product 1 build. Due to the effect of temperature on the technical semi-finished product during pyrolysis shrinkage cracks of various shapes and sizes are observed. But there are also relatively uniformly distributed microchannels, which are due to the tensile stresses arising in the layers due to the shrinkage obstruction of adjacent layers.

Since the shrinkage behavior is essential for the fact that on the one hand in technical semi-finished a defined crack structure is to build, but on the other hand, the technical semi-finished product is to be dimensioned so that a component can be made of a SiC ceramic with defined dimensions, investigations of six different technical semi-finished products, which are given in the table below. The parameters, density, open porosity and shrinkage behavior in the pyrolyzed state were investigated. The six different technical semi-finished products differed by density values g / cm ³ , which were between 0.5 and 0.62. The respective open porosity e '[%] was nearly constant with values between 66.3 and 70.4%. Based on the specified shrinkages measured for units BF1, BF2, BF5 and BF6. It can be seen that the shrinkage behavior in the plane and thickness direction is very different and is strongly influenced by the orthotropy of the layer structure. The 18-22% change in length approximately corresponded to the width change, while the 34-36% thickness shrinkage was significantly higher. It follows that the resulting cracks are transverse to the layer structure greater than parallel to the layer structure. This results in a SiC ceramic with a structure that is characterized by a pronounced layer structure, which leads to a material with orthotropic properties.

TABLE 1

Due to the shrinkage behavior, it has been investigated that it is precisely with the layer structure and the orientation of the main fiber direction in the individual layers that these mechanical and physical properties can be strongly influenced. In the 4 to 7 different layer structures are shown with layers stacked in the z-direction.

In 4 the technical semi-finished product is stacked from individual layers, which have their main fiber direction oriented exclusively in the x-direction (so-called plywood). In contrast, the technical semi-finished product of 5 layered in the z-direction so that each successive veneer layers have their main fiber direction each aligned at 90 ° to each other (so-called plywood). Finally shows 6 a layer structure in the z-direction, in which the individual veneer layers are alternately offset, viewed in the z direction, at 45 ° to each other (so-called star wood).

With regard to the shrinkage behavior, the same type of wood, the same binder and identical process parameters are expected to show identical changes in thickness in all three cases. However, the shrinkage behavior in the length and width direction differs significantly and leads to different microchannels, characterized by different cross-sections and orientations, after pyrolysis and as a result to various structures or properties in the SiC component.

While a plywood after 1 preferably for one-dimensional components, such as bars or beams, can be used, locking and star woods after 5 and 6 preferably used for sheet-like components, such as plates or disks. With decreasing angle change between adjacent layers and decreasing layer thickness, the SiC microstructure becomes finer and more homogeneous in the x, y plane and approaches a homogeneous structure, the layer structure in the z direction usually being retained.

7 shows an example in which an annular or tubular, technical semi-finished product of individual plate sections, each forming ring segments, which in turn are interconnected, is constructed. These individual plate segments are stacked on top of each other and each offset with their seam against each other. The fiber direction in the individual sections is arranged extending in the circumferential direction. This technical semi-finished product already has approximately the shape of the component to be produced from SiC ceramic. This figure shows that even complicated structures can be constructed in a simple manner with the measures according to the invention.

An example of the technical semi-finished product 1 as it is in 1 was prepared as follows:
Wood chips were used, pressed with a resin based on phenols. The density of the plate was ρ = 0.71 g / cm ³ . The proportion of open porosity was 52.3% based on the volume of the compressed technical semi-finished product, which had a total thickness of 22 mm.

This technical semi-finished product was then left for 76 hours at a temperature up to 900 ° C, under conditioner with nitrogen, pyrolyzed. The flushing with nitrogen had the Purpose that the while The pyrolysis released fission products transported away quickly were and thus an overpressure and as a result, destruction of the technical semi-finished product could be avoided.

In addition, the technical semi-finished product was loaded during the pyrolysis with a weight of 2 kPa in the z-direction. After pyrolysis, the density of the pyrolyzed, technical semi-finished product was ρ = 0.64 g / cm ³ with an open porosity of 47.4% based on the remaining total volume of the technical semifinished product.

Subsequently, the pyrolyzed technical semi-finished product was silicated with liquid Si for a total of 32 hours, at a temperature of up to 1,500 ° C. and at a heating rate of 80 K / h under reduced pressure. The silicon uptake was 215% based on the mass of the pyrolyzed semifinished product. The density of the siliconized and thus ceramized technical semi-finished product was 1.88 g / cm ³ with a residual porosity of 40.0%. The SiC ceramic component produced in this way no longer has carbon components and can be used, for example, as a filter element because of the relatively large, accessible porosity.

In a second example, a technical semi-finished product was constructed, as in 2 is shown. Selected peeled beech veneers, with a veneer thickness of 0.65 mm, were glued with urea resins (in accordance with DIN 68705 Part 2). The individual veneer layers were glued in the z-direction by 90 ° to their main fiber direction.

The initial state of this technical semi-finished product could be determined with a density of 0.79 g / cm ³ and an open porosity of 42.1%.

The subsequent pyrolysis was carried out for a total of 192 hours at a temperature up to 900 ° C, a variable heating rate and again a purging with nitrogen gas. The technical semi-finished product was weighted during the pyrolysis with 13.6 kPa, in the z-direction. After pyrolysis, a density of the technical semi-finished product of 0.64 g / cm ³ and an open porosity of 49.6% based on the volume of the pyrolyzed semifinished product.

Subsequently was a silicate for a total of 40 hours, at a temperature of 1650 ° C and a Heating rate of 70 K / h, carried out under vacuum.

The silicon uptake during siliciding was determined to be 314.0% (based on the mass of the pyrolyzed semifinished product). The ceramized member had a density of 2.53 g / cm ³ , a residual porosity of 0.3% and a flexural strength of 143.7 MPa.

A comparison of the two examples listed above, in which in each case a technical half according to the 1 and 2 has been provided as a starting material for producing a component made of SiC ceramic shows that despite high porosities in the pyrolysed state, depending on the microstructures dense or porous ceramics are produced. Layered wood according to Example 2, due to their layer structure, generally permit denser and stronger ceramics than those made of chipboard as a technical semi-finished product.

In the 8th and 9 are sectional views (in z-direction) shown.

This shows 8th an image of a technical semi-finished product, with a structure according to 1 , while 9 a section in the z-direction of a technical semifinished product accordingly 2 shows.

In the sectional view of the 8th , which shows a chipboard in the siliconized state at a magnification of 100 times, the silicon carbide is visible on the bright surfaces, while the pores are visible on the basis of the dark areas. This sectional view shows that porous SiC ceramics with large, freely accessible surfaces can be produced in a simple manner.

9 shows the layered structure. For this component, a technical semi-finished product of a variety of veneer layers, which were each glued, built. The individual veneer layers, layered in the z-direction, on the one hand had a main winding direction in the x-direction, these layers being identified by the reference numerals 4 while the layers having a major fiber direction in the y-direction, ie perpendicular to the layers or veneer layers 4 , With 5 are designated. It can be seen that the individual layers to a center plane, with the reference numeral 6 , had a symmetrical structure, wherein the two middle layers each had an orientation of the main fiber direction in the y-direction. The respective black lines between the individual layers show the original gluing levels of the individual veneer layers, as were the case with the technical semi-finished product before the pyrolysis. The bright areas in turn show the pure silicon that is contained in the ceramic component, the dark or black areas represent silicon carbide. Based on the 9 It can be seen that very dense structures based on Si and SiC are easy to produce, which can be used for example as structural ceramics in thin-walled components.

Claims (31)

A method of making a SiC ceramic device comprising providing a cellulosic pyrolytic binder treated material and pyrolyzing the starting body thus prepared and subsequently infiltrating it with silicon which at least partially reacts with carbon to SiC, characterized that a technical semifinished product of cellulosic, cellular material in the form of chips and / or in the form of one or more layer (s) is used, which is bound and pressed with binder, wherein the setting of the structure of the component of the content of the binder of the technical Semi-finished less than 50 mass% is set and the porosity of the technical semi-finished product to a maximum of 60% by volume. is set. Method according to claim 1, characterized in that that this Silicon by capillary action parallel to the preferred direction the cell structure is infiltrated. Method according to claim 1, characterized in that that liquid silicon at a temperature above 1420 ° C under inert gas or vacuum is infiltrated into the pyrolyzed technical semi-finished product. Method according to claim 1, characterized in that that silicon under protective gas or vacuum at a temperature above 1600 ° C in the pyrolyzed technical semi-finished product is infiltrated. Method according to claim 1, characterized in that that the Pyrolysis of the technical semi-finished product in several, successive Temperature steps with respective cooling between them to room temperature carried out becomes. Method according to claim 5, characterized in that the existence first temperature step of the pyrolysis in a temperature range from 230 ° C to 300 ° C. Method according to claim 1, characterized in that that after the pyrolysis of technical semi-finished this binder again supplied and subsequently the technical semi-finished product is subjected to further pyrolysis. Method according to claim 1, characterized in that that before the infiltration of silicon the pyrolyzed technical semi-finished product Under vacuum or inert gas atmosphere of a graphitization a temperature of at least 1,600 ° C is subjected. Method according to claim 1, characterized in that that during the Pyrolysis to prevent a delay mechanical compressive loads on the technical semi-finished product transverse to the main fiber direction with 0,001 - 0,1 MPa be applied. A method according to claim 1, characterized in that the chips and / or layers are pressed with binder to the technical semi-finished product under a slight pressure of <5 MPa to a density of <1.0 g / cm ³ . Method according to claim 10, characterized in that that the Chips and / or Layers are coated with the binder before pressing. Method according to claim 1, characterized in that that as Binder phenol, glue resin and / or a ceramic-forming polymer be used. Method according to claim 12, characterized in that the existence Si-organic polymer is used. Method according to claim 1, characterized in that the existence Semi-finished product is produced, in which the layers with the same position orientation with respect to their main fiber direction. Method according to claim 1, characterized in that the existence technical semi-finished product is produced, in which at least two layers with different attitude orientation with respect to their major fiber directions to be ordered. Method according to claim 15, characterized in that that this technical semi-finished product is produced with a positional orientation, wherein every other layer in a rotated by 90 ° position orientation is arranged. Method according to claim 15, characterized in that that this technical semi-finished as a composite panel with a repeating Structure is built. Method according to claim 1, characterized in that that the Layers are constructed symmetrically to the plate center plane. Method according to claim 1, characterized in that that this technical semi-finished products made up of layers with a thickness of <1.5 mm becomes. Method according to claim 19, characterized that this technical semi-finished product is built up from layers of <0.7 mm. Method according to claim 1, characterized in that that this Semi-finished product made by pressing different types of wood becomes. Method according to claim 1, characterized in that that as pyrolysable binder phenolic resin is used. Method according to claim 1, characterized in that that to Production of a minimum residual mass fraction of carbon having SiC ceramic silicon at least 2.35 times the mass of the pyrolyzed, technical semi-finished product is added. Method according to claim 23, characterized that to Producing a porosity of <5% SiC ceramic silicon infiltration to the 3-4.2 times, based adjusted to the mass of the technical semi-finished product before siliciding becomes. Method according to claim 1, characterized in that that the Chips and / or one or more layer (s) pyrolysed prior to the addition of binder become. Semi-finished product according to one of claims 1 to 25th Semifinished product according to claim 26, characterized that the Carbon content of the binder is at least 30%. Semifinished product according to claim 26, characterized that the Layers of plywood are layers. Semifinished product according to one of Claims 26 to 28, characterized that the Chips and / or the layer (s) are made of wood. Semifinished product according to claim 26, characterized that the Content of binder in the technical semi-finished product <25 mass%. Semifinished product according to claim 26, characterized that this technical semi-finished product has a porosity> 5%.