AT12389U1 - COMPOSITE MATERIAL AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

Austrian Patent Office AT 12389 U1 2012-04-15

Description: [0001] The invention relates to a material according to the preamble of claim 1, in particular a composite material which is composed of several components and which offers the possibility of setting the thermal properties in a wide range via the composition or via the synthesis parameters. It is mainly about the thermal expansion and the thermal conductivity or the thermal conductivity. At the same time, density, electrical properties as well as mechanical properties are affected in a wide range.

Increasingly, there are requirements for materials that can not be covered by the properties of metals or ceramics. In many cases, materials with a high thermal conductivity (> 50 W / mK) also have a high expansion coefficient (> 10 ppm / K) or, conversely, materials with a low thermal expansion coefficient (<10 ppm / K) also have a low thermal conductivity Conductivity (<50 W / mK). Exceptions are, for example, W and Mo with a conductivity> 100 W / mK with a thermal expansion coefficient <10 ppm / K. These materials have the disadvantage that they have a high density and also have a high melting temperature, whereby high process temperatures are required.

According to the invention described below, these limitations of various metals can be solved by composites to obtain a material with tailored thermal properties (thermal conductivity / thermal conductivity, thermal expansion, specific heat) and / or lower density. For this purpose, a carbon-based filler is used, as well as another additive that causes a very good mechanical and / or thermal bonding of the metal particles to the filler. This makes it possible either to increase the thermal conductivity of the matrix material and / or to lower the thermal expansion coefficient of the matrix material and / or to reduce the density of the matrix material.

[0004] Applications for Such Materials: [0005] Due to the advantageous combinations of properties, various fields of application result for the material group described here, some are mentioned below: [0006] a) Use of the new material described as heat sink / heat sink of electronic assemblies: These can be simple cooling plates or complex 3D structures (eg with fins for air cooling) or with cooling channels for cooling with a liquid medium.

B) use of the described material, especially with a matrix of titanium or a

Titanium alloy for heat exchangers in high-temperature applications (where additionally lower weight is required) and / or when using corrosive media and / or erosive media c) Use of the described material as a heat sink / heat sink of a con centrator solar cell. In this case, the sunlight is optically focused and directed to a concentrator solar cell. This results in a much higher heat input than in a conventional solar cell. Therefore, the concentrator cell must be cooled accordingly, which is made possible by the new materials described d) Use of the described material in combination as a heating or cooling plate:

In this case, the advantageous thermal conductivity of the composite material over the pure matrix is utilized. Fields of application are, for example, cooking plates and / or trays or inserts in cooking pots. [0010] e) Use of the described material as a cooling plate in vacuum coating systems for the production of thin layers by means of sputtering as a cooling plate for the sputtering targets used: In this case, one in the vicinity of the so-called Targets (consisting of the material that is to be deposited as a layer) generates a plasma (typically consisting of, for example, argon ions) which erodes the target material layer by layer atom by atom. The interaction of the ions with the target material leads to a gradual heating of the target, which is undesirable or needs to be controlled, and therefore requires effective cooling. Particularly in the case of target materials with low coefficients of thermal expansion, due to the temperature gradients, internal stresses can occur between the target - which is usually applied to a copper cooling plate ("coated-on") and underground. The use of thermally highly conductive materials, which also have an adapted coefficient of thermal expansion, significantly minimizes this problem.

The main approach of this patent is the use of metal borides or the element boron, which allow to change the mechanical and / or thermal transition between the matrix and filler in an advantageous manner. In particular, the use of these additives has a beneficial effect on the thermal properties (thermal expansion or thermal conductivity).

The use of metal borides or elemental boron can be found in connection with carbon-based fillers, in particular diamond, in the following publications: WO 2005106952 A1 and WO 2007101282 A1 describe a diamond-based multicomponent system in the Relationship with copper is used. Both writings are limited to copper as a matrix. These papers also give a good overview of the state of the art in the application of carbon or diamond based materials for thermal applications.

US 4,902,652 A describes a sintered material of diamonds which is coated with transition metals of groups 4A, 5A and 6A (subgroups) and with boron and silicon. In this case, coated diamonds are directly sintered to produce essentially a diamond-bearing material that is present in a metal-carbide matrix.

W005078041 A1 describes the coating of abrasive materials inter alia with titanium boride, these coated particles (for example diamond particles) being used for cutting and grinding applications.

The material according to the invention comprises a matrix A, which is formed from a metal or an alloy.

Suitable matrix materials A are: a) metals with a thermal conductivity &gt; 50 W / mK, in particular Al, Mg, Cu, Ag,

Ni, Co, Cr, Nb, Ta, W, Mo, Si, Fe and / or b) metals having a thermal expansion coefficient of less than 10 ppm / K (at

Room temperature) such as Ti, Cr, Nb, Ta, W, Mo, Si, Zr and all combinations (real alloys and multiphase systems) of a) and b) with each other.

C) alloys consisting of at least one of the above-mentioned metals with other alloying elements, wherein the alloys may contain up to 20 wt.% Of alloying elements. The alloying elements fulfill the task of melting point reduction, the improvement of the mechanical properties and / or the improvement of the processability.

D) Multiphase systems consisting of the above metals with other fillers (elements and compounds). These can be up to 20 wt.% Contained. The fillers should also reduce the melting point and cause the improvement of the mechanical properties and / or the improvement of the processability. The filler B is or are a carbon-based filler, carbon nanofibers or nanotubes, preferably carbon fibers, carbon or graphite particles, particularly preferably diamond particles. There are also possible mixtures of the various carbon-based fillers.

Additive C: The role of this additive is to improve the interface, especially the thermal and / or mechanical transition between the matrix and the filler B. The additive C is present predominantly directly at the interface between the matrix and the filler, ideally as a layer around the filler. Excess amounts of the additive C can also be distributed in the matrix A.

As an additive for the improvement of the heat transfer and / or the mechanical connection between metal and the carbon-based fillers, in particular diamond, metal borides or elemental boron are used.

Depending on the manufacturing processes used, intermediate phases may also be present in the composite material, as: a) Reaction products of reactions between the matrix A (metal or alloy) and the additive C (metal boride or boron) or their decomposition products B) reaction products of reactions between the filler B and the matrix A or their decomposition products c) reaction products of reactions between filler B and the additive C or their decomposition products d) reaction and / or decomposition products of matrix A and / or filler B and / or

Additive C with the atmosphere used in the preparation (eg reaction products with oxygen, nitrogen, etc.) e) Amorphous carbon formed by conversion of the filler B Property and function of the metal borides or the element boron In For many metal-carbon systems, the design of the interface between the metal matrix A and the filler B is of central importance, especially if it is a very good thermally conductive filler.

To achieve a high thermal conductivity and / or a low thermal expansion of the composite material relative to the matrix A, a good thermal connection and / or mechanical connection between matrix A and the filler B is required.

Exactly this connection is favored by the use of metal borides or of the element boron and leads to the fact that the advantageous thermal properties of the filler B (high thermal conductivity and / or low thermal expansion) can be exploited to a high degree ,

The majority of metal borides are characterized by high melting temperatures and characterized by good thermal conductivity (> 20 W / mK) for ceramic materials. Metal borides are for the most part chemically stable, even at high temperatures, as a result of which they can simultaneously act as a protective layer for the filler B in the form of a coating, thereby allowing processability at higher temperatures.

Due to an onset of conversion of the diamond into graphite at temperatures of 800-900 ° C, this is an advantage, especially when matrix materials are used with high melting temperatures.

Examples of metal borides (MexBy), which are of interest as additive C, are simple borides with the possible stoichiometric composition MeB, MeB2, Me2B5, MeB6, etc. In addition, complex borides such. Me (1) x Me (2) yBz (ternary, e.g., AIMgB14) or Me (1) wMe (2) x Me (3) yBz (quaternary, e.g., AICuFe-B). "Me &quot; designates a metal, the 3/12 Austrian Patent Office AT 12389 U1 2012-04-15

Designations (1), (2), etc. accordingly indicate various metals contained; w, x, y, z = 1, 2, 3, etc. denote the stoichiometric index numbers of the respective substances.

Depending on the field of use and application, the material consists of a material, in particular having a higher thermal conductivity / temperature conductivity and / or a low thermal expansion compared to the pure matrix material, the following material compositions: [0039] a ) Matrix material A as metal or alloy or mixture of the described metals and / or the alloys. These can be present with a volume fraction in the range of 10 to 90 vol%.

B) A filler B: The filler B is a carbon-based filler, which is characterized above all by a high thermal conductivity / at least in one spatial direction) and a low thermal expansion (at least in one spatial direction). The carbon-based filler can be considered as: carbon / graphite particles (typical particle size in the range 1 - 500 pm) carbon / graphite fiber (typical diameter: 5-1 Opm, length: 50 pm - 2 mm) carbon / Graphite nanofiber (typical diameter: 50-500nm, length: 1pm-100pm) carbon / graphite nanotubes (typical diameter: 5-100nm, length: 1pm-2mm) diamond (typical diameter: 1pm) 500pm).

The filler B may be present with a volume fraction of 10 to 80 vol%. C) Additive C: The additive C is a metal boride, which is ideally present as an additive or additional phase, but also in Consequence of a reaction of the elemental boron with a corresponding metal in-situ (ie during the manufacturing process) can be formed. In this case, residual amounts of elemental boron in the matrix A or their reaction products with the filler B may be present.

Alternatively, the additive C may also be applied to the filler B in the form of a coating. In this case, when using matrix materials A with a melting point below 1200 ° C., a completely covering layer is not necessarily required. It is also sufficient if at least 20% of the diamond surface is covered with the layer and / or the layer is in the form of non-contiguous islands.

In addition to matrix A, filler B and additive C can be present in the material up to 10 vol% of intermediate phases. These can:

In the form of amorphous carbon, from a conversion of filler B.

In the form of reaction products of the matrix (metal / alloy) with the filler B (eg formation of carbides) in the form of reaction products of the matrix (metal / alloy) A with the atmosphere used in the course of the preparation (eg of oxides, nitrides) in the form of reaction products of the metal borides or elemental boron C with the filler B and / or in the form of reaction products with the atmosphere used in the course of the preparation.

By a clever combination of matrix, filler or additive content, it is possible to vary the properties of the materials in a wide range and thus each optimal properties in terms of thermal Conductivity, thermal expansion or material density to achieve.

Role of the additive C

The use of the additive C in the composite material fulfills various functions depending on the selected matrix A or, depending on the objective, which material properties of the material are of primary interest.

A) improvement of the thermal connection (reduction of the thermal Kontaktwi

Residue) between matrix A and filler B.

B) Improvement of the mechanical bond / adhesion between matrix A and filler B or improvement of the temperature cycling properties c) Protection of the filler B from thermal decomposition / conversion or protection of the filler B against excessive reactions with the matrix A. In this case, the additive C is ideally present as a coating on the filler B. Metal borides with a high melting point, such as TiB 2 or ZrB 2, are particularly suitable for this purpose.

The use of the additive C, if this is elemental boron, in combination with copper (matrix A) and a filler B is not the subject of the invention, thus excluded. The following production methods are used for the production of the composite materials Liquid phase infiltration processes can be usefully used if the

Matrix material A has a melting temperature below 1500 ° C.

Here, pressureless or pressure-assisted methods are useful. In both cases, either a preform or powder bed of the filler B can be placed in a mold, on which a corresponding starting material (matrix A + additive C) is placed. The bulk material is melted and infiltrated pressure-less or pressure-assisted powder bed. Alternatively, a powder bed consisting of matrix A powder, filler B or additive C can be compacted in a mold under mechanical pressure at room or moderate temperature and subsequently in an oven under appropriate conditions, the matrix A can be brought into the liquid state , It is recommended that the exercise of additional mechanical pressure, so that a dense body is achieved. Another possibility is to coat the filler with a layer of a metal boride C and then perform the infiltration according to the above statements.

The infiltration process is preferably carried out in vacuo or under protective gas, occasionally under nitrogen or under hydrogen or mixtures thereof.

Various methods such as gas pressure infiltration or squeeze casting can be used as common methods for producing a shaped body, to name only the best known.

[0068] Solid phase processes, commonly known as sintering or hot pressing processes.

For the preparation of the composite materials first powder of the matrix A, the filler B and the additive C are mixed accordingly homogeneous. It is also possible to add additives of organic binders to a small extent. Thereafter, these powder mixtures may be compacted in a compression mold under pressure (typically at pressures between 10 to 500 MPa), followed by a sintering process at a temperature correspondingly selected for the matrix A. This is typically below the melting point of the main component of the matrix, in the case of a eutectic alloy below the melting point of the Austrian Patent Office AT 12389 U1 2012-04-15

Eutectic. The sintering process is preferably carried out in vacuo or under protective gas, occasionally under nitrogen or under hydrogen or their mixtures.

A more advanced process which also makes it possible to produce complex components in final form is the powder injection molding process. The above powder mixtures are provided with a binder and homogenized accordingly. This powder-binder mixture is injected with an injection molding machine in a corresponding tool. The green part thus obtained is subsequently debinded and sintered.

Typical sintering parameters (sintering temperature / hold time / atmosphere) are obvious to the person skilled in the art for the various metal / alloy systems and are typically in the range of 0.7Tm <T &lt; Tmeit (Tmeit denotes the melting temperature of the matrix A). The holding time can be in the range of a few minutes or a few hours, depending on the sintering temperature used.

PRESSURE SUPPORTED SINTERING METHOD

Pressure-assisted sintering processes are particularly advantageous when the filler content B is greater than 20% by volume or when a material with the lowest possible porosity is desired. Again, it is assumed that a powder mixture of substances A, B and C.

Among the possible pressure-assisted sintering methods, the following (but not exclusive) may be used. All of these methods are characterized in that the powder mixtures are compacted in a mold (metallic or ceramic mold or graphite mold) at elevated temperature and use of mechanical pressure.

The mechanical pressures used during the hot pressing process may range from a few MPa up to a few GPa. Typically, pressures in the range of 10 to 100 MPa are used. The hot press temperatures used are for composite materials using matrix materials A with a melting point &gt; 1500 ° C in a range of 0.5 - 0.8 Tmeit the melting temperature.

When using matrix materials A with a melting point <1500 ° C, the hot pressing temperature used may be in the range 0.7-1.1. A Heißpresstemperatur above the melting temperature brings advantages insofar as by the simultaneous application of mechanical pressure, especially for rigid fillers B (eg diamond), only a small squeezing takes place, whereby the filler content B in the composite material is additionally increased and ensures that as possible Pores are present in the material. At the same time, a liquid phase also allows the diffusion or reaction.

Advantageous and, in particular, cost-effective production methods for the composite material are rapid hot pressing processes, e.g. directly heated hot pressing, inductively heated hot pressing or processes such as spark plasma sintering and molds derived therefrom. In any case, these methods are characterized by high heating rates / cooling rates in combination with a short hold time and thus low cycle time.

The sole mixing of matrix A and filler B brings with it the following problems, which are eliminated by the use of additive C to a high mass or are substantially defused. A) Poor thermal bonding of matrix A to the filler B, so that the thermal cal conductivity of the filler B is not or only insufficiently utilized in the composite material. As an example copper is mentioned here where a bad thermal contact between copper and carbon is observed. This is due, on the one hand, to the lack of wetting of carbon by copper and also to the different heat conduction mechanisms: metal (atoms bound by metal bond) = electron conductor, while e.g. Diamond (in which the atoms are covalently bonded) conducts heat through phonons. The additive C helps to reduce the thermal contact resistance. B) Good thermal contact between matrix A and filler B is often accompanied by good mechanical bonding. This is particularly necessary if the low thermal expansion of the filler B is to be exploited.

C) Especially for matrix materials A, which either require high process temperatures (> 1000 ° C.) or long cycle times and / or in which direct reactions can occur between the matrix A and the filler B, it is advisable to to deposit the additive C as an opaque layer on the filler B. In this case, a variety of methods for the coating can be used. The best known are physical and chemical coating processes (PVD and CVD).

What are the preferred in the context of the invention process for the preparation of the new

As regards composite materials, the following addition should be made:

Here, a mixture of filler B and additive C or filler B is infiltrated with a mixture of matrix A and additive C, or preferably filler B, which is coated with additive C, is infiltrated with matrix A. The infiltration can be done without pressure but also pressure assisted. In this case, the matrix material A or the mixture of matrix material A and additive C before reaching the melting point is present as a body (so-called bulk material). The selected infiltration temperature is usually at temperatures greater than the melting temperature of the matrix A (> Tmelt) or below 1.3 times the melting temperature instead (<1.3 * Tmelt). Ideally, heating rates of> 5 K / min, preferably> 10 K / min, particularly preferably> 5 K / min. 20K / min used. The holding time to maximum temperature is in the range of 0.1 min to 120 min, preferably less than 60 min, more preferably less than 30 min. The infiltration - if operated under pressure - can take place with pressures of up to 500 MPa, preferably below 300 MPa, preferably below 100 MPa. Powder Metallurgical Processes Hiebei is a powder mixture of matrix A, filler B and additive C in the form of a powder mixture before or as a powder mixture of matrix A powder with filler B coated with additive C. A homogeneous mixture is either pressed at room temperature or shaped by means of a binder via an injection molding process. In the latter case, the binder is removed in an intermediate step and for both processes the sintering process follows, i. the porous shaped body produced is sintered at a suitable temperature to form a compact shaped body. In this case, the required process temperature (sintering temperature) is (0.7 - 0.99) times the melting temperature. The holding time is in the range of 5 minutes to 6 hours, preferably less than 3 hours, more preferably less than 1 hour. As an alternative manufacturing method, the sintering process may be pressure assisted, i. During the sintering process, the sample may be pressurized (e.g., mechanically or by gas), thereby enabling or accelerating the densification.

Preferred process forms are - but not exclusively - hot pressing or

Hot isostatic pressing or more preferably rapid hot pressing method, such as direct heated hot pressing, inductively heated hot pressing and spark plasma sintering and modified embodiments whose characteristics are a high heating and cooling rate, mechanical pressure and a short cycle time.

In this case, the selected process temperatures for the production include: a heating rate / cooling rate of> 5 K / min, preferably> 10 K / min, and more preferably> 20 K / min. The holding times at the respectively selected temperature (between 0.5 and 1.1 Melt Tmelt) are less than 300 min, more preferably less than 100 min, more preferably less than 30 min. For both sintering processes (pressure-less or pressure-assisted), suppression is used, in particular precipitation gas, in particular nitrogen, hydrogen or their mixture. In the case of the pressure-assisted processes, the pressing pressure may be in the range of 5 MPa to 5 GPa, preferably in the range of less than 100 MPa, more preferably less than 50 MPa.

The procedure according to the invention for producing materials according to the invention is explained below with reference to the examples. Example 1: 2.76 g of 120/140 (US mesh) synthetic diamond powder was mixed with 0.26 g of CrB2 powder and 6.60 g of Cu powder for 2 hours. In the reference sample, 2.76 g diamond powder was mixed with 7.01 g Cu powder.

In each case about 2 g of the mixture were introduced into a graphite tool sprayed with boron nitride with a diameter of 10 mm and precompacted at a mechanical pressure of 5 MPa and placed under vacuum in a spark plasma sintering plant (10'2 mbar). brought to a temperature of 1000 ° C at a heating rate of 150K / min and the mechanical pressure was increased to 35 MPa. After a holding time of 15 minutes, the samples were cooled to 300 ° C and then removed from the plant.

The temperature conductivity was subsequently measured on the sample. The sample without CrB2 additive showed a value of 71 mm 2 / s, while the sample with CrB 2 additive a thermal conductivity of 128 mm 2 / s. EXAMPLE 2 A powder mixture consisting of 1.66 g of synthetic diamond having a particle size was prepared 120/140 (US mesh), in which case 0.026 g ZrB2 and 4.17 g Cu were used. The reference powder mixture used was the composition of copper and diamond without boride addition described in Example 1.

In each case about 2 g of the mixture of each powder mixture were introduced into a boron nitride-sprayed graphite tool with a diameter of 10 mm and precompacted at a mechanical pressure of 5 MPa and in an inductive hot press under vacuum (10 2 mbar) and a pressure of 30 MPa at a heating rate of 100K / min brought to a temperature of 1000 ° C. After a holding time, the samples were cooled at 30 K / min to 250 ° C and then removed from the hot press.

The temperature conductivity was subsequently measured on the sample. The sample without ZrB2 showed a value of 74 mm2 / s, whereas the sample with ZrB2 addition showed a thermal conductivity of 124 mm2 / s. The presence of the ZrB2 phase of the additive in the resulting composite is documented in the XRD diagram in Fig. 1. EXAMPLE 3: 2.76 g of synthetic diamond powder having a grain size of 120/140 US mesh were prepared by a CVD method with a 1 pm TiB2 coating and subsequently mixed with 3.53 g of Ti powder. As a reference sample, 2.76 g of diamond powder was mixed with 3.53 g of Ti.

In each case 1 g of the powder mixtures was brought in a graphite tool (10 mm) sprayed with boron nitride in a hot inductive press at a heating rate of 150 K / min to a temperature of 800 ° C and held for a period of 20 min at this temperature. In this case, a mechanical pressure of 50 MPa was applied. After the hold time, the samples were cooled to room temperature at a cooling rate> 20 K / min.

The measurement of the thermal diffusivity on the reference sample showed a value of 22 mm 2 / s, while those on the TiB 2 -coated sample a value of 31 mm 2 / s. EXAMPLE 4 671.3g 70/80 (US mesh) 70/80 size synthetic diamond powder was mixed with 12.2g MgB2 and 505.5g Al powder.

180 g of the powder mixture were introduced into a boron nitride-sprayed graphite tool (size 150 mm × 150 mm) and brought to a temperature of 700 ° C. in a conventional hot press at a heating rate of 10 K / min. In the process, a mechanical pressure of 30 MPa was successively built up. After a hold time of 30 minutes, the sample was cooled to room temperature. From the plate, samples for thermal analysis were cut out by means of a water jet and the thermal diffusivity was determined.

The average thermal conductivity of the plate was in the range of 284 ± 29 mm 2 / s and the average coefficient of thermal expansion at various points on the plate was found to be 8.4 ± 0.5 ppm / K (measured at 50 ° C.).

For the reference sample (without MgB2), a thermal conductivity of 249 ± 24 mm 2 / s was determined. The presence of the MgB 2 phase was confirmed by XRD, see FIG. 2. EXAMPLE 5 2.76 g 70/80 (US mesh) synthetic diamond powder were mixed with 0.04 g boron powder and 1, 4 g Mg powder mixed for 2 hours. In the reference sample, 2.76 g of diamond powder was mixed with 1.37 g of Mg powder.

In each case about 1 g of each powder mixture was introduced into a 10 mm diameter graphite tool sprayed with boron nitride, precompacted at a mechanical pressure of 5 MPa and heated in an inductive hot press under argon at a heating rate of 100 K / min to a temperature of 600 ° C brought. After a holding time of 5 minutes, the samples were cooled at 30 K / min to 250 ° C and then removed from the hot press.

The temperature conductivity was subsequently measured on the sample. The reference sample without addition of boron showed a value of 70.6 mm 2 / s, whereas the sample with boron addition had a thermal conductivity of 91.4 mm 2 / s. EXAMPLE 6 1.66 g 70/80 (US mesh) synthetic diamond powder was mixed with 0.075 g AIMgB14 powder and 3.96 g Cu powder for 2 hours. In the reference sample, 1.66 g of diamond powder was mixed with 4.19 g of Cu.

In each case about 2 g of each powder mixture were introduced into a 10 mm diameter graphite tool sprayed with boron nitride, precompacted at a mechanical pressure of 5 MPa and heated in an inductive hot press under argon at a heating rate of 100 K / min to a temperature of 1020 ° C brought. After a holding time of 15 minutes, the samples were cooled at 30 K / min to 250 ° C and then removed from the hot press.

Subsequently, the temperature conductivity was measured on the sample. The reference sample without AIMgB14 additive showed a value of 72 mm2 / s, whereas the sample with AIMgB14 additive showed a thermal conductivity of 165 mm2 / s. EXAMPLE 7 0.8 g of 120/140 (US mesh) synthetic diamond powder coated by a CVD process with a 1 pm layer of TiB2 was charged into a boron nitride sprayed graphite mold. A copper disc of 1.3 g was placed thereon and covered with a graphite stamp sprayed with boron nitride. This assembly was heated under hydrogen to 1200 ° C at a heating rate of 50 K / min, and after reaching the temperature, a pressure of 0.5 MPa was applied to infiltrate the diamond fill. 12.9

Claims (11)

Austrian Patent Office AT 12389 U1 2012-04-15 The sample was cooled accordingly and thereafter the temperature conductivity of the sample was determined. This was 112.7 mm2 / s. The thermal expansion coefficient was found to be 7.4 ppm / K (at 50 ° C). Claims 1. Composite material with the base components thermally highly conductive metal, carbon and boron, excluding the combination of copper or copper alloys as matrix A, filler B and elemental boron as additive C and comprising a) a matrix A, consisting of a metal or alloy having a thermal conductivity &gt; 50 W / mK (at room temperature), from the group of the metals Al, Mg, Cu, Ag, Ni, Cr, Co, Nb, Ta, W, Mo, Si and Fe and their combinations or of - a metal with a coefficient of thermal expansion of less than 10 ppm / K (at room temperature) from the group of Ti, Cr, Nb, Ta, W, Mo and Si and their combinations, which are real alloys or multiphase systems, or of an alloy of the above-mentioned metals and their Combinations with the alloying elements Sn, Zn, Ce, Mn, La, Li, Sc, Y and / or V, which alloy may contain up to 20 wt .-% of the just mentioned alloying elements, and / or from a - multi-phase system consisting of the abovementioned metals or alloys with at least one other ceramic filler (dispersoid), from the group Al 2 O 3, ZrO 2, SiC, Si 3 N 4, AIN and BN in amounts of up to 20% by weight, where the matrix A is a fraction on the composite of 10 to 90 vol .-%, preferably from 25 to 75 vol .-%, in particular b) a filler B which is based on at least one of the modifications of the carbon, which has a high thermal conductivity and / or a low thermal expansion in at least one spatial direction, from the Group carbon or graphite particles including nanotubes, more preferably diamond particles, or mixtures of these carbon fillers with each other, wherein it is preferably provided that the filler B is coated with the additive C, and wherein the filler B in total in a proportion of 10 to 80 % By volume, preferably from 20 to 70% by volume, more preferably from 30 to 65% by volume, preferably homogeneously distributed, present in the matrix A and finally c) an additive C, namely metal borides and / or Boron, from the group simple Bo-ride with the stoichiometric composition MeB, MeB2, Me2B5, or MeB6, complex borides from the group Me (1) xMe (2) yBz, eg AIMgB14 or Me (1) w-Me (2) x-Me (3) y-Bz, e.g. AICuFe-B or its mixture, where "Me &quot; represents metal, the designations (1), (2) and (3) indicate various metals contained and w, x, y, z = 1, 2, 3, .. denote the stoichiometric index numbers of the respective substances, and wherein the additive C in total with a proportion of 0.1 to 20 vol .-%, preferably from 0.1 to 10 vol .-%, especially from 0.1 to 5 vol .-%. Present. 2. Composite material according to claim 1, characterized in that in addition to the components A, B and C an intermediate phase, from the group. Reaction products and / or decomposition products between matrix A and additive C, reaction and / or decomposition products between filler B and matrix A, reaction and / or decomposition products between filler B and additive C, reaction and / or decomposition products of matrix A and / or filler B and / or additive C with the gas used in each manufacturing atmosphere, in particular reaction products with oxygen or nitrogen, and - amorphous carbon, formed from a conversion of filler B are included, wherein the intermediate phases up to a Content of not more than 10% by volume, preferably less than 5% by volume, more preferably less than 3% by volume. 10/12 Austrian Patent Office AT12 389U1 2012-04-15 3. Material according to claim 1 or 2, characterized in that the additive C is present on the filler B in the form of a coating with a surface coverage of at least 20% of the filler B either in the form of a layer and / or as separate islands on the filler B. and wherein the proportion of the coating in the range of 0.1 to 20 vol .-%, preferably from 0.1 to 10 vol .-%, particularly preferably in the range 0.1 to 5 vol .-%, is located. 4. Composite material according to one of claims 1 to 3, characterized in that it is present as a gradient material with varying filler content and / or varying particle size of the filler B, or as a sandwich material, wherein the composite material is preferably present as a sandwich material, the on the outside either over the entire surface or on the two outer sides with a metallic zone consisting of the matrix A and / or coating with the same, surrounded, wherein the metallic zone has a thickness in the range of 10 pm to several mm, preferably from 10 to 500 pm, more preferably from 20 to 200 pm. 5. Composite material according to one of claims 1 to 4, characterized in that it has a density of more than 80%, preferably of more than 90%, in particular of more than 95%. 6. Composite material according to one of claims 1 to 5, characterized in that it is created by liquid phase infiltration or - by sintering or pressure-assisted sintering of a powder mixture of matrix A, filler B and additive C, or - by soldering or bonding, at least one side is bonded directly to a metallic or ceramic plate. 7. A method for producing the composite material with a low coefficient of thermal expansion and / or high thermal conductivity or thermal conductivity according to one of claims 1 to 6, characterized in that the same is formed by means of liquid phase infiltration, in which a mixture of the filler B with the additive C or the filler B is infiltrated with a mixture of the matrix A and the additive C or the filler B, which is coated with the additive C, with the matrix A at elevated temperature, optionally pressure-assisted infiltrated. 8. A process for producing the composite material according to any one of claims 1 to 6, characterized in that by powder metallurgy matrix A, filler B and additive C in the form of a powder mixture or a powder mixture of matrix A powder with the filler B, the coated with the additive C is used. 9. The method according to claim 7 or 8, characterized in that a filler B forming carbon-based powder, in particular diamond powder, is used, wherein the particles coated with a coating of the additive C at least 20% of the surface of said particles is. 10. The method according to any one of claims 7 to 9, characterized in that the heating of the mixture and / or the sintering process in the atmosphere of a technical gas from the group of hydrogen, argon and / or nitrogen or at reduced pressures of less than 10'1 mbar , is made. 11. The method according to any one of claims 7 to 10, characterized in that the filler B - in the case of diamond with a particle size of 1 to 500 .mu.m, preferably from 20 to 350 .mu.m, more preferably from 30 to 250 pm, and - im Case of carbon nanotubes with a diameter in a range of 5 to 100 nm and a length in a range of 1 to 200 pm, preferably from 1 to 100 pm, used or added to a respective starting mixture. 11/12