DE102015221853B4 - Process for the preparation of carbonaceous ceramic components - Google Patents

Abstract

Process for the production of carbonaceous ceramic components, characterized
in that an aqueous slip comprising a gelling agent, which is later graphitizable carbon carrier and composed of at least one oxide grain and / or non-oxide grain, is conveyed into an aqueous hardener solution containing at least 0.05% by weight of metal cations for gelling and forming therein a 2- or 3- dimensional component is formed,
that the 2- or 3-dimensional component is separated from the aqueous solution after a gelation time of 1 sec to 30 min, dried and thermally treated to pyrolysis of the carbon support,
wherein the aqueous slurry contains as gelling agent an alginate in a proportion of 0.1 to 5 wt.% Of the solids content of the aqueous slurry,
wherein the oxide grain and / or non-oxide grain, the graphitizable carbon carrier and the alginate are mixed and processed with water and with the aid of additives to form a stable suspension, the aqueous slip,
wherein as additives dispersing agents, wetting agents, temporary binders and defoaming agents are used,
wherein the green bodies formed and gelled in the aqueous hardener solution are impregnated after drying with an identical or different kind of ceramic slip.

Description

The invention relates to the production of carbonaceous ceramic components with a macrostructure. Depending on the material used, the resulting components can be used as heat-transferring materials because of their large surface area for the filtration of fluids, as catalyst or catalyst support.

Methods are known for producing complex structures, such as robocasting or fused deposition modeling (FDM). These methods are based on robotic deposition processes in which colloidal so-called polymer inks or gels are extruded and produce a continuous strand of material. As a result, among other things, two-dimensional structures that form a complex three-dimensional geometry by layered superimposition are generated. Exemplary is in EP 0833237 B1 described the fused deposition modeling, which is basically independent of the material to be used, as long as there is sufficient adhesion of the individual layers with each other and the material is basically extrudable, that has appropriate rheological properties. This is exemplified in DE 102006017595 A1 describe how to make and process a ceramic slip for robocasting to produce medical implants. Other manufacturing processes based on the "solid free-forming" principle are stereolithography or selective laser sintering. In these additive manufacturing processes, thin layers of the material to be produced are applied and irradiated by UV radiation (in stereolithography ( WO 2009128902 A1 )) or via a short laser pulse (in selective laser sintering ( WO 2004089851 A1 )) hardened. This results in layers complex components, but this brings the disadvantage of a complex data processing with it.

Another possibility for producing components with a linear, endless structure is the extrusion process already established in the ceramics industry. Depending on the type of extruder, a viscous mass is pressed either by means of a screw conveyor or by means of a hydraulically operated punch through a so-called mouthpiece with a defined geometry. The resulting green body has a linear geometry and, in the case of a screw extruder, can be continuously produced. The operation of a piston extruder, however, is discontinuous. Regardless of the type of extruder, the plastic mass can be evacuated under vacuum and / or the process temperature can be changed. As a result, it is possible to generate so-called honeycomb structures which, as macroporous components which can be flowed through, find above all manifold applications in the filtration of fluids and, in particular, in soot particle filters for diesel-operated engines (Offenlegungsschrift WO2009000664 A2 ). The extrusion process is used not only in the ceramic industry, but also for the production of graphite electrodes. This is possible because, as in EP 0109839 B1 described coarse-grained material used up to 6.35 mm grain size and the extrusion mass is processed at a temperature of 110 ° C. This is possible by using a, at this temperature, low viscosity resin. The extrusion of fine - grained ceramic materials with a proportion of graphite as carbon support for water - based systems is known in US 5344799 A described. However, the graphite does not serve to form a carbon matrix but is burned out during the sintering process in order to produce a high porosity. These produced, almost carbon-free, foamed ceramics are to be used for the filtration of various materials.

Due to the good environmental compatibility, alginates are also used in ceramic gel casting ( WO 2006027593 A2 ). WO 2006027593 A2 describes a process for the preparation of catalyst supports by means of gel casting, wherein the ceramic slurry is poured into a casting mold for shaping. In this shaping process, synthetically prepared monomers harmful to health and the environment, such as monofunctional acrylamide and difunctional methylenebisacrylamide, are usually added to a ceramic slip ( EP 1306148 B1 ). Addition of an initiator and a catalyst causes a pH change and the monomers polymerize, thereby forming a gel network. The result is a dimensionally stable ceramic green body with a geometry close to the final dimensions, which can also be green-painted if required. This process is developed for the production of three-dimensional complex components in discontinuous operation. By using alginate, the usual toxic acrylamides are replaced by non-toxic natural materials, thus reducing costly occupational safety measures.

In general alginates are often used in medicine as auxiliaries for bandages because of their good compatibility in the human body (food additives E 401-404) and their gelling properties at room temperature ( WO 2003045293 A1 ) or as an impression material for dental technology ( DE 3831043 A1 ) used. Other uses include alginates as gelling agents or as immobilizing carrier material ( DE 59004966 D1 ) in food technology and in cosmetic technology ( EP 0391803 B1 ).

DE 10 2004 002 561 A1 describes a process for producing refractory grain carbonaceous carbonaceous refractory products and organic binder which comprises, as an organic binder, a powdered graphitizable coal tar pitch having a benzo (a) pyrene content of less than 500 mg / kg and a coking residue of at least 80% by weight DIN 51905 and a graphitizable binder which is liquid at room temperature and has a coking residue of at least 15% by weight and a benzo [a] pyrene content of less than 500 ppm in accordance with DIN 51905, mixes this with the other constituents, converts it into a shaped body and then with a Temperature of 150 to about 400 ° C heat treated.

WO 2015/077130 A1 discloses the production of ceramic proppant particles (proppants) with 0.45 to 0.90 mm diameter as filling and supporting particles, in particular filling material in geological columns in connection with the oil and gas production. For this purpose, a ceramic slurry is pressed through a perforated membrane to form particles. The particles are collected and dried.

Ceramic foam filters are usually used especially for the filtration of steel and metal melts. These filters can consist of oxide materials (use for aluminum melts) or of a carbon-bonded ceramic material (use in steel melt filtration) ( DE 102011109684 B4 and DE 102011109681 B4 ). The carbon bond exhibits a non-wetting behavior to molten steel, which reduces the corrosion of the filters and can also positively influence the filtration properties. In addition, due to the lower thermal expansion and the higher thermal conductivity, carbon-bonded ceramics exhibit better thermal shock behavior compared to ceramic-bonded systems. In order to be able to use these good thermal and thermo-mechanical properties of carbon-bonded ceramics in particular, open-cell foam structures are generated via the replica method. For this purpose, a polymer foam, usually polyurethane, used as a carrier material and impregnated with a ceramic slip. Optionally, after drying the first slurry layer, a second functionalized ceramic layer may be applied by a spray process. The subsequent pyrolysis process burns out the polymer foam and leaves triangular concave cavities within the individual webs of the ceramic foam which lead to a significant reduction in the mechanical properties of the carbon-bonded foam ceramics.

The object of the invention is therefore to provide an improved process for the production of fine-grained carbonaceous ceramic components with a macrostructure that allows the production of components with improved mechanical properties, in particular for use as a filter for molten metals, but also as a catalyst or as a heat transfer material.

The object is achieved by a method according to the main claim. Advantageous embodiments are specified in the dependent claims.

According to the invention, a method is provided for producing carbonaceous ceramic components having a macrostructure, wherein a gelling agent-containing, aqueous slip of a later graphitisable carbon support and of at least one oxide grain and / or non-oxide flow into an aqueous hardener solution with at least 0.05 wt.% Metal cations promoted for gelation and is formed into a 2- or 3-dimensional component, that the 2- or 3-dimensional component after a gelation time of 1 sec to 30 min separated from the aqueous solution, dried and thermally treated to pyrolysis of the carbon support wherein the aqueous slurry as gelling agent contains an alginate in a proportion of 0.1 to 5 wt.% Of the solids content of the aqueous slurry, wherein the oxide grain and / or non-oxide grain, the graphitisable carbon carrier and the alginate mixed and mixed with water and with Additives too a stable suspension, the aqueous slurry, are used as dispersants, wetting agents, temporary binders and defoaming agents are used as additives, wherein the shaped and gelled in the aqueous hardener solution green body are impregnated after drying with a same or different kind of ceramic slurry.

The later graphitisable carbon carriers are advantageously used with a content of 5 to 90% by weight, based on the solids content of the aqueous slip and at least one oxide grain and / or non-oxide grain, with 10 to 95% by weight, based on the solids content of the aqueous slip.

Peche, synthetic pitches, phenol-based resins, bitumen, tar, wood, coke, coal, biomass or combinations thereof with a content of from 5 to 90% by weight, based on the solids content of the aqueous slip, are advantageously used as later graphitisable carbon carriers.

Al ₂ O ₃ , MgO, CaO, SiO ₂ , ZrO ₂ , Fe ₂ O ₃ , TiO ₂ , Na ₂ O, K ₂ O, P ₂ O ₅ , BaO, Li ₂ O, SrO, Cr _{2 are} preferred as the oxide grains O ₃ or combinations thereof and / or as non-oxide grains are preferably SiC, Si ₃ N ₄ , AlN, B ₄ C, ZrB ₂ , ZrC or combinations thereof with a content of 10 to 95% by weight, based on the solids content of the aqueous Schlickers used.

Preference is given to using fine-grained ceramic materials as oxide or non-oxide streams having a d ₉₀ value greater than 0.1 μm and less than 100 μm.

The fine-grained materials of the oxide and / or non-oxide grain, the graphitizable carbon carrier and the alginate are mixed and processed with water and with the aid of additives to form a stable suspension, the so-called aqueous slip. The additives used are dispersing aids, wetting agents, temporary binders and defoaming agents.

The dispersing agents change the surface properties of the individual carbon and ceramic particles sterically, electrostatically or via a bilayer that forms so that they do not sink immediately and are distributed homogeneously. The dispersants may be, for example, synthetic polyelectrolytes (eg Dolapix PC 21) which change the surface of the solid particles due to electrochemical interactions and thus shield the particles from each other. Depending on the dispersant used and the intended use, the content of dispersants in the ceramic industry is between 0.05% by weight and 1% by weight.

A similar effect, such as dispersing aids, have wetting agents which allow the wetting of, in particular, carbon particles with water and promote stabilization of the solid particles in the slurry. The wetting agents are often not used individually, but the effect to be achieved is usually accompanied by other effects, such as a dispersing effect. For this reason, the wetting agent is usually also the same dispersant and is not listed individually.

To ensure a certain green strength of the components formed in the hardener solution or to increase these, temporary binders are added to the slurry. The temporary binders are mostly long-chain organic compounds, which may also be derived from natural sources. These include u.a. Cellulose ethers, xanthan or polyvinyl alcohol as a non-natural raw material. The temporary binders are present in dissolved form in the slip or bind the solvent - usually water - and mechanically bind the solid particles to themselves. During the subsequent drying of the green body, the water is released again and the ceramic particles are now "interlocked" with the temporary binder, which results in an increase in the green strength. Depending on the nature of the binder and on the purpose or desired properties, typical contents are between 0.1% by weight and up to 10% by weight.

In the homogenization of the slurry, a large proportion of air is introduced into the slurry produced. These inclusions would lead to increased porosity in the later component, which would lead to a lowering of the mechanical properties. In order to prevent this, defoamers are added to ceramic slips. These are often based on silicone oils in the ceramics industry, but for other applications can also be made, for example, of alkyl polyalkylene glycol ether (Contraspum K 1012). preferably defoamer based on silicone oils buried. This changes the surface tension of the slurry and the trapped air can be more easily removed by applying a vacuum. The usual contents are very low and are in the range between about 0.01 wt.% And 0.5 wt.%.

Advantageously, the method for producing the carbonaceous ceramic components with a three-dimensional periodic macrostructure is performed so that an aqueous slip with a later graphitisable carbon support with at least 5 wt.% And at least one oxide grain and / or non-oxide grain with at least 10 wt.% And an alginate is treated with at least 0.1 wt.% And continuously conveyed by means of a pump and a hose connection from a reservoir via a tapered fitting into an aqueous solution containing at least 0.05 wt.% Metallcationen, so that during gelation a strand is formed, which is converted to macrostructures on the movement of the tapered molding and dried after removal from the metal cations-containing aqueous solution and thermally treated.

The gelling agent used is preferably sodium alginate, potassium alginate, calcium alginate, ammonium alginate, propylene glycol alginate and / or combinations thereof of at least 0.1% by weight.

Aginates used are salts of the water-insoluble alginic acid obtained by extraction processes. These salts consist of two main components, the α-L-guluronate (G) and the β-D-mannuronate (M). Both monomers form homopolymers in the form of MM and GG blocks and heteropolymers with alternating M and G blocks (-MG-). The most important constituents for the gelling of alginates are the GG blocks, since only these form the so-called "egg-box" structure, which leads to an interconnection of the individual molecular chains into a gel structure by an additional supply of predominantly divalent metal cations. The other polymers (MM, GG and MG blocks) do not or do not participate in the gelation, but cause a higher elasticity in the resulting gel structures.

Preferably, the aqueous hardener solution Ca ^2+, Ba ^2+, Mg ^2+, Sr ^2+, Al ³⁺ or Fe ²⁺ ions, or combinations of at least 0.01 weight thereof.% But at most up to the complete saturation of the solution as metal cations.

On the one hand, calcium chloride CaCl ₂ and barium nitrate Ba (NO ₃ ) ₂ in aqueous solution have proved to be the hardener solution on the one hand because of the good solubilities and on the other hand because of the good gelation properties.

The prepared green bodies with a single strand diameter of 1 - 2 mm can be left for less than 10 min in a 1 wt .-% aqueous barium nitrate solution, which is sufficient for a complete gelation.

After sufficient gelation, the components formed in the hardener solution are rinsed with distilled water to remove excess hardener solution and thus impurities on the surface of the components.

This is followed by a drying process in which the green bodies formed and gelled in the aqueous solution are dried at temperatures of up to 50 ° C. and until the components have a constant mass, and are pyrolyzed in the last treatment step to 1400 ° C. during a suitable heat treatment.

In a subsequent pyrolysis process, the component is coked at temperatures up to 1400 ° C with the exclusion of oxygen. The bituminous and / or tar-based pitches added in the range 10-40% by weight form a carbon matrix as the continuous phase, with the addition of 0-15% by weight of graphite and 0-15% by weight of carbon black Promoted carbon matrix and the total carbon content in the coked product is increased. This carbon bond contains the ceramic grain as a discontinuous phase.

According to the invention, the green bodies shaped and gelled in the aqueous hardener solution are impregnated after drying with an identical or different kind of ceramic slip.

The impregnation takes place by means of spraying, dipping or similar coating methods (such as, for example, thermal spraying, electrospinning, chemical vapor deposition and / or physical vapor deposition and serves, on the one hand, to increase the strength of the shaped green bodies and, on the other hand, to functionalize the surface For the functionalization, the base material of the molded component is to be impregnated with a slurry, thereby achieving the desired properties which are adapted to the respective intended use, for example for use as a steel melt filter, a high resistance to corrosion and thermal shock Heat exchangers should the material have a high thermal conductivity and use as a catalyst requires a high surface area (reaction surface).

Advantageously, the green bodies formed and gelled in the aqueous hardener solution after drying with a ceramic slip of maximum carbon content by introduced graphitizable carbon support in the form of pitches, synthetic pitches, phenol-based resins, bitumen, tar, wood, coke, coal, biomass or Combinations thereof of at most 95 wt.% Has and a ceramic grain consisting of Al ₂ O ₃ , MgO, CaO, SiO ₂ , ZrO ₂ , Fe ₂ O ₃ , TiO ₂ , Na ₂ O, K ₂ O, P ₂ O. ₅ , BaO, Li ₂ O, SrO, Cr ₂ O ₃ or combinations thereof as oxide grain and / or SiC, Si ₃ N ₄ , AIN, B ₄ C, ZrB ₂ , ZrC and combinations thereof are used as non-oxide grain to maximum 100 wt.% Of the solids content of the coating slip used.

The fine-grained materials of oxide and / or non-oxide Kömung, the graphitizable carbon support and the alginate are mixed and processed with water and with the help of additives to a stable suspension, the aqueous coating slurry. The additives used are dispersing aids, wetting agents, temporary binders and defoaming agents.

The method according to the invention makes it possible to produce fine-grained carbon-bonded ceramic components with an open through-flow macroporosity from a water-based ceramic slurry via a continuous shaping process. This process is carried out by adding powdered alginate to a ceramic slip, consisting of ceramic filler, carbon in the form of graphite, carbon black or carbon-producing tars, pitches and resins. This slurry is withdrawn from a reservoir, preferably with an integrated agitator, to avoid sedimentation and segregation, through a hose (made of PVC, silicone or other materials resistant to slip) using a suitable pump (in which case a peristaltic pump was used) a container with a low percentage (1 - 10 wt .-%) polyvalent metal cations containing solution (hardener solution) pumped. The slip leaves the delivery hose within the hardener solution and can be withdrawn by suitable processes as a continuous strand or deposited as an ordered structure within the hardener solution.

According to an advantageous embodiment of the method according to the invention, the slip mass conveyed into the hardener solution is transferred by means of a computer-assisted handling system into a two-dimensional strand structure, which is transferred into a three-dimensional green body by repeated superimposition.

In order to achieve open flow-through macroporous structures of the components, the production of the components is supported by a computer-controlled handling system. As a result, previously generated computer-generated structures can be produced reproducibly. Since the gelation of the endless strands takes place in situ, only the near-surface layers of the strands are initially gelled by direct contact with polyvalent metal cations. The inner core remains liquid for a certain time and the gel formation taking place there is determined by diffusion processes of the metal cations into the interior of the strands produced.

The slurry required for the production of the green body is conveyed from a storage container. For this purpose, an outlet must be installed in order to be able to pump the slurry out of the storage tank, through the hose and into the aqueous solution by means of the peristaltic pump. The reservoir is chosen so that there is enough slurry for the manufacture of the components. Also advantageous is a device for refilling slips so as to be able to ensure continuous production. In order to avoid possible sedimentation of the sludge in the reservoir through longer service life, an agitator is available to maintain sufficient homogeneity. The Schlickerfördernden hose a so-called mouth or fitting is adapted, which may have a smaller cross section and a different geometry than the hose. In addition, a difference in cross-section between the hose and the tapered fitting, independent of the pump, can provide a higher velocity of the slip at the outlet, if necessary. The slip-carrying components of the system, the reservoir, the hose, as well as the tapered fitting are to be selected from materials which show no reactions with the slurry and can also be cleaned if necessary.

The green bodies can be produced on a suitable base to facilitate removal from the hardener solution and also to facilitate later process steps. After the preparation of the green body, these are, depending on the thickness of the individual webs, left for 1 sec to 30 min in the hardener solution to ensure complete gelation. Subsequently, the still moist green bodies are removed and subjected to a drying process at up to 50 ° C and to constant mass. By a subsequent coating process, preferably spraying process, especially the mechanical properties of the components are improved, since a connection of the individual layers takes place with each other. The slurry used for the coating may be of the same material or otherwise designed to achieve a targeted functionalization.

The invention also includes a ceramic component produced by the method according to the invention from one or more layers of arranged strands.

Advantageously, two-dimensional green bodies are initially formed by means of the computer-aided handling system, which form a three-dimensional green body that is periodic from one layer to the next as a result of multiple stacking.

The replica (Schwartzwalder) method uses as a preform to produce the open-cell structure, polypropylene foams with more or less chaotically distributed porosity and webs. This structure is coated in a multi-step procedure with ceramic slips (mostly aqueous dispersions of ceramic powders) and dried. Due to the manufacturing method, trikonkave cavities are formed during ceramic firing, which result from the burnout of the former polypropylene preform. These cavities, in particular their angular shape, acts as a strength-reducing error under mechanical stress, ie the theoretically possible strength falls on a fraction of this.

Because of their large surface area, the components produced according to the invention are used as filters for the filtration of fluids, in particular for the filtration of metal melts, as catalyst or catalyst support or as heat-transferring materials.

By means of the method according to the invention components without internal and strength-reducing macroporosity are obtained. Depending on the desired batch type of strands produced in the process, it is possible to produce regular filter structures tailored and reproducible. As a result, among other things, the flow conditions occurring in the filter can be better modeled and a targeted adaptation of the structure to the respective requirements can be made. Due to the full webs, the strength potential of the materials used can be better exploited, which technologically more opportunities to use the generated porous structures.

Advantage of the manufacturing method according to the invention over the "conventional" gel casting in the ceramic industry is better environmental compatibility, since natural substances are used, which are also used in food and medical technology and not based on environmentally and harmful substances such as acrylamides. In addition, the inventive method can be used in continuous operation, whereas the gel casting is designed for discontinuous operation.

The field of "additive manufacturing" currently being researched in ceramic technology mainly refers to processes such as known FDM or robocasting. Due to the significantly lower viscosity of the alginate slurry according to the invention, the processing and especially the effort required during the production of the components according to the inventive method is significantly lower. In addition, the slip does not have to have strongly adhesive properties, as is the case with robocasting or FDM due to the layered structure. This situation is circumvented in other processes, such as selective laser sintering or stereolithography by short laser pulses or microwaves. As a result, in turn, new investment costs and stronger occupational safety measures must be taken, which is omitted in the case of the manufacturing method described according to the invention. Nevertheless, there are other ways to produce three-dimensional periodic structures, such. B. the extrusion. However, due to the fact that a plastic mass is needed for this, it is not yet possible to use carbonaceous materials, which is a great advantage of the new process, since slurry technology is used and thus carbonaceous and / or carbonaceous materials can be used , In order to generate comparable structures by means of extrusion, as by means of the method according to the invention, either the base on which the component is to be produced or the complete extruder must be moved. In the method according to the invention, only a part of the transport tube together with the mouthpiece (if present) has to be moved. The effort and thus the costs are significantly lower with the new alginate-based method. In addition, industry usually uses horizontally constructed extruders, which is not possible in the case of three-dimensional periodic structures. As a result, additional costs are incurred in order to arrange and operate extruders vertically. The new production method also offers advantages over the replica method established for the production of ceramic filters for metal melt filtration, above all with regard to the mechanical properties of the later components. The strength-reducing cavities formed during pyrolysis within the individual webs of the foam filter are not present in the structures of the new process. Also, different structures and geometries can be realized. The replica process offers only a selection of different pore sizes of the polymer foams.

To implement the invention, it is also expedient to combine the above-described embodiments and features of the claims.

The invention will be explained in more detail with reference to an embodiment for producing a component made of an Al ₂ O ₃ -C material, without limiting it thereto.

embodiment

Table 1 gives the composition of the slips for the production of the molding and for spray coating. Table 1: Composition of the slip raw material Slip for the production of the molded part [% by mass] Slip for spray coating [% by weight] Al ₂ O ₃ Martoxid MR 70 66 66 Carbores P® 15 15 Graphite AF 96/97 8th 8th Carbon black MT N-991 6 6 additives * Sodium alginate Ceroga NA 4012 1 0 Dolapix PC 21 0.9 0 polyvinyl alcohol 4 0 Contraspum K 1012 0.1 0.1 Castament VP 95 L 0 0.3 ammonium lignosulphonate 0 1.5 * based on the solids content

In the first process step, the dry substances (graphite, carbon black, Carbores P®, alumina, and sodium alginate) for 2 min in a tumble mixer with the same mass grinding balls (Al ₂ O ₃ , 10 mm diameter) mixed to a homogeneous distribution and agglomeration with addition of water to avoid. Thereafter, the liquid ingredients (water, 4 wt.% Aqueous polyvinyl alcohol solution, Dolapix PC 21 and Castament VP 95 L) are added and mixed on a roll bar for at least 4 h. The resulting carbonaceous ceramic slurry is now evacuated by a vacuum pump for about 30 minutes to remove trapped air from the slurry, thus allowing us to generate less porosity in the final molded body.

The slip prepared for the production of the molded article is stored in a storage container and conveyed by means of a peristaltic pump through a silicone tube with an inner diameter of 1.6 mm into a 1% strength by weight aqueous barium nitrate solution. In this case, a continuous strand production of about 10 mm / s can be realized, with higher speeds are possible. The hose end reaching into the barium nitrate solution is guided by a computer-aided handling system. With the computer-aided handling system, a two-dimensional periodic strand structure with a strand spacing of 2 mm and thereafter each in a changed direction 4 further periodic strand structures are placed on a arranged in the barium nitrate carrier with an area of 5x5 cm, so that a three-dimensional molded body is formed.

The moldings thus produced were rinsed with distilled water and then dried at 40 ° C to constant mass. Thereafter, the molding is coated by spraying with the spray slurry listed in Table 1. This is followed by another drying process at 50 ° C also to constant mass. The green body thus obtained is fired in a reducing atmosphere in a coke bed and thus pyrolyzed the carbon support. The temperature regime used consisted of a heating rate of 1 K / min up to a maximum temperature of 800 ° C, which was maintained for a period of 3 h. The heating curve also included intermediate steps of all 100 K, each with a 30-minute hold time. The cooling curve was not controlled and took place freely.

The component produced in this way was processed for a test mold so that it could be used as a filter for a molten steel.

Claims (8)

Process for the production of carbonaceous ceramic components, characterized in that an aqueous slip comprising a gelling agent, which is later graphitizable carbon carrier and composed of at least one oxide grain and / or non-oxide grain, is conveyed into an aqueous hardener solution containing at least 0.05% by weight of metal cations for gelling and forming therein a 2- or 3- dimensional component is formed so that the 2- or 3-dimensional component after a gelation time of 1 sec to 30 min separated from the aqueous solution, dried and thermally treated to pyrolysis of the carbon support, wherein the aqueous slurry as a gelling agent alginate with a proportion from 0.1 to 5% by weight of the solids content of the aqueous slurry, wherein the oxide grain and / or non-oxide grain, the graphitizable carbon carrier and the alginate are mixed and processed with water and with the aid of additives to a stable suspension, the aqueous slurry, wherein as additives dispersing agents, wetting agents, temporary Binder and defoaming agents are used, wherein the molded and gelled in the aqueous hardener solution green body are impregnated after drying with a same or different kind of ceramic slurry. Method according to Claim 1 characterized in that are used as later graphitisable carbon support pitches, synthetic pitches, phenol-based resins, bitumen, tar, wood, coke, coal, biomass or combinations thereof with a content of 5 to 90 wt.% Based on the solids content of the aqueous slurry , Method according to Claim 1 or 2 , characterized in that as the oxide grain Al ₂ O ₃ , MgO, CaO, SiO ₂ , ZrO ₂ , Fe ₂ O ₃ , TiO ₂ , Na ₂ O, K ₂ O, P ₂ O ₅ , BaO, Li ₂ O, SrO , Cr ₂ O ₃ or combinations thereof and / or that as a non-oxide grain SiC, Si ₃ N ₄ , AIN, B ₄ C, ZrB ₂ , ZrC or combinations thereof with a content of 10 to 95 wt.% Based on the solids content of the aqueous slip. Method according to one of Claims 1 to 3 , characterized in that are used as gelling agent sodium alginate, potassium alginate, calcium alginate, ammonium alginate, propylene glycol alginate or combinations thereof to at least 0.1 wt.%. Method according to one of Claims 1 to 4 , characterized in that the hardener solution contains Ca ²⁺ , Ba ²⁺ , Mg ²⁺ , Sr ²⁺ , Al ³⁺ or Fe ²⁺ ions or combinations thereof to at least 0.01% by weight as metal cations. Method according to one of Claims 1 to 5 , characterized in that the slip mass conveyed into the hardener solution is transferred by means of a computer-assisted handling system into a two-dimensional strand structure, which is transferred into a three-dimensional green body by the repeated superimposition. Method according to one of Claims 1 to 6 , characterized in that the molded and gelled in the aqueous solution components are dried at temperatures up to 50 ° C and to the constancy of mass of the components and pyrolized in the last treatment step during a suitable temperature treatment to 1400 ° C. Use of the after one of Claims 1 to 7 manufactured components as filters for the filtration of fluids or as a catalyst or catalyst support or as heat transfer materials.