DE102019108968A1 - Process for the production of a granulate, granulate, 3D printing process and process for the production of a ceramic component - Google Patents

Abstract

A method is provided for producing a granulate (100), the method comprising producing a thermoplastic polymer composition (118) in an extrusion device (108), extrusion of the thermoplastic polymer composition (118), comminution of the extruded thermoplastic polymer composition (118), and the addition of a crosslinking agent (132) to the thermoplastic granulate (128), wherein the crosslinking agent (132) forms a coating on or on the granulate (100) and wherein the crosslinking agent (132) is a thermally activatable crosslinking agent (132) , which is activated at temperatures of 3D printing processes.

Description

The present invention relates to a method for producing a granulate.

The present invention also relates to a granulate which has a coating.

The invention also relates to a 3D printing method, in particular for producing a green body for ceramization.

The present invention also relates to a method for producing a ceramic component and a ceramic component produced by the method according to the invention.

The present invention is based on the object of providing a method with which a granulate can be produced, which can be 3D-printed in an extrusion-based process and with which a green body can be produced which is suitable for later ceramization.

• - Herstellen einer thermoplastischen Polymerzusammensetzung in einer Extrusionsvorrichtung;
• - Extrusion der thermoplastischen Polymerzusammensetzung;
• - Zerkleinerung der extrudierten thermoplastischen Polymerzusammensetzung unter Ausbildung eines thermoplastischen Granulats; und
• - Zugabe eines Vernetzungsmittels zu dem thermoplastischen Granulat, wobei das Vernetzungsmittel ein Coating auf dem oder an dem thermoplastischen Granulat bildet und wobei das Vernetzungsmittel ein thermisch aktivierbares Vernetzungsmittel ist, welches bei Temperaturen von 3D-Druckverfahren aktiviert wird.

The above-mentioned object is achieved by a method comprising:

• - producing a thermoplastic polymer composition in an extrusion device;
• - extrusion of the thermoplastic polymer composition;
• Comminution of the extruded thermoplastic polymer composition to form thermoplastic granules; and
• Addition of a crosslinking agent to the thermoplastic granules, the crosslinking agent forming a coating on or on the thermoplastic granules, and the crosslinking agent being a thermally activatable crosslinking agent which is activated at temperatures of 3D printing processes.

Because the crosslinking agent is added to the thermoplastic granulate and forms a coating for the granulate, materials from a layer applied immediately beforehand can be crosslinked in a 3D printing process with materials from previously applied layers. A removal of already applied layers in a 3D printing process can thus be avoided.

The crosslinking agent preferably envelops individual or essentially all particles of the granulate and / or forms a layer thereon.

The selection of a thermally activatable crosslinking agent, which is activated at temperatures of 3D printing processes, means that crosslinking of polymer molecules of the granulate, which has the coating, only occurs in the melted state during the 3D printing process.

By using the crosslinking agent according to the invention, a thermoplastic granulate can be produced by means of which green bodies for ceramization can be produced in a 3D printing process.

The 3D printing process in turn enables the green body to be manufactured close to its final shape.

The thermoplastic polymer composition preferably comprises one or more fillers.

Preferably the thermoplastic polymer composition is extruded into a filament.

The comminution is preferably carried out in the form of pelleting.

A conventional pelletizer is preferably used to pellet the extruded thermoplastic polymer composition.

Temperatures at which 3D printing processes are typically carried out are preferably in a range from approximately 140 ° C. to approximately 250 ° C., in particular in a range from approximately 150 ° C. to approximately 190 ° C., for example in a range of approximately 150 ° C to around 180 ° C.

The granulate can be melted in this temperature range without degradation occurring.

The selection of the crosslinking agent is based in particular on its thermal activation temperature. At or above the thermal activation temperature, the crosslinking agent is in particular reactive and a crosslinking reaction takes place.

The thermal activation temperature should preferably be in the range of a processing temperature in a subsequent 3D printing process or just above it, for example 10 ° C to 20 ° C above. This in turn depends on the thermoplastic polymer composition used.

Organic peroxides have proven particularly useful as crosslinking agents. In particular, liquid organic peroxides are preferred and / or easy to handle.

Preferably, the crosslinking agent comprises an organic peroxide or consists essentially of an organic peroxide. Thermal activation temperatures of organic peroxides are typically in a temperature range in which 3D printing processes are carried out, or just above, for example 10 ° C to 20 ° C above.

Even if the activation temperature is just above the temperature range in which 3D printing processes are carried out, crosslinking takes place - in particular due to a shear force which acts on the granulate with the coating during processing.

It has proven to be particularly advantageous if the crosslinking agent comprises 3,3,5,7,7-pentamethyl-1,2,4-trioxepane (PMTO) or essentially consists of 3,3,5,7,7-pentamethyl- 1,2,4-trioxepane (PMTO) consists.

PMTO can in particular be processed safely and / or has a thermal activation temperature of approximately 180 ° C. or more.

It can be advantageous if the crosslinking agent is added in a proportion of less than 2% by weight, in particular less than 1% by weight. The proportion of the crosslinking agent is based on a total mass of the thermoplastic granulate.

Such a small proportion is particularly sufficient for crosslinking of polymer molecules of the melted granulate to take place during the 3D printing process.

For example, the crosslinking agent is added in a proportion of approximately 0.25% by weight to approximately 1% by weight, based on the total mass of the thermoplastic granulate.

It has proven to be particularly preferred if approximately 0.28% by weight of crosslinking agent, based on the total mass of the thermoplastic granulate, is added to the thermoplastic granulate.

It can be advantageous if the thermoplastic polymer composition comprises a thermoplastic binder. As already mentioned, the thermoplastic polymer composition preferably comprises several fillers.

In addition to the multiple fillers, the thermoplastic polymer composition can also contain further fillers and / or one or more additives, in particular conventional plastic additives, for example pigments, tackifiers, lubricants and / or compatibilizers.

The thermoplastic binder preferably comprises or is formed from an ethylene-vinyl acetate copolymer (EVA). The thermoplastic binder is preferably an EVA with a vinyl acetate content of approximately 9% by weight to approximately 20% by weight, in particular approximately 14% by weight vinyl acetate, based on the total mass of the EVA.

A proportion of the ethylene-vinyl acetate copolymer is in particular in a range from about 20% by weight to about 35% by weight, for example in a range from about 30% by weight to about 35% by weight, based on a Total mass of the thermoplastic polymer composition.

A proportion of approximately 32.5% by weight of an ethylene-vinyl acetate copolymer is particularly preferably used.

This proportion is sufficient to connect the multiple fillers to one another as a matrix material. The fillers are in particular embedded in the polymer material acting as a binder.

It can be advantageous if the multiple fillers are nanofillers and / or microfillers.

In particular, the multiple fillers are selected from the following materials: carbon black, powdered silicon carbide (SiC), carbon fibers, activated carbon.

The carbon fibers are preferably ground carbon fibers.

Carbon black is preferably used in a proportion of up to 35% by weight, in particular about 15% by weight to about 20% by weight, based on the total mass of the thermoplastic polymer composition.

Instead of carbon black, other electrically conductive particles can also be used.

The powdery silicon carbide preferably has an average grain size d _s50 of approximately 4 μm to approximately 5 μm, in particular approximately 4.5 μm.

Powdered silicon carbide - in the following also referred to as silicon carbide powder - has in particular a small influence on the viscosity of the melted thermoplastic binder during the 3D printing process.

The grain size d _s50 is preferably based on the median of the diameter distribution of the Silicon carbide particles related to powdered silicon carbide.

Preferably about 35% by weight to about 45% by weight, in particular 40% by weight, silicon carbide powder, based on a total mass of the thermoplastic polymer composition, are used.

In order to maintain a viscosity of the granulate in the melted state, it has proven to be advantageous if the multiple fillers have an average diameter of approximately 60 μm or less.

The polymer composition preferably comprises or consists essentially of the following substances: an ethylene-vinyl acetate copolymer, carbon black, powdered silicon carbide, ground carbon fibers, activated carbon.

In particular, the fillers reduce a loss of mass of a resulting green body in a pyrolysis during ceramization.

• - 32,5 Gew.-% EVA;
• - 17,5 Gew.-% Carbon Black;
• - 40 Gew.-% SiC-Pulver (d_s50 = 4,5 µm);
• - 10 Gew.-% gemahlene Kohlenstofffasern und Aktivkohle in einem Gewichtsverhältnis von 2:1.

The following composition has proven to be particularly advantageous as a thermoplastic polymer composition:

• - 32.5% by weight EVA;
• - 17.5% by weight of carbon black;
• 40% by weight of SiC powder (d _s50 = 4.5 μm);
• - 10% by weight of ground carbon fibers and activated carbon in a weight ratio of 2: 1.

The mixture of ground carbon fibers and activated carbon can alternatively also be used in a proportion of approximately 5% by weight to approximately 15% by weight.

To produce the thermoplastic polymer composition, its polymeric constituents are preferably melted in a heated screw device, for example a twin screw device with two kneading elements, and all the constituents are mixed with one another in the extrusion device.

It can be favorable if the thermoplastic polymer composition is produced at a temperature in a range from approximately 180.degree. C. to approximately 200.degree. In particular, the thermoplastic polymer composition is then extruded into a filament. The filament is then comminuted, for example pelletized.

The thermoplastic granules are preferably dried before the addition of the crosslinking agent. During drying, the thermoplastic granulate hardens, in particular, essentially completely. The drying is carried out in particular at around 70 ° C to around 90 ° C in a drying oven.

The crosslinking agent is preferably added at a temperature which is lower than a thermal activation temperature of the crosslinking agent, in particular at about 20 ° C to about 80 ° C, for example at about 50 ° C.

In particular, after the addition of the crosslinking agent, the granules are dried at around 40 ° C to around 100 ° C, in particular at around 80 ° C. In particular, the thermoplastic granulate is dried for about an hour or longer. For example, the granulate is dried for up to 16 hours, in particular in a drying oven.

The invention further relates to a granulate that has a coating for 3D printing processes, the granulate comprising a thermoplastic granulate made from a thermoplastic polymer composition and the coating comprising or consisting of a thermally activatable crosslinking agent which is activated at temperatures of 3D printing processes is formed. The granulate, which has a coating, is in particular produced by a method according to the invention.

The granulate which has a coating preferably has one or more of the features mentioned in connection with the method according to the invention and / or one or more of the advantages mentioned in connection with the method according to the invention.

The granulate, which has a coating, can be used in conventional 3D printing devices in which granulate is used as the starting material.

• - Herstellen eines Granulats, welches ein Coating aufweist, in einem erfindungsgemäßen Verfahren oder Verwendung eines erfindungsgemäßen Granulats;
• - 3D-Drucken des Granulats in einem additiven Verfahren, wobei ein Formkörper, insbesondere ein Grünkörper für eine Keramisierung, gebildet wird.

The invention also relates to a 3D printing method, in particular for producing a green body for ceramization. The 3D printing process includes:

• Production of a granulate which has a coating in a method according to the invention or use of a granulate according to the invention;
• - 3D printing of the granulate in an additive process, whereby a shaped body, in particular a green body for ceramization, is formed.

The 3D printing is preferably carried out by means of a 3D printing device which comprises a print head. The granulate, which has a coating, is in particular in the Filled in printhead and melted for 3D printing by means of an extrusion element which is arranged in the printhead.

The crosslinking agent which forms the coating, in particular, reduces the elasticity of the binder, for example EVA, in the thermoplastic granulate. As a result, the extruded material of the granulate is more dimensionally stable compared to a material without a crosslinking agent.

Activation of the crosslinking agent is increased and / or accelerated by a shear movement resulting from a rotation of the kneading elements of the extrusion element.

The 3D printing is preferably carried out by means of an extrusion-based method. In particular, material extrusion is used in combination with additive application, for example in layers.

The 3D printing device is, for example, a Pellets Additive Manufacturing (PAM) 3D printing device.

By using an extrusion-based 3D printing process, material can be saved compared to, for example, a powder bed process, since only as much granulate has to be used as is required for the respective shaped body. A use of material as a support structure and / or a filling of the entire installation space can thus be dispensed with.

• - Herstellen eines Grünkörpers gemäß einem erfindungsgemäßen Verfahren;
• - Pyrolysieren des Grünkörpers, wobei ein offenporöser Kohlenstoffkörper resultiert; und
• - Durchführen einer Keramisierung an dem aus der Pyrolyse resultierenden offenporösen Kohlenstoffkörper.

The invention also relates to a method for producing a ceramic component, comprising:

• - producing a green body according to a method according to the invention;
• Pyrolyzing the green body, an open-pore carbon body resulting; and
• - Carrying out a ceramization on the open-pore carbon body resulting from the pyrolysis.

Due to the aforementioned selection of fillers in the granulate, a mass of the open-pore carbon body after pyrolysis is in particular approximately 50% by weight or more of the mass of the green body before pyrolysis.

For example, one or more of the following substances form a framework of the open-pore carbon body: carbon black, silicon carbide powder, carbon fibers, activated carbon.

Due to the high proportion of fillers, cavity formation - so-called blistering effects - can be avoided during pyrolysis and / or ceramization.

Due to the high proportion of fillers which do not change during pyrolysis, shrinkage of the green body during pyrolysis is preferably approximately 5% or less.

The ceramization is preferably carried out by infiltrating the open-pore carbon body with a liquid carbide former. A particularly preferred liquid carbide former is silicon.

Alternatively, tungsten can also be used as a carbide former.

It can be favorable if the open-pore carbon body is brought into contact with a carbide former for ceramization in a 180% by weight to 200% by weight excess based on the mass of the open-pore carbon body.

In particular, the open-pore carbon body is infiltrated with a carbide former, in particular silicon, in a 180% by weight to 200% by weight excess based on the mass of the open-pore carbon body for ceramization.

The invention also relates to a ceramic component produced by a method according to the invention.

Ceramic components produced according to the invention are particularly suitable for optical components and / or components for satellites or other missiles.

Further areas of application are ceramic heat exchangers and resistance heating elements.

A proportion of carbide in the ceramic component is preferably approximately 60% by volume or more, in particular approximately 65% by volume or more, for example approximately 70% by volume, based on a total volume of the ceramic component.

A proportion of free carbide former is in particular about 40% by volume or less, in particular about 35% by volume or less, for example about 30% by volume or less.

In particular, the ceramic component has little or no carbon residues.

The following description of preferred embodiments is used in conjunction with the drawings to explain the invention in greater detail.

• 1 ein schematischer Ablauf einer Ausführungsform eines Verfahrens zur Herstellung eines Granulats;
• 2 eine schematische Darstellung einer Ausführungsform eines 3D-Druckverfahrens;
• 3 eine schematische Darstellung eines Ablaufs einer Ausführungsform eines Verfahrens zur Keramisierung;
• 4 eine schematische Draufsicht auf eine Ausführungsform eines keramischen Bauteils, wobei das Bauteil eine Wabenstruktur aufweist und versteift ist;
• 5 eine schematische Seitenansicht des Bauteils aus 4;
• 6 eine schematische Draufsicht auf eine weitere Ausführungsform eines Bauteils, bei welchem ein durch 3D-Druck hergestellter Grünkörper keramisiert wurde, in einem Zustand nach der Keramisierung;
• 7 eine schematische Seitenansicht auf das Bauteil aus 6;
• 8 ein mit einem Rasterelektronenmikroskop aufgenommenes Schliffbild eines Querschnitts eines Stegs einer Wabenstruktur bei 100-facher Vergrößerung; und
• 9 ein mit einem Rasterelektronenmikroskop aufgenommenes Schliffbild bei 500-facher Vergrößerung.

Show it:

• 1 a schematic sequence of an embodiment of a method for producing a granulate;
• 2 a schematic representation of an embodiment of a 3D printing process;
• 3 a schematic representation of a sequence of an embodiment of a method for ceramization;
• 4th a schematic plan view of an embodiment of a ceramic component, wherein the component has a honeycomb structure and is stiffened;
• 5 a schematic side view of the component from 4th ;
• 6th a schematic plan view of a further embodiment of a component in which a green body produced by 3D printing has been ceramized, in a state after the ceramization;
• 7th a schematic side view of the component 6th ;
• 8th a micrograph taken with a scanning electron microscope of a cross section of a web of a honeycomb structure at 100-fold magnification; and
• 9 a micrograph taken with a scanning electron microscope at 500-fold magnification.

Identical or functionally equivalent elements are provided with the same reference symbols in all figures.

In 1 a schematic sequence of a preferred embodiment of a method for producing a granulate is shown. The granules 100 is suitable for use in a 3D printing process for producing a green body for ceramization. The granules 100 has a coating.

That by that in connection with 1 described method produced granules 100 , which has a coating, is here as in connection with 2 described further processed in a 3D printing process, creating a green body 164 arises.

This green body 164 will then - as in connection with 3 described - subjected to ceramization, whereby a ceramic component 180 will be produced.

Also when making the granules 100 , which has a coating, the 3D printing process and the process for ceramization are described coherently below, they can also be carried out independently of one another.

Regarding the procedures in detail:

In a first process step 102 becomes a thermoplastic polymer material 104 via a funnel 106 into an extrusion device 108 given. A thermoplastic polymer material is used here 104 used in granular form.

In a first processing section of the extrusion device 108 becomes the thermoplastic polymer material 104 by means of a present as a twin screw device 112 trained screw device 110 mixed and along a longitudinal direction of the extrusion device 108 promoted.

Due to helically designed kneading elements arranged close to one another, which essentially form the twin screw device 112 will form a homogeneous mixture of the thermoplastic polymer material 104 achieved, which in the extrusion device 108 is melted.

The extrusion device 108 is heated to about 180 ° C to 200 ° C by means of a heating device, not shown.

In the present case, the two kneading elements of the twin screw device are in different processing sections 112 Separated from one another by kneading disks arranged eccentrically to one another, which further improves mixing.

In a second processing section of the extrusion device 108 are in a second process step 115 multiple fillers 116 via another funnel 106 added and with the melted thermoplastic polymer material 104 mixed together to form a thermoplastic polymer composition 118 arises.

As a thermoplastic polymer material 104 an ethylene-vinyl acetate copolymer (EVA) with a vinyl acetate content of approximately 14% by weight is used in the present case. The thermoplastic polymer material 104 forms the binder of the thermoplastic polymer composition 118 .

Alternatively, other polyolefin compounds, in particular polyethylene compounds, which can be melted in a temperature range from approximately 140 ° C. to approximately 250 ° C., can also be used. The temperature to which the extrusion device 108 is heated up, must then be adjusted accordingly.

• - Carbon Black;
• - Siliziumcarbid-Pulver;
• - gemahlene Kohlenstofffasern und Aktivkohle.

The following fillers are used 116 used:

• - carbon black;
• - silicon carbide powder;
• - ground carbon fibers and activated carbon.

Instead of carbon black, other electrically conductive fillers can also be used.

All fillers 116 in the present case have a diameter of 60 µm or less.

The composition of the thermoplastic polymer composition 118 is preferably adjusted so that based on the total mass of the thermoplastic polymer composition 118 about 32.5% by weight of the ethylene-vinyl acetate copolymer, about 17.5% by weight of carbon black, about 40% by weight of silicon carbide powder and about 10% by weight of a mixture of ground carbon fibers and activated carbon in a weight ratio of 2: 1.

Alternatively, it can also be provided that the thermoplastic polymer composition 118 additionally comprises at least one additive. The proportion of the binder or the proportion of fillers can be used for this purpose 116 be reduced or both.

According to a third process step 120 becomes the thermoplastic polymer composition 118 by means of a hotmelt process, in the present case at around 180 ° C to around 200 ° C, to form a filament 122 extruded.

In a fourth process step 124 becomes the filament 122 in a pelletizer 126 , the knives of which are indicated schematically here and rotate during the comminution, to form thermoplastic granules 128 crushed, with individual particles of thermoplastic granules 128 have a length of approximately 3 mm to approximately 4 mm, in the present case approximately 2 mm.

The thermoplastic granulate 128 after being crushed by the pelletizer 126 in a container 130 collected and especially dried before a crosslinking agent 132 is added (fifth process step 135 ).

The crosslinking agent 132 is selected depending on a downstream 3D printing process. It becomes a thermally activated crosslinking agent 132 selected whose thermal activation temperature is in a range at which the granules 100 is processed, in particular melted, during the 3D printing process and / or in which the granules are applied to a substrate in melted form.

The activation temperature of the crosslinking agent 132 can also be 10 ° C to 20 ° C above the temperature at which the granules 100 is melted in the 3D printing process.

As the thermoplastic polymer composition 118 present as thermoplastic polymer material 104 EVA includes a print head 140 for printing to a temperature of about 150 ° C to about 170 ° C, for example about 165 ° C.

At these temperatures there is a viscosity of the granules 100 on the one hand so high that it can be applied additively. On the other hand is the viscosity of the granulate 100 not so high that the granules 100 dissolves.

For the thermoplastic composition described above 118 are organic peroxides as crosslinking agents 132 particularly suitable.

3,3,5,7,7-pentamethyl-1,2,4-trioxepane (PMTO) has proven to be particularly advantageous. PMTO is, for example, under the name Trigonox 311® from AkzoNobel Functional Chemicals B.V. available.

The present is the crosslinking agent 132 with a proportion of approximately 0.28% by weight based on a total mass of the thermoplastic granulate 128 the thermoplastic granulate 128 added.

The crosslinking agent 132 and the thermoplastic granules 128 are then in a sixth process step 138 mixed with the crosslinking agent 132 a coating on and / or on the thermoplastic granulate 128 forms so that a granulate 100 , which has a coating, is formed.

The formation of the coating reduces the elasticity of the EVA and the granulate 100 which the coating has is compared to the thermoplastic granulate 128 before adding the crosslinking agent 132 more dimensionally stable.

After adding the crosslinking agent 132 the granulate is presently dried overnight, in particular at around 80 ° C., in a drying oven.

As in 2 shown schematically, the granules 100 , which has a coating, in a sixth process step 142 into a filling device 144 a 3D printing device 150 is filled, the filling device 144 in the present case is funnel-shaped.

A Pellets Additive Manufacturing (PAM) 3D printing device is used here.

The printhead 140 The 3D printing device 150 in the present case comprises the filling device 144 one as an extruder 152 formed extrusion element in which a screw 154 is arranged to rotate.

By means of a heating device, not shown, the extruder 152 to a temperature in a range of about 150 ° C and 170 ° C, for example about 165 ° C, and the granules 100 , which has a coating, melted and in the screw 154 mixed and / or kneaded (seventh process step 156 ).

Due to the temperature and the mechanical shear stress from the screw 154 becomes the crosslinking agent 132 activated and the molecules within the polymer mass via oxygen molecules of the peroxide functionality of the crosslinking agent 132 networked with one another immediately before and / or during application.

Via an application element 158 is the melted and partially crosslinked polymer material in an eighth process step 160 on a substrate 162 applied.

The application is typically done in rows side by side before another layer is applied.

The crosslinking via molecules of the crosslinking agent 132 ensures adhesion between layers lying one on top of the other or adjacent webs. A detachment of already applied layers or tracks when the printhead applies a new layer or track at the corresponding point can be avoided.

In the present case, a green body is produced using the 3D printing process described above 164 manufactured.

The green body produced in this way 164 is then subjected to pyrolysis. The pyrolysis 170 is a ninth process step. It is part of the schematic in 3 illustrated method for producing a ceramic component.

The pyrolysis 170 takes place in the absence of oxygen at relatively high temperatures for a certain time, with pyrolysis 170 Volatile components of the green body with exclusion of oxygen 164 , which is a molded body, can be removed.

The pyrolysis is preferably carried out 170 in a temperature range from approx. 900 ° C to approx. 1700 ° C.

The result of pyrolysis 170 is an open-pore carbon body 172 .

The open-pore carbon body 172 will follow the pyrolysis 170 with a carbide former 174 infiltrated (tenth procedural step 176 ).

In the present case it is used as a carbide former 174 Silicon is used and an LSI (Liquid Silicon Infiltration) process is carried out.

The liquid silicon penetrates the open-pore carbon body 172 and reacts with the carbon to form silicon carbide. A ceramic component is created 180 .

The LSI process is carried out at around 1450 ° C to around 1700 ° C. There are 280 wt .-% silicon based on a total mass of the open-pore carbon body 172 used.

During ceramization, a free carbide-forming phase (in the case of silicon as a carbide-forming agent 174 a free silicon phase) remain and a free carbon phase can remain, depending on how the process is carried out.

In particular, the method is carried out in such a way that a free carbon phase is minimized.

One embodiment of a ceramic component 180 is in the 4th and 5 shown.

The ones in the 4th and 5 illustrated embodiment of a ceramic component 180 is at least approximately disk-shaped and has a honeycomb structure on one side of the ceramic component 180 is reinforced by a reinforcement structure. The honeycomb structure essentially corresponds to the honeycomb structure according to the further embodiment in FIG 6th and 7th , which is why reference is made to the following explanations in this regard.

In the present case, the reinforcement structure is formed from a lattice structure of essentially equilateral triangles that are linked to one another.

The ceramic component 180 is particularly suitable for optical devices due to the low thermal expansion of silicon carbide.

Another embodiment of a ceramic component 180 is in the 6th and 7th shown.

Like the ones in the 4th and 5 The embodiment shown is the ceramic component 180 according to the 6th and 7th intended for use in optical structures.

A base wall of the ceramic component 180 has a hexagon shape with rounded corners in a cross section taken along a main extension plane.

A honeycomb structure made up of structural walls connected to form hexagons is arranged on the base wall. The structural walls each extend essentially perpendicularly away from the base wall. The structural walls form webs 182 .

Individual honeycombs of the honeycomb structure have essentially the same shape. The structural walls in the present case each have essentially the same length in a direction arranged parallel to the base wall.

In 8th is a micrograph of a ceramic component 180 shown, which according to the previously described embodiments of the method from the granules 100 , which has a coating, was produced.

It's a jetty 182 a honeycomb structure of the ceramic component 180 in 8th to see which one goes through the receptacle from top to bottom. The dark areas on either side of the bridge 182 result from a conductive material for embedding, which is used to fasten the web for the receptacle. The dark areas are not part of the ceramic component 180 .

The micrograph was taken with a scanning electron microscope at an acceleration voltage of 15 kV and a 100-fold magnification.

The light gray, almost white areas show free silicon phases, while silicon carbide is shown in darker gray. Based on the electron microscope image, a proportion of free silicon of around 30% by volume and a proportion of silicon carbide of around 70% by volume could be determined.

The density of the material of the ceramic component is due to the free silicon 180 reduced from around 3.2 g / cm ³ to around 2.8 g / cm ³ to around 3.0 g / cm ³ .

The individual strips, which were gradually applied during the 3D printing process, are in the receptacle in the edge areas of the web 182 recognizable.

It can be seen from the recording that there is an essentially homogeneous distribution of free silicon and silicon carbide. There are no more carbon residues. This shows that the ceramization has taken place completely.

9 shows the ceramic component 180 - Taken with a scanning electron microscope - at a magnification of 500 times. The micrograph was taken at an accelerating voltage of 15 kV.

From this compared to the in 9 A further enlarged photo shows that a fine distribution of silicon carbide and free silicon has arisen.

Ceramic components 180 which are produced with the method described above can be used, for example, in ceramic heat exchangers, resistance heating elements, and support structures for optical benches and / or as optical parts in satellites.

List of reference symbols

100

granules

102

first procedural step

104

thermoplastic polymer material

106

funnel

108

Extrusion device

110

Screw device

112

Twin screw device

115

second process step

116

filler

118

thermoplastic polymer composition

120

third process step

122

Filament

124

fourth procedural step

126

Pelletizer

128

thermoplastic granulate

130

container

132

Crosslinking agents

135

fifth procedural step

140

Printhead

142

sixth process step

144

Filling device

150

3D printing device

152

Extruder

154

slug

156

seventh procedural step

158

Application element

160

eighth procedural step

162

Substrate

164

Green body

170

Pyrolysis

172

open porous carbon body

174

Carbide formers

176

Infiltrate

180

ceramic component

182

web

Claims (20)

A method for producing a granulate (100), the method comprising: - producing a thermoplastic polymer composition (118) in an extrusion device (108); - extrusion of the thermoplastic polymer composition (118); - Comminution of the extruded thermoplastic polymer composition (118) to form thermoplastic granules (128); - Addition of a crosslinking agent (132) to the thermoplastic granulate (128), wherein the crosslinking agent (132) forms a coating on or on the thermoplastic granulate (128) and wherein the crosslinking agent (132) is a thermally activatable crosslinking agent which at temperatures activated by 3D printing processes. Procedure according to Claim 1 , characterized in that the crosslinking agent (132) comprises an organic peroxide or consists essentially of an organic peroxide. Procedure according to Claim 1 or 2 , characterized in that the crosslinking agent (132) comprises or consists essentially of 3,3,5,7,7-pentamethyl-1,2,4-trioxepane (PMTO). Method according to one of the preceding claims, characterized in that the crosslinking agent (132) is added in a proportion of less than 2% by weight based on a total mass of the thermoplastic granulate (128). Method according to one of the preceding claims, characterized in that the thermoplastic polymer composition (118) comprises a thermoplastic binder and / or a plurality of fillers (116). Procedure according to Claim 5 , characterized in that the thermoplastic binder comprises an ethylene-vinyl acetate copolymer (EVA) or is formed therefrom and, in particular, that a proportion of the ethylene-vinyl acetate copolymer in a range from about 20% by weight to about 35% by weight % based on a total mass of the thermoplastic polymer composition (118). Procedure according to Claim 5 or 6th , characterized in that the plurality of fillers are selected from one or more of the following materials: carbon black, powdered silicon carbide (SiC), carbon fibers, activated carbon. Method according to one of the preceding claims, characterized in that the thermoplastic polymer composition (118) comprises several fillers (116), in particular nanofillers and / or micro-fillers, which have an average diameter of 60 µm or less. Method according to one of the preceding claims, characterized in that the thermoplastic polymer composition (118) comprises or essentially consists of the following substances: an ethylene-vinyl acetate copolymer (EVA), carbon black, powdered silicon carbide (SiC), ground carbon fibers, activated carbon . Method according to one of the preceding claims, characterized in that to produce the thermoplastic polymer composition (118) its polymeric constituents are melted in a heated screw device (110) and / or all constituents of the thermoplastic polymer composition are mixed with one another in the extrusion device (108). Method according to one of the preceding claims, characterized in that the thermoplastic polymer composition (118) is produced at a temperature in a range from approximately 180 ° C to approximately 200 ° C and / or is then extruded to form a filament (122), which is then crushed, in particular pelletized. Method according to one of the preceding claims, characterized in that the thermoplastic granulate (128) is dried before the addition of the crosslinking agent (132) and preferably that the addition of the crosslinking agent (132) takes place at a temperature which is lower than a thermal activation temperature of the crosslinking agent (132), in particular at about 20 ° C to about 80 ° C. Granules (100), which have a coating, for 3D printing processes, the granules (100) comprising a thermoplastic granulate (128) made of a thermoplastic polymer composition (118) and the coating comprising a thermally activatable crosslinking agent (132), which at Temperatures of 3D printing processes is activated, in particular produced according to a process Claim 1 to 12 . 3-D printing method, in particular for producing a green body (164) for ceramization, the 3-D printing method comprising: - producing a granulate (100) according to one of the Claims 1 to 12 or using a granulate (100) Claim 13 ; and - 3D printing of the granulate (100) in an additive process, a shaped body, in particular a green body (164) for ceramization, being formed. 3D printing process according to Claim 14 , characterized in that the 3D printing is carried out by means of a 3D printing device (150) which comprises a print head (140), and that the granulate (100), which has a coating, is filled into the print head (140) and for 3D printing by means of an extrusion element (152) which is arranged in the print head (140) is melted. 3D printing process according to Claim 14 or 15th , characterized in that the 3D printing is carried out using an extrusion-based method. A method for producing a ceramic component (180), comprising: - producing a green body (164) according to a 3D printing method according to one of the Claims 14 to 16 ; - Pyrolysing the green body (164), an open-pore carbon body (172) resulting; and performing a ceramization on the open-pore carbon body (172) resulting from the pyrolysis. Procedure according to Claim 17 , characterized in that a mass of the open-pore carbon body (172) after the pyrolysis is approximately 50 wt .-% or more of the mass of the green body (164) before the pyrolysis. Procedure according to Claim 17 or 18th , characterized in that the open-pore carbon body (172) for ceramization in a 180 wt .-% to 200 wt .-% excess based on the mass of the open-pore carbon body (172) with a carbide former (174), in particular silicon, in Is brought into contact, the open-pored carbon body (172) preferably being infiltrated with the carbide former (174), in particular silicon. Ceramic component (180) produced by a method according to one of the Claims 17 to 19th In particular, a proportion of carbide in the ceramic component (180) is approximately 60% by volume or more, in particular approximately 65% by volume or more, based on a total volume of the ceramic component (180).

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