DE102008022664A1 - Production of green ceramic articles comprises forming layer containing ceramic powder and binder on substrate, applying layer containing inorganic nanoparticles and dispersant, repeating stages and removing dispersant and unbound powder - Google Patents

Abstract

Production of green ceramic articles comprises: (A) forming a layer containing ceramic powder and a binder on a substrate; (B) applying a consolidating layer over this which contains 0.1 - 50 wt% of inorganic particles of average diameter 5 - 1000 nm and 50 - 99.9 wt% of dispersing agent; (C) repeating these stages at least twice; (D) removing some or all of the dispersing agent; and (E) removing unbound ceramic powder. Independent claims are included for: (A) green ceramic articles produced using the method; (B) producing ceramic moldings by sintering the green articles; and ceramic moldings produced using this process.

Description

The The present invention relates to a process for producing a ceramic green body, a method of manufacture a ceramic shaped body and the green body and the ceramic molding itself.

Of the development effort required in the development of ceramic components can be considerable by the rapid provision of prototypes be reduced. Design changes can be immediate, based on eg CAD data, converted into components without having to change tools.

Of the Term rapid prototyping refers to the rapid production of Prototypes and refers to a technology that has been in business since the beginning the 1990s through continuous development with more powerful, Computer-aided control technology for generative manufacturing process is suitable. The name Rapid Prototyping uses terms such as "Rapid Tooling" and "Rapid Manufacturing "subordinate. This is development of the actual process, the specific application and application areas describe. The term rapid prototyping generally refers to the technology, while rapid tooling is the additive toolmaking industry as an application area, while the term rapid manufacturing stands for generative series production.

In belongs to the metal and especially in the plastics industry the method of rapid prototyping to the state of the art. Thereby It is usually possible to base components directly on to produce 3D CAD data. Leave within a few hours Cost-effective highly complex and filigree structures realize. Thus, development times and costs be significantly reduced and also the time to market is new Components significantly shortened.

ceramic At the moment, materials still have the fundamentals Problem that their potential with engineers and designers is not is well known. Therefore, for this group of materials the use of very fast, computer-aided procedures for the production of prototypes of particular importance.

Of the so far relatively long and costly manufacturing process, consisting from model development, mold making, optimization of working form, processing the raw materials, shaping, sintering process and post-processing usually to long development cycles. For manufacturers and users is a fast and cost effective method Provision of prototypes required.

to Realization of time-saving, cost-effective prototype production Different methods can be used. Next The well-known green processing is specifically research on the topics laser sintering, hot casting and 3D printing in front.

It Methods have already been provided that make it possible in short time (5-10 days) prototypes made of ceramic materials to generate. The prototypes should have the appropriate properties have the later series product.

DE 103 06 887 A7 describes a method for producing a ceramic green body, wherein particles of ceramic powder can be provided with a coating containing different nanoparticles thereof.

DE 10 2006 029 298 A1 describes a material system for 3D printing, wherein the method described can also lead to a ceramic molding.

DE 20 2005 020 596 U1 describes a powder for rapid prototyping, wherein a ceramic molded body is formed by laser sintering.

DE 10 2005 058 118 A1 describes a method for producing ceramic components, wherein the ceramic components are formed by laser sintering.

DE 10 2005 058 116 A1 describes a method for producing ceramic implants, wherein these are locally cured with a laser.

DE 10 2006 015 014 A1 describes a method and apparatus of three-dimensional ceramic shaped bodies wherein a suspension of ceramic particles is printed with an ink jet printer.

DE 10 2005 058 121 A1 describes a method for producing ceramic components, wherein the green compact can be cured locally with a laser.

DE 602 07 204 T2 describes three-dimensionally structured printing for the production of polymer bodies. Nanoparticles can also be incorporated in these polymer bodies.

DE 10 2004 008 122 A1 describes coated powder particles for the production of three-dimensional bodies by means of layer-building processes, wherein the powder particles can be coated.

The item "Production of Ceramic-Metallic Moldings by 3D Printing" (Melcher et al., Keramische Materialien, January 2007, 3.4.2.4.) describes printed alumina-dextrin green bodies and resulting ceramic shaped bodies.

The Previously known methods have various disadvantages. So will in some processes, the ceramic material which is the later makes ceramic shaped body, printed in a suspension. This requires a high concentration of solids in the print to be printed Suspension, whereby the pressure nozzles are clogged. With the above-mentioned method can the properties of the resulting ceramic molding does not have the spatial Extension of the ceramic molded body varies become. Although it is already known, additional particles to add to the ceramic powder. this happens but so far, for example by coating the ceramic article and then printing for the production of the green body. This allows the ceramic Shaped bodies, although properties are awarded by not the originally used ceramic powder can be generated. These properties can However, they should not be generated in different ways Positions of the molding differently pronounced are. In addition, so far has been a complex coating process the ceramic particles necessary.

task Therefore, the present invention is a simple process to provide a ceramic molding independently of the originally used ceramic material certain property can be awarded.

• a) eine Schicht auf einer Unterlage bildet, die – ein keramisches Pulver und gegebenenfalls Bindemittel enthält,
• b) mindestens eine Verfestigungszusammensetzung auf die zuvor genannte Schicht auf zumindest einen Teil davon appliziert, die – 0,1 bis 50 Gew.-% anorganische Partikel mit einem durchschnittlichen Durchmesser in einem Bereich von 5 bis 1000 nm, und – 50 bis 99,9 Gew.-% Dispergiermittel enthält,
• c) Schritte a) und b) mindestens einmal wiederholt,
• d) das Dispergiermittel unter Bildung eines Grünkörpers wenigstens teilweise oder vollständig entfernt, und
• e) das nicht gebundene keramische Pulver entfernt, wobei der Grünkörper freigelegt wird.

This object of the invention is based is achieved in a first embodiment by a method for producing a ceramic green body, in which

• a) forming a layer on a substrate which contains - a ceramic powder and optionally binder,
• b) applying at least one solidifying composition to the aforesaid layer on at least a part thereof comprising: from 0.1 to 50% by weight of inorganic particles having an average diameter in a range from 5 to 1000 nm, and from 50 to 99.9 Wt .-% dispersant contains,
• c) steps a) and b) repeated at least once,
• d) the dispersant at least partially or completely removed to form a green body, and
• e) removing the unbonded ceramic powder exposing the green body.

at the process according to the invention is a generative process in which material is not processed is, but new moldings or green body arise.

steps d) and e) can also be performed in reverse order become.

dispersants For the purposes of the invention, the liquid phase of the dispersion of inorganic particles.

At the 3D printing can bind binder and ceramic powder on each other be matched. The binder must ensure that the "Stick together" powder particles and the Greening receives a sufficient strength. When applying the solidification composition, for example by means of Push button is applied, this may not be lost, but must map the contour exactly. For this it is necessary that this reacted in a short time with a few particles. The proportion of organic Additive should preferably be so low that no separate Debarking process is necessary. The goal is to create the "printed" green to be able to sinter immediately after removal from the powder bed.

Around to ensure the dimensional accuracy of the component It is important to know the shrinkage exactly and this in the CAD model to be considered as a measure for the printing process.

One The main goal is that the manufactured prototypes material properties have, as they are expected in mass production.

For this especially the density counts. To achieve a compression, Is it possible the green body in one infiltrate another step and in this way a closed Surface to achieve.

The Compliance with tolerances and the reproducibility of the geometry are essential for manufacturing. through 3D printed ceramic components have a reproducibility of ± 50 μm. On this scale is also the procedural formation of steps on curved Surfaces.

The invention aims to selectively place dispersions containing particles at a microscopic level in a component produced from a powder in such a way that a ceramic structure is produced after sintering, that in precisely defined regions different properties with regard to chemical composition, phasing exist and / or grain size. This makes it possible to a ceramic component on the respec To give load structure adapted microstructure with local property differences.

alternative You can also do the same with the material of the ceramic powder Choose the material of the inorganic particles, as this for example, has the advantage that the sintering temperature is so to humiliate.

It also no binder can be used. Then this has the Advantage that in the resulting ceramic molding less organic impurities are present, provided organic dispersants be used, and this lower porosity having.

Preferably one selects the material of the inorganic particles in the Solidification composition different from the material of the ceramic Powder off. This can be within the green body and the resulting ceramic shaped body not only achieve a grain size or density variation, but it can also represent countless other properties. For example, as the material for the ceramic powder alumina chosen, so can the resulting ceramic molding photocatalytic activity can be lent by the inorganic particles in the solidification composition of photocatalytic consist of active titanium oxide.

Preferably is chosen as the dispersant water or an organic Dispersant or a mixture thereof. Especially the proportion of water in the dispersant is at least 50 Wt .-%. This can avoid too much organic residue remain and during sintering carbon pollution to lead. As an organic dispersant, for example Alcohols, ketones or polyethers.

you chooses in the process according to the invention advantageously a layer thickness of the ceramic powder and of the binder in a range of 10 to 300 microns, in particular from 50 to 120 μm. Would you have a lower one Select layer thickness, the process would be over Slow down fee. If one chooses the layer thickness on the other hand too large above the areas, reduced the image accuracy significantly. In addition, would be the surface roughness through the formation of staircase effects increase.

you Preferably, a ceramic powder of oxide, silicide, nitride and / or carbide of the elements Al, B, Bi, Ca, Ce, Cr, Cu, K, Fe, Ga, Ge, In, Li, Mg, Mn, Mo, Na, Si, Sn, Sr, Ta, Ti, W, Y and / or Zr or mixtures thereof. Very particularly preferred is as ceramic powder alumina, silica or a mixed oxide, in particular silicates, these oxides used. equally According to the invention are also mixed oxides of the above mentioned oxides, as well as mixed nitrides, mixed carbides, carbonitrides, Oxynitrides or oxicarbides of the aforementioned elements. This ceramic Materials have proven to be particularly suitable for the invention Proven procedure. The ceramic powder preferably has a Grain size in the range of 0.1 to 500 μm, in particular in a range of 50 to 300 microns. Thereby On the one hand, too high a surface roughness in the later Shaped body avoided and on the other hand contamination by absorption at the high BET surface area with too small grains also avoided.

The Ceramic powder is preferably used in an amount of 85 to 99% by weight. As a result, the content of ceramic material is sufficiently high still enough room for example to have the optionally present binders.

The necessary binder in turn are advantageously selected of saccharides, gum arabic, resin, cellulose linseed, wax, casein, Epoxy resin, polyurethane or mixtures thereof. Especially the binder is selected from the group starch, Sugar and / or dextrin. It turned out that this Binder on the one hand a high compatibility with ceramic materials and on the other least undesirable ceramic Create contaminants in the resulting moldings.

The Binder is preferably used in an amount of 1 to 15 wt .-% one. Below 1% by weight, it loses its effect. Above of 15 wt .-% it comes too much to unwanted organic Contaminations in the green body or in the molding.

The Binder, for example, has a particle size in the range of 0.1 to 500 microns, especially in one area from 50 to 300 μm.

Should with the inventive method objects be prepared, which has an overhang compared to have wetted part of the first layer (for example, a ball), it is thus preferable to choose the layer dimension of the first layer so that they are the maximum extent of the resulting green body having.

The pad according to the invention is not associated with the green body for the first layer and the respective previous layer for the following layers. The backing on which the first layer is formed is preferably selected from plastic and / or metal. The layer is formed, for example, by applying the powder to the Un terlage or the previously formed layer and then leveling of the applied powder by, for example, with a straight object in a desired layer thickness corresponding distance from the previous layer or pad on the applied powder is driven and so excess powder is removed.

The Solidification composition is advantageously provided with a printhead an inkjet printer, a microdispenser, a microdispenser, a piezo print head or a freely programmable dosing system applied. This allows standard components from others Application areas are used and so the process clearly simplify.

Preferably if the material used for the inorganic particles is metal, Oxide, silicide, nitride and / or carbide of the elements Al, B, Bi, Ca, Ce, Cr, Cu, K, Fe, Ga, Ge, In, Li, Mg, Mn, Mo, Na, Si, Sn, Sr, Ta, Ti, W, Y and / or Zr or mixtures thereof. They are natural Silicides of Si and other compounds that do not chemically exist, except. In this case, mixed oxides, mixed nitrides, Including mixed carbides, carbonitrides, oxynitrides and oxicarbides. These inorganic particles have proven to be particularly suitable the green body or the resulting molded body To give properties that are not due to the ceramic powder can be awarded. One sets the inorganic particles in the solidification composition advantageously in one Amount of 0.3 to 40 wt .-%, in particular in an amount of 2 to 20% by weight. Substituting more than 20 wt .-% of inorganic particles a, so it may cause blockages, for example in the printheads come. If you use less than 2 wt .-%, so is a small Effect achieved by the inorganic particles. As inorganic particles are preferably particles with a particle size used in the range of 10 to 200 nm. By this much lower Particle size as the grain size of the ceramic powder may be the inorganic particles especially easy between the individual grains of the ceramic Arrange powder and so a homogeneous property profile of the resulting Effect properties.

When Material for the inorganic particles for the Solidification composition is preferably used alumina, Silica, molybdenum disilicide, titania, zirconia, a mixed oxide of the abovementioned oxides, titanium nitride, tantalum nitride, chromium nitride, Boron nitride, aluminum nitride, silicon nitride, carbon nitride, titanium carbide, Tungsten carbide, silicon carbide, boron carbide or mixtures of the foregoing Connections. These materials can be ceramic Moldings particularly interesting properties like one particularly high strength or photocatalytic activity to lend.

In The solidification composition may, for example also conventional additives such as surfactants, dispersants, pH adjusting agents, emulsifying agents, adjusting agents, defoamers, Preservatives, drying retardants, additives to control rheology, wetting agents, antioxidants, UV absorbers, Be included light stabilizers or a combination thereof. For example, these additives are in an amount in one range from 0.05 to 2 wt .-%.

Advantageously, the viscosity of the solidification composition is at most 10 ⁵ mPas · s, preferably at most 100 mPa · s at 20 ° C and 1 bar. The viscosity can be measured with a Brookfield CAP 1000+ viscometer with the CAP-S-01 spindle at a speed of 750 rpm.

In Step c), the steps a) and b) are preferably at least 50 times, in particular at least 100 times repeated, so that at inherent in these processes always existing staircase effects minimized on the surface as possible.

The Removal of the dispersant, especially the water happens for example by drying. The time duration of the removal can be of the dispersant, for example, in a range of 8 to 48 h lie. The temperature is for example in one Range of 15 to 150 ° C, especially in one area from 30 to 80 ° C. The atmosphere in which the distance the dispersant takes place, for example, air. While The removal of the dispersant may be a flow the atmosphere through a fan, by mooring of a vacuum or by convection. Depending on the used ceramic powder or inorganic particles forms a hydrate shell or other compounds with the Dispersant, so that the dispersant is difficult to complete can be removed. For the purposes of the invention is therefore preferred the removal of the dispersant as completely closed consider, if towards the end of the drying no further departure from Dispersant can be observed, so the weight substantially remains constant.

The Removal of the unbound ceramic powder takes place, for example by shaking or blowing.

For example, in applying the solidification composition, a nozzle orifice is selected in a range of 10 to 100 μm and, independently, a drop size in a range from 5 to 100 μm. Due to the drop size according to the invention, the surface of the ceramic powder can be wetted particularly uniformly.

advantageously, If another solidification composition containing 0 is used to 50 wt .-%, in particular 0.3 to 40 wt .-%, most preferably 2 to 20 wt .-%, inorganic particles with an average Diameters in a range of 5 to 1000 nm, and 50 to 100% by weight Dispersant, wherein the further solidification composition from the first solidification composition by the concentration and / or nature of the inorganic particles. This can be a property gradient in the resulting very easy Shaped body can be achieved. For example, the first solidification composition contain photocatalytically active titanium oxide particles while another consolidation composition contains titanium nitride particles. These two solidification compositions can different areas are applied so that the resulting ceramic moldings photocatalytically in some places is active and elsewhere by the introduced titanium nitride is particularly hard.

The another solidification composition becomes, for example, immediately mixed with the first solidifying composition prior to application. For example, this may be in a printhead of an inkjet printer happen.

The method according to the invention is therefore suitable a 3D-structural design of a ceramic molding to create, which can be made very flexible. So can the ceramic moldings with the most diverse Properties are provided spatially resolved. this will thereby possible that any concentrations of the very different materials very precisely in the ceramic molding can be positioned. Different nanoparticles can be placed as specific. These different nanoparticles can in the process according to the invention in the same step for example from different tanks with the same printhead on the layer with the ceramic powder be applied.

The inventive method is about it In addition, not only to create prototypes, but also can find use in series production.

In the process of the invention can, for example first in a computer a 3D model of the green body to be created. This can then be broken down into slices in the computer are the thickness of the desired layer thickness of ceramic powder correspond. It can, for example, with color gradients be controlled, which of the possibly different tanks with solidification composition this composition to the printhead emits. For example, in the tank, in an ordinary Ink jet printer contains blue ink, a solidification composition containing titanium oxide particles are introduced. In a another tank can be a solution of titanium nitride particles as a solidification composition, which is usually yellow Contains ink. With the help of a computer you can now, for example in the 3D model a gradient from blue to yellow over the Define moldings. Will this data now on transferred to the printer, the result is a green body, which leads to a shaped body, on the one hand Side of the gradient, for example, photocatalytically active, on the other side of the gradient is particularly hard, and in between a fluid transition of these properties having.

To For example, a processed by means of spray granulation Powder with an organic binder, for example potato starch, mixed and placed in a Z-Printer 510 (Z Corporation, USA). Using the water-based binder solution (ZB54, Z Corporation), which was applied over an inkjet push button is, the component to be manufactured in layers, accordingly CAD data. For example, after the printing process a drying and blowing out of the parts as well as the final sintering fire.

The Z-Printer 310 is commonly offered to make colored plaster models. For this he is, according to an inkjet printer, equipped with 4 colors. Instead of colored binder, it is conceivable, for example, to use dispersions with different nanoscale oxides. As a result, the base Al ₂ O ₃ powder can be sprayed, for example, in variable amount with the various nano-oxides. The printer usually has three color chambers available. By filling with nano-dispersions, for example ZrO ₂ , SiO ₂ and TiO ₂ , the desired composite or mixed oxide ceramics can be printed on a μm scale down to the mm scale. According to the FEM simulation can be used in areas subject to high stress z. B. ZrO ₂ -nano dispersion are sprayed. During sintering, a material with significantly higher load capacity is formed in this area.

For example, it is also possible to selectively lay three-dimensionally electrical conductor tracks in ceramic molded bodies by using the conductive molybdenum disilicide as the material for the inorganic particles. This can be used, for example, to produce individually adapted heating elements, when the remaining ceramic material is selected as insulator.

The The object underlying the invention is in a further embodiment solved by a green body, which after produced by the method according to the invention.

In Yet another embodiment will be that of the invention underlying problem solved by a method for Production of a ceramic molding, wherein first carried out the inventive method and then the green body is sintered.

there For example, if you choose the sintering temperature in one Range between 1000 and 2000 ° C and independent of it the holding time in a range of 0.5 to 10 h, in particular 1 until 4 h.

In Another embodiment is the basis of the invention lying problem solved by a ceramic molding, produced by the process according to the invention has been.

Of the Shaped body has, for example, a porosity in the range of 20 to 60%. Of which independently the ceramic molding, for example, an E-module in one Range from 100 to 400 GPa. Of which, in turn, independent For example, the ceramic shaped body has a strength in a range of 150 to 400 MPa.

embodiment

It was an alumina powder (CT3000SG, Almatis, Ludwigshafen, Germany) by means of fluidized bed granulation (GPCG, Glatt, Dresden, Germany). The granules were screened <150 microns and then with 7% by mass of potato dextrin powder, grain size 115 μm (Superior yellow F, South Strength, Schrobenhausen, Germany), mixed.

To the water-based binder solution (ZB54, Z Corporation, USA) was added 10% by mass of a TiO ₂ dispersion (VP Disp. W740X, Evonik-Degussa GmbH, Hanau, Germany) with a solids concentration of 40% by mass. The components were mixed in a beaker by magnetic stirrer for 5 minutes.

With A CAD program became rod-shaped bodies (1 cm x 1 cm x 5 cm) for the purpose of sample preparation designed. These were colored from one end of the bar to the other graded (yellow to blue). The dataset was taken from the 3D printer (Z-510, Z Corporation, USA). The layer thickness was 0.088 mm and the maximum saturation.

In a binder tank, a pure binder solution (ZB 54) was filled, in the second, the mixture of the binder solution with a TiO ₂ dispersion. According to the colored graduation, the two binders were placed on the powder bed in different proportions during the printing process.

The printed samples were stored at room temperature in the powder bed of the 3D printer Dried for 12 h. Thereafter, the specimens were removed and in a drying oven at 60 ° C for a further 12 h complete dried. Subsequently, the specimens were freed of unbound powder by brush and compressed air.

The Sintering of the specimens took place at 1600 ° C, 2 h holding time.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10306887 A7 [0009]
• - DE 102006029298 A1 [0010]
• - DE 202005020596 U1 [0011]
• - DE 102005058118 A1 [0012]
• - DE 102005058116 A1 [0013]
• - DE 102006015014 A1 [0014]
• - DE 102005058121 A1 [0015]
• - DE 60207204 T2 [0016]
• - DE 102004008122 A1 [0017]

Cited non-patent literature

• - "Production of ceramic-metal moldings by 3D printing" (Melcher et al., Keramische Materialien, January 2007, 3.4.2.4.) [0018]

Claims (10)

Method for producing a ceramic green body, in which one a) forms a layer on a base, the - one contains ceramic powder and binder, b) at least a solidification composition on the aforementioned layer applied to at least part of it, the - 0.1 to 50 wt .-% of inorganic particles with an average Diameter in a range of 5 to 1000 nm, and - 50 contains up to 99.9% by weight of dispersant, c) steps a) and b) repeated at least once, d) the dispersant at least partially forming a green body or completely removed, and e) the unbound removed ceramic powder, wherein the green body is exposed. Process according to claim 1, characterized characterized in that the material of the inorganic particles in solidification composition different from the material of ceramic powder selects. Process according to claim 1, characterized in that the dispersant used is water or organic Selecting dispersant. Process according to claim 1, characterized characterized in that one has a layer thickness of the ceramic powder and the binder in a range of 10 to 300 μm, especially in a range of 50 to 120 microns selects. Process according to claim 1, characterized characterized in that a ceramic powder of oxide, silicide, Nitride and / or carbide of the elements Al, B, Bi, Ca, Ce, Cr, Cu, K, Fe, Ga, Ge, In, Li, Mg, Mn, Mo, Na, Si, Sn, Sr, Ta, Ti, W, Y and / or Zr or mixtures thereof. Process according to claim 1, characterized characterized in that as inorganic particles in the solidification composition Metals, oxides, silicides, nitrides and / or carbides of the elements Al, B, Bi, Ca, Ce, Cr, Cu, K, Fe, Ga, Ge, In, Li, Mg, Mn, Mo, Na, Si, Sn, Sr, Ta, Ti, W, Y and / or Zr or mixtures thereof. Process according to claim 1, characterized characterized in that at least one further solidification composition containing 0 to 50 wt .-% of inorganic particles with an average Diameters in a range of 5 to 1000 nm, and 50 to 100% by weight Dispersant, wherein the further solidification composition from the first solidification composition by the concentration and / or nature of the inorganic particles. Green body, made after the Process according to claim 1, comprising the material of contains inorganic nanoparticles. Process for producing a ceramic shaped body, wherein first the method according to claim 1 is performed and then the green body is sintered. Ceramic molded body, manufactured according to the Method according to claim 3, comprising the material of contains inorganic nanoparticles.