DE102017104166A1 - METHOD FOR MANUFACTURING HIGH-DENSITY AND DEFECT-ARMED SINTERED COMPONENTS, TRANSPARENT CERAMIC COMPONENT AND USE OF SUCH A - Google Patents

Abstract

The invention relates to a method for producing high-density and low-defect sintered components, in particular of transparent ceramic components. The process comprises dispersing (10, 11) a powder of a sinterable inorganic material with a wax-containing emulsion into a suspension, drying (12) the suspension to dryness, melting and homogenizing (14) the dry matter to a homogeneous mass, introducing (15) the homogeneous mass for molding moldings into a mold and heat-treating (17, 18, 19) the moldings to the high-density and low-defect sintered components. Furthermore, the invention relates to a transparent ceramic component and a use of a transparent ceramic component.

Description

FIELD OF THE INVENTION

The present invention relates to a method for producing high-density and low-defect sintered components, in particular transparent ceramic components, using a powder of a sinterable inorganic material, in particular a sinterable inorganic non-metallic material, and a wax-containing emulsion. Furthermore, the present invention relates to a high-density and low-defect sintered component, in particular a transparent ceramic component, which is made according to the inventive method, and a use of such a high-density and low-defect sintered component, in particular of such a transparent ceramic component.

BACKGROUND OF THE INVENTION

It is generally known to produce translucent and also transparent ceramic elements from sinterable inorganic materials such as zirconium oxide (ZrO ₂ ) for visible light. To produce such ceramic elements, the sinterable inorganic material is mixed with various additives and then subjected to shaping. The shaping can be done for example by pressing, casting or injection molding.

The DE 10 2007 002 079 A1 and the DE 10 2009 000 553 A1 describe a number of process variants for producing transparent ceramic components.

However, optical properties of ceramic components manufactured in accordance with the known methods are impaired by lack of homogeneity of the components. In many cases, only a translucency or low transparency can be achieved.

The object of the present invention is therefore to provide an improved process for producing high-density and low-defect sintered components, such as transparent ceramic components. Likewise, a high-density and low-defect sintered component, such as a transparent ceramic component with improved properties, in particular improved optical properties, is to be provided.

This object is achieved by the method according to the invention for producing high-density and low-defect sintered components according to claim 1, the transparent ceramic component according to claim 11 and the use of the transparent ceramic component according to claim 12.

SUMMARY OF THE INVENTION

• Dispergieren eines Pulvers eines sinterfähigen anorganischen Materials mit einer wachshaltigen Emulsion zu einer Suspension;
• Trocknen der Suspension zu Trockengut;
• Aufschmelzen und Homogenisieren des Trockenguts zu einer homogenen Masse;
• Einbringen der homogenen Masse zum Formen von Formlingen in eine Form; und Wärmebehandeln der Formlinge zu den hochdichten und defektarmen gesinterten Bauteilen.

According to a first aspect, the present invention relates to a method for producing high-density and low-defect sintered components, in particular of transparent ceramic components, comprising:

• Dispersing a powder of a sinterable inorganic material with a wax-containing emulsion into a suspension;
• Drying the suspension to dryness;
• Melting and homogenizing the dry matter to a homogeneous mass;
• Introducing the homogeneous mass for molding moldings into a mold; and heat treating the moldings to the high density and low defect sintered components.

According to a second aspect, the invention relates to a transparent ceramic component comprising a sinterable inorganic material, wherein the transparent ceramic component is manufactured by means of a method according to the first aspect.

According to a third aspect, the present invention relates to a use of the transparent ceramic component according to the second aspect as a component in optics, in lighting technology, in dentistry, in medicine, in medical technology, as a window element, as a component of a piece of jewelry and / or as Component of a clock.

Further aspects and features of the present invention will become apparent from the dependent claims, the accompanying drawings and the following description of preferred embodiments.

The present invention relates to a method for producing high-density and low-defect sintered components, in particular of transparent ceramic components. The transparent ceramic components may be translucent components of a sinterable material, which may have a transmission of 25% or more, in particular in a certain wavelength range.

According to the method of the invention, first a powder of a sinterable inorganic material, for example a sinterable inorganic non-metallic or metallic material, is dispersed with a wax-containing emulsion into a suspension. For example, the powder of the sinterable inorganic material can be prepared by stirring, for example in a Ball mill, in particular a stirred ball mill, are dispersed with the wax-containing emulsion. By dispersing the sinterable inorganic material, hydrophobization can be improved and surface smoothness of the sintered components can be increased.

The sinterable inorganic material may be an inorganic material which sinters upon exposure to heat and optionally pressure. During sintering, the inorganic powder may be subjected to a solid phase sintering process caused by temperature and optionally pressure, for example volume and surface diffusion processes optionally with gas transport. The sinterable inorganic material may have a high chemical purity, in particular a purity of more than 99%, in particular more than 99.9%, in particular more than 99.99%. The inorganic material may have a cubic or non-cubic crystal system and preferably possess optically isotropic properties.

The waxy emulsion may contain wax beads or wax particles. The wax beads may be a few micrometers in size. The wax beads may comprise a wax compound or consist of a wax compound whose melting point is in a range of 45 ° C to 75 ° C, in particular in a range of 55 ° C to 65 ° C, especially at 60 ° C. For example, the wax beads may contain a paraffin wax. The wax beads may have a high purity, for example of 99% or more, in particular more than 99.9%. The waxy emulsion may, for example, contain a proportion of wax beads in a range of 50% by mass to 60% by mass, especially 55% by mass.

According to the method of the invention, the suspension is dried to dryness with the powder of the sinterable inorganic material. The drying can be done for example by heat drying, for example in a drying oven. Preferably, the heat-drying at a temperature in the range of 100 ° C to 120 ° C, in particular at 110 ° C, are performed. The heat-drying can be continued until a moisture content of the dry matter is less than 0.1%, in particular less than 0.05%.

According to the method of the invention, the dry material is melted and homogenized to a homogeneous mass. The homogeneous mass is in particular a homogeneous melt. The melting and homogenization can preferably take place simultaneously. For example, the dry material in a heated stirrer at a temperature in the range of 110 ° C to 130 ° C, especially at 120 ° C, melted and homogenized. Optionally, an additional homogenization of the molten mass in a rolling apparatus, such as a three-roll mill, take place.

According to the method of the invention, the homogeneous mass for molding moldings is introduced into a mold, preferably by means of a thermoplastic molding process. The shape may be a dimensionally stable shape, for example of metal. Alternatively, the mold may be a flexible mold, for example made of plastic, in particular of silicone. The mold may be formed so that molded articles in the form of tablets, platelets, optical components such as lenses, prisms or other optical components, window panes and other shapes can be produced.

According to the inventive method, the moldings are heat-treated to the high-density and low-defect sintered components, in particular the transparent ceramic components. The heat treatment may include debinding, sintering, hot isostatic densification (hot isostatic pressing - HIP) and / or other heat treatment.

By dispersing the powder of the sinterable inorganic material (sinterable powder) with the wax-containing emulsion, a homogeneous suspension can be provided, from which transparent ceramic components with a high degree of filling and a high density and thus increased transparency can be produced.

By means of a thermoplastic shaping, moreover, complex components can be realized, in particular without drying the mass in the mold.

In some embodiments, the ceramic components may be oxide ceramic components, non-oxide ceramic components, and / or components of another ceramic material.

The sinterable material comprises one or more oxides or consist of one or more oxides. For example, the sinterable material may include zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), scandium oxide (Sc ₂ O ₃ ), yttria (Y ₂ O ₃ ), one or more oxides of the rare Contain (for example, SE ₂ O ₃ and / or SEO ₂ ), zinc oxide (ZnO) and / or other oxides or consist of one or more of these oxides. The sinterable material may also contain compounds having crystalline "perovskite structure", for example lead zirconate titanate (Pb [Zr _1-x Ti _x ] O ₃ where 0≤x≤1), barium / strontium titanate (Ba _1-x Sr _x TiO ₃ with 0≤x≤1) and / or potassium / sodium niobate / tantalate ((K _1-x , Na _x ) (Ta _1-y Nb _y ) O ₃ where 0≤x≤1; 0≤y≤1 ), Yttrium vanadate YVO ₄ , which may be undoped or doped with elements of the rare earth group (YVO ₄ : SE), compounds with crystalline garnet structure, wherein the term "garnet structure" in particular means a cubic material and / or comprises, in particular of the general structure A ₃ B ₂ [XO ₄ ] ₃ , where A is a bivalent, B is a trivalent and X is a tetravalent cation and / or the general structure A ₃ B ₂ [RO ₄ ] ₃ , where A, B, R represent trivalent cations and wherein B and R may also be identical or contain mixtures of these structures or consist of one or more of these compounds. Exemplary of these are undoped or rare-earth elements, in particular cerium-doped, representatives such as (Y _1-x Gd _x ) ₃ (Al _1-y Ga _y ) ₅ O ₁₂ : Ce, (Y _1-x Tb _x ) ₃ (Al _1-y Ga _y ) ₅ O ₁₂ : Ce, (Y _1-x D _{y x} ) ₃ (Al _1-x Ga _y ) ₅ O ₁₂ : Ce, (Lu _1-x ) ₃ (Al _1-y Ga _y ) ₅ O ₁₂ : Ce, Lu ₃ (Al _1-x Sc _x ) ₅ O ₁₂ : Ce, (Y _1-x Gd _x ) ₃ (Al _1-y Sc _y ) ₅ O ₁₂ : Ce, (Y _1-x Tb _x ) ₃ (Al _1-y Sc _y ) ₅ O ₁₂ : Ce or mixtures thereof.

The sinterable inorganic material may contain one or more stabilizers, in particular in the form of oxides. For example, zirconia (ZrO ₂ ) may contain a stabilizer such as yttria (Y ₂ O ₃ ) and alumina (Al ₂ O ₃ ) may contain a stabilizer such as magnesium oxide (MgO). Preferably, the sinterable inorganic material may be yttria-stabilized zirconia. For example, the zirconia is stabilized with 6 mol% to 10 mol% of yttrium oxide, in particular with 8 mol% of yttrium oxide.

The sinterable material may also contain compounds of crystalline pyrochlore structure of the general composition A _{2 + x} B _y D _z E ₇ or consist of one or more of these compounds, where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2 and 0 ≤ z ≤ 1.6 and 3x + 4y + 5z = 8 and wherein A is at least one trivalent cation from the group of rare earth oxides, preferably Y, Gd, Yb, Lu, La and / or Sc, B at least one tetravalent cation , in particular Ti, Zr, Hf, Sn and / or Ge, D is at least one pentavalent cation, in particular Nb and / or Ta, and E is at least one anion which is essentially divalent.

The sinterable material may also contain or consist of one or more inorganic phosphors.

Alternatively, the sinterable material may comprise one or more silicates, nitrides, oxynitrides, in particular aluminum oxynitride (AlON), (Sr _1-x Ca _x ) Si ₂ N ₂ O ₂ : Eu and / or BaSi ₂ O ₂ N ₂ : Eu, and / or contain carbides or consist of one or more of these substance.

Alternatively, the high-density and low-defect sintered components may also be metallic components or components made of an alloy. The sinterable inorganic material may in this case contain or consist of a metal and / or an alloy.

In some embodiments, powder particles of the powder of the sinterable inorganic material may have a size of a few micrometers or smaller, in particular a size in the nanometer range. Preferably, the sinterable powder may be a nanopowder having, for example, an average particle size of 0.1 .mu.m to 1 .mu.m, in particular from 0.4 .mu.m to 0.6 .mu.m, in particular of 0.5 .mu.m.

In some embodiments, the waxy emulsion may be an aqueous wax emulsion. The aqueous wax emulsion may contain wax beads of one or more wax compounds and water, in particular desalted or mono- or multi-distilled water. The wax compound may have a melting point in a range of 45 ° C to 75 ° C, in particular in a range of 55 ° C to 65 ° C, in particular of 60 ° C. Preferably, the waxy emulsion is a nonionic aqueous emulsion of a paraffin wax.

In some embodiments, when dispersing the powder of sinterable inorganic material with the wax-containing emulsion, the powder of the sinterable inorganic material may be predispersed with a dispersant and / or water to a pre-suspension and the pre-suspension dispersed with the wax-containing emulsion. The dispersant may contain or consist of an ester, especially long chain alcohols, preferably a polar acid ester of long chain alcohols. The dispersant may also be another organic dispersant, for example a polyacrylate, citrate, titrate and / or polysulfonate based dispersant. When dispersing inorganic fillers such as the sinterable powder, for example, at most 5%, in particular from 1% to 3%, of dispersant can be used. The dispersant can adsorb to particle surfaces of inorganic filler particles, whereby improved processing and dispersion of the particles can be achieved. In particular, the viscosity can be reduced by the dispersant. The water can be a desalted or simply distilled water.

Preferably, a proportion of the sinterable powder suspension may vary between 60% and 70% by mass. A ratio between a share of water and Dispersant on the one hand and a content of wax-containing emulsion on the other hand can be between 4/3 and 2/1, in particular at 5/3.

In some embodiments, in accordance with the method of manufacturing high density and low defect sintered components, particularly transparent ceramic components, a wetting agent may further be mixed with the dry matter. Preferably, the wetting agent is mixed before starting melting and homogenizing the desiccant with the dry material or added at the beginning of melting and homogenizing the desiccant to the dry material and mixed with this, in particular stirred. The wetting agent can serve to reduce interfacial tension between two phases and aid in the formation of a homogeneous mass. In addition, the wetting agent can increase the transparency of the transparent ceramic component and reduce the viscosity of the mass. The wetting agent may contain or consist of a copolymer. The copolymer may, for example, have groups which interact with the particles of the sinterable powder. When mixing inorganic fillers, for example, a maximum of 15%, in particular from 5% to 10%, of wetting agents can be used.

In some embodiments, according to the method for manufacturing high-density and low-defect sintered components, in particular of transparent ceramic components, it is furthermore possible to add a phosphor before introducing the homogeneous mass into the mold. For example, the phosphor may be mixed below the sinterable powder, added and mixed in dispersing the sinterable powder with the wax-containing emulsion, mixed under the dry material, or added to the homogeneous mass during mixing and homogenization of the dry matter. Alternatively, the powder itself may be the inorganic phosphor, thus producing a transparent phosphor ceramic.

The phosphor may comprise a material which is energized by the application of energy by radiation in an excited, high-energy state. The phosphor may contain inorganic, crystalline particulate matter of micro- or nanoscale order. For example, the phosphor may be based on Yttrium Aluminum Garnet (YAG) or Lutetium Aluminum Garnet (LuAG). Preferably, the phosphor YAG: Ce, which is used, for example, for the production of white light in LEDs, or LuAG: Ce, wherein an existing of YAG or LuAG host lattice Ce ³⁺ ions were added. The phosphor preferably has a high chemical purity, in particular a purity of 99.9% or more.

Examples of inorganic phosphors are (Ba _1-x Sr _x ) MgAl ₁₀ O ₁₇ : Eu, (Ba _1-x Sr _x ) Mg ₃ Al ₁₄ O ₂₅ : Eu, (Sr, Ca, Mg) ₂ Si ₂ O ₆ : Eu, CaAl ₂ O ₄ : Eu, (Ba _1-x Sr _x ) Al ₂ Si ₂ O ₈ : Eu, (Ba _1-x Sr _x ) 6 _B P ₅ O ₂₀ : Eu, (Ca _1-xy Sr _x Ba _y ) ₅ (PO ₄ ) ₃ (F _1-a Cl _y ): Eu, (Y, Gd) (Nb _1-x ) O ₄ , (Ba, Sr, Ca) ₂ MgSi ₂ O ₇ : Eu, ( Ba _1-x Sr _x ) ZrSi ₃ O ₉ : Eu and / or other inorganic phosphors. Further examples of inorganic phosphors are Li ₃ Ba ₂ (Tb _1-xy Eu _x Ln _y ) ₃ (Mo _1-z W _z ) ₈ O ₃₂ , A ₃ AE ₂ (Tb _1-xy Eu _x Ln _y ) ₃ (Mo _1-z W _z ) ₈ O ₃₂ , A (Tb _1-xy Eu _x Ln _y ) (Mo _1-z W _z ) ₂ O ₈ , (Tb _1-xy Eu _x Ln _y ) ₂ (Mo _1-z W _z ) O ₆ , (Tb _1-xy Eu _x Ln _y ) ₂ (Mo _1-z W _z ) ₂ O ₉ , (Tb _1-xy Eu _x Ln _y ) ₂ (Mo _1-z W _z ) ₄ O ₁₅ (Tb _1-xy Eu _x Ln _{y) 2} SiO _5, (Tb _1-xy Eu _x Ln _{y) 2} Si ₂ O _7, A (Tb _1-xy Eu _x Ln _y) SiO _4, Ba ₂ (Tb _{1 -xy} Eu _x Ln _y ) ₂ Si ₄ O ₁₃ , AE ₂ (Tb _1-xy Eu _x Ln _y ) ₂ Si ₄ O ₁₃ , Sr ₂ (Tb _1-xy Eu _x Ln _y ) ₂ Si ₆ O ₁₈ , AE ₃ (Tb _1-xy Eu _x Ln _y ) ₂ Si ₆ O ₁₈ , (Tb _1-xy Eu _x Ln _y ) ₂ G _e O ₅ , (Tb _1-xy Eu _x Ln _y ) ₂ Ge ₂ O ₇ , A (Tb _1-xy Eu _x Ln _y ) ₂ Si ₂ O ₇ , Ba ₂ (Tb _1-xy Eu _x Ln _y ) ₂ Ge ₄ O ₁₃ , AE ₂ (Tb _1-xy Eu _x Ln _y ) ₂ Ge ₄ O ₁₃ , Sr ₃ (Tb _1-xy Eu _x Ln _y ) ₂ Ge ₆ O ₁₈ , AE ₃ (Tb _1-xy Eu _x Ln _y ) ₂ Ge ₆ O ₁₈ , (Tb _1-xy Eu _x Ln _y ) ₂ ( Ge _1-ab Zr _a Hf _b ) O ₅ , (Tb _1-xy Eu _x Ln _y ) ₂ (G _e1-ab Zr _a Hf _b ) ₂ O ₇ , A (Tb _1-xy Eu _x Ln _y ) (Ge _1-ab Zr _a Hf _b ) O ₄ , B _a2 (Tb _1-xy Eu _x Ln _y ) ₂ (G _e1-ab Zr _a Hf _b ) ₄ O ₁₃ , Sr ₃ (Tb _1-xy Eu _x Ln _y ) ₂ (Ge _1-ab Zr _a Hf _b ) ₆ O ₁₈ with (each independently for each material) Ln = La, Gd, Lu, Y or mixtures thereof, A = Li, Na, K, Rb, Cs or mixtures thereof, preferably Li, AE = Sr, Ca , Br or mixtures thereof, preferably Ba and / or Sr, x> 0 and <1 and y ≥ 0 and <1 and 1-xy> 0 and a, b ≥ 0 and <0.2 and z ≥ 0 and ≤ 1 or mixtures of these materials.

In some embodiments, the introduction of the homogeneous mass in the mold by means of injection molding, in particular by means of low-pressure injection molding, take place. The low pressure injection molding may, for example, at a temperature of the homogeneous mass in a range of 100 ° C to 140 ° C, in particular in a range of 115 ° C to 125 ° C, and an injection pressure in a range of 0.5 bar to 10 bar, in particular in a range of 3 bar to 7 bar, take place. Alternatively, the homogeneous melt can also be introduced into the mold in other ways, for example by pouring or pouring the mass into the mold.

After introduction of the homogeneous mass into the mold, the mold can be shaken with the homogeneous mass, for example by means of a vibrating table, in order to eliminate air pockets.

After the homogeneous mass has solidified in the mold, for example cooled and solidified, The moldings can be removed from the mold.

In some embodiments, the moldings may be debinded during heat treatment of the moldings. When debindering the moldings wax components of the moldings are at least partially melted and withdrawn to the moldings due to a capillary suction of an embedding in a debindering bed, such as a powder bed, a granule bed or a ball bed, or on a (for example ceramic) porous and thus have capillary forces underlay , The embedding material or the temperature-resistant (for example ceramic) pad can have a high porosity, in order to promote the capillary suction for receiving the wax during debindering. The potting material or pad is preferably selected so that it does not chemically react with the high density and low defect sintered components. For example, the potting material may be alumina, zirconia, or other oxide ceramic material. Preferably, a size of the powder or granule particles or the beads has an average diameter in the range of 0.1 μm to 5 mm.

The debinding may, for example, have two binder removal phases, wherein a heating rate in a first binder removal phase is lower than in a second binder removal phase. For example, in a first debindering phase, the shaped articles can be heated to a first temperature, for example a temperature of 200 ° C. to 300 ° C., at a first heating rate, for example a heating rate of 0.1 K / min to 1 K / min and then maintained at the first temperature for a first period of time, for example, a period of from 100 minutes to 200 minutes. Subsequently, the moldings in a second binder removal phase with a second heating rate, for example a heating rate of 0.5 K / min to 1 K / min, to a second temperature, for example a temperature of 450 ° C to 550 ° C, heated and then maintained at the second temperature for a second period of time, such as a period of 15 minutes to 30 minutes.

If necessary, further binder removal phases can be added. For example, in a third debinding phase, which is carried out before the first debindering phase, the shaped articles can be heated to a third temperature, for example a temperature, at a third heating rate, for example a heating rate of 0.1 K / min to 1 K / min from 100 ° C to 200 ° C, and then maintained at the third temperature for a third period of time, for example, a period of 100 minutes to 200 minutes.

In some embodiments, the blanks, preferably the debindered blanks (brown pieces), may be sintered and / or post-compacted, in particular hot isostatically recompressed, and / or tempered during the heat-treatment of the blanks. During sintering, residues of the wax constituents can be burned in the debindered moldings.

The sintering can take place, for example, in a high-temperature furnace under air atmosphere. The debindered briquettes (brownlings) can be placed on an alumina plate and at a heating rate of 1.5 K / min to 2 K / min to a temperature in a range of 1200 ° C to 2000 ° C with subsequent holding time of 1.5 Sintered for hours to 2.5 hours to Whites or ceramics with a density> 95% of the theoretical density.

In hot isostatic densification, the whitenesses or ceramics having a density> 95% of the theoretical density at a temperature of 1300 ° C to 2000 ° C under a pressure of 150 MPa to 200 MPa and with a holding time of 1.5 hours to 2.5 Hours, for example, under an argon atmosphere hot isostatically recompressed. Preferably, the densified moldings are subjected to an annealing firing at a temperature of 900 ° C to 1200 ° C with a holding time of 0.5 hours to 1.5 hours, since the samples after hot isostatic recompression have a dark color.

The heat-treated blanks or the high-density and low-defect sintered components, in particular the transparent ceramic components, can subsequently be reworked. For example, the sintered components can be cut, ground and / or polished. Also, a trowalizing similar machining process to reduce the surface roughness and improve the surface quality can be applied.

The inventive method for producing high-density and low-defect sintered components, in particular of transparent ceramic components, high-quality, especially transparent ceramic components can be provided, which are characterized by high homogeneity and density and thus high transparency and are also robust against environmental influences.

The present invention further relates to a high-density and low-defect sintered component, in particular a transparent ceramic component comprising a sinterable inorganic material, for example an inorganic non-metallic or metallic material as listed above with reference to the process of the invention. The ceramic component can be, for example, an oxide ceramic component, a non-oxide ceramic component and / or a component made from another ceramic material. The high-density and low-defect sintered component, in particular the transparent ceramic component, is manufactured by means of the method described in detail above for the production of high-density and low-defect sintered components. The transparent ceramic component is characterized by a high transparency and at the same time high robustness against environmental influences.

The present invention further relates to a use of a high-density and low-defect sintered component, in particular a transparent ceramic component, which comprises a sinterable inorganic material and by means of the method described in detail above for producing high-density and low-defect sintered components, in particular of transparent ceramic components, as Component in optics, in lighting technology and / or in dentistry, medicine, medical technology, as a window element, as a component of a piece of jewelry and / or as a component of a clock. For example, the transparent ceramic component can be used as a lens or as a prism in optics or as a laser component or as an LED component, for example as a filter, in lighting technology. Alternatively, the transparent ceramic component can be used as a window in a piping system, for example for the optical monitoring of currents or in thermally and / or chemically stressed reactors and / or as a window in a ballistic protection.

list of figures

• 1 ein Flussdiagramm eines ersten Ausführungsbeispiels eines Verfahrens zum Fertigen von transparenten Keramikbauteilen;
• 2 eine schematische Darstellung einer Negativform und eines tablettenförmigen Grünlings;
• 3 eine Darstellung eines Programms zum Entbindern von Grünlingen;
• 4 ein Flussdiagramm eines zweiten Ausführungsbeispiel eines Verfahrens zum Fertigen von transparenten Keramikbauteilen; und
• 5 eine schematische Darstellung der Entstehung von weißem Licht in der LED-Technik.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. Show it:

• 1 a flowchart of a first embodiment of a method for manufacturing transparent ceramic components;
• 2 a schematic representation of a negative mold and a tablet-shaped green compact;
• 3 a representation of a program for the removal of greenlings;
• 4 a flowchart of a second embodiment of a method for manufacturing transparent ceramic components; and
• 5 a schematic representation of the formation of white light in LED technology.

DESCRIPTION OF EMBODIMENTS

1 shows a flowchart of a first embodiment of a method 1 for the production of transparent ceramic components.

at 10 For example, a high-purity zirconium oxide powder with a polar acid ester of long-chain alcohols as dispersants and demineralized water is predispersed to a presuspension. For this purpose, the zirconium oxide powder in a stirred ball mill with the dispersant and the deionized water 15 predispersed at 2500 min ^{-1 for} min.

The zirconia powder consists of a zirconia raw material stabilized with 8 mol% yttrium, which has a small specific surface area and thus allows a very good flow behavior in ceramic injection molding. The zirconium oxide powder has a round particle shape with a d ₅₀ value of 0.6 μm and a primary particle size of 0.06 μm. The specific surface area is 7 ± 2 m ² / g. The true density of the material is 5.90 g / cm ² .

at 11 For example, the pre-suspension of the zirconia powder, the dispersant and the deionized water is dispersed with an aqueous wax emulsion to form an aqueous suspension. For this purpose, a liquid aqueous wax emulsion is added to the pre-suspension in the stirred ball mill and dispersed at 3000 min ^{-1 for} 30 min.

The wax emulsion is a nonionic aqueous emulsion of a paraffin wax. It is liquid at room temperature and has a white color. It has an aqueous base and a solids content is 55 percent by mass. A density is 0.95 g / cm ³ . The melting point of the wax component is 65 ° C and the boiling point at 100 ° C.

The aqueous suspension comprises 100 parts by weight of zirconia powder, 0.5 part by weight of dispersant, 24.6 parts by weight of desalted water and 15.52 parts by weight of wax emulsion.

at 12 the aqueous suspension is dried to dryness. For this purpose, the aqueous suspension is dried for 48 hours in a drying oven at 110 ° C until a moisture content of the dry matter is less than 0.05%.

at 13 a wetting agent is stirred into the dry matter. For this purpose, the wetting agent is stirred together with the dry material in a heated with 120 ° C agitator to a flowable mass. The stirring of the dry material is preferably carried out simultaneously with the subsequent step 14 ,

at 14 The dry material is melted and homogenized. This is the dry material in the Stirred at 120 ° C stirred for about one hour to a melt until a homogeneous mass is formed. Subsequently, the melt is homogenized and dispersed in a single pass through a three-roll mill with a gap size of 15 μm and 5 μm and a rotational speed of the rolls of 160 min ^-1 .

at 15 The homogeneous melt is introduced into a mold. This is done with a Niederbis medium pressure injection molding. The homogeneous melt is heated at a temperature of 120 ° C and injected under a pressure of 5 bar in cavities of a negative molds to green compacts.

at 16 the green compacts are cooled and removed from the negative mold. 2 schematically shows a negative mold 2 with cavities 20 and a tablet-shaped green body taken from this negative mold 3 ,

at 17 the greenlings are released to brownlings. For this purpose, the green compacts in Al ₂ O ₃ granules in the form of pressed granules with a grain size of 180-230 microns with 2 microns primary grain size, which was previously treated thermally, embedded and thermally debinded in a binder removal furnace.

Debt relief can be a debit program, as described below with reference to 3 is described, follow. In a first interval t ₁ , the green compacts are heated up to a temperature T ₁ = 150 ° C. at a heating rate of 0.5 K / min. In a second interval t _2, the green compacts, for 150 min at the temperature T ₁ are held. In a third interval t ₃ , the green compacts are heated at a heating rate of 0.5 K / min up to a temperature T ₂ = 250 ° C. In a fourth interval t ₄ , the green compacts are held at the temperature T ₂ for 150 minutes. In a fifth interval t ₅ , the green compacts are heated at a heating rate of 0.75 K / min to a temperature T ₃ = 500 ° C. In a sixth interval t ₆ , the green compacts are kept at the temperature T ₃ for 20 minutes.

at 18 the brownlings are sintered to white. The sintering takes place in a high-temperature furnace under air atmosphere. The brownlings are heated on an aluminum oxide plate at a heating rate of 1.7 K / min to 1325 ° C and then held for 2 hours at 1325 ° C in order to sinter them to Whites or in this case to ceramics.

at 19 the ceramics are post-densified hot isostatically. For this purpose, the ceramics are densified at 1350 ° C under a pressure of 170 MPa and a holding time of 2 hours under an argon atmosphere hot isostatic. Subsequently, the shaped articles are subjected to an annealing firing at 1000 ° C. with a holding time of 1 hour, since the samples have a dark color after the compacting process.

at 20 The heat-treated moldings are post-processed. For this purpose, the moldings are ground and polished.

A second embodiment differs from the first embodiment in the manner of introducing the homogeneous melt into the mold at 15. The remaining process steps are unchanged.

According to the second embodiment, the homogeneous mass is introduced in molten form into a silicone mold. For this purpose, the homogeneous mass and the silicone mold are pre-heated in a drying oven at 110 ° C and the homogeneous mass is then poured into a vibrating table manually in the silicone mold, whereby a good compaction of the mass is achieved.

For example, the silicone mold can be made by placing a 24.50 mm diameter, 3.45 mm height molded tablet in a plastic cup and potting it with silicone. After curing of the silicone, the resulting silicone mold is used for shaping.

4 shows a flowchart of a third embodiment of a method 1' for producing transparent ceramic components having a phosphor.

In addition to the process steps 10 to 20 of the procedure 1 of the first embodiment, which are performed unchanged, includes the method 1' for manufacturing transparent phosphor components having a phosphor, adding a phosphor to the dry matter.

at 21 are added during the melting and homogenization of the dry material with 14 phosphor particles of YAG: Ce to the dry matter and stirred in the heated at 120 ° C agitator to the melt. In other embodiments, the phosphor particles may also be during the steps 10 to 13 or between steps 10 to 14 be added.

YAG: Ce is used for the production of white light in LEDs. The principle is based on that of luminescence. The phosphor is excited with light of a particular wavelength so that electrons are raised from the valence band to the higher conduction band within which the electrons are free to move through the crystal. As a result, the electrons release energy and fall back from the conduction band into the valence band.

The transparent, a phosphor having ceramic components are suitable for a semiconductor chip, the z. B. blue light emitted to be applied. The mixture of the blue light transmitted through the ceramic member and the yellow light emitted by the YAG: Ce powder gives white light as in FIG 5 indicated schematically.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007002079 A1 [0003]
• DE 102009000553 A1 [0003]

Claims (12)

Process for the production of high-density and low-defect sintered components, in particular of transparent ceramic components, comprising: Dispersing (10, 11) a powder of a sinterable inorganic material with a wax-containing emulsion into a suspension; Drying (12) the suspension to dryness; Melting and homogenizing (14) the dry matter to a homogeneous mass; Introducing (15) the homogeneous mass for molding molded articles into a mold; and Heat treatment (17, 18, 19) of the moldings to the high-density and low-defect sintered components. Method according to Claim 1 wherein the ceramic components are oxide ceramic components, non-oxide ceramic components and / or components of a different ceramic material. Method according to Claim 1 or 2 in which powder particles of the powder of the sinterable inorganic material have a size of a few micrometers or smaller, in particular a size in the nanometer range. A process according to any one of the preceding claims, wherein the wax-containing emulsion is an aqueous wax emulsion comprising particles of one or more wax compounds and water, a melting point of the one or more wax compounds especially from 45 ° C to 75 ° C, especially from 55 ° C to 65 ° C, is. A method according to any one of the preceding claims, wherein dispersing the powder of sinterable inorganic material with the wax-containing emulsion comprises; Predispersing (10) the powder of sinterable inorganic material with a dispersing agent and / or with water to a presuspension; and Dispersing (11) the pre-suspension with the wax-containing emulsion. The method of any one of the preceding claims, further comprising: Mixing (13) a wetting agent with the dry material, in particular before or at the beginning of the melting and homogenization (14) of the drying agent. The method of any one of the preceding claims, further comprising: Adding (21) a phosphor before introducing (15) the homogeneous mass into the mold. Method according to one of the preceding claims, wherein the introduction (15) of the homogeneous mass into the mold by injection molding, in particular by low-pressure injection molding, in particular a temperature of the homogeneous mass in a range of 100 ° C to 140 ° C, in particular in a Range of 115 ° C to 125 ° C, and is an injection pressure in a range of 0.5 bar to 10 bar. Method according to one of the preceding claims, wherein the heat treatment of the moldings comprises: Debinding (17) of the moldings, wherein the binder removal in particular has two binder removal phases, wherein a heating rate in a first binder removal phase is lower than in a second binder removal phase. Method according to one of the preceding claims, wherein the heat treatment of the moldings comprises: Sintering (18) the moldings; and or Subjecting (19) the moldings to hot isostatic densification. A transparent ceramic member comprising a sinterable inorganic material, wherein the transparent ceramic member is made by a method (1, 1 ') according to any one of the preceding claims. Use of the transparent ceramic component according to Claim 11 as a component in optics, in lighting technology, in dentistry, in medicine or in medical technology, as a window element, as a component of a piece of jewelry and / or as a component of a clock.

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