DE102005031955B4 - Process for the production of two- and three-dimensional moldings and their use - Google Patents

Abstract

method for the production of oxide or ceramic moldings, wherein to the green bodies too Underlying separation body by electrophoretic deposition of oxide or ceramic Particles are formed from a suspension, wherein one of the electrodes for the Electrophoretic deposition is arranged in the suspension, and the particles are disposed on and / or in suspension structured porous Form are deposited, which are the negative form of each separating body and has a space filled with an electrically conductive fluid, in which the other electrode for the electrophoretic deposition is arranged, characterized that the porous one Form due to laser interference or holographic lithography. or periodically structured three-dimensionally.

Description

The The invention relates to a method according to the preamble of the claim 1, for the production of oxidic or ceramic green bodies for Manipulating the propagation of electromagnetic waves, from which two-dimensional moldings or three-dimensional moldings produced by sintering, wherein the green bodies underlying the deposition by Electrophoretic deposition of oxide or ceramic particles are formed from a suspension, wherein one of the electrodes for the electrophoretic deposition is arranged in the suspension.

State of the art:

devices to manipulate the propagation of electromagnetic waves in the youngest Past among other things as an alternative to electrical circuits established because they transmit signals at the speed of light. The advantage is a much faster transmission of signals in the Compared to conventional Devices. The advantage of oxide and ceramic particles lies in the necessarily high refractive index required for such devices becomes.

Especially has titanium dioxide as a material for making devices for manipulating the propagation of electromagnetic waves, in particular Photonic structures, very well proven and has the advantage that in addition to the very good strength of the green body and molded body too a very good transparency for a wide wavelength range given the electromagnetic spectrum. Has silicon dioxide itself as an optical fiber for the optical data transmission very well proven and has the advantage of ensuring very good availability is. The disadvantage of both materials, however, the high impact Melting temperature and the high surface tension of the melt. It is therefore desirable oxidic or ceramic devices for propagation manipulation electromagnetic waves by means of an electrophoretic method wet-chemically produce near-net shape.

Independent of The use of the device requires every manufacturing process meet several basic requirements. Above all, it is important the high accuracy of the structure. It must comply with very tight tolerances become. Furthermore, the production of the moldings should cost and the manufacturing process must be quick and easy to carry out. Furthermore, a good reproducibility of the process is important also to ensure a low failure rate.

From the EP 0 200 242 A2 and EP 0 196 717 A1 is a method for producing a glass body is known in which formed from an aqueous suspension with highly dispersed solids a porous green body and this is then cleaned and sintered, wherein the green body is prepared by separation of the phases of the suspension by means of electrophoresis.

However, it can be neither in EP 0200 242 A2 still in EP 0 196 717 A1 References to the fact that titanium dioxide or silicon dioxide or ceramic or oxide particles can generally be deposited by means of the process described there. In addition, there are no indications that a device for manipulating electromagnetic waves can be produced by the described method.

Out DE 103 19 300 A1 For example, a method for producing a silica glass body is known. It can be, however, in DE 103 19 300 A1 find no evidence that the membrane at which the deposition takes place has two-dimensional structures or three-dimensional structures. In addition, there is no evidence that titanium dioxide can be deposited by this process.

Out DE 102 04 318 A1 For example, a method for producing a photonic crystal is known. The production of the same from titanium dioxide is described. However, there are no indications that this is a process based on electrophoretic deposition. A disadvantage of this method is the long production time of the template, which is given as 2 weeks. In addition, after receiving the template 4 further steps are necessary until the entire manufacturing process is completed.

Out DE 195 81 662 T1 For example, a method for producing a catalyst element by electrophoretic deposition of a porous ceramic oxide on a metal foil is known. The latter can be at least partially structured, so that the oxide deposition has this contour. From the document, however, it is not known to use the metal foil only as a negative mold, from which the oxide layer can be removed, so that the oxide layer could find use as a separate molding. Furthermore, can be in DE 195 81 662 T1 find no evidence to give the metal foil by the method according to the invention by means of laser interference or holographic lithography, a two- or three-dimensional structure, which would then be found in the deposition.

From "Electrophoretic Deposition of Latex-Based 3D Colloidal Photonic Crystals: A Technique for Rapid Production of High-Quality Opals "(Chemistry of Materials 12, 2000, p. 2721-2726, Authors: A.L. Rogach, N.A. Kotov et al.) Is a method for Preparation of a three-dimensional photonic crystal of polystyrene or Cadmiumtellurit (CdTe) by means of electrophoretic Deposition known. However, there are no indications that this process with titania or silica or ceramic or oxidic particles can generally be carried out. Furthermore There is no indication that the particles are on a porous Form are deposited. Furthermore, no hints find that the process with water as the dispersing medium carried out can be.

Task:

It is the object of the invention, an initially mentioned method form such that it for the production of oxidic or ceramic particles existing green bodies is suitable.

The solution This object is apparent from the features of the characterizing Part of claim 1. Advantageous developments of the invention emerge from the dependent claims.

According to the invention is a method for producing oxidic or ceramic green bodies for Manipulation of electromagnetic waves from which shaped bodies by means of Sintering can be produced, wherein the green bodies underlying the deposition body by Electrophoretic deposition of oxide or ceramic particles are formed from a suspension, wherein one of the electrodes is arranged in the suspension, so that the particles on one arranged in the suspension two-dimensionally structured or in a three-dimensionally structured one arranged in the suspension porous Form are deposited, which are the negative form of each separating body has and about has a space filled with an electrically conductive liquid, in which the other electrode for the electrophoretic deposition is arranged.

Thereby, that the oxide or ceramic particles on one in the suspension arranged two-dimensionally structured porous form or in one in the Suspension arranged three-dimensionally structured porous form are deposited, which has the negative shape of the Abscheidekörpers, becomes easily by electrophoretic deposition collecting bodies formed, whose geometry corresponds to the inverse geometry of the molding, if necessary, except for minor differences. This is extremely beneficial because, as previously reported, a very high accuracy necessary is.

By the arrangement of the other electrode for the electrophoretic deposition in the space filled with an electrically conductive liquid a very good deposition of oxide or ceramic particles on the two-dimensionally structured or in the three-dimensional structured porous Shape achieved. Because the form is permeable to ions, can in the electrolytic decomposition of the dispersion medium water resulting ions and all other free in the system Ions penetrate the mold, causing them to pass to the other electrode. The gases resulting from the recombination are therewith on the other electrode and not on the shape. This can be a aqueous Suspension are used because the gas bubbles are not in the separation body built so that no defects in the Abscheiderbziehungsweise Green bodies arise. This is especially true in the manufacture of devices for Manipulation of electromagnetic waves, in particular during manufacture Photonic crystals, of great advantage. The usage of water as dispersing medium is therefore particularly advantageous because of its high dielectric constant very high deposition rates achieved, which shortens the process duration.

The two-dimensionally structured porous shape or the three-dimensional structured porous form is electrically non-conductive and also has no semiconducting Properties and has a pore size of 10 nanometers to 10 Micrometer, preferably 500 nanometers to 1 micrometer, especially preferably between greater than 60 nanometers and 1 micron. About that It is also wettable by water. The contact angle between porous Shape and water is accordingly smaller than 90 °, preferably less than 80 °. As material for the porous one Shape are known in the art plastics, in particular Polystyrene (PS), more preferably polyethersulfone (PES). If meets the above criteria Other materials are suitable for the production of the porous form.

The electrodes used are chemically resistant and electrically conductive materials. Furthermore, it is also possible to use materials that are coated with chemically resistant and electrically conductive materials. Preferred electrode material are tungsten, tantalum, graphite, precious metals or electrically conductive plastics. Furthermore, the electrodes can also consist of alloys of the aforementioned materials and / or be coated with materials above. As a result, the contamination of the deposited molded body is avoided. The dispersing medium is water, in particular deionized water, preferably distilled water, particularly preferably used bidistilled water.

When very advantageous, an embodiment of the invention has been found when the silica particles or the titanium dioxide Particles one as possible have round shape.

Furthermore has the addition of a dispersing aid, preferably tetramethylammonium (TMAH) or sodium hydroxide (NaOH) or hydrochloric acid (HCl) proved to be advantageous. This can be done easily adjust the pH. Furthermore, sodium is in the glass network known as a network converter, so that additionally the sintering temperature is lowered.

When advantageous for the conductivity the electrically conductive liquid has a value of 0.5 millisiemens per centimeter to 175 millisiemens per centimeter, especially 1.5 millisiemens per centimeter to 100 millisiemens per centimeter, preferably greater than 2 millisiemens per centimeter to 75 millisiemens per centimeter proved.

When advantageous for the drying of the separation body has about it In addition, the known to those skilled supercritical drying proven. About that In addition, it is also advantageous to the separation body at room temperature dry. Another special drying method is drying in saturated The atmosphere, as this cracking is avoided.

When has also been beneficial the sintering in a zone sintering furnace at temperatures between 1200 ° C and 1700 ° C, preferably between greater than 1250 ° C and 1500 ° C proven. At a speed of 1 to 15 millimeters per minute, in particular 5 to 12 millimeters per minute, preferably 8 millimeters per minute, respected. In another embodiment of the method, the green body is in sintered a vacuum sintering furnace or a Kammersinterofen.

1 shows an arrangement for carrying out the method according to the invention. As 1 can be removed, the arrangement has a two-dimensionally structured or three-dimensionally structured porous shape 1 on, extending between the two electrodes 2 located. It has proven to be very advantageous if the electrodes are plane-parallel to one another or the surface normals of opposite points run parallel. The two-dimensional structure or three-dimensional structure is introduced into the porous mold by methods known to those skilled in the art, such as casting the viscous polymer in a shape corresponding to the later structure, by means of laser interference, in particular holographic lithography, especially four-beam laser interference.

In addition, the porous shape divides 1 the arrangement for carrying out the method according to the invention in two rooms 4 and 5 where the space 4 serves to receive the suspension with the oxide or ceramic particles. The space 5 serves to accommodate the electrically conductive liquid. The entire assembly is of a housing 3 surrounded, which consists of a non-porous, electrically non-conductive, chemically resistant material, in particular plastic, preferably polycarbonate (PC), more preferably polymethyl methacrylate (PMMA). For carrying out the invention, it is also necessary, a DC voltage source 6 to the electrodes 2 to apply.

2 shows the top view of the arrangement for carrying out the method according to the invention.

3 shows a further particular embodiment of the arrangement. This is the case 3 through a plate 7 covered in order to avoid contamination of the suspension, which contains the oxide particles or the ceramic particles, and the contamination of the electrically conductive liquid.

4 shows a further particular embodiment of the arrangement for carrying out the method according to the invention. It shares the porous form 1 the arrangement in the two rooms 4 and 5 , In addition, lies at the electrodes 2 a DC voltage source 6 at. The two rooms 4 and 5 be from a housing 3a surrounded, which must be closed to a leakage of the rooms 4 and 5 prevent, because the gravity 8th an undesirable emptying of the rooms favors. In this particular embodiment of the arrangement, the movement of the oxide particles or the ceramic particles in the electrophoretic deposition is opposite to the gravitational attraction 8th instead of. As a result, higher green densities of the separation body are achieved.

Another particular embodiment of the arrangement for carrying out the method according to the invention is shown in FIG 5 shown. It shares the porous form 1 the arrangement in the two rooms 4 and 5 , In addition, lies at the electrodes 2 a DC voltage source 6 at. The two rooms 4 and 5 be from a housing 3a surrounded, which must be closed to a leakage of the rooms 4 and 5 prevent, because the gravity 8th an undesirable emptying of the rooms favors. In this particular embodiment of the arrangement, the movement of the oxide particles or of the ceramic particles takes place the electrophoretic deposition in the direction of gravitational attraction 8th instead of.

EXAMPLES

Example 1:

Into a 300 ml plastic beaker was charged 54.72 g bidistilled water. Further, 5.28 g of tetramethylammonium hydroxide (TMAH) was added. With the help of a commercially available dissolver, a powder mixture consisting of 32 g of stirred Degussa Aerosil ^® OX50 and 8 g of Degussa Aerosil ^® A380. Accordingly, the suspension prepared in this way had a solids content of 40.0% by weight. The pH of the suspension thus prepared was 12.0, the conductivity at 4.08 millisiemens per centimeter.

The suspension thus prepared was placed in the room 4 filled. The space 5 was charged with bidistilled water added with 0.96 g of TMAH. As electrodes 2 was used with platinum coated plastic. As material for the porous form 1 was used polyethersulfone (PES), which was structured by laser interference.

The Structure was a periodic arrangement of round recesses in the PES, which had a period of 2 microns.

The applied electrical DC voltage of the DC voltage source 6 was 20 V at a distance of the electrodes 2 of 4.5 cm, created for a duration of 5 minutes.

To the deposition became the green body the porous one Mold removed and dried at room temperature for 48 hours. The Density of the green body thus produced was determined by Archimedes' principle and was 1.14 grams per cubic centimeter. The green body thus produced was at a temperature of 1300 ° Celsius in a zone sintering oven at a feed rate of 0.8 Sintered millimeters per minute. After that, the structure had a Density of 2.2 grams per cubic centimeter. The linear shrinkage was 18%. About that there was a band gap in the range of one wavelength from 5.0 microns to 6.67 microns for transverse electrical (TE) polarized light in front of, which is a size of the band gap of 25.04% corresponds.

Example 2:

In A 300 ml plastic cup was 53.42 g bidistilled water filled. Further, 6.58 g of tetramethylammonium hydroxide (TMAH) was added. With the help of a commercial dissolver 40 g of titanium dioxide P25 from Aerosil Nippon were stirred in. The Suspension produced in this way had accordingly one Solids content of 40.0 wt .-%. The pH of the thus prepared Suspension was 12.2, the conductivity was 4.96 millisiemens per centimeter.

The suspension thus prepared was placed in the room 4 filled. The space 5 was charged with bidistilled water, added with 1.43 g of TMAH. As electrodes 2 was used with platinum coated stainless steel. As material for the porous form 1 was used polyethersulfone (PES), which was structured three-dimensionally by holographic lithography.

The Structure was cubic-face centered (fcc) with a lattice parameter of 1.5 microns.

The applied electrical DC voltage of the DC voltage source 6 was 17.5 V at a distance of the electrodes 2 of 4.5 cm, created for a duration of 5 minutes.

To the deposition was the green body in the porous one Mold at room temperature for Dried for 72 hours. Thereafter, the green body became the porous form in a chamber furnace, which at 10 Kelvin per minute to 800 ° Celsius was heated, held for one hour at 800 ° Celsius. The cooling rate was 20 Kelvin per minute. In this way became the porous form removed so that the separation body remain. The density of the green body thus produced was determined with the help of Archimedesschen Principle and was 1.92 grams per cubic centimeter. Of the thus produced green body was after all at a temperature of 1400 ° Celsius in a zone sintering oven at a feed rate of 0.8 Sintered millimeters per minute. After that, the structure had a Density of 2.895 grams per cubic centimeter. The linear shrinkage was 14%. About that there was a band gap in the range of one wavelength from 2.5 microns to 3 microns for transverse electrical (TE) polarized and transversely magnetic (TM) polarized light before, which is a size of the bandgap of 16.67% corresponds.

Example 3:

In A 300 ml plastic cup was 53.42 g bidistilled water filled. Further, 6.58 g of tetramethylammonium hydroxide (TMAH) was added. With the help of a commercial dissolver 40 g of titanium dioxide P25 from Aerosil Nippon were stirred in. The Suspension produced in this way had accordingly one Solids content of 40.0 wt .-%. The pH of the thus prepared Suspension was 12.2, the conductivity was 4.96 millisiemens per centimeter.

The suspension thus prepared was placed in the room 4 filled. The space 5 was filled with bidistilled water, added with 1.43 g TMAH. As electrodes 2 was used with platinum coated stainless steel. As material for the porous form 1 was used polyethersulfone (PES), which was structured in two dimensions by four-beam laser interference. The structure was a periodic array of round recesses in the PES that had a period of 2 microns. The period was interrupted so that a rectangular line was present in the middle of the recesses, along which no recesses were introduced.

The applied electrical DC voltage of the DC voltage source 6 was 17.5 V at a distance of the electrodes 2 of 4.5 cm, created for a duration of 5 minutes.

To the deposition became the green body the porous one Mold demolded and in a saturated atmosphere during 72 Hours dried. The density of the green body thus produced was determined by Archimedes' principle and amounted to 1.77 Grams per cubic centimeter. The green body thus produced was after all at a temperature of 1400 ° Celsius in a zone sintering oven at a speed of 0.8 millimeters sintered per minute. Thereafter, the structure had a density of 3.892 Grams per cubic centimeter. The linear shrinkage was 14%. About that there was a band gap in the range of one wavelength from 5.0 micrometers to 6.67 micrometers for transverse electrical (TE) polarized light in front of, which is a size of the band gap of 25.04% corresponds. Along the right-angled line defect could the wavelength spread out of 5.5 microns and was targeted along the defect deflected by 90 °. The loss in the deflection was 1% of the initial intensity.

Example 4:

In A 300 ml plastic cup was 53.42 g bidistilled water filled. Further, 6.58 g of tetramethylammonium hydroxide (TMAH) was added. With the help of a commercial dissolver 40 g of titanium dioxide P25 from Aerosil Nippon were stirred in. The Suspension produced in this way had accordingly one Solids content of 40.0 wt .-%. The pH of the thus prepared Suspension was 12.2, the conductivity was 4.96 millisiemens per centimeter.

The cell used is in 4 outlined. The suspension thus prepared was placed in the room 4 filled. The space 5 was filled with bidistilled water, added with 1.43 g TMAH. As electrodes 2 was used with platinum coated stainless steel. As material for the porous form 1 was used polyethersulfone (PES), which was structured three-dimensionally by holographic lithography.

The Structure was cubic-face centered (fcc) with a lattice parameter of 1.5 microns, with a rectangular Line defect was introduced.

The applied electrical DC voltage of the DC voltage source 6 was 17.5 V at a distance of the electrodes 2 of 4.5 cm, created for a duration of 5 minutes.

To the deposition was the green body in the porous one Mold at room temperature for Dried for 72 hours. Thereafter, the green body became the porous form in a chamber furnace, which at 10 Kelvin per minute to 800 ° Celsius heated, one hour at 800 ° Celsius held. The cooling rate was 20 Kelvin per minute. The density of the green body thus produced was determined by Archimedes' principle and amounted to 1.92 Grams per cubic centimeter. The green body thus produced was after all at a temperature of 1400 ° Celsius in a zone sintering oven at a speed of 0.8 millimeters sintered per minute. Thereafter, the structure had a density of 3.888 grams per cubic centimeter. The linear shrinkage was 14%. Furthermore there was a band gap in the range of one wavelength from 2.5 microns to 3 microns for transverse electrical (TE) polarized and transversely magnetic (TM) polarized light before, which is a size of the bandgap of 16.67% corresponds. Along the line defect has light the wavelength 2.75 microns and transverse electric (TE) polarization spread and was thereby deflected by 90 ° with a loss of intensity of 2.47%.

Claims (3)

Process for the production of oxidic or ceramic shaped bodies, wherein the precipitation bodies underlying the green bodies are formed by suspension of oxidic or ceramic particles from a suspension by electrophoretic deposition, one of the electrodes for the electrophoretic deposition being arranged in the suspension, and / or or in a structured porous mold arranged in the suspension, which has the negative mold of the respective deposition body and has a space filled with an electrically conductive liquid, in which the other electrode for the electrophoretic deposition is arranged, characterized in that the porous mold is structured periodically by laser interference or holographic lithography two- or three-dimensional. Method according to claim 1, characterized in that that particles on a porous Form are deposited, the pores of a size of 10 nanometers to 2 microns having. Use of the method according to one of the preceding claims for the Production of moldings for manipulating the propagation of electromagnetic waves, preferably for the Production of photonic crystals.