JP2019181930A - Ceramic powder, ceramic powder production method and production method of ceramic structure using ceramic powder - Google Patents

Abstract

To provide a ceramic powder for obtaining a high-definition ceramic structure in a short time in the production of a ceramic structure using an additive manufacturing method in which modeling is performed by irradiating a raw material powder with laser light.SOLUTION: A ceramic powder used in an additive manufacturing method in which modeling is performed by irradiating a raw material powder with laser light, including a first particle group which consists of particles of a first inorganic compound, and whose average particle size is 10 μm or greater and 100 μm or less and a second particle group which consists of a second inorganic compound having an absorption band at the wavelength of the laser beam and having an average particle size smaller than the first particle group, and the particle included in the second particle group is disposed on a surface of the particle included in the first particle group.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a raw material powder used when manufacturing a ceramic model by three-dimensional modeling using melting and solidification (including sintering of the raw material powder) of the raw material powder by laser light irradiation, and The present invention relates to a method for forming ceramics.

  In recent years, an additive manufacturing method using laser light (also referred to as additive manufacturing or three-dimensional modeling technology) has been developed, and the technical level thereof is increasing. In particular, in the metal field, a selective laser sintering method (Selective Laser Sintering: SLS) or a selective laser melting method (Selective Laser Melting: SLM), which is a kind of powder bed fusion bonding method (powder laminating method), is dense and diverse. The production of a characteristic shaped article has been realized. In these methods, a raw metal powder is melted and bonded in a desired shape by laser drawing or sintered. As a drawing laser, a small, high-power, low-cost near-infrared laser such as a YAG laser or a fiber laser is exclusively used.

  SLS or SLM can be applied to ceramic powder in principle. However, many common insulating ceramics are highly permeable to light in the visible to infrared region. That is, the ceramic particles as a raw material hardly absorbs laser light in this wavelength region. For this reason, when ceramics are additionally manufactured using an SLS or SLM apparatus, it is necessary to irradiate laser light having an excessive power as compared with the thermal energy necessary for melting the material of the processed part. In this case, most of the irradiated laser light is transmitted and diffused through the ceramic particles, so that a region larger than the beam diameter of the laser light is melted, and it becomes difficult to form a clear boundary. For this reason, conventionally, it has been difficult to perform high-definition ceramic modeling with SLS and SLM.

For such a problem, for example, Non-Patent Document 1 proposes an additive manufacturing of eutectic oxide ceramics by laser light irradiation. Specifically, the Al ₂ O ₃ —ZrO ₂ eutectic system is used to lower the melting point of the molding powder and to reduce the power of laser light necessary for melting. This method also has an advantage that a ceramic structure having high mechanical strength can be formed by forming a fine structure peculiar to a eutectic system during solidification. Although this method has improved the fineness to some extent, the modeling accuracy is still not sufficient, such as a large number of surface protrusions. In addition, the modeling of the ceramic structure by the laser beam has a problem that it takes time because the heat transfer rate and the reaction rate are slower than those of the metal.

Physics Procedia 5 (2010) 587-594

  This invention solves such a subject, and provides the ceramic raw material powder for obtaining a high-definition ceramic structure in a short time in the addition manufacture of the ceramic structure by an SLS and an SLM apparatus. Moreover, the manufacturing method of such raw material powder and the method for obtaining a high-definition ceramic structure using such raw material powder are provided.

  According to the first aspect of the present invention, there is provided a ceramic powder used in an additive molding method in which modeling is performed by irradiating a raw material powder with a laser beam, and the average particle diameter is made of particles of a first inorganic compound. A first particle group of 10 μm or more and 100 μm or less, and a second particle group comprising particles of a second inorganic compound having an absorption band at the wavelength of the laser beam, and an average particle diameter smaller than the first particle group; A ceramic powder is provided in which the particles contained in the second particle group are disposed on the surfaces of the particles contained in the first particle group.

  According to a second aspect of the present invention, there is provided a method for producing a ceramic powder as described above, wherein the surface of the particles contained in the first particle group becomes a precursor of the second particle group. A step of covering with a metal component-containing liquid, and heating the particles contained in the first particle group covered with the metal component-containing liquid, whereby the particles contained in the second particle group are formed on the surface of the particles. There is provided a method for producing ceramic powder having at least a step of arranging.

  According to a third aspect of the present invention, there is provided a method for manufacturing a ceramic structure using an additive modeling method in which modeling is performed by irradiating a raw material powder with laser light, wherein (i) the ceramic powder described above And (ii) selectively irradiating the ceramic powder disposed in the laser irradiation portion with laser light to thereby irradiate the portion of the ceramic powder irradiated with the laser light. There is provided a method for producing a ceramic structure, which comprises a step of solidifying after melting and producing a ceramic structure by repeating the steps (i) and (ii).

It is a cross-sectional schematic diagram which shows an example of the apparatus for irradiating the ceramic powder of this invention with a laser beam. It is a cross-sectional schematic diagram which shows an example of the apparatus of the system different from FIG. 1 for irradiating the ceramic powder of this invention with a laser beam. FIG. 3A is an enlarged schematic diagram showing a part of the present invention and a ceramic powder for comparison. FIG. 3A shows a case where the second particle group is relatively small, and FIG. The case where a particle group is relatively large is shown. It is a photograph which shows the electron microscope observation image which expanded and observed a part (one grain) of the Example of the ceramic powder of this invention.

Hereinafter, modes for carrying out the present invention will be described.
The present invention relates to a ceramic powder that is suitably used as a raw material powder for obtaining a ceramic structure (shaped object) by an additive manufacturing technique using laser light. The ceramic powder of the present invention comprises an average particle composed of a first particle group composed of particles of a first inorganic compound serving as an aggregate of a ceramic structure, and particles of a second inorganic compound serving as a laser beam absorber. And a second particle group having a diameter smaller than that of the first particle group. And the particle | grains contained in the 2nd particle group are arrange | positioned in the surface part of the particle | grains contained in the 1st particle group (normally plural). Such ceramic powder absorbs laser light by the second particle group and raises the temperature, and can efficiently transfer the heat to the first particle group. As a result, the laser beam can be scanned and melted at a high speed, and as a result, the modeling speed is increased.

The ceramic powder of the present invention has the following characteristics.
(1) Melting and solidification occur by irradiation with laser light. Thereby, a ceramic structure can be constituted.
(2) A first particle group composed of particles of the first inorganic compound and having an average particle diameter of 10 μm or more and 100 μm or less is included.
(3) A second particle group comprising particles of the second inorganic compound and having an average particle diameter smaller than that of the first particle group is included.
(4) The particles contained in the second particle group are disposed on the surface of the particles contained in the first particle group, and the second inorganic compound is an absorber having an absorption band at the wavelength of the laser beam.
Hereinafter, each feature will be described in detail.

(Feature 1)
The ceramic powder of the present invention is a raw material for obtaining a ceramic structure, and contains ceramic as a main component. In addition, when irradiated with laser light, the powder at the irradiated part melts and solidifies when laser light irradiation is stopped. In the present invention, in the case of “melting and solidifying”, not only the case of solidifying after being completely liquid (viscous fluid), but also each particle (surface) of the powder is softened. In other words, the case of binding to each other (so-called sintering) is also included. This characteristic is preferably manifested when the powder has features 2, 3, and 4 described later.

  Although there is no restriction | limiting in the kind of laser to use, The laser used for the metal three-dimensional modeling apparatus can be used as it is. For example, it is possible to use a solid laser such as a small-sized, high-output, relatively inexpensive fiber laser or YAG laser used in an SLS apparatus or an SLM apparatus. The oscillation wavelength of a general solid-state laser is 800 nm to 1200 nm, and this is included in the so-called near infrared region (0.75 to 2.5 μm). The laser oscillation method may be continuous oscillation or pulse oscillation.

  In order to obtain a high-definition ceramic structure (modeled object), the laser beam irradiation diameter is preferably 10 μm or more and 200 μm or less. On the other hand, when an attempt is made to obtain a large shaped article in a short time with an emphasis on the shaping speed, the irradiation diameter of the laser light is preferably 200 μm or more and 2000 μm or less.

  FIG. 1 is a schematic sectional view showing an example of an apparatus for irradiating a ceramic powder of the present invention with laser light. FIG. 1 shows an apparatus configuration in the case of selective laser sintering (SLS), which is a kind of powder bed fusion bonding method. This method is also called a powder bed direct modeling method. The apparatus shown in FIG. 1 includes a powder basket 11, a modeling stage unit 12, a recoater unit 13, a scanner unit 14, and a laser 15. The powder basket 11 is filled with the ceramic powder of the present invention. The powder basket 11 and the modeling stage unit 12 have a mechanism that moves in the vertical direction, and the recoater unit 13 can transfer the ceramic powder from the powder basket 11 to the modeling stage unit 12. In the modeling stage unit 12, the ceramic powder is spread over an area wider than the maximum horizontal section of the target ceramic model.

  Subsequently, the laser 15 and the scanner unit 14 perform drawing by irradiating a portion of the ceramic powder (for the uppermost layer) on the modeling stage unit 12 to be solidified with laser light. The ceramic powder in the portion irradiated with the laser light has the second particle group that absorbs the laser light and changes its energy to heat, and the second particle group melts and the heat is transmitted to the first particle. The group melts. When the laser beam irradiation part moves to another location, the melted part is cooled and solidified. By this process, a one-layer shaped object is obtained. The portion of the ceramic powder that was not melted remains in the same layer. One layer of ceramic powder is laid on this layer and irradiated with laser light to melt and solidify the powder at any location, so that it is integrated with the previously modeled object. Is formed. By repeating such steps, a ceramic structure (modeled object) having an arbitrary three-dimensional shape can be manufactured.

  FIG. 2 is a schematic cross-sectional view showing an example of another type of apparatus for irradiating the ceramic powder of the present invention with laser light. FIG. 2 is a diagram for explaining a modeling method called a directed energy deposition method or a cladding method. The cladding nozzle 21 has a plurality of powder supply holes 22 and has a function of ejecting the ceramic powder of the present invention from the powder supply holes 22 at a desired flow rate. A laser molded object can be additionally provided at a desired location of the substrate 20 by irradiating the laser 23 to a region where the ejected ceramic powder beam is focused. That is, in this case, the ceramic powder is ejected (arranged) from the cladding nozzle 21 to the laser irradiation unit and selectively irradiated with the laser beam in the above-described (focused) region. This method has an advantage that it can be shaped on a curved surface, unlike the powder lamination method.

(Feature 2)
The ceramic powder of the present invention includes a first particle group having an average particle diameter of 10 μm or more and 100 μm or less. By setting the average size of the first particle group to be an aggregate of the ceramic shaped article to 10 μm or more and 100 μm or less on average, the fluidity required for powder transfer by the recoater unit or the cladding nozzle during shaping (for example, 40 seconds) / 50 g or less), and the molded article can have sufficient strength. From the same viewpoint, the more preferable average particle diameter of the first particle group is 15 μm or more and 40 μm or less. Each particle included in the first particle group is preferably spherical from the viewpoint of fluidity, but may be indeterminate or an anisotropic shape such as a plate shape or a needle shape. The average particle diameter can be calculated as a circle-equivalent diameter of the projected image from a micrograph of the powder. For example, particles included in 100 or more first particle groups constituting the powder are selected at random, and the value of the equivalent circle diameter excluding the particles included in the second particle group arranged on the surface portion is determined. The average particle diameter can be obtained by obtaining and averaging for each particle. When there is variation in the size of each particle, micrographs having different observation magnifications may be combined. However, the dispersion of the equivalent circle diameter of each first particle is small, and the particle diameter (circle) of 99% by number or more is small. The equivalent diameter) is more preferably 10 μm or more and 100 μm or less.

  In the present invention, the powder refers to an aggregate of particles that can be recognized as isolated particles. The particle group refers to an aggregate of particles that satisfy a predetermined condition. As long as the first particle group has the predetermined average particle diameter, the first particle group may not be composed of particles having a single composition, and a plurality of types of particles having different compositions may be mixed.

  In the present invention, the term “inorganic compound” refers to an oxide, nitride, or acid containing one or more elements in an element group in which antimony and bismuth are added to elements in groups 1 to 14 of the periodic table excluding hydrogen. Refers to nitride, carbide, or boride. Moreover, the particle | grains which consist of an inorganic compound may be comprised by 1 type of inorganic compounds, and the thing which 2 or more types of inorganic compounds compounded. By using inorganic compound particles as the main constituent of the powder for modeling, the result of melting and solidification reaction when irradiated with laser light can be made into a ceramic form.

  The particles of the first inorganic compound contained in the first particle group are preferably made of a metal oxide as a main component. When ceramic powder has a metal oxide as a main component, a high-strength shaped article can be obtained. Here, the metal oxide contains one or more kinds of elements in the element group excluding boron, carbon, silicon, germanium, and group 13 (nitrogen group) and group 14 (oxygen group) elements from the above element group. Refers to oxide. The particles contained in the first particle group are preferably composed mainly of aluminum oxide, silicon dioxide, or zirconium oxide among metal oxides. Aluminum oxide, silicon dioxide, or zirconium oxide is the main component of the modeled object, and by forming an aggregate, it is possible to manufacture a modeled article with excellent mechanical strength, heat resistance, electrical insulation, and environmental compatibility. .

  The particles contained in the first particle group may be composed of a single type of metal oxide, but may be more desirable if they are used in combination with other substances to develop a new function. For example, a combination of aluminum oxide and zirconium oxide, or a combination of aluminum oxide and rare earth metal oxide such as gadolinium oxide or yttrium oxide can be given. When the particles included in the first particle group are composed of a combination of these metal oxides, the eutectic is formed during heating, so that the melting temperature is lower than that of a single metal oxide. However, the melting and solidification reaction by laser light irradiation becomes relatively easy. In addition, a eutectic structure is expressed in the solidified product after melting, and the mechanical strength may be higher than that of a single metal oxide. From this viewpoint, it is desirable that the particles included in the first particle group contain aluminum oxide and gadolinium oxide. Further, the particles of the first particle group may contain the metal oxide and aluminum nitride or boron nitride, and these oxides are used only as an oxide by combining these compositions. In some cases, lighter weight and higher strength may be realized.

(Feature 3)
The ceramic powder according to the present invention includes, in addition to the first particle group consisting of particles of the first inorganic compound, a second particle having an average particle diameter smaller than that of the first particle group consisting of particles of the second inorganic compound. Includes particles. The second inorganic compound has a light absorbing ability with respect to laser light having a wavelength used in the additive molding method. And the particle | grains contained in a 2nd particle group are arrange | positioned at the surface part of the particle | grains contained in a 1st particle group. That is, the first particle group made of the first inorganic compound and the second particle group made of the second inorganic compound have different chemical compositions, but both are the main components of the ceramic powder of the present invention. Become an ingredient.

  In the surface portion of the particles included in the first particle group, a plurality of particles included in the second particle group whose average particle diameter is smaller than the first particle group are usually arranged. 3 (a) and 3 (b) are included in one particle 1 included in the first particle group and a plurality of second particle groups arranged on the surface thereof, which constitute the ceramic powder of the present invention. It is a schematic diagram which expands and shows the particle | grains 2 or 3. FIG. The ceramic powder of the present invention is an aggregate in which a large number of particles having a form as shown in FIGS.

  3A and 3B, the particles 1 are substantially spherical, but the shape for obtaining the effects of the present invention is not particularly limited. A large number of particles 2 or 3 are present on the surface of the particle 1, and these particles 2 and 3 are particles included in the second particle group. The particle diameter of the particles contained in the second particle group strongly related to the effect expression of the present invention is smaller than the particles contained in the first particle group as an average particle diameter. A small amount of particles contained in the second particle group equivalent to or more than the particles contained in the particle group may be present. In that case, the ceramic powder contains a small amount of composite particles that cannot necessarily be said to contain the particles contained in the second particle group on the surface of the particles contained in the first particle group. However, there is no problem as long as the effect of the present invention is not inhibited. The particle diameter can be calculated as a circle-equivalent diameter of the projected image from a micrograph of the powder. As will be described in detail in the feature 4 below, the second particle group has a function of absorbing laser light and generating heat. When the average particle diameter of the second particle group is 0.05 μm or more and 2 μm or less, the heat transfer rate to the particles 1 is further increased, which is more preferable.

  FIG. 3A shows a state in which particles 2 having an average particle diameter of 0.05 μm or more and 2 μm or less are arranged on the surface of the particles 1. When the average particle diameter of the particles 2 is 0.05 μm or more, the energy absorption efficiency by the particles 2 when irradiated with laser light is increased. On the other hand, when the average particle diameter of the particles 2 is 2 μm or less, the contact area between the particles 1 and the particles 2 increases, and the heat transfer rate from the particles 2 to the particles 1 increases. Further, the average particle diameter of the particles 2 is preferably 0.05 μm or more and less than 1 μm.

  FIG. 3B shows one particle 1 included in the first particle group constituting the ceramic powder of the present invention, and particles 3 included in the plurality of second particle groups arranged on the surface thereof. In the schematic diagram, the particle 3 is relatively larger than the particle 2 of FIG. 3A, and the particle 3 has a particle diameter larger than 2 μm (but less than 10 μm). In FIG. 3A and FIG. 3B, only the particle diameters of the particles 2 and the particles 3 are different, and the chemical composition and the crystal structure are the same. Furthermore, the same particle 1 is used, and the adhesion amount of the particle 2 or the particle 3 to the particle 1 is also set to an equal mass. At this time, when the ceramic powders in FIGS. 3A and 3B are irradiated with laser light under the same conditions, the amount of heat generated by each of the particles 2 and 3 in each ceramic powder is substantially equal.

  However, in the ceramic powder of FIG. 3 (a), since the total contact area between the particles 2 and the particles 1 is large, the heat generated by the particles 2 is quickly transferred to the particles 1 and the particles 1 are rapidly and efficiently processed. Melting begins. On the other hand, in the ceramic powder of FIG. 3B, since the contact area between the particles 3 and the particles 1 is relatively small, the heat transfer rate is slow and much heat is lost by diffusing to the surrounding environment. As a result, the melting is slowed down, and the molding speed is slow compared to the case of FIG.

  However, the comparison of the heat transfer rates using FIG. 3 (a) and FIG. 3 (b) is a comparison within the range of the molding powder of the present invention, and the configuration of FIG. 3 (b). However, modeling is possible in a shorter time than conventional molding powder.

  Since the effects of the present invention can be obtained if the particles 2 and 3 are in contact with the surface of the particles 1, the strength and method of adsorption are not limited. Further, the particles 1 and the particles 2 or the particles 3 may be chemically bonded to each other, so that the particles 2 or the particles 3 may partially penetrate into the particles 1.

  When these particles 2 and 3 are arranged on the surface of the particle 1, it is desirable to adhere to the particle 1 with as high a coverage as possible. For example, when the particle 1 is observed two-dimensionally with a microscope, the coverage of the particle 2 or the particle 3 is desirably 10 area% or more. The ideal coverage is 100 area%.

  On the surface of the particles 1, not only the particles 2 having an average particle diameter of 0.05 μm to 2 μm but also particles 3 having an average particle diameter exceeding 2 μm may be disposed together with the particles 2. It is preferable that the covering area exceeds the covering area by the particles 3.

  Although the mass ratio of the first particle group and the second particle group contained in the ceramic powder is not limited, for example, the mass of the second particle group is 2% or more and 20% or less with respect to the first particle group. It is preferable because the modeling speed, the modeling accuracy, and the strength of the model are all good. Hereinafter, particle 2 and particle 3 are collectively referred to as particle 2 without being distinguished from each other.

  The ceramic powder of the present invention contains a particle group other than the first particle group and the second particle group for the purpose of improving the characteristics of the ceramic powder itself or the ceramic structure formed therefrom. Also good. However, in order to sufficiently obtain the effects of the present invention, the ratio of the first particle group and the second particle group in the ceramic powder of the present invention is 80% by mass or more, more preferably 90% by mass. The above is desirable. In addition, the ratio of only the first particle group in the ceramic powder of the present invention is desirably 70% by mass or more.

(Feature 4)
The second particle group is composed of particles of a second inorganic compound that is an absorber having an absorption band at the wavelength of the laser beam. Absorbers suitable for the second group of particles are those that absorb laser light efficiently, raise the temperature of the particles themselves, and spread to the non-absorbing composition present in the surrounding area, resulting in an increase in temperature. It is. This realizes local heating in the laser light irradiation range, forms an interface between the irradiated region and the non-irradiated region, and enables accurate modeling.

  The particles of the second inorganic compound included in the second particle group undergo a composition change due to laser light irradiation, and have a characteristic that the absorption rate of the laser light is lower than that before laser light irradiation in the molded object after solidification. It is preferable to have. If the absorption rate of the laser beam is low in the area after the laser beam is irradiated and the modeling process is completed, the ceramic in the molded area will change when the laser beam is irradiated to the adjacent area after that. Can be suppressed.

  The particles of the second inorganic compound contained in the second particle group are preferably made of a metal oxide, and the change in the laser light absorptance is preferably caused by the change in the valence of the metal element. When the absorption rate of the laser beam changes due to the change in valence, the volume does not change. On the other hand, when the absorptance changes due to the release of volatiles from the particles as the absorber, the effect of volume change is large. Examples of metal oxides whose valence changes with laser light irradiation and the absorption rate of laser light decreases or disappears include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, and Nb. , Mo, Hf, Ta, W, In, Sn, Bi, Ce, Pr, Sm, Eu, Tb, and Yb oxides. A combination of a plurality of these metal oxide particles may be used as the second particle group.

As a laser beam used for ceramic modeling, a laser having a wavelength of about 1000 nm, such as an Nd: YAG laser and a Yb fiber laser, is preferable from the viewpoint of availability and controllability of irradiation energy. As a material having a high absorption rate of laser light at a wavelength in this range and causing a decrease in the absorption rate, terbium oxide containing tetravalent terbium (Tb ₄ O ₇ ) or oxidation containing tetravalent praseodymium is used. Praseodymium (Pr ₆ O ₁₁ ) is preferably used. When the second particle group of the present invention is composed mainly of terbium oxide containing tetravalent terbium or praseodymium oxide containing tetravalent praseodymium, the valence is reduced after effectively generating heat by laser light absorption. Loss of absorption by change.

Terbium oxide and praseodymium oxide have various states of metal part valence. Taking terbium oxide as an example, there are typically a state called Tb ₄ O ₇ and a state called Tb ₂ O ₃ . The former state is expressed as Tb ₄ O ₇ in the molecular formula, but the ratio of metal to oxygen is not exact and includes a composition in the vicinity of 4: 7. The metal part of Tb ₄ O ₇ in the former state is composed of approximately half of Tb ⁴⁺ and Tb ³⁺ , whereas the metal part of Tb ₂ O ₃ in the latter state consists of only Tb ³⁺ .

Tb ₄ O ₇ has a high infrared absorptance in the vicinity of a wavelength of 1000 nm, and the absorptance sometimes exceeds 60% and reaches 70%. On the other hand, as the fraction of Tb ⁴⁺ decreases, the absorptance decreases, and in Tb ₂ O ₃ composed only of Tb ³⁺ , the absorptance is about 7%. Accordingly, terbium oxide (Tb ₄ O ₇ ) containing tetravalent terbium as an absorber is suitable as the main component of the inorganic compound particles B that realize the present invention. Similarly, praseodymium oxide (Pr ₆ O ₁₁ ) in which the absorber contains tetravalent praseodymium is also suitable as the main component of the inorganic compound particles B that realize the present invention.

  As a method for evaluating the valence, X-ray absorption fine structure analysis (XAFS) can be applied. The valence can be evaluated from the profile using the characteristic that the rising energy at the absorption edge differs for each valence.

(Production method)
Although the manufacturing method of the ceramic powder which has the said characteristic is not specifically limited, A preferable manufacturing method is demonstrated below. The method for producing a ceramic powder of the present invention has the following characteristics.
(5) It has the process of covering the surface of the particle | grains contained in a 1st particle group with the metal component containing liquid used as the precursor of the particle | grains contained in a 2nd particle group.
(6) The particles contained in the first particle group covered with the metal component-containing liquid by the above step are heated, and the particles contained in the second particle group are formed on the surface of the particles contained in the first particle group. A step of arranging.

(Feature 5)
In a production method suitable for producing the ceramic powder of the present invention, the surface of the particles 1 contained in the first particle group is used as a precursor for the particles 2 contained in the second particle group. The process of covering with.

  Suitable materials for the particles 1 are as described above. For example, commercially available metal oxide particles can also be used. For the purpose of improving the wettability and adhesiveness of the surface of the particle 1, surface modification of the particle 1 may be performed. Examples of the surface modification method include irradiation with energy rays such as ultraviolet rays, and application or immersion treatment of a surface modifier such as a silane coupling agent or a phosphonic acid derivative.

  The metal oxide-containing liquid that becomes the precursor of the particle 2 is a solution or dispersion of a composition that can be converted into the particle 2 by heating. Examples of the composition include hydrolyzable or thermally decomposable organometallic compounds. More specifically, metal complexes such as metal alkoxides, organic acid salts, and β-diketone complexes of the above metals can be used. As another example of the metal complex, an amine complex can be used. Examples of the β-diketone include acetylacetone (= 2,4-pentanedione), heptafluorobutanoylpivaloylmethane, dipivaloylmethane, trifluoroacetylacetone, and benzoylacetone. Since it is coordinated to a metal by a β-diketone complex and an oxygen element, it can be said to be one form of a metal alkoxide.

  For example, when the main component of the particles 2 is terbium oxide, there is a technique of including terbium alkoxide in the precursor metal component-containing liquid. Examples of terbium alkoxides include terbium-n-butoxide, terbium-t-butoxide, terbium-methoxypropoxide, terbium-2,4-pentandionate, terbium-methoxyethoxide, terbium-2,4-pentanedio And terbium-2,2,6,6-tetramethyl-3,5-heptanedionate.

  Examples of praseodymium alkoxides include praseodymium-n-butoxide, praseodymium-t-butoxide, praseodymium-methoxypropoxide, praseodymium-hexafluoropentanedionate, praseodymium-2,4-pentanedionate, praseodymium-2, 2,6,6-tetramethyl-3,5-heptanedionate, praseodymium (III) -6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octane Dionate etc. are mentioned. The same applies to alkoxides of other metal species.

  As the metal alkoxide and its solution, commercially available ones may be used, or the metal alkoxide and the solution thereof may be synthesized by the method described in the claims and [0003] of JP-A-9-157272. The composition containing each component metal can be prepared as a metal component-containing liquid by dissolving or dispersing in an appropriate solvent. The solvent is appropriately selected from known various solvents in consideration of dispersibility and coatability.

  Solvents used for preparing the metal component-containing liquid include alcohol solvents such as methanol, ethanol, n-butanol, n-propanol, and isopropanol, ether solvents such as tetrahydrofuran and 1,4-dioxane, methyl cellosolve, ethyl cellosolve, and the like. Cellosolve-based, N, N-dimethylformamide, N, N-dimethylacetamide, amide-based solvents such as N-methylpyrrolidone, and nitrile-based solvents such as acetonitrile. When a metal alkoxide is used as the metal component, an alcohol solvent is preferably used.

  The amount of the solvent used for the preparation of the metal component-containing liquid is not particularly limited, but when the amount of the solvent is adjusted so that the metal solid content concentration is about 5% by mass to 20% by mass, the surface of the particles 1 is covered. Preferred.

  The method of covering the surface of the particle 1 with the metal component-containing liquid is not particularly limited, but there are a method of immersing the particle 1 in the liquid, a method of adding the liquid to the particle 1, a method of spraying the liquid on the particle 1 and the like. is there.

(Feature 6)
After the said process, the process of forming the particle | grain 2 on the surface of the particle | grain 1 is implemented by heating the particle | grains 1 and the metal component containing liquid adhering to the surface simultaneously.

  By this heating, the solvent in the metal component-containing liquid is volatilized, the metal component is further oxidized and granulated, and the particles 2 are deposited on the surfaces of the particles 1. When the composition of the precursor is hydrolyzable, the hydrolysis reaction proceeds and a bond between metal and oxygen is formed, so that fine metal oxide particles having a particle diameter of less than 1 μm are formed. In addition, since the particles 2 are formed by a chemical reaction, the bond with the particles 1 as a base is strong and the contact area increases. Therefore, the heat transfer rate from the particle 2 to the particle 1 is increased when the laser beam is irradiated.

  As the heating temperature, an optimum temperature is selected depending on the type of material. For example, in order to volatilize the solvent, heating is performed at about 150 ° C. to 300 ° C., and then particles are formed by heating at about 550 ° C. to 750 ° C. It is preferable to perform stepwise heating.

  The heating means is not limited, and a dryer, a hot plate, an electric furnace, an atmospheric furnace, or the like can be used. After heating, the obtained powder may be crushed again to make fine powder, or the powder may be sieved to make the particle diameter uniform.

(how to use)
The method for producing a ceramic structure (modeled object) by using the ceramic modeling powder of the present invention as a raw material and performing laser irradiation on the material has the following characteristics.
(7) It has the process (i) which arrange | positions the powder for ceramic modeling of this invention to a laser irradiation part.
(8) By selectively irradiating a laser beam to the ceramic molding powder arranged in the laser irradiation section, the ceramic molding powder is sintered or melted and then solidified (including the case of sintering). Step (ii) is included.
(9) It has the process (iii) which manufactures a ceramic structure (molded article) by repeating the said process (i) and process (ii).

(Feature 7)
The technique for arranging the ceramic molding powder of the present invention in the laser irradiation part is as described in the feature 1. For example, in the apparatus as shown in FIG. 1, the ceramic molding powder of the present invention filled in the powder basket 11 can be arranged on the modeling stage unit 12 by the recoater unit 13. In addition, as described in the feature 1 with reference to FIG. 2, when a ceramic modeling powder is ejected to a predetermined location and laser light is irradiated to the location, a modeled object can be formed on the curved base. It becomes possible.

(Feature 8)
The method of selecting the laser beam for solidifying after melting the ceramic molding powder is as described in the feature 1. As described above, in the present invention, sintering is one form of operation for melting and then solidifying. Strictly speaking, sintering refers to a reaction in which a powder is bound in a solid phase (without melting) and grows, and melting refers to a reaction in which the powder becomes a liquid phase. Including a state in which a solid phase and a liquid phase are mixed. Prior to the step (ii), it is preferable to spread the ceramic modeling powder arranged in the laser irradiation unit and then irradiate the laser beam thereafter, because a model with higher density can be obtained.

(Feature 9)
When the step (i) and the step (ii) are performed once, a patterned one-layer ceramic shaped article is obtained. A ceramic shaped article having a desired three-dimensional shape can be manufactured by spreading a new powder for ceramic shaping on this and repeating steps (i) and (ii) with different patterns.

  After the modeling, heat treatment may be performed for the purpose of increasing the density of the modeled object, improving the strength, and reoxidizing. At that time, it is also possible to apply and impregnate an organic compound or an inorganic compound as a glaze. There is no limitation on the heating means, and it can be used according to purposes such as a resistance heating method, an induction heating method, an infrared lamp method, a laser method, and an electron beam method.

[Example]
The ceramic powder of the present invention, its production method, and use method will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

Example 1
The ceramic powder of the present invention was produced by the following procedure.
As the first particle group, mass-produced Al ₂ O ₃ powder (purity 99% or more, average particle diameter 20 μm) and Gd ₂ O ₃ powder (purity 99% or more, average particle diameter 20 μm) commercially available as industrial products. What was mixed so that it might become 1: 1 by ratio was used.

As the metal component-containing liquid serving as the precursor of the particles constituting the second particle group, a terbium metal alkoxide solution, which is a hydrolyzable organometallic compound, was prepared. Specifically, terbium-2,4-pentandionate, which is commercially available as a general reagent, is dissolved in 1-methoxy-2-propanol as a solvent, and the converted concentration of metal oxide (Tb ₄ O ₇ ) It prepared so that it might become 10 mass%.

  In a high-purity alumina container, 97 g of the first particle group was measured and placed, and 25 g of the metal component-containing liquid was added and stirred well.

  The container was placed in an electric furnace in an air atmosphere, and heat treatment was performed by executing a program that maintained a maximum temperature of 600 ° C. for 3 hours. After the electric furnace was cooled to room temperature, the contents were taken out from the alumina container and pulverized to obtain the ceramic powder of the present invention.

An image obtained by magnifying and observing a part of the produced powder with an electron microscope is shown in FIG. FIG. 4 is an image observed at a magnification of 5000 so that a typical structure of the ceramic powder of Example 1 can be seen, but the other particles constituting the powder also had the same structure. In FIG. 4, the spherical particles having a diameter of about 20 μm that occupy most of the observation field are aluminum oxide according to SEM-EDX analysis and X-ray diffraction measurement, and are found to be particles 1 included in the first particle group. . According to SEM-EDX analysis and X-ray diffraction measurement, the fine particle group adhering to the surface portion of the particle 1 is terbium oxide (Tb ₄ O ₇ ), and it was found to be the second particle group. The average particle diameter of the second particle group obtained by image processing of the observed image was 0.3 μm even if estimated to be large. Since the second particle group includes particles that are too fine to be recognized by image processing, the actual flat particle size is considered to be even smaller. The coverage of the particles 1 with the particles 2 included in the second particle group calculated from the observed image was about 14 area%. Further, although not shown in the observed image of FIG. 4, there is also an aggregate in which gadolinium oxide is the particle 1 in the vicinity of the particle, and the fine particle 2 is similarly attached.

When the ceramic powder of Example 1 was heated and dissolved with dilute sulfuric acid and composition analysis was performed by ICP emission spectroscopy, the mass occupied by Al ₂ O ₃ , Gd ₂ O ₃ and Tb ₄ O ₇ was 46. 6 to 50.3 to 2.46. The content of other components was less than 0.1% by mass with respect to the ceramic powder. Al ₂ O ₃ and Gd ₂ O _{3 corresponded} to the first particle group and accounted for 96.9% by mass in total.

(Example 2 and Example 3)
A ceramic powder of the present invention was produced in the same manner as in Example 1 except that the raw material species and the mixing ratio were changed according to Table 1.
As the zirconium oxide as the first particle group, ZrO ₂ powder (purity 99% or more, average particle size 15 μm) marketed as an industrial product was used. As the metal alkoxide of praseodymium, praseodymium-2,4-pentandionate commercially available as a general reagent was used.
The addition amount of the metal component-containing liquid serving as the precursor of the second particle group with respect to the first particle group was appropriately changed.

(Example 4 and Example 5)
A ceramic powder of the present invention was produced in the same manner as in Examples 1 to 3 except that the raw material species and the mixing ratio were changed according to Table 1.
However, the commercially available Tb ₄ O ₇ powder (average particle diameter 3 μm) and Pr ₆ O ₁₁ powder (average particle diameter 4 μm) were used for the second particle group without using those derived from the metal alkoxide solution.

(Comparative Examples 1 to 3)
According to the blending ratio shown in Table 1, a comparative ceramic powder was produced in the same manner as in Example 1. However, in Comparative Example 1, the ceramic powder was composed of only the first particle group without adding the second particle group. In Comparative Example 2, an average particle diameter of 40 μm was prepared by calcining a commercially available Tb ₄ O ₇ powder in an electric furnace at 700 ° C. without using a metal component-containing liquid serving as a precursor of the second particle group. and constituting the ceramic shaping powder by mixing powder and _Pr 6 _{O 11} powder (average particle size 50 [mu] m).

Table 1

(Use of ceramic molding powder)
In order to clarify the difference in the molding speed of the ceramic powders of the examples and comparative examples, the powders were spread on a flat plate-like alumina substrate so as to have a thickness of about 50 μm. Then, laser irradiation was performed on the surface. The laser focal spot size was 100 μm, and the output was 30 W. The laser beam was irradiated so that a length of 4.5 mm was scanned and two lines were drawn at a pitch of 50 μm. The scanning speed was 100 mm / second, 250 mm / second, 500 mm / second, and 1000 mm / second, and the melting states were compared.
Table 2 shows the observation results of observation using a microscope as to whether or not the powder in the laser light irradiation part is solidified after laser light irradiation and can be formed into a ceramic shape.

  When the ceramic powders of Examples 1, 2, and 3 were irradiated with laser light, ceramic shaped objects could be obtained at any scanning speed. In particular, in the case of a scanning speed of 250 to 1000 mm / sec, the width of the boundary between the laser irradiation region and the non-irradiation region was 15 μm or less, and the modeling accuracy was high. In this way, when a ceramic model with very excellent modeling accuracy was obtained, “a” was recorded in Table 2. On the other hand, in the case of a scanning speed of 100 mm / second, there was a fluctuation in the line at the boundary of the ceramic shaped object, and the width was slightly large, about 40 μm. As described above, “b” is recorded in Table 2 when there is a little difficulty in modeling accuracy although it is a sufficient condition for obtaining a ceramic model.

  As described above, the ceramic modeling powder that satisfies the requirements of the present invention can perform ceramic modeling even at a high scanning speed, and can reduce the time required to obtain a desired model to more than twice as much as before. it can.

  When the ceramic powder of Comparative Example 1 was irradiated with laser light, a ceramic model was obtained when the scanning speed was 100 mm / sec. However, the boundary part was indefinite and some parts were not melted. There were some. Furthermore, when the scanning speed was 250 mm / second or more, melting did not proceed and conversion from powder to a model was not observed. In this way, when a ceramic molded article could not be obtained with sufficient accuracy, “c” was recorded in Table 2.

  When the ceramic powders of Comparative Example 2 and Comparative Example 3 were irradiated with laser light, a molded article with excellent modeling accuracy was obtained at a scanning speed of 100 to 250 mm / sec. However, when the scanning speed was 500 mm / second, the molded product contained a small amount of powder, and at 1000 mm / second, melting did not proceed and conversion from powder to molded product was not observed.

Example 4
The ceramic modeling powders of Examples 1 to 3 are put into the SLS apparatus shown in FIG. 1, and the layered modeling process is repeated a plurality of times with a laser beam scanning speed of 1000 mm / second, thereby obtaining a desired shape of the three-dimensional ceramics. A model was obtained.
(Industrial applicability)

  If the ceramic molding powder of the present invention is used, a fine ceramic model can be obtained by three-dimensional modeling, and can be used in the field of ceramic parts that require complex shapes.

DESCRIPTION OF SYMBOLS 1 Particle 2 contained in 1st particle group, 3 Particle contained in 2nd particle group 11 Powder basket 12 Modeling stage part 13 Recoater part 14 Scanner part 15 Laser 20 Base | substrate 21 Cladding nozzle 22 Powder supply hole 23 Laser

Claims (11)

A ceramic powder used in an additive molding method in which a raw material powder is irradiated with laser light to perform modeling,
A first particle group consisting of particles of a first inorganic compound and having an average particle size of 10 μm or more and 100 μm or less;
A second particle group consisting of particles of a second inorganic compound having an absorption band at the wavelength of the laser light, and an average particle size smaller than the first particle group,
Ceramic particles, wherein the particles contained in the second particle group are arranged on the surface of the particles contained in the first particle group.   2. The ceramic powder according to claim 1, wherein the second particle group has an average particle diameter of 0.05 μm to 2 μm.   2. The ceramic powder according to claim 1, wherein an average particle diameter of the second particle group is 0.05 μm or more and less than 1 μm.   The ceramic powder according to any one of claims 1 to 3, wherein the second particle group is melted and solidified by irradiation with the laser beam to cause a composition change to reduce the absorption rate of the laser beam. .   5. The ceramic powder according to claim 4, wherein the second particle group is made of a metal oxide, and the decrease in the absorption rate is due to a change in the valence of the metal element.   6. The ceramic powder according to claim 5, wherein the second particle group includes terbium oxide containing tetravalent terbium or praseodymium oxide containing tetravalent praseodymium as a main component.   The ceramic powder according to any one of claims 1 to 6, wherein the first particle group is mainly composed of either aluminum oxide or zirconium oxide. It is a manufacturing method of the ceramic powder according to claim 1,
Covering the surface of the particles contained in the first particle group with a metal component-containing liquid that is a precursor of the second particle group;
Heating the particles contained in the first particle group covered with the metal component-containing liquid, and arranging the particles contained in the second particle group on the surface of the particle;
A method for producing a ceramic powder, comprising: A method of manufacturing a ceramic structure using an additive manufacturing method in which a raw material powder is irradiated with a laser beam to perform modeling,
(I) a step of arranging the ceramic powder according to claim 1 in a laser irradiation part;
(Ii) a step of selectively irradiating the ceramic powder disposed in the laser irradiation unit with laser light to melt and then solidify the portion of the ceramic powder irradiated with the laser light; ,
A method for producing a ceramic structure, comprising producing a ceramic structure by repeating the steps (i) and (ii).   The method of manufacturing a ceramic structure according to claim 9, wherein the steps (i) and (ii) include irradiating the laser beam after the ceramic powder is spread and leveled.   The ceramic according to claim 9, wherein the steps (i) and (ii) include ejecting the ceramic powder to a predetermined location and irradiating the predetermined location with the laser beam. Manufacturing method of structure.

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