Porous ceramic structure

Abstract

The present invention provides a porous ceramic structure which can achieve low thermal conductivity, can be directly disposed on a substrate or the like using an adhesive or the like, and can facilitate the disposition of a block. The porous ceramic structure includes one sheet (12) and a plurality of porous ceramic particles (16) adhered to the sheet (12), and the gap (d) between adjacent porous ceramic particles (16) is 10 to 80 μm.

Description

Technical Field

[0001] The present invention relates to a porous ceramic structure, and more particularly to a porous ceramic structure suitable for reducing the thermal conductivity of a component including the porous ceramic structure. Background Art

[0002] As fillers filled in heat insulators, films, etc., there are compositions, hollow particles, etc. described in Patent Documents 1 to 3.

[0003] Patent Document 1 describes a curable organopolysiloxane composition capable of forming a porous organopolysiloxane cured product having a low thermal conductivity.

[0004] Patent Document 2 describes the formation of a film having a low thermal conductivity using a coating material employing hollow particles having a low thermal conductivity.

[0005] Patent Document 3 describes the following: composite particles obtained by nano - coating are manufactured by adsorbing additive particles on the surface of base particles through electrostatic interaction, and then a composite material is manufactured using the composite particles via a general powder metallurgy process.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid - Open No. 2010 - 155946

[0009] Patent Document 2: Japanese Patent Application Laid - Open No. 2004 - 10903

[0010] Patent Document 3: Japanese Patent Application Laid - Open No. 2010 - 64945 Summary of the Invention

[0011] Regarding the technologies described in Patent Documents 1 and 2, the reduction of thermal conductivity is insufficient. Regarding the technology described in Patent Document 3, since it is intended to produce a composite material by powder metallurgy, it is necessary to coat fine particles with a nanometer - sized diameter on the base particles. Therefore, the distance between the base particles becomes shorter, and in this case, the reduction of thermal conductivity is still insufficient.

[0012] If the particles added to the binder are small, it is difficult to uniformly disperse the particles in the binder. In addition, since it is necessary to set the binder pre - added with particles on, for example, an object after firing to form a block, it is difficult to set it on a partial area of the object or along a complex shape.

[0013] The present invention is implemented in consideration of the above problems, and the object is to provide a porous ceramic structure that can achieve low thermal conductivity, can be directly provided on an object or the like using an adhesive or the like, and can facilitate the setting of the block.

[0014] [1] The porous ceramic structure according to the present invention is characterized by including: one sheet and a plurality of porous ceramic particles adhered to the sheet, and the gap between adjacent porous ceramic particles is 10 to 80 μm.

[0015] [2] In the present invention, it is preferable that when the maximum gap between adjacent porous ceramic particles is dmax and the maximum thickness of the porous ceramic particle is tmax, the aspect ratio (dmax / tmax) is 0.02 or more.

[0016] [3] In the present invention, it is preferable that when the gap between adjacent porous ceramic particles, the gap on the surface in contact with the sheet is da and the gap on the surface opposite to the surface in contact with the sheet is db, da ≤ db is satisfied.

[0017] [4] In this case, the gap da and the gap db may satisfy da < db, and the width between the opposing side surfaces of adjacent porous ceramic particles gradually narrows.

[0018] [5] Alternatively, the gap da and the gap db may satisfy da < db, and the opposing side surfaces of adjacent porous ceramic particles are stepped.

[0019] [6] Alternatively, the gap da and the gap db may satisfy da = db, and the opposing side surfaces of adjacent porous ceramic particles are parallel.

[0020] [7] In the present invention, it is preferable that the porosity of the porous ceramic particles is 20 to 99%.

[0021] [8] In the present invention, it is preferable that the average pore diameter of the porous ceramic particles is 500 nm or less.

[0022] [9] In the present invention, it is preferable that the thermal conductivity of the porous ceramic particles is less than 1.5 W / mK.

[0023]

[10] In the present invention, it is preferable that the heat capacity of the porous ceramic particles is 1000 kJ / m 3 K or less.

[0024] The porous ceramic structure according to the present invention can achieve low thermal conductivity, and can be directly provided on an object or the like using a binder or the like, and can facilitate the setting of the block body. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a perspective view showing the porous ceramic structure according to the present embodiment.

[0026] Figure 2A It is a top view showing an example of forming a porous ceramic aggregate with one planar shape, Figure 2B It is a top view showing an example of forming a porous ceramic aggregate with two planar shapes, Figure 2C It is a top view showing an example of forming a porous ceramic aggregate with three planar shapes.

[0027] Figure 3A It is a top view showing an example in which curves are respectively included in the planar shapes of two porous ceramic particles, Figure 3B It is a top view showing an example in which curves are respectively included in the planar shapes of six porous ceramic particles.

[0028] Figure 4A It is a cross-sectional view showing a case where the gaps between the porous ceramic particles are wide and the sides of the adjacent porous ceramic particles facing each other are parallel, Figure 4B It is a cross-sectional view showing a case where the gaps between the porous ceramic particles are wide and the width between the sides of the adjacent porous ceramic particles facing each other gradually narrows, Figure 4C It is a cross-sectional view showing a case where the gaps between the porous ceramic particles are wide and the sides of the adjacent porous ceramic particles facing each other are stepped.

[0029] Figure 5 It is a process diagram showing the first manufacturing method of the porous ceramic structure according to the present embodiment.

[0030] Figure 6 It is a schematic view showing an example of a doctor blade device.

[0031] Figure 7 It is a process diagram showing the second manufacturing method of the porous ceramic structure according to the present embodiment.

[0032] Figure 8 Among them, (A) is a process diagram showing the state of disposing the porous ceramic structure on an object, (B) is a process diagram showing the state of peeling the sheet from the porous ceramic structure, and (C) is a process diagram showing the state of applying a resin material on the porous ceramic aggregate on the object.

[0033] Figure 9It is a cross-sectional view showing a part of the block and the object omitted.

[0034] Figure 10A It is an explanatory view showing a part of the state in which multiple particles are dispersed in a slurry in the prior art example. Figure 10B It is an explanatory view showing a part of the state in which a block is made by drying, firing, and solidifying the slurry.

[0035] Symbol Explanation

[0036] 10... Porous ceramic structure, 12... Sheet, 14... Porous ceramic aggregate, 16... Porous ceramic particles, 18... Resin material, 20... Block, 22... Object, 24... Straight line, 26... Curve, 27... Portion, 28... Normal, 30... Molded body, 40... Sintered body. Detailed Embodiment

[0037] Hereinafter, with reference to Figures 1 to 10B , embodiments of the porous ceramic structure according to the present invention will be described. It should be noted that in this specification, "~" indicating a numerical range is used to mean including the values described before and after it as the lower limit value and the upper limit value.

[0038] For example Figure 1 As shown, the porous ceramic structure 10 according to the present embodiment includes one sheet 12 and a porous ceramic aggregate 14 adhered to the sheet 12. The porous ceramic aggregate 14 has a plurality of porous ceramic particles 16 that are respectively divided. Here, the term "adhered" means being fixed in a state where it can be peeled off, that is, the fixed state is released due to time change or the application of external factors, and the adhered object is separated. Therefore, it includes the state fixed by adhesive force, and also includes the state temporarily firmly fixed at the adhesion interface. An adhesive or other special material can also be used for adhesion between the sheet 12 and the porous ceramic aggregate 14.

[0039] The term "porous" means a state that is neither dense nor hollow, and means a state composed of a plurality of air holes or particles. It should be noted that the term "dense" means a state in which a plurality of fine particles are combined without gaps and there are no air holes. The term "hollow" means a state in which the inside is hollow and the outer shell part is dense.

[0040] The aspect ratio of the porous ceramic particles 16 is preferably 3 or more. More preferably, it is 5 or more, and still more preferably, it is 7 or more. In this case, the aspect ratio refers to the maximum length La / minimum length Lb. Here, the so-called maximum length La refers to the maximum length on the widest surface (here, one main surface 16a) among the multiple surfaces constituting the porous ceramic particles 16. If the wide surface is a square, rectangle, trapezoid, parallelogram, polygon (pentagon, hexagon, etc.), the length of the longest diagonal corresponds to the maximum length. If the wide surface is a circle, the diameter corresponds to the maximum length. If the wide surface is an ellipse, the length of the major axis corresponds to the maximum length. On the other hand, the so-called minimum length Lb, as Figure 1 shown, is the thickness ta of the porous ceramic particles 16.

[0041] The minimum length Lb is preferably 50 to 500 μm, more preferably 55 to 400 μm, still more preferably 60 to 300 μm, and particularly preferably 70 to 200 μm.

[0042] The sheet 12 can be, for example, a resin sheet or a film having adhesiveness, and preferably a material that can be peeled off due to external factors such as heat, electricity, and external force and changes over time.

[0043] As described later (refer to Figure 8 (C) and Figure 9 ), the porous ceramic aggregate 14 is coated with a resin material 18 (matrix) such as a binder and is provided as a block 20 on the object 22.

[0044] In this case, compared with the case where each porous ceramic particle 16 is separately provided on the object 22, it is easier to transfer a plurality of porous ceramic particles 16 to the object 22 together, and it is also easier to control the gaps between the porous ceramic particles 16.

[0045] The planar shape obtained by observing the porous ceramic aggregate 14 from the upper surface is preferably the same as the planar shape obtained by observing the region of the object 22 where the porous ceramic aggregate 14 is to be provided (hereinafter referred to as the setting region of the object 22) from the upper surface. Here, the setting region of the object 22 is a concept including a part of the object 22. The so-called "same" includes the case of being completely the same, and also includes a shape in a similar relationship with the planar shape of the setting region of the object 22. Here, the so-called similar relationship means a shape obtained by enlarging the planar shape of the setting region of the object 22 by 1.1 times to 2.0 times or a shape obtained by reducing the planar shape of the setting region of the object 22 by 1.1 times to 2.0 times. Thus, a plurality of porous ceramic particles 16 can be transferred onto objects 22 of various shapes without causing material loss (loss of porous ceramic particles 16).

[0046] In addition, among the plurality of porous ceramic particles 16 included in the porous ceramic aggregate 14, at least one porous ceramic particle 16 having a planar shape, as viewed from the upper surface, surrounded by a plurality of straight lines 24 (see Figures 2A to 3B ) may exist. Of course, the planar shape of all the porous ceramic particles 16 may also be a polygon surrounded by a plurality of straight lines 24.

[0047] For example, as shown in Figure 2A , it may be composed of one planar shape, or as shown in Figure 2B , it may be composed of two planar shapes. In addition, as shown in Figure 2C , it may be composed of three planar shapes.

[0048] Figure 2A In the example of Figure 2B , a case is given where the planar shape of all the porous ceramic particles 16 is a quadrilateral. Figure 2C In the example of

[0049] , a case is given where the porous ceramic aggregate 14 is composed of a combination of a quadrilateral and a triangle, and an example is given where six triangles are arranged inside and six quadrilaterals are arranged outside. Figure 3A and Figure 3B In addition, as shown in

[0050] , among the plurality of porous ceramic particles 16 included in the porous ceramic aggregate 14, the proportion of the porous ceramic particles 16 having a planar shape including a curve 26, as viewed from the upper surface, may be greater than 0% and 50% or less.

[0051] When calculating the proportion of the porous ceramic particles 16 having a planar shape including a curve 26, as viewed from the upper surface, it is only necessary to count the total number Nz of the porous ceramic particles 16 on the sheet 12 and the number Nw of the porous ceramic particles 16 having a planar shape including a curve 26, and calculate (number Nw / number Nz) × 100 (%).

[0052] Figure 3A In Figure 3AThe planar shape of the porous ceramic particles 16 shown in (1) to (7) is quadrilateral, and the remaining two porous ceramic particles 16( Figure 3A The planar shapes of the porous ceramic particles 16 shown in (8) and (9) respectively include curves 26. Figure 3B Among the 24 porous ceramic particles 16, 18 porous ceramic particles 16( Figure 3B The planar shapes of the porous ceramic particles 16 shown in (3) to (14), (16) to (18), and (20) to (22) are quadrilateral, and the remaining six porous ceramic particles 16( Figure 3B The planar shapes of the porous ceramic particles 16 shown in (1), (2), (15), (19), (23), and (24) respectively include curves 26.

[0053] In addition, as Figure 2B shown, the porous ceramic aggregate 14 may further have a portion 27 obtained by arranging five or more porous ceramic particles 16 with one vertex facing each other. Thus, even if the surface of the object 22 has a curved surface or unevenness locally, it is easy to arrange a plurality of porous ceramic particles 16 along the surface shape of the object 22.

[0054] Moreover, the gap d (refer to Figures 4A to 4C ) between adjacent porous ceramic particles 16 is preferably 10 to 80 μm. The gap d is obtained by measuring between adjacent porous ceramic particles 16 in the porous ceramic aggregate 14 adhered to the sheet 12 using an optical microscope.

[0055] In this case, as Figure 4A shown, when the gap d between adjacent porous ceramic particles 16, the gap on the surface (lower surface) in contact with the sheet 12 is da, and the gap on the opposite surface (upper surface) of the surface in contact with the sheet 12 is db, the gap da and the gap db may satisfy da = db, and the side surfaces of adjacent porous ceramic particles 16 facing each other are parallel. Thus, it is easy to transfer a plurality of porous ceramic particles 16 onto the object 22, and a plurality of porous ceramic particles 16 can be transferred onto the object 22 uniformly. If the gap d is too wide, the amount of the resin material 18 (binder) entering between the porous ceramic particles 16 increases, and thus the thermal conductivity increases.

[0056] Conversely, when the gap d between adjacent porous ceramic particles 16 is less than 10 μm, if the surface of the object 22 is curved or the like, when the sheet 12 is bent to transfer the plurality of porous ceramic particles 16 onto the object 22, the adjacent porous ceramic particles 16 come into contact with each other, and cracks and notches are likely to occur. As a result, when the plurality of porous ceramic particles 16 are provided on the object 22, the gap d between the porous ceramic particles 16 increases, and the thermal conductivity increases.

[0057] Therefore, as described above, the gap d (see Figures 4A to 4C ) between adjacent porous ceramic particles 16 is preferably 10 to 80 μm.

[0058] Further, when the maximum gap in the gap d between adjacent porous ceramic particles 16 is dmax and the maximum thickness in the thickness ta of the porous ceramic particles 16 is tmax, the aspect ratio (dmax / tmax) is preferably 0.02 or more. This is because if the aspect ratio is too small, even if the gap d between adjacent porous ceramic particles 16 is wide, when the sheet 12 is bent, the adjacent porous ceramic particles 16 will come into contact with each other and cracks or notches will occur. It should be noted that a constant-pressure thickness measuring instrument or the like can be used to measure the thickness tmax.

[0059] In addition, it is preferable that the gap da on the lower surface and the gap db on the upper surface between adjacent porous ceramic particles 16 satisfy da ≤ db. In this case, as Figure 4B shown, the gap da and the gap db may satisfy da < db, and the width between the opposed side surfaces of adjacent porous ceramic particles 16 gradually narrows. As Figure 4C shown, the opposed side surfaces of adjacent porous ceramic particles 16 may be stepped. Thus, even if the gap d and the aspect ratio are small, when the sheet 12 is bent, the adjacent porous ceramic particles 16 hardly come into contact with each other, and cracks or notches do not occur. As a result, the yield of the porous ceramic structure 10 is improved.

[0060] It should be noted that when the width between the side surfaces of the porous ceramic particles 16 gradually narrows, the inclination angle θ of the side surface with respect to the normal 28 of the sheet 12 is preferably 45 degrees or less, that is, 0 degrees or more and 45 degrees or less. The inclination angle θ is obtained by measuring the inclination angle θ between adjacent porous ceramic particles 16 in the porous ceramic aggregate 14 adhered to the sheet 12 with an optical microscope.

[0061] In addition, it is preferable that the number density of the porous ceramic particles 16 in the porous ceramic aggregate 14 is locally different. In addition, it is preferable that the sizes of the planar shapes of the plurality of porous ceramic particles 16 are different.

[0062] For example, the number density is decreased in the flat portion of the surface of the object 22 (the size of the porous ceramic particles 16 is relatively large), and the number density is increased in the curved surface portion of the surface of the object 22 and its periphery (the size of the porous ceramic particles 16 is relatively small). Thus, when transferring a plurality of porous ceramic particles 16 onto the object 22, the plurality of porous ceramic particles 16 can be arranged following the surface of the object 22.

[0063] Preferably, the ratio of the maximum value to the minimum value of the number density (maximum number density / minimum number density) is greater than 1.2.

[0064] The number density can be calculated as follows. That is, in the porous ceramic aggregate 14 adhered to the sheet 12, observe any 10 fields of view with an optical microscope, and count the number of porous ceramic particles 16 included in each field of view. Each field of view can be, for example, a square area of 3 mm × 3 mm.

[0065] Then, divide the number of porous ceramic particles 16 included in each measured field of view by the area of the field of view (= 9 mm 2 ), thereby calculating the number density per unit area (number / mm 2 ). Compare the number densities corresponding to these 10 fields of view, select the maximum number density and the minimum number density, and calculate their ratio (maximum number density / minimum number density).

[0066] In addition, preferably, the ratio of the maximum value to the minimum value of the size of the planar shape (maximum value / minimum value) is greater than 1.2.

[0067] The size of the planar shape can be calculated as follows. That is, in the porous ceramic aggregate 14 adhered to the sheet 12, observe any 10 fields of view with an optical microscope respectively. Then, for each field of view, draw any 5 straight lines respectively, measure the length of the line segments inside the porous ceramic particles 16 intersecting with the straight lines, and use the average value as the size of the porous ceramic particles 16 in that field of view. Compare the sizes of the porous ceramic particles 16 in these 10 fields of view, select the maximum value and the minimum value of the size of the porous ceramic particles 16, and calculate their ratio (maximum value / minimum value).

[0068] The porosity of the porous ceramic particles 16 is preferably 20 to 99%. The pores are at least one of closed pores and open pores, and both can also be included. In addition, as the shape of the pores, that is, the shape of the opening surface, it can be any one of a square, a quadrilateral, a triangle, a hexagon, a circle, etc. and an irregular shape.

[0069] The average pore diameter is preferably 500 nm or less, more preferably 10 to 500 nm. This size is effective in hindering the occurrence of lattice vibrations (phonons), which are the main cause of heat conduction.

[0070] The porous ceramic particles 16 have a structure in which fine particles are three-dimensionally connected. The particle diameter of the fine particles is preferably 1 nm to 5 μm, more preferably 50 nm to 1 μm. The porous ceramic particles 16 composed of fine particles within this range are effective in achieving low thermal conductivity because they hinder the occurrence of lattice vibrations (phonons), which are the main cause of heat conduction. The fine particles can be particles composed of a single crystal grain (single crystal particles) or particles composed of multiple crystal grains (polycrystalline particles). That is, the porous ceramic particles 16 are preferably an aggregate of fine particles within this range. It should be noted that the particle diameter of the fine particles is obtained as follows: Observation is performed with an electron microscope to obtain an image, and the size of one fine particle in the particle group constituting the framework of the porous ceramic particles 16 is measured from this image (if it is spherical, it is the diameter; if it is non-spherical, it is the maximum diameter).

[0071] The thermal conductivity of the porous ceramic particles 16 is preferably less than 1.5 W / mK, more preferably 0.7 W / mK or less, further preferably 0.5 W / mK or less, and particularly preferably 0.3 W / mK or less.

[0072] The heat capacity of the porous ceramic particles 16 is preferably 1000 kJ / m 3 K or less, more preferably 900 kJ / m 3 K or less, further preferably 800 kJ / m 3 K or less, and particularly preferably 500 kJ / m 3 K or less.

[0073] As the constituent material of the porous ceramic particles 16, it is preferable to contain a metal oxide, and more preferably to be composed only of a metal oxide. This is because: If a metal oxide is contained, the ionic bond between the metal and oxygen is stronger than that of a non-oxide of a metal (such as a carbide or a nitride), and therefore, the thermal conductivity is likely to decrease.

[0074] The metal oxide is preferably an oxide of one element selected from the group consisting of Zr, Y, Al, Si, Ti, Nb, Sr, La, Hf, Ce, Gd, Sm, Mn, Yb, Er, and Ta, or a composite oxide of two or more elements. This is because: If the metal oxide is an oxide or a composite oxide of these elements, heat conduction is less likely to occur due to lattice vibrations (phonons).

[0075] As specific materials, materials obtained by adding Gd2O3, Yb2O3, Er2O3, etc. to ZrO2 - Y2O3 can be cited. More specifically, ZrO2 - HfO2 - Y2O3, ZrO2 - Y2O3 - La2O3, ZrO2 - HfO2 - Y2O3 - La2O3, HfO2 - Y2O3, CeO2 - Y2O3, Gd2Zr2O7, Sm2Zr2O7, LaMnAl 11 O 19 、YTa3O9, Y 0.7 La 0.3 Ta3O9, Y 1.08 Ta 2.76 Zr 0.24 O9, Y2Ti2O7, LaTa3O9, Yb2Si2O7, Y2Si2O7, Ti3O5, etc.

[0076] Here, with reference to Figures 5 to 7 , the first manufacturing method and the second manufacturing method of the porous ceramic structure 10 will be described.

[0077] First, the first manufacturing method will be described. First, Figure 5 in step S1 of Figure 6 , a pore former, a binder, a plasticizer, and a solvent are added to the powder of the constituent material of the above-mentioned porous ceramic particles 16 and mixed to prepare a forming slurry 36 (refer to

[0078] ). Then, in step S2, the forming slurry 36 is subjected to a vacuum degassing treatment, and after adjusting the viscosity, a green sheet 30 (green body) is produced by tape casting (green body production process). For example, the forming slurry 36 is poured onto a polyester film 34 for ceramic demolding of a doctor blade device 32 as shown in Figure 6 , and the green sheet 30 (green body) is produced by the doctor blade 38 to have a specified thickness after firing.

[0079] Then, Figure 5 in step S3 of

[0080] Then, in step S4, the recovered formed body 30 is fired to obtain a sheet-shaped sintered body 40 (firing process). Next, in step S5, the sintered body 40 is adhered to the sheet 12 (adhesion process). As described above, since the peeling surface 30a of the formed body 30 is a mirror surface, the end face 40a (the surface that was once the peeling surface 30a) of the sintered body 40 after the firing treatment is also a mirror surface. Therefore, by adhering the end face 40a of the sintered body 40 to the sheet 12, the sintered body 40 is firmly adhered to the sheet 12.

[0081] Then, in step S6, the sintered body 40 is divided into a plurality of porous ceramic particles 16 (division process). Thereby, a porous ceramic structure 10 is obtained, which includes one sheet 12 and a porous ceramic aggregate 14 adhered to the sheet 12 and composed of a plurality of porous ceramic particles 16. It should be noted that surface modification treatment can also be performed on the sintered body 40 after the firing process or the porous ceramic particles 16 after the division process. The surface modification treatment is a treatment for controlling the degree of penetration of a resin material 18 such as a binder (matrix: refer to Figure 8 (C) and Figure 9 ) into the porous ceramic particles 16 (mainly a treatment to make it difficult to penetrate).

[0082] The division process in step S6 described above divides the sintered body 40 into a plurality of small pieces, that is, a plurality of porous ceramic particles 16. Of course, the division process can be carried out by various methods: cutting (dividing) by pressing a cutting tool against the sintered body 40 to divide it into a plurality of porous ceramic particles 16, or cutting the sintered body 40 with a laser to divide it into a plurality of porous ceramic particles 16, etc. In this case, since the sintered body 40 is firmly adhered to the sheet 12, it is possible to prevent the sintered body 40 and the porous ceramic particles 16 from peeling off the sheet 12 during division.

[0083] Next, with reference to Figure 7 , the second manufacturing method will be described. In steps S101 to S103 of this second manufacturing method, the preparation of the forming slurry 36, the production of the formed body 30, and the recovery of the formed body 30 are carried out in the same manner as steps S1 to S3 described above.

[0084] Then, in step S104, laser processing or pressing processing is performed to form a plurality of cut marks 42 from the upper surface of the formed body 30. At this time, by controlling the cutting depth and width of the laser while performing the processing, it is possible to gradually narrow the width between the opposing side surfaces of adjacent porous ceramic particles 16 or form a stepped shape.

[0085] Then, in steps S105 to S107, in the same manner as steps S4 to S6 described above, the recovered molded body 30 is fired to obtain a sheet-like sintered body 40. The sintered body 40 is adhered to the sheet 12 and divided into a plurality of porous ceramic particles 16.

[0086] Thereby, a porous ceramic structure 10 is obtained. The porous ceramic structure 10 includes one sheet 12 and a porous ceramic aggregate 14 adhered to the sheet 12 and composed of a plurality of porous ceramic particles 16. It should be noted that in this second manufacturing method, the above-mentioned surface modification treatment may also be performed on the sintered body 40 after the firing process or the porous ceramic particles 16 after the dividing process.

[0087] Next, with reference to Figure 8 (A) to Figure 9 , a method of forming a single block 20 using the porous ceramic structure 10 will be described.

[0088] First, as shown in Figure 8 (A), an adhesive 44 is applied to the object 22. The porous ceramic structure 10 is provided on the adhesive 44 applied to the object 22. In this case, the porous ceramic structure 10 is provided in such a manner that the adhesive 44 on the object 22 and the porous ceramic aggregate 14 are opposed to each other.

[0089] As shown in Figure 8 (B), for example, the sheet 12 is peeled off by heating the sheet 12, and the porous ceramic aggregate 14 is transferred onto the adhesive 44 of the object 22.

[0090] Then, as shown in Figure 8 (C) and Figure 9 , the entire porous ceramic aggregate 14 is covered with a resin material 18 (matrix) such as an adhesive, thereby forming a block 20. That is, a block 20 is provided on the object 22.

[0091] In the past, as shown in Figure 10A , since the particles 52 added to the slurry 50 are small, it is difficult to uniformly disperse the particles 52 in the slurry 50. Therefore, as shown in Figure 10B , when the slurry 50 is cured to form a block 54, since a plurality of particles 52 are not uniformly dispersed in the binder 56 obtained by curing the slurry 50, there are many regions 58 where only the binder 56 having a higher thermal conductivity than the particles 52 exists, resulting in insufficient reduction of the low thermal conductivity of the block 54.

[0092] In contrast, in the present embodiment, a porous ceramic structure 10 including a porous ceramic aggregate 14 composed of a plurality of porous ceramic particles 16 adhered to a sheet 12 is provided on an object 22. Then, the sheet 12 is peeled off, the porous ceramic aggregate 14 is transferred onto the object 22, and the porous ceramic aggregate 14 is coated with a resin material 18 (matrix) such as an adhesive, thereby forming a block 20.

[0093] Therefore, a plurality of porous ceramic particles 16 can be uniformly dispersed and arranged in the resin material 18. And since only the region of the resin material 18 having a higher thermal conductivity than the porous ceramic particles 16 becomes narrower, the thermal conductivity of the block 20 can be suppressed to a lower level. Also, the homogenization of the thermal conductivity between the blocks 20 can be achieved, and it is not necessary to change the block 20 according to the position where the block 20 is arranged, and the simplification of the arrangement process and the reduction of man-hours can be realized.

[0094] In addition, since the sintered body 40 adhered to the sheet 12 is divided into a plurality of porous ceramic particles 16, different from the existing situation, a plurality of porous ceramic particles 16 can be uniformly arranged on the object 22. And regardless of whether the surface of the object 22 is an irregular shape (such as warping) or a curved surface, a plurality of porous ceramic particles 16 can be easily arranged along the surface shape of the object 22, and the degree of freedom in design can be improved. In addition, since the porous ceramic structure 10 is composed of the sheet 12 and the porous ceramic aggregate 14 having a plurality of porous ceramic particles 16 adhered to the sheet 12, the operation of the porous ceramic structure 10 is easy, and the operation of transferring a plurality of porous ceramic particles 16 onto the object 22 is also very simple. This is conducive to the simplification of the manufacturing process.

[0095] The adhesive force (JIS Z0237) of the sheet 12 is preferably 1.0 N / 10 mm or more, the tensile elongation (JIS K7127) is preferably 0.5% or more, and the thickness is preferably 5 mm or less. Thus, the following effects can be exerted.

[0096] (a) The higher the adhesive force, the more firmly the porous ceramic particles 16 can be fixed.

[0097] (b) The higher the tensile elongation, the more it can follow a curved surface.

[0098] (c) The thinner the thickness, the easier it is to follow a curved surface.

[0099] More specifically, the adhesive force of the sheet 12 is as follows. That is, the adhesive force when holding the porous ceramic particles 16 is 1.0 N / 10 mm or more, and the adhesive force when peeling off the porous ceramic particles 16 is 0.1 N / 10 mm or less.

[0100] The evaluation method for the adhesion of the sheet 12 is the same as that for the adhesion of the adhesive tape. The sheet 12 is attached to a stainless steel plate, and the sheet 12 is stretched at 180 degrees or 90 degrees. The force when the sheet 12 is peeled off from the stainless steel plate is taken as the adhesion force.

[0101] In addition, the sheet 12 is formed by coating an adhesive on a substrate (support). In this case, the following selection is preferred for the type of the substrate.

[0102] That is, when transferring the porous ceramic particles 16 onto the planar object 22, it is preferable to use a film, a metal foil, paper, etc. as the substrate. Since the substrate of the sheet 12 is hard, the sheet 12 can be formed on the planar object 22 without wrinkles.

[0103] When transferring the porous ceramic particles 16 onto the object 22 having a curved surface (convex surface, concave surface, uneven surface) shape, it is preferable to use cloth, a rubber sheet, a foam body, etc. as the substrate. Since the substrate of the sheet 12 is soft and has stretchability, the sheet 12 can be formed following the curved surface shape.

[0104] In addition, under the action of heat, water, solvent, light (ultraviolet light), and microwave, the adhesion force of the sheet 12 becomes weak and it can be easily peeled off. At this time, the adhesion force of the sheet 12 is preferably weaker than that of the adhesive 44 used between the object 22 and the porous ceramic structure 10.

[0105]

Examples

[0106] Using the porous ceramic structures 10 involved in Examples 1 to 5, the porous ceramic structures 10 involved in Reference Examples 1 and 2, and the porous ceramic structures involved in Comparative Example 1 respectively to form the blocks 20, and confirming the difficulty of defect of the porous ceramic particles 16 when transferring each of the blocks 20 to the object 22 at this time.

[0107] (Example 1)

[0108] As the plurality of porous ceramic particles 16 constituting the porous ceramic structure 10, porous ceramic particles 16 with a porosity of 60% and a thickness of 500 μm are respectively used, and the block 20 involved in Example 1 is manufactured according to the above manufacturing method. That is, first, a porous ceramic structure 10 including a sheet 12 and a plurality of porous ceramic particles 16 adhered to one surface of the sheet 12 is used. Then, after coating the adhesive 44 (thermal conductivity 2 W / mK) on the object 22, the above sheet 12 is used to transfer a plurality of porous ceramic particles 16 onto the adhesive 44 of the object 22, and the sheet 12 is peeled off by applying heat. After coating the resin material 18 (matrix) from above, the resin material 18 is cured, thereby disposing the block 20 on the surface of the object 22.

[0109] <Fabrication of Porous Ceramic Structure 10>

[0110] In Example 1, the porous ceramic structure 10 for porosity measurement and the porous ceramic structure 10 for blocks were fabricated as follows. The same applies to Examples 2 to 5, Reference Examples 1 and 2, and Comparative Example 1 described later.

[0111] First, a pore former (latex particles or melamine resin particles), polyvinyl butyral resin (PVB) as a binder, DOP (dioctyl phthalate) as a plasticizer, xylene and 1-butanol as solvents were added to yttria partially stabilized zirconia powder, and the mixture was ball-milled for 30 hours to prepare a forming slurry 36. After subjecting the forming slurry 36 to a vacuum degassing treatment to adjust the viscosity to 4000 cps, a green sheet 30 was fabricated using a doctor blade device 32 to have a fired thickness of 500 μm. Then, laser processing was performed to form a plurality of notches 42 from the upper surface of the green sheet 30. At this time, the width of the laser was controlled and adjusted so that the gap between adjacent porous ceramic particles 16 after completion was 0.1 μm. Then, the green sheet 30 was fired at 1100 °C for 1 hour to obtain a sintered body 40. Then, the sintered body 40 was adhered to the upper surface of the sheet 12. Furthermore, the sintered body 40 was divided to fabricate a plurality of porous ceramic particles 16. That is, a porous ceramic structure 10 in which a porous ceramic aggregate 14 composed of a plurality of porous ceramic particles 16 is adhered to the sheet 12 was fabricated.

[0112] The planar shape of the porous ceramic aggregate 14 on the sheet 12 is a square with a length of 100 mm and a width of 100 mm, and the porous ceramic structure 10 is in a form in which about 40,000 porous ceramic particles 16 are arranged on the sheet 12.

[0113] For the porous ceramic structure 10 according to Example 1, the planar shapes of the plurality of porous ceramic particles 16 constituting the porous ceramic structure 10 are all polygons surrounded by straight lines 24. The thickness ta of the plurality of porous ceramic particles 16 is 500 μm, the gap d between the porous ceramic particles 16 is 10 μm, and the aspect ratio of the vertical and horizontal dimensions is 0.02. The gap da on the lower surface and the gap db on the upper surface in the gap d between adjacent porous ceramic particles 16 are substantially the same, and the side surfaces of adjacent porous ceramic particles 16 facing each other are substantially parallel.

[0114] (Example 2)

[0115] As the porous ceramic structure 10, a porous ceramic structure 10 is used in which the thickness ta of the plurality of porous ceramic particles 16 is 500 μm, the gap d between the porous ceramic particles 16 is 50 μm, and the aspect ratio is 0.10. Except for this, the block 20 according to Example 2 is produced in the same manner as in Example 1.

[0116] (Example 3)

[0117] As the porous ceramic structure 10, a porous ceramic structure 10 is used in which the thickness ta of the plurality of porous ceramic particles 16 is 500 μm, the gap d between the porous ceramic particles 16 is 80 μm, and the aspect ratio is 0.16. Except for this, the block 20 according to Example 3 is produced in the same manner as in Example 1.

[0118] (Example 4)

[0119] As the porous ceramic structure 10, a porous ceramic structure 10 is used in which the thickness ta of the plurality of porous ceramic particles 16 is 500 μm, the gap db on the upper surface in the gap d between the porous ceramic particles 16 is 50 μm, the gap da on the lower surface is 10 μm, and the width between the opposing side surfaces of the adjacent porous ceramic particles 16 gradually narrows. Except for this, the block 20 according to Example 4 is produced in the same manner as in Example 1.

[0120] (Example 5)

[0121] As the porous ceramic structure 10, a porous ceramic structure 10 is used in which the thickness ta of the plurality of porous ceramic particles 16 is 500 μm, the gap db on the upper surface in the gap d between the porous ceramic particles 16 is 50 μm, the gap da on the lower surface is 10 μm, and the opposing side surfaces of the adjacent porous ceramic particles 16 are stepped. Except for this, the block 20 according to Example 5 is produced in the same manner as in Example 1.

[0122] (Reference Example 1)

[0123] As the porous ceramic structure 10, a porous ceramic structure 10 is used in which the thickness ta of the plurality of porous ceramic particles 16 is 500 μm, the gap d between the porous ceramic particles 16 is 5 μm, and the aspect ratio is 0.01. Except for this, the block 20 according to Reference Example 1 is produced in the same manner as in Example 1.

[0124] (Reference Example 2)

[0125] As the porous ceramic structure 10, a porous ceramic structure 10 is used in which the thickness ta of a plurality of porous ceramic particles 16 is 500 μm, the gap d between the porous ceramic particles 16 is 100 μm, and the aspect ratio of the length to the width is 0.2. Except for this, the block 20 according to Reference Example 2 is produced in the same manner as in Example 1.

[0126] (Comparative Example 1)

[0127] As Figure 10A shown, a slurry 50 containing particles 52 (commercially available porous ceramic particles) having a porosity of 90% and a particle size of 50 μm, polystyrene resin fine particles, and water is prepared, then poured into a mold, dried, fired, and solidified to produce the block 54 according to Comparative Example 1.

[0128] In Table 1 below, the detailed compositional contents of Examples 1 to 5, Reference Examples 1 and 2, and Comparative Example 1 are given.

[0129] [Measurement method, determination method, and evaluation criteria]

[0130] [Measurement of porosity]

[0131] For Examples 1 to 5, Reference Examples 1 and 2, 10 porous ceramic particles 16 are arbitrarily selected from the plurality of porous ceramic particles 16 constituting the porous ceramic structure 10 for measuring porosity, and embedded in resin, and polished to an observation position where the porous ceramic particles 16 can be observed using an electron microscope, to produce an embedded resin polished surface. Then, the embedded resin polished surface is observed (image analysis) using an electron microscope. From the image analysis, the porosity of each of the 10 porous ceramic particles 16 is calculated, and the average value of the 10 porous ceramic particles 16 is used as the porosity of the porous ceramic particles 16.

[0132] [Measurement of average pore diameter]

[0133] An automatic porosimeter (trade name “Autopore 9200”) manufactured by Shimadzu Corporation is used to measure the average pore diameter of the porous ceramic particles 16.

[0134] [Measurement method for the gap d between the porous ceramic particles 16]

[0135] The gap d between the plurality of porous ceramic particles 16 constituting the porous ceramic aggregate 14 is measured separately using an optical microscope.

[0136] [Measurement method for the thickness ta of the porous ceramic particles 16]

[0137] The thickness ta of the plurality of porous ceramic particles 16 constituting the porous ceramic aggregate 14 is measured separately using an optical microscope.

[0138] [Evaluation of the ease of defect of the porous ceramic particles 16 during transfer to the object 22]

[0139] Using an optical microscope, the number Nc of the porous ceramic particles 16 with peripheral defects among the porous ceramic particles 16 present on the object 22 was confirmed, and the ratio of the number Nc to the total number Nz of the porous ceramic particles 16 on the sheet 12, that is, (number Nc / total number Nz) × 100 (%) was calculated. Then, based on the following evaluation criteria, Examples 1 to 5, Reference Examples 1 and 2, and Comparative Example 1 were evaluated.

[0140] A: Less than 1%

[0141] B: 1% or more and less than 5%

[0142] C: 5% or more and less than 10%

[0143] D: 10% or more

[0144] <Evaluation results>

[0145] The evaluation results of Examples 1 to 5, Reference Examples 1 and 2, and Comparative Example 1 are shown in Table 1 below.

[0146] Table 1

[0147]

[0148] As can be seen from Table 1: In Comparative Example 1, the ease of defect during transfer was 10% or more. It is considered that this is because the particles were not uniformly dispersed in the binder, the particles were locally aggregated, and the particles contacted each other, resulting in notches.

[0149] In contrast, in Examples 1 to 5, the ease of defect during transfer was less than 5%, and particularly in Examples 2 to 5, the ease of defect during transfer was less than 1%, which was good.

[0150] On the other hand, the gap d in Reference Example 1 was narrower than that in Example 1. Therefore, notches were generated during transfer, and the ease of defect during transfer was 5% or more. The gap d in Reference Example 2 was wider, being 100 μm. Therefore, the ease of defect during transfer was less than 1%, which was good. However, the thermal conductivity of Example 3 and Reference Example 2 was measured by the measurement method shown below. As a result, Example 3 was evaluated as B and Reference Example 2 was evaluated as C according to the following evaluation criteria. For Reference Example 2, it is considered that since the gap was wide, being 100 μm, there were many regions with only the resin material 18, so the thermal conductivity increased.

[0151] <Measurement method and evaluation criteria for the thermal conductivity of the block 20>

[0152] First, the density of the block 20 is measured using a mercury porosimeter. Next, the specific heat of the block 20 is measured using the DSC (Differential Scanning Calorimeter) method. Next, the thermal diffusivity of the block 20 is measured using the laser flash method. Then, the thermal conductivity of the block 20 is calculated from the relationship of thermal diffusivity × specific heat × density = thermal conductivity, and Examples 1 to 5, Reference Examples 1 and 2, and Comparative Example 1 are evaluated based on the following evaluation criteria.

[0153] A: 0.9 W / mK or less

[0154] B: 1.0 W / mK or more and 1.4 W / mK or less

[0155] C: 1.5 W / mK or more and 1.9 W / mK or less

[0156] D: 2.0 W / mK or more

[0157] It should be noted that the porous ceramic structure according to the present invention is not limited to the above-described embodiments, and of course, various configurations can be adopted as long as the gist of the present invention is not deviated from.

[0158] In the above example, when the block 20 is manufactured, the porous ceramic aggregate 14 is covered with the resin material 18. However, in addition to this, the block 20 can also be manufactured by covering a part of the porous ceramic aggregate 14 with the resin material 18, or the block 20 can be manufactured without using the resin material 18 and only by providing the porous ceramic aggregate 14 on the object 22.

Claims

1. A porous ceramic structure, characterized in that Including: it includes one sheet and a plurality of porous ceramic particles adhered to the sheet, the gap between adjacent porous ceramic particles is 10 μm to 50 μm, when the maximum gap between adjacent porous ceramic particles is dmax and the maximum thickness of the porous ceramic particle is tmax, the aspect ratio dmax / tmax is 0.02 to 0.16, and the maximum thickness tmax of the porous ceramic particle is 55 μm to 500 μm.

2. The porous ceramic structure according to claim 1, characterized in that when the gap between adjacent porous ceramic particles, the gap on the surface in contact with the sheet is da, and the gap on the surface opposite to the surface in contact with the sheet is db, da ≤ db is satisfied.

3. The porous ceramic structure according to claim 2, characterized in that the gap da and the gap db satisfy da < db, and the width between the opposing side surfaces of adjacent porous ceramic particles gradually narrows.

4. The porous ceramic structure according to claim 2, characterized in that the gap da and the gap db satisfy da < db, and the opposing side surfaces of adjacent porous ceramic particles are stepped.

5. The porous ceramic structure according to claim 2, characterized in that the gap da and the gap db satisfy da = db, and the opposing side surfaces of adjacent porous ceramic particles are parallel.

6. The porous ceramic structure according to any one of claims 1 to 5, characterized in that the porosity of the porous ceramic particles is 20% to 99%.

7. The porous ceramic structure according to any one of claims 1 to 5, characterized in that the average pore diameter of the porous ceramic particles is 500 nm or less.

8. The porous ceramic structure according to any one of claims 1 to 5, characterized in that the thermal conductivity of the porous ceramic particles is less than 1.5 W / mK.

9. The porous ceramic structure according to any one of claims 1 to 5, characterized in that The heat capacity of the porous ceramic particles is 1000 kJ / m 3 K or less.

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