Zirconia Sintered Body and Method for Producing the Same

Abstract

To provide a zirconia sintered body having a low monoclinic phase ratio and excellent hydrophilicity, and to provide a manufacturing method of the same.SOLUTION: A zirconia sintered body has zirconia crystal particles having nanopores on the surface thereof.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a zirconia sintered body and a method for manufacturing the same.

Background Art

[0002] Conventionally, as a means for improving the hydrophilicity of a base material used in a water-containing atmosphere, research has been conducted on forming a fine structure on the surface of the base material. As an example of these base materials, a zirconia sintered body having high mechanical strength can be mentioned. It is known that a zirconia sintered body can be directly bonded to bone by osseointegration by forming a fine structure on the surface to improve hydrophilicity. In order to apply it as a biomaterial such as an artificial joint or a dental implant, research has been conducted on forming a fine structure on the surface of the zirconia sintered body.

[0003] Examples of the processing method for forming a fine structure on the zirconia sintered body include a mechanical processing method such as sandblasting or a chemical processing method such as an etching treatment. For example, Patent Document 1 discloses that in a dental implant using zirconia as a base material, a fine structure is formed on at least a part of the outer surface of the anchor portion by a processing method of polishing blast, sandblast, or etching treatment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the processing method of Patent Document 1 has concerns such as a phase transition from the tetragonal phase to the monoclinic phase of zirconia and the adhesion of contaminants generated due to the direct contact of the zirconia sintered body with a machine or the like. It is known that a zirconia sintered body undergoes a phase transition due to the influence of stress, heat, etc. Due to the volume change accompanying the phase transition, there has been a problem that defects such as cracks and fractures occur on the surface and inside of the sintered body, resulting in a decrease in mechanical strength. For this reason, a processing method of a zirconia sintered body capable of suppressing the phase transition to the monoclinic phase by processing has been demanded.

[0006] Therefore, the present disclosure aims to solve the above problems. That is, an object of the present disclosure is to provide at least one of a zirconia sintered body having less phase transition to the monoclinic phase and excellent hydrophilicity and a method for producing the same. [Means for Solving the Problems]

[0007] The present inventors have studied a zirconia sintered body and a method for producing the same. As a result, it has been found that by irradiating the surface of the sintered body with an ultrashort pulse laser under specific conditions, a zirconia sintered body having less phase transition to the monoclinic phase and excellent hydrophilicity can be obtained.

[0008] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] A zirconia sintered body including zirconia crystal particles having nano pores on the surface. [2] The zirconia sintered body according to [1], wherein the average diameter of the nano pores is 10 nm or more and 400 nm or less. [3] The zirconia sintered body according to [1] or [2], wherein the average depth of the nano pores is 50 nm or more and 800 nm or less. [4] The zirconia sintered body according to any one of [1] to [3], wherein the contact angle of water on the surface of the zirconia sintered body is 60° or less. [5] The zirconia sintered body according to any one of [1] to [4], wherein the monoclinic phase ratio in the zirconia sintered body is 10% or less. [6] The zirconia sintered body according to any one of [1] to [5], having debris on the surface. [7] The method for manufacturing a zirconia sintered body according to any one of [1] to [6], characterized by including a step of irradiating the surface of the zirconia sintered body with an ultrashort pulse laser. [8] The method for manufacturing a zirconia sintered body according to [7], wherein the ultrashort pulse laser is an ultrashort pulse laser having a pulse width of 1000 fs or less. [9] The method for manufacturing a zirconia sintered body according to [7] or [8], wherein the ultrashort pulse laser is an ultrashort pulse laser having a laser output of 200 mW or more and 800 mW or less.

Effect of the Invention

[0009] According to the present disclosure, it is possible to provide at least one of a zirconia sintered body having less phase transition to a monoclinic phase and excellent hydrophilicity and a method for manufacturing the same.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an example of an embodiment of the zirconia sintered body of the present disclosure will be described while showing an example.

[0012] (Zirconia Sintered Body) The zirconia sintered body of the present embodiment is characterized by including zirconia crystal particles having nanopores on the surface.

[0013] In the present embodiment, the "zirconia sintered body" is a sintered body having zirconia as a matrix (main phase), and is a sintered body in which the ratio of zirconia (ZrO2) in the total composition of the sintered body is the highest. The zirconia sintered body of the present embodiment preferably has a mass ratio of zirconia (ZrO2) to the mass of the zirconia sintered body (when the zirconia contains a stabilizing element, the total mass ratio of the stabilizing element and zirconia) of 90% by mass or more and 100% by mass or less, or 95% by mass or more and 100% by mass or less, further 95% by mass or more and 99% by mass or less, and still further 99.5% by mass or more and 100% by mass or less.

[0014] The zirconia sintered body of the present embodiment preferably contains a stabilizing element. The stabilizing element is an element having a function of stabilizing zirconia. The stabilizing element is preferably at least one selected from the group consisting of yttrium (Y), scandium (Sc), calcium (Ca), magnesium (Mg), and cerium (Ce), more preferably at least one selected from the group consisting of calcium, magnesium, and yttrium, and still more preferably yttrium.

[0015] The content of the stabilizing element (hereinafter, the content of the stabilizing element such as when the stabilizing element is yttrium is also referred to as "yttrium amount", etc.) is not particularly limited, but since a zirconia sintered body excellent in mechanical strength is easily obtained, it can be exemplified as 1 mol% or more and 6 mol% or less, preferably 1 mol% or more and 5 mol% or less, or 2 mol% or more and 4 mol% or less. As the content of the stabilizing element that particularly increases the mechanical strength, 3 mol% can be exemplified.

[0016] The zirconia sintered body of the present embodiment may contain alumina (Al2O3) and may be composed of zirconia, a stabilizing element, and alumina. The alumina content can be exemplified as 0% by mass or more and 0.2% by mass or less, 0% by mass or more and 0.15% by mass or less, or 0% by mass or more and less than 0.1% by mass. Since the inclusion of a small amount of alumina facilitates sintering, the alumina content can be exemplified as more than 0% by mass and 0.2% by mass or less, 0.005% by mass or more and 0.15% by mass or less, 0.01% by mass or more and 0.12% by mass or less, 0.015% by mass or more and less than 0.1% by mass, or 0.02% by mass or more and 0.07% by mass or less.

[0017] As long as the effect of the zirconia sintered body of the present embodiment is not impaired, it may contain an element having a function of coloring zirconia (hereinafter also referred to as a "coloring agent"). The coloring agent is an element having a function of coloring zirconia and may be an element having a function of suppressing the phase transition of zirconia. Specific examples of the coloring agent include at least one of transition metal elements and lanthanoid rare earth elements, preferably one or more selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), erbium (Er), and ytterbium (Yb); more preferably one or more selected from the group consisting of iron, cobalt, manganese, praseodymium, neodymium, terbium, and erbium; and still more preferably one or more selected from the group consisting of iron, cobalt, and erbium.

[0018] The zirconia sintered body of the present embodiment may contain inevitable impurities such as hafnia (HfO2). The content of hafnia as an inevitable impurity varies greatly depending on the starting materials and the manufacturing method, but for example, it may be 2.0% by mass or less. However, it is preferable that the zirconia sintered body of the present embodiment does not contain elements that have a large impact on the effect of the zirconia sintered body. For example, the zirconia sintered body of the present embodiment satisfies at least one of the following conditions: the content of silicon in terms of silica (SiO2) is 0 mass ppm or more and 500 mass ppm or less, and the content of titanium in terms of titania (TiO2) is 0 mass ppm or more and 500 mass ppm or less. It is preferable that the contents of silicon and titanium are each 0 mass ppm or more and 500 mass ppm or less. In the present embodiment, when calculating values based on the composition such as the content and density, hafnia may be regarded as zirconia for calculation.

[0019] As described above, the zirconia sintered body of the present embodiment includes zirconia crystal particles having nano-pores on the surface. The zirconia crystal particles having nano-pores preferably have pores formed by irradiating the surface of the sintered body with an ultra-short pulse laser described later.

[0020] In the present embodiment, "nano-pores" refer to nano-sized pores, particularly nano-sized pores formed by an ultra-short pulse laser. As a method for "confirming that zirconia crystal particles having nano-pores are provided on the surface", for example, a method of observing the surface of the zirconia sintered body using an electron microscope such as SEM (Scanning Electron Microscope) or TEM (Transmission Electron Microscope) can be mentioned.

[0021] Figures 1 and 2 are SEM images of the surface and cross-section of the zirconia sintered body of Example 1. As shown in Figure 1, it can be confirmed that the zirconia crystal particles 1 on the surface of the zirconia sintered body 10 of the present embodiment have nano-pores 2. In addition, the zirconia sintered body 10 of the present embodiment has debris on the surface. That is, the zirconia sintered body 10 of the present embodiment has debris 3 in which molten zirconia crystal particles generated during laser processing are re-solidified at the opening of the nano-pores 2. Further, as shown in Figure 2, it can be confirmed that only the zirconia crystal particles 1 on the surface of the zirconia sintered body 10 of the present embodiment have nano-pores 2. That is, the ones having nano-pores 2 are limited to only the outermost surface of the zirconia sintered body 10, and nano-pores 2 are not formed in the zirconia crystal particles 1 deeper than the outermost surface. Note that the crystal particles on the outermost surface are crystal particles exposed on the surface of the zirconia sintered body and observable with an electron microscope. Therefore, the zirconia sintered body of the present embodiment has an excellent hydrophilic surface, and the zirconia crystal particles 1 deeper than the outermost surface are not affected by the processing.

[0022] In contrast, in the case of the surface of the sintered body by conventional sandblasting or laser processing with high energy intensity, processing marks are formed across the crystal grain boundaries and inside the sintered body of the zirconia sintered body. This is clearly different from the zirconia sintered body of the present embodiment, which has nano-pores on the surface of the zirconia crystal particles. Also, in the zirconia sintered body of the present embodiment, the nano-pores possessed by the zirconia crystal particles are open pores. This is different from the closed pores (isolated pores) that exist isolated inside the crystal particles. Therefore, if the above characteristics are observed by observing the surface of the zirconia sintered body, the zirconia sintered body of the present embodiment can be clearly distinguished from the conventional sintered body.

[0023] Although not all the mechanisms for obtaining the nano-pores as described above are clear, an example of the presumed mechanism for nano-pore formation will be described. FIG. 3 is a schematic diagram for explaining the mechanism of nano-pore formation. As shown in FIG. 3, when an ultra-short pulse laser is irradiated onto the zirconia sintered body 10 under specific conditions, the laser light is reflected at the grain boundaries of the zirconia crystal particles 1. As a result, a part of the zirconia crystal particles 1 on the surface of the zirconia sintered body absorbs the energy of the laser light and is excited (in (a) in FIG. 3). Next, a high-density plasma is generated by the interaction between the laser light and the bottom side of the zirconia crystal particles 1, and it becomes a high-energy state and voids are formed (in (b) in FIG. 3). The formed voids absorb the laser light and further expand inside the zirconia crystal particles (in (c) and (d) in FIG. 3). Finally, it is presumed that the high-density plasma existing in the voids is discharged to the sintered body surface side of the zirconia crystal particles 1, thereby forming nano-pores 2 (in (e) and (f) in FIG. 3).

[0024] The average crystal grain size of the zirconia crystal particles is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. On the other hand, the average crystal grain size of the zirconia crystal particles is preferably 10 μm or less, and more preferably 5.0 μm or less.

[0025] The average crystal grain size can be determined by the planimetric method using SEM images. That is, draw a circle with a known area on the SEM image, measure the number of crystal grains (Nc) inside the circle and the number of crystal grains (Ni) on the circumference of the circle, and after making the total number of crystal grains (Nc + Ni) be 250 ± 50, the average crystal grain size can be determined using the following formula.

[0026] Average crystal grain size = 2 / {π × (Nc + (1 / 2) × Ni) / (A / M 2 )} 0.5 In the above formula, Nc is the number of crystal grains inside the circle, Ni is the number of crystal grains on the circumference of the circle, A is the area of the circle, and M is the magnification of scanning electron microscope observation (for example, 5000 - 10000 times). When the number of crystal grains (Nc + Ni) in one SEM image is less than 200, (Nc + Ni) may be made 250 ± 50 using a plurality of SEM images.

[0027] The average diameter of the nano - pores is preferably 10 nm or more and 400 nm or less, more preferably 20 nm or more and 200 nm or less, and still more preferably 50 nm or more and 180 nm or less. If the average diameter of the nano - pores is within the above range, it is easy to obtain a zirconia sintered body having an excellent hydrophilic surface. The average diameter of the nano - pores can be measured using an electron microscope and image analysis software. For example, for the SEM image of the surface of the zirconia sintered body and the laser irradiation range using the analysis software ImageJ (ver. 1.52), the region surrounded by the inner peripheral edge of the opening of the crystal grains is regarded as the nano - pores, and the maximum diameter can be determined as the diameter of the nano - pores. By measuring this for all the nano - pores in the image and averaging those values, the average diameter can be calculated. The number of nano - pores to be measured is not particularly limited, but for example, it may be 200 or more and 1000 or less.

[0028] The average depth of the nano-pores is preferably 50 nm or more and 800 nm or less, more preferably 100 nm or more and 700 nm or less. If the average depth of the nano-pores is within the above range, it is easy to obtain a zirconia sintered body having an excellent hydrophilic surface. The average depth of the nano-pores can be measured using an electron microscope and image analysis software. For example, using the analysis software ImageJ (ver. 1.52), for the SEM image of the cross-section of the sintered body (the cross-section perpendicular to the surface of the sintered body) in the laser irradiation range of the zirconia sintered body, from the position of the outermost surface side end of the opening of the crystal grains to the deepest part of the pores, the depth of the nano-pores can be obtained by performing image analysis on the vertical distance. By measuring this for all the nano-pores in the image and averaging their values, the average depth can be measured. The number of nano-pores to be measured is not particularly limited, but for example, it may be 3 or more and 20 or less.

[0029] In addition, in the zirconia sintered body of the present embodiment, grain boundary pores may or may not be present at the grain boundaries which are the boundaries between adjacent crystal grains. When grain boundary pores are present, the average diameter of the grain boundary pores is usually 0.01 μm or more and 0.3 μm or less. Since the nano-pores of the crystal grains in the zirconia sintered body of the present embodiment and the grain boundary pores present at the grain boundaries are located differently, they can be clearly distinguished from each other by electron microscope observation or the like.

[0030] The zirconia sintered body of the present embodiment preferably has a monoclinic phase ratio of 10% or less, more preferably 7% or less, and even more preferably 5% or less. When the monoclinic phase ratio is below the above upper limit value, hydrothermal deterioration of the sintered body hardly progresses, and it can withstand longer-term use as a biomaterial. The monoclinic phase ratio may be 0% or more, and examples thereof include 1% or more, or 2% or more.

[0031] Here, the monoclinic phase ratio (hereinafter, also referred to as "M phase ratio") means that Raman spectroscopic measurement is performed on the zirconia sintered body, and 147 ± 5 cm -1 , 181 ± 5 cm -1 and 190 ± 5 cm -1The peak intensity of each peak having a peak top is obtained, and the value calculated by the following mathematical formula 1 is referred to.

[0032]

Equation

[0033] In the above formula, V m is the M-phase ratio, It(147) is the peak intensity derived from the cubic crystal of 147±5 cm -1 Im(181) is the peak intensity derived from the monoclinic crystal of 181±5 cm -1 Im(190) is the peak intensity derived from the monoclinic crystal of 190±5 cm -1 is the peak intensity derived from the monoclinic crystal.

[0034] Raman spectroscopic analysis can be measured by a microscopic laser Raman spectrophotometer (for example, InVia Raman Microscope manufactured by Renishaw), and the peak intensity in each measurement region can be obtained using analysis software (for example, OriginPro manufactured by lightstone).

[0035] The M-phase ratio of the zirconia sintered body of the present embodiment is preferably obtained by Raman spectroscopic measurement under the following conditions. Laser wavelength: 532 nm Laser beam diameter: 1 μm Measurement wavelength resolution: 0.4 cm -1 Exposure time: 2 to 3 seconds Number of integrations: 1 time Gratings: 1800 and 3000

[0036] The contact angle of the zirconia sintered body of the present embodiment with water is preferably 60° or less, and more preferably 50° or less. Since the zirconia sintered body of the present embodiment includes zirconia crystal particles having nano-pores on the surface, the hydrophilicity of the zirconia sintered body surface is effectively enhanced. Note that, as the lower limit value of the contact angle, 0° can be mentioned, and it can be exemplified that the contact angle is 5° or more or 30° or more.

[0037] The contact angle with water is a value measured based on the droplet method for measuring the static contact angle in an environment at room temperature (for example, 20 to 30 °C). Also, analysis can be performed by using the θ / 2 method. That is, in a temperature environment of 23 °C, a water droplet (purified water) is placed on the sample surface, and for an image taken horizontally with a CCD camera of a stable water droplet 10 seconds after dropping, the contact angle can be measured using the θ / 2 method. The analysis of the contact angle from the taken image can be performed, for example, using a contact angle meter Simage Entry 5 and contact angle calculation software Simage (ver. 5.01) manufactured by Eximer Co., Ltd.

[0038] As described above, the zirconia sintered body of the present embodiment has a low M phase ratio and excellent hydrophilicity, and thus can be suitably used for a base material used in a water-containing atmosphere. In particular, it can be suitably used for a biomaterial such as an artificial joint or an implant that is implanted and directly contacts tissues and body fluids. Also, it can be suitably used for a base material that is not implanted but directly contacts tissues and body fluids, such as an orthodontic bracket. The zirconia sintered body of the present embodiment can be used not only for biomaterials but also for various applications that require hydrophilicity.

[0039] (Method for manufacturing a zirconia sintered body) The method for manufacturing a zirconia sintered body of the present embodiment includes a step of irradiating the surface of the zirconia sintered body with an ultrashort pulse laser. By irradiating the surface of the zirconia sintered body with an ultrashort pulse laser, zirconia crystal particles having the above-described nano pores can be formed.

[0040] Irradiation with an ultrashort pulse laser can achieve surface processing with almost no phase transition to the monoclinic phase of zirconia under specific conditions. The ultrashort pulse laser has a very short pulse width. Therefore, when laser irradiation is performed under specific irradiation conditions, the absorbed heat can be non-thermally scattered (hereinafter also referred to as "ablation") only in the irradiated part without diffusing from the irradiated surface to the inside or the periphery of the surface. As a result, laser processing can be selectively performed on the surface of the zirconia sintered body. Further, under specific conditions, since the influence of thermal energy reaching the periphery of the irradiated part is small, the phase transition of zirconia to the monoclinic phase in the periphery of the irradiated part occurs only in a narrow range compared with mechanical processing such as sandblasting. Thus, the zirconia sintered body of the present embodiment is less affected by the phase transition to the monoclinic phase due to processing and has high mechanical strength. Also, since processing is performed on the zirconia sintered body in a non-contact manner, the influence of adhesion of contaminants through a contact member is significantly suppressed. Further, the ultrashort pulse laser is excellent in directivity and focusing properties, and not only can selectively process only the irradiated part, but also can perform processing with a shallower grinding depth compared with mechanical processing. Therefore, unlike mechanical processing methods, no machining allowance is required for the zirconia dimensions.

[0041] The manufacturing method of the present embodiment can perform processing to form nano-pores only on the outermost surface of the sintered body and not on the zirconia crystal particles deeper than the outermost surface by setting various laser irradiation conditions such as a laser light source (wavelength), repetition frequency, pulse width of the laser, laser output, laser scanning speed, and number of laser scans. Since the zirconia crystal particles deeper than the outermost surface are not affected by the processing, a zirconia sintered body having a hydrophilic surface can be obtained without impairing the mechanical strength of the entire zirconia sintered body. An example of suitable laser irradiation conditions in the manufacturing method of the present embodiment will be described below.

[0042] The laser light source of the ultrashort pulse laser is preferably a titanium sapphire laser (wavelength: about 0.8 μm) or a laser of ytterbium (wavelength: about 1 μm). Alternatively, a wavelength tunable femtosecond pulse light source by a parametric amplification device based on a nonlinear wavelength conversion process may be used. The wavelength of the ultrashort pulse laser is not particularly limited. The wavelength of the ultrashort pulse laser may be, for example, a wavelength within the range of the ultraviolet region to the near-infrared region, and can be appropriately selected from 200 nm or more and 2500 nm or less.

[0043] The laser output is preferably 200 mW or more and 800 mW or less, and more preferably 400 mW or more and 750 mW or less. Also, the pulse width of the laser is preferably 10 -15 seconds or more and 10 -12 seconds or less. If the laser output and the pulse width of the laser are within the above ranges, the energy density can be appropriately suppressed, and it becomes easier to ablate only the surface of the zirconia sintered body. As a result, it is easy to obtain nano-pores having the desired shape, and it is easy to obtain a zirconia sintered body having a low monoclinic phase ratio.

[0044] The repetition frequency is preferably 20 Hz or more and 300 kHz or less. The number of laser scans is preferably 1 or more and 5 or less at the same position in order to form nano-pores having a suitable average depth. If the number of laser scans is 5 or less, it is easy to obtain a sintered body having a low monoclinic phase ratio. The laser scanning speed is preferably 200 mm / s or more and 4000 mm / s or less. If the scanning speed is within the above range, the processing accuracy and production efficiency are excellent.

[0045] The laser irradiation method may be a method in which continuous irradiation is performed at the same position and then movement is performed, or a method in which continuous irradiation is performed at the same position while slightly moving with respect to the irradiation beam diameter.

[0046] The zirconia sintered body to be irradiated with the ultrashort pulse laser is not particularly limited, and for example, those having conventionally known physical properties such as particle diameter, density, and composition can be used, and can be manufactured by conventionally known methods. For example, when the zirconia sintered body contains a stabilizing element, a manufacturing method including a molding step of molding a mixed powder containing a zirconia raw material and a stabilizing element raw material to obtain a molded body, and a sintering step of sintering the obtained molded body to obtain a sintered body, etc., can be used to manufacture a zirconia sintered body for laser irradiation.

[0047] In the molding step, a mixed powder containing a zirconia raw material and a stabilizing element raw material is provided. If the zirconia raw material and the stabilizing element are uniformly mixed, the manufacturing method of the mixed powder is arbitrary and can be either wet mixing or dry mixing. Since the uniformity of the obtained mixed powder is higher, the mixing method is preferably wet mixing, more preferably wet mixing by at least one of a wet ball mill and a wet stirring mill.

[0048] The zirconia raw material is zirconia or its precursor, and examples thereof include zirconia powder having a BET specific surface area of 4 m 2 / g or more and 20 m 2 / g or less.

[0049] The stabilizing element raw material is preferably a powder of a compound containing at least one selected from the group consisting of yttrium, scandium, calcium, magnesium, and cerium, and preferably includes a powder of a compound containing yttrium or its precursor. Furthermore, in addition to or instead of the zirconia raw material and the stabilizing element raw material, a zirconia raw material in which the stabilizing element is dissolved, for example, yttrium-stabilized zirconia powder, may be used.

[0050] In the molding step, the mixed powder is molded to obtain a molded body. The molding method is arbitrary as long as a molded body having a desired shape is obtained. Examples of the molding method include at least one selected from the group consisting of press molding, injection molding, sheet molding, extrusion molding, and casting molding, and it is preferably at least one of press molding and injection molding.

[0051] The shape of the formed body is arbitrary. Examples of shapes other than dental implant shapes include disk shapes, columnar shapes, polyhedral shapes, and any shape according to the purpose and application, such as orthodontic brackets, artificial joints, semiconductor manufacturing jigs, and other complex shapes.

[0052] The sintering method in the sintering process is arbitrary. As the sintering method, for example, at least any one selected from the group of atmospheric pressure sintering, pressure sintering, and vacuum sintering can be mentioned, and atmospheric pressure sintering and pressure sintering are preferable. The heating temperature in the sintering process is arbitrary.

Examples

[0053] Hereinafter, the present disclosure will be specifically described by way of examples and comparative examples. However, the present disclosure is not limited to the examples.

[0054] (Measurement of average crystal grain size) The average crystal grain size of the zirconia sintered body was determined by the planimetric method using SEM images. As the measurement sample, a zirconia sintered body with a surface roughness of Ra ≦ 0.02 μm, which was treated in the air at a temperature 50 °C lower than the sintering temperature, was used, and SEM observation was performed at a magnification (5000 - 10000 times).

[0055] A circle with a known area was drawn on the obtained SEM image, and the number of crystal particles (Nc) inside the circle and the number of crystal particles (Ni) on the circumference of the circle were measured. After making the total number of crystal particles (Nc + Ni) 250 ± 50, the average crystal grain size was determined using the following formula. Here, A is the area of the circle, and M is the magnification of scanning electron microscope observation. Average crystal grain size = 2 / {π × (Nc + (1 / 2) × Ni) / (A / M 2 )} 0.5

[0056] (Measurement of average diameter and average depth of nano - pores) The average diameter and average depth of the nano - pores were measured by image analysis using a scanning electron microscope (SEM) and image analysis software (ImageJ (ver.1.52)). The average diameter of the nano-pores was determined by image analysis. For the SEM images of the sintered body surface and the laser irradiation range, the region surrounded by the inner peripheral edge of the opening of the crystal grains was defined as the nano-pores, and the maximum diameter was taken as the diameter of the nano-pores. The average value was calculated by measuring all the nano-pores in the image and averaging their values. The number of nano-pores measured was 301 in Example 1 and 855 in Example 2. The average depth of the nano-pores was measured by image analysis of the vertical distance from the position of the outermost surface side end of the opening of the crystal grains to the deepest part of the pores for the SEM image of the cross-section of the sintered body (a cross-section perpendicular to the sintered body surface) in the laser irradiation range of the sintered body. The average depth of the nano-pores was measured by measuring all the nano-pores in the image and averaging their values. The number of nano-pores measured was 8 for both Example 1 and Example 2.

[0057] (Measurement of contact angle) The contact angle with water was measured using the θ / 2 method for an image of a stable water droplet after 10 seconds of dropping, which was taken horizontally with a CCD camera after dropping a water droplet (purified water) onto the surface of the zirconia sintered body in a temperature environment of 23°C. The measurement of the contact angle was performed using a contact angle meter Sim age Entry 5 and contact angle calculation software Sim age (ver. 5.01) manufactured by Exima Co., Ltd.

[0058] (Measurement of monoclinic phase ratio) The monoclinic phase ratio refers to the value calculated by performing Raman spectroscopic measurement on the surface of the zirconia sintered body, obtaining the diffraction intensities of the (111) and (11 - 1) planes of the monoclinic phase, the (111) plane of the tetragonal phase, and the (111) plane of the cubic phase, respectively, and using the following mathematical formula.

[0059] [Equation]

[0060] In the above formula, V m is the M phase ratio, It(147) is the peak intensity of the tetragonal phase derived from 147 ± 5 cm -1 and Im(181) is the peak intensity at 181 ± 5 cm -1The peak intensity derived from the monoclinic crystal and Im(190) are 190 ± 5 cm -1 and are the peak intensities derived from the monoclinic crystal.

[0061] Raman spectroscopic analysis was measured using a microscopic laser Raman spectrophotometer (Renishaw InVia Raman Microscope). The peak intensity in each measurement region was determined using analysis software (for example, OriginPro manufactured by Lightstone).

[0062] The conditions for Raman spectroscopic measurement are shown below. Laser wavelength: 532 nm Laser beam diameter: 1 μm Measurement wavelength resolution: 0.4 cm -1 Exposure time: 2 - 3 seconds Number of integrations: 1 time Gratings: 1800 and 3000

[0063] (Example 1) As the raw material powder, 3 mol% yttrium-stabilized zirconia powder (trade name; TZ-3YS, manufactured by Tosoh Corporation, average particle size 0.3 μm, surface area 7 m 2 / g) was used.

[0064] (Production of the primary sintered body) After the raw material powder was molded by a die press at a pressure of 50 MPa, it was further CIP molded at a pressure of 200 MPa using a cold isostatic pressing (hereinafter referred to as "CIP") apparatus to obtain a flat molded body with dimensions of 30 mm × 30 mm and a thickness of 5 mm.

[0065] The obtained flat molded body was placed in an alumina container and fired (primary sintering) to obtain a zirconia sintered body (primary sintered body).

[0066] For the primary sintering, the temperature was raised from room temperature to 1500 °C at a heating rate of 100 °C / hour in the atmosphere, held at the sintering temperature of 1500 °C for 2 hours, and then cooled to room temperature at a high temperature rate of 100 °C / hour.

[0067] (Fabrication of HIP-treated body) A zirconia sintered body (primary sintered body) obtained by sintering in the atmosphere was HIP-treated to obtain a HIP-treated body. The obtained HIP-treated body was used as the zirconia sintered body of this example.

[0068] The HIP treatment conditions were a temperature of 1350 °C, a HIP pressure of 150 MPa, and a holding time of 1 hour. Note that argon gas with a purity of 99.9% was used as the pressure medium, and the sample was treated using an alumina sealed container.

[0069] The obtained zirconia sintered body was irradiated with an ultrashort pulse laser under the laser irradiation conditions shown in Table 1, and the average diameter and average depth of the nano-pores, the contact angle, and the M-phase ratio were measured. The results are shown in Table 1. Also, SEM images of the zirconia surface of Example 1 after laser irradiation are shown in FIGS. 1 and 2.

[0070] (Example 2) The average diameter and average depth of the nano-pores, the contact angle, and the M-phase ratio were measured in the same manner as in Example 1, except that the laser irradiation conditions were changed to the conditions shown in Table 1. The results are shown in Table 1.

[0071] (Comparative Example 1) The contact angle and the M-phase ratio were measured in the same manner as in Example 1, except that ultrashort pulse laser irradiation was not performed. The results are shown in Table 1. In Table 1, "-" indicates that the measurement was not performed.

[0072] (Comparative Example 2) The contact angle and the M-phase ratio were measured in the same manner as in Example 1, except that the laser irradiation conditions were changed to the conditions shown in Table 1. The results are shown in Table 1. In Table 1, "-" indicates that the measurement was not performed.

[0073]

Table 1

[0074] From the measurement results of the sintered bodies of Examples 1 and 2, it can be confirmed that the sintered body of the present embodiment has a low monoclinic phase ratio, the phase transition to the monoclinic phase is suppressed, and it has excellent hydrophilicity. On the other hand, it can be confirmed that the sintered body of Comparative Example 1 without ultrashort pulse laser irradiation has a high contact angle and low hydrophilicity. Also, although ultrashort pulse laser irradiation was performed, it can be confirmed that the sintered body of Comparative Example 2 in which nano-pores were not formed has excellent hydrophilicity but a large monoclinic phase ratio. The laser irradiation conditions of Comparative Example 2 have a higher energy intensity on the zirconia sintered body compared to the conditions of Examples 1 and 2. For this reason, it is presumed that even the zirconia crystal particles deeper than the outermost surface were thermally affected by ablation, resulting in a high monoclinic phase ratio.

Explanation of Signs

[0075] 1…Zirconia crystal particle, 2…Nano-pore, 3…Debris, 10…Zirconia sintered body, 11…Laser light, 12…Excitation part, 13…Grain boundary reflection, 14…High-density plasma, 15…Void, 16…Laser light absorption, 17…Void expansion, 18…Plasma discharge

Claims

1. A zirconia sintered body comprising zirconia crystal particles having nano-pores on the surface and having debris on the surface.

2. The zirconia sintered body according to Claim 1, wherein the average diameter of the nano-pores is 10 nm or more and 400 nm or less.

3. The zirconia sintered body according to Claim 1 or 2, wherein the average depth of the nano-pores is 50 nm or more and 800 nm or less.

4. The zirconia sintered body according to any one of Claims 1 to 3, wherein the contact angle of water on the surface of the zirconia sintered body is 60° or less.

5. The zirconia sintered body according to any one of Claims 1 to 4, wherein the monoclinic phase ratio in the zirconia sintered body is 10% or less.

6. The zirconia sintered body according to any one of Claims 1 to 5, wherein the average crystal grain size of the zirconia crystal particles is 0.1 μm or more and 10 μm or less.

7. A method for manufacturing a zirconia sintered body according to any one of Claims 1 to 6, comprising a step of irradiating the surface of the zirconia sintered body with an ultrashort pulse laser.

8. The method for manufacturing a zirconia sintered body according to Claim 7, wherein the ultrashort pulse laser is an ultrashort pulse laser having a pulse width of 1000 fs or less.

9. The method for manufacturing a zirconia sintered body according to Claim 7 or 8, wherein the ultrashort pulse laser is an ultrashort pulse laser having a laser output of 200 mW or more and 800 mW or less.

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