TW442447B - Method for producing zirconia suspension and high density sintered body - Google Patents

Abstract

The present invention discloses a well-dispersed neutral or weak alkaline suspension containing sub-micron zirconia powder, and a method for making the same. The sub-micron zirconia powder contains 2 to 5 mole % of yttrium oxide. The suspension contains a neutral to weak alkaline aqueous solution. A ultrasonic or ball milling process is used to mix the abovementioned powder and solution, thereby obtaining a solid volume fraction of 0.1 vol% to 45 vol% (solid weight fraction of 5.7 wt% to 83.1 wt%) of a dispersed suspension liquid. The present invention also discloses a forming method of using the abovementioned stable dispersed suspension, through sedimentation, centrifugation or gas pressure filtration, to produce a high density ceramic blank which is used to be sintered into a ceramic with high density, high strength and good strength reproducibility.

Description

442447

V. Description of the invention α) The present invention 1 relates to a suspension containing submicron oxidation errors: a suspension with good hygienic dispersion ... making such a suspension and floating suspension = cost invention and does not use the above-mentioned stable dispersion suspension, or gas The filter press forming method 'produces high-density ceramic research chains, two: raw sintering produces high density, high strength, and strength manufacturing methods. 1 Good pottery is free from the company's strength and good toughness. 'It has been widely used in m structure and abrasion resistance in the past, such as fiber optic connectors, knives, artificial bones, and stretch eye molds. The application uses the material's phase transformation and toughening properties. It has a very good absorption capacity for external stress damage, so wear-resistant applications at room temperature or applications with high-strength structures. The higher purity of the oxide file material is to achieve oxidation errors. The effect of phase transformation is to add magnesia, calcium oxide, cerium oxide, yttrium oxide, or a mixture of these oxides to the oxide to maintain the tetragonal phase of the oxide to room temperature. The phase is a metastable state 'only under the action of stress or thermally triggered, the so-called "Matian loose iron" phase transition occurs, that is, the tetragonal phase is transformed into a monoclinic phase, but the resulting phase is toughened.' Make zirconia have very high toughness [Readey, Heuer and Steinbrech, J. Am. Ceram.

Soc, ’71 [1], C-2, (1988)], this type of oxidation is partially stabilized zirconia with the addition of magnesium oxide.

Zirconia (abbreviated as psz). Another series of zirconia is represented by a tetragonal phase oxide junction containing yttrium oxide, which is called Tetragonal Zirconia Polycrystals

C: \ Progratn Files \ Patent \ 〇231-3853-E.ptd page 4 442447 5 'Invention Description (2) (referred to as TZP), with high strength features, its microstructure is composed of sub-micron square grains If the yttrium oxide content in the composition is unevenly distributed, cubic grains of large grains will often be formed, and the strength of TZP will be reduced accordingly. Y. Imanshi, M. Matsui in his patent [US patent 4'610, 967] uses two phase stabilizers, one is yttrium oxide, and the other is oxide 'with a tetragonal phase with a high ratio of 4 to. Dransfield and King [US Patent 5, 336, 521] use liquid phase plating to deposit phase-stabilizing components such as yttrium oxide, alkaline earth metal oxides or rare earth oxides on the surface of the powder. Surface-polished zirconia samples are stronger than other types of hafnium oxide. When submicron ceramic powder is used as the raw material for the process, finer particles can be obtained, but the relative surface area of the powder is high, and the surface force is also increased, so the phenomenon of agglomeration is more serious. Comparing various ceramic process technologies' found that the high-strength ceramics obtained with the gel process can obtain higher strength [Neil and Pasto, Advanced Ceram. Mat., 3 [3] 225-230 (1988)], which can be attributed to This process can effectively remove agglomerates formed between particles [Halloran, pp. 40 7-417 in U1trasructure Processing of Ceramics, Glass and composites, 1984]. The agglomeration of powder particles in the mud often causes poor accumulation of the green body, which has a significant negative impact on subsequent processes and results [Aks ay et al.t Am. Ceram. Soc., 66 [10] C190-C192 (1983)] For example, the porosity is high, the shrinkage is uneven, and the strength is low, which further affects the microstructure and mechanical properties of the sintered body. Therefore, how to effectively remove the agglomerated powder and obtain a uniform green body will be a colloidal particle process (c0 1 〇 da 1

in I C: \ Program Files \ Patent \ 0231-3853-E.ptd page 5 44244 7 V. Description of the invention (3) 'processing) is the most important subject. Generally speaking, by adding a dispersant or controlling the pH value, electrostatic repulsion, steric hindrance, or a combination of the two effects can be produced between the colloidal particles, thereby achieving a well-dispersed slurry. Oxidation # produces an electrical double layer due to surface chemical reactions in an aqueous solution, and its iso-electric point (iep) is approximately between 4-8 according to different reports. In the declarative aqueous solution, because the surface of the oxidized surface has little or close charge balance, the potential between the particles can be too small to provide sufficient electrostatic repulsion to achieve stable dispersion of the particles. Therefore, in the past literature [Obitsu et al., US patent 5, 223,176, 1993] [Kaga et al. US patent 5,643 497 1 997] uses strong acidic or highly alkaline aqueous solution as the dispersion ultrafine (5 ^ IHQ ) The carrier of zirconia powder is based on the principle that it is far away from "卩", so that the surface of the oxidized rubber particles has a high potential energy, which can produce a stable dispersion effect in the solution. In addition to the use of inorganic acids or Alkali is used for the preparation of strong acid or strong aqueous solution '. Organic acids or organic bases can also be used [〇bitsu e, al., US patent 5'2 23,176, 1 93], or a single molecule of organic acid is used. And resynthesize polymer acid agents [Bogan, US patent 5'380'782 'and US patent 5,532,307]. The amount of these acid testers can be as high as 5-50%.' However, the use of strong acid or strong alkali solution will have engineering applications. Corrosion problem * And strong acid solution will gradually deviate due to the addition of tritium phase stabilizers, such as oxidation ball, oxidized period, or oxidized decoration. Finally, the stability of the particles in the suspension will be deteriorated. The powder agglomerates, this Many follow-up applications have negative effects: ΙΜΜ1ΗΗ C: \ Prc ^ ram Files \ Patent \ 0231-3853-E. Ptd No. 6 ϊ " " 442 44 7 V. Description of the invention (4) Impact. Oxidation with different solid content The surface potential of the zirconium suspension will be changed by the pH value. This phenomenon is similar to most oxides. The oxidized sawdust particles in aqueous solution are positively charged surface in acidic solution (pHCiep), and in alkaline solution (pH >; iep) presents a negatively charged surface. However, according to past research reports, the iep value of the oxidized oxide suspension is about 5.4, but the added oxidized oxide powder will increase to 8.1, and the changed The measurement will be affected by the content of the oxidized powder in the suspension. Yasrebi et al. [J. Am.

Ceram. Soc., 79 [5] 1 2 23-27 (1 996)] has previously proposed that yttrium oxide will dissociate positively charged ions γ3 +, y2 (oh) 2 4+, Y in alkaline aqueous solution. (0H) 2+ 'reduces the hydroxide in water, so compared to the low solid content zirconia suspension, if you want the higher solid content suspension to reach the i ep point', you need to provide additional hydroxide, so The iep point moves towards higher pH values. Zirconia suspensions have begun to be used in the field of chemical polishing (chemi cal polishing). The zirconia used is mainly produced by gas-phase reaction or the technology of solution chemical dissolution and precipitation to produce fine particles. The characteristics of these powders It has a monoclinic phase, high surface area (up to 200m2 / gm), small particle size (down to 10nm), and the suspensions made are mostly acidic (pH < 6) 'suspension The solid content of the particles in the liquid is less than 50 wt% (about equal to 14¾ volume content). Because such fine-grained zirconia particles are too fine, there has been research on the use of electrophoresis (e 1 e t rophore s is) technology to make thin films or thin film composites on general substrates [Sarkar and Nicholson, J. Am.

Ceram. Soc., 79 [8] 1 9 87-2002, 1 996], but not suitable for manufacturing

C: \ ProgramFUes \ Patent \ 0231-3853-E.ptd page 7 442447 V. Description of the invention (5) Made of sintered body of high density zirconia. In view of this, the main object of the present invention is to provide a method for preparing a well-dispersed oxidation suspension, which is particularly suitable for the case where a zirconia powder containing yttria is made into a suspension with a high powder solid content (50% by weight). 'And a method for manufacturing a high-density ceramic green body by using such a stably dispersed zirconia suspension, and then sintering the green body to produce a ceramic material with high density, high strength, and good reproducibility of strength. In the above, the oxidized sub-micron powder contains a yttrium oxide component in the range of 2 to $ mole, and the pH of the suspension is medium to weakly alkaline (pH 6 9). Adjust, the method of this dispersion is to use an effective dispersant, add this dispersant in the aqueous solution (0.1 to 5.0%), to maintain the aqueous solution between neutral to weak base. After ball milling (or ultrasound), the mixed solution and the solid volume fraction of the waiting solid are dispersed from 0. 45% (solid weight fraction # 1 1%), and the solid volume fraction is preferably-^ 3. (Solid The weight fraction is 66176, W. "Production of high density, high strength and strength. The present invention also discloses a series of stable and dispersed oxidized hammer suspensions that are shaped and sintered. After natural settlement, gas pressure filtrati ) Step " A method of uniformly producing the body and sintering the green body to produce a high-density, reproducible ceramic block. The advantages of using this process include: 1. The use of high-purity zirconia powder, due to its high surface texture Faster speed 'easy to obtain higher density and thinner' value will also be higher; intensity

442447 V. Description of the invention (6) 2 Both the settlement density obtained from the well-dispersed YTZP zirconia suspension using appropriate neutral or weakly basic dispersants and the density of the raw embryonic chain bodies obtained by centrifugation It is higher than other samples; 3. The zirconia material with the highest green density and sintered density can be obtained by optimizing the solid content of the suspension liquid and the amount of dispersant added; In addition to reducing the time required for filter press, the zirconium green body can also reduce the disadvantages of particle size separation produced by mud slurry during filter press; 5. Using the filter press forming process, it is possible to produce embryos with more complex shapes and uniform texture; 6. It can sinter high temperature (> 99, 5% TD), high-strength YTZP zirconia material at a temperature between 1 400 ° C and 1 500 ° c. In order to make the above and other objects, features, and advantages of the present invention more obvious and easy, only the preferred embodiments are described below, and in conjunction with the accompanying drawings, the detailed description is as follows: Brief description of the drawings FIG. 1 · Shows the green density value of a green body made of zirconia slurry containing 25 ~ 33% volume solids content and adding 1.0 to 4.0 wt% A6 dispersant. Figure 2 shows the sintered density and grain size of YTZP after being oxidized by the colloidal granulation process or dry pressing process and sintered at 1400 ° C ~ 16 0 ° C. Detailed description of preferred embodiments In the following examples and comparative examples of the present invention, TZ-3Y zirconia powder ceramic powder (YTZP powder) produced by Japan Tosoh Company is used. Its specific surface area (BET surface area) is 15.7 raVg, crystal

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I 442447 V. Description of the invention (7) Size 2 7. 5 nm 'Average particle size 0.3 / zm, containing yttrium oxide (Υ203) phase stabilizing component 5.07wt%' Other impurities include aluminum halide ( Α 1203) < 0.005wt% 'silicon oxide (SiO2) < 0.002wt%, iron halide (Fe203) < 0.02 0wt%' sodium oxide (Na20) is 0.023wt%. Comparative example one uses pure water with a resistance value greater than 15 moh m-cm, and adjusts the pH value of the aqueous solution with reagent-grade NaO Η or HC1 chemical solution. The ρ is 10. 1 + 0.1, 6.8 + 0.1 and 3.3 + 0.1 'is called 1 ^, and then the aforementioned ¥ 72? Powder is added to the acid or alkaline solution in three volume percentages (ν〇ι%) of 0.03, 0.1, and 1.0.' Using hot-pressed oxidized honing balls, After ball milling for 2 hours and aging for 30 minutes, the pH of the suspension was measured and called pHf. In the acidic aqueous solution, the value of ρ ， does not change much, but in the aqueous solution of alkali (mouth 11 = 10.10) and strong acid (1) 11-2 3.23), the addition of γ 72? Will make the pH of the solution tend to be neutral, and With the increase of 3Υ-ΤΤΡ powder, the pH value of the solution changes more significantly, and the above-mentioned phenomenon of acidification is related to the dissociation of the oxidized period contained in hafnium oxide. (PH = 6.5) 'Because of the addition of zirconia powder, the pH value of the solution will change' Relatively, the surface chemical properties of zirconia will also change.

C: \ Program Files \ Patent \ 0231-3853-E.ptd page 10 442447 V. Description of the invention (8) Table 1 Changes in pH value (ΔρΗ) of the solution with different amounts of 3Y-TZP powder added vol% pH *. PH £ ApHt-〇.l) 0.03 3.23 3.26 0.03 0.1 3.23 3.47 0.24 to 1.0 3.23 4.80 1.57 0.03 6.76 6.84 0.08 0.1 6.76 7.22 0.42 to 1.0 6.76 7.11 0.35 — 0.03 10.13 9.83 -0.3 to 0.1 10.13 8.88 -1.25 1.0 10.13 8.08- 2.05 ~ Comparative Example 2 The TZZP zirconia powder in Comparative Example 1 was used. Five chemical dispersants in Table 2 were used, and the zirconia suspension was added to the 'chemical dispersant addition amount based on the quality of TZZP powder'. 0.25 '0.5, 1.0, 2.0 or 4.0 weight percent (wt%). The prepared zirconia suspension was added to a zirconia grinding ball, and after 18 hours of grinding, it was sieved with a 150-mesh sieve. The sieved mud was slowly poured into a 25ml graduated cylinder, and the seal was left to stand for 40 days. The pH of the liquid in the three preparation stages was measured including an aqueous solution containing a chemical agent, a suspension containing powder and ground and sieved, and a suspension standing for 40 days. The results are shown in Table 3. Among them, A5 reagent has the largest change in the pH value of the aqueous solution before and after adding YTZP powder, which will change from weak test (PH = 8. 4) to weak acidity (pH = 5.48 or 6.47). ΔρΗ) are all between + 0.2 ', the change is not large.

C: \ Program Files \ Patent \ 023 Bu 3853-E.ptd Page 11 442447 V. Description of the invention (9) Table 2 Five chemical dispersant codes Function keys (organofunctionality) Solute 2% aqueous solution Ph value Manufacturing companies and products Specifications A1 amino group 2-butoxyethanol / ethylene glycol 5.0 Chartwell Intemation, Inc., USA, 515.1 A2 amino group ethylene glycol 8.5 Chartwell Intemation, Inc., USA, 515.4 A3 oxygen carbon group (Carboxyl group) 2-butoxyethanol / ethylene glycol 5.0 Chartwell Intemation, Inc., USA, 525.1 A4 * Hydrocarbon group 2-butoxyethanol / ethylene glycol 4.6 Chartwell Intemation, Inc., USA, 535.1 A5 ** acid group (carboxylic acid) Water 8.0 RT Vanderbilt Comp., Inc. USA, Darvan C • A4 * Used as a dispersant for oxidized oxide / oxidized composite powder [R Yoshimatsu ^ A. Osaka, T.

Yabuki and H. Kawasaki, Materials Letters, Vol. 4, no. 10,426-428 (1986)] ° • A5 has been used as a dispersant for dispersing 3Y-TZP [W. Huisman, T. Graule and LJ Gauckler, ^ Centrifugal slip casting of zirconia (TZP), J. Europ. Ceram. Soc., 13 (1994) 33-39] C: \ ProgramFiles \ Patent \ 0231-3853-E.ptd page 12

442447 V. Description of the invention α〇) Table 3 The three modulation stages of the rhenium oxide suspension with different chemical dispersants are added. The change in pH value is divided into dispersive dose powder steps. 0.25% by weight 0.5% by weight 1% by weight 2% by weight 4% by weight 4.74 4.68 4.55 4.51 4.46 A1 with added powder 5.15 4.84 4.81 4.51 4.39 after settling for 40 days 5.11 5.06 4.99 4.81 4.65 without added powder 6.53 6.51 6.44 6.52 6.73 A2 with added powder 5.31 5.42 5.76 6.33 6.77 after settling for 40 days 5.27 5.15 5.65 6.44 6.71 without powder 4.93 4.81 4.60 4.47 4.34 A3 powder added 5.07 5.04 4.80 4.37 4.21 after settling for 40 days 5.09 4.99 4.84 4.58 4.51 without powder added 5.04 4.97 4.62 4.43 4.22 A4 added for powder 4.88 4.96 4.83 4.78 4.63 40 days after settled 5.18 5.24 5.03 4.82 4.59 without powder 8.40 8.42 --A5 added powder 5.48 6.47---5.97 6.50 after 40 days sedimentation--

C: \ ProgramFiles \ Patent \ 0231-3853-E, ptd page 13 p 442447 V. Description of the invention (11) The aforementioned sample of 40 days of sedimentation 'measures the accumulation height (Hf) and sedimentation of sedimentary sludge below the sedimentation tube. The former mud height (H.) ratio (Hf / H.), The results obtained are shown in Table 4, where the ratio of the settlement height of A5 and A2 is significantly higher than the other three agents, and the dispersion of A5 and A2 in YTZP at t The effect is not good, the other three have scattered effects. Table 4 Settling ratio of zirconia powder (γτζρ) with different chemical dispersants Dispersant dispersant dosage (wt%, based on powder JK mass) 0.25 wt% 0.5 wt% 1.0 wt% 2.0 wt% 4, 0 wt% A1 0.12 0.104 0.1 0.112 0.12 A2 0.096 0.096 0.28 0.456 0.32 A3 0.096 0.112 0.12 0.112 0.12 A4 0.14 0.128 0.136 0.136 0.128 A5 0.52 0.52---Example 1 uses the suspension preparation method in Comparative Example 2 to increase the amount of powder in the suspension. The solid content is '25 to 35 volume percent. In addition, a weakly basic polymer dispersant, called A6 dispersant (Dai-Ichi Kogyo Seiyaku Co., Ltd., Japan, product specification D-134, functional bond is acid group "Ammonia salt electrolyte dispersant)" First, add the chemical dispersant to pure water in accordance with the weight percentage of YTZP powder, add zirconia grinding balls, and grind it for 4 to 24 hours. Shimadzu, Japan), the effective average particle size of the particles in the suspension was analyzed, and the results obtained are shown in the table

C: \ ProgramFiles \ Patent \ 023 Bu3853-E.ptd page 14 442447 V. Description of the invention (12) 5. The results show that grinding and mixing for more than 18 hours can effectively disperse the particles in YTZP, so the average particle size displayed can reach a stable value. Table 5 Particle size and distribution of suspensions with different solid contents after grinding and dispersing at different times Solid content 25 vol% 28 vol% 30 vol% 35 vol% Particle size (; um) dso d90-dlO ^ 50 d9〇-di〇 ^ 50 d9〇-di〇d $ 〇dgo-dio 4-hour grinding 0.95 2.03 0.97 2.5 0.87 1.81 0.97 2.36 8-hour grinding 0.78 1.74 0.80 1.8 0.84 1.88 0.86 1.64 12-hour grinding 0.69 1.38 0.69 1.71 0.81 1.68 0.73 1.81 16-hour grinding 0.69 1.38 0.63 1.45 0.71 1.52 0.66 1.61 20-hour grinding 0.56 1.2 0.58 1.29 0.65 1.22 24-hour grinding 0.43 1.08----_ Example 2 uses the suspension preparation method in Example 1, using two chemical dispersions One is used in Example 1), and the other is the acidic organometallic dispersant (A1 dispersant) used in Comparative Example 2. First, the chemical dispersant is dispersed in pure water at 2% by weight of the YTZP powder weight percentage. Then, the powder is mixed into a solid-liquid ratio of 3 v ο 1%, and zirconia grinding balls are added, and after 8 hours of grinding and sieving, the sieved suspension is settled in a sedimentation tube for 40 days, and the suspension is used. Neat liquid, Shang-speed centrifuge (Z380, HERMLE, Germany), the rotational speed of 5000 rpm, a relative centrifugal force of about 4500G, were centrifuged 13 minutes, settling of the particles from settling equivalent to stand for 40 days, measured green density plot of the underlying stack. The stacked green body after sedimentation and centrifugation is dried at 105 ° C for one day to complete

C: \ ProgramFiles \ Paten1A023 Bu 3853 ~ E.ptd page 15 442447 V. Description of the invention (13) Drying steps. The dried raw chain was coated with a waterproof film on its surface, and the apparent density was calculated using Archimedes' method. The results are not shown in Table 6. Table 6 Settling ratio of two kinds of chemical dispersants and green density value Type of chemical dispersant added Hf / H0 Relative density of green body after sedimentation * (%) Relative density of green body after centrifugation * (%) A1 13.2 % 41.8 43.7 A6 5.6% 42.8 46.4 * The theoretical density of YTZP is 6.03g / cm3. After 40 days of sedimentation and centrifugation, the wet billet has a significant difference in sedimentation height ratio and relative density of raw chains. Adding 2wt% of 46 dispersant in the suspension has good dispersion between the powders, and the upper end of the sedimentation cylinder is still turbid, making the thickness of the sedimentary embryo relatively thin (5 6%). The thickness is relatively thick (13.2%). Regardless of natural settlement or centrifugal settlement, the green density of the A6 dispersant is better than that of A1, which also proves that A6 can achieve better dispersion effect, so the sedimentation rate is slow and the embryo body is more dense. In addition, the green body prepared by the centrifugation method has a faster settling speed and a higher green body density. '' Example 3 uses two different chemical dispersants in Example 2 ^ and ", formulating suspensions of oxide files with different dispersant contents, and directly placing YTZP osmium oxide powder into two aqueous solutions without chemical dispersants, These two aqueous solutions use reagent-grade NaOΗ or HC 1 chemical liquid, and adjust the acidity of pure water to 〇〇〇 or

C: \ Program Files \ Patent \ 0231-3853-E.ptd page 16 442447 V. Description of the invention (14) 2.0. The above six suspensions are made into a raw chain by a gas pressure method. The first step is to pour the mud into a hollow circular acrylic mold. The bottom of the mold is a porous copper-based filter copper mesh. The general filter paper is placed on the copper mesh, sealed, and then pressure-filtered at a pressure of 10 kg / cm2. Forming. After a period of time, a mud cake having a diameter of 2.5 cm 'and a thickness of about 0.5 cm can be obtained. Put the acrylic mold on the gypsum board together with the mud cake and let it dry naturally. After drying, it will shrink slightly. After one day of dry in the shade, it was dried at 105C for one day, and the obtained field was used to measure the density of the green chain. The dried green body is placed in a high-temperature sintering furnace, and the temperature is increased to 1480 ° C per minute, and the temperature is maintained for one hour. After the furnace is cooled, the sample is taken out, and the sintering density is measured by the Archimedes method. The results are shown in Table 7. In Table 7, the density of the green body and sintered body made by adding the suspension of A6 dispersant was the highest, which were 53.4% and 99.7%, respectively. Table 7 Density dispersant and dosage of YTZP oxide sintered green body and sintered body with different dispersants and added amounts Green density (g / cm2) Sintered density (%) A6, 1.0 wt% 50.7 99.6 A6, 2.0 wt% 53.4 99.7 Al'l.Owt% 48.9 98.8 Al, 2.0 wt% 34.7 98.0 pH 10 water 48.9 99.2 pH 2 water 49.7 98.9 * The theoretical density of ΥTZP is 6.03 g / cm3

C: \ ProgramFUes \ Patent \ 023 Bu 3853-E, ptd page 17 442447 V. Description of the invention (15) Example 4 The method of preparing YTZP zirconia suspension in Example 3 was used to change the solid content of the powder 'from 25¾ To 33% volume solids content, and based on the mass of the powder ', adding 1.0 to 4.0% by weight of A6 dispersant, a total of ten suspensions of zirconia were obtained. These suspensions were prepared by gas pressure filtration to produce green bodies. The Archimedes method described in 4 measures the green density, and the results are shown in FIG. 1. By comparing the distribution of raw chain density, the suspension with a solid content of 28ν〇1% and the addition of A6 dispersant 2wt% can obtain the highest density (53. 4%), compared to similar colloidal processes The reported green density of 40-48% is high. In addition, the density of the green body varies with different solid-phase loadings and dispersing doses. Increase the dispersant. For example, the solid content of 3 (^ 〇1% 'dispersant 2 in% of the green body in Figure 1 has only about 51.8 % Density, which can no longer increase the density of the green body. Example 5 Using the colloidal granulation process method of Example 4, a suspension with a solid content of 28 vol% and 2% by weight of A6 dispersant was added. The other group of samples was made of the same γτZρ powder, and the long rectangular test piece was made by 120 MPa uniaxial dry pressing method with a size of 6x7x5 Omm3. The two test pieces passed through 1 40 0 ° C to 1 60 0 ° The sintered body was sintered for one hour. The bulk density of the sintered body was measured. The grain size of the sample was measured from a scanning electron microscope (SEM) photograph of the polished surface. The results of the bulk density and particle size are shown in Figure 2 Figure 2. The sintered density of the dry-formed samples in the second figure is lower than the sample density of the rubber pellet process at the same sintering temperature, and the grains are the samples of the rubber pellet process.

C: \ ProgramFiles \ Patent \ 0231-3853-E.ptd page 18 4ΔΡΔΔ7 _____ V. Description of the invention (16) is small, about 0.3 to 0.8 mm. The sample of the rubber particle process is better than the dry pressed sample. In Figure 2, the sample sintered at 1480 ° C for one hour has a density higher than 99.5% TD. After grinding and polishing, and then displaying the grain boundary by thermal erosion, the result is observed by sEm. The structure is shown in Annex 1, and its average grain size is 0 '38 mm. Zirconium oxide that has undergone a colloidal processing or a dry pressing process (di ep res sing ng) undergoes 148 t: a test piece sintered for one hour. There are two types of test pieces for the stern knee system, one It is a 325mesh money stone grinding wheel for surface flatness processing. The speed of the grinding platform is 6 m / sec 'and the other is 2. lm / sec. The sample names are CP (I) and CP (II). The test piece was tested with a dynamic tester (m0del 810, MTS Co., USA) 'in accordance with the J IS 16 0 7 standard, and the four-point breaking strength of the test piece was tested. The measured results are shown in Table 8. From the strength measurement results, In comparison, the sample strength of the gel system is better. Table 8 Mean four-point failure average strength (0f) of zirconia sintered body by dry pressing or colloidal pellet production method Number of test pieces Dry compaction sample 544 MPa 30 Colloidal pellet sample, CP (I) 661 MPa 5 Granular process sample, CP (II) 748 MPa 5 Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. 'Any person skilled in the art, without departing from the spirit and scope of the present invention, Various modifications and retouching can be made, so the protection of the present invention

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Claims (1)

442 4 pT7-- VI. Application for U Scope IB, i Revision 1. A method for preparing holmium oxide suspensions, including the following steps: (a) adding yttrium oxide submicron powder to an aqueous solution containing dispersed spines Wherein the zirconia submicron powder contains 2 to 5 mol% yttrium oxide; and (b) the above-mentioned powdered aqueous solution is thoroughly mixed by a ball milling method to form a medium to weakly alkaline suspension. 2. The method according to item 丨 of the scope of patent application, wherein the solid volume fraction (v0l%) of the powder contained in the suspension is 0.1 to 45.0%. 3. The method according to item 2 of the scope of patent application, wherein the solid volume fraction of the powder contained in the suspension is 25 to 35%. 4. The method according to item 1 of the scope of patent application, wherein the pH value of the suspension ranges from 6 to 9. 5. The method according to item 1 of the scope of patent application, wherein the dispersant is an ammonium salt compound containing an organic acid functional group. 6. The method according to item 5 of the scope of patent application, wherein the dispersant contained in the suspension is based on the mass of the zirconia powder contained in the suspension, and the content is 0.1 to 5.0% by mass. 7+ A hafnium oxide suspension comprising: a hafnium oxide submicron powder containing 2 to 5 mole% yttrium oxide; and an aqueous solution containing a dispersant, wherein the dispersant is an ammonia salt containing an organic acid functional group Compound; wherein the zirconia submicron powder is thoroughly mixed with the dispersant-containing aqueous solution to become a medium to weakly alkaline suspension. —A method for manufacturing a high-density sintered body 'refers to the use of a zirconium halide suspension prepared by the method described in the first item of the scope of patent application, using ceramic slurry to form a ceramic green body, and obtained by pre-sintering—ceramic Sintered body '442447 _ case number 87115720_ year month day 日 Zheng _ VI. Scope of patent application. 9. The method according to item 8 of the scope of patent application, wherein the above-mentioned slurry forming method is formed by natural sedimentation, high-speed centrifugation, or gas pressure filtration, or a combination of any two or more forming methods. 10. The method according to item 8 of the scope of the patent application, wherein the solid volume fraction (vo i%) of the oxidized file powder contained in the zirconia suspension is 25 ~ 45 ° / 〇. 11. The method according to item 8 of the scope of patent application, wherein the sintering temperature of the green body is from 1 400 ° 01600 ° C. 1 2. The method as described in item 8 of the scope of patent application, wherein the relative bulk density of the sintered body exceeds 99.5%. 0231-3853-EFl-ptc Page 22