EP3921292A1 - Dispersion de zircone destinée à être utilisée dans la formation de nanocéramiques - Google Patents

Dispersion de zircone destinée à être utilisée dans la formation de nanocéramiques

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Publication number
EP3921292A1
EP3921292A1 EP19706303.5A EP19706303A EP3921292A1 EP 3921292 A1 EP3921292 A1 EP 3921292A1 EP 19706303 A EP19706303 A EP 19706303A EP 3921292 A1 EP3921292 A1 EP 3921292A1
Authority
EP
European Patent Office
Prior art keywords
dispersion
nanoparticles
aqueous dispersion
particle size
green body
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19706303.5A
Other languages
German (de)
English (en)
Inventor
William Wiseman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Magnesium Elektron Ltd
Original Assignee
Magnesium Elektron Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Magnesium Elektron Ltd filed Critical Magnesium Elektron Ltd
Publication of EP3921292A1 publication Critical patent/EP3921292A1/fr
Pending legal-status Critical Current

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Definitions

  • This invention relates to aqueous dispersions of zirconia particles, the particles optionally comprising yttria and alumina, for use in the formation of nano ceramics.
  • Nano ceramics are ceramics which have a mean grain size in the range 1- 200 nm. Advantages of nano ceramics are known and include that they exhibit greatly improved mechanical and optical properties along with other phenomena that traditional sub-micron ceramics do not exhibit. Work performed by Binner et al (US 2011/0230340 A1) asserts that yttrium doped zirconia ceramics with a mean grain size of 190 nm or less exhibit hydrothermal resistance along with excellent wear resistance properties. These enhanced properties make nano ceramics excellent materials for a wide range of applications including use in the electronics industry in phone cases, glasses and watch cases, in the abrasives market through tougher wearing materials and in the healthcare market such as in implants.
  • US 2016/0095798 A1 and US 9,820,917 B1 relate to zirconia dental ceramics which are formed from suspensions of zirconia nanoparticles, and gels made from such suspensions.
  • the ceramics described in these documents are stated as having translucency, opalescence and desirable physical properties.
  • US 2016/0095798 A1 also contains an extensive discussion of earlier patents relating to zirconia dental articles, as well as patents, patent applications and journal articles in the more general field of zirconia ceramics and processing methods.
  • the process of forming a zirconia dental article which is described in US 2016/0095798 A1 involves the steps of (i) forming a zirconia nanoparticle suspension into a suitable shape to form a wet zirconia green body, (ii) drying the wet green body to produce a zirconia green body, (iii) heating the zirconia green body to for a zirconia brown body, and (iv) sintering the zirconia brown body to form an opalescent zirconia sintered body.
  • a problem with drying nanomaterials such as those described in US 2016/0095798 A1 and US 9,820,917 B1 is that the particles can aggregate and no longer possess the properties of a true nanoparticle.
  • a potential problem with this extended drying process is that when a dense green body has been formed, de-binding must occur to remove any organics or volatiles from the ceramic.
  • a dense green body will result in smaller voids in the material and if these are not sufficiently large enough to allow the organics or volatiles to escape, pressure can build up inside the body and lead to cracking and failures in the resulting ceramics.
  • This invention relates to an aqueous dispersion of nanoparticles, the nanoparticles comprising, on an oxide basis:
  • dispersion has a polydispersity index of 0.10-0.17.
  • nanoparticles is used to refer to particles where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm - 100 nm. At the time of writing, this is the recommended definition of a nano material as described in “COMMISSION RECOMMENDATION of 18 th October 2011 on the definition of nano materials (2011/696/EU)”.
  • a dispersion is a system in which solid particles are dispersed in a continuous phase of a different composition.
  • the term “dispersion” is used in relation to the invention to refer to a system in which solid nanoparticles are dispersed in a liquid phase or medium (in this case, water).
  • the dispersion may optionally comprise additives, such as surfactants, in order to increase the stability of the dispersion. Such additives are known to those skilled in the art.
  • nanodispersion is used to refer to a dispersion of nanoparticles.
  • the dispersions of the invention may be defined as a colloid, ie a dispersion of particles having at least one dimension in the size range 1 nm - 1 pm. More particularly, the dispersions may be defined as a colloidal sol, ie a colloid where the dispersed phase is a solid and the continuous phase is a liquid.
  • aqueous is used to refer to a dispersion in which the liquid phase may comprise at least 75 wt% water, more particularly at least 90 wt% water, even more particularly at least 95 wt%.
  • the liquid phase may comprise at least 98 wt% water, more particularly substantially 100 wt% water. It may be necessary for the liquid phase to comprise a solvent, for example an organic solvent and specifically a polar solvent such as an alcohol.
  • a suitable dispersant is one which is capable of providing an electrostatic repulsion between nano particles, a steric interaction between particles or an electro-steric repulsion between particles.
  • suitable dispersants include Amino Acids such as Glycine (2- Aminoethanoic acid), Alanine and its isomers (2-Aminopropanoic acid, 3- Aminopropanoic acid) and Valine and its isomers (D-2-Amino-3-methylbutanoic acid, L-2-Amino-3-methylbutanoic acid).
  • the dispersant may be 3- Aminopropanoic acid.
  • the dispersion may comprise 0.5-6 wt% of a dispersant (based on oxide content), more particularly 1.0-4.0 wt%, even more particularly 1.5-3.0 wt%.
  • the nanoparticles may comprise, on an oxide basis, 90-100 wt% ZrC>2 + HfC>2. More particularly, the nanoparticles may comprise, on an oxide basis, 0.5-10 wt% Y2O3, more particularly 1-9 wt% Y2O3. In particular, the nanoparticles may comprise, on an oxide basis, 0-1 wt% AI2O3, more particularly, 0-0.5 wt% AI2O3.
  • the dispersion may have a nanoparticle content of 0.5-65 wt%, more particularly 10-63 wt%, even more particularly 20-62 wt%.
  • the dispersion may have a nanoparticle content of 50-60 wt%. This may also be referred to as the solids content.
  • the solids content can be varied by techniques such as, dilution, evaporation, membrane filtration, microfiltration, centrifugation. More particularly, the technique may be dilution, evaporation or membrane filtration.
  • the dispersion may have a polydispersity index of 0.11-0.16. More particularly, the polydispersity index (PDI) may be measured by dynamic light scattering (DLS).
  • PDI polydispersity index
  • DLS dynamic light scattering
  • the dispersion may have a pH of 1-7, even more particularly 2-6, more particularly 3-5.
  • the dispersion may have a Z-average particle size of 30-60 nm, more particularly 35-55 nm, even more particularly 40-50 nm.
  • the Z- average particle size may be measured by dynamic light scattering (DLS).
  • the dispersion may have a Zeta potential of 20-50 mV, even more particularly 25-45 mV, more particularly 30-42 mV.
  • any second or subsequent peak in the particle size distribution by intensity of the dispersion may have an intensity of 0-15 %, even more particularly 0-10 %.
  • the term“second or subsequent peak” is used to refer to any peaks other than the highest intensity peak in a particle size by intensity distribution as measured by dynamic light scattering (DLS). The percentage is a measure of the area under the peak, ie if there are two peaks, peak 1 has an area of (100-x) and peak 2 has an area of x.
  • the dispersion may have a PDI width of 10-20 nm, more particularly 12-18 nm. More particularly, the PDI width may be measured by dynamic light scattering (DLS).
  • DLS dynamic light scattering
  • the dispersion may have a particle size distribution as measured by intensity having a d10 value in the range 25-40 nm, even more particularly in the range 26-34 nm.
  • the dispersion may have a particle size distribution as measured by intensity having a d50 value in the range 35-60 nm, more particularly in the range 45-53 nm.
  • the dispersion may have a particle size distribution as measured by intensity having a d90 value in the range 60-100 nm, even more particularly in the range 65-90 nm.
  • the d10, d50 and d90 may be measured by dynamic light scattering (DLS).
  • DLS dynamic light scattering
  • the green density of a green body formed from the dispersions of the invention by following the method Example 1 in US2016/0095798 is preferably ⁇ 2.800 g/cm 3 and even more preferably, ⁇ 2.760 g/cm 3 .
  • These green density figures are lower than that usually obtained by forming a green body from a powder. Without wishing to be bound to any theory, it is understood that this increases the survival rate of the green body during drying.
  • the dispersions may have a viscosity of ⁇ 100 cPs, more particularly ⁇ 30 cPs, even more particularly ⁇ 20 cPs. More particularly, the viscosity may be measured using a shear rate of 200 s 1 at 20 °C.
  • a solid metal oxide obtainable by drying the dispersion described above.
  • the metal oxide may be in the form of a powder. More particularly, the drying may be at 130°C until a substantially constant mass is reached.
  • the powder may be obtainable by grinding.
  • the nanoparticles may comprise a crystalline phase of monoclinic and combined tetragonal / cubic when measured by powder X-ray diffraction (XRD) between 10° and 85° 2theta.
  • XRD powder X-ray diffraction
  • the crystallite size of the nanoparticles may be 10-20 nm, more particularly 10-15nm.
  • the nanoparticles may comprise a crystalline phase of monoclinic and tetragonal / cubic when measured by Raman spectroscopy.
  • the level of minor constituents in ceramics is desirable to control the level of minor constituents in ceramics, especially when used as a precursor to dental implants where colour is important.
  • it may be desirable to control minor constituents in the dispersion such as Fe, Cr, Ni, Ce, Co, Mn, Er, Pr, Nd, Tb, Cu, Bi and their compounds such as oxides.
  • the amount of each of these minor constituents in the dispersion may individually be ⁇ 20 ppm, even more particularly ⁇ 10 ppm. This is because they can all add colour to sintered ceramics.
  • the amount of each of these minor constituents in the dispersion may individually be ⁇ 20 ppm, more particularly ⁇ 10 ppm.
  • the amounts of other elements in the dispersions may also need to be controlled to avoid detrimental sintering effects, for example Na, K, S, N, C, Cl, Si and Ti, in particular Na, Cl, Si and Ti. More particularly, the amount of each of these components in the dispersion may individually be ⁇ 200 ppm, even more particularly ⁇ 100 ppm.
  • this invention relates to a method of forming a ceramic article comprising the steps of:
  • step (c) sintering the green body to form the ceramic article.
  • step (c) may comprise, after sintering, the steps of grinding and/or polishing the ceramic article.
  • the method may comprise, between steps (b) and (c), the step of pre-sintering the green body to remove any dispersant and form a pre-sintered body.
  • Step (c) would then comprise sintering the pre-sintered body to form the ceramic article. More particularly, the method may comprise, after the pre-sintering step but before step (c), the step of shaping the pre- sintered body.
  • the composition of the nanoparticles of the invention can be varied in order to produce ceramics for a range of applications.
  • Undoped ZrC>2 nanoparticle dispersions have applications in filtration and non-temperature sensitive applications.
  • Y2O3 doped ZrC>2 nanoparticle dispersions offer a wide range of uses from structural applications, such as wear parts and abrasives, to functional applications such as oxygen sensors and fuel cells. It is therefore useful to control the Y2O3 level in the nanoparticle dispersion in order to control the phase of the material with regards to its crystal structure whilst retaining the desired Z-average particle size and polydispersity index (PDI).
  • PDI polydispersity index
  • Figure 1 shows a graph of particle size distribution by intensity for Example 1 and Comparative Example 10,
  • Figure 2 shows a graph of particle size distribution by intensity for Example 1 and Comparative Examples 13,
  • Figure 3 shows a TEM image of dried particles of Example 1 .
  • Figure 4 shows XRD overlays of Examples 4-9 showing the elimination of monoclinic phase in the materials
  • Figure 5 shows a the green bodies of Example 1 (left) and Comparative Example 10 (right) showing the difference in green density.
  • Nanodispersions were prepared as set out below. The dispersions were tested as set out below, with the results shown in Tables 2, 3 and 4 below. [0040] Solids content
  • % solids of dispersion (dry weight of dispersion (g)/initial weight of dispersion (g)) x
  • Particle size measurements were made using a Malvern Zetasizer Nano ZS instrument, model ZEN3600, using a red laser of wavelength 633nm. Each sample was first diluted to 0.5 wt. % using deionised water. 1 ml of the diluted sample was then placed in a DTS0012 disposable cuvette. The cuvette was loaded into the instrument and allowed to equilibrate to 25°C. A standard operating procedure (SOP) was created with the following parameters set: material refractive index 2.20, and material absorption value of 0.01 units. The dispersant refractive index (in this case, the continuous phase, ie water) was 1.33 and the dispersant viscosity was 0.8872 cP.
  • SOP standard operating procedure
  • the instrument was set to automatically adjust the laser position and attenuator settings to obtain the best measurement of particle size.
  • a backscattering angle of 173° was used.
  • the method of Dynamic Light Scattering (DLS) was used to calculate the particle size.
  • a total of three measurements were taken with the cuvette being inverted between measurements. The three measurements were then averaged to give a final particle size result.
  • the Z-average size or cumulant mean is a mean calculated from the intensity distribution and the calculation is based on assumptions that the particles are mono-modal, mono-dispersed and spherical.
  • the polydispersity index (PDI) is a measure of the breadth of the particle size distribution and is calculated along with the Z-average size in the cumulant analysis of the intensity distribution.
  • the PDI width is calculated by taking the square root of the PDI and multiplying this by the Z-average.
  • the calculations for the Z-average size, polydispersity index and PDI width are defined in the ISO 22412:2017“Particle size analysis - by Dynamic Light Scattering (DLS)”.
  • Zeta potential and conductivity measurements were made using a Malvern Zetasizer Nano ZS instrument, model ZEN3600. Each sample was first diluted to 0.5 wt. % using deionised water and placed in a DTS1070 disposable folded capillary cell. The cell was loaded into the instrument and allowed to equilibrate to 25°C. A standard operating procedure (SOP) was created with the following parameters set: material refractive index 2.20, and material absorption value of 0.01 units. The dispersant refractive index was 1.33, the dispersant viscosity was 0.8872 cP and the dielectric constant was 78.5. The instrument was set to automatically adjust the number of runs taken and was set to take five sets of measurements with a thirty second delay between measurements. The five measurements were then averaged to give the final zeta potential and conductivity.
  • SOP standard operating procedure
  • XRD powder X-ray diffraction
  • Topas software was used to determine phase analysis whereas the default monoclinic, tetragonal and cubic structures were loaded into the software and each scan run against the defaults. Note tetragonal and cubic phases are reported combined in the examples.
  • Viscosity measurements were collected using the DIN 53019 coaxial cylinder - 30mm diameter and loaded with 20 ml of sample. Each sample was left to equilibrate to 20°C by placing it in a water bath for thirty minutes before running the measurement. Measurements were carried out using a Bohlin Visco 88 Viscometer. Ten measurements would be taken at 200 s 1 shear rate with an average being calculated. This procedure was carried out for all samples by diluting a small portion of the sols with deionised water to a solids content of 55.0 wt%. The measured solids content as described above was used to calculate the dilution to ensure all samples were tested under equivalent solids loadings.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738 a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an total oxide content of 25 % by weight.
  • This dispersion had a starting particle size of 1.4 microns measured via laser diffraction.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear (> 1 ,000,000 s 1 ) in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide (ie 2 wt% relative to the weight of the oxide).
  • the final concentration was increased to 56.0 % solids using membrane filtration.
  • the powder XRD results gave a crystallite size of 12 nm and a phase analysis of 1.4 % monoclinic and 98.6 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.748 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 58.0 % solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 46.8 nm, a PDI of 0.142 and a PDI Width of 17.6 nm.
  • the powder XRD results gave a crystallite size of 12 nm and a phase analysis of 0.9 % monoclinic and 99.1 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.720 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 59.5 % solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 42.8 nm, a PDI of 0.122 and a PDI Width of 15.0 nm.
  • the powder XRD results gave a crystallite size of 12 nm and a phase analysis of 1.5 % monoclinic and 98.5 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.710 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of a zirconium hydrous oxide was prepared by taking XZ02732, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 100 : 0 : 0, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.5 % solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 45.0 nm, a PDI of 0.115 and a PDI Width of 15.3 nm.
  • the powder XRD results gave a crystallite size of 14 nm and a phase analysis of 32.9 % monoclinic and 67.1 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.732 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02733, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 98.2 : 1.8 : 0, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.5% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 46.1 nm, a PDI of 0.139 and a PDI Width of 17.2 nm.
  • the powder XRD results gave a crystallite size of 13 nm and a phase analysis of 22.1 % monoclinic and 77.9 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.749 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02734, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 96.4 : 3.6 : 0, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.0% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 42.4 nm, a PDI of 0.140 and a PDI Width of 15.8 nm.
  • the powder XRD results gave a crystallite size of 13 nm and a phase analysis of 7.1 % monoclinic and 92.9 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.750 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02735, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.7 : 5.3 : 0, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 58.0% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 45.2 nm, a PDI of 0.116 and a PDI Width of 15.4 nm.
  • the powder XRD results gave a crystallite size of 14 nm and a phase analysis of 2.3 % monoclinic and 97.7 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.725 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02736, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 92.9 : 7.1 : 0, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2.25 wt% on oxide. The final concentration was increased to 56.5% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 44.4 nm, a PDI of 0.159 and a PDI Width of 17.7 nm.
  • the powder XRD results gave a crystallite size of 11 nm and a phase analysis of 0.8 % monoclinic and 99.2 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.731 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02737, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 91.2 : 8.8 : 0, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under high shear in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2.5 wt% on oxide. The final concentration was increased to 59.5% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 43.5 nm, a PDI of 0.152 and a PDI Width of 17.0 nm.
  • the powder XRD results gave a crystallite size of 11 nm and a phase analysis of 0.6 % monoclinic and 99.4 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.733 g/cm 3 . All of the green bodies survived de-binding and sintering at 1150 °C for 2 hours to form a crack free ceramic piece.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under low shear (50,000 s 1 ) in the presence of an amino acid dispersant (3- aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.0% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 73.2 nm, a PDI of 0.226 and a PDI Width of 34.8nm.
  • the powder XRD results gave a crystallite size of 11 n and a phase analysis of 3.9 % monoclinic and 96.1 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 3.040 g/cm 3 . Upon de-binding, all of the green bodies fractured inside of the furnace.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged at >80 °C and subjected to at least 24 hours mixing under lower shear (35,000 s 1 ) in the presence of an amino acid dispersant (3- aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.0% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 93.3 nm, a PDI of 0.208 and a PDI Width of 42.6nm.
  • the powder XRD results gave a crystallite size of 11 nm and a phase analysis of 4 % monoclinic and 96.0 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.881 g/cm 3 . Upon de-binding, all of the green bodies fractured inside of the furnace. This comparative example demonstrates the importance of using high shear mixing when preparing the dispersions of the invention.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged and subjected to milling for 1 hour as per patent US 9,822,039 B1 Comparative Example 1 , in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.0% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 39.2 nm, a PDI of 0.180 and a PDI Width of 16.6 nm.
  • the powder XRD results gave a crystallite size of 14 nm and a phase analysis of 6.0 % monoclinic and 94.0 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.881 g/cm 3 . Upon de-binding, small cracks appeared inside the ceramic. Upon sintering at 1150 °C for 2 hours, the cracks propagated and the ceramics split into multiple pieces. This comparative example demonstrates the importance of the ageing and mixing techniques used when preparing the dispersions of the invention.
  • An aqueous dispersion of an yttrium doped zirconium hydrous oxide was prepared by taking XZ02738, a material grade from Luxfer MEL Technologies with a ratio of oxides of zirconium : yttrium : aluminium of 94.45 : 5.3 : 0.25, which was made up to 500 g using deionised water to give an active content of 25 % by weight.
  • This dispersion was aged and subjected to milling for 2 hours as per patent US 9,822,039 B1 Comparative Example 1 , in the presence of an amino acid dispersant (3-aminopropanoic acid), added at 2 wt% on oxide. The final concentration was increased to 57.5% solids using membrane filtration.
  • the final particle size distribution of the dispersion was a Z-Ave of 30.3 nm, a PDI of 0.181 and a PDI Width of 13.0 nm.
  • the powder XRD results gave a crystallite size of 13 nm and a phase analysis of 2.4 % monoclinic and 97.6 % tetragonal / cubic phase.
  • a green body was prepared by following the method of Example 1 of US 2016/0095798 A1 , resulting in a green density of 2.873 g/cm 3 . Upon de-binding, small cracks appeared inside the ceramic. Upon sintering at 1150 °C for 2 hours, the cracks propagated and the ceramics split into multiple pieces. This comparative example is the same as Comparative Example 12 except that the milling time is 2 hours.
  • compositions of the nanodispersions are summarised in Table 1 below:
  • Figure 1 compares particle size by intensity graphs for Example 1 and Comparative Example 10. This shows a monomodal peak of smaller size for Example 1 compared to the bimodal and larger size peak for Comparative Example 10.
  • Figure 2 shows a similar comparison for Examples 1 and Comparative Example 13. In this case, this shows the larger size peak achieved by Example 1.
  • Figure 3 shows a TEM image of the dried particles obtained in Example 1. This confirms that the particle size distribution is close to that measured by DLS, as well as highlighting the narrow distribution of the particles.
  • FIG. 4 The XRD overlays in Figure 4 show the crystallinity of the nanoparticles of the invention.
  • the arrows in Figure 4 indicate the reduction in the 28 2theta peak relating to the monoclinic phase as the level of Y2O3 is increased through Examples 4-9.
  • Figure 5 is a photograph of green bodies formed in accordance with Example 1 (left) and Comparative Example 10 (right). As is clearly indicated, the left disc is wide and thin, whereas the right one is taller and narrower. Also, the green body formed by Comparative Example 10 had a crack in it, indicated by the circle in Figure 5. This is understood to be due to the packing of the particles in the respective green bodies.
  • the left disc (Example 1) has a narrower particle size range (essentially, more particles of a similar size). These particles pack together leaving voids in the green body for moisture/organics to escape during drying. This allows the green body to dry quicker and retain its shape.
  • the right disc (Comparative Example 10) has a bimodal particle size distribution, allowing smaller particles to fit into the voids around the larger particles. This means that the green body dries slower, the outside of the disc drying first whilst the middle retains moisture and then contracts. This results in a taller, narrower disc.

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Abstract

La présente invention concerne une dispersion aqueuse de nanoparticules, les nanoparticules comprenant, sur une base d'oxyde : (a) 85-100 % en poids de ZrO2 + HfO2, (b) 0-15 % en poids de Y2O3 et (c) 0-2 % en poids de Al2O3, la dispersion présentant un indice de polydispersité de 0,10-0,17. La présente invention concerne également un procédé de formation d'un article céramique, comprenant les étapes consistant à : (a) verser la dispersion aqueuse dans un moule, (b) sécher la dispersion aqueuse dans le moule pour former un corps cru et (c) fritter le corps cru pour former l'article en céramique.
EP19706303.5A 2019-02-05 2019-02-05 Dispersion de zircone destinée à être utilisée dans la formation de nanocéramiques Pending EP3921292A1 (fr)

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WO2006024098A1 (fr) 2004-09-01 2006-03-09 Advanced Nanotechnology Limited Céramique de zircone
WO2009085926A2 (fr) * 2007-12-28 2009-07-09 3M Innovative Properties Company Procédé de fabrication de nanoparticules de zircone
GB0821674D0 (en) 2008-11-27 2008-12-31 Univ Loughborough Ceramic
JP5703549B2 (ja) 2009-09-14 2015-04-22 住友大阪セメント株式会社 アルミナドープジルコニアナノ粒子及びその製造方法
US9139670B2 (en) * 2010-12-22 2015-09-22 3M Innovative Properties Company Surface-modified zirconia nanoparticles
ES2815073T3 (es) 2013-06-27 2021-03-29 Ivoclar Vivadent Inc Circona nanocristalina y métodos de procesamiento de la misma
WO2016191534A1 (fr) * 2015-05-28 2016-12-01 3M Innovative Properties Company Sol contenant des nano particules de zircone à utiliser dans des procédés de fabrication additive pour la fabrication d'articles en trois dimensions
JP6835742B6 (ja) * 2015-05-28 2021-03-24 スリーエム イノベイティブ プロパティズ カンパニー ナノサイズ粒子を含有するゾルを用いたセラミック物品を作製するための付加製造方法
US9822039B1 (en) 2016-08-18 2017-11-21 Ivoclar Vivadent Ag Metal oxide ceramic nanomaterials and methods of making and using same
JP6543433B2 (ja) 2016-12-31 2019-07-10 大研化学工業株式会社 ジルコニア系ナノ粒子の製造方法
US11180417B2 (en) * 2017-02-15 2021-11-23 3M Innovative Properties Company Zirconia article with high alumina content, process of production and use thereof

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WO2020161451A9 (fr) 2020-09-17
JP7330277B2 (ja) 2023-08-21
CN113727956A (zh) 2021-11-30
CN113727956B (zh) 2023-02-21
JP2022521369A (ja) 2022-04-07
WO2020161451A1 (fr) 2020-08-13

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