Sintered zircon beads

Abstract

The invention relates to sintered zircon beads. The sintered beads have a crystalline phase based on mass: 25% < = zircon or Z1 < = 94%; 10% lt; stable zirconium oxide + stable hafnium oxide or Z2 is less than or equal to 61%; monoclinic zirconium oxide + monoclinic hafnium oxide or Z3 is less than or equal to 50%; corundum < = 57%; other crystalline phases lt; 4%; the chemical composition is as follows: ZrO2 + HfO2 is greater than or equal to 33% and less than or equal to 83.4%; hfO2 < = 2%; 10.6% < = SiO2 < = 34.7%; al2O3 is less than or equal to 50%; 0% < = Y2O3 or Z5; 0% < = CeO2 or Z6; 0.3% < = CeO2 + Y2O3 < = 19%, provided that CeO2 + 3.76 * Y2O3 > = 0.128 * Z and CeO2 + 1.3 * Y2O3 < = 0.318 * Z, Z = Z4 + Z5 + Z6-(0.67 * Z1 * (Z4 + Z5 + Z6) / (0.67 * Z1 + Z2 + Z3)); mgO < = 5%; caO < = 2%; other oxides lt; 5.0%.

Description

[0001] This application is a divisional application of Chinese patent application No. 201880060111.8, filed on July 18, 2018, entitled "Sintered Zircon Beads". Technical Field

[0002] The present invention relates to sintered zircon beads, methods for manufacturing such beads, and the use of such beads as abrasives, wet dispersants, or for surface treatment. Background Technology

[0003] Beads are also used in the coatings, inks, dyes, magnetic paints, and agrochemical compounding industries to disperse and homogenize liquid and solid components.

[0004] The mineral industry uses beads to finely grind materials that can be dry-ground using traditional processes, especially calcium carbonate, titanium oxide, gypsum, kaolin, and iron ore.

[0005] In the field of micro-grinding, round abrasive, glass beads, metal beads, and ceramic beads are used.

[0006] - Round sand (such as Ottawa sand) is a natural and inexpensive product, but it is not suitable for modern pressurized high-flow mills. In fact, sand is not very durable, has low density, varies in quality, and is abrasive to materials.

[0007] - Widely used glass beads offer better strength, lower abrasion, and greater availability over a wider diameter range.

[0008] Metal beads, especially steel beads, have low inertia to the processed product, leading to contamination of mineral fillers and ashing of coatings, and their excessive density necessitates specialized crushers. They particularly involve high energy consumption, high heating, and high mechanical stress in the equipment.

[0009] - Ceramic beads have better durability, higher density and excellent chemical inertness than glass beads.

[0010] The size of the beads is typically 0.005 mm to 10 mm.

[0011] It can be distinguished as follows:

[0012] - Molten ceramic beads are typically obtained by melting ceramic components, forming spherical droplets from the molten material, and then solidifying the droplets; and

[0013] - Sintered ceramic beads are typically obtained by cold-forming ceramic powder and then solidifying it through high-temperature firing.

[0014] Unlike sintered beads, molten beads typically possess a very rich intergranular glassy phase that fills the network of crystalline grains. Therefore, the problems encountered by sintered and molten beads in their respective applications, and the technological solutions employed to address these problems, are generally different. Furthermore, due to significant differences in manufacturing processes, compositions developed for producing molten beads are a priori unsuitable for producing sintered beads, and vice versa.

[0015] To serve all of the aforementioned markets, the beads must simultaneously possess good abrasion resistance and high density.

[0016] One object of the present invention is to provide beads that satisfy these limitations. Summary of the Invention

[0017] This invention relates to a sintered bead, which has the following characteristics:

[0018] - The following crystalline phases are listed as a percentage by mass of the crystalline phases, totaling 100%:

[0019] 25% ≤ zircon, or “Z1” ≤ 94%;

[0020] 4% ≤ stabilized zirconium oxide + stabilized hafnium dioxide, or “Z2” ≤ 61%;

[0021] Monoclinic zirconium oxide + monoclinic hafnium dioxide, or "Z3" ≤ 50%;

[0022] Corundum ≤ 57%;

[0023] Crystalline phases other than Z1, Z2, Z3 and corundum < 10%;

[0024] - The following chemical compositions are expressed as mass percentages based on oxides and total 100%:

[0025] 33% ≤ ZrO2 + HfO2, or “Z4” ≤ 83.4%;

[0026] HfO2 ≤ 2%;

[0027] 10.6% ≤ SiO2 ≤ 34.7%;

[0028] Al2O3 ≤ 50%;

[0029] 0% ≤ Y2O3, or “Z5”;

[0030] 0% ≤ CeO2, or “Z6”;

[0031] 0.3% ≤ CeO2 + Y2O3 ≤ 19%, under the condition that

[0032] (1) CeO2 + 3.76×Y2O3 ≥ 0.128×Z, and

[0033] (2) CeO2 + 1.3×Y2O3 ≤ 0.318×Z,

[0034] Where Z = Z4 + Z5 + Z6 - (0.67 × Z1 × (Z4 + Z5 + Z6) / (0.67 × Z1 + Z2 + Z3));

[0035] MgO ≤ 5%;

[0036] CaO ≤ 2%;

[0037] Oxides other than ZrO2, HfO2, SiO2, Al2O3, MgO, CaO, CeO2 and Y2O3 < 5.0%.

[0038] In the embodiment, the sintered beads have:

[0039] - The following crystalline phases are listed as a percentage by mass of the crystalline phases, totaling 100%:

[0040] 31% ≤ zircon, or “Z1” ≤ 94%;

[0041] 4% ≤ stabilized zirconium oxide + stabilized hafnium dioxide, or “Z2” ≤ 61%;

[0042] Monoclinic zirconium oxide + monoclinic hafnium dioxide, or "Z3" ≤ 50%;

[0043] Corundum ≤ 40%;

[0044] Crystalline phases other than Z1, Z2, Z3 and corundum < 10%;

[0045] - The following chemical compositions are expressed as mass percentages based on oxides and total 100%:

[0046] 37% ≤ ZrO2 + HfO2, or “Z4” ≤ 83.4%;

[0047] HfO2 ≤ 2%;

[0048] 12.6% ≤ SiO2 ≤ 34.7%;

[0049] Al2O3 ≤ 35%;

[0050] 0% ≤ Y2O3, or “Z5”;

[0051] 0% ≤ CeO2, or “Z6”;

[0052] 0.3% ≤ CeO2 + Y2O3 ≤ 19%, under the condition that

[0053] (3) CeO2 + 3.76×Y2O3 ≥ 0.128×Z, and

[0054] (4) CeO2 + 1.3×Y2O3 ≤ 0.318×Z,

[0055] Where Z = Z4 + Z5 + Z6 - (0.67 × Z1 × (Z4 + Z5 + Z6) / (0.67 × Z1 + Z2 + Z3));

[0056] MgO ≤ 5%;

[0057] CaO ≤ 2%;

[0058] Oxides other than ZrO2, HfO2, SiO2, Al2O3, MgO, CaO, CeO2 and Y2O3 < 5.0%.

[0059] As will be discussed in more detail in the following description, the inventors unexpectedly discovered that the combination of these features significantly improved abrasion resistance while providing high density.

[0060] Therefore, the sintered beads according to the present invention are particularly well suited for wet dispersion, micro-grinding, heat exchange and surface treatment applications.

[0061] The sintered beads according to the present invention may also have one or more of the following optional features:

[0062] - The content of ZrO2 + HfO2, based on the mass percentage of oxides, is greater than or equal to 31%, preferably greater than 35%, preferably greater than 40%, preferably greater than 45%, preferably greater than 50%, and / or less than 80%, preferably less than 75%, preferably less than 70%;

[0063] - The SiO2 content, based on the mass percentage of oxides, is greater than or equal to 12.6%, preferably greater than 14%, preferably greater than 15%, and / or less than 30%, preferably less than 25%;

[0064] The ratio of ZrO2 + HfO2 content to SiO2 content is greater than 1.2, preferably greater than 1.5, preferably greater than 2, preferably greater than 2.2, preferably greater than 2.5 and / or less than 5, preferably less than 4.5, preferably less than 4, preferably less than 3.5;

[0065] - Based on the mass percentage of oxides, the Al2O3 content is greater than 5%, preferably greater than 10%, and / or less than 40%, preferably less than or equal to 35%, preferably less than 30%, preferably less than 25%, and preferably less than 20%. Advantageously, the density of the beads is increased;

[0066] - The MgO content, based on the mass percentage of oxides, is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, or even greater than 0.3%, and / or less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%;

[0067] - The CaO content, based on the mass percentage of oxides, is greater than 0.1%, preferably greater than 0.2%, preferably greater than 0.3%, and / or less than 1.5%, preferably less than 1%;

[0068] - The content of CeO2 + Y2O3, based on the mass percentage of oxides, is greater than 0.65%, preferably greater than 0.95%, preferably greater than 1.3%, preferably greater than 1.6%, preferably greater than 1.95%, preferably greater than 2.2%, preferably greater than 3%;

[0069] - The chemical composition is such that CeO2 + 3.4×Y2O3 ≥ 0.16×Z, preferably CeO2 + 2.89×Y2O3 ≥ 0.185×Z, preferably CeO2 + 2.39×Y2O3 ≥ 0.212×Z, preferably CeO2 + 1.84×Y2O3 ≥ 0.224×Z, preferably CeO2 + 1.76×Y2O3 ≥ 0.229×Z;

[0070] - The content of CeO2 + Y2O3, based on the mass percentage of oxides, is less than 15.5%, preferably less than 14.3%, and more preferably less than 11.6%;

[0071] - The chemical composition makes CeO2 + 1.4×Y2O3 ≤ 0.259×Z;

[0072] - In a preferred embodiment, the CeO2 content is less than 0.2%, preferably less than 0.1%, and preferably substantially zero;

[0073] - The chemical composition results in Y2O3 ≥ 1.82×Z, preferably Y2O3 ≥ 3.44×Z, and preferably Y2O3 ≥ 5.38×Z;

[0074] - Based on the mass percentage of oxides, the content of oxides other than ZrO2, HfO2, SiO2, Al2O3, Y2O3, CeO2, CaO, and MgO is less than 4%, preferably less than 3%, preferably less than 2%, or even less than 1.5%, or even less than 1%. Preferably, the Na2O content is less than 0.8%, preferably less than 0.5%, preferably less than 0.3%, preferably less than 0.2%, and / or the K2O content is less than 0.8%, preferably less than 0.5%, preferably less than 0.3%, preferably less than 0.2%.

[0075] - Oxides other than ZrO2, HfO2, SiO2, Al2O3, Y2O3, CeO2, CaO, and MgO are impurities;

[0076] - Preferably, the oxide content of the beads according to the invention accounts for more than 99%, more preferably more than 99.5%, more preferably more than 99.9%, and more preferably substantially 100% of the total mass of the beads;

[0077] - The zircon (ZrSiO4 phase) content is greater than or equal to 31%, preferably greater than 35%, preferably greater than 40% and / or less than 90%, preferably less than 85%, preferably less than 80%, preferably less than 76%, preferably less than 72%, preferably less than 68%, based on the total mass percentage of the crystalline phase;

[0078] - The content of stabilized zirconium oxide (ZrO2 phase) + stabilized hafnium dioxide (HfO2 phase) is greater than 5%, preferably greater than 8%, preferably greater than 10%, preferably greater than 12%, preferably greater than 15%, preferably greater than 18%, preferably greater than 20%, preferably greater than 24%, preferably greater than 27% and / or less than 55%, preferably less than 50%, preferably less than 47%, based on the total mass percentage of the crystalline phase;

[0079] - The content of monoclinic zirconium oxide (ZrO2 phase) + monoclinic hafnium dioxide (HfO2 phase) is less than 45%, preferably less than 40%, preferably less than 35%, preferably less than 35%, preferably less than 30%, preferably less than 25%, preferably less than 20%, preferably less than 15%, preferably less than 10%, preferably less than 5%, preferably essentially zero, based on the mass percentage of the total amount of crystalline phases.

[0080] - The content of corundum (Al2O3 phase) is greater than 5%, preferably greater than 10% and / or less than 50%, preferably less than or equal to 40%, preferably less than 35%, preferably less than 30%, preferably less than 25%, and preferably less than 20%, based on the mass percentage of the total amount of crystalline phase;

[0081] - The content of "other crystalline phases" (i.e., crystalline phases other than zircon, stabilized zirconium oxide, stabilized hafnium dioxide, monoclinic zirconium oxide, monoclinic hafnium dioxide and corundum) is less than 8%, preferably less than 6%, or even less than 5%, or even less than 4%, based on the mass percentage of the total amount of crystalline phases;

[0082] - More than 90% by mass, more than 95% by mass, and essentially 100% by mass of “other crystalline phases” are mullite and / or cristobalite;

[0083] - In the implementation method, the measurement method described in the example cannot detect the content of mullite;

[0084] - The mass percentage of the amorphous phase, i.e. the glassy phase, is less than 25%, preferably less than 20%, and more preferably less than 17%, based on the mass percentage of the bead mass;

[0085] - The amorphous phase (represented as oxides) contains MgO and SiO2, and / or Y2O3 and / or Al2O3 and / or CaO and / or Na2O and / or K2O and / or P2O5;

[0086] - Amorphous phases (represented as oxides) include MgO and SiO2 and Y2O3 and Al2O3 and Na2O and K2O and P2O5;

[0087] - Total porosity less than 6%, preferably less than 5.5%, preferably less than 5%, preferably less than 4.5%, or even less than 4%, or even less than 3%, or even less than 2%;

[0088] - The size of the sintered beads is less than 10 mm, preferably less than 2.5 mm and / or greater than 0.005 mm, preferably greater than 0.5 mm;

[0089] - The sphericity of the sintered beads is greater than 0.7, preferably greater than 0.8, preferably greater than 0.85 or even greater than 0.9;

[0090] - The density of the sintered beads is greater than 4.2 g / cm³. 3 Preferably greater than 4.3 g / cm³ 3 or even greater than 4.4 g / cm 3 and / or less than 4.9 g / cm³ 3 Preferably less than 4.8 g / cm³ 3 .

[0091] In a preferred embodiment, the sintered beads according to the present invention most preferably have:

[0092] - The following crystalline phases are listed as a percentage by mass of the crystalline phases, totaling 100%:

[0093] 31% ≤ Zircon ≤ 68%;

[0094] 25% ≤ stabilized zirconium oxide + stabilized hafnium dioxide ≤ 47%;

[0095] Monoclinic zirconium oxide + monoclinic hafnium dioxide ≤ 5%;

[0096] 4% ≤ Corundum ≤ 25%;

[0097] Crystalline phases other than zircon, stabilized zirconium oxide, stabilized hafnium dioxide, monoclinic zirconium oxide, monoclinic hafnium dioxide, and corundum < 5%;

[0098] - The following chemical compositions are expressed as mass percentages based on oxides and total 100%:

[0099] 50% ≤ ZrO2 + HfO2 ≤ 70%;

[0100] HfO2 ≤ 2%;

[0101] 15% ≤ SiO2 ≤ 25%;

[0102] 5% ≤ Al2O3 ≤ 20%;

[0103] 3% ≤ Y2O3 ≤ 8.3%;

[0104] CeO2 ≤ 0.1%;

[0105] 0.1% ≤ MgO ≤ 1%;

[0106] 0.3% ≤ CaO ≤ 1%;

[0107] Oxides other than ZrO2, HfO2, SiO2, Al2O3, MgO, CaO, CeO2 and Y2O3 account for less than 3%.

[0108] In this embodiment, the sintered beads preferably have:

[0109] - Based on the mass of the beads, less than 25% amorphous phase, and

[0110] - Total porosity less than or equal to 6%.

[0111] Preferably, the CeO2 content is essentially zero.

[0112] The present invention also relates to a bead powder, which, by weight percentage, contains more than 90%, preferably more than 95%, and preferably substantially 100% beads according to the invention.

[0113] The present invention also relates to a method for manufacturing sintered beads according to the present invention, the method comprising the following steps performed in sequence:

[0114] a) Optionally, one or more raw material powders are ground, preferably by co-grinding.

[0115] A measured amount of the optionally ground raw material powder is added.

[0116] This results in a particulate mixture having a median particle size of less than 0.6 μm, and a composition suitable for obtaining sintered beads with a composition consistent with that of sintered beads according to the invention at the end of step g).

[0117] The particulate mixture comprises zircon particles, stabilized zirconium oxide particles, and glass particles containing MgO and / or SiO2, and / or glass-ceramic particles containing MgO, and / or compound particles containing MgO and SiO2, and / or powders of precursors of these oxides.

[0118] b) Optionally, dry the particulate mixture.

[0119] c) A starting feed is prepared from the particulate mixture, which is optionally dried.

[0120] d) The initial feed is shaped into raw beads.

[0121] e) Optionally, wash,

[0122] f) Optionally, dry.

[0123] g) Sintering at a sintering temperature above 1330°C and below 1450°C to obtain sintered beads.

[0124] Finally, the present invention relates to bead powder according to the invention, particularly bead powder manufactured according to the method of the invention, as an abrasive; a wet dispersant; a proppant, particularly a proppant for preventing the closure of deep geological fractures formed in the walls of production wells (especially oil wells); a heat exchanger, for example a heat exchanger for fluidized beds; or for use in surface treatment.

[0125] definition

[0126] - The sum of oxide content or crystalline phase content (i.e., the formula connecting these contents with the symbol "+") does not mean that the two oxides or crystalline phases connected by the symbol "+" must exist simultaneously.

[0127] - "Granular" refers to solid products that are individually packaged in powder form.

[0128] - "Sintering" is the process of solidifying the original particles (granular agglomerates) through heat treatment at temperatures above 1100°C, during which some (but not all) of their components may be partially or completely melted.

[0129] - "Bead" refers to a particle with a sphericity (i.e., the ratio between its smallest Feret diameter and its largest Feret diameter) greater than 0.6, regardless of how that sphericity was obtained. Preferably, the beads according to the invention have a sphericity greater than 0.7.

[0130] - The "size" of a bead is its minimum Ferete diameter.

[0131] - Usually by D 50 The "median particle size" of a powder representing raw material particles is the size at which the powder particles are divided into two groups of equal mass, one group containing only particles larger than or smaller than the median particle size. For example, a laser particle size analyzer can be used to estimate the median particle size.

[0132] - "Sintered beads" refers to solid beads obtained by sintering original beads.

[0133] - "Impurities" refer to unavoidable components that are necessarily introduced along with the raw materials. Specifically, in embodiments, compounds belonging to the group consisting of oxides, nitrides, nitrides, carbides, carbon oxides, and carbonitrides of sodium and other alkali metals, iron, vanadium, and chromium are impurities. Examples include Fe₂O₃ and TiO₂. Residual carbon is one of the impurities in the composition of the particles according to the invention.

[0134] When referring to ZrO2 or (ZrO2 + HfO2), this is understood to mean ZrO2 and less than 2% HfO2, expressed as a mass percentage of ZrO2 + HfO2. In fact, some HfO2, chemically inseparable from ZrO2 and possessing similar properties, is always naturally present in the ZrO2 source at levels typically below 2% (expressed as a mass percentage of ZrO2 + HfO2). Hafnium oxide is not considered an impurity.

[0135] - The "precursor" of the oxide is a component that can provide the oxide during the manufacturing process of the beads according to the invention.

[0136] - "Stabilized zirconia" refers to zirconia in the secondary and / or cubic crystal forms.

[0137] For clarity, the terms "ZrO2," "HfO2," "SiO2," and "Al2O3" are used to indicate the content of these oxides in the composition, while "zirconium oxide," "hafnium dioxide," and "corundum" indicate the crystalline phases of these oxides, respectively, composed of ZrO2, HfO2, SiO2, and Al2O3. However, these oxides can also exist in other phases. In particular, ZrO2 and SiO2 can exist as zircon (ZrSiO4).

[0138] Unless otherwise stated, all percentages in this specification are based on the mass percentage of oxides.

[0139] All characteristics of the beads can be measured according to the scheme described in the example.

[0140] Unless otherwise stated, the terms “containing one,” “comprising one,” or “including one” should be interpreted broadly without limitation. Detailed Implementation

[0141] To produce the sintered beads according to the present invention, steps a) to g) described above and detailed below can be performed.

[0142] In step a), if the mixture of raw material powders in a proportion suitable for manufacturing beads according to the invention does not form a mixture of particles with a median particle size of less than 0.6 μm, the raw material powders can be ground individually or preferably co-ground. This grinding can be wet grinding.

[0143] Preferably, the particulate mixture is ground or co-ground in such a way that the median particle size is less than 0.5 μm, preferably less than 0.4 μm.

[0144] Preferably, the powders used, particularly zircon ZrSiO4 powder, stabilized zirconium oxide ZrO2 powder, optionally alumina Al2O3 powder, glass powder containing MgO and / or SiO2, and / or glass-ceramic powder containing MgO, and / or powder of compounds containing MgO and SiO2, each have a median particle size of less than 5 µm, or even less than 3 µm, less than 1 µm, less than 0.7 µm, preferably less than 0.6 µm, preferably less than 0.5 µm, or even less than 0.4 µm. Advantageously, grinding is optional when the median particle size of each of these powders is less than 0.6 µm, preferably less than 0.5 µm, or even less than 0.4 µm.

[0145] In the method according to the invention, the particulate mixture comprises zircon ZrSiO4 powder, stabilized zirconium oxide ZrO2 powder, glass powder containing MgO and / or SiO2, and / or glass ceramic powder containing MgO and / or powder of compounds containing MgO and SiO2, and optionally alumina Al2O3 powder.

[0146] These powders can also be at least partially replaced by powders of precursors of these oxides introduced in equal amounts.

[0147] Preferably, the zircon powder used has a specific surface area greater than 5 m² calculated by the BET method. 2 / g, preferably greater than 8m 2 / g, preferably greater than 10 m 2 / g, and / or less than 30 m 2 / g. Advantageously, the grinding in step a) is usually promoted in a suspension. Additionally, the sintering temperature in step f) can be reduced.

[0148] Preferably, the stabilized zirconia powder used has a specific surface area greater than 0.5 m² calculated by the BET method. 2 / g, preferably greater than 1 m 2 / g, preferably greater than 1.5 m 2 / g and / or less than 20 m 2 / g, preferably less than 18 m 2 / g, preferably less than 15m 2 / g. Advantageously, the grinding in the suspension in step a) is beneficial. Additionally, the sintering temperature in step f) can be reduced.

[0149] Preferably, the median particle size of the alumina powder used is less than 7 μm, more preferably less than 6 μm, or even less than 3 μm, or even less than 2 μm, or even less than 1.5 μm.

[0150] In step (b), optionally, the ground raw material powder is dried, for example, in an oven or by spray drying, particularly if the ground raw material powder was obtained by wet grinding. Preferably, the temperature and / or duration of the drying step are adjusted such that the residual moisture content of the raw material powder is less than 2% or even less than 1.5%.

[0151] In step c), the starting feed is prepared, preferably at room temperature.

[0152] The starting feed contains zircon powder (i.e., ZrSiO4 particles) in an amount greater than 35%, preferably greater than 40%, and / or less than 94%, preferably less than 90%, preferably less than 85%, preferably less than 80%, preferably less than 76%, preferably less than 72%, preferably less than 68%, based on the mass of the starting feed.

[0153] Based on the mass of the initial feed, the initial feed contains, in an amount greater than 5%, preferably greater than 10%, preferably greater than 15%, preferably greater than 20%, preferably greater than 25% and / or less than 60%, preferably less than 55%, preferably less than 50%, a powder containing ZrO2, HfO2, Y2O3 and CeO2 particles in an amount capable of stabilizing zirconium oxide. Preferably, it is a powder containing ZrO2, HfO2, Y2O3 and CeO2 particles in an amount capable of stabilizing zirconium oxide in a homogeneous mixture. More preferably, it is a powder of stabilized zirconium oxide particles, i.e., a powder of ZrO2 particles stabilized by Y2O3 and / or CeO2.

[0154] Preferably, the stabilized zirconia powder is Y2O3 stabilized zirconia powder and contains virtually no CeO2.

[0155] Preferably, the stabilized zirconium oxide powder is stabilized in a cubic crystal form. Surprisingly, the inventors found that the wear resistance of the beads was greatly improved.

[0156] In a first preferred embodiment, the stabilized zirconia powder is zirconia powder stabilized in a cubic crystal form using Y₂O₃ and substantially free of CeO₂. In this embodiment, the molar content of Y₂O₃ is from 7.5 mol% to 11 mol% based on the total content of ZrO₂, Y₂O₃, and CeO₂.

[0157] In a second preferred embodiment, the initial feed contains alumina powder (i.e., Al2O3 particles) in an amount greater than 5%, preferably greater than 10%, and / or less than 45%, preferably less than 35%, preferably less than 30%, preferably less than 25%, preferably less than 20%, based on the mass of the initial feed. Preferably, the alumina powder is active alumina powder and / or calcined alumina powder and / or transition state alumina powder. Preferably, the alumina powder is active alumina powder.

[0158] In the third embodiment, the initial feed contains silica powder (i.e., SiO2 particles) in an amount preferably greater than 0.5%, preferably greater than 1% and / or less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, based on the mass percentage of the initial feed.

[0159] By weight, glass powder containing MgO and / or SiO2 and / or glass-ceramic powder containing MgO preferably contain more than 40%, more preferably more than 50%, or even more than 60%, or even more than 70%, or even more than 80% silicon dioxide.

[0160] The compound containing MgO and SiO2 preferably also contains Al2O3. Preferably, the compound is selected from talc, cordierite, and mixtures thereof. Preferably, the compound is cordierite.

[0161] In the fourth embodiment, the initial feed contains cordierite in an amount preferably greater than 0.5%, preferably greater than 1%, preferably greater than 1.5% and / or less than 15%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, based on the mass percentage of the initial feed.

[0162] In the fifth embodiment, the initial feed preferably contains clay in an amount greater than 0.5%, more preferably greater than 1%, more preferably greater than 1.5% and / or less than 5%, more preferably less than 4%, more preferably less than 3%.

[0163] In the implementation, the first to fifth embodiments described above are combined.

[0164] The powder providing the oxide or precursor is preferably selected such that the total content of oxides other than ZrO2, HfO2, SiO2, Al2O3, MgO, CaO, CeO2 and Y2O3 is less than 5% by mass percentage based on the oxides.

[0165] Preferably, no other raw materials are actively introduced into the starting feed except for zircon ZrSiO4 powder, stabilized zirconium oxide ZrO2 powder, optionally alumina Al2O3 powder, glass powder containing MgO and / or SiO2, and / or glass ceramic powder containing MgO, and / or powder of compounds containing MgO and SiO2, and other oxides present are impurities.

[0166] The initial feed may also contain a solvent, preferably water, in an amount suitable for the molding method in step d).

[0167] As is well known to those skilled in the art, the initial feed is suitable for the molding process in step d).

[0168] Molding can be caused, in particular, by a gelation process. For this purpose, a solvent (preferably water) is added to the initial feed to achieve a suspension.

[0169] The suspension preferably has a dry matter content of 50% to 70% by mass.

[0170] The suspension may also contain one or more of the following components:

[0171] - Dispersant, in a ratio of 0 to 10% based on dry matter mass percentage;

[0172] - Surface tension modifier, in a ratio of 0 to 3% based on dry matter mass percentage;

[0173] - Gelling agent, in a ratio of 0 to 2% based on dry matter mass percentage.

[0174] Dispersants, surface tension modifiers, and gelling agents are well-known to technicians.

[0175] Examples include,

[0176] - As dispersants, the sodium or ammonium polymethacrylate family, the sodium or ammonium polyacrylate family, the citrate family (e.g., ammonium citrate), the sodium phosphate family, and the carbonate family;

[0177] - Organic solvents (e.g., fatty alcohols) can be used as surface tension modifiers.

[0178] - Natural polysaccharides as gelling agents.

[0179] Preferably, the oxide powder and / or precursor powder are added to a mixture of water and dispersant / antiflocculator in a ball mill. After stirring, water, in which the gelling agent has been pre-dissolved, is added to obtain a suspension.

[0180] If the molding is the result of extrusion, a thermoplastic or thermosetting polymer can be added to the initial feed.

[0181] In step d), any conventional forming process known for manufacturing sintered beads can be used.

[0182] Examples of these processes include:

[0183] - Granulation processes, such as granulators, fluidized bed granulators, or granulation discs.

[0184] - Gel process,

[0185] - Injection molding or extrusion molding process, and

[0186] - Pressing process.

[0187] In the gelation process, droplets of the suspension are obtained by passing the suspension through a calibration orifice. The droplets exiting the orifice fall into a bath of gel solution (an electrolyte suitable for reacting with a gelling agent), where they harden after regaining their substantially spherical shape.

[0188] In step e), optionally, the raw beads obtained in the previous step are washed (e.g., with water).

[0189] In step f), optionally (e.g., in an oven) the raw beads, which may have been washed, are dried.

[0190] In step g), the raw beads, which may have been washed and / or dried, are sintered. Preferably, sintering is carried out in air, more preferably in an electric furnace, and more preferably at atmospheric pressure.

[0191] The sintering in step g) is carried out at a temperature above 1330°C, preferably above 1340°C, preferably above 1350°C, preferably above 1360°C, preferably above 1370°C and below 1450°C, preferably below 1430°C, preferably below 1410°C, preferably below 1400°C, and preferably below 1390°C. A sintering temperature of 1375°C is very suitable. Sintering temperatures below 1330°C do not produce particles with a total porosity of 6% or less. On the other hand, sintering temperatures above 1450°C lead to excessive dissociation of zircon, which is detrimental to wear resistance.

[0192] Preferably, the sintering time is 2 to 5 hours. A sintering time of 4 hours is very suitable.

[0193] The obtained sintered beads preferably have a minimum diameter greater than 0.005 mm, more preferably greater than 0.5 mm and less than 10 mm, and more preferably less than 2.5 mm.

[0194] If relations (1) and (2) are not observed, the wear resistance is not improved. These relations allow for the limitation of the total amount of CeO2 and Y2O3 as the amount of ZrO2 provided substantially uniquely by the stabilized zirconia varies.

[0195] Therefore, relation (1) indicates that Y2O3 and CeO2 exist in amounts theoretically suitable for stabilizing all existing zirconium oxides, and relation (2) indicates that there are no compounds other than stabilized zirconium oxides that contain zirconium and yttrium in oxide form or zirconium and cerium in oxide form.

[0196] The sintered beads according to the invention are particularly well-suited for use as abrasives or wet dispersants, as well as for surface treatment. Therefore, the invention also relates to the use of bead powder according to the invention or beads manufactured by the method according to the invention as abrasives or as dispersants in humid environments.

[0197] The properties of the beads according to the invention, particularly their mechanical strength, density, and ease of production, make them suitable for other applications, especially as a proppant or heat exchanger, or for surface treatment (particularly by spraying the beads according to the invention).

[0198] Therefore, the present invention also relates to objects selected from suspension bodies, grinding mills, surface treatment equipment and heat exchangers, said objects comprising bead powder according to the present invention.

[0199] Example

[0200] For the purpose of illustrating the present invention, the following non-limiting embodiments are provided.

[0201] Measurement scheme

[0202] The following methods were used to determine certain properties of different sintered bead mixtures. These methods provide excellent simulations of the actual operational behavior in micro-grinding applications.

[0203] To determine the sphericity of the beads, the minimum and maximum Ferrette diameters were measured on a Camsizer XT sold by Horiba.

[0204] To determine the so-called "planetary" abrasion resistance, 20 ml (volume measured using a graduated cylinder) of test beads (size 1.6 mm to 2.0 mm) was weighed (mass m0) and placed into one of four 125 ml drums coated with dense sintered alumina in a high-speed planetary mill (PM400, RETSCH). In the same drum already containing the beads, 2.2 g of Presi brand silicon carbide (median particle size D) was added. 50The drum was filled with 23 µm of water and 40 ml of water. The drum was then shut off and rotated at 400 rpm (planetary motion), reversing the rotation direction every minute for 1.5 h. The contents of the drum were then washed through a 100 µm sieve to remove residual silicon carbide and material tearing caused by abrasion during the grinding process. After sieving through the 100 µm sieve, the beads were dried in an oven at 100 °C for 3 h and then weighed (mass m1). The beads (mass m1) were again introduced into one of the drums containing a suspension of SiC (same concentration and amount as before) and a new grinding cycle was performed as before. The contents of the drum were then washed through a 100 µm sieve to remove residual silicon carbide and material tearing caused by abrasion during the grinding process. After sieving through the 100 µm sieve, the beads were dried in an oven at 100 °C for 3 h and then weighed (mass m2). The beads (mass m2) are reintroduced into one of the drums containing a SiC suspension (same concentration and amount as before), and a new grinding cycle is performed as before. The contents of the drum are then washed on a 100 µm sieve to remove residual silicon carbide and material tearing caused by abrasion during the grinding process. After sieving on the 100 µm sieve, the beads are dried in an oven at 100°C for 3 hours and then weighed (mass m3).

[0205] Planetary wear (PW) is expressed as a percentage (%) and is equal to the loss of bead mass relative to the initial bead mass, i.e., 100(m0-m3) / (m0); PW results are given in Table 1.

[0206] If the planetary wear resistance (PW) of the product is improved by at least 15% compared with Example 1 (Reference Example), the result is considered particularly satisfactory.

[0207] The quantification of the crystalline phase present in the sintered beads according to the invention is performed by a sample of polished beads prepared according to the following method: for each embodiment, substantially continuous monolayer beads with a size of 1.6 mm to 2 mm are partially embedded in acrylic resin at a temperature equal to 180°C.

[0208] The outer diameter of the resin block containing the beads is 25 mm.

[0209] The block was polished with 65 μm sandpaper until the center of the bead was visible. Then, the block was polished more finely. The penultimate polishing step was done using Mecaprex LD32-E 1 µm diamond polishing material sold by PRESI, and the final polishing step was done using a 0.04 µm colloidal silica solution.

[0210] The crystalline phase present in the sintered beads according to the invention is measured by X-ray diffraction, for example using a Panalytical X'Pert PRO diffractometer equipped with a copper DX tube. The device thus acquires diffraction patterns in a 2θ angle range of 5° to 80° with a step size of 0.017° and a counting time of 150 seconds per step. The front optics have a fixed 1 / 4° programmable divergence groove, a 0.04 rad Soller groove, a 10 mm diaphragm, and a fixed 1 / 2° anti-scattering groove. The sample itself is rotated to constrain the preferred orientation. The rear optics have a fixed 1 / 4° programmable anti-scattering groove, a 0.04 rad Soller groove, and a Ni filter.

[0211] Then, the diffraction pattern was qualitatively analyzed using EVA software and the ICDD2016 database.

[0212] Once the existing phase is identified, the diffraction pattern is quantitatively analyzed using Rietveld-refined High Score Plus software according to the following strategy:

[0213] - Use the "Process" function, "Define Background," and select the following options to refine the background signal: "Bend Factor" equals 0, and "Graininess" equals 40. Note that if resin-induced halos are observed, baselines can be manually drawn point by point.

[0214] - Typically, the ICDD tables of the prominent and quantifiable phases are selected and thus taken into account during refinement;

[0215] - Then, perform automatic refinement by selecting the previously determined "Use available background" bottom signal and choosing the "Auto: Options: Phase Fit - Default Rietveld" mode.

[0216] Then, the "B total" parameter of all selected phases is manually refined simultaneously.

[0217] Finally, if the automatic function is not executed, the Caglioti parameter W of both the secondary zirconia phase and the cubic zirconia phase is manually refined simultaneously. In this case, "W" is selected for the zirconia phase, and the refinement is performed again. The result is retained only if the "goodness of fit" parameter of the second refinement is lower than that of the first refinement.

[0218] The amount of amorphous phase present in the sintered beads according to the invention is measured by X-ray diffraction, for example using a Panalytical X'Pert PRO diffractometer equipped with a copper DX tube. The diffraction pattern is acquired by this instrument in the same manner as for determining the crystalline phase present in the beads, and the sample being analyzed is in powder form. The method used involves adding a known amount of a fully crystalline standard, in this case, zinc oxide (ZnO) powder in an amount equal to 20% (based on the mass of zinc oxide and the sample of milled sintered beads according to the invention). The maximum size of the zinc oxide powder is 1 μm, and the beads according to the invention are milled to obtain powder with a maximum size of less than 40 μm.

[0219] The maximum size of the ZnO particles was input into the High Score Plus software to limit the micro-absorption effect.

[0220] Calculate the ratio of the amorphous phase (expressed as a percentage) using the following formula: Q ZnO The amount of ZnO is determined based on the diffraction pattern:

[0221] The ratio of amorphous phases = 100 × (100 / (100-20)) × (1-(20 / Q)) ZnO ))

[0222] For example, if Q ZnO If the ratio is 22%, then the ratio of the amorphous phase is 100×(100 / (100-20))×(1-(20 / 22)) = 11.4%.

[0223] Total porosity (expressed as a percentage) is calculated using the following formula:

[0224] Total porosity = 100 × (1 - (d) 珠粒 / d 研磨的珠粒 )),in

[0225] - d 珠粒 The density of the unground beads was obtained using a helium specific gravity bottle (AccuPyc 1330 from Micromeritics®) and a method based on the volume of displacement helium gas.

[0226] - d 研磨的珠粒 The density of the powder is obtained by grinding the beads using an Auric ring dry mill for 40 seconds and then sieving them to retain only the powder that passes through a 160 μm sieve for measurement.

[0227] Manufacturing solutions

[0228] Sintered beads are prepared as follows:

[0229] - Specific surface area is approximately 8 m² 2 Zircon powder with a median particle size of 1.5 µm and a total oxide content of 1.1% excluding ZrO2 and SiO2, per g.

[0230] - Cordierite powder with a purity greater than 95% and a median particle size less than 63 µm.

[0231] - Clay powder with a median particle size of less than 53 μm, a loss on ignition of 10% to 15% at 1000℃, and a total SiO2 + Al2O3 content of greater than 82%.

[0232] - Silica powder with a purity greater than 98.5% and a median particle size of 1.5 µm, and, according to the resulting examples,

[0233] - Alumina powder with a purity of 99.5% and a median particle size of less than 5 µm.

[0234] - Cerium oxide powder with a purity greater than 99.5% and a median particle size of 2.8 µm.

[0235] - Monoclinic unstable zirconia powder CZ-5 sold by Saint-Gobain ZirPro.

[0236] - Stabilized zirconium oxide powder CY3Z, sold by Saint-Gobain ZirPro, with a Y2O3 molar content of 3% and primarily in a secondary crystal form.

[0237] - Stabilized zirconia powder TZ-10Y, sold by TOSOH, with a Y2O3 molar content of 10% and exhibiting a substantially fully cubic crystal form.

[0238] Table 1 summarizes the initial feed of the embodiments.

[0239] These powders were mixed and then co-milled in a humid environment until a granular mixture with a median particle size of less than 0.4 µm was obtained. The granular mixture was then dried.

[0240] The starting feed consisting of an aqueous suspension is then prepared from this particulate mixture, which contains 0.5% carboxylic acid dispersant, 0.6% sodium phosphate dispersant and 0.4% gelling agent (i.e., polysaccharides of the alginate family) based on the dry matter mass percentage.

[0241] To achieve good initial feed uniformity, a ball mill was used in this preparation process: first, a solution containing a gelling agent was formed. Then, the particulate mixture and dispersant were added to water. Next, the gelling agent solution was added. The resulting mixture was stirred for 8 hours. Particle size (median < 0.4 µm) was controlled by sedimentation using a Micromeritics® Sedigraph 5100 sedimentation particle size analyzer, and a predetermined amount of water was added to obtain an aqueous suspension with a dry matter content of 68% and a viscosity (measured using a Brookfield viscometer with an LV3 rotor at 20 rpm) of less than 5000 centipoise. After adjustment with a strong alkali, the pH of the suspension was approximately 9.

[0242] In this embodiment, the suspension is passed through a calibration orifice at a flow rate that produces beads of approximately 1.6 mm to 2.0 mm after sintering. Droplets of the suspension fall into an electrolyte-based (divalent cation salt) gel bath and react with a gelling agent. The raw beads are collected, washed, and dried at 80°C to remove moisture. The beads are then transferred to a sintering furnace, where they are heated to a temperature of 1375°C at a rate of 100°C / h. After 4 hours at this temperature, the temperature is reduced by natural cooling.

[0243] result

[0244] The results are summarized in Table 2.

[0245]

[0246]

[0247] The bead powder in the examples has an average sphericity greater than 0.9.

[0248] The beads in Examples 2 to 9 have an amorphous phase content of less than 20% by mass.

[0249] The reference beads in Example 1 of the prior art are sintered zircon beads commonly used in grinding applications, and their composition is similar to that of Example 4 of US 2004 / 007789.

[0250] Z=Z4+Z5+Z6-(0.67×Z1×(Z4+Z5+Z6) / (0.67×Z1+Z2+Z3))

[0251] For example, for Example 2, Z is determined as follows:

[0252] Z = 0.667 + 0.06 + 0 - (0.67 × 0.68 × (0.667 + 0.06 + 0) / (0.67 × 0.68 + 0.32 + 0)) = 0.3, or 30%.

[0253] The verification of conditions (1) and (2) is determined as follows:

[0254] 0.128×Z equals 0.128×30=3.84, 0.318×Z equals 0.318×30=9.54.

[0255] CeO2 + 3.76×Y2O3 equals 0 + 3.76×6 = 22.56, which is much higher than 3.84 (0.128×Z): For Example 2, condition (1) is indeed verified.

[0256] CeO2 + 1.3×Y2O3 equals 0 + 1.3×6 = 7.8, which is much lower than 9.54 (0.318×Z): For Example 2, condition (2) is indeed verified.

[0257] Comparing the prior art embodiment 1 with the present invention embodiment 2, it is shown that the planetary wear PW is reduced by 58%, which is in particular attributed to the addition of zirconium oxide stabilized with Y2O3 and which is essentially cubic.

[0258] Comparing Example 1 of the prior art with Example 6 of the present invention, it is shown that the planetary wear PW is reduced by 38%, which is mainly due to the addition of stabilized zirconium oxide, which is mainly in the secondary crystal form.

[0259] A comparison of Examples 1, 2, and 6 shows that, surprisingly, it is preferable to add substantially cubic stabilized zirconia rather than predominantly secondary stabilized zirconia, compared to the wear of Example 1, which has an wear of 4.5%: the wear amounts are 1.9% and 2.8%, respectively.

[0260] A comparison of Examples 2 to 4 of the present invention shows that, with the increase of alumina addition, wear PW decreases and density decreases.

[0261] A comparison of Examples 1 and 5 of the prior art shows that by adding 34% of unstable zirconium oxide powder, wear PW deterioration occurs.

[0262] A comparison of Examples 1 and 7, and Examples 8 and 9 shows that for the zirconium oxide beads according to the present invention, which have a SiO2 content of 30.5%, an Al2O3 content of 36.3%, and Y2O3 and CeO2 stabilized respectively, the wear PW is reduced.

[0263] The examples unexpectedly show that the tested beads according to the invention have superior performance compared to reference beads.

Claims

1. A sintered bead, having: - The following crystalline phases are listed as a percentage by mass of the crystalline phases, totaling 100%: 25% ≤ zircon, or "Z1" ≤ 94%; 10% < stabilized zirconium oxide + stabilized hafnium dioxide, or "Z2" ≤ 61%; Monoclinic zirconium oxide + monoclinic hafnium dioxide, or "Z3" ≤ 50%; Corundum ≤ 57%; Crystalline phases other than Z1, Z2, Z3 and corundum < 4%; - The following chemical compositions are expressed as mass percentages based on oxides and total 100%: 33% ≤ ZrO2 + HfO2, or "Z4" ≤ 83.4%; HfO2 ≤ 2%; 10.6% ≤ SiO2 ≤ 34.7%; Al2O3 ≤ 50%; 0% ≤ Y2O3, or "Z5"; 0% ≤ CeO2, or "Z6"; 0.3% ≤ CeO2 + Y2O3 ≤ 19%, under the condition that (1) CeO2 + 3.76×Y2O3 ≥ 0.128×Z, and (2) CeO2 + 1.3×Y2O3 ≤ 0.318×Z, in, Z=Z4+Z5+Z6-(0.67×Z1×(Z4+Z5+Z6) / (0.67×Z1+Z2+Z3)); MgO ≤ 5%; CaO ≤ 2%; Oxides other than ZrO2, HfO2, SiO2, Al2O3, MgO, CaO, CeO2 and Y2O3 < 5.0%.

2. The sintered beads according to claim 1, wherein, Based on the mass percentage of oxides, Al2O3 ≤ 35%, ZrO2 + HfO2 ≤ 37%, and SiO2 ≤ 12.6%; and based on the mass percentage of the total amount of crystalline phases, the content of corundum is 40% or less, and the content of zircon is 31% or more.

3. The sintered beads according to any one of the preceding claims, wherein, 50% ≤ ZrO2+HfO2 and / or SiO2 > 14% and / or Al2O3 > 5% and / or MgO > 0.1% and / or CaO > 0.1%.

4. The sintered beads according to any one of the preceding claims, wherein, 25% > Al2O3 > 10%.

5. The sintered beads according to any one of the preceding claims, wherein, 1.0% > MgO > 0.15%.

6. The sintered beads according to any one of the preceding claims, wherein, 1.0% > CaO > 0.2%.

7. The sintered beads according to any one of the preceding claims, wherein, The content of CeO2 + Y2O3 is greater than 2.2% based on the mass percentage of oxides.

8. The sintered beads according to the immediately preceding claim, wherein, The content of CeO2 + Y2O3 is greater than 3% by mass percentage based on oxides.

9. The sintered beads according to any one of the preceding claims, wherein, CeO2 + 2.39×Y2O3 ≥ 0.212×Z.

10. The sintered beads according to the immediately preceding claim, wherein, CeO2 + 1.84×Y2O3 ≥0.224×Z.

11. The sintered beads according to the immediately preceding claim, wherein, CeO2 + 1.76×Y2O3 ≥0.229×Z.

12. The sintered beads according to any one of the preceding claims, wherein, The content of CeO2 + Y2O3 is less than 15.5% based on the mass percentage of oxides.

13. The sintered beads according to the immediately preceding claim, wherein, The content of CeO2 + Y2O3 is less than 11.6% based on the mass percentage of oxides.

14. The sintered beads according to any one of the preceding claims, wherein, CeO2 + 1.4×Y2O3 ≤ 0.259×Z.

15. The sintered beads according to any one of the preceding claims, wherein, The CeO2 content is less than 0.2%, preferably less than 0.1%.

16. The sintered beads according to any one of the preceding claims, wherein, Y2O3 ≥ 3.44×Z, preferably Y2O3 ≥ 5.38×Z.

17. The sintered beads according to any one of the preceding claims, wherein, The content of oxides other than ZrO2, HfO2, SiO2, Al2O3, Y2O3, CeO2, CaO, and MgO is less than 2% by mass percentage.

18. The sintered beads according to any one of the preceding claims, wherein, The content of oxides accounts for more than 99% of the total mass of the beads.

19. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a zircon content of greater than 35% and less than 90% by mass percentage based on the total amount of crystalline phase.

20. The sintered beads according to the preceding claim, wherein, The zircon content is less than 68% by mass percentage based on the total amount of crystalline phase.

21. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a content of less than 50% stabilized zirconium oxide + stabilized hafnium dioxide, based on the mass percentage of the total amount of crystalline phase.

22. The sintered beads according to the preceding claim, wherein, The content of stabilized zirconium oxide + stabilized hafnium dioxide is greater than 27% and less than 47% by mass percentage based on the total amount of crystalline phase.

23. The sintered beads according to any one of the preceding claims, wherein, The content of monoclinic zirconium oxide + monoclinic hafnium dioxide is less than 35% by mass percentage based on the total amount of crystalline phases.

24. The sintered beads according to the preceding claim, wherein, The content of monoclinic zirconium oxide + monoclinic hafnium dioxide is less than 10% by mass percentage based on the total amount of crystalline phases.

25. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a corundum content of greater than 10% and less than 25% by mass percentage based on the total amount of crystalline phase.

26. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a content of less than 8% of crystalline phases other than zircon, stabilized zirconium oxide, stabilized hafnium dioxide, monoclinic zirconium oxide, monoclinic hafnium dioxide and corundum, based on the mass percentage of the total amount of crystalline phases.

27. The sintered beads according to the preceding claim, wherein, The mullite content is essentially zero.

28. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have less than 25% amorphous phase by mass percentage based on the mass of the beads.

29. The sintered beads according to the immediately preceding claim, wherein, Represented as an oxide, the amorphous phase comprises: MgO and SiO2, and / or Y2O3, and / or Al2O3, and / or CaO, and / or Na2O, and / or K2O, and / or P2O5.

30. The sintered beads according to the immediately preceding claim, wherein, Represented by oxides, the amorphous phase comprises MgO and SiO2 and Y2O3 and Al2O3 and Na2O and K2O and P2O5.

31. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a total porosity of less than 6%.

32. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a sphericity greater than 0.

7.

33. The sintered beads according to the immediately preceding claim, wherein, The sintered beads have a sphericity greater than 0.

85.

34. The sintered beads according to any one of the preceding claims, wherein, The sintered beads have a size of less than 10 mm and greater than 0.005 mm.

35. A powder comprising more than 90% by weight beads according to any one of the preceding claims.

36. An object selected from suspended bodies, grinding mills, surface treatment equipment, and heat exchangers, the object comprising bead powder according to the immediately preceding claim.

37. A method for manufacturing sintered beads according to any one of claims 1 to 34, the method comprising the following steps performed sequentially: a) Optionally, one or more raw material powders are ground, preferably by co-grinding. A measured amount of the optionally ground raw material powder is added. This results in a particulate mixture having a median particle size of less than 0.6 μm, and a composition suitable for obtaining sintered beads with a composition consistent with that of the sintered beads according to any one of claims 1 to 34 at the end of step g). The particulate mixture comprises: - Zircon particles and stabilized zirconium oxide particles, and - Glass particles containing MgO and / or SiO2, and / or glass-ceramic particles containing MgO and / or compound particles containing MgO and SiO2, b) Optionally, dry the particulate mixture. c) A starting feed is prepared from the particulate mixture, which is optionally dried. d) The initial feed is shaped into raw beads. e) Optionally, the original beads are washed. f) Optionally, the raw beads are dried, and the raw beads have optionally been washed. g) The original beads are sintered at a sintering temperature above 1330°C and below 1450°C to obtain sintered beads, wherein the original beads are optionally dried and / or washed.

38. The method according to the immediately preceding claim, wherein, In step c), no other raw materials are actively introduced into the initial feed except for zircon ZrSiO4 powder, stabilized zirconium oxide ZrO2 powder, optionally alumina Al2O3 powder, glass powder containing MgO and / or SiO2, and / or glass ceramic powder containing MgO, and / or compound powder containing MgO and SiO2.

39. The method according to any one of the preceding two claims, wherein, In step c), the stabilized zirconia powder is Y2O3 stabilized zirconia powder and is substantially free of CeO2.

40. The method according to any one of the preceding three claims, wherein, In step c), the stabilized zirconium oxide powder is stabilized in a cubic crystal form.

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