Flaky non-oxide ceramic particles and pigments being based thereon

Abstract

The present invention relates to a method for manufacturing a MAX phase ceramic, use of a MAX phase ceramic as a pigment, and a pigment comprising a MAX phase ceramic. In particular the MAX phase ceramics of the invention are characterized by a predefined and controllable particle morphology allowing for tailored compositions of flake particles particularly suitable as pigments and in various coatings.

Description

[0001] P7097PC00

[0002] Flaky non-oxide ceramic particles and pigments being based thereon

[0003] Technical field

[0004] The present disclosure relates to a method for manufacturing a MAX phase ceramic, use of a MAX phase ceramic as a pigment, and a pigment comprising a MAX phase ceramic.

[0005] Background

[0006] Pigments are used in a wide range of technologies, such as for paints in the automotive industry, cosmetics, and various types of functional and / or aesthetic coatings.

[0007] Pigments composed of flaky particles are becoming popular as substrate for effect pigments. Effect pigments may for example be based on inorganic flaky materials coated with metal oxides with a higher refractive index. This difference in refractive index and the thickness of the metal oxide results in the interference of white light resulting in spectacular colour profiles. Examples of flaky materials include mica, glass flakes, titanium oxide, bismuth oxychloride, aluminium oxide, boron nitride, graphite flakes etc. Effect pigments based on alumina flakes coated with metal oxides like titanium oxide, iron oxide, indium oxide etc. may have very high luminosity as compared to mica and glass flakes. However, most effect pigments based on mica, glass, alumina etc. have very low hiding power and effect pigments based on metallic flakes may not be coated with any metal oxides because of poor adherence. Moreover, the existing effect pigments coated with iron oxide for a darker colour with low saturation may render the pigment magnetic and in some cases toxic as well.

[0008] Thus, pigments and particularly effect pigments of lower toxicity and with more flexible and improved optical properties are desirable. For example, automotive paints for autonomous driving vehicles may require certain optical properties for safe navigation. Thus there is a need for improved and more efficient pigments.

[0009] Summary

[0010] The present disclosure relates to a non-oxide ceramic substrate with controllable and predefined morphology which advantageously can be used for effect pigments, such as effect pigments with very high hiding power, and / or effect pigments with a colour profile P7097PC00

[0011] being grey, black, or combinations thereof.

[0012] The present disclosure further relates to the production of non-oxide ceramic powders with controllable and predefined morphology, such as flake morphology with a defined thickness and diameter, and to its use as pigment in automotive paints, cosmetics and any whatsoever aesthetic coating. The non-oxide ceramic flake can serve the purpose of a standalone effect pigment or as a substrate for effect pigments with a multitude of metal oxide coatings. The non-oxide ceramic based effect pigment is also found to be reflective in the near-infra red region for the purpose of autonomous driving using a LiDaR sensor.

[0013] Thus, the current disclosure pertains to the synthesis of a new flaky material which can be used both as standalone and the substrate of an effect pigment formulation. The new material is a non-oxide ceramic material also referred to as MAX phases. MAX phases are ternary carbides and nitrides with the empirical formula of Mn+iAXnwhere n can be 1, 2 or 3. M is an early transition element like Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta, A is an element from group 13 or 14, i.e. Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb, and X is C, N, or B. These materials are layered and possess a hexagonal crystal lattice. It is found that the synthesis of such material may include molten salt media and post processing steps to obtain flaky particles which can be used as a standalone and / or substrate for effect pigments. Specifically, it is surprisingly found that a controllable and predefined morphology may be obtained by a synthesis based on selected steps, e.g. including certain starting materials, starting materials having certain dimensions and molar ratios, certain salt variations or salt weight ratios, heating, hydrothermal treatment, and / or delamination steps. It is for example found that a sequence of purification and post-processing steps may provide a MAX phase powder of particularly high purity and desirable aspect ratio for its use as an effect pigment, such as effect pigments in darker colour with low saturation to facilitate a high hiding power.

[0014] A first aspect of the disclosure relates to a method for manufacturing a MAX phase ceramic having the empirical formula Mn+iAXn, said method comprising the sequential steps

[0015] i) mixing individual powders of ‘M’, ‘A’, and ‘X’ elements with aluminium (Al) to obtain a first mixture; P7097PC00

[0016] ii) adding and mixing into the first mixture a salt, such as KBr, to obtain a second mixture having a salt to M+A+X+AI weight ratio from 1:2 to 5:1; iii) subjecting said second mixture to a first heat treatment at a temperature of 700 °C to 1600 °C, said first heat treatment optionally comprising holding said temperature for a period of 20 minutes to 5 hours before allowing said second mixture to cool down to room temperature; iv) subjecting said second mixture to a washing step, such as with demineralized water, to remove any residual salt, thereby obtaining a washed second mixture;

[0017] v) subjecting said washed second mixture to a second heat treatment at a temperature of 300 °C to 1600 °C to oxidize any formed binary MX into a corresponding M-oxide, thereby obtaining a crude product;

[0018] vi) a hydrothermal treatment step of said crude product, the step comprising mixing said crude product with an aqueous alkaline solution at a temperature between 120 °C to 400 °C to solubilize the formed M- oxide, preferably under autogenous pressure to obtain a final MAX phase ceramic; and

[0019] vii) isolation of said formed MAX phase ceramic from the aqueous solution by centrifugation and aqueous washing of the solid, such as with demineralized water, and

[0020] wherein

[0021] ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb; and

[0022] ‘X’ is C or N; and

[0023] n can be 1, 2 or 3.

[0024] It is preferred that ‘M’ is Ti, ‘A’ is Si and ‘X’ is C. In such embodiments, the binary MX is TiC and the corresponding M-oxide is TiO2.

[0025] A second aspect of the disclosure relates to a non-oxide MAX-phase ceramic having the empirical formula Mn+iAXncharacterized by a particle morphology comprising more than 50% of individual non-agglomerated particles, such as in particular a non-oxide MAX-phase ceramic comprising Ti, Si and C in a molar ratio of approximately 3:1:2 characterized by a particle morphology of individual non-agglomerated particles having P7097PC00

[0026] an average aspect ratio of 10-50 and further characterized by a composition comprising Ti: (73.0(±2.0) wt%), Si: (14(±2.0) wt%), C: (12(±2.0) wt%), Al: (below 0.25 wt%, such as below 0.05 wt%).

[0027] A third aspect of the disclosure relates to use of a MAX phase ceramic having the empirical formula Mn+iAXnas a pigment and / or as a component in a pigment, such as an effect pigment and / or pearlescent pigment.

[0028] Description of Drawings

[0029] Figure 1: Schematic of the comparative synthesis of Ti3SiC2 via the molten salt shielded synthesis procedure as outlined in [1] Dash et al (2019).

[0030] Figure 2: SEM images at different magnification of Ti3SiC2 product obtained following the procedure outlined in Figure 1 and Comparative Example 1.

[0031] Figure 3: SEM image of the synthesized flaky MAX phase obtained following the procedure outlined in Example 1 according to the present invention. The imaged particles are individual non-agglomerated flakes with an average aspect ratio A / B of approximately 10.

[0032] Figure 4: Low-resolution photographs of: (A) an uncoated test-panel, (B) a test-panel coated with conventional black paint, and (C) a test-panel coated with the Ti3SiC2 MAX phase obtained according to the present invention (C).

[0033] Figure 5: Schematic representation of the flaky particle morphology with ‘A’ and ‘B’ representing particle dimensions, the former representing the length of a flaky particle and the latter representing the height of the same particle. The values of ‘A’ and ‘B’ are used to determine the aspect ratio of the flaky particle which may be denoted as ‘C’ herein. That is to say, C may be formulated as the ratio A / B.

[0034] Detailed description

[0035] Definitions

[0036] As used herein, the term "pigment" refers to a finely divided solid material that imparts colour to a substance by absorbing, reflecting, or scattering light. Pigments are typically insoluble in the medium they are dispersed in and are used to provide colour, opacity, P7097PC00

[0037] or other functional properties in various applications, such as coatings, plastics, inks, and cosmetics. Unlike dyes, pigments do not dissolve but remain suspended as particles within the medium. The specific characteristics of a pigment depend on its chemical composition and physical form.

[0038] As used herein, the term "coating" refers to a material applied to the surface of a pigment to influence or modify its characteristics. Such coatings may consist of metal oxides or other compounds and can affect various properties, including optical appearance, stability, or compatibility with different applications.

[0039] As used herein, the term "effect pigment" refers to a ‘non-metallic effect pigment’ also known as a ‘pearlescent pigment’. Thus, as used herein the term “effect pigment” refers to a pigment composed of non-metallic substrates, such as mica, silica, or synthetic flakes, that produce visual effects like shimmer, gloss, iridescence, or a pearllike luster. These pigments do not contain metal particles but produce metallic-like or pearlescent appearances, making them suitable for applications in coatings, cosmetics, plastics, decorative finishes, etc. The optical effects of these pigments are achieved by controlling the thickness, composition, and layering of the pigment particles, resulting in unique visual properties like colour shifts and brilliance.

[0040] As used herein the term ’’hiding power” refers to the capacity of a pigment to obscure or mask the surface beneath it, thereby providing opacity when incorporated into a medium. It is influenced by factors such as pigment particle size, dispersion, and optical properties. A pigment with high hiding power requires less material to achieve full coverage, making it important for applications in coatings, paints, plastics, and inks. Opacity may be measured both for a wet film coating or a dry film coating. In addition to the pigment in question, a wet film coating is characterized by also comprising a dispersing liquid such as an alcohol or other non-interacting low-boiling liquid configured for dispersing the pigment evenly onto a substrate and / or surface. Ethanol and isopropyl alcohol are examples of alcohols suitable for use as dispersing liquids, a Opacity of a dry film coating may be evaluated by first applying the pigment as a wet film coating and allowing the dispersion liquid to evaporate. This may result in a more dense coating with a higher hiding power as the pigment particles are in closer proximity due to the absence of solvent molecules. P7097PC00

[0041] Opacity may be determined by applying coating layers of varying size / thickness on a substrate having both a black and white background and determining at which thickness the background is no longer distinguishable and / or detectable. In one embodiment of the present disclosure, a wet film coating of 2 vol% Ti3SiC2 is characterized by full hiding and / or an opacity of 90% or more, such as 91% oir more, such as 92% or more, such as 93% or more, such as 94% or more, such as 95% or more at a film thickness of 250 microns or more, such as 300 microns or more. In one embodiment, a wet film coating of 2 vol% Ti3SiC2 is characterized by full hiding and / or opacity of 96% at a film thickness of 300 microns.

[0042] In one embodiment of the present disclosure, a dry film coating of 2 vol% Ti3SiC2 is characterized by full hiding and / or an opacity of 95% or more, such as more than 96%, more than 97%, more than 98%, or more than 99% at a film thickness of 70 microns or more, such as 75 microns or more, preferably of 77 microns or more. In one embodiment, a dry film coating of 2 vol% Ti3SiC2 is characterized by full hiding and / or opacity of 99.3% at a film thickness of 77 microns.

[0043] As used herein, the terms “morphology” or "particle morphology" refer to characteristics such as the shape, size, surface texture, and structural arrangement of individual pigment particles. The particle morphology may include features like the overall form (e.g., spherical, plate-like, flake-like or irregular), dimensional attributes, and the nature of the surface. These characteristics can influence various aspects of the pigment’s performance, including its optical properties, dispersibility, and interaction with different media. Control or adjustment of particle morphology may be considered in optimizing the pigment's function for various applications, including coatings, plastics, and inks.

[0044] The morphology may be evaluated by the particle aspect ratio. As used herein, the term "aspect ratio" refers to the ratio between the largest dimension of a pigment particle, such as its length or diameter, and its smallest dimension, typically its thickness or height. This ratio provides a measure of the particle’s shape, particularly for non-spherical particles, including plate-like or flake-like pigments. A higher aspect ratio indicates a particle that is significantly longer or wider relative to its thickness, which can influence properties such as opacity, light reflection, gloss, and colour strength in various applications, including coatings, plastics, and inks. P7097PC00

[0045] Much like a deck of cards, when dropped on the floor, most of the cards will lay flat on top of each over providing a broad coverage, while only very few (if any) can be expected to land on their narrow side. The flaky particles of the present invention are characterized by having a large aspect ratio (see Fig. 5) favouring a uniform particle orientation when coated on a surface and / or substrate.

[0046] As used herein, the terms "agglomerated" and "non-agglomerated" refer to different states of particle assembly in a pigment composition. " Agglomerated" may describe particles that are physically or chemically bound together or intergrown, forming larger clusters or aggregates. In contrast, "non-agglomerated" can refer to particles that remain individually dispersed, without significant clustering or binding. The degree of agglomeration may affect various properties of the pigment, including its dispersibility, surface area, and performance in applications such as coatings, inks, and plastics.

[0047] As used herein, the terms "delamination" and "delaminating agent" refer to the process of separating layered or stacked particles, such as those in inorganic effect pigments, into individual layers or flakes. Delamination may occur through chemical, mechanical, or thermal means, and the extent of separation may impact particle morphology and properties. A "delaminating agent" can include any substance or treatment used to assist or promote the separation of layers, potentially influencing factors like particle size, aspect ratio, and dispersibility in various applications, such as coatings, plastics, or inks.

[0048] As used herein, the term "scanning electron microscopy (SEM)" refers to a technique that utilizes a focused beam of electrons to scan the surface of a sample, generating high-resolution images. Thereby, SEM can provide insights into surface morphology, topography, and compositional features.

[0049] As used herein, the term " CIELAB profile" refers to the representation of a pigment's colour characteristics within the CIELAB colour space, expressed through the values of lightness (L*), red-green axis (a*), and yellow-blue axis (b*). The CIELAB profile may be used to assess and compare the optical properties of pigments. A different representation of a pigment’s colour characteristics also embodied herein is the Hue-Chroma-Luminance (HCL or LCh) colour space and may in some instances be referred to as a pigment’s “LCh profile”. P7097PC00

[0050] As used herein, the term “MAX phase ceramic” has the same meaning as conventionally used within the technical field of ceramics, and is to be construed as referring to MAX phases of ternary carbides and / or nitrides with the empirical formula of Mn+iAXnwhere n can be 1, 2 or 3. M is an early transition element like Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta, A is an element from group 13 or 14, i.e. Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb, and X is C, N, or B. when the term ‘MAX phase ceramics’ are used within the context of the present invention, it should be understood, unless explicitly stated otherwise, that the term refers to MAX phase ceramics characterized by a nonagglomerated particle morphology.

[0051] Pigment manufacture

[0052] Pigments based on flaky materials may provide a variety of colour profiles as well as facilitate colour effects (i.e. effect pigments) and high refractive index and luminosity. The specific optical properties of a pigment may depend on several characteristics, such as the material and purity of the flakes, the morphology of the flaky material, e.g. the aspect ratio of a flake, and the degree of agglomeration between multiple flakes. For example, it may be found that the aspect ratio of the flakes affects the hiding power of a pigment and / or the possible colour profile, and thus the flexibility of using the pigment, and / or affects the reflectivity degree of certain wavelengths, e.g. the near-infra red region relevant for LiDAR sensors.

[0053] Control of pigment morphology is especially important, because particles that are agglomerated cannot be used as effect pigments. The present disclosure is directed towards a new method of preparing non-oxide ceramic powders (MAX phase ceramics) providing non-agglomerated particle morphologies, which are advantageously used as effect pigments, either on their own or in combination with a metal oxide coating. It is found that the method allows for the preparation of a MAX non-oxide ceramic material of different possible morphologies and aspect ratios in a controllable manner.

[0054] The method involves a molten salt shielded synthetic step followed by a series of purification and post-processing steps in order to obtain a non-oxide ceramic powder with a controllable and predefined morphology, such as in the form of individual nonagglomerated flakes with a high aspect ratio. It is surprisingly found that the sequence of purification and post-processing steps may lead to a final MAX phase powder with P7097PC00

[0055] advantageous optical properties due to particularly high purity and desirable aspect ratio suitable for use as an effect pigment, such as an effect pigment with high hiding power, darker colour profiles, and / or specific reflectivity.

[0056] One embodiment of the present disclosure provides for a method for manufacturing a MAX phase ceramic having the empirical formula Mn+iAXn, said method comprising the sequential steps

[0057] i) mixing individual powders of ‘M’, ‘A’, and ‘X’ elements with aluminium (Al) to obtain a first mixture;

[0058] ii) adding and mixing into the first mixture a salt, such as KBr, to obtain a second mixture having a salt to M+A+X+AI weight ratio from 1:2 to 5:1; iii) subjecting said second mixture to a first heat treatment at a temperature of 700 °C to 1600 °C, said first heat treatment optionally comprising holding said temperature for a period of 20 minutes to 5 hours before allowing said second mixture to cool down to room temperature; iv) subjecting said second mixture to a washing step, such as with demineralized water, to remove any residual salt, thereby obtaining a washed second mixture;

[0059] v) subjecting said washed second mixture to a second heat treatment at a temperature of 300 °C to 1600 °C to oxidize any formed binary MX into a corresponding M-oxide, thereby obtaining a crude product;

[0060] vi) a hydrothermal treatment step of said crude product, the step comprising mixing said crude product with an aqueous alkaline solution at a temperature between 120 °C to 400 °C to solubilize the formed M- oxide, preferably under autogenous pressure to obtain a final MAX phase ceramic; and

[0061] vii) isolation of said formed MAX phase ceramic from the aqueous solution by centrifugation and aqueous washing of the solid, such as with demineralized water, and

[0062] wherein

[0063] ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb; and

[0064] ‘X’ is C or N; and

[0065] n can be 1, 2 or 3. P7097PC00

[0066] Starting materials

[0067] MAX phases are ternary carbides and / or nitrides with the empirical formula of Mn+iAXnwhere n can be 1, 2, or 3. M is an early transition element like Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta, A is an element from group 13 or 14, i.e. Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb, and X is C, N, or B.

[0068] It is found that certain combinations of ‘M’, ‘A’, and ‘X’ elements may lead to a MAX phase powder with desirable optical properties for effect pigments, and / or that certain combinations may facilitate the synthesis of MAX phase flakes with a controllable and predefined morphology. For example, the MAX phase advantageously is a carbide or a nitride, such as the MAX phase where M = Ti, A = Si, and X = C, such as TiaSiC2 (as further described in Example 2). It will be apparent to the skilled person in the art that similar advantageous MAX phases can be obtained following the disclosed method, by using one or more different elements with similar properties to those of Ti, Si, and C, and providing similar optical properties..

[0069] In one embodiment, ‘X’ is C. In one alternative embodiment, ‘X’ is N.

[0070] In one embodiment, ‘M’ is Ti, V or Cr. In a further embodiment, ‘M’ is Ti.

[0071] In one embodiment, ‘A’ is Si, Al, Ga, Ge or Sn. In one embodiment, ‘A’ is Si.

[0072] In one embodiment, ‘M’ is Ti or Cr, ‘A’ is Si or Al, and ‘X’ is C or N. In one embodiment, ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C or N. In one embodiment, ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C.

[0073] In one embodiment, the MAX phase ceramic is TiaSiC2, TisAIC2, or C^AIC.

[0074] In one embodiment, when ‘X’ is C, the ‘X’ element powder is graphite. In one embodiment, when ‘X’ is N, the ‘X’ element powder may be combined with the ‘M’ element powder in the form of a binary nitride, such as binary nitrides of Ti, V or Cr, such as TiN.

[0075] In one embodiment, it is preferred that ‘M’ is Ti, ‘A’ is Si and ‘X’ is C. In such embodiments, the binary MX is TiC and the corresponding M-oxide is TiO2.

[0076] Starting materials: dimensions and molar ratios P7097PC00

[0077] A factor which may affect the aspect ratio of the final MAX phase powder is the initial particle size of the elemental C in the form of graphite, when making carbide MAX phases. The particles of graphite are insoluble in the molten salt phase and, without wishing to be bound by theory, they are believed to act as points of nucleation for the crystallization of MAX phase particles during the synthesis step. To obtain carbide MAX phases with a high aspect ratio, C particles with a diameter in the range of about 50 nm to about 50 microns may advantageously be used, as further described in Example 2.

[0078] In one embodiment, the particle size of the graphite powder used when ‘X’ is C, is between 50 nm and 100 μm. In one embodiment, the graphite powder particle size is between 50 nm and 100 μm, more preferably between 50 nm and 50 μm, such as most preferably 10 μm. In one embodiment, the graphite powder particle size is between 50 nm and 100 μm, such as between 100 nm and 200 nm, such as between 200 nm and 300 nm, such as between 300 nm and 500 nm, such as between 500 nm and 750 nm, such as between 750 nm and 1 μm, such as between 1 μm and 2 μm, such as between 2 μm and 5 μm, such as between 5 μm and 10 μm, such as between 10 μm and 20 μm, such as between 20 μm and 30 nm, such as between 30 μm and 50 μm, such as between 50 μm and 100 μm.

[0079] It is found that the addition of Al may be beneficial for the synthesis of MAX phases where ‘A’ is not Al. The inclusion of Al may enhance the purity of the obtained MAX phase and the amount of Al used may affect the thickness of the MAX phase platelets. For example, a higher loading of Al may result in a lower thickness, while a lower loading of Al may result in a higher thickness. In one instance, 0.2 moles of Al (relative to 1.0 moles of ‘A’) resulted in a platelet thickness of 700 nm, while 0.5 moles of Al (relative to 1.0 moles of ‘A’) resulted in a reduced platelet thickness of 300 nm, as further described in Example 2.

[0080] It follows that the molar mixing ratios may affect the particle morphology, specifically the molar ratios of ‘M’, ‘A’, and ‘X’ and aluminium (Al).

[0081] In one embodiment, the powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 2.5-3.5: 0.5-1.5: 1.5-2.5: 0-1.0 to obtain said first mixture. In one embodiment, said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3: 1: 2: 0.1-1.0 to obtain said first mixture. In one embodiment, said powders P7097PC00

[0082] of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.1-0.5 to obtain said first mixture. In one embodiment, said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.2 to obtain said first mixture.

[0083] In one embodiment, ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C and said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.2 to obtain said first mixture. In one embodiment, ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C and said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 2.5-3.5: 0.5-1.5: 1.5-2.5: 0-1.0 to obtain said first mixture. In one embodiment, the molar ratio of Al to ‘A’ element is between 0 and 0.5, such as between 0 and 0.1, such as between 0.1 and 0.2, such as between 0.2 and 0.3, such as between 0.3 and 0.4, such as between 0.4 and 0.5.

[0084] Salt variations

[0085] Alternatively or in addition, the salt or salt mixture may play a role in the synthesis of MAX phase ceramics. For example by creating a liquid protective medium around the reactants, intermediates, and products, effectively limiting their exposure to oxygen during the high-temperature process. Thus, a suitable salt or salt mixture have a low melting point to allow the synthesis to occur under optimal conditions, be non-reactive with the materials involved, and possess high water solubility for easy removal after synthesis. An example of a suitable salt include KBr, as further described in Example 2, as well as salt and salt mixtures with similar properties as known by the skilled person in the art.

[0086] In one embodiment of the presently disclosed method, the salt may be a halide, carbonate, sulphate, phosphate or chloride salt of a metal. Preferably, said salt used in the presently disclosed method is a metal halide salt, such as an alkali metal halide salt or an alkaline earth metal halide salt or a combination thereof. Preferably, the alkali metal halide salt or alkaline earth metal halide salt is KBr, KCl, NaCI, NaBr, LiCI, CaCl2or a combination thereof, but most preferably the salt is KBr.

[0087] Salt to M+A+X+AI weight ratios:

[0088] The ratio of salt to precursor is another factor that may affect the particle size and aspect ratio of the MAX phase flakes. For example, a higher amount of salt between graphite particles may create more space for the flakes to grow. As the salt-to- P7097PC00

[0089] precursor ratio increases, both the particle size and aspect ratio of the flakes may increase. Conversely, a lower salt-to-precursor ratio may lead to smaller particle sizes and lower aspect ratios. For example, this ratio can be adjusted within the range of 1:2 to 5:1, allowing for control over the synthesis process.

[0090] If there is too little salt in the reaction mixture, the molten salt-assisted synthesis may not proceed effectively. On the other hand, too much salt can reduce the reaction yield due to the longer diffusion distances required for metal ions to overcome to interact with graphite particles. A lower salt-to-precursor ratio (e.g. 1:1) may result in an agglomerated product of higher purity, while a higher salt-to-precursor ratio (e.g. 2:1) can produce an un-agglomerated product of lower purity. Selecting the right balance between salt and precursor is crucial for controlling both the morphology and purity of the final MAX phase flakes.

[0091] Thus, in one embodiment, the salt to M+A+X+AI weight ratio is between 1:2 and 5:1, such as between 1:2 and 1:1, such as between 1:1 to 2:1, such as between 2:1 to 3:1, such as between 3:1 to 4:1, such as between 4:1 to 5:1. In one preferred embodiment, the salt to M+A+X+AI weight ratio is 1:1.

[0092] Mixing of salt and M+A+X+AI powder mixture

[0093] The mixing process may affect the particle size and aspect ratio of the MAX phase flakes as well as the agglomeration. For example, the salt and elements may advantageously be mixed into a slurry using a solvent, and using an efficient mixing process known to the skilled person.

[0094] In one embodiment, the salt is mixed into the first mixture of M+A+X+AI in a slurry obtained using a solvent, preferably a short chain alcohol or water, and most preferably ethanol. In one embodiment, the salt and first mixture of M+A+X+AI are mixed as dry powders. In one embodiment, the salt and first mixture of M+A+X+AI are mixed to obtain the second mixture by shaking or by stirring, using a mixing instrument, such as a magnetic stirrer or a ball mill or most preferably a multidirectional mixer. In one embodiment, the solvent, used to mix the salt and the first mixture of M+A+X+AI as a slurry, is removed from the slurry by evaporation once the mixing to obtain said second mixture is complete. P7097PC00

[0095] First heating step

[0096] The synthesis of MAX-phase ceramics involves high temperatures (typically >1,000°C) due to the strong covalent bonds between atoms and the high melting points of these materials. Elevated temperatures help overcome the energy barrier for the solid-state reaction between the primary reactants, leading to the formation of the desired layered ternary carbide or nitride structures. High temperatures also enhance atomic diffusion and bonding, which are crucial for developing dense, well-crystallized MAX phases. These phases combine ceramic-like stiffness with metal-like machinability.

[0097] Furthermore, maintaining high temperatures supports the production of highly pure MAX-phase powders, which is important for industrial applications where material purity is essential.

[0098] It is found that the heating process, including the maximum temperature, ramp rate, and atmosphere, may affect the resulting particle morphology.

[0099] Thus, in one embodiment, said second mixture is subjected to said first heat treatment at a temperature from 700 °C to 1600 °C, such as between 700 °C to 1500 °C, such as between 800 °C to 1500 °C, such as between 900 °C to 1400 °C, such as between 950 °C and 1350 °C, such as between 900 °C and 1300 °C, such as between 950 °C and 1250 °C, such as between 1000 °C and 1200 °C, such as between 1050 °C and 1150 °C. In one embodiment, said second mixture is subjected to said first heat treatment at a temperature from 1000 °C to 1400 °C, such as from 1250 °C to 1350 °C. In a preferred embodiment, said second mixture is subjected to said first heat treatment at a temperature from 700 °C to 1300 °C.

[0100] In one embodiment, the temperature of the first heat treatment is increased with a ramp rate between 0.1 °C / min and 10 °C / min, such as between 0.1 °C / min and 1 °C / min, such as between 0.5 °C / min and 1.5 °C / min, such as between 1 °C / min and 2 °C / min, such as between 1.5 °C / min and 2.5 °C / min, such as between 3 °C / min and 4 °C / min, such as between 3.5 °C / min and 4.5 °C / min, such as between 4 °C / min and 5 °C / min, such as between 4.5 °C / min and 5.5 °C / min, such as between 6 °C / min and 7 °C / min, such as between 6.5 °C / min and 7.5 °C / min, such as between 7 °C / min and 8 °C / min, such as between 7.5 °C / min and 8.5 °C / min, such as between 8 °C / min and 9 °C / min, such as between 8.5 °C / min and 9.5 °C / min, such as between 9 °C / min and 10 °C / min. In one embodiment, the temperature of the first heat treatment is increased with a ramp P7097PC00

[0101] rate between 2.5 °C / min and 7.5 °C / min, more preferably between 3.5 °C / min and 6.5 °C / min, and most preferably between 4 °C / min and 6 °C / min. In one embodiment, the temperature of the first heat treatment is increased with a ramp rate of 5 °C / min.

[0102] In one embodiment, said second mixture is heated in air, in vacuum, or in an inert atmosphere of argon or nitrogen.

[0103] In one embodiment, said second mixture is subjected to said first heat treatment at a temperature above the melting point of the salt used or at least above the melting point of the salt with the lowest melting point if more than one salt is being used. That is to say, in one embodiment of the present disclosure, said first heat treatment is conducted at a temperature above the melting point of the salt used such as to provide a liquid salt media.

[0104] Second heating step (oxidation)

[0105] The synthesis may include a step of washing and oxidation, as further described in Example 2. After the washing step, the second mixture contains the targeted MAX phase along with unwanted secondary phases formed during the first heating step, such as TiC and Al2O3. As a step towards obtaining the pure MAX phase, the second mixture may be subjected to a second heating step in air, which causes the TiC to be oxidized to TiO2, which can be removed in a subsequent step along with Al2O3.

[0106] Thus, in one embodiment, said second mixture is subjected to said second heat treatment at a temperature of 300 °C to 1600 °C, such as between 300 °C to 1500 °C, such as between 300 °C to 1400 °C, such as between 300 °C and 1300 °C, such as between 300 °C and 1200 °C, such as between 300 °C and 1100 °C, such as between 300 °C and 1000 °C, such as between 300 °C and 900 °C, such as between 300 °C and 800 °C, such as between 300 °C and 700 °C, such as between 300 °C and 600 °C, such as between 300 °C and 500 °C, such as between 350 °C and 450 °C.

[0107] Preferably, said second mixture is subjected to said second heat treatment at a temperature between 300 °C to 450 °C to oxidize TiC to TiO2. At this temperature the MAX phase is insensitive to oxidation.

[0108] In one embodiment, the temperature of the second heat treatment is increased with a ramp rate between 0.1 °C / min and 10 °C / min, such as between 0.1 °C / min and 1 P7097PC00

[0109] °C / min, such as between 0.5 °C / min and 1.5 °C / min, such as between 1 °C / min and 2 °C / min, such as between 1.5 °C / min and 2.5 °C / min, such as between 3 °C / min and 4 °C / min, such as between 3.5 °C / min and 4.5 °C / min, such as between 4 °C / min and 5 °C / min, such as between 4.5 °C / min and 5.5 °C / min, such as between 6 °C / min and 7 °C / min, such as between 6.5 °C / min and 7.5 °C / min, such as between 7 °C / min and 8 °C / min, such as between 7.5 °C / min and 8.5 °C / min, such as between 8 °C / min and 9 °C / min, such as between 8.5 °C / min and 9.5 °C / min, such as between 9 °C / min and 10 °C / min. In one embodiment, the temperature of the second heat treatment is increased with a ramp rate between 2.5 °C / min and 7.5 °C / min, more preferably between 3.5 °C / min and 6.5 °C / min, and most preferably between 4 °C / min and 6 °C / min. In one embodiment, the temperature of the second heat treatment is increased with a ramp rate of 5 °C / min.

[0110] Hydrothermal treatment

[0111] The synthesis may include a step of hydrothermal treatment to control the particle morphology and degree of agglomeration, as further described in Example 2. It follows that the obtained particle morphology and agglomeration degree may depend on the selected treatment parameters.

[0112] For example, the preparation of individual, un-agglomerated flakes may be achieved through a post-processing step involving the hydrothermal dissolution of Al2O3and TiO2. This process employs a highly concentrated basic solution at elevated temperatures and pressure, enabling the breakdown of large agglomerates formed by grains of Al2O3and TiO2. By performing the hydrothermal treatment within a temperature range of about 120 °C to about 400 °C and about 5 bars of pressure, full dissolution of Al2O3and TiO2may be accomplished.

[0113] During this step, the MAX phase may remain intact and undissolved and may be separated from the solution by means of centrifugation. This step further serves to disrupt the MAX phase agglomerates, resulting in the production of free, individual flakes. In a preferred embodiment (Example 2), the basic solution has been prepared from NaOH. It will be apparent to the skilled person in the art to replace or to combine NaOH with any other water soluble metal hydroxide to achieve an equally suitable basic solution for this hydrothermal treatment step. P7097PC00

[0114] In one embodiment, the aqueous alkaline solution used in the hydrothermal treatment is obtained using a metal hydroxide, such as an alkali metal hydroxide, such as an alkaline earth metal hydroxide, such as a mineral containing one or more alkali metal or alkaline earth metal hydroxides, or such as a combination hereof. In one embodiment, the aqueous alkaline solution is obtained using a metal hydroxide selected from the group consisting of LiOH, NaOH, KOH, Mg(OH)2, Ca(OH)2, Al(OH)3ora combination thereof, preferably NaOH, KOH, or a combination thereof, and most preferably NaOH.

[0115] In one embodiment, the molarity of said aqueous alkaline solution is selected from the ranges consisting of 0.5 M to 10 M, 5 M to 15 M, 10 M to 20 M, 15 M to 25 M, 20 M to 30 M, 25 M to 35 M, 30 M to 40 M, or a combination thereof. In one embodiment, the molarity of the aqueous alkaline solution used in the hydrothermal treatment is between 0.5 M and 40 M, such as between 5 M and 35 M, such as between 7.5 M and 32.5 M, such as between 10 M and 30 M, such as between 12.5 M and 27.5 M, such as between 15 M and 25 M, such as between 17.5 M and 22.5 M. In one preferred embodiment, the molarity of said aqueous alkaline solution is 20 M.

[0116] In one embodiment, the hydrothermal treatment step is carried out at a temperature between 120 °C and 400 °C, such as between 150 °C and 250 °C, such as between 200 °C and 300 °C, such as between 250 °C and 350 °C, such as between 300 °C and 400 °C, and preferably at about 200 °C.

[0117] In one embodiment, the hydrothermal treatment step is carried out under a pressure of 1 to 20 bar, such as 1 to 5 bar, such as 5 to 10 bar, such as 10 to 15 bar, such as 15 to 20 bar. In one embodiment, the hydrothermal treatment step is carried out under a pressure of at least 2 bar, such as at least 5 bar, such as at least 7 bar, such as at least 10 bar. In one embodiment, the hydrothermal treatment step is carried out at a pressure of 5 bar. In one embodiment, the hydrothermal treatment step is carried out under autogenous pressure.

[0118] In one embodiment, the hydrothermal treatment step is carried out over a period of 5 to 48 hours, such as 5 to 10 hours, such as 10 to 18 hours, such as 18 to 24 hours, such as 24 to 36 hours, such as 36 to 48 hours. In one embodiment, the hydrothermal treatment step is carried over a period of at least 5 hours, such as at least 10 hours, such as at least 18 hours, such as at least 24 hours. In one embodiment, the P7097PC00

[0119] hydrothermal treatment step is carried out over a period of 24 hours.

[0120] Delamination step

[0121] The synthesis may include a delamination step to control the particle morphology and degree of agglomeration, as further described in Example 2. It follows that the obtained particle morphology and agglomeration degree may depend on the selected delamination agent.

[0122] For example, the reaction product obtained after the hydrothermal treatment may consist of flakes that are not agglomerated; however, these flakes tend to stack together. To achieve full delamination of the MAX phase flakes, a delaminating agent may be employed optionally in combination with ultrasonic treatment. Thus, the stacked flakes may be completely separated, ensuring a thorough and effective delamination process. This method may enhance the dispersion and individualization of the flakes, improving their usability in subsequent applications.

[0123] Thus, in one embodiment, the isolated MAX phase ceramic is subjected to a delamination step carried out using a delaminating agent in the form of a tetraalkylammonium hydroxide compound, such as tetrabutylammonium hydroxide (TBAOH) or tetramethylammonium hydroxide (TMAOH), dimethylsulfoxide (DMSO), sodium hydroxide (NaOH) or a combination thereof, optionally with the aid of ultrasonication using an ultrasonication apparatus. In one preferred embodiment, the delamination step was carried out using tetrabutylammonium hydroxide (TBAOH).

[0124] In one embodiment, the delamination step is combined with the hydrothermal treatment step.

[0125] Isolated MAX Phase

[0126] It is found that a controllable and predefined morphology may be obtained by the synthesis method according to the present disclosure, as further described in Example 2. Further, the particle morphology and specifically the aspect ratio, may provide specific optical properties making them suitable for effect pigments, such as effect pigments in darker colour with low saturation to facilitate a high hiding power. P7097PC00

[0127] For example, the inventor has surprisingly found a MAX-phase with a colour profile that is not known among effect pigments presently on the market. Thus, in providing a grey or black colour profile, this MAX phase has the advantage of adding a new colour profile among effect pigments, thereby allowing for the combination of such a colour profile together with the pearlescent properties of an effect pigment. It will be apparent to the skilled person working in the art that this new colour profile will allow for the obtainment of other new colour profiles, for example, by combining said MAX phase with one or more coatings, such as one or more metal oxide coatings.

[0128] One embodiment of the present disclosure provides a method for manufacturing MAX-phase ceramic particles characterized by an aspect ratio A / B above 2, such as above 4, such as above 5, such as above 7, such as above 8, such as above 9, such as above 10. In one embodiment, the aspect ratio A / B is from 5 to 50, such as from 5 to 10, such as from 10 to 15, such as from 15 to 20, such as from 20 to 30, such as from 30 to 50. In one embodiment, the aspect ratio A / B is from 5 to 8, such as from 8 to 10, such as from 10 to 12, such as from 12 to 15.

[0129] One embodiment of the present disclosure provides for a non-oxide MAX-phase ceramic comprising Ti, Si and C in a molar ratio of approximately 3:1:2 characterized by a particle morphology demonstrating an average aspect ratio A / B of 10-50 and further characterized by a composition comprising Ti: (73.0(±2.0) wt%), Si: (14(±2.0) wt%), C: (12(±2.0) wt%), Al: (below 0.25 wt%, such as below 0.05 wt%). In one preferred embodiment, the non-oxide MAX-phase ceramic is characterized by a particle morphology demonstrating an average aspect ratio A / B of 10-20.

[0130] Thus, in another preferred embodiment, the non-oxide MAX-phase ceramic comprising Ti, Si and C in a molar ratio of approximately 3:1:2 is in the form of non-agglomerated particles, as evidenced by SEM and particle size distribution. In another preferred embodiment, the non-oxide MAX-phase ceramic comprising Ti, Si and C in a molar ratio of approximately 3:1:2 exhibits a grey-black colour profile, as evidenced by its optical properties, such as its CIELAB colour profile and / or colour space.

[0131] In one embodiment of the present disclosure, the MAX phase ceramic is characterized by the following CIELAB colour space

[0132] L* 31.10 P7097PC00

[0133] a* -0.55

[0134] b* 1.86

[0135] In one embodiment of the present disclosure, the MAX phase ceramic is characterized by the following LCh colour space:

[0136] L 31.05

[0137] C 1.96

[0138] h 106.54

[0139] In one embodiment of the present disclosure, the MAX phase ceramic is characterized by a reflectance of 5.91 at 400 nm (room temperature, standardized UV-VIS spectrophotometer).

[0140] CIELAB colour profiles may be measured using dedicated colorimeters such as exemplary PCE-TCD 100 (PCE Instruments) which is suitable for the purpose or alternatively a UV-Vis spectrophotometer such as ColorLite spectrophotometer sph870 or sph900 (Colorlite GmbH).

[0141] In one embodiment, the CIELAB colour profile is measured according to ISO 11664-4.

[0142] In one embodiment of the presently disclosed system, the MAX phase ceramic is a non-oxide ceramic. In another embodiment, the MAX phase ceramic is non-magnetic. In a preferred embodiment, the MAX phase ceramic or non-oxide MAX phase ceramic is obtained as disclosed herein. In another preferred embodiment, the MAX phase is Ti3SiC2.

[0143] Use of MAX phase ceramic

[0144] One embodiment of the present disclosure provides for a use of a MAX phase ceramic as a pigment and / or as a component in a pigment, such as an effect pigment and / or pearlescent pigment, preferably being implemented in an automotive coating, in an aesthetic coating, in a cosmetic, and / or in a LIDAR detectable coating on a vehicle.

[0145] In one embodiment, the use described herein regards use of the MAX phase ceramics described herein.

[0146] One embodiment of the present disclosure provides for use of a MAX phase ceramic, P7097PC00

[0147] as one or more base materials for effect pigments, in formulations from the areas of paints, coatings, automobile coatings, automotive finishing, industrial coatings, paints, powder coatings, printing inks, security printing inks, plastics, ceramic materials, cosmetics, glasses, paper, paper coating, toners for electrophotographic printing processes, seeds, greenhouse sheeting and tarpaulins, thermally conductive, self-supporting, electrically insulating, flexible sheets for the insulation of machines or devices, as absorber in the laser marking of paper and plastics, absorber in the laser welding of plastics, pigment pastes with water, organic and / or aqueous solvents, in pigment preparations and dry preparations.

[0148] One embodiment of the present disclosure provides for use of a MAX phase ceramic as a substrate in a pigment, such as a special effect pigment and / or pearlescent pigment. The pigment may comprise the MAX phase ceramic alone or include one or more layers of coating consisting of oxides, such as a metal oxide.

[0149] In one embodiment, the exemplary metal oxide may a high-refractive metal oxide such as one or more of TiO2, ZrC>2, SnC>2, ZnO, Ce2O3, Fe2O3, Fe3C>4, FeTiOs, O2O3, CoO, CO3O4, VO2, V2O3, NiO, Ti3C>5, Ti2O3, TiO or FeO(OH), including mixtures thereof.

[0150] In one embodiment, the exemplary metal oxide may be a low-refractive metal oxide such as SiC>2, Al2O3, AI(O)OH or B2O3, including mixtures thereof.

[0151] In effect pigments, the pigments may be realized and / or provided in the form of multilayered materials comprising the MAX phase ceramic described herein and further more comprising one or more of a high-refractive metal oxide and / or low-refractive metal oxide, such as in interference pigments or pearlescent pigments.

[0152] One embodiment of the present disclosure provides for use of a MAX phase ceramic as a substrate in a pigment, said pigment characterized by its composition of a substrate with one or more layers of coating following the sequence:

[0153] MAX phase + TiO2 / Fe2O3;

[0154] MAX phase + Fe2O3;

[0155] MAX phase + TiO2+ Fe2O3;

[0156] MAX phase + TiO2+ Fe3O4;

[0157] MAX phase + TiO2+ SiO2+ TiO2; P7097PC00

[0158] MAX phase + TiO2 / Fe2O3+ SiO2+ TiO2;

[0159] MAX phase + TiO2+ SiO2+ TiO2 / Fe2O3;

[0160] MAX phase + TiO2+ SiO2;

[0161] MAX phase + TiO2 + SiO21 Al2O3;

[0162] MAX phase + TiO2 + Al2O3;

[0163] MAX phase + SnO2;

[0164] MAX phase + SnO2+ TiO2;

[0165] MAX phase + SnO2+ Fe2O3;

[0166] MAX phase + SiO2;

[0167] MAX phase + SiO2+ TiO2;

[0168] MAX phase + SiO2+ TiO2 / Fe2O3;

[0169] MAX phase + SiO2+ Fe2O3;

[0170] MAX phase + SiO2+ TiO2+ Fe2O3;

[0171] MAX phase + SiO2+ TiO2+ Fe2O4;

[0172] MAX phase + SiO2+ TiO2+ SiO2+ TiO2;

[0173] MAX phase + SiO2+ Fe2O3+ SiO2+ TiO2;

[0174] MAX phase + SiO2+ TiO2 / Fe2O3+ SiO2+ TiO2;

[0175] MAX phase + SiO2+ TiO2+ SiO2+ TiO2 / Fe2O3;

[0176] MAX phase + SiO2+ TiO2+ SiO2;

[0177] MAX phase + SiO2 + TiO2 + SiO21 Al2O3;

[0178] MAX phase + SiO2 + TiO2 + Al2O3;

[0179] MAX phase + TiO2 + Prussian Blue; or

[0180] MAX phase + TiO2 + Carmine Red.

[0181] Of particular preference for the present disclosure if the use of a MAX phase ceramic as a substrate in any of the foregoing pigment compositions, wherein the pigment is a pearlescent and / or special effect pigment. Compared to MAX phase P7097PC00

[0182] Examples

[0183] Comparative Example 1: Synthesis of Ti3SiC2 following experimental procedure of sample TSA0.2C as outlined in [11 Dash et al (2019).

[0184] Synthesis of Ti3SiC2 where elemental powders of Ti, Si, Al (>99.5%, Alfa Aesar, -325 mesh) and graphite (Alfa Aesar, 2 pm) were mixed in the stoichiometric molar ratio 3:1:0.2:2.

[0185] KBr (Alfa Aesar) in a 1:1 weight ratio was added to the resulting mix. The mixture was milled in slurry form with ethanol and zirconia milling balls (05 mm) for 24 h in a multidirectional mixer (Turbula, WAB).

[0186] The resulting slurry was dried in a vertical column rotary evaporator at 60 °C for 30 min., followed by sieving through 300 pm sieve to homogenize the agglomerate size. The dried powder was uni-axially pressed in a steel die (013 mm) under a pressure of 200 MPa. The encapsulation was done by placing the already-consolidated specimen in a larger steel die (020 mm) with KBr salt on top, bottom and circumference of the pellet.

[0187] The re-consolidation of the KBr-sample assembly was done under a uniaxial pressure of 200 MPa followed by an isostatic pressure of 300 MPa in a cold isostatic press. The consolidated specimen was further encapsulated with KBr (Fig. 1a, I) and placed in a KBr salt bed inside a cylindrical alumina crucible covered with an alumina lid without any sealant. The KBr salt bed was supplied with enough salt after melting to completely submerge the specimen with molten salt for protection against the ambient oxidizing atmosphere. The chemical composition of the protective encapsulation and the salt bed should always be the same to avoid the formation of inhomogeneous eutectic at the interface of the salt bed and the encapsulated material. The encapsulation with KBr was achieved by repressing the already consolidated green sample in a larger steel die with KBr on all sides of the green sample.

[0188] The samples were heated in a resistance furnace (Nabertherm, Germany) from 700 to 1300 °C at a rate of 5 °C / min with a holding time of 1 h at the peak temperature. (Fig.

[0189] 1a, 11). After cooling, the alumina crucibles were washed with water to dissolve the salt and recover the specimen. The specimens were crushed in mortar pestle and washed repeatedly with hot water to remove the salt content. (Fig. 1a, III) followed by filtration (Fig. 1a, IV). P7097PC00

[0190] Results

[0191] As illustrated in Figure 2, the particles obtained by the prior art synthesis according to Comparative example 1 result in highly agglomerated particles. Due to the agglomeration, the prior art particles cannot be said to have a well-defined aspect ratio and would additionally not be considered as suitable for use in special effect pigments, in particular pearlescent pigments where flakes with uniform morphology are preferred and / or required to obtain a sufficient result. Furthermore, the agglomerated particles obtained by Comparative example 1 must be subjected to a further milling step to break apart the agglomerates. Such milling can however be detrimental to the particle morphology and while it may not change the average particle size, it can have drastic effects on the aspect ratio of the flakes post-milling.

[0192] Example 1: Synthesis of non-agglomerated individual Ti3SiC2flakes using the method according to the present invention

[0193] Elemental powders of Ti, Si, Al (>99.5% pure, -325 mesh, Alfa Aesar) and C (10 pm) were mixed in a different molar ratio of 3: 1:0.2:2.

[0194] Although Al is not the part of the crystal structure of Ti3SiC2, it is included to enhance the aspect ratio of the Ti3SiC2platelets formed. It is found that the amount of Al added may decide the thickness of the platelets with 0.2 moles of Al corresponding to 700 nm of thickness. A higher Al content of 0.5 may further reduce the thickness to 300 nm.

[0195] The particle size of starting graphite powder is found to influence the final Ti3SiC2 flakes thickness and diameter. Graphite powder particle sizes of 50 nm, 1 pm, 10 pm, 45 pm, 60 pm, and 100 pm were tested, resulting in increasing Ti3SiC2 flake diameter.

[0196] KBr (Alfa Aesar) was mixed in a 1:1 wt. ratio to the resulting mix. Mixing was done in a slurry form with ethanol and zirconia milling balls (0 5 mm) for 24 h in a multidirectional mixer (Turbula, WAB, Switzerland). The ratio of salt added to the reaction mixtures may span from 1:1 to 1:5, where higher the amount of salt, lower is the yield of Ti3SiC2but higher is the flake diameter. The right control of reactant to salt ratio enables the fine tuning of Ti3SiC2flake diameter and thickness.

[0197] The samples were heated treated in a resistance furnace (Nabertherm, Germany) from 700 to 1300 °C at a rate of 5 °C / min with a holding time of 1 h at the peak temperature. P7097PC00

[0198] The reaction mixture is composed of Ti3SiC2, TiC and Al2O3. The flakes of Ti3SiC2are in an agglomerated form, the aim is to obtain individual Ti3SiC2flake from the agglomerates to separate the TiC and Al2O3from the reaction mixture.

[0199] The reaction mixture is subjected to oxidation at 400 °C for 1 h, this resulted in the oxidation of TiC to TiO2. Al2O3is an oxide by itself and Ti3SiC2is insensitive to oxidation at 400 °C.

[0200] Now the mixture of Ti3SiC2, TiO2and Al2O3is subjected to hydrothermal treatment in presence of 20 M NaOH solution at 200 °C and 5 bars pressure for 24 h. This results in the dissolution of TiO2and Al2O3in NaOH forming water soluble products. Ti3SiC2is insensitive to hydrothermal aging in the presence of NaOH and is still insoluble.

[0201] The reaction product is then centrifuged at 2000 rpm for 4 minutes to separate the Ti3SiC2, the supernatant was removed and the Ti3SiC2was washed repeatedly to remove all the NaOH and water-soluble by-products.

[0202] The obtained Ti3SiC2is 100% pure and is in individual flake morphology and the TiC and Al2O3which was bonding the flakes together has now been dissolved.

[0203] Finally the obtained reaction product was dissolved in TBAOH to delaminate the individual flakes, it is also this step which can be controlled to further tune the aspect ratio of flaky MAX phase.

[0204] Figure 3 shows an embodiment of the synthesized 100% pure Ti3SiC2. The individual flakes were seen to have an aspect ratio A / B of between 10-50, and more specifically between 10-20 evaluated using image analysis of a representative sample.

[0205] When comparing the SEM images of Figures 2 and 3, the degree of agglomeration of the MAX flakes obtained according to the present invention are seen to be much lower in Figure 3. The low degree of agglomeration allows for determination of individual particle aspect ratios which is not possible when the particles are agglomerated and partially embedded within one another. P7097PC00

[0206] Figure 4C shows a photograph of the synthesized 100% pure Ti3SiC2 MAX phase applied to a test-panel. For comparison, an uncoated test-panel is shown in Figure 4A, and a panel coated with conventional black paint is shown in Figure 4B.

[0207] The obtained Ti3SiC2 may be included in a pigment as a substrate, optionally a substrate with one or more layers of coating. The optical properties of the resulting pigment may facilitate effect pigments in darker colour with low saturation to facilitate a high hiding power, and in particular non-magnetic effect pigments of dark colour are provided within the scope of the present invention.

[0208] References

[0209] [1]Dash, A.; Sohn, Y. J.; Vaßen, R.; Guillon, O.; Gonzalez-Julian, J. Journal of the European Ceramic Society 2019, 39, 3651-3659. P7097PC00

[0210] Items

[0211] The presently disclosed may be described in further detail with reference to the following items.

[0212] 1. A method for manufacturing a MAX phase ceramic having the empirical formula Mn+iAXn, said method comprising the sequential steps

[0213] i) mixing individual powders of ‘M’, ‘A’, and ‘X’ elements with aluminium (Al) to obtain a first mixture;

[0214] ii) adding and mixing into the first mixture a salt, such as KBr, to obtain a second mixture having a salt to M+A+X+AI weight ratio from 1:2 to 5:1; iii) subjecting said second mixture to a first heat treatment at a temperature of 700 °C to 1600 °C, said first heat treatment optionally comprising holding said temperature for a period of 20 minutes to 5 hours before allowing said second mixture to cool down to room temperature; iv) subjecting said second mixture to a washing step, such as with demineralized water, to remove any residual salt, thereby obtaining a washed second mixture;

[0215] v) subjecting said washed second mixture to a second heat treatment at a temperature of 300 °C to 1600 °C to oxidize any formed binary MX into a corresponding M-oxide, thereby obtaining a crude product;

[0216] vi) a hydrothermal treatment step of said crude product, the step comprising mixing said crude product with an aqueous alkaline solution at a temperature between 120 °C to 400 °C to solubilize the formed M- oxide, preferably under autogenous pressure to obtain a final MAX phase ceramic; and

[0217] vii) isolation of said formed MAX phase ceramic from the aqueous solution by centrifugation and aqueous washing of the solid, such as with demineralized water, and

[0218] wherein

[0219] ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb; and

[0220] ‘X’ is C or N; and

[0221] n can be 1, 2 or 3.

[0222] 2. The method according to any one of the preceding items, wherein ‘X’ is C. 3. The method according to any one of the preceding items, wherein ‘X’ is N, P7097PC00

[0223] 4. The method according to any one of the preceding items, wherein ‘M’ is Ti, V or Cr.

[0224] 5. The method according to any one of the preceding items, wherein ‘M’ is Ti. 6. The method according to any one of the preceding items, wherein ‘A’ is Si, Al, Ga, Ge or Sn.

[0225] 7. The method according to any one of the preceding items, wherein ‘A’ is Si. 8. The method according to any one of the preceding items, wherein ‘M’ is Ti or Cr, ‘A’ is Si or Al, and ‘X’ is C or N.

[0226] 9. The method according to any one of the preceding items, wherein ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C or N.

[0227] 10. The method according to any one of the preceding items, wherein ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C further wherein the binary MX is TiC and the corresponding M-oxide is TiO2..

[0228] 11. The method according to any one of the preceding items, wherein the MAX phase ceramic is Ti3SiC2, Ti3AlC2, or Cr2AlC.

[0229] 12. The method according to any one of the preceding items, wherein when ‘X’ is C, the ‘X’ element powder is graphite.

[0230] 13. The method according to any one of the preceding items, wherein when ‘X’ is N, the ‘X’ element powder may be comprised with the ‘M’ element powder in the form of a binary nitride, such as binary nitrides of Ti, V or Cr, such as TiN. 14. The method according to any one of the preceding items, wherein the particle size of the graphite powder used when ‘X’ is C, is between 50 nm and 100 pm.

[0231] 15. The method according to any one of the preceding items, wherein the graphite powder particle size is between 50 nm and 100 pm, more preferably between 50 nm and 50 pm, such as most preferably 10 pm.

[0232] 16. The method according to any one of the preceding items, wherein the graphite powder particle size is between 50 nm and 100 pm, such as between 100 nm and 200 nm, such as between 200 nm and 300 nm, such as between 300 nm and 500 nm, such as between 500 nm and 750 nm, such as between 750 nm and 1 pm, such as between 1 pm and 2 pm, such as between 2 pm and 5 pm, such as between 5 pm and 10 pm, such as between 10 pm and 20 pm, such as between 20 pm and 30 nm, such as between 30 pm and 50 pm, such as between 50 pm and 100 pm.

[0233] 17. The method according to any one of the preceding items, wherein said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 2.5-3.5: 0.5- P7097PC00

[0234] 1.5: 1.5-2.5: 0-1.0 to obtain said first mixture.

[0235] 18. The method according to any one of the preceding items, wherein said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3: 1: 2: 0.1- 1.0 to obtain said first mixture.

[0236] 19. The method according to any one of the preceding items, wherein said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.1 -0.5 to obtain said first mixture.

[0237] 20. The method according to any one of the preceding items, wherein said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.2 to obtain said first mixture.

[0238] 21. The method according to any one of the preceding items, wherein ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C and said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.2 to obtain said first mixture.

[0239] 22. The method according to any one of the preceding items, wherein ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C and said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 2.5-3.5: 0.5-1.5: 1.5-2.5: 0-1.0 to obtain said first mixture.

[0240] 23. The method according to any one of the preceding items, wherein the molar ratio of Al to ‘A’ element is between 0 and 0.5, such as between 0 and 0.1, such as between 0.1 and 0.2, such as between 0.2 and 0.3, such as between 0.3 and 0.4, such as between 0.4 and 0.5.

[0241] 24. The method according to any one of the preceding items, wherein said salt is a metal halide salt.

[0242] 25. The method according to any one of the preceding items, wherein said metal halide salt is an alkali metal halide salt or an alkaline earth metal halide salt or a combination.

[0243] 26. The method according to any one of the preceding items, wherein said metal halide salt is an alkali metal halide salt.

[0244] 27. The method according to any one of the preceding items, wherein said metal halide salt is a potassium halide salt or a sodium halide salt.

[0245] 28. The method according to any one of the preceding items, wherein said metal halide salt is an alkali metal halide salt, such as KBr, KCl, NaCI, NaBr or a combination thereof, optionally with other alkaline halide or alkaline earth metal halide salts.

[0246] 29. The method according to any one of the preceding items, wherein said metal P7097PC00

[0247] halide salt is KBr.

[0248] 30. The method according to any one of the preceding items, wherein said metal halide salt is NaCI.

[0249] 31. The method according to anyone of the preceding items, wherein said metal halide salt is selected from the group consisting of LiCI, NaCI, KCl, KBr, CaCl2and combinations thereof.

[0250] 32. The method according to any one of the preceding items, wherein said metal halide salt is replaced with a salt mixture of LiCI, KBr, and CaCl2.

[0251] 33. The method according to any one of the preceding items, wherein the salt to M+A+X+AI weight ratio is between 1:2 and 5:1, such as between 1:2 and 1:1, such as between 1:1 to 2:1, such as between 2:1 to 3:1, such as between 3:1 to 4:1, such as between 4:1 to 5: 1.

[0252] 34. The method according to any one of the preceding items, wherein the salt to M+A+X+AI weight ratio is 1:1.

[0253] 35. The method according to any one of the preceding items, wherein said salt is mixed into the first mixture of M+A+X+AI in a slurry obtained using a solvent, preferably a short chain alcohol or water, and most preferably ethanol.

[0254] 36. The method according to any one of the preceding items, wherein said salt and first mixture of M+A+X+AI are mixed as dry powders.

[0255] 37. The method according to any one of the preceding items, wherein said salt and first mixture of M+A+X+Al are mixed to obtain said second mixture by shaking or by stirring, using a mixing instrument, such as a magnetic stirrer or a ball mill or most preferably a multidirectional mixer.

[0256] 38. The method according to any one of the preceding items, wherein the solvent, used to mix said salt and said first mixture of M+A+X+Al as a slurry, is removed from said slurry by evaporation once the mixing to obtain said second mixture is complete.

[0257] 39. The method according to any one of the preceding items, wherein said second mixture is subjected to said first heat treatment at a temperature from 700 °C to 1600 °C.

[0258] 40. The method according to any one of the preceding items, wherein said second mixture is subjected to said first heat treatment at a temperature from 700 °C to 1500 °C, such as between 800 °C to 1500 °C, such as between 900 °C to 1400 °C, such as between 950 °C and 1350 °C, such as between 900 °C and 1300 °C, such as between 950 °C and 1250 °C, such as between 1000 °C and 1200 P7097PC00

[0259] °C, such as between 1050 °C and 1150 °C.

[0260] 41. The method according to any one of the preceding items, wherein said second mixture is subjected to said first heat treatment at a temperature from 1000 °C to 1400 °C, such as from 1250 °C to 1350 °C.

[0261] 42. The method according to any one of the preceding items, wherein said second mixture is subjected to said first heat treatment at a temperature from 700 °C to 1300 °C.

[0262] 43. The method according to any one of the preceding items, wherein said second mixture is subjected to said first heat treatment at a temperature above the melting point of the salt used or at least above the melting point of the salt with the lowest melting point if more than one salt is being used.

[0263] 44. The method according to any one of the preceding items, wherein the temperature of the first heat treatment is increased with a ramp rate between 0.1 °C / min and 10 °C / min, such as between 0.1 °C / min and 1 °C / min, such as between 0.5 °C / min and 1.5 °C / min, such as between 1 °C / min and 2 °C / min, such as between 1.5 °C / min and 2.5 °C / min, such as between 3 °C / min and 4 °C / min, such as between 3.5 °C / min and 4.5 °C / min, such as between 4 °C / min and 5 °C / min, such as between 4.5 °C / min and 5.5 °C / min, such as between 6 °C / min and 7 °C / min, such as between 6.5 °C / min and 7.5 °C / min, such as between 7 °C / min and 8 °C / min, such as between 7.5 °C / min and 8.5 °C / min, such as between 8 °C / min and 9 °C / min, such as between 8.5 °C / min and 9.5 °C / min, such as between 9 °C / min and 10 °C / min.

[0264] 45. The method according to any one of the preceding items, wherein the temperature of the first heat treatment is increased with a ramp rate between 2.5 °C / min and 7.5 °C / min, more preferably between 3.5 °C / min and 6.5 °C / min, and most preferably between 4 °C / min and 6 °C / min.

[0265] 46. The method according to any one of the preceding items, wherein the temperature of the first heat treatment is increased with a ramp rate of 5 °C / min.

[0266] 47. The method according to any one of the preceding items, wherein said second mixture is heated in air, in vacuum, or in an inert atmosphere of argon or nitrogen.

[0267] 48. The method according to any one of the preceding items, wherein said second mixture is subjected to said second heat treatment at a temperature of 300 °C to 1600 °C.

[0268] 49. The method according to any one of the preceding items, wherein said second P7097PC00

[0269] mixture is subjected to said second heat treatment at a temperature of 300 °C to 1600 °C, such as between 300 °C to 1500 °C, such as between 300 °C to 1400 °C, such as between 300 °C and 1300 °C, such as between 300 °C and 1200 °C, such as between 300 °C and 1100 °C, such as between 300 °C and 1000 °C, such as between 300 °C and 900 °C, such as between 300 °C and 800 °C, such as between 300 °C and 700 °C, such as between 300 °C and 600 °C, such as between 300 °C and 500 °C, such as between 350 °C and 450 °C.

[0270] 50. The method according to any one of the preceding items, wherein said second mixture is subjected to said second heat treatment at a temperature between 300 °C to 450 °C to oxidize TiC to TiO2.

[0271] 51. The method according to any one of the preceding items, wherein said second mixture is subjected to said second heat treatment to oxidize TiC to TiO2at a temperature of 375 °C to 425 °C, such as 400 °C.

[0272] 52. The method according to any one of the preceding items, wherein the temperature of the second heat treatment is increased with a ramp rate between 0.1 °C / min and 10 °C / min, such as between 0.1 °C / min and 1 °C / min, such as between 0.5 °C / min and 1.5 °C / min, such as between 1 °C / min and 2 °C / min, such as between 1.5 °C / min and 2.5 °C / min, such as between 3 °C / min and 4 °C / min, such as between 3.5 °C / min and 4.5 °C / min, such as between 4 °C / min and 5 °C / min, such as between 4.5 °C / min and 5.5 °C / min, such as between 6 °C / min and 7 °C / min, such as between 6.5 °C / min and 7.5 °C / min, such as between 7 °C / min and 8 °C / min, such as between 7.5 °C / min and 8.5 °C / min, such as between 8 °C / min and 9 °C / min, such as between 8.5 °C / min and 9.5 °C / min, such as between 9 °C / min and 10 °C / min.

[0273] 53. The method according to any one of the preceding items, wherein the temperature of the second heat treatment is increased with a ramp rate between 2.5 °C / min and 7.5 °C / min, more preferably between 3.5 °C / min and 6.5 °C / min, and most preferably between 4 °C / min and 6 °C / min.

[0274] 54. The method according to any one of the preceding items, wherein the temperature of the second heat treatment is increased with a ramp rate of 5 °C / min.

[0275] 55. The method according to any one of the preceding items, wherein said aqueous alkaline solution is obtained using a metal hydroxide.

[0276] 56. The method according to any one of the preceding items, wherein said aqueous alkaline solution is obtained using a metal hydroxide selected from the group P7097PC00

[0277] consisting of an alkali metal hydroxide, an alkaline earth metal hydroxide, or a mineral containing one or more alkali metal or alkaline earth metal hydroxides, or a combination hereof.

[0278] 57. The method according to any one of the preceding items, wherein said aqueous alkaline solution is obtained using a metal hydroxide selected from the group consisting of LiOH, NaOH, KOH, Mg(OH)2, Ca(OH)2, Al(OH)3ora combination thereof.

[0279] 58. The method according to any one of the preceding items, wherein said aqueous alkaline solution is obtained using a metal hydroxide selected from the group consisting of NaOH, KOH, or a combination thereof.

[0280] 59. The method according to any one of the preceding items, wherein said aqueous alkaline solution is obtained using NaOH.

[0281] 60. The method according to any one of the preceding items, wherein the molarity of said aqueous alkaline solution is between 0.5 M and 40 M.

[0282] 61. The method according to any one of the preceding items, wherein the molarity of said aqueous alkaline solution is between 0.5 M and 40 M, such as between 5 M and 35 M, such as between 7.5 M and 32.5 M, such as between 10 M and 30 M, such as between 12.5 M and 27.5 M, such as between 15 M and 25 M, such as between 17.5 M and 22.5 M.

[0283] 62. The method according to any one of the preceding items, wherein the molarity of said aqueous alkaline solution is selected from the ranges consisting of 0.5 M to 10 M, 5 M to 15 M, 10 M to 20 M, 15 M to 25 M, 20 M to 30 M, 25 M to 35 M, 30 M to 40 M, or a combination thereof.

[0284] 63. The method according to any one of the preceding items, wherein the molarity of said aqueous alkaline solution is 20 M.

[0285] 64. The method according to any one of the preceding items, wherein the hydrothermal treatment step is carried out at a temperature between 120 °C to 400 °C.

[0286] 65. The method according to any one of the preceding items, wherein the hydrothermal treatment step is carried out at a temperature between 120 °C and 400 °C, such as between 150 °C and 250 °C, such as between 200 °C and 300 °C, such as between 250 °C and 350 °C, such as between 300 °C and 400 °C.

[0287] 66. The method according to any one of the preceding items, wherein the hydrothermal treatment step is carried out at a temperature between 120 °C P7097PC00

[0288] and 400 °C, such as between 125 °C and 300 °C, such as between 125 °C and 275 °C, such as between 175 °C and 225 °C.

[0289] 67. The method according to any one of the preceding items, wherein the hydrothermal treatment step is carried out at a temperature of 200 °C.

[0290] 68. The method according to any one of the preceding items, wherein said isolated MAX phase ceramic is subjected to a delamination step carried out using a delaminating agent in the form of

[0291] a tetraalkylammonium hydroxide compound, such as tetrabutylammonium hydroxide (TBAOH) or tetramethylammonium hydroxide (TMAOH), dimethylsulfoxide (DMSO), sodium hydroxide (NaOH) or a combination thereof, optionally with the aid of ultrasonication using an ultrasonication apparatus. 69. The method according to any one of the preceding items, wherein the delamination step is combined with the hydrothermal treatment step.

[0292] 70. A non-oxide MAX-phase ceramic having the empirical formula Mn+iAXncharacterized by a particle morphology comprising more than 50% of individual non-agglomerated particles, such as comprising more than 75% of individual non-agglomerated particles, such as comprising more than 90% of individual non-agglomerated particles, wherein

[0293] ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb;

[0294] ‘X’ is C or N; and

[0295] n can be 1, 2 or 3.

[0296] 71. The non-oxide MAX-phase ceramic according to any one of the preceding items, characterized by consisting essentially of individual non-agglomerated particles.

[0297] 72. The non-oxide MAX-phase ceramic according to any one of the preceding items, characterized by comprising Ti, Si and C in a molar ratio of approximately 3:1:2 characterized by a particle morphology demonstrating an average aspect ratio A / B of 10-50 and further characterized by a composition comprising Ti: (73.0(±2.0) wt%), Si: (14(±2.0) wt%), C: (12(±2.0) wt%), Al:

[0298] (below 0.25 wt%, such as below 0.05 wt%).

[0299] 73. The non-oxide MAX-phase ceramic according to any one of the preceding items, characterized by comprising or consisting of individual non-agglomerated particles, preferably wherein the individual particles have a morphology in the P7097PC00

[0300] form of flakes.

[0301] 74. The non-oxide MAX-phase ceramic according to any one of the preceding items, characterized by a particle morphology demonstrating an average aspect ratio A / B of 10-20.

[0302] 75. The non-oxide MAX-phase ceramic according to any one of the preceding items, characterized by individual flakes with an aspect ratio A / B above 2, such as above 4, such as above 5, such as above 7, such as above 8, such as above 9, such as above 10.

[0303] 76. A non-oxide MAX-phase ceramic comprising Ti, Si and C in a molar ratio of approximately 3:1:2 in the form of non-agglomerated individual particles, optionally as characterized by SEM image analysis.

[0304] 77. A non-oxide MAX-phase ceramic comprising Ti, Si and C in a molar ratio of approximately 3:1:2 with a grey-black colour profile, characterized by its optical properties, such as its CIELAB profile, such as characterized by the following CIELAB colour space:

[0305] a. L* 31.10;

[0306] b. a* -0.55; and

[0307] c. b* 1.86.

[0308] 78. Use of a MAX phase ceramic having the empirical formula Mn+iAXnas a pigment and / or as a component in a pigment, such as an effect pigment and / or pearlescent pigment, wherein

[0309] ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb;

[0310] ‘X’ is C or N; and

[0311] n can be 1, 2 or 3.

[0312] 79. The use according to any one of the preceding items, being implemented in an automotive coating.

[0313] 80. The use according to any one of the preceding items, being implemented in a cosmetic.

[0314] 81. The use according to any one of the preceding items being implemented in an aesthetic coating.

[0315] 82. The use according to any one of the preceding items being implemented in a LIDAR detectable coating on a vehicle. P7097PC00

[0316] 83. Use of a MAX phase ceramic having the empirical formula Mn+iAXnwherein ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb;

[0317] ‘X’ is C or N; and

[0318] n can be 1, 2 or 3,

[0319] optionally obtained according to item 1, as one or more of base material for effect pigments, in formulations from the areas of paints, coatings, automobile coatings, automotive finishing, industrial coatings, paints, powder coatings, printing inks, security printing inks, plastics, ceramic materials, cosmetics, glasses, paper, paper coating, toners for electrophotographic printing processes, seeds, greenhouse sheeting and tarpaulins, thermally conductive, self-supporting, electrically insulating, flexible sheets for the insulation of machines or devices, as absorber in the laser marking of paper and plastics, absorber in the laser welding of plastics, pigment pastes with water, organic and / or aqueous solvents, in pigment preparations and dry preparations.

[0320] 84. Use of a MAX phase ceramic having the empirical formula Mn+iAXnas a substrate in a pigment, such as in a special effect pigment and / or pearlescent pigment.

[0321] 85. Use of a MAX phase ceramic having the empirical formula Mn+iAXnas a substrate in a pigment together with a metal oxide.

[0322] 86. Use of a MAX phase ceramic having the empirical formula Mn+iAXnas a substrate in a pigment together with one or more layers of coating consisting of oxides, such as a metal oxide.

[0323] 87. Use of a MAX phase ceramic having the empirical formula Mn+iAXnas a substrate in a pigment, wherein

[0324] ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb;

[0325] ‘X’ is C or N; and

[0326] n can be 1, 2 or 3,

[0327] said pigment characterized by its composition of a substrate with one or more layers of coating following the sequence:

[0328] MAX phase + TiO2 / Fe2O3;

[0329] MAX phase + Fe2O3; P7097PC00

[0330] MAX phase + TiO2+ Fe20s;

[0331] MAX phase + TiO2+ FesOt;

[0332] MAX phase + TiO2+ SiC>2 + TiCh;

[0333] MAX phase + TiO21 Fe20a + SiC>2 + TiCh;

[0334] MAX phase + TiO2+ SiC>2 + TiO21 Fe20s;

[0335] MAX phase + TiO2+ SiCh;

[0336] MAX phase + TiO2+ SiC>21 Al2O3;

[0337] MAX phase + TiO2+ Al2O3;

[0338] MAX phase + SnO2;

[0339] MAX phase + SnC>2 + TiCh;

[0340] MAX phase + SnC>2 + Fe20s;

[0341] MAX phase + SiO2;

[0342] MAX phase + SiC>2 + TiCh;

[0343] MAX phase + SiC>2 + TiO21 Fe20s;

[0344] MAX phase + SiC>2 + Fe20s;

[0345] MAX phase + SiC>2 + TiO2+ Fe20s;

[0346] MAX phase + SiC>2 + TiO2+ Fe2C>4;

[0347] MAX phase + SiC>2 + TiO2+ SiC>2 + TiCh;

[0348] MAX phase + SiC>2 + Fe20s + SiC>2 + TiCh;

[0349] MAX phase + SiC>2 + TiO21 Fe20s + SiC>2 + TiCh;

[0350] MAX phase + SiC>2 + TiO2+ SiC>2 + TiO21 Fe20s;

[0351] MAX phase + SiC>2 + TiO2+ SiCh;

[0352] MAX phase + SiC>2 + TiO2+ SiC>21 Al2O3;

[0353] MAX phase + SiC>2 + TiO2+ Al2O3;

[0354] MAX phase + TiO2+ Prussian Blue; or

[0355] MAX phase + TiO2+ Carmine Red;

[0356] 88. The use according to any one of the preceding items, wherein the MAX phase ceramic is a non-oxide ceramic.

[0357] 89. The use according to any one of the preceding items, wherein the MAX phase ceramic is non-magnetic.

[0358] 90. The use according to any one of the preceding items, wherein the MAX phase is Ti3SiC2.

[0359] 91. The use according to any one of the preceding items, wherein the MAX phase ceramic or non-oxide MAX phase ceramic is obtained according to the method of item 1.

Claims

P7097PC00Claims1. A method for manufacturing a MAX phase ceramic having the empirical formula Mn+iAXn, said method comprising the sequential stepsi) mixing individual powders of ‘M’, ‘A’, and ‘X’ elements with aluminium (Al) to obtain a first mixture;ii) adding and mixing into the first mixture a salt, such as KBr, to obtain a second mixture having a salt to M+A+X+AI weight ratio from 1:2 to 5:1; iii) subjecting said second mixture to a first heat treatment at a temperature of 700 °C to 1600 °C, said first heat treatment optionally comprising holding said temperature for a period of 20 minutes to 5 hours before allowing said second mixture to cool down to room temperature; iv) subjecting said second mixture to a washing step, such as with demineralized water, to remove any residual salt, thereby obtaining a washed second mixture;v) subjecting said washed second mixture to a second heat treatment at a temperature of 300 °C to 1600 °C to oxidize any formed binary MX into a corresponding M-oxide, thereby obtaining a crude product;vi) a hydrothermal treatment step of said crude product, the step comprising mixing said crude product with an aqueous alkaline solution at a temperature between 120 °C to 400 °C to solubilize the formed M- oxide, preferably under autogenous pressure to obtain a final MAX phase ceramic; andvii) isolation of said formed MAX phase ceramic from the aqueous alkaline solution by centrifugation and aqueous washing of the solid, such as with demineralized water, andwherein‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb; and‘X’ is C or N; andn can be 1, 2 or 3.

2. The method according to any one of the preceding claims, wherein ‘M’ is Ti or Cr, ‘A’ is Si or Al, and ‘X’ is C or N.P7097PC003. The method according to any one of the preceding claims, wherein ‘M’ is Ti, ‘A’ is Si, and ‘X’ is C, further wherein the binary MX is TiC and the corresponding M-oxide is TiO2.

4. The method according to any one of the preceding claims, wherein when ‘X’ is C, ‘X’ is provided in the form of graphite powder characterized by a particle size between 1 pm and 10 pm.

5. The method according to any one of the preceding claims, wherein said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 2.5- 3.5: 0.5-1.5: 1.5-2.5: 0-1.0 to obtain said first mixture.

6. The method according to any one of the preceding claims, wherein said powders of ‘M’, ‘A’, and ‘X’ and aluminium (Al) are mixed in a molar ratio of 3.0: 1.0: 2.0: 0.1 -0.5 to obtain said first mixture.

7. The method according to any one of the preceding claims, wherein said salt is an alkali metal salt, preferably KBr or NaCI.

8. The method according to any one of the preceding claims, wherein the salt to M+A+X+AI weight ratio is between 1:2 and 5:1, preferably the salt to M+A+X+AI weight ratio is 1:1.

9. The method according to any one of the preceding claims, wherein the molarity of said aqueous alkaline solution is 20 M, and wherein the hydrothermal treatment step is carried out at 200 °C and 5 bars pressure for 24 h.

10. The method according to any one of the preceding claims, wherein said isolated MAX phase ceramic is subjected to a delamination step carried out using a delaminating agent in the form of a tetraalkylammonium hydroxide compound, such as tetrabutylammonium hydroxide (TBAOH) or tetramethylammonium hydroxide (TMAOH), dimethylsulfoxide (DMSO), sodium hydroxide (NaOH) ora combination thereof, optionally with the aid of ultrasonication using an ultrasonication apparatus.P7097PC0011. The method according to any one of the preceding claims, wherein the delamination step is combined with the hydrothermal treatment step.

12. A MAX phase ceramic having the empirical formula Mn+iAXnobtained by the method according to anyone of the preceding claims, wherein‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb;‘X’ is C or N; andn can be 1, 2 or 3;further wherein the MAX phase ceramic is characterized by comprising more than 50% of, such as consisting essentially of, individual non-agglomerated particles, preferably wherein said individual non-agglomerated particles are characterized by an aspect ratio A / B of more than 5.

13. A coated component for use in LIDAR detection, the coating comprising the MAX phase ceramic of formula Mn+iAXnaccording to claim 12, characterized by a reflectance at 400 nm of at least 5.9 as measured by UV-Vis spectroscopy.

14. Use of a MAX phase ceramic having the empirical formula Mn+iAXnwherein ‘M’ is an early transition element, such as Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, or Ta; ‘A’ is an element from group 13 or 14, such as Si, Al, Ga, Ge, As, Cd, In, Sn, TI, or Pb;‘X’ is C or N; andn can be 1, 2 or 3,as a pigment and / or as a component in a pigment, such as an effect pigment and / or pearlescent pigment.

15. The use according to claim 14, wherein the MAX phase ceramic of formula Mn+iAXn is characterized by a flaky non-agglomerated particle morphology, such as characterized by scanning electron microscopy (SEM) image analysis.

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