Coated (core-shell) nanoparticles for nanocomposite optical ceramics

Abstract

The nanocomposite optical ceramic (NCOC) material comprises a plurality of coated (core-shell) nanoparticles having nanoparticles of a first material coated with a coating of a second material. The first and second materials are insoluble in each other and each have at least 80% transmittance at a wavelength of interest. The first and second materials have a refractive index difference of less than 25%. The first and second materials have crystal grains with diameters less than 1 / 20 of the wavelength of interest. The coating of the second material on the nanoparticles of the first material is up to 50 nm thick. The NCOC contains no more than 0.01% voids per unit volume.

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Application No. 18 / 083,204, filed December 16, 2022, for "COATED (CORE-SHELL) NANOPARTICLES FOR NANOCOMPOSITE OPTICAL CERAMICS," the entire contents of which are incorporated herein by reference. [Background technology]

[0002] The present disclosure relates generally to optical elements, and more particularly to the fabrication of optical elements formed from nanocomposite opto-ceramic (NCOC) materials.

[0003] NCOC materials have been developed for use in military optical imaging systems. NCOC materials have been used to form optical elements, including domes and windows, which can provide infrared (IR) transmission while shielding the imaging components from the external environment in which they are deployed. NCOC domes and windows have been successfully manufactured using near-net-shape powder processing techniques. Nanosized ceramic powders are filled into a mold and pressed to produce a green body with the general shape of the optical element but with an increased thickness. The green body is then sintered to remove any organic matter added during powder processing and reach a high density (greater than 96% theoretical density). Finally, the sintered body is hot isostatically pressed (applied pressure and heat) to form a fully densified blank with the near-net shape of the optical element. Final shape finishing, including precision grinding and polishing, is then performed to obtain the final shape of the optical element.

[0004] New compositions are desired to provide more stable optical properties and enhanced mechanical integrity. Summary of the Invention

[0005] The nanocomposite optical ceramic (NCOC) material includes a plurality of coated nanoparticles having nanoparticles of a first material coated with a coating of a second material. The first and second materials are insoluble in each other and each have at least 80% transmittance at a wavelength of interest. The first and second materials have a refractive index difference of less than 25%. The first and second materials have crystal grains with diameters less than 1 / 20 of the wavelength of interest. The coating of the second material on the nanoparticles of the first material is up to 50 nm thick. The NCOC contains no more than 0.01% voids per unit volume.

[0006] A method for producing coated nanoparticles for use in nanocomposite optical ceramic (NCOC) materials includes providing a first amount of uncoated nanoparticles of a first material and coating the first amount of uncoated first material nanoparticles with a second material to form coated nanoparticles. The first and second materials are insoluble in each other and each have at least 80% transmittance at a wavelength of interest. The first and second materials have a refractive index difference of less than 25% and have crystal grains with diameters of less than 1 / 20 of the wavelength of interest. The coating of the second material on the first material nanoparticles is up to 50 nm thick. The coated nanoparticles are densified and sintered to form the NCOC material. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a coated nanoparticle of the present disclosure. [Figure 2] 1 is a phase diagram of magnesium oxide (MgO) and yttrium(III) oxide (YO). DETAILED DESCRIPTION OF THE INVENTION

[0008] The present disclosure relates to nanocomposite optical ceramic (NCOC) materials for optical applications, including, but not limited to, electro-optical sensors used for target acquisition, identification, and guidance. Optical domes and windows must be transparent in the infrared (IR) region of the electromagnetic spectrum and be able to protect the electro-optical sensors and other components they shield from harsh environmental conditions. NCOC materials enhance the mechanical strength and thermal shock resistance of IR domes and windows and have been shown to have low emissivity, even at high temperatures. Current NCOC elements undergo grain growth when subjected to high temperatures. As the grain size increases, the transmittance of the NCOC decreases. As discussed in this disclosure, nanoparticles used to form NCOC can be modified by adding a coating surrounding at least a portion of the nanoparticles prior to sintering to form coated nanoparticles, which may also be referred to as core-shell nanoparticles. The coating on the coated (core-shell) nanoparticles can inhibit grain growth. The NCOC materials described in this disclosure maintain their grain size and transmittance after being subjected to high temperatures, both in flight and during sintering.

[0009] As used in this disclosure, the term "nanocomposite optical ceramic (NCOC)" refers to a composite material formed from a mixture of ceramic nanoparticles containing materials that are insoluble in each other. As used in this disclosure, the term "nanoparticle" refers to particles having an average diameter of less than 1 μm. In some embodiments, the nanoparticles of the present disclosure have an average diameter of less than 20 nm, less than 10 nm, or less than 5 nm. In the context of this disclosure, "diameter" refers to the largest dimension of a particle or grain, without requiring a strictly circular cross-section. As used in this disclosure, the term "insoluble in each other" refers to a nanoparticle material that forms a multiphase grain structure with a distinct phase separation between the two components. The multiphase grain structure remains distinct after processing, allowing the separation between the phases to be observed. The NCOC material of the present disclosure is a composite material having two or more different nanocrystalline grain materials dispersed in each other. The different nanocrystalline grains form a material barrier against the grain growth of other nanocrystalline grains, thereby inhibiting grain growth during processing. The nanocrystalline grains can be uniformly dispersed in the NCOC material. As used in this disclosure, the term "uniformly dispersed" refers to dispersion in a generally uniform manner such that the spacing between nanograins of the same material is generally consistent throughout the NCOC material.

[0010] FIG. 1 is a schematic diagram of a coated nanoparticle 10 formed from nanoparticles 12 of a first material coated with a second material 14. The coated nanoparticle 10 constitutes a majority of NCOC. After densification, as described below, the NCOC contains crystal grains each smaller than the wavelengths for which the NCOC is intended to be transparent (the "intended wavelengths"). In certain applications, it may be desirable for the NCOC to be transparent to near-infrared (NIR; wavelengths 0.75 μm to 1.4 μm), short-wavelength infrared (SWIR; wavelengths 1.4 μm to 3 μm), mid-wavelength infrared (MWIR; wavelengths 3 μm to 8.5 μm), long-wavelength infrared (LWIR; wavelengths 8 μm to 12 μm), or possibly a portion of the visible band (wavelengths 0.4 μm to 0.75 μm). For example, the wavelength of interest may be between 1.5 μm and 8.5 μm. In some embodiments, the grain diameter in the densified NCOC is less than 1 / 20 of the wavelength of interest, less than 1 / 25 of the wavelength of interest, or less than 1 / 30 of the wavelength of interest. In some embodiments, the grains in the densified NCOC are less than 175 nm, less than 160 nm, or less than 150 nm in diameter. The first and second materials are insoluble in each other and have very similar refractive indices. In some embodiments, the difference in refractive indices is less than 25%, less than 20%, or less than 15%. The first and second materials may be oxides. In some embodiments, the first material may be magnesium oxide (MgO) and the second material may be yttrium(III) oxide (YO). In other embodiments, the first material may be YO and the second material may be MgO. As described below, MgO and YO are insoluble in each other. In still other embodiments, other material pairs that are insoluble in each other may be used as either the first or second material as required for a particular application.Examples of other insoluble material pairs useful as NCOC materials include gallium arsenide (GaAs) and silicon (Si) as either the first or second material; aluminum oxide (Al2O3) and zirconium oxide (ZrO2) as either the first or second material; aluminum nitride (AlN) and silicon (Si) as either the first or second material; and calcium lanthanum sulfide (CaLa2S4) and zinc sulfide (ZnS) as either the first or second material. The material pair of MgO and YO3 as either the first or second material will be used as a non-limiting example throughout the remainder of this disclosure.

[0011] NCOC materials can be used in optical applications, including, but not limited to, electro-optical sensors used for target acquisition, identification, and aircraft and missile guidance. Optical domes and windows must be able to protect the electro-optical sensors and other components from harsh environmental conditions, including heat from air friction. During flight, temperatures outside the domes and windows can reach 1200°C or higher. At these high temperatures, nanocrystalline grain size can grow. The primary components of NCOC can be two materials that are insoluble with each other. An exemplary embodiment is an NCOC composed of MgO and YO. Figure 2 shows the MgO-YO phase diagram, which shows that YO is insoluble in MgO up to the eutectic temperature (approximately 2100°C), and that MgO has negligible solubility in YO below 1000°C and less than 10% solubility up to the melting point of YO. In single-phase systems, grain boundary diffusion or bulk diffusion can occur during high-temperature densification or plastic deformation, which leads to grain growth. Changes in grain size can alter the optical and mechanical properties of NCOC materials. In mutually immiscible systems, the absence of atomic transport (i.e., Mg2 +(Ions do not move freely through the YO phase or vice versa), thus reducing grain growth relative to single-phase materials. Further reduction in grain growth can be achieved by adding a second material coating on the NCOC first material nanoparticles. The addition of the second material coating creates a barrier to the growth of the NCOC first material nanoparticles and helps maintain the desired grain size at higher temperatures. The coated NCOC nanoparticles described in this disclosure can have 80% transmittance at a wavelength of 3 μm. When subjected to temperatures of 1400°C, 1500°C, or 1600°C for 1 hour, the coated NCOC nanoparticles will experience less than 20% grain growth.

[0012] The second material coating 14 can be applied to the uncoated first material nanoparticles 12 by any method capable of providing a uniform, pinhole-free coating of the desired thickness. Useful coating methods include chemical vapor deposition and atomic layer deposition. Other methods now known or later developed can also be used. Other techniques known to enhance the deposition of uniform, pinhole-free coatings, such as fluidized bed processes, can be used in combination with the selected coating method to produce the coated nanoparticles 10. The second material coating 14 can be up to 50 nm thick. In some embodiments, the second material coating 14 can be between 10 nm and 20 nm thick. In still other embodiments, the second material coating 14 can be 1 nm thick or less. In any case, the second material coating 14 must be thick enough to inhibit grain growth in the first material nanoparticles 12 when the NCOC is exposed to operating temperatures of 1200°C or greater.

[0013] Nanoparticles of the first and second materials (described below) useful in the NCOC of the present disclosure can be formed using powder processing techniques or other methods known in the art capable of forming densified multiphase NCOC materials. Powder processing can include powder preparation and preparation, densification, and polishing. Powder precursors can be used with flame spray pyrolysis (FSP) or other powder production methods to form desired nanoparticles. NCOC nanoparticles formed using the FSP process can have high purity due to controlled nanoparticle size and crystallinity. The nanoparticle-containing slurry formed from FSP can be milled and mixed, for example, in a mill or similar device, to break down agglomerates of material. The slurry can be filtered to remove impurities and / or particles exceeding the maximum desired particle size. In the granulation step, liquid can be removed from the solution, and the nanoparticles can be dried.

[0014] The NCOC of the present disclosure can be formed entirely from coated nanoparticles 10 as described above. In such embodiments, the second material coating 14 can form a continuous or semi-continuous band of the second material when the coated nanoparticles 10 are densified into the NCOC. In some embodiments, the NCOC can include an additional amount (i.e., a second amount) of uncoated first material nanoparticles and an amount of uncoated second material nanoparticles. In such embodiments, the additional amounts of uncoated first material nanoparticles and uncoated second material nanoparticles will have particle sizes comparable to the coated nanoparticles 10 contained in the NCOC. For example, some embodiments can be formed from at least 80% by volume of coated nanoparticles 10, with the remainder being a mixture of uncoated first material nanoparticles and uncoated second material nanoparticles. Other embodiments can be formed from at least 90% by volume or at least 95% by volume of coated nanoparticles 10, with the remainder being a mixture of uncoated first material nanoparticles and uncoated second material nanoparticles. In NCOCs of the present disclosure that include additional amounts of uncoated first material nanoparticles and uncoated second material nanoparticles, the relative amounts of uncoated first material nanoparticles and uncoated second material nanoparticles can be approximately equal or can be biased toward a greater proportion of either uncoated first material nanoparticles or uncoated second material nanoparticles, depending on the particular application. When additional amounts of uncoated first material nanoparticles and uncoated second material nanoparticles are used to form an NCOC as described herein, the resulting NCOC can include coated nanoparticles 10 dispersed in and / or surrounded by a multiphase NCOC material that includes grains of the first and second materials.

[0015] To form a near-net-shape NCOC, a desired amount of coated nanoparticles 10 and additional amounts of uncoated first material nanoparticles and uncoated second material nanoparticles (if present) can be dry-pressed and compacted (i.e., densified) into a mold of appropriate size and shape to reduce voids. The compacted nanoparticles can be sintered to form a densified, molded body. Sintering can increase the density of the molded body to greater than about 96% of theoretical density. Final densification can be achieved by applying hot isostatic pressing (HIP) to eliminate all remaining voids and provide a fully dense NCOC. In the context of this disclosure, "fully dense" means 0.01% or less voids per unit volume. Final finishing, including grinding and polishing, can be performed as needed. Measurement of the grain size of the NCOC material and / or characterization of the optical and mechanical properties of the NCOC can be performed to verify that the optical and mechanical properties of the NCOC meet the material specifications for the optical element. The NCOCs of the present disclosure can be formed into optical elements of any size and shape, including, but not limited to, disks, hemispherical and ogive domes, lenses, flats, and windows of various sizes (e.g., several centimeters (cm) in diameter and / or lengths up to tens of cm in diameter and / or length).

[0016] Discussion of Possible Embodiments The following is a non-exclusive description of possible embodiments of the present invention.

[0017] The nanocomposite optical ceramic (NCOC) material includes a plurality of coated nanoparticles having nanoparticles of a first material coated with a coating of a second material. The first and second materials are insoluble in each other and each have at least 80% transmittance at a wavelength of interest. The first and second materials have a refractive index difference of less than 25%. The first and second materials have crystal grains with diameters less than 1 / 20 of the wavelength of interest. The coating of the second material on the first material nanoparticles is up to 50 nm thick. The NCOC contains 0.01% or less voids per unit volume.

[0018] The NCOC of the preceding paragraph may optionally and / or alternatively include any one or more of the following features, configurations, and / or additional components:

[0019] A further embodiment of the aforementioned NCOC, wherein the NCOC comprises at least 80% by volume of the plurality of coated nanoparticles, and the remainder of the NCOC comprises a plurality of uncoated nanoparticles of the first material having grains no larger than 1 / 20 of the wavelength of interest, and a plurality of uncoated nanoparticles of the second material having grains no larger than 1 / 20 of the wavelength of interest.

[0020] A further embodiment of the aforementioned NCOC, wherein the NCOC comprises at least 90% by volume of the plurality of coated nanoparticles, and the remainder of the NCOC comprises a plurality of uncoated nanoparticles of the first material having grains no larger than 1 / 20 of the wavelength of interest, and a plurality of uncoated nanoparticles of the second material having grains no larger than 1 / 20 of the wavelength of interest.

[0021] A further embodiment of the aforementioned NCOC, wherein the NCOC comprises at least 95% by volume of the plurality of coated nanoparticles, and the remainder of the NCOC comprises a plurality of uncoated nanoparticles of the first material having grains no larger than 1 / 20 of the wavelength of interest, and a plurality of uncoated nanoparticles of the second material having grains no larger than 1 / 20 of the wavelength of interest.

[0022] Further embodiments of the aforementioned NCOC, wherein the NCOC comprises up to 100% by volume of the plurality of coated nanoparticles.

[0023] A further embodiment of any one of the preceding NCOCs, wherein the first material comprises magnesium oxide (MgO) and the second material comprises yttrium oxide (YO), or the first material comprises YO and the second material comprises MgO.

[0024] A further embodiment of any one of the preceding NCOCs, wherein the first material comprises gallium arsenide (GaAs) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises GaAs.

[0025] A further embodiment of any one of the preceding NCOCs, wherein the first material comprises aluminum oxide (Al2O3) and the second material comprises zirconium oxide (ZrO2), or the first material comprises ZrO2 and the second material comprises Al2O3.

[0026] A further embodiment of any one of the preceding NCOCs, wherein the first material comprises aluminum nitride (AlN) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises AlN.

[0027] Further embodiments of any one of the preceding NCOCs, wherein the first material comprises calcium lanthanum sulfide (CaLa2S4) and the second material comprises zinc sulfide (ZnS), or the first material comprises ZnS and the second material comprises CaLa2S4.

[0028] A method for producing coated nanoparticles for use in nanocomposite optical ceramic (NCOC) materials includes providing a first amount of uncoated nanoparticles of a first material and coating the first amount of uncoated first material nanoparticles with a second material to form coated nanoparticles. The first material and the second material are insoluble in each other and each have at least 80% transmittance at a wavelength of interest. The first material and the second material have a refractive index difference of less than 25% and have crystal grains with diameters of less than 1 / 20 of the wavelength of interest. The coating of the second material on the first material nanoparticles is up to 50 nm thick. The coated nanoparticles are densified and sintered to form the NCOC material.

[0029] The method of the preceding paragraph may optionally include any one or more of the following features, configurations, and / or additional components, in addition and / or in the alternative.

[0030] A further embodiment of the aforementioned method, wherein the second material coating is applied to the first material nanoparticles by chemical vapor deposition and atomic layer deposition.

[0031] A further embodiment of any one of the preceding methods, wherein the first material comprises magnesium oxide (MgO) and the second material comprises yttrium oxide (YO), or the first material comprises YO and the second material comprises MgO.

[0032] A further embodiment of any one of the preceding methods, wherein the first material comprises gallium arsenide (GaAs) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises GaAs.

[0033] A further embodiment of any one of the preceding methods, wherein the first material comprises aluminum oxide (Al2O3) and the second material comprises zirconium oxide (ZrO2), or the first material comprises ZrO2 and the second material comprises Al2O3.

[0034] A further embodiment of any one of the preceding methods, wherein the first material comprises aluminum nitride (AlN) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises AlN.

[0035] A further embodiment of any one of the preceding methods, wherein the first material comprises calcium lanthanum sulfide (CaLa2S4) and the second material comprises zinc sulfide (ZnS), or the first material comprises ZnS and the second material comprises CaLa2S4.

[0036] providing a second quantity of uncoated first material nanoparticles, the second quantity of uncoated first material nanoparticles having grains with a diameter less than 1 / 20 of the wavelength of interest; providing uncoated second material nanoparticles, the second quantity of uncoated second material nanoparticles having grains with a diameter less than 1 / 20 of the wavelength of interest; mixing the coated nanoparticles with the second quantity of uncoated first material nanoparticles and the uncoated second material nanoparticles; Further embodiments of any one of the preceding methods, comprising dry-pressing and compressing the mixture of uncoated first material nanoparticles and the uncoated second material nanoparticles; sintering the mixture of the dry-pressed and compressed coated nanoparticles, the second quantity of uncoated first material nanoparticles, and the uncoated second material nanoparticles to form a densified shaped body; and hot isostatically pressing the densified shaped body to form the NCOC material, such that the NCOC material comprises at least 80 vol% of the coated nanoparticles.

[0037] A further embodiment of the aforementioned method, wherein the NCOC material comprises at least 90% by volume of the coated nanoparticles.

[0038] Further embodiments of the aforementioned method, wherein the NCOC material comprises at least 95% by volume of the coated nanoparticles.

[0039] Although the present invention has been described with reference to exemplary embodiment(s), those skilled in the art will recognize that various modifications can be made and equivalents can be substituted for elements of the embodiments without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is not intended that the invention be limited to the particular embodiment(s) disclosed, but rather, the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. 1. A nanocomposite optical ceramic (NCOC) material, comprising: a plurality of coated nanoparticles comprising nanoparticles of a first material coated with a coating of a second material; the first material and the second material are insoluble in each other; the first material and the second material each have a transmittance of at least 80% for a wavelength of interest; the first material and the second material have a refractive index difference of less than 25%; the first material and the second material have grains with diameters less than 1 / 20 of the wavelength of interest; the coating of the second material on the nanoparticles of the first material is up to 50 nm thick; The nanocomposite optical ceramic (NCOC) material, wherein the NCOC contains 0.01% or less voids per unit volume.

2. 2. The NCOC of claim 1, wherein the NCOC comprises at least 80% by volume of the plurality of coated nanoparticles, and the remainder of the NCOC comprises a plurality of uncoated nanoparticles of the first material having crystal grains sized 1 / 20 or less of the target wavelength, and a plurality of uncoated nanoparticles of the second material having crystal grains sized 1 / 20 or less of the target wavelength.

3. 3. The NCOC of claim 2, wherein the NCOC comprises at least 90% by volume of the plurality of coated nanoparticles, and the remainder of the NCOC comprises a plurality of uncoated nanoparticles of the first material having crystal grains sized 1 / 20 or less of the wavelength of interest, and a plurality of uncoated nanoparticles of the second material having crystal grains sized 1 / 20 or less of the wavelength of interest.

4. 3. The NCOC of claim 2, wherein the NCOC comprises at least 95% by volume of the plurality of coated nanoparticles, and the remainder of the NCOC comprises a plurality of uncoated nanoparticles of the first material having crystal grains sized 1 / 20 or less of the wavelength of interest, and a plurality of uncoated nanoparticles of the second material having crystal grains sized 1 / 20 or less of the wavelength of interest.

5. 3. The NCOC of claim 2, wherein the NCOC comprises up to 100% by volume of the plurality of coated nanoparticles.

6. The first material includes magnesium oxide (MgO) and the second material includes yttrium oxide (Y ２ O ３ ) or the first material comprises Y ２ O ３ and the second material comprises MgO.

7. 2. The NCOC of claim 1, wherein the first material comprises gallium arsenide (GaAs) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises GaAs.

8. The first material is aluminum oxide (Al ２ O ３ ), and the second material comprises zirconium oxide (ZrO ２ ) or the first material comprises ZrO ２ and the second material comprises Al ２ O ３ 2. The NCOC of claim 1, comprising:

9. The NCOC of claim 1 , wherein the first material comprises aluminum nitride (AlN) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises AlN.

10. The first material is calcium lanthanum sulfide (CaLa ２ S ４ ) and the second material comprises zinc sulfide (ZnS), or the first material comprises ZnS and the second material comprises CaLa ２ S ４ 2. The NCOC of claim 1, comprising:

11. 1. A method for producing coated nanoparticles for use in nanocomposite opto-ceramic (NCOC) materials, comprising: providing a first amount of uncoated nanoparticles of a first material; coating the first amount of uncoated nanoparticles of a first material with a second material to form coated nanoparticles; the first material and the second material are insoluble in each other; the first material and the second material each have a transmittance of at least 80% for a wavelength of interest; the first material and the second material have a refractive index difference of less than 25%; the first material and the second material have grains with diameters less than 1 / 20 of the wavelength of interest; forming a coating of the second material on the nanoparticles of the first material that is up to 50 nm thick; dry pressing and compacting, sintering, and hot isostatically pressing the coated nanoparticles to form an NCOC material.

12. The method of claim 11 , wherein the coating of the second material is applied to the first material nanoparticles by chemical vapor deposition and atomic layer deposition.

13. The first material includes magnesium oxide (MgO) and the second material includes yttrium oxide (Y ２ O ３ ) or the first material comprises Y ２ O ３ and the second material comprises MgO.

14. 12. The method of claim 11, wherein the first material comprises gallium arsenide (GaAs) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises GaAs.

15. The first material is aluminum oxide (Al ２ O ３ ), and the second material comprises zirconium oxide (ZrO ２ ) or the first material comprises ZrO ２ and the second material comprises Al ２ O ３ The method of claim 11 , comprising:

16. 12. The method of claim 11, wherein the first material comprises aluminum nitride (AlN) and the second material comprises silicon (Si), or the first material comprises Si and the second material comprises AlN.

17. The first material is calcium lanthanum sulfide (CaLa ２ S ４ ) and the second material comprises zinc sulfide (ZnS), or the first material comprises ZnS and the second material comprises CaLa ２ S ４ The method of claim 11 , comprising:

18. providing a second quantity of uncoated first material nanoparticles; providing the second quantity of uncoated nanoparticles of a first material having grains with diameters less than 1 / 20 of the wavelength of interest; providing uncoated nanoparticles of a second material, the uncoated nanoparticles of a second material having grains with diameters less than 1 / 20 of the wavelength of interest; mixing the coated nanoparticles with the second amount of uncoated first material nanoparticles and uncoated second material nanoparticles; dry pressing and compressing the mixture of the coated nanoparticles, the second amount of uncoated first material nanoparticles, and the uncoated second material nanoparticles; sintering the dry-pressed and compressed mixture of the coated nanoparticles, the second quantity of uncoated first material nanoparticles, and the uncoated second material nanoparticles to form a densified shaped compact; 12. The method of claim 11, further comprising hot isostatically pressing the densified compact to form the NCOC material such that the NCOC material comprises at least 80 volume percent of the coated nanoparticles.

19. 20. The method of claim 18, wherein the NCOC material comprises at least 90% by volume of the coated nanoparticles.

20. 20. The method of claim 18, wherein the NCOC material comprises at least 95% by volume of the coated nanoparticles.

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