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Nb4AlC3 block ceramic synthesized by hot pressing at in-situ reaction and preparation method thereof

An in-situ reaction and block technology, applied in the field of single-phase bulk ceramics and preparation, can solve the problems of complex and impractical dense block process, and achieve the effects of good damage tolerance, low cost and high density

Inactive Publication Date: 2009-04-29
INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

But using this method to prepare dense bulk Nb 4 AlC 3 The process is complicated and impractical

Method used

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  • Nb4AlC3 block ceramic synthesized by hot pressing at in-situ reaction and preparation method thereof
  • Nb4AlC3 block ceramic synthesized by hot pressing at in-situ reaction and preparation method thereof
  • Nb4AlC3 block ceramic synthesized by hot pressing at in-situ reaction and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0022] With 24.78 grams of niobium powder, 1.98 grams of aluminum powder, and 2.16 grams of graphite powder as raw materials (the molar ratio is 4:1.1:2.7, and the particle size of the raw material powder is 200 mesh), ball milling in a resin tank under dry conditions for 12 hours, after sieving Put it into a graphite mold for cold pressing (10MPa), sinter in a hot-press furnace with argon gas, the heating rate is 15°C / min, sinter at 1650°C, the holding time is 60 minutes, and the applied pressure is 25MPa. The density measured by the Archimedes method is 6.97g / cm 3 , 99% of the theoretical density. According to X-ray diffraction analysis, it is basically all Nb 4 AlC 3 . Determination of Nb 4 AlC 3 The Vickers hardness of the bulk ceramic is 2.6GPa, the compressive strength is 515MPa, and the shear strength is 116MPa.

Embodiment 2

[0024] The difference from Example 1 lies in that the molar ratio of raw material powder is different, and the sintering temperature, holding time and applied pressure are different.

[0025] Using 24.78 grams of niobium powder, 2.16 grams of aluminum powder, and 2.24 grams of graphite powder as raw materials (the molar ratio is 4:1.2:2.8), they were ball milled in a resin tank for 24 hours under dry conditions, and then sieved and put into a graphite mold for cold pressing. (10MPa), sintered in a hot-press furnace with argon gas, the heating rate is 15°C / min, sintered at 1700°C, the holding time is 120 minutes, and the applied pressure is 30MPa. The density measured by the Archimedes method is 6.98g / cm 3 , 99% of the theoretical density. According to X-ray diffraction analysis, it is basically all Nb 4 AlC 3 . Determination of Nb 4 AlC 3 The bulk ceramics have an elastic modulus of 306GPa and a shear modulus of 127GPa.

Embodiment 3

[0027] The difference from Example 1 is that the molar ratio of raw material powder is different, and the sintering temperature, heating rate, holding time and applied pressure are all different.

[0028] With 24.78 grams of niobium powder, 2.34 grams of aluminum powder, and 2.32 grams of graphite powder as raw materials (the molar ratio is 4:1.3:2.9, and the particle size of the raw material powder is 200 mesh), ball milling in a resin tank under dry conditions for 20 hours, after sieving Put it into a graphite mold for cold press molding (20MPa), sinter in a hot-press furnace with argon gas, the heating rate is 10°C / min, sinter at 1600°C, the holding time is 120 minutes, and the applied pressure is 20MPa. The density measured by the Archimedes method is 6.94g / cm 3 , 98% of the theoretical density. According to X-ray diffraction analysis, it is basically all Nb 4 AlC 3 . Determination of Nb 4 AlC 3 The bending strength of the bulk ceramic is 346MPa, and the fracture tou...

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Abstract

The invention relates to an in-situ reactive synthesized Nb4AlC3 bulk ceramic by hot pressing and a preparation method thereof. The Nb4AlC3 bulk ceramic belongs to a hexagonal system with the space group being P63 / mmc, the single-celled lattice parameter a being 3.15, parameter c being 24.22 and the theoretical density being 7.06g / cm<3>. Al and Nb in the crystal structure are combined with a weak covalent bond, thus causing the Nb4AlC3 to generate shear deformation along the base surface (0001) under stress action and grains to easily kink and spall, and then the grains show microscopic plasticity in macroscopic view and can be mechanically processed by common tool steels. The specific preparation method of the single-phase Na4AlC3 is as follows: firstly, niobium powders, aluminum powders and graphite powders are used as materials which are ball milled for 12 to 24 hours under dry condition in a resin tank, then the materials are put in a graphite die for cold molding (10 to 20 MPa) after sieving, and then the materials are sintered in vacuum or a hot pressing furnace introduced with argon, with the heating rate of 10 to 15 DEG C / min, the sintering temperature of 1600 to 1700 DEG C, the heat preserving time of 60 to 120 minutes and applied pressure of 20 to 30 MPa. The Nb4AlC3 bulk ceramic of the invention has the advantages of high purity, high relative density, low hardness and good rigidity under high temperature.

Description

technical field [0001] The invention relates to single-phase bulk ceramics and a preparation method thereof, in particular to an in-situ reaction hot pressing synthesis of Nb 4 AlC 3 Bulk ceramics and methods of making them. Background technique [0002] m n+1 AX n (M is a transition group metal, A is a group A element, X is C or N, n=1-3) has a layered hexagonal structure. Since M.W.Barsoum et al. (American Ceramic Society, J.Am.Ceram.Soc.79(1996)1953) synthesized bulk Ti for the first time by reactive hot pressing technique 3 SiC 2 Since, M n+1 AX n With its unique characteristics, it attracts more and more scientific researchers in the world. Briefly, M n+1 AX n The phase has the characteristics of both ceramics and metals: low density, low hardness, high modulus, high fracture toughness, good thermal shock resistance, good electrical and thermal conductivity, and has become a structural material for high-temperature applications with great potential. C.F.Hu et...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/56C04B35/622
Inventor 周延春胡春峰李方志包亦望
Owner INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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