Rare earth ion doped beta-SiAlON / h-BN composite ceramic and preparation method thereof

Abstract

The invention discloses a rare earth ion doped beta-SiAlON / h-BN composite ceramic and a preparation method thereof, and relates to the technical field of ceramic materials, the original powder of the composite ceramic comprises hexagonal boron nitride (h-BN) powder, alpha-silicon nitride (alpha-Si3N4) powder, rare earth oxide (Re2O3) powder (Re = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Sc) and aluminum oxide (Al2O3) powder, the volume ratio range of h-BN to alpha-Si3N4 is 8: 2-5: 5, and the volume ratio range of alpha-SiAlON / h-BN is 1: 2-3: 5. And 5-15 vol% of Re2O3-Al2O3 (the molar ratio is 3: 5) is additionally added. The preparation method comprises the following steps: weighing the raw materials according to the proportion, carrying out ball milling and mixing on the raw materials, zirconium oxide balls and absolute ethyl alcohol, then drying, loading into a graphite mold, and carrying out hot pressed sintering at 1700-1900 DEG C and 10-40MPa in a nitrogen atmosphere to obtain a finished product. According to the method, the rare earth ion doped beta-SiAlON phase is generated in situ in the sintering process, interface bonding with an h-BN matrix is improved, the problems that traditional h-BN is difficult to sinter and low in mechanical property are effectively solved, and the composite ceramic has excellent characteristics of the rare earth ion doped beta-SiAlON and the h-BN and is suitable for the field of ceramic materials with advanced structures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic materials, in particular to a rare earth ion doped β-SiAlON / h-BN composite ceramic and a preparation method thereof. BACKGROUND

[0002] Hexagonal boron nitride (h-BN) has a layered structure similar to graphite, with B-N atoms in the layer being combined by strong covalent bonds and the layers being maintained by weak van der Waals forces. This unique structure endows h-BN with a series of excellent physical and chemical properties, such as high temperature resistance, thermal shock resistance, chemical inertness, high thermal conductivity, electrical insulation, etc., combined with good processability, making it have application potential in many fields. However, pure h-BN ceramic has problems of difficult sintering densification, limited mechanical strength and fracture toughness due to weak interlayer bonding and low self-diffusion coefficient, which limits its wide application in the field of structural materials. SUMMARY

[0003] The present application provides a rare earth ion doped β-SiAlON / h-BN composite ceramic and a preparation method thereof to solve the above problems in the prior art.

[0004] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] In a first aspect, the present application provides a rare earth ion doped β-SiAlON / h-BN composite ceramic, the raw materials of which are composed of h-BN powder, α-Si3N4 powder, Re2O3 powder and Al2O3 powder, wherein the volume ratio of h-BN powder to α-Si3N4 powder is 8:2-5:5, 5-15% of Re2O3-Al2O3 is additionally added, and the molar ratio of Re2O3 to Al2O3 is 3:5. The particle size and purity of each raw material powder meet the following requirements: the median particle size of h-BN powder is ≤1 μm, and the purity is ≥99%; the median particle size of α-Si3N4 powder is ≤1 μm, and the purity is ≥99%; the median particle size of Re2O3 powder is ≤2 μm, and the purity is ≥99.9%; and the median particle size of Al2O3 powder is ≤0.5 μm, and the purity is ≥99%.

[0006] In a second aspect, the present application provides a preparation method of the above-mentioned rare earth ion doped β-SiAlON / h-BN composite ceramic, which comprises the following steps:

[0007] Step 1: h-BN powder, α-Si3N4 powder, Re2O3 powder and Al2O3 powder are weighed according to the raw material ratio, and the weighed raw material powder, zirconia balls and anhydrous ethanol are put into a mixing tank together to mix, obtaining a uniform slurry;

[0008] Step 2: the uniform slurry obtained in step 1 is dried to obtain a mixed powder;

[0009] Step 3: the mixed powder obtained in step 2 is loaded into a mold for hot-press sintering, and then naturally cooled to room temperature with the furnace to obtain a rare earth ion-doped β-SiAlON / h-BN composite ceramic.

[0010] Further, the rare earth oxide (Re2O3) in step 1 includes Y2O3, La2O3, Ce2O3, Pr6O 11 , Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3 and Sc2O3.

[0011] Further, the heating rate of the hot-press sintering in step 4 is 10℃ / min, the sintering temperature is 1700-1900℃, the sintering pressure is 10-40MPa, and the holding time is 0.5-2 hours.

[0012] Compared with the prior art, the following beneficial effects are achieved:

[0013] The rare earth ion-doped β-SiAlON / h-BN composite ceramic and the preparation method thereof have the following advantages: by compounding β-SiAlON and h-BN, the high strength of β-SiAlON and the layered toughening mechanism of h-BN are synergistically used, the excellent properties of h-BN such as high-temperature resistance, thermal shock resistance and electrical insulation are retained, and the good interface bonding between the in-situ generated rare earth ion-doped β-SiAlON phase and the h-BN matrix is achieved, which significantly improves the mechanical strength and fracture toughness of the composite ceramic, effectively solves the problems of difficulty in sintering densification and insufficient mechanical properties of pure h-BN ceramic, and makes the composite ceramic more widely applicable in the fields of high-temperature resistant, thermal shock resistant and electrically insulated structural component manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The flowchart of the preparation method of the present application is shown.

[0015] Figure 2 The X-ray diffraction pattern of the β-SiAlON / h-BN composite ceramic of the present application is shown. DETAILED DESCRIPTION

[0016] Example 1

[0017] A preparation method of a rare earth ion-doped β-SiAlON / h-BN composite ceramic includes the following processes:

[0018] Step 1: Measure the raw materials according to the proportion (for example, to prepare 100 g of composite ceramic): h-BN powder 35.64 g (median particle size 0.5 μm, purity 99%), α-Si3N4 powder 50.13 g (median particle size 0.5 μm, purity 99%), the volume ratio of the two is 5:5, and an additional volume fraction of 10% Y2O3-Al2O3 is added, wherein the molar ratio of Y2O3 powder 8.11 g (median particle size 1 μm, purity 99.9%) to Al2O3 powder 6.10 g (median particle size 0.4 μm, purity 99%) is 3:5;

[0019] Step 2: Measure the h-BN powder, α-Si3N4 powder, Re2O3 powder and Al2O3 powder according to the proportion of the raw materials, and put the weighed raw material powder, zirconia balls and anhydrous ethanol into a mixing tank for mixing to obtain a uniform slurry;

[0020] Step 3: Dry the uniform slurry obtained in step 2 to obtain a mixed powder;

[0021] Step 4: Put the mixed powder obtained in step 3 into a hot-pressing sintering furnace in a nitrogen atmosphere, heat to 1800℃ at a heating rate of 10℃ / min, and keep the pressure at 25 MPa for 1 hour; then naturally cool to room temperature with the furnace to obtain Y-doped β-SiAlON / h-BN composite ceramic.

[0022] The composite ceramic obtained according to the above embodiment has a density of 2.75±0.01 g / cm³, a bending strength of 479.2±52.0 MPa, and a fracture toughness of 6.78±0.49 MPa·m 1 / 2 .

[0023] Example 2

[0024] A preparation method of a rare earth ion-doped β-SiAlON / h-BN composite ceramic, comprising the following processes:

[0025] Step 1: Measure the raw materials according to the proportion (for example, to prepare 100 g of composite ceramic): h-BN powder 35.64 g (median particle size 0.5 μm, purity 99%), α-Si3N4 powder 50.13 g (median particle size 0.5 μm, purity 99%), the volume ratio of the two is 5:5, and an additional volume fraction of 10% Y2O3-Al2O3 is added, wherein the molar ratio of Y2O3 powder 8.11 g (median particle size 1 μm, purity 99.9%) to Al2O3 powder 6.10 g (median particle size 0.4 μm, purity 99%) is 3:5;

[0026] Step 2: h-BN powder, α-Si3N4 powder, Re2O3 powder and Al2O3 powder were weighed according to the raw material ratio, and the weighed raw material powder, zirconia balls and anhydrous ethanol were put into a mixing tank for mixing to obtain a uniform slurry;

[0027] Step 3: The uniform slurry obtained in step 2 was dried to obtain a mixed powder;

[0028] Step 4: The mixed powder obtained in step 3 was placed in a hot-pressing sintering furnace in a nitrogen atmosphere, and the temperature was raised to 1800℃ at a heating rate of 10℃ / min, and the pressure was 25MPa for 1 hour; then the furnace was naturally cooled to room temperature to obtain Y-doped β-SiAlON / h-BN composite ceramic.

[0029] The density of the composite ceramic obtained according to the above embodiment is 2.63±0.01g / cm3, the bending strength is 509.1±38.2MPa, and the fracture toughness is 8.62±0.37MPa·m 1 / 2 .

[0030] Example 3

[0031] A preparation method of a rare earth ion-doped β-SiAlON / h-BN composite ceramic, comprising the following processes:

[0032] Step 1: Raw materials (for example, to prepare 100g of composite ceramic): h-BN powder 52.96g (median particle size 0.5μm, purity 99%), α-Si3N4 powder 31.95g (median particle size 0.5μm, purity 99%), the volume ratio of the two is 7:3, and an additional volume fraction of 10% Y2O3-Al2O3 is added, wherein the molar ratio of Y2O3 powder 8.62g (median particle size 1μm, purity 99.9%) to Al2O3 powder 6.48g (median particle size 0.4μm, purity 99%) is 3:5;

[0033] Step 2: h-BN powder, α-Si3N4 powder, Re2O3 powder and Al2O3 powder were weighed according to the raw material ratio, and the weighed raw material powder, zirconia balls and anhydrous ethanol were put into a mixing tank for mixing to obtain a uniform slurry;

[0034] Step 3: The uniform slurry obtained in step 2 was dried to obtain a mixed powder;

[0035] Step 4: The mixed powder obtained in step 3 was placed in a hot-pressing sintering furnace in a nitrogen atmosphere, and the temperature was raised to 1800℃ at a heating rate of 10℃ / min, and the pressure was 25MPa for 1 hour; then the furnace was naturally cooled to room temperature to obtain Y-doped β-SiAlON / h-BN composite ceramic.

[0036] The composite ceramic obtained according to the above embodiment has a density of 2.49±0.01 g / cm3, a bending strength of 398.4±5.7 MPa, and a fracture toughness of 5.57±0.34 MPa·m 1 / 2 .

[0037] Experimental Part

[0038] I. Experimental Purpose

[0039] Verify the "strengthening and toughening" effect of the prepared rare earth ion doped β-SiAlON / h-BN composite ceramic in mechanical strength (bending strength), fracture toughness and density.

[0040] II. Preparation of Experimental Samples

[0041] 1. Experimental Group

[0042] 1.1. Raw material ratio: h-BN powder (median particle size 0.5 μm, purity 99%) and α-Si3N4 powder (median particle size 0.5 μm, purity 99%) in a volume ratio of 6:4, with an additional 10% by volume of Y2O3-Al2O3, wherein the molar ratio of Y2O3 powder (median particle size 1 μm, purity 99.9%) to Al2O3 powder (median particle size 0.4 μm, purity 99%) is 3:5;

[0043] 1.2. Preparation process: zirconia balls + anhydrous ethanol + raw material powder are put into a mixing tank for mixing for 24 h → drying → 1800℃, 25MPa hot-pressing sintering for 1h (heating rate 10℃ / min) in a nitrogen atmosphere.

[0044] 2. Comparative Example 1 (pure h-BN powder)

[0045] 2.1. Raw material ratio: only h-BN powder (same specifications as the experimental group);

[0046] 2.2. Preparation process: except for no α-Si3N4, Y2O3-Al2O3, the mixing, drying and sintering parameters are consistent with those of the experimental group.

[0047] 3. Comparative Example 2 (h-BN / β-SiAlON composite ceramic without Y2O3-Al2O3)

[0048] 3.1. Raw material ratio: h-BN and α-Si3N4 in a volume ratio of 6:4 (same specifications as the experimental group), without Y2O3-Al2O3 additive;

[0049] 3.2. Preparation process: same as the experimental group.

[0050] III. Performance Test Method

[0051] 1. Bulk density: Archimedes method (GB / T 25995-2010);

[0052] 2. Bending strength: three-point bending method (GB / T 6569-2006), sample size 3mm x 4mm x 36mm, span 30mm, loading rate 0.5mm / min;

[0053] 3. Fracture toughness: single-edge notched beam method (SENB, GB / T 23806-2009), sample size 2mm x 4mm x 20mm, notch depth 2mm, span 16mm, loading rate 0.05mm / min;

[0054] 4. Test repetition number: 5 parallel samples for each group of samples, and take the average value.

[0055] Four, experimental results

[0056]

[0057] Five, experimental conclusions

[0058] The bulk density, bending strength and fracture toughness of the experimental group are significantly better than those of Comparative Examples 1 and 2, proving that the technical scheme of "Y2O3-Al2O3 additive + in-situ generated Y-doped β-SiAlON phase" can effectively solve the problems of sintering difficulty and low mechanical properties of pure h-BN, and realize the "rare earth ion doped" characteristics of the composite ceramic.

[0059] Although the present application has been described in detail in the foregoing with general description and specific embodiments, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, are within the scope of the present application claimed.

[0060] The terms such as "up", "down", "left", "right", "middle" and the like cited in the specification are only for the convenience of clear description, and are not intended to limit the scope of the present application. The change or adjustment of the relative relationship without substantial change of the technical content is also considered as the scope of the present application.

Claims

1. A rare earth ion doped β-SiAlON / h-BN composite ceramic, characterized in that, The raw materials are composed of h-BN powder, alpha-Si3N4 powder, Re2O3 powder and Al2O3 powder, wherein the volume ratio of h-BN powder to alpha-Si3N4 powder is 8:2-5:5, and 5-15% of Re2O3-Al2O3 is additionally added, and the molar ratio of Re2O3 to Al2O3 is fixed at 3:

5.

2. The rare earth ion-doped β-SiAlON / h-BN composite ceramic of claim 1, wherein The particle size and purity of each raw material powder meet the following requirements: the median particle size of h-BN powder is ≤1 μm, and the purity is ≥99%; the median particle size of alpha-Si3N4 powder is ≤1 μm, and the purity is ≥99%; the median particle size of Re2O3 powder is ≤2 μm, and the purity is ≥99.9%; and the median particle size of Al2O3 powder is ≤0.5 μm, and the purity is ≥99%.

3. The rare earth oxide (Re2O3) of claims 1-2 comprises Y2O3, La2O3, Ce2O3, Pr6O 11 3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, and Sc2O3.

4. The rare earth ion-doped β-SiAlON / h-BN composite ceramic of claim 1, wherein In the hot-pressing sintering process, a rare earth ion-doped beta-SiAlON phase is generated in situ and uniformly dispersed in the h-BN matrix, and the interface is well combined.

5. The method of producing a rare earth ion-doped β-SiAlON / h-BN composite ceramic according to claims 1 to 4, characterized in that, The method comprises the following steps: Step 1: h-BN powder, alpha-Si3N4 powder, Re2O3 powder and Al2O3 powder are weighed according to the raw material ratio, and the weighed raw material powder, zirconia balls and anhydrous ethanol are put into a mixing tank together to obtain a uniform slurry; Step 2: the uniform slurry obtained in step 1 is dried to obtain a mixed powder; Step 3: the mixed powder obtained in step 2 is loaded into a mold, and hot-pressing sintering is performed, followed by natural cooling in the furnace to room temperature to obtain a rare earth ion-doped beta-SiAlON / h-BN composite ceramic.

6. The method of claim 5, wherein the method further comprises the step of sintering the green body at a temperature of 1600-1800°C in a nitrogen atmosphere. The heating rate of the hot-pressing sintering in step 3 is 5-20 ℃ / min, the sintering temperature is 1700-1900 ℃, the sintering pressure is 10-40 MPa, and the holding time is 0.5-2 hours.

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