A high-strength transparent silicon nitride ceramic and its preparation method

Abstract

The present invention belongs to the technical field of advanced ceramic materials, and in particular to a kind of high-strength transparent silicon nitride ceramic and its preparation method. The present invention adopts nano-α-silicon nitride and nano-aluminum oxide as raw materials, and its specific surface area is large, and the compatibility of the two is good. Preheating and calcining are carried out under the protection of inert atmosphere. By the segmented heating of the above two, transparent silicon nitride ceramic can be obtained after cooling, and its strength is considerable. Its strength is more than 1800MPa, and its mechanical properties are excellent. It can be used in the fields of aerospace and bulletproof cars. The high-strength transparent silicon nitride ceramic provided by the present invention can be used in aerospace and bulletproof cars, and is particularly suitable for safety and protective components with observation needs, and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of advanced ceramic materials, and in particular relates to a high-strength transparent silicon nitride ceramic and a preparation method thereof. Background Art

[0002] With the advancement of science and technology and military capabilities, transparent armor and space shuttles have become current research hotspots. These devices often need to operate under extremely harsh conditions, such as high temperature, high pressure, impact, explosion, and combustion. How to protect the safety of workers as much as possible puts new demands on the performance of materials.

[0003] The visualization of protective materials not only allows workers to observe surrounding conditions in real time, but also protects them from external hazards. Transparent materials are beginning to emerge, with transparent ceramics becoming a key research topic for researchers. Meeting these challenges requires transparent materials to possess excellent comprehensive properties, such as good light transmittance, superior mechanical properties, and a moderate density.

[0004] At present, the transparent ceramics developed by scientific researchers mainly include MgAl2O4 and Al2O3, but their mechanical properties and thermal shock resistance cannot fully cope with external damage. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength transparent silicon nitride ceramic and a preparation method thereof. The high-strength transparent silicon nitride ceramic provided by the present invention

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing high-strength transparent silicon nitride ceramics, comprising the following steps:

[0008] Nano-alpha silicon nitride, nano-aluminum oxide and a sintering aid are mixed and then preheated, calcined and cooled in an inert atmosphere to obtain high-strength transparent silicon nitride ceramics.

[0009] Preferably, the mass ratio of the nano-α-silicon nitride to the nano-aluminum oxide is 70-90:10-15;

[0010] The mass ratio of the nano-α-silicon nitride to the sintering aid is 70-90:8-15.

[0011] Preferably, the particle size of the nano-α-silicon nitride is 20 to 80 nm;

[0012] The particle size of the nano-aluminum oxide is 10-80 nm.

[0013] Preferably, the sintering aid includes one or more of silicon dioxide, magnesium oxide and calcium oxide.

[0014] Preferably, the preheating temperature is 200-400° C., the pressure is 3-7 MPa, and the holding time is 10-35 min.

[0015] Preferably, the calcination temperature is 1250-1350° C., the pressure is 760-1000 MPa, and the holding time is 10-25 min.

[0016] Preferably, the cooling rate is 20-160°C / min.

[0017] Preferably, the inert atmosphere is nitrogen.

[0018] The present invention also provides high-strength transparent silicon nitride ceramics obtained by the preparation method described in the above scheme.

[0019] The present invention also provides the application of the high-strength transparent silicon nitride ceramics described in the above solution in aerospace and bulletproof vehicles.

[0020] The present invention provides a method for preparing high-strength transparent silicon nitride ceramics. The method uses nano-α-silicon nitride and nano-aluminum oxide as raw materials, which have large specific surface areas and good compatibility. Preheating and calcining are performed under an inert atmosphere. Through staged heating and cooling, a transparent silicon nitride ceramic is obtained. The ceramic exhibits considerable strength, with a flexural strength exceeding 1800 MPa and excellent mechanical properties, making it suitable for applications in aerospace, bulletproof vehicles, and other fields.

[0021] The present invention also provides a high-strength transparent silicon nitride ceramic obtained by the preparation method described in the above scheme. The high-strength transparent silicon nitride ceramic provided by the present invention has high transparency and excellent mechanical properties.

[0022] The present invention also provides applications of the high-strength transparent silicon nitride ceramics described in the above solution in aerospace and bulletproof vehicles. The high-strength transparent silicon nitride ceramics provided by the present invention can be used in aerospace and bulletproof vehicles, and are particularly suitable for safety and protective components requiring observation, with broad application prospects. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing high-strength transparent silicon nitride ceramics, comprising the following steps:

[0024] Nano-alpha silicon nitride, nano-aluminum oxide and a sintering aid are mixed and then preheated, calcined and cooled in an inert atmosphere to obtain high-strength transparent silicon nitride ceramics.

[0025] In the present invention, the particle size of the nano-α-silicon nitride is preferably 20 to 80 nm, more preferably 30 to 70 nm, further preferably 40 to 60 nm, and even more preferably 45 to 50 nm.

[0026] In the present invention, the particle size of the nano-aluminum oxide is preferably 10 to 80 nm, more preferably 20 to 70 nm, further preferably 30 to 60 nm, and even more preferably 40 to 50 nm.

[0027] In the present invention, the sintering aid preferably includes one or more of silicon dioxide, magnesium oxide and calcium oxide.

[0028] In the present invention, the mass ratio of the nano-α-silicon nitride to the nano-aluminum oxide is preferably 70-90:10-15, more preferably 75-88:10-14, further preferably 79-84:11-13, and even more preferably 81-83:12-13.

[0029] In the present invention, the mass ratio of the nano-α-silicon nitride to the sintering aid is preferably 70-90:8-15, more preferably 74-86:8-13, further preferably 78-83:9-13, and even more preferably 81-83:11-12.

[0030] In the present invention, the mixing is preferably stirring; the stirring speed is preferably 200 to 800 rpm, more preferably 300 to 600 rpm, and the stirring time is preferably 20 to 90 min, more preferably 30 to 50 min.

[0031] In the present invention, the preheating temperature is preferably 200-400°C, more preferably 230-380°C, further preferably 250-340°C, further preferably 280-310°C, the pressure is preferably 3-7 MPa, more preferably 4-6 MPa, further preferably 5 MPa, the holding time is preferably 10-35 min, more preferably 15-30 min, further preferably 20-25 min, further preferably 22-23 min; the preheating is carried out in an inert atmosphere; the inert atmosphere is preferably nitrogen.

[0032] In the present invention, the calcination temperature is preferably 1250-1350°C, more preferably 1270-1310°C, further preferably 1290-1310°C, further preferably 1300-1305°C, the pressure is preferably 760-1000 MPa, more preferably 790-960 MPa, further preferably 820-930 MPa, further preferably 850-880 MPa, the holding time is preferably 10-25 min, more preferably 14-24 min, further preferably 17-21 min, further preferably 19-20 min; the calcination is carried out in an inert atmosphere; the inert atmosphere is preferably nitrogen.

[0033] In the present invention, the cooling rate is preferably 20 to 160°C / min, more preferably 40 to 130°C / min, and further preferably 70 to 100°C / min; the final temperature of the cooling is preferably room temperature; the cooling is carried out in an inert atmosphere; and the inert atmosphere is preferably nitrogen.

[0034] The present invention also provides high-strength transparent silicon nitride ceramics obtained by the preparation method described in the above scheme.

[0035] The high-strength transparent silicon nitride ceramic provided by the present invention has high transparency and excellent mechanical properties, and its bending strength is above 1800 MPa.

[0036] The present invention also provides the application of the high-strength transparent silicon nitride ceramics described in the above solution in aerospace and bulletproof vehicles.

[0037] The high-strength transparent silicon nitride ceramics provided by the present invention can be used in aerospace and bulletproof vehicles, and are particularly suitable for safety and protective components requiring observation, and have broad application prospects.

[0038] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0039] Example 1

[0040] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0041] Mixing nano-α-silicon nitride with a particle size of 20 nm, nano-aluminum oxide with a particle size of 10 nm, and a sintering aid (silicon dioxide);

[0042] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 70:15, and the mass ratio of nano-α-silicon nitride to sintering aid is 70:15;

[0043] Then, it was preheated in a nitrogen atmosphere at a temperature of 200°C, a pressure of 7 MPa, and a holding time of 35 min.

[0044] Then calcined in nitrogen atmosphere at a temperature of 1250°C, a pressure of 760 MPa, and a holding time of 25 min;

[0045] The product was then cooled in a nitrogen atmosphere at a cooling rate of 20°C / min to obtain high-strength transparent silicon nitride ceramics.

[0046] Example 2

[0047] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0048] Mixing nano-α-silicon nitride with a particle size of 80 nm, nano-aluminum oxide with a particle size of 80 nm, and a sintering aid (calcium oxide);

[0049] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 90:10, and the mass ratio of nano-α-silicon nitride to sintering aid is 90:8;

[0050] Then, it was preheated in a nitrogen atmosphere at a temperature of 400°C, a pressure of 3 MPa, and a holding time of 10 min.

[0051] Then, the product was calcined in a nitrogen atmosphere at a temperature of 1350°C, a pressure of 1000 MPa, and a holding time of 10 min.

[0052] The product was then cooled in a nitrogen atmosphere at a cooling rate of 160°C / min to obtain high-strength transparent silicon nitride ceramics.

[0053] Example 3

[0054] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0055] Mixing nano-α-silicon nitride with a particle size of 80 nm, nano-aluminum oxide with a particle size of 70 nm, and a sintering aid (silicon dioxide);

[0056] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 80:12, and the mass ratio of nano-α-silicon nitride to sintering aid is 80:13;

[0057] Then, it was preheated in a nitrogen atmosphere at a temperature of 300°C, a pressure of 5 MPa, and a holding time of 25 min.

[0058] Then, the product was calcined in a nitrogen atmosphere at a temperature of 1300°C, a pressure of 900 MPa, and a holding time of 15 min.

[0059] The product was then cooled in a nitrogen atmosphere at a cooling rate of 100°C / min to obtain high-strength transparent silicon nitride ceramics.

[0060] Example 4

[0061] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0062] Mixing nano-α-silicon nitride with a particle size of 20 nm, nano-aluminum oxide with a particle size of 30 nm, and a sintering aid (silicon dioxide);

[0063] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 90:10, and the mass ratio of nano-α-silicon nitride to sintering aid is 90:8;

[0064] Then, it was preheated in a nitrogen atmosphere at a temperature of 250°C, a pressure of 4 MPa, and a holding time of 18 min.

[0065] Then, the product was calcined in a nitrogen atmosphere at a temperature of 1310°C, a pressure of 800 MPa, and a holding time of 25 min.

[0066] The product was then cooled in a nitrogen atmosphere at a cooling rate of 70°C / min to obtain high-strength transparent silicon nitride ceramics.

[0067] Example 5

[0068] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0069] Mixing nano-α-silicon nitride with a particle size of 30 nm, nano-aluminum oxide with a particle size of 30 nm, and a sintering aid (calcium oxide);

[0070] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 70:13, and the mass ratio of nano-α-silicon nitride to sintering aid is 80:11;

[0071] Then, it was preheated in a nitrogen atmosphere at a temperature of 350°C, a pressure of 6 MPa, and a holding time of 30 min.

[0072] Then, the calcination was carried out in a nitrogen atmosphere at a temperature of 1290°C, a pressure of 950 MPa, and a holding time of 10 min.

[0073] The product was then cooled in a nitrogen atmosphere at a cooling rate of 120°C / min to obtain high-strength transparent silicon nitride ceramics.

[0074] Example 6

[0075] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0076] Mixing nano-α-silicon nitride with a particle size of 60 nm, nano-aluminum oxide with a particle size of 60 nm, and a sintering aid (calcium oxide);

[0077] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 90:10, and the mass ratio of nano-α-silicon nitride to sintering aid is 90:12;

[0078] Then, it was preheated in a nitrogen atmosphere at a temperature of 280°C, a pressure of 5 MPa, and a holding time of 25 min.

[0079] Then calcined in nitrogen atmosphere at a temperature of 1290°C, a pressure of 870 MPa, and a holding time of 15 min;

[0080] The product was then cooled in a nitrogen atmosphere at a cooling rate of 70°C / min to obtain high-strength transparent silicon nitride ceramics.

[0081] Example 7

[0082] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0083] Mixing nano-α-silicon nitride with a particle size of 70 nm, nano-aluminum oxide with a particle size of 50 nm, and a sintering aid (calcium oxide);

[0084] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 85:14, and the mass ratio of nano-α-silicon nitride to sintering aid is 85:11;

[0085] Then, it was preheated in a nitrogen atmosphere at a temperature of 380°C, a pressure of 6 MPa, and a holding time of 27 min.

[0086] Then, the calcination was carried out in a nitrogen atmosphere at a temperature of 1305°C, a pressure of 840 MPa, and a holding time of 25 min.

[0087] The product was then cooled in a nitrogen atmosphere at a cooling rate of 30°C / min to obtain high-strength transparent silicon nitride ceramics.

[0088] Example 8

[0089] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0090] Mixing nano-α-silicon nitride with a particle size of 80 nm, nano-aluminum oxide with a particle size of 80 nm, and a sintering aid (silicon dioxide);

[0091] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 80:11, and the mass ratio of nano-α-silicon nitride to sintering aid is 80:11;

[0092] Then, it was preheated in a nitrogen atmosphere at a temperature of 330°C, a pressure of 5 MPa, and a holding time of 25 min.

[0093] Then, the calcination was carried out in a nitrogen atmosphere at a temperature of 1260°C, a pressure of 910 MPa, and a holding time of 22 min.

[0094] The product was then cooled in a nitrogen atmosphere at a cooling rate of 110°C / min to obtain high-strength transparent silicon nitride ceramics.

[0095] Example 9

[0096] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0097] Mixing nano-α-silicon nitride with a particle size of 50 nm, nano-aluminum oxide with a particle size of 50 nm, and a sintering aid (silicon dioxide);

[0098] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 88:13, and the mass ratio of nano-α-silicon nitride to sintering aid is 88:13;

[0099] Then it was preheated in nitrogen atmosphere at a temperature of 255°C, a pressure of 5 MPa, and a holding time of 11 min;

[0100] Then calcined in nitrogen atmosphere at a temperature of 1350°C, a pressure of 760 MPa, and a holding time of 15 min;

[0101] The product was then cooled in a nitrogen atmosphere at a cooling rate of 26°C / min to obtain high-strength transparent silicon nitride ceramics.

[0102] Example 10

[0103] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0104] Mixing nano-α-silicon nitride with a particle size of 80 nm, nano-aluminum oxide with a particle size of 80 nm, and a sintering aid (calcium oxide);

[0105] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 79:15, and the mass ratio of nano-α-silicon nitride to sintering aid is 79:15;

[0106] Then, it was preheated in a nitrogen atmosphere at a temperature of 240°C, a pressure of 7 MPa, and a holding time of 10 min.

[0107] Then calcined in nitrogen atmosphere at a temperature of 1250°C, a pressure of 760 MPa, and a holding time of 25 min;

[0108] The product is then cooled in a nitrogen atmosphere at a cooling rate of 150°C / min to obtain high-strength transparent silicon nitride ceramics.

[0109] Example 11

[0110] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0111] Mixing nano-α-silicon nitride with a particle size of 20 nm, nano-aluminum oxide with a particle size of 10 nm, and a sintering aid (magnesium oxide);

[0112] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 80:15, and the mass ratio of nano-α-silicon nitride to sintering aid is 80:15;

[0113] Then, it was preheated in a nitrogen atmosphere at a temperature of 210°C, a pressure of 7 MPa, and a holding time of 35 min.

[0114] Then, the product was calcined in a nitrogen atmosphere at a temperature of 1350°C, a pressure of 1000 MPa, and a holding time of 10 min.

[0115] The product was then cooled in a nitrogen atmosphere at a cooling rate of 20°C / min to obtain high-strength transparent silicon nitride ceramics.

[0116] Example 12

[0117] The preparation of the high-strength transparent silicon nitride ceramic of this embodiment includes the following steps:

[0118] Mixing nano-α-silicon nitride with a particle size of 80 nm, nano-aluminum oxide with a particle size of 60 nm, and a sintering aid (magnesium oxide);

[0119] The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 90:15, and the mass ratio of nano-α-silicon nitride to sintering aid is 90:15;

[0120] Then, it was preheated in a nitrogen atmosphere at a temperature of 390°C, a pressure of 7 MPa, and a holding time of 15 min.

[0121] Then calcined in nitrogen atmosphere at a temperature of 1350°C, a pressure of 760 MPa, and a holding time of 15 min;

[0122] The product was then cooled in a nitrogen atmosphere at a cooling rate of 50°C / min to obtain high-strength transparent silicon nitride ceramics.

[0123] Comparative Example 1

[0124] The preparation method of this comparative example is the same as that of Example 1, with the only difference being that nano-α-silicon nitride with a particle size of 20 μm is used.

[0125] Comparative Example 2

[0126] The preparation method of this comparative example is the same as that of Example 1, with the only difference being that nano-α-silicon nitride with a particle size of 0.1 nm is used.

[0127] Comparative Example 3

[0128] The preparation method of this comparative example is the same as that of Example 1, with the only difference being that the calcination temperature is 1100°C.

[0129] Comparative Example 4

[0130] The preparation method of this comparative example is the same as that of Example 1, with the only difference being that the calcination temperature is 1900°C.

[0131] The mechanical properties and transparency of the high-strength transparent silicon nitride ceramics prepared in Examples 1 to 12 and Comparative Examples 1 to 4 were tested. The results are shown in Table 1.

[0132] Table 1 Test results of high-strength transparent silicon nitride ceramics of Examples 1 to 12 and Comparative Examples 1 to 4

[0133]

[0134]

[0135] Note: The transparency in this table is a relative ratio.

[0136] As can be seen from Table 1, the high-strength transparent silicon nitride ceramic provided by the present invention not only has strong mechanical properties, high strength, good rigidity, but also high transparency, and its bending strength is above 1800 MPa, and its mechanical properties are excellent.

[0137] As can be seen from the above examples, the high-strength transparent silicon nitride ceramics provided by the present invention are transparent and high-strength, have outstanding mechanical properties, and excellent comprehensive performance, and can be used in fields such as aerospace and bulletproof vehicles.

[0138] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength transparent silicon nitride ceramics, characterized in that: For the following steps: A mixture of nano-α-silicon nitride with a particle size of 60nm, nano-aluminum oxide with a particle size of 60nm, and calcium oxide; The mass ratio of nano-α-silicon nitride to nano-aluminum oxide is 90:10, and the mass ratio of nano-α-silicon nitride to calcium oxide is 90:12; Then, it was preheated in a nitrogen atmosphere at a temperature of 280°C, a pressure of 5 MPa, and a holding time of 25 min. Then calcined in nitrogen atmosphere at a temperature of 1290°C, a pressure of 870 MPa, and a holding time of 15 min; The product was then cooled in a nitrogen atmosphere at a cooling rate of 70°C / min to obtain high-strength transparent silicon nitride ceramics.

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