Low-temperature sintering silicon nitride ceramic powder, silicon nitride ceramic and preparation method thereof

Abstract

The application provides a low-temperature sintering silicon nitride ceramic powder, a silicon nitride ceramic and a preparation method thereof, and uses beta silicon nitride powder as raw material and low-melting-point glass powder as a sintering aid. The beta silicon nitride powder with a content of 75-90wt% and a particle size range of 0.5-1um is selected, and the low-melting-point glass powder with a content of 10-25wt% is added. The mixed powder is ball milled, dried and pressed into a sheet, and then cold isostatic pressing is carried out, and pressureless sintering is carried out at 1400-1600 DEG C under a nitrogen atmosphere to obtain a silicon nitride ceramic material. The beta silicon nitride powder provided by the application can directly sinter the beta silicon nitride ceramic at low temperature. The preparation method of the silicon nitride ceramic provided by the application reduces the sintering temperature of the silicon nitride, improves the preparation efficiency of the silicon nitride ceramic, and is mainly applied to refractory fire-resistant materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of advanced structural ceramics, in particular to a low-temperature sintering silicon nitride ceramic powder, a silicon nitride ceramic and a preparation method thereof. BACKGROUND

[0002] Silicon nitride ceramics have good physical and mechanical properties, with high hardness, corrosion resistance, high temperature resistance, high strength, good thermal shock resistance, low thermal expansion coefficient and good stability. However, due to the high degree of covalent bond, low diffusion coefficient and small sintering driving force of silicon nitride, sintering densification of silicon nitride ceramics can only be achieved at a high sintering temperature by adding sintering aids.

[0003] The commonly used sintering aid is a composite sintering aid of MgO, Al2O3 and rare earth oxides. Under pressureless sintering conditions, the sintering temperature needs to be higher than 1600℃, and the relative density of the ceramic can reach 90%. When the temperature is above 1650℃, α-silicon nitride can be completely converted into β-silicon nitride. Therefore, to obtain a silicon nitride ceramic with high β-silicon nitride content, the pressureless sintering temperature is generally 1700-1800℃. In this case, pressureless sintering of silicon nitride ceramics requires extremely high temperature, high sintering equipment and high energy consumption, resulting in high preparation cost.

[0004] Therefore, there is an urgent need to provide a silicon nitride ceramic preparation method capable of sintering at a low temperature of 1450℃ under pressureless conditions.

[0005] The information in the background is only to illustrate the general background of the present application, and should not be regarded as admitting or implying in any form that the information constitutes prior art known to those skilled in the art. SUMMARY

[0006] To solve the above technical problems, the present application provides a low-temperature sintering silicon nitride ceramic powder, a silicon nitride ceramic and a preparation method thereof. Specifically, the present application includes the following contents.

[0007] In one aspect, the present application provides a low-temperature sintering silicon nitride ceramic powder, which comprises at least β-silicon nitride powder and low-melting point glass powder; the addition amount of the β-silicon nitride powder is 75-90wt%; the addition amount of the low-melting point glass powder is 10-25wt%; and the low-melting point glass powder at least contains boron oxide, silicon oxide, aluminum oxide, yttrium oxide and magnesium oxide.

[0008] In one embodiment, the content ratio of the boron oxide, the silicon oxide, the aluminum oxide, the yttrium oxide and the magnesium oxide is 15-20wt%:45-50wt%:10-20wt%:5-15wt%:5-15wt%.

[0009] In one embodiment, the β-silicon nitride powder is sub-micron powder, and the particle size of the powder ranges from 0.5 to 1 μm.

[0010] In one embodiment, the particle size of the β-silicon nitride powder ranges from 0.7 to 0.8 μm.

[0011] Another aspect of the present application provides a low-temperature sintered silicon nitride ceramic prepared using the low-temperature sintered silicon nitride ceramic powder of any one of the above embodiments.

[0012] The present application also provides a method for preparing a low-temperature sintered silicon nitride ceramic, which comprises at least the following steps:

[0013] Step one, melting a glass liquid by mixing boron oxide, silicon oxide, aluminum oxide, yttrium oxide and magnesium oxide in a predetermined ratio;

[0014] Step two, drying and grinding the glass liquid after quenching and agglomerating to obtain a low-melting-point glass powder with a melting point of 1000-1400 °C;

[0015] Step three, mixing and grinding the low-melting-point glass powder and the β-silicon nitride powder in a predetermined ratio, and then drying and tabletting;

[0016] Step four, placing the tablet under pressure for a certain period of time at 100-200 MPa, and then sintering under a nitrogen atmosphere at a temperature lower than 1600 °C for 3-12 h to obtain the silicon nitride ceramic.

[0017] Further, the method for melting a glass liquid by mixing boron oxide, silicon oxide, aluminum oxide, yttrium oxide and magnesium oxide in a predetermined ratio comprises the following steps: mixing 15-20 wt% of boron oxide, 45-50 wt% of silicon oxide, 10-20 wt% of aluminum oxide, 5-15 wt% of yttrium oxide and 5-15 wt% of magnesium oxide, and mixing the mixture on a jar mill for at least 1 h, and then placing the mixed raw materials in a melting furnace at 1600 °C for at least 2 h to obtain a glass liquid.

[0018] Further, the method for mixing and grinding the low-melting-point glass powder and the β-silicon nitride powder in a predetermined ratio, and then drying and tabletting comprises the following steps: placing the mixed powder of the β-silicon nitride powder and the low-melting-point glass powder in a ball mill jar, and ball milling for 12 h using alcohol as a grinding medium, and then drying and tabletting.

[0019] In one embodiment, the time for placing the tablet under pressure at 200 MPa is 3-5 min.

[0020] In one embodiment, the pressed small pieces are kept under pressure for 5 minutes at 200 MPa, and then pressureless sintering is carried out at 1450 DEG C in a nitrogen atmosphere, and the silicon nitride ceramic is obtained after 12 hours of heat preservation.

[0021] The low-temperature sintered silicon nitride ceramic powder, the silicon nitride ceramic and the preparation method thereof have at least one of the following beneficial effects:

[0022] Firstly, the silicon nitride ceramic powder, the silicon nitride ceramic and the preparation method thereof of the present application use beta silicon nitride as raw material, and the problem that alpha silicon nitride cannot completely phase change during low-temperature sintering is avoided.

[0023] Secondly, the silicon nitride ceramic preparation method of the embodiment of the present application uses low-melting-point glass powder as a sintering aid of the silicon nitride ceramic, and the aid has good wettability with the silicon nitride in a molten state, and the silicon nitride ceramic with high density is obtained at a lower temperature.

[0024] Thirdly, the silicon nitride ceramic preparation method of the embodiment of the present application has a sintering temperature lower than 1600 DEG C, and is pressureless sintering, which reduces the requirement for sintering equipment, greatly reduces the preparation cost of the silicon nitride ceramic, and the sintered silicon nitride ceramic can be applied to refractory materials.

[0025] Fourthly, the silicon nitride ceramic preparation method of the embodiment of the present application combines beta silicon nitride powder with low-melting-point glass powder, and the volume density of the sintered silicon nitride ceramic at a lower temperature of 1450 DEG C can reach 2.8 g / cm 3 The above, and the good high-temperature resistance of the silicon nitride ceramic is retained.

[0026] After reading the specific embodiments and after viewing the drawings, those skilled in the art will realize additional features and advantages. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort.

[0028] Figure 1 is a flow chart of the silicon nitride ceramic preparation method of the embodiment of the present application. DETAILED DESCRIPTION

[0029] Now, various exemplary embodiments of the present application will be described in detail, and the detailed description should not be considered as a limitation of the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0030] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that the upper and lower limits of the range and every intermediate value between them are specifically disclosed. Any stated value or intermediate value within a stated range, as well as any other stated value or every smaller range between intermediate values ​​within a range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0031] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention. All references to literature in this specification are incorporated by way of citation to disclose and describe the methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. Unless otherwise stated, “%” means percentage based on weight.

[0032] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of the embodiments of the present invention. In the description of the present invention, it should be noted that, unless otherwise stated, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0033] Furthermore, the terms "comprising," "including," "having," or any other variations thereof are intended to cover non-exclusive inclusion, such that a structure or component that includes a list of elements includes not only those elements but also other structural elements that are not expressly listed or inherent to the structure or component. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the article or apparatus that includes the element.

[0034] Spatial relation terms such as "below," "under," "under," "low," "above," "on," and "high" are used for descriptive convenience to explain the positioning of one element relative to a second element, indicating that these terms are intended to cover different orientations of the device, in addition to those different from those shown in the figure. Furthermore, phrases such as "one element on / below another element" can indicate that two elements are in direct contact, or that there are other elements between the two elements. In addition, terms such as "first" and "second" are also used to describe individual elements, areas, parts, etc., without specifically indicating order or sequence, and should not be considered restrictive. Similar terms are used throughout the description to represent similar elements.

[0035] It will be apparent to those skilled in the art that the present invention can be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention.

[0036] This invention provides a low-temperature sintering silicon nitride ceramic powder, comprising at least β-silicon nitride powder and low-melting-point glass powder. This invention uses β-silicon nitride powder as the raw material and low-melting-point glass powder as a sintering aid. The amount of β-silicon nitride powder added is 75-90 wt%, and the amount of low-melting-point glass powder added is 10-25 wt%. The low-melting-point glass powder contains at least: boron oxide, silicon oxide, aluminum oxide, yttrium oxide, and magnesium oxide.

[0037] In one embodiment, the content ratio of boron oxide, silicon oxide, aluminum oxide, yttrium oxide, and magnesium oxide is 15-20 wt% : 45-50 wt% : 10-20 wt% : 5-15 wt% : 5-15 wt%. Silicon oxide, aluminum oxide, magnesium oxide, and yttrium oxide can increase the wettability between glass powder and silicon nitride powder, thereby promoting silicon nitride particle rearrangement and liquid phase filling, achieving the goal of low-temperature sintering of silicon nitride.

[0038] Preferably, in this embodiment, the low-melting-point glass powder contains 17.5% boron oxide, 47.5% silicon oxide, 15% aluminum oxide, 10% yttrium oxide, and 10% magnesium oxide.

[0039] In the above embodiments, the β-silicon nitride powder is a submicron powder with a particle size range of 0.5-1 μm.

[0040] See Figure 1 Another aspect of the present invention provides a low-temperature sintered silicon nitride ceramic, prepared using the low-temperature sintered silicon nitride ceramic powder from any of the above embodiments. The present invention also provides a method for preparing low-temperature sintered silicon nitride ceramic, comprising at least the following steps:

[0041] S100: Boron oxide, silicon oxide, aluminum oxide, yttrium oxide and magnesium oxide are thoroughly mixed in proportion and then melted to obtain a glass melt.

[0042] S200: After quenching and solidifying the molten glass, dry and grind it to obtain low-melting-point glass powder with a melting point of 1000℃-1400℃.

[0043] S300: After thoroughly mixing low-melting-point glass powder and β-silicon nitride powder according to the specified ratio, grind them, then dry and compress them into tablets.

[0044] S400: After pressing the small pieces under 200MPa for a certain period of time, pressureless sintering is carried out in a nitrogen atmosphere below 1600℃, and the silicon nitride ceramic is obtained after holding at this temperature for 3-12 hours.

[0045] Furthermore, the method for obtaining glass melt by fully mixing boron oxide, silicon oxide, aluminum oxide, yttrium oxide and magnesium oxide in the specified proportions is as follows: 15-20 wt% boron oxide, 45-50 wt% silicon oxide, 10-20 wt% aluminum oxide, 5-15 wt% yttrium oxide and 5-15 wt% magnesium oxide are mixed and placed on a pot mill for 24 hours. The uniformly mixed raw materials are then placed in a melting furnace at 1600℃ and kept at that temperature for 2 hours. After melting, glass melt is obtained.

[0046] Furthermore, the S300 method for fully mixing low-melting-point glass powder and β-silicon nitride powder according to the specified ratio, grinding them, and then drying and pressing them into tablets is as follows: the mixed powder of β-silicon nitride powder and low-melting-point glass powder is placed in a ball mill jar, ball milled for 12 hours with alcohol as the grinding medium, and then dried and pressed into tablets.

[0047] The following are examples of the silicon nitride ceramic preparation method of the present invention:

[0048] Example 1

[0049] 80 g of 0.8 μm β-silicon nitride powder and 20 g of low-melting-point glass powder were placed in a ball mill jar and milled for 12 hours at 400 rpm using alcohol as the grinding medium. After drying, the powder was pressed into small sheets. The sheets were then subjected to cold isostatic pressing at 200 MPa for 3 minutes, followed by pressureless sintering at 1450℃ under a nitrogen atmosphere for 8 hours to obtain silicon nitride ceramic. The bulk density of the obtained product was found to be 2.9 g / cm³. 3 .

[0050] Example 2

[0051] 85g of 0.7μm β-silicon nitride powder and 15g of low-melting-point glass powder were placed in a ball mill jar and milled for 12 hours at 400 rpm using alcohol as the grinding medium. After drying, the powder was pressed into small sheets. The sheets were then subjected to cold isostatic pressing at 200 MPa for 3 minutes, followed by pressureless sintering at 1500℃ under a nitrogen atmosphere for 8 hours to obtain silicon nitride ceramic. The bulk density of the obtained product was found to be 2.93 g / cm³. 3 .

[0052] Example 3

[0053] 90 g of 0.7 μm β-silicon nitride powder and 10 g of low-melting-point glass powder were placed in a ball mill jar and milled for 12 hours at 400 rpm using alcohol as the grinding medium. After drying, the powder was pressed into small sheets. The sheets were then subjected to cold isostatic pressing at 200 MPa for 5 minutes, followed by pressureless sintering at 1450℃ under a nitrogen atmosphere for 12 hours to obtain silicon nitride ceramic. The bulk density of the obtained product was found to be 3.0 g / cm³. 3 .

[0054] Example 4

[0055] 75g of 0.7μm β-silicon nitride powder and 25g of low-melting-point glass powder were placed in a ball mill jar and ball-milled for 12 hours at 400 rpm using alcohol as the grinding medium. After drying, the powder was pressed into small sheets. The sheets were then subjected to cold isostatic pressing at 200 MPa for 5 minutes, followed by pressureless sintering at 1450℃ under a nitrogen atmosphere for 12 hours to obtain silicon nitride ceramic. The bulk density of the obtained product was found to be 2.7 g / cm³. 3 .

[0056] Example 5

[0057] 95g of 0.7μm β-silicon nitride powder and 5g of low-melting-point glass powder were placed in a ball mill jar and milled for 12 hours at 400 rpm using alcohol as the grinding medium. After drying, the powder was pressed into small sheets. The sheets were then subjected to cold isostatic pressing at 200 MPa for 5 minutes, followed by pressureless sintering at 1450℃ under a nitrogen atmosphere for 12 hours to obtain silicon nitride ceramic. The bulk density of the obtained product was found to be 2.4 g / cm³. 3 .

[0058] Example 6

[0059] 70g of 0.7μm β-silicon nitride powder and 30g of low-melting-point glass powder were placed in a ball mill jar and milled for 12 hours at 400 rpm using alcohol as the grinding medium. After drying, the powder was pressed into small sheets. The sheets were then subjected to cold isostatic pressing at 200 MPa for 5 minutes, followed by pressureless sintering at 1400℃ under a nitrogen atmosphere for 12 hours to obtain silicon nitride ceramic. The bulk density of the obtained product was found to be 2.5 g / cm³. 3 .

[0060] In the above embodiments, to achieve a higher bulk density in the sintered silicon nitride ceramic, the pressed wafers can be held at 200 MPa for 3-5 minutes, and then pressureless sintered at 1450°C under a nitrogen atmosphere for 12 hours to obtain a bulk density of 3.0 g / cm³. 3 Silicon nitride ceramics.

[0061] Based on the above experimental results, it can be concluded that:

[0062] Based on the test results in the examples, β-silicon nitride powder with a particle size range of 0.7-0.8μm can be used to manufacture silicon nitride ceramics, and the optimal addition amount of glass powder is 10%.

[0063] In this embodiment of the invention, by combining β-silicon nitride powder with low-melting-point glass powder, the bulk density of the silicon nitride ceramic sintered at a relatively low temperature of 1450°C can reach 3.0 g / cm³. 3 above.

[0064] The above embodiments can be combined with each other and have corresponding technical effects.

[0065] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. Various adjustments or changes may be made to the exemplary embodiments described in this specification without departing from the scope or spirit of the invention. The scope of the claims should be interpreted in the broadest possible sense to cover all modifications and equivalent structures and functions.

Claims

1. A low temperature sinterable silicon nitride ceramic powder, characterized by, at least comprising β-silicon nitride powder and low-melting point glass powder; the addition amount of the β-silicon nitride powder is 75-90wt%; the addition amount of the low-melting point glass powder is 10-25wt%; the low-melting point glass powder comprises boron oxide, silicon oxide, aluminum oxide, yttrium oxide and magnesium oxide, and the content ratio of the boron oxide, the silicon oxide, the aluminum oxide, the yttrium oxide and the magnesium oxide is 15-20wt%:45-50wt%:10-20wt%:5-15wt%:5-15wt%; the β-silicon nitride powder is submicron powder, and the particle size of the particles is in the range of 0.5-1μm.

2. The low temperature sintered silicon nitride ceramic powder according to claim 1, characterized in that, the particle size of the β-silicon nitride powder is in the range of 0.7-0.8μm.

3. A method for preparing a low-temperature sintered silicon nitride ceramic, which is prepared from the low-temperature sintered silicon nitride ceramic powder according to claim 1, characterized in that, at least comprising the following steps: melting the boron oxide, the silicon oxide, the aluminum oxide, the yttrium oxide and the magnesium oxide after being mixed in a proportion to obtain a glass liquid; after quenching and agglomerating the glass liquid, drying and grinding to obtain low-melting point glass powder with a melting point of 1000-1400℃; after mixing the low-melting point glass powder and the β-silicon nitride powder in a proportion and grinding, drying and tabletting are carried out; after the pressed small tablets are kept under the pressure of 100-200MPa for a certain time, pressureless sintering is carried out in a nitrogen atmosphere below 1600℃, and the silicon nitride ceramic is obtained after keeping warm for 3-12h.

4. The method of claim 3, wherein the sintering is performed at a temperature of 1,500°C or lower. the method for melting the boron oxide, the silicon oxide, the aluminum oxide, the yttrium oxide and the magnesium oxide after being mixed in a proportion to obtain a glass liquid is: the 15-20wt% boron oxide, the 45-50wt% silicon oxide, the 10-20wt% aluminum oxide, the 5-15wt% yttrium oxide and the 5-15wt% magnesium oxide are mixed and placed on a jar mill for at least 1h, and the mixed raw materials are put into a melting furnace at 1600℃ for at least 2h, and the glass liquid is obtained after melting.

5. The method for preparing low-temperature sintered silicon nitride ceramics according to claim 3, characterized in that, the method for mixing the low-melting point glass powder and the β-silicon nitride powder in a proportion, grinding, and then drying and tabletting is: the mixed powder of the β-silicon nitride powder and the low-melting point glass powder is put into a ball mill tank, alcohol is used as a grinding medium, and ball milling is carried out for 12h, and then drying and tabletting are carried out.

6. The method for preparing low-temperature sintered silicon nitride ceramics according to claim 3, characterized in that, the time for keeping the pressed small tablets under the pressure of 200MPa is 3-5min.

7. The method for preparing low-temperature sintered silicon nitride ceramics according to claim 3, characterized in that, after the pressed small tablets are kept under the pressure of 200MPa for 5min, pressureless sintering is carried out in a nitrogen atmosphere at 1450℃, and the silicon nitride ceramic is obtained after keeping warm for 12h.

8. A low temperature sintered silicon nitride ceramic, characterized by, obtained by using the preparation method of the low-temperature sintering silicon nitride ceramic according to any one of claims 3-7.

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