A ceramic powder material and its preparation method and application

Abstract

The present invention discloses a ceramic powder material and a preparation method and application thereof. The ceramic powder material is Si 3 N 4 Powder is used as the main raw material, and SiC powder is added as the auxiliary material. 2 C 2 O 4 Powder, MgSiN 2 Powder, BaCO 3 Powder and YF 3 The powder is used as a sintering aid, and the raw materials and liquid medium are added into a ball mill for mixing, and spray granulation is performed to obtain the ceramic powder material of the present invention; the ceramic powder material of the present invention is subjected to high-pressure densification molding and high-temperature sintering in a nitrogen atmosphere to obtain a silicon nitride ceramic material with high thermal conductivity and mechanical strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and in particular relates to a silicon nitride ceramic powder material with high thermal conductivity and high mechanical strength, and a preparation method and application thereof. Background Art

[0002] Silicon nitride ceramics is a covalent bond compound composed of silicon and nitrogen. It has the characteristics of high strength, high toughness, small thermal expansion coefficient, high temperature resistance, corrosion resistance, and stable chemical properties. Due to these characteristics, silicon nitride ceramic materials have been widely used in aerospace engines, mechanical industry, and electronic packaging fields.

[0003] The theoretical thermal conductivity of silicon nitride is as high as 300W / m / K, but the actual thermal conductivity of silicon nitride ceramics is much lower than the theoretical value. This is because silicon nitride ceramics undergo a crystal phase transition from α phase to β phase during sintering, and Si-N is a high-energy covalent bond. The breaking and generation of Si-N chemical bonds require high energy, resulting in a relatively low atomic diffusion coefficient during sintering, making it difficult to sinter. Therefore, the sintering process generally uses sintering aids to promote the crystal phase transition of silicon nitride grains from α phase to β phase, so as to achieve sintering densification of silicon nitride materials. The sintering aids of silicon nitride generally include metal oxides such as aluminum oxide, magnesium oxide, and yttrium oxide, which can reduce the formation temperature and viscosity of the eutectic liquid phase and promote grain growth. However, sintering aids inevitably introduce oxygen, which will produce silicon vacancies and cause lattice distortion, thereby affecting the thermal conductivity of silicon nitride ceramic materials. At the same time, the high content of sintering aids also has an adverse effect on the thermal conductivity and mechanical properties of silicon nitride ceramic sintered bodies. Summary of the invention

[0004] The invention discloses a ceramic powder material and a preparation method and application thereof. The ceramic powder material uses Si3N4 powder as a main raw material, adds SiC powder as an auxiliary material, and uses Li2C2O4 powder, MgSiN2 powder, BaCO3 powder and YF3 powder as sintering aids. The raw materials and a liquid medium are added into a ball mill for mixing, and spray granulation is performed to obtain the ceramic powder material of the invention. The ceramic powder material of the invention is subjected to high-pressure densification molding and high-temperature sintering in a nitrogen atmosphere to obtain a silicon nitride ceramic material with high thermal conductivity and mechanical strength.

[0005] Specifically, the present invention provides a ceramic powder material, characterized in that the ceramic powder material comprises: Si3N4 powder as a main raw material, SiC powder as an auxiliary material, and MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder as sintering aids; wherein the total mass of SiC powder: Li2C2O4 powder and BaCO3 powder is >3; and the total mass of YF3 powder: Li2C2O4 powder and BaCO3 powder is >1.

[0006] Furthermore, the mass ratios of Si3N4 powder, SiC powder, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder are as follows: Si3N4 powder 100%, SiC powder 5.5-8.0%, MgSiN2 powder 2.5-3.5%, Li2C2O4 powder 1.2-1.8%, BaCO3 powder 0.5-1.0%, and YF3 powder 2.0-3.0%.

[0007] Furthermore, the ceramic powder material uses Si3N4 powder as the main raw material, SiC powder as the auxiliary material, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder as sintering aids, and each raw material and liquid medium are added into a ball mill and mixed according to a predetermined mass ratio, and spray dried and granulated to obtain the ceramic powder material.

[0008] Furthermore,

[0009] 1) Weigh Si3N4 powder, SiC powder, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder according to the mass ratio, add them into a ball mill, add anhydrous ethanol as a liquid medium, add silicon nitride balls as a grinding medium, and mix them by ball milling to obtain a mixed slurry;

[0010] 2) Adding a binder into the mixed slurry, and then spray drying and granulating to obtain the ceramic powder material.

[0011] Further, 1) Si3N4 powder, SiC powder, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder are weighed in mass proportion, added into a ball mill, anhydrous ethanol is added as a liquid medium, and silicon nitride balls are added as grinding media, wherein the mass ratio of the total mass of solid, anhydrous ethanol and grinding media is 1:1-1.5:2-2.5; ball milling is performed at a mixing speed of 250-300 r / min and a mixing time of 4-24 h to obtain a mixed slurry;

[0012] 2) adding a binder to the mixed slurry, wherein the mass ratio of the binder to the mixed slurry is 0.5-3.0:100; then spray drying and granulation are performed to obtain the ceramic powder material, and the spray drying temperature is 100-150°C.

[0013] Furthermore,

[0014] 1) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body;

[0015] 2) placing the ceramic blank in a heating furnace for preheating at a temperature of 400-500° C.;

[0016] 3) placing the silicon nitride ceramic blank obtained in step 2) in a pressure heating furnace in a nitrogen atmosphere for sintering, first heating to 1100-1200° C. for the first stage of sintering; then heating to 1450-1550° C. for the second stage of sintering; then cooling to 950-1000° C. for tempering;

[0017] 4) processing and cutting the silicon nitride ceramic blank obtained in step 3);

[0018] 5) The silicon nitride ceramic product obtained in step 4) is placed in a pressure heating furnace in a nitrogen atmosphere for sintering, firstly heating to 1650-1750° C. for sintering, and then cooling to 1000-1100° C. for tempering.

[0019] Furthermore,

[0020] 1) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 20-30 MPa and a temperature of 150-200° C.;

[0021] 2) placing the ceramic blank in a heating furnace for preheating at a temperature of 400-500° C., keeping the temperature for 6-24 hours, and taking it out after cooling to room temperature;

[0022] 3) The silicon nitride ceramic blank obtained in step 2) is placed in a pressure heating furnace in a nitrogen atmosphere for sintering, firstly the temperature is raised to 1100-1200°C for the first stage of sintering, the first stage of sintering time is 4-6 hours, the nitrogen pressure is 1.5-2.0MPa; then the temperature is raised to 1450-1550°C for the second stage of sintering, the second stage of sintering time is 8-12 hours, the nitrogen pressure is 6.0-6.5MPa; then the temperature is lowered to 950-1000°C for tempering, the tempering time is 0.5-1h, the nitrogen pressure is 1.5-2.0MPa; and then taken out after cooling to room temperature;

[0023] 4) processing and cutting the silicon nitride ceramic blank obtained in step 3);

[0024] 5) The silicon nitride ceramic product obtained in step 4) is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1650-1750°C for sintering, the sintering time is 1-2 hours, and the nitrogen pressure is 50-80MPa; then the temperature is lowered to 1000-1100°C for tempering, the time is 0.5-1 hour, the nitrogen pressure is 50-80MPa, and then taken out after cooling to room temperature.

[0025] Furthermore, the present invention seeks protection for a ceramic product, which is prepared by the method described.

[0026] Beneficial technical effects:

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1) The present invention optimizes the sintering aids and adopts Li2C2O4 powder, MgSiN2 powder, BaCO3 powder and YF3 powder as sintering aids. Li2C2O4 powder, MgSiN2 powder, BaCO3 powder and YF3 powder work synergistically during the sintering process. Li2C2O4 powder, MgSiN2 powder and BaCO3 can promote the breaking and formation of Si-N chemical bonds and promote the transformation of Si3N4 from α phase to β phase. At the same time, the calcination temperature of the second stage is as high as 1450°C or more. The Li2C2O4 powder and BaCO3 powder are decomposed to generate CO2 for discharge during the sintering process. The MgSiN2 powder does not contain oxygen, which can reduce the use of oxygen.

[0029] 2) The inventors found that adding YF3 powder to the sintering aid increases the atomic diffusion coefficient in Si3N4 powder and promotes the growth of β-phase Si3N4 grains. When the total mass of YF3 powder: Li2C2O4 powder and BaCO3 powder is greater than 1, the effect of improving the thermal conductivity of the material will be better.

[0030] 3) SiC powder is also added to the auxiliary materials. During the high-temperature sintering process in a nitrogen atmosphere, the Si-C bond breaks, Si reacts with free nitrogen elements to form Si-N bonds, and the C element and the residual oxygen element in the material generate carbon dioxide and are discharged, further reducing the oxygen content in the product, thereby improving the thermal conductivity and mechanical properties of silicon nitride materials.

[0031] 4) The inventors found that when the total mass of SiC powder: Li2C2O4 powder and BaCO3 powder is greater than 3, the effect of improving the mechanical properties of the material will be better. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific embodiments. However, the protection scope of the present invention is not limited to the following embodiments, and any non-essential adjustments and modifications made to the present invention based on the above invention content still fall within the protection scope of the present invention.

[0033] Example 1

[0034] 1) Weigh 100g Si3N4 powder, 5.5g SiC powder, 2.5g MgSiN2 powder, 1.2g Li2C2O4 powder, 0.5g BaCO3 powder, and 2.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0035] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0036] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0037] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 500° C., keeping the temperature for 6 hours, and taking it out after cooling to room temperature;

[0038] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1200°C for the first stage of sintering. The first stage of sintering time is 4 hours and the nitrogen pressure is 2.0 MPa; then the temperature is raised to 1500°C for the second stage of sintering. The second stage of sintering time is 8 hours and the nitrogen pressure is 6.5 MPa; then the temperature is lowered to 1000°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.5 MPa; and then taken out after cooling to room temperature;

[0039] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0040] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1750°C for sintering, the sintering time is 1 hour, and the nitrogen pressure is 80 MPa; then the temperature is lowered to 1100°C for tempering, the time is 0.5 hour, the nitrogen pressure is 80 MPa, and then taken out after cooling to room temperature.

[0041] Example 2

[0042] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.8g Li2C2O4 powder, 0.5g BaCO3 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0043] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0044] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0045] 4) placing the ceramic blank in a heating furnace for preheating at 400° C. for 24 hours, and taking it out after cooling to room temperature;

[0046] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1100°C for the first stage of sintering. The first stage of sintering time is 6 hours and the nitrogen pressure is 1.5 MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 12 hours and the nitrogen pressure is 6.0 MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 1 hour and the nitrogen pressure is 2.0 MPa; and then taken out after cooling to room temperature;

[0047] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0048] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1650°C for sintering, the sintering time is 2 hours, and the nitrogen pressure is 50 MPa; then the temperature is lowered to 1000°C for tempering, the time is 1 hour, the nitrogen pressure is 50 MPa, and then taken out after cooling to room temperature.

[0049] Example 3

[0050] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.5g Li2C2O4 powder, 1.0g BaCO3 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0051] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0052] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0053] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0054] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0055] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0056] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0057] Example 4

[0058] 1) Weigh 100g Si3N4 powder, 7.0g SiC powder, 3.0g MgSiN2 powder, 1.5g Li2C2O4 powder, 0.8g BaCO3 powder, and 2.5g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0059] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0060] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0061] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 6 hours, and taking it out after cooling to room temperature;

[0062] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1100°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.5 MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 8 hours and the nitrogen pressure is 6.0 MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.6 MPa; and then taken out after cooling to room temperature;

[0063] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0064] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1650°C for sintering, the sintering time is 1 hour, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1100°C for tempering, the time is 0.8 hours, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0065] Comparative Example 1

[0066] 1) Weigh 100g Si3N4 powder, 3.5g MgSiN2 powder, 1.5g Li2C2O4 powder, 1.0g BaCO3 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0067] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0068] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0069] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0070] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0071] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0072] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0073] Comparative Example 2

[0074] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.5g Li2C2O4 powder, and 1.0g BaCO3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0075] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0076] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0077] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0078] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0079] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0080] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0081] Comparative Example 3

[0082] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 1.5g Li2C2O4 powder, 1.0g BaCO3 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0083] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0084] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0085] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0086] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0087] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0088] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0089] Comparative Example 4

[0090] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.5g Li2C2O4 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0091] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0092] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0093] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0094] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0095] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0096] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0097] Comparative Example 5

[0098] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.0g BaCO3 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0099] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0100] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0101] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0102] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0103] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0104] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0105] Comparative Example 6

[0106] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.5g Li2C2O4 powder, 1.8g BaCO3 powder, and 3.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0107] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0108] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0109] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0110] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0111] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0112] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0113] Comparative Example 7

[0114] 1) Weigh 100g Si3N4 powder, 8.0g SiC powder, 3.5g MgSiN2 powder, 1.5g Li2C2O4 powder, 1.0g BaCO3 powder, and 2.0g YF3 powder; add them into a ball mill, add 150g anhydrous ethanol as a liquid medium, and add 250g silicon nitride balls as a grinding medium; ball mill and mix at a mixing speed of 300r / min for 12h to obtain a mixed slurry;

[0115] 2) adding a binder PVDF to the mixed slurry, wherein the mass ratio of PVDF to the mixed slurry is 1.5:100; and then spray drying and granulation to obtain the ceramic powder material, wherein the spray drying temperature is 120°C.

[0116] 3) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 25 MPa and a temperature of 180° C.;

[0117] 4) placing the ceramic blank in a heating furnace for preheating at a temperature of 450° C., keeping the temperature for 12 hours, and taking it out after cooling to room temperature;

[0118] 5) The obtained silicon nitride ceramic blank is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1150°C for the first stage of sintering. The first stage of sintering time is 5 hours and the nitrogen pressure is 1.7MPa; then the temperature is raised to 1450°C for the second stage of sintering. The second stage of sintering time is 10 hours and the nitrogen pressure is 6.0MPa; then the temperature is lowered to 950°C for tempering. The tempering time is 0.5 hours and the nitrogen pressure is 1.8MPa; and then taken out after cooling to room temperature;

[0119] 6) Processing and cutting the obtained silicon nitride ceramic blank;

[0120] 7) The obtained silicon nitride ceramic product is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1700°C for sintering, the sintering time is 1.5 hours, and the nitrogen pressure is 60MPa; then the temperature is lowered to 1050°C for tempering, the time is 1 hour, the nitrogen pressure is 60MPa, and then taken out after cooling to room temperature.

[0121] Performance Testing

[0122] The properties of the silicon nitride ceramic materials of the embodiments of the present invention and the comparative examples were tested, and the test results are shown in the following table.

[0123] Vickers hardness (HV) determination refers to GB7997-1987 "Vickers hardness test method for cemented carbide"

[0124] The flexural strength is measured according to ISO 14704:2016, using the four-point bending test method.

[0125] Thermal conductivity is measured in accordance with ISO 22007-2 2015 using a BXT-DR-5 rapid thermal conductivity meter.

[0126] Table 1

[0127]

[0128] Results Data

[0129] It can be seen from the data of the embodiments and comparative examples that Li2C2O4 powder, MgSiN2 powder, BaCO3 powder and YF3 powder work together during the sintering process to jointly improve the hardness, thermal conductivity and flexural strength of the material; YF3 has a significant effect on the thermal conductivity of the material. When the total mass of YF3 powder: Li2C2O4 powder and BaCO3 powder is less than 1, the thermal conductivity of the material will be significantly reduced. The addition of SiC powder can significantly improve the thermal conductivity of silicon nitride materials, and can also improve the flexural strength. When the total mass of SiC powder: Li2C2O4 powder and BaCO3 powder is less than 3, the mechanical properties of the material are significantly reduced. It can be seen that among the auxiliary materials and sintering aids, when the total mass of SiC powder: Li2C2O4 powder and BaCO3 powder is greater than 3; the total mass of YF3 powder: Li2C2O4 powder and BaCO3 powder is greater than 1, the thermal conductivity and flexural strength of silicon nitride materials can be significantly improved.

[0130] Although the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention.

Claims

1. A ceramic powder material, comprising: The main raw material is Si3N4 powder, the auxiliary material is SiC powder, and the sintering aids are MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder; it is characterized in that the mass ratio of Si3N4 powder, SiC powder, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder is: Si3N4 powder 100%, SiC powder 5.5-8.0%, MgSiN2 powder 2.5-3.5%, Li2C2O4 powder 1.2-1.8%, BaCO3 powder 0.5-1.0%, YF3 powder 2.0-3.0%; and the total mass of SiC powder: Li2C2O4 powder and BaCO3 powder is >3; YF3 powder: the total mass of Li2C2O4 powder and BaCO3 powder is >1.

2. A method for preparing the ceramic powder material as claimed in claim 1, characterized in that: The ceramic powder material uses Si3N4 powder as the main raw material, SiC powder as the auxiliary material, and MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder as sintering aids. The raw materials and liquid medium are added into a ball mill according to a predetermined mass ratio and mixed, and spray-dried and granulated to obtain the ceramic powder material.

3. A preparation method according to claim 2, characterized in that: Weigh Si3N4 powder, SiC powder, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder according to the mass ratio, add them into a ball mill, add anhydrous ethanol as a liquid medium, add silicon nitride balls as a grinding medium, and mix by ball milling to obtain a mixed slurry; The binder is added into the mixed slurry, and then the mixed slurry is spray-dried and granulated to obtain the ceramic powder material.

4. A preparation method according to claim 3, characterized in that: 1) Weigh Si3N4 powder, SiC powder, MgSiN2 powder, Li2C2O4 powder, BaCO3 powder and YF3 powder according to the mass ratio, add them into a ball mill, add anhydrous ethanol as a liquid medium, add silicon nitride balls as grinding media, wherein the mass ratio of the total mass of solid, anhydrous ethanol and grinding media is 1:1-1.5:2-2.5; ball mill mixing, the mixing speed is 250-300r / min, the mixing time is 4-24h, and a mixed slurry is obtained; 2) adding a binder to the mixed slurry, wherein the mass ratio of the binder to the mixed slurry is 0.5-3.0:100; then spray drying and granulation are performed to obtain the ceramic powder material, and the spray drying temperature is 100-150°C.

5. A method for applying the ceramic powder material according to claim 1, characterized in that: 1) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body; 2) placing the ceramic blank in a heating furnace for preheating at a temperature of 400-500° C.; 3) placing the silicon nitride ceramic blank obtained in step 2) in a pressure heating furnace in a nitrogen atmosphere for sintering, first heating to 1100-1200° C. for the first stage of sintering; then heating to 1450-1550° C. for the second stage of sintering; then cooling to 950-1000° C. for tempering; 4) processing and cutting the silicon nitride ceramic blank obtained in step 3); 5) The silicon nitride ceramic product obtained in step 4) is placed in a pressure heating furnace in a nitrogen atmosphere for sintering, firstly heating to 1650-1750° C. for sintering, and then cooling to 1000-1100° C. for tempering.

6. The application method according to claim 5, characterized in that: 1) hot pressing the ceramic powder material to obtain a silicon nitride ceramic green body at a pressure of 20-30 MPa and a temperature of 150-200° C.; 2) placing the ceramic blank in a heating furnace for preheating at a temperature of 400-500° C., keeping the temperature for 6-24 hours, and taking it out after cooling to room temperature; 3) The silicon nitride ceramic blank obtained in step 2) is placed in a pressure heating furnace in a nitrogen atmosphere for sintering, firstly the temperature is raised to 1100-1200°C for the first stage of sintering, the first stage of sintering time is 4-6 hours, the nitrogen pressure is 1.5-2.0MPa; then the temperature is raised to 1450-1550°C for the second stage of sintering, the second stage of sintering time is 8-12 hours, the nitrogen pressure is 6.0-6.5MPa; then the temperature is lowered to 950-1000°C for tempering, the tempering time is 0.5-1h, the nitrogen pressure is 1.5-2.0MPa; and then taken out after cooling to room temperature; 4) processing and cutting the silicon nitride ceramic blank obtained in step 3); 5) The silicon nitride ceramic product obtained in step 4) is placed in a pressure heating furnace in a nitrogen atmosphere for sintering. First, the temperature is raised to 1650-1750°C for sintering, the sintering time is 1-2 hours, and the nitrogen pressure is 50-80MPa; then the temperature is lowered to 1000-1100°C for tempering, the time is 0.5-1 hour, the nitrogen pressure is 50-80MPa, and then taken out after cooling to room temperature.

7. A ceramic product, characterized in that: The ceramic product is prepared by the application method described in any one of claims 5-6.

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