Preparation method of high-wear-resistance ceramic material for air valve plate

Abstract

The application relates to the field of wear-resistant ceramic materials, in particular to a preparation method of a high-wear-resistant ceramic material for a gas valve plate, wherein ceramic powder is ball milled to obtain slurry, a binder composed of carboxymethyl cellulose and fatty acid modified nanocellulose and a sulfuric acid ester surfactant are added into the slurry, the ball milling is continuously carried out, spray granulation is carried out to obtain composite powder, the composite powder is pressed into a blank, and finally, the blank is sintered in an inert gas atmosphere, the ceramic material prepared by the method has excellent mechanical properties, and has good compression resistance, heat resistance, corrosion resistance and wear resistance; through comparison, it is found that the addition of zirconium oxide, samarium oxide, ytterbium oxide, carboxymethyl cellulose, fatty acid modified nanocellulose and sodium dodecyl sulfate has a positive effect on improving the various properties of the ceramic material.

Description

TECHNICAL FIELD

[0001] The application relates to the field of wear-resistant ceramic materials, in particular to a preparation method of high-wear-resistant air valve plate ceramic material. BACKGROUND

[0002] As an important part of the engine valve train, the valve is not only a component of the combustion chamber, but also a passage for fresh air and high-temperature exhaust gas to enter and exit the combustion chamber. The intake valve controls the introduction of fresh air into the cylinder, and the exhaust valve discharges the burned exhaust gas. Good valve quality is the guarantee for the engine to provide good power performance, environmental protection performance and economic performance.

[0003] During the working process, the valve needs to withstand high temperature, high pressure and several hundred or even thousands of mechanical and thermal loads per minute, and is subjected to the actions of constantly changing tension, pressure, impact, friction and thermal stress. In order to meet the harsh working conditions of the exhaust valve, the material for manufacturing the valve plate must have good wear resistance, corrosion resistance and high-temperature resistance. At present, alloy materials are mostly used as raw materials for manufacturing valve plates. Although the alloy materials have the advantages of good thermal conductivity and relatively low price, they are prone to softening and deformation at high temperatures and have poor corrosion resistance. SUMMARY

[0004] The application aims at the above technical problems and provides a preparation method of high-wear-resistant air valve plate ceramic material.

[0005] The technical scheme adopted is as follows:

[0006] A preparation method of high-wear-resistant air valve plate ceramic material comprises the following steps:

[0007] The ceramic powder is ball milled to obtain a slurry, a binder composed of carboxymethyl cellulose and fatty acid modified nanocellulose and a sulfuric ester surfactant are added to the slurry, and then the slurry is continuously ball milled and spray granulated to obtain a composite powder. The composite powder is pressed into a blank, and finally the blank is sintered in an inert gas atmosphere.

[0008] Further, the ceramic powder comprises alumina, zirconia and rare earth oxides.

[0009] Further, the weight ratio of the alumina, zirconia and rare earth oxides is 80-100:10-20:1-3.

[0010] Further, the rare earth oxides are composed of samarium oxide and ytterbium oxide in a weight ratio of 1-5:1-5.

[0011] Further, the amount of the binder is 5-10% of the weight of the ceramic powder.

[0012] Further, the weight ratio of the carboxymethyl cellulose and the fatty acid modified nanocellulose is 1-5:1-5.

[0013] Further, the preparation method of the fatty acid modified nanocellulose is as follows:

[0014] The nanocellulose is dissolved with a LiCl / DMAc solution, then fatty acid, 4-toluenesulfonyl chloride and pyridine are added, the obtained mixture is reacted at 70-90 DEG C for 18-36h, the reaction solution is poured into a water / methanol solution, the precipitated solid is filtered out, and then the solid is extracted with a methanol solution for 18-36h and dried.

[0015] Further, the fatty acid is any one or a combination of lauric acid, myristic acid and palmitic acid.

[0016] Further, the sintering is performed by first heating to 800-850 DEG C for 1-3h, then heating to 1100-1200 DEG C for 1-3h, then heating to 1450-1550 DEG C for 1-3h, cooling to 800-1000 DEG C, and finally cooling to room temperature.

[0017] Further, the heating speed of the first stage is 10-20 DEG C / min, the heating speed of the second stage is 1-5 DEG C / min, the heating speed of the third stage is 1-5 DEG C / min, and the cooling speed is 1-5 DEG C / min.

[0018] The beneficial effects of the present application are as follows:

[0019] The present application provides a preparation method of a high wear-resistant ceramic material for a gas valve plate, the carboxymethyl cellulose forms a firm network structure in the slurry by means of hydrogen bond and Van der Waals force, thereby showing a bonding performance, the nanocellulose modified by fatty acid can play a dispersing role together with the sulfated surfactant during ball milling, and forms a stable emulsion with the carboxymethyl cellulose and the sulfated surfactant, thereby forming a composite powder with uniform texture after spray granulation, laying a foundation for compression molding, and also serving as a carbon source to generate different types of carbides in the ceramic material matrix through a carbothermal reduction reaction, thereby improving various performances of the ceramic material, the zirconium oxide and rare earth oxides can optimize the microstructure of the ceramic material, refine the ceramic grains, and improve the mechanical and wear-resistant performances, and also serve as raw materials for the carbothermal reduction reaction, the ceramic material prepared by the present application has excellent mechanical performance, and has good pressure resistance, heat resistance, corrosion resistance and wear resistance, and through comparison, it can be seen that the addition of the zirconium oxide, samarium oxide, ytterbium oxide, carboxymethyl cellulose, fatty acid modified nanocellulose and sodium dodecyl sulfate plays a positive role in improving various performances of the ceramic material. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1A schematic diagram of a test device for testing wear resistance in performance testing of the present application. DETAILED DESCRIPTION

[0021] Unless otherwise specified, the specific conditions in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are conventional products that can be obtained by commercial purchase. The techniques not mentioned in the present application refer to the prior art. Unless otherwise specified, the following examples and comparative examples are parallel tests using the same processing steps and parameters.

[0022] Example 1:

[0023] A method for preparing a high-wear-resistant ceramic material for a gas valve plate:

[0024] 180 g of alumina, 35 g of zirconia, 2 g of samarium oxide, and 1 g of ytterbia were mixed uniformly, and the mixed powder was placed in a grinding tank at a ratio of 1:2 of material:ball for dry grinding at 180 r / min for 30 min. Then, deionized water with the same weight as the powder was added for wet grinding for 12 h to obtain a slurry. 7.5 g of carboxymethyl cellulose, 7.5 g of fatty acid modified nanocellulose, and 10 g of sodium dodecyl sulfate were added to the slurry, and the ball milling was continued for 30 min before spray granulation. The inlet temperature was set to 180℃, the outlet temperature was set to 100℃, the peristaltic pump speed was set to 60 r / min, and the atomizer speed was set to 6000 r / min. The composite powder obtained after spray granulation was collected, and after standing for 24 h, the green body was pressed under a cold isostatic pressing pressure of 100 MPa. The green body was placed in a muffle furnace under argon protection, and first heated to 850℃ at a rate of 15℃ / min, and then sintered for 1.5 h. Then, the temperature was increased to 1150℃ at a rate of 5℃ / min, and then sintered for 1 h. Then, the temperature was increased to 1550℃ at a rate of 2℃ / min, and then sintered for 2 h. Then, the temperature was decreased to 850℃ at a rate of 1℃ / min, and finally cooled to room temperature in the furnace.

[0025] The preparation method of the fatty acid modified nanocellulose is as follows:

[0026] 20 g of nanocellulose (polymerization degree 1000) was dissolved with 500 ml of 9wt% LiCl / DMAc solution, and then 0.15 g of lauric acid, 0.14 g of 4-toluenesulfonyl chloride, and 0.12 g of pyridine were added. The obtained mixture was reacted at 80℃ for 24 h. The reaction solution was poured into a 5L water / methanol solution (water and methanol in a volume ratio of 1:1), and the precipitated solid was filtered out. The solid was extracted with methanol solution for 24 h, and then dried.

[0027] Example 2:

[0028] A method for preparing a high-wear-resistant ceramic material for a gas valve plate:

[0029] Mix 200 g of alumina, 40 g of zirconia, 1 g of samaria oxide and 1 g of ytterbia uniformly, put the mixed powder into a grinding tank at 180 r / min for dry grinding for 30 min at a ratio of powder:ball = 1:2, then add deionized water with the same weight as the powder to continue wet grinding for 12 h to obtain a slurry, add 7.5 g of carboxymethyl cellulose, 7.5 g of fatty acid modified nanocellulose and 10 g of sodium dodecyl sulfate to the slurry, continue ball milling for 30 min, then spray granulation, set the inlet temperature to 180℃, the outlet temperature to 100℃, the peristaltic pump speed to 60 r / min, the atomizer speed to 6000 r / min, collect the composite powder obtained after spray granulation, and then press the powder into a green body under a cold isostatic pressure of 100 MPa after aging for 24 h. Put the green body into a muffle furnace under argon protection, first heat to 850℃ at a rate of 20℃ / min, keep sintering for 1 h, then heat to 1200℃ at a rate of 5℃ / min, keep sintering for 1 h, then heat to 1550℃ at a rate of 2℃ / min, keep sintering for 2 h, then cool to 1000℃ at a rate of 2℃ / min, and finally cool to room temperature in the furnace.

[0030] The preparation method of the fatty acid modified nanocellulose is the same as that in Example 1.

[0031] Example 3:

[0032] A preparation method of a high-wear-resistant ceramic material for a gas valve plate:

[0033] Mix 160 g of alumina, 20 g of zirconia, 3 g of samaria oxide and 3 g of ytterbia uniformly, put the mixed powder into a grinding tank at 180 r / min for dry grinding for 30 min at a ratio of powder:ball = 1:2, then add deionized water with the same weight as the powder to continue wet grinding for 12 h to obtain a slurry, add 7.5 g of carboxymethyl cellulose, 7.5 g of fatty acid modified nanocellulose and 10 g of sodium dodecyl sulfate to the slurry, continue ball milling for 30 min, then spray granulation, set the inlet temperature to 180℃, the outlet temperature to 100℃, the peristaltic pump speed to 60 r / min, the atomizer speed to 6000 r / min, collect the composite powder obtained after spray granulation, and then press the powder into a green body under a cold isostatic pressure of 100 MPa after aging for 24 h. Put the green body into a muffle furnace under argon protection, first heat to 800℃ at a rate of 10℃ / min, keep sintering for 2 h, then heat to 1100℃ at a rate of 5℃ / min, keep sintering for 1 h, then heat to 1450℃ at a rate of 1℃ / min, keep sintering for 2 h, then cool to 800℃ at a rate of 1℃ / min, and finally cool to room temperature in the furnace.

[0034] The preparation method of the fatty acid modified nanocellulose is the same as that in Example 1.

[0035] Comparative Example 1:

[0036] The same as example 1, except that no zirconium oxide is added.

[0037] Comparative example 2:

[0038] The same as example 1, except that no samarium oxide is added.

[0039] Comparative example 3:

[0040] The same as example 1, except that no ytterbium oxide is added.

[0041] Comparative example 4:

[0042] The same as example 1, except that no carboxymethyl cellulose is added.

[0043] Comparative example 5:

[0044] The same as example 1, except that no fatty acid modified nanocellulose is added.

[0045] Comparative example 6:

[0046] The same as example 1, except that no fatty acid modified nanocellulose is added.

[0047] Comparative example 7:

[0048] The same as example 1, except that no sodium dodecyl sulfate is added.

[0049] Performance testing:

[0050] The ceramic materials prepared in examples 1-3 and comparative examples 1-7 of the present application were tested for performance as samples;

[0051] ① The flexural strength of the samples was tested by the three-point bending method, and the test method referred to GB / T 6569-2006 "Fine Ceramic Flexural Strength Test Method". The loading speed was 1 mm / min.

[0052] ② The fracture toughness of the samples was tested by the single edge pre-cracked beam method, and the test method referred to GB / T 23806-2009 "Fine Ceramic Fracture Toughness Test Method Single Edge Pre-cracked Beam (SEPB) Method".

[0053] ③ Referring to Figure 1The test device is as follows: the test sample is fixed on a sample table by tabletting, a 5mm-diameter Si3N4 ceramic ball is selected as the grinding material, the lifting support and the balance weight are adjusted to make the beam horizontally balanced, and the experimental parameters are set as follows: friction type: room temperature dry friction, load size: 3N, rotation speed: 150r / min, friction circle radius: 2mm, test time: 1800s; the white light interference three-dimensional profilometer is used to scan the grinding track surface to obtain the grinding track cross-sectional morphology, the position-depth curves of four positions are selected to obtain the grinding track cross-sectional area by integral calculation through the origin drawing software and the average value is obtained, and the grinding track volume is calculated by the ring volume formula, that is, the wear volume.

[0054] The ring volume formula is: V=2πRS

[0055] (R is the distance from the cross-sectional centroid to the center of the ring, and S is the cross-sectional area)

[0056] The performance test results are shown in Table 1 as follows:

[0057] Table 1:

[0058]

[0059] From the above Table 1, it can be seen that the ceramic material prepared by the application has excellent mechanical properties and good wear resistance.

[0060] It can be known through comparison that the addition of zirconium oxide, samarium oxide, ytterbium oxide, carboxymethyl cellulose, fatty acid modified nanocellulose and sodium dodecyl sulfate has a positive effect on improving the performance of the ceramic material.

[0061] The above examples are only used to illustrate the technical solutions of the application, but not to limit it; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A method of making a high wear resistant valve plate ceramic material, characterized by, The ceramic powder is ball milled to obtain a slurry, a binder composed of carboxymethyl cellulose and fatty acid modified nanocellulose and a sulfate surfactant are added to the slurry, the slurry is continuously ball milled and then spray granulated to obtain a composite powder, the composite powder is pressed into a green body, and finally the green body is sintered in an inert gas atmosphere to obtain the ceramic product. The ceramic powder comprises alumina, zirconia and rare earth oxide. The weight ratio of the alumina, zirconia and rare earth oxide is 80-100:10-20:1-3. The fatty acid modified nanocellulose is prepared by the following method: The nanocellulose is dissolved in a LiCl / DMAc solution, fatty acid, 4-toluenesulfonyl chloride and pyridine are added, the obtained mixture is reacted at 70-90℃ for 18-36h, the reaction solution is poured into a water / methanol solution, the precipitated solid is filtered out, and the filtered solid is extracted with a methanol solution for 18-36h and then dried to obtain the fatty acid modified nanocellulose.

2. The method of making a high wear resistant valve plate ceramic material of claim 1, wherein, The rare earth oxide is composed of samarium oxide and ytterbium oxide at a weight ratio of 1-5:1-5.

3. The method of making a high wear resistant valve plate ceramic material of claim 1, wherein, The amount of the binder is 5-10% of the weight of the ceramic powder.

4. The method of making a high wear resistant valve plate ceramic material of claim 1, wherein, The weight ratio of the carboxymethyl cellulose and the fatty acid modified nanocellulose is 1-5:1-5.

5. The method of making a high wear resistant valve plate ceramic material of claim 1, wherein, The fatty acid is any one or a combination of lauric acid, myristic acid and palmitic acid.

6. The method of making a high wear resistant valve plate ceramic material of claim 1, wherein, The sintering is performed by first heating to 800-850℃ for 1-3h, then heating to 1100-1200℃ for 1-3h, and then heating to 1450-1550℃ for 1-3h, and then cooling to 800-1000℃, and finally cooling to room temperature.

7. The method of making a high wear resistant valve plate ceramic material of claim 6, wherein, The heating rate of the first stage is 10-20℃ / min, the heating rate of the second stage is 1-5℃ / min, the heating rate of the third stage is 1-5℃ / min, and the cooling rate is 1-5℃ / min.

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