A method for preparing a titanium felt toughened boron carbide ceramic

Abstract

The application relates to a preparation method of titanium felt toughened boron carbide ceramics and belongs to the technical field of composite materials. Firstly, boron carbide ceramic powder is pre-ground and pre-mixed, different particle size sintered two phases are crushed and uniformly mixed, Al powder is added in a small number of times and a large amount for pre-mixing, and mixed powder with good sphericity and solid rate is obtained through spray granulation; secondly, a titanium fiber felt pretreatment process is carried out, titanium fiber felt cutting is carried out by using a modified tooling, a cold pressing device or an upper-middle-lower three-layer ceramic green body is used, and a more dense and closely fitted titanium fiber felt-boron carbide (Al)-titanium fiber felt-boron carbide (Al)-titanium fiber felt sintering structure is obtained through cold isostatic pressing; thereby, a high-strength cold blank is obtained, a sintering process is set through different reaction stages, and finally, high-toughness high-strength boron carbide-based ceramics are obtained. After final sintering, the average hardness of the titanium felt toughened boron carbide ceramics is above 49 Gpa, the fracture toughness can reach 8.5 MPa.m 1 / 2 The above, the bending strength can reach above 580 MPa.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a preparation method of titanium felt toughened boron carbide ceramic. BACKGROUND

[0002] With higher pursuit of combat capability and equipment lightening in China, high-performance boron carbide ceramic is widely applied to individual protection field due to excellent high strength, high toughness, low density and corrosion resistance brought by unique rhombohedral structure. In the research process of boron carbide in China, the toughness of boron carbide has been an index that all scholars care about and strive to improve. By adding low-melting-point metals, metal oxides and other sintering two-phase means, the toughness of boron carbide ceramic has been gradually improved. In addition, the toughening phase generated by in-situ synthesis makes the preparation of boron carbide ceramic reach a new level.

[0003] Metal fiber felt is also a new research hotspot in recent years, especially in the fields of aerospace, petrochemical industry, national defense and military, and medicine. This porous felt pressed from metal fibers with a certain length ratio extends the excellent performance of the metal itself and expands its application range through fiberization. Titanium metal plays an important role in ceramic toughening due to its excellent performance such as light weight and high strength, and fiberized titanium metal can achieve a wider range of applications than single functional materials.

[0004] With the further application of boron carbide ceramic, people have become increasingly aware of the drawbacks of simply adding sintering two-phase. The cleanliness of sintering two-phase and the mixing degree with the matrix material seriously affect the performance of boron carbide ceramic. SUMMARY

[0005] The application uses the porous characteristics of titanium fiber felt to in-situ synthesize Al3Ti / Al intermetallic compound toughening phase at a certain temperature, and the EDS detection shows that the compound is mainly Al3Ti. The in-situ synthesized Al3Ti toughening phase has the characteristics of low density 3.3 g / cm 3 , high elastic modulus about 220 GPa. By adjusting the sintering system and giving enough space for in-situ reaction, the thermal dynamics is further given to make the liquid phase continuously react and the product uniform. The bulletproof ceramic forms uniform toughening phase on the bullet-impact surface, back convex surface and even the inside, thereby enhancing the toughness of the whole ceramic from the sintered product level.

[0006] A preparation method of titanium felt toughened boron carbide ceramic, comprising the following steps:

[0007] (1) Ceramic powder premixing: ball milling boron carbide ceramic and ceramic two-phase Al powder to a particle size of 0.5-1.0 μm, and then mixing at a ratio of 8:1-9:1 to obtain a ceramic powder mixture;

[0008] (2) The tower slurry preparation: a small amount of admixture is added to the ceramic powder mixture for several times, and mechanical stirring is used at a speed of 30-60 r / min, and the stirring time is 3-10 h, and the solid content of the ceramic slurry is controlled to be greater than 60%;

[0009] (3) Spray granulation and standing aging: the ceramic slurry is sprayed in a spray granulation tower, and then sealed and stood for more than 12 h, and then cold-pressed to obtain ceramic granulation, and the water content of the ceramic granulation is controlled to be 3%-5%;

[0010] (4) Titanium fiber felt pretreatment: a blanking tool is used for shape correction to obtain a titanium fiber felt with a purity of 99.9%, The titanium fiber felt is pretreated to obtain a pretreated titanium fiber felt.

[0011] (5) Cold pressing and cold isostatic pressing: cold powder laying is performed through a profiling tool, and the laying sequence from bottom to top is: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt; a formed piece is obtained.

[0012] The formed piece is uniformly coated with a cold-pressing release agent, and then cold isostatic pressing is performed to obtain a pressed green charge.

[0013] (6) Hot pressing and sintering system setting: the pressed green charge is placed in a graphite mold for sintering, and the placement mode is to lay 4-8 layers of 0.2-0.5 mm thick graphite paper as a separation layer around the top and bottom, and then the titanium felt toughened boron carbide ceramic is obtained after cooling in the furnace.

[0014] Further, the ball mill in step (1) uses polyurethane or nylon as the ball barrel material, and 6 mm, 8 mm and 10 mm zirconium dioxide balls are put in at a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1-3.5:1, the powder loading amount is 1 / 3-1 / 2 of the ball barrel volume, and the roller speed is 10-15 r / min.

[0015] Further, the admixture in step (2) is: ① water reducing agent: polycarboxylic acid water reducing agent, ammonium citrate and polyethylene glycol (PEG), one or more, the addition amount is controlled to be 0.5%-1.5%; ② water retaining agent: light yellow hydroxypropyl methyl cellulose ether, the addition amount is 0.3%-0.5%; ③ binder: polyacrylic acid water solution resin and wax polyvinyl alcohol (PVA) are used as the binder, the former is added in an amount of 0.05%-0.08%, and the latter needs to be mixed with water PVA, the ratio is about 0.5:1-1.4 (after hydrolysis and wax dissolution), and the addition amount is controlled to be 0.03%-0.07%.

[0016] Further, the spray granulation tower of step (3) is provided with an inlet temperature of 240-300 DEG C, a peristaltic pump feeding rate of 30-90 g / min, an outlet temperature of 80-120 DEG C, an atomizer speed of 3000-5000 r / min, and a negative pressure maintained in the tower.

[0017] Further, the titanium fiber felt of step (4) is composed of pure Ti, TC4 and TB series partial alloys, and has an average thickness of 0.1-0.3 mm per layer.

[0018] Further, the pretreatment of step (4) is to place the titanium fiber felt in a pure water ultrasonic instrument, with a wavelength of 60-80%, and treat for 1-2 h, then take out, soak in 3-5% HF for 5-10 s, and then place in acetone, soak for 1-2 h, and then clean with pure water ultrasonic, and dry for standby.

[0019] Further, the cold powder laying of step (5) is provided with a pressure of 100-150 t, a pressing speed of 0.3-0.5 mm / min, and a pressure maintaining time of 15-30 min.

[0020] Further, the cold pressure releasing agent of step (5) is selected from boron nitride spray lubricant or high-purity graphite powder; and the cold isostatic pressing is to seal the formed piece in a nylon vacuum bag, and place in an oil pressure isostatic pressing device, with a pressure increasing mechanism of 1-10 MPa / min, a pressure increasing to 180-200 MPa for 30-60 min, and a slow pressure releasing mechanism of 5-20 MPa / min.

[0021] Further, the sintering system of step (6) is provided with a temperature of 0-500 DEG C, a temperature increasing speed of 5-10 DEG C / min, and a sintering pressure of 10 MPa; a temperature of 500 DEG C, a temperature maintaining time of 1-2 h, and an unchanged pressure; a temperature of 500-800 DEG C, a temperature increasing speed of 2-5 DEG C / min, and a sintering pressure of 10 MPa; a temperature of 800-1300 DEG C, a temperature increasing speed of 5-10 DEG C / min, and a sintering pressure of 10 MPa; a temperature of 1300-1400 DEG C, a temperature increasing speed of 1 DEG C / min, and a sintering pressure of 10 MPa, with a temperature maintaining time of 1-2 h at 1350 DEG C; and a temperature of 1400-1900 DEG C, a temperature increasing speed of 10-15 DEG C / min, and a pressure of 20-50 MPa.

[0022] The present application has the following beneficial effects:

[0023] Compared with the existing preparation technology of boron carbide ceramic, the present application firstly pre-grinds and pre-mixes the boron carbide ceramic powder, uniformly mixes the sintered two-phase of different particle sizes by crushing, and pre-mixes the Al powder with less times and more amounts, so that the water reducing agent is fully combined with the powder surface functional group, and the mixed powder with good sphericity and solid rate is obtained by spray granulation; secondly, the pretreatment process of titanium fiber felt is carried out, the titanium fiber felt is cut by using a shaping tool, and a more dense and close titanium fiber felt-boron carbide (Al)-titanium fiber felt-boron carbide (Al)-titanium fiber felt sintering structure is obtained through a cold pressing device or an upper-middle-lower three-layer ceramic green body, and then through cold isostatic pressing; so as to obtain a high-strength cold body, and through different reaction stages, a sintering process is set to finally obtain a high-toughness high-strength boron carbide-based ceramic; the final cold body strength can be increased by more than 15%, and the average hardness of the ceramic after final sintering is more than 49Gpa, and the fracture toughness can reach 8.5MPa.m 1 / 2 The bending strength can reach more than 580MPa.

[0024] The present application breaks through the traditional means of toughening boron carbide, providing a new idea for future boron carbide ceramic toughening. Secondly, the present application provides a green path for comprehensive recycling of titanium alloy cutting waste in the future, which can replace the high-cost pure titanium and titanium alloy fine materials with low-cost cutting waste, and then realize the industrialized production of boron carbide toughening. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is a schematic diagram of the profiled powder laying tool;

[0026] Figure 2 It is a schematic diagram of the cold pressing tool sequence. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0028] Embodiment 1

[0029] A preparation method of titanium felt toughened boron carbide ceramic, specifically comprising the following steps:

[0030] (1) Ceramic powder premixing: Selecting a three-rod double-layer horizontal dry ball mill for ball milling, mixing boron carbide ceramic with a particle size of 0.5 μm and Al powder with the same particle size at a ratio of 8:1 to obtain a ceramic powder mixture; the ball barrel material is selected to be polyurethane organic material, the grinding balls are selected to be 6 mm, 8 mm and 10 mm zirconium dioxide balls at a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1, and the powder loading amount is 1 / 3 of the barrel volume with a rolling rod rotation speed of 15 r / min;

[0031] (2) Slurry preparation for entering the tower: the selection of admixtures is as follows: ① water reducing agent: selecting polycarboxylic acid water reducing agent, the addition amount is controlled to be 0.5%; ② water retaining agent: selecting light yellow hydroxypropyl methyl cellulose ether, the addition amount is 0.3%; ③ binder: the binder is selected to be polyacrylic acid aqueous solution resin, the addition amount is 0.05%; the admixtures are added to the ceramic powder mixture in small amounts and multiple times, and mechanical stirring is used at a speed of about 60 r / min for 10 h, so that the water reducing agent is fully combined with the powder surface functional groups to obtain ceramic slurry, and the solid content of the ceramic slurry is controlled to be 65%;

[0032] (3) Spray granulation and standing aging: after the ceramic slurry is spray granulated in a spray granulation tower, it is sealed and stood for 24 h for subsequent cold pressing to obtain ceramic granulation, and the water content of the ceramic granulation is controlled to be 5%; the inlet temperature of the spray granulation tower is 300℃, the feeding rate of the peristaltic pump is 90 g / min, the outlet temperature is 120℃, the speed of the atomizer is 5000 r / min, and the tower is kept under negative pressure;

[0033] (4) Titanium fiber felt pretreatment: the titanium fiber felt is composed of pure Ti, and is subjected to profile processing by a blanking tool to obtain titanium fiber felt with a purity of 99.9% and a diameter of φ0.2 mm; the titanium fiber felt is placed in a pure water ultrasonic instrument, treated for 2 h at a wavelength of 80%, immersed in 5% HF for 10 s, taken out and placed in acetone for 2 h, then cleaned with pure water ultrasonic wave, and dried for standby use to obtain pretreated titanium fiber felt;

[0034] (5) Cold pressing and cold isostatic pressing: a four-beam 200t two-way press is adopted, and cold powder laying is performed through a profiling tool as shown in Figure 1 The laying sequence from bottom to top is: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt; the pressure for cold powder laying is selected to be 150 t, the pressing rate is 0.3 mm / min, and the pressure holding time is 30 min; the mold used for laying and the laying method are as shown in Figure 2 ;

[0035] After the forming piece is evenly coated with high-purity graphite powder and cold isostatic pressing, a pressed green material is obtained; the cold isostatic pressing is that the forming piece is sealed in a nylon vacuum bag and placed in an oil pressure isostatic pressing device, the pressure increasing mechanism is 5 MPa / min, the pressure is increased to 200 MPa and kept for 60 min, and the slow pressure relief mechanism is 5 MPa / min;

[0036] (6) The hot pressing sintering system is set as follows: the pressed green material is placed in a graphite mold, 5 layers of graphite paper with a thickness of 0.2 mm are laid as isolation layers on the upper and lower four sides; the sintering system is as follows: when the temperature is 0-500℃, the heating rate is 10℃ / min, and the sintering pressure is 10 MPa; when the temperature is 500℃, the pressure is kept for 1.5 h; when the temperature is 500-800℃, the heating rate is 5℃ / min, and the sintering pressure is 10 MPa; when the temperature is 800-1300℃, the heating rate is 10℃ / min, and the sintering pressure is 10 MPa; when the temperature is 1300-1400℃, the heating rate is 1℃ / min, and the sintering pressure is 10 MPa; when the temperature is 1350℃, the pressure is kept for 2 h; when the temperature is 1400-1900℃, the heating rate is 15℃ / min, and the pressure is 50 MPa. After cooling in the furnace, a titanium felt toughened boron carbide ceramic is obtained.

[0037] The strength of the titanium felt toughened boron carbide ceramic prepared in this embodiment can be increased by 16.4%, the density measured by the Archimedes drainage method is 99.4 g / cm 3 , the hardness is 40.67 Gpa, the fracture toughness measured by the single-edge opening beam method can reach 9.3 MPa.m 1 / 2 , and the bending strength can reach 588 MPa.

[0038] Example 2

[0039] A preparation method of a titanium felt (TC4) toughened boron carbide ceramic, specifically comprising the following steps:

[0040] (1) Ceramic powder premixing: a three-rod double-layer horizontal dry ball mill is selected for ball milling, boron carbide ceramic with a particle size of 0.5 μm and Al powder with the same particle size are mixed in a ratio of 9:1 to obtain a ceramic powder mixture; the ball barrel material is selected to be polyurethane organic material, 6 mm, 8 mm and 10 mm zirconium dioxide balls are selected to be put in at a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1, and the powder loading amount is 1 / 3 of the barrel volume with a rolling rod speed of 15 r / min;

[0041] (2) Slurry preparation: the selection of admixtures is as follows: ① water reducing agent: polycarboxylic acid water reducing agent is selected, and the addition amount is controlled at 0.5%; ② water retaining agent: light yellow hydroxypropyl methyl cellulose ether is selected, and the addition amount is 0.3%; ③ binder: polyacrylic acid aqueous solution resin is selected as the binder, and the addition amount is 0.05%; the admixtures are added into the ceramic powder mixture in small amounts and multiple times, and mechanical stirring is used at a speed of about 60 r / min for 10 h, so that the water reducing agent is fully combined with the functional groups on the surface of the powder, and a ceramic slurry is obtained, and the solid content of the ceramic slurry is controlled at 65%;

[0042] (3) Spray granulation and standing aging: the ceramic slurry is spray granulated in a spray granulation tower, and then sealed and aged for 24 h, and then cold pressed to obtain ceramic granulation, wherein the water content of the ceramic granulation is controlled at 5%; the inlet temperature of the spray granulation tower is 300℃, the feeding rate of the peristaltic pump is 90 g / min, the outlet temperature is 120℃, the speed of the atomizer is 5000 r / min, and the negative pressure is maintained in the tower;

[0043] (4) Titanium fiber felt pretreatment: the titanium fiber felt is TC4, and is subjected to shaping treatment by a blanking tool to obtain titanium fiber felt with a purity of 99.9% and a diameter of φ0.2 mm; the titanium fiber felt is placed in a pure water ultrasonic instrument, and is treated for 2 h at a wavelength of 80%; then the titanium fiber felt is taken out, soaked in 5% HF for 10 s, taken out, placed in acetone, soaked for 2 h, and then cleaned with pure water ultrasonic wave, and dried for standby, to obtain pretreated titanium fiber felt;

[0044] (5) Cold pressing and cold isostatic pressing: a four-beam 200t two-way press is used to lay the cold powder through a profiling tool, and the profiling tool is as shown in Figure 1 , and the laying sequence from bottom to top is: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt; the pressure for laying the cold powder is selected as 150t, the pressing rate is 0.3 mm / min, and the pressure holding time is 30 min; the mold used for laying and the laying method are as shown in Figure 2 ;

[0045] The shaped piece is uniformly coated with high-purity graphite powder and then cold isostatic pressed to obtain a pressed green material; the cold isostatic pressing is that the shaped piece is sealed in a nylon vacuum bag and placed in an oil pressure isostatic pressing device, the pressure increasing mechanism is 5 MPa / min, the pressure is increased to 200 MPa and held for 60 min, and the slow pressure relief mechanism is 5 MPa / min;

[0046] (6) Hot-pressing sintering system setting: the pressed green mixture is placed in a graphite mold with 5 layers of 0.2 mm-thick graphite paper as the isolation layer; the sintering system is as follows: the temperature is raised at a rate of 10℃ / min from 0-500℃ under a sintering pressure of 10 MPa; the temperature is kept at 500℃ for 1.5 h under the same pressure; the temperature is raised at a rate of 5℃ / min from 500-800℃ under a sintering pressure of 10 MPa; the temperature is raised at a rate of 10℃ / min from 800-1300℃ under a sintering pressure of 10 MPa; the temperature is raised at a rate of 1℃ / min from 1300-1400℃ under a sintering pressure of 10 MPa; the temperature is kept at 1350℃ for 2 h under the same pressure; the temperature is raised at a rate of 15℃ / min from 1400-1900℃ under a pressure of 50 MPa; the titanium felt toughened boron carbide ceramic is obtained after furnace cooling.

[0047] The strength of the titanium felt toughened boron carbide ceramic prepared in this example can be increased by 15.2%, the density measured by the Archimedes drainage method is 99.7 g / cm 3 , the hardness is 41.22 Gpa, the fracture toughness measured by the single-edge open beam method is up to 8.9 MPa.m 1 / 2 , and the bending strength is up to 576 MPa.

[0048] Example 3

[0049] A method for preparing a titanium felt (TA2) toughened boron carbide ceramic, specifically comprising the following steps:

[0050] (1) Ceramic powder premixing: a three-rod double-layer horizontal dry ball mill is selected for ball milling, boron carbide ceramic with a particle size of 0.5 μm and Al powder with the same particle size are mixed at a ratio of 8:1 to obtain a ceramic powder mixture; the ball barrel material is selected to be polyurethane organic material, 6 mm, 8 mm and 10 mm zirconium dioxide balls are selected to be put in at a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1, and the powder loading amount is 1 / 3 of the barrel volume with a roller speed of 15 r / min;

[0051] (2) Slurry preparation: the selection of external additives is as follows: ① water reducing agent: a polycarboxylic acid water reducing agent is selected, and the addition amount is controlled to be 0.8%; ② water retaining agent: a light yellow hydroxypropyl methyl cellulose ether is selected, and the addition amount is 0.5%; ③ binder: a polyacrylic acid water solution resin is selected as the binder, and the addition amount is 0.07%; the external additives are added to the ceramic powder mixture in small amounts and multiple times, and mechanical stirring is performed at a speed of about 60 r / min for 10 h, so that the water reducing agent is fully combined with the functional groups on the surface of the powder, to obtain a ceramic slurry, and the solid content of the ceramic slurry is controlled to be 65%;

[0052] (3) Spray granulation and standing aging: the ceramic slurry is spray granulated in a spray granulation tower and then sealed and stood for 24 h, and then cold-pressed to obtain ceramic granulation, the water content of the ceramic granulation is controlled to be 5%; the inlet temperature of the spray granulation tower is 300℃, the feeding rate of the peristaltic pump is 90 g / min, the outlet temperature is 120℃, the speed of the atomizer is 5000 r / min, and the tower is kept under negative pressure;

[0053] (4) Titanium fiber felt pretreatment: the titanium fiber felt is TA2, after being processed by a blanking tool, the titanium fiber felt (TA2) with a diameter of 0.5 mm is placed in a pure water ultrasonic instrument, the wavelength is 80%, and the titanium fiber felt is treated for 2 h, then taken out, immersed in 5% HF for 7 s, taken out and placed in acetone, immersed for 2 h, and then cleaned by pure water ultrasonic, and dried for standby, to obtain the pretreated titanium fiber felt;

[0054] (5) Cold pressing and cold isostatic pressing: a four-beam 200t two-way press is used to perform cold powder laying through a profiling tool (as shown in Figure 1 The laying sequence from bottom to top is: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt; the pressure for cold powder laying is selected to be 150 t, the pressing rate is 0.3 mm / min, and the pressure maintaining time is 30 min;

[0055] The formed piece is uniformly coated with high-purity graphite powder and then cold isostatic pressed to obtain a pressed green material; the cold isostatic pressing is performed by sealing the formed piece in a nylon vacuum bag and placing it in an oil pressure isostatic pressing device, the pressure increasing mechanism is 5 MPa / min, the pressure is increased to 200 MPa and maintained for 40 min, and the slow pressure releasing mechanism is 7 MPa / min;

[0056] (6) Hot pressing and sintering system setting: the pressed green material is placed in a graphite mold, and 5 layers of graphite paper with a thickness of 0.2 mm are laid as isolation layers on the upper and lower four sides; the sintering system is as follows: when the temperature is 0-500℃, the temperature increasing rate is 10℃ / min, and the sintering pressure is 10 MPa; when the temperature is 500℃, the pressure is maintained for 1.5 h; when the temperature is 500-800℃, the temperature increasing rate is 5℃ / min, and the sintering pressure is 10 MPa; when the temperature is 800-1300℃, the temperature increasing rate is 10℃ / min, and the sintering pressure is 10 MPa; when the temperature is 1300-1400℃, the temperature increasing rate is 1℃ / min, and the sintering pressure is 10 MPa; when the temperature is 1350℃, the pressure is maintained for 2 h; when the temperature is 1400-1900℃, the temperature increasing rate is 15℃ / min, and the pressure is 50 MPa. After cooling in the furnace, a titanium felt toughened boron carbide ceramic is obtained.

[0057] The strength of the titanium felt toughened boron carbide ceramic prepared in this embodiment can be increased by 17.2%, and the density measured by the Archimedes drainage method is 98.2 g / cm 3; hardness 45.73 GPa, the fracture toughness can reach 8.3 MPa.m 1 / 2 , the bending strength can reach 523 MPa.

[0058] Example 4

[0059] A method for preparing a titanium felt (TA2) toughened boron carbide ceramic, specifically comprising the following steps:

[0060] (1) Ceramic powder premixing: a three-rod double-layer horizontal dry ball mill is selected for ball milling, boron carbide ceramic with a particle size of 0.5 μm and Al powder with the same particle size are mixed in a ratio of 8:1 to obtain a ceramic powder mixture; the ball barrel material is selected to be polyurethane organic material, the grinding balls are selected to be 6 mm, 8 mm and 10 mm zirconium dioxide balls in a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1, and the powder loading amount is 1 / 3 of the barrel volume; the rolling rod rotation speed is 15 r / min;

[0061] (2) Slurry preparation: the selection of external additives is as follows: ① water reducing agent: a polycarboxylic acid water reducing agent is selected, and the addition amount is controlled to be 0.8%; ② water retaining agent: a light yellow hydroxypropyl methyl cellulose ether is selected, and the addition amount is 0.5%; ③ binder: a polyacrylic acid aqueous solution resin is selected as the binder, and the addition amount is 0.07%; the external additives are added to the ceramic powder mixture in small amounts and multiple times, and mechanical stirring is performed at a speed of about 60 r / min for 10 h, so that the water reducing agent is fully combined with the functional groups on the surface of the powder, to obtain a ceramic slurry, and the solid content of the ceramic slurry is controlled to be 65%;

[0062] (3) Spray granulation and standing aging: after the ceramic slurry is spray granulated in a spray granulation tower, it is sealed and stood for 24 h for subsequent cold pressing, to obtain ceramic granulation, and the water content of the ceramic granulation is controlled to be 5%; the inlet temperature of the spray granulation tower is 300℃, the feeding rate of the peristaltic pump is 90 g / min, the outlet temperature is 120℃, the speed of the atomizer is 5000 r / min, and the tower is kept under negative pressure;

[0063] (4) Titanium fiber felt pretreatment: the titanium fiber felt is composed of TA2, after shape correction treatment by a blanking tool, the φ0.2 mm titanium fiber felt (TA2) is placed in a pure water ultrasonic instrument, the wavelength is 80%, the treatment time is 2 h, after taking out, it is soaked in 5% HF for 7 s, after taking out, it is placed in acetone for 2 h, and then it is cleaned by pure water ultrasonic wave and dried for standby, to obtain the pretreated titanium fiber felt;

[0064] (5) Cold pressing and cold isostatic pressing: a four-beam 200t two-way press is adopted, and the cold powder is laid by a profiling tool, the profiling tool is as shown in Figure 1The laying sequence from bottom to top is: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt. The cold powder laying pressure is selected as 150 t, the pressing speed is 0.3 mm / min, the pressure maintaining time is 30 min, and the mold and laying method are as follows Figure 2 as shown.

[0065] The formed piece is uniformly coated with high-purity graphite powder and then cold isostatic pressed to obtain a pressed green material. The cold isostatic pressing is performed by sealing the formed piece in a nylon vacuum bag and placing it in an oil pressure isostatic pressing device. The pressure increasing mechanism is 5 MPa / min, the pressure is increased to 200 MPa and maintained for 60 min, and the slow pressure relief mechanism is 5 MPa / min.

[0066] (6) The hot pressing sintering system is set as follows: the pressed green material is placed in a graphite mold, 5 layers of 0.2 mm thick graphite paper are laid as isolation layers around the top and bottom, and the sintering system is as follows: 500℃ for 1.5 h, the pressure is unchanged; the temperature is increased to 800℃ at a rate of 5℃ / min, the sintering pressure is 10 MPa; the temperature is increased to 1300℃ at a rate of 10℃ / min, the sintering pressure is 10 MPa; the temperature is increased to 1400℃ at a rate of 1℃ / min, the sintering pressure is 10 MPa; the temperature is maintained at 1350℃ for 2 h; the temperature is increased to 1900℃ at a rate of 15℃ / min, the pressure is 50 MPa. After cooling in the furnace, a titanium felt toughened boron carbide ceramic is obtained.

[0067] The strength of the titanium felt toughened boron carbide ceramic prepared in this embodiment can be increased by 16.2%, the density of the titanium felt toughened boron carbide ceramic measured by the Archimedes drainage method is 96.2 g / cm 3 , the hardness is 39.27 Gpa, the fracture toughness measured by the single-edge opening beam method is 7.9 MPa.m 1 / 2 , and the bending strength is 566 MPa.

[0068] Example 5

[0069] A method for preparing a titanium felt (TC 11 ) toughened boron carbide ceramic, specifically comprising the following steps:

[0070] (1) Ceramic powder premixing: a three-rod double-layer horizontal dry ball mill is selected for ball milling, boron carbide ceramic with a particle size of 0.5 μm and Al powder with the same particle size are mixed in a ratio of 8:1 to obtain a ceramic powder mixture; the ball barrel material is selected to be polyurethane organic material, 6 mm, 8 mm and 10 mm zirconium dioxide balls are selected and put in according to a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1, and the powder loading amount is 1 / 3 of the barrel volume, and the rolling rod speed is 15 r / min;

[0071] (2) into the tower slurry preparation: the selection of admixture is: ① water reducing agent: poly carboxylic acid water reducing agent is selected, the amount of addition is controlled at 0.5%; ② water retention agent: light yellow hydroxypropyl methyl cellulose ether is selected, the amount of addition is 0.5%; ③ binder: the binder is polyacrylic acid aqueous solution resin, the amount of addition is 0.07%; a small amount of admixture is added to the ceramic powder mixture in multiple times, and mechanical stirring is used, the rate is about 60r / min, the stirring time is 10h, so that the water reducing agent is fully combined with the powder surface functional group, the ceramic slurry is obtained, and the solid content of the ceramic slurry is controlled to be 75%;

[0072] (3) spray granulation and standing aging: after the ceramic slurry is spray granulated in a spray granulation tower, it is sealed and standing for 24h, and then cold pressing is carried out, so that ceramic granulation is obtained, and the water content of the ceramic granulation is controlled to be 5%; the inlet temperature of the spray granulation tower is 300 DEG C, the feeding rate of the peristaltic pump is 90g / min, the outlet temperature is 120 DEG C, the speed of the atomizer is 5000r / min, and the negative pressure is kept in the tower;

[0073] (4) titanium fiber felt pretreatment: the titanium fiber felt is TC 11 , after the blanking tool is used for shaping treatment, the titanium fiber felt (TC11) with a diameter of 0.5mm is placed in a pure water ultrasonic instrument, the wavelength is 80%, the treatment time is 2h, after being taken out, it is soaked in 5% HF for 10s, after being taken out, it is placed in acetone, soaked for 2h, and then cleaned with pure water ultrasonic wave, and dried for standby, so that the pretreated titanium fiber felt is obtained;

[0074] (5) cold pressing and cold isostatic pressing: the cold powder is laid through a profiling tool, the profiling tool is shown in Figure 1 , and the laying sequence from bottom to top is: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt; the pressure selected for the cold powder laying is 140t, the pressing rate is 0.3mm / min, the pressure maintaining time is 30min, and the mold and laying method used for laying are shown in Figure 2 ;

[0075] The shaped piece is uniformly coated with high-purity graphite powder and then cold isostatic pressed to obtain a pressed green material; the cold isostatic pressing is that the shaped piece is sealed in a nylon vacuum bag and placed in an oil pressure isostatic pressing equipment, the pressure increasing mechanism is 5MPa / min, the pressure is increased to 200MPa and maintained for 60min, and the slow pressure releasing mechanism is 5MPa / min;

[0076] (6) Hot-pressing sintering system setting: the pressed green mixture is placed in a graphite mold with 5 layers of 0.2 mm-thick graphite paper as the isolation layer; the sintering system is as follows: the temperature is raised at a rate of 10℃ / min from 0-500℃ under a sintering pressure of 10 MPa; the temperature is kept at 500℃ for 1.5 h under the same pressure; the temperature is raised at a rate of 5℃ / min from 500-800℃ under a sintering pressure of 10 MPa; the temperature is raised at a rate of 10℃ / min from 800-1300℃ under a sintering pressure of 10 MPa; the temperature is raised at a rate of 1℃ / min from 1300-1400℃ under a sintering pressure of 10 MPa; the temperature is kept at 1350℃ for 2 h under the same pressure; the temperature is raised at a rate of 15℃ / min from 1400-1900℃ under a pressure of 50 MPa; the titanium felt toughened boron carbide ceramic is obtained after furnace cooling.

[0077] The strength of the titanium felt toughened boron carbide ceramic prepared in this example can be increased by 17.5%, the density measured by the Archimedes drainage method is 92.2 g / cm 3 , the hardness is 36,73 Gpa, the fracture toughness measured by the single-edge open beam method is up to 8.2 MPa.m 1 / 2 , and the bending strength is up to 509 MPa.

[0078] Example 6

[0079] A method for preparing a titanium felt (TB8) toughened boron carbide ceramic, specifically comprising the following steps:

[0080] (1) Ceramic powder premixing: a three-rod double-layer horizontal dry ball mill is selected for ball milling, boron carbide ceramic with a particle size of 0.5 μm and Al powder with the same particle size are mixed at a ratio of 8:1 to obtain a ceramic powder mixture; the ball barrel material is selected to be polyurethane organic material, 6 mm, 8 mm and 10 mm zirconium dioxide balls are selected and put in at a ratio of 1:2:1, the ball-to-material ratio is controlled to be 2.5:1, and the powder loading amount is 1 / 3 of the barrel volume with a rolling rod speed of 15 r / min;

[0081] (2) Slurry preparation: the selection of external additives is as follows: ① water reducing agent: a polycarboxylic acid water reducing agent is selected, and the addition amount is controlled to be 0.5%; ② water retaining agent: a light yellow hydroxypropyl methyl cellulose ether is selected, and the addition amount is 0.5%; ③ binder: a polyacrylic acid water solution resin is selected as the binder, and the addition amount is 0.07%; the external additives are added into the ceramic powder mixture in small amounts and multiple times, and mechanical stirring is performed at a speed of about 60 r / min for 10 h, so that the water reducing agent is fully combined with the functional groups on the surface of the powder, to obtain a ceramic slurry, and the solid content of the ceramic slurry is controlled to be 75%;

[0082] (3) Spray granulation and standing aging: the ceramic slurry is spray granulated in a spray granulation tower and then sealed and stood for 24 h after which cold pressing is performed to obtain ceramic granulation, the water content of the ceramic granulation being controlled at 5%; the spray granulation tower has an inlet temperature of 300℃, a peristaltic pump feeding rate of 90 g / min, an outlet temperature of 120℃, and an atomizer speed of 5000 r / min, and the tower is kept under negative pressure;

[0083] (4) Titanium fiber felt pretreatment: the titanium fiber felt has a composition of TB8, is subjected to profile processing using a blanking tool, and then is placed in a pure water ultrasonic instrument for 2 h at a wavelength of 80%, is then immersed in 5% HF for 5 s, is then placed in acetone, is immersed in the acetone for 2 h, and is then cleaned using a pure water ultrasonic cleaner and dried for use, to obtain pretreated titanium fiber felt.

[0084] (5) Cold pressing and cold isostatic pressing: a four-beam 200t two-way press is used to perform cold powder laying using a profile tool as shown in Figure 1 , the laying sequence from bottom to top being: pretreated titanium fiber felt-ceramic granulation-pretreated titanium fiber felt-ceramic granulation-titanium fiber felt; the pressure used for cold powder laying is 150t, the pressing rate is 0.3 mm / min, and the pressure is maintained for 30 min, and the mold used for laying and the laying method are as shown in Figure 2 .

[0085] The shaped piece is uniformly coated with high-purity graphite powder and then cold isostatic pressed to obtain a pressed green mixture; the cold isostatic pressing is performed by sealing the shaped piece in a nylon vacuum bag and placing it in an oil pressure isostatic pressing device, the pressure increasing mechanism being 5 MPa / min, the pressure being increased to 200 MPa and maintained for 60 min, and the slow pressure release mechanism being 5 MPa / min.

[0086] (6) Hot pressing and sintering system setting: the pressed green mixture is placed in a graphite mold, 0.2 mm thick graphite paper is used as a separation layer, and a total of 5 layers are laid around the top and bottom; the sintering system is as follows: the temperature is increased at a rate of 10℃ / min from 0-500℃, the sintering pressure is 10 MPa; the temperature is maintained at 500℃ for 1.5 h, the pressure is unchanged; the temperature is increased at a rate of 5℃ / min from 500-800℃, the sintering pressure is 10 MPa; the temperature is increased at a rate of 10℃ / min from 800-1300℃, the sintering pressure is 10 MPa; the temperature is increased at a rate of 1℃ / min from 1300-1400℃, the sintering pressure is 10 MPa; the temperature is maintained at 1350℃ for 2 h; the temperature is increased at a rate of 15℃ / min from 1400-1900℃, the pressure is 50 MPa. After furnace cooling, a titanium felt toughened boron carbide ceramic is obtained.

[0087] The strength of the titanium felt toughened boron carbide ceramic prepared in the embodiment can be increased by 14.4%, the density measured by the Archimedes drainage method is 97.8 g / cm 3 , the hardness is 50 Gpa, the fracture toughness measured by the single-edge opening beam method can reach 6.33 MPa.m 1 / 2 , and the bending strength can reach 470 MPa.

[0088] The AlTi / Al toughened boron carbide ceramic is synthesized in situ, pure titanium or TC4 titanium alloy containing Al element is used as raw material, the traditional powder material is abandoned, titanium fiber felt is innovatively selected, the infiltration of titanium and the matrix material is changed by using the loose and porous titanium fiber, with the increase of heat power, it can be seen from the SEM that the toughening phase can be better directional toughening along the fiber direction, the green body quality can also be greatly improved in the green body stage. The boron carbide and the intermediate product are energized by hot pressing, the Al3Ti phase is uniformly distributed in the contact surface range, so that the ceramic layer can present the phenomenon of high strength and high toughness mutual interpenetration. The boron carbide ceramic compensates for the deficiency in fracture toughness and bending strength on the basis of not sacrificing the excellent properties such as high strength and high hardness. The whole process is strong in implementability and simple in operation, and the application of the boron carbide based series ceramic can be maximized.

Claims

1. A method for preparing titanium felt-toughened boron carbide ceramic, characterized in that, Includes the following steps: (1) Premixing of ceramic powder: Boron carbide ceramic and ceramic two-phase Al powder are ball-milled to a particle size of 0.5~1.0μm and then mixed in a ratio of 8:1~9:1 to obtain a ceramic powder mixture; (2) Preparation of slurry for tower feeding: Add additives to the ceramic powder mixture in small amounts and multiple times, and stir mechanically at a rate of 30~60 r / min for 3~10 h to obtain ceramic slurry. The solid content of the ceramic slurry is controlled to be greater than 60%. (3) Spray granulation and static aging: The ceramic slurry is spray granulated in a spray granulation tower, then sealed and allowed to stand for more than 12 hours before being cold pressed to obtain ceramic granules. The moisture content of the ceramic granules is controlled at 3%~5%. (4) Titanium fiber felt pretreatment: Titanium fiber felt with a purity of 99.9% and φ0.2~0.5mm is obtained by using blanking tooling for shaping treatment; the titanium fiber felt is pretreated to obtain pretreated titanium fiber felt. (5) Cold isostatic pressing: Cold powder is laid by using a contour tooling. The laying sequence from bottom to top is: pretreated titanium fiber felt - ceramic granulation - pretreated titanium fiber felt - ceramic granulation - pretreated titanium fiber felt; to obtain the molded part. The molded part is evenly coated with cold-pressing release agent and then cold isostatically pressed to obtain the pressed raw material. (6) Hot pressing sintering system setting: The pressed raw materials are placed in a graphite mold for sintering. The placement method is to use graphite paper with a thickness of 0.2~0.5mm as an isolation layer, and lay 4~8 layers on the top, bottom and sides. After cooling in the furnace, titanium felt toughened boron carbide ceramics are obtained. The sintering regime described in step (6) is as follows: when the temperature is 0~500℃, the heating rate is 5~10℃ / min, and the sintering pressure is 10MPa; Hold at 500℃ for 1-2 hours with constant pressure; at 500-800℃, the heating rate is 2-5℃ / min and the sintering pressure is 10MPa; at 800-1300℃, the heating rate is 5-10℃ / min and the sintering pressure is 10MPa; at 1300-1400℃, the heating rate is 1℃ / min and the sintering pressure is 10MPa; hold at 1350℃ for 1-2 hours; at 1400-1900℃, the heating rate is 10-15℃ / min and the pressure is 20-50MPa.

2. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, The ball mill used in step (1) uses polyurethane or nylon polymer organic material for the ball barrel. The grinding balls are 6mm, 8mm and 10mm zirconia balls added in a ratio of 1:2:

1. The ball-to-material ratio is controlled at 2.5:1~3.5:

1. The amount of powder added is 1 / 3~1 / 2 of the ball barrel volume. The roller speed is 10~15r / min.

3. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, The additives mentioned in step (2) are: ① Water-reducing agent: one or more of polycarboxylate water-reducing agent, ammonium citrate and polyethylene glycol (PEG) are selected, and the amount added is controlled at 0.5%~1.5%; ② Water-retaining agent: pale yellow hydroxypropyl methylcellulose ether is selected, and the amount added is 0.3%~0.5%; ③ Binder: the binder is polyacrylic acid aqueous resin and wax-based polyvinyl alcohol (PVA). The former is added at 0.05%~0.08%, and the latter needs to be mixed with water-based PVA. After hydrolysis or wax hydrolysis, the ratio is 0.5:1~1.

4. The amount added of wax-based polyvinyl alcohol and water-based PVA is controlled at 0.03%~0.07%.

4. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, The spray granulation tower described in step (3) is set with an inlet temperature of 240℃~300℃, a peristaltic pump feed rate of 30~90g / min, an outlet temperature of 80℃~120℃, an atomizer speed of 3000~5000r / min, and a negative pressure inside the tower.

5. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, The titanium fiber felt described in step (4) is composed of pure Ti, TC4 and some alloys of the TB series, with an average thickness of 0.1~0.3 mm per layer.

6. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, The pretreatment described in step (4) involves placing the titanium fiber felt in a pure water ultrasonic instrument at a wavelength of 60%~80% for 1~2 hours, then removing it and soaking it in 3%~5% HF for 5~10 seconds, then placing it in acetone and soaking it for 1~2 hours, followed by ultrasonic cleaning with pure water and drying for later use.

7. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, When laying the cold powder in step (5), the pressure is 100~150t, the pressing rate is 0.3mm~0.5mm / min, and the pressure is maintained for 15~30min.

8. The method for preparing titanium felt-toughened boron carbide ceramic according to claim 1, characterized in that, The cold pressing release agent mentioned in step (5) is selected from boron nitride spray lubricant or high-purity graphite powder; the cold isostatic pressing is to seal the molded part in a nylon vacuum bag and place it in a hydraulic isostatic pressing equipment. The pressure increase mechanism is 1~10MPa / min, and the pressure is increased to 180~200MPa and held for 30~60min. The slow pressure release mechanism is 5~20MPa / min.

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