Method for Making Bulletproof Inserts Based on Boron Carbide Bulletproof Ceramics

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The invention belongs to the field of bulletproof ceramics, in particular to a bulletproof insert plate based on boron carbide bulletproof ceramics.

Background technology:

The core component of ceramic matrix composite bulletproof materials is bulletproof ceramics. Among the existing bulletproof ceramics, boron carbide (B4C) ceramics have the lightest specific gravity, the highest hardness and elastic modulus. It is the hardest material except diamond and cubic boron nitride. It is the first choice of modern lightweight bulletproof materials. B4C has a melting point of 2350 ℃, poor plasticity and great resistance to grain boundary movement. Therefore, the preparation of B4C ceramics is relatively difficult. At present, the preparation of B4C ceramics mainly includes three processes: hot press sintering, pressureless sintering and reaction sintering. Hot press sintering requires fine powder with particle size ≤ 3.5 microns, and the process cost is very high. Pressureless sintering requires ultrafine powder with particle size ≤ 1 micron, and the sintering temperature is high, The product has the advantages of large shrinkage, uncontrollable dimensional accuracy, low reaction sintering temperature and net size sintering. At present, the reactive sintering B4C process adopts the vacuum siliconization method. In the production process of this process, the solid phase of boron carbide is greatly consumed due to the liquid phase silicon reaction, which weakens the advantages of boron carbide materials.

Technical realization elements:

The object of the invention is to provide a bulletproof insert plate based on boron carbide bulletproof ceramics. The bulletproof insert plate comprises an impact surface, a back plate surface and an interface. The impact surface is boron carbide bulletproof ceramics. The preparation method of boron carbide bulletproof ceramics comprises the following steps:

1) B4C powder and modified phenolic resin were milled in a ball mill for 12-24 hours to form slurry;

2) Granulate the slurry obtained in step 1) with a granulator, drive the peristaltic pump motor, and transport the slurry in the slurry barrel milled in step 1) to the spray tray at the top of the granulator through the pump. The spray tray motor drive system drives the spray tray to rotate, and the rotating spray tray disperses the slurry through centrifugation, The blower blows the dispersed slurry to the water with ultrasonic device at the bottom through the air outlet, and the particles are insoluble in water and precipitated to the bottom; Separating particles and water through the discharge port of the granulator; Drying the obtained particles to obtain granulation powder;

3) Selecting a mold and molding the obtained granulation powder to obtain a compact;

4) Then the compact is heated in a mesh belt furnace, and the modified phenolic resin is decomposed to produce coated carbon source to obtain the compact;

5) Then it is sintered in a vacuum sintering furnace with a vacuum degree of ≤ 10Pa. An appropriate amount of silicon particles are pressed into silicon cake, which is placed on the upper layer of the green body. The silicon cake melts during the heating process, penetrates into the pores of the green body, and reacts with carbon to form silicon carbide;

6) After sintering, grind a small amount of residual silicon on the product surface with a grinding wheel.

Preferably, the interface is an interface adhesive, the back plate surface is an ultra-high molecular weight polyethylene back plate, and the impact surface is compounded with the back plate surface through the interface adhesive.

Preferably, the ball milling raw materials in step 1) also include PVA, glycerol, PEG and absolute ethanol; The ball milling medium is silicon carbide ball.

Preferably, the weight ratio of B4C powder to modified phenolic resin in step 1) is 10:1-15:1.

Preferably, B4C in step 1) includes powder gradation of three particle sizes, one B4C powder has an average particle size of 8-10 microns, and the mass accounts for 50% of the total mass of B4C; The average particle size of the other B4C powder is 20-25 microns, accounting for 30% of the total mass of B4C; The average particle size of the third B4C powder is 2-4 microns, accounting for 20% of the total mass of B4C.

Preferably, the disc speed in step 2) is 300 rpm and the ultrasonic frequency is 40-60 kHz.

Preferably, the drying temperature in step 3) is 110 ℃.

Preferably, in step 4), the maximum decomposition temperature of medium pressure billet in mesh belt furnace is 820-850 ℃, and the mesh belt rate is 80-90mm / min.

Preferably, in step 5), the silicon cake and green body are put into a vacuum sintering furnace, and the sintering temperature is set to 1580-1600 ℃; The ratio of the weight of the silicon cake to the weight of the green body is 1.2:1.

Compared with the prior art, the invention has the following beneficial effects:

Compared with the existing boron carbide bulletproof insert plate, the bulletproof performance of the bulletproof insert plate provided by the invention is greatly improved.

Description of drawings

Fig. 1 is a simple structural diagram of the granulator provided by the invention;

Fig. 2 shows the impact surface of boron carbide in the bulletproof test of the bulletproof insert plate provided by the invention;

Fig. 3 shows the penetration of UHMWPE back plate in the bulletproof test of the bulletproof insert plate provided by the invention.

Specific embodiments

The invention will be described in detail below in combination with the accompanying drawings.

Eg 1：

1) B 4C powder and modified phenolic resin were milled in a ball mill for 12 hours to form slurry; The raw material formula for ball milling is 900g B4C, 80g modified phenolic resin, PVA 5g, 4G glycerol, PEG 2G and 1000g absolute ethanol, and B4C is graded by three particle sizes. The ball milling medium is silicon carbide ball, and the weight ratio of the silicon carbide ball to the above raw material formula is 1:2, in which the average particle size of B4C powder is 8-10 microns, accounting for 50% of the total mass of B4C; The average particle size of the other B4C powder is 20-25 microns, accounting for 30% of the total mass of B4C; The average particle size of the third B4C powder is 2-4 microns, accounting for 20% of the total mass of B4C.

2) The granulator is a granulator made by the inventor of the present application. The specific structure of the granulator is shown in Figure 1, including slurry barrel 1, peristaltic pump motor, peristaltic pump 2, spray plate 3, spray plate motor, granulator barrel 4, ultrasonic device 6, discharge port 7, the slurry barrel 1 is connected with peristaltic pump 2, and the peristaltic pump 2 is connected with spray plate 3, The spray tray 3 is connected with the granulator barrel 4, the granulator barrel 4 is connected with the ultrasonic device 6, and the spray tray is provided with an air outlet, wherein the air outlet can be a through hole opened around the central axis of the spray tray. The air outlet is connected with the blower, and deionized water 5 is introduced into the ultrasonic device.

The specific working steps of the granulator are as follows: 1) set the rotating speed of the spray plate 3 to 300 rpm and the frequency of the ultrasonic device to 40-60 kHz; Drive the peristaltic pump motor to transport the slurry in the slurry barrel milled in step 1) above to the spray plate 3 at the top of the granulator through the peristaltic pump 2. The spray plate motor driving system drives the spray plate 3 to rotate. The rotating spray plate 3 disperses the slurry through centrifugal action. The blower blows the dispersed slurry to the water with ultrasonic device 6 at the bottom through the air outlet, and the particles are insoluble in water and precipitated to the bottom, In this way, phenolic resin is well and evenly coated on B4C surface; After atomization, the particles and water are separated through the outlet 7 of the granulator, and the obtained particles are dried. The drying temperature is 110 ℃, and the granulated powder is obtained after drying.

3) Select the mold and press the obtained granulation powder to obtain the compact.

4) Then, the pressed billet is heated in the mesh belt furnace, the resin is decomposed and the coated carbon source is generated to obtain the billet. The maximum decomposition temperature of the pressed billet in the mesh belt furnace is 820-850 ℃, and the mesh belt rate is 80-90mm / min.

5) Then it is sintered in a vacuum sintering furnace, the vacuum degree is ≤ 10Pa, an appropriate amount of silicon particles are pressed into silicon cake, the silicon cake is placed on the upper layer of the blank, and the ratio of silicon cake weight to blank weight is 1.2:1; The vacuum sintering temperature is set at 1580-1600 ℃; After holding the temperature and pressure for 30min, the silicon cake melts during the heating process, penetrates into the pores of the green body, and reacts with carbon to form silicon carbide.

6) After sintering, grind a small amount of residual silicon on the surface of the product with a grinding wheel.

The final product properties obtained in step 6 are: density of 2.64-2.67g/cm3, microhardness of 2900-3100hv0 2. The bending strength is 450 MPa and the fracture toughness is 4.5 MPa · M1 / 2.

The bulletproof ceramic comprises the following components by mass percentage: b4c50-60%; sic25-30％； si15-25％。

Eg 2：

Example 2 replaces the ratio of the ball milling formula in step 1) of Example 1. For example, the mass of b4c is changed to 1200g or 800g, and the modified phenolic resin is 80g. The other masses are the same as that of Example 1. The results show that the bending strength of the obtained product is uniform. ≥450mpa, fracture toughness ≥4.5mpa·m1/2.

Eg 3：

The traditional boron carbide process is used to obtain boron carbide bulletproof ceramics. The only difference between the traditional process and the process of Example 1 is that the granulation method is different; it is difficult for the traditional granulator to evenly coat the phenolic resin on the boron carbide ceramic Surface, thereby obtaining granulated powder with uniform carbon distribution.

The results show that compared with the ballistic ceramic obtained in Example 2, the microhardness, flexural strength and fracture toughness of the sintered ballistic ceramic obtained in Example 1 are increased by 18%, 33% and 35%, respectively.

Eg 4：

According to the process flow of Example 1, a suitable mold is selected to obtain a 5mm-thick boron carbide bulletproof ceramic, and the 5mm boron carbide bulletproof ceramic prepared above is combined with a 10kg/m2 ultra-high molecular weight polyethylene backplane. The composite method uses an interface adhesive , Get a bulletproof flapper.

Eg 5：

Test the ballistic performance of the sample bulletproof insert obtained in Example 4:

Test environment: room temperature, temperature 23℃, humidity 40%rh;

The main equipment for testing and testing: general standard measuring tools; ballistic testing system; electronic scale; firearms (95 type 5.8mm automatic rifle); ammunition (87 type 5.8mm ordinary ammunition);

Under normal temperature conditions, the shooting distance is 10m and the shooting angle is 0°. With a 95-type 5.8mm automatic rifle with a 87-type 5.8mm ordinary projectile, there are 3 effective projectiles, all of which have not penetrated, and the maximum recessed depth of the backing material is 22.4mm. Detailed data is shown in Table 1. In addition, as shown in Figures 2 and 3, the bulletproof insert provided by the present invention will crack and grind the warhead when impacted by bullets, and the backplane fibers will be stretched, broken, and other forms are further absorbed. The kinetic energy of the bullet, thereby protecting personnel or equipment.

According to the above experimental results, compared with the traditional boron carbide bulletproof insert plate, the bulletproof ability of the bulletproof insert plate is enhanced. In the conventional reaction sintering boron carbide process, silicon melts in heating and penetrates into the pores of the blank through capillary force, reacts with the carbon in the blank to form silicon carbide, and fills the remaining pores. However, in the actual process, the main phase of boron carbide reacts with Si and loses a lot, weakening the material advantage of B4C. In this patent, the modified phenolic resin is used as the carbon source, After dewaxing, C coating on B4C particles is formed. C coated B4C can effectively reduce the dissolution of boron carbide particles and the increase of particle size in the process of reactive sintering, and a large number of nano SiC particles are generated in the products. Therefore, the microhardness, flexural strength and fracture toughness of the material can be greatly improved, so as to enhance the elastic resistance.

The above is only the preferred specific embodiment of the invention, and the protection scope of the invention is not limited to this. Any person skilled in the art shall be covered by the protection scope of the invention by equivalent replacement or change according to the technical scheme of the invention and its inventive concept within the technical scope disclosed by the invention.

Technical summary

The invention provides a bulletproof insert plate based on boron carbide bulletproof ceramics. The bulletproof insert plate comprises an impact surface, a back plate surface and an interface. The impact surface is boron carbide bulletproof ceramics, and its bulletproof performance is greatly improved compared with the existing bulletproof ceramics.