JP5116353B2 - Protective member and protective equipment using the same - Google Patents

Description

The present invention relates to a protective member that is lightweight and has high mechanical properties, and a protective device using the protective member. In particular, the human body to prevent penetration of the projectile or sharp blade, such as bullets and artillery shells, vehicles, ships, protective member for protecting an aircraft or the like, body armor employing the protective member and child, stab vest, anti blade shields, bullet-proof function with a bag, protection such as bulletproof helmet again and again about.

  Due to the recent tightening of the international situation, the demand for protective members has been increasing. Such a protective member is required to be lightweight, and a high compressive strength is required because a large compressive stress is applied from a bullet or a shell. Examples of lightweight materials having high mechanical properties include boron carbide sintered bodies and silicon carbide sintered bodies, which are actually used as materials for protective members against bullets and shells. ing.

  Thus, as a protective member using a boron carbide sintered body or silicon carbide sintered body having high compressive strength, in Patent Document 1, ceramics are mainly used at positions corresponding to the front and back of the helmet. An anti-ballistic appendage for helmets has been proposed in which the impact-resistant reinforcement as the material is enclosed in a cover that covers the exterior of the helmet, and the main component of the ceramic is selected from silicon carbide, boron carbide, silicon nitride, and alumina. It is supposed to be composed of more than one kind.

Further, Patent Document 2 proposes a ceramic style in which the planar shape is a polygonal ceramic tile, and the thickness of the apex portion of the tile polygon is thicker than the thickness of the center portion of the tile. The ceramic tile is made of alumina, silicon nitride, silicon carbide, zirconia or boron carbide, and is used for a bulletproof plate, a bulletproof vest or a blade-proof vest.
JP 2002-294512 A JP 2002-326861 A

  However, the bulletproof appendage for helmets proposed in Patent Document 1 and the bulletproof plates, bulletproof vests and blade-proof vests using ceramic tiles proposed in Patent Document 2 are light and improved in impact resistance and elasticity. However, since the ceramic sintered body itself absorbs impact, the penetration performance of bullets and shells has been dramatically improved, and it is no longer possible to fully protect it. .

The present invention has been made in view of such problems, and it is an object of the present invention to provide a lightweight protective member having improved penetration performance against bullets and shells with high penetration performance, and a protective device using the same.

To solve the problems described above, the protective member of the present invention, the impact receiving portion having a receiving衝面 is composed of a ceramic mainly composed of carbides, base located on the back side of the impact receiving portion, It is characterized by comprising ceramics whose main component is silicon nitride having higher fracture toughness than the impact receiving part.

Further, in the protection member of the present invention , the impact receiving portion having the impact receiving surface is composed of a ceramic containing boron carbide as a main component and containing graphite and silicon carbide, and a base portion located on the back side of the impact receiving portion, It is characterized by being made of a ceramic material having a higher fracture toughness than the impact receiving portion .

Further, the protective member of the present invention is characterized in that said said impact receiving portion base are bonded through a bonding layer.

Further, the protective member of the present invention is characterized in that the bonding layer is made of a resin.

Further, the protective member of the present invention is characterized in that the impact receiving surface has a convex curved surface.

Furthermore, the protective equipment of this invention is provided with two or more said protective members , It is characterized by the above-mentioned .

According to the protective member of the present invention, the impact receiving portion having impact receiving surface is formed of a ceramic mainly composed of carbides, base located on the back side of the impact receiving portion is broken Ri by the impact receiving portion the壊靱highly silicon nitride since it is composed of ceramics mainly, the material constituting the impact receiving portion hardness, stiffness, and more high mechanical characteristics of such compressive strength, landed bullets or shells or deform the distal end, it is possible or to small fragments, by the material forming the base portion, deformation can be absorbed or dissipating kinetic energy of the pieces of the bullet or projectile. In addition, since the base is made of ceramics whose main component is silicon nitride, the specific gravity can be reduced and the fracture toughness can be increased. Can do.

Also, the progress of a crack generated in the impact receiving portion, since it is stopped at the boundary between the base portion, the characteristics of both the material is sufficiently exhibited, it is possible to increase the protection performance by the synergistic effect.

Further, according to the protection member of the present invention, the impact receiving portion having the impact receiving surface is composed of ceramics containing boron carbide as a main component , graphite and silicon carbide, and is located on the back side of the impact receiving portion. However, since it is made of ceramics having a higher fracture toughness than the impact receiving portion , in addition to the above-described effects, the specific gravity of the impact receiving portion can be further reduced, so that the human body is particularly protected. When used in bulletproof vests, bulletproof helmets, etc., it is light and suitable.

Further, according to the protective member of the present invention, since the impact receiving portion and the base portion when it is bonded via the bonding layer, which by this bonding layer, stress generated by bonding is relaxed, the impact receiving The functions inherently provided in the base and the base are hardly impaired.

Further, according to the protective member of the present invention, when the bonding layer is made of resin, since the resin absorbs and relaxes the stress generated in connection with the bonding layer, the function that the impact receiving portion and the base portion essentially include. Can be fully expressed.

Furthermore, according to the protective member of the present invention, when the impact receiving surface has a convex curved surface, a probability that a normal bullet or projectile flight direction and an impact receiving surface side of the surface of the match greatly reduced Can be made. As a result, bullets and shells land while sliding on the surface of the impact receiving surface, so that the destruction energy is absorbed or dissipated, and the protection performance can be further improved.

The armor of the present invention, since it is provided with a plurality of high protective member having protective performance, as described above, it is possible to prevent the penetration of such a bullet or projectile with a high probability.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings schematically shown.

  FIG. 1 is a perspective view schematically showing one embodiment of the protection member of the present invention, and FIGS. 2 to 3 are perspective views showing other embodiments of the protection member of the present invention. In addition, the same code | symbol is used when showing a common site | part in drawing.

As shown in FIG. 1, in the protective member 1 of the present invention, the impact receiving portion having an impact receiving surface for receiving impacts from flying objects such as bullets and shells, blades, and other external impacts is mainly made of carbide. is composed of ceramics as a component (the ceramic sintered body 2 in the figure), the base which is located on the back side of the impact receiving portion, a ceramic (FIG mainly comprising high silicon nitride of fracture壊靱resistance Ri by receiving shock unit The ceramic sintered body 3) in the inside.

With such a structure, the impact receiving portion, the hardness, rigidity, because have mechanical properties such as compressive strength high, for example, can be deformed tip of the landed bullets or shells, can or to small pieces it can.

Further, silicon nitride constituting the group portion has high fracture toughness, may be deformed, thereby absorbing or dissipating the kinetic energy of the pieces of the bullet or projectile.

Also, the progress of a crack generated in the impact receiving portion, since it is stopped at the boundary between the base portion, the characteristics of both the material is sufficiently exhibited, it is possible to increase the protection performance. As these two materials, for example, as a carbide , for example, a ceramic sintered body 2 mainly composed of boron carbide and a ceramic sintered body 3 mainly composed of silicon nitride having higher fracture toughness than the ceramic sintered body 2. And it is sufficient.

  These ceramic sintered bodies 2 and 3 do not necessarily have to be joined. For example, the ceramic sintered bodies 2 and 3 are stacked and inserted into a bag, or fixed using a fixing member such as a clip, a band, a tape, or a screw. You can do it. Moreover, you may adhere | attach the surface 2a, 3a which ceramic sintered compacts 2 and 3 each oppose with an adhesive agent or a double-sided tape. An example of this is shown in FIG.

  As shown in FIG. 2, the sintered ceramics 2 and 3 are bonded to each other through the bonding layer 4 on the opposing surfaces 2a and 3a, and the bonding layer 4 relaxes the stress generated by the bonding. The function can be exhibited without substantially impairing the function that both ceramic sintered bodies 2 and 3 essentially have. The bonding layer 4 is formed of at least one of epoxy resin, phenol resin, polyurethane resin, acrylic resin, vinyl acetate resin, vinyl chloride resin, and urea resin, and has a thickness of 5 μm to 2 mm. Alternatively, the ceramic sintered bodies 2 and 3 may be joined by sintering.

  Note that the bonding layer 4 preferably has a low Young's modulus because it can relieve the stress generated when the ceramic sintered bodies 2 and 3 are joined together. It is optimal in that it can fully exhibit the functions inherently provided in the base.

The ceramic sintered body 2 of the receiving part includes a sintered body mainly composed of boron carbide (hereinafter referred to as boron carbide sintered body) and a sintered body mainly composed of silicon carbide (hereinafter referred to as silicon carbide based sintered body). Or a composite sintered body of these, and it is optimal to use a boron carbide sintered body in terms of low specific gravity and high hardness.

  In the present invention, among the components constituting the material of interest, the component occupying 70% by mass or more is referred to as a main component. However, in the composite sintered body, this is not limited to 40% by mass or more. Furthermore, in order to increase mechanical properties such as hardness, rigidity, and compressive strength, the relative density of the sintered body is desirably 95% or more.

The ceramic sintered body 2 of the receiving part is preferably a boron carbide sintered body. Since boron carbide has a low specific gravity, it is possible to increase the protective performance by increasing the thickness of the ceramic sintered body 2 and has high hardness, rigidity, and compressive strength. High ability to make small pieces. In order to increase the hardness and rigidity, the purity of boron carbide is preferably as high as possible, and boron carbide is preferably 90% by mass or more, and more preferably 98% by mass or more with respect to 100% by mass of the boron carbide sintered body.

  Further, in order to increase the hardness, rigidity, and compressive strength, it is important to make the sintered body dense. In any sintered body, the relative density should be 95% by mass or more, and further 99% by mass or more. desirable.

The above boron carbide sintered bodies have Vickers hardness, Young's modulus, fracture toughness and compressive strength of 22 to 38 GPa, 330 to 500 GPa, ² to 5 MPa · m ^1/2 and 1.5 to 5 GPa, respectively. The mechanical properties can be determined in accordance with the indenter press-in (IF) method or the SEPB method and JIS R1608-2003 defined by JIS R 1610-2003, JIS R 1602-1995, and JIS R1607-1995, respectively.

  However, when the thickness of the ceramic sintered body 2 is thin and the test piece defined by the JIS standard cannot be cut out from the ceramic sintered body 2, the thickness of the ceramic sintered body 2 may be the thickness of the test piece.

  Further, when the ceramic sintered body 2 is a boron carbide sintered body, the compressive strength, which is a required characteristic of the protective member, can be further increased by containing graphite and silicon carbide. Graphite and silicon carbide act as a sintering aid in the firing process of the boron carbide sintered body, and graphite suppresses abnormal grain growth of boron carbide particles and progresses densification of the boron carbide sintered body. Since silicon carbide strongly binds the boron carbide particles by the evaporation and condensation mechanism in the firing step, the compressive strength of the boron carbide sintered body can be increased. In particular, the silicon carbide is preferably α-type silicon carbide (αSiC). During firing, the α-type silicon carbide grows into a plate shape to form α-type silicon carbide crystal particles, and the boron carbide sintered body has a minute amount. Even if a crack occurs, the crack is difficult to progress due to the presence of α-type silicon carbide crystal particles.

  In general, under compressive stress, a number of cracks develop in a direction substantially parallel to the compression direction by deviating from the crack propagation direction from the tip of the irregularly present cracks in the boron carbide sintered body. Destruction occurs after forming. The higher the compressive strength, the slower the progress of the cracks, so it can be said that it is an excellent protective member.

The boron carbide sintered body preferably has 90% by mass or more of boron carbide as a main component with respect to 100% by mass of the boron carbide sintered body, and graphite and silicon carbide are boron carbide. What is necessary is just to include 0.8 mass% or more in total with respect to 100 mass% of elementary sintered bodies. By doing in this way, the compressive strength which is a required characteristic of a protection member can be made still higher.

  FIG. 4 schematically shows the crystal structure of carbon, (a) is a schematic diagram showing the crystal structure of graphitizable carbon, and (b) is a schematic diagram showing the crystal structure of non-graphitizable carbon. . The crystal structure of graphite affects the pores in the crystal grains of graphite, and when the crystal structure of graphite is a structure in which the carbon layer surface has an orderly orientation as shown in FIG. Since the pores in the particles are reduced, the compressive strength can be increased. As shown in FIG. 4B, when the graphite crystal structure is a disordered three-dimensional network structure twisted so that ribbon-like stacks with long carbon layers are entangled, pores in the graphite crystal particles increase. Therefore, the compressive strength is reduced.

  In the boron carbide sintered body forming the protective member of the present invention, the graphite has a half-value width from the (002) plane of 0.3 ° or less (excluding 0 °) as measured by the X-ray diffraction method. Is preferred. Further, the crystal structure of graphite is the structure shown in FIG. 4A, and further, mechanical properties such as compressive strength, such as bending strength, Young's modulus, hardness, etc., can be increased.

  FIG. 5 is an example of an X-ray diffraction chart of a boron carbide based sintered body forming the protective member of the present invention. As shown in FIG. 5, the peak from the (002) plane is represented as a peak (p). Here, the half width from the (002) plane refers to the width of the diffraction angle (2θ) at the half value of the peak (p). By setting this width to 0.3 ° or less (excluding 0 °), the crystal structure of graphite becomes the structure shown in FIG. 4 (a). As a result of the reduction of pores in the graphite crystal particles, the compression strength is increased. can do. In particular, the crystal structure of graphite is a hexagonal system called 2H graphite, and is preferably a crystal structure shown by JCPDS card # 41-1487.

  Further, graphite is 1% by mass to 10% by mass with respect to 100% by mass of boron carbide sintered body, and silicon carbide is 0.5% by mass to 5% by mass with respect to 100% by mass of boron carbide sintered body. It is preferable to include below. As a result, boron (B) and carbon (C) atoms are easily moved during firing, and as a result of sufficient densification, the compressive strength, which is one of the required characteristics of the protective member, can be increased.

  The graphite and silicon carbide in the boron carbide sintered body can be identified by, for example, an X-ray diffraction method using CuKα rays. In addition, quantitative analysis of graphite can be performed using X-ray diffraction using the Rietveld method.

Specifically, first, a calibration curve is created in advance. That is, a mixed powder of graphite powder and boron carbide powder is prepared. For mixed powders with different composition ratios, the area I (C) of the X-ray diffraction peak attributed to the (002) plane of graphite and the X-ray diffraction peak attributed to the (021) plane of boron carbide (B ₄ C) After obtaining the ratio I (C) / I (B ₄ C) of the area I (B ₄ C) and plotting it on a graph, a calibration curve consisting of a straight line is created using the least square method. FIG. 6 is an example of a calibration curve obtained from a mixed powder of graphite powder and boron carbide powder.

Next, the graphite content in the boron carbide sintered body is determined using this calibration curve. That is, the ratio I (C) / I (B ₄ C) of the boron carbide sintered body can be obtained, and the graphite content can be measured from the calibration curve.

  Furthermore, the quantitative analysis of silicon carbide can be measured using an ICP (Inductively Coupled Plasma) emission analysis method. Specifically, the Si content is measured by ICP, and all of Si is considered to be SiC, and converted to SiC, which can be used as the SiC content.

  Since such a protective member is required to be lightweight, it is preferable that the ceramic sintered bodies 2 and 3 have a flat plate shape. For example, each ceramic sintered body 2 and 3 has a length of 10 to 400 mm. The flat plate has a width of 10 to 400 mm and a thickness of 1 to 20 mm.

Further, when the ceramic sintered body 3 is a silicon nitride sintered body, the composition formula Si _6-Z Al _Z O _Z N _8-Z (z = 0. 1-1) as a main phase, and the constituent ratio of Al, Si, RE (RE is Group 3 element of the periodic table) is converted into Al ₂ O ₃ , SiO ₂ , RE ₂ O ₃ respectively. Al ₂ O ₃ is 5 to 50 mass%, SiO ₂ is 5 to 20 mass%, the grain boundary phase and the balance is predominantly _{RE 2 O 3 RE-Al-} SiO-N, the main phase and the grain boundary A silicon nitride sintered body containing 4 to 20% by volume of a sintered body composed of a phase and containing 0.02 to 3% by mass of Fe silicide particles with respect to the sintered body in terms of Fe It is preferable to form by.

  Here, the solid solution amount z can be calculated as follows. That is, a silicon nitride-based sintered body is pulverized to a particle size of 200 mesh or less, and a high-purity α-silicon nitride powder (E product made by Ube Industries, Ltd.) is used as a sample for correcting the diffraction angle in the powder X-ray diffraction method. −10 grade, Al content of 20 ppm or less) is added and mixed uniformly in a mortar, and the analysis range 2θ is 33 to 37 ° and the scanning step width is 0.002 ° by powder X-ray diffraction method. The profile intensity is measured with Cu-Kα ray (λ = 1.54056４０). The angle is corrected using the maximum peak value obtained from the angle correction sample.

That is, the difference (Δ2θ ₁ ) between the average 2θ of the upper 10 points of peak intensity obtained every 0.002 ° of α (102) that appears in the vicinity of 2θ = 34.565 ° (Δ2θ ₁ ), and 2θ = 35 The difference (Δ2θ ₂ ) between the average 2θ of the top 10 peak intensities obtained every 0.002 ° of α (210) appearing near .333 ° and Δ35.333 ° (Δ2θ ₂ ) is obtained, respectively, Let ₁ + Δ2θ ₂ ) / 2 be the correction Δ2θ. Next, the angle obtained by correcting the average 2θ of the top 10 peak intensities obtained every 0.002 ° of β (210) appearing in the vicinity of 2θ = 36.055 ° by the correction Δ2θ is the peak position of β (210) ( 2θ _β ). Then, the lattice constant a (Å) is calculated by substituting the peak position (2θ _β ), λ = 1.54056Å, (hkl) = (210) into the following equation.

sin ² θ _β = λ ² (h ² + hk + k ² ) / (3a ² ) + λ ² l ² / (4c ² )
In this equation, the calculated lattice constant a (Å) and the lattice constant a (Å) −solid solution amount z described in KH Jack, J. Mater. Sci., 11 (1976) 1135-1158, FIG. From this graph, the solid solution amount z can be determined.

The grain boundary phase consists RE-Al-SiO-N, Al, Si, the component ratio of RE is _{Al 2 O 3, SiO 2,} RE 2 O 3 in terms of in _Al 2 _{O 3} is from 5 to 50 mass %, SiO ₂ is 5 to 20% by mass, and the balance is mainly RE ₂ O ₃ , and it is preferable that the sintered body composed of the main phase and the grain boundary phase is included in the range of 4 to 20% by volume. . In the present invention, the composition ratio of the grain boundary phase is expressed with the sum of Al ₂ O ₃ , SiO ₂ , RE ₂ O ₃ and N being 100 mass%.

Here, in general, an oxide containing RE-Al-Si-O promotes densification of silicon nitride and sialon. Powder materials such as Al ₂ O ₃ , SiO ₂ , and RE ₂ O ₃ react as the temperature rises to generate a liquid phase that is well wetted with silicon nitride and sialon at 1400 ° C. or higher, and then dissolve silicon nitride and sialon. By doing so, a grain boundary phase composed of RE-Al-Si-O-N is formed.

  The volume ratio of the grain boundary phase to the sintered body affects the strength of the silicon nitride sintered body, and the ratio is preferably 4 to 20% by volume.

Such a composition ratio of Al ₂ O ₃ , SiO ₂ , RE ₂ O ₃ and a volume ratio of the grain boundary phase can be obtained as follows. First, each ratio (mass%) of RE and Al in the sintered body was measured by ICP (Inductivity Coupled Plasma) spectroscopy, and this ratio (mass%) was set to RE ₂ O ₃ and Al ₂ O ₃ , respectively. Convert to the ratio (mass%). Next, the ratio of all oxygen in the sintered body is measured by an oxygen analysis method using an oxygen analyzer manufactured by LECO (TC-136 type), and the ratio of oxygen in RE ₂ O ₃ and Al ₂ O ₃ is determined. The ratio of the remaining oxygen is subtracted and converted into the ratio (mass%) of SiO ₂ . The balance in the sintered body is regarded as Si ₃ N _4, and the respective ratios (mass%) are set to respective theoretical densities (Y ₂ O ₃ : 5.02 g / cm ³ , Er ₂ O ₃ : 8.64 g / cm ³ , Yb ₂ O ₃ : 9.18 g / cm ³ , Lu ₂ O ₃ : 9.42 g / cm ³ , Al ₂ O ₃ : 3.98 g / cm ³ , SiO ₂ : 2.655 g / cm ³ , Si ₃ N ₄ : 3.18 g / cm ³ ) to calculate the volume ratio of the grain boundary phase.

Next, the ratio (mass%) of nitrogen (N) contained in the grain boundary phase is calculated using energy dispersive X-ray spectroscopy (EDS), and Al ₂ O ₃ , SiO ₂ , RE ₂ O ₃ and The composition ratio of the grain boundary phase is calculated with the sum of the ratios (mass%) of nitrogen (N) as 100%. However, since the composition ratio of nitrogen contained in the grain boundary phase of the silicon nitride-based sintered body used in the present invention is very small and usually 0.1% by mass or less, it is included in RE ₂ O ₃ hereinafter. write.

  The RE in the grain boundary phase may be a Group 3 element of the periodic table, such as Er, Yb, Lu, etc., but RE is preferably Y. This is because Y is a light element among the Group 3 elements of the periodic table and can be reduced in weight. Moreover, what is necessary is just to measure 4-point bending strength based on JISR1604-1995.

  Moreover, since the Fe silicide particles in the sintered body affect the fracture toughness and strength of the sintered body, the Fe silicide particles are 0.02 to 3 mass% with respect to the sintered body in terms of Fe. It is preferable to constitute a silicon nitride sintered body containing.

  Fe silicide has a large coefficient of thermal expansion and is thought to generate residual stress on β-sialon particles and grain boundary phase. This is one of the effects and forms of fracture that improve the fracture toughness of sintered bodies. When the grain boundary slip occurs, it acts as a wedge that prevents the β-sialon particles from slipping, and has the effect of improving the strength. The Fe silicide acts as one of the liquid phase components during firing, and is effective in improving the sinterability. The form of such Fe silicide can be confirmed by elemental analysis using a powder X-ray diffraction method or X-ray microanalyzer (EPMA), and can be quantified by ICP spectroscopy.

The Fe silicide is interspersed as particles having a particle size of 50 μm or less, preferably 2 to 30 μm in the grain boundary phase composed of β-sialon particles or RE-Al—Si—O—N. _{and, FeSi 2, FeSi, Fe 3} Si, is preferably present in the form of _Fe 5 Si _3, it is preferable that particularly FeSi ₂ (JCPDS # 35-0822).

  Further, as shown in FIG. 3, the protective member of the present invention preferably has a convex curved surface on the surface of the impact receiving surface. Such a convex curved surface can greatly reduce the probability that the flight direction of bullets and shells coincides with the normal of the surface of the ceramic sintered body 2. As a result, bullets and bullets land while sliding on the surface of the ceramic protective member 1, so that the destructive energy is absorbed or dissipated and the protective performance can be further enhanced.

Further, the protective member of the present invention, preferably it is a ceramic sintered body 3 groups portion in contact with the rear surface of polyethylene fibers, and at least one kind of fiber reinforced plastics comprising aramid fibers and carbon fibers (FRP) It is. Polyethylene fiber, aramid fiber, and carbon fiber have high knot strength, so they can absorb or dissipate the destructive energy of bullets and shells and prevent secondary disasters caused by ceramic fragments that scatter when landing. It is.

Since the protective member of the present invention has a high protective performance as described above, a protective plate, a bulletproof vest, a blade-proof vest, a blade-proof shield, a bag with a bulletproof function can be obtained by fixing a plurality of protective members on an appropriate substrate. It is also suitable for use in protective equipment such as a bulletproof helmet.

Here, as an example of a protective member of the present invention, the impact receiving portion of the protective member is a boron carbide sintered body, group unit is described a method for manufacturing the case of the silicon nitride sintered body.

When the receiving part of the protective member is a boron carbide sintered body, first, boron carbide powder having an average particle diameter (D ₅₀ ) of 0.5 to 2 μm is prepared. The boron carbide powder to be prepared is composed of powder having a molar ratio of boron (B) to carbon (C) (B / C ratio) having a stoichiometric ratio of 4, ie, boron carbide (B ₄ C). In addition to the powder, mixing of a powder having a molar ratio (B / C ratio) of 3.5 or more and less than 4 or a molar ratio (B / C ratio) of greater than 4 and 10 or less, such as B ₁₃ C ₂ Or powder mixed with free carbon, boric acid (B (OH) ₃ ), boric anhydride (B ₂ O ₃ ), iron (Fe), aluminum (Al), silicon (Si), or the like.

  When these powders are used, by adding graphite powder and silicon carbide powder as sintering aids to these powders, sintering can be performed without applying mechanical pressure during firing. The boron carbide powder is desirably a fine powder having an average particle diameter of 0.5 to 2 μm, but a powder having a large average particle diameter of about 20 μm, for example, or boron carbide powder obtained by pre-grinding this powder is also used. Is possible. Here, the preliminary pulverization is preferably pulverization by a jet mill or the like that does not use a pulverization medium in order to reduce the mixing of impurities.

  Note that graphite is included in an amount of 1% by mass to 10% by mass with respect to the boron carbide sintered body, and silicon carbide is included in an amount of 0.5% by mass to 5% by mass with respect to the boron carbide sintered body. The graphite powder may be 1% by mass to 10% by mass with respect to the total powder, and the silicon carbide powder may be 0.5% by mass to 5% by mass with respect to the total powder.

  In addition, in order for the graphite contained in the boron carbide sintered body to have a half-value width of 0.3 ° or less (excluding 0 °) from the (002) plane measured by the X-ray diffraction method, ( A graphite powder having a half width from the (002) plane of 0.34 ° or less (excluding 0 °) may be used. When the half width of the graphite powder is wide, the crystallinity of the graphite powder is low, and when the half width is narrow, the crystallinity of the graphite powder is high. In order to obtain graphite powder with high crystallinity, it is only necessary to limit the distance that carbon atoms can move in the step of graphitizing from carbon. Specifically, the orientation of carbon may be controlled during this step. As such graphite powder, for example, highly oriented pyrolytic graphite (HOPG) powder may be used.

In addition to graphite powder and silicon carbide powder, the sintering aid is zirconium boride (ZrB ₂ ), titanium boride (TiB ₂ ), chromium boride (CrB ₂ ), zirconium oxide (ZrO ₂ ) in order to promote sintering. ) And yttrium oxide (Y ₂ O ₃ ) may be added.

  Second, the prepared boron carbide powder and sintering aid are put into a mill such as a rotary mill, a vibration mill, a bead mill, etc., and wet mixed with at least one of water, acetone, isopropyl alcohol (IPA), Make a slurry. As the grinding media, media composed of various sintered bodies such as media coated with imide resin on the surface, boron nitride, silicon carbide, silicon nitride, zirconia, alumina, etc. can be used as impurities. A medium made of a boron nitride sintered body, which is a material with little influence of mixing, or a medium whose surface is coated with an imide resin is preferable. Moreover, you may add a dispersing agent before a grinding | pulverization in order to reduce the viscosity of the obtained slurry.

  Third, the obtained slurry is dried to produce a dry powder. Prior to this drying, the slurry is passed through a mesh smaller than 200 mesh to remove coarse impurities and debris, and iron and its compounds are removed by removing iron with a magnetic iron remover. It is preferable to do. Moreover, 1-10 mass parts of organic binders, such as paraffin wax, polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyethylene oxide (PEO), and acrylic resin, are added to the slurry with respect to 100 mass parts of the powder in the slurry. It is preferable to mix them because the occurrence of cracks and cracks in the molded article can be suppressed in the molding step described later. As a method for drying the slurry, the slurry may be heated in a container and dried, or may be dried by a spray drying method using a spray dryer or the like, or may be dried by other methods. .

  Fourth, the dry powder is formed into a desired shape having a relative density of 45 to 70% using a known molding method, for example, a powder pressure molding method using a molding die or an isotropic pressure molding method using hydrostatic pressure. And In order to produce a protective member having a structure that can sufficiently prevent the penetration of a flying object such as a bullet or a bullet, it is preferable that the shape of the molded body is a convex curved surface on the tip side.

  Fifth, when the molded body contains an organic binder, the organic binder is degreased. Degreasing may be performed while flowing nitrogen gas at a temperature of 500 to 900 ° C.

  Sixth, a molded body or a degreased body (hereinafter collectively referred to as a molded body) is fired. A firing furnace heated by a graphitic resistance heating element is used as the firing furnace, and the compact is placed in the firing furnace. Preferably, it is placed in a firing container that can enclose the entire compact (hereinafter referred to as a firing jig). This is because foreign matter that may adhere to the molded body from the atmosphere in the firing furnace (for example, carbon pieces scattered from a graphite heating element or a carbon insulation material, or other inorganic materials incorporated in the firing furnace) This is for the purpose of preventing adhesion of small pieces of the heat insulating material made of the product, and for preventing volatile components from scattering from the molded body. The material of the firing jig is desirably graphite, and may be a material such as silicon carbide or a composite thereof. Further, it is preferable to surround the entire compact with the firing jig.

  Seventh, the compact placed on the firing jig is placed in a firing furnace, and as described above, the temperature is 1800 ° C. or higher and lower than 2200 ° C. in argon gas or He gas, or in vacuum. Holding for 10 minutes to 10 hours in the zone (the first step) and then holding at a temperature of 2200 to 2350 ° C. for 10 minutes to 20 hours (the second step) to make the relative density more than 90%. . The heating rate is preferably 1 to 30 ° C./min. Here, the holding in the first and second steps means the total time spent in a predetermined temperature range. For example, the holding time, the temperature rising time, and the temperature falling time are holding times. include. In addition, since it decomposes | disassembles a boron carbide and an additive component when it hold | maintains at 2000 degreeC or more, it is desirable to hold | maintain in argon gas or He gas.

  In order to further promote densification, pressurization may be performed with a higher pressure gas when the open porosity becomes 5% or less. As this pressurizing method, it is preferable to use a method of pressurizing at a gas pressure of 1 to 300 MPa by a high pressure GPS (Gas Pressure Sintering) method or a hot isostatic press (HIP) method, and relative to this. In particular, the density can be increased to 95% or more. Moreover, you may sinter by the method of applying a mechanical pressure like the hot press method and SPS (Spark Plasma Sintering) method as needed.

When the group portion is a silicon nitride sintered body, first, beta ratio of siliceous nitride powder is not more than 40%, the composition formula _{Si 6-Z Al Z O Z} N solid solution amount z of _8-Z A silicon nitride powder having an A of 0.5 or less and Al ₂ O ₃ , SiO ₂ , RE ₂ O ₃ , Fe ₂ O ₃ powders as additive components, barrel mill, rotary mill, vibration mill, bead mill, etc. Is wet-mixed and pulverized into a slurry.

Here, the total of the powders of Al ₂ O ₃ , SiO ₂ , and RE ₂ O ₃ that are additive components is, when the total sum of the silicon nitride powder and the powder of these additive components is 100% by volume, What is necessary is just to make it become 4-20 volume%.

  There are two types of silicon nitride, α-type and β-type, due to the difference in crystal structure of silicon nitride. The α type is stable at low temperatures, the β type is stable at high temperatures, and the phase transition from α type to β type occurs irreversibly at 1400 ° C. or higher.

Here, the β conversion is the sum of the peak intensities of the α (102) diffraction line and the α (210) diffraction line obtained by the X-ray diffraction method, I _α , β (101) diffraction line and β ( 210) A value calculated by the following equation, where I _β is the sum of the peak intensities with the diffraction line.

β conversion rate = {I _β / (I _α + I _β )} × 100 (%)
The β conversion rate of the silicon nitride powder affects the strength and fracture toughness value of the silicon nitride sintered body. The reason why silicon nitride powder having a β conversion rate of 40% or less is used is that both strength and fracture toughness values can be increased. Silicon nitride-based powder having a β conversion ratio exceeding 40% becomes the core of grain growth in the firing step, tends to be coarse and have a small aspect ratio, and both strength and fracture toughness values are reduced. In particular, it is preferable to use a silicon nitride-based powder having a β conversion rate of 10% or less, whereby the solid solution amount z can be made 0.1 or more.

  The media used for pulverizing the silicon nitride-based powder can be media composed of various sintered bodies such as silicon nitride, zirconia, and alumina. However, a material that does not easily contain impurities, or silicon nitride having the same material composition. A medium made of a sintered material is suitable.

Note that the silicon nitride powder is pulverized until the particle size (D ₉₀ ) at which the cumulative volume is 90% when the total cumulative volume of the particle size distribution curve is 100% is 3 μm or less. This is preferable from the viewpoints of improvement in cohesiveness and formation of needles in the crystal structure. The particle size distribution obtained by grinding can be adjusted by the outer diameter of the media, the amount of the media, the viscosity of the slurry, the grinding time, and the like. In order to reduce the viscosity of the slurry, it is preferable to add a dispersant, and in order to pulverize in a short time, it is preferable to use a powder having a particle size (D ₅₀ ) of 1 μm or less with a cumulative volume of 50% in advance.

  Next, the obtained slurry is passed through a mesh having a particle size smaller than 200 mesh and then dried to obtain granules. Moreover, it is preferable for moldability to mix organic binders, such as paraffin wax, polyvinyl alcohol (PVA), and polyethyleneglycol (PEG), with respect to 100 mass% of powder at the stage of a slurry. Drying may be performed with a spray dryer, and there is no problem even if other methods are used.

  Next, the obtained granule is made into a flat molded body having a relative density of 45 to 60% using a dry pressure molding method. And it is better to degrease in nitrogen atmosphere or vacuum atmosphere. The degreasing temperature varies depending on the kind of the added organic binder, but it is preferably 900 ° C. or lower, and particularly preferably 500 to 800 ° C.

Next, the compact is placed in a firing furnace using a graphite resistance heating element used for firing a general silicon nitride shaped compact, and fired. In the firing furnace, a co-material containing components such as Al ₂ O ₃ , SiO ₂ , and RE ₂ O ₃ may be disposed in order to suppress volatilization of the components contained in the compact.

Further, as a method of arranging the molded body, if a method of embedding the molded body in a silicon nitride powder or a silicon carbide powder is used, it can be fired in the air in an electric furnace. When such a method is used, since the molded body is embedded in the powder, oxygen gas in the atmosphere is shut off, and the firing atmosphere is substantially a nitrogen atmosphere. About temperature, it heats up in a vacuum atmosphere from room temperature to 300-1000 degreeC, Then, nitrogen gas is introduce | transduced and nitrogen partial pressure is maintained at 500-300 kPa. At this time, since the open porosity of the molded body is about 40 to 55%, the molded body is sufficiently filled with nitrogen gas. In the vicinity of 1000 to 1400 ° C., additive components Al ₂ O ₃ and RE ₂ O ₃ undergo a solid phase reaction to form a liquid phase component, and β-sialon is precipitated in a temperature range of about 1400 ° C. or higher. Densification starts. β-sialon is a solution in which Al ³⁺ , N ³⁻ and O ²⁻ are substituted and dissolved in the Si ⁴⁺ position of β-Si ₃ N ₄ , and Si ₃ N ₄ -AlN—Al ₂ O ₃ —SiO ₂ type As shown in many phase diagrams (for example, KH Jack, J. Mater. Sci., 11 (1976) 1135-1158, Fig. 11), the stable region of the β-sialon phase is Si ₃ N ₄ -Al ₂ O. N ³⁻ is insufficient to stabilize the valence with respect to the _3- SiO ₂ system, and it is necessary to supply N ³⁻ from the outside. This is because the nitrogen gas filled in the molded body becomes N ^{3 −,} and the solid solution amount z of β-sialon can be lowered by keeping the nitrogen partial pressure low.

That is, in the stage until the open porosity reaches from 40 to 55% to 5%, it is necessary to set the nitrogen partial pressure as low as possible, and it is important to set it to 50 to 300 kPa. When the nitrogen partial pressure exceeds 300 kPa, substitutional solid solution of Al ³⁺ , N ³⁻ , O ²⁻ progresses with respect to β-Si ₃ N ₄ , the solid solution amount z tends to exceed 1, and the corrosion resistance decreases. When the nitrogen partial pressure is less than 50 kPa, the equilibrium nitrogen partial pressure of β-sialon becomes smaller, the β-sialon decomposition reaction proceeds, and Si melts, so that a normal silicon nitride sintered body cannot be obtained. When the temperature exceeds 1800 ° C., substitutional solid solution of Al ³⁺ , N ³⁻ , and O ²⁻ advances, and the solid solution amount z tends to exceed 1. When the sintering progresses and the open porosity is less than 5%, the supply amount of nitrogen gas into the silicon nitride sintered body is reduced, so the nitrogen partial pressure may exceed 300 kPa. You may bake at the temperature of 1800 degreeC or more. Ultimately, a silicon nitride sintered body having high strength and high fracture toughness can be obtained by proceeding densification to a relative density of 96% or more. A fine crystal structure is obtained in the silicon nitride based sintered body. In this case, the firing temperature may be 1700 ° C. or higher and lower than 1800 ° C. Moreover, it is desirable from an economical viewpoint that the nitrogen partial pressure is set to 150 kPa or less after the temperature is raised in a vacuum atmosphere. In order to promote further densification, gas pressure sintering treatment or hot isostatic pressing (HIP) treatment of 200 MPa or less may be performed when the open porosity becomes 5% or less. In this case, after promoting the sintering to an open porosity of 1% or less and a relative density of 97% or more, further 99% or more, a gas pressure sintering process or a hot isostatic pressing (HIP) process is performed. Is preferred.

In addition, the added Fe ₂ O ₃ powder reacts with β-sialon, which is the main phase, by firing to release oxygen components and produce Fe silicide particles.

Above boron carbide sintered body obtained by the production method and the silicon nitride sintered body was respectively processed into a predetermined shape, and inserting the bag overlapping a receiving shock portion and the base portion, a clip, band, tape, Fix with screws. Alternatively, the opposing surfaces may be bonded with an adhesive or a double-sided tape. Alternatively, a boron carbide sintered body and a silicon nitride sintered body may be joined by sintering. As described above, the protective member of the present invention can be obtained.

Further, according to the protective device of the present invention, a plurality of protective members obtained by the above-described method are arranged on a substrate (for example, fiber reinforced plastic (FRP) including polyethylene fiber, aramid fiber, and carbon fiber), for example, urethane type It is obtained by fixing with an adhesive, and penetration of bullets and shells can be prevented with high probability.

It is a perspective view which shows one Embodiment of the protection member of this invention. It is a perspective view which shows other embodiment of the protection member of this invention. It is a perspective view which shows other embodiment of the protection member of this invention. FIG. 2 schematically shows a crystal structure of carbon, (a) is a schematic diagram showing a crystal structure of graphitizable carbon, and (b) is a schematic diagram showing a crystal structure of non-graphitizable carbon. It is an example of the X-ray diffraction chart of the boron carbide sintered compact which makes the protection member of this invention. It is an example of a calibration curve obtained from a mixed powder of graphite powder and boron carbide powder.

Explanation of symbols

1: Protective member 2: Ceramic sintered body 3: Ceramic sintered body 4: Bonding layer

Claims (6)

Principal component impact receiving portion having impact receiving surface is formed of a ceramic mainly composed of carbides, base located on the back side of the impact receiving portion, a high silicon nitride of fracture壊靱resistance Ri by the impact receiving portion A protective member characterized by comprising ceramics . An impact receiving portion having an impact receiving surface is composed of ceramics containing boron carbide as a main component and containing graphite and silicon carbide, and a base portion located on the back side of the impact receiving portion has higher fracture toughness than the impact receiving portion. proof protection member you characterized in that it is made of a material of the ceramic. Protective member according to claim 1 or claim 2, characterized in that said said impact receiving portion base are bonded through a bonding layer. The protective member according to claim 3 , wherein the bonding layer is made of a resin. Protective member according to any one of claims 1 to 4, characterized in that said impact receiving surface has a convex curved surface. Armor characterized in that it comprises a plurality of protective members according to any one of 請 Motomeko 1 to 5.

Images