阅读说明：本技术 复合材料及其制备方法 (Composite material and preparation method thereof ) 是由 毛咏发 李忠军 李文涛 张允继 毛桂江 于 2020-06-28 设计创作，主要内容包括：本发明公开了一种复合材料及其制备方法。该复合材料包括脆性材料和塑性材料,在所述脆性材料的表面形成纳米级和/或微米级的孔洞结构,所述塑性材料附着在所述表面上,部分所述塑性材料嵌入所述孔洞结构内,所述塑性材料的收缩系数大于所述脆性材料的收缩系数,所述塑性材料的断裂韧性大于所述脆性材料的断裂韧性,所述塑性材料对所述脆性材料形成收缩应力。(The invention discloses a composite material and a preparation method thereof. The composite material comprises a brittle material and a plastic material, wherein a nano-scale and/or micro-scale hole structure is formed on the surface of the brittle material, the plastic material is attached to the surface, part of the plastic material is embedded into the hole structure, the shrinkage coefficient of the plastic material is greater than that of the brittle material, the fracture toughness of the plastic material is greater than that of the brittle material, and the plastic material forms shrinkage stress on the brittle material.)

1. A composite material comprising a brittle material and a plastic material, wherein a nano-scale and/or micro-scale pore structure is formed in a surface of the brittle material, the plastic material is attached to the surface, a portion of the plastic material is embedded in the pore structure, a coefficient of contraction of the plastic material is greater than a coefficient of contraction of the brittle material, a fracture toughness of the plastic material is greater than a fracture toughness of the brittle material, and the plastic material exerts a compressive stress on the brittle material.

2. The method according to claim 1, wherein the brittle material has a thickness of 0.3 to 4 mm.

3. The method according to claim 1, wherein the pore structure has a pore size of 30nm to 1000 nm.

4. The method according to claim 1, wherein the hole structure is a micro-scale groove or a micro-scale hole having a three-dimensional structure.

5. The method of claim 4, wherein the pore structure has a size of 5-200 microns.

6. The method according to claim 1, wherein the plastic material is plastic or rubber.

7. A method of making a composite material, comprising:

forming a nano-scale and/or micro-scale hole structure on the surface of the brittle material;

heating the plastic material to a molten state;

injecting a plastic material in a molten state at a set pressure onto the surface, wherein a portion of the plastic material is embedded within the void structure;

cooling the plastic material and the brittle material to cause the plastic material to form a shrinkage stress on the brittle material, wherein the plastic material has a coefficient of shrinkage greater than the coefficient of shrinkage of the brittle material, and the plastic material has a fracture toughness greater than the fracture toughness of the brittle material.

8. The method of claim 7, wherein the step of injecting the plastic material in a molten state into the surface at a set pressure, wherein a portion of the plastic material is embedded in the cavity structure further comprises:

the brittle material is heated to a set temperature.

9. The method of claim 8, wherein the set temperature is 80 ℃ to 250 ℃.

10. The production method according to claim 7, wherein the set pressure is 200bar to 2500 bar.

Technical Field

The invention relates to the technical field of material preparation, in particular to a composite material and a preparation method thereof.

Background

The brittle material is a material which undergoes a small deformation, i.e., fracture, under an external force, and is, for example, a brittle material such as ceramics and glass. These materials have high hardness but are susceptible to chipping or bulk cracking.

Ceramic materials such as oxide ceramics, nitride ceramics and carbide ceramics have the characteristics of high hardness and scratch resistance of brittle materials, no signal shielding, high stability (high reliability), good heat dissipation performance, warm and moist hand feeling and the like, and can well meet the requirements of 5G communication and wireless charging technologies on intelligent wearable shells and mobile phone shell body materials.

However, the fracture toughness of ceramic materials is usually only 1-10MPa m^1/2The toughness of the material is improved by improving the powder granularity and the granularity distribution of the ceramic material, or the toughness of the material is improved by a phase-change toughening mode or a whisker toughening mode, but the improved toughness is limited in general, and the anti-falling requirement of an intelligent wearable product or a mobile phone rear cover product cannot be met

Disclosure of Invention

One object of the present invention is to provide a new technical solution for composite materials.

According to a first aspect of the present invention, a composite material is provided. The composite material comprises a brittle material and a plastic material, wherein a nano-scale and/or micro-scale hole structure is formed on the surface of the brittle material, the plastic material is attached to the surface, part of the plastic material is embedded into the hole structure, the shrinkage coefficient of the plastic material is greater than that of the brittle material, the fracture toughness of the plastic material is greater than that of the brittle material, and the plastic material forms shrinkage stress on the brittle material.

Optionally, the brittle material has a thickness of 0.3-4 mm.

Optionally, the pore size of the pore structure is 30nm-1000 nm.

Optionally, the hole structure is a micron-sized groove or a micron-sized hole of a three-dimensional structure.

Optionally, the pore structure has a size of 5-200 microns.

Optionally, the plastic material is plastic or rubber.

According to another aspect of the present disclosure, a method of making a composite material is provided. The preparation method comprises the following steps:

forming a nano-scale and/or micro-scale hole structure on the surface of the brittle material;

heating the plastic material to a molten state;

injecting a plastic material in a molten state at a set pressure onto the surface, wherein a portion of the plastic material is embedded within the void structure;

cooling the plastic material and the brittle material to cause the plastic material to form a shrinkage stress on the brittle material, wherein the shrinkage coefficient of the plastic material is greater than the shrinkage coefficient of the brittle material, and the fracture toughness of the plastic material is greater than the fracture toughness of the brittle material.

Optionally, before the step of injecting the plastic material in a molten state to the surface under the set pressure, the step of embedding a part of the plastic material in the hole structure further includes:

the brittle material is heated to a set temperature.

Optionally, the set temperature is 80 ℃ to 250 ℃.

Optionally, the set pressure is 200bar to 2500 bar.

According to one embodiment of the present disclosure, since the shrinkage coefficient of the plastic material is greater than the shrinkage coefficient of the brittle material, the fracture toughness of the plastic material is greater than the fracture toughness of the brittle material, and the plastic material forms a shrinkage stress on the brittle material, a tensile stress can be formed between portions of the plastic material entering into the adjacent two hole structures. The tension stress can effectively reduce the occurrence of the micro-cracks on the surface of the brittle material and obstruct the expansion of the micro-cracks, prevent the brittle material from being cracked, and obviously improve the toughness of the brittle material.

Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 is a schematic structural diagram of a composite material according to an embodiment of the present disclosure.

10: a brittle material layer; 11: a pinning point; 12: a plastic material.

Detailed Description

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

According to one embodiment of the present disclosure, a composite material is provided. The composite material includes a brittle material 10 and a plastic material 12. And forming a nano-scale and/or micro-scale hole structure on the surface of the brittle material 10. The plastic material 12 adheres to the surface. A portion of the plastic material is embedded within the void structure. The coefficient of contraction of the plastic material is greater than the coefficient of contraction of the brittle material 10. The toughness of the plastic material 12 is greater than the fracture toughness of the brittle material 10. The plastic material exerts a shrinkage stress on the brittle material 10.

For example, the brittle material 10 is a material that undergoes only a small deformation, i.e., fracture, under an external force (e.g., tension, impact, etc.). Brittle materials include inorganic non-metallic materials. The inorganic non-metallic material is, for example, at least one of a ceramic material, a glass material and a stone material. The plastic material includes at least one of plastic, rubber, and silicone. In one example, the plastic material 12 is a mixture of a plastic material and a fiber material, which has high toughness and structural strength

The brittle material 10 has a small coefficient of contraction, e.g., typically on the order of 10^-6. The shrinkage factor of plastic materials is generally between 0.6% and 1.5%. The shrinkage coefficients of the two materials are very different.

The plastic material 12 is of an integral sheet structure or a block structure, and a part of the plastic material 12 enters the hole structure on the surface of the brittle material 10 to form the pinning points 11. Since the coefficient of contraction of the plastic material 12 is greater than the coefficient of contraction of the brittle material 10, and the plastic material 12 exerts a contraction stress on the brittle material 10, a tensile stress can be exerted between the portions of the plastic material 12 that enter the adjacent two hole structures. The tightening stress can effectively reduce the occurrence of the micro cracks on the surface of the brittle material 10 and hinder the propagation of the micro cracks, prevent the brittle material 10 from being broken, and significantly improve the toughness of the brittle material 10.

In one example, the brittle material 10 has a thickness of 0.5mm to 4 mm. Within the thickness range, the toughness of the ceramic material is greatly improved, and the ceramic material can adapt to the development trend of thinning electronic equipment.

In one example, the pore size of the pore structure is from 30nm to 1000 nm. In this range, the plastic material easily enters the pore structure, and the filling rate is high.

In one example, the hole structure is a micron-scale groove or a micron-scale hole of a three-dimensional structure. The micron-sized groove of the three-dimensional structure means that the width of the groove is micron-sized, and a plurality of grooves are connected with each other to form the three-dimensional structure. The micron-sized grooves of the three-dimensional structure can accommodate more plastic materials, which makes the pinning effect more significant, the shrinkage stress of the plastic material 12 on the formation of the brittle material 10 is greater, and the overall structural strength of the composite material is higher.

The micron-sized hole means that the inner diameter of the hole structure is micron-sized. In this example, the plastic material 12 forms pinning within each hole structure to form an array of distributed pinning sites 11, with adjacent pinning sites 11 being strained relative to each other to prevent the formation of micro cracks on the surface of the brittle material 10 and to impede the propagation of micro cracks.

In addition, the hole structure reduces defects formed on the surface of the brittle material 10, and makes it difficult to form micro cracks on the surface, as compared to the groove structure.

In addition, since the hole structure is in the micron order, more plastic material can be accommodated, which makes the tension stress of the plastic material to the brittle material 10 larger.

In one example, the pore structure has a size of 5 microns to 200 microns. The larger the size of the hole structure, the more plastic material is accommodated, but defects are easily formed on the brittle material 10, resulting in the generation of cracks; conversely, the smaller the size of the pore structure, the fewer the above-mentioned defects, but the less plastic material contained, the lower the strain stress. Within the above range, the surface of the brittle material 10 has few defects, and the plastic material has a large tightening force.

According to another embodiment of the present disclosure, a method of making a composite material is provided. The preparation method comprises the following steps:

nano-scale and/or micro-scale pore structures are formed on the surface of the brittle material 10.

The plastic material is heated to a molten state.

The plastic material 12 in the molten state is injected onto the surface at a set pressure, wherein a portion of the plastic material 12 is embedded within the hole structure.

Cooling the plastic material 12 and the brittle material 10 such that the plastic material 12 forms a shrinkage stress on the brittle material 10, wherein a coefficient of shrinkage of the plastic material 12 is greater than a coefficient of shrinkage of the brittle material 10.

In the disclosed embodiment, the plastic material 12 has good flowability in the molten state and is able to flow into the pore structure of the brittle material 10. During cooling, the plastic material solidifies and undergoes a volume contraction. Since the plastic material 12 has a greater coefficient of contraction than the brittle material 10, the plastic material 12 shrinks more volumetrically than the brittle material 10 during the curing process, and the pinning points 11, which have been cured and fixed in the hole structure, are strained, thereby forming a shrinkage stress on the surface of the brittle material 10. In this way, adjacent pinning points 11 may develop a tensile stress. The tightening stress can effectively reduce the formation of micro cracks on the surface of the brittle material 10 and prevent the micro cracks from expanding, so that the brittle material 10 is not easy to break when being subjected to an external force.

The brittle material 10 and the plastic material 12 are as previously described. The skilled person can select the desired one according to the actual need.

Injection molding of the plastic material 12 onto the surface of the brittle material 10 is typically performed in a mold. Firstly, placing a brittle material 10 into a mold; then, the plastic material is injected from the gate. The plastic material 12 covers a partial surface or the entire surface of the brittle material 10. The temperature within the mold cavity is maintained such that the plastic material 12 is sufficiently fluid to successfully embed into the void structure.

The brittle material 10 typically has a thermal conductivity greater than that of the plastic material 12. When the cooling rate of the brittle material 10 is less than that of the plastic material 12, the heat of the brittle material 10 may cause the pinning points 11 to re-melt, so that the pinning points 11 may be detached from the inside of the hole structure and a tensile stress cannot be formed.

In one example, the brittle material 10 and the plastic material 12 can be cooled simultaneously during the cooling process, or the cooling rate of the brittle material 10 is greater than the cooling rate of the plastic material 12, so that the plastic material 12 can be effectively prevented from developing a small shrinkage stress due to the inconsistent cooling rate of the composite material.

In one example, the nano-scale and/or micro-scale hole structure is formed on the surface of the brittle material 10 by chemical etching. For example, when the brittle material 10 having a predetermined shape is placed in an acidic solution, the acidic solution chemically reacts with an oxide or the like on the surface of the brittle material 10, thereby forming a cavity structure on the surface. The pore structure is as described above. The acidic solution may be selected from hydrochloric acid, nitric acid, sulfuric acid, and the like. The concentration of the acidic solution is 20g/L-150 g/L.

Or, a hole structure is formed on the surface by adopting a laser etching mode. The size, the depth and the like of the hole structure can be controlled by controlling the intensity of the laser and the etching time.

In one example, before the step of injecting the plastic material 12 in a molten state into the surface under the set pressure, the step of pressing a portion of the plastic material 12 into the hole structure further includes: the brittle material 10 is heated to a set temperature.

Under the heating condition, the brittle material 10 can be completely matched with the cavity of the mold, so that the injection position and the injection amount of the plastic material can be more accurate.

Furthermore, the size of the hole structure can temporarily be increased under heating conditions, which enables the plastic material 12 to be embedded more into the hole structure. After cooling shrinkage, more plastic materials 12 can be fixed in the hole structure, so that the tension stress between the adjacent pinning points 11 is larger, the pinning effect can be obvious, the shrinkage stress of the plastic materials 12 on the brittle materials 10 is larger, the toughness of the composite material is larger, and the structural strength is higher.

Further, the plastic material 12 has better fluidity on the surface of the brittle material 10 under heating conditions.

In one example, the set temperature is 120 ℃ to 200 ℃. At this temperature, the brittle material 10 is better able to match the mold. The plastic material has good fluidity and can fully enter the hole structure.

In one example, the set pressure is 200bar to 2500 bar. The set pressure refers to the outlet pressure of the injection molding apparatus. Within the above pressure range, the plastic material in a molten state can be more effectively embedded into the pore structure.

< example 1>

The brittle material 10 is a zirconia ceramic material with a set shape, and a uniform pore structure is formed on the surface of the zirconia ceramic material by adopting an acid liquor corrosion mode, wherein the pore size of the pore structure is 30nm-1000 nm. The plastic material is a mixed material of PPS and glass fiber, wherein the mass fraction of the PPS is 60%, the mass fraction of the glass fiber is 40%, and the shrinkage coefficient of the glass fiber is 0.4% -0.5%.

Firstly, putting a zirconia ceramic material into a mould, wherein the temperature in the mould is 160 ℃;

and then, injecting the mixed material into a hole structure on the surface of the zirconia ceramic material by adopting a high-speed high-pressure injection molding mode, wherein the injection molding pressure is 1200bar, the injection molding speed is 150mm/s, the pressure holding pressure is 1500bar, and the pressure holding time is 3 s. A layer of plastic material 12 with the thickness of 1mm is attached to the surface of the zirconia ceramic material.

Finally, the brittle material 10 and the plastic material 12 are cooled at room temperature.

And (3) testing items: the composite material of this example was subjected to the following tests:

A. air tightness test

And placing the composite material in an air tightness testing tool for testing. Under the condition of an internal air pressure of 5MPa, the leakage rate is measured to be 7 Pa/min.

B. Roller drop test

And placing the composite material in a roller drop test roller for roller drop. The maximum falling height of the roller is 1.5m, and after the roller falls for 12 times, the composite material does not crack.

C. Free drop test

And placing the composite material on a free drop test platform for free drop. The falling ground is marble ground. The height of the free falling platform is 1.5 m. And the falling is carried out from the free falling platform to different directions. The composite did not crack or chip when dropped 2 times per direction for a total of 12 times.

< example 2>

The brittle material 10 is an alumina ceramic material with a set shape, and a laser etching method is adopted to form a micro-scale gully or a micro-scale hole with a three-dimensional structure on the surface of the alumina ceramic material, wherein the size of the hole structure is 5 μm-2000 μm. The plastic material 12 is a blend of polypropylene and glass fibers. Wherein, in the mixed material, the mass fraction of the glass fiber is 30 percent. The shrinkage factor of the mixed material was 0.6%.

Firstly, putting a zirconia ceramic material into a mould, wherein the temperature in the mould is 160 ℃;

then, the mixed material is injected into a hole structure on the surface of the zirconia ceramic material by adopting a hot-pressing injection molding mode, wherein the injection molding pressure is 800bar, and the injection molding temperature is 175 ℃. A layer of plastic material 12 with the thickness of 1mm is attached to the surface of the zirconia ceramic material.

Finally, the brittle material 10 and the plastic material 12 are cooled at room temperature.

Measurement items: A. air tightness test

And (3) placing the composite material in an air tightness testing tool for testing, and measuring the leakage rate to be 12Pa/min under the condition of 10MPa of internal air pressure.

B. Roller drop test

The composite material is placed in a roller drop test roller, roller drop is carried out, the roller drop height is 1.8m at most, and the composite material does not crack after the roller drop height is 12 times.

C. Free drop test

And placing the composite material on a free drop test platform for free drop. The falling ground is marble ground. The height of the free falling platform is 1.8 m. And the falling is carried out from the free falling platform to different directions. The composite did not crack or chip when dropped 2 times per direction for a total of 12 times.

< comparative example >

The brittle material is a zirconia ceramic material with a set shape, the plastic material is a mixture of PBT and glass fiber, wherein the mass fraction of the PBT is 60%, and the mass fraction of the glass fiber is 40%.

Firstly, putting a zirconia ceramic material into a mould, wherein the temperature in the mould is 80 ℃;

then, a plastic material is injected and enters the surface of the zirconia ceramic material by adopting an injection molding mode of an in-mold insert, wherein the injection molding pressure is 1200bar, and the injection molding temperature is 190 ℃. A layer of plastic material with the thickness of 1mm is attached to the surface of the zirconia ceramic material.

Finally, the brittle and plastic materials are cooled at room temperature.

And (3) testing items:

air tightness test

And (3) placing the injection-molded composite material in an air tightness testing tool for testing, and measuring the leakage rate to be 250Pa/min under the condition of 5MPa of internal air pressure.

Roller drop test

The composite material in the specific shape after injection molding is placed in a roller drop test roller for roller drop, the roller drop height is 1.2m at most, and after the composite material is dropped for 8 times, the composite material is locally cracked and separated, so that the requirement of a test standard is not met.

Free drop test

And placing the injection-molded composite material with the specific shape on a free fall test platform for free fall, wherein the falling ground is marble ground. The height of the free falling platform is 1.2 m. And the falling is carried out from the free falling platform to different directions. Each direction falls for 2 times, the total number is 12 times, the composite material has local gaps, and the requirements of the test standard are not met.

In the above embodiments, the differences between the embodiments are described in emphasis, and different optimization features between the embodiments can be combined to form a better embodiment as long as the differences are not contradictory, and further description is omitted here in consideration of brevity of the text.

Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.