Application of Ion Implantation Technology in Surface Modification of Polymer Materials

Chinese figure number: TB324: A 1 Jiazi withdrawal Tim furnace only modified from the leave! Sub-injection toe current domestic research than via gl ion injection. Into the riAN, bookmark1 1 Introduction In recent decades, with the rapid development of high technology, the surface properties of various types of materials are increasingly high requirements. Therefore, the use of new technologies, new processes to improve the surface properties of the material is more and more important. Ion implantation can selectively improve the wear resistance, corrosion resistance, oxidation resistance and fatigue resistance of the material surface without changing the basic properties of the material.

2 Characteristics of Ion Implantation In the vacuum target chamber of the sub-implanter, ions of the desired element are implanted into the workpiece surface at a voltage of several tens to several hundreds of kilovolts, forming a layer different from the substrate in structure and structure. The injection layer improves the material's performance.

The surface modification of ion-implanted materials has its unparalleled advantages, mainly in the following aspects: The process of ion-implantation of the matrix is ​​a non-thermal equilibrium process. Therefore, in principle, any element can be injected into the solid, the type of the injected element, Both energy and dose can be selected and precisely controlled.

Because ions are forced into the matrix in a high-energy state, the matrix material is not limited and is not constrained by the physical alloying rules such as thermodynamics, phase equilibrium, and solid solubility. Other methods are not available. The new alloy phase.

The injected element is Gaussian after entering the matrix, and no new interface is formed. There are no defects that are easily caused by corrosion, cracking, peeling, peeling and other coatings caused by the interface, thus solving the problem of adhesion in many coating technologies. And thermal expansion coefficient mismatch problem.

Since the ion implantation process can be performed under conditions close to room temperature, there is no problem of thermal deformation, and the parts need not be reprocessed or reheated.

The ion implantation process is carried out under high vacuum conditions, free from environmental influences, and has no residue on the exterior surface of the substrate. It can maintain the original dimensional accuracy and surface finish, and is particularly suitable for the final process of high-precision components.

Ion injection power consumption is low, with the surface alloy instead of the whole alloy, saving a lot of scarce metals and precious metals, and no toxicity, which is conducive to environmental protection.

The disadvantage of the ion implantation process is that the device has a large investment at one time, a long injection time, a shallow injection depth, and line-of-sight processing, and is not suitable for modification of complex morphological members.

3 The mechanism of surface modification of the ion implanted polymer material is achieved by changing the crystallographic structure, composition, and spatial position of the molecule. It is a method that uses physical methods to achieve chemical purposes. It can do doping of any element, and the energy and dose of the implanted ions can also be arbitrarily selected, and is not limited by certain conditions in chemical methods. Therefore, the composition and structure of the material can be rapidly changed, resulting in changes in the chemical and physical properties of the material.

When ions are injected into the surface of a polymer material, its energy is lost through two major mechanisms. One is that the target atom is excited to be ionized by an inelastic collision with the valence electrons of the target atom, which is an electron blocking process; and the second is an elastic collision with the target nuclei that causes displacement of the target nuclei, which is called nuclear prevent.

Generally, the electron blockade plays a major role at low injection doses (approximately 1014 ions/cm2), and the shift of the nuclei gradually becomes apparent when the dose exceeds 5×1015 ins/cm2 or more.

Ion implantation causes polymer chain scission and cross-linking, which is the main reason for its improved surface properties. During the ion implantation process, ion energy is transmitted to the crystal lattice, and the structural surface of the polymer material undergoes drastic structural changes. With the increase of electronic energy loss prevention, the degree of cross-linking of polymer materials is also correspondingly increased, resulting in changes in the surface mechanical properties of polymer materials. The degree of improvement in this mechanical property depends on the type of ion implantation, the energy of ion implantation, and the mode of implantation (single injection or simultaneous injection). In addition, X-ray diffraction analysis shows that ion implantation also results in micro-alloy ion implantation that results in the formation of new chemical bonds. On the one hand, macromolecular chains are broken into active radicals, and radicals combine to form a three-dimensional network cross-linked structure. On the other hand, polymer materials are bombarded by ions, and carbon-nitrogen, carbon-hydrogen, and carbon-oxygen bonds are broken. Hydrogen, nitrogen, and oxygen atoms that combine hydrogen, nitrogen, and oxygen are released from the surface by quadrupole mass spectrometry. The efficiency of discharge decreases with the increase of intra-membrane damage and the injected dose. The RBS (backscattering spectrum) shows that the amorphous carbon-rich layer appears on the surface of the polymer film after ion implantation, and the resistivity of the injected film is greatly reduced.

4 Application of Ion Implantation in Surface Modification of Polymer Materials Ion implantation is an effective means of controlling surface aggregation by using physical methods to control the aggregation state of molecules. Through ion implantation of polymer materials, it can not only improve the surface mechanical properties of the material, but also Improve the electrical conductivity, optical properties and magnetic properties of polymer materials.

(1) Ion implantation improves surface hardness, and strong wear resistance improves the friction and wear properties of polymer materials by ion implantation. Ion implantation technology is applied to the surface modification of polymer materials. Chen Hui et al. 0, Si, Al, Ti, As A variety of halogens such as Ni, Ag, etc. are injected into the surface of the polymer material, thereby effectively improving the surface hardness of the material and the strong surface wear resistance. Studies have shown that during the ion implantation process, ion energy is transmitted to the crystal lattice, forming a cross-linked structure on the surface of the polymer material, which is the main reason for the improvement of its surface properties. The Xiong Dangsheng used oxygen ions of energy 450 and energy of 100 keV and a dose of 3Xl16ins/cm2 to perform 0+ infusion of nylon 1010 respectively. It was found that the wear resistance of nylon 1010 was strengthened by the 0+ injection of several processes, and it was more effective to increase the injection energy than the injection dose to the abrasion resistance of the strong nylon 1010. Tsinghua University Umbrella Jin Fu et al. respectively applied Al, Ti, and Fe ions to the epoxy resin in three doses, and studied the tribological properties of the injected modified layer using the MM200 friction and wear tester. The results show that the three kinds of ion implantation can improve the wear resistance of epoxy resin and reduce the friction coefficient. Among them, Al ion implantation has the best tribological surface modification effect for epoxy resin, and it corresponds to the minimum wear volume loss of epoxy resin. The implanted doses were Al ions 2X10 ions/cm, Ti ions 1X10 ions/cm, and Fe ions 1X1016 ions/cm2. Zhu Fuying et al. measured the amount of wear caused by injection of ultra-high molecular polyethylene C3H8+ at 80keV. It can be seen that the amount of wear on the surface of the sample after ion implantation is reduced to varying degrees, in particular, a dose of 1×10 14 ions/cm 2 is the best, and the abrasion resistance is 47.5 times stronger. Beijing Normal University, Wu Yuguang et al. chose to use an acceleration voltage of 4CkeV and an ion current density of 4X doses ranging from 5X1015 to 200X1015 ions/cm2 to perform Si ion implantation on polyester films (PET). The results show that after the Si ions are injected into the polymer, the covalent bond of the polymer is broken, resulting in broken bond or cross-linking, forming carbon accumulation and deposition of silicide particles on the surface of the polyester film, thereby significantly increasing the surface hardness of the polyester film. And Young's modulus, strong surface anti-wear properties.

Ion implantation can effectively improve the conductivity and optical properties of polymer materials, make the surface anti-static, and can be made into photosensitive materials and photovoltaic cells.

The conductive mechanism of ion-implanted polymer materials can be explained by the conductive island model: During the ion implantation process, the injected ions collide with the molecules of the injected material, along the ion implantation inside the material, the direction of the incident path forms many discontinuous, not Evenly conductive islands. When the implantation dose and energy are low, the collision probability of injected ions with the molecules of the injected material is small, and there are less conductive islands formed, so their conductance does not contribute much to the conductivity; when the injection dose is further large, the number of conductive islands is made Addition, and the size of the conductive island is rapidly increased to form a new large conductive island, so that the conductivity sharply increases; but when the dose is further increased, the number of conductive islands and the increase rate of the size decrease, so that the rate of increase of the electrical conductivity becomes slower At this point, the molecular conductance in the polymer will dominate the total conductance. With high-energy ion implantation, the resistivity decreases by more than a dozen orders of magnitude with a dose within a certain dose range. When the dose is further increased, the resistivity changes very slowly and a saturation trend occurs. The saturated resistivity value decreases with the addition of injected energy. Zheng Jianbang et al. used low-energy N+ to ion-implant the polyaniline film. The results showed that the conductivity of the film after injection increased with the increase of injection energy and dose, and the conductivity increased by 9 orders of magnitude at the same time. Stronger than. Wu Yuguang greatly reduced the resistivity of the polyester film by injecting Cu and Ni ions into the polyester film, and the ultraviolet and infrared absorption characteristics of the injected surface were significantly stronger. Sun Jianping et al. used ion implantation of poly(25 dibutoxy)-phenylacetylene (PDBOPV) with an energy of 10 ~ 35keV and a dose of 3.0X1015~4.8X1017ions/cm2 for ion implantation to modify the conductivity of PD-BOPV film. Increases with the addition of ion energy and dose. Liu Song's research shows that the surface conductivity of organic polymer materials PMMA and PE implanted with N+ is significantly improved, and the conductivity can be controlled by selecting an appropriate dose.

5 Development Prospects of Surface Modification of Ion Implantation Polymer Materials Ion implantation technology has achieved great success in the surface modification of materials, but there are still many fields worth studying. Ion implantation of polymer materials not only enhances the friction and wear properties of the surface, but also increases the surface conductivity. This technology has now become an important tool for studying the surface modification of polymer materials. Experimental studies have shown that double-ion implantation and co-injection are more effective than single-ion implantation in terms of surface modification of metallic materials. The author believes that this method can also be used for the study of surface modification of polymer materials, but no similar reports have been found in China.