Study On Preparation And Properties Of Electroless Plated Functional Particles And Their Flexible Conductive Film

In recent years, flexible electronic conductive materials have a rapid development because of their excellent mechanical stretchability and high electrical conductivity. In other words, there are little variation of electrical conductivity under the large tensile strain(100%) and hundreds of stretching cycle,which have potential application in flexible sensor, flexible thin film solar cells, flexible supercapacitor and so on. At present, the main conductive fillers are carbon nanotubes(CNTs) and their hybrid materials. However, large-scale production is limited because of their high cost and complex preparation technology of conductive fillers. The key way of industrialization is to develop low cost and high electrical conductivity of filler, and design robust structure of flexible conductive film. In this paper, Co, Cu and Ag flexible conductive film were prepared which electroless plated conductive composite particles including Co/glass microspheres(or fibers), Cu/glass microspheres(or fibers), and Ag/fibers composites(For short as Co/GMs(or GFs), Cu/GMs(or GFs) and Ag/GFs) were served as conductive filler, and liquid silicone rubber was used as flexible matrix.The main research contents and results were listed as follows:(1) The influences of electroless cobalt solution temperature, contents of complexing agent, reducing agent and p H adjusting agent and time parameters on the microstructure and conductivity of Co/GMs(or GFs) electromagnetic composite particles were systematically studied. Results showed that the layer of Co/GMs(or GFs) composites was smooth, dense, and complete, with strong bonding strength at the optimum technological conditions, showing the close-packed hexagonal structure(hcp). The volume resistivity of Co/GMs and Co/GFs composites were 3.50×10-3 Ω·cm and 4.20×10-3 Ω·cm, respectively. In addition, the saturation magnetization intensity of Co/ GMs composites was 21.1 emu/g, and the coercive force was 382.9 Oe, which revealed obvious soft magnetic property.(2) Herein, hydrazine hydrate was regarded as reductant, the effects of electroless copper solution temperature, the main salt, complexing agent, p H adjusting agent dosages on the microstructure and the conductivity of Cu/GMs conductive composite particles were systematically investigated. The results showed that the volume resistivity was 4.28×10-4 Ω·cm at optimum conditions which owing good microstructure, and the copper coating exhibited face-centered cubic(fcc) crystal structure. The layer of Cu/GFs conductive composites was consisted of closely packed Cu particles with 300~500 nm under Na3C6H5O7·2H2O/NH3·H2O complex system, and the layer was uniform, density, and no extra particles. However, when EDTA·2Na/Na OH was used as complexation system to prepare Cu/GFs conductive composites, there were extra particles surrounding the copper coating. The volume resistivity of Cu/GFs conductive composites under two types of complexing system were 5.78×10-4 Ω·cm and 1.0×10-3 Ω·cm, respectively, both showing fcc crystal structure.(3) The innovative design concept of "sandwich" structure(matrix/(fillers+matrix) /matrix) flexible conductive membrane was proposed, and large-scale flexible conductive membrane was prepared by flow casting method at room temperature, which Co/GMs and Co/GFs composites were regarded as conductive fillers, and liquid silicone rubber was served as the flexible matrix. In this paper, Co/glass fiber flexible conductive membrane was prepared, and the conductivity, tensile strain electrical conductivity and magnetoinductive effect at different Co/GFs contents were studied. The experimental data showed that the volume resistivity of "sandwich" structure Co/GFs film was 0.464 Ω·cm when the filler contents was 23.08 wt.%, and the volume resistivity was 8.54 Ω·cm at strain of 100%. With the increasing intensity of magnetic field, the volume resistivity decreased first and then increased, and the electrical conductivity of the parallel and vertical direction were different. When the intensity of magnetic field was 100 m T, both the volume resistivity of the parallel and vertical direction reached to the minimum value of 0.15 Ω·cm and 0.21 Ω·cm. However, "simple" structural film showed poor conductivity, and more obvious conductive anisotropy. The volume resistivity increased with the increasing strength of the magnetic field.(4) Cu flexible conductive films including "simple" and "sandwich" structure were prepared using Cu/GMs and Cu/GFs composites as conductive filler, liquid silicone rubber as the flexible matrix. The influences of fillers, solvent, curing agent contents on the conductivity and mechanical property of "sandwich" Cu/glass fiber flexible film were studied, and focused on analysis the mechanical-electrical conductivity and oxidation resistance of Cu/glass fiber flexible conductive membrane at different filler contents. Experimental results exhibited that the volume resistivity of "sandwich" structure Cu/GFs film was 0.0248 Ω·cm when the filler contents was 13.79 wt.%, and up to 0.0765 Ω·cm at strain of 100%. After repeatedly stretched for two hundred times, the conductivity became 0.0534 Ω·cm and showing good luminous effect with the LED connection. However, "simple" Cu/GFs film showed poorer electrical conductivity, mechanical-electrical conductivity and oxidation resistance than "sandwich" Cu/GFs film.(5) Based on the research of Cu flexible conductive film, "sandwich" structure of Ag/GFs flexible conductive film with different content of Ag/GFs composites was prepared by using the same process. By mean of analyzing its mechanical-electrical conductivity and oxidation resistance at different Ag/GFs contents, we found that the percolation threshold of "sandwich" structure Ag/GFs film was low at 1.5 wt.%, and the dimension parameter was 1.787, belonging to the typical three dimensional conductive network. When the content of Ag/GFs composites was 13.79 wt%, the volume resistivity of film increased from 0.0434 to 0.281 Ω·cm when the tensile strain changed from 0 up to 100%. The electrical conductivity changed a little after repeatedly a hundred of stretching cycles, and showing more excellent oxidation resistance for the conductivity was almost no change which stored at room temperature for two months, and the tensile strain had a linear relation with the log of relative volume resistivity flexible conductive membrane by linear fitting.