Light Electromagnetic Wave Shielding Preparation And Properties Of The Composite Coatings

It is said that the electromagnetic wave is the fourth pollution because it not only hurts people's organ, but also affects the electrical equipment. We can use the electromagnetic shielding dope to coat on the surface of the source of electromagnetic wave or anywhere we want to keep out of electromagnetic wave. However, the common dope which is widely used now contains silver, nickel, copper and other metals. And the metals would deposit in the whole dope which is also with a large density because of the large density of metals. What's more, the wave consuming theory in the shielding materials is a popular theory that is widely researched now.So, in this research, we use the hollow glass particle whose diameter is between 50-100μm, accumulation density is about 0.3g/cm³ as the basal body, then coat silver, ferro-nickel alloy on the surface of it in the method of electroless plating. Then, coat silver on the surface of ferro-nickel alloy glass particle and coat ferro-nickel on the surface of silver glass particle to make out the particle with strong electric ability and outstanding magnetic ability. Then, we use the apparatus of SEM, EDS, XRD, electric resistivity measure device, magnet measure device, Gan-gravity bottle to measure the surface pattern, element, phase, electric resistivity, magnet, density of the electroless plating particle.Then we take the four particle, which are Ag/particle, FeNi/particle, Ag/FeNi/particle, FeNi/Ag/particle, to mix with the acroleic acid separately to get the four different dope. We measure the dope's electric ability with the method of coating on flat glass and the electromagnetic wave shielding and depletion with the device of Agilent S-8720ET vector network apparatus and Agilent E 8363 PNA network apparatus which are fit in different frequency. And we also measure the electric constant, magnetic conductivity in different frequency. Then we compare the different particle, volume percentage, thickness, and find out the relationship between these parameter and the electromagnetic wave shielding ability.In the research of particle electroless plating silver, we confirm the best reaction parameter and coating parameter, those is: AgNO₃ 17.5g/L,NaOH7g/L, HCOH11.0mL.L, and with the room-temperature, 90min's time. In this method, the utilization ratio of silver is about 85%. We can change the loading capacity in order to make out particle with different silver percentage. The particle's electric resistivity can get to 0.0023Ω·cm and the density is 0.75g/cm³ with the silver content of 30wt%.In the research of ferro-nickel electroless plating, we confirm the best parameter, it is: NiCl₂·6H₂O 7.0g/L, FeSO₄(NH₄)₂SO₄·6H₂O 7.8g/L, NH₃·H₂O 37.0mL/L, C₄H₄KNaO₆·4H₂O 60.0g/L, NaH₂PO₂·H₂O 29.0g/L. Take the half of NH₃·H₂O and NaH₂PO₂·H₂O and mix them with water and used it as dripping liquid. The temperature is 75℃, dripping time is 60min and whole reaction time is 90 min. The utilization ratio of ferro-nickel can be about 90%. We can also change the loading capacity to make out particle with different alloy just as plating silver, the ratio of ferro and nickel is about 1:6, if the alloy percentage is about 32wt%, the particle's density is about 0.8g/cm³, and it also have outstanding magnet ability. The remnant magnetism is 2.5emu/mL, coercive force is 0.8kOe(63.6kA/m), saturation intensity is 5.9emu/mL.In the research of electro-magnet particle, we can plating silver on the surface of ferro-nickel/particle to get the particle with 34wt% silver and 29wt% ferro-nickel, whose density is.98g/cm³, and we can also plating ferro-nickel on the surface of silver/particle to get the particle with 29wt% ferro-nickel and 21wt% silver, whose density is 0.88 g/cm³. The former's electrical resistivity is 0.012Ωcm, coercive force is 0.9kOe, remnant magnetism is 1.2emu/mL while the latter's electrical resistivity is 0.19Ω·cm, coercive force is also 0.9kOe and remnant magnetism is 3.0emu/mL.In the research of electro-magnetic compound particle, it shows that the particle has a good plating ability and electric ability if the volume percentage is 40%. The Ag/particle dope and Ag/FeNi/particle's electrical resistivity is 0.42Ω·cm and 0.9Ω·cm. So the dope made from these two electric particle have a good electromagnetic wave shielding ability. It can get a shielding effectiveness of-35dB of 1mm, and -43dB of 2mm because the shielding is affected by the dope's thickness.On the other hand, the dope made from the ferro-nickel/particle and ferro-nickel/silver/particle's shielding ability is not as good as silver particle dope, but they have certain electromagnetic wave depletion ability. Compare with the shielding ability, ferro-nickel/silver/particle's dope is strong than ferro-nickel/particle's dope. The former's shielding effectiveness can be -16.5dB with the thickness of 1mm, while the latter's is only -13dB with the same thickness. What's more, we can deduce the dope's depletion ability from the reflecting intensity of electromagnetic wave. The ferro-nickel/silver/particle dope's reflecting intensity is -1.0dB while the ferro-nickel/priticle dope's is -2.8dB and the silver/ferro-nickel/particle dope's is -0.5dB, the silver/particle dope's is -0.3dB with the same thickness of 1mm.Use the Ag/ferro-nickel/particle dope that contains 34wt% silver and 29wt% ferro-nickel to prepare the dope. Its density is 0.93g/cm³ and more lower than the dope with same volume percentage of silver particle, whose is 4.5g/cm³, and these two dope have nearly same electromagnetic wave shielding ability, which are both about -35dB.