The preparation and micwave-absorbing behavior of nanosize PSZFe magnetic particles were studied.Nanosize PSZFe magnetic particles were prepared as following:nanosize Fe particles generated by themal decomposition of Fe(CO)-5 in organic solvents were encapsulated with synthesized polysilazane(PSZ) precursor and then irradiated under ultraviolet light.PSZFe particles were characterized by using transmission election microscope(TEM),X-Ray powder diffraction(XRD) and vibrating sample magntometer(VSM),and their microwave-adsorbing properties were measured by means of a vector network analyzer.The influence of the polysilazation layer on corrosion and magnetization of PSZFe particles and the relationship between polysilazation layer and micwave-absorbing behavior of PSZFe particles were investigated.Results showed that the average diameter of PSZFe particles was 30 nm,the structure of iron in PSZFe magnetic particles was α-Fe.The formation of a PSZ layer on nanosize Fe particles enchanced the corrosion resistance of PSZFe.In addition,PSZFe particles coated with 3 wt% PSZ demonstrated high corrosion resistance and fine microwave-absorbing ability as well.The reflection loss was less than -10 dB in the range of 9^8～16 GHz,and a reflection loss value of -20 dB was detected at 13 GHz.
The microwave-absorbing behavior o f substituted M-type barium ferrite nano-particles was investigated.T he nano-particles were synthesized wi th coprecipitation-melted salt method.For the purpose of comparison,c orre-sponding micro-particles were also prepared through direct coprecipitation and sintering.XRD and TEM of th e nano-particles showed that the ferr ite was hexagonal in structure and wi dely distributed in size with partic le size being less than 100nm,the complex permittivity and permeability of a 1.50mm thick specimen and a 1.40mm thick specimen containing 60%by weight of substituted M-type barium ferrite n ano-particles and micro-particles were measured respectively in X band(8.2～12.4GHz )range,from which the reflection loss(R.L.)of microwaves was calculated and two comparative abso rption curves were given.The results showed that the synthetic nano-particles could well absorb microwaves in X ban d.The absorption was larger than 10dB in the range of 9.2～12.4GHz while the maximum absorption was 38.6dB at10.6GHz.
The preparation and microwave absorbing behavior of micrometric silica modified platelet iron particles (SMPLIP) were investigated. Through precipitation, hydrothermal reaction, silica modification and reduction with hydrogen, micrometric porous SMPLIP were yielded. The permittivity values of SMPLIP had been significantly decreased due to the presence of silica. Measurements and calculations showed that a 1.93mm thick sample containing SMPLIP as much as 60%by weight was capable of absorbing X band(8.2～12.4GHz) microwaves with reflection loss being greater than -10dB within the frequency range of 8.2～11.36GHz, while the maximum reflection loss was -14.8dB at 9.4GHz. The results had also shown that it was practicable to prepare thin, light weight microwave absorbent with SMPLIP.
