| Nowadays,the missile plays an important role in modern war,and the precision of guidance system determines the advancement of missile.The radome,the shell of the missile’s head that is responsible for the guidance function,is usually made of quartz composite ceramic.Although the quartz composite ceramic meets a series of demanding requirements for the thermal and electrical performance,its own high porosity of 25%and a large number of Si-OH bonds on the surface determine the characteristics of water absorption and moisture,which will seriously affect the dielectric and wave permeability of quartz materials,leading to the decline of the accuracy of guidance system.The traditional organic resins,using as hole sealing materials,have natural disadvantages in heat resistance and weather resistance,and which tend to crack at high temperatures to produce carbon residue and will cause the absorbing effect.To solve such problem,the low temperature glass glaze was innovatively developed as hole sealing materials in this research work.Compared with the common porcelain glaze with the sintering temperature of 1100℃,a series of low temperature lead-free glass glaze with the preparation temperature lower than 560℃have been designed and studied systematically,and which can well meet the needs of moisture-proof and wave-permeable.The topic also discusses the common glaze defects and the related parameters in processing.The main research contents and results are as follows:（1）After screening the raw material system of low temperature glass glaze in the early stage,the experimental scheme around bismuth system was determined.According to the glass network system theory,the glass forming body,the glass outer body and the enhanced melting components were selected,and the core components were determined as Bi2O3,B2O3,Zn O and Si O2,respectively.Through a series of prepatation processes including melting at 1050℃,quenching in water at 800℃,wet grinding and drying,XRD analysis showed that amorphous powder of glass glaze was successfully prepared.（2）It is found that,with the increase of B2O3 content,the glass network tends to be three-dimensional,and leads to the rise of the Tg and Tf of glass powder,indicating that B2O3 acts as a network forming body in the network.However,the glass network structure changes little with the increase of Zn O proportion,and the corresponding Tg and Tf increase slightly.Thus,Zn O acts as an outbody of the network in the system and does not directly participate in the network composition.The effect of single or mixed doping of sodium and potassium oxides on the properties of glass powder was also studied.It was found that the effect of single doping of sodium oxide was the best when the total amount of doping was the same.Its Tg and Tf were385℃and 447℃respectively,which had the potential application for the ultra-low temperature sintering below 500℃.The dielectric properties of our materials are tested,and the dielectric constant is less than 2.7 and dielectric loss is less than 0.03 at high frequency,meeting the requirements of the transmitting and receiving of the electromagnetic wave.（3）The glaze defects and the related processing parameters were studied,and the ball milling time of 2h and two times brush coating process with enough thickness were determined.Glycerin was innovatively used as the glaze solvent,and it was found that glycerin had good leveling property and proper viscosity when applied to the surface of Si O2/Si O2 body,which was conducive to produce uniform glaze.The optimum components,sintering temperature and sintering curve of the samples were determined by the means of radial shrinkage,SEM,XRD and other characterization methods,and the defects of glaze shrinkage,pinhole and crack are greatly improved.（4）Group C and Group D glazes were sintered at low temperature（500-560℃）according to the optimized process parameters.The quality of glaze was characterized by appearance morphology,waterproof performance test and SEM.The results show that C4 and D1-D3samples have good sealing performance and have practical value,among them,D3 has the best performance,and the water absorption rate is as low as 0.098%,0.148%and 0.012%respectively in the three kinds of waterproof performance tests of normal temperature immersion,high temperature water vapor and sea fog simulation.Which can replace the traditional silicone resin.After glazing,the contact angle of the surface of the Si O2/Si O2 body increases significantly and it is not easy to hang water.In general,this thesis work covers the design and the study of the glass powder glaze formula,preparation process,glazing process,sintering process system and a series of performance tests.The cryogenic glass glaze was successful prepared and found to possess good moisture-proof and wave-permeable performance.This research paves the way of the novel use of glass glazes for the radome systems. |
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