Preparation Of Porous Silicon Ceramics With Low Dielectric Constant

At present, developed countries have adopted sual-frequency radar signals to control the missiles,which needs the attenna has the band with wide range. The band of the material is inversely proportional to the dielectric constant. So it is demanded that the attenna is made of the low dielectric constant materialsAs present,there are two ways adoped widely to prepare the low dielectric constant materials:One is choosing materials with good molecular symmetry structure as raw material;The other is introducing hole in the process of preparation of materials.In this experiment,the way choosed to prepare the low-k dielectric constant materials is introducing hole into materials.There are two ways used in this experiment to produce hole:One is that the volatile material such as graphite is used as raw materials.In the process of sintering,the graphite evaporates and produces holes;The other is that the silicon hollow spheres are used to introduce hole.The silicon hollow spheres are made in the laboratory,which are the hollow spherical materials with the diameter between 10 and 50 microns. The research of the silicon hollow spheres shows that The diameter of the silicon hollow spheres ranges from 10 microns to 50 microns.The thickness of the wall of silicon hollow spheres is between 3 microns and 5 microns.The silicon hollow spheres are amorphous.The density test,the bend strength test,the dielectric properties test,the SEM test are used to examine the effect of the hole agent and sintering additives on the properties of materials;The XRD test,the DTA test are carried out to study sintering temperature on the properties of materials made of sintering additives.The properties of the sample made with sintering additives are showed as follows:The density ranges from 1.72g/cm~3 to 2.28g/cm~3;The minimum of the dielectric constant can reach 4.54;The maxmum of the Q value can reach 478;The highest value of the flexural strength can reach 15.88MPa.Researching results of the porous ceramic samples show that:The graphite is a useful hole agent. The properties of the samples made with graphite are showed as follows:The minimum of the dielectric constant of this materials is 3.12;Q can achieve the highest value of 1149.The largest flexural strength can be reached at 14.44MPa.The density ranges from 1.08g/cm~3 to 1.43g/cm~3.The properties of the samples made with silicon hollow spheres are showed as follows:The density ranges from 1.45g/cm~3 to 1.8g/cm~3.The largest flexural strength is 22.54MPa. The minimum of the dielectric constant is 4.07.The highest value of Q is 504.The SEM of the section of the sample shows that the silicon hollow spheres don'nt collaps under the sintering temperature of 960°C.