| With the development of human society, the crucial problem is energy shortage. Solar energy is a kind of inexhaustible clean energy. But it's difficult to develop and utilize in large scale, because of its low energy density when it reaches the earth. Solar thermal power generation is an important direction of solar thermal utilization, which is one of the green economy methods leading to high power generation and the replacement of fossil energy sources. According to the problem of low efficiency in heat absorber in solar thermal power generation system, this article relies on the national 973 Program of "Design and property control of high-temperature heat transfer and storage materials", carrying out the research on absorbing materials and designation of absorber structure.In this paper, grading silicon carbide, silicon nitride and andalusite were used as the main materials to prepare andalusite bonded silicon carbide material and silicon nitride bonded silicon carbide material, which will be used as the absorbing materials in solar thermal power generation system with pressureless firing method. XRD, SEM and other modern analysis test methods were used to investigate the physical and chemical reaction, phase composition, microstructure and surface morphology of the samples after the firing.The relationship among the formula of material composition, preparation process, structure and properties were also studied.The results showed that andalusite combines silicon carbide material and silicon nitride combines silicon carbide ceramic can meet the requirement of absorbing materials in solar thermal power generation system. The absorber designed has a simple structure, which also meets the demands of solar tower heat absorber.The samples in B formula of andalusite bonded silicon carbide heat absorbing ceramics were prepared through dry ball-milling, semidry pressing and pressureless firing method with the main materials of silicon carbide with 150mesh,320mesh,700 mesh and andalusite. The properties and structure were tested through XRD and SEM modern testing methods. The results indicated that the thermal expansion coefficients decreased with the increasing of SiC content, and increased with the increasing of andalusite content. The increasing of SiC content could accrescent the oxidation weigh gaining rate, and the adding of spodumene can boost the thermal shock resistance, while lower the refractoriness.The adding of potash feldspar have worsen thermal shock resistance.The best firing temperature of best formula B2 is 1340℃Its porosity is 23.22%, water absorption is 10.68%, bulk density is 2.17g·cm-3 with a drying shrinkage of -0.02% and firing shrinkage rate of 0.69%. Besides that, the re-firing shrinkage is -0.03%, the bending strength is 86.07MPa, and the rate of intensity loss is -0.3%when the sample went through thermal shock for 20 times, which showed a good thermal shock resistance of the sample. The thermal expansion coefficient of formula B2 fired at 1340℃is 6.357×10-6℃-1, and the oxidation weigh gaining rate is 1.741mg.cm-2. XRD analysis showed that both of the main phases in the samples of series B are a-SiC, andalusite, mullite and cristobalite before and after thermal shock. The peaks of andalusite decrease, while mullite increase, and there is no change of other crystalline phases. SEM study reflected that there are little connected pores before and after thermal shock, and the diameter of the pores are 5～15μm after thermal shock, the pores are smaller than before. The small SiC grains concentrate on the big SiC grains after thermal shock. There appeared mullite woven arranging like wove in the pores and at the surface of big crystal particles which give the samples high strength and good thermal shock resistance.To further improve the thermal shock resistance and inoxidizability of andalusite bonded silicon carbide composite heat absorbing ceramic, formulas of C series were designed, and andalusite combine silicon carbide materials were prepared through dry ball-milling, semidry pressing and pressureless firing method with the main materials of 150mesh,700 mesh silicon carbide and andalusite. Testing methods such as XRD, SEM were used to test the properties and structure. The results showed the thermal expansion coefficient remains unchanged, the adding of 700 mesh silicon carbide could increase the oxidation weigh gaining rate, and the thermal shock resistance became better when the 700 mesh silicon carbide increased to 8% to 32%, but the thermal shock resistance lowered when it increased to 40%. The best firing temperature of best formula C4 is 1460℃. Its porosity is 30.74%, water absorption is 14.60%, and bulk density is 2.05g·cm-3 with a drying shrinkage of 0.03%. Besides that, the re-firing shrinkage is -0.21%, the bending strength is 32.52MPa, all of the rate of intensity loss were negative number after 30 times thermal shock, which showed a good thermal shock resistance. The thermal expansion coefficient fired at 1460℃is 6.320×10-6℃-1, and the growth rate of oxidation weight is 2.769mg.cm-2, the refractoriness is 1630～1650℃, and the thermal conductivity is 10.03W/(m-K) when the temperature is 28℃.XRD analysis showed that both of the main phases in the samples of series B are a-SiC, andalusite, mullite and cristobalite before and after thermal shock. The peaks of mullite increase, and there is no change of other crystalline phases.SEM study reflected that there are a little connected pores before and after thermal shock, and the diameter of the pores are 5～15μm after thermal shock, the pores are smaller than before. Wove structure which formed with clubbed mullite was filled by SiC grains, and these woven bodies concentrate on the big SiC grains, which gives the samples high strength and good thermal shock resistance.Formulas of D series of silicon nitride bonded silicon carbide composite heat absorbing ceramics were designed, and the samples were prepared by dry ball-milling, semidry pressing and pressureless firing method with the main materials of silicon carbide, silicon nitride and andalusite. Testing methods such as XRD, SEM were used to test the properties and microstructure. The results showed the thermal expansion coefficient decreased with the increasing of SiC content and augmented with the increasing of andalusite. Moreover, the oxidation weigh gaining rates all increased with the increasing of SiC content. Adding spodumene and potash feldspar individually combined with andalusite could improve the thermal shock resistance, while potash feldspar also could improve the strength, and the thermal shock resistance would turn bad if spodumene and potash feldspar together combined with andalusite. The best formula D has best firing temperature of 1360℃, porosity of 22.23%, water absorption of 10.32%, bulk density of 2.15g-cm-3, re-firing shrinkage is-0.19%, and the bending strength is 79.60MPa. All the rate of intensity loss of the samples are negative number after 30 times thermal shock, which showed a good thermal shock resistance.The thermal expansion coefficient is 6.401×10-6℃-1, and the growth rate of oxidation weight is 1.333mg.cm-2, the refractoriness is 1630～1650℃, and the thermal conductivity is 7.83W/(m·K) when the temperature is 36℃.XRD phase analysis showed that both of the main phases in the samples are a-SiC, mullite, silicon nitride and cristobalite before and after thermal shock. The peaks of cristobalite increase, glass phases increase, and there is no change of other crystalline phases. SEM analysis reflected that there are a few connected pores before and after thermal shock, and the diameter of the pores is 5～15μm after thermal shock, the pores are smaller than before. The crystalline grains grow well and the size is 10～20μm, which are wrapped by glass phase. These woven bodies concentrate on the big SiC grains, which gives the samples high strength and good thermal shock resistance.A heat air absorber structure of cavity style and volume style were designed, in which diversion channels of porous ceramic make the flow air stable and the temperature field uniform. The heat capacity of the absorber can play a role of heat storage which also can provide an absence heating air when the solar energy is insufficient. When there is no air flow, the radiant energy that absorber have absorbed all changes into its own thermal capacity in order to improve its own temperature for clear heat storage, which will be used for the start moment of the air absorber.
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