Study On The Composite Technology Of High-performance Al-Si@Al₂O₃ Phase Change Capsule And Ceramic For High Temperature Application

The energy storage technology（EST）can solve the problem of mismatching between energy supply and demand in time and space through storing unnecessary thermal energy and releasing it when needed.The phase change materials is the key of the above technology.The Al-Si phase change materials（PCMs）,which possess high energy storage capacity and excellent thermal conductivity,is of great value in industrial application.However,it is difficult to encapsulate because of the corrosivity of molten Al-Si in the high temperature,which limites its large-scale applications.In this paper,in order to solve the problem of encapsulation,the core/shellα-Al₂O₃/Al-Si microcapsule materials and alumina porous ceramics subtrate have been prepared.Meanwhile,the PCM composite materials combining alumina ceramics and PCMs have been prepared.Some conclusion can be drawn follows:（1）The core/shell Al-Si@Al₂O₃ phase change microcapsules was prepared with atmospheric pressure hydrothermal method and heat treatment.It revealed that the maximum latent heat value of 202 J/g can be achieved after sintered at 900°C.Through7 thermal cycles,the latent heat of the samples was decreased by only 5%.SEM revealed that the sample possessed core-shell structure and the shell thikness was about500nm.（2）Porous alumina-mullite ceramics were prepared using the raw materials of mullite,tabular corundum,α-Al₂O₃ micro-powder,silica powder as principal constituents.Polystyrene spheres（PS）was used as a pore-forming agent and the phase s of silica sol andρ-Al₂O₃ powder was applied as binder.It showed that with the PS addition increasing from 0 vol%to 50 vol%,all the performance of the bulk density,cold modulus of rupture,cold crushing strength,the hot modulus of rupture and the thermal conductivity of the specimens decreased correspondingly.The in-situ formed mullite bonding in the matrix can increase its hot modulus of rupture to 2.64 MPa when the porosity is 61%.（3）The study on composite phase change ceramics reaveled that the bulk density of specimen decreased and the cold crushing strength increased with the increase of MEPCMs content.Meanwhile,the ratio of residual flexural strength increased from60%to 90%.When the heat treatment temperature exceeded 900°C,a large number of Al would be oxidized.The results of SME exhibited that MEPCMs comprise of core-shell structure.The certain gap between the core and shell can tolarant the stress during thermal cycling.