| Thermal insulation materials play a vital part in mitigating energy crisis and improving energy efficiency.It's also the requirements for many devices in application.Nowadays,thermal insulation materials are everywhere in our life,from chemical equipment containers,houses,ships,spacecraft and other large-scale equipment and buildings,to small household appliances such as air conditioners and water heaters.Among them,like flat-plate solar water heaters or many devices which are composed of glass,good thermal insulation properties and excellent mechanical properties are always required.Moreover,the requirements for lighter weight and safety of the thermal insulation materials are also increasingly high.Therefore,it is of great significance to study thermal insulation materials with excellent comprehensive performance,and nano-multilayer film materials are one of the most promising materials for achieving this goal.For this experiment,W and Al2O3 was used as the component material of nano-multilayer film,and W/Al2O3 nano-multilayer thermal insulation film with different period thickness was prepared by magnetron sputtering technology at room temperature.The structure and properties of the film were characterized by GIXRD,XPS,SEM,TEM,nanoindenter and transient thermoreflectance(TTR).The results showed that the individual layer in the nano-multilayer films was uniform and continuous,no fault phenomenon was observed.The interface between the layers was clear.The deposited Al2O3 film exhibited an amorphous morphology,and the W layer had a preferential orientation of metastable ?-W(210).It also exhibited an amorphous state while the periodic thickness was 5 nm.With an increase of the interface density,both the thermal resistance and hardness of the multilayer films increased,and the thermal conductivity decreased.The multilayer films with a periodic thickness of 5 nm exhibited an excellent thermal insulation and mechanical properties.The thermal resistance was 3.14×10-7 m2·K·W-1,the effective thermal conductivity was 0.36 W·m-1·K-1,the hardness reached to 8.53 GPa,and the binding force between film and substrate was 42.20 mN.The prepared multilayer films had a good thermal stability in the temperature range of room temperature to 500?.For further improving the thermal insulation performance of the material,the effects of different O2/Ar ratios on the structure and properties of partially oxidized W/Al2O3 nano-multilayer thermal insulation film were investigated.A series of partially oxidized W/Al2O3 nano-multilayer films were prepared.Through structural characterization studies,it was found that the Al2O3 monolayer in the multilayer film was amorphous,while the partially oxidized W monolayer was mainly composed of two phases,?-W and ?-WO3,and with the increase of O2/Ar ratio,the crystallinity of WO3 in the sample was getting better.Also,the interface between the partially oxidized multilayer films was clear,and the layers were uniform and continuous.The partially oxidized systems had a lower thermal conductivity than the unpartially oxidized(O2/Ar was 0)W/Al2O3 multilayer film.And when O2/Ar was 0.0125,the partially oxidized W/Al2O3 nano-multilayer film had better thermal insulation performance and better mechanical properties than other multilayer films,and its thermal resistance was 4.18×10-7 m2·K·W-1,effective thermal conductivity was 0.35 W·m-1·K-1,nano hardness reached to 8.22 GPa,and the binding force between film and substrate was 21.79 mN.And the prepared partially oxidized multilayer film still had good thermal stability between room temperature and 500?. |
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