Preparation And Properties Of Paraffin@Lead Tungstate/Silicone Rubber Phase Change Composites

With the rapid growth of fossil fuel consumption and the continuous growth of energy demand,it is essential to improve energy efficiency and develop new renewable energy.Phase change materials?PCMs?,as thermal energy storage materials,are considered as an excellent candidate to reduce excessive dependence on fossil energy.However,organic solid-liquid PCMs,as the most commonly used PCMs,tend to diffuse to the surface and leakage during the phase change process.Microencapsulated phase change materials?MEPCMs?are formed by encapsulating PCMs into the shell material,which can effectively solve these problems.In order to achieve latent heat storage function in the field of nuclear technology,lead tungstate?PbWO₄?,an important gamma radiation shielding material,is used as the shell of MEPCMs,and paraffin?Pn?is used as the core of MEPCMs to synthesize bifunctional inorganic shell phase change microcapsules.At the same time,in order to study the performance of the bifunctional MEPCMs in the application,MEPCMs were added to the silicone rubber?SR?matrix to prepare SR/MEPCM composite materials.The main contents of this thesis are the following:?1?A series of Pn@PbWO₄ MEPCMs with different core/shell mass ratios and lead-to-tungsten molar ratios were successfully prepared by self-assembly and in-situ precipitation methods.MEPCMs exhibit perfect spherical morphology,with diameters ranging from 400nm to 1?m.Under the protection of the PbWO₄ shell,MEPCMs have good heat storage capacity and thermal stability and enhanced heat conductivity and leakage prevention.When the core/shell ratio reaches the highest,the latent heat of MEPCMs is 125.8 J/g and the highest thermal conductivity is 0.66 0.66 W/?m?K?.The encapsulation efficiency of MEPCMs with different WO₄^2-/Pb²⁺molar ratios is above 73%.As the core/shell ratio decreases and the WO₄^2-/Pb²⁺molar ratio increases,the gamma-radiation shielding performance of MEPCMs is gradually increasing.?2?A series of novel thermoregulated gamma radiation shielding materials were prepared by using MEPCMs as phase change functional fillers and SR materials as the matrix.The series of composites have different filling amounts of MEPCMs and different core/shell mass ratios of filled MEPCMs.The scanning image results showed that the MEPCMs were successfully added to the SR,and have intact and evenly distributed shape without cracking.SR/MEPCM composites have good heat storage properties,the maximum latent heat can reach 52.72 J/g,and have enhanced leakage prevention,thermal conductivity,and mechanical properties.The tensile strength can reach 0.6261 MPa,which is superior to SR materials.Compared with pure SR materials,SR/MEPCM composites have excellent temperature regulation and gamma-radiation shielding capabilities.The mass attenuation coefficient of SR/MEPCM composites with MEPCMs filled has increased significantly,the highest being the core/shell ratio of 1:2,which was 2.05 cm²/g at an energy of 105.3 KeV.That was an increase of 144.05%over the pure SR sample of the same condition.