Synthesis And Properties Of Intelligent Color-changing Sensing Materials With Temperature Response

Thermochromic materials belong to a class of intelligent color-change sensing materials with a temperature memory function,and the materials can autonomously sense the changes in temperature and respond to these changes.Thermochromic materials will undergo color changes under the stimulation of external temperature,which belong to a new type of functional materials and can be used in temperature indication,temperature sensing,thermal energy storage,energy-saving and environmentally-friendly smart windows,thermochromic clothing,and energy-saving building coating layer,medical,military and other fields.Although some inorganic compounds,organic compounds,hybrid molecular compounds,ionic liquids,composites and other materials have been reported to have thermochromic properties,few types of thermochromic materials have been reported.In addition,thermochromic materials are limited by the discoloration temperature and other conditions in practical applications,and may not meet the needs of certain environmental conditions.Therefore,the development of new thermochromic materials is very important to enrich the types of thermochromic materials,expand the scope of use of thermochromic materials,and improve the practicality of thermochromic materials.The development of intelligent materials promotes the progress of intelligence.The development of new functional materials is the premise and foundation of intelligent development.The research field of this thesis is mainly thermochromic sensing materials based on inorganic compounds.Based on the research of inorganic compounds,this thesis attempts to develop new thermochromic functional materials and adjust the discoloration performance of thermochromic materials through element doping,transition metal ion regulation,etc.,and conduct structural analysis,characterization and discoloration mechanism of the materials.The results obtained during the research are as follows:1.Based on three cationic crystal sites in Sm₃Fe₅O₁₂ structure,Ca²⁺-doped Sm₃Fe₅O₁₂ were designed and Ca²⁺was successfully introduced into Sm₃Fe₅O₁₂ host,the series of thermochromic materials of Ca²⁺-doped Sm₃Fe₅O₁₂2 were prepared and characterized.The samples have slight color changes with Ca²⁺doping,and the samples showed reversible thermochromic phenomenon in the temperature range from room temperature to 240^oC.When the temperature increased from room temperature to240^oC,the color of the sample gradually changed from dark green to dark brown.X-ray diffraction analysis at different temperatures is consistent,which implies that the variation in temperature did not cause a phase transformation,and the lattice parameter gradually increases with temperature,which is correlated with the lattice expansion caused by high temperature.2.Bi³⁺was successfully introduced into the main lattice of Sm₃Fe₅O₁₂ and a series of Bi³⁺-doped thermochromic materials were prepared,and compounds with different particle size were prepared by different synthetic methods and investigated.We designed heating temperature control accessories in UV-vis spectrometer and Raman spectrometer to monitor the in-situ uv-vis diffuse reflectance spectra and in-situ Raman spectra in the temperature range of room temperature to 240^oC.The band gap of the samples for Bi³⁺doped Sm₃Fe₅O₁₂ gradually decreased with increasing temperature.At the same time,the lattice parameters of the materials increase linearly with increasing temperature.Based on the previous research,the relationship between the structural change of the material and the band gap movement is explored to further understand the discoloration effect of the material.3.Multi-color thermochromic materials with transition metal elements doped were designed and prepared.Transition metal compound displayed certain color with the d-d transition in the visible region,and the transition were related to the local crystal field.Therefore,the behavior of the absorption spectrum can be affected by chaning the crystal field of the transition metal ion.In our previous work,we have investigated the thermochromic phenomenon of iron-based garnet materials.In this work,we designed the thermochromic material based on light-colored gallium-based garnet and doped with transition metal elements,and successfully prepared series thermochromic material with Cr/Mn/Fe/Co-doped Er₃Ga₅O₁₂,these materials exhibit significant thermochromic phenomena in the temperature range from room temperature to 460^oC,and we have performed structural analysis,characterized their properties and explored their discoloration mechanism on the samples.4.During the preparation and characterization of gallium-based garnet materials,we observed that the materials have strong resistance to acid and alkali corrosion.In this work,we focused on the acid and alkali resistance of Fe³⁺doped Dy₃Ga₅O₁₂materials.The samples were immersed in 10%HCl,10%HNO₃,10%H₂SO₄,and 10%NaOH solutions for 10 days to investigate the structure,mass loss,and morphology of the materials.5.Thermochromic materials that have been reported was rare.The design and development of new thermochromic materials is essential.In this work,a novel thermochromic host Ca₁₄Zn₆Ga₁₀O₃₅ were proposed.Cr,Mn,Fe,Co were successfully incorporated,series of samples Ca₁₄Zn₆Ga_10-x0-x M_xO₃₅?M=Cr,Mn,Fe,Co?were prepared and investigated.