•Surfactant-free pickering emulsion was employed to fabricate MicroPCM with polymer-silica hybrid shell.•The polymerization process can be carried out at ambient temperature only for 5 min ultraviolet radiation.•SiO2/PMMA-MicroPCM achieved a good thermal stability and the core content in the microcapsules reached 62.19%.We designed a photocurable pickering emulsion polymerization to create microencapsulated phase change materials (MicroPCM) with polymer-silica hybrid shell. The emulsion was stabilized by modified SiO2 particles without any surfactant or dispersant. The polymerization process can be carried out at ambient temperature only for 5 min ultraviolet radiation, which is a low-energy procedure. The resultant capsules were shown a good core-shell structure and uniform in size. The surface of the microcapsules was covered by SiO2 particles. According to the DSC and TGA examinations, the microcapsules has good thermal energy storage-release performance, enhanced thermal reliability and thermal stability. When ratio of MMA/n-octadecane was 1.5/1.5. The encapsulation efficiency of the microcapsules reached 62.55%, accompanied with 122.31 J/g melting enthalpy. The work is virtually applicable to the construction of a wide variety of organic-inorganic hybrid shell MicroPCM. Furthermore, with the application of this method, exciting opportunities may arise for realizing rapid, continuous and large-scale industrial preparation of MicroPCM.

•Microencapsulated PCMs were prepared by suspension-like polymerization.•Modified TiO2 nanoparticles as inorganic UV absorber were doped into PMMA shell.•The microcapsules had two functions of thermal energy storage and UV-shielding.•The microcapsules performed well in thermal storage, stability and UV-shielding.Microcapsules with thermal energy storage and UV-shielding functions were successfully prepared by the method of suspension-like polymerization in order to reduce the damage of ultraviolet light. The bifunctional microcapsules (MPCMs/TiO2) consist of n-octadecane as core material and poly (methyl-methacrylate) (PMMA) doped with titanium dioxide nanoparticles as shell material. The scanning electronic microscope (SEM) micrographs and particle size distributions showed that the as-prepared microcapsules are spherical and about 10–20 µm in average diameter. It was confirmed by Fourier transformation infrared spectroscope (FTIR) and energy dispersive spectrometer (EDS) spectra that modified TiO2 nanoparticles had been well fixed in the cross-linked network structure of PMMA shell. In addition, the results of differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA) and ultraviolet visible spectrophotometer (UV–vis) measurements demonstrated that the microcapsules exhibited high thermal storage capability, good thermal reliability and stability, and good UV-shielding property. The resultant samples of MPCMs/TiO2 may become the potential materials in the advanced applications of intelligent textile.

•Silk fibroins were used to microencapsulate PCMs using a facile method.•Mechanism of influence of surfactants on formation of MicroPCMs was indicated.•Mixed surfactants acting as emulsifiers improved thermal performances of MicoPCMs.•Mixed surfactants acting as crosslinkers enhanced mechanical strength of MicroPCMs.The microencapsulation of phase change materials (PCMs) with regenerated silk fibroin (SF) as a shell by means of SF self-assembling was studied. Nonionic, ionic and mixed surfactants were applied to increase the emulsion stability and enhance encapsulating capacity of SF microcapsules. Effects of different types of surfactants on diverse properties of PCM microcapsules including morphology, energy storage density, mechanical strength and thermal stability have been investigated. It was observed that mixed surfactants promoted significantly the formation and stability of n-octadecane/SF emulsion. With the effects of co-emulsifiers, mixed surfactants acted simultaneously as excellent emulsifiers and cross-linkers in SF microencapsulation processing. Adding mixed surfactants to n-octadecane/SF system improved the surface morphology and energy storage density, along with the mechanical strength.

•A new high thermal conductivity microcapsules were synthesized.•Thermal behavior was detected by Forward Looking Infra-red System.•Thermal conductivity is enhanced by 58%.•Silicon nitride is more economically preferred in promoting the thermal conductivity of phase change materials.Thermal behavior is one of the most important properties for phase change microcapsules in solar energy storage. Here, a new type of phase change microcapsules was synthesized based on n-octadecane core and polymethylmethacrylate shell supplemented with modified silicon nitride powders, aiming to achieve improvement of thermal property in the phase change materials. SEM micrographs showed that the as-prepared microcapsules have a regular spherical shape with a well-defined core-shell structure. FTIR curves and EDS spectrogram demonstrated that silicon nitride can be well cross-linked with microcapsules after surface modification. In addition, TGA, forward looking infra-red system and DSC (before and after 500 heating and cooling cycles) analyses were performed to investigate the thermal property of the as-prepared microcapsules. The results indicated that the microcapsules have high thermal storage capability, enhanced thermal reliability and stability, and increased thermal conductivity. Especially, the thermal conductivity of microcapsules is enhanced by 56.8% compared with that of the microcapsules without the addition of silicon nitride.

•A new type of microPCMs with an additional function of thermochromic performance was synthesized.•Provide a feasible approach for endowing microPCMs an additional function.•The microcapsules present dual functions of thermochromic and latent-heat storage feature.•The microcapsules achieved a good thermal stability and high thermal storage capability.In this study, a new type of microencapsulated phase change materials (microPCMs) with an additional function of thermochromic performance was designed and synthesized successfully. Thermochromatic pigments were firstly assembled on the interface of n-octadecane droplets in oil/water emulsion. And then a thermochromic pigment/PMMA shell was fabricated through suspension-like polymerization. The microstructures and chemical compositions of the resultant microcapsules were investigated by scanning electronic microscope (SEM) and Fourier transformation infrared spectroscope (FT-IR). SEM images display that these microcapsules presented a spherical shape and well-defined core-shell structure. According to DSC and TGA examinations, these dual functionalized microPCMs exhibited excellent thermal energy storage-release performance, high thermal storage capability (higher than 97%), and good thermal stability. In addition, these microPCMs successfully achieved thermochromic function as their temperature exceeded the target temperature. The dual functionalized microcapsules developed in this work showed great potential in applications for solar energy storage, thermo-sensors, food and medicine package and intelligent textiles or fabrics, etc.

•Microencapsulated n-octadecane with TiO2 was prepared in o/w emulsion.•A green solvent was used as continuous phase in the emulsion.•The process is simple, high-efficiency, and environmentally friendly.•The microcapsules have high heat storage capability and good thermal stability.Microencapsulated n-octadecane with titanium dioxide (TiO2) shell was prepared by a sol–gel method in a nonaqueous oil-in-water (o/w) emulsion using a green solvent as the dispersion medium. The morphology, chemical structure, and crystalloid phase of the resultant microcapsules were determined by scanning electronic microscope (SEM), Fourier transformation infrared spectroscope (FT-IR), and X-ray diffractometer (XRD), respectively. The differential scanning calorimeter (DSC) and the thermogravimetric analyzer (TGA) were used to investigate the thermal properties and thermal stabilities of the samples. The resulting microcapsules presented spherical shape with average size of 2–5 μm. The results of FT-IR and XRD showed that n-octadecane was well microencapsulated in TiO2 shell. DSC and TGA results indicated that the samples exhibited good performance of storing and releasing the latent heat during phase-change cycles and high thermal reliability. The microencapsulation process in this study is simple, high-efficiency, and environmentally friendly. The microencapsulated n-octadecane with TiO2 shell will be a potential candidate material for thermal energy storage applied in the fields of solar energy storage, building energy conservation, air-conditioning systems, and waste heat recovery.

•Adding a little amount of 20% NaCl solution is more beneficial in thermal performance.•The reduction in supercooling degree is up to 6 °C.•The latent heat capacity of PCMs is improved.•The crystallization mechanical PCMs was employed to explain the phenomenon.Phase change materials (PCMs) are the effective substances for thermal energy storage. Unfortunately, various problems such as high supercooling degree, low crystal growth rate and poor thermal conductivity greatly hinder the large-scale utilization of PCMs. The present study focuses on improving the crystallization and decreasing supercooling degree by adding various proportions of NaCl/NaCl solutions into the n-octadecane-based PCMs for thermal energy storage. The experimental results show that 20 wt% NaCl solutions have the greatest effect on the thermal performance of PCMs. The supercooling degree has been minimized up to 6 °C with the addition of NaCl. It can not only promote crystallization under 1 wt% addition rate, but also enhance latent heat storage performance. Such observations have been verified by the kinetics of crystallization. The researches on supercooling could advance the application of PCMs on solar energy.

•Silicon nitride was employed to enhance the performance of PCM.•Modified silicon nitride takes more advantage than unmodified silicon nitride.•The high latent heat capacity is 121.11 J/g with 10% addition rate.•The mechanical strength of MPCM was four times higher than that of PCM.Silicon nitride was applied to enhance the thermal performance and mechanical properties of phase change microencapsulation (PCM) based on polymethyl methacrylate (PMMA) shell and n-octadecane core. ‘A molecular bridge’ was constructed to modify the surface of silicon nitride and to eliminate boundary layer between inorganic silicon nitride particle and organic PMMA shell. Thus, an innovative modified silicon nitride phase change microencapsulation (MPCM) with which silicon nitride uniformly disperses in PMMA as shell and n-octadecane as core was successfully prepared. The microencapsulation was characterized using Fourier transformed infrared spectrophotometer (FTIR), field emission scanning electron microscope (FESEM), differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA). A micro/nano-hardness tester was also employed, in order to investigate mechanical performance of shell. The result shows that the MPCM containing 66.4% n-octadecane has 121.11 J/g latent heats of melting and 122.01 J/g latent heats of crystallization with the modified silicon nitride percentage up to 10 wt.%. The modified silicon nitride could not only enhance thermal performance, but also improve mechanical strength up to 16.24 mN which is 4 times higher than that of PCM. Additionally, wrinkles on the surface of MPCM improved special surface area as well as adaptation of volume changes during phase change process. The prepared MPCM is expected to exhibit better performance in solar energy storage technology.