Distinct Core-shell Structure Research Articles

Preparation of TiO2 hybrid SiO2 wall environment-friendly microcapsules based on interfacial polycondensation: Realize the integration of self-cleaning and self-healing functions

The purpose of this study is to extend the service life of decorative coating by repairing micro-cracks with self-healing microcapsules, while giving them hydrophobic self-cleaning and photocatalytic self-cleaning functions. The interfacial polycondensation approach was employed to synthesize TiO2/SiO2 hybrid microcapsules with self-cleaning and self-repairing capabilities. These microcapsules were made by employing TiO2 as the photocatalyst hybrid SiO2 wall material and linseed oil as the core material. The attributes of the microcapsules, including their particle characteristics, micromorphology, chemical structure, thermal stability, and self-cleaning properties, were evaluated. Additionally, the impacts of self-cleaning and self-repairing on coatings were also examined. The findings indicate that the microcapsules possess a rough surface, excellent sphericity, separation, and thermal stability, as well as a distinct core-shell structure. Moreover, the hybrid microcapsules exhibit a disintegration rate of over 70.0 % towards the 10.0 mg/L methylene blue solution. The contact angle can be augmented to 131.3°. At a microcapsule concentration of 20.0 % in the coating, the degradation rate of methylene blue is 44.4 %, the self-repairing rate of microcracks is as high as 58.7 %, and the contact angle measures 91.2°.

The preparation and luminescence properties of Gd2SiO5:Tb3+@SiO2 core-shell spherical particles

Rare-earth spherical particles (RE-SPs) have garnered significant interest as nanomaterials for biomedical applications due to their high luminescence intensity and tunable luminescence lifetimes. In this study, Tb3+-doped Gd2SiO5@SiO2 (GSO: Tb3+@SiO2) core-shell spherical particles were prepared by coprecipitation and Stöber methods. Firstly, the phase transitions and core-shell structures of GSO:Tb3+@SiO2 SPs during preparation were discussed. The obtained core-shell SPs exhibited excellent dispersion and a well-defined spherical morphology with sizes ranging from 250 to 350nm. Secondly, the luminescence properties of GSO:Tb3+@SiO2 SPs were investigated, delving into the concentration quenching mechanisms of Tb3+ ion and the energy transfer (ET) from Gd3+ to Tb3+ in SPs. Thirdly, the potential biomedical applications of the GSO:Tb3+@SiO2 SPs were evaluated by examining properties such as radioluminescence, luminescence stability and surface charge. The results of present work indicates that the obtained novel spherical particles material with distinct core-shell structures has potential application in X-ray induced photodynamic therapy (X-PDT).

Carboxymethyl cellulose-assisted preparation of magnetic metal–organic framework nanocomposites with antifouling for efficient uranium enrichment

A magnetic metal–organic frameworks nanocomposite (FCMCZA) was prepared by solvothermal and in situ growth method for efficient antifouling and uranium enrichment. A series of characterization tests were carried out by SEM, XRD, XPS, FTIR and N2 adsorption–desorption analyses. The FCMCZA exhibited the distinct core–shell structure with high specific surface areas (793.86 m2/g) and abundant functional groups. The saturated magnetization and algae death rate of FCMCZA reached 33.5 emu/g and 41 %, respectively. The maximum adsorption capacity of FCMCZA was 238.66 mg/g at pH 8.0, calculated from Langmuir model. Importantly, the removal capacity of FCMCZA remained 87.29 mg/g after four cycles. The high removal rate (62.9 %) and uranium uptake (11.7 μg/g) in actual seawater further proved its application potentiality.

Self-ratiometric photoluminescence carbonized polymer dots with Junas structure for hypochlorite selective sensing

The Janus structure of carbonized polymer dots (CPDs) is characterized by an independent yet interdependent core and shell structure, potentially enabling them to function as a self-ratiometric photoluminescence (PL) sensor. However, to our best knowledge, the current lacking understanding and development of the Janus structure of CPDs lead to the unfortunate loss of its position as PL sensors that could have supported life analysis to some extent. Therefore, it is crucial to comprehensively explore the structural characteristics of CPDs and furtherly develop its potential as self-ratiometric sensors. Herein, green and red double-emitting CPDs has been rationally designed and synthesized, incorporating a distinct core-shell structure to create a self-ratiometric sensor for hypochlorite (ClO−). Leveraging the low toxicity and high-water solubility of CPDs, we have successfully achieved exogenous and endogenous ClO− sensing in cells. This approach offers a novel strategy for developing CPDs-based sensors and sets the stage for a more in-depth exploration of the Janus structure of CPDs.

Preparation and properties of PCL coaxial electrospinning films with shell loaded with CEO and core coated LEO nanoemulsions

During storage and transportation, the reduction of microbial contamination and management of the exudation of fluids from the fish can effectively mitigate spoilage and degradation of fish fillets. In this work, the coaxial electrospinning films loaded with natural plant preservatives, namely laurel essential oil (LEO) and clove essential oil (CEO), were prepared by the coaxial electrospinning method synergistic with nanoemulsion techniques, and the hydrophilic preservation pads were prepared. The morphology of the film fiber is clear, without beads or damage, with fiber diameters falling within the 230–260 nm range. It has a distinct core–shell structure, exceptional thermal stability, and strong antibacterial and antioxidant properties. The core–shell structure of the fiber subtly regulates the release of preservatives and significantly improves the utilization efficiency. At the same time, the synergistic use of two essential oils can reduce the amount while amplifying their effectiveness. The pads significantly slowed down the increase of key indicators of spoilage, such as total viable count (TVC), pH, thiobarbituric acid reactive substances (TBA), and total volatile base nitrogen (TVB-N), during the storage of the fish fillets. Furthermore, the pads effectively slowed down the decline in water-holding capacity, the deterioration of textural qualities, and the negative changes in the microstructure of the fish muscle. Ultimately, the pads notably delayed the spoilage of fish fillets, extending their shelf life from 5 d to 9 d. The efficient utilization of biological preservatives in this film can provide technical support for the development of food preservation materials.

Efficient adsorption of Congo red (CR) dye onto novel lignin-based magnetic core-shell adsorbent: Synthesis, characterization and experimental studies

BackgroundFurfural residue is a by-product in the furfural production from the biomass, and enriched in cellulose and lignin. Lignin is considered efficient candidates for the preparation of bio-based adsorbents because of a variety of functional groups and reactive sites involved. MethodsIn this study, we prepared the tunable covalent binding of the aldehyde-based furfural residue lignin onto amine-functionalized Fe3O4 magnetic nanoparticles using cyanuric chloride as a chemoselective cross-linker. The novel lignin-based magnetic adsorbent in core-shell structure was reported for the first time to remove Congo red from aqueous solution. Significant FindingsA distinct core-shell structure is formed, according to the SEM, TEM, FTIR, BET, XPS, and VSM techniques. Adsorption studies suggested that endothermic processes occured for CR adsorption onto AFRL@AMNP, and both pseudo-first and pseudo-second order models could provide a good description of the adsorption kinetics. The Langmuir model estimated the qmax of CR by AFRL@AMNP were 218.2 mg/g at 290 K. According to FTIR, XPS, and DFT calculations, electrostatic interactions, hydrogen bonds, and π-π interactions were identified as main mechanisms for CR onto AFRL@AMNP. More importantly, due to the incorporation of Fe3O4 magnetic nanoparticle, AFRL@AMNP can be easier to separate from the aqueous solutions and be reused.

Heat-treated alginate-polycaprolactone core-shell nanofibers by emulsion electrospinning process for biomedical applications

Fabrication of Core-shell nanofibrous mat which is a promising tool for a wide range of applications in tissue engineering can be developed using water in oil (W/O) or oil in water (O/W) emulsion electrospinning. In this study, for the first time, we fabricated an O/W emulsion-based electrospun core-shell mat using polycaprolactone (PCL) as a core and the blend solution of alginate (Alg) and polyethylene oxide (PEO) as shell material. To achieve a stable core-shell mat, firstly, Alg was modified with heat treatment to decrease the molecular weight of Alg. Then, to improve the chain flexibility of Alg, PEO as a second polymer was added to facilitate its electrospinnability. The different volume ratios of O/W were then fabricated by adding PCL to the Alg-PEO solution to find an optimized emulsion solution. The morphology, swelling, and porosity of the construct were evaluated. At the same time, the mechanical characteristic of fibers was evaluated in both dry and wet conditions. This study also examined cell-scaffold interactions to address the need for a scaffolding material to be suitable for tissue engineering and biomedical applications. Finally, the result exhibited a distinct core-shell structure with better mechanical properties compared to the Alg-PEO.

Isocyanate microcapsules recovering automatically impermeability of cement paste through self-hydrophobic broken panels

Cracks are inevitable in the use of cement-based materials. It takes a lot of resources to repair these cracks and prolong the service life of cement-based materials. Self-healing cement-based materials that can automatically repair cracks and improve the self-healing ability of cement-based materials have become the focus of current research. The current self-healing systems achieve impermeability recovery of matrix by the filling cracks. Few scholars have paid attention to the impermeability recovery through self-hydrophobic broken panels. In this paper, SEM, FTIR, core content titration, water flux test and contact angle test were carried out. The morphology, composition, core content and impermeability recovery effect of self-healing cement paste were prepared and characterized. Carbon nanotubes are used to improve the water resistance of isocyanate microcapsules, which possess a diameter of 237.6 ± 59.1 μm, distinct core-shell structure, and good dispersibility. The residual core fraction is 58.2 % after 21 days in Ca(OH)2 aqueous solutions. The microcapsules maintain integrity without breakage when mixed with fresh cement paste and have good bonding compatibility with cement matrix. When microcapsules are embedded into cement paste, the cracks could break the microcapsules releasing isocyanate to wet the broken panels. The isocyanates react with the moisture with the formation of polyurea, changing the contact angle of broken panels from near 0° to 118.4 ± 0.1°. The hydrophobic panels could retard the water penetration and recover the impermeability of cement paste. Based on this, a new self-healing mechanism of self-hydrophobic fracture surface to realize self-healing of impermeability of cement matrix is proposed.

Cellulose-based materials in tailoring a novel defective titanium‑carbon‑phosphorus hybrid composites for highly efficient photocatalytic activity

Until now, black titania has attracted much interest as a potential photocatalyst. In this contribution, we report the first demonstration of the effective strategy to fundamentally improve the photocatalytic performance using a novel sustainable defective titanium‑carbon-phosphorous (TCPH) hybrid nanocomposite. The prepared TCPH was used for photocatalytic degradation of the main organic pollutants, which is methyl orange (MO) dye. The physico-chemical properties of as-prepared samples were characterized by various techniques to observe the transformations after carbonization and the interaction between different composite phases. The existence of Ti+3 and oxygen vacancies at the surface, and a notable increase in surface area, are all demonstrated by TCPH, together with the distinct core-shell structure. These unique properties exhibit excellent photocatalytic performance due to the boosted charge transport and separation. The highest degradation efficiency of methyl orange (MO) was attained in the case of TCPH when compared with titanium-cellulose-phosphorous (TCeP) and titanium‑carbon-phosphorous (TCPN). Accordingly, the highest degradation efficiency was achieved by applying the optimal operational conditions of 1 g/L of TCPH catalyst, 10 mg/L of MO, pH of 7 and the temperature at 25 ± 3 °C after 3 min under LED lamp (365 nm) with light intensity 100 mW/cm2. The degradation mechanism was investigated, and the trapping tests showed the dominance of hydroxyl radicals in the degradation of MO. TCPH showed high stability under a long period of operation in five consecutive cycles, which renders the highly promising on an industrial scale. The fabrication of highly active defective titanium‑carbon-phosphorous opens new opportunities in various areas, including water splitting, and CO2 reduction.

Development and application of low-melting-point microencapsulated phase change materials for enhanced thermal stability in cementing natural gas hydrate layers

In the exploration of deep-water oil and gas resources, encountering natural gas hydrate (NGH) layers poses significant challenges, particularly during cementing operations critical for wellbore stabilization. This study proposes a strategy employing cement slurries integrated with micro-encapsulated phase change materials (MPCMs) to address the destabilization of NGH layers, a key obstacle in deep-water cementing. MPCMs containing BaCO3 shell and low-melting binary PCMs in the core were synthesized by the self-assembly method. The structure and thermal properties of MPCMs were thoroughly characterized. MPCMs exhibited a distinct core-shell structure with a hydrophilic and well-sealed shell. Their phase change temperatures were in closely matched the temperatures found in NGH formations, at 3.5 °C and 13.9 °C. A comprehensive evaluation of the fundamental properties of cement slurries containing MPCMs (CSM) was conducted, including thermal stability, setting time, pore structure, and mechanical strength. Additionally, a laboratory device was employed to simulate cementing operations, allowing for intuitive analysis of the impact of hydration heat evolution on NGH stability—a notably underexplored aspect in related literature. The results demonstrated that MPCMs effectively reduced the hydration heat generated by cement slurry within the initial 36 h. Specifically, at a 9% MPCMs dosage, the hydration heat of CSM decreased by 19.0%, resulting in the sustained stability of NGH. In contrast, the control group's cementing process directly led to the complete decomposition of NGH. Even at lower MPCMs concentrations, the decomposed NGH was more likely to recrystallize and return to a stable state due to the slower hydration heat release rate of CSM. This study not only provides evidence of the effectiveness of MPCMs as heat inhibitors in reducing the disruption of hydrate stability during well cementing but also provides theoretical guidance for the design and application of cement slurries for NGH reservoirs. By enhancing the stability of NGH layers, this work supports the safe and efficient exploitation of undersea hydrocarbon resources, contributing to shaping future global energy strategies.

Fabrication of core-shell polyacrylate latex pressure sensitive adhesives modified by fluorinated monomer and film properties

In this work, a series of fluorinated core-shell polyacrylate latex pressure sensitive adhesives (PSAs) were successfully synthesized through monomer-starved seeded semi-continuous emulsion polymerization. Specifically, (meth)acrylate monomers were employed as the main materials, with dodecafluoroheptyl methacrylate (DFMA) were used as modified monomer. The impact of fluorine monomer DFMA on the resulting core-shell latex and PSA properties was thoroughly examined. FTIR analysis confirmed the successful incorporation of DFMA into the latex copolymer through emulsion polymerization. TEM images illustrated that the morphology of latex particles exhibit a distinct core-shell structure. The results also showed that with the addition of DFMA, the water absorption and water whitening of the latex films decreased, while the water contact angle and thermal stability are improved. Interestingly, the latex films with DFMA added to the shell phase exhibit a larger WCA value when compared to those with DFMA in the core phase, further confirmed by XPS results. Finally, the adhesive properties of the fluorinated core-shell acrylate PSA were evaluated. The results of shear strength and gel content demonstrate that the prepared PSA exhibits excellent cohesive properties. Thus, this work could present a feasible strategy for optimizing the comprehensive properties of acrylate latex PSAs.

In Vitro Cytotoxicity and In Vivo Antitumor Activity of Lipid Nanocapsules Loaded with Novel Pyridine Derivatives.

This study demonstrates high drug-loading of novel pyridine derivatives (S1-S4) in lipid- and polymer-based core-shell nanocapsules (LPNCs) for boosting the anticancer efficiency and alleviating toxicity of these novel pyridine derivatives. The nanocapsules were fabricated using a nanoprecipitation technique and characterized for particle size, surface morphology, and entrapment efficiency. The prepared nanocapsules exhibited a particle size ranging from 185.0 ± 17.4 to 223.0 ± 15.3 nm and a drug entrapment of >90%. The microscopic evaluation demonstrated spherical-shaped nanocapsules with distinct core-shell structures. The in vitro release study depicted a biphasic and sustained release pattern of test compounds from the nanocapsules. In addition, it was obvious from the cytotoxicity studies that the nanocapsules showed superior cytotoxicity against both MCF-7 and A549 cancer cell lines, as manifested by a significant decrease in the IC50 value compared to free test compounds. The in vivo antitumor efficacy of the optimized nanocapsule formulation (S4-loaded LPNCs) was investigated in an Ehrlich ascites carcinoma (EAC) solid tumor-bearing mice model. Interestingly, the entrapment of the test compound (S4) within LPNCs remarkably triggered superior tumor growth inhibition when compared with either free S4 or the standard anticancer drug 5-fluorouracil. Such enhanced in vivo antitumor activity was accompanied by a remarkable increase in animal life span. Furthermore, the S4-loaded LPNC formulation was tolerated well by treated animals, as evidenced by the absence of any signs of acute toxicity or alterations in biochemical markers of liver and kidney functions. Collectively, our findings clearly underscore the therapeutic potential of S4-loaded LPNCs over free S4 in conquering EAC solid tumors, presumably via granting efficient delivery of adequate concentrations of the entrapped drug to the target site.

Synthesis and properties of La-Fe-Si/La-Co magnetocaloric composites

LaFe11.8Si1.2/16wt%La65Co35 samples were prepared by spark plasma sintering (SPS) and subsequent annealing. The La65Co35 binder increased the desired 1:13 phase content in these samples during annealing at 1323 K. Interestingly, the α-Fe phase formed between the LaFe11.8Si1.2 particles and the La65Co35 binder and then disappeared as the annealing time extended. The sample annealed for 0.5 h had a distinct core-shell structure with Co in the shell, a desirable table-like (−∆SM)−T curve was obtained and its RC (153 J·kg−1) was 107% higher compared to the sample before annealing. The diffusion of Co from La3Co to the 1:13 phase was hampered by the growth of La5Si3 phase. Relatively large (−∆SM)max of 8.51 J·kg−1·K−1 (Δμ0H=2 T) and (σbc)max of 374 MPa for the sample annealed for 24 h were obtained. These results indicated that the method combining SPS and diffusion annealing is promising to prepare La-Fe-Si based magnetocaloric composites with good properties.

Fabrication of a Magnetic Porous Organic Polymer for α-Glucosidase Immobilization and Its Application in Inhibitor Screening

The technology based on immobilized enzymes was employed to screen the constituents inhibiting disease-related enzyme activity from traditional Chinese medicine, which is expected to become an important approach of innovative drug development. Herein, the Fe3O4@POP composite with a core-shell structure was constructed for the first time with Fe3O4 magnetic nanoparticles as the core, 1,3,5-tris (4-aminophenyl) benzene (TAPB) and 2,5-divinylterephthalaldehyde (DVA) as organic monomers, and used as the support for immobilizing α-glucosidase. Fe3O4@POP was characterized by transmission electron microscopy, energy-dispersive spectrometry, Fourier transform infrared, powder X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Fe3O4@POP exhibited a distinct core-shell structure and excellent magnetic response (45.2 emu g-1). α-Glucosidase was covalently immobilized on core-shell Fe3O4@POP magnetic nanoparticles using glutaraldehyde as the cross-linking agent. The immobilized α-glucosidase possessed improved pH stability and thermal stability as well as good storage stability and reusability. More importantly, the immobilized enzyme exhibited a lower Km value and enhanced affinity for the substrate than the free one. The immobilized α-glucosidase was subsequently used for inhibitor screening from 18 traditional Chinese medicines in combination with capillary electrophoresis analysis among which Rhodiola rosea exhibited the highest enzyme inhibitory activity. These positive results demonstrated that such magnetic POP-based core-shell nanoparticles were a promising carrier for enzyme immobilization and the screening strategy based on immobilized enzyme provided an effective way to rapidly explore the targeted active compounds from medicinal plants.

Performance evaluation of polymer nanolatex particles as fluid loss control additive in water-based drilling fluids

The development of various nanoparticles and their successful application in oil and gas drilling engineering is an extremely interesting and crucial area of research, particularly in the field of drilling fluids. In this study, styrene, butyl acrylate, acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid were used as the main raw materials to synthesize a polymer nanolatex (SBAA) employing a conventional emulsion polymerization approach (one-pot method). SEM, TEM, and PSD experiments demonstrated that SBAA is a nanoparticle with a particle size of around 150 nm and a distinct core-shell structure. The TGA analysis revealed that SBAA had a decomposition temperature of 296 °C. Particularly, the unique self-assembly behavior of nanolatex particles is discussed for the first time using TEM and UV–Vis experiments. Additionally, filtration and permeability plugging tests were used to evaluate the filter loss reduction and micro-pore plugging ability of the SBAA in water-based drilling fluids. The findings showed that SBAA could reduce the medium pressure filtration loss by around 33% compared with the basic bentonite fluid, and the reduction rate after aging at 200 °C is around 41%. Particularly, it can reduce the filtrate loss velocity of water-based drilling fluid in heterogeneous pores, and the effects of filtration reduction and mud cake quality enhancement outperform those of commercial nanosilica particles. This study offers a novel reference approach for developing novel nanomaterials for water-based mud to plug microscopic pores and maintain wellbore stability.

Preparation of MoSi2@ZrO2 core-shell powders by hydrothermal-calcination and evaluation of low-temperature oxidation resistance

MoSi2 is a promising candidate for high-temperature, structural materials. However, their oxidation resistance is poor below 600 °C. To prevent MoSi2 from being oxidized at low temperatures, core-shell structured MoSi2@ZrO2 powder were prepared by hydrothermal-calcination approach. First, MoSi2@Zr(OH)4 core-shell composite powder with nano-sized Zr(OH)4 shell particles were synthesised using a hydrothermal method. Subsequently, the MoSi2@ZrO2 core-shell structured powder were obtained by calcination of the MoSi2@Zr(OH)4 powders at 900 °C for 2h. Finally, microstructure and oxidation behaviour of the MoSi2@ZrO2 powder at 400 °C–600 °C in air were investigated systematically. Microstructural analysis revealed that all samples had a distinct core-shell structure, and the ZrO2 shells coated the surface of the MoSi2 core. Oxidation behaviour studies showed that the dense ZrO2 shell layer could isolate the MoSi2 surface from oxygen, improving the low-temperature oxidation resistance and providing better low-temperature antioxidant properties than those of the MoSi2 and MoSi2@Zr(OH)4 core-shell structures.

Defect control of Yb-doped dielectric ceramics on improving the reliability for MLCC application

A fine-grained Yb-doped (Ba1-xCax)mTiO3 (BCT)-based ceramic, possessing high dielectric properties and outstanding reliability under a reducing atmosphere sintering, was synthesized by the chemical coating method. The mean grain size of the ceramics was 170 nm. A distinct core-shell structure of ceramics was observed by the TEM-EDS measurement. With increasing content of Yb, the curie temperature increased and the DC-bias capacitance change rate decreased under a DC field at 40 kV/cm. The optimal component showed a dielectric constant of 2200 and met the requirement of the X8R MLCCs application. Moreover, the outstanding highly accelerated life-time and higher grain boundary activation energy substantiated that Yb dopant prominently improved the reliability of dielectric materials of MLCCs. All these studies provide meaningful recommendations for the research on dielectric materials of high-performance, high-reliability base-metal MLCCs.

Preparation and release of novel frog egg-like microspheres by coaxial electrostatic spray technique

• novel frog egg-like microspheres were prepared by coaxial electrostatic spray process. • The microspheres have a distinct core-shell structure. • The microspheres showed porous structures on the surface and inside after drying. • The microspheres can prolong the release of ME. Novel frog egg-like microspheres, referred to as SA@Ca 2+ /PCL-ME microspheres, were created by coaxial electrostatic spray technique, applying a gel formed by cross-linking sodium alginate (SA) with calcium ions as the shell material and a mixture of methyl eugenol (ME) and polycaprolactone (PCL) solution as the core material in the current study. Using optical microscopy, a uniform spherical shape was observed in the microspheres along with a distinct core-shell structure, while its porous internal and external features were visible in SEM images after drying. Furthermore, ME was released in microspheres for more than 12 weeks due to the dual sustained release method comprising a calcium alginate gel and PCL. During 8 weeks of trapping tests, ME-loaded microspheres were shown to be consistently effective.

Facile and safety synthesis of highly loaded phase change microcapsules with paraffin/butyl stearate core and their feasible application in polymer composite

Highly paraffin/butyl stearate-loaded phase change microcapsules were synthesized by cosolvent-free interfacial polymerization using low-toxicity dicyclohexylmethane-4, 4′-diisocyanate as the shell material. The formation of the microcapsules and their distribution in the epoxy were studied by means of optical microscope and scanning electron microscopy, respectively. The chemical composition of microcapsules was confirmed through Fourier transform infrared spectrometer. And the phase change properties, thermal stability and cyclic thermal stability of microcapsules and their thermal insulation properties and thermal response behavior in the epoxy were investigated through differential scanning calorimetry, thermogravimetric analysis, leakage prevention test, thermal conductivity test and temperature response experiment, respectively. The synthesized spherical microcapsules have distinct core-shell structure with an average diameter of 220.6 μm. The microcapsules achieve an encapsulation rate of 78.5%, with the melting enthalpy and the crystallization enthalpy being 148.5 J/g and 159.2 J/g, respectively. They not only exhibit good thermal stability and cyclic thermal stability, but also can disperse in the epoxy uniformly and combine with the epoxy tightly. In addition, compared with the pure epoxy, the epoxy containing 15 wt% microcapsules experiences a 10.1% decreases in thermal conductivity and a 55.4% increase in delayed time of temperature rise/fall, showing an excellent temperature regulation ability. • HMDI was employed as the shell material due to low toxicity. • The microcapsules with core-shell structure achieve an encapsulation rate of 78.5%. • High enthalpy microcapsules exhibit 99.2% of heat-storage efficiency. • The microcapsules have high thermal stability, reliability and applicability. • 15 wt% microcapsules increase the time delay by 55.4% for temperature rise/fall.

Synthesis and application of paraffin/silica phase change nanocapsules: Experimental and numerical approach

The present study has been focused on the synthesis of silica encapsulated paraffin phase change materials and its application in cement-based systems. One-pot in-situ hydrolysis of tetraethyl orthosilicate as silica precursor and subsequent polycondensation have successfully encapsulated the paraffin droplets into nano-sized capsules of phase change materials (PCMs). The fabricated nanoencapsulated PCMs (NEPCMs) possess distinct core-shell structures with spherical geometry. Encapsulation ratio and encapsulation efficiency have been accomplished up to 92.9 and 90.24% with the latent heats of melting and solidification of 173.79 and 158.93 J/g, respectively. Calorimetry studies of the fabricated NEPCMs with ordinary Portland cement (OPC) have demonstrated 11% temperature reduction during the evolution of the heats of hydration, with the addition of only 3% NEPCMs. The synthesized PCMs are found to perform as high thermal energy storage materials with the capability of congruent heat storage and release without affecting their structure and geometry, therefore, can be considered as reliable and durable PCMs for concrete and building materials. The use of these NEPCMs can control the maximum temperature rise due to heat of hydration and therefore reducing the defects and cracks formation inside the mass concrete structures.