A Dual Encapsulation Strategy for High-Temperature Micro PCM Particles with High Cyclic Durability.

Addressing critical issues such as high-temperature corrosion,  leakage, degradation, and subpar cyclic performance is imperative for phase change materials (PCMs), prompting the development of appropriate encapsulation techniques to surmount these challenges. In this study, a dual encapsulation strategy is proposed for high-temperature micro PCM particles. Al-Si core is microencapsulated via the "solvent evaporation-heating curing" method. Subsequently, TiO2 is employed as the skeleton material for form-stable encapsulation of PCM microcapsules by "cold pressed sintering". Detailed analysis of the crystalline phase transformation mechanism in the sintering synthesis pathway of TiO2 underscore its potential as a robust structural material with exceptional thermal stability. Furthermore, the incorporation of hexagonal boron nitride (hBN) results in a substantial enhancement of the thermal conductivity of the composites, increasing by 121.1-131.3%. The prepared form-stable phase change microcapsules (FSPCMs) are subjected to 5000 thermal cycles in the air atmosphere. There is no observed PCM leakage or composite ruptures in the FSPCM. Moreover, the oxidized mass gain is merely 3.3%, signifying exceptional oxidation resistance. Thermophysical analysis indicates that FSPCM can retain 91.3% of the enthalpy after 2000 cycles, with over 80% preservation after 5000 cycles, underscoring its remarkable cyclic thermal durability.

Oblique impingement of binary droplets at the nanoscale on superhydrophobic surfaces: A molecular dynamics study.

The impacting phenomenon of nanodroplets has received much attention due to their importance in various industrial applications. The oblique impingement of single droplets is well understood; however, the effect of oblique angle on impacting the dynamics of multiple droplets at the nanoscale is very limited. To address this gap, we perform molecular dynamics (MD) simulations to study the impacting dynamics of binary nanodroplets with various oblique angles (αob) and Weber numbers (We). Using MD simulations, we directly capture the detailed morphological evolution of the impacting binary droplets with various given conditions. Compared to the oblique impingement of a single droplet, the evolution of impacting binary droplets involves two novel dynamic characteristics: the asymmetric dynamics with droplet preferential spreading in the y direction and the rotating of the coalescing droplet. The mechanisms underlying are well studied. The asymmetric dynamics is a result of the velocity gradient of the outer edge of the spreading droplet, and the rotating effect is due to the change in angular momentum induced by surface force. The analysis and study of these phenomena have never been mentioned in previous studies of single droplet. Finally, we investigate the effect of αob and We on normalized moving distance (L/Dsin) and contact time (tc). This work paves the way for offering a comprehensive understanding of the oblique impingement of binary nanodroplets.

A Eulerian Numerical Model to Predict the Enhancement Effect of the Gravity-Driven Motion Melting Process for Latent Thermal Energy Storage.

Latent thermal energy storage (LTES) devices can efficiently store renewable energy in thermal form and guarantee a stable-temperature thermal energy supply. The gravity-driven motion melting (GDMM) process improves the overall melting rate for packaged phase-change material (PCM) by constructing an enhanced flow field in the liquid phase. However, due to the complex mechanisms involved in fluid-solid coupling and liquid-solid phase transition, numerical simulation studies that demonstrate physical details are necessary. In this study, a simplified numerical model based on the Eulerian method is proposed. We aimed to introduce a fluid deformation yield stress equation to the "solid phase" based on the Bingham fluid assumption. As a result, fluid-solid coupling and liquid-solid phase transition processes become continuously solvable. The proposed model is validated by the referenced experimental measurements. The enhanced performance of liquid-phase convection and the macroscopic settling of the "solid phase" are numerically analyzed. The results indicate that the enhanced liquid-phase fluidity allows for a stronger heat transfer process than natural convection for the pure liquid phase. The gravity-driven pressure difference is directly proportional to the vertical melting rate, which indicates the feasibility of controlling the pressure difference to improve the melting rate.

Depolymerization-Induced Electrochemiluminescence of Insoluble Porphyrin in Aqueous Phase.

Exploring efficient and robust electrochemiluminescence (ECL) performance of liposoluble porphyrins in aqueous phase for analytical purposes especially for important biological targets is still very challenging. In this work, a novel depolymerization-induced electrochemiluminescence (DIECL) of porphyrin and ß-cyclodextrin (ß-CD) self-assembly through a coreactant route was discovered. Among the studied meso-tetrasubstituted porphyrins, self-assembly of 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (THPP) and ß-CD (THPP@ß-CD) exhibits the best DIECL behavior with high efficiency (21.8%) as well as good reproducibility and stability. A mechanistic study suggests that the facile complexation of porphyrins with amphiphilic ß-CD via hydrogen bonding interaction greatly improves the water insolubility and the aggregation-caused deficient ECL of liposoluble porphyrins in aqueous solution. Furthermore, because of the strong hydrogen bonding between the hydroxyl groups on THPP@ß-CD and a highly electronegative substrate, such THPP@ß-CD is found to serve as an efficient luminophore for recognition of most electronegative fluoride (F-) in the aqueous phase with high sensitivity and selectivity, together with a low limit of detection (0.74 µΜ). The simplicity of this THPP@ß-CD and its unique DIECL property in current work provides a new guide for the ECL applications of liposoluble porphyrins in aqueous phase.

Fabrication of magnetic trimetallic metal-organic frameworks for the rapid removal of tetracycline from water.

The metal-organic framework (MOF-74) series has the most open metal sites. The metal ions have different bonding strengths with the ligand in MOF-74 and the bond of the ligand can be successively broken to obtain highly active heteroparticles by controlling the temperature, which is difficult to achieve using traditional methods. Magnetic NiCo/Fe3O4-MOF-74, which is fabricated using trimetallic NiCoFe-MOF-74 as a precursor, is simple and rational in comparison with the traditional magnetic core and tunable MOF shell hybrid composites that are formed using a step-by-step assembly strategy. After thermal treatment under a specific atmosphere, NiCo/Fe3O4-MOF-74 shows higher stability, strong magnetism and more active metal sites compared to the original MOF. NiCo/Fe3O4-MOF-74 shows excellent enrichment capability for the removal of tetracycline, with a high removal efficiency that reached 94.1% within 5 min, which is much higher than that of NiCoFe-MOF-74. The main interaction between the adsorbent and analyte is most likely attributed to the open metal sites that can form a stable metal-ligand with the antibiotic molecules. Furthermore, the material can be reused five times without considerable loss. The prepared material has potential applications for removing antibiotics with high efficiency at low cost. Therefore, the experiments described in this study provide a route to a broad class of MOF-based materials for detecting organic contaminants.

A Study of Manufacturing Processes of Composite Form-Stable Phase Change Materials Based on Ca(NO3)2-NaNO3 and Expanded Graphite.

The fabrication of form-stable phase change materials (FS-PCMs) usually involves four manufacturing processes: mixing, immersion, stabilization, and sintering. In each process, the operation parameters could affect the performance of the fabricated PCM composite. To gain an efficient and low-cost method for large-scale production of the molten salts/expanded graphite (EG) composite FS-PCMs, the effects of different operating parameters were investigated, including the stirring speed, evaporation temperature, melt-impregnation, cold-pressing pressure, and sintering temperature on the densification, microstructure, and thermophysical properties of the composite FS-PCMs. It was found that the microstructure, the morphology and durability, and the thermophysical properties such as thermal conductivity and specific heat enthalpy depended highly on the operating parameters. The following optimal operating parameters of the Ca(NO3)2-NaNO3/EG composite FS-PCMs are suggested: the stirring speed of 20 rpm, the evaporation temperature of 98 °C, the melt-impregnation temperature of 280 °C, the cold-pressing pressure of 8 MPa, and the sintering temperature of 300 °C. The results of the present work can provide valuable insights for the large-scale production of the composite FS-PCMs.

Periodic solution of a chemostat model with Beddington-DeAnglis uptake function and impulsive state feedback control.

In this paper, a chemostat model with Beddington-DeAnglis uptake function and impulsive state feedback control is considered. We obtain sufficient conditions of the global asymptotical stability of the system without impulsive state feedback control. We also obtain that the system with impulsive state feedback control has periodic solution of order one. Sufficient conditions for existence and stability of periodic solution of order one are given. In some cases, it is possible that the system exists periodic solution of order two. Our results show that the control measure is effective and reliable.

Exposure to environmental tobacco smoke in Chinese new mothers decreased during pregnancy.

OBJECTIVE: To determine the current status of environmental tobacco smoke (ETS) exposure in new mothers living in urban Shanghai. STUDY DESIGN AND SETTING: A cross-sectional study was carried out in three communities of Shanghai from June 2005 to August 2006. A total of 950 new mothers with infants aged 5-8 months were recruited in community health centers by trained health workers. The prevalence of ETS exposure was determined for before, during, and after pregnancy. Chi-square test and logistical regression analysis were used in statistical analysis. RESULTS: The prevalence of ETS exposure was 55.9% (95% confidence interval [CI]: 52.2, 59.6) before pregnancy and decreased significantly to 41.9% (95% CI: 38.2, 45.6) during pregnancy. However, the amount and time of exposure to ETS changed little before, during, and after pregnancy for those exposed. Among husbands who ever smoked, 14.4% stopped smoking before pregnancy, 38.1% changed smoking behaviors during pregnancy, and after pregnancy 10.7% quit smoking, whereas three nonsmoking husbands began to smoke. CONCLUSION: Pregnancy is a very important time period to implement tobacco control projects targeting young male smokers.