română EUGENIA TANASĂ
Abstract
One extremely promising method for producing hydrogen sustainably and storing energy is the photoelectrochemical (PEC) splitting of water with solar energy. Hematite is a good photoanode material for water splitting because of its advantageous qualities, according to recent study in this area: it is an n-type semiconductor, possesses a band gap appropriate for visible light absorption, exhibits high chemical stability, and is abundantly available on Earth. This review presents various strategies for modifying hematite to enhance its performance. These modifications include element doping, nanostructure design and fabrication, co-catalyst integration, heterostructure formation and the interdependence between the structure and performance of hematite.
Keywords
solar energy, hematite, photoanoes
XIANWU JING, XIAOJIN ZHOU, TENG GONG, TAO WANG, YANG WANG, GUOQING LIU, KAIJUN WANG
Abstract
This research employed molecular dynamics simulations to explore the distribution of sodium dodecyl sulfate (SDS) at the n-hexane/water interface. Once the SDS concentration surpasses the critical micelle concentration(cmc), a large portion of SDS migrates to the n-hexane/water interface, establishing a thin layer where sulfonic acid groups are oriented towards the water phase and carbon-hydrogen chains are directed towards n-hexane, a small amount of SDS forms spherical micelle with sulfonic acid groups facing the water phase, while carbon-hydrogen chains aggregate in the interior of these spherical structures. The sulfonic acid group of SDS forms multiple h-bonds with water, shows strong interaction energy; while the carbon hydrogen chain itself has only weak van der Waals interactions with surrounding molecules. The thickness of SDS- layer at the n-hexane/water interface is about 2.06 nm, with a maximum number density of about 0.25 per nm3, and average area occupied by a single SDS- is about 0.21 nm2. According to radial distribution function (RDF) result, due to the attractive effect of positive and negative charges, the first coordination layer of Na+ ions and oxygen atoms on sulfonic acid groups is about 0.21 nm. This study investigated the distribution of SDS at n-hexane/water interface, vividly demonstrating the mechanism by which SDS reduces the interfacial tension between oil and water, and providing guidance for oilfield development.
Keywords
N-hexane/water interface; Molecular dynamic simulation; Sodium dodecyl sulfate; Weak interaction analysis
ZHI LI, PING JIANG
Abstract
To address the performance limitations of single silica (SiO2) encapsulated phase change materials, a novel shape-stable composite microencapsulated phase change material (CA/CS/SiO2 MEPCM) was prepared using the sol-gel method. Capric acid (CA) was used as the phase change material (PCM), while chitosan/silica (CS/SiO2) served as the composite encapsulation material. Fourier transform near infrared spectroscopy (FT-NIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to characterize the chemical structure, crystalline phase, and microstructure of the CA/CS/SiO2 MEPCM. The thermal storage properties and thermal stability of the MEPCM were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM results indicated that CA was effectively encapsulated within the CS/SiO2 shell, and the reticulated structure of the shell contributed to the high shape stability of the MEPCM. The results demonstrate that CA is effectively encapsulated within the CS/SiO2 shell, and the network structure of the shell significantly enhances the shape stability of the MEPCM. The encapsulation process preserves the chemical integrity of CA, as no structural changes were observed. The synthesized MEPCM exhibits excellent sealing performance at 102 °C, and the thermal stability of the CS/SiO2 composite shell surpasses that of conventional single-shell structures. Furthermore, the material displays a moderate phase transition temperature and a maximum latent heat of 69.38 J/g, meeting the requirements for variable thermal regulation. In conclusion, the CA/CS/SiO2 MEPCM developed in this study is a green, non-toxic, and structurally stable phase change material with a tunable phase transition temperature, offering promising potential for sustainable thermal energy storage applications.
Keywords
capric acid, chitosan, silicon dioxide, microencapsulated phase change materials
VISWANATH KRISHNAN, MOHAN EKAMBARAM, VINOTHKUMAR RAVI, SHEEBA RANI SOUNDARAPANDIAN
Abstract
In this study, powdered magnesium and aluminum particles were combined with a smaller quantity of silicon carbide (SiC) particles, and the sintering process was used to form the metal matrix composite (MMC). The specimens were made at three distinct temperatures such as 4500C, 5000C, and 5400C. The addition of silicon carbide to the magnesium and aluminium leads to increase the hardness. Based on the scanning electron microscopy (SEM), a large number of holes were commensurate with the sintered specimen produced at the minimal sintering temperature. The development of pore was significantly reduced at high temperature, and strong metallurgical bonding was also attained. The hardness of the sintered specimen was also raised at high sintering temperatures. When compared to other traditional machining methods, the reason for using spark erosion machining or electric discharge machining (EDM) is to maintain the optimal surface roughness (SR) and increase material removal rate (MRR). An atomic force microscopy (AFM) and SEM examination was carried out specifically to evaluate the surface parameters of the magnalium MMC. The pit and valley surface was observed in the machining surface. Current and voltage played a crucial role in metal removal and surface roughness.
Keywords
Magnalium composite, sintering, powder metallurgy, hardness, spark erosion machining
QIAN HONG, XIAOFENG CHEN, WEIQING YU, XIAOXIAO MA, YANBING WANG, CHONGQING WANG, CHAO LIU
Abstract
Faced with the defects of engineering disturbed slope soil, such as easy erosion and evaporation of water, this paper uses polyvinyl alcohol (PVA) hydrogel as a soil conditioner to improve the water erosion resistance and water retention performance of engineering disturbed slope soil, and studies the vegetation performance and microstructure of modified soil. The results showed that PVA hydrogel changed the soil structure by using its excellent cementation and water holding capacity. PVA hydrogel completely wrapped the soil particles to form the overall structure of network gel, which significantly improved the soil erosion resistance, water stability and water retention capacity of the soil. With the increase of PVA concentration, the soil erosion resistance, water stability and water retention performance are significantly improved. In addition, the effect of increasing PVA concentration on soil vegetation performance shows a trend of first strengthening and then weakening, with the best soil vegetation performance observed when PVA concentration was 3%. The results show that PVA hydrogel has important application value for reducing soil and water loss of engineering disturbed slope and promoting vegetation restoration.
Keywords
disturbed slope, ecological restoration, erosion resistance, water retention performance, vegetation performance
PREPARATION METHOD OF DIATOM-BASED EARTH AND ZINC OXIDE COMPOSITE HIGH-DENSITY POLYETHYLENE MATERIAL
KUN LU, HAN KONG, YAOWEN ZHANG, JIAXING ZHU, YUANYUAN DING, XIYU HUANG, CHAO ZHANG
Abstract
In order to cope with the increasingly severe environmental nanotechnology problems and energy shortage, the development of green new materials has become an inevitable trend in today society. In this paper, a preparation method and application of diatom-based earth and zinc oxide composite high-density polyethylene material are provided, which belong to the solid adsorbent composition material. Firstly, high-density polyethylene composites were prepared according to a certain proportion of diatom-based earth and zinc oxide and polyethylene. Then, to improve its performance and UV resistance, Tinuvin 770 is added and mixed with a composite polyethylene material in a gear mixer. Subsequently, the twin-screw extruding machine is set to a certain temperature and speed, extruded, and the extrusion is cut into composite pellets using a tray machine. Finally, these composite pellets are injected into the injection molding machine, where the target mold is selected and molded. At the same time, it can be used as a food packaging bag material, which can inhibit the growth of Staphylococcus aureus and E. bacillus, so that it has the minimum UV stabilizer content, which is a cost-effective and high-performance choice, and its ability to block ultraviolet rays is strong, and it can well protect the quality of packaged food.
Keywords
diatom-based, Zinc Oxide, High-Density polyethylene, Tinuvin 770
IOANA ION, CIPRIAN MIHAI MITU, EMANUEL VIRGIL MARINESCU, ANDREI CUCOS, ALINA RUXANDRA CARAMITU
Abstract
This study presents an eco-friendly synthesis route for a novel hybrid hydrogel (HHy) designed for wastewater remediation using dual crosslinking method: freezing–thawing (FT) and gamma irradiation (GIrr). Polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC) form the polymeric matrix, silver nanoparticles (AgNPs), and AgNPs decorated graphene oxide (AgNPs/GO) are incorporated to enhance adsorption and photocatalytic properties. Methylene blue (MB) dye was employed as a model pollutant to assess improved adsorption performance. The HHy demonstrated significant improvements compared to unmodified Hy for equilibrium adsorption capacity (EAC): 20% increase with HyAgNPs and 130% for HyAgNPs/GO; swelling ratio (SWR) measurement revealed an increase of 6% for HyAgNPs, 109% for HyAgNPs/GO; water content (WCR) had an increase of 1 % for HyAgNPs, 14 % for HyAgNPs/GO compared to unmodified Hy. Thermal analysis revealed that total carbonaceous residue after pyrolysis at 800 ⁰C, reached approximately 20% of the Hy’s mass for HyAg and HyAgNPs/GO. This indicates effective char formation due to the catalytic role of the AgNPs and graphene oxide (GO) as nucleation sites. The study optimizes the design of functional Hy for water treatment, and also proposes a viable end-of-life strategy through controlled pyrolysis. The synergistic effects of CMC, graphene oxide (GO), and AgNPs enhance both the structural and functional performance of the HHy system, positioning this approach as a promising avenue for advanced wastewater treatment technologies.
Keywords
wastewater remediation, hybrid hydrogel, silver nanoparticles, graphene oxide, graphene oxide decorated with silver nanoparticles, methylene blue adsorption