Search Results (34,894)

When it comes to the disposal of paperboard and cardboard packaging waste to reduce their environmental impact, recycling is one of the most desirable options. With innovations and development of biopolymer coatings and their application in packaging materials, new paper-based packaging solutions are expected on the market. Besides evaluating their mechanical and barrier properties, it is essential to assess their environmental impact. Therefore, this study investigated the impact of biodegradable polycaprolactone (PCL) polymer coating, as well as PCL modified with SiO₂, Al₂O₃, and ZnO nanoparticles, on the recycling behavior of paperboard. The coating samples were prepared by dissolving PCL polymer in ethyl acetate and nanoparticle dispersion. Paperboard (230 g/m²) was printed by offset printing process and then coated with PCL and PCL nanocomposite coatings. Recycling was performed under controlled laboratory conditions following a standardized method. Deinkability was assessed by evaluating the optical properties and using an image analysis system. From the obtained results, it can be concluded that the use of PCL coatings and PCL coating modified with SiO₂, Al₂O₃, and ZnO nanoparticles do not significantly impact the optical properties of the recycled pulp, thereby not restricting the implementation in paperboard production and waste management. Full article

This study investigates the performance of biobased and nano-additive lubricants for the sustainable machining of Al6082 alloy. The experiments were conducted in five different cutting environments: dry cutting, olive oil-based minimum quantity lubrication (MQL), sunflower oil-based MQL, olive oil-based MQL with nano-SiO₂ additives, and sunflower oil-based MQL with nano-SiO₂ additives. The machining performance was evaluated in terms of key parameters such as surface roughness, cutting forces, tool wear, cutting temperature, and chip morphology. The results show that nano-additive lubricants reduce friction, reduce tool wear, and reduce cutting forces, thus providing lower surface roughness. The nano-SiO₂-additive olive oil-based MQL method showed the optimum performance by providing the lowest cutting force and temperature values. It was also determined that nano-additive lubricants contributed to more regular chip formation. The study reveals that the use of biobased nano-lubricants in sustainable machining processes offers environmental and economic advantages. In the future, it is recommended to examine different types and concentrations of nanoparticles, conduct long-term tool wear analyses, and evaluate the effects on other machining methods. Full article

The interglacial period of the Cryogenian glaciation is a pivotal interval in geological history, marked by two “Snowball Earth” events and the emergence of early animals. Currently, there is considerable debate regarding the paleo-oceanic environment and the dominant factors controlling organic matter enrichment. Here, based on inorganic geochemical data and mineral composition from the Datangpo Formation in Xiangtan (South China), combined with previous research, we have analyzed the paleo-climate, redox condition, seawater restriction, and primary productivity across different sedimentary facies during this critical interval. The results exhibit that the Datangpo Formation can be divided into three members (Da1–Da3) based on lithology. Paleoclimatic proxies suggest the environment was relatively cold during the deposition of the Da-1 Member, while it was relatively warm and humid during the deposition of the Da 2–3 members. Compared to shallow water areas, deep-water areas experienced a more rapid transition in paleotemperature following the Sturtian glaciation event. Combining Mo-U elements, Ce_N/Ce*_N, and C_org/P ratios, the environment was characterized by an oxic environment during the early deposition period of the Datangpo Formation, then gradually transitioned to suboxic, and finally anoxic conditions. Furthermore, the decompression of terrestrial magma chambers led to intense volcanic/hydrothermal activity during the deglaciation period. Hydrothermal activity was most intense during the Da-1 depositional period, followed by Da-2, and gradually declined during Da-3 depositional period. Hydrothermal activity not only provided essential materials for the formation of Mn carbonate ores but also significantly enhanced the primary productivity by introducing large amounts of nutrients in the paleo-ocean. The primary productivity indicators (Ni/Al, Cu/Al) exhibited an obvious coupling with Ce_N/Ce*_N and C_org/P ratios in the Datangpo Formation, indicating that oxygen-rich environments were favorable for biological proliferation, thereby providing abundant organic matter. Anoxic conditions further facilitated the preservation of organic matter, which may be the primary factor driving organic matter enrichment in the Datangpo Formation. Full article

This study examined the hierarchical structuring of *BEA zeolite using two distinct approaches: double aluminum removal with solid ammonium hexafluorosilicate (2x-AHFS) and a solution of 0.2 M sodium hydroxide followed by 0.5 M hydrochloric acid (T-NaOH). Additionally, niobium pentoxide (Nb₂O₅) was impregnated at different loadings (5, 10, 15, and 20 wt.%) onto the hierarchized materials. Both treatments increased the SiO₂/Al₂O₃ ratio and produced crystals with domains of about the same size. The hierarchization methods generated secondary mesopores and reduced the micropores in the treated HB zeolite. The solid-state NMR analysis by ²⁷Al and ²⁹Si indicated that the 2x-AHFS treatment increased the hydrophobic character of the zeolite, while the treatment with NaOH/HCl resulted in a less hydrophobic material. A balanced quantity of Brønsted and Lewis sites was observed for all treated zeolites. Thus, these combined physicochemical characteristics of the new catalysts may explain their superior performance in the dehydration reactions. In the case of ethanol dehydration at 230 °C, the 20 wt.% Nb₂O₅ supported on the T-NaOH catalyst produced an 84% conversion and 86% selectivity for ethylene (EE), with 14% diethyl ether (DEE) as the only products. Conversely, in the 1-propanol dehydration reaction, the 20 wt.% Nb₂O₅ supported on 2x-AHFS achieved 99% conversion, producing 99% propene. Full article

Chemical recycling of plastic waste, especially polyolefins, into valuable liquid fuels is of considerable significance to address the serious issues raised by their threat on environmental and human health. Nevertheless, the construction of efficient and economically viable catalytic systems remains a significant hurdle. Herein, we developed an efficient bifunctional catalyst system comprising γ-Al₂O₃-supported ruthenium nanoparticles (Ru/γ-Al₂O₃) and β-zeolite for the conversion of polyolefins into gasoline-range hydrocarbons. A yield of C_5–12 paraffins up to 73.4% can be obtained with polyethene as the reactant at 250 °C in hydrogen. The Ru sites primarily activate the initial cleavage of C–H bonds of polymer towards the formation of olefin intermediates, which subsequently go through further cracking and isomerization over the acid sites in β-zeolite. Employing in situ infrared spectroscopy and probe–molecule model reactions, our investigation reveals that the optimized proportion and spatial distribution of the dual catalytic sites are pivotal in the tandem conversion process. This optimization synergistically regulates the cracking kinetics and accelerates intermediate transfer, thereby minimizing the production of side C_1–4 hydrocarbons resulting from over-cracking at the Ru sites and enhancing the yield of liquid fuels. This research contributes novel insights into catalyst design for the chemical upgrading of polyolefins into valuable chemicals, advancing the field of plastic waste recycling and sustainable chemical production. Full article

In this paper, a series of graded Al-based composites, including Al@AP, Al@AP/BM−52, and Al@AP/BPE−1735, have been prepared by spray drying technology. The thermal decomposition characteristics, kinetic parameters of the decomposition reaction, and Pyro-GC/MS products were comprehensively investigated. The results showed that two inhibitors, BM−52 and BPE−1735, had a significant effect on the thermal decomposition of AP. The addition of BM−52 conspicuously enhanced the thermal interaction, resulting in a more complete decomposition reaction of AP. Meanwhile, the incorporation of BPE−1735 significantly enhanced the heat releases of AP, leading to a significant enhancement in the energetic performance during the decomposition process of AP. BM−52 and BPE1735 inhibit AP decomposition as evidenced by higher activation energies for thermal decomposition and altered physical models of decomposition. Pyro-GC/MS results reveal that the fundamental pathway of Al@AP thermal decomposition remains unaltered by BM−52. However, the proportion of oxygen-containing compound products is moderately reduced. In contrast, for Al@AP/BPE−1735, in addition to the same products as those from Al@AP pyrolysis, new pyrolysis peaks emerge. It is implied that specific chemical reactions or interactions are triggered during the thermal decomposition process, thereby resulting in the formation of distinct chemical species. Full article

This research focuses on the structural and bonding characteristics of the Al(111)/CrB2(0001) interface, aiming to clarify the adhesion mechanisms of CrB₂ coatings on aluminum composites. Utilizing first-principles calculations grounded in density functional theory (DFT), we systematically examined the interfacial properties of both clean and doped Al(111)/CrB₂(0001) systems. And key aspects such as binding energy, electron density distribution, and chemical bonding types were thoroughly evaluated. The results demonstrate that the Cr-terminated HCP stacking arrangement at the Al(111)/CrB₂(0001) interface achieves the maximum adhesion work and minimal interfacial energy. This is primarily due to the strong covalent interactions between Al-p and Cr-p orbitals, which contribute to exceptional interfacial strength and stability. Furthermore, the incorporation of Fe, Mg, and Mn at the interface not only markedly improves working adhesion but also effectively lowers the interfacial energy for the Cr-terminated HCP stacking configuration. This phenomenon significantly enhances the overall bonding performance of the Al/CrB₂ system. Conversely, the addition of Cu, Zn, and Si leads to an increase in interfacial energy, negatively impacting the bonding quality. Analysis of binding energies at the doped interface revealed a consistent trend among the elements: Fe > Mn > Mg > Si > Zn > Cu. These findings offer valuable guidance for the design and optimization of Al-based surface coatings with improved performance. Full article

Over the past two decades, the high hydrogen content and favorable dehydrogenation conditions of multi-metallic amidoboranes have gained significant attention for their potential in hydrogen storage. Among them, Al-based complex hydrides have shown promise because of their high polarizing power, light weight, and abundant natural presence. In this work, we successfully synthesized two novel tetrahedrally coordinated Al-based amidoboranes, namely, Li[Al(BH₃NHCH₂CH₂NHBH₃)₂] and Na(THF)[Al(BH₃NHCH₂CH₂NHBH₃)₂], using BH₃NH₂CH₂CH₂NH₂BH₃ (EDAB) as a precursor. The structure of Na(THF)[Al(BH₃NHCH₂CH₂NHBH₃)₂] was determined through modeling based on synchrotron powder X-ray diffraction. Additionally, the formation of the Al-N bond in Li[Al(BH₃NHCH₂CH₂NHBH₃)₂] and Na(THF)[Al(BH₃NHCH₂CH₂NHBH₃)₂] was confirmed with IR spectra. Na(THF)[Al(BH₃NHCH₂CH₂NHBH₃)₂] is more stable in air than Li[Al(BH₃NHCH₂CH₂NHBH₃)₂]. Importantly, thermal gravimetric analysis and mass spectroscopic characterization confirmed that both compounds release hydrogen without the presence of ammonia, diborane, or ethylenediamine. Our work represents the first example of Al-based amidoboranes with chelation coordination geometry, which provides an essential foundation for understanding the relationship of complex multi-metallic amidoboranes in terms of synthesis, structure, and properties. Full article

Based on the flexible adjustment of the seven-wire, this study will assemble a new toughened seven-wire which is combined with a common single welding wire and the existing welding wire containing ductile alloy element (Ni element), and the microstructure properties, mechanical properties and toughening mechanism of the welding seams were studied. The results show that the microstructure of the four combinatorial seven-wire welding seams is mainly composed of coarse proeutectoid ferrite (PF) and fine acicular ferrite (AF). Among them, the core of inclusions that induce AF nucleation and growth are mainly composed of Al, Ti, Si, and Mn-based oxides, and the edge of inclusions is mainly composed of Mn and Cu sulfides (MnS, CuS). The addition of Ti compounds further promotes AF nucleation. This is also a reason why the impact toughness of the combinatorial seven-wire W2/W3 welding seams is higher than that of other combinatorial seven-wire welding seams, but the impact toughness of the rich Ni seven-wire can meet the standard requirements of the China Classification Society (CCS). Among the four combinatorial seven-wire welding seams, the proportions of large angle grain boundaries (grain orientation difference ≥ 15°) that improve the ability of materials to prevent brittle fracture are 65.9%, 68.8%, 66.0%, 61.7%, respectively, that is, the larger proportion of large angle grain boundaries in combinatorial seven-wire W2 welding seams (Ni content is 0.0897%) is one of the reasons for the higher impact toughness of the welding seams. With the increase of Ni content in the welding seam, the AF content first increased and then decreased, the yield strength and tensile strength increased, and the elongation and section shrinkage first increased and then decreased. When the combinatorial seven-wire W2/W3 was used, the welding seam plasticity was the best. Full article

In this paper, the quantitative feasibility of time-of-flight secondary ion mass spectrometry (tof-SIMS) for major and minor elements in spodumene was evaluated in terms of calibration method with a matrix-matched or non-matrix-matched standard and an internal standard element using Al or Si. The matrix-matched standard calibration method was studied using spodumene 503R as the external standard and unknown sample, with signal intensities collected under positive ion mode using 100 µm of raster size. The sensitivities of Li, Na, Al, Si, Mn, and Fe were obtained by applying the sample-standard bracketing method, and the corresponding concentrations were given as the division of signal intensities by sensitivities. It was found that there were no significant differences between concentration results using Al and Si as the internal standard element. After 100% normalization, the concentrations at a 95% confidence level of matrix Li₂O, Al₂O₃, and SiO₂ in oxide form were found to be 7.62 ± 0.27%, 27.68 ± 0.10%, and 64.32 ± 0.29%, respectively, which agreed with those from LA-ICPMS measurements and/or EPMA analyses. The comparison of the minor components including Na₂O, MnO, and FeO showed that the contents from tof-SIMS were consistent with references from LA-ICPMS, giving ratios within 0.98–1.02. Furthermore, the element behavior investigation of NIST SRM 610 showed that the ionization efficiencies differentiated among the studied elements, resulting in far lower sensitivities of Li, Na, Mn, and Fe in spodumene than the values from the proposed matrix-matched standard calibration method. Thus, the matrix-matched standard calibration method for element determination of spodumene by tof-SIMS was recommended. The successful determination of major and minor elements in spodumene also promises the future application of tof-SIMS to trace element quantification. Full article

Red melilite structure CaY_1−xAl₃O₇: Eu_x (x = 0.04–0.24) phosphors for white LEDs were synthesized through a straightforward solid-state reaction process. These phosphors exhibit efficient excitation under near-ultraviolet light at 398 nm (⁷F₀ → ⁵L₆), producing the desired emission peak at 622 nm from the transitions of ⁵D₀ → ⁷F₂. The Eu doping concentration was also optimized as x = 0.16. The complete 3003 × 3003 energy matrix was constructed based on an effective Hamiltonian including both free-ion and crystal-field interactions within a complete diagonalization method (CDM). Eighteen experimental fluorescent spectra for Eu³⁺ ions at the Y³⁺ site of CaYAl₃O₇ crystal were quantitatively identified with high accuracy through fitting calculations. The fitting values are in reasonable agreement with the experimental results, thereby showcasing the efficacy of the CDM in probing luminescent phosphors for white LEDs. Full article

The four-quadrant detector (4QD), as a highly sensitive and fast-response position-sensitive device, is widely used in laser guidance, target tracking, and related fields. However, traditional visible and infrared 4QDs exhibit significant vulnerability to ambient light interference, particularly under high-intensity background illumination. To address this issue, this paper presents a solar-blind ultraviolet (UV) 4QD and a spot positioning system based on AlGaN diodes, achieving a UV/visible suppression ratio of 2.17 × 10⁴ (without solar-blind filters). The system employs a high-linearity, low-noise capacitive transimpedance amplifier (CTIA) as the readout circuit for the high-sensitivity and rapid-response solar-blind UV detectors, enabling the precise conversion of weak photocurrent signals into voltage signals for digitization. Utilizing a third-order polynomial least-squares fitting algorithm without introducing complex filtering techniques, the system achieves a maximum positioning error of 0.0101 mm and a root-mean-square error (RMSE) of 0.0057 mm, among of one the best-performing solar-blind UV 4QDs. The experimental results demonstrate exceptional spot positioning performance under a 275 nm laser source, meeting the high-precision requirements for space target detection. This research provides a reference for the application of solar-blind UV 4QDs in positioning, alignment, and monitoring scenarios, thereby holding significant practical implications. Full article

SmF₃ cannot be reduced to metallic samarium by aluminum due to variable valence states of Sm. This study investigates the reduction products of SmF₃ via an aluminothermic reduction. The effect of molar ratios of Al/SmF₃ on the morphology, elemental distribution, crystal structure, and chemical valence of the samples were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The thermodynamic results show that it is feasible for SmF₃ reduction by Al to form SmF₂ in 933~1356 K. SmF_2.413, AlF₃, and Sm(AlF)₅ are obtained under the condition of the molar ratio of Al to SmF₃ at 1:3, 2:3, 3:3, 4:3, and 5:3. The samarium of the reduction products exhibits mixed valence states of Sm³⁺ and Sm²⁺, with the ratio δ of F to Sm determined by a(δ) = −0.1794δ + 5.819 (0 ≤ δ ≤ 0.4615). The presence of adsorbed oxygen in the products facilitates the oxidation process from Sm²⁺ to Sm³⁺. These findings may provide a theoretical basis on the development of valence states for other rare earth elements in aluminothermic reduction. Full article

This study introduces a method aimed at enhancing both the accuracy and the range of magnetic field sensors, which are two critical parameters, in a novel NiCo₂O₄-based anomalous Hall effect sensor. To fine-tune the linear range of the sensor, we introduced epitaxial strain using a MgAl₂O₄ cover layer, which significantly influenced the strain-modulated magnetic anisotropy. A NiCo₂O₄/MgAl₂O₄/NiCo₂O₄/MgAl₂O₄ heterostructure was further constructed, achieving differentiation in the material characteristics across both upper and lower NiCo₂O₄ layers through the modulation of thickness and strain. A dual-layer Hall bar was designed to enhance the integration of the sensor, offering varied detection ranges. This approach enabled the realization of ultrahigh sensitivity, measuring 10,000 V/(AT) within a ±0.1 mT range, and a competitive sensitivity of 60 V/(AT) within a ±5 mT range. By reducing the thickness of the top NiCo₂O₄ layer, an ultra-wide measurement range of ±1000 mT was also achieved. These results highlight the considerable promise of NiCo₂O₄-based anomalous Hall effect devices as compact, multi-range tools in the domain of magnetic sensing technology. Full article