Search Results (27)

Ammonia borane (AB), with a theoretical hydrogen content of 19.6 wt%, is constrained by its low crystalline density (0.758 g/cm³) and poor thermal stability (decomposing at 100 °C). In this study, AB/ammonium perchlorate (AP) composites were synthesized via freeze-drying at a 1:1 molar ratio. The integration of AP introduced intermolecular interactions that suppressed AB decomposition, increasing the onset temperature by 80 °C. Subsequent vacuum calcination at 100 °C for 2 h formed oxygen/fuel-integrated ammonium perchlorate borane (APB), which achieved decomposition temperatures exceeding 350 °C. The proposed mechanism involved AB decomposing into borazine and BN polymers at 100 °C, which then NH₃BH₂⁺/ClO₄⁻ combined to form APB. At 350 °C, APB underwent the following redox reactions: 4NH₃BH₂ClO₄ → N₂↑ + 4HCl↑ + 2B₂O₃ + N₂O↑ + O₂↑ + 7H₂O↑ + H₂↑, while residual AP decomposed. The composite exhibited improved density (1.66 g/cm³) and generated H₂, N₂, O_2, and HCl, demonstrating potential for hydrogen storage. Additionally, safety was enhanced by the suppression of AB’s exothermic decomposition (100–200 °C). APB, with its high energy density and thermal stability, was identified as a promising high-energy additive for high-burning-rate propellants. Full article

This study investigates the synergistic enhancement of molecular oxygen activation (MOA) in silver phosphate (Ag₃PO₄) photocatalysts modified with oxygen vacancies (OVs) and silver nanoparticles (Ag⁰). The vacuum-calcined Ag₃PO₄ exhibited a 2.05-fold increase in the degradation efficiency of cylindrospermopsin (CYN), reaching 88.00% within 5 min, compared to its pristine counterpart. This work proposes a novel dual-modification approach—rarely explored in previous MOA studies—by introducing OVs and Ag⁰ simultaneously. The characterization results confirmed that OVs improved the charge transfer and adsorption of molecular oxygen, while the Ag⁰ nanoparticles facilitated electron–hole separation and interfacial charge transfer. Reactive oxygen species (ROS) such as ·O₂⁻, ¹O₂, H₂O₂, and ·OH were confirmed via ESR analysis and chemical assays. A detailed mechanism was proposed and illustrated, showing how OVs and Ag⁰ synergistically promote MOA. These findings highlight a cost-effective method for enhancing photocatalysis and environmental remediation. Full article

Heavy metal pollution in landfill soil poses a dual challenge of environmental toxicity and resource depletion. Enzyme-induced carbonate precipitation (EICP) was systematically evaluated as a sustainable stabilization method for cadmium (Cd), lead (Pb), and chromium (Cr) under both solution- and soil-phase conditions. Laboratory-scale experiments demonstrated that EICP achieved over 80% removal efficiency for Cd, Pb, and copper (Cu) in solution-phase systems, while soil-phase trials focused on Cd, Pb, and Cr to simulate realistic field conditions. Optimal performance was achieved using a 1:1 molar ratio of soybean-derived urease (1.0 U/mL) to CaCl₂ (0.5 M), with Cd stabilization reaching 91.5%. Vacuum-assisted filtration improved treatment uniformity by 29.2% in clay soils. X-ray diffraction identified crystalline otavite in Cd systems, while Pb and Cu were stabilized via surface adsorption. Sequential extraction confirmed that over 70% of Cd was transformed into carbonate-bound phases. Treated soils met TCLP leaching standards and reuse criteria, maintaining neutral pH (7.2–8.1) and low salinity. Compared to cement-based methods, EICP avoids CO₂ release from calcination and fossil fuel use. Carbon in urea is retained as solid CaCO₃, reducing emissions by 0.3–0.5 t CO₂-eq per ton of soil. These findings support EICP as a scalable, low-carbon alternative for landfill soil remediation. Full article

In this study, bentonite clay was modified through silane treatment and calcination to enhance its compatibility with basalt fiber (BF) and epoxy in multiscale composites. The as-received bentonite (ARB) was subjected to silane treatment using APTES, producing silane-modified bentonite (STB), while calcination yielded calcined bentonite (CB). The modified clays were incorporated into basalt fiber-reinforced epoxy (BFRP) composites, which were fabricated using the vacuum-assisted resin transfer method (VARTM). Analytical techniques, including X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, confirmed the structural changes in the clays. BET surface area analysis revealed a 314% increase in the surface area of STB and a 176% increase for CB. The modified clays also demonstrated reduced hydrophilicity and swelling behavior. Thermogravimetric analysis (TGA) indicated a minimal improvement in thermal stability, with the degradation onset temperatures increasing by less than 3 °C. However, tensile tests showed significant gains, with CB- and STB-reinforced composites achieving 48% and 21% higher tensile strength than ARB-reinforced composites. Tribological tests revealed substantial reductions in wear, with CB- and STB-reinforced composites showing 90% and 84% decreases in the wear volume, respectively. These findings highlight the potential of modified bentonite clays to improve the mechanical and wear properties of basalt fiber–epoxy composites. Full article

This study aims to explore the viability of adding a hybrid blend of eggshell and banana fibers treated with NaOH to improve the structural characteristics of epoxy composites. In order to determine their appropriateness for different applications, the study includes assessments of mechanical performance, water permeability, and heat transfer properties. Chicken eggshell was used to make calcined eggshell particulate (CEP), and bananas were used to obtain processed banana fibers (TBF). For the creation of bio-composites, NaOH-treated banana fiber (30 wt.%) was integrated into an epoxy matrix with different weight percentages of CEP (like 0, 4, 8, 12, 16, and 20 wt.%) through the hand layup with a vacuum backing technique. Examination of the data revealed that, in comparison to epoxy with no reinforcement, the addition of bio-fillers improved the thermal insulation (4 wt.% of CEP exhibits 0.052 W/mk), water absorption (4 wt.% of CEP produced 5.31%), flexural strength (20 wt.% of CEP exhibit 36.57 MPa), and modulus (12 wt.% of CEP exhibit 300.12 MPa) of the hybrids. This suggests that by lowering the conductivity of the bio-based composites, the inclusion of these bio-based reinforcements improved their thermal insulation ability. The resistance to temperature fluctuations is stronger when there is less thermal conductivity. Full article

Nitrogen and sulfur co-doped graphene-like carbon nanosheets (CNSs) with a two-dimensional structure are prepared by using methylene blue as a carbon source and expanded vermiculite as a template. After static negative pressure adsorption, high-temperature calcination, and etching in a vacuum oven, they are embedded in the limited space of the vermiculite template. The addition of an appropriate number of mixed elements can improve the performance of a battery. Via scanning electron microscopy, it is found that the prepared nitrogen–sulfur-co-doped carbon nanosheets exhibit a thin yarn shape. The XPS results show that there are four elements of C, N, O, and S in the carbon materials (CNS-600, CNS-700, CNS-800, CNS-900) prepared at different temperatures, and the N atom content shows a gradually decreasing trend. It is mainly doped into a graphene-like network in four ways (graphite nitrogen, pyridine nitrogen, pyrrole nitrogen, and pyridine nitrogen oxide), while the S element shows an increasing trend, mainly in the form of thiophene S and sulfur, which is covalently linked to oxygen. The results show that CNS-700 has a discharge-specific capacity of 460 mAh/g at a current density of 0.1 A/g, and it can still maintain a specific capacity of 200 mAh/g at a current density of 2 A/g. The assembled lithium-ion capacitor has excellent energy density and power density, with a maximum power density of 20,000 W/kg. Full article

This study conducts low-vacuum sulfidation to form a sulfidation layer on the serpentinite-derived magnesium iron silicate, thereby enhancing its electrochemical properties. Results show (Mg,Fe)₂SiO₄ calcined at 900 °C has the best crystallinity, and the cubic FeS₂ is synthesized on the surface of the orthorhombic magnesium iron silicate (MFS). Two distinct charge plateaus can be distinguished during the first charge process, and the discharge capacities increased significantly. This study confirms that the surface FeS₂ layer provides extra ion pathways, allowing more lithium/magnesium ions to be extracted and inserted in the serpentinite-derived magnesium iron silicate. Accordingly, the serpentinite electrode boasts straightforward exploitation with low-cost advantages and potential. Full article

To alleviate the increasing energy crisis and achieve energy saving and consumption reduction in building materials, preparing shape-stabilized phase-change materials using bio-porous carbon materials from renewable organic waste to building envelope materials is an effective strategy. In this work, pine cone porous biomass carbon (PCC) was prepared via a chemical activation method using renewable biomaterial pine cone as a precursor and potassium hydroxide (KOH) as an activator. Polyethylene glycol (PEG) and octadecane (OD) were loaded into PCC using the vacuum impregnation method to prepare polyethylene glycol/pine cone porous biomass carbon (PEG/PCC) and octadecane/pine cone porous biomass carbon (OD/PCC) shape-stabilized phase-change materials. PCCs with a high specific surface area and pore volume were obtained by adjusting the calcination temperature and amount of KOH, which was shown as a caterpillar-like and block morphology. The shape-stabilized PEG/PCC and OD/PCC composites showed high phase-change enthalpies of 144.3 J/g and 162.3 J/g, and the solar–thermal energy conversion efficiencies of the PEG/PCC and OD/PCC reached 79.9% and 84.8%, respectively. The effects of the contents of PEG/PCC and OD/PCC on the temperature-controlling capability of rigid polyurethane foam composites were further investigated. The results showed that the temperature-regulating and temperature-controlling capabilities of the energy-storing rigid polyurethane foam composites were gradually enhanced with an increase in the phase-change material content, and there was a significant thermostatic plateau in energy absorption at 25 °C and energy release at 10 °C, which decreased the energy consumption. Full article

Aiming to promote the application of D-mannitol in the field of phase change thermal storage, obstacles, including low thermal storage efficiency and high supercooling, should be properly disposed of. The adoption of adaptable and low-cost supporting materials to make shape-stable phase change materials (ss-PCMs) affordable is a primary solution to solve the above shortcomings. In this study, high-performance ss-PCM for effective medium-temperature heat storage was prepared using expanded vermiculite as the support for D-mannitol preservation. Among the three candidates that treated the raw vermiculite by dilute acid, calcination, and microwave heating, the calcinated expanded vermiculite (CV) was characterized as the most suitable one. After impregnating D-mannitol into the CV carrier by vacuum, a melting enthalpy of 205.1 J/g and a crystallization enthalpy of 174.1 J/g were achieved by the as-received CV/D-mannitol ss-PCM. Additionally, the supercooling of the ss-PCM was reduced to 45.6 °C. The novel CV/D-mannitol ss-PCM also exhibited excellent reusability and stability. All the findings indicate that the abundant and inexpensive CV exhibited great potential as the supporting material for D-mannitol-based ss-PCMs, which allow effective waste heat recovery and temperature regulation. Full article

Molybdenum carbide co-catalyst and carbon nanofiber matrix are suggested to improve the nickel activity toward methanol electrooxidation process. The proposed electrocatalyst has been synthesized by calcination electrospun nanofiber mats composed of molybdenum chloride, nickel acetate, and poly (vinyl alcohol) under vacuum at elevated temperatures. The fabricated catalyst has been characterized using XRD, SEM, and TEM analysis. The electrochemical measurements demonstrated that the fabricated composite acquired specific activity for methanol electrooxidation when molybdenum content and calcination temperature were tuned. In terms of the current density, the highest performance is attributed to the nanofibers obtained from electrospun solution having 5% molybdenum precursor compared to nickel acetate as a current density of 107 mA/cm² was generated. The process operating parameters have been optimized and expressed mathematically using the Taguchi robust design method. Experimental design has been employed in investigating the key operating parameters of methanol electrooxidation reaction to obtain the highest oxidation current density peak. The main effective operating parameters of the methanol oxidation reaction are Mo content in the electrocatalyst, methanol concentration, and reaction temperature. Employing Taguchi’s robust design helped to capture the optimum conditions yielding the maximum current density. The calculations revealed that the optimum parameters are as follows: Mo content, 5 wt.%; methanol concentration, 2.65 M; and reaction temperature, 50 °C. A mathematical model has been statistically derived to describe the experimental data adequately with an R² value of 0. 979. The optimization process indicated that the maximum current density can be identified statistically at 5% Mo, 2.0 M methanol concentration, and 45 °C operating temperature. Full article

MnOx-ZrO₂ catalysts prepared by co-precipitation and vacuum impregnation were calcined at 400–800 °C and characterized by powder X-ray diffraction, textural studies, high-resolution transmission electron microscopy, temperature-programmed reduction, X-ray absorption near edge structure, and X-ray photoelectron spectroscopy. The catalytic activity was tested in the CO oxidation reaction. The activity of the co-precipitated samples exceeds that of the catalysts prepared by vacuum impregnation. The characterization studies showed that the nature of the active component for the catalysts obtained by co-precipitation differs from that of the catalysts obtained by impregnation. In the impregnation series, the most active catalyst was obtained at a temperature of 400 °C; its increased activity is due to the formation of MnO₂ oxide nanoparticles containing Mn⁴⁺ and low-temperature reducibility. An increase in the synthesis temperature leads to the formation of less active Mn₂O₃, catalyst sintering, and, accordingly, deterioration of the catalytic properties. In the case of co-precipitation, the most active CO oxidation catalysts are formed by calcination at 650–700 °C in air. In this temperature interval, on the one hand, a Mn_yZr_1−yO_2−x solid solution is formed, and on the other hand, a partial separation of mixed oxide begins with the formation of highly dispersed and active MnOx. A further increase in temperature to 800 °C leads to complete decomposition of the solid solution, the release of manganese cations into Mn₃O₄, and a drop in catalytic activity. Full article

As a result of preliminary air calcination and subsequent reduction in a flowing NH₃ atmosphere of the precursor from the liquid precipitation method for the first time, pure-phase Tb₂O₃ powder with an average particle size of 135 nm was prepared. The Tb₂O₃ magneto-optical transparent ceramics with the average grain size of 1.3 μm were successfully fabricated by vacuum pre-sintering and hot isostatic pressing post-treatment from the as-synthesized Tb₂O₃ powder. In-line transmittance values of Tb₂O₃ ceramics reach 70.3% at 633 nm, 78.1% at 1064 nm, and 79.4% at 1400 nm, respectively. Thanks to the high intrinsic concentration of Tb³⁺, Tb₂O₃ ceramics present high Verdet constants of −427.3 and −123.7 rad·T⁻¹·m⁻¹ at 633 and 1064 nm, which are about 3.1 and 3.4 times higher than those of commercial Tb₃Ga₅O₁₂ crystals, respectively. Due to the excellent magneto-optical properties, Tb₂O₃ ceramics are promising candidates for the development of Faraday isolator toward compaction used in visible and near-infrared bands. Full article

A cost-effective solution for the synthesis of high-porosity TiO₂ aerogels, which can be used as a mesoporous perovskite network charge-carrier material during the manufacture of solar cells, is described. The effects of the synthesis parameters (precursor (titanium (IV) isopropoxide (TIP) and tetrabutyl orthotitanate (TBOT)), additional solvent exchange (n-hexane (nH), cyclohexane (CH), and diethyl ether (DE)), subcritical drying (800 mbar vacuum, 70 °C, 8 h), aging, and calcination on the aerogel’s structure have been investigated. Methods of XRD, FT-IR, BET, Raman, STA, SEM, UV–vis, and thermal conductivity measurements were applied to find out the relation between the synthesis conditions and the properties of the synthesized aerogels. Amorphous aerogels are polydispersed systems with the highest probability of pore diameter from 0.5 to 15 nm. An nH-exchanged, aged aerogel synthesized from the precursor TIP shows the highest diameter of pores. After calcination, the aerogels tend to crystallize into an anatase phase and the size of the crystallites depends on the precursor’s nature. Calcination leads to a significant increase in both the apparent and true density of the aerogels, and it also results in an increase in porosity and thermal conductivity. Full article

The present preparation methods of molybdenum dioxide (MoO₂) quantum dots (QDs) are often cumbersome and not environmentally friendly, and more importantly, the prepared MoO₂ QDs are usually wrapped in surfactants, which are difficult to be removed and impact their intrinsic characterization and performance. Herein, we present a facile, scalable and sustainable approach to obtain clean and pure MoO₂ QDs (1.5~3 nm), which consists of a hydrothermal reaction and a further calcination process in vacuum following freeze drying. Furthermore, the influence of calcination temperature, atmosphere and time is also studied. The calcination at 400 °C for 2 h in vacuum can efficiently remove the surfactants wrapping on the MoO₂ QDs without obvious size change, whereas the calcination in nitrogen will lead to a slight increase in size, and the calcination in air could transform MoO₂ QDs into MoO₃ nanoplates. In addition, the pseudocapacitive performance of the as-prepared samples is tested and compared by electrochemical methods, and the specific capacitance of the clean MoO₂ QDs is about 1.4 times larger than that of MoO₂ QDs with surfactants at 5 mV s⁻¹. This study also demonstrates a possible way to efficiently remove the organic substance wrapping on quantum dot materials. Full article

This work aimed at synthesizing MoO₃ and MoO₂ by a facile and cost-effective method using extract of orange peel as a biological chelating and reducing agent for ammonium molybdate. Calcination of the precursor in air at 450 °C yielded the stochiometric MoO₃ phase, while calcination in vacuum produced the reduced form MoO₂ as evidenced by X-ray powder diffraction, Raman scattering spectroscopy, and X-ray photoelectron spectroscopy results. Scanning and transmission electron microscopy images showed different morphologies and sizes of MoO_x particles. MoO₃ formed platelet particles that were larger than those observed for MoO₂. MoO₃ showed stable thermal behavior until approximately 800 °C, whereas MoO₂ showed weight gain at approximately 400 °C due to the fact of re-oxidation and oxygen uptake and, hence, conversion to stoichiometric MoO₃. Electrochemically, traditional performance was observed for MoO₃, which exhibited a high initial capacity with steady and continuous capacity fading upon cycling. On the contrary, MoO₂ showed completely different electrochemical behavior with less initial capacity but an outstanding increase in capacity upon cycling, which reached 1600 mAh g⁻¹ after 800 cycles. This outstanding electrochemical performance of MoO₂ may be attributed to its higher surface area and better electrical conductivity as observed in surface area and impedance investigations. Full article