International Journal of Mechanical and Materials Engineering最新文献

A titanium oxynitride catalyst for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells was synthesized through the direct ammonia nitridation of titanium complexes. Titanium polyacrylate was employed as the catalyst precursor, and the effect of the calcination temperature between 600 and 1000 °C on the catalyst structure was studied. The catalysts were characterized via X-ray diffraction, X-ray absorption spectroscopy, transmission electron microscopy, cyclic voltammetry, and powder electrical resistivity measurements. The formation of titanium oxynitride particles and deposited carbon was observed for all the samples; however, significant variations in the catalyst structure and catalytic activity were also observed. With an increase in the calcination temperature, nitridation of titanium oxynitride progressed, and the conductivity of the catalyst powder increased. The highest rest potential and ORR current density were achieved with calcination at 800 °C. Importantly, the results suggest that maintaining an optimal nitrogen doping level within the catalyst particles, along with ensuring the formation of electroconductive deposited carbon, is essential for achieving a high ORR current. This work introduces the direct ammonia nitridation of metal complexes as a promising process for designing metal oxynitride catalysts.

Okra fiber is the bast fiber, extracted from the stem of the Abelmoschus esculentus plant which belongs to the Malvaceae family. In the whole world, India is the largest producer of okra for the cultivation of “okra fruit”, which is one of the main vegetables in the Indian Diet. After collecting vegetables, a huge amount of okra plant stem is discarded on the field annually as agricultural waste. Okra stem is an abundant source of okra fiber which can be used for various textile applications. This study aims understand the basic morphological, thermal and structural characteristics of okra fibre and compare it with other bast fibres generally used for textile application to prove the suitability of okra fibre for textile application.

The shift towards renewable energy sources like geothermal energy has become desirable due to the recurrent energy crisis and global warming challenges influenced by fossil fuels. Geothermo-mechanical energy conversion using shape memory alloy (SMA) heat engines presents a novel and sustainable approach for harnessing geothermal energy. Shape memory alloys, known for their ability to undergo reversible phase transformations driven by temperature changes, are ideal for thermal-to-mechanical energy conversion. This paper explores the design and performance of an SMA heat engine that utilizes geothermal heat sources to drive mechanical work. The engine operates by cycling between the high-temperature geothermal environment and a cooler sink, exploiting the shape memory effect to generate mechanical motion. By integrating geothermal energy and SMA technology, this system offers a potential solution for renewable energy generation, with applications in remote or off-grid locations. The paper also investigates output power and the thermodynamic efficiency. A model is formulated and the engine behavior is simulated. A series of experiments are conducted for engine output power and efficiency. The model is compared to the experimental data for validation. The engine developed a maximum power of 3.5, 8.5, and 11.5 watts at 60, 80, and 90 °C respectively. The proposed SMA-based geothermo-mechanical energy conversion system offers a promising solution for efficient, reliable, and scalable geothermal energy harvesting. This research contributes to the development of innovative, efficient geothermal energy conversion technologies, supporting global renewable energy goals and reducing greenhouse gas emissions. This innovative energy conversion mechanism could play a key role in the future of sustainable power generation.

Incomplete removal of antibiotics by most known wastewater treatment plants is a global challenge. Therefore, graphitic carbon nitride-modified cerium ferrite (CeFe₂O₄@g-C₃N₄) was synthesized to remove antibiotics (ampicillin, ciprofloxacin and erythromycin) from water. CeFe₂O₄@g-C₃N₄ showed activity in the visible light with a Tauc plot revealing the bandgap energy (2.46 eV). The scanning electron micrograph (SEM) result revealed the surface of CeFe₂O₄@g-C₃N₄ to be heterogeneous, while the transmission electron micrograph (TEM) image confirmed a flaky with rod and oval shaped surface (average particle size of 42.22 nm). CeFe₂O₄@g-C₃N₄ exhibited a 100% removal of all the studied antibiotics from aqueous solution in a photocatalytic degradation that is described by pseudo-1st-order kinetics. CeFe₂O₄@g-C₃N₄ demonstrated a high regeneration capacity, which is above 90% at the 12th cycle of treatment without any observable changes in its phase structure which suggests a promising chemical stability and reusability. CeFe₂O₄@g-C₃N₄ compared favourably with some selected antibiotic degradable photocatalysts suggesting the economic viable of CeFe₂O₄@g-C₃N₄ as photocatalyst for the purification of antibiotics-contaminated water.

Graphical Abstract

In this study, we have successfully developed and tested sealing concepts for symmetrical, planar proton-conducting ceramic cells (PCCCs). Three glass sealants from the field of solid oxide cells were investigated as potential compatible sealing materials for PCCCs. The most promising results were obtained with a SiO₂-MgO-CaO-Na₂O-Al₂O₃-ZrO₂-B₂O₃ glass, which provided a dense, crack-free sealant between the proton-conducting ceramic cells and the Al₂O₃-coated ferritic steels. During the sealing process, a reaction layer between the interface of the BaCe_0.2Zr_0.7Y_0.1O_3-δ contained in the PCCCs and the glass–ceramic, occurred. Here, we propose a reaction mechanism for this interaction and discuss its impact on potential applications. Moreover, next to evaluating potential glass sealants, we have successfully designed and demonstrated a new sealing geometry that prevents a potential gas crossover in the symmetrical proton-conducting ceramic cell.

Natural materials are becoming a reliable alternative to traditional artificial materials used in sound absorption insulation. The present study was conducted to investigate the acoustic insulation of micro-perforated panel (MPP) based on sugarcane fibers and bagasse as an available and environmentally friendly material. The absorption properties of single- and double-leaf natural micro-perforated panels (MPP) made of bagasse and also nonnatural MPPs made of Plexiglass were measured using an impedance tube based on ISO 10534–2. Then the effect of bagasse and sugarcane fibers composite on the air gap of MPP was investigated. The results showed the peak sound absorption of the bagasse composite is in the range of 1000 to 2000 Hz, and the sugarcane fiber composite has a higher sound absorption coefficient than the bagasse composite. Also, natural MPPs have a higher absorption coefficient than nonnatural MPPs at all frequencies, and as the panel thickness increases, the peak absorption coefficient shifts to lower frequencies. The peak sound absorption coefficient of double-leaf MPPs made of bagasse is 76%, in the range of 160 to 200 Hz. Using sugarcane fiber composite in the air gap of single- and double-leaf natural MPPs causes the absorption peak to shift to frequencies below 100 Hz. According to the results, natural MPPs have a high sound absorption coefficient at low frequencies. These panels can control sounds with much lower frequencies, especially in a double layer and along with cane fiber composite in their air gap.

Abstract

As part of the development of a new organic entity, we synthesized three new reduced forms of Schiff bases named 2,2’-(((2,2-dimethylpropane-1,3-diyl)bis(azanediyl)bis(methylene)disphenol (I1), 4,4’-(((2,2-dimethylpropane-1,3-diyl)bis (azanediyl)bis(methylene)bis(2-methoxyphenol) (I2), and 6,6’-(((2,2-dimethylpropane-1,3-diyl) bis(azanediyl)bis(methylene)bis(2-methoxyphenol) (I3). In order to develop new organic ligands to inhibit steel corrosion in 1M HCl solution, various electrochemical methods, such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP), along with surface visualization through atomic force microscopy (AFM), were employed. PDP results revealed excellent inhibition by compound I3 (71%) at a concentration of 1 mg/L. These findings were supported by the observation of a protective layer formation during prolonged immersion of steel in a corrosive solution, with or without inhibitors. In addition to gaining insights into the interaction mechanism and adsorption mode, density functional theory, Monte Carlo, and molecular dynamic simulations were conducted, revealing valuable information about the interaction of the inhibitors with the steel surface. Average surface roughness (R_a) values obtained for the artificial seawater in the absence and presence of inhibitor are 887 nm for blank, 195 nm for I1, 158 nm for I2, and 105 nm for I3.

Metakaolin phosphate geopolymers comprising poly-phospho-siloxo units are known for their structural performance, additionally advancing their microstructure with the transformation of crystalline berlinite phases at elevated temperatures. The intrinsic reaction of Al of metakaolin in the acid exploited, but the reaction of secondary silica phases is limitedly known. Metakaolin as a primary precursor (M) with the addition of 2% and 5% of nano silica (MS2 and MS5) and micro silica (MM2 and MM5) cast using 8-M phosphoric acid was cured at 80 °C. To enhance the utilization of geopolymer in any high-temperature applications, the structural transformations were studied after heating to various temperatures (200, 400, 600 and 800 °C) by XRD, Raman, TGA-DTA, SEM, XPS, FTIR and MAS-NMR. Sample M attained a strength of 46.2 MPa enhanced to 63.6 MPa in MS5 and 54.2 MPa in MM5. This can be ascribed from the transformation of Si–O–Al–O–Si into Si–O–Al–O–P from Raman bands. Comparing the chemical shift of Al (IV) to control, micro silica addition shifts the signal to a lower field (53 to 50 ppm) related to the increase of the number of Al-connected Si to give a tougher network. Nanoindentation is visualized from hardness and elasticity, and the corresponding values are 1.4 to 2.1 GPa and 0.8 to 1.4 GPa for loads ranging from 20 to 100 mN in silica-reinforced samples that are much higher than M. The micro and macro hardness is due to the reinforcement of quartz in micro silica around the gel. TGA-DTA showed that the reduction of mass loss is as high as 25.4% in control whereas 17.2% in MS5 and 15.8% in the MM5. Further, shrinkage rate in MS5 and MM5 was as low as − 1.1% and − 0.8% throughout the temperature range from 25 to 1000 °C and thus provides the way of use of nano and micro form of silica for better thermal resistance.

Graphical Abstract

Environmental pollution is a major global issue due to the increase of various pollutants all over the world. Enhancing pollutant remediation strategies for environmental sustainability necessitates increasing the efficiency of conventional methods or introducing innovative approaches. Nanotechnology, particularly carbon-based nanomaterials, offers substantial promise due to their high surface area and absorption potential. Concurrently, organocatalysts have emerged as sustainable and versatile alternatives to traditional metal-based catalysts in modern chemical research. This study highlights the synthesis and application of organo-nanocatalysts derived from biomass, specifically a spherical carbon nanocatalyst synthesized from sugar beet pulp. This novel green catalyst, characterized by high selectivity and efficiency, successfully converts epoxides and CO₂ into valuable cyclic carbonates under solvent-free conditions. The hydroxyl groups on the Sugar Beet-derived Carbon NanoSphere (SCNS) surface act as Bronsted acid sites, facilitating epoxide activation via hydrogen bonding. The integration of carbon-based nanomaterials and organocatalysis represents a promising, sustainable solution for pollutant remediation and green chemistry advancements.

Graphical Abstract