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Stabilization Method for Speed Observer of Induction Machine
- Marcin Morawiec
- Lelisa Wogi
- Piotr Kołodziejek
2025 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
This article proposes the speed estimation principles dedicated to the observer structures based on the machine mathematical model. The rotor speed is reconstructed based on the mathematical model of a machine by using both adaptive and nonadaptive schemes. The presented principle is generalized to the classical nonlinear system in the vector form and can be applied to induction machines. The proposed rotor speed reconstruction approach is based on an algebraic relationship, and the observer system mathematical model has the same rank as the induction machine. The speed observer structure can be unstable due to the challenge of stabilizing the sensorless control of the induction machine at low-speed, near zero speed, or in the low-speed regenerating mode of operation. As a result, the new stabilizing functions based on Lagrange identity are proposed in this work to improve the range of observer stability. The proposed approach includes newly developed stabilization mechanisms that ensure observer stability under both motoring and regenerating modes of operations at the low rotor speed and improve the observer range of stability. The Lyapunov theorem is used during the design procedure for stability purposes. The simulation and experimental studies are carried out for an induction machine adaptive and nonadaptive full-order observer. The experimental results show that stable operation of the system is obtained, and the range of observer stability is improved, especially at low-speeds and in a regenerating mode of operation, concluding that the proposed solution is suitable for use in industrial applications.
Strategies for feature-assisted development of topology agnostic planar antennas using variable-fidelity models
- Adrian Bekasiewicz
- Khadijeh Askaripour
- Mariusz Dzwonkowski
- Tom Dhaene
- Ivo Couckuyt
2025 Journal of Computational Science
Design of antennas for contemporary applications presents a complex challenge that integrates cognitive-driven topology development with the meticulous adjustment of parameters through rigorous numerical optimization. Nevertheless, the process can be streamlined by emphasizing the automatic determination of structure geometry, potentially reducing the reliance on traditional methods that heavily rely on engineering insight in the course of antenna development. In this work, which is an extension of our conference paper [1], a specification-oriented design of topologically agnostic antennas is considered by utilizing two strategies focused on bandwidth-specific design and bandwidth-enhanced optimization. The process is embedded within a variable-fidelity framework, where the low-fidelity optimization involves classification of randomly generated topologies, followed by their local tuning using a trust-region algorithm applied to a feature-based representation of structure response. The final result is then tuned using just a handful of high-fidelity simulations. The strategies under consideration were verified on a case study basis concerning automatic generation of three radiators with varying parameters. Benchmarks of the algorithm against more standard optimization methods, as well as comparisons of the obtained topologies with respect to state-of-the-art antennas from literature have also been considered.
Structure, performance, and photooxidative stability of Mater-Bi/brewers' spent grain composites as a function of filler thermomechanical and chemical modification
- Aleksander Hejna
- Mateusz Barczewski
- Paulina Kosmela
- Olga Mysiukiewicz
2025 INDUSTRIAL CROPS AND PRODUCTS
Nowadays, to provide a step towards circularity, the development of sustainable polymer composites should include the application of waste-based materials that can act not only as simple fillers, reducing the use of polymers but also as functional additives, limiting or eliminating the use of synthetic components. Herein, in the presented study, the main by-product of the brewing industry, brewers' spent grain (BSG), was applied as a functional filler for biocomposites based on poly(butylene adipate-co-terephthalate)/thermoplastic starch/poly(ε-caprolactone) matrix – Mater-Bi. To enhance its stabilizing functionalities and interfacial adhesion with the matrix, BSG was subjected to thermomechanical modification in a twin-screw extruder and chemical treatment with isophorone diisocyanate. Combined treatments reduced the interfacial hydrophilicity gap, facilitating melt processing, which was expressed by even a 30 % decrease in melt viscosity. Moreover, despite the incorporation of 30 wt% of low-cost BSG filler, flexural and tensile strength were hardly affected, while moduli increased even by 174 and 139 %, respectively. In situ generation of Maillard reaction products during BSG thermomechanical treatment enhanced the thermal stability of composites in an oxidative atmosphere, shifting degradation onset even by 30 °C. The stabilizing impact was also evidenced by the hindered photooxidative degradation of biocomposites. The unfavorable changes in biocomposites' surface roughness, as well as thermal properties and stability, have been limited by the increasing temperature of BSG thermomechanical treatment. Composites developed in the presented study could be effectively applied in manufacturing disposable or multi-use products, e.g., packaging materials, food containers, or cosmetic accessories like brushes, combs, or toothbrushes.
Study of vibrational surface topography measurement errors of LPBF Inconel 718 alloy after shot peening process
- Przemysław Podulka
- Anna Rudawska
- Wojciech Macek
2025 MEASUREMENT
A study of surface topography can provide valuable information on the product. Since the material finishing relies on the measured topography, the manufacturing process can be controlled by studying the roughness. The Laser Power Bed Fusion (LPBF) materials belong to the commonly used surfaces in the industry. Measuring this type of material with a contactless method can be found in many practical implementations. The white light interference method can be classified as one of the most encouraging surface topography measurement techniques in the last decade. Due to its fast application and data collection, it can be proposed for many demanding production processes. However, this measuring method is fraught with many errors, some caused by external environmental disturbances. One of them is a vibration, which can cause the occurrence of high-frequency measurement noise. This vibrational measuring noise can influence the ISO 25178 surface texture parameters significantly. It was found that the high-frequency noise distorted some surface topography parameters more than 100 %. In this study, the methodology of reduction of vibrational surface topography measurement noise was proposed using general functions and digital filters. Advantages of application of the proposed method against standardized, generally proposed S–filter were indicated. Finally, the new methodology was validated in terms of ISO 25178 surface texture parameters evaluation.
Sustainability, reliability, and durability of civil engineering structures
- Agnieszka Tomaszewska
- Jacek Szafran
- Bettina Brune
- Krzysztof Wilde
2025 Pełny tekst Bulletin of the Polish Academy of Sciences-Technical Sciences
Considering the Bulletin Readers’ interest in civil engineering,the Special Section “Sustainability, reliability, and durability of civil engineering structures” is now presented, with papers that, by studying specific cases, fully embrace all aspects related to the topic, starting from geometry design, determination of load acting on a structure, characteristics of the material for construction purpose, characteristics of structural behaviour under a certain load, identification of structural parameters or model, safety assessment, and finally, comfort of use. Most of the papers included in this Special Section were orally presented during the 29th International Conference “Lightweight Structures in Civil Engineering”, held in December 2023 at the Gdansk University of Technology.
Technological Considerations of Periodic Repair Works of Concrete Industrial Floors
- Sylwia Świątek-Żołyńska
- Maciej Niedostatkiewicz
2025 Pełny tekst Civil and Environmental Engineering Reports
Concrete floors are among the elements in construction facilities whose design requires engineering experience, workmanship requires the maintenance of a technological regime, while during their operation it is necessary to conduct periodic repairs. Concrete floors are most often used as working and communication space in industrial facilities, and very often they are also a functional element in objects that are immovable monuments. Regardless of the place of installation, concrete floors require periodic maintenance works whose scope should each time be individually adapted to the current use of the object. Improper selection of maintenance work technology and incorrect application of technological solutions related to the renovation of floors can cause rapid deterioration of their technical condition, which may lead to the need to take them out of service, which in turn may result in the need to interrupt the use of the building facility, including production facilities of industrial facilities. The paper presents a collection of practical information related to conducting periodic repair work on concrete industrial floors The article is a case study and addresses specific situations related to the loss of serviceability of concrete industrial floors.
The Impact of 8- and 4-Bit Quantization on the Accuracy and Silicon Area Footprint of Tiny Neural Networks
- Paweł Tumialis
- Marcel Skierkowski
- Jakub Przychodny
- Paweł Obszarski
2025 Electronics
In the field of embedded and edge devices, efforts have been made to make deep neural network models smaller due to the limited size of the available memory and the low computational efficiency. Typical model footprints are under 100 KB. However, for some applications, models of this size are too large. In low-voltage sensors, signals must be processed, classified or predicted with an order of magnitude smaller memory. Model downsizing can be performed by limiting the number of model parameters or quantizing their weights. These types of operations have a negative impact on the accuracy of the deep network. This study tested the effect of model downscaling techniques on accuracy. The main idea was to reduce neural network models to 3 k parameters or less. Tests were conducted on three different neural network architectures in the context of three separate research problems, modeling real tasks for small networks. The impact of the reduction in the accuracy of the network depends mainly on its initial size. For a network reduced from 40 k parameters, a decrease in accuracy of 16 percentage points was achieved, and for a network with 20 k parameters, a decrease of 8 points was achieved. To obtain the best results, knowledge distillation and quantization-aware training methods were used for training. Thanks to this, the accuracy of the 4-bit networks did not differ significantly from the 8-bit ones and their results were approximately four percentage points worse than those of the full precision networks. For the fully connected network, synthesis to ASIC (application-specific integrated circuit) was also performed to demonstrate the reduction in the silicon area occupied by the model. The 4-bit quantization limits the silicon area footprint by 90%.
The influence of chitosan's molecular weight, concentration, and dissolution method on the properties of electrophoretically deposited coatings on the Ti13Nb13Zr alloy surface
- Łukasz Pawłowski
- Szymon Mania
- Adrianna Banach-Kopeć
- Karol Staszczyk
- Aleksandra Mirowska
- Aleksandra Mielewczyk-Gryń
- Robert Tylingo
2025 MATERIALS CHEMISTRY AND PHYSICS
In this study, the effects of molecular weight (high, medium, and low), concentration (0.1 and 0.5 %) and dissolution method (in a rarely used hydroxyacetic acid and utilizing a novel CO2 saturation) of chitosan on the microstructure, chemical composition, wettability, surface roughness, adhesion, corrosion resistance and antibacterial activity of chitosan coatings electrophoretically deposited (10 V, 1 min) on β titanium alloy Ti13Nb13Zr were investigated. Microstructural analysis showed that low molecular weight chitosan at low concentrations formed uniform coatings while increasing these parameters resulted in uneven coatings with agglomerates. Energy-dispersive X-ray and Fourier transform infrared spectroscopy analyses confirmed the presence of chitosan on all coated samples. Higher concentrations of chitosan yielded thicker coatings. Wettability tests confirmed hydrophilic properties for all samples, with contact angles around 70°. Surface roughness varied with chitosan concentration, showing increased roughness for higher concentrations. Adhesion tests showed the highest critical load for high molecular weight chitosan coatings with a concentration of 0.1 %. Corrosion tests revealed that low molecular weight chitosan coatings provided the best protection. Antimicrobial assays showed that chitosan coatings prepared using acid dissolution had strong bactericidal activity against both Gram-positive and Gram-negative bacteria, while those prepared using CO2 saturation showed limited bacteriostatic activity. These findings suggest that chitosan coatings, especially those prepared using acid dissolution, hold promise for biomedical applications requiring corrosion resistance and antibacterial properties.
The Laser Processing of the Stainless-Steel Surface Layer of a Heat Exchanger Membrane in Order to Enhance Its Heat Transfer Coefficient
- Ewa Kozłowska
- Marek Szkodo
- Tomasz Muszyński
- Paulina Adamska
2025 Coatings
Research on temperature regulation is essential for ensuring thermal comfort and optimizing machine performance. Effective cooling systems are critical in industrial processes and everyday electronic devices in order to prevent overheating. Laser-modified heat exchangers can enhance heat dissipation without increasing weight, addressing the need for energy-efficient solutions in the market. The main aim of this experimental research was to establish an efficient method for altering the surface layer of AISI 316L stainless steel with laser pulses and to determine the effectiveness of the laser alterations to the surface layer in the context of intensifying the convective heat transfer. A series of laser-texturing processes was performed on the surface layer of AISI 316L steel using a Nd: YAG pulse laser. Selected samples were subjected to a series of measurements using a recuperator-type heat exchanger. Based on the measurements’ results, the heat transfer coefficients, α, obtained from the modified surfaces were determined. The results were compared with other data from the existing literature and those obtained from unmodified reference samples. The intensification of the convective heat transfer was achieved for 43% of the modifications conducted with a pulsed laser. The highest observed average increase in the heat transfer coefficient, α, was 16.53%. However, the effective intensification of the convective heat transfer, in some cases, was only observed for a certain range of temperatures or flow dynamics parameters.
Theoretical design of nanocatalysts based on (Fe2O3)n clusters for hydrogen production from ammonia
- Sapajan Ibragimov
- Andrey Lyalin
- Sonu Kumar
- Yuriko Ono
- Tetsuya Taketsugu
- Maciej Bobrowski
2025 JOURNAL OF CHEMICAL PHYSICS
The catalytic activities of high-spin small Fe(III) oxides have been investigated for efficient hydrogen production through ammonia decomposition, using the artificial force induced reaction method within the framework of density functional theory with the B3LYP hybrid exchange–correlation functional. Our results reveal that the adsorption free energy of NH3 on (Fe2O3 )n (n = 1–4) decreases with increasing cluster size up to n = 3, followed by a slight increase at n = 4. The strongest NH3 adsorption energy, 28.55 kcal/mol, was found for Fe2O3 , where NH3 interacts with a two-coordinated Fe site, forming an Fe–N bond with a length of 2.11 Å. A comparative analysis of NH3 dehydrogenation and H2 formation on various Fe(III) oxide sizes identifies the rate-determining steps for each reaction. We found that the rate-determining step for the full NH3 dehydrogenation on (Fe2 O3 )n (n = 1–4) is size-dependent, with the NH* → N* + H* reaction acting as the limiting step for n = 1–3. In addition, our findings indicate that H2 formation is favored following the partial decomposition of NH3 on Fe(III) oxides.
Thermoelectric and electrical properties of triple-conducting multicomponent oxides based on substituted barium cerate-zirconate
- Martyna Czudec
- Daniel Jaworski
- Jagoda Budnik
- Aleksandra Mielewczyk-Gryń
- Tamilarasan Subramani
- Maria Gazda
- Alexandra Navrotsky
- Tadeusz Miruszewski
2025 Pełny tekst DALTON TRANSACTIONS
Multicomponent oxides often have exceptional thermal stability and interesting electronic properties. The present work presents the thermoelectric and electrical properties of the Ba(Zr0.2Hf0.2Sn0.2Ti0.2Fe0.2)O3−δ and Ba(Zr0.1Hf0.1Sn0.1Ti0.1Co0.1Ce0.1Bi0.1Fe0.1Y0.1Zn0.1)O3−δ multicomponent perovskites. Single-phase cubic perovskites were synthesized using the solid-state reaction method. They were characterized using X-ray diffraction, drop-solution calorimetry, and thermogravimetry methods. The total electrical conduc tivity and Seebeck coefficient measurements were performed in dry and wet air at temperatures between 600 and 1050 K. It was found that Ba(Zr0.1Hf0.1Sn0.1Ti0.1Co0.1Ce0.1Bi0.1Fe0.1Y0.1Zn0.1)O3−δ is thermo dynamically less stable than Ba(Zr0.2Hf0.2Sn0.2Ti0.2Fe0.2)O3−δ. Moreover, this oxide incorporates a higher amount of water and exhibits higher conductivity and lower Seebeck coefficient. Charge transport in both perovskites can be assigned to the small-polaron hopping process via electron holes. An interesting temperature dependence of the Seebeck coefficient was found and, at temperatures above 750 K, related to hopping between energetically inequivalent states
Thermoelectric and electrical transport properties of mixed-conducting multicomponent oxides based on Ba(Zr,Ce)O3-δ
- Konrad Kuc
- Martyna Czudec
- Daniel Jaworski
- Jagoda Budnik
- Aleksandra Mielewczyk-Gryń
- Maria Gazda
- Tadeusz Miruszewski
2025 JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
In this work, the chosen physicochemical properties of single-phase multicomponent oxides BaTi1/8Fe1/8Co1/8Y1/8Zr1/8Sn1/8Ce1/8Hf1/8O3-δ and BaTi1/9Fe1/9Co1/9Y1/9Zr1/9Sn1/9Ce1/9 Hf1/9Bi1/9O3-δ were studied. The microstructure of the compounds strongly depended on the presence of bismuth in the structure. The electrical transport studies showed a level of electrical conductivity of ∼10−3 - 10−2 S/cm in the temperature range 673–1073 K. Electrical conductivity was thermally activated and the dominant conduction mechanism was the hopping of small polarons. Moreover, total electrical conductivity changes in the dry and humidified atmosphere at lower temperatures due to the presence of protonic defects in the structure. Thermoelectric measurements showed a relatively high value of the Seebeck coefficient for studied ceramics. Its values ranged between 50 and 250 μV/K depending on the sample and temperature. The Seebeck coefficient sign was positive, meaning that electron holes and/or oxygen vacancies were predominant charge carriers in oxidizing atmospheres. Additionally, the Seebeck coefficient was found to be different in the humidified atmosphere which indicates an influence of protonic defects on thermoelectric transport. The obtained power factor Pf turned out to be low and dependent on the presence of protonic defects in the structure. This indicates, that the efficiency of the MOs-based operating thermoelectric generators can be controlled by changing the partial pressure of water vapor
Trimethyl Lock Based Tools for Drug Delivery and Cell Imaging – Synthesis and Properties
- Andrzej Skwarecki
- Joanna Stefaniak-Skorupa
- Michał Nowak
2025 CHEMISTRY-A EUROPEAN JOURNAL
Trimethyl lock (TML) systems have become increasingly important in medicinal and bioorganic chemistry, particularly for their roles in the targeted delivery of therapeutic agents and as integral components in fluorogenic probes for cellular imaging. The simplicity and efficiency of their synthesis have established TML systems as versatile platforms for the controlled release of active molecules under particular physiological conditions. This review consolidates recent advancements in the application of TML systems, with a focus on their use in drug delivery, cellular imaging, and other areas where precise molecular release is crucial. Additionally, we discuss the synthetic strategies employed to construct TML-based conjugates, underscoring their potential to enhance the specificity and efficacy of bioactive compounds in various biomedical applications.
Ultra-Compact Quintuple-Band Terahertz Metamaterial Biosensor for Enhanced Blood Cancer Diagnostics
- Musa N. Hamza
- Mohammad Tariqul Islam
- Sunil Lavadiya
- Iflikhar ud Din
- Bruno Sanches
- Sławomir Kozieł
- Seyda Iffat Naqvi
- Ali Farmani
- Md. Shabiul Islam
2025 Pełny tekst PLOS ONE
Cancer and its diverse variations pose one of the most significant threats to human health and well-being. One of the most aggressive forms is blood cancer, originating from bone marrow cells and disrupting the production of normal blood cells. The incidence of blood cancer is steadily increasing, driven by both genetic and environmental factors. Therefore, early detection is crucial as it enhances treatment outcomes and improves success rates. However, accurate diagnosis is challenging due to the inherent similarities between normal and cancerous cells. Although various techniques are available for blood cancer identification, high-frequency imaging techniques have recently shown promise, particularly for real-time monitoring. Notably, terahertz (THz) frequencies offer unique advantages for biomedical applications. This research proposes an innovative terahertz metamaterial-based biosensor for high-efficacy blood cancer detection. The proposed structure is ultra-compact and operates across five bands within the range of 0.6 to 1.2 THz. It is constructed using a polyethylene terephthalate (PET) dielectric layer and two aluminum (Al) layers, with the top layer serving as a base for the THz-range resonator. Careful design, architectural arrangement, and optimization of the geometry parameters allow for achieving nearly perfect absorption rates (>95%) across all operating bands. The properties of the proposed sensor are extensively evaluated through full-wave electromagnetic (EM) analysis, which includes assessing the refractive index and the distribution of the electric field at individual working frequencies. The suitability for blood cancer diagnosis has been validated by integrating the sensor into a microwave imaging (MWI) system and conducting comprehensive simulation studies. These studies underscore the device's capability to detect abnormalities, particularly in distinguishing between healthy and cancerous cells. Benchmarking against state-of-the-art biosensors in recent literature indicates that the proposed sensor is highly competitive in terms of major performance indicators while maintaining a compact size.
Unveiling per- and polyfluoroalkyl substances contamination in e-cigarette refill liquids: A comprehensive analytical assessment
- Paweł Kubica
- Tomasz Majchrzak
- Khrystyna Vakh
2025 SCIENCE OF THE TOTAL ENVIRONMENT
A robust analytical method was developed for the determination of per- and polyfluoroalkyl substances (PFAS) in e-cigarette refill liquids using solid-phase extraction (SPE) with weak anion-exchange sorbent, followed by detection with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The design of experiment approach was employed to optimize sample preparation, leading to the validation of the method with limits of detection for PFAS ranging from 0.24 to 1.1 pg/mL. The method demonstrated inter-day repeatability of <17 % and relative recovery values between 89 % and 123 %. Additionally, the study explored the composition of e-cigarette refill liquids, focusing on the concentrations of primary constituents, such as vegetable glycerine and propylene glycol. Direct PFAS exposure through e-cigarette use might be of significant health concern due to vaping. Additionally, such products may serve as new source of PFAS release raising emerging issues about environment. Potential PFAS contamination in e-cigarette refill liquids may include manufacturing processes, packaging materials, or components of the e-cigarette devices, in result, leading to exposure during inhalation. A total of 31 e-cigarette refill liquid samples from various brands were analysed, revealing that PFAS were present mainly at trace levels. However, elevated concentrations exceeding 25 pg in 1 mL of commercial e-cigarette refill liquids were determined for PFNA, PFHxA, PFBS, HFPO-DA (GenX), and N-EtFOSAA. Among these, PFBS exhibited the highest detection frequency, occurring in 39 % of the samples. Notably, at least one of PFAS compounds was detected in 84 % of the samples analysed. Moreover, the higher PFAS content was determined in e-cigarette refill liquids with a nicotine content of 20 mg/mL than those with 6 mg/mL.
Upcycling of medium-density fiberboard and polyurethane foam wastes into novel composite materials
- Aleksander Hejna
- Mateusz Barczewski
- Joanna Aniśko
- Adam Piasecki
- Roman Barczewski
- Paulina Kosmela
- Jacek Andrzejewski
- Marek Szostak
2025 Resources, Conservation and Recycling Advances
While plastic and e-waste dominate public discourse, municipal waste, particularly bulky wastes pose a significant challenge due to their large-scale generation aligning with the enrichment of society. Their efficient collection and keeping in a loop should be considered among the priorities of municipal waste management. Herein, the presented work presents novel composite materials obtained from flexible polyurethane foams used as mattresses and medium-density fiberboards applied in furniture products. Composites have been prepared using compression molding, with the addition of an innovative binder composed of a diisocyanate and inorganic salt, whose in situ decomposition led to the gas generation providing the porous structure and strengthening the interfacial bonding inside the material. The impact of changes induced by the chemical interactions on the appearance, morphology, mechanical, thermal, acoustic and insulation performance of composites has been evaluated. Observed changes pointed to the auspicious conclusions on the further applications of the examined binder composition.
Utilizing UAV and orthophoto data with bathymetric LiDAR in google earth engine for coastal cliff degradation assessment
- Paweł Tysiąc
- Rafał Ossowski
- Lukasz Janowski
- Damian Moskalewicz
2025 Scientific Reports
This study introduces a novel methodology for estimating and analysing coastal cliff degradation, using machine learning and remote sensing data. Degradation refers to both natural abrasive processes and damage to coastal reinforcement structures caused by natural events. We utilized orthophotos and LiDAR data in green and near-infrared wavelengths to identify zones impacted by storms and extreme weather events that initiated mass movement processes. Our approach included change detection analysis to estimate eroded areas. Next, by applying Random Forest classifier within Google Earth Engine, we evaluated the importance of features in detecting these degraded zones. We tested the algorithm’s performance using datasets of varying resolutions (10 cm, 20 cm, 50 cm, and 100 cm), and a UAV dataset acquired two years later to validate results. The classifier achieved an overall accuracy of approximately 90% across all datasets. The findings indicate that DEM products in green and near-infrared wavelengths are similarly important, while reflectance maps and orthophotos suggest that red and near-infrared wavelengths play a significant role in identifying degradation. These results suggest that it is feasible to monitor coastal degradation caused by natural disasters using diverse sensors within a single training framework.
UV light-activated gas mixture sensing by ink-printed WS2 layer
- Katarzyna Drozdowska
- Janusz Smulko
- Artur Zieliński
- Andrzej Kwiatkowski
2025 Pełny tekst SENSORS AND ACTUATORS B-CHEMICAL
We fabricated a sensing layer from ink-printed WS2 flakes and utilized it for UV-activated gas sensing. The optical imaging of the structure made by repeated printing revealed the continuous layer comprising sub-µm flakes, confirmed independently by small-area AFM images (1×1 µm2). The activity of the sensing surface was investigated locally via AFM scanning of the surface with a polarized probing tip. The results indicated that the applied UV light amplifies the existing conducting paths in the dark. These hot spots are associated with the sensing activity of the WS2 surface (local adsorption-desorption centers). Gas sensing experiments revealed that the DC resistance of the WS2 sensor changes in the opposite direction for increasing concentrations of NO2 and NH3, which correlates with the electron-accepting and electron-donating properties of these species. On the contrary, low-frequency noise intensifies gradually in both gases, and relative changes in noise responses are higher than DC resistance responses for all investigated concentrations. The lowest detection limit obtained was 103 ppb from DC responses for NO2 and 168 ppb from noise responses for NH3. The studies of sensing responses for mixtures of the mentioned target gases revealed that the amplitude of resistance fluctuations is not a direct summation of spectra obtained for pure compounds. Such an effect observed for mixed gases indicates that the intermittent reactions between both species before adsorbing at the sensing surface or in the adsorption centers impact their detection.
Valorization of waste plastics to a novel metal-organic framework derived cobalt/carbon nanocatalyst as peroxymonosulfate activator for antibiotics degradation
- Chongqing Wang
- Xiuxiu Zhang
- Luyao Wang
- Gonggang Liu
- Grzegorz Boczkaj
2025 JOURNAL OF CLEANER PRODUCTION
Metal-organic frameworks (MOFs), with excellent structural properties, exhibit unique advantages as promising catalysts in the degradation of emerging organic contaminants (EOCs) by PS-AOPs. Herein, Co-MOF-71 was prepared by hydrothermal method using terephthalic acid (TPA) obtained from the hydrolysis of waste PET plastics as an organic ligand, and the derived cobalt/carbon composite (PETC) was prepared by carbonizing Co-MOF-71 under N2 atmosphere. Characterizations revealed that PETC800 carbonized at 800 °C possessed a loose and porous layered morphology with a surface area of 148 cm2/g, and had a porous structure rich in active sites that are effective in peroxymonosulfate (PMS) activation and tetracycline (TC) degradation. Degradation experiments revealed that the maximum degradation rate of TC by PETC800 could reach 90.94% within 20 min, with a maximum rate constant of 0.2700 min−1 and activation energy of 19.50 kJ/mol, which was lower than that of previous reports. Additional studies confirmed high effectiveness also towards other pharmaceuticals degradation such as metronidazole, levofloxacin and doxorubicin. More importantly, PETC800 could degrade TC efficiently in a broad pH region (3.0–9.0). The degradation performance of TC could be 72.18% after four cycles, demonstrating good reusability. Both radical (•OH, SO4•−, and O2•−) and nonradical pathways (singlet oxygen (1O2) and electron transfer) contributed to the TC degradation process, with the non-radical pathway dominating. LC-MS and toxicity analyses have postulated the degradation of TC into intermediates with lower levels of toxicity. The preparation of MOFs-derived catalysts from waste plastics allows resourceful utilization of waste plastics as well as enhances the catalytic performance of MOFs-derived cobalt/carbon-based catalysis for efficient degradation of emerging organic contaminants.
Vitamin B9 as a new eco-friendly corrosion inhibitor for copper in 3.5% NaCl solution
- Hubert Kwiatkowski
- Stefan Krakowiak
- Łukasz Gaweł
2025 Pełny tekst JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
Folic acid salt (sodium folate) was studied as an eco-friendly and non-toxic copper corrosion inhibitor in 3.5% NaCl solution. Electrochemical impedance spectroscopy, polarization resistance and weight-loss measurements show that the inhibitor efficiency increases with concentration (the highest value- approx. 96% was reported for the solution containing 16 mM sodium folate after 24 h). EIS data and Tafel plots indicate that sodium folate is a barrier, mixed-type (with predominant cathodic character) inhibitor. Inhibitor efficiency decreases with temperature, which suggests that adsorption has physical character rather than chemical one - adsorption free energy calculated using the Langmuir model is consistent with this statement. Activation energy determined from the Arrhenius plot increases as a result of inhibitor presence. Efficiency of the inhibitor increases systematically during the first 12 hours of immersion. Potential chemical changes in sodium folate solution were investigated using UV-VIS spectroscopy. Furthermore, copper surface after immersion in the presence and absence of inhibitor was characterized with scanning electron microscopy, energy-dispersive X-Ray spectroscopy and microscopic photographs.