Bulk Particles Research Articles

Size-dependent anatase to rutile phase transition under acoustic shocked conditions – A case study of TiO2 bulk and nanoparticles

In the present work, we attempt to explore the size-dependent structural stability of bulk (0.28 µm) and nano-sized (25 nm) anatase TiO2 particles under acoustic shocked conditions. Based on the observed X-ray diffractometric, Raman spectroscopic and transmission electron microscopic results with respect to the number of shock pulses, at the 90-shocked condition, the nano-size particles undergo the anatase to the rutile phase transition, whereas the bulk size TiO2 particles remain to be in the anatase phase. From the comprehensive assessment, it is demonstrated that the bulk TiO2 samples have higher structural stability compared to the nano-size samples. The nano-sized anatase-TiO2particles have values of lower thermal conductivity compared to the bulk-sized particles such that the value of lower thermal conductivity is a prominent crucial factor in initiating the dynamic recrystallization which results in the anatase-to-rutile phase transition. Based on the observed present experimental results and previous reports, it has been authenticated that, while increasing the particle size from nano-scale to micro-scale, the critical shock number for the anatase to rutile phase transition is significantly increased.

Evaluation of antioxidant, catalytic and antidiabetic activity of Phaseolus vulgaris (French green bean) mediated nickel oxide and copper doped nickel oxide bimetallic nanoparticles

In this study, nickel oxide nanoparticles (NPs) and copper doped NiO bimetallic nanoparticles (Cu@NiO BMNPs) were synthesized using Phaseolus vulgaris extracts as reducing and stabilizing agents by sol gel methods. The chemical and physical properties of synthesized NiO NPs and Cu@NiO BMNPs were confirmed by various techniques, like UV Visible spectrophotometer (UV–Vis), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), Transmission Electron Microscope (TEM) and X-ray diffraction (XRD) analysis. The optical properties of both NPs observed by UV–Vis analysis with well-defined peak and band gap value 3.2 eV & 2.62 eV. FTIR analysis confirmed the presence of functional group of NPs with fruits extract. The morphology of NPs was confirmed by SEM and TEM analysis as polygonal, rod and spherical shape. The elements present in NPs were confirmed by EDX analysis. The crystalline size calculated based on the XRD analysis was 49.78 nm and 53.66 nm for NiO and Cu@ NiO NPs respectively which were found to be slightly smaller than particle size determined from SEM and TEM micrograph. Antioxidant activity of NPs was examined using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging radicals, Catalytic activities were screened by the degradation of Methylene blue (MB) and by the inhibition of alpha-amylase enzyme, antidiabetic activity of NPs were evaluated using acarbose as standard drug. The Cu@NiO BMNPs showed 77.60 % antioxidant, 76.98 % photocatalytic and 88.86 % antidiabetic activity, which were found to be more as compared to NiO NPs. The NiO and Cu@NiO BMNPs were synthesized for the first-time using P. vulgaris extracts. This study clearly showed that P. vulgaris extracts mediated mono- and bimetallic NPs were more stable and biocompatible than their respective bulk particles.

Design of a pilot-scale microwave freeze dryer for in situ neutron imaging.

The gentle yet cost-effective drying of sensitive products in the food and pharmaceutical industries is becoming increasingly important. To maintain sensitive ingredients, color, structure, and viability of micro-organisms, often freeze-drying is the only possible way to preserve the product. As many products come in as bulk material, they are dried on heated shelves resulting in poor heat and mass transport through the bed. Resulting in a very time and cost intensive process. Therefore, efforts are being made to improve the mass and heat transport of the process. The outer mass transport through the bulk can be improved by continuous mixing of the pellets, facilitating the removal of water vapor from the condenser. In addition, the issue of limited heat transport can be addressed by using volumetric energy input from microwaves. This process is called dynamic microwave freeze-drying. As dynamic microwave freeze-drying is a combined drying and mixing process, with particle properties continuously changing during drying, it is necessary to gain a more detailed insight into the process. For this purpose, a drier is designed that is capable of in situ neutron imaging, a method sensitive to a material's hydrogen content. This paper presents the design of a pilot-scale microwave freeze dryer for in situ neutron imaging and shows the first images taken during the dynamic microwave freeze-drying of bulk particles at the Center for Energy Research, Budapest Neutron Center in Budapest, Hungary.

Sulfated Alginate for Biomedical Applications.

Alginate (Alg) polymers have received much attention due to the mild conditions required for gel formation and their good bio-acceptability. However, due to limited interactions with cells, many drugs, and biomolecules, chemically modified alginates are of great interest. Sulfated alginate (S-Alg) is a promising heparin-mimetic that continues to be investigated both as a drug molecule and as a component of biomaterials. Herein, the S-Alg literature of the past five years (2017-2023) is reviewed. Several methods used to synthesize S-Alg are described, with a focus on new advances in characterization and stereoselectivity. Material fabrication is another focus and spans bulk materials, particles, scaffolds, coatings, and part of multicomponent biomaterials. The new application of S-Alg as an antitumor agent is highlighted together with studies evaluating safety and biodistribution. The high binding affinity of S-Alg for various drugs and heparin-binding proteins is exploited extensively in biomaterial design to tune the encapsulation and release of these agents and this aspect is covered in detail. Recommondations include publishing key material properties to allow reproducibility, careful selection of appropriate sulfation strategies, the use of cross-linking strategies other than ionic cross-linking for material fabrication, and more detailed toxicity and biodistribution studies to inform future work.

Biosynthesis of Silver Nanoparticles and Their Roles in the Biomedical Field: A Review

Abstract Developing novel antibiotics, traditional pharmaceuticals, and chemically altered drugs addresses medical concerns and underscores the need for sustained and productive implementation of metallic nanotechnology across various domains. Nanoparticles (NPs) present a range of advantages over bulk particles due to their targeting capabilities, wound repair characteristics, capacity for biocomposite preparation, and potential as a gene and drug delivery system. Silver nanoparticles (AgNPs) have garnered significant interest among researchers as a result of their exceptional conductivity, chemical stability, catalytic behavior, and antimicrobial properties compared with other metal NPs. This study aims to provide a basic understanding of AgNPs and their functions in biomedical research.

Source and fate of atmospheric iron supplied to the subarctic North Pacific traced by stable iron isotope ratios

The availability of dissolved iron (Fe) limits primary production over some regions of the surface ocean, especially in regions such as the subarctic North Pacific. In this work, we use Fe stable isotope ratios (δ56Fe) in bulk and size-fractionated marine aerosol particles and dissolved Fe of surface seawater in the subarctic North Pacific on Japanese GEOTRACES cruise GP02 (Summer 2017) as a tracer to clarify the relative contribution of combustion and natural Fe in both marine aerosol particles and surface seawater. The bulk aerosols collected in the coastal regions of both East Asia and western North Pacific have total δ56Fe values that are as low as −0.5 ‰ when compared to crustal (+0.1 ‰), with both the water-soluble phase and the fine particles even more fractionated (as low as −1.9 and −2.8 ‰, respectively). The negative correlation between the aerosol δ56Fe signatures and the enrichment factors of Fe and other elements dominated by anthropogenic sources (e.g., lead and cadmium) in these coastal regions indicates the presence of Fe emitted from high-temperature combustion sources, such as coal combustion and metal smelting. In these regions, combustion Fe accounts for 4–13 and 13–45 % of the total and water-soluble aerosol Fe, respectively. The results demonstrate that soluble aerosol Fe sourced from combustion Fe can be equivalent to that sourced from natural dust Fe in these coastal regions. By contrast, the aerosol particles in pelagic regions were near crustal δ56Fe in all particle size fractions, indicating the dominance of natural Fe and little to no combustion Fe. The relationships among the fractional Fe solubility, major ion concentration, Fe species, and δ56Fe indicate that the presence of combustion Fe is the dominant reason for the solubility increase in the coastal regions and that the atmospheric processing of mineral dust during transport is more important in the pelagic regions. The dissolved Fe of the surface seawater at 10 m depth had a consistently higher δ56Fe by up to +1.5 ‰ than that of the simultaneously collected water-soluble aerosol Fe. The pattern of the elevated δ56Fe in the surface seawater corresponds to decreasing Fe concentrations and can be approximated by Rayleigh fractionation; we attribute these elevated surface δ56Fe values to the effect of biological uptake. New Fe fluxes from both the atmosphere and deeper depths are limited at least in summer compared with the biological uptake in the open ocean of the subarctic North Pacific.

Rational construction of surface doping of Cu in WO3 nano platelets with Fe rich layer oxyhydroxide on the porous BiVO4 catalyst: A solar driven heterostructure photoanode for efficient water oxidation

The (Cu:WO3/BiVO4/FeOOH) photoanode heterostructure is a significant semiconductor for solar water splitting owing to its wide absorption of visible light photons. The bulk particles are experiencing charge recombination, which limits the PEC performance of the WO3 and BiVO4. Wherein, the heterostructure Cu:WO3/BiVO4/FeOOH catalysts have a staggered connection of band edges and morphological variation that outperforms the photoelectrochemical properties. The FeOOH layer on the surface of the PEC catalyst efficiently boosts water oxidation and quickens water splitting under light illumination. As anticipated, the doping in the WO3 and BiVO4 loading on the WO3 plates attains an outstanding increase in the water splitting performance. The 2% copper doping in the WO3 exhibits 1.2 mA/cm2, which is increasing by 40 cycles of coated BiVO4 to 2.0 mA/cm2. The FeOOH-grown heterostructure photoanode results in a higher overall photocurrent density (2.8 mA/cm2) at water oxidation potential. Moreover, the photoanode exhibits good stability and low resistance (385.7 Ohm/cm2). The photon-to-electron conversion efficiency has been attained at 1.2% at the applied potential of 0.4 V vs. RHE. These results from the photoanode could be a good candidate for high-performance PEC applications.

Effectiveness of nanomaterials and their counterparts in improving rice growth and yield under arsenic contamination.

Arsenic (As) pollution in rice (Oryza sativa L.), a staple food for over 3.5 billion people, is a global problem. Mixed effects of Zn, Cu, and Si amendments on plant growth and yield, including in the presence of As pollution have been reported in previous studies. To better investigate the effectiveness of these amendments on rice growth, yield, and As accumulation, we conducted a rice greenhouse experiment with 11 treatments, including control pots with and without As contamination and pots with amendments of ZnO, CuO, and SiO2 nanoparticles (ZnO NPs, CuO NPs, and SiO2 NPs), their ionic counterparts (ZnSO4, CuSO4, and Na2SiO3), and bulk particles (ZnO BPs, CuO BPs, and SiO2 BPs). Compared with the background soil, the treatment of adding As decreased rice plant height, panicle number, and grain yield by 16.5%, 50%, and 85.7%, respectively, but significantly increased the As accumulation in milled rice grains by 3.2 times. Under As contamination, the application of Zn amendments increased rice grain yield by 4.6-7.3 times; among the three Zn amendments, ZnSO4 performed best by fully recovering grain yield to the background level and significantly reducing grain AsIII/total As ratio by 46.9%. Under As contamination, the application of Cu amendments increased grain yield by 3.8-5.6 times; all three Cu amendments significantly reduced grain AsIII/total As ratio by 20.2-65.6%. The results reveal that Zn and Cu amendments could promote rice yield and prevent As accumulation in rice grains under As contamination. Despite the observed reduction in As toxicity by the tested NPs, they do not offer more advantages over their ionic counterparts and bulk particles in promoting rice growth under As contamination. Future field research using a broader range of rice varieties, investigating various As concentrations, and encompassing diverse climate conditions will be necessary to validate our findings in achieving more extensive understanding of effective management of arsenic contaminated rice field.

Fluidization characteristics of ore particles for downstream hydrogen mineral phase transformation equipment

Fluidized roasting is an effective way to deal with refractory iron ores. Fluidization is a prerequisite for the effective occurrence of physical and chemical reactions. This article conducts cold state experiments on Single-layer Overflow type Reaction Chamber, using hematite ore and quartz as bulk particles，processing pressure drop signals to analyze and explain gas-solid motion. The results indicate that the gas flow average pressure drop being stable is the criterion for the fluidized bed, the bulk properties significantly affect the critical fluidization characteristics. Pressure drop pulsation is an important characteristic of fluidized bed, fluidized gas velocity, initial bed height, and bulk properties all affect the amplitude of bed pressure drop pulsation, and the spectrum analyses of bed pressure drop signals all exhibit “High-energy and Low-frequency”. This study has certain guiding significance for the structural design optimization and engineering scaling of Downstream Hydrogen Mineral Phase Transformation Equipment.

Microstructure and formation mechanism of the transition layer at the interface of Al–Cu EMPW joint

In the dissimilar metal welding field, electromagnetic pulse welding (EMPW) is a kind of potential technology. To further reveal the bonding mechanism of EMPW, this work carried out a Cu–Al sheet EMPW experiment with a discharge voltage of 15 kV and a gap of 1.5 mm. It analyzed the microstructure and formation mechanism of the Cu–Al EMPW joint bonding interface transition layer in detail by SEM, EDS, TEM, and FIB. The transition layer was found at the vortex zone, and there was an isolated long strip Cu particle separated from the main body of the Cu sheet. The tested results showed that the transition layer contained Al-rich intermetallic compound (IMC) Al2Cu, and some bulk particles in the transition layer were Cu-rich IMCs Al4Cu9 and AlCu4. There were Cu-rich IMCs Al4Cu9, AlCu4, and AlCu between the long strip Cu particle and the IMC transition layer. In the violent impact process between the Cu sheet and Al sheet, the Cu rapidly diffused in the Al matrix to form the Al-rich IMC (Al2Cu) as the primary transition layer, and the interface was high temperature and high pressure, forming a plastic flow and vortexes swirling. Some Cu particles separated from the Cu sheet and became the vortex piece during the plastic flow process, and continued to interact with the Al2Cu primary transition layer to form the secondary transition layer. This work could provide a basis for revealing the structure composition and formation mechanism of the Cu–Al EMPW joint interface transition layer.

The state-of-art polyurethane nanoparticles for drug delivery applications.

Nowadays, polyurethanes (PUs) stand out as a promising option for drug delivery owing to their versatile properties. PUs have garnered significant attention in the biomedical sector and are extensively employed in diverse forms, including bulk devices, coatings, particles, and micelles. PUs are crucial in delivering various therapeutic agents such as antibiotics, anti-cancer medications, dermal treatments, and intravaginal rings. Effective drug release management is essential to ensure the intended therapeutic impact of PUs. Commercially available PU-based drug delivery products exemplify the adaptability of PUs in drug delivery, enabling researchers to tailor the polymer properties for specific drug release patterns. This review primarily focuses on the preparation of PU nanoparticles and their physiochemical properties for drug delivery applications, emphasizing how the formation of PUs affects the efficiency of drug delivery systems. Additionally, cutting-edge applications in drug delivery using PU nanoparticle systems, micelles, targeted, activatable, and fluorescence imaging-guided drug delivery applications are explored. Finally, the role of artificial intelligence and machine learning in drug design and delivery is discussed. The review concludes by addressing the challenges and providing perspectives on the future of PUs in drug delivery, aiming to inspire the design of more innovative solutions in this field.

Uniform Al Doping in LiCoO2 for 4.55 V Lithium-Ion Pouch Cells.

As the classic cathode material, lithium cobalt oxide (LiCoO2, LCO) suffers from severe structural and interfacial degradation at voltage >4.5 V, which induces fast capacity decay of the cells. Herein, we adopt a simple and effective method, doping aluminum (Al) cations in precursors, to improve the structural stability of LCO and systematically investigate the effect of Al doping on the electrochemical performances. Doping in precursors rather than bulk particles is beneficial to realize uniform Al ions distribution. Even at 4.5 V charging voltage, the LCO/graphite pouch cells with high Al doping levels (8500 ppm) deliver initial and reversible discharge capacities of 386 and 369 mAh after 500 cycles, respectively. The capacity retention is as high as 95.5%. When the cutoff voltage reaches 4.55 V, the pouch cell maintains 79.0% of the first-cycle discharge capacity after 500 cycles. With optimized electrolyte, the pouch cell realizes 87.3% of the initial discharge capacity after 500 cycles at 45 °C. Moreover, the thermal safety performance of the pouch cells with Al doping is promising. Our work displays an excellent inspiration for developing high-voltage, long-cycle, and safe LCO cathode for commercial lithium-ion batteries.

Controllable synthesis and morphology-dependent light emission efficiency of Zn2GeO4 nanophosphors.

Zn2GeO4 is considered a very promising alternative to current luminescent semiconductors. Previous results suggest that its emitted wavelength may depend on different variables, such as particle size and morphology, among others. In this work, we have prepared pure and highly homogeneous Zn2GeO4 nanorods under hydrothermal synthesis conditions with a willemite-like structure. Their luminescent properties have been explored and their band gap is estimated, which are distinct from those of previously reported Zn2GeO4 bulk particles. Therefore, our results identify particle morphology as a crucial factor for maximizing and fine-tuning the luminescence of Zn2GeO4 nano-phosphors.

Upconversion luminescence and temperature sensing properties of Ho3+,Yb3+-codoped Bi2WO6.

Ho3+ and Yb3+-codoped Bi2WO6 upconversion luminescent materials at different concentrations were prepared via a high-temperature solid-phase method. The X-ray diffraction patterns showed that Ho3+ and Yb3+ doping basically did not affect the orthorhombic crystal system structure of the Bi2WO6 matrix material. Scanning electron microscopy images showed that 3%Ho3+,10%Yb3+:Bi2WO6 consisted of irregular bulk particles with sizes in the range of 0.5-2 μm and some powder agglomeration. SEM mapping and EDS measurements of the powder showed that the elements were relatively uniformly distributed. Under 980 nm excitation, the emission intensity of Ho3+ was the largest for the 3%Ho3+- and 10%Yb3+-doped sample. With an excitation power ranging from 45 mW to 283 mW for the 3%Ho3+,10%Yb3+:Bi2WO6 sample, the relationship between the luminescence intensity and pump power was determined; the results indicated that the Ho3+ (538 nm, 546 nm, 660 nm, 756 nm) emission peaks originated from two-photon absorption. In the temperature range of 298 K-573 K, under 980 nm laser excitation, the maximum absolute temperature sensitivity Sa was 0.029% K-1 (373 K), the maximum relative temperature sensitivity Sr was 0.034% K-1 (348 K) for the Ho3+ thermally coupled energy levels 5F4/5S2, and the minimum temperature resolution δT was 1.2857 K (298 K). Under the same conditions, the maximum Sa was 51.02% K-1 (573 K), the maximum Sr was 1.85% K-1 (523 K) for the Ho3+ nonthermally coupled energy levels 5F5/5F4, and the minimum δT is 0.2477 K (448 K). The colour coordinates showed that the luminescence of the 3%Ho3+,10%Yb3+:Bi2WO6 sample gradually shifted from the green region to the red region with increasing temperature.

Assessment of Banknotes as a Matrix for Detecting Post-Explosion Residues of Fuel-Oxidizer Explosive Mixtures Using Ion Chromatography

Banknotes are commonly subjected to chemical analysis in forensic laboratories in the search for post-explosion residues. This matrix presents unique challenges due to the potential presence of target analytes resulting from everyday use, as well as the lack of control samples for comparison. In addition to their relevance in attacks against Automated Teller Machines (ATMs), banknotes are of significant interest when confiscated from suspicious individuals, vehicles, and locations, as they can provide valuable evidence in establishing a connection to this type of crime scene. In such cases, the absence of bulk particles, alternative materials, and control samples is common. This study employed ion chromatography to analyze uncirculated, circulated, and seized banknotes, aiming to determine their ionic profiles. This investigation provides insights into the background levels of target ions in banknotes and aids in the analysis of post-explosion residues. A simple, fast, and precise extraction method was proposed, yielding RSD values below 10% for most analytes in uncirculated banknotes. The study revealed the presence of various ions of interest, some in significant concentrations, even in uncirculated banknotes. PCA analysis demonstrated a clear separation of uncirculated notes based on their banknote value. However, this clustering behavior was not observed in circulated banknotes due to natural variations in analyte concentrations. Interestingly, when uncirculated, circulated, and seized R$ 100 banknotes were analyzed together, the seized samples from an ATM robbery showed a distinct separation from the other groups, indicating the potential for developing classification models.

Effects of particle size and content of cladding powder on in situ synthesized WC‐reinforced Ni‐based cladding layers

AbstractLaser cladding technology can obtain a cladding layer with good metallurgical bonding with the substrate and excellent performance. In situ growth of hard phase can effectively solve the problem of uneven distribution of reinforcements directly doped with hard particles. In this paper, 45# steel was adopted as the matrix material, WO3, B4C, Al, and Ni60 powder were used to prepare laser cladding and in situ synthesized WC (Tungsten Carbide) hard phase reinforced Ni‐based cladding layers. The effects of different laser cladding parameters, powder particle size, hard phase content on the microstructures and electrochemical properties of in situ synthesized WC hard phase reinforced Ni‐based cladding layer were analyzed. The results revealed that when the (WO3 + B4C + Al) mixed powder content was 25%, the bulk particles of WC phase in the cladding layer were most uniformly distributed in the cladding layer, which enhances the mechanical properties of the cladding layer. When the B4C particle size was 5 μm, the microhardness of the cladding layer was significantly higher than other cladding layers, and the enhancement mechanism of hardness by B4C is due to the Orowan strengthening caused by too small particle size of B4C.

Non-magnetic regenerator material of silver oxide for 4 K cryocoolers

In regenerative cryocoolers, magnetic specific heat is often utilized for heat regeneration at cryogenic temperature, such as below 20 K. Magnetic regenerator materials of rare earth compound which have sufficient specific heat enabled cryocooler to reach below 4 K. However, the magnetic noise emitted from the magnetic materials during the refrigeration cycle affects the performance of noise-sensitive devices. In this study, we propose a non-magnetic regenerator material having “optical phonon degree of freedom” even at cryogenic temperatures, in which silver oxide (Ag2O) is selected. Ag2O decomposes at temperature above 410 K in ambient atmosphere, whereas we succeeded in fabricating a sintered Ag2O bulk and small particles of the size of 0.5 mm with high-density more than 90%. Specific heat measurement down to 100 mK was performed for the sintered bulk sample of Ag2O. Below 10 K, a non-Debye behavior was observed, suggesting the contribution from optical phonon modes. Calculation of the phonon density of state (phDOS) performed by the Evolution Strategy algorithm in addition to the first-principles calculation reveals that phDOS has several distinct peaks at low energies, and the low-energy optical phonons contribute to the non-Debye behavior. The low temperature specific heat of Ag2O enhanced by the optical phonons is larger than conventional non-magnetic regenerator materials when compared in terms of specific heat per volume. Moreover, the calculation of cooling performance of cryocooler using Ag2O particles is found to be reached below 4.2 K. This study shows that non-magnetic material with low temperature specific heat enhanced by optical phonon mode can be used as a regenerator material for regenerative cryocoolers.

Effects of Zinc Oxide Particles with Different Sizes on Root Development in Oryza sativa

Given the consistent release of zinc oxide (ZnO) nanoparticles into the environment, it is urgent to study their impact on plants in depth. In this study, grains of rice were treated with two different concentrations of ZnO nanoparticles (NP-ZnO, 10 and 100 mg/L), and their bulk counterpart (B-ZnO) were used to evaluate whether ZnO action could depend on particle size. To test this hypothesis, root growth and development assessment, oxidative stress parameters, indole-3-acetic acid (IAA) content and molecules/enzymes involved in IAA metabolism were analyzed. In situ localization of Zn in control and treated roots was also performed. Though Zn was visible inside root cells only following nanoparticle treatment, both materials (NP-ZnO and B-ZnO) were able to affect seedling growth and root morphology, with alteration in the concentration/pattern of localization of oxidative stress markers and with a different action depending on particle size. In addition, only ZnO supplied as bulk material induced a significant increase in both IAA concentration and lateral root density, supporting our hypothesis that bulk particles might enhance lateral root development through the rise of IAA concentration. Apparently, IAA concentration was influenced more by the activity of the catabolic peroxidases than by the protective action of phenols.

Coexistence of Intermetallic Complexions and Bulk Particles in Grain Boundaries in the ZEK100 Alloy

Magnesium-based alloys are highly sought after in the industry due to their lightweight and reliable strength. However, the hexagonal crystal structure of magnesium results in the mechanical properties’ anisotropy. This anisotropy is effectively addressed by alloying magnesium with elements like zirconium, zinc, and rare earth metals (REM). The addition of these elements promotes rapid seed formation, yielding small grains with a uniform orientation distribution, thereby reducing anisotropy. Despite these benefits, the formation of intermetallic phases (IP) containing Zn, Zr, and REM within the microstructure can be a concern. Some of these IP phases can be exceedingly hard and brittle, thus weakening the material by providing easy pathways for crack propagation along grain boundaries (GBs). This issue becomes particularly significant if intermetallic phases form continuous layers along the entire GB between two neighboring GB triple junctions, a phenomenon known as complete GB wetting. To mitigate the risks associated with complete GB wetting and prevent the weakening of the alloy’s structure, understanding the potential occurrence of a GB wetting phase transition and how to control continuous GB layers of IP phases becomes crucial. In the investigation of a commercial magnesium alloy, ZEK100, the GB wetting phase transition (i.e., between complete and partial GB wetting) was successfully studied and confirmed. Notably, complete GB wetting was observed at temperatures near the liquidus point of the alloy. However, at lower temperatures, a coexistence of a nano-scaled precipitate film and bulk particles with nonzero contact angles within the same GB was observed. This insight into the wetting transition characteristics holds potential to expand the range of applications for the present alloy in the industry. By understanding and controlling GB wetting phenomena, the alloy’s mechanical properties and structural integrity can be enhanced, paving the way for its wider utilization in various industrial applications.

UNPRECEDENTED INCREASE IN THE CHARCOAL MACROPARTICLES IN THE BOTTOM SEDIMENTS OF THE LAKES OF THE NORTH-MINUSINSK VALLEY (SOUTH OF SIBERIA) IN THE RECENT TIME AS A POSSIBLE EVIDENCE OF ANTHROPOGENIC INFLUENCE

In the bottom sediments of lakes Shira and Uchum, located in the south of Siberia in the steppe zone of the North Minusinsk depression (Republic of Khakassia and Krasnoyarsk Territory), distributions of charcoal particles 100 µm. The age of the studied sediments of the two lakes was up to 1400 and 500 years ago, respectively. Charcoal particles of three types were found in the sediments of both lakes. The first group has an elongated shape and is interpreted as the remains of herbaceous plants and/or needles. The second group looks like thin flat blades and is interpreted as the remains of leaves. The third group consists of bulk particles of various irregular shapes, which are presumably the remains of the combustion of wood and coal. Particles of the first type are mainly indicators of natural fires, and their flux does not show a noticeable increase in the modern period. The flow of coal particles of the second and, to the greatest extent, the third groups has increased sharply in the last about a hundred years, which reflects an increase in the amount of wood and coal burned by people in the vicinity of the studied lakes in the modern industrial period. The data obtained reflect an increase in the amount of wood and coal burned by people in the modern industrial period, as well as a possible increase in the number of wildfires, which may also be due to human activities in the form of accidental or deliberate arson. Thus, for the first time for this region, an increase in the influx of charcoal particles into the bottom sediments of lakes over the past about a hundred years has been revealed, which is unprecedented over the period covered by our study. Thus, evidence of the anthropogenic impact on the dynamics of charcoal particles in bottom sediments has been obtained. The information obtained can be useful for reconstructing the dynamics of natural fires and paleo-climate in this region of southern Siberia in the Late Holocene.