Search Results (503)

To investigate the corrosion resistance of 60Si2MnA spring steel coated with Zn-Al in a domestic atmospheric environment containing harmful salts, the corrosion environmental factors (temperature, humidity, deposited salts, and pH) were obtained through field research. The deliquescence and weathering behavior of harmful salts were studied using impedance methods to establish their characteristic curves. Additionally, a self-designed salt deposition test apparatus was employed to conduct accelerated atmospheric corrosion tests under constant salt deposition (10 g/m²) and controlled temperature and humidity conditions (20 °C/75% RH and 40 °C/75% RH) over different corrosion periods. The results show that noticeable red rust appeared on the samples after one month of corrosion. As the temperature increased, the consumption of the coating accelerated. XRD and Raman analyses reveal that the main corrosion products of the coating materials were ZnO, Zn(OH)₂, and Zn₅(CO₃)₂(OH)₆, while the red rust primarily consisted of iron oxides and hydroxides. In the early stages of corrosion, the self-corrosion current density was relatively low due to the protective effects of the coating and the corrosion product layer, indicating good corrosion resistance. However, in the later stages, the integrity of the coating and the corrosion product layer deteriorated, leading to a significant increase in the self-corrosion current density and a decline in corrosion resistance. This study provides a data foundation for understanding the corrosion behavior of Zn-Al-coated spring steel in atmospheric environments and offers theoretical insights for developing more corrosion-resistant coatings and optimizing anti-corrosion measures. Full article

In this work, hybrid membranes were fabricated by depositing polyvinyl chloride (PVC) fibers onto PET track-etched membranes (TeMs) using the electrospinning technique. The resulting structures exhibited enhanced hydrophobicity, with contact angles reaching 155°, making them suitable for applications in both water–oil mixture separation and membrane distillation processes involving low-level liquid radioactive waste (LLLRW), saline solutions, and natural water sources. The use of hybrids of TeMs and nanofiber membranes has significantly increased productivity compared to TeMs only, while maintaining a high degree of purification. Permeate obtained after MD of LLLRW and river water was analyzed by conductometry and the atomic emission spectroscopy (for Sr, Cs, Al, Mo, Co, Sb, Ca, Fe, Mg, K, and Na). The activity of radioisotopes (for ¹²⁴Sb, ⁶⁵Zn, ⁶⁰Co, ⁵⁷Co, ¹³⁷Cs, and ¹³⁴Cs) was evaluated by gamma-ray spectroscopy. In most cases, the degree of rejection was between 95 and 100% with a water flux of up to 17.3 kg/m²·h. These membranes were also tested in the separation of cetane–water emulsion with productivity up to 47.3 L/m²·min at vacuum pressure of 700 mbar and 15.2 L/m²·min at vacuum pressure of 900 mbar. Full article

For the first time, the deposition area of heavy metals and other trace elements (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, P, Pb, S, Sr, Sb, V, Zn, and Hg) on the territory surrounding a landfill of domestic (municipal) waste at the 9th km of the Vilyuisky tract of Yakutsk within a radius of 51 km was assessed using the method of moss biomonitors and ICP-OES as an analytical technique. Mosses were analyzed for radionuclide content (⁴⁰K, ¹³⁷Cs, ²¹² Pb, ²¹⁴Pb, ²¹²Bi, ²¹⁴Bi, ²⁰⁸Tl, ⁷Be, and ²²⁸Ac) in a number of selected samples by semiconductor gamma spectrometry. The results of the examination of moss samples by ICP-OES indicate the presence of large amounts of toxic Ba and metal debris (Al, Co, Cr, Fe, S, and Pb) at the landfill. In addition, it is shown that the investigated samples contain elements such as Cd, Co, Cr, Cu, Cu, Mn, Ni, Pb, Sr, V, Zn, and Hg. The method of gamma spectrometry revealed that the studied samples contain such radioactive elements as ¹³⁷Cs, daughter products of ²³⁸U and ²³²Th. Detection of the same heavy metals and radionuclides in the atmospheric air of the city and in the vegetation near the landfill may indicate that one of the sources of environmental pollution may be products of incineration of the landfill contents at the 9th km of the Vilyuisky tract. Full article

This study investigates the influence of environmental variables on the elemental composition of Hypnum cupressiforme Hedw. mosses in Georgia and the Republic of Moldova, within moss biomonitoring studies aimed at analyzing atmospheric deposition patterns. Moss samples of Hypnum cupressiforme, characterized by a cosmopolitan distribution and a wide range of habitats, were collected from diverse geographical and climatic zones and analyzed for Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V, and Zn. Statistical methods (Spearman correlations, PCA, Kruskal–Wallis tests) were applied to evaluate interactions between elemental concentrations and factors such as topography, climate, land cover, etc. Results revealed strong correlations among lithogenic elements (Al, Co, Cr, Fe, Ni, and V), indicating natural weathering sources, while Cu exhibited potential anthropogenic origins in the Republic of Moldova. Elevated Cd and Pb levels in Georgian high-altitude regions were linked to wet deposition and steep slopes, whereas Moldovan samples showed higher Sr and Zn concentrations, likely driven by soil erosion in carbonate chernozems. The study highlights geogenic and climatic influences on element accumulation by moss, offering insights into the effectiveness of moss biomonitoring across heterogeneous landscapes. Full article

Propylene production through the CO₂-assisted oxidative dehydrogenation of propane (CO₂-ODP) is an effective route able to address the ever-increasing demand for propylene and simultaneously utilize CO₂. In this study, a series of alumina-supported gallium oxide catalysts of variable Ga₂O₃ loading was synthesized, characterized, and evaluated with respect to their activity for the CO₂-ODP reaction. It was found that both the catalysts’ physicochemical characteristics and performance were strongly affected by the amount of Ga₂O₃ dispersed on Al₂O₃. Surface basicity was maximized for the sample containing 20 wt.% Ga₂O₃, whereas surface acidity was monotonically increased with increasing Ga₂O₃ loading. A volcano-type correlation was found between catalytic performance and acid/base properties, according to which propane conversion and propylene yield exhibited optimum values for intermediate surface basicity and acidity, which both correspond to the sample containing 30 wt.% Ga₂O₃. The dispersion of a suitable amount of Ga₂O₃ on the Al₂O₃ surface not only enhances the conversion of propane to propylene but also suppresses the formation of side products (C₂H₄, CH₄, and C₂H₆) at temperatures of practical interest. The 30%Ga₂O₃-Al₂O₃ catalyst exhibited very good stability at 550 °C, where byproduct formation and carbon deposition were limited. Mechanistic studies indicated that the reaction proceeds through a two-step oxidative route with the participation of CO₂ in the abstraction of H₂, originating from propane dehydrogenation, through the reverse water–gas reaction (RWGS) reaction, shifting the thermodynamic equilibrium towards propylene generation. Full article

The Qieliekeqi siderite deposit, located in the Tashkurgan block of western Kunlun, is a carbonate-hosted iron deposit with hydrothermal sedimentary features. This study integrates whole-rock geochemistry, stable isotopes, and zircon U–Pb–Hf data to investigate its metallogenic evolution. Coarse-grained siderite samples, formed in deeper water, exhibit average Al₂O₃/TiO₂ ratios of 29.14, δEu of 2.69, and δCe of 0.83, indicating hydrothermal fluid dominance with limited seawater mixing. Banded samples from shallower settings show an average Al₂O₃/TiO₂ of 17.07, δEu of 3.18, and δCe of 0.94, suggesting stronger seawater interaction under oxidizing conditions. Both types are enriched in Mn, Co, and Ba, with low Ti and Al contents. Stable isotope results (δ¹³C_PDB = −6.0‰ to −4.6‰; δ¹⁸O_SMOW = 16.0‰ to 16.9‰) point to seawater-dominated fluids with minor magmatic and meteoric contributions, formed under open-system conditions at avg. temperatures of 53 to 58 °C. Zircon U–Pb dating yields an age of 211.01 ± 0.82 Ma, with an average εHf(t) of −3.94, indicating derivation from the partially melted ancient crust. These results support a two-stage model involving Late Cambrian hydrothermal sedimentation and Late Triassic magmatic overprinting. Full article

A novel processing route of producing CrFeNiMo, Co_0.5CrFeNiMo, and Al_0.5CrFeNiMo high-entropy alloy coatings was proposed in this work. Pre-alloyed HEAs were consolidated by spark plasma sintering (SPS) in order to fabricate electrodes for electrospark deposition (ESD) coatings on carbon steel substrates. Investigations were performed to observe aspects such as phase composition and stability, contamination level, homogeneity, elemental distribution, and microstructural integrity. The results indicated phase stability and lower porosity when increasing the SPS temperature by 50 °C for all cases, with tetragonal distortion related to the HEAs’ severe lattice distortion core effect. The coating surface analysis indicated that a continuous and compact coating was obtained, correlated with the ESD layering count, but microfissures were present after 6 layers were applied due to the reduced ductility combined with rapid cooling under Ar atmosphere. The chemical integrity of both the sintered samples and the coatings was preserved during the processing, revealing a uniform elemental distribution with no contaminations or impurities present. The results indicated successful HEA sintering and deposition, highlighting the potential of the combined SPS-ESD process for high-performance material fabrication with possible applications in aggressive environments. Full article

AlCoCrFeNi coatings were electrospark-deposited (ESD) on H13 steel substrates, and their nano-mechanical and tribological properties under a load of 2 N, 4 N, 6 N, 8 N, and 10 N were investigated by utilizing a nanoindentation instrument and a reciprocating friction and wear tester, respectively. The morphologies, composition, and phase structure of the as-deposited and worn AlCoCrFeNi coating were characterized using SEM (Scanning electron Microscope), EDS (Energy dispersive spectrometer), and XRD (X-Ray Diffraction). The results showed that the as-deposited AlCoCrFeNi coating with a nanocrystalline microstructure mainly consists of a BCC and B2 phase structure, and a gradient transition of elements between the coating and the substrate ensures an excellent bond between the coating and the substrate. The hardness of the AlCoCrFeNi coating exhibits an 8% increase, while its elastic modulus is reduced by 16% compared to the H13 steel. The AlCoCrFeNi coating remarkably increased the tribological property of the H13 steel under various loads, and its wear mechanism belongs to micro-cutting abrasive wear whilst that of the H13 steel can be characterized as severe adhesive wear. The friction coefficient and weight loss of the AlCoCrFeNi coating decrease with increasing load, both following a linear relationship with respect to the applied load. As the load intensifies, the work hardening sensitivity and oxidation degree on the worn surface of the coating are significantly enhanced, which collectively contributes to the improved tribological performance of the AlCoCrFeNi coating. Full article

Titanium and its alloy scaffolds are widely utilized in clinical settings; however, their biologically inert surfaces and inherent mechanical characteristics impede osteogenesis and soft tissue integration, thereby limiting their application. Selective laser melting (SLM) was employed to fabricate scaffolds with matched cortical bone mechanical properties, achieving a composite coating of hydroxyapatite complexed with trace elements of silicon, strontium, and fluoride (mHA), along with type I collagen (Col I) and fibrinogen (Fg), thus activating the scaffold surface. Initially, we utilized the excellent adhesive properties of dopamine to co-deposit mHA and polydopamine (PDA) onto porous Ti-6Al-4V scaffolds, which was followed by immobilization of type I collagen and fibrinogen onto PDA. This bioinorganic/bioprotein composite coating, formed via PDA bonding, exhibits excellent stability. Moreover, in vitro cell experiments demonstrate excellent biocompatibility of the porous Ti-6Al-4V scaffold with composite bioactive coatings on its surface. Preosteoblasts (MC3T3-E1) and human keratinocytes (HaCaT) exhibit enhanced adhesion and proliferation activity, and the osteogenic performance of the scaffold is significantly improved. The PDA-mHA-Col I-Fg composite-coated porous titanium alloy scaffold holds significant promise in enhancing the efficacy of percutaneous bone transplantation and requires further investigation. Full article

The Minghuazhen Formation in the Cangdong Sag of the Bohai Bay Basin is a key sedimentary unit for investigating regional provenance evolution, paleoclimate variations, and hydrocarbon potential in Eastern China. This study integrates mineralogical and geochemical analyses to explore sedimentary characteristics. Techniques include X-ray diffraction (XRD), major/trace element compositions, rare earth element (REE) distributions, and organic carbon content. XRD data and elemental ratios (e.g., Al/Ti, Zr/Sc) suggest a predominant felsic provenance, sourced from acidic magmatic rocks. The enrichment with light rare earth elements (LREE: La–Eu) and notable negative Eu anomalies in the REE patterns support the interpretation of a provenance from the Taihangshan and Yanshan Orogenic Belts. Geochemical proxies, such as the Chemical Index of Alteration (CIA) and trace element ratios (e.g., U/Th, V/Cr, Ni/Co), indicate a warm and humid depositional environment, characterized by predominantly oxic freshwater conditions. Organic geochemical parameters, including total organic carbon (TOC), total nitrogen (TN), and C/N ratios, suggest that organic matter primarily originates from aquatic algae and plankton, with C/N values predominantly below 10 and a strong correlation between TOC and TN. The weak correlation between TOC and total carbon (TC) indicates that the organic carbon is mainly biological in origin rather than carbonate-derived. Although the warm and humid climate promoted the production of organic matter, the prevailing oxic conditions hindered its preservation, resulting in a relatively low hydrocarbon generation potential within the Minghuazhen Formation of the Cangdong Sag. These findings provide new insights into the sedimentary evolution and hydrocarbon potential of the Bohai Bay Basin. Full article

This paper presents a comprehensive analysis of recent advancements in the application of thermal spraying techniques to enhance the durability and wear resistance of agricultural machinery components, with a particular focus on disc harrow assemblies. Given the harsh conditions under which tillage tools operate—characterized by abrasive wear, impact stresses, and chemical exposure from various soil types—thermal sprayed coatings have emerged as a viable solution to extend the service life of these components. The study discusses various deposition methods, particularly Atmospheric Plasma Spraying (APS), and evaluates their effectiveness in creating high-performance surface layers that resist wear, corrosion, and mechanical degradation. The review also summarizes experimental and field test results for coatings based on materials such as NiCrBSi, WC-Co-Cr, TiO₂, Al₂O₃, Cr₂O_3, and ceramic–metal composites, highlighting their significant improvements in hardness, friction reduction, and resistance to delamination and oxidation. The paper highlights research using thermal spraying techniques, especially APS for agricultural applications, with emphasis mostly on components intended for soil processing and requiring good resistance to abrasive wear. Full article

Titanium (Ti) and its alloys have attracted more interest, as they are widely employed as biomaterials due to their great biocompatibility, excellent strength ratio, and lightweight. However, corrosion occurs slowly due to an electrochemical reaction once the Ti material has been placed in the human body, contributing to infection and failure of implants in medical applications. Thus, the corrosion phenomenon has caused great concern in the biomedical field. It is desirable to make the surface modification to provide better corrosion resistance. The fabrication techniques of the coatings fabricated onto Ti and/or Ti alloy surfaces have been reported, including sol–gel, annealing, plasma spraying, plasma immersion ion implantation, physical vapor deposition, chemical vapor deposition, anodization, and micro-arc oxidation. This review first describes the corrosion types, including localized corrosion (both pitting and crevice corrosion), galvanic corrosion, selective leaching, stress corrosion cracking (SCC), corrosion fatigue (CF), and fretting corrosion. In the second part, the effects of corrosion on the human body were discussed, and the primary cause for clinical failure and allergies has been identified as the excessive release of poisonous and dangerous metal ions (Co, Ni, and Ti) from corroded implants into bodily fluids. The inclusion and exclusion criteria during the selection of literature are described in the third section. In the last section, we emphasized the current research progress of Ti alloy (particularly Ti6Al4V alloy) coatings in biomaterials for medical applications involving dental, orthopedic, and cardiovascular implants for anticorrosive applications. However, there are also several problems to explore and address in future studies, such as the release of excessive metal ions, etc. This review will draw attention to both researchers and clinicians, which could help to increase the coatings fabricated onto Ti and/or Ti alloy surfaces for anticorrosive applications in biomaterials for medical applications. Full article

Environmental pollution remains one of the most pressing challenges facing modern society, with the removal of toxic substances from water sources being of particular concern. In this study, a composite material was synthesized by combining Cu-Al layered double hydroxides (CuAl-LDHs) with modified silica particles, aiming to develop an efficient and environmentally friendly adsorbent for the removal of phosphate and arsenate ions from water. CuAl-LDH, with a Cu²⁺/Al³⁺ molar ratio of 2:1, was synthesized using the co-precipitation method in the presence of modified silica maintaining an LDH/SiO₂ mass ratio of 2:1. The silica particles were functionalized with 3-glycidyloxypropyltrimethoxysilane (GLYMO) followed by modification with polyethyleneimine (PEI) to enhance their adsorption properties. X-ray diffraction (XRD) confirmed the successful deposition of CuAl-LDH on the silica surface, while scanning electron microscopy (SEM) revealed the porous structure of the silica and the uniform deposition of LDH. Adsorption experiments were performed to evaluate the removal efficiency of phosphate and arsenate ions under varying conditions. Equilibrium adsorption capacities, based on the Langmuir isotherm model, were determined to be 44.6 mg·g⁻¹ for phosphate (PO₄³⁻) and 32.3 mg·g⁻¹ for arsenate (As(V)) at 25 °C. The sorption behavior was better described by the Freundlich isotherm model, which yielded K_F values of 15.4 L·mg⁻¹ for phosphate and 13.9 L·mg⁻¹ for arsenate. Both batch and kinetic experiments confirmed the high adsorption efficiency of the composite, demonstrating its potential as a promising material for water treatment applications. Full article

Metal carbonyl clusters, which can be seen as monodispersed and atomically defined nanoparticles stabilized by CO ligands, were used to prepare Ru-based catalysts with tuned basic properties to conduct the 5-hydroxymethylfurfural (HMF) aerobic oxidation to produce 2,5-furandicarboxylic acid (FDCA) in base-free conditions. The controlled decomposition of the carbonyl cluster [HRu₃(CO)₁₁]⁻, a methodology not yet applied to Ru catalysts for this reaction, on different supports focusing on controlling and tuning the basic properties of support allowed the formation of small Ru nanoparticles with a mean diameter of around 1 nm. The catalytic systems obtained resulted in more activity in the HMF oxidation than those prepared through a more common salt-impregnation technique, and the deposition of Ru nanoparticles on materials with basic functionalities has allowed avoiding the use of basic solutions in the reaction. The characterization by CO₂-TPD of Mg(Al)O catalysts obtained from decomposition of layered double hydroxide hydrotalcites with different composition and activation has allowed disclosure of an important correlation between the selectivity of FDCA and the fraction of weak basic sites, which is decreased by the calcination treatment at increased temperature. Full article

This study assessed air quality in Yancheng, China, using moss biomonitoring. The moss species, Haplocladium microphyllum was chosen, and mosses were collected from 67 sites across Yancheng during July and August 2022. The concentrations of Al, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn, V, and nitrogen in mosses were determined, and the spatial distribution and temporal trends of atmospheric trace metals and nitrogen deposition in Yancheng were explored by comparing the current data with that of a similar study conducted in 2017. In 2022, high concentrations of metals and nitrogen in mosses were found in northern and southwestern Yancheng, whereas lower concentrations were observed in southern and southeastern Yancheng for metals and central Yancheng for nitrogen. Since 2017, the moss concentrations of Zn, Cu, Ni, and Cr have increased, while that of V has declined, with no notable changes observed in other metals and nitrogen. Contamination factor analysis indicated that Pb and Cu contamination levels escalated from moderate and slight (2017) to severe and moderate (2022), respectively. The Positive Matrix Factorization (PMF) model identified five dominant contamination sources of metals and nitrogen in 2022 mosses: natural source (21.4%), traffic emission (17.84%), fuel combustion derived from coal and heavy oil (22.71%), agricultural activities (19.37%), and industrial activities (18.68%). This study highlights the significance of moss biomonitoring, along with data analysis and emission source inventories, as essential tools for evaluating air quality in Yancheng. Full article