Scanning Electron Microscopy-energy Dispersive X-ray Spectroscopy Research Articles

WO3 dispersed on a titanium porous clay heterostructure as a highly efficient visible light-active photocatalyst

Nanocomposites of WO3-dispersed titanium-porous clay heterostructures (W/Ti-PCH) from montmorillonite raw clay were synthesized and reported for the first time in this paper. The nanocomposite was prepared by impregnating tungstophosphoric acid into the titanium-porous clay heterostructure (Ti-PCH). The physicochemical features of the nanocomposite were characterized by using X-ray diffraction (XRD), scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HRTEM), UV–visible diffuse reflectance UV–visible spectroscopy (UV-DRS), X-ray photoelectron spectroscopy (XPS) and gas sorption analyses. Identification using XRD and XPS revealed that the dispersion of WO3 anchored on the Ti-PCH surface led to an increase in the band gap energy of the material from 3.1 eV in Ti-PCH to 3.22 eV in W/Ti-PCH. The improved characteristics support the excellent photocatalytic activity for RhB degradation, as 99.99 % removal was achieved after 15 min of treatment.

Rare Earth Element Characterization of Bledug Kuwu Mud Volcano, Central Java, Indonesia, based on Geochemical Analyzes (Susceptibility, XRF, XRD, SEM-EDS and ICP-EOS)

Mud volcano material is generally rich in oxides, while oxides are the main compounds forming rare earth elements. Bledug Kuwu, Central Java, Indonesia, is one of the active mud volcanoes, so there may be rare earth elements. This research is the characterization of rare earth elements (REE) in the Bledug Kuwu mud using magnetic and geochemical methods. Magnetic characterization uses magnetic susceptibility measurements. The geochemical characterization of the mud samples consisted of the XRF (X-Ray Fluorescence), XRD (X-Ray Diffraction), ICP-EOS (inductively coupled plasma) test, and the SEM-EDS (Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy) test. The results of the geochemical analysis of the Bledug Kuwu mud sample were the content of quartz, kaolinite, and calcite with an average concentration of 42.26%, 23.67%, and 33.96%. The susceptibility of Kuwu's mud is 0 because the concentration of metal elements is low; according to the results of XRF, XRD, and SEM tests identified the main mud elements as C, O, Si, Ca, and Al. The rare earth elements in Kuwu's mud are Ce, Dy, Eu, Gd, Ho, La, Nd, Pr, Sm, Tb, Y, and Sc. The highest concentrations were Ce 52.22 ppm and La 47.95 ppm.

Effect of a harsh circular environment on self-healing microbial-induced calcium carbonate materials for preventing Pb2+ migration

Microbially induced carbonate precipitation (MICP) is increasingly being explored for Pb-contaminated water bodies and soil remediation. However, the Pb-related precipitate resulting from the MICP process can possibly leach acid over time when subjected to harsh environments, causing serious threats to human health. In this study, for the first time, self-healing microbial-induced calcium carbonate (MICC) materials are proposed and applied to prevent Pb2+ migration where the Pb-related precipitate is acid leached after spore germination, spore-vegetative cell transformation, urease secretion, and urea hydrolysis, thereby producing spore-containing precipitation. This process was repeated five times to explore the effect of a harsh circular environment on self-healing MICC materials. Results indicated that Pb immobilization would have deteriorated if the inosine and trace elements had not been intervened during spore germination and spore-vegetative cell transformation, respectively. The spores and vegetative cells provided extra nucleation sites for Pb2+ and minerals to attach. The extracellular polymeric substances (EPSs) combined Pb2+ with functional groups and chemical bonds to prevent their migration to surrounding environments. The scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDS) images also indicated that the cerussite mineral was precipitated prior to the calcite mineral because Pb2+ had more affinity to combine with CO32- and OH-. An immobilization efficiency of greater than 95% remained nearly the same after five cycles, while it reduced very quickly to less than 10% after three cycles when neglecting the self-healing MICC materials, thus highlighting their relative merits.

Synthesis and characterization of eco-friendly TiO2 nanoparticle from combine extract of onion and garlic peel

Plant extracts are increasingly being used to make green nanoparticles since they are harmless and environmentally friendly. The process provides a cheap technique to create nanoparticles. TiO2 nanoparticles were created in this work using titanium isopropoxide and a combination of onion and garlic peel extracts. X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), ultraviolet–visible spectroscopy (UV–Vis), and Fourier transform infrared (FTIR) spectroscopy were used to analyze the green-generated TiO2 nanoparticles containing the extract. The sharp and potent peaks at 2 values of 27.45°, 37.97°, 44.07°, 54.40°, and 69.85° have been used to confirm the configuration of the crystalline nanoparticles (NPs) of TiO2. With the exception of the inescapable adsorption of moisture on the surface in the open air, calcined TiO2 NPs exhibit FT-IR absorption bands that show the purity of the produced nanoparticles. The bactericidal activity of green TiO2 NPs and unprocessed extracts of onion and garlic peels were examined using the disc diffusion method. In comparison to a crude mixed extract, NP is more efficient against Gram-positive and Gram-negative bacteria because to its smaller average crystalline size and consistent shape, which are visible in SEM pictures.

The Influence of Alumina Airborne-Particle Abrasion on the Properties of Zirconia-Based Dental Ceramics (3Y-TZP)

The objective of this study was to assess the effect of airborne-particle abrasion with alumina particles of various sizes (50 μm, 110 μm, 250 μm) on the surface properties of 3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals). The analysis comprised the Vickers hardness test (HV1kp), a surface roughness evaluation (Ra, Rq, Rz, Rsk, Rsm, Rt, Vo, profile displays), and SEM–EDS microanalysis (scanning electron microscopy–energy-dispersive X-ray spectroscopy). Any statistical relationships were assessed using the Kruskal–Wallis one-way analysis-of-variance-by-rank test (p = 0.05). While airborne-particle abrasion with 50 µm alumina significantly increases the Vickers hardness of 3Y-TZP (1678.8 HV1kp), 110 μm and 250 μm alumina particles do not appear to have any such effect. The surface roughness of 3Y-TZP increases with the size of the alumina particles (Ra, Rq, Rz, Rt, Vo: vertical plane and retention volume assessment); a higher Rsm (horizontal plane assessment) was noted for specimens air-abraded with 250 µm alumina particles; air abrasion with 50 μm alumina particles yielded a symmetrical surface roughness profile (Rsk). The major topographic pattern of the surface of 3Y-TZP is altered by alumina airborne-particle abrasion, with larger alumina particles causing more severe changes. Aluminum traces on the 3Y-TZP surface are observed. The shape of the alumina particles is irregular, with rough edges; the size of the alumina particles plays a significant role in the air abrasion of zirconia-based dental ceramics, affecting their morphology and properties.

Optimised repairment properties of waterborne epoxy resin–cement composite material: An experimental and simulation study

The demand for high-performance repair materials has significantly increased owing to continuous infrastructure construction. However, current research on epoxy resin–cement mortar composites lacks a theoretical investigation of the proportion of epoxy resin and hardener necessary to prepare a composite material with optimal performance. Composite material preparation often relies on the results of empirical studies. To address this issue, this study used E44 (waterborne epoxy resin, WER) and D230 (hardener) as raw materials to theoretically determine the optimal ratio for preparing a composite material. The optimal ratio and content were validated considering various test parameters, such as workability, mechanical properties, self-developed shear bond strength, and impermeability performance. The results indicated that the epoxy resin-to-hardener ratio of the composite material should be 4:1, with a 30% content. In addition, the microstructure of the composite material was analysed using various test methods, including scanning electron microscopy (SEM), SEM–energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and mercury intrusion porosimetry (MIP), to investigate its influence on the interfacial transition zone (ITZ), composition, and pore structure. Furthermore, molecular dynamics simulations were performed to analyse the mechanical properties, adsorption energy, mean square displacement (MSD), and radius dispersion function (RDF) of the calcium silicate hydrate (C-S-H) and epoxy resin molecule (cross-linked structure) composite, explaining the effect of water molecules on the composite material from an atomic-scale perspective. By combining experimentation and simulation, this study proposes a computational ratio design method that could provide new insights into the research and development of WER–cement composites while creating a simple shear bond strength test method for repair materials.

Application of Cold Sintering Process for Stabilizing Heavy Metals in Municipal Solid Waste Incineration Fly Ash

Municipal solid waste incineration fly ash (MSWI FA) consists predominantly of compounds comprising elements such as calcium, aluminum, silicon, sodium, and others. Additionally, it encompasses a complex mixture of heavy metals, chlorides, sulfates, organic pollutants, and other constituents. The effective and economically viable treatment of MSWI FA poses a formidable challenge for resource cycling at the current stage. In this research report, we adopt a novel low-temperature sintering method called the “Cold Sintering Process” (CSP) as a means to immobilize heavy metals within the fly ash. By utilizing a Taguchi orthogonal array method, we will adjust five control factors in the CSP, including sintering temperature, uniaxial pressure, sintering time, initial water addition, and sodium carbonate dosage. The leaching of cadmium from the fly ash, as measured by the Toxicity Characteristic Leaching Procedure (TCLP), will serve as the quality indicator of products. Through the application of CSP, MSWI FA was transformed into structurally stable ceramic blocks, and the heavy metals within the blocks were effectively immobilized. The results of the experiments showed that MSWI FA under the conditions of a temperature of 300 °C, uniaxial pressure of 312 MPa, sintering time in 60 min, 25 wt% water addition, and 9 wt% Na2CO3 addition could effectively reduce the leaching of cadmium by 77.71%, lead by 21.14%, zinc by 42.37%, and chromium by 99.99%, as compared to the original MSWI FA TCLP results. The X-ray Diffraction (XRD) results indicate that during the CSP, fly ash forms phases such as calcium silicate, rankinite, hydrogrossular, anorthite, and marilite. These phase transformations are considered beneficial for preventing the leaching of internal heavy metals. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) results reveal that CSP is advantageous for compacting the overall structure, and EDS results further demonstrate that some of the Pb and Zn are carried out from the interior of the blocks, with uneven distribution on the surface of fly ash particles. The aforementioned experimental results serve as preliminary indications of CSP’s capability to stabilize detrimental components within high-purity fly ash. Future research endeavors may entail the refinement of material proportions, modification of experimental parameters, and other methodologies, thus facilitating potential scalability to industrial applications. Such developments align with the overarching goal of resource utilization.

Nano Ag/PPy Biocomposites Based on Graphene Oxide Modified Bacterial Cellulose from the Juice of Xinhui Citrus and Its Antibacterial Activity.

Bacterial cellulose (BC) is a green, natural biopolymer with excellent biocompatibility and a film-forming ability. However, its lack of inherent antibacterial activity restricts its application in medical materials and food preservation. In this study, BC derived from the juice of discarded Xinhui citrus was obtained through fermentation and further modified in situ with graphene oxide (GO) to obtain BC(GO). Subsequently, BC(GO) was loaded with cell-compatible polypyrrole (PPy) and antibacterial agent silver nanoparticles (AgNPs) to prepare Ag-PPy/BC(GO) composite films. Composite films were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) to evaluate their chemical structure and morphology. The results demonstrate effective adsorption of PPy and AgNPs onto the surface of BC nanofibers modified with GO. Antibacterial experiments reveal synergistic antibacterial effects of PPy and AgNPs. The Ag-PPy/BC(GO) membranes exhibit strong antibacterial activity against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with 48-h growth inhibition rates of 75-84% and 82-84%, respectively.

Identification of the Pigments on the Mural Paintings from an Ancient Chinese Tomb of Tang Dynasty Using Micro-Raman and Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy Analysis

The tomb of Hanxiu, a prime minister of the Tang dynasty who died in 740 CE, was decorated with elaborate mural paintings. The pigments used in the mural paintings were collected from representative colours before a restoration process and analyzed using micro-Raman and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS) analysis to characterize the chemical compositions. The results reveal the chromatic palette and the painting technique used in the mural paintings. Most of the pigments are natural mineral pigments similar to those excavated in previous archaeological works, except the yellow pigment is unusual. A rare mineral pigment, vanadinite [Pb5(VO4)3Cl], was employed in a large amount as the yellow pigment. This phenomenon was analyzed and compared with tomb mural paintings from varied periods and locations in ancient China. Notably, the identification of vanadinite via Raman spectra has to be performed carefully and combined with an elemental analysis to avoid misidentification.

Activated Carbon Electrodes for Bioenergy Production in Microbial Fuel Cells Using Synthetic Wastewater as Substrate

The growing global energy demand drives the need to develop new clean energy technologies. In this context, microbial fuel cells (MFC) are one of the emerging technologies with great potential for eco-friendly energy generation; however, the correct choice of electrode material is a significant limitation in the optimal configuration of MFCs. Therefore, this research evaluated the efficiency of activated carbon (AC) anode electrodes for bioenergy production in MFC using synthetic wastewater as a substrate. Peak values of voltage (1120 ± 0.050 mV), current (4.64 ± 0.040 mA), power density (208.14 ± 17.15 mW/cm2), and current density (5.03 A/cm2) were generated, and the Rint obtained was 214.52 ± 5.22 Ω. The substrate was operated at pH values from 5.31 to 7.66, maximum ORP values (858 mV) were reached, and turbidity was reduced to 25.11 NTU. The SEM-EDS (scanning electron microscopy–energy-dispersive X-ray spectroscopy) analyses allowed us to observe the morphology and composition of the AC electrodes, revealing a predominance of O, C, Si, Al, Fe, K, and Ca. It is concluded that the AC electrodes have the potential to produce bioenergy at a laboratory by means of MFC.

Insights into the chemical characteristics of atmospheric aerosols from urban-industrial and rural sites in south-east of Poland during winter

This study focusses on a short-term characterisation of atmospheric aerosols from three locations in south- east of Poland with different land use characteristics, population density and sources of pollution (Katowice: urban-industrial; Strzyżowice near Lublin: rural; Kielce: urban). Twenty-four hour PM2.5 and PM10 samples were collected on the quartz filter and their chemical compositions were monitored and measured using OCEC thermo-optical analysis and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS). The highest concentrations of PM2.5 and PM10 were measured at the urban-industrial area in Katowice (29.6 µg ∙ m−3 and 31.0 µg ∙ m−3, respectively), whereas the highest organic carbon (OC) and elemental carbon (EC) levels were observed at the Kielce urban site (23.3 ± 4.2 µg and 3.6 ± 0.3 µg, respectively). The lowest values were obtained at the rural site for PM2.5 (10.4 ± 2.7 µg ∙ m−3) and PM10 (11.8 ± 2.7 µg ∙ m−3) and for OC (17.8 ± 1.6 µg) and EC (1.0 ± 0.1 µg). SEM-EDS analysis of samples from Kielce allows identification of internal chemical mixtures of carbon, silicon, calcium, chlorine, sodium and aluminium.

Rhubarb: A novel model plant to study the conundrum of calcium oxalate synthesis

The study investigated calcium oxalate (CaOx) crystal composition, accumulation, synthesis, and degradation in five rhubarb species from the North-Western Indian Himalayas. Techniques like optical and scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy (SEM-EDS), inductively coupled plasma-optical emission spectrometry (ICP-OES), X-ray diffraction spectroscopy (XRD), and real-time (qRT-PCR) expression analysis of strategic genes were used to understand the processes of oxalate synthesis and precipitation. Results showed crystals tend to accumulate around vascular bundles in all species, irrespective of size, indicating a consistent pattern. Crystal synthesis and accumulation were stress-driven, linked to substrate composition, and in planta soluble oxalate and calcium levels, paralleling oxalate precursors. Based on their availability, CaOx crystals precipitated heavy metals mostly associated with its weddellite form. Crystal content correlated positively with mRNA levels of calcium/oxalate/ascorbate-related and stress-responsive genes, and negatively with oxalate oxidation/decarboxylation genes. CaOx crystals were suggested as potential biominerals for addressing heavy metal stress in agriculture.

N-cyanoguanidine modified-black peanut shell biochar: fabrication and its sorption for Cu(II) and Co(II) in a single and mixed solutions

A N-cyanoguanidine (NCY)-modified black peanut shell biochar was fabricated via NCY to modify waste black peanut shell. X-ray diffraction, Fourier transform infrared, scanning electron microscope–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were used to characterize its performance. Sorption experiments were made to perceive its sorption for Cu(II) and Co(II) and disclosed that Cu(II) had higher sorption selectivity in mixed binary and four-metal solution. Sorption kinetics showed that Cu(II) and Co(II) sorption fitted well with pseudo-1st–order kinetic and diffusion-chemisorption models. Sorption isotherms revealed that Langmuir model can better describe its sorption behavior for Cu(II) and Co(II) and its maximum Qm could reach up to 185.66 and 80.59 mg/g at 45 °C, respectively. Thermodynamic factors indicated that Cu(II) and Co(II) sorption on NCY-modified black peanut shell biochar was an endothermic and spontaneous manner. Both effective diffusion coefficients (kIp) and mass-transfer coefficients (DEx) proved that Cu(II) and Co(II) sorption comprised multiple-step paces. The major mechanism included electrostatic attraction, mass transfer, complex and chelation, and diffusion-chemisorption. This finding suggests that NCY-modified black peanut shell biochar can be potentially applied to dispose Cu(II) and Co(II)-bearing wastewater from spent new power batteries.

Surface modification of TiO2 with a less expensive metal (iron) to exploit solar energy in photocatalysis: An ecological and economical solution

To degrade the tryptophan molecule through photocatalysis, the exploitation of solar energy in the present study necessitated the use of visible light active photocatalysts. Iron-transition metal nanoparticles were deposited on the surface of TiO2 powders through an impregnation method to obtain X%Fe-TiO2 for the purpose of improving the optical absorption of TiO2 in the visible light region. The effects of iron percentage (X%: 2,4 and 5), iron oxidation state and pH on the photocatalytic performance of TiO2 modified under solar irradiation were thoroughly studied. The characterization results by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM-EDS) indicate that iron nanoparticles were successfully fixed on the TiO2 surface. The absorption wavelengths of all X%Fe-TiO2 photocatalysts shifted towards the visible, confirming successful modification of the TiO2 surface with iron. Based on the empirical results, X%Fe-TiO2 nanomaterials demonstrate a higher activity compared with the unmodified TiO2 under solar irradiation. The 4%Fe(III)-TiO2 photocatalyst, in particular, displayed the highest photocatalytic activity at natural pH. The degradation was complete in 60 min. Therefore, it is interesting to note that iron had more functions and benefits than noble metals. The mechanism of the Fe-TiO2 system has been proposed in detail.

Measurement of helium diffusion in Lotsberg Salt cores: A proxy to evaluate hydrogen diffusion

Hydrogen can be a critical part of the energy transition and salt caverns have been considered for underground hydrogen storage. Although there have been some successful experiences of hydrogen storage in salt caverns in Europe and the United States, it is essential to exercise caution when selecting caverns for storage to ensure safe operations. This study investigates the relationship between rock heterogeneity and helium diffusion by testing salt-rock cores from the Lotsberg Formation, Alberta, Canada. We characterized salt rock heterogeneity by analyzing the results of X-ray diffraction (XRD) analysis, thin-section microscopy, scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS), and high-resolution CT scans. Then, diffusion tests were conducted using a custom-designed HPHT visualization cell on core samples with different compositions and crystal sizes. The samples in this study were categorized as Lotsberg Salt and Lotsberg Marlstone. Lotsberg Salt mainly consisted of halite with trace amounts of carbonate impurities, while Lotsberg Marlstone comprised halite with a carbonate matrix containing carbonates, clays, quartz, and muscovite. Helium diffusion through pure and intact halite crystals was negligible, and the micro-scale halite crystal boundaries are non-open or poorly unconnected for helium diffusion. Halite samples with macro-scale grain boundaries and carbonate impurities exhibited more interconnected pore networks, resulting in increased rates of helium diffusion. However, the formation of secondary halite veins between grain boundaries can lead to tightly sealed boundaries that have poor connectivity, limiting helium diffusion within the sample. Salt-rock cores with intergranular fractures and unsealed grain boundaries showed accelerated pressure declines, attributed to the preferential diffusion of helium through these fracture and crack pathways.

Catalytic pyrolysis of olive pomace for biofuel production: Application of metal oxide-modified zeolite catalysts

Catalytic pyrolysis of olive pomace (OP) was studied in a quartz fixed bed reactor at 500 °C. Due to the presence of high amounts of oxygenated components (OC) in bio-oil, the aim of this research was upgrading of bio-oil to valuable biofuel. Synthesized MgO, CaO, NiO, and Co3O4 modified zeolite catalysts were examined at several catalysts to biomass (C/B) ratios (0.2, 0.3, 0.4, 0.5, and 5). Different characterization method including Brunauer–Emmett–Teller (BET) and N2 adsorption/desorption isotherm analysis, X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) were performed to identify the synthesized catalysts. Results showed that the bio-oil yield decreases in catalytic pyrolysis. All metal-modified zeolite catalysts reduce the content of OC as undesirable compounds and increase aromatic and aliphatic hydrocarbons as valuable products in the bio-oil. Using MgO, CaO, NiO and Co3O4 supported on zeolite catalysts, increase notably the aromatic hydrocarbons content to 82.43%, 79.10%, 79.91%, and 79.19%, respectively at C/B ratio of 5. At the C/B ratio of 5, the elimination rate of total OC for MgO/zeolite and CaO/zeolite catalysts reach to 90.56% and 86.94%, respectively. For NiO/Zeolite and Co3O4/zeolite, this value is equal to 89.30% and 86.39%, respectively.

Lead Scale from a Lead Pipe Detected Using Electrochemical Methods

Electrochemical methods, such as square wave voltammetry, can detect lead in drinking water. However, these methods can only detect lead ions. Lead contamination in drinking water can be from both Pb2+ and particulate lead. Particulate lead comes from the inner walls of lead pipes and is often called lead scale. Lead scales forms from years of water with varying parameters such as pH, alkalinity, and disinfectants flowing through the pipes. The lead scale used in this work was collected from a lead pipe used in Cincinnati, Ohio. Characterization using x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) showed lead carbonate and lead oxides within the scale. These lead compounds are insoluble in drinking water which can have a pH between 7 and 9; however, if the pH is lowered to below pH 2, these lead compounds have an increased solubility. This work uses membrane electrolysis (ME) to acidify a tap water solution containing lead scale. The standard addition method is then used to collect a standard addition curve, then the unknown lead concentration from the lead scale can be calculated. Inductively coupled plasma mass spectroscopy (ICP-MS) was used as a standard method to compare the SWV results to the actual amount of lead within the unknown sample.

Adsorption behavior of ruthenium in tri-n-butyl phosphate functionalized multi walled carbon nanotubes

This paper deals with adsorption behavior of ruthenium on Tri-n-butyl phosphate functionalized Multi Walled Carbon Nanotubes (MWCNTs-COO-TBP) from aqueous solution. Adsorption method is significant for trace levels (expected level) removal of ruthenium in bioassay (urine) samples which is mandatory requirement of radiation workers in nuclear environment. Multi Walled Carbon Nanotubes (MWCNTs) were initially converted to carboxylated Multi Walled Carbon nanotubes (MWCNTs-COOH) and subsequently treated with Tri-n-butyl phosphate to MWCNTs-COO-TBP. The synthesized MWCNTs-COOH and MWCNTs-COO-TBP were confirmed by Fourier Transform Infrared Spectroscopy (FTIR). Spectroscopic and microscopic techniques such as X-Ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) and High Resolution Transmission Electron Microscopy (HR-TEM) were used for its characterization before and after adsorption. Various adsorption parameters such as contact time, pH, metal ion concentration and temperature were studied. Langmuir adsorption isotherm model and Pseudo second order kinetics model were found to be best fitted in terms of standard deviation and regression coefficient. Thermodynamics parameters such as enthalpy (ΔH°), entropy (ΔS°), Gibbs energy (ΔG°), activation energy (Ea) and sticking probability (SP*) were calculated. The adsorption capacity was calculated and found to be 141.23 mg.g−1.Moreover, quantification of defects, strains with charge doping states were calculated from Raman mapping and correlation plot.

Modulating tribological properties and degradation rate in Hank's solution of Zn–Mn alloys electrodeposited on Mg with variable Mn content

Zn–Mn alloy coatings with small amounts of Mn (Zn-0.19 wt.% Mn, Zn-0.21 wt.% Mn, Zn-0.26 wt.% Mn and Zn-0.34 wt.% Mn) were formed by electrodeposition, onto pre-treated Mg substrates (Mgt) covered with a Zn film (Zn/Mgt). The chemical composition in depth profiles, morphological and structural characteristics of the Zn–Mn coatings on Zn/Mgt (labeled as Zn–Mn/(Zn/Mgt)) were analyzed using Glow Discharge Optical Emission Spectroscopy (GD-OES), Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDS), and X-ray diffraction (XRD). When the manganese content was greater than 0.19 wt.%, the results reveal the formation of two Zn–Mn phases: η-ZnMn and ζ-MnZn13; while the formation of the ζ-MnZn13 phase was favored by increasing the Mn content in the alloy. On the other hand, microhardness, wear resistance, and coefficient of friction significantly increase when coating Zn/Mgt substrate with the Zn–Mn alloy. The corrosion performance of this alloy was evaluated by potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The degradation rate in Hank's solutions of the pristine Mg substrate (0.29 mm yr−1) decreases due to the Zn–Mn coating. Furthermore, the degradation rate of Zn–Mn was further decreased from 0.051 to 0.022 mm yr−1, by varying the amount of Mn in the Zn–Mn alloy from 0.19 to 0.26 wt.% Mn, respectively. However, the rate of degradation increases up to 0.064 mm yr−1 at higher Mn content, Zn-0.34 wt.% Mn. Therefore, the microhardness, wear volume, and degradation rate of Zn–Mn/(Zn/Mg) in Hank's solution can be modulated by varying the Mn composition in the alloy.

Characterization of art materials and degradation processes in the exterior wall paintings of the main church of Rila Monastery, Bulgaria

The present study focused on the characterization of the art materials and the degradation processes in the exterior (exonarthex) mural paintings of the main church of the Nativity of the Virgin in Rila monastery, Bulgaria, which is believed to be the last large-scale example of Eastern Orthodox wall painting. For the first time the art materials used to create a unique and colourful polychrome decoration of the outer gallery and the possible degradation products, caused by atmospheric influence - permanent exposure to open air and moisture - were revealed by a multi-technique approach. The mineral pigments were identified by means of attenuated total reflectance Fourier transform infrared (ATR-FTIR), micro-Raman spectroscopy, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The natural yellow, red ochre, and green earth pigments, as well as some synthetic ones such as ultramarine and vermillion, were found in stable condition. Minium and emerald green pigments showed chemical transformations due to adverse environmental conditions which lead to chromatic changes of wall paintings. Black discolouration occurred due to the conversion of orange minium to black plattnerite (PbO2) and white discolouration – due to its transformation to white lead carbon oxide (PbCO3). The copper acetoarsenite (Cu(CH3COO)2.3Cu(AsO2)2) in the emerald green pigment showed partial transformation to arsen-containing mineral phases clinoclase and lindackerite, which fortunately did not affect much the colour appearance. Gypsum and calcium oxalate were found in the majority of the microsamples as decay products. Analysis of the binders by enzyme-linked immunosorbent assay (ELISA) implied the use of the Orthodox Church post-Byzantine egg-tempera technique. The registered Ca metal oxalates in accordance with ELISA results suggested binder chemical degradation induced by external factors. Most of the used painting materials are close to the those found in other Eastern Orthodox Byzantine and post-Byzantine monuments which indicates that the wall painting decoration of the main church of Rila monastery continues the post-Byzantine traditions. On the other hand, the study showed that the exonarthex wall paintings of the main charge of Rila monastery bear some new features as the religious artists supplemented the colourful scheme by emerald green as a new pigment and replaced smalt by the brighter synthetic ultramarine.