Scanning Electron Microscopy With Energy Dispersive Spectroscopy Research Articles

Ion Fluence-Dependent Structural and Electrical Characteristics of Electrochemically Synthesized PANI/ZnO Nano

The electrochemical synthesis and ion irradiation effects of polyaniline/zinc oxide (PANI/ZnO) nanocomposite films on stainless steel substrates were investigated in this study. The structural, morphological and electrical properties of the films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and current-voltage (I-V) measurements. The results show that the films have a nanofiber network structure with an average diameter of 50-60 nm. The vibrational modes and structural properties of the films are influenced by ion fluence. The electrical conductivity and mobility of the films increase significantly at low fluence (1.0 × 1011 ions/cm2), reaching values of 1.14 × 10-2 S/cm and 3.56 × 10-5 cm2/V-s, respectively. However, at high fluence, electrical properties degrade due to the damage caused by the ion irradiation. This study demonstrates the potential of PANI/ZnO nanocomposite films for applications in the optoelectronic devices and energy storage devices.

The ability of drinking water treatment sludge to degrade methylene blue in water through combined adsorption/photo Fenton-like process

In the present study, drinking water treatment sludge (DWTS) was reused as a catalyst in advanced oxidation processes for the removal of methylene blue (MB) from aqueous solutions. After determining their chemical and mineralogical compositions by X-ray Powder Diffraction (XRD), BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), Inductively Coupled Plasma (ICP), and FT-IR spectra. DWTS has been used as a heterogeneous photo Fenton-Like catalyst for the oxidation of MB under different parameters, including pH (3-6), H2O2 concentration (9.79-29.37 mM), and dose (1-2.5 g/L). The results showed that within 180 min and under UV light irradiation, more than 86% of MB having a concentration of 50 mg/L were removed using a catalyst loading of 1.5 g/L, a H2O2 dosage of 23.17 mM and a solution pH of 5. The DWTS has a satisfactory stability as the catalyst is stable and have very less iron leaching property.

Coconut waste to green nanomaterial: Large scale synthesis of N-doped graphene nano sheets

In this paper, a breakthrough was achieved in large-scale production of N-doped Graphene Nano Sheets (N-GNS) using coconut fruits. The main objectives were to produce N-GNS on a large scale and assess its electrical conductivity. The process involved two key steps: first, producing GNS from coconut fruits through pyrolysis, and then generating N-GNS by doping with nitrogen using ammonia solution at room temperature. Various analytical techniques were used to characterize the produced N-GNS, including X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and electrochemical cyclic voltammetry and electrochemical impedance spectroscopy. The XRD data indicated that the C (002) peak of N-GNS shifted to a higher 2θ value (2θ = 24.72°) compared to GNS (2θ = 23.86°), suggesting an incorporation of nitrogen into carbon structure in N-GNS. This was further supported by XPS data, which identified N-pyridine (BE = 402.0 eV) and C-N (BE = 286.8 eV) in N-GNS. TEM images showed that N-GNS had a flat surface, and the distance between graphene layers slightly expanded (0.36 nm) compared to graphene layers (0.34 nm). SEM images and EDX data validated the morphology, resembling honeycomb lattices, with a significant content of N atoms. Raman data successfully identified the D-band and G-band in N-GNS, further validating its production. Most importantly, N-GNS exhibited electrical conductivity, making it a promising candidate for conductive and supporting materials in various applications. The significance of this research extends beyond N-GNS production, opening up new avenues for the sustainable synthesis of valuable nanomaterials from coconut fruit waste, contributing to both graphene technology and environmental conservation.

Decomposition of monazite in Bayan Obo rare earth ore by roasting of Na2CO3 pellets

To resolve the issue of rotary kiln agglomeration during the sodium carbonate roasting of dolomite rare earth ore, this study introduces an oxidation-sodization pellet roasting method for decomposing mixed rare earth concentrates. The focus of this paper lies in understanding the bonding and roasting mechanism of sodium polyacrylate as a binder to dolomite ore and examining the process index of Na2CO3 pellets roasting-acid leaching using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and zeta potential analysis. The results indicate that sodium polyacrylate facilitates the bonding of sodium carbonate to monazite via adsorption of positive and negative charges, and upon roasting at 750 °C for 1.5 h to obtain rare earth oxides. Under conditions of a hydrochloric acid (HCl) concentration of 9 mol/L, a reaction for 60 min, a solid-to-liquid ratio (g:mL) of 1:5, and reaction temperature of 90 °C, the leaching rates of rare earth elements and thorium (Th) reached maxima of 85.14% and 95.53%, respectively. The process results in a yield of 47.61% for fluorine (F) and 89.25% for phosphorus (P). This research forms a foundation for the sodium carbonate roasting decomposition of mixed rare earth concentrates.

Hydrogen diffusion in cerium oxide thin films fabricated by pulsed laser deposition

Cerium oxide (CeO2) is well known to be reducible by hydrogen (H2), yet the diffusion and solution properties of hydrogen in ceria at elevated temperatures have remained challenging to evaluate. We therefore fabricated nanometer-thin (∼100 nm) cerium oxide films on Si(111) substrates by pulsed laser deposition (PLD) and quantitatively investigated the H depth distributions therein by means of resonant 1H(15N,αγ)12C nuclear reaction analysis (NRA) before and after annealing in H2 gas at 773–973 K. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) reveal that the as-deposited films exhibit single phase CeO2 structure and partially reduced stoichiometry (CeO1.69). H2 annealing does not largely change the H content of the as-deposited films; in all conditions several atomic percent of hydroxyl (OH) are found to exist in a thin (∼4 nm) surface layer, whereas stably bound hydrogen in the bulk of the films is almost uniformly distributed and of much smaller quantity (∼0.2 at.%) than the oxygen vacancy concentration in the partially reduced ceria. Its low concentration and high thermal stability identify this bulk H species as likely being strongly bound to defects in the polycrystalline films rather than as a hydride species that interacts weakly with O-vacancies. The H diffusion coefficient and activation energy in the ceria films are determined as > 10−18 m2 s−1 at 773–973 K and <1.69 eV, respectively. The observed diffusion activation energy is somewhat larger than theoretical predictions for thermal diffusion of H in stoichiometric bulk CeO2, suggesting that defects and oxygen vacancies in the PLD-fabricated ceria thin films possibly have an impact on the H mobility.

Improved oxidation resistance of Cr/FeCrAl coating on Zr alloy in high-temperature steam environment

A new bi-layer Cr/FeCrAl coating was successfully fabricated on the Zr-4 plates through multi-arc ion plating in order to take advantage of the two materials of FeCrAl and Cr. The high-temperature steam oxidation behavior of the Cr/FeCrAl-coated Zr-4 at 1000–1200 °C was investigated and compared with that of bare and single-layer FeCrAl-coated Zr-4. Various analytical techniques including scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for the microstructural and compositional analysis of the as-deposited and oxidized samples. Results indicated that the FeCrAl-coated Zr-4 could only withstand up to 1000 °C because of the severe FeZr interdiffusion. Whereas the introduction of the Cr interlayer effectively prevented fast FeZr interdiffusion and consequently improves the overall oxidation resistance of the Zr substrate below 1200 °C steam environment. After 1100 °C steam oxidation, the weight gain of the Cr/FeCrAl-coated Zr-4 was about 8 times and 2 times lower than that of the uncoated and FeCrAl-coated Zr-4 alloys, respectively. These facts make possible the use of FeCrAl coating on Zr cladding which has excellent high-temperature mechanical properties and oxidation resistance.

Analysis of neptunium oxides produced through modified direct denitration

Production of neptunium-237 (237Np) target materials for plutonium-238 (238Pu) radioisotope thermoelectric generators (RTGs) for deep space exploration requires advanced chemistry and engineering development. Currently, the domestic Pu-238 Supply Program at Oak Ridge National Laboratory produces neptunium dioxide (NpO2) for target material using a modified direct denitration (MDD) flowsheet. Although the chemistry, reaction mechanisms, and product characteristics of MDD are well understood for uranium, corresponding studies of the neptunium system are still needed to continue optimization of target material properties, production equipment design, and production flowsheets. The objective of this work is to characterize crystalline phases, morphology, surface texture, and particle size of NpO2 produced via MDD reactions. Solid-phase characterization techniques, including powder X-ray diffraction (pXRD) and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), were employed to achieve this objective. Subsequent data processing using the Morphological Analysis for Material Attribution (MAMA) software was performed to analyze particle morphology and size. Broadly, the powders were found to contain a mixture of NpO2 and Np2O5 after denitration with a variety of morphologies. After high-firing, the product was found to be NpO2 with a typical polycrystalline oxide morphology and a grain size ranging from 0.72 to 0.94 µm. These analyses provide knowledge on the reaction pathway for a non-traditional NpO2 synthesis method and offer additional unique insight into production-scale environments for transuranic materials.

Electrochemical preparation and alkaline water splitting activity of ternary Co–Fe–Mo non-crystalline coatings

The influence of Na2MoO4 concentration on the electrochemical deposition of Co–Fe and Co–Fe–Mo alloy coatings from slightly acidic citrate baths and their electrocatalytic performance for alkaline water electrolysis in 1 M NaOH solution have been examined. The chemical composition and the evolution of the crystallographic structure have been analyzed by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) measurements. Increasing concentration of Mo in the alloy led to gradual amorphization of the crystalline structure. Electrochemical studies revealed that the cathodic Tafel slope reduced to 69 mV/dec for Co–Fe–Mo alloys. Furthermore, a low overpotential value of −121 mV was observed from polarization studies, which confirmed a good catalytic activity for the alkaline water splitting process.

Bioleaching of available silicon from coal tailings using Bacillus mucilaginosus: a sustainable solution for soil improvement.

In China, a large amount of soil lack available silicon, which leads to a decrease in crop yield. Furthermore, the solid waste coal tailings contain abundant minerals that are rich in silicon, which have not been fully utilized. In this work, we used Bacillus mucilaginosus as the leaching agent to convert insoluble silicon in coal tailings into available silicon for crop. After single-factor experiments, the optimal leaching conditions with bacterial dosage, coal tailings weight, initial pH, leaching temperature, and shaking speed were obtained. Kinetic analysis showed that the controlling process of the leaching was a chemical reaction. The leaching process was characterized by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectrometer (FT-IR), and high-performance liquid chromatography (HPLC). The results showed that bioleaching is a feasible and efficient method to extract silicon from coal tailings, with a maximum leaching amount of 260 mg L-1 after 16 days, which occupied 93% of the total effective silicon. In conclusion, this work demonstrates that bioleaching technology can effectively solve the problem of the environmental utilization of coal tailings by converting them into a soil improver that can provide beneficial nutrients for crop growth.

Photocatalytic degradation of methylene blue and Congo red dyes from aqueous solutions by bentonite-Fe3O4 magnetic

This study describes the co-precipitation synthesis of magnetic bentonite-Fe3O4 for photocatalytic degradation of methylene blue and Congo red pigments under visible light. Bentonite-Fe3O4 composites were produced using the mass ratio of 2:1 and 1:1 for bentonite to Fe3O4, respectively. X-ray Powder Diffraction (XRD), Fourier Transform Infra-Red (FTIR), BET surface area, Vibrating-Sample Magnetometer (VSM), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), and Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV DRS) were used to characterize the materials. The bentonite-Fe3O4 (1:1) composite exhibited a greater surface area in comparison to the bentonite-Fe3O4 (2:1) composite with a measured value of 106.6 m2/g. It is a superparamagnetic material with a band gap of 2.25 eV and a saturation magnetization of 69.64 emu/g. The photocatalytic degradation of dye using bentonite-Fe3O4 (1:1) with the initial dye concentration of 25 mg/L, volume of 50 mL, catalyst dose of 0.05 g/L, addition of 3 mL H2O2, and 90 minutes of visible irradiation resulted in 94.34% and 98.45% degradation efficiency of methylene blue and Congo red dyes, respectively. The study determined that the most favorable pH for the photocatalytic degradation of methylene blue was pH 11, whereas the optimal pH for Congo red was found at pH 5. For methylene blue and Congo red dyes, photocatalytic degradation followed pseudo-first-order with the constant rates of 0.0356 min-1 and 0.0348 min-1, respectively. After five cycles of use in the photocatalytic process, the catalyst's degradation efficiency fell into below 5%. This research demonstrated that catalysts could be utilized in wastewater treatment technology.

High-Entropy Composite Coating Based on AlCrFeCoNi as an Anode Material for Li-Ion Batteries

In this study, a high entropy composite coating was synthesized by oxidizing a high entropy alloy, AlCrFeCoNi, at elevated temperatures in a pure oxygen atmosphere. X-Ray diffraction (XRD) analysis revealed that the prepared material was a dual-phase composite material consisting of a spinel-structured high entropy oxide and a metallic phase with a face-centered cubic structure. The metallic phase can improve the electrical conductivity of the oxide phase, resulting in improved electrochemical performance. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis unveiled the compositional homogeneity of the composite material. The prepared material was utilized as an anode active material in lithium-ion batteries. Cyclic voltammetry (CV) revealed the oxidation and reduction regions, while the electrochemical impedance spectroscopy (EIS) measurements showed a decrease in the charge transfer resistance during the cycling process. A long-term rate capability test was conducted at various current densities: 100, 200, 500, 1000, and 2000 mA g−1. During this test, a notable phenomenon was observed in the regeneration process, where the capacity approached the initial discharge capacity. Remarkably, a high regeneration efficiency of 98% was achieved compared with the initial discharge capacity. This phenomenon is typically observed in composite nanomaterials. At a medium current density of 500 mA g−1, an incredible discharge capacity of 543 mAh g−1 was obtained after 1000 cycles. Based on the results, the prepared material shows great potential for use as an anode active material in lithium-ion batteries.

Methodologies for the Characterization and Identification of Natural Atacamite as a Pigment in Andean Colonial Painting

Painting materials used in Spanish American Colonial art comprised pigments and binders from European origin as well as those that were already known in pre-Hispanic times. In recent years, we have identified for the first time the mineral atacamite, a basic copper chloride (Cu2Cl(OH)3), in Andean Colonial art pieces (Viceroyalty of Peru, 16th–18th centuries). This work proposes a methodology based on a multitechnical approach to identify and establish the origin (natural or synthetic) of the atacamite pigment in Andean cultural heritage objects. Optical microscopy (OM), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), portable X-ray fluorescence spectroscopy (pXRF), attenuated total reflection infrared spectroscopy (FTIR-ATR), micro-Raman spectroscopy, and wide-angle X-ray scattering (WAXS) were applied to analyse green pigments from the altarpiece of the Church of Ancoraimes, atacamite mineral samples from Chile, and atacamite obtained as a secondary product from traditional recipes used to produce verdigris, a copper acetate. Viride salsum by Teófilo Presbítero (SXII) and the Spanish translation by Andrés de Laguna (1566) of “De Materia Médica” from Dioscorides are both texts that include recipes involving the use of metallic copper as a starting material. These studies will contribute to the history of Spanish American Colonial art and to the knowledge on technological capacities and skills in the Andean region during this period.

Extraction of andradite from flotation tailings as a potential material for As(III) removal from simulated wastewater

Arsenic is a toxic and carcinogenic metalloid widely distributed in nature. It can enter water bodies through natural or man-made routes, posing a serious threat to the ecological environment and human health. In recent years, arsenic pollution in water has become a global problem. This study introduces the utilization of andradite from scheelite flotation tailings as a potential material for As(III) removal. The experimental results showed that after 30 min of milling, 5 g/L andradite achieved a removal rate of over 90 % for As(III), reducing its concentration from 1 mg/L to 0.09 mg/L. Scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) were carried to reveal the underlying mechanism of As(III) removal with andradite. Results indicated that the calcium atom and iron atom on the surface of andradite may react with As(III) to form calcium arsenite and ferric arsenite, and the products adhere to the surface of andradite. Based on the obtained results, andradite is a promising material for the remediation of arsenic pollution. Moreover, the source of andradite is very wide, and the cost of extraction and preparation is low. The extraction of andradite from non-ferrous metal flotation tailings as an adsorbent to remove As(III) not only improves the utilization rate of tailings resources, but also provides a new method for the prevention and control of arsenic pollution.

Solidification Behavior of Dy-Tb-Fe Alloys through Experimental Study and Thermodynamic Calculation.

In this work, the solidification microstructure and phase transitions of Dy-Tb-Fe alloy samples were studied by using scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) and differential thermal analysis (DTA). No stable ternary compound was detected in the present experiments. The phase transformation temperatures of eight Dy-Tb-Fe alloy samples were measured. Based on the experimental results determined in this work and reported in the literature, the phase equilibria of the Dy-Tb-Fe system was calculated using the CALPHAD method. The calculated vertical sections are consistent with the experimental results determined in this work and reported in the literature. Furthermore, in combination with the experimental solidification microstructure, the solidification behavior of Dy-Tb-Fe alloy samples was analyzed through the thermodynamic calculation with the Gulliver-Scheil non-equilibrium model. The simulated results agree well with the experimental results. This indicates that the reasonable thermodynamic parameters of the Dy-Tb-Fe system were finally obtained.

Research on microwave hydrothermal alkaline leaching defluorination of spent cathode carbon from aluminum electrolysis

Soluble fluoride present in spent cathode carbon (SCC) is a serious concern for both the environment and human health. To address this issue, the microwave hydrothermal alkaline leaching (MHAL) was used to removed the soluble fluoride from SCC. The structural characteristics and elemental distribution of SCC before and after MHAL treatment were analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). The effect of the primary parameters, i.e., temperature, time, and alkali concentration in the MHAL process, on the soluble fluoride removal rate was assessed using the Box-Behnken design (BBD) in response surface methodology (RSM), and subsequently optimized. The optimization results illustrate that the soluble fluoride removal rate of SCC could reach up to 98.06% under the optimum reaction conditions of 80 °C, 1.16 mol/L alkali concentration, and 8.4 min of reaction time. Under this condition, the experimental data showed that the average soluble fluoride removal rate was 97.11% and were in good agreement with the model predicted values. Furthermore, the MHAL process reduced the treatment process time by 99.4% and increased the soluble fluoride removal rate by 5.8% compared to the traditional hydrothermal treatment process. The MHAL process ensures rapid and efficient hazardous treatment of SCC while minimizing environmental pollution.

Characterizing Lung Particulates Using Quantitative Microscopy in Coal Miners With Severe Pneumoconiosis.

Current approaches for characterizing retained lung dust using pathologists' qualitative assessment or scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) have limitations. To explore polarized light microscopy coupled with image-processing software, termed quantitative microscopy-particulate matter (QM-PM), as a tool to characterize in situ dust in lung tissue of US coal miners with progressive massive fibrosis. We developed a standardized protocol using microscopy images to characterize the in situ burden of birefringent crystalline silica/silicate particles (mineral density) and carbonaceous particles (pigment fraction). Mineral density and pigment fraction were compared with pathologists' qualitative assessments and SEM/EDS analyses. Particle features were compared between historical (born before 1930) and contemporary coal miners, who likely had different exposures following changes in mining technology. Lung tissue samples from 85 coal miners (62 historical and 23 contemporary) and 10 healthy controls were analyzed using QM-PM. Mineral density and pigment fraction measurements with QM-PM were comparable to consensus pathologists' scoring and SEM/EDS analyses. Contemporary miners had greater mineral density than historical miners (186 456 versus 63 727/mm3; P = .02) and controls (4542/mm3), consistent with higher amounts of silica/silicate dust. Contemporary and historical miners had similar particle sizes (median area, 1.00 versus 1.14 μm2; P = .46) and birefringence under polarized light (median grayscale brightness: 80.9 versus 87.6; P = .29). QM-PM reliably characterizes in situ silica/silicate and carbonaceous particles in a reproducible, automated, accessible, and time/cost/labor-efficient manner, and shows promise as a tool for understanding occupational lung pathology and targeting exposure controls.

Characterization, risk assessment, and potential utilization of fly ash from PLTSa Merah Putih at Bantargebang, Bekasi, Indonesia

Municipal solid waste incineration (MSWI) has been adopted in Indonesia to reduce the volume and mass of municipal solid waste. However, as a by-product of waste combustion, fly ash generation cannot be avoided. It can cause an environmental problem if not managed properly. Hence, this study aims to investigate the characteristics of fly ash generated from Indonesia’s first waste-to-energy incineration pilot plant and its potential utilization. Fly ash was characterized using X-Ray fluorescence (XRF), BET surface area measurement, pore size distribution (PSD), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS), and X-ray diffraction (XRD). The characterization results showed that calcium was predominant, around 28%, followed by titanium, silica, iron, and aluminum, with values of 7.10%, 5.70%, 4.40%, and 4.30%, respectively. These results demonstrated that MSW incineration fly ash was classified as a very active high-calcium fly ash. The surface structure of fly ash was flaky and complex, with some irregular material. The particle size distribution of fly ash shows that the diameters of most particles were nearly 12 μm. The specific surface area of fly ash was 3.06 m2/g, the total-pore volume was 0.01 cm3/g, and the average pore size was 11.82 nm. In addition, the environmental risk assessment was evaluated using the toxicity characteristic leaching procedure (TCLP). TCLP concentrations of heavy metals, including arsenic, barium, beryllium, cadmium, chromium hexavalent, copper, lead, mercury, nickel, selenium, and zinc, were lower than the regulatory level, indicating a low environmental risk. Therefore, it has great potential for utilization as a paving block mixture material.

Associated Effects of Sodium Chloride and Dihydrate Gypsum on the Mechanical Performance and Hydration Properties of Slag-Based Geopolymer

The associated effect of sodium chloride and dihydrate gypsum on the mechanical performance of a slag-based geopolymer activated by quicklime was investigated by compressive strength, shrinkage, and square circle anti-cracking tests of mortar with a 0.5 water–binder ratio and a 1:3 binder–sand ratio, as well as paste soundness, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and mercury intrusion porosimetry (MIP) of the paste. The results indicate that (1) when dihydrate gypsum is used alone, it combines with calcium aluminate hydrate (C-A-H) to form calcium sulfoaluminate hydrate (AFt), which encourages the hydration process of slag. A 7.5% addition can result in an increase of 97.33% and 36.92% in 3-day and 28-day compressive strengths, respectively. When NaCl is used by itself, it facilitates the condensation of the aluminum silicate tetrahedron unit and generates zeolite. A 2% dosage can lead to a 66.67% increase in the 3-day compressive strength, while causing a 15.89% reduction in the 28-day compressive strength. (2) The combined effect of 2% NaCl and 7.5% gypsum results in the formation of needle-like and rod-shaped AFt, Friedel’s salt, and plate-like Kuzel’s salt in the geopolymer. This leads to an increase in 3-day and 28-day compressive strengths by 148% and 37.85%, respectively. Furthermore, it reduces the porosity by 18.7%. (3) Both NaCl and gypsum enhance the paste soundness of the slag-based geopolymer, and they do no harm to the crack resistance of the geopolymer. The drying shrinkage of the geopolymer at 28 days is just 0.48 × 10−3, which is only 66.7% of OPC. This slag-based geopolymer has a simple preparation process, good volume stability, low raw material cost, low energy consumption, and low carbon emissions. It can be used instead of 32.5 slag Portland cement in plain concrete applications, and has high engineering, economic, and environmental values.

Study of an Iron Age Gilded Silver Earring by XRF, SEM-EDS and Multifocus OM

The use of gold for artefact productions underwent substantial developments during Iron Age in western Europe, with the diversification of alloy compositions and the introduction of new technologies and aesthetics. This work presents a detailed study of a Late Iron Age earring from the western Iberian Peninsula and a discussion taking into consideration the alloys and technologies used at the time. The earring has a complex structure, composed of block- and strip-twisted wires and granulation. Characterization by multifocus optical microscopy, portable X-ray fluorescence spectrometry (pXRF), micro-XRF and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were performed to obtain information on the chemical composition and manufacturing techniques. Results show that the earring was manufactured with wires and granules made of a silver-rich alloy, covered with a gold-rich layer 45 μm thick on average, which acted as an external coating making the entire earring resemble gold. This is a rare example of an Iron Age gilded earring, and its detailed study provides further information on the manufacturing solutions adopted by the Iron Age goldsmiths.

Colour of the past in South Caucasus: The first archaeometric investigation on rock art and pigment residues from Georgia

This research is the first archaeometric investigation of Damirgaya and Trialeti painted rock art and pigments from grinding tools from the Neolithic settlement of Khramis Didi Gora, in South Caucasus, Georgia. The aims of this research are to characterise the rocks and pigments including identification of organic binder, as well as investigate the compatibility of inorganic pigments with locally available supplies and methods of production.Stylistic similarities and influences are compared with adjacent archaeological sites from Armenia and Azerbaijan, where traces of monochromatic red pigment were recovered in settlements, barrows and artefacts.Optical microscopy (OM) on loose samples and thin sections, X-ray powder diffraction (XRPD), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were used to determine the mineralogical and chemical composition of the samples. Employing micro-Fourier-transform infrared (μ-FTIR) and Raman spectroscopy, compounds were further characterized in both rock paintings and grinding tools.It was not possible to identify or ascertain the presence of binders, either because of their low concentration or complete molecular breakdown deterioration. From the pigment residues on both the rock art and grinding tools, hematite was the main colouring agent, with different associated minerals. For the rock samples, it was found that the rock art at Trialeti is on a dacite, whereas the one from Damirgaya is on a rock composed of quartz, with traces of iron oxides and phyllosilicates, suggesting that the rock originated from hydrothermal activity. The research presented here is the first chemical and mineralogical characterization of pigment residues and rock art from South Caucasian prehistory.