Scanning Electron Microscopy And Energy Dispersive Spectroscopy Research Articles

Structure and Chemical Composition of ca. 10-Million-Year-Old (Late Miocene of Western Amazon) and Present-Day Teeth of Related Species.

Molecular information has been gathered from fossilized dental enamel, the best-preserved tissue of vertebrates. However, the association of morphological features with the possible mineral and organic information of this tissue is still poorly understood in the context of the emerging area of paleoproteomics. This study aims to compare the morphological features and chemical composition of dental enamel of extinct and extant terrestrial vertebrates of Crocodylia: Purussaurus sp. (extinct) and Melanosuchus niger (extant), and Rodentia: Neoepiblema sp. (extinct) and Hydrochoerus hydrochaeris (extant). To obtain structural and chemical data, superficial and internal enamel were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (SEM-EDS). Organic, mineral, and water content were obtained using polarizing microscopy and microradiography on ground sections of four teeth, resulting in a higher organic volume than previously expected (up to 49%). It is observed that both modern and fossil tooth enamel exhibit the same major constituents: 36.7% Ca, 17.2% P, and 41% O, characteristic of hydroxyapatite. Additionally, 27 other elements were measured from superficial enamel by inductively coupled mass spectrometry (ICP-MS). Zinc was the most abundant microelement detected, followed by Pb, Fe, Mg, and Al. Morphological features observed include enamel rods in the rodent teeth, while incremental lines and semiprismatic enamel were observed in the alligator species. The fossil enamel was in an excellent state for microscopic analyses. Results show that all major dental enamel’s physical, chemical, and morphological features are present both in extant and extinct fossil tooth enamel (>8.5 Ma) in both taxa.

Immobilization mechanism of cesium in geopolymer: Effects of alkaline activators and calcination temperature

Geopolymer is always regarded as a promising material for the immobilization of radioactive waste. In the present study, the stabilization of Cs in geopolymers activated by NaOH and Na2SiO3 solutions and calcined at various temperatures was studied via toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope and energy dispersive spectroscopy (SEM-EDS), solid-state nuclear magnetic resonance (SSNMR), and N2 adsorption-desorption isotherm. For both NaOH-activated and Na2SiO3-activated geopolymers, the leaching concentrations of Cs decreased with the increase of calcination temperature. Specifically, most of the amorphous substance was crystallized to nepheline at 1000 °C for NaOH-activated geopolymer, and Cs+ can be incorporated into the structure of nepheline, contributing to the reduction of Cs leaching concentration. However, the amorphous structure was still maintained for Na2SiO3-activated geopolymer even after calcination at 1000 °C. It has been deduced that the main structure of Na2SiO3-activated geopolymer after calcination at 1000 °C should be in short-range order and Cs+ can be locked in a micro “crystal” structure. In addition, the change of specific surface area was not fully consistent with the decreasing trend of Cs leaching concentration. Therefore, the inner structure and the specific surface area of geopolymer should have a combined effect on the leaching behavior of Cs. This study can provide new insights into the application of geopolymer to immobilize radionuclides.

Metal(loid)s removal by zeolite-supported iron particles from mine contaminated groundwater: Performance and mechanistic insights

Iron-based materials have been widely investigated because of their high surface reactivity, which has shown potential for the remediation of metal(loid)s in groundwater. However, the disadvantages of structural stability and economic feasibility always limit their application in permeable reactive barrier (PRB) technology. In this study, zeolite-supported iron particles (Zeo-Fe) were synthesized by an innovative low-cost physical preparation method that is suitable for mass production. The removal efficiency and mechanism of typical metal(loid)s (Pb2+, Cd2+, Cr6+ and As3+) were subsequently investigated using various kinetic and equilibrium models and characterization methods. The results of scanning electron microscopy and energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) confirmed that zero valent iron (Fe0) and oxidation product (Fe3O4) were successfully loaded and efficiently dispersed on zeolite. The synthesized Zeo-Fe exhibited excellent adsorption and redox capacities for the cations Pb2+, Cd2+ and anions Cr6+, As3+. The increase in the pH resulting from Fe0 corrosion also enhanced the precipitation of Fe-metal(loid)s. The maximum removal capacity for Pb2+, Cd2+, Cr6+ and As3+ was up to 70.00, 9.12, 2.35 and 0.36 mg/g, respectively. The removal processes were well described by the pseudo-second-order kinetic model for Pb2+ and Cd2+, Lagergren pseudo first-order kinetics model for As3+ and double phase first order kinetics model l for Cr6+. Cr6+ was rapidly reduced to Cr3+ by the Fe0 stabilized on Zeo-Fe, and the oxidation of As3+ to As5+ was attributed to the Fe0/Fe2+ oxidation process at the interface over time, which was further demonstrated by the mineral phase and element valence analyses of reacted Zeo-Fe. The removal mechanism for metal(loid)s was a combination of physical and chemical processes, including adsorption, co-precipitation and reduction-oxidation. Conclusively, Zeo-Fe has been shown to have potential as an effective and economical material for removing various metal(loid)s used in PRB.

Anti-Corrosion Performance of Migratory Corrosion Inhibitors on Reinforced Concrete Exposed to Varying Degrees of Chloride Erosion.

This study investigated the anti-corrosion performance of commercial amino alcohol migratory corrosion inhibitors (MCIs) on concrete that underwent varying degrees of chloride erosion. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PD), scanning electron microscopy, and energy dispersive spectroscopy (SEM-EDS) analyses were performed to study the anti-corrosion performance and mechanism of the MCIs on the steel bars. The results indicated that the corrosion resistance of the steel bars in concrete was significantly improved by coating with the MCIs, and the earlier the specimens were coated with the MCIs, the higher the anti-corrosion efficiency. The anti-corrosion efficiency was 55.35% when the MCIs coating was applied before chloride erosion; however, the anti-corrosion efficiency decreased to 3.40% when the MCIs coating was applied after the ninth drying–wetting cycle. The improvement in corrosion resistance of the steel bar in concrete coated with MCIs was due to the protective MCIs-molecule film that formed on the steel bar surfaces, and the oxidative dissolution of iron at the anode was effectively inhibited by the MCIs coating.

A 14-year study on ceramic waste slag-based lightweight aggregate concrete

Lightweight aggregate concrete (LWAC) characterized with low dead weight and high performance, has been applied widely in concrete structures in the past two decades. Mostly, LWAC components play a crucial role in reducing structural weight and keeping structures in good service condition. However, long-term properties of LWAC, especially those prepared with industrial waste-based aggregate, directly affect the durability of structure but have not been explored yet. In the present study, 14-year LWAC incorporating with ceramic waste-based lightweight aggregate (CLWA) were experimentally studied. Traditional LWAC with furnace slag lightweight aggregate (FLWA) was designed as a contrast. Properties of 14-year LWAC such as compressive strength, chloride ion permeability, X-ray diffraction and open porosity were evaluated. In addition, high magnification electron microscope, scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) were adopted to characterize the interfacial transition zone (ITZ) and microstructure of LWAC. Results indicates that after 14 years’ curing, no strength reduction is detected and the chloride ion permeability maintains in very low level for LWAC. Long-term performance of LWAC with CLWA is superior to that with FLWA, thanks to the disconnected uniform pores/rough particle surface distributed in CLWA and the compact ITZ between aggregates and mortar.

Experimental and material characterization of composites, including waste iron and marble powder.

Due to its fine particle size, waste marble slurry originating in cutting and processing units mixes into the air after drying, causing environmental and health problems in nearby areas. On the other hand, large amounts of iron particles are generated as metalworking industry waste, affecting the environmental system. In this study, 0%, 10%, and 20% marble powder (instead of cement) and iron particles (instead of fine aggregate) were used in mixtures, and the composites produced were subjected to two different curing periods: 7 and 28days. The physical, mechanical, microstructural, and thermal properties of the fresh and hardened composites were ascertained via bulk density, consistency, porosity, water absorption, capillary water absorption, strength tests, particle size distribution, X-ray diffraction (XRF), X-ray fluorescence (XRF), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), and thermogravimetric analyses (TGA). The results revealed that minimum water absorption (8.5%) and porosity (19.8%) values were achieved in 28-day composites produced with 10% marble-20% iron wastes among all composites. Thus, iron particles substituted for natural aggregates were mainly responsible for the increase in mechanical performance. A maximum flexural strength of 5.9MPa and a compressive strength of 26.7MPa were observed in 28-day composites containing 0% marble-20% iron wastes. Furthermore, capillary water absorption tended to decrease with the substitution of 10% marble powder.

Microplastic Extraction from the Sediment Using Potassium Formate Water Solution (H2O/KCOOH)

Microplastics (MPs) are considered an important stratigraphic indicator, or ‘technofossils’, of the Anthropocene. Research on MP abundance in the environment has gained much attention but the lack of a standardized procedure has hindered the comparability of the results. The development of an effective and efficient method of MP extraction from the matrix is crucial for the proper identification and quantifying analysis of MPs in environmental samples. The procedures of density separation used currently have various limitations: high cost of reagents, limited solution density range, hazardous reagents, or a combination of the above. In this research, a procedure based on density separation with the use of potassium formate water solution (H2O/KCOOH) in controlled conditions was performed. Experimental sediment mixtures, spiked with polyethylene (PE), polystyrene (PS), polyurethane (PUR) and polyethylene terephthalate (PET) particles were prepared and an extraction procedure was tested in the context of a weight-based quantitative analysis of MPs. This article discusses the effectiveness and safety of the method. It additionally provides new information on the interactions between MP particles and the mineral matter of the sediment. Results were acquired with the use of instrumental methods, namely thermogravimetry (TG), Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron microscopy and Energy Dispersive spectrometry (SEM/EDS), as well as X-ray fluorescence (XRF) analysis.

A new intumescent insulation emergency material for thermal protection of storage tanks –potassium polyacrylate & organic modified hectorite & intumescent flame retardant

Thermal protection of adjacent equipment such as chemical storage tanks is very important when a fire accident occurs. In this paper, a new intumescent insulation emergency material, potassium polyacrylate & organically modified hectorite & intumescent flame retardant (PPHI), was prepared successfully. The material was characterized by Fourier Transform Infra-Red (FTIR) and X-ray photoelectron spectroscopy(XPS). Thermal insulation performance and thermal stability of the material were studied by cone calorimeter, fire resistance test, scanning electron microscope and energy dispersive spectroscopy (SEM/EDS), and thermogravimetric analysis (TGA), respectively. The results showed that thermal insulation performance of PPHI was the best when the addition content of intumescent flame retardant (IFR) reached 0.54 wt%. The morphology and structures by SEM gave positive evidence that char layers formed from the PPHI composites were improved greatly due to the addition of intumescent flame retardant. Finally, a possible thermal insulation mechanism of PPHI was presented.

Comparative analysis of the surface properties and corrosion resistance of Co-Cr dental alloys fabricated by different methods

Statement of problemsThe complex oral environment leads to the corrosion of dental alloy materials and the release of metal ions that may have a negative impact on health. Digital manufacturing is increasingly being used in dentistry, but whether digitally manufactured prostheses have better resistance to corrosion than traditional cast prostheses is unclear. PurposeThe purpose of this in vitro study was to determine the surface properties and corrosion resistance of dental cobalt-chromium (Co-Cr) alloys fabricated by lost-wax casting (CAST), selective laser melting (SLM), and computer numerical control milling (CNC). Material and methodsThe surface characteristics of the specimens were analyzed via scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), metallurgical observation, and X-ray diffraction (XRD). For corrosion resistance, the specimens were immersed in artificial saliva at a pH 2.3 and 6.8 for 1, 4, and 7 weeks. Then, inductively coupled plasma-mass spectrometry (ICP-MS) was used to detect the main metal ion. Electrochemical impedance spectroscopy (EIS) was conducted based on a 3-electrode system to assess the electrochemical corrosion resistance. An ANOVA test was used to evaluate statistically significant differences among the groups (α=.05). ResultsThe SLM and CNC specimens showed more homogenous microstructures, less ion release at different times and pH, and more charge transfer resistance than CAST specimens. ConclusionsCompared with casting, SLM-printing and CNC-milling have advantages in terms of surface properties and corrosion resistance.

Surface coating preparation of spherical magnetic materials

Magnetic materials are being increasingly used in anti-counterfeiting coatings, but the dark colors of magnetic materials greatly limit their applications. This necessitates the development of light-colored magnetic materials. In this study, the heterogeneous precipitation method was used to deposit a layer of titanium dioxide (TiO2) on the surface of magnetic spherical metal particles, followed by the deposition of a layer of Ag by the reduction method, in order to achieve a light color. In the experiment, the particles were initially coated with a few tens of nanometers of TiO2 with a strong shading effect, followed by a further coating of Ag of the same thickness with a similar shading performance. Not only did this achieve a lighter color, but there was no reduction in the magnetic properties of the material after the application of the coating. Scanning electron microscopy (SEM), scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), X-ray diffractometry (XRD), and other methods were used to study the changes in morphology and composition before and after the magnetic material was coated. A magnetic tester was used to study the changes in magnetic strength before and after the magnetic material was coated.

Influence of Slag Viscosity and Composition on the Inclusion Content in Steel

Influence of slag viscosity and composition on the inclusion content in the steel is studied using laboratory experiments and modeling simulations. The steel samples are taken during the experimental process to record the inclusion content change. Afterwards the prepared samples are analyzed using automated scanning electron microscope and energy dispersive spectroscopy (SEM/EDS) method. A simple steel/slag reaction model is constructed based on the effective equilibrium reaction zone (EERZ) method. The inclusion content evolution process is discussed by combining the experimental and calculated results. It is found that the inclusion content evolution in the steel is determined by the inclusion generation and removal.

Synthesis and Characterization of Novel Calcium-Silicate Nanobioceramics with Magnesium: Effect of Heat Treatment on Biological, Physical and Chemical Properties

Glass-ceramic nanopowder with a composition of 55SiO2-35CaO-10MgO (mol %) was synthesized by the sol–gel method and was heat treated at three temperatures (T1 = 835 °C, T2 = 1000 °C, T3 = 1100 °C) in order to obtain different materials (C1, C2, C3, respectively) varying in crystal structure. Bioactivity and oxidative stress were evaluated in simulated body fluid (SBF) for various time periods (up to 10 days). The structure of the synthesized materials and their apatite-forming ability were investigated by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM/EDS). The antibacterial properties of the synthesized materials were evaluated against three Gram-positive and four Gram-negative bacterial strains and their biocompatibility was verified on a primary cell line of human gingival fibroblasts (HGFs) by the MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide) assay. The crystallization of the materials was increased by sintering temperature. Heat treatment did not inhibit the bioactive behavior of the materials as apatite formation started after 3 days in SBF. C2, C3 showed some indications of apatite forming even from the first day. Regarding cell viability, a variety of biological behaviors, concerning both dose and time points, was observed between the positive control and the tested materials by both the MTT assay and oxidative stress analysis. In conclusion, the nanobioceramic materials of this study possess a multitude of attractive physicochemical and biological properties that make them suitable candidates for bone regeneration applications, fillers in nanocomposite scaffolds, or as grafts in bone cavities and periodontal lesions.

Adsorption Characteristics of Pb(Ⅱ) on Eucalyptus Biochar Modified by Potassium Permanganate

Eucalyptus biochar(BC) was prepared and potassium permanganate was used to modify the biochar(KBC). Static adsorption experiments on Pb(Ⅱ) in aqueous solution were carried out to investigate the effects of pH, adsorbent dosing, adsorption time, temperature, and initial concentration on the adsorption of Pb(Ⅱ). The results showed that the optimum pH was 5 while the adsorption reached saturation after 6 h. When the temperature was 25℃, the initial concentration of Pb(Ⅱ) was 100 mg·L-1 with an adsorbent dosage of 0.06 g; the maximum adsorption of Pb(Ⅱ) by KBC was 83.059 mg·g-1, with a removal rate of 99.67%. The adsorption of Pb(Ⅱ) by KBC followed the pseudo-second-order kinetic model and the Langmuir isothermal adsorption model, which is a monolayer adsorption occurring on a homogeneous surface. The adsorbents were characterized using the BET method, scanning electron microscopy and energy dispersive spectroscopy(SEM-EDS), X-ray diffraction(XRD), Fourier transformed infrared(FT-IR) and X-ray photoelectron spectroscopy(XPS). The adsorption mechanism of Pb(Ⅱ) by KBC oxygen-containing and manganese-containing groups was through complexation and precipitation, and the formation of -O-Pb-O- bidentate complexes on the surface of the biochar. Therefore, potassium permanganate-modified BC can be used as a good Pb(Ⅱ) adsorbent.

Effect of the nano-titanium dioxide (nano-TiO2) coating on the photoaging properties of thermally treated bamboo

ABSTRACT Moso bamboo was firstly treated in a vacuum chamber at 150°C, 170°C, 190°C, and 210°C for 1, 2, and 3 h, respectively. Nano-TiO2 gel were then coated on the surface of thermally treated (TM) bamboo. Finally, specimens were radiated by an accelerated aging chamber of xenon lamp for 144 h. Chroma Meter, Scanning electron microscopy and Energy-dispersive spectroscopy (SEM-EDS) were applied to investigate the effect of nano-TiO2 coating on the surface color stability of TM bamboo. Results revealed that TM imposed a significant effect on the surface color of bamboo, e.g. when treatment temperature and duration increased, bamboo surface became darker. The color parameters of TM bamboo coated with nano-TiO2 gel after aging were close to the bamboo before aging, indicating that the photo-discoloration resistance of the TM bamboo has been improved. The nano-TiO2 gel with a concentration of 10% shows a better effect than that of 5%. After aging for 144 h, the ΔE of TM bamboo (190°C/2 h) coated by nano-TiO2 gel with a concentration of 10% was 2.90, which decreases by 25% compared with that of uncoated bamboo. Furthermore, the nano-TiO2 coating had no obvious aging failure after 144 h aging, which avoided the leaching of TiO2 particles during the long-term service.

Microbiologically induced calcite precipitation technology for mineralizing lead and cadmium in landfill leachate

As a new bioremediation technology for toxic metals, microbiologically induced calcite precipitation (MICP) is gradually becoming a research focus. This study investigated the application of MICP to mineralize toxic metals (lead and cadmium) in landfill leachate for the first time. In the experiment of remediating synthetic landfill leachate (SLL) contaminated by Pb2+, 100% of the 20 mg/L Pb2+ was removed when the maximum urease activity was only 20.96 U/ml. Scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) and laser particle size characterizations of the precipitates indicate the formation of agglomerated square particles, 76.9% of which had sizes that ranged from 33.93 to 57.06 μm. Fourier transform infrared spectroscopic and X-ray diffraction analyses confirmed that the precipitates consisted predominantly of calcite crystals, and the unit cell lattice constants of the precipitates (a = b = 4.984 Å, c = 17.171 Å) matched those of calcite, while lead was fixed as hydrocerussite. In addition, the Pb-MICP precipitates were stable under continuous acid degradation (pH = 5.5), and only 1.76% of the lead was released after 15 days. In the verification test of toxic metals remediation in a real landfill leachate (RLL), all of the Pb2+ and Cd2+ (initial concentrations: Pb2+ = 25 mg/L; Cd2+ = 5.6205 mg/L) was mineralized simultaneously, which further confirmed the feasibility of MICP for toxic metal remediation in landfill leachate. However, optimizing the urea dosage and combining the ammonium recovery are necessary strategies required for improving the economic and environmental benefits of the MICP process.

Zn-0.8Mg-0.2Sr (wt.%) Absorbable Screws-An In-Vivo Biocompatibility and Degradation Pilot Study on a Rabbit Model.

In this pilot study, we investigated the biocompatibility and degradation rate of an extruded Zn–0.8Mg–0.2Sr (wt.%) alloy on a rabbit model. An alloy screw was implanted into one of the tibiae of New Zealand White rabbits. After 120 days, the animals were euthanized. Evaluation included clinical assessment, microCT, histological examination of implants, analyses of the adjacent bone, and assessment of zinc, magnesium, and strontium in vital organs (liver, kidneys, brain). The bone sections with the implanted screw were examined via scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). This method showed that the implant was covered by a thin layer of phosphate-based solid corrosion products with a thickness ranging between 4 and 5 µm. Only negligible changes of the implant volume and area were observed. The degradation was not connected with gas evolution. The screws were fibrointegrated, partially osseointegrated histologically. We observed no inflammatory reaction or bone resorption. Periosteal apposition and formation of new bone with a regular structure were frequently observed near the implant surface. The histological evaluation of the liver, kidneys, and brain showed no toxic changes. The levels of Zn, Mg, and Sr after 120 days in the liver, kidneys, and brain did not exceed the reference values for these elements. The alloy was safe, biocompatible, and well-tolerated.

CO 2 mineral trapping comparison in different regions: predicted geochemical reactivity of the Precipice Sandstone reservoir and overlying Evergreen Formation

Injected CO 2 streams may have geochemical reactivity to different rock types in a CO 2 storage complex depending on solubility and formation water chemistry. The Precipice Sandstone and Evergreen Formation are a low-salinity reservoir–seal pair in the Surat Basin, Australia, targeted for potential CO 2 storage. The kinetic geochemical CO 2 reactivity of different rock facies from three regions were predicted over 30 and 1000 year time periods. No material CO 2 mineral trapping in the quartz-rich Precipice Sandstone reservoir was predicted, owing to the low rock reactivity. Predicted CO 2 mineral trapping in the Evergreen Formation was more variable due to different amounts of more reactive feldspars, clays, calcite and siderite. Predicted mineral trapping as siderite and ankerite was between 0.03 and 8.4 kg m −3 CO 2 , and mainly depends on chlorite and plagioclase content. Predicted pH was between 5 and 7.5 after 1000 years. Pyrite precipitation was also predicted with SO 2 present in the injectate. QEMSCAN and SEM-EDS (scanning electron microscopy and energy-dispersive spectroscopy) spot imaging of samples from the seal containing natural fractures filled by siderite, pyrite, clays, ankerite, calcite, barite and apatite represent a natural analogue for natural mineral trapping. These are in good agreement with our model predictions. This study suggests that, from a geochemical perspective, the Precipice Sandstone is a suitable storage reservoir, whereas mineral trapping would occur in the overlying Evergreen Formation. Supplementary material: Additional model inputs, characterization and model images, and an excel file of QEMSCAN mineral and porosity components, are available at https://doi.org/10.6084/m9.figshare.c.5395393 Thematic collection: This article is part of the Geoscience for CO 2 storage collection available at: https://www.lyellcollection.org/cc/geoscience-for-co2-storage

A preliminary study of the weathering mechanism of fossilized Cretaceous Hamipterus bones

The discovery of Hamipterus tianshanensis had important scientific significance because three-dimensional preserved fossils can provide unique information about the reproduction, development, and evolution of pterosaurs. However, the pterosaur fossils exhibited violent weathering, including noticeable cracking and spalling, since the preservation environment changed dramatically after excavation, which severely influenced the preservation of these fossils and the scientific research conducted on them. To determine the weathering mechanism of these fossil bones, the samples were analyzed using X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM-EDS). The results indicate that calcite is the main mineral in the hollow bones, but it is mixed with a small amount of other minerals, such as quartz, feldspar, and other debris particles. Moreover, the main component of the pterosaur bones is hydroxyapatite, and carbonate has substituted for some of the phosphate (B-type carbonated apatite) in the fossil bones. A small amount of calcite and manganese oxides has precipitated in the vascular canals. The phosphate crystallinity index (PCI) is 4.17. These results indicate that the fossils have undergone severe diagenesis. Apart from these alterations, the fossil bones have high contents of anions and cations such as Cl−, NO3−, SO42−, Na+, and Ca2+, and the total content of soluble salts is 35584.41 μg g−1. Based on these results, it is inferred that the weathering mechanism of the fossil bones is as follows. First, the fragile hollow bones cracked easily because of the enormous thermal stress caused by the dramatic temperature changes in the Gobi Desert and the differences in the thermal expansion coefficients (TEC) of the surrounding rocks, the fossil bones, and the different fillers. Second, a large amount of stress is generated by salt crystallization when the temperature and humidity change, and the pterosaur fossils will be damaged when the crystallization pressure exceeds the tensile strength of the fossils. These results suggest that the preservation of pterosaur fossils requires suitable desalination and consolidation conditions. Moreover, they should be preserved in a constant temperature and humidity environment.

КЕРАМИЧЕСКИЕ ЛИТЕЙНЫЕ ФОРМЫ ИЗ ПАМЯТНИКА КРУГЛАЯ ДОЛИНА В ПРИМОРЬЕ: ОПЫТ МЕЖДИСЦИПЛИНАРНОГО ИССЛЕДОВАНИЯ

The article presents an interdisciplinary study of casting molds as one of the kinds of old technical (“metalworking”) ceramics. The material of the study is ceramic molds (47 whole and fragmented samples) unearthed at the Kruglaya Dolina settlement in the central Primorye region. The molds and other objects of technical ceramics (crucibles, nozzle) were found in destroyed, non-stratified cultural deposits and connected with the remains of bronze-casting workshops complex which was dated supposedly to the Bohai state period, 698-926. The study aimed (1) to examine the morphological and technological characteristics of the molds, and (2) to detect traces of alloys at the working surfaces of the molds. The study employed methods of binocular microscopy and laboratory refiring testing for (1), and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), portable X-Ray fluorescence spectroscopy (pXRF) for (2). The analyzed ceramic molds were intended for the casting of semi-spherical buttons, several kinds of pendants, rosette-shaped openwork ornaments. Original bronze items which could be cast in these molds were not found at Kruglaya Dolina. According to the data on the morphological variability of the molds together with the results of the examination of the ceramic pastes technology, one can suppose that the casting molds were produced by different craftsmen or different workshops. SEM-EDS and pXRF analyses detected the traces of bronze alloys at 15 mold samples with carbonized working surfaces. Chemical elements - metals - lead (Pb), tin (Sn), and copper (Cu) are traced in various combinations at various samples. In some cases together with metals arsenic (As) is detected. The interpretation of these results follows methodological recommendations based on the published data of experimental research. The presence of certain elements can be stated, and their relative concentrations in the spectrum composition can be evaluated. However, it is necessary to take into account that the amounts of certain elements in the spectrum do not correspond to their amounts in the original alloy composition. Therefore, qualitative characteristics of the alloys can be determined, but not quantitative ones. According to the results, the three-component alloys containing copper, tin, and lead are recognized certainly. The tin-copper non-lead alloy and the “pure copper” alloy are supposed in some cases. Previous investigations on the old bronzes chemical compositions in southern Russian Far East revealed that three-component alloys (lead-tin-copper) containing arsenic had been used widely during the Bohai state period. Tin-copper and “pure copper” alloys were known at that time as well. It seems to be likely that the casting molds from the Kruglaya Dolina site are dated to the Bohai state period. Further researches of this site's bronze-casting workshops complex remains will focus on other categories of technical ceramics.

Petrographic and geochemical investigations of the late antiquity unguentaria from the archaeological site of Tripolis, Denizli (southwestern Turkey)

Petrographic and geochemical analyses were performed on unguentarium samples from Tripolis, Denizli, which was in the crossroads of the Phrygia, Caria and Lydia region during the late Antique period. In particular, optical microscopy, X-ray diffraction (XRD), X-Ray Fluorescence (XRF) and Scanning Electron Microscopy and Energy Dispersive Spectroscopy (SEM-EDS) were used for the determination of the morphological, mineralogical and chemical characteristics of the unguentaria. Thin section and XRD analyses show that unguentaria are composed of an amorphous matrix with various minerals and rock fragments and/or voids and were categorized into three petrographic groups. Group 1 samples consist of abundant quartz, plagioclase (anorthite), gehlenite, clinopyroxene (diopside), rarely calcite and iron minerals. Group 2 samples have similar mineralogical compositions but they have lesser quartz and further calcite than group 1. Group 3 samples have porous matrix and rarely quartz, plagioclase (anorthite), gehlenite. Petrographic differences between groups are further supported by the chemical compositions. The presence of Ca-silicate minerals and bloating pores in the sample matrix indicated higher firing temperatures (approximately 900 or 1000 °C) in a reducing atmosphere. The coexistence of calcite and gehlenite can be practically interpreted as a secondary calcite, which has formed in samples as a result of post-burial deposition processes. Results further showed that illitic clays were used for the production and the unguentaria were manufactured by using Başkarcı clays from Denizli region.