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

An Archaeometallurgical Study of Medieval Knives from Kinet Höyük, Turkey

This paper examines the knives of the medieval period (13th -14th century AD) from Kinet Höyük in Cilicia, one of the most important areas of Anatolia for the history of iron production. The materials and production processes of 12 knives were revealed using archaeometry methods, such as Optical Microscopy (OM), Scanning Electron Microscope-Energy Dispersive X-Ray Spectrometer (SEM-EDS) analyses, and micro-hardness tests. An examination of the relationship between the shape and size of these knives was undertaken, along with a discussion of the factors involved in the manufacturing techniques. Among the medieval knives from Kinet Höyük that were analyzed, the results of the study indicate that besides blades made entirely of steel or wrought iron there are examples of forge-welding steel to wrought iron in a variety of ways. The largest group of knives is composed of small blades made only of steel. A particular example of this group is a blade made of crucible steel, which was skillfully forged and heat-treated. The medieval blades from Kinet Höyük exhibit a direct relationship between their shapes and their dimensional proportions. A specific production method, however, seems not to have been chosen in accordance with a given shape. The dimensions of the knives were more significant, particularly when only steel or only wrought iron was used. Based on the historical iron-producing activities in the region and the traces of intense blacksmithing practices found in the medieval layers of Kinet Höyük, it is argued that these knives are remnants of a skilled metal production culture.

Graphene-magnetite functionalized diatomite for efficient removal of organochlorine pesticides from aquatic environment

A unique composite based on graphene oxide, magnetite, and diatomite was synthetized by eco-friendly dry coating technique for the removal of four toxic organochlorine pesticides from agricultural drainage. The prepared composite was fully characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), particle size analyzer, Vibrating-sample magnetometer (VSM), magnetic susceptibility meter, zeta potential, scanning electron microscopy-energy dispersive X-ray spectrometer (SEM-EDS), and Brunauer–Emmett–Teller analysis (BET) techniques. The characterization results confirmed the fabrication of a discrete core/shell structured composite possess both adsorptive and magnetic nature. The surface area, pore volume and pore diameter were 23.4 m2/g, 0.0026 cm3/g, and 4.5 nm, respectively. The amenability to use the fabricated composite as an adsorbent for some organochlorine pesticides was investigated under different conditions of concentration, time, pH, and temperature. Batch adsorption experiment showed that 97% removal efficiency was observed for all the studied pesticides with adsorption capacities of 7.78 mg/g after 2 h contact time and at any pH region. The adsorption was exothermic (ΔH < 0), spontaneous (ΔG° < 0), followed pseudo 2nd order kinetics (R2 > 0.998), and fitted well to Langmuir's isotherm pattern for all pesticides (R2 > 0.98). It is assumed that organochlorine pesticides were initially physisorbed by the graphene nanoplatelets via hydrophobic and π-π interactions along with chemisorption for forming monolayer. Moreover, the pesticides molecules could diffuse in the DMG composite micropores and be trapped in the structural defects. The regeneration of the composite exhibited over 90% removal efficiency even after seven cycles. The fabricated composite was examined to remove organochlorine from a real water sample, the obtained results suggest the possibility to use this composite as an economical, effective and sustainable adsorbent for the treatment of pesticides contaminating water.

Preparation of phosphorus-modified biochar for the immobilization of heavy metals in typical lead-zinc contaminated mining soil: Performance, mechanism and microbial community

The use of modified biochar for the remediation of heavy metal (HM) has received much attention. However, the immobilization mechanism of biochar to multiple HMs and the interaction of different forms of HMs with microorganisms are still unclear. K2HPO4-modified biochar (PBC) was produced and used in a 90-days immobilization experiment with soil collected from a typic lead-zinc (Pb–Zn) mining soil. Incubation experiments showed that PBC enhanced the transformation of Cd, Pb, Zn and Cu from exchangeable (Ex-) and/or carbonate-bound forms (Car-) to organic matter-bound (Or-) and/or residual forms (Re-). After scanning electron microscopy-energy dispersive X-ray spectrometer (SEM-EDS), X-ray diffractometry (XRD), fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) analysis, the mechanisms of HM immobilization by PBC were proposed as precipitation (PO43-, HPO42-, OH- and CO32-), electrostatic attraction, complexation (–COOH, –OH and R–O–H) and the indirect roles of soil parameter variations (pH, moisture and microbial community). Microbial community analysis through high-throughput sequencing showed that PBC reduced bacterial and fungal abundance. However, addition of PBC increased the relative proportions of Proteobacteria by 15.04%–42.99%, Actinobacteria by 4.74%–22.04%, Firmicutes by 0.76%–23.35%, Bacteroidota by 0.16%–12.34%, Mortierellomycota by 4.00%–9.66% and Chytridiomycota by 0.10%–13.7%. Ex-Cd/Pb/Zn, Car-Cd/Zn and Re–Cd/Pb/As were significantly positively (0.001<P≤0.05) correlated with bacterial phyla of Crenarchaeota and Methylomirabilota, and Re–Cu and Ex-/Car-/Fe–Mn oxide-bound (Fe–Mn-)/Or-As were significantly positively correlated (0.001<P≤0.05) with the bacterial phyla of Proteobacteria and Bacteroidota. While Car-Cd/Zn and Re–Pb/As were positively correlated (0.01<P≤0.05) with fungal phyla of Ascomycota, Glomeromycota, Kickxellomycota, Basidiomycota and Mucoromycota. The bacterial network contained more complex interactions than the fungal network, suggesting that bacteria play a larger role in HMs transformation processes. The results indicate that PBC is an effective agent for the remediation of HMs polluted soil in Pb–Zn mining areas.

Kinetics and Mechanisms of Artificial Willemite Leaching in Low-Sulfuric-Acid Solution at Elevated Temperature

The present study was undertaken to investigate the effects of temperature, sulfuric acid concentration, agitation speed, and particle size on the high-temperature leaching kinetics of artificial willemite in low sulfuric acid solution. A mathematical model taking into account the change in acid concentration was evaluated for the leaching rate increased with increasing sulfuric acid concentration, temperature, and agitation speed and decreasing particle size. The kinetic analysis indicated that the leaching process was well interpreted by a modified grain model with product layer diffusion as the main rate-controlling step, and the shrinking core model was used to represent the reaction of each grain. The characteristic changes of the sample before and after leaching were studied using a scanning electron microscope/energy dispersive X-ray spectrometer (SEM/EDS) and X-ray diffraction (XRD) to elucidate the leaching mechanism. The apparent activation energy was found to be 22.06 kJ/mol at 373–413 K, and the reaction order with sulfuric acid concentration was 1.6472. On the basis of the grain model, the following rate equation was established: 1.07ln(1−0.93x)−[1.28ln0.17+(1−x)23−0.42(1−x)130.17+(1−x)23+0.84(1−x)13+4.5arctan(2.76(1−x)13−0.58)]+3.8=43.55e−22060RTt.

Preparation of Powdered Activated Carbon Composite Material and Its Adsorption Performance and Mechanisms for Removing RhB

For solving the problem of low efficiency about dyes and slow precipitation rate for powdered activated carbon (PAC), this study successfully prepares a kind of powdered activated carbon-based composites (PACMC) to remove Rhodamine B (RhB) in wastewater as an adsorbent. PACMC derived from potassium humate and polyaluminium chloride (PACl)-modified PAC were fabricated via a chemical precipitation method. We confirmed the micro-morphology and chemical composition of PACMC by scanning electron microscopy energy-dispersive X-ray spectrometer (SEM-EDS) and fourier infrared spectroscopy (FT-IR), certifying that PACMC was synthesized by chemical reaction of raw materials. PACMC has layered porous structure and functional groups, which is beneficial to the transport and diffusion of RhB molecules. The specific surface area (10.098 m2·g−1) and average particle size (142.9 µm) of PACMC and the specific surface area (710.1 m2·g−1) and average particle size (11.9 µm) of PAC were measured. By comparison, it can be seen that PACMC has larger average particle size conducive to solid–liquid separation. The static adsorption experiments were carried out to investigate the adsorption properties of RhB by PACMC. The results showed that the adsorption capacity of PACMC for RhB was 2–3 times as high as that of PAC. The pH value of the solution had a significant effect on the adsorption of RhB by PACMC and the maximum adsorption was observed at pH = 4.5 (qe = 28.56 mg·g−1, C0 = 40 mg·L−1). The adsorption of RhB by PACMC can be well described by the pseudo-second-order kinetics. The kinetic results revealed that the adsorption process involved several steps, where the chemical adsorption and intra-particle diffusion both played the important roles. The isothermal adsorption data were in accordance with the Dubinin–Radushkevich model, which indicated that the adsorption was dominated by the chemisorption mechanism. Therefore, the adsorption mechanisms included chemical binding/chelation effect and electrostatic adsorption effect.

Differentiation of multilayered automotive coatings with Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscope/energy dispersive Xray spectrometer

PurposeThis study aims to using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscope/energy dispersive Xray spectrometer to identify different automotive coatings for forensic purpose.Design/methodology/approachTwo four-layered samples in a hit-and-run case were compared layer by layer with three different methods. FTIR spectroscopy was used to primarily identify the organic and inorganic compositions. Raman spectrum and scanning electron microscope/energy dispersive Xray spectrometer (SEM-EDS) were further used to complement the FTIR results.FindingsTwo weak and tiny peaks in one layer found between two samples by FTIR, Raman microscope and SEM-EDS verified the result of differences. The study used the three instruments in combination and found it’s effective in sensing coatings, especially in the inorganic additives.Research limitations/implicationsUsing these three instruments in combination is more accurate than individually in multilayered coating analysis for forensic purpose.Practical implicationsThe three different instruments all present unique information on the composition, and provided similar and mutually verifiable results on the two samples.Originality/valueWith this method, scientists could identify and discriminate important coating evidences with tiny but characteristic differences.

Eficiência da técnica de encapsulamento em solo argiloso com elevadas concentrações de cloreto de zinco com agentes tradicionais

ABSTRACT Although the encapsulation technique has been used in environmental remediation for over three decades, there are few studies evaluating its efficacy for high contaminant concentrations. Therefore, this study aims to evaluate the encapsulation technique efficiency of clayey soil contaminated with 5% and 10% of zinc chloride, using lime and cement. Chemical, mechanical, mineralogical, and microscopic analyses were performed for pure, contaminated, and encapsulated soil, based on X-ray fluorescence (XRF/EDX), unconfined compression strength (UCS), atomic absorption spectrometry (AAS), scanning electron microscopy/energy dispersive X-ray spectrometer (SEM/EDS), and X-ray micro-computed tomography (micro-CT) tests. Although chemical interactions between zinc and lime negatively affected the gains when compared to cement, both encapsulating agents increased the strength over the curing periods of 7, 28, and 60 days. The leachates presented a significant reduction in the contaminant concentration, above 77% for critical experimental conditions. The contaminant reduced the presence of chemical elements that compose the soil matrix, consequently causing the voids to increase; in contrast, pozzolanic reactions promoted by the addition of lime and cement resulted in homogeneous voids distribution, enhancing the mechanical behavior and the capability of zinc chloride retention.

Elemental profiling of total gunshot residue using total reflection X-ray fluorescence spectrometry.

Gunshot residue (GSR) is a composite of unburnt and partially burnt particles from various components of firearm ammunition cartridges. GSR is customarily sampled from small, localized spots and analyzed visually and elementally. The conventional analytical methods for localized GSR are most commonly done through a paired scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) to look for the presence of lead, barium, and antimony, the inorganic components of ammunition primer. Previous GSR analysis primarily focused on the material deposited on a shooter's hands and used swabbing or adhesive stubs to collect GSR. In this study, total gunshot residue (tGSR) from six types of ammunition was collected from fabric that was shot at a muzzle-to-target distance of 15cm. Subsequently, each tGSR sample was digested in nitric acid and analyzed with total reflection X-ray fluorescence spectrometry (TXRF). The TXRF technique can simultaneously identify the individual elements in the tGSR and provide absolute elemental quantification. In contrast, EDS scans report the relative elemental compositions of localized GSR samples rather than giving absolute quantitation. This study reliably revealed distinct patterns in six key elements (lead, copper, barium, antimony, iron, and zinc) of tGSR among the ammunition investigated. Elemental profiles were developed from the analyses to represent each ammunition type and the elemental quantities obtained could be used to suggest the category of ammunition that was used.

Characteristics and possible formation process of ferromanganese beachrock in an intertidal zone of East China Sea influenced by buried ancient woods

The ferromanganese (FeMn) deposits could be found in many shallow water and deep-ocean places. Lots of studies have been performed to explore the occurrence, formation and economic value of FeMn nodules or crusts on the deep ocean floor. However, the occurrence and formation of FeMn beachrocks at the coastal zones has rarely been reported. In the present study, we collected two types of dendritic FeMn beachrock samples from an intertidal zone of Zhoushan Archipelago, East China Sea, where was significantly amended by an ancient wood layer formed during 5900–5600 cal. yr B.P. Then the microscale analysis including electron microprobe analyzer (EMPA), X-ray powder diffraction (XRD), and scanning electron microscopy-energy dispersive X-ray spectrometer (SEM-EDS) were performed to study the microscale characteristics on these FeMn beachrocks. Combined with our previous studies, a possible formation process was proposed: (1) Buried ancient woods produced enough organic acids to accelerate the weathering of nearby bedrock via chemical or biological reactions; (2) The seepage water could be regarded as a bridge to connect the ancients woods and the intertidal zones, and large amounts of dissolved Fe2+ and Mn2+ can be transported to the sandy beach and intertidal zones; (3) Precipitation of insoluble FeMn oxides occurred with the involvement of microbial processes and direct inorganic chemical sorption under mixing of seepage water and seawater; (4) After that, these FeMn oxides would experience nucleation, crystallization growth, and then diagenetic process to form the FeMn beachrocks. The present study spotted a light on the microscale features, formation process and biogeochemical cycling of nearshore/coastal diagenetic Fe-Mn deposits.

Effect of Inorganic Nanocomposite Based Liners on Deodorization of Kimchi

This study aims to reduce the rancid odor generated during the fermentation process of kimchi by inserting zinc oxide (ZnO) into an inorganic porous material with a high surface area to decompose or adsorb the fermentation odor. ZnO activated by the presence of moisture exhibits decomposition of rancid odors. Mixed with Titanium dioxide (TiO2), a photocatalyst. To manufacture the packaging liner used in this study, NaOH, ZnCl2, and TiO2 powder were placed in a tank with diatomite and water. The sludge obtained via a hydrothermal ultrasonication synthesis was sintered in an oven. After being pin-milled and melt-blended, the powders were mixed with linear low-density polyethylene (L-LDPE) to make a masterbatch (M/B), which was further used to manufacture liners. A gas detector (GasTiger 2000) was used to investigate the total amount of sulfur compounds during fermentation and determine the reduction rate of the odor-causing compounds. The packaging liner cross-section and surface were investigated using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) to observe the adsorption of sulfur compounds. A variety of sulfur compounds associated with the perceived unpleasant odor of kimchi were analyzed using gas chromatography-mass spectrometry (GC-MS). For the analyses, kimchi was homogenized at room temperature and divided into several sample dishes. The performance of the liner was evaluated by comparing the total area of the GC-MS signals of major off-flavor sulfur compounds during the five days of fermentation at 20oC. As a result, Nano-grade inorganic compound liners reduced the sulfur content by 67 % on average, compared to ordinary polyethylene (PE) foam liners. Afterwards SEM-EDS was used to analyze the sulfur content adsorbed by the liners. The findings of this study strongly suggest that decomposition and adsorption of the odor-generating compounds occur more effectively in the newly-developed inorganic nanocomposite liners.

Structure of Hard And Soft Carapace Exoskeleton Biomaterial Through SEM-EDXRS at Various Stages of Development Scylla paramamosain Mud Crab

Crustacean carapace has various functions which can be seen from the composition of the biomaterial in it. Various concentrations of inorganic biomaterial elements were investigated from the hard carapace and the newly molted (soft-shelled) (Scylla paramamosain) with SEM-EDXRS (scanning electron microscopy-Energy Dispersive X-ray Spectrometer) technique. This study traced the composition of the inorganic elements of the premolt, postmolt, intermolt and soft (exuvium) crab hard carapace tissue of mangrove crabs from the point of view. Various stages of development. Important elements such as C, O2, Mg, P, Ca, S, Na, Si, Cl, and others, are reabsorbed from the carapace into the body tissues to fulfill further needs in soft-shelled crabs and are reused to some extent during formation new carapace. This study provides evidence that, inorganic elements in freshly molted soft carapace crabs are less common than hard carapace crabs

Behaviors of Perfluorocarbon Emulsion during Dissolution of Oxide Layers.

This study investigates the dissolution behavior of oxide layers containing radionuclides using perfluorocarbon (PFC) emulsion as a reusable medium. Chemicals such as PFC, anionic surfactant, and H2SO4 are used for preparing the PFC emulsion, and emulsified using an ultrasonication process. The FTIR results show O–H stretching that is formed by the interaction of the carboxyl group of the anionic surfactant with the hydroxyl group of water containing H2SO4, and find that the H2SO4 can be homogeneously dispersed in the PFC–anionic surfactant–H2SO4 emulsion. The dissolution test of the simulated Cr2O3 specimen is conducted using PFC emulsion containing KMnO4. Through the weight losses of specimens and Scanning Electron Microscope-Energy Dispersive X-ray Spectrometer (SEM-EDS) analysis, it is confirmed that the Cr2O3 layer on the SUS304 specimen is easily dissolved using PFC emulsion. During the dissolution of the Cr2O3, it is observed that the dispersed H2SO4–KMnO4 became unstable and separated from PFC emulsion. Based on these results, the behavior of the PFC emulsion during the dissolution of the oxide layer is explained.

Zr-89 Labeled PAMAM Dendrimers 5G without a Chelator for a Cancer Diagnostic Agent

Dendrimer nanoparticles (DNPs), which have been studied extensively as drug delivery systems, can be synthesized easily with zirconium without chelators. A UV/Vis spectrophotometer and a Dynamic Light Scattering (DLS) analysis were used to confirm the synthesis and the particle size of the composite. Compound B synthesized using a chelator compound was found to be more complex than compound A, and natZr was found to bind at a low yield through Scanning Electron Microscopy-Energy Dispersive X-ray Spectrometer (SEM-EDS) and Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). In PBS (1×), The binding was confirmed to be strong and stable at 99% stability or more. The stability to human serum was very good with a value of about 98%. The stability of the bound 89 Zr was confirmed to be stable for 160 minutes through the evaluation of serum stability. Using CT-26 and MDA-MB-231, We also were able to confirm the difference in the cell uptake of 89Zr-DNPs. After 24 hours, a high cell uptake of close to 40% was observed. Positron Emission Tomography (PET) images were observed, it was confirmed that no accumulation of 89 Zr-DNPs in the bones and its stability in the body.

Application of scanning electron microscopy-energy dispersive X-ray spectrometer to characterize the chemical composition of deposits on the surface of dried day lily

An innovative and simplified method to characterize the chemical composition of the residual sulphite deposits on dried day lily using scanning electron microscopy- energy dispersive X-ray spectrometer (SEM-EDS) was developed in this study. Granular deposits were observed by SEM on the surface of dried day lily overdosed with sulphiting agents. Laboratory scale model studies showed that soaking in 3% sodium bisulphite without subsequent washing may lead to the accumulation and precipitation of sodium bisulphite crystals. EDS analysis indicated that these deposits are sodium bisulphite. A strong correlation (R2 = 0.8994) was obtained between Sulfur/Carbon ratio calculated from SEM-EDS data and sulfur dioxide concentration determined by modified Monier-Williams method in day lily samples without crystals on the surface.

Boron reduces aluminum deposition in alkali-soluble pectin and cytoplasm to release aluminum toxicity

Boron (B) is indispensable for plant growth and has been reported in the mitigation of aluminum (Al) toxicity in different plants. This study focused on the efficacy of B in reducing Al toxicity to trifoliate orange seedlings in a hydroponic experiment. Boron supply had a positive effect on root length and plant growth-related parameters and attenuated Al-induced inhibition of plasma membrane H+-ATPase activity. X-ray photoelectron spectroscopy (XPS) in conjunction with scanning electron microscope-energy dispersive x-ray spectrometer (SEM-EDS) revealed that B reduced Al accumulation in root cell wall, especially on pectin fractions (alkali-soluble pectin), accompanied by suppressing pectin synthesis, pectin methylesterase (PME) activity and PME expression. Furthermore, B application inhibited NRAT1 expression while increased ALS1 expression, indicating restraining Al transport from external cells to cytoplasm and accelerating accelerating vacuolar sequestration. The results were further demonstrated by transmission electron microscope-energy dispersive x-ray spectrometer (TEM-EDS) analysis. Taken together, our results indicated that B mainly promoted the efflux of H+ by regulating the plasma membrane H+-ATPase activity, and reduced the demethylation of pectin to weaken Al binding to carboxyl. More importantly, B alleviated some of the toxic effects of Al by compartmentalizing Al into vacuoles and decreasing the deposition of Al in cytoplasm.

Micro-structural study of colored porcelains of Changsha kiln using imaging and spectroscopic techniques

Changsha kiln was an ancient factory from the Tang Dynasty (618–907 CE) to the Five Dynasties (907–960 CE), famous for its colored porcelain production. It was one of the pioneer sites to master the poly-color technique at high temperature. In this work, by using Energy Dispersive X-Ray Fluorescence (EDXRF), Raman spectroscopy and Scanning Electron Microscopy Energy Dispersive X-ray Spectrometer (SEM-EDS), the composition and structure of two of its emblematic colored glazes were studied. The results confirmed that the chromogenic elements of brown and green colored glazes are well iron and copper respectively. They also revealed a significant presence of hematite (α-Fe2O3) phase with dendritic shape close to the glaze surface and oddly a substantial amount of ε-Fe2O3 phase at the body/glaze interface. It is the second type of ancient Chinese glaze in which the very rare and metastable iron(III) oxide polymorph was found. No Cu-based particle was identified in green glaze. The green color is certainly due to Cu2+ dispersed in the glassy matrix. Our study confirmed that Cassiterite (SnO2) was used as opacifier compound to obtain opaque green color.

Characterization of the interfaces formed at the silicon nitride superalloy joints

In this study, silicon nitride ceramics (Si3N4) were joined by using a capacitor discharge technique with an Inconel 718 superalloy interlayer and heat-treated in order to determine possible reactions between these two materials. After capacitor discharge joining, some of the samples were heat-treated at 1100 °C under air and the resulting interfacial microstructure was characterized by using a scanning electron microscope (SEM) attached with an energy-dispersive x-ray spectrometer (EDS) and wavelength dispersive x-ray spectrometer (WDS). According to back-scattered electron images (BSE), all the joining samples were well bonded through the interlayer and cracks were not observed along the interlayer, interface and the ceramics. According to point SEM–EDS and SEM–WDS analysis, the reaction layer and nitrogen (N) were not detected but a small amount of silicon (Si) and aluminium (Al) was detected at the interlayer of as-joined samples. For the heat-treated samples at 1100 °C, the symmetrical reaction layer was observed at both sides of the interlayer which is expanding towards the ceramic side and approximately 25-nm-thick another continuous reaction layer next to this was also determined. According to SEM–EDS and SEM–WDS point-line scan analysis along the metallic interface and ceramic side, nickel (Ni), iron (Fe) and chromium (Cr) were detected at the reaction layer next to the ceramic side, whereas mainly Cr, niobium (Nb), molybdenum (Mo), titanium (Ti) and Al were concentrated at the 25-nm-thick reaction layer.

Performance enrichment on tribological characteristics of powder metallurgy processed aluminium particulate composites by inclusion of rutile (TiO2)

Abstract

Sintering Characteristic in Catalytic Gasification of China Inner Mongolia Bituminous Coal Ash

To determine the ash characteristics, catalysts transformation and the sintering mechanism during catalytic coal gasification, the investigation of the effect of ashing temperature, K2CO3 and CaO catalysts addition on the ash sintering behavior of bituminous coal was conducted under catalytic gasification conditions. The ash sintering temperature was determined at 3.5 MPa using a pressure-drop sintering device with H2O, H2, CO inlets. The ash morphology was analyzed using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS). An X-ray diffractometer (XRD) in combination with FactSage were used to predict the reactions occurring between minerals as well as the mineral transformation and slag formation. The results showed that different ashing temperature affected both ash transformation reactions and volatilization amount of added catalyst, which influenced the ash fusion temperatures and the sintering temperature. The ash-550 °C was chosen to investigate the sintering behavior. The...

Deterioration of Concrete by the Oxidation of Sulphide Minerals in the Aggregate

Cases of degradation of concrete associated to iron sulphides in aggregates were recently recognized in the Trois-Rivieres area, Canada. The aggregate used to produce concrete was an anorthositic gabbro containing various proportions of pyrite, pyrrhotite, chalcopyrite and pentlandite. Quantitative microanalysis on sulphide minerals show that pyrrhotite contains small amount of Ni, Co, Cu and As substituting for Fe in the mineral structure. Considering element substitution, x value in the chemical formula (Fe1-xS) was calculated to 0.099 in the pyrrhotite studied. Petrographic examination of damaged concretes showed the presence of oxidized pyrrhotite. The observation of polished samples shows, in several cases, that the pyrite is intact while the pyrrhotite presents evident signs of oxidation. In the presence of water and oxygen, pyrrhotite oxidizes to form iron oxyhydroxides and sulphuric acid. The acid then reacts with the phases of the cement paste and provokes the formation of gypsum and ettringite. These minerals were observed by SEM-EDS (scanning electron microscope/energy dispersive x-ray spectrometer) and their precipitation causes a volume increase that creates expansion and cracking of the concrete.