Scanning Electron Microscopy With Energy Dispersive Spectroscopy Research Articles

High stable Hb/Pt/BDD electrode for determining acrylamide in coffee samples

A novel electrochemical hemoglobin-platinum-modified boron-doped diamond (Hb/Pt/BDD) biosensor was developed for the detection of acrylamide (AA) in coffee samples. The Hb-Pt-BDD electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectrons (XPS). The cyclic voltammetry of Hb-Pt-BDD in 0.2 M sodium acetate buffer (ABS, pH 4.8) containing acrylamide in the concentration range of 0.00213 to 0.00711 ppb, showed linear responses with a detection limit of 0.00155 ppb. The excellent stability of the prepared Pt-modified BDD was proven through the Pt-BDD reusability by removing the Hb adduct without eliminating Pt on the BDD surface. Finally, employing the biosensor was proposed to determine AA in 1 g of coffee showed the AA content of 15.55 ppb. The result was comparable with the reference method using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Effect of tricalcium aluminate and sodium aluminate on thaumasite formation in cement paste

The purpose of this paper was to study the effect of different aluminum phases on the formation of thaumasite in cement paste. In the present study, tricalcium aluminate (C3A) and sodium aluminate (NaAlO2) were chosen as two kinds of aluminum phase sources. Two cement pastes were designed: one was prepared with tricalcium silicate (C3S), calcium carbonate (CaCO3) and C3A, another was prepared with C3S and CaCO3. Two samples were cured for 28 days and then immersed in sodium sulfate (Na2SO4) solution with/without NaAlO2 at 5 °C for a certain time. The cement corrosive products were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Nuclear magnetic resonance (NMR), and Scanning electron microscope with energy dispersive spectroscopy (SEM/EDS). Results showed that thaumasite-ettringite solid solution could be formed in cement paste containing C3A, but the formation time of thaumasite was much longer compared with that of ettringite, in agreement with the woodfordite route. In the case of using NaAlO2 as aluminum phase, ettringite was formed in the sample, while no thaumasite was formed in cement paste after being cured for 14 months. According to the analysis of 27Al NMR, the peak of hexahedrally coordinated aluminum (AlO4) at 58.6 ppm was proved to be Al(OH)3, which would probably restrain the formation of thaumasite. It was indicated that the use of sodium aluminate was unfavorable for the formation of the thaumasite in cement paste.

The Vesuvianite Gems of the Val d’Ala (Piedmont, Italy)

In Val d’Ala (Western Alps in Piedmont, Italy), the most interesting rocks for mineralogical research are represented by rodingite (rich in mineralized veins and fractures) associated with serpentinite in the eclogitized oceanic crust of Piedmont Zone, south of Gran Paradiso Massif. Among the vein-filling minerals, vesuvianite is well appreciated for its potential as gem-quality materials, even though it has never been characterized in detail. This study provides a gemological characterization of eleven vesuvianite crystals from different localities of the Val d’Ala. The refractive index (1.717–1.708) and density (1.705–1.709) values of our vesuvianite are in the range of those in the literature. Scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) established that the samples are pretty compositionally homogeneous in terms of major elements, while trace and rare earth elements (REE) contents are more variable. All REE patterns are characterized by pronounced positive Eu anomalies. The variations in color (from olive green to dark green with chocolate (reddish-brown color shades and polychrome bands) are due to the relevant presence of Fe and, to a lesser extent, Ti and Cr. The X-ray powder diffraction (XRPD) analyses and SEM/EDS quantitative study indicate that the other phases associated with vesuvianite are represented by diopside, garnet, clinochlore.

Resistance improvement of cement mortar containing silica fume to external sulfate attacks at normal temperature

This paper investigates the resistance performance and resistance enhancement mechanism of cement mortar containing silica fume (SF) exposed to external sulfate attacks (ESA) at a temperature of 20 °C. The visual inspection, strain development, and mechanical performance of specimens made of 100% high sulfate-resistant Portland cement of grade 42.5 (P•HSR 42.5), 100% ordinary Portland cement of grade 42.5 (P•O 42.5), and binary blends of P•O 42.5 and SF, respectively, are evaluated using the mortar bar test. The mortar bars are exposed to a 5% Na2SO4 solution for 12 months and measured up to 12 months. The deterioration products are studied in terms of their types, amounts, and micro-structures by the means of x-ray diffraction (XRD), thermo gravimetric analysis (TGA), scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), and mercury intrusion porosimetry (MIP). The results show cement mortars, which contain different dosages of SF (i.e., 3% and 5% by weight of cementitious materials), that have no visual damage after 12 months of exposure to ESA. The exponential increase in the expansion strain of P•HSR 42.5 cement mortars and P•O 42.5 cement mortars are observed, with strain values reaching up to 5825 × 10−6 and 8824 × 10−6, respectively, after 12 months of immersion. However, it is noteworthy that the tendency of increase in the expansion strain of cement mortar containing SF becomes a hyperbolic curve. Specifically, the expansion strain of cement mortar containing 3% and 5% SF are only 65.0 × 10−6 and 29.0 × 10−6, respectively, after 12 months of immersion. The resistance improvement mechanism of SF in cement mortars may be because the SF can effectively reduce the formation of the deterioration products, namely, ettringite (AFt) and gypsum. On the other hand, SF can significantly refine the pore structures, causing a drastic increase in the incidence of harmless pores (<20 nm). The pore structure refinement effect of SF plays a critical role in enhancing the resistance performance of cement mortars exposed to ESA. Therefore, cement containing appropriate SF will significantly improve the resistance performance of cement mortars exposed to ESA.

Nanoparticle Emission and Characterization from Pre-Dried Lignite and Bituminous Coal Co-Combustion

Nowadays, the high share of electricity production from renewables drives coal-fired power plants to adopt a more flexible operation scheme and, at the same time, maintain flue gas emissions within respective standards. A 500 kWth pulverized coal furnace was used to study pre-dried lignite combustion or co-combustion as an available option for these plants. Bituminous coal from Czech Republic and pre-dried lignite from Greece were blended for the experiments. Particle emissions measurements with a heated Electrical Low Pressure Impactor (ELPI+) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) analyses were performed. The effect of the pre-dried lignite proportions in the fuel feed and the combustion conditions regarding the combustion air staging were the two parameters selected for this study. Skeletal density values were measured from the cyclone prior to the impactor. Results are depicted with respect to the aerodynamic and Stokes diameter for impactor stages. The presence of pre-dried lignite in the fuel blend lowers the particle matter (PM) PM2.5, PM1 and PM0.1 emissions, thus having a positive impact on ESP’s fractional and overall efficiency. The staged combustion air feed reduces the particle emissions in all cases. Sulfur content follows a pattern of higher concentration values for finer particles.

Investigations on alloy-burial environment interaction of archaeological bronze coins

This study is focused on ten Roman leaded coins from the archaeological site of the Magna Mater Temple (Rome, Italy). These coins, buried for centuries in a peculiar environment of the archaeological area (i.e., the latrinae), were investigated to explore the chemical composition and microstructure of the inner alloy. The opportunity to examine the core of the alloy permitted to disclose information about the original composition as well as to infer the interaction and the modification of the metal core during burial condition over centuries. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and Electron Microprobe Analysis (EMPA) techniques have been employed to study each sample from rim to inner un-corroded core. The results showed that the coins are a Cu-Sn based alloy enriched in Pb. The content of Cu in the Cu-rich area (i.e., the α-phase) is ca 99 wt% and that of the Pb islands (i.e. the β-phase) reaches 97 wt%. The X-ray maps of the interface between the sub-external layer/inner-core revealed the occurrence of high chloride content, in which the distribution of Cl and Pb indicated the presence of lead chloride minerals. SEM-imaging highlighted also a deep corrosion of the patina with cracks and pits. Underneath the corrosion layer, an area of the almost unaltered β-phase composing the bulk material of the coin has been detected.

Green Microalgae Scenedesmus Obliquus Utilization for the Adsorptive Removal of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) from Water Samples.

In view of the valorisation of the green microalga Scenedesmus obliquus biomass, it was used for the biosorption of two nonsteroidal anti-inflammatory drugs, namely salicylic acid and ibuprofen, from water. Microalgae biomass was characterized, namely by the determination of the point of zero charge (pHPZC), by Fourier transform infrared (FT-IR) analysis, simultaneous thermal analysis (STA) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Kinetic and equilibrium batch experiments were carried out and results were found to fit the pseudo-second order equation and the Langmuir isotherm model, respectively. The Langmuir maximum capacity determined for salicylic acid (63 mg g−1) was larger than for ibuprofen (12 mg g−1), which was also verified for a commercial activated carbon used as reference (with capacities of 250 and 147 mg g−1, respectively). For both pharmaceuticals, the determination of thermodynamic parameters allowed us to infer that adsorption onto microalgae biomass was spontaneous, favourable and exothermic. Furthermore, based on the biomass characterization after adsorption and energy associated with the process, it was deduced that the removal of salicylic acid and ibuprofen by Scenedesmus obliquus biomass occurred by physical interaction.

Mineralogical-Geochemical Study of Corroded Iron-Based Metals from a Salt Mine Environment

Metal fragments (pipe, chain, valves), at advanced stages of corrosion, were collected underground in the Wieliczka salt mine. Macroscopically distinct zones of corroded material, as well as black blisters on the surface of different metal fragments, were studied using scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Mössbauer spectroscopy (MS). SEM-EDS studies showed various morphological forms with different chemical compositions. The original outer zone of the iron artifacts is mainly composed of aggregates of needle-shaped goethite crystals with idiomorphic crystals of halite. A subsequent zone, toward the inner margin, is composed mainly of fine granular aggregates of magnetite. Goethite (α-FeOOH) and akaganeite (β-FeOOH) form spherical, fibrous, and structureless aggregates in the next internal zone. Forms of aggregates seem to depend on the chloride content, 1 wt% to 3.5 wt% Cl in the structureless aggregates and 5 wt% to 9 wt% Cl in the regular ones. In addition, in the internal zone crystals of lepidocrocite form rosettes. Blisters are built of the acicular akaganeite crystals, which form fibrous aggregates in the shell and spherical ones in the interior. The relative concentrations of iron bearing minerals in the studied zones, i.e., akaganeite, hematite, goethite, magnetite, and lepidocrocite are established. Where they dominate, the zones are: black (magnetite), orange (goethite, lepidocrocite, akaganeite), and light brown (goethite).

Behavior and mechanism of low-concentration rare earth ions precipitated by the microbial humic-like acids.

The disposal of bulky low-concentration rare earth solutions (usually ≤ 200mgL-1) is difficult and it can easily lead to the waste of rare earth resources. The precipitant separation method is a simple and effective technique that is commonly used for rare earth recovery, but the application of biological component precipitants is rarely reported. In this study, the effects of the precipitation of low concentrations of rare earth ions by excess sludge humic-like acids were evaluated. Scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) and infrared (IR) spectroscopy revealed that the addition of humic-like acids to low-concentration rare earth solutions could produce a flocculent precipitate. The precipitation rate was more than 89%. The content of rare earth metals such as Nd, Y, and La in the rare earth precipitate reached 23.72%, and the elution rate of 1.25molL-1 hydrochloric acid was 90.50%. It was concluded that the humic-like acids might contain many functional groups capable of adsorbing rare earth ions. It was inferred that the possible mechanism might be that rare earth ions were precipitated by a series of net catch, ion exchange, and adsorption processes. These findings provide a reference for the future recovery of rare earth resources.

Conservation of the Lyre from Grave 48 in the Area between the So-Called ‘Eriai’ Gates and the Dipylon (470–50 BC)

Abstract This paper focuses on the conservation of the lyre (chelys) of Grave 48, from the area between the so-called ‘Eriai’ Gates and the Dipylon. First, it describes the lifting of the lyre (sound box) from the ground and the recovery of the fragile plaques and fragments from the compact block of soil in the laboratory. Subsequently, it presents the extensive conservation work undertaken by the present writer and her team. Furthermore, it summarizes the conclusions of the X-Radiography and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) examinations of the sound box and the string holder and provides information about the biochemistry, structure and decay of the tortoise shell. In conclusion, the collaboration between conservator and archaeomusicologist, during the remedial conservation treatment, was of great importance, and helped with the identification of the plaques and restoration of the lyre.

Efficiency of zinc ions (II) adsorption using activated carbon from palm kernel shell

The adsorption of wastewater from various industrial sources is important and one of the dangerous challenges the environment. This study focuses on the investigation of the efficiency of zinc ions adsorption by using activated carbon in synthetic wastewater. Activated carbon was prepared from palm kernel shells that were obtained from Songkhla province, Thailand. Activated carbon was prepared from palm kernel shells containing sodium chloride as a catalyst at the ratio 1:0, 1:1 and 1:2 (w/w), respectively. Activated carbon was calcined at 700 °C for 2 h. Next, it was washed with hot distillate water until pH = 7. After that, it was dried at 105 °C for 24 h. Iodine number was analyzed by using CHNS/O analyzer. The concentration of solution was examined by using atomic absorption spectrophotometer (AAS). The prepared activated carbon was characterized by thermogravimetric analysis (TGA), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), X-ray fluorescence spectrophotometer (XRF), X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy (FTIR). For the pure activated carbon, it was noteworthy that the major components were O (37.25%), N (30.95%) and C (26.54%), whilst a minor content was H (2.23%), C (1.73%) and Si (0.76%). This result was strongly consistent with the XRF analysis. The ratio of activated carbon to sodium chloride 1:2 (w/w) exhibited the highest iodine number (180.95±10.82 mg/g). The factors of adsorption including initial concentration (20-150 ppm) and adsorption time (2-10 h.) The result showed that the optimum conditions of adsorption containing concentration were 65 ppm and adsorption time was 10 h. The efficiency of adsorption was 69.73 %.

Effect of Sludge-Based Additive on Ash Characteristic and Potassium Fixation during the Rice Straw Combustion Process

The effects of a sludge-based additive (mainly composed of calcium phosphate) on the retention of potassium in bottom ash and ash melting characteristics during rice straw (RS) combustion were studied with a bench-scale tube furnace reactor at the reaction temperatures of 600, 700, 800, and 900 °C. The potassium content in bottom ash and ash composition characteristics were analyzed using powder X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results showed that the addition of sludge-based additive into rice straw at a mass fraction of 2.5–7.5% could effectively improve the potassium fixation rate and retain potassium in the bottom ash during combustion process by the formation of potassium aluminosilicates and K–Ca–P compounds. The ash melting characteristic was enhanced and the sintering of bottom ash was prevented by the addition of sludge-based additive. For instance, the soft temperature (ST) of RS wa...

Metals and Environment: Chemical Outputs From the Interaction Between Gilded Copper-Based Objects and Burial Soil

Three-dimensional chemical mapping was adopted to investigate an ancient fire-gilded buckle found in Rome. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were used to detect and locate degradation products aiming to identify the alteration processes. Inorganic and organic compounds present in the outermost part of such a class of cultural heritage objects can be considered the result of long-term interaction with the burial environment. ToF-SIMS depth profiling experiments can provide chemical information at the molecular level and high resolved spatial information (about 1 μm laterally, and 1 nm in depth). In this work, the attention was focused on the identification and localization of the ionic and molecular species involved in the degradation process. Results showed the presence of copper oxides, chlorides, and sulfides as common corrosion products but also the presence of species related to copper and bronze corrosion process such as atacamite and its polymorphs. 3D maps for all the relevant molecular species allowed to visualize at the same time the eruption of copper chlorides throughout the micro/nanochannels present on the gold surface, the recrystallization of compounds of minor elements from the substrate, a pathway followed by silico-aluminates from the surface towards the internal corrosion layers, but mostly the evidence of biological activity of Sulphur Reducing Bacteria (SRB) living in anaerobic conditions.

Relation of degree of substitution and metal protecting ability of cinnamaldehyde modified chitosan

Considering the advancements in the applications of biopolymers such as Chitosan due to its biocompatibility, biodegradability and non-toxic properties, five different Chitosan cinnamaldehyde Schiff bases (Chi-Cn1-5) using chitosan and cinnamaldehyde as monomer units were synthesized by varying the degree of substitution. Further, anti-corrosion property of all these biopolymers against corrosion of mild steel was studied in 0.5 M H2SO4 by gravimetric and electrochemical methods. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM), scanning electrochemical microscopy (SECM) and X-ray photoelectron spectroscopy (XPS) were utilized to affirm the adsorption of studied biopolymers at the metal/electrolyte interface by inhibiting mild steel (MS) corrosion. The shift (<85 mV) in the value of corrosion potential by the presence of biopolymers affirmed their mixed-type nature of inhibition. The results depicted that Chi-Cn5 performs best against corrosion of mild steel in acid medium among all other biopolymers due to its maximum degree of substitution.

Oxidation resistance of Ni-Cr-TiO2 powder HVOF coating on carbon steel at elevated temperature

In this research a Chromium Carbide (Cr3C2)-based powder consisting of 80% Cr3C2 and 20% Titanium dioxide (TiO2) is sprayed to SA 210 Grade C boiler tube material for better performance of power plant boilers. Cr3C2-TiO2 coating is deposited by high velocity oxygen fuel (HVOF) process with powder particle of size 45 ± 15 μm. High temperature oxidation test under cyclic condition is performed in air environment up to 900 °C. The properties of specimen are characterized by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). The results shown that the Cr3C2-TiO2 coating exhibit excellent corrosion resistance at 900 °C compared to bare SA 210 Grade C boiler tubes and the coating also reduces the weight gain of the steel by about 50%. High temperature oxidation resistance imparted by Cr3C2-TiO2 coating may be attributed to the formation of alloy phases during the powder processing and coating processes.

Solar photocatalytic degradation of diclofenac aqueous solution using fluorine doped zinc oxide as catalyst

The photocatalytic degradation of a sodium diclofenac (DCF) solution (10 mg/L) under simulated solar radiation was evaluated using a ZnO semiconductor modified by the incorporation of 10, 15, and 20 wt.% fluorine (ZnO-F10, ZnO-F15 and ZnO-F20). The ZnO-F catalysts were synthesized by the sol-gel method using zinc acetate as a precursor of zinc oxide and NH4F as a fluorine source. The photocatalytic performance of the F-doped ZnO material was compared to that of bare ZnO. The obtained photocatalysts were characterized using X-ray diffraction (XRD), Scanning electron microscopy with Energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The Brunauer-Emmett-Teller (BET) surface area, pH of zero charge (pHpzc), and band gap of the solids were also evaluated. An experimental Box-Behnken design combined with response surface methodology was applied to establish the optimal conditions for the photocatalytic degradation of the DCF solution. Complete DCF degradation, total release of chloride ions, and approximately 90% mineralization were achieved during degradation of the drug at an accumulated energy of 400 kJ/m2 under the optimized experimental conditions (1 g/L of ZnO-F20 catalyst with the pH of the DCF solution maintained at 6.5).

Characterization and application of magnetic biochar for the removal of phosphorus from water.

Activated biochars were prepared from residues of medium density fiberboard (MDF) produced by the furniture industry. Biomass residue was pre-treated with FeCl3 in two different FeCl3:biomass ratios (0.5:1 and 1:1, w/w) aiming to produce a matrix embedded with iron oxide. The pyrolysis process produced maghemite on the biochar surface and its magnetic properties were confirmed by its attraction to a hand magnet and its magnetic susceptibility. Samples were also characterized using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), surface area by BET-N2, Fourier transform infrared (FTIR), X-ray diffraction, magnetic susceptibility, and cation exchange capacity (CEC). Magnetic biochar exhibited up to twelve-fold higher surface area than the non-magnetic biochar, which varies according the maghemite particles content. Iron oxide on biochar surface also contributed for increasing CEC around ten-fold compared to non-magnetic biochars. Phosphorus adsorption isotherms showed that these magnetic biochars have high capacity to sorb oxyanions like phosphate, especially at lower pH. Thus, these magnetic biochars could be used to clean water bodies contaminated with oxyanions in acidic conditions.

Research on the Properties of Low Temperature and Anti‐UV of Asphalt with Nano‐ZnO/Nano‐TiO2/Copolymer SBS Composite Modified in High‐Altitude Areas

Strong ultraviolet light and low‐temperature are the typical environmental characteristics in high‐altitude areas. The performance of SBS‐modified asphalt in the above environmental characteristics needs further study. To improve the resistance ultraviolet (UV) ageing and low‐temperature performance of copolymer‐ (SBS‐) modified asphalt, an SBS‐modified asphalt containing nano‐ZnO and nano‐TiO2 is proposed. In this paper, nano‐ZnO, nano‐TiO2, and SBS were used as modifiers with the silane coupling agent (KH‐560) as the nanomaterial surface modification. The orthogonal test table was used to analyse the effects of the three modifiers on the physical properties of modified asphalt at different dosages. On this basis, the physical properties, low‐temperature properties, and ageing indices (carbonyl index and sulfoxide index) were studied for base asphalt, SBS‐modified asphalt, nano‐ZnO/SBS‐modified asphalt, and nano‐ZnO/nano‐TiO2/SBS composite‐modified asphalt before and after photoaging. The content changes of characteristic elements (Zn and Ti) in the nano‐ZnO/nano‐TiO2/SBS composite‐modified asphalt before and after ageing were studied by scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), and the UV ageing mechanism was revealed. The results indicate that two nanoparticles show the best compatibility with asphalt after surface modification and can improve the binding ability between SBS and base asphalt. The orthogonal test analysis shows that nano‐ZnO has a highly significant effect on the low‐ and high‐temperature performance of the nano‐ZnO/nano‐TiO2/SBS composite‐modified asphalt, and nano‐TiO2 has a significant effect on the high‐temperature performance. Three optimal composite‐modified systems for base asphalt including 4% nano‐ZnO/1.5% nano‐TiO2/3.2% SBS were proposed and had the best antiaging ability. Compared with the sulfoxide index, the carbonyl index changed most obviously before and after ageing. Additionally, the results reveal that nano‐TiO2 has a good absorption effect at a wavelength of 365 nm (ultraviolet light), while nano‐ZnO is liable to photolysis, and its activity decreases at this wavelength.

Application of analytical techniques to the unveiling of the glazing technology of medieval pottery from the Belgrade Fortress

Medieval glazed ceramics, dated to the early 15th century, excavated at the Belgrade Fortress, Serbia, were investigated by combining optical microscopy, X-ray powder diffraction (XRPD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), micro-Raman spectroscopy and multivariate statistical analysis. The decoration and style of the investigated ceramics were characteristic of workshops from different areas of the medieval Serbian State: Ras, Krusevac and Belgrade/Smederevo. Comparison was made with ceramic samples from the same period excavated at the Studenica Monastery, the hitherto earliest workshop discovered, which were used as reference material for the Ras area. Ceramics from the Belgrade Fortress were covered with a transparent, lead-based glaze. The majority of the glazes were produced by application of mixture of lead oxide and quartz to the clay body, whereas only two samples were glazed by application of lead oxide by itself. The brown colours of the glaze originated from Fe-based spinel, whereas copper and iron were responsible for the colouring of the green and yellow glazes. The obtained results revealed glazing technology taken from Byzantine tradition.

Self-compacting mortars produced with fine fraction of calcined waste foundry sand (WFS) as alternative filler: Fresh-state, hydration and hardened-state properties

This work investigated the use of the <150 μm fraction of a calcined waste foundry sand (WFS) as filler in self-compacting mortars. WFS was calcined at 600–900 °C, referred to as calcined foundry sand (CFS). Self-compacting mortars were produced with cement replacement levels of 0–30 vol% with CFS and a limestone filler. WFS and CFS were characterized by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS) and thermogravimetric analysis (TGA). The fresh-state properties (mini slump flow and mini V-funnel), cement hydration (isothermal calorimetry and XRD), compressive strength and microstructure (SEM-EDS) of the mortars were evaluated. EDS showed that WFS calcination reduced its carbon content and XRD indicated the loss of the montmorillonite crystalline structure present in the clay material. CFS-containing mortars required superplasticizer contents from 2% to 10% higher than the reference to reach the target flow range (240–260 mm), while increased the mini V-funnel from 4.9 (reference) to 10.3 s (30% CFS). Nonetheless, all the mortars met EFNARC’s requirements. Calorimetry and XRD indicated that CFS enhanced the early age hydration of cement, increasing the main heat flow peak from 6.85 to 7.81 mW/g of cement and 72-h cumulative heat from 407 to 462 J/g of cement compared to limestone, with higher calcium hydroxide and lower alite contents at 3 days. CFS-containing mortars showed strength values about 14% higher than those containing limestone, for the same replacement level and age. Cement replacement with 10% CFS resulted in strengths equivalent to those of the reference mix at all ages (about 39, 45 and 54 MPa, respectively at 3, 7 and 28 days). SEM-EDS showed no significant differences between the microstructure of the mortars containing CFS and limestone. Overall, 10% CFS incorporation reduced 76 kg of cement and incorporated 58 kg of WFS per m³ of mortar, with equivalent performance.