Scanning Electron Microscope And Energy Dispersive Spectrometer Research Articles

Effect of the characteristics of lightweight aggregates presaturated polymer emulsion on the mechanical and damping properties of concrete

In this paper, the mechanical and damping properties of concrete modified with lightweight aggregates (LAs) presaturated polymer emulsion were investigated. The effect of four variables, namely, LA type, maximum LA particle size, LA presaturated different polymer emulsions, and the sand ratio of concrete, on the mechanical and dynamic behavior were analyzed. Test results indicated that the damping ratio of concrete prepared using shale aggregates was lower than that of concrete prepared using clay aggregates, but has higher mechanical properties. The mechanical and damping properties of concrete decreased when the maximum LA particle size increased, especially after the particle size exceeded 20 mm, at which decreasing tendency became obvious. Concrete modified with LAs presaturated styrene-acrylic polymer emulsion had a higher damping ratio than concrete modified with LAs presaturated polyvinyl alcohol polymer emulsion. The damping ratio of concrete decreased as the sand ratio increased, and the compressive strength of concrete peaked at 40% sand ratio. The results of scanning electron microscope and energy dispersive spectrometer (SEM-EDS) showed that the free and constrained layers formed during the mixing process of concrete, which could provide damping capacity effectively and reveal the damping mechanism of the concrete.

A clean and efficient down processing technology based on two physical methods

In this study, a clean and efficient down processing technology improved the bulkiness of the down fibers by two physical methods. On the one hand, amino polysiloxane compound SI-G was used to modify down fibers physically. On the other hand, the structure of down fibers keratin was changed and the elasticity of down was increased by adjusting the temperature, so the bulkiness of down fibers was improved. The results showed that the most suitable condition for down fibers in the air-blast dusting machine was a temperature of 60 ± 2°C when the SI-G dosage was 2% of the weight of down, the performance of down fibers was the best. The bulkiness increased by 49%, the cleanliness increased by 92%, and the residual fat rate did not change significantly. Evidence was provided by scanning electron microscope and energy dispersive spectrometer (SEM-EDS), nuclear magnetic resonance spectrometer (13C-NMR), X-ray Diffractometer (XRD) and Raman spectroscopy analysis. The results showed that, on the one hand, amino polysiloxane SI-G adsorbed on the down surface, making the fiber smooth, soft, and elastic. On the other hand, the conformation of down fibers keratin changed, the conformation of keratin macromolecule α-helix increased relatively, and the random crimp conformation decreased relatively, which makes the protein structure more regular and elastic, so the bulkiness of the down fibers improved.

Removal of silver nanoparticles in aqueous solution by activated sludge: Mechanism and characteristics

The increasing production and use of silver nanoparticles (AgNPs) have attracted more and more attention due to their environmental and health risks. Municipal sewage biological treatment unit has been playing an important role in the removal of AgNPs. This study investigated the mechanism and characteristics of AgNPs and their removal from aqueous solution by activated sludge. Results from Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM/EDS) showed that mixed AgNPs were immobilized by activated sludge. It was shown by X-ray photoelectron spectroscopy (XPS) that the fixed AgNPs had an oxidation state of +1. It was inferred by fourier transform infra-red (FTIR) spectra that AgNPs were adsorbed by activated sludge via binding with its primary amino (R-NH2) radical groups on the surface. These results revealed that the major mechanism for the removal of AgNPs by activated sludge was adsorption. The experiment data were in agreement with the Langmuir and Redlich-Peterson isotherms. The maximum adsorption capacity ranged from 12–32 mg g−1 at temperatures of 10–30 °C. Thermodynamic experiment showed that the adsorption of AgNPs by activated sludge was a spontaneous and endothermic reaction. The adsorption kinetics data were in good agreement with the pseudo-second-order model. The factor results indicated that the adsorption of AgNPs onto activated sludge was influenced by electrostatic repulsion, agglomeration, and the process of oxidation and sulfurization.

Phase change, micro-structure and reaction mechanism during high temperature roasting of high grade rare earth concentrate

The deposit of Bayan Obo in Inner Mongolia is the world's largest rare earth element (abbreviated as REE) resource. The exploration of the theory of mineral formation of Bayan Obo is an important foundation for mineralogical research, and is the scientific basis for mining, industrial beneficiation, smelting and extraction, and processing and utilization. With the rapid development of science and technology, the demand for the utilization of rare earth elements is increasing, and the separation process between rare earth elements needs to be developed. The purpose of this paper is to provide high temperature experimental information for the formation and application of rare earth minerals. To this end, the mineral evolution of high-grade rare earth concentrates with increasing temperature and the migration of rare earths at different stages and their reaction mechanisms were studied. According to thermogravimetric analysis and differential scanning calorimetry (TG-DSC), calcination was carried out at different temperature ranges, and the calcined products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope and energy dispersive spectrometer (SEM-EDS) and other analytical techniques. The results are shown in this process, the rare earth phase is first converted into rare earth oxide and rare earth oxyfluoride. As the temperature increases, Ca5(PO4)3F and a large number of self-shaped spherical Ca-RE-OF and Ca-RE-PO4 particles are formed, and the separation of La and Ce elements is discovered. According to the phase diagram analysis, the production of Ca5(PO4)3F is due to the reaction of monazite and fluorite, and the phases CeF2 and CeF3 are formed during the reaction. When it reaches 1500 °C, barium ferrite is produced and a new substance containing Ba2+ is formed.

Extraction of Boron from Ludwigite Ore: Mechanism of Soda-Ash Roasting of Lizardite and Szaibelyite

Ludwigite ore is a typical low-grade boron ore accounting for 58.5% boron resource of China, which is mainly composed of magnetite, lizardite and szaibelyite. During soda-ash roasting of ludwigite ore, the presence of lizardite hinders the selective activation of boron. In this work, lizardite and szaibelyite were prepared and their soda-ash roasting behaviors were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) analyses, in order to shed light on the soda-ash activation of boron within ludwigite ore. Thermodynamics of Na2CO3-MgSiO3-Mg2SiO4-Mg2B2O5 via FactSage show that the formation of Na2MgSiO4 was preferential for the reaction between Na2CO3 and MgSiO3/Mg2SiO4. While, regarding the reaction between Na2CO3 and Mg2B2O5, the formation of NaBO2 was foremost. Raising temperature was beneficial for the soda-ash roasting of lizardite and szaibelyite. At a temperature lower than the melting of sodium carbonate (851 °C), the soda-ash roasting of szaibelyite was faster than that of lizardite. Moreover, the melting of sodium carbonate accelerated the reaction between lizardite with sodium carbonate.

Geochemical, mineralogical and statistical characteristics of arsenic in groundwater of the Lanyang Plain, Taiwan

High arsenic concentrations (average 0.1 mg/L) of groundwater were found in Lanyang plain of Taiwan. In this study, 39 groundwater samples from 23 wells were collected and 14 hydro-geochemical parameters were analyzed. Factor analysis was applied to determine major influence factors of the arsenic enriched groundwater quality, and PHREEQC was used to calculate the distribution of aqueous species and saturation index of which affected the hydrogeochemistry of groundwater. 393 geological core samples from 9 drilling wells were collected and analyzed the contents of total arsenic and iron. Moreover, core samples associated with high arsenic concentration groundwater were selected, mineralogical phases were analyzed using X-ray fluorescence (XRF), high resolution X-ray photoelectron (XPS) and scanning electron microscope and energy dispersive spectrometer (SEM-EDS). Results of the arsenic enrichment factor determined by factor analysis indicated that infiltration of the organic and nitrogen pollutants from anthropogenic activities to shallow groundwater, and the reductive dissolution from iron oxyhydroxides in the deep aquifer were the main processes of arsenic release to groundwater from the sediment. Total arsenic and iron contents of the core samples were well correlated in marine sequences. The presence of clay layer within the subsurface may increase in the As contamination in groundwater aquifer. However the time for As release from clay layer to lower aquifer may require tens or hundreds years to complete under natural environment condition. Surface analyses of core sample performed by XPS showed that arsenic was adsorbed or co-precipitated with non-crystalline iron oxyhdroxides and sulfides. After a long term burial of sediment, microbial metabolism of organic matter creates a more reducing environment, arsenic may then be gradually released from iron oxyhydroxides by reductive dissolution or desorption to aqueous phase. The framboidal-diagenetic type phase was identified by XPS and the groundwater is supersaturated with respect to pyrite and orpiment determined by PHREEQC are suggesting sulfide minerals co-precipitate As. Arsenic in sediments is released into groundwater primarily by the reductive dissolution of As-bearing Fe-oxyhydroxides in reducing environment in the Lanyang plain.

A Green Synthesis of 3, 4-Dihydropyrimidin-2(1H)-ones via One-Pot Multi-Component Reaction by Using Cuttlebone as a Natural Catalyst under Solvent-Free Conditions

In this paper, an efficient, green and eco-friendly method for synthesis of 3,4-dihydropyrimidin-2(1H)-ones via one-pot multi-component reaction of aldehydes, urea and ethyl acetoacetate is shown at the presence of cuttlebone as an effective, reusable and natural heterogeneous catalyst. The advantages of this method are short reaction times, high yields, simple work-up, and reusable natural catalysts. The structure of cuttlebone was characterized by FT-IR spectrum, scanning electron microscopy (SEM) and energy dispersive spectrometer (SEM-EDS).

Self-assembly Synthesis and Properties of Microencapsulated n-Tetradecane Phase Change Materials with a Calcium Carbonate Shell for Cold Energy Storage

Sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10) mixed templates, microencapsulated phase change materials (MEPCMs) with an n-tetradecane core, and calcium carbonate (CaCO3) shell were prepared by a self-assembly method. The effects of the core/shell mass ratio and the SDS/OP-10 mass ratio on the morphology and the phase change enthalpy of the synthesized MEPCMs were investigated by polarized optical microscope (POM) and differential scanning calorimetry (DSC), respectively. The structure and the thermal performance of the MEPCMs were systematically characterized by the method of Fourier transform infrared spectroscopy (FT-IR), an X-ray diffractometer (XRD), a scanning electron microscope and energy dispersive spectrometer (SEM-EDS), thermogravimetric analysis (TG), and a thermal constants analyzer. The results demonstrated that the self-assembly technique with SDS/OP-10 mixed templates could be successfully applied for the synthesis of n-tetradecane@CaCO3 MEPCMs with an encapsul...

Removal of the heavy metal ions from aqueous solution using modified natural biomaterial membrane based on silk fibroin

Water-insoluble silk fibroin (WSF) membrane was prepared by co-blending and interaction of fibroin and silane coupling agent. A novel Schiff base with a chelating group, 3,5-bis-{2-hydroxyphenyl-5- [(2-sulphate-4- sulphatoethylsulphonyl-azobenzol) methylene amino]} benzoic acid (BHSABA), was applied to modify WSF membrane. The morphological structure and surface element analysis of WSF and its modified membrane (MWSF) were investigated by scanning electron microscopy (SEM) and energy dispersive spectrometer (SEM-EDS). The sorption behavior of MWSF membrane for six metal ions, Cu(II), Co(II), Ni(II), Cr(III), Pb(II) and Cd(II), were measured. MWSF membrane had the significantly selective sorption for Pb(II) and Cd(II) metal ions and the removal percentage being 82% and 56%, respectively. The adsorption kinetics of MWSF membrane for Cd(II) was analyzed by the pseudo-first-order and pseudo-second-order equations. The adsorption removal process for Cd(II) metal ion was in line with the pseudo-second-order model. MWSF membrane as bioabsorbent has potential application for removal heavy metal ions from the aqueous solution.

Improving Beneficiation of Copper and Iron from Copper Slag by Modifying the Molten Copper Slag

In the paper, a new technology was developed to improve the beneficiation of copper and iron components from copper slag, by modifying the molten slag to promote the mineralization of valuable minerals and to induce the growth of mineral grains. Various parameters, including binary basicity, dosage of compound additive, modification temperature, cooling rate and the end point temperature of slow cooling were investigated. Meanwhile, optical microscope, scanning electron microscope and energy dispersive spectrometer (SEM-EDS) was employed to determine the mineralogy of the modified and unmodified slag, as well as to reveal the mechanisms of enhancing beneficiation. The results show that under the proper conditions, the copper grade of rougher copper concentrate was increased from 6.43% to 11.04%, iron recovery of magnetic separation was increased significantly from 32.40% to 63.26%, and other evaluation indexes were changed slightly, in comparison with unmodified copper slag. Moreover, matte and magnetite grains in the modified slag aggregated together and grew obviously to the mean size of over 50 μm, resulting in an improvement of beneficiation of copper and iron.

Treatment and Characterization Analysis of Electrolytic Manganese Anode Slime

This research aims at providing the basic database for reasonable treatment of electrolytic manganese anode slime by comparing its composition, phase and crystal structure before and after the specific treatment. To describe original samples’ surface physical and chemical characteristics, X-ray fluorescence (XRF), Flame Atomic Absorption Spectrometry (FAAS), X-ray diffraction (XRD), Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS) and TG-DTA were used. Then, used XRD and SEM-EDS to describe the system features and characterization of the anode slime performed by Washing-Roasting. Through application of XRF and FAAS, element content in anode slime and the source of each element were analyzed. The results show that the original samples of anode slime mainly contains Mn, Pb, Ca, Se and Sr and averagely the contents of manganese and lead are 47% and 7.46%, respectively. XRD analysis shows that main phases of the anode slime are KxMn8O16,MnO2,PbMn8O16 and Pb2Mn8O16, and MnO2 in the slime has a mixed crystal structure of α-MnO2,β-MnO2,γ-MnO2,δ-MnO2. SEM-EDS analysis indicates that the anode slime has dense “mineral” phase. TG-DTA/DTG analysis shows that at the temperature of 0 ∼ 573 ̊C, water in δ-MnO2 lattice is desorbed; 573 ∼ 655 ̊C, MnO2 starts to lose oxygen and turn into Mn2O3; 900 ∼ 1000 ̊C Mn2O3 loses oxygen and turn into Mn3O4. Anode slime under different roasting temperature were characterized by XRD and SEM-EDS. The result shows that when roasting temperature reaches higher than 700 ̊C, bond energy of Pb-O is broken; when higher than 800 ̊C, the crystallinity of anode slime further increases and the dense structure of anode slime is broken, which provides an effective way to remove lead from the slime; when higher than 900 ̊C, Mn2O3 turns into Mn3O4 and the channels in the anode slime become much looser and wider for better leaching of impurity ions.

Electrodeposition of Tb on Mo and Al electrodes: Thermodynamic properties of TbCl3 and TbAl2 in the LiCl-KCl eutectic melts

The electrochemical behavior of Tb(III) in the LiCl-KCl eutectic melts was studied on Mo and Al electrodes by cyclic voltammetry, square wave voltammetry and open circuit chronopotentiometry in the temperature range of 773–873K. On a Mo electrode, the reduction of Tb(III) was one-step electrochemical process. The diffusion coefficient of Tb(III) was determined by applying the Berzins and Delahay equation. The activation energy for diffusion of Tb(III) ions was found to be 30.5kJmol−1. The equilibrium potential of Tb(III)/Tb(0) redox couple was measured by open circuit chronopotentiometry, with subsequent calculation of the apparent standard potential, ETb(III)/Tb(0)*0, and the apparent Gibbs free energy of formation, ΔGf*0(TbCl3). The activity coefficients for Tb(III), γTb(III) was also determined from the difference of apparent and standard Gibbs free energies of formation, ΔGf*0(TbCl3)−ΔGf0(TbCl3,SC). On an Al electrode, the reduction potential of Tb(III)/Tb was observed at more positive potential values than that on Mo electrode, due to the formation of Al-Tb intermetallic compound when Tb(III) ions react with the Al substrate. The TbAl2 intermetallic compound characterized by XRD (X-ray diffraction) and SEM-EDS (scanning electron microscopy and energy dispersive spectrometer), was obtained in the LiCl-KCl melts containing Tb(III) by potentiostatic electrolysis at −1.8V and −1.9V (vs Ag/Ag+), respectively. The activity of Tb, in the Al phase, as well as the standard Gibbs free energy, enthalpy and entropy of formation for TbAl2 were estimated from the open circuit chronopotentiometric measurements.

Synergistic Effect of Nanosilica Aerogel with Phosphorus Flame Retardants on Improving Flame Retardancy and Leaching Resistance of Wood

Nanosilica (Nano‐SiO2) sol fabricated by a sol‐gel process was introduced into wood modification with phosphorus flame retardants to improve the flame retardancy and leaching resistance of wood. The obtained materials were characterized by scanning electron microscopy and energy dispersive spectrometer (SEM‐EDS), thermogravimetric analysis (TGA), cone calorimetric (CONE), and infrared spectroscopy (FT‐IR). The residual rate of flame retardants before and after leaching was determinated by a leaching resistance. The results showed that the phosphorus flame retardants and SiO2 sol could reside in the poplar wood and are widely distributed in the vessels, pits, wood timber, and the spaces between wood cells of poplar substrate. TGA and CONE results indicated that the introduction of nano‐SiO2 aerogel with phosphorus flame retardants had a significantly synergistic effect on improving the flame retardancy and inhibiting the release of smoke and toxic gases. In addition, the leaching resistance test, combined with infrared analysis and EDS analysis, confirmed that the phosphorus flame retardants were able to be fixed by SiO2 aerogel in the wood.

Reaction Mechanism of Coal Chemical Looping Process for Syngas Production with CaSO4 Oxygen Carrier in the CO2 Atmosphere

Chemical looping combustion process for gaseous and solid fuel has been investigated widely. Recently, particular attention is paid to syngas and hydrogen generation from natural gas or solid fuels. CaSO4 has been proved to be a promising oxygen carrier for the chemical looping process with the merit of low price and environmental friendliness. The reaction mechanism of coal and pure CaSO4 for syngas production in the CO2 atmosphere was investigated using the simultaneous thermal analyzer in this paper. First, the thermodynamic analysis of reaction between coal and CaSO4 with different mass ratios was carried out respectively in N2 and CO2 atmospheres. It predicted that the CO2 can promote the reactions, while the coal-CaSO4 mass ratios affected the fate of sulfurous gaseous species greatly. Subsequently, thermogravimetric experiments were conducted by the peak fitting technique. It concluded that the drying and pyrolysis of the coal were main reactions before 800 °C, while the complex reactions, including the reaction between CaSO4 and coal char, gasification of coal char, and the decomposition of CaSO4, occurred during 800–1100 °C. The reaction kinetics and types of the reaction between coal and CaSO4 for syngas in the CO2 atmosphere were explored by isoconversional method. It indicated that the complex processes were controlled by the diffusion of gas–solid or solid–solid first, followed by parallel competing reactions. Finally, the reaction residues between coal and pure CaSO4 with different mole ratios were analyzed using scanning electron microscopy and energy dispersive spectrometer (SEM-EDS).

Microscopy, porosimetry and chemical analysis to estimate the firing temperature of some archaeological pottery shreds from India

In recent times, science and technology have been applied to the world of cultural heritage, preservation and conservation. In the present study, the pottery samples belonging to 4th century were collected from Tandikkudi in Dindugul district of Tamilnadu, India and were subjected to chemical analysis to outline the information about the raw materials and technological–productive aspect such as firing temperature. Investigations such as Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM/EDS) are also done for the accurate observation of the morphology and the qualitative and Semi-quantitative determination of the chemical elements present in the sample. The firing temperature of the samples at the time of manufacturing is also estimated from apparent porosity of the samples which agrees well with the SEM analysis. The results obtained from different analytical techniques on pottery shreds provide information of the firing temperature of the pottery which lies in the range of 800 °C–1000 °C in the oxidizing atmosphere. Moreover it was observed that the samples collected from this site are low refractory in nature and the artisans of Tandikkudi have used both calcareous and non-calcareous clays for their household utilities, but were unaware of firing their artifacts at reduced atmosphere or closed kiln. Hence this paper is a useful analytical tool for predicting the firing atmosphere, type of clay (calcareous, non calcareous) and its nature (fine and coarse). Hence this paper is suitable for estimating the firing temperature of ancient potteries.

Phylogenetic analysis and arsenate reduction effect of the arsenic-reducing bacteria enriched from contaminated soils at an abandoned smelter site

Microbial reduction of As(V) (i.e., arsenate) plays an important role in arsenic (As) mobilization in aqueous environment. In this study, we investigated As(V) reduction characteristics of the bacteria enriched from the arsenic-contaminated soil at an abandoned smelter site. It was found that As(V) was completely reduced to As(III) (i.e., arsenite) in 21 h. After 3-d incubation, a yellow solid was precipitated and the concentration of As(III) decreased sharply. After 150 h incubation, ca. 65% of soluble arsenic was removed from the solution. The analysis of the precipitate by scanning electron microscopy and energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) revealed that the main component was crystalline arsenic sulfide (AsS). Microbial mediated reduction and mobilization of adsorbed As(V) on ferric hydroxide was also examined. In the microcosm slurry experiment, ca. 53% of the adsorbed As(V) was reduced to As(III) by the bacteria, which resulted in an appreciable release of arsenic into aqueous phase. The released arsenic was present predominantly as As(III). The microbial diversity was analyzed by 16S rDNA-dependent molecular phylogeny. A near-full-length 16S rDNA gene clone library was constructed. The 197 clones were analyzed using RFLP (restriction fragment length polymorphism) and 72 OTUs were obtained, which contributed 51% of the content for total clone number in six OTUs. Six bacterial clones in these six OTUs were selected for sequencing and the sequenced clones were found to belong to the group Caloramator, Clostridium, and Bacillus.