Scanning Electron Microscopy EDS Research Articles

The Effect of a Hydrophilic Polymer on the Morphology of Polymeric Membranes and the Retention of Metals

Polyethylene glycol (PEG) is a preferred hydrophilic polymer as an additive for casting solutions. In this study, polymeric membranes containing 1,10-phenanthroline and different molecular weights of polyethylene glycol (PEG) are tested for the morphological change and metal retention on the membrane surface. Additives in the form of PEGs with molecular weights of 400 Da, 600 Da, and 6000 Da were used. The morphology of each membrane was examined using scanning electron microscopy (SEM). It appears that copper has more retention than cadmium in all membrane components in SEM–EDS analysis. FTIR spectra findings provided evidence that PEG binds to the PVC backbone through hydrogen bonds involving chlorine atoms in the PVC and hydrogen atoms in the hydroxyl groups of PEG. The porosity of the membrane was determined by gravimetric method. The molecular weight of PEG in the membrane seems to be increasing, the porosity of the membrane improved. The porosity of the membrane obtained with PVC/ PEG/ 1,10-phenanthroline is 62.85 for PEG 400, 80.00 for PEG 600 and 83.50 for PEG 6000. The order of metal retention on the surface of the membranes consisting of PVC-1,10 phenanthroline and PEGs are Cu > Cd, indicating that with its large diameter (140 pm), cadmium cannot settle into the pores as much as copper. Except for PEG 600, the retention of both metals decreased with the addition of phenanthroline to the membrane containing PEG. The amorphous structure was detected from the XRD of the membranes. Thermal analysis of the membrane was determined by TG-DSC.Graphical

Geo-mechanical and geo-morphology characterisation of the cap rocks in the Niger Delta for potential carbon capture and storage

The world has been battling climate change which is caused by an excessive amount of carbon dioxide in the atmosphere. Carbon sequestration in geological sinks was identified as one of the major methods to curb and reduce the amount of carbon dioxide in the atmosphere. The carbon dioxide stored in the geological formations must not escape back into the atmosphere. Characterisation of potential reservoirs for geological sequestration is pertinent for injectivity, capacity, and most importantly containment of carbon dioxide. The cap rock is one of the most important factors determining carbon sequestration success. This study focuses on the preliminary characterisation of the caprocks for evaluating potential subsurface storage of carbon dioxide based on their petrophysical characteristics. X-ray Diffraction and X-ray Fluorescence provided the mineralogical composition and geochemical data of the cap rocks while Scanning Electron Microscopy-EDS was used to identify the qualitative information on the micromorphological textural structure of the cap rocks in the Niger Delta. Conventional Triaxial experiments were used to determine the elastic and geo-mechanical strength of the caprocks. It was identified that the grain skeleton of caprocks in the region is predominated by Quartz, Albite, and Muscovite. The ratio of the tectosilicate and phyllosilicate minerals indicates that the cap rocks are silicate shale. The peak strength of the caprocks ranged from 48.85 to 80.50 MPa and are classified as strong rocks. The cap rocks showed a quasi-elastic behaviour after being subjected to compressive axial force. The elastic modulus of the caprocks was also observed. The characteristics exhibited by the shale caprock at the rock matrix level are highly favourable for sealing carbon dioxide and hence indicate capability for use in carbon sequestration.

Understanding the influence of ultrasonic power on the hydration of cement paste

This paper studied the dispersion and hydration of cement paste prepared by power ultrasound (PUS)-assisted mixing technology. The ultrasonic power used were 0 W, 480 W and 912 W. The hydration process and microstructure were tested by using isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), solid-state nuclear magnetic resonance silicon (29Si-NMR) spectroscopy, mercury intrusion porosimetry (MIP), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (SEM‒EDS). The results indicated that the dynamic hydration kinetics of cement paste under ultrasonic irradiation can be categorized into crystallization nucleation and growth (NG), phase boundary (I) and diffusion (D) processes. The apparent rate constant KNG in the NG process and KI in the I process both increased as the ultrasonic power increased, suggesting that PUS-assisted mixing accelerated the early hydration process. PUS shortened the dormant period and enhanced the total hydration heat release. The capillary pores and gel pores were both reduced at 28 days. Similarly, compared with those of C0 and C480, the gel porosities of C912 decreased by 35.17% and 31.87%, respectively. In addition, the mean chain length of the C–S–H gel increased with increasing ultrasonic power, which effectively filled the nanoscale defects. PUS improved the early strength and increased the strength at late hydration ages. Compared with that in the reference group, the compressive strength in the C912 group was enhanced by 26.1% at 1 day and 18.3% at 28 days. These findings demonstrate that power ultrasound-assisted mixing is advantageous for enhancing the sustainability of building materials, thereby contributing to the development of future circular buildings.

Graphite-sheathed ZnMn2O4 microspheres for electrochemical detection of As(III)

In the current research work, the authors report the synthesis of ZnMn2O4 microspheres and G@ZnMn2O4 with a facile hydrothermal process followed by calcination. The as-synthesized materials have been used as a cost-effective strategy for the electrochemical detection of As(III). The composites are characterized for structural and morphological advances using X-ray diffraction (XRD), Scanning electron microscopy EDS, High-resolution transmission electron microscopy (HRTEM), Raman Spectroscopy and X-ray photoelectron spectroscopy (XPS). The ZnMn2O4 microspheres and G@ZnMn2O4 showed excellent electrocatalytic activity towards the reduction of As(III). The G@ZnMn2O4 modified electrode attained a sensitivity of 12.528μAppb−1cm−2 with a lower detection limit (LOD) of 0.87 ppb within the range of 0.33 ppb–5.61 ppb.

Microstructural characteristics and seasonal growth patterns observed in Metoposaurus krasiejowensis teeth

The tooth microstructure of Metoposaurus krasiejowensis was studied to observe external morphology, internal microstructure (comprising dentine structure and directional porosity as possible predatory adaptations) and enamel/enameloid mineral composition. Scanning electron microscopy (SEM) observation and thin-section inspection by light microscope enabled us to recognize a directional porosity in the tooth cross-sections, interpreted here as a part of the labyrinthodont structure displayed by temnospondyls and related groups. This network of canals is highly complicated and reveals a three-dimensional structure. The teeth present different cross-sections based on the distance from the tip, with a wide, circular, reinforced base and lateral compressed, directional cuspidal section with cutting edge. Interestingly, the internal structure observed in M. krasiejowensis teeth exhibit a peculiar variation of internal structure of temnospondyl teeth, as the convoluted canal-like structure seems to be irregular and appears in the upper section of teeth, while teeth bases show a regular structure with a pulpal cavity circled by pores. Furthermore, bands of incremental growth marks interpreted as Andresen lines, characterized by pronounced colour variation, were observed with strong implications for seasonal growth patterns in dentine. Additionally, a significant proportion (1.43–2.73%) of fluoride was observed as a component of enamel by scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) point and mapping analyses, suggesting a fluorapatite mineralogy of enamel.

Nitrogen Removal From Nitrate-Containing Wastewaters in Hydrogen-Based Membrane Biofilm Reactors via Hydrogen Autotrophic Denitrification: Biofilm Structure, Microbial Community and Optimization Strategies.

The hydrogen-based membrane biofilm reactor (MBfR) has been widely applied in nitrate removal from wastewater, while the erratic fluctuation of treatment efficiency is in consequence of unstable operation parameters. In this study, hydrogen pressure, pH, and biofilm thickness were optimized as the key controlling parameters to operate MBfR. The results of 653.31 μm in biofilm thickness, 0.05 MPa in hydrogen pressure and pH in 7.78 suggesting high-efficiency removal and the removal flux was 1.15 g·m−2 d−1. 16S rRNA gene analysis revealed that Pseudomonas, Methyloversatilis, Thauera, Nitrospira, and Hydrogenophaga were the five most abundant bacterial genera in MBfRs after optimization. Moreover, significant increases of Pseudomonas relative abundances from 0.36 to 9.77% suggested that optimization could effectively remove nitrogen from MBfRs. Membrane pores and surfaces exhibited varying degrees of calcification during stable operation, as evinced by Ca2+ precipitation adhering to MBfR membrane surfaces based on scanning electron microscopy (SEM), atomic force microscopy (AFM) analyses. Scanning electron microscopy–energy dispersive spectrometer (SEM–EDS) analyses also confirmed that the primary elemental composition of polyvinyl chloride (PVC) membrane surfaces after response surface methodology (RSM) optimization comprised Ca, O, C, P, and Fe. Further, X-ray diffraction (XRD) analyses indicated the formation of Ca5F(PO4)3 geometry during the stable operation phase.

Variations in mineralogy of dust in an ice core obtained from northwestern Greenland over the past 100 years

Abstract. Our study is the first to demonstrate a high-temporal-resolution record of mineral composition in a Greenland ice core over the past 100 years. To reconstruct past variations in the sources and transportation processes of mineral dust in northwestern Greenland, we analysed the morphology and mineralogical composition of dust in the SIGMA-D ice core from 1915 to 2013 using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results revealed that the ice core dust consisted mainly of silicate minerals and that the composition varied substantially on multi-decadal and inter-decadal scales, suggesting that the ice core minerals originated from different geological sources in different periods during the past 100 years. The multi-decadal variation trend differed among mineral types. Kaolinite, which generally formed in warm and humid climatic zones, was abundant in colder periods (1950–2004), whereas mica, chlorite, feldspars, mafic minerals, and quartz, which formed in arid, high-latitude, and local areas, were abundant in warmer periods (1915–1949 and 2005–2013). Comparison to Greenland surface temperature records indicates that multi-decadal variation in the relative abundance of these minerals was likely affected by local temperature changes in Greenland. Trajectory analysis shows that the minerals were transported mainly from the western coast of Greenland in the two warming periods, which was likely due to an increase in dust sourced from local ice-free areas as a result of shorter snow/ice cover duration in the Greenland coastal region during the melt season caused by recent warming. Meanwhile, ancient deposits in northern Canada, which were formed in past warmer climates, seem to be the best candidate during the colder period (1950–2004). Our results suggest that SEM–EDS analysis can detect variations in ice core dust sources during recent periods of low dust concentration.

A parametric study of layer-by-layer deposition of CaCO3 on glass surfaces towards fabricating carbonate reservoirs on microfluidic chips

Recently, geomaterial-functionalized microfluidic chips have been receiving increased attention as they facilitate material representation to mimic surface mineralogy in addition to direct visualization and quantification of multiphase flow and transport processes in a porous media. In particular, calcite-coated glass surfaces have been used to mimic the solid-fluid interactions involved in carbonate reservoirs. The coating procedure usually involves the deposition of calcium carbonate layers on a functionalized glass surface. Depending upon experimental conditions, the deposited calcium carbonate could be one or more of the three polymorphs: calcite, vaterite, and aragonite. Hence, it is essential to analyze and control the formation of the desired calcium carbonate polymorph. In this study, we transformed glass surfaces into carbonate surfaces by growing calcium carbonate particles in-situ using a layer-by-layer deposition procedure. The influences of process parameters involved in the deposition procedure on the formation of calcium carbonate polymorphs were analyzed. The parameters evaluated were: initial glass surface cleaning phase – DI water, plasma, piranha and NaOH as substrate cleaners; surface functionalization phase – DI water and chloroform as silane solvents; and calcite crystals growth phase – effect of number of coating cycles and concentration of CaCl2 and Na2CO3 solutions on the coating. After CaCO3 deposition, strategies to transform kinetically favorable vaterite to thermodynamically stable calcite are discussed. Coating uniformity, morphology, elemental atomic percentage of coating, and the CaCO3 polymorphs were examined by optical microscopy, Scanning Electron Microscopy (SEM), SEM Energy Dispersive X-Ray Spectroscopy (SEM EDS), and Raman spectroscopy, respectively.

The potential using of organic nanoparticles synthesized from Gmelina (Gmelina arborea Roxb.) wood bark as nanofiller of wood adhesive: physical, chemical and thermal properties

Gmelina (Gmelina arborea Roxb.) is one of several species of wood found in the community forest that grows in Indonesia, especially in the West Java province. To obtain maximum benefit results from the community forest, more than timber needs to be used. Scientists need to find alternative uses for the wood bark waste. The objective of this research was to study the characteristics of organic nanoparticles produced from Gmelina wood bark (GWB), using a conventional balls milling method. GWB an organic waste material from the community forest was converted into nanoparticles using a conventional balls milling method for 96 h and was then filtered using four sieve types (T77, T90, T120 and T200). The nanoparticle was characterized and studied for its particle size, morphology and particle size, chemical components, functional groups and crystallinity using transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning electron microscopy that extended with energy dispersive X-ray spectroscopy (SEM–EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The nanoparticle sizes measured using TEM analysis was less than 100 nm, produced from T90 sieve type, whereas based on a SEM analysis was found to be 104–254 nm, 71–104 nm, 33–47 nm and 33–38 nm; produced from T77, T90, T120 and T200 sieve types, respectively. The proportions of nanoparticle sizes were 11.2%, 82.9%, 3.5% and 0.6%; produced from T77, T90, T120 and T200 sieve types, respectively, and the remaining (1.8%) nanoparticles was retained on T77 sieve type. The chemical components obtained from SEM–EDS analysis were carbon, oxygen, potassium and calcium. The FTIR analysis shows the presence of C–O–C in plane and symmetric band at 829 cm−1 in the nanoparticle produced from T200 sieve type, while there is no C–O–C from the nanoparticle produced from T77, T90 and T120 sieve types. The crystalline structure obtained from XRD analysis found was calcium oxalate hydrate (C2CaO4·H2O) with crystalline diameter size of 20 nm. This result is similar, either produced by T77 or T200 sieve types.

Effect of Artificial Aging Process on Aluminum Foam Made of Etial 160

In this study, aluminum foam made of Etial 160 (AlSi8Cu3Fe) was produced using vacuum die casting method and the process of artificial aging was implemented. The mechanical properties and microstructure of the fabricated foam were investigated. Results of the present study indicate that the artificial aging process has a significant effect on mechanical behavior of aluminum foam. The microstructure, surface morphology, hardness and composition of the Al alloy foam were investigated using scanning electron microscopy (SEM), the Vickers hardness test and X-ray diffraction method. The SEM–EDS and the Vickers hardness measurements show that the best temperature for precipitation hardening is 170 °C for 30 min.

Durable, highly hydrophobic modification of cotton fabric with fluorine-free polysiloxanes obtained via hydrosilylation and hydrothiolation reactions

Cotton fabrics were subjected to modification with fluorine-free polysiloxanes. In the first stage a series of polysiloxanes substituted with alkoxysilyl groups and/or alkyl chains were synthesized. Two methods of functionalization of vinyl group-containing polysiloxanes were used, i.e. hydrosilylation and hydrothiolation. Cotton fabrics were modified via dip-coating technique in solutions of the prepared compounds or by thiol–ene click reaction directly on the surface of cotton. In the first stage of the latter method cotton fabrics were modified by sol–gel technique with 3-mercaptopropyltrimethoxysilane in order to obtain mercapto-functionalized samples. After grafting SH groups on the surface, the fabrics were easily functionalized using the photoclick thiol–ene reaction with vinyl groups containing polysiloxane or vinyl- and alkyl-groups containing polysiloxane. The hydrophobicity was determined by measuring the water contact angle. Changes in the surface morphology were examined by FTIR spectroscopy and scanning electron microscopy (SEM). The coatings of the modified fabrics were subjected to elemental analysis using SEM–EDS techniques. All modified cotton fabrics showed highly hydrophobic properties. All obtained hydrophobic fabrics were fully resistant to the washing process, which proves the durability of the developed modifications.

Effect of bioglass nanoparticles on the properties and bioactivity of poly(lactic acid) films.

Bioglass nanoparticles (n-BGs, 54SiO2 :40CaO:6P2 O5 mol %) with about 27 nm diameter were synthesized by the sol-gel method and incorporated into a poly(lactic acid) (PLA) matrix by the melting process in order to obtain nanocomposites with filler contents of 5, 10, and 25 wt %. Our results showed that during the cooling scan, the crystallization temperature (Tc ) of the PLA/n-BG nanocomposites decreased 13°C as compared to neat PLA. The presence of nanoparticles also decreased the thermal stability of the PLA matrix, as nanocomposites presented up to about 20°C lower degradation temperatures in a nitrogen atmosphere. The presence of n-BG increased the stiffness of the polymer matrix, and for instance the composite with 25 wt % of filler presented about 52.6% higher Young's modulus than neat PLA. n-BG incorporation into PLA increased also the hydrolytic degradation of the polymer over time. When the PLA composites were immersed in simulated body fluid, an apatite layer was formed on their surface, as verified by Fourier transform infrared, X-Ray Diffraction (XRD), and scanning electron microscopy-EDS, showing that the presence of n-BG induced bioactivity on the PLA matrix. Moreover, the viability of cervical uterine adenocarcinoma cells was higher on PLA/n-BG nanocomposite with 25 wt % of filler. The presence of n-BG barely gave an antibacterial effect on the polymer matrix, despite the well-known biocidal properties of these nanoparticles. Our results show that the presence of n-BGs is a proper route for improving the bioactivity of PLA with potential application in tissue engineering.

Synthesis of silver nanoparticles decorated on reduced graphene oxide nanosheets and their electrochemical sensing towards hazardous 4-nitrophenol

In this study, an electrochemical sensor for the detection of 4-Nitrophenol (referred to as 4-NP) was developed based on templated silver nanoparticles (AgNPs) on reduced graphene oxide (rGO) nanosheets (Ag-rGO) and utilized as an electrocatalyst. It was found that the resulting composite exhibits enhanced catalytic activity towards the reduction of 4-NP. The cubic shaped AgNPs templated on rGO nanosheets has been successfully fabricated by a chemical reduction method using sodium borohydride (NaBH4), and it was well characterized through morphological and electrochemical techniques: Ultraviolet–Visible spectroscopy (UV -Vis), scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (SEM–EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and chronoamperometry. The obtained results revealed that the AgNPs scattered on rGO sheets are spherical in shape, and it’s estimated to be a dimension of ~ 60 nm in size. The prepared crystalline Ag-rGO nano sheets were further applied as an electrode material for the electrochemical examination with three electrode system to sense the hazardous material 4-NP in PBS. The electrochemical studies were conducted through CV under the condition of bare and coated electrode (Ag-rGO/GCE) with influence of concentration (4-NP from 2 to 150 mM), scan rate, reproducibility (RSD-2.87%) and stability test (4-NP-20 µM) were examined. The data reveal that the Ag-rGO/GCE exhibit highly reproducible and sustainable for the reduction of toxic 4-NP. The chronoamperometry study for current and time response was also studied at two different potentials (− 0.3 V & − 0.6 V), respectively.

Preclassic Mesoamerican dental inlays: study of the raw material by SEM–EDS

ABSTRACT Dental modifications, especially dental inlays, were one of the most characteristic biocultural traditions in Ancient Mesoamerica. The main objective of this brief report is to identify the raw material used to elaborate dental inlays in the archaeological site of Reynosa, located in the Southern Pacific Coast of Guatemala. The recent discovery of a massive burial, dated roughly in the Middle-Late Preclassic Period (500 BC–200 BC), put the site in the spotlight. There were found some of the earliest carriers of dental incrustations in Mesoamerica, which represent part of the beginning of the inlay tradition. The analytical method used to determine the raw material was scanning electron microscopy (SEM) with X-ray spectroscopy. The identified raw materials were pyrite and hematite. These findings have opened new concerns about the obtaining and the usage of those materials in this millennial tradition.

Mold resistance of bamboo treated with copper complexes-grafted silica gel and its microdistribution in treated bamboo

Bamboo is readily discolored by mold fungi, which greatly limits its applications. An effective antifungal agent, copper(II) chloride (CuCl2)-grafted silica gel, was prepared by a sol–gel process using tetraethoxysilane (TEOS)/3-aminopropyltriethoxysilane (APTES) mixtures. The elemental composition and the chemical combinations of homogeneous sol mixture (HSM) and bamboo were determined via Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM–EDS). The mold resistance of bamboo treated with HSM, alkaline copper quat (ACQ), chromated copper arsenate (CCA), and purified water was characterized by an indoor mold test. The micro-morphology of bamboo treated with HSM was investigated using scanning electron microscopy (SEM). HSM penetrated into the bamboo vessels, and formed xerogels, which was able to coordinate copper(II) cations. SEM–EDS investigations suggest that Si–O–Cu linkages may be formed through an exchange reaction between silanol groups and copper complexes. The bamboo samples treated with HSM showed highly efficient mold resistance due to a good penetration of HSM. Furthermore, no fungal hyphae were found in the structure of HSM-treated bamboo after a 5-week mold test. The copper complexes grafted to silica gel developed in this work provide an efficient antifungal agent for a wide range of potential applications in bamboo protection.

Evaluation of photocatalytic performance for novel Cr2S3–SiO2 nano-catalyst: optimization, quenching, antimicrobial studies

In this study, The Cr2S3 which incorporated SiO2 was synthesized by ultrasonic sol-gel method. In this sense, the mutagenic dyes were removed by the Cr2S3–SiO2 nanocomposites under UV light. The structure of the prepared catalyst was evaluated by x-ray diffraction and photoelectron spectroscopy. The morphology of the nanomaterial was studied by scanning electron microscopy-EDS and dynamic light scattering. In order to evaluate the band gap energy, the Cr2S3–SiO2 nanocomposites were analyzed by diffuse reflectance spectroscopy (DRS). The crystallite size and band-gap values of Cr2S3-SiO2-1 were 37.11 nm, and 2.9 eV, respectively. The activity of Cr2S3–SiO2 nanocomposites demonstrated the exceptional performance in the Disperse Blue 291 and Dispersed Violet 93 dyes degradation after 50 min at pH: 10 under UV light illumination. The result demonstrates that the quencher does not have an influence on photo-degradation of the Disperse Blue 291 and Dispersed Violet 93 dyes. The antimicrobial data of Cr2S3–SiO2 were studied and the results show that the Cr2S3–SiO2 has fungicidal and bactericidal attributes.

Manganese disulfide-silicon dioxide nano-material: Synthesis, characterization, photocatalytic, antioxidant and antimicrobial studies

The sol-gel/ultrasonically rout produced the novel MnS2-SiO2 nano-hetero-photocatalysts with the various ratio of MnS2. Prepared nano-catalyst were investigated in the photo-degradation of methylene blue under UV light illumination. Structural and optical attributes of as-prepared nano-catalysts were evaluated by X-ray diffraction and photoelectron spectroscopy. The morphological were studied by scanning electron microscopy-EDS, and dynamic light scattering. The diffuse reflectance spectroscopy was applied to examine the band gap energy. The Eg values of SiO2, MnS2-SiO2–0, MnS2-SiO2–1, and MnS2-SiO2–2 nanocomposites are 6.51, 3.85, 3.17, and 2.67 eV, respectively. The particle size of the SiO2 and MnS2-SiO2–1 nanocomposites were 100.0, and 65.0 nm, respectively. The crystallite size values of MnS2-SiO2–1 were 52.21 nm, and 2.9 eV, respectively. MnS2-SiO2 nano-photocatalyst was recognized as the optimum sample by degrading 96.1% of methylene blue from water. Moreover, the influence of pH of the solution, and contact time as decisive factors on the photo-degradation activity were investigated in this project. The optimum data for pH and time were found 9 and 60 min, respectively. The photo-degradation capacity of MnS2-SiO2–2 is improved (96.1%) due to the low band gap was found from UV–vis DRS. The antimicrobial data of MnS2-SiO2 were studied and demonstrated that the MnS2-SiO2 has fungicidal and bactericidal attributes.

The Effect of Homogenization Procedure on Mechanical Properties of High-Performance Concrete with Partial Replacement of Cement by Supplementary Cementitious Materials

High-performance concrete is a very specific type of concrete. Its production is sensitive to both the quality of compounds used and the order of addition of particular compounds during the homogenization process. The mechanical properties were observed for four dosing procedures of each of the three tested concrete mixtures. The four dosing procedures were identical for the three mixes. The three mixes varied only in the type of supplementary cementitious material used and in water content. The water content difference was caused by variable k-value of particular additives. The water-to-binder ratio was kept constant for all the concretes. The additives used were metakaolin, fly ash and microsilica. The comparison of particular dosing procedures was carried out on the values of basic mechanical properties of concrete. The paper compares compressive strength and depth of penetration of water under pressure. Besides the comparsion of macro-mechanical properties, the effect of microsilica and fly ash additives on micro-mechanical properties was observed with the use of scanning electron microscopy (SEM) and nanoindentation data analysis. Nanoindentation was used to determine the thickness and strength of interfacial transition zone (ITZ) for different sequence of addition of cement, additive and aggregate. The thickness obtained by nanoindentation was further investigated by SEM EDS line scanning.

Microstructural Tuning of a Laser-Cladding Layer by Means of a Mix of Commercial Inconel 625 and AISI H13 Powders.

The aim of this work is to evaluate the microstructural evolutions developed by mixing a corrosion-resistant and high-performance material with a high-hardness material in a coating obtained by laser-cladding technology. In this paper, five different mixtures of Inconel 625 alloy and AISI H13 steel powders have been deposited on a plate of 42CrMo4 steel using a 2.2 kW diode pumped Nd:YAG laser. The effect of adding tool steel to a Ni-based superalloy has been analyzed by the characterization of each cladded sample using optical microscopy and scanning electron microscopy (SEM). The precipitates observed in the samples have been analyzed by energy dispersive X-ray spectroscopy (EDS X-ray). SEM micrographs and EDS analysis indicate the existence of Laves phase. It has been observed that the presence of these precipitates is stabilized in a certain range of AISI H13 addition.

REMOCIÓN DEL COLORANTE ROJO CONGO USANDO HIDROXIDO METÁLICO ELECTROCOAGULADO EN UNA COLUMNA DE LECHO FIJO: CARACTERIZACIÓN, OPTIMIZACIÓN Y ESTUDIOS DE MODELADO

The reuse of a Metal Hydroxide Sludge generated by an electrocoagulation process was used as an adsorbent for the removal of Congo red dye in a fixed bed column. The obtained adsorbent was characterized by N2 physisorption, Fourier transform infrared spectroscopy and scanning electron microscopy-EDS measurements. Continuous column experiments were carried out with a Central Composite Design (CCD) to study parameters such as adsorbent mass (4-8 g), initial concentration of Congo red (20-50 mg·L-1) and feed flow (20-50 mL·min-1) in the breakthrough time, breakthrough volume and saturation time. The high value of the correlation coefficient and the low value of p (<0.0001) indicates the adequacy of the response surface of quadratic models developed for the variable responses in the optimization process. The capacity of adsorption under conditions optimized in the operation of the column was estimated at 3.57 mg·g-1. In addition, it was found that the Thomas, Bohart-Adams and Yoon-Nelson models adjusted adequately to the column data obtained.