Acta Microscopica

ELECTRODEPOSITION OF Co/Cu MAGNETIC MULTILAYERS AND THEIR CHARACTERIZATION USING AUGER DEPTH AND LINE PROFILES AND MAGNETIZATION MEASUREMENTS

A. Monsalve, C. Rojas — Mon, 04 Aug 2025 00:00:00 +0000

An automated system was built for the electrodeposition of binary multilayers using two electrochemical cells, which allows the number and thickness of successive layers to be programmed and executed by moving the substrate and immersing it into the corresponding bath, with predetermined current and deposition time values. This system was used for the fabrication of planar magnetic Co/Cu (magnetic/non-magnetic) multilayers with layers of nanometric thickness. These multilayers were characterized by obtaining Auger depth composition profiles, as well as line composition profiles in images of the footprint left on the sample surface by sputtering with a focused Ar⁺ beam. For the magnetization measurements in the flat samples, as a function of the in-plane applied magnetic field, an 860 nm thick Co film deposited on a Cu substrate was prepared as a reference sample. Three other samples were prepared with this same amount of Co, but distributed into 20 layers of 43 nm each, separated respectively from each other by 22, 11 and 5 nm-thick Cu layers. The obtained magnetization results suggests with an antiferromagnetic coupling between successive Co layers when the separation between them is 5 nm of Cu.

ESTUDIO DE LA MORFOLOGÍA DE HIDROGELES HÍBRIDOS OBTENIDOS A PARTIR DE MATERIALES ARCILLOSOS MODIFICADOS Y SU USO EN LA ABSORCIÓN DE IONES Co2+ y Fe2+

A. Ramírez, B. Rojas de Gáscue, L. Gómez, C. Urbina de Navarro — Mon, 04 Aug 2025 21:20:42 +0000

In the following work, red mud (RM) and ferrosilicomanganese fines (FeSiMn) were used as clay materials in the synthesis of hybrid hydrogels. These inorganic phases are obtained as waste from production processes carried out by the Venezuelan mining industry. The research is focused on the development of new applications for these wastes, using them to improve the properties of conventional hydrogels. In this study, these inorganic phases were modified through two treatments aimed at reducing their pH. The first treatment used synthetic seawater and the second treatment was acidification with HCl. For the synthesis, acrylamide (AAm) was used as a monomer, and N,N`-methylenebisacrylamide (NMBA) as a cross-linking agent. The hydrogels were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and the ability to absorb Co²⁺ and Fe²⁺ ions was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). The results show that modifications decreased the water absorption capacity of the hydrogels, in the same way the micrographs obtained by SEM revealed that modification with HCl was the one that had the most effect on the surface morphology of hydrogels, increasing the population of pores with lengths less than 4 μm from 21% to 74% in the PAAm/FeSiMn hydrogels. The results are explained by new interactions between the inorganic phases and the PAAm matrix and indicate that modifications made constitute a way to control the microstructure and properties of the hybrid hydrogels.

CHARACTERIZATION OF PLASTIC PARTICLES IN COASTAL SEDIMENTS OF PLAYA SAN LUIS, CUMANÁ, VENEZUELA

A. Gamboa, B. Rojas de Gascue, J. I. Ramírez, C. Pinto, G. Gutiérrez, V. Brito — Tue, 05 Aug 2025 00:00:00 +0000

Due to their versatility and affordability, plastics have become widely used in packaging and various other sectors, significantly increasing plastic waste generation. Environmental concerns arise as plastics degrade into microplastics; particles smaller than 5 mm when exposed to the environment. Despite increased research on plastic pollution, there are many information gaps worldwide, particularly in Venezuela. Additionally, there is a lack of chemical characterization of these pollutants. This study aims to reduce the information gap by characterizing plastic particles collected on an urban beach in Sucre state, Venezuela. In February 2021, thirty sediment samples of two sectors were collected from San Luis Beach in Cumaná for examining the plastic particle content. Density separation using a 5 mol/L NaCl solution was employed to extract particles, which were subsequently categorized by size, shape, and color. Furthermore, FTIR analysis and photographs with a digital optical microscope of selected particles were conducted. A total of 485 items in Sector A and 251 items in Sector B were recovered from the sediments, with fragments being the predominant shape and blue and green as the dominant colors. These analyses allowed for the identification of poly(ethylene-co-vinyl acetate) and polyester, as well as the presence of moisture, adsorption of other contaminants, and the presence of pigments on the particles.

EVALUATION OF MORPHOLOGICAL CHANGES IN POLYPROPYLENE MICROPLASTICS PRODUCTS OF PHOTOOXIDATION INDUCED BY UV LIGHT

A. M. Materano F., J. A. Lezama G., B. Rojas de Gascue — Tue, 05 Aug 2025 00:00:00 +0000

The controlled photooxidation process of polypropylene J-643 microplastics (MP) was experimentally evaluated under the incidence of UV-B light up to a maximum exposition time of 75 days, by determining the carbonyl index (IC) from analysis by FTIR spectroscopy. Likewise, the morphological changes in the oxidized polypropylene microplastics were analyzed using an Olympus optical microscope model BX50. Morphologically, an increase in roughness and the appearance of blackened areas was evident in the oxidized PP MPs, not observed in the non-chemically modified MP; This is due to the increase in the exposure time of the samples to UV radiation. In turn, there was a decrease in the mechanical resistance of the material and an increase in its fragility. These changes can be explained from a macromolecular point of view, by the fragmentation of the polymer chains that generates cracks and surface irregularities. Additionally, the calculated IC values suggest a relationship between the longer exposure time to UV radiation and the increase in oxidation of the MP.

MORPHOLOGICAL CHARACTERIZATION OF TYPE I COLLAGEN FIBERS IN FOSSIL SAMPLES FROM THE BREAL DE OROCUAL, EDO. MONAGAS, VENEZUELA.

Tue, 05 Aug 2025 00:00:00 +0000

The objective of this study was the chemical and morphological characterization of type I collagen fibers in a cortical bone sample of the humerus bone of a mammal belonging to the extinct genus Toxodon, whose fossil was extracted from “Breal de Orocual”, in Monagas state, Venezuela. The fossil bone samples measuring 1 cm long x 1 cm wide x 0.5 cm deep, were cut in half with a silicon carbide disc and subsequently polished with sandpaper. A preliminary analysis by FT-IR spectroscopy reveals the characteristic absorption bands corresponding to collagen protein. Morphological analysis was carried out by scanning electron microscopy. At the microstructural level, osteons with corresponding Havers, duct, lamellae and lacunae were observed, all of which are characteristic elements of the anatomical and structural unity of cortical bone. Collagen fibers were also observed. The final verification of the presence of the fibers was carried out at a sub-micrometer scale using Atomic Force Microscopy. The periodic spacing between bands, characteristic of this type of organic structures, was identified, thus revealing their existence and state of preservation.

EXPLORATION OF NANOSTRUCTURED MATERIALS FOR SELECTIVE ACETONE DETECTION IN DIABETES DIAGNOSIS

A. Alviarez, D. Rangel, S. Briceño, E. Ávila, P. Silva, Y. Sánchez-León — Tue, 05 Aug 2025 04:43:48 +0000

In the present study, the potential of ferrite nanoparticles (MnFe₂O₄ and CoFe₂O₄) in combination with multi-walled carbon nanotubes (MWCNTs) will be evaluated in order to develop a gas sensor to rapidly detect the presence of gaseous acetone in closed environments. The MWCNTs were prepared by chemical vapor deposition (CVD), while the ferrite nanoparticles were obtained by a solvothermal method with 4 and 16 hour reaction times. The size of nanoparticles was determined from X-Ray Diffractograms (XRD) using the Scherrer equation and was found to range from 11 to 13 nm. Scanning Electron Microscopy (SEM) micrographs showed that the nanoparticles showed tend to agglomerate against the reaction time. The electrical resistance of the materials was evaluated in the presence and absence of acetone and its behavior was determined as a function of absorption time, gas recovery, repeatability of the measurements as a sign of sensor stability; it was found that the sensor responses depend on both the type of ferrite and the reaction time. Developing this type of sensor based on ferrite nanoparticles and MWCNTs represents a fast and effective alternative for detecting acetone, with potential application in the prevention of acetone-related diseases as a biomarker.

EVIDENCES OF ELONGATED CELL MORPHOLOGY OF PROTEUS MIRABILIS ASSOCIATED WITH ENVIRONMENTAL SURVIVAL BY ELECTRON MICROSCOPY TECHNIQUES

A. Bendayan, F. Sánchez, V. Salazar, Z. Duque, P. Suárez, M. Fernández-Delgado — Tue, 05 Aug 2025 04:45:13 +0000

Proteus mirabilis is an opportunistic pathogen resistant to multiple antibiotics, known to cause urinary tract infections and to form biofilms on catheters. Although pathogenicity and biofilm formation mechanisms in clinical strains have been studied, there is little information on environmental isolates that may be potential pathogens and reservoirs of virulence genes. For the first time, this work evaluated the elongated cell morphology of P. mirabilis in cultures of an environmental strain isolated from oyster tissue, as well as in biofilms formed in vitro on chitin surfaces, using transmission electron microscopy and environmental scanning electron microscopy, respectively. A similar evaluation was also performed on a clinical reference strain used as a control for the study. These microscopy techniques show cell elongation in environmental P. mirabilis and the presence of virulence factors such as fimbriae, flagella, and pili. These findings suggest that the elongated morphology in this bacterial species may be a strategy of survival and resistance to adverse conditions, as well as a mechanism of pathogenicity that allows the bacterium to colonize the upper areas of the urinary tract with the formation of biofilms. Our results contribute to the knowledge of the survival, virulence, and pathogenicity mechanisms of clinical and environmental strains of P. mirabilis, whose importance is constantly growing in public health.

MORPHOLOGICAL STUDY AND COMPATIBILITY OF PMMA BLENDS WITH PVA PREPARED IN SOLUTION

Tue, 05 Aug 2025 04:59:07 +0000

In this work, mixtures of polymethyl methacrylate (PMMA) with polyvinyl alcohol (PVA) were prepared by dissolution, to study their miscibility and possible future applications in the development of bone cements. Formulations were prepared in proportions of 70/30 and 50/50 (PMMA/PVA). The compatibility was studied by Fourier Transform Infrared (FTIR) and Differential Scanning Calorimetry (DSC). Thermogravimetric Analysis (TGA) was used to evaluate the thermal stability of the materials. The morphology of all materials was exposed using Scanning Electron Microscopy (SEM). Significant shifts in the absorptions of the carbonyl groups of PMMA and hydroxyl groups of PVA were detected by infrared, which would be associated with the formation of intermolecular hydrogen bonds of the type PVA−O−H−O=C−PMMA. The thermal behavior of the polyblends obtained by DSC showed a direct correlation with their composition, with two well-defined T_g values shifted to values lower than the T_g of the pure polymers. These results would indicate the formation of partially miscible mixtures between both polymers. The thermal stability of the mixtures obtained by TGA was slightly higher than that of the polymers alone. SEM revealed a morphology consisting of dense droplets and particles for PMMA, with a multimodal size distribution between 5 and 50 um, embedded in a highly porous structure with interconnected multichannels, associated with PVA. These results were decisive in corroborating the formation of partially miscible mixtures prepared in solution from PMMA and PVA.

CHARACTERIZATION OF A DUPLEX STAINLESS STEEL UNS S31803 HEAT TREATED AT 650 °C

D. Díaz, A. Rosales, E. Rodríguez — Tue, 05 Aug 2025 05:08:00 +0000

The aim of this study was the microstructural characterization of UNS S31803 duplex stainless steel samples thermally treated at 650 °C for 2, 3, 4, 6 and 8 h in order to promote the precipitation of intermetallic phases. The study was carried out using optical microscopy, scanning electron microscopy and energy dispersed X-ray spectroscopy. To reveal the microstructure of the material, a combined electrolytic attack was designed considering two steps: the first with 10% oxalic acid and the second, 20% NaOH. The monitoring of the microstructural evolution revealed the increase in the fraction of austenitic phase, which suggested the formation of secondary austenite and also the presence of precipitates after 2 h of treatment. According to their location and morphology these could be nitrides and carbides of chromium, whose fraction increased with treatment time, presenting more notable agglomerations after 6 hours. Additionally, the results of the elemental analysis reported the enrichment in chromium of the regions where the different precipitates were concentrated, which coincide with the presumed presence of the Cr₂N and M₂₃C₆ phases. Likewise, the analyses using scanning electron microscopy suggested the possibility of formation of the sigma phase at longer treatment times.

CHARACTERIZATION OF A STAINLESS STEEL UNS S31803 HEAT TREATED AT 800°C

D. Zencoff, A. Rosales, E. Rodríguez — Tue, 05 Aug 2025 05:16:21 +0000

The aim of this research is to study the formation of intermetallic phases in a duplex stainless steel as a result of heat treatment at 800 °C for 30 min, 1 h, 3 h, 5 h, and 6 h. This was carried out using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Elemental Analysis by Energy Dispersive X-ray Spectroscopy (EDS). The microstructural analysis revealed that the as-received sample has a ferrite (α) content of 52.05 ± 1.91 % and an austenite (γ) content of 47.95 ± 1.91 %. On the other hand, the samples subjected to heat treatment showed the presence of intermetallic phases such as the sigma phase (σ), chi phase (χ), and secondary austenite (γ₂), resulting from the decomposition of ferrite through the eutectoid reaction α → σ + γ₂, which occurs at α/γ or α/α interfaces. Additionally, as the treatment time increases, the amount of precipitated sigma phase increases, decreasing the ferritic phase fraction and increasing the austenitic fraction compared to the original amount. Thus, the α phase after 6 h of treatment presented an area fraction of 15.44% and the γ phase showed an increase up to 56.70% at 3 h, decreasing then to 46.92% at 6 h. Regarding the fraction of intermetallic phases, mainly the sigma phase, the results reported 37.64% at 6 h.

CHARACTERIZATION OF A SENSITIZED AISI 304H STEEL SUBJECTED TO DISSOLUTION TREATMENTS AT 900ºC

F. Rodríguez, O. Rodríguez, E. Rodríguez — Tue, 05 Aug 2025 05:24:21 +0000

The objective of this study is to characterize the microstructure of a sensitized AISI 304H steel subjected to a dissolution treatment at 900°C and to evaluate it through ultrasonic techniques. The monitoring of microstructural evolution was carried out by Scanning Electron Microscopy (SEM) and the determination of acoustic variables by ultrasound, using the pulse-echo detection technique. The results demonstrated the characteristic microstructure of these grain steels, exhibiting polygonal morphologies and highly contrasted zones along the grain boundaries. This was attributed to the presence of the sigma phase and chromium carbides, which were preferentially located in these high-energy zones. However, as the dissolution treatment time increased, the presence of small precipitates of chromium carbides were observed along the entire surface. This could be due to the dissolution of the sigma phase and the chromium carbide nucleation process, which occurs after three hours of treatment. Ultrasonic measurements revealed a variation in velocity as the treatment time increased, attributed to the influence of the fraction of sigma phase and carbides presented in the microstructure, as well as the material's inherent anisotropy. Conversely, the attenuation coefficient exhibited a tendency primarily associated with dispersion losses, resulting from the microstructural alterations observed in the material during dissolution treatments of the precipitates.

IDENTIFICATION OF THE CONSTITUENT MATERIALS OF PLASTIC FILTERS OF ARTIFICIAL RESPIRATORS

Tue, 05 Aug 2025 05:35:03 +0000

This work describes the identification and characterization process of the constituent materials of commercial disposable air filters, used in artificial respirators and nebulizers in clinics and hospitals. The characterization of these materials served as input for a study carried out to determine the possibility of producing these medical devices in the country, due to the increase in patients with COVID-19, who required the use of artificial respirators and medical oxygen with nebulizers. Clinical air filters are made up of a transparent plastic casing that allows you to see the inside of the product, which contains two types of filter elements. In addition, on the filter housing there is a small opaque plastic cover that allows the entry of medications to nebulize the patient. The characterization of the materials was carried out by DSC, TGA, FTIR and SEM-EDX. The material from which the housing and the plastic filter element are made was identified, as polypropylene.

SYNTHESIS AND OPTICAL CHARACTERIZATION OF MODIFIED GRAPHENE WITH METAL MATERIALS AND ITS APPLICATION AS ELECTROCHEMICAL CAPACITORS

E. Bastidas, J. A. Castillo, M. Rodríguez-García — Tue, 05 Aug 2025 05:42:11 +0000

In the present work, we report the synthesis of graphene oxide (GO) and its derivatives using a biogenic process, treating rice husk ash (RHA) with KOH at high temperatures. The obtained GO was modified by incorporating copper nanoparticles (CuNPs) into its structure through an impregnation process and subsequent wet chemical reduction of the metal using L-ascorbic acid as a reducing and stabilizing agent. The synthesized materials were characterized using FTIR, XRD, SEM, and AFM techniques, demonstrating their shape, structure, and chemical composition. The nanocomposites, identified as partially oxidized graphene (GpO) and GpO-Cu, were employed as electrodes in cyclic voltammetry experiments to determine their conductive properties using a 5 mM potassium ferricyanide solution in 1 M potassium chloride as a reference and a saline solution (KCl) as the working electrolyte solution. The results show the formation of materials that, by modifying their chemical composition, can be used as conductors or capacitors.

EVALUACIÓN DE BIOPELÍCULAS EN IMPLANTES DE TITANIO POR MICROSCOPÍA ELECTRÓNICA DE BARRIDO: CASO CLÍNICO CON INFECCIÓN MÚLTIPLE Y RESISTENCIA A ANTIBIÓTICOS

Tue, 05 Aug 2025 05:53:22 +0000

In this study titanium implants from a patient undergoing spinal column surgery were evaluated to determine cellular morphologies and structures associated with the formation of biofilms. The patient presented postoperative infection by Klebsiella pneumoniae identified through microbiological culture and biochemical tests performed on the implants once they were removed. Subsequently, this person develops multiple infections with Pseudomonas aeruginosa, Burkholderia cepacia, and Candida spp. For observation by scanning electron microscopy (SEM), the implants were fixed in 2.5% glutaraldehyde in sterile PBS and stored at 4 °C. One replica was washed three times with PBS and distilled water, dehydrated in 50% ethanol, dried in an oven for 40 min, and covered with gold. SEM images demonstrated the formation of biofilms with bacterial cell morphologies such as cocci and bacilli of approximately 0.5-1 μm and a well-developed extracellular matrix. The coccoid forms are suggestive of the viable but nonculturable state described for K. pneumoniae as a defense mechanism for its survival, allowing this pathogen to remain for a long time in the biofilm, causing infection to the host and conferring immunological and antibiotic resistance. Crystal-like structures were evident, probably of bacterial origin. This research constitutes the first report that shows the formation of biofilms on titanium implants using SEM, associated with a clinical state of multiple infections and antibiotic resistance. This microscopy technique offers great utility in diagnosing biofilms related to bone implants.

THE MICRO/NANOENCAPSULATION OF COLCHICINE DRUG IN PLA MATRIX

J. A. Orellano, G. Rodríguez, J. V. Lopes da Silva, A. H. Romero, M. A. Sabino — Tue, 05 Aug 2025 06:02:14 +0000

The need to obtain drug delivery systems (DDS) for the treatment of various diseases including cancer has become an increasingly present priority to reduce the side effects of tratament. The administration of conventional drugs often requires high doses and prolonged treatments, which can reduce overall efficacy and even cause toxicity. In recent decades, biomaterials have been developed as a matrix component for the manufacture of materials that contain encapsulated medication for precise drug delivery, at predetermined rate and period of time. Colchicine is an alkaloid, one of many commercially available drugs that has been used for the treatment of arthritis and other ailments, but also as an anticancer drug, but its availability has always been in free drug form and not in controlled delivery systems. For this reason in this work it was carried out the encapsulation into micro/nanoparticle systems, using Polylactic acid (PLA) as a vehicle, and resorting to the microemulsification technique to carry out this process. It was possible to verify using a scanning electron microscope (SEM) that the particles presented spherical morphology, with size distribution between the nanometric and micrometric scale. The encapsulation of colchicine in the micro/nanoparticles could be demonstrated using indirectly the X-ray energy dispersion technique (EDX). Subsequently, using UV-Visible spectroscopy, the hydrolytic degradation at 37 °C of the polymeric systems was evaluated for 2 weeks, under two different conditions: at pH 7.4 and at pH 4.8. A controlled release curve was obtained with a release of 35% for the buffer at neutral pH and 30% for the buffer at acidic pH.

ELECTRODEPOSITION OF NICKEL FILMS AND THEIR CHARACTERIZATION BY AFM AND STM

Lesvia López, Carlos Rojas, Antonio Monsalve, José Daniel Martínez — Tue, 05 Aug 2025 14:43:19 +0000

This work reports the results obtained from depositing metallic Ni thin films (TF) on Cu and Si substrates via Electrodeposition and deposition by cathodic cyclic voltammetry. Initially, Electropolishing (EP) was conducted on Cu samples to reduce surface roughness, while Si substrates underwent HF immersion to remove superficial Si oxide and enhance substrate conductivity. The nanostructures were morphologically characterized using Scanning Electron Microscopy (SEM) and Proximity Microscopy: Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM). Additionally, sharp tips of W were electrochemically etched (EE) for STM characterization. AFM measured the nickel thin films thicknesses, congruent with theoretically estimated values for each technique, ranging from 128nm to 236nm. EE-fabricated W tips for STM had minimum radii of 167nm. Spatial resolution of 2D and 3D topographic images measured with STM exceeded that of AFM, primarily due to smaller dimensions of EE-fabricated tips compared to AFM probes. Results highlight the importance of flat substrates for facilitating topography and thickness observation of deposited films with Proximity Microscopies. Prior characterization of substrates enables distinguishing between contributions to topography from the film and substrate.

THE TAURINE EFFECT ON THE VASO-OBLITERATION OF THE CEREBELLAR MICROVASCULATURE OF THE RAT EXPOSED TO POSTNATAL HYPEROXIA

L. M. Rojas, A. Liscano, E. Marín, A. Rojas, A. Boada-Sucre, P. Rodríguez — Tue, 05 Aug 2025 14:57:19 +0000

The purpose of this study was to evaluate the effect of taurine on the vessel-obliteration of the cerebellum microvasculature of rats exposed to postnatal hyperoxia. For this, two groups of newborn Sprague-Dawley strain rats were exposed to hyperoxia together with their mother, from birth until day P6, P9 and P12. The mother of one group drank 3% taurine solution as drinking water and the mother of the other group only drank water. Two similar groups, but without hyperoxia, were used as controls. For histological and ultrastructural analysis, samples were taken from the cerebellum, specifically from the gray matter at the level of the vermis, and were processed using the plastic embedding technique for semi-thin (0,7μm) and thin (70nm) sections. To characterize the damage to the vascular system, it was taken into consideration whether the capillaries were permeable or obliterated and whether the extensions of the pericapillary astrocytes were edematous or not. In the hyperoxia group, 77% of obliterated vessels were observed, and only 23% of permeable vessels were observed, while in the hyperoxia taurine group, 67% of permeable vessels were observed. Ultraestructurally, the obliterated vessels of the hyperoxia group showed edematous mitochondria with fragmented ridges, unlike the hyperoxia taurine group where the mitochondria were observed to be normal. The results demonstrate that the administration of taurine had a beneficial effect by preventing vaso-obliteration of the capillaries of the cerebellar cortex on rats exposed to postnatal hyperoxia.

AQUEOUS SYNTHESIS OF PAAm/PVA/Ag NANOHYDROGELS

M. C. Hernández, C. Rojas, P. Estévez, N. Bandres — Tue, 05 Aug 2025 15:10:21 +0000

In this work a novel synthesis methodology in aqueous medium of semi-interpenetrated nanohydrogels (HGNCs), of polyacrylamide (PAAm) with polyvinyl alcohol (PVA) and silver nanoparticles (AgNPs) is presented. The synthesis of the HGNCs/AgNPs was carried out in two phases: in a first stage, the AgNPs were obtained using the polyol method with PVA as a reducing agent and stabilizer of the metal nanoparticles, and in a second stage, the hydrogel semi IPN PAAm/PVA/AgNPs was synthesized in situ. A weight ratio of 2:1 PVA:AgNO₃ and 4:1 PAAm:PVA is used. To evaluate the quality of the HGNCs/AgNPs obtained, the morphological and swelling properties of PAAm and PAAm/PVA blank samples are also analyzed. The dispersion in the polymer matrix, polydispersity and particle size of the metallic nanophase is evaluated through Transmission Electron Microscopy (TEM). The structure and pore size of the synthesized hydrogels are analyzed by Scanning Electron Microscopy (SEM) from lyophilized samples.

SEM - EDS ON THE STUDY OF THE EFFECTS OF pH FOR THE REMOVAL OF Al (III) USING MORINGA OLEÍFERA PODS AS A BIOADSORBENT FROM AQUEOUS SYSTEMS

Mirla Rodríguez, Saúl Flores, Damarys Soto, Ramses Montaño — Tue, 05 Aug 2025 15:20:34 +0000

Nowadays, water contamination by heavy metals has become a world-wide environmental problem. Recently, bioadsorption has been proposed as an alternative treatment procedure. Moreover, enhancement of agro-industrial waste is the great interest. In this sense, the aim of this study is to perform a chemical characterization of moringa pods and subsequent study as bioadsorbent for removal of aluminum (III) from aqueous systems. The pods used were collected from Guárico, Venezuela. After dried, ground and sieved to a particle size of 595 um, were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FT-IR) and point of zero charge (pH_PZC). The potential of pods was tested under different pH conditions (2 to 9), biomass (0.25 g), metal concentration (50.0 mg/L), contact time (30 min) and volume of solution (30.0 ml) by batch system. The residual metal concentration was measured by atomic absorption spectrophotometry (AAS). The results showed that this biomaterial containing functional groups and adequate morphological profile for the retention of metal ions. Additionally, present a point of zero charge of 6. The optimal removal of Al (III) ions was achieved at pH 7 (99%). According to achieved results, moringa pods have promising characteristics for applications aluminum (III) remediation from contaminated waters at low cost, easy acquisition, eco-friendly and relatively neutral pH.

ELECTROCHEMICAL CONVERSION OF CO2 WITH COPPER NANOPARTICLES

Tue, 05 Aug 2025 15:32:34 +0000

In the present research work, copper nanoparticles were synthesized using 2.5% sodium dodecyl sulfate (SDS) as stabilizer in an aqueous solution with a pH of 5.66, and they were dispersed on two types of carbon supports with the aim of being used in the electrochemical reduction of CO₂ to obtain products with greater added value. The nanoparticles obtained showed electrocatalytic activity in the CO₂ reduction reaction. During the electroreduction of CO₂, some products, such as formate and methanol, were detected. Using SEM, a change in the arrangement of the copper nanoparticles on the support was observed after 45 minutes of reaction, and through electrochemical analysis, an increase in current density was observed.

COMPARATIVE STUDY OF THE MORPHOLOGICAL, STRUCTURAL AND TEXTURAL CHARACTERISTICS OF GRAPHENE DERIVATIVES OBTAINED BY DIFFERENT OXIDATION OR REDUCTION TREATMENTS

E. Lucena-Mendoza, S. Voelger, G. Rodríguez, Y. Díaz, R. S. Del Toro — Tue, 05 Aug 2025 15:41:38 +0000

This is a comparative study of the nature of oxygenated functional groups incorporated or removed from the graphene derivative, through different synthetic study methodologies, as well as its correlation with the crystalline/amorphous structure, morphology and porous texture generated in the synthesized material. For this purpose, three graphene oxide (GO) derivatives were synthesized by reaction of graphite with an oxidizing mixture. GO1 and GO2 were obtained using the traditional Hummers method and GO3 by a modified Hummers method, with variations in stoichiometry, temperature, and reaction time. In addition, a green synthesis of reduced graphene oxide (r-GO), starting from GO3 and L-ascorbic acid as reducing agent was investigated. The solids were characterized by FT-IR, XRD, SEM, UV-Vis and textural analysis by N2 physisorption.

SCANNING ELECTRON MICROSCOPY FOR THE CHARACTERIZATION OF A CERAMIC MEMBRANE COMPOSED OF LaFeO3-CeO2 AND La2O3-Al2O3

Tue, 05 Aug 2025 15:50:26 +0000

The chemical composition, crystalline structure and microstructure of ceramic membranes play an important role in their mechanical properties, thermal stability, permeation and catalytic behavior. In the present work, a mixed ceramic membrane with potential application in catalysis was prepared and characterized. The ceramic membrane was made of two layers of ceramic oxides with a dense and porous structure. The dense layer was prepared with a solid composite based on LaFeO₃ of perovskite-like structure and CeO₂. The porous layer was prepared with a La₂O₃-Al₂O₃ composite oxide. The constituent powders and the ceramic membrane were characterized by XRD, SEM-XEDS, BSC and nitrogen physisorption. The microstructure results showed an adequate compaction of the dense and porous ceramic powders, with a grain consolidation boundary zone of the two ceramic phases up to a certain depth (˂ 200 μm) and relative roughness without fracture between the two ceramic oxide layers.

STUDY OF THE ABSORPTION AND DESORPTION PROCESS OF AN ANTIBIOTIC IN SPHERICAL ACRYLIC POLYMER-BASED HYDROGELS

V. Rojas, G. Rodríguez, P. Boschetti, M. Sabino — Tue, 05 Aug 2025 16:00:09 +0000

Acrylic-based hydrogels with spherical geometry were characterized and subjected to a study of absorption/desorption to evaluate the encapsulation and release of a commercial solution of the antibiotic Ciprofloxacin (200 mg/100 ml) at 25 °C. The characterization was performed by means of infrared spectroscopy, macro magnifying glass, scanning electron microscopy and X-ray energy dispersion. Based on the experimental adsorption and desorption results, mass percentage (g/g) and volumetric percentage (mm³/mm³) curves were constructed for both processes. Additionally, using the mass swelling percentages, diffusivity was analyzed using Fick's Second Law and employing the lattice-Boltzmann computational method (LBM) to simulate the behavior. Consequently, the gels were demonstrated to be superabsorbent, and the effectiveness of the diffusion process in polyacrylic based hydrogels with spherical geometry was verified.

COMPARATIVE STUDY OF THE ELECTROCHEMICAL BEHAVIOR OF VECALLOY B AND ALPHA PLUS COATINGS DEPOSITED BY THERMAL SPRAYING USING THE ELECTRIC ARC TECHNIQUE.

W. Flores, W. González, E. Rodríguez, J. B. León, A. Scagni, M. Suárez — Tue, 05 Aug 2025 16:07:55 +0000

The present study aims to characterize microstructurally and evaluate the electrochemical behavior of Vecalloy B® and Alpha Plus®+SS420 metallic coatings deposited by thermal spraying using the electric arc technique. For the microstructural caracterization of the coatings, X-ray diffraction (XRD), optical microscopy (OM) and scanning electronic microscopy (SEM) techniques were used. Regarding the electrochemical behavior, potentiodynamic polarization tests were carried out, as well as electrochemical impedance spectroscopy tests. From the microstructural characterization, it was found that both coatings are mainly composed of lamellae, pores, oxides and unmolten particles. In the electrochemical tests, it was found that Vecalloy B coating has a higher resistance against corrosion by presenting a lower corrosion current density and nobler corrosion potential compared to Alpha Plus+SS420 coating, this probably due to a lower porosity and to the presence of some alloying elements that have a higher resistance against electrochemical attacks.

SYNTHESIS AND CHARACTERIZATION OF THE FeIn0.8Cr1.2S4 SEMICONDUCTOR VIA CHEMICAL VAPOUR TRANSPORT: INFLUENCE OF TRANSPORTING AGENT ON CRYSTAL MORPHOLOGY AND MAGNETIC PROPERTIES

Y. Sánchez-León, P. Silva — Tue, 05 Aug 2025 16:16:40 +0000

SYNTHESIS, CHARACTERIZATION AND EVALUATION OF THE PHOTOCATALYTIC ACTIVITY OF COPPER-DOPED TITANIUM DIOXIDE NANOPARTICLES IN THE DEGRADATION OF ACETOMINOPHEN

Y. Franco, J. Castillo, J. C. Pereira — Tue, 05 Aug 2025 16:24:24 +0000

In photocatalytic reactions, titanium dioxide (TiO₂) has been widely used as a photocatalyst for air and water decontamination, proving to be highly effective over the years. However, its activation capacity with visible light is limited by the high bandgap value of this compound. To overcome this limitation, various modifications have been implemented, such as metal doping. The aim of this study was to synthesize, characterize and evaluate the photocatalytic activity of copper-doped titanium dioxide nanoparticles (NPs) in the degradation of acetaminophen (ACF), an emerging contaminant of pharmaceutical origin. For the synthesis of Cu/TiO₂ NPs, mechanical milling and wet impregnation techniques with copper sulfate pentahydrate as a precursor were used. The characterization was carried out using various techniques, such as dynamic light scattering (DLS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) and ultraviolet-visible spectroscopy (UV-Vis). The results obtained reveal a reduction of the bandgap in the Cu/TiO₂ sample, indicating a higher efficiency in the absorption of visible light. In the photocatalytic evaluation, a significant improvement in the degradation of acetaminophen (77%) was observed when using copper-doped titanium dioxide nanoparticles. These findings suggest a great potential in the application of Cu-doped TiO₂ NPs for the decontamination of waters with the presence of emerging contaminants.

DEGRADATION STUDY IN FIRST STAGE RENE® 77 GAS TURBINE BLADES EXPOSED TO TEN THOUSAND HOURS OF SERVICE

Y. Salerno, A. Suárez, G. Navas, L. Martínez, D. Rodríguez — Tue, 05 Aug 2025 16:37:19 +0000

The René 77 nickel-based superalloy is used for critical elements such as industrial gas turbine blades. In this case, it is used in the first stage of the GE MS 7000 1B turbine. This type of blade is manufactured using the lost wax casting method, they are high-quality pieces. This work presents the microstructural study of Rene 77 blades, with rejuvenation heat treatment, which, in routine borescopic inspection, after 10,000 hours of service, presented surface cracking. At this stage of the turbine, the blades have a cooling system to preserve their integrity, so it is necessary to study the cracking mechanism present to corroborate whether the remaining ones can continue operating, be recovered or replaced. Several evaluations were carried out, including macroscopic and visual inspection of the outer surface of the blade and microstructural and chemical evaluation by SEM-EDS of samples extracted from the hottest zone, to the coldest zone of the root. The results obtained show a significant degradation that affects the microstructural stability throughout the blade structure. The thickening of the ' phase caused a change in its morphology, which affects the mechanical properties, since the ' phase acts as a barrier to the movement of dislocations, retarding thermo-creep, so the resistance to this mechanism decreased significantly. It is suggested that restoration of microstructure and properties can be effected with appropriate rejuvenation heat treatment.

MICROSTRUCTURAL CHARACTERIZATION OF PELLETS MADE WITH HEMATITIC MINERAL ASSOCIATED WITH HIGH DEGRADATION

Tue, 05 Aug 2025 16:47:06 +0000

In batches of pyroconsolidated pellets, produced at the Siderúrgica Del Orinoco SIDOR, C.A. From direct iron ore from the train and ore stored in the yards, similar deviations were detected in terms of Compressive Strength (C.R.), Abrasion Index (A.I.) and increase in the fraction <1/4" that are associated with degradation mechanisms. In order to explain this behavior, representative samples were selected from both batches of pellets, which were analyzed using optical microscopy and scanning electron microscopy techniques coupled with an energy-dispersive microanalyzer, complemented by analysis by X-ray Diffraction. , with the interest being the identification of the compounds or phases formed in pyroconsolidation. It is determined from these analyzes that both pellet samples are microstructurally similar, characterized by presenting sintered iron particles with molten silicate unions and untransformed gangue fractions. The presence of particles made up of magnesium-rich phases related to possible MF-Magnetite compounds (Magnesium ferrite dissolved in magnetite) with a faceted appearance, with a darker tone than the grain matrix, stands out. The origin of this last phase is attributed to operating conditions of high pyroconsolidation temperatures added to high MgO/SiO2 ratios in the pellet, which can negatively impact the resistance and favor its degradation. The XRD analysis confirms the presence of complex silicates associated with calcium - magnesium in a smaller proportion that is also related to slag enriched in magnesium.

MICROSTRUCTURAL AND THERMAL EVALUATION OF REFRACTORIES USED AS HEART MASS IN ELECTRIC ARC FURNACES (EAF) FOR THE MANUFACTURING OF STEEL

W. Barrios, E. Díaz, G. Basanta, M. Barrera, R. Basanta — Tue, 05 Aug 2025 16:55:30 +0000

The tamponable cold hearth mass refractory material is a mixture of high purity Fused Magnesia particles with sintered sand particles of magnesium, calcium, iron that is installed in bulk at the bottom of the melting furnace tank. This work presents the results of the study of representative samples of sole masses from different manufacturers, which presented varied performances in the plant. For its characterization, qualitative chemical microreactivity tests were carried out to determine the presence of carbonates in the refractory since their presence in this type of materials is unfavorable. In addition, a combination of techniques such as X-ray Diffraction (XRD), Thermogravimetry ( TGA), Differential Scanning Calorimetry (DSC) and the microscopic techniques of Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) coupled with an energy dispersive microanalyzer (EDX). A correlation was observed between the performance of the different types of screed masses and the microstructural observations obtained by MO and SEM. The proportions of the sinter and fused magnesia, the morphological aspects of the particles and details of the unions of the sinter particles were revealed, as well as their elemental chemical composition, the presence of hydrated compounds, carbonates present and sintering temperature were also detected. All of this allows us to predict the sintering behavior of a sole mass when it is subjected to working temperature and therefore estimate the quality of performance in the melting furnaces of the SIDOR electric billet steelworks.

STUDY OF THE EFFECT OF PH ON THE MORPHOLOGY AND CHEMICAL COMPOSITION OF ZIRCON AND ILMENITE USING SCANNING ELECTRON MICROSCOPY

N. G. Mendoza Duarte, C. E. Barrios Navarro, C. Urbina de Navarro — Tue, 05 Aug 2025 17:02:20 +0000

Zircon and ilmenite are heavy minerals that provide information about the geochemical evolution of different environments, and are also used in prospecting and exploration of mineral deposits. Therefore, this study aims to investigate the morphological, chemical and textural effects that take place in environments of acid mine drainage, acid rain, carbonatic environment and extreme conditions, after selecting crystals with well-defined faces and simulating the pH scenarios that characterize them. For each condition studied, the crystals were observed with a binocular loupe and a Scanning Electron Microscope (SEM), performing the chemical analysis using characteristic X-rays. Results obtained in this study indicate that zircon has greater textural, morphological and chemical alteration under basic pH conditions, obtaining a decrease in area, variations in the Si/Zr ratio and relative enrichment of rare earth elements, Ca, Al and Fe. Ilmenite presented its greatest changes in the most acidic pH conditions, producing precipitates, significantly smaller areas in extreme acidic pH, relative enrichment of Cu, Ti and, on the other hand, an evolution of chemical phases as the pH decreases.