Leandro García-González

• PhD
• Researcher at University of Veracruz

Titanium sheets were anodized using a solution composed of HCl, ethylene glycol, and deionized water. To incorporate the doping elements, the salts K2Cr2O7 and Co(NO3)2·6H2O were added individually. The anodized sheets were heated to 600 °C, leading to a combination of anatase and rutile. A decrease in the intensity of the Raman spectra in the anat...

Electrochemical anodization (EA) of Ti–6Al–4V alloy was performed to evaluate the effect of NH4F concentrations (0.15–0.45 M), anodization times (5–120 min), and applied voltages (10–60 V) on surface morphology. The anodized samples were then subjected to thermal annealing (TA) at temperatures ranging from 400 to 650 °C. The main objective was to u...

Surface-Enhanced Raman Spectroscopy (SERS) has become of relevance over the years due to the increased number of substances that can be analyzed compared with conventional Raman spectroscopy. In the present work, TiO2 nanotubes were synthesized by electrochemical anodization with ammonium fluoride, ethylene glycol, and water-based electrolyte. Ag n...

In this research work, the effect of pH on the formation of the hexagonal phase of tungsten oxide was systematically studied using the hydrothermal method. The pH of the precursor solution was varied at 1, 2 and 3 and a 50 and 200 ml hydrothermal autoclave reactor was used. Post synthesis heat treatments were performed at 350 °C and 400 °C for a ti...

Up-conversion emission from HfO2 nanoparticles, as a host lattice, doped with Er³⁺ and Yb³⁺ ions and codoped with alkaline cations Li⁺ and Na⁺ obtained. The HfO2 nanoparticles, about 80 nm in diameter, were synthesized by the hydrothermal method at 200 °C for 1.3 h, and an additional heat treatment at 1000 °C was necessary to ensure the dopants inc...

The Internet of Things (IoT) requires non-pollution energy sources to power small electronic devices. These energy sources can be harvested using triboelectric nanogenerators formed by lightweight and eco-friendly components. Herein, we develop a novel triboelectric layer of coffee grounds for a triboelectric nanogenerator with ability to harvest t...

Acetaldehyde is a volatile organic compound that can cause damage at the cellular and genomic levels. The monitoring of acetaldehyde gas at low concentrations requires fast-response and low-cost sensors. Herein, we propose the design of an acetaldehyde gas sensor based on a low-cost Microelectromechanical System (MEMS) process. This sensor is forme...

One of the most challenging goals in materials science is to shift the absorption band of TiO2 toward the visible region of the electromagnetic spectrum. This is a fundamental strategy to improve its photocatalytic performance. In this paper, we present a simple methodology based on the sol-gel method, which allows the displacement of the band edge...

The room temperature synthesis of the core-shell-shell (CSS) nanoparticles was demonstrated to be green, low-cost, and reproducible. The magnetic core of Fe 3 O 4 nanoparticles was coated with TiO 2 and ZnO in two steps. The obtained CSS nanoparticles were extensively characterized by XPS, TEM, XRD, DRS-UV-vis, N 2 Phys-isorption, Electromagnetic,...

This work uses a simple one-step hydrothermal method to synthesize reinforced TiO2 nanomaterials with functionalized carbon nanotubes (F-CNTs) and PEDOT: PSS. Pure anatase TiO2 was obtained at 180 °C while TiO2 reinforced with F-CNTs helped to obtain anatase at 140 °C. Particularly, TiO2 reinforced with PEDOT: PSS yields ordered anatase at temperat...

In this work silver nanoparticles were deposited on ZnO nanorods by photoreduction of a solution without and with previously formed Ag nanoparticles (NPs): a process labelled as photodecoration where NPs firstly are synthesized and next photofixed over ZnO NRs under a laser irradiated solution and other method labelled as photogrowing where NPs sim...

Electrochemical anodization of the Ti–6Al–4V alloy was performed using two types of organic electrolytes, one of NH4F in ethylene glycol and the other of NH4F in glycerol. The anodization times and voltages were varied to observe changes in the hardness and friction coefficients. Hardness values of 4.14 GPa and 4.68 GPa were achieved for ethylene g...

Carbon nanostructures have an important role in research and technological progress due to their unique properties. A negative environmental impact can be caused by their synthesis. This work proposes to compare the influence of the carrier gas (low and high flow) in the synthesis of CNSs using recycled expanded polystyrene as a precursor. CNSs wer...

One-step chromium incorporation into TiO2 films was performed by an electrochemical anodizing process, using HCl as anodizing base solution and K2Cr2O7 as chromium precursor salt. Due to the corrosion process that arises from the use of high concentrations of HCl, the preparation of two different electrolytes was considered in order to carry out th...

Currently, electrochemical anodizing is one of the most common processes in materials science, since, under the right conditions, it allows to modify the material surface without damaging it by means of redox reactions, generating an oxide layer that protects the material and improves its properties. In this paper, grade 2 titanium was anodized usi...

Natural oxidation of Titanium allows the formation of a TiO2 coating that is known to present relevant tribological and photocatalytic properties. These aspects can be enhanced with nano-structural tailoring of the TiO2 surface, which can be achieved by electrochemical anodization. This work proposes the use of oxalic acid as an alternative for the...

In this work, structural, morphological, and luminescent properties of ZnO nanocolumns growth in different time 2 and 6 h, over a ZnO nanoparticles seed layer deposited on glass substrate at different temperatures by ultrasonic spray pyrolysis technique were studied. By scanning electron microscopy, the best vertical alignment was observed at 400 °...

Currently, different surface treatments have been studied to improve wear resistance and increase the hardness values of grade 2 titanium, based on morphological and structural changes. For this work, the impact of the annealing temperature on grade 2 titanium surfaces obtained by the electrochemical anodization technique using HCl in aqueous solut...

In this work, the methanolic fraction obtained from a rum distillation process was recycled as a precursor for the synthesis of carbon nanostructures by chemical vapor deposition. The nanostructures obtained were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. SEM micrographs showed the presence...

In a search for new alternatives for obtaining carbon nanostructures (CNSs) through more economical, environmentally friendly processes and for their possible industrial-scale production, chemical vapor deposition is the preferred method that can satisfy these requirements. This research proposes the synthesis of CNSs using expanded polystyrene as...

Ternary solar cells have proven to be a solution to absorb more photons at different wavelengths and reduce the recombination of charge carriers. Here, we propose a new hybrid organic-inorganic ternary planar solar-cell structure using a novel boron compound. The role of this material on the performance of the device with a polymer/borinate/ZnO con...

This article presents oxidation tests of titanium Grade 2 subjected to temperatures of 450 °C, 550 °C, 650 °C, 750 °C, and 1000 °C for 2 h. An analysis of the morphology of the oxidized surfaces was carried out and it was possible to observe the formation of oxide crystals from 750 °C. The cross section of the oxidized samples was analyzed to obtai...

ZnO nanostructures such as nanoislands, nanosheets, microflowers and nanoparticles were obtained successfully using a facile and rapid solution route employing low temperatures and reduced molar concentrations from precursor without using any surfactant agent or additional procedures. In this route, we use ZnCl2 as precursor ranging from 0.05 to 0....

The avocado seeds, considered as waste, were used for the extraction of oil rich in pentosans and starch. The avocado starch (AS) and a commercial starch (CS) are then used for the formation of polymeric films by casting. Avocado oil (AO, as natural crosslinker) and ethylene glycol (EG) are utilized as crosslinkers to modify the properties of the f...

Rosin derivatives used as coatings on a variety of substrates provide electrical insulation and corrosion protection. This paper explores the feasibility of using two chemically modified rosins, which are the glycerol rosin ester (GRE) and GRE-poly(methyl methacrylate) (GRE-PMMA) used as stainless steel coatings to reduce friction and wear rate. Th...

Grade 2 titanium was anodized with HCl, producing a TiO2 layer containing nanotubes. After annealing at various temperatures between 400 and 800 °C, the nanotubes in the layer were transformed into oxide grains due to a sintering process. It was determined that the anatase phase is present in the layers with formation of nanotubes and/or nanopartic...

In this study, coatings of 4, 8 and 16 Ti/TiN bilayers were synthesized by sputtering at a total deposition time of 64 min to control the total thickness. Hardness and adhesion are enhanced with increasing number of Ti/TiN bilayers, where 16 Ti/TiN bilayers shown the maximum hardness of 8.40 GPa, without decreasing the adhesion to the substrate ach...

The purpose of this research is to evaluate the effect of thermal oxidation on the surface of a Ti6Al4V alloy in terms of increasing hardness and improving its tribological values. A two-hour heat treatment was carried out at the following temperatures: 450 °C (TT450), 550 °C (TT550), 650 °C (TT650), 750 °C (TT750) and 1000 °C (TT1000). Starting wi...

In this work, the structure, morphology, and local electrical properties of lead sulfide films growth by Successive Ionic Layer Adsorption and Reaction was studied. Films were deposited from 100 to 500 cycles onto glass substrates. Film thickness increase from 100 to 800 nm with the number of deposition cycles. The deposited films are single phase,...

Currently the integration of sensors with a readout circuit and display are implemented in embedded systems for industrial, medical, chemical, and agricultural applications. This study presents the development of the conversion stage from analogical to digital, the calibration and the signal conditioning for an extended gate ion sensitive field-eff...

Abstract In this work, the electrochemical anodization process was carried out on titanium grade 2, using an electrolytic solution of 3 M and 0.15 M HCl with voltages of 11 V, 12 V and 15 V, as well as time variations in the experimental process and later an annealing process at 750 °C. According to the results obtained, the TiO2 coatings presented...

It was possible to obtain TiO 2 doped with K and Cr by electrochemical anodizing technique. An unexplored synthesis route was considered where the electrolyte used for the anodization was HCl and K 2 Cr 2 O 7 as the precursor of the incorporated metals. Subsequently, the heat treatment temperatures of 400, 500, 600, 600, 700 and 800 °C were varied...

Electrochemical anodization was performed for surface modification of Ti-6Al-4V, using an HCl-based electrolyte. The effect of increasing the electrode spacing of the electrochemical cell by 1, 2, and 2.5 cm on the hardness and COF was investigated. Using a 0.5 M solution of HCl and glycerol in different percentages (85, 90, and 95 %), a voltage of...

Synthesizing nanostructure’s importance is due to the applications that these materials can offer. Electrochemical anodization is considered an easily accessible technique; variables control allows to obtain diverse morphologies (from nanopores to nanotubes). The main reaction is oxide – reduction, it produces a protective oxide layer to metals and...

In this work, coatings based on hafnium/hafnium nitride (Hf/HfN) bilayers were synthesized by the magnetron sputtering technique, producing coatings with 4, 8 and 16 Hf/HfN bilayers on AISI 316L steel and silicon (100). The surface morphology was studied, which shows a high uniformity of grain cluster groupings. Their microhardness was evaluated wh...

A lo largo de la historia los seres humanos han desarro-llado capacidades físicas artificiales para facilitar la vida cotidiana, la posibilidad de aumentar la capacidad sen-sorial a partir de transductores y, en específico, mediante sensores, fundamentales en el avance y consolidación de la cuarta revolución industrial. Los sensores son dis-positiv...

Surface enhanced Raman spectroscopy (SERS) is considered a versatile and multifunctional technique with the ability to detect molecules of different species at very low molar concentration. In this work, hierarchical ZnO microspheres (ZnO MSs) and Ag/ZnO MSs were fabricated and decorated by hydrothermal and photodeposition methods, respectively. Fo...

With the use of the sputtering technique, carbon incorporation was carried out on TiO2 anodized with HCl. FE-SEM study revealed the formation of tubes and/or fibers nanostructures on the surface of the acquired samples. It was possible to identify the presence of carbon by vibrational modes and EDS analysis. The nanoindentation test demonstrated ho...

El acero inoxidable AISI 316L por sus características de resistencia a la corrosión en ambientes alcalinos, estabilidad mecánica a altas temperaturas es atractivo para diversas industrias como aeronáutica, automotriz, petroquímica, alimenticia e incluso instrumentos quirúrgicos. No obstante, cuando se encuentra en ambientes ácidos ricos en cloruros...

Volatile organic compounds pollute air in and out of homes, which effects human health when inhaled. It is necessary to monitor these gases with rapid response sensors at low concentrations, such as with electromechanical systems. We designed and simulated of a multilayer cantilever sensor using finite element method, which is 3 mm long, 2 mm wide,...

Currently, there are different synthesis techniques to obtain new materials, however, one of the most used is electrochemical anodizing, which, by means of oxide-reduction reactions, allows modifying the surface of a metal, thus generating an oxide layer that protects the material in such a way that it improves its hardness values. In this research...

Electrochemical anodizing is one of the processes that due to its practicality, versatility, and excellent results has been used for decades for the oxidation of any metallic surface and the formation of nanostructures. In the present work was anodized commercially pure titanium using a solution based on hydrochloric acid, ethylene glycol, and deio...

In this study, the titanium grade 2 surface was modified by the thermal oxidation process, generating an oxide layer that protects the material, to improve its tribological properties and increase the Vickers hardness values. For the thermal oxidation process, titanium was subjected to different oxidation temperatures, 750, 800, 825 and 850 °C for...

In this paper, we present a novel algorithm for the automatic detection and measurement of Vickers indentation hardness, using image processing. This algorithm uses image segmentation via binarization, automatically evaluating the mean and extreme gray values by means of standard histogram equalization so as to determine the optimal binarization th...

A student's t-test was applied in carbon nanospheres synthesis from cis-1,4-polyisoprene considering the green chemical principles. The synthesis was carried out by Chemical Vapor Deposition method with a quartz tube reactor using an AISI 304 steel bar as catalyst. It was possible to obtain two types of different samples, one from the surface of th...

TiO 2 titanium oxide is a material with many applications, due to its electronic and optical properties, the characterization of the nanostructures developed with this material is carried out in order to determine its physical, chemical, and mechanical properties. This article presents the results of TiO 2 multilayered thin film deposited in Cornin...

Titanium oxide (TiO 2 ) film was deposited on 304 stainless steel substrates using the spin coating technique. The synthesis of the deposited solution was with the sol-gel method at room temperature, using titanium isopropoxide as a precursor. Obtained film was thermally treated at temperatures of 500 °C, 550 °C and 600 °C. The X-ray diffraction (X...

Since the discovery of carbon nanotubes, they have been intensely studied as filler materials into different matrices, including polymers to obtaining composites with enhancing properties. Carbon spheres are other type of nanostructures that have not been enough studied as reinforcement material. Polymeric composites with enhanced properties have g...

Microstructured Coating of TiO2 on Titanium Grade 2 Generated by Thermal Oxidation to Improve its Hardness - Volume 26 Supplement - A. Maytorena-Sánchez, L. García-González, L. Zamora-Peredo, J. Hernández-Torres, M.A. Hernández-Campos, F. López-Huerta

Surface Evaluation of Photoactivated TiO2 Films - Volume 26 Supplement - R. M. Woo-Garcia, L. García-González, A. L. Herrera-May, C. Zuñiga-Islas, W Calleja- Arriaga, J. Molina-Reyes, M. Pacio-Castillo, F. López-Huerta

Zinc oxide nanostructures such as nanosheets (NS) and nanoflowers (NF) were obtained by a facile hydrothermal synthesis using zinc chloride (ZnCl2) as precursor with low molar concentrations and a short synthesis time (2 hours) at 200 °C. By means of X-Ray diffraction and Raman spectroscopy measurements, the wurtzite-type ZnO structure was confirme...

Hexagonal ZnO nanocolumns were synthesized by chemical bath deposition on previously deposited ZnO nanoseeds on Corning glass substrates, at deposition temperatures from 300 to 550 °C in steps of 50 °C, by ultrasonic spray pyrolysis technique. The ZnO nanoseeds were previously suspended in the spraying solution, with and without ultrasonic dispersi...

Nanoparticles and nanopores of iron oxide were synthesized by electrochemical anodization, in an electrolytic medium of ammonium fluoride (NH 4 F), deionized water and ethylene glycol. After anodization, the Fe foils were annealed at 450 °C for 2 hours. Different anodization times and two concentrations of NH 4 F (0.1 M and 1.2 M) were evaluated, u...

In this work, the anodization of grade 2 titanium was performed using a HCl-based electrolyte in order to obtain Titania nanostructures. Different glycerol concentrations were added to the HCl electrolyte to study the effect it has on the shape and density of the nanostructures, additionally, anodization time and voltage was also varied. The anodiz...

We studied the surface morphology and biocompatibility of hydrogenated amorphous silicon-germanium (a-Si1-xGex:H) thin films prepared by Low Frequency Plasma Enhanced Chemical Vapor Deposition (LF-PECVD). These films were deposited on a Corning 2947 glass substrate having a thickness of 3 μm, the electrical performance showed a decreased electrical...

Different nanostructures such as: CuOH nanorods, CuO nanosheets and Cu2O nanograins were obtained by anodization approach at room temperature during times from 10 to 40 minutes. By scanning electron microscopy technique, it was found that Cu2O nanograins were formed at 10 minutes, CuO nanosheets vertically oriented on nanograins were observed at 20...

Carbon spheres used as filler materials are ideal and promising nanostructures to obtain composites with enhanced electrical and mechanical properties. Solid carbon spheres synthesized previously in this research by chemical vapor deposition were incorporated in poly(methyl methacrylate) through solution mixing at different loads (5 wt.%, 7 wt.% an...

Calcium silicate-based materials have been shown to be bioactive due to their ability to produce biologically compatible carbonated apatite. The objective of this study was to analyze the bioactivity of Biodentine ™ and MTA Repair HP® in contact with human dentine discs, which were sealed and divided randomly to form four groups: group 1 Biodentine...

Uniform shaped carbon spheres, a material with several potential applications, were synthesized from a serial of aromatic hydrocarbon pyrolysis precursors (benzene, naphthalene, anthracene and pyrene), by chemical vapor deposition at atmospheric pressure, and at moderately low temperatures with stainless steel catalyst. A high carbon sphere yield,...

Titanium-Silicon Oxynitride (TiSiNO) coatings were synthetized by reactive co-sputtering technique on stainless steel 304 substrates varying the substrate temperature during the deposition. Two targets were used simultaneously, the first one of Ti on a DC source at 100 W and the second was a Ti-Si-O target on a pulsing RF source at 180 W. X-ray dif...

Composites from carbon nanotubes and polymers have been synthesized and studied. The composites were obtained joining carbon nanotubes with polymethyl methacrylate, nylon-6 and polystyrene. The materials were observed through scanning electron microscopy to evaluate the carbon nanotubes dispersion in the polymeric matrices. FTIR and Raman spectrosc...

Rosin resin is constituted by rosin acids, in particular, abietic acid, which is an inexpensive substance. This paper concerns the study of the molecular interactions between a bifunctional monomer of abietic acid with isocyanate to form polyurethane. Polyurethane is a varnish that can be applied to any timber surface protecting it from chemical an...

Several electronic applications have been developed through the use of carbon nanotubes and polymer composites. Multiwalled carbon nanotubes (MWCNTs), functionalized and pristine, were incorporated in polycaprolactam matrix; hydrochloric acid (19 and 38%) and formic acid (88%) were used as polymer solvents. Mechanical stirring method was employed t...

The aim of this paper was to study the effect of Fe at low concentration in self-organized titania nanotube (TNT) arrays by using a convenient one-step synthesis process. The synthesis was done by electrochemical anodization of titanium sheets in an electrolyte solution formed by ethylene glycol (EG), ammonium fluoride (NH4F) and deionized water. I...

Calcium silicate-based materials have been shown to be bioactive due to their ability to produce biologically compatible carbonated apatite. The objective of this study was to analyze the bioactivity of Biodentine ™ and MTA Repair HP® in contact with human dentine discs, which were sealed and divided randomly to form four groups: group 1 Biodentine...

Nanostructured TiO 2 and TiO 2 /W thin films were deposited on Corning glass substrates by RF and DC mag-netron co-sputtering at room temperature, using three targets of TiO, Ti and W. After deposition, samples were subjected to an annealing treatment in air at 500 °C for 3 hrs. The effect of the annealing treatment and tungsten addition to the TiO...

The effect of annealing temperature on the structural properties of Al-N codoped ZnO films were studied by X-ray diffraction, photoluminescence and Raman spectroscopy. ZnO films were deposited by sputtering technique on silicon substrates at 20 ºC, Al-concentration was kept constant and N-flow was changed to 6, 12 and 15 sccm. A thermal treatment w...

The principal carbon nanotubes synthesis processes also involve the production of nanoparticles with different dimensions and morphology. In this research carbon nanotubes and carbon nanobeads were synthesized by one-pot chemical vapor deposition method, using a quartz experimental reactor at 760 °C. Benzene was used as carbon source, ferrocene as...

This work presents the experimental results of the study of the pericarp of unripe and ripe fruits of different varieties of habanero chili peppers (Capsicum chínense Jacq.) - Mayan Kisin, Mayan Ek and Mayan Kiin - using Raman spectroscopy. The unripe fruits of the three varieties were green, but they turned different colors at maturity: yellow (Ma...

Carminic acid (CA) was added by two processes: dipping or in situ, to cellulose nanoparticles previously obtained using Span 80 and 85 as emulsifiers. The resulting nanoparticles were analyzed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Fourier Transform Infrared (FTIR) spectroscopy. According to both SEM and AFM studie...

Titanium carbide derived carbons were obtained from hydrochlorination reaction at 300, 500, 700 and 900 °C. The effect of the mixture hydrogen/chlorine, as reaction atmosphere, has been analyzed using X-ray diffraction, Fourier transform infrared, Raman and electron energy loss spectroscopies. Infrared spectroscopy showed several bands related to t...

The aim of this research is to ameliorate the dispersion of pristine and functionalized Carbon Nanotubes (CNTs) into polystyrene with hydroxyl end groups (PSOH) matrices using low magnetic fields. The Multi-Walled Carbon Nanotubes (MWCNTs) were synthesized by chemical vapor deposition (CVD) using benzene as carbon source; to produce CNTs with and w...

In this work, we present a theoretical study of methyl methacrylate (MMA) living anionic polymerization. The study was addressed to understanding two important experimental observations made for Michael Szwarc in 1956. The unexpected effect of reactive sites concentration in the propagation rate, and the self-killer behavior of MMA(deactivating of...

This work presents the experimental results of the study of the pericarp of unripe and ripe fruits of different varieties of habanero chili peppers (Capsicum chinense Jacq.) - Mayan Kisin, Mayan Ek and Mayan Kìin - using Raman spectroscopy. The unripe fruits of the three varieties were green, but they turned different colors at maturity: yellow (Ma...

Variation of the reaction time at 30, 60, 90 and 120 min, respectively, on the chlorination of Ti(C 5 H 5 )Cl 2 , at 900°C, has delivered carbon materials with a tuneable mixture of mesopores and micropores, surface areas as high as 855 m2g ⁻¹ and pore volume of 0.56 cm ³ g ⁻¹ . The cyclic voltammetry measurements yielded capacitances as high as 19...