bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of exfoliation method on graphite oxide. A comparison between exfoliation by ball milling and sonication in different media
Authors: Casallas-Caicedo F M , Vera-López E , Agarwal A , Drozd V , Durigin A , Wang C 
Published: November 2019

Abstract
Graphene oxide and reduced graphene have been exfoliated from graphite oxide synthesized by Hummer’s method. In order to establish a comparison, the exfoliation process was performed using two different methods, high energy ball milling and sonication. Each one was studied in two different media, organic solvent N-methyl 2 pyrrolidone and deionized water, obtaining four different products. The quality of the graphene and graphene oxides was studied using Raman spectroscopy. Structural characterization was performed using X-ray diffraction technique. The presence of oxygen-containing functional groups was determined by Fourier transform infrared spectra, while the morphology was investigated by scanning electron microscopy and energy-dispersive spectroscopy. The aim of this work is present a process to obtain graphene and graphene oxide of high quality at lower cost and better environmental conditions.
A study of zirconium plasma flow generated by a vacuum arc evaporator
Authors: Parada-Becerra F F , Dugar-Zhabon V D , Garníca H , Tsygankov P A 
Published: November 2019

Abstract
In the industry of hard coatings, the vacuum arc evaporator is one of the commonly used devices due to its high productivity, reliability and ability to operate in a non-gaseous medium. Apart from this, the imposition of an external magnetic field allows to control the localization of the arc spots both on the simple and sectioned (i.e. made from different materials) cathode surfaces. Another important feature of the vacuum arc evaporators is their capability to generate multi-charged ions. Applying a high voltage negative bias to the substrate, there can be formed the coatings with high adhesion due to the implantation effect. This paper presents some results of the study of the plasma flows generated by an industrial vacuum arc evaporator with a sectioned disk cathode composed of a zirconium in its central part with a titanium ring surrounding it. The mode of evaporator functioning is such that the arc spot motion gets limited by the zirconium disk, which results in producing the zirconium plasma flow. The quantitative characteristics and the energy distribution function of ions have been measured by a multigrid probe with a retarding potential. It has been proved that the multiply charged ions make up a significant part of the flow. The relations between the detected ion components are found as 87.4% Zr
+, 10.6% Zr
2+, 1.5% Zr
3+ and 0.3% Zr
4+. The presence of multi-charged ions is also confirmed by optical spectrometry measurements.
Analysis of contamination level of gases generated during the surface cleaning process of metal sheets with low-pressure cold plasma
Authors: López L M , Fajardo J I , Carrasquero E J , Villavicencio I J , López C P 
Published: November 2019

Abstract
The research addresses an analysis of the level of contamination generated by the gases produced when applying low-pressure cold plasma in a cleaning process of metal sheets used in the manufacture of white goods. A mixture of argon and oxygen ionized gases at 50% was utilized to break down the lubricating oil molecules deposited on the surface of the sheet metal. A statistically significant number of samples were selected, with different volumes of oil on the surface, between 6 ml and 34 ml. The samples were later subjected to a plasma discharge with a time of 72 s, a gas pressure of 0.6 bar and 50% power to determine the correlation of the oil volume with the levels of gases generated by the discharge, maintaining the degree of surface cleanliness, as given by contact angle values between 67.5 and 79 degrees, constant. For the analysis of results a Pearson correlation was applied for each detected gas. An analysis was later conducted of the relationship between the degree of cleanliness of the metallic surface, as given by contact angles at 16, 36 and 53 degrees, with the levels of the gases generated by the plasma discharge, keeping the volume of the lubricating oil on the surface constant at 5 ml. For the analyses, statistical tests were carried out to find the correlation between the predictor variables and the dependent variable to establish a multivariate linear statistical model. The results allowed the behavior of the level of contamination to be determined, establishing that the volume of oil does not influence the level of the gases generated by the use of low-pressure cold plasma. The results obtained allow us to understand the relationship between the contact angle that represents the quality of surface cleaning of oil-impregnated sheet metal and the level of contamination generated in the process.
The effects of edges on the electronic localization properties of graphene
Authors: Espitia J S , Gutierrez W , Páez C J 
Published: November 2019

Abstract
In this numerically work, we study the effects of edges on the electronic properties of graphene lattices in the quantum Hall regime using a proposed quantity called participation ratio, that is employed to analyze the localization properties of edge states. We use the tight- binding model to include the effects of the magnetic field and disorder. The effect of the edges on the energy levels of the system is studied through Hofstadter’s butterfly-like spectrum. Using the participation ratio and analyzing the contributions of the armchair and zigzag edges separately, we find that there are energy regions where the wave functions are clearly more localized in a specific edge type. The zigzag preferential localization is a reminiscence of the case without magnetic field and the armchair localization which is dependent on the disorder and the strength of the magnetic field, comes from the presence of magnetic field in the system. The results obtained contribute to the understanding of the localization properties of graphene lattices with edges.
Tensile mechanical behavior of a polymeric composite reinforced with 4-axial carbon fiber woven
Authors: Villegas D F , Pedraza-Rosas S L , Toloza-Meza S A 
Published: November 2019

Abstract
During the last thirty years, there has been a growth in the study and analysis of composite materials for automotive and aerospace industry which require lightweight materials with demanding mechanical properties. textile reinforce composite materials have advantages with respect to laminated composite materials such as better formability and out-of-plane properties. Therefore, the purpose of this research is to determine the mechanical behavior for uniaxial testing of a carbon fiber of a composite material reinforced with a quadriaxial carbon fiber woven in order to decrease the anisotropy of the woven composite material. Five specimens for each of the different orientations at 0, 30, 45, and 90 degrees; In addition, six specimens of a plain woven (the most common on the market) were tested, two specimens per orientation at 0, 45 and 90 degrees, in order to contrast the behavior of these with the proposed tissue. It was obtained that the properties in the composite materials change according to the direction in which the fibers are oriented; therefore, the results showed that the quadriaxial tissue and the stress value are less than the plain tissue, by 39%, only in the zero degrees orientation, then the plaint woven has a greater number of fibers in that orientation, the orientation of ninety degrees is higher by 17%, and in the case of forty-five degrees orientation, the value is 82% higher. In the same way, when we study the orientations in there is no fiber, in the plain woven of the direction in which there is no fiber, is forty-five degrees’ orientation and in the proposed tissue it is the thirty-degree one 30 degrees and it can be seen that, in this case, in the behavior of the quadriaxial tissue is greater the stress value by 66%.
Estimation of injection parameters of a bio-based composite material from the rheological characterization
Authors: Fajardo J I , Paltán C , López L M 
Published: November 2019

Abstract
This research work presents an analysis of the injection molding process of a natural fiber-reinforced composite, from the characterization of its rheological properties by the technique of capillary rheometry. Two of the main parameters of injection molding were estimated: the injection pressure and the clamping force. The rheological coefficients obtained were used as inputs in analytical and finite element models, for the prediction of the injection parameters. The results were compared, and it was observed that there is good agreement between them. The percentage errors between the two estimation methods were less than 5% for injection pressure and less than 10% for the clamping force. Also, the behavior of the material using different natural reinforcing contents (compositions of 20%, 30% and 40% fiber with a coupling agent at 4% and 8%) and the effect of its rheological properties on both the injection pressure and clamping force were evaluated. The study is of particular interest given that from the rheological characterization, the experimental values were adjusted to the Cross-WLF viscosity model and the adjustment coefficients, which contain both the reinforcing and coupling agent effects, were fed into the two methods of estimation of the injection parameters. The methodology used and the results obtained allow the prediction of the main parameters of injection molding of new bio-based composites, facilitating their use on an industrial scale.
Graphite formation in abnormal glow discharge
Authors: Alvarez B , Sarmiento-Santos A , Hernández Y 
Published: November 2019

Abstract
Graphite is made up of flat sheets of carbon atoms that form a periodic system of hexagonal rings of six atoms. Along the perpendicular direction of the sheets it has a low electrical conductivity, whereas this is greater throughout them. The possibility of separating the constituent sheets of the graphite and obtaining individual layers of it has led to the current scientific and technological revolution. Graphite can be produced synthetically in the laboratory, with low energy consumption, through the plasma of the abnormal glow discharge in direct current. In this work the abnormal glow discharge graphite formation is reported. The glow was initiated throughout a gaseous atmosphere containing acetylene, utilizing direct current power. In plasma generated in this type of discharge the secondary electrons, coming from the cathode, transfer their kinetic energy to the neutral molecules of the hydrocarbon causing dissociation, ionization and excitation of them. These processes generate active species that react with each other and with the substrate, producing carbon deposits on it. Under controlled conditions of temperature, acetylene content and deposition time, carbon deposits, with the characteristic structure of graphite, in abnormal glow discharge can be obtained. For this purpose, the abnormal glow discharge was established in an atmosphere composed of a mixture of 20% acetylene, 60% argon and 20% hydrogen at low pressure, in a temperature range from 400 °C to 900 °C. Under these conditions, on a copper substrate, a time of 15 minutes was used to obtain the carbon deposits. These deposits were analyzed by infra-red spectroscopy, Raman spectroscopy and scanning electron microscopy, identifying the structure of the graphite and observing the morphology of the deposits on the copper substrate.
Acetylene polymerization in plasma of direct current
Authors: Alvarez B , Sarmiento-Santos A , Vera-López E 
Published: November 2019

Abstract
Plasma polymerization is a technique that allows obtaining polymer of any type of hydrocarbon, including the non-polymerizable by standard methods. This because of in the plasma state the activation energy can be reduced for the realization of reactions difficult to be presented under standard experimental conditions. For plasma polymerization only the implementation of different types of discharges in the radio frequency regime has been reported, leaving aside the application of direct current discharges for this process. The acetylene polymer consists of carbon chains with alternation of single and double covalent bonds. The formation of this polymer has been reported using radio frequency discharges in the abnormal regime. The paper reports the formation of polymer from acetylene using the abnormal glow discharge in the direct current regime, a novel process not yet reported in the literature. The deposition of the polymer is carried out at different times on a polycrystalline copper substrate previously treated in a glow discharge of argon and hydrogen. For the generation of this polymer an atmosphere of 60% Ar+35% H2+5% C2H2 at 2 torr pressure and a temperature of 600 °C is used. The structural and morphological analysis of the deposits is carried out by infrared spectroscopy and scanning electron microscopy, respectively.
Manufacture and evaluation of the tensile properties of a biodegradable composite material reinforced with Colombian coconut fibers
Authors: Arciniegas M , Delgado W , Lesmes S , Pertuz A 
Published: November 2019

Abstract
The mechanical properties of a biodegradable composite material made with Colombian coconut fibers were studied. The study was carried out considering a random distribution of fibers within the composite material for three fiber/matrix compositions (10, 20 and 30) in weight-to-weight percentage. Each of these was subjected to tensile tests to evaluate the effect of the fibers in each composition, taking into account the mechanical properties of ultimate tensile strength and elastic modulus that allow selecting the composition of greater rigidity and subsequently evaluating its properties under the effects of compression forces. The results obtained show that the more rigid composite material corresponds to the fiber/matrix 20 percent composition, which presented a tensile strength of 13.83 MPa and an elastic modulus of 924.46 MPa comparable with those reported in the literature. This composition is the most fragile with a percentage of elongation is 2.27% and with low tenacity to withstand impact efforts. Finally, the behavior of the more rigid material was compared with the mechanics of Ramberg-Osgood and Hollomon, the latter being the most adjusted allowing to predict the properties of this type of materials. The results obtained expand the uses of Colombian coconut fibers as a biodegradable composite.
Effect of wetting/drying and heating/cooling cycles on geomechanical behavior of mudrocks in the Lutitas de macanal formation
Authors: Chaparro C A , Jiménez O J , Espitia J M 
Published: November 2019

Abstract
The mudrocks are weatherable materials, an intrinsic condition of mineralogy and sedimentary formation. In the Eastern Cordillera of the Colombian Andes lies this rocky material, which implies the degradation of physical and mechanical properties in the face of environmental factors, such as changes in humidity and temperature that are intensively propitiated in the tropical climate of the region, factors not considered in the design of civil works. The present study determines an experimental procedure in laboratory to reproduce the effect of the cycles of wetting/drying and heating/cooling in conditions and periods similar to the original ones of the geomaterials, by means of the steam equilibrium technique and thermal change, the processes were carried out on rock cores extracted from the Lutitas de Macanal formation that emerges in the municipality of Pajarito, Boyacá, Rancheria sector, Colombia. The results quantitatively determined the degradation of Young’s module and the resistance to uniaxial compression with the applied treatments, having a greater effect on the heating/cooling cycles in a period equal to that of wetting/drying generating greater damage to the rock due to pronounced cracking.
Characterization of the metallic phase and the slag phase obtained during the inertization of the cathodes of spent alkaline batteries using liquid aluminum
Authors: Molina-Silva J , Vera-Serna P , Delvasto P 
Published: November 2019

Abstract
In this work, a reactive melting procedure was implemented for the inertization of the manganese-containing cathodes of spent alkaline batteries. The process consisted of adding the cathode powder mixed with borax on top of molten aluminum at 1000 °C. By means of an aluminothermic reaction, manganese oxides are reduced and incorporated into the alloy. The presence of borax in the reactive mixture was found to be fundamental to obtain the Al-Mn alloy. The characterization of the metal phase and the slag phase by scanning electron microscopy and X-ray diffraction showed that manganese is reduced to form manganese borides in the slag and Al-Mn intermetallics in the alloy. This process could make feasible to use aluminum casting shops as processors of spent alkaline batteries.
Ablation energy, water volume and ablation time: Gold nanoparticles obtained through by pulsed laser ablation in liquid
Authors: Hernández-Maya M , Rivera-Quintero P , Ospina R , Quintero-Orozco J H , García-Castro A C 
Published: November 2019

Abstract
It was studied the production of gold nanoparticles from a gold target by pulsed laser ablation in liquid medium. This technique allows replacing conventional methods of preparing nanoparticles without the need for precursors, where gold is used in its metallic state. Experimental tests were performed to determine the appropriate synthesis conditions to achieve small particle sizes. The variables studied were water volume, ablation time and ablation energy. Gold nanoparticles with spherical geometry, in metallic, and nanocrystalline state were obtained without the need to use precursors and stabilizers. Ablation energy is the most influential variable on the particle size, because it was observed that when is increased the ablation energy is generate greater particle sizes.
Compositional, thermal and morphological characterization of recycled and modified elastomers for inclusion in commercial cement mixtures
Authors: Mora-Rodríguez G K , Hernández Carrillo C G , Pineda-Triana Y 
Published: November 2019

Abstract
Elastomers are natural or synthetic polymers used in the automotive, mining, mold, assembly and other industries, due to their mechanical resistance in a wide temperature range from 60 °C to 320 °C; however, the waste generated is not disposed of properly, especially in the manufacture of tires, which generates environmental problems like inadequate final disposal, generation of toxic gases and public health problems; Therefore, in order to recycle these wastes, the present investigation modified elastomers superficially in order to produce strong adhesion with inorganic compounds like cement, through oxidation and sulfonation processes. For this purpose, NaOH and KMnO4 solutions were prepared at a concentration of 5% and then impregnated in saturated NaHSO3 solution. Subsequently, the modified elastomer was morphologically characterized by scanning electron microscope, thermogravimetrically by differential scanning calorimeter; compositionally by infrared spectroscopy, Raman spectroscopy, X-ray fluorescence, energy dispersive X-ray analysis and hydrophobic tests using contact angle techniques, in order to establish morphological and chemical compatibility with inorganic compounds. Results evidenced inclusion of functional groups OH, C = O and SO3, the reduction of carbon present in weak bonds and the presence of inorganic components such as potassium, sodium, manganese and sulfur were evident. The scanning electron microscope shows an increase in the roughness and contact surface of the elastomer as a function of the inclusion of polar functional groups by surface chemical treatment. These characteristics are to generate greater inclusion and compatibility of elastomers of an organic nature in inorganic compounds like cement matrices.
Synthesis and characterization of a hybrid perovskite to be applied as an absorbent layer in solar cell
Authors: Soracá-Pérez G Y , Gómez-Reyes D K , Gómez-Cuaspud J A , Vera-López E , Pineda-Triana Y 
Published: November 2019

Abstract
This study is based on the synthesis and characterization of a hybrid perovskite based on tin chloride and methylammonium (CH3NH3SnCl3) as an absorbent layer in solar cells. Preparation of the hybrid material was carried out using the wet method from a precursor of methylammonium chloride CH3NH3Cl and tin chloride (II) (SnCl2). The solid obtained was heated to a temperature of 60°C in order to obtain the final product. The hybrid material was then characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The structural and morphological results showed the characteristic traits corresponding to the material. The formation of conglomerates with irregular spherical geometry and cubic forms associated with the precursor of tin chloride were also present. The application of this type of perovskite in solar cells is preferable due to its environmentally friendly impact, making it a promising material for photovoltaic technology.
Evaluation of the structural, thermal, rheological and morphological properties of polyethylene functionalized with a maleinized hyperbranched polyester
Authors: Ararat C A , Murillo E A 
Published: November 2019

AbstractThis experimental study was carried out with the aim of establishing and analyzing the thermal, structural, morphological, and rheological properties of a polyethylene functionalized with a maleinized hyperbranched polyester. This area of study has scarcely been reported. It is important to study the properties of this material, since it can be employed as functionalizing agent in blends of low density polyethylene and hydrophilic polymers. In addition, it also may be used as alternative for replacing the importation of polyethylene functionalized with maleic anhydride in our country. Therefore, in this experimental study, dicumyl peroxide was utilized to catalyze a functionalization reaction between low density polyethylene and maleinized hyperbranched polyester. In the experiment, dicumyl peroxide concentrations were maintained at 0.50 wt%, 1.0 wt%, 1.5 wt%, and 2.0 wt%. The resultant material after of the functionalization was characterized by various analytic methods including infrared analysis, contact angle, thermogravimetric analysis, X ray diffraction, rheological analysis and scanning electronic microscopy. The functionalization degree of the polyethylene functionalized with a maleinized hyperbranched increased with the dicumyl peroxide amount and in all cases it was higher than 8 weight percent.