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Your search keyword '"Raquel Garza"' showing total 3 results
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3 results on '"Raquel Garza"'

1. Fine-Tuning Cathode Performance: The Influence of Argon Deposition Pressure on LiMn2O4 Thin Film Electrochemistry for Li-Ion Batteries

Author

Fabián Ambriz-Vargas, Raquel Garza-Hernández, José Salvador Martínez-Flores, Francisco Servando Aguirre-Tostado, Eduardo Martínez-Guerra, and Manuel Quevedo-López

Subjects
lithium-ion battery, LiMn2O4 cathode materials, sputtering deposition, Production of electric energy or power. Powerplants. Central stations, TK1001-1841, Industrial electrochemistry, TP250-261
Abstract

Lithium manganese oxide (LiMn2O4) is an effective cathode material for high-capacity lithium-ion (Li-ion) batteries. Therefore, to optimize battery efficiency, it is essential to understand how sputtering deposition conditions affect the quality and performance of LiMn2O4. This research examines how argon deposition pressure affects the stoichiometric characteristics and electrochemical performance of LiMn2O4. The study finds that changing argon deposition pressures, from a low of 5 mTorr to a high of 30 mTorr, results in the formation of different coating stoichiometries. At low argon deposition pressures, stoichiometric LiMn2O4 cathode coatings formed, exhibiting the highest discharge capacity of 115 mAh/g. Conversely, at high argon deposition pressures, non-stoichiometric LiMn2O4 with lithium deficiency was produced. These coatings exhibited diminished electrochemical behavior, achieving a discharge capacity of only 70 mAh/g at 5 mTorr. The lack of lithium resulted in a significant reduction in electrochemical performance, indicated by a high surface charge transfer resistance (R2 = 48,529 Ω), which led to a low discharge capacity of 40 mAh/g.

Published
2024
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2. The Development and Characterization of a Cotton–Chitosan Composite for Lead Removal from Water

Author

Jorge Luis Menchaca-Arredondo, Diana Alonso-Segura, Luis Hernández-García, Belén Chamorro-Garza, Mario Sánchez, and Raquel Garza-Hernández

Subjects
lead, Materials science, Aqueous solution, Polymers and Plastics, technology, industry, and agriculture, Infrared spectroscopy, Organic chemistry, macromolecular substances, General Chemistry, Article, Chitosan, chemistry.chemical_compound, Adsorption, cotton fiber, QD241-441, chemistry, X-ray photoelectron spectroscopy, Chemical engineering, Ultimate tensile strength, composite, Cellulose, Fourier transform infrared spectroscopy, chitosan
Abstract

Heavy metals in water are a serious environmental problem due to their accumulation and toxicity, there are several processes we can use to address this issue, but adsorption is the most popular due to its simplicity and efficiency. Polysaccharides such as cellulose have received attention as adsorbents for heavy metals, and cotton–chitosan composites (CCs) were developed here with nontoxic reagents such as carboxylic acids as crosslinkers and NaH2PO4 as a catalyst to achieve chitosan covalent crosslinkage into oxidized cotton textiles with H2O2. The composites were characterized by fourier-transform infrared spectroscopy (FTIR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), atomic-force and scanning electron microscopy (AFM and SEM), and tensile strength, the adsorption of lead ions (Pb) was evaluated with cotton–chitosan composites and quantified by microwave plasma atomic emission spectroscopy (MP-AES). The composites showed a maximum incorporation of chitosan of 27.62 mg per gram of cotton textile. A tensile strength analysis of the composite showed a Young’s modulus approximately 1 MPa higher than that of cotton textile. The adsorption of lead ions with composites in an aqueous solution at pH 5 and 25 °C was circa 74% after 6 h of contact, as determined by MP-AES. This work is an approach to demonstrate the potential of these polysaccharides, modified by “green” procedures to remove pollutants from water.

Published
2021

3. Chitosan Functionalized with 2-Methylpyridine Cross-Linker Cellulose to Adsorb Pb(II) from Water

Author

Edgar F. Morán-Palacio, Luis Hernández-García, Mario Sánchez, Raquel Garza-Hernández, Mario Almada, Jorge Lozano-Montante, and Guillermo Niño-Medina

Subjects
Aqueous solution, Polymers and Plastics, 2-Methylpyridine, Succinic anhydride, Organic chemistry, General Chemistry, Article, cellulose, Chitosan, chemistry.chemical_compound, QD241-441, Adsorption, chemistry, adsorption, kinetics, Succinic acid, Pyridine, isotherms, chitosan, Cellulose, Nuclear chemistry
Abstract

In this study, chitosan was chemically modified with 2-methylpyridine. Subsequently, the modified chitosan was cross-linked to cellulose using succinic anhydride. Additionally, the capacity of cellulose derivatives to adsorb Pb(II) ions in an aqueous solution was studied through the determination of Pb(II) ions concentration in water, using microwave plasma atomic emission spectroscopy (MP-AES). A maximum adsorption capacity of 6.62, 43.14, 60.6, and 80.26 mg/g was found for cellulose, cellulose-succinic acid, cellulose-chitosan, and cellulose-chitosan-pyridine, respectively. The kinetic data analysis of the adsorption process showed a pseudo-second-order behavior. The increase in metal removal from water is possibly due to metal chelation with the carbonyl group of succinic acid, and the pyridine groups incorporated into chitosan.

Published
2021
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