Search

Your search keyword '"Vasquez, Magdaleno R."' showing total 43 results
Start Over Author "Vasquez, Magdaleno R."
43 results on '"Vasquez, Magdaleno R."'

12. Elucidating the Mechanism of Large Phosphate Molecule Intercalation Through Graphene Heterointerfaces

Author

Liang, Jiayun, Ma, Ke, Zhao, Xiao, Lu, Guanyu, Riffle, Jake V., Andrei, Carmen, Dong, Chengye, Furkan, Turker, Rajabpour, Siavash, Prabhakar, Rajiv Ramanujam, Robinson, Joshua A., Vasquez, Magdaleno R., Trinh, Quang Thang, Ager, Joel W., Salmeron, Miquel, Aloni, Shaul, Caldwell, Joshua D., Hollen, Shawna M., Bechtel, Hans A., Bassim, Nabil, Sherburne, Matthew P., and Balushi, Zakaria Y. Al

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

Intercalation is a process of inserting chemical species into the heterointerfaces of two-dimensional (2D) layered materials. While much research has focused on intercalating metals and small gas molecules into graphene, the intercalation of larger molecules through the basal plane of graphene remains highly unexplored. In this work, we present a new mechanism for intercalating large molecules through monolayer graphene to form confined oxide materials at the graphene-substrate heterointerface. We investigate the intercalation of phosphorus pentoxide (P2O5) molecules directly from the vapor phase and confirm the formation of confined P2O5 at the graphene heterointerface using various techniques. Density functional theory (DFT) corroborate the experimental results and reveal the intercalation mechanism, whereby P2O5 dissociates into small fragments catalyzed by defects in the graphene that then permeates through lattice defects and reacts at the heterointerface to form P2O5. This process can also be used to form new confined metal phosphates (e.g., 2D InPO4). While the focus of this study is on P2O5 intercalation, the possibility of intercalation from pre-dissociated molecules catalyzed by defects in graphene may exist for other types of molecules as well. This study is a significant milestone in advancing our understanding of intercalation routes of large molecules via the basal plane of graphene, as well as heterointerface chemical reactions leading to the formation of distinctive confined complex oxide compounds.

Published
2023

42. Grafting of acrylic acid onto microwave plasma-treated polytetrafluoroethylene (PTFE) substrates

Author

Kenneth, John, Nakajima, Hideki, and Vasquez, Magdaleno R.

Abstract

Polytetrafluoroethylene (PTFE) has limited use in biomedical applications due to its poor wettability and low adhesion strength. Enhancing these properties through modification via plasma treatment coupled with grafting can further improve its surface properties ideal for biomedical applications. In this study, hydrophilic PTFE samples were successfully realized using a modified 2.45 GHz microwave oven as the plasma treatment device followed by grafting copolymerization using acrylic acid (AAc). This resulted to an increase in surface free energy (SFE) where samples subjected to air plasma treatment and AAc grafting exhibited the largest increase in SFE of 58 mJ m[?]2 compared to 17 mJ m[?]2 for the untreated samples. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy revealed new functional groups in the O1s and C1s regions of PTFE after plasma treatment and grafting. Atomic force microscopy analysis showed increase in surface roughness with the largest value of 67.7 nm found in air plasma-treated and grafted samples compared to 20.9 nm for the untreated PTFE sample. The plasma-treated and grafted PTFE surfaces did not exhibit hydrophobic recovery during a 7 d observation period as compared to plasma-treated samples only. The effective combination of plasma treatment and grafting process would broaden potential applications of PTFE as a biomaterial.

Published
2019

43. Mechanical properties of epoxy composites with plasma-modified rice-husk-derived nanosilica

Author

Athena, Fatima, Panghulan, Glenson R., Pechardo, Jason, and Vasquez, Magdaleno R.

Abstract

In this study, we explored the use of rice-husk-derived nanosilica (nSiO2) as fillers in epoxy resins. The nSiO2 was irradiated with a capacitively coupled 13.56 MHz radio frequency (RF) plasma using an admixture of argon (Ar) and hexamethyldisiloxane (HMDSO) or 1,7-octadiene (OD) monomers. The plasma-polymerized nSiO2 was loaded at various concentrations (1-5%) into the epoxy matrix. Surface hydrophobicity of the plasma-treated nSiO2-filled composites increased, which is attributed to the attachment of functional groups from the monomer gases on the silica surface. Microhardness increased by at least 10% upon the inclusion of plasma-modified nSiO2 compared with pristine nSiO2-epoxy composites. Likewise, hardness increased with increasing loading volume, with the HMDSO-treated silica composite recording the highest increase. Elastic moduli of the composites also showed an increase of at least 14% compared with untreated nSiO2-filled composites. This work demonstrated the use of rice husk, an agricultural waste, as a nSiO2 source for epoxy resin fillers.

Published
2018

Catalog

Books, media, physical & digital resources
See catalog results