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You searched for +publisher:"Drexel University" +contributor:("Barsoum, Michel W."). Showing records 1 – 2 of 2 total matches.

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Drexel University

1. Halim, Joseph. An X-Ray Photoelectron Spectroscopy Study of Multilayered Transition Metal Carbides (MXenes).

Degree: 2016, Drexel University

Recently, a new family of two-dimensional (2D) early transition metal carbides and carbonitrides, labeled MXenes, was discovered at Drexel University. MXenes are produced by selectively etching mostly Al from Al-containing MAX phases and replacing Al with surface termination groups. Theoretically it has been predicted that changing the nature of the surface terminations, T, can change MXenes' properties, such as electronic and optical, resulting in changes in performance in various applications such as electrodes for Li-ion batteries. Prior to this work, there had been little systematic effort devoted to carefully identifying and quantifying the exact nature of T. In this work, high resolution XPS spectra of multilayered Ti3C2Tx, Ti2CTx, Ti3CNTx, Nb2CTx, Nb4C3Tx, V2CTx, Mo2CTx, Mo2TiC2Tx, and Mo2Ti2C2Tx were acquired and analyzed. The influence of the M and X elements, the order of MXene, n, aging, Ar+ sputtering, and the concentration/nature of the etchants on the amounts of -O, -OH and -F, were systematically investigated. XPS analysis confirmed the intercalation of Li+ ions upon etching Ti3AlC2 using a mixture of LiF and HCl or LiCl and HF; when Ti3C2Tx multilayers is immersed in RbCl or NaCl solutions, cation exchange resulted in the replacement of Li+ ions with Rb+ or Na+, respectively. Similar cation intercalations were confirmed when treating HF-etched Ti3C2Tx samples with Ti3C2Tx with alkali metal hydroxides, such as NaOH and KOH. Based on quantification of the various chemical species before and after treatment, a mechanism was suggested where the reduction of -F terminations took place by exchanging with -OH and -O terminations and/or complete removal of Ti-F species and converting them to TiO2-Fx. From XPS peak fits for all MXene samples in this study, it was established that x was ≈ 2.0±0.2. Both -F and -OH terminations are formed during etching through the reaction of MXene with HF or H2O, respectively. However, for the -O terminations to form, a mechanism was suggested were some of the -OH terminations dissociate into -O termination and H+, where the latter reacts with an intercalated H2O forming [H3O]+. The latter are then replaced with cations via ion exchange. This reaction has been suggested based on the trend that, for most MXenes analyzed, the ratio between -O terminations and adsorbed water plus cations is equal to unity or lower, suggesting that all H+ that dissociates from the -O terminations reacts with H2O molecules to form H3O+. Only five compounds out of the sixteen studied were found not to follow this trend (in those cases the ratio was higher than unity) where further investigation is needed to determine the cause of this anomaly. Given that recent work reported that the average oxidation state of Ti in Ti3C2Tx is + 2.4, the average oxidation state of C - for 8 different samples - was determined to be ≈ -2.6±0.1. It is thus reasonable to conclude that the average oxidation states of Ti and C in Ti3C2Tx are weakly dependent on the etching conditions and/or intercalated cations. Similarly,… Advisors/Committee Members: Barsoum, Michel W..

Subjects/Keywords: Materials science; Nanostructured materials; Transition metal carbides; X-ray photoelectron spectroscopy

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APA (6th Edition):

Halim, J. (2016). An X-Ray Photoelectron Spectroscopy Study of Multilayered Transition Metal Carbides (MXenes). (Thesis). Drexel University. Retrieved from http://hdl.handle.net/1860/idea:6912

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Halim, Joseph. “An X-Ray Photoelectron Spectroscopy Study of Multilayered Transition Metal Carbides (MXenes).” 2016. Thesis, Drexel University. Accessed March 20, 2019. http://hdl.handle.net/1860/idea:6912.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Halim, Joseph. “An X-Ray Photoelectron Spectroscopy Study of Multilayered Transition Metal Carbides (MXenes).” 2016. Web. 20 Mar 2019.

Vancouver:

Halim J. An X-Ray Photoelectron Spectroscopy Study of Multilayered Transition Metal Carbides (MXenes). [Internet] [Thesis]. Drexel University; 2016. [cited 2019 Mar 20]. Available from: http://hdl.handle.net/1860/idea:6912.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Halim J. An X-Ray Photoelectron Spectroscopy Study of Multilayered Transition Metal Carbides (MXenes). [Thesis]. Drexel University; 2016. Available from: http://hdl.handle.net/1860/idea:6912

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Nelson, Matthew Jared. Synthesis and Characterization of Ti3SiC2/Mg and Cr2AlC/Mg Composites.

Degree: 2014, Drexel University

High strength, light-weight materials are in high demand in many applications; especially aerospace and the military. The focus of this work is to report on the fabrication and characterization of Ti3SiC2 and Cr2AlC MAX phase reinforced Mg and Mg-alloy metal matrix composites synthesized by pressureless melt infiltration. Pure Mg and Al-containing Mg-alloys (AZ31, AZ61 & AZ91) with varying Al content were matrices with loadings of ~ 45 1 vol. %. The resulting microstructures and mechanical properties were characterized by X-ray diffraction, scanning electron microscopy (SEM), and compressive stress testing. SEM revealed kinked, delaminated, and elongated Ti3SiC2 grain, and non-deformed, rounded Cr2AlC grain morphologies. Like in the Ti2AlC/Mg composite system, increasing the Al wt. % content in the matrix enhanced the mechanical properties of the Ti3SiC2 composite system, but had a deleterious effect on the properties of the Cr2AlC composite system. At 1.9 0.1 GPa, 346 4 MPa and 617 10 MPa, the Vickers hardness, yield strength and ultimate compressive strength, respectively, of the Ti3SiC2/AZ91 composite were the highest in this study. All composites fabricated in this work exhibited fully and spontaneously reversible hysteresis loops due to the back and forth motion of dislocations. A small change in reinforcement volume fraction was found to affect the measured mechanical properties.

M.S., Materials Science and Engineering  – Drexel University, 2014

Advisors/Committee Members: Barsoum, Michel W., College of Engineering.

Subjects/Keywords: Materials science; Alloys – Mechanical properties; Magnesium – Metallurgy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Nelson, M. J. (2014). Synthesis and Characterization of Ti3SiC2/Mg and Cr2AlC/Mg Composites. (Thesis). Drexel University. Retrieved from http://hdl.handle.net/1860/4486

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Nelson, Matthew Jared. “Synthesis and Characterization of Ti3SiC2/Mg and Cr2AlC/Mg Composites.” 2014. Thesis, Drexel University. Accessed March 20, 2019. http://hdl.handle.net/1860/4486.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Nelson, Matthew Jared. “Synthesis and Characterization of Ti3SiC2/Mg and Cr2AlC/Mg Composites.” 2014. Web. 20 Mar 2019.

Vancouver:

Nelson MJ. Synthesis and Characterization of Ti3SiC2/Mg and Cr2AlC/Mg Composites. [Internet] [Thesis]. Drexel University; 2014. [cited 2019 Mar 20]. Available from: http://hdl.handle.net/1860/4486.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nelson MJ. Synthesis and Characterization of Ti3SiC2/Mg and Cr2AlC/Mg Composites. [Thesis]. Drexel University; 2014. Available from: http://hdl.handle.net/1860/4486

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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