Chemical Engineering Master's Theses

Towards rare-earth-free permanent magnets: exchange bias in binary Mn-based alloys

Joshua Marion — Thu, 16 May 2013 07:33:15 PDT

Quantum–mechanical exchange interactions between phases in ferromagnetic/antiferromagnetic (FM/AF) magnetic nanocomposite systems can result in useful effects such as exchange bias (H_ex) and remanence enhancement. These effects are more pronounced in nanostructured systems than in their coarse–grained counterparts due to improved interphase contact and can be developed to create good permanent magnetic behavior, but are currently poorly understood in bulk three–dimensional systems. To achieve this goal, factors such as the magnetic and structural phase identity, chemistry, size, shape, and character are investigated. To this end, synthesis, characterization and analysis of the magnetic and structural properties of nanocomposites are carried out on...

Electrodeposition of NiW, NiWMo and NiMo alloy thin films and NiW nanowires

Tetiana Bairachna — Thu, 15 Mar 2012 13:30:29 PDT

Tungsten and molybdenum alloys with iron-group metals, particularly NiW and NiMo alloys, are well known to possess outstanding functional properties such as thermal, wear and corrosion resistance, high microhardness, and excellent catalytic activity towards hydrogen evolution. They have been electrodeposited as thin films, and rarely as nanowires, despite the potentially superior properties and applications that nanowires can offer. The research presented is the first demonstration of NiW nanowires.

The electrolytes for deposition of NiW, NiWMo and NiMo alloy thin films and NiW nanowires were developed. One challenge in depositing these alloys is in reaching a high amount of W or...

Multi-scale replication of small intestine basement membrane via chemical vapor deposition

Brian Jarrett McMahon — Wed, 12 Oct 2011 07:30:24 PDT

In 2010, oral drug delivery was a $49 billion industry. The major portal for the uptake of medicines delivered orally is the small intestine. One of the greatest features of the small intestine is the large surface area, created by an intricate structure of finger-like projections called villi and well-like invaginations called crypts. To help predict bioavailability of rapidly developed candidate drug compounds, cell culture models are frequently used. However, these tests are often inaccurate. It is hypothesized that the lack of cell culture substrate biochemistry and topography are major factors in the difference in cell function between in vivo...

Enhancement of oxygen reduction reaction (ORR) by electrodeposited PtFeCo multilayered alloys

Alex Avekians — Fri, 08 Jul 2011 08:11:55 PDT

The oxygen reduction reaction (ORR) for low temperature fuel cell applications limits its performance due to sluggish kinetics. A new attempt to improve the ORR reaction kinetics were investigated through fabrication of multilayered PtFeCo alloys, by means of pulse potential deposition, to create catalysts with a nano-layered structure. The distinct nano-scaled layers had a Pt-rich or FeCo-rich composition. Prior to making multilayer catalysts, thin films were deposited under constant potential. Data obtained from from thin film electrodeposits facilitated the identification of elemental composition and thickness at the applied potentials of interest.

Potentiostatic deposition of the ternary alloys occurred at more...

Synthesis of nano anatase for titanosilicate ETS-10 synthesis

Shihara Shafeque — Tue, 26 Apr 2011 10:06:32 PDT

Functionalized textiles present a vast and growing niche in the global textile market at US $400 billion [1, 2]. Engelhard Titanium Silicate 10 (ETS-10), a photocatalytic zeo-type material if coated on textiles, is expected to impart useful properties similar to TiO₂, such as stain-resistant, odor repellant, bactericidal and enhanced UV protection [3, 4]. Typically, small ETS-10 crystals of size ~300-800 nm are synthesized using solid titania (e.g., anatase or P25) sources [5, 6, 7]. However, smaller ETS-10 crystals are required for a uniform surface coating with highly effective surface area. The dissolution of titania particles (i.e., their size) is hypothesized...

Size-based cell sorting by deterministic lateral displacement

Deepa Sritharan — Fri, 18 Dec 2009 11:52:38 PST

Microfluidic devices offer several advantages over conventional, large scale cell sorting systems. Creating microfluidics technology for lab-on-a-chip adaptations of these systems provides several benefits: simplicity of operation, improved transport control, portability, greater accessibility, reduced cost and potential for integration with other analytical techniques. This technology supplies important tools for biomedical applications such as tissue culture, drug discovery and point-of-care diagnostic systems. This work presents a microfluidic device which uses asymmetric bifurcation of laminar flow around objects for the continuous separation of cell subpopulation from a heterogeneous cell suspension. Based on their size, each cell chooses its path through the device...

Investigation on in-situ growth of carbon nanotube network by chemical vapor deposition for electrical interconnect applications

Eko Ariyanto Pandowo — Fri, 18 Dec 2009 11:52:37 PST

According to Semiconductor Industry Association (SIA), global sales of semiconductors reached $247.7 billion in 2006, an increase of 8.9 percent from the $227.5 billion reported in 2005. Due to the increasing consumer demand for smaller computers that process data at a much faster rate, processors that have a large number of transistors and interconnects per chip are required. For more than 40 years, the semiconductor industry has been able to improve the performance of electronic systems by doing continuous miniaturization or scaling of electronic devices that has led to faster and denser circuitry. This trend has resulted in feature sizes...

Evaluation of titanium dioxide for the adsorption and reactivity of the sulfur mustard simulant 2-chloroethyl ethyl sulfide

Edward Viveiros — Fri, 18 Dec 2009 11:52:36 PST

This thesis reports the investigation of the degradation of the sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) over the metal oxide TiO2. The ultimate goal is the development of catalytic adsorbent materials that more effectively decontaminate surfaces at ambient conditions once they have been exposed to chemical warfare agents (CWAs) such as sulfur mustard (HD). TiO2 is an appealing candidate for this application because of its reported use in photocatalysis and pollution control under ambient conditions. For this reason, the interactions of CEES on commercially available polycrystalline Evonik-Degussa Aeroxide® P25 and amorphous NanoActiveTM TiO2 were investigated. Each commercial sample was...

Electron transport mechanism of titania chains in the framework of titanosilicates ETS-4 and ETS-10

Önnaz Özkanat — Fri, 18 Dec 2009 11:52:35 PST

Current techniques for preparation of low dimensional devices present technical difficulties and concomitant costs. This is especially true in the fabrication of aligned quantum wire arrays. Microporous crystalline titanosilicate materials, ETS–,4 and ETS–,10, are hypothesized to have naturally occurring quantum wires in their framework. They contain monatomic titania chains (…,Ti–,O–,Ti–,O–,Ti…,) isolated from each other by a highly siliceous matrix. These titania chains (6.7 Å, in diameter) in ETS-4 run in only the b direction, while they run in both a and b directions in ETS–,10. Electron transport properties of titania chains –,as hypothesized quantum wires–, in the framework of individual...

Controlled growth of uniform diameter multi-wall carbon nanotube arrays via chemical vapor deposition for application in field emission devices

Jonathan Gar-Sing Leong — Fri, 18 Dec 2009 11:52:34 PST

With the flat panel display industry eclipsing $101 Billion in 2007 and consumer demand for improved picture quality ever growing, field emission has received increased attention. Traditional field emitters have higher pixel density than current displays, but their contrast ratio suffers due to insufficient emission current. An ordered array of multi-wall carbon nanotubes (MWCNTs) should produce much higher emission currents due to their >100x increase in aspect ratio. However, such a device has not yet been demonstrated due, in part, to the challenge of fabricating an ordered vertical array of straight, uniform diameter MWCNTs. MWCNTs were grown in a chemical...

Electrosynthesis of TiO2-Au composites for water splitting applications and their photoelectrochemical characterization

Jessy Elhajj — Fri, 18 Dec 2009 11:52:34 PST

Hydrogen is one alternative clean fuel for micro-scale devices when generated by solar irradiation through water splitting. The photoelectrolysis of water has been intensively studied since the seminal work of Fujishima and Honda in 1972 where titania was used as an anode photocatalyst [1]. While TiO2 is an attractive material because it is inexpensive and a well known catalyst for water dissociation, one of the major drawbacks that limits its practicality is that it only absorbs light in the UV region. Recent results of combining Au nanoparticles with TiO2 has been suggested to prevent electron hole recombination of the photoexcited...

Chemical vapor deposition of low-dielectric constant organosilicon-based thin films

Nariné Razmik Malkhasyan — Fri, 18 Dec 2009 11:52:33 PST

In contemporary semiconductor devices speed and functionality depends on signal propagation and, subsequently, on the geometrical design of the device and its material properties. Power dissipation, current leakage, and cross-talk noise are the issues plaguing signal propagation. These issues can be crucial at the dimensions of ultra-large scale integrated devices, as they increase exponentially with decreasing dielectric layer thickness. Thus, having a dielectric with excellent insulating properties is critical, since it can abate these issues. Organosilicon thin films are a natural choice for dielectric layers, since they are similar to the previously used silicon dioxide, can be deposited using the...

Application of the x-ray photoelectron spectroscopy for development of the niobium chemical mechanical process, photomodification of silicon for the field release mass spectrometer, and analysis of the multifunctional oxide heterostructures

Natalia Maximova — Fri, 18 Dec 2009 11:52:32 PST

X-ray photoelectron spectroscopy (XPS) provides information about the elemental chemical composition of a surface and the bonding states of those elements. This information is critical to diverse applications where the surface of the material determines its functionality such as tuned catalysts, engineered polymer coatings, and nanoelectronic heterostructures. For this thesis, XPS has been applied in both traditional and novel ways to niobium surface polishing, silicon surface modification, and electronic structure measurement. The current method for fabricating niobium superconducting cavities produces rough and defective surfaces. A proof-of-concept project to develop a niobium Chemical Mechanical Polishing (CMP) process used XPS to monitor...