Undergraduate Projects:

It is NOT your grandma’s Cleaner! Or is it?

Light(,) Anyone?

A journey into the Nanoworld: How thin can you separate the layers of hydroxides obtained from controlled cement reactions? Atomically thin?

Proj. 491-492
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2003 Spring Semester
By Drs. M. Ali Gulgun and Y. Menceloglu

It is NOT your grandma’s Cleaner! Or is it?

Layered clay minerals are known to suck up ions from solutions and accumulate them among the layers of the mineral. During the process – which is called ion exchange intercalation of the clay – the clay mineral swells up, i.e. increases the distance between the layers. In doing this clays can actually clean the solution from unwanted heavy metal ions. Since 1970’s certain forms of carbon (graphitic) have been used with the same concept in mind to prepare reinforced polymer composites. In this case polymer molecules may be filling the space between the graphite layers to have a strong interface bonding in the composite.

In this project we would like to investigate the ability of clay minerals to suck up not metal ions but polymer molecules of different kind and length. Actually, your grandma or her grandmother may already have the answer to this question. For centuries, housewives in Anatolia have used clay minerals to clean rugs and kilims. Perhaps they were doing pseudo-ion exchange and intercalation with clay minerals and dirt (some of which is polymeric) for the last thousand year. The project involves ion exchange and intercalation of polymer molecules into clay minerals from solutions, and x-ray diffraction measurements of degree of swelling of the intercalated minerals.
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2005 Spring Semester

By Profs. M. Ali Gulgun & Cleva Ow-Yang

Light(,) Anyone?

Luminescence is the name generally given to the emission of light by a material upon absorbing energy. Depending on the type of excitation they get different names: Photoluminescence, electroluminescence, cathodoluminescence and so on. Among photoluminescence materials, two types of luminescence events are distinguished: short time lapse (< 10 E-8 sec) or long time decay processes. The first one is called fluorencence and ceases as soon as the excitation source is removed. The second one is called phosphorescence and may continue long after the source of excitation is gone.

The projects will involve chemically synthesizing photoluminescent materials (phosphors) with different colors of emission (but mostly in visible range) and characterizing these materials. One of the most important success criteria of the projects is making new luminescent materials from inexpensive raw materials. One of the ultimate goals is finding a new additive for making phosphorescent road paints. We will be working with more than one material and can accommodate a few enthusiastic students.
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2007 Fall Semester

By Prof. M. A. Gulgun

A journey into the Nanoworld: How thin can you separate the layers of hydroxides obtained from controlled cement reactions? Atomically thin?

There are a number of layered structures among ceramics, like clays, calcium silicate hydrates, calcium aluminate hydrates, aluminum hydroxides, and magnesium hydroxides.  They are rather soft and slippery because although the bonds in the plane of the sheets are strong the boding between the layers are rather weak like in graphite. Thus they slide easily over each other.  We are actually more interested in the strong bonds in the layers. We would like to use these layers as strong reinforcement for other materials. But this requires that we can separate the layers from each other. In this process those weak bonds between the layers are best helpers. Since they are weak it is relatively easy to overcome them.  Some moderate shear may do the job. In this project first we will obtain (either buy or produce) the layered structures of calcium (silicate,aluminate) hydrates which look like a flower garden made up of thin hexagonal sheets. Then we will try chemical and mechanical ways to separate them from each other such that we can use them as reinforcements.

Project 491-492

 2007 Fall Semester

By Prof. M. A. Gulgun

Crystallographic and Morphological investigation of Potassium Sodium Niobate Phases

During the synthesis of potassium sodium niobate, an important lead-free piezoelectric ceramic, many secondary phases appear in the powder batch. They all have rather distinct morphologies like cubes, pyramids, and other prismatic shapes. Their shapes closely reflect their crystallography, and we would like to characterize their crystallography and morphology. The project will entail some chemical processing, rather extensive x-ray diffraction, some electron microscopy and electron diffraction. The student should be good in wet processing in the wet labs, he or she must have some experience with x-ray diffraction and electron microscopy (at least at the SEM level).

Microwave assisted deposition of ZnO ceramic thin films and production of ZnO nanoparticles with microwave energy.

Zinc oxide is an interesting wide bandgap semiconductor (E_g= 3.37 eV) and can be doped rather easily to become a conductor. In the insulting (no-doping) case it is a piezoelectric ceramic. Beyond its interesting electronic properties ZnO forms in various morphologies ranging from tripods to rings to helical springs, to sails, to hexagonal prisms like pills, to hexagonal prisms like pencils. The shape of the particles is strongly influences by the pressure, temperature, and the atmosphere that ZnO particles are formed in. Using Microwaves and a reductive-oxidative sequence we formed various ZnO morphologies. In this project we will try to coat ZnO thin films onto various substrate materials using ZnO, graphite, gold-island and inert gasses. The project requires a lot of patience and good microscopy skills. An understanding of electronic structures of ceramics and electrical measurement techniques are advantageous. 

Growth of Epitaxial Single Crystalline Thin and Thick Yttrium Ferrite Garnet (YIG) Ceramic Films for High Frequency Filter Applications

Tunable yttrium ferrite garnet (YIG, Y₃Fe₅O₁₂) filters cover a broad band between 7 and 11 GHz, supporting a rather wide-range of microwave communications and instrumentation applications. YIG also has a high transmittance for shortwave energy.  In line with the trend in miniaturization, in most of the applications, YIG is needed in the thin film form.  In order to maximize the properties, single crystalline thin films are most desired. In this project, the aim is to grow epitaxial, single crystalline YIG thin films on suitable substrates. The steps include producing our won YIG powders with optimized chemistry for best properties, and with optimized physical properties.  Next is choosing the substrate that will allow the best epitaxial growth.  Designing and building a setup to deposit thin films on suitable substrates will be accomplished. The deposited films and produced powders will be characterized for their microwave range dielectric properties at TUBITAK MAM collaborating with Prof. Alex Vertii’s Group.

Yttrium Iron Garnet (Y3Fe5O12-YIG) is a ferrimagnetic-spin wave material which is widely used in various high speed microwave devices  due to its suitable magnetic and magneto-optical properties such as high degree of faraday rotation (-3000 degrees/cm), very small linewidth in spin wave resonance, relatively low absorption and high quality factor in millimeter waveband. In our study, we will focus on producing and characterization of YIG structures for construction of  a novel near field microcope. However constructing and characterization of YIG delay lines for high speed millimeter waveband tomography devices will be proposed side aim of the project.

The project will involve establishing all required technology for production and characterization of YIG structures from raw materials. Recently we were able to produce over %99,5 purity very fine YIG powders with a novel organic-complexing strategy. The proposed project will include further required steps after powder production, mainly;

 Production of YIG single crystalline structures.

Growth of bulk single crystalline with small sizes.

Growth of YIG thin films on Gadolinium Gallium Garnet (GGG) via Liquid Phase Epitaxy (LPE).

Studying of launching and detection of magnetostatic waves on YIG produced samples (The study of the dispersion characteristics) .

The construction and characterization of delay lines from YIG thin film.

Diffraction of magneto-static waves on YIG thin film surface from processed periodic structures.          

Peculiar Precipitation Behavior in Yttrium Doped a-Al₂O₃

Yttrium was observed to enhance the creep resistance in polycrystalline alumina (a-Al₂O₃) by two orders of magnitude. Electron microscopy and spectroscopy studies revealed that the observed beneficial influence of yttrium is closely related to its segregation to the grain boundaries in the ceramic.  Careful investigations indicated that segregation levels (G_Y) are increasing monotonically with grain size and /or with the total amount of the dopant in the dilute regime, following a Langmuir-MacLean type of absorption isotherm.  At higher concentrations, G_Y shows a supersaturation behavior, which is followed by precipitation of a second phase.

Recently, we have shown that the first precipitate to form in the system is not the yttrium aluminate garnet (YAG) phase (Y₃Al₅O₁₂), as predicted by the equilibrium binary phase diagram between Al₂O₃ and Y₂O₃, but is instead the yttrium aluminate perovskite (YAP) phase (YAlO₃).  In this project we will map out the temperature, time, and concentration ranges where these two precipitates form and transforms (if at all).