The aim of this study is to improve the understanding of the water infiltration within Bituminized Waste Products (BWP) and the associated phenomena such as the development of the porous layer, the matrix swelling or the water uptake kinetics. Two sets of leaching experiments have been performed on synthesized model samples that are constituted by inactive soluble and/or insoluble salts (40% wt) embedded in bitumen. Large samples were used to quantify the water uptake kinetics and to control the macroscopic swelling of the matrixes during experiments. Smaller samples were used to characterize the depth distribution of the infiltrated water and its motion properties by NMR techniques (1H-T1 relaxation times and 1D-NMR imaging). These techniques enabled us to study the influence of the matrix chemical composition on the water advance in depth as a function of the leaching time. Results show that insoluble salts have a significant influence on water transport while soluble salts entail the development of large porosities. Preliminary results obtained with an original method based on the measurement of NMR relaxation times along the water concentration in depth are presented. They illustrate the great potential of the approach to further improve our knowledge on the establishment of the aqueous network.

The interface problems in nanomaterial based electronics play important roles. We have learned that the nanocontact, due to its reduced contact area, could give a high electrical contact resistance and a nonlinear current-voltage behavior though the specific contact resistance is in the same order of magnitude as that of macroscopic contacts. Through the current-voltage and temperature behaviors, the nanocontact properties could be categorized into Ohmic and Schottky types. The electrical properties of the nanowire based two-probe devices could be rationalized as two Ohmic contacts, one Ohmic and one Schottky contacts, and two back-to-back Schottky contacts. Moreover, the nanocontact could be treated as a one-dimensional disordered electron system for further studies. After the intrinsic nanowire and contact resistances are separated from each other, the electron transport and the carrier concentration of native doping in ZnO and InP nanowires can be determined. The nanowires are determined to have low carrier concentrations, implying a high sensitivity to light and gas. The contact and nanowire dominated two-probe devices are exposed to light and gas to identify the contact effects. In addition to the inorganic nanowires, the organic nanomaterials, the HCl-doped polyaniline nanofibers, can be analyzed by using the same approach. The dielectrophoresis technique is implemented to position nanofibers into an electron-beam lithographically patterned nanogap. To shine the electron-beam on contact areas, the organic/inorganic nanocontact resistance is reduced so as to probe the intrinsic electrical property of a single polyaniline nanofiber.

Co-evaporated CuIn0,5Ga0,5Se2 thin film solar cells were grown using a sequential Cu-Poor/Rich/Poor process (CUPRO). During the growth process, the substrate temperature was either kept constant at 570 °C (iso-CUPRO) or decreased during the first step to either 360 or 430 or 500 °C (bi-CUPRO). According to atomic force microscopy (AFM) measurements, the lower the temperature is in the first step the smoother the final CIGS surface becomes. By decreasing the first step temperature, cross-section scanning electron microscopy (SEM) and θ-2θ x-ray diffraction (XRD) do not reveal clearly any important changes of morphology and crystallographic preferred orientation. SLG/Mo/CIGS/Buffer layer/i-ZnO/ZnO:Al/grid(Ni/Al/Ni) solar cells with either a chemical bath deposited CdS or an atomic layer deposited Zn(O,S) buffer layer were fabricated. For both buffer layers, the bi-CUPRO processes lead to higher efficiencies. Besides, using Zn(O,S), the electronic collection was improved for the infrared spectrum as well as for the ultraviolet spectrum. This resulted in efficiencies close to 14,5% for the Zn(O,S) cells.

We have studied effects of H atom source on deposition profiles of carbon films, deposited by H assisted anisotropic plasma CVD method. Deposition rate normalized by that for the aspect ratio of 1 at sidewall and bottom decreases with increasing discharge power of H atom source from 0 W to 500 W, because the incident H atom flux per surface area in a trench increases and H atoms etch carbon films.

We will show the synthesis of new donor-acceptor copolymers based on 2,7-carbazole or 2,7-dibenzosilole and acenaphtho[1,2-b]thieno[3,4-e]pyrazine. After the synthesis of these new copolymers, we have characterized the materials by UV-vis, DSC, and XRD to determine the degree of organization. Afterward, we have fabricated and investigated field-effect transistors and photovoltaic cells from these polymers. The optimization of the thin film by thermal treatment have led to a field-effect mobility of 0.04 cm2/(V.s) and power conversion efficiency of 0.44%.

Glass matrices were selected to immobilize fission products because glass is capable of chemically incorporating a wide spectrum of elements within a single matrix. Some of these elements can be found at different oxidation states. The redox equilibrium constants of multivalent species can be used to develop thermodynamic models for a better description of nuclear glasses. Some of the multivalent species loaded in nuclear glass, such as iron and sulfur, have already been a subject of investigation by conventional glassmakers or geochemists in the earth sciences. Other redox species more specifically related to nuclear glass, including cerium and ruthenium, have also been investigated. These studies have demonstrated the advantages of using electrochemical techniques, voltammetry and potentiometry, to determine the equilibrium constants. Oxygen potential measurements are also particularly suitable for characterizing the redox state of the multivalent dissolved species in molten glass.

There has been significant recent interest in the use of surface-functionalized thin film and nanowire wide bandgap semiconductors, principally GaN, InN, ZnO and SiC, for sensing of gases, heavy metals, UV photons and biological molecules. For the detection of gases such as hydrogen, the semiconductors are typically coated with a catalyst metal such as Pd or Pt to increase the detection sensitivity at room temperature. Functionalizing the surface with oxides, polymers and nitrides is also useful in enhancing the detection sensitivity for gases and ionic solutions. The wide energy bandgap of these materials make them ideal for solar-blind UV detection, which can be of use for detecting fluorescence from biotoxins. The use of enzymes or adsorbed antibody layers on the semiconductor surface leads to highly specific detection of a broad range of antigens of interest in the medical and homeland security fields. We give examples of recent work showing sensitive detection of glucose, lactic acid, prostate cancer and breast cancer markers and the integration of the sensors with wireless data transmission systems to achieve robust, portable sensors.

Two different methods have been used to synthesize sodalite for conditioning of chloride salt wastes coming from pyroprocesses: the first one, starting from kaolinite through the intermediate nepheline phase; the second one, starting from silica and sodium aluminate reagents, directly. The obtained products have been characterized by means of several analyses. In particular, different instrumental techniques – stereomicroscopy, scanning electron microscopy (SEMEDS), density measurements, thermogravimetric analysis, X-rays diffraction, FTIR spectroscopy – were performed revealing that the synthesis from kaolinite is the best method, provided that rigorous conditions are followed. The use of an argon atmosphere for the preparation of pellets of reagents is strictly necessary for the obtainment of a good quality product.

We compare the turn-on voltage, P-I, and EL responses between the MISLEDs made by Si-rich SiNx and SiOx films. Active layer thickness enlarged from 120 to 360 nm is achieved by lengthening deposition time from 10 to 30 min, which inevitably increases the forward turn-on voltage from 3 to 41 V. We observe that the forward turn-on voltage of SiNx based MISLED is only 10.43 V and that of SiOx based one is 69 V with the same film thickness of 100 nm. The tunneling-based carrier transport mechanism is dominated due to the exponential like V-I behavior, while the tunneling probability is strongly dependent on the height of the barriers between metal/dielectric and dielectric/nc-Si matrices. The P-I slope of SiNx and SiOx based MISLEDs are 1.6 and 115.2 mW/A, respectively. The SiNx MISLED reveals threshold current and voltage of only 4 A and 12 V due to lower barrier height of both ITO/SiNx and SiNx/nc-Si, whereas the threshold current and voltage of SiOx based MISLED are 400 A and 78 V, respectively. In comparison, the higher tunneling current through the SiNx MISLED fails to promote the larger external quantum efficiency of the MISLED, indicating that such lower barriers are not beneficial to the confinement of tunneling carriers and the enhancement of light-emission efficiency.

We present results of printing solution-processable organic light emitting diodes (OLEDs) based on electrophosphorescent Ir(III) stellate polyhedral oligomeric silsesquioxane (POSS) macromolecules. The macromolecules are doped into a polymer-based ink containing a hole transporting polymer, poly(9-vinylcarbazole) (PVK) and an electron transporting material, 2-4-biphenylyl-5-4-tertbutyl-phenyl-1,3,4-oxadiazole (PBD), and the resulting ink is printed on a layer of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) spin-coated on indium tin oxide (ITO). An exciton-blocking layer consisting of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) is thermally evaporated onto the printed ink layers, followed by a LiF/Al cathode. While the photoluminescence (PL) spectrum of printed ink on glass indicates a significant contribution from the PVK:PBD exciplex, electroluminescence measurements (EL) suggest a much smaller effect of these states, which implies significant charge trapping at dopant molecular sites. Our latest experiments with devices printed on PEDOT:PSS/ITO/glass indicate that the devices exhibit high luminances (∼ 13,000 cd/m2 at 70 mA/cm2) and a fairly consistent quantum efficiency (∼ 2.5%) across a wide range of luminances. The corresponding figures for spin-coated devices are expectedly higher, with efficiencies ∼ 4.5% at similar levels of brightness. We use white light interferometry as a non-contact technique to quantify surface roughness and thickness of printed layers. Our current results thus indicate that inkjet printing of macromolecular phosphor doped polymer inks is suitable for fabrication of OLEDs with high brightness, in spite of the low glass transition temperature of some of the species. Our initial work with these devices on flexible ITO-coated plastic substrates shows devices with moderately high luminance values (∼ 2,500 cd/m2 at 35 mA/cm2). Our more recent devices show higher brightnesses (∼ 9, 600 cd/m2). We are working on the development of inkjet printing materials and processes for pure macromolecular OLEDs that are not performance and reliability limited by the presence of the PVK:PBD matrix with low glass transition temperatures. This requires the development of macromolecules that subsume all the functions of the host matrix and have high enough Tg to be usable in high concentrations needed. In conjunction with the inkjet printing technology demonstrated in this work, this has the potential to yield low-cost manufacturing of these devices.

We have prepared a number of Pt-TM(transition metals) alloys with various TM elements and evaluated their catalytic abilities by means of hydrogenation of methyl acrylate. High catalytic activities are obtained when the crystalline structures are similar, i.e., fcc structure, indicating that the crystal structure of a catalyst plays an important role in hydrogenation of methyl acrylate. Furthermore, for a certain TM element, i.e., Mo, the catalytic activity is found to surpass that of Pt metal.

We report on a novel photodetector structure based on III-nitride materials. A layered configuration is used to create a barrier with voltage-tunable height. The barrier is used as a filter on photoexcited holes and electrons, and could form the basis for a dynamically tunable pixel in a hyperspectral imaging array. This would eliminate the need for external gratings and filters used in conventional hyperspectral instruments; in addition, the tunability of pixels allows decrease of the array dimension by one. The III-nitride materials family is a good candidate for this device, combining large band offsets with the ability for epitaxial growth. We have demonstrated the feasibility of using III-nitride materials to fabricate layered tunnel barriers, and have demonstrated tunability of photodetection using these structures. External quantum efficiencies of > 12% have been achieved with prototype devices.

We investigate the origin of fill factor changes induced by reverse bias treatment. Evolution of current-voltage characteristics have been measured during application of reverse voltage bias. Two different cell behaviors have been identified. At elevated temperatures one kind of the devices strongly deteriorates and exhibit so called double diode behavior. On the other hand, in the same conditions another cells keep their fill factor almost constant. We correlate the fill factor changes with the kinetics of capacitance and show that although increased number of shallow acceptors itself cannot induce this severe FF deterioration, it may strongly influence position of the Fermi level at the heterointerface that in a presence of an electron barrier is crucial for the device behavior.

Catalytic-FGA, a combination of the standard forming gas anneal with a catalytic metal gate, has been applied to study the hydrogen passivation of III-V/Ge MOS systems. Pd (or Pt) metal gate catalytically dissociates molecular hydrogen into atomic hydrogen atoms, which then diffuse through the dielectric layer and neutralize certain semiconductor/dielectric interfacial defects. MOS systems with various interfacial qualities, including lattice-matched (n/p) In0.53Ga0.47As/10nm ALD-Al2O3 (or ZrO2)/Pd capacitors, an undoped Ge/˜1nm GeO2/4nm ALD-Al2O3/Pt capacitor, and an nGe/8nm ALD-Al2O3/Pt capacitor are fabricated to evaluate the effectiveness of C-FGA.

Indium Gallium Nitride (InxGa1-xN) alloys are currently playing an ever increasing role in optoelectronic devices as the bandgap of such alloys can theoretically be tuned between 0.7eV and 3.4eV–covering the entire visible spectrum. Although growth of high quality InxGa1-xN alloys with high indium mole fractions are difficult or presently unattainable, InGaN alloys are still a viable choice for light emitters and detectors over the visible (blue/green) to ultraviolet spectrum. However, many inherent problems during InGaN growth via Metal Organic Vapor Phase Epitaxy (MOVPE) arise due to the large lattice mismatch and low miscibility between GaN and InN–leading to the formation of Inverted Hexagonal Pyramid (IHP) defects at the termination of threading dislocations. Additionally, growth of InGaN at lower temperatures to promote increased indium incorporation results in poor surface morphology. Several methods such as strained layer superlattices and low mole fraction InGaN layers before the growth of the InGaN/GaN MQW structures have been shown to relive strain in the MQWs, thus reducing the density of IHP defects and/or improving the optical output characteristics. This work focuses on the application of GaN monolayer insertions during InGaN quantum well growth via Metal Organic Vapor Phase Epitaxy (MOVPE) as a means to reduce the IHP defect density and passivate effects on surface roughness while observing variations in indium concentration. Observations include the reduction of IHP defect density by nearly twofold as the number of GaN monolayer interruptions increase from zero to three while sustaining only slightly lower effective indium concentrations.

The US Navy continues to pursue electrochemical power sources with high energy density for low rate, long endurance air independent, undersea applications. The use of borohydride and hydrogen peroxide as fuel and oxidant sources offer several different fuel cell configurations; each with their own advantages and technical challenges.

The direct electro-oxidation and electro-reduction of sodium borohydride and hydrogen peroxide is conceptually a simple system. In the fuel cell configuration where Nafion 115 is used and both electrolyte solutions are allowed to have a pH >8, high efficiencies (>70%) can be maintained with careful control of the concentration of reactants in the flowing electrolyte, choice of catalyst and electrode architecture. The onset of borate precipitation is offset by diffusion of water created by the osmotic pressure between anode and cathode.

The direct liquid/liquid system has the potential to be a “2V” system if the pH of the hydrogen peroxide catholyte is maintained at a pH<1. In order to make this a viable system for Naval applications, the amount of acid used in the catholyte to establish the desired pH needs to be minimized. The key enabling technology is the development of a suitable anion exchange membrane. The characteristics of the anion membrane are: 1) conduct hydroxides generated at the cathode to the anode in order to minimize its concentration buildup in the catholyte solution and to maintain the desired pH.<1, 2) minimize hydrogen peroxide cross-over and 3) afford high ionic conductivity.

Efforts are currently underway to improve the understanding of the reaction mechanism of borohydride at the catalyst surface and to identify membranes with higher ionic conductivity. These efforts have been identified as critical paths for the successful development of a liquid/liquid borohydride/hydrogen peroxide fuel cell.

As engineering becomes more and more specialized, both the faculty resources and number of interested students become limited. Consequently, very frequently highly specialized graduate courses are not offered, especially in disciplines like Materials with small faculty and enrollment. NSF's International Materials Institute for New Functionality in Glass (IMI-NFG) has successfully addressed this problem by successfully introducing the concept of multi-institution team teaching (MITT). It brings together via internet both the expert professors and students from many universities. By pooling the talent of various instructors, the courses become technically stronger and students learn advanced topics that would be available otherwise. As an example, a recent MITT course included instructors from 10 US institutions, and students from many more US and international universities.

Software such as ‘Adobe Connect’ is used for the live delivery of lectures, wherein students can see the instructor and Power Point slides as in a normal classroom. The students may ask questions any time during the lecture, and the instructor would respond immediately. They register and pay tuition at their home institution, so that no exchange of funds is involved between universities. Survey results support that a majority of the enrolled students liked the format and delivery of the course, and more than 75% students felt that multiple instructors, who “taught information of their expertise”, made the course stronger. In conclusion, the concept of MITT has been successfully demonstrated for teaching highly specialized graduate courses.

The thermoelectric (TE) properties, such as the Seebeck coefficient, the electrical and thermal conductivities, and the output power, of Sb-doped n-type Mg2Si were studied. A commercial polycrystalline source was used for the source material for the Mg2Si. TE elements with Ni electrodes were fabricated by using a monobloc plasma-activated sintering (PAS) technique. Compared with undoped samples, the ZT values of the Sb-doped samples were higher over the whole temperature range in which measurements were made; the maximum value for the Sb doped Mg2Si was 0.72 at 864 K. The TE characteristics of Sb-doped samples were found to be comparable to those of Bi-doped ones, and no significant difference in ZT value was observed between them. Provisional results showed that the maximum value of the output power was 6.75 mW for the undoped sample, 4.55 mW for a 0.5 at% Sb doped sample, and 5.25 mW for a 1 at% Sb doped sample with ΔT = 500 K (between 873 K and 373 K).

We report on a pair of MSP (Mathematics & Science Partnership) START pilot projects designed to identify nanoscience experiments that will fit within the Alabama course of study for use in Alabama K-12 classrooms. As part of the first project we are testing the development, refinement and evaluation of an activity already partly developed. The form of this activity has had input from a focus group of RETs who were tasked to provide input into the activity and how it can be matched to components of the Alabama Course of Study. This activity consists of using sparks generated by abrasion of misch metal by sand paper of different grit size. Different grit sizes produce metal particles of different sizes, resulting in sparks of different size and length. If done in a dry box no sparks are produced and the powder left is not pyrophoric, demonstrating that high surface area, heat and oxygen are all required to produce sparks. SEM characterization of the powder allows the particle sizes to be determined, giving the correlation between size, grit size and spark track length. The activity was tested on groups of middle school science campers at McWane Science Center, and after evaluation, further modified to increase student interest and impact. The activity was then tested on grades 6-8 in a middle school classroom by a graduate student/undergraduate student team.

In this work, microwave heating curves and microstructural evolution of nanocrystalline Au thin films were studied so the heating behavior of metals could be better understood. Films with different thickness were irradiated by the H and E maximums of microwave in a single-mode cavity. These samples were more efficiently heated by H field than by E field. With the increase of film thickness, the attained highest temperature increased. This phenomenon was compared with the theory of the transmission line analysis. Peaks appearing at the initial stage of the heating curves were also compared with similar heating behaviors observed in metal powder compacts, and the possible mechanisms related to the heating behavior were explored.