The effects of solute and vacancy segregation on APB migration in Ti3Al, and their dependence on composition, have been investigated by using a phase-field simulation in which vacancy distribution is taken into account. Al-atoms are depleted and vacancies segregate at APB in stoichiometric Ti3Al (Ti-25Al), whereas Al-atoms segregate and vacancies are depleted in Alrich one (Ti-28Al). The simulation indicates that APB in Ti3Al migrates much faster in Ti-25Al than in Ti-28Al with the effect of vacancy segregation whereas it migrates slightly faster in Ti-28Al than in Ti-25Al in the absence of the effect of vacancy segregation.

A mechanical vibration system was made by sandwiching an array of parylene-C microsprings between two flat plates of Si. This system was driven mechanically in forced oscillation using a piezo transducer attached to the bottom Si plate. An atomic force microscope was used to record the displacement of the top plate in both the contact and non-contact modes. At the resonance, the system was observed to give large vertical displacement amplitude of up to 100 nm with a Q-factor of up to 900.

We report the first disposable fluorescent biosensor based on algae, with an organic light emitting diode and an organic photodetector (OPD) miniaturized into a microfluidic chip. A DPVBi OLED was used as the excitation source, while a blend of PTB3/PCBM was used for the organic photodetector. The fluorescence biosensor is integrated in a microfluidic chip made from polymeric materials such as (poly)dimethylsiloxane (PDMS), which is transparent, biocompatible and can easily be processed by conventional lithography. The complete detector is designed to detect Chlamydomonas reinhardtii green algae fluorescence in the microfluidic chamber. Algal chlorophyll fluorescence is a physiological parameter routinely used to measure the photochemical efficiency of PSII. This measurement is a reliable and non-invasive method to determine the toxicity of pollutants like herbicides and metals.

Precipitation kinetics in the wrought alloy AA5182 during homogenization was investigated by various experimental methods. The constituents generated during casting were identified with energy dispersive X-ray spectroscopy (EDS) analysis. Their volume fraction was measured with optical microscopy. The size evolution of dispersoids during the heat treatment was studied in TEM. The EDS analysis shows that the dispersoids were mainly Al6Mn and α-Al(MnFe)Si. The dispersoids number was counted from a large number of electron back scatter images to yield good statistics. Electrical resistivity measurements were performed to study precipitation indirectly via the solute content. With the above experimental information, the thermodynamics based precipitation model ClaNG was calibrated for the alloy AA5182. Unknown parameters like interface energies of precipitates were adjusted accordingly. ClaNG is capable of describing the simultaneous nucleation, growth and coarsening of all important precipitates in multi-component systems for arbitrary heat treatments. After the unknown parameters were determined, the model was able to predict the volume and size distribution of dispersoids and the matrix composition for varied heat treatments. The predictions were used to design and optimize the heating process with respect to the microstructure of the homogenized ingot.

A multiscale approach was adopted for the calculation of confined states in self-assembled semiconductor quantum dots (QDs). While results close to experimental data have been obtained with a combination of atomistic strain and tight-binding (TB) electronic structure description for the confined quantum states in the QD, the TB calculation requires substantial computational resources. To alleviate this problem an integrated approach was adopted to compute the energy states from a continuum 8-band k.p Hamiltonian under the influence of an atomistic strain field. Such multiscale simulations yield a roughly six-fold faster simulation. Atomic-resolution strain is added to the k.p Hamiltonian through interpolation onto a coarser continuum grid. Sufficient numerical accuracy is obtained by the multiscale approach. Optical transition wavelengths are within 7% of the corresponding TB results with a proper splitting of p-type sub-bands. The systematically lower emission wavelengths in k.p are attributable to an underestimation of the coupling between the conduction and valence bands.

A series of porous aluminum-based materials are prepared by the reduction of solutions of metal chlorides with lithium powder in diethyl ether under dry argon. The reactants must be combined slowly, but either order of addition is used. The reduction of AlCl3 produces hollow Al balls composed of ~100 nm aluminum particles in nearly quantitative yield after the LiCl byproduct is washed away with dry tetrahydrofuran. Similar structures are formed when mixtures of AlCl3 and SiCl4, are reduced, except that the second component has the effect of reducing the Al nanoparticle size. Mixtures of AlCl3 with FeCl3 reduce to similar ball-like porous structures that are composed of Al, Fe, and Fe-Al intermetallic nanoparticles. When AlCl3 and ZnCl2 are co-reduced, flake-like nanoporous structures are obtained, and solutions of AlCl3 + VCl3 produce more compact nanoporous structures. Some side reactions involving ether cleavage that produces aluminum alkoxides and alkyls do occur, and the amount of side reaction is dependent on the identity of the second metal. The reduction of AlCl3 with excess (4 eq) Li powder produces LiAl nanomaterials. NMR shows the intermetallic compound LiAl to be the only Li-Al intermetallic present.

The CaFeOX(CFO) and LaFeO3(LFO) thin films as well as superlattices were fabricated on SrTiO3(100) substrates by pulsed laser deposition (PLD) method. The tetragonal LFO film grew with layer-by-layer growth mode until approximately 40 layers. In the case of CFO, initial three layers showed layer-by-layer growth, and afterward the growth mode was transferred to two layers-by-two layers (TLTL) growth mode. The RHEED oscillation was observed until the end of the growth, approximately 50nm. Orthorhombic twin CaFeO2.5 (CFO2.5) structure was obtained. However, it is expected that the initial three CFO layers are CaFeO3 (CFO3) with the valence of Fe4+. The CFO and LFO superlattice showed a step-terraces surface, and the superlattice satellite peaks in a 2θ-θ and reciprocal space mapping (RSM) x-ray diffraction (XRD) measurements, indicating that the clear interfaces were fabricated.

Long distance intercellular communication between astrocytes on nanofibrillar and planar surfaces was investigated by epi-fluorescence microscopy and atomic force microscopy. We found that astrocytes on nanofibrillar surfaces and astrocytes on planar surfaces diverged in apparent cell-cell contact structures. Astrocytes on nanofibrillar surfaces exhibited a “single cellular process” response, while astrocytes on planar surfaces exhibited a filopodial network response. The possibility that astrocytes can sense their geometrical environment and form different cell-to-cell contacts on nanofibrillar versus planar surfaces, with activation of different signaling pathways, is discussed.

Immobilization of oligonucleotide-functionalized magnetic nanobeads by hybridization in DNA-coils formed by rolling circle amplification has been investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The TEM results supported earlier made observations that small beads with low oligonucleotide surface coverage preferably immobilize in the interior of the DNA-coils and do not tend to link several DNA-coils together whereas large beads with high surface coverage to a larger extent connect several DNA-coils together to clusters of several DNA-coils with beads. AFM provided direct visualization of the DNA-coils as thread-like objects. DNA-coils with immobilized beads appeared as a collection of beads with thread-like features in their near vicinity.

Yungang Grottoes in Shanxi, China, which represent outstanding example of Chinese outdoor immovable stone artifacts, are precious world cultural heritage. In the present study, the preparation and assessment of superhydrophobic hybrid coatings with photocatalytic activity on the sandstone substrate collected from Yungang were explored preliminarily. The protection efficiency of coating is investigated by measuring the water-stone contact angles, water vapor permeability, water absorption, and resistance to acid and salt corrosion. Results show that the superhydrophobic organic-inorganic hybrid coatings with photocatalytic and self-cleaning properties are highly suitable for the conservation of stone monuments.

This report covers the resistive switching characteristics of cross-bar type semi-transparent (or see-through) resistive random access memory (RRAM) devices based on ZnO. In order to evaluate the transmittance of the devices, we designed the memory array with various electrode sizes and spaces between the electrodes. To prevent read disturbance problems due to sneak currents, we employed a metal oxide based p-NiO/n-ZnO diode structure, which exhibited good rectifying characteristics and high forward current density. Based on these results, we found that the combined metal oxide diode/RRAM device could be promising candidate with suppressed read disturbances of cross-bar type ZnO RRAM device.

The fluorocarbon/SiO2 hybrid sol (L) for low refractive index coating was made by tetraethoxysilane (TEOS) and polytetrafluoroethylether derivative(PTFEED) with the hydrolysis and condensation in ethanol to get with coating refractive index as (nL=1.38). It can be coated on glass with single layer by quarter wave, the anti-reflective (AR) coating glass would have less than 3 % reflection. The TiO2 hybrid sol are prepared by tetraisopropyl orthotitanate(TPOT) with silane coupling agent and acrylic resin. The TiO2 hybrid sol with the coating refractive index (nH=1.75) used as high refraction coating sol (H). More acrylic resin added to get less coating refractive index (nM=1.65) used as middle refractive coating sol (M). Three layers AR coating glass can be made by M/H/L design to get 1.0 % reflection, have 3H hardness, 500g scratch resistance, and 107° water contact angle. These two kinds AR coating with fluorocarbon /SiO2 hybrid sol (L) coating on surface has anti-stain efficacy, which can be applied on the touch panel screen of flat panel display for mobile phone, PDA and e-book.

The primary objective of this study is to discuss the optimum operating conditions of magnetocaloric heat pumps according to the fundamental heat transfer characteristics of an active magnetic regenerator (AMR) bed. The AMR cycle has four sequential processes: magnetization, heat exchange fluid flow, demagnetization, and heat exchange fluid blow. The fundamental heat transfer characteristics of each process of the AMR cycle is investigated minutely. Moreover, the cooling power and the overall system performance are evaluated when the system is running continuously.

In addition to the aforementioned investigation, we have developed a prototype rotational magnetocaloric heat pump having a compact component arrangement and an uncomplicated control system. A performance evaluation has been conducted to obtain the optimum conditions for practical operation. The operation parameters such as the heat transfer fluid flow rate, rotational frequency, and initial temperature of the heat transfer fluid are examined, and the variations of the maximum temperature span between the inlet and outlet for the heat transfer fluid are discussed. As a result, the values of the optimum rotational frequency and flow rate are obtained to obtain the maximum temperature span between the inlet and outlet of the present magnetocaloric heat pump.

We report on the investigation of large area a-Si:H/a-SiGe:H double-junction and a-Si:H/a-SiGe:H/a-SiGe:H triple-junction solar cells prepared by our proprietary High Frequency (HF) glow discharge technique. For investigative purposes, we initially used the simpler double-junction structure. We studied the effect of: (1) Ge content, (2) cell thickness, and (3) SiH4 and GeH4 gas flow on the light-induced degradation of the solar cells. Our results show that the double-junction cells with different Ge concentration have open-circuit voltage (Voc) in the range of 1.62-1.75 V. Voc exhibits a flat plateau in the range of 1.65-1.72 V for both initial and stabilized states. The light-induced degradation for cells in this range of Voc is insensitive to the Ge content. In terms of thickness dependence of the intrinsic layers, we found that the initial efficiency increases with cell thickness in the thickness range 2000-4000 Å. However, light-induced degradation increases with increasing thickness. Consequently, the stabilized efficiency is invariant with cell thickness in the thickness range studied. The results of SiH4 and GeH4 gas flow on cell characteristics demonstrate that the deposition rate decreases by only 20% when the active gas flow is reduced to 0.25 times standard flow. The initial and stabilized efficiencies are similar. The information gleaned from the study was used to fabricate high efficiency, large area (~464 cm2) double- and triple-junction solar cells. The highest stable efficiency, as measured by NREL, was 9.8% and 11.0% for the double- and triple-junction structures, respectively.

In-situ laboratory measurements in X-ray diffraction (XRD) high-temperature chamber and detailed XRD measurements at room temperature were used for the study of the thickness, temperature and time dependences of crystallization of amorphous TiO2 thin films. The films deposited by magnetron sputtering, plasma jet sputtering and sol-gel method were analyzed. Tensile stresses were detected in the first two cases. They are generated during the crystallization and inhibit further crystallization that also depends on the film thickness. XRD indicated quite rapid growth of larger crystallites unlike the sol-gel films when the crystallites grow mainly by increasing of annealing temperature.

Over the past three years the Departments of Materials Science and Engineering and Mechanical Engineering at Iowa State University have conducted a study-abroad course for ISU undergraduates in a small, isolated, village in the country of Mali, in western, sub-Saharan Africa. Most, if not all, of the people in the village live under conditions that the World Bank refers to as extreme poverty. The focus of the course is on the development of sustainable technologies that are appropriate for the people in this village and villages similar to it. Our goal is to offer students a chance to develop such technologies, in the end changing how they view engineering and their role as engineers. One of the challenges of the course is how to integrate this high value off-campus experience into the on-campus curriculum. To do this we have linked two on-campus sustainable engineering courses (sustainable engineering systems and appropriate technology design) with this study abroad course. In this paper, we discuss the course in more detail, with a focus on an assessment of how well we are meeting our objectives. We shall also discuss the challenges of holding such a course and will offer some advice for those who may wish to venture along the same path.

In this work, we report the results of studies of the transverse magnetoresistance (MR) of single-crystal Bi nanowires with diameter d<80 nm. The single-crystal nanowire samples were prepared by the Taylor-Ulitovsky technique. Due to the semimetal-to-semiconductor transformation and high density of surface states with strong spin-orbit interactions, the charge carriers are confined to the conducting tube made of surface states. The non monotonic changes of transverse MR that are equidistant in a direct magnetic field were observed at low temperatures in a wide range of magnetic fields up to 14 T. The period of oscillations depends on the wire diameter d as for the case of longitudinal MR. An interpretation of transverse MR oscillations is presented.

Exposure to highly focussed flash light (photonic flash sintering) has been developed as a technology to successfully cure printed metal inks on temperature sensitive plastic substrates. In contrast to the traditional approach of thermal oven sintering, conductivities up to 30 % of the value of bulk silver can be achieved within a few seconds without foil deformation. The compatibility of this technology with R2R production has been demonstrated with line speeds up to 5 m/min. As a consequence, our approach is expected to enable the high throughput fabrication of current collecting grids for organic solar cells in order to replace transparent electrodes based on metal oxides such as ITO. Additionally, our new sintering technology has enabled us to process a new generation of conductive inks, based on copper complexes, which cannot be processed by oven sintering.

Indium containing III-Nitride layers are predominantly grown by heteroepitaxy on foreign substrates, most often Al2O3, SiC and Si. We have investigated the epitaxial growth of InxGa1-xN (InGaN) alloys on Ge substrates. First we looked at the influence of buffer layers between the InGaN and Ge substrate. When applying a high temperature (850 °C) GaN buffer, the InGaN showed superior crystal quality. Furthermore the influence of growth parameters on the structural quality and composition of InGaN layers has been looked into. For a fixed gallium and nitrogen supply, the indium beam flux was increased incrementally. For both nitrogen- as well as for metal (Ga + In) rich growth conditions, the In incorporation increases for increasing In flux. However, for metal rich growth conditions, segregation of metallic In is observed. An optimum in crystal quality is obtained for a metal:nitrogen flux ratio close to unity. The XRD FWHM of the GaN (0002) reflection increases significantly after InGaN growth. Apparently the presence of indium deteriorates the GaN buffer during InGaN growth. The mechanism of the effect is not known yet.

The effect of Nb addition on phase equilibria among Ni (A1), Ni3Al (L12) and Ni3V (D022) phases was investigated in the Ni-rich Ni-Al-V ternary system. The addition of Nb to the Ni-Al-V ternary system shifts the three-phase coexisting region of A1 + L12 + D022 towards the Ni-rich side at 950 ºC. Nb is partitioned into the D022 phase more strongly than the A1 and L12 phases. These results suggest that the addition of Nb stabilizes the D022 phase against the A1 and L12 phases in the systems. The alloying element raises the temperature of a eutectoid-like reaction (A1→L12+D022) by ~30 ºC in the vertical section of Ni-Al-V ternary system at 75 at. % Ni.