The Renewable Fuels Standard (RFS) and Energy Independence and Security Act of 2007 (EISA) mandated that 36 billion gallons of biofuels should be blended into transportation fuel by 2022. Implementing this will help reduce greenhouse gas emissions, reduce petroleum imports and encourage the development and expansion of US renewable fuels sector within rural America. Of the 36 billion gallons of biofuels, 16 billion gallons is expected to be from lignocellulosic biomass such as trees and grasses. The Black Hills of South Dakota is rich in ponderosa pine. This feedstock for bioethanol production, which is widely available due to recent pine beetle infestation, will not only add to the RFS requirement, it will also have a positive impact on rural economies in South Dakota. From the wood chips of pine, after acid pretreatment and enzymatic hydrolysis, the fermentable sugars obtained are relatively dilute in concentration (∼20-30 g/L). Hence, within a biorefinery, to increase the fermentation efficiency and decrease downstream processing cost of the biofuels, concentrating the sugars can be beneficial. In this study, Reverse Osmosis (RO) and Nanofiltration (NF) membranes were tested with complex lignocellulosic hydrolysate samples for their ability to concentrate sugars prior to fermentation. Fouling analysis and membrane characterization for both RO and NF membranes were performed by SEM, AFM, BET, contact angle and FTIR spectroscopy. Efficiency of membranes for their ability to separate fermentation inhibitors (e.g., organic and mineral acids, furans and phenolic compounds) from sugars, while simultaneously concentrating the sugars was studied to make the bio-ethanol production process cost and energy efficient. Three commercial nanofiltration membranes GE-R, TS40 and SR100 showed very promising results. GE-R concentrated sugars to more than 2.5 fold in the retentate, and simultaneously separated more than 50% of the inhibitory components into permeate. These results will increase the fermentation efficiency and reduce downstream purification costs of the produced fuel.

An exhaustive analysis of the frequency-dependent series resistance associated with the on-chip interconnects is presented. This analysis allows the identification of the regions where the resistance curves present different trending due to variations in the current distribution. Furthermore, it is explained the apparent discrepancy of experimental curves with the well-known square-root-of-frequency models for the resistance considering the skin-effect. Measurement results up to 40 GHz show that models involving terms proportional to the square root of frequency are valid provided that the section of the interconnect where the current is flowing is appropriately represented.

In this study, we report the design and fabrication of a dual-phase energy harvester which can synchronously harvest both mechanical and magnetic energy in the absence of DC magnetic field. The harvester consists of a magnetostrictive cantilever beam and a magnetostrictive/ piezoelectric (M/P) self-biased laminate composite structure. This structure allows us to utilize piezoelectric and self-biased magnetoelectric effect simultaneously. By combining these mechanisms together, a sum effect for harvesting both magnetic and vibration energy was realized under DC magnetic field free condition. The bilayer structure provides a simplified geometry that can be easily incorporated into MEMS devices. We demonstrate a hybrid synthesis method for fabrication of complex three-dimensional thin films using a cost-effective and mask-less aerosol jet deposition process. The combination of the hybrid aerosol jet process with dual phase harvester design provides the opportunity to fabricate small scale power sources required for structural health monitoring applications.

Horizontal carbon nanotube (CNT) interconnects are fabricated using a novel integration scheme yielding record wall densities >1013 shell/cm2, i.e. close to the density required for implementation in advanced integrated circuits. The CNTs are grown vertically from individual via structure and subsequently flipped onto the horizontal wafer surface. Various electrode designs are then used to produce different geometries of metal-to-tube contact such as side contact or end contact. CNT lines - 50 to 100 nm wide and up to 20 µm long - are realized and electrically characterized. The sum of the contact resistances from both ends of the lines is close to 500 Ω for 100 nm diameter lines which leads to a specific contact resistance of 1.6 10-8 Ω.cm2 per tube. With the developed technology, post-annealing of the contact does not improve the resistance values. Both chromium and palladium are used as contact metal. While contact resistance is equivalent with the two metals, the resistance per unit length of the lines does change and is better with palladium. This dependence is explained using a tunnelling model which shows that statistics of individual tube-metal contact is required to properly model the electrical results. Direct experimental evidences showing that only a part of the CNTs in the bundle is electrically connected are also given. Our best line resistivity achieved is 1.6mΩ.cm which is among the best results published for horizontally aligned CNTs and the only one with a realistic geometry for future VLSI interconnects.

Thermal stability of the luminescent properties of CdSe and CdSe/ZnS quantum dots (QDs) in polymer films of gelatin and polyvinyl alcohol (PVA) is studied. Thermal annealing of the films at the air ambience at 100 °C is found to result in two effects in the photoluminescence (PL) spectra: (i) an enhancement of the PL intensity and (ii) a red spectral shift of the PL bands. The first effect is observed in both QDs-gelatin and QDs-PVA composites, while the second one - in the QDs-gelatin only. The passivation of CdSe QDs with ZnS shell reduces the effects. The enhancement of the PL intensity is supposed to be due to the decrease of nonradiative defect density. The red shift is explained by dissociation of coordination bonds between surface Cd atoms and amino-groups of gelatin. This dissociation decreases the PL intensity too. This effect competes with the effect of PL enhancement and is supposed to be responsible for non-monotonous dependence of the PL intensity versus annealing time in the QDs-gelatin composite.

Quantum dot gate (QDG) field-effect transistors (FET) have shown three-state transfer characteristics. Quantum dot channel (QDC) field-effect transistors (FET) have exhibited fourstate ID-VG characteristics. This project aims at studying the effect of incorporating cladded quantum dot layers in the gate region of QDC-FET. Four-state characteristics are explained by carrier transport in narrow energy mini-bands which are manifested in a quantum dot superlattice (QDSL) channel. QDSL is formed by an array of cladded quantum dots (such as SiOx-Si and GeOx-Ge). Multi-state FETs are needed in multi-valued logic (MVL) that can reduce the number of gates and transistors in digital circuits. The fabricated device showed the four-state characteristic (OFF, ‘I1’, ‘I2’, ON).

A high temperature ceramic selective emitter for thermophotovoltaic (TPV) electric generators is described with a spectral match to GaSb IR cells. While solar cells generate electricity quietly and are lightweight, traditional solar cells are used with sunlight and only generate electricity during the day. Workers at JX Crystals invented the GaSb IR cell as a booster cell to demonstrate a solar cell conversion efficiency of 35%. JX Crystals now makes these IR cells. In TPV, these cells can potentially be used with flame heated ceramic emitters to generate electricity quietly day and night. One of the most important requirements for TPV is a good spectral match between the ceramic IR emitted and the IR PV cells. The first problem is to find, demonstrate, and integrate a doped ceramic IR emitter with a spectral match to these GaSb cells. Recently, nickel oxide and cobalt oxide doped MgO-based ceramics have been shown experimentally and theoretically to have spectral selectivity but no attempts have been made to integrate these ceramic IR emitters into a fully operational TPV generator. Herein, we review the history of TPV and note that a key to future progress will be the integration of an appropriate ceramic emitter with cells and a burner to demonstrate an operational TPV generator. Integrating TPV into a residential boiler is discussed as a potential future large volume commercial market.

High temperature multi-source co-evaporation has been the most successful approach to fabricate record efficiency Cu(InGa)Se2 devices, yet many groups have been unable to replicate this success when transferring these methods to the Cu2ZnSnSe4 system. The difficulties stem from the dramatic differences in the thermochemical properties which result in decomposition and loss of volatile species, such as Zn and SnSe, at temperatures needed for growth. In co-evaporation, decomposition and element loss must be managed throughout the entire growth process, from the back contact interface to the final terminating surface of the film. The beginning and ending phases of deposition encompass different kinetic regimes suggesting a phased approach to growth may be helpful. A series of depositions with different effusion profiles were used to demonstrate the effects of decomposition during different stages of growth. Secondary phase detection can be challenging in CZTSe, but a combination of SEM imaging and thin cross-section depth profile by EDS were found to best identify and locate the secondary phases that occur during different phases of growth for co-evaporated Cu2ZnSnSe4 films.

Deposition with a uniform incident flux followed by shuttered vacuum cool-down yielded films with a ZnSe phase at the absorber/Mo interface and Cu-rich composition at the surface of the exposed film. Devices from these absorber layers never exceeded conversion efficiencies of 1%. Decomposition at the surface could be prevented by continuing effusion of Se and Sn during the cool-down of the substrate. Resulting films demonstrated more faceted grains as well as significantly improved device performance. Secondary phases that traditionally form at the back contact during the beginning of growth were minimized by decreasing the substrate temperature to 300°C during the initial stages of deposition which reduced the ZnSe formed at the Mo interface. The thermochemical origin of the secondary phases will be discussed and the performance of representative devices will be presented.

Electrodes made of single-walled carbon nanotubes (SWCNTs) chemically modified by a series of anthraquinone derivatives (AQ) have been prepared and characterized by cyclic voltammetry in 0.1M H2SO4, using the standard 3 electrode set-up and by Raman spectroscopy. It has been demonstrated that a AQ modified SWCNT electrode provided between 114 to 220% higher specific capacitance, compared to pristine SWCNT electrode, depending on the length of the spacer between SWCNT and AQ.

This multi-phased study investigates the learning outcomes of courses taught in the K-14 classroom. Specifically, the methods and practices teachers use to develop and encourage 21st Century Skills including critical thinking skills and technological fluency in all subject areas, STEM and non-STEM related, are of great interest. Currently, these skills are in high demand in fields which develop advanced materials and are the backbone of the National Academiesdeveloped Frameworks for K-12 Science Education. Phase I participants in this study included high school and college educators while Phase II of the study will involve K-14 students. In this study, educators were asked to rate their teaching self-efficacy in two primary areas: critical thinking skills and technological fluency. This included questions related to components in their current curriculum as well as methods of assessment [e.g., rubrics]. The instrument created to measure self-efficacy was based on a modified ‘Science Teaching Efficacy Belief Instrument' (STEBI). All participants were from Connecticut. Results indicate that both STEM and non-STEM related subject areas offer an equally rich array of opportunities to effectively teach critical thinking and technological fluency at a variety of educational levels. The impact of Professional Development on teacher self-efficacy was of particular importance, especially in K-12 education.

In this report we develop a complete mathematical model for a porous scaffold from nitinol (NiTi – intermetallic phase) with a shape memory effect (SME), fabricated layerwise via the selective laser sintering (SLS) process. The operation of the SME bio-fluidic MEMS involves such physical process as a heat transfer, a phase transformation with a temperature hysteresis, stress-strain and electrical resistance variations accompanied the phase transformation. The simulations were conducted for the electro- and a thermo- mechanical hysteresis phenomenon, during the SME in the porous nitinol structures of the cylinder shape, which allow to formulate a recommendations for SLS. Previously done the temperature evolution of electrical resistivity was compared with our present calculations as a function of the laser-processing parameters for three dimensional nitinol samples. This model can be used for an estimation of a drug delivery system route during a porous phase volume changing.

Within an inverse design approach applied to a nitrogen-fixation catalyst we discuss options for calculating “jacket” potentials that fulfill a purpose-oriented target requirement. As a target requirement we choose the vanishing geometric gradients on all atoms of a subsystem consisting of a metal center binding the small molecule to be activated - in our case dinitrogen. The additional potential can be represented within a full quantum model or by a sequence of approximations of which a field of electrostatic point charges is the simplest. In order to analyze the feasibility of this approach, we dissect a known dinitrogen-fixating complex and analyze its ligand environment expressed by the “jacket” potential. It is discussed how this ligand-bypotential replacement can be generalized for future applications that eventually allow us to find a competitive synthetic nitrogen-fixation transition metal complex. It can be expected that such a ligand-by-potential replacement approach will be applicable to any type of host-guest chemical process.

Nanofluids are nano-size-powder suspensions in liquids that are of interest for their enhanced thermal transport properties. They are studied as promising alternatives as compared to ordinary cooling fluids, but the effects of nanofluids on wall materials are largely unknown. The authors developed an instrument that uses a low-speed jet on material targets to test such effects.

The work is presented of the authors’ experimental research on the early interactions of selected nanofluids (2% weight of alumina nanopowders in distilled water, and in solutions of ethylene glycol in water) with aluminum and copper samples as typical cooling-system materials. The observed surface changes (and possible nanoparticle deposition) for test periods as long as 14 hours were assessed by roughness and volumetric-removal wear measurements, and by microscope studies. Comparative roughness measurements indicate that alumina nanofluids in water and ethylene glycol solutions can start surface changes on aluminum surfaces, but show no effects on copper for the same testing conditions. These investigations set a baseline for further research and provide a suitable method for the testing of nanofluids effects in cooling system-materials.

The electrical and electromechanical properties of lithium niobate single crystals are investigated at high-temperatures. The total electrical conductivity is determined as a function of temperature by impedance spectroscopy for Z-cut crystals with different lithium content. For stoichiometric lithium niobate (sLN) the activation energy is found to be (1.49 ± 0.03) eV in the temperature range from 500 to 900 °C.

Further, the piezoelectric properties (resonance frequency, Q-factor) of X-cut lithium niobate crystals are determined at high temperatures for samples with compositions ranging from congruent to stoichiometric and, subsequently, compared to the conductivity data in order to identify loss contributions.

In this context, the high-temperature stability is examined for X- and Z-cut samples with compositions ranging from congruent to stoichiometric. Series of samples with and without additional alumina protection layers are annealed in air at 900 °C for approximately 50 h. Subsequently, depth profiles are measured by SNMS. In all cases, no lithium loss is observed and, therefore, a high-temperature stability of sLN for at least 50 h at 900 °C can be assumed in ambient air.

Further, the influence of protective layers with different thicknesses and compositions is investigated for X- and Z-cut samples. A lithium loss in the first 300 nm is observed for the Z-cut samples, while the X-cut samples show a behavior dependent on the type of protecting layer.

Ti-Ni-Sn type half-Heusler alloys which have the versatility to be either p- or n-type depending on the type of substitution, have been synthesized and investigated in the present work. The added advantage of doping them with multiple elements is that they will be amenable to bulk amorphous phase formation. The hole doped alloys were predominantly single phase with a cubic structure, while the electron doped alloys were found to have minor additional phases. All the alloys exhibit extremely weak metallic-like or degenerate semiconductor transport behaviour in the temperature range 20 K to 1000 K. The resistivity of p-type alloys exhibits semi-metallic-to-semiconducting transition at ∼ 500 K while the n-type alloys exhibit a weak metallic-like behaviour in the complete temperature range. The Seebeck coefficient has strong temperature dependence with a maximum of 45 μV K−1 in the temperature range 600-700 K in the p-type alloys. The n-type alloys however exhibit a linear variation of the Seebeck coefficient with temperature. The total thermal conductivity of the alloys increases with increasing temperature without any peak at low temperatures indicating significant disorder induced scattering. The p-type alloys have the lowest thermal conductivity compared to the n-type alloys. These alloys become amorphous after pulsed laser deposition except one alloy which exhibits compensated transport behaviour.

A fundamental challenge in solar-thermal-electrical energy conversion is the thermal stability of materials and devices at high operational temperatures. This study focuses on the thermal stability of selective emitters for solar thermophotovoltaic (STPV) systems to enhance the conversion efficiency. 2-D photonic crystals are periodic micro/nano-scale structures that are designed to affect the motion of photons at certain wavelengths. The structured patterns, however, lose their structural integrity at high temperature, which disrupts the tight tolerances required for spectral control of the thermal emitters. Through analytical studies and experimental observations, the four major mechanisms of thermal degradation of 2-D photonic crystal are identified: oxidation, grain growth and re-crystallization, surface diffusion, and evaporation and re-condensation. In this work, the design of a flat surface photonic crystal (FSPC) is proposed and experimental validations are performed.

In this study, slurry formulations in the presence of self-assembled surfactant structures were investigated for Ge/SiO2 CMP applications in the absence and presence of oxidizers. Both anionic (sodium dodecyl sulfate-SDS) and cationic (cetyl trimethyl ammonium bromide-C12TAB) micelles were used in the slurry formulations as a function of pH and oxidizer concentration. CMP performances of Ge and SiO2 wafers were evaluated in terms of material removal rates, selectivity and surface quality. The material removal rate responses were also assessed through AFM wear rate tests to obtain a faster response for preliminary analyses. The surfactant adsorption characteristics were studied through surface wettability responses of the Ge and SiO2 wafers through contact angle measurements. It was observed that the self-assembled surfactant structures can help obtain selectivity on the silica/germanium system at low concentrations of the oxidizer in the slurry.

This study reports on the fabrication of nanofluids/microfluids (NFs/MFs) with experimental and theoretical investigation of thermal conductivity (TC) and viscosity of diethylene glycol (DEG) base NFs/MFs containing copper nanoparticles (Cu NPs) and copper microparticles (Cu MPs). For this purpose, Cu NPs (20-40 nm) and Cu MPs (0.5-1.5 μm) were dispersed in DEG with particle loading between 1 wt% and 3 wt%. Ultrasonic agitation was used for dispersion and preparation of stable NFs/MFs, and thus the use of surfactants was avoided. The objectives were investigation of impact of size of Cu particle and concentration on TC and viscosity of NFs/MFs on DEG as the model base liquid. The physicochemical properties of all particles and fluids were characterized by using various techniques including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS) techniques. Fourier Transform Infrared Spectroscopy (FTIR) analysis was performed to study particles’ surfaces. NFs and MFs exhibited a higher TC than the base liquid, while NFs outperformed MFs showing a potential for their use in heat exchange applications. The TC and viscosity of NFs and MFs were presented, along with a comparison with values from predictive models. While Maxwell model was good at predicting the TC of MFs, it underestimated the TC of NFs, revealing that the model is not directly applicable to the NF systems.