Hybrid solar receivers utilizing both photovoltaic cells and thermal collectors are capable of collecting the entire solar spectrum for use in energy systems. Such systems provide efficient solar energy conversion using PV in addition to dispatchability through thermal storage by incorporating a thermal collector in conjunction with the PV. Proposed hybrid systems typically invoke spectrum splitting so to redirect photons optimized for PV electric conversion to a cell while non-PV efficient photons are directed to a thermal absorber. This work discusses a hybrid system with a selective solar filter using a suspended nanoparticle fluid to directly absorb non-PV photons. Non-absorbed photons pass through the filter and impact the PV. Choice of nanoparticles in the fluid allow absorption and transmission of specific wavelengths. Nanoparticles were chosen based on optimization simulations for a bandpass filter to a cSi solar cell. The synthesized fluid has been experimentally characterized to show the effects of high temperature on nanoparticle stability and optical properties. Thermodynamic modeling of the system suggests solar to electric efficiency of the total system is 23.2% if all thermal energy is converted to electricity through an organic Rankine cycle (ORC). However, high temperature generation could be used for industrial process heat at a specific temperature by changing parameters such as absorbed energy and flow rates. Furthermore, a prototype is being developed with 14x concentration to demonstrate the technology on-sun with initial testing targeted for the 2nd quarter of 2016. Overall, the hybrid nanoparticle filter concentrating solar collector can be modified to fit a variety of applications through easily changeable parameters in the system.

Silicon wafers coated with a 5μm thick layer of polyimide were treated with different surface modification techniques such as chemical adhesion promoters, oxygen plasma and an Ar+ sputter etch. After surface modification, the wafers were molded with a 1mm thick layer of PDMS. The adhesion of the PDMS was tested by peel testing and by using a Nordson DAGE wedge shear tester. It was found that commercially available chemical adhesion promoters and oxygen plasma treatment resulted in a very poor PI/PDMS adhesion, whereas the Ar+ sputter etch resulted in an adhesion so strong that the PDMS could not be delaminated from the PI surface without the failure of the material.

Large stores of unstable waste uranic materials such as fluorides or nitrates exist internationally due to legacy civil nuclear enrichment activities. Conversion of these uranic materials to layered metal uranates prior to disposal is possible via aqueous quench - precipitation type reactions. Previous studies1 have shown facile in-situ formation of geologically persistent and labile uranate colloids2 under simulated nuclear waste repository conditions, though the effects of local solution metal-uranium ratios on uranate stoichiometry have yet to be covered. This affects our understanding of how key radionuclides present in repository porewaters such as strontium or caesium may be sequestered in these uranate structures. In this work, we demonstrate a synthesis reaction for calcium monouranate particles via rapid anhydrous curing of a sol-gel. We present some results showing aqueous nucleation of uranate nanoparticles and their phase transformations during thermal curing as well as the effects of solution phase calcium loading on uranate phase purity in the cured particles.

In this work, we have explored the prospects of MoS2 and WS2, both of which are semiconducting 2D materials, for potential composite applications. In order to form 2D materials composites we have to first disperse them chemically in solution. MoS2 and WS2 powders were oversaturated in N-Methyl-2-pyrrolidone (NMP) solution at 37.5 mg/mL and sonicated at room temperature (RT) for sonication times ranging from 30 minutes to close to 24 hours. After solution processing, the samples with the 2D flakes were transferred to an Isopropyl Alcohol (IPA) bath for particle size distribution analysis. We have observed significant changes in particle size distribution spanning two orders of magnitude as a function of the sonication conditions. Specifically, the observed changes in particle size distribution for MoS2 and WS2 powders ranged from 44 microns down to 0.409 microns, and 148 microns down to 0.409, respectively, as compared to the untreated materials. Structural analysis was conducted using the SEM and X-Ray diffraction. The structural analysis using the SEM revealed morphological signatures between the two materials, where the MoS2 flakes had a randomly oriented distribution with occasional triangular flakes. In the case of the WS2, regardless of the sonication conditions, the WS2 flakes seemed to have a characteristic 120° angular distribution at the vertices, representing a rhombus with concave edges. The XRD analysis showed a minute shift in the characteristic peaks that maybe due to strain-induced effects as a result of the solution processing. Optical characterization of the materials was also conducted using Raman Spectroscopy to validate the average layer number resulting from the solution dispersions and the spatial and compositional uniformity of the two material samples.

This work is focused on the laser ablation synthesis of Cu/Ag nanocolloids in chitosan-based aqueous solution using a flow cell. A two-step process using femtosecond laser pulses was applied to consecutively ablate each metal. As-prepared nanomaterials were morphologically and spectroscopically characterized by Transmission Electron Microscopy, UV-Vis and X-ray Photoelectron spectroscopies. Application of Cu/Ag nanomaterials is envisaged as antibacterial materials for food packaging.

Density Functional Theory calculations of electronic and optical properties of NiO, with and without O vacancies, are the focus of this work. Two bands, one fully occupied and the other unoccupied, induced by an O vacancy, are found in the gap. These energy levels are identified and analyzed by means of a local density of states (LDOS) calculation, and notable crystal field splitting can be seen. The real and imaginary parts of the dielectric function are calculated, and an additional optical transition can be seen at lower energy, which can be attributed to the O vacancy induced state in the band gap.

Integrating oxide heterostructures on silicon has the potential to leverage themultifunctionalities of oxide systems into semiconductor device technology. Wepresent the growth and characterization of two-dimensional electron gas (2DEG)oxide systems LaTiO3/SrTiO3 (LTO/STO) andGdTiO3/SrTiO3 (GTO/STO) on Si(001). We showinterface-based conductivity in the oxide films and measure high electrondensities ranging from ∼9 × 1013 cm-2interface-1 in GTO/STO/Si to ∼9 ×1014 cm-2 interface-1 in LTO/STO/Si. Weattribute the higher measured carrier density in the LTO/STO films to a higherconcentration of interface-bound oxygen vacancies arising from a lower oxygenpartial pressure during growth. These vacancies donate conduction electrons andresult in an increased measured carrier density. The integration of such 2DEGoxide systems with silicon provides a bridge between the diverse electronicproperties of oxide systems and the established semiconductor platform andpoints toward new devices and functionalities.

A reverse micro-emulsion method has been investigated to control crystal morphology in a nanometer region and to increase specific surface area for calcium phosphate. The nanocrystals with the control of its morphology is a candidate of drug delivery carriers. This study investigated the effects of mixing volume ratios of two surfactants, tween80 (T) and aliquate 336 (A) in kerosene as an oil phase, and pH values in the nano-region on crystalline phases and specific surface area of calcium phosphate synthesized by the reverse micro-emulsion method. A di-ammonium hydrogen phosphate solution including phosphoric acid at pH of 6.3 and a calcium nitrate solution at pH of 5.7 were adjusted, and both the solutions were separately added into the kerosene with the surfactants. Both the emulsions were then mixed at the same volume and the Ca/P ratio of 1.0, and stirred at room temperature for 24 hours. The crystalline phases were dependent on the T amounts; pure DCPD with the specific surface area of 6.7 to 12 m2/g was obtained at the T/A ratio of 4, the mixture of DCPD and DCPA with that of 48 to 162 m2/g was at the ratios of 5 to 8, and a low crystalline HAp with 163 m2/g was at the ratio of 9. These specific surface areas of DCPD (T/A=4) and HAp (T/A=9) were apparently higher than those prepared with a wet method, 7.8 times and 1.8 times respectively. DCPA with 43 m2/g was successfully produced to decrease the pH of phosphate solution at T/A of 9. The change of crystalline phases would be explained as follows; the increase of T amount decreased the micro-emulsion sizes to reduce bulk water to be DCPA, and increased the pH to precipitate HAp nanocrystals.

Two different methods were used to synthesize 200 nm thick single-phase, orthorhombic-PtSi films: (i) e-beam co-evaporation (EBC) of Pt and Si onto r-sapphire substrates and (ii) solid-state reaction (SSR) of sputtered Pt films on Si (100) wafers. Morphology, electrical conductivity, and crystalline structure were characterized for as-grown films and for films annealed in air at 1000 °C via scanning electron microscopy (SEM), 4-pt conductivity measurements, and in situ X-ray diffraction (XRD). As-grown EBC films exhibit columnar grain morphology and slight (101) crystalline texture, while SSR films exhibit granular morphology with many voids and a strong (002) texture. Above 600 °C, EBC PtSi films rapidly oxidize to form crystalline Pt3Si and amorphous SiO2 phases. Around 1000 °C, the Pt3Si phase melts and c-Pt grains nucleate. After air annealing for 6 h at 1000 °C, room-temperature XRD shows that the oxidized EBC films consist of Pt3Si and Pt phases within a SiO2 matrix and become electrically insulating. SSR films initially form with a (002) o-PtSi orientation and above 900 °C they recrystallize to preferred (101) texture and exhibit an unchanged electrical conductivity and a stable film morphology during 48 h of air annealing at 1000 °C. Separate oxidation mechanisms are proposed for the two film types.

Methylammonium lead halide perovskites have been developed as highly promising materials to fabricate efficient solar cells in the past few years. We have investigated degradation of co-evaporated CH3NH3PbI3 films in ambient air, oxygen and water respectively using x-ray photoelectron spectroscopy (XPS), small angle x-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The CH3NH3PbI3 film has an excellent atomic ratio and crystallinity. XPS results indicate that the film is not sensitive to oxygen and dry air, while ambient and water exposures achieve similar effects. XRD further indicates a structural conversion to PbI2 and a drastic morphology change from smooth to rough is revealed by AFM and SEM. The experiment indicated that H2O plays a dominated role in the degradation of CH3NH3PbI3 films. The degradation can be characterized by almost complete removal of N, substantial reduction of I, residual of PbI2, C, O, and I compounds on the surface.

Water degradation of glass waste forms has been studied extensively under a variety of conditions including of bulk glass immersed completely in static or dynamic water. In practice, the vitrified nuclear waste cracks as soon as poured into a container because of differences in thermal expansion coefficients. In addition, in repository the canisters may be only partially immersed in water. Later, water condenses on the surface of glass which corrodes releasing ions. In this work experiments have been performed to understand these effects on the degradation of International Simple Glass (ISG). Simulated cracks were found to develop pitting corrosion in the crack openings when tested by immersing ISG in water. Under load, these pits concentrated stress and grew as large planar cracks inside the glass. The condensation of water on glass surfaces leads to formation of pits and growth of calcium silicate crystals.

During the activation and charge process, vacancies are generated in the Li2MnO3 component in lithium-rich layered cathode materials. The chemical expansion coefficient tensor associated with oxygen vacancies, lithium vacancies and a Li-O vacancy pair were calculated for Li2-xMnO3-δ. The chemical expansion coefficient was larger for oxygen vacancies than for lithium vacancies in most directions. Additionally, the chemical expansion coefficient for a Li-O vacancy pair was shown to not be a linear sum of the chemical expansion coefficients of the two vacancy types, suggesting that the oxygen vacancies and lithium vacancies in Li2-XMnO3-δ exhibit a coupling effect.

The performance of new type three dimensional buried-in electrode structure ultraviolet photodetector fabricated on single crystal diamond epitaxial layer was investigated. The epitaxial layer was grown on high-pressure-high-temperature Ib-type diamond substrate. Then the buried-in electrodes with different depths were formed by oxygen plasma reactive ion etching method and radio frequency magnetron sputtering technique on this diamond layer. Compared with that of traditional planar electrode photodetector, the responsivity of buried-in electrode photodetector shows higher value, which reaches the highest when the electrode depth is 100 nm.

Persistent current joints are a critical component of commercial superconducting magnets.The standard jointing method widely used in the magnet industry for technological low temperature superconducting wires such as NbTi and Nb3Sn wires uses a superconducting solder (e.g. PbBi). In these joints the physical and superconducting properties of the solder materials inevitably play an important role in the overall performance of the joint. Key requirements for superconducting solders include low melting point to prevent degradation of the superconducting filaments during joining, good wettability of the superconducting filaments, suitable liquid phase viscosity, and finally adequate superconducting properties to enable sufficient supercurrent to pass through the joint under typical operating conditions (typically at 4.2K in a field of 1 T for an MRI magnet). PbBi solder satisfies all these criteria, but restrictions on the use of lead in the magnet industry are expected in the relatively near future, so new lead-free jointing techniques need to be developed.

One approach is the development of superconducting lead-free solder materials. In our work, we have focussed on the In-Sn system and ternary systems involving In and Sn as two of the elements. Thermodynamic modelling has been used to produce ternary phase diagrams of potential alloy systems, and various formulations have been fabricated in order to explore how microstructure and phase chemistry influence the superconducting properties of the solders. Alternative approaches to fabricating lead-free joints, including spot welding and cold-pressing, have also been investigated. These methods have the potential advantage of achieving direct NbTi-NbTi joints with no intermediate, lower performance superconducting material. The spot welding method produced joints with the best superconducting performance, signifiantly better than the currently used PbBi solder, but the lack of reproducibility in this technique may be a problem from an industrial point of view.

Cellulose nanocrystals (CNCs) are high-strength sustainable nanomaterials, theincorporation of which to a host polymer matrix can potentially lead tonanocomposites with superior mechanical properties. However, the mismatch insurface energy of CNCs and common structural polymers is a challenge that needsto be overcome to prevent the aggregation of CNCs and ensure the robustintegration of CNCs into a polymer matrix. Herein, we report an approachinvolving the functionalization of CNCs with maleated-anhydride polypropylene(MAPP) through diethylenetriamine (DETA) linkers to significantly enhance thecompatibility between CNCs and polypropylene. Polypropylene/modified CNCnanocomposites displayed 74% and 76% increase in elastic modulus in comparisonto neat polypropylene and polypropylene/untreated CNC nanocomposites,respectively. The tensile strength was also higher for nanocomposites withmodified CNC than neat polypropylene, as well as nanocomposites with untreatedCNCs. The tensile strength at 5.5% strain of polypropylene/modified CNCnanocomposites was 32% and 28% larger that of polypropylene andpolypropylene/untreated CNC nanocomposites, respectively. Finally, suchCNC-based nanocomposites have a lower density than many competitive systemsresulting in opportunities to propagate this environmentally-responsibletechnology to nanocomposites used in additive manufacturing, automotiveapplications, construction materials and consumer products.

A method for synthesizing and structuring 2D-MoS2/rGO (molybdenum disulfide/reduced graphene oxide) nanocomposite-based electric double layer capacitor (EDLC) that has a slower discharge rate and higher energy density than rGO-based EDLC (RG-EDLC) is reported. The rGO electrode and the nanocomposite were characterized using powder XRD and SEM for their physical and structural properties. Cyclic voltammetry (CV) was used to analyze the electrochemical behavior of the EDLCs. A maximum current density at which the MoS2/rGO nanocomposite-based EDLC (MRG-EDLC) can charge and discharge was 2.5 A/g, while it was 1A/g for the RG-EDLC. The specific capacitance of the MRG-EDLC was 14.52 F/g at 0.5 A/g with an energy density of 8.06 Wh/kg.

The U.S. Department of Energy (DOE)’s SunShot Initiative is a collaborative national effort to reduce the price of solar energy to 6¢/kWh without subsidy for utility scale installations by 2020. Thin-film photovoltaics offer a promising path to reach this goal. Analysis of the levelized cost of energy (LCOE) from photovoltaics (PV) highlights the dependence on the module and system efficiency and lifetime in addition to module price. Here we summarize challenges and opportunities for CdTe and CIGS PV research and show that a substantial effort is still needed in areas such as device design and material improvement to reach higher efficiency and reliability connected with low-cost and robust module-scale implementation. We also discuss how SunShot Initiative funding is addressing key research areas in CdTe and CIGS PV and show how recent progress in SunShot projects is guiding funding priorities in thin-film PV research.

The present paper has suggested a new non-observational method to calculate electronic structure of carbynes taking into consideration the influence of the spin-orbital coupling. The method is demonstrated by calculations of the structure splitting at the Fermi level in cumulene and polyyne carbynes having semiconductor and metallic electronic structure correspondingly. These couplings result in 2 - 3 meV gaps.

Finite element modelling has been used to optimise the current/ voltage (I/V) characteristics of metal/ n-SiC and metal/ n-Si diodes incorporating a thin interfacial layer. The electrical properties of the diodes have been examined in relation to the polytype of SiC (3H, 4H or 6C), the doping level, NA, (1015 - 1018cm3) of the substrate, the defect state density, Dit and the work function of the Schottky metal, Φm. The modelling by Technology Computer-Aided Design (TCAD) has shown that the presence of an interfacial insulating layer with a thickness of 1.0 nm has reduced the reverse leakage current of the diode by a factor of ∼102 in Si and 1013 (from 10-19 A to 10-6 A) for SiC with only a minor reduction (∼ 0.8 times) in the forward current in SiC. The properties of the diodes have been modelled at room temperature without thermal annealing.