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The impact of nanostructured broadband antireflection (AR) coatings on solar panel performance has been projected for a broad range of panel tilt angles at various locations. AR coated films have been integrated on test panels and the short-circuit current has been measured for the entire range of panel tilts. The integration of the AR coatings resulted in an increase in short-circuit current of the panels by eliminating front sheet reflection loss for a broad spectrum of light and wide angle of light incidence. The short-circuit current enhancement is 5% for normal light incidence and approximately 20% for off-angle light incidence. The National Renewable Energy Laboratory (NREL) System Advisor Model (SAM) predicts that this AR coating can yield at least 6.5% improvement in solar panel annual power output. The greatest enhancement, approximately 14%, is predicted for vertical panels. The AR coating’s contributions to vertical mount panels and building-integrated solar panels are significant. This nanostructured broadband AR coating thus has the potential to lower the cost per watt of photovoltaic solar energy.
The phase equilibrium and oxidation behavior of the disilicides that form in the Nb-Cr-Si ternary system have been investigated. Although NbSi2 and CrSi2 both exhibit a C40 crystal structure, they form separate ranges of compositional homogeneity in the ternary system. Their phase boundaries at 1300 °C have been experimentally determined in this study. The binary NbSi2 exhibited poor oxidation resistance, showing pest-like behavior during oxidation at temperature above 800 °C. In contrast, the alloys containing Cr showed much better oxidation resistance up to 1200 °C.
The complete ternary system Co-Al-W was fabricated as a thin film materials library by combinatorial magnetron sputtering. The materials library was investigated using high-throughput characterization methods such as optical measurements as well as automated resistance screening. The obtained data indicate possible phase regions and compositional regions which show early surface oxidation. The demonstrated approach illustrates that using high-throughput measurement methods provides a fast access to data of relatively unexplored materials systems. The gained data provides a valuable basis for further in-depth studies of the investigated materials systems.
HER-conjugated hollow nanoparticles (HER–HNP, ca. 50 nm in diameter) are fabricated using a dissolution and re-deposition method and used to encapsulate camptothecin (CPT). The HER-HNP-CPT is used as an anti-cancer agent for human breast cancer SK-BR-3. It has excellent mono-dispersity and a high loading efficiency for CPT. Two kind of cell lines are used in this study; SK-BR-3 and RAW 264.7. SK-BR-3 and RAW 264.7 are used as targeting and controlling cell line, respectively. When SK-BR-3 cells are treated with HER-HNP-CPT, the viability decreased to 55%, which is ca. 1.5 times higher anti-cancer efficiency in comparison to RAW 264.7. The HER-HNP-CPT system offers a new opportunity to facilitate implementation of a hydrophobic drug for effective anti-cancer treatment of SK-BR-3 cells.
Chalcogenide materials have regained attention after the recent recognition of the compatibility of transition metal dichalcogenides with graphene. Additionally, there has been a recent appreciation for the rich variety of properties they support due to the anomalies in the materials’ intrinsic band structure. These materials generally have layered structures and weak interlayer connection through the chalcogen layer and its van der Waals type bonding. We have synthesized orthorhombic copper telluride and measured its electrical transport properties. The results of these measurements reveal that the conduction is metallic in both the in-plane and out-of-plane directions. The range of stability of this structure is examined along with the lattice constants. The independence of the resistivity in samples to changes in excess copper indicates that the transport is essentially within the conducting planes. This result shows that the material hosts two-dimensional character likely due to its covalent interlayer bonding.
Long term stability of mixed perovskite compounds is one of the important concerns for prolonged viability and economical use of perovskite based solar cells. Degradation in perovskite films mainly occurs due to exposure to moisture. Hence, a controlled atmospheric condition and lower humidity is preferred for device fabrication and use. Many different strategies such as use of thin and wide band gap semiconductor layer, improvement in pour filling of metal oxide film, and utilization of AgTFSI have been attempted to improve device stability. However, for long term durability, there is an urgent need to increase stability of parent perovskite layer, apart from use of protective layers. In this study we examined water resistant additive, structural modifications, and stoichiometric modification for enhanced film durability. These strategies and preliminary results are discussed in this report.
Shape memory alloys (SMA) are metallic attractive engineering materials due to their capacity to store pre-defined shapes through a thermally induced phase transition from a solid state. This paper aims to evaluate the influence of solubilization thermal treatments on a NiTi shape memory alloy originally fabricated by vacuum induction melting and then reprocessed by plasma melting followed by injection molding (Plasma Skull Push Pull process) into different metal molds (steel, aluminum, brass and copper) in order to compare the thermal properties regarding to its raw state. The thermal treatments of solubilization were carried out at 850°C in different times (2n function, n = 0, 1, 2 and 3, in hours). The influence of solubilizing treatments in the NiTi shape memory alloy was analyzed using the following characterization techniques: Differential Scanning Calorimetry (DSC) and Electrical Resistance as a function of Temperature (ERT). The results demonstrate that the solubilization heat treatments applied on the reprocessed NiTi shape memory alloy through the plasma skull push pull process, provides important changes in the phase transformation of the material. Therefore, it was demonstrated that it is necessary to solubilize the material after melting or remelting the NiTi shape memory alloy via this process to obtain mini-actuators products with homogeneous properties.
The effect of W addition on microstructure and mechanical properties of Ni3Al (L12) and Ni3V (D022) two-phase intermetallic alloys has been investigated. W was added to the base alloy composition, Ni75Al10V12Nb3 (at. %) in place of either Ni, Al or V. The W-added alloy ingots were heat-treated in vacuum at 1575 K for 5 h. The majority of W-added alloys showed a dual two-phase microstructures while the alloy in which 3 at. % W substituted for Ni exhibited the dual two-phase microstructure containing W solid solution dispersions. Vickers hardness was significantly enhanced by W addition, which is primarily due to solid-solution strengthening.
In situ transmission electron microscopy (TEM) has become anincreasingly important tool for materials characterization. It provides keyinformation on the structural dynamics of a material during transformations andthe ability to correlate a material’s structure and properties. Withthe recent advances in instrumentation, including aberration-corrected optics,sample environment control, the sample stage, and fast and sensitive dataacquisition, in situ TEM characterization has become morepowerful. In this article, a brief review of the current status and futureopportunities of in situ TEM is provided. The article alsointroduces the six articles in this issue of MRS Bulletinexploring the frontiers of in situ electron microscopy,including liquid and gas environmental TEM, dynamic four-dimensional TEM,studies on nanomechanics and ferroelectric domain switching, andstate-of-the-art atomic imaging of light elements (i.e., carbon atoms) andindividual defects.
Land-Grant Universities including those that were developed under the second Morrill Act in 1890 have historically been a key resource for the best scientifically based information for agricultural production. The University of Maryland Eastern Shore (UMES) is situated on the Eastern Shore of Maryland, a critical area, with small farms and underserved farmers. This unique location serves as an interface between University specialty crop research and those farmers. While prices of crops such as corn and soy, which traditionally have been a major source of income for local farmers, have increased dramatically over the past years, small farms cannot generate enough income from these commodity crops alone, and a need alternatives for extra income. At UMES agricultural, chemical and material research specialists formed a special research and training cluster in which they work jointly on non-traditional and non-food related applications of specialty crops in the field of material research leading to non-traditional applications of such crops. Examples of such research are: (i) blending natural specialty crops extracts with polymers to develop natural and effective anti-foaling coating to prevent biofilm formation on objects including military ships, platforms etc.; (ii) using biocompatible polymeric chitosan-based blends as sorbents for reversible carbon dioxide capturing and controlled release in algae-growing reactors and in the process of transforming biomass into alcohol by fermentation to increase the effectiveness of biomass use. Only about 20% of students-researchers in the cluster are graduate students and the rest are undergraduates. The main focus is to provide undergraduate students with research experience as a powerful tool for their education and career development. Focus on students performing outstanding research through their undergraduate education is the main priority in UMES. Working on the material research projects described above, our material cluster has developed some educational practices for effectively involving undergraduate students into research. These practices include early involvement, the development of special workshops and training settings for fast project starts, working in small groups lead by more experienced students, picking projects that can be easily divided into small tasks suitable to undergraduate student’s schedules, and participation in scientific conferences for undergraduates and others. In this presentation we will review two material research projects for undergraduate students mentioned above and will show how our best practices are implemented in each of these projects.
We study the electronic transport through epitaxial GaAs nanopillars that are only 16 nm long, with diameters of about 100 nm at the upper and 40 nm at the lower end. The pillars can be considered to be very short conical nanowires embedded in AlGaAs. They represent quantum point contacts between two perfectly lattice matched three-dimensional GaAs charge reservoirs. Distinctive asymmetries are found in the current-voltage characteristics. We associate them with the conical shape of the pillars. Although contact reservoirs and pillars are made from the same material, the transport through the pillars is dominated by tunneling across shallow barriers. This is explained by the quantum size effect on the electronic states within the pillars.
The optimization of the figure of merit of thermoelectric materials requires the simultaneous control of the material composition and microstructure. Assembly of nanoparticles obtained by a solution route is an attractive bulk fabrication method because size and shape of the nanoparticles can be tuned by variation of the synthesis conditions. Recently, new synthetic pathways were reported among which reducing agent assisted, surfactant free processes. We report here the evaluation of this method for the synthesis of Bi2TexSe3-x alloyed nanoparticles with varying selenium concentrations. X-ray diffraction studies conducted on powder and pellet samples show that two alloyed phases are present in the sample even at low selenium content. The careful study of the position of the diffraction peaks as function of the formulation shows that this behaviour could arise from the difference in reactivity of selenium and tellurium. Moreover, the electrical conductivity of the samples is shown to increase upon selenium addition while the Seebeck coefficient is reduced. Power factor shows an optimum value around 20% selenium content with a large tolerance in composition.
Adenosine triphosphate (ATP) has numerous biological functions both intra- and extracellularly, including effects on the directed migration of cells with a regenerative potential in brain tissue. Therefore, carrier systems would be of interest that would be capable to be loaded with ATP and release it in a controlled manner. In the present study, poly(n-butylcyanoacrylate) (PBCA) nanoparticles as a potential carrier system were prepared by anionic polymerization using different polymerization media, which resulted in different zeta potential values and in some cases aggregation of nanoparticles. By decorating the particle surface with positively charged diethylaminoethyl dextran, multivalent ionic interaction allowed to load ATP to the nanoparticles by adsorption. In release experiments, an ATP release over 6 hours was observed. ATP-loaded nanoparticles may thus be suitable to explore biological effects of short-term ATP delivery for biomedical applications.
Recent studies of single-walled carbon nanotubes (CNTs) in aqueous media have showed that water can significantly affect the tube mechanical properties. CNTs under hydrostatic compression can preserve their elastic properties up to large pressure values, while exhibiting exceptional resistance to mechanical loadings. It was experimentally observed that CNTs with encapsulated linear carbon chains (LCCs), when subjected to high hydrostatic pressure values, present irreversible red shifts in some of their vibrational frequencies. In order to address the cause of this phenomenon, we have carried out fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations for model structures mimicking the experimental conditions. We have considered the cases of finite and infinite (cyclic boundary conditions) CNTs filled with LCCs (LCC@CNTs) of different lengths (from 9 up to 40 atoms). Our results show that increasing the hydrostatic pressure causes the CNT to be deformed in an inhomogeneous way due to the LCC presence. The LCC/CNT interface regions exhibit convex curvatures, which results in more reactive sites, thus favoring the formation of covalent chemical bonds between the chain and the nanotube. This process is irreversible with the newly formed bonds continuing to exist even after releasing the external pressure and causing an irreversibly red shift in the chain vibrational modes from 1850 to 1500 cm−1.
A monolithic fuel design based on U–Mo alloy has been selected as the fuel type for conversion of United States’ high-performance research reactors (USHPRRs) from highly enriched uranium (HEU) to low-enriched uranium (LEU). In this fuel design, a thin layer of zirconium is used to eliminate the direct interaction between the U–Mo fuel meat and the aluminum-alloy cladding during irradiation. The co-rolling process used to bond the Zr barrier layer to the U–Mo foil during fabrication alters the microstructure of both the U–10Mo fuel meat and the U–Mo/Zr interface. This work studied the effects of post-rolling annealing treatment on the microstructure of the co-rolled U–Mo fuel meat and the U–Mo/Zr interaction layer. The U–Mo/Zr interaction-layer thickness increased with the annealing temperature with an Arrhenius constant for growth of 184kJ/mole, consistent with a previous diffusion-couple study. The phases in the U–Mo/Zr interaction layer produced by co-rolling, however, differ from those reported in the previous diffusion-couple study.
Some potential applications of the nanoribbons and nanorods occur in the medical field, using gold nanoribbon therapies against cancer cells because they have absorption in the near infrared region. In this paper, the nanoribbons were obtained by physical-chemical method based on multilayer carbon nanotubes functionalized with carboxylic radical groups (-COOH). The obtained material was characterized by Scanning Transmission Electron Microscopy (STEM) and Infrared Spectroscopy (FTIR). The obtained nanoribbons have a diameter of 320 nm with preferably 126° angle in their morphology.
Nanostructured anatase TiO2 is a promising material for gas sensing and photocatalysis. In order to modify its catalytic properties, the lanthanide (Ln) ions Eu3+, Gd3+, Nd3+ and Yb3+ were precipitated on the surface of TiO2 nanoparticles (NPs) by hydrothermal treatment. Results from Raman spectroscopy and X-ray diffraction (XRD) measurements show that the anatase structure of the TiO2 nanoparticles was preserved after hydrothermal treatment. SEM and TEM show a heterogeneous distribution in size and a nanocrystallite morphology of the TiO2 NPs (∼ 14 nm in size) and EDX confirmed the presence of the Ln-ion surface doping after hydrothermal treatment. An increase in photoluminescence (PL) was observed for the Ln-surface-doped TiO2 NPs when measurements were made in forming gas (5% H2 + 95% Ar) at 520 °C. In contrast, the PL measurements made at room temperature did not show any noticeable difference in forming gas or in ambient air. Our temperature-dependent PL results obtained in different gas environments are consistent with modification of oxygen-vacancies and hole-defects due to a combination of hydrothermal treatment and surface Ln-doping.
This paper presents a method for noise-free recording of the keyboard-based musical instruments. By integrating an r-shaped triboelectric generator (TEG) into the keyboard of a piano, it can produce electric signal while playing music due to the combination of contact electrification and electric induction. We investigated the electric signal and developed a graphical user interface to convert the electric signal back to music. Using the piano and the graphical user interface, active noise-free recording can be realized. Namely, only the sound produced by the piano can be converted and recorded, while other noise in the environment can be filtered automatically.