High temperature solid state sodium (23Na) magic angle spinning (MAS) NMR spin lattice relaxation times (T1) were evaluated for a series of NASICON (Na3Zr2PSi2O12) materials to directly determine Na jump rates. Simulations of the T1 temperature variations that incorporated distributions in Na jump activation energies, or distribution of jump rates, improved the agreement with experiment. The 23Na NMR T1 relaxation results revealed that distributions in the Na dynamics were present for all of the NASICON materials investigated here. The 23Na relaxation experiments also showed that small differences in material composition and/or changes in the processing conditions impacted the distributions in the Na dynamics. The extent of the distribution was related to the presence of a disordered or glassy phosphate phase present in these different sol-gel processed materials. The 23Na NMR T1 relaxation experiments are a powerful tool to directly probing Na jump dynamics and provide additional molecular level details that could impact transport phenomena.

This paper reports on the progress of an ongoing strategy for dissemination of a set of science communication workshops targeted to students participating in undergraduate research experiences on university campuses. Previous MRS Proceedings papers by the first author and collaborators focused on (1) the development and validation of the REU Science Communication Workshop (REU SCW) model through iterative practice, research and evaluation between 2005 and 2009, and (2) the 2012 testing of a scaffolded and piggybacked "beyond train-the-trainer” mode of dissemination of the REU SCW model to multiple university campuses, as compared to a highly-validated but less efficient one-to-one transfer process deployed between Boston and Madison between 2010 and 2012. This new paper reports on the follow-up effort to confirm and validate the success of the REU SCW workshop model as implemented at the second-wave of dissemination sites by the new cohort of participating undergraduate research program directors. We analyze data gathered in 2013 and 2014 from the participating students, faculty, and providers. The results indicate that the second-wave providers were able to reproduce the successful results achieved at the origination and first dissemination sites, and that providers and stakeholders at these additional sites value the model enough to continue providing it and in some cases to laterally expand it to other programs on campus. These findings suggest that it is possible to greatly expand the number of undergraduate research experience students receiving quality coaching in professional science communication skills by providing their program directors with a comprehensive professional development experience, employing the scaffolded, piggybacked, “beyond train-the-trainer” professional development model.

We consider the simplest one-constant model, put forward by J. Eriksen, for nematic liquid crystals with variable degree of orientation. The equilibrium state is described by a director field n and its degree of orientation s, where the pair (n, s) minimizes a sum of Frank-like energies and a double well potential. In particular, the Euler-Lagrange equations for the minimizer contain a degenerate elliptic equation for n, which allows for line and plane defects to have finite energy. Using a special discretization of the liquid crystal energy, and a strictly monotone energy decreasing gradient flow scheme, we present a simulation of a plane-defect in three dimensions to illustrate our method.

Na2Ti3O7, a potential negative electrode for Na batteries, is investigated by combining experiments and first-principles calculations at the Density Functional Theory (DFT) level. A structural model is proposed for the reduced phases (A 2+xTi3O7), with all alkali ions in octahedral coordination, leading to a distorted rocksalt type structure. The calculated elastic constants support the mechanical stability of the proposed Na4Ti3O7 structure. Calculated average intercalation potentials are 0.37 V for Na insertion in Na2Ti3O7 and 1.46 V for Li insertion in Li2Ti3O7, being in very good agreement with the values observed experimentally (0.3 V and 1.6 V respectively). The higher polarizing character of Li ions vs Na ions acts as a key-factor to bring the Li intercalation voltage 0.7 V above that of Na intercalation in layered-A 2Ti3O7 materials.

Photodynamic therapy (PDT) is an alternative to traditional cancer treatments. This approach involves the use of photosensitizer (PS) agents and their interaction with light. As a consequence, cytotoxic reactive oxygen species (ROS) are generated that, in turn will destroy tumors. On the other hand, ZnO is a biocompatible, nontoxic, and biodegradable material with the capability to generate ROS, specifically singlet oxygen (SO), which makes this material a promising candidate for 2-photon PDT. Doping ZnO with Li species is expected to induce defects in the host oxide structure that favors the formation of trap states that should affect the electronic transitions related to the generation of SO. The present work reports the effect of the level of Li-doping on the ZnO structure and its capability to generate SO. Li-doped ZnO nanoparticles were synthesized under size-controlled conditions using a modified version of the polyol method. XRD measurements confirmed the development of well-crystallized ZnO Wurtzite; the average crystallite sizes ranged between 13.3nm and 14.2 nm, with an increase in Li content. The corresponding band gap energy values, estimated from UV-vis measurements, decreased from 3.33 to 3.25 eV. Photoluminescence (PL) measurements of Li-ZnO revealed the presence of emission peaks centered on 363nm, 390nm, and 556 nm; these emission peaks correspond to the exciton emission, transition of shallow donor levels near of the conduction band to valence band such as interstitial Zn, and oxygen vacancies, respectively. The observed increase of the emission intensity of the 390 nm emission peak, relative to the intensity of the main emission peak at 363nm, was attributed to the promote of trap states due to interstitial Zn or Li-incorporation into the host oxide lattice. SO measurements evidenced the enhancing effect of the Li concentration on the capability of the doped ZnO to generate this species. This Li-dependence of SO generation can be attributed to the enhancement of the concentration of trap states in the host ZnO, as suggested by PL measurements. Accordingly, Li-ZnO would become cytotoxic to cancer cells via photo-induced ROS generation enabling this nanomaterial to be considered as a potential direct PS agent for the 2-photon PDT route.

Incorporation of properly designed nanostructures in solar cells improves light trapping and consequently their power conversion efficiencies. Due to its unique structure, a silicon nanowire (SiNW) matrix provides excellent light trapping and thus offers a promising approach for cost-effective, stable and efficient silicon thin film photovoltaics. Moreover, by decoupling the light absorption and carrier collection directions, radial junction solar cells built around the SiNWs allow the use of very thin active layers. As a matter of fact, radial PIN junctions with 9.2% power conversion efficiency have already been demonstrated on glass substrates with only 100 nm thick intrinsic hydrogenated amorphous silicon layers. The most straightforward way to further improve the short circuit current density is to use an active layer with a lower band gap. In this work, the performances of devices with two different low band gap materials, e.g., hydrogenated microcrystalline silicon (μc-Si:H) and hydrogenated amorphous silicon germanium alloy (a-SiGe:H) are presented. To the best of our knowledge, this is the first demonstration of a-SiGe:H radial junction solar cell.

The impact of mass and lattice difference on thermal boundary conductance is investigated using non-equilibrium molecular dynamics with the Lennard-Jones interatomic potential. Results show that the maximum thermal boundary conductance is achieved when the mass and the lattice of two dissimilar materials are matched, although the composite thermal conductance is not necessarily a maximum. It is observed that the small difference in mass and potential well depth has as significant an impact as large differences, and that the frequency mismatch is an important factor that affects thermal boundary conductance. It is, also, found that inelastic scattering begins to play a role at the interface as the temperature increases.

This paper investigates the development process of emergent materials for architecture by looking at the example of Phase Change Materials. In the context of the complex nature of the constructed environment and the functional and performance requirements for buildings, emergent materials have to be carefully tuned for maximum performance. Investigating the relationship of time, space and matter in the design and development process through interdisciplinary endeavors is at the heart of this investigation. Furthermore, a shift from multidisciplinary endeavors to truly interdisciplinary collaboration that crosses the traditional boundaries of the individual fields is suggested.

The study of corrosion behavior of polyurethane/nanohydroxyapatite hybrid coating in aerated Hank solution at 25 °C by Potentiodinamic and Electrochemical Impedance techniques was realized. The nanohydroxyapatite (nHA) powders were synthesized by ultrasonic assisted co-precipitation wet chemical method and then mixed with pure polyurethane (PU) during the polymerization. Results were supported by SEM morphologic characterization. Results showed that good corrosion resistance of hybrid coating, showing small corrosion product layer formation. Corrosion mechanisms are affected by an increasing of polarization resistance, promoting decreasing in the corrosion rates. Diffusion of ionic species was the governing mechanism in the corrosion behavior of polyurethane/nanohydroxyapatite hybrid coating.

The European Spallation Source is Europe’s next generation high-power neutron source utilising a linear accelerator and a rotating tungsten target to produce neutrons that will be used for fundamental research and industrial applications. The facility is co-hosted by the states of Denmark and Sweden, and while the main site will be placed in Lund, Sweden, the Data Management and Software Centre will be located in Copenhagen, Denmark. The facility will cover a broad range of scientific applications in the fields of physics, chemistry, biology, or life sciences. A focus will also be materials science and engineering, and dedicated instruments will gradually become available to the user community once neutrons will be produced neutrons from 2019 onwards.

Microstructures and mechanical properties of directionally solidified (DS) MoSi2 / Mo5Si3 / Mo5Si3C ternary eutectic composites were investigated. Ternary eutectic microstructure of a script-lamellar type that is characterized by rod-shaped Mo5Si3 and Mo5Si3C phases extending along the growth direction in the MoSi2 single crystalline matrix was developed simply by directional solidification at a growth rate of 10 mm/h. Compression tests along $[{\rm{1}}\mathop 1\limits^- 0]_{MoSi_2 }$ nearly parallel to the growth direction revealed that the DS ternary eutectic composites were plastically deformed above 1000 °C. Yield stresses of the DS ternary eutectic composites were much higher than those of binary composites mainly because of a smaller average thickness of MoSi2 matrix.

Despite recent advancements in digital fabrication and manufacturing, limitations associated with computational tools are preventing further progress in the design of non-standard architectures. This paper sets the stage for a new theoretical framework and an applied approach for the design and fabrication of geometrically and materially complex functional designs coined Fabrication Information Modeling (FIM). We demonstrate systems designed to integrate form generation, digital fabrication, and material computation starting from the physical and arriving at the virtual environment. The paper reviews four computational strategies for the design of custom systems through multi-scale trans-disciplinary data, which are classified and ordered by the level of overlap between the modeling media and the fabrication media: (1) the first model takes as input biological data and outputs 3D printed digital materials organized according to functional constraints; (2) the second model takes as input geometry and environmental data and outputs robotically wound fibers organized according to functional constraints; (3) the third model takes as input material and environmental data and outputs CNC deposited pastes organized according to functional constraints; (4) the forth model takes as input biological, material and environmental data and outputs robotically deposited polymers organized according to functional constraints. The analysis of these models will demonstrate the FIM approach and point towards its value to designers who seek to inform their work through multi-scale transdisciplinary data, a capability that is currently missing from standard design-to-fabrication workflows.

Fundamental understanding of the oxygen reduction reaction (ORR) electrocatalyzed by nitrogen-doped carbon requires a well-defined structure to correlate structure to function. Well-characterized N-doped graphitic nanostructures derived from benzene derivatives have been synthesized in our group, and shown to catalyze a four-electron ORR under alkaline conditions. Density functional theory calculations have been performed on a model N-doped graphitic nanostructure, C50N2H20, to determine an oxygen activation mechanism. With guidance through an experimentally determined Pourbaix diagram, DFT calculations clearly indicate that the catalyst must undergo a 2e−,1H+ reduction to generate a reactive carbanionic intermediate that activates oxygen with a spin inversion.

The aim of this research was to work out the technology of ceramics for finding optimal sintering temperatures and to study their mechanical properties. Samples were prepared from powders with different volumetric ratio of the components. The powders underwent a prolonged co-milling in a vibratory mill, followed by uniaxial pressing, cold isostatic pressing (CIP) and pressureless sintering in a vacuum furnace under an argon atmosphere. Hot pressing (HP) was applied to some powder formulations. This study showed that it is advisable to carry out the first stage of the heat treatment up to 1550 ̊C under vacuum, with the aim of refining the grain surface from the oxygen-containing impurities due to their dissociation and evaporation. The studied area of formulations has a very narrow range of sintering (1940-1945 ̊C). It was established that the sinterability of the materials is affected by the amount of silicon carbide in the ternary system. Under pressureless sintering, the relative density of the material directly depended on the volume fraction of SiC. However, a change in the concentration of B4C had no appreciable effect on the sinterability of the materials. The application of HP helped us to reduce the negative impact of large amounts of SiC. Under HP at temperatures close to Teut, a certain decompaction of materials was observed with a significant amount of B4C (3-5% loss in density).

In this work, a systematic study on the factors that influence the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM) solutions during remote radiofrequency (RF) heating, using Fe3O4 magnetic nanoparticles (MNPs) is reported. A series of PNIPAM solutions with varying concentrations of Fe3O4 MNPs were prepared and characterized using transmission electron microscopy and Raman spectroscopy. Preliminary studies showed the highest specific absorption rate (SAR) for 15 nm sized Fe3O4 MNPs, which monotonically decreased as the MNP sizes increased to 20-30 nm. In-situ transmission measurements were used to determine the LCST of PNIPAM under various aqueous concentrations with dispersed Fe3O4 MNPs. A systematic decrease in the LCST from 34 °C to 31 °C was observed as the concentration of PNIPAM was increased from 0.3 wt. % to 1.0 wt. %, keeping the concentration of Fe3O4 MNPs constant. On the other hand, varying the concentrations of the MNPs did not drastically affect the LCSTs of PNIPAM solutions. However, varying the ion concentration of the PNIPAM solutions by adding adjusted KOH pellets, showed a pronounced lowering of the LCST by 2-3 °C at all PNIPAM concentrations. The remote triggering of phase transitions in PNIPAM solutions by raising the temperature above the LCST using Fe3O4 MNPs as reported here is important in targeted drug-delivery applications using thermo-responsive polymers.

In nature, water assembles basic molecules into complex multi-functional structures with nano-to-macro property variation. Such processes generally consume low amounts of energy, produce little to no waste, and take advantage of ambient conditions. In contrast digital manufacturing platforms are generally characterized as uni-functional, wasteful, fuel-based and often toxic. In this paper we explore the role of water in biological construction and propose an enabling technology modeled after these findings. We present a water-based fabrication platform tailored for 3-D printing of water-based composites and regenerated biomaterials such as chitosan, cellulose or sodium alginate for the construction of highly sustainable products and building components. We demonstrate that water-based fabrication of biological materials can be used to tune mechanical, chemical and optical properties of aqueous material composites. The platform consists of a multi-nozzle extrusion system attached to a multi-axis robotic arm designed to additively fabricate extrusion-compatible gels with graded properties. Applications of the composites include small and medium-scale recyclable objects, as well as temporary largescale architectural structures.

In the present work, the microstructure and mechanical properties of Gilsocarbon graphite have been characterized over a range of length-scales. Optical imaging, combined with 3D X-ray computed tomography and 3D high-resolution tomography based on focus ion beam milling has been adopted for microstructural characterization. A range of small-scale mechanical testing approaches are applied including an in situ micro-cantilever technique based in a Dualbeam workstation. It was found that pores ranging in size from nanometers to tens of micrometers in diameter are present which modify the deformation and fracture characteristics of the material. This multi-scale mechanical testing approach revealed the significant change of mechanical properties, for example flexural strength, of this graphite over the length-scale from a micrometer to tens of centimeters. Such differences emphasize why input parameters to numerical models have to be undertaken at the appropriate length-scale to allow predictions of the deformation, fracture and the stochastic features of the strength of the graphite with the required confidence. Finally, the results from a multi-scale model demonstrated that these data derived from the micro-scale tests can be extrapolated, with high confidence, to large components with realistic dimensions.

The reliability of InAlGaN multiple quantum well LEDs emitting around 308 nm has been investigated. The UV-B LEDs were stressed at constant current and current density, while the heat sink temperature was varied between 15°C and 80°C. The results reveal two different modes of the decrease of the optical power during aging. First, a fast reduction of the optical power within the first 100 h (mode 1) can be observed, followed by a slower degradation for operation times >100 h (mode 2). Mode 1 can be described as an initial degradation activation process which saturates after a certain time, whereas the second degradation mode can be described by a square-root time dependence of the optical power, suggesting a diffusion process to be involved. Both degradation modes are accompanied by changes of the I-V characteristic, particularly the reverse-bias leakage current and the drive voltage. Furthermore, the degradation behavior is strongly influenced by the temperature. Both, the maximum reduction of the optical power and the increase of the leakage current become stronger at higher temperatures.