Here we present new materials obtained using, either fungal or isolated tobacco cells in association with different percentages of carbon nanotubes (CNTs). As a proof of concept, we used either Candida albicans or a non-green Tobacco BY-2 cell line combined with multi-walled CNTs. The electrical, mechanical, and conductivity vs temperature properties for some of these materials have been determined. C. albicans-based tissues have high conductivity and are stable at elevated temperatures. By lowering the CNTs content, we obtained a stable, electrically conductive optical transparent film, though with a relatively high sheet resistance. Further, we produced, using tobacco cells, a material that exhibits good electrical as well as mechanical properties.

Plasmon waveguide resonance (PWR) Raman spectroscopy provides chemical content information with interface or thin film selectivity. Near the plasmon waveguide interface, large increases in the interfacial optical energy density are generated at incident angles where plasmon waveguide resonances are excited. When a polymer of sufficient thickness is deposited on a gold film, the interface acts as a plasmon waveguide and large enhancements in the Raman signal can be achieved. This paper presents calculations to show how polymer thickness and excitation wavelength are predicted to influence PWR Raman spectroscopy measurements. The results show the optical energy density (OED) integrated over the entire polymer film using 785 nm excitation are 1.7× (400 nm film), 2.17× (500 nm film), 2.48× (600 nm film), 3.08× (700 nm film) and 3.62× (800 nm film) higher compared to a 300 nm film. Accounting for the integrated OED and frequency to the fourth power dependence of the Raman scatter, a 532 nm excitation wavelength is predicted to generate the largest PWR Raman signal at the polymer waveguide interface. This work develops a foundation for chemical measurements of numerous devices, such as solar energy capturing devices that utilize conducting metals coated with thin polymer films.

It is frequently observed that as-grown single-walled carbon nanotubes (SWCNTs) contain defects. Controlling the defect density is a key issue for the control of nanotube properties. However, little is known about the influence of the growth conditions on the formation of nanotube defects. In addition, SWCNT samples frequently contain carbonaceous by-products which affect their ensemble properties. Raman spectroscopy is commonly used to characterize both features from the measurement of the defect-induced D band. However, the contribution of each carbonaceous species to the D band is usually not known making it difficult to separately extract the defect density and relative abundance of each. Here, we report on the correlated evolution of the D and G’ bands of SWCNT samples with increasing growth temperature. In the general case, three to four Lorentzian components are required to fit them. Coupled with HRTEM characterization, the low frequency components of the D and G’ can be attributed to the contribution of SWCNTs while high frequency components are associated with defective carbonaceous by-products. The nature of these defective by-products varies with the type of catalysts and with the growth conditions.

There are several significant challenges that must be overcome for PEM fuel cell commercialization such as electrode flooding, carbon corrosion, and significant cost due to the high loading of the platinum catalyst. Thus, a new structure is proposed for the cathode catalyst support consisting of Si/TiOx core/shell nanowires with branched structures, which has the potential to reduce electrode flooding, increase stability, and dramatically reduce the required Pt loading. In this study, Pt-coated Si/TiOx core/shell nanowires with and without branches are compared. The Pt surface area on supports with branch structures was calculated to be more than 4 times larger than on supports without branch structures, while keeping the Pt loading at only about 0.1 mg/cm2 (for the samples with branched structures). SEM, XRD, AES, and TEM were used to characterize the morphologies and structures of the as-prepared samples. Branched Si/TiOx core/shell nanowire structures may be a promising catalyst support to enable commercialization of highly cost-efficient PEM fuel cells and to promote an era of clean energy usage.

Although additive layer manufacturing is well established for rapid prototyping the low throughput and historic costs have prevented mass-scale adoption. The recent development of the RepRap, an open source self-replicating rapid prototyper, has made low-cost 3-D printers readily available to the public at reasonable prices (<$1,000). The RepRap (Prusa Mendell variant) currently prints 3-D objects in a 200x200x140 square millimeters build envelope from acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). ABS and PLA are both thermoplastics that can be injection-molded, each with their own benefits, as ABS is rigid and durable, while PLA is plant-based and can be recycled and composted. The melting temperature of ABS and PLA enable use in low-cost 3-D printers, as these temperature are low enough to use in melt extrusion in the home, while high enough for prints to retain their shape at average use temperatures. Using 3-D printers to manufacture provides the ability to both change the fill composition by printing voids and fabricate shapes that are impossible to make using tradition methods like injection molding. This allows more complicated shapes to be created while using less material, which could reduce environmental impact.

As the open source 3-D printers continue to evolve and improve in both cost and performance, the potential for economically-viable distributed manufacturing of products increases. Thus, products and components could be customized and printed on-site by individual consumers as needed, reversing the historical trend towards centrally mass-manufactured and shipped products. Distributed manufacturing reduces embodied transportation energy from the distribution of conventional centralized manufacturing, but questions remain concerning the potential for increases in the overall embodied energy of the manufacturing due to reduction in scale. In order to quantify the environmental impact of distributed manufacturing using 3-D printers, a life cycle analysis was performed on a plastic juicer. The energy consumed and emissions produced from conventional large-scale production overseas are compared to experimental measurements on a RepRap producing identical products with ABS and PLA. The results of this LCA are discussed in relation to the environmental impact of distributed manufacturing with 3-D printers and polymer selection for 3-D printing to reduce this impact. The results of this study show that distributed manufacturing uses less energy than conventional manufacturing due to the RepRap's unique ability to reduce fill composition. Distributed manufacturing also has less emissions than conventional manufacturing when using PLA and when using ABS with solar photovoltaic power. The results of this study indicate that open-source additive layer distributed manufacturing is both technically viable and beneficial from an ecological perspective.

The vibrational properties of kesterite Cu2ZnSnS4 (CZTS) single crystals were studied by polarization-dependent Raman scattering measurements. The CZTS crystals grown by chemical vapor transport technique using iodine trichloride as a transport agent consist of several mirror-like planes. The detailed analysis of the experimental spectra obtained from different planes allows determining the symmetry assignment of the observed Raman-active modes. The wavenumber values of Raman-active modes are compared with the results of recent theoretical calculations. The presented data are useful for examination of CZTS absorber films applied for solar cells to clarify the existence of structural or phase inhomogeneities.

In this work is discussed the synthesis of a novel antishrinking agent (SOC DA) and the evaluation of its performance in an acrylic dental resin. SOC DA was photopolymerized in conjunction with the components of a conventional acrylic resin, which includes a mixture of diacrylate monomers [glycerolate bisphenol A dimethacrylate (BIS-GMA) / Urethane dimethacrylate (UDMA) / triethyleneglycol dimethacrylate (TEGDMA)] in 50/30/20 molar ratio). SOC DA was added in a range between 5.0-20.0 mol % with respect to the total amount of moles of the acrylic monomers. It was found that increasing concentrations of SOC DA, promoted higher conversions of the dimethacrylate monomers without decreasing the photopolymerization rate of the acrylate monomers. The study of the effect of SOC DA on the mechanical properties of the dental composite filled with 70 % of silicon dioxide, revealed that the presence of the antishrinking agent improved both the compressive and the flexural strength of the dental materials. Besides, it was found that by using the SOC DA at 20%, the shrinkage was reduced 52%, compared with the same formulation without SOC DA.

Developments of composites materials had begun in the 1970's. They aimed in improving mechanical properties due to the presence of reinforcement particles. The addition of particles in a matrix led to different modifications: considering the nature of the phases and the microstructure, we can mention interface reactivity between matrix and particles, changes in the chemical composition of the matrix and modified kinetics of microstructure evolution in the matrix (as compared to the matrix without particles); considering the mechanical aspects, thermal stresses may be generated due to the differences in expansion coefficients between the particles and the matrix, or any changes in the matrix leading to a phase transformation. In the present work, we studied the evolution of the phases and the behavior of a steel based MMC during thermal treatments, for which a phase transformation occurred on cooling. Experiments and numerical simulation are considered.

Ionic liquid (IL) is used as the working electrolyte in ionic polymer metal composite (IPMC) electromechanical bending actuators because of its high stability and conductivity, which are crucial for the consistency and speed of the actuation. Because the bending actuation is caused by the migration and accumulation of the cations and anions of the IL, it is clear that both the overall number of ions and the effectiveness of ion transport and accumulation play important roles in the actuation behavior. In this paper, the effect of enhancing the ion accumulation by the self-assembled conductive network composite (CNC) layers is investigated by comparing the bending behavior of actuators with and without CNC layers. In addition, IPMC actuators with various IL uptakes are also tested in order to study the dependence of the bending performance on the amount of the ions available. It is found that, with the CNC layers, the maximum bending curvature of the actuator increases with increased IL, which shows the crucial role played by the IL. However, under the same conditions, the performance improvement of actuators without CNC layers saturates when the IL uptake reaches around 10% wt. This demonstrates the role of the CNC layers to provide a porous electrode with increased capacitance that thus accommodates accumulation of more ions near the electrodes, which in turn boosts the overall bending curvature of the actuator.

Magnesium doped ZnO films were electrochemically grown on the NESA conductive glass substrate from the magnesium nitrate aqueous solution with zinc sulfate, kept at 323K and the cathodic potential of -0.9V vs. Ag/AgCl. The Mg/(Mg+Zn) atomic ratio of Zn1-xMgxO films increased with the decrease in the zinc sulfate concentration. The optical band gap energy of these Zn1-xMgxO films decreased with increasing content of zinc sulfate. Thus, the optical band gap energy and Mg/(Mg+Zn) atomic ratio of Zn1-xMgxO films would depend on the zinc sulfate concentration.

Much attention has been given to bulk metallic glasses (BMG) in recent years, particularly those based on binary alloys due to the simplicity of their atomic composition. Although efforts to understand the atomistic features that give rise to their exceptional properties have been made, the electronic and vibrational properties have been disregarded. We undertook the task of simulating the Cu64Zr36 glassy metal using a supercell with 108 atoms and a different simulational approach: the undermelt-quench approach [1]. The structure was characterized by means of the radial (pair) distribution function and the bond-angle distribution and the electronic density of states was calculated. We find that our results agree well with experimental data.

The narrow gap Mott insulators AM4Q8 (A = Ga, Ge; M= V, Nb, Ta; Q = S, Se) exhibit very interesting electronic properties when pressurized or chemically doped. We have recently discovered that the application of short electrical pulses on these compounds induces a new phenomenon of volatile or nonvolatile resistive switching. The volatile transition appears above threshold electric fields of a few kV/cm, while for higher electric fields, the resistive switching becomes non-volatile. The application of successive very short electric pulses enables to go back and forth between the high and low resistance states. All our results indicate that the resistive switching discovered in the GaM4Q8 compounds does not match with any previously described mechanisms. Conversely, our recent work shows that the volatile resistive switching is related to a purely electronic mechanism which suggests that the AM4Q8 compounds belong to a new class of Mott-memories for which Joule heating, thermochemical or electrochemical effects are not involved. Finally, it is possible to deposit a thin layer of GaV4S8 and to retrieve the reversible resistive switching on a metal-insulator-metal (MIM) device which proves the potential of this new class of Mott-memories for applications.

In-situ transmission electron microscopy (TEM) method is powerful in a way that it can directly correlate the atomic-scale structure with physical and chemical properties. We will report on the construction and applications of the homemade in-situ TEM electrical and optical holders. Electrical transport of carbon nanotubes and photoconducting response on bending of individual ZnO nanowires have been studied inside TEM. Oxygen vacancy electromigration and its induced resistance switching effect have been probed in CeO2 films.

Aqueous solutions containing Cd2+ and S2- ions have been brought together in a T-mixer, and the formation of CdS nanoparticles has been monitored by ultrafast X-ray small angle scattering down to 0.2 ms. While no particle formation is observed for a laminar flow, their growth can be followed in-situ for conditions of turbulent flow.

Corundum structured α-(GaFe)2O3 alloy thin films were obtained on c-plane sapphire substrates by the mist chemical vapor deposition method. Wide range of X-ray diffraction 2θ/θ scanning measurements indicated that these crystals were epitaxially grown on c-plane sapphire substrates and these are no other crystal oriented phase. The cross-sectional and plane-view transmission electron microscope images showed the growth along the c-axis of α-(GaFe)2O3 thin films on sapphire substrates, forming joint of columnar structure. The non-doped α-(GaFe)2O3 thin films showed ferromagnetic properties at 300 K, though the origin of ferromagnetism still remained unresolved. In order to enhance the spin-carrier interaction, Sn doped α-(GaFe)2O3 alloy thin films were fabricated on c-plane sapphire substrates. X-ray diffraction 2θ/θ and ω scanning measurement results indicated that the highly-crystalline films were epitaxially grown on substrates in spite of the Sn-doping.

Piezoelectric Microelectromechanical Systems (MEMS) has been proven to be an attractive technology for harvesting small energy from the ambient vibration. Recent advancements in piezoelectric materials and harvester structural design, individually or in combination, have improved MEMS energy harvesters to achieve high enough power density, compactness and ultra wide bandwidth, bringing us closer towards battery-less autonomous sensors systems and networks in near future. Among the breakthroughs, non-linear resonating beam for wide bandwidth resonance is the key development to enable robust operation of MEMS energy harvesters over the unpredictable and uncontrollable frequency spectra of ambient vibration. We expect that a coin size harvester will be able to harvest about 100μW continuous power at below 100 Hz and less than 0.5 g input vibration and at reasonable cost.

We present an in-depth transmission electron microscopy (TEM) study about the character of the Gd atom distribution in epitaxial GaN:Gd thin films grown by molecular beam epitaxy. High-resolution TEM (HRTEM) imaging reveals local lattice distortions of dimensions of a few atom planes only. Geometric phase analysis of HRTEM lattice images quantifies the associated displacement field. The results are explained by means of thin coherently strained GdN clusters with platelet shape being located along the basal plane. This is consistent with the observations obtained from strain contrast dark-field TEM images. Theoretically derived structure models provided by calculations based on density functional theory are used to simulate the HRTEM contrast and to determine the corresponding displacement field for matching the experimental data. Best fit is achieved in case of a coherent GdN bi-layer cluster that conclusively reflects the energy favorable configuration. The formation of the platelet clusters is explainable in the framework of spinodal decomposition.

The fracture behaviour of individual grain boundaries has been studied in order to understand the mechanisms controlling stress corrosion cracking in nuclear reactors. In particular, the role of oxidation in facilitating crack initiation and propagation has been reviewed. Nickel alloys from pressurized water reactors (PWRs) have been tested in simulated primary water conditions to induce grain boundary oxidation. Microcantilevers containing an oxidized grain boundary plane have been prepared and tested for fracture. The brittle nature of the oxide was demonstrated and the required stress to fracture measured.

Hexagonal boron nitride (h-BN), also known as white graphite, is the inorganic analogue of graphite. Single layers of both structures have been already experimentally realized.

In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics of hydrogenation of h-BN single-layers membranes.

Our results show that the rate of hydrogenation atoms bonded to the membrane is highly dependent on the temperature and that only at low temperatures there is a preferential bond to boron atoms. Unlike graphanes (hydrogenated graphene), hydrogenated h-BN membranes do not exhibit the formation of correlated domains. Also, the out-of-plane deformations are more pronounced in comparison with the graphene case. After a critical number of incorporated hydrogen atoms the membrane become increasingly defective, lost its two-dimensional character and collapses. The hydrogen radial pair distribution and second-nearest neighbor correlations were also analyzed.