Several processing methods were developed and evaluated for synthesizing empty silicon clathrates. A solution synthesis method based on the Hofmann-elimination oxidation reaction was successfully utilized to produce 20 mg of empty Si46. Half-cells using the Si46 electrodes were successfully cycled for 1000 cycles at rate of 5.3C. The capacity of the Si46 electrode in long-term tests was 675 mAh/g at the 4th cycle, but increased to 809 mAh/g at 50 cycles. The corresponding Coulombic efficiency was better than 99%. The capacity dropped from 809 to 553 mAh/g after 1000 cycles while maintaining a 99% Coulombic efficiency. In comparison, a Ba8Al8Si38 electrode could be cycled for about 200 cycles with a lower capacity and Coulombic efficiency. Potential applications of empty silicon clathrates as anode materials in Li-ion batteries are discussed.

AlN thin film structures have many useful and practical piezoelectric and pyroelectric properties. The potential enhancement of the AlN piezo- and pyroelectric constants allows it to compete with more commonly used materials. For example, combination of AlN with ScN leads to new structural, electronic, and mechanical characteristics, which have been reported to substantially enhance the piezoelectric coefficients in solid-solution AlN-ScN compounds, compared to a pure AlN-phase material.

In our work, we demonstrate that an analogous alloying approach results in considerable enhancement of the pyroelectric properties of AlN - ScN composites. Thin films of ScN, AlN and Al1-x ScxN (x = 0 – 1.0) were deposited on silicon (004) substrates using dual reactive sputtering in Ar/N2 atmosphere from Sc and Al targets. The deposited films were studied and compared using x-ray diffraction, XPS, SEM, and pyroelectric characterization. An up to 25% enhancement was observed in the pyroelectric coefficient (Pc = 0.9 µC /m2K) for Sc1-x Alx N thin films structures in comparison to pure AlN thin films (Pc = 0.71 µC/m2K). The obtained results suggest that Al1-x ScxN films could be a promising novel pyroelectric material and might be suitable for use in uncooled IR detectors.

Boron sub-2,3-naphthalocyanine chloride (SubNc) was investigated as a potentialred-sensitive organic photoconductive film (OPF). A photoconductive cell wasfabricated, and its current–voltage characteristics, both with andwithout light irradiation, and external quantum efficiency (EQE) weredetermined. The structure of the photoconductive cell was as follows, withthicknesses in nm given in parentheses: glasssubstrate/In–Zn–O (100)/spiro-2CBP (30)/SubNc(50)/Alq3 (30)/Al (50) (spiro-2CBP =2,7-bis(carbazol-9-yl)-9,9-spirobifluorene; Alq3 =tris(8-hydroxyquinolinato)aluminum). The spiro-2CBP and Alq3 layerswere inserted between the SubNc layer and the electrodes to block dark currentinjection. The three organic layers were successively deposited by evaporationin a vacuum on the In–Zn–O-patterned substrate. SubNc filmabsorbed light in the red region well, with an absorption peak at 695 nm. TheEQE of the cell reached 80% when the applied bias was 15 V. In addition, theblocking layers effectively suppressed dark current in the OPF, whichcorresponded to a current density of 20 nA/cm2 at 15 V. These resultsindicate that SubNc is a promising candidate as a red-sensitive OPF.

Interfacial dislocations (IDs) and half-loop arrays (HLAs) present in theepilayers of 4H-SiC crystal are known to have a deleterious effect on deviceperformance. Synchrotron X-ray Topography studies carried out on n-type 4H-SiCoffcut wafers before and after epitaxial growth show that in many cases BPDsegments in the substrate are responsible for creating IDs and HLAs during CVDgrowth. This paper reviews the behaviors of BPDs in the substrate during theepitaxial growth in different cases: (1) screw-oriented BPD segmentsintersecting the surface replicate directly through the interface during theepitaxial growth and take part in stress relaxation process by creating IDs andHLAs (Matthews-Blakeslee model [1] ); (2) non-screw oriented BPD half loopintersecting the surface glides towards and replicates through the interface,while the intersection points convert to threading edge dislocations (TEDs) andpin the half loop, leaving straight screw segments in the epilayer and thencreate IDs and HLAs; (3) edge oriented short BPD segments well below the surfaceget dragged towards the interface during epitaxial growth, leaving two longscrew segments in their wake, some of which replicate through the interface andcreate IDs and HLAs. The driving force for the BPDs to glide toward theinterface is thermal stress and driving force for the relaxation process tooccur is the lattice parameter difference at growth temperature which resultsfrom the doping concentration difference between the substrate and epilayer.

This work presents a comparison of the structural, chemical and electronic properties of multi-layer graphene grown on SiC(000-1) by using two different growth approaches: thermal decomposition and chemical vapor deposition (CVD). The topography of the samples was investigated by using atomic force microscopy (AFM), and scanning electron microscopy (SEM) was performed to examine the sample on a large scale. Raman spectroscopy was used to assess the crystallinity and electronic behavior of the multi-layer graphene and to estimate its thickness in a non-invasive way. While the crystallinity of the samples obtained with the two different approaches is comparable, our results indicate that the CVD method allows for a better thickness control of the grown graphene.

Structural and magnetic properties of nanocrystalline P6/mmm R(Fe,M)9C are presented. Their structure is explained with a model based on the R1–s(Fe,M)5+2s formula (s = vacancy rate) where s R atoms are statistically substituted by s transition metal pairs. The maximum coercivity is obtained for low Ga/Si content for auto-coherent diffraction domain size 30 nm. This controlled microstructure might lead to hard permanent magnet materials. Furthermore, the influence of small amount of Dy substitution on magnetocaloric properties of R-Fe systme is reported. The potential for using these low-cost iron based nanostructured RFe9 powders in magnetic refrigeration at room temperature is also discussed.

Fiber optic temperature sensors are used in a variety of harsh environment applications. We have explored use of such temperature sensors in commercial gas turbines to measure the temperature at various regions of interest within the turbine system. More specifically, fiber optic temperature rakes were designed and installed on a commercial gas turbine under full load conditions. This work will focus on failure mechanisms observed at multiple length scales that impact the performance of high temperature optical fiber sensors. It was found that Au-coated silica fibers, which are a standard in the industry, undergo various failure modes when subjected to combinations of high temperature and high vibration. More specifically, the Au coating became soft/ductile as the temperature is increased. We also observed that the Au coating was not well bonded to the silica fiber, as expected since there were no adhesion layers present. These effects led to significant damage of the fiber optic under high vibrations. We also found that vibrations from the gas turbine coupled into fundamental modes of the fiber optic probe assembly, which were analyzed by detailed dynamic mechanical analysis. This led to the fiber impacting the internal wall of the probe assembly, which caused further damage and failure of the fiber and the Au coating. The silica fibers returned from the field also exhibited significant twisting throughout most of their length. This suggests the fibers reached temperatures above their strain point (about 1000 C for pure silica glass), which is explained by either a) the strain point had been significantly reduced by the presence of the Ge dopant, or b) the temperature was higher than expected in the gas turbine exhaust region. It was also hypothesized that complex anelastic effects may play a role under the high temperature, high vibration environment experienced by the probes. Detailed structural analysis of the fiber optic temperature sensors by scanning electron microscopy, ToF-SIMS, and X-ray microscopy will be presented to corroborate the above simulations and proposed damage mechanisms. Finally, we note that the fiber Bragg gratings (FBG) present within the temperature probes provided promising temperature data, and were in fact not damaged/erased by the high temperature environment.

We have synthesized and investigated electronic properties of several non-centrosymmetric actinide compounds, which do not have an inversion center in the crystal structure “globally” or “locally”, under high pressure. The Néel temperature of an antiferromagnet UIrSi3 with “globally” non-centrosymmetric structure increases with increasing pressure at a rate of 2.5 K/GPa up to 5 GPa. On the other hand, T Ns of U2Rh3Si5 and U2Ir3Si5, which are “locally” non-centrosymmetric compounds, decrease with -1 K/GPa and -0.5 K/GPa with increasing pressure, respectively. Here, U2Ir3Si5 is a new antiferromagnet crystallizing in the U2Co3Si5-type of orthorhombic structure. Below T N = 36.5 K, U2Ir3Si5 shows magnetic order-order transition at T 0 = 26.1 K with a first-order nature. Electrical resistivity in U2Ir3Si5 shows semiconducting-like behavior due to the formation of the super-zone gap in the antiferromagnetic state. T N and T 0 as well as semi-conducting-like behavior in resistivity are suppressed by external pressure.

Corrected scanning transmission electron microscopy (STEM) was used to characterise a novel thin film displaying a complex three dimensional nanostructure. The film was prepared by plasma deposition in such a way that it self-organises into layers of silver islands (each with typical dimensions of a few nanometres) within an aluminium nitride matrix. Successful application of STEM imaging and subsequent analysis was able to determine critical information about the material structure, namely island size, shape and crystalline orientation and the detection of island – matrix intermixing. Such information is essential in being able to predict the properties of this material and the approach adopted here is applicable to any similarly structured material.

We have investigated plant growth response to atmospheric air plasma treatments of seeds on their growth for 5 plant speces; Radish sprout (Raphanus sativus L.), rice (Oryza Sativa), Zinnia, Arabidopsis L. Thaliana and Plumeri. The average length of Radish sprout, rice, Arabidopsis Thaliana, Plumeria and Zinnia, are 250%, 80%, 60%, 30% and 20% longer than those without plasma treatments, respectively. We have obtained correlation between the growth enhancement and O3 and NOx concentration. The optimum radical dose for the growth enhancement depends on plant species.

Carbon steel (C-steel) is studied to be the reference material for the metallic components in the high level waste (HLW) repository concepts of several European countries such as France, Switzerland, Belgium.

Electrochemical impedance spectroscopy (EIS) was performed over a period of 7 years, to determine the instantaneous corrosion rate (CR) of carbon steel (C-steel) in contact with clay porewater in diffusive regime. The study was conducted at the Mont Terri underground research laboratory (URL) located in Switzerland. The test chamber was at a depth of 8 m under anoxic conditions at 90°C in a vertical and descending borehole drilled in Opalinus clay (OPA). Microbial and chemical investigations were conducted on porewater in contact with C-steel as well as directly on C-steel surface further to dismantling.

The results showed clearly a decrease of the CR over time followed by a steady state below 1 µm/year. Sulphate and thiosulphate reducing bacteria were observed in porewater and at the metal surface, with a higher concentration of mesophilic and thermophilic bacteria respectively. The metal surface characterizations revealed the presence of magnetite, mackinawite, hydroxychloride and siderite with local traces of oxidizing species such as goethite.

Heteroepitaxial growth of high-quality II-VI-alloy materials on Si substrates is a well-established commercial growth process for infrared (IR) detector devices. However, it has only recently been recognized that these same processes may have important applications for production of high-efficiency photovoltaic devices. This submission reviews the process developments that have enabled effective heteroepitaxy of II-VI alloy materials on lattice-mismatched Si for IR detectors as a foundation to describe recent efforts to apply these insights to the fabrication of multijunction Si/CdZnTe devices with ultimate conversion efficiencies >40%. Reviewed photovoltaic studies include multijunction Si/CdZnTe devices with conversion efficiency of ∼17%, analysis of structural and optoelectrical quality of undoped CdTe epilayer films on Si, and the effect that a Te-rich growth environment has on the structural and optoelectronic quality of both undoped and As-doped heteroepitaxial CdTe.

Titanium dioxide (TiO2) loaded with gold (Au) as noble metal, acts as an efficient photocatalyst that has been extensively investigated for water splitting processes. In this paper, we report on the microstructure of atomic layer deposited titanium dioxide and the crystallinity modification of the material using energetic electron beam irradiation. A rapid high-energy electron beam induced crystallization of the nanostructures has been observed in-situ inside a High-Resolution Transmission Electron Microscope (HRTEM). The systematic crystallization of the nanomaterial occurring under the electron beam irradiation (300 KV) indicates the transformation of the near amorphous material into a mixture of two nuances of TiO2 polymorphs, namely rutile and anatase. We believe that this transformation will enhance the efficiency of water splitting process, as the mixed phases of rutile and anatase are known to possess better optical properties than the individual polymorphs of TiO2. This finding may be of particular interest in developing appropriate heat treatment methods for these nanostructures dedicated to water splitting to increase their efficiency.

Here we discuss requirements for high performance and solution processable organic semiconductors, by presenting a systematic investigation of 7-alkyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophenes (Ph-BTBT-Cn ’s). We found that the solubility and thermal properties of Ph-BTBT-Cn ’s depend systematically on the substituted alkyl-chain length n. The observed features are well understood in terms of the change of molecular packing motif with n: The compounds with n ≤ 4 do not form independent alkyl chain layers, whereas those with n ≥ 5 form isolated alkyl chain layers. The latter compounds afford a series of isomorphous bilayer-type crystal structures that form two-dimensional carrier transport layers within the crystals. We also show that the Ph-BTBT-C10 afford high performance single-crystalline field-effect transistors the mobility of which reaches as high as 15.9 cm2/Vs. These results demonstrate a crucial role of the substituted alkyl chain length for obtaining high performance organic semiconductors and field-effect transistors.

Thin metal films on compliant polymer substrates are of major interest for flexible electronic technologies. The suitability of a film system for flexible applications is based on the electro-mechanical performance of the metal film/polymer substrate couple. This study demonstrates how a 10 nm Cr interlayer deteriorates the electro-mechanical performance of 50 nm Au films on polyimide substrates by inducing the formation of cracks in the ductile layer. Combined in-situ measurements of the film lattice strains with x-ray diffraction and electrical resistance with four point probe of the Au-Cr and Au layers during uniaxial straining confirmed different electro-mechanical behaviours. For Au films with a Cr interlayer the film stress decreases rapidly as cracking initiates and reaches a plateau as the saturation crack spacing is reached. Crack formation and stress drop correspond to a rapid increase in the film resistance. Without the interlayer the Au film stress reaches a maximum around 2% engineering strain and remains constant throughout the experiment. The film resistance is unaffected by the applied elongation up to a maximum strain of 15%, giving no sign of cracking in the metal layer. The outstanding electro-mechanical performance of the gold film indicates that adhesion layers, like Cr, may not be necessary to improve the performance of ductile films on polymers.

Nowadays there are clear evidences from both experiments and MD-simulations proving that the chain Rouse modes correlation functions are non-exponential in unentangled polymer blends and also in pure polymers at low temperature (with respect to that of the glass transition Tg) even for the long wavelengths modes where local potentials and chain stiffness should not play any role. In a recent paper [S. Arrese-Igor et al, Phys. Rev. Lett.113, 078302 (2014)] it has been proposed that this non-exponential behavior depends on the ratio between the so-called Rouse time - i.e., the characteristic time of the slowest chain mode relaxation - and the time scale of the α-relaxation. This parameter is in some way ‘universal’ in the meaning that it can encode many different experimental situations. In this paper, we show that this behavior can be quantitatively explained in the framework of a theoretical approach based on: (i) a generalized Langevin equation (GLE) formalism and (ii) a memory function which takes into account the effect of collective dynamics on the chain dynamics of a tagged chain and which was constructed taking inspirations from the original ideas of the reptation model proposed by de Gennes.

One of the major concerns regarding the clinical translation of metal nanoparticles is related to the question of their persistence in organisms that can increase the likelihood of toxicity and the interaction/interference with common medical diagnoses.

In order to overcome these issues we have recently introduced a versatile 90 nm nano-architecture composed by: i) arrays of 3 nm gold nanoparticles, ii) functionalizable commercial polymers surrounding the gold nanoparticles, and iii) biodegradable and derivatizable silica shell embedding the polymer-nanoparticle assembly. These robust nanocapsules maintain the intriguing features of gold nanospheres but are biodegraded in physiological media to their potentially renal clearable building blocks.

Cartilage is a load bearing tissue that has multiple biological functions. Themajor proteoglycan in cartilage is the bottlebrush shaped aggrecan whosecomplexes with hyaluronic acid provide the compressive resistance of cartilage.The negatively charged aggrecan-hyaluronic acid complexes generate an osmoticswelling pressure within the tissue, which is balanced by the collagen network.To better understand the function of cartilage at the tissue level, we studyaggrecan assemblies using an array of microscopic and macroscopic techniques.The organization of aggrecan assemblies at the supramolecular level is probed bylight scattering, small-angle neutron scattering and small-angle X-rayscattering. Osmotic and rheological measurements are used to investigate themacroscopic physical properties.

The present work investigates sol-gel synthesized vanadium oxyhydrate (V2O5·H2O) nanowires decorated with Au nanoparticles as potential photolytic H2 generators. As determined by UV photoelectron and optical spectroscopies, the conduction band edge of V2O5·H2O lies 0.6 eV below standard H+ reduction potential, implying no H2 can be generated. On the contrary, as measured by gas chromatography, our nanoconjugates yield reproducible light-to-hydrogen conversion efficiency of 5.3%, for the first hour of photolysis under 470 nm excitation. To explain the observed hydrogen reduction, we have hypothesized the vanadia electron energy levels are raised by some negative surface charge. With the objective of validating this hypothesis, we have performed cyclic current-voltage measurements. The derived conduction and valence band edge energies are not only consistent with the optical band gaps, but also validate the hypothesized energy increase by 1.6 eV, respectively. The negative surface charge is also corroborated by the ζ-potential. Based on the measured pH of 2.4, we attribute the negative surface charge to Lewis acid nature of the nanowires, establishing dative bonding with OH−. The present work establishes the importance of surface charge in photoelectrochemical reactions, where it can be instrumental and enabling in photolytic fuel production.

Near real-time visualization of complex two-phase flow in a porous medium was demonstrated with dynamic 4-dimensional (4D) (3D + time) imaging at the 2-BM beam line of the Advanced Photon Source (APS) at Argonne National Laboratory. Advancing fluid fronts through tortuous flow paths and their interactions with sand grains were clearly captured, and formations of air bubbles and capillary bridges were visualized. The intense X-ray photon flux of the synchrotron facility made 4D imaging possible, capturing the dynamic evolution of both solid and fluid phases. Computed Tomography (CT) scans were collected every 12 s with a pixel size of 3.25 μm. The experiment was carried out to improve understanding of the physics associated with two-phase flow. The results provide a source of validation data for numerical simulation codes such as Lattice-Boltzmann, which are used to model multi-phase flow through porous media.