This study demonstrates the feasibility of introducing a TaN thin film as a copper diffusion barrier for p-type (BiSb)2Te3 thermoelectric material. Compared to conventional Ni diffusion barrier, remarkably little void generation in Cu bulk or near Cu/TaN interface originated from Cu penetration is observed for TaN barrier after suffering the thermal budget of close to soldering. Diffusion behaviors of the barriers were analyzed by transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS) to make a deep understanding in clarifying interface diffusion effects among the Cu electrode, the barrier layer, and the (BiSb)2Te3thermoelectric layer.

This study examined the crystallization of vanadate glasses by using microwave irradiation. A second aim was comparing the thermoelectric properties of crystallized glasses when using microwave irradiation to conventional heating. V2O5-P2O5-Fe2O3-CuO glasses were prepared by using the melt quenching method. These glasses were irradiated by 2.45-GHz microwaves and heated in an electric furnace. MxV2O5 (M= Cu, Fe x=0.26-055) crystals were selectively precipitated by using the microwave irradiation. The crystal growth was also promoted by it. As a result, precipitation crystals formed a fiber-like structure. The electrical conductivity of the microwave irradiated glass was 6.3×101S/m at room temperature, which was three times higher than the value of conventionally-heated glass. The Seebeck coefficient of the microwave irradiated glass was -127 μV/K at room temperature, which was two times higher than that of conventionally-heated glass. This caused the power factor to be improved about 12 times. These results show that microwave irradiation is a potential candidate for obtaining conductive crystallized vanadate glasses.

The Tritium, Carbon-14 and Cobalt-60 content of a trepanned sample from one of the Wylfa Magnox reactor have been experimentally determined using beta liquid scintillation counting and gamma spectroscopy. The WIMS9a reactor code and FISPACT-2007 neutron activation software have also been used to calculate this inventory for the sample, considering only a model which is isolated from the reactor circuit. Comparison between experimental and calculated results has shown that the calculated values for 14 C are within 26%, 60 Co within 24% and 3 H 120%. These results show that the original impurity levels are sufficient to explain the experimentally determined end of life activity, without additional consideration of contamination from other materials in the reactor circuit, in this type of simulation. Additionally the calculations show that the production of 14 C from 14 N is approximately equal to that produced from 13 C. These results are only applicable to the isolated system models developed here, and do not explicitly model existing reactor conditions, where external operating conditions may interact with the graphite and the core environment

Nanomechanical and structural properties of pulsed laser deposited niobium nitride thin films were investigated using X-ray diffraction, atomic force microscopy, and nanoindentation. NbN film reveals cubic δ-NbN structure with the corresponding diffraction peaks from the (111), (200), and (220) planes. The NbN thin films depict highly granular structure, with a wide range of grain sizes that range from 15-40 nm with an average surface roughness of 6 nm. The average modulus of the film is 420±60 GPa, whereas for the substrate the average modulus is 180 GPa, which is considered higher than the average modulus for Si reported in the literature due to pile-up. The hardness of the film increases from an average of 12 GPa for deep indents (Si substrate) measured using XP CSM and load control (LC) modes to an average of 25 GPa measured using the DCM II head in CSM and LC modules. The average hardness of the Si substrate is 12 GPa.

We report, for the first time, the application of the photoacoustic spectroscopy for monitoring the optical absorption spectra in aquatic lirium (Eichhornia Crassipes), before and after it was exposed to ultrasonic irradiations. We obtained a decrease in the amplitude of the bands of the chlorophylls a and b for the irradiated samples with ultrasound of 17 kHz and 1.5 mW/cm 2 of power density, and therefore, damage in the centers producing the photosynthesis, due to the irradiation. These results show the utility of the ultrasonic irradiation, as well as, of the photosynthesis monitoring by means of the photoacoustic technique, for the elaboration and establishment of methodologies in the control of this aquatic plant, whose propagation causes many consequences extremely unfavorable for the environment, as well as for the diverse human activities that are developed in the bodies of water in the tropical and sub-tropical regions of the world.

Contemporary Art has the characteristic of being made with a wide diversity of materials. In this plastic age many of the artists employ polymers to create their works, but do not consider the degradation that their art will suffer eventually.

This work presents the studies performed for improving the manufacture of a series of sculptures made of latex rubber that belong to the Museo Universitario Arte Contemporáneo (MUAC), UNAM, in Mexico City. These sculptures made by César Martínez are blow up and deflated continuously during their exhibition. Techniques such as Fourier Transformed Infrared (FT-IR), X-ray fluorescence (XRF) and Raman spectroscopies were used for characterizing the manufacturing techniques of the artist. Dynamical Mechanical Analysis (DMA) was carried out to correlate the mechanical properties with the raw materials.

These analyses provide a comprehensive understanding of the material and the main factors that affect the degradation of the pieces. The combination of these studies made possible to suggest a new methodology to the artist in order to improve the quality and therefore enlarge the lifetime of his work.

TiO2 is one of the most promising photoanodes for solar-hydrogen conversion by water splitting. Recently, hydrothermally synthetic rutile TiO2 nanorods (NRs) show outstanding photoelectrochemical (PEC) performance in water splitting because of its large surface area, fast carrier transport, and short diffusion length. However, light absorption and carrier transport conflict. Few have investigated the dependence of PEC performance on NR length. This study examines how different TiO2 NR lengths grown on an FTO substrate affects their PEC performance when splitting water. The results show that the optimal absorption length of rutile TiO2 NRs is 3.75 μm. However, under simulated solar illumination (AM1.5 G), the maximum PEC efficiency of these TiO2 NRs is 0.33% at a length of 500 nm. This suggests that carrier transport is the most important variable for improving PEC efficiency.

An experimental set up has been designed to suppress electron currents generated during energetic ion irradiation to obtain accurate current integration for Heavy Ion Rutherford Backscattering Spectroscopy (HIRBS) measurements of heavy element concentrations and target depth profiles. A combination of an electron trap to suppress any electrons ejected from beam collimators and slits, and a biased aluminum mesh to suppress any secondary electrons ejected from the target was used. Two samples that produce cleanly interpreted spectra have been used as targets to check the accuracy of the system for 3.0 and 4.5 MeV O+2 projectile ions. Details of the experimental set up and data are presented.

An ultra-small tactile sensor with functions of signal processing and digital communication has been prototyped based on MEMS-CMOS integration technology. The designed analog-digital mixed signal ASIC allows many tactile sensors to connect each other on a common bus line, which drastically reduces the number of wire. The ASIC capacitively detects the deformation of a force sensor and sends digital data to the common bus line when the force exceeds a threshold. The digital data contain a physical ID of each sensor, 32-bit sensing data and 16-bit cyclic redundancy check (CRC) code. In this study, a novel wafer-level integration and packaging technology were developed, and a chip-size-packaged tactile sensor with a small footprint (2.5mm×2.5mm) and a low profile (0.27mm) was prototyped and tested. The sensor autonomously sends digital data like a tactile receptor of human.

The effects of surrounding gaseous environment on the reaction behaviors and product formation for sputter-deposited Ti/2B reactive multilayers are reported. With the surrounding environment set to different air pressures, from atmospheric conditions to 10-4 Torr, Ti/2B samples were reacted in a self-propagating mode, and the average reaction wave velocities were determined through high-speed imaging. Propagation speeds for 3.0 μm-thick multilayers were in the range of 10.89 to 0.05 m/s depending on bilayer thickness (i.e., reactant layer periodicity) and ambient pressure. X-ray diffraction analysis showed that single-phase TiB2 forms within multilayers that have small bilayer thickness. Multilayers that have a large bilayer thickness developed a mixture of TiB2, TiB and TiO2.

Composites of single-walled carbon nanotubes (SWNTs) and polyaniline (PAni) were synthesized using different approaches. SWNT/PAni nanocomposite with controlled core/shell morphology was achieved. Our chemical sensing tests showed that such core/shell morphology resulted in superior sensor performance, with an increased sensitivity to acetone vapors, and a reversible detection of hydrazine vapors. The reversible detection of parts-per-billion concentrations of hydrazine offers promise for a portable solid-state detector that has potential application in aerospace.

Small molecular thin films using solution-based method is a challengeable subject in organic optical and electronic devices. In our previous research, we successfully deposited aluminum tris(8-hydroxyquinoline) (Alq3) films on glass substrate. In this paper, aiming at future exploration of electroluminescent devices, we deposited N, N ’-Bis(3-methylphenyl)-N,N’- diphenylbenzidine) (TPD) films on indium-tin-oxide (ITO) substrates using the vapor-deposition method. Photoluminescence characteristics evidenced the actual formation of TPD thin films. Together with the good surface morphology and low leakage current of the films, the results are promising for actual device fabrication at low cost and low material loss.

Ventilator associated pneumonia (VAP) is a serious and costly clinicalproblem. Specifically, receiving mechanical ventilation for over 24 hoursincreases the risk of VAP and is associated with high morbidity, mortalityand medical costs. Cost effective endotracheal tubes (ETTs) that areresistant to bacterial infection could help prevent this problem. Theobjective of this study was to determine differences in the growth of Staphylococcus aureus (S. aureus) onnanomodified and unmodified polyvinyl chloride (PVC) ETTs under dynamicairway conditions. PVC ETTs were modified to have nanometer surface featuresby soaking them in Rhizopus arrhisus, a fungal lipase.Twenty-four hour experiments (supported by computational models) showed thatair flow conditions within the ETT influenced both the location andconcentration of bacterial growth on the ETTs especially within areas oftube curvature. More importantly, experiments revealed a 1.5 log reductionin the total number of S. aureus on the novel nanomodifiedETTs compared to the conventional ETTs after 24 hours of air flow. Thisdynamic study showed that lipase etching can create nano-rough surfacefeatures on PVC ETTs that suppress S. aureus growth and,thus, may provide clinicians with an effective and inexpensive tool tocombat VAP.

Often, silver nanoparticles (AgNps) are looked at in the realm of their plasmonic effects that are characterized by unique absorptional bands in the visible spectrum. Herein, the kinetics of a simple gravity mediated sedimentation process of AgNps, in aqueous suspensions. The surface energy mismatch between the AgNps and the receiver substrate allow for the formation of irregularly shaped AgNp microclusters with interconnected microchannels with dimensions and particle density controlled by the distance between the exposed substrate surface and the water/suspension interface. An investigation of the interplay between these properties and the films’ nanoparticle density is presented.

We present comparative studies of optical properties of GaN nanowires (NWs) obtained by two different self-formation techniques: Plasma-Assisted Molecular Beam Epitaxy (PAMBE) growth; and plasma etching of GaN layers deposited by Metal-Organic Vapor Phase Epitaxy (MOVPE). The effects of the coalescence process on grown NW and plasma-induced defects in etched NWs have been studied by photoluminescence (PL) and Raman scattering. In MBE grown NWs, the coalescence-associated defects are extended toward the NW top for intermediate Ga flux. Using High Resolution Electron Microscopy of reactive plasma etching (RIE) NWs, it was found that NWs obtained with an optimal combination of inductive (ICP) and capacitive (RF) plasma are free of extended structural defects. The PL efficiency is strongly increased in plasma etched NWs. However, plasma-induced point defects have to be taken into account for explaining the changes of the PL spectra. Less plasma-induced degradation is observed for high ICP/RF power ratios.

A zeroth order dendritic carbosilane structure, SiFA4H with four hexafluoroisopropanol (HFIP) functional groups attached via propyl ligand arms to a central silicon atom, has been developed as a model hydrogen-bond (HB) acid sorbent coating and candidate reference HB acid. The HB donor interaction, through the hydroxyl of the HFIP moiety, with a solute HB base can be monitored by observing the hydroxyl stretching frequency through measurements of SiFA4H FTIR spectra before and during vapor exposure. HFIP hydroxyl stretch shifts, upwards of 700 cm-1 have been observed depending on the HB base. For a range of HB bases, the resulting hydroxyl stretch shifts correlate directly with the solute HB basicity scale, “B”, developed by Abraham et al [1]. A variety of techniques exist to measure solute HB basicity, however, the applicability to examine HB bases delivered as vapors or gases and the simplicity of the measurements described herein, with a reusable reference HB acid sorbent coating and standard FTIR spectrophotometer techniques is attractive for some applications including those with hazardous chemicals. Moreover, as an extension of this work we propose employing SiFA4H or related sorbents as molecular sensing coatings, where the semi-selective sorbent is examined by various infrared (IR) spectroscopic techniques to monitor and identify hazardous chemicals, taking advantage of molecular binding phenomena which occur in the sorbent [2].

Using an ab initio density functional theory (DFT), we study thin film electronic properties of topological insulators (TIs) based on ternary compounds of Tl (thallium) and Bi (bismuth). We consider TlBiX2 (X=Se, Te) and Bi2X2Y (X, Y=Se, Te) compounds. Here we discuss the nature of surface states, their locations in the Brillouin Zone (BZ) and their interactions within the bulk region. Our calculations suggest a critical film thickness to maintain the Dirac cone which is smaller than that in binary Bi-based compounds. Atomic relaxations are found to affect the Dirac cone in some of these compounds. We discuss the penetration depth of surface states into the bulk region.

Recently, the usage of optical fiber coils has increased significantly, especially in the design of physic and chemical sensors. Therefore, it is important to test the theoretical current models developed to predict the power loss throughout optical fiber. In this paper a pioneer and popular model, the Marcuse model of power loss, was studied and evaluated for optical fiber coils of small radii. Power attenuation in a bent fiber data was collected using an Optical Time Domain Reflectometer (OTDR), and it was compared to the theoretical predictions of the Marcuse model. It was observed that the model predicts correctly the attenuation behavior for usual curvature radii, however, it fails to predict accurately the attenuation behavior for small curvature radii, underestimating considerably the actual power loss. Also, it has been observed that at small radii the power loss parameter 2α and the mode propagation constant of the wave guide β stop being constants and become functions of the optical path, particularly of the number of loops in the coil. It is possible that new mechanisms of light leaking are present, due to the extreme distortion of the modes configuration into the fiber at small radii. Those mechanisms cannot be described by a model that considers a power loss parameter 2α, and more specifically the mode propagation constant of the wave guide (β) as constants. Then it is important to develop other models where the previous parameters can be considered as functions of the optical path.

Relative stabilities and electronic structure of graphene/h-BN superlattices are discussed in the framework of the density functional theory. Most importantly, relative stabilities between commensurate and incommensurate superlattices are studied. Commensurate graphene/h-BN monolayer superlattices are found to be definitely more stable than incommensurate superlattices. In graphene/h-BN bilayer superlattices, commensurate superlattices are found to be slightly more stable than incommensurate superlattices. Results also imply that a finite pressure can induce transition from an incommensurate superlattice to a commensurate superlattice.

The damage that the products of microorganism metabolism, in particular biogenic sulfuric acid, do to hardened concrete is known as concrete biodeterioration. These microorganisms, Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans and sulfate-reducing bacteria (SRB) are ubiquitous in the environment and they produce either hydrogen sulfide or sulfuric acid that can dissolve and disintegrate the concrete matrix. Their activity plays a very important function in the whole spectrum of degradation processes such as corrosion of reinforced metals and concrete.

In Canada and in the northern part of the United States, concrete structure failures from concrete biodeterioration are less common than in the southern part of the United States and in Mexico, nevertheless, it is a serious and expensive problem in hydraulic structures and sewage collection systems, which rapidly deteriorate. Also, leaking sewage systems result in the loss of groundwater resources particularly important in this arid region. Almost every city in the Mexican-American border region, who’s combined population is more than 15 million people, faces this problem. The U.S. cities have made some provision to face these concrete structure problems, but the Mexican cities have made less effort. Additives and admixtures are used to improve the properties of the concrete; nonetheless, we have exposed here the importance of the factual composition of the Portland cement and concrete to mitigate concrete biodeterioration in the hydraulic structures and sewage collection systems.