It has been an increase on the number of concrete structures with corrosion induced damage in Mexico in recent years. It is also well known that cathodic protection (CP) is the only method that stops corrosion in an efficient way. Since the 1990’s Florida and other USA states have been installing in concrete pile substructures, in bridges and piers, a three part hybrid galvanic CP system. This hybrid galvanic CP system includes a thermal sprayed part (located at the aerial zone of the pile), a zinc mesh encapsulated in mortar and inside a glass fiber jacket (located at the change in ties zone), and a submerged zinc bulk anode (in the submerged zone). From a previous investigation performed by the present authors, it has been found that the mortar inside the fiberglass form may decrease the mesh anode activation and thus decrease the CP system efficiency. Therefore, this investigation includes an evaluation of different additions placed in mortar to increase its electrical and ionic conductivity to increase the efficiency of the entire hybrid system. Additions include carbon, zinc and alumina powders, and this investigation presents preliminary experimental results obtained from the tested mortars (i.e. mortar physical characterization: electrical resistivity, ultrasonic pulse velocity, and total void content).

Opal particles, with diameter ca. 80 nm, were synthesized by the Stöber method. Samples were exposed to 100 Gy of beta particle irradiation and its thermoluminescence (TL) emission was recorded. TL response presents good reproducibility, standard deviation 1 %. The glow curve displays two TL peaks 86 and 400 °C and the afterglow (AG) phenomenon is observed immediately after irradiation (< 150°C). The synthetic opal-C exhibits a linear dependence of AG response as function of dose from 0.25 to 8 Gy. This dose range is of interest for personal and clinical dosimetry. Moreover, a previous study indicates that cytotoxic and genotoxic effects caused by opal nanoparticles, did not induce unrepairable DNA damage neither a cellular harm. Therefore, our results show synthetic opal-C is a material useful for in vivo radiation dosimetry.

With extremely disordered atomic structures, a glass possesses a thermal conductivity k that approaches the theoretical minimum of its composition, known as the Einstein’s limit.1 Depending on the material composition and the extent of disorder, the thermal conductivity of some glasses can be down to 0.1-0.3 W/m∙K at room temperature,2,3 representing some of the lowest k values among existing solids. Such a low k can be further reduced by the interfacial phonon scattering within a nanocomposite that can be used for thermal insulation applications. In this work, nanocomposites hot pressed from the mixture of glass nanopowder (GeSe4 or Ge20Te70Se10) and commercial SiO2 nanoparticles, or pure glass nanopowder, are investigated for the potential k reduction. It is found that adding SiO2 nanoparticles will instead increase k if the measured k values for usually porous nanocomposites are converted into those for the corresponding solid (k Solid) with Eucken’s formula. In contrast, pure glass nano-samples always show k Solid data significantly reduced from that for the starting glass. For a pure GeSe4 nano-sample, k Solid would beat the Einstein’s limit for its composition.

The boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) oriented Type Ib diamond substrates using a Microwave Plasma Chemical Vapor Deposition (MPCVD) technique. Raman spectrum showed a few additional bands at the lower wavenumber regions along with the zone center optical phonon mode for diamond. The change in the peak profile of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. A modification in surface morphology of the film with increasing boron content had been observed by atomic force microscopy. Four point probe electrical measurement indicated that different conduction mechanisms are operating in various temperature regions for these semiconducting films.

The objective of this work is to examine the feasibility of electrically conductive hydrogel composites as scaffolds in tissue engineering and tissue regeneration, and to understand the properties of the composites as a growth matrix for clinically relevant cell lines. The composite is comprised of carbon nanobrushes embedded in a biocompatible poloxamer gel. This work assesses the ability of such composite gels to support the growth of fibroblasts and myocytes and eventually serve as a matrix to stimulate wound closure. In such a model, fibroblasts and myocytes are seeded on the hydrogel and bathed in culture medium. The experimental model assesses the ability of fibroblasts and myocytes to grow into and adhere to the gel. The work demonstrates that carbon nanobrushes can be dispersed within poloxamer gels, and that fibroblasts and myocytes can proliferate within homogenously dispersed carbon nanobrush-containing poloxamer gels. This work also examines the effects of carbon nanobrush content on the rheological properties of the poloxamer gel matrix and shows an improvement in several areas in the presence of carbon nanobrushes. Future work will examine the effects of design parameters such as carbon nanobrush content and matrix structure on wound healing, as well as the growth of tendons and other cell lines within the hydrogel composites. This work has relevance for tissue and cellular engineering and tissue regeneration in clinical medicine.

A temperature dependent Hall Effect measurement system with software based data acquisition and control was built and tested. Transport measurements are shown for boron-doped single crystal diamond (SCD) films deposited in a microwave plasma-assisted chemical vapor deposition (MPCVD) reactor. The influence of Ohmic contacts and temperature control accuracy are studied. For a temperature range of 300K-700K IV curves, Hall mobilities and carrier concentrations are presented.

Periodically textured back reflectors with hexagonal dimple arrays are applied to thin-film microcrystalline silicon (μc-Si:H) solar cells for enhancing light trapping. The period and aspect ratio of the honeycomb textures have a big impact on the photovoltaic performance. When the textures have a moderate aspect ratio, the optimum period for obtaining a high short circuit current density (J SC ) is found to be equal to or slightly larger than the cell thickness. If the cell thickness exceeds the texture period, the cell surface tends to be flattened and texture-induced defects are generated, which constrain the improvement in J SC . Based on these findings, we have fabricated optimized μc-Si:H cells achieving a high active-area efficiency exceeding 11% and a J SC of 30 mA/cm2.

In this paper, the Lattice Statics formalism is used to perform Monte Carlo simulations of alloy microstructures when elastic effects are present. It provides sets of long-range effective pair interactions (EPIs), defined in a rigid average reference state, that allow us to compute microstructural evolutions on diffusion time scale. A wide composition range is investigated in order to characterize the different precipitation processes with elasticity (nucleation and growth, spinodal decomposition). An advantage of the approach is to include the concentration dependence of both the effective chemical interactions and the elastic properties of the reference state. The importance of this point is illustrated by comparing the precipitation sequences in two alloys with symmetric average concentrations.

Flexible substrates, like plastic, paper and cotton fabrics can be of interest for several reasons in connection to the appealing issue of generating voltage-current from piezoelectric ZnO nanowires (NWs). Zinc oxide NWs have shown very high voltage generation and they are possible to grown on plastic, paper and cotton. Since we with these substrates can get a new freedom to bend and also stretch the NWs and to incorporate them into new applications they are of great potential. Here we will describe the mechanical and piezoelectric properties of ZnO NWs grown on ordinary clean room paper and on cotton fabrics substrates as well as possibility of coating the ZnO NWs to maximize the output generated power. An enhancement of 160 times in the piezo-potential was observed from ZnO NWs coated with P3HT p-type polymer compared to non-coated NWs.

To investigate template releasing process in nanoimprint lithography, template releasing energy (i.e. surface energy between the template and the resist polymer) in various releasing conditions is evaluated using multi-axial controlled releasing system. The releasing energy is in proportion to the surface free energy of the template, but does not depend on the velocity of releasing. Also, a peeling mode where the template is released from a single side and a lift-off mode where the template is removed in the perpendicular direction to the resist are examined. The result shows that the releasing energy by peeling mode is lower than that by lift-off modes.

Quaternary semiconductors, Cu2ZnSnS4 and Cu2ZnSnSe4 which contain only earth-abundant elements, have been considered as the alternative absorber layers to Cu(In,Ga)Se2 (CIGS) for thin film solar cells although CIGS-based solar cells have achieved efficiencies over 20 %. In this work we report an air-stable route for preparation of Cu2ZnSn(Sx,Se(1-x))4 (CZTSSe) thin film absorbers by a solution process based on the binary and ternary chalcogenide nanoparticle precursors dispersed in organic solvents. The CZTSSe absorber layers were achieved by spin coating of the ink precursors followed by annealing under Ar/Se atmosphere at temperature up to 580°C. We have investigated the influence of the annealing temperature on the reduction or elimination of detrimental secondary phases. X-ray diffraction combined with Raman spectroscopy was utilized to better identify the secondary phases existing in the absorber layers. Solar cells were completed by chemical bath deposited CdS buffer layer followed by sputtered i-ZnO/ZnO: Al bi-layers and evaporated Ni/Al grids.

Electronic systems are a very good platform for sensing biological signals for fast point-of-care diagnostics or threat detection. One of the solutions is the lab-on-a-chip integrated circuit (IC), which is low cost and high reliability, offering the possibility for label-free detection. In recent years, similar integrated biosensors based on the conventional complementary metal oxide semiconductor (CMOS) technology have been reported. However, post-fabrication processes are essential for all classes of CMOS biochips, requiring biocompatible electrode deposition and circuit encapsulation.

In this work, we present an amorphous silicon (a-Si) thin film transistor (TFT) array based sensing approach, which greatly simplifies the fabrication procedures and even decreases the cost of the biosensor. The device contains several identical sensor pixels with amplifiers to boost the sensitivity. Ring oscillator and logic circuits are also integrated to achieve different measurement methodologies, including electro-analytical methods such as amperometric and cyclic voltammetric modes. The system also supports different operational modes. For example, depending on the required detection arrangement, a sample droplet could be placed on the sensing pads or the device could be immersed into the sample solution for real time in-situ measurement. The entire system is designed and fabricated using a low temperature TFT process that is compatible to plastic substrates. No additional processing is required prior to biological measurement. A Cr/Au double layer is used for the biological-electronic interface. The success of the TFT-based system used in this work will open new avenues for flexible label-free or low-cost disposable biosensors.

Supersulphated cements (SSC) are environmentally friendly binders that incorporate several raw materials, including byproducts. A systematic study was considered opportune considering the wide range of formulations found in the literature. The effect of the type and proportioning of components in the strength of SC was investigated using the Taguchi method to optimize the experimental work and to define the optimal conditions. The factors were: [A] %blast furnace slag (82.5-90%), [B] CaSO4 - alkaline activator ratio (1:0, 3:1, 1:1, 1:3 and 0:1), [C] type of CaSO4 (5 types) and [D] type of alkaline activator (portland cement, Ca(OH)2, KOH and NaCO3 and 2 combinations of these). Pastes were prepared and characterized for up to 28 days at 20°C. In general, for all values of [A] the best strength was for levels of [C] at 3:1, followed by the 1:1 and 1:0 ratios. The optimal conditions using the 28 day strength consisted of [A]= 82.5%, [B]= 3:1, [C]= flyorgypsum and [D] = portland cement, which developed excellent strength from day one and 35MPa. X-ray diffraction showed ettringite and C-S-H formation from the early ages. The microstructures showed dense matrices of reaction products well bonded to partially reacted slag grains, which in some cases showed rims of hydration products.

Environmental issues related to CO2 emissions have become a key focus for many different industries, including the cement and concrete industry. An environmentally optimized ‘green’ concrete can provide a much needed alternative to conventional concrete to reduce the carbon foot-print of the construction industry. This can be achieved through high Portland cement replacement by fly ash and with the inclusion of activators to enhance the rate of development of strength and other properties. This study evaluates different fly ashes and different activators (Na2SO4, lime and quicklime) that are added to enhance the reaction of the fly ash to achieve a comparable performance to that of standard Portland cement in mixes of much lower CO2 emissions. TGA, XRD and SEM are used to determine the development of hydration products and the consumption of portlandite by the fly ash. It is found that the amorphous content of the fly ash is an important parameter influencing compressive strength evolution. Based on the results, Na2SO4 as an activator, and a fly ash with high reactive SiO2 and Al2O3 contents and low Fe2O3 are found to provide the best options for producing a high volume fly ash matrix with the potential to show comparable behavior to a Portland cement control mix.

3D integration enabled by through-silicon-via (TSV) allows continued performance enhancement and power reduction for semiconductor devices, even without further scaling. For TSV wafers with all Applied Materials unit processes, we evaluate the integrity of oxide liner and copper barrier by capacitance-voltage (C-V) and current-voltage (I-V) measurements, from which oxide capacitance, minimum TSV capacitance, and leakage current are extracted. The capacitance values match well with model predictions. The leakage data also demonstrate good wafer-scale uniformity. The liner and barrier quality are further verified with microanalysis techniques.

A fast proton conducting glass with proton transport number t H = 1 was successfully prepared by using conventional melting method. In-situ FTIR (Fourier transform infrared) measurements under hydrogen atmosphere, temperature of 300°C and applying 1 V between Pt electrodes were carried out in order to monitor the proton concentration. The electrode reaction on Pt in these conditions is similar to that under intermediate-temperature fuel cell operation. It was found from the in-situ FTIR measurements that the absorbance around 2900 cm-1 increases clearly after applying 1 V, whereas no significant change was observed around 3400 cm-1. Proton infiltration into the glass is discussed based on the in-situ FTIR and impedance results.

Wafer level metal bonding involving copper material is widely used to achieve 3D functional integration of ICs and ensure effective packaging sealing for various applications. In this paper we focus on thermocompression bonding technology where temperature and pressure are used in parallel to assist the bonding process. More specifically a broad range of conditions was explored and interesting results were observed and are reported. Indeed, despite a relatively high roughness, the presence of a native oxide and the lack of surface preparation, there still exists a process window where wafer level bonding is allowed. In these conditions, limiting the bonding mechanisms to basic copper diffusion is no longer satisfactory. In this study, a specific scenario inspired by both wafer bonding and metal welding state of the art is put forward. Accordingly, pure copper diffusion through the bonding interface is lined with plastic deformation and metallic oxide fracture. In addition, polycrystalline film deformation due to thermomechanical stress is highlighted and grain growth and voiding formation are observed and confirmed.

Valence state and local environment of Fe in complex glasses related to the system Al2O3-B2O3-Fe2O3-Na2O-SiO2 were studied. In all the glasses, the major fraction of Fe exists as Fe3+ ions but a minor fraction of Fe2+ ions especially in the glass with the lowest K=[SiO2]/[B2O3] ratio was also present. Average Fe—O distance in the first shell is 1.80-1.85 Å and coordination number is 4-6. The intensity due to the second sphere is rather weak demonstrating homogeneous distribution of Fe ions in the glass.