The intermetallic Pu6Fe is a precipitate commonly found in standard-purity Pu alloys. We are interested in measuring thermophysical properties of this intermetallic, so we are developing methods for producing Pu6Fe with potential for being scaled up. We had success using a powder-based method, where finely divided PuH2 powder was mechanically mixed with Fe powder and reacted in vacuum. Differential scanning calorimetry was used to analyze the phase content of the product. We estimate ∼90% yield of Pu6Fe by weight, with the remainder being Pu. Enthalpy of melting for Pu6Fe was measured to be 31.2 J/g, and the onset temperature was 411.5°C. The product was melted 3 times and appeared to become more homogeneous after each cycle.

Selenium (Se) is an important element for assessing the safety of high-level waste disposal. Se is redox-sensitive, and its oxidation state varies from -2 to 6 depending on the redox conditions and pH of the solution. Large quantities of ferrous ions formed in bentonite due to corrosion of carbon steel overpack after the closure of a repository are expected to maintain a reducing environment near the repository. Therefore, the migration behavior of Se in the presence of Fe in bentonite was investigated by electrochemical experiments. Na2SeO3 solution was used as tracer solution. Dry density range of bentonite was from 0.8 to 1.4 ×103 kg/m3.

Results indicated that Se was strongly retained by the processes such as precipitation reaction with ferrous ions in bentonite. Se K-edge X-ray absorption near-edge structure (XANES) measurements were performed at the BL-11 beamline at SAGA Light Source, and the results revealed that the oxidation state of Se in the bentonite remained Se(IV).

In order to study the oriented aggregation of BaTiO3nanocrystals in the ultrasound-assisted synthesis in an aqueous solution [F.Dang et al., Jpn.J.Appl.Phys. 48, 09KC02 (2009)], the electric dipole-dipole interaction model has been studied by numerical simulations. The results of the numerical simulations are consistent with the experimental ones if the electric dipole moment of a primary particle (a nanocrystal) of 5 nm in diameter is about 10 D =3.3 x 10-29 (C m). It suggests that a 5-10 nm BaTiO3 nanocrystal synthesized in an aqueous solution with ultrasound has spontaneous polarization.

Adding single walled carbon nanotubes (SWCNT) to a polymer matrix can improve the delamination properties of the composite. Due to the complexity of polymer molecules and the curing process, few 3-D Molecular Dynamics (MD) simulations of a polymer-SWCNT composite have been run. Our model runs on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), with a COMPASS (Condensed phase Optimized Molecular Potential for Atomistic Simulations Studies) potential. This potential includes non-bonded interactions, as well as bonds, angles and dihedrals to create a MD model for a SWCNT and EPON 862/DETDA (Diethyltoluenediamine) polymer matrix. Two simulations were performed in order to test the implementation of the COMPASS parameters. The first one was a tensile test on a SWCNT, leading to a Young’s modulus of 1.4 TPa at 300K. The second one was a pull-out test of a SWCNT from an originally uncured EPON 862/DETDA matrix.

Analysis of surface images indicates that GaAs(001) surfaces can be patterned directly by applying interferential irradiation of high power laser pulses on the surface. Atomic force microscopy (AFM) was used to image the patterned surfaces. The patterned surface shows strips that have the same separation as the interference period used. The direct laser patterning leaves the surface with trenches. The depth of trenches increases with the laser intensity and can be varied from few nanometers to a few hundred nanometers. At low laser intensity, strip shaped mound appears at the both edges of a trench, leaving a plateau area between them. The width of mound increases with the laser intensity, making the plateau area smaller. With a higher laser intensity, the plateau area disappear as the mounds merge together, forming a single strip between the adjacent trenches. AFM images from the patterned surface indicate that direct laser patterning can be used to fabricate nanostructures with a period smaller than that of the interference period as well as the wavelength of the laser used.

To improve the integrated circuits’ performance and continue the downscaling of dimensions, it is necessary to use low dielectric constant materials as interconnects insulators. Current porous SiCOH low-k dielectrics are now reaching their limits since their porosity enables the diffusion of species that modify the inner surface of the pores. To further reduce the dielectric constant, it is necessary to change paradigm in interconnects fabrication. In this paper, we discuss the most promising innovations in terms of process, materials and architectures to reduce the interconnects insulators dielectric constant.

Nanowire arrays have been proposed to enhance light trapping, increase efficiencies, and reduced material cost in photovoltaic solar cells. In this work we present a new crystalline silicon nanowire array structure, inspired by fractal geometry. The array structure is assumed to be an infinite 2D array in the x and y directions, and composed of vertically aligned SiNW suspended in air. Hexagonal fractal-like geometry is adapted in arranging cylindrical SiNW in these arrays. Full-wave finite element method 3D simulation is used to compute reflectance, transmittance and absorptance of the array for a normal incidence plane wave. The proposed fractal-like distribution of SiNW arrays yield broad absorption spectrum and enhanced efficiency while using less material. The efficiency of the proposed fractal-like SiNW arrays achieve ∼100% enhancement over that of the equivalent thickness flat c-Si film, and ∼18% enhancement over an equivalent height hexagonal array. The proposed optimized structures achieved a filling ratio ∼25%, which is ∼33% less than the corresponding hexagonal array.

In this paper, we propose a wrap around field termination technique for a vertical Schottky barrier diode fabricated on a free standing GaN substrate. Unlike conventional field plate designs, in the wrap around structure the field plate surrounds the active device area. This allows for better control of the electric field distribution, and reduces field-crowding. 2D finite element simulations using ATLAS show a uniform field distribution across the device. Calculations show that the Ron increases relative to the conventional field plate. A break down voltage of 1300V was predicted for a 5um thick epilayer.

The historical monuments such as cathedrals, public buildings and so on, are a fundamental part of artistic heritage of a country. They reflect, ultimately, much of its culture and history. For several decades, their aspect has been seriously changed by graffiti, which clearly endangers their preservation state and causes loss of their esthetic appearance and historic value. This damages seriously the self-esteem of residents who witness the continued and strong degradation of their cultural heritage. The aim of this work is to study the removal of graffiti from a characteristic stone which is used in Morelia (México) as the raw material for architectural monuments, using a high power diode laser treatment. We concluded that continuous wave regime leads to better results than modulated wave regime; additionally, a two laser passes process demonstrated a high performance.

In this work, we demonstrate the label-free and ultrasensitive detection of troponin-T, cardiac biomarker using nanoporous membrane integrated on a microelectrode sensor platform. The nanoporous membrane allows for spatial confinement of the protein molecules. Antigen interaction with thiol immobilized antibody perturbs the electrical double layer. Charge perturbations are recorded as impedance change at low frequency using the principle of electrochemical impedance spectroscopy (EIS). The measured impedance change is used to quantitatively determine the concentration of troponin-T in tested sample. We have shown that sensitivity of sensor for troponin-T to be 1pg/mL. The accuracy and reliability of this sensor was tested by comparing the experimental troponin-T concentration values with a commercially available electrochemiluminescence assay measured with Roche Elecsys analyzer. Using this technique we were successful in detecting protein biomarkers in whole blood, human serum, and ionic buffers. This technology provides a robust analytical platform for rapid and sensitive detection of protein biomarkers, thus establishing this technology as an ideal candidate for biomarker screening in clinical settings.

A set of computer programs has been developed to draw chemical-equilibrium diagrams. This new software is the Java-language equivalent to the Medusa/Hydra software (developed some time ago in Visual basic at the Royal Institute of Technology, Stockholm, Sweden). The main program, now named “Spana” calls Java programs based on the HaltaFall algorithm. The equilibrium constants that are needed for the calculations may be retrieved from a database included in the software package (“Database” program). This new software is intended for undergraduate students as well as researchers and professionals.

The “Spana” code can be easily applied to perform radionuclide speciation and solubility calculations of minerals, including solubility calculations relevant for the performance assessment of a nuclear waste repository. In order to handle ionic strength corrections in such calculations several approaches can be applied. The “Spana” code is able to perform calculations based on three models: the Davies equation; an approximation to the model by Helgeson et al. (HKF); and the Specific Ion-Interaction Theory (SIT). Default SIT-coefficients may be used, which widens the applicability of SIT significantly.

A comparison is made here among the different ionic strength approaches used by “Spana” (Davies, HKF, SIT) when modelling the chemistry of radionuclides and minerals of interest under the conditions of a geological repository for nuclear waste. For this purpose, amorphous hydrous Thorium(IV) oxide (ThO2(am)), Gypsum (CaSO4·2H2O) and Portlandite (Ca(OH)2) solubility at high ionic strengths have been modelled and compared to experimental data from the literature. Results show a good fitting between the calculated values and the experimental data especially for the SIT approach in a wide range of ionic strengths (0-4 M).

4H-SiC substrates were annealed at 1500 °C for 30 min in 0.01 MPa Ar gas flow to make a graphene film. To clarify the effect of Al ion implantation and pre-plasma treatment, the graphene was fabricated on four different kinds of SiC substrates: without plasma treatment, with plasma treatment, Al ion-implanted without plasma treatment and Al ion-implanted with plasma treatment. The graphene films were analyzed by AFM and Raman spectroscopy. The Al ion implanted sample, which was then processed by CF4 plasma, showed small surface roughness of 3.49 nm (RMS), while the sample without CF4 plasma treatment showed large surface roughness of 8.41nm. Similar results were also observed for SiC samples without Al ion implantation. In Raman spectra, strong D-band, G-band and 2D-band signals were detected on both ion-implanted samples after annealing at 1500 °C, but weak D-band were observed on both samples without Al ion implantation. Raman mapping (2D-FWHM) showed that the graphene on ion-implanted SiC treated with CF4 plasma was more homogeneous than the one without CF4 plasma treatment. Hall measurements for SiC without Al ion implantation showed that graphene on SiC treated with CF4 plasma has higher mobility (389 cm2/Vs) than that without plasma treatment (136 cm2/Vs). Additionally, p-type graphene can be fabricated on Al ion-implanted SiC by CF4 plasma treatment.

This paper reports a novel means of integrating a high-performance dual-modal ZnO piezoelectric transducer with a flexible stainless steel substrate (SUS304) to construct dual-modal vibration-power transducers. To fabricate vibration-power transducers, the off-axis RF magnetron sputtering method for the growth of ZnO piezoelectric thin films is adopted. The stainless steel substrate has a higher Young’s modulus than those of the other substrates, and behaves the long-term stability under vibration. The transducer includes a ZnO piezoelectric thin film deposited on the stainless steel substrate combined with Pt/Ti layers at room temperature, which is fabricated by an RF magnetron two-step sputtering system. In this report, the ZnO piezoelectric thin films deposited with the tilting angle of 34° are set by controlling the deposition parameters. Scanning electron microscopy and X-ray diffraction of ZnO piezoelectric thin films reveal a rigid surface structure and a high dual-modal orientation. To investigate the generating characteristics of the dual-modal transducer, two basic experiments of longitudinal and shear modes are carried out. Based on cantilever vibration theory, the cantilever length of 1 cm and a vibration area of 1 cm2 are used to fabricate a transducer with a low resonant-frequency of 65 Hz for the natural vibration. A mass loading at the front-end of the cantilever is critical to increase the amplitude of vibration and the power generated by the piezoelectric transducer. The maximum open circuit voltage of the power transducer is 19.4 V.

We present a comparative study of optical absorption, photoluminescence (PL), and photoconductivity in bulk heterojunctions comprising a high performance functionalized anthradithiophene (ADT) derivative or the benchmark polymer P3HT as donor and functionalized pentacene (Pn) derivative or PCBM as acceptor. Of all D/A blends studied, the ADT/PCBM blend exhibited the highest charge photogeneration efficiencies under 532 nm excitation, leading to the highest amplitudes of time-resolved and continuous wave (cw) photocurrents. At nanosecond time scales after photoexcitation, both ADT-TES-F-based blends and the P3HT/Pn-TIPS-F8 blend exhibited photocurrents which were higher by a factor of 2-10, depending on the blend, than that in the P3HT/PCBM blend. However, cw photocurrents showed a different trend, with the ADT-TES-F/PCBM blend exhibiting only a factor of ∼2.5 higher photoresponse than that in the P3HT/PCBM blends, and the ADT-TES-F- and P3HT- based blends with Pn-TIPS-F8 showing a factor of ∼1.5-2.5 lower photoresponse than that in the P3HT/PCBM blend, due to other contributions, such as that of charge trap-limited transport, to cw photoresponse.

We report the recent progress of crystallization of amorphous silicon (a-Si), amorphous germanium (a-Ge) and amorphous silicon germanium alloy (a-SiGe) using a pulsed-Xenon-lamp system with multiple lamps. The precursor materials were deposited using a sputtering machine on display glass substrates maintained on a rotary holder. The RF powers on the silicon and germanium targets were varied to control the Ge/Si ratio in the materials. The film thickness was in the range of 50-100 nm, targeting the application in thin film transistors (TFT). The samples were pre-heated to 350-450°C in a conveyer chamber with nitrogen flow before the crystallization. The materials were characterized using AFM, Raman and Spectroscopic Ellipsometry. We demonstrated that we can uniformly crystallize a-Si, a-SiGe, and a-Ge with a single-pulse or multiple-pulse process on 10×5 cm2 glass substrates. We found that the required crystallization power for a-Ge is much lower than for a-Si. The power needed to crystallize a-SiGe is between the power required for a-Ge and a-Si crystallizations, and it increased with increasing Si fraction. No Raman signal was measurable in the as-deposited films. Strong Raman peaks at 520 cm-1 and 290 cm-1 were observed in the pulsed-lamp crystallized poly-Si and poly-Ge films, respectively. Distinct Ge-Ge, Si-Ge, and Si-Si vibration modes were observed at ~285 cm-1, ~390 cm-1, and ~470 cm-1, respectively, in the poly-SiGe films formed after the pulsed-light treatments. Their intensity ratios and the peak positions depended on the Ge/Si ratio and the light intensity used for the crystallization. AFM images showed the formation of large grains with increased surface roughness.

Shape Memory Alloys (SMA) are characterized by the capacity to recover a permanent deformation after being heated above a critical temperature called Final Austenite Temperature (Af). The Ni-Ti SMA are the most commercially used, however recent studies showed that the Cu-Al-Mn SMA present significant shape recovery and mechanical properties, showing a strong potential for developing new applications. In this context, the main goal of this work is to manufacture a Cu-Al-Mn SMA through a plasma melting process followed by injection molding of liquid metal and then characterize the samples, using the following techniques: Optical Microscopy (OM), Differential Scanning Calorimetry (DSC), Electrical Resistance as a function of Temperature (ERT) tests, Dynamical Mechanical Analysis (DMA) and Microhardness (MH).

To assess the stability of spent fuel in the highly alkaline chemical environment of the Belgian Supercontainer design, static leach experiments were performed with depleted UO2 and 238Pu-doped UO2 at different SA/V ratios for 1.5 years in cement waters (11.7< pH < 13.5) at ambient temperature and under argon atmosphere. The influence of the calcium concentration on the uranium release was also investigated. While the ultrafiltered U(IV) concentration was 10-9-10-8 mol.L-1 and independent of the pH, the U(VI) release from the UO2 surface was enhanced by the OH- concentration, leading to soluble U concentrations up to 10-5 mol.L-1 at high SA/V and under the influence of radiolysis. Together with the high Ca concentration, this can lead to the formation of Ca-U(VI) colloids as precursor of Ca-U(VI) secondary phases, decreasing the soluble U concentration. The precipitation of Ca-U secondary phases was however not clearly evidenced by surface analyses.