We report the effect of nitrogen and boron incorporation in the structure of spherical nanodiamond particles using ab initio density-functional theory. We changed the site of boron and nitrogen impurity from the center to the surface of the particles and calculated structural, electronic, cohesive and surface charge properties of each configuration. By moving the impurity from the center toward the surface, the internal strain of N and B doped nanodiamond drops. Unlike nitrogen, doping of boron causes lower broken bonds around impurity in the central region and also replacement of boron in the surface releases the strain of nanoparticle. We explain this observation by calculating the variation of the surface charge or polarity of the doped particles versus the site of dopant during the movement of impurities toward the surface which reduces the polarity in contrast to behavior of nitrogen doped particle. By moving the boron atom from the center toward the surface of the particle, p-type conduction occurs whereas nitrogen impurity does not create an n-type conduction. Results suggest that boron is a more effective dopant than nitrogen provided that it has not been placed in the central region of nanoparticle.

The concentration and temperature dependence of the self-diffusion of benzene adsorbed in the metal-organic framework MOF-5 (IRMOF-1) is studied by pulsed field gradient (PFG) NMR spectroscopy. When increasing the loading from 10 to 20 molecules per unit cell of MOF-5, the experimental diffusion data drop by a factor of about 3 while current molecular dynamic (MD) simulations predict slightly increasing diffusion coefficients for this range of loadings. The observation is rationalized using the recently predicted clustering of adsorbate molecules in microporous systems for temperatures well below the adsorbate critical temperature. Necessary improvements of molecular simulation models for predicting diffusivities under such conditions are discussed.

Thin films of a (Se80Te20)100−xAgx (1 ≤ x ≤ 4) were prepared by vacuum evaporation technique in a base pressure of 10−5 mbar onto well-cleaned glass substrates. The photoconductive measurements have been carried out on (Se80Te20)100−xAgx (1 ≤ x ≤ 4) thin films at different intensities 0–1200 lx in the temperature range 263–333 K. Dark conductivity (σd) and photoconductivity (σph) increase but the activation energy decreases as Ag concentration increases in the present glass composition. The measurements of intensity dependence of photoconductivity show that the photoconductivity increases with intensity as a power law where the power is found to be between 0.5 and 1.0. The photosensitivity (σph/σd) decreases with increase in Ag concentration. The results are explained on the basis of increase in the density of the localized states.

Plasma enhanced chemical vapor deposition was used to grow vertically aligned carbon nanotubes (CNTs) on silicon substrate. Field emission from these nanotubes was realized and used to fabricate a field emission-based sensor. Titanium dioxide was used as spacing layer between the emitters and a flexible anode made of silicon membrane. The variation of the emission current during mechanical vibration of the silicon membrane was measured and compared with a theoretical prediction. Experimental results show that field emission from CNTs is a good candidate for high frequency vibration sensing, measurement of resonance frequency, fabrication of accelerometer and other types of mechanical sensors. The fabricated device, due to a low distance between its electron emitters and the anode, works at low voltages with high emission current.

In order to investigate the formation reason and influence factors of anode melting pool rotation in high-current vacuum arcs (HCVAs) subjected to axial magnetic field (AMF), the rotational symmetric magnetohydrodynamic (MHD) model of anode melting pool flow (AMPF) phenomena in HCVA is established. Based on this model, the influence of different anode current density distributions (ACDDs) on AMPF is simulated and analyzed. Simulation results show that the influence of ACDDs on rotational velocity of AMPF is significant. According to simulation results, the more nonuniform ACDDs can lead to the more rotational velocity. That is to say, the more serious current constriction in HCVA will lead to the larger rotational velocity of AMPF. The changing trend of rotational velocity in simulation results at different moments is in agreement with the experimental observation. Experimental and simulation results both show that the maximal rotational velocity appears at 9–10 ms moments.

The cobalt/polyacrylonitrile (Co/PAN)-based carbon fibrous composites were prepared. The PAN incorporated with cobalt ions was in situ polymerized by initiating the complex solution of acrylonitrile (AN)/cobalt (II) chloride (CoCl2) in which the contents of cobalt ions were 0 wt.%, 0.29 wt.%, 0.56 wt.% and 1.14 wt.%, respectively. The ultrathin blue fibers were formed from the cobalt/PAN composites by the electrospinning method. The electrospun cobalt-incorporated PAN fibers were successfully stabilized in air and subsequently carbonized to form the carbon fibrous composites in a nitrogen (N2) atmosphere. Based on the scanning electron microscopy (SEM), we noticed that beads and beaded fibers were produced during the electrospinning process. When the content of cobalt ions in the complex solution was as high as 1.14 wt.%, there were many honeycomb-like structures and nanopores formed in both stabilized and carbonized fibers. The X-ray photoelectron spectra (XPS) were used to characterize the structure of the composite fibers.

A very large surface to volume ratio of nanoporous silicon (PS) produces a high density of surface states, which are responsible for uncontrolled oxidation of the PS surface. Hence it disturbs the stability of the material and also creates difficulties in the formation of a reliable electrical contact. To passivate the surface states of the nanoporous silicon, hydrocarbon films prepared by plasma enhanced chemical vapor deposition of methane (PECVD) have been deposited on porous silicon (PS). Conduction properties as well as optical characteristics of the as-deposited samples and annealed ones have been studied by current-voltage (I-V) and capacitance-voltage (C-V) measurements, spectral response, ellipsometry and Fourier transform infrared spectroscopy (FTIR) as a function of the annealing temperature, ranging from 200 to 750 °C. By high-temperature treatment, the low rectifying I-V curves become strong rectifying and C-V curves are similar to those of metal-insulator-semiconductor structures. These characteristics were explored and can be appropriately used in the fabrication of optoelectronics and sensor devices based on PS.

The change in dielectric constant relaxation time over temperature (35–590 °C) and frequency (45 Hz–5 MHz) in ceramics of Pb0.77K0.115Gd0.115Nb2O6 (PKGN, Tc = 340 °c) has been studied. Powder X-ray diffraction revealed the single-phase formation with orthorhombic crystal structure. The P-E hysteresis loop parameters are Ps = 21.77 μC/cm2, Pr = 17.09 μC/cm2, Ec = 11.86 kV/cm; the piezoelectric constants, Kp = 31.7%, Kt = 47%, d33 = 115 × 10−12 C/N, d31 = −41 × 10−12 C/N, are determined in the material and some transducer applications are discussed. Cole-Cole (Zll vs. Zl) plots showed a non-Debye type relaxation. Conductivity obeyed Jonscher’s universal power law, σ = σ0 + Aωn. The theoretical values of εl and σ are computed using the parameters ‘A(T)’ and ‘n(T)’ (0 < n < 1) and are well fitted with the experimental data. The hopping ion frequency (ωp) and charge carrier concentration (Kl) have been analyzed using Almond-West formalism. The dielectric relaxation processes are associated with localized oxygen vacancies conduction at high frequency region. A long-range conductivity by Gd3+ ions is found to be predominant at low frequency region. The activation energies from impedance and modulus formalisms revealed the ionic type conduction in PKGN.

Local order changes determined in an aluminosilicate matrix by calcination and addition of iron, yttrium or dysprosium oxides were investigated by X-ray diffraction and infrared spectroscopy. The nanocrystalline phase is reached only by Fe doping and not by the other two dopings. After calcination at temperatures as high as 1200 °C, nanocrystalline cristobalite alone is formed in the aluminosilicate matrix, while the doped samples favor the additional growth of mullite and quartz nanocrystals. The aluminosilicate spinel phase was not detected in any of these samples. An additional crystalline phase was only observed in the samples doped with yttrium and dysprosium. The structural units evidenced by FTIR analysis are associated with the crystalline phases identified by X-ray diffraction.

ZnO/Si heterojunctions were prepared by the sol-gel method and hexagonal polycrystalline wurtzite structures with pores were observed by a field emission scanning electron microscope. The steady photovoltage properties of ZnO/Si heterojunctions were obtained under the illumination of a 532 nm continuum solid state laser with a 50 Hz chopper. In addition ns photoresponse signals were found when the samples were excited by a ps pulsed laser at room temperature. A possible mechanism was proposed to describe the photovoltaic process in the ZnO/Si heterojunction.

We present a numerical modeling of the effect of optical pulse position on the impulse response of a GaAs back-gated Metal-Semiconductor-Metal (MSM) photodetector at low bias voltages. The backside contact of the photodetector is set to the floating condition (disconnected from the external circuit). Experimentally the device response to the optical pulse is strong only when the position of the optical pulse is around the anode contact. We have used a one-dimensional time-dependent nonlinear ambipolar transport equation to model this behavior. Our numerical modeling results agree well with the reported experimental findings.

The interfacial magnetoelectric (ME) effect in ferromagnetic-ferroelectric (FM-FE) tunneling junctions was investigated in this work. We found that the tunneling magnetoresistance (TMR) changes with the reversing of the electric polarization of the FE barrier. The theoretical results also indicated that TMR is strongly dependent on the electric polarization, the exchange splitting energy, the screening lengths in the electrodes, and the dielectric constant of the FE barrier layer. These results may provide some insights into switching magnetization electrically for spintronics and presenting independent tunneling states in a single junction for multi-value storage memory applications.

There is increasing evidence that animal morphogenesis consists of a large scale tissue flow, which defines the gross characteristics of the animal body at a very early developmental stage. We have studied the vertebrate embryo cell trajectories between a moment when it is flat and formless, to a moment when the body plan is recognizable (chicken embryo days 2–3 of development). We find that a large vortex flow patterns the vertebrate bauplan, and especially the limb territories, both hindlimbs and forelimbs. In vivo velocity measurements show that the vortices are dragged by a localized shear oriented along the median axis. A simple hydrodynamic model accounts for the lenticular shape of the limb plates. On the hindlimb plate, the flow propagates in the form of a solid-body vortex on the limb plate, dragged by a Poiseuille flow along the backbone. In vivo tonometry measurements show that there exist stress gradients in the embryonic tissue, and that the flow pattern is congruent with the direction of decrease of stress magnitude.

Laser-induced breakdown spectroscopy (LIBS) was applied to the quantitative analysis of elemental composition of soil. The experiment was performed in air at atmospheric pressure and at room temperature. A Nd:YAG laser with the fundamental wavelength of 1064 nm was employed to generate the soil plasma. The emission spectra from the plasma were collected by the Cerny-Turner type of spectrometer, which was equipped with an intensified charge-coupled device (ICCD). The plasma temperature and electron density were evaluated by the Boltzmann plot method and the Saha-Boltzmann equation respectively. Then the concentrations of elements in soil were further obtained by the internal standard of iron element and some selected atomic/ionic lines. In order to prove the credibility and reliability of the present LIBS results, a comparison between the LIBS results and the nominal concentrations was performed. It was found that the LIBS results agree with the nominal concentrations. Therefore the LIBS technique promises to fast and in simultaneous multi-element quantitative analysis of soil.

In this paper, a new model is proposed for the heat transfer characteristics of power law non- Newtonian fluids. The effects of power law viscosity on temperature field were taken into account by assuming that the temperature field is similar to the velocity field with modified Fourier’s law of heat conduction for power law fluid media. The solutions obtained by using Boubaker Polynomials Expansion Scheme (BPES) technique are compared with those of the recent related similarity method in the literature with good agreement to verify the protocol exactness.

Synthesis of ZnO microprisms was achieved on Si substrates coated with Ce(NO3)3 thin films by a simple carbon-thermal evaporation method. The pre-deposited Ce(NO3)3 films may decompose at about 200 °C to be CeO2 microparticles, which can provide growing sites for the ZnO microstructures. The structural and optical properties of the as-obtained ZnO microstructures were characterized by a number of techniques, including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectrum and photoluminescence. The results indicate that the as-prepared ZnO microprisms exhibit hexagonal prism-like platforms showing well-defined crystallographic facets and hexagonal pyramid-like tops. Room temperature photoluminescence spectrum of the microstructures shows a strong ultraviolet emission band accompanied by a broad weak green emission band. Finally, the growth mechanism was discussed based on the experimental conditions and the ZnO crystal growth habits.

In this paper an original experimental device is presented. It allowed to obtain, for the first time, the total amount of liquid and vapour of metal created on the electrode surface by a non stationary electric arc (600 A/20 ms) burning in air at atmospheric pressure. The results are presented for two different materials Ag and AgSnO2 and for electrode gap values in the range 1–10 mm. The amount of liquid and vapour created under the arc action is compared with usual erosion rate in the same experimental conditions. In the case of Ag electrodes the amount of liquid metal created on the anode may be 3 to 5 times higher than on the cathode although the usual erosion rates are more important at the cathode. For the anode, the usual erosion may represent a very low percentage (<10%) of the total amount of metal liquid created showing then that a very small part of the liquid created during the arc is ejected. In the case of AgSnO2 electrodes the amount of liquid metal is smaller. The usual erosion rates at the cathode are higher than for the anode and the usual erosion represent 10 to 50% of the amount of liquid and vapour created.

An atmospheric pressure plasma source supplied by an electrical circuit consisting of two voltage sources in parallel connection is reported. One of them is a low-power self-oscillating flyback converter which produces negative voltage pulses with an amplitude of several kilovolts. The high voltage pulses are necessary to ignite an electrical discharge between the electrodes at atmospheric pressure. An additional dc source delivering several hundreds of volts at a few hundred milliamps is used to sustain the electrical discharge. The circuit configuration allows the control of the discharge current over a wide range, in a simple manner. By using argon as a working gas, a stable plasma plume up to 8 mm long can be obtained either in a transferred or non-transferred arc mode.

Recent smart textile fabrication methods that are aimed at increasing the integration of electronics with textiles have involved fabricating micro-electronic components directly at the yarn level. Our approach to creating smart textiles is to fabricate thin-film devices and interconnects on plastic strips to create ‘e-fibers’ and weave them into a textile using a commercial weaving machine. e-Fibers are exposed to bending radii as small as 165 μm during weaving. If patterned interconnect lines and device layers on the surface of the e-fiber are not designed correctly, they will crack due to the high strain and lose their electronic functionality. Brittle sensor and transistor device layers may be protected locally using rigid encapsulation materials, but cracking remains an issue for long metal interconnect lines which require flexibility. We investigated two strain-control methods to prevent the thin-film interconnect lines from cracking during weaving: (1) patterning the metal interconnect lines with a geometric design to slow propagation and merging of cracks and (2) encapsulation of interconnect lines to shift the deposited films to the neutral plain of the substrate. The mechanical behavior of interconnect lines exposed to tensile bending was studied by measuring the change in interconnect resistance versus bending radii ranging from 5 mm to 50 μm. The critical bending radius, XC, defined as the radius at which the normalized interconnect resistance changes to 1.1 (indicating the onset of film rupturing) was 150 μm for standard interconnect lines. Patterned interconnect lines had a radius XC of 115 μm while encapsulated interconnect lines never reached this critical bending radius and showed a maximum resistance change of 1.02 at 100 μm. These results show that it is possible to design interconnect lines with reduced cracking behavior when exposed to high strain during commercial weaving.

Research and development activities in organic solar cells have been intensified in the last two decades, and the reported energy conversion efficiency in small cell samples is rapidly increased. However, the relation between cell performance and material preparation conditions is not fully understood. In this work charge carrier recombination processes in hybrid poly-3-octylthiophene (P3OT)/cadmium sulfide (CdS) photovoltaic cells were analyzed as a function of structural and optoelectronic properties of chemical bath deposited CdS thin films. The temperature of the bath solution varied between 60 and 80 °C, and the deposition time from 1 to 3 h. Charge carrier recombination times in CdS films were measured with photoconductance decay technique, whereas the same time in P3OT films was estimated by Time-of-Flight method. Charge carrier recombination rates at CdS/P3OT interface were determined by transient photovoltage technique. It is found that CdS films grown at lower solution temperature (60 °C) give a higher charge carrier recombination rate at CdS/P3OT interface and larger short-circuit current density and energy conversion efficiency values in the corresponding solar cells, in comparison with the 80 °C deposited ones. This improvement could come from the reduction of charge carrier trap density inside grains as well as at grain boundaries in lower temperature deposited CdS films.