The effects of N2O gas addition on the properties of zinc oxide films grown on a-plane (11-20) sapphire (a-Al2O3) substrates were investigated, using a chemical vapor deposition method based on the reaction between dimethylzinc and high-energy H2O produced by a Pt-catalyzed H2-O2 reaction. By employing an optimal N2O gas pressure, both the film crystallinity and crystal orientation were improved. Subsequent to treatment with N2O, the electron mobility of films at room temperature increased from 207 to 234 cm2/Vs while the electron concentration decreased at low temperatures. In addition, the photoluminescence peak intensity of the nearband-edge emission was increased.

Adsorption of charged biomolecules onto atomically flat mica substrates is facilitated by the deposition of metal ions. Despite successfully acting as preferential anchoring sites, the presence of ions on the mica surface also changes its physicochemical characteristics something that is rarely quantified from a nanoscale point of view. In this study the nanoscale physicochemical properties of nickel-functionalized Muscovite mica are investigated by reconstructing the conservative force profile between an atomic force microscopy (AFM) tip and the surface. Various nickel ion concentrations (i.e. 1.0 mM to 20.0 mM) along with different incubation times (30 seconds and 5 minutes) are directly analyzed. Details in the spatial and temporal variations in surface properties due to the ion mediated adsorption of water are presented in details and in light of the binding efficiency of the metal ions. This insight benefits our understanding in the behavior of ion distribution that plays a crucial role in biomolecule imaging using AFM.

Carbon fine particles including single-walled carbon nanotubes (SWNTs) were synthesized by hot-filament and plasma assisted chemical vapor deposition. Specific surface area was evaluated for carbon fine particles synthesized under optimized conditions along with purified SWNTs and multi-walled carbon nanotubes (MWNTs) for comparison. The value of specific surface area for the synthesized carbon fine particles was smaller than the SWNTs, but larger than the MWNTs. Pore size distribution was analyzed with desorption isotherms by the DH method. Although smaller pores are included in the purified SWNTs than the synthesized carbon fine particles, pores of size larger than several nm were included more in the synthesized carbon fine particles.

In this contribution we report on the optical properties of cubic AlN/GaN asymmetric multi quantum wells (MQW) structures on 3C-SiC/Si (001) substrates grown by radio-frequency plasma-assisted molecular beam epitaxy (MBE). Scanning transmission electron microscopy (STEM) and spatially resolved cathodoluminescence (CL) at room temperature and at low temperature are used to characterize the optical properties of the cubic AlN/GaN MQW structures. An increasing CL emission intensity with increasing film thickness due to the improved crystal quality was observed. This correlation can be directly connected to the reduction of the linewidth of x-ray rocking curves with increasing film thickness of the c-GaN films. Defects like stacking faults (SFs) on the {111} planes, which also can be considered as hexagonal inclusions in the cubic crystal matrix, lead to a decrease of the CL emission intensity. With low temperature CL line scans also monolayer fluctuations of the QWs have been detected and the observed transition energies agree well with solutions calculated using a one-dimensional (1D) Schrödinger-Poisson simulator.

This work reports a carbon-free, blue-enhanced a-Si:H n-i-p photodiode with an optimized protocrystalline p-layer. Although the used deposition conditions for the p-layer correspond to the microcrystalline regime, thin layers are mostly protocrystalline due to the amorphous underlying undoped layer. This conclusion is supported by Raman spectroscopy measurements. We have also found that the optical band gap of the p-layer can be varied by adjusting the rf power. By widening the band gap and tuning the impurity concentration in the p-layer, absorption and recombination losses at the p-i interface were reduced. The current-voltage, capacitance-voltage, and spectral-response characteristics of fabricated photodiodes are correlated with the doping level, optical band gap, and deposition conditions for p-layers. The optimized device exhibits a leakage current of about ∼80 pA/cm2 at 5 V reverse bias. The external quantum efficiency reaches a peak value of 92% at a wavelength of 510 nm, and, at shorter wavelengths, decreases down to 66%@400nm.

The formation of the structure of geopolymer binders based on low-calcium fly ash is a multifactorial process that depends on the degree of solubility of aluminosilicate components in the solution of alkali activator. It is observed that the geopolymer binders based on fly ash with an identical chemical and mineral composition, the same grain size, and also activated by the same alkalis can result in a different strength.

This study is based on the assumption that there is dependence between the solubility of aluminosilicate components and the degree of polymerization of the silicates in glass phase. The degree of SiO2-polymerization is an integral parameter that is equal to the Si molar ratio (f Si ) of the silicate component in the glass phase of fly ash. The degree of SiO2-polymerization can be estimated from the molar composition of glass phase, which is determined from the chemical composition and quantitative X-ray diffraction analysis including identification of the amorphous phase composition.

The SiO2 polymerization rates of investigated fly ash specimens are confirmed by the IR results, specifically, by comparison of absorption bands of silicate fragments with varying levels of connectivity (Q0-4) in the range of wave numbers of 650–1350 cm-1.

The comparative analysis of the correlation of 28-day strength of geopolymer binders based on fly ash from different sources and level of SiO2-polymerization demonstrated an inverse relationship with f Si molar ratio and compressive strength.

To provide a counter electrode with lower-cost and simple production method for dye-sensitized solar cells (DSSCs), we developed polyaniline/graphene nanoplatelet/multi-walled carbon nanotube (PANi/GNP/MWCNT) composite films growing on glass substrates by using chemical/electrochemical deposition method and on fluorine-doped tin oxide (FTO)/glass substrates by using electrochemical deposition method respectively. A proper weight ratio of PANi/GNP/MWCNT (1/0.0030/0.0045) composite film depositing on FTO substrate as counter electrode with sheet resistance of 8.25±0.13 Ω/sq for DSSCs yielded power conversion efficiency (PCE) up to 7.45±0.08%, which has potential to replace the conventional Pt cell (7.62±0.07%). In addition, we also fabricated the DSSCs composed of a proper weight ratio of PANi/GNP/MWCNTs (1/0.0045/0.0060) composite film depositing on glass substrate as counter electrode. The sheet resistance of resulting composite film was 59.34±12.34 Ω/sq. These solar cells with FTO-free counter electrode exhibited a PCE of 2.90±0.09%.

Duplex stainless steels are commonly used for various applications owing to their superior corrosion resistance and/or strength. They have ferromagnetic behavior together with a good thermal conductivity and a lower thermal expansion as a result of higher ferrite content than austenitic steels. Their ferrite matrix suffers a decomposition process during aging in the temperature range 650-950° C producing precipitation of austenite, σ and χ, carbides and nitrides. These intermetallic phases are known to be deleterious for corrosion resistance and mechanical properties.

In this work the effect of aging time during isothermal treatment at 850°C and 900°C on the microstructure of SAF 2205 Duplex Stainless Steels welded plates has been investigated. The aim of this work is to determine the morphology of σ phase, and perform a quantitative analysis of the precipitation process.

Submerged Arc Welding is used for processing. It produces a high content of δ ferrite in the heat affected zone and low content of austenite in the weld. Microstructural examination shows that the σ phase precipitates at δ ferrite/γ interphases. Longer aging treatments give rise to an increase of volume fraction together with a coarser morphology.

This paper presents the first attempts to study the large conductance mechano-sensitive channel (MscL) activity in an artificial droplet interface bilayer (DIB) system. A novel and simple technique is developed to characterize the behavior of an artificial lipid bilayer interface containing mechano-sensitive (MS) channels. The experimental setup is assembled on an inverted microscope and consists of two micropipettes filled with PEG-DMA hydrogel and containing Ag/AgCl wires, a cylindrical oil reservoir glued on top of a thin acrylic sheet, and a piezoelectric oscillator actuator. By using this technique, dynamic tension can be applied by oscillating axial motion of one droplet, producing deformation of both droplets and area changes of the DIB interface. The tension in the artificial membrane will cause the MS channels to gate, resulting in an increase in the conductance levels of the membrane. The results show that the MS channels are able to gate under an applied dynamic tension. Moreover, it can be concluded that the response of channel activity to mechanical stimuli is voltage-dependent and highly related to the frequency and amplitude of oscillations.

In the recent time spinel ferrite magnetic nanoparticles have been largely studied owing to various applications of these materials in the information storage, ferro-fluid technology, magnetocaloric effect, refrigeration and medical diagnostics. In this category cobalt ferrite (CoFe2O4) nanoparticles specifically gained huge research attention and prepared by various chemical methods. However, further investigations are still needed on the substituted CoFe2O4 (CFO) nanoparticles to explore their various characteristics. In this paper we present our results on Mn and Zn substituted cobalt ferrite (Co0.6Zn0.4Mn0.3Fe1.7O4 ) nanoparticles prepared by chemical co precipitation method. The x ray diffraction pattern of as prepared Co0.6Zn0.4Mn0.3Fe1.7O4 (CZFMO) nanoparticles indicated their average particle size =20 nm. Magnetic properties of these nanoparticles before and after thermal annealing have been compared. Magnetization (M) vs. field (H) loop measurements at T = 293 K on as prepared and thermally annealed CZFMO nano powders revealed an unusual feature contrary to CFO nanoparticles prepared under same conditions. The saturation magnetization (Ms) decreases after the thermal annealing unlike the usual increase in Ms observed for CFO nanoparticles. These nano sized CZFMO powder samples are further characterized by low temperature magnetic measurements; Raman spectroscopy and Fourier transform infrared spectroscopy.

Physically crosslinked polyvinyl alcohol (PVA) hydrogels with high mechanical properties can be made by a low temperature crystallization method using a mixed solvent of dimethyl sulfoxide (DMSO) and water. Such hydrogels are studied as the artificial articular cartilage material. But DMSO shows cytotoxycity, and it is also have the effect of accelerating the absorption of harmful substances. Therefore completely elimination must be required for clinical application but the process is difficult.

However, PVA hydrogel made by water as a sole solvent by freeze-thawing method became cloudy because of micro-heterogeneous structure, and shows low mechanical properties.

Therefore, in this study, we developed the novel hot pressing method for preparing transparent and uniformly cross-linked PVA hydrogels without DMSO from highly concentrated aqueous solution. By this method, PVA hydrogels with high mechanical property and high transparency can be obtained without any harmful organic solvent because of the fast crystallization even at room temperature. The mechanical properties of PVA hydrogels were remarkably depended on their water contents after gelation, regardless of solution concentration.

Transparent conducting cadmium tin oxide (CTO) thin films were obtained from a mixture of CdO and SnO2 precursor solutions by the dip-coating sol-gel technique. The thin films studied in this work were made with 7 coats (∼200 nm) on corning glass and quartz substrates. Each coating was deposited at a withdrawal speed of 2 cm/min, dried at 100°C for 1 hour and then sintered at 550°C for 1 hour in air. In order to decrease the resistivity values of the films, these were annealed in a vacuum atmosphere and another set of films were annealed in an Ar/CdS atmosphere. The annealing temperatures (Ta) were 450°C, 500°C and 550°C, as well as 600°C and 650°C, when corning glass and quartz substrates were used, respectively. X-Ray diffraction (XRD) patterns of the films annealed in a vacuum showed that there is only the presence of CTO crystals for 450°C≤ Ta ≤ 600°C and CTO+SnO2 crystals for Ta=650°C. The films annealed in Ar/CdS atmosphere were only constituted of CTO crystals independent of the Ta. The minimum resistivity value obtained was ∼4 x 10-4 Ωcm (Rsheet= 20 Ω/□) for the films deposited on quartz and annealed at Ta=600°C under an Ar/CdS atmosphere. The films deposited on quartz showed the higher optical transmission (∼90%) with respect to the films deposited on corning glass substrates (∼85%) in the Uv-vis region. For their optical and electrical characteristics, these films are good candidates as transparent electrodes in solar cells.

The nucleation, growth and coarsening of carbides is investigated in high niobium containing TiAl alloys by diffraction and transmission electron microscopy. Higher carbon content increases the dissolution temperature of carbides. The solubility of carbon is much higher in a γ/α2-phase alloy than in the γ phase alone. Hereby no significant influence of Nb on carbon solubility is found. Crystallographic defects as grain boundaries and dislocations promote carbide nucleation which results in a carbide precipitation sequence starting first at grain boundaries, then at dislocations and only later in the γ matrix away from crystallographic defects. The consumption of carbon by grain boundary carbides or neighboring α2 grains also generates a precipitate free zone in γ grains near the grain boundary.

Helium embrittlement poses a great threat to materials used in both fusion and fissionreactor systems due to (n,α) transmutation reactions. Because of this, materials capable of moderating the helium content reaching grain boundaries and voids must be developed and improved to prevent catastrophic failure of reactor materials. Nanostructured ferritic alloys (NFAs) have shown great promise in preventing helium embrittlement due to the large number density of nanoscale precipitates acting as trapping sites for helium clusters and helium bubbles. In this study, we present density functional theory calculations on the interaction of helium with nanoscale precipitates found in NFAs as a preliminary study to furthering our understanding of the energetic mechanisms causing the precipitates to act as trapping sites for helium.

The density-functional-theory model for plutonium metal is shown to be consistent with recent magnetic measurements that suggest anti-ferromagnetism in Pu-Ga alloys at low temperatures. The theoretical model predicts a stabilization of the face-centered-cubic (fcc, δ) form of plutonium in an anti-ferromagnetic configuration when alloyed with gallium. The ordered magnetic phase occurs because Ga removes the mechanical instability that exists for unalloyed δ-Pu. The cause of the Ga-induced stabilization is a combination of a lowering of the band (kinetic) and electrostatic (Coulomb) energies for the cubic relative to the tetragonal phase.

The release of radionuclides measured during washing cycles of spent nuclear fuel samples in a series of experiments using different solutions are analyzed with respect to the fission products Cs, Sr, and Tc and the actinides U, Pu, and Am. Based on the concentrations of the dissolved radionuclides, their release rates are evaluated in terms of fraction of inventory in the aquatic phase per day. The application of this information on the fast/instant radionuclide release fraction (IRF) is discussed and following issues are addressed: Duration of the wash steps, solution chemistry, and radionuclide sorption onto surface of the experimental vessels. Data for the IRF are given and the correlation between the mobilization of the various elements is analyzed.

Here we introduce a highly stretchable Printed Circuit Board (PCB) inter-connection technology achieved through the combination of flexibility allowed by the silver nanowire (AgNW)-based electrode and stretchability provided by the meander-shaped substrate. Horseshoe-shaped elastic material, polydimethylsiloxane, is used as a substrate of the AgNW conductors for relaxed stress concentration. Continuously maintained 2-D percolation of stretchable AgNW networks overcomes the usage restrictions with ordinary rigid Printed Circuit Board (PCB). The horseshoe-shaped inter-connection is physically reliable with repeated stretching/releasing processes and maintains its conductivity under tensile strains up to 20 %, allowing the durable and stretchable PCB inter-connecting applications.

ZnO nanowire (NW) arrays were examined with Transmission Electron Microscopy (TEM) in cross-section after preparation by Focused Ion Beam (FIB) milling. This technique revealed that ZnO nanowires grown using a Au catalyzed vapor technique typically have Au particles at the NW tips, and also randomly dispersed across the base crystal growth that joins adjacent NWs. It is shown the adjacent NWs and the combined base growth is one crystal structure which can be used as a back electrical contact making fabrication of vertical array devices possible. However, the base growth displays detrimental features such as embedded Au particles and lattice defects which can affect the electrical output through depletion regions and scattering centers. In an effort to overcome these problems we investigate a growth method that is nucleated through a minor alteration of the a-plane sapphire surface roughness via a weak chemical etch. Observations of various stages of the growth show the growth nucleates as separate nanoislands that grow in c-plane alignment with Sapphire (1-210), and as growth continues these islands meet and form a polycrystalline film. Further growth initiates nanowire growth and the formation of a single crystal base layer and NW structure that can cover several square millimeter’s. This allows high quality arrays that are relatively free from defects to be formed without any metals contamination and ready for further device processing.

This paper reports on the development of a new type of low cost artificial aggregates based on granulated reactive silica (AAGS) for application in lightweight concrete. The functional principle of AAGS is based on the formation of polysilicate solutions under heat treatment (up to 80 °C) and migration of these solutions into the porous space of concrete under the thermal gradients, resulting in strengthening of inter-porous space. Developed AAGSs are based on low cost local raw materials, which may contain different amounts of amorphous silica. The activity coefficient (AC) and amorphous silica content are used to evaluate the performance of raw materials by suggested accelerated method.

Silica components with different genesis are investigated and ranked according to their AC. It is found out that chemogenic and biogenic siliceous rocks with a low degree of diagenetic transformations, which are mostly represented by CT-opals (a low-temperature nanoscale modification of tridymite and crystobalite, such as diatomite, tripoli and opoka) are the most highly active raw materials for AAGS. All tested siliceous materials including natural and artificial components are divided into three groups: highly active (with AC of 51–100%), active (with AC of 21–50 %) and low-active (with AC of 5–20 %). Based on theoretical and experimental studies, the requirements for AAGS raw materials are developed.