Two major causes of hardening and subsequent embrittlement in ferrite steels are the spinodal decomposition of the binary Fe-Cr solid solution and the carbide formation due to the presence of carbon as foreign interstitial atoms. In the present work, simulations of the microstructure evolution due to thermal ageing are performed by means of a kinetic Monte Carlo code and using a state-of-the-art interatomic potential based on density functional theory (DFT) predictions and experimental data. The main issues concern the possibility to perform thermal ageing simulations in an acceptable computational time frame and to reproduce a realistic behavior of carbon kinetics and carbide formation. The simulations on the binary system show the microstructural evolution during thermal ageing and allowed to find an exponential trend related to the acceleration as a function of temperature. With the insertion of carbon in the model, the chromium precipitation tends to accelerate. The carbon clustering, analyzed separately, is faster with higher C concentrations and in lattices with segregated chromium.

The roll of lubricants in the cold-drawn process is very important to obtain a good quality on the surface of aluminum and copper wires. The viscosity of a lubricant is closely related to its ability to reduce friction. When the viscosity of a lubricant is too low, the lubricated component will have inadequate protection and will therefore be subject to excessive wear. When the viscosity of the lubricant is too high, the lubricated component will expend additional energy to complete its task. In this work, the rheology behavior of traditional lubricants for the cold drawn of Al and Cu is determined from experimental data of viscosity Vs shear rate. To evaluate the efficiency of each lubricant, the roughness surface of each wire is measured by Atomic Force Microscopy (AFM). In this way a minimum of roughness in wires corresponds to the viscosity required for each cold-drawn process. It is known that different lubricants are used for the cold drawn of Al and Cu. In this work, a new lubricant developed with the aim to be used in both process is characterized by FTIR, rheometer analysis and AFM. Results have indicated that, this new lubricant with a low viscosity that promotes a lower energy process, also decreases the roughness of Al and Cu wires compared with conventional lubricants, i.e.it has an important influence in the quality of the wires surface. This means that this new lubricant could be used during the process of both metals without making important changes, which means low operations costs and flexibility for the manufacturing plant.

We present an extensive theoretical study of the phonon conductivity and thermoelectric properties of SiGe alloys. Phonon dispersion relations and group velocities – required for conductivity calculations – are obtained by employing the density-functional-perturbation scheme. The cubic anharmonic potential has been expressed by treating the Gr¨uneisen constant as a semi-adjustable mode-averaged parameter. Calculations are also performed, within the nearly-free-electron approximation, for the temperature variation of the Fermi energy, Seebeck coefficient, electrical conductivity, and electronic polar and bipolar contributions to thermal conductivity. Results are compared with experimental measurements for n-doped pressure-sintered Si0.754Ge0.246 alloy. Using these results, we compare our results for the thermoelectric figure-of-merit with previously reported results based on an empirical approach for phonon conductivity.

We report the deposition and field emission properties of nanostructured composites consisting of carbon nanowalls (CNWs) and nanocrystalline diamond films by introducing two kinds of substrate scratching pretreatment, i.e., undulation and ultrasonic vibration. With increasing duration of scratching pretreatment, the morphology of the deposits changes from simple CNWs to a film/CNW composite and lastly to CNWs on a film, and then the space between the walls is increased. The emission turn-on field is reduced from 2.1 V/μm for simple CNWs to around 1.2 V/μm for the composite films, accompanied by an increase in field enhancement factor. The results indicate that electric field screening between the walls is successfully suppressed by widening of the wall spacing.

An efficient implementation of PNP-cDFT, a multiscale method for computing the chemical potentials of charged species is designed and evaluated. Spatial decomposition of the multi particle system is employed in the parallelization of classical density functional theory (cDFT) algorithm. Furthermore, a truncation strategy is used to reduce the computational complexity of cDFT algorithm. The simulation results show that the parallel implementation has close to linear scalability in parallel computing environments. It also shows that the truncated versions of cDFT improve the efficiency of the methods substantially.

Possibility of feedback and inflation mechanism among carrier captures by a deep-level defect and transient induced lattice vibrations is discussed using proper configuration coordinate diagrams for many carriers. Treating the lattice motion classically we selfconsistently simulate the time evolution of the interaction mode and a series of athermal captures of electron(s) and hole(s). When both the activation energies E act e and E act h are small, a series of successive athermal captures is enhanced and probable for high carrier densities, however, we find that the possibility of inflation in the amplitude of the lattice vibration critically depends on the minority capture rate and the relative width of the phonon frequency distribution.

Hybrid inorganic-organic proton-conducting membranes are prepared by a standard solvent casting procedure. Nafion® is used as the host polymer and [(ZrO2)·(Ta2O5)0.119] “core-shell” nanoparticles (d ~ 10-50 nm) are incorporated as the nanofiller. This filler is characterized by a “core” of ZrO2 nanoparticles covered by a Ta2O5 “shell”. The mechanical properties of the resulting hybrid membranes determined by dynamic mechanical analysis are better than those of pristine Nafion. The elastic modulus of the hybrid membranes with a filler content greater than 5 wt% is at least 1 MPa up to 200°C, while pristine Nafion undergoes an irreversible elongation at 160°C. The hybrid membranes are characterized by promising conductivities above 115°C (7.5×10-2 S·cm-1 for 9 wt% nanofiller vs. 3.3×10-2 S·cm-1 for pristine Nafion), as determined by broadband electric spectroscopy. The single fuel cell performance at low levels of hydration of the best-performing hybrid membrane (9 wt% nanofiller) is better than that of pristine recast Nafion. The maximum power densities yielded by the MEAs fabricated with pristine Nafion and the hybrid membrane are 0.026 and 0.108 W·cm-2, respectively, at 85°C, aH2O = 0.13, a reagent back pressure = 1 bar and using pure oxygen as the oxidant.

Ceria has been aggressively explored for applications as a fuel cell electrolyte or in catalytic converter due to its high oxygen ion conductivity, or as a UV absorption material. It is proven that the properties and applications of ceria nanoparticles are related to their morphologies and sizes. This ability to control the shape and morphology of CeO2 nanoparticles allows the corresponding tuning of their chemical and physical properties. Most of the applications require the use of non-agglomerated nanoparticles, as aggregated nano-particles lead to inhomogeneous mixing, poor sinterability and compromised properties. However, nano-crystals with a primary particle size < 5 nm have a strong tendency to agglomerate. In this work, nano-crystalline particles of CeO2 have been synthesized by a low temperature hydrothermal and solvent thermal synthesis process. Using the precursors of Ce(NO3)3.6H2O:NaOH in different mixing ratio, using polyvinylpyrrolidone (PVP) as the surfactant, the CeO2 particles were synthesized via 24 h hydrothermal and solvent thermal process treatment at reaction temperature of 100 °C and 180 °C using Teflon-lined hydrothermal autoclave. We have optimized the conditions for the two synthesized methods, hydrothermal and solvent thermal, to yield highly crystallized particle with controllable shape, sizes and morphology. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HR-TEM) analysis were used to characterize the crystalline and morphology of the synthesized CeO2 nanoparticles. The optimal reaction condition to prepare the CeO2 of the desired octahedron shaped fluorite structure was established. Based on the results, the hydrothermal synthesis method yields nanocrystalline CeO2 sizes of ∼6 nm, while the solvent synthesis method yields nanocrystalline CeO2 sizes of 2-3 nm at the optimal conditions. The hydrothermal synthesis method produced better particles in terms of crystallinity and morphology under HR-TEM. Temperature also plays a part in crystallinity and sizes of the CeO2 nanoparticles. The crystallinity and size of the CeO2 nanoparticles increases when using higher treatment temperature for both hydrothermal and solvent thermal methods. The growth mechanism of the shape and morphology of the CeO2 will also be discussed.

Creep tests of monocrystalline Co–Al–W-based alloys with a tensile stress of 137 MPa at 1000 °C were carried out. The microstructures of the crept specimens were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). The γ′ phase in the specimens was not only elongated along the stress direction as expected by the sign of the lattice misfit but also elongated in one of the <100> directions perpendicular to the stress direction. As a result, the shape of the γ′ phase is not a rod but a plate. In the TEM images, it was observed that many SISFs are induced in the γ′ phase by creep. A similar microstructure is also observed in Ni-based superalloys, but the microstructure was formed under relatively lower temperatures and higher applied stresses. The observation of numerous stacking faults in the γ′ phase is a clear indication that the γ′ phase precipitated in the present alloy is weaker than that in many modern Ni-based superalloys.

The present work reports the covalent functionalization of few-wall CNTs (FWCNTs) by ferrocene derivatives to i) improve their dispersion efficiency in water and ii) to graft electroactive chemical groups on their side-walls in order to promote electron transfer to biomolecules. The functionalized CNTs (f-CNTs) are used to modify a glassy carbon electrode and this modified electrode is used for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide).

The density, Vickers microhardness and crystallization fraction of glass-ceramic materials synthesized from parent glasses are determined in which CaO is gradually substituted by SrO. The chemical composition (in mol.%) of the parent glasses is 54SiO2-(23-X)CaO-12MgO-5Al2O3-6CaF2-XSrO, where X is the employed CaO substitution level (X = 0, 3, 6 and 9 mol.%, with X = 0 corresponding to the reference material). In order to determine the type of crystallization occurring in the glass-ceramic samples, as well as the crystalline phases formed in them, these are characterized by both Scanning Electron Microscopy (SEM/EDS) and X-Ray Diffraction (XRD). Independently of the CaO substitution level employed, the glass-ceramics show the formation of a solid solution corresponding to diopside-type pyroxene, with chemical formula Ca(Mg,Al)(Al,Si)2O6, as a single crystalline phase. The synthesized glass-ceramic materials with the reference composition show the highest Vickers microhardness and crystallization fraction, as well as the lowest density.

The template-based approach has been employed for the synthesis of nanomaterials with the potential application in the development of new material, energy and microelectronic devices. The templates are carbon nanotubes, to which the external contour is applied. Both plasmaenhanced chemical vapour deposition (PECVD) and atomic layer deposition (ALD) processes have been studied for various materials, including SiO2 and Al2O3. It is found that PECVD processes can give conformal coating on the template of carbon nanotubes, and the plasmaenhanced ALD (PEALD) processes do not show obvious damage to the morphology of carbon nanotubes. Pretreatment is also not necessary for the formation of conformal coatings of SiO2 and Al2O3. Moreover, the carbon nanotubes can be treated as the sacrificial template and removed to prepare the nanostructures with original contour. As an example, the 3-dimensional structure of Al2O3 has been demonstrated. This can be explored to develop 2D and 3D nanostructures of the intended materials. The approach of using PECVD and ALD processes makes it possible to integrate in a continuous way such kind of synthesis process with production processes of current semiconductor and energy industries.

Metallic nanoparticles are often obtained by chemical decomposition or reactive techniques involving the extensive usage of harmful reducing or stabilizing agents. A facile green synthesis technique resulting in readily exploitable nanoparticle dispersion in ionic liquid without the use of any additional agents is reported here. 1-Propyl- 3- Methyl Imidazolium Iodide (PMIM(I)) is a non-volatile, thermally stable and non-toxic ionic liquid. This eco-friendly liquid is used as the substrate for thermal evaporation of gold to obtain stable gold nanoparticles. On being examined by Transmission Electron Microscopy the high monodispersity in their sizes was revealed. The byproduct free, ‘clean’ processing technique helps in obtaining un-contaminated particles. The thermal evaporation method used (for the generation of metallic vapor) plays a significant role in the difference in kinetics of the formation and growth of nanoparticles, unlike the widely reported sputtering technique for vapor generation. The formed particles are deposited only on the top surface of the liquid. Thus the nucleation and growth of the particles can be considered to have occurred by surface diffusion process only. A deeper investigation into the formation kinetics has the potential application for synthesizing other nanomaterials via this environmental friendly approach.

A compact, single element concentrator comprising a near linear array of prisms has been designed to simultaneously split and concentrate the solar spectrum. Laterally aligned solar cells with different bandgaps are devised to be fabricated on a common Si substrate, with each cell absorbing a different spectral band optimized for highest overall power conversion efficiency. Epitaxial Ge on Si is used as a low cost virtual substrate for III-V materials growth. Assuming no optical loss for the prism concentrator, no shadowing and perfect carrier collection for the solar cells, simulations show that 39% efficiency can be achieved for a parallel four-junction (4PJ) InGaP-GaAs-Si-Ge cell under 200X concentration, and higher efficiency is possible with more junctions.

The synthesis of mullite from kaolin clay and two precursors of aluminum: α-Al2O3 and Al(NO3)3 was investigated. In order to study the temperature effect, the system kaolin-α-Al2O3 was calcined in air in a range of 1200 to 1500°C, for 2 h. For the system kaolin-Al(NO3)3, the combustion method was employed, using urea as fuel, and calcined in air at 1500°C for 2 h. The products were characterized by X-ray diffraction, scanning electronic microscopy (SEM), energy dispersive spectroscopy and particle size analysis in order to analyze and compare their morphology and structure. The crystallographic study revealed an incomplete reaction between the kaolin and the α-Al2O3. Nevertheless, in the system kaolin-Al(NO3)3, it was obtained mullite with high purity and trace amounts of cristobalite.

Silicon (Si) has been the dominating material platform of microelectronics over half century. Continuous technological advances in circuit design and manufacturing enable complementary metal-oxide semiconductor (CMOS) chips with increasingly high integration complexity to be fabricated in an unprecedently scale and economical manner. Conventional Si-based planar lightwave circuits (PLCs) has benefited from advanced CMOS technology but only demonstrate passive functionalities in most circumstances due to poor light emission efficiency and weak major electro-optic effects (e.g., Pockels effect, the Kerr effect and the Franz–Keldysh effect) in Si. Recently, a new hybrid III-V-on-Si integration platform has been developed, aiming to bridge the gap between Si and III-V direct-bandgap materials for active Si photonic integrated circuit applications. Since then high-performance lasers, amplifiers, photodetectors and modulators, etc. have been demonstrated. Here we review the most recent progress on hybrid Si lasers and high-speed hybrid Si modulators. The former include distributed feedback (DFB) lasers showing over 10 mW output power and up to 85 oC continuous-wave (cw) operation, compact hybrid microring lasers with cw threshold less than 4 mA and over 3 mW output power, and 4-channel hybrid Si AWG lasers with channel space of 360 GHz. Recently fabricated traveling-wave electro-absorption modulators (EAMs) and Mach-Zehnder interferometer modulators (MZM) on this platform support 50 Gb/s and 40 Gb/s data transmission with over 10 dB extinction ratio, respectively.

In this contribution, we report on a numerical study demonstrating how to realize Electrostatic Force Microscopy (EFM) tomography. Based on the Equivalent Charge Method, both force and force gradient between a buried object (or trapped charges) and the Atomic Force Microscope tip are calculated. The main idea is to scan the sample at different tip sample distances and obtain the position and charge value of the object using reconstruction algorithms. The quantitative analysis here presented is a first step toward tomography for samples presenting “dilute” point charges creating non correlated signals by the interpretation of EFM signals. Lateral resolution, sensitivity (i.e. ability to detect an object), performance and limitations of EFM are also discussed in the paper.

Photoembossing is a technique used to create relief structures using apatterned contact photo-mask exposure and a thermal development step.Typically, the photopolymer consists of a polymer binder and a monomer in a1/1 ratio together with a photo-initiator which results in a solid andnon-tacky material at room temperature. Here, new mixtures forphotoembossing are presented which are potentially biocompatible. A polymerbinder such as poly (methyl methacrylate) with triacrylate monomer andbiocompatible photo-initiator Irgacure 369 is used. Photopolymer filmsproduced are successfully embossed with height of relief structurescontrolled by UV dosage and developing temperature. Furthermore, thephotopolymer blend is electrospun to form fibres with diameters of 5 μmwhich are then photoembossed. The photoembossed fibres showed homogenousreproducible surface textures. Biocompatibility is evaluated by culturinghuman umbilical vein endothelial cells (HUVECs) on films of thisphotopolymer blend. The study shows that photoembossing is a feasible methodof producing surface texturing on both films and electrospun fibres fortissue engineering applications.

In the present work, a comparison study of the NiMo hydrodesulfurization (HDS) catalysts supported on different nanostructured supports of MCM-41 and SBA-15-types and the same ones modified by TiO2 grafting was undertaken. The aim of this study was to inquire on the effect of the characteristics of the primary silica supports on the activity and selectivity of the NiMo catalysts modified with titania in deep HDS. Supports and catalysts were characterized by nitrogen physisorption, small-angle and powder XRD, TPR, UV-vis DRS, and HRTEM, and tested in the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It was found that titania grafting on all silica supports resulted in a slight decrease of BET surface area and total pore volume. However, the characteristic p6mm hexagonal pore arrangement of the used nanostructured silica materials was not affected. Powder X-ray diffraction pointed out a good dispersion of Mo and Ni oxide species in all prepared catalysts. TPR characterization of the NiMo catalysts revealed some increase in the metal-support interaction after titania grafting on the silica surface. Further DRS characterization indicated that the best dispersion of Mo oxide species was obtained on the TiSBA-15 support. Titania addition to the silica supports also produced an increase in the dispersion of the sulfided NiMo phase, which was more marked for SBA-15 support than for the MCM-41 (HRTEM). The most active NiMo/Ti-SBA-15 catalyst resulted to be significantly more active (∼40 %) than the conventional NiMo/γ-Al2O3 catalyst in HDS of 4,6-DMDBT.