Composition Of Individual Layers Research Articles

A mobile setup for simultaneous and in situ neutron reflectivity, infrared spectroscopy, and ellipsometry studies.

Neutron reflectivity at the solid/liquid interface offers unique opportunities for resolving the structure-function relationships of interfacial layers in soft matter science. It is a non-destructive technique for detailed analysis of layered structures on molecular length scales, providing thickness, density, roughness, and composition of individual layers or components of adsorbed films. However, there are also some well-known limitations of this method, such as the lack of chemical information, the difficulties in determining large layer thicknesses, and the limited time resolution. We have addressed these shortcomings by designing and implementing a portable sample environment for in situ characterization at neutron reflectometry beamlines, integrating infrared spectroscopy under attenuated total reflection for determination of molecular entities and their conformation, and spectroscopic ellipsometry for rapid and independent measurement of layer thicknesses and refractive indices. The utility of this combined setup is demonstrated by two projects investigating (a) pH-dependent swelling of polyelectrolyte layers and (b) the impact of nanoparticles on lipid membranes to identify potential mechanisms of nanotoxicity.

Research into landslide processes in the coastal zone of the Takhtakorpureservoir using vertical electrical sounding method (the southeastern slope of the Great Caucasus)

Landslide-prone areas on the coastal zone of the downstream of the Takhtakorpu reservoir located on the arid-hilly part of the southeastern slope of the Great Caucasus mountain system (Azerbaijan) were investigated using vertical electrical sounding (VES) method. The entire research area is geologically active. It is complicated by seismicity (with an intensity of 8—9 points on the MSK-64 scale), vertical (uplift of the Earth’s crust about +6 mm/year) and horizontal (4 ± 1 mm/year, generally north-north-east) movements, landslides (in more than 5 centers) as well as the Gaynarja mud volcano, in the form of hill ≥100 m in diameter with griffins. Tectonically, the mud volcano is timed to the consolidated part of the anticline of the same name, which currently is located in the right-bank zone, closer to the water of the Takhtakorpu reservoir. Therefore, the erupted products of the mud volcano come into contact with the aquatic environment. The geological structure of the territory is dominated by rocks of the Pliocene Productive Stratum (N2). With respect to lithology, they consist of clays and argillaceous rocks. Groundwater occurs sporadically, with a total salinity of 7 g/l and a filtration coefficient of 4 m/day. Geological sections of the area were studied to a depth of 40 m, the thickness and composition of individual layers of rocks were described. 3D models of the study area were developed completely in an arbitrary cut and also along the X, Y and Z axes. It was revealed that the layers composing the geological section of the region are subject to the impact of plicative dislocations due to the geodynamic processes. It is assumed that landslides in the study area are mainly formed at the contact of eluvial-deluvial deposits with bedrocks. One of the main reasons for the formation of landslide phenomena, apparently, is also associated with the steepness of the slopes and their constituent rocks, which absorbing atmospheric precipitation become waterlogged. The depths of the assumed slip planes in individual landslide blocks were revealed and the thickness and direction of the landslide body were determined.

Functionally graded laminated composites fabricated from MAX-phase filled preceramic papers: Microstructure, mechanical properties and oxidation resistance

This paper describes the fabrication and characterization of novel preceramic paper-derived functionally graded materials (FGMs) based on Ti3(Si,Al)C2 MAX phase. The FGMs with different architecture were fabricated via spark plasma sintering of stacked preceramic papers at 1250 °C for 5 min. Microstructure, phase composition and elemental distribution were analyzed by scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy, respectively. Oxidation tests were performed in air at 1300 °C for 5 h. FGMs containing Al- and Si-enriched MAX-phase layers were formed. The fabricated materials exhibit high flexural strength (over 600 MPa), which are dependent on microstructure and composition of individual layers as well as the architecture of composites. It was found that texturing of MAX phase grains during SPS results in anisotropic hardness of the composite. The difference in the composition of the individual layers also provides a hardness gradient in the composite. It was shown that the formation of the outer layer from the Al-enriched Ti3Al(Si)C2 MAX phase increases the corrosion resistance of Ti3SiC2-based composites. The high corrosion resistance of FGMs is due to the growth of a continuous and dense Al2O3 oxide layer.

Synthesis of Multicompositional Onion‐like Nanoparticles via RAFT Emulsion Polymerization

AbstractSynthesis of multicompositional polymeric nanoparticles of diameters 100–150 nm comprising well‐defined multiblock copolymers reaching from the particle surface to the particle core was conducted using surfactant‐free aqueous macroRAFT emulsion polymerization. The imposed constraints on chain mobility as well as chemical incompatibility between the blocks result in microphase separation, leading to formation of an onion‐like multilayered particle morphology with individual layer thicknesses of approximately 20 nm. The approach provides considerable versatility in particle morphology design as the composition of individual layers as well as the number of layers can be tailored as desired, offering more complex particle design compared to approaches relying on self‐assembly of preformed diblock copolymers within particles. Microphase separation can occur in these systems under conditions where the corresponding bulk system would not theoretically result in microphase separation.

Synthesis of Multicompositional Onion-like Nanoparticles via RAFT Emulsion Polymerization.

Synthesis of multicompositional polymeric nanoparticles of diameters 100-150 nm comprising well-defined multiblock copolymers reaching from the particle surface to the particle core was conducted using surfactant-free aqueous macroRAFT emulsion polymerization. The imposed constraints on chain mobility as well as chemical incompatibility between the blocks result in microphase separation, leading to formation of an onion-like multilayered particle morphology with individual layer thicknesses of approximately 20 nm. The approach provides considerable versatility in particle morphology design as the composition of individual layers as well as the number of layers can be tailored as desired, offering more complex particle design compared to approaches relying on self-assembly of preformed diblock copolymers within particles. Microphase separation can occur in these systems under conditions where the corresponding bulk system would not theoretically result in microphase separation.

Spatially resolved structure and domain wall propagation in defect induced SmCo/Co exchange spring magnet

Abstract SmCo5/Co exchange-coupled films with high saturation magnetization, and hence high energy product were fabricated on MgO substrates by sequential deposition of elemental Sm and Co layers at 450 °C followed by subsequent annealing at the same temperature for 1 h. Formation of defects induced multi-layered structures and the composition of individual layers were confirmed through high resolution Scanning Transmission Electron Microscopy (HRSTEM) imaging acquired on high angle annular dark field (HAADF) detector and Energy Dispersive X-ray (EDX) spectroscopy. Micromagnetic simulations and magnetic measurements further confirmed that the observed structure is coupled in rigid phase between soft and hard magnetic layers and the enhancement in coercivity results due to the domain wall pinning at the defects sites. This leads to the magnetic energy density in the film of the order of 22.2 MGOe which is close to the bulk value and have potential applications towards Micro-Electro-Mechanical Systems.

Structure of Cu/Ni Nanowires Obtained by Matrix Synthesis

The structure of layered Cu/Ni nanowires obtained by template synthesis in 100-nm channels of track membranes has been investigated by transmission and scanning electron microscopy. The phase composition and main structural features of individual nanowires are determined. It is shown that nanowires consist of alternating Ni (Fm3m) and Cu (Fm3m) layers with grains up to 100 nm in size. It is found that nanowires contain also copper oxide crystallites up to 20 nm in size. The elemental composition of individual layers and their mutual arrangement are determined.

Temperature stability of (Pt/Co)3/IrMn multilayers

The effect of annealing on the structural stability of (Pt2nm/Co0.4 nm)3/IrMn7nm multilayers has been investigated using atom probe tomography. The composition of individual layers was measured after annealing at 300, 400, 500, and 700 °C. While results show that the (Pt/Co)3/IrMn stacking sequence is preserved up to 400 °C, there is an almost complete destruction of the multilayered structure when annealing at higher temperatures (500 and 700 °C). Co layers no more alternate with Pt-rich layers. The whole stack is transformed into an IrCo/PtMn bilayer. These results are interpreted on the basis of atomic mobilities and chemical affinities. Diffusion of Co and Mn is shown to become important when annealing temperature approaches 500 °C. Results are well accounted for by thermodynamics arguments considering the Co-Ir and Pt-Mn phase diagrams.

Accelerated testing of HT-9 with zirconia coatings containing gallium using Raman Spectroscopy and XPS

Laser Raman spectroscopy and X-ray photoelectron spectroscopy were used to study the evolution of composition of oxide films in the presence of zirconia coatings on miniature HT-9 alloy specimens subjected to elevated temperature in air. The experiments expanded on previous efforts to develop a quick-screening technique for candidate alloys for cladding materials (HT-9) and actinide-based mixed oxide fuel mixtures (represented by the zirconia coating) by investigating the effect of both coating composition and annealing conditions on the high temperature reactions. In particular, the presence of the element Ga (a potential impurity in mixed oxide fuel) in the initial zirconia coating was found to accelerate the rate of oxide growth relative to that of yttria-stabilized zirconia studied previously. In addition, HT-9 samples that were subjected to different annealing conditions gave different results. The results suggest that the presence of Ga in a mixed oxide fuel will enhance the oxidation of HT-9 cladding under the conditions of this study, although the extent of enhancement is influenced by the type of annealing previously applied to the cladding material. Due to the multi-component layered structure of the oxidation products discovered in this fuel-cladding combination, it appears unlikely that Raman spectroscopy would be applicable as a stand-alone technique for the intended quick-screening approach to all but the simplest systems. Other techniques with better depth resolution, such as photoelectron spectroscopy, are required to follow the changes in composition of individual layers as they evolve during the oxidation process.

Tunnelling cracks in Al 2O 3/Al 2O 3–ZrO 2 layered composites

Two sizes of symmetrical, five-layered ceramic composites with alumina surface layers and alumina–zirconia inner layers were produced. Each composite had the same sequence and composition of individual layers; however, the measured strength of the large-sized sample was only 76 MPa to 115 MPa. This is due to the presence of tunnelling cracks that appear as a consequence of the tensile thermal residual stresses in the inner layers that develop during the cooling of the samples from the sintering temperature. The small-sized composite, with the slightly smaller layer thicknesses, had a higher strength: 317–378 MPa. The number and the position of the tunnelling cracks in the large-sized composite was not uniform through the depth of the sample, indicating the presence of crack splitting. The main reason for the different strengths of the small- and large-sized samples seems to be the different thicknesses of the innermost layers. Analytical calculations confirmed that tunnelling cracks can occur in the large-sized composite, providing that typical values of the material parameters from the literature are taken into account. According to these calculations, a thinner innermost layer in the large-sized composite would result in a crack-free material.

Study of intercalated fullerene films by medium-energy ion scattering

This paper reports on a study of films of fullerenes and their halogen compounds, deposited on mica and silicon, by medium-energy ion scattering (MEIS). The film thickness nonuniformity was determined. A considerable increase in the halogen concentration was found at the interface, which is associated with the specific film deposition conditions. It was demonstrated that the composition of individual layers of a film can be determined using MEIS.

Characterization of WC x/B 4C multilayers sputtered in reactive argon/methane atmospheres

Two series of WC x /B 4C thin film multilayers were produced by d.c. magnetron sputtering in reactive atmospheres of argon with methane additions (up to 18%). Thin films of boron carbide and tungsten were also deposited separately to provide information about the composition of individual layers. The microstructure and chemistry of the sputtered films were characterized using transmission/high resolution electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, secondary ion mass spectroscopy, and ion beam analysis with MeV helium beams. High-resolution imaging showed that the structure of the individual layers was completely amorphous, although diffraction (electron and X-ray) indicated well-defined layer ordering. Chemical analysis revealed that, in addition to carbon incorporation, the multilayers contained significant levels of hydrogen. As the methane percentage was increased, the amounts of hydrogen and carbon present increased, and oxygen (which was present in all samples) and hydrogen were preferentially incorporated into the boron carbide layer. The peak reflectivity for Mg Kα radiation depended on the methane concentration, with the sample sputtered in a 12% methane atmosphere showing the highest reflectivity of 30%. Annealing of a representative multilayer caused substantial hydrogen loss, and a decrease of the bilayer spacing.

Formation of spermatophore in ejaculatory duct of yellow mealworm beetle, Tenebrio molitor: SEM study

Main role of the accessory glands of Tenebrio molitor male is to facilitate transfer of sperm to the females. They produce heterogeneous secretions. Two anatomically distinct glands are present. While the tubular accessory glands (TAG) are composed of the secretory cells of one type only, the bean-shaped accessory glands (BAG) consist of eight cellular types. Low viscosity secretion of the TAG mix with sperms forming seminal fluid while high viscosity secretions (spermatophorins) of the BAG are largely transformed into the insoluble wall and core of the spermatophore. The prespermatophoric mass is transferred to the ejaculatory duct (EJD) where solidify and forms the complex spermatophore. Immunocytochemical experiments with monoclonal antibodies based on the colloidal gold technique were used in order to understand exact composition of individual layers of the spermatophore. In the recent study we have used SEM to observe the whole process of the formation of spermatophore in the ejaculatory duct.