Papers by Keyword: Multilayer

Abstract: Co/Pd magnetic multilayers have been prepared by using a sputtering method. Lattice distances and magnetic hysteresis curves have been measured by X-ray diffraction (XRD) measurements and magnetization measurements using a vibrating sample magnetometer (VSM). The XRD measurements have shown that the samples with thinner Pd layers have shorter lattice distances, and the VSM measurements have shown that the samples of thinner Co and thicker Pd layers are closer to those of perpendicular magnetic anisotropy. We have applied the X-ray magnetic diffraction method to the Co/Pd multilayer for the first time and have succeeded in observing a change in the X-ray diffraction intensities by the reversal of the magnetization direction.

Abstract: Precision grinding of a multilayered thin film solar panel is recognized as the bottleneck in its manufacturing process. A primary challenge is the significantly high stress induced at the thin film interfaces during grinding. Such stress concentration can result in interfacial delamination between two dissimilar materials and thus device malfunction. This study used a finite element modelling analysis to understand the stress evolution of the multilayer thin film structure during a single grit scratching that simulates the individual interaction between abrasive grits and work materials in grinding. The results demonstrated that significant tensile and shear stresses were formed at interfaces during scratching, which could be traced back to the experimental evidence obtained from the nanoscratching process. The maximum stresses undertaken by the interfaces were simulated.

Abstract: Friction stir processing (FSP) in a lap configuration of a metal sheet and an alloy plate has been examined to produce surface alloy layer with nanostructures. The 1-pass friction stir lap processing (FSLP) over 0.5 mm-thick Cu sheet on an AZ91 substrate produced multilayer structure with nanograins and/or nanoprecipitates in each layer, but the structure distributed only partially in the stir zone (SZ). Through the 3-pass FSLP along the same line, the multilayer structure has disappeared and the fine structure with precipitates in size ranging from several 100 nanometer to 3 micrometer has yielded among the entire SZ. 2-dimensional microhardness mapping have shown that the standard deviation of microhardness values in the SZ has decreased by half from 1-pass to 3 pass FSLP. Homogeneous microstructure involving nanostructures has been successfully produced via multi-pass FSLP.

Abstract: Magnetron sputtering techniques was used to deposit TiN, TiO₂ single layer and TiN/TiO₂ multilayer coatings on 316L stainless steel (316L SS) substrates. The crystallinity, surface topography and roughness parameters of uncoated (316L SS) and coated specimens were examined. The anti adhesion and antibacterial behavior of S.aureus (gram (+) ve) and E.coli (gram (-) ve) strains on uncoated and coated substrates were determined by live/dead staining using epifluorescence microscopy. Results demonstrate that the coated samples undergo drastic reduction of bacterial adhesion and negligible effect of antimicrobial activity. Further, coated substrates exhibit less platelets activation than that of uncoated substrates.

Abstract: A broadband multi-layer radar absorbing coating (RAC) and transparent shielding film (TSF) operating within the frequency range of 7 to 12 GHz are designed and fabricated for the purpose of a radar cross section (RCS) reduction of complex naval targets such as submarines and ships. The proposed RAC consists of three layers, a shop primer, a main absorbing material, and epoxy resin paint. In addition, a TSF was fabricated by coating an ITO/Ag/ITO multilayer on a polyethylene terephthalate (PET) substrate using roll-to-roll DC plasma deposition technique. The experimental results demonstrate that the proposed RAC guarantees an RCS reduction of 10 to 15 dB from 7 to 12 GHz.

Abstract: High efficiency of light-to-energy conversion in dye-sensitized solar cell (DSSC) was achieved by applying anthocyanin as photosensitizer and TiO₂ as photoelectrode. TiO₂ anatase phase was synthesized by using co-precipitation method from TiCl₃ precipitate. Anthocyanin (A) from Garcinia mangostana pericarp was combined with β-carotene (B) from Daucus carota and curcumin (C) pigments from Curcuma longa. According to UV-Vis analysis the wavelength absorptions of anthocyanin, β-carotene, and curcumin are 399 nm, 471 nm, and 470 nm, respectively. The A–B–C produced the short-circuit current density (J_SC) of 77.7 μA, the open-circuit voltage (V_OC) of 343.2 mV, the fill factor (FF) of 32.3, and the efficiency (η) of 0.042%. It is found that there exists a synergistic effect between anthocyanin and curcumin as indicated by broader absorption wavelengths, whilst the mixture between anthocyanin and β-carotene does not show the synergistic effect. The high efficiency of layered co-sensitization is attributed to the high adsorption capacities of curcumin in the outer layer. On the other hand, the effect can be explained on the basis of light scattering effect.

Abstract: Increasing the functional parameters and endurance of the turbines, blades systems, rocket engines, high-performance metallurgical installations, power energy require the creation of new systems for integrated assessment, testing-investigating.From the ensemble of wear factors acting simultaneously on the multilayer ceramic materials, associated to the coatings structures, the quick thermal shock acts most disruptive.To illustrate the effect of gradients with high value for heating-cooling the authors have designed and developed a versatile installation with semi-automatic functioning and monitoring test parameters. The fundamental testing parameter that the installation uses is heating-cooling speed up to 100 ° C/s, which is superior to the performances of the known testing installations.The extreme thermal shock testing parameters generate in the multilayers ceramic structures, triplex type with intermediate layer, structural, morphological and composition modifications which initiate and develop the ceramic layer spallation.

Abstract: Zirconia-based ceramics have gained considerable interest for several applications (e.g. solid electrolytes in fuel cells and in oxygen sensors, thermal barrier coatings and biomaterials for dental and orthopaedic applications) due to their high mechanical strength, improved fracture toughness and easy affordability. Zirconia occurs in three crystal modifications at low-pressure conditions: monoclinic, tetragonal and cubic. The monoclinic phase is the natural room temperature stable phase, while the tetragonal and the cubic phase can be stabilized at room temperature by doping with the right amount of some oxide dopants (e.g. CaO, MgO, CeO₂ and Y₂O₃). The stabilization of the tetragonal phase results in a remarkable increase in mechanical toughness, whereas the stabilization of the cubic phase results in an increase of the ionic conductivity to values significantly higher than for other ceramics. In order to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase, we established an EPD layering process with nanometric sized powders of Y-TZP with different mol percentages of yttrium oxide (3 % and 8 %) and produced multilayers of alternating tetragonal and cubic phases with a clearly defined interface. The crack propagation through this interface was studied by means of micro-indentation

Abstract: Service and downtimes of waste incineration plants generate high expenses for their operators. State of the art is to protect high corrosion exposed components by cladding them with a nickel based alloy. The welded overlay is 2-3 mm thick and very expensive. It needs to be repaired at each service interval. An alternative coating consists of a thermal sprayed multilayer of a nickel based bondcoat and a ceramic topcoat. Thickness and costs of this multilayer are assumed to be in the range of about 10% of the currently used coating. A solvothermal treatment chemically densifies the coating. This leads to a significantly lower porosity whilst improving cohesion and hardness properties. This innovative process leads to a self-healing layer caused by the high temperature waste gas exposition as the driving force.

Abstract: Structure and magnetic properties of FeNi/Ti multilayers prepared by magnetron sputtering were studied. The dependences of the spontaneous magnetization and hysteresis features of the films on the thickness of the magnetic layers were established. It was shown that these properties were to a large extent determined by interlayer interfaces, in which the effective magnetization decreases. The possible reason for the interface peculiarities was the interlayer mixing. The presence of (FeNi)Ti phase which was formed by the interdiffusion of FeNi and Ti layers was confirmed by X-ray diffraction measurements.