Nanomechanical testing of Ti/Ni multilayer thin films

The main aim of the present work was to study the dependence of mechanical properties of Ti/Ni multilayer thin films on the thicknesses of constituent Ti and Ni layers. The multilayer thin films were made by depositing Ti and Ni layers alternately on single crystalline silicon substrates using magnetron sputtering method. Thickness of individual Ti and Ni layers varied from 1.7 nm to 100 nm, the total multilayer thickness was around 1 µm. The mechanical properties were characterized by means of nanoindentation experiments using a Hysitron dual head TI950 triboindenter equipped with diamond Berkovich tip in both static and dynamic loading regime in the load range from 50 µN to 11 mN. Moreover, nanoindentation tests were performed at elevated temperatures up to 500 oC using a Hysitron xSol heating stage. The nanoindentation data were evaluated using the recently developed home-made Nanoindentation General Evaluation Tool (NIGET) [1] software for independent analysis of loading and unloading curves which includes among others a basic treatment of uncertainties and systematic errors that are missing in commercial software provided together with instrumented indentation testing devices. The NIGET software has a graphical interface which uses libraries of the open source software Gwyddion [2]. The nanoindentation results were correlated with microstructure studies using XRD (X-ray diffraction technique), a Tescan LYRA 3XMU FEG/SEM×FIB scanning electron microscope (SEM), a Philips CM12 STEM transmission electron microscope (TEM) and a JEOL JEM-2100Fhigh resolution TEM. Thin lamellar cross sections for TEM observations were prepared using a focused ion beam (FIB) in SEM from two locations in each sample: an undisturbed layer and a central region of indentation print made with Berkovich tip with a relatively high load from the range of 0.5 to 1N. Please click Additional Files below to see the full abstract

Properties of HPT-Processed Large Bulks of p-Type Skutterudite DD0.7Fe3CoSb12 with ZT > 1.3

The influence of shear strain on the microstructural, physical, and mechanical properties was studied on large bulk samples (diameter: 30 mm, thickness: 1 or 8 mm), which were consolidated by high-pressure torsion (HPT) from a commercial powder DD0.7Fe3CoSb12. Particularly, the thick sample (mass similar to 53 g) allowed measuring the thermoelectric (TE) properties with respect to various orientations of the specimen in the sample. All data were compared with those of a hot-pressed (HP) reference sample, prepared with the same powder. Transmission electron microscopy, as well as X-ray powder diffraction profile analyses, Hall measurements, and positron annihilation spectroscopy, supported these investigations. Furthermore, synchrotron data for the temperature range from 300 to 825 K were used to evaluate the changes in the grain size and dislocation density as well as the thermal expansion coefficient via the change in the lattice parameter during heating. In addition, hardness and direct thermal expansion measurements of the HPT samples were performed and compared with the HP reference sample's values. With the increase of the shear strain from the center to the rim of the sample, the electrical resistivity becomes higher, whereas the thermal conductivity becomes lower, but the Seebeck coefficient remained almost unchanged. For the thin as well as thick samples, the enhanced electrical resistivity was balanced out by a decreased thermal conductivity such that the maximum ZT values (ZT = 1.3-1.35 at 856 K) do not vary much as a function of the shear strain throughout the sample, however, all ZTs are higher than that of the HP sample. The thermal-electric conversion efficiencies are in the range of 14-15% (for 423-823 K). With similar high ZT values for the n-type skutterudites, fabricated in the same fast and sustainable way, these p- and n-type skutterudites may serve as legs for TE generators, directly cut from the big HPT bulks.Peer reviewe

Cu–Ni nanoalloy phase diagram – Prediction and experiment

The Cu-Ni nanoalloy phase diagram respecting the nanoparticle size as an extra variable was calculated by the CALPHAD method. The samples of the Cu-Ni nanoalloys were prepared by the solvothermal synthesis from metal precursors. The samples were characterized by means of dynamic light scattering (DLS), infrared spectroscopy (IR), inductively coupled plasma optical emission spectroscopy (ICP/OES), transmission electron microscopy (TEM, HRTEM), and differential scanning calorimetry (DSC). The nanoparticle size, chemical composition, and Cu-Ni nanoparticles melting temperature depression were obtained. The experimental temperatures of melting of nanoparticles were in good agreement with the theoretical CALPHAD predictions considering surface energy.Fázový diagram nanoslitiny Cu-Ni respektující velikost nanočástic jako další proměnné byl vypočten metodou CALPHAD. Vzorky Cu-Ni nanoslitin byly připraveny solvotermální syntézou z prekurzorů kovů. Tyto vzorky byly charakterizovány pomocí dynamického rozptylu světla (DLS), infračervené spektroskopie (IR) s indukčně vázanou plazmou a optickou emisní spektroskopií (ICP / OES), transmisní elektronovou mikroskopií (TEM, HRTEM) a diferenciální skenovací kalorimetrií (DSC). Velikost nanočástic, chemické složení a Cu-Ni deprese teploty tání nanočástic byly získány experimentálně a v dobré shodě s teoretickou předpovědí metodou CALPHAD s uvážením povrchové energie nanočástic

Experimental study of the Sb-Sn-Zn alloy system

experimental description of the SbSn-Zn system by methods scanning electron microskope and differetial scanning calorimetryexperimentální popis ternární soustavy Sb-Sn-Zn metodami skenovací elektronové mikroskopie a diferenční skenovací kalorimetrieexperimental description of the SbSn-Zn system by methods scanning electron microskope and differetial scanning calorimetr

Fracture Resistance Enhancement in Hard Mo-B-C Coatings Tailored by Composition and Microstructure

State-of-the-art protective coatings often suffer from brittleness. Therefore, the coatings are intensively sought which would simultaneously exhibit high hardness and stiffness with moderate ductility and fracture resistance. In this paper, we report on the nanostructure designing of coatings containing metal, boron, and carbon enabling the simultaneous presence of stiff boridic and carbidic bonds together with weaker metallic bonds to provide coatings with these desirable properties. Three designs are presented with different relative amounts of nanocrystalline and amorphous phases, ranging from near-amorphous to prevalently crystalline microstructure. All presented coatings exhibit an unusual combination of high fracture resistance and high hardness that cannot be achieved with state-of-the-art protective coatings. Indentation tests at high loads revealed that no cracks are present at the surface of the investigated coatings while state-of-the-art ceramic protective coatings already exhibit significant cracking. Cracks in the bulk of the presented coating are detected only when the deformation is so severe that the substrate itself fails