Preparation of dispersion strengthened nanocomposite with Al2O3 and MgO particles by spark plasma sintering

Nanocomposites are multiphase materials in which at least one of the structural compounds has a size below 100 nm. The subject of this work is creation of a dispersion-strengthened nanocomposite (DSC) with copper matrix. There are many dispersions that are possible to be used in DSC with copper matrix, such as Al2O3, Y3O2, TiO2, and WC. In this work we used Al2O3 due to the possibility of making even dispersion in the material and its economical availability. Such composites exhibit thermal stability of their mechanical properties up to 900 °C for at least 1 hour exposure, which opens new possibilities for use of such materials in high-temperature, high-strength applications. Materials created by our team exhibited good mechanical properties, namely hardness, which was up to 136 HB; however, it has to be noted that amount of dispersion particles had a direct effect on the hardness of the composite. Properties of the DSC´s are also dependent on the method of its preparation and compactization. Composites in this work were prepared by powder metallurgy method and sintered by spark plasma sintering, which allowed these composites to reach 99% density. Furthermore, DSCs were tested for their thermal stability, and their properties were evaluated and compared even with precipitation-strengthened copper-chrome material in order to show potential of possible usage of DSCs in spot welding applications, which require high strength, hardness, and electric conductivity

GOLD NANOSTRUCTURES SPUTTERED ON ZINC OXIDE THIN FILM AND CORNING GLASS SUBSTRATES

Forming of Au nanostructures on Corning glass substrates and transparent conductive oxide ZnO:Al thin films by the RF diode sequential sputtering is presented. The morphology of Au structures was analysed by scanning electron microscopy (SEM) with the free ImageJ software, the optical properties were evaluated by UV-Vis spectrometry and micro-Raman spectroscopy. The sputtering power density (deposition rate) and nominal Au thickness caused changes in the sizes (10 – 1000 nm2) and nearest neighbour NN distances (4 – 40 nm) of Au nanostructures. The morphology of nanostructures exhibited the LogNormal distribution of the size of nanostructures. The lowest sputtering power density/deposition rate (9 mW/mm2/0.12 nm s–1) was optimal to get both the high optical transparency and a superior activity surface-enhanced Raman scattering of 11-mercaptoundecanoic acid adsorbed on the Au/ZnO:Al film

Hydrogen-Terminated Diamond Surface as a Gas Sensor: A Comparative Study of Its Sensitivities

A nanocrystalline diamond (NCD) layer is used as an active (sensing) part of a conductivity gas sensor. The properties of the sensor with an NCD with H-termination (response and time characteristic of resistance change) are measured by the same equipment with a similar setup and compared with commercial sensors, a conductivity sensor with a metal oxide (MOX) active material (resistance change), and an infrared pyroelectric sensor (output voltage change) in this study. The deposited layer structure is characterized and analyzed by Scanning Electron Microscopy (SEM) and Raman spectroscopy. Electrical properties (resistance change for conductivity sensors and output voltage change for the IR pyroelectric sensor) are examined for two types of gases, oxidizing (NO2) and reducing (NH3). The parameters of the tested sensors are compared and critically evaluated. Subsequently, differences in the gas sensing principles of these conductivity sensors, namely H-terminated NCD and SnO2, are described

Fabrication of Structured Boron-Doped Diamond Films for Electrochemical Applications

In the present study, we introduce various technological approaches for fabrication of structured boron-doped diamond (BDD) electrodes, i.e., nanocones and nanorods which are used as working electrodes for electrochemical measurements. Structured BDD were realized either by reactive ion etching employing gold nanoclusters as the mask or by thermo-catalytically induced modification of the diamond surface. All samples were characterized in terms of surface morphology (scanning electron microscopy images), chemical composition (Raman spectroscopy) and electrochemical properties (anodic stripping voltammetry)

Real-Time Monitoring of Stem Cells by Diamond-Based Impedance Sensors

Cell-based impedance spectroscopy is a promising label-free method for electrical monitoring of cell activity. Here we present a diamond-based impedance sensor with built-in gold interdigitated electrodes (IDEs) as a promising platform for simultaneous electrical and optical monitoring of adipose-derived stem cells (ASC). The impedance spectra were collected in a wide frequency range (from 100 Hz to 50 kHz) for 27 h of cultivation in chambers designed for static cultivation. Absolute impedance spectra were analyzed in terms of measurement frequencies and cell properties monitored by high-resolution digital camera

Single-gap superconductivity in Mo8Ga41

International audienc

Protection of Ising spin-orbit coupling in bulk misfit superconductors

International audienceIsing superconductivity is present due to the combined effect of broken-inversion symmetry and spin-orbit coupling that locks the spins out of plane, features that are associated with two-dimensional materials. We show that bulk misfit superconductors, (LaSe) 1.14 (NbSe 2) and (LaSe) 1.14 (NbSe 2) 2 , comprising monolayers and bilayers of NbSe 2 , exhibit unexpectedly strong Ising protection with a Pauli-limit violation comparable to monolayer NbSe 2. We establish these misfit compounds as Ising superconductors using complementary experimental methods in combination with first-principles calculations. A concerted effect of charge-transfer, defects, reduction of interlayer hopping, and stacking enables Ising superconductivity in these compounds and therefore provides a possible pathway to design of bulk superconductors that are resilient to magnetic fields