Dimension changes on the order of 0.1% or above in response to an applied voltage have been reported for many types materials, including ceramics, polymers, and carbon nanostructures, but not, so far, metals. We show that reversible strain amplitudes comparable those commercial piezoceramics can be induced metals by introducing a continuous network nanometer-sized pores with high surface area controlling electronic charge density through potential relative electrolyte impregnating pores.

Nanometer-sized polycrystalline materials are polycrystals prepared by compacting very small crystallites (5--10 nm in diameter) under high pressures. The initial studies of Gleiter and co-workers indicate a wide distribution interatomic distances within the disordered intercrystalline phase, which can be investigated accurately due to its relative volume fraction these materials. In present paper investigation nanometer-sized Fe positron lifetime spectroscopy is reported. influence pressure...

Nanoglasses are solids consisting of nanometer-sized glassy regions connected by interfaces having a reduced density. We studied the structure Sc75Fe25 nanoglasses electron microscopy, positron annihilation spectroscopy, and small-/wide-angle X-ray scattering. The spectroscopy measurements showed that as-prepared consisted 65 vol% 35 interfacial regions. By applying temperature annealing to measuring in situ small-angle scattering, we observed width increased exponentially as function...

The diffusion of oxygen in ultrafine grained, undoped monoclinic ZrO2 was studied using O18 as tracer and secondary ion mass spectroscopy profiling. Samples with a relative density 97%–99% average crystallite sizes 80 or 300 nm were prepared from Zr by sputtering, inert-gas-condensation, oxidation, situ consolidation nanocrystalline (n-)ZrO2 powder subsequent pressureless sintering at 950 1050 °C vacuum. Volume interface diffusivities directly determined the profiles n-ZrO2 type B A regime...

In order to study the vacancy formation and migration temperature variation equilibration process of thermal concentration in $B$2-type Fe aluminides ( ${\mathrm{Fe}}_{63}{\mathrm{Al}}_{37}$, ${\mathrm{Fe}}_{61}{\mathrm{Al}}_{39}$) were measured by means positron lifetime technique using a diffused ${}^{58}$Co emitter. The occurs rather slowly, indicating low mobility. present values for enthalpies...

Abstract Diffusion is a key property determining the suitability of nanocrystalline materials for use in numerous applications, and it crucial to assessment extent which interfaces samples differ from conventional grain boundaries. The present article offers an overview diffusion metals alloys. Emphasis placed on interfacial characteristics that affect materials, such as structural relaxation, growth, porosity, specific type interface. In addition, influence intergranular amorphous phases...

The formation of thermal vacancies in the intermetallic compound ${\mathrm{Fe}}_{76.3}$${\mathrm{Al}}_{23.7}$ was investigated between 20 and 1060 \ifmmode^\circ\else\textdegree\fi{}C by positron-lifetime measurements. positron lifetime ${\mathrm{\ensuremath{\tau}}}_{\mathit{f}}$=112 ps at indicates that no structural can be detected. increase mean \ensuremath{\tau}\ifmmode\bar\else\textasciimacron\fi{} due to vacancy starts relatively low temperatures (${\mathit{T}}_{3}$=475...

A maximum excess volume ΔV/V ≈ 1.9 × 10(-3) in ultrafine-grained Fe prepared by high-pressure torsion is determined measurements of the irreversible length change upon annealing employing a high-resolution differential dilatometer. Since dislocations and equilibrium-type grain boundaries cannot fully account for observed released volume, present study yields evidence high concentration free volume-type defects inherent to nanophase materials, which considered be main source their particular...

Abstract Since severe plastic deformation (SPD) has demonstrated its capability of producing bulk nanomaterials with highly advanced mechanical properties, research is increasingly focusing on the question as to whether functional can be achieved by SPD and in shape, too. This paper presents promising results reaching properties SPD‐processed nanocrystalline magnetic alloys, shape memory nanoalloys, well nanometals alloys for hydrogen storage, also reports problems other like those...

The grain boundary excess volume, i.e., the expansion, e{GB}, was experimentally determined for high-angle boundaries in nickel using direct technique of high-precision difference dilatometry. Values e{GB}=(0.35±0.04)×10{-10} m and e{GB}=(0.32±0.04)×10{-10} were obtained by measuring removal volume upon growth two different types ultrafine-grained samples. results are discussed comparison to values so far from indirect techniques computer simulations. It demonstrates strength presented...

The release of excess volume upon recrystallization ultrafine-grained Cu deformed by high-pressure torsion (HPT) was studied means the direct technique high-precision difference dilatometry in combination with differential scanning calorimetry (DSC) and electron microscopy. From length change associated removal grain boundaries wake crystallite growth, a structural key quantity boundaries, boundary or expansion eGB=(0.46±0.11)×10-10 m directly determined. value is quite similar to that...

The formation of thermal vacancies, which is a key issue with respect to the high-temperature properties ordered intermetallic compounds, was studied in \ensuremath{\gamma}-TiAl by means positron lifetime spectroscopy between ambient temperature and 1400 K. An estimate atomic concentration vacancies yields value similar as pure fcc metals an effective vacancy enthalpy 1.41\ifmmode\pm\else\textpm\fi{}0.06 eV good agreement nearest-neighbor-bond model calculations. A comparison these data...

In the present paper a characterization of atomic vacancies in intermetallic compounds is given by means positron-lifetime measurements after electron irradiation and comparison with states preparation, long-time annealing, or high-temperature equilibrium. TiAl, ${\mathrm{Ti}}_{3}$Al, ${\mathrm{Ni}}_{3}$Al no structural (detection limit ${\mathit{C}}_{\mathit{V}}$=${10}^{\mathrm{\ensuremath{-}}6}$) are observed at ambient temperature. This confirms that these slight deviations from...

Magnetic properties of 6 nm maghemite nanoparticles (prepared by microwave plasma synthesis) have been studied ac and dc magnetic measurements. Structural characterization includes x-ray diffraction transmission electron microscopy. The temperature scans zero field cooled/field cooled (ZFC/FC) magnetization measurements show a maximum at 75 K. ZFC/FC data are fitted to the Brown-Néel relaxation model using uniaxial anisotropy log-normal size-distribution function figure out effective...

Mössbauer spectroscopy of FePt nanoparticles demonstrates the presence two iron phases: one consistent with a bulk alloy, other due to polarized phase (Fen+), in agreement negative polarization on oleate moiety. metallic (see Figure for TEM image Fe50Pt50 phase) are important materials new sensors and magnetic recording devices high information densities.

The authors report on positron lifetime studies which investigate vacancy-type defects in elemental and compound semiconductors after electron irradiation or thermal equilibrium concentrations at high temperatures. In Si the upper limits of lifetimes monovacancies (272 ps) divacancies (285 as well phosphorus-vacancy complexes ( approximately 255 are determined low-temperature annealing. addition, influence doping trapping defect annealing is studied. electron-irradiated GaAs between 200 K...

Abstract Electrochemical reactions represent a promising approach to control magnetization via electric fields. Favorable reaction kinetics have made nanoporous materials particularly interesting for magnetic tuning experiments. A fully reversible ON and OFF switching of magnetism in Pd(Co) at room temperature is demonstrated, triggered by electrochemical hydrogen sorption. Comprehensive characterization combination with high‐resolution scanning transmission electron microscopy reveals the...