Stress relaxation in cadmium-silver alloy single crystals

A series of cadmium — silver alloy single crystals containing up to 0·25 at % Ag were deformed in tension at a strain rate of 1×10^?4s^?1. The tensile tests were carried out at temperatures between 77 and 199 K. Stress relaxation experiments were performed to investigate the concentration dependence of the activation volume. Over the temperature range investigated, the activation volume at beginning of deformation decreases proportionally toc ^?2/3 wherec is the atomic concentration of silver as solute. The results are discussed on the basis of the interaction between dislocations and solute atoms.     

Surface microstructure and morphology study of thin films produced from volatile fluorine-containing rare-earth β-diketonate complexes and their adducts

We present the results of a surface microstructure and morphology study of thin films produced from volatile fluorine-containing rare-earth β-diketonate complexes and their adducts. Films 0.2–0.4 μm in thickness were synthesized in vacuum by means of thermal deposition of the parent substances at a pressure of 5 × 10^?4?1 × 10^?3 Pa and a deposition rate of 3 × 10^?3 μm s^?1 (for NaNd(FOD)₄ films, the deposition rate was 8 × 10^?2 μm s^?1). The microstructure of films depends on the deposition conditions. The films of [NaNd(PTFA)₄] and [NaNd(FOD)₄] complexes and Ln(PTFA)₃ · S₁ adducts have an amorphous structure. The [NaNd(PTFA)₄(Phen)] and Nd(PTFA)₃ · S₂ films are characterized by a more ordered polycrystalline structure with the grain size ranging from 0.2 to 1.5 μm.     

A study of the α ↔ γ transformation in pure iron: rate variations revealed by means of thermal analysis

The α???γ transformation in nominally high purity Fe is shown to occur with a stepped peak in differential thermal analysis on both heating and cooling at rates between 0.5?K?min^?1 and 10?K?min^?1. The composite peaks mark changes in the transformation rate. To endorse the findings, the instrumental output has been thoroughly analyzed providing evaluations of time lags, suggestions for calibration and for the use of the derivative of the peak. The change in rate occurred in all samples irrespective of their grain size (average values from 91?µm to 1100?µm). The rate of movement of the interface in the α???γ transformation is estimated between 4?×?10^?5?m?s^?1 and 3?×?10^?6?m?s^?1. The present results extend previous dilatometric work in which the rate variation was detected only for large grain size and low undercooling. Possible reasons for the variation in rate are outlined: local development of strain in the austenite due to lattice misfit with respect of the growing ferrite, formation of a ragged microstructure and pinning of the boundaries by impurity.     

Structure and strength of Al-Si alloys obtained by the Stepanov method

Al-Si alloy samples with a silicon content from 8 to 15 wt % were obtained by the Stepanov method at solidification rates of 10² and 10³ µm s^?1. Tensile and bending strain diagrams were studied at a strain rate of about 10^?4 s^?1. The microstructure of the samples was investigated. It was found that the silicon content in the eutectic structure of the alloy grows as the solidification rate increases. The yield stress and the tensile strength increase as the silicon content grows.     

Electrical Impedance Spectroscopic Study of CNT/Ethylene-alt-CO/Propylene-alt-CO Polyketones Nanocomposite

Impedance spectroscopy was utilized to investigate the dielectric properties, ac conductivity and charge transport mechanisms in propylene-alt-CO/ethylene-alt-CO (EPEC) random terpolymer filled with multi-walled carbon nanotubes (MWCNT) as a function of nanofiller content, frequency, and temperature. Equivalent resistor-capacitor (RC) circuit models were proposed to describe the impedance characteristics of the unfilled terpolymer and the nanocomposite at different temperatures. For the nanocomposites, the ac conductivity tended to be frequency independent at low frequencies. At high frequencies, the ac conductivity increased with frequency. The dc conductivity (i.e., plateau of the ac conductivity at low frequencies) at room temperature increased from 10^?9 (Ω·m)^?1 for the unfilled polymer to l0^?3 (Ω·m)^?1 for the 6 wt% MWCNT/EPEC nanocomposite. At low temperatures, the equivalent RC model for EPEC-0 and EPEC-2 was found to consist of a parallel RC circuit. However, for 6 wt% MWCNT/EPEC nanocomposite, an RC model consisting of an R/constant phase element (CPE) circuit and a resistor in series was required to describe the impedance behavior of the nanocomposite.     

The influence of pressure on spontaneous magnetization of Fe60Mn20B20 amorphous alloy at temperature range 77.4–300 K

Abstract

Amorphous, ferromagnetic, invar like, Fe₆₀ Mn₂₀ B₂₀ alloy has been investigated. Two kinds of experiments were carried out for this alloy. The first, using high pressure technique, revealed the influence of pressure on B(H) dependencies within the wide range of temperature under pressure of 0.5 GPa. From the magnetization curves obtained during these experiments the decrease of spontaneous magnetization caused by applied pressure 0.5 GPa at temperature -180°C has been calculated at the rate about 7 10^?11T/Pa.

In the second kind of experiments the measurements of volume magnetostriction up to 720 kA/m magnetic field intensity have been done. Volume magnetostriction coefficient at temperature 77.4 K has been determined to be about 2 10^?11 [A/m]^?1.     

Energy gap,transition temperature and electron-electron interaction of the weak coupling superconductors tin and indium as a function of the mean free path of the electrons

The energy gap and the transition temperature of the weak coupling superconductors tin and indium are measured as a function of the mean free path of the electrons. Both of them increase with decreasing mean free path. The ratioα=2Δ ₀/kT_c increases proportionally to the reciprocal mean free path from 3.6 to 4.0 for tin and from 3.6 to 3.95 for indium. A theoretical consideration is presented showing that the electron-electron interaction is increased in dirty superconductors. Without any fit we find from the theoretical calculation an increase inNV for indium ofδNV=5 · 10^?10 m/l _tr and for tinδNV=2 · 10^?10 m/l _tr (l_tr is the transport mean free path of the electrons). The experiments give an increase inNV for indium ofδNV=4.2 · 10^?10 m/l_tr and for tinδNV=1.7 · 10^?10 m/l _tr. The agreement is surprisingly good.     

Influence of paired light pulses on the rothstein effect

The influence of paired light pulses with a duration of 1.5 × 10^?6 s and a repetition period from 1.5 × 10^?6 s to 7.2 × 10^?6 s on the Rothstein effect is investigated for the RETINA X-ray film. It is shown that depending on the synchronization of the second light pulse with a single electric field pulse in a photolayer with field strengths of 6 × 10⁶ and 1.5 × 10⁷ V/m, the effect of variation of the integrated optical density of images changes towards higher values as compared to the density of the images formed only by a pair of light pulses. In this case, no negative “field effect” was observed in the given film.     

Structure and physicomechanical properties of Al-Si alloys

Al-Si alloy samples with a silicon content of 8–15 wt % are grown by the Stepanov method at a solidification rate of 10² and 10³ μm/s. The microstructure of the samples is examined, and the stress-strain curves obtained during tension and bending at a strain rate of 10^?4 s^?1 are studied. The behavior of Young’s modulus, the modulus defect, and ultrasonic attenuation is investigated. The silicon content in a eutectic structure is found to increase with the solidification rate. The yield strength and the ultimate tensile strength increase with the silicon content up to a eutectic composition. The quality index (which characterizes the strength and plasticity of the material) of Stepanov-grown samples is higher than the quality indices of traditional modified ingots.     

The synthesis of organic molecules in a laser plasma similar to the plasma that emerges in hypervelocity collisions of matter at the early evolutionary stage of the Earth and in interstellar clouds

Ions of organic molecules and polymers as well as multiply ionized hydrocarbons were synthesized and detected with a time-of-flight mass analyzer in laboratory experiments simulating with a laser the plasma processes that accompany a hypervelocity micrometeorite impact on the target surface. A hypervelocity impact of micrometeorites moving at velocities of 80 km s^?1 on a inorganic target was simulated with a Q-switched laser. The laser provided a power density of 10⁹?10¹¹ W cm^?2 in a spot with an impact diameter of 30–150 μm for a pulse duration of 7–10 ns and a laser plasma electron density of 10⁵?10⁶ K. The ions of organic compounds are shown to be synthesized mostly during the free expansion of a hot laser plasma at the stage of its cooling and recombination if, initially, the plasma was completely atomized and ionized. Molecular ions have high yields only for a carbon target. The results obtained indicate that organic or other polyatomic compounds can be abiogenically synthesized in intense hypervelocity meteorite impacts on the Earth’s surface at the early stage of its formation during meteorite showers and in hypervelocity collisions of dust particles in interstellar molecular clouds.     

Growth of high quality non-linear optical crystal zinc germanium phosphide for Mid-infrared optical parametric oscillator

ZnGeP₂ single crystals were grown from Vertical Bridgman method. High-quality near-stoichiometric ZnGeP₂ single crystals were obtained in the diameter of 30 mm and length of 120 mm. The results showed that after thermal annealing of the crystals the optical absorption coefficient was below 0.03 cm^?1 at 2.05 μm, and ～0.02 cm^?1 at 3–8 μm. The low absorption loss ZnGeP₂ samples with dimension of 6 × 6 × 18 mm³ were cut from the annealed ingots for 3–5 μm optical parametric oscillation (OPO) experiments. For OPO experiment, we obtained up to 8.7 W output in the 3–5 μm wavelength range (with signal of 3.80 μm and idler of 4.45 μm, respectively) pumped by a 16.3 W 2.05 μm Tm,Ho:GdVO₄ laser at pulse repetition rate of 10 kHz, which corresponded to a conversion efficiency of 53.4% and slope efficiency of 64.8%, respectively.     

Experimental study of conditions for the 3D laser cladding of nickel aluminide

The layerwise laser cladding of powdered alloy based on intermetallic gamma Ni₃Al phase is studied. The effect deposition parameters have on the geometry of the deposited beads is shown. Microstructures are investigated and the cracking susceptibility of the deposited material is analyzed. The effective deposition parameters are determined within a range of specific laser energy inputs of (2–8) × 10⁶ J kg^?1 at beam scanning rates of (1.67–10) × 10^?3 m/s and a powder feed of 6.3 × 10^?5 kg/s^?1.     

DESIRS: a state‐of‐the‐art VUV beamline featuring high resolution and variable polarization for spectroscopy and dichroism at SOLEIL

DESIRS is a new undulator‐based VUV beamline on the 2.75 GeV storage ring SOLEIL (France) optimized for gas‐phase studies of molecular and electronic structures, reactivity and polarization‐dependent photodynamics on model or actual systems encountered in the universe, atmosphere and biosphere. It is equipped with two dedicated endstations: a VUV Fourier‐transform spectrometer (FTS) for ultra‐high‐resolution absorption spectroscopy (resolving power up to 10⁶) and an electron/ion imaging coincidence spectrometer. The photon characteristics necessary to fulfill its scientific mission are: high flux in the 5–40 eV range, high spectral purity, high resolution, and variable and well calibrated polarizations. The photon source is a 10 m‐long pure electromagnetic variable‐polarization undulator producing light from the very near UV up to 40 eV on the fundamental emission with tailored elliptical polarization allowing fully calibrated quasi‐perfect horizontal, vertical and circular polarizations, as measured with an in situ VUV polarimeter with absolute polarization rates close to unity, to be obtained at the sample location. The optical design includes a beam waist allowing the implementation of a gas filter to suppress the undulator high harmonics. This harmonic‐free radiation can be steered toward the FTS for absorption experiments, or go through a highly efficient pre‐focusing optical system, based on a toroidal mirror and a reflective corrector plate similar to a Schmidt plate. The synchrotron radiation then enters a 6.65 m Eagle off‐plane normal‐incidence monochromator equipped with four gratings with different groove densities, from 200 to 4300 lines mm^?1, allowing the flux‐to‐resolution trade‐off to be smoothly adjusted. The measured ultimate instrumental resolving powers are 124000 (174 µeV) around 21 eV and 250000 (54 µeV) around 13 eV, while the typical measured flux is in the 10¹⁰–10¹¹ photons s^?1 range in a 1/50000 bandwidth, and 10¹²–10¹³ photons s^?1 in a 1/1000 bandwidth, which is very satisfactory although slightly below optical simulations. All of these features make DESIRS a state‐of‐the‐art VUV beamline for spectroscopy and dichroism open to a broad scientific community.     

In situ study of self-ion irradiation damage in W and W–5Re at 500 °C

In situ self-ion irradiations (150?keV?W⁺) have been carried out on W and W–5Re at 500?°C, with doses ranging from 10¹⁶ to 10¹⁸ W⁺m^?2 (～1.0?dpa). Early damage formation (10¹⁶W⁺m^?2) was observed in both materials. Black–white contrast experiments and image simulations using the TEMACI software suggested that vacancy loops were formed within individual cascades, and thus, the loop nucleation mechanism is likely to be ‘cascade collapse’. Dynamic observations showed the nucleation and growth of interstitial loops at higher doses, and that elastic loop interactions may involve changes in loop Burgers vector. Elastic interactions may also promote loop reactions such as absorption or coalescence or loop string formation. Loops in both W and W–5Re remained stable after annealing at 500?°C. One-dimensional hopping of loops (b?=?1/2 ?111>) was only seen in W. At the final dose (10¹⁸W⁺m^?2), a slightly denser damage microstructure was seen in W–5Re. Both materials had about 3–4?×?10¹⁵ loops m^?2. Detailed post-irradiation analyses were carried out for loops of size???4?nm. Both b?=?1/2 ?111? (～75%) and b?= ?100> (～25%) loops were present. Inside–outside contrast experiments were performed under safe orientations to determine the nature of loops. The interstitial-to-vacancy loop ratio turned out close to unity for 1/2 ?111? loops in W, and for both 1/2 ?111? and ?100? loops in W–5Re. However, interstitial loops were dominant for ?100? loops in W. Re seemed to restrict loop mobility, leading to a smaller average loop size and a higher number density in the W-Re alloy.     

Frequency stability and reproducibility of the 3.39 μm He−Ne laser stabilized on the methane line

Physical factors determining the frequency reproducibility of a gas laser with nonlinear absorption are analyzed. On the basis of experimental and theoretical results it is shown that the collisional shift, the second-order Doppler effect, the recoil effect, and the magnetic hyperfine structure do not reprsent the limitation in achieving a frequency reproducibility of the order of 10^?13?10^?14. This paper reports on experiments achieving frequency stability of 5·10^?15 and reproducibility of 3·10^?14 for the 3.39 μm He?Ne laser with an internal methane cell.     

Vacancy–solute interactions during ageing of a cold-worked Mg–RE-based alloy

The vacancy–solute interactions during artificial ageing at 250^○C of cold worked samples of a commercial magnesium alloy WE54 (Mg–RE based) were studied by coincidence Doppler broadening of positron annihilation radiation and positron annihilation lifetime spectroscopy. The results show that, in the as-cold-worked state, the vacancies are associated with dislocations that are generated by the cold work and that, after artificial ageing at 250^○C, the vacancies are associated with solute elements and help the formation of precipitate precursors. This mechanism accelerates the formation of hardening precipitates without any apparent changes in the precipitation sequence and in the products of the decomposition of the supersaturated solid solution. The present study demonstrates that the stronger hardening response achieved in the cold-worked samples originates from the presence of a higher concentration of vacancies that is introduced by the cold work and is retained in the first few minutes of ageing.     

Precise Underwater Distance Measurement by Dual Acoustic Frequency Combs

Underwater acoustics is of fundamental importance for marine science and technology. However, acoustic waves transmitted by state‐of‐the‐art underwater acoustic systems are not inherently phase locked, which hinders the development of underwater acoustic technology. For example, the precision of underwater distance measurement can only achieve centimeter level. As a versatile tool, optical frequency combs have enabled revolutionary progress in optical metrology and precision measurement. In parallel with optical frequency combs, here, the generation of fully stabilized, underwater acoustic frequency combs is reported, in which equidistant acoustic modes are produced via a hydroacoustic transducer. The precision of each individual acoustic mode is measured to be 10^?9 at 1 s and 10^?12 at 1000 s averaging times. Underwater distance measurements are carried out in an anechoic pool using a dual‐comb scheme. Comparison with reference values shows consistency within 50 µm (7 × 10^?6 in relative). The relatively long‐duration experiments at 7 m distance yield an Allan deviation of 1.8 µm (2.6 × 10^?7 in relative) at 1 s and further 480 nm (6.8 × 10^?8 in relative) at 40 s averaging times. The approach to acoustic frequency comb generation offers a promising and powerful platform for future underwater distance measurement, positioning, and navigation.     

A “comb” structure measurement of a micrometer displacement in laser plasma propulsion

A “comb” structure of beam intensity distribution is achieved to measure target displacements at the micrometer level in laser plasma propulsion experiments. Compared with single-beam and double-beam detection, the “comb” structure is more suitable for a thin film targets with a velocity lower than 10^?2 m/s. Combined with a light-electric monitor, the “comb” structure can be used to measure a velocity range from 10^?3 to 1 m/s. Using this “comb” structure, the coupling coefficient of aluminum ablated by nanosecond pulse laser in air is determined and compared. The results indicate that this “comb” structure is an effective experimental approach.     

Recent hyperfine structure investigations in the configurations 4f 136s 2, 4f 136s6p,and 4f 125d6s 2 of Tm I

By use of optical hyperfine structure investigations in the Tm I spectrum theA- values of 20 levels of the configurations 4f ¹³ 6s 6p and 4f ¹² 5d 6s ² and theA-value of 4f ¹³ 6s ^{2 2} F _5/2 were determined very accurately. These data and tenA-factors from former experiments are used for theoretical calculations. 30A-factors have been interpolated from intermediate coupling wave functions using 9 effective mono-electronic parameters. The r.m.s. deviation between experimental and theoreticalA- values amounts to 0.5 10^?3 cm^?1 and represents 3/100 of the average value of the measuredA-factors.