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A beam line dedicated to high-energy electron radiography experimental research with linear achromat and imaging lens systems has been designed. The field of view requirement on the target and the beam angle-position correlation correction can be achieved by fine-tuning the fields of the quadrupoles used in the achromat in combination with already existing six quadrupoles before the achromat. The radiography system is designed by fully considering the space limitation of the laboratory and the beam diagnostics devices. Two kinds of imaging lens system, a quadruplet and an octuplet system are integrated into one beam line with the same object plane and image plane but with different magnification factor. The beam angle-position correlation on the target required by the imaging lens system and the aperture effect on the images are studied with particle tracking simulation. It is shown that the aperture position is also correlated to the beam angle-position on the target. With matched beam on the target, corresponding aperture position and suitable aperture radius, clear pictures can be imaged by both lens systems. The aperture is very important for the imaging. The details of the beam optical requirements, optimized parameters and the simulation results are presented. [ABSTRACT FROM AUTHOR]

Different morphologies of tin dioxide (SnO 2 ) architectures were prepared by increasing reaction time (12, 18, 24 and 48 h) under a facile hydrothermal process and followed by calcination. The crystal structures and morphologies of the hierarchical architecture were characterized in detail by means of powder X-ray diffraction (XRD), energy dispersive X-ray detector (EDX), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the porous flower-like SnO 2 architecture was obtained by 24 h hydrotherm treatment. Most importantly, the sensors based on porous flower-like SnO 2 architecture exhibited perfect sensing performance toward ethanol with excellent selectivity, high response and fast response-recovery capability compared with other SnO 2 nanoflowers for the same ethanol concentration at 300 °C. The response value was about 208 and the response-recovery time was around 8 and 7 s for 500 ppm ethanol, respectively. The enhancement in gas sensing properties was attributed to the unique structures, including the flower-like structure and porous feature, which provided more gas active center and diffusion pathways. The results indicated that porous flower-like SnO 2 architecture was a potential candidate for fabricating effective ethanol sensor. Furthermore, the possible growth mechanism and the ethanol sensing mechanism of the architecture were discussed, too. [ABSTRACT FROM AUTHOR]

Highlights: [•] High pressure and high temperature studies on MnWO4 compounds. [•] Pressure induced a reversible phase transition happened at 17.7GPa. [•] Temperature induced phase transition from monoclinic to molten state started at 1100K. [ABSTRACT FROM AUTHOR]

Abstract: Environmentally assisted crack growth in thermally treated Alloy 690 cold worked one-dimensionally to the thickness reduction of 25% in primary water was investigated. In the water at 50°C and dissolved hydrogen (DH) of 2.7–2.9ppm, the alloy showed a crack growth rate of <2.2×10−9 mm/s at a stress intensity factor of 35MPa√m. In the water at 340°C, stress corrosion crack growth rate of <1×10−8 mm/s was observed in the alloy over a DH range of 0.37–2.6ppm. Further, it was found that hydrogen could promote SCC growth when increasing DH from a very low level. [Copyright &y& Elsevier]

Abstract: This paper reports detailed analyses of Nb and Ta concentrations of 19 eclogite samples and their principal mineral constituents from the main drill hole of the Chinese Continental Scientific Drilling Project (CCSD) and nearby outcrops. We observe highly fractionated and overall suprachondritic Nb/Ta values in minerals, e.g., rutile (4.8–87), titanite (12–62) and amphibole (2.0–67). Amphiboles in amphibolites (retrograded from eclogite) can be classified into two groups: a low Nb/Ta group that bears higher Al contents and is thus of higher pressure origin, and a high Nb/Ta, lower pressure group. The former group was likely formed during subduction; the latter may have formed during exhumation in the presence of rutile and titanite. The significant Nb/Ta fractionation in rutile and other minerals may reflect early dehydration of the subducted slab at shallow depths before the formation of rutile, which occurs at depths ≥50km. The dehydration, with amphiboles existing as the main Nb–Ta-bearing phase, would lead to Nb/Ta fractionation, i.e., forming subchondritic Nb/Ta ratios in the released fluids and, complementarily, suprachondritic Nb/Ta ratios in the residual phases. While a large proportion of the fluids may escape from the slab to the mantle wedge, considerable amounts of the fluids can be retained in hydrous minerals within the descending slab, thus forming hydrated cold eclogites with subchondritic Nb/Ta characteristics. As subduction continues to depths over 50km, rutile appears and consequently controls the Nb–Ta budget. In the presence of rutile, melting of the hydrated cold eclogites with very low Nb/Ta ratios would form magmas with negative Nb, Ta anomalies and subchondritic Nb/Ta. Further dehydration of the continuously descending slab results in even more fractionated Nb/Ta ratios in subsequently released fluids and residues, providing a feasible explanation for the large Nb/Ta variation observed in the modern arc magmas and residual eclogites. [Copyright &y& Elsevier]

Abstract: There has been an increased interest on the development of micro/nanostructures with desired radiative properties for energy conversion systems and radiative cooling devices. A detailed experimental study is reported on the spatial and temporal coherence of thermal radiation in asymmetric Fabry–Perot resonance cavities. The reflectance of the fabricated samples was measured for both polarizations using a Fourier-transform infrared spectrometer, at several incident angles in the near-infrared region, and a laser scatterometer at the wavelength of 891nm. The spectral measurement demonstrates sharp reflectance dips, while narrow angular lobes are observed in the angle-resolved measurement. Experimental results suggest strong spectral and directional selectivity in thermal emission, which is related to the reflection by Kirchhoff’s law since the samples are opaque. Theoretical calculations with the fitting geometric parameters agree well with the measurement results. This easy-to-fabricate structure has potential applications in solar cells, thermophotovoltaic devices, and radiation emitters. [Copyright &y& Elsevier]

Abstract: This paper elucidates the energy transfer and conversion processes in near-field thermophotovoltaic (TPV) systems, considering local radiation absorption and photocurrent generation in the TPV cell. Radiation heat transfer in a multilayered structure is modeled using the fluctuation–dissipation theorem, and the electric current generation is evaluated based on the photogeneration and recombination of electron–hole pairs in different regions of the TPV cell. The effects of near-field radiation on the photon penetration depth, photocurrent generation, and quantum efficiency are examined in the spectral region of interest. The detailed analysis performed in the present work demonstrates that, while the near-field operation can enhance the power throughput, the conversion efficiency is not much improved and may even be reduced. Subsequently, a modified design of near-field TPV systems is proposed to improve the efficiency. [Copyright &y& Elsevier]

Abstract: This paper reports quantitative topographical measurements using a heated atomic force microscope (AFM) cantilever probe. The study compares topographies measured by the cantilever thermal signal to topographies measured by the laser-deflection signal of an AFM system. The experiment used 20 and 100nm tall Si gratings as topographical test samples. The cantilever heater temperature ranged from 130 to 640°C, and the cantilever power ranged from 1.5 to 6.6mW. The measured topography sensitivity, which is the fractional change of the heated cantilever resistance, has a |ΔR cant|/R cant of 4.5×10−5 to 1.1×10−3 per vertical nanometer, which is 10–100 times greater than that of similarly sized piezoresistive cantilevers. In a proof of concept demonstration, the heated cantilever measures the topography of a microfabricated platinum line of thickness 100nm on a silicon dioxide substrate. [Copyright &y& Elsevier]

Abstract: Nanocrystalline diamond films were deposited on Co-cemented tungsten carbides using bias-enhanced hot filament CVD system with a mixture of acetone, H2 and Ar as the reactant gas. The effect of Ar concentration on the grain size of diamond films and diamond orientation was investigated. Nanocrystalline diamond films were characterized with field emission scan electron microscopy (FE-SEM), Atomic force microscopy (AFM), Raman spectroscopy and X-ray diffraction spectroscopy (XRD). Rockwell C indentation tests were conducted to evaluate the adhesion between diamond films and the substrates. The results demonstrated that when the Ar concentration was 90%, the diamond films exhibited rounded fine grains with an average grain size of approximately 60–80 nm. The Raman spectra showed broadened carbon peaks at 1350 cm−1 and 1580 cm−1 assigned to D and G bands and an intense broad Raman band near 1140 cm−1 attributed to trans-polyacetylene, which confirmed the presence of the nanocrystalline diamond phase. The full width at half maximum of the <111> diamond peak (0.8°) was far broader than that of conventional diamond film (0.28°–0.3°). The Ra and RMS surface roughness of the nanocrystalline diamond film were measured to be approximately 202 nm and 280 nm with 4 mm scanning length, respectively. The Ar concentration in the reactant gases played an important role in the control of grain size and surface roughness of the diamond films. Nanocrystalline diamond-coated cemented tungsten carbides with very smooth surface have excellent characteristics, which made them a promising material for the development of high performance cutting tools and wear resistance components. [Copyright &y& Elsevier]

Abstract: The phenomenon of surface excitation is competitive in nature for elastic and other inelastic scattering processes in surface electron spectroscopies; the knowledge of influence of surface excitations in electron energy loss spectra is then essential for quantitative surface analysis with these spectroscopies. The inelastic scattering of an electron moving in the vicinity of a surface is considered in a self-energy formalism to estimate the contribution of surface excitation in electron–solid interactions via the total surface excitation probability. The formulation uses the optical bulk dielectric function and provides the spatial and angular dependence of the differential and total inelastic cross-sections. The kinetic energy range of probing electrons considered is 100–5000eV and the numerical evaluation of total surface excitation probabilities are performed for several metals, Au, Ag, Cu, Ni, Fe and Ti; empirical formulae for the surface excitation probability are given for each of these materials and compared with experimental results for the surface excitation parameter. The total surface excitation probability is higher in Ag as compared to other metals under consideration, for identical conditions of electron–solid interactions. [Copyright &y& Elsevier]

Abstract: The pressure effect on photoluminescence (PL) and Raman spectra of the poly (para-phenylene vinylene) (PPV) has been investigated with a diamond anvil cell (DAC) under the hydrostatic pressure condition. The intensity ratios, I 1167/I 1622 and I 1543/I 1622, increase with pressure. This indicates that the conjugated length of PPV is enhanced at high pressures. In addition, appearance of a new Raman band corresponding to CC stretch at 1190cm−1 shows that the chain conformation defects decreased with increasing pressure. The redshift of the PL spectra and shift to higher frequencies for Raman bands with increase in pressure are explained by combining the conjugation model with amplitude mode model. [Copyright &y& Elsevier]

Abstract: A comparison has been made on the fluorescence of the poly (p-phenylenevinylene) (PPV) that without filtering the low molecular weight molecules (sample A) with the PPV of the low molecular weight molecules filtered (sample B). Although there is no obvious difference found in the FT-IR and Raman spectra between two samples, in the photoluminescence spectrum of the sample A, the peak at 510nm is not appeared and the fluorescence intensity for the peak at 550nm is increased. Under the high pressure condition the fluorescence peak at 520nm, which corresponds to the peak at 510nm of the usual PPV, is observed. Applying high pressure to the sample A or by filtering the low molecular weight molecules, the chain aggregated structure is modified, resulting in a change in the PPV chain distortion degree. [Copyright &y& Elsevier]

When an intense positron burst impinges upon a target within nano or picoseconds, a pulse of gamma-rays is created. The gamma-ray pulse contains many annihilation events about the positron burst. A spatial detecting method with a detector array is able to exploit the timing information in such gamma-ray pulses by mounting many independent detector cells of the array spherically around the target. It is possible that multiple annihilated photons in the pulse will fall into the same solid angle of one detector unit, and when one more gamma-ray is detected, a multi- γ signal is generated. In this paper, the principle, the influence factors of the multi- γ signals generation and the effect of multi- γ signals on the time detection of the positron burst are studied by experiment and simulation. Furthermore, a method of eliminating multi- γ signals is also proposed and evaluated. The results can provide support for the design of the detector array applied to measure the positron lifetimes in the burst, such as the detector distance to the source and the method dealing with the multi- γ signals. [ABSTRACT FROM AUTHOR]

In this study, the microstructures and mechanical properties of the as-extruded and as-aged Mg-1.4Gd-1.2Y-0.4Zn-0.5Al (at.%) sheets with two extrusion ratios (ERs) of 10 and 22 have been studied. During the extrusion process, the 18R LPSO structure goes through the process of kink deformation, breaking into pieces, bending-delamination, finally separating and kink again. The as-extruded sheet with ER of 22 exhibits smaller dynamically recrystallized grains and weaker basal texture. Different extrusion ratios play little effect on the aging process. Dense nano-scaled β′ phase precipitates from the α-Mg matrix, resulting in significant precipitation strengthening. The as-aged sheet with ER of 22 exhibits the higher comprehensive mechanical property, where the ultimate tensile strength, yield strength, and tensile elongation to failure are 440 MPa, 328 MPa and 7.0%, respectively. The enhanced strength is mainly attributed to the thin strip-shaped 18R LPSO structure distributed along the grain boundaries, which can effectively refine the grains and strengthen the alloy by acting as reinforcing fibers. • A deformation model of the 18R LPSO structure based on the kink deformation was proposed. • A new 18R LPSO structure containing Al element was found. • The relationship between microstructure and mechanical properties was investigated in detail. [ABSTRACT FROM AUTHOR]

• Rough surface is modeled as effective medium with gradient distribution of dielectric function. • Plasmonic resonance coupling inside rough layer red-shifts the peak of spectral heat flux. • Rough layer provides more surface modes at longer wavelength. • Total net radiative heat flux between rough surfaces exceeds that between smooth plates. Near-field radiative heat transfer (NFRHT) between rough surfaces, due to its widespread presence in engineering practice of near-field energy utilization, requires indepth studies, especially from the perspective of physical mechanism. In this paper, an effective multilayer model is built to approach the NFRHT between random rough surfaces of silicon carbide (SiC). Using the effective medium theory (EMT), the effective dielectric function of each layer is obtained, which forms a gradient distribution of dielectric function along the depth of the medium. The influence of the effective dielectric function on surface phonon polaritons (SPhPs) is analyzed, showing that the effective layers with small filling fraction of SiC feature lower SPhP resonance frequencies than SiC bulk. The coupling of SPhPs from the gradient distribution of dielectric function produces new surface modes that dominates the NFRHT. Investigation on the effect of root mean square height (RMS height, σ) reveals that the peaks of local density of states (LDOS) and spectral heat flux are red-shifted as σ increases, while the spectral heat flux below the peak frequency gets larger. This can be attributed to the coupling of SPhPs inside the rough layer. We also found the total net heat flux between rough surfaces separated by an average distance exceeds that between smooth plates and increases with increasing σ , which offer a new way to enhance NFRHT. This work provides a reference for the simulation and understanding of the NFRHT between rough surfaces. [ABSTRACT FROM AUTHOR]