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Tungsten is one of the prime candidates for a first-wall material near the divertor area due to its high temperature strength, high thermal conductivity, low erosion rate and low tritium retention. The erosion resistance of tungsten to the edge plasmas and transient events are carefully investigated in a simulated fusion environment. Here, we use the dense plasma focus (DPF) device operated in a D2 as a source for pulsed fusion plasma. The tungsten (α-W) substrates with a preferential growth direction along (110) plane were used. These pristine-W samples were nanostructurized using a (i) low-temperature continuous nitrogen RF plasma system and (ii) coated with 60 nm tungsten film, using high-temperature argon plasma in a dense plasma focus (DPF) device. The low- temperature plasma treatment created mesh-like porous nanostructure on the surface of pristine-W with change in crystalline orientation to (200), while the DPF-based deposition resulted in a nanocrystal (30–50 nm) decorated surface with enhanced (200) orientation. The crack propagation and bubble formation during DPF D2 plasma exposure were significantly controlled by the surface modification of tungsten. The mesh-like structure was modified to form loosely bound spherical nanoparticles, while the nanocrystals remained tightly bound and grew in size with D2 plasma exposure. The better adhesion of the nanocrystals and controlled growth along the (200) direction resulted in least change in hardness measurements for the nanocrystal decorated samples. Thus, nanocrystal decoration of tungsten with a preferential growth direction of (200) can help reduce the fusion-induced damage in first-wall materials.

The design of existing tribometers mainly focuses on normal contact and lubricant conditions and aims to evaluate the effect of the load, speed, and environmental conditions on the rubbing pair properties. The effect of the contact angle and variable speed on the rubbing pair properties is often not considered. In this study, a multidirectional adjustment tribometer is developed to evaluate the tribological behavior of cylinder liner–piston rings under dry sliding or oil lubrication conditions. The dynamic, specimen clamping, measuring, and control systems are redesigned according to the structural characteristics of the SKODA-SAVIN tribometer and special requirements of research on the net texture effect on tribological properties. Using LabVIEW software, a man–machine interface is designed to achieve converter control, data acquisition, and other functions. A fail-safe analysis is performed through reproducibility, comparability, and sensitivity tests. From the experiments, it is proved that the tester can provide more detailed, abundant, and reliable data for the performance testing and development of cylinder liner–piston ring materials.

The rheological behavior of Polyethylene (PE) modified bitumen is investigated. It is found that a rheological plateau under high temperature presented on the curve of storage modulus (G *) variation with temperature. By the addition of little wax, the rutting resistance of bitumen/PE blend can be further improved. Moreover, the wax incorporation into bitumen/PE can significantly decrease the starting temperature of rheological plateau to accommodate the actual service temperature of bituminous pavement, making a potential application of PE/wax modified bitumen in pavement engineering. The reason for this rheological property enhancement by wax is explored in terms of phase separation structure and thermal behavior of bitumen/PE blends. Main focus is put on the relationship between PE crystallinity and rheological behavior.

Novel high salt superabsorbent composites were synthesised through free radical graft polymerisation of partially neutralised 2-acrylamido-2-methylpropanesulphonic acid onto attapulgite (APT) in aqueous solution using microwave irradiation. The potassium persulphate and N,N-methylene-bis-acrylamide were used as initiator and cross-linking agent respectively. The structure of the composites was characterised by the Fourier transform infrared spectroscopy (FTIR). The effect of microwave power and APT amount on water absorbency of the superabsorbent composites was investigated. The mechanism for synthesis of the superabsorbent composites was proposed. Results show that the graft copolymerisation takes place between the APT and organic monomers. The addition of an appropriate amount of APT in the composites can effectively improve the water absorbency and salt water performance of the superabsorbent composites. The water absorbency of the superabsorbent composites decreases with increasing concentrati...

The joint of cubic boron nitride (CBN) grits to 0·45%C steel were obtained by using TiB2 modified Ag–Cu–Ti active filler at the brazing temperature of 920°C for the holding time of 5 min. The microstructure characteristics of the brazing interface were detected by means of optical microscope, scanning electron microscope, energy dispersion spectrometer, X-ray diffraction and microhardness measuring equipment as well. It has been found that the microstructure of Ag–Cu–Ti filler layer is significantly refined by TiB2 particles. The almost well proportioned distribution of TiB2 particles in the filler layer is realised. Negative influence of TiB2 particles has not occurred on the chemical reaction of CBN particles and the filler at elevated temperatures. Reliable joining of CBN grits to 0·45%C steel is accomplished dependent on the resultant reaction products at the brazing interface.

Thermodynamic and kinetic analysis was performed in order to study the interfacial reaction mechanism of cubic boron nitride (CBN) abrasive grains and Ti activated Ag–Cu filler alloy during high temperature brazing. Meanwhile, microstructure of the interfacial layer was experimentally detected using scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and X-ray diffraction (XRD) in the present paper. The results indicate that according to the thermodynamic theory, the interfacial reaction has been proved feasible, and during brazing the special active element Ti concentrated to and reacted with the CBN abrasive to form TiB2 and TiN, which joined hard the abrasive grain and steel substrate. Furthermore, the diffusion activation energy of the growing process in the interfacial reaction layer has discovered that the layer growth largely depends on the new formed TiN under conditions of 1153–1193 K and 5–30 min.

AbstractThe synthesis and applications of black ceramic formed by recycling of industrial wastes are presented. Black ceramic was synthesised using vanadium residue, kaolin and earthenware clay as starting materials. The stable phase structures in the black ceramic include ilmenite, haematite and iolite. The V–Ti black ceramic that was produced can be used as black pigment, black tiles, infrared radiating elements and for solar absorber coatings.

The formation of Schottky potential barriers and their complex interplay with current transport across electrically active grain boundaries (GBs) give rise to many novel properties of electroceramics such as the varistor behavior. The origin of the GB electrical activity lies in the defect chemistry, and associated variations in geometry, chemistry and electronic structure at GBs. Motivated by the recent experimental results of dopant identification and spatially resolved quantification of GB charge and associated space-charge across GBs in SrTiO3, we have performed atomic-level electronic structure calculations on GBs in SrTiO3. The first-principles density-functional embedded-cluster Discrete-Variational (DV) method is used to determine charge densities and densities of states (DOS) for several idealized models of symmetrical tilt GBs in SrTiO3 which have been derived from a combination of atomistic latticestatic simulations and experimental electron microscopy analysis.

A controlled coprecipitation technique has been used to synthesize precursors of superconducting BiPbSrCaCuO ceramics. The oxalate precursors were nano-sized powders with high homogeneity, low crystallinity, and well-defined stoichiometry. These precursors have been used to fabricate superconducting tapes by the powder-in-tube technique, which involves the use of Ag sheaths. The nano-sized homogeneous powders require considerably reduced tape-processing (sintering) times for Bi-2223 formation, and provide 'clean' intergrain boundaries within the sintered tapes. As a result, high critical transport current density, Jc, can be obtained even in multiphase composites that do not necessarily exhibit a high degree of texture. To gain further insight into the role of microstructural details at each step of the tape fabrication, extensive X-ray diffraction analyses and scanning electron microscopy measurements have been made. The influence of homogeneity and grain size distribution on the superconducting properties of the Ag-clad tapes is discussed. We have reproducibly achieved, within 60 h of the thermal processing, Jc values as high as 4.4*104 A cm-2 at 77 K in zero applied magnetic field.

In this paper, the compression experiments of picosecond optical pulses from a gain-switched InGaAsP distributed feedback (DFB) laser at a 1.5 μm wavelength range using a Gires-Tournois (G-T) interferometer are reported. Ultrashort optical pulses with a pulsewidth of 6.6 ps, repetition rate of 2.4 GHz, and peak power in excess of 200 mW are obtained. The compression ratio is close to 5. The explanation for the experimental results is given, and the pulse's compression characteristics of a G-T inteferometer are discussed by a computer simulation analysis.

The paper reports the impact of TiN metal gate composition (Ti-rich vs. N-rich) and preparation methodology (atomic layer deposition -ALD vs. physical vapor deposition -PVD) on its thermal stability with HfO 2 high-K dielectric, via both physical characterization (X-ray Photoelectron Spectroscopy -XPS, High Resolution TEM combined with Electron Energy Loss Spectroscopy -EELS), and electrical characterization (capacitance voltage -CV & current voltage -IV measurement). After annealing at 1000°C for 30s, it is observed that: 1) Nitrogen tends to out-diffuse from both PVD and ALD TiN; 2) Oxygen from the interfacial layer (IL) between HfO 2 and Si tends to diffuse towards TiN for all the samples. PVD Ti-rich TiN can scavenge more oxygen from IL, but also shows signal of Ti penetration into HfO 2 , which poses a concern on its thermal stability; 3) The oxygen out-diffusion from HfO 2 /IL stack can be significantly suppressed for ALD TiN compared to the PVD TiN, which is critical to maintain the HfO 2 integrity. The effective work function of TiN metal gate is correlated with its thermal stability.

In-situ YBa2Cu3O7 films of high quality (from a Jc(T, H) and Tc point of view) have been fabricated by both, pulsed laser deposition (PLD), and on-axis rf magnetron sputtering techniques on SrTiO3 (100) and LaA103 (100) substrates. In the PLD method, a pulsed Nd:YAG laser with the 355 nm tripled wave length and the energy density of 8 J/cm2 has been used. In the on-axis rf magnetron sputtering method, the effects of negative oxygen ion re-sputtering have been nearly eliminated by introducing a grounded metallic mask between the target and the substrate. We have been successful in producing in-situ superconducting films at relatively low pressures as well as low substrate temperatures well outside the empirical Hammond-Bormann regime. Our films show zero resistance critical temperatures as high as 91.5 K. XRD measurements and Rocking curves of a (005) peak revealed that the films are highly c-axis oriented normal to the substrate and with the FWHM of less than 0.3 degree. The critical currents in these films determined from SQUID magnetometry at 77 K is found to be more than 106 A/cm2 with an exponential field and temperature dependencies. Some comparisons of the properties of the superconducting films obtained by the two different techniques are also presented.

In this paper, the thermal stability of TiN metal gate with various composition prepared by different preparation technology [(e.g., atomic layer deposition (ALD) or physical vapor deposition (PVD)] on HfO2 high-K dielectric is investigated and compared by physical and electrical analysis. After annealing of the TiN/HfO2 stack at 1000 °C for 30 s, it is observed that: (1) Nitrogen tends to out-diffuse from TiN for all the samples; (2) Oxygen from the interfacial layer (IL) between HfO2 and Si tends to diffuse toward TiN. PVD Ti-rich TiN shows a wider oxygen distribution in the gate stack, and a thinner IL than the N-rich sample. Ti penetration into HfO2 is also observed in the Ti-rich sample, which can potentially lead to the dielectric break-down. Besides, the oxygen out-diffusion can be significantly suppressed for ALD TiN compared to the PVD TiN samples.

Current sophisticated electronic structure simulations are at the forefront of understanding and predicting a variety of materials properties of intermetallic compounds. Several examples are given here that illustrate how first principles total energy local density methods have addressed the problems of (i) phase stability and the effect of ternary additions, (ii) anti-phase boundaries (APB’s) in B2 NiAl, FeAl and RuAl aluminides and other faults in determining their structural and bonding character. A key objective has been to attempt to understand, at the electronic level, fundamental quantities that may be related to the crucial ductility issue in high temperature intermetallics. Differences between observed ductility properties of related systems may relate to their differing electronic and bonding properties, particularly the nature of p-d hybridization and the directional charge distributions of the states near the Fermi energy.

Experimental evidence of light induced drift of sodium atoms in absence of wall adsorption is here reported. The adsorption energy is reduced down to ∼ 0.1 eV by coating the cell with a thin and transparent film of silane which lowers the adsorption time to ∼ 10 -12 s and inhibits the formation of a sodium monolayer. The drift velocity is evaluated to be in agreement with the theoretical calculations.

The electronic structure of Al3V vs its two different crystal structures (DO22 and Ll2) were investigated using local density total energy approach. The calculated results of the total energy showed that in Al3V the tetragonal DO22 phase is energetically favored as compared to the cubic Ll2 phase, the total energy in the former case is about 60 mRy/F.U. lower than that in the later case. The calculated lattice constant (a=3.72 Å, c=8.20 Å) is in fairly good agreement with experiment (a=3.778 Å, c=8.326 Å),and the bulk modulus (1.3 Mbar) is comparable with the experimental Young modulus (150 GPa) for Al3Ti. Furthermore, it is interesting to note that the density of states at EF in the tetragonal DO22 phase (0.14 states/eV-F.U.) is about one order magnitude smaller than that in the Ll2 phase (2.89 states/eV-F.U.). The electronic structure of Al3V seems to be fairly satisfactory in explaining its phase stability.

It is here described a very long cavity dye-laser (maximum length about 18 m ) obtained by modifying a commercial dye-laser ( Coherent Radiation mod. 599 ). Its main property is to cover with continuity the atomic -molecular inhomogeneously Doppler broadened line having a longitudinal mode separation comparable to the homogeneous absorption line. The spectral characteristics, the preliminary tests and the possible applications of this kind of laser are presented.

There is more and more the growing recognition that technological advances depend strongly on a thorough understanding of the thermodynamic, mechanical, and electronic properties of materials. These, in turn, depend on our predictive ability regarding these properties. Understanding the structure and stability of the phases of compounds and alloys is an area of vital importance to materials science and technology. Such an understanding is starting to emerge from our first steps into carrying out all-electron quantum mechanical investigations on materials of aerospace interest. Briefly put, our emphasis has been on obtaining an understanding of the effects of alloying on bonding, crystal structure and phase stability of structural materials and to use this information to help design new alloy systems — in close collaboration with experimental efforts at a number of laboratories. In this paper, a brief indication is given of the progress made in a number of illustrative areas.