Effect of process factors and chemical composition of steels on the structure and properties of nickel-bearing diffusion coatings

The effect of the medium and regime of saturation and of the composition of the steel on the composition, structure, and properties of nickel, nickel-copper, and nickel-chromium diffusion coatings formed by selective transfer of the elements of the coating in a medium of low-melting liquid-metal solution is considered. The regular features of formation of nickel-bearing diffusion coatings on various steels are determined, which makes it possible to control the saturation process and form coatings with specified composition, structure, and properties. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 38–43, April, 2007.     

Calculation of suction capacity of centrifugal pumps

Information about cavitation characteristics of centrifugal pumps and critical cavitation conditions is given. Depending on the position of the leading edge, impellers are divided into three groups. The spatial lattice of the impeller is presented as a set of elementary lattices on the axisymmetric surfaces of a current of equal-velocity meridional flow. Equations have been derived from the determination of the cavitation margin and the equation of the energy in relative motion for the critical cavitation margin containing a cavitation coefficient referred to the impeller inlet. General equations have been obtained for the critical cavitaion coefficient of specific speed, which can be used to analyze the influence of geometric and operating conditions on the suction capacity of centrifugal impellers, which must be taken into account in designing them. The selection of the typical inlet diameter of the impeller has been substantiated and the critical cavitation coefficients of the elementary lattices have been found. An empirical equation, valid in the whole range of parameters encountered in practice, has been derived for the cavitation coefficient of type-3 impellers with a leading edge located roughly on the diameter of the impeller neck. An analytical equation, applicable for type-1 and-2 impellers, is given for the critical cavitation coefficient with empirical force coefficient values. A scheme for calculation of the suction capacity of such impellers is presented.     

Effect of temperature on aggregation/dissociation behavior of interpolymer complexes stabilized by hydrogen bonds

The effect of temperature on the aggregation/dissociation behavior of interpolymer complexes based on poly(acrylic acid) and various nonionic polymers—poly(vinyl pyrrolidone), poly(ethylene oxide), poly(acrylamide), hydroxypropylcellulose, hydroxyethylcellulose, poly(vinyl methyl ether), poly(vinyl ether of ethyleneglycol), and vinyl ether of ethyleneglycol‐co‐vinyl butyl ether—has been studied in aqueous solutions. It was shown that nonionic polymers could be classified into two groups according to the stability of their polycomplexes with respect to temperature. The first group of nonionic polymers forms interpolymer complexes, which are stable and undergo further aggregation upon increase in temperature. The second group forms polycomplexes, which dissociate at higher temperatures. The nature of forces stabilizing different interpolymer complexes in aqueous solutions is discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1946–1950, 2004     

Allowable gas temperature at outlet from furnace subject to slagging

The paper is devoted to substantiation and prediction of the allowable gas temperature at the outlet from a furnace subject to slagging. The non-optimality of values recommended by effective methodical instructions regarding the design of furnace devices is demonstrated. Utilizing knowledge gained from temperature measurements in boilers, and the situation regarding the slagging of heating surfaces located at the outlet from the furnace, new, frequently higher values are proposed. A method for evaluating the allowable gas temperature at the outlet froma furnace subject to slagging is suggested on the basis of data regarding the chemical composition of the mineral portion of coals. __________ Translated from élektricheskie Stantsii, No. 2, February, 2007, pp. 23–28.     

Sodium storage properties of thin phosphorus-doped graphene layers developed on the surface of nanodiamonds under hot pressing conditions

Abstract

Phosphorus-doped graphene layers have been formed on the surface of nanodiamond (ND) particles by hot pressing of a mixture of purified detonation ND powder and triphenylphosphine (TPP) at 1000?°C and 100?bar. X-ray photoelectron spectroscopy detected about 1.7 at.% of phosphorus in the product, most of which was in the oxidized form. The same treatment conditions of the ND powder without the addition of TPP resulted in the only partial covering of some ND particles by sp²-hybridized carbon layers. The tests in Na-ion half-cells found that the pure carbon sample can reversibly sustain 42 mAh g^?1 at a current density of 0.1?A g^?1. For the phosphorus-doped sample, this value increases up to 54 mAh g^?1 due to mainly accumulation of sodium at various defects created in the graphitic layers as a result of phosphorus incorporation. Taking into account inertness of inner diamond cores, specific capacity values are 417 mAh g^?1 for phosphorus-doped graphene layers and 587 mAh g^?1 for non-doped ones.     

Fully Solution‐Processed Photonic Structures from Inorganic/Organic Molecular Hybrid Materials and Commodity Polymers

Managing the interference effects from thin (multi‐)layers allows for the control of the optical transmittance/reflectance of widely used and technologically significant structures such as antireflection coatings (ARCs) and distributed Bragg reflectors (DBRs). These rely on the destructive/constructive interference between incident, reflected, and transmitted radiation. While known for over a century and having been extremely well investigated, the emergence of printable and large‐area electronics brings a new emphasis: the development of materials capable of transferring well‐established ideas to a solution‐based production. Here, demonstrated is the solution‐fabrication of ARCs and DBRs utilizing alternating layers of commodity plastics and recently developed organic/inorganic hybrid materials comprised of poly(vinyl alcohol) (PVAl), cross‐linked with titanium oxide hydrates. Dip‐coated ARCs exhibit an 88% reduction in reflectance across the visible compared to uncoated glass, and fully solution‐coated DBRs provide a reflection of >99% across a 100 nm spectral band in the visible region. Detailed comparisons with transfermatrix methods (TMM) highlight their excellent optical quality including extremely low optical losses. Beneficially, when exposed to elevated temperatures, the hybrid material can display a notable, reproducible, and irreversible change in refractive index and film thickness while maintaining excellent optical performance allowing postdeposition tuning, e.g., for thermo‐responsive applications, including security features and product‐storage environment monitoring.     

Intrinsic Quantum Dissipation in Superconducting Weak Links

We evaluate the frequency spectrum for an intrinsic quantum dissipative environment for the Josephson phase φ formed by subgap Andreev bound states in superconducting weak links. We also analyze the problem of macroscopic quantum tunneling (MQT) of φ in highly transparent weak links and identify several MQT regimes. Within the exponential accuracy, we derive the expression for the supercurrent quantum decay rate both at low temperatures and in the vicinity of the quantum-to-classical crossover.     

Enrichment of Inorganic Martian Dust Simulant with Carbon Component can Provoke Neurotoxicity

Carbon is the most abundant dust-forming element in the interstellar medium. Tremendous amount of meteorites containing plentiful carbon and carbon-enriched dust particles have reached the Earth daily. National Institute of Health panel accumulates evidences that nano-sized air pollution components may have a significant impact on the central nervous system (CNS) in health and disease. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the CNS. Based on above facts, here we present the study, the aims of which were: 1) to upgrade inorganic Martian dust simulant derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, nanodiamonds and carbon dots; 2) to analyse acute effects of upgraded simulant on key characteristics of synaptic neurotransmission; and 3) to compare above effects with those of inorganic dust and carbon components per se. Acute administration of carbon-containing Martian dust analogues resulted in a significant decrease in transporter-mediated uptake of L-[¹⁴C]glutamate (the major excitatory neurotransmitter) and [³H]GABA (the main inhibitory neurotransmitter) by isolated rat brain nerve terminals. The extracellular level of both neurotransmitters increased in the presence of carbon-containing Martian dust analogues. These effects were associated with action of carbon components of upgraded Martian dust simulant, but not with its inorganic constituent. This fact indicates that carbon component of native Martian dust can have deleterious effects on extracellular glutamate and GABA homeostasis in the CNS, and so glutamate- and GABA-ergic neurotransmission disballansing exitation and inhibition.     

Elastic Gallium Phosphide Nanowire Optical Waveguides—Versatile Subwavelength Platform for Integrated Photonics

Emerging technologies for integrated optical circuits demand novel approaches and materials. This includes a search for nanoscale waveguides that should satisfy criteria of high optical density, small cross-section, technological feasibility and structural perfection. All these criteria are met with self-assembled gallium phosphide (GaP) epitaxial nanowires. In this work, the effects of the nanowire geometry on their waveguiding properties are studied both experimentally and numerically. Cut-off wavelength dependence on the nanowire diameter is analyzed to demonstrate the pathways for fabrication of low-loss and subwavelength cross-section waveguides for visible and near-infrared (IR) ranges. Probing the waveguides with a supercontinuum laser unveils the filtering properties of the nanowires due to their resonant action. The nanowires exhibit perfect elasticity allowing fabrication of curved waveguides. It is demonstrated that for the nanowire diameters exceeding the cut-off value, the bending does not sufficiently reduce the field confinement promoting applicability of the approach for the development of nanoscale waveguides with a preassigned geometry. Optical X-coupler made of two GaP nanowires allowing for spectral separation of the signal is fabricated. The results of this work open new ways for the utilization of GaP nanowires as elements of advanced photonic logic circuits and nanoscale interferometers.     

A combined technique for amplifier oriented small‐signal noise model extraction

Based on the earlier experimental investigation of the existing GaAs pHEMT small‐signal modeling approaches and their applicability to different manufacturing processes, a combined automatic small‐signal noise model extraction technique, suitable for design of low‐noise and buffer amplifiers is proposed. The technique is based on the usage of measured S‐parameters of passive test structures and S‐parameters of the transistor in cold modes. Expressions are given for extraction of the intrinsic parameters of an equivalent circuit using linear regression. It is shown that the application of the proposed method allows extracting a small‐signal GaAs pHEMT model both in the probe‐tip reference planes and at on‐wafer calibration planes. The moving average algorithm was applied for preprocessing the results of measurements of the 50 Ohm noise figure during extraction of the noise model. The results of S‐parameters and noise figure simulation agree well with the measurements. The new technique was implemented as a plugin in a commercial EDA tool and enables to derive a ready‐to use small‐signal noise model from measured S‐parameters and 50 Ohm noise figure of a 0.15 μm GaAs pHEMT.