Application of detonation coatings to design a new metal cutting tool

This paper presents the results of a research and development study of a new metal-working tool using detonation spray hard alloy coating. The influence of a heat-insulating sublayer on thermal flows occurring at flow drilling has been studied. New design and technology to manufacture punches for plastic drilling with heat-insulating ceramic sublayer aimed at decreasing a parasitic thermal flow through the tool to the lathe’s spindle have been developed. In addition, a new design and manufacturing technology for replaceable cutting plates for lathe working involving the use of detonation spray hard alloy coating have been created. The proposed application of the new tool allows reduction of its conversion cost and improving of performance characteristics.     

Atomic force microscopy examination of tobacco mosaic virus and virion RNA

The majority of early-onset familial Alzheimer's disease (FAD) is associated with mutations in the presenilin-1 (PS1) gene. We describe a novel Polish PS1 mutation of Pro117Leu, associated with the earliest average age of onset and death so far reported in a PS-linked, FAD kindred. Human kidney 293 and mouse neuroblastoma N2a cells were stably transfected with wild-type and PS1 P117L. There was a significant increase in the amyloid beta42/40 ratio in the N2a P117L PS1 transfected cells compared with N2a transfected with wild-type PS1. What role PS has in the pathogenesis of AD remains to be determined, however, the severity of the clinical picture associated with this PS1 mutation stresses the importance of presenilin.     

Investigation of the nature of low-frequency fluctuations of the field emission current using a two-dimensional distribution function

A two-dimensional distribution function in the frequency range 0.03–1 Hz was used to investigate the statistical characteristics of the fluctuations of the field emission current from single crystals of tungsten and p-type silicon. In order to determine the type of nonlinearity predominating in the low-frequency noise of the emission current, calculations were made of the two-dimensional distribution function for a Gaussian random process subjected to a given type of nonlinear transformation and the profiles of the experimental two-dimensional distribution functions were compared with dependences obtained by numerical methods. It was established that fluctuations of the effective emitting surface of the cathode, the barrier transmission, the work function, and of the electric field strength near the emitter surface may act as primary sources of low-frequency noise in the field emission current. Pis’ma Zh. Tekh. Fiz. 24, 87–93 (November 12, 1998) Paper presented at the International Conference on Emission Electronics, Tashkent, Republic of Uzbekistan, 4–6 November 1997.     

Active layer materials coated with Teflon AF nano-films deposited from solutions in supercritical CO2 for fuel cell applications

In the present work we suggest a new approach to the thin-film design of active layers for electrodes of fuel cells with phosphoric acid electrolyte in a polymer matrix. A fluoropolymer binder is introduced into common Pt@C active layer materials using supercritical (SC) CO₂ as a solvent. Unique wetting properties of this non-hazardous and environmentally friendly solvent allow one to deposit highly uniform thin fluoropolymer films on dispersed carbon supports. As a result, well-percolated gas-permeable fluoropolymer phases are produced in active layers already at comparatively small polymer loadings. Teflon AF 2400 was chosen as a stable high-molecular-weight fluoropolymer soluble in SC CO₂ with high oxygen permeability and high T_g value. Fluoropolymer-containing active layer materials prepared via the SC CO₂ deposition routes were studied by means of cyclic voltammetry and were tested in operating fuel cells using steady state voltammetry and electrochemical impedance spectroscopy. Polarization curves of operating fuel cells indicate that the optimal content of deposited from SC CO₂ fluoropolymer in active layer is about 3–5%. Results of impedance spectra fitting yield information used to explain the detected values of optimal loading.     

Synthesis and surface properties of amphiphilic fluorine-containing diblock copolymers

Amphiphilic diblock copolymers (DCs) of 2,3,4,5,6-pentafluorostyrene (PFS) and 2-hydroxyethyl methacrylate (HEMA) of different composition and molecular weights were prepared by two-step reversible addition–fragmentation chain transfer (RAFT) polymerization and first used for preparation of superhydrophobic coatings for cotton/polyester fabrics. The transition from hydrophobic to superhydrophobic coatings is controlled by the ratio between poly(2,3,4,5,6-pentafluorostyrene) (PPFS) block and poly(2-hydroxyethyl methacrylate) (PHEMA) block lengths (P_n^PFS/P_n^HEMA). The increase in P_n^PFS/P_n^HEMA is accompanied by a significant increase in water (θ^Н₂^О) and diiodomethane (θ^CH₂^I₂) contact angles, which reach the plateau at P_n^PFS/P_n^HEMA = 3.5 and remains almost constant up to P_n^PFS/P_n^HEMA = 6.2. Surface modification of the cotton/polyester fabric with the DC having P_n^PFS/P_n^HEMA = 6.2 produced superhydrophobic surface with θ^Н₂^О = 158 ± 4° and contact angle hysteresis CAH = 5 ± 2°, and θ^CH₂^I₂ = 107 ± 3°.     

Scanning tunneling microscopy study of cytochrome P450 2B4 incorporated in proteoliposomes

In the present paper, the application of scanning tunneling microscopy in cytochrome P450s membrane topology is discussed. The method enables visualization of heme location in the lipid-bilayer-incorporated protein. It is supposed that the membrane-bound cytochrome P450 on the tunneling microscope substrate should behave as 'molecular diode'. A model explaining the liposome and the proteoliposome images observed is proposed.     

Performance of high temperature fuel cells with different types of PBI membranes as analysed by impedance spectroscopy

In order to study how PBI membranes influence the operation of HT-PEFC cathode we analyse the performance of HT-PEFC based on three different PBI membrane types (meta-PBI, ABPBI and PBI-O-PhT) by means of stationary voltamperometry and impedance spectroscopy. For impedance spectra interpretation we use an equivalent circuit containing transmission line distributed element. This approach allows us to measure the distributed ohmic resistance of proton transport inside cathode catalyst layer. It is shown that this resistance depends on the membrane type used and has even more pronounced influence on the FC performance than ohmic resistance of the membrane itself.     

Ion transport properties of porous polybenzimidazole membranes for vanadium redox flow batteries obtained via supercritical drying of swollen polymer films

A novel method of membrane preparation for use in vanadium redox flow batteries by preswelling of poly(2,5‐benzimidazole) films in organic solvent followed by supercritical CO₂ assisted solvent removal is proposed. Influence of the organic solvent type on the morphology, proton, and vanadyl ion transport properties is studied. The performance of the obtained membranes inside single cells of vanadium redox flow batteries is compared to pristine dense poly(2,5‐benzimidazole) and Nafion 115 membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46262.     

Novel polyolefin/silicon dioxide/H3PO4 composite membranes with spatially heterogeneous structure for phosphoric acid fuel cell

Novel composite membranes based on polyolefins for intermediate and high temperature (120–160 °C) phosphoric acid fuel cells with polymer matrices have been synthesized and their properties have been studied, including testing in operating fuel cells. In contrast to polybenzimidazoles uniformly swelling with H₃PO₄, which are typically used as membrane-separators in such a type of fuel cells, the proposed materials have heterogeneous internal structure with spatially separated condensed bundles of non-swelling rigid polymer-silica composite matrix and proton-conducting channels filled with phosphoric acid. Such a heterogeneous structure may potentially provide improved balance between proton conductivity and mechanical stability of the membranes in comparison with the homogeneously swollen PBI structures. The composite porous films based on polyethylene and polypropylene have been prepared in several different ways and filled with network of silicon dioxide. The SiO₂ phase forms hydrophilic three-dimensional well-percolated channels. The affinity between the SiO₂ phase and the liquid phosphoric acid is responsible for capillary retention of the liquid electrolyte in the porous matrix (phosphoric acid wets SiO₂ surface). Besides, the framework of SiO₂ phase enhances the mechanical stability of the membranes at high temperatures. Maximum proton conductivity of 0.033 S/cm is achieved at 160 °C for fuel cell with the obtained polyethylene-based membrane. The best performance is detected for fuel cells on polypropylene-based membrane, which provides 0.5 V at 0.4 A/cm² at 140 °C being supplied with hydrogen and air. The proposed concept is aimed to mimic spatially-non-uniform Nafion-type membranes instead of using uniformly swollen polybenzimidazoles.