Comparison analysis of graphene oxide reduction methods

Abstract

Graphene oxide was reduced by aspartic acid, β-mercaptoethanol in the acidic mixture, hydrothermal method and by atomic hydrogen (deuterium and tritium). Raman spectroscopy and FTIR indicate high reduction efficiency of hydrothermal method. FTIR indicates that atomic hydrogen results in the formation C_sp3H-bonds on the graphene surface. Graphene oxide can be effectively reduced by β-mercaptoethanol in the acidic mixture even at room temperature.     

Heat transfer during condensation of moving steam in a narrow channel

The paper presents the results of experimental investigation of heat transfer and hydrodynamics during condensation of moving steam in a narrow channel of square cross-section 2 mm × 2 mm. The channel had a serpentine shape, the channel length was 660 mm. An experimental cell simulated conditions of heat transfer in the condenser of loop heat pipes. The steam velocity at the channel inlet ranged from 13 to 52 m/s, the pressure was 1 atm. The temperature of the cooling water varied from 70 to 95 °C. The annular flow pattern was noted in the whole range of the regime parameters. There was a clear boundary between the condensation zone and the zone occupied by the condensed phase downstream. Temperature has measured along the channel, and the heat-transfer coefficients have been determined. The coefficient values varied from 10,000 to 55,000 W/K m² depending on the steam velocity at the channel inlet and the cooling temperature. The efficiency of the condenser – heat exchanger has been investigated.     

Study of Emulsions of Solutions of Film-Forming Polymers in Methylene Chloride Related to the Problem of Microencapsulation of Proteins

The properties of oil-in-water, water-in-oil, and double emulsions of solutions of cellulose triacetate (CTA) and polycarbonate (PC) in methylene chloride containing aqueous solutions of a model protein, albumin, are investigated. Such emulsions are intended for production of microcapsules. The effect of the nature and concentration of the film-forming polymer on the particle size and polydispersity of the emulsions is established. The correlation of the viscosity, interfacial surface tension, and dispersity of oil-in-water emulsions of solutions of CTA and PC in methylene chloride is determined. It is shown that the dispersity of the emulsions increases with a decrease in the ratio of the viscosity of the disperse phase to the viscosity of the dispersion medium and the decrease in the interfacial surface tension.     

Effect of compact porosity and prior sintering on the properties of hot-forged brass parts

Conclusions The above-described investigation has demonstrated the feasibility of producing blanks of high density (up to 99% of theoretical) from atomized powders of various brass grades. Two production schedules can be employed, with or without a sintering operation preceding the hot forging of pressed blanks. However, if good mechanical properties are to be obtained in parts, use should be made of the former schedule. A high level of properties, particularly ductility, is attained at high initial compact porosities. It has been established that the sintering weight loss due to evaporation of zinc diminishes with decreasing zinc concentration in the powder and with increasing initial compact density. An empirical formula has been derived enabling the weight loss to be calculated for sintering under the conditions employed in this work.Translated from Poroshkovaya Metallurgiya, No. 8(260), pp. 61–66, August, 1984.     

Use of tritium-labeled lysozyme for studying its adsorption on porous carbon materials

The kinetics and isotherm of lysozyme adsorption and the strength of lysozyme binding to two carbon materials, activated charcoal and carbon foil, were studied using tritium-labeled lysozyme. Polyethylene films were used as a model nonporous material. The lysozyme adsorption resulted in modification of the surface of the materials, making it more hydrophilic, and the rate at which the adsorption equilibrium was attained depended on the capability of the lysozyme solution to penetrate into pores of carbon materials. The specific coverage of the surface of graphite foil, activated carbon, and polyethylene with lysozyme appeared to be virtually equal when taking into account only pores accessible to the protein. The lysozyme adsorption on the polyethylene surface is reversible, whereas on the surface of activated charcoal and graphite foil it is practically irreversible. The possibility of modification of the carbon foil surface with a lysozyme solution to increase the adsorption zone was confirmed by autoradiography.     

Increase in the length of poly(ethylene oxide) blocks in amphiphilic copolymers facilitates their cellular uptake

Amphiphilic nonionic block copolymers induce different biological effects on living cells. In particular, the hydrophobic members of the Pluronics family suppress drug efflux systems in multidrug‐resistant cells, whereas hydrophilic Pluronics support cell viability. However, the relationship between the copolymer structure and its binding to cells is still unclear. Using a tritium‐labeling approach, we analyzed interactions of nine Pluronics and three diblock copolymers with human and murine cells in vitro and revealed that the binding efficiency of the copolymers increased in line with the length of their poly(ethylene oxide) (PEO) blocks. In contrast, partitioning of the same polymers into artificial lipid bilayers determined by Isothermal Titration Calorimetry (ITC) decreased with increasing length of the PEO block. The opposite influence of hydrophilic blocks on the copolymer affinity to living cells and artificial lipid bilayers implied the binding of long PEO blocks to the hydrophilic moieties of cellular membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45492.     

Numerical simulation of transient heat and mass transfer in a cylindrical evaporator of a loop heat pipe

The paper investigates the transient processes of heat and mass transfer in a cylindrical evaporator of a loop heat pipe (LHP) during the device start-up. One of the most “arduous” prestart situations, which is characterized by the absence of a liquid in the evaporator central core and filled vapor removal channels, has been considered. With such liquid distribution a successful start-up of an LHP becomes possible only after formation of the vapor phase in the vapor removal channels and their liberation from the liquid. The aim of the investigations is to determine conditions that ensure the boiling-up of a working fluid in vapor removal channels. The problem was solved by a numerical method. Simulation of start-up regimes has been performed for different heat loads and different structural materials of the evaporator. Copper, titanium and nickel wick have been examined. Calculations have been made for three different working fluids; water, ammonia and acetone. Account has been taken of the conditions of heat exchange between the compensation chamber and surrounding medium.