Limited Amount Of Air Research Articles

Applications of electric arc metallization method with pulsating air-spraying flow for application of coatings made from a cored wire

In order to reduce the oxidizing effect of the spraying flow on the liquid metal of the ends of the molten electrodes the method of periodic (pulsating) impact of the air spraying flow on the liquid metal of the electrodes has been previously proposed and developed, considering that the pause between the moments of the flow impacts allows ensuring the melting of the electrodes with a limited amount of air. The design of the device which provides pulsations of a stream with various frequency and duration is developed, data on the influence of a pulsing stream on technological characteristics of coatings, in particular, a considerable decrease in losses of alloying elements are received.As a solution to the problem of energy saving in arc metallization, the use of oxygen of the air spraying flow was considered in order to obtain wear-resistant coatings with high adhesion strength through the formation of solid oxides from non-deficient powders of metals and alloys.Due to a limited range of compositions of solid cross-section wires, it is suggested to use cored wires consisting of low-carbon shell and rod made of non-deficient, widely spread metal and ferroalloy powders, which provide high wear-resistant coatings with increased adhesion strength.Theeconomically alloyed flux-cored wire PP-MM-2 developed at the Department of Automation and Mechanization of Welding Production of the Priazovsky State Technical University was taken as the investigated one.In this paper, the influence of spraying airflow pulsation frequency in arc metallization on microstructure and micro hardness value of coatings obtained by using powder wires is considered

Antifouling Surface Coating Using Droplet-Based SI-ARGET ATRP of Carboxybetaine under Open-Air Conditions.

The formation of a dense zwitterionic brush through surface-initiated atom transfer radical polymerization (SI-ATRP) is a typical graft-from approach used to achieve antifouling surfaces with high fidelity; however, their air-tightness may cause inconvenience to users. In this context, activator regenerated by electron transfer (ARGET) ATRP is emerging as an alternative surface-coating tool because limited amount of air is allowed to form a dense polymer brush. However, the degree of air tolerance that can ensure a thick polymer brush has not been clearly defined, limiting its practical usage under ambient-air conditions. In this study, we investigated the SI-ARGET ATRP of carboxybetaine (CB) by changing the air conditions, along with the air-related parameters, such as the concentration of the reducing agent, the volume of the polymerization solution (PS), or the solvent composition, and correlated their effects with the poly(CB) thickness. Based on the optimized reaction conditions, a poly(CB) brush with reliable thickness was feasibly formed even under open-air conditions without a degassing step. In addition, a microliter droplet (∼100 μL) of PS was sufficient to proceed with the SI-ARGET ATRP for the covering of a poly(CB) brush on the surface area of interest. By applying an optimized SI-ARGET ATRP of CB, antifouling was feasibly achieved in the surface region of interest using an array to form a large surface area under fully exposed air conditions. In other words, optimized SI-ARGET ATRP enabled the formation of a thick poly(CB) brush on the surfaces of various dimensions under open-air conditions.

Reversible chain transfer catalyzed polymerization (RTCP) in nitrogen-based solvents without additional catalysts

N,N-Dimethylformamide (DMF) andN-methyl-2-pyrrolidone (NMP) as typical nitrogen-based solvents were used as the catalyst for RTCP without additional catalyst, which could also be carried out in the presence of a limited amount of air.

Iron-mediated AGET ATRP of styrene and methyl methacrylate using ascorbic acid sodium salt as reducing agent

Atom transfer radical polymerization of styrene (St) and methyl methacrylate (MMA) in bulk and in different solvents using activators generated by electron transfer (AGET ATRP) were investigated in the presence of a limited amount of air using FeCl3·6H2O as the catalyst, ascorbic acid sodium salt (AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide (TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.

Synthesis of Poly(methyl Methacrylate)-Silica Hybrid Materials through Activators Generated by Electron Transfer

Activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) of methyl methacrylate (MMA) on silica nanoparticles were conducted to create controllable shell on silica surfaces. SiO2–Br, the macroinitiator, was prepared by the reaction of amido groups previously indroduced on silica with 2-bromoisobutyryl bromide, followed by the ATRP of MMA using CuBras the catalyst and ascorbic acid (VC) as the reducing agent in the presence of a limited amount of air. The resulting particles were examined by SEM and TEM. The results indicated that the particles were composed of a silica core and a densely grafted outer poly(methyl methacrylate) (PMMA) layer.

Synthesis of Sn2P2S6

A process that presents no explosion hazard is proposed for the preparation of tin(II) hexathiohypodiphosphate(IV) in a limited amount of air. The reaction of tin(II) sulfide with a mixture of phosphorus sulfides with the overall composition “P4S8” is studied, and the influence of synthesis temperature and duration on the completion of the reaction is analyzed.

ARGET ATRP of methyl methacrylate with 2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethylamine (OLC) as both ligand and reducing agent in the presence of air

Copper(II)-mediated activators regenerated by electron transfer for atom transfer radical polymerization of methyl methacrylate (MMA) was successfully carried out in a limited amount of air in the presence of 2-(8-heptadecenyl)-4,5-dihydro-1H-Imidazole-1-ethylamine as ligand that served not only as ligand but also as reducing agents. Reduction of Cu(II) to Cu(I) by an excess amount of nitrogen-based ligand was followed by UV–visible spectroscopy. The kinetics of the polymerizations and effect of different polymerization conditions are investigated. It is found that the polymerization of MMA can be conducted well even if the amount of Cu(II) is as low as 1 mol% catalyst relative to initiator. The results of the polymerizations demonstrate the features of “living”/controlled free-radical polymerization, such as the number-average molecular weights being close to their corresponding theoretical values and increasing linearly with monomer conversion, and narrow molecular weight distributions. Chain extension of poly(methyl methacrylate)s with MMA was successful and demonstrated well-maintained end-group functionality.

A Highly Active Iron‐Based Catalyst System for the AGET ATRP of Styrene

The atom transfer radical polymerization of styrene using activators generated by electron transfer (AGET ATRP) has been carried out in bulk in a limited amount of air at 110 °C, using 1,3,5-(2'-bromo-2'-methylpropionato)benzene (BMPB) as an initiator and FeCl(3) · 6H(2) O/tris(3,6-dioxaheptyl) amine (TDA-1)/ascorbic acid (VC) as a novel Fe(III) -mediated catalyst system. The results of the polymerizations demonstrate the features of 'living'/controlled free-radical polymerization, such as the number-average molecular weights being close to their corresponding theoretical values and increasing linearly with monomer conversion, and narrow molecular weight distributions ($\overline M _{\rm w} /\overline M _{\rm n}$ = 1.18-1.26). The end functionality of the obtained polymers was confirmed by (1) H and (13) C NMR spectra as well as a chain-extension reaction.

SYNTHESIS, CRYSTAL STRUCTURE AND MAGNETIC PROPERTIES OF AN ASYMMETRIC, MIXED-VALENCE, TETRANUCLEAR CoII 3CoIII COMPLEX WITH 2-MERCAPTOPHENOL AND DIMETHYLPHENYLPHOSPHINE LIGANDS

A neutral mixed-valence tetranuclear complex [Co4(mp)4(Hmp)(PMe2Ph)3] (PMe2Ph = dimethylphenylphosphine, H2mp = 2-mercaptophenol) was isolated from me reaction of CoCl2, H2mp, NaOMe, and PMe2Ph in 1:1:2:1 mol ratio in the presence of a limited amount of air with CoII partially oxidized to CoIII. The molecule consists of a CoII 3CoIII core with a cyclic arrangement, and which is unsymmetrically bridged by μ2-S and μ2-O atoms from three mp2− ions in ObSb−T and one in OtSb mode, while the monoanion Hmp−is terminally chelated to the CoIII ion in HOtSt mode. The three CoII centres are located in approximately square-based pyramidal environments, and the CoIII ion in distorted trigonal bipyramidal geometry. Variable-temperature magnetic susceptibility measurements showed that the complex exhibits weak antiferromagnetic exchange interactions due to the inefficiency of the μ2−S and μ2−O bridges in facilitating coupling between cobalt atoms with Co− distances of 2.6−3.4 Å. Least-squares fitting of the experimental data shows coupling constants in the range −0.3 to −3.2 cm−1.

Detailed Measurements on a Modern Combustor Dump Diffuser System

An experimental investigation has been carried out to determine the flow characteristics and aerodynamic performance of a modern gas turbine combustor dump diffuser. The system comprised a straight walled prediffuser, of area ratio 1.35, which projected into a dump cavity where the flow divided to pass either into the flame tube or surrounding feed annuli. In addition, a limited amount of air was removed to simulate flow used for turbine cooling. The flame tube was relatively deep, having a radial depth 5.5 times that of the passage height at prediffuser inlet, and incorporated burner feed arms, cowl head porosity, cooling rings, and primary ports. Representative inlet conditions to the diffuser system were generated by a single-stage axial flow compressor. Results are presented for the datum configuration, and for a further three geometries in which the distance between prediffuser exit and the head of the flame tube (i.e., dump gap) was reduced. Relatively high values of stagnation pressure loss were indicated, with further significant increases occurring at smaller dump gaps. These high losses, which suggest a correlation with other published data, are due to the relatively deep flame tube and short diffuser length. Furthermore, the results also focus attention on how the presence of a small degree of diffuser inlet swirl, typical of that which may be found within a gas turbine engine, can result in large swirl angles being generated farther downstream around the flame tube. This is particularly true for flow passing to the inner annulus.

Hypothermia Prolongs Survival in a Confined Atmosphere

Survival in a confined atmosphere where O2 is limited may be extended by hypothermia. Rats were placed in a thermoregulated sealed chamber which contained a limited amount of air. Rats were studied at low ambient temperatures, in which their terminal rectal temperatures (TB) were 33.2-8.3 degrees C. Rats which had a terminal TB of 20 degrees C achieved maximal O2 extraction. Maximal survival time may be expected with an initial thermoneutral temperature followed by hypothermia with a final TB of 20 degrees C. Resuscitation with no obvious signs of injury was possible after half of the rats succumbed.

Waste incineration and pyrolysis

Waste materials may be treated by incineration (burning) or by thermal processing in the absence of air or oxygen (pyrolysis), or, similarly, by thermal processing with a limited amount of air or oxygen (gasification). Incineration gives waste reduction by weight and volume, a sterile residue, and the possibility of heat recovery as hot water and/or steam. Thermal processing gives waste reduction by weight and volume, a sterile residue, plus the following products and possibilities: (i) gas with a low to medium calorific value for use as a fuel or feedstock for chemical conversion; (ii) a solid or char which can be used as a fuel, or alternatively an ash; or (iii) liquid tars and/or heavy oils which may be used as a fuel oil substitute or as a feed for thermal cracking, accompanied by a volume of water containing dissolved organic materials. The latter may pose a considerable disposal problem. The waste material used as a feed for thermal processing may be: raw refuse; sorted material in that the combustible portion has been separated or concentrated (termed refuse-derived fuel); sorted and prepared material in that most of the noncombustible portion has been removed and the combustible portion densified into a form meeting a specification as a fuel (termed densified refuse-derived fuel). The incineration of waste may yield steam or hot water which can be used to do work (e.g. generate electricity). Thermal processing may yield a storable, transportable fuel.