Применение дуговой сварки при ремонте ковшей экскаваторов в условиях Крайнего Севера

Цель работы – разработка технологии ремонта ковшей экскаваторов ручной дуговой наплавкой в условиях Крайнего Севера. В процессе исследования установлена основная причина выхода их из строя зубьев ковшей, описаны свойства стали 110Г13Л, отражены причины плохой свариваемости стали и меры по снижению сварочных деформаций, подобран оптимальный способ наплавки, сварочное оборудование и наплавочные материалы для работы в условиях низких температур, рассчитаны параметры режима наплавки. В результате исследования разработана технология ремонта ковшей экскаваторов ручной дуговой наплавкой покрытыми электродами в условиях Крайнего Севера.The purpose of the work is to develop a technology for repair of excavators buckets by manual arc welding in the Far North. In the course of the study, the main reason for their failure of the bucket teeth is established, the properties of 110G13L steel are described, the causes of poor weldability of steel and measures to reduce welding deformations are reflected, the optimal method of surfacing, welding equipment and surfacing materials for operation at low temperatures are selected, the parameters of the surfacing mode are calculated. As a result of the study, the technology of repair of excavators buckets by manual arc welding with covered electrodes in the Far North was developed

Coordinative supramolecular assembly of electrochromic thin films

The article is concerned with the layer-by-layer (LbL) assembly of electrochromic films using coordinative interactions between compounds. At first the concepts of coordinative supramolecular assembly are explained and examples are presented. Subsequently electrochromic LbL assemblies prepared upon electrostatic and/or coordinative interactions are briefly discussed. In the focus of the article are films of terpyridine(tpy)-functionalized polyiminoarylene metal ion complexes, which are prepared upon coordinative LbL assembly of the tpy-substituted polyiminoarylenes and metal ions. The films exhibit reversible electrochromic behavior with high contrast and fast response times. It is demonstrated that the electrochromic behavior of the films can be modified by a variation of polymer structure, metal ions, and counterions. (C) 2011 Elsevier Ltd. All rights reserved

Electrochromic polyiminocarbazolylenes with latent hydrogen bonding

Polyiminoarylenes with carbazole (cbz) units in the main chain, or main and side chain and thermally cleavable t-butyloxycarbonyl (boc) groups were prepared upon palladium-catalyzed coupling reactions. Polymers were prepared from 2,7-dibromo-9-(2-ethylhexyl)-carbazole M1 and 9-(4-aminophenyl) carbazole hydrochloride M3 (P1-EH), 2,7-dibromo-9-t-butyloxycarbonyl-carbazole M2 and M3 (P1-BOC), M1 and 4-t-butylaniline M4 (P2-EH), or M2 and M3 (P2-BOC). Thermal treatment of boc-substituted polymers P1-BOC and P2-BOC at 180 degrees C for >= 4 h led to removal of the boc groups and formation of insoluble polymers P1-H and P2-H with strong adhesion to the substrate due to hydrogen bonding ('latent hydrogen bonding'). For P1-BOC the rate constant k of deprotection could be determined to be about 0.050 min(-1). Size exclusion chromatography indicated that the molecular weights of the polymers were between 14 100 and 28 100 g mol(-1). Polymers P1-EH, P1-BOC, P2-EH and P2-BOC were readily soluble in toluene, THF, dichloromethane, chloroform, and benzene, and insoluble in acetone and methanol. After removal of the boc groups the resulting polymer films of P1-H and P2-H were insoluble in common organic solvents. Optical and electrochemical properties of the polymers were investigated. Due to the electron-rich nitrogen atoms in the main chain, the polymers can be easily oxidized. Oxidation starts at about 0.31 V vs. SCE with formation of cation radicals. Further oxidation occurs at 0.55 V with formation of dications, and at 0.71 V with oxidation of main chain cbz units. At about 1 V the side chain cbz units are oxidized. The polymers are electrochromic and exhibit color changes from colorless via orange to green and blue. Cbz oxidation at potentials >= 0.71 V leads to the formation of dimers in a side reaction. Thermal cleavage of the boc groups leads to well-adhering films of P1-H and P2-H due to hydrogen bonding of the carbazole N-H-groups between polymer chains, and polymer and ITO-substrate. The best performance with regard to reversible oxidation and adhesion was found for P1-H. For this polymer a reversible electrochromism was found. A contrast ratio of 12% at 900 nm, and a switching time of 400 ms were determined

QCM-D study of layer-by-layer assembly of polyelectrolyte blend films and their drug loading-release behavior

Preparation of multilayered polyelectrolyte and polyelectrolyte blend films and their drug uptake/release properties are studied using quartz crystal microbalance-dissipation (QCM-D). Polyvinylamine hydrochloride (PVA), polystyrene sulfonate sodium salt (PSS), and polyacrylic acid (PM) were used as polyelectrolytes. Either films of the pure polyelectrolytes (PVA/PSS and PVA/PAA) or blends (PVA/PAA PSS) were used. Our studies indicate that multilayer growth and drug loading/release properties of ibuprofen (IBF) can be successfully followed using QCM-D. Simultaneous UV vis and QCM-D studies also show that the blend composition of the films always differs from the mixture composition of the dipping solution independent of pH of the dipping solutions. While PM is more adsorbed at pH 5.5, PSS is almost completely adsorbed at pH 1.7. On the other hand, it is found that the films prepared from polyelectrolytes at pH 1.7 without salt are stable in neutral and acidic pH, while the Ibl blend films prepared at pH 5.5 with or without salt decompose at pH 2 and 11. Pure PVA/PAA films exhibit a faster release of IBF than those of pure PVA/PSS and blend films due to the fact that the pH probably triggered a burst disintegration. IBF release characteristics of blend films differ from pure systems and a two-step release behavior is observed. It is emphasized that hydrogen bonding between PM and IBF has an important role for the retarded IBF release from the blend films if PSS lead to hydrophobic interactions with the drug. In conclusion, pH stimuli lbl assembled films are prepared and their drug loading/release can be fine-tuned depending on multilayer structure. (C) 2013 Elsevier B.V. All rights reserved

Coordinative Layer-by-Layer Assembly of Thin Films Based on Metal Ion Complexes of Ligand-Substituted Polystyrene Copolymers and Their Use as Separation Membranes

Polystyrene copolymers containing either 4-vinyl-2,2:6,2-terpyridine (P1) or 2,6-bis(1-methyl-1H-benzo[d]imidazol-2-yl)pyridin-4-yloxy)-methacrylate (P2) as comonomers are prepared and studied on metal ion coordination in solution and coordinative sequential assembly of films and membranes. Permeation and separation of ions and neutral aromatic molecules across the membranes are investigated. UV-vis titration of P1 with zinc acetate in chloroform/methanol (25:1) indicates formation of 2:1 ligand:metal bis-complexes, while titration of P2 led to 1:1 monocomplexes. It is demonstrated that coordinative interactions between the ligand groups and metal ions such as Zn(II) or Cu(II) can be used for layer-by-layer assembly of ultrathin films on solid quartz supports and porous supporting membranes. Formation of coordination polymer assemblies is characterized using UV-spectroscopy, quartz crystal microbalance measurements, scanning electron microscopy, and thickness measurements. Coordinative films prepared on porous polyacrylonitrile/polyethylene terephthalate supporting membranes exhibit a selective transport of ions and small molecules. Ion transport in aqueous and alcoholic solution is controlled by a sieving effect and by electrostatic rejection at the ligand-metal ion complexes in the membrane. The transport of organic aromatic molecules is only controlled by the sieving effect. Separation factors (NaCl/BaCl2) up to 4.2 and (naphthalene/perylene) up to 4.8 are found

Conjugated polymers containing benzo- and naphthodione units in the main chain

Monomers and conjugated polymers based on benzodifuranone, benzodipyrrolidone, naphthodifuranone and naphthodipyrrolidone are reviewed. Synthetic pathways to monomers and polymers, and the characteristic properties such as optical and electrochemical properties, and device properties are described