Cooperative localization-delocalization in the high Tc cuprates

The intrinsic metastable crystal structure of the cuprates results in local dynamical lattice instabilities, strongly coupled to the density fluctuations of the charge carriers. They acquire in this way simultaneously both, delocalized and localized features. It is responsible for a partial fractioning of the Fermi surface, i.e., the Fermi surface gets hidden in a region around the anti-nodal points, because of the opening of a pseudogap in the normal state, arising from a partial charge localization. The high energy localized single-particle features are a result of a segregation of the homogeneous crystal structure into checker-board local nano-size structures, which breaks the local translational and rotational symmetry. The pairing in such a system is dynamical rather than static, whereby charge carriers get momentarily trapped into pairs in a deformable dynamically fluctuating ligand environment. We conclude that the intrinsically heterogeneous structure of the cuprates must play an important role in this type of superconductivity.Comment: 14 pages, 8 figures, Proceedings of the "International Conference on Condensed Matter Theories", Quito, 2009 Int. J. Mod. Phys. B 2010 (Accepted

Superconductivity in charge Kondo systems

We present a theory of superconductivity in charge Kondo systems, materials with resonant quantum valence fluctuations, in the regime where the transition temperature is comparable to the charge Kondo resonance. We find superconductivity induced by charge Kondo impurities, study how pairing of a superconducting host is enhanced due to charge Kondo centers and investigate the interplay between Kondo-scattering and inter-impurity Josephson coupling. We discuss the implications of our theory for Tl-doped PbTe, which has recently been identified as a candidate charge Kondo system.Comment: 4 pages, 4 figures; revised version; detailed discussion on the physics of Tl-doped PbTe adde

Charge Kondo anomalies in PbTe doped with Tl impurities

We investigate the properties of PbTe doped with a small concentration $x$ of Tl impurities acting as acceptors and described by Anderson impurities with negative onsite correlation energy. We use the numerical renormalization group method to show that the resulting charge Kondo effect naturally accounts for the unusual low temperature and doping dependence of normal state properties, including the self-compensation effect in the carrier density and the non-magnetic Kondo anomaly in the resistivity. These are found to be in good qualitative agreement with experiment. Our results for the Tl s-electron spectral function provide a new interpretation of point contact data.Comment: 5 pages, 3 figures; published versio

Sedimentation of Ultradispersed Diamonds in the Citrate Copper-Plating Electrolyte

Abstract—The aggregation and sedimentation of ultradispersed diamonds (UDDs) in a citrate copper-plating electrolyte (CCPE) used to fabricate composite electrochemical coatings are investigated. The sedimentation and aggregation stability is investigated in order to select the UDD concentration in the CCPE. This is necessary to fabricate composite copper coatings with improved operational characteristics (increased hardness, wear resistance, and corrosion resistance), as well as impart them new properties (antifriction and catalytic). The UDD content in the electrolyte varies in limits from 0.2 to 2.0 g/L. The size distribution of the UDD particles in the electrolyte immediately after the suspension preparation and after the 10-day holding is determined using a Malvern Mastersizer 2000 laser diffraction analyzer. The aggregation and sedimentation stability of the UDD suspension in the CCPE is investigated by the gravimetric method with the continuous weighing of a quartz small cap immersed into this suspension. The quartz cap is associated with a Sartorius R200D analytical balance with the help of a quartz wire. The experimentally determined time dependence of the weight of settling UDD particles is Q = f(t). The relative size distribution of the particles is determined from this dependence. It is established that the sedimentation stability is substantially affected by the aggregation of the particles, the intensity of which increases with an increase in the UDD concentration. The results satisfying the requirements on the aggregation and sedimentation stability are found for the UDD suspension in the CCPE with a concentration of 1.0 g/L. In this case, the high content of the dispersed phase is combined with aggregation and sedimentation stability, which makes it possible to fabricate copper composite coatings with improved operational properties. © 2019, Allerton Press, Inc

Optimization of PET ion-track membranes parameters

Nowadays polymer ion-track membranes are used for a wide range of practical applications, which include various levels of filtration (micro-, ultra-, nanofiltration and osmosis), the creation of flexible electronic circuits and sensors based on polymer substrate, and using as templates for shape-controlled nanostructures synthesis. New applications demand clear understanding of the processes that occur during track membranes formation. For high-precision control of the end-product parameters, it is necessary to establish the correlation between etching conditions and track membranes characteristics (pores dimensions, porosity and membranes thicknesses). For this purpose, in the paper it is considered the technique of membranes formation with 10 nm - 10 μm cylindrical pores and correlation between their parameters and processing modes is studied. © 2019 Elsevier Ltd

Влияние цитратного электролита меднения, его компонентов и добавок ультрадисперсных алмазов на поверхностные свойства стали

The state of the steel substrate (steel 3) was studied before the application of composite copper coatings from citrate copper-plating electrolyte. The properties of steel base in the investigated copper-plating electrolyte with the addition of ultradispersed diamonds (UDD) have been studied. A component-by-component analysis of the citrate copper-plating electrolyte was carried out, and the effect of each component on the properties of the steel electrode was evaluated. The possibility of using the considered electrolyte for coating directly on steel is shown, which significantly distinguishes it from currently used ethylenediamine, pyrophosphate, acid and other electrolytes. Electrochemical impedance spectroscopy and cathodic polarization were used as research methods. It was found that the lowest resistance of the steel surface (about 15 Ω) corresponded to the sample immersed in citrate copper-plating electrolyte with the addition of 1.0 g/l of UDD. Diffusion current density for suspensions with 1.0 g/l UDD in citrate copper-plating electrolyte was 2.6 A/dm2. Ultradispersed diamonds in citrate copper-plating electrolyte shielded the surface of the steel sample, while reducing the total resistance of the passive layer of steel 3. Equivalent electrical circuits of the surface of steel samples immersed in citrate copper-plating electrolyte and its components are also presented.  Проведены исследования состояния стальной подложки (Ст 3) перед нанесением композиционных медных покрытий из цитратного электролита меднения. Изучены свойства стальной основы в исследуемом электролите меднения с добавкой ультрадисперсных алмазов (УДА). Проведен покомпонентный анализ цитратного электролита меднения и оценено влияние каждого компонента на свойства стального электрода. Показана возможность применения рассматриваемого электролита для нанесения покрытий непосредственно на сталь, что значительно отличает его от используемых в настоящее время этилендиаминовых, пирофосфатных, кислотных и других электролитов. В качестве методов исследования применяли электрохимическую импедансную спектроскопию и катодную поляризацию. Установлено, что наименьшее сопротивление поверхности стали (около 15 Ом) отвечало образцу, погруженному в цитратный электролит меднения с добавлением 1,0 г/л УДА. Диффузионная плотность тока для суспензий с 1,0 г/л УДА в цитратном электролите меднения составила 2,6 А/дм2. Ультрадисперсные алмазы в цитратном электролите меднения экранировали поверхность стального образца, при этом снижая общее сопротивление пассивного слоя стали Ст 3. Также представлены эквивалентные электрические схемы поверхности стальных образцов, погруженных в цитратный электролит меднения и составляющие его компоненты.

Электрохимическое осаждение желтой латуни в условиях импульсного электролиза

Electrodeposition of copper-zinc alloy of non-cyanide sorbate electrolyte at current densities of 1,0-3,5 A/dm2 allows to produce yellow brass with a copper content of about 63-64 wt.°%. Using pulsed current allows to intensify the process of deposition 1,3-1,6 times and to increase the current efficiency of the alloy by 1,2-4,2 %. Coatings obtained by pulsed electrolysis have fine-grained structure, more compact and with good adhesion to the steel substrate. Imposition of pulsed current allows deposition of homogeneous phase coating and eliminates formation of intermetallic compounds.Приведены результаты исследований бесцианистого сорбатного электролита латунирования и полученных из него покрытий. Исследованы кинетические особенности совместного осаждения меди и цинка. Изучено влияние импульсного тока и параметров нестационарности на диапазон рабочих плотностей тока и качество латунных покрытий. Выбраны оптимальные режимы осаждения латунных покрытий в условиях импульсного электролиза. Приведены результаты исследования влияния импульсного тока на фазовый состав и микроструктуру осажденного сплава

Charge Kondo Effect in Thermoelectric Properties of Lead Telluride doped with Thallium Impurities

We investigate the thermoelectric properties of PbTe doped with a small concentration $x$ of Tl impurities acting as acceptors and described by Anderson impurities with negative on-site (effective) interaction. The resulting charge Kondo effect naturally accounts for a number of the low temperature anomalies in this system, including the unusual doping dependence of the carrier concentration, the Fermi level pinning and the self-compensation effect. The Kondo anomalies in the low temperature resistivity at temperatures $T\leq 10\, {\rm K}$ and the $x$-dependence of the residual resistivity are also in good agreement with experiment. Our model also captures the qualitative aspects of the thermopower at higher temperatures $T>300\, {\rm K}$ for high dopings ($x>0.6$) where transport is expected to be largely dominated by carriers in the heavy hole band of PbTe.Comment: chapter contributed to 'New Materials for Thermoelectric Applications: Theory and Experiment' Springer Series: NATO Science for Peace and Security Series - B: Physics and Biophysics, pp. 67-80, ed. Veljko Zlati\'c, and Alex Hewson (Editor). ISBN: 978-94-007-4983-2 (2013

ОСОБЕННОСТИ СТРУКТУРЫ ПОВЕРХНОСТИ МЕДНЫХ ПОКРЫТИЙ ПРИ ВВЕДЕНИИ В ЭЛЕКТРОЛИТ МЕДНЕНИЯ УЛЬТРАДИСПЕРСНЫХ АЛМАЗОВ И АЛМАЗНОЙ ШИХТЫ

The properties of composite copper coatings with inclusions of ultradispersed diamonds (UDD) and diamond soot (DS) in copper citrate electrolyte have been investigated. The concentrations of diamond-containing additives have been varied in the range of 0.2–2 g/l. Sizes of copper microcrystals, UDD and DS particles were determined from the scanning electron microscopy images. By means of the X-ray fluorescent analysis, the interrelation between concentration of diamondbearing additives in electrolyte and their content in the obtained coatings has been established. The minimal microporosity and the maximal microhardness correspond to concentration of 1.0 g/l for both UDD and DS suspensions in citrate copper coating electrolytes. Copper-UDD coating has increased protective properties (porosity 2 time/cm2 ) and uniformity of distribution of diamond-bearing particles on a surface in comparison with a monocoating and copper-DS coating. Using UDD in citrate copper coating electrolyte with a concentration of diamond-bearing additive of 1.0 g/l is more preferable for production of composite electrochemical coatings. Исследованы свойства композиционных медных покрытий с включениями ультрадисперсных алмазов (УДА) и алмазной шихты (АШ) в цитратном электролите меднения. Концентрации алмазосодержащих добавок варьировали в диапазоне 0,2–2 г/л. По изображениям, полученным с помощью растрового электронного микроскопа, определили размеры микрокристаллов меди, частиц УДА и АШ. С помощью рентгенофлуоресцентного анализа установили взаимосвязь между концентрацией алмазосодержащих добавок в электролите и их содержанием в полученных покрытиях. Минимальная микропористость и максимальная микротвердость соответствует концентрации 1,0 г/л как для суспензии с УДА, так и для суспензии с АШ в цитратных электролитах меднения. Покрытия медь-УДА обладают повышенными защитными свойствами (пористость 2 пор/см2 ) и однородностью распределения алмазосодержащих частиц по поверхности в сравнении с монопокрытием и медь-АШ. Для получения композиционных электрохимических покрытий предпочтительнее использовать УДА в цитратном электролите меднения с концентрацией алмазосодержащей добавки 1,0 г/л.