This dissertation deals with the study of electric and dielectric properties of composite structures on the base of alkali-activated aluminosilicates with admixtures of various carbon particles. These materials fabricated from alkali-activated blast furnace slag, quarz sand, natrium water glass as alkali activator, water, dispersant and small amount of carbon admixture (carbon black, graphite powder, carbon fibers or carbon nanotubes) to increase electric conductivity may be used for example to construction of snow-melting, deicing and self-monitoring systems. Their current-voltage characteristics and impedance spectra were used for determination of electric and dielectric properties of these structures. The equivalent circuits were used for evaluation of impedance spectra. The results were correlated with thermal properties of these structures.

The thesis is focused on the study of electric and dielectric properties of thin film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the glass substrates, which consist of a thin active layer of phthalocyanines. On the samples were first measured current-voltage characteristics (in the dark and during the exposure) and the basic parameters of the photovoltaic conversion were determined. Finally were measured frequency dependencies (impedance spectra, in the dark and during the exposure) and the parameters of a model of the structure with organic semiconductor were determined. The obtained results will be used to optimize the properties of photovoltaic cells.

Объекты разработки и исследования: канал лазерной стимуляции для измерения электрофизических параметров структуры Ti/TiO2-НТ/Au и канал оптической стимуляции для исследования люминесцентных свойств нанопорошка гексагонального нитрида бора. Цель работы – разработать измерительные каналы лазерной стимуляции исследуемых образцов на основе контроля и управления параметрами излучения в различных режимах в ходе экспериментальных исследований оптически стимулированных и родственных процессов в широкозонных наноструктурированных материалах. В результате работы разработан канал лазерной стимуляции для существующего комплекса по измерению вольт-амперных характеристик на базе микрозондовой станции Cascade Microtech MPS 150, а также модернизирован канал оптической стимуляции на базе люминесцентного спектрометра Perkin Elmer LS 55 со встроенной высокотемпературной приставкой. Реализованные программно-аппаратные измерительные комплексы позволили успешно применить на практике методики исследования широкозонных наноструктур посредством оптически стимулированных процессов. Полученные в ходе работы данные, как для образцов Ti/TiO2-НТ/Au, так и для наноструктурированного порошка h-BN, отлично согласуются с результатами различных исследовательских работ из независимых научных источников. / Objects of development and research: a laser stimulation channel for measuring the electrophysical parameters of the Ti/TiO2-HT/Au structure and an optical stimulation channel for studying the luminescent properties of a hexagonal boron nitride nanopowder. The aim of the work is to develop measuring channels of laser stimulation of the studied samples based on the control and operating of radiation parameters in various modes during experimental studies of optically stimulated and related processes in wide-gap nanostructured materials. As a result of the work, a laser stimulation channel was developed for the existing complex for measuring current-voltage characteristics based on the Cascade Microtech MPS 150 microprobe station, and the optical stimulation channel was modernized on the basis of a Perkin Elmer LS 55 luminescence spectrometer with a built-in high-temperature attachment. The implemented software and hardware measuring systems made it possible to successfully apply in practice the methods of studying wide-gap nanostructures by means of optically stimulated processes. The data obtained during the work, both for the Ti / TiO2-NT / Au samples and for the nanostructured h-BN powder, are in excellent agreement with the results of various research works from independent scientific sources.

La presente Tesis Doctoral consiste en la determinación de las propiedades de transporte de diferentes especies catiónicas a través de membranas de intercambio catiónico. Las membranas de intercambio iónico son un componente clave de los reactores electroquímicos y de los sistemas de electrodiálisis, puesto que determinan el consumo energético y la eficiencia del proceso. La utilización de este tipo de membranas para el tratamiento de efluentes industriales no es muy extendida debido a los requisitos de elevada resistencia química y durabilidad que deben cumplir las membranas. Otro asunto importante radica en la eficiencia en el transporte de los iones que se quieren eliminar a través de la membrana. Normalmente, existe una competencia por el paso a través de las membranas entre diferentes especies debido al carácter multicomponente de los efluentes a tratar. Sin embargo, una mejora en las propiedades de las membranas de intercambio iónico permitiría la implantación del tratamiento mediante reactores electroquímicos de efluentes industriales con un contenido importante en compuestos metálicos, tales como los baños agotados de las industrias de cromado. La utilización de una tecnología limpia como la electrodiálisis conllevaría diferentes ventajas, entre las cuales destacan la recuperación de los efluentes para su reutilización en el proceso industrial, el ahorro en el consumo de agua y la disminución de la descarga de contaminantes al medio ambiente. La determinación de las condiciones de operación óptimas así como la mejora de las propiedades de transporte de las membranas constituye el principal tema de la presente investigación. Para ello, se emplearán diferentes tipos de membrana. En primer lugar, se estudiará el comportamiento de las membranas poliméricas comerciales que poseen unas propiedades de resistencia química elevadas, las cuales se tomarán como referencia. De forma paralela, se producirán membranas conductoras de iones a partir de materiales cerámicos económicos, ya que la resistencia de los materiales cerámicos a sustancias oxidantes y muy ácidas es mayor que la de los materiales poliméricos. Este punto constituye la parte más innovadora de la investigación, puesto que la mayoría de las membranas de intercambio iónico comerciales están basadas en materiales poliméricos que no pueden resistir las condiciones específicas de los efluentes industriales. Una vez determinadas las condiciones de operación óptimas, se realizarán ensayos en plantas piloto con el fin de confirmar los resultados obtenidos mediante las técnicas de caracterización y determinar el grado de recuperación y coste energético asociado a los procesos electrodialíticos de tratamiento de efluentes industriales. / Martí Calatayud, MC. (2014). STUDY OF THE TRANSPORT OF HEAVY METAL IONS THROUGH CATION-EXCHANGE MEMBRANES APPLIED TO THE TREATMENT OF INDUSTRIAL EFFLUENTS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/46004 / Premios Extraordinarios de tesis doctorales

The factors governing electronic transport properties of copper and gold atomic-size contacts are theoretically examined in the present work. A two-terminal conductor using crystalline electrodes is adopted. The non-equilibrium Green’s function combined with the density functional tight-binding method is employed via gDFTB simulation tool to calculate the transport at both equilibrium and non-equilibrium conditions. The crystalline orientation, length, and arrangement of electrodes have very weak influence on the electronic characteristics of the considered atomic wires. The wire width is found to be the most effective geometric aspect determining the number of conduction channels. The obtained conductance oscillation and linear current-voltage curves are interpreted. To analyze the conduction mechanism in detail, the transmission channels and their decomposition to the atomic orbitals are calculated in copper and gold single point contacts. The presented results offer a possible explanation for the relation between conduction and geometric structure. Furthermore, the results are in good agreement with available experimental and theoretical studies. / In der vorliegenden Arbeit werden die wesentlichen Faktoren, die die elektronischen Transporteigenschaften von Kontaktstrukturen atomarer Größe aus Kupfer bzw. Gold bestimmen, theoretisch untersucht. Untersuchungsgegenstand ist eine leitfähige Struktur zwischen zwei kristallinen Elektroden. Um Transportberechungen sowohl unter Gleichgewichts- als auch unter Nicht-Gleichgewichts-Bedingungen durchführen zu können, wird die Simulations-Software gDFTB, die auf dem Nicht-Gleichgewichts-Green-funktionenformalismus in Kombination mit der Dichtefunktional-Tight-Binding-Methode beruht, eingesetzt. Die elektronischen Eigenschaften der betrachteten atomaren Drähte werden nur sehr schwach von ihrer kristallinen Orientierung, ihrer Länge und der Elektrodenanordnung beeinflusst. Als effektivster geometrischer Faktor wurde der Leiterquerschnitt gefunden, weil dieser die Anzahl der Leitungskanäle bestimmt. Darüber hinaus werden die erhaltenen Leitfähigkeitsoszillationen und die linearen Strom-Spannungs-Kennlinien erklärt. Für eine detaillierte Analyse des Leitungsmechanismus werden bei den Ein-Atom-Kontakten aus Kupfer und Gold die Übertragungskanäle und ihre Aufspaltung in Atomorbitale betrachtet. Die präsentierten Ergebnisse bieten eine mögliche Erklärung für den Zusammenhang zwischen Leitfähigkeit und geometrischer Struktur. Die Resultate zeigen eine akzeptable Übereinstimmung mit den verfügbaren experimentellen und theoretischen Studien.

My diploma thesis is focused on a comparison of direct-current and high frequency (15-80 kHz) electric discharge, which generates non-thermal plasma in water solution of sodium chloride. Mainly current-voltage and Lissajous charts are discussed in the first part of this thesis. These charts describe different discharge phases: electrolysis, bubble formation, discharge breakdown and discharge regular operation in a pin-hole of a dielectric barrier. Influence of frequency, electrolyte conductivity, thickness of the diaphragm (or length of the capillary) and pin-hole diameter on discharge breakdown and bubble generation was studied, too. Measurements were realized in a polycarbonate reactor with total volume of 110 ml, which was divided by a changeable polyacetal insulating wall. This wall divided the reactor into two approximately equal spaces with one stainless steel planar electrode in each part. The Shapal-MTM ceramic discs (thickness of 0.3–1.5 mm and diameter of the central pin-hole of 0.3-0.9 mm) were mounted in the centre of the insulating wall. Initial conductivity of sodium chloride solution was chosen within the interval of 100900 S/cm. The second part of my thesis compares an influence of the direct-current (DC) and high frequency (HF) power sources on physical solution properties (conductivity, pH and temperature) and generation of hydrogen peroxide. A plasma reactor with total volume of 4 l and with mixing set up was divided into two equal spaces with one planar platinum electrode in each part. Diaphragm with thickness of 0.6 mm and pin-hole diameter of 0.6 mm was installed in the middle of the separating wall. Experiment was held at discharge operation of 45 W for 40 minutes with both power sources. Detection of hydrogen peroxide was realised by using a titanium reagent forming a yellow complex, which was analysed by absorption spectroscopy. If HF discharge power is plotted as a function of applied frequency, exponential decrease of frequency with increasing power can be observed. Higher breakdown voltage is necessary for thicker dielectric barriers, on the other hand for bigger diameter of the pin-hole lower breakdown voltage and higher power is needed in DC as well as in HF regime. Breakdown voltage is decreased by the increasing conductivity in both regimes; due to more charge carriers in the higher conductivity lower breakdown voltage is needed. However frequency in HF regime and DC discharge power increases. HF discharge power is decreased by the increasing conductivity. Solution conductivity and temperature are increased by initial conductivity value in both discharge regimes. Solution pH drops to acidic conditions when HF or DC positive regime is applied due to the generation of reactive species and electrolysis (in DC regime). However solution becomes alkaline when DC negative regime is applied. Concentration of hydrogen peroxide is produced linearly when HF or DC negative regime is applied and it depends on initial solution conductivity.

The exact mechanism of the discharge in liquids ignition is not sufficiently known up to now. Although during the last years was achieved the great progress and overloading which some of them are written in this theoretical part of thesis. This thesis is divided into two experimental parts. When the first part deals with diagnostics of diaphragm discharge in electrolyte solutions and the second part is focused on its use for uncoiling (higher homogenization) of carbon nanotubes in solutions. In experiment 1, three different sized (4 l, 100 ml, 50 ml) diaphragm discharge configurations were used to diagnose diaphragm discharge in electrolyte solutions. Diagnostics is done through current and voltage waveforms with the addition of synchronized ICCD camera images that have been connected to a four-channel oscilloscope. The V-A characteristic can be described by three events occurring in the electrolyte solution with a gradual increase in voltage. Slowly increasing of the voltage in the solution leads first to electrolysis. The next phase is the formation of microbubbles or bubbles, which is characteristic of the curve by a slight decrease in the increase of the current passing between electrodes. The sudden increase in the current flow is characteristic of the last phase, namely the discharge phase. The distance of the electrodes from the diaphragm does not significantly affect the V-A characteristic. The higher diameter of the pin hole, therefore, has a higher voltage, but this does not affect the origin of bubble generation or breakdown. The higher thickness of diaphragm, the higher voltage is needed to the beginning of the bubbles generation, and consequently the discharge breakdown. Comparison of the voltage of the start generation of the bubbles and breakdown for PET diaphragms and diaphragms from the ceramic there was no mark able difference. One of the most important parameters is the conductivity of the electrolyte solution. The lower voltage is needed for the start generation of the bubbles at the higher solution conductivity, and also the discharge generation is observed at a lower breakdown voltage. The second experimental part is focused on the study of the diaphragm discharge effect on carbon nanotubes. A specially designed U-shaped reactor is used to modify carbon nanoparticles. Tap water and aqueous solutions of organic compounds are used as the electrolytic solutions. The discharge is generated by a non-pulsed DC high source with a voltage in the range of 0-2.8 kV supplied to platinum electrodes located in the electrolyte solution. The experimental results have shown that the diaphragm discharge has positive effects on the disintegration of clusters and agglomerates of carbon nanotubes. The primary effect on disintegration is probably the shock waves generated by the discharge. It turned out that it depends on the electrode configuration, where the treatment in anode space has far greater effects than the treatment in cathode half of the reactor. Effects of carbon nanotubes disintegration in solution are long-lasting and the treatment effect is not loosed after several months. There were detected no significant changes in the structure of plasma-treated nanotubes by Infra-red spectroscopy.

The factors governing electronic transport properties of copper and gold atomic-size contacts are theoretically examined in the present work. A two-terminal conductor using crystalline electrodes is adopted. The non-equilibrium Green’s function combined with the density functional tight-binding method is employed via gDFTB simulation tool to calculate the transport at both equilibrium and non-equilibrium conditions. The crystalline orientation, length, and arrangement of electrodes have very weak influence on the electronic characteristics of the considered atomic wires. The wire width is found to be the most effective geometric aspect determining the number of conduction channels. The obtained conductance oscillation and linear current-voltage curves are interpreted. To analyze the conduction mechanism in detail, the transmission channels and their decomposition to the atomic orbitals are calculated in copper and gold single point contacts. The presented results offer a possible explanation for the relation between conduction and geometric structure. Furthermore, the results are in good agreement with available experimental and theoretical studies. / In der vorliegenden Arbeit werden die wesentlichen Faktoren, die die elektronischen Transporteigenschaften von Kontaktstrukturen atomarer Größe aus Kupfer bzw. Gold bestimmen, theoretisch untersucht. Untersuchungsgegenstand ist eine leitfähige Struktur zwischen zwei kristallinen Elektroden. Um Transportberechungen sowohl unter Gleichgewichts- als auch unter Nicht-Gleichgewichts-Bedingungen durchführen zu können, wird die Simulations-Software gDFTB, die auf dem Nicht-Gleichgewichts-Green-funktionenformalismus in Kombination mit der Dichtefunktional-Tight-Binding-Methode beruht, eingesetzt. Die elektronischen Eigenschaften der betrachteten atomaren Drähte werden nur sehr schwach von ihrer kristallinen Orientierung, ihrer Länge und der Elektrodenanordnung beeinflusst. Als effektivster geometrischer Faktor wurde der Leiterquerschnitt gefunden, weil dieser die Anzahl der Leitungskanäle bestimmt. Darüber hinaus werden die erhaltenen Leitfähigkeitsoszillationen und die linearen Strom-Spannungs-Kennlinien erklärt. Für eine detaillierte Analyse des Leitungsmechanismus werden bei den Ein-Atom-Kontakten aus Kupfer und Gold die Übertragungskanäle und ihre Aufspaltung in Atomorbitale betrachtet. Die präsentierten Ergebnisse bieten eine mögliche Erklärung für den Zusammenhang zwischen Leitfähigkeit und geometrischer Struktur. Die Resultate zeigen eine akzeptable Übereinstimmung mit den verfügbaren experimentellen und theoretischen Studien.