Experimental determination of the eutectic temperature in air of the CuO-TiO2 pseudobinary system

Eutectic temperature and composition in the CuO–TiO2 pseudobinary system have been experimentally determined in air by means differential thermal analysis (DTA), thermogravimetry (TG) and hot-stage microscopy (HSM). Samples of the new eutectic composition treated at different temperatures have been characterized by X-ray diffraction (XRD) and X-ray absorption near-edge structural spectroscopy (XANES) to identify phases and to determine the Cu valence state, respectively. The results show that the eutectic temperature in air is higher by 100 °C (∼1000 °C) for a Ti-richer composition (XTiO2=25 mol%) than the one calculated in the literature. The reduction of Cu2+ to Cu+ takes places at about 1030 °C. The existence of Cu2TiO3 and Cu3TiO4 has been confirmed by XRD in the temperature range between 1045 and 1200 °C

Effect of the Synthesis Route on the Microstructure and the Dielectric Behavior of CaCu3Ti4O12 Ceramics

CaCu3Ti4O12 (CCTO) was prepared by a conventional synthesis (CS) and through reaction sintering, in which synthesis and sintering of the material take place in one single step. The microstructure and the dielectric properties of CCTO have been studied by XRD, FE-SEM, EDS, AFM, and impedance spectroscopy to correlate structure, microstructure, and electrical properties. Samples prepared by reactive sintering show very similar dielectric behavior to those prepared by CS. Therefore, it is possible to prepare CCTO by means of a single-step processing method

Towards materials with enhanced electro-mechanical response: CaCu3Ti4O12-polydimethylsiloxane composites

We describe a straightforward production pathway of polymer matrix composites with increased dielectric constant for dielectric elastomer actuators (DEAs). Up to date, the approach of using composites made of high dielectric constant ceramics and insulating polymers has not evidenced any improvement in the performance of DEA devices, mainly as a consequence of the ferroelectric nature of the employed ceramics. We propose here an unexplored alternative to these traditional fillers, introducing calcium copper titanate (CCTO) CaCu3Ti4O12, which has a giant dielectric constant making it very suitable for capacitive applications. All CCTO-polydimethylsiloxane (PDMS) composites developed display an improved electro-mechanical performance. The largest actuation improvement was achieved for the composite with 5.1 vol% of CCTO, having an increment in the actuation strain of about 100% together with a reduction of 25% in the electric field compared to the raw PDMS matrix

Organic covalent patterning of nanostructured graphene with selectivity at the atomic level

Organic covalent functionalization of graphene with long-range periodicity is highly desirable-it is anticipated to provide control over its electronic, optical, or magnetic properties-and remarkably challenging. In this work we describe a method for the covalent modification of graphene with strict spatial periodicity at the nanometer scale. The periodic landscape is provided by a single monolayer of graphene grown on Ru(0001) that presents a moiré pattern due to the mismatch between the carbon and ruthenium hexagonal lattices. The moiré contains periodically arranged areas where the graphene-ruthenium interaction is enhanced and shows higher chemical reactivity. This phenomenon is demonstrated by the attachment of cyanomethyl radicals (CH2CN•) produced by homolytic breaking of acetonitrile (CH3CN), which is shown to present a nearly complete selectivity (>98%) binding covalently to graphene on specific atomic sites. This method can be extended to other organic nitriles, paving the way for the attachment of functional molecules

Comparison of herbarium label data and published medicinal use: herbaria as an underutilized source of ethnobotanical information

The use of herbarium specimens as vouchers to support ethnobotanical surveys is well established. However, herbaria may be underutilized resources for ethnobotanical research that depends on the analysis of large datasets compiled across multiple sites. Here, we compare two medicinal use datasets, one sourced from published papers and the other from online herbaria to determine whether herbarium and published data are comparable and to what extent herbarium specimens add new data and fill gaps in our knowledge of geographical extent of plant use. Using Brazilian legumes as a case study, we compiled 1400 use reports from 105 publications and 15 Brazilian herbaria. Of the 319 species in 107 genera with cited medicinal uses, 165 (51%) were recorded only in the literature and 55 (17%) only on herbarium labels. Mode of application, plant part used, or therapeutic use was less often documented by herbarium specimen labels (17% with information) than publications (70%). However, medicinal use of 21 of the 128 species known from only one report in the literature was substantiated from independently collected herbarium specimens, and 58 new therapeutic applications, 25 new plant parts, and 16 new modes of application were added for species known from the literature. Thus, when literature reports are few or information-poor, herbarium data can both validate and augment these reports. Herbarium data can also provide insights into the history and geographical extent of use that are not captured in publications

Dielectric behaviour of Hf-doped CaCu3Ti4O12 ceramics obtained by conventional synthesis and reactive sintering

CaCu3(Ti4xHfx)O12 ceramics (JC = 0.04, 0.1 and 0.2) were prepared by conventional synthesis (CS) and through reactive sintering (RS), in which synthesis and sintering of the material take place in one single step. The microstructure and the dielectric properties of Hf-doped CCTO (CCTOHf) have been studied by XRD, FE-SEM, AFM, Raman and impedance spectroscopy (IS) in order to correlate the structure, microstructure and the electrical properties. Samples prepared by reactive sintering show slightly higher dielectric constant than those prepared by conventional synthesis in the same way than the pure CCTO. Dielectric constant and dielectric losses decrease slightly increasing Hf content. For CCTOHf ceramics with x> 0.04 for CS and x> 0.1 for RS, a secondary phase HfTi04 appears. As expected, the reactive sintering processing method allows a higher incorporation of Hf in the CCTO lattice than the conventional synthesis one

Product development: Ergonomic support tool for hydraulic bolting

This thesis is about product development and manufacturing based on ideas gathered from personal experience from the industry. By performing bolt inspection at the top flange in a wind turbine, where the operator manually holds the heavy torque wrench, an idea was formed to find a solution where the job could be done safer, faster and more comfortably. Both group members were interested in coming up with a project where they could be working with the theoretical aspects of development, design and calculations in combination with the physical manufacturing of a final product. The scientific approach of this thesis is based on Action based research, Case study research and Product Development Process (PDP), where the group have mainly depended on the principals and methods of the product development process. Through brain storming, discussions with other bolting operators from the work in the wind turbines and more formal interviews with the most experienced field engineer in Hytorc Norge, data was gathered to start the process of finding the key attributes of the support tool. After having generated and discarded different concepts, a final combination of attachment bracket and lift mechanism concepts were chosen. The design was based on using existing standard parts, such as the steel pipes used for the different tube sections of the body and piston, and the spring used to drive the piston. The first part that was chosen was the spring driving the piston, and from there the group could start choosing the other components. If the tool were to be designed without taking the dimensions of the standard components into account from the start, it would likely turn out very difficult or even impossible to manufacture. It would be a hard realization to find out that there are no springs available with a sufficient spring constant in the needed diameter and length after all other dimensions were set. Taking this approach has made a design that is highly over-dimensioned for buckling and plastic deformation, but it is a design that can be made with existing parts available on the market. Through the project the group has been working a lot with Autodesk Inventor. In the beginning for making the first drafts for the concepts, to in the end doing the full assemblies and final revisions of the drawings. Mechanical strength calculations have been made by a combination of “hand calculations” in MathCad Prime and Ansys Mechanical for buckling analysis and other calculations. For the manufacturing, a lot of different tools and techniques have been used. Additive layer manufacturing has been used for prototypes and final parts. For the remaining steel parts, everything has been manufactured by CNC machines. By making use of use of Marcus’ experience with machining, the CNC programs used has been created by the group itself. The manufacturing and the testing and refinement processes each had their unforeseen challenges. The group has done a lot of modifications and found creative solutions to the different challenges that iii arose. Dealing with these real-life challenges is a part of what makes this kind of thesis special. There are a lot more complications to doing actual manufacturing than to making a model to do analysis on in Inventor 3D-space. After a lot of work and modifications a final product was formed. The project has been very interesting and educational. New tools and techniques have been learned, and the process has given a lot of perspective regarding all the factors that needs to be taken to account to create a well-functioning product. Both the group and Hytorc were pleased with the final product. A demonstration of the work scenario and the finished tool can be seen on Vimeo: https://vimeo.com/826654158This thesis is about product development and manufacturing based on ideas gathered from personal experience from the industry. By performing bolt inspection at the top flange in a wind turbine, where the operator manually holds the heavy torque wrench, an idea was formed to find a solution where the job could be done safer, faster and more comfortably. Both group members were interested in coming up with a project where they could be working with the theoretical aspects of development, design and calculations in combination with the physical manufacturing of a final product. The scientific approach of this thesis is based on Action based research, Case study research and Product Development Process (PDP), where the group have mainly depended on the principals and methods of the product development process. Through brain storming, discussions with other bolting operators from the work in the wind turbines and more formal interviews with the most experienced field engineer in Hytorc Norge, data was gathered to start the process of finding the key attributes of the support tool. After having generated and discarded different concepts, a final combination of attachment bracket and lift mechanism concepts were chosen. The design was based on using existing standard parts, such as the steel pipes used for the different tube sections of the body and piston, and the spring used to drive the piston. The first part that was chosen was the spring driving the piston, and from there the group could start choosing the other components. If the tool were to be designed without taking the dimensions of the standard components into account from the start, it would likely turn out very difficult or even impossible to manufacture. It would be a hard realization to find out that there are no springs available with a sufficient spring constant in the needed diameter and length after all other dimensions were set. Taking this approach has made a design that is highly over-dimensioned for buckling and plastic deformation, but it is a design that can be made with existing parts available on the market. Through the project the group has been working a lot with Autodesk Inventor. In the beginning for making the first drafts for the concepts, to in the end doing the full assemblies and final revisions of the drawings. Mechanical strength calculations have been made by a combination of “hand calculations” in MathCad Prime and Ansys Mechanical for buckling analysis and other calculations. For the manufacturing, a lot of different tools and techniques have been used. Additive layer manufacturing has been used for prototypes and final parts. For the remaining steel parts, everything has been manufactured by CNC machines. By making use of use of Marcus’ experience with machining, the CNC programs used has been created by the group itself. The manufacturing and the testing and refinement processes each had their unforeseen challenges. The group has done a lot of modifications and found creative solutions to the different challenges that iii arose. Dealing with these real-life challenges is a part of what makes this kind of thesis special. There are a lot more complications to doing actual manufacturing than to making a model to do analysis on in Inventor 3D-space. After a lot of work and modifications a final product was formed. The project has been very interesting and educational. New tools and techniques have been learned, and the process has given a lot of perspective regarding all the factors that needs to be taken to account to create a well-functioning product. Both the group and Hytorc were pleased with the final product. A demonstration of the work scenario and the finished tool can be seen on Vimeo: https://vimeo.com/82665415

New Avenues for the chemical modification of 1D and 2D nanomaterials

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Orgánica. Fecha de lectura: 30-06-2017En este trabajo se presentan tres resultados principales: i) El uso de naftaleno bisimidas como motivo de reconocimeinto para la síntesis de derivados mecánicamente enlazados de SWNTs. La naturaleza de los enlaces mecánicos y y la formación de polímeros de NDI ha sido probada a través de técnicas analíticas, espectroscópicas (TGA, NMR, UV-vis-NIR y Raman) y los correspondientes experimentos control. Además ha sido posible observar la presencia de macrociclos individules alrededor de los nanotubos gracias al microscopio de transmisión electrónica. ii) El desarrolo de un metodo simple para la modificación covalente de grafeno con una cierta periodicidad, este método se basa en la adsorción selectiva de radicales de cianometilo (CH2CN•) producidos mediante ruptura homolítica de acetonitrilo (CH3CN), El cual presenta una gran selectividad para enlazar covalentemente sobre sitios atómicos específicos del grafeno crecido sobre Ru(0001). Los resultados expermientales obtenidos fueron confirmados a través de cálculos DFT. iii) El desarrollo de fotodetectores de alto rendimiento a través de funcionalziación no covalente reversible y reproducible de dispositivos de MoS2 mediante el uso de distintas moléculas. A través de este trabajo hemos obtenido un incremento de la fotorespuesta de cuatro órdenes de magnitud y responsividades de hasta 100AW-1.In this work we presented three main results: i) The use of naphthalene bisimides as recognition motifs for the synthesis of mechanicallyinterlocked derivatives of SWNTs. The mechanically interlocked nature and polymer wrapping of NDI was probed by analytical and spectroscopic techniques (TGA, NMR, UVvis- NIR and Raman) and adequate control experiments. Furthermore, individual macrocycles were be seen around the nanotubes under TEM scrutiny. ii) The development of a simple method for the covalent modification of graphene with strict spatial periodicity at the nanometer scale, based on selective adsorption of cyanomethyl radicals (CH2CN•) produced by homolytic breaking of acetonitrile (CH3CN), which present a nearly complete selectivity to bind covalently to graphene grown on Ru(0001) on specific atomic sites. The results obtained experimentally were validated through Density Functional Theory (DFT) calculations. iii) The development of a high performance photodetector through reversible, and reproducible noncovalent functionalization of MoS2-devices with molecular dyes. We found an enhancement of the photoresponse of four orders of magnitude and responsivities up to 100 AW-1

Estudio de materiales cerámicos de alta constante dielétrica basados en CaCu3Ti4O12

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Inorgánica. Fecha de lectura: 16-12-201