XVI SBPMat 2017 Gramado
Em setembro de 2017 LAMATE participou do XVI Brazilian MRS meeting, em Gramado no Rio Grande do Sul, realizado pela Brazilian Materials Research Society. Neste congresso foram apresentados alguns dos trabalhos desenvolvidos no laboratório.
Parabéns a todos os envolvidos pela participação.
Todos os resumos do evento podem ser conferidos aqui.
Na sequência temos resumos dos trabalhos apresentados, oralmente e em posters, respectivamente.
Modeled Perovskite solar cell’s efficiency basedon state of the art material properties
Manfred Georg Kratzenberg1, Carlos Renato Rambo1, Ricardo Ruther1 ;
1 Federal University of Santa Catarina, Brazil;
Organic-inorganic hybrid perovskite solar cells (PSCs) are thin film solar cells,which can be assembled at relatively low temperatures in comparison to otherstate-of-the-art solar cells, presenting, therefore, a manufacturing process whichdemands low energy, while its state-of-the-art efficiency is relatively high. Thiswork presents, by means of an analytical model simulation, the maximal possibleconversion efficiency by combining the state-of-the-art manufacturing methods toproduce the highest efficient PSC. The combined application of the state-of-the-art materials for PSCs to the analytical PSC model returned a complete set ofideal material properties. Those properties are necessary to manufacture a solarcell that presents the highest possible efficiency with state of the art methods. Asresults two modeled I-V curves, of an ideal perovskite solar cell are obtained: (i)the curve in the dark and (ii) the curve under reference light conditions, fromwhich the power conversion efficiency (PCE) in the maximum power point (MPP)is calculated are presented.
High surface niobium oxide ambigel forsimulated nuclear waste immobilization
Graciano Bay de Souza1, Daliana Muller1, Sonia Regina H. Mello-Castanho2,Gilberto Falk1, Dachamir Hotza1, Carlos Renato Rambo1
1Universidade Federal de Santa Catarina, 2Nuclear and Energy Research Institute
Niobium is predominantly found in Brazil, and it is, therefore, of great interest to find new technological applications for Nb and its compounds. It has been demonstrated that porous niobium oxide glasses can be used to trap nuclear waste [1]. Glass frits require high energy processes and high sintering temperature for their production. Ambigels on the other hand can be produced under ambient conditions (~25 °C, 1 atm.) and due to their high specific area they require much lower sintering temperatures, two characteristics that attract their use as hosts for nuclear waste immobilization [2]. In this work, we produced niobium oxide ambigels intended as host matrix for simulated multicomponent liquid nuclear waste. We synthetized ambigels using niobium pentachloride (NbCl5) as precursor, ethanol as solvent and nitric acid as catalyst. Following rapid gelation the gels were left to age in ethanol, passing to hexane through sequential solvent exchange until 100% hexane were reached. In the last step, thegels were dried under ambient conditions for 48 hours. We have produced ambigels with high specific surface area (> 110 m²/g) and amorphous niobium oxide phase. The ambigels were impregnated with saline solutions that simulate a multicomponent nuclear waste. The weight gain after thermal treatment was determined and used as indicator for the amount immobilized. Nb2O5-basedambigels can be used as a mesoporous host matrix for nuclear waste immobilization.
Synthesis and characterization of Pdincorporated TiO2 aerogels
Joseane Caroline Bernardes1, Daliana Muller1, Eloah Latocheski1, JosielDomingos1, Carlos Renato Rambo1
1Universidade Federal de Santa Catarinae
The sol-gel process for aerogel synthesis represents an efficient bottom-upstrategy for the creation of nano structures, extending the unique properties of nanomaterials to the macroscale via self-assembly. Aerogels composed by metal oxides with photocatalytic properties, like TiO2, incorporated with Pd-nanoparticles (Pd-NPs) with catalytic activity, resulting in nanocomposites with catalytic duality are of great interest for applications in catalysis processes that require no reactions’ byproducts. This work reports the synthesis and characterization of Pd-TiO2 aerogels by the sol-gel process and CO2 supercritical drying. As the mesoporous material has a large specific surface area, the catalyst contact with the reagents to be processed is optimized, which accelerates the reactions. The Pd-NPs were previously prepared from Pd(OAc)2, using KI as a reductant and PVP as a stabilizer, precipitating by centrifugation. Alcoholgels ofTiO2/Pd a solution of titanium isopropoxide with diferente Pd concentrations(0.02, 0.05 and 0.10 mmol) dispersed in etanol was prepared. This solution waskept in an ice bath and stirred. To promote the acid hydrolysis, HCl was added and, for solution gelation, propylene oxide was slowly incorporated. After gelation, ethanol was replaced by acetone and the gels were subjected to a solvent extraction process under supercritical CO2 conditions, to obtain the Pd-TiO2 aerogels. The Pd nanoparticles reacheda mean diameter of 4.2 ± 1.2 (nm)and approximately 19% of Pd-NPs. The TiO2 aerogels exhibit highly porous structures (80% to 99% porosity) with pore sizes of 0.23 ± 0.05 nm and por evolume of 0.12 ± 0.03 cm³/g, with high specific surface area (reaching 256 ± 42m²/g). The results revealed the potential of Pd-TiO2 aerogels for applications in catalysis processes.
Optoelectronic properties of flexible nanocellulose membranes incorporated with CdTe
Geneviève Kreibich Pinheiro1, Daliana Muller1, Rafael Bento Serpa1, Françoise Toledo Reis1, Marco Antonio Schiavon2, Carlos Renato Rambo1
1Universidade Federal de Santa Catarina, 2Universidade Federal de São João Del Rei
Incorporation of quantum dots (QDs) into porous matrices has driven the development of novel optical devices [1]. In this work, flexible luminescent membranes composed of CdTe/ Cellulose based on bacterial cellulose were successfully fabricated immersing bacterial nanocellulose (BNC) membranes in an aqueous solution of CdTe. CdTe/GSH QDs were prepared by size-selective precipitation technique [2]. The membranes were electrically characterized by I-V curves and IPCE measurements were performed to verify their optoelectronic properties. For IPCE analysis a thin layer of TiO2 was deposited on the membranes to form an interface with the BNC-CdTe. Fluorescence spectroscopy analysis revealed that the luminescence intensity increased with immersion timeof BNC membranes in the CdTe solution. Moreover, an enhancing in the quantum efficiency was also observed, indicating that the amount of CdTe incorporated increased with immersion time. Transmission electron microscopy (TEM) images revealed that the QDs CdTe nanoparticles were homogeneously dispersed on the cellulose nanofibers. A maximum photo current was obtained for the QDs thatexhibit an absorption peak at 536 nm. The flexible CdTe-BNC photoluminescent membranes can be useful for applications in flexible photovoltaic systems and sensors.
Nanostructured TiO2/PEDOT:PSS ambigels as Schottky barrier diodes
George Paes de Barros1, Ingrid Carolini Cezário1, Ana Beatriz Mattos1, DalianaMuller1, Carlos Renato Rambo1
1Universidade Federal de Santa Catarina
Organic semiconductor based devices, despite often suffering from disadvantages such as lower charge carrier mobility when compared to their conventional counterparts, are at an advantage regarding manufacturing costs and complexity[1]. Additionally, such manufacturing processes can be greener, less wasteful.This work examines the behavior of nanostructured TiO2/PEDOT:PSS ambigels applied as Schottky barrier diodes. The composite ambigels were prepared by incorporation through immersion of TiO2 gels in a 10 wt.% PEDOT:PSS suspension. The composite gels were subjected to several solvent exchange from ethanol to hexane and drying. The tested device used gold and tungsten electrodes applied to theTiO2/PEDOT:PSS ambigels displayed a diode behavior,albeit with a high forward voltage of approximately 2.5 V and high leakage current (500 μA at a 5 V reverse potential). These parameters may be improved upon by fine tuning the processes and concentrations. The developed ambigel-based devices can be used as low cost, low-weight diodes in a range of different electronic applications.
One-step synthesis and electrical characterization of BNC/PPy.CuO conductive membranes
Daliana Muller1, Bruno Neckel Wesling1, Dachamir Hotza1, Carlos Renato Rambo1
1Universidade Federal de Santa Catarina
The search for new flexible materials, with specific electrical properties for electronic applications has challenged researchers in recent years [1,2]. Devices that can be produced with reduced synthesis steps and low cost raw materials are of great interest for the industry. In this work, conducting polypyrrole-coated bacterial nanocellulose membranes were prepared through in situ oxidative polymerization of pyrrole on the cellulose nanofiber’s surface using copper chloride dehydrate as oxidant. The hydrated BNC membranes with 30 mm of diameter were immersed in alcoholic (Isopropyl Alcohol) solution containing the monomer Py with different concentrations and molar ratios. The polymerization was carried out at 25°C in during 4 hours. After polymerization, theBNC/PPy.CuO membranes were thoroughly washed with acetone in order to extract the byproducts and residues of the reaction and, then, vacuum dried at room temperature. The effect of polymerization conditions on electrical conductivity, morphology, dielectric constant and loss tangent of BNC/PPy.CuO was investigated. Through DRX and Raman analysis, one can observe characteristic peaks of CuO that, in turn, contributes for enhancing the electrical properties of the composites. The electrical conductivity of BNC/PPy.CuO membranes increased with increasing the monomer concentration and reaction time due to the formation of a continuous PPy.CuO layer that completely coated the nanofiber surface. It was also observed that the oxidizing agent monomer ratio influenced the electrical properties.
Characterization of flexible CB/PPy.CuO membranes for supercapacitors
Bruno Neckel Wesling1, Daliana Muller1, Dachamir Hotza1, Carlos Renato Rambo1
1Universidade Federal de Santa Catarinae-mail: brneckel@gmail.com
Advances in energy storage devices include flexible supercapacitors, which have attracted considerable attention due to their high energy density(specific/volumetric) and high power energy, in addition to long life cycle [1,2]. This work reports the electrochemical characterization of flexible bacterial nanocellulose (BNC) membranes incorporated with polypyrrole (PPy) and CuO for supercapacitors. Hydrated BNC membranes were immersed in isopropyl alcohol containing pyrrole with concentrations of 0.04 and 0.08 mol L-1. Under magnetic stirring, copper chloride dehydrate alcoholic solution was added gently as oxidantagent for polymerization. Devices were assembled by placing CB/PPy.CuO membrane disks between a 2M NaCl impregnated in BNC (separator and electrolyte). The contacts were closed with gold foils. Cyclic voltammetry was measured in a range from -1V to 1V with different scanning rates. To analyze the charge/discharge curves, the galvanostatic method was applied. A small increase in specific capacitance from 78.55 mF/cm2 to 88.75 mF/cm2 was observed with the increase of Py concentration in the BNC/PPy.CuO membranes. However, therewas a significant increase of ten times with the increase of CuCl2. The results revealed the potential of flexible, hybrid membranes for applications that require high electrical conductivity and high ionic mobility such as supercapacitors.