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.

No início deste ano o LAMATE participou do Electronic Materials and Applications 2017, em Orlando nos Estados Unidos, realizado pela The American Ceramic Society. Neste congresso foram apresentados três 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.

Nanostructured ZnO/Graphene xerogels with photosensing properties

I. C. Cezário*1 ; D. Muller2 ; F. R. Moreira1 ; C. R. Rambo1 ; 1. Federal University of Santa Catarina, Brazil; 2. Federal University of Santa Catarina, Brazil

Graphene based nanocomposites with emerging optoelectronic properties have been developed for applications as photodiodes and solar cells. In this work ZnO/graphene nanocomposites were produced in situ with different graphene concentrations through the sol-gel method. Drying in air for 24 h led to a bulk xerogel structure. Electrical characterization was performed by tracing the I-V curves of the nanocomposites in the dark and under different illumination conditions (visible and UV light). Significant current variation, from 10 nA to 10 μA, was observed for the different graphene containing samples depending on the wavelength and light intensity. Moreover the photocurrent increased with graphene content for the same lightning condition. The highest photosensibility was recorded for the nanocomposite with 5 wt.% graphene. The results indicate the potential of the developed ZnO/Graphene nanocomposite in applications like photodiodes, photoresistors and solar cells.

Nanostructured ZnO/graphene for hybrid supercapacitor devices

I. C. Cezário*1 ; F. R. Moreira1 ; D. Muller2 ; C. R. Rambo1 ; 1. Federal University of Santa Catarina, Brazil; 2. Federal University of Santa Catarina, Brazil

The development of complementary energy storage devices has been study in the last years. Efforts have been made to satisfy the requirements of electrochemical energy storage, such as supercapacitors, using materials with high cost-benefit relation. Transitions metal oxides, like ZnO, are promising materials for supercapacitors due to their excellent pseudocapacitive properties, fast and reversible redox reactions. Graphene, on the other hand exhibits high electrical conductivity and suitable double layer properties for supercapacitors. In this work, ZnO/graphene nanocomposites were produced by sol-gel process. Graphene was incorporated in situ in different concentrations, from 3 wt.% to 10 wt.%(relative to the precursor, ZnCl2). Supercapacitors were assembled using the nanocomposites as active electrodes and PVA/H3PO4 as gel electrolyte. The device mounted with pure ZnO presented specific capacitance of 19 F/g. Incorporation of graphene provided a double layer capacitance in addition to the pseudocapacitance of the ZnO. The ZnO/3%graphene device presented a capacitance of 423F/g, while the ZnO/5% graphene presented 378F/g. Addition of 10%graphene, however decreased the specific capacitance to 161F/g. The device assembled with ZnO/ 3%graphene presented values of energy density and power density that classify them in the supercapacitor category, delivering a maximum energy density of 2.5Whkg-1 and a maximum power density of 96kWkg-1.

Modeling multicomponent circuits in ZnO\graphene nanocomposites: A bottom-up approach

I. C. Cezário*1 ; D. Muller3 ; F. R. Moreira2 ; G. A. de Barros2 ; H. P. Roldán2 ; C. R. Rambo2 ; 1. Federal University of Santa Catarina, Brazil; 2. Federal University of Santa Catarina, Brazil; 3. Federal University of Santa Catarina, Brazil

Nanocircuits are being developed for diverse applications from increasing computer performance to new tools for medicine and especially in nanoeletronics. In this work, bulk ZnO/Graphene nanocomposites were produced through an in situ sol-gel method, followed by controlled drying. The nanostructured gels were electrically characterized through I-V curves under different input conditions and their behavior was modelled using multicomponent circuits where the synthesis parameters, final compositions and working electrodes could be related to the elements of the equivalent integrated circuit. Graphene (50-100 nm) with concentrations in the range of 1-10 wt.% was in situ incorporated into zinc oxide gel precursor during gel synthesis. The nanocomposites were characterized according to the crystalline structure and surface area. Modeling of the electrical behavior of the composite was performed using PSpice software. Results revealed that discrete electronic models could be extracted from the nanocomposites.

Estão disponíveis no YouTube os vídeos dos seminários dos alunos de iniciação científica do LAMATE.

Parabéns aos alunos pelos trabalhos desenvolvidos.

Bruno Neckel Wesling – Síntese e caracterização de nanoestruturas de ZnO/Al3+/Mn2- para dispositivos supercapacitivos

George Antonio Paes de Barros – Diodos Orgânicos baseados em Compósito NCB:PEDOT

Gusner Jean – Desenvolvimento de células fotovoltaicas flexíveis de alta eficiência via impressão direta

A partir do dia 22/08/2016 os serviços e as análises de caracterização de amostras, listados abaixo, realizados no LAMATE serão cobrados, via FEESC. A medida foi tomada frente à escassez de recursos para manutenção, calibração e insumos consumíveis necessários às análises e servioços.

Para informações sobre disponibilidade, agendamento e valores cobrados, envie um email ao seguinte endereço:

lamate.ufsc@gmail.com

Qualquer outra dúvida, entre em contato via email, ou pelo telefone (3721-2301). Os valores de cada serviço estarão, em breve, disponíveis no site do LAMATE.

Lista de análise e serviços cobrados:

– Análise de área superficial e porosidade (BET);

– Recobrimento de amostras via sputtering;

– Ensaios mecânicos (texturômetro);

– Análise de propriedades piezoelétricas;

– Caracterização elétrica (ponte RLC, traçador de curvas IxV e condutividade elétrica);

– Espectroscopia UV-Vis.

Electronic Materials and Applications 2017

http://ceramics.org/ema2017E