Effect of fiber alignment in gelled electrospun membranes based on poly(vinylidene fluoride) for battery applications

Battery separators based on electrospun membranes of poly(vinylidene fluoride) (PVDF) have been prepared in order to study the effect of fiber alignment on the performance and characteristics of the membrane. The prepared membranes show an average fiber diameter of 272 nm and a degree of porosity of 87 %. The gel polymer electrolytes are prepared by soaking the membranes in the electrolyte solution. The alignment of the fibers improves the mechanical properties for the electrospun membranes. Further, the microstructure of the membrane also plays an important role in the ionic conductivity, being higher for the random electrospun membrane due to the lower tortuosity value. Independently of the microstructure, both membranes show good electrochemical stability up to 5.0 V versus Li/Li+. These results show that electrospun membranes based on PVDF are appropriate for battery separators in lithium-ion battery applications, the random membranes showing a better overall performance.

Applying complex network theory to the understanding of high-aspect-ratio carbon-filled composites

This work demonstrates that the theoretical framework of complex networks typically used to study systems such as social networks or the World Wide Web can be also applied to material science, allowing deeper understanding of fundamental physical relationships. In particular, through the application of the network theory to carbon nanotubes or vapour-grown carbon nanofiber composites, by mapping fillers to vertices and edges to the gap between fillers, the percolation threshold has been predicted and a formula that relates the composite conductance to the network disorder has been obtained. The theoretical arguments are validated by experimental results from the literature.

Carbon Nanofiber Type and Content Dependence of the Physical Properties of Carbon Nanofiber Reinforced Polypropylene Composites

The variation of the physical properties of four differ- ent carbon nanofibers (CNFs), based-polymer nano- composites incorporated in the same polypropylene (PP) matrix by twin-screw extrusion process was investigated. Nanocomposites fabricated with CNFs with highly graphitic outer layer revealed electrical isolation-to-conducting behaviors as function of CNF’s content. Nanocomposites fabricated with CNFs with an outer layer consisting on a disordered pyro- litically stripped layer, in contrast, revealed better mechanical performance and enhanced thermal sta- bility. Further, CNF’s incorporation into the polymer increased the thermal stability and the degree of crystallinity of the polymer, independently on the filler content and type. In addition, dispersion of the CNFs’ clusters in PP was analyzed by transmitted light opti- cal microscopy, and grayscale analysis (GSA). The results showed a correlation between the filler concentration and the variance, a parameter which measures quantitatively the dispersion, for all composites. This method indicated a value of 1.4 vol% above which large clusters of CNFs cannot be dispersed effectively and as a consequence only slight changes in mechanical performance are observed. Finally, this study establishes that for tailoring the physical properties of CNF based-polymer nanocomposites, both adequate CNFs structure and content have to be chosen.

Composite synthetic hydroxyapatite 30%, in two physical states, as dermal filler

The aim of this study was to evaluate the response to the implantation of synthetic hydroxyapatite 30% (HAP-91®) in different physical states as dermal filler. Eighteen New Zealand rabbits were used, distributed randomly into two equal groups and then divided into three groups according to the postoperative period at 8, 21 and 49 days. One mL of HAP-91®, fluid and viscous, was implanted in the subcutaneous tissue, 1 cm proximal to the cranial crest of the right scapula. The thickness of the skin was measured before and after implantation and for the following 15 days. Pain sensitivity assessment was conducted, assigning the following scores: 0 - when the animal allowed the touch of the implant area and expressed no signs of pain; 1 - when the animal allowed the touch, but pain reaction occurred, like increase of the respiratory rate or attempt to escape; 2 - when the animal did not allow the touch to the implanted area. At 8, 21 and 49 days, biopsy of the implanted area was performed. No difference was observed between the thickness of the skin (p>0.05) and all animals received a score 0 for soreness. Histological analysis did not reveal any obvious inflammatory process, showing a predominance of mononuclear cells in samples of eight days and tissue organization around the biomaterial with a tendency to encapsulation. The results indicate that HAP-91®, both viscous and fluid, is biocompatible and suitable for dermal filling.

Effect of filler content on morphology and physical-chemical characteristics of poly(vinylidene fluoride)/NaY-zeolite filled membranes

Poly(vinylidene fluoride) electrospun membranes have been prepared with different NaY zeolite contents up to 32%wt. Inclusion of zeolites induces an increase of average fiber size from ~200 nm in the pure polymer up to ~500 nm in the composite with 16%wt zeolite content. For higher filler contents, a wider distribution of fibers occurs leading to a broader size distributions between the previous fiber size values. Hydrophobicity of the membranes increases from ~115º water contact angle to ~128º with the addition of the filler and is independent on filler content, indicating a wrapping of the zeolite by the polymer. The water contact angle further increases with fiber alignment up to ~137º. Electrospun membranes are formed with ~80 % of the polymer crystalline phase in the electroactive  phase, independently on the electrospinning processing conditions or filler content. Viability of MC3T3-E1 cells on the composite membranes after 72 h of cell culture indicates the suitability of the membranes for tissue engineering applications.

Effect of fiber orientation in gelled poly (vinylience fluoride) electrospun membranes for Li-ion battery applications

Battery separators based on electrospun membranes of poly(vinylidene fluoride) (PVDF) have been prepared in order to study the effect of fiber alignment on the performance and characteristics of the membrane. The prepared membranes show an average fiber diameter of ~272 nm and a degree of porosity of ~87 %. The gel polymer electrolytes are prepared by soaking the membranes in the electrolyte solution. The alignment of the fibers improves the mechanical properties for the electrospun membranes. Further, the microstructure of the membrane also plays an important role in the ionic conductivity, being higher for the random electrospun membrane due to the lower tortuosity value. Independently of the microstructure, both membranes show good electrochemical stability up to 5.0 V versus Li/Li+. These results show that electrospun membranes based on PVDF are appropriate for battery separators in lithium-ion battery applications, the random membranes showing a better overall performance.

The surplus value of Azorean macroalgae as health-promoting food. Protein, fiber, carbohydrates, lipids and vitamins determination

AICMA 2012 (BIT's 1st Annual International Congress of Marine Algae), World Expo Center, Dalian, China, 20-23 de Setembro.

Layer-by-layer immobilization of carbon dots fluorescent nanomaterials on single optical fiber

We report within this paper the development of a fiber-optic based sensor for Hg(II) ions. Fluorescent carbon nanoparticles were synthesized by laser ablation and functionalized with PEG200 and N-acetyl-l-cysteine so they can be anionic in nature. This characteristic facilitated their deposition by the layer-by-layer assembly method into thin alternating films along with a cationic polyelectrolyte, poly(ethyleneimine). Such films could be immobilized onto the tip of a glass optical fiber, allowing the construction of an optical fluorescence sensor. When immobilized on the fiber-optic tip, the resultant sensor was capable of selectively detecting sub-micromolar concentrations of Hg(II) with an increased sensitivity compared to carbon dot solutions. The fluorescence of the carbon dots was quenched by up to 44% by Hg(II) ions and interference from other metal ions was minimal.

The D1822V APC polymorphism interacts with fat, calcium, and fiber intakes in modulating the risk of colorectal cancer in Portuguese persons

Background - Both genetic and environmental factors affect the risk of colorectal cancer (CRC). Objective - We aimed to examine the interaction between the D1822V polymorphism of the APC gene and dietary intake in persons with CRC. Design - Persons with CRC (n = 196) and 200 healthy volunteers, matched for age and sex in a case-control study, were evaluated with respect to nutritional status and lifestyle factors and for the D1822V polymorphism. Results - No significant differences were observed in energy and macronutrient intakes. Cases had significantly (P < 0.05) lower intakes of carotenes, vitamins C and E, folate, and calcium than did controls. Fiber intake was significantly (P = 0.004) lower in cases than in controls, whereas alcohol consumption was associated with a 2-fold risk of CRC. In addition, cases were significantly (P = 0.001) more likely than were controls to be sedentary. The homozygous variant for the APC gene (VV) was found in 4.6% of cases and in 3.5% of controls. Examination of the potential interactions between diet and genotype found that a high cholesterol intake was associated with a greater risk of colorectal cancer only in noncarriers (DD) of the D1822V APC allele (odds ratio: 1.66; 95% CI: 1.00, 2.76). In contrast, high fiber and calcium intakes were more markedly associated with a lower risk of CRC in patients carrying the polymorphic allele (DV/VV) (odds ratio: 0.50; 95% CI: 0.27, 0.94 for fiber; odds ratio: 0.51; 95% CI: 0.28, 0.93 for calcium) than in those without that allele. Conclusion - These results suggest a significant interaction between the D1822V polymorphism and the dietary intakes of cholesterol, calcium, and fiber for CRC risk.

Estudo de uma solução alternativa para o prolongamento do Molhe - Cais do Porto das Velas, Açores

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil Especialização em Hidráulica

Material compósito - propriedades do aglomerado de gesso e partículas fragmentadas de bambu (phyllostachys edulis)

Neste trabalho estudou-se um compósito de gesso FGD reforçado com fibras vegetais. As fibras utilizadas neste estudo são provenientes de bambu da espécie Phyllostachys edulis e foram trituradas até se obter uma granulometria apropriada à composição de uma pasta de gesso que permitisse a execução de placas de gesso laminado. As placas produzidas foram ensaiadas à flexão e posteriormente submetidas à análise de humidade para aferir a percentagem de água de cristalização nas amostras. Foram ainda produzidos provetes cúbicos com 7cm de aresta para permitira a execução de ensaio à compressão. Foram produzidos dois tipos de pastas, uma sem a adição de partículas de bambu (controlo) e outra com adição de 15% de partículas de bambu.

Optical fiber sensor for Hg(II) based on carbon dots

An optical fiber sensor for Hg(II) in aqueous solution based on sol–gel immobilized carbon dots nanoparticles functionalized with PEG200 and N-acetyl-l-cysteine is described. This sol–gel method generated a thin (about 750 nm), homogenous and smooth (roughness of 2.7±0.7 a˚ ) filmthat immobilizes the carbon dots and allows reversible sensing of Hg(II) in aqueous solution. A fast (less than 10 s), reversible and stable (the fluorescence intensity measurements oscillate less than 1% after several calibration cycles) sensor system was obtained. The sensor allow the detection of submicron molar concentrations of Hg(II) in aqueous solution. The fluorescence intensity of the immobilized carbon dots is quenched by the presence of Hg(II) with a Stern-Volmer constant (pH = 6.8) of 5.3×105M−1.

Análise de tecnologias de impermeabilização e isolamento em reabilitação da envolvente de edifícios

Neste trabalho é abordado o estágio efectuado por um período de sete meses na E.A. (Engenheiros Associados) e um estudo de caso sobre as tecnologias aplicadas no isolamento térmico de paredes exteriores. Na primeira parte deste relatório é efectuada uma breve caracterização da empresa e da sua actividade no mercado. A Engenheiros e Associados tem a sua estrutura assente nos seguintes sectores: Técnico-Comercial, de Aprovisionamento e de Gestão Administrativa; da qual foi efectuada uma descrição do trabalho desenvolvido em cada um desses sectores, nomeadamente a permanência na obra e as visitas e diligências às obras. A segunda parte deste relatório, que é a parte fulcral do trabalho desenvolvido, assenta sobre o sistema de ETICS (External Thermal Insulation Composite System), ou seja, o sistema de reboco delgado armado sobre isolamento térmico. Foi utilizado o sistema Cappotto na Obra de Requalificação da Urbanização de Vila d’Este – 1ª Fase. Após uma breve apresentação e evolução da história do ETICS ao longo do tempo, é exposta a caracterização da obra onde vai ser aplicado o sistema, que recai sobre a tipologia dos edifícios. Refira-se que, neste relatório, os edifícios por serem de construção túnel se dividem em três tipos: tipo plana ou corrente, tipo ângulo e tipo topo. Na Analise de Patologias efectuada evidenciam-se as fissuras e a humidade presentes em quase toda a extensão dos referidos edifícios antes do tratamento, tornando-as assim as principais anomalias destes edifícios. Foram elemento de foco as anomalias existentes nos edifícios, como: Deterioração do fibrocimento; Insuficiência das caleiras; Deficiências das impermeabilizações; Ausência de rufos; Deficiência das ligações; Degradação do revestimento e pintura; Fissuração do reboco; Degradação dos forros exteriores; Deterioração das padieiras; Deterioração dos peitoris; Deterioração das juntas de dilatação; Infiltrações e condensações; Ruptura das canalizações; Deslocamentos; Deficiências de ventilação; Deficiências de estanqueidade; Inexistência de Sistema de combate a incêndios. Para estas patologias são apresentadas as propostas de solução de forma a eliminar as mesmas. Sendo o ETICS escolhido por ser o sistema que elimina a maior parte destas patologias, tendo em conta uma relação de qualidade/preço, é abordada de uma forma detalhada e extensiva da aplicação do sistema antes, durante e depois da obra em si. Assim como, é feita uma descrição pormenorizada do material utilizado para a implementação do sistema. A análise dos pontos críticos refere-se a zonas sensíveis onde há a necessidade de reforço do sistema com vista a eliminar o aparecimento posterior de patologias, como por exemplo as características de suporte. Após a aplicação do sistema podem aparecer algumas patologias das quais se destaca o facto dos produtos serem preparados em obra, o erro humano nas dosagens do fabricante e no acrescento de água sem necessidade e a par das condições climatéricas, são as causas mais comuns do aparecimento de anomalias no sistema de ETICS, provocando fissurações e infiltrações, que são descritas neste relatório. É também abordada a manutenção e reparação do sistema, onde a manutenção refere-se à lavagem e à remoção de microorganismos das paredes e posterior pintura. A reparação dos danos divide-se em dois tipos, áreas até 2 cm2 e áreas maiores que 2 cm2. Por fim, são apresentados alguns rendimentos, que foram possíveis obter ao longo do desenvolvimento do trabalho, dos materiais e da mão-de-obra, dando origem aos custos directos. Sendo também abordadas as vantagens e desvantagens do sistema desde o seu início até à sua conclusão.

Determination of ochratoxin A in bread: evaluation of microwave-assisted extraction using an orthogonal composite design coupled with response surface methodology

An analytical method using microwave-assisted extraction (MAE) and liquid chromatography (LC) with fluorescence detection (FD) for the determination of ochratoxin A (OTA) in bread samples is described. A 24 orthogonal composite design coupled with response surface methodology was used to study the influence of MAE parameters (extraction time, temperature, solvent volume, and stirring speed) in order to maximize OTA recovery. The optimized MAE conditions were the following: 25 mL of acetonitrile, 10 min of extraction, at 80 °C, and maximum stirring speed. Validation of the overall methodology was performed by spiking assays at five levels (0.1–3.00 ng/g). The quantification limit was 0.005 ng/g. The established method was then applied to 64 bread samples (wheat, maize, and wheat/maize bread) collected in Oporto region (Northern Portugal). OTAwas detected in 84 % of the samples with a maximum value of 2.87 ng/g below the European maximum limit established for OTA in cereal products of 3 ng/g.

Mix design process of polyester polymer mortars modified with recycled GFRP waste materials

In this study, the effect of incorporation of recycled glass fibre reinforced plastics (GFRP) waste materials, obtained by means of shredding and milling processes, on mechanical behaviour of polyester polymer mortars (PM) was assessed. For this purpose, different contents of GFRP recyclates, between 4% up to 12% in weight, were incorporated into polyester PM materials as sand aggregates and filler replacements. The effect of the addition of a silane coupling agent to resin binder was also evaluated. Applied waste material was proceeding from the shredding of the leftovers resultant from the cutting and assembly processes of GFRP pultrusion profiles. Currently, these leftovers as well as non-conform products and scrap resulting from pultrusion manufacturing process are landfilled, with additional costs to producers and suppliers. Hence, besides the evident environmental benefits, a viable and feasible solution for these wastes would also conduct to significant economic advantages. Design of experiments and data treatment were accomplish by means of full factorial design approach and analysis of variance ANOVA. Experimental results were promising toward the recyclability of GFRP waste materials as partial replacement of aggregates and reinforcement for PM materials, with significant improvements on mechanical properties of resultant mortars with regards to waste-free formulations.