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Evaluation of Biodegradation in Aqueous Medium of Poly(Hydroxybutyrate-Co-Hydroxyvalerate)/Carbon Nanotubes Films in Respirometric System

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Journal of Renewable Materials 2019年第2期7卷 117-128页

作者： Larissa Stieven Montagna Isabela CÉSAR Oyama Rita de CÁSSIA Barbosa Camargo Lamparelli Ana Paula Silva THAIS Larissa do Amaral Montanheiro Ana Paula Lemes Federal University of São Paulo(UNIFESP) Institute of Science and TechnologyTechnology Laboratory of Polymers and Biopolymers(TecPBio)Talim330São Josédos CamposSP12231-280BrazilSão Josédos CamposSPBrazil

Biodegradable polymers have been increasingly used for scientific and commercial applications because they are similar to some conventional thermoplastics and exhibit the ability of ***(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)nanocomposites films with 1 and 2 wt% of carbon nanotubes(CNT)were prepared by solution mixing,followed by solvent *** this work,PHBV/CNT nanocomposites were submitted to biodegradation in an aqueous medium for 34 days through a respirometric ***,the PHBV films were analyzed by the CO2 production and mineralization as a response of a microbial attack,which was monitored by back titration during all the *** films were also characterized by measuring the weight loss;crystallinity was evaluated by differential scanning calorimetry(dsC)and the surface morphology by scanning electron microscopy(SEM).By analyzing the weight loss of the films,it was observed that adding CNT increases the resistance to biodegradation *** obtained values of CO2 production and mineralization of the samples,as well as the values of weight loss,showed that the biodegradation of PHBV/CNT nanocomposites was minor in comparison to neat *** addition of CNT in PHBV matrix influences the surface morphology,causing the presence of cavities and an increase of roughness.

关键词： Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) carbon nanotube nanocomposites biodegradation in aqueous medium

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Why Sustainable Porous Carbon Should be Further Explored as Radar-Absorbing Material? A Comparative Study with Different Nanostructured Carbons

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Journal of Renewable Materials 2024年第10期12卷 1639-1659页

作者： Alan F.N.Boss Manuella G.C.Munhoz Gisele Amaral-Labat Rodrigo G.A.Lima Leonardo I.Medeiros Nila C.F.L.Medeiros Beatriz C.S.Fonseca Flavia L.Braghiroli Guilherme F.B.Lenz e Silva Department of Metallurgical and Materials Engineering University of de São PauloAvenida Mello MoraesCidade UniversitáriaSão PauloSP 05508-030Brazil Coordination of Applied Research and Technological Development National Institute for Space ResearchAvenida dos AstronautasJardim da GranjaSão Josédos CamposSP 12227-010Brazil Department of Exact and Technological Sciences Santa Cruz State UniversityRodovia Jorge Amadokm16IlhéusBA 45662900Brazil Institut de recherche sur les forêts Universitédu Québec en Abitibi-TémiscamingueRouyn-Noranda445 Bd de l’UniversitéRouyn-NorandaQC J9X 5E4Canada

Radar Absorbing Materials(RAM)are a class of composites that can attenuate incident electromagnetic waves to avoid radar *** carbon allotropes that have the potential to be used as RAM are either carbon nano-tubes(CNTs),graphene,carbon black(CB)and ultimately,sustainable porous carbon(SPC).Here,black wattle bark waste(following tannin extraction)was used as a sustainable source to produce SPC made from biomass *** was characterized and used as afiller for a silicone rubber matrix to produce aflexible *** elec-tromagnetic performance of this composite was compared with composites made with commercial CB and CNT through reflection loss(RL),where-10 dB is equivalent to 90%of *** composites were evaluated in single-layer,double-layer,and as radar absorbing structures(RAS)with the aim of improving their effective absorption bandwidth(EAB)performances and a reduction in *** CNT composite presented a RL of-26.85 dB at 10.89 GHz and an EAB of 2.6 GHz with a 1.9 mm thickness,while the double-layer structures using CNT and SPC provided a RL of-19.74 dB at 10.75 GHz and an EAB of 2.51 ***,the double-layer structures are~42%cheaper than the composite using only CNT since less material is ***,the largest EAB was achieved with a RAS using SPC,reaching~2.8 GHz and a RL of-49.09 dB at 10.4 ***,SPC made of black wattle bark waste can be a competitive,alternative material for use as RAM and RAS since it is cheaper,sustainable,and suitable for daily life uses such as absorbers for anechoic chambers,sensors,and elec-tromagnetic interference shields for electronics,wallets,vehicles,and others.

关键词： Microwave absorption material tannin waste dielectric constant carbon composite reflectivity

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MJO Modulation of Station Rainfall in the Semiarid Serido,Northeast Brazil

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Atmospheric and Climate Sciences 2015年第4期5卷 408-417页

作者： Cati E.A.Valadao Paulo S.Lucio Rosane R.Chaves Leila M.V.Carvalho Programa de Pos-Graduacao em Ciencias Climaticas Universidade Federal do Rio Grande do NorteNatalBrazil Earth Research Institute and Department of Geography University of CaliforniaSanta BarbaraUSA

The influence of the Madden Julian Oscillation (MJO) on station rainfall over the Seridó region of Rio Grande do Norte state, Northeast Brazil is examined based on 17 raingauge daily data over 30-year period (1 January-31 December, 1981-2010). The Seridó is one of the driest regions in Northeast Brazil and is recognized as particularly vulnerable to desertification by the United Nations Convention to Combat Desertification. Firstly, daily anomalies were calculated by removing the 30-year daily climatology. Then, to distinguish the MJO signal from other patterns of climate variability, the daily anomalies were band pass filtered in the frequency domain (20 - 90 days) by applying Fast Fourier Transform (FFT). Composites of rainfall anomalies were computed for each of the eight phases of the MJO during February-May (FMAM) rainy season, based on the Jones-Carvalho MJO index. Only days classified as MJO events were considered in the composites. For each phase composite, statistical significance tests were computed independently at each individual station by applying a two-tailed Student’s t-test at 5% significance level. Preliminary results showed that the rainfall anomalies have a spatial coherence throughout the MJO cycle. Extreme positive (negative) anomalies occurred in phase 2 (phase 5), where 13 (12) out of the 17 stations showed statistically significant anomalies in the range of 0.9 - 1.9 mm/day (0.8 - 1.7 mm/day). The typical difference between the wet MJO phase 2 and dry phase 5 represented at least 50% modulation of the daily mean rainfall.

关键词： Madden-Julian Oscillation Intraseasonal Raingauge

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