Banca de DEFESA: ADRIANA SOARES DE CARVALHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ADRIANA SOARES DE CARVALHO
DATE: 30/09/2024
TIME: 14:00
LOCAL: Programa de Pós-Graduação em Ciência de Materiais
TITLE:

NANOCOMPOSITES BASED ON GRAPHENE AEROGEL AND METAL OXIDE NANOPARTICLES (CoxFeyOz @Aerographene): Synthetic Routes and Application Prospects

KEY WORDS:

nitrogen-doped graphene; aerogel; magnetite; ferrite; ex-situ method; electromagnetic shielding; supercapacitors.

PAGES: 75
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

In this work, hybrid nanocomposites based on metal oxide nanoparticles (CoxFeyOz) and reduced graphene oxide (Aerographenes) aerogels, both undoped (rGO) and nitrogen-doped (NrGO), were synthesized using simple, scalable ex-situ approaches. Doping imparts prominent physical and mechanical properties to the aerographenes, related to porosity, surface area, flexibility, and, most notably, electrical conductivity. The NrGO exhibited 7.96 at% N, demonstrating efficient doping and a high content of active nitrogen sites in the aerogel matrix. Characteristic C-N/C=N bond bands were identified, with a high N/O ratio of 1.37. The conductive NrGO matrix showed only 5 layers, indicating excellent quality, and a mesoporous morphology with high pore interconnectivity, resulting in a surface area of 995.6 m2 /g. The rGO matrix also displayed 5 layers, but with a surface area of 738.0 m2 /g. The first method used to produce the nanocomposites was direct mixing, which allowed for a good distribution of Fe3O4 (magnetite) NPs in the NrGO aerogel matrix and explored the intriguing swelling mechanism. This mechanism led to a significant increase in surface area, reaching 1317.0 and 1456.0 m2 /g for rGO and NrGO, respectively. Direct mixing ensured that the NPs maintained the same crystal phase in the nanocomposites. This was confirmed for both Fe3O4 and CoFe2O4 (cobalt ferrite). This result was different from that obtained using the ex-situ hydrothermal method, which showed changes to more oxidized phases, such as Fe2O3 (hematite), and structures with notable morphologies. The Fe3O4@NrGO nanocomposite obtained by direct mixing was investigated in the field of electromagnetic interference shielding effectiveness (EMI SE), achieving an average of 1593 dB/cm or dB/g in the X-band range for ultra-thin and lightweight binder-free pellets. The thickness and mass-normalized values were higher than those reported in the literature. The advantages of Fe3O4@NrGO pellets were also explored for applications in energy storage systems, specifically in supercapacitors, indicating promising prospects in the current landscape.

COMMITTEE MEMBERS:
Externa à Instituição - ANDREZZA CAROLINA CARNEIRO TOMAS - IFPE
Presidente - 2457389 - EDUARDO PADRON HERNANDEZ
Externa ao Programa - 2053365 - JULIANA ANGEIRAS BATISTA DA SILVA - nullExterno à Instituição - RAMÓN RAUDEL PEÑA GARCIA - UFRPE
Externo à Instituição - YURIMILER LEYET RUIZ - UFAM