Banca de DEFESA: TOMAZ RODRIGUES DE ARAÚJO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : TOMAZ RODRIGUES DE ARAÚJO
DATE: 15/12/2023
TIME: 15:00
LOCAL: Google Meet
TITLE:

SYNTHESIS OF ZnFe₂O₄-Fe₂O₃-ZnO NANOCOMPOSITE VIA MICROWAVE ASSISTED SELF-COMBUSTION AND GREEN SYNTHESIS USING JATOBÁ WASTE (Hymenaea Courbaril L.)

 

KEY WORDS:

nanocomposite; ZnFe₂O₄-Fe₂O₃-ZnO; Green synthesi; Microwave-assisted self-combustion; Jatobá wood wast

PAGES: 120
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

The purpose of this work was to synthesize the ZnFe₂O₄-Fe₂O₃-ZnO nanocomposite by two synthesis routes using waste (liquid and solid) from Jatobá wood. The first route was microwave-assisted self-combustion and the second was an adaptation of the green synthesis route. The residues (liquid and solid) used were extracted by a hot process (temperatures: 50, 60, 80 ºC), and the liquid part was used in microwave-assisted self-combustion replacing water by 50 and 100%; and the solid part in green synthesis as a structure and pore driver. X-ray diffraction, scanning electron microscopy (SEM-EDS and SEM-FEG), thermogravimetric analysis; immediate analysis; calorific value and thermal capacity; to helium gas density; cellulose hemicellulose, lignin and phenolic contents; infrared spectrophotometry, Raman, in the ultraviolet and visible region, diffuse reflectance, Mossbauer, magnetic properties, in addition to particle size by light scattering (DLS) and specific area pore size volume (BJH), were the techniques used in the characterizations. In addition, yield analyzes of the extraction process and syntheses were carried out. Results: The extraction yield was close to 2% (by mass) for the aqueous extract; and greater than 70% (volume) for soluble ones. Immediate analysis shows humidity below 20%, high percentages of volatiles, low ash and fixed carbon content. The unnatural and post-extraction residues have specific heat of 950.13 to 9091.98 cal/gºC and thermal capacity (2433.10 - 2504.03 cal/ºC). ZnFe₂O₄-Fe₂O₃-ZnO was formed by the green synthesis route and ZnFe₂O₄-Fe₂O₃ by microwave-assisted self-combustion, and also the ZnFe₂O₄ phase. The crystallite size was from 14.2 to 26.39 nm, crystallinity from 40.39 to 57.45 nm and band-gap from 1.48 to 2.46 eV. Microscopies show diverse morphologies with signs of cavities and channels with orientations consistent with the orientation of the fibers. The DLS shows the residues provided stable hydrodynamic size between 507.72 and 5711.20 nm and negative surface charge. The liquid part of the waste (synthesis used in self-combustion) provided a specific area between 80.41-99.74 cm².g-1 (~100% increase) while the solid waste provided a maximum increase of 49%. Jatobá solid residues in green nanocomposite syntheses produced stable structures with low ferromagnetic properties and consistent high magnetization for applications in devices subject to alternating magnetic fields. These results show a technological application in the synthesis of these ternary nanocomposites (ZnFe₂O₄-Fe₂O₃-ZnO) capable of adding value to this class of lignocellulosic waste.

COMMITTEE MEMBERS:
Interna - 349770 - DULCE MARIA DE ARAUJO MELO
Externo ao Programa - 1674707 - MARCO ANTONIO MORALES TORRES - UFRNExterno ao Programa - 6347420 - MARCUS ANTONIO DE FREITAS MELO - UFRNExterna ao Programa - 1979301 - RENATA MARTINS BRAGA - UFRNExterno à Instituição - DENER DA SILVA ALBUQUERQUE - IFRN
Externo à Instituição - GILVAN PEREIRA DE FIGUEREDO - IFMA