Figure 1:
XRD patterns of: a) as received untreated alumina powder; b) raw alumina after heat treatment of the as-received alumina (heating rate of 10 °C/min, in ambient air, at 1300 °C for 90 min), used for the preparation of the porous alumina ceramic samples; and c) sintered product obtained using 60 wt% of ground sunflower seed shells (SSS).
Figura 1:
Padrões de DRX de: a) pó de alumina como recebido, não tratado; b) alumina de partida após tratamento térmico da alumina recebida (taxa de aquecimento de 10 °C/min, ao ar, a 1300 °C por 90 min), utilizada na preparação das amostras de cerâmica de alumina porosa; e c) produto sinterizado obtido utilizando 60% em massa de cascas de sementes de girassol moídas (SSS).
Figure 2:
TGA curve (a) of the as-received untreated alumina powder (heating rate of 10 °C/min, in ambient air); and TGA (b) and DSC (c) curves of the used SSS (heating rate of 5 °C/min, in ambient air).
Figura 2:
Curva de TGA (a) do pó de alumina como recebido, não tratado (taxa de aquecimento de 10 °C/min, ao ar); e curvas de TGA (b) e DSC (c) de SSS usado (taxa de aquecimento de 5 °C/min, ao ar).
Figure 5:
Total (a), open (b), and closed (c) porosity of small alumina ceramic pellets (compacted at 125 MPa), and total porosity (d) of large disks (compacted at 38 MPa) versus the SSS content in the green bodies.
Figura 5:
Porosidade total (a), aberta (b) e fechada (c) de pequenos discos de alumina (compactados a 125 MPa) e porosidade total (d) de discos grandes (compactados a 38 MPa) versus o teor de SSS nos corpos verdes.
Figure 6:
SEM micrographs of porous alumina ceramic samples prepared with SSS content of 0 wt% (A), 20 wt% (B), 40 wt% (C), and 60 wt% (D).
Figura 6:
Micrografias de MEV de amostras de alumina porosa preparadas com teor de SSS de 0 wt% (A), 20 wt% (B), 40 wt% (C) e 60 wt% (D).
Figure 9:
Weibull plots for the tensile strength data of the porous alumina samples prepared with SSS content of 0 wt% (a), 20 wt% (b), 40 wt% (c), and 60 wt% (d).
Figura 9:
Gráficos de Weibull para os dados de resistência à tração das amostras de alumina porosas preparadas com teor de SSS de 0 wt% (a), 20 wt% (b), 40 wt% (c) e 60 wt% (d).
Figure 11:
Indirect tensile strength measured by the Brazilian disk test for porous alumina ceramics prepared by the sacrificial phase method with different pore formers (PFs): a) sunflower seed shells (this study); b) graphite waste 1212 M.S. Ali, M.A.A. Hanim, S.M. Tahir, C.N.A. Jaafar, M. Norkhairunnisa, K.A. Matori, J. Ceram. Soc. Jpn. 125, 5 (2017) 402.; c) active yeast 1212 M.S. Ali, M.A.A. Hanim, S.M. Tahir, C.N.A. Jaafar, M. Norkhairunnisa, K.A. Matori, J. Ceram. Soc. Jpn. 125, 5 (2017) 402.; d) commercial rice husk ash 1212 M.S. Ali, M.A.A. Hanim, S.M. Tahir, C.N.A. Jaafar, M. Norkhairunnisa, K.A. Matori, J. Ceram. Soc. Jpn. 125, 5 (2017) 402.; and e) naphthalene 2121 S. Surabhi, “Production of alumina based porous ceramics using naphthalene as the pore former”, Bach. Thesis, Nat. Inst. Technol., Rourkela (2012)..
Figura 11:
Resistência à tração indireta medida pelo ensaio de compressão diametral para cerâmicas porosas de alumina preparadas pelo método da fase de sacrifício com diferentes formadores de poros: a) cascas de sementes de girassol (este estudo); b) resíduo de grafita 1212 M.S. Ali, M.A.A. Hanim, S.M. Tahir, C.N.A. Jaafar, M. Norkhairunnisa, K.A. Matori, J. Ceram. Soc. Jpn. 125, 5 (2017) 402.; c) levedura ativa 1212 M.S. Ali, M.A.A. Hanim, S.M. Tahir, C.N.A. Jaafar, M. Norkhairunnisa, K.A. Matori, J. Ceram. Soc. Jpn. 125, 5 (2017) 402.; d) cinza comercial de casca de arroz 1212 M.S. Ali, M.A.A. Hanim, S.M. Tahir, C.N.A. Jaafar, M. Norkhairunnisa, K.A. Matori, J. Ceram. Soc. Jpn. 125, 5 (2017) 402.; e e) naftaleno 2121 S. Surabhi, “Production of alumina based porous ceramics using naphthalene as the pore former”, Bach. Thesis, Nat. Inst. Technol., Rourkela (2012)..
