Synthesis and characterization of mullite–zirconia nanostructured composite by combined mechanical activation and reaction sintering

Ashrafi, H.; Emadi, Rahmatollah; Foroushani, R. Zamani

doi:10.1016/j.apt.2015.08.001

Cited by 23 publications

(18 citation statements)

References 24 publications

(35 reference statements)

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“…Mechanical activation (MA) is an effective method to enhance the contact and the interaction of reactants. It can change the structure of reactants, such as reducing the particle size, increasing the uniformity, and forming a new surface, thus improving the reactivity of reactants [22,23]. MA combined with solid phase synthesis can greatly improve the efficiency of the reaction, simplify the operation, and make full use of mechanical energy for the activation and reaction, which can be performed using the same equipment.…”

Section: Introductionmentioning

confidence: 99%

Acylation of Lignin with Different Acylating Agents by Mechanical Activation-Assisted Solid Phase Synthesis: Preparation and Properties

et al. 2018

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Acylated lignins with substituents consisting of different lengths of carbon chains were prepared by a mechanical activation-assisted solid phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor. The structures and properties were analyzed by UV/Vis, FTIR, NMR, SEM, DSC, and TG. The results showed that the acylated lignins were successfully prepared with either non-cyclic or cyclic anhydrides as the acylating agents. Both aliphatic hydroxyl and phenolic hydroxyl groups of lignin reacted with non-cyclic anhydrides, and different reactivity of acylating agents resulted in different relative contents of phenolic and aliphatic substituents in the products. The reactivity of the cyclic anhydrides was weaker than that of the non-cyclic anhydrides, and the reactivity of the acylating agents decreased with increasing carbon chain length and unsaturated bonds of acyl groups. All of the acylated lignins except maleylated lignin had a lower glass transition temperature (Tg) than the original lignin. The acylated lignins prepared with non-cyclic anhydrides had better thermal stability than original lignin, and the thermal stability increased, but Tg decreased with an increasing chain length of the acyl groups. The acylated lignins prepared with cyclic anhydrides had higher a Tg than those with non-cyclic anhydrides with the same carbon number, and the thermal stability was not obviously improved.

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Section: Introductionmentioning

confidence: 99%

Acylation of Lignin with Different Acylating Agents by Mechanical Activation-Assisted Solid Phase Synthesis: Preparation and Properties

et al. 2018

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“…Two sets of mullite/Ag cermets were prepared with different proportions of silver (X = 0, 1, 3, 5, 10, 20 and 30 wt.%) at 1500 and 1600 °C, the Archimedes technique was used to measure the density of cermets (ρ measured ), and the relative density (ρ relative ) was calculated by the following relation: (4) where: ρ theory is the theoretical density which can be determined from the weight percentage of the phase silver and mullite according to the following equation [15]: (5) where ρ silver and ρ mullite are the densities of silver and mullite (g/cm 3 ) with their respective weight percentage, X silver and X mullite .…”

Section: Resultsmentioning

confidence: 99%

“…Mullite is an attractive potential engineering ceramic due to high strength and high creep resistance [4][5][6][7][8][9] as well as other applications at high temperature due to its high-thermal and chemical stability and the excellent thermo-shock behavior [10][11][12][13][14] owing its unique combination of properties like high melting point (1830 °C), low thermal expansion coefficient (4.5 X 10 -6 K -1 ), and low dielectric constant (ε = 56.5 at 1 MHz) [1,12]. However, mullite by itself suffers from low fracture toughness (∼ 2MPa m 1/2 ) at room temperature and difficulties in sintering to full density material [3,[15][16].…”

Section: Introductionmentioning

confidence: 99%

Effect of silver nanoparticless in the structure and mechanical properties of mullite/Ag cermets

et al. 2019

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The objective of this work was to study the influence of the addition of silver nanoparticles in the microstructure of mullite at two different temperatures of sintering (1500 and 1600 °C), in order to decrease the porosity and increase the density as well better the hardness and fracture toughness. The microstructural characteristics were studied by scanning electron microscopy, confocal scanning microscopy and X-ray diffraction. Mullite/Ag cermets with homogenous microstructure were and a fracture toughness of 2.42 MPа·m 1/2 .

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“…Mullite (3Al 2 O 3 •2SiO 2 ) is the only stable silicoaluminate in the binary system of SiO 2 -Al 2 O 3 at atmospheric pressure [1,2] and is a very important refractory material with high melting temperature, high hot strength, excellent thermal shock resistant, and high creep resistance; it is volume stable at very high temperatures, it has a low coefficient of thermal expansion, and it has excellent electrical insulation properties [3,4]. It has outstanding hot load-bearing properties, and it is resistant to many corrosive environments.…”

Section: Introductionmentioning

confidence: 99%

Effect of Particle Size and Sintering Temperature on the Formation of Mullite from Kyanite and Aluminum Mixtures

Hernández

Labra

Guerrero

et al. 2021

Advances in Materials Science and Engineering

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The effect of particle size and sintering temperature of the mixtures of kyanite and metallic aluminum related to the thermal transformation of kyanite into primary mullite and free silica was studied. In addition, the reaction between α-Al2O3 (in situ produced by aluminum oxidation) and the silica was obtained in cristobalite structure from kyanite to obtain secondary mullite. The kyanite powders were milled by 0.5, 3, 6, and 12 hours and then were mixed with aluminum powder, which were previously milled by 3 hours. After that, the powders were characterized by X-ray diffraction technique (XRD), scanning electronic microscopy (SEM), differential thermal analysis (DTA), and thermogravimetric analysis (TGA), and the particle size was determined in a centrifugal analyzer particle size Shimadzu model SA-CP4. The mixed powders were pressed uniaxially into cylindrical samples (compacts), and then sintering was conducted at 1100, 1200, 1300, 1400, 1500, and 1600°C; these samples were characterized by XRD, SEM, and thermodilatometry analysis (TD); density and open porosity measurements were performed by the Archimedes method. The samples were thermally etched to observe the microstructure, which consisted of mullite equiaxial grains contained in a glassy phase. It was observed that the nonmilled kyanite mineral becomes into mullite plus silica at temperatures between 1400 and 1500°C. When the particle size was reduced at sizes less than 1 µm, the transformation temperature was low until 200°C; the X-ray patterns of the sintered samples at 1400°C, ground for 6 hours, showed mullite peaks with small reflections of cristobalite and α-Al2O3, and these samples exhibited high density and low open porosity.

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Synthesis and characterization of mullite–zirconia nanostructured composite by combined mechanical activation and reaction sintering

Cited by 23 publications

References 24 publications

Acylation of Lignin with Different Acylating Agents by Mechanical Activation-Assisted Solid Phase Synthesis: Preparation and Properties

Acylation of Lignin with Different Acylating Agents by Mechanical Activation-Assisted Solid Phase Synthesis: Preparation and Properties

Effect of silver nanoparticless in the structure and mechanical properties of mullite/Ag cermets

Effect of Particle Size and Sintering Temperature on the Formation of Mullite from Kyanite and Aluminum Mixtures

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