Synthesis and Consolidation of Zirconia Nanopowders via A Unique Reverse Micelle Synthesis Process and Spark Plasma Sintering

Graeve, Olivia A.; Singh, Harpreet; Clifton, Andrew

doi:10.1002/9780470082751.ch19

Cited by 8 publications

(6 citation statements)

References 19 publications

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“…Indeed, it has been found that for some materials, the particle (i.e., agglomerate) size of powders tends to define the final grain size of the dense compact under typical SPS conditions. [5,6] Thus, characterizing the crystallite size of a powder from X-ray diffraction or transmission electron microscopy is necessary, but not sufficient, in order to determine the sintering behavior of a powder and the final grain size after completion of sintering.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Particle and Crystallite Size in Tungsten Nanopowder Synthesis

Graeve

Madadi

Kanakala

et al. 2010

Metall Mater Trans A

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Tungsten nanopowders were synthesized by a low-temperature technique and then heat treated in a gaseous reductive atmosphere in order to study the phase evolution, crystallite size, and particle size of the powders as the heat treatment temperature was modified. Synthesis of the powders was carried out in aqueous media using NaBH 4 as a reducing agent using careful control of the pH of the solutions. The XRD patterns of the as-synthesized powders showed an amorphous phase. After washing, energy dispersive spectroscopy showed that the powders had peaks for oxygen and tungsten. In order to promote crystallization and eliminate the oxygen, the powders were heat treated at 773 K, 923 K, and 1073 K (500°C, 650°C, and 800°C) in a H 2 /CH 4 reducing atmosphere for 2 hours. XRD after heat treatment showed a-W peaks for the powders treated at 1073 K and 923 K (800°C and 650°C) and a mixture of b-W and a-W for the powders treated at 773 K (500°C). The crystallite sizes determined from X-ray peak broadening were 12, 16, and 20 nm, whereas the average particle sizes from dynamic light scattering were 260, 450, and 750 nm, for heat treatment temperatures of 773 K, 923 K, and 1073 K (500°C, 650°C, and 800°C), respectively. The average crystallite size and particle sizes increased proportionally with the treatment temperature, in contrast to what has been found for some ceramics, in which as the heat treatment temperature is increased, the crystallite size increases, but the particle size stays constant.

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Section: Introductionmentioning

confidence: 99%

Analysis of Particle and Crystallite Size in Tungsten Nanopowder Synthesis

Graeve

Madadi

Kanakala

et al. 2010

Metall Mater Trans A

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“…Heating rates on the order of 10 2 -10 4 K/s can be used to suppress crystallization in metallic glass alloys with critical casting thicknesses down to a few millimeters [52]. Heating rates up to 10 3 K/s can be obtained by the spark plasma sintering technique [53][54][55][56][57], and can be used to avoid crystallization in many alloys to facilitate effective viscous forming. Applied stress can also facilitate densification of glass powders [51].…”

Section: Introductionmentioning

confidence: 99%

Designing in situ and ex situ bulk metallic glass composites via spark plasma sintering in the super cooled liquid state

et al. 2016

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Crystallization inhibits metallic glass forming in the super cooled liquid state and can be avoided if sufficiently fast heating rates can be obtained, but becomes increasingly difficult for marginal glass formers. We propose that dynamic pressing can enhance formability, and demonstrate that density of an iron-based marginal glass forming alloy (Fe 49.7 Cr 17.1 Mn 1.9 Mo 7.4 W 1.6 B 15.2 C 3.8 Si 2.4 ) can be enhanced by coupling loading rate to fast heating rate during spark plasma sintering. We also describe the transformation kinetics for devitrification in a time-temperature-crystallinity diagram. The combination of coupled loading/fast heating and the time-temperature-crystallinity diagram define the processing requirements for obtaining a dense X-ray amorphous structure and can also be used to design a wide variety of dense in situ composites. Finally, we demonstrate that the design approach also applies to ex situ composites by adding microcrystalline W or Ta, enabling systematic control of atomic-, nano-, and micro-structure. This multi-scale structure control of bulk metallic glass composites has implications for developing a fundamental understanding of structure-property relationships. We expect this general approach will be applicable to other bulk metallic glass composites, and especially beneficial for marginal glass formers that are otherwise difficult to process.

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“…This method produces spherical mesoporous CuO-SDC particles by homogeneous precipitation of a microspherical precursor in aqueous solution followed by calcination. Kelly and Graeve illustrate similar spherical particles by using a reverse micelle process − to produce mesoporous YSZ powders. In general, surfactant-directed morphology evolution is a promising strategy in the formation of a variety of nanomaterials …”

Section: Introductionmentioning

confidence: 99%

Development of Mesoporosity in Scandia-Stabilized Zirconia: Particle Size, Solvent, and Calcination Effects

et al. 2014

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We present the mechanisms of formation of mesoporous scandia-stabilized zirconia using a surfactant-assisted process and the effects of solvent and thermal treatments on the resulting particle size of the powders. We determined that cleaning the powders with water resulted in better formation of a mesoporous structure because higher amounts of surfactant were preserved on the powders after washing. Nonetheless, this resulted in agglomerate sizes that were larger. The water-washed powders had particle sizes of >5 μm in the as-synthesized state. Calcination at 450 and 600 °C reduced the particle size to ∼1-2 and 0.5 μm, respectively. Cleaning with ethanol resulted in a mesoporous morphology that was less well-defined compared to the water-washed powders, but the agglomerate size was smaller and had an average size of ∼250 nm that did not vary with calcination temperature. Our analysis showed that surfactant-assisted formation of mesoporous structures can be a compromise between achieving a stable mesoporous architecture and material purity. We contend that removal of the surfactant in many mesoporous materials presented in the literature is not completely achieved, and the presence of these organics has to be considered during subsequent processing of the powders and/or for their use in industrial applications. The issue of material purity in mesoporous materials is one that has not been fully explored. In addition, knowledge of the particle (agglomerate) size is essential for powder handling during a variety of manufacturing techniques. Thus, the use of dynamic light scattering or any other technique that can elucidate particle size is essential if a full characterization of the powders is needed for achieving postprocessing effectiveness.

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Synthesis and Consolidation of Zirconia Nanopowders via A Unique Reverse Micelle Synthesis Process and Spark Plasma Sintering

Cited by 8 publications

References 19 publications

Analysis of Particle and Crystallite Size in Tungsten Nanopowder Synthesis

Analysis of Particle and Crystallite Size in Tungsten Nanopowder Synthesis

Designing in situ and ex situ bulk metallic glass composites via spark plasma sintering in the super cooled liquid state

Development of Mesoporosity in Scandia-Stabilized Zirconia: Particle Size, Solvent, and Calcination Effects

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