Microgravity experiments on colloidal crystallization of silica spheres in the presence of sodium chloride

Tsuchida, Akira; Taguchi, K.; Takyo, E.; Yoshimi, Hideki; Kiriyama, Shunya; Okubo, Tsuneo; Ishikawa, Masamichi

doi:10.1007/s003960000349

Cited by 11 publications

(9 citation statements)

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“…Tsuchida et al calculated the formation rates for colloidal crystallization of silica spheres. It was shown that rate constants were significantly smaller in microgravity [42]. Smith et al reported that formation of silica crystals to be slower under microgravity environment due to diffusion-limited crystallization where mass transfer dominates the aggregation of particles rather than reaction kinetics [43].…”

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confidence: 99%

Effect of Microgravity on Synthesis of Nano Ceria

et al. 2015

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Cerium oxide (CeO2) was prepared using a controlled-precipitation method under microgravity at the International Space Station (ISS). For comparison, ceria was also synthesized under normal-gravity conditions (referred as control). The Brunauer-Emmett-Teller (BET) surface area, pore volume and pore size analysis results indicated that the ceria particles grown in space had lower surface area and pore volume compared to the control samples. Furthermore, the space samples had a broader pore size distribution ranging from 30-600 Å, whereas the control samples consisted of pore sizes from 30-50 Å range. Structural information of the ceria particles were obtained using TEM and XRD. Based on the TEM images, it was confirmed that the space samples were predominantly nano-rods, on the other hand, only nano-polyhedra particles were seen in the control ceria samples. The average particle size was larger for ceria samples synthesized in space. XRD results showed higher crystallinity as well as larger mean crystal size for the space samples. The effect of sodium hydroxide concentration on synthesis of ceria was also examined using 1 M and 3 M solutions. It was found that the control samples, prepared in 1 M and 3 M sodium hydroxide solutions, did not show a significant difference between the two. However, when the ceria samples were prepared OPEN ACCESSCatalysts 2015, 5 1307 in a more basic medium (3 M) under microgravity, a decrease in the particle size of the nano-rods and appearances of nano-polyhedra and spheres were observed.

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Section: +mentioning

confidence: 99%

Effect of Microgravity on Synthesis of Nano Ceria

et al. 2015

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“…The growth rates increased substantially in microgravity up to about 1.7 times those in normal gravity, which was mainly caused by the absence of particle segregation that took place under normal gravity. Tsuchida et al 24 studied the effect of added salt on the crystallization kinetics of silica particles. The authors found that the rate coefficients decreased as the salt concentration increased and that those in microgravity were smaller than those in normal gravity.…”

Section: Introductionmentioning

confidence: 99%

“…This question is what drove scientists to perform experiments under microgravity conditions in so-called parabolic flights that can be performed by airplanes, 23,24 and also in the Space Shuttle 17,18 and the International Space Station. 21,22 The main findings, with a focus on solidification and phase separation, will be briefly reviewed in the following.…”

Section: Introductionmentioning

confidence: 99%

A qualitative confocal microscopy study on a range of colloidal processes by simulating microgravity conditions through slow rotations

et al. 2012

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We report qualitatively on the differences between colloidal systems left to evolve in the Earth's gravitational field and the same systems for which a slow continuous rotation averaged out the effects of particle sedimentation on a distance scale small compared to the particle size. Several systems of micron-sized colloidal particles were studied: a hard sphere fluid, colloids interacting via long-range electrostatic repulsion above the freezing volume fraction, an oppositely charged colloidal system close to either gelation and/or crystallization, colloids with a competing short-range depletion attraction and a long-range electrostatic repulsion, colloidal dipolar chains, and colloidal gold platelets under conditions where they formed stacks. Important differences in structure formation were observed between the experiments where the particles were allowed to sediment and those where sedimentation was averaged out. For instance, in the case of colloids interacting via long-range electrostatic repulsion, an unusual sequence of dilute-fluid-dilute-crystal-dense-fluid-dense-crystal phases was observed throughout the suspension under the effect of gravity. This was related to the volume fraction dependence of the colloidal interactions, whereas the system stayed homogeneously crystallized with rotation. For the oppositely charged colloids, a gel-like structure was found to collapse under the influence of gravity with a few crystalline layers grown on top of the sediment, whereas when the colloidal sedimentation was averaged out, the gel completely transformed into crystallites that were oriented randomly throughout the sample. Rotational averaging out of gravitational sedimentation is an effective and cheap way to estimate the importance of gravity for colloidal self-assembly processes.

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“…Gravity was found to have an important influence on the occurrence of intra-and intermolecular condensation reactions [1][2][3][4][5]. Under reduced gravity buoyancy driven free convection is limited and silica polymerization occurred in a diffusion limited regime.…”

Section: Introductionmentioning

confidence: 99%

“…Sol-gel derived silicon dioxide materials synthesized under varied gravity conditions has also yielded new materials with significant increases in surface areas and molecular complexities [1,2]. Research into the effects of varied gravity, such as the removal of convective fields that are present during synthesis, on the sol-gel process is currently limited to only the silicon sol-gel system [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of titanium sol–gels in varied gravity

Hales¹,

Steinberg²,

Martens³

2014

Journal of Non-Crystalline Solids

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Two unique test systems were designed and built to allow the effects of varied gravity (high, normal, reduced) during synthesis of titanium sol-gels to be studied. A centrifuge capable of providing high gravity environments of up to 70 g for extended periods while applying a 100 mbar vacuum and a temperature of 40-50°C to the reaction chambers was developed. The second system was used in the QUT Microgravity Drop Tower Facility also provided the same thermal and vacuum conditions used in the centrifuge, but was required to operate autonomously during free fall. Through the use of post synthesis instrumental characterization, it was found that increased gravity levels during synthesis, had the greatest effect on the final products. Samples produced in reduced and normal gravity appeared to form amorphous gels containing very small particles with moderate surface areas. Whereas crystalline anatase (TiO 2 ), was found to form in samples synthesized above 5 g with significant increases in crystallinity, particle size and surface area observed when samples were produced at gravity levels up to 70 g. It is proposed that for samples produced in higher gravity, an increased concentration gradient of water is forms at the bottom of the reacting film due to forced convection. The particles formed in higher gravity diffuse downward toward this excess of water, which favors the condensation reaction of remaining sol-gel precursors with the particles promoting increased particle growth. Due to the removal of downward convection in reduced gravity, particle growth due to condensation reaction processes are physically hindered hydrolysis reactions favored instead. Another significant finding from this work was that anatase could be produced at relatively low temperatures of 40-50°C instead of the conventional method of calcination above 450°C solely through sol-gel synthesis at higher gravity levels.

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Microgravity experiments on colloidal crystallization of silica spheres in the presence of sodium chloride

Cited by 11 publications

References 0 publications

Effect of Microgravity on Synthesis of Nano Ceria

Effect of Microgravity on Synthesis of Nano Ceria

A qualitative confocal microscopy study on a range of colloidal processes by simulating microgravity conditions through slow rotations

Synthesis and characterization of titanium sol–gels in varied gravity

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