Novel supercritical fluid processing techniques for the production of an aerosol

most synthesis methods for these types of particles require multiple, complicated synthesis procedures and are typically nonconductive to be scaled up manufacturing as yields are typically milligram or less quantities of material. Examples of this includes template, chemical vapor deposition, hydrothermal, electrochemical anodization, etc. [12][13][14][15] Almquist and Biswas prepared anatase powders with sizes ranging from 5 to 165 nm employing various synthesis methods and found that an optimum particle size range of 25-40 nm within all photocatalytic experiments regardless of fabrication processes. [16] The authors suggest that the optimum particle size is a function of several competing mechanisms such as light absorption and scattering efficiency of the particles, as well as electron-hole pair combination and interfacial charge transfer. Therefore, cost effective and mass production available synthesis for titania nanomaterials with at least 1D close to the optimum size of photocatalyst will be a revolution of the whole titania fabrication.In this study, micrometer sized titania flakes having a thickness ≈40 nm were successfully synthesized by spreading an oil phase consisting of titanium tetraisopropoxide and a low surface tension hydrocarbon on the surface of water. [17] These nanoflakes were produced by restricting the hydrolysis of titania precursor within dimension of the organic thin film due to the difference of surface energy to water. The flakes were also calcined at 400 °C resulting in high purity anatase having near identical dimensions to the uncalcined material. Investigations have shown the described method to be efficient and economical at producing gram to kilogram quantities of material. This study examines these nanoflakes which were characterized by scanning electron microscopy (SEM), laser diffraction analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), physisorption techniques, and UV-visible spectrometer.The surface morphology of synthesized titania nanoflakes was investigated using SEM images, shown in Figure 1. The major diameter of the flakes was found to be of the order of 10-20 µm ( Figure 1A,B), and the thickness of these flakes was ≈40 nm (Figure 1C,D). The flakes were further treated by calcination at 400 °C for 2 h. Aggregation was not apparent when comparing these treated flakes ( Figure 1B) with those obtained directly from synthesis ( Figure 1A). Moreover, the thickness of calcined flakes did not change by the heat High aspect ratio TiO 2 nanoflakes are synthesized by a one-step modified surface hydrolysis method. Surface morphology and physical dimensions are characterized using scanning electron microscopy, laser diffraction analysis, and transmission electron microscopy. Microsized flakes having a thickness ≈40 nm are successfully synthesized by spreading an oil phase consisting of titanium tetraisopropoxide and a low surface tension hydrocarbon on the surface of water. Pure anatase phase crystalline titania nanoflakes are obtained by calcining at 4...

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“…This was repeated a total of five. Finally, the nanoflakes were dried by a supercritical fluid drying process described elsewhere …”

Section: Methodsmentioning

confidence: 99%

A One‐Step Approach to the Synthesis of High Aspect Ratio Titania Nanoflakes

2017

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“…10 g of powder was slowly added to the solution while stirring and the solution was allowed to continue mixing for one hour. After the allowed time, the mixture was solvent exchanged to remove any excess silane via dilution and centrifugation (Beckman JA-21) and dried using a supercritical fluid drying process described elsewhere 18) .…”

Section: Methodsmentioning

confidence: 99%

“…This requires a systematic study of these factors and their effect on the dispersion of the resultant aerosol. In previous work, the efficacies of different dr ying methods were investigated and two novel CO2 based drying methods developed 18) as was the use of surface modification to control capillary adhesion 19) . During this research, the ef fect of humidity and hydrophobicity, flow aids and interparticle contact area, and dispersion methods have been studied and the results analyzed through the guidance of a statistical experimental design.…”

Section: Introductionmentioning

confidence: 99%

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Improving Aerosol Dispersion through Processing and Dissemination Techniques

Tedeschi

Powers

Ranade

et al. 2009

KONA

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The state of dispersion is a vital aspect of powder technology impacting both traditional and emerging technologies in many diverse areas of interest including health care, industry, the environment, and the military. In such applications, the properties and quality of the resultant product will be directly and noticeably affected by the degree to which the particles are dispersed. In any operation where satisfactory particle dispersion is imperative, a reduction in dispersion, or increased agglomeration, leads to poor efficiency and ultimately results in lower yields and increased cost. As powder technology moves into the nano-age, the challenges of maintaining and improving particle dispersion become increasingly important. Decreasing particle size into the submicron range can significantly increases the effect of surface forces leading to an increase in the cohesive forces of the powder, thus, making an understanding of dispersion even more essential. In order to develop the knowledge base to understand and control aerosol dispersion, a fundamental study into significant powder characteristics and environmental conditions that influence dispersion has been conducted. This paper discusses the results of testing various techniques employed to improve the dispersion of sub-micron aluminum flakes such as using a fumed silica spacer to reduce interparticle contact area and, in turn, attractive van der Waals forces, as well as examining the effect of dissemination pressure on the state of dispersion of the particles. This research was conducted using statistical experimental design in order to efficiently study significant factors.

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“…The resulting slurry was washed with Nanopure water and isoproponal thoroughly to remove impurities. Dried and well dispersed particles were collected by the supercritical fluid drying process [40]. The following heat treatment for phase transformation was conducted at 400°C.…”

Section: One-step Synthesis Of Titania Nanoflakesmentioning

confidence: 99%

Novel Two-Dimensional Nanomaterial: High Aspect Ratio Titania Nanoflakes

Lee¹

2018

Titanium Dioxide - Material for a Sustainable Environment

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A novel 2D nanomaterial, high aspect ratio TiO 2 nanoflakes were synthesized by a onestep method. Surface morphology and physical dimensions were characterized using Scanning Electron Microscopy (SEM), Laser Diffraction technology, and Transmission Electron Microscopy (TEM). Micro-sized flakes having a thickness approximately 40 nm were successfully synthesized by spreading a mixture of titanium alkoxide and hydrocarbon on the water surface. Relatively higher specific surface area (2-6 times) and less crystal defects enhanced photocatalytic activities of nanoflakes due to more surface reaction sites. By performing dye degradation under ultraviolet (UV) illumination, titania nanoflakes exhibited the higher photocatalytic efficiency over the commercial photocatalyst, Degussa P25. To the best of our knowledge, this is the first time to continuously synthesize low-dimensional nanomaterials in an efficient and cost effective manner. In practical water purification, traditional separation processes such as sedimentation or filtration could be utilized to easily extract the titania flakes from the treated water. Other applications such as anode material for lithium ion batteries and conducting paste in dye sensitized solar cells (DSSC) were also investigated. The cycling performance of Li-ion battery and energy conversion efficiency of DSSC were significantly improved.

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Novel supercritical fluid processing techniques for the production of an aerosol

Cited by 4 publications

References 16 publications

A One‐Step Approach to the Synthesis of High Aspect Ratio Titania Nanoflakes

A One‐Step Approach to the Synthesis of High Aspect Ratio Titania Nanoflakes

Improving Aerosol Dispersion through Processing and Dissemination Techniques

Novel Two-Dimensional Nanomaterial: High Aspect Ratio Titania Nanoflakes

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