Morphological Characterization of Fumed Silica Aggregates

Boldridge, David

doi:10.1080/02786820903499462

Cited by 38 publications

(43 citation statements)

References 26 publications

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“…For this study, concentrated (∼20-34% (w/w)) fumed silica CMP slurries provided by Cabot Microelectronics Corporation (Aurora, IL, USA) are investigated. Fumed silica (ρ=2.0 g/cm 3 ) is formed through the oxidation of silicon tetrachloride (SiCl 4 ) under a hightemperature flame to produce small, spherical primary particles on the order of 5-50 nm (Boldridge 2010). These primary particles collide during the flaming process to form rigid, covalently bonded aggregates around 100-200 nm in size (Yokoyama et al 2007).…”

Section: Cmp Slurrymentioning

confidence: 98%

Shear thickening of chemical mechanical polishing slurries under high shear

et al. 2012

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Chemical mechanical polishing (CMP) is a fundamental technology used in the semiconductor manufacturing industry to polish and planarize electronic materials. During the high shear (≥1,000,000 s −1 ) polishing process, it is hypothesized that individual slurry particles begin to interact and collide with one another forming large agglomerates (≥0.5 μm). These agglomerates are suspected of causing defects such as scratches or gouges during polishing, which costs the semiconductor industry billions of dollars annually. We have developed a method for investigating the shear thickening behavior of fumed silica slurries (20-34 wt.%) under high shear using a parallel-plate geometry in a conventional rotating rheometer. The CMP slurries displayed irreversible thickening at shear rates exceeding 10,000 s −1 . Viscous heating and sample evaporation are shown to be inconsequential to the witnessed shear thickening behavior. Also, the observed thickening is not a result of a critical rheometer speed, as the thickening was independent of the experimental gap height. In agreement with previous work, the slurries thickened at lower shear rates as silica concentration was increased. The shear thickening of the fumed N. Crawford · M. Liberatore (B) silica slurries is truly shear-induced, and therefore, the thickening of CMP slurries can be examined using a rotational rheometer at small gap heights (≤100 μm).

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Section: Cmp Slurrymentioning

confidence: 98%

Shear thickening of chemical mechanical polishing slurries under high shear

et al. 2012

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“…The appearance of the E551 food additive as aggregates is very typical for this substance, and is a result of the manufacturing process. 48,53 It can also be noticed that the majority of the particles, and even aggregates (as shown in Figure 1), were smaller than 100 nm. Thus the food additive used in this product would be classed as an NM.…”

Section: Case Study: Application Of High Vacuum Electron Microscopy Fmentioning

confidence: 88%

“…Refs 46,47. In addition to providing data regarding the size and shape of NMs, EM allows investigation of crystallinity, primary particle size (if aggregates/agglomerates have been formed), 48 associations with matrix components, 49 and chemical composition, by means of coupling the EM to spectroscopic methods. The European Food Safety Authority (EFSA) recommended EM as the primary method (with a second method being optional) for the detection and size characterization of NMs in food and feed products, 26 due to its versatile applicability.…”

Section: Electron Microscopymentioning

confidence: 99%

Case Study – Characterization of Nanomaterials in Food Products

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Dudkiewicz

Boxall

et al. 2015

Characterization of Nanomaterials in Complex Environmental and Biological Media

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“…The fractal dimension (D f ) of the silica particles provides further insight on their sphericity (DeCarlo et al, 2004;Boldridge, 2010;Keskinen et al, 2011): for perfect spheres D f = 3 and for line-like structures D f = 1.…”

Section: Non-sphericity Of Particlesmentioning

confidence: 99%

CCN activation of fumed silica aerosols mixed with soluble pollutants

et al. 2015

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Abstract. Particle-water interactions of completely soluble or insoluble particles are fairly well understood but less is known of aerosols consisting of mixtures of soluble and insoluble components. In this study, laboratory measurements were performed to investigate cloud condensation nuclei (CCN) activity of silica particles mixed with ammonium sulfate (a salt), sucrose (a sugar) and bovine serum albumin known as BSA (a protein). The agglomerated structure of the silica particles was investigated using measurements with a differential mobility analyser (DMA) and an aerosol particle mass analyser (APM). Based on these data, the particles were assumed to be compact agglomerates when studying their CCN activation capabilities. Furthermore, the critical supersaturations of particles consisting of pure and mixed soluble and insoluble compounds were explored using existing theoretical frameworks. These results showed that the CCN activation of single-component particles was in good agreement with Köhler-and adsorption theory based models when the agglomerated structure was accounted for. For mixed particles the CCN activation was governed by the soluble components, and the soluble fraction varied considerably with particle size for our wet-generated aerosols. Our results confirm the hypothesis that knowing the soluble fraction is the key parameter needed for describing the CCN activation of mixed aerosols, and highlight the importance of controlled coating techniques for acquiring a detailed understanding of the CCN activation of atmospheric insoluble particles mixed with soluble pollutants.

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Morphological Characterization of Fumed Silica Aggregates

Cited by 38 publications

References 26 publications

Shear thickening of chemical mechanical polishing slurries under high shear

Shear thickening of chemical mechanical polishing slurries under high shear

Case Study – Characterization of Nanomaterials in Food Products

CCN activation of fumed silica aerosols mixed with soluble pollutants

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