Sublimation

Robertson, Georgina

doi:10.1021/ed009p1713

Cited by 3 publications

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“…Sublimation has long been employed as a purification method for organic compounds under solvent-free conditions. − Though approximately two-thirds of organic compounds are able to sublime, the use of sublimation as a crystal growth method for small molecule organics is less frequently used than solution growth methods. This may be in part because it often yields crystalline or polycrystalline thin films which are not amenable to characterization by single crystal X-ray diffraction, though high quality crystals have been obtained in some cases. − Greater recognition of the advantages sublimation offerssuch as eliminating the possibility of solvated phases ,− and in some cases the realization of unexpected polymorphs − could facilitate its wider use.…”

Section: Introductionmentioning

confidence: 99%

Polymorph Selection via Sublimation onto Siloxane Templates

Solomos

Capacci-Daniel

Rubinson

et al. 2018

Crystal Growth & Design

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Diphenylurea (PU) crystallizes via slow evaporation from a range of solvents as phase pure α-PU or in a concomitant mixture with the less stable β-PU phase. Sublimation onto glass also yields α-PU in high phase purity. In contrast, sublimation onto siloxane-coated glass templates with various terminal groups (e.g., isocyanate, acetate, bromine) resulted in primarily β-PU. Scanning electron microscopy showed that the individual crystals on siloxanes exhibit a range of different morphologies (e.g., plates, needles, hollow tubes, spirals) which appear to be influenced by the terminal siloxane functionality. Under extended sublimation times (>5 h), mixtures of β and α become apparent on most siloxanes. Grazing incidence X-ray diffraction studies showed that the β:α ratio changes as a function of distance from the siloxane, with more α-PU appearing at higher angles. Diffraction line intensities also indicate strong preferred orientations for β-PU crystallites within the polycrystalline layer with the fastest growth direction (b-axis) parallel to the template, but more varied orientations for α-PU. This suggests α-PU may nucleate elsewhere in the sublimation apparatus rather than on the β-coated siloxane. This study demonstrates the utility of templatedirected sublimation methods as a way to engineer metastable phases but also illustrates some of the challenges associated with achieving high phase purity on templates with limited surface area.

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Section: Introductionmentioning

confidence: 99%

Polymorph Selection via Sublimation onto Siloxane Templates

Solomos

Capacci-Daniel

Rubinson

et al. 2018

Crystal Growth & Design

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A review study of solid–gas sublimation flow for refrigeration: From basic mechanism to applications

Chen¹,

Zhang²

2014

International Journal of Refrigeration

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New Mechanisms for Cryogenic Solid-Gas Sublimation Refrigeration

Chen

2015

Handbook of Research on Advances and Applications in Refrigeration Systems and Technologies

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Sublimation is one phase change mechanism which usually happens under low-to-moderate temperatures and at the same time large amounts of latent heat is absorbed or released. Low temperature sublimation has been proposed in a lot of applications as one useful fast cooling/refrigeration mechanisms, such as medical cooling, food engineering, chemical synthesis, domestic cooling and many industrial sectors. In this brief chapter, the basic mechanisms of static sublimation process and sublimation two-phase flows are clarified and analyzed first, which covers the theoretical and physical problems of sublimation phase-change. Then the previous studies are classified into numerical modeling and experimental verifications. Representative refrigeration systems are also introduced and compared in this chapter, which may give useful indications for future innovations in this field. Future research focuses are also summarized and proposed in this chapter.

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Sublimation

Cited by 3 publications

References 0 publications

Polymorph Selection via Sublimation onto Siloxane Templates

Polymorph Selection via Sublimation onto Siloxane Templates

A review study of solid–gas sublimation flow for refrigeration: From basic mechanism to applications

New Mechanisms for Cryogenic Solid-Gas Sublimation Refrigeration

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