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Phone: þ74 752 532 680, Fax: þ74 752 710 307 Nanofibrous zirconia was fabricated by calcination of electrospun zirconium oxychloride/polyethylene oxide (PEO) composite fibers with different mass fraction of the components. ZrO 2 nanofibers were characterized by scanning electron microscopy (SEM), nitrogen adsorption at 77 K, and X-ray diffractometry (XRD). It was revealed that increase in ZrOCl 2 /PEO mass ratio above the threshold value significantly decreases tetragonal phase (t-ZrO 2 ) content and increases monoclinic phase (m-ZrO 2 ) content in final ceramic nanofibers. Distinct t-ZrO 2 ! m-ZrO 2 transformation takes place when average ZrO 2 grain size approaches to 30 nm.

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“…t-ZrO 2 þ m-ZrO 2 ! m-ZrO 2 [24]. The t-ZrO 2 is preferential phase during crystallization of amorphous zirconia as noted above.…”

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confidence: 65%

The influence of zirconia precursor/binding polymer mass ratio in the intermediate electrospun composite fibers on the phase transformation of final zirconia nanofibers

Rodaev

Zhigachev

Коренков

et al. 2016

Physica Status Solidi (a)

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“…This difference can be related to the presence of HPC, which has been reported to affect the phase composition of oxides synthesized via sol–gel reactions. 17 …”

Section: Resultsmentioning

confidence: 99%

Sol–Gel Synthesis of CaTiO₃:Pr³⁺ Red Phosphors: Tailoring the Synthetic Parameters for Luminescent and Afterglow Applications

et al. 2017

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Two sol–gel synthetic routes for the preparation of CaTiO3:Pr3+ red emitting phosphors were compared, with the aim of producing nanostructured materials with tailored luminescence/afterglow properties. The effect of the synthetic parameters, such as the addition of a stabilizer and calcination temperature, on the structural, morphological, and optical properties was investigated. The desired perovskite phase was obtained at a calcination temperature of 800 °C or higher. Although the use of acetic acid as the chelating agent leads to micrometric particles with heterogeneous composition, the presence of hydroxypropylcellulose (HPC) results in smaller, less aggregated particles as well as in a high phase purity. At the highest HPC content, surface Ca-rich impurities were detected, although no segregated Ca-rich phases were detectable by X-ray powder diffraction analyses. Luminescence properties were found to be positively related to the phase purity of the oxide, with the highest quantum yields at temperatures equal to or higher than 1000 °C. On the contrary, persistent luminescence properties were highest at intermediate calcination temperatures and for samples synthesized with acetic acid. Overall, a notable role of oxygen vacancies resulting from local Ca excess was observed, acting as trap levels promoting longer relaxation pathways. Thanks to the small-sized particles and best steady-state luminescent properties due to a substantial decrease of lattice defects, the HPC synthesis is a promising strategy for light-emitting diode applications. On the other hand, the acetic acid synthesis promoted a higher defect density, which is required for an efficient yield of light emission in the long time range and is thus more suitable for afterglow applications.

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“…A simple criterion commonly applied to determine the ''gel state'' in the dynamic modulus spectrum, is based on the point at which G 0 and G 00 are equal at frequencies from 1 to 10 Hz (s -1 ). Figure 1 plots the evolution of the dynamic moduli, G 0 and G 00 , near the sol/gel transition (SGT) (Shukla et al 2003(Shukla et al , 2002Rwei et al 2005;Carotenuto and Grizzuti 2006), with concentration. The sol-like (G 0 \ G 00 ) behavior exhibited at low concentration gradually becomes gel-like (G 0 [ G 00 ) as the concentration rises.…”

Section: Resultsmentioning

confidence: 99%

Sol/gel transition and liquid crystal transition of HPC in ionic liquid

Rwei

Lyu

et al. 2008

Cellulose

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This work uses an ionic liquid (IL), 1-butyl-3-methylimidazolium acetate, as a solvent to study the sol/gel transition (SGT) and liquid crystal transition (LCT) of hydroxypropylcellulose (HPC) solution. The LCT concentration of HPC at room temperature is 7 wt%, which is slightly higher than its SGT concentration of 6 wt%. For HPC concentrations of over 7 wt%, three rheological approaches were utilized, and the parameters relaxation time, hysteresis ratio and loss modulus (G 00 ) are measured to determine the LCT temperature. The relaxation study concludes that the LC-critical concentration of HPC is 7 wt%. When HPC exceeds 7 wt%, the LC transition temperatures, ranging from 45 to 51°C, can be measured and are proportional to the HPC concentration. The rheological results are then confirmed by making observations under a polarized optical microscope. All results are highly mutually consistent. Most significantly, the rheological parameters adopted herein can be used as good indicators of the LC transition. Of those indicators, G 00 changes distinctly at the LCT point, and can thus be suggested to be the most helpful indicator in determining the LCT temperature.

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Cited by 62 publications

References 18 publications

The influence of zirconia precursor/binding polymer mass ratio in the intermediate electrospun composite fibers on the phase transformation of final zirconia nanofibers

The influence of zirconia precursor/binding polymer mass ratio in the intermediate electrospun composite fibers on the phase transformation of final zirconia nanofibers

Sol–Gel Synthesis of CaTiO₃:Pr³⁺ Red Phosphors: Tailoring the Synthetic Parameters for Luminescent and Afterglow Applications

Sol/gel transition and liquid crystal transition of HPC in ionic liquid

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Untitled

Cited by 62 publications

References 18 publications

The influence of zirconia precursor/binding polymer mass ratio in the intermediate electrospun composite fibers on the phase transformation of final zirconia nanofibers

The influence of zirconia precursor/binding polymer mass ratio in the intermediate electrospun composite fibers on the phase transformation of final zirconia nanofibers

Sol–Gel Synthesis of CaTiO3:Pr3+ Red Phosphors: Tailoring the Synthetic Parameters for Luminescent and Afterglow Applications

Sol/gel transition and liquid crystal transition of HPC in ionic liquid

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Product

Resources

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Sol–Gel Synthesis of CaTiO₃:Pr³⁺ Red Phosphors: Tailoring the Synthetic Parameters for Luminescent and Afterglow Applications