Structural modification of synthetic opals during thermal treatment

Samarov, É. N.; Mokrushin, A. D.; Масалов, В. М.; Abrosimova, G. E.; Емельченко, Г. А.

doi:10.1134/s1063783406070109

Cited by 26 publications

(15 citation statements)

References 10 publications

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“…From this point of view, the measured oxygen excess (compared to the calculated) in the SEM analysis can be explained by the presence of physically adsorbed water, which is in good agreement with the DTA and TGA data and [ 13 ]. The measured oxygen deficiency (compared to the calculated one) in the XPS analysis indicates the absence of physically adsorbed water on the coating surface.…”

Section: Discussionsupporting

confidence: 80%

“…Usually, peaks in the X-ray diffraction patterns of amorphous silicon oxide appear after annealing at temperatures well above 870 °C, for example, at 1200 °C [ 12 ], or at several tens of h, for example, 32 h at 950 °C [ 13 ]. The observed “low-temperature” crystallization of cristobalite can most likely be explained by the presence of an impurity of potassium carbonate.…”

Section: Discussionmentioning

confidence: 99%

“…The first endothermic peak in the DTA curve is observed at 106 °C; it can be associated with the loss of physically adsorbed water [ 13 ]. It corresponds to the largest inflection in the TGA curve.…”

Section: Discussionmentioning

confidence: 99%

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Heat Treatment Effect on the Phase Composition of the Silica Electrochemical Coating and the Carbon Fiber Strength

et al. 2021

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This work is devoted to the study of the chemical and phase composition of a carbon fiber coating obtained by the electrochemical sol-gel method. The experimental data obtained using several independent complementary methods, including X-ray phase analysis, thermogravimetric and differential thermal analysis, scanning electron microscopy and elemental analysis, and X-ray photoelectron spectroscopy, are in good agreement with each other. It was found that the resulting coating consists of amorphous silicon oxide and crystalline potassium carbonate. Heating above 870 °C leads to the crystallization of cristobalite from amorphous silicon dioxide. At a temperature of about 870 °C, the coating acquires a smooth surface, and heating above 1170 °C leads to its destruction. Thus, the optimum temperature for the heat treatment of the coating is about 870 °C. The loss of strength of carbon fiber at each stage of coating was estimated. A full coating cycle, including thermal cleaning from the sizing, coating, and heat treatment, results in a loss of fiber strength by only 11% compared to the initial state.

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Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

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Heat Treatment Effect on the Phase Composition of the Silica Electrochemical Coating and the Carbon Fiber Strength

et al. 2021

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“…Bulk synthetic opals were obtained by natural sedimentation of α-SiO 2 globules with the following annealing of samples at 800 0 C during several hours. Annealing was performed in order to remove organic residua, extra-and intra-globular ethoxygroups, and chemically bound water (Samarov et al, 2006). Dimensions of obtained samples were about 1.0x1.0x0.2 cm 3 .…”

Section: Characterisation Of Samples and Experimental Setupmentioning

confidence: 99%

“…Thus, all elicited regularities together with chosen conditions of the samples heat treatment (Samarov et al, 2006) are the reasons to exclude the fluorescence of nano-composite components and the OH-groups fluorescence observed in synthetic opals within a 520 nm -650 nm range (Gruzintsev et al, 2008). Taking into account angular dependences of spectral intensity, the emission observed may be interpreted as spontaneous parametric downconversion in spatially nonuniform nonlinear optical media.…”

Section: Spontaneous Parametric Down-conversionmentioning

confidence: 99%

Quantum Optics Phenomena in Synthetic Opal Photonic Crystals

Moiseyenko¹,

Dergachov²

2012

Quantum Optics and Laser Experiments

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Quantum Optics and Laser Experiments 88 allows modifying optical properties of such systems by filling the pores with various substances. Synthetic opal photonic crystals containing nonlinear optical substances give a good chance to observe quantum optics phenomena in spatially nonuniform media where the photon mean free path is close to the light wavelength. Moreover, in this case the input optical power that is necessary to observe phenomena may be lower than the power required usually for observing the same phenomena in uniform nonlinear substances. The reason for it is the existence of diffuse transfer of photons that can result in photon accumulating inside photonic crystals and, consequently, in local optical power increasing. In particular, the possibility of experimental manifestation of Raman scattering and spontaneous parametric down-conversion in synthetic opals is discussed (Gorelik, 2007). The latter phenomenon is of special interest as it is convenient method to obtain bi-photon fields consisting of correlated photon pairs (Kitaeva & Penin, 2005). In the recent years, crystals with chirped structure of quadratic susceptibility (Kitaeva & Penin, 2004), and materials with spatially regular and stochastic distribution of quadratic optical susceptibility (Kalashnikov et al., 2009), are considered as sources of bi-photons. It is quite possible synthetic opal photonic crystals will be ranked with these sources.

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Vibrational spectra of DNA in the confined interglobular volume of photonic crystal

Boiko

Romanyuk²,

Gnatyuk

et al. 2018

J Biol Phys

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The impact of confinement of DNA molecules in a limited volume of the cavity of photonic crystals (PC) on the vibrational properties of the DNA molecule and its conformation is studied. According to our preliminary study, the aqueous shell is removed when the DNA molecules are infiltrated into the PC cavities. Raman scattering (RS) DNA marker lines showed a dramatic conformational change of DNA in the PC cavities and the appearance of new unknown conformational states. We observed the enhancement of vibrational modes of DNA in the PC in comparison with free DNA of about tenfold and the absence of vibrational modes in DNA bases in a region of 1450-1700 cm. The observed features in the RS spectra of DNA are explained by the impact of confined interglobular volume and strong localization of the electromagnetic field. Namely, FDTD simulations in linear regime demonstrate the localization of light in cavities of PC with an approximately ninefold enhancement of the electric field within the photonic stop-band, which is the main reason for RS amplification.

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Structural modification of synthetic opals during thermal treatment

Cited by 26 publications

References 10 publications

Heat Treatment Effect on the Phase Composition of the Silica Electrochemical Coating and the Carbon Fiber Strength

Heat Treatment Effect on the Phase Composition of the Silica Electrochemical Coating and the Carbon Fiber Strength

Quantum Optics Phenomena in Synthetic Opal Photonic Crystals

Vibrational spectra of DNA in the confined interglobular volume of photonic crystal

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