arXiv subjects

G. Dovbeshko

Publications and source records attributed to G. Dovbeshko.

4 recordsLinked to original sources

arXiv2025

Low-Temperature Heat Capacity and Phonon Dynamics in Expanded Graphite and EG--MWCNTs Composites

The specific heat of expanded graphite (EG) and EG--multiwalled carbon nanotube (MWCNT) composites (1.0 and 3.0 wt.\% MWCNTs) was measured between 2 and 300~K. The low-temperature heat capacity is dominated by out-of-plane flexural phonons with quadratic dispersion, characteristic of two-dimensional layered systems. Compared with crystalline graphite, EG exhibits enhanced heat capacity due to increased defect density and reduced interlayer coupling. Structural characterization (XRD, Raman, EDS) confirmed variations in stacking order and defect concentration. The data were fitted using a three-term model ($C_{1}T + C_{3}T^{3} + C_{5}T^{5}$), where the negative $C_{5}$ term indicates quadratic phonon dispersion. The results demonstrate the influence of MWCNT integration and structural disorder on phonon dynamics and anisotropic heat capacity in EG-based composites.

cond-mat.mtrl-sci↗

arXiv2017

Ordered carbon nanotubes and globular opals as a model of multiscaling photonic crystals

Experimental data on carbon nanotube carpet and synthetic opals have been compared by visible, infrared spectroscopy, and electron microscopy. Spectral features of the objects under study in infrared region are registered. Three regions of abnormal behavior of reflectance and absorbance for carbon nanotube carpet and two regions for opals in the 7000-2000 cm-1 are observed in comparison with the separated nanotubes or SiO2 globules in disordered states and/or condensed state. The spectroscopic features of the photonic crystals caused by their different microstructures at different length scales and basis for development of a proper model for light propagation through the photonic crystals in the IR region are presented for discussion.

physics.optics↗

arXiv2012

The study of influence of the Teslar technology on aqueous solution of some biomolecules

The possibility of recording physical changes in aqueos solutions caused by a unique field generated by the Teslar chip (TC) inside a quartz wristwatch has been studied using holographic interferometry. We show that the refraction index of degassed pure distilled water and aqueous solutions of L-tyrosine and b-alanine affected by the TC does not change during the first 10 minutes of influence. In contrast, a 1% aqueous solution of plasma extracted from the blood of a patient with heart-vascular disease changes the refractive index when affected by the TC. The characteristic time of reaction is about 100 s. Based on our prior research experience we state that the response of the system studied to the TC's field is similar to that stipulated by the action of a constant magnetic field with the intensity of 1.1 x 10^{-3} T. Nevertheless, our team could unambiguously prove that the TC generates the inerton field, which is associated with a substructure of the matter waves (and, therefore, it does not relate to the electromagnetic nature).

physics.gen-ph↗

arXiv2012

Secondary emission from synthetic opal infiltrated by colloidal gold and glycine

A comparison of the secondary emission (photoluminescence) and Bragg reflection spectra of photonic crystals (PC), namely, synthetic opals, opals infiltrated by colloidal gold, glycine, and a complex of colloidal gold with glycine is performed. The infiltration of colloidal gold and a complex of colloidal gold with glycine into the pores of PC causes a short-wavelength shift (about 5-15 nm) of the Bragg reflection and increases the intensity of this band by 1.5-3 times. In photoluminescence, the infiltration of PC by colloidal gold and colloidal gold with glycine suppresses the PC emission band near 375-450 nm and enhances the shoulder of the stop-zone band of PC in the region of 470-510 nm. The shape of the observed PC emission band connected with defects in synthetic opal is determined by the type of infiltrates and the excitation wavelength. Possible mechanisms of the effects are discussed.

physics.optics↗