Papers by Keyword: Ordered Structure

Abstract: Experimental studies of bending deformation of carbon - and fiberglass samples after 8-month exposure in full-scale conditions were performed and the modulus of transverse elasticity was determined. It was found that the influence of the external environment on fiberglass samples is more significant. For carbon fiber, there was an average decrease of 7.1%, and for fiberglass-by 14%. Modification of samples in ultrahigh frequencies (UHF) electromagnetic field reduces the negative influence of the environment: the values of the transverse elastic modulus of carbon fiber and fiberglass samples are reduced by 5% and 11%, respectively. It is shown that the UHF electromagnetic field in rational modes can increase the modulus of transverse elasticity of carbon fiber by (27-30)%, fiberglass – by (20.8-25.6)% with a significant increase in the uniformity of this parameter. Experimental studies of the bending deformation of carbon-and fiberglass specimens after 8-month exposure in natural conditions have been carried out, and the shear elastic modulus has been determined. It has been established that the influence of the external environment on fiberglass samples is more significant. For carbon fiber reinforced plastic, a decrease was noted on average by 7.1%, for fiberglass - by 14%. Modification of samples in a microwave electromagnetic field helps to reduce the negative influence of the external environment: the values ​​of the shear modulus of the prototypes of carbon fiber reinforced plastic and fiberglass are reduced by 5% and 11%, respectively. It is shown that the microwave electromagnetic field in rational modes allows increasing the transverse elastic modulus of carbon fiber reinforced plastic by (27-30)%, fiberglass - by (20.8-25.6)% with a significant increase in the uniformity of this parameter.

Abstract: The influence of modification of fiberglass in the cured state in the microwave electromagnetic field on the value of the limit stresses is significantly manifested when testing samples in the initial state. The increase in limit voltages is on average 7%. Tests of modified samples after exposure in full-scale conditions showed a decrease in the effect with an increase in the exposure time from 6% for exposure of 3 months to 3% for exposure of 8 months. This significantly increases the uniformity of the bending strength values in the batch, which is manifested in a decrease in the coefficient of variation of limit stresses relative to the control samples by 33%. Functional dependencies in the form of 2nd-order polynomials are obtained, which allow predicting the stability of products made of modified fiberglass for long-term operation under the influence of environmental factors with a confidence of up to 98%.

Abstract: This article is concerned with the analysis of ordering the arrays of TiO₂ and Al₂O₃ nanotubes using the correlation-spectral methods. As the tools, the spatial Fourier spectrum and one-dimensional autocorrelation function of SEM-image have served. It was shown that the arrays of the aluminum oxide nanotubes can have a nearly ideal ordering on a small scale at the expense of two-stage anodizing. It this case, the degree of order depends also on the purity of initial aluminum and sample preparation method. The introduced characteristics can serve as the measures of the structure order-disorder sensitive to both type and degree of order as a whole and to configuration of structural elements themselves.

Abstract: The methods of segmentation and statistical processing of the data on the relief formation on the self-organized surface of the statically deformed alloy D16chT are used. This allowed determining the signal parameters, segment structure and morphological peculiarities of self-organization as the data of the cyclic random process model. The mathematical methods are proposed, which allow increasing the accuracy, reliability and informative value of the profilometric data processing in diagnostic systems of control of the surface condition.

Abstract: Colloidal crystal has attracted much attention both in fundamental crystal growth science and optical applications. This paper reports a simple and efficiency spin-coating method to fabricate high ordered colloidal crystals which have specific structures. We used the cleaned glass slide as substrates, the well dispersity 300nm (±1.2%) polystyrene (PS) spheres aqueous suspension (6.6 wt%) to assemble, and obtained highly organized colloidal crystal thin film by controlling spin-coating condition. Mostly, we got the large area plane hexagonal structure at the first layer and tetragonal construction at the second layer. The mechanism for this stacking way was studied. The obtained thin films were demonstrated by Field emission scanning electron microscope (FESEM) and Fast Fourier transform (FFT).

Abstract: Ordered nanoporous carbon (ONC) was synthesized by adopting sucrose as precursor and SBA-15 as template. The thermal stability of sucrose and its SBA-15 composite were detected by thermogravimertic analysis. Transmission Electron Microscope, X-ray diffraction and nitrogen adsorption technology were used to characterize the morphology, microstructure and specific surface area of resultant ONC. The effects of carbonization temperature and pre-carbonization on the microstructure of ONC were investigated. The results have shown that SBA-15 is a kind of ideal template for preparing ONC, from which ONC with the diameter around 8 nm was obtained. When carbonized at 700 °C, the specific surface area of ONC derived is 2884.05 m²/g.

Abstract: . In intermetallic compounds, random vacancy motion is not possible as it would disrupt the equilibrium ordered arrangement of atoms on lattice sites. In view of this limitation, various atomistic models have been proposed, which allow atom-vacancy exchanges to take place without concomitant long range disordering. For a L12 -type A3B structure, the major element A diffuses faster than the minor element B. The trend is attributed to the different diffusing paths; A atoms can diffuse through site exchanges with a neighbouring vacancy on its own sublattice, while the jump of a B atom to a neighbouring site always creates wrong bonds. For L10-type structures such as γ-TiAl, significant diffusion anisotropy is observed; Ti atoms diffuse on the Ti sublattice, while Al atoms also diffuse on the Ti sublattice. The formation of hollow metal oxide nanoparticles through the oxidation process has been studied by transmission electron microscopy for Cu, Zn, Al, Pb and Ni. The hollow structure is obtained as a result of vacancy aggregation, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process. This suggests the occurrence of two different diffusion processes in the formation of hollow oxides.