Papers by Keyword: IR Spectra

Abstract: Reducing the pressing temperature of plywood on the FF binder allows you to reduce its cost, but at the same time, the physical and mechanical characteristics of plywood deteriorate. Modification of the phenol-formaldehyde binder with hydrogen peroxide reduces the curing time of the phenolic binder, the pressing temperature of the FSF plywood, and improves the physical and mechanical properties of the FSF plywood. Regression models have been developed for dependence of the plywood strength during cleavage along the adhesive seam, strength during static bending, and thickness swelling after 24 hours in water on the factors varied in the experiment – the proportion of hydrogen peroxide addition and the pressing temperature. The IR spectra of plywood allow us to estimate the effect of H₂O₂ on the bonds involved in the structure formation of material. With the addition of hydrogen peroxide, the number of active methylene groups decreases, which indicates an increase in degree curing of modified binder.

Abstract: Thermochromic properties were found in bimetallic hybrid inorganic-organic complex compounds of hexa (thiocyanate-N) chromates (III) of IIIb-group rare-earth metals and lanthanides complexes with dimethylsulfoxide [M(C₂H₆SO)₈]L, dimethylformamide [M (C₃H₇NO)₈]L, ε-caprolactam [M(εC₆H₁₁NO)₈]L and nicotinic acid [M(C₅H₅NCOO)₃(H₂O)₂]L·nH₂O, n=1,2, L=[Cr (NCS)₆]^3-, M=Sc³⁺, Y³⁺, Ln³⁺, obtained by means of direct synthesis from the aqueous solutions, the composition of substances was studied by methods of chemical and electron microscopic analyzes, solubility and chemical resistance were determined. Radiographic and thermogravimetric characteristics, IR spectra, magnetic properties are studied. The experimental data obtained indicate the antiferromagnetic nature of the interaction between paramagnetic centers in the studied ionic compounds, the crystallographic parameters of which were determined by the method of X-ray diffraction analysis of single crystals at low temperatures. In the temperature range of 383-493 K, substances, without changing the physicochemical characteristics, reversibly change color, withstanding many heating-cooling cycles.

Abstract: The IR absorption spectra of hexagonal crystals of lithium iodate α-LiIO₃, used in laser shutters for ship wiring, where the quality, transparency and power of laser radiation are of great importance, are studied. The transmission spectra allowed us to determine the width of the crystal band gap 4.37 eV along the Z-axis (C₆ [0001]) and 4.46 eV along the axis perpendicular to the Z axis. The activation energies and the wavelength of the vibrational centers associated with the vibrations of the H₃O⁺, OH^-, H₂O groups, heavy D₂O and semi-heavy molecules HDO are determined. It is established that the band 1450-1650 cm^-1 is a superposition of at least two broad absorption maxima centered at ~1550 and ~1600 cm^-1. It was experimentally established that the ratio of the absorption coefficients of these bands was ~1:1 (75:74 cm^-1) for crystals grown in H₂O, and ~2:1 (161:84 cm^-1) – for crystals grown in D₂O. This allows us to assume that in a lithium iodate crystal grown in D₂O, the bands 1550 cm^-1 and 1600 cm^-1 correspond to the vibrations of the bound HDO and H₂O molecules, the band 1150 cm^-1 corresponds to the vibrations of heavy water molecules. The results of the study allowed us to propose a mechanism of transport and translational diffusion of protons and to determine the presence of heavy water molecules in crystalline materials, as well as to diagnose the quality of laser crystals.

Abstract: Membrane technologies are currently among the most demanded. This is evidenced by their variety and a wide range of membrane applications in the most topical areas of human life. This work proposes a simple and inexpensive method for producing composite membranes for ultrafiltration and nanofiltration with a surface layer of cellulose acetate for water purification and water treatment processes. A nylon microfiltration membrane was used as a membrane base. The surface layer was obtained by immersion in a solution of cellulose acetate in acetone. Composite membranes with different retention properties were obtained depending on the number of deposited layers. The resulting membranes were examined for total porosity, water absorption, cellulose acetate content, contact angle, and IR absorption spectra. The specific productivity of the obtained membranes with respect to distilled water was also established.

Abstract: Stable electronic configuration between the interface of an n-type oxide semiconductor core and a p-type polymer shell is necessary in order to guarantee a consistent functioning core-shell structure. This research aims to use silane-aniline to link between an n-type Titanium (IV) oxide (TiO₂) core and p-type polyaniline emeraldine salt (PANI-ES) shell. Core-shell structure was created by functionalizing TiO₂ powders with silane aniline molecules using simple soaking technique and then polymerizing the attached aniline molecules using an oxidative technique. Infrared spectroscopy reveals the presence of Si-O bonds signifying the presence of linkage between the inorganic core and polymeric shell. Polymerization of the attached aniline molecules may have led to coupling of aromatic rings to form long polymeric structures which caused widening and shifting of aromatic rings’ IR peak to lower wavenumber. In conclusion, silane-aniline was successfully utilized to connect the n-type TiO₂ core and p-type PANI-ES shell.

Abstract: The influence of the concentration of the initial solution on the size and composition of the particles obtained by the method of ultrasonic spray pyrolysis (USP) was investigated. An aqueous solution of Fe (NО₃)₃·9Н₂О, the concentration of which varied in the range of 0,0025–0,03 mol/l, was used as the starting material. As a result of the process, iron oxide particles were obtained, the average size of which varied from 123 to 292 nm. Based on FTIR and XRD, powders consist of several phases and have crystalline inclusions α-Fe₂O₃, β-Fe₂O₃, and γ-Fe₂O₃.

Abstract: The results of studies of mechanical activation of mineral layered silicate - vermiculite as a method of improving compatibility with polytetrafluoroethylene (PTFE) are presented. The influence of mechanoactivation on the crystalline structure of silicate as well as on deformation-strength, tribotechnical characteristics and coefficient of thermal expansion of composites is considered. The effectiveness of the use of mechanical activation to improve the combination of vermiculite with a polymer matrix is ​​confirmed by the results of the tests. It is shown that the preliminary mechanoactivation of the layered silicate leads to an increase in the elasticity, modulus of elasticity and wear resistance of the developed composites while maintaining the breaking strength at the level of the original PTFE.

Abstract: Degradation of toxicants in photocatalytic reactor is studied. To an array of data on the photochemical properties of Methylene Green (MG) when exposed to UV radiation in photoreactors was obtained. Based on the analysis of the results obtained, conclusions can be drawn about the relationship between the structure of pollutants, their initial concentration, oxidizer concentration, etc., with the efficiency of utilization, and schemes for photochemical processes was constructed. The role of polypropylene microfiber materials (PMM) in the degradation of MG under UV irradiation was studied.

Abstract: The aim of this study is to investigate the incorporation of Al₂O₃ in SiO₂ glass with emphasis on reducing the phonon energy in the SiO₂ matrix. Pure SiO₂ glass has very high phonon energy of about 1100 cm^-1, while Al₂O₃ has 780 cm^-1. By incorporating Al₂O₃ into SiO₂ glass structure, the relative phonon energy of the SiO₂ matrix is expected to reduce. However, the composition of Al₂O₃ has been limited to a desired amount so as not to perturb other properties of SiO₂, such as optical absorption. The Infrared (IR) spectra for a portion of SiO₂ glass with the Al dopants were simulated at different molar ratio of the composition using Molecular Mechanic and Density Functional Theory (DFT). The Al₂O₃-SiO₂ structures show a significant change in the simulated IR spectra compared to pure SiO₂ glass. The Al₂O₃-SiO₂ structures in the present work were constructed by replacing some Si atoms with Al atoms in the host lattice of SiO₂ glass. In addition, some O atoms were removed from SiO₂ host lattice to get the correct chemical balance. With increasing of Al₂O₃ content, the relative intensity of ~1100 cm^-1 band associated with the asymmetrical O-Si-O/Si-O stretching vibrations is decreased. The decreasing in relative intensity of the IR spectra demonstrates that Al dopants are forming – [Al-O-Si] – linkages in the structure.

Abstract: The effects of gamma radiations on the optical, physical and structural properties of zinc lead borate xZnO-2xPbO-(1-3x)B₂O₃ and zinc lead borosilicate xZnO-2xPbO-1/2(1-3x)B₂O₃-1/2(1-3x)SiO₂ glasses have been investigated. Differential Scanning Calorimetry (DSC), Ultraviolet-Visible (UV-Vis) and Fourier Transmission Infra-red (FTIR) spectroscopic techniques have been used to compare the properties of samples before and after gamma irradiation by a dose of 2.5 kGy. The variation of density, optical band gap (E_g), IR absorption bands and glass transition temperature (T_g) indicates that the structure of glasses changes due to irradiation. The radiation induced changes created by-ray in the optical, physical and thermal parameters in both the prepared series of glasses have been discussed for their possible application as radiation shielding material.