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Synthesis of PMMA-HoVO4 nanocomposites by emulsifier-free emulsion polymerization: radical effects

Abstract

Poly(methyl methacrylate)-holmium orthovanadate (PMMA-HoVO4) nanocomposites were synthesized using emulsifierfree emulsion polymerization system in two ways. In the first one, the HoVO4 nanoparticle dispersion was added to the emulsion system before or after polymerization start (in situ polymerization). In the other one, nanoparticle dispersion and polymeric latex were mixed together at room temperature (blending). Crystalline HoVO4 nanoparticles (about 60 nm) were synthesized by coprecipitation method. Three different composite latexes were synthesized by varying the potassium persulfate concentration and the time of HoVO4 nanoparticles addition. According to the dynamic light scattering analysis, the size of the polymer beads in the latexes is between 244.8 nm and 502.5 nm and the PDI values are in the range of 0.005 to 0.206. Infrared spectral analysis showed that HoVO4 caused some changes in the structure of the polymer. Luminescence measurements attempted to determine optical properties of the nanocomposites. The results have shown that HoVO4 nanoparticles do not protect their structure due to the reaction with persulfate radicals but that they enter the polymer beads and change the luminescence properties of the polymer forming a new material with different properties.

Open access
Growth, spectral, optical, dielectric and third order nonlinear studies on 2-amino 4-methylpyridinium salicylate single crystals

Abstract

Optically transparent single crystals of 2-amino 4-methylpyridinium salicylate were successfully grown by slow evaporation solution growth technique at room temperature. The grown crystal was characterized by various characterization techniques such as single crystal X-ray diffraction, Fourier transform infrared microscopy, optical, dielectric and Z-scan studies. The presence of various functional groups was identified by Fourier transform infrared technique. UV-Vis-NIR studies implied the absence of absorption in the visible region. Dielectric studies were carried out in the frequency range from 50 Hz to 5 MHz. Thermogravimetric/differential thermal analysis and nuclear magnetic resonance spectra studies were also performed for the grown crystal. Nonlinear refractive index, absorption coefficient and third order nonlinear optical susceptibility of the crystals were evaluated by Z-scan studies.

Open access
Growth, spectroscopic, electrical and mechanical studies on hexamethylenetetramine succinate crystal: a new third harmonic generation material

Abstract

Hexamethylenetetramine succinate was synthesized and good quality single crystals with the size of 14 mm × 6 mm × 4 mm were grown by the slow evaporation solution growth technique at room temperature. The single crystal XRD revealed that the grown crystal belongs to the monoclinic system with the space group of P21/c. The presence of functional groups in the crystal was identified using FT-IR technique. The optical behavior was examined through UV-Vis-NIR studies. The photoconductivity study exhibited the positive photoconductivity nature of the grown crystal. Microhardness studies revealed the soft nature of the crystal. The nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third order nonlinear optical susceptibility χ(3) of the crystals were measured by Z-scan studies.

Open access
Research on the influence of the filtrating electrode on the structure and optical properties of TiO2 thin films prepared by the energy filtering magnetron sputtering technique

Abstract

TiO2 thin films were deposited by the energy filtrating magnetron sputtering (EFMS) technique and the traditional direct current magnetron sputtering (DMS) technique. The influence of the filtering electrode mesh number on the structure and optical properties of TiO2 thin films was investigated. The structure, surface morphology and optical properties were characterized by XRD, SEM and ellipsometric spectroscopy, respectively. Results show that the TiO2 thin films deposited by the DMS and EFMS techniques at the same deposition parameters are composed of the anatase phase exclusively. TiO2 thin films deposited at lower deposition rate by the EFMS technique have lower crystallinity, smaller particle size and smoother surface. With increasing the mesh number, the refractive index, extinction coefficient and optical band gap are larger.

Open access
Stereometric analysis of Ta2O5 thin films

Abstract

The purpose of this work is the study of the correlation between the thickness of tantalum pentoxide thin films and their three-dimensional (3D) micromorphology. The samples were prepared on silicon substrates by electron beam evaporation. The differences in surface structure of the processed and reference samples were investigated. Compositional studies were performed by energy-dispersive X-ray spectroscopy. Stereometric analysis was carried out on the basis of atomic force microscopy (AFM) data, for tantalum pentoxide samples with 20 nm, 40 nm, 60 nm, 80 nm and 100 nm thicknesses. These methods are frequently used in describing experimental data of surface nanomorphology of Ta2O5. The results can be used to validate theoretical models for prediction or correlation of nanotexture surface parameters.

Open access
Synthesis, photophysical properties and electrochemical polymerization of a new blue fluorescent compound based on 3,4-ethylenedioxythiophene moiety

Abstract

New monomer, 4,4’-[(2,3-dihydrothieno[3,4-b][1,4]diorin-5-yl)vinyl]-1,1’-biphenyl (BPE), was synthesized, characterized and polymerized electrochemically via a potentiostatic method. The corresponding polymer poly(4,4’-[(2,3-dihydrothieno[3,4-b][1,4] diorin-5-yl)vinyl]-1,1’-biphenyl) (PBPE) obtained as a thin-layer film, was characterized by cyclic voltammetry, X-ray photoelectron spectroscopy, infrared spectroscopy and UV-Vis spectroscopy. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the obtained polymer were determined from cyclic voltammograms as –4.89 eV and –3.81 eV, respectively. Its optical and electrochemical band gaps were calculated, and found to be 1.08 eV and 1.49 eV, respectively. PBPE can be used as a donor material in bilayer organic photovoltaic solar cells having PCBM as acceptor material.

Open access
RPAS Satellite Communication Channel Based on Long-Term Evolution (LTE) Standard

Abstract

MIMO-OFDM models of RPAS communication channels based on LTE Standard were built. Dependencies of the BER on the SNR for Extended Pedestrian A and Extended Vehicular A models using 2-by-2 multiple antennas were obtained. Dependencies of the BER on the SNR for different levels of Frequency Offset at satellite transponder were studied.

Open access
Studies on new material: carbon dot-graphene oxide-zinc oxide nanocomplex

Abstract

In the present work, with an aim of developing new useful materials, carbon dot-graphene oxide-zinc oxide (CGZ) nanocomplexes were synthesized by the wet chemical method. Structure, morphology and chemical composition of prepared GCZ nanoparticles were determined by carrying out X-ray diffraction, scanning electron microscopy, Fourier transform infrared and energy dispersive X-ray absorption spectral measurements. The strong absorption band observed in the UV region for the prepared samples can be attributed to the band edge absorption. The dielectric parameters, viz. dielectric constant (∈r), dielectric loss (tanδ) and AC electrical conductivity (σ AC) were determined at various temperatures in the range of 30 °C to 150 °C at two different frequencies (100 Hz and 1 kHz). DC conductivity (σDC) measurement was also carried out at various temperatures in the range of 30 °C to 150 °C. In addition, the enhanced photocatalytic activity of CGZ has been explained and the mechanism elucidating the excellent performance of CGZ has been proposed.

Open access
Agricultural knowledge transfer: A case study for small farms and young farmers’ beneficiaries of European funds

Abstract

Common Agricultural Policy represents the main instrument of the European Union for the development of agriculture and rural areas. European funds are vital for the productivity and competitiveness of agricultural holdings, as well as for the transfer of agricultural knowledge and innovation. Supporting small and young farms is essential for the vitality of rural areas and for the renewal of generations of farmers. The aim of this work is to transfer agricultural knowledge in order to improve the productivity of agricultural holdings, especially among young farmers and small farms. We implemented training program through European funds related to Measure 1. “Actions for knowledge transfer and information actions” from Rural Development Programme of Romania. The characteristic of 100 participants and their responses were analyzed. Most of the participants were young people up to 40 years old (59%). The vast majority of the participants were from the rural area and only 17% were from the urban area. 53% from participants were strongly agree with the fact that level of knowlegde influence farm productivity. Actions for knowledge transfer improve the adaptation of farmers to the new challenges of agriculture, as well as productivity.

Open access
Analysis of the causes of control panel inconsistencies in the gravitational casting process by means of quality management instruments

Abstract

All castings can have defects caused by, for example, deviations in material characteristics, structure or properties, but the skillful use of available technologies and quality management tools allows for the detection and elimination of casting incompatibilities as well as the prevention of their recurrence in the future. The aim of the article was to analyse the types of defects in castings, locate the areas with the most frequent occurrence of defects and identify the reasons for the presence of defects in castings of the control panel and its cover. The paper presents the usefulness of a combination of quality management instruments for diagnosing material discontinuities in the analyzed castings.

Open access