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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.

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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.

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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.

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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.

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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
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.

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Advances in Carbon Fiber Reinforced Polyamide-Based Composite Materials

Abstract

Carbon fiber has been used to reinforce both aliphatic and aromatic polyamides. Aliphatic polyamide is known as nylon and aromatic polyamide is often referred to as aramid. Among aliphatic polyamides, polyamide 6, polyamide 6,6, polyamide 11, polyamide 12, and polyamide 1010 have been used as matrices for carbon fiber. Factors affecting the properties of polyamide/carbon fiber composites are: fiber amount, fiber length, fiber orientation, matrix viscosity, matrix-fiber interactions, matrix-fiber adhesion, and conditions encountered during manufacturing processes. This article presents a state-of-the-art review on polyamide/carbon fiber composites. Polyamide/carbon fiber composites are lightweight and exhibit high strength, modulus, fatigue resistance, wear resistance, corrosion resistance, gear, electrical conductivity, thermal conductivity, chemical inertness, and thermal stability. Incorporation of oxidized or modified carbon fiber and nanoparticle modified carbon fiber into polyamide matrices have been found to further enhance their physical properties. Applications of polyamide/carbon fiber composites in aerospace, automobile, construction, and other industries have been stated in this review. To fully exploit potential of polyamide/carbon fiber composites, concentrated future attempts are needed in this field.

Open access
Application of the 3D Digital Image Correlation to the Analysis of Deformation of Joints Welded With the FSW Method After Shot Peening

Abstract

The three dimensional Digital Image Correlation (3D DIC) method is used for measurements of deformations and displacement in plane elements exposed to loading. The paper presents the experimental tests of an application of the ARAMIS system to the analysis of deformation of joints welded with the FSW method after shot peening treatment. The butt joints were made of 2024-T3 aluminum alloy sheets with the thickness of 1 mm, which next were peened with glass beads about granulation in range 500 ÷ 900 µm. Tests of residual stresses by X-ray diffraction were also carried out. The aim of the study was to analyze the impact of shot peening on the value of stresses and the location of deformations in butt joints.

Open access
Atmospheric Plasma Spraying of Al2O3 + 13% TiO2 Coatings Using External and Internal Injection System

Abstract

The ceramic coatings based on mixture of Al2O3 and TiO2 have better properties in comparison to the pure alumina ones. Among many techniques, plasma spraying is very useful method of ceramic coatings manufacturing. In this paper, the results of microscopic, mechanical and tribological properties investigations of Al2O3 + 13 wt% TiO2 coatings manufactured by atmospheric plasma spraying are presented. The cylinder substrates made from stainless steel (X5CrNi18-10) had a diameter equal to 25 mm and thickness equal to 2 mm. The plasma spray experimental parameters included three variables: (i) type of injection system (external or internal), (ii) size of corundum particles for sandblasting and (iii) torch linear speed. The results confirm, that type of injection system is a dominant parameter. Internal injection results in better degree of particles melting, what influences on wear resistance performance, as well as higher values of bond strength.

Open access