Polymer nanocomposites based on Cu(Cu
2
O)-LDPE with a volume fraction of 0.1–0.4 copper filler in the form of spherical nanoparticles with sizes from 10 to 25 nm were synthesized. The electrical ...conductivity of such composite nanomaterials was measured, which is 4.5–5 times higher than the electrical conductivity of a polyethylene matrix. To predict the electrical conductivity of such materials, an analysis of well-known mathematical models is carried out and models for predicting the electrical conductivity of such materials are selected that are adequate to the experimental data.
CdS nanoparticles (NPs) as quantum dots (QDs) added into low density polyethylene (LDPE) can significantly change the MW dielectric properties of the composites. Introducing into the matrix of low ...density polyethylene CdS QDs increase the dielectric constant of more than twice. CdS QDs with concentration of 5 wt % to 20 wt % were prepared by the method of high-speed thermal decomposition. The size of CdS nanoparticles ranged from 2 nm to 7 nm. Experimental samples based on polymer-based nanocomposite in the form of thick films with a thickness of 80 to 100 microns were prepared by thermocompression. Complex dielectric permittivity of thick film samples was measured by T/R method from 2 to 8 GHz at room temperature (25°C). For samples with 20 wt % CdS NPs size effect was found. The change of dielectric properties of polymer composite materials is associated with the size of QDs. The dielectric constant and dielectric loss increases with decreasing size of the quantum dots. It is shown that the highest mean value of the dielectric constant and dielectric loss at a frequency range of 5 GHz to 8 GHz for cadmium sulfide nanoparticles with size of 4 nm were 12 and 189 dB/m, respectively. For QDs with ones of 6 nm average dielectric constant and dielectric loss were 5.8 and 134 dB/m, respectively. The effective dielectric constant and dielectric losses in the microwave range can be changed by CdS QDs of different sizes what consequently increases the possibility of using polymer nanocomposites as core elements of the microwave band-pass filters for various purposes.
The article presents the results of an experimental study of the thermo-optical properties of a polymer composite nanomaterial based on 10 wt % CdS-LDPE. It is shown that the temperature dependences ...of the refractive index have a hysteresis in the heating-cooling cycle. The thermo-optical coefficients of the material during its heating and cooling, which had a negative value from –0.00026 to –0.0076 1/K were estimated. In the temperature range of 55–75°C, a strong nonlinearity of the temperature dependences of the refractive index of the width and energy gap of the material was observed. With increasing temperature up to 65°C, a decrease in the width of the forbidden zone was observed, and at temperatures above 65°C an increase in the width of the energy gap was observed. The maximum change in the band gap was about 0.2 eV. A strong change in the band gap in the temperature range 55–75°C is associated with a phase transition in the material. The detected thermo-optical properties of the polymer composite nanomaterial can be useful in the development of nanophotonic information-processing devices.
Background and Objectives: Using sol-geltechnology, silicate mesoporous single layer coatings based on SiO2@CuO(ZnO) compositions were obtained to increase glass transparency. The phase composition ...and properties of powders obtained from dried sols were studied. The optical properties of the obtained silicon oxide sols were explored by the turbidimetric method. To identify the characteristics of gelation and coagulation, a spectrophotometric study of the silicon oxide sol was carried out. The resulting sols were applied to glass by adsorption from solution (dip-coating) at room temperature (23 ± 10°C). The rate of extraction from the solution varied from 105 to 160 mm/min. Glasses with coatings applied to both sides were dried at room temperature until a film formed and subjected to heat treatment in a muffle furnace at a temperature of 500°C. At the moment of annealing, the decomposition of copper and zinc salts and the formation of a composite composition of SiO2@CuO and SiO2@ZnO films occurred. Spectral measurements of the transmittance and reflection of glasses with single layer mesoporous coatings were carried out in the range of 400-800 nm. Materials and Methods:To obtain sols with copper and zinc, metal salts Zn(CH3CO2)2 ·2H2O and (CH3COO)2Cu·H2O (6% or 10% by weight SiO2) were added to the SiO2 sol. Using a magnetic stirrer, the resulting mixtures were stirred at room temperature for 15 ± 0.5 min. To study the optical properties of the sols, a base SiO2 sol and SiO2 sols with the addition of zinc acetate and copper acetate (6% and 10% by weight of silicon dioxide) were prepared. After heat treatment, the thickness of the applied coatings was determined by contact method using a Dektac-150 profilometer. It was determined that the thickness of the coatings on glass varied from(95 ± 20) to (137 ± 7) nm at drawing speeds of 105 and 160 mm/min, respectively. Results: The developed methods for producing mesoporous silicate coatings on glass have ensured the creation of homogeneous coatings with good adhesion, uniform thickness and roughness. The results of measuring the transparency spectra of glass with a single layer coating of sols with different compositions and drawing rates have been presented. It has been shown that double-sided single-layer mesoporous SiO2@CuO(ZnO) composite coatings with different compositions demonstrate an increase in glass transparency by 2-3% in a wide optical range of 400-1000 nm. Conclusion: The proposed composition of compositions in single layer film structures makes it possible to solve the problem of broadband antireflection of glasses in a wide range of optical wavelengths (400-1000 nm).
Background and Objectives: Membranes in the form of highly ordered nanostructures of porous anodic aluminum oxide (PAAO) with adjustable pore properties were obtained by electrochemical anodizing. ...PAAO nanostructures were prepared in an oxalic acid electrolyte at a direct current electrochemical potential of 30-60 V. The ready-made nanoporous membranes were modified with thin silver films 1.8, 3.6 and 5.4 nm thick. The study of the membrane surface by scanning electron microscopy has shown that nanoporous membranes have hexagonally arranged and highly ordered arrays of pores with a diameter of (30±4) nm and a packing density of about 1.8 · 10¹⁰ cm-2. Optical interference spectra of PAAO were recorded in the wavelength range of 300-900 nm. The optical properties of nanoporous membranes with a free and silver-modified surface changed depending on the time of interaction of the membrane surface with the ammonia gas flow, which led to changes in the interference pattern and, in turn, to changes in the effective optical thickness (EOT) of the membranes. Features of the influence of the membrane surfacemodified with silver onthe shape and sensitivity ofthe optical signal ofthe sensor have been revealed. The aim ofthis work was to experimentally study the temporal characteristics of the optical spectral response of nanoporous anodic alumina membranes with a free pore surface and modified with thin silver films in an ammonia gas flow. Materials and Methods: The thickness of the PAAO membrane, determined profilometrically, did not exceed 1.0 µm. The average inner diameter of Al2O3 nanopores is (30±4) nm. The silver films were deposited by magnetron sputtering at direct current. Changes in the effective optical thickness are used to quantify changes in the optical properties of the membrane. Changes in the effective optical thickness will be mainly determined by the effective refractive index of the PAAO-Ag molecular film of the adsorbed gas structure. The effective refractive index of the membrane was determined from the measured position of the interference maxima and the given membrane thickness. Results: Association processes have been considered, i.e. binding of analyte molecules to the surface of the PAAO nanoporous membrane. A stream of gaseous ammonia was chosen as the analyte. According to the Langmuir isotherm model, the sensor response during real-time measurements should follow a negative exponential trend. It has been shown that the shape of the sensor's optical signal qualitatively repeats the shape of the theoretical curve of real-time optical probing in the regions of molecular binding and equilibrium. The molecular association time of the free surface of the PAAO nanoporous membrane was 7 ± 1 minutes. The deposition of thin silver films on the surface of a nanoporous PAAO membrane leads to a change in the shape of the optical signal and a decrease in its magnitude. Conclusion: On the basis of the synthesized nanoporous PAAO membranes with a free surface and modified with ultrathin silver films, experimental studies of the effect of ammonia flow on multibeam light interference in such membranes have been carried out. It has been found that the surface roughness and size effect of the silver film thickness have a significant effect on the transmission spectra and sensory sensitivity of the membranes. It has been shown that the largest relative change in the refractive index of the membrane in an ammonia flow is observed for the thinnest silver film 1.8 nm thick. It has been noted that there is a threshold value of the thickness of a silver film deposited on the surface of a nanoporous PAAО membrane, above which the use of such films in optical sensors with the mechanism of multipath light interference is not advisable, and the use of a different mechanism is required, for example, the mechanism of localized surface plasmon resonance.
CdS nanoparticles in polymer matrices Kuznetsova, V. Yu; Makarova, A. V.; Kosobudsky, I. D.
Inorganic materials,
08/2011, Letnik:
47, Številka:
8
Journal Article
Recenzirano
This paper examines the mechanisms of metal sulfide formation with the participation of metal complexes with thiourea. We have synthesized cadmium sulfide nanoparticles using carbon-chain polymers as ...stabilizers and investigated the effect of the polymer matrix on the properties of the nanoparticles.
We have developed a strengthening coating based on silica nanoparticles for soda-lime-silica glass, examined conditions for the synthesis of SiO
2
particles with tailored structure and application of ...coating of necessary thickness to glass through adsorption from solution, and optimized heat treatment of the coated glass. The nanohardness and centrosymmetric bending strength of the coated glass have been measured, and the mechanism behind the coating-induced increase in glass strength is discussed.
Nanocomposites of cadmium sulfide and high-pressure polyethylene have been synthesized. The mechanism of the thermal decomposition of thiourea complexes during the synthesis of cadmium sulfide ...nanoparticles has been investigated. The nanoparticle size, composition, and structure of the nanocomposites have been determined by x-ray diffraction, transmission electron microscopy, IR spectroscopy, and EXAFS spectroscopy, and the thermal decomposition of the nanomaterials has been studied.
