TiO2 based nanomaterials and nanostructures for green convergent technologies and environmental protection

Imajući u vidu značaj razvoja naprednih nanomaterijala za zaštitu prirodne okoline, u ovome radu su prezentovane primene nanomaterijala i nanostruktura na bazi TiO2 u oblastima obnovljivih izvora energije, hemijske i bio dekontaminacije. Objašnjena je uloga TiO2 u formiranju kompozitnih hibridnih struktura za prikupljanje solarne energije, kao i primena različitih antimikrobnih materijala na bazi TiO2 koji se koriste za fotokatalitičko uklanjanje polutanata. Naročita pažnja je posvećena strukturi i svojstvima titan dioksidnih nanotuba dobijenih primenom metode elektrohemijske anodizacije i njihova primena u bio dekontaminaciji.Taking into account the importance of development of the advanced nanomaterials for the environmental protection, in this article the application of TiO2 based nanomaterials and nanostructures in the fields of renewable energy, chemical and bio decontamination has been presented. The role of TiO2 in formation of composite hybrid structures for solar energy harvesting has been explained, as well as the use photocatalytic degradation of pollutants. properties of TiO2 nanotubes obtained by decontamination

TiO2 based nanomaterials and nanostructures for green convergent technologies and environmental protection

Imajući u vidu značaj razvoja naprednih nanomaterijala za zaštitu prirodne okoline, u ovome radu su prezentovane primene nanomaterijala i nanostruktura na bazi TiO2 u oblastima obnovljivih izvora energije, hemijske i bio dekontaminacije. Objašnjena je uloga TiO2 u formiranju kompozitnih hibridnih struktura za prikupljanje solarne energije, kao i primena različitih antimikrobnih materijala na bazi TiO2 koji se koriste za fotokatalitičko uklanjanje polutanata. Naročita pažnja je posvećena strukturi i svojstvima titan dioksidnih nanotuba dobijenih primenom metode elektrohemijske anodizacije i njihova primena u bio dekontaminaciji.Taking into account the importance of development of the advanced nanomaterials for the environmental protection, in this article the application of TiO2 based nanomaterials and nanostructures in the fields of renewable energy, chemical and bio decontamination has been presented. The role of TiO2 in formation of composite hybrid structures for solar energy harvesting has been explained, as well as the use photocatalytic degradation of pollutants. properties of TiO2 nanotubes obtained by decontamination

Automatic microstructure analysis of sintered materials

U ovom radu je prezentovana nova metoda za automatsku mikrostrukturnu analizu materijala. Metoda je bazirana na prepoznavanju kontura i dekompoziciji digitalne slike na osnovu fotometrijskih zakona, kao i na primeni log hiperbolične distribucije. Ova metoda je uspešno primenjena za mikrostrukturnu analizu neizotermski sinterovanog barijum-titanata.In this article the new approach to automatic microstructure analysis of the sintered materials has been presented. The method is based on contour recognition and decomposition of digital image, according to their gray scale intensity and the use of log-hyperbolic grain size distribution and it has been successfully applied on microstructure analysis of BaTiO3 sintered under non isothermal conditions

Automatic microstructure analysis of sintered materials

U ovom radu je prezentovana nova metoda za automatsku mikrostrukturnu analizu materijala. Metoda je bazirana na prepoznavanju kontura i dekompoziciji digitalne slike na osnovu fotometrijskih zakona, kao i na primeni log hiperbolične distribucije. Ova metoda je uspešno primenjena za mikrostrukturnu analizu neizotermski sinterovanog barijum-titanata.In this article the new approach to automatic microstructure analysis of the sintered materials has been presented. The method is based on contour recognition and decomposition of digital image, according to their gray scale intensity and the use of log-hyperbolic grain size distribution and it has been successfully applied on microstructure analysis of BaTiO3 sintered under non isothermal conditions

Mehanohemijska sinteza nikal i nikal-cink feritnih prahova sa Nicolson-Ross analizom absorpcionih koeficijenata

The interest in finding new methods for the preparation of nickel ferrite (NiFe2O4) and nickel-zinc ferrite (NixZn1-xFe2O4) powders has recently increased, because the physical and chemical properties of these soft magnetic materials depend strongly on the preparation conditions. In this study, powder samples of ferrites were obtained by: 1) a classic sintering procedure (NixZn1-xFe2O4, x = 0.9) and 2) planetary mill synthesis (both NiFe2O4 and the NixZn1-xFe2O4). The mechano-chemical reaction leading to the formation of the spinel phase of NixZn1-xFe2O4 (x = 1 or 0.9) was monitored by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analysis. The values of the real and imaginary parts of the permittivity and permeability were measured for the obtained nickel and nickel-zinc ferrite samples in the 7-12 GHz frequency range. Based on the obtained results, the electromagnetic radiation (EMR) absorption coefficients were calculated for all three types of sample. It was concluded that the method of preparation and the final particle size influence the EMR absorption coefficient of nickel and nickel-zinc ferrites.U novije vreme povećan je interes za pronalaženje novih metoda za sintezu nikal-ferita (NiFe2O4) i nikal-cink-feritnih (NixZn1-xFe2O4) prahova, zbog činjenice da fizička i hemijska svojstva ovih 'mekih' magnetnih materijala u mnogome zavise od uslova pripreme. Dobijeni feritni prahovi, opisani u ovom radu, sintetisani su: 1) klasičnom procedurom sinterovanja (NixZn1-xFe2O4, x = 0,9 ili 2) sintezom u planetarnom mlinu (NiFe2O4 i NixZn1-xFe2O4). Prosečna veličina čestica dobijenih prvom metodom iznosi 3-5 μm, dok druga metoda daje čestice veličine 10-12 nm. Karakterizacija uzoraka praćena je skenirajućom elektronskom mikroskopijom (SEM), transmisionom elektronskom mikroskopijom (TEM), kao i difrakcionom analizom X-zracima (XRD). Realni i imaginarni delovi koeficijenata permitivnosti i permeabilnosti su mereni na dobijenim uzorcima nikal i nikal-cink-ferita u frekventnom opsegu 7-12 GHz. Na osnovu dobijenih rezultata, izračunati su EMR apsorpcioni koeficijenti za sve dobijene uzorke. Zaključeno je da je način pripreme, kao i dobijena veličina čestica, utiču na EMR apsorpcione koeficijente nikal i nikal-cink-ferita

Evaluation of Fly Ash Pysico-chemical Characteristics as Component for Eco-ceramic and Sintered Materials

The aim of the presented study is to evaluate utilization potential of the fly ash which is the main residue from the coal combustion thermal-plants. Decades long high production of fly ash represents extreme hazard for the environment. The storage problem of this waste material is also alerting. Thus, recycling and reapplication of fly ash in construction materials industry is the only economic solution. The well-known examples of fly-ash reapplication as a component in cement, mortar, concrete, bricks and tiles are not enough in means of reusing extreme amounts of this waste material. Therefore, new applications in ash-based composites have to be developed: eco-ceramic materials and sintered materials for refractory performances. In this investigation, characterization of three different fly ash capacities was used as base for further fly ash utilization possibilities analysis. Accent was on the investigation of the fly ash mineralogical and chemical composition. Thermal stability of crystalline phases was investigated with DTA. Macro-performance was correlated with the microstructure of fly ash studied by means of XRD and SEM analysis. Furthermore, content of trace elements, physico-chemical characteristics and leaching toxicity tests were carried out. Comparing the properties of investigated fly ashes with standard values, it could be presumed that fly ash originating from Serbian power plants can be potentially useful for high value products - eco-ceramic and refractory/sintered materials manufacturing. Key words: fly ash, microstructure, potential reusing, eco-ceramic, sintering. Acknowledgements: This investigation was supported by Serbian Ministry of Science and Education and it was conducted under following projects: 172057 and 45008

Piezoelectric polymer/ceramic nanostructures for mechanical energy harvesting

Vibration-based mechanical energy is one of the most accessible energy source in the surroundings. Harvesting this type of energy exhibits a great potential for remote/wireless sensing, charging batteries, and powering electronic devices. Piezoelectric and ferroelectric materials, including PZT, BaTiO3, ZnO, polyvinylidene fluoride (PVDF), etc., can be used for converting ambient mechanical energy into electricity. Based on these materials, a variety of micro- or nanoelectromechanical systems can be developed for harvesting energies from random vibrations, mechanical waves, or body movements like walking, running, or typing. Recent investigations on nanocomposites of electroactive ceramics and ferroelectric polymers exploit this approach in order to produce new multifunctional materials for mechanical energy harvesting. Taking into account that mechanical activation is one of the methods for modification of physico-chemical properties of the filler, in this study we investigate the influence of mechanical activation of ZnO particles on structural properties of ZnO/polyvinylidene fluoride nanocomposites. The nanocomposite films were prepared by solution casting method and investigated by X-ray diffraction (XRD) method and Raman spectroscopy, while the microstructure morphology has been analyzed by scanning electron microscope (SEM). Presented results will enable optimization of PVDF processing techniques for the production of new mechanical energy harvesting devices

Pulsed Laser Deposition of BaTiO3 on PVDF substrate

Piezoelectric materials play an important role in development of advanced Micro-electromechanical systems (MEMS) and Nano-electro-mechanical systems (NEMS). Their applications span the aero-space industry, communications, defense systems, national security, health care, information technology and environmental monitoring. Materials used in MEMS/NEMS mustsimultaneously satisfy numerous requirements for chemical, structural, mechanical and electrical properties. Although traditionally MEMS in particular have relied on silicon, the materials used in MEMS/NEMS are becoming more heterogeneous. Taking into account that materials nanostructuring can produce unique mechanical, electrical and piezoelectric properties, in this article the investigation of pulsed laser deposition of BaTiO3 on PVDF substrate has been performed. The titanium-saphire laser operated at 800 nm with 40-fs pulse duration and 1 kHz repetition rate was focused onto a mechanically activated BaTiO3 target. Deposition on PVDF substrate was done at an oxygen partial pressure of 10-7 Torr using a laser pulse frequency of 1 kHz at room temperature. The crystal structure and the microstructure of the films were examined using an X-ray diffractometer and scanning electron microscope, while the surface morphology was observed by atomic force microscopy.It was found that pulsed laser deposition of BaTiO3 on PVDF substrate offers a new set of opportunities for development of advanced flexible piezo-films for the next generation of NEMS

Analysis of early-stage sintering mechanisms of mechanically activated BaTiO3

Prah barijum-titanata je mehanički aktiviran u planetarnom mlinu sa kuglicama 60 i 120 minuta. Neizotermsko sinterovanje neaktiviranog i aktiviranih uzoraka proučeno je u dilatometru u temperaturskom intervalu od sobne do 1380oS sa tri različite brzine zagrevanja (10, 20 i 30oS/min). Mehanizmi ranih stadijuma sinterovanja su analizirani za sva tri tipa uzoraka i uočene su značajne razlike između neaktiviranih i mehanički aktiviranih uzoraka.Barium-titanate powder was mechanically activated in a planetary-ball mill for 60 and 120 minutes. Non-isothermal sintering of non-activated and activated powder samples was investigated using a dilatometer in the temperature interval from room to 1380oC with three different heating rates (10, 20 and 30oC/min). Early-stage sintering mechanisms for all three types of samples were analyzed, showing significant differences between the non-activated and mechanically activated samples

Lightweight construction ceramic composites based of pelletized fly ash aggregate

As coal combustion byproduct fly ash represents a risk for environment: direct ash emission from open land-fills causes pollution of air, soil and water. The solution for this severe pollution problem is fly ash reapplication in various construction ceramic composite materials. Although pelletization of waste powdery material is a known technique in the production of artificial aggregates, it still has not been widely used in construction sector. Here investigated cold-bonded fly ash aggregate was produced in semi-industrial pelletizing device. The fly ash particles were bonded with water-glass (Sodium silicate - Na2SiO3) and used as substitution for aggregate in Portland cement based composite. Half of the produced lightweight aggregate was submitted to thermal treatment and afterwards applied in the construction composite in the same ration as in the case of cold-bonded pellets. The performance characteristics of two types of lightweight composites were mutually compared and afterwards correlated with characteristics of normal-weight concrete. Compressive strength, modulus of elasticity and tensile strength were used as represents of the composites mechanical behavior. Mineral constituents of fly ash pellets were analyzed by means of X-ray diffraction analysis, differential thermal analysis was applied in crystalline phase investigation, and scanning electron microscopy in microstructural analysis. The leaching behavior and environmental impact of hazardous elements were also analyzed. It was concluded that content of potentially toxic elements found in leachate of fly-ash based composites was far below tolerance limit proposed by actual standards for the building materials, characterizing the fly ash non-harmful secondary raw material and enabling its reapplication in building materials industry. Utilizing fly ash to produce quality aggregates should yield significant environmental benefits