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

Structural analyses of sintered MT and BZT ceramics

Development of dielectric materials is increasing with a rapid progress in mobile and satellite communications systems, where magnesium titanates find their place owing to good dielectric properties. Recently it has been established that, these materials, which are based on binary magnesium titanates (MgTi03 and Mg2Ti04) can be applied in MW engineering. These materials differ extremely low dielectric loss in the microwave range and high dielectric constant. On the other hand, barium-titanate compounds have attracted great attention for their specific microwave properties, as well. They were commonly used as parts of resonators, filters and multilayer ceramic capacitors, in the microwave region. The crystal phase with the structure BaZn2Ti40 11 is present in various commercial microwave dielectric materials based on barium-titanate compounds. Taking all this into account, in this article, the influence of mechanical activation of the MgO-Ti02 and BaCOr ZnO-Ti02 systems on phase composition, crystal structure and microstructure before and after sintering process, has been reported

Analysis of the Initial-Stage Sintering of Mechanically Activated SrTiO3

The initial-stage of sintering plays a significant role in determining the final microstructure that defines the main characteristics of electroceramics materials such as functional properties. In this article non-isothermal sintering of non-activated and mechanically activated SrTiO3 samples was investigated up to 1300 degrees C. Dilatometric curves indicate that mechanical activation leads to an earlier onset of sintering, suggesting that it should lead to a more homogenous and denser sintered product. Analysis of the initial stage of sintering reveals that the sintering process of all examinated samples consists of two or three overlapping single-step processes, with a change in the dominant mass transport mechanism. The values of apparent activation energy of the considered single-step process exhibit a significant decrease with an increase in mechanical activation time. The values of the density of samples after isothermal sintering indicate that the final stage of sintering has not been reached by 1300 degrees C

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

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

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