Microstructural analysis and magnetic characterization of native and magnetically modified montmorillonite and vermiculite

Two clay minerals of the similar 2 : 1 layer structure and chemical composition, vermiculite and montmorillonite, were studied using a wide spectrum of experimental methods in their original states and the magnetically modified states after mixing with microwave-synthesized iron oxide particles. This magnetic modification led to different microstructural morphology influencing magnetic behaviour at room and more pronounced at low temperatures.Web of Scienceart. no. 373810

Functional and eco-friendly nanocomposite kaolinite/ZnO with high photocatalytic activity

Highly photoactive nanocomposites kaolinite/ZnO with various amounts of ZnO nanoparticles (10 wt.%, 30 wt.%, and 50 wt.%) were prepared using simple hydrothermal method. Calcination of the nanocomposites at 600 °C led to the kaolinite–metakaolinite phase transformation, to further growth of ZnO crystallites, and to significant increase of photodegradation activity. The nanocomposites were studied using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared, diffuse reflectance and photoluminiscence spectroscopies, scanning and transmission electron microscopies, BET analysis, and molecular modeling using empirical force field. Photodegradation activity was evaluated by the discoloration of Acid Orange 7 aqueous solution under UV irradiation. Leaching tests confirmed strong interaction between kaolinite matrix and ZnO nanoparticles, and, therefore, high stability of prepared nanocomposites.Web of Science16240039

Preparation and Properties of Transition Metal Oxide Nanoparticles on the Kaolinite Matrix

Import 02/12/2011Příprava nanokompozitů kaolinit/TiO2 probíhala hydrolýzou směsi kaolinu s titanyl sulfátem, vybrané vzorky nanokompozitů kaolinit/TiO2 byly dopovány mědí. Postup přípravy nanokompozitů byl optimalizován z hlediska dosažení maximální fotokatalytické aktivity při minimální energetické a materiálové náročnosti. Poměr výchozích reaktantů byl zvolen tak, aby výsledný obsah oxidu titaničitého v takto připravených kompozitech představoval požadované množství TiO2. Fixací oxidu titaničitého na povrchu kaolinitu získáváme kompozit typu kaolinit/TiO2, jehož tepelnou úpravou získáváme kompozit metakaolinit/TiO2. Kompozity modifikované různými navrženými způsoby hydrolýzy byly následně charakterizovány použitím kombinací metod rentgenové fluorescenční spektrofotometrie, infračervené spektroskopie, Ramanovy spektroskopie, difúzně reflektanční spektroskopie, skenovací elektronové mikroskopie, rentgenové práškové difrakční analýzy. Molekulární modelování s využitím empirických silových polí v modelovacím prostředí „Materials Studio“ bylo použito jako doplňková metoda studia struktury a vlastností těchto nanokompozitů.Preparation of nanocomposites kaolinite/TiO2, using hydrolysis of titanyl sulfate in the presence of kaolin was addressed. Copper-doping has been carried out for selected samples of nanocomposites. The preparation procedure has been optimized in order to achieve the maximum photoactivity by minimum energy and material saving. A variable (kaolinite)/(titanyl sulfate) ratio has been used in order to achieve the desired TiO2 content in prepared nanocomposites. Calcination of the composites at 600 °C led to the transformation of the kaolinite to metakaolinite and to origination of metakaolinite/TiO2 composites. The prepared samples were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and diffuse reflectance spectroscopy in the UV-VIS region. Structural ordering of TiO2 on the kaolinite particle surface was modeled using empirical force field atomistic simulations in the „Materials Studio“ modeling environment. Photodegradation activity of the composites prepared was evaluated by the discoloration of Acid Orange 7 aqueous solution.Prezenční9360 - Centrum nanotechnologiívyhově

Effects of continuous and pulsating water jet on CNT/concrete composite

This paper presents first results of the study of the resistance of carbon nanotube concrete composite (CNT/concrete composite) to the action of continuous and pulsating water jets. The experiments oriented at the determination of erosion effects of pulsating and continuous water jets impinging the surface of reference (concrete) and CNT/concrete composite samples were performed. Tested samples were characterized by X-ray powder diffraction and scanning electron microscope. Samples were exposed to pulsating and continuous water jets at various operating parameters. Erosion effects of pulsating and continuous jets were evaluated in terms of material removal rate. The possible influence of addition of CNTs to the concrete on its resistance to the action of continuous and pulsating water jets is discussed in the paper. The experiments proved that CNT/concrete composite exhibits higher resistance than reference concrete to the action of both pulsating and continuous water jet under the given testing conditions.Web of Science631058958

Influence of thermal and UV treatment on the polypropylene/graphite composite

Electrically conductive polypropylene/graphite (PP/graphite) composites were prepared via blending granulated PP with maleic anhydride grafted PP and natural graphite. Electrical conductivity of prepared samples containing either 65, 70, or 75 wt% of graphite was measured and the most conductive sample containing 75 wt% of graphite was exposed to UV irradiation for 1 and 24 h or thermally treated at 170 °C for 1 h. The influence of thermal and UV exposure on the structural and electrical changes in such treated samples was studied. Local current measurements on the surface were made using scanning spreading resistance microscopy and morphology of the surface was studied by atomic force microscopy. X-ray diffraction analysis, infrared and Raman spectroscopy were also used for the structural characterization. Properties of treated and untreated samples are compared and differences are discussed.Web of Science52534

Polyaniline/TiO2/kaolinite: The composite material with high electrical anisotropy

Kaolinite–TiO2 nanocomposite matrix (KATI) coated with polyaniline (PANI) layer has been prepared in powder form and pressed into tablets. The conductivity was studied in dependence on (1) wt.% of TiO2 in KATI matrix and (2) thermal pre-treatment of KATI matrix. The anisotropy factor α, i.e. the ratio of in-plane conductivity and conductivity in the direction perpendicular to the tablet plane, was found to be very high for PANI/KATI tablet (α is of the order of 103–104) in comparison with pure PANI tablet (α is of the order of 102). Structure has been studied using Raman spectroscopy, X-ray diffraction analysis, scanning electron microscopy and molecular modeling. The possibility of using the tablets as a load sensors have been tested and tablets pressed from composites containing calcined KATI seem to be promising material for this purpose.Web of Science1461-215214

A low-cost photoactive composite quartz sand/TiO2

The photoactive quartz sand/TiO2 composites were prepared by thermal hydrolysis of the suspension obtained by addition of quartz sand to a titanyl sulfate solution. The required amount of TiO2 in the prepared composites (i.e. 9, 22 and 45 wt.%, respectively) was achieved using a variable titanyl sulfate/quartz ratio. As reference materials, pure TiO2 was prepared using the thermal hydrolysis of the titanyl sulfate solution under the same condition as used during the preparation of composite quartz/TiO2. The composite samples, dried at 105 °C and calcined at temperatures of 500–900 °C, were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy. Structural ordering of TiO2 particles on the quartz surface was studied using atomistic simulations in a Material Studio modeling environment. Photodegradation activity of the composites was evaluated by the discoloration of Acid Orange 7 aqueous solution. The composite containing 22 wt.% of TiO2 and calcined at 800 °C exhibits the highest photoactivity. Higher and lower amounts of TiO2 led to worse results. The quartz/TiO2 composite is a promising material able to replace pure TiO2 in a wide range of building materials.Web of Science22249748

Monitoring conductivity and optical homogeneity during the growth of polyaniline thin films

In order to optimize the technology with respect to maximum conductivity, transmittance and optical homogeneity, the time-controlled chemical bath deposition process was used to prepare polyaniline (PANI) thin films on glass substrate. Two different precursors have been used for PANI thin films preparation: anilinium sulfate and aniline hydrochloride. Optical homogeneity has been evaluated by transmittance maps obtained using spectrometer equipped with light collecting multi-mode optical fibers. Results showed the strong dependence of conductivity and optical homogeneity on the deposition time during early stages of films growth. The increase of conductivity during deposition time is accompanied with the increase of optical inhomogeneity. Optimum deposition time has been estimated about 30 min with maximum optical homogeneity, keeping still the reasonable transmittance and conductivity values.Web of Science537645

Enhanced electrical conductivity of polyaniline films by postsynthetic DC high-voltage electrical field treatment

New approach of chemical bath deposition combined with drying of freshly polymerized PANI films in DC high-voltage static electrical field 0.6–2.7 kV/cm has been applied in present work. AFM and SEM microscopy revealed the significant changes of structure and morphology of PANI films, however the most important result of high-voltage treatment was the strong increase of conductivity of PANI films from 88 S/m for the reference sample untreated in high-voltage field up to 374 S/m for samples dried in the electric field (1.0 kV/cm). The dependence of PANI conductivity on the intensity of high-voltage field showed the maximum conductivity for 1.0 kV/cm. Effects of corona discharge observed for high-voltage field intensity above 2.0 kV/cm on the samples are also presented. Results showed the possibility to change the nanostructure, morphology and conductivity using high-voltage electrical field.Web of Science17912111