Search results for " COMPOSITES"
showing 10 items of 1620 documents
Growth of nano-porous Pt-doped cerium oxide thin films on glassy carbon substrate
2013
Abstract Glassy carbon (GC) substrates were treated by the oxygen plasma over several periods of time. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) study showed the dramatic influence of oxygen plasma on the morphology of glassy carbon. The treatment leads to the formation of nanostructured surface, which consists of well separated rod-like nanostructures oriented perpendicularly to the substrate surface. The surface roughness was found to increase with increasing treatment time. By using magnetron co-sputtering of platinum and cerium oxide we can prepare oxide layers continuously doped with Pt atoms during the growth. This tec…
Enhanced quantum sieving of hydrogen isotopes via molecular rearrangement of the adsorbed phase in chabazite
2020
Coadsorption experiments reveal an unexpected increase of the D2/H2 selectivity with loading in pure silica chabazite at 47 K. This effect is correlated with the appearance of a step in the adsorption isotherms of H2 and D2. Grand canonical Monte Carlo simulations show that this phenomenon is related to a molecular rearrangement of the adsorbed phase induced by its strong confinement. In the case of a H2 and D2 mixture, this rearrangement favors the adsorption of D2 having a smaller size due to quantum effects.
Chromogenic and fluorogenic reagents for chemical warfare nerve agents' detection
2008
The ease of production, the extreme toxicity of organophosphorus-containing nerve agents, and their facile use in terrorism attacks underscores the need to develop accurate systems to detect these chemicals. Among different technologies we review here recent advances in the design of chromo-fluorogenic methods for the specific detection of nerve agents. Optical sensing (especially colorimetric detection) requires usually low-cost and widely used instrumentation and offers the possibility of so-called “naked eye detection”. Recent reported examples suggest that the application of chromo-fluorogenic supramolecular concepts for the chromogenic or fluorogenic sensing of nerve agents might be an…
Creep and recovery of epoxy/MWCNT nanocomposites
2012
Abstract Creep and creep–recovery of epoxy/multi-wall carbon nanotube (MWCNT) composites was studied in a wide range of applied loads in order to evaluate the contribution of nanotubes on the time-dependent behaviour of the epoxy matrix. Incorporation of up to 1 wt.% of C150P MWCNTs has negligible influence on the elastic, viscoelastic and viscoplastic response of the epoxy system. No systematic changes of the creep characteristics depending on the content of nanotubes are noticed in the range of stresses from 0.3 up to 0.75 from the ultimate strength. Creep resistance and recovery performance of the epoxy matrix is not negatively affected by the addition of MWCNTs and the same analytical m…
Discrimination of nerve gases mimics and other organophosphorous derivatives in gas phase using a colorimetric probe array.
2012
A colorimetric array for the chromogenic discrimination of organophosphorous derivatives in gas phase has been developed. The array allows us to classify the nerve agent simulants DFP, DCP and DCNP.
Biomolecule-corona formation confers resistance of bacteria to nanoparticle-induced killing: Implications for the design of improved nanoantibiotics
2018
Abstract Multidrug-resistant bacterial infections are a global health threat. Nanoparticles are thus investigated as novel antibacterial agents for clinical practice, including wound dressings and implants. We report that nanoparticles' bactericidal activity strongly depends on their physical binding to pathogens, including multidrug-resistant primary clinical isolates, such as Staphylococcus aureus , Klebsiella pneumoniae or Enterococcus faecalis . Using controllable nanoparticle models, we found that nanoparticle-pathogen complex formation was enhanced by small nanoparticle size rather than material or charge, and was prevented by 'stealth' modifications. Nanoparticles seem to preferentia…
Studies of structures and properties of polymeric systems containing bis-(hydroxy-arylidene)alkanones as NLO-active chromophores
2002
Abstract NLO-properties of polymer systems containing bis-(hydroxy-arylidene)alkanone chromophores were studied experimentally and analyzed using ab initio quantum chemical calculations. A monoclinic crystal structure (space group P2111) of the polyester containing fragments of such chromophores in the backbone was simulated and a reasonable agreement between the experimental and simulated X-ray powder diffraction patterns was achieved. Ab initio quantum-mechanical estimations of the SHG-observable macroscopic second-order non-linearity tensor coefficients, obtained for the polymer crystal structure at the HF SCF level, led to the major dXZZ-coefficient of 1.9 pm/V. Films of ionic complexes…
Experimental evidence of E’_gamma centers generation from oxygen vacancies in a-SiO2
2007
Abstract We report on the thermal treatment effects in a γ-ray irradiated oxygen deficient amorphous silicon dioxide (a-SiO2) containing Al impurities. We observed that by thermal treatments the intensity of the 7.6 eV optical absorption band, associated to an oxygen deficient center, and the EPR signal amplitude of irradiation induced [AlO4]0 centers gradually decrease. During these thermal treatments, the E γ ′ centers concentration is found to increase in a correlated way to the decrease of the 7.6 eV absorption amplitude. These results are interpreted assuming an hole-transfer process from the [AlO4]0 centers to the diamagnetic oxygen vacancies, resulting in the generation of E γ ′ cent…
Evidences for the Formation of Chromium in the Unusual Oxidation State Cr(IV)
1999
Abstract Magnetic measurements on Tl x Cr 5 Se 8 (0≤ x ≤1) reveal that stoichiometric TlCr 5 Se 8 is a three-dimensional antiferromagnet with a Neel temperature T N of about 55 K. In contrast, samples with a reduced Tl content show highly unusual magnetic properties that are without precedent in the literature of magnetically coupled systems: upon lowering the temperature from 300 K the susceptibility reaches a maximum at about 125 K and then steeply drops to a value comparable to that obtained at room temperature. The height of this maximum increases first with decreasing Tl abundance reaching its largest value at a composition Tl 0.2 Cr 5 Se 8 and then decreases again for samples with x 3…
Synthesis of Uvarovite Garnet
1989
A garnet with interesting optical properties is synthesized by means of the ceramic method and the formation of gels. Colloidal silica or tetraethoxysilane (TEOS) is used as a starting reagent in the latter method of synthesis, together with nitrate and chloride salts of the remaining components. Use is made of ultraviolet-visible and infrared spectroscopy techniques and X-ray diffraction in studying the evolution of the system. Formation of the garnet phase at lower temperatures is observed when using the gel methods, as well as the absence of chromates during the process in the samples which contained chlorides.