Search results for "visual_art"

Ceramic/metal nanocomposites by lyophilization: Spark plasma sintering and hardness

2014

The present study is focused on the procedure of spray-drying and lyophilization techniques for the preparation of ceramic/metal nanocomposites. The results of the study at all stages are compared with those corresponding to powders conventionally dried by heating in furnace. Starting from aqueous solutions of metal salts and ceramic powders, the procedure follows with spray-drying, lyophilization, calcination of the resulting powders and subsequent Spark Plasma Sintering (SPS). X-ray diffraction analysis of the powders at different stages of the processing routes was used for phase indexing; further characterization was performed by Transmission Electron Microscopy and Energy Dispersive X-…

Structure, micromechanical and magnetic properties of polycarbonate nanocomposites

2013

The current study evaluates the applicability of polycarbonate (PC) for development of magnetic polymer nanocomposites with CoFe2O4 nanofiller, the amount of which was changed from 0 to 5 wt. %. Ethylene-vinyl acetate elastomer in the amount of 10 wt. % was added as toughener. Upon introduction of the magnetic filler a magnetic hysteresis loop was observed: at 5 wt.% of CoFe2O4 saturation magnetization of the nanocomposite was 2,2 emu/g, remanent magnetization was 0,8 emu/g and coercivity is 1200 G. Nanoindentation tests showed that nanofiller-reinforced samples maintain reasonable plasticity characterized by work of plastic indentation, while their modulus and hardness were improved by up …

Giant Enhancement in the Supercapacitance of NiFe–Graphene Nanocomposites Induced by a Magnetic Field

2019

The rapid rise in energy demand in the past years has prompted a search for low-cost alternatives for energy storage, supercapacitors being one of the most important devices. It is shown that a dramatic enhancement (≈1100%, from 155 to 1850 F g-1 ) of the specific capacitance of a hybrid stimuli-responsive FeNi3 -graphene electrode material can be achieved when the charge/discharge cycling is performed in the presence of an applied magnetic field of 4000 G. This result is related to an unprecedented magnetic-field-induced metal segregation of the FeNi3 nanoparticles during the cycling, which results in the appearance of small Ni clusters (<5 nm) and, consequently, in an increase in pseudoca…

Non-conventional Fe3C-based nanostructures

2011

Novel Fe3C-based nanostructures with an inner layered structure have been synthesized by a simple medium-temperature (T = 700 °C) process based on carbothermal reduction. In this process, the iron precursor reacts with a selected nitrogen rich carbon source (namely, 4,5-dicyanoimidazole) to form wrapped nano-sheets of Fe3C@C(N). The nanosheets are composed of 5 nm crystalline Fe3C nanoparticles, which are integrated into a nitrogen-doped carbon phase giving rise to the wrapped morphology. By variation of reaction parameters (such as initial concentration, temperature, reaction time), the typical accompanying side products of iron carbide such as metallic iron and amorphous carbon can be kep…

Nanoporous Thin Films Based on Polylactide-Grafted Norbornene Copolymers

2008

Thermally stable vinyl polymerized polynorbornene (PNB) is one of the challenging materials in porous low dielectric films for packaging applications. Nanoporous PNB thin films were obtained with poly(d,l-lactide) (PLA)-grafted norbornene copolymers. Thermally labile PLA chains act as pore generators in PNB films. Thermally stable PNB main chains were synthesized by Pd-catalyzed vinyl polymerization and PLA side chains were grafted onto the PNB main chains by ring opening polymerization. The brittle and poor processible properties of PNB could easily be controlled by the copolymerization with norbornene derivatives. In thin films, the PLA chains were found to thermally decompose at about 25…

Cover Picture: Reversible Self-Assembly of Metal Chalcogenide/Metal Oxide Nanostructures Based on Pearson Hardness (Angew. Chem. Int. Ed. 41/2010)

2010

Spectroscopic and Theoretical Study of the Grafting Modes of Phosphonic Acids on ZnO Nanorods

2013

Metal oxides are versatile substrates for the design of a wide range of SAM-based organic-inorganic materials among which ZnO nanostructures modified with phosphonic SAM are promising semiconducting systems for applications in technological fields such as biosensing, photonics, and field-effect transistors (FET). Despite previous studies reported on various successful grafting approaches, issues regarding preferred anchoring modes of phosphonic acids and the role of a second reactive group (i.e., a carboxylic group) are still a matter of controversial interpretations. This paper reports on an experimental and theoretical study on the functionalization of ZnO nanorods with monofunctional alk…

Mechanical characterization of dry asphalt rubber concrete for base layers by means of the four bending points tests

2012

The mechanical characterisation of the asphalt concrete in terms of both the fatigue resistance and the stiffness modulus is necessary to use any design method of the flexible road pavements. Even more the determination of these mechanical properties is necessary if the asphalt concrete investigated is an innovative material as a dry asphalt rubber concrete DARC (i.e. a bituminous mixture with rubber via dry process). Such material is less known and investigated than the asphalt rubber concrete via wet process, even if its application implies peculiar economical and environmental advantages such as no specialized equipment or significant plant modifications and large quantity of recycled wa…

Fundamental and technological aspects of the surface properties and reactivity of some metal oxides

1997

Abstract As is usually accepted for many inorganic compounds, the surface properties often play a fundamental role in the overall properties of metal oxides, in particular when the oxide materials are used in the form of fine grains. One difficulty in characterizing these surface properties is to apply the results of studies performed on ideal surfaces to the actual materials in use. A way to accept this challenge can be to successively consider initial powders, polycrystalline pellets formed after thermal or mechanical treatment of these powders and, finally, monocrystalline surfaces prepared from these powders or pellets. This principle can be applied to the study of the surface propertie…

Mixed oxide Ti Si O prepared by non-hydrolytic Xerogel method as a diluter of nickel oxide for the oxidative dehydrogenation of ethane

2018

Abstract Mixed Ti Si O materials prepared by non-hydrolytic xerogel method have been employed as diluters for nickel oxide and used in the catalytic oxidative dehydrogenation of ethane. These catalysts have been characterized by several physicochemical techniques such as N2 adsorption, XRD, TPR, TEM, HR-TEM, and XPS. Supported nickel oxide catalysts have been reported to be efficient but only if the nature and the amount of support are controlled. In the present article it is shown that highly loaded (80 wt% NiO) nickel catalysts are more efficient when diluted on mixed Ti Si O materials with appropriate Ti/Si ratios than on pure TiO2 and SiO2 diluters. The catalytic results have been expla…