Summary In this work the kinetics of the high-temperature oxidation of the powder amorphous carbon and bulk single-wall carbon nanotubes is studied. The thermal degradation of the sample is measured by differential scanning calorimetry using the continuous heating regime up to 1273 K. Also, the oxidation resistance of the samples is evaluated by the mass loss in a thermogravimetric analyzer. Both flowing and static oxygen and dry-air atmospheres are used. The specific role of the external diffusivity of the reagent gas is analyzed. The kinetics of the chemical reaction is specified using the Kissinger, Coats and Redfern methods.
Summary Polymers have a great interest for the study and design of new materials. Among these materials are epoxy resins, that have good properties, such as low shrinkage during cure, good adhesion, high water and chemical resistance, etc. They have also fast and easy cure in a broad range of temperatures. TTT diagrams are very helpful to design new epoxy materials as they allow the search for very important final properties, such as thermal stability, conversion or glass transition temperature of a material cured through a selected curing cycle. In this work the dependence of the thermal stability on the selected curing cycle for a DGEBA/1,2 DCH system was studied.
Authors:C. Tonin, A. Aluigi, M. Bianchetto Songia, C. D'Arrigo, M. Mormino, and C. Vineis
In the wool textile industry, several processes serve to improve the commercial properties of the fibres such as fineness,
softness, length, strength and lustrous. For example, wool is chemically treated with reductive agents then stretched and
set. This leads to modifications of the original protein structure causing changes in thermal behaviour, dyeing, colouristic
and wet resistance properties. A multidisciplinary approach was used to investigate treated and untreated wools, with the
aim of exploiting the nature of the structural changes. SEM and TEM revealed changes on the cuticle and cortical cell morphology;
structure modification were studied by FT-IR and DSC.
Authors:J. Delben, P. Candelorio, F. de Oliveira, T. Spontoni, Angela Delben, M. Coelho, and L. Andrade
Petroleum natural gas (PNG) reserves will last even when the oil reserves are exhausted, requiring the development of technologies
for PNG storage. Activated charcoal is the best material for such a purpose. Under vacuum samples of aroeira (Astronium Urundeuva)
underwent pyrolysis in diverse conditions. The samples were characterized by thermal analysis, scanning electronic microscopy
and infrared spectroscopy. When the pyrolysis temperature increased, mechanical anisotropy resistance tended to disappear.
The pyrolysis became complete only at high temperatures and using a long time of treatment.
The surface reactions of uranium metal with carbon monoxide at 25 and 200 °C have been studied by X-ray photoelectron spectroscopy (XPS); respectively. Adsorption of carbon monoxide on the surface layer of uranium metal leads to partial reduction of surface oxide and results in U4f photoelectron peak shifting to the lower binding energy. The content of oxygen in the surface oxide is decreased and O1s/O4f ratio decreases with increasing the exposure of carbon monoxide. The investigation indicates the surface layer of uranium metal has resistance to further oxidation in the atmosphere of carbon monoxide.
Authors:O. Zakurdaeva, S. Nesterov, and V. Feldman
Polyethylene oxide hydrogels containing physically immobilized dicyclohexano-18-crown-6 were prepared by radiation chemical synthesis. Doses of gel formation were found to depend on the molecular weight of the polyethylene oxide and were about 20 and 4 kGy for Mw of 105 and 3·106, respectively. An increase in the crown ether concentration resulted in the decrease of the efficiency of hydrogel formation, whereas the effect of polymer concentration was less pronounced. It was found that dicyclohexano-18-crown-6 immobilized in the PEO hydrogel showed relatively high resistance toward washout in aqueous media.
This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties.
The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to
either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance
of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent
screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National
Authors:K. Nomura, Y. Ujihira, E. Kuzmann, and K. Kurosawa
Sn-plating of aluminum alloy before and after a post-molybdate treatment is characterized by 119Sn conversion electron Mössbauer spectrometry (CEMS). CEMS results gave the direct evidence that the oxidation resistance of Sn-coated aluminum alloy is improved by the post-molybdate treatment. Depth selective CEMS showed that the coating structures consist of SnO2 on the top coating and the mixed Sn(0) and Sn(II) species in the intermediate layers. The Sn(II) oxide exists abundantly near the interface between the aluminum alloy and the Sn coating rather than beneath SnO2 layer.
Authors:C. Tamain, A. Özgümüs, N. Dacheux, F. Garrido, L. Thomé, C. Corbel, and E. Mendès
The effect of external irradiation on β-thorium phosphate-diphosphate (tetravalent actini des bearing storage matrix) and
the influence on its dissolution in aqueous media were studied. Highly energetic heavy ions were used to get the amorphization
of the crystalline structure of the ceramic. The ex-situ dissolution expenments showed an increase of the dissolution versus
amorphous fraction in several pH and temperature conditions. The in-situ dissolution experiments highlighted the primordial
importance of radiolytic produced free radical species. From these results, the ceramic presents a good resistance to aqueous
alteration even in amorphous state.
Authors:R. Ozao, H. Ogura, M. Ochiai, and S. Tsutsumi
A DSC method for evaluating the surface area of etched Al foils for use in high performance electrolytic capacitors is presented. A linear relationship between the etching degree (effective surface area) and the thermal resistance of the sample is obtained by means of DSC, based on the transient phenomenon. This method using the transient state in DSC measurement is not only novel, but also rapid and simple in evaluating the surface area of an etched aluminum foil. The method is effective even when the Al foil has a naturally oxidized surface.