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Cerrillo C.,Tribology Unit | Jimenez A.,University of Extremadura | Rufo M.,University of Extremadura | Paniagua J.,University of Extremadura | Pachon F.T.,University of Extremadura
Ultrasonics | Year: 2014

Ultrasound evaluation permits the state of rocks to be determined quickly and cheaply, satisfying the demands faced by today's producers of ornamental stone, such as environmental sustainability, durability and safety of use. The basic objective of the present work is to analyse and develop the usefulness of ultrasound testing in estimating the physico-mechanical properties of granite. Various parameters related to Fast Fourier Transform (FFTs) and attenuation have been extracted from some of the studies conducted (parameters which have not previously been considered in work on this topic, unlike the ultrasonic pulse velocity). The experimental study was carried out on cubic specimens of 30 cm edges using longitudinal and shear wave transducers and equipment which extended the normally used natural resonance frequency range up to 500 kHz. Additionally, a validation study of the laboratory data has been conducted and some methodological improvements have been implemented. The main contribution of the work is the analysis of linear statistical correlations between the aforementioned new ultrasound parameters and physico-mechanical properties of the granites that had not previously been studied, i.e., resistance to salt crystallization and breaking load for anchors. Being properties that directly affect the durability and safety of use of granites, these correlations consolidate ultrasonics as a nondestructive method well suited to this type of material. © 2013 Elsevier B.V. All rights reserved.


Martinez de Arenaza I.,University of the Basque Country | Meaurio E.,University of the Basque Country | Coto B.,Tribology Unit | Sarasua J.-R.,University of the Basque Country
Polymer | Year: 2010

This paper analyzes the miscibility state of Poly(L-Lactide) (PLLA) and Poly(DL-Lactide) (PDLLA) with Poly(styrene) (PS) and Poly(vinyl phenol) (PVPh) by means of Molecular Dynamics (MD) simulations performed using the COMPASS force-field. Immiscibility was found in polylactide/PS blends while miscibility was the result in polylactide/PVPh blends, both previsions agreeing with the experimental behaviour. The values calculated for the Flory-Huggins interaction parameter, χ, have been compared with the experimental results and with estimations based on existing miscibility models. Even though the dependence of χ with composition and the prediction of miscibility is correct, both the solubility parameters and the interaction parameters obtained prove that molecular modelling tends to underestimate the strength of the interactions. The observed differences are explained in terms of the absence of cooperativity effects for oligomeric chains used in molecular modelling of high molecular weight polymer blends. © 2010 Elsevier Ltd.


Mahrova M.,Tribology Unit | Conte M.,Anton Paar | Conte M.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Roman E.,CSIC - Institute of Materials Science | Nevshupa R.,IETCC CSIC
Journal of Physical Chemistry C | Year: 2014

Processes of mechanochemical degradation of imidazolium bis((trifluoromethyl)sulfonyl)imide ionic liquids with alkyl and monomethoxypoly(ethylene glycol) (mPEG) side groups were studied using the novel technique of mechanically stimulated gas emission spectroscopy. Mechanical stimulus caused degradation of both the anionic and cationic moieties. For the latter, the degradation was concentrated on the alkyl and ether chains rather than on the imidazole. For the anionic moiety, various degradation steps associated with the emission of CHxFy volatile products followed by SO2 and SO3 emission were identified. Simulation of frictional heat dissipation revealed that tribochemical reactivity was induced by the mechanical energy supply rather than the temperature increase. Thermal degradation of the same ionic liquids studied using thermogravimetric analysis and Fourier transform infrared spectroscopy was concentrated mainly on the cationic moiety. Thermal stability significantly depended on the side chains. The decomposition of mPEG-functionalized ionic liquids was a two-step process, where the lower temperature step corresponded to mPEG decomposition. © 2014 American Chemical Society.


Mahrova M.,University of Vigo | Pagano F.,Tribology Unit | Pejakovic V.,Ac2t Research Gmbh | Valea A.,University of the Basque Country | And 3 more authors.
Tribology International | Year: 2015

A series of eight new dicationic ionic liquids incorporating polyethylene glycol chains linking two N-alkylpyridinium moieties through rings position 2, were synthesized and investigated for their potential use as lubricants or lubricant additives. Alkylsulfate and bis(trifluoromethanesulfonyl)imide [NTf2] were selected as anions. Dicationic ionic liquids containing [NTf2] anion demonstrated good properties as neat lubricants showing low coefficient of friction and wear comparable with the reference lubricant (glycerol). Even more interesting could be their use as friction modifier additives since an important decrease in the coefficient of friction was achieved with a really low concentration of ionic liquid. The thermal analysis of all ionic liquids by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) is also described. © 2014 Elsevier Ltd. All rights reserved.


Stolte S.,University of Bremen | Stolte S.,Tribology Unit | Steudte S.,University of Gdansk | Igartua A.,Tribology Unit | Stepnowski P.,University of Gdansk
Current Organic Chemistry | Year: 2011

The idea of green or sustainable chemistry is to develop highly efficient technical processes and applications using chemicals with a reduced or zero hazard potential for man and the environment. This approach is perfectly applicable to ionic liquids (ILs). These substances have potential applications in different fields (economic interests), and so far millions of possible structures have been designed, thousands of which have actually been produced, providing a broad base for the structural design of ILs with optimal technological properties and at the same time posing a reduced hazard to humans and the environment. In parallel with the rapidly growing (eco)toxicological knowledge regarding ILs, the available data regarding their biodegradability are also increasing. The following sections introduce the reader to biodegradation test procedures and present an overview of existing aerobic and anaerobic biodegradation data concerning ILs. Besides pure biodegradation kinetics, this discussion covers data on biological degradation products (metabolites) and abiotic degradation processes. Throughout this review special emphasis will be placed on structure-biodegradability relationships and the question whether the 10th principle of Green Chemistry, namely, Design chemicals and products to degrade after use: design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment, is or is not fulfilled for some IL structures. The discussion of this data should help to improve the future design of inherently safer ILs, thereby reducing the risks they may pose to humans and the environment. © 2011 Bentham Science Publishers Ltd.

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