Effect of ball milling in a tumbling ball mill on the properties of multi-wall carbon nanotubes

The effects of ball milling on various properties of ground multi-wall carbon nanotubes were studied. These properties were granulometry, SEM,specific surface area, density, crystalline structure, surface chemical analysis and thermogravimetry. The mean size of agglomerates, initially at 35 m, decreases to reach a limit value of 2.5m, corresponding to a competition between agglomeration and fragmentation. A kinetic study,based on a decomposition of size distributions measured for different times, has permitted to propose a grinding mechanism. As grinding proceeds, the specific surface area first increases from 175 to 244m2 g−1 and then decreases, while the real density increases from 1800 to 2150 kgm−3 to level off at 2070 kgm−3. Moreover, macroporosity disappears totally, giving access first to mesoporosity and then to microporosity. The nanotubes are probably cut to give access to the internal porosity. An increase of the proportion of oxygen adsorbed on carbon (from 3% to 8.7% after 600 min grinding) implies that it may be possible to functionalise the nanotubes. Thanks to these different morphological changes numerous applications of ground nanotubes can be considered. Moreover, the use of a tumbling ball mill allows a massive production of cut nanotubes

Matrix-filler interactions in a co-ground ecocomposite: surface properties and behaviour in water

Ecocomposites made up of polystyrene and starch were produced by co-grinding. The mechanism by which the composite is formed was identified by following the particle size and morphology. The size reduction of the matrix particles is favoured by the presence of starch which adheres on polystyrene surface, playing the role of agglomeration inhibitor between matrix particles. Thus, the filler is well dispersed in the matrix, permitting a good homogeneity of the composite properties. The hydrophilic behaviour of starch is reduced by co-grinding, resulting of a decrease of the acid and non dispersive components of the surface energies. Consequently the interactions between the initially hydrophobic matrix and hydrophilic filler are enhanced without using a compatibilizer. Thus, the water-resistance of the co-ground composite materials is better compared to blends since blends pellets introduced in water are rapidly disintegrated while an adapted co-grinding time permits to avoid this problem. It was seen that the diffusion coefficient of water in the composite pellets decreases with an increase of the co-grinding time for the lower filler rates, while it is the opposite for high filler rates. Moreover, the diffusion coefficient increases with the filler ratio

On the interest of using degradable fillers in co-ground composite materials

The article presents the results of a study whose objective is to show the interest of using vegetable and biodegradable fillers in composite materials. The incorporation of fillers made up of starch in the synthetic polymeric matrix was carried out by co-grinding, a process supporting the dispersion of one component in another one and thus supporting the homogeneity of the composite properties. The follow-up of the particle size and morphology has permitted to identify how the composite is formed. We could note that co-grinding makes it possible to improve the mechanical properties of the composite material, not only through a better dispersion of the filler in the matrix, but also thanks to a modification of the interface properties. Finally a study on the material degradation in water has shown that the incorporation of a vegetable, degradable and cheap filler in the synthetic matrix and the application of co-grinding during an adapted time offer interesting water-resistant properties

Co-grinding significance for calcium carbonate–calcium phosphate mixed cement. Part I: effect of particle size and mixing on solid phase reactivity

In part I of this study we aim to evaluate and control the characteristics of the powders constituting the solid phase of a vaterite CaCO3–dicalcium phosphate dihydrate cement using a co-grinding process and to determine their impact on cement setting ability. An original methodology involving complementary analytical techniques was implemented to thoroughly investigate the grinding mechanism of separated or mixed reactive powders and the effects on solid phase reactivity. We showed that the association of both reactive powders during co-grinding improves the efficiency of this process in terms of the particle size decrease, thus making co-grinding adaptable to industrial development of the cement. For the first time the usefulness of horizontal attenuated total reflection Fourier transform infrared spectroscopy to follow the chemical setting reaction at 37°C in real time has been demonstrated. We point out the antagonist effects that co-grinding can have on cement setting: the setting time is halved; however, progress of the chemical reaction involving dissolution–reprecipitation is delayed by 30 min, probably due to the increased contact area between the reactive powders, limiting their hydration. More generally, we can take advantage of the co-grinding process to control powder mixing, size and reactivity and this original analytical methodology to better understand its effect on the phenomena involved during powder processing and cement setting, which is decisive for the development of multi-component cements

Utilisation des TICE dans la formation des élèves ingénieurs de l'ENSIACET de Toulouse

Cet article présente un retour d’expérience sur l’utilisation des TICE dans la formation des élèves – ingénieurs de l’ENSIACET de Toulouse. Des enseignements ont été dispensés en semi-présentiel : les cours sont proposés en auto-formation par le biais d’une plateforme de téléenseignement et les séances de travaux dirigés sont effectuées en présence d’un enseignant qui reprend alors les points délicats du cours. Ceci permet aux apprenants d’être plus autonomes dans leurs formations, d’adapter leurs rythmes de travail et ainsi de mieux maîtriser le cours lors des exercices

Production of a diluted solid tracer by dry co-grinding in a tumbling ball mill

This paper presents a study on the production by co-grinding of a diluted solid tracer, sized less than 10 mm and containing less than 2 wt. % of active product, used in the field of grounds contamination and decontamination. Co-grinding was performed in a tumbling ball mill and permits to produce easily a diluted tracer without implementing several apparatus. The two products were ground separately first and then together. The follow-up of the particles size and morphology, as well as the modelling of the grinding kinetics have permitted to propose a mechanism by which the diluted solid tracer is produced. The influence of the operating conditions (nature and initial size of the diluting medium, ball and powder filling rates, proportion of the polluting tracer) on products grinding was studied. Thus, we have defined optimum co-grinding conditions permitting to produce a tracer offering the required properties. These ones are classical for tumbling ball mills. This kind of mill is very interesting since its sizes can easily be extrapolated to answer to an industrial demand

Le co-broyage en voie sèche : une alternative pour la formulation de mélanges de poudres et la production de matériaux composites

L’article présente différentes applications du co-broyage en voie sèche dans des broyeurs à corps broyants (broyeur à boulets et broyeur à billes agité). Nous avons tout d’abord montré comment une étude cinétique basée sur une analyse d’images prises au microscope électronique à balayage permet d’expliquer les mécanismes de production des matériaux composites. L’influence du co-broyage sur les propriétés d’usage (mécaniques, électriques, de surface) de matériaux composites à matrice polymère a ensuite été caractérisée. Nous avons enfin présenté quelques applications du co-broyage

Intérêt du co-broyage pour la formulation de mélanges

L'article présente différentes applications du co-broyage en voie sèche dans des broyeurs à corps broyants (broyeurs à boulets et broyeur à billes agité). Nous avons tout d'abord montré comment une étude cinétique basée sur une analyse d'images prises au microscope à balayage permet d'expliquer les mécanismes de production des matériaux composites. L'influence du co-broyage sur les propriétés d'usage (mécaniques, électriques, de surface ou de porosité) de matériaux composites à matrice polymère a ensuite été caractérisée. Nous avons enfin présenté quelques applications du co-broyage pour des systèmes ne contenant pas de polymères

How to combine a hydrophobic matrix and a hydrophilic filler without adding a compatibilizer – Co-grinding enhances use properties of renewable PLA-starch composites

In order to avoid the use of compatibilizers or plasticizers, co-grinding was performed to produce PLA – starch composite materials. Fragmentation and agglomeration phenomena were analysed to propose a production mechanism. Co-grinding enhances dispersion of the filler in the matrix and interactions between the materials. Consequently while blending the two materials has a negative effect on mechanical properties, co-grinding permits to improve them if optimized operating conditions are applied. Water uptake and diffusion are also controlled by co-grinding conditions. This treatment allows the production of composite materials offering good use properties without any use of a compatibilizer or a plasticizer

Chemistry course for radiochemistry engineers on the platform Moodle: a support to self-education for undergraduate students

The education challenges at present times include the incorporation of information and communication technologies (ICT) in the learning-teaching process. In Higher Education the agreement between the volume of information to be processed by the student, the available student’s time and the assimilation of the courses contents is very important. The new study plans in Cuban Universities include the reduction of the number of face to face hours and the increase of the available time for the student’s independent study. Then, it is necessary to develop abilities that upgrade learning capacity during a lifetime through the self-education. The first version of a course on chemistry for radiochemistry students using the platform Moodle and Open Educational Resources (OER) as a support to the undergraduate course is presented. The detailed topic plan of the course of chemistry for radiochemists, which was distributed week by week, and different activities combining communication, interactive and collaborative modules were implemented on the platform Moodle. The whole system was tested during the first semester of the 2010-2011 academic year. The course evaluation results were carried out through a survey among the students and discussion forums. The results showed a good acceptance by the students, a better efficiency in the teaching-learning process given by better planning of the individual study, a better preparation to perform the laboratory practices, the new possibilities of communication between students and teachers, the access to OER and greater self-conscious of the students on their own process of learning