1,720,995 research outputs found
Thermogravimetric Analysis to Evaluate Surface Modifications induced by superplacistizer on Calcium Salts
No full textInorganic film formers. Material and use
No full textThe paper aims to get in evidence some aspect of the synthesis and the use of sol-gel materials as film formers. Silica molecules modified with hydrocarbon chains carrying halogen atoms (F), aromatic function (C6H4;5) achieve a very impressive variety of applications. While the silica chemistry has been studied by long time, the sol-gel process get a new vitality from the better understanding of the microscopic structural changes induced by the different organic modified silica compound (chemical changes), by the addition of functional molecules and by the choice of solvents for the reactions and the application of the material before the use. From this point of view is very imperative to establish the kinetic of the hydrolysis and condensation reaction. The understanding of the possibility to use silica organically modified polymer as film formers is a interesting field where chemistry, material science, technology of the application and industrial constraints get together. The paper is the first from a study devoted to design sol-gel pigmented formulations for metal surface and we try to organise the enormous number of information on the sol-gel dispersion
“Structural effect of comb-polymer on the hydration of C3S phase”,
No full textAbstract
One of the main topics of the research on cement admixtures is the organic-inorganic interaction at the surface of the cementitious phases to understand the way the polymer acts. The aim of this work is to study the effect of polycarboxylate comb-polymer (PCP), used as dispersing agent, on hydration delay.
In order to evaluate the role of the polymer structure on hydration we separated the PCP in two main parts: the backbone (PAA) and the dispersing chain. An active unit that reduces the PCP complexity was “ad hoc” synthesized. It consisted of a single chain based on ethylene oxide polymer(Mw=1000) O-methoxy terminated, at one end and having at the other a carboxylate group able to link the inorganic surface and representing the repetitive unit of the comb-polymer.
The hydration delay of C-S-H formation induced by comb-polymer was analyzed by conduction calorimetry and the morphology of the crystalline structure in growth by SEM, specially investigating the relation between structure and hydration time. Because of the several complexities of the cementitious system undergoing hydration reactions we focussed the attention on one of the most important silicate phases of cement, the tricalcium silicate (C3S) and we studied the formation of portlandite crystals.
Observing the results we noticed that the hydration delay is ascribable to the comb-shaped structure because ethylene oxide chain can assume conformations able to act as “crown ethers” modifying the salt concentration near the cement surface. Moreover we noticed that organic admixtures can influence portlandite growth better arranging its crystalline structure
Environmental odour monitoring by means of electronic noses: definition of instrumental minimum performance requirements
Full text linkInvestigation of the interactions between dispersing carboxylate polymers and cement component phases by coarse grained modelling
No full textLow surface energy ceramic coatings
No full textThe research aims to coat aluminium surfaces with a film composed by hybrid organic-inorganic network and an high metal oxide content. The coating must have acceptable mechanical strength, release characteristic and must be produced through a not toxic, low temperature process. The study is connected to the industrial production of food (cookwares) and rotating cylinders for paper and plastic shaping. Thin hybrid coating films with a contact angle of 100-140° were obtained with the sol gel process using methyl and/or ethyl alkoxy silanes. They were obtained enclosing colloidal silica, α-Al2O3, and other fillers and using HNO3 as catalyst. Several different formulations has been used and the film are obtained after an appropriate thermal treatment. The choice of inorganic fillers appear critical. The increase of the colloidal silica (CS) increases the contact angle and the hardness but decreases the abrasion resistance. SEM analysis indicate that a thin homogeneous layer, free of inorganic fillers, is formed on the surface probably due to rheology behaviour of the colloidal mixture during the application. Due to the relevance of the CS content and of the other fillers on the surface performance, we needed to analyse the total fillers distribution along the thickness with GDOES instrument and SEM analysis.
The mechanical and morphological observations are discussed trying also to suggest some corrections in the ingredient content to optimise the formulation and the process parameters
Ceramic films on cast iron for high temperature treatments.
No full textThe research aims the deposition of low thickness ceramic films on the surface of cast iron forms that are used for recycled Pb moulding. The films will establish a thermal insulating coating to delate the metal solidification for a short time in order to complete an unforced mechanical scorification. Moreover the bars will assume a more uniform and market acceptable surface. The thermal conductivities of the cast iron (Meehanite HE type) and the ceramic material are 55 W/m°C and 2.2 W/m°C respectively. High temperature ceramic coating not suited to thin film production so the sol gel process seems appropriate to homogeneously apply a mixture of metal oxides at low temperature. To avoid the film shrinkage due to the phase evolution of the inorganic components, at first, we prepared the inorganic oxide mixture by the conventional frit manufacturing process; the mixture was homogenized in a water suspension, dried and melted at temperature between 1000 and 1200°C. Then the glass was quenched in air or poured in water; after it was milled and sieved at 325 mesh (< 40 μm). The powder was added to the sol-gel acid mixture (hydrolysis step) prepared from tetralkylalkoxysilanes, and applied on the cast iron surface by dipping, spraying or spreading with a blade. The cast iron surface was prepared by alternate washings with acids and bases followed by drying. To improve the adhesion largely influenced by the differences between the thermal expansion properties of the substrate and the film (the CTE, linear is 13.0 μm/m-°C for the cast iron and 2-5 μm/m-°C for the ceramic film) and corrosion resistance, the surface was treated with an activating agent like fluoro-metal acid (metal = Zr, Si) before the sol-gel colloid application. Thermal treatment at temperature between 750 and 930°C were adopted and the film evolution was investigated by SEM.
The frits were characterized by XRD analysis checking the influence of annealing temperature on the film structure and the phase evolution was investigated, so as to obtain films with superior performance. GDOES analysis was used to characterized the film composition.
The thickness was 100-150 μm with an adhesion value measured with the ASTM 3359-02 method of about 2B-3B probably due to an high hardness characteristic. More investigation on the metal oxide mixture and film properties are in course
Electronic Nose for continuous emission monitoring and odour concentration measurement: case study at a waste water treatment plant
Full text linkThermal Evidences of the Interaction Between Plastcizers and Ca salts in cement
No full textThe interactions between an organic polymer with plasticizing activity and a model surface (CaCO3), with a surface activity similar to
the cement one, have been analysed by volumetric analysis and thermal analysis: TG/DTG and DSC. The synthesized polymer has a
negative link site (carboxylate) that is able to interact with the substrate and a long ethylene oxide chain that contribute to the dispersing
activity. The pattern of the adsorption isotherm suggests the occurring of a step like adsorption, initially characterised by a coil conformation
of PEO chain followed by a more PEO strained, linear, conformation as the amount of polymer increases. The polymer adsorption
appears to modify the crystalline phase and morphology of the CaCO3 surface as the thermal analysis puts in evidence through the
CaCO3 decomposition temperature shifts. SEM analysis confirms the morphology changes induced by polymer adsorption
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