This paper reports on the effect of surface functionalization of multi-wall carbon nanotubes on the strength and structure of portland cement composites. Reference nanotubes and nanotubes functionalized by carboxylic groups are used in this research.

Grafting of functional groups on the surface of the nanotubes allows the acceleration of cement hydration. It is established that the use of carboxylated nanotubes contributed to early strength development. The multi-wall carbon nanotubes reinforced composites are characterized by the high content of the calcium silicate hydrates and a very dense structure.

Melting of Direct Reduced Iron (DRI) pellets in Electric Arc Furnaces (EAF) in steelmaking production is a common practice worldwide. Mathematical models are proper tools to study the phenomena involved in melting DRI. In this work we develop a mathematical model to predict melting kinetics of DRI in a liquid slag bath. The model is successfully validated against experimental results and it is used to develop a process analysis to estimate the effects of DRI size, stirring conditions, and temperatures of the bath and pellet on the melting kinetics of DRI.

In this work results are presented regarding carbon composites produced by high energy mechanical milling and consolidated by spark plasma sintering. The involved energy input in such a processing method has been used to develop composite materials and to synthesize effective in-situ reinforcement. In the as milled and sintered composites various dispersions of graphene, graphitic carbon, and diamonds in an amorphous matrix are found. The graphene, graphitic carbon and diamond phases are synthesized primarily during milling. The TEAM-05 microscope has been used for characterization that is complemented with Raman results. The spark plasma sintering method enhances the presence of graphene, graphitic carbon and diamonds.

In this work we report the fractographic study of polymer matrix composites specimens reinforced with glass and carbon fibers. Specimens of a polyester matrix composite with 30% of E-glass fibers are prepared and fractured in flexure mode. We also test an epoxy matrix composite with 30% carbon fibers, which is fractured in flexure mode. All specimens are manufactured based on the D790 ASTM standard for bending mode at room temperature. As an exception, the composites with epoxy matrix and reinforced with carbon fiber are cured in an autoclave. The most commonly observed fracture mechanisms are debonding in the interphase, delamination, Chevron lines, microbuckling, river patterns and radial fracture on the fibers.

Ba3-xKxHx(PO4)2 is a candidate solid-state proton conductor for solid acid fuel cells that is water-insoluble. The measured conductivity of ∼ 2.4 10-5 S cm-1 for the composition x=0.80 at 250°C is not competitive for solid acid fuel cell applications. This work investigates a methods for synthesizing solid acid electrolytes with the strategy of increasing proton conductivity by cation substitution and decreasing particle size. We report on the synthesis of nano Ba3-xKxHx(PO4)2 to a novel Ba3-xNaxHx(PO4)2. X-ray diffraction was used to confirm the Ba3(PO4)2 crystal structure and measure lattice strain as a function of cation substitution. SEM confirmed the morphology of micro Ba3-xNaxHx(PO4)2 is substantially different from micro Ba3-xKxHx(PO4)2, suggesting that Ba3-xNaxHx(PO4)2 has a different growth kinetics.

This article reports on a new composite gypsum binder (CGB) with nanostructured silica-based admixture (NSS). NSS is obtained by a wet ultrafine milling of quartz sand resulting in the formation of an inorganic polydisperse binding system, which has a high concentration of active nanoscale phase (about 10%). Developed CGB contains hemihydrate gypsum and nano-component based on quartz sand. It is observed that the addition of 15–20 % of NSS improves the rheological properties of gypsum systems through the formation of solvate shells hindering the access of water to gypsum particles; this process also retards the setting of binder.

The experimental program used infrared IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) to reveal the contribution of NSS. The porosity of CGB is analyzed by the kinetics of water adsorption and BET. The XRD and IR investigations determined the formation of a new sulfosilicate phase, hydroxyellestadite during the hydration of CGB. With the addition of NSS an overall reduction in pore volume, as well as the shifts in macro-, meso- and nano- porosity values are observed.

Analysis of CGB microstructure reveals that in the presence of the NSS the size and morphology of crystals are changed contributing to the formation of dense fine-grained structure. Experimental studies have demonstrated that the composite gypsum binders with NSS are characterized by reduced water absorption and increased density, as well as improved mechanical performance especially, higher compressive strength.

Rocks are composed of minerals, bounding matrix, cracks and pores. The study of changes in the physical properties of rocks as a function of heat treatment is relevant to various engineering and industrial applications. The effect of thermal damage on the compression, strength, ultimate compression strain, color and loss of mass of two different limestones extracted from the Yucatan Peninsula is studied. Different thermal treatments are applied by heating the sample from room temperature up to 600°C, with steps of 100°C. The results show a high correlation between the heat transport characteristics, mechanical properties, content of organic matter and the presence of carbonates and iron oxides in each type of limestone rock.

Duplex stainless steels are commonly used for various applications owing to their superior corrosion resistance and/or strength. They have ferromagnetic behavior together with a good thermal conductivity and a lower thermal expansion as a result of higher ferrite content than austenitic steels. Their ferrite matrix suffers a decomposition process during aging in the temperature range 650-950° C producing precipitation of austenite, σ and χ, carbides and nitrides. These intermetallic phases are known to be deleterious for corrosion resistance and mechanical properties.

In this work the effect of aging time during isothermal treatment at 850°C and 900°C on the microstructure of SAF 2205 Duplex Stainless Steels welded plates has been investigated. The aim of this work is to determine the morphology of σ phase, and perform a quantitative analysis of the precipitation process.

Submerged Arc Welding is used for processing. It produces a high content of δ ferrite in the heat affected zone and low content of austenite in the weld. Microstructural examination shows that the σ phase precipitates at δ ferrite/γ interphases. Longer aging treatments give rise to an increase of volume fraction together with a coarser morphology.