New production of TiCxN1-x-based cermets by one step mechanically induced self-sustaining reaction: Powder synthesis and pressureless sintering

TiCxN1-x-based powdered cermets were synthesized by a one step mechanically induced self-sustaining reaction (MSR) process from mixtures of elemental powders, and subsequently sintered by a pressureless method. The composition and microstructure of the ceramic and binder phases before and after the sintering process were studied by X-ray diffraction, scanning and transmission electron microscopy, and electron…

Thermal characterization of montmorillonite clays saturated with various cations

Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior during dehydration of natural Na montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite (MMT) samples saturated with different cations, i.e. Li+, Cs+, NH4+, Mg2+ and Al3+. ETA results characterized radon mobility and microstructure changes that accompanied the mass loss of…

A simple and precise linear integral method for isoconversional data

A simple and precise linear integral method to evaluate the activation energy dependence oil the extent of conversion has been proposed. The method leads to consistent results with those from differential and integral non-linear procedure (Vyazovkin method). Moreover, the new procedure yields the pre-exponential factor and the kinetic model. The method was evaluated from isothermal,…

Nitriding study of titanium silicide intermetallics obtained by mechanical alloying

Titanium and silicon powder blends were ball-milled under an inert atmosphere and subsequently annealed in a nitrogen atmosphere. Ti62.5Si37.5, Ti55.6Si44.4, and Ti50Si50 mixtures suffered a mechanically induced self-propagating reaction during milling. The products of the combustion were Ti5Si3 for the Ti62.5Si37.5 mixture and a combination of intermetallic phases for the Ti55.6Si44.4 and Ti50Si50 mixtures. The Ti33.3Si66.7 blend did not show an MSR process,…

A simple and precise linear integral method for isoconversional data

A simple and precise linear integral method to evaluate the activation energy dependence oil the extent of conversion has been proposed. The method leads to consistent results with those from differential and integral non-linear procedure (Vyazovkin method). Moreover, the new procedure yields the pre-exponential factor and the kinetic model. The method was evaluated from isothermal,…

Polymorphic transformation from body-centered to face-centered cubic vanadium metal during mechanosynthesis of nanostructured vanadium nitride determined by extended x-ray absorption fine structure spectroscopy

The pathway for vanadium nitride (VN) formation obtained by milling treatment has been traced out. At the initial stages of the process, the reactant, vanadium metal, showing body-centered cubic (bcc) structure, becomes highly distorted. Simultaneously, the formation of a small nucleus of the product, VN, takes place. X-ray absorption spectroscopy (XAS) has allowed the quantification…

Crystallization behavior of (GeS2)(0.1)(Sb2S3)(0.9) glass

The crystal growth kinetics of antimony trisulfide in (GeS2)(0.1)(Sb2S3)(0.9) glass has been studied by microscopy and DSC. The linear crystal growth kinetics has been confirmed in the temperature range 492 <= T <= 515 K (E-G = 405 +/- 7 kJ mol(-1)). The applicability of standard growth models has been assessed. From the crystal growth…

Transport properties and microstructure changes of talc characterized by emanation thermal analysis

Thermal behavior of talc samples (from locality Puebla de Lillo, Spain) were characterized by emanation thermal analysis (ETA), DTA and TG. The ETA, based on the measurement of radon release rate from samples, revealed a closing up of surface micro-cracks and annealing of microstructure irregularities of the talc samples on heating in the range 200-500 degrees C. For ground talc sample a crystallization of non-crystalline phase formed by grinding, into orthorhombic enstatite was characterized as a decrease of radon mobility in the range 785-825 degrees C…