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$$\hbox {MgO}{-}\hbox {Al}_{2}\hbox {O}_{3}{-}\hbox {SiO}_{2}$$ (MAS)-based glass-ceramic system was prepared using very-low-cost raw materials, i.e., talc, calcined alumina and calcined china clay with titanium dioxide as a nucleating agent. Glass-ceramics were prepared by a two-step process. In the first step, raw materials were mixed in the required proportion and melted at $$1450^{\circ }\hbox {C}$$ followed by water quench into a glassy frit. In the second step, powdered glass frit was uniaxially dry pressed into pellets followed by sintering at $$1200^{\circ }\hbox {C}$$ for 3 h. X-ray diffraction pattern of the sintered compact shows well-defined peaks of cordierite along with some anorthite and magnesium titanium oxide. The microstructure study of sample shows the presence of crystalline and glassy phases. Permittivity and permeability measurements were performed in the microwave frequency range 12.4-17 GHz. The permittivity value of 5.7-6.0 and the permeability value of $${\sim }1$$ were obtained. The reflection and transmission measurements show that the material possesses a shielding effectiveness in the range 2-10 dB over the frequency range 12.4-17 GHz. [ABSTRACT FROM AUTHOR]

The present investigation reveals the effect of processing parameters on the properties of alumina–titania (Al2O3–TiO2) nanocomposites. A polymer-assisted (Pluronic P123 triblock co-polymer) co-precipitation route has been employed to synthesize Al2O3–TiO2 nanoparticles. As a surfactant, pluronic P123 polymer exhibits hydrophobic as well as the hydrophilic nature simultaneously which detains the agglomeration and hence the nano size particle have been obtained. Effect of surfactant concentration on morphology and particle size of product has also been investigated. Thermal behaviour of the prepared powder samples have been studied using differential scanning calorimeter/thermal gravimetric analysis and dilatometer. Formation of aluminium-titanate (Al2TiO5) phase has been confirmed using X-ray diffraction analysis. It has been observed by field emission scanning electron microscopy analysis that the particle size reduced effectively (below 100 nm) when polymer-assisted co-precipitation route is used instead of the simple co-precipitation technique. A highly dense microstructure of sintered samples has been obtained, driven by reduced particle size. [ABSTRACT FROM AUTHOR]

The present paper reports the effect of height to diameter ( h/ d) ratio on the deformation behaviour of Fe-AlO metal matrix nanocomposites (MMNCs) during bulk processing. Sintered compacts were machined to the required size with different h/ d ratios. Test specimens were subjected to deformation at room temperature under three different interfacial friction conditions such as dry, solid and liquid lubrications. Deformed specimens show a significant improvement in the density and hardness. Results also revealed the formation of a nanosize iron aluminate phase due to reactive sintering, which in turn contributes to grain refinement. Experimental density of the specimens was also verified with the theoretical density using the standard equations. It is expected that the present work will be useful in designing and developing MMNC products with better quality at competitive cost. [ABSTRACT FROM AUTHOR]

Glasses were made by melt-quench method in the system [(SrPb)O·TiO]-[2SiO·BO]-5[KO-BaO] (0·0 ≤ x ≤ 0·4) with addition of 1 mol% NbO. Perovskite strontium lead titanate in solid solution phase has been crystallized in borosilicate glassy matrix with suitable choice of composition and heat treatment schedule. Addition of 1 mol% of NbO enhances the crystallization of lead strontium titanate phase in the glassy matrix. Scanning electron microscopy (SEM) is performed to study the surface morphology of the crystallites and crystalline interface to the glass. Dielectric properties of these glass ceramics were studied by measuring capacitance and dissipation factor as a function of temperature at a few selected frequencies. NbO doped strontium lead titanate glass ceramic shows a high value of dielectric constant. It is of the order of 10,000 while the dielectric constant of undoped glass ceramic sample is of the order of 500. Complex impedance and modulus spectroscopic techniques were used to find out the contributions of polarization of crystallites and glass crystal interfaces to the resulting dielectric behaviour. [ABSTRACT FROM AUTHOR]