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Composites based on a commercial grade polystyrene (PS) resin containing non commercial perovskite particles were prepared by melt mixing and analyzed in terms of mechanical properties, dynamic-mechanical behavior and morphology. In particular, with the aim to study the influence of the filler size on the ultimate properties of PS based composites micro- and nano-sized perovskite La0.5Sr0.5MnO3 crystal particles, synthesized by using an efficient and rapid microwave-assisted hydrothermal route, were considered. Measurements of flexural parameters such as modulus and strength by static tests and storage modulus and damping factor by dynamic-mechanical evaluations showed better performance for nanofilled systems with respect to the ones containing micro particles, with the same filler content. Mechanical evidences were explained also by morphological observations from which a different level of filler dispersion seems to be obtained with the organization of perovskite nanosized crystals in superstructures able to support viscoelastic results.

Microwaves at 2·45 GHz have been used to ignite the self-propagating high temperature synthesis of Ni and Al powder mixtures (50∶50 at-%) to produce a duplex intermetallic coating on Ti substrates. Owing to the high β-NiAl synthesis reaction enthalpy and the energy provided by the electromagnetic field, the newly formed aluminide is in the liquid phase. Thus, it can react with the underlying Ti substrate, forming a ternary eutectic at the interface, belonging to the Ni–Al–Ti system. The peculiar interlocking microstructure of such ternary layer is responsible for an increase in toughness and hardness compared to the parent NiAl coating. Moreover, the ternary layer’s oxidation resistance was tested, showing the possibility of replacing the functionality of hard and brittle NiAl, but limitedly up to 750°C. This can be ascribed to the relatively low Al content in the ternary layer, which hinders the formation of a continuous and protective Al2O3 scale. For this reason, the increase in Al content, or the addi...

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This paper has been retracted at the request of the authors. A more detailed description of the research has been published in Surface & Coatings Technology (SCT 243, pages 65–70 (http://dx.doi.org/10.1016/j.surfcoat.2012.03.030).

Nanocrystalline zirconia powders have been prepared by microwave-hydrothermal synthesis starting from aqueous solution of ZrOCl2·8H2O. Results of investigations on the aqueous suspension stability of the washed zirconia nanopowders by dynamic light scattering showed that the suspension, constituted by superaggregates of nanoparticles (131 ± 10 nm), was stable up to 15 days. Nanopowders were investigated by means of transmission electron microscopy and small angle x-ray scattering measurements which proved that the zirconia nanopowder is constituted by small primary nanoparticles of ca. 8 nm that agglomerate forming bigger aggregates of 50 ± 1 nm.

The use of microwave (MW) energy as an ignition source for combustion synthesis and compaction of intermetallics-based functionally graded materials (FGMs) is suggested. Numerical simulation was used to investigate the temperature distribution in reacting powders before, during, and after combustion synthesis, showing that microwaves are capable of continuing to convey energy to the reactants and products, despite an adverse temperature gradient. Examples of the application of Microwave-Assisted Combustion Synthesis (MACS) are reported, involving principally neat intermetallic-based FGMs belonging to the CoAl-NiAl system, both as free-standing samples and as coatings on titanium Grade 5 alloy. Some other preliminary results on the reliability of the here proposed experimental approach to the synthesis of free-standing samples based on intermetallic-matrix ceramic particles reinforced FGMs are presented.

The paper examines the influence of Al2O3/SiO2 ratio, bulk chemical composition and temperature in mullite nucleation and growth from kaolinitic clays. Samples from NTAMUKA (TAN), Mayouom (MAY) and Wabane (WAB), region of high hills of West-Cameroon, undergo series of phase changes during sintering between 1000 and 1500°C. Phases transformation included: amorphous SiO2 and Al2O3 as result of breakdown of kaolin above 700°C, nuclei of mullite that growth with temperature development to fine and then large grains at high temperature. The microstructure of the sintered products consisted on the elongated secondary mullite (types II and III) interlocking with primary (type I) mullite in a compact matrix with relative amount of liquid film for MAY and WAB. The morphology of mullite grains in TAN was more different being larger cuboid grains aggregated to form together with cristobalite a compact microstructure. The formation of TiO2 crystals and then Ti–Al (tialite: Al2TiO5) crystals influenced the mi...

Nanosized titanium oxide (TiO2) powders have been prepared by conventional and microwave hydrothermal methods by forced hydrolysis of TiOCl2. As-prepared powders have been completely characterised by qualitative and quantitative XRD and TEM. The obtained titania powders have been redispersed (45 and 60 wt.%) in an aqueous hydroxypropylcellulose (HPC) solution (0.5–1 wt.%). Rheological characterisation has been performed in order to evaluate the influence of HPC on particles agglomerations. The effect of mixing time, HPC and TiO2 concentration and their mutual interactions on shear stress have been evaluated with a design of experiment (DOE) approach. © 2008 Elsevier Ltd. All rights reserved.

The management of electrical and electronic equipment waste (WEEE) is a significant problem of industrialized countries, in the last decades it has been noticed an appreciable increase of this residue, consisting of about 80% of television sets and computers containing end of life (EOL) cathode ray tubes (CRT). Specific technologies permit to dismantle the kinescope, obtaining different glasses with high quality level and specific chemical compositions. The presence of dangerous elements makes critical the re-use in many fields of application. The present work proposes the feasibility of CRT glass recycling in ceramic field using it into a base glaze formulation as substitute of “ceramic frits”. The study was conducted in two phases, laboratory scale in order to study the suitable glaze formulation and semi-industrial scale with the technological support of an Italian ceramic glaze producer. The glazes obtained have aesthetic and mechanical properties extremely similar to the standard ones.

Background, Aims and Scope The interest in recycling materials at the end of their life is growing in the industry in general. As regards the Wastes of Electrical and Electronic Equipment (WEEE), an appreciable increase of these materials has been noticed in the last decades, 117 · 103 tons of WEEE have been produced in Italy in 2002 according to Ecohitech [1] and the increase in this kind of waste is three times higher than that of the municipal waste according to the FISE ASSOAMBIENTE report [2]. Within WEEE, End-of-Life Cathode Ray Tube (EOL CRT) glass, the main part of TV sets and PC monitors, is here analysed using both a technical approach to establish a possible reuse of the glass in a open-loop recycling field (ceramic industry) and a methodology (LCA) capable of providing environmental evaluations.

Monodispersed silica colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of tetraethylorthosilicate (TEOS) by using a continuous microwave synthesis process. The flow rate was varied from 43 to 101 mL/min in order to establish the optimum conditions required to obtain unagglomerated silica nanopowders. The results were compared with those obtained in batch systems. In particular the mean particle diameter became smaller than 50 nm as the residence time was decreased by increasing the flow rate to 101 mL/min.

Changes in the structural properties of Er3+ doped soda-lime silicate glasses were investigated as a function of Al2O3 content. A combined approach of experimental techniques and molecular dynamic simulations (MD) was used to evaluate the structural features directly correlated to the glass properties. The experimental results in term of density, thermal properties as well as microstructural and mineralogical data showed a significant variation when increasing the alumina content from 10 mol% to 15 mol%. These results were compared to the MD information and discussed: changes in erbium and aluminium local configuration, due to the glass structural evolution as a function of the alumina concentration, have been investigated.

Nanocrystalline ceria powders (CeO2) have been prepared by adding NaOH to a cerium ammonium nitrate aqueous solution under microwave–hydrothermal conditions. In particular the effect of the synthesis conditions (time, pressure and concentration of both the precursor and the precipitant agent solutions) on the physical properties of the crystals have been evaluated. Microwave– hydrothermal treatment of 5 min at 13.4 atm allows to obtain almost crystallized powders (amorphous phase 4%) as underlined by Rietveld-reference intensity ratio (RIR) results. # 2005 Elsevier Ltd. All rights reserved.

Molecular dynamic simulations of glasses belonging to the anorthite-diopside system have been performed in order to ob- tain an atomistic description of the material's structure. The structural parameters obtained by the simulations allow to con- firm that the glass materials are characterized by a very similar short-range environment. The main differences have been ob- served in the intermediate-range order of the structure that de- scribe the distribution and the packing of the tetrahedra constituting the three-dimensional networks. It is shown that the glass materials with composition close to the two extremes, corresponding to the pure glass anorthite or pure glass diopside, display the typical structural features of the tectosilicates and inosilicates subclass of minerals, respectively, to which anorthite and diopside crystals belong. largely used in the last few years for industrial applications. 1-3 The knowledge of the atomistic arrangement in glass materials is an essential requirement for the interpretation of their physical and chemical properties. Unfortunately, while the structure of a crystalline solid can be considered as the repetition of a basic unit cell, no long-range order can be detected in the glass and the structure shows only a short- and an intermediate-range order (IRO). The assumption of dominant disorder in glasses has been in- vestigated by several methods; generally a good approach con- sists in the analysis of the similarities between microscopic and macroscopic properties of glasses and correspondent crystals. 4 The structure of a glass material is constituted by SiO4-based networks distorted by the presence of the network modifier ions that break the three-dimensional (3D) framework to satisfy their coordination. It is well known that the structure of a single- chain metal silicate lattice depends on the size and the charge of the metal atoms: the number of SiO4 tetrahedra forming the re- peating unit, and their relative disposition, is a sensitive function of these parameters. 4 In this sense, the metal cations exert an important, perhaps even dominant, influence on the structure. The diopside mineral belongs to the subclass of silicates called inosilicates. This subclass contains two distinct groups: the sin- gle- and double-chain silicates. In the single-chain group, the tetrahedra share two oxygens with two other tetrahedra and form a seemingly endless chain. The ratio of silicon to oxygen is thus 1:3. The tetrahedra alternate to the left and then to the right along the line formed by the linked oxygens although more complex chains seem to spiral. In cross-section, the chain forms a trapezium and this shape produces the angles between the crystal faces and cleavage directions. In the single-chained sili- cates, the two directions of cleavage are at nearly right angles (close to 901), forming nearly square cross-sections. The anorthite belongs to the tectosilicates subclass of miner- als. This subclass is often called the ''Framework Silicates'' be- cause the structure is composed of interconnected tetrahedra going outward in all directions forming an intricate framework analogous to the framework of a large building. In this subclass all the oxygens are shared with other tetrahedra, giving a silicon- to-oxygen ratio of 1:2. In the near-pure state of only silicon and oxygen, the mineral is quartz (SiO2). But the tectosilicates are not that simple. It turns out that the aluminum ion can easily substitute for the silicon ion in the tetrahedra up to 50%. In other subclasses this substitution occurs to a more limited extent, but in the tectosilicates it is a major basis of the varying struc- tures. While the tetrahedron is nearly the same with an aluminum at its center, the charge is now a negative five (5) instead of the normal negative four (4). Since the charge in a crystal must be balanced, additional cations are needed in the structure and this is the main reason for the great variations within this subclass. 5 In this work, the study of the glass materials has been carried out by means of an elaboration of a theoretical model, subse- quently validated with the experimental data available, in order to obtain a detailed characterization of the glass network. It is well known that computer simulations, exploring the structure and the behavior of materials at the atomic level of detail, allow the static features determination and the quantification of the relationships existing between the structure and properties of materials. 6

An aluminosilicate glass of composition 61SiO26Al2O310MgO6ZnO·12Li2O·5TiO2 (mol%) has been prepared by a melting process and investigated as far as crystallization is concerned. Glass-ceramic is easily obtained because glass shows a high tendency to crystallize starting from 700°C. The crystalline phases evolve with temperature, showing the aluminosilicates to be the main phase up to 1050°C, followed by metasilicates and silicates, some of which have lower melting points. The titanates of Mg and Zn develop from the phase-separated glass, soon after Tg, and grow to form nucleation centers for the other crystalline phases. The evolution from phase-separated glass to glass-ceramic has been followed by many thermal, diffractometric, spectroscopic, and microscopic techniques.

The nucleation and growth of diopside Ca(Mg,Al)(Si,Al)2O6crystals on the free surface of a 24 wt% MgO, 14 wt% CaO, 9 wt% Al2O3, and 53 wt% SiO2glass, with a 2 wt% addition of steel fly ash, were investigated through DTA, XRD, SEM, and optical microscopy. Crystallization was complete at ∼920°C with an activation energy of 589 kJ/mol. Samples with polished free surfaces were nucleated at selected temperatures in the range of 730° to 820°C, and then heat-treated at 870°C for 15 min for crystal growth. Nucleation was predominantly observed at the surface, and the number of diopside crystals per unit of area and the mechanism of crystallization were determined. It was concluded that nucleation reaches a maximum at 750°C, corresponding to an average density of diopside crystals of 8.4 × 106 nuclei/cm2, and that between 900° and 1100°C, a uniformly crystallized layer is formed at an exponential rate. The crystallized volume fraction increased significantly in the 880°–890°C growth range, and remained almost constant at higher temperatures. In the 860°–910°C range, the size of the diopside crystals formed in the samples nucleated at the temperature of the maximum nucleation rate, and linearly increased, reaching values between 1.0 and 3.0 μm at 870° and at 910°C, respectively.

The glasses belonging to the CaO–MgO–Al2O3–SiO2 quaternary system are materials largely used in industrial applications by virtue of their melting and devitrifible properties. A systematic study of several compositions falling in the anorthite (CaO–Al2O32SiO2)-diopside (CaO–MgO–2SiO2) system has been carried out by means of thermal and physical measurements in order to obtain the relationships between the structure and the properties of the glasses. The experimental evidence has been compared to molecular dynamic simulation results. Attention has been devoted to the definition of the structural role in the glass formulation played by Al3+ and Mg2+ which can behave as network formers or modifiers depending on their coordination number in the structure.

The influence of the introduction of ZrO2 in concentrations of up to 5 mol% into a 30K2O-70SiO2 base glass composition has been investigated with the aid of differential thermal analysis (DTA), FT-IR spectroscopy, as well as chemical durability tests (pH, conductivity and AES-Inductively Coupled Plasma measurements) and refraction index determination. Several differences have been found by comparison with similar compositions belonging to the Li2O—ZrO2—SiO2 system. The higher ionic radius and the lower field strength of K+ with respect to Li+ is responsible for higher stability towards crystallisation and lower chemical durability. Moreover, even though Zr4+ increases glass polymerisation (higher glass transition temperature, chemical durability and refraction index), the presence of high water content as highlighted by spectroscopy measurements, seems to weaken the glass structure.

Actually, the inertization, recovery and valorisation of the wastes coming from municipal and industrial processes are the most important goals from the environmental and economical point of view. An alternative technology capable to overcome the problem of the dishomogeneity of the raw material chemical composition is the vitrification process that is able to increase the homogeneity and the constancy of the chemical composition of the system and to modulate the properties in order to address the reutilization of the waste. Moreover, the glasses obtained subjected to different controlled thermal treatments, can be transformed in semy-cristalline material (named glass-ceramics) with improved properties with respect to the parent amorphous materials. In this review the tailoring, preparation and characterization of glasses and glass-ceramics obtained starting from municipal incinerator grate ash, coal and steel fly ashes and glass cullet are described.

The system zirconia−praseodymia (Pr content 0−15 mol %) has been investigated to evaluate the praseodymium solubility and its role in the zirconia phase stability. The powders have been synthesized by coprecipitation and subsequent calcination at different temperatures (400−1000 °C) for 2 h. The crystal structure of the obtained nanocrystalline (Zr, Pr)O2 powders has been studied by X-ray diffraction. By applying the Rietveld method, the dopant effect on the zirconia phase stability was found and discrimination between the different zirconia polymorphs was possible.

Reactions between 1-chloro-2,4,6-trinitrobenzene and 2-hydroxypyridine, 3-hydroxypyridine, and 4-hydroxypyridine are reported. 4-Hydroxypyridine produces the product of attack at the nitrogen atom, while 3-hydroxypyridine reacts at the oxygen atom. 2-Hydroxypyridine reacts as an ambidentate nucleophile, providing a mixture of products arising from attack at both the oxygen and the nitrogen atom. Reactions between X-substituted-3-hydroxypyridines (X = H, 5-Cl, 6-CH3) and 1-chloro-2,4,6-trinitrobenzene provided 3-pyridinyl 2,4,6-trinitrophenyl ethers, analysed by 1H and 13C NMR spectra and by X-ray diffraction. Moderate heating of methanolic solutions of 3-pyridinyl 2,4,6-trinitrophenyl ether and of 6-methyl-3-pyridinyl 2,4,6-trinitrophenyl ether caused a methylation reaction of the pyridine nitrogen ring through trinitroanisole, providing 3-hydroxy-1-methylpyridinium picrate and 1,2-dimethyl-5-hydroxypyridinium picrate. Kinetic data are compared and discussed.

The electrical behaviour of different glass compositions obtained from mixing waste glass deriving from a community glass recycling program and silicate waste from the incineration of municipal solid residues (from Reggio Emilia city) have been investigated as a function of temperature and frequency. The electrical and dielectric properties were related to structural studies performed on the same glassy materials. As the amount of incinerator wastes increases, on account of lower alkali and higher alkaline-earth content in the final glass composition, conductivity and dielectric losses decrease approaching the behaviour of type E glass fibres, so envisaging a possible use of waste-containing glasses in the production of high voltage insulators.

The feasibility of utilising solid residues of the municipal wastes incineration such as grate (bottom) ash and electrofilter and sleeve filter fly ash, in combination with a porcelain stoneware body, in the preparation of tiles has been investigated. While the chemical, mineralogical, thermal and rheological characterisation of the waste raw materials carries out some problems arising by using fly ash, these seem to be overcome with the bottom ash. The introduction of up to 20 wt% of this powder into the ceramic body does not substantially change the mineralogical and thermal behaviour of the product.

The crystal structures of three polymeric bidimensional piperazinium, N,N'-dimethylpiperazinium, and N-benzylpiperazinium hydrate haloplumbates(II) and one polymeric monodimensional N,N'-dimethylpiperazinium hydrate haloplumbate(II) were determined by means of X-ray analysis. The (pipzH2)[PbCl4] salt is monoclinic, space group P2(1)/c, with a = 5.778(2) A, b = 22.612(26) A, c = 9.061(4) A, beta = 95.37(6) degrees, Z = 4; (me2pipzH2)[PbBr4] crystallizes in the monoclinic P2(1) space group with a = 6.101(3) A, b = 18.822(12) A, c = 6.229(2) A, beta = 98.62(4) degrees, Z = 2; the crystals of (me2pipzH2)2[Pb3I10].4H2O are monoclinic, space group P2(1)/c, a = 19.054(4) A, b = 12.239(3) A, c = 18.273(4) A, beta = 93.42(12) degrees, Z = 4; (benzpipzH2)3[Pb2Br10].2H2O crystallizes in the monoclinic P2(1)/c space group with a = 22.380(22) A, b = 9.304(15) A, c = 24.577(25) A, beta = 94.28(11) degrees, Z = 2. Different model type structures, such as one-dimensional linear chain, ribbonlike, and perovskite-like, were observed, and factors governing these structural arrangements are pointed out. The compounds were also investigated by means of thermal and electrical measurements, and correlations between electrical properties and crystal structures were noted.