Solid Combustion Synthesis Research Articles

Solid combustion synthesis of MnO2/NiO/Ag nanocomposites for efficient degradation of methylene blue and their antibacterial activity

This study was undertaken to design simple, eco-friendly, and easy recoverable MnO2/NiO/Ag (MnCs) nanocomposites, which were synthesized by solid combustion method. Various techniques were utilized to analyze the morphology, composition, functional groups, and optical properties of both MnO2 and its MnCs composites. SEM and TEM images confirmed the surface morphology and particle distribution. The bandgap energies of MnO2, MnCs-1 and MnCs-2 were determined through Kubelka-Munk equation as 1.8, 1.77 and 1.75 eV, respectively. The binding energies obtained from the XPS spectra were 642.89 and 654.04 eV confirming the presence of Mn2p3/2 and Mn2p1/2. The photocatalytic activity of MnO2, MnCs-1, and MnCs-2 was investigated for the degradation of MB dye, revealing that approximately 43.24 %, 75.50 %, and 91.25 % of MB was degraded under UV-light after 120 min. Furthermore, the MnO2/NiO/Ag nanocomposites exhibited a zone of inhibition against pathogens, including Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and Klebsiella pneumoniae.

ChemInform Abstract: A Review on Combustion Synthesis Intensification by Means of Microwave Energy

AbstractReview: 140 refs.

A review on combustion synthesis intensification by means of microwave energy

Combustion synthesis (CS) is a materials manufacturing technique, which gained increased attention by both academia and industries, due to its intrinsic energy saving characteristics and high purity of the products. Energy requirements for CS are limited to the ignition step, since the desired products are obtained by using the heat generated by exothermic reactions occurring between the reactants.CS has been here addressed from a process intensification perspective, since CS characteristics perfectly fit into several process intensification definitions, aims and approaches.Particular attention has been dedicated to the use of microwaves as energy source for CS, and the benefits deriving from the combination of these two techniques have been reviewed. The doubtless better energy transfer efficiency of microwaves, with respect to conventional heating techniques, arising from the direct interaction of the electromagnetic energy with the reactants, contributes to further intensify both solid state and solution CS processes.Moreover, microwaves peculiarities, such as their selective and volumetric nature, together with their energy transfer nature, open new attractive opportunities for CS in different fields of materials science, like joining and advanced protective coatings. Innovative strategies of microwaves-ignited and/or sustained CS for the process intensification of advanced materials manufacturing are proposed as well.

Synthesis, consolidation and characterization of monolithic and SiC whiskers reinforced HfB2 ceramics

Abstract Spark Plasma Sintering is used for the fabrication of highly dense HfB2 monolithic and HfB2–26 vol.% SiCw composite. Reactive SPS from elemental reactants is preferred for the preparation of bulk HfB2 instead of classical sintering. The desired phase is rapidly formed through a solid–solid combustion synthesis mechanism, while full densification is achieved in 30 min at 1350 A when the applied pressure is switched from 20 to 50 MPa after the synthesis reaction. A 99.4% dense whiskers-reinforced HfB2 ceramic matrix composite is also obtained in 30 min by SPS (I = 1350 A, P = 20 MPa) using SHSed HfB2 powders and SiCw. Nevertheless, whiskers degradation into SiCp resulted under such conditions (temperature up to 1830 °C). On the other hand, the presence of whiskers is clearly evidenced in 96% dense products obtained when the applied current was decreased down to 1200 A (1700 °C) while P was increased to 60 MPa.

Probing the Surface of Ceria−Zirconia Catalysts Using NOx Adsorption/Desorption: A First Step Toward the Investigation of Crystallite Heterogeneity

Ce−Zr mixed oxides with a targeted composition of Ce0.76Zr0.24O2 have been synthesized from nitrate precursors following different synthesis methods: coprecipitation, solid combustion synthesis with urea, citrate complexation, reverse microemulsion, and synthesis with an activated carbon fiber template. Though their real nominal compositions were nearly equal in most cases, the characterization by XRD, Raman, N2 adsorption, FTIR, and XPS revealed distinct surface and bulk properties. The monitoring of NO + O2 adsorption/desorption processes by in situ DRIFTS and TPD-MS allowed distinguishing the type, amount, and relative thermostabilities of nitrite/nitrate species on the different surfaces. A detailed analysis of these spectroscopic data was carried out in order to estimate the respective participation of Ce and Zr sites to the adsorption and further reaction of NOx on ceria−zirconia surfaces. In the most favorable cases, the adsorption of (NO + O2) or NO2 can be used to assess the relative enrichment of the different surfaces in Ce or Zr, but this method was found more difficult to apply than the FTIR of adsorbed methanol.

Contributions of surface and bulk heterogeneities to the NO oxidation activities of ceria–zirconia catalysts with composition Ce0.76Zr0.24O2 prepared by different methods

The study of the catalytic activity towards NO oxidation to NO(2) was approached by using ceria-zirconia mixed oxides with the same nominal composition (Ce(0.76)Zr(0.24)O(2)) but prepared by different routes of synthesis: coprecipitation, solid combustion synthesis with urea, citrate complexation route, reversed microemulsion and template synthesis. The characterisation of the catalysts was performed by N(2) adsorption at -196 °C, XRD, Raman Spectroscopy, H(2)-TPR and XPS in order to ascertain the relationships between their catalytic activities and their bulk and surface properties. The results showed that the preparation method is critical for the physico-chemical properties of the mixed oxides, exhibiting very different BET surface areas, crystalline phase/s contributions and bulk oxygen mobility. The distribution of Ce and Zr on the surface with regard to the bulk is very much influenced by the preparation method as well. The NO(2) production from NO oxidation was shown to be mostly correlated with the Ce/Zr surface atomic ratio and the proportion of Ce(4+) (presumably in a doped cubic phase) in the uppermost layers.

Role of crystallite size on the photoluminescence properties of SrIn 2O 4:Eu 3+ phosphor synthesized by different methods

Photoluminescence (PL) of Eu 3+ was studied in SrIn 2O 4 host lattice. A complete solid solubility of Eu 3+ has been found in the series SrIn 2− x Eu x O 4 [ x=0–2.0]. The phase formation at a relatively low temperature and in a very short duration was achieved by combustion synthesis (CS). Concentration quenching of luminescence has been observed in SrIn 2− x Eu x O 4 [ x=0.1–2.0] and the critical concentration for maximum emission was found to be with x=0.3. In order to find the role of crystallite size on the PL properties of SrIn 2O 4:Eu 3+, the results obtained with phosphors synthesized by solid state reaction (SSR) and CS methods were compared.

The solid combustion synthesis of small REBa 2Cu 3O x samples (RE  Y, Er)

We critically assess the solid combustion synthesis (SCS) of small (about 23 g) REBa 2Cu 3O x samples (RE  Y, Er) from mixtures of Cu, RE 2O 3 and BaO 2 in an oxygen atmosphere. We examined the dynamics of the SCS process by means of temperature profile analysis and, for the first time on such a complex system, employed time-resolved X-ray diffraction using synchrotron radiation. We determined the phase composition, structure and magnetic properties of the resulting combustion product, which is a multiphase composite containing only about 30 wt.% of superconducting material. The superconducting phase exhibits transition temperatures of 80–90 K and oxygen transport and diffusion into the material appear to be sufficient. In contrast to results reported for large combustion samples, the absence of a sufficiently developed reaction zone seems to preclude complete formation of the superconducting phase in small combustion bodies. While combustion synthesis may have its advantages in technical-scale production of ceramic superconductors, it does not appear to be suitable for laboratory synthesis of small amounts of high-quality material.

Advanced materials for high temperature applications. New ways of elaboration

Abstract

The calculation and analysis of the adiabatic temperature of solid combustion reactions

The adiabatic temperature ( T ad ) presents a key parameter for the understanding of Solid Combustion Synthesis (SCS) reactions. Based on a generalized treatment of the underlying formalism, a microcomputer program for the calculation and analysis of adiabatic temperatures of SCS reactions is introduced, and representative types of SCS reactions are discussed. Examples include reactions with liquid formation and liquid-solid phase equilibria as well as complex combustion systems with additional inert diluents. The program ADIBAT is fully menu driven and provides graphic presentation of the the reaction temperature vs. the heat of reaction, phase equilibria information, and graphic presentation of the T ad vs. the diluent concentration.

Solid combustion synthesis of refractory carbides: (A review)

The specific mechanisms of heterogeneous reactions which are likely to occur during solid combustion synthesis in the TiSiC system are reviewed. Also discussed are the properties of some products of solid combustion as compared with these from other advanced methods of synthesis and the competitiveness of this process with other advanced methods of production of ceramic carbide powders.

Solid combustion synthesis of Ti3SiC2

Using powders of Ti and Si and carbon black as reactants, a material composed mainly of the ternary compound Ti 3 SiC 2 and of minor amounts of TiC was synthesized by the method of solid combustion. Following ignition at 1050°C, complete conversion of the reactants to the products was observed in a time of 2 to 5 s. The product obtained from the molar composition 3Ti:Si:2C has properties similar to the CVD-derived polycrystalline Ti 3 SiC 2 , which is a ‘soft’ ceramic material capable of being shaped by metalworking methods and shows a high resistance to oxidation and to aggressive environments. Ausgehend von Titan- und Siliziumpulvern und Ruß als Reaktanden wurde durch exotherme Reaktion ein Material hergestellt, das hauptsächlich aus der ternären Verbindung Ti 3 SiC 2 und geringen Gehalten von TiC besteht. Nach der Zündung bei 1050°C erfolgte die vollständige Umwandlung der Edukte zum Produkt in c. 2–5 Sekunden. Die Eigenschaften des Produkts (Zusammensetzung 3Ti:Si:2C) sind vergleichbar mit denen von CVD-synthetisiertem, polykristallinem Ti 3 SiC 2 , das ein ‘weicher’ keramischer Werkstoff ist, der durch Metallbearbeitungsmethoden geformt werden kann. Außerdem weist dieses Materials einen hohen Oxidationswiderstand auf und ist in chemisch aggressiven Umgebungen beständig. Un matériau composé principalement de Ti 3 SiC 2 et de petites quantités de TiC a été synthétisé à partir de poudres de Ti, Si et de noir de carbone par la méthode de combustion solide. Aprés amorçage à 1050°C, on observe une conversion complète au bout de 2 à 5 secondes. Le produit obtenu à partir de la composition molaire 3Ti:Si:2C présente des propriétés similaires à celles du Ti 3 SiC 2 polycristallin produit par CVD, qui est une céramique ‘douce’, apte à être mise en forme par des méthodes métallurgiques traditionnelles et qui montre une résistance élevée à l'oxydation et aux milieux agressifs.

Solid combustion synthesis of β SiC powders

A method of obtainment of β SiC powders under conditions of the self-propagating high-temperature synthesis (SHS), based on the exothermic reaction between silicon micropowders and active carbon substrates (carbon black and charcoal), has been developed. The method described in the paper is characterised by a low ignition temperature (1250–1300°C) and a short duration of synthesis (3–5 minutes). The product retains the morphology of the carbon substrates used what indicates the occurrence of a mechanism similar to the one suggested in the case of carbon fibres-silicon systems, namely the occurrence of alternating steps of solution of carbon in liquid silicon and crystallisation of SiC from supersaturated solution.