Self-propagating Combustion Synthesis Research Articles

Phase formation, microstructure and mechanical properties of TaB2–SiC composites synthesized by reaction hot pressing: Effects of SiC contents and oxygen impurity

TaB2–SiC composites with 0–20 wt% SiC contents were prepared by reaction hot pressing using Ta, B and SiC powders as starting materials. Densification, constituent phases, microstructure and mechanical properties, namely Vickers hardness, fracture toughness and flexure strength, were evaluated by means of inspection of sintering shrinkage, density measurement, XRD, SEM, TEM, HRTEM, EDS, SAED, indentation and three-point bending tests. Phase formation, including dominant (TaB2, SiC) and minor (TaC, glassy SiO2) phases, was checked by thermodynamic assessment relevant with Ta2O5 and B2O3 impurities introduced into the reaction system by the starting powders. The results showed that mixtures of Ta, B and SiC powders would initiate self-propagating combustion synthesis (SPCS) at about 900 °C; a transient hold at 800 °C for 1 h could suppress this reaction. Volatilization of B2O3 impurity in association with local high temperature due to SPCS helped reduce the TaC and glassy SiO2 minor phase formation. TaB2–SiC composites could reach 99 % relative densities with 3 wt% SiC addition and above. Compositions with <7.5 wt% SiC additions showed uniform dispersion of SiC particles at multi-TaB2 grain junctions while compositions with higher SiC content revealed SiC segregation. Bending strength of 503 MPa and fracture toughness of 6.69 MPa⋅m1/2 could be reached with 7.5–20 wt% SiC addition.

Magnetic CuFe2O4 nanoparticles anchored on N-doped carbon for activated peroxymonosulfate removal of oxytetracycline from water: Radical and non-radical pathways

In this work, magnetic CuFe2O4 was prepared for the removal of oxytetracycline (OTC) by a self-propagating combustion synthesis method. Almost complete degradation (99.65%) of OTC was achieved within 25 min at [OTC]0 = 10 mg/L, [PMS]0 = 0.05 mM, CuFe2O4 = 0.1 g/L under pH = 6.8 at 25 °C for deionized water. Specially, the addition CO32− and HCO3− induced the CO3•- appearance enhancing the selective degradation to electron-rich OTC molecule. The prepared CuFe2O4 catalyst exhibited desirable OTC removal rate (87.91%) even in hospital wastewater. The reactive substances were analyzed by free radical quenching experiments and electron paramagnetic resonance (EPR), and the results demonstrated that 1O2 and •OH were the main active substances. Liquid chromatography-mass spectrometry (LC-MS) was used to analyze the intermediates produced during the degradation of OTC and thus to speculate on the possible degradation pathways. Ecotoxicological studies were conducted to unveil large-scale application prospect.

Carbon-Nitride Popcorn-A Novel Catalyst Prepared by Self-Propagating Combustion of Nitrogen-Rich Triazenes.

The interest in development of non-graphitic polymeric carbon nitrides (PCNs), with various C-to-N ratios, having tunable electronic, optical, and chemical properties is rapidly increasing. Here the first self-propagating combustion synthesis methodology for the facile preparation of novel porous PCN materials (PCN3-PCN7) using new nitrogen-rich triazene-based precursors is reported. This methodology is found to be highly precursor dependent, where variations in the terminal functional groups in the newly designed precursors (compounds 3-7) lead to different combustion behaviors, and morphologies of the resulted PCNs. The foam-type highly porous PCN5, generated from self-propagating combustion of 5 is comprehensively characterized and shows a C-to-N ratio of 0.67 (C3 N4.45 ). Thermal analyses of PCN5 formulations with ammonium perchlorate (AP) reveal that PCN5 has an excellent catalytic activity in the thermal decomposition of AP. This catalytic activity of PCN5 is further evaluated in a closer-to-application scenario, showing an increase of 18% in the burn rate of AP-Al-HTPB (with 2wt% of PCN5) solid composite propellant. The newly developed template- and additive-free self-propagating combustion synthetic methodology using specially designed nitrogen-rich precursors should provide a novel platform for the preparation of non-graphitic PCNs with a variety of building block chemistries, morphologies, and properties suitable for a broad range of technologies.

Combustion synthesis of β-SiAlON from a mixture of aluminum ferrosilicon and kaolin with nitrogen-containing additives using acid enrichment

In the work, single-phase β-SiAlON was prepared from a powder mixture based on aluminum ferrosilicon and aluminosilicate (kaolin) with nitrogen-containing additives (product of nitriding of the starting mixture and NH4F) by combustion synthesis followed by acid enrichment of the synthesized product. Self-propagating combustion synthesis was conducted under natural nitrogen filtration. The synthesis parameters (nitrogen pressure, sample diameter, density of the starting mixture) and the conditions of acid enrichment of the synthesized products (acid concentration, temperature of acid enrichment and dispersion of the starting powder) were determined. After acid enrichment of the synthesized product, which contained β-SiAlON and α-Fe phases, the phase content of β-SiAlON was 99.5 wt%.

Enhancing the strength-ductility synergy of Fe-based composites by changing interface bonding between matrix and TiCx with various stoichiometric ratios

The increase of strength in composites usually comes at the cost of ductility. This work proposed a strategy of design and synthesis of TiCx nanoparticles with controlled Ti/C stoichiometric ratios to adjust the microstructure and thus enhance the mechanical properties of the TiCx nanoparticles reinforced iron matrix composites. The changes of size and morphology of TiCx nanoparticles were investigated by self-propagating combustion synthesis (SHS) in the Fe–Ti–C reaction system. The influences of Ti/C stoichiometric ratios on the interface bonding and mechanical properties of Fe/TiCx were analyzed by lattice mismatch calculation. The results indicate that the morphology of TiCx nanoparticles changes from polyhedral to near-spherical sometimes accompanied by a few cubes with an increase in Ti/C stoichiometric ratios. The maximum yield strength (1525 MPa) compressive strength (2224 MPa) and microhardness (691.5 HV) of the TiCx/Fe composites are obtained when the C/Ti stoichiometric ratio reaches 1.0. The TiC0.8/Fe composites present a remarkable ductility up to 8.34%. Based on the lattice mismatch calculation, the good mechanical properties are mainly because the low lattice mismatch reduces the interfacial energy and thus leads to the higher mechanical properties. Effective design and control of the morphology of TiC particles and the interface bonding in Fe melt can maximize comprehensive performances and applications.

Self-propagating combustion synthesis of few-layer graphene for supercapacitors from CO and Mg

Graphene is considered as a promising electrode material for supercapacitors due to its large specific surface area, excellent electrical conductivity and so on. In this paper, few-layer graphene is prepared by self-propagating combustion reaction between CO and metal magnesium, using powder MgO as deposition template. Graphene with a high specific surface area of up to 928 m 2 g −1 replicates the morphological feature of powder MgO. Raman spectroscopy analysis demonstrates that the graphene layer decreases when the dosage of MgO template is increased. The specific capacitance of as-prepared sample exhibits the highest specific capacitance of 222 F g −1 at the current density of 1 A g −1 in EMI [TFSI] electrolyte. The sample demonstrates a "double high" performance with high specific energy density and high specific power density. A high energy density of 76.3 Wh kg −1 can be achieved at a specific power density of 1.75 kW kg −1 , and it can still remain 48.6 Wh kg −1 when the specific power density reaches a high level of 35 kW kg −1 . • Self-propagating combustion reaction synthesis graphene. • Synthesis graphene from CO and Mg. • Synthesized graphene has good structural properties. • Excellent capacitive performances in the electrolyte of EMI [TFSI].

Co/Mg Self-Propagating Combustion Synthesis of Few-Layer Graphene for Supercapacitors

Co/Mg Self-Propagating Combustion Synthesis of Few-Layer Graphene for Supercapacitors

Combustion synthesis of luminescent Eu-doped single phase Mayenite

Rare earth luminescent materials based on alkali metal oxides such as calcium aluminates have grabbed the attention due to their high luminescent efficiency, non-toxic and eco-friendly nature. Calcium aluminates as host materials for luminescent applications are extremely stable, suppressing the release of non-radiative energy resulting in the characteristic emission of rare earth luminescent centre. Moreover, calcium aluminates are inexpensive for their use as host material for luminescent applications. With texture and color giving the aesthetic contribution, Europium (Eu) doped single phase Mayenite may find potential applications in the design of energy efficient buildings when used as a coating material. Eu doped single phase Mayenite powders in varying concentrations (0%, 0.5%, 1%, and 1.5%) were prepared using self-propagating combustion synthesis method using metal nitrates and glycine as the fuel. The X-ray diffractograms confirmed the formation of single phase Mayenite with some of the Ca2+ ions getting replaced by Eu3+ ions. The photoluminescence emission spectra revealed 5D0 → 7F2 transition due to the crystal field effect and was characterized by the bright red luminescence. The doping of Eu resulted in a decrease of band gap from 4.8 ​eV for undoped Mayenite to 3.5 ​eV for 1.5% Eu doped Mayenite. The samples were found to exhibit excellent fluorescent properties under UV irradiation.

A series of novel carbohydrate-based carbon adsorbents were synthesized by self-propagating combustion for tetracycline removal

Herein, a series of novel adsorbents derived from glucose, maltose, and starch zinc oxide (ZnO) loaded carbohydrate-based carbon materials (Zn-Cs) were synthesized by a fast and efficient self-propagating combustion synthesis method (SCS). The experimental results show that Zn-Cs exhibits excellent adsorption performance (>375 mg/g) to tetracycline, and the pseudo-second-order model and Freundlich model can better describe the adsorption data. The adsorption capacities of Zn-Cs were over 300 mg/g throughout the wide pH range (6–9), while various coexisting ions in the concentration range of 0–10 mg/L and the presence of humic acid had nearly no impact on the adsorption of tetracycline. Moreover, the adsorption experiment of simulated hospital wastewater shows that the adsorption capacity of Zn-Cs for tetracycline exceeds 185 mg/g. The adsorption mechanism of tetracycline are H-bond, complexation, and conjugation effect. This work provides an efficient, excellent versatility and time-saving strategy for preparing high-performance carbohydrate-based carbon materials for adsorbents.

Synthesis, characterization of phyto-functionalized CuO nano photocatalysts for mitigation of textile dyes in waste water purification, antioxidant, anti-inflammatory and anticancer evaluation

In this scientific paper we report, cost-effective synthesis of unique copper oxide nanoparticles (CPC NPs) coupled with properties from phytocompounds of Pouteria campechiana (PC) and copper metal precursor with variegated morphology. The synthesis included variation in the volume of PC extract, keeping the amount of metal precursor constant and adapting self-propagating Solution Combustion Synthesis with nano-size not more than 23 nm. Various microscopic and analytical techniques like FT-IR, p-XRD, FESEM-EDS, UV-DRS and BET and BJH studies were adapted for the characterization of unique rice grain shaped CPC NPs. The advanced activity of the CPC NPs involved photocatalytic degradation against cationic and anionic textile dyes namely, Methylene Blue and Methyl orange respectively, with magnificent degradation more than 84%, and its reusability over 5 cycles owing to its stability. The anti-inflammatory results of CPC NPs proved to exhibit notable protective action of 67–92% for human red blood cells owing to its biocompatibility. Anticancer activity studies of CPC NPs against adenocarcinoma human alveolar basal epithelial cells have proven to show the cytotoxic effect with appreciable IC50 value.

Preparation of silicon boride SiBx (x = 3, 4, 5, 6) powders by chemical oven self-propagating combustion synthesis

Abstract A new method was developed for quickly preparing a highemissivity silicon boride compound of SiBx (x = 3, 4, 5, 6) by highly exothermic Ti-TiO2-Si-Al chemical oven preheating. The SiBx combustion synthesis process and adiabatic combustion temperature were investigated. A large exothermic reaction occurred at the combustion temperature of 1 700 K. X-ray diffraction results indicate that an SiBx phase and a substantial amount of unreacted Si were identified in the products. By increasing the boron content until the Si-B ratio reached to 1 : 6, the diffraction peaks primarily indicated SiB6, SiB4, and Si11B33 in the final product. According to the spectra and quantitative results, the atomic chemical composition ratio of Si and B was close to the nominal composition. Thus, this method offers an efficient way to produce Si-B compounds with less time and energy consumption than current methods.

Preparation of silicon boride SiBx (x = 3, 4, 5, 6) powders by chemical oven self-propagating combustion synthesis

Abstract A new method was developed for quickly preparing a highemissivity silicon boride compound of SiBx (x = 3, 4, 5, 6) by highly exothermic Ti-TiO2-Si-Al chemical oven preheating. The SiBx combustion synthesis process and adiabatic combustion temperature were investigated. A large exothermic reaction occurred at the combustion temperature of 1 700 K. X-ray diffraction results indicate that an SiBx phase and a substantial amount of unreacted Si were identified in the products. By increasing the boron content until the Si-B ratio reached to 1 : 6, the diffraction peaks primarily indicated SiB6, SiB4, and Si11B33 in the final product. According to the spectra and quantitative results, the atomic chemical composition ratio of Si and B was close to the nominal composition. Thus, this method offers an efficient way to produce Si-B compounds with less time and energy consumption than current methods.

Annealing effects on the structural and optical properties of undoped and Zr-doped Ba titanate prepared by self-propagating high-temperature synthesis

Undoped and Zr-doped BaTiO powders have been prepared by self-propagating combustion synthesis from suitable precursors. The obtained powders have been subjected to thermal annealing in air at temperatures between 400 and 1200 °C. Experimental findings indicate that annealing affects compositional, structural and optical properties. XRD analysis reveals the presence of a metastable hexagonal phase in powders obtained by SHS. Its relative amount drastically decreases during high-temperature annealing. As-synthesized powders have broad photoluminescence due to the degree of structural order in the powders. This can be also seen from the absorbance spectra, which exhibit a band at 650 nm. F color centers form as a consequence of electron trapping in oxygen vacancies.

Effect of annealing temperature in the emission properties of nanocrystalline CaZr0.9SmxDy0.1−xO3 systems prepared via self-propagating combustion synthesis

This study investigates the photoluminescent properties of Samarium and Dysprosium co-doped nanocrystalline CaZrO3 perovskites that were prepared through self-propagating combustion synthesis. The prepared nanopowders were characterized using X-ray diffraction, Fourier Transform Infrared spectroscopy, Transmission Electron Microscopy, UV-Visible spectroscopy and photoluminescence spectroscopy. The orthorhombic (Pnma) perovskite structure of the prepared samples were confirmed using X-ray diffraction studies and the particle size of the samples were calculated to be in the range of 20-30 nm using transmission electron microscopic studies. The nanocrystalline Sm3+/Dy3+ doped CaZrO3 samples were annealed at 600°C, 800°C, 1000°C, 1200°C, 1250°C and 1400°C for 2 hours and the effect of annealing temperatures on the emission properties were also studied. Sm3+/Dy3+ co-doped CaZrO3 systems yield two different emissions at two different excitations when annealed at high temperatures. Emissions corresponding to the transition between 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 levels in Dy3+ ions were observed at 484 nm and 575 nm respectively while peaks corresponding to that of Sm3+ ions were observed at 567 nm, 602 and 650 nm due to the 4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G→65/2H11/2 transitions of Sm3+ ions. Chromaticity diagrams of the emission spectra of nanopowders, based on their luminescence studies were also investigated.

Effect of Cr content on microstructure and mechanical properties of annealed large-dimensional bulk nanocrystalline Fe–Al–Cr alloys by self-propagating combustion synthesis

Large-dimensional bulk nanocrystalline Fe–Al–Cr alloys with different chromium contents (5, 10, 15 and 20 wt.%) were prepared by self-propagating combustion synthesis. After isothermal treatment at 1000 °C for 16 hours, the microstructure transformation and the deformation behavior of Fe–Al–Cr alloys were studied and discussed. After annealing, the nanocrystalline matrix of the alloys changed slightly, and the average grain size remained as approximately 20 nm. Owing to the changes in the distribution and shape of the second phase, the annealed nanocrystalline Fe–Al–Cr alloys with different chromium contents provided good plasticity and strength. The annealed Fe–Al–Cr alloy with 15 wt.% chromium achieved the best comprehensive mechanical properties.

Effect of Cr Content on Microstructure and Mechanical Properties of Annealed Large-dimensional Bulk Nanocrystalline Fe-Al-Cr Alloy by Self-propagating Combustion Synthesis

Effect of Cr Content on Microstructure and Mechanical Properties of Annealed Large-dimensional Bulk Nanocrystalline Fe-Al-Cr Alloy by Self-propagating Combustion Synthesis

Application of SHS process for fabrication of copper-titanium silicon carbide composite (Cu-Ti3SiC2)

The results of the study of possibility of using a simple, energy-saving powder technology, based on the process of self-propagating high-temperature synthesis (SHS) or combustion synthesis, for the single-stage preparation of Cu-Ti3SiC2 composite from relatively inexpensive powders of its constituent elements are presented. Placing the Cu powder briquette between two adjacent charge briquettes 3Ti + 1,25Si + 2C for the synthesis of MAX-phase of Ti3SiC2, it was possible to use a large heat effect of SHS for melting the Cu briquette and infiltration of Ti3SiC2 porous skeleton by Cu melt. For the successful realization of this process, it is necessary to ensure the required fluidity of Cu melt and wetting Ti3SiC2 through a high temperature of the melt and the alloying of the melt with silicon, as well as to ensure the delay in the transfer of the melt into pores of SHS product.

Application of SHS auxiliary reaction of titanium carbide for introduction of AlN nanoparticles into aluminum melt

For ex-situ introduction of AlN nanopowder, obtained by azide technology of self-propagating high-temperature synthesis (SHS) or combustion synthesis in the mixture with the flux cryolite: (AlN-35%Na3AlF6), into the aluminum melt, an exothermic master powder composite (EMPC) of different composition (AlN-35%Na3AlF6) – (Ti + C) – Na2TiF6 was first used, leading to the realization of in-situ process of SHS of reinforcing phase TiC in the combustion mode in the aluminum melt. The conditions were found for reliable ignition of the EMPC and fabrication of cast hybrid nanocomposites Al-Al-TiC, including the calculated composition Al-7.7%AlN-19%TiC with an increased content of AlN reinforcing phase.

Facile self-propagating combustion synthesis of MgO: Eu3+ orange-red nanophosphor and luminescence investigation by Judd-Ofelt intensity parameters

In the present work we demonstrate the potential of one pot combustion derived Eu3+ doped nano MgO as efficient orange-red luminescent host. Surface morphology and size of the particles are characterized by scanning and transmission electron microscopic techniques. Optimization of the luminescence output is carried out by varying the dopant (Eu3+) concentration of Mg1−xO:xEu3+ (0.01 < x < 0.09). Upon excitation at 395 nm the emission spectra of the phosphor show sharp peaks at 542, 577, 594, 653 and 690 nm corresponding to f-f transitions of rare earth dopant. The optimal Eu3+ content was found to be x = 0.05 at which Mg1-xO:xEu3+ show enhanced sharp orange red emission. Beyond x = 0.05, concentration quenching was observed and critical distance calculations revealed the mechanism of quenching to be electric multipole-multipole interactions. Judd-Ofelt intensity parameters were calculated in order to evaluate the influence of the host lattice on the emission behaviour of the Eu3+ dopant in MgO. The branching ratios Ω2 and Ω4 were calculated and with increasing Eu3+ concentration, Ω2 was found to increase. Further, Ω2 > Ω4 indicates that the covalency of EuO bonds increases and this suggests that host lattice crystal field has significant effect on Eu3+ emission. Thermoluminescence (TL) studies performed for γ-irradiated samples and TL glow curve suggest multiple types of traps in the host. TL intensity parameters were calculated and analysed in detail to understand the applicability of the phosphor for dosimetric use.

Structural and band gaps studies of novel Al2-xHfxO3 materials toward MOS applications

Developments of new materials for MOS applications are important due to the problems of downscaling of SiO2. In this work, Hf doped Al2O3 materials were studied as a possible new material for use in metal oxide semiconductor (MOS) application. Novel Al2-xHfxO3 (x = 0.001, 0.002 and 0.003) materials were prepared by a self-propagating combustion synthesis method. X-Ray diffraction (XRD) results showed that all samples were pure with hexagonal crystal structure. Quantitative analysis via Rietveld refinements showed that Hf was successfully substituted in the hexagonal Al2O3 crystal structure. The Hf content was confirmed via energy dispersive X-Ray spectroscopy (EDS). UV–visible spectroscopy showed that Al2-xHfxO3 materials exhibited band gap narrowing with respect to pure Al2O3 materials and it is dependent on the Hf content following an exponential function.