Self-propagating Combustion Method Research Articles

Facile one-pot synthesis of porous Ln2Ti2O7 (Ln = Nd, Gd, Er) with photocatalytic degradation performance for methyl orange

Porous nanocrystalline Ln2Ti2O7 (Ln=Nd, Gd, Er) was prepared by a facile self-propagating combustion method using metal nitrates (Ln(NO3)3 (Ln=Nd, Gd, Er), TiO(NO3)2) and glycine. The photocatalytic activity of Ln2Ti2O7 (Ln=Nd, Gd, Er) was evaluated by the photocatalytic degradation of methyl orange (MO). The results showed that the photocatalytic activity of Ln2Ti2O7 (Ln=Gd, Er) with cubic pyrochlore structure was higher than that of Nd2Ti2O7 with monoclinic perovskite structure and Gd2Ti2O7 showed the best photocatalytic activity. The different photocatalytic activities observed for Ln2Ti2O7 (Ln=Nd, Gd, Er) could be related to its different crystal structures and Ln 4f shells.

Simple Preparation of Well-Dispersed Nanosized α-Fe2O3

Well-dispersed α-Fe2O3 nanocrystalline was prepared by a convenient self-propagation combustion method using low-toxic glycine as fuel, low-cost Fe (NO3)2·9H2O as raw materials. The XRD results indicate that the glycine doses have an important effect on the control of the average size and the order of the crystalline phase. The UV-vis results indicate that the α-Fe2O3 nanocrystals prepared by this method have a broad absorption peak whose center is at about 221 nm. TEM images revealed that the products were composed of well-dispersed particles with an average size about 35 nm.

Effect of High-Energy Ball Milling on the Charge-Discharge Behaviour of LiCo<sub>0.3</sub>Ni<sub>0.7</sub>O<sub>2</sub>

Li-ion cathode materials in the nanodimension should show improvement in capacity retention from the normal material. This is because the electrochemical performance of the cathode material in lithium secondary batteries depends on the electrochemical redox reaction which is affected by the surface area to volume ratio of the particles. In this work, LiCo0.3Ni0.7O2 powder will be prepared via a self-propagating combustion method and the high-energy ball milling method will be used to prepare LiCo0.3Ni0.7O2 nanopowders. X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) are used to characterize the materials. The materials are observed to be phase pure. Li-ion cells are then fabricated and tested. The cells are subjected to a series of charge-discharge cycling in the voltage range of 3.0 to 4.3 V. It was found that the nanomaterial exhibit specific capacities less than that of the normal material.

Electrochemical Behavior of LiCo<sub>(1-x)</sub>Mn<sub>x</sub>O<sub>2</sub> Crystalline Powders

LiCoO2 is a well-known cathode material used in commercial Li-ion batteries but it has its own limitations in terms of cost and toxicity. Improvement of the material by partial substitution of Co with other transition metals is one of the alternative and effective ways to overcome the limitations and improve the electrochemical performance of cathode materials. The transition metal element used for the substitution has to be cheaper and non-toxic thus Mn is chosen here. LiCo(1-x)MnxO2 (x= 0.1, 0.2, 0.3) we synthesized by a novel route using a self-propagating combustion (SPC) method. The samples are analyzed using X-Ray Diffraction (XRD) for phase purity and Field Emission Scanning Electron Microscopy (FESEM) for morphology and particle size studies. The materials obtained are phase pure. In terms of electrochemical activity, though it does not show better first cycle discharge capacity, the Mn doped materials have improved capacity retention. Results showed that LiCo0.9Mn0.1O2 and LiCo0.8Mn0.2O2 exhibited less than 8 % capacity loss in the 20th cycle compared to 12 % for LiCoO2.

Effect of N<sub>2</sub> Pressure on the Phase Composition and Morphology of Ti<sub>2</sub>AlN Prepared by Self-Propagating Combustion Method

Ti2AlN ceramic have been prepared by self-propagating high-temperature synthesis method using Ti, Al and TiAl mixture as raw materials under different N2 pressures. X-ray diffraction (XRD) and scanning electron microscope (SEM) have been used to determine the phase composition and micro morphology of the products. XRD analysis indicates that the main phase of the products is layered ternary compound Ti2AlN, but there are TiN and AlTi3 impurities in the products. With increasing N2 pressure, the relative content of TiN increases, whereas the relative content of AlTi3 decreases. SEM imagines exhibits that layered grains of the products become larger and tighter with increasing N2 pressures.

Synthesis of LaFeO<sub>3</sub> Nano-Powders by Self-Propagating Combustion Method of Sol-Gel

Nanocrystalline LaFeO3 with particle size of about 50 nm was directly synthesized by sol–gel auto-combustion method at room temperature. The overall process involves three steps: formation of homogeneous sol; formation of dried gel; and combustion of the dried gel. Single phase nanocrystalline LaFeO3 powders were successfully synthesized by the sol–gel self-propagation combustion method using glycin (C2H5NO2) as the chelating agent. Discuss the synthesis products by DTA/TG, XRD and SEM. The experiment results show that the LaFeO3 nano-powder was got from dried gel of G/M=1:1 at 300°C ignition temperature and then holding 2h at 800°C.The LaFeO3 nano-powder is about 50nm with excellent dispersibility. The hysteretic loop show LaFeO3 nanopowders have the character of ferromagnetism, the coercivity of the nanocrystalline LaFeO3 is 99G, while the saturation is only 2.8 emug-1.

Influence of Nitrogen Pressure and TiN Addition on Combustion Synthesis of Ti2AlN Powders

It has a relatively rapid reaction with self-propagating combustion method to synthesize Ti-Al-N powder. This can effectively avoid uneven phenomenon of aluminum melting reunion during the reaction of raw materials. So you can use lower-cost aluminum as raw materials. In addition, the combustion synthesis method also has a simple process and low-cost advantage. Thus this method has the potential to become the optimum process method to prepare Ti2AlN and Ti4AlN3. In this paper, Ti, Al elemental powders and N2 were used as raw materials. The powder of Ti2AlN was successfully prepared for the first time by combustion synthesis method. This substance is a nitrogen compound of single-phase and three yuan. The results from the XRD diffraction analysis and SEM show that synthetic product is high purity Ti2AlN with a small sample to combustion synthesis when the pressure of nitrogen is in 5 MPa, but the content of synthesis products Ti2AlN is small when the sample is magnified, and the TiN and AlN has a higher content. It can burn synthetic Ti2AlN to control the nitrogen pressure and add the amount of TiN, and the pressure of N2 is better 2 MPa, and the amount of TiN added is better 30 wt.%.

Mn as a Substituted Cation in LiCoO<sub>2</sub> Cathode Materials

LiCoO2is the commercial cathode material for Li-ion battery application with many advantages such as ease of preparation and good electrochemical properties. However, it has some limitations especially Co being expensive and toxic. Therefore, the substitution of Co in the LiCoO2by non-toxic and inexpensive transition metal elements will be an improvement. Partial substitution of Co by Mn has been done in this work via the self-propagating combustion (SPC) method. The materials are then characterized. The materials obtained were phase pure but the electrochemical discharge capacity is about 24 – 27 % less than that of LiCoO2. However, the cycling behaviour of LiCo0.9Mn0.1O2and LiCo0.8Mn0.2O2over 15 cycles improved over that of LiCoO2.

Synthesis of CuGa2O4 nanoparticles by precursor and self-propagating combustion methods

Copper gallate spinels, CuGa2O4, have been synthesized by two wet chemical routes: precursor method and self-propagating combustion involving a glycine-nitrate system. All complex precursors have been characterized by chemical analysis, infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV–vis), electron paramagnetic resonance spectroscopy (EPR), thermal analysis and scanning electron microscopy (SEM). The copper gallate spinel oxides have been further investigated by X-ray diffraction (XRD), SEM, IR, UV–vis, magnetic measurements and EPR. The crystallite size of the copper gallate was found about 280Å.

Mn Substitution with Co in LiCo<sub>(1-X)</sub>Mn<sub>x</sub>O<sub>2</sub> Cathode Materials and their Charge-Discharge Characteristic

LiCoO2 has been used as a cathode material in commercial Li-ion batteries. This is due to advantageous properties of the LiCoO2 like ease of preparation and good electrochemical characteristics. However, the high cost and toxicity of Co has limited its use. Therefore, the substitution of Co in the LiCoO2 by non-toxic and inexpensive transition metallic element is needed. Mn is considered as one of the promising candidates to fulfill all the requirements. Partial substitution of Co by Mn has also been considered to enhance the stability of LiCoO2 lattice, minimize capacity fading and increase cycle life of the Li-ion battery. LiCo(1-x)MnxO2 (x= 0.1, 0.2, 0.3) were prepared by using a self-propagating combustion (SPC) method. X-ray diffraction (XRD) of the samples were carried out for phase analysis and showed that all the materials are pure. The samples were also analyzed using the Field Emission Scanning Electron Microscope (FESEM) to study its morphology and particle size. Finally cathodes were fabricated and assembled in an inert gas-filled fabrication box. Discharge profiles of the materials were carried out in the voltage range of 4.3 V – 3 V. The materials obtained were phase pure and improved the capacity fading of the materials compared to LiCoO2. All of the materials exhibited less than 10% capacity loss even though it does not improve the first cycle discharge capacity.

Low-temperature combustion synthesis of nanocrystalline HoFeO3 powders via a sol–gel method using glycin

Single phase nanocrystalline HoFeO3 powders were successfully synthesized by the sol–gel self-propagation combustion method using glycin (C2H5NO2) as the chelating reagent at a low combustion temperature. Four different mole ratios of glycin to metal nitrate (G/M) were used to prepare HoFeO3 powders in the experiment. The XRD patterns indicate monophasic HoFeO3 powders can be formed by further calcination, the SEM micrographs show that the nano-sized grains with distinguishable boundaries had been obtained. The M–H curves show HoFeO3 powders had the characteristic of antiferromagnetism at 50K, while the powders had the characteristic of paramagnetism as the ambient temperature reached 100K or 300K. The FC/ZFC magnetic measurement results demonstrate that there was a transition from antiferromagnetism to paramagnetism in HoFeO3 nanopowders as the temperature was increased.

The regeneration of waste foundry sand and residue stabilization using coal refuse

The processes for recycling waste foundry sand are divided between regeneration and beneficial reuse, and the potential for regeneration is higher than that of reuse. In this study, two processes for the recycling and residue stabilization of waste foundry sands were considered. One is the dry mechanical process for recycling, and the other is the stabilization process for powdered residue. The dry mechanical process of regeneration consists of crushing, grinding, separation, and classification. To stabilize the residues that were generated through the regeneration process, powdered residues were pelletized by a high-shear pelletizer, and the surfaces of the pellets were subsequently coated with coal refuse powders that contained sodium silicate as a binder. Coated pellets were sintered by a self-propagating combustion method. The refractory index of the recycled sands, as measured by the Seger cone method, was over −34, and their SiO 2 contents of 94% was similar to that of green sand. The general conclusion that coal refuse and sodium silicate stabilize heavy metals better than other processes may lead to the development of a cost-effective solution for stabilizing heavy metals in residues.

Barium ferrite nanoparticles prepared by self-propagating low-temperature combustion method and its characterization

The barium ferrite particles were prepared using a self-propagating low-temperature combustion method using polyethylene glycol (PEG) as a fuel. The process was investigated with simultaneous thermo-gravimetric-differential thermal analysis (TG-DTA). The crystalline structure, morphology and the magnetic properties of the barium ferrite particles were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and SQUID susceptometer. The results show that the ignition temperature of PEG is lower compared with other combustion methods and gives nanocrystalline barium ferrite.

Synthesis and characterization of zinc ferrite nanoparticles obtained by self-propagating low-temperature combustion method

The self-propagating low-temperature combustion method was used to produce nanocrystalline particles of zinc ferrite. The products were characterized for chemical and phase composition, morphology and magnetic properties. The results obtained showed the formation of single-phase zinc ferrite nanoparticles with an average particle size of about 40 nm. As-synthesized powder displayed good magnetic property. Due to the simplicity and low cost of this process, it could also become a valuable starting point for the generation of other mixed and complex ferrites.

Synthesis of Air Stable Iron Nanopowders with Various Methods

Magnetic properties and microstructures of iron-based nanopowders fabricated by several methods, such as sol-gel, thermal decomposition, and self-propagating combustion methods, were investigated. During a subsequent reduction annealing, added aluminum atoms formed coherent oxide shells with a hercynite structure around iron cores in all the nanopowders. In particular, the nanopowders synthesized by the self-propagating combustion method showed the highest saturation magnetization of 175.68 emu/g and oxidation stability to 200 degrees C in air.

Synthesis of ferromagnetic nanoparticles with a core/shell structure by a self-propagating combustion method

Ferromagnetic nanoparticles with a core/shell structure were fabricated by a self-propagating combustion method and subsequent hydrogen reduction process. Before the reduction process, synthesized particles were Fe oxide phases. Transmission electron micrographs confirmed that the nanoparticles were composed of α-Fe core and Fe–Al oxide shell after the reduction process. The saturation magnetization of the nanoparticles was measured about 180 emu/g and the permeability kept constant value of about 1.8 up to 10 GHz without any noticeable loss. These microstructural and magnetic analyses showed that the oxide phase changed into α-Fe and then Al atoms diffused out to the surface of the particles during the reduction process.

Synthesis of Titanium Disilicide by the “Chemical Oven” Self-Propagating Combustion Method

TiSi2 (Titanium disilicide) has attracted great research interest due to its large silicon content, remarkably low electrical resistivity (about13–16μΩcm), good photocatalytic property, high temperature stability, and good corrosion resistance. It is an excellent electronic material and potential photocatalyst and high temperature structure material. In this work, TiSi2 was prepared by using the “chemical oven” enhanced self-propagating combustion method from the elemental powder compact. The mixture of Si and Ti (atomic ratio 3:5) were ignited as chemical oven. The composition of product was detected by XRD. Result shows the product is a single phase titanium disilicide with trace impurities. The maximum combustion temperature of Ti+2Si compact was up to 1472°C, which exceeds the lowest eutectic point (1330°C) of the Ti-Si binary mixture. Thus it can be predicted the formation of TiSi2 is primarily dominated by the solid-liquid mechanism, which includes dissolving solid reactants and precipitating silicide product. It could also be convinced by SEM photos of the combustion product and reacting zone of the compact.

Chemical synthesis and studies on structural and magnetic properties of fine grained nickel cadmium ferrites

The cadmium substituted nickel ferrites Ni 1− x Cd x Fe 2O 4 ( x=0.2, 0.4, 0.6) has been prepared by the self-propagating auto combustion method. Phase identification of the samples was studied by XRD patterns which are characteristics of cubic spinel structure ferrites. As the content of cadmium in the ferrites increases the lattice parameter. The tetrahedral and octahedral vibrations in the samples were studied by Fourier Transform Infrared (FT-IR) spectra. The SEM study reveals the fine-grained nature of ferrites with little agglomeration. The decrease in the drift mobility is found with increase in cadmium content. DC resistivity indicates the semiconducting nature of the samples. The Super Quantum Interference Device measurements were taken to study the magnetic properties of the samples.

Synthesis and luminescence properties of Ce 3+ doped nanoporous 12CaO·7Al 2O 3 powders and ceramics

Ce 3+ doped nanoporous 12CaO·7Al 2O 3 (C12A7) was synthesized using the self-propagating combustion method and solid state reaction. Ceramics of high density were produced using the melt-solidification process in a carbon crucible. The obtained samples were characterized using XRD and SEM methods and studied by means of low temperature time resolved luminescence under laser and synchrotron radiation excitation. It was shown that the Ce 3+ ion in C12A7 emits broad-band 5d–4f luminescence peaked at ∼3.0 eV. The decay curves of Ce 3+ emission in the studied samples have complicated nature depending on the excitation energy with the main decay component of 20–30 ns life time, typical for parity and spin allowed transitions of Ce 3+. The emission of Ce 3+ ions is efficiently excited through the intra-centre as well as in the intrinsic absorption region of C12A7.

Synthesis and Magnetic Properties of BaFe$_{12- {\rm x}}$Al$_{\rm x}$O$_{19}$ Nanopowders

The effect of Al contents on the magnetic properties of Ba hexaferrite powders has been investigated in order to increase the coercivity. In this study, a self-propagating combustion method has been developed to form Ba hexaferrite nanopowders. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed that nanopowders with a size of 40-60 nm were successfully produced. With increasing Al contents, the coercivity of the nanopowders increased until the powders had a magnetoplumbite structure. We obtained a coercivity of 7559 Oe in BaFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> powders calcined at 850deg for 1 h.