Self-propagating Combustion Reaction Research Articles

Synthesis, Characterization and Studies of Nanosized BaSnO3 and Its Poly (vinylalcohol) Nanocomposite Film

Synthesis of nanosized materials integrates the materials synthetic technology. Nanosized bimetallic oxides constitute class materials in concerned with its applications. The present work reports the synthesis of barium stannate (BaSnO3)nanopowder by self-propagating combustion reaction using polyvinyl alcohol (PVA) as a fuel. Initially basic oxides barium oxide (BaO) and tin oxide (SnO2) are also prepared by combustion route. Further barium stannate-PVA nanocomposite (BaSnO3-PVA) is prepared by dispersion of BaSnO3 material into PVA matrix using solvent casting method. Structural characterization of oxide and nanocomposite was studied by X-ray diffraction (XRD) tool and bonding nature by Fourier transfer infrared study (FT-IR) respectively. Thermal behavior of both the sample is well studied by thermo gravimetric analysis (TGA). Electrochemical study of the sample is carried out by cyclic voltammetry (CV) instrumentation. Varied morphology and particle size of the sample was analysed through Transmission electron microscope (TEM) tool.

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].

Microwave Sol-gel Synthesis of Co, Ni, Cu, Mn Ferrites and the Investigation of Their Activity in the Oxidation Reaction of Carbon Monoxide

Background: The study effect of microwave radiation on the catalytic properties of transition metal ferrites synthesized by ceramic and sol-gel methods in the oxidation reaction of carbon monoxide into dioxide. Objective: This work aims to study the effect of microwave radiation on the production of cobalt, copper, nickel, and manganese ferrites by sol-gel combustion technology using various organic reagents and to study their catalytic activity in the oxidative conversion of carbon monoxide into dioxide. Methods: Microwave treatment was carried out on a setup based on an EM-G5593V microwave oven (Panasonic) with a magnetron power varying from 300 to 800 W with an operating frequency of 2450 MHz. X-ray phase analysis of the products was carried out on a Bruker D 2Phazer automatic diffractometer. The measurement of the specific surface area of the samples was determined by low-temperature nitrogen adsorption by the multipoint BET method on a SORBI-MS instrument (ZAO META, Russia). IR spectra were recorded using FT-IR LUMOS Bruker spectrometers. The micrographs of samples were analyzed on the Sigma VP (Carl Zeiss Jena) equipment. Results: It was determined that the most active catalysts for the oxidation of carbon monoxide to dioxide are ferrites obtained by the sol-gel combustion method using microwave radiation to "ignite" the gel. Conclusion: The use of microwave radiation in the preparation of ferrites by the sol-gel method with combustion can initiate a self-propagating exothermic combustion reaction in the entire volume of the sample in a very short time, measured in seconds. The catalytic activity in the oxidative conversion of carbon monoxide obtained by this method of ferrites is comparable to the activity of ferrites obtained by the sol-gel method with traditional combustion.

Self-propagating synthesis of Zn-loaded biochar for tetracycline elimination

Herein, a novel Zn-loaded biochar (Zn-LBC) originating from Fraxinus pennsylvanica Marsh leaves was successfully prepared through a simple and rapid self-propagating combustion reaction (SHS) and could serve as an efficient adsorbent for tetracycline (TC) elimination from water. The adsorption performance was analyzed via a series of characterizations and batch adsorption experiments. The results showed that the novel adsorbent Zn-LBC exhibited an excellent TC adsorption capacity (159.64 mg/g), which was 2.63 times higher than that of the original biochar (60.78 mg/g). The pseudo-second-order kinetic model and Freundlich isothermal model fit the adsorption data well. It is noteworthy that Zn-LBC had little effect on the adsorption capacity of TC in the 0–10 mg/L various coexisting ion range and presence of humic acid (HA). In addition, the adsorption test of TC using hospital wastewater as the water sample also achieved satisfactory results (raw influent: 52.65 mg/g, final effluent: 85.64 mg/g). FT-IR and XPS investigations showed that the TC adsorption mechanism included surface complexation, π-π interactions, and hydrogen bonds. The results provide new ideas for exploring low-cost and highly efficient modified biochar adsorbent for TC elimination.

The effect of adding graphene nanoparticles to the thermal performance of LiCo0.525Ni0.475O2 cathode materials in Li-ion batteries

In this work, the effect of adding graphene to the performance of layered LiCo0.525Ni0.475O2 (LCNO) cathode materials was investigated. Cathode materials LiCo0.525Ni0.475O2 (LCNO) were prepared using a self-propagating combustion reaction. Graphene (G) was added to the prepared compound (LCNO) in different weight percentages to obtain LCNO/G (LCNOG) to improve cathode performance. The powder was divided into four parts weighing 10 g each, and the parts were mixed with percentages weighing 0, 0.5, 2, 4 and 6% of graphene with 200 ml of ethanol; they were then stirred several times at room temperature to dry completely The effect of graphene weight percentages on LCNOG mass loss was studied using thermo-gravimetric analysis (TGA). It was concluded that all of the added percentages of graphene behaved the same in all temperatures, except for 6% added graphene, where it demonstrated inverse behaviour at a high temperature. To determine the optimum annealing temperature range, TGA was identified at 650, 750 and 850 °C for 12 hours in the air. The X-ray diffraction (XRD) patterns of the LCNO and LCNOG showed the crystallisation of all powders in the space group R-3m and hexagonal axes for the crystal system. Energy dispersive spectrometry (EDS), field emission scanning electron microscopy (FE-SEM), a vibrating sample magnetometer (VSM) and atomic force microscopy (AFM) were also used. The LCNOG surface morphology consisted of regular coverage of nano-crystalline grains and random orientation.

Synthesis, characterization and studies of BaFe2O4/PMMA nanocomposite

Synthetic nanotechnology has attracted a great deal of attention from researchers for the synthesis of assorted materials at nanoscale dimension. Researchers are more attracted to microwave-assisted route for the synthesis of ferrite nanomaterials due to its simplicity. Barium ferrite (BF) nanomaterials are prepared by two strategies: the barium oxalate and the iron oxalate strategy. Thermal decomposition of barium oxalate precursor and ferrous oxalate precursor has been done using polyvinyl alcohol (PVA) as a fuel. Self-propagating combustion reaction of metal oxalates takes place with fuel, which controls the size of the particle. Solvent casting method is used for the preparation of barium ferrite-dispersed poly(methyl methacrylate) (BF–PMMA) nanocomposite. The structure of the as-prepared samples was carried out by X-ray diffraction (XRD) study and particle morphology of the sample done by scanning electron micrograph (SEM) technique. The presence of barium and iron metals in the sample is confirmed by EDX analysis. Bonding nature of the ferrite is studied by Fourier transform (FT-IR) tool. Thermal and electrical studies of the samples are also undertaken to know the thermal electrical behaviour. UV absorbance study of the said composite is also undertaken.

Improvement of Li-ion batteries energy storage by graphene additive

In this work, the layered compound of LiCo0.525Ni0.475O2, (LCNO) was prepared by self-propagating combustion reaction for the cathode of lithium-ion battery. We used self-propagating combustion reaction to prepare the compound of LiCo0.525Ni0.475O2, (LCNO) as a cathode material of lithium-ion battery, then we added Graphene (G) to LCNO as additive to obtain LCNO/G (LCNOG). Graphene weight is (4 %) of the total weight of LCNO, in a typical preparation, 10 g of LCNO, 0.4 g from G and 200 ml of ethanol were stirred together at room temperature to reach full dryness. We used thermo-gravimetric analysis (TGA) to determine the optimum range of annealing temperatures of LCNO and LCNOG. The value found were (650, 750 and 850) ∘C for 12 h in air. Changes in the structural and morphological properties were also studied.The structural properties of LCNO and LCNOG powder were studied by means of X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectrometry (EDS), Atomic Force Microscopy (AFM) and a Vibrating Sample Magnetometer (VSM). XRD analysis shows that all the powders are crystallized in the Space group R-3m, crystal system is trigonal (hexagonal axes) and present a random orientation and surface morphology of the LCNOG powder consists of Nano-crystalline grains with uniform coverage of the substrate surface with randomly oriented. XRD analysis showed that all the powders are crystallized in the Space group R-3m, crystal system is trigonal (hexagonal axes) and present a random orientation. Surface morphology of the LCNOG powder consists of Nano-crystalline grains with uniform coverage of the substrate surface with random orientation. Hysteresis behavior analysis proved that the powder possessed soft magnetic properties. Thermo-gravimetric analysis showed that the best annealing temperature and duration that leads to particles in the range several nm of the targeted composition are 750 °C for 12 h.

Influences of Ignition Temperature, Urea-to-Metal Nitrates Molar Ratio, and Further Calcination on Synthesis of C4AF via the SPCR Method

The self-propagating combustion reaction (SPCR) method was employed to synthesize C4AF using metal nitrates as cation precursors and urea as fuel. Thermal decomposition behavior of dried gels, phase identification and crystallinity of synthesized C4AF, and impact of urea to metal nitrates (UR/MN) molar ratio on synthesis effect were investigated with the aid of differential thermogravimetric analysis, X-ray diffraction and Fourier transform inferred spectrometry. It is found that pure C4AF can be prepared by the SPCR method in 2 h at 500 °C. The UR/MN molar ratio plays a significant role in the thermal decomposition behavior of dried gel, purity, crystallinity and crystallite size of synthesized C4AF. Ignition temperature should be not lower than 500 °C but higher temperatures were unnecessary. No trace of free lime in synthesized C4AF is detected and calcium carbonate is the transition phase. Further calcining the synthesized C4AF at high temperatures is beneficial for increasing crystallinity, purity and crystallite size. Reaction activation energy of the further calcination process is 119.6 kJ/mol. It is more efficient to improve the synthesis effect by increasing UR/MN molar ratio than further calcination at high temperatures.

Synthesis Mechanism and Material Characterization of C4AF Obtained by the Self-propagating Combustion Reaction Method

To investigate the influence of preparation process on the properties of synthesized C4AF, the powder was prepared via the self-propagating combustion reaction (SPCR) method using urea as fuel and metal nitrates as cation precursors. Synthesis mechanism of the SPCR method, calculation and adjusting principles of urea dosage were detailedly introduced. Material characterization of synthesized C4AF was performed with the aid of X-ray diffractometry, Fourier transform infrared spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, 27Al nuclear magnetic resonance and isothermal microcalorimetric technique. Remaining content of transition phase of calcium carbonate in synthesized C4AF was determined by quantitative analysis of X-ray diffractometry. It was found that there was no difference in the hydration behavior of C4AF synthesized by the SPCR method and the traditional solid-state reaction (SSR) method. C3AH6 and amorphous iron (III) hydroxide (Fe(OH)3) would be formed during the hydration of C4AF while CH not. Crystallite size of synthesized C4AF was 16.1 A and the apparent activation energy was 36.2 kJ/mol. Coordinated condition of Al in C4AF can be detected by 27Al NMR technique, but the peaks were broadened and the intensities were relatively low, supporting the use of 27Al NMR for the quantitative analysis of C3A in Portland cements.

Preparation and characterization of LiCo0.5Ni0.45Ag0.05O2 cathode material for lithium\u2013ion battery

In this work, the layered compound of LiCo0.5Ni0.45Ag0.05O2, (LCNAO) was prepared by self-propagating combustion reaction for the cathode of lithium–ion battery. The as-synthesized material was subjected to thermo-gravimetric (TGA) analysis to determine the optimum range of annealing temperatures. Accordingly were annealed at 800, 900 and 1000 °C for 8 h in air and changes in the structural and morphological properties were studied. The structural properties of LCNAO powder were studied by means of X-ray diffraction (XRD), Field emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive Spectrometry (EDS), Atomic Force Microscopy (AFM) and a vibrating samples magnetometer (VSM). XRD analysis shows that all the powders are crystallized in the Phase structure R-3m and present a random orientation and surface morphology of the LCNAO powder consists of Nano-crystalline grains with uniform coverage of the substrate surface with randomly oriented. Hysteresis behavior analysis that the possessed soft magnetic properties. Thermo-gravimetric analysis show that the best annealing temperature and duration that leads to particles in the range 86–103 nm of the targeted composition are 900 °C for 8 h.

Tridimensional Interconnected Nickel-Iron Alloy Structures As Cathode Materials for Sodium–Metal Halide Batteries

Extensive global efforts are underway to employ renewable energy as a future primary electric energy source.1 The renewable energy sources are intermittent, therefore low-cost and reliable energy storage system is necessary.1,2 In this scenario, the use of anode materials as sodium has become relevant due to it is high abundance, low cost, high capacity and adequate redox potential to increase the energy density of batteries.3 Among all types of sodium batteries, sodium-metal halide batteries that utilizes transition metals (such as, nickel and iron) as active materials has commercially received considerable attention, because it offers higher specific energy, is chemically safe, has longer cycle-life and is recyclable3. An active challenge in sodium-metal halide technology cathodes is to minimize the quantities of the metals used without decreasing the good electrical conductive of the cathode material in the charging and discharging process.4 To overcome the issues of the cathode material, i.e., optimized metal content as well as good electrical contact, the synthesis of higher surface area materials with an interconnected structure may be a promising option. By this away, one of the most utilized methods for synthetizing tridimensional products is through combustion reaction.5 , 6 From an industrial point of view, this approach has several advantages, such as lower energy consumable, simple and easily scalable, formation of pure products and high yield.6 Herein a synthesis method of obtaining tridimensional interconnected metallic porous structures composed by NixFey alloys was developed, aiming higher electrical conductivity with lower amount of metal in the cathode. Briefly, the overall synthesis method involves (i) the pre-formation of a tridimensional (3D) material, followed by a (ii) self-propagating combustion reaction and then a (iii) thermal treatment to generate the porous metallic structures. The combustion reaction step was based on a method previously reported5. In the step (i), metallic nitrates (Ni(NO3)2 and Fe(NO3)3) and triblock copolymer (Pluronic® F-127) were milled, mixed and then heated up to 80 °C to generate a 3D macromolecule. After holding at 80 °C for 18 hours, in the step (ii), the sample was heated to 300 °C and maintained for 1h, allowing the bimetallic structure formation. Finally, in the step (iii), the synthetized samples were reduced under hydrogen atmosphere (4% in N2) at different temperatures (300, 400, 500 and 600 °C) for 1 hour. XRD patterns showed that the synthesis method employed is effective in the formation of monometallic and bimetallic samples. Morphological analysis indicates that the materials are formed by a porous matrix structure at macro and micro range, with interconnected tridimensional network. The Ni-richer alloys (Ni3Fe), as well as monometallic nickel, revealed the formation of foam morphology, while Fe-richer alloys (NiFe3), and also monometallic iron, have agglomerate-collapsed structures. The presented results showed that the developed method is versatile and effective for synthesizing both monometallic and bimetallic (Ni-richer alloys) cathode materials. REFERENCES Larcher, D. & Tarascon, J.-M. Towards greener and more sustainable batteries for electrical energy storage. Nat. Chem. 7, 19–29 (2014).Chiang, Y. Electrochemical Energy Storage for the Grid. World (2010).Ellis, B. L. & Nazar, L. F. Sodium and sodium-ion energy storage batteries. Curr. Opin. Solid State Mater. Sci. 16, 168–177 (2012).Li, G., Lu, X., Kim, J. Y., Lemmon, J. P. & Sprenkle, V. L. Cell degradation of a Na–NiCl2 (ZEBRA) battery. J. Mater. Chem. A 1, 14935 (2013).Liang, J., Wang, Y.-Z., Wang, C.-C. & Lu, S.-Y. In situ formation of NiO on Ni foam prepared with a novel leaven dough method as an outstanding electrocatalyst for oxygen evolution reactions. J. Mater. Chem. A 4, 9797–9806 (2016).Liu, G., Li, J. & Chen, K. Combustion synthesis. (Wiley Online Library, 2015).

Mechanical activation on aluminothermic reduction and magnetic properties of NiO powders

We report the mechanically activated aluminothermic reduction of NiO [NiO–Al(x wt.%) with x = 0, 20, 40] into NiO–Ni–Al2O3 nanocomposites using high-energy planetary ball milling under dry milling and the resulting structural and magnetic properties. Structural studies reveal that both NiO and NiO–Al powders exhibit a face centered cubic structure with large crystal size reduction. However, the NiO–Al milled powders unveil the process of aluminothermic reaction kinetics, which changes from gradual reaction as a function of milling time for x = 20 powders to self-propagating combustion reaction for x = 40. This allows us to achieve a maximum NiO reduction of 40% and 90% for x = 20 and 40, respectively. The process of NiO reduction by Al is further confirmed through thermal studies. Pure NiO shows an antiferromagnetic (AFM) nature, which transforms into a ferromagnetic (FM) one with the moderate magnetization of about 1 emu g−1 with decreasing crystal size. The formation of FM Ni from AFM NiO matrix in milled NiO–Al powders could be precisely monitored by the change in the magnetization, which increases up to 4 emu g−1 and 28 emu g−1 for the gradual and combustion reactions, respectively. This results in a considerable exchange bias and its magnitude strongly depends on the relative fractions of NiO and Ni phases. Thermomagnetization data confirm the presence of mixed magnetic phases and the component of induced FM phase fades out due to the formation of Ni from the reduction of NiO. The changes in the structural and magnetic properties of milled NiO–Al powders are discussed on the basis of milling time-dependent mechanically activated reduction reaction of NiO into NiO–Ni–Al2O3 nanocomposites. The process of mechanical activation on the aluminothermic reduction allows for a controlled reduction of NiO; thus, it is suitable for the applications in catalysis and the ore reduction process.

Combustion synthesis of a blue Co-doped zinc aluminate near-infrared reflective pigment

A near-infrared reflective blue pigment with a low cobalt content, Zn0.9Co0.1Al2O4, was prepared by solution combustion synthesis, which proved to be time-effective and energy-efficient. No additional annealing was required as the elevated temperature developed during the exothermic self-propagating combustion reaction (1428 °C) enabled the direct formation of a Zn0.9Co0.1Al2O4 solid solution having an appealing blue color: L* = 67.9, a* = −3.7, b* = −39.0. The resulting blue pigment had an average particle size of 6.1 μm and a BET surface area of 6.5 m2/g. The total solar reflectance of the pigment (63%) recommends the use of Zn0.9Co0.1Al2O4 as a near-infrared reflective blue pigment for cool coatings. The ability of the pigment to reflect the near-infrared radiation was confirmed by measuring the surface temperature of an aluminum sheet painted with an acrylic coating containing 30 % wt. pigment, that had a total solar reflectance of 59%. The excellent properties of Zn0.9Co0.1Al2O4, color and solar reflectance, together with the low cobalt content and the advantages of self-propagating combustion reaction recommend the use of combustion synthesis for the preparation of blue Zn0.9Co0.1Al2O4 near-infrared reflective pigments.

Low-temperature synthesis of C4AF by self-propagating combustion reaction

Low-temperature synthesis of tetracalcium aluminoferrite (C4AF) by the self-propagating combustion reaction (SPCR) method using urea as fuel and metal nitrates as cation precursors is studied, and the mechanism of the combustion reaction is also introduced. Decomposition behaviour of metal nitrates and urea is analysed by differential thermogravimetric analysis, and characterisation of synthesised C4AF is performed by X-ray diffractometry and Fourier transform infrared spectroscopy. It is found that C4AF with good crystallinity and high purity could be synthesised in a straightforward way by the SPCR method in 2 h at 500°C. The free lime content of synthesised C4AF is below the detection limit. Further calcination of synthesised C4AF at higher temperatures is only beneficial for improving the crystallinity. It has no effect on chemical structure, and the corresponding hydration behaviour.

Synthesis, structural and magnetic behavior of undoped andMn-doped anataseTiO2nanoparticles

Ti1-xMnxO2(x = 0, 0.05) nanoparticles have been synthesized using chemically derived self-propagating combustion reaction method. X-ray diffraction studies demonstrate the formation of anatase phase of TiO2belonging to 141/amd space group in both samples without the formation of any impurity phase. The incorporation of 5 at.% Mn content does not produce any changes in crystal structure which reveals the exact substitution of Mn atoms at Ti sites. Some change in lattice parameters and crystallite size is observed in Mn -doped composition, attributed to the difference in ionic radii. The size of grains obtained using scanning electron micrographs shows the consistent trend with the crystallite size evaluated from X-ray diffraction analysis. Energy dispersive X-ray analysis confirms the incorporation of Mn content in TiO2structure. Ferromagnetic behavior detected only in Mn -doped TiO2composition correspond to the strong Mn d-shell contribution.

The mechanical alloying mechanism of various Fe2O3–Al–Fe systems

The mixed powders of in situ Al2O3 particles and Fe (Al) solid solution were prepared via self-propagating combustion reaction initiated by mechanical alloying (MA), and the MA mechanism of several Fe2O3–Al–Fe systems with different Al2O3 mass fractions were studied. The adiabatic temperature (Tad) of each system was calculated to estimate whether the self-propagating combustion reaction could be initiated in theory. The microstructure of the mixed powders was investigated by SEM, EDS and TEM. The phase analysis was evaluated by XRD, and the Fe lattice parameter was calculated from the XRD patterns. The results showed that with the addition of Fe during the MA process, the activation period was prolonged and the sharp increase of temperature occurred, and when the Al2O3 mass fraction was decreased to 10.94%, the self-propagating combustion reaction could not occur in theory and practice. When there was no added Fe, the final product was homogeneous Fe (Al) solid solution.

Effect of Precursor's Composition and Thickness on Foaming Behavior of Al-Tiintermetallics in Volume Combustion and Self-propagating High-temperature Synthesis Modes

Sheet type precursors made of aluminum, titanium, and boron carbide (B4C) powders were prepared by rolling, and porous Al-Ti intermetallics were fabricated by a combustion reaction in volume combustion synthesis (VCS) and self-propagating high-temperature synthesis (SHS) modes. The effects of precursor's composition and thickness on the foaming behavior were investigated.The microstructure of the precursor was not affected by rolling. In the VCS mode, the thin precursor (1 mm) with a high Al/Ti blending ratio (Al/Ti = 7.0) did not expand sufficiently. The microstructure of the specimen after the reaction revealed that the reaction between titanium and aluminum was not completed in this specimen. This means that the maximum temperature during the reaction decreased by decreasing the thickness and increasing the Al/Ti blending ratio. The self-propagating high-temperature synthesis mode combustion reaction propagated through the whole specimen when the Al/Ti ratio was 4.0 and the thickness of the precursor was 4 mm or more. However, by reducing the thickness of the precursors to 2 mm or less, the reaction front did not propagate through the whole specimen. The self-propagation also became difficult by increasing the Al/Ti ratio to 7.0. Theseresults imply that the SHS mode reaction was more susceptible to precursor's composition and thickness than the VCS mode reaction. Fine pores with diameters below 1 mm are dispersed in the specimen by the SHS mode reaction.

Combustion synthesis of tungsten powder from sodium tungstate

Abstract Tungsten powders were prepared by Self-propagating High-temperature Synthesis (SHS) method directly from hitherto unreported system: sodium tungstate (Na 2 WO 4 ) and magnesium (Mg). The adiabatic temperatures of self-propagating combustion reactions with different amount of Mg in Na 2 WO 4 + Mg system were calculated. The influences of different starting conditions (molar ratios of Mg/Na 2 WO 4 and relative densities of samples) on the compositions and microstructure of reaction products were investigated. It shown that, the complete reduction of WO 3 required a 60% excess of magnesium over the stoichiometric molar ratio Mg/Na 2 WO 4 of 3. The amount of the impurities is minimal at appropriate relative density. At last, tungsten powders can be obtained after the acid enrichment and distilled water washing.

Interfacial products in SiC fiber reinforced Ti-Al based intermetallic alloys

Continuous SiC fiber reinforced Ti-Al based intermetallic alloys were prepared by sintering pure Ti and Al foils as well as SiC fibers. Owing to a complex self-propagating combustion reaction and diffusion reactions occurring during sintering process, the emphasis of the present paper is on identifying the interfacial products between SiC fibers and matrix, which is crucial for the mechanical properties of the sintered materials. Microstructure observation reveals that the sintered alloys contain lamellar matrix and SiC fibers with various interfacial products. The lamellar matrix compose chicly of TiAl3, TiAl2, TiAl, Ti3Al and α-Ti phases, the SiC fibers locate in TiAl3/TiAl layer and/or Ti3Al/α-Ti layer. The Al content is very little in the interfacial reaction zone. The main interfacial products are considered to mainly be compounds of Ti5Si3Cx, Ti3AlC, and Al4C3Six, etc. The interfacial reaction layer in the Ti-rich phase (Ti3Al and α-Ti) is thicker than in the Al-rich phase layer (TiAl3, TiAl2 and TiAl).

ChemInform Abstract: The Use of Self-Propagating Combustion Reactions for the Preparation and Consolidation of Metallic and Ceramic Powders

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