Combustion Synthesis Precursors Research Articles

Transparent AlON ceramics by nitriding combustion synthesis precursors and pressureless sintering method

Fine AION powders (D50 = 607 nm) with high sintering activities were synthesized by a high-efficiency solution combustion-based method, and a high-transmittance AlON ceramics can be achieved by a subsequent sintering process. Moreover, the influences of various aluminum resources (Al(NO3)3, AlCl3 and Al2(SO4)3) on the morphology of precursors and nitride-functionalized products have been studied in detail. Using Al(NO3)3 as aluminum source resulted in more active precursors and was beneficial for the preparation of ultrafine AlON powders. Then, single-phase AlON powders were obtained by calcining precursors at 1700 °C for 10 min, while residual Al2O3 was observed in the calcined products synthesized by other two aluminum sources. As a result, transparent AlON ceramics with high in-line transmittance of 85.9% at 2 μm were obtained. This research provides valuable reference for rapid preparation of AlON powders and transparent ceramics.

Rapid synthesis of AlON powders by nitriding combustion synthesis precursor

Polycrystalline aluminum oxynitride (AlON) powders have been prepared by the carbothermal reduction nitridation of amorphous precursor obtained by solution combustion synthesis (SCS). Firstly, a mixed precursor of amorphous transition alumina and incompletely combusted organic matter has been combustion synthesized of a mixed solution of aluminum nitrate, urea and glucose. Then the pure phase AlON powders with D50 = 0.846 μm can be prepared by calcining the SCS precursor at 1700 °C for only 10 min. The influences of different urea/aluminum nitrate nonahydrate ratio, calcining temperature and holding time on the properties of products have been discussed in detail. The research can provide a valuable reference for the efficient synthesis of AlON powders.

Marked Cofuel Tuning of Combustion Synthesis Pathways for Metal Oxide Semiconductor Films

AbstractThin‐film combustion synthesis (CS), driven by the exothermic reaction of liquid fuel+oxidizer+metal precursors is an important methodology for growing smooth, transparent, amorphous, and polycrystalline metal oxide (MO) films at low temperatures. In optimized MO CS precursors, the fuel combines a primary coordinating ligand [e.g., acetylacetone (AcAcH)] with an additional cofuel. Several studies suggest a structure–property relationship between the resulting MO film composition/microstructure and macroscopic charge transport characteristics. However, the structural and compositional details of solution‐phase precursors remain poorly defined. Here a diverse series of cofuels (urea, glycine, sorbitol, L‐ascorbic acid) are selected and mechanistic details of the fuel‐assisted CS process are provided, focusing on technologically relevant indium gallium zinc oxide (IGZO). Thermal analysis, proton nuclear magnetic resonance, mass spectrometry, and X‐ray diffraction are used to probe how the cofuel affects AcAcH‐metal ion binding and how it influences the MO precursor response. The charge transport characteristics of cofuel‐derived IGZO films stimulate additional cofuel studies and the results support the primary cofuel role of enhancing CS heat generation, hence IGZO film microstructure densification and carrier mobility. These results provide new insight into precursor design and its relationship to thin‐film CS processes, yielding guidance for more efficient, environmentally benign (co)fuels for high‐performance solution‐processed MO electronics.

Synthesized Fe-doping Li3V2(PO4)3/C cathode material from combustion synthesis precursors with enhanced electrochemical performance

Fe-doping Li3V2(PO4)3/C material was successfully synthesized from combustion synthesis precursors. The Li3V2(PO4)3 is layered by amorphous carbon with a porous structure and doped with Fe, which can improve the Li+ transfer rate and conductivity. The 1% Fe-doped products used as cathode electrode for lithium-ion batteries exhibit enhanced electrochemical performance. In 3.0~4.8 V, it has a specific discharge capacity of 180 mAh g−1 after 20 cycles at 0.1 C, 142.5 mAh g−1 after 500 cycles at 1 C, and 132.5 mAh g−1 after 500 cycles at 10 C. Moreover, it shows stabilized specific discharge capacity of 65.9 mAh g−1 after 500 cycles at a rate of 20 C, and the capacity retention is 98%. Thus, it could infer the Fe-doping Li3V2(PO4)3/C material is a permission candidated material for application in lithium-ion batteries with high performance.

Effect of fuel type on the aminolysis synthesis of CrN powders from combustion synthesis precursors

CrN nanopowders were synthesized by the aminolysis method by using the low temperature combustion synthesis (LCS) precursor derived from the mixed solution of chromium nitrate and alanine, or urea, or glycine, or citric acid. Effects of fuel type on the particle size and morphology of precursors and their corresponding aminolysis powders were studied in detail. It was found that the use of different types of fuel in solution, had a significant effect on the particle size and morphology of precursors and their corresponding aminolysis powders. Moreover, the optimized fuel type (glycine) yielded the precursor with high specific surface area and reactivity. The characteristics of aminolysis powders were found similar to those of their corresponding precursor. The CrN powders derived from glycine and synthesized at 750 °C for 6 h were comprised of well-distributed spherical particles, exhibiting high specific surface area (32.5 m2/g) with an average size of 30–50 nm.

Growth mechanism and magnetism in carbothermal synthesized Fe3O4 nanoparticles from solution combustion precursors

Magnetic Fe3O4 nanoparticles were prepared by carbothermal reduction using solution combustion synthesis precursors derived from ferric nitrate (oxidizer), glycine (fuel) and glucose (carbon source) mixed solution. In this paper, the growth mechanism and magnetism in Fe3O4 nanoparticles were investigated by adjusting the glucose content in precursor and the heat temperature in carbothermal process. The products were analyzed by X-ray diffraction, Field emission scanning electron microscopy, Infrared adsorption method and Vibrating sample magnetometry. The results revealed that the more amount of glucose, the earlier Fe3O4 phase generated as temperature increasing. Depending on glucose content and thermal temperature, the average grain size of Fe3O4 nanoparticles varied from 19.9nm to 48nm and saturation magnetization changed from 21.2emu/g to 71.77emu/g, which indicated that the saturation magnetization of Fe3O4 nanoparticles fell off as the average grain size decreasing. These results were crucial not only from the application stand-point, but more importantly leaded to a new platform for further studies of high quality magnetic Fe3O4 particles at nanoscale.

Effect of Glucose on the Synthesis of Iron Carbide Nanoparticles from Combustion Synthesis Precursors

Iron carbide (Fe3C) nanoparticles have been successfully synthesized by combining low‐temperature combustion synthesis method with carbothermal reduction. A homogeneous precursor powder (Fe2O3 + C) derived from iron nitrate, glycine, and glucose mixed solution was subsequently calcined under nitrogen at 450°C–700°C for 2 h. Effects of glucose on the size and morphology of the precursors as well as the synthesized Fe3C powders were studied in details. The results showed a regular variation in the particle size and morphology of the precursors and Fe3C powders with the increasing molar ratio of glucose to iron nitrate (G/Fe). XRD analysis indicated that the initial transformation of the precursor for (G/Fe = 1) to Fe3C occurred at 500°C. Meanwhile, magnetic properties of the Fe3C have been tested by vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of Fe3C powders synthesized using different G/Fe ratios (G/Fe = 1, 2, 3) was 51.2, 37.0, and 27.1 emu/g, respectively. This made the Fe3C a promising candidate for magnetic materials.

Polyacrylamide-assisted combustion-carbothermal synthesis of well-distributed SiC nanowires

SiC nanowires are produced by employing a novel synthesis process involving the carbothermal reduction reaction of Polyacrylamide (PAM)-assisted low-temperature combustion synthesis (LCS) precursors. PAM-assisted LCS mixtures with high specific surface area and fibers with various size are used as precursors. The precursors, derived from silicic acid (Si source), PAM (additive), nitric acid (oxidizer), urea (fuel), and glucose (C source) mixed solution, are prepared by PAM-assisted LCS method. The prepared precursors have exhibited a high contact area of reactants. The carbothermal reduction of these high specific surface area precursors results in the formation of pure and well-distributed SiC nanowires with a diameter of 50nm and a length of up to several micrometers. The effects of PAM contents and carbothermal reduction parameters on the production of SiC nanowires are discussed in detail. The precursors and corresponding carbothermal reduction products are investigated by FESEM, TEM, HRTEM, and XRD analyses.

Effect of glycine on the synthesis of CrN nanopowder using nitridation combustion synthesis precursors

CrN nanopowder was synthesized by nitridation method using a combustion synthesis precursor derived from chromium nitrate and glycine mixed solution. Effects of glycine on the morphology and nitridation rate of the precursors, the particle size and morphology of synthesized CrN were studied in detail. The results indicated that Cr2O3 precursor with a high specific surface area of 162 m2 g−1 could be prepared by selecting an optimum molar ratio of glycine to chromium nitrate (G/C). Furthermore, a regular variation in the morphology of precursors had been observed with increasing (G/C). The nitridation products retained the morphology of Cr2O3 in the precursors. The nitridation products, prepared with (G/C = 4), comprised well-distributed spherical particles of CrN with the average size of 30 nm. Moreover, the nitridation rate of products with (G/C = 4) was significantly higher than that of the nitridation products prepared with (G/C = 0.5, 5/3, 3).

Carbothermal synthesis of Si3N4 powders using a combustion synthesis precursor

Si3N4 powders were synthesized by a carbothermal reduction method using a SiO2 + C combustion synthesis precursor derived from a mixed solution consisting of silicic acid (Si source), polyacrylamide (additive), nitric acid (oxidizer), urea (fuel), and glucose (C source). Scanning electron microscopy (SEM) micrographs showed that the obtained precursor exhibited a uniform mixture of SiO2 + C composed of porous blocky particles up to ∼20 μm. The precursor was subsequently calcined under nitrogen at 1200–1550°C for 2 h. X-ray diffraction (XRD) analysis revealed that the initial reduction reaction started at about 1300°C, and the complete transition of SiO2 into Si3N4 was found at 1550°C. The Si3N4 powders, synthesized at 1550°C, exhibit a mixture phase of α- and β-Si3N4 and consist of mainly agglomerates of fine particles of 100–300 nm, needle-like crystals and whiskers with a diameter of about 100 nm and a length up to several micrometers, and a minor amount of irregular-shaped growths.

Carbothermal synthesis of ZrC powders using a combustion synthesis precursor

ZrC powders were synthesized by carbothermal reduction of a combustion synthesized precursor derived from zirconium nitrate, urea, and glucose mixed solution. The results showed that the obtained precursor was comprised of polyporous blocky particles. The precursor powders were subsequently calcined under argon at 1200–1600°C for 3h. The transformation of ZrO2 to ZrC, by adopting this route, occurred at 1300°C. The preparation of ZrC experienced an intermediate phase of ZrOxCy. ZrC powders synthesized at 1500°C are characterized by the spherical shape, small particle size (120–180nm in diameter), low oxygen content (1.4wt.%) and non-aggregated particles.

Delayed Ignition of Autocatalytic Combustion Precursors: Low-Temperature Nanomaterial Binder Approach to Electronically Functional Oxide Films

Delayed ignition of combustion synthesis precursors can significantly lower metal oxide film formation temperatures. From bulk In(2)O(3) precursor analysis, it is shown here that ignition temperatures can be lowered by as much as 150 °C. Thus, heat generation from ~60 nm thick In(2)O(3) films is sufficient to form crystalline In(2)O(3) films at 150 °C. Furthermore, we show that the low processing temperatures of sufficiently thick combustion precursor films can be applied to the synthesis of metal oxide nanocomposite films from nanomaterials overcoated/impregnated with the appropriate combustion precursor. The resulting, electrically well-connected nanocomposites exhibit significant enhancements in charge-transport properties vs conventionally processed oxide films while maintaining desirable intrinsic electronic properties. For example, while ZnO nanorod-based thin-film transistors exhibit an electron mobility of 10(-3)-10(-2) cm(2) V(-1) s(-1), encasing these nanorods within a ZnO combustion precursor-derived matrix enhances the electron mobility to 0.2 cm(2) V(-1) s(-1). Using commercially available ITO nanoparticles, the intrinsically high carrier concentration is preserved during nanocomposite film synthesis, and an ITO nanocomposite film processed at 150 °C exhibits a conductivity of ~10 S cm(-1) without post-reductive processing.

Effect of Carbon Source Content on the Carbothermal Synthesis of AlN Powders Using a Combustion Synthesis Precursor

AlN powders were synthesized by carbothermal reduction method using a combustion synthesis precursor derived from aluminum nitrate (oxidizer), glucose (carbon source), and urea (fuel) mixed solution. Effects of carbon source content on the combustion temperature of solutions, the particle size and morphology of the precursors and the synthesized AlN were studied in detail. The results indicated that a regular variation in the particle size and morphology of precursors had been observed with the increasing molar ratio of glucose to aluminum nitrate (C/Al). The products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, could have completed the nitridation reaction, while the nitridation products prepared with (C/Al=4 and 16) are opposite. The nitridation products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, are comprised of well-distributed spherical particles of AlN with the average size ranging from 50 to 80 nm.

Effect of aluminum source on the synthesis of AlN powders from combustion synthesis precursors

In the present work, the carbothermal reduction method was employed to fabricate the AlN powders by utilizing the combustion synthesized precursor derived from the mixed solution comprised of an aluminum source (Al(NO3)3 or Al2(SO4)3 or AlCl3), glucose, nitric acid, and urea. Effects of aluminum source on the particle size and morphology of precursors as well as synthesized AlN powders were studied in detail. The size and morphology of precursors, derived from various aluminum sources, had exhibited significant differences. The precursor from Al(NO3)3 source had completed the nitridation reaction at 1500°C in 2h. However, the nitridation reactions of the precursors from Al2(SO4)3 or AlCl3 source furnished at increased temperature of 1550°C in 2h. Moreover, the AlN powders from various aluminum sources have been synthesized directly from γ-Al2O3 without γ-Al2O3 to α-Al2O3 phase transition. The AlN powders from Al(NO3)3, calcined at 1550°C for 2h, were comprised of well-distributed spherical particles with an average size of 80nm. While the AlN powders from AlCl3 or Al2(SO4)3 consisted of heterogeneously distributed spherical particles ranging from 100 to 200nm or from 80 to 150nm, respectively.

Citric Acid‐Assisted Combustion‐Carbothermal Synthesis of Well‐Distributed Highly Sinterable AlN Nanopowders

Aluminum nitride (AlN) nanopowders were synthesized by carbothermal reduction of a citric acid‐assisted combustion synthesis precursor derived from aluminum nitrate, glucose, citric acid, and urea mixed solution. Effects of citric acid on the size and morphology of precursors as well as synthesized AlN powders were studied in detail. The results indicated that the precursor synthesized from citric acid (0.02 M), was comprised of paper‐thin flaky particles with high specific surface area (14.6 m2/g). Moreover, the precursor, synthesized from citric acid (0.02 M), had exhibited the completion of the nitridation at 1400°C for 2 h. On the contrary, the nitridation reactions for the precursors, synthesized from citric acid (0 and 0.04 M), were incomplete under the same conditions. The decarburized as well as nondecarburized AlN powders from citric acid (0.02 M), synthesized at 1400°C, maintained its appearance similar to that of the original precursor. In addition, the decarburized AlN powders were found to be free of any hard agglomeration, and exhibited the well distributed and high sinterability spherical particles of 60–100 nm. The relative density of the sintered AlN pellet, calcined at 1800°C for 2 h with pressureless and additive free sintering, was found to be 99.05% of its theoretical density.

Effect of urea on the size and morphology of AlN nanoparticles synthesized from combustion synthesis precursors

AlN nanoparticles were synthesized by carbothermal reduction method using a combustion synthesis precursor derived from aluminum nitrate, glucose, and urea mixed solution. Effects of urea on the combustion temperature of solutions, the particle size and morphology of precursors, the intermediate formed γ-alumina, and the synthesized AlN were studied in detail. The results indicated that the homogeneous mixture of amorphous (Al2O3+C) precursor might be prepared by selecting an optimum molar ratio of urea to aluminum nitrate (U/Al) in solution by combustion synthesis method. Furthermore, a regular variation in the particle size and morphology of precursors had been observed with increasing (U/Al). The nitridation products, synthesized at 1500°C, retained the characteristics of γ-alumina in the precursors. The nitridation products, prepared with (U/Al=0.5–2), comprised of well-distributed spherical particles of AlN with the average size ranging from 30 to 80nm. Moreover, the nitridation reactivity of products with (U/Al=0.5–2) had been found at 99%, which was significantly higher than that of the nitridation products prepared with (U/Al=0.3, 2.5, 3) and without urea.

Influence of carbon on the synthesis of AlN powder from combustion synthesis precursors

AlN powders were synthesized by carbothermal reduction of combustion synthesis precursors. Water-soluble organics and carbon black were used as carbon sources. The effects of carbon on the synthesis of AlN powders were studied. Results showed that AlN powders were synthesized directly from γ-Al 2O 3 without γ-Al 2O 3 to α-Al 2O 3 phase transition when water-soluble organics were used as carbon sources, and the nitridation of the precursors could be completed at 1400 °C. However, AlN powders were synthesized from the nitridation of α-Al 2O 3 when carbon black was used as carbon source, and the reaction temperature for a complete conversion increased to 1500 °C. The particles of AlN powders synthesized with water-soluble organics was smaller than the particles of AlN powders synthesized with carbon black and their particle size distribution was sharper. The specific surface area of synthesized AlN powders increased with the increase of carbon content in the precursors.

Synthesis of aluminum nitride powder by carbothermal reduction of a combustion synthesis precursor

A new homogeneous mixing precursor of alumina and carbon (Al 2O 3 + C) was prepared by low temperature combustion synthesis (LCS) with aluminum nitrate (Al(NO 3) 3·9H 2O), urea (CO(NH 2) 2), and glucose (C 6H 12O 6·H 2O) as starting materials. The precursor prepared was a foamy and porous mass due to the large amount of gases liberated in the combustion reaction and composed of nanosize particles. XRD analysis showed that this precursor consisted of amorphous alumina and carbon. The amorphous alumina in the precursor first transformed into γ-Al 2O 3, and then γ-Al 2O 3 was directly nitrided to yield AlN during the calcination process. The reaction temperature needed for a complete conversion for the precursor was about 1400 °C, which is much lower than that when using alumina and carbon black as starting materials. The synthesized AlN powder was composed of very fine particles and had good dispersability.

Method for continuous production of catalysts for synthesis of carbon nanotubes

AbstractA new method for continuous production of carbon nanotube (CNT) catalysts is proposed in this study. The method is a modification of the solution combustion synthesis and was called continuous solution combustion synthesis (CSCS). The method consists of the atomization of the modified combustion synthesis precursor solution in a pilot flame. A combustible, like ethanol, is added to the precursor solution to improve the evaporation of the solvent and the atomization. The ignition of the precursor solution is self‐sufficient. A fine and porous powder is produced. The powder, collected through an electrostatic precipitator, has superior performance as a carbon nanotube catalyst. When comparing the production of Fe–Mo/MgO catalyst synthesized by the continuous method with the conventional route, it was observed that the amount of carbon nanotubes increased by 52 wt%, and the G/D ratio was also higher. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)