• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.47-52
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• 2000

Lanthanides such as La, Gd and Ce have recognized as elements of high level radioactive wastes immobilized by forming solid solution with $CaTiO_3$. For easy forming solid solution between $CaTiO_3$and lanthanides, the combustion synthesis process was applied and the powder characteristics and sinterability were investigated. The proper selection of the type and the composition of fuels are important to get the crystalline solid solution of $CaTiO_3$and lanthanides. When glycine or the mixtures of urea and citric acid with stoichiometric composition was used as a fuel, the solid solution of $CaTiO_3$with $La_2O_3$or $Gd_2O_3$or $CeO_2$was produced very well by the combustion process. The combustion synthesized powder seemed to have a good sinterability with the linear shrinkage of more than 25% up to $1500^{\circ}C$, while that of the solid state reacted powder was less than 10% at the same condition.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.385-392
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• 2023

A solution combustion process for the synthesis of hollandite (BaAl₂Ti₆O₁₆) powders is described. SYNROC (synthetic rock) consists of four main titanate phases: perovskite, zirconolite, hollandite and rutile. Hollandite is one of the crystalline host matrices used for the disposal of high-level radioactive wastes because it immobilizes Sr and Lns elements by forming solid solutions. The solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between a nitrate and organic fuel, generates an exothermic reaction and that heat converts the precursors into their corresponding oxide products in air. The process has high energy efficiency, fast heating rates, short reaction times, and high compositional homogeneity. To confirm the combustion synthesis reaction, FT-IR analysis was conducted using glycine with a carboxyl group and an amine as fuel to observe its bonding with metal element in the nitrate. TG-DTA, X-ray diffraction analysis, SEM and EDS were performed to confirm the formed phases and morphology. Powders with an uncontrolled shape were obtained through a general oxide-route process, confirming hollandite powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using these methods.

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.797-801
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• 2001

In this study, the solution combustion method was employed to synthesize stoichiometric mullite, and hence the attrition process was employed to prepare ultrafine mullite particles with nano size. The thermal decomposition behavior and partial pressure of equilibrium species of both oxidizer and fuel were considered during solution combustion process. The synthesized product was mullite phase with 40 nm crystalline size, and the alumina contents of the product by TEM/EDS quantity analysis was 3.12$\pm$04 mole. The result showed that the synthesized mullite was almost close to the it's stoichiometric composition. For attrition process, the dispersion behavior of the mullite suspension was controlled and was comminuted with the condition of 800 rpm for 4 hours using 0.3 mm zirconia ball media. As a result of comminution, the mean particle size was 80 nm.

• Journal of Powder Materials
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• v.8 no.1
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• pp.13-19
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• 2001

Ni and NiO particles were made by a combustion synthesis process. The characteristics of synthesized powders were investigated with various kinds and amounts of fuels such as urea, citric acid and glycine. Ni phase particles without NiO phase were obtained through combustion synthesis process in air atmosphere with-out further calcinations process, when the content of glycine was 2.44 times of the stoichiometric ratio in the precursor solution. Primary particle sizes of synthesized Ni and NiO particles were about 20∼30 nm.

• Journal of the Korean Society of Combustion
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• v.13 no.1
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• pp.17-22
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• 2008

A partly implicit/quasi-explicit method is introduced for the solution of detailed chemical kinetics with stiff source terms based on the standard fourth-order Runge-Kutta scheme. Present method solves implicitly only the stiff reaction rate equations, whereas the others explicitly. The stiff equations are selected based on the survey of the chemical Jaconian matrix and its Eigenvalues. As an application of the present method constant pressure combustion was analyzed by a detailed mechanism of hydrogen-air combustion with NOx chemistry. The sensitivity analysis reveals that only the 4 species in NOx chemistry has strong stiffness and should be solved implicitly among the 13 species. The implicit solution of the 4 species successfully predicts the entire process with same accuracy and efficiency at half the price.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1078-1084
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• 1998

lanthanum chromite(LaCrO3) powder was synthesized by the combustion of a solution of metal nitrates La(NO3).6H2O and Cr(NO3)3.9H2O and urea. The pH of solution affected a yield of the combustion products but did not influence the morphology of the products. When the pH of the solution was in the range of 0.7-4, the yield of the combustion products was more than 90% The morphology of the combustion products was af-fected by heating methods for the solution. The hot-plate induced heating of the solution yielded powders hav-ing two-dimensionally interconnected agglomerates whereas microwave-induced heating produced a fine and non-agglomerated powders. The specific surface area(BET) of the combustion products using microwave-in-non-agglomerated powders. The specific surface area(BET) of the combustion products using microwave-in-duced heating method were larger(25~32m2/g) than that of hot plate heating method(10-14m2/g)

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.74-78
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• 2002

In this study, the solution combustion method was employed to synthesize perovskite PZT ceramics. Multicomponent oxides can be prepared by the solution combustion synthesis using redox exothermic reaction of precursor solutions. The results of DTA/TG showed exothermic peaks in 214$^{\circ}C$ and 350$^{\circ}C$. Those were caused by the differences of the thermal decomposition behavior of oxidizer and fuel. The combustion reaction was completed at 370$^{\circ}C$ during heating procedure, but the product was not transformed into perovskite. The thermal decomposition behavior of both oxidizer and fuel were considered during solution combustion process at 600$^{\circ}C$, which showed tetragonal single phase PZT ceramics with 50 nm crystalline size. The lattice constant a was 3.997 ${\pm}$ 0.001 ${\AA}$ and the lattice constant c was 4.147${\pm}$0.001 ${\AA}$.

• Journal of the Korean Ceramic Society
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• v.35 no.5
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• pp.451-457
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• 1998

$Li_2$$ZrO_3$ powder which is one of the candidates of breeding materials for the fusion reactor was syn-thesized by a precipitation-combustion process. Although precipitates from the reaction between zirconium nitrate and citric acid were existed in a precursor solution. $Li_2$$ZrO_3$ could easily be obtained by using the mixed fuel of urea and citric acid in stoichiometric composition. The phases of as-synthesized powder con-sisted of $Li_2$$ZrO_3$ and small amounts of $Li_6$$Zr_2O_3$ and $Li_2$$ZrO_3$ The latter phases disappeared after the cal-cination at $1100^{\circ}C$ for 2 h. The primary particle size and the specific surface area of as-synthesized powders were smaller than 20nm and 10-14 $M^2$/g, respectively. The primary particle size of the precipitation-combustion synthesized powders was affected by the size of precipitates present in a precursor solution.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.411-417
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• 1996

Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.256-260
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• 2014

Interior of the building is used as a MDF plywood if there is a fire in order to delay the ignition, flame retardant paint, flame retardant solution and flame retardant film are being handled by the flame retardant. Combustion characteristics anf flame retardant performance results can be summarized as follows: General film with a sample showed that short of the criteria in terms of carbonation area, and the results of flame retardant paint, flame retardant solution and flame retardant film products satisfied the criteria. Toxic gases generated in the combustion process results in a film samples using a high incidence of carbon monoxide and the creation of a smoke could be seen. This confirm that is estimated that result from incomplete combustion of PVC film that attach, and displays high toxicity index and hazard class relatively.