Flash Light Sintered Lanthanum Strontium Cobalt Ferrite(LSCF) Electrode for High Performance IT-SOFCs

The high temperature(900oC~) thermal sintering process is necessary to fabricate the Solid oxide fuel cells(SOFCs). However, the chemical reaction has occurred between solid oxide material components, electrode and electrolyte. In the case of lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ, LSCF) electrode, the SrZrO3(SZO) secondary phase is produced at the electrolyte interface even when using the gadolinium doped ceria(GDC) buffer layer for blocking the strontium and zirconium diffusion. The SZO layer hinders the oxygen ion transfer and deteriorates fuel cell performance. By using a novel flash light sintering(FLS) method, we have successfully solved the problem of secondary phase formation in the conventional high temperature thermal sintering process. The microstructure and thickness of the LSCF electrode are analyzed using a field emission scanning electron microscope(FE-SEM). The strontium diffusion and secondary phase are confirmed by X-ray diffraction (XRD), energy dispersive spectrometer method of SEM, TEM (SEM-, TEM-EDS). The NiO-YSZ anode supported LSCF cathode cells are adopted for electro chemical analysis which is measured at 750oC. The maximum power density of the thermal sintered LSCF cathode at 1050oC is 699.6mW/cm2, while that of the flash light sintered LSCF cathode is 711.6mW/cm2. This result proves that the electrode was successfully sintered without a secondary phase using flash light sintering.

Investigation of laser and thermal sintering processes of silver nanoparticles agglomerates synthesized by spark discharge

Changes in the shape and size of silver nanoparticles (NPs) during their laser and thermal sintering have been studied experimentally and theoretically. Aerosol silver NPs forming dendrid-like agglomerates 180 nm in size were synthesized by spark discharge and exposed to laser radiation and high temperature of 750 °C. The shape and size of the NPs were investigated depending on the power of the laser radiation and the temperature of the gas. It is estimated that, at a power density of laser radiation of the order of 103-104 W/cm2, the formation of spherical NPs with an average size of 140 nm is expected. Such particles turn out to be similar to NPs thermally heated in a gas flow at 750 °C for 6 seconds.

Oxygen Sensors for Industrial Application

The present work aimed to study a family of solid ceramic electrolytes based on magnesium oxide doped zirconium oxide, usually identified as Mg-PSZ (zirconia partially stabilized with magnesia), used in the manufacture of oxygen sensors for molten metals. A set of electrolytes was prepared by mechanical (milling) and thermal (sintering) processing, varying the composition in magnesia and the cooling rate from the sintering temperature. These two parameters are essential in terms of phase composition and microstructure of Mg-PSZ, determining the behavior of these materials. The structural and microstructural characterization was done by means of X-ray diffraction (XRD). The electrical properties were analyzed by impedance spectroscopy in air. In general, the results obtained from various concentrations of dopant, different cooling rates and the same sintering step condition showed an increased conductivity for samples with predominance of high temperature stable phases (tetragonal and cubic).

Study of the Effect of Y2O3 Doping on the Resistance to Radiation Damage of CeO2 Microparticles under Irradiation with Heavy Xe22+ Ions

This paper presents the results of a study on the influence of Y2O3 doping on the resistance to radiation damage and an assessment of structural changes associated with the accumulation of radiation defects in CeO2 microparticles under irradiation with heavy Xe22+ ions. The relevance of this study consists of the prospects for the use of CeO2 microparticles as materials and candidates of inert matrices of nuclear fuel. A method of solid-phase synthesis was applied to obtain microparticles with different concentrations of dopant. It included grinding of CeO2 and Y2O3 microparticles followed by thermal sintering at 1100 °C in an oxygen-containing medium to produce highly ordered microparticles. During the study of the structural characteristics of the synthesized microparticles, it was found that increasing the dopant concentration from 0.05 mol.% to 0.15 mol.% leads to an increase in the crystallinity degree as well as a decrease in dislocation density. According to the results of the assessment of the resistance of microparticles to radiation damage, it was found that an increase in the dopant concentration leads to a decrease in swelling and structural distortion by more than 2.5–3 times, which indicates an increase in the radiation resistance.

STRUCTURAL FEATURES OF NANOPRISE GLASSES AFTER HIGH-TEMPERATURE SINTERING

Nanoporous glass is a matrix for composite optical materials, in which, by impregnating various activators, it is possible to initiate the appearance of properties uncharacteristic of composite materials. In this case, the main parameter of the structure of nanoporous glass is porosity, which can be controlled by the method of hightemperature sintering. In this work, we have studied the effect of thermal sintering on the structure of porous glass.

Study of Resistance to Helium Swelling of Lithium-Containing Ceramics under High-Temperature Irradiation

The aim of this work was to study resistance to helium accumulation processes in the structure of the surface layer of lithium-containing ceramics and the subsequent destruction and embrittlement processes, depending on radiation fluence. The objects of study were Li2TiO3-type ceramics obtained by thermal sintering. The fluence dependency of changes in the structural and strength properties of ceramics was determined to be in the range from 1018 to 1022 ion/m2, which corresponded to the concentration of implanted helium from 0.01% to 0.8–1 at.%. Irradiation was carried out at a temperature of 700 °C, which made it possible to simulate the processes of radiation damage that were closest to the real conditions in the reactor core. During the studies carried out, it was found that, at irradiation fluences of 1018–1020 ion/m2, the formation of point radiation defects was equaled by the process of thermal annealing of defects, as a result of which the concentration of defects and their effect on the change in the structural and strength properties of ceramics were insignificant. An increase in the concentration of implanted helium in the structure of the surface layer to above 0.5 at.% led to the dominance of radiation damage processes over the annealing of defects and the formation of gas-filled cavities, which negatively affects the strength of ceramics.

Investigation of the influence of the mode of heat treatment of the initial powder on the efficiency of sintering zirconium ceramics by dilatometry

Using methods of synchronous thermal and X-ray structural analyzes applied to zirconium dioxide powders partially stabilized with yttrium obtained by chemical coprecipitation the processes of dehydration of these powders during annealing in air have been investigated. Using the dilatometry method, the regularities of compaction of powder compacts have been investigated with thermal sintering. It was found that the resulting powders mainly consist of the tetragonal modification zirconium dioxide and are nano-sized. The average particle size was 25 nm. The resulting powders are characterized by a high degree of agglomeration. It is shown that an increase in the thermal annealing temperature from 500 to 700ºС leads to partial baking of individual particles inside the agglomerate, and causes the formation of hard agglomerates, the presence of which complicates the processes of compaction and subsequent sintering. The presence of such agglomerates prevents the production of ceramics with high mechanical characteristics: density and porosity. Thermal annealing temperature increase leads to a decrease in the density of the sintered ceramic and a decrease in its hardness.

STUDY OF PHASE FORMATION IN FE2O3-ND2O3→NDFEO3/FE2O3 NANOCOMPOSITES AS A RESULT OF THERMAL ANNEALING

The aim of this work is systematic study of the thermal annealing effect on the preparation of nanostructured composites NdFeO3/Fe2O3 with a spinel type structure. The interest in these nano­composites is due to the enormous potential of their application as a basis for magnetic devices, catalysts, and magnetic carriers for targeted drug delivery. As a synthesis method, two­stage syn­thesis was used, which includes mechanochemical grinding of nanopowders Fe2O3 and Nd2O3 in a planetary mill, followed by thermal annealing of the resulting mixture in a wide temperature range: 600­1000°C. During the studies carried out, it was found that in the initial state the obtained nano­composites are a mixture of a solid solution of interstitial and substitutional Fe2O3 and Nd2O3. At an annealing temperature of 600°C, the onset of the formation of the NdFeO3 phase is observed, which at a temperature of 1000°C is fully formed and dominates in the composite structure (content more than 85%). It was also found that during thermal sintering, the processes of phase transformations of the Fe2O3­Nd2O3→NdFeO3/Fe2O3 type are accompanied by an increase in the particle size by a factor of 1.5­2