Some properties of sintered ceria ceramics

Conclusions Sintering of finely dispersed ceria occurs intensely in the 1300–1500°C range.In an atmosphere of inert gas and in vacuum the sintered CeO₂ is reduced with changes in crystal structure, which is accompanied by a reduction in the refractory and thermomechanical properties of the material.Unreduced CeO₂ is a highly refractory material which in oxidizing conditions can be used at temperature above 1900°C.     

An overview of geoengineering of climate using stratospheric sulphate aerosols

We provide an overview of geoengineering by stratospheric sulphate aerosols. The state of understanding about this topic as of early 2008 is reviewed, summarizing the past 30 years of work in the area, highlighting some very recent studies using climate models, and discussing methods used to deliver sulphur species to the stratosphere. The studies reviewed here suggest that sulphate aerosols can counteract the globally averaged temperature increase associated with increasing greenhouse gases, and reduce changes to some other components of the Earth system. There are likely to be remaining regional climate changes after geoengineering, with some regions experiencing significant changes in temperature or precipitation. The aerosols also serve as surfaces for heterogeneous chemistry resulting in increased ozone depletion. The delivery of sulphur species to the stratosphere in a way that will produce particles of the right size is shown to be a complex and potentially very difficult task. Two simple delivery scenarios are explored, but similar exercises will be needed for other suggested delivery mechanisms. While the introduction of the geoengineering source of sulphate aerosol will perturb the sulphur cycle of the stratosphere signicantly, it is a small perturbation to the total (stratosphere and troposphere) sulphur cycle. The geoengineering source would thus be a small contributor to the total global source of 'acid rain' that could be compensated for through improved pollution control of anthropogenic tropospheric sources. Some areas of research remain unexplored. Although ozone may be depleted, with a consequent increase to solar ultraviolet-B (UVB) energy reaching the surface and a potential impact on health and biological populations, the aerosols will also scatter and attenuate this part of the energy spectrum, and this may compensate the UVB enhancement associated with ozone depletion. The aerosol will also change the ratio of diffuse to direct energy reaching the surface, and this may influence ecosystems. The impact of geoengineering on these components of the Earth system has not yet been studied. Representations for the formation, evolution and removal of aerosol and distribution of particle size are still very crude, and more work will be needed to gain confidence in our understanding of the deliberate production of this class of aerosols and their role in the climate system.     

Rapid Solidification of ZrO2–8 mol % Y2O3Melt

This paper deals with the singularities of crystallization of a pool with a melt produced by local heating of ZrO₂–8 mol % Y₂O₃ceramic by concentrated laser radiation. The effect of the semitransparency of the oxide, of the thickness of the melt, and of the rate of its cooling on the behavior of crystallization and on the structure of solidified layer is analyzed. The obtained results are compared with the results of crystallization of the melt of pure ZrO₂.     

Shock d eformation diagram of fireclay

A method is proposed for constructing the shock compression and load-relief diagrams of a foam material when a one-dimensional stress-strain is realized in it. The method is based on the mathematical analysis of experimental information. The shock-compression and load-relief diagrams of fireclay (strain rate ε=10² sec⁻¹) are constructed from the experimental data obtained in experiments on the compression of samples of this foam material. 5 figures. 10 references. NITs TIV OIVT RAN. Translated from Atomnaya énergiya, Vol. 88, No. 1, pp. 38–43, January, 2000     

Interaction of Dioxyzirconium Ceramics with the Sacrificial Material of the European Reactor Trap

The present paper discusses the complications that can arise in using in the core melt trap of the European nuclear reactor being designed a sacrificial material of 40% FeO _x –60% SiO₂ composition. The investigation of the interaction of zirconium dioxide ceramics with the sacrificial material has permitted the conclusion that at a local baring of the refractory layer its destruction can occur. The addition of neodymium oxide to the melts lowers erosion and excludes regeneration of the ceramics structure.     

Shock‐Wave Deformation and Fracture of Zirconium Dioxide Ceramics of Various Fractional Composition and Porosity

The paper reports results from measurements of freesurface velocity profiles of shockloaded zirconium dioxide ceramics with a porosity of 16–22% produced from compositions with a size of the coarse fraction of 0.5–2.0 mm. Shockwave loading of ZrO₂ samples 5–20 mm thick was performed by aluminum impactors 3–12 mm thick with a velocity of 10–100 m/sec. The measured freesurface velocity profiles were used to assess the dynamic compressive and tensile strengths of the ceramics and thedamping properties of the ceramics.     

Estimate of the Thermal Regimes of a Flat Zirconium Dioxide Ceramic Trap during a Serious Reactor Accident

Physical and mathematical models are constructed and a medium-term forecast is made of the thermal state of a flat trap consisting of zirconium dioxide ceramic for a serious accident in a nuclear reactor.It is shown in the radiation-thermal conductivity approximation that radiation transfer strongly influences the dynamics of thermal processes developing in the trap.It is established that the time during which the temperature of the cold boundaries of the bottom and roof of the trap reaches the critical value is much shorter than the values predicted in models which neglect the role of radiation.The influence of partial permeation of melted iron oxides into the trap bottom on the quasistationary state is investigated.     

Cerium Dioxide-Based High Temperature Heaters for Operation in Air

Refractories and Industrial Ceramics - The paper discusses a possibility of developing cerium dioxide-based electric heaters for operation in air within the temperature range of 300 – 2500 K....     

Luminescent-plasmonic core–shell microspheres,doped with Nd3+ and modified with gold nanoparticles,exhibiting whispering gallery modes and SERS activity

Multifunctional core/shell type,luminescent-plasmonic material composed of lanthanide doped microspheres(≈50 μm) and gold nanoparticles(Au NPs;≈10-20 nm) deposited onto their surface,were successfully prepared(Nd~(3+):YAS@Au).The material was synthesized to combine the luminescence properties of the Nd~(3+)-doped microspheres,i.e.whispering resonance with plasmonic activity of the surface Au NPs,i.e.surface enhanced Raman scattering(SERS) effect,within a single,micro-sized material.The luminescent-plasmonic microspheres were used as the active SERS substrate for detection of the organic probe,and for generation of Whispering Gallery Modes(WGM),which red-shift together with increasing laser power(temperature elevation).The products obtained were analysed with optical,scanning and transmission electron microscopy(SEM and TEM),as well as by Raman,absorption and photoluminescence spectroscopies.