Corrosion Of Ceramics Research Articles

Corrosion of Ceramic and Carbon-Based Materials in FLiNaK

Molten salt nuclear fast nuclear reactor (MSNFR) is one of the prospective design in frame of Generation IV concept. This technology is also required for reprocessing of spent nuclear fuel (SNF) in molten salts to extract valuable components. Recycling SNF consists of extraction uranium and plutonium with the disposal of minor actinides and fission products. These stages need the materials that retain their corrosion and mechanical properties for long time under the influence of high temperatures, radiation fields and contact with molten salts. Various steels and alloys were widely studied to assess their use under such extreme conditions. Alternative materials include ceramics, composite and carbon materials, which have high corrosion resistance in various media and can be used up to 1000 °C.In the present work the corrosion and mechanical properties of nitride ceramics (Si3N4 and BN) and carbon-based materials (carbon-carbon composite material (C/C) and high-density carbon) were studied in a molten mixture of lithium, sodium, and potassium fluorides (FLiNaK) in the temperature range of 550–750 °C under inert atmosphere. Corrosion tests were performed under static conditions, and the duration of each test was 100 h to enable the comparison of the experimental data.It was found that carbon-containing materials (C/C and high-density carbon) showed high corrosion resistance in the melt. C/C samples had lower corrosion rates (less than 0,1 mm/year in the entire temperature range), while the high-density carbon showed better mechanical properties. The main disadvantage of these materials is their impregnation by molten salt due to relative high porosity. However, C/C composite and high-density carbon are promising structural materials for salt media based on FLiNaK in the selected temperature range.Tested nitride ceramics (BN, Si4N3) demonstrated relatively low corrosion resistance in fluoride systems compare to carbon-containing and metallic materials. The corrosion rates of these materials in FLiNaK exceeded the value of 1 mm/year. The plastic properties of nitride ceramics were also poor. Possible application of such materials for MSNFR and SNF reprocessing is under further investigation.

Corrosive and mechanical resistance of MgO ceramics under metallizing and mild chlorination of spent nuclear fuel in molten salts

The present work is aimed at the study of the unirradiated and irradiated MgO ceramics corrosion and mechanical properties in the molten LiCl at 650–750 °C with addition of UCl3 and Li2O(LiCl + nLi2O and LiCl + mUCl3 molten salts with n = 1.0 and 2.0 mol. % and m = 0.25, 0.5 and 1.0 mol. %). MgO ceramics is suggested to be used as one of materials for pyrochemical technology for recycling of spent nuclear fuel.The gravimetric method with the exposure time during 100 h was the primary method of investigation. The investigation of surface and bulk corrosion of MgO samples by scanning electron microscopy (SEM) and X-ray spectroscopy (MRSA) was performed using scanning electron microscope equipped with a x-Act 6 energy-dispersive analytic system for X-rays characteristic (XRС). Determination of corrosion losses and average corrosion rates of MgO samples was based on the assumption that the ejection of the radionuclides 95Zr, 175Hf and 181Hf from the MgO samples.Incorporation of Li2O and UCl3 in molten LiCl result in increase in the rate of MgO ceramic corrosion both at 650 °C and 750 °C and acts on MgO compressive strength (σcs) and on the elemental composition of MgO surface layers. Besides the increasing of UCl3 concentration led to the bulk corrosion of MgO sample grains.Short-term mechanical tests demonstrated the transition of MgO sample destruction pattern depending on the concentration of Li2O and UCl3 additions in LiCl melt.Doping of molten LiCl by 0.5 mol. % of UCl3 at 650 °C and by 0.25 mol. % of UCl3 at 750 °C had no influence on the ultimate compression strength of irradiated and unirradiated MgO samples. Increased UCl3 concentration totaling 0.5 mol. % in the LiCl melts at 750 °C reduced the ultimate compression strength of irradiated MgO ceramic samples by ~15%.

Effect of pH Cycling Frequency on Glass-Ceramic Corrosion.

The effect of pH changes on the chemical durability of dental glass–ceramic materials was evaluated using weight loss and ion release levels. The hypothesis that increased pH changes will exhibit greater corrosion was investigated. The ion concentration was analyzed using inductively coupled plasma atomic emission spectrometer (ICP). The surface compositions were investigated using X-ray photoelectron spectroscopy (XPS). The surface morphologies were examined using scanning electron microscopy (SEM). Dental glass–ceramics were tested in constant immersion, 3-day cycling, and 1-day cycling with pH 10, pH 2, and pH 7 for 3, 15, and 30 days. The 1-d cycling group demonstrated the highest levels of weight loss compared with 3-d cycling and constant immersion. For the ion release, Si4+ and Ca2+ had the highest rates of release in 1-d cycling, whereas the Al3+ release rate with constant pH 2 was highest. The alteration/passivation layer that was formed on the surface of disks possibly prevented further dissolution of pH 10 corroded disks. XPS analysis demonstrated different surface compositions of corroded disks in pH 10 and pH 2. Si4+, K+, Na+, Al3+, and Ca2+ were detected on the surface of corroded pH 10 disks, whereas a Si4+ and P5+-rich surface formed on corroded pH 2 disks. SEM results demonstrated rougher surfaces for corroded disks in cycling conditions and pH 2 constant immersion. In conclusion, increased pH changes significantly promote the corrosion of dental glass–ceramic materials.

Corrosion of ceramics for vinasse gasification in supercritical water

Abstract Supercritical water gasification (SCWG) is a very efficient process to convert wet biomass into energetic gases. Unfortunately, SCWG reactor may strongly corrode due to the addition of temperature, pressure and the presence of corrosive species. In the present paper, the corrosion of various ceramic materials in subcritical and supercritical water (SCW) gasification process was studied in a batch reactor. We compare the corrosion in distillated water and the corrosion in sugar beet slurry that will be gasified under supercritical conditions. The experimental temperatures were 350 °C and 550 °C and the pressure was 25 MPa. Technical ceramics (SiC, alumina, Y stabilized zirconia, Si3N4, BN, aluminosilicate, cordierite-mullite) show poor capability to sustain corrosion whereas graphite and glassy carbon are the highest performance materials in our working conditions.

Sliding wear corrosion of ceramics

This paper describes experiments to examine how sliding wear corrosion experiments can be carried out with simple laboratory equipment that is in common usage in tribological testing laboratories. Experiments were conducted on three ceramics; two aluminas with different alumina volume fractions and one tetragonally stabilised zirconia. Three different test fluids were examined; these were de-ionised water, 0.1 M HCl and 0.1 M NaOH. It was found that the sliding wear corrosion test system performed well, with the two aluminas both exhibiting increasing wear with decreasing pH, and the zirconia showing decreasing wear with decreasing pH.

Corrosion of Ceramics

AbstractFor Abstract see ChemInform Abstract in Full Text.

Oxidation and corrosion of ceramics and ceramic matrix composites

Ceramics and ceramic matrix composites are candidates for numerous applications in high temperature environments with corrosive gases and deposits. High temperature oxidation and corrosion issues must be considered for these materials. The most important oxidation and corrosion studies have recently focused on four major areas. These are: (I) oxidation of precursor-based ceramics, (II) studies of the interphase material in ceramic matrix composites, (III) water vapor interactions with ceramics, particularly in combustion environments, (IV) development of refractory oxide coatings for silicon-based ceramics. This paper explores the most current work in each of these areas.

Wettability and corrosion of TiN, TiN–BN and TiN-AlN by liquid steel

The wettability and corrosion behaviour of titanium nitride by liquid steel has been studied. Due to its thermodynamic stability and low solubility in liquid iron, TiN has a good resistance to corrosion by liquid steel. However, its good wettability promotes adhesion to steel. Also, the effects of BN and AlN addition to TiN on the wetting parameters and the mechanisms of the ceramic corrosion by liquid steel have been investigated.

Corrosion of Ceramics in Aqueous Hydrofluoric Acid

A variety of commercially available ceramic‐based oxides, carbides, nitrides, and borides were evaluated for chemical attack in an azeotropic aqueous hydrofluoric acid (HF) test protocol at 90°C. Weight change measurements and microstructure analysis showed that HF corrosion in polycrystalline ceramics generally occurred at grain boundaries by the dissolution of grain boundary phases although the bulk single crystal may inherently resist attack. Virtually all commercially prepared polycrystalline oxide ceramics (i.e., Al2O3, TiO2, ZrO2) and nonoxide ceramics (i.e., Si3N4, AlN, BN) were extensively corroded while polycrystalline pure carbides (i.e., SiC, TiC, B4C, WC) resisted corrosion. Equilibrium thermodynamic calculations show that these materials are soluble in HF; however, the kinetics of dissolution are slow enough in some cases to permit useful engineering lifetimes.

環境有害物質処理プロセスと装置材料 超臨界水環境におけるセラミックス材料の腐食

環境有害物質処理プロセスと装置材料 超臨界水環境におけるセラミックス材料の腐食

Kinetics of Sintering at a Constant Rate of Heating By Yusuke Moriyoshi and Wazo Komatsu.

Sintering is an extremely old technology, which has been used since prehistory. However, it is so complicated that a quantitative study just began to start in the 1950's. A theory for sintering in a simple model was separately derived by Frenkel, Kuczynski, Kingery, and Coble. They elucidated the mechanism of material transport in sintering by the rate of interface growth and distance between the centers of two spherical particles. The equation derived was successfully applied to the shrinkage data of powder compacts. Since then, these so-called log-log plots of data have been widely used by many researchers in order to elucidate the mechanisms of the sintering shrinkage.In such a situation, Moriyoshi and Komatsu pointed out that the log-log plot method was not necessarily suitable because of the effect of many factors such as the combined mechanisms of sintering, the size distribution of particles, particle shape, and so on. They reported this in a series of papers (Kinetics of Initial Sintering with Grain Growth, J. Am. Ceram. Soc., 53, No. 12, 621-675 (1970); Analysis of Initial Combined Sintering, Yogyo-Kyokai-Shi, 81 [3], 102-107 (1973); Initial Sintering of Glass, Yogyo-Kyokai-Shi, 82 [8], 426-429 (1974); A Method for Obtaining Surface Diffusion Coefficients from Initial Sintering Data, Yogyo-Kyokai-Shi, 86 [2], 130-136 (1978)), in which they suggested that various processes such as surface and volume diffusion, grain boundary and volume diffusion, and other processes proceeded concurrently during sintering. The above paper was the first one in the series, in which a different method was used to evaluate and to define a sintering mechanism. The paper also served as an important trial encouraging other sintering studies of ceramics.Moriyoshi and Komatsu pointed out that the method of log-log plots was not necessarily reliable and that the decision of a mechanism at the initial stage of sintering should be carried out by the comparison of activation energies obtained from sintering data with those obtained from the tracer diffusion of ions. From these viewpoints, they derived theoretically an equation to obtain activation energies from shrinkage data at a constant rate of heating. As a result, it was shown that activation energies of sintering shrinkage can be simply obtained with precision by using the equation derived. Then, they indicated that the activation energies obtained in the shrinkage data of ZnO, NiO, and Fe2O3 compacts were in good agreement with the values obtained from tracer measurements. Based on these results, they discussed the rate determining steps in the sintering process.This paper not only provides fundamental information to understand sintering processes such as sintering shrinkage, grain growth, and others, but also stimulates the studies concerning solid state reactions, erosion and corrosion of ceramics, creeps associated with ion diffusion, and so on. The study also gave basic information to fabricate ceramic materials.

Corrosion of ceramics in halogen-containing atmospheres

Most single component oxide ceramics undergo active corrosion in halogen-containing gases such as HCl to form gaseous corrosion products only. At high temperatures, such corrosion reactions are controlled by gaseous diffusion of the product gases away from the solid surface. As a result, the reaction kinetics and the corrosion rate can be predicted if the thermodynamics of the reaction are known. Similar behaviour is expected for nitride ceramics. However, several multicomponent oxides, typified by NiAl2O4, and carbides may react to form a porous solid product layer through which diffusion takes place and controls the corrosion rate. Nevertheless, even in these cases, if gaseous diffusion still controls, the rate of corrosion can be modeled and predicted.

Strong Effects of Electrochemical Polarization on Corrosion of Ceramics in Molten Glass

Strong Effects of Electrochemical Polarization on Corrosion of Ceramics in Molten Glass

Material Specifications of Advanced Ceramics and Other Issues in the Use of Property Databases with Corrosion Analysis Models

Abstract The growing interest in linking analysis models with distributed materials property databases gives rise to new database design requirements. This paper discusses the conditions encountered in the modeling of the corrosion of a ceramic material as a time-dependent phenomenon. In the corrosion of ceramics, numerous distinct contributing processes occur in different regions of the specimen simultaneously. These different regions usually have different compositions, native microstructures, and environmentally intrusive agents. Both predictive modeling efforts and post-test diagnostic analyses, therefore, require chemical and physical property data that are related to the specific material substructures. There are significant problems in the practice of representing such information in general-purpose materials property databases. The essential issues pertain to the form of the representation, the accessibility of the data, and the uniqueness of the value set. This paper addresses these issues in the context of a multipurpose database into which access is needed by an automated, external, analysis program. The corrosion of silicon carbide is used as a prototypic case in discussing the standards for the database, the expectations of the user, and the implications of the practical design of the property database. It is concluded that the required analysis tools include the model with constraints on the material and the environment, a property database that distinguishes the material's substructure types and locations, a reactions database for all significantly reacting species in the system, and an expert system interface to assess the performance level options available by means of the property data.

Corrosion of Ceramics in Halogen-Containing Atmospheres

Abstract Most single component oxide ceramics undergo active corrosion in halogen-containing gases such as HCl to form gaseous corrosion products only. At high temperatures, such corrosion reactions are controlled by gaseous diffusion of the product gases away from the solid surface. As a result, the reaction kinetics and the corrosion rate can be predicted if the thermodynamics of the reaction are known. Similar behaviour is expected for nitride ceramics. However, several multicomponent oxides, typified by NiAl2O4, and carbides may react to form a porous solid product layer through which diffusion takes place and controls the corrosion rate. Nevertheless, even in these cases, if gaseous diffusion still controls, the rate of corrosion can be modeled and predicted.

The Corrosion of Ceramics: Where Do We Go from Here?

The Corrosion of Ceramics: Where Do We Go from Here?

‘Corrosion of ceramics’

‘Corrosion of ceramics’

Fracture strength, surface roughness and corrosion of ceramics

Fracture strength, surface roughness and corrosion of ceramics

Use of Raman Spectroscopy for Determining the Corrosion of Ceramics in Molten Fluorides

Use of Raman Spectroscopy for Determining the Corrosion of Ceramics in Molten Fluorides

High Temperature Corrosion of Ceramics

This book describes high temperature corrosion of ceramics. The materials investigated in this particular study were silica, alumina, silicon nitride and silicon carbide. In addition to the pure single crystals or CVD materials, typical engineering materials of various purities have been included in the study.