High-temperature corrosion of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho)environmental barrier coating materials by volcanic ash

Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine blades.Notably,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EBC due to its coefficient of thermal expansion(CTE)compatible with substrates and high resistance to water vapor corrosion.The target operating temperature for next-generation tur bine blades is 1400°C.Corrosion is inevitable during adhesion to molten volcanic ash,and thus,understanding the corrosion behavior o the material is crucial to its reliability.This study investigates the high-temperature corrosion behavior of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho).Samples were prepared using a solid-state reaction and hot-press method.They were then exposed to volcanic ash at 1400°C for 224,and 48 h.After 48 h of exposure,volcanic ash did not react with Yb_(2)Si_(2)O_(7)but penetrated its interior,causing damage.Meanwhile Ho_(2)Si_(2)O_(7)was partially dissolved in the molten volcanic ash,forming a reaction zone that prevented volcanic ash melts from penetrating the interior.With increasing heat treatment time,the reaction zone expanded,and the thickness of the acicular apatite grains increased The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb_(2)Si_(2)O_(7)but decreased considerably over time for Ho_(2)Si_(2)O_(7).Th Ca in volcanic ash was consumed and formed apatite,indicating that RE^(3+)ions with large ionic radii(Ho>Yb)easily precipitated apatit from the volcanic ash.

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.

Using zircon saturation thermometry of source magma in strongly altered volcanic ashes

The present study deals with the possibilities of applying the zircon saturation thermometry, which is based on the equilibrium between the zircon crystals and the melt, to strongly altered volcanic ashes—bentonites. It proposes an alternative to a widely used method of calculating magma temperature from Zr content and major component composition(Boehnke in Chem Geol351:324–333, 2013), that is not suitable for bentonites, as most of the major components have been largely altered in these rocks. For calculating source magma temperatures in strongly altered volcanic ashes, the exponential function from the Zr(ppm)/Al_(2)O_(3)(%) ratio with compositional corrections from the TiO_(2)/Al_(2)O_(3) ratio was found applicable. The idea to use the ratios of these elements is based on the low mobility of these elements in the earth’s surface conditions. Temperatures of magma, forming in the partial melting process, are assessed from the bulk rock composition. Pre-eruption temperatures were estimated from the composition of fine fractions of bentonites. The accuracy of the new method was established from comparison with the method by Boehnke et al.(Chem Geol 351:324–333,2013). The difference between the two methods was mostly less than ± 30° to ± 50°. The comparison with the magma temperature, estimated from the sanidine composition,revealed 13° lower values on average. Although the proposed method for estimating the source magma temperatures is less precise than the method of accounting for detailed rock compositions, it can be used in strongly altered rocks, where other methods are not usable. The new method still enables differentiation between felsic source magmas originating at low or high temperatures. Early Palaeozoic bentonites in the Baltic Basin can be divided,according to the source magma temperatures, into two types:(1) Low temperature(650–790 ℃), containing potassium-rich sanidine and abundant biotite(S type),(2)high temperature(770–850 ℃) with sodium-rich sanidine and scarce biotite(I type).

STUDY ON THE STRUCTURE OF ARTIFICIAL SILICA FUME AND THE ACTIVITY OF VOLCANIC ASH

The present experimental technique is used to study the image, crystal phase, pore structure and microstructure of artificial silica fume, and the experimental results show that artificial silica fume is a non-crystalline and porous matter with a high specific surface area and the high activity of volcanic ash. Therefore, it is a type of ideal material which can replace silica fume. (Author abstract) 5 Refs.

Sedimentary environment shift and organic matter enrichment mechanism in response to volcanic ash influence:A case study of the Permian Lucaogou Formation,Santanghu Basin,NW China

The second member of the Lucaogou Formation(P_(2)l_(2))in the Tiaohu and Malang Sags of the Santanghu Basin(study area)underwent periodic volcanic activity and frequent lithological changes.This study comprehensively analyzed the organic geochemistry,mineral composition,organic matter(OM)types,volcanic cycle,and palaeoenvironment of shale in the study area.Techniques such as total organic carbon(TOC),rock pyrolysis(Rock-Eval),organic petrology,scanning electron microscopy(SEM)with energydispersive spectrum(EDS)analysis,X-ray diffraction(XRD),trace elements,and saturated hydrocarbon gas chromatography and mass spectrometry(GC-MS)were employed.The findings suggest that limited terrigenous input during the sedimentary period of the P_(2)l_(2) led to the deposition of a distinctive mixture of volcanic ash(felsic)and carbonate(dolomite and calcite),with a low average clay mineral content of 6%.The P_(2)l_(2) shale emerged as a high-quality source rock,predominantly composed of type I and II kerogens,with moderate OM maturity.The deposition environment was characterized by hot and arid conditions,high salinity,and intensive reducibility,which was favorable for algae development and conducive to OM preservation.Notably,two lamalginite types,labeled as lamalginite“A”and lamalginite“B,”were identified.Lamalginite“B”-rich shales were deposited in a hotter and drier climate compared to lamalginite“A”-rich shales.Lamalginite“B”-rich shale inexhibited high levels of C_(28)regular sterane andβ-carotenes,distinguishing it from lamalginite“A”-rich shale.A comprehensive analysis involving organic petrology,SEM,sedimentary environment,and biomarker characteristics suggests that lamalginite“B”may be a salt-tolerant green alga,while lamalginite“A”may be a cyanobacterium.Finally,an OM enrichment model for the P_(2)l_(2) shale was established.

Satellite remote sensing of volcanic ash cloud in complicated meteorological conditions

Volcanic ash cloud has serious impacts on aviation.With volcanic ash dispersion,it also has a profound and long-term impact on climate and the environment.A new volcanic ash cloud detecting method (SWIR-TIR Volcanic Ash method,STVA) is presented that uses satellite images of Medium Resolution Spectral Imager (MERSI) and Visible and Infrared Radiometer (VIRR) on board the second generation Polar-Orbiting meteorological satellite of China (FY-3A).STVA is applied in detecting Iceland's Eyjafjallajokull volcano eruption.Compared with the traditional Split Window Temperature Difference method (SWTD),the results show that STVA is more sensitive to volcanic ash cloud than SWTD and can fairly extract volcanic ash information from the background of meteorological cloud and the ocean.Ash Radiance Index (ARI) and Absorbing Aerosol Index (AAI) derived from Metop-A satellite images are used to validate the performance of STVA.It is shown that STVA provides similar results with ARI and AAI.FY-3A/MERSI,VIRR and Terra /MODIS data are used to test STVA and SWTD.It is demonstrated that STVA derived from FY-3A satellite data is more effective in complicated meteorological conditions.This study shows great potential of using China's own new generation satellite data in future global volcanic ash cloud monitoring operation.

Retrieval of Volcanic Sulfate Aerosols Optical Parameters from AHI Radiometer Data

This paper presents a method for retrieving optical parameters from volcanic sulfate aerosols from the AHI radiometer on board the Himawari-8 satellite.The proposed method is based on optical models for various mixtures of aerosol components from volcanic clouds,including ash particles,ice crystals,water drops,and sulfate aerosol droplets.The application of multi-component optical models of various aerosol compositions allows for the optical thickness and mass loading of sulfate aerosol to be estimated in the sulfuric cloud formed after the Karymsky volcano eruption on 3 November 2021.A comprehensive analysis of the brightness temperatures of the sulfuric cloud in the infrared bands was performed,which revealed that the cloud was composed of a mixture of sulfate aerosol and water droplets.Using models of various aerosol compositions allows for the satellite-based estimation of optical parameters not only for sulfate aerosol but also for the whole aerosol mixture.

Effect of interfacial properties on mechanical stability of ash deposit

The paper presents a study on the cohesion of volcanic ash particles using surface free energy determination and zeta potential analyses.This is a subject of great interest in physical volcanology,as many researches on volcanic particle aggregation are frequently reported.In this case,special attention is paid to the role of structural or hydration forces between hydrophilic surfaces,which are a consequence of the electron-donor/electron-acceptor character of the interface.From this point of view,the results are potentially interesting as they could give valuable insights into this process.The results are presented in terms of the total energy of interaction between dispersed particles,computed from the extended DLVO theory.Contributions to the total free energy of interaction were determined from the zeta potential and surface free energy of ash,measured under different experimental conditions.Two samples of basaltic volcanic ash(black and white)with silica contents of 44% and 63% respectively are studied.The surface free energy and zeta potential were analysed for ashes immersed in different electrolytes(NaCl,CaCl,FeCl).The presence of electrolytes changes the surface properties of the solid materials.The analysis of total interaction energy between the ash particles in aqueous medium shows that soil cohesion strongly depends on ash surface properties,chemical nature,the adsorbed cation on the surface,and p H value.

Impact of volcanism on the formation and hydrocarbon generation of organic-rich shale in the Jiyang Depression, Bohai Bay Basin, China

Globally,most organic-rich shales are deposited with volcanic ash layers.Volcanic ash,a source for many sedimentary basins,can affect the sedimentary water environment,alter the primary productivity,and preserve the organic matter(OM)through physical,chemical,and biological reactions.With an increasing number of breakthroughs in shale oil exploration in the Bohai Bay Basin in recent years,less attention has been paid to the crucial role of volcanic impact especially its influence on the OM enrichment and hydrocarbon formation.Here,we studied the petrology,mineralogy,and geochemical characteristics of the organic-rich shale in the upper submember of the fourth member(Es_(4)^(1))and the lower submember of the third member(Es_(3)^(3))of the Shahejie Formation,aiming to better understand the volcanic impact on organic-rich shale formation.Our results show that total organic carbon is higher in the upper shale intervals rich in volcanic ash with enriched light rare earth elements and moderate Eu anomalies.This indicates that volcanism promoted OM formation before or after the eruption.The positive correlation between Eu/Eu*and Post-Archean Australian Shale indicates hydrothermal activity before the volcanic eruption.The plane graph of the hydrocarbon-generating intensity(S1+S2)suggests that the heat released by volcanism promoted hydrocarbon generation.Meanwhile,the nutrients carried by volcanic ash promoted biological blooms during Es_(4)^(1 )and Es_(3)^(3) deposition,yielding a high primary productivity.Biological blooms consume large amounts of oxygen and form anoxic environments conducive to the burial and preservation of OM.Therefore,this study helps to further understand the organic-inorganic interactions caused by typical geological events and provides a guide for the next step of shale oil exploration and development in other lacustrine basins in China.

The petrological characteristics and signif icance of organic-rich shale in the Chang 7 member of the Yanchang Formation,south margin of the Ordos basin,central China

The organic-rich shale of the Chang 7 member is the most important source rock in the Ordos basin.The sedimentary environment and the controlling factors of organic matter enrichment,however,are still in contention.In this investigation,the Yishicun outcrop,located on the south margin of the Ordos basin,has been considered for the study.X-ray diffraction,polarizing microscopy,field emission scanning electron microscopy and cathodoluminescence(CL)were used to investigate the petrological features of the organic-rich shale.The content of volcanic ash and the diameter of pyrite framboid pseudocrystals were measured to illustrate the relationship between oxygen level,ash content and the enrichment of organic matter.It has been found that the diameter of pyrite framboid pseudocrystals has a strong correlation with the total organic carbon,demonstrating that the redox status degree of the water column has a positive impact on the enrichment of organic matter.Additionally,with an increase in the ash content,the content of organic matter increased at first and then decreased,and reached a maximum when the ash content was about 6%,illustrating that the ash input has a double effect on the enrichment of organic matter.

Black shale formation enviro nment and its control on shale oil enrichment in Triassic Chang 7 Member,Ordos Basin,NW China

Based on geochemical analysis results of core samples from the Triassic Chang 7 Member of Well Feng 75 drilled in the northwest margin of Ordos Basin,combined with geological characteristics of this region,the formation environment of the black shale and its control on shale oil enrichment are comprehensively studied.From the Chang 73 to Chang 71 Sub-members,the black shale have organic carbon contents decreasing from 5.70%to 3.55%,hydrogen indexes decreasing from 345 mg/g to 269 mg/g,while the oxygen indexes increasing gradually from 6 mg/g to 29 mg/g,indicating that the sedimentary environment during the depositional period of Chang 72 and Chang 73 Sub-members was anoxic.Biomarkers in the black shale change regu-larly,and have an obvious“inflection point”at the depth of 2753–2777 m in the Chang 73 Sub-member,indicating that the input of terrigenous organic matter increased.However,there is a negative drift about 2%of organic carbon isotopic composition near the“inflection point”,which is in conflict with the results of biomarker compounds.This is because the extreme thermal and anoxic events caused by continental volcanic activity in the ancient Qinling region caused negative drift of carbon isotopic composition of the black shale in the Ordos Basin.The volcanic activity caused rise of temperature,polluted air,extreme weathers,more floods and thus more input of terrigenous organic matter,and gave rise to extremely anoxic environment con-ducive to the preservation of organic matter.Terrigenous organic matter is more conducive to the formation of light oil than aquatic organic matter,so these sections in Yanchang Formation are major“sweet spots”for shale oil enrichment.

USE OF INDUSTRIAL WASTE OF PERLITE IN BUILDING MATERIALS INDUSTRY

We have observed the components, structure and properties of perlite ore. Through a series of ex- periments, it has been proved that the perlite has higher pozzolanic activity and maybe used as addi- tion of cement in manufacturing pozzolanic cement. The paper also proposes the way to increase the early strength of this kind of cement and utilize it to make many kinds of silicate concrete products.

Seasonal Change in CO2 Production Rate along Depth in a Grassland Field

Soil is a large terrestrial carbon pool so that the evaluation and prediction of soil respiration is important for understanding and managing carbon cycling between the pedosphere and the atmosphere. For better understanding about characteristics and mechanisms of soil respiration, this study monitored seasonal behaviors of soil gaseous CO2 concentration profile with relevant soil physical conditions in a meadow field, and numerically analyzed the monitored data sets to inversely determine time-series of depth distributions of CO2 production rate in the field by assuming optimum ranges of depth and moisture condition for aerobic respiration of soil fauna and flora. The results of the inverse analyses showed that the depth range of intense CO2 production resided in top soil layers during summer and moved down into subsoil layers in winter, implying that the depth range of main CO2 sources can change dynamically with seasons. The surface CO2 emission rates derived from the inverse analyses fell in the range typically found in the same kind of land use. The evaluated mean residence time of gaseous CO2 in the study field was around half a day. These findings suggested that the modelling assumptions about soil respiration in this study are effective to probe spatial and temporal behavior of respiratory activity in a soil layer, and it is still important to integrate facts about in-situ CO2 concentration profiles with soil physical parameters for quantitatively predicting possible behaviors of soil respiration in response to hypothetical changes in atmospheric and soil climates.

Effects of yttria content on the CMAS infiltration resistance of yttria stabilized thermal barrier coatings system

The effects of YO(1.5)doping in yttria-zirconia based thermal barrier coatings(TBCs)against CMAS interaction/infiltration are discussed.The TBCs with an YO(1.5)content ranging from 43–67 mol.%(balance Zr O2)were produced by electron beam physical vapor deposition(EB-PVD)techniques.The results reveal a trend of higher apatite formation probability with the higher free YO(1.5)available in the yttriazirconia system.Additionally,the infiltration resistance and amount of consumed coating appears to be strongly dependent on the YO(1.5)content in the coating.The thinnest reaction layer and lowest infiltration was found for the highest produced 67 YO(1.5)coating.Complementary XRD experiments with volcanic ash/YO(1.5)powder mixtures with higher yttria contents than in the coatings(80 YO(1.5)and pure YO(1.5))also showed higher apatite formation with respect to increasing yttria content.The threshold composition to promote apatite-based reaction products was found to be around 50 YO(1.5)in zirconia which was proved in the coatings and XRD powder experiments.An YO(1.5)-ZrO2-Fe O-TiO2 bearing zirconolite-type phase was formed as a reaction product for all the coating compositions which implicates that TiO2 in the melt acts as a trigger for zirconolite formation.This phase could be detrimental for CMAS/volcanic ash infiltration resistance since it can be formed alongside with apatite which controls or limits the amount of Y^(3+)available for glass crystallization.The Fe rich garnet phase containing all the possible elements exhibited a slower nucleation compared to apatite and its growth was enhanced with slow cooling rates.The implications of phase stability and heat treatment effects on the reaction products are discussed for tests performed at 1250°C.