Alkali Metal Content Research Articles

11.88% Efficient Flexible Ag-Free CZTSSe Solar Cell: Spontaneously Tailoring the Alkali Metal Level.

Alkali metal is the requirement for highly efficient Cu2ZnSn(S, Se)4 (CZTSSe) solar cells, thus it is crucial to additionally incorporate alkali metal into the absorber layer for flexible solar cells. However, the efficiency of flexible CZTSSe devices reported to date, based on the conventional alkali incorporation strategies, still lags behind those made on rigid substrates. One of the main issues is the inability to control the alkali content and distribution in the absorber layer. Here, a facile alkaline incorporation approach is proposed, effectively regulating the content and distribution of alkali metals in the film. Such a method can spontaneously tailor the alkali metal content to a proper level, thus leading to the suppression of non-radiative recombination and a better carrier transport through the enhanced film quality and the optimized band binding structure. Finally, a champion flexible CZTSSe solar cell with an efficiency of 11.88% is achieved, the highest reported efficiency for a CZTSSe solar cell without noble Ag doping. This study affords an innovative spontaneous alkali-doping design for the preparation of high-performance flexible CZTSSe solar cells and provides a deeper insight into the extent of alkali metal doping.

Effects of different low-temperature pyrolysis treatments on the biotoxicity of biochar derived from tobacco stalks

The pyrolytic treatment of tobacco stalk (TS) waste results in the production of a large amount of biochar, which is usually used for environmental remediation. However, little attention has been given to the effects of different pyrolysis methods on the biotoxicity of TS biochar. This study examined the effects of three different pyrolysis methods at 350 °C (fast pyrolysis, slow pyrolysis, and low-temperature carbonization) on the biotoxicity of TS biochar (Escherichia coli (E. coli) growth and wheat germination). The results revealed that the dissolved organic matter (DOM) of the three types of biochar promoted the growth of E. coli, and the maximum growth of E. coli was ranked as DOM-F350 > DOM-S350 > DOM-350. However, the DOM inhibited the growth of the wheat seeds, with the growth index (below 0.8) of the wheat seeds ranked as DOM-350 > DOM-F350 > DOM-S350. The alkali metal content, pH and humus-like substance content of biochar may be responsible for the biotoxicity of biochar through various mechanisms. In addition, TS-S350 exhibited greater biotoxicity than did TS-F350 because of the greater content of toxic nitrogen-containing organic compounds. These findings can provide reliable theoretical guidance for the effective management and safe utilization of TS waste.

Corrosion behavior of co-gasification slag of furfural residue and coal on alumina-silica refractories

Gasification of furfural residue with coal can realize its efficient and clean utilization. But the high alkali metal content in furfural slag is easy to cause the corrosion of gasifier refractory. Two gasification coals with different silica alumina ratio and a furfural residue were selected in the study. The effects of furfural residue additions on corrosion of silica brick, corundum brick, high alumina brick and mullite brick were investigated by using XRD, SEM-EDS and Factsage Software, and the corrosion mechanism was analyzed. With increasing furfural residue addition, the permeability of the slags to high-aluminium-bearing refractories first decreases and then increases, while the permeability on silica brick shows a slight decrease trend. Leucite (KAlSi2O6) with high-melting temperature is generated from the reaction of K2O and SiO2 in slag with Al2O3 in refractories after furfural residue is added, which hinders the infiltration of slag in refractories. Kaliophilite (KAlSiO4) of low-melting point is formed when K2O content increases, and this contributes to the infiltration of slag in refractories. The acid-base reaction between slag and silica brick is distinctly occurred, more slag reacts with SiO2 in the silicon brick, resulting in a decrease in the amount of slag infiltrating into the silicon brick as furfural residue is added. The corrosion of silica brick is mainly caused by the acid-base reaction, while the corrosion of three alumina based refractory bricks of corundum, mullite and high alumina brick is determined by slag infiltration. A linear correlation between the percolation rate and slag viscosity is established, the slag permeability increases with decreasing viscosity, resulting in stronger permeability for the high Si/Al ratio slag with lower viscosity.

Experimental constraints on the role of temperature and pyrogenic mineral assemblage in wildfire-induced major and trace element mobilisation

Wildfires impact a large and increasing proportion of the Earth’s surface. With documented soil surface temperatures of up to ∼850 °C, wildfires may fundamentally alter the mineralogy and geochemistry of soils and regolith, more conventionally thought to be dominated by low temperature weathering processes. Here we use an experimental approach to test the effect of temperature on the formation of pyrogenic minerals, and on the distribution and mobility of major, trace and rare earth elements following post-fire chemical weathering. We focus on ferruginous nodules, common Fe-oxide cemented components of soils, which transform from non-magnetic to maghemite-bearing, magnetic nodules under wildfire conditions. These transformations provide a valuable record of fire impacts and facilitate the study of thermal processes and element mobility. Our results show heating produces a typical pyrogenic mineral assemblage of hematite, maghemite, metakaolin and transition alumina. At 900 °C the high temperature Fe2O3 polymorph luogufengite forms, which has never been reported in natural fire-affected substrates and therefore places an upper boundary on palaeowildfire temperatures at the soil-fire interface. Chemical leaching, employed to simulate the impacts of post-fire weathering, demonstrates that formation and subsequent breakdown of these pyrogenic minerals results in increased mobility of several elements including Li, Si, Sc, Cr, Co, Cu, Zn, Rb, Cs, La, Pb and U. Further, we propose that incongruent dissolution of pyrogenic metakaolin may be responsible for the formation of fusic material, an aluminous cement commonly found in soils. We conclude by discussing the significance of these results for the release of potentially toxic metals following a fire, identify trace elements that have the greatest potential to be used as palaeowildfire geochemical proxies (decreased alkali metal concentrations, decreased U/Th ratios, and decreased La compared to other rare earth elements), and the potential impact of wildfire on global geochemical cycles.

Biochar Derived from Sewage Sludge: The Impact of Pyrolysis Temperature on Chemical Properties and Agronomic Potential

The rising volume of sewage sludge from urbanization poses substantial environmental and public health concerns, underscoring the urgency for the implementation of effective waste management strategies. The objective of this study was to evaluate the influence of pyrolysis temperature on the chemical composition and agronomic potential of biochar derived from sewage sludge. The pyrolysis process was conducted at temperatures ranging from 400 °C to 800 °C, and the resulting biochar was analyzed for pH, electrical conductivity, metal content, and carbon fractions. Additionally, phytotoxicity tests were conducted to assess the impact of the biochar on plant germination. The findings indicated that elevated pyrolysis temperatures resulted in an elevated alkalinity, electrical conductivity, and concentration of alkali metals in the biochar. Conversely, these processes resulted in a reduction in total organic carbon content and an increase in heavy metal content, which may limit the potential for biochar to be used in agricultural applications. The phytotoxicity tests indicated that the biochar produced at lower temperatures (400 °C) exhibited positive effects on plant growth when administered at doses of 5 and 10 t·ha−1. Conversely, the biochar produced at higher temperatures (800 °C) demonstrated significant toxicity. The findings indicate that the pyrolysis temperature is a critical factor in determining the suitability of biochar for agricultural applications. The production of biochar at lower temperatures may offer agronomic benefits, whereas the use of higher temperatures increases stability but is associated with the risk of higher heavy metal concentrations.

Formic and lactic acids from the conversion of xylose with the use of modified clinoptilolite by sonication

AbstractBACKGROUNDA material of natural origin, clinoptilolite, was modified with selected metals in order to obtain a catalyst for the conversion of xylose – the main component of the hemicellulose fraction present in lignocellulosic biomass – to selected carboxylic acids.RESULTSThe starting material without modification (0‐parent), the hydrogen form (0‐hydrogen) of zeolite and zeolite after hierarchization with hydrochloric acid (0‐dealuminated) were used. Iron, copper and cobalt ions were introduced as active centers using the sonication technique. The catalytic process was carried out in a pressure autoclave for 2 h at a temperature of 220 °C. Compounds such as formic acid with a yield of 91% (0‐parent) and lactic acid with a yield of 66.1% (Fe‐hydrogen) were obtained.ConclusionThe catalytic processes carried out using xylose lead to the obtaining of a mixture of carboxylic acids: lactic acid, pyruvic acid and formic acid. An important role here is played by the presence of iron as an active site, which leads to the transformation of xylose into lactic acid by dehydration, and the presence of Lewis and Brønsted active sites. In the case of formic acid, which has never been reported in publications on a similar topic, the starting zeolite without modification contributed to its preparation. It is possible that the content of alkali metals contributed to its preparation along with the coupling of the oxidation reaction of the intermediate product, because of the presence of small amounts of iron, which are present in the natural material. © 2024 Society of Chemical Industry (SCI).

A Metatitanic Acid Particulate Xerogel: Green Synthesis, Structure Determination, and Detailed Characterization.

The manuscript focuses on an original method of preparation of metatitanic acid when only environmentally safe base substances are used in the synthesis process. The synthesis is based on the reaction of solid titanyl sulfate in an aqueous solution of sodium hydroxide. This method allows for (i) a full preservation of the morphology of the starting titanyl sulfate and (ii) a preparation of metatitanic acid substances with specific parameters. This can be achieved via a precise control of the alkali metal/titanyl sulfate ratio resulting in substances with varying contents of alkali metals or even sulfate anions. The prepared metatitanic acid then also contains very small weakly crystalline particles (2-3 nm) and forms pseudomorphic aggregates whose shape and dimensions correspond to those of the starting titanyl sulfate. These aggregates exhibit regular nanoporosity with a high surface area of up to 500 m2·g-1, have no tendency to form colloids, and are mechanically highly resistant even by high-energy ultrasound. The characterization of the resulting products is done via their chemical composition and methods of structural analysis, as well as by electron microscopy and local analysis. The mechanism of product formation is discussed based on the structure of the precursor, including the so far unknown structure of metatitanic acid.

In-situ measurement of alkali metal concentrations and temperatures during the incineration of municipal solid waste and sludge

The release of alkali metals in municipal solid waste (MSW) incineration caused corrosion of thermal equipment and slagging in incinerator. By using a spectrometer and multispectral camera, the concentrations of Na and K, flame temperatures and emissivities in an industrial incinerator with different proportions of food waste, sludge, waste paper and waste fabric were measured in this study. The flame temperatures on the left wall decreased from 1479.5 K to 1366.2 K as the height increased from 13.4 m to 16.9 m. Flame temperatures near the left side of the incinerator were 8.9 % higher than those near the right side, which were caused by the ununiform distribution of MSW. The concentrations of Na and K increased by 67.16 % and 86.9 % with the primary air flow increased by 3969.35 t/h. The average concentrations of Na and K at 16.9 m of the left wall decreased by 25.87 % and 37.53 % with the decreasing of food waste and increasing of sludge. The Na and K contents in fixed carbon were greater than those in volatile matter and ash in fuels. Compared with waste paper and waste fabric, the blending of sludge with food waste was more effective on reducing the release of Na and K. When the proportion of food waste: sludge was set as 8:2, the lowest releases of Na 20.75 ppm and K 5.30 ppm existed in the incineration of food waste and sludge. The concentrations of Na and K decreased by 17.3 % and 46.9 % with the increasing of waste paper, the waste paper was a better alternative to sludge when mixed with MSW.

Beyond microwave susceptors: Exploring 5525 MHz frequency for efficient biomass pyrolysis

The transition from fossil fuels to renewable energy sources necessitates innovative approaches to biomass utilization. Despite the recognized benefits of microwave-assisted biomass pyrolysis, the reliance on costly microwave susceptors poses challenges. This study centers on the innovative utilization of a variable-frequency microwave approach, particularly at 5525 MHz, eliminating the need for microwave susceptors. Remarkably, at this frequency, corn stalk pyrolysis achieved a temperature of 589 °C with a rapid heating rate of 327.7 °C/min, showcasing a 69.5% conversion rate without susceptors. Furthermore, the study investigated the interplay between microwave frequency and alkali metal content, revealing a direct correlation between K+ and biomass conversion rates. Our findings highlight the transformative potential of 5525 MHz in biomass pyrolysis, offering a cost-effective and environmentally friendly alternative to microwave susceptors, with implications for sustainable energy and industrial applications.

Review on Mercury Control during Co-Firing Coal and Biomass under O2/CO2 Atmosphere

Combining biomass co-firing with oxy-fuel combustion is a promising Bioenergy with Carbon Capture and Storage (BECCS) technology. It has the potential to achieve a large-scale reduction in carbon emissions from traditional power plants, making it a powerful tool for addressing global climate change. However, mercury in the fuel can be released into the flue gas during combustion, posing a significant threat to the environment and human health. More importantly, mercury can also cause the fracture of metal equipment via amalgamation, which is a major risk for the system. Therefore, compared to conventional coal-fired power plants, the requirements for the mercury concentration in BECCS systems are much stricter. This article reviews the latest progress in mercury control under oxy-fuel biomass co-firing conditions, clarifies the impact of biomass co-firing on mercury species transformation, reveals the influence mechanisms of various flue gas components on elemental mercury oxidation under oxy-fuel combustion conditions, evaluates the advantages and disadvantages of various mercury removal methods, and finally provides an outlook for mercury control in BECCS systems. Research shows that after biomass co-firing, the concentrations of chlorine and alkali metals in the flue gas increase, which is beneficial for homogeneous and heterogeneous mercury oxidation. The changes in the particulate matter content could affect the transformation of gaseous mercury to particulate mercury. The high concentrations of CO2 and H2O in oxy-fuel flue gas inhibit mercury oxidation, while the effects of NOx and SO2 are dual-sided. Higher concentrations of fly ash in oxy-fuel flue gas are conducive to the removal of Hg0. Additionally, under oxy-fuel conditions, CO2 and metal ions such as Fe2+ can inhibit the re-emission of mercury in WFGD systems. The development of efficient adsorbents and catalysts is the key to achieving deep mercury removal. Fully utilizing the advantages of chlorine, alkali metals, and CO2 in oxy-fuel biomass co-firing flue gas will be the future focus of deep mercury removal from BECCS systems.

Suppressing Deep-Level Trap Toward Over 13% Efficient Solution-Processed Kesterite Solar Cell.

Cu2ZnSn (S,Se)4 (CZTSSe), a promising absorption material for thin-film solar cells, still falls short of reaching the balance limit efficiency due to the presence of various defects and high defect concentration in the thin film. During the high-temperature selenization process of CZTSSe, the diffusion of various elements and chemical reactions significantly influence defect formation. In this study, a NaOH-Se intermediate layer introduced at the back interface can optimize Cu2ZnSnS4 (CZTS)precursor films and subsequently adjust the Se and alkali metal content to favor grain growth during selenization. Through this back interface engineering, issues such as non-uniform grain arrangement on the surface, voids in bulk regions, and poor contact at the back interface of absorber layers are effectively addressed. This method not only optimizes morphology but also suppresses deep-level defect formation, thereby promoting carrier transport at both interfaces and bulk regions of the absorber layer. Consequently, CZTSSe devices with a NaOH-Se intermediate layer improved fill factor, open-circuit voltage, and efficiency by 13.3%. This work initiates from precursor thin films via back interface engineering to fabricate high-quality absorber layers while advancing the understanding regarding the role played by intermediate layers at the back interface of kesterite solar cells.

Computational Investigation of Carbon Based Anode Materials for Li- and Post-Li- Ion Batteries.

Due to its negligible capacity with respect to sodium intercalation, graphite is not suited as anode material for sodium ion batteries. Hard carbon materials, on the other hand, provide reasonably high capacities at low insertion potential, making them a promising anode materials for sodium (and potassium) ion batteries. The particular nanostructure of these functionalized carbon-based materials has been found to be crucially linked to the material performance. However, there is still a lack of understanding with respect to the functional role of structural units, such as defects, for intercalation and storage. To overcome these problems, the intercalation of Li, Na, and K in graphitic model structures with distinct defect configurations has been investigated by density functional theory. The calculations confirm that defects are able to stabilize intercalation of larger alkali metal contents. At the same time, it is shown that a combination of phonon and band structure calculations are able to explain characteristic Raman features typically observed for alkali metal intercalation in hard carbon, furthermore allowing for the quantification of the alkali metal intercalation inbetween the layers of hard carbon anodes.

Aluminum‐Based Chalcopyrite Thin Films and Solar Cells

AbstractAluminum‐based chalcopyrite materials have attracted attention because of the wide controllability range of their material properties and potential for use in energy‐conversion devices. Herein, CuAlSe2‐based thin‐film growth and solar cell device properties are discussed. Ternary CuAlSe2 thin films are relatively unstable and decompose weeks after film growth, even when preserved in a dry box. However, alloying with elemental In led to significant improvements in stability. Cu(In,Al)Se2 (CIAS) solar cells yield better photovoltaic performance than CuInSe2 cells, although the effective range of Al concentration that can improve device performance is narrower than that of elemental Ga in Cu(In,Ga)Se2 (CIGS). A decrease in the alkali metal concentration in CIAS films with increasing Al concentration is observed, indicating that the formation energy of alkali‐metal substitutional defects on the Cu site is high, and/or Al‐related complex defects formed are kinetically stable and difficult to replace with alkali metals once they form. Although the direct observation of alkali metals in the bulk (grain interior) of chalcopyrite CuInSe2 and CIGS films has been difficult to date, this result can serve as indirect evidence of the presence of alkali metals in the bulk of CuInSe2 films.

Feasibility analysis and environmental impact evaluation of biochar derived from mango pit for blast furnace injection

Biochar, produced by the pyrolysis of carbon–neutral biomass, has great potential to replace pulverized coal (PC) injection in blast furnace (BF) ironmaking. Herein, this study aimed to develop a low-ash and low-alkali metal biochar from mango pit (MP) and evaluate its environmental impact as an alternative fuel for BF ironmaking. This paper first studied the feasibility of mango pit biochar (MPB) as an alternative fuel. Compared with other preparation conditions, MPB prepared at 600 °C for 60 min (MPB-600–60) had the most similar fuel performance to PC, which was confirmed by principal component analysis (PCA). Moreover, MPB-600–60 exhibited lower ash and alkali metal content compared to PC. The co-combustion experiment demonstrated that MPB-600–60 could promote the combustion of mixed fuel, and the optimal combustibility was achieved when the addition ratio of MPB-600–60 was 80%. Comprehensive life cycle assessment (LCA) revealed that the reduction of global warming potential (GWP) amounted to 220 kg CO2 eq/tHM if MPB 100% replaced PC. These results indicated that MPB could significantly reduce the greenhouse gas emissions and the environmental impact of BF ironmaking. This study provides a novel and promising approach for developing low-carbon and clean alternative fuels in BF ironmaking.

In-situ measurement of potassium and sodium concentrations in a 16 MW MSW incinerator employing the FES system

To comprehensively understand the release characteristics of alkali metals which can cause corrosion and slagging problems in municipal solid waste (MSW) incinerators, the temporal concentrations of sodium (Na) and potassium (K) in a 16 MW MSW incinerator were measured employing a calibrated flame emission spectroscopy (FES) system. The experimental results revealed that the concentrations of alkali metals increased first and then decreased from the left side to the right side of the MSW incinerator. The maximum concentrations of Na and K were 111 ppm and 184 ppm, respectively. The peak and average concentrations of K near the left wall were 27 % and 58 % higher than those near the right wall at the same height of the MSW incinerator, owing to the different combustion stages of the MSW. The differences of the peak and average concentrations of K at the different heights of the MSW incinerator were 33.7 % and 23.5 %, respectively. Moreover, a positive correlation between the concentration of alkali metals and flame temperature was confirmed during the char phase combustion stage. Since the primary air distribution pattern of MSW incinerator decreased form the left side to the right side, the concentration of alkali metals near the left wall was positively correlated with the primary air flow, and that near the right wall exhibited a positive correlation with the garbage caloric value. This research provided an effectual solution for in-situ measurement of alkali metal concentration and flame temperature in MSW incinerators.

Ash melting and slagging and residual K ion content in biomass pellet combustion

ABSTRACT Combustion of biomass pellets is an effective way to reduce greenhouse gas emissions and achieve carbon neutrality. However, the alkali metal content (represented by K) in ash directly affects its slagging behavior, which can corrode the reactor and shorten its service life. In this study, the ash fusion slag and residual K ion contents were investigated at different combustion times (2, 5, 10, 20, 30 and 60 min) and temperatures (600, 700, 800, 900 and 1000°C). At the same combustion temperature, the residual content of K ions in ash decreases as the combustion time increases; at the same combustion time, the residual content of K ions decreases as the combustion temperature increases. The addition of 5% CaO promotes K precipitation, but at 10% CaO addition, the K precipitation rate is less than that at 5% CaO addition, indicating that the addition of CaO is beneficial to K ion precipitation only within a certain range. Adding CaO also generates high-melting-substances, such as CaSiO3 and calcite, which improve the overall slag resistance of the fuel.

Devolatilization characteristics of a bio-residue (potato stems) with high contents of alkali metals and non-structural components – Influences of the washing pretreatment severity

A bio-residue (potato stems), rich in alkali metals and non-structural components, is subjected to hot (353 K) or acidic (0.1 mol/L hydrochloric acid) water washing. The acidic pretreatment is more effective for the demineralization, with alkalis reduced by 99 (powders) or 90 (particles) %, corresponding to organic matter dissolution around 35 or 17 wt%, respectively. The latter figures remain approximately the same for hot water washing (38 and 19 wt%) but alkalis are reduced only by 78 or 64 %. The leachate properties are significantly dependent on the solvent type and the residue granulometry, as indicated by thermogravimetric and SEM-EDX analysis. Washed bio-residues decompose at temperatures and with rates progressively increasing as the pretreatment becomes more severe (fine granulometry and acidic water washing). Multi-step global kinetics, previously developed for the untreated material and properly revisited to incorporate washing effects, reveals trends with important compositional changes. Despite starch dissolution, volatile product yields for the absolute peak rate zone increase by about 40–65 %, testifying augmented cellulose contents. The pectin compounds are almost eliminated, to the advantage of the shoulder rate zone, representing hemicellulose decomposition, with an increase in the volatile product yields around 22–78 %.

Ultrafast adsorption of hexavalent chromium from aqueous effluents using covalent triazine frameworks

We have synthesized low-cost high performance covalent triazine framework (CTF) through Schiff base reaction of melamine and terephthalaldehyde with different proportions of the reactants. The synthesized adsorbents showed excellent capacity for adsorption of Cr (VI) at acidic pH while almost negligible adsorption at higher pH. The adsorbent displays excellent reusability, with a little decrease in adsorption capacity with the increasing number of cycles. Moreover, Cr (VI) the adsorption is unaffected by the presence of 50–500 times higher concentration of alkali metal and halide ions in solution, while sulphate ions demonstrate shielding behavior decreasing the adsorption capacity. Mechanistic studies indicate electrostatic attractions, ion exchange and reduction being responsible for the adsorption mediated by abundant nitrogen sites that also imbibes the adsorbent with high capacity. The adsorbent was also utilized to recover chromium from an industrial electroplating effluent, which demonstrates applicability of material for practical applications.

Bonneville basin critical zones

Playa margin wetlands in the Bonneville basin are sustained by groundwater-fed brackish springs, which transport salts and other solutes into the playa basin. These wetlands are sensitive to changing water availability and quality, which are impacted by changing climate and land use, and whose sediments also provide important records of changing environmental conditions. Gastropods building their shells in these springs provide important recorders of water chemistry and may reflect changing aqueous conditions. In this paper, we analyze spring water chemistry, gastropod ecology and gastropod shell chemistry of Blue Lake (BL) and Horseshoe Springs (HRS), two groundwater-fed wetlands in the Great Salt Lake watershed. We report the physical parameters including pH, temperature, and specific conductivity across the spring pond at Horseshoe springs. There was a slight but statistically significant variation in these physical characteristics between the deeper and shallower parts of the pool, providing evidence that there are different subsite microclimates, which may impact the populations and the isotopic composition of gastropod shells. We measured gastropod population diversity amongst nearly 12,000 shells sampled at Horseshoe springs, finding low population diversity (Shannon’s Diversity Index of 0.432), although the populations of shallow and deep snails are slightly different. The dominant snail at HRS is the Pyrgulopsis which is imperiled, and we also note that we did not find living snails here. We evaluated the bulk shell variation of stable carbonate isotopes (δ13C, and δ18O) across sites and genera. We show that there were no significant subsite-level differences in gastropod δ13C compositions, suggesting that water depth and productivity were not impacting the isotopic signal. We found subsite- and genera-specific differences in snail δ18O compositions, which we interpret to be more dependent on the geography and microclimate of where the snail lived rather than the genera’s physiology (pulmonate versus gil-breathing). We report concentrations of alkali metals (Li, Na, K, Rb, Cs), alkali earth metals (Be, Mg, Ca, Sr, Ba), and metals and metalloids (Al, Sc, Mn, Fe, Cu, Ni, Zn, As) at spring site waters and in bulk shells as potential baseline data for interpreting future or past environmental changes as recorded in shell material. We found trace element concentration and certain elemental ratio differences between genera at the same site (particularly of note were Li, Zn, Mn and Al) that will be important to constrain if these shells are to be applied as a paleoenvironmental proxy and are sometimes attributed to land use change.

Influence of surface ablation on plasma and its interaction with electromagnetic field

Surface ablation significantly affects the distribution of plasma in high-speed flow and the characteristics of its interaction with electromagnetic fields. Considering the mechanism of ablation and ejection on the surface of hypersonic vehicle, the participation of ablation products in the plasma generating process in the flow field, the conduction mechanism of mixed ionized gas containing alkali metal and the electromagnetic dynamics mechanism, the coupled calculation method of high-speed flow/plasma/electromagnetic field with alkali metal ablation is established by solving the three-dimensional thermochemical non-equilibrium flow governing equation with electromagnetic source term, the electric field Poisson equation and the magnetic vector Poisson equation. Combined with the common ablation and pyrolysis process of carbon-carbon materials and silicon-based phenolic resin materials, the mechanism and law of the interaction between surface ablation and electromagnetic field on the hypersonic plasma sheath under various conditions are systematically studied. The results show that the ablation effect affects the plasma distribution in the flow field, which is affected by the ablation mass ejection rate and the mass proportion of alkali metal. When the alkali metal content is high, the alkali metal ionization reaction is dominant, and the electron number density can increase by 1–2 orders of magnitude. The influences of different materials on plasma are different. The mass ejector ratio of silicon-based phenolic resin is larger, and the molar concentration of CO<sup>+</sup> and C<sup>+</sup> produced by ionization is close to that of NO<sup>+</sup> and <inline-formula><tex-math id="Z-20240520210947">\begin{document}${\mathrm{O}}_2^+ $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20231733_Z-20240520210947.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20231733_Z-20240520210947.png"/></alternatives></inline-formula>, which cannot be ignored. Alkali metal in ablative material can significantly improve the control effect of magnetohydrodynamics. With the increase of the proportion of alkali metal, the coupling effect of electromagnetic field increases, and the relationship between them is nonlinear. When the speed is low, the ionization degree of air itself is low and the coupling effect of electromagnetic field is weak. But the efficiency of “improving the electromagnetic effect by ablation of alkali metal” is higher.