Heterogeneous Chemical Composition Research Articles

Regional Zoning of a Li-Cs-Ta Pegmatite Field: Insights from Monazite-Cheralite Chemistry, U-Th-Pb and Sm-Nd Isotopes

Abstract Li-Cs-Ta (LCT ) rare-element pegmatites occur as late-stage and highly fractionated bodies at the margins of regionally zoned granite pegmatite fields. The evolution of the granitic pegmatite system, including its rare-metal metallogeny, is often difficult to determine due to complex textures involving variable crystal size and a heterogeneous chemical composition. The Renli-Chuanziyuan pegmatite field (South China) displays a well-developed regional zonation sequence, involving a core of biotite-, two-mica- and muscovite monzogranites (MMs) that grades outward into microcline (K-zone), microcline-albite (K-Na-zone), albite (Na-zone) and albite-spodumene (Na-Li-zone) pegmatites. Monazite and the Th, Ca–end-member (i.e. cheralite) provide valuable age, rare earth element (REE) geochemical and Sm-Nd isotopic data for understanding the regional zoning process within the Renli-Chuanziyuan pegmatite. Monazite (from the MM and the K-, K-Na- and Na-zone pegmatites) and cheralite (from the Na-Li-zone pegmatite) have variable compositions and complex internal microtextures. The monazite and cheralite grains contain irregular areas with subtle heterogeneous BSE response along cracks and grain margins, suggesting that they have experienced alkali-bearing fluid-aided modification. However, these features are rarely seen in monazite from the K-zone pegmatite. Common Pb contamination and/or Pb loss during fluid-aided modification may have disturbed the monazite and cheralite U-Th-Pb isotopic system, due to the differential mobility of U, Th and Pb. The unaltered Na-zone monazite and Na-Li-zone cheralite yielded Th-Pb ages of 140.42 ± 2.30 Ma (2 σ, mean standard weighted deviation (MSWD) = 2.4, n = 14) and 139.58 ± 2.15 Ma (2 σ, MSWD = 2.9, n = 21), respectively. The unaltered MM, K-zone and K-Na-zone monazite yielded 206Pb-238U ages of 138.03 ± 2.18 (2 σ, MSWD = 2.5, n = 18), 140.39 ± 2.18 (2 σ, MSWD = 3.0, n = 20) and 140.58 ± 2.14 Ma (2 σ, MSWD = 2.0, n = 52), respectively. These ages for the four pegmatite zones are temporally consistent with a syngenetic origin for the magmatic sequence of biotite-, two-mica- and MM and the pegmatite system and rare-metal (Li-Nb-Ta-Rb-(Cs)-(Be)) mineralization. The Sm-Nd isotopic analyses of the unaltered monazite and cheralite from the MM and four pegmatite zones yield similar initial Nd isotopic composition with εNd(t) = −9.9 to −7.9, indicating an identical single-source region (i.e. the Neoproterozoic South China lower crust). The Sm/Nd ratios display a gradual decrease across the four pegmatite zones from the unaltered K-zone monazite to Na-Li-zone cheralite, i.e. 0.39–0.63 (avg. = 0.43) for K-zone, 0.29–0.35 (avg. = 0.31) for K-Na-zone, 0.26–0.30 (avg. = 0.28) for Na-zone and 0.21–0.27 (avg. = 0.24) for Na-Li-zone. Such progressive variations suggest their derivation from the same parental magma, which experienced varying degrees of fractionation before the extraction of pegmatitic melts. Comprehensive monazite and cheralite geochemistry, as well as in situ U-Th-Pb and Sm-Nd isotopic results indicate that Rayleigh-type fractional crystallization controls the mineralogical and geochemical evolution from a chemically zoned granite source.

Systematic homogenization of heterogenous biomass batches – Industrial-scale production of solid biofuels in two case studies

Biomass is a heterogeneous material with respect to its chemical composition due to different plant species and components as well as the potential content of impurities. Especially in the production of large fuel batches heterogeneous chemical compositions are a challenge with respect to the required compliance with fuel standards and emission thresholds during utilization. This can be avoided by fuel pre-treatment and systematic homogenization during fuel production. For this reason, the study analyses the effects of biomass leaching in combination with homogenization of biomass batches on industrial-scale. Within two case studies, low-quality herbaceous biomasses, i.e. foliage and wheat straw were pretreated and homogenized in quantities ranging from 8 to 51 tons. In the first case study, foliage was first leached, then mixed with sawdust and homogenized by separating batch parts with high ash content, followed by systematic recombination of the batches. In the second case study, homogenization of straw pellets (untreated and leached) was attempted by a layering approach during bagging. Both case studies (i) confirm earlier findings that critical fuel components can be substantially reduced by leaching (i.e. reduction of ash content MV by 45 w-%) but indicate that material agitation during leaching is necessary; (ii) underscore that systematic homogenization is necessary for fuel batches consisting of materials from different origins and reduce i.e.-the ash content RSD by 48%, and (iii) demonstrate that even low-quality fuels from herbaceous biomass assortments can comply with the requirements of fuel standards if dedicated fuel pretreatment is employed.

Hyphenation of liquid chromatography and pyrolysis-flame ionization detection/mass spectrometry for polymer quantification and characterization

Size-exclusion chromatography (SEC) hyphenated to pyrolysis-gas chromatography (Py-GC) has been demonstrated as a powerful tool in polymer analysis. A main limitation to the wider application of the method are the long second-dimension Py-GC analysis times, resulting in limited first-dimension sampling and/or long overall run times. Therefore, we set out to develop an online hyphenated SEC×Py-MS/FID method, removing the GC separation and allowing for a drastically reduced second-dimension analysis time compared to SEC-Py-GC. The pyrolysis method had a cycle time of 1.31 min, which was facilitated by liquid nitrogen cooling of the programmable temperature vaporizer (PTV) used for pyrolysis. The developed method featured no molar mass discrimination for masses above ±1.3 kDa, rendering it applicable to most commercial polymer systems. The method was demonstrated on multiple samples, including a complex industrial sample, yielding chemical composition heterogeneity and in some cases sequence heterogeneity information over the molar mass distribution.

Interpreting ramped combustion thermograms using 13C NMR spectroscopy to characterize soil organic matter composition

While many advanced analytical methods have been applied to soil organic matter (SOM), its highly complex and heterogeneous chemical composition still eludes complete characterization. Analytical thermal analysis has been proposed as a relatively rapid, inexpensive method for SOM characterization that requires no pre-treatment, but is challenging due to a lack of direct information about chemical composition. The goal of this study was to inform the interpretation of coupled differential scanning calorimetry and evolved gas analyses (DSC, CO2-EGA) using spectral correlations with solid phase 13C NMR data. We used a subset of soils collected as part of the Australian National Soil Carbon Research Program (SCaRP), which were physically fractionated and characterized using conventional analytical methods. Correlating the well-understood NMR spectra with the less-understood DSC and CO2-EGA thermograms provided some indications of which chemical compounds combust at which temperatures. Overall, the EGA data generated stronger correlations compared to correlations with DSC data, which was attributable to greater variability in DSC data due thermal reactions associated with minerals. Direct comparison of NMR and thermal data for the mineral associated organic matter in the fine (<50 µm) fraction was not possible due to the need to demineralize samples prior to NMR analyses. Thermal analyses showed substantial differences in samples pre- and post-HF pretreatment, and the NMR data for HF treated samples showed scattered and weak correlation patterns with DSC and EGA data for untreated samples. While precise chemical compositions cannot be gleaned directly from thermal analyses results, thermal approaches provide an avenue of investigation into SOM reactivity based on bioenergetics that may be a quantitative representation of SOM persistence.

Bespoke multi-step homogenization heat-treatment for a laser powder bed fused AlSi10Mg4Cu alloy synthesized via in-situ alloying

Although in-situ alloying is a flourishing technique for developing novel metal alloys for Laser Powder Bed Fusion (LPBF), the mixed alloying elements regularly segregate, causing a heterogeneous chemical composition enriched with new metastable phases. Hence, the present study focuses on the homogenization of an in-situ alloyed AlSi10Mg4Cu metal system by pursuing various heat-treatment pathways. We firstly investigated the alloy homogenization behavior upon conducting single-step heat-treatments at 485, 500, and 515 °C for set times. Experimental findings revealed that the alloy was challenging to homogenize in one-go. Heat-treating at 485 °C did not enable the complete dissolution of Cu-rich phases. By increasing temperature at 500 °C, the alloy was neither homogenized nor near-fully dense due to the untimely incipient melting of metastable Q-Al 4 Cu 2 Mg 8 Si 7 phase which caused pores. Lastly, homogenization at 515 °C led to the enhanced dissolution of θ -Al 2 Cu phase and its precursors but simultaneously exacerbated the incipient melting process of Q-Al 4 Cu 2 Mg 8 Si 7 phase observed at 500 °C. Based on the analyses of single-step homogenization behaviors, we designed a multi-step homogenization heat-treatment to dissolve the low-melting Q- phase selectively avoiding its deleterious incipient melting. The material underwent then a homogenization treatment with three consecutives steps at 495 °C for 4 h, 505 °C for 6 h and 515 °C for 6 h. The homogenization response was satisfying this time: incipient melting of Q-Al 4 Cu 2 Mg 8 Si 7 phase was annihilated, and Cu solubilization was greatly enhanced. The supersaturation level was comparable with that of the as-built condition, i.e., optimal for following age-hardening treatments. • AlSi10Mg + 4Cu alloy is produced by LPBF in-situ alloying. • Various heat-treatment pathways are investigated to homogenize the alloy chemical composition. • Single-step homogenization at 485 °C did not entirely dissolve θ -Al 2 Cu phase; • Single-step homogenization at 500 °C partially solubilized θ - phase but induced early-stage incipient melting of Q-Al 4 Cu 2 Mg 8 Si 7 phase; • Single-step homogenization conducted at 515 °C dissolved θ -Al 2 Cu while causing incipient melting of Q- phase; • Multi-step homogenization solubilized Cu segregations avoiding incipient melting of Q- phase.

Wide-field optical imaging of electrical charge and chemical reactions at the solid–liquid interface

From molecules and particles to macroscopic surfaces immersed in fluids, chemical reactions often endow interfaces with electrical charge which in turn governs surface interactions and interfacial phenomena. The ability to measure the electrical properties of a material immersed in any solvent, as well as to monitor the spatial heterogeneity and temporal variation thereof, has been a long-standing challenge. Here, we describe an optical microscopy-based approach to probe the surface charge distribution of a range of materials, including inorganic oxide, polymer, and polyelectrolyte films, in contact with a fluid. The method relies on optical visualization of the electrical repulsion between diffusing charged probe molecules and the unknown surface to be characterized. Rapid image-based measurements enable us to further determine isoelectric points of the material as well as properties of its ionizable chemical groups. We further demonstrate the ability to optically monitor chemically triggered surface charge changes with millisecond time resolution. Finally, we present a scanning-surface probe technique capable of diffraction-limited imaging of spatial heterogeneities in chemical composition and charge over large areas. This technique will enable facile characterization of the solid-liquid interface with wide-ranging relevance across application areas from biology to engineering.

Study of the composition and properties of the beneficiation tailings of currently produced loparite ores

The increase in demand for rare earth metals and the depletion of natural resources inevitably causes the need to search for alternative unconventional sources of rare metal raw materials. The article presents the results of a study of the composition and properties of the beneficiation tailings of currently produced loparite ores. Sieve, mineralogical, chemical, and radionuclide analyses were carried out. The average content of loparite in tailings was determined. Using scanning electron microscopy, minerals-concentrators of rare earth elements in the loparite ore beneficiation tailings were diagnosed. The distribution of valuable components and thorium in the tailings was determined depending on the particle size class. The radium-thorium nature of radioactivity was established, the values of the effective specific activity of the samples were calculated. We concluded that it is necessary to develop an integrated technology for processing the beneficiation tailings of loparite ore, due to the complex and heterogeneous mineral and chemical composition of the tailings material.

Grain Size and Heterophase Effects on Mechanical Properties of Mg-Cu Nanoglasses

Tailoring heterogeneities in amorphous alloys is a promising strategy for promoting the strength-ductility synergy. Here, molecular dynamics simulations are performed to investigate the effects of grains size and heterogeneous chemical composition on the mechanical properties of Mg-Cu nanoglasses (NGs). The reduced grain size in single-phase NGs improves the plasticity but at the expense of strength. In addition, the mechanical properties of dual-phase NGs composed of two chemical compositions depend critically upon the fraction of softer phase. In particular, the plasticity is improved for the low fraction of the softer phase, but is deteriorated for the high fraction of the softer phase, which is in striking contrast to the observations of the plasticity improvement reported in the traditional nanostructured metals/alloys. This is because that heterogeneities at the glass-glass interfaces intentionally introduce more stress concentration sites which are easier to accelerate the shear band formation. For an appropriate fraction of heterogeneous composition, a balance among strength and plasticity can be realized, which is useful for the design of novel NGs with high strength and superior ductility.

Effect of crystallographic orientations on shock-induced plasticity for CoCrFeMnNi high-entropy alloy

Using nonequilibrium molecular dynamics simulations, we studied the crystallographic-orientation-dependence shock-induced plasticity for the face-centered cubic (FCC) equiatomic CoCrFeMnNi high-entropy alloy (HEA). The local FCC-BCC (body-centered cubic) structural transition was identified by shock loading in the [001] direction, which is attributed to the compression along the <001> direction of original body-centered tetragonal (BCT) structure, and then the BCC structures trend to activate the dislocation nucleation. Further, dislocations slip to produce HCP (hexagonal close-packed) structures in the FCC lattice. In contrast, for the shock loading along the [110] and [111] directions, numerous disordered structures were found due to the insufficient lattice displacement along the <112> direction on the {111} crystal plane of FCC structure and the nonsynergistic behavior of the deformation between the <001>, <110> and <111> directions of BCT structure. In particular, both BCC structures and disordered structures with the Mn-rich composition characteristics play a significant role to promote the development of localized plastic deformation, which is related to the stress concentration around Mn caused by the inherent local inhomogeneity in the CoCrFeMnNi HEA. Moreover, under shock loading, the high atomic fraction of the local BCC structures and disordered structures can further promote chemical composition heterogeneity in these structures. Our results provide some significant insights for understanding the shock-induced plasticity of the CoCrFeMnNi HEA.

Spatial heterogeneity in chemical composition and stability of glomalin-related soil protein in the coastal wetlands

GRSP is widely distributed in coastal wetlands, and there is a tendency for it to degrade with increasing burial depth. However, the dynamic changes in the chemical composition and stability of GRSP during the burial process are still unclear. The purpose of this study is to clarify the chemical composition and accumulation characteristics of GRSP during the burial process in the Zhangjiang estuary. In a field study, soil cores to the depth of 100 cm were collected in the estuary from mangrove forests dominated by Kandelia obovata and Avicennia marina, and from mudflat. The results showed that the concentration of GRSP in mangrove forest soil was significantly higher than that in the mudflat (p < 0.05), and the C/N ratio of GRSP increased with depth at all sites. Analysis of Fourier transform infrared (FTIR) data showed that the degradation rates of the GRSP's compositions varied with increasing burial depth, with microbial action and pH possibly being the main factors affecting degradation. Values of recalcitrance index (RI) showed that the stability of GRSP increased with increasing depth, and the contribution of GRSP to soil organic carbon (SOC) also increased. This suggests that the burial process plays a role in screening and storing the stable components of GRSP. Overall, our findings suggest that the concentration and chemical composition of GRSP vary dynamically according to habitat and burial processes. In addition, the improved stability of GRSP could contribute to carbon sequestration in coastal wetlands.

Syn-Eruptive Processes During the January–February 2019 Ash-Rich Emissions Cycle at Mt. Etna (Italy): Implications for Petrological Monitoring of Volcanic Ash

Low-intensity emission of volcanic ash represents the most frequent eruptive activity worldwide, spanning the whole range of magma compositions, from basalts to rhyolites. The associated ash component is typically characterized by heterogeneous texture and chemical composition, leading to misinterpretation of the role of syn-eruptive processes, such as cooling and degassing during magma ascent or even magma fragmentation. Despite their low intensity, the ash emission eruptions can be continuous for enough time to create problems to health and life networks of the communities all around the volcano. The lack of geophysical and/or geochemical precursor signals makes the petrological monitoring of the emitted ash the only instrument we have to understand the leading mechanisms and their evolution. Formation of low-level plumes related to ash-rich emissions has increasingly become a common eruptive scenario at Mt. Etna (Italy). In January–February 2019, an eruptive cycle of ash-rich emissions started. The onset of this activity was preceded on 24 December 2018 by a powerful Strombolian-like eruption from a fissure opened at the base of the New Southeast Crater. A lava flow from the same fissure and an ash-rich plume, 8–9 km high a.s.l., from the crater Bocca Nuova occurred concurrently. After about 4 weeks of intra-crater strombolian-like activity and strong vent degassing at summit craters, starting from 23 January 2019, at least four episodes of ash-rich emissions were recorded, mainly issued from the Northeast Crater. The episodes were spaced in time every 4–13 days, each lasting about 3–4 days, with the most intense phases of few hours. They formed weak plumes, up to 1 km high above the crater, that were rapidly dispersed toward different directions by dominant winds and recorded up to a distance of 30 km from the vent. By combining observations on the deposits with data on textural and chemical features of the ash components, we were able to discriminate between clasts originated from different crater sources and suggest an interpretive model for syn-eruptive processes and their evolution. Data indicate the occurrence of scarce (&amp;lt;10 vol.%) fresh juvenile material, including at least four groups of clasts with marked differences in microlite content and number density, and matrix glasses and minerals composition. Moreover, a large amount of non-juvenile clasts has been recognized, particularly abundant at the beginning of each episode. We propose that the low amount of juvenile ash results from episodic fast ascent of small magma batches from shallow reservoirs, traveling within a slow rising magma column subjected to cooling, degassing, and crystallization. The large number of non-juvenile clasts deriving from the thick crater infill of variably sealed or thermally altered material at the top of the magma column is suggested to contribute to the ash generation. The presence of a massive, granular crater infilling accumulating in the vent area may contribute to buffer the different geophysical signals associated with the active magma fragmentation process during the low-energy ash eruptions, as already evidenced at other volcanoes.

Improvement of ignition and combustion performance of micro-aluminum particles by double-shell nickel-phosphorus alloy coating

• A novel, inexpensive and controllable ‘one-step’ in-situ electroless plating strategy was proposed. • Three types of spherical core-shell structured energetic Al@Ni-P composites with a double shell were designed and fabricated. • Al@Ni-P composites showed enhanced thermal reactivity, shorter ignition delay time and higher rate of energy release. • The coating formation and combustion mechanisms of energetic Al@Ni-P composites were revealed. A novel ‘one-step’ in-situ electroless plating method capable of controlling phosphorus content was proposed for the fabrication of spherical core-shell energetic Al@Ni-P composites, aiming to prompt particle ignition by adding easy-to-ignite P element. In this experimental study, the preparation and characterization of Al@Ni-P composites, as well as the effect of coating an alloy shell on the Al particle surface were mainly addressed. The morphology and chemical composition heterogeneity demonstrated that the Al@Ni-P composites possessed comparatively dense double-shell structure. Thermal analysis showed that these composites could accelerate the rate of energy release by decreasing the apparent activation energy ( E a ) for particles oxidation. Laser ignition experiments were then conducted to examine the influence of Ni-P alloy on breaking through the barrier of ceramic phase Al 2 O 3 shell to improve the ignition and combustion performances. Moreover, the composites with surface P of 12.68 at.% exhibited extremely shorter laser ignition delay time of 86 ms under 1 atm O 2 atmosphere, reducing by 65.46% compared with that of raw Al particle (249 ms); and the pressurization rate reached 88.08 kPa/s under 10 atm O 2 atmosphere, which is approximately 11 times that of raw Al particle (8.09 kPa/s). These drastic improvements were attributed to the synergistic effects of double-shell structure and intermetallic compound exothermic reaction, which enhanced mass and heat transfer. These results demonstrate that Al@Ni-P composites have a promising future in solid composite propellants, which exhibit shorter ignition delay time and more vigorous combustion than raw Al. This strategy is expected to provide a new method for the construction of complex core-shell structural materials in other research fields.

Effects of chemical composition on the lung cell response to coal particles: Implications for coal workers' pneumoconiosis.

Background and objectiveCoal mine dust has a complex and heterogeneous chemical composition. It has been suggested that coal particle chemistry plays a critical role in determining the pathogenesis of coal workers' pneumoconiosis (CWP). In this study, we aimed to establish the association between the detrimental cellular response and the chemical composition of coal particles.MethodsWe sourced 19 real‐world coal samples. Samples were crushed prior to use to minimize the impact of particle size on the response and to ensure the particles were respirable. Key chemical components and inorganic compounds were quantified in the coal samples. The cytotoxic, inflammatory and pro‐fibrotic responses in epithelial cells, macrophages and fibroblasts were assessed following 24 h of exposure to coal particles. Principal component analysis (PCA) and stepwise regression were used to determine which chemical components of the coal particles were associated with the cell response.ResultsThe cytotoxic, inflammatory and pro‐fibrotic response varied considerably between coal samples. There was a high level of collinearity in the cell responses and between the chemical compounds within the coal samples. PCA identified three factors that explained 75% of the variance in the cell response. Stepwise multiple regression analysis identified K2O (p <0.001) and Fe2O3 (p = 0.011) as significant predictors of cytotoxicity and cytokine production, respectively.ConclusionOur data clearly demonstrate that the detrimental cellular effects of exposure to coal mine dusts are highly dependent on particle chemistry. This has implications for understanding the pathogenesis of CWP.

Deciphering the Distribution and Crystal-Chemical Environment of Arsenic, Lead, Silica, Phosphorus, Tin, and Zinc in a Porous Ferrihydrite Grain Using Transmission Electron Microscopy and Atom Probe Tomography

The interaction of contaminants and nutrients with soil constituents is controlled by processes in intergranular and intragranular pore spaces of organic matter or/and common secondary minerals such as ferrihydrite, ∼Fe3+10O14(OH)2. This contribution shows that distribution and clustering of the contaminants As, P, Pb, Si, Sn, and Zn in a porous ferrihydrite grain is greatly affected by the heterogeneous size distribution and chemical composition of the pores as well as the ability of their polyhedra to polymerize with the same type of polyhedron. Transmission electron microscopy (TEM) and atom probe tomography (APT) studies are conducted on focused ion beam (FIB) sections extracted from a porous ferrihydrite grain from the smelter-impacted topsoil in Sudbury, Ontario, Canada. The ferrihydrite grain has pore spaces ranging in diameter from tens to hundreds of nanometers. TEM and scanning-TEM studies indicate that the surfaces of the pore walls are enriched in Si. APT data in conjunction with First Near Neighbor (1NN) analyses indicate different degrees of clustering of Pb, As, Sn, Zn, Si, and P within the sample and selected domains. Careful evaluations of 3D atomic plots and 1NN distances indicates the occurrence of polymerized arsenite-, silica-, Sn-, and Zn-polyhedra within pore spaces of the ferrihydrite. Deciphering adsorption, polymerization, and nucleation processes in porous Fe-(hydr)oxides and other soil constituents requires multianalytical approaches and, in this regard, we discuss the advantages and disadvantages of the combination of TEM and APT for characterizing complex environmental samples at the atomic to nanometer scale.

Soil dust aerosol in the atmosphere: sources, quantities, properties (overview)

Dust is a major component of atmospheric aerosols – 75% of the global aerosol load. Natural and anthropogenic sources are listed, as well as dust research methods. According to different estimates, the average mineral dust load in the atmosphere ranges from 20 to 33 Tg, and the annual dust emission is 1 200–5 900 Tg/year. Reports from the Intergovernmental Panel on Climate Change (IPCC) inform about the total direct radiative forcing of dust ranging from -0.56 to +0.1 W/m2, with little scientific understanding of the processes leading to this result. The particle size, including soil aerosol, is divided into fine (&lt;5 μm), medium (5–10(20) μm) and coarse (&gt;20 μm) dust. Fine dust cools the global climate due to dispersion of solar radiation, while coarse dust (greater than 5 μm) warms the climate by absorbing solar and thermal radiation. However, the coarse dust (above 20 μm) remains poorly investigated, with very little data on its content and emission. Recent studies suggest that coarse dust (17 Tg), missed by the global models, contributes on average 0.15 W/m2 (0.10 to 0.24 W/m2) to atmospheric heating and also affects the global distribution of clouds and precipitation. In addition, soil dust is characterised by a complex and diverse particle shape and structure, heterogeneous mineralogical and chemical composition; due to its dispersion ability and large surface area dust reacts with other types of aerosols, resulting in the formation of different films on the particle surface or internal mixing. All this significantly changes the optical properties of mineral dust and complicates the development of models for its investigation.

Nanostructured PEO-coatings on silumin as environmental catalysts

The process of the formation of mixed oxide coatings on a high-silicon aluminum alloy in the cobalt-containing pyrophosphate electrolyte by the plasma-electrolytic oxidizing (PEO) method has been studied. It has been shown that AK12M2MgN chemical composition heterogeneity causes the consumption of part of the anode current to homogenize the treated surface, which is reflected in minimizing the content of doping components at the initial processing stage. It has been established that the growth of mixed oxides Al2O3·CoOx relative mass is a function of time with the maximum at 55 min. The chemical, phase composition and surface morphology of the formed oxide layer depend on the oxidizing time. The catalytic component content in the surface oxides varies from 0.2 to 23.3 at.% with an increase in processing time from 10 to 60 min. Maximum cobalt incorporation into the oxide layer occurs at PEO of 35–50 min, while the silicon content in the surface layers does not exceed 2 at.%, which is favorable for the catalytic properties. The cobalt oxide, preliminary Co3O4, incorporation in alumina α-Al2O3 matrix is visualized by the blue-violet color spheroid surface structures at the sites of micro-arc discharges. The mixed alumina and cobalt oxides layer are characterized by a developed micro globular surface consisting of conglomerate spheroids with an average size of 1–2 µm. There are some amorphous phases in the structure of mixed oxides due to non-equilibrium PEO conditions. The set of detected factors is a prerequisite for the high catalytic properties of oxide coatings. A promising field of Al2O3·CoOx systems application is an intra-cylinder catalysis in the internal combustion engines.

Vapor Deposition of Silicon-Containing Microstructured Polymer Films onto Silicone Oil Substrates.

In this study, a silicon-containing cross-linked polymer, poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane-co-ethylene glycol diacrylate) (p(V4D4-co-EGDA)), was deposited onto high-viscosity silicone oil using initiated chemical vapor deposition (iCVD). The ratio of the feed flow rate of V4D4 to EGDA was systematically studied, and the chemical composition and morphology of the top and bottom surfaces of the films were analyzed. The films were microstructured, and the porosity and thickness of the films increased with increasing V4D4 content. The top of the film was composed of densely packed and loosely packed microstructured regions. X-ray photoelectron spectroscopy on the top and bottom surfaces of the films showed a heterogeneous chemical composition along the thickness of the film, with higher silicon content on the top surface compared to that on the bottom surface. To the best of our knowledge, this is the first study of iCVD deposition of a silicon-containing polymer film onto silicone oil. The results of this study can be used for the synthesis of polymer precursor films for the fabrication, via pyrolysis, of silicon-based inorganic membranes for use in hydrogen production using silicone oil to prevent infiltration of monomer into the underneath membrane support structure during vapor deposition.

The Extraordinary Passage of Comet C/2020 F3 NEOWISE: Evidence for Heterogeneous Chemical Inventory in Its Nucleus

Abstract Upon its discovery in 2020 March, we requested Director Discretionary Time (DDT) at the NASA/IRTF facility to observe comet C/2020 F3 (NEOWISE), with the high-resolution spectrograph iSHELL. The comet approached the Sun, down to 0.3 au, in early 2020 July, providing a spectacular perihelion passage and revealing itself as one of the brightest comets that have appeared in the northern hemisphere in recent decades. Daytime observations with iSHELL/IRTF were performed to study the comet immediately after its perihelion passage, from 9 July to 1 August. In early August, a DDT at Keck Observatory was requested to continue following the comet with NIRSPEC 2.0. We acquired comprehensive high-resolution spectra of the comet as it progressively retreated from perihelion. We detected many cometary emission lines in the (2.8–5.3) μm range, identifying 12 molecular species: 9 primary volatiles (H2O, HCN, NH3, CO, C2H2, C2H6, CH4, CH3OH, and H2CO) and 3 product species (CN, NH2, OH). In this paper, we present the analysis and discussion of the molecular abundances found in this comet, and we compare them to reference median values for Oort Cloud Comets. Measured molecular mixing ratios showed drastic changes during our observing campaign, which spanned nearly one month from 2020 July 9 to August 6. Here, we provide a detailed discussion of the molecular spatial distributions and their role in identifying the presence of extended sources in the coma. Our investigations provided evidence for the heterogeneous chemical composition of the comet’s nucleus.

Physical\u2013chemical properties of cell wall interface significantly correlated to the complex recalcitrance of corn straw

BackgroundTissue heterogeneity significantly influences the overall saccharification efficiency of plant biomass. However, the mechanisms of specific organ or tissue recalcitrance to enzymatic deconstruction are generally complicated and unclear. A multidimensional analysis of the anatomical fraction from 12 corn cultivars was conducted to understand the essence of recalcitrance.ResultsThe results showed that leaf, leaf sheath, stem pith and stem rind of corn straw exhibited remarkable heterogeneity in chemical composition, physical structure and cell type, which resulted in the different saccharification ratio of cellulose. The high saccharification ratio ranging from 21.47 to 38.96% was in stem pith, whereas the low saccharification ratio ranging from 17.1 to 27.43% was in leaf sheath. High values of lignin, hemicelluloses, degree of polymerization and crystallinity index were critical for the increased recalcitrance, while high value of neutral detergent soluble and pore size generated weak recalcitrance. Interestingly, pore traits of cell wall, especial for microcosmic interface structure, seemed to be a crucial factor that correlated to cellulase adsorption and further affected saccharification.ConclusionsHighly heterogeneity in cell wall traits influenced the overall saccharification efficiency of biomass. Furthermore, the holistic outlook of cell wall interface was indispensable to understand the recalcitrance and promote the biomass conversion.Graphic abstract

Optimal removal of diclofenac and amoxicillin by activated carbon prepared from coconut shell through response surface methodology

Agricultural residues like coconut shell are widely available in Benin Republic and can be used as adsorbent. In this study, we determine the limits of pharmaceutical substances adsorption by activated carbon from coconut shells. The synthesis of this adsorbent was optimized by the Response Surface Methodology (RSM) with two factors: the impregnation ratio IR and activation temperature. The iodine value was considered as the performance (response) parameter of this synthesis. After characterizing the prepared activated carbon, adsorption tests were performed on diclofenac sodium (DCF) and amoxicillin (AMX) by varying the contact time and the adsorbate-adsorbent ratio Rads. The synthesis results showed that the optimal physicochemical properties of the activated carbon were observed at 740 °C with phosphoric acid (IR = 1.66). Under these optimal conditions, the activated carbon from the coconut shells presented a large microporous specific surface (SBET = 437 m2/g and Vmicro = 0.21 cm3/g), optimal iodine adsorption (930.28 mg/g), amorphous and low heterogeneous chemical composition. In addition, the prepared activated carbon was an excellent adsorbent for the removal of the pharmaceutical substances studied. The experimental adsorption data followed the Langmuir isotherm and the pseudo first-order kinetic model. However, the efficiency varied depending on the nature of the adsorbate and the adsorbate-adsorbent ratio was the main limiting factor in the adsorption process. Optimal elimination greater than 98% was noticed with Rads = 0.10 and a contact time of 15 min (90 min) for DCF (AMX). However, we noticed the complete elimination of AMX (DCF) for Rads ≤ 0.075 (Rads ≤ 0.040). It was observed that the removal efficiency of pollutant was not defined by the adsorption rate constant but the reactivity with the adsorbent.