•Riverbed biofilms were examined in situ during colonization and over four seasons.•The impact of pollution with PET fibres was investigated.•PET inhibited biofilm activity and affected ...community-level metabolic profiles.•Utilization of synthetic polymers was higher in sediments with more PET fibres.
Worldwide, the production of plastics is increasing, and plastic pollution in aquatic environments is a major global concern. Under natural conditions, plastic weathers to smaller pieces called microplastics (MP), which come in various shapes, with fibers often being the most common in freshwater sediments. The hyporheic zone, an ecotone between surface and groundwater, is important for the transport and fate of all MP particles. The main metabolic pathways in rivers take place in the hyporheic zone and are driven by a diverse microbial community. The objective of this study was to investigate in situ whether the presence of PET fibers in riverbed sediments affects patterns of colonization and the seasonal dynamics of microbial metabolic activities in the hyporheic zone. The effects of the presence of PET on microbial metabolism were evaluated in situ over a month (colonization study) and over a year (seasonal study) by measuring total protein content (TPC), and microbial respiration as respiratory electron transport system activity (ETSA) and by community-level physiological profiling (CLPP). Additionally, PET fibers were examined under a scanning electron microscope (SEM), and isotopic analysis (δ13C) of PET was performed after one year of exposure to field conditions. The findings demonstrated that during colonization and biofilm formation, and also over the seasons, the date had a large and significant impact on biofilm growth and activity, while PET presence slightly suppressed microbial biomass (TPC) and respiratory activity (ETSA). Overall microbial activity was repressed in the presence of PET fibers but there was a higher capacity for the utilization of complex synthetic polymer substrates (i.e., Tween 40) which have previously been linked to polluted environments. SEM micrographs showed diverse microbial communities adhering to PET fibers but little surface deterioration. Similarly, isotopic analysis suggested little deterioration of PET fibers after one year of in situ conditions. The study indicated that PET fibers present in riverbed sediments could have impacts on the metabolic functioning in rivers and thus affect their self-cleaning ability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Optimized quantitative electron-probe microanalysis was applied for compositional characterization of a ferroelectric ceramic single crystal that was made from the complex perovskite-type ...solid-solution (1–x)Pb(Mg1/3Nb2/3)O3×xPbTiO3 (PMNT). Cation concentrations were determined with high accuracy and ultimate relative experimental uncertainty of ≤±1%, showing that the average chemical composition of the crystal corresponds to Pb(Mg1/3Nb2/3)0.67Ti0.33O3 (i.e., x=0.33), which is close to the morphotropic phase boundary composition. Over the PMNT single crystal slight compositional heterogeneity was measured for concentrations of the perovskite B-site cations Ti4+, Mg2+, and Nb5+, with variations up to ±2.3%, whereas the Pb concentration remained uniform within a variation below ±0.5%.
This work deals with the influence of gallium addition on the constitution and formation of the phases in the Al-rich corner of the Al–Mn system during casting. Al-rich binary Al–Mn and ternary ...Al–Mn–Ga alloys were cast into a copper mould with a cavity diameter of 5 mm. The microstructures of the produced alloys were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction and X-ray diffraction. The characterization revealed the presence of αAl, Al6Mn, λ-Al4Mn, L-Al4Mn, icosahedral quasicrystals (IQCs) and decagonal quasicrystals (DQCs). As the amount of gallium in the synthesized alloys increased, the proportion of the phases varied and IQCs and DQCs were formed. Microanalysis revealed that IQCs contained more gallium and less manganese than DQCs.
•Binary Al–Mn and ternary Al–Mn–Ga alloys were cast in a copper mould and characterized by SEM, EDS, EBSD and XRD.•Characterization of the alloys shows that αAl, Al6Mn, λ-Al4Mn, L-Al4Mn, IQCs and DQCs are present.•The EDS microanalysis shows that more gallium is present in the IQCs than in the DQCs.•The results reveal that with the addition of gallium to the binary Al–Mn system, L-Al4Mn, IQCs and in some cases DQCs form.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Optimized quantitative electron-probe microanalysis was applied for compositional characterization of a ferroelectric ceramic single crystal that was made from the complex perovskite-type ...solid-solution (1–
x
)Pb(Mg
1/3
Nb
2/3
)O
3
×
x
PbTiO
3
(PMNT). Cation concentrations were determined with high accuracy and ultimate relative experimental uncertainty of ≤±1%, showing that the average chemical composition of the crystal corresponds to Pb(Mg
1/3
Nb
2/3
)
0.67
Ti
0.33
O
3
(i.e.,
x
=0.33), which is close to the morphotropic phase boundary composition. Over the PMNT single crystal slight compositional heterogeneity was measured for concentrations of the perovskite B-site cations Ti
4+
, Mg
2+
, and Nb
5+
, with variations up to ±2.3%, whereas the Pb concentration remained uniform within a variation below ±0.5%.
•TRE-lean jet-milled Nd-Fe-B powders can be consolidated to full density with SPS.•The rapid non-equilibrium SPS hinders the grain growth during the sintering step.•The electrical effects associated ...with the SPS govern the microstructure formation.•A post-SPS thermal treatment is necessary for the final hard-magnetic properties.
Sintered Nd-Fe-B permanent magnets are the first choice for electro-mechanical devices that rely on hard-magnetic materials to provide strong magnetic fields in a variety of operating conditions. However, the limitations of conventional powder-metallurgy methods regarding the complexity of the magnet’s geometry restrict the design freedom for electrical motors. Here, we propose a spark-plasma-sintering (SPS) approach to the waste-free net-shape manufacture of anisotropic Nd-Fe-B magnets. We investigated the effect of the SPS parameters on the density, magnetic properties and microstructure of disc-shaped samples prepared from a rare-earth-lean jet-milled powder. The absence of a grain-boundary phase and the presence of α-Fe in the as-sintered samples were identified as the main factors hindering the development of the intrinsic coercivity. The observed microstructural features were correlated with electrical effects specific to the rapid, non-equilibrium SPS. A post-SPS thermal treatment was found to be necessary for achieving the hard-magnetic properties. Our findings pave the way towards developing an SPS-based sintering procedure with great potential for the manufacture of complex- and net-shape permanent magnets for high-performance electrical devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study investigated the mineralogical and isotopic composition of groundwater and precipitation to identify and constrain geochemical processes within stacked Pliocene and Triassic aquifers in ...the Velenje coal basin. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic analysis revealed that suspended matter in the Pliocene aquifer consists of feldspars and quartz, while dolomite, calcite and feldspars are present in the aquifer dewatering Triassic strata. The concentrations of trace elements in Triassic and Pliocene aquifers range from highest to lowest Zn > Fe > Ni > Al > Ba > Mn > B>Li > Mo > As with the majority of trace element concentrations below international drinking water health guidelines. Multivariate principal component analysis indicated that concentrations of Mn, Ba, Eu, Cs, Y, Li and T, pH, conductivity and dissolved oxygen in samples were the best chemical parameter for distinguishing the two aquifers. A significant positive correlation (
p
< 0.05) was found between Ni, Mn, Co, Zn, As and Mo. Groundwater in the Pliocene aquifer likely has an external source of carbon based on the
δ
13
C
CO2
values (− 12.3 to − 3.6‰). The groundwater also has detectable levels of dissolved methane with isotopic values (− 77.7 to − 51.4‰
δ
13
C
CH4
; − 247 to − 162‰
δ
2
H
CH4
) consistent with microbial methanogenesis. The groundwater in the Triassic aquifer has tritium values (up to 4.1 TU
3
H) characteristic of modern recharge (< 50 years), while the lack of detectable
3
H (0 TU) in the Pliocene aquifer is consistent with longer residence times.
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EMUNI, NUK, OBVAL, SBMB, SBNM, UL, UM, UPUK
The solid solubility of R ions (R = Ho3+, Dy3+, and Y3+) in the BaTiO3 perovskite structure was studied by quantitative electron‐probe microanalysis (EPMA) using wavelength‐dispersive spectroscopy ...(WDS), scanning electron microscopy (SEM), and X‐ray diffractometry (XRD). Highly doped BaTiO3 samples were prepared using mixed‐oxide technology including equilibration at 1400° and 1500°C in ambient air. The solubility was found to depend mainly on the starting composition. In the TiO2‐rich samples a relatively low concentration of R incorporated preferentially at the Ba2+ lattice sites (solubility limit ∼Ba0.986R0.014Ti0.9965(V″Ti″)0.0035O3at 1400°C). In BaO‐rich samples a high concentration of R entered the BaTiO3 structure at the Ti4+ lattice sites (solubility limit ∼BaTi0.85R0.15O2.925(VO••)0.075at 1500°C). Ho3+, Dy3+, and Y3+incorporated preferentially at the Ti4+ lattice sites stabilize the hexagonal polymorph of BaTiO3. The phase equilibria of the Ho3+–BaTiO3 solid solutions were presented in a BaO–Ho2O3–TiO2phase diagram.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
A novel implementation of an electrochemical sensors making use of Screen-Printed Electrodes (SPE) has been discussed. SPE's modified with Carbon-supported Platinum (Pt/C) and Gold (Au/C) were used ...to detect the three benzenediol isomers, Catechol (CC), Hydroquinone (HQ) and Resorcinol (RS) in acidic media using traditional electrochemical analytical methods such as Cyclic Voltammetry (CV), Chronoamperometry (CA) and Differential Pulse Voltammetry (DPV). Detection of each benzenediol in isolation was possible by CV measurements, and peak oxidation potentials for each isomer were noted. Simultaneous detection of more than one, or all analytes in the same solution was also observed through DPV, once again noting the peak oxidation potentials. Quantification limits were observed using CA's across concentration values ranging from close to saturation down to 1 mM for CC and HQ, and 100 nM for RS, until the recorded current values were nearly indistinguishable to a blank 1 M HCl solution containing no analyte(s), and also evaluating the maximum possible linear range of sensing. The analytes were introduced to the sensor elements in controlled amounts and the electrochemical responses of the sensor elements were recorded and processed. Measurements were repeated across two potentiostats to ensure reproducibility. With these results, successful detection of benzenediols in acidic environment was possible using modified SPE's, proving a potential viable mechanism for quick, simple and inexpensive Volatile Toxic Organic Compounds (VTOC) detection and monitoring.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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