This investigation deals with the influence of calcium, strontium and zinc on the formation of primary, metastable quasicrystals in Al-Mn-Si alloys as these can enhance the mechanical properties of ...alloys. The synthesized alloys were cast into a copper mould. The castings were characterized using standard tools for studying microstructure. The Al-Mn-Si-Zn-Ca-Sr alloy contained more of the primary icosahedral quasicrystalline (iQc) phase and less of the approximant α-Al-Mn-Si phase than the Al-Mn-Si alloy. The higher volume fraction of the primary iQc phase in the Al-Mn-Si-Zn-Ca-Sr alloy is explained by the reduction of the critical radius size for nucleation and by an increase in the number of nucleation sites for the iQc phase. Increased number of nucleation sites and higher volume fraction of the primary iQc are both related to a reduction of the surface tension for the Al-based melt caused by the presence of calcium and strontium. These two elements do not become incorporated into the iQc phase but have a large effect on the course of the solidification of the investigated alloys and their constitution at room temperature.
We investigated the effects of dual doping of SnO2 varistor ceramics with 1mol% CoO and different amounts of Nb2O5 (0.1–2mol%) on the formation of twin boundaries, microstructure development and ...electrical properties. Nb2O5 addition shifts densification to higher temperatures (up to 1430°C), producing microstructures composed of twinned SnO2 grains. Already 0.1mol% Nb2O5 triggers a three-fold increase in growth rate via the diffusion induced grain boundary mobility (DIGM). At 0.5mol% of Nb2O5 chemical equilibrium is achieved and SnO2 grains undergo normal grain growth. Electron back-scatter diffraction (EBSD) has shown that the prevailing type of twins is {101}. Cyclic twins are common. High-angle annular dark-filed scanning transmission electron microscopy (HAADF-STEM) image analysis revealed non-uniform segregation of Nb along the twin boundaries, indicating that they are not directly triggered by Nb2O5, but are a result of yet unexplained sequence of topotaxial replacement reactions. Energy dispersive spectroscopy (EDS) has shown that by dual doping of SnO2 with CoO and Nb2O5 the amount of Co dissolved in SnO2 grains is always ~4x lower compared to the amount of incorporated Nb and propose the following mechanism of tin out-diffusion: 6SnIVSn(IV)×⇋SnIISn(IV)''+CoIISn(IV)''+4NbVSn(IV)⋅. Optimal electrical properties were achieved at 1mol% Nb2O5 addition displaying high nonlinearity (α=50), moderate break-down voltage (571±12V/mm) and low leakage current (IL = 4.2µA). The addition of 2mol% of Nb2O5 has an inhibiting effect on densification and SnO2 grain growth, resulting in a collapse of nonlinearity and increase of leakage current.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The present communication reports the variation in surface characteristics of bilayered coating of phosphate free bioactive glass (PFBG) on SS316L substrate at simulated conditions, w.r.t both pH and ...temperature, to understand the suitability of the same for load bearing applications. The coated substrates were subjected to both physiological (7.4) and pathophysiological (4.5) pH conditions, considering two working temperatures of 37 °C and 45 °C, related to the real time scenario, in the post implantation period. Herewith, a faster dissolution of the PFBG network could be obtained at higher temperature (45 °C) and acidic pH (4.5) conditions, leading to a degraded surface texture, while the same at 37 °C and pH 7.4, exhibited an almost intact surface. The observation was corroborated using atomic force microscopy which exhibited an exponential increase in the nanoscale surface roughness of the coating at lower pH and at higher temperature conditions. The ionic Ca2+ dissolution kinetics of the PFBG coating followed by their cellular interaction were assessed using MC3T3 cell line, which showed a distinct difference compared to the as prepared PFBG coated substrate. Further, we made an attempt to assess the role of the calcium binding protein, calmodulin and its major target, calcium-calmodulin kinase II alpha (CAMKIIα) in osteoblast (MC3T3) differentiation, cultured on the PFBG coated SS316L substrates, subject to the experimental parameters as abovementioned. The results indicated significance of the real time conditions at the site of application of a bioactive glass coating on load bearing SS316L based implant material.
•Variation in surface characteristics of bilayered coating of phosphate-free bioactive glass (PFBG) on SS 316L substrate.•Faster dissolution of Ca2+ ion at lower pH and elevated temperature.•Demonstration of the effect of Ca2+ ion on CAMKIIα in osteoblast (MC3T3) differentiation.
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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 confirms that the stable icosahedral quasicrystal (iQc) phase Al65Cu20Fe15 (iQc–AlCuFe) can serve as a substrate for the nucleation of the metastable iQc–AlMnSi phase formed in rapidly ...solidified Al–Mn–Si alloys. The results reveal that a continuous, thin layer of the metastable iQc–AlMnSi phase can be formed on a stable iQc–AlCuFe particle. Electron backscatter diffraction patterns and selected-area electron diffraction patterns confirmed that epitaxy exists between the stable and the metastable iQc phases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The consumption of critical raw materials, especially those in permanent magnets of Nd–Fe–B and Sm–Co-type, has significantly grown in the past decade. With predictions on further electrification ...growing exponentially the demand for these materials will even increase. This implies that efforts in assuring sustainability must involve recycling from secondary resources. In recent years the electrochemical approaches in recycling have been extensively investigated and applied owing to their advantages of high efficiency and selectivity, easy operation, low energy consumption, and environmental friendliness. In this paper, we investigate the Sm
2
(Co,Fe,Cu,Zr)
17
permanent magnet leaching process using the anodic oxidation to be paired with the metal deposition on the cathode. Linear sweep voltammetry was performed from − 0.15 to 1 V versus Pt quasi reference electrode that indicated current peaks that would correspond to some preferential leaching of the crystal phases contained in the magnet. The latter was confirmed using the SEM/EDXS analysis. The continuous leaching of the Sm
2
(Co,Fe,Cu,Zr)
17
magnet was performed at a direct current density of 2, 4 and 8 mA cm
−2
at the time period of 0–240, 240–480 and 480–720 min, respectively. The ICP-MS results confirmed the leaching of all the metals from the original Sm
2
(Co,Fe,Cu,Zr)
17
permanent magnet. The concentration of Sm
3+
, Cu
2+
, Fe
2+
and Zr
2+
increases linearly along with the leaching time. Reversely the concentration of Co
2+
decreases linearly due to its consumption by electrodeposition of Co, Fe and Cu on the cathode. The presented paired electrochemical process could serve as a starting point for the recycling and recovery of critical raw materials without any acid usage and waste generation.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The surface water geochemistry and carbon cycling studied here depend mainly on geological composition of the river catchment. The investigated surface waters in the river Pesnica catchment that are ...heavily hydromorphologicaly altered (reservoirs, channelization, land melioration systems) represent waters inflenced by chemical weathering of carbonates and of mostly clastic rocks (claystone, sandstones, marlstones and siltstones). The objectives of our study were to analyze hydrogeochemical and isotopic composition of dissolved (δ13CDIC) and particulate carbon (δ13CPOC) with characterization of suspended matter and evaluate biogeochemical processes in Pesnica River in Slovenia before and after the retention. Surface waters are generally close to saturation regarding calcite and dolomite, dissolved CO2 is 49 to 1000 times oversaturated relative to atmosphere. δ13C DIC was in the range from -14.8 to -4.2 ‰ and shows following biogeochemical processes in river system: degradation of organic matter, dissolution of carbonates and biological activity, which was confimed with SEM microscopy and EDXS microanalysis. Results of SEM/EDXS showed that suspended matter is composed of K, Mg and Ca from locations Pesnica 1 and Pesnica 2 (above retention Perniško lake). Sample from Pesnica 3 (below retention) shows higher biological activity, while sample from Pesnica 4 (tributary of Pesnica, drainage channel Biš) contains a lot of particles of microporous structure and fier structure, which are probably of anthropogenic origin. δ13CPOC is changing from -29.5 to-27.6‰ and showed different stages of degraded terrestrial material. More negative δ13CPOC are shown at location at drainage channel Biš and show higher terrestrial input in river system as locations 1, 2 and 3 Pesnica, which have higher δ13CPOC values. This fist results about suspended matter in Pesnica watershed serve for evaluation of anthropogenic inflences specially in relation with further inflences and longer time planning of sustainable river water management.
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))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(Mg(1/3)Nb(2/3))(0.67)Ti(0.33)O3 (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%.
The green transition initiative has exposed the importance of effective recycling of Nd-Fe-B magnets for achieving sustainability and foreign independence. In this study, we considered strip-cast, ...hydrogenated, jet-milled Nd-Fe-B powder as a case study to explore the potential for selective chemical leaching of the Nd-rich phase, aiming to extract the Nd
Fe
B matrix phase. Diluted citric and nitric acids at concentrations of 0.01, 0.1, and 1 M were considered potential leaching mediums, and the leaching time was 15 min. Microstructural investigation, magnetic characterization, and elemental compositional analysis were performed to investigate leaching efficiency and selectivity. Based on SEM analysis, Nd/Fe ratio monitoring via ICP-MS, and the high moment/mass value at 160 emu/g for the sample leached with 1 M citric acid, 1 M citric acid proved highly selective toward the Nd-rich phase. Exposure to nitric acid resulted in a structurally damaged Nd
Fe
B matrix phase and severely diminished moment/mass value at 96.2 emu/g, thus making the nitric acid unsuitable for selective leaching. The presence of hydrogen introduced into the material via the hydrogen decrepitation process did not notably influence the leaching dynamics. The proposed leaching process based on mild organic acids is environmentally friendly and can be scaled up and adopted for reprocessing industrial scrap or end-of-life Nd-Fe-B magnets to obtain single-phase Nd-Fe-B powders that can be used for novel magnet-making.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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