Bi Content Research Articles

Electronic properties of metamorphic GaSbBi films on GaAs

We report on the electronic, structural, and optical properties of epitaxial GaSbBi films with varying Bi-concentration (up to 7%Bi) grown on semi-insulating GaAs(100) substrates. The 1 μm thick GaSbBi epilayers exhibit fully relaxed narrow x-ray diffraction peaks and smooth surface morphology comparable to that of high-quality GaSb epilayers on GaAs. Low temperature photoluminescence spectra exhibit bandgap shrinkage consistent with Bi alloying. Electrical Hall measurements indicate a reduction in hole concentration and no change in the hole mobilities with increasing Bi content for the nominally undoped GaSbBi alloy. The residual hole concentration reduces from the 1018 cm−3 level for a reference GaSb sample to the low 1017 cm−3 level with increasing Bi content. Hole mobility values of around 300 cm2/Vs are observed independent of the Bi content. These dependencies are attributed to the Bi surfactant effect and Bi-induced defect formation.

Influence of Bi2O3 Concentration on Optical and Gamma Ray Shielding Properties of BaTiO3 Ceramics

ABSTRACTThis study elaborated on the influence of bismuth oxide (Bi2O3, Bi) on optical and radiation shielding properties of Barium titanate (BaTiO3, BTO) when added with different wt% concentrations. To study these properties, BaTiO3–xBi2O3; x = 0,2,4,6 and 8 wt% ceramics samples were fabricated via solid state reaction method. The optical properties of prepared samples were inspected with the help of the UV–Vis technique. The absorption coefficient increased while transmittance decreased with increasing the wt% of Bi content. Samples show a decrement in indirect optical bandgap values from 3.44 to 3.35 eV while direct bandgap from 3.19 to 3.02 eV when Bi content increases from x = 0 wt% to 8 wt%. The other optical parameters, such as Urbach energy, refractive index, extinction coefficient, and dielectric constant, were also calculated. The FESEM (field emission scanning electron microscope) technique was used to identify the homogeneity in the samples. The prepared samples were tested at 356, 511, 600, 1173, 1275, and 1333 keV energies to estimate radiation shielding properties with radioactive sources 133Ba, 22Na, 137Cs, and 60Co. As Bi content increased in prepared samples, the mass attenuation coefficient (MAC) increased. At energy 356 keV, the observed MAC values are 12.685, 12.983, 13.282, 13.58, and 13.898 cm2/g while at 1333 keV, the values noticed as 5.054, 5.066, 5.079, 5.091, and 5.103 cm2/g as Bi content increased from x = 0 wt% to x = 8 wt%. Both atomic cross‐section (ACS) and electronic cross‐section (ECS) were calculated. ACS values are improved from 9.825 to 11.1967 barn/atom while the ECS values enhanced from 3.8949 to 4.0226 barn/electron at 356 keV as Bi content increased from x = 0 wt% to x = 8 wt%. This similar trend was observed at other energies (511, 600, 1173, and 1275 keV) for all prepared samples. The theoretical values obtained from Phy‐X/PSD software were compared with calculated values and found a close agreement between them. From results, it was clear that prepared samples showed enhanced optical and radiation shielding properties when Bi content increased in BTO ceramics.

First-principles study of the effect of Bi content on the photocatalytic performance of bismuth bromide oxide-based catalysts.

A comprehensive analysis of BixOyBrz has been carried out using first-principles density-functional theory (DFT) to explore the electronic structure, energy band structure, and essential properties related to its photocatalytic performance. DFT calculations reveal that BiOBr, Bi4O5Br2, Bi12O16Br5, Bi24O31Br10, Bi3O4Br, and Bi5O7Br have different indirect bandgap values of 2.46 eV, 2.51 eV, 1.67 eV, 2.21 eV, 2.21 eV, and 2.87 eV, respectively, and these differences reflect the influence of material composition and structure on its electronic structure. When analyzing their optical characteristics, we observe that the dielectric function's real and imaginary components show peaks in the low-energy regime, indicating a material that is more responsive to light in these energy ranges. The absorption spectra show that the BixOyBrz material absorbs the highest amount of UV light absorption, and as the ratio of Bi to Br changes, the absorption spectra exhibit a red shift, which enhances the material's visible light absorption and thus improves the utilization of light. These light absorption properties make BixOyBrz materials potentially advantageous for enhancing photoelectric conversion efficiency, which is particularly important for producing microelectronic and optoelectronic devices.

Effect of Ni–Bi Alloying on the Microstructure and Self‐Lubricating Properties of CoCrNi‐Based Coatings Across a Wide Temperature Range

This study investigates the use of bismuth (Bi) as a lubricating additive in laser cladding Co‐based composite coatings, addressing the issue of Bi segregation and agglomeration through Ni–Bi alloying. The microstructure, mechanical properties, and tribological properties of composite coatings with varying Ni–Bi contents are systematically evaluated at temperatures between 30 and 800 °C. Analysis reveals that Ni and Bi elemental powders are successfully alloyed to form BiNi and Bi3Ni intermetallic compounds following vacuum sintering. Incorporation of Ni–Bi alloying powder significantly enhances the friction coefficient and wear rates of the composite coating across the temperature range. Adhesive wear and abrasive wear are identified as primary wear mechanisms. Notably, the formation of BiNi, multiple oxides, and Bi16CrO27 compounds on the surface of the 85:15 (at%) Bi:Ni composite coating at 600 °C created a self‐lubricating friction layer, synergistically reducing friction. Consequently, compared to Co‐based alloy coatings without Ni–Bi alloying, the composite coating exhibited a three‐fold reduction in friction coefficient and a two‐order‐of‐magnitude improvement in wear rate, demonstrating exceptional tribological properties.

Typochemistry of magnetite from massive sulfide and iron deposits of the Urals according to LA-ISP-MS data

The aim of the study is the determination of mineralogical and geochemical features of magnetite from massive sulfde and iron deposits to develop forecasting criteria of ore objects. The layered magnetitolites of sulfde (Mauk, Letnee, Sibai and Molodezhnoe) and stratiform iron (Kachar, Sarbai, Estyuninskoe, Osokino-Aleksandrovskoe and Techa) deposits of volcanosedimentary association are the objects of study. It is established using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) that, in contrast to magnetite of iron deposits, magnetite of ore-controlling volcanosedimentary horizons of the Urals massive sulfde deposits is characterized by a higher content and stable associations of Bi, Te, Co, As, Cd, Zn, Cu and Mo due to relict inclusions of sulfde clasts and products of their halmyrolysis. The elevated Ti, V and Zr contents, as well as the mixed associations of lithophile, siderophile and chalcophile elements, are more typical of magnetite of iron deposits after hyaloclastites. Typochemistry of magnetite from volcanosedimentary horizons can be a criterion for searching the massive sulfde deposits.

Effect of Superstoichiometric Bismuth Addition on the Structure and Dielectric Characteristics of the Solid Solutions (1−x)BiFeO3-xBaTiO3

Ceramic samples of solid solutions of the binary system (1−x)BiFeO3-xBaTiO3 + 2 wt.% Bi2O3 (0.29 ≤ x ≤ 0.33, Δx = 0.01) were prepared using the conventional solid-phase reaction method with and without mechanical activation. Using X-ray studies, it was found that the objects have a pseudocubic crystal structure, and limited solubility occurs in solid solutions of the studied composition, as evidenced by the presence of regions with an increased Bi or Ba content and similar cell parameters. A diffuse phase transition occurred from the FE to PE state in the temperature ranges of (650–850) K. Relaxor-like behavior and the smearing of the phase transition in the studied ceramics can be associated with the presence of non-interacting regions with an increased content of Bi or Ba, different modulation, and crystal lattice symmetry. The grain morphology and dielectric characteristics of the selected solid solutions were investigated. The highest piezoelectric coefficient, d33 = 120 pC/N, was obtained in the mechanically activated ceramics 0.71BiFeO3-0.29BaTiO3 + 2 wt.% Bi2O3.

Ratiometric luminescence detection of Bi(III) ions in water using a europium coordination polymer

A ratiometric luminescent probe for detecting Bi(III) in water using a functionalized Eu(III) coordination polymer was developed. The raw materials guanosine monophosphate (GMP), Eu(III), and 2,6-pyridine dicarboxylic acid (DPA) were used to synthesize the GMP-Eu-DPA polymer, which contained Eu(III) coordinated with GMP and DPA and gave red emission at a wavelength of 614 nm when excited at a wavelength of 282 nm. Adding Bi(III) decreased the intensity of luminescence of the GMP-Eu-DPA coordination polymer at 614 nm and caused a GMP–Bi complex that strongly luminesced at 373 nm under excitation at 282 nm to form. Under optimal conditions, the luminescence intensity ratio I 373/I 614 had a good linear relationship with the Bi(III) concentration in the range 1.0–230 μM, and the detection limit was low (0.6 μM). The dual emission reverse rate of change luminescent probe can eliminate environmental influences, making the proposed detection method highly selective. This method has been successfully used to detect Bi(III) in water samples.

Hydrothermally Synthesized Bi‐Cr‐Te Nanocomposites With Enhanced Nonlinear Two‐Photon Absorption

This study highlights the importance of exploring BiCrTe nanocomposites to uncover their distinctive properties and potential applications. Three BiCrTe samples were synthesized using hydrothermal methods by varying the concentrations of Bi and Cr while maintaining a constant Te content. X‐ray diffraction (XRD) confirmed the presence of Bi₂Te₃ and Cr₂Te₃ phases, supported by transmission electron microscopy (TEM) observations. A reduction in Bi content led to smaller crystallite sizes. Raman spectroscopy revealed characteristic vibrational modes associated with Bi₂Te₃ and Cr. Field emission scanning electron microscopy (FESEM) confirmed the nanoparticle‐like morphology of the composites. X‐ray photoelectron spectroscopy (XPS) provided detailed surface composition and electronic structure data, verifying the presence of all constituent elements. UV‐Vis spectroscopy demonstrated a blueshift in absorbance with decreasing Bi content, with bandgap (Eg) values ranging from 3.31 to 3.61 eV. This increase in bandgap correlated with a reduction in refractive index (n). Nonlinear optical (NLO) studies revealed two‐photon absorption behavior, along with a positive nonlinear absorption coefficient (β), third‐order susceptibility (χ (3)), and refractive index (n2). These findings indicate that BiCrTe nanocomposites hold significant promise for advanced optoelectronic applications.

Superb thermal stability achieved in Na0.25K0.25Bi2.5Nb2O9-based piezoelectric ceramics via Bi deficiency

Na0.25K0.25Bi2.5Nb2O9-based ceramics woule become one of the excellent candidate materials suitable for high-temperature applications, given that their piezoelectric properties can be effectively improved. In this work, a strategy of reducing the Bi content was used to improve the piezoelectric properties and thermal stability of Na0.25K0.25Bi2.5Nb2O9-based ceramics by means of designing the compositions of the Na0.25K0.25Bi2.5+xNb2O9+3x/2 (−100xBi-NKBN, x = 0, −0.01, −0.03, −0.05, −0.07, −0.10). The effect of the Bi deficiency on the crystal structure, microscopic morphology, and electrical properties of NKBN-based ceramics was systematically investigated. By comparison, the Na0.25K0.25Bi2.45Nb2O8.925 ceramic obtains a large d33 of 20 pC/N, a high Tc of 651 ℃, and a high resistivity ρdc of 3.3 × 105 Ω cm at 600 ℃. The results demonstrate that the good d33 mainly stems from the increased lattice distortion and reduced oxygen vacancy concentration. More importantly, the d33 value can maintain 97 % of its initial value after it was annealed at 600 ℃, showing excellent thermal stability. This work provides a new idea for solving the problem of poor piezoelectricity of NKBN-based ceramics and lays the foundation for applying NKBN-based ceramics in the high-temperature field.

Influence of Bi substitution on structural and optical properties of LaFeO\(_{3}\) perovskite

The sol-gel self-ignition method has successfully synthesized a series of homogenous perovskites La1-xBixFeO3 (x=0.0, 0.2, 0.4, 0.6, and 0.8) nanoparticles. Rietveld refinement results from XRD patterns revealed no secondary phases in pure and Bi-substituted LaFeO3 samples. The structural transition from orthorhombic at x = 0.0 until x=0.6 (space group Pbnm) to rhombohedral at x=0.8 (space group R3c) was observed. Lattice parameter values increase slightly with Bi concentration due to the substitution of Bi in the LaFeO3 structure. The average crystallite size D was found to vary between 19 nm and 50 nm. The combination of XRD and SEM demonstrated that the prepared Bi-doped LaFeO3 is a single-phase perovskite with a relatively homogeneous particle size distribution. SEM images revealed quasi-spherical particle shapes. FTIR spectra identify the metal oxide bending vibrations at about 536 cm‒1 and 717 cm‒1 attributed to Fe-O and La-O bonds, respectively. No significant effect of Bi substitution from 0% up to 60% on crystal volume was observed, as confirmed by FTIR spectroscopy, which showed no shift in La/Fe-O bending vibration modes with increasing Bi content. The obtained results indicated that the Eg values exhibited a monotone decrease with an increase in Bi ratio. The band gap values varied from 2.2 eV for pure LaFeO3 to 1.85, 1.76, 1.54 and 1.35 eV for the substitutions of 20%, 40%, 60% and 80% respectively. Hence, the sample La0.2Bi0.8FeO3 with the small band gap value can be used as a promising candidate in solar cell applications.

Modulation of BixSb2-xTe3 Alloy Application Temperature via Optimizing Material Composition.

Bi2Te3-based alloys are representatively commercialized thermoelectric materials for refrigeration and power generation. Refrigeration mainly utilizes thermoelectric properties near room temperature, while the power generation temperature is relatively high. However, it is difficult for bismuth telluride to maintain good thermoelectric properties throughout the entire temperature range of 300-500 K. Herein, a series of BixSb2-xTe3 alloys with different Bi contents were prepared by a simple preparation method and systematically investigated, and their best application temperature range was found. The Bi content can modulate carrier concentration and band gap, and the maximum dimensionless figure of merit (ZT) value of BixSb2-xTe3 can be achieved in the corresponding application temperature range. The maximum ZT of Bi0.3Sb1.7Te3 with a Bi content equal to 0.3 reaches 1.14 at 400 K, and the average ZT is 1.06 in the range of 300-500 K, which is suitable for both power generation and refrigeration. Therefore, power generation technologies with higher application temperatures should be selected from BixSb2-xTe3 materials with Bi content less than 0.3, and refrigeration technologies with lower application temperatures should be selected with Bi content greater than 0.3. This work provides experimental guidance for finding the composition of Bi2Te3-based alloys in scientific research and practical applications.

Enhanced Spin-Thermoelectric Generation in Generators Incorporating Liquid Phase Epitaxial Bi-Substituted Yttrium Iron Garnet Films for Constructing an Energy Storage System Combined with Supercapacitors

Recently, energy harvesting, which converts waste heat into energy, has been attracting attention as a highly beneficial future technology. We have focused our attention on the spin Seebeck effect, based on spintronics technology, which enables thermoelectric power generation. The spin Seebeck effect is a phenomenon that enables the conversion of thermal energy into spin-thermoelectric (STE) voltage. An insulator-based STE generator is composed of a thin paramagnetic metal (PM) layer for generating a voltage V STE via the inverse spin Hall effect (ISHE) and a ferrimagnetic insulator (FMI) film used for producing spin-wave spin currents under a temperature gradient ∇T.(1) We studied thick yttrium iron garnet (Y3Fe5O12, YIG) films of ~ 10 μm grown by using liquid phase epitaxy (LPE), and confirmed that the films were of acceptable crystallinity.(2) Pt, a paramagnetic heavy metal, and YIG, an FMI, are typical substances used for the thin PM layer and the FMI film, respectively. We previously proposed a role of spin–orbit coupling with local 3d-electron spins in Fe3+ ions for thermal energy transfer from the phonon system to the spin system in a STE generation,(3) and also proposed that the exchange interaction acting between neighboring spins creates the role of driving force for generating spin-wave spin currents in YIG.(4) Spin-wave spin currents produced in the YIG from the effects of ∇T, which carry spin-angular-momenta between neighboring spins, are pumped up at the Pt/YIG interface into the Pt layer, and the spin currents produced in the Pt layer are converted into charge currents by means of the ISHE. The charge currents generate the electric voltage V STE (or V ISHE) in the Pt layer. A figure included in this abstract shows the dependence of the spin-thermoelectric voltage V STE on ∇T and that of the V STE on the temperature difference in the range of a maximum ΔT of 150 °C between the top cold Cu block and the bottom hot block as shown in the inset of the figure. The probe distance l d was set to 5 mm, and the Pt layer width w Pt was 1 mm. A high V STE value of 90 µV was observed at Δ T = 150 °C (∇T = 300 × 10−3 °C/µm) for the generator incorporating a Y2.35Bi0.65Fe5O12 film of 10 µm thickness. An issue to be addressed on the STE generator is whether the generator can be utilized for the generation of electric power. A semiconductor Seebeck device is a practical choice in the generation of electrical energy. However, the stable operation of the semiconductor Seebeck device is limited to 100 °C or less. The STE generators using Bi-substituted YIG films that have a Curie temperature of 280 °C are expected to operate in a higher temperature range of 100-250 °C. From the measurement of load characteristics, we have confirmed that the STE generators can function as a voltage source. By connecting the STE generator to a Supercapacitor(5) that exhibits a large capacitance and a shorter charging time than a rechargeable battery, it may be possible to construct an innovative energy storage system. The system proposed in our presentation is considered to have a capability of recovering the waste heat of relatively high temperatures exhausted in factories and power plants. We are aiming for observing the V STE value of 250–500 mV at ΔT = 150–250 °C (∇T ≈ 400×10−3 °C/mm) by incorporating the Bi:YIG films of high Bi content into STE generators.(1) M. Imamura et al., Electr. Eng. Jpn. 208, 10‒20 (2019). (2) M. Imamura et al, AIP Advances 11, 035143-1- 035143-5. (3) M. Imamura et al., IEEE Trans. Magn. 58, 4500111-1−4500111-11 (2022). (4) M. Imamura et al., AIP Advances 13, 025001-1−025001-5 (2023). (5) T. Ryu et al., Journal of Physics: Conference Series 2368, 012002-1−012002-8 (2022). Figure 1

Magnetooptical gyrotropic effects in nanosized BiYIG films and diamagnetic YAG substrates

Magneto-optical gyrotropic Faraday and Kerr effects are studied in the BiY2Fe5O12 films with thicknesses ranging from 16 to 55 nm, in the wavelength range of 295 nm < λ < 830 nm (4.2–1.5 eV), and under magnetic fields of up to 1.2 T. It is shown that films produced by ac magnetron sputtering on the single-crystalline diamagnetic yttrium aluminum garnet substrates Y3Al5O12 (001) exhibit high structural and magneto-optical quality. The Verdet constant for diamagnetic Y3Al5O12 is determined, and the magnitude of the Kerr effect is estimated for the polished substrate. It is shown experimentally that for a substrate with diffusely reflective backside, the Kerr effect is about zero, except in the high-energy region. For all BiY2Fe5O12 films investigated, in the saturating magnetic fields of approximately 0.16–0.2 T, the value of specific Faraday rotation reaches 20 deg/μm (200 000 deg/cm), while the value of the Kerr effect reaches approximately 20 min (5.8 mrad). The critical thickness of the film–substrate interface was estimated, highlighting variations in the Kerr effect spectra associated with a decrease in the Bi content in thin films with the thicknesses of below 27 nm.

The Effect of Bi on the Kinetics of Growths, Microstructure and Corrosion Resistance of Hot-Dip Galvanized Coatings.

This paper presents the results of studies on the growth kinetics, microstructure (SEM/EDS) and corrosion behavior of coatings obtained by hot-dip galvanizing process in baths containing Bi additive. The coatings for testing were produced on low-silicon steel in a Zn bath containing 0.04, 0.12 and 0.4 wt.% Bi. The corrosion resistance of the coatings was determined comparatively in standard Neutral Salt Spray Tests (NSST) (ISO 9227) and sulfur dioxide test (SDT) in a humid atmosphere (ISO 22479). Potentiodynamic tests and electrochemical impedance spectroscopy measurements were conducted. It was found that the addition of 0.04 and 0.12 wt.% Bi reduces the total thickness of the coatings and the thickness of intermetallic layers, while the content of 0.4 wt.% Bi in the bath increases the thickness of the layers forming the coating. Direct corrosion tests (NSST and SDT) and electrochemical tests showed that the addition of Bi to the zinc bath reduces the corrosion resistance of the coatings. The corrosion resistance of the coatings decreases with increasing Bi concentration in the zinc bath. In the microstructure of the coatings, it was found that Bi precipitates mainly on the surface of the coating, but also on the cross-section of the outer layer and ζ intermetallic layer. Bi precipitates, due to their cathodic nature, affect the reduction of the corrosion resistance of the coatings with the increase of their content in the bath.

Controlled synthesis of Mn\\M-doped NiP3/Cu3P (M=Cr, Ce, Bi and Co) as electrocatalysts for urea splitting reactions in alkaline solutions

Urea is generally used in agricultural fertilization to provide nutrients they need with the crops, however overuse of urea for fertilization can pollute the environment. Electrolysis urea is a greener way of treating urea, and in recent years electrolysis urea has been studied as a hot topic. It is mainly due to the fact that the potential of urea electrolysis is 0.37 V, which is smaller than the potential of traditional water splitting of 1.23 V. In this paper, a series of synthetic experiments were carried out by doping with the same content of Cr, Ce, Bi and Co into Mn-NiP3/Cu3P. It is found that Cr-doped Mn-NiP3/Cu3P possesses excellent electrochemical properties compared to nickel foam doped with the other three elements. At an iR compensation value of 70 %, Mn\\Cr-doped NiP3/Cu3P has strong catalytic activity and durability for urea oxidation reaction (UOR). At an ultra-low voltage of 1.352 V, the Mn\\Cr-doped NiP3/Cu3P catalyst had a catalytic current of 10 mA cm−2, a low Tafel slope (102.03 mV dec−1), a high Cdl (9.35 mF cm−2), and catalytic stability of more than 50 hours. The enhanced activity of Mn\\Cr-doped NiP3/Cu3P is attributed to rapid charge transfer, improved electrical conductivity, and increased electrochemical area. Density Functional Theory (DFT) calculations showed that synergic catalytic effect of Mn-Cr-NiP3 and Mn-Cr-Cu3P in the catalysts can effectively improve the adsorption capacity of the catalysts, this provides a new ideas of exploration for the electrolysis of urea with cheap and relatively low toxicity catalysts, which can effectively reduce the cost.

Effect of Bi(III) on flotation of copper sulfide from leaching residue of copper smelting dust

Flotation is a potential method for extracting residual copper sulfide (CuS) from the acid-leaching residue of copper smelting dust; however, the inhibitory impact of Bi(III) in the flotation pulp significantly hampers its practical application. In this study, we systematically investigated the inhibition mechanism of Bi(III) on CuS flotation and propose a method to prevent inhibition. Microflotation test results show that a pulp environment with pH 3 and a Bi(III) concentration greater than 1 × 10–2 mol/L significantly depresses the floatability of CuS. Scanning electron microscopy and energy-dispersive spectroscopy results confirmed that Bi(III) hydrolyzes on the surface of CuS to form a precipitate cover layer, which adsorbs onto the surface of CuS. This precipitate was confirmed by X-ray photoelectron spectroscopy analysis and thermodynamic calculations to be BiOCl. Fourier transform infrared analysis revealed that BiOCl reduces the recovery of CuS by hindering the adsorption of xanthate. Finally, the pre-treatment of the leaching residue with H2SO4 + NaCl solution can dissolve BiOCl precipitates on the surface of CuS, eliminate the influence of Bi(III), and result in efficient flotation recovery of CuS from leaching residue.

Antibacterial and biological properties of MAO treated Mg-Bi alloys

The clinical application of Mg implant is limited due to the poor corrosion resistance, antibacterial and biological properties. In our previous work, Mg-Bi alloy with micro-arc oxidation (MAO) treatment was prepared and proved to have good corrosion resistance, so in this work, their antibacterial property and bioactivity were also investigated to evaluate its potential application in clinics. The results showed that, the Mg-Bi alloy has good antibacterial performance, and with the increase of Bi content, the antibacterial property was enhanced. After MAO treatment, the antibacterial performance was slightly decreased, however the MAO-Mg-6Bi and MAO-Mg-9Bi still showed excellent antibacterial property, additionally, they can also induce apatite formation in simulated body fluid (SBF), indicating improved bioactivity. Based on the good comprehensive properties, the MAO treated Mg-Bi alloy has a great potential to be used as an implant material in clinics.

Influence of Engine Oil Degradation on Sliding Bearings, with Special Focus on Different Degrees of Nitration

Bismuth (Bi) can be considered for use as a green substitute for lead in bearing applications. However, accelerated Bi oxidation can occur during operation, creating a brittle surface and resulting in premature seizure failure. Thus, the aim of this study was to evaluate the influence of engine oil degradation, especially nitration processes, on the oxidation of Bi. Tailor-made artificially aged oils with different degrees of nitration were produced and utilized in static bearing oxidation tests. By means of X-ray photoelectron spectroscopy (XPS), the Bi surfaces were analyzed regarding their chemical compositions after the tests. The results were correlated with the respective oil conditions determined via conventional parameters as well as high-resolution mass spectrometry. The findings obtained revealed a direct correlation between the amount of Bi-oxide and the nitration values of the oil, proving there was a positive impact of nitration products on the oxidation of the Bi surfaces. A comparison with the Bi content in the oils demonstrated a protective effect of the oxide layer as the Bi content declined with an increase in nitration. Overall, valuable insight into understanding the impact of oil condition on engine parts is given, and the importance of testing engine parts with aged lubricants is emphasized.

Genesis of high-grade lode gold shoot dominated by ore fluid overprinting during a ductile-brittle shear event

Lode gold deposits hosted by ductile-brittle shear zones account for more than one-third of the world’s gold production. High-grade ore shoots from this type of deposit are the most critical exploration targets. The ore shoots can form through the post-depositional deformation of auriferous sulfides or overprinting of ore fluids accompanied by coupled dissolution-reprecipitation (CDR) reactions. However, the mechanism that dominates ore shoot genesis remains unknown, primarily due to the controversial single progressive or polyphase nature of ore-bearing shear zones. Here, we report on geological and geochemical analyses we conducted at the large Hetai goldfield, South China, to construct an accurate gold upgrading model for the formation of ore shoots. Stages 1−3 of mineralization at Hetai show features typical of ductile shearing, while Stage 4 is characterized by quartz-sulfide veinlets in brittle fractures. 40Ar/39Ar ages of ca. 184 Ma and 157 Ma for the mineralization of stages 1 and 4 overlap with the regionally dextral ductile-brittle shear that occurred during ca. 210−162 Ma. Thus, the gold event at Hetai should have been controlled by a single progressive ductile-brittle shear episode, rather than polyphase structural events. The auriferous fluids at Hetai precipitated minor invisible gold in pyrites (mean 0.173 ppm) produced during stages 1−4 through fluid-rock interaction. The systematic increase of elements Au, As, Sb, Bi, Ag, and Cu and δ34S values in ductile-deformed pyrites from stages 1−3 indicate that early invisible gold upgrading should be the result of the post-depositional remobilization of auriferous sulfides during the long-lived ductile-brittle transition. Cataclastic pyrites hosting invisible gold from Stage 4 have zoned and porous mantles with elevated invisible gold (mean 0.503 ppm) and Sb, Bi, Pb, Co, Ni, and Ti contents. These pyrites are further replaced by chalcopyrite and pyrrhotite with increasing invisible gold, Co, and Ni contents. In addition, numerous visible native gold grains in Stage 4 are included in sulfides formed by replacement and develop along the microfractures and grain boundaries of these sulfides. We suggest the late invisible and visible gold upgrading events in Stage 4 can be attributed to the auriferous fluid superposition and subsequent replacement of pyrite via CDR reactions in a brittle regime. Therefore, the gold upgrading process at Hetai is jointly caused by the early remobilization induced by ductile-brittle deformation and the late ore fluid superposition with accompanying CDR reactions within a brittle domain. As the ore fluid superposition and CDR reactions in Stage 4 produce a significant amount of visible gold, they exert a first-order control on the genesis of ore shoots at Hetai. The refined model may be widely applicable to lode gold deposits elsewhere and can be used to identify regions with promising exploration targets.

Structural Modifications due to Bi-Doping in MAPbBr3 Single Crystals and Their Impact on Electronic Transport and Stability.

Doping strategy in lead halide perovskites is essential to enhance its optoelectrical properties and expand the potential applications. In this work, the mechanisms, for how dopants affect the overall structural, optical, electrical, and chemical properties and stability of lead halide perovskite materials, are investigated. This is done by specifically considering various bismuth (Bi)doping concentrations in MAPbBr3 single crystals grown using the inverse temperature crystallization method. The resultant doped single crystals exhibit a saturation point when Bi concentration exceeds 0.063% which is considered an optimum doping point. The highest thermal stability is also achieved at this doping concentration among the doped single crystals. This study clearly identifies how Bi doping affects the properties of MAPbBr3 and extends to consider stability, which has not been fully considered for MA-based perovskites previously. This will provide a clear understanding of evaluating doped perovskite materials for enhanced material properties, device performance, and stability.