Dispersive Spectroscopy Research Articles

Comparison of iron deposits removing material from the marine archaeological wood of Nanhai I shipwreck

Iron deposits are commonly found in marine archaeological wood, causing acidification, degradation, and mechanical damage to marine archaeological wood. This study focused on extracting iron deposits from loose wood samples taken from the Nanhai Ⅰ shipwreck. The removal efficiency of iron deposits in wood using materials, such as EDTA-2Na, DTPA, C6H17N3O7, Na2C2O4, amidoxime cellulose, DFO, EDTA-2Na-H2O2, DTPA-H2O2, EDTA-2Na-Na2S2O4, and DTPA-Na2S2O4, was evaluated. Analysis using scanning electron microscopy/energy dispersive spectroscopy and X-ray diffraction identified the presence of iron deposits in the wood of the Nanhai I shipwreck including goethite (FeOOH) and pyrite (FeS2). The removal efficiency was evaluated by ICP-AES and results showed that amidoxime cellulose and DTPA had higher removal efficiency for iron deposits in wood. The difference between the iron deposits removal efficiency of DTPA and EDTA was significant after the addition of oxidant (H2O2) and reductant (Na2S2O4) to the systems, respectively. The addition of oxidant H2O2 to DTPA improved the iron deposits removal efficiency of DTPA from wood within 30 days. Furthermore, the addition of reductant Na2S2O4 to EDTA-2Na significantly improved the iron deposits removal efficiency of EDTA-2Na from wood. These findings provide a valuable reference for developing efficient methods for removing iron deposits during the practical protection of the Nanhai I shipwreck.

Design and preparation of novel LaFeO3/NiFe2O4 nanohybrid for highly efficient photodegradation of methylene blue dye under visible light illumination

Most dyes are carcinogenic; thus, they must be removed from the water to save aquatic and human life. Among the various methods, the photocatalytic degradation of dyes is attracting much attention due to the easy strategy driven by the solar light. Herein, we report the fabrication of nickel ferrite (NiFO), lanthanum ferrite (LFO) and their composite are utilized as a light-driven catalyst for the deprivation of significant commercial dyes. The straightforward microemulsion method is used to produce both pure ferrite materials and their composite counterparts. The phases of the synthesized materials were verified through XRD analysis while scanning electron microscopy was employed to examine their morphology. The average crystallite size of the LFO, NiFO and their composite was 53, 62 and 42 nm, respectively. The elemental composition of the pristine and composite was confirmed by the energy dispersive spectroscopic analysis, indicating no other impurity in the materials. The optical properties are analyzed via UV visible and photoluminescence to measure the band gap value of 2.05, 1.73 and 1.9 eV for LFO, NiFO and their composite, respectively. It is observed that the LaFeO3/NiFe2O4 has the highest photodegradation efficiency (92 %) as compared to the LFO (LaFeO3) and NiFO (NiFe2O4). The composite material also showed excellent reusability as well as good stability. It was also confirmed that OH radicals are the major contributor toward the dye degradation, as confirmed by the scavenger tests. The higher mineralization of methylene blue in the occurrence of composite as a catalyst may cause rapid charge transfers, as confirmed by EIS, and it may stop the recombination of electrons/hole pairs due to suitable band alignments.

Modelling, synthesis, fabrication, and characterization of a novel lead-free organo-inorganic iodide perovskite for photovoltaic application

This work is aimed at modelling, synthesizing, and characterizing of a novel lead-free organo-inorganic halide perovskite for photovoltaic application. A planar solar cell device architecture was employed in the fabrication with graphite anode. Thermo-gravimetry analyzer (TGA) was used to determine the thermal stability under nitrogen flow from 20 oC to 870 oC. The TGA result exhibits thermal stability above 200 oC. X-Ray Diffraction (XRD) was used to confirm the crystallinity formation, several peaks were observed with the most prominent peaks at 2Ө = 19.0o, 29.5o, and 33.3o with average crystalline size of 42 nm calculated using Scherrer’s equation. The Field Emission Scan Electron Microscope/Energy Dispersion Spectroscope (FESEM/EDS) results showed a plate-like/cubic structure of hexagonal crystal shapes. These shapes are agglomerated in nature with fine and coarse grains, which might improve the photo-excited electrons diffusion through aggregating the light scattering properties and effective mean path of light of perovskite solar cell. Differential Scanning Calorimetry (DSC) results showed that gradual decomposition of the material can only be visible between 200 oC and 240 oC with the peak at 223.9 oC. The photoluminescence properties of the synthesized perovskites light absorbing layers exhibit a broad band spectrum emission within the range of 340 to 588nm, which is within visible spectrum. The UV-vis spectrum exhibits a strong optical absorption band in the visible region, which extends from 360 nm to 725 nm. The band gap energy was calculated from the plotted Tauc fit and estimated to be 1.99 eV. The J-V of the synthesized material recorded the highest PCE of 4.6 % with a fill factor of 19.56.

The Mechanism of Fluid Exsolution and Sn–W Precipitation: Example from the Hongling Pb–Zn Polymetallic Deposit and the Surrounding Area in Northern China

Metal migration and precipitation in hydrothermal fluids are important topics in economic geology. The Hongling polymetallic deposit comprises one of the most important parts of the Huanggangliang–Ganzhuermiao polymetallic metallogenic belt, which is in eastern Inner Mongolia. Except for lead–zinc skarn, minor cassiterite in the skarn and disseminated W–Sn mineralization in granitic rocks have also been found. The dominant Sn–W mineralization is in the northern part of the deposit, occurring as disseminated wolframite and cassiterite in aplite hosted in Mesozoic granite porphyry. The aplite together with pegmatite K-feldspar–quartz comprises vein dikes hosted in the granite porphyry, providing evidence for the transition from melt to fluid. The veins, dikes, and Sn–W mineralization in the aplite provide an opportunity to investigate fluid exsolution and the mechanics of metal precipitation. Based on field observations, the micrographic and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) results of the vein dikes, chronology, and the whole-rock geochemistry of the host rock, together with the fluid inclusion results, this paper discusses the characteristics of the causative magma, the mechanics of fluid exsolution and W–Sn precipitation. Our results show that the causative magma is of highly fractionated A-type granite affinity and has an intrusive age of late Mesozoic (133.3 ± 0.86 Ma). The magmatic evolution during shallow emplacement led to immiscibility between highly volatile, high-silica, and W- and Sn-enriched melts from the parent magma, followed by fluid exsolution from the water-rich melt. The alkaline-rich fluid exsolution led to a change in the redox state of the magma and the chilling of the melt. Fluid boiling occurred soon after the fluid exsolution and was accompanied by the degassing of CO2. The boiling and escape of CO2 from the fluid led to changes in fluid redox and W and Sn precipitation; thus, the W and Sn mineralization are mostly hosted in causative intrusions or peripheral wall rocks, which can be used as indicators for Sn–W exploration in the area.

Heterogeneous reactivity of soybean/palm biodiesel soot with NO2 and CF3COOH in a Knudsen reactor and DRIFTS/TGA/SEM characterization of the soot

The characteristics and atmospheric reactivity of soot generated from an alternative fuel (soybean/palm biodiesel) have been investigated for the first time using a Knudsen flow reactor with a mass spectrometer as detector for gaseous species. The heterogeneous reactions with nitrogen dioxide (NO2) and trifluoroacetic acid (CF3COOH, TFA) have been investigated. Uptake coefficients calculated for the reaction of NO2 (γ0= (3.85 ± 0.70) ∙10–3) are one order of magnitude higher than the corresponding TFA reactions (γ 0= (6.06 ± 0.24) ∙10–4). NO is the only product observed in the gas phase. Knudsen cell reactor has also been used in the characterization of chemical functions on the surface since NO2 can be used to identify reducing groups, while TFA is used to evaluate basic sites. Compared to other soot samples, biodiesel soot shows higher reactivity with NO2 which has implications in the regeneration process of the diesel particulate filter (DPF). IR bands attributable to polycyclic aromatic compounds have been observed by Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTs). Bands of carbonyl compounds are also clearly observed. Thermogravimetric analysis/ differential scanning calorimetry-mass spectrometry (TGA/DSC-MS) is used to obtain more information about the volatile organic compounds present on the soot surface. Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) analysis indicates a particle size in the range 14–40 nm and carbon as the major element (92 %). According to the obtained results, a mechanism of processes occurring at the surface has been proposed.

Preparation and characterization of (Yb0.25Lu0.25Sc0.25Tm0.25)2Si2O7 as a potential environmental barrier coating

AbstractA novel high‐entropy rare‐earth disilicate (Yb0.25Lu0.25Sc0.25Tm0.25)2Si2O7 ((4RE0.25)2Si2O7) was proposed as an advanced environmental barrier coating (EBC) materials in this work. The (4RE0.25)2Si2O7 powders were synthesized using the solid‐state sintering method. Based on the X‐ray diffraction (XRD) and scanning electron microscope/energy‐dispersive spectroscopy analysis, the uniform solid solution was detected in the (4RE0.25)2Si2O7, which had a monoclinic β‐phase structure in the space group of C2/m. The lattice parameter of the structure was derived based on the Rietveld refinement analysis to the XRD results. The coefficient of thermal expansion of the bulk (4RE0.25)2Si2O7 was similar to that of the SiC‐SiC ceramic matrix composite substrate of the environmental barrier coating. In addition, this (4RE0.25)2Si2O7 bulk material had a very low thermal conductivity, which was beneficial for the application of environmental barrier coatings. The hot water‐vapor corrosive experiments were conducted in an environment of 90% air and 10% H2O at 1300°C. The results indicated a better water‐vapor corrosion performance than the commercialized Yb2Si2O7 EBC materials. The (4RE0.25)2Si2O7 material prepared in this work showed great potential to work as the environmental barrier coating.

Dynamical Franz-Keldysh Effect in Diamond in the Deep Ultraviolet Probed by Transient Absorption and Dispersion Spectroscopy Using a Miniature Beamline.

Here, we introduce a miniature beamline for transient absorption and dispersion spectroscopy, using a tailored deep ultraviolet field immediately after the noncollinear generation without subsequent optical elements. We explore the near-band-gap region in diamond in the presence of a few-femtosecond pump pulse where the delayed dynamical Franz-Keldysh effect and the almost instantaneous optical Kerr effect coexist.

Gas sensing with 7-decade dynamic range by laser vector spectroscopy combining absorption and dispersion

Laser absorption spectroscopy (LAS) has been widely used for unambiguous detection and accurate quantification of gas species in a diverse range of fields. However, up-to-date LAS-based gas sensors still face challenges in applications where gas concentrations change in a wide range, since it is extremely difficult to balance spectral analysis strategies for different optical thicknesses. Here we present laser vector spectroscopy that combines absorption spectroscopy with dispersion spectroscopy, simultaneously taking advantage of the former’s high sensitivity in the low-concentration region and the latter’s high linearity in the high-concentration region. In the proof-of-concept demonstration of acetylene measurement, it achieves a linear dynamic range of 6×107 (R2>0.9999), which surpasses all other state-of-the-art LAS techniques by more than an order of magnitude, with the capability of highly accurate quantification retained. The proposed laser spectroscopic method paves a novel way of developing large-dynamic-range gas sensors for environmental, medical, and industrial applications.

Electroanalysis of ethyl-centralite propellant stabiliser at magnetic nanoparticle modified glassy carbon and screen-printed electrodes with extension to forensic firearm residue analysis

Electroanalysis of organic residues of the propellant stabiliser ethyl-centralite (1,3 diethyl-1,3 diphenyl urea, EC) generated from the discharge of a weapon or improvised explosive devices is examined. Comparative effects of an electrode modifier, nanoparticles of magnetite (Fe3O4), on the sensor performance was of interest, with customised printed prototype development and analysis of organic firearm residue (OFAR) samples. Differential pulse voltammetry (DPV) calibration studies realised sensitivity of 6.37 × 10−2 μA∙μM−1 (over the concentration range 2.5–50 μM) at the magnetic nanoparticle modified electrode, representing a 1.65 fold signal increase relative to unmodified electrodes with limit of detection 4.39 µM. Inclusion of the OFAR co-existing diphenylamine (DPA) stabiliser realised signal discrimination and sensitivity of 7.49 × 10−2 and 5.49 × 10−2 μA∙μM −1 for DPA, and EC respectively, using DPV over the same range. The work culminated in the qualitative and quantitative analysis of propellant stabilisers in firearm residue acquired from a single base shotgun shell, with recovery from a target sample cloth, together with unburnt propellant, making promising first steps towards a customised screen-printed prototype for use by forensic professionals. Scanning electron microscopy/energy dispersive spectroscopy and atomic force microscopy were employed for particle confirmatory analysis.

Electrochemical, mechanical, and antibacterial properties of the AZ91 Mg alloy by hybrid and layered hydroxyapatite and tantalum oxide sol–gel coating

Abstract The corrosion and bacterial behavior of AZ91 magnesium alloy coated with sol–gel-deposited amorphous tantalum oxide and hydroxyapatite have been investigated. The objective was to assess the potential suitability of AZ91 for permanent prosthesis applications. The coatings were applied in layered and hybrid configurations and characterized using various techniques including X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectrometry, and drop analyses. The antibacterial properties were evaluated through interactions with Staphylococcus aureus and Escherichia coli strains. Mechanical properties and adhesion were determined via linear scratch tests, and electrochemical corrosion tests were conducted in different media. The release of aluminum ions from the samples in Dulbecco’s Modified Eagle’s Medium was monitored over 28 days. The findings revealed that the amorphous tantalum oxide coating, particularly in combination with hydroxyapatite, improved antibacterial properties and positively influenced corrosion and scratch resistance. The layered and hybrid coatings demonstrated the highest corrosion resistance. The release of aluminum ions remained within acceptable levels in the tested medium. Overall, the study provides valuable insights into the potential of sol–gel coatings on AZ91 for prosthetic applications, considering antibacterial behavior, corrosion resistance, and aluminum release.

Wear behavior and tribo-surface characteristics of nano magnesium composites

A nano magnesium composite was synthesized with the addition of 5.6 wt.% of titanium, 3 wt.% of aluminum and 2.5 wt.% of nano boron carbide particles through the disintegrated metal deposition process. To validate the metallurgical features of the synthesized magnesium composite, the samples were exposed to X-ray diffraction study and scanning electron microscopic analysis with dispersive spectroscopy analysis. Wear behavior of the nano magnesium composite was studied through pin-on-disc dry sliding wear experiments by changing the load and sliding velocity over a sliding distance of 3000 m. Further, wear rate of the produced material was analyzed for varied wear parameters. Wear behavior of the magnesium composite revealed an adverse effect with an increased load and a positive effect with increased sliding velocity. The microscopic analysis of the worn surface and the collected debris revealed the characteristics of the wear surface of the nano magnesium composite. Adhesion, abrasion, delamination, oxidation and thermal softening were the mechanisms observed in the post-failure analysis.

Influence of solution pH on the properties of biogenic jarosite produced from ferrous ion bio-oxidation in a bioreactor

Precipitation process of ferric ions from bio-oxidation of ferrous ions is influenced by pH and solution chemistry. Accumulation of iron precipitate may reduce extraction efficiency in bioleach operations. Firstly, this study investigates the impact of pH on the properties of iron precipitate generated in a continuous stirred bioreactor at three pH levels (1.7, 1.9, and 2.2). Characterization of precipitates was performed and identified predominantly as potassium jarosite using Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope/energy dispersive spectroscopy (SEM/EDS). Results showed properties of the formed jarosites altered in response to the influent solution pH, with a major effect on the surface area. Secondly, results showed that pseudo-order-kinetic model can accurately describe the sorption performance of the biogenic jarosite with respect to copper uptake. Monomolecular adsorption capacities (qm) at 303 K were 17.12 and 13.32 mg/g for jarosite generated at pH 2.2 and 1.7, respectively. The sorption thermodynamic data showed the process was endothermic and nonspontaneous. Activation energy in this investigation was calculated to be 21.01 and 23.39 kJ/mol for jarosite produced at pH 2.2 and 1.7, respectively, implying that the rate-limiting step is chemically controlled for both adsorption processes. Results of this study may provide some insights into the management of iron precipitation in biohydrometallurgical processes.

Simulations and Experiments on the Microstructure and Property Evolution of In Situ TiC+Al3Ti-Reinforced Aluminum Coatings on AZ91D Magnesium Alloy

With the development of computational thermodynamics, it is possible to design a material based on its simulated microstructure and properties before practical operations. In order to improve the surface properties of AZ91D magnesium alloy, Jmatpro was used in this study to design an alloy system with in situ TiC+AlTi3-reinforced aluminum coatings. The Gibbs free energy, hardness, and phase diagrams of aluminum coatings with different ratios of Ti to B4C were simulated. According to the simulation results, TiB2, TiC, Al3Ti_DO22, and Al4C3 were formed in the coating while TiB2, TiC, Al3Ti_DO22, Al4C3, and Al3Mg2 were formed in the transition zone between the base metal and the coating. Based on the simulation results, different amounts of Ti were used with B4C (the ratios were 3:1, 4:1, 5:1, and 6:1) to fabricate TiC+Al3Ti reinforced aluminum coatings on AZ91D magnesium alloy via laser cladding. The microstructure and phase composition of the coating were studied using scanning electron microscopy (SEM) incorporated with energy- dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results indicated that intermetallic phases, such as AlTi3(C, N)0.6, AlMg, Al3Mg2, Al3Ti, and TiC were formed in the coatings. As the Ti content increased, the content of Al3Ti increased and the content of TiC decreased in the coatings, which is consistent with the simulation results. The average hardness of the coatings was approximately four to five times that of the magnesium alloy substrate, and the corrosion current density of the coatings was around 2.5 × 10−6, which is two orders of magnitude lower than that of AZ91D magnesium alloy.

Extraction of niobium in one step from tin slag by NH4F‐HCl leaching process

AbstractNiobium and tantalum are generally found together in nature in ores such as columbite, tantalite, and pyrochlore. These ores can occasionally associate with cassiterite, the tin ore. The pyrometallurgical processes of cassiterite produces a slag that can contain Nb and Ta from the associated ores. Cassiterite processing for tin extraction has generated a considerable quantity of residue. This work aims to study the extraction of Nb from tin slag while leaving the Ta solid. The process of separation consists in one step by leaching using a combined solution of HCl‐NH4F. The slag was characterized by X‐ray fluorescence (EDXRF), atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectrometry (ICP‐OES), X‐ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and granulometric analysis. The effect of parameters of the leaching processes was investigated, such as the time of the process, HCl concentration, liquid‐to‐solid ratio, temperature, and salt‐to‐slag ratio. It was possible to recover 100% of Nb and 5% of Ta in liquor of leaching within 4 h, at 85°C, using an L:S ratio of 20:1, NH4F:slag ratio of 0.12 g, and HCl concentration equal to 9.79 mol/L.

Effect of zinc oxide on corrosion resistance of magnesium ammonium phosphate cement-based coating

In order to improve the anticorrosive performance of magnesium ammonium phosphate cement (MAPC) coating, a small amount of zinc oxide was added to the MAPC coating to modify and coat the surface of Q235 steel. The anti-corrosion resistance and mechanism of MAPC coating modified by zinc oxide were analyzed based on electrochemical test results, and the morphology and composition changes of the coating before and after immersion were observed and tested using X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), and a thermogravimetric analyzer (TG-DTG). Low field nuclear magnetic resonance testing was used to determine the porosity of the coating and the corrosion resistance of the modified coating was tested by a neutral salt spray test. The results show that after immersion in a 3.5% NaCl solution for 28 days, the MAPC coating with 3% (mass fraction) zinc oxide exhibited a corrosion current density of 2.96 × 10-4 μA/cm2 at a corrosion potential of −0.870 V, demonstrating a favorable outcome with a positive shift.; Meanwhile, the 28 days polarization resistance of the modified coating was 97436 Ω∙cm2, which was 78% higher than that of the blank. The shielding performance of the coating was enhanced, and the charge transfer resistance was also significantly improved. The porosity of the modified coating before and after immersion was lower than that of the blank group. After 1440 h of neutral salt spray testing, there was no swelling or peeling on the coating surface, and there was no trace of corrosion on the internal substrate.

Microstructural Modification by Redesigning the Chemical Composition of Ni 620 Filler Metal

Ni 620 is a widely used brazing alloy, especially in cases where high‐temperature strength and corrosion resistance are required. The formation of undesirable intermetallic phases in the brazing joint due to the addition of boron and silicon as melting point depressants affects the mechanical properties of the joint. Reducing the formation of intermetallic phases during brazing is an important issue in the application of Ni 620. In this study, two approaches, inoculation with Nb and variation of the B and Si content in Ni 620, are pursued to selectively influence the microstructure of the brazed joint. Therefore, the solidus and liquidus temperatures of the new brazing alloys are investigated by means of differential scanning calorimetry measurements. Also, the microstructure of brazed joints is analyzed and evaluated by scanning electron microscope/electron‐dispersive spectroscopy as well as the hardness properties using nanoindentaion. It is observed that the addition of Nb, as well as the variation of the B and Si content, leads to a change in the brittle phase band. Especially brittle borides can be reduced in this way. The results contribute to produce brazing joints with more adapted properties, despite low brazing temperatures and short holding times.

Adhesion of veneering composite to metal-free CAD/CAM materials: effect of surface conditioning and adhesive resin type

ObjectivesThis study aimed to investigate the adhesion of veneering composite to metal-free computer-aided design/computer-aided manufacturing (CAD/CAM) materials with different compositions after surface conditioning and application of adhesive resins.Materials and MethodsA total of one hundred and sixty specimens were divided into four groups (n = 40) manufactured either from polyetheretherketone (PEEK; KERAstar PEEK), polyetherketoneketone (PEKK; Pekkton), fiber-reinforced composite (FRC; Trinia), or high-impact polymer composite (COMP; Bredent HIPC) CAD/CAM discs. Each group was then randomly subdivided into four different subgroups of adhesive systems (n = 10) as Visiolink (Bredent), Single Bond Universal (3M), G-Premio BOND (GC), and OptiBond Universal (Kerr). The shear bond strength (SBS) of each specimen with veneering composite material was tested with a universal testing machine following thermocycle aging (5000 times). The modes of failure resulting from the tests were determined with scanning electron microscope (SEM), dispersive spectroscopy (EDS), and analytical imaging. The data were statistically analyzed with two-way ANOVA and Bonferroni post hoc tests (alpha = 0.05).ResultsThe highest SBS values among all groups were found for the COMP material (20.28 ± 2.08 MPa) with OptiBond Universal adhesive, while the lowest for the PEEK material (10.33 ± 2.47 MPa) with G-Premio BOND. The most common failure mode for the PEEK and PEKK specimens was adhesive failure, for the FRC and COMP groups mixed failures were common.ConclusionsBond strength values of at least 10 MPa were achieved for all tested between metal-free CAD/CAM materials and adhesive resin application.

Photoelectrocatalysis Synthesis of Ammonia Based on a Ni-Doped MoS2/Si Nanowires Photocathode and Porous Water with High N2 Solubility

The synthesis of ammonia through photocatalysis or photoelectrochemistry (PEC) and nitrogen reduction reaction (NRR) has become one of the recent research hotspots in the field, where the catalyzed materials and strategies are critical for the NRR. Herein, a Ni-doped MoS2/Si nanowires (Ni-MoS2/Si NWs) photocathode is prepared, where the Si NWs are formed on the surface of a Si slice by the metal-assisted chemical etching method, and the hydrothermally synthesized Ni-MoS2 nanosheets are then cast-coated on the Si NWs electrode. Porous water with high solubility of N2 is prepared by treating a hydrophobic porous coordination polymer with hydrophilic bovine serum albumin for subsequent aqueous dispersing. The relevant electrodes and materials are characterized by electrochemistry, UV-vis spectrophotometry, scanning electron microscopy/energy dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller method, and zeta potential method. The uses of the Ni-MoS2/Si NWs photocathode and the porous water with high nitrogen solubility for PEC-NRR give a yield of NH3 of 12.0 mmol h-1 m-2 under optimal conditions (e.g., at 0.25 V vs RHE), and the obtained apparent Faradaic efficiency higher than 100% is discussed from the inherent photocurrent-free photocatalysis effect of the photoelectrodes and the suggested classification of three kinds of electrons in PEC, which may have some reference value in understanding and improving other PEC-based processes.

Synthesis of chemically exfoliated reduced graphene oxide from as-grated graphite rods recovered from used household batteries for utilization in tribological applications

The research objective of this work is to reuse graphite rods recovered from used batteries and utilize them as an additive in SAE20W40 oil to improve the engine parts’ lubrication ability and wear resistance. The graphite rods are grated to obtain ultra-fine particles and then chemically exfoliated using an Improved Hummer's process that results in graphene oxide. Then, it is thermally reduced at 350 °C to yield reduced graphene oxide. Different ratios (0.25, 0.50, 0.75, and 1.00 wt.%) of as-grated graphite particles and reduced graphene oxide were dispersed in the above oil to form a colloidal solution and then used for tribological studies. The graphite particles and synthesized reduced graphene oxide were characterized using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. X-ray diffraction data confirms the presence of graphite, graphene oxide, and reduced graphene oxide in the prepared powders and matches with the standard files. High-resolution transmission electron microscopy images reveal the presence of multilayer sheets with an interplanar distance of 0.34 nm having wrinkles, folds, and gas holes. The G and D band positions of Raman spectra prove the formation of oxygenated functional groups, and the ID/ IG ratio confirms the defects in graphene oxide and reduced graphene oxide. The viscosity of prepared lubricant increases by 35% and 21% for graphite and reduced graphene oxide, respectively. The results of tribological studies with 0.25 wt.% graphite and 0.5 wt.% reduced graphene oxide lubricants showed improvement in coefficient of friction by 32% and 36%, respectively. At these optimal concentrations, the specific wear rate dropped by 51% for reduced graphene oxide. Scanning electron microscopy/energy dispersive spectroscopy, images show that the nanolubricant's mending effect over the worn surface improves reduced graphene oxide added SAE20W40 oil tribological characteristics. From the results, reduced graphene oxide synthesized from as-grated graphite rods proves to be a low-cost, sustainable, and effective friction modifier for engine oils.

A Cobalt-Based Metal-Organic Framework Nanosheet as the Electrode for High-Performance Asymmetric Supercapacitor.

Inspired by the significant advantages of the bottom-up synthesis whose structures and functionalities can be customized by the selection of molecular components, a 2D metal-organic framework (MOF) nanosheet Co-BTB-LB has been synthesized by a liquid-liquid interface-assisted method. The as-prepared Co-BTB-LB is identified by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX) and X-ray photoelectron spectroscopy (XPS), and the sheet-like structure is verified by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). Co-BTB-LB electrode exhibits an excellent capacity of 4969.3Fg-1 at 1Ag-1 and good cycling stability with 75% capacity retention after 1000 cycles. The asymmetric supercapacitor device with Co-BTB-LB as the positive electrode shows a maximum energy density of 150.2Whkg-1 at a power density of 1619.2Wkg-1 and good cycling stability with a capacitance retention of 97.1% after 10000 cycles. This represents a state-of-the-art performance reported for asymmetric supercapacitor device using electroactive bottom-up metal-complex nanosheet, which will clearly lead to a significant expansion of the applicability of this type of 2D nanomaterials.